text:
Is your mother proud of you being a crook?

I have asked this question many times in recent months; basically, every time I receive a call from the “computer support department”, trying to tell me how my computer is full of viruses or whatever.

I usually don’t expect an answer; as a matter of fact, I usually just hang up, although more often than not, the other party hangs up first before I get a chance. Understandable… that’s what they are trained to do by their criminal masters.

Today, for some reason, I chose not to hang up. And the gentleman on the other and of the line asked me to repeat myself instead of hanging up on me. I obliged. After a moment of silence, I actually got an answer.

“Well, sir, I need the money.”

That was an unexpectedly candid admission, not that I was not aware of this basic truth. These callers, usually in boiler rooms somewhere in India or Pakistan, do this because they need to earn a living.

But it’s one thing to earn a living, it’s another to defraud vulnerable people, old ladies and whatnot. I told that much to this agent. He just repeated himself, defensively: “But I need the money.”

So I told him that I understand. That I, too, was a refugee once 30 years ago. (True.) But even when I had no money, I did not start defrauding people. I asked him to think about this, please; then thanked him and hung up.

Did I accomplish anything? I don’t know. Is it valid to compare my situation 30 years ago: granted, a refugee, but a refugee in a first world country (Austria) with no family to worry about and with guaranteed shelter and food at the Traiskirchen refugee camp, which I declined to take advantage of only because I found work (no fraud involved, but it’s true that I had no work permit) and I was able to afford better accommodations?

Yes, I read Les Misérables. No, I do not want the poor to be disproportionately punished, with no grace or mercy.

Still, I think there is an ethical line to be drawn here. No matter how great your need is, I still don’t think this moral justification applies when you work for a criminal enterprise, earning a living from defrauding vulnerable people halfway around the world.

Moments ago, Anderson Cooper made his opinion clear about a guest on his show who was defending Trump:

LOL. Well said, Anderson.

I am no photo artist, and my best camera is, well, my phone. That’s it.

Even so, a few minutes ago I felt compelled to take a couple of photographs. We are a few minutes away from sunset and a big storm just began. Then I looked out my window and I found the building across the street brighter than the sky above.

The light came from the other side of the sky. The Sun was not visible but the sky in that direction was bright enough to light things up.

Photographs (especially, photographs taken with a phone) really don’t do these sights justice. The contrasts were amazing.

In my copious amounts of free time (yeah, right) I’ve been playing with the second installment in the Metro 2033 game franchise, Metro Last Light. Like its predecessor, it is set in (or mostly, under) post-apocalyptic Moscow, in what remains of the tunnels of the Moscow Metro, with stations acting as city states, and the protagonist fighting mutants, aliens and human enemies alike.

My only complaint about these games is that the gameplay is very linear: you just advance the story, your actions do not alter it in any meaningful way, apart from contributing to the choice of ending that is shown after the final battle.

But the atmosphere of the game is brilliant. Brilliantly dark, that is. And the game is beautifully crafted.

Here is one example: midway through the game, you find yourself in a station named Venice, so called because it is half-flooded. (Or was it the station under the Bolshoi Theatre? Not sure.) As you wonder around, you encounter… a shadow play artist, entertaining a small group of children, showing shadows, some of which are quite recognizable as the monsters of the game.

This character plays no role in the story. You do not interact with it. It does not advance the game in any which way. It’s just… there. Because… well, what would a post-apocalyptic subway station be like without a shadow play artist?

It was when I encountered this scene that I became fully hooked by the atmosphere of the Metro games. This is no more just entertainment… this is a form of art.

Sergei Lavrov, Russia’s foreign minister, is in Washington today.

Reacting to a shouted question by a journalist, he felt it was appropriate to respond with a joke:

I am not even sure what words to use to characterize it. I think the video speaks for itself. Очень смешно, министр.

Not only is there severe flooding in our region (I’ve lived in Ottawa for nearly 30 years, and I’ve never seen anything remotely like this) but this “spring” weather is anything but.

In fact, yesterday CTV News almost apologized for their forecast:

And the saddest part? They were not wrong. I see flurries outside.

Fortunately, the flooding doesn’t affect us, despite our proximity to the Rideau River.

One of the major events during last year’s presidential campaign was the hacking of e-mails of the Democratic National Congress. In particular, the hacking of the e-mails of campaign chairman John Podesta.

How it happened is simple. Podesta received a bogus e-mail, purportedly from Google, that there was an unauthorized attempt to log in to his account, and that he should change his password. A helpful link in the form of a button was provided.

Podesta’s assistant was suspicious and asked for expert help. The expert inadvertently described the e-mail as “legitimate” (presumably, he meant to write “not legitimate” or “illegitimate”) but advised that Podesta should change his password, and provided the correct (Google) link for password changes.

The assistant forwarded the e-mail to Podesta, adding in her own words that “The gmail one is REAL”. This prompted Podesta to change his password… using the fraudulent link provided to him in the original message. By doing so, Podesta inadvertently disclosed his e-mail password to Russian hackers.

How do we know that they are Russian? There are many reasons to believe this to be the case, but I just noticed another peculiarity. (It is possible that I am not the first to notice this, of course.) Look at the subject line of the Podesta e-mails:

Now try searching for the word “Someone” on this page using your Web browser’s built-in search feature (hitting Control-F activates this feature in most browsers). Can you see (or rather not see) how nothing in this Subject line is highlighted?

That is because several of the o’s in this subject line were typed on a Cyrillic keyboard, and they are Cyrillic characters. A Cyrillic ‘о’ appears very much the same as a Latin ‘o’, but it has a different code (hexadecimal 043e as opposed to 006f):

Funny thing is… I got this subject line straight from Wikileaks. You know, the same Wikileaks who are protesting high and low that the e-mail dump is not from Russia. Yet on their very own Web site, the e-mails that resulted in the Podesta hack contain Cyrillic characters. Go figure.

I am watching a live interview on CNN with Hillary Clinton.

As I am listening to her eloquently chosen words and watch her classy demeanor, I am reminded of the thin-skinned, narcissistic, pussy-grabbing (his own words, not mine!) boor who currently occupies the White House and feel compelled to ask again from my American friends, especially those who still think that this sad misogynist is going to make America great “again”: What the fuck is wrong with you?

I sometimes take pictures of our cats.

Very rarely, the pictures are actually interesting. (I am no photo artist.)

This morning, I snapped a picture of our cats Kifli and Rufus, as they found a place on top of some Amazon shipping boxes.

What I didn’t expect is the effect of light, filtered through the blinds, on their fur, especially Rufus’s.

Here is today’s gem of a survey question from CTV Ottawa:

My answer is greenish-pink, with whipped cream.

(To their credit, a corrected question appears on their Web site.)

Remember what radio used to be like, especially shortwave?

Many stations had an interval signal. This signal, usually just a few musical notes, was played whenever the station would otherwise be silent (e.g., between the end of a program and the time signal at the top of the hour.) I remember many an interval signal fondly.

But one of them, I just cannot identify. Namely this one:

Bugs the devil out of me.

My current phone is a Nexus 6P.

I picked this phone for one all-important reason: It is a “pure Android” phone, directly supported by Google. Which means that instead of being at the manufacturer’s mercy when it comes to updates, I receive monthly security updates from Google. In this day and age, this is a deciding factor for me.

I got the phone in September. Sometime in the winter, I noticed that a speck appeared in photographs taken by the phone’s main camera.

Its appearance suggests that it is a small dust particle stuck between the camera visor and the camera itself, or inside the camera optics perhaps. Others apparently encountered the same issue. Some were able to shake the phone until the speck vanished. I tried to do the same but to no avail. Obviously I do not want to damage or destroy the phone.

I was trying to decide whether or not to live with it. A friend of mine suggested that I should contact the manufacturer since the phone is under warranty. I decided to do just that. Here is the exchange of e-mails that followed:

From: Viktor T. Toth
Sent: Tuesday, April 4, 2017 10:24 PM
Subject: Nexus 6P warranty issue

Greetings,

I obtained a Nexus 6P from Rogers Canada in September 2016.

A few months ago, I noticed that its camera developed a speck (see attached, lower right corner; the picture is of a uniformly illuminated white sheet of paper). Researching online, I found out that it is not an uncommon problem, and may be due to a loose dust particle inside the camera. Some people had luck shaking the speck lose. I tried gently tapping/shaking the phone, to no avail.

I also learned that this issue may be covered under warranty.

Please enlighten me if this is the case and, if so, how the warranty process works.

Sincerely,

Viktor Toth

Attachment: IMG_20170404_221736.jpg

Sent: Wednesday, April 5, 2017 2:41 PM
To: Viktor T. Toth
Subject: Nexus 6P black spot

Dear Mr. Toth, receive a warm greeting.

We widely appreciate the information you provided us, and gladly inform you that on the attachment you can find information concerning your inquiry.

Best regards.
C.B.W.

