Beijing Institute of Technology

www.bit.edu.cn
Beijing, China

Beijing Institute of Technology , is a co-educational public university, located in Beijing, China. Established in 1940 in Yan'an, the university is now under the direct administration of the Ministry of Industry and Information Technology.As a member university of National Key Universities, “Project 211” and “Project 985”, it has been given priority for development from the Chinese government, the Commission of Science, Technology and Industry for National Defense, the Ministry of Education and the Beijing Government. Wikipedia.


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The present disclosure is to provide a divided-aperture laser differential confocal Brillouin-Raman spectrum measuring method and the device thereof, which belongs to microscopic spectrum imaging field. By using the abandoned Rayleigh scattering light in the traditional confocal Raman spectrum detection, a divided-aperture laser differential confocal microscopy is constructed to realize high resolution imaging of three-dimensional geometrical structure of the measured sample. In addition, the characteristic that the zero-crossing point of the divided-aperture laser differential confocal imaging device accurately corresponds to the focus of objective is used to control the spectrum detector to accurately capture the excited Raman spectrum information excited at the focus of the objective, thereby achieving the detection of micro-area geometrical structure and spectrum information of the measured sample with high-spatial resolution, that is achieving mapping-spectrum with high-spatial resolution, and balancing resolution and measuring range. By complementing the advantages of confocal Raman spectrum detecting technology and confocal Brillouin spectrum detecting technology, the confocal spectrum detecting solution which detects the Raman spectrum and Brillouin spectrum at the same time is designed, the multi-property parameters of materials are measured and decoupled in composite.


A method for simulating a posture of a flexible cable based on a spring-mass model combining bending and torsion includes: establishing a physical property model of the cable, wherein a torsion property is represented by a torsion spring attached at each 55 cable segment; obtaining an initial position of each discrete mass point based on a total length of the cable and the number of the cable segments; identifying discrete mass points at both ends as fixed points, and obtaining their position information; calculating stress information of other discrete mass points whose position information is not determined based on the physical property model; sequentially calculating 10 10 equilibrium positions of the other discrete mass points by using the stress information and the initial positions to obtain their the position information; and simulating a stable posture of the cable based on the position information of the fixed points and the other discrete mass points.


Patent
Beijing Institute of Technology | Date: 2017-01-09

The invention relates to a method for reducing the PAPR in FRFT-OFDM systems, which belongs to the field of broadband wireless digital communications technology. The method is based on fractional random phase sequence and fractional circular convolution theorem, which can effectively reduce the PAPR of the system. The method of the invention has the advantages of simple system implementation and low computational complexity. In this method, the PAPR of the system can be effectively reduced while maintaining the reliability of the system. When the number of candidate signals is the same, the PAPR performance of the present method was found to be almost the same as that of SLM and better than that of PTS. More importantly, the present method has lower computational complexity than that of SLM and PTS methods.


Patent
Beijing Institute of Technology | Date: 2016-10-14

The present invention provides a system and a method for reducing the space charge effect in a linear ion trap. The system includes a linear ion trap, a first AC power supply, a second AC power supply, and a RF power supply. The linear ion trap includes four identical electrode rods, where two poles of the first AC power supply are respectively connected to two of the electrode rods, and two poles of the second AC power supply are respectively connected to the other two electrode rods. Two poles of the RF power supply are respectively connected to the first AC power supply and the second AC power supply. The first AC power supply and the second AC power supply provide sinusoidal AC signals. The present invention reduces the resolution decrease caused by the space charge effect, thereby improving analytical performance in mass spectroscopy.


