Dakota Alexander produces comic book art in the ukiyo-e style of traditional Japanese woodblock painting that became popular during the Edo period:
Comic book art in the ukiyo-e style
Saturday, September 15th, 2018Flown for recreational purposes over water and uncongested areas
Friday, September 14th, 2018The Kitty Hawk Flyer does look like fun:
Flyer is Kitty Hawk’s first personal flying vehicle and the first step to make flying part of everyday life.
Flyer is designed to be easy to fly and flown for recreational purposes over water and uncongested areas. In just a couple of hours, you will experience the freedom and exhilaration of flight.
Flyer maintains an altitude of 3 meters/10 feet for our first riders’ flights.
We have adjusted the flight control system to limit the speed to 20 mph for our first riders’ flights.
Flyer creates thrust through all-electric motors that are significantly quieter than any fossil fuel based equivalent. When Flyer is in the air, depending on your distance, it will sound like a lawnmower (50ft) or a loud conversation (250ft).
In the US, Flyer operates under FAA CFR Part 103 – Ultralight. FAA does not require aircraft registration or pilot certification though flight training is highly encouraged. Ultralights may only be flown over uncongested areas.
More false positives among the hypochondriac set
Thursday, September 13th, 2018The new ECG Apple Watch could do more harm than good:
“Do you wind up catching a few undiagnosed cases? Sure. But for the vast majority of people it will have either no impact or possibly a negative impact by causing anxiety or unnecessary treatment,” says cardiologist Theodore Abraham, director of the UCSF Echocardiography Laboratory. The more democratized you make something like ECG, he says, the more you increase the rate of false positives — especially among the hypochondriac set. “In the case of people who are very type-A, obsessed with their health, and fitness compulsive, you could see a lot of them overusing Apple’s tech to self-diagnose and have themselves checked out unnecessarily.”
The cases in which Apple’s new watch could be most helpful are obvious: People with atrial fibrillation, family histories of heart disease, heart palpitations, chest pain, shortness of breath, and so on. Sometimes, Abraham says, patients come in with vague cardiovascular symptoms that they can’t reproduce during their visit. Folks like that, he says, often require more expensive, prescription-based monitoring systems. If a doctor could ask that kind of patient to record their symptoms on a gadget they already own, that could be a win for the healthcare provider and the patient.
As for everyone else, it’s hard to say what benefit Apple Watch’s on-demand ECG could have, and existing evidence suggests it might actually do more harm than good.
There is, however, the matter of life-saving potential to consider, which AHA president Ivor Benjamin mentioned not once but twice in his presentation at yesterday’s Apple Event. If there’s a silver lining to putting electrocardiograms on every Apple Watch wearer’s wrist, it’s that their data (if they choose to share it — Apple emphasized at the event that your data is yours to do with as you please) could help researchers resolve the uncertainty surrounding ECG screening in seemingly healthy people. Apple’s new wearable might not be the handy heart-health tool it’s advertised as, but it could, with your permission, make you a research subject.
The Lazy Goldmaker is Azeroth’s most famous financial guru
Thursday, September 13th, 2018The Lazy Goldmaker is the World of Warcraft’s financial guru:
In August, shortly after the release of World of Warcraft’s seventh expansion, Battle For Azeroth, The Lazy Goldmaker posted one of his meticulous spreadsheets to the WoW economy subreddit. It contains a set of expertly appraised auction house margins for all of Azeroth’s many tradeskills—blacksmithed weapons, stat-buffing cooking recipes, excavated gems.
[...]
The Goldmaker himself chooses to remain anonymous, but he does disclose that he is 30 years old and Norwegian. It was during the Burning Crusade, more than a decade ago, that he first became interested in the economic side of Blizzard’s immortal MMO, and he’s been operating The Lazy Goldmaker blog—where he posts columns, analysis, and other musings—since 2016, shortly after the launch of the Legion expansion.
[...]