Attachment: Black spots on camara.pdf

From: Viktor T. Toth
Sent: Wednesday, April 5, 2017 3:17 PM
Subject: RE: Nexus 6P black spot

Dear Huawei support,

I thank you for your response but I find it quite unacceptable. If you had looked at the image that I sent to you, you would have seen that the “impurity spot” is actually about 100 pixels in diameter and very prominently noticeable in every picture that I take (attached enlarged, cropped image should also appear below):

If this is an acceptable impurity to you, I pity your customers. (This a crop from an actual photo of a white sheet of paper taken by the phone; I did not enlarge or manipulate it in any way.)

I also wonder if you perhaps misunderstood my inquiry and thought that I was referring to the display of the phone, as opposed to its main camera.

I’ll probably learn to live with this speck or attempt a repair. Your response as well as what I read online about your Canadian warranty support gives me little confidence that I can seek help from you.

However, I thank you for reminding me that when it comes to my next phone purchase, I should take into account the manufacturer’s support policy as well as the quality and capabilities of the device when I make my decision. The Nexus 6P may be a premium quality device, but your support perhaps isn’t.

Sincerely,

Viktor Toth

Sent: Wednesday, April 5, 2017 6:55 PM
To: Viktor T. Toth
Subject: Huawei Mail Support

Dear Mr. Toth.

We appreciate your preference, and deeply regret any inconvenience that you are experiencing with your Huawei device, however in order to correct this situation, in the attached file you will find a detailed answer to your question.

Best regards.
C.B.W.

From: Viktor T. Toth
Sent: Wednesday, April 5, 2017 8.02 PM
Subject: RE: Huawei Mail Support

I have not received an attachment in your response to my second inquiry.

Sincerely,

Viktor Toth

Sent: Thursday, April 6, 2017 12:43 PM
To: Viktor T. Toth
Subject: Huawei Mail Support

Dear Mr. Toth, receive a warm greeting.

We widely appreciate the information you provided us, and gladly inform you that on the attachment you can find information concerning your inquiry.

Best regards.
C.B.W.

Attachment: Service Center Information. Toth.pdf

Somehow, in light of this exchange, I do not feel particularly confident that it is a good idea to send in my phone for repair.

FYI, Huawei: The long-distance prefix in North America is 1, not 001.

I don’t often post pictures of my friends, but this time, I have my friend Perry’s permission.

Perry was flying west the other day. While waiting at the airport, he encountered a familiar face. The familiar face belonged to Canada’s Minister of National Defence, Harjit Singh Sajjan.

The Honourable Minister was probably flying back to his Vancouver riding, which he represents in Parliament.

Whatever the reason, the remarkable thing is this: Mr. Sajjan was traveling the same way most other Canadian would travel. On a commercial airliner, flying coach.

Let me repeat that, this time in boldface: Canada’s Minister of National Defence, traveling cross-country on a commercial airliner, flying coach.

I am so glad Mr. Sajjan allowed Perry to take this selfie, and that Perry kindly permitted me to repost it. This was not a moment designed for publicity. As far as I know, Mr. Sajjan does not publicize the manner in which he travels. He just… does the right thing.

And the other remarkable thing is that he can do this. It speaks volumes about our country and our government.

Donald Trump told us that if necessary, the US will act alone on North Korea.

In a discussion on this topic, a commentator on CNN remarked on the dangers of having to deal with a madman armed with nukes.

If I were in Kim Jong-un’s shoes, I’d worry about that, too.

Here is an old friend from the neighborhood that we have known for 12 years already, but whom we haven’t seen since October:

But today, he was outside, enjoying the warmth of the early spring sun.

Hello, MJ. It is so good to see you again.

Without further ado, this video sums up my thoughts for the day:

Retired counterintelligence officers rarely give interviews. It is even more unusual for them to do so without anonymity.

Yet this is exactly what Ferenc Katrein, a former Hungarian counterintelligence officer did, when he was interviewed by the independent Hungarian news portal index.hu.

The full interview is available in English.

Katrein tells us of a secret service offensive that is waged by Russia against the European Union. He speaks of a corrupt Hungarian leadership that offered an opportunity for many Russian citizens to enter and even settle in the country in return for a modest investment with little or no effective background checks. He speaks of the role of Russia in far right movements in Europe, and their campaigns of disinformation.

All in all, it is a rare glimpse into how a counterintelligence service works on the eastern fringes of the European Union, and the extraordinary challenges that Europe faces in light of an aggressive (and in many ways, unrestrained) Russian foreign policy agenda.

I saw this image of North Korea’s leader, Kim Jong-un earlier today on CNN:

The joy on these faces seems genuine. To think that an officer so forgot himself in that moment of celebration, he actually jumped onto the shoulders of the country’s all-powerful leader!

What they were celebrating was the successful test firing of a new rocket engine.

But what this picture reveals, the genuine joy on these faces, suggests something much worse: namely that North Korea’s leaders may truly believe their own propaganda. They may truly believe that governing via a totalitarian regime is the right thing to do. That sinking money into a gigantic but, in many ways, very backward military is the right thing to do. That pissing off the United States is the right thing to do.

And thus, self-fulfilling prophecies are born. North Korea may think that it is defending itself from US aggression. But they do not seem to realize that it is precisely their stance and their weapons program that make them a subject of US threats and sanctions.

And they especially don’t seem to realize that with a genuinely unhinged leadership in the White House, further provocation may achieve the exact opposite of what they want: Instead of being able to preserve the regime, they might see it come to an hasty end as Washington decides to intervene after all, leading to a tremendous loss of life no matter the outcome.

Recently, I answered a question on Quora on the possibility that we live in a computer simulation.

Apparently, this is a hot topic. The other day, there was an essay on it by Sabine Hossenfelder.

I agree with Sabine’s main conclusion, as well as her point that “the programmer did it” is no explanation at all: it is just a modern version of mythology.

I also share her frustration, for instance, when she reacts to the nonsense from Stephen Wolfram about a “whole civilization” “down at the Planck scale”.

Sabine makes a point that discretization of spacetime might conflict with special relativity. I wonder if the folks behind doubly special relativity might be inclined to offer a thought or two on this topic.

In any case, I have another reason why I believe we cannot possibly live in a computer simulation.

My argument hinges on an unproven conjecture: My assumption that scalable quantum computing is really not possible because of the threshold theorem. Most supporters of quantum computing believe, of course, that the threshold theorem is precisely what makes quantum computing possible: if an error-correcting quantum computer reaches a certain threshold, it can emulate an arbitrary precision quantum computer accurately.

But I think this is precisely why the threshold will never be reached. One of these days, someone will prove a beautiful theorem that no large-scale quantum computer will ever be able to operate above the threshold, hence scalable quantum computing is just not possible.

Now what does this have to do with us living in a simulation? Countless experiments show that we live in a fundamentally quantum world. Contrary to popular belief (and many misguided popularizations) it does not mean a discretization at the quantum level. What it does mean is that even otherwise discrete quantities (e.g., the two spin states of an electron) turn into continuum variables (the phase of the wavefunction).

This is precisely what makes a quantum computer powerful: like an analog computer, it can perform certain algorithms more effectively than a digital computer, because whereas a digital computer operates on the countable set of discrete digits, a quantum or analog computer operates with the uncountable infinite of states offered by continuum variables.

Of course a conventional analog computer is very inaccurate, so nobody seriously proposed that one could ever be used to factor 1000-digit numbers.

This quantum world in which we live, with its richer structure, can be simulated only inefficiently using a digital computer. If that weren’t the case, we could use a digital computer to simulate a quantum computer and get on with it. But this means that if the world is a simulation, it cannot be a simulation running on a digital computer. The computer that runs the world has to be a quantum computer.

But if quantum computers do not exist… well, then they cannot simulate the world, can they?

Two further points about this argument. First, it is purely mathematical: I am offering a mathematical line of reasoning that no quantum universe can be a simulated universe. It is not a limitation of technology, but a (presumed) mathematical truth.

Second, the counterargument has often been proposed that perhaps the simulation is set up so that we do not get to see the discrepancies caused by inefficient simulation. I.e., the programmer cheats and erases the glitches from our simulated minds. But I don’t see how that could work either. For this to work, the algorithms employed by the simulation must anticipate not only all the possible ways in which we could ascertain the true nature of the world, but also assess all consequences of altering our state of mind. I think it quickly becomes evident that this really cannot be done without, well, simulating the world correctly, which is what we were trying to avoid… so no, I do not think it is possible.

Of course if tomorrow, someone announces that they cracked the threshold theorem and full-scale, scalable quantum computing is now reality, my argument goes down the drain. But frankly, I do not expect that to happen.

Chemistry is weird. Even in inorganic chemistry, there are some really strange compounds. There is, for instance, phosphotungstic acid: $${\rm H}_3{\rm P}{\rm W}_{12}{\rm O}_{40}$$. Never heard of it until today.

