the energy doesn't just disappear, the reflected wave also carries some energy.

I like to think of that extreme example as "edge effects". Obviously there are limitations to the recovery technique, but "deblurring" is absolutely a thing both in imaging and similarly in non-imaging applications.

https://en.wikipedia.org/wiki/Blind_deconvolution

In a sense, electronic engineering (which I can say I'm a specialist in) concepts like emphasis, equalization, etc are just compensations for channel effects, which one could think as time varying signal equivalents for blurring in imaging.

In that sense, recovery of a "blurred" signal via equalization is absolutely used everywhere that uses high speed digital signals like USB, DDR, PCIe, etc.

Most of the people here are wrong. It is possible to un-blur an image within reasonable fidelity, provided that you know how the blur was done (i.e. which method, what the parameters for the method were, etc).

The naive way of blurring an image basically averages the input pixels from its neighbors and outputs it on the output. This is a reversible process, provided you know how the averaging window was created.

The averaging window can also be estimated to potentially get a "good enough" reproduction of the image before it was blurred.

the bottom drill bit is rolling around in the velvet, that's likely picking up charge.

the bandgap of a photodiode determines the minimum energy of a photon that can trigger conduction, so you could use that to your advantage, but it won't be band-selective unless you forgo single photon detection.

The actual regulation in a car is done by the ECU or some circuit inside the alternator that limits the output voltage to a certain amount.

The battery is mostly there so that when there is a load transient, the regulator mentioned above can have a relaxed response time--the battery takes up the slack when there's a sudden load increase or decrease.

If a control system has to react quickly, it's more liable to instability like oscillation and divergence. Better to keep it safe by making it slow to react, especially if you already have a big ass battery that can smooth things out that you need to start the car.

Capacitors are devices that store energy by moving charge carriers (usually electrons) in places it really doesn't want to be in--which means they have to be forced in that position--which takes energy that you can get back later, quite easily. Charge carriers like electrons can move around efficiently and quickly in conductors like metal, so capacitors generally can be charged and discharged rapidly.

Batteries are devices that store energy by making ions stay in energetically excited conditions that it doesn't really want to be in. Ions are generally floating charged particles in a liquid solution, so they take much longer to float around and do their chemistry to get your energy back. The upside is that you get to store a lot more energy into the structure, but the downside is that the rate at which you can charge and discharge is beholden to the chemistry and the speed at which ions move, so it's quite slow. They are also inefficient since ions aren't efficiently transported, as much as electrons are in metal.

There's also one more fact that I think other commentators glanced over. One of the many approaches you can have towards gain and directivity of an antenna is the idea of an effective cross section of an antenna.

Think about a simple dipole. It basically has no cross sectional area, but yet it is still capable of capturing free air propagation and confining it to a conducted EM wave (into coax, for example).

This is because the presence of the dipole creates a disturbance in the way free air propagating EM waves (which can be approximated greatly since it's in free air), and creates more complex "near field" phenomena which essentially increases the cross sectional area of the antenna.

In this sense, all antennas disturb the free air propagation and create near field cross sectional areas that it will use to capture EM energy and send it through a conductor.

Indeed, there's actually a relationship between directivity/gain and this imaginary cross sectional area. I haven't done this in a while but I believe for parabolic antennas (or any antenna where the physical size >> wavelength) this cross sectional area is essentially the same as the physical size, and hence this is one way to think about the high gain of parabolic antennas like the ones used for radio astronomy.

In that sense, in certain degenerate scenarios, the flat plate might have a larger cross sectional area than an actual semi-spherical dish (hint: it has to do with physical size vs wavelength of the wave you're dealing with)

One more concept to realize is that since antennas are passive devices, they have to be reciprocal. In other words, radiation that goes through a reciprocal system has to work the same way forwards and backwards. In simpler words, if you imagine transmitting through the antenna and looking at the radiation pattern from far away--that antenna behaves exactly the same when the radiation shows up from far away receiving into the antenna--it behaves the same in transmission and reception.

Each phased array antenna element can be thought of as a radiator, and if its an active array, the radiating element can be thought of having a tuneable amplitude and phase. And the combined radiation pattern of the array is a superposition of all the individual elements.

When you have that kind of control, you can change the far-field radiation pattern by adding delays and changing the amplitude to tune the radiation pattern. It's quite ingenious actually.

> how does any sort of flat plate collect incoming radio waves as well as or better than a semi-spherical (?) dish?

So the really counterintuitive fact here is that the amount of far field energy that an antenna can collect is a tradeoff between how directive it is and how much it can collect from a particular direction.

i.e. assuming your antenna is 100% efficient, and say antenna A collects energy from all directions, and say antenna B collects energy only from the "top" hemisphere, antenna B collects energy from that direction twice as much as antenna A. In more technical terms, the directivity integral is always constant.

What's also kind of wacky is that generally speaking the bigger the antenna is, the more directive the antenna is--e.g. an antenna that's big generally collects better from its "boresight". The first paragraph still applies, so a big antenna is poor at collecting energy off-boresight.

A phased array is a curious idea. Start with a passive phased array, where you have one antenna element, and you add the contributions from that one antenna element copy-pasted in space.

generally speaking the further an antenna element is spaced apart, the more directivity you get, since the physical size is larger. If you have many of these elements copied across a large surface, your directivity increases a lot.

A passive array is kind of dumb since you might as well just have a parabolic reflector antenna ("dish")--but an active array is where it shines.

You can tune the exact phase and amplitude contribution from each phased array element, and when you do that, you can tune the exact radiation pattern of the phased array. You can steer the "boresight" by delaying the input from some elements; you can make the antenna less directive or more directive; you can make it so that there are multiple boresights (useful if you want to track multiple radar targets); etc.

For pure efficiency and directivity, a parabolic reflector is best. That's why it's used in radio astronomy. Active phased arrays are used in military and high performance radios since you can change the radiation pattern pretty much instantaneously.

Do you determine K with a bolt stretch gauge?

Motorcycles are subject to significantly more vibration, and some motorcycles are even designed such that the fasteners aren't guaranteed to not back out (in cars, they are guaranteed to not back out, at least if designed right)

I've seen the paint on the mating surface of the lug nuts sometimes degrades and causes the nut to loosen.

yeah, in hindsight, i think the lockdown had some pretty good compliance before the vaccine came out, and the lockdown worked pretty decently, and we were able to contain it decently until the vaccine came out.

and the vaccine came out rather rapidly and the sensible people who wanted to get it could get it fairly easily.

I'd dare to say the system worked?