World of Warcraft lets The Goldmaker experiment—he’ll spend hours tinkering with the untapped capital of, say, the profit yields of the new Inscription recipes—and he’ll report back on his blog detailing each of his successes and failures, much to the glee of his international bulwark of disciples. After all, it’s not like he’s risking anything truly disastrous or life-changing. As the Goldmaker reiterates to me, we’re talking about the currency of elves, dwarves, and orcs in a computer game. He can afford to be a little cavalier with his investments, because “it’s just pixels at the end of the day.”
“I’m always looking for markets that players aren’t focusing on,” he says. “Because there are only so many people in the gold-making scene, so there’s always going to be something that players aren’t looking at.”
[...]
You can read the fundamentals of how The Goldmaker breaks down his economic principles in a beginner’s guide he posted to his website this March. “World of Warcraft is a game about constantly improving your character,” he writes, and as a financial opportunist, it’s your job to provide avenues to either help those characters boost their power levels or beautify their models. So, as an upstart auction house shark, you’ll learn to farm efficient materials in Azeroth, target specific high-value recipes that you can turn around quickly, and buy out supplies when they’re abundant and repost them when they’re scarce.
Google’s leadership was quite dismayed by Trump’s election
Wednesday, September 12th, 2018Breitbart just shared a video recorded by Google shortly after the 2016 presidential election, where the leadership is obviously dismayed:
- (00:00:00 – 00:01:12) Google co-founder Sergey Brin states that the weekly meeting is “probably not the most joyous we’ve had” and that “most people here are pretty upset and pretty sad.”
- (00:00:24) Brin contrasts the disappointment of Trump’s election with his excitement at the legalization of cannabis in California, triggering laughs and applause from the audience of Google employees.
- (00:01:12) Returning to seriousness, Brin says he is “deeply offen[ded]” by the election of Trump, and that the election “conflicts with many of [Google’s] values.”
- (00:09:10) Trying to explain the motivations of Trump supporters, Senior VP for Global Affairs, Kent Walker concludes: “fear, not just in the United States, but around the world is fueling concerns, xenophobia, hatred, and a desire for answers that may or may not be there.”
- (00:09:35) Walker goes on to describe the Trump phenomenon as a sign of “tribalism that’s self-destructive [in] the long-term.”
- (00:09:55) Striking an optimistic tone, Walker assures Google employees that despite the election, “history is on our side” and that the “moral arc of history bends towards progress.”
- (00:10:45) Walker approvingly quotes former Italian Prime Minister Matteo Renzi’s comparison between “the world of the wall” with its “isolation and defensiveness” and the “world of the square, the piazza, the marketplace, where people come together into a community and enrich each other’s lives.”
- (00:13:10) CFO Ruth Porat appears to break down in tears when discussing the election result.
- (00:15:20) Porat promises that Google will “use the great strength and resources and reach we have to continue to advance really important values.”
- (00:16:50) Stating “we all need a hug,” she then instructs the audience of Google employees to hug the person closest to them.
- (00:20:24) Eileen Noughton, VP of People Operations, promises that Google’s policy team in DC is “all over” the immigration issue and that the company will “keep a close watch on it.”
- (00:21:26) Noughton jokes about Google employees asking, ‘Can I move to Canada?’ after the election. She goes on to seriously discuss the options available to Google employees who wish to leave the country.
- (00:23:12) Noughton does acknowledge “diversity of opinion and political persuasion” and notes that she has heard from conservative Google employees who say they “haven’t felt entirely comfortable revealing who [they] are.” and urged “tolerance.” (Several months later, the company would fire James Damore allegedly for disagreeing with progressive narratives.)
- (00:27:00) Responding to a question about “filter bubbles,” Sundar Pichai promises to work towards “correcting” Google’s role in them
- (00:27:30) Sergey Brin praises an audience member’s suggestion of increasing matched Google employee donations to progressive groups.
