text:
# AppleScript browser tab weirdness

I was playing around with an AppleScript tonight and ran into an odd bug when trying to write a script that worked whether my default browser was Safari or Chrome. It happens when I use a variable to hold the browser’s application ID—com.google.chrome, for example—and try to access any information about its tabs.

For example, this

set browser to "com.google.chrome"

tell application id browser
get active tab index of front window
end tell

won’t compile. It throws a syntax error at the word tab and says

Expected end of line but found property.

I get a similar thing when I try this

set browser to "com.apple.Safari"

tell application id browser
get URL of tab 1 of front window
end tell

In this case, the syntax error is at the 1, and the error message is

Expected end of line but found number.

Since both this

tell application id "com.google.chrome"
get active tab index of front window
end tell

and this

tell application id "com.apple.Safari"
get URL of tab 1 of front window
end tell

compile and run just fine, you might think the problem lies with using a variable to hold the application ID instead of using a string literal. But you’d be wrong, because this

set browser to "com.google.chrome"

tell application id browser
get bounds of front window
end tell

and this

set browser to "com.apple.Safari"

tell application id browser
get visible of front window
end tell

both work even though I’m using a variable. Window properties like visible, name, id, and zoomable work regardless of whether I use a variable or a literal, but tab properties only work with a literal.

In the script I’m noodling with, the browser variable isn’t set by a simple assignment as in these examples, it’s set according to the user’s default browser. I can certainly get around the bug by doing something like this

if browser is "com.google.chrome"
tell application "Google Chrome"
<whatever>
end tell
else
if browser is "com.apple.Safari"
tell application "Safari"
<whatever>
end tell
end if
end if

but I was hoping to write something that was a little less clumsy and redundant. The Chrome and Safari AppleScript libraries are enough alike that you can often use the same code for either, and I was hoping to take advantage of that by doing something clever and sleek, like

tell application id browser
set theURL to URL of tab n of front window
end tell

Sadly, this simplicity isn’t to be.

## 8 Responses to “AppleScript browser tab weirdness”

1. Tobias says:

I think the problem is that AppleScript needs to look up terms like tab at compile time, and without a literal tell block it doesn’t know where to look. Also you can’t assume that just because Safari and Chrome use the same term, their dictionaries map it to the same event ID.

A workaround might be writing a file full of handlers and saving it once with Safari and after search and replace with Chrome as the target. Then load the appropriate copy from your main script.

Or just use pyappscript :)

py-appscript

2. Yeah, you can’t use app-specific terms, just ones in Standard Suite.

set a to "Finder"
tell app a to windows -- works
tell app a to insertion location -- doesn't work
tell app a to activate -- works

Application references in variables behave the same way:

set a to app "Finder"
tell a to windows -- works
tell a to insertion location -- doesn't work
tell a to activate -- works

Another appscript-ism that works only partially:

app "Finder"'s windows -- works
app "Finder"'s insertion location -- doesn't work
app "Finder"'s activate -- doesn't work

3. The active tab index property appears in the Standard Suite section of Chrome’s dictionary, but it’s clearly specific to Chrome, so Lri’s explanation makes sense. Tobias’s compile time/run time distinction seems plausible, too. Maybe the limited knowledge the script has at compile time is the reason app-specific properties can’t be accessed when the application is provided in a variable.

4. Clark says:

I’m surprised you even bother programming in Applescript. Of course Appscript has its own big flaws.

A lot of us wish Apple would come up with something different. However Apple’s stretched so thin right now and even iOS5 won’t make iOS mature. Probably not until iOS6. With the focus on the consumer space I think pro-users will be left in the cold a little longer.

5. Honestly, Clark, I don’t find Appscript syntax like

frontIndex = app('Google Chrome').windows[1].active_tab_index.get()

especially intuitive. My rule of thumb for choosing between AppleScript and Python/Appscript is this: If all I’m doing is getting info from or giving a command to an application, I stick with AppleScript; if I need to do any string or list manipulation, I shift to Python/Appscript.

6. Clark says:

Really? Huh. That seems way more intuitive (and far less ambiguous) than Applescript. Maybe I’ve just done object oriented programming of that style for too long.

7. Well, there’s the fact that windows and tabs arrays are 1-based instead of the more Pythonic 0-based. Worse, perhaps, is that 0 is a synonym for 1, so you can happily be using windows[0] and then later run into a bug when windows[1] refers to the same window instead of the one behind it.

And don’t get me started on get(), which always strikes me as superfluous.

8. Clark says:

You can ignore the get typically. So windows[1].name() is the same as windows[1].name.get()


text:
# Ubuntu – ignore files by pattern in deja-dup (Backup)

backupdeja-dupduplicity

My Déjà Dup backups have become quiet large and I noticed they contain a huge number of unnecessary files (e.g. *.pyc files, **__pycache__ folders and other build related temporary stuff).

I know that I can ignore specific folders, but is there a way to exclude files and or folders by patterns?

I thought there might be more options usable trough a configuration file, but Déjà Dup doesn't use one. So I looked at duplicity (the CLI it is based on), but the man page doesn't mention a configuration file either. I know that duplicity can ignore files and folders based on patterns (--exclude, --exclude-filelist), but I have no idea how to combine this with Déjà Dup.

Do I have to ditch Déjà Dup and use duplicity manually? Or is there a way to set the needed options, so that they are used automatically, when duplicity is used by Déjà Dup?

• You can edit the exclude list like:

gsettings get org.gnome.DejaDup exclude-list
# remove comment to execute
# gsettings set org.gnome.DejaDup exclude-list ['path1', 'path2']

I tried to add patterns like '**/.git' and '**/build' into that list, like this:

gsettings get org.gnome.DejaDup exclude-list > exclude-list
gedit exclude-list
gsettings set org.gnome.DejaDup exclude-list "cat exclude-list"

But to me it seems like the **'s were not passed to duplicity. So instead I ended up doing seaches like

locate "/home/*/.svn"
locate "/home/*/build"

and added them to the exclude-list manually

format: plain


text: In general, what are the strategies for showing the completeness of a solution set for Diophantine Equations? For example, take the $\textit{Pell-type}$ equation $x^2 - dy^2 = a$. Say, you have a set ...


text:
for Journals by Title or ISSN for Articles by Keywords help
 Subjects -> ENGINEERING (Total: 2291 journals)     - CHEMICAL ENGINEERING (192 journals)    - CIVIL ENGINEERING (187 journals)    - ELECTRICAL ENGINEERING (105 journals)    - ENGINEERING (1209 journals)    - ENGINEERING MECHANICS AND MATERIALS (385 journals)    - HYDRAULIC ENGINEERING (55 journals)    - INDUSTRIAL ENGINEERING (68 journals)    - MECHANICAL ENGINEERING (90 journals) ENGINEERING (1209 journals)                  1 2 3 4 5 6 7 | Last
 Arabian Journal for Science and Engineering   [SJR: 0.345]   [H-I: 20]   [5 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1319-8025    Published by Springer-Verlag  [2352 journals]
• Development and Analysis of a Multi-evaporator Cooling System with
Electronic Expansion Valves
• Authors: Şafak Ataş; Mustafa Aktaş; İlhan Ceylan; Hikmet Doğan
Pages: 4513 - 4521
Abstract: Abstract In this study, a vapor compression cooling system with three evaporators and electronic expansion valves was designed, manufactured and tested experimentally. Compressor of this system was converted to be inverter driven which enabled it to run at variable speeds. Temperature values of cold rooms were controlled more sensitive by using electronic expansion valves. Energy analysis was done by comparing the operating parameters of the system with constant and variable speeds. Programmable logic control (PLC) and cold room controls were used to control the system. The PLC device provided the variable operation of the system by determining the required operation frequency of the compressor according to the changes at the suction line. Using this program, the desired values are set on the PLC screen and the multi-evaporator cooling system was tested at various conditions. The desired conditions are determined for the system at 0, $$+5$$ and $$-5\,^{\circ }\hbox {C}$$ temperatures. Calculations on the experimental results revealed that the cooling coefficient of performance is 1.86 for the constant frequency operation and 2.22 for the variable frequency operation. Besides, it was determined experimentally that the system running on variable frequency consumed 20% less electrical energy than the constant frequency system.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2523-1
Issue No: Vol. 42, No. 11 (2017)

• Frequency Domain Long-Term Efficiency of Viscous Damper in Jacket
• Authors: Mohammad Reza Tabeshpour; Hossein Janbazi Rokni
Pages: 4523 - 4534
Abstract: Abstract Various types of controlling mechanisms have been investigated to decrease vibrations of different structures, and in many cases, the reliability has been increased with respect to conventional methods of structural optimization. Among them, using passive viscous damper is one of the useful methods to control structure response due to environmental loads. Hence, in this study, the effect of viscous damper on vibration control of jacket platform (case study oil platform SPD2 and Resalat) exposed to wave loads is investigated, and with the sea state, long-term performance of damper to reduce the structural response is introduced for the first time the more suitable than the responses in an especial case. To keep up this purpose, the platform is modeled by finite element method, and wave spectra are radiated to it. Spectral analysis is adopted to investigate the structural response of the jacket platform equipped with viscous dampers, and also, conventional arrangements of dampers are analyzed to acquire optimal one. Then, the economically optimal arrangement of damper is determined. The novelty of this paper is that the results based on the sea states recorded in the long term help one find the optimal arrangement of damper.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2534-y
Issue No: Vol. 42, No. 11 (2017)

• The Effect of Lanthanum Addition on the Microstructure and Mechanical
Properties of A390 Aluminium Alloy
• Authors: Salem A. Bagaber; Tijjani Abdullahi; Zawati Harun; Nateq Daib; Mohd Hafiz D. Othman
Pages: 4559 - 4564
Abstract: Abstract Aluminium alloys are widely used in the industries and for biomedical applications, because when compared with other materials they provide a high strength-to-weight ratio, better wear resistance, less density, and low coefficient of thermal expansion. However, these alloys possess some limitations in terms of the interactive effects of additives. Therefore, the target of this research is to study the influence of Lanthanum addition of 0.5, 1.0, and 1.5 wt% on the microstructure and mechanical properties of hypereutectic Al–Si alloy. Optical microscopic test, FESEM spectroscopy, XRD, and mechanical properties testing, such as tensile, impact, and hardness test were carried out for characterization purposes. The result indicates the formation of intermetallic compounds, while the value of the secondary dendrite arm spacing became smaller with increasing La addition. The optimum modification of A390 alloy eutectic structure was at 1.0 wt% of La, which improved the ductility from 0.7 to 1.8% and a recorded increase in tensile strength from 100 to 150 MPa.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2553-8
Issue No: Vol. 42, No. 11 (2017)

