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Elon Musk Plans To Build Hyperloop Test Track

hamjudo The columns are engineered for earthquakes (165 comments)

An earthquake might move the ground north of a fault to the west, and the ground south of the fault to the east. The tube has to stay straight enough that the train can come to a complete stop safely. This means a whole bunch of columns will have to bend.

about two weeks ago

6 Terabyte Hard Drive Round-Up: WD Red, WD Green and Seagate Enterprise 6TB

hamjudo Re:Who cares about rotational speed these days? (190 comments)

If your data is valuable, you will need to mirror the drives or use RAID. So one limitation is how quickly you can add a drive to your mirror system.

It would take 11 hours to fully mirror from one 6 TByte WD drive to another, if your system can actually manage to sustain 138Mbytes per second as shown on page 5 of the article. Obviously, the transfer will be slower, if the data is actually used for something.

If a disk dies, at best you are looking at half a day before the system is fully redundant again. Probably multiple days in the real world.

about a month ago

Single Pixel Camera Takes Images Through Breast Tissue

hamjudo Chicken tissue is a stand in for human soft tissue (81 comments)

They are working with 6 mm samples. They need to improve that by a factor of 5. Only a small percentage of women at risk for breast cancer can tolerate having their breasts compressed to 30 mm for imaging, but it is a large enough percentage to start doing human test trials. Assuming the image quality is high enough.

With existing xray based mammogram machines the more the breast is compressed, the better the image. There is abundant research on breast compression for imaging, just a google away.

Perhaps in a few years, this technique will be refined to the point where it can image through 3 cm of tissue in a reasonable amount of time, and produce a clinically useful image. Then we will hear about this technique again. Hopefully, it will be improved to the point where it is suitable for use on the entire population.

about 2 months ago

Riecoin Breaks World Record For Largest Prime Sextuplet, Twice

hamjudo Re: your car analogy is umm close. (51 comments)

It's like there is this long, infinite road and along this road are mile markers and every so often one of these mile markers has a rest stop at it. Mile marker 3, 5, 9, and so on. The farther your drive however the more you notice how spread out these rest stops are, eventually having thousands upon thousands of miles between them. Then, as in this article, you discover a pack of six rest stops very close to each other when all the other ones were thousands of mile markers apart. Thats probably the closest I can get this to a car analogy.

There are rest stops at 2, 3, 5, 7, 11, 13, and so on, but 9 is not a rest stop. The first two overlapping sets of six rest stops aren't spaced the same as the rest, and thus don't have the same mathematical properties. The Riecoin compliant prime sextuplets, err, I mean rest stops on the infinite highway are {7, 11, 13, 17, 19, 23} and {97, 101, 103, 107, 109, 113}, except they are too small for cryptography.

about 2 months ago

Home Depot Says Hackers Grabbed 53 Million Email Addresses

hamjudo Home Depot is getting off cheap (99 comments)

TFA says that Home Depot expects to pay "$62 million this year to recover from the incident", referring to exposing the details on 56 million credit cards. That's only $1.11 per exposed card. I used a credit card there during the period, so my Credit Union sent me a new card, plus two other physical letters about the incident. That had to cost them more than $1.11 per affected customer.

about 3 months ago

FTDI Reportedly Bricking Devices Using Competitors' Chips.

hamjudo Is it legal to make code compatible alternatives? (700 comments)

The fake chips that have FTDI stamped on the outside of the package are clearly misusing the FTDI trademark. On the other hand, those that don't cheat with the labels, and only use the string "FTDI" so they will inter-operate with existing software should be legal. I am not a lawyer. My opinion of what should be legal may not match what the courts rule as legal.

about 3 months ago

Ask Slashdot: Where Can I Find Good Replacement Batteries?

hamjudo Re:Variation in online reviews (131 comments)

Sometimes the variations in reviews is due to variations in the product. Many years ago I worked in a brick and mortar store and resold electronics. I'd buy a small number of units from a supplier and test them. If they were good, I'd buy a bunch for resale. Assuming the customers didn't bring them back, I would buy more of the same, from the same vendor. Customers who were happy with units from the first few batches, were not at all happy with units from later batches.

I dissected customer returns. Again and again, the products in later shipments looked identical on the outside, but were "cost reduced" on the inside. For example, I would see empty places on the circuit boards where the filter capacitors were supposed to go. In one batch of one product, many of the units were dead on arrival, on the ones that worked when I unpacked them, the solder joints only lasted a few weeks. Once opened, I could see that the boards were either soldered at the wrong temperature, it was the wrong type of solder, or badly made solder. Every connection was visibly a cold solder joint. Either the factory had no quality control, or they ignored the quality control.

Other products looked identical inside and out, but based on the failure rate, the factory must have gotten a bad batch of one the components.

Even longer ago, I worked on a product that logged data to a Compact Flash memory card. It was an embedded product that needed to work across a wide temperature range, including in the winter in Minnesota. The big names like SanDisk would randomly swap component suppliers. Our largest customer saw less than a 2% failure rate, but that was way too much. We found a specialty supplier that charged 5 times as much, but they had a rigorous quality control process. They paid attention to the specifications. They tracked where parts came from, and promised that we would be able to test sample units if they needed to switch suppliers. Alas, the 2% failure rate from the earlier parts had already doomed that product line.

about 5 months ago

3D-Printed Material Can Carry 160,000 Times Its Own Weight

hamjudo Re:This is not really new (60 comments)

The Fine article compares this type of lattice structure to the structure of the Eiffel Tower. They didn't claim anything more than being able to do it at a very fine scale, and to do it sufficiently precisely to get something that can support 160,000 times its one weight. They are just claiming refinements on centuries of engineering advances. The strength of well engineered 3D printed structures is still impressive. Even some printers that hobbyists can afford can beat out solid materials. It's only getting better.

about 7 months ago

Intel Rolling Out 800Gbps Cables This Year

hamjudo It is all a matter of cost and size (101 comments)

These will be used in data centers where it is common to have redundant systems connected with redundant cables, in order to maintain really high uptimes. Say a hypothetical system has a cluster which consists of 16 compute nodes and 2 storage nodes, Each of CPUserver01 through CPUserver16 will have two of these cables going to storageServerA, and two going to StorageServerB. For a total of 64 of these cables, for that one little compute cluster. Which would leave it an island, so of course there will be more network interfaces.