- (00:34:40) Brin compares Trump voters to “extremists,” arguing for a correlation between the economic background of Trump supporters and the kinds of voters who back extremist movements. Brin says that “voting is not a rational act” and that not all of Trump’s support can be attributed to “income disparity.” He suggests that Trump voters might have been motivated by boredom rather than legitimate concerns.
- (00:49:10) An employee asks if Google is willing to “invest in grassroots, hyper-local efforts to bring tools and services and understanding of Google products and knowledge” so that people can “make informed decisions that are best for themselves.” Pichai’s response: Google will ensure its “educational products” reach “segments of the population [they] are not [currently] fully reaching.”
- (00:54:33) An employee asks what Google is going to do about “misinformation” and “fake news” shared by “low-information voters.” Pichai responds by stating that “investments in machine learning and AI” are a “big opportunity” to fix the problem.
- (00:56:12) Responding to an audience member, Walker says Google must ensure the rise of populism doesn’t turn into “a world war or something catastrophic … and instead is a blip, a hiccup.”
- (00:58:22) Brin compares Trump voters to supporters of fascism and communism, linking the former movement to “boredom,” which Brin previously linked to Trump voters. “It sort of sneaks up sometimes, really bad things” says Brin.
- (01:01:15) A Google employee states: “speaking to white men, there’s an opportunity for you right now to understand your privilege” and urges employees to “go through the bias-busting training, read about privilege, read about the real history of oppression in our country.” He urges employees to “discuss the issues you are passionate about during Thanksgiving dinner and don’t back down and laugh it off when you hear the voice of oppression speak through metaphors.” Every executive on stage – the CEO, CFO, two VPs and the two Co-founders – applaud the employee.
- (01:01:57) An audience member asks if the executives see “anything positive from this election result.” The audience of Google employees, and the executives on stage, burst into laughter. “Boy, that’s a really tough one right now” says Brin.
Mechanical jokes and flat cats
Wednesday, September 12th, 2018
Despite their great sizes and tremendous power spaceships are surprisingly simple machines. Every technology goes through three stages: first a crudely simple and quite unsatisfactory gadget; second, an enormously complicated group of gadgets designed to overcome the short-comings of the original and achieving thereby somewhat satisfactory performance through extremely complex compromise; third, a final proper design therefrom.
In transportation the ox cart and the rowboat represent the first stage of technology.
The second stage may well be represented by the automobiles of the middle twentieth century just before the opening of interplanatery travel. These unbelievable museum pieces were fro their time fast, sleek and powerful — but inside their skins were assembled a preposterous collection of mechanical buffoonery. The prime mover for such a juggernaut might have rested in one’s lap; the rest of the mad assembly consisted of afterthoughts intended to correct the uncorrectable, to repair the original basic mistake in design — for automobiles and even the early aeroplanes were “powered” (if on may call it that) by “reciprocating engines.” A reciprocating engine was a collection of miniature heat engines using (in a basically inefficient cycle) a small percentage of an exothermic chemical reaction, a reaction which was started and stopped every split second. Much of the heat was intentionally thrown away into a “water jacket” or “cooling system,” then wasted into the atmosphere through a heat exchanger.
What little was left caused blocks of metal to thump foolishly back-and-forth (hence the name “reciprocating”) and thence through a linkage to cause a shaft and flywheel to spin around. The flywheel (believe it if you can) had no gyroscopic function; it was used to store kinetic energy in a futile attempt to cover up the sins of reciprocation. The shaft at long last caused the wheels to turn and thereby propelled this pile of junk over the countryside.
The prime mover was used only to accelerate and to overcome “friction” — a concept then in much wider engineering use. To decelerate, stop, or turn, the heroic human operator used his own muscle power, multiplied precariously through a series of levers.
Despite the name “automobile” these vehicles had no autocontrol circuits; control, such as it was, was exercised second by second for hours on end by a human being peering out through a small pane of dirty silica glass, and judging unassisted and often disastrously his own motion and those of other objects. In almost all cases the operator had no notion of the kinetic energy stored in his missile and could not have written the basic equation. Newton’s Laws of Motion were to him mysteries as profound as the meaning of the universe.
