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# Fax Machines

This article was initially written as part of the IEEE STARS program.

## Citation

The concept of electrically transmitting an exact copy (from the Latin fac-simile, "make similar") has been credited to the Scottish inventor, Alexander Bain (1810-76) who received a patent in Great Britain and Ireland on 27 May 1843, then by the US Patent Office as US 5957 on 5 December 1848 that described his process of electronically copying and transmitting images between distant locales. The first commercial service operated in the 1860s but the first profitable service appeared only after World War I. The mid-1960s saw the first sustained efforts to produce fax machines for general business use. Fax became an essential communications tool in the 1980s, first in Japan, followed by the United States and the rest of the world. By 2000, however, e-mail and the Internet had rendered the fax machine obsolescent, though not obsolete.

## Introduction

The basic concept of a facsimile, or fax, machine–a machine that electrically transmits an image–has not changed since 1843. The three main components remain the scanner-transmitter, the transmitting medium, and the receiver-recorder. Three broad, intertwined, technical trends help define the history of facsimile. First, the complexity of fax equipment vastly increased over time. Second, as machines became more sophisticated, they became "black boxes," their technical aspects increasingly hidden from view. Third, and ironically enough, they became easier to use while more sophisticated in capability. Beyond the black, or gray, or white box of the machine, there were changes in facsimile’s enabling and supporting technologies, the social environment, its competition, and the expectations and assumptions of its promoters and users.

The history of the fax machine reflects the changing nature of “high technology,” a phrase signifying a technology on the cutting edge of novelty and almost–or actually–practical. Facsimile’s history relies on technical and business advances in the telecommunications, electronics, and computer industries; without them, there would be no fax industry. Fax history is therefore a global tale, involving the competition and diffusion of ideas, research, and manufacturing from Europe to North America to Japan and back. These shifts reflected larger movements of technology, manufacturing, and capital, and thus changes in the relative capabilities and status of countries.

An integral part of fax’s evolution was competition—within the technology, and without. From Alexander Bain and Frederick Bakewell in the 1840s; Giovanni Caselli and Bernhard Meyer in the 1860s; Arthur Korn and Eduoard Belin in the 1910s; Wirephoto and Soundphoto in the 1930s; Times Facsimile Inc. and Radio Inventions Inc. after World War II; to Western Union and Xerox in the 1950s-60s, there was no area of the fax market, no niche too small, for players to struggle against each other for commercial acceptance. (Figure 1)

Figure 1: The French telegraph administration operated the world’s first fax service in 1865 with Abbé Caselli’s pantelegraph. Louis Figuier, Les Merveilles de la Science Vol. 2 (Paris: Librarie Furne, Jouvet et Cie, 1870)

Until the 1950s, individuals were the key developers and rivals. Alexander Bain, a Scotsman who immigrated to London to pursue clockmaking opportunities, patented the first facsimile machine in 1843. Unlike his electrochemical paper, his machine never reached the market. Nor did Frederick Bakewell’s 1848 invention, which was displayed at the 1851 Crystal Palace exhibition in London. Some, like Thomas Edison or John V. L. Hogan, operated their own companies while others, like Austin Cooley or John Young, worked within larger corporate structures. While individuals remained critically important, after the 1950s the growing amount of technical expertise, financial resources, and marketing ability needed to create a commercially viable product meant corporations became the main players. The failure of numerous startups with good ideas but little else reinforces this point.

Optimism about fax’s potential resided in a procession of enthusiasts and advocates whose visions outran the technically and commercially possible until the 1980s. Facsimile document transmission was a “coming wonder” in the 1930s, a “Cinderella” in the 1940s, a “commercial infant” in the 1950s, and a “sleeping giant” in the 1960s. Time after time, manufacturers and potential customers proposed uses years or decades ahead of their successful implementation. The many proposed and attempted uses meant that fax’s consumers changed with the technology. In the 19th and early 20th centuries, telegraph and telephone companies actually bought or built the machines, then operated them. The ultimate customers were indirect users, who chose to buy newspapers with the most recent photographs. By the 1970s, however, the ultimate customer was increasingly the actual user, as fax machines migrated to desktops.

## Commercial Challenges

If the idea of transmitting images was such a good idea, why did it take so long to succeed commercially? Certainly it was not for lack of trying, for over the decades scores of inventors and companies tried to develop and market fax machines. The overwhelming majority failed. Indeed, a theme running like a river through fax’s history is failure–of ideas, technologies, projects, and companies that never succeeded. Given that daunting history, what motivated individuals and firms to commit resources to create new markets and technology for facsimile?

Most important was the belief, “This time it will be different.” Promoters of a new product or service explained that previous failures occurred because the machines were too expensive, too slow, or in other ways lacking. Often the new versions did improve upon the old–but not significantly enough. One reason was that the criteria for success became stricter as expectations increased. What would have been spectacular in 1965 was obsolete in 1980. As historian Ruth Schwartz Cowan has observed, the rising capabilities of a technology usually increase expectations of what the technology should do. Faxing’s desired generic goals of easy operation, low cost, quality copy, and high speed changed remarkably little over time, but expectations always outpaced capabilities as prospective and actual users kept raising the standard of those goals.

Fax inventors and entrepreneurs also competed with established and new alternatives for transmitting information: the telegraph, telephone, letter, telex, express delivery, and finally email and the Internet. These served as benchmarks for users to decide whether to use facsimile. Faxing differed qualitatively from other forms of communication. Like the telephone, fax arrived instantaneously. Like regular mail and overnight delivery, fax delivered images as well as graphics. Like email, faxes arrived by computer. Unlike the telephone and television, fax provided a written record. No other form of communications combined these attributes of immediacy, imagery, and hard copy. The importance of these attributes changed greatly over time, however, affecting the attractiveness of fax systems for different users in different contexts.

For most of fax’s history, mail and telegraphy worked very well at far less cost and effort. Consequently, faxing, like many other technologies, first found success not as a general-purpose machine for many customers but in filling specific niches, primarily newspaper, weather and military uses, even as numerous attempts to find larger markets failed.

The commercial challenge was to create a product that could either compete with existing telegraphy or find a niche market sufficiently sheltered from competition to profit. Underlying that financial hurdle were technological challenges that included every aspect of faxing as well as more generic issues, such as providing power and constant speed for scanning and printing. Early inventors employed clockwork, which could be controlled by weights or pendulums, but achieving uniform motion proved very hard. Only in the 1870s did electric motors become sufficiently reliable and regular. Gearing was another perennial problem for electromechanical systems.

## Technical Challenges

The basics of facsimile remained constant over the decades. The message had to be created, scanned, converted to electrical impulses, transmitted to the receiving machine, and then reconverted and reproduced. In the first decades, that meant an electrically conductive stylus scanned a message written with insulating ink on a metal foil. A telegraph line transmitted the signal to a receiver, which copied the message onto chemically treated paper. This simple explanation hides the myriad challenges that inventors had to recognize, understand, and solve.

Consequently, fax developers depended on craftsmen and mechanics to turn their ideas into reality. What held true in 1847 was equally true 100 years later; as the February 1947 Electronic Engineering noted, “Perhaps the most important factor in a really first class Picture Telegraphy system is the standard of mechanical design and workmanship which goes into the scanning and optical systems.” (p. 46)

Preparing a fax message took more effort and materials, such as metallic paper and special ink, than a telegram. The sender did not simply dash off a note and hand it to the telegraph clerk. To be scanned, the message had to physically contrast with its medium. Only by physically sensing the surface could a stylus scan the message accurately. (Figure 2)

Figure 2: If there were no problems with synchronism and interference, the quality of a Caselli transmission could be quite good. Courtesy Marius Rensen, http://www.hffax.de/history/

Transmitting faced major challenges of synchronization and the quality of wires. Line quality was often outside the developer’s control; synchronization was not but effective solutions were elusive. Both problems often resulted in resending illegible messages, adding to the cost and time of faxing.

Recording was the final bottleneck. A paper soaked in an electrochemical solution was the medium of choice because a current could mark the paper. Although electrochemical paper had problems of preparation and the short (a few days or weeks) life of a moistened material, it continued to dominate as a print medium. It could most easily transform the received signal into an image despite attempts to use pens, pencils, and other means of recording.

A functioning system was only the first step to success. Fax machines also had to prove fast, reliable, comparatively easy to maintain and operate, and financially feasible. The comparison was with other message technologies, and facsimile inventors spent the 19th century improving its capabilities while falling further behind their competition. It is striking how clearly fax developers understood the obstacles they faced, possibly because many experimenters had successful telegraph inventions to their credit and they understood telegraphy’s weaknesses. Inventors and ideas flowed easily between faxing and telegraphy. The prize of augmenting or replacing the latter, worldwide, system of instant communication continued to attract inventors like moths to a flame.

## Birth of a Practical Technology, 1865-1910s

The French telegraph service initiated the world’s first operational fax service in 1865, using Abbé Giovanni Caselli’s Pantelegraph system to link Paris and Lyon until 1867, and then Bernhard Meyer’s Kopiertelegraphen in 1868-69. Meyer's fax system proved superior to Caselli’s as well as the telegraphs of William Cook and Samuel Morse. Unfortunately for Meyer, Morse was yesterday’s telegraphy. Improved equipment that transmitted faster and automatically, like the printing telegraph of David Hughes, proved more attractive than his Pantelegraph.

Photo-electric faxing, the technique used today, began in 1881 when English physicist Shelford Bidwell transmitted images electrically using a selenium cell, the forerunner of the photoelectric cell. Over two decades elapsed, however, before the first selenium system transmitted a picture for a newspaper. The lag was not for lack of effort, but practicality. Selenium was a difficult material to handle, proving sensitive to aging, changes in temperature, and other environmental shifts.