And then there is this one (if it exists at all):

Somebody posted this on Google+. They wanted to know what its properties are. And now, so do I. There are a few tungsten compounds listed in online databases, but this is not one of them. Does it even exist? I don’t know. For some reason, I expect it to have properties not unlike those of tungsten carbide, but I could be completely off the mark.


text:
Article

Full entry | PDF   (0.2 MB)
Keywords:
one-sided weights; one-sided singular integrals
Summary:
We prove weighted inequalities for commutators of one-sided singular integrals (given by a Calder'on-Zygmund kernel with support in $(-\infty, 0)$) with BMO functions. We give the one-sided version of the results in C. Pérez, Sharp estimates for commutators of singular integrals via iterations of the Hardy-Littlewood maximal function, J. Fourier Anal. Appl., vol. 3 (6), 1997, pages 743–756 and C. Pérez, Endpoint estimates for commutators of singular integral operators, J. Funct. Anal., vol 128 (1), 1995, pages 163–185. We improve these results for one-sided singular integrals by putting in the right hand side of the inequalities a smaller operator and a wider class of weights.
References:
Aimar H., Forzani L., Martín-Reyes F.J.: On weighted inequalities for one-sided singular integrals. Proc. Amer. Math. Soc. 125 (1997), 2057-2064. MR 1376747
Bennett C., Sharpley R.: Interpolation of Operators. Academic Press, New York, 1988. MR 0928802 | Zbl 0647.46057
Coifman R.: Distribution function inequalities for singular integrals. Proc. Acad. Sci. USA 69 (1972), 2838-2839. MR 0303226 | Zbl 0243.44006
Coifman R., Rochberg R., Weiss G.: Factorization theorems for Hardy spaces in several variables. Ann. of Math. 103 (2) (1976), 611-635. MR 0412721 | Zbl 0326.32011
Martín-Reyes F.J., Pick L., de la Torre A.: $A_{\infty}^+$ condition. Canad. J. Math. 45 (1993), 1231-1244. MR 1247544
Martín-Reyes F.J., de la Torre A.: One sided ${BMO}$ spaces. J. London Math. Soc. (2) 49 (1994), 529-542. MR 1271548
O'Neil R.: Fractional integration in Orlicz spaces. Trans. Amer. Math. Soc. 115 (1963), 300-328.
Pérez C.: Weighted norm inequalities for singular integral operators. J. London Math. Soc. 49 (1994), 296-308. MR 1260114
Pérez C.: Sharp estimates for commutators of singular integrals via iterations of the Hardy-Littlewood maximal function. J. Fourier Anal. Appl. 3 (6) (1997), 743-756. MR 1481632
Pérez C.: Endpoint estimates for commutators of singular integral operators. J. Funct. Anal. 128 1 (1995), 163-185. MR 1317714
Pérez C.: On sufficient conditions for the boundedness of the Hardy-Littlewood maximal operator between weighted $L^p$-spaces with different weights. Proc. London Math. Soc. 71 (3) (1995), 135-157. MR 1327936
Riveros M.S., de Rosa L., de la Torre A.: Sufficient conditions for one-sided operators. J. Fourier Anal. Appl 6 (6) (2000), 607-621. MR 1790246 | Zbl 0984.42010
Sawyer E.T.: Weighted inequalities for the one-sided Hardy-Littlewood maximal functions. Trans. Amer. Math. Soc. 297 (1986), 53-61. MR 0849466 | Zbl 0627.42009
Wilson J.M.: Weighted norm inequalities for the continuous square functions. Trans. Amer. Math. Soc. 314 (1989), 661-692. MR 0972707 | Zbl 0689.42016

Partner of

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text:
### Just Rolling Round

P is a point on the circumference of a circle radius r which rolls, without slipping, inside a circle of radius 2r. What is the locus of P?

### Just Opposite

A and C are the opposite vertices of a square ABCD, and have coordinates (a,b) and (c,d), respectively. What are the coordinates of the vertices B and D? What is the area of the square?

### Building Tetrahedra

Can you make a tetrahedron whose faces all have the same perimeter?

# Coke Machine

##### Age 14 to 16Challenge Level

This is another tough nut and perhaps the diagram of the 50p piece will help.

A 50 pence piece is a 7 sided polygon ABCDEFG with rounded edges, obtained by replacing the straight line DE with an arc centred at A and radius AE; replacing the straight line EF with an arc centred at B radius BF ...etc..

The 50p piece can roll in the same chute as a disc of radius $r$. Suppose the seven arcs forming the edge of the 50p piece (the arcs AB, BC etc. ) all have radius $R$ (where $R$=AD=AE=BE=BF...) then you need to find $R$ in terms of $r$. These seven arcs subtend angles of $2\pi /7$ at the centre of the disc and $2\pi /14$ at the opposite edge.


text:
# Weaviate#

One can use Weaviate as the document store for DocumentArray. It is useful when one wants to have faster Document retrieval on embeddings, i.e. .match(), .find().

Tip

This feature requires weaviate-client. You can install it via pip install "docarray[weaviate]".

Here is a video tutorial that guides you to build a simple image search using Weaviate and Docarray.

## Usage#

### Start Weaviate service#

To use Weaviate as the storage backend, it is required to have the Weaviate service started. Create docker-compose.yml as follows:

---
version: '3.4'
services:
weaviate:
command:
- --host
- 0.0.0.0
- --port
- '8080'
- --scheme
- http
image: semitechnologies/weaviate:1.11.0
ports:
- "8080:8080"
restart: on-failure:0
environment:
QUERY_DEFAULTS_LIMIT: 25
AUTHENTICATION_ANONYMOUS_ACCESS_ENABLED: 'true'
PERSISTENCE_DATA_PATH: '/var/lib/weaviate'
DEFAULT_VECTORIZER_MODULE: 'none'
ENABLE_MODULES: ''
CLUSTER_HOSTNAME: 'node1'
...

Then

docker compose up

### Create DocumentArray with Weaviate backend#

Assuming service is started using the default configuration (i.e. server address is http://localhost:8080), one can instantiate a DocumentArray with Weaviate storage as such:

from docarray import DocumentArray

da = DocumentArray(storage='weaviate')

The usage would be the same as the ordinary DocumentArray.

To access a DocumentArray formerly persisted, one can specify the name, the host, the port and the protocol to connect to the server. name is required in this case but other connection parameters are optional. If they are not provided, then it will connect to the Weaviate service bound to http://localhost:8080.

Note, that the name parameter in config needs to be capitalized.

from docarray import DocumentArray

da = DocumentArray(
storage='weaviate', config={'name': 'Persisted', 'host': 'localhost', 'port': 1234}
)

da.summary()

Other functions behave the same as in-memory DocumentArray.

## Config#

The following configs can be set:

Name Description Default
host Hostname of the Weaviate server 'localhost'
port port of the Weaviate server 8080
protocol protocol to be used. Can be 'http' or 'https' 'http'
name Weaviate class name; the class name of Weaviate object to presesent this DocumentArray None
serialize_config Serialization config of each Document None
ef The size of the dynamic list for the nearest neighbors (used during the search). The higher ef is chosen, the more accurate, but also slower a search becomes. None, defaults to the default value in Weaviate*
ef_construction The size of the dynamic list for the nearest neighbors (used during the construction). Controls index search speed/build speed tradeoff. None, defaults to the default value in Weaviate*
timeout_config Set the timeout configuration for all requests to the Weaviate server. None, defaults to the default value in Weaviate*
max_connections The maximum number of connections per element in all layers. None, defaults to the default value in Weaviate*
dynamic_ef_min If using dynamic ef (set to -1), this value acts as a lower boundary. Even if the limit is small enough to suggest a lower value, ef will never drop below this value. This helps in keeping search accuracy high even when setting very low limits, such as 1, 2, or 3. None, defaults to the default value in Weaviate*
dynamic_ef_max If using dynamic ef (set to -1), this value acts as an upper boundary. Even if the limit is large enough to suggest a lower value, ef will be capped at this value. This helps to keep search speed reasonable when retrieving massive search result sets, e.g. 500+. None, defaults to the default value in Weaviate*
dynamic_ef_factor If using dynamic ef (set to -1), this value controls how ef is determined based on the given limit. E.g. with a factor of 8, ef will be set to 8*limit as long as this value is between the lower and upper boundary. It will be capped on either end, otherwise. None, defaults to the default value in Weaviate*
vector_cache_max_objects For optimal search and import performance all previously imported vectors need to be held in memory. However, Weaviate also allows for limiting the number of vectors in memory. By default, when creating a new class, this limit is set to 2M objects. A disk lookup for a vector is orders of magnitudes slower than memory lookup, so the cache should be used sparingly. None, defaults to the default value in Weaviate*
flat_search_cutoff Absolute number of objects configured as the threshold for a flat-search cutoff. If a filter on a filtered vector search matches fewer than the specified elements, the HNSW index is bypassed entirely and a flat (brute-force) search is performed instead. This can speed up queries with very restrictive filters considerably. Optional, defaults to 40000. Set to 0 to turn off flat-search cutoff entirely. None, defaults to the default value in Weaviate*
cleanup_interval_seconds How often the async process runs that “repairs” the HNSW graph after deletes and updates. (Prior to the repair/cleanup process, deleted objects are simply marked as deleted, but still a fully connected member of the HNSW graph. After the repair has run, the edges are reassigned and the datapoints deleted for good). Typically this value does not need to be adjusted, but if deletes or updates are very frequent it might make sense to adjust the value up or down. (Higher value means it runs less frequently, but cleans up more in a single batch. Lower value means it runs more frequently, but might not be as efficient with each run). None, defaults to the default value in Weaviate*
skip There are situations where it doesn’t make sense to vectorize a class. For example if the class is just meant as glue between two other class (consisting only of references) or if the class contains mostly duplicate elements (Note that importing duplicate vectors into HNSW is very expensive as the algorithm uses a check whether a candidate’s distance is higher than the worst candidate’s distance for an early exit condition. With (mostly) identical vectors, this early exit condition is never met leading to an exhaustive search on each import or query). In this case, you can skip indexing a vector all-together. To do so, set "skip" to "true". skip defaults to false; if not set to true, classes will be indexed normally. This setting is immutable after class initialization. None, defaults to the default value in Weaviate*

