I am using "Switching Power Supply Design" from Pressman, Billings and Morey and "Switmode Power Supply Handbook" from Billings and Morey.

Both are excellent resources and look at design from a bit different point of view.

I think the biggest problems with swithing designs are not what you have listed, although both noise and failure modes are a huge problem and main cause of concern (and cost) when certifying your designs.

The biggest problem is that they are just so damn complex and they have so damn complex characteristics over time and operating parameters. You might think you understand how a switching PSU works but that's just an illusion. There are people who spent their entire life specialising in switching PSU design and are still learning. At best we can understand how they behave within certain parameters and then try to make sure to shut it down safely when we leave those parameters.

Those books have good advice if you already know the basics of how to analyze a converter.

Yeah. I use a lot of linear regulators. And they have even more advantages. For example, they are simple. They do exactly what you think they do. They don't leak. They don't create noise. They convert voltage right away and you don't need to wait for it to stabilise. And they have simple failure modes. You just throw in one part and it magically converts voltages. What simpler thing you would really want?

In most realistic designs you put multiple power supply rails in your designs because you need a lot of parts that don't need a lot of power but have different voltage requirements or might need voltage offset. In those cases linear regulators are perfect solution.

More than that, those power supply rails usually have standard voltages and there exist standard linear regulators that output those voltages to make everything even easier.

My strategy is to use linear regulators default and only use anything more complex on those voltage rails where I need to step the voltage up or where the inefficiencies would affect my design's performance significantly enough for me to care.

Oh, and use voltage dividers if you want to convert signal levels (unless it is fast signal and you care about signal integrity).

Contrary to some opinions here, I think this is very good advice.

I am always giving as much notice as I can. And also try to finish my projects and accommodate my employer/client as much as I can at the end of the project.

Regardless how unprofessionally they may act, I resolve to always act professionally myself.

I think it is more about the attitude rather than simple cost/benefit calculation.

But even if you are just looking at cost/benefit, after two decades of doing this I am finally seeing people noticing and coming back to me. I have my past bosses bringing new work to me, I have my colleagues spreading information about me by word of mouth. I have CEOs of unknown companies reach out to me because they learned about me from somebody who worked with me in the past.

Maybe you will not get noticed when you are junior level but when you get a bit more exposed position it starts becoming more and more important.

> The key point though is that their mechanism cannot work in vacuum. It absolutely requires that the light travels significantly slower than the gravitational radiation

I am not a physicist, but I understand we are talking about Universe so early after Big Bang that it wasn't yet transparent to light. There simply wasn't vacuum yet if by vacuum you mean electromagnetic waves being able to travel long distances.

I am not sure what you're getting at exactly. Although the paper does touch on early universe cosmology, the authors do their principal analysis using the refractive value for water, and there were no interstellar water clouds before early supernovae started generating oxygen. The authors also explicitly contemplate observables generated by LIGO-accessible compact binary mergers ("compact" here means black holes and neutron stars), all of which postdate the first stars.

In physical cosmology (and especially considering alternatives to General Relativity) it is very common to consider the possibility that some effect is strong in the very early universe and so weak as to be undetectable at present times (or even as early as the first galaxies or the surface of last scattering). Examples include auxiliary gravitational fields ("bimetric" theories, for example) that decay in the early universe, variable-speed-of-light/variable-Newton's-constant theories, and so forth.

Although one might think "hm, it's very convenient that an important effect only happens so early that we cannot use telescopes to see it", there is very good evidence for electroweak unification and cosmic inflation, both of which terminated (in different ways) in the very early universe, and are (or arguably were) too difficult to directly observe this late in the universe's history. Additionally there is ample indirect evidence that (if it exists) is within our reach.