Dr. Arthur Korn at the University of Munich not only created the first practical selenium-based system but proved an excellent promoter, inspiring picture telegraphy networks over telephone wires. Korn began working on facsimile in 1901 and in 1904 transmitted his first long-distance photograph, in 42 minutes, between newspapers in Berlin and Nuremberg. In 1907 German, French, and English newspapers began publishing photographs transmitted in twelve minutes via his phototeleautograph. (Figure 3)

Figure 3: This schematic of Arthur Korn’s 1907 teleautograph depicts the basics of facsimile: scanning, transmitting, and reproducing an image. Instead of physical scanning, a beam of light scanned the image in Korn’s selenium-based system, which used electric motors for smooth movement of the cylinders. Scientific American, 16 February 1907.

## Early Applications, 1910s-1960s

In World War I, the German military experimented with faxing maps and photographs by landlines and faxing artillery targets from airplanes by radio, the first application of wireless fax. More important were war-spurred improvements in electronics that prompted a surge of research. (Figure 4)

Figure 4: Facsimile’s black boxes are opened to show the complexity of the electronic and mechanical components in Richard Ranger’s fax system as he works with Albert J. Koenig in 1924. Courtesy David Sarnoff Library

By 1928 at least nineteen different systems were under development in Europe, the United States, and Japan, with four operating commercially. (Figure 5)

Figure 5: The Siemens-Karolus Picture Telegraphy system operating in the Berlin post office in 1927 literally needed a room of supporting equipment. Courtesy Siemens Corporate Archives, Munich

Three major forms of facsimile appeared: picture telegraphy (also called telephotography and wirephoto), direct telegram replacement, and message facsimile.

Although more technologically demanding, picture telegraphy appeared first because it provided a unique product: rapid transmission of photographs for newspapers willing to pay premium prices. The number of fax machines was actually not that great—approximately 100 in 1933—but their significance extended far beyond their numbers. In 1930, newspaper photographs and the occasional document crossed large expanses of the earth in minutes via telegraph, telephone, and radio circuits, finally matching the speed of the telegraphed word.

Replacing telegrams, the dream of early fax pioneers, became partially feasible with systems pioneered by Eduoard Belin in France and Western Union in the United States. More novel was the concept of message fax, transmitting documents between offices. Although promising a wider audience, this faced such formidable technical challenges and strong competition from telegraphy and mail that its implementation remained on the horizon. The other new business model involved an alliance with newspapers and radio stations to provide facsimile newspapers printed at home. (Figure 6)

Figure 6: Hugo Gernsback’s Radio-Craft predicted in 1935 that consumers would pay to receive an abbreviated newspaper by radio fax, but the market that he, RCA, Finch, and others envisioned never materialized. Courtesy http://www.americanradiohistory.com

RCA, Finch Telecommunications, Hogan Laboratories, and newspapers in many American cities demonstrated the convenience, resolution, and condensed nature of faxed editions of the news before and after World War II. The costs and qualitative disadvantages of this system were joined by the versatility of television in putting it to rest by 1950, as millions of Americans bought boxy video receivers for news and entertainment. World War II saw a massive increase in the deployment of fax machines, primarily by the American military for transmitting weather maps and reconnaissance photographs. (Figure 7)

Figure 7: In Washington, DC, Thomas Whitely reviews a weather map printed in 1946 on one of the fax machines developed and constructed under U.S. Weather Service sponsorship. Courtesy of the family of Thomas D. Whitely, NOAA

More publicly, the military faxed hundreds of photographs for newspapers back in the United States. While military interest had existed earlier, the demands and ready funding of wartime greatly increased the visibility of facsimile. Fax manufacturers had trouble, however, fulfilling contracts, thereby demonstrating the challenges of building the complex equipment. Military interest continued after the war; until the 1960s, the military was the main R&D patron and consumer of fax technology. At the same time, faxing entered many businesses in the 1950s via Western Union’s Desk-Fax, which sent telegrams to central offices. Over 40,000 machines, many formed into networks, sent millions of handwritten and typed messages. Ironically Western Union viewed Desk-Fax as a cost-cutting extension of the telegraph, and not as the forerunner of a new type of communication. (Figure 8)

Figure 8: After introducing its Desk-Fax prototype in 1949 in eight U.S. cities, Western Union manufactured tens of thousands of the machines into the 1960s, a quantity unequaled by telephone-based fax machines until the 1970s. Courtesy William Conlon, Jr., http://william_martin.conlon.org/?page_id=18

## Faxing Goes Mainstream, 1970s-1980s

In the mid-1960s, American and Japanese firms brought facsimile out of its niche markets and began promoting it for general business purposes. Three factors explain the success of fax after so many false starts. New innovators, like Xerox and Graphic Science, changed the dynamics of the fax world, creating new excitement. (Figure 9)

Figure 9: Xerox expanded into facsimile with its LDX (Long Distance Xerography) system in 1964. Weighing nearly 1100 pounds together, the LDX scanner and printer leased for $800 per month and could transmit 8 pages a minute. Courtesy Xerox Historical Archives Second, in both countries, deregulation of the telephone system (very gradually in the United States starting in 1968 and rapidly in Japan in 1972) eased access to the public telephone network by new devices and reduced the price of telephony, thus spurring the fax market. Third, the International Telecommunications Union (ITU) released the G1 (1968) and G2 (1976) standards, which reduced the scan and transmission time to six and three minutes respectively. Because fax machines had to be compatible to communicate with each other, agreement on standards was essential to the diffusion of facsimile. Forging and enforcing such agreements represented some of the most contentious challenges in the technology’s evolution. The first two generations of analog fax machines in the 1960s-70s still suffered from incompatibility among competing machines, despite creation of the ITU standards. Not until the approval of the ITU G3 standard in 1980 did manufacturers offer truly compatible equipment that could, in addition, scan and transmit a page in one minute. The result, which appeared first in Japan, was an explosion in fax sales. That country’s ideographic language provided the demand, and manufacturing expertise in consumer electronics provided the supply. (Figure 10) Figure 10: After the CCITT agreement on the Group 3 facsimile standard in 1980, Sharp introduced its FO2000 fax machine, the “HAYAX” in honor of Sharp founder Tokuji Hayakawa, in 1981. The world’s smallest G3 fax machine, it weighed 70 kg and used 175 w to transmit an A4 sheet in 20 seconds on a 9600 bps modem. The HAYAX retailed in the Japanese office machine market for about 3 million yen. Courtesy Sharp Corporation In the United States, the number of fax machines grew from 25,000 in 1970 to 250,000 in 1980, but then exploded from 500,000 machines installed in 1985 to 5 million in 1990–nearly all made in Japan. This rapid growth of increasingly inexpensive machines turned faxing into the essential technology of an evolving global telecommunications network. Thoughtful design engineers in Japan blended several different technologies into a small, cheaper, faster, and more versatile machine that needed minimal training to operate. Machines now scanned and recorded digitally in less than fifteen seconds, encouraged by the G3 and G4 (1985) standards for digital compression; only transmission remained analog. Powerful data compression algorithms and microprocessors reduced transmission to less than a minute per page. New illumination and sensors accompanied the switch to digital scanning. Instead of photocells receiving the bright light reflected from the image, the light from low-power helium-neon lasers or light-emitting diodes (LEDs) reflected from a small segment of paper onto a long bar of solid-state photodiodes or charge-coupled devices (CCDs). For recording, an array of 1,728 film resistors, one per pixel, selectively warmed heat-sensitive paper. Thermal recording sharply cut the cost of fax machines, making them even more affordable. No less important were the economic and social changes resulting from the liberalization of telephone networks in the United States and Japan, the growing internationalization of business, and the "just-in-time" mentality promoted by Federal Express, whose proprietary ZapMail facsimile service lost over$300 million in 1984-6. Coupled with the mounting costs and decreasing quality of traditional methods of communication, such as postal services, faxing appeared increasingly advantageous.

## Fax’s Social Effects

In the mid-1980s, economics and technology finally caught up with the vision. The ease of experimentation and use, combined with its low cost and near universal adoption, made facsimile a democratic technology, accessible to all. Innovation in use proved even more intriguing and important as innovation in technology. During the student protests in China in 1989, for example, Chinese expatriates evaded the government’s censorship policies by faxing news of and responses to the protests back to readers in their home country.

The rapid acceptance and diffusion of fax equipment into the business community strengthened the globalization of the world economy by vastly easing the transfer of information worldwide. Most importantly, the fax machine circumvented time zones and eased the actual conduct of business. Faxing lunch orders to a deli sounds trivial, yet it embodied the virtues of fast, error-free transmission of information with a record for both parties, which just as useful when ordering agricultural equipment across the Pacific Ocean.

Facsimile strengthened the advantages of the written over the spoken word. Many people read and write English, the international language of commerce, better than they speak it. Faxing allowed written communications instead of telephony. The fax machine also allowed writers of ideograph-based alphabets to exchange information instantly, a major reason for the technology’s success in Japan.

Like any technology, the fax presented problems as well as opportunities. Questions about the legality, authenticity, and security of the transmitted message challenged users. More visibly, faxing’s easy operation quickly turned into a torrent of information, often unwanted or unnecessary, and all paid for by the recipient. In a variation of Gresham's law, bad data crowded out good, as junk faxes presaged the bane of e-mail: spam.

## When Fax and Computers Converged

Even as stand-alone machines metastasized, a new wave of computer-based faxing emerged in the late 1980s and early 1990s that vastly extended the capabilities and value of fax. The merger of fax with computers was not accomplished easily and users found computer-based fax far more difficult and frustrating than stand-alone faxing, emblematic of changes in all technologies undergoing computerization. Consequently, although the first computer fax board appeared in 1986, computer-based faxing did not grow substantially until the early 1990s.

Four trends dominated this period. Prices dropped, products became easier to use and integrated into computers, and capabilities increased greatly in a competitive environment that drove firms to innovate continually. In less than a decade, computer-based faxing evolved from an interesting technical demonstration to an essential corporate tool. One of the most powerful and unexpected extensions of facsimile in the 1990s was fax-on-demand. More accurately described as automated faxed information-on-demand, this service merged faxing with computer databases and interactive voice technology to provide unprecedented and rapid access to information.