*You can read more about the HNSW parameters and their default values here

## Minimum Example#

The following example shows how to use DocArray with Weaviate Document Store in order to index and search text Documents.

First, let’s run the create the DocumentArray instance (make sure a Weaviate server is up and running):

from docarray import DocumentArray

da = DocumentArray(
storage="weaviate", config={"name": "Persisted", "host": "localhost", "port": 8080}
)

Then, we can index some Documents:

from docarray import Document

da.extend(
[
Document(text='Persist Documents with Weaviate.'),
Document(text='And enjoy fast nearest neighbor search.'),
Document(text='All while using DocArray API.'),
]
)

Now, we can generate embeddings inside the database using BERT model:

from transformers import AutoModel, AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained('bert-base-uncased')
model = AutoModel.from_pretrained('bert-base-uncased')

def collate_fn(da):

da.embed(model, collate_fn=collate_fn)

Finally, we can query the database and print the results:

results = da.find(
DocumentArray([Document(text='How to persist Documents')]).embed(
model, collate_fn=collate_fn
),
limit=1,
)

print(results[0].text)

Persist Documents with Weaviate.


text:
How do you simplify (8sqrt[6] + 3sqrt[2])(4sqrt[6] – 5sqrt[2])?

Dec 1, 2017

Use binomial multiplication (FOIL)

Explanation:

Going directly to the solution and not rewriting the problem, binomial multiplication gives:

$8 \sqrt{6} \cdot 4 \sqrt{6} - 8 \sqrt{6} \cdot 5 \sqrt{2} + 3 \sqrt{2} \cdot 4 \sqrt{6} - 3 \sqrt{2} \cdot 5 \sqrt{2}$

Simplifying:
$32 {\sqrt{6}}^{2} - 40 \sqrt{12} + 12 \sqrt{12} - 15 {\sqrt{2}}^{2}$

Next:
$32 \cdot 6 - 28 \sqrt{12} - 15 \cdot 2$

$192 - 28 \sqrt{12} - 30$

$162 - 28 \sqrt{12}$

Then simplify $\sqrt{12} = \sqrt{4 \cdot 3} = 2 \sqrt{3}$

So, $162 - 28 \cdot 2 \sqrt{3} = 162 - 56 \sqrt{3}$


text:
# How does a photo detector detect?

1. Apr 16, 2006

### einstein2603

How does a photo detector detect? Can you also tell me where you got the info from.

thanks

einstein2603

2. Apr 16, 2006

### Hootenanny

Staff Emeritus
Hello again einstein,

All 'photodetectors' operate using the photoelectric effect (or variants of). Basically, the photoelectric effect can be explained using quantum physics. Have you heard of the wave-particle duality of light? The photoelectric effect was the first source of firm evidence for the particle nature of light. Basically, light can be considered as a massless particle called the photon which has an energy of $E = hf$. This site is very useful and should have all the information you need. If you have any questions, you can post them here

http://hyperphysics.phy-astr.gsu.edu/hbase/quacon.html#quacon

Regards,
~Hoot

3. Apr 16, 2006

### andrevdh

Basically the photons causes the material that it falls on to become conductive - electrons (or their counterparts - holes) are generated (freed) from their bound states and become part of the sea of free charges that can flow in the material - that is the charge carriers are raised to a higher energy level by absorbing the energy from the photon. This increase in conductivity is sensed as an increase in current through the detector by a circuit connected to it. See for instance http://en.wikipedia.org/wiki/Photodiode

Last edited: Apr 16, 2006


text:
# Log mean temperature difference

Log mean temperature difference

The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems (most notably in heat exchangers). The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger. The use of the LMTD arises straightforwardly from the analysis of a heat exchanger with constant flow rate and fluid thermal properties.

For Countercurrent flow (i.e. where the hot stream, liquid or gas, goes from say left to right, and the cold stream, again liquid or gas goes from right to left), is given by the following equation:

:$LMTD=frac\left\{\left(T_1-t_2\right)-\left(T_2-t_1\right)\right\}\left\{lnfrac\left\{\left(T_1-t_2\right)\right\}\left\{\left(T_2-t_1\right)$

And for Parallel flow (i.e. where the hot stream,nliquid or gas, goes from say left to right, and so does the cold stream), is given by the following equation:

:$LMTD=frac\left\{\left(T_1-t_1\right)-\left(T_2-t_2\right)\right\}\left\{lnfrac\left\{\left(T_1-t_1\right)\right\}\left\{\left(T_2-t_2\right)$

:$T_1=$Hot Stream Inlet Temp. :$T_2=$Hot Stream Outlet Temp.

:$t_1=$Cold Stream Inlet Temp. :$t_2=$Cold Stream Outlet Temp.

It makes no difference which temperature differential is 1 or 2 as long as the nomenclature is consistent.The larger the LMTD, the more heat is transferred.

Yet a third type of unit is a cross-flow exchanger, in which one system (usually the heat sink) has the same nominal temperature at all points on the heat transfer surface. This follows similar mathematics, in its dependence on the LMTD, except that a correction factor F often needs to be included in the heat transfer relationship.

There are times when the four temperatures used to calculate the LMTD are not available, and the NTU method may then be preferable.

Derivation

Assume heat transfer is occurring between two fluids ($T_1$ and $T_2$) with a temperature "difference" of $Delta T\left(A\right)$ at point A and $Delta T\left(B\right)$ at point B (where $Delta T\left(z\right)=T_2\left(z\right)-T_1\left(z\right)$). The direction of fluid flow does not need to be considered. Since LMTD is the "average" temperature difference of the two streams between points A and B the following formula defines LMTD:

:$LMTD=frac\left\{int^\left\{B\right\}_\left\{A\right\} Delta T\left(z\right),dz\right\}\left\{int^\left\{B\right\}_\left\{A\right\},dz\right\}$ where $z$ is the distance parallel to the motion of the two fluids.

The rate of change of the temperature of the two fluids, $T_1$ and $T_2$ respectively, is proportional to the temperature difference between the two fluids:

:$frac\left\{dT_1\right\}\left\{dz\right\}=k_a \left(T_1\left(z\right)-T_2\left(z\right)\right)=-k_aDelta T\left(z\right)$

:$frac\left\{dT_2\right\}\left\{dz\right\}=k_b \left(T_2\left(z\right)-T_1\left(z\right)\right)=k_bDelta T\left(z\right)$

Therefore:

:$frac\left\{d\left(Delta T\right)\right\}\left\{dz\right\}=frac\left\{d\left(T_2-T_1\right)\right\}\left\{dz\right\}=frac\left\{dT_2\right\}\left\{dz\right\}-frac\left\{dT_1\right\}\left\{dz\right\}=KDelta T\left(z\right)$ where $K=k_a+k_b$

This gives us a value for $dz$:

:$dz=frac\left\{1\right\}\left\{K\right\},frac\left\{d\left(Delta T\right)\right\}\left\{Delta T\right\}$

Substituting back into our formula for LMTD:

:$LMTD=frac\left\{int^\left\{B\right\}_\left\{A\right\} Delta T\left(z\right),dz\right\}\left\{int^\left\{B\right\}_\left\{A\right\},dz\right\}=frac\left\{int^\left\{Delta T\left(B\right)\right\}_\left\{Delta T\left(A\right)\right\} frac\left\{1\right\}\left\{K\right\},d\left(Delta T\right)\right\}\left\{int^\left\{Delta T\left(B\right)\right\}_\left\{Delta T\left(A\right)\right\} frac\left\{1\right\}\left\{K\right\},frac\left\{d\left(Delta T\right)\right\}\left\{Delta T$

