1

New Theories / Re: How close are we from building a virtual universe?

« on: 14/05/2022 22:23:20 »

https://www.zdnet.com/article/microsoft-veteran-bob-muglia-relational-knowledge-graphs-will-transform-business/

We're at the start of a whole new era' with knowledge graphs, says Microsoft veteran Bob Muglia, akin to the arrival of the modern data stack in 2013.


Microsoft veteran Bob Muglia: Relational knowledge graphs will transform business
'We're at the start of a whole new era' with knowledge graphs, says Microsoft veteran Bob Muglia, akin to the arrival of the modern data stack in 2013.


Bob Muglia says twenty years of work on database innovation will bring the relational calculus of E.F. Codd to knowledge graphs, what he calls "relational knowledge graphs," to revolutionize business analysis.

Bob Muglia is something of a bard of databases, capable of unfurling sweeping tales in the evolution of technology.

That is what Muglia, former Microsoft executive and former Snowflake CEO, did Wednesday morning during his keynote address at The Knowledge Graph Conference in New York.

The subject of his talk, "From the Modern Data Stack to Knowledge Graphs," united roughly fifty years of database technology in one new form.

The basic story is this: Five companies have created modern data analytics platforms, Snowflake, Amazon, Databricks, Google, and Azure, but those data analytics platforms can't do business analytics, including, most importantly, representing the rules that underly compliance and governance.

"The industry knows this is a problem," said Muglia. The five platforms, he said, representing "the modern data stack, have allowed a "new generation of these very, very important data apps to be built." However, "When we look at the modern data stack, and we look at what we can do effectively and what we can't do effectively, I would say the number one problem that customers are having with all five of these platforms is governance." 

"So, if you wanted to perform a query to say, 'Hey, tell me all of the resources that Fred Jones has access to in this organization' — that's a hard query to write," he said. "In fact, it's a query that probably can't execute effectively on any modern SQL database if the organization is very large and complex."

The problem, said Muglia, was that the algorithms based off of structured query language, or SQL, can't do such complex "recursive" queries.

He described the problem I faced when I started this thread.

2

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 14/05/2022 13:12:57 »

Nope; the definition of "cow" is still correct, regardless of whether it is understood.

The same is true of "flash point".

The ignorance or knowledge of the reader isn't relevant to the definition.

Have you heard that someone defined pi = 3?

3

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 14/05/2022 13:10:39 »

I also learned that gravity and buoyancy play significant role in determining the results, which need to be addressed in upcoming experiments.

It turns out that ice-water bath is not adequate to keep the outer sides of the glasses at 0C. The ice tends to float, which makes lower part of the bath warmer, even when it's only a few centimeters deep. This temperature difference seems to cause the heat transfer through the glass.
So, obviously the next step to improve the experiment setup is to keep the ice at the bottom of the bath. Convection will make temperature of the bath more uniform around 0C.

4

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 14/05/2022 12:22:37 »

Definitions involve assumptions.

Wrong.  A definition is an absolute statement that creates truth.

A cow is defined as a mature female bovine quadruped. No assumptions involved.

You assume that someone who read your definition knows and agrees with the meaning of mature, female, bovine, and quadruped.

5

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 14/05/2022 12:17:54 »

Your picked answer is different than what the actual results are.

Where are the details of the experiment that gave you these "actual answers"?

Here's my idea to minimize noise over signal:
- Prepare 50/50 ice-water mixture at around 0°C in a large plastic bowl. Let it in refrigerator for an hour to reach equilibrium.
- Fill a metal cup with 90% water and 10% ice from the mixture.
- Fill another metal cup with 10% water and 90% ice from the mixture.
- Put both metal cups into the bowl containing the remaining of the mixture.
- Let them in refrigerator for an hour to reach equilibrium.
- See the result, if the ratio of ice-water in the cups change.

OK. I've finished my first round of experiment as described above. But I can't get the metal cups, so I just used ordinary drinking glasses. I guess the heat conductance is enough for this experiment since they are quite thin.
The temperature of the refrigerator is 4C, as shown by a thermometer left there for an hour. The result is the ice in both glasses decreased from initial ratio.
So I moved the system to the freezer, which is kept at -4C, as measured by a thermometer left there for an hour. The result is the ice in both glasses increased from initial ratio.
These results show that energy transfer between the system and the environment overwhelmed the energy transfered through the glasses. It means that the noise over signal ratio is too high to get reliable conclusion. Hence the experimental setups need to be improved.
I also learned that gravity and buoyancy play significant role in determining the results, which need to be addressed in upcoming experiments.