In the mid-1990s, the promise of faxing over the Internet (FoIP) attracted small businesses, mainly startups, which introduced new hardware, software, and services. In a demonstration of how international Internet development had become, several Israeli firms played important pioneering roles. By the new millennium, the FoIP market imploded, victim of the new Internet business model of free services, reduced long-distance telephone charges, and the dot-com collapse. The market continued, but in drastically altered form as FoIP providers emphasized services such as storage and enhanced recordkeeping, instead of reduced long-distance charges.

## The Decline of Fax and Rise of Email

Within another five years, faxing had been eclipsed. It became its own worst enemy, laying the groundwork for email and the web. People became accustomed to exchanging messages easily in minutes, compressing the communications cycle from days or weeks. Computer-based faxing trained people to communicate from a computer and expect a quick reply. Fax-on-demand taught people to obtain information instantly and companies to provide it.

Email’s triumph stood on four foundations. Foremost was the 1982 creation of the Simplified Mail Transport Protocol (SMTP), which extended compatibility throughout incompatible networks. Second, the 1992 establishment of the Multimedia Internet Mail Extension (MIME) greatly encouraged email’s acceptance as a business tool. MIME enabled email to convey files of different types, content, and format from computer to computer, negating one of fax’s biggest advantages, binary file transfer. Together with Adobe’s development of the Portable Document Format and its decision to offer the reader free, emails could finally transmit documents effectively. This removed one of faxing’s major advantages.

Third, the changing office environment greatly benefited email. From 1991 to 2004, the number of PCs worldwide grew from 130 million to 775 million. Many of these machines were connected through modems and networks, and the number of email accounts exploded in the late 1990s, reaching an order of magnitude greater than fax machines. Email also benefited from a generation of users trained in Microsoft Word and other software, who now found it easy to operate email systems based on the GUI (graphical user interface) principles of Apple and Windows. Improvements in scanners enabled easier conversion of written documents into electronic form, allowing their manipulation and storage by computer while eliminating the need to send a document by a stand-alone fax machine.

Fourth, the World Wide Web made fax-on-demand obsolete. The search engine proved an overwhelming advantage in the quest for instant information. Fax’s advantages receded as email became increasingly easy to use and more common, thus benefiting from positive network externalities. Sales of stand-alone fax machines peaked in 1997 in the United States and 2000 in Japan. Unlike telex, which declined sharply after the fax boom of the 1980s, faxing declined slowly. For email, the critical point occurred when it became easier to use and less expensive than faxing, an accomplishment that took far longer than its advocates expected. Perhaps the best indicator of this transition was in the 2000s, when criminals switched their trolling for fraud or scam victims from fax to email.

## Timeline

• 1843, First patent received by Alexander Bain in Great Britain (No. 9745)
• 1863, First commercial operating system begun by Abbé Giovanni Caselli in France
• 1904, First transmission by telephone sent by Arthur Korn in Germany
• 1925, First commercial wirephoto system by AT&T
• 1928, First Japanese fax system initiated by NEC’s Yasujiro Niwa and Masatsugu Kobayashi
• 1935, Associated Press begins AP Wirephoto service
• 1964, Xerox introduces Long Distance Xerography (LDX)
• 1966, Xerox introduces Magnafax Telecopier
• 1977, Japanese approve READ standard
• 1980, CCITT approves Group 3 standard
• 1985, First personal computer (PC) fax board introduced by GammaLink
• 1997, Fax machine sales peak in United States
• 2000, Fax machine sales peak in Japan

## Bibliography

### References of Historical Significance

Bain, Alexander. 1843. British patent no. 9745, granted 27 November 1843.

Callahan, John North, and Alfred Goldsmith, eds. 1938. Radio Facsimile: An Assemblage of Papers from Engineers of the RCA Laboratories relating to the Radio Transmission and Recorded Reception of Permanent Images, Volume 1. New York: RCA Institutes Technical Press

Jones, Charles R.. 1949. Facsimile. New York: Rinehart Books

Korn, Arthur, and Bruno Glatzel. 1911. Handbuch der Phototelegraphie und Telautographie. Leipzig: Otto Nemnich Verlag

Ministry of Posts and Telecommunications Fax Survey Research Group (Fakushimiri choosa kenkyuu kai). 1980. Facsimile. Its present state and future (Fakushimiru. Sono genjyoo to tenbaa). Tokyo: Ministry of Posts and Telecommunications

Hiromasa Sasaki, Matahira Kotani, and Takeo Tsumura. 1981. "Sharp Facsimile HAYAX FO1000 (Medium Speed G2 Machine), FO 2000 Series (High Speed G3 Machine)". Sharp Technical Journal 20 (March 1981), p. 125-32

Coopersmith, Jonathan. February 1993. “Facsimile's False Starts,”. IEEE Spectrum, p. 46-9

Coopersmith, Jonathan. July 2010. “Creating Fax Standards: Technology Red in Tooth and Claw?”. Kagakugijutsushi. The Japanese Journal for the History of Science and Technology 11, p. 37-66

McConnell, Kenneth R., Dennis Bodson, and Stephen Urban. 1999. FAX: Facsimile Technology and Systems, 3rd ed.. Boston: Artech House

Remsen, Marius. December 2004. Fax History. www.hffax.de/history/index.html

Wakabayashi, Kaoru. 2009. “Research and Events that Permitted Facsimile Use to Explode in Japan”. GLOBECOM Workshops (IEEE), p.1-6


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• 综 述 •

### 雄性棉铃虫感受性信息素的分子和神经机制研究进展

1. (1. 河南农业大学植物保护学院, 郑州450002; 2. 中国农业科学院植物保护研究所, 植物病虫害生物学国家重点实验室, 北京 100193)
• 出版日期:2020-09-20 发布日期:2020-09-30

### Research progress in the molecular and neural mechanisms of sex pheromone reception in maleHelicoverpa armigera (Lepidoptera: Noctuidae)

LIU Xiao-Lan1,2, YIN Xin-Ming1, WANG Gui-Rong2,*, ZHAO Xin-Cheng1,*

1.  (1. College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China; 2. State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China)
• Online:2020-09-20 Published:2020-09-30

Abstract: The cotton bollworm, Helicoverpa armigera, mainly relies on sex pheromone communication for mate orientation and reproduction. The mechanisms of pheromone reception in H. armigera are the hot topic in the field of chemical ecology in China. In this article, we reviewed the reception mechanism to female sex pheromone in male H. armigera, hoping to provide references for further investigation of the molecular and neural mechanisms of sex pheromone perception in H. armigera and other related insects. In the sex pheromone glands of female adult, long-chain, saturated or unsaturated fatty aldehydes, and alcohols were synthesized, among which Z11-16∶Ald was used as the main sex pheromone component, while Z9-16∶Ald and Z9-14∶Ald as the secondary sex pheromone components. The blends of these components at certain ratios show enhanced attraction to male H. armigera. Z11-16∶OH and a high-dose Z9-14∶Ald inhibit the attractiveness of pheromone blends to male H. armigera. Correspondingly, three types of trichoid sensilla, types A, B, and C, on the antennae of male H. armigera could detect these compounds. The receptor OR13 responding to Z11-16∶Ald is expressed in the type-A trichoid sensillum, OR14b responding to Z9-14∶Ald is expressed in the type-B trichoid sensillum, and OR6 and OR16 responding to Z9-16∶Ald, Z9-14∶Ald, and Z11-16∶OH are expressed in the type-C trichoid sensillum. The expression sites and functions of the receptors are consistent with the electrophysiological characteristics of different types of trichoid sensilla. In addition, the results of calcium imaging showed that three macroglomeruli tune to these odors, among which the glomerulus of cumulus tunes to Z11-16∶Ald, the posterior dorsomedial glomerulus to Z9-16∶Ald, and the anterior dorsomedial glomerulus to Z9-14∶Ald, Z11-16∶Ac and Z11-16∶OH. These results revealed the mechanisms of pheromone reception in male H. armigera at the levels of sensillum, receptor and central nervous system. Based upon these studies, we think it is necessary to make further studies on the following aspects: (1) further identifying the function and location of the related sex pheromone receptors; (2) further studying the processing and integration of sex pheromone information in high brain center; (3) clarifying the influences and mechanisms of such environmental factors as host plant, photoperiod, temperature and humidity on the sex pheromone perception in H. armigera.

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Trouble with the numerical evaluation of a series

The series is $$\;S=\displaystyle{\sum_{n=0}^\infty 2^{-n+\sin(n\pi/5)}}$$.

Mathematica doesn't find a closed form for Sum[2^(-n + Sin[n Pi/5]), {n, 0, Infinity}], so I tried both:

N[Sum[2^(-n + Sin[n Pi/5]), {n, 0, Infinity}], 100]
NSum[2^(-n + Sin[n Pi/5]), {n, 0, Infinity}, WorkingPrecision -> 100]

They return the same result:

2.621953360503001622580428627210775515701951638633391919349668089988053230383633286891962065806603221

However, as I discovered later, this result is wrong. Indeed, the series is not difficult to evaluate, thanks to the periodicity of $$\sin(n\pi/5)$$:

$$S=\left(\sum_{n=0}^\infty2^{-10n}\right)\left(\sum_{n=0}^92^{-n+\sin(n\pi/5)}\right)=\frac{1}{1-2^{-10}}\sum_{n=0}^92^{-n+\sin(n\pi/5)}$$

And N[1/(1 - 2^-10) Sum[2^(-n + Sin[n Pi/5]), {n, 0, 9}], 100] yields:

2.621953365022156800044269458734842788555304465923212022625632939238430813027293562013936284925892294

So the initial sum only had 9 correct digits. It's so bad that I am almost certain I am missing an important option, but I have no idea which (I tried playing with AccuracyGoal and PrecisionGoal, but it led me nowhere so far).

Any idea to get the numerical answer directly?