Integrating gives:

:$LMTD=frac\left\{int^\left\{Delta T\left(B\right)\right\}_\left\{Delta T\left(A\right)\right\} frac\left\{1\right\}\left\{K\right\},d\left(Delta T\right)\right\}\left\{int^\left\{Delta T\left(B\right)\right\}_\left\{Delta T\left(A\right)\right\} frac\left\{1\right\}\left\{K\right\},frac\left\{d\left(Delta T\right)\right\}\left\{Delta T=frac\left\{Delta T\right] ^\left\{Delta T\left(B\right)\right\}_\left\{Delta T\left(A\right)\left\{ln\left\{Delta T\right\}\right] ^\left\{Delta T\left(B\right)\right\}_\left\{Delta T\left(A\right)=frac\left\{Delta T\left(B\right)-Delta T\left(A\right)\right\}\left\{ln\left(frac\left\{Delta T\left(B\right)\right\}\left\{Delta T\left(A\right)\right\}\right)\right\}$

Trivial case:

:$\left\{Delta T\left(z\right) = C\right\}$ for all $z$

:$LMTD=frac\left\{int^\left\{B\right\}_\left\{A\right\} Delta T\left(z\right),dz\right\}\left\{int^\left\{B\right\}_\left\{A\right\},dz\right\}=frac\left\{Cint^\left\{B\right\}_\left\{A\right\},dz\right\}\left\{int^\left\{B\right\}_\left\{A\right\},dz\right\}=C$

Assumptions

It has been assumed that the rate of change for the temperature of both fluids is proportional to the temperature difference; this assumption is valid for fluids with a constant specific heat, which is a good description of fluids changing temperature over a relatively small range. However, if the specific heat changes, the LMTD approach will no longer be accurate.

A particular case where the LMTD is not applicable are condensers and reboilers, where the latent heat associated to phase change makes the hypothesis invalid.

References

Kay J M & Nedderman R M (1985) "Fluid Mechanics and Transfer Processes", Cambridge University Press

Simple LMTD calculator: http://www.fridgetech.com/calculators/lmtd2.html

Advanced LMTD calculator: http://www.chemsof.com/lmtd/lmtd.htm

Wikimedia Foundation. 2010.

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text:
# Which of the following is used to manage Data Base ?

1. Operating System
2. Compiler
3. DBMS
4. None of the above

Option 3 : DBMS

## Detailed Solution

Key Points

• A Database is an organized collection of data so that it can be easily accessed and managed.
• DBMS stands for Database Management System.
• A Database Management System (DBMS) is software designed to store, retrieve, define, and manage data in a database.
• Database Management System removes redundancy and Integrity.
• Database Management System reduces Application Development Time.
• DBMS follows the concepts of Atomicity, Consistency, Isolation, and Durability (normally shortened as ACID).
• DBMS supports a multi-user environment and allows them to access and manipulate data in parallel.
• Types of DBMS Systems are:
• Hierarchical Database
• Network Database
• Relational Database
• Object-Oriented Database
• The three-schema architecture of DBMS:

• Some popular DBMS systems:
• MySQL
• Microsoft Access
• Oracle
• LibreOffice Base
• Microsoft SQL Server

Important Points

• In 1960, Charles Bachman designed the first DBMS system.
• In 1970, Codd introduced IBM'S Information Management System (IMS)
• In 1976, Peter Chen coined and defined the Entity-relationship model also know as the ER model.
• In 1991, Microsoft ships MS Access, a personal DBMS and that displaces all other personal DBMS products.

• Operating System
• An operating system acts as an intermediary between the user of a computer and computer hardware.
• Operating systems were first developed in the late 1950s to manage tape storage.
• The General Motors Research Lab implemented the first OS in the early 1950s for their IBM 701.
• Operating System allows disk access and file systems Device drivers Networking Security.
• Operating System Handling I/O operations.
• Operating System has error detection and handling technic.
• An Operating System is concerned with the allocation of resources and services, such as memory, processors, devices, and information.
• The Kernel is the central component of a computer operating system.
• Compiler
• The compiler translates source code written in a high-level language into a set of machine-language.
• Compilers are very large programs, with error-checking and other abilities.
• The object code is machine code that the processor can perform one instruction at a time.
• The first Autocode and compiler in the modern sense were developed by Alick Glennie in 1952.
• John W. Backus at IBM introduced the first commercially available compiler, in 1957.

# In C language a Union member variable is generally accessed using the:

1. comma operator
3. dot operator
4. ternary operator

Option 3 : dot operator

## Detailed Solution

The correct answer is dot operator.

• Concept:
• A union is a user-defined type similar to structs in C except for one key difference. Structs allocate enough space to store all its members wheres unions allocate the space to store only the largest member.
• We use .(dot) operator to access the member of union

# “Structure of database” is known as _______.

1. Attribute
2. Entity
3. Schema
4. All
5. None of these

Option 3 : Schema

## Detailed Solution

• database schema is the skeleton structure that represents the logical view of the entire database. It defines how the data is organized and how the relations among them are associated. It formulates all the constraints that are to be applied to the data.
• database schema defines its entities and the relationship among them. It contains a descriptive detail of the database, which can be depicted by means of schema diagrams. It’s the database designers who design the schema to help programmers understand the database and make it useful.
• A database schema can be divided broadly into two categories −
• Physical Database Schema − This schema pertains to the actual storage of data and its form of storage like files, indices, etc. It defines how the data will be stored in secondary storage.
• Logical Database Schema − This schema defines all the logical constraints that need to be applied to the data stored. It defines tables, views, and integrity constraints.

# In C Programming a function can return:

1. Double value
2. Single value
3. As many as values
4. No value

Option 2 : Single value

## Detailed Solution

The correct answer is Single value.

Concept:

A function in C can be called either with arguments or without arguments.

• Always, Only one value can be returned from a function.
• If you try to return more than one value from a function, only one value will be returned that appears at the rightmost place of the return statement.
• For example, if you use “return a,b,c” in your function, value for c only will be returned, and values a, b won’t be returned to the program.

# ______ constraint ensures that no two 'rows' have same value in specified column / columns

1. All option are wrong
2. Check
3. Unique
4. Default

Option 3 : Unique

## Detailed Solution

Concept

CHECK

The CHECK constraint is used to limit the value range that can be placed in a column.

UNIQUE

The UNIQUE constraint ensures that no two 'rows' have the same value in specified column/columns.

DEFAULT

The DEFAULT constraint is used to provide a default value for a column.

# 53 in 2's complement form is?

1. 1001011
2. 001011
3. 001010
4. 011010

Option 2 : 001011

## Detailed Solution

Concept:

The binary equivalent for 53 is 110101

The 1's complement of the given binary digit will be:

110101 → 001010

Adding 1 to the above, we get the 2's complement as:

001010 → 001011

Hence the correct answer is Option 2

1's complement of Binary: 1's complement of a Binary number is defined by the value obtained by inverting all the bit, i.e, 0 as 1 and 1 as 0.

2's complement of Binary: It is the sum of 1's complement of Binary number and 1 to the least significant bit (LSB).

∴ 2's complement = 1's complement + 1 (LSB)

# The Correct order of SQL expression is

1. Select, group by, where, having
2. Select, having, group by, where
3. Select, having, where, group by
4. Select, where, group by, having

Option 4 : Select, where, group by, having

## Detailed Solution

The correct answer is Select, where, group by, having.

Six Operations to Order: SELECT, FROM, WHERE, GROUP BY, HAVING, and ORDER BY. Because the database executes query components in a specific order,

SELECT select_list [ INTO new_table ]  [ FROM table_source ]

[ WHERE search_condition ]

[ GROUP BY group_by_expression ]

[ HAVING search_condition ]

[ ORDER BY order_expression [ ASC | DESC ] ]

Hence Option 4 is correct

# FTP stands for

1. File  Translate Protocol
2. File Transit Protocol
3. File Tying Protocol
4. File Transfer Protocol

Option 4 : File Transfer Protocol

## Detailed Solution

The correct answer is File Transfer Protocol.

Key Points

• File Transfer Protocol:
• The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network.
• FTP is built on a client–server model architecture using separate control and data connections between the client and the server.
• FTP users may authenticate themselves with a clear-text sign-in protocol, normally in the form of a username and password, but can connect anonymously if the server is configured to allow it.
• For secure transmission that protects the username and password, and encrypts the content, FTP is often secured with SSL/TLS (FTPS) or replaced with SSH File Transfer Protocol (SFTP).