Nevertheless millions of these mechanical jokes swarmed over our home planet, dodging each other by inches or failing to dodge. None of them ever worked right; by their nature they could not work right; and they were constantly getting out of order. Their operators were usually mightily pleased when they worked at all. When they did not, which was every few hundred miles (hundred, not hundred thousand), they hired a member of a social class of arcane specialists to make inadequate and always expensive temporary repairs.
Despite their mad shortcomings, these “automobiles” were the most characteristic form of wealth and the most cherished possessions of their time. Three whole generations were slaves to them.
The book is also the source of the original tribble and its associated troubles:
The similarities to the flat cats and the some specific story events involving them was brought to the attention of the Star Trek staff when Desilu/Paramount’s primary in-house clearance group, Kellam de Forest Research, submitted a report on the script on August of 1967, noting the similarities of “a small, featureless, fluffy, purring animal, friendly and loving, that reproduces rapidly when fed, and nearly engulfs a spaceship”. So worrisome was this matter that the producers contacted Heinlein and asked for a waiver, which Heinlein granted. In his authorized biography Heinlein said he was called by producer Gene Coon about the issue and agreed to waive claim to the “similarity” to his flat cats because he’d just been through one plagiarism lawsuit and did not wish to embroil himself in another. He had misgivings upon seeing the actual script but let it go, an action he later regretted.
The ability to choose something simpler and more likely to endure
Tuesday, September 11th, 2018Megan McArdle writes to a refrigerator dying young:
It turns out that refrigerators like the My First Fridge — the kind that quietly chug along decade after decade while needing only minor repairs — really are a thing of the past. According to the National Association of Home Builders, the average life span of a refrigerator is now just 13 years. And the German environmental agency found that between 2004 and 2013, the proportion of major appliances that had to be replaced in less than five years due to a defect rose from 3.5 percent to 8.3 percent. These days, we do not so much own our appliances as rent them from fate.
How did we become renters in our own homes? Peruse the Web, and you’ll discover a variety of explanations: outsourcing to suppliers who opt for cheapness rather than longevity; fancy computer-controlled features that add fancy problems; faster innovation cycles that leave inadequate time for testing; and government-imposed energy-efficiency standards that require a lot of fiddly engineering to comply with. But essentially, all of them boil down to one word: complexity. The more complicated something is, the more ways it can break.
When you are standing over the corpse of an appliance that died too young, it’s tempting to long for simpler days. But then, simpler isn’t the same as better. Replacement cycles may have shortened, but we can afford to replace our appliances sooner, because prices have fallen so dramatically. In 1979, a basic 17-cubic-foot Kenmore refrigerator cost $469 — or in today’s dollars, $1,735, which would have taken an average worker about 76 hours of labor to earn. It came with an ice maker, automatic defrost and some shelves. The nearest equivalent today has an extra cubic foot of storage, offers humidity-controlled crisper drawers and costs about a third as much to run. At $529, it represents under 20 hours of work at the average wage.
[...]
That’s the irony of modern life in so many ways, multiplying all our choices while taking away the most fundamental one: the ability to choose something simpler and more likely to endure.
We need to completely rewrite the textbooks on how to teach teachers
Monday, September 10th, 2018We need to completely rewrite the textbooks on how to teach teachers:
That’s according to a new report just published by the National Council on Teacher Quality. The report describes a vast and severe failure of teacher-training courses and the textbooks that accompany them to convey evidence-based practices; while delivering unsupported anecdotal evidence and well-debunked myths in spades. The report is accompanied by a letter of support signed by an assortment of professors of psychology and learning sciences from universities around the world.
The report finds that out of 48 texts used in teacher-training programs none accurately described fundamental evidence-based teaching strategies comprehensively. Only 15 percent had more than a single page devoted to evidence-based practices; the remainder contained either zero or only a few sentences on methods that have been backed up by the decades of scientific findings that exist in the field of educational psychology.