The same method as above can be used to evaluate $$\displaystyle{\sum_{n=0}^\infty 2^{-n+(-1)^n}}$$, and the sum is $$3$$, however, Mathematica fails with a message that starts with NIntegrate::ncvb: NIntegrate failed to converge to prescribed accuracy after 9 recursive bisections. So again I must be missing somthing important. The failure occurs with:

N[Sum[2^(-n + (-1)^n), {n, 0, Infinity}], 100]

My guess would be that it fails for this one because the correct answer is an integer, and thus it's impossible to give even a single correct digit since the sum could be 2.99999... or 3, but I'm not sure what really happens here, nor how to deal with this.

I'm not entirely new to Mathematica, but I have always found that numerical computations are difficult to handle with it. If someone can point to a good tutorial on this kind of problem or similar ones with NIntegrate, it would be really helpful!

• Not sure what your version is but running the first two lines in Version 12.1 returns exactly the same value for me. – anon248 Dec 28 '20 at 22:07
• @anon248 Oh, sorry, 12.1.1.0. And indeed, as I wrote just under those two lines, they yield the same result. Which is wrong. – user74736 Dec 28 '20 at 22:07
• Got it, my bad! – anon248 Dec 28 '20 at 22:09
• Does this answer your question? Numerical evaluation of a sum – m_goldberg Dec 29 '20 at 14:48

What seems to help at least with NSum is increasing the number of terms that are computed explicitly via the option NSumTerms. This way one can get agreement for all first $$100$$ digits:

NSum[2^(-n + Sin[n Pi/5]), {n, 0, Infinity}, NSumTerms -> 400, WorkingPrecision -> 100]

2.621953365022156800044269458734842788555304465923212022625632939238430813027293562013936284925892294

N[1/(1 - 2^-10) Sum[2^(-n + Sin[n Pi/5]), {n, 0, 9}], 100]

2.621953365022156800044269458734842788555304465923212022625632939238430813027293562013936284925892294

• Ah, yes, indeed I can find the correct result with larger NSumTerms. I didn't know this option. However, it's a bit disappointing if I have to know the correct answer beforehand to compute a numerical value to the desired accuracy. How am I supposed to know the first answer I found is wrong? What is frustrating with NSum and others is that I often get an answer, with no hint that something went wrong. But maybe I am asking too much. – user74736 Dec 28 '20 at 22:23
• I completely agree that there should be a better option. There are some previous questions on NSum, e.g. here and here. Particularly the second one has some more info on tweaking the internal methods, maybe something can be gained by that. – Hausdorff Dec 28 '20 at 22:52
• Damn. The second one is a question I asked 6 years ago, and I had completely forgotten about this. Shame shame shame... This time it's my bad, I should have known about NSumTerms. Thanks for having unearthed this! (incidentally, in the meantime I confess I have not made much progress on numerical evaluation with Mathematica, which is both embarrassing and annoying). – user74736 Dec 28 '20 at 23:01
Clear["Global*"]

To find the number of terms required, find the minimum value of n for which the last term is less than 10^-100

min = MinValue[{n, 2^(-n + Sin[n Pi/5]) < 10^-100}, n, Integers]

(* 334 *)

sum1 = NSum[2^(-n + Sin[n Pi/5]), {n, 0, Infinity}, NSumTerms -> 400,
WorkingPrecision -> 100]

(* 2.6219533650221568000442694587348427885553044659232120226256329392384308130272\
93562013936284925892294 *)

sum2 = NSum[2^(-n + Sin[n Pi/5]), {n, 0, Infinity}, NSumTerms -> min,
WorkingPrecision -> 100] // Quiet

(* 2.6219533650221568000442694587348427885553044659232120226256329392384308130272\
93562013936284925892294 *)

sum1 === sum2

(* True *)

You can look at the Sin[] term in the exponent as some periodic noise. It would be good to smooth that out before trying numeric methods by summing over a period at a time:

sum = NSum[
Sum[2^(-(10 n + k) + Sin[(10 n + k) Pi/5]), {k, 0, 9}],
{n, 0, Infinity}, WorkingPrecision -> 100]
(*
2.62195336502215680004426945873484278855530446592321202262563293923843\
0813027293562013936284925892294
*)

1/(1 - 2^-10) Sum[2^(-n + Sin[n Pi/5]), {n, 0, 9}] == sum

(*  True  *)

If you compare for high m

m = 10^5; N[ParallelSum[2^(-n + Sin[n*(Pi/5)]), {n, 0, m*10 + 9}], 16]

with

N[Sum[2^(-10*n), {n, 0, m}]*Sum[2^(-n + Sin[n*(Pi/5)]), {n, 0, 9}], 16]

you get the same value. But if you then set m=Infinity the values differ, which is understandable, because any numeric sum up to infinity must include some approximation (or it would take forever...). You may notice that the calculation for m=10^5 takes much longer than the one up to Infinity.

Your second sum you can split into odd and even terms like to get

Sum[2^(-n + (-1)^n), {n, 0, Infinity}] =
Sum[2^(-(2 n) + (-1)^(2 n)), {n, 0, Infinity}] +
Sum[2^(-(2 n + 1) + (-1)^(2 n + 1)), {n, 0, Infinity}] = 3
`


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4-port Multiplex

Combines four real input signals into an output signal

Important: The 4-port Multiplexer component has been deprecated. Instead, use the n-port Boolean Multiplexer to combine boolean input signals into an output signal, the the n-port Integer Multiplexer to combine integer input signals into an output signal or the n-port Real Multiplexer to combine real input signals into an output signal. The number of output ports can be set by the dimension of the parameter between 2 and 10.

 Description The 4-port Multiplex component combines the input signals, ${u}_{1}$, ${u}_{2}$, ${u}_{3}$ and ${u}_{4}$, in an output signal, $y$.

Connections

 Name Description ${u}_{1}$ Real input signal ${u}_{2}$ Real input signal ${u}_{3}$ Real input signal ${u}_{4}$ Real input signal ${y}_{}$ Real output signal

Variables

 Symbol Units Description $u$ - Physical signal at the input port $y$ - Physical signal at the output port

Parameters

 Symbol Default Units Description Modelica ID ${n}_{1}$ $1$ - Dimension of input signal connector 1 n1 ${n}_{2}$ $1$ - Dimension of input signal connector 2 n2 ${n}_{3}$ $1$ - Dimension of input signal connector 3 n3 ${n}_{4}$ $1$ - Dimension of input signal connector 4 n4


text:
# Quark confinement and meson confinement

tom.stoer
see my post #21

A. Neumaier
2019 Award
see my post #21

tom.stoer
Can you please show - in terms of post #21 - what goes wrong? It is nothing else but standard Dirac constraint quantization. I already said that the argument may by problematic in non-compact space; but it is strictly valid in compact space, e.g. for the 3-torus.

A. Neumaier
2019 Award
Can you please show - in terms of post #21 - what goes wrong? It is nothing else but standard Dirac constraint quantization. I already said that the argument may by problematic in non-compact space; but it is strictly valid in compact space, e.g. for the 3-torus.
Well, on the 3-torus there are no asymptotic states, so my argument against your conclusion becomes obsolete. So it is the non-compactness that must be the culprit.

Note that rigorous QFT on compact spaces is much easier since both Haag's theorem and the IR problem are absent. Indeed, the infinite-volume limit (which is not needed for compact space-time) is the hardest step in constructive field theory since it requires the most stringent estimates.

Arthur Jaffe and Edward Witten write in their description of the quantum Yang-Mills theory Millennium Problem (http://www.claymath.org/library/MPP.pdf#page=114): [Broken]
''So even having a detailed mathematical construction of Yang–Mills theory on a compact space would represent a major breakthrough. Yet, even if this were accomplished, no present ideas point the direction to establish the existence of a mass gap that is uniform in the volume. Nor do present methods suggest how to obtain the existence of the infinite volume limit.''

Last edited by a moderator:
tom.stoer
Well, on the 3-torus there are no asymptotic states, so my argument against your conclusion becomes obsolete. So it is the non-compactness that must be the culprit.

Note that rigorous QFT on compact spaces is much easier since both Haag's theorem and the IR problem are absent. Indeed, the infinite-volume limit (which is not needed for compact space-time) is the hardest step in constructive field theory since it requires the most stringent estimates.'
So we agree. The argument is fine for compact spaces but there's a loophole for non-compact spaces - unfortunately I don't know how to save the idea - but I think I do not have to be more clever than Witten and Jaffe :-)

A. Neumaier
2019 Award
So we agree. The argument is fine for compact spaces but there's a loophole for non-compact spaces - unfortunately I don't know how to save the idea - but I think I do not have to be more clever than Witten and Jaffe :-)
Yes, but since the argument fully breaks down for QED, I wouldn't call it a loophole but complete lack of argument.

I believe that a single quark in a sea of gluons is a valid sector of QCD, though not one realized in Nature, because the real universe contains many quarks and is colorless.

tom.stoer
Yes, but since the argument fully breaks down for QED, I wouldn't call it a loophole but complete lack of argument.
Certainly not. It is used in all canonical, non-perturbative approaches to QCD! There are numerous groups doing exactly that.

The appraoch is always identical:
- solve Gauss law = eliminate unphysical degrees of freedom
- solve QCD in the color-neutral sector

A. Neumaier
2019 Award
Certainly not. It is used in all canonical, non-perturbative approaches to QCD! There are numerous groups doing exactly that.

The appraoch is always identical:
- solve Gauss law = eliminate unphysical degrees of freedom
- solve QCD in the color-neutral sector
But the second step involves an additional assumption. One could instead solve QCD in a colored sector, and would get meaningful mathematical results at the same level of approximation as for the color-neutral case. But since this is not useful for phenomenology, it is not being done.

tom.stoer
That's not true. As I said G(x) ~ 0 which is (in the Dirac-formalism) translated into G(x)|phys> = 0 requires Q|phys> = 0. So if we restrict to localized states there should be no difference between the spectrum in R³ and T³ and therefore color-neutrality is not assumptions but strictly proven.

The only assumption I can see is that T³ and R³ have (approximately) the same physical content (for localized states / hadron spectroscopy, form factors, ...).

