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This 3D printer doesn’t gloss over the details

A new system enables realistic variations in glossiness across a 3D-printed surface; the advance could aid fine art reproduction and

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A new system enables realistic variations in glossiness across a 3D-printed surface; the advance could aid fine art reproduction and the design of prosthetics

Shape, color, and gloss.

Those are an object’s three most salient visual features. Currently, 3D printers can reproduce shape and color reasonably well. Gloss, however, remains a challenge. That’s because 3D printing hardware isn’t designed to deal with the different viscosities of the varnishes that lend surfaces a glossy or matte look.

MIT researcher Michael Foshey and his colleagues may have a solution. They’ve developed a combined hardware and software printing system that uses off-the-shelf varnishes to finish objects with realistic, spatially varying gloss patterns. Foshey calls the advance “a chapter in the book of how to do high-fidelity appearance reproduction using a 3D printer.”

He envisions a range of applications for the technology. It might be used to faithfully reproduce fine art, allowing near-flawless replicas to be distributed to museums without access to originals. It might also help create more realistic-looking prosthetics. Foshey hopes the advance represents a step toward visually perfect 3D printing, “where you could almost not tell the difference between the object and the reproduction.”

Foshey, a mechanical engineer in the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL), will present the paper at next month’s SIGGRAPH Asia conference, along with lead author Michal Piovarči of the University of Lugano in Switzerland. Co-authors include MIT’s Wojciech Matusik, Vahid Babaei of the Max Planck Institute, Szymon Rusinkiewicz of Princeton University, and Piotr Didyk of the University of Lugano.

Glossiness is simply a measure of how much light is reflected from a surface. A high gloss surface is reflective, like a mirror. A low gloss, or matte, surface is unreflective, like concrete. Varnishes that lend a glossy finish tend to be less viscous and to dry into a smooth surface. Varnishes that lend a matte finish are more viscous — closer to honey than water. They contain large polymers that, when dried, protrude randomly from the surface and absorb light. “You have a bunch of these particles popping out of the surface, which gives you that roughness,” says Foshey.

But those polymers pose a dilemma for 3D printers, whose skinny fluid channels and nozzles aren’t built for honey. “They’re very small, and they can get clogged easily,” says Foshey.

The state-of-the-art way to reproduce a surface with spatially varying gloss is labor-intensive: The object is initially printed with high gloss and with support structures covering the spots where a matte finish is ultimately desired. Then the support material is removed to lend roughness to the final surface. “There’s no way of instructing the printer to produce a matte finish in one area, or a glossy finish in another,” says Foshey. So, his team devised one.

They designed a printer with large nozzles and the ability to deposit varnish droplets of varying sizes. The varnish is stored in the printer’s pressurized reservoir, and a needle valve opens and closes to release varnish droplets onto the printing surface. A variety of droplet sizes is achieved by controlling factors like the reservoir pressure and the speed of the needle valve’s movements. The more varnish released, the larger the droplet deposited. The same goes for the speed of the droplet’s release. “The faster it goes, the more it spreads out once it impacts the surface,” says Foshey. “So we essentially vary all these parameters to get the droplet size we want.”

The printer achieves spatially varying gloss through halftoning. In this technique, discrete varnish droplets are arranged in patterns that, when viewed from a distance, appear like a continuous surface. “Our eyes actually do the mixing itself,” says Foshey. The printer uses just three off-the-shelf varnishes — one glossy, one matte, and one in between. By incorporating these varnishes into its preprogrammed halftoning pattern, the printer can yield continuous, spatially varying shades of glossiness across the printing surface.

Along with the hardware, Foshey’s team produced a software pipeline to control the printer’s output. First, the user indicates their desired gloss pattern on the surface to be printed. Next, the printer runs a calibration, trying various halftoning patterns of the three supplied varnishes. Based on the reflectance of those calibration patterns, the printer determines the proper halftoning pattern to use on the final print job to achieve the best possible reproduction. The researchers demonstrated their results on a variety of “2.5D” objects — mostly-flat printouts with textures that varied by half a centimeter in height. “They were impressive,” says Foshey. “They definitely have more of a feel of what you’re actually trying to reproduce.”

The team plans to continue developing the hardware for use on fully-3D objects. Didyk says “the system is designed in such a way that the future integration with commercial 3D printers is possible.”

This work was supported by the National Science Foundation and the European Research council.