That the hypothesized graviton-photon mechanism cannot work in vacuum makes it at least very difficult to test (or observe with telescopes) today, however the final section of the paper does suggest that if it happens in nature, where it happens is likely to become accessible to us in due course. This is not a theory that has a hard cut-off in the early universe; it is just a hypothesis that to be realized requires a configuration of e.g. binaries and molecular clouds that is not very close to what we commonly observe. (Double-binary compact objects in dusty environments might end up being commonplace though, and in those settings one could expect changes in "multimessenger" signals if the authors' ideas are correct. It's amazing how many star systems are turning out to be triples, and we know of triple-compact-star systems; there are a number of known quadruples like DI Chamaelontis; and Gamma Cassiopeiae is a system of at least seven ~stellar mass bodies.)

What you say doesn't make much sense.

AFAIK there exists no popular belief that physics was different in early universe. The physics was the same, the only thing that was different was physical conditions. Meaning everything was densely packed together.

If you, even for a moment, assume that laws were different in early universe then you essentially lost any possibility to predict anything.

It's not that things become unpredictable, it's that it can capture mispredictions (actual and possible) of things colloquially called "laws" of physics.

Spontaneous symmetry breaking has been at the root of at least three Nobel prizes, and is crucial to understanding the differences in physical systems at very high energies both in laboratories and in extreme astrophysical settings, at both early and approximately present times in the universe.

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

The early universe was in a high energy state, being very much hotter and denser than the later universe, as you say. There are several epochs -- notably the https://en.wikipedia.org/wiki/Electroweak_epoch -- where symmetry breaking is important, and using the lower energy theory (electromagnetism, in this example) simply does not work: results are (if even calculable) manifestly wrong, leading to a universe with a very different cosmic microwave background, and very different chemistry and nuclear physics.

I think at best one might say that theories with broken symmetries could still have those symmetries (i.e., the breaking may be reversible under "different ... physical conditions", like if our universe surprisingly evolved to a Big Crunch), however treating that as a denial of the possibility of different physics in the early universe is probably something you'd have to take up with philosophers or lexicographers for now.

Additionally, there is no reason to just assume (and refuse to trace out implications if wrong, or to validate) that physical constants are constants everywhere and everywhen. Putting some spacetime-___location-dependent function on constants like G, k_B, \alpha, \Lambda, c has at the very least proven instructive in further understanding the concordance (standard) models of particle physics and cosmology, where those constants are taken as constant everywhere and at all times in the universe. Indeed paramaterizing apparent constants is outright productive science. See e.g. <https://en.wikipedia.org/wiki/Test_theories_of_special_relat...> for a scratch-the-surface set of details, and additionally <https://en.wikipedia.org/wiki/Variable_speed_of_light#Relati...> are at least [a] interesting [b] testable and [c] improves testability of the families of theories in which these constants are assumed truly constant (i.e, everywhere and everywhen).

> popular belief

Well, I guess your popular is could outweigh a literature search. But for scientists:

<https://duckduckgo.com/?q=%22spontaneous+symmetry+breaking%2...>

<https://duckduckgo.com/?q=%22new+physics%22+early+universe+s...>

etc.

Finally,

> lost any possibility to predict anything

It's been about half a century since Kenneth Wilson and Nikolay Bogolyubov explored rescaling and renormalization, and nowadays practically every physical theory is written down as, considered as, or is being adapted towards <https://en.wikipedia.org/wiki/Effective_field_theory> (EFT). It is common that different EFTs apply to the same physical configuration as some characteric scale is crossed, and it is possible that physical theories will be EFTs all the way down (and all the way up), with the concept of fundamental becoming a relation between families of theories. (For example, Newtonian gravitation is less fundamental than General Relativity, because the former can be derived from the latter (and not the reverse), not because General Relativity is known to be correct at all scales).

I think you have very different idea of what "change in laws of physics" means.

No. That's far beyond our capabilities. Somebody calculated that LHC would have to be over 1000 light years in diameter to do this (and then still we would have to wait for thousands of years for particles to get accelerated).

I am not a huge fan of AI but I cannot deny this is probably biggest game changer since smartphones came out.