[But afaik there is not one single mathematically exact result b/c already at the classical level one cannot get rid of all gauge = Gribov ambiguities which is required for solving the Gauss law constraint. So there are always artefacts like isolated Gribov copies or ghosts or ... The only way out is lattice QCD where gauge fixing is not required b/c the path integral over the gauge group is finite and gauge fixing can safely be replaced by gauge averaging (it may slow down computations; I don't know]

A. Neumaier
2019 Award
That's not true. As I said G(x) ~ 0 which is (in the Dirac-formalism) translated into G(x)|phys> = 0 requires Q|phys> = 0. So if we restrict to localized states there should be no difference between the spectrum in R³ and T³ and therefore color-neutrality is not assumptions but strictly proven.
The unproved assumption used in your argument is that the states are localized.
But precisely this assumption is violated in charged stated, because of infrared issues, which are closely related to the infinite volume limit, i.e., noncompactness.
This can already be seen in QED, where the IR problem is tractable, and the physical charged states (involving a coherent admixture of photons) are associated to superselection rules coming from asymptotic conditions at infinity. There is no reason to believe that in QCD the situation should be much simpler than in QED.

tom.stoer
So you say one should throw away all QCD results based on T³

A. Neumaier
2019 Award
So you say one should throw away all QCD results based on T³
I never said that. One should view the QCD results based on the torus as results that may need modification in the infinite-volume limit, at least those modifications that are already needed in case of QED.

tom.stoer
There are of course known differences regarding topology, large gauge transformations / winding number, gauge field zero modes etc. It would not be a disaster to add some more topics to that list.

But: as long as we do not know how the topology of the universe looks like, this is academic; I can't believe (and I hope that I am not completely wrong) that the cosmological constant doe not affect the QCD spectrum :-)

A. Neumaier
2019 Award
There are of course known differences regarding topology, large gauge transformations / winding number, gauge field zero modes etc. It would not be a disaster to add some more topics to that list.

But: as long as we do not know how the topology of the universe looks like, this is academic; I can't believe (and I hope that I am not completely wrong) that the cosmological constant doe not affect the QCD spectrum :-)
You have here a double negation. Did you intend that not not x = x? I'd be surprised....

For the purposes here on earth, the universe can be regarded as being topologically
flat, and gravitation can be treated as an external field. Under these conditions, I believe that both QED and the standard model or its variants are consistent.

tom.stoer


text:
# When $1$ wasn't really a number in Greece

I'm reading "Professor Stewart's Incredible Numbers," by Ian Stewart and in there it is claimed that

In early Greece, the list of numbers started $2, 3, 4,$ and so on: $1$ was special, not "really" a number. Later, when this convention started to look really silly, $1$ was deemed to be a number as well.

This is new to me. What evidence is there of this and when did the change occur?

• Much the same question here: hsm.stackexchange.com/questions/5326/… – fdb Sep 19 '17 at 14:52
• Well, 1 is not prime either :-) . It's always been a sort of special number, so it depends on what "number" means (like what the meaning of 'is' is) – Carl Witthoft Sep 20 '17 at 11:45

The opening words of the Platonic dialogue Timaeus are:

Σωκράτης:

εἷς, δύο, τρεῖς: ὁ δὲ δὴ τέταρτος ἡμῖν, ὦ φίλε Τίμαιε, ποῦ τῶν χθὲς μὲν δαιτυμόνων, τὰ νῦν δὲ ἑστιατόρων;

Socrates:

One, two, three, — but where, my dear Timaeus, is the fourth of our guests of yesterday, and our hosts of today?

clearly showing that the word εἷς "one" was used for counting in the same way as all other positive integers.

If at some point later on (some) Greek mathematicians accorded a special status to the number $$1$$, I would be tempted to compare this to a modern discussion of whether $$0$$ is or is not to be included in the natural numbers -- or whether the zero ring is an integral domain or not. It is a technicality, of the sort that only becomes meaningful once one has run into the necessity of "constructing" objects that have already been understood on a more intuitive level.

To be sure, there seems to be a certain attraction to the statement as presented by Ian Stewart: it is intriguing to consider the possibility that the Greeks somehow thought "differently" about numbers than we do. It is a statement that borders on the unprovable. Heidegger is even more outrageous, writing somewhere (in "Modern Science, Metaphysics, and Mathematics", which is reprinted in the "Basic Writings" collection) that the Greeks didn't even consider 2 to be a number: since 1 is the unit, and 2 is only ever a "pair", and not a collection of "two" separate objects. Only when the number three is first encountered, does the concept of number really start to shine forth -- or so the the little magician from Messkirch would have it. It sounds good, but I have yet to be convinced that there is more to it than idle speculation.

• I do not see how a passage with 1 and 2 separated by a comma "clearly shows" anything at all, let alone what Greek mathematicians (rather than the general populace, or Plato) considered 1 to be. Or how a direct consequence of Euclid's definition from the Elements (explicitly ascribed to Pythagoreans by Aristotle) "is a statement that borders on the unprovable". – Conifold Nov 27 '18 at 6:05
• @Conifold You disagree with my construal of the passage "one, two, three, but where is the fourth?" as a 'clear example of counting'? I mean, you are fully entitled to your scepticism, but there is such a thing as 'taking it too far'... – RP_ Nov 27 '18 at 9:48
• By the way I do not mean the statement by Stewart is itself unprovable. What I am saying is that I can see that it could exert a certain type of fascination, since it seems to convey the idea that the Greeks had a different conception of what a 'number' really is. It is this latter idea that I called unprovable. (One's concept of number is not unlike Wittgenstein's beetle in the box.) It is germane to the ideas of Jacob Klein, for example, who busied himself with exactly this type of metaphysical arguments. – RP_ Nov 27 '18 at 9:51
• Badiou wrote books using what he considers to be set theory, and I wouldn't take that as reflecting modern mathematical practice either. But nevermind that. Greek populace at large happily used letter based arithmetic, and yet there is not a trace of it in the mathematics of Euclidean tradition, derived from Pythagoreans. "Tempted to compare this to a modern discussion of whether 0..."? Don't be. – Conifold Nov 27 '18 at 9:58
• Well, I won't if you could offer any good arguments against doing so. Right now you just seem to rely on your dismissive tone for doing the job, if you will pardon me saying so. What I'm claiming is that the whole fact that Greek mathematicians rejected 1 as a number is an artifact of their attempts at formalization, just like arguing over whether the zero ring is an integral domain is an artifact of our way of doing number theory (i.e. partly via modern algebra). Since the Greeks saw a number as a multitude of monads, the monad itself couldn't be a number, if they wanted to avoid circularity. – RP_ Nov 27 '18 at 10:03

Euclid's Elements Book VII:

Definition 1: A unit is that by virtue of which each of the things that exist is called one.

Definition 2: A number is a multitude composed of units.

See also: Aristotle on unit (monas) and number (arithmos) and Metaphysics, Book N, 1088:

"One" evidently means a measure. And in every case it is some underlying thing with a distinct nature of its own [...] And this is reasonable; for the one means the measure of some plurality, and number means a measured plurality and a plurality of measures. Thus it is natural that one is not a number; for the measure is not measures, but both the measure and the one are starting-points.

These speculations affect the "theory of numbers" of Pythagorean origin and not the everyday counting practice; see Plato, Republic, Book 7, 525a, with the distinction between the "science of arithmetic" (ἀριθμητική) and the "art of calculation" (λογιστική).

• I don't think this addresses the claims made by the OP. A "multitude" could be composed of a single unit. – Carl Witthoft Sep 20 '17 at 11:41
• @Carl Witthoft. No. The old Greek had healthy opinions. – Wilhelm Sep 20 '17 at 14:47
• @K.B. Absolutely, if you consider the acceptance of slavery a healthy opinion. But I agree that Aristotle's text quite explicitly contradicts Carl Witthoft's point: "the measure is not measures" really means that a single individual can never be regarded as a "group". (This somehow reminds me of the insistence of Euclid that the whole be always greater than the part -- distinctions such as these were more rigidly enforced in Greek mathematical thought.) – RP_ Sep 21 '17 at 13:49
• @René: In their time the acceptance of slavery was a healthy opinion. You musr not judge everything from the modern standpoint. – Wilhelm Oct 1 '17 at 19:54


text:
#41
who the fuck ever heard of five dollars for a button anyways. aren't they supposed to be handing these things out like rain on a sunday
#42
who the fuck ever heard of five dollars for a button anyways. aren't they supposed to be handing these things out like rain on a sunday
#43
#44

germanjoey posted:
who the fuck is gonna spend $450 bucks on a fucking obama pin collection http://store.barackobama.com/buttons.html?source=site_tout3 i guess you're too poor to understand what lapel means Edited by ChatBot () #45 whoa. i could be a Grassroots Donator. #46 seeing that gear reminded me of the 2003 conservative leadership convention here. i was a delegate for a dude. the convention floor was just loaded with people all chanting for their candidates and cheering and wearing colour-coded clothing and such and i just looked around and was like "this is tribal." but it was also beautiful in a way. i have the political bug so those sorts of situations, narrow contests where anything can happen, are cool to me. terrifying but i miss it a lot. #47 germanjoey posted: http://store.barackobama.com/accessories/obama-dog-collar.html i will wear this for$1000

#48

babyfinland posted:

germanjoey posted:
http://store.barackobama.com/accessories/obama-dog-collar.html

i will wear this for \$1000

Barrack's Best Friend

#49
to be fair most of that shit is for campaign staff and they give it to them for free or whatever and the main campaign staff probably secretly thinks lowly of people who buy them. this is not strange though because the main campaign staff thinks lowly of everyone. that is why a political event that has millions of participants has only like five people who can speak for the campaign and everyone else just chants hope.
#50
[account deactivated]
#51
[account deactivated]
#52
i don't even think there is any statistical reason to vote. the only people who really matter in election campaigns are like people with money or people who can convince thousands of people to do what they want. so like unless you are a union bureaucrat or banker or something you are basically irrelevant to american presidential politics. but i think it is probably good to vote or something if you want to because it sort of affirms your position in society in a weird way. like it says "this is the sort of society i want" and says you are willing to compromise with people about that too. so let's vote for barack obama, who is a good man and a fine father.
#53

discipline posted:
I would rather stab myself in the stomach and throw myself in traffic than vote for barack obama. I am literally offended that anyone irl thinks I should/would vote for him. do they think so little of me??

we're not asking you to joystick a predator drone on to pakistani children or something here, we're looking for a vote in a presidential race. and a phonebank. and a button collection purchase. and a credit card max-out. and a beef jerky purchase.