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Written by Daniel Ackerman, MIT News Office

Additional background

Paper: “Towards Spatially Varying Gloss Reproduction for 3D Printing”
https://gfx.cs.princeton.edu/pubs/Piovar%C4%8Di_2020_TSV/glossprint_sga20.pdf

Source: https://bioengineer.org/this-3d-printer-doesnt-gloss-over-the-details/

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Bioengineer

The factors that improve job resiliency in North American cities have been identified

Credit: UC3M The researchers in this study reached this conclusion by drawing on network modelling research and mapped the job

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The researchers in this study reached this conclusion by drawing on network modelling research and mapped the job landscapes in cities across the United States during economic crises.

Knowing and understanding which factors contribute to the health of job markets is interesting as it can help promote faster recovery after a crisis, such as a major economic recession or the current COVID pandemic. Traditional studies perceive the worker as someone linked to a specific job in a sector. However, in the real-world professionals often end up working in other sectors that require similar skills. In this sense, researchers consider job markets as being something similar to ecosystems, where organisms are linked in a complex network of interactions.

In this context, an effective job market depends on many aspects, such as diversity and the number of job offers or training opportunities that workers have in order to acquire new skills, for example. In this scientific study, researchers have found that cities where all of these factors are very similar respond differently in regard to recovering from an economic crisis. Why? “We have discovered that the difference comes, in part, from the jobs ‘map’, a network that tells us how jobs within a city are related, according to the similarity of the skills required to perform those jobs,” explains Esteban Moro, an associate professor at the UC3M’s Department of Mathematics and co-author of the study, who is currently a visiting professor at the MIT Media Lab.

“When that map is extremely limited, in other words, when there is very little chance of finding another similar job (what we call “job connectivity”), cities are less prepared for a job crisis. In contrast, when that map offers lots of possibilities of moving from one job to another similar one, the city is better prepared. It also has an effect on workers’ wages: workers in cities that have a more diverse network earn more than those in the same occupation in cities where this network is more limited,” adds Esteban Moro.

Ecology, complex networks and job connectivity

In ecology and other domains where complex networks are present, resilience has been closely linked to the “connectivity” of the networks. In nature, for example, ecosystems with lots of connections have proven to be more resistant to certain shocks (such as changes in acidity or temperature) than those with fewer connections. Inspired by this idea and drawing on previous network modelling research, the authors of the study modelled the relationships between jobs in several cities across the United States. Just as connectivity in nature fosters resilience, they predicted that cities with jobs connected by overlapping skills and geography would fare better in the face of economic shock than those without such networks.

In order to validate this, the researchers examined data from the Bureau of Labor Statistics for all metropolitan areas in the US from the beginning to the end of the Great Recession (2008-2014). Based on this data, they created maps of the job landscape in each area, including the number of specific jobs, their geographical distribution, and the extent to which the skills they required overlapped with other jobs in the area. The size of a given city, as well as its employment diversity, played a role in resilience, with bigger, more diverse cities obtaining better results than smaller and less-diverse ones. However, by controlling size and diversity and taking job connectivity into account, predictions of peak unemployment rates during the recession improved significantly. In other words, cities where job connectivity was higher before the crash were significantly more resilient and recovered faster than those with less-connected markets.

Even in the absence of temporary crises like the Great Recession or the COVID pandemic, phenomena, such as automation, might radically change the job landscape in many areas in the coming years. How can cities prepare for this disruption? The researchers in this study extended their model to predict how job markets would behave when facing job loss due to automation. They found that while cities of similar sizes would be affected similarly in the early stages of automation shocks, those with well-connected job networks would provide better opportunities for displaced workers to find other jobs. This prevents widespread unemployment and, in some cases, even leads to more jobs being created as a result of the initial automation shock.

The findings of this study suggest that policymakers should consider job connectivity when planning for the future of employment in their regions, especially where automation is expected to replace a large number of jobs. Furthermore, increased connectivity does not just result in lower unemployment, it also contributes to a rise in overall wages. These results provide a new perspective on discussions about the future of employment and may help guide and complement current decisions about where to invest in job creation and training programmes, say researchers.