I find it a bit strange (although entirely predictable) that some people would try to forget about whole matter and hide from it as if it did not exist. The reality is that the IT world is going to go through some fundamental shifts in near future and very likely a lot of people will either lose jobs or do completely different work or do it with a completely different set of tools and skills.

We are now all trying to figure out what's in store for us and prepare for it, or be left out.

I find articles on HN actually pretty useful. And unlike some other hysterias, the whole preoccupation with AI to be healthy and useful.

> ...the IT world is going to go through some fundamental shifts in near future and very likely a lot of people will either lose jobs or do completely different work or do it with a completely different set of tools and skills.

We have been hearing this for a decade, that's why we are sick of hearing it again. Just do the fundamental shifts already.

> We have been hearing this for a decade,

But that's not true. What we have been seeing was attempts that looked marginally useful. Helpdesk chats that were only able to handle simplest problems and would respond with something stupid more often than not. Things that did not really look threatening to actual people doing their jobs well.

What I saw recently, on the other hand, is something that can actually perform useful, novel work and that can actually replace some marginally productive people. And this is very important difference.

each time I read a article about AI, I become frustrated again and again. If the end of world is coming, why I live?

It's not the end of the world. Someone once found out that people part with their money easier when they think it's the end of the world, and now that ploy is run amok. It's easier than trying to do something good.

One thing is sure, I would not want to be a UI dev in Mongolia...

Oh, I recently moved to Israel, and at first was shocked with how much worse design in general is. Like, typography, ads and of course UI. There are maybe 3-4 common fonts used everywhere, and I think it's a common problem for "rare" scripts. It seems you need some "critical mass" of visual content to come up with good design practices and figure out what looks good in your cultural landscape.

My first thought was about how browser tabs would be displayed.

Can confirm. Just at this moment I have a Dexcom G7 attached to my arm and I don't even have diabetes. Just using it to learn a little bit about my blood glucose patterns.

But these devices are not really built for non-diabetics. There is a constant barrage of alerts as my blood sugar regularly dips into hypoglycemic levels. I feel fine but the device purposefuly does not have any way to disable the alarm.

You can adjust the alerts a little bit. If you are actually going below 60 on a regular basis then you are hypoglycemic and the alerts are probably useful. It’s possible that your readings were slightly off though. Thanks for driving down prices for the rest of us! Keep on ordering em, big spender! I mean that.

My blood sugar goes below 60 but I am not hypoglycemic and no, the alerts are not useful. And yes, the measurements are correct -- I have more than one way to measure blood sugar level.

Hypoglycemic means your body is dependant on sugar, can't get sugar and has adverse reaction to it.

My body can't get sugar, true, but is not dependant on it (fat adapted) and I have no reaction to it.

As I have not eaten any carbs for about two months any notion of hypoglycemia due to not eating sugar is a bit meaningless.

I know people who get much, much lower blood sugar levels and feel fine. The levels they get would (below 40? below 30?) would be lethal to "normal" person, if sugar addiction can be called normal at all. But they all feel fine and are probably healthier than most.

I put CGM on my arm to learn how my blood sugar levels look when on my diet and then what happens when I switch carbs back on -- I expect my body to "freak out" a little bit and then stabilise within couple of days and that's what I would like to see in a bit clearer detail using my CGM.

As to driving the prices down... nah, I am not making a dent. These devices are too expensive to use regularly even for me (software devs salary). I will just put a couple of them to learn a bit about myself and then stop when I got what I needed.

Very interesting experiments as a data nerd would love to see a write up about how your diet effected your sugar. I know it's unlikely you will publish it but if you would I'd love to read it.

It is interesting but my data is useless. I lost over 70 pounds since July last year but I don't have any good record of blood sugar measurements. I did measurements whenever I liked either to confirm I am in ketosis or just to check my blood sugar / ketone levels in response to how I felt or to check how much various meals raised my sugar. But I did not keep any log.