The technique involves projecting a grayscale pattern of light and dark shapes onto a thin layer of liquid acrylate polymer placed in a plate or between two glass slides. A photoinitiator material mixed into the polymer initiates a crosslinking reaction when struck by light from an ordinary LED projector, causing a solid film to form. A light-absorbing dye in the polymer serves as a regulator for the light. Due to the complicated interaction between the evolution of the polymer network and volume shrinkage during photo curing, areas of the polymer that receive less light exhibit more apparent bending behavior. When the newly-created polymer film is removed from the liquid polymer, the stress created in the film by the differential shrinkage causes the folding to begin. To make the most complex origami structures, the researchers shine light onto both sides of the structures. Origami structures produced so far include tiny tables, capsules, flowers, birds and the traditional miura-ori fold—all about a half-inch in size. The origami structures could have applications in soft robots, microelectronics, soft actuators, mechanical metamaterials and biomedical devices. "The basic idea of our method is to utilize the volume shrinkage phenomenon during photo-polymerization," said Jerry Qi, a professor in the Woodruff School of Mechanical Engineering at Georgia Tech. "During a specific type of photopolymerization, frontal photopolymerization, the liquid resin is cured continuously from the side under light irradiation toward the inner side. This creates a non-uniform stress field that drives the film to bend along the direction of light path." Details of the work are scheduled to be published April 28 in the journal Science Advances. The research was supported by the National Science Foundation, the Air Force Office of Scientific Research and the Chinese Scholarship Council. It is believed to be the first application to create self-folding origami structures through the control of volume shrinkage during patterned photopolymerization. The process that creates the shrinkage phenomenon is considered harmful in other uses of the polymer. "Volume shrinkage of polymer was always assumed to be detrimental in the fabrication of composites and in the conventional 3-D printing technology," said Daining Fang, a co-author of the paper and a professor at Peking University when the research was done. "Our work shows that with a change of perspective, this phenomenon can become quite useful." Fang is now at Beijing Institute of Technology. To make the most complex shapes with bending in both directions, the researchers can flip the patterned film over to create crosslinking on the other side. "We have developed two types of fabrication processes," said Zeang Zhao, a Ph.D. student at Georgia Tech and Peking University. "In the first one, you can just shine the light pattern towards a layer of liquid resin, and then you will get the origami structure. In the second one, you may need to flip the layer and shine a second pattern. This second process gives you much wider design freedom." Light is shined onto the film for five to ten seconds, which produces a film about 200 microns thick. "The areas that receive light become solid; the other parts of the pattern remain liquid, and the structure can then be removed from the liquid polymer," said Qi. "The technique is very simple." Frontal photopolymerization is a process in which a polymer film is continuously cured from one side in a thick layer of liquid resin. In the presence of strong light attenuation, the solidification front initiates at the surface upon illumination and propagates toward the liquid side as the irradiation time increases. The process can be delicately tuned by controlling the illumination time and the light intensity, and the method has been used to fabricate microfluidic devices and synthesize microparticles. The researchers used poly(ethylene glycol) diacrylate in this demonstration, but the technique should work with a broad range of photocurable polymers. An orange dye was used in the demonstration, but other dyes could produce structures in a range of different colors. For the proof-of-principle, Zhao created a PowerPoint pattern by hand. To scale the process up, the system could be connected to a computer-aided design (CAD) tool for generating more precise grayscale patterns. Qi believes the technique could be used to produce structures as much as an inch in size. "The self-folding requires relatively thin films which might not be possible in larger structures," he said. Added Qi, "We have developed a simple approach to fold a thin sheet of polymer into complicated three-dimensional origami structures. Our approach is not limited by specific materials, and the patterning is so simple that anybody with PowerPoint and a projector could do it." More information: "Origami by frontal photopolymerization," Science Advances  28 Apr 2017: Vol. 3, no. 4, e1602326 DOI: 10.1126/sciadv.1602326, http://advances.sciencemag.org/content/3/4/e1602326