6

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 14/05/2022 12:15:37 »

Do you have an idea how to get the first possible result, i.e. both cups retain their ice/water ratio?

Of course!  Why are you asking, haven't you read your own thread?

7

New Theories / Re: what is temperature?

« on: 14/05/2022 03:53:12 »

That you are a little less than half way between the flat bits of the graph at 3 and 4.

What's the physical interpretation of that?
What makes it better than interpreting that rotational energy hasn't been fully activated?

8

New Theories / Re: what is temperature?

« on: 14/05/2022 03:47:52 »

I never suggested otherwise.

It seems you did.

It depends.
What would you actually do with the information if I told you?

Incidentally, you forgot to answer my questions.
Please do so.

Which one?

9

New Theories / Re: How many times would a light ray be reflected inside a circular mirror?

« on: 14/05/2022 03:21:16 »

"When an honest man discovers he is mistaken, he will either cease being mistaken, or cease being honest." - Anonymous.

So, did you change the thread title to " How many times would THE CENTRE OF a light ray be reflected inside a circular mirror?" or did you cease being honest about it?

It also applies to the edge of a light ray.

10

New Theories / Re: How many times would a light ray be reflected inside a circular mirror?

« on: 14/05/2022 03:20:35 »

The mirror at G is concave, which reduces the divergence.

No.
A parallel beam striking a concave mirror is brought to a focus, but after that the beam diverges strongly.

I see you still haven't actually drawn what happens.

It's reduced compared to flat mirror. That's why I said that the width increases linearly to the number of reflection, instead of exponentially.

11

General Science / Re: Double hairdryer charcoal foundry

« on: 13/05/2022 17:07:13 »

Do you accept that powdered charcoal forms an ignitable mixture with air in the presence of an igneous source and continues burning after the trigger source is removed?

12

New Theories / Re: How many times would a light ray be reflected inside a circular mirror?

« on: 13/05/2022 16:48:52 »

What is the width of the beam after it's reflected at G?

Immediately after it is reflected (before it has gone back across the sphere) its width is still about 3W.
But it's strongly divergent. Even if the mirror at G was flat, it would reach about 3 or 4 W by the time it reached the opposite side of the sphere.

But the real question here is why do you have to ask me?

If you can't work it out for yourself, go and learn science.

Does it increase exponentially by the number of reflection?
The mirror at G is concave, which reduces the divergence.
Because you're the one who said

Diffraction stops it being scientific.

But to a rough approximation, the width of the beam, after n reflections is (at least) 3^n times bigger than the original beam.

While I suggested to consider only the center of the beam.

It depends on the width of the light beam and the curvature of the mirror. But you can restrict the calculations for the center of the light beam.

"When an honest man discovers he is mistaken, he will either cease being mistaken, or cease being honest." - Anonymous.

13

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 13/05/2022 16:27:01 »

Did you make correct prediction?

Yes, I predicted your experiment would fail because there is going to be a delta T between the environment and your ice bath since you do not have the equipment to accurately hold the temp at exactly 0C.

I already knew that. What I want to know is, what else drives heat transfer?

If there is no delta T, then nothing else matters since there will be no heat transfer.

Your picked answer is different than what the actual results are.
Do you have an idea how to get the first possible result, i.e. both cups retain their ice/water ratio?

14

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 13/05/2022 16:21:09 »

In another thread, a scientific disagreement was finally resolved by making a bet.

In the UK it is illegal to bet on events where the outcome is already known.
We have repeatedly pointed out that the outcome of your experiment is already known.

That's a pity in a way; it might be fun to take your money.

I didn't propose to involve money.

15

General Science / Re: Double hairdryer charcoal foundry

« on: 13/05/2022 15:55:41 »

Was that a yes or a no?

The article tells that a charcoal is not a homogenous chemical substance. It contains volatile parts which are easier to evaporate than the solid part.
Your question is like asking if a wet cloth evaporates at 40C.