There is couple things I learned. When you are on a strict ketogenic diet your blood sugar pretty much stays the same throughout the day. Even if I eat one huge meal for entire day, my sugar after the meal is pretty much the same as before the meal or within 10mg/dL. My exercise and circadian rhythm affect sugar more than meals.

Given this I wonder if it is possible at least for some people with diabetes to skip carbs completely and live carb-free but also insulin-free life.

Another thing I learned is that as I started my first keto month, your blood sugar starts dropping, then goes back up after about two weeks. Coincidentally, I also felt pretty poorly for those two weeks and my running performance dropped dramatically until my body adapted. The second time I started keto (after two months of break from it) I have seen nothing of the sort. Actually, I feel (but don't have good enough record to be sure) my blood sugar got a bit higher. But I have only been doing regular sugar measurements when I was in keto so I don't have data for sure.

As a type 1 I still need insulin even if I'm completely keto. It's not just carbs that affect blood glucose; as you pointed out, exercise and sleep can affect sugar among other things (stress, infections, meditation, using the toilet, drinking, various drugs...).

If my blood sugar goes up, to some degree, exercise and water can help - but they're not replacements for insulin. The suggestion that diabetics may not really need insulin is both ignorant and dangerous. You are not a doctor. People of hn, please go to your doctor for medical advice instead of hackernews comments.

Thanks for sharing your experiences with keto and measuring its effects.

Again. Missing big fat disclaimer. "Correlation does not imply causation". It is wrong to jump from "Weight loss relapse associated with exposure to perfluoroalkylate substances" to "Obesogenic PFASs may cause weight gain and thus contribute to the obesity pandemic".

Here, the word "may" is correct but it should really be "we just don't know, it is possible". But "obesogenic" suggest that the link has been proven which it has not.

I am not defending PFAS. But our history is full of missed opportunities and billions of people doing stupid shit for decades because somebody jumped to conclusions to fast. We have still not eradicated notion that fats are all wrong and need to be removed from the diet where it is exactly the opposite -- it is very likely that removal of fats from the diet is responsible for the large part of obesity epidemic. Right after people believing you need to eat multiple meals a day to be healthy.

It is important to keep focus on stuff that we already know is detrimental to our health and these are excessive amounts of carbohydrates (filling the void when fats were removed from the diet), refined sugars and reduced time between meals not allowing people to exercise their lipid transport in reverse.

History is full of huge disasters where absence of proof of negative effects was seen as proof of absence of negative effects. PFAS are such an example. There are already proven negative effects, many correlations are probable causations because we have good explanations like endocrine disruption for them, and worst of all bioaccumulation means that we cannot turn the clock backwards and all the more reason to use the precautionary principle.

All chemicals should be considered dangerous without any other knowledge. Coevolution of humans with chemicals (which has a big overlap with “natural” in contrast to synthetic chemicals) is just a prior that makes danger less likely.

Yeah... I'd love to see a "reset" to foods that were generally available 150 years ago. Before industrialized foods were broadly available. Meat, Eggs, common veg, and pre-gmo grains and legumes. And kind of start over. I understand modern farming allows the world as it is to be fed... but there's plenty of room for states/countries that are able to financially to try to do much better.

> reduced time between meals not allowing people to exercise their lipid transport in reverse.

I hadn't heard of this before, but it's interesting; despite receiving guidance to consume smaller, more frequent meals, I've found the practice has a negative effect on my own energy levels and weight stability.

Would you mind elaborating on this point, or providing links to further reading?

It is called fasting. It has been practiced for entirety of human history in all societies except for last couple of decades.

Fasting is an opportunity for the body to burn stored fats. Insulin is a hormone that tells every cell in the body to take sugars from the bloodstream and effectively prevents burning stored fats. When cells are used to burning sugars all the time, when given access to sugars and fats they will chose sugars preferentially. So as long as they have supply of sugar there is very little fat burning happening.

