﻿ oipapio

### heat - How to create a regional google heatmap

For a real estate project I need to demonstrate the property rates by regional(not markers) on google map by means of geochart/intensitymap/ drilldown highchart. I found that geochart is not capable to show states. The map I need is of Australian suburbs not the five states.Any advice is appreciated....Read more

### Paraphrasing speed and heat capacity

Can we call speed the change in distance per time?Further, would you phrase heat capacity as change in heat per temperature or change in temperature per heat?The reason for this question is that some people refer to heat capacity by change in temperature per heat and if I were to write down an equation based on that formulation, I would write it down as $C_{[p|V]} = \left( \frac{\partial T}{\partial U}\right)_{[p|V]}$, which is not the way it's usually written....Read more

### heat - What are the patterns appear after kernel averaging?

Having a 2D map filled uniformly by random values (Figure:top-left) to demonstrate a disordered phenomena, the next maps are kernel averaged with a kernel of sizes 3x3, 5x5, ..., 11x11.The questions are:What are the patterns appeared in the kernel averaged maps?What is the physical explanation of existence of such patterns? For image please see this link.Note:To generate the maps a kernel based averaging system type C was applied on the original data....Read more

### heat - What's the best strategy to fully fill the fridge with beer bottles and have them all cooled?

I'm having a party.Suppose I'd like to have a fridge full of cold ($6~^\circ\text{C}$ or below) beer bottles, in as short a time frame as possible. The fridge indicates that it is targeting (and presumably currently at) $4~^\circ\text{C}$. All the bottles are currently at $30~^\circ\text{C}$, which is the temperature outside the fridge, and together the bottles will fill the fridge completely (as in: no further bottles could be fitted in).What is the best strategy to achieve this aim?(Should I put in all bottles at once? Should I put the bottle...Read more

### time - The heat equation in relation to smoothing algorithm

Recently I learned about a technique in image processing, which has its roots in something called the 'heat equation' from physics. The original creators of this technique were inspired by the physics of how heat diffuses through an object. The objective of course is to 'smooth out' the image, for general noise removal. This was done by taking a Gaussian kernel, and convolving it with the image. However, the professor says that the heat-equation is actually a generalization of this process, and in fact, we can get much better techniques using t...Read more

### heat - Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth?

Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth?It's not just a subtle difference, but significant in my opinion. I'm inclined to discredit the notion that it's just a matter of speed because I can blow fast with an open mouth and still, it's hot; and blow slow with an almost closed (tighter) mouth and again, it's cold....Read more

### thermal conductivity - Why do some metal containers not conduct heat, while some do?

Some metal containers such as the Nissan Thermos ones, even if 100 C water is filled inside, the container is still cold to the touch on the outside. It won't be even warm:At the same time, some that look similar are so hot on the outside that holding it for a couple of seconds won't be possible:Also, some teapot at Chinese restaurant or Vietnamese Restaurant, it can be boiling hot water inside, but the handle is also cold to the touch:The question is, for the Nissan one and the ones at Chinese restaurants, if the metal part is all connected, ...Read more

### heat - What determines bubble locations in boiling water?

Something a little different to our usual fare. I was boiling a pan of water for cookery the other day, and got to wondering what caused the location of the bubble streams from the bottom of the pan. The stream of bubbles seems to come from the same spot of the pan, is this a quirk of the fluid flow? Imperfections in the pan? These streams of bubbles appear to continue for several minutes until the water fully boils and it becomes too turbulent to follow anything. Any thoughts?...Read more

### heat - Why does wet skin sunburn faster?

There is a popular belief that wet skin burns or tans faster. However, I've never heard a believable explanation of why this happens.The best explanation I've heard is that the water droplets on the skin act as a lens, focusing the sunlight onto your skin. I don't see how this would affect an overall burn, because the amount of sunlight reaching the skin is the same (ignoring reflection).Is this 'fact' true, and if so, what causes it?...Read more

### heat - Does stirring water in a bucket in whirlpool keeps it warm?

I did an experiment when I was a teenager. I want to prove/see what really went on in that experiment.When taking a bath, take a warm water in bucket and start taking a bath. You will notice that the water will get cold in lets say 10 minutes. Because the water is bucket is stagnent.In second instant take the same water and stir the water in bucket in whirlpool motion. You will notice that this water keeps warmer for longer? Now the heat from my hands could get the water a bit warmer but I think it might have to do with the motion of the molecu...Read more

### heat - Can we explain physical similarities between Black Scholes PDE and the Mass Balance PDE (e.g. Advection-Diffusion equation)?

Both the Black-Scholes PDE{*} and the Mass/Material Balance PDE have a similar mathematical form of the PDE which is evident from the fact that on change of variables from Black-Scholes PDE we derive the heat equation (a specific form of Mass Balance PDE) in order to find analytical solution to the Black-Scholes PDE.I feel there should be some physical similarity between the two phenomena which control these two analogous PDEs (i.e. Black-Scholes and Mass/Material Balance). My question is, can one relate these two phenomena physically through t...Read more

### heat - Heatsink on underside of PCB

I have prototyped some DC-DC converter modules, and they work well. However due to size, I don't have a huge amount of copper pour for them to dissipate their heat. I have used 2oz copper but the bottom layer copper pours get really hot at higher current. Even through the solder mask!I experimented with adding a heatsink to this bottom side of the PCB with some thermal grease and the results were surprisingly good. The heatsinks get hot under heavy load. The buck-boost-inverter went from maxing out at about 1.5A to being stable at 2.5A! This is...Read more

### heat - How much disolved oxygen is removed by boiling water?

Apologies if this is a chemistry questionI've read that drinking water contains dissolved oxygen to the tune of $10\:\rm{ppm}$.I've also read that raising the temperature of water will remove some dissolved gases.Given standard temperature and pressure, what percentage of disolved oxygen will be removed from the water by boiling?Specifically there's a running arguement in the office that when making tea one should never reboil the kettle, the reason being that the tea will taste bad because the dissolved oxygen has been removed.Thanks for your ...Read more

### thermal conductivity - Why the heat flux vector at a point must be perpendicular to the temperature isothermal surface? Is it a definition or a deduction?

Before the question: I am working on numerical calculation of three dimension parabolic equation that based on Fourier's Law of which I am a little confused.Here comes the law in modern mathematics language. "The local heat flux is proportional to temperature gradient" $$\vec{q}=-k\nabla T,$$ where $k$ is the material's conductivity.How extremely concise it is, but how to understand the Law? I read the book written by Fourier in 1822 but I know neither of the law in modern mathematics language nor in Fourier's language. I found that every ...Read more

### heat - What does a beginner need to know to build a programmable heater based on resistance heating?

To build a programmable deep fryer, as a learning project for more serious checmical reactors, I need to build a programmable heat source that can be controlled in response to sensor readings and a schedule. I'm a programmer and I have some metalworking skills that I am currently expanding on, but my knowledge on electronics is basic at best.I'm pretty much in love with induction heating, but I was advised on this question that it might not be the wisest choice to start with, so let's try resistance heating first....Read more