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https://www.uc3m.es/ss/Satellite/UC3MInstitucional/en/Detalle/Comunicacion_C/1371308984892/1371215537949/Identifican_los_factores_que_mejoran_la_resiliencia_laboral_en_las_ciudades_norteamericanas

Source: https://bioengineer.org/the-factors-that-improve-job-resiliency-in-north-american-cities-have-been-identified/

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Benefits of AstraZeneca COVID-19 vaccine outweigh its risks

Pausing AstraZeneca vaccinations because of suspected links to deadly blood clots could allow COVID-19 to continue to spread, cause more

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Pausing AstraZeneca vaccinations because of suspected links to deadly blood clots could allow COVID-19 to continue to spread, cause more deaths.

Credit: Davide Faranda, Tommaso Alberti, Maxence Arutkin, Valerio Lembo, and Valerio Lucarini

WASHINGTON, April 27, 2021 — The AstraZeneca COVID-19 vaccine is suspected of being linked to a small number of deep vein thrombosis (DVT) cases, which recently emerged within Europe as millions of people received vaccinations. This led several countries to suspend AstraZeneca injections and investigate the causal links to DVT.

Researchers within Europe teamed up to explore a hypothesis that pausing AstraZeneca vaccinations, even for a short duration, could cause additional deaths from the faster spread of COVID-19 within a population of susceptible individuals.

In Chaos, from AIP Publishing, researchers report using an epidemiological susceptible-exposed-infected-recovered (SEIR) model and statistical analysis of publicly available data to estimate excess deaths resulting from suspending AstraZeneca vaccinations and those potentially linked to DVT-adverse events in France and Italy.

They concluded the benefits of deploying the AstraZeneca vaccine greatly outweigh its associated risks, and relative benefits are wider in situations where the reproduction number is larger.

The SEIR model was discussed in a paper, published by Chaos, titled “Modeling the second wave of COVID-19 infections in France and Italy via a stochastic SEIR model.” It was able to predict the magnitude and timing of the second wave of the disease in France and Italy.

“Despite its simplicity, the model is able to propagate uncertainties via adding interactivity as a source of randomness within the data,” said Davide Faranda, from Laboratoire des Sciences du Climat et de l’Environnement and the London Mathematical Laboratory. “It mimics our ignorance of the exact parameters of the model due to testing capacities and evolving political and medical protocols.”

Risk-benefit analysis is performed by using a methodology inspired by the Fermi estimates. The group compares the excess deaths due to temporal restriction of the AstraZeneca vaccine’s deployment and excess deaths due to its possible side effects. Given the many uncertainties of possible side effects of the vaccine, they resorted to making worst-case scenario calculations to provide a robust upper bound to the related excess deaths.

“Our work shows suspending AstraZeneca vaccinations in France and Italy for three days without replacing it with another vaccine led to about 260 and 130 additional deaths, respectively,” said Faranda. “The difference between the two countries’ number of deaths is due to their different epidemiological situations and, in particular, to the higher basic reproduction number R0 measured in Italy with respect to France on March 15, 2021.”

The group analyzed the case of resuming vaccinations at a doubled rate for the same number of days as the vaccination interruption.

“Excess deaths are still on the same order of magnitude as those observed by resuming vaccinations at the same rate as before the interruption but scaled down by a factor of two,” said Faranda. “This is an evident outcome of nonlinear effects of epidemiological dynamics. Those who have not been vaccinated can contaminate other individuals before vaccination resumes.”

Even if several countries have resumed or are about to resume AstraZeneca vaccinations, the researchers show the effect of the interruption is hard to counterbalance and will require doubling down on deployment of vaccines. For large countries where AstraZeneca vaccinations have resumed, confidence in vaccines has been reduced by a nonnegligible percentage.

“The analysis presented here was performed with a parsimonious but well posed and tested model, and we hope our results will be the starting point for more detailed, more advanced, and more mature investigations with sophisticated models and data collection exercises,” said Faranda.

A first proof of the validity of their estimates is the report of seven DVT deaths per 18 million vaccinations within the U.K., a value that is in line with the group’s work based on data available a few weeks ago and assuming a standard fatality rate of DVT from AstraZeneca vaccinations.

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The article “Interrupting vaccination policies can greatly spread SARS-CoV-2 and enhance mortality from COVID-19 disease: The AstraZeneca case for France and Italy” is authored by Davide Faranda, Tommaso Alberti, Maxence Arutkin, Valerio Lembo, and Valerio Lucarini. It will appear in Chaos on April 27, 2021 (DOI: 10.1063/5.0050887). After that date, it can be accessed at https://aip.scitation.org/doi/10.1063/5.0050887.