What's more, when you stop eating for a moment, for whatever reason, your body still does not have ability to burn much fat for energy because the metabolic pathways to do it are too dormant to provide enough energy on a moments notice. You become hungry which is your body telling you it can't get energy and you resolve the only way to fix the issue is by putting more carbohydrate-rich food in your mouth.

Fasting periods are necessary for the body to train those metabolic pathways. For example, by eliminating breakfast and not snacking in the evening you can easily double the time it takes between two meals giving couple of hours each day during which your body has to get energy from the fats. Over time your body relearns to burn fats and when you don't eat for a moment for whatever reason it is able to start burning fats faster and start providing more energy lessening the feeling of hunger and immediate need to put more food in your mouth.

Fasting is the normal state of the human body. We have evolved in conditions where food was relatively scarce and when we finally caught something, we had to eat it here and now and then move on and wait until we are able to catch something else at unknown future time.

This means we have evolved to accept food for a relatively short portion of time, be very good at storing energy as fat and then to use this fat for a long time until we could catch something else.

Very interesting, thank you!

This correlates perfectly with my experience: When I've tried to incorporate breakfast or other frequent small meals into my diet, I've found it wreaks havoc on my energy levels and feeling of fullness throughout the day. Without attempting to "fast," I've found that I feel best and experience fewer "crashes" when I skip breakfast and after-dinner snacks. You've just explained a convincing reason why that would be the case.

Next level is removing most or all carbs from your diet and restricting your eating window to a short time every day, no more than 4 hours. Which is what I do besides longer fasts.

I now don't even need to eat every day -- I had situations where I skipped entire days of eating because I simply forgot about it.

If you think about it most people have hundreds of thousands of calories on them in form of a huge fat layer covering most of the body which is enough for even lean people to live off for weeks at a time. If you think about it, it is pretty silly to complain one is hungry when there is so much energy stored on us.

I remember this thought struck me when I was reading about first Inuits trading in Canadian outposts. They would sell their furs and buy food. When a curious scientist decided to follow them he discovered they would stop outside the outpost, eat ALL food they just bought in one huge binge and then travel back home for many days or even weeks without eating anything. They were not only good at storing fat, but they were also good at recovering the energy when they needed for however long they needed. This is what means to be fat adapted -- being able to completely separate intake of food from burning stored fat for energy.

People nowadays are like a car that does not have a tank for gas. You have to keep pouring the gasoline into the engine constantly or it will shut down. What you want is a large tank from which you can be constantly supplying energy to your engine but you can fill this tank at your convenience.

Yeah. But no. I naturally seem to eat once a day and am thoroughly overweight.

And this is meant to be proof of what exactly?

Somehow doing one thing right is supposed to prevent obesity in every single case?

That all obesity must necessarily be because of people eating multiple meals?

And you're not losing weight? What/how much are you eating?

>Correlation does not imply causation

Correlation does not guarantee causation. But the stronger the correlation, the more you suspect that two phenomena are causally linked somehow. In this case, three pounds over half a year is a surprisingly large effect. If it were to continue, even if it slowly approaches an equilibrium, it could be responsible for a substantial increase in total body weight in millions of people. It's very possible that PFAS is just acting as a proxy for exposure to packaged foods, but that would be interesting in itself.

In this case, the best course of action is to study the phenomenon more closely, mostly because it is large.

Causal link requires an investigation to understand what is the nature of the link.

Is it possible that people who are likely to be more obese are also likely to eat garbage food delivered in low quality plastic packaging? And more healthy people are more likely to cook their food from higher quality ingredients like fresh produce that is not delivered in plastic?

See, the above explanation, I think very reasonable (though requiring a proof), could explain why obese people could have higher PFAS?

Another possible explanation (again, I am just sayin', no proof for it): imagine all food is contaminated with PFAS, but obese people have different chemistry that is worse at removing PFAS from their bodies.

This is why we say "correlation does not imply causation". Yes, highly correlated things are interesting and require further investigation. Even if PFAS is not causing obesity we still might learn something interesting about either PFAS or obesity or something else that is connected to both.

