Computers Math

Despite years of hype, virtual reality headsets have yet to topple TV or computer screens as the go-to devices for video viewing. One reason: VR can make users feel sick. Nausea and eye strain can result because VR creates an illusion of 3D viewing although the user is in fact staring at a fixed-distance 2D display. The solution for better 3D visualization could lie in a 60-year-old technology remade for the digital world: holograms.
Holograms deliver an exceptional representation of 3D world around us. Plus, they’re beautiful. (Go ahead — check out the holographic dove on your Visa card.) Holograms offer a shifting perspective based on the viewer’s position, and they allow the eye to adjust focal depth to alternately focus on foreground and background.
Researchers have long sought to make computer-generated holograms, but the process has traditionally required a supercomputer to churn through physics simulations, which is time-consuming and can yield less-than-photorealistic results. Now, MIT researchers have developed a new way to produce holograms almost instantly — and the deep learning-based method is so efficient that it can run on a laptop in the blink of an eye, the researchers say.
“People previously thought that with existing consumer-grade hardware, it was impossible to do real-time 3D holography computations,” says Liang Shi, the study’s lead author and a PhD student in MIT’s Department of Electrical Engineering and Computer Science (EECS). “It’s often been said that commercially available holographic displays will be around in 10 years, yet this statement has been around for decades.”
Shi believes the new approach, which the team calls “tensor holography,” will finally bring that elusive 10-year goal within reach. The advance could fuel a spillover of holography into fields like VR and 3D printing.
Shi worked on the study, published in Nature, with his advisor and co-author Wojciech Matusik. Other co-authors include Beichen Li of EECS and the Computer Science and Artificial Intelligence Laboratory at MIT, as well as former MIT researchers Changil Kim (now at Facebook) and Petr Kellnhofer (now at Stanford University).

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The quest for better 3D
A typical lens-based photograph encodes the brightness of each light wave — a photo can faithfully reproduce a scene’s colors, but it ultimately yields a flat image.
In contrast, a hologram encodes both the brightness and phase of each light wave. That combination delivers a truer depiction of a scene’s parallax and depth. So, while a photograph of Monet’s “Water Lilies” can highlight the paintings’ color palate, a hologram can bring the work to life, rendering the unique 3D texture of each brush stroke. But despite their realism, holograms are a challenge to make and share.
First developed in the mid-1900s, early holograms were recorded optically. That required splitting a laser beam, with half the beam used to illuminate the subject and the other half used as a reference for the light waves’ phase. This reference generates a hologram’s unique sense of depth. The resulting images were static, so they couldn’t capture motion. And they were hard copy only, making them difficult to reproduce and share.
Computer-generated holography sidesteps these challenges by simulating the optical setup. But the process can be a computational slog. “Because each point in the scene has a different depth, you can’t apply the same operations for all of them,” says Shi. “That increases the complexity significantly.” Directing a clustered supercomputer to run these physics-based simulations could take seconds or minutes for a single holographic image. Plus, existing algorithms don’t model occlusion with photorealistic precision. So Shi’s team took a different approach: letting the computer teach physics to itself.

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They used deep learning to accelerate computer-generated holography, allowing for real-time hologram generation. The team designed a convolutional neural network — a processing technique that uses a chain of trainable tensors to roughly mimic how humans process visual information. Training a neural network typically requires a large, high-quality dataset, which didn’t previously exist for 3D holograms.
The team built a custom database of 4,000 pairs of computer-generated images. Each pair matched a picture — including color and depth information for each pixel — with its corresponding hologram. To create the holograms in the new database, the researchers used scenes with complex and variable shapes and colors, with the depth of pixels distributed evenly from the background to the foreground, and with a new set of physics-based calculations to handle occlusion. That approach resulted in photorealistic training data. Next, the algorithm got to work.
By learning from each image pair, the tensor network tweaked the parameters of its own calculations, successively enhancing its ability to create holograms. The fully optimized network operated orders of magnitude faster than physics-based calculations. That efficiency surprised the team themselves.
“We are amazed at how well it performs,” says Matusik. In mere milliseconds, tensor holography can craft holograms from images with depth information — which is provided by typical computer-generated images and can be calculated from a multicamera setup or LiDAR sensor (both are standard on some new smartphones). This advance paves the way for real-time 3D holography. What’s more, the compact tensor network requires less than 1 MB of memory. “It’s negligible, considering the tens and hundreds of gigabytes available on the latest cell phone,” he says.
“A considerable leap”
Real-time 3D holography would enhance a slew of systems, from VR to 3D printing. The team says the new system could help immerse VR viewers in more realistic scenery, while eliminating eye strain and other side effects of long-term VR use. The technology could be easily deployed on displays that modulate the phase of light waves. Currently, most affordable consumer-grade displays modulate only brightness, though the cost of phase-modulating displays would fall if widely adopted.
Three-dimensional holography could also boost the development of volumetric 3D printing, the researchers say. This technology could prove faster and more precise than traditional layer-by-layer 3D printing, since volumetric 3D printing allows for the simultaneous projection of the entire 3D pattern. Other applications include microscopy, visualization of medical data, and the design of surfaces with unique optical properties.
“It’s a considerable leap that could completely change people’s attitudes toward holography,” says Matusik. “We feel like neural networks were born for this task.”
The work was supported, in part, by Sony. More

Researchers have published a study revealing their successful approach to designing much quieter propellers.
The Australian research team used machine learning to design their propellers, then 3D printed several of the most promising prototypes for experimental acoustic testing at the Commonwealth Scientific and Industrial Research Organisation’s specialised ‘echo-free’ chamber.
Results now published in Aerospace Research Central show the prototypes made around 15dB less noise than commercially available propellers, validating the team’s design methodology.
RMIT University aerospace engineer and lead researcher Dr Abdulghani Mohamed said the impressive results were enabled by two key innovations — the numerical algorithms developed to design the propellers and their consideration of how noise is perceived in the human ear — as part of the testing.
“By using our algorithms to iterate through a variety of propeller designs, we were able to optimise for different metrics such as thrust, torque, sound directivity and much more. We also formulated a new metric, which involves how the human ear perceives sound, and propose to use that in future designs,” he said.
“Our method for optimising design can be applied to small propellers used on drones to much larger ones used for future urban air mobility vehicles — or air taxis — designed to carry human passengers.”
The team, which also included Melbourne-based aerospace company XROTOR, explored how various manipulations of propeller blade noise affected how it was perceived by the human ear.

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Mohamed said this modulation had the potential to be used as an important design metric for future propellers.
“The modulation of high frequency noise is a major factor in the human perception of rotor noise. Human ears are more sensitive to certain frequencies than others and our perception of sound also changes as we age,” he explained.
“By designing to such metrics, which take into account human perception, we can design less annoying propellers, which one day may actually be pleasant to hear.”
XROTOR Managing Director, Geoff Durham, said it was exciting to see prototype testing show the new designs could significantly reduce the sound impact of drones.
“Not only were the designs appreciably quieter to the human ear, but the propellers had a higher thrust profile against standard market propellers at the same throttle signal input,” he said.
The RMIT research team also included Dr Woutijn Baars, Dr Robert Carrese, Professor Simon Watkins and Professor Pier Marzocca. The prototypes were 3D printed at RMIT’s Advanced Manufacturing Precinct.

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Materials provided by RMIT University. Original written by Grace Taylor and Michael Quin. Note: Content may be edited for style and length. More

Material behaviors depend on many things including not just the composition of the material but also the arrangement of its molecular parts. For the first time, researchers have found a way to coax carbon nanotubes into creating moiré patterns. Such structures could be useful in materials research, in particular in the field of superconducting materials.
Professor Hiroyuki Isobe from the Department of Chemistry at the University of Tokyo, and his team create nanoscopic material structures, primarily from carbon. Their aim is to explore new ways to create carbon nanostructures and to find useful applications for them. The most recent breakthrough from their lab is a new form of carbon nanotube with a very specific arrangement of atoms that has attracted much attention in the field of nanomaterials.
“We successfully created different kinds of atom-thick carbon nanotubes which self-assemble into complex structures,” said Isobe. “These nanotubes are made from rolled up sheets of carbon atoms arranged hexagonally. We made wide ones and narrow ones which fit inside them. This means the resulting complex tube structure has a double-layered wall. The hexagonal patterns of these layers are offset such that the two layers together create what is known as a moiré pattern. And this is significant for materials researchers.”
You may see moiré patterns in your everyday life. When repeating patterns overlay one another a new resultant pattern emerges. If you then move one of the layers, or if you move relative to the layers, this resultant pattern will change slightly. For example, if you look at a screen door through a mesh curtain, or if you hold two sieves together. In the case of the team’s moiré patterns, they are made when one hexagonal grid of carbon atoms is rotated slightly relative to another similar hexagonal grid.
These patterns aren’t just for show, they can imbue materials with functional properties. Two areas that might especially benefit from the properties created here are synthetic chemistry, as the moiré carbon bilayer tubes could be challenging yet attractive targets of molecular self-assembly, and superconducting materials, which could lead to a generational leap in electrical devices which require far less power to run and would be far more capable than current devices.

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Researchers from University of Texas-Arlington, University of Virginia, Sun Yat-Sen University, and University of Washington published a new paper in the Journal of Marketing that seeks to advance the discipline of avatar-based marketing.
The study, forthcoming in the Journal of Marketing, is titled “An Emerging Theory of Avatar Marketing” and is authored by Fred Miao, Irina Kozlenkova, Haizhong Wang, Tao Xie, and Robert Palmatier.
In 2020, Samsung’s Star Labs brought digital avatars to CES 2020. However, this promotion was burned by its own fanfare. The avatars looked realistic and successfully answered some questions, but only when they were heavily controlled. As this example illustrates, avatar-based marketing is still in its nascent stage.
A pressing question is “How to design effective avatars?” Given the considerable amount of ambiguity about the definition of avatar, the researchers first identify and evaluate key conceptual elements of the term avatar and offer this definition: digital entities with anthropomorphic appearance, controlled by a human or software, that have an ability to interact.
Based on this definition, they present a typology of avatar design to isolate elements that academics and managers can leverage to ensure avatars’ effectiveness for achieving specific goals (e.g., providing standard vs. personalized solutions). Design elements affect avatars’ form realism and behavioral realism. Form realism refers to the extent to which the avatar’s shape appears human, while behavioral realism captures the degree to which it behaves as a human would in the physical world. Form realism includes design elements such as spatial dimension (2D/3D), movement (static vs. dynamic), and human characteristics (e.g., name, gender), whereas behavioral realism captures the avatar’s communication modality (e.g., verbal), response type (scripted vs. natural response), social content, and its controlling entity.
The study reveals a key limitation in avatar design: lack of consideration of the alignment between form and behavioral realism of avatars. As Miao explains, “If the levels of form and behavioral realism are mismatched, the consequences for avatars’ effectiveness may be profound and can help explain inconsistent avatar performance.”
Integrating form and behavioral realism, the study features a 2 x 2 avatar taxonomy that identifies four distinct categories of avatars: simplistic, superficial, intelligent unrealistic, and digital human avatars. A simplistic avatar has an unrealistic human appearance (e.g., 2D, visually static, cartoonish image) and engages in low intelligence behaviors (e.g., scripted, only task-specific communication). For example, in the Netherlands, ING Bank’s 2D, cartoonish-looking avatar Inge responds to simple customer inquiries from a set of predetermined answers. In contrast, a superficial avatar has a realistic anthropomorphic appearance (e.g., 3D, visually dynamic, photorealistic image), such as Natwest Bank’s Cora, but low behavioral realism in that it is only able to offer preprogrammed answers to specific questions. An intelligent unrealistic avatar (e.g., REA) is characterized by humanlike cognitive and emotional intelligence, but exhibits an unrealistic (e.g., cartoonish) human image. These avatars can engage customers in real-time, complex transactions without being mistaken for human agents. Finally, a digital human avatar such as SK-II’s YUMI is the most advanced category of avatars, characterized by both a highly realistic anthropomorphic appearance and humanlike cognitive and emotional intelligence, and is designed to provide the highest degree of realism during interactions with human users.

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Based on observations of relative effectiveness of these avatars in practice, the researchers present propositions that predict outcomes of avatar marketing. In particular:
-As the form realism of an avatar increases, so do customers’ expectations for its behavioral realism.
-Differences between the avatar’s form and behavioral realism have asymmetric effects, such that customers experience positive (negative) disconfirmation when an avatar’s behavioral realism is greater (less) than its form realism.
Recall the avatar of Samsung’s Star Labs, which is high in form realism but low in behavioral realism. Kozlenkova says that “Our analysis indicates that Samsung’s avatar sets audience expectations too high, which may have led to a negative disconfirmation, thereby resulting in an unfavorable customer experience.”
Avatars’ effectiveness may be highly contingent on the level of perceived uncertainty users experience during their interactions with avatars as well as choice of media channel (e.g., smartphones vs. desktops). Finally, design efforts should take the customer relationship phase into account because the relative effects of customers’ cognitive, affective, and social responses differ across relationship stages.
The framework generates practical implications that urge firms to consider five interrelated areas: (1) when to deploy avatars, (2) avatar form realism, (3) avatar behavioral realism, (4) form-behavioral realism alignment, and (5) avatar contingency effects for optimal avatar-based marketing applications. More

Most teenagers don’t remember life before the internet. They have grown up in a connected world, and being online has become one of their main sources of learning, entertaining and socializing.
As many previous studies have pointed out, and as many parents worry, this reality does not come risk-free. Whereas time on the internet can be informative, instructive and even pleasant, there is already significant literature on the potential harm caused by young children’s problematic internet use (PIU).
However, a new study led by István Tóth-Király, a Horizon Postdoctoral Fellow at the Substantive-Methodological Synergy Research Laboratory in Concordia’s Department of Psychology, is one of only a few that examines PIU’s effects on older adolescents. The paper was co-written by professor of psychology Alexandre Morin and Lauri Hietajärvi and Katariina Salmela-Aro of the University of Helsinki.
The paper, published in the journal Child Development, looks at data gathered by a longitudinal study of 1,750 high school students in Helsinki over three years.
It begins by asking three big questions: what were some of the predictors or determinants of PIU? How did PIU change over the course of late adolescence, in this case, ages 16-19? And what are the consequences of PIU among the age group?
At-risk signals
The researchers identified three principal determinants of PIU among adolescents. The first was loneliness, defined as a lack of satisfying interpersonal relationships or the perceived inadequacy of social networks. Other studies on PIU also identified loneliness as a predictor.

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Parenting practices, as perceived by the teen, also predicted PIU. The researchers looked at both parental caring, such as the expressions of warmth, empathy, interest and closeness towards the child, and parental neglect, defined as the uneven availability or unresponsiveness to the child’s needs.
Not surprisingly, better parenting is linked to lower PIU, while neglectful parenting is linked to higher PIU. The researchers noted the differences in how maternal and paternal behaviour affected usage.
Maternal caring especially was associated with lower PIU, suggesting that high-quality mother-child relationships might have led to a decrease in the need to use the internet excessively. Paternal neglect, on the other hand, had a stronger relationship with higher PIU, as a lack of guidance and limits hindered a teen’s ability to set personal boundaries.
Finally, the researchers considered gender. They found boys more likely to engage in PIU than girls, as they tend to be prone to more addictive-like behaviour, are more impulsive and, as suggested by other studies, may have more online options such as gaming or watching YouTube videos or pornography. Girls may be more likely to be online for socializing purposes.
Circular and harmful effects
The researchers then looked at outcomes associated with PIU, again identifying three broad categories.

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The first is depressive symptoms. If left unchecked, PIU appears to come with higher levels of depression. The two have been linked in previous studies, but Tóth-Király says their findings suggest a new interpretation.
“Our study tries to understand this relationship in a bi-directional or reciprocal way,” he says. “We think that PIU and depressive symptoms are likely to be co-occurring instead of one determining the other. They likely reinforce one another over time.”
The other outcomes linked to PIU are higher levels of substance abuse and lower levels of academic achievement. These were to be expected, and were also believed to be co-occurring.
Tóth-Király says some teens go through a phase of heavy internet use, usually around mid-adolescence. Time spent online tends to decrease as the children mature, develop their own goals and boundaries and form their first romantic relationships. He adds that being online for hours is not necessarily damaging, even if it does seem excessive to parents.
“If adolescents spend a lot of time on the internet but it doesn’t really impact their mental health or their grades or doesn’t seem to have any substantial negative consequences, then we cannot really say this is problematic behaviour,” he says. More

A new study led by Head of the Rokers Vision Laboratory and NYUAD Associate Professor of Psychology Bas Rokers explored why the severity of motion sickness varies from person to person by investigating sources of cybersickness during VR use.
In the new study, Variations in visual sensitivity predict motion sickness in virtual reality published in the journal Entertainment Computing, Rokers and his team used VR headsets to simulate visual cues and present videos that induced moderate levels of motion sickness. They found that a person’s ability to detect visual cues predicted the severity of motion sickness symptoms. Specifically, discomfort was due to a specific sensory cue called motion parallax, which is defined as the relative movement of different parts of the environment.
A previously reported source of variability in motion sickness severity, gender, was also evaluated but not confirmed. The researchers conclude that previously reported gender differences may have been due to poor personalization of VR displays, most of which default to male settings.
These findings suggest a number of strategies to mitigate motion sickness in VR, including reducing or eliminating specific sensory cues, and ensuring device settings are personalized to each user. Understanding the sources of motion sickness, especially while using technology, not only has the potential to alleviate discomfort, but also to make VR technology a more widely accessible resource for education, job training, healthcare, and entertainment.
“As we tested sensitivity to sensory cues, a robust relationship emerged. It was clear that the greater an individual’s sensitivity to motion parallax cues, the more severe the motion sickness symptoms,” said Rokers. “It is our hope that these findings will help lead to the more widespread use of powerful VR technologies by removing barriers that prevent many people from taking advantage of its potential.”

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Researchers at Uppsala University have developed a digital self-test that trains users to assess news items, images and videos presented on social media. The self-test has also been evaluated in a scientific study, which confirmed the researchers’ hypothesis that the tool genuinely improved the students’ ability to apply critical thinking to digital sources.
The new tool and the scientific review of it are part of the News Evaluator project to investigate new methods of enhancing young people’s capacity for critical awareness of digital sources, a key component of digital literacy.
“As research leader in the project, I’m surprised how complicated it is to develop this type of tool against misleading information — one that’s usable on a large scale. Obviously, critically assessing digital sources is complicated. We’ve been working on various designs and tests, with major experiments in school settings, for years. Now we’ve finally got a tool that evidently works. The effect is clearly positive and now we launch the self-test on our News Evaluator website http://www.newsevaluator.com, so that all anyone can test themselves for free,” says Thomas Nygren, associate professor at Uppsala University.
The tool is structured in a way that allows students to work with it, online, on their own. They get to see news articles in a social-media format, with pictures or videos, and the task is to determine how credible they are. Is there really wood pulp in Parmesan cheese, for instance?
“The aim is for the students to get better at uncovering what isn’t true, but also improve their understanding of what may be true even if it seems unlikely at first,” Nygren says.
As user support, the tool contains guidance. Students can follow how a professional would have gone about investigating the authenticity of the statements or images — by opening a new window and doing a separate search alongside the test, or doing a reverse image search, for example. The students are encouraged to learn “lateral reading” (verifying what you read by double checking news). After solving the tasks, the students get feedback on their performance.
When the tool was tested with just over 200 students’ help, it proved to have had a beneficial effect on their ability to assess sources critically. Students who had received guidance and feedback from the tool showed distinctly better results than those who had not been given this support. The tool also turned out to provide better results in terms of the above-mentioned ability than other, comparable initiatives that require teacher participation and more time.
Apart from practical tips such as opening a new search tab, doing reverse image searches and not always choosing the search result at the top of the hit page (but, rather, the one that comes from a source you recognise), Nygren has a general piece of advice that can help us all become more critically aware in the digital world:
“Make sure you keep up to date with information and news from trustworthy sources with credible practices of fact-checking, such as the national TV news programmes or an established daily newspaper. It’s difficult and arduous being critical about sources all the time.”

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Researchers at Toshiba Corporation in Japan have studied the operation of a small device fabricated in the write gap of a hard disk drive’s write head to extend its recording density. The device, developed by HWY Technologies, is based on a design concept known as microwave-assisted magnetic recording, or MAMR.
This technology, reported in the Journal of Applied Physics, by AIP Publishing, uses a microwave field generator known as a spin-torque oscillator. The spin-torque oscillator emits a microwave field causing the magnetic particles of the recording medium to wobble the way a spinning top does. This makes them much easier to flip over when the write head applies a recording magnetic field in the writing process.
In a computer’s hard drive, each bit of data is stored in magnetic particles known as grains. The magnetic orientation of the grains determines whether the bit is a 0 or a 1.
Making the grains smaller allows them to be packed together more tightly. This increases the storage capacity, but it also makes the data bits unstable. The development of MAMR allows more stable magnetic materials to be used but also limits the type of recording media that can be developed.
The investigators focused on another effect known as the flux control (FC) effect, which also occurs in MAMR. This effect improves the recording field and is maximized when the magnetization of the spin torque oscillator is completely reversed against the gap field.
The advantage of the FC effect is that improvement is obtained in any magnetic recording, according to author Hirofumi Suto. This is significant, since it would no longer be necessary to use recording media specially designed for the MAMR technology.
The FC device, a type of spin-torque oscillator designed to maximize the FC effect, consists of two magnetic layers fabricated directly in the write gap of the write head. A bias current supplied to the device reverses the magnetization of one of the layers through an effect known as spin-transfer torque.
The investigators experimented with different bias currents and found the reversal of magnetization occurred more quickly at higher currents. Upon comparing their experiments to a computational model, they also determined the recording field was enhanced by the FC effect, improving the writability of the write head and exceeding the performance of conventional write heads.
The FC device operates effectively at a fast write rate of approximately 3 gigabits per second, according to Suto. These results provide evidence that the FC device operates as designed and show that FC-MAMR is a promising technology for extending the areal density of hard disk drives.
Toshiba plans to introduce hard disk drives using MAMR technology that will increase hard disk capacity to 16-18 terabytes.

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Materials provided by American Institute of Physics. Note: Content may be edited for style and length. More