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Researchers have developed a dolphin-inspired compact sonar with a new echo processing method.
The sonar allows for clearer visual imaging underwater compared to the conventional signal processing method of visualizing sound echoes.
Underwater imaging sonars are an essential technology for ocean exploration. Biomimetic sonars inspired by marine mammals such as dolphins are an emerging development in this field.
The new sonar incorporates information on the sparsity of objects which helps interpret sound echoes better. This processing method is based on the hypothesis that dolphins use prior information about their environment, apart from broadband sound pulses, to interpret their echoes.
Compared to other sonars of similar sizes and purposes, the new sonar provides a better trade-off between sonar-image clarity, the number of sensors, and the size of the sensor array used. Conventional methods of processing sound echoes usually break down when sensors are too few or spread out.
However, the new sonar processing method will be able to extract information and still yield image clarity in such a scenario.
Scientists at the National University of Singapore observed that dolphins were able to acoustically scan objects underwater and pick matching objects visually, demonstrating that a dolphin’s sound echoes emitted off an object contain information of the object’s shape. They then recorded dolphin echoes emitted when scanning an object underwater.
Based on their observations, the team built a biomimetic sonar that replicates a dolphin’s sonar. The sonar, which is about 25 cm (about 10 inches) in width and around the size of a dolphin’s head, is designed to emit sharp, impulsive click sounds similar to a dolphin’s echolocation.
Three transmitters are used to send sounds from different directions. The researchers then processed the sounds from both the dolphin and their sonar to visualize what the echoes revealed about the object shape.
To complement the hardware, the team came up with an innovative software that allowed the sonar to improve the visualization of the echoes.
Based on the hypothesis that dolphins use prior information to process their echoes, the researchers incorporated the concept of sparsity into the sonar’s software. This assumes that out of the space scanned, only a small percentage is occupied by the object.
“Using prior information, such as the idea of sparsity, is intuitive. It is something humans do all the time—we turn our understanding of reality into expectations that can speed up our inferences and decisions,” says Hari Vishnu, senior research fellow at NUS Tropical Marine Science Institute (TMSI).
“For example, in the absence of other information, the human brain and vision system tend to assume that in an image, the light on an object will be falling from above.”
The researchers demonstrated the effectiveness of the software when it was able to visualize information from a dolphin’s sonar echoes when scanning an object, as well as sonar signals produced by their compact sonar.
A conventional approach of processing both sonar echoes resulted in noisy images. However, the new processing approach gave better resolution and therefore sharper images. The software is also able to generate visualizations with a mere three clicks from the sonar, thus allowing it to be operationally fast.
The new sonar processing method could have potential benefits in underwater commercial or military sonars. For example, it could be used to scan the seabed to search for features that can be used to aid navigation. The sonar’s compactness also makes it suitable to be mounted on underwater robots for ocean exploration.
The study appears in Communications Engineering.
Source: NUS
The post Dolphins inspire sonar for clearer underwater images appeared first on Futurity.
Engineers have developed wooden seed carriers that mimic the behavior of self-burying seeds.
Before a seed can grow into a tree, flower, or plant, it needs to successfully implant itself in soil—a delicate and complex process.
For the Erodium flower to implant a seed, its stalk forms a tightly wound, seed-carrying body with a long, curved tail at the top. When it begins to unwind, the twisting tail engages with the ground, causing the seed carrier to push itself upright. Further unwinding creates torque to drill down into the ground, burying the seed.
Inspired by Erodium’s magic, Teng Zhang, professor of mechanical and aerospace engineering at Syracuse University, Lining Yao from Carnegie Mellon University, and a team of collaborators worked to engineer a biodegradable seed carrier called E-seed.
Their seed carrier, fashioned from wood veneer, could enable aerial seeding of difficult-to-access areas, and could work for a variety of seeds or fertilizers and adapt to many different environments. The carriers also could be used to implant sensors for environmental monitoring. They might also assist in energy harvesting by implanting devices that create current based on temperature fluctuations.
“This is a perfect example demonstrating the beauty and power of bioinspired design. We learn from nature and eventually achieve superior performance by leveraging the freedom of engineering design,” says Zhang.