• Effect of External Perimeter on Flexural Strength of FDM Build Parts
• Authors: Swayam Bikash Mishra; Rameez Malik; S. S. Mahapatra
Pages: 4587 - 4595
Abstract: Abstract Current manufacturing trend adopts newer technology that can reduce both the design and manufacturing lead time in order to face the challenging demands of the customer in an effective manner. In this regard, rapid prototyping technology, among all newly developed technologies, is reliable one because it is capable of manufacturing accurate and durable parts with 3D complex geometry within a stipulated time with less material waste. In this research work, effect of six relevant controllable input parameters (contour number or external perimeter, layer thickness, raster width, part orientation, air gap and raster angle) on flexural strength of the fused deposition modelling (FDM) build parts is analysed. Experimentation has been carried out using face-centred central composite design to reduce the number of experimentation. Contour number appears to be more influencing parameter because it helps to move the stress concentration zone from outer edge to the centre avoiding premature failure of the specimen. The study develops a statistically valid empirical model relating flexural strength with process parameters to ease prediction of flexural strength by tool engineers. Scanning electron microscope micrographs are used to explain the microstructure behaviour of FDM build parts when subjected to three point bend test. Finally, one nature-inspired metaheuristic approach known as Firefly algorithm is adopted to obtain optimal parameter setting for improving the flexural strength.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2598-8
Issue No: Vol. 42, No. 11 (2017)

• Microstructure and Wear Properties of Laser-Cladded cBN/Ti $$_{3}$$ 3 Al
on Pure Titanium
• Authors: K. K. Sobiyi; E. T. Akinlabi
Pages: 4597 - 4604
Abstract: Abstract In order to improve the tribological properties of titanium alloys at high temperature, the possibility of producing Ti $$_{3}$$ Al intermetallic with the addition of ceramic (cBN) coatings on titanium substrate using laser technique cladding was investigated. cBN is generally known for its high hot hardness, wear resistance and chemical stability. Laser cladding is an emerging material processing technique which is an efficient and cost-effective technique for improving the surface properties of general metallic materials. This paper presents the effects of laser cladding on the phase combination, microstructure, hardness and wear resistance of titanium aluminide/cBN IMC composites at different variations in quantity of cBN in the composite. Optical microscopy, X-ray diffraction and scanning electron microscopy with EDX were used for characterising the microstructure of the coating. In addition, the composite coating was subjected to wear testing using the ball-on-disc, friction and wear apparatus. The XRD results revealed phases with small cBN, $$\hbox {Ti}_{2}\hbox {N}$$ and $$\hbox {TiB}_{2}$$ peaks in addition to the rich $$\gamma$$ -Ti, $$\alpha 2\hbox {-Ti}_{3}\hbox {Al}$$ and TiAl intermetallics phases in the coatings after cladding process, whereas the microstructure of the cBN cladded layer contained partially melted cBN grains evenly dispersed within the laths of alpha Widmanstätten phase in the form of dendrites, precipitate of $$\alpha _{2}\hbox {-Ti}_{3}\hbox {Al}$$ and spherical-shaped pure titanium. The effect of the addition of cBN into $$\hbox {Ti}_{3}\hbox {Al}$$ alloy at increasing weight percentages showed an improvement in the hardness and wear resistance of the coatings. The increase is attributed to reacted boron nitrides particles with titanium, being distributed uniformly in the intermetallic matrix.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2585-0
Issue No: Vol. 42, No. 11 (2017)

• Experimental and Numerical Investigation of the Performance of a
Centrifugal Pump When Pumping Water and Light Crude Oil
• Authors: M Hamid Siddique; Sayed Ahmed Imran Bellary; Abdus Samad; Jin-Hyuk Kim; Young-Seok Choi
Pages: 4605 - 4615
Abstract: Abstract In the oil and gas industry, crude oil is frequently transported and centrifugal pumps are used extensively. The pump impeller works under both design and off-design conditions in the applications, and the flow pattern deviates from the ideal case because of viscosity and density changes. An experimental as well as a numerical study was conducted to study the performance of a pump delivering water and light crude oil under design and off-design conditions. A 3D steady incompressible flow in the centrifugal pump was simulated by solving the Reynolds-averaged Navier–Stokes equations and SST turbulence model. At a low flow rate, extensive reverse flow occurs at the inlet of the impeller in the case of water, whereas the opposite was found for light crude oil. Recirculation was observed in the impeller flow passage for both water and the crude oil, but this diminished at higher flow rates.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2592-1
Issue No: Vol. 42, No. 11 (2017)

• An Experimental Work on Tool Wear Affected by Die Clearance and Punch
Hardness
• Authors: Ferhat Akyürek; Kemal Yaman; Zafer Tekiner
Pages: 4683 - 4692
Abstract: Abstract Die clearance is a widely known parameter affecting both tool life and edge quality of parts in blanking operations. Selecting the optimum punch–die clearance can give a longer tool life and better product quality by minimizing tool wear. In experimental studies, the effects of cutting die clearance and punch hardness on the punch edge and face wear were investigated. AISI D2 cold work steel with 50, 55 and 60 HRC-hardness punches was used as tool material. Three different cutting die clearances 3, 5 and 8% of sheet thickness were used. A modular punch–die set was prepared, and 2000, 4000, 6000 and 8000 samples are pressed. The results of the experiments showed that the punch edge and face wear decreased with increasing punch hardness and that smooth-sheared parts are strongly dependent on the clearance.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2621-0
Issue No: Vol. 42, No. 11 (2017)

• Control, Modeling and Evaluation of a Magnetic Piston Miniature Pump
• Authors: A. T. Al-Halhouli; N. A. Rawashdeh; M. Sanna; S. Büttgenbach; A. Dietzel
Pages: 4693 - 4700
Abstract: Abstract This paper presents the control design and performance evaluation of a novel meso-scale electromechanical fluid pump. Such pumps have the potential for applications in biomedical, chemical and pharmaceutical engineering fields. The pumping concept is based on reciprocating a hard magnet working as a double-acting piston in a circular channel, and synchronizing this movement with two electromagnetically actuated valves located at the pump inlet and outlet ports. The actuation system is programmed to allow sequential energization of a set of coils that control the magnet positions. Each pump port has an inlet and outlet channel. According to the piston movement direction, i.e. clockwise or counter clockwise, the valve magnets will change their positions to allow for inflow or outflow. The pump concept was tested using three control configurations, where piston stroke length, stroke frequency, and energization schemes were varied. Calculations showed that the second configuration has the highest volumetric efficiency of about 90% and the maximum flow rate of 8 mL/min at 78 piston strokes per minute (spm). The maximum pressure was achieved using the third configuration with about 575 Pa at 70 spm.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2575-2
Issue No: Vol. 42, No. 11 (2017)

• Deposition-Path Generation of SS308 Components Manufactured by TIG
Welding-Based Shaped Metal Deposition Process
• Authors: Adnan A. Ugla; Oguzhan Yilmaz
Pages: 4701 - 4711
Abstract: Abstract Wire plus arc-based shaped metal deposition is a metal rapid manufacturing technique whereby 3D complex parts are produced by building up metallic parts in layer by layer. In the present work, a type of shaped metal deposition using tungsten inert gas welding plus SS308LSi Wire technique was developed and integrated it with a new computer-aided metal deposition machine (CAMDM). The intent of this paper is to investigate the CAMDM system capabilities about the part modeling and slicing, deposition-path planning, and the part depositing processes. Additionally, this paper highlights the capabilities and limitations of the developed system. The results show that the current manufacturing system is capable to produce various features for metal components with accepted surface quality and free internal defects. The most suitable deposition-path strategy for depositing the solid and hollow components is the combined pattern method, which comprises of the spiral/contour path pattern for the outside/inside boundaries of the part and either spiral or zigzag/raster path pattern for the interior spaces. The controlling system of the present setup allows tuning the deposition parameters during deposition process which usually contributes with selecting of the proper path pattern to manufacture a free defects deposited parts.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2582-3
Issue No: Vol. 42, No. 11 (2017)

• Using an Imaginary Planar Rack Cutter to Create a Spherical Gear Pair with
Continue Involute Teeth
• Authors: Hsueh-Cheng Yang
Pages: 4725 - 4735
Abstract: Abstract This paper presents an imaginary planar rack cutter having two parameters of motion to create a spherical gear pair with two degrees of freedom. The working region of the imaginary planar rack cutter is that of symmetrical straight lines. The relationship between the coordinate system of the imaginary planar rack cutter and that of the spherical gear pair having two parameters of motion is illustrated. The two-parameter family of imaginary planar rack cutter surfaces is obtained by using the homogeneous coordinate transformation matrix to transfer the coordinate system of the planar rack cutter to that of the spherical pinion or the spherical gear. Based on the two-parameter enveloping theory, the mathematical models of the spherical gear pair with two degrees of freedom were proposed. The developed mathematical model of the gear pair with two degrees of freedom can be used to analyze undercutting analysis of the imaginary planar rack cutter. Based on the undercutting equation, a minimum number of teeth of the spherical pinion are determined. A line of singular points on the spherical pinion’s teeth are displayed. Results show that a minimum number of teeth of the spherical pinion can be determined in order to avoid undercutting.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2630-z
Issue No: Vol. 42, No. 11 (2017)