#54

discipline posted:
I can't believe you said the N word you racist. racist.

i was quoting the old d&d thread which means it wasn't really me saying it.

#55
[account deactivated]
#56

getfiscal posted:
i don't even think there is any statistical reason to vote. the only people who really matter in election campaigns are like people with money or people who can convince thousands of people to do what they want. so like unless you are a union bureaucrat or banker or something you are basically irrelevant to american presidential politics. but i think it is probably good to vote or something if you want to because it sort of affirms your position in society in a weird way. like it says "this is the sort of society i want" and says you are willing to compromise with people about that too. so let's vote for barack obama, who is a good man and a fine father.

what if youre one of those thousands

#57

discipline posted:
you know that beef jerky is really pretty good

yeah i often think to myself, "is there some way i can fill my mouth with salt, but also get repulsive meat involved?"

#58

babyfinland posted:
what if youre one of those thousands

well the chances that you are substantially going to affect the outcome are essentially zero. obviously in some weird kantian way obviously if almost everyone took the advice not to vote (which i'm not giving) then we would end up with a bad result. but as a matter of personal action it isn't like your decision to smoke up instead of voting for ron paul or whatever is going to change things.

#59
polling is fun. if you ask a registered voter "would you vote for the republican nominee or obama" then the winner is pretty clearly republican. but if you say rick perry versus obama then the same people break obama 50 - 45. romney gets like 49 to obama's 47 but that means nothing so far out. i'm not sure which way it would go in the general. like there's a billion dollars in advertising between us and the vote, so who knows how it will shape up. personally i wouldn't even care much if romney wins. the worst he could do is let republicans in congress pass some dumb shit but he's so politiciany that he'll probably shut them up for message control.
#60
romney has embraced the revolutionary tricolor

#61

getfiscal posted:

babyfinland posted:

what if youre one of those thousands

well the chances that you are substantially going to affect the outcome are essentially zero. obviously in some weird kantian way obviously if almost everyone took the advice not to vote (which i'm not giving) then we would end up with a bad result. but as a matter of personal action it isn't like your decision to smoke up instead of voting for ron paul or whatever is going to change things.

#62
that was an excellent youtube reference, top points. i'm "feeling it"
#63

discipline posted:
you know that beef jerky is really pretty good

it really is, its so fucking delicious...

#64
zizek said that his contacts in chicago who know obama say he is a total atheist. he just knows that is political suicide to admit publicly. so im sorry but i cant vote for a godless heathen.
#65

aerdil posted:
zizek said that his contacts in chicago who know obama say he is a total atheist. he just knows that is political suicide to admit publicly. so im sorry but i cant vote for a godless heathen.

did he add some shit about how god is himself an atheist and how we can see in this paradox that the subject is prevented from true atheism. in fact, remember the case of wheaties: a carb-heavy cereal that does little to promote health, but we associate it with health because of the athletes on the box. is this not like the capitalist economy writ large? because we look at the rich and see beautiful celebrities and assume the basic foundation is sound, when in fact it is rotten and so on and so on

#66

germanjoey posted:
it really is, its so fucking delicious...

in america does "delicious" mean "more salt than the dead sea combined with meats that couldn't be fed to pigs with a good conscience"

#67

getfiscal posted:

aerdil posted:
zizek said that his contacts in chicago who know obama say he is a total atheist. he just knows that is political suicide to admit publicly. so im sorry but i cant vote for a godless heathen.

did he add some shit about how god is himself an atheist and how we can see in this paradox that the subject is prevented from true atheism. in fact, remember the case of wheaties: a carb-heavy cereal that does little to promote health, but we associate it with health because of the athletes on the box. is this not like the capitalist economy writ large? because we look at the rich and see beautiful celebrities and assume the basic foundation is sound, when in fact it is rotten and so on and so on

zizek slobbers and is gross and neurotic so we associate him with authentic anti-capitalist theory. is this not like my jorts shart large

#68
zizek is a genius and would always have become famous for his synthesis of lacan and marx. but i was thinking yesterday again about how true it is that a lot of interest in him is just because he re-asserts the primacy of class. it's the same for david harvey and fredric jameson. like they are smart people and they can package the narrative about it but they are so popular mostly because of whining about postmodernism not being class-centered enough. but none of them offers a pretty good argument for this, they just sort of re-assert it. like i was temporarily convinced by zizek's line about how class underpins other oppressions but that's just re-hashing base/superstructure. in retrospect i just wanted to be reconvinced of marxism when it is obviously dead.
#69
[account deactivated]
#70
[account deactivated]
#71
yeah but you took a look at philosophy and decided to endorse islam so really people in glass houses
#72
[account deactivated]
#73
actually god is dead and marx is alive, sorry for both of you.
#74

discipline posted:
aahhaa what's your point, that perhaps I should have read more philosophy before deciding it was mostly a hack skip (that's british english for dumpster) for aristocracy?

well you know i love ya but if your encounter with philosophy ended with endorsing the idea of books written by micromanagerial spirit beings then i think you did it wrong

#75

aerdil posted:
actually god is dead and marx is alive, sorry for both of you.

this woman is the head of the IMF and i think she looks like she'd have a lot of advice for james bond.

#76
[account deactivated]
#77
yes if theres one thing theology isn't, it's definitely not weird semantic garbage about texts written two thousand years ago
#78
[account deactivated]
#79
[account deactivated]
#80
[account deactivated]


text:
Welcome to tobilehman.com!
%

# web posts

## PDFs and the Permanent Web

I remember reading this article Deurbanising the web from January 2021. It argued that the web had gotten so bad that they wanted to do something drastic, so they converted the web pages on their site to PDF. The badness they were complaining about was familiar, too many ads, too much surveillance. Link rot, infinite scrolls, paywalls, GDPR cookie consent buttons, etc. The reason they chose PDFs? Reasons why Lab6 argued PDFs were a good format for web pages it’s a file standard format still has media and links easy to copy and backup (avoids link rot and lost pages) freedom At first I was skeptical.


text:
# Proof involving the Pigeonhole principle

Prove that among any given $n + 1$ positive integers, there are always two whose difference is divisible by $n$

Using Pigeonhole principle:

From a set of at least $2$ different $n+1$ positive integers the difference between $n+1$ integers will always have a case where it is divisible by $n$. Because if there is $n+1$ integers which can be pigeons in this case then there must be at least $n$ holes where $n+1$ integers can divide by $n$. Although this does not mean all $n+1$ integers can be divisible by $n$ but there are cases where they can be.

Examples:

• $(16 - 13) / 2$ is not divisible by $n$ for $n+1$ integers, where $n = 2$.
• $(15 - 13) / 2 = 1$ is divisible by $n$, where $n = 2$.
• $(13-12) + (16-14) / 4$ is not divisible by $n$, where $n = 4$.

Try using as the holes the set of integers mod $n$. Then for each of the $n+1$ given integers $m_k$ create a "pigeon" by mapping $m_k \mapsto (m_k \mod n)$.
Any two $m_k$ with the same values mod $n$ will have a difference divisible by $n$.
Now if no difference is divisible by $n$ you have fit $n+1$ pigeons into $n$ holes, which is a contradiction.


text:
http://iet.metastore.ingenta.com
1887

Condition-based maintenance and asset management

• Author(s):
• DOI:

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Condition Monitoring of Rotating Electrical Machines — Recommend this title to your library

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This book is concerned with the process of early detection but greater benefits could be achieved from condition monitoring if the information from monitoring is used to schedule maintenance, allowing planned shut-downs so that the life of plant, of which the electrical machine forms a part, can be extended. This is the process of condition-based maintenance, first described in Chapter 1. However, further benefits could be realised from condition monitoring if the total life-cycle costs of the machine and the plant it serves could be reduced by its application. This in turn requires an estimate of the running costs of plant and forecasts of its variation throughout its life. In the light of this knowledge the plant or asset owner can operate, maintain, renew or dispose of that asset on the basis of the information made available through these processes. This is asset management. This chapter describes how these techniques could be applied to rotating electrical machines.

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Condition-based maintenance and asset management, Page 1 of 2

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text:
Publication
Title
Search for supersymmetry in events with photons and low missing transverse energy in pp collisions at $\sqrt{s}=7TeV$
Author
Institution/Organisation
CMS Collaboration
Abstract
 Many models of new physics, including versions of supersymmetry (SUSY), predict production of events with low missing transverse energy, electroweak gauge bosons, and many energetic final-state particles. The stealth SUSY model yields this signature while conserving R-parity by means of a new hidden sector in which SUSY is approximately conserved. The results of a general search for new physics, with no requirement on missing transverse energy, in events with two photons and four or more hadronic jets are reported. The study is based on a sample of proton-proton collisions at root s = 7 TeV corresponding to 4.96 fb(-1) of integrated luminosity collected with the CMS detector in 2011. Based on good agreement between the data and the standard model expectation, the data are used to determine model-independent cross-section limits and a limit on the squark mass in the framework of stealth SUSY. With this first study of its kind, squark masses less than 1430 GeV are excluded at the 95% confidence level. (c) 2012 CERN. Published by Elsevier B.V. All rights reserved.
Language
English
Source (journal)
Physics letters: B. - Amsterdam, 1967, currens
Publication
Amsterdam : 2013
ISSN
0370-2693
Volume/pages
719:1-3(2013), p. 42-61
ISI
000315065600007
Full text (Publisher's DOI)
Full text (open access)
UAntwerpen
 Faculty/Department Research group Publication type Subject Affiliation Publications with a UAntwerp address
External links
 Web of Science
Record
 Identification Creation 30.04.2013 Last edited 14.07.2017 To cite this reference


text:
# Mathematica cannot generate the random variables for a given Probability Distribution

I need to generate a large number of random variables from the distribution generated by the following code. Distribution is given by DistributionF. The code is getting stuck at the the execution of the command RandomVariate[DistributionF,1000]. It does not output the R.V.s. How can I resolve this issue.