For this technology to get any market penetration, it will need to be cost effective at these bandwidths, and fit in the racks. Historically, Dense Wavelength Division Multiplexing, DWDM has been great at getting a lot of bandwidth on to a very long single strand (comparatively) inexpensive fiber, which allows in fiber signal amplification, and is the winner at going the distance, but not so good at being cost effective, or space efficient. These things, with the associated drivers should take up far less space inside the servers, and cost less, but they only will get 800Gbits in each direction, only go 300 meters, and use much more expensive (per kilometer of cable) 64 strand fiber.

about a year ago

Hard Silicon Wafers Yield Flexible Electronics

hamjudo Re:What's the killer app for flexible ICs? (15 comments)

Rigid silicon requires rigid interconnects. Flexible ICs allow flexible packaging, or different packaging. Instead of building from the printed circuit board up, build from the heatsink up. Use a precision pick and place system to glue the thin, wimpy, inexpensive silicon to the strong massive heatsink. Then mask on the solder balls. Then apply a thin, wimpy, inexpensive circuit "board". Attach all the old style surface mount components to the other side of the circuit "board". "Board" is in quotes because it would get all of its mechanical strength from heatsink. It might be so thin, it is no longer board like.

The big win here, is that one wafer is good for at least 5 sets of circuits. The lose is the grid of holes etched through the silicon as part of the pealing process. Assuming the grid of holes doesn't use up a significant portion of the surface area, the factory is getting close to 5 times as many devices out of each ingot of silicon.

about a year ago

Revolutionary Scuba Mask Creates Breathable Oxygen Underwater On Its Own

hamjudo It is a student design project (3 comments)

You can see the student's portfolio on his website: cargocollective.com/jeabyundesign/TRITON . He probably got a good grade. The case looks nice, if not plausible. The design for the guts of the device is lacking. He got the biology wrong, divers don't want pure oxygen. They need a mixture of gasses. The machine would have to process a whole lot of water to get enough oxygen to support a human. This means a whole lot of water would have to continuously flow through the device. Moving that much water takes a lot of energy.

1 year,12 days

Website Checkout Glitches: Two Very Different Corporate Responses

hamjudo Real time double entry bookkeeping (303 comments)

A few trading firms have learned to have a second system that monitors transactions to keep tabs on profit and loss. If the things swing out of the expected range, it is time to have a human look at the situation. If things get really out of hand, it is time to rate limit transactions, or halt them out right. Sudden extreme profits usually indicates a data entry error on your system, not that the rest of the market has gotten really stupid.

Most inventory systems have a way to track cost of goods, age of inventory, and expected profit margin. Eventually retailers will start filling in those details, and tracking them, so they can notice when something goes expensively wrong.

about a year ago

Google Nexus Gets Wireless Charger

hamjudo I've got a Qi charger (223 comments)

It works even if my Nexus 5 is more than 5 mm above the charging pad. That is many orders of magnitude less than the range for most wireless communication technologies.

The useful features are

  1. no connector to wear out,
  2. alignment is simple.
  3. The USB/thinport connector is available for other uses. (More of a theoretical benefit, as I don't use the USB port for anything, but I could if I wanted to. I've got the cable, I could even plug in an SD card reader.)

about a year ago

Not All USB Power Is Created Equal

hamjudo Re:won't help for Samsung note 2 (240 comments)

The error was an extra "m". The poster meant 0.14 Ohms per meter. I've seen higher resistance USB cable than that in the real world. Think of how much copper they saved by using such thin wires...

about a year ago

How Your Coffee Table Could Pass Your Coffee

hamjudo sort my Duplos (55 comments)

I was going to use the subject, Sort My Legos, but the prototype resolution is too low. With more actuators, you could dump Lego bricks on the table and have it sort them for you. Or for the more practical minded, sort wrenches, nuts and bolts.

about a year ago

AMD Intentionally Added Artificial Limitations To Their HDMI Adapters

hamjudo Re:HDMI has limitation built in to the spec (256 comments)

I have a monitor hooked up to my ComCast cable box in the exercise room. After I exercised for a while, I would get the stupid HDCP warning and/or the video would just cut out. I switched cables, I switched HDMI - DVI adapters, I switched monitors. It seemed like every time I started exercising, the video would stop.

It got worse recently, making it easy to diagnose. It got to the point where the video went away within a second of starting the treadmill. It is an EMI issue. Either the treadmill is emitting too much, or the ComCast box's suicide circuit is too sensitive.

I am so pleased that my ComCast has a suicide circuit to protect me from evildoers who modify treadmills to steal valuable copy righted material.

about a year ago


hamjudo hasn't submitted any stories.



I took down the wireless link

hamjudo hamjudo writes  |  more than 13 years ago

The roofers are coming tomorrow to rip off the old roof and put in a new one.

So I pulled the Pentium 90 with the 802.11 antenna out of the attic tonight. I bet it could handle some wind and a little rain, but there will probably be amazing amounts of dust.

Dave's internet connection will be down until Friday.

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