• Influence of Substrate Temperature on Adhesion Strength of TiN Coating of
Biomedical Ti–13Zr–13Nb Alloy
• Authors: A. Shah; S. Izman; Mohammed Rafiq Abdul-Kadir; H. Mas-Ayu
Pages: 4737 - 4742
Abstract: Abstract Adhesion strength between the coating and the substrate is considered as a significant factor, which may help determine both the successful implantation and the long-term stability of any coated implant. A weakly adhered coating on a medical implant may delaminate after the process of implantation, which in turn may severely limit the effectiveness along with the life of the implant itself. Related previous studies have shown that process parameters may have a direct influence on the quality of TiN coating. In the present work, the effect of substrate temperature on adhesion strength of TiN coating on Ti–13Zr–13Nb biomedical grade alloy was investigated. The coating parameter, which varied in this study, was the substrate temperature (i.e., 100, 200 and $$300\,^{\circ }\hbox {C}$$ ). The adhesion strength of TiN coating was examined by means of scratch testing method. In addition, calibrated optical images were also used to verify the total coating failures on the scratched coated samples. Results indicated that an increase observed in the substrate temperature may have resulted in a decrease in the microdroplet form on TiN coating. In contrast, the adhesion strength of TiN coating was observed to equally increase when substrate temperature increased. It is believed that the higher mobility of atom at a higher substrate temperature (i.e., $$300\,^{\circ }\hbox {C}$$ ) filling up the defect appears on the surface to provide a mechanical interlock and thus providing better adhesion strength.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2647-3
Issue No: Vol. 42, No. 11 (2017)

• Study on the Fluid–Structure Interaction at Different Layout of Stacked
Chip in Molded Packaging
• Authors: M. H. H. Ishak; M. Z. Abdullah; M. S. Abdul Aziz; A. A. Saad; M. K. Abdullah; W. K. Loh; R. C. Ooi; C. K. Ooi
Pages: 4743 - 4757
Abstract: Abstract This study investigates fluid–structure interaction (FSI) analysis of stacked chip in the encapsulation of molded underfill packaging using ANSYS Coupling Work bench with fluid and structural solvers. During encapsulation, FSI analysis is applied to a molded package with different layouts, namely cases 1–4 of stacked chip. An even ratio of inlet and outlet gate pressures is used to produce a regular melt front advancement. An experimental setup is fabricated to validate the simulation results in the FSI study. A digital camera is used to capture the melt front advancement and structural deformation. The interaction between structures (silicon chip) and epoxy molding compound (EMC) is displayed in the displacement profile. Maximum deformation is evaluated during the final stage of filling. The silicon die experiences von Mises stresses, which are monitored to observe the risk of die cracking. The results of this study showed that, the EMC flow front advancement was the fastest in case 4. The pressure distribution of each case was nearly identical, and the maximum von Mises stress was distributed unevenly at the middle of the stacked chip. The proposed analysis can serve as a reference and guide in designing and improving 3D integration packages in industry.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2659-z
Issue No: Vol. 42, No. 11 (2017)

• The Recrystallization Behavior in Ultrafine-Grained Structure Steel
Fabricated by Cold Rolling and Annealing
• Authors: Qing Yuan; Guang Xu; Jun-yu Tian; Wei-cheng Liang
Pages: 4771 - 4777
Abstract: Abstract A simple process of 50% cold-rolled and annealed at different temperatures and times to obtain ultrafine-grained structured low-carbon steel with superior mechanical properties is utilized in this investigation. The microstructure evolves from bulky austenite to lathy martensite and then ultrafine ferrite grain with nanocarbide particles. Recovery occurs in the specimen annealed at about $$500\,{^{\circ }}$$ C and 30 min, while recrystallization happens in the specimen annealed at $$550\,{^{\circ }}$$ C and 30 min. The optimal balance between the tensile strength (867 MPa) and elongation (16.7%) is obtained in the specimen annealed at $$550\,{^{\circ }}$$ C and 30 min, in which the mean size of ferrite grains and nanocarbides is 330 and 55 nm, respectively. Moreover, the distribution of ferrite grain conforms to the Gaussian distribution. The recrystallization activation energy of low-carbon steel with ultrafine grain is calculated to be $$320,682\,\hbox {J}\, \hbox {mol}^{-1}$$ based on the Arrhenius equation.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2633-9
Issue No: Vol. 42, No. 11 (2017)

• Dynamic Modeling and Feedback Linearization Control of Wheeled Mobile
Cable-Driven Parallel Robot Considering Cable Sag
• Authors: M. H. Korayem; M. Yousefzadeh; S. Susany
Pages: 4779 - 4788
Abstract: Abstract Cable robots are one of the subcategories of parallel robots used particularly for the applications where the large workspace is required. This type of robots can cover larger workspace compared with serial robots or parallel robots with rigid links. The main issues of cable robots are the cable flexibility due to the need to long cable length as well as inappropriate cable tension distribution in the proximity of the workspace boundaries. By combining a cable robot with a wheeled mobile robot, an unlimited area of workspace can be reached with shorter cable length. Moreover, as the end-effector does not need to come close to its boundary in the mobile platform frame to reach any desired point in the workspace, the tensions are distributed appropriately. The cable sagging in the cable robots is another issue that increases the system error and deviation of the end-effector from the desired trajectory. Therefore, this paper presents the dynamic modeling and control of a cable-suspended parallel robot with a wheeled mobile platform considering the weight of the cable. To this end, the dynamic equations of the wheeled mobile cable robot are obtained using Gibbs–Appel method. Then, the equations related to the weight and sagging of the cable are added to the equations of motion. Control of the system using feedback linearization method is presented. Furthermore, investigating the effect of cable sag on the tension and the end-effector pose of the closed-loop system is demonstrated. Finally, verification is carried out by comparing the simulation and experimental results.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2658-0
Issue No: Vol. 42, No. 11 (2017)

• Load Assessment on the Horizontal Braces of Semi-submersible Drilling
Platform Under Ocean Wave
• Authors: Wang Fei; Liang Zheng
Pages: 4789 - 4799
Abstract: Abstract In order to make sure the horizontal braces of semi-submersible drilling platform are safe during its service life, this research studies the load assessment on the horizontal braces of a platform under harsh wave loads. The hydrodynamic structure model of the platform has been established, and hydrodynamic conditions have been determined firstly. The model test in a wave tank is used to verify the accuracy of the established model in this research. Then, the loads response of the horizontal braces under several typical wave loads which affect the strength of floating structures greatly are evaluated. The results of the research indicate that (a) the splitting force between pontoons and vertical bending moment are found affecting the strength of the horizontal braces greater than the other loads; (b) both the splitting force and vertical bending moment would occur when the platform encounter beam wave; (c) the horizontal braces are loaded on 4.16% of splitting force between pontoons and 2.78% of the vertical bending moment respectively during its service life.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2676-y
Issue No: Vol. 42, No. 11 (2017)

• Effect of PCA on Nanosized Ulexite Material Prepared by Mechanical Milling
• Authors: Sezai Kutuk; Tuba Kutuk-Sert
Pages: 4801 - 4809
Abstract: Abstract Raw ulexite (U-3 mm) mineral used as a initial material was milled by using mechanical milling method, the milling time of which is from 0 to 8 h. Particle size, morphology, elemental and crystal structure measurements of the U-3 mm material and milled powder (U_3%, process control agent amount: 3%) were performed. In particle size analysis, minimum $$d_{50},d_{10}$$ and $$d_{\mathrm{min}}$$ values of U_3% powder have been found to be 5.921  $$\upmu \hbox {m}$$ , 641 nm and 240 nm, respectively. Therefore, it has been reached to submicron level in particle size for the U_3% powder. Besides, optimum milling time has been detected to be 0.5 h. In morphology analysis, the U_3% powder has been observed to be more homogeneous compared to the U-3 mm material. In the analysis of element, the U_3% powder has been determined not to be a pure compound ( $$\hbox {Na}_{2}\hbox {O}{\cdot }2\hbox {CaO}{\cdot } 5\hbox {B}_{2}\hbox {O}_{3}{\cdot } 16\hbox {H}_{2}\hbox {O}$$ ). In crystal structure analysis, crystalline size of the U_3% powder has reduced to 10.3 nm at the end of 8 h. Moreover, crystal structure deformation caused by milling process of the U-3 mm material has improved thanks to PCA. The findings obtained from this work will be beneficial for nanoworks and industrial applications, e.g., civil engineering-pavement engineering materials, of ulexite (boron mineral) material.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2643-7
Issue No: Vol. 42, No. 11 (2017)

• Fuzzy TOPSIS-Based Selection of Laser Beam Micro-marking Process
Parameters
Pages: 4825 - 4831
Abstract: Abstract The process parameter selection in any machining process is one of the most challenging criteria for effective machining. Selection of an optimal parametric combination always results in efficient machining. In the current work, a fuzzy TOPSIS method for selection of optimal laser beam micro-marking process parameters, such as current, pulse frequency, and scanning speed, during laser beam marking on gallium nitride is adopted. Response surface methodology (central composite design) is adopted for the experimental design. The mark width, mark depth, and mark intensity are considered as the process responses. The mark width and mark depth are measured with the help of a precision optical microscope. Microscopic images are then treated using image processing software to calculate the mark intensity. A multi-criteria decision-making model is developed considering the effect of process parameters on process response for selection of optimal process parameter in the laser beam micro-marking process. The triangular fuzzy number is used to calculate the weight of each performance criteria, and the fuzzy TOPSIS hybrid approach is used for selection of optimal parametric combination. The results indicate that a small pulse frequency and high current and scanning speed lead to increase in mark intensity.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2673-1
Issue No: Vol. 42, No. 11 (2017)

• Computational Assessment of the Heat Transfer Coefficient Under Forced
Convection of Multiple Metal Foam Fins Heat Sinks
• Authors: Khaled S. Al-Athel
Pages: 4853 - 4861
Abstract: Abstract The use of metal foams in thermal applications such as heat sinks, heat exchangers, and other heat recovery systems has been increased in the last 2 decades. That being said, the studies were mostly experimental in nature. Due to the complexity of metal foams, most of the results were useful from a qualitative point of view rather than quantitative. With the improvement in computational means, micro-CT scan has been used to develop realistic 3D metal foam models. These models in the literature mostly focus on extracting mechanical and thermal properties, or study the behavior of the metal foam material. In this work, a micro-CT scan metal foam heat sink model is used to study the effect of having multiple metal foam fins on the heat transfer coefficient (h). The calibration of the heat transfer coefficients show that the assumption used in the literature of a fixed h value is not valid. The variation of the h value of each metal foam fin is used to study its effect on the performance of a two and three metal foam fins heat sinks by investigating the thermal resistance and the effectiveness of the heat sink. It was found that even though there is an increase in the thermal resistance, increasing the number of fins will improve the effectiveness in a nonlinear fashion. It is suggested that even with the improvement in the effectiveness, a variation in the height of the metal foam fins will improve the efficiency.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2656-2
Issue No: Vol. 42, No. 11 (2017)