> Again. Missing big fat disclaimer. "Correlation does not imply causation". It is wrong to jump from "Weight loss relapse associated with exposure to perfluoroalkylate substances" to "Obesogenic PFASs may cause weight gain and thus contribute to the obesity pandemic".

That's correct, but it's interesting to ask: what should public policy be in light of these findings?

None? There is nothing actionable here.

We already know PFAS are dangerous for other reasons and the war against them is warming up.

And policy is not/should not be made based on just one study. Sadly, there are too many contradicting studies. Things like this need to be re-checked so that policymakers and societies don't waste time chasing things that don't bring any results.

Even then, we need to understand what is magnitude of this effect, what level of PFAS translate to what increase in obesity risk, etc. Then put it in context of already planned PFAS reductions.

Then if I was policymaker I would also look at what are potential projects we are not working on and where are highest return on investments. Just because there is something you can fix doesn't mean you should fix it. There might be another thing with more ROI where you should be spending your efforts.

That is assuming the conclusions of this study are correct, which I don't believe they are.

The findings of this one study should be rigorously evaluated and replicated first, not that much of our public policy is based on any kind of evidence but that would be the right way to go about it.

You mean, it's correct that the facts are not actionable, but what should we do?

Of course the switch off to the likes of margarine, seed oils and other high omega-6/3 ratio fats doesn't help. Was just looking up the cost of Beef tallow, say if someone did want to try to convince a restaurant to switch back and it's now 5x the cost of the "vegetable" seed based oils. It may last longer in a commercial setting, but that's a hard pill.

You are right. Just because food is fatty doesn't mean it is healthy. I did not want to make the comment too long but there is the concern for the quality of fats which is pretty complicated problem. There are some simple rules -- for example you definitely want to stay away from highly processed fats. But further than that things get more complicated.

As an example, we are told that fish is generally one of the healthiest fats around. But what people forget is that this is assuming wild fish and the kind that does not accumulate rare metals. Salmon is pretty health... unless we are talking farmed salmon. Farmed salmon is fed with highly processed, carbohydrate-rich feed which completely changes the fat content of the salmon making it very high omega 6 to 3 ratio. And God knows what else...

Beef tallow -- I have simple solution for this at least for my home use. I buy lots of quality red meat. Whenever I may broth or render fats for any reason, I gather them all and store them for later.

That's cool.. honestly, when I've made beef broth myself, it never really tastes that good. But I will do a filter through a fine mesh chinoise, and take the fat out as it settles to cook with. I do try to keep about half my meat/egg intake "clean" (pasture raised, etc) but it can be cost prohibitive sometimes.

I can make good tasting beef broth but I usually don't even bother.

I make a huge, 15L pot of broth. I use various pieces of meat, especially ones that have a lot of collagen. If I think I have too little cartilage I will add achilles tendons which are pretty much pure collagen. I brown everything them either on a pan or in the oven and I simmer it for at least 12h until all meat disintegrates and all collagen and fats dissolve. I then remove and discard meat and bones and small particles by filtering it through fine mesh strainer, I remove (and store) the tallow. And then I reduce everything about four-five times to get the meatiest substance on Earth. Cool it down, it should completely congeal in room temperature. I cut it into cubes, throw it into plastic bags and into the freezer. Then whenever I want to make soup or a sauce or risotto or whatever else, I just take some cubes from the freezer and drop directly into the pan or pot.

I also make and freeze other useful things. For example, I always keep a supply of bolognese sauce which I make 9L at a time and then lasts me for a year.

Yeah, my SO has been volunteering with a charity that does a feed the homeless thing on Saturdays, so have a lot of staple items around... Though making from scratch takes effort, it does cost a lot less at anything resembling scale, even for a few hundred portions once a week. Basically she spends 2-3 days a week just on food prep. I help when/where I can.

Do you assume engineers who build these things and point cameras at other satellites are unable to plan to make in-focus images?

No, I assume most satellites aren't built to point at other satellites.