For me it is lack of high end mechanical/electrical CAD software.

bleach is also antibiotic then

so is lava then

In a different perspective, the magnetic field itself is a result of special relativity. The magnetic field is an alternative way to explain electromagnetism without citing special relativity. (Or to say, electrostatic field and special relativity are sufficient to explain everything in electromagnetism, the existence of magnetic field is unnecessary.)

If the existence of magnetic field is unnecessary, there is no reason to even search for a magnetic monopole.

I paid WinRAR to use its zip function. There a lot of convenience features even if you don’t use rar format.

Would you mind listing some features you use? I use 7-zip and can't really think of anything i miss there

XRD used here only shows crystal lattice information for random orientated polycrystalline. It does not mean the two samples are identical. It does not prove whether they had single crystal or polycrystal.

You will need a four-circle diffractometer to prove two samples are identical, that also only work on single crystal if anyone can make it.

I am confused at the beginning, but it seems to me the author did not know the difference between diffractive optics and Fresnel lens. That significant reduce the credibility of the author. It is embarrassing for someone in academia to confuse these two different things.

>It is embarrassing for someone in academia to confuse these two different things.

I've been digging through the academic publications for a completely different field and it appears that they have very little or outdated knowledge of parallel fields, almost siloed.

Perhaps they should have started at the Wikipedia entry for “Zone Plate” instead

Also don’t forget US domestic PCB vendor often have to go through quoting process. Which can add significant delay.

This is also the difference between JLCPCB and many others.

I go to JLC and they show me a price. First thing, in my face. Including the (very reasonable) constraints that I have to meet to get that specific price.

I go to PCBway... price, in my face.

I go to Aisler... "upload your Gerber file here". This is fine for returning hobbyists who already have a file, but if you're considering whether you want to invest the time into the project, not knowing whether it will be $2 or $200 puts a serious damper on even wanting to start.

With hobbyists, this isn't just a deciding factor to get customers choose the competitors, it creates customers: Seeing the JLCPCB prices actually motivated me to learn KiCAD and make my own PCB.

Yes, absolutely. In three different instances, I received boards from China faster than I received quotes from American board shops.

I you are located close to a DHL hub, then the order from China can come in 2 days, which make the international order a moot point as disadvantage. JLCPCB provide 24-hour run on 2-layer board.

the author should talk to an FPGA engineer about build/compile time. That will make any computer programming language look like lightning speed.

No, I'll stay far away from them, thanks. ;P

Or talk to a web developer.

Magnet there is probably used as an isolator. The laser can only go out,but not come back.( yes, there will be laser coming back from reflection, which also interrupt the operation of the source laser.