• Effect of Composition and Thickness on the Hardness and Scratch Resistance
of Copper and Copper Alloy Coatings
• Authors: Khaled S. Al-Athel; Mohamed Ibrahim; Abul Fazal M. Arif; Syed Sohail Akhtar
Pages: 4895 - 4904
Abstract: Abstract Coatings are extensively used as corrosion resistance, wear resistance, and antibacterial surfaces. Copper and copper alloys are among the most widely applied coating materials for industrial and medical applications. In this work, mechanical assessment of Cu, Cu 4%Sn, Cu 17%Ni 10%Zn (German Silver), and Cu 17%Al 1%Fe coatings deposited on stainless steel 316L substrates using twin wire arc thermal spraying is studied experimentally. Microstructure, hardness, and scratch resistance were studied for all coated samples. The effects of having different coating compositions on the mechanical properties are analyzed. The effect of the coatings thickness is also investigated for Cu 17%Ni 10%Zn and Cu 17%Al 1%Fe coatings with different thicknesses between 200 and $$400\,\upmu \hbox {m}$$ . The study focused on how the scratch resistance increases with increasing the coating thickness on the expense of the adhesion. A comparison of the coating hardness profile between different copper and copper alloy compositions was presented. An interesting observation was that even though scratch hardness increases with the coating thickness, hardness decreases as a function of the distance from the interface.
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2661-5
Issue No: Vol. 42, No. 11 (2017)

• Erratum to: The Efficacy of Process Capability Indices Using Median
Absolute Deviation and Their Bootstrap Confidence Intervals
Pages: 4957 - 4957
PubDate: 2017-11-01
DOI: 10.1007/s13369-017-2807-5
Issue No: Vol. 42, No. 11 (2017)

JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327

Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs


text:
# Which type of Axe head design will require the least amount of effort force to chop wood short and wide long and wide long and thin short and thin

###### Question:

Which type of Axe head design will require the least amount of effort force to chop wood
short and wide
long and wide
long and thin
short and thin

### Question 5a: What is the measure of h?* 6 points m ת 150 O 25 O 150° O 125 O 30° 55° O 175

Question 5a: What is the measure of h?* 6 points m ת 150 O 25 O 150° O 125 O 30° 55° O 175...

### In a group of 30 people, 9 people study French and 14 people study Spanish. Seven people study both French and Spanish. What is the probability of studying French or Spanish?

In a group of 30 people, 9 people study French and 14 people study Spanish. Seven people study both French and Spanish. What is the probability of studying French or Spanish?...

### Como responder en las tareas q qquieren respuesta con respondo de esta apk

como responder en las tareas q qquieren respuesta con respondo de esta apk ...

### A pendulum has a mass of 0.060 kg swinging at a small angle from a light string, with a period of 1.4 s. What is the length of the pendulum?

A pendulum has a mass of 0.060 kg swinging at a small angle from a light string, with a period of 1.4 s. What is the length of the pendulum?...

### 8. Benny pushes Betty on her skateboard with a force of 150 N. If she accelerates at 3.0 m/s? what is her mass? Type the formula and answer.

8. Benny pushes Betty on her skateboard with a force of 150 N. If she accelerates at 3.0 m/s? what is her mass? Type the formula and answer....

### The Fugitive Slave Act Part of the Compromise of 1850 was the Fugitive Slave Act. Anyone who helped a fugitive could be fined or imprisoned. Some Northerners refused to obey the new law. In his 1849 essay "Civil Disobedience," Henry David Thoreau wrote that if the law "requires you to be the agent [cause] of injustice to another, then I say, break the law." Northern juries refused to convict people accused of breaking the new law. People gave money to buy freedom for enslaved people. Free Africa

The Fugitive Slave Act Part of the Compromise of 1850 was the Fugitive Slave Act. Anyone who helped a fugitive could be fined or imprisoned. Some Northerners refused to obey the new law. In his 1849 essay "Civil Disobedience," Henry David Thoreau wrote that if the law "requires you to be the agent [...

### Which tool could be used to model wave motion during a scientific investigation? A: beam balance B: mirror C: prism D: slinky spring

Which tool could be used to model wave motion during a scientific investigation? A: beam balance B: mirror C: prism D: slinky spring...

### Find the difference of 3/4 and 1/28

find the difference of 3/4 and 1/28...

### England's mercantilist principles:________. a. were active from the early 1600s. b. were active from the early 1700s. c. were a response to Spanish tariffs. d. were pursued by Charles II after 1685.

England's mercantilist principles:________. a. were active from the early 1600s. b. were active from the early 1700s. c. were a response to Spanish tariffs. d. were pursued by Charles II after 1685....

### How can i make the sentence Tú escuchar___________ música rock. (ESCUCHAR) right?

how can i make the sentence Tú escuchar___________ música rock. (ESCUCHAR) right?...

### 2x-y=-8 2x+y=-8 systems of equations

2x-y=-8 2x+y=-8 systems of equations...

### 10. What was the result of the Stono Rebellion? A. The slaves were able to make it to Spanish Florida and get their freedom. B. The Slave Codes were strengthened to control slave life. C. The slave trade was restricted in the colony of South Carolina. D. The slaves were able to make it the west and gain the land of their own

10. What was the result of the Stono Rebellion? A. The slaves were able to make it to Spanish Florida and get their freedom. B. The Slave Codes were strengthened to control slave life. C. The slave trade was restricted in the colony of South Carolina. D. The slaves were able to make it the west and ...

### How many deaths per day if approximately 32200 citizens of a country died in automobile accidents in 2015.

How many deaths per day if approximately 32200 citizens of a country died in automobile accidents in 2015....

### Aneta sold an apartment building for $713,470 in 2019. She purchased the building in 2013 for$600,000 and has taken $151,806 in depreciation on the building. Assuming Aneta is married with regular taxable income of$500,000 and in the 35% tax bracket, how is her gain taxed? a. $113,470 at 0% and$151,806 at 28%. b. $113,470 at 25% and$151,806 at 15%. c. $151,806 at 28% and$113,470 at 15%. d. $151,806 at 25% and$113,470 at 15%.

Aneta sold an apartment building for $713,470 in 2019. She purchased the building in 2013 for$600,000 and has taken $151,806 in depreciation on the building. Assuming Aneta is married with regular taxable income of$500,000 and in the 35% tax bracket, how is her gain taxed? a. $113,470 at 0% and$1...

### What is the value of x in the equation 2x2 + 6x = –5?

What is the value of x in the equation 2x2 + 6x = –5?...

### What happens when 1 branch gets too strong?

What happens when 1 branch gets too strong?...

### A publishing company is looking for new employees to type novels that will soon be published. The publishing company wants to find someone who can type at least 45 words per minute. Dominique discovered she can type at a constant rate of 704 words in 16 minutes. Does Dominique type at a fast enough rate to qualify for the job? Explain why or why not.

A publishing company is looking for new employees to type novels that will soon be published. The publishing company wants to find someone who can type at least 45 words per minute. Dominique discovered she can type at a constant rate of 704 words in 16 minutes. Does Dominique type at a fast enough ...


text:
# Finding maximum likelihood function for 2 normally distributed samples

1. Apr 2, 2012

### Gullik

1. The problem statement, all variables and given/known data
The question is about how to combine to different samples done with 2 different methods of the same phenomena.

Method 1 gives normally distributed variables $X_1,X_2,...X_{n_1}$, with $\mu$ and $\sigma^2_1$

Method 1 gives normally distributed variables $Y_1,Y_2,...,Y_{n_2}$, with $\mu$ and $\sigma^2_2$

All measurements can be considered independent.

Define $\overline{X}=1/n_1*\Sigma^{n_1}_{i=1}X_i$ and $\overline{Y}={1/n_2}*\Sigma^{n_2}_{j=1}Y_j$

Both the samples are taken from the same population so they have the same $\mu$

The question is set up a likelihood function for the $n_1 + n_2$ measurements, and show that the maximum likelihood estimator is given by

$\mu_{mle}={(\sigma^2_2n_1\overline{X}+\sigma_1^2n_2\overline{Y})/(\sigma_2^2n_1+\sigma^2_1n_1)}$

2. Relevant equations

The likelihood function for 1 sample of a normally distributed function.

$L(\mu)=L(X_1,X_2,...X_n;\mu,\sigma^2)=1/((2\pi\sigma^2)^{n/2})*e^{-1/2*\Sigma^{n}_{i=1}(X_i-\mu)/\sigma}$

3. The attempt at a solution

The main problem is that I don't know how I should handle the 2 samples instead of 1, I'm not sure how those two should combine.

Edit; I think I came up with the solution while I was writing up this which took quite some time since I don't know latex. I'll see when I try it out.

Since the measurement is presumed independent does the likelihood function become something like?

$L(\mu)=L(X_1,X_2,...X_{n_1};\mu,\sigma^2_1)*L(Y_1,Y_2,...,Y_{n_2};\mu,\sigma_2^2)$

Last edited: Apr 2, 2012


text:
The Mathematical Description of a Wave Video Lessons

Concept

# Problem: The nodes of a standing wave are points at which the displacement of the wave is zero at all times. Nodes are important for matching boundary conditions, for example, that the point at which a string is tied to a support has zero displacement at all times (i.e., the point of attachment does not move). Consider a standing wave, where y represents the transverse displacement of a string that extends along the x direction. Here is a common mathematical form for such a wave: y(x,t) = Asin(kx)sin(ωt), where A is the maximum transverse displacement of the string (the amplitude of the wave), which is assumed to be nonzero, k is the wave number, ω is the angular frequency of the wave, and t is time.Part AWhat is the displacement of the string as a function of x at time T/4, where T is the period of oscillation of the string?Express the displacement in terms of A, x, k, and other constants; that is, evaluate ω•T/4 and substitute it in the expression for y(x,t).Part B:At which three points x1, x2, and x3 closest to x = 0 but with x > 0 will the displacement of the string y(x,t) be zero for all times? These are the first three nodal points.Express the first three nonzero nodal points in terms of the wavelength λ. List them in increasing order.