Missing from these textbooks were detailed explanations of six core strategies that have been found to be backed by evidence, which every teacher should know and use. The strategies aren’t new; they were identified by the Institute of Education Sciences, the research arm of the U.S. Department of Education, as being the most effective techniques in all classrooms regardless of age or subject in guidance released in 2007.
Hamsters really do love wheels
Sunday, September 9th, 2018Like other rodents, hamsters are highly motivated to run in wheels:
It is not uncommon to record distances of 9 km (5.6 mi) being run in one night. Other 24-h records include 43 km (27 mi) for rats, 31 km (19 mi) for wild mice, 19 km (12 mi) for lemmings, 16 km (9.9 mi) for laboratory mice, and 8 km (5.0 mi) for gerbils.
Hypotheses to explain such high levels of running in wheels include a need for activity, substitute for exploration, and stereotypic behaviour. However, free wild mice will run on wheels installed in the field, which speaks against the notion of stereotypic behaviour induced by captivity conditions. Alternatively, various experimental results strongly indicate that wheel-running, like play or the endorphin or endocannabinoid release associated with the ‘runner’s high’, is self-rewarding. Wheel use is highly valued by several species as shown in consumer demand studies which require an animal to work for a resource, i.e. bar-press or lift weighted doors. This makes running wheels a popular type of enrichment to the captivity conditions of rodents.
Captive animals continue to use wheels even when provided with other types of enrichment. In one experiment, Syrian hamsters that could use tunnels to access five different cages, each containing a toy, showed no more than a 25% reduction in running-wheel use compared to hamsters housed in a single cage without toys (except for the running wheel).
In another study, female Syrian hamsters housed with a nest-box, bedding, hay, paper towels, cardboard tubes, and branches used a wheel regularly, and benefited from it as indicated by showing less stereotypic bar-gnawing and producing larger litters of young compared to females kept under the same conditions but without a wheel. Laboratory mice were prepared to perform more switch presses to enter a cage containing a running wheel compared to several meters of Habitrail tubing or a torus of Habitrail tubing.
Running in wheels can be so intense in hamsters that it may result in foot lesions, which appear as small cuts on the paw pads or toes. Such paw wounds rapidly scab over and do not prevent hamsters from continuing to run in their wheel.
A hamster in a running wheel equipped with a generator can generate up to 500 mW electric power, enough for illuminating small LED lamps.
(Hat tip to our Slovenian Guest.)
eSports update
Saturday, September 8th, 2018Tyler Cowen shares an eSports update:
Tournament prize pools now rival those for some of the biggest events in traditional sports, and global audiences for some big gaming events have surpassed 100 million viewers, driven largely by esports’ exploding popularity in Asia.
The lion’s share of esports revenue comes from corporate sponsorships, according to industry analysis firm Newzoo, with ticket sales, merchandising and broadcasting rights bringing in additional revenue. Newzoo estimates that esports will generate $345 million in revenue in North America this year, in addition to more than half a billion dollars in revenue overseas.
Commenter Stuart “worked in an earlier era of this business (2008)” and notes that “it is a weird world”:
A key challenge I perceived then as now is the opaque visible display of athleticism. The gap between a great tennis player and myself is quite easy to see. I can pick up a racket, but I can’t do much more. In contrast, I can play the same games as these pros and feel accomplished by virtue of a sliding scale of difficulty which games have relied on for decades. Certainly a youth league for Tennis offers a similar analogy to this, but games are designed to be winnable, creating some ambiguity about the difference between the average joe and the pros. The more one plays, the clearer the contrast becomes, but the level of understanding on the part of the general public to the nuance of this struck me then as the reason why it would not gain mass appeal.
What has happened in the intervening decade seems to be a continued disregard for any ‘mainstream’ audience but the continued development of a formerly niche viewership which can appreciate the nuance, strategy and skill on display.
Like other ‘nerdy’ pursuits, eSports still seem to wrestle with a hunger for mainstream acceptance (e.g. lobbying for inclusion in the Olympics), but are clearly at their best when speaking to their core, which is growing by the year.