A = 1/2;
k = 1; τ = 1;
m = 1; β = .6931; σ = 1.8421;

W = {0.0000, 0.0013, 0.0339, 0.2401, 0.6109, 0.6109, 0.2401, 0.0339,
0.0013, 0.0000};

T = {3.4362, 2.5327, 1.7567, 1.0366,
0.3429, -0.3429, -1.0366, -1.7567, -2.5327, -3.4362};

G[t_] := Exp[-Exp[-Sqrt[2]*σ*t - β]*m*
x^2]*(Exp[Sqrt[2]*σ*t + β])^(-m);

f[x_] = (1 - A)*
FullSimplify[
2*(1 + k)*x/τ*Exp[-k - (1 + k)*x^2/τ]*
BesselJ[0, 2*Sqrt[k*(1 + k)/τ]*x]] +
A*(x^(2*m - 1)*2*m^m)/(Sqrt[π]*Gamma[m])*W.(G /@ T);

DistributionF = TransformedDistribution[x^2,
x \[Distributed] ProbabilityDistribution[f[x], {x, 0, Infinity}]];

RandomVariate[DistributionF,1000]

• If f[x] is a PDF then NIntegrate[f[x], {x, 0, ∞}] should return 1 since you have defined {0, ∞} as the domain of f. However, it returns 0.567652. – Edmund Feb 8 '17 at 4:14
• @Edmund - The Method option can handle this. ProbabilityDistribution[f[x], {x, 0, Infinity}, Method -> "Normalize"] – Bob Hanlon Feb 8 '17 at 4:18
• @BobHanlon Nice! I did not notice that before. Still taking forever to evaluate for just 1 sample. – Edmund Feb 8 '17 at 4:22
• Works for me, 10.x on Windows... – ciao Feb 8 '17 at 4:41
• @ciao, I have been using 11.01 on Mac.. – George Harnandez Feb 8 '17 at 4:49


text:
1

### JEE Main 2019 (Online) 9th January Morning Slot

The highest value of the calculated spin- only magnetic moment (in BM) among all the transition metal complexes is :
A
5.92
B
6.93
C
3.87
D
4.90

## Explanation

In transition metal contains d orbital, and in d orbital maximum no of unpaired electron possible = 5.

Spin only magnetic moment,

${\mu _{spin}} = \sqrt {n\left( {n + 2} \right)}$    B. M

here n $=$ Number of unpaired electrons.

$\therefore$    ${\mu _{spin}} = \sqrt {5\left( {5 + 2} \right)}$0    B. M

$=$ 5.92   B. M
2

### JEE Main 2019 (Online) 9th January Morning Slot

For emission line of atomic hydrogen from ni = 8 to nf = n, the plot of wave number $\left( {\overline v } \right)$ against $\left( {{1 \over {{n^2}}}} \right)$ will be (The Rydberg constant, RH is in wave number unit)
A
Linear with intercept $-$RH
B
Non linear
C
Linear with slope RH
D
Linear with slope $-$RH

## Explanation

We know,

$\overline v = {1 \over \lambda } = {R_H}{Z^2}\left[ {{1 \over {n_f^2}} - {1 \over {n_i^2}}} \right]$

here ni $=$ 8 and nf $=$ n

Z $=$ 1 for hydrogen

$\therefore$   $\overline v = {1 \over \lambda } = {R_H}\left[ {{1 \over {{n^2}}} - {1 \over {{8^2}}}} \right]$

So, graph is $\to$

So, graph will be linear with slope RH.
3

### JEE Main 2019 (Online) 9th January Evening Slot

Which of the following combination of statements is true regarding the interpretation of the atomic orbitals ?

(a) An electron in an orbital of high angular momentum stays away from the nucleus than an electron in the orbital of lower angular momentum.

(b) For a given value of the principal quantum number, the size of the orbit is inversely proportional to the azimuthal quantum number.

(c) According to wave mechanics, the ground state angular momentum is equal to ${h \over {2\pi }}$.

(d) The plot of $\psi$ vs r for various azimuthal quantum numbers, shows peak shifting towards higher r value.
A
(a), (b)
B
(a), (d)
C
(b), (c)
D
(a), (c)
4

### JEE Main 2019 (Online) 10th January Evening Slot

The ground state energy of hydrogen atom is – 13.6 eV. The energy of second excited state of He+ ion in eV is :
A
$-$ 6.04
B
$-$ 54.4
C
$-$ 27.2
D
$-$ 3.4

## Explanation

(E)nth = (EGND)H . ${{{Z^2}} \over {{n^2}}}$

E3rd (He+) = ($-$13.6eV) . ${{{2^2}} \over {{3^2}}}$ = $-$ 6.04 eV


text:
Efficient Program Synthesis Using Constraint Satisfaction in Inductive Logic Programming

John Ahlgren, Shiu Yin Yuen; 14(Dec):3649−3681, 2013.

Abstract

We present NrSample, a framework for program synthesis in inductive logic programming. NrSample uses propositional logic constraints to exclude undesirable candidates from the search. This is achieved by representing constraints as propositional formulae and solving the associated constraint satisfaction problem. We present a variety of such constraints: pruning, input-output, functional (arithmetic), and variable splitting. NrSample is also capable of detecting search space exhaustion, leading to further speedups in clause induction and optimality. We benchmark NrSample against enumeration search (Aleph's default) and Progol's $A^{*}$ search in the context of program synthesis. The results show that, on large program synthesis problems, NrSample induces between 1 and 1358 times faster than enumeration (236 times faster on average), always with similar or better accuracy. Compared to Progol $A^{*}$, NrSample is 18 times faster on average with similar or better accuracy except for two problems: one in which Progol $A^{*}$ substantially sacrificed accuracy to induce faster, and one in which Progol $A^{*}$ was a clear winner. Functional constraints provide a speedup of up to 53 times (21 times on average) with similar or better accuracy. We also benchmark using a few concept learning (non-program synthesis) problems. The results indicate that without strong constraints, the overhead of solving constraints is not compensated for.

[abs][pdf][bib]


text:
INTELLIGENT WORK FORUMS
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#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Why petroleum engineering?

## Why petroleum engineering?

(OP)
Hello everyone,

I was wondering if it does worth pursuing a PhD in petroleum engineering considering the low oil prices as well as the fact that oil and gas in general are fossil fuels and world will run out of them eventually. I very much appreciate you.

### RE: Why petroleum engineering?

With a PhD in Petroleum Engineering you once upon a time had a very viable career path at the research centers of the Majors (Amoco's facility in Tulsa is still talked about today even though it has been closed for nearly 20 years, there were several others, all closed today). The industry bought into the foolishness that proper research could only be done at universities. Today I would say a PhD in Petroleum Engineering would never get out of Academia (although I do know a half dozen PhD's, most with MBA as well who are in reservoir groups at various companies, none in drilling or production). The biggest problem with planning on a career at a University is the schools are all chasing a buck and with $120/bbl oil several new programs opened up and all of the established programs expanded. When the price dropped to$45/bbl last year some of those programs started closing, and others started making tenure harder and harder to get. I get the feeling that Pet Eng professors is even more of a boom/bust than the rest of the industry.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

### RE: Why petroleum engineering?

With all due respect, you will be dead long before the earth runs out of oil and gas......way long before.

Agree with Zdas04. A good friend just retired from ExxonM and thought he would enjoy teaching a drilling class at the local university. They offered him a whopping \$10K annual salary. Ouch!! He took it just so we all would have to call him "Professor" now.

### RE: Why petroleum engineering?

Fossil fuels WILL run out. No one has a clue when, but my guess is the year 3400 (I make that "prediction" firm in the knowledge that I'll be long dead and way forgotten when that date is shown to be wrong). But it does not matter because actual hydrocarbon requirements (whatever they are, it will evolve) will be satisfied from harvesting contemporary biogenic methane so some version of Petroleum Engineering will always be around--the field has evolved since its creation and will never stop evolving.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

### RE: Why petroleum engineering?

Atomic fusion will supply all power.
Petroleum derivatives will be highly valued lubricants.

Maybe we can list those under this one,
There is no future in AC. <Thomas A. Edison>

### RE: Why petroleum engineering?

(OP)
Great Replied I received. Thank you very much for providing much information. I also appreciate other people if they have more comments.

### RE: Why petroleum engineering?

I do think that they should first learn not to work on shale oil developent and other things that tend to put them out of business.

### RE: Why petroleum engineering?

Well the stone age didnt end because the world ran out of stone, and even though E&P is my own bread an butter i hope the oil age will end way before we run out of oil. As a chem eng i believ there will always be a need for gas (and oil) as a feed stock for chemical processing but as an energy source i sincerely hope we have the alternatives within 20-30 years.

### RE: Why petroleum engineering?

MortenA,
I agree, but I don't think that the "solution" will be evolutionary from today's technology. I'm expecting someone to stumble upon a relationship between things that creates an energy revolution that we can't even imagine today. When they do, engineers in the energy business will design the parts and pieces that will make it usable. I absolutely don't feel threatened by some future non-fossil energy source. I also don't fee threatened by wind and solar because they are both to diverse and too intermittent to ever be anything but an expensive sideshow.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

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text:
The particles which of the following gases has the highest/lowest average speed? Which gas particles have the highest/lowest average kinetic energy? a.) argon at 20°C. b.)nitrogen at 20°C b.) nitrogen at 100°C. c.) helium at 100°C

Mar 11, 2018

Highest speed: Helium at 100°C.
Lowest speed: Argon at 20°C.

Highest kinetic energy: Nitrogen and helium at 100°C.
Lowest kinetic energy: Nitrogen and argon at 20°C.

Explanation:

Temperature is a measure of average kinetic energy.