• FTP may run in active or passive mode, which determines how the data connection is established.
• This sense of "mode" is different from that of the MODE command in the FTP protocol, and corresponds to the PORT/PASV/EPSV commands instead.
• In both cases, the client creates a TCP control connection from a random, usually an unprivileged, port N to the FTP server command port 21.
• In active mode, the client starts listening for incoming data connections from the server on port M.
• It sends the FTP command PORT M to inform the server on which port it is listening.
• The server then initiates a data channel to the client from its port 20, the FTP server data port.
• In situations where the client is behind a firewall and unable to accept incoming TCP connections, passive mode may be used.
• In this mode, the client uses the control connection to send a PASV command to the server and then receives a server IP address and server port number from the server, which the client then uses to open a data connection from an arbitrary client port to the server IP address and server port number received.
• Both modes were updated in September 1998 to support IPv6.
• Further changes were introduced to the passive mode at that time, updating it to extended passive mode.

# To collect information and store them in computer in more than one interlinked files is called  _________.

1. data cleaner
2. data managing
3. data logging
4. data storing

Option 2 : data managing

## Detailed Solution

Concept:

Data Managing

Data management is the process of collecting, organizing, protecting, and storing an organization's data so it can be analyzed for decisions making. As organizations create and consume data at unprecedented rates, data management solutions become essential for making sense of the vast quantities of data. The goal of data management is to help people, organizations, and connected things, optimize the use of data within the bounds of policy and regulation so that they can make decisions and take actions that maximize the benefit to the organization

Therefore Option 2 is correct

Data Logging

Data logging is a collection of data over time. It is often used in scientific experiments and can monitor a process using sensors linked to a computer. Most data logging can be done automatically

Data Cleaner

Data cleaning is the process of detecting and correcting corrupt or inaccurate records from a record set, table, or database and refers to identifying incomplete, incorrect, inaccurate, or irrelevant parts of the data and then replacing, modifying, or deleting the dirty or coarse data.

Data Storing

Data storage refers to the use of recording media to retain data using computers or other devices. The most prevalent forms of data storage are file storage, block storage, and object storage, with each being ideal for different purposes.

# An application system analyst is concerned about all of the database at the ______ level.

1. Logical
2. Internal
3. Physical
4. All options are wrong

Option 1 : Logical

## Detailed Solution

There are mainly three levels of database

• Internal Level
• Conceptual Level
• External level

Internal Level

It is also called the Physical Level. It defines the physical storage structure of the database

Conceptual Level

It is also called Logical Level describes the Database structure of the whole database for the community of users. It Defines all database entities, their attributes, and their relationships It also takes care of Security and integrity information. Application System Analyst is concerned about the Logical level

External Level:

It is also known as View Level. It describes the part of the database in which a specific user is interested

# Developing database and maintaining standards and controls for an organization’s databases is called

1. End user database
2. Hypermedia database
3. Data resource management

## Detailed Solution

Concept:

Database administration is an important function in any organization that is dependent on one or more databases.

The primary role of database administration is to ensure maximum uptime for the database so that it is always available when needed. This will typically involve proactive periodic monitoring and troubleshooting.

• Database backup and recovery
• Database backout
• Monitoring databases
• Tuning databases
• Modifying databases
• Converting database types

# Which of the following is an advantage of view in databases?

1. Data security
2. Hiding of complex queries
3. Derived columns
4. All of the above

Option 4 : All of the above

## Detailed Solution

The Correct Answer is "All of the above".

Important Points

• Security
• Each user can be given permission to access the database only through a small set of views that contain the specific data the user is authorized to see, thus restricting the user's access to stored data.
• Query Simplicity
• A view can draw data from several different tables and present it as a single table, turning multi-table queries into single-table queries against the view.
• Structural simplicity
• Views can give a user a "personalized" view of the database structure, presenting the database as a set of virtual tables that make sense for that user.
• Consistency
• A view can present a consistent, unchanged image of the structure of the database, even if the underlying source tables are split, restructured, or renamed.
• Data Integrity
• If data is accessed and entered through a view, the DBMS can automatically check the data to ensure that it meets the specified integrity constraints.
• Logical data independence.
•  The view can make the application and database tables to a certain extent independent. If there is no view, the application must be based on a table. With the view, the program can be established in view of above, to view the program with a database table to be separated.

• Performance
• Views create the appearance of a table, but the DBMS must still translate queries against the view into queries against the underlying source tables. If the view is defined by a complex, multi-table query then simple queries on the views may take considerable time.
• Update restrictions
• When a user tries to update rows of a view, the DBMS must translate the request into an update on rows of the underlying source tables. This is possible for simple views, but more complex views are often restricted to read-only.

Key Points

• View is the simple subset of the table which is stored logically in a database means a view is a virtual table in the database whose contents are defined by a query.
• To the database user, the view appears just like a real table, with a set of named columns and rows of data. SQL creates the illusion of the view by giving the view a name as a table name and storing the definition of the view in the database.

# In Boolean Algebra this is a law of De-Morgan's Theorem:

1. AB + AC = (A + C) (A + B)
2. A+A.B=A
3. $$\overline {AB} = \overline A + \overline B$$
4. A.1=A

Option 3 : $$\overline {AB} = \overline A + \overline B$$

## Detailed Solution

The correct answer is $$\overline {AB} = \overline A + \overline B$$

De Morgan’s first theorem:

According to De Morgan’s first theorem, a NOR gate is equivalent to a bubbled AND gate.

The Boolean expressions for the bubbled AND gate can be expressed by the equation shown below.

$$\overline {A + B} = \bar A.\bar B$$

De Morgan’s second theorem:

According to De Morgan’s first theorem, a NAND gate is equivalent to a bubbled OR gate.

The Boolean expressions for the bubbled OR gate can be expressed by the equation shown below.

$$\overline {A.B} = \bar A + \bar B$$

Therefore Option 3 is correct

# If the sequence of operation - push(1), push(2), pop, push(1), push(2), pop, pop, pop, push(2), pop are performed on stack, the sequence of popped out values are:

1. 2,2,1,1,2
2. 2,2,2,1,1
3. 2,2,1,2,2
4. 2,2,1,2,1

Option 1 : 2,2,1,1,2

## Detailed Solution

The pop sequence can be seen from the following table:

 Operation Stack Pop Push 1 1 Push 2 1, 2 Pop 1 2 Push 1 1, 1 Push 2 1, 1, 2 Pop 1, 1 2,2 Pop 1 2,2,1 Pop Empty 2,2,1,1 Push 2 2 Pop Empty 2,2,1,1,2

# Data bases that support the major business process of an organization are

1. Direct database access
2. Operational database
3. Data warehouse

Option 2 : Operational database

## Detailed Solution

Concept:

Operational databases are described as databases that store detailed data needed to support the business processes and operations of the business enterprise.

An operational database is designed to run the day-to-day operations or transactions of your business.

It may also be called upon to support analytic processing either by providing real-time dashboards or supporting the ability to embed analytics into operational processes.

The Operational Database is the source of information for the data warehouse. It includes detailed information used to run the day to day operations of the business. The data frequently changes as updates are made and reflect the current value of the last transactions.

Operational Database Management Systems also called as OLTP (Online Transactions Processing Databases), are used to manage dynamic data in real-time.

Data Warehouse Systems serve users or knowledge workers in the purpose of data analysis and decision-making. Such systems can organize and present information in specific formats to accommodate the diverse needs of various users. These systems are called as Online-Analytical Processing (OLAP) Systems.

Data Warehouse and the OLTP database are both relational databases. However, the goals of both these databases are different.

# Educational institutions, libraries, hospitals and industries store concerned information by

1. data management
2. word processing
3. operating system
4. informing system

Option 1 : data management

## Detailed Solution

Concept :

Today’s organizations need a data management solution that provides an efficient way to manage data across a diverse but unified data tier. Data management systems are built on data management platforms and can include databases, data lakes and warehouses, big data management systems, data analytics, and more. Educational institutions, libraries, hospitals and industries store concerned information by Data management platform to access data without needing to know where it is stored and without needing to manually transform it into a usable format

A data management platform is the foundational system for collecting and analyzing large volumes of data across an organization. Commercial data platforms typically include software tools for management, developed by the database vendor. They perform typical tasks such as:

• Identifying, alerting, diagnosing, and resolving faults in the database system or underlying infrastructure
• Allocating database memory and storage resources
• Making changes in the database design
• Optimizing responses to database queries for faster application performance

# If a relation is in 2NF, then it can be in 3NF by removing

1. repeating groups
2. partial dependencies
3. transitive dependencies
4. overlapping dependencies

Option 3 : transitive dependencies

## Detailed Solution

The correct answer is transitive dependencies.