News Article | April 28, 2017
Site: www.eurekalert.org

Researchers at the Georgia Institute of Technology and Peking University have found a new use for the ubiquitous PowerPoint slide: Producing self-folding three-dimensional origami structures from photocurable liquid polymers. The technique involves projecting a grayscale pattern of light and dark shapes onto a thin layer of liquid acrylate polymer placed in a plate or between two glass slides. A photoinitiator material mixed into the polymer initiates a crosslinking reaction when struck by light from an ordinary LED projector, causing a solid film to form. A light-absorbing dye in the polymer serves as a regulator for the light. Due to the complicated interaction between the evolution of the polymer network and volume shrinkage during photo curing, areas of the polymer that receive less light exhibit more apparent bending behavior. When the newly-created polymer film is removed from the liquid polymer, the stress created in the film by the differential shrinkage causes the folding to begin. To make the most complex origami structures, the researchers shine light onto both sides of the structures. Origami structures produced so far include tiny tables, capsules, flowers, birds and the traditional miura-ori fold -- all about a half-inch in size. The origami structures could have applications in soft robots, microelectronics, soft actuators, mechanical metamaterials and biomedical devices. "The basic idea of our method is to utilize the volume shrinkage phenomenon during photo-polymerization," said Jerry Qi, a professor in the Woodruff School of Mechanical Engineering at Georgia Tech. "During a specific type of photopolymerization, frontal photopolymerization, the liquid resin is cured continuously from the side under light irradiation toward the inner side. This creates a non-uniform stress field that drives the film to bend along the direction of light path." Details of the work are scheduled to be published April 28 in the journal Science Advances. The research was supported by the National Science Foundation, the Air Force Office of Scientific Research and the Chinese Scholarship Council. It is believed to be the first application to create self-folding origami structures through the control of volume shrinkage during patterned photopolymerization. The process that creates the shrinkage phenomenon is considered harmful in other uses of the polymer. "Volume shrinkage of polymer was always assumed to be detrimental in the fabrication of composites and in the conventional 3-D printing technology," said Daining Fang, a co-author of the paper and a professor at Peking University when the research was done. "Our work shows that with a change of perspective, this phenomenon can become quite useful." Fang is now at Beijing Institute of Technology. To make the most complex shapes with bending in both directions, the researchers can flip the patterned film over to create crosslinking on the other side. "We have developed two types of fabrication processes," said Zeang Zhao, a Ph.D. student at Georgia Tech and Peking University. "In the first one, you can just shine the light pattern towards a layer of liquid resin, and then you will get the origami structure. In the second one, you may need to flip the layer and shine a second pattern. This second process gives you much wider design freedom." Light is shined onto the film for five to ten seconds, which produces a film about 200 microns thick. "The areas that receive light become solid; the other parts of the pattern remain liquid, and the structure can then be removed from the liquid polymer," said Qi. "The technique is very simple." Frontal photopolymerization is a process in which a polymer film is continuously cured from one side in a thick layer of liquid resin. In the presence of strong light attenuation, the solidification front initiates at the surface upon illumination and propagates toward the liquid side as the irradiation time increases. The process can be delicately tuned by controlling the illumination time and the light intensity, and the method has been used to fabricate microfluidic devices and synthesize microparticles. The researchers used poly(ethylene glycol) diacrylate in this demonstration, but the technique should work with a broad range of photocurable polymers. An orange dye was used in the demonstration, but other dyes could produce structures in a range of different colors. For the proof-of-principle, Zhao created a PowerPoint pattern by hand. To scale the process up, the system could be connected to a computer-aided design (CAD) tool for generating more precise grayscale patterns. Qi believes the technique could be used to produce structures as much as an inch in size. "The self-folding requires relatively thin films which might not be possible in larger structures," he said. Added Qi, "We have developed a simple approach to fold a thin sheet of polymer into complicated three-dimensional origami structures. Our approach is not limited by specific materials, and the patterning is so simple that anybody with PowerPoint and a projector could do it." This research was supported by NSF awards CMMI-1462894, CMMI-1462895, and EFRI-1435452; and the Air Force Office of Scientific Research grant 15RT0885. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring organizations.


News Article | June 5, 2017
Site: www.techtimes.com

The first Chinese science mission aboard the International Space Station will soon be ready to begin. On Saturday, June 3, SpaceX launched its refurbished Dragon capsule atop the Falcon 9 rocket, carrying scientific research equipment and experiments from China along with food and other essentials. The Chinese devices will be delivered to the space station on June 6, when the unmanned Dragon spacecraft is scheduled to dock with the ISS. The focus of China's first scientific mission aboard the ISS is the problem of space radiation and its effects on astronauts' DNA. Specifically, the mission aims to study the rate of DNA mutations in the space environment, according to Deng Yulin, project leader and life science professor at the Beijing Institute of Technology. As Deng points out, gene mutation is one of the biggest risks that astronauts face during space missions. This is because radiation levels are 10 times higher in space than on Earth, he explains. "The research team caught evidence of the gene mutation after the first experiment via Shenzhou-8 [launched by China in 2011], which proves the space environment can cause DNA mutation and biomolecular changes," said Deng in a statement. The current research project will continue that previous work aboard the ISS, where it is set to investigate whether space radiation and microgravity dictate a pattern of gene mutation, Deng stated. This experiment is the first Chinese-led research done on the U.S. side of the station. The project is expected to run for about 30 days aboard the ISS, after which the Dragon capsule will return the results back to Earth. Due to the nature of the research project, this endeavor could have important implications for long-duration human spaceflight. For the purpose of this experiment, the Beijing Institute of Technology teamed up with the American private company NanoRacks. The U.S. firm was paid about $200,000 to deliver the payload to the space station, as well as to collect data from the experiment and provide storage inside the company's racks. Apart from the SpaceX launch last weekend, China has also sent scientific equipment in space aboard its Tianzhou-1 cargo spacecraft earlier this spring. China's first cargo spacecraft, Tianzhou-1 docked with its orbiting space laboratory, known as the Tiangong-2, on April 22, after being launched into space inside the Long March-7 Y2 rocket. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