Therefore, at the same temperature, gases have the same average kinetic energy.
But different gas particles move at different speeds with this kinetic energy—gases with smaller particles tend to be moving faster at the same temperature, which means they have a higher speed.

At variable temperatures, gases with both smaller particles and higher temperatures will have a higher speed.

Here are our choices:

1. Argon at 20°C.
2. Nitrogen at 20°C.
3. Nitrogen at 100°C.
4. Helium at 100°C.

Helium has both the smallest particles and is at the high temperature of 100°C , so it will be the gas with the highest speed.
Argon has the biggest particles and is at the low temperature of 20°C, so it will be the gas with the highest speed.

Particles at the same temperature have the same average kinetic energy, so argon and nitrogen, which are at 20°C, are the gases with the lowest average kinetic energy.
Nitrogen and helium, at 100°C, have the highest average kinetic energy because they have the highest temperature.


text:
# Article

Full entry | PDF   (0.2 MB)
Keywords:
Fréchet space; regular method of summability; summable sequence; Galvin-Prikry theorem; Erdös-Magidor theorem
Summary:
Suppose that $X$ is a Fréchet space, $\langle a_{ij}\rangle$ is a regular method of summability and $(x_{i})$ is a bounded sequence in $X$. We prove that there exists a subsequence $(y_{i})$ of $(x_{i})$ such that: either (a) all the subsequences of $(y_{i})$ are summable to a common limit with respect to $\langle a_{ij}\rangle$; or (b) no subsequence of $(y_{i})$ is summable with respect to $\langle a_{ij}\rangle$. This result generalizes the Erdös-Magidor theorem which refers to summability of bounded sequences in Banach spaces. We also show that two analogous results for some $\omega_{1}$-locally convex spaces are consistent to ZFC.
References:
[1] Balcar B., Pelant J., Simon P.: The space of ultrafilters on $\mathbb N$ covered by nowhere dense sets. Fund. Math. 110 (1980), 11--24. MR 0600576
[2] Dunford N., Schwartz J.T.: Linear Operators I: General Theory. Pure and Applied Mathematics, vol. 7, Interscience, New York, 1958. MR 0117523 | Zbl 0084.10402
[3] Ellentuck E.: A new proof that analytic sets are Ramsey. J. Symbolic Logic 39 (1974), 163--165. DOI 10.2307/2272356 | MR 0349393 | Zbl 0292.02054
[4] Erdös P., Magidor M.: A note on regular methods of summability and the Banach-Saks property. Proc. Amer. Math. Soc. 59 (1976), 232--234. MR 0430596
[5] Galvin F., Prikry K.: Borel sets and Ramsey's theorem. J. Symbolic Logic 38 (1973), 193--198. DOI 10.2307/2272055 | MR 0337630 | Zbl 0276.04003
[6] Kechris A.: Classical Descriptive Set Theory. Springer, New York, 1995. MR 1321597 | Zbl 0819.04002
[7] Plewik S.: On completely Ramsey sets. Fund. Math. 127 (1986), 127--132. MR 0882622 | Zbl 0632.04005
[8] Rudin W.: Functional Analysis. McGraw-Hill, New York, 1973. MR 0365062 | Zbl 0867.46001
[9] Tsarpalias A.: A note on the Ramsey property. Proc. Amer. Math. Soc. 127 (1999), 583--587. DOI 10.1090/S0002-9939-99-04518-9 | MR 1458267 | Zbl 0953.03058

Partner of


text:
## Ugly Number II

07/17/2016 Dynamic Programming Heap Math

## Question

Write a program to find the n-th ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers.

Note that 1 is typically treated as an ugly number.

Hint:

1. The naive approach is to call isUgly for every number until you reach the $n^{th}$ one. Most numbers are not ugly. Try to focus your effort on generating only the ugly ones.
2. An ugly number must be multiplied by either 2, 3, or 5 from a smaller ugly number.
3. The key is how to maintain the order of the ugly numbers. Try a similar approach of merging from three sorted lists: L1, L2, and L3.
4. Assume you have Uk, the $k^{th}$ ugly number. Then Uk+1 must be Min(L1 * 2, L2 * 3, L3 * 5).

## Solution

Result: Accepted Time: 4 ms

Here should be some explanations.

int data[2000]={0};

int nthUglyNumber(int n)
{

if(!data[0])
{
int p2, p3, p5, v2, v3, v5, cnt, tmp;
cnt = data[0] = 1;
p2 = p3 = p5 = 0;
while(cnt < 2000)
{
tmp = v2 = data[p2] * 2;
v3 = data[p3] * 3;
v5 = data[p5] * 5;
if( tmp > v3 ) tmp = v3;
if( tmp > v5 ) tmp = v5;
p2 += v2 == tmp;
p3 += v3 == tmp;
p5 += v5 == tmp;
data[cnt++] = tmp;
}
}
return data[n - 1];
}

Complexity Analytics

• Time Complexity: $O(1)$
• Space Complexity: $O(1)$


text:
nLab Simon Donaldson

Simon Donaldson is professor for pure mathematics at Imperial College London.

Selected writings

category: people

Last revised on November 19, 2019 at 02:28:02. See the history of this page for a list of all contributions to it.


text:
# Subject GRE exam 0568 Q.54

The question with its answer is given in the following 2 pictures:

But I have a problem in understanding this paragraph:

Could anyone clarify this for me please?

There are three types of circles in the question.

In Figure $1$, we see $1$ big circle and $4$ medium circles.

In Figure $2$, we see $1$ big circle, $4$ medium circles and $16$ small circles.

Note that the ratio of the intermediate circles to the big circle is equal to the ratio of small circle to the medium circle since they are scaling of each other.

The ratio of area of shaded circles of Figure $2$ to the ratio of area of circles of Figure $1$ is equal to the ratio of area of $4$ small circle to the area of a medium circle, which is also equal to the ratio of the area of $4$ medium circle to the big circle.

• In the fifth line, they are scaling to each other because they are similar?
– user426277
Jul 10, 2017 at 11:03
• yup, they are similar. Jul 10, 2017 at 14:48


text:
## McGregor’s Theory X and Y

### Douglas McGregor (1967)

McGregor worked entirely on different hypothesis and sought an answer to motivation in the nature of man. Theory X and Y reflect McGregor’s efforts in understanding human motivation vis-a-vis the nature of the person. Theory X’ and Theory Y’ are quite different, almost poles apart and have different sets of assumptions. Theory X identifies the four assumptions held by the managers as:

• Employees inherently dislike work. Therefore if possible, they try to avoid it.
• As they dislike work, they must be coerced or threatened with punishment. Such control, will force them to achieve desired goals.
• Employees generally shirk responsibilities. They prefer to seek formal directions.
• Most employees want security as against other factors related to work. They do not have much ambition.

According to McGregor this is a traditional theory of what workers are like and what management should do to manage work. The assumptions contained in theory X do not reveal the true nature of human being in practices. So he gave another set of assumptions called theory Y. Theory Y identifies four other assumptions held by the managers as:

• Employees view work as being as natural as rest or play.
• Employees will exercise self direction and self control when they are committed to the goals.
• The average person can learn to accept and can even seek responsibility.
• The capacity to exercise a high degree of imagination, ingenuity, and creativity in the solution of organizational problems is widely, not narrowly distributed in the worker population.

### Implications of the Two-Factor Theory

In support to the assumptions embodied in theory Y, McGregor has cited a few practices wherein the subordinates are given freedom to direct their activities to assume responsibility and importantly to satisfy their egoistic needs. These practices include decentralization and delegation, job enlargement participation and consultative management and management by objectives.

### Advantages / Merits / Pro’s

1. These theories are important tools in understanding the behaviour of human being and in designing incentives to motivate employees.
2. Theory X is applicable to unskilled and uneducated operative workers whereas theory Y is more applicable to skilled and educated employees who are mature enough and understand their responsibility.

### Disadvantages / Limitations / Demerits / Con’s

1. There is no proof that either of these assumptions is valid.
2. No man would belong exclusively either to theory X or theory Y. He shares the traits of both in varying degrees under different situations.


text:
# Revision history [back]

An alternative way of doing this without having to look at the graph is to use

    from rosgraph.masterapi import Master
master = Master("/bag_helper")
all_topics = sorted([topic_tuple[0] for topic_tuple in master.getTopicTypes()])
published_topics = [topic_tuple[0] for topic_tuple in master.getPublishedTopics("/")]
subscribed_topics = list(set(all_topics) - set(published_topics))

An alternative way of doing this without having to look at the graph is to use

    from rosgraph.masterapi import Master
master = Master("/bag_helper")
all_topics = sorted([topic_tuple[0] [topic_tuple[0] for topic_tuple in master.getTopicTypes()])
master.getTopicTypes()]
published_topics = [topic_tuple[0] for topic_tuple in master.getPublishedTopics("/")]
subscribed_topics = list(set(all_topics) - set(published_topics))

An alternative way of doing this without having to look at the graph is to use

    from rosgraph.masterapi import Master
master = Master("/bag_helper")
Master("/my_node")
all_topics = [topic_tuple[0] for topic_tuple in master.getTopicTypes()]
published_topics = [topic_tuple[0] for topic_tuple in master.getPublishedTopics("/")]
subscribed_topics = list(set(all_topics) - set(published_topics))

An alternative way of doing this without having to look at the graph is to use

    #!/usr/bin/env python
from rosgraph.masterapi import Master
master = Master("/my_node")
all_topics = [topic_tuple[0] for topic_tuple in master.getTopicTypes()]
published_topics = [topic_tuple[0] for topic_tuple in master.getPublishedTopics("/")]
subscribed_topics = list(set(all_topics) - set(published_topics))

An alternative way of doing this without having to look at the graph is to use

    #!/usr/bin/env python
from rosgraph.masterapi import Master
master = Master("/my_node")
all_topics = [topic_tuple[0] for topic_tuple in master.getTopicTypes()]
published_topics = [topic_tuple[0] for topic_tuple in master.getPublishedTopics("/")]
subscribed_topics = list(set(all_topics) - set(published_topics))