Concept:

A relation is in third normal form, if there is no transitive dependency for non-prime attributes as well as it is in second normal form. Therefore Option 3 is correct

A relation is in 3NF if at least one of the following condition holds in every non-trivial function dependency X –> Y:

1. X is a super key.
2. Y is a prime attribute (each element of Y is part of some candidate key).

# A backup is a ____________ against data loss.

1. Security
2. Countermeasure
3. Threat
4. Software

Option 2 : Countermeasure


text:
# Report file for Re Porter; Re Transport Workers Union of Australia(1989) 34 IR 179

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\begin{document}

\subsection*{Employee area}

\subsubsection*{Instant case}

The law distinguishes between a contract of service (between
employer and employee) and a contract for services (between
principal and independent contractor). This distinction
affects the terms that will be implied in the absence of an
express agreement, the liability of the employer to third
parties, the applicability of industrial awards, the
applicability of statutes which may affect workers'
compensation, occupational health and safety, long-service
leave, fringe benefits tax, etc.\par The terms employer''
and worker'' are used here to mean employer'' and
employee'' (in the case of a contract of service) or
principal'' and independent contractor'' (in the case of a
contract for services).

\medskip\noindent In the instant case,
the employer directed the manner in which the work was to be
done;
the worker was not allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the worker was an integral part of the employer's business;
the worker owned the tools or provided the transport with
which she/he performed the work;
it is not known whether the employer would make a
profit/loss if the work performed by the worker cost
less/more than expected;
the work was not performed on the employer's premises;
it is not known whether the employer supervised or inspected
the work;
the worker was not in business on her/his own account;
the worker was not allowed to employ others to assist with
her/his work;
the worker was obliged to work only for the employer;
the worker was not required to work at specified times;
the employer paid the worker by time;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer deducted PAYE tax instalments from the worker's
pay;
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

\medskip\noindent In my opinion---following \frenchspacing
{\it Ferguson v. John Dawson and Partners (Contractors) Ltd\/}\nonfrenchspacing---%
the worker is an employee.

\medskip\noindent In \frenchspacing
{\it Ferguson v. John Dawson and Partners (Contractors) Ltd}\nonfrenchspacing,%
\footnote{[1976] 1 WLR 1213.}
a 1976 decision of
the English Court of Appeal,
Ferguson fell off a roof while removing some scaffolding
boards. He claimed damages against Dawson (the building
contractors) for breach of statutory duty relying on the
{\it Construction (Working Places) Regulations 1966\/}
(UK). This duty would only be owed if Ferguson was an
employee of Dawson.\par Megaw and Browne LJJ held that,
despite the fact that both parties labelled Ferguson a
self-employed labour only
subcontractor'',\footnote{ibid. at 1219 per Megaw LJ, at
1225 per Lawton LJ, at 1228 per Browne LJ.} the reality of
the relationship between them was that of
employer/employee.

There are several significant similarities
between the instant case and \frenchspacing
{\it Ferguson v. Dawson\/}\null\nonfrenchspacing:
the employer directed the manner in which the work was to be
done;
the worker was not allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the worker was an integral part of the employer's business;
the work was not performed on the employer's premises;
the worker was not in business on her/his own account;
the worker was not allowed to employ others to assist with
her/his work;
the employer paid the worker by time;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, the instant case is not on all fours with \frenchspacing
{\it Ferguson v. Dawson}\null\nonfrenchspacing.
In that case
the worker neither owned the tools nor provided the
transport with which she/he performed the work;
the employer would make a profit/loss if the work performed
by the worker cost less/more than expected;
the employer supervised or inspected the work;
the worker was not obliged to work only for the employer;
the worker was required to work at specified times; and
the employer did not deduct PAYE tax instalments from the
worker's pay.

Nevertheless, I believe that \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
should be followed.

\medskip\noindent If \frenchspacing
{\it Ready Mixed Concrete (South East) Ltd v. Minister of Pensions and National Insurance\/} \nonfrenchspacing
is followed then the worker is an independent contractor.

\medskip\noindent In \frenchspacing
{\it Ready Mixed Concrete (South East) Ltd v. Minister of Pensions and National Insurance}\nonfrenchspacing,%
\footnote{[1968] 2 QB 497.}
a 1967 decision of
the Queen's Bench Division of the English High Court,
Latimer worked for Ready Mixed as an owner-driver''. He
was paid at mileage rates, and was obliged to buy the
truck through a financial organization associated with
Ready Mixed. The truck was painted in the company's
was obliged to meet the costs of maintenance, repair and
insurance of the truck (and the attached mixing unit,
which belonged to Ready Mixed). The Minister determined
that Latimer was employed under a contract of service and
therefore an employed person'' under s. 1(2) of the
National Insurance Act 1965 (UK), making Ready Mixed
liable to make weekly contributions.\par MacKenna J
examined the contract and held that the rights it
conferred, and the duties it imposed, between Latimer and
Ready Mixed were not such as to make it a contract of
service.

There are several similarities
between the instant case and \frenchspacing
the worker was an integral part of the employer's business;
the worker owned the tools or provided the transport with
which she/he performed the work;
the work was not performed on the employer's premises;
the worker was not in business on her/his own account;
the worker was obliged to work only for the employer;
the worker was not required to work at specified times;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, there are several significant differences
between the instant case and \frenchspacing
In that case
the employer did not direct the manner in which the work was
to be done;
the worker was allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the employer would not make a profit/loss if the work
performed by the worker cost less/more than expected;
the employer neither supervised nor inspected the work;
the worker was allowed to employ others to assist with
her/his work;
the employer did not pay the worker by time; and
the employer did not deduct PAYE tax instalments from the
worker's pay.
Note also that \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
is only a decision of
the Queen's Bench Division of the English High Court
and not as good authority as a case decided by
the English Court of Appeal%
---like \frenchspacing
{\it Ferguson v. Dawson}\null\nonfrenchspacing.

Consequently, there is nothing in \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
to warrant any change in my conclusion.

\subsubsection*{Instantiation 4}

It may be that the following is true of the instant case:
the employer would not make a profit/loss if the work
performed by the worker cost less/more than expected; and
the employer neither supervised nor inspected the work.

\medskip\noindent If that is so then in my opinion---following \frenchspacing
{\it Ready Mixed Concrete (South East) Ltd v. Minister of Pensions and National Insurance\/}\nonfrenchspacing---%
the worker is an independent contractor.

\medskip\noindent Details of \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
are summarized above.
There are several significant similarities
between the instantiated case and \frenchspacing
the worker was an integral part of the employer's business;
the worker owned the tools or provided the transport with
which she/he performed the work;
the employer would not make a profit/loss if the work
performed by the worker cost less/more than expected;
the work was not performed on the employer's premises;
the employer neither supervised nor inspected the work;
the worker was not in business on her/his own account;
the worker was obliged to work only for the employer;
the worker was not required to work at specified times;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, the instantiated case is not on all fours with \frenchspacing
In that case
the employer did not direct the manner in which the work was
to be done;
the worker was allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the worker was allowed to employ others to assist with
her/his work;
the employer did not pay the worker by time; and
the employer did not deduct PAYE tax instalments from the
worker's pay.

Nevertheless, I believe that \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
should be followed.

\medskip\noindent If \frenchspacing
{\it Ferguson v. John Dawson and Partners (Contractors) Ltd\/} \nonfrenchspacing
is followed then the worker is an employee.

\medskip\noindent Details of \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
are summarized above.
There are several similarities
between the instantiated case and \frenchspacing
{\it Ferguson v. Dawson\/}\null\nonfrenchspacing:
the employer directed the manner in which the work was to be
done;
the worker was not allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the worker was an integral part of the employer's business;
the work was not performed on the employer's premises;
the worker was not in business on her/his own account;
the worker was not allowed to employ others to assist with
her/his work;
the employer paid the worker by time;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, there are several significant differences
between the instantiated case and \frenchspacing
{\it Ferguson v. Dawson}\null\nonfrenchspacing.
In that case
the worker neither owned the tools nor provided the
transport with which she/he performed the work;
the employer would make a profit/loss if the work performed
by the worker cost less/more than expected;
the employer supervised or inspected the work;
the worker was not obliged to work only for the employer;
the worker was required to work at specified times; and
the employer did not deduct PAYE tax instalments from the
worker's pay.

Despite the fact that \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
is a decision of
the English Court of Appeal
(and better authority than a case decided by
the Queen's Bench Division of the English High Court%
---like \frenchspacing
there is nothing in \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
to warrant any change in my conclusion.

\subsubsection*{Hypothetical 1}

Consider the instant case changed so that the following is true:
the worker was not obliged to work only for the
employer; and
the employer did not deduct PAYE tax instalments from the
worker's pay.

\medskip\noindent If that were so then I would be more strongly of the
opinion that---following \frenchspacing
{\it Ferguson v. John Dawson and Partners (Contractors) Ltd\/}\nonfrenchspacing---%
the worker is an employee.

\medskip\noindent Details of \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
are summarized above.
There are several significant similarities
between the hypothetical case and \frenchspacing
{\it Ferguson v. Dawson\/}\null\nonfrenchspacing:
the employer directed the manner in which the work was to be
done;
the worker was not allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the worker was an integral part of the employer's business;
the work was not performed on the employer's premises;
the worker was not in business on her/his own account;
the worker was not allowed to employ others to assist with
her/his work;
the worker was not obliged to work only for the employer;
the employer paid the worker by time;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer did not deduct PAYE tax instalments from the
worker's pay;
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, the hypothetical case is not on all fours with \frenchspacing
{\it Ferguson v. Dawson}\null\nonfrenchspacing.
In that case
the worker neither owned the tools nor provided the
transport with which she/he performed the work;
the employer would make a profit/loss if the work performed
by the worker cost less/more than expected;
the employer supervised or inspected the work; and
the worker was required to work at specified times.