###### FREE Expert Solution

Part A

At t = T/4, the displacement is expressed as:

y(x,T/4) = Asin(kx)sin(ωT/4)

But, ω = 2π/T

85% (40 ratings)
###### Problem Details

The nodes of a standing wave are points at which the displacement of the wave is zero at all times. Nodes are important for matching boundary conditions, for example, that the point at which a string is tied to a support has zero displacement at all times (i.e., the point of attachment does not move). Consider a standing wave, where y represents the transverse displacement of a string that extends along the x direction. Here is a common mathematical form for such a wave: y(x,t) = Asin(kx)sin(ωt), where A is the maximum transverse displacement of the string (the amplitude of the wave), which is assumed to be nonzero, k is the wave number, ω is the angular frequency of the wave, and t is time.

Part A

What is the displacement of the string as a function of x at time T/4, where T is the period of oscillation of the string?

Express the displacement in terms of A, x, k, and other constants; that is, evaluate ω•T/4 and substitute it in the expression for y(x,t).

Part B:

At which three points x1, x2, and x3 closest to = 0 but with > 0 will the displacement of the string y(x,t) be zero for all times? These are the first three nodal points.

Express the first three nonzero nodal points in terms of the wavelength λ. List them in increasing order.


text:
show · ring.unique_factorization_domain all knowls · up · search:

A unique factorization domein, or UFD, is an integral domain $R$ such that for every non-zero non-unit $a\in R$ there exists irreducibles $p_1, \ldots, p_n$ such that $a = p_1\cdots p_n,$ and this representation is unique up to the order of the factors and up to associates.

Authors:
Knowl status:
• Review status: beta
• Last edited by John Jones on 2019-03-20 10:06:12
Referred to by:
History:


text:
# Paul Julian II, PhD

Ecologist, Wetland Biogeochemist, Data-scientist, lover of Rstats.

# June 25, 2019 Eco DataViz

Written on June 25, 2019

Keywords: dataviz, R, GIS

Last week I started a Github repository (Link) to practice my data visualization. The data I used last week was Microcystin concentration from Iowa lakes to show trends and evaluate the current year relative to the period of record. Much like #TidyTuesday, as part of the data visualization practice I share the plots and code to spread inspiration and insight into data visualization techniques…the first post went live on Twitter last week with a pretty good reception (couple dozen “likes” and could of “re-tweets”)…couldn’t have been happier!

My Eco #DataViz is pretty basic, its not done in the tidyverse coding style or visualized in ggplot. Everything I do is in base R because that is what I am comfortable doing. The whole goal of Eco #DataViz much like #TidyTuesday is to practice wrangling and visualizing data. In general I follow the guidelines of #TidyTuesday:

• This is NOT about criticizing the original article or graph. Real people made the graphs, collected or acquired the data! Focus on the provided dataset, learning, and improving your techniques in R.

• This is NOT about criticizing or tearing down your fellow #RStats practitioners! Be supportive and kind to each other! Like other’s posts and help promote the #RStats community!

• Share the visualization on Twitter.

• Include a copy of the code used to create your visualization. I attempt to comment your code wherever possible to help myself and others understand my process (I know scary)!

• Focus on improving your craft, even if you end up with something simple!

• Give credit to the original data source whenever possible.

This blog post is the next iteration of Eco #DataViz where I can provide a more in-depth look into the process, share code and data visualizations.

This week I decided to move out of aquatic ecosystem and into something I have always been interested in…climate change science. Recently a version of this image has been making the rounds on twitter sparking concern and interest.

Being the data nerd I am I decided to dig into the data after reading Lisa Charlotte’s blog post on this data and some additional data visualizations of the data. Also an r-script to pull data from the National Snow & Ice Data Center(NSIDC)! A huge thanks to the NSIDC for making this data available!

Before grabbing the data lets load the necessary libraries I used.

#Libraries
library(AnalystHelper)
library(plyr)
library(reshape)
library(rjson)

The AnalystHelper library is a package I put together of the functions I use on a daily basis…most are helper functions for plotting some actually pull data and others do things. Check out the package here…most likely this will never make it on CRAN but if it helps you out great!!

Alright lets get the data…

years=seq(1979,2019,1)
green.melt=data.frame()

for(i in 1:length(years)){
# pulls the data from the web
d1=fromJSON(file=paste0('https://nsidc.org/api/greenland/melt_area/', years[i]));
#puts in into a temporary file (natively its a list)
tmp=data.frame(Date=as.Date(names(unlist(d1))), MeltArea.sqkm=unlist(d1))
#fixes the row names
row.names(tmp)=1:nrow(tmp)
#combines with the prior year
green.melt=rbind(tmp,green.melt)
}

You can write green.melt to a file if needed (i.e. write.csv) or use it in your process. This data represents melt area of the Greenland ice sheet in square kilometers. Granted there are some limitation to this data because it is remotely sensed data but given the period or record some valuable insights into trends and magnitude of change can be determined. If you are interesting about the data, NSIDC has an “About the data” page.

Before really jumping into the data lets work with the date field (screaming is allowed at this point…now that is done let get to it). I use date.fun(), a function in AnalystHelper to help me format dates…I work with lots of time-series data so I made a quick helper function, check out ?date.fun for more info.

green.melt$Date=date.fun(green.melt$Date,tz="GMT");
green.melt$DOY=format(green.melt$Date,"%j");# Day of the Year
green.melt$CY=as.numeric(format(green.melt$Date,"%Y"));# Calendar Year

In the original image, the units are in percent of area…the data we just downloaded is in square kilometers. After some digging I figured out the Greenland ice-sheet is approximately 1,710,000 km2 so lets insert a variable

greenland.ice.area=1710000

Now we can convert the melt area in km2 to percent area like in the original image and calculate some statistics.

green.melt$MeltArea.per=(green.melt$MeltArea.sqkm/greenland.ice.area)*100

green.melt.POR.stats=ddply(subset(green.melt,CY%in%seq(1979,2018,1)),"DOY",
summarise,
N.val=N(MeltArea.per),
decile.10=quantile(MeltArea.per,probs=0.1,na.rm=T),
decile.90=quantile(MeltArea.per,probs=0.9,na.rm=T),
Q25=quantile(MeltArea.per,probs=0.25,na.rm=T),
Q75=quantile(MeltArea.per,probs=0.75,na.rm=T),
median=median(MeltArea.per,na.rm=T))

green.melt.ref.stats=ddply(subset(green.melt,CY%in%seq(1981,2010,1)),"DOY",
summarise,
N.val=N(MeltArea.per),
median=median(MeltArea.per,na.rm=T))

## Goal: Replicate Greenland Daily Melt Plot

DONE! and with some added flair.

While digging through the data a couple of questions come to mind…here are two.

## Q1 Has the average trend in Greenland melt area increased?

To answer this question we need to calculate annual mean melt area across the period of record. I also included a calculation of $$\pm$$ 95% Confidence Interval. I limited the data to just years with a full amount of data and since we are in the middle of the year, 2019 was excluded. N() is a function in AnalystHelper essentially length(which(x!=NA)) to give an actual count of the data…check out ?AnalystHelper::N.

alpha=0.95;
greenland.melt.mean=ddply(subset(green.melt,CY%in%seq(1979,2018,1)),"CY",
summarise,
mean.val=mean(MeltArea.sqkm,na.rm=T),
sd.val=sd(MeltArea.sqkm,na.rm=T),
N.val=N(MeltArea.sqkm))

#Degree of freedom
greenland.melt.mean$Df=greenland.melt.mean$N.val-1;
#Test Statistic
greenland.melt.mean$Tp=with(greenland.melt.mean,abs(qt(1-alpha,Df))); #Lower CI greenland.melt.mean$LCI=with(greenland.melt.mean,
mean.val-sd.val*(Tp/sqrt(N.val)));
#Upper CI
greenland.melt.mean$UCI=with(greenland.melt.mean, mean.val+sd.val*(Tp/sqrt(N.val)));  Now to see if this trend is significant we can apply a basic Kendall correlation analysis. with(greenland.melt.mean,cor.test(mean.val,CY,method="kendall")) ## ## Kendall's rank correlation tau ## ## data: mean.val and CY ## T = 632, p-value = 1.074e-09 ## alternative hypothesis: true tau is not equal to 0 ## sample estimates: ## tau ## 0.6205128 I would say the annual mean melt area has significantly increased over the entire period of record!! ## Q2 Has the peak melt area increased during the period of record? Let figure out when the peak melt area has occurred every year. I did this by looping through each year to find the max melt area and extract the date/DOY. max.melt.CY=data.frame() for(i in 1:length(seq(1979,2018,1))){ CY.max=max(subset(green.melt,CY==years[i])$MeltArea.sqkm,na.rm=T)
tmp.dat=subset(green.melt,CY==years[i]&MeltArea.sqkm==CY.max)

tmp.dat.final=data.frame(CY=years[i],
DOY.max.melt=as.numeric(min(tmp.dat\$DOY,na.rm=T)),
max.melt=CY.max)
max.melt.CY=rbind(tmp.dat.final,max.melt.CY)
}

Lots of variability in the data with some years occurring relatively yearly and others later in the year. More digging is needed to pull this trend out and mechanisms behind it…exciting (and worrisome) frontiers in Arctic and data science.


text:
Repeated measures design matrix controlling for covariates age and sex
2
0
Entering edit mode
20 days ago
ASid ▴ 10

Hi Gordon Smyth ; I need to perform an analysis on repeated measures paired data ; an example is below; I want to control for two covariates sex and age ; and want to find out the differentiall expression on my metabolites expression data which is similar to gene expression data for day 7 versus day 0; however I want to account for sex and age effect and also want to identify the metabolites that are only affected by sex or only affected by age;

Dummy Data: has four columns is is my subject id ; there are 11 unique subjects ; time is pre and post vaccination thus T1=prevaccination; T2=postvaccination day7; sex as factor and age as continuous covariate;

> data
id time exp sex age
1   M1   T1 1.0   m  46
2   M2   T1 1.0   m  12
3   M3   T1 1.2   f  20
4   M4   T1 1.0   f  13
5   M5   T1 1.5   m  30
6   M6   T1 1.3   f  21
7   M7   T1 0.8   f  23
8   M8   T1 0.7   m  26
9   M9   T1 0.6   f  60
10 M10   T1 1.3   f  65
11 M11   T1 1.5   f  68
12  M1   T2 2.0   m  46
13  M2   T2 2.4   m  12
14  M3   T2 2.0   f  20
15  M4   T2 2.3   f  13
16  M5   T2 2.1   m  30
17  M6   T2 1.7   f  21
18  M7   T2 5.4   f  23
19  M8   T2 6.7   m  26
20  M9   T2 3.1   f  60
21 M10   T2 3.4   f  65
22 M11   T2 3.7   f  68

theoretically I was under impression that for one gene or one metabolite (dummy data below) the model using the design matrix below should work where first

model.matrix(~0+id+time+sex+age, data=data) mymodel<-lm(exp~0+id+time+sex+age, data=data)

> design
idM1 idM10 idM11 idM2 idM3 idM4 idM5 idM6 idM7 idM8 idM9 timeT2 sexm age
1     1     0     0    0    0    0    0    0    0    0    0      0    1  46
2     0     0     0    1    0    0    0    0    0    0    0      0    1  12
3     0     0     0    0    1    0    0    0    0    0    0      0    0  20
4     0     0     0    0    0    1    0    0    0    0    0      0    0  13
5     0     0     0    0    0    0    1    0    0    0    0      0    1  30
6     0     0     0    0    0    0    0    1    0    0    0      0    0  21
7     0     0     0    0    0    0    0    0    1    0    0      0    0  23
8     0     0     0    0    0    0    0    0    0    1    0      0    1  26
9     0     0     0    0    0    0    0    0    0    0    1      0    0  60
10    0     1     0    0    0    0    0    0    0    0    0      0    0  65
11    0     0     1    0    0    0    0    0    0    0    0      0    0  68
12    1     0     0    0    0    0    0    0    0    0    0      1    1  46
13    0     0     0    1    0    0    0    0    0    0    0      1    1  12
14    0     0     0    0    1    0    0    0    0    0    0      1    0  20
15    0     0     0    0    0    1    0    0    0    0    0      1    0  13
16    0     0     0    0    0    0    1    0    0    0    0      1    1  30
17    0     0     0    0    0    0    0    1    0    0    0      1    0  21
18    0     0     0    0    0    0    0    0    1    0    0      1    0  23
19    0     0     0    0    0    0    0    0    0    1    0      1    1  26
20    0     0     0    0    0    0    0    0    0    0    1      1    0  60
21    0     1     0    0    0    0    0    0    0    0    0      1    0  65
22    0     0     1    0    0    0    0    0    0    0    0      1    0  68

first eleven parameters are created by 0~id accounts for each individual and pairing of samples at T1; t2 should give difference between t2 and t1 ; however I am not sure about other two covariates if I am accounting them correctly; I will really appreciate your help. Best amnah

analysis Paired • 328 views
0
Entering edit mode
20 days ago
Gordon Smyth ★ 3.5k

I want to account for sex and age effect

Paired analyses already completely control for all subject-specific characteristics including age and sex. That's the whole reason for doing a paired analysis. You can't "correct" for these variables a second time by adding to the design matrix as extra variables. If you try to do so in a limma analysis, limma will simply remove the age and sex variables as superfluous.

I also want to identify the metabolites that are only affected by sex or only affected by age

Sorry, that doesn't make sense. The purpose of your experiment is to determine the effect of vaccination for each patient. The age or sex of the patient doesn't change when they get vaccinated so there are no changes with age or sex.

You could conceivably find vaccination effects that are specific to patients of one gender or specific to certain age groups. That would be a meaningful analysis to do, although the number of patients you have is minimal for that type of analysis. The analysis would look for an interaction between vaccination and age or between vaccination and sex.

0
Entering edit mode
19 days ago
ASid ▴ 10

Thank You very much for the explanation Gordon Smyth , that makes sense to me. Also I was educating myself and and there are arguments that fixed subject specific effect in paired data design in LMM can be better modeled by modeling subject specific effects using mixed effect model e.g using lme4 package in r. Two things that I understand about their use instead of fixed effect model is that the data for missing values can be handled and also fixed models eats up degrees of freedom which reduces statistical significance ? What is your opinion on that. I am sorry if it is naive question but I am kind of new in this area.

Many thanks. Amnah

0
Entering edit mode

• limma fits random effects models using the duplicateCorrelation function (see the User's Guide section on multi-level models)
• random effects models are appropriate for some datasets and some scientific purposes but there is no merit in a random effects model for the dataset in your question above. Mixed models are statistically very subtle, but essentially they only offer more information than a fixed model approach when the factor of interest is unbalanced with respect to the blocking variable.
• limma always has more power than lme4 because it is able to borrow information between genes

If you have a question in the future about using limma for a particular dataset then I will try to help you. I don't have any more time for general discussions however.

Traffic: 2423 users visited in the last hour
FAQ
API
Stats

Use of this site constitutes acceptance of our User Agreement and Privacy Policy.


text:
# Relationship between matrix 2-norm and orthogonal basis of eigenvectors

Given the following matrix: $$A = \left( \begin{array}{cc} 3 & 4 \\ 0 & 5 \\ \end{array} \right)$$

calculate $\|A\|_2$, with $\|A\|_2 = max_{x \in \mathbb{R}^2 -\{0\}} \frac{\langle Ax,Ax \rangle}{\langle x,x\rangle}$.

Hint: Calculate an orthonormal basis consisting of eigenvectors of $A^TA$ and express $x \in \mathbb{R}^2$ in terms of that basis.

Can anybody tell me please how an orthonormal basis and the value for which $\frac{\langle Ax,Ax \rangle}{\langle x,x\rangle}$ is largest relate to each other? How does the vector x expressed in terms of that orthonormal basis of eigenvectors help me find the desired x?

• The 2-norm of a (square) matrix is the square root of the largest eigenvalue of $A^TA$. – ABC Jun 10 '14 at 19:00
• ...and the desired maximizer $x$ is the corresponding eigenvector. – PA6OTA Jun 10 '14 at 19:10
• Thanks. But why is that the case, can anybody link me to a proof please? – eager2learn Jun 10 '14 at 19:13
• – ABC Jun 10 '14 at 19:21

First off, I believe you are missing a square root in the definition since it is the $2$-norm.
The reason it is asking you to find such a basis is to make it easier to compute the norm since $\langle Ax,Ax\rangle = \langle x, A^T A x \rangle$. Suppose $\{e_1,e_2\}$ is the ONB of eigenvectors of $A^T A$ with corresponding eigenvalues $\lambda_1$ and $\lambda_2$, and suppose $x$ is represented as $x = a e_1 + b e_2$ against the basis. Then \begin{align*} \dfrac{\langle Ax,Ax\rangle}{\langle x,x\rangle} &= \dfrac{\langle x,A^T A x\rangle}{\langle x,x\rangle} = \dfrac{\langle a e_1 + b e_2, A^TA(a e_1 + b e_2)\rangle}{\langle a e_1 + b e_2,a e_1 + b e_2 \rangle}\\ &= \dfrac{\langle a e_1 + b e_2, \lambda_1 a e_1 + \lambda_2 b e_2\rangle}{\langle a e_1 + b e_2,a e_1 + b e_2 \rangle}\\ &= \dfrac{\lambda_1 a^2 + \lambda_2 b^2}{a^2 + b^2} \end{align*} and so you need to maximize this over $a$ and $b$, which is easier than just writing $$x = \left(\begin{array}{c} x_1 \\ x_2 \end{array}\right)$$ and computing directly. The top of the fraction turns into a huge mess.
Now, note first that this could have been done for even larger square matrices except it would be $x = a_1 e_1 + a_2 e_2 + \cdots + a_n e_n$ and the computation would follow out similiarly to get $$\dfrac{\lambda_1 a_1^2 + \lambda_2 a_2^2 + \cdots \lambda_n a_n^2}{a_1^2 + a_2^2 + \cdots + a_n^2}. \quad (**)$$ Also, notice that this did not rely on anything about $A$ except that it was square, so it's true for all square matrices $A$. Finally, the maximum of $(**)$ is obtained by taking the coefficient of the largest eigenvalue to be one and the rest being zero. For instance, if $\lambda_1 > \lambda_2$, then taking $a = 1$ and $b = 0$ gives the maximum value. So, as said in the comments, the maximum is the square root of the largest eigenvalue and since $a = 1$ and $b = 0$ (in the case $\lambda_1 > \lambda_2$), then the eigenvector corresponding to said eigenvalue gives the maximum.


text:
# Homework Help: Simple Integral

1. Sep 1, 2010

### PhysicsMark

1. The problem statement, all variables and given/known data

Hello. I have a simple integral here that has been stumping me for the last 30 minutes. It appears that my basic integration skills have gotten very rusty.

2. Relevant equations

$$\int{x^3}\sqrt{1+x^2}dx$$

3. The attempt at a solution
I am pretty sure a simple substitution will do, but I have yet to find it. I have tried simplifying the expression various ways, integration by parts, and I have also tried a few substitutions. Any ideas?

2. Sep 1, 2010

### Dick

u=1+x^2 will do it.

3. Sep 1, 2010

### jgens

The substitution x=tan(u) also works.

4. Sep 1, 2010

### PhysicsMark

Thank you Dick and Jgens.

$$\int{x^3}\sqrt{1+x^2}dx$$

Let u=1+x^2$$\rightarrow$$du=2xdx

$$\int{x^3}\sqrt{1+x^2}dx=\frac{1}{2}\int(u-1)\sqrt{u}du$$

$$\frac{1}{2}\int(u-1)\sqrt{u}du=\frac{1}{2}(\int{u^{\frac{3}{2}}}du-\int{u^{\frac{1}{2}}du)$$

$$\int{u^{\frac{3}{2}}}du=\frac{2}{5}u^{\frac{5}{2}}$$

$$\int{u^{\frac{1}{2}}du=\frac{2}{3}u^{\frac{3}{2}}$$

$$\frac{1}{2}\int(u-1)\sqrt{u}du=\frac{2}{10}u^{\frac{5}{2}}-\frac{2}{6}u^{\frac{3}{2}}$$

It appears I made a mistake somewhere. I believe my result should be multiplied by 1/2, and I can't find where I left that out.

5. Sep 1, 2010

### PhysicsMark

Nevermind. I guess the second part of the problem is incorrect. Mathematica has arrived at the same conclusion as this also. Thanks for all the help.


text:
# Solar Analemma - but with a star instead

We (homeschool students and I) are trying to find the answer to this question. Does a star also create Solar Analemma figure 8 when photographed daily for a year?

