kenny1999

Blocking the sensor? Did you mean when I touch it so there is no air in between, then it will block the sensor and doesn't work?

I was waiting for someone in a park and saw this bird. Its neck is full of black and white dots. What is this bird?

I mean, I wish to know the principle. What is the sensor doing? Emitting infrared or other radiations? However, I think light or radiation could easily pass through our body!

but why when I put my hand near it, it will work correctly and does not block the sensor?

Light beam? Sound wave? Can I have some understanding of how it works? Does the device continuously emit light wave and when someone get close to it, it will interrupt the light wave? I have some physics knowledge but not too much. IR source and detector? Can I have some brief understanding of how it works? Yes, when I touch it, it doesn't work, when I am far from it, it doesn't work. Only when I put my hand close to it (but not touching it), it works. Is it using sound wave or light wave or something otherwise? I don't think there is any emitter around, does it itself emit light wave or sound wave so that when I get close to it, the wave is interrupted? P.S. As I said, this is not a door for security, it's in the public area, and our building isn't very modern. I only wish to learn about the working principle behind.

OK, my language problem, Let's make it clear, I mean, it detects ANY part of human body and unlock the door immediately, there is nothing about fingerprint or ID, it's not a security door, anyone who puts their hand (or any part of their body) near the "sensor" then it will unlock the door (but it won't unlock if you touch on it, it only works when your hand puts near it but not too far away, and not touching it). I only want to know the working principle of such device.

I am not living in a very modern building and the budget of the management company is not high so I think the technology employed shouldn't be something new. The public entrance door is normally closed and locked and it can only be unlocked when I put my hand close to the door "sensor" then it will detect my hand and unlock the door, but if I touch the "sensor" it will not unlock the door and doesn't show any response. What is the general working principle of such device? I don't know if it's actually a sensor so I use quote and quote in the above context.

I am buying a tool that has two options to power - rechargeable battery or dry cell. Personally I prefer rechargeable battery but it is not a tool that will be used so often - probably only used once every year. Does a rechargeable battery that is seldom charged and discharged last much longer than one that is charged and discharged daily? Or will it just degrade at more or less the same speed no matter what?

I DO NOT mean when someone who possibly has mental illness and eat food taken from garbage bin. I mean, when you normally eat outside, you have little control over where they buy the food from and how the food is prepared, even if they are having an open kitchen that you can see through. The first thing is they will not usually wash the food so clean as you cook it for yourself, they are just working for money and focusing to have things finished quickly. Secondly, they may have touched their mobile phone full of dirt and bacteria and do not wash their hand afterwards. (It's very common). In some cases, not even rare, their body fluid may go into the food from cough or sneeze, nobody knows. And it's also not uncommon to find insects and rats in commercial kitchen. Is there any research or doctor's comments on this area? What is the worst possible adverse effect if eating outside at a legal and approved food provider?

What is the actual chemical compound of the texture of our clothes that are commonly available in the commercial market? Is different color of clothes due to addictive added during the manufacturing process or the natural color of the compound of the raw materials? What are usually the chemical reactions that will be done to raw materials to make it become clothes? I know it's a broad question but I am looking for some understanding on this issue.

I know that some flies or mosquitoes some parts of Africa could spread serious or even fatal disease to human if bitten. I am wondering why it looks like they will not travel to other continents and reproduce there? Is it because they are not able to travel a long distance or because they are already satisfied with their current environment so they don't need to travel so they are mostly localized?

As a result, so Yes or No? For example, I don't think the skin of my finger will have any reaction with a metal object or a plastic object when I touch them, however, is there still any atoms/molecules that would transfer/jump from the surface of the object to my skin? Penetration to any significant depth? What does that mean?

When we touch something, even lightly, is it true that some of atoms/molecules from our skin will pass into that thing while some of atoms/molecules from that thing will pass into our skin?

I think many substances, if not all, can be degraded or destroyed when temperature is high enough because heat facilitates many chemical reactions. On the other hand, is there any chemical reaction that would be accelerated when temperature drops? Or is there almost never any chemical reaction that would be favored at low temperature while inactive at high temperature?

Hi all, I am living in an apartment where I don't have any plant or pots so it was purely an accident. I forgot a bag of vegetables which were hidden under other stuff until it smelt. When I picked it up some climbed on my hand, I rinsed my hands, but I wasn't sure if they were all gone, from Google search, some could hide under my skin or penetrate into my body???? Could it be that serious??

I once forgot to throw away some uncooked vegetable and they were not refrigerated for weeks. I only happened to remember it when it started to give out disgusting smell. The vegetable was decayed. What interested me was that there were a lot of small white bugs / worms slowing climbing and staying around the dead vegetables but there were two interesting things I found. 1. They were very well localized and didn't seem to go out of the dead vegetables so I felt safe. I was so worried that they would have migrated to somewhere else and reproduced in my kitchen, which didn't happen. I couldn't find any bug in nearby area where the dead vegetable was put. 2. They looked so small and weak but I could hardly kill or hurt them any with great effort, I could only throw them away out of my room or rinse them into drain. Why is that?

Have anyone ever tried using this freeware? Is it reliable and reputable? Sorry, OpenOffice and LibreOffice often crash for no reason and it is so annoying that's why I am avoiding them. However, I have never heard about FreeOffice before. I find that they are likely created by German because their official site has some German text. What do you think? Is it reliable to use?

I am living in a subtropical region and we are in summer now. Every time when I come out from a hot bath (I never bath with cool water) and before I dry my body, I feel quite cool, but room temperature at night is still over 85 F. Is it because of the high heat capacity of water droplets on my body which has absorbed heat around my skin?

Is it always worse or better to heat a plastic container with food above boiling water, rather than to microwave it? I do not have a microwave oven and I am always heating up packaging food above boiling water that is supposed to be microwaved, is it better, worse, or shouldn't have any difference, in terms of the effects to the food?

I have come across many elderly, and I have never, ever heard one of them saying that they are free of all of the common chronic disease e.g. heart disease, diabetes, high blood pressure etc. Except that I once met one who looked so gorgeous, sporty, and healthy with good body shape at her age (e.g. probably around 65 and she was obviously very active in sports and exercises for a long time) and she said she didn't have any disease but I finally figured out that she was still diagnosed with high blood pressure, it was only because she didn't see it as a problem or she didn't even want to mention about it. I start to wonder if it's just almost going to be impossible to be free of those common chronic disease when one gets old enough even if they eat healthily and exercise regularly during their younger age? The difference is only about one disease or two or three but never none? It's just impossible to be free of ALL of them?

no air or atmosphere to protect him against the direct sun, in that case, won't he be burnt vigorously and dead in short time?

but the atoms used to produce laser shouldn't leak under daily stresses and should be safe most of the time, am I right?

break a wire? What is the wire?

Aren't some wireless mouse operated by laser? I'm hearing "laser mouse" very often.

won't he be killed by direct sun radiation first???