16

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 13/05/2022 15:40:40 »

I also learned that gravity and buoyancy play significant role in determining the results, which need to be addressed in upcoming experiments.

What you should have learned is that heat transfer is driven by the delta T.

I already knew that. What I want to know is, what else drives heat transfer?

17

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 13/05/2022 15:39:22 »

I didn't ask what thermodynamics theory says. I can google it and quickly get an answer.
I asked what would happen if I do an experiment as described previously. What currently existing theories predict, and what factors can significantly affect the results.

Which you were told and you ignored.

Did you make correct prediction?

18

General Science / Re: Double hairdryer charcoal foundry

« on: 13/05/2022 15:09:49 »

The flash point is the lowest temperature at which a volatile substance evaporates to form an ignitable mixture with air

Does charcoal evaporate at 40C (or even at 400C)?

https://www.fao.org/3/x5328e/x5328e0b.htm#10.1.2.%20volatile%20matter%20other%20than%20water

The volatile matter other than water in charcoal comprises all those liquid and tarry residues not fully driven off in the process of carbonization. If the carbonization is prolonged and at a high temperature, then the content of volatiles is low. When the carbonization temperature is low and time in the kiln is short, then the volatile matter content increases.

These effects are reflected in the yield of charcoal produced from a given weight of wood. At low temperatures (300°C) a charcoal yield of nearly 50% is possible. At carbonization temperatures of 500-600°C volatiles are lower and retort yields of 30% are typical. At very high temperatures (around 1000°C) the volatile content is almost zero and yields fall to near 25%. As stated earlier, charcoal can reabsorb tars and pyroligneous acids from rain wash in pit burning and similar processes. Thus the charcoal might be well burned but have a high volatile matter content due to this factor. This causes an additional variation in pit burned charcoal in wet climates. The resorbed acids make the charcoal corrosive and lead to rotting of jute bags - a problem during transport. Also it does not burn cleanly.

The volatile matter in charcoal can vary from a high of 40% or more down to 5% or less. It is measured by heating away from air, a weighed sample of dry charcoal at 900°C to constant weight. The weight loss is the volatile matter. Volatile matter is usually specified free of the moisture content, i.e. volatile matter - moisture or (V.M. - moisture).

High volatile charcoal is easy to ignite but may burn with a smoke flame. Low volatile charcoal is difficult to light and burns very cleanly. A good commercial charcoal can have a net volatile matter content - (moisture free) of about 30%. High volatile matter charcoal is less friable than ordinary hard burned low volatile charcoal and so produces less fines during transport and handling. It is also more hygroscopic and thus has a higher natural moisture content.

19

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 13/05/2022 14:45:25 »

The negative comments are probably due to your posting style.  You ask a question and people take the time to answer you and then you ignore the answer.  That is going to lead to people ignoring you or getting frustrated with you.  I suggest you change your attitude or expect negative comments.

I didn't ask what thermodynamics theory says. I can google it and quickly get an answer.
I asked what would happen if I do an experiment as described previously. What currently existing theories predict, and what factors can significantly affect the results.

20

New Theories / Re: How many times would a light ray be reflected inside a circular mirror?

« on: 13/05/2022 14:39:35 »

mirror ball.jpg (37.2 kB . 615x618 - viewed 290 times)Here's a very bad sketch, but it illustrates the point.
I drew the incoming beam. The thin lines represent the outside edges of the outgoing beam

If you shine a beam of light at a concave mirror it is brought to a focus.
The focal length is half the radius of curvature.
So the distance from the focal point (F) to the point (P) where the light strikes the mirror is half the radius of the sphere and, the distance to the other side of the sphere (G) is 3 times as big. (It's 3/4 times the diameter as opposed to 1/4 times the diameter)
That means the edges of the light form (roughly) two similar triangles , one 3 times as big as the other .
So the width of the beam when it strikes G is about 3 times W.

Now that (divergent) light beam is bounced back across the mirror.
If it was a parallel beam then the same thing would happen to it as happened to the original beam. It would be 3 times as big when it hit the mirror for a third time.
So it would be 9 times W.
But it was already diverging after the first reflection, so the width will be even bigger.

But to a rough approximation, the width of the beam, after n reflections is (at least) 3^n times bigger than the original beam.

This is essentially why integrating spheres work.

What is the width of the beam after it's reflected at G?