ABOUT THE JOURNAL

Chaos is devoted to increasing the understanding of nonlinear phenomena in all areas of science and engineering and describing their manifestations in a manner comprehensible to researchers from a broad spectrum of disciplines. See https://aip.scitation.org/journal/cha.

Researchers within Europe teamed up to explore a hypothesis that pausing AstraZeneca vaccinations, even for a short duration, could cause additional deaths from the faster spread of COVID-19 within a population of susceptible individuals.

Source: https://bioengineer.org/benefits-of-astrazeneca-covid-19-vaccine-outweigh-its-risks/

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Army technique enhances robot battlefield operations

Credit: (Photo illustration / U.S. Army) ADELPHI, Md. — Army researchers developed a technique that allows robots to remain resilient

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Credit: (Photo illustration / U.S. Army)

ADELPHI, Md. — Army researchers developed a technique that allows robots to remain resilient when faced with intermittent communication losses on the battlefield.

The technique, called α-shape, provides an efficient method for resolving goal conflicts between multiple robots that may want to visit the same area during missions including unmanned search and rescue, robotic reconnaissance, perimeter surveillance and robotic detection of physical phenomena, such as radiation and underwater concentration of lifeforms.

Researchers from the U.S. Army Combat Capabilities Development Command, known as DEVCOM, Army Research Laboratory and the University of Nebraska, Omaha Computer Science Department collaborated, which led to a paper featured in ScienceDirect’s journal Robotics and Autonomous Systems.

“Robots working in teams need a method to ensure that they do not duplicate effort,” said Army researcher Dr. Bradley Woosley. “When all robots can communicate, there are many techniques that can be used; however, in environments where the robots cannot communicate widely due to needing to stay covert, clutter leading to radios not working for long distance communications, or to preserve battery or bandwidth for more important messages, the robots will need a method to coordinate with as few communications as possible.”

This coordination is accomplished through sharing their next task with the team, and select team members will remember this information, allowing other robots to ask if any other robot will perform that task without needing to communicate directly with the robot that selected the task, Woosley said.

The robot that remembers a task is based on the topology of their wireless communications network and the geometric layout of the robots, he said. Each robot is assigned a bounding shape representing the area of the environment that they are caching goal locations for, which enables a quick search in the communications network to find the robot that would know if there were any goals requested in that area.

“This research enables coordination between robots when each robot is empowered to make decisions about its next tasks without requiring it to check in with the rest of the team first,” Woosley said. “Allowing the robots to make progress towards what the robots feel is the most important next step while handling any conflicts between two robots as they are discovered when robots move in and out of communications range with each other.”

The technique uses a geometric approximation called α-shape to group together regions of the environment that a robot can communicate with other robots using multi-hop communications over a communications network. This technique is integrated with an intelligent search algorithm over the robots’ communication tree to find conflicts and store them even if the robot that selects the goal disconnects from the communication tree before reaching the goal.

The team reported experimental results on simulated robots within multiple environments and physical Clearpath Jackal Robots.

“To our knowledge, this work is one of the first attempts to integrate geometry-based prediction of potential conflict regions to improve multi-robot information collection under communication constraints, while gracefully handling intermittent connectivity loss between robots,” Woosley said.

According to Woosley, other available approaches can only get input from the robots that are inside the same communications network, which is less efficient when robots can move in and out of communications range with the team.

In contrast, he said, this research provides a mechanism for the robot to quickly find potential conflicts between its goal and the goal another robot selected, but is not in the communications network anymore.

What specifically makes this research unique includes:

    -Providing an efficient method (fast and with few messages) for resolving goal conflicts between multiple robots that is robust to intermittent communications loss and robots joining or leaving local sets of robots that are in communications with each other

    -Performing as good as querying every robot in the communications range while saving radio bandwidth for more important communications

    -Performing better than each robot operating fully on its own without communications

Woosley said that he is optimistic this research will pave the way for other communications limited cooperation methods that will be helpful when robots are deployed in a mission that requires covert communications.

He and the research team, including DEVCOM ARL researchers Dr. John Rogers and Jeffrey Twigg and Naval Research Laboratory research scientist Dr. Prithviraj Dasgupta, will continue to work on collaboration between robotic team members through limited communications, especially in directions of predicting the other robot’s actions in order to avoid conflicting tasks to begin with.

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Source: https://bioengineer.org/army-technique-enhances-robot-battlefield-operations/

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