News Article | June 7, 2017
Site: news.yahoo.com

SpaceX celebrated a successful rocket launch on Saturday, sending a reused cargo spacecraft to resupply the International Space Station in orbit approximately 250 miles above the earth. But Elon Musk’s California-based company kept quiet about the spacecraft’s stowaway — a Chinese science experiment now installed in the Space Station. It’s a sign that aerospace’s swiftly-advancing private sector may have found yet another innovation: A way to evade the years-long ban on official cooperation in space between the United States and China. The Chinese experiment carried aloft by SpaceX’s Falcon 9 rocket will test how space radiation effects gene mutation, with potential ramifications for extended human space travel. It was designed by the Beijing Institute of Technology, who partnered with NanoRacks, paying the U.S. company approximately $200,000 to assist with transportation and data collection. It marks the first time a Chinese experiment has been conducted in the Space Station’s U.S. section, according to tech news site ARS Technica. International space cooperation these days, if not in the early years of the space race, is common, as it helps offset the extraordinarily high costs of technology and space travel. Russia and the United States jointly operate the Space Station, and NASA has signed a deal shelling out $490 million for Russia’s Soyuz space modules to deliver six U.S. astronauts to the space station. But cooperation has its limits: Congress banned bilateral cooperation between NASA and Chinese state-owned enterprises and Chinese citizens in 2011, citing national security risks. Rep. John Culberson (R-TX) upheld the ban after he became chair of the House subcommittee that funds NASA in 2014. “China’s space program is owned and controlled entirely by the People’s Liberation Army and the Chinese government have proven to be the world’s most aggressive in cyber-espionage,” Culberson said in an October 2015 statement. “I intend to vigorously enforce the longstanding prohibitions designed to protect America’s space program.” China’s space program, as with many state-owned Chinese firms from energy outfits to port developers, has close ties to its military. But the extent of such ties and even basic information about Chinese space programs, such as how much funding they receive, is uncertain due to lack of transparency. An even greater concern is technology transfer and theft. In 1998, a congressional investigation discovered that China had developed intercontinental ballistic missile systems incorporating U.S. technology originally offered to Chinese companies for commercial use. As a result, Congress shifted licensing requirements for all satellites and related technology to the State Department, which is in charge of approving commercial arms exports. For this launch, however, no State Department license was required, according to a person involved. SpaceX declined to comment on the licensing aspects of the launch. China’s space program is highly advanced and extremely ambitious. In 2013, China became the third country after the United States and Russia to land on the moon; the Jade Rabbit rover spent 31 months gathering data before shutting down. China has put two space laboratory modules into orbit and hopes to have its own full-size space station within the next decade. In January, the China National Space Administration announced plans to land a probe on Mars by 2020. NanoRacks took steps to prevent any technology transfer during the course of its partnership with the Chinese institute, according to the company, including isolating its research platforms to guarantee there was no interface between external researchers and the Space Station system. NanoRacks spokesperson Abby Dickes says these measures meant that the company did not need permission from the State Department for its partnership with Beijing Institute of Technology. Dan Huot, a NASA spokesperson, confirmed that no part of the project connected into the Space Station’s IT system, and that NASA properly notified Congress of the project. Commercial partnerships have “no ‘flags,’” NanoRacks CEO Jeffrey Manber told Chinese state news agency Xinhua. “I believe commercial is the pathway forward for greater cooperation with Chinese companies and educational organizations.”


News Article | June 12, 2017
Site: cen.acs.org

Materials that reversibly trap water from air could provide a vital source of drinking water in areas where it is scarce, or offer energy-efficient air conditioning. But to be commercially viable, these materials need a large water capacity and low energy requirements during water adsorption and desorption. Now, Mircea Dincă and his research group at MIT report record-setting performance for water-trapping in a metal-organic framework (MOF) that may bring both applications closer to reality (ACS Cent. Sci. 2017, DOI: 10.1021/acscentsci.7b00186). Porous materials can spontaneously pull water out of the air even at low humidity if their pores are the right size and their interior surfaces are hydrophilic. To maximize water capacity, the pores must be spacious, but not so big that the trapped water condenses into liquid that permanently clogs them. At the sweet spot, the water adsorbs to the MOF’s pores and desorbs with modest energy input, explains study co-author Adam Rieth. “Both adsorption and desorption are very important,” he says. In the new study, the researchers worked with a group of MOFs that had previously been used for the reversible capture of ammonia, chlorine, and bromine gases. These MOFs have just about optimal pore size—around 2 nm—and are made with manganese, cobalt, or nickel ions bound to triazolate linkers. In ambient air, the interior surface is naturally hydrophilic. When testing the MOFs, the researchers found that water spontaneously enters the pores at as low as 28% relative humidity. At 30% relative humidity, consistent with night-time conditions in arid climates, the cobalt MOF adsorbed almost 90% of its own weight in water, approximately double that of the next-highest-performing known material. The researchers calculated that if the cobalt-containing MOF were used in a hypothetical adsorption heat pump, the trapped water could be stripped from the material at just 55 °C. This means the device could potentially be powered by waste heat from a car engine, for example. Bo Wang, a MOF researcher from Beijing Institute of Technology who was not involved in the study calls it a “great addition” to the field. “It’s a very thorough study and helps to guide the design of MOFs.” However, this study looked only at the MