Computers Math

The LiDAR sensor, which recognizes objects by projecting light onto them, functions as eyes for autonomous vehicles by helping to identify the distance to surrounding objects and speed or direction of the vehicle. To detect unpredictable conditions on the road and nimbly respond, the sensor must perceive the sides and rear as well as the front of the vehicle. However, it has been impossible to observe the front and rear of the vehicle simultaneously because a rotating LiDAR sensor was used.
To overcome this issue, a research team led by Professor Junsuk Rho (Department of Mechanical Engineering and Department of Chemical Engineering) and Ph.D. candidates Gyeongtae Kim, Yeseul Kim, and Jooyeong Yun (Department of Mechanical Engineering) from POSTECH has developed a fixed LiDAR sensor that has 360° view, in collaboration with Professor Inki Kim (Department of Biophysics) from Sungkyunkwan University.
This new sensor is drawing attention as an original technology that can enable an ultra-small LiDAR sensor since it is made from the metasurface, which is an ultra-thin flat optical device that is only one-thousandth the thickness of a human hair strand.
Using the metasurface can greatly expand the viewing angle of the LiDAR to recognize objects three-dimensionally. The research team succeeded in extending the viewing angle of the LiDAR sensor to 360° by modifying the design and periodically arranging the nanostructures that make up the metasurface.
It is possible to extract three-dimensional information of objects in 360° regions by scattering more than 10,000 dot array (light) from the metasurface to objects and photographing the irradiated point pattern with a camera.
This type of LiDAR sensor is used for the iPhone face recognition function (Face ID). The iPhone uses a dot projector device to create the point sets but has several limitations; the uniformity and viewing angle of the point pattern are limited, and the size of the device is large.
The study is significant in that the technology that allows cell phones, augmented and virtual reality (AR/VR) glasses, and unmanned robots to recognize the 3D information of the surrounding environment is fabricated with nano-optical elements. By utilizing nanoimprint technology, it is easy to print the new device on various curved surfaces, such as glasses or flexible substrates, which enables applications to AR glasses, known as the core technology of future displays.
Professor Junsuk Rho explained, “We have proved that we can control the propagation of light in all angles by developing a technology more advanced than the conventional metasurface devices.” He added, “This will be an original technology that will enable an ultra-small and full-space 3D imaging sensor platform.”
Recently published in Nature Communications, this study was conducted with the support from the Samsung Research Funding & Incubation Center.
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Materials provided by Pohang University of Science & Technology (POSTECH). Note: Content may be edited for style and length. More

Biomedical and electrical engineers at UNSW Sydney have developed a new way to measure neural activity using light — rather than electricity — which could lead to a complete reimagining of medical technologies like nerve-operated prosthetics and brain-machine interfaces.
Professor François Ladouceur, with UNSW’s School of Electrical Engineering and Telecommunications, says the multi-disciplinary team has just demonstrated in the lab what it proved theoretically shortly before the pandemic: that sensors built using liquid crystal and integrated optics technologies — dubbed ‘optrodes’ — can register nerve impulses in a living animal body.
Not only do these optrodes perform just as well as conventional electrodes — that use electricity to detect a nerve impulse — but they also address “very thorny issues that competing technologies cannot address,” says Prof. Ladouceur.
“Firstly, it’s very difficult to shrink the size of the interface using conventional electrodes so that thousands of them can connect to thousands of nerves within a very small area.
“One of the problems as you shrink thousands of electrodes and put them ever closer together to connect to the biological tissues is that their individual resistance increases, which degrades the signal-to-noise ratio so we have a problem reading the signal. We call this ‘impedance mismatch’.
“Another problem is what we call ‘crosstalk’ — when you shrink these electrodes and bring them closer together, they start to talk to, or affect each other because of their proximity.”
But because optrodes use light and not electricity to detect neural signals, the problems of impedance mismatch is redundant and crosstalk minimised. More

Remember iron-on decals? All you had to do was print something out on special paper with a home printer, then transfer it onto a T-shirt using an iron. Now, scientists have developed a very similar scheme, but instead of family photos or logos, it prints circuitry. The method, reported in ACS Applied Materials & Interfaces, can print functional circuits onto items ranging from ukuleles to teacups.
As electronics continue to evolve, so too do the circuit boards that control them. Most boards used today are rigid, built on solid fiberglass backings. As electronic systems are integrated into floppy and pliable items, such as clothing and soft robots, electronics need to be flexible too. This has led to increased interest in liquid metal circuits, which often include a special alloy of gallium metal that is a liquid at room temperature. One way to make these devices is to print them out with a modified inkjet or 3D printer. But these methods require complicated steps and sophisticated equipment, making the resulting devices expensive and unsuitable for large-scale manufacturing. To make the fabrication process quicker, easier and cheaper, Xian Huang and colleagues wanted to develop a method of creating liquid metal circuitry using a desktop laser printer that could place the electronics onto many types of surfaces.
To create the circuits, the researchers printed out a connected design onto heat-transferrable thermal paper with an ordinary laser printer. The printer laid down a carbon-based toner, which was transferred to a pane of glass by heating it. These toner patterns roughened the surface and created a hydrophobic gap of air between the carbon and the liquid metal. This prevented the metal from sticking when brushed on top, so the electronic ink-based pattern only adhered on the exposed parts of the surface.
This circuit could then be stuck directly to a smooth surface, such as a plastic soda bottle. If the surface was too uneven, like the bumpy skin of an orange, the device was first placed on a piece of flexible plastic, then onto the rougher surface. Regardless of how they were attached, however, the simple electronics all functioned as intended on their various substrates — from displaying images, to RFID tagging, to sensing temperature and sound. The researchers say that this protocol should greatly expand the applications of liquid metal circuits.
The authors acknowledge funding from the Key Research and Development Program of Zhejiang Province and the National Natural Science Foundation of China.
Video: https://youtu.be/HQattovte08
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Materials provided by American Chemical Society. Note: Content may be edited for style and length. More

For students learning a second or foreign language, text is often simplified to ensure that they can comprehend it well enough to understand the core message. Usually, complicated text in a foreign language is simplified manually by teachers or material designers. However, with the advent of artificial intelligence (AI)-based software, automatic simplification of text is now a reality. One such tool is the automatic text simplification (ATS) software, which simplifies text in second and foreign languages for L2 learners. Currently, there is limited data on the effectiveness of an ATS software in an educational setting.
To address this, Professor Dennis Murphy Odo from the Department of English Education at Pusan National University conducted a study, published in Applied Linguistics, to assess how L2 learners comprehend English language text simplified by an ATS tool. For this purpose, he recruited 61 native Korean speakers who had been studying English for the past 10 years, with reading proficiencies ranging from low to high.
These L2 learners were divided into low and high L2 reading proficiency groups and assigned to read either authentic English text derived from the Scientific American website, or automatically simplified version of that same text using a ‘Yet Another Text Simplifier’ (YATS) ATS tool. Following this, the L2 learners from both groups took a free recall test and a multiple-choice (MC) comprehension test, that tested their ability to recall and comprehend the text.
The key finding, derived from an analysis of the free recall test scores was that L2 learners with a higher reading proficiency found automatically simplified text more comprehensible, as compared to L2 learners with a lower reading proficiency.
While discussing this finding Prof. Odo remarks, “Although online automated text simplification tools can prove to be highly useful in making authentic materials more comprehensible for L2 learners beyond a certain level of foreign language reading proficiency, they may not do so for learners with a lower level of reading proficiency.”
Hence, ATS software can help L2 students with a high reading proficiency understand complicated text, and support teachers in simplifying challenging text for their students.
However, there is a need for ATS tools to be developed further, in order to make text comprehensible enough for L2 learners with low reading proficiencies. “On the positive side, software developers will continue to develop AI-enhanced tools that will make challenging texts more and more comprehensible to foreign language learners with different reading proficiencies,” says Prof. Odo in conclusion.
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In a study that confirms its promise as the next-generation semiconductor material, UC Santa Barbara researchers have directly visualized the photocarrier transport properties of cubic boron arsenide single crystals.
“We were able to visualize how the charge moves in our sample,” said Bolin Liao, an assistant professor of mechanical engineering in the College of Engineering. Using the only scanning ultrafast electron microscopy (SUEM) setup in operation at a U.S. university, he and his team were able to make “movies” of the generation and transport processes of a photoexcited charge in this relatively little-studied III-V semiconductor material, which has recently been recognized as having extraordinary electrical and thermal properties. In the process, they found another, beneficial property that adds to the material’s potential as the next great semiconductor.
Their research, conducted in collaboration with physics professor Zhifeng Ren’s group at the University of Houston, who specialize in fabricating high-quality single crystals of cubic boron arsenide, appears in the journal Matter.
‘Ringing the Bell’
Boron arsenide is being eyed as a potential candidate to replace silicon, the computer world’s staple semiconductor material, due to its promising performance. For one thing, with an improved charge mobility over silicon, it easily conducts current (electrons and their positively charged counterpart, “holes”). However, unlike silicon, it also conducts heat with ease.
“This material actually has 10 times higher thermal conductivity than silicon,” Liao said. This heat conducting — and releasing — ability is particularly important as electronic components become smaller and more densely packed, and pooled heat threatens the devices’ performance, he explained. More

Using a simple set of magnets, MIT researchers have come up with a sophisticated way to monitor muscle movements, which they hope will make it easier for people with amputations to control their prosthetic limbs.
In a new pair of papers, the researchers demonstrated the accuracy and safety of their magnet-based system, which can track the length of muscles during movement. The studies, performed in animals, offer hope that this strategy could be used to help people with prosthetic devices control them in a way that more closely mimics natural limb movement.
“These recent results demonstrate that this tool can be used outside the lab to track muscle movement during natural activity, and they also suggest that the magnetic implants are stable and biocompatible and that they don’t cause discomfort,” says Cameron Taylor, an MIT research scientist and co-lead author of both papers.
In one of the studies, the researchers showed that they could accurately measure the lengths of turkeys’ calf muscles as the birds ran, jumped, and performed other natural movements. In the other study, they showed that the small magnetic beads used for the measurements do not cause inflammation or other adverse effects when implanted in muscle.
“I am very excited for the clinical potential of this new technology to improve the control and efficacy of bionic limbs for persons with limb-loss,” says Hugh Herr, a professor of media arts and sciences, co-director of the K. Lisa Yang Center for Bionics at MIT, and an associate member of MIT’s McGovern Institute for Brain Research.
Herr is a senior author of both papers, which appear today in the journal Frontiers in Bioengineering and Biotechnology. Thomas Roberts, a professor of ecology, evolution, and organismal biology at Brown University, is a senior author of the measurement study. More

Extreme miniaturization of infrared (IR) detectors is critical for their integration into next-generation consumer electronics, wearables and ultra-small satellites. Thus far, however, IR detectors have relied on bulky (and expensive) materials and technologies. A team of scientists lead by Empa researcher Ivan Shorubalko now succeeded in developing a cost-effective miniaturization process for IR spectrometers based on a quantum dot photodetector, which can be integrated on a single chip, as they report in Nature Photonics.
Miniaturization of infrared spectrometers will lead to their wider use in consumer electronics, such as smartphones enabling food control, the detection of hazardous chemicals, air pollution monitoring and wearable electronics. They can be used for the quick and easy detection of certain chemicals without using laboratory equipment. Moreover, they can be useful for the detection of counterfeit medical drugs as well as of greenhouse gases such as methane and CO2.
A team of scientists at Empa, ETH Zurich, EPFL, the University of Salamanca, Spain, the European Space Agency (ESA) and the University of Basel now built a proof-of-concept miniaturized Fourier-transform waveguide spectrometer that incorporates a subwavelength photodetector as a light sensor, consisting of colloidal mercury telluride quantum dot (Hg Te) and compatible with complementary metal-oxide-semiconductor (CMOS) technology, as they report in the recent issue of Nature Photonics.
Tremendous effects on spectrometers of different kinds — and in various fields
The resulting spectrometer exhibits a large spectral bandwidth and moderate spectral resolution of 50 cm−1 at a total active spectrometer volume below 100 μm × 100 μm × 100 μm. This ultra-compact spectrometer design allows the integration of optical-analytical measurement instruments into consumer electronics and space devices. “The monolithic integration of subwavelength IR photodetectors has a tremendous effect on the scaling of Fourier-transform waveguide spectrometers,” says Empa researcher Ivan Shorubalko. “But this may also be of great interest for miniaturized Raman spectrometers, biosensors and lab-on-a-chip devices as well as the development of high-resolution snapshot hyperspectral cameras.”
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Materials provided by Swiss Federal Laboratories for Materials Science and Technology (EMPA). Note: Content may be edited for style and length. More

A new paper in Cell Systems explores the importance of using multiple data types in drug discovery. The paper screens over 1,000 drugs tested in six doses and demonstrates that gene expression and cell morphology provide different information for drug prioritization.
Led by biomedical data scientist Gregory Way, PhD, MS, the study showcases that by using these two data types simultaneously, scientists can measure fundamentally different aspects of the drug’s biology.
“We believe these two popular methods can be used to our advantage in designing drugs that address the full complexity of biology,” said Way, who is an assistant professor in biomedical informatics at the University of Colorado Anschutz Medical Campus.
Way and a team of data scientists found that the two data types provide a partially shared but also complementary view of drug mechanisms. They said using both approaches can advance drug discovery, functional genomics and precision medicine in unique directions.
“While labeling drugs based on mechanism of action is incredibly powerful, the approach risks missing a bigger picture. Both data types, collected via phenotypic drug screening, embrace the complexity of biology and can allow scientists to study and leverage the multifaceted effects drugs can offer,” Way adds.
Their paper shows how the assays compare with each other on useful biological tasks (e.g., mechanism of action prediction) given all the sources of variation/noise and current best practices in data processing. The phenotypic drug screening approach allows researchers to measure thousands of features of thousands of different drugs in a single experiment.
“We hope our analysis can guide researchers in experimental design and in understanding the limitations of their particular profiling modality to provide more consistent measurements and maximize potential for drug discovery successes,” Way said.
The paper guides scientists in planning experiments that profile cells for reversing disease phenotypes, quantifying cell response to chemical or genetic perturbation and querying drug mechanisms.
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Materials provided by University of Colorado Anschutz Medical Campus. Original written by Julia Milzer. Note: Content may be edited for style and length. More