Has anyone published an experiment where the same star is photographed every night at the same time?

We tried answering this ourselves by googling it, but only come up with websites mentioning the sun. Is this because it is only possible with the sun?

The Sun only has an analemma (the figure-8 shape traced on the sky as a result of imaging the Sun at the same time (good luck avoiding clouds) each day) because of two factors.

• The Earth is tilted on its axis and that axis remains pointed in the same direction in space (toward the direction of Polaris).

(A more precise explanation is that the axis does precess (or "wobble" like a spinning top) ... but in a very long cycle that takes nearly 26,000 years to complete. So on the scale of single human lifespan ... it doesn't appear to move by any noticeable amount and requires very precise measurements to detect.)

• The Earth's orbit is an ellipse ... not a circle.

While nearly circular ... it isn't perfect. The point along an orbit when an object is nearest to the barycenter of the orbit (in our case... to the Sun) is called the periapsis. But since this periapsis is for an object orbiting the Sun, it gets a special named called the "perihelion". The point of the orbit located farthest from the barycenter is called the apoapsis. Again... it gets a special name because it's an orbit around the Sun so it is called the "aphelion".

But the consequences of the Earth getting nearer to the Sun during half of its orbit ... then getting farther from the Sun during the other half of its orbit ... means Earth's velocity through space changes. As we get nearer to the Sun it is as if we are "falling" so we speed-up (our velocity through space is faster) and as we get farther from the Sun we slow-down (our velocity through space is slower).

Earth needs roughly 365 days (365.24) to complete an orbit. There are 360° in a circle. This means that each ordinary day on Earth (formally known as a "solar day") is 24 hours. In that 24 hours, we've moved forward in our orbit around the Sun by just slightly less than 1°.

It turns out that the amount of time needed for the Earth to spin 360° on it's axis (one "sidereal day") is just slightly less than a solar day. It's roughly 23 hours and 56 minutes (roughly 4 minutes short of a solar day ... that's a roughly rounded value).

So why the difference between a "solar" day vs. a "sidereal" day?

Side note: sidereal translates to mean "of the stars". This comes from the notion that ancients noticed that the debris left by a "falling star" (meteorites) that landed on Earth was mostly made of iron. They surmised that stars must be made out of iron (not realizeing that meteors are not actual stars that fall from the sky). Their word for iron is "sidero" (or "sider" pronounced like "cider" ... the juice you squeeze from apples and possibly ferment into a beverage. It is pronounced the same. Sidereal is not pronounced like "side-real". It is pronounced like "cider-eal". Alas, I digress). Sidereal day means the "day of the stars". In other words, if you note the time when a star passes through the meridian (the imaginary north/south line that separates the "west" side of the sky from the "east" side of the sky) ... and then wait to see when that same star passes through the meridian on the following day, the amount of time that has passed will be roughly 23 hours and 56 minutes.... not 24 hours.

Once the Earth has completed one 360° revolution on its axis (one sidereal day) it will also have moved forward in its orbit by nearly 1°. This means that while distant stars would appear in the same point in the sky, the Sun will not... it will be slightly behind the meridian. We will need to let the Earth spin for another 4 minutes until the Sun returns to the same position. But alas... even this has exceptions...

Recall that the Earth speeds up and slows down as it travels through space between it's perihelion and aphelion points. This means the Sun wont precisely be at the same position in the sky... it'll be fractionally ahead or behind depending on if the Earth is speeding up ... or slowing down. This accounts for the left/right variation in the Sun's position in the analemma. The Earth's axial tilt accounts for the up/down variation in the Sun's position. And when you trace out a whole year, you get a shape that resembles a figure-8.

Stars, on the other hand, are much farther away. If you image a star once every 24 hours (assuming no clouds block your view) then each night, the star will shift forward by roughly 1° ... after enough days the Star will be below the horizon and you will no longer be able to image the star. This means the shape you'll get... is that that the star will trace out an long arc ... but after a few months it will no longer be visible at the same time (you would have to observe it at a different time of the day ... and/or it may be lost in the daytime sky depending on the location of Earth in our annual orbit around the Sun.

• Thank you Tim Campbell. Based on your answer, can we assume that if a camera were placed on every planet and a timed photograph of the sun was taken based on that planet's rotation, that a Solar Analemma would result? – Bookaholic Oct 22 '20 at 5:52
• Yes but the shape will be different. This page shows the analemma for Mars: en.wikipedia.org/wiki/Timekeeping_on_Mars You can see it isn't a figure 8 ... but it's rather egg-shaped. The shape is determined by the relationship between the direction of the axial tilt (the solstices) and the dates of perihelion and aphelion. – Tim Campbell Oct 22 '20 at 18:42

An analemma shows the position of the Sun in the sky from a fixed location on Earth at the same mean solar time. It gets its north-south shape because of the tilt of Earth's axis makes the declination of the sun change across the year, and the sideways shape due to the orbit nonuniformity.

The star analemma would get a point at the same time every sidereal day (slightly different from the solar day). To a first approximation that fixes the star's right ascension: it will not move along the celestial equator. The celestrial equator of course rotates one turn per year as seen from the ground, so in one sense the analemma is just a circle around the pole of the sky. But if you look at it in the coordinate system of the celestial sphere the star is fixed.

...Except that there will be some stellar parallax due to Earth's different locations along its orbit during the year. The star will seem to move along a tiny ellipse when compared to distant stars in the background. I think the parallax ellipse is the closest counterpart to the sun analemma.

• Can you explain what you mean by orbit non-uniformity – Kai Oct 22 '20 at 4:30
• The orbit is an ellipse, and the speed the planet moves along it changes as per Kepler's laws. – Anders Sandberg Oct 22 '20 at 14:29
• Stellar parallax resulting from the Earth's orbit is really really really tiny. A major objection to the heliocentric model, historically, was that if the position of stars weren't fixed relative to the earth, it should be possible to observe stellar parallax unless stars were so absurdly far away that it should be impossible to see them unless they were absurdly big. The notion that stars were fixed relative to the earth was less of a scientific stretch than the notion that anything could exist that was large enough to be visible despite being far enough away not to exhibit parallax. – supercat Oct 22 '20 at 21:58

Fortunately the free planetarium software Stellarium makes it easy to simulate this experiment. If you pause its clock and repeatedly press = to step forward 24 hours at a time, the stars appear to move westward about 1° per night as the Earth moves around the Sun. Stepping by 23h56m04s sidereal days with Alt = eliminates this effect. Unfortunately you can only do this for a few months before daytime skyglow dominates the view; 3m56s per day adds up to 24 hours per year. Fortunately you can disable the atmosphere model with A and pretend to take images year round.

If you disable the ground model with G, set an equatorial frame with Ctrl M, set a 1° field of view with Ctrl Alt 9, and timestep by sidereal years with Shift Ctrl Alt ], the stars appear to move roughly eastward about 50.3" (arcseconds) per year. This is due to precession and can be eliminated by selecting a star and centering it with  Space . If you step for a few centuries, you'll see some field rotation due to precession, plus some linear changes in star positions relative to each other (proper motion). Only a few stars have proper motions larger than 1" per year.

A camera on a telescope and professional-grade equatorial mount would record the effects of aberration (20.5", 1 year cycle) and nutation (17.2" × 9.2", 18.6 year cycle). Unfortunately parallax is much smaller, e.g. 0.1" for a star only 10 parsecs away. Fortunately, within a small field of view, aberration and nutation affect all stars equally and can be eliminated by aligning images on the fainter background stars. Stellarium models nutation but not aberration or stellar parallax.

Dennis di Cicco, who made a famous solar analemma photograph in 1978-79, also made analogous observations of Barnard's Star in 1994-96. The resulting wavy line, about 10,000 times smaller than the solar analemma, is plotted here. The north-south extent is due to proper motion, for which Barnard's Star holds the record. In the east-west dimension, there is a linear component due to proper motion and an oscillating component due to parallax.

In the professional arena, the Hipparcos mission did this on a large scale in the early 1990s, and the Gaia mission is currently doing it on a massive scale. The end product, a catalog of star positions with parallaxes and proper motions, comes from analysis of the wavy trails produced by each star's combined parallax and proper motion.

PS: If you set a location on Mars with F6, the = timestep changes to the Martian mean solar day of 24h39m35s, and you can see the Sun follow the Martian analemma. This has a teardrop shape instead of a figure 8 because Mars's orbit is 5.6 times as eccentric as Earth's. The other factors, axial tilt and solstice-perihelion relationship, are currently similar to Earth's.

The stars are very very far away. So far away that only the rotation of the Earth matters for their position in the sky.

If you photograph a star every time the Earth completes a rotation, it will appear as a single point.

But that's not what happens if you photograph it "at the same time". A day is slightly longer than one rotation of the Earth, to keep up with the Sun. During 365 days, the Earth rotates 366 times.

As such, the celestial sphere appears to complete one rotation every year. Thus, your experiment will show the stars moving in circles around the celestial poles.

• Hello! Your answer is great, but can be a bit confusing because the word "rotation" might refer to the rotation of the Earth on itself or to the rotation of the Earth around the Sun. Would you please consider being extra explicit in your answer? – Stef Oct 21 '20 at 15:39
• I recommend Anders Sandberg's answer for a more robust treatment of exactly what the differences between the various rotational periods are. I'll let this answer stay as informal as possible. – SE - stop firing the good guys Oct 21 '20 at 15:42
• @Stef The planets revolve around the sun while rotating on their axes. – Ross Presser Oct 21 '20 at 18:37

As far as:

Has anyone published an experiment where the same star is photographed every night at the same time?

I don't know but if you did it would just be a dotted line across the sky. The stars cross the meridian about 4 minutes earlier at each night.

If you photographed at local midnight and you saw a star low in the East and photographed every night after that, it would move almost 1 degree along a circle each night.

360/365.25 = 0.986 degrees.

It will cross the meridian about 4 minutes earlier each night

24 * 60 / 365.25 = 3.94 minutes.

All you get is a dotted line from East to West.

And like @AndersSandberg's answer says if you photographed the same sidereal time ever day (which would be the 3.94 minutes earlier each day) then the star would stay almost exactly the same place.