Nevertheless, I believe that \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
should be followed.

\medskip\noindent If \frenchspacing
{\it Ready Mixed Concrete (South East) Ltd v. Minister of Pensions and National Insurance\/} \nonfrenchspacing
is followed then the worker is an independent contractor.

\medskip\noindent Details of \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
are summarized above.
There are several similarities
between the hypothetical case and \frenchspacing
the worker was an integral part of the employer's business;
the worker owned the tools or provided the transport with
which she/he performed the work;
the work was not performed on the employer's premises;
the worker was not in business on her/his own account;
the worker was not required to work at specified times;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer did not deduct PAYE tax instalments from the
worker's pay;
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, there are several significant differences
between the hypothetical case and \frenchspacing
In that case
the employer did not direct the manner in which the work was
to be done;
the worker was allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the employer would not make a profit/loss if the work
performed by the worker cost less/more than expected;
the employer neither supervised nor inspected the work;
the worker was allowed to employ others to assist with
her/his work;
the worker was obliged to work only for the employer; and
the employer did not pay the worker by time.
Note also that \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
is only a decision of
the Queen's Bench Division of the English High Court
and not as good authority as a case decided by
the English Court of Appeal%
---like \frenchspacing
{\it Ferguson v. Dawson}\null\nonfrenchspacing.

Consequently, there is nothing in \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
to warrant any change in my conclusion.

\subsubsection*{Hypothetical 2}

Consider the instant case changed so that the following is true:
the worker was allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand; and
the employer did not deduct PAYE tax instalments from the
worker's pay.

\medskip\noindent If that were so then my opinion would be
that---following \frenchspacing
{\it Ready Mixed Concrete (South East) Ltd v. Minister of Pensions and National Insurance\/}\nonfrenchspacing---%
the worker is an independent contractor.

\medskip\noindent Details of \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
are summarized above.
There are several significant similarities
between the hypothetical case and \frenchspacing
the worker was allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the worker was an integral part of the employer's business;
the worker owned the tools or provided the transport with
which she/he performed the work;
the work was not performed on the employer's premises;
the worker was not in business on her/his own account;
the worker was obliged to work only for the employer;
the worker was not required to work at specified times;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer did not deduct PAYE tax instalments from the
worker's pay;
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, the hypothetical case is not on all fours with \frenchspacing
In that case
the employer did not direct the manner in which the work was
to be done;
the employer would not make a profit/loss if the work
performed by the worker cost less/more than expected;
the employer neither supervised nor inspected the work;
the worker was allowed to employ others to assist with
her/his work; and
the employer did not pay the worker by time.

Nevertheless, I believe that \frenchspacing
{\it Ready Mixed v. Minister\/} \nonfrenchspacing
should be followed.

\medskip\noindent If \frenchspacing
{\it Ferguson v. John Dawson and Partners (Contractors) Ltd\/} \nonfrenchspacing
is followed then the worker is an employee.

\medskip\noindent Details of \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
are summarized above.
There are several similarities
between the hypothetical case and \frenchspacing
{\it Ferguson v. Dawson\/}\null\nonfrenchspacing:
the employer directed the manner in which the work was to be
done;
the worker was an integral part of the employer's business;
the work was not performed on the employer's premises;
the worker was not in business on her/his own account;
the worker was not allowed to employ others to assist with
her/his work;
the employer paid the worker by time;
the money that the employer paid to the worker was not
stated to be a fee'';
the money that the employer paid to the worker was not
stated to be wages'' or salary'';
the employer did not deduct PAYE tax instalments from the
worker's pay;
the employer paid the worker neither sick pay nor holiday
pay;
the employer and the worker did not express any intention
that the relationship would be one of employer and
employee; and
the employer and the worker expressed an intention that the
relationship would be one of principal and independent
contractor.

However, there are several significant differences
between the hypothetical case and \frenchspacing
{\it Ferguson v. Dawson}\null\nonfrenchspacing.
In that case
the worker was not allowed to use her/his own discretion in
doing an aspect of the work that was not specified
beforehand;
the worker neither owned the tools nor provided the
transport with which she/he performed the work;
the employer would make a profit/loss if the work performed
by the worker cost less/more than expected;
the employer supervised or inspected the work;
the worker was not obliged to work only for the
employer; and
the worker was required to work at specified times.

Despite the fact that \frenchspacing
{\it Ferguson v. Dawson\/} \nonfrenchspacing
is a decision of
the English Court of Appeal
(and better authority than a case decided by
the Queen's Bench Division of the English High Court%
---like \frenchspacing


text:
applying single pole filter to simple signal

How to apply single pole filter to simple signal

fs = 500;
ts = 1/fs;
t = 0:ts:1-ts;
fc = 50;
S = cos(2*pi*fc*t);

Given the transfer function of a single pole filter (without a zero):
$$H(z)= \frac{Y(z)}{X(z)} = \frac{1}{1-pz^{-1}}$$ Using the inverse z transform leads to the following equation: $$y[n] = x[n] + p y[n-1]$$

Your single pole filter can be implemented using a for-loop.

fs = 500;
fc = 50;
K = fs;  % 1 second of data
k = 0:(K-1);
x = cos(2*pi*fc/fs*k);

y = zeros(K,1);

p = 0.5;
y(1) = 0;  % Choose some initialization for y(1)
for n = 2:K
y(n) = x(n) + p*y(n-1);
end

Another 'simple' test signal that can be used to visualize the behaviour of your filter is a random signal.

x = randn(K,1);

The spectrum of the filtered random signal shows the frequency characteristics of the filter.

If your pole is at $z=p$ (real or complex), this will do:

Y = filter( [1], [1, -p], S );

Free bonus: if you also want a zero at $z = c$:

Y = filter( [1, -c], [1, -p], S);

This last expression corresponds to the filter:

$$H(z) = \frac{1 - c z^{-1}}{1 - p z^{-1}}$$


text:
CLUSTER_NATOMS
 This is part of the adjmat module It is only available if you configure PLUMED with ./configure –enable-modules=adjmat . Furthermore, this feature is still being developed so take care when using it and report any problems on the mailing list.

Gives the number of atoms in the connected component

As discussed in the section of the manual on Exploiting contact matrices a useful tool for developing complex collective variables is the notion of the so called adjacency matrix. An adjacency matrix is an $$N \times N$$ matrix in which the $$i$$th, $$j$$th element tells you whether or not the $$i$$th and $$j$$th atoms/molecules from a set of $$N$$ atoms/molecules are adjacent or not. When analysing these matrix we can treat them as a graph and find connected components using some clustering algorithm. This action is used in tandem with this form of analysis to output the number of atoms that are connected together in a particular connected component. It is important to note that the quantity that is output by this action is not differentiable. As such it cannot be used as a collective variable in a biased simulation.

Compulsory keywords
 CLUSTERS the label of the action that does the clustering CLUSTER ( default=1 ) which cluster would you like to look at 1 is the largest cluster, 2 is the second largest, 3 is the the third largest and so on.
Options
 NUMERICAL_DERIVATIVES ( default=off ) calculate the derivatives for these quantities numerically NOPBC ( default=off ) ignore the periodic boundary conditions when calculating distances SERIAL ( default=off ) do the calculation in serial. Do not parallelize LOWMEM ( default=off ) lower the memory requirements TIMINGS ( default=off ) output information on the timings of the various parts of the calculation
Examples

The following input uses PLUMED to calculate a adjacency matrix that connects a pair of atoms if they both have a coordination number that is greater than 2.0 and if they are within 6.0 nm of each other. Depth first search clustering is used to find the connected components in this matrix and then the number of atoms in the largest cluster is found. This quantity is then output to a file called colvar

# Calculate coordination numbers
c1: COORDINATIONNUMBER SPECIES=1-512 SWITCH={EXP D_0=4.0 R_0=0.5 D_MAX=6.0}
# Select coordination numbers that are more than 2.0
cf: MFILTER_MORE DATA=c1 SWITCH={RATIONAL D_0=2.0 R_0=0.1} LOWMEM
# Build a contact matrix
mat: CONTACT_MATRIX ATOMS=cf SWITCH={EXP D_0=4.0 R_0=0.5 D_MAX=6.0}
# Find largest cluster
dfs: DFSCLUSTERING MATRIX=mat
clust1: CLUSTER_PROPERTIES CLUSTERS=dfs CLUSTER=1
nat: CLUSTER_NATOMS CLUSTERS=dfs CLUSTER=1
PRINT ARG=nat FILE=COLVAR