As another commenter noted, the incentives are unusual in eSports, where a developer owns the game. “Imagine what the NFL would do differently if they were trying to maximize the number of people playing football instead of the number of people watching football.”
Scientists identify a new kind of human brain cell
Friday, September 7th, 2018Scientists have identified a new kind of human brain cell:
The research team, co-led by Lein and Gábor Tamás, Ph.D., a neuroscientist at the University of Szeged in Szeged, Hungary, has uncovered a new type of human brain cell that has never been seen in mice and other well-studied laboratory animals.
Tamás and University of Szeged doctoral student Eszter Boldog dubbed these new cells “rosehip neurons” — to them, the dense bundle each brain cell’s axon forms around the cell’s center looks just like a rose after it has shed its petals, he said. The newly discovered cells belong to a class of neurons known as inhibitory neurons, which put the brakes on the activity of other neurons in the brain.
The study hasn’t proven that this special brain cell is unique to humans. But the fact that the special neuron doesn’t exist in rodents is intriguing, adding these cells to a very short list of specialized neurons that may exist only in humans or only in primate brains.
The researchers don’t yet understand what these cells might be doing in the human brain, but their absence in the mouse points to how difficult it is to model human brain diseases in laboratory animals, Tamás said. One of his laboratory team’s immediate next steps is to look for rosehip neurons in postmortem brain samples from people with neuropsychiatric disorders to see if these specialized cells might be altered in human disease.
Every specimen is arguably irreplaceable
Thursday, September 6th, 2018Brazil’s National Museum in Rio de Janeiro burned down, which is terrible, but not terribly surprising:
The burned building was the largest natural-history museum in Latin America, but it had never been completely renovated in its 200-year history. It had long suffered from obvious infrastructure problems including leaks, termite infestations, and — crucially — no working sprinkler system. Recognizing these problems in the 1990s, museum staff began planning to move the collection into a different site, but without stable funding, those plans proceeded in fits and starts.
[...]
The museum’s herbarium, its main library, and some of its vertebrates were housed in a different building that was untouched by the fire. But together, these reportedly account for just 10 percent of the museum’s collection. For comparison, the remaining 90 percent includes twice as many specimens as the entire British Museum. Museum staff carried out whatever they could by hand, including parts of the mollusk collection. Time will tell what else survived, and some losses are already clear: The floor beneath the entomology collection collapsed, for example, and the 5 million butterflies and other arthropods within were likely lost.
The museum’s archeological collection had frescoes from Pompeii, and hundreds of Egyptian artifacts, including a 2,700-year-old painted sarcophagus. It housed art and ceramics from indigenous Brazilian cultures, some of whose populations number only in their thousands. It contained audio recordings of indigenous languages, some of which are no longer spoken; entire tongues went up in flames. It carried about 1,800 South American artifacts that dated back to precolonial times, including urns, statues, weapons, and a Chilean mummy that was at least 3,500 years old.
Older still was the museum’s rich trove of fossils, from crocodile relatives like Pepesuchus to one of the oldest relatives of today’s scorpions. It harbored some of the oldest human remains in the Americas: the 11,500-year-old skull and pelvis of a woman who was unearthed in 1975 and nicknamed Luzia. “The skull is very fragile,” the artist Maurilio Oliveira told The New York Times. “The only thing that could have saved it is if a piece of wood or something fell and protected it.”
One might think that fossils, being rock, would be immune to fire. But as Mariana Di Giacomo, a paleontologist from the University of Delaware, described in a Twitter thread, fires can reach temperatures that are high enough to crack stone. It destroys buildings, causing walls and ceilings to fall on fragile specimens. It burns the labels attached to fossils and the numbers that are painted onto them, turning something that’s part of the scientific record into uninformative rock. “Without data, we only have old bones/shells/logs,” wrote Di Giacomo. Even the water that’s used to quench the flames can make things worse, causing fossils to swell and crack, dissolving adhesives, ruining labels even further, and stimulating the growth of mold.