The only deviations would be due to things like parallax or the Earth's rotation speeding up or slowing down, which are very, very tiny effects.


text:
# Is the Food Industry Promoting Obesity?

The US population has a high rate of obesity, perhaps the highest in the world (see the WHO and CDC obesity websites for the numbers).  The simplest explanation, the one without nuance, is that people are eating more calories than they need. The nuanced explanation involves all the reasons why we are consuming too many calories.  For example, one reason is that we don't know how many calories we need.  Another is that, even those who know their caloric needs, cannot reasonably (or accurately) estimate the amount of calories in the food and beverages available to them.  Still another, the food and beverages most readily available and heavily promoted are (ridiculously) high in calories.
So is the food industry a culprit?
I give you three reasons why I think the answer is yes, but note, I said a culprit not the culprit.  They are:

1. The french fry burger
2. Endless bowls of pasta
3. And the Bacon Pepperoni pizza burger

There are many factors that promote an over consumption of calories.  The cause will always involve an interaction between the person and his or her environment.  But really, does the environment have to be this over the top?  Cheap, calorically- dense, nutrient-poor food is much easier to access than it is to avoid.  That's a problem, but its one we CAN address.

Top


text:
Examining the smooth and nonsmooth discrete element approaches to granular matter M. Servin, D. Wang, C. Lacoursière, K. Bodin, Examining the smooth and nonsmooth discrete element approaches to granular matter, accepted for publication in International Journal for Numerical Methods in Engineering (2013). preprint pdf, sample data, videos, calculator, plots, pseudocode, Interactive physics and complex mechanical systems

Abstract
The smooth and nonsmooth approaches to the discrete element method (DEM) are examined from a computational perspective. The main difference can be understood as using explicit versus implicit time integration. A formula is obtained for estimating the computational effort depending on error tolerance, system geometric shape and size, and on the dynamic state. For the nonsmooth DEM, a regularized version mapping to the Hertz contact law is presented. This method has the conventional nonsmooth and smooth DEM as special cases depending on size of time step and value of regularization. The use of the projected Gauss-Seidel solver for nonsmooth DEM simulation is studied on a range of test systems. The following characteristics are found. Firstly, the smooth DEM is computationally more efﬁcient for soft materials, wide and tall systems, and with increasing ﬂow rate. Secondly, the nonsmooth DEM is more beneﬁcial for stiff materials, shallow systems, static or slow ﬂow and with increasing error tolerance. Furthermore, it is found that just as pressure saturates with depth in a granular column, due to force arching, also the required number of iterations saturates and become independent of system size. This effect make the projected Gauss-Seidel solver scale much better than previously thought.
Videos
Calculator
 Formula: \begin{equation*} \begin{array}[l] \\ \frac{\tau_{{\tiny NDEM}}}{\tau_{{\tiny SDEM}}} = \sqrt{\frac{ \max\left(\epsilon^2 m v{n}^2, 2\epsilon mgd\right)}{kd^2}} \frac{K^{{\tiny GS}}_{{\tiny NDEM}}}{K{{\tiny SDEM}}} \frac{N_{c}}{N_\text{p}}\cdot\nonumber\\ \quad\quad\quad\cdot\frac{c_0 (1 + c_1 I )}{\epsilon} \left\{ \begin{array} [l]{lr}% w( 1 - \exp[-\tfrac{c_2 l} {w}]) & \text{ , if } w \gtrsim 5\\ c_2 l & \text{ , if } w < 5 \end{array} \right.\\ \frac{}{}\\ \frac{}{}\\ \tau_{\tiny SDEM} = \sqrt{\frac{k}{m}} K_{\tiny SDEM}N_{\text{p}}\tau_{\text{real}}\\ \frac{}{}\\ \frac{}{}\\ \tau_{\tiny NDEM} = \frac{K^{\tiny GS}_{\tiny NDEM}N_{\text{it}} N_{c}} {\min\left(\epsilon\frac{ d}{v_{n}}, \sqrt{\frac{ 2\epsilon d}{g}}\right)}\tau_{real}\\ N_{\text{it}}^{\epsilon} (l,w,I) = \tfrac{c_0 (1 + c_1 I )}{ \epsilon } \left\{ \begin{array} [l]{lr}% w( 1 - \exp[-\tfrac{c_2 l} {w}]) & \text{ , if }w \gtrsim 5\\ c_2 l & \text{ , if }w < 5 \end{array} \right. \end{array} \end{equation*}

 $g$ : [${\tiny m/s^{2}}$] $\rho$ : [${\tiny kg/m^3}$] $\nu$ : $K_{\tiny SDEM}$ : $K^{\tiny GS}_{\tiny NDEM}$ : $c_0$ : 0.3 $c_1$ : 2.0 $c_2$ : 0.44

 $\epsilon$ : $w$ : $l$ : $I$ : $Y$ : [GPa] $d$ : [m]

 $\frac{\tau_{{\tiny NDEM}}}{\tau_{{\tiny SDEM}}}$ : $\frac{\tau_{{\tiny SDEM}}}{\tau_\text{real}}$ : $\frac{\tau_{{\tiny NDEM}}}{\tau_\text{real}}$ : $h_{N}$ : [ms] $h_{S}$ : [ms] $N_\text{P}$ : $N_\text{it}$ : $V_{n}$ : [m/s]
Input all values. Selected value (red colored) will be used as domain variable.
$I$:
 0~
$w$:
 [d]
$l$:
 [d]
Input all values. Selected value (red colored) can have multi (< 8) values, each correspond to one curve
$\epsilon$:
 Input 1~ values
$Y$:
 [Pa]
$d$:
 [m]
Related plots
 Force network The contact forces form force networks. These are weighted graphs with the particles as nodes and contact forces as edges. We use the normal force magnitude for the edge weight. In granular materials with too few iterations the strong force chains that are a characteristic feature of granular materials do not appear. Instead, the force distributes as the hydrostatic pressure in a fluid, i.e., increases linearly with depth from the top surface. When increasing the number of iterations, strong force chain structures emerge and with this the pressure force saturate and become independent of depth in the column. This is the well-known Janssen effect of granular materials, which is due to an arching effect of the force chains whereby the container walls carry part of the weight of the material Click here for more force network figures. Velocity fields On sufficiently large scales of length and time a granular material may be considered as a continuous solid represented by continuous fields of mass distribution, flow velocity and stresses and strains. The averaging process of sampling microscopic particle properties and inter-particle forces to macroscopic quantities is referred to as coarse graining (or homogenization). A cubic grid is introduced and the fields are evaluated at the grid points. The smoothing length is chosen to 1.5 times particle diameter and we use grid size L = 0.5 d. Click here for more velocity fields Scalar fields On sufficiently large scales of length and time a granular material may be considered as a continuous solid represented by continuous fields of mass distribution, flow velocity and stresses and strains. The averaging process of sampling microscopic particle properties and inter-particle forces to macroscopic quantities is referred to as coarse graining (or homogenization). A cubic grid is introduced and the fields are evaluated at the grid points. The smoothing length is chosen to 1.5 times particle diameter and we use grid size L = 0.5 d. Click here for more scalar field plots of mass density, pressure, strain rate and inertial number.
Pseudo code


text:
1. ## bits n bobs

few little grey areas:

1) how would i work this one out:

find the vloume generated by rotationg the area bounded by y=x^2 and y=4 around the line y=1

2. It is the same as rotating $(x+1)^2$ around $y=0$. Use the volume of rotation formula.

3. Originally Posted by ThePerfectHacker
It is the same as rotating $(x+1)^2$ around $y=0$. Use the volume of rotation formula.

what formula is that?
x

4. $\int_a^b \pi f^2(x)dx$.

5. Originally Posted by Rebesques
$\int_a^b \pi f^2(x)dx$.
It should be,
$2\pi \int_a^b xf(x) dx$

6. I doubt it

This random page says otherwise:

Volume of A Solid of Revolution

Are you talking about surface area maybe?


text:
# 환경재해에 관한 생물정보로서의 이온화 방사선과 살충제의 인체 위해성 비교 연구

• Published : 2001.12.30

#### Abstract

Environmental risk factors such as ionizing radiations, heavy metals, and pesticides can cause environmental disasters when they exist in excess. The increases in use of ionizing radiation and agricultural pesticide are somewhat related to the possibility of the disaster. The risk of radiation and pesticide was evaluated by means of the single cell gel electrophoresis (SCGE) assay on the human blood lymphocytes. The lymphocytes were irradiated with $0{\sim}2.0Gy$ of $^{60}Co$ gamma ray. Another groups of lymphocytes were exposed to various concentrations of parathion. Significantly increased tail moment, which was a marker of DNA strand breaks in SCGE assay, showed a clear dose- or concentration-response relationship. Parathion of a recommended concentration for agricultural use ($1mg {\ell}^{-1}$ ) has a strong cytotoxic effect on lymphocytes, which is equivalent to damage induced by 0.1 Gy of ${\gamma}$-ray. Furthermore, $2mg{\ell}^{-1}$ of parathion can give rise to DNA damage equivalent to that induced by 0.25 Gy at which the radiation-induced damage can start to develop into clinical symptoms. The comparative results of this study can provide an experimental basis and biological information for the prevention of environmental disaster.


text:
PREPRINT

Deep Learning application for stellar parameters determination: II- Application to observed spectra of AFGK stars

Marwan Gebran, Frédéric Paletou, Ian Bentley, Rose Brienza, Kathleen Connick

Submitted on 31 October 2022

Abstract

In this follow-up paper, we investigate the use of Convolutional Neural Network for deriving stellar parameters from observed spectra. Using hyperparameters determined previously, we have constructed a Neural Network architecture suitable for the derivation of Teff, log g, [M/H], and vesini. The network was constrained by applying it to databases of AFGK synthetic spectra at different resolutions. Then, parameters of A stars from Polarbase, SOPHIE, and ELODIE databases are derived as well as FGK stars from the Spectroscopic Survey of Stars in the Solar Neighbourhood. The network model average accuracy on the stellar parameters are found to be as low as 80 K for Teff , 0.06 dex for log g, 0.08 dex for [M/H], and 3 km/s for vesini for AFGK stars.

Preprint

Comment: 13 pages, 7 figures. Accepted for publication in Open Astronomy, De Gruyter

Subjects: Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Instrumentation and Methods for Astrophysics; Physics - Computational Physics