The team’s work appears in the journal Nature.
“Seed burial has been heavily studied for decades in terms of mechanics, physics, and materials science, but until now, no one has created an engineering equivalent,” says Yao, director of the Morphing Matter Lab in the School of Computer Science’s Human-Computer Interaction Institute at Carnegie Mellon.
“The seed carrier research has been particularly rewarding because of its potential social impact. We get excited about things that could have a beneficial effect on nature.”
Additional collaborators are from Carnegie Mellon, the University of Pennsylvania, Zhejiang University, and Accenture Labs.
Source: Syracuse University, Byron Spice for Carnegie Mellon University
The post Wooden carrier unwinds to bury seeds appeared first on Futurity.
Labels made with inexpensive photonic fibers could improve clothing recycling, researchers report.
Less than 15% of the 92 million tons of clothing and other textiles discarded annually are recycled—in part because they are so difficult to sort.
“It’s like a barcode that’s woven directly into the fabric of a garment,” says Max Shtein, a professor of materials science and engineering at the University of Michigan and corresponding author of the study in Advanced Materials Technologies.
“We can customize the photonic properties of the fibers to make them visible to the naked eye, readable only under near-infrared light or any combination.”
Ordinary tags often don’t make it to the end of a garment’s life—they may be cut away or washed until illegible, and tagless information can wear off. Recycling could be more effective if a tag was woven into the fabric, invisible until it needs to be read. This is what the new fiber could do.
Recyclers already use near-infrared sorting systems that identify different materials according to their naturally occurring optical signatures—the PET plastic in a water bottle, for example, looks different under near-infrared light than the HDPE plastic in a milk jug.
Different fabrics also have different optical signatures, but those signatures are of limited use to recyclers because of the prevalence of blended fabrics, explains lead author Brian Iezzi, a postdoctoral researcher in Shtein’s lab.
“For a truly circular recycling system to work, it’s important to know the precise composition of a fabric—a cotton recycler doesn’t want to pay for a garment that’s made of 70% polyester,” Iezzi says. “Natural optical signatures can’t provide that level of precision, but our photonic fibers can.”
To develop the technology, the team combined Iezzi and Shtein’s photonic expertise—usually applied to products like displays, solar cells, and optical filters—with the advanced textile capabilities at MIT’s Lincoln Lab. The lab worked to incorporate the photonic properties into a process that would be compatible with large-scale production.
They accomplished the task by starting with a preform—a plastic feedstock that comprises dozens of alternating layers. In this case, they used acrylic and polycarbonate. While each individual layer is clear, the combination of two materials bends and refracts light to create optical effects that can look like color. It’s the same basic phenomenon that gives butterfly wings their shimmer.
The preform is heated and then mechanically pulled—a bit like taffy—into a hair-thin strand of fiber. While the manufacturing process method differs from the extrusion technique used to make conventional synthetic fibers like polyester, it can produce the same miles-long strands of fiber. Those strands can then be processed with the same equipment already used by textile makers.
By adjusting the mix of materials and the speed at which the preform is pulled, the researchers tuned the fiber to create the desired optical properties and ensure recyclability. While the photonic fiber is more expensive than traditional textiles, the researchers estimate that it will only result in a small increase in the cost of finished goods.
“The photonic fibers only need to make up a small percentage—as little as 1% of a finished garment,” Iezzi says. “That might increase the cost of the finished product by around 25 cents—similar to the cost of those use-and-care tags we’re all familiar with.”
In addition to making recycling easier, the photonic labeling could be used to tell consumers where and how goods are made, and even to verify the authenticity of brand-name products, Shtein says. It could be a way to add important value for customers.
“As electronic devices like cell phones become more sophisticated, they could potentially have the ability to read this kind of photonic labeling,” Shtein says. “So I could imagine a future where woven-in labels are a useful feature for consumers as well as recyclers.”
The team has applied for patent protection and is evaluating ways to move forward with the commercialization of the technology.
The National Science Foundation and the Under Secretary of Defense for Research and Engineering funded the work.
Source: University of Michigan
The post Butterfly wings inspire labels for better clothing recycling appeared first on Futurity.
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