The burned building housed skeletons of several dinosaurs, including Maxakalisaurus, a 44-foot-long, armor-backed, long-necked titan, and Santanaraptor, a lithe predator that contained beautifully preserved soft tissues in its legs, down to individual muscle fibers. “That really stabs me in the heart as a scientist,” said John Hutchinson from the Royal Veterinary College. “I always wanted to go study that specimen. It could have been revelatory. Now that probably will be impossible for anyone.”
The museum was also home to an irreplaceable collection of pterosaurs — flying reptiles that soared over the dinosaurs’ heads. Brazil was something of a “heaven for pterosaurs,” and the discovery of spectacular creatures such as Tapejara, Tupandactylus, and Tupuxuara, with their marvelously complete skeletons and improbably ornate crests, helped to reshape our understanding of these animals. “We may have lost dozens of the best preserved pterosaurs in the world,” said the paleontologist Mark Witton. “There really is no collection comparable … We find them elsewhere in the world, but the quality of the Brazilian material is remarkable.”
Many of these presumably lost specimens were holotypes — the first, best, and most important examples of their kind. Every specimen is arguably irreplaceable, but holotypes are especially so. Losing them is like losing the avatar of an entire species. Some of these specimens have been drawn and described in the scientific literature, but that information is often patchy, which is why scientists frequently return to holotypes to study them with their own eyes.
I’m reminded of all the Middle Eastern artifacts housed in London — where they’re a good deal safer.
Bulk metallic glasses can be readily extruded and 3D-printed
Wednesday, September 5th, 2018The 3-D printing of thermoplastics is highly advanced, but the 3-D printing of metals is still challenging and limited:
The reason being that metals generally don’t exist in a state that they can be readily extruded.
“We have shown theoretically in this work that we can use a range of other bulk metallic glasses and are working on making the process more practical and commercially-usable to make 3-D printing of metals as easy and practical as the 3-D printing of thermoplastics,” said Prof. Schroers.
Unlike conventional metals, bulk metallic glasses (BMGs) have a super-cooled liquid region in their thermodynamic profile and are able to undergo continuous softening upon heating — a phenomenon that is present in thermoplastics, but not conventional metals. Prof. Schroers and colleagues have thus shown that BMGs can be used in 3-D printing to generate solid, high-strength metal components under ambient conditions of the kind used in thermoplastic 3-D printing.
The new work could side-step the obvious compromises in choosing thermoplastic components over metal components, or vice-versa, for a range of materials and engineering applications. Additive manufacturing of metal components has been developed previously, where a powder bed fusion process is used, however this exploits a highly-localized heating source, and then solidification of a powdered metal shaped into the desired structure. This approach is costly and complicated and requires unwieldy support structures that are not distorted by the high temperatures of the fabrication process.
The approach taken by Prof. Schroers and colleagues simplifies additive manufacturing of metallic components by exploiting the unique-amongst-metals softening behavior of BMGs. Paired with this plastic like characteristics are high strength and elastic limits, high fracture toughness, and high corrosion resistance. The team has focused on a BMG made from zirconium, titanium, copper, nickel and beryllium, with alloy formula: Zr44Ti11Cu10Ni10Be25. This is a well-characterized and readily available BMG material.
The team used amorphous rods of 1 millimeter (mm) diameter and of 700mm length. An extrusion temperate of 460 degrees Celsius is used and an extrusion force of 10 to 1,000 Newtons to force the softened fibers through a 0.5mm diameter nozzle. The fibers are then extruded into a 400°C stainless steel mesh wherein crystallization does not occur until at least a day has passed, before a robotically controlled extrusion can be carried out to create the desired object.
(Hat tip to Jonathan Jeckell.)
Fitbit heart data reveals its secrets
Monday, September 3rd, 2018Fitbit has now logged 150 billion hours’ worth of heart-rate data from tens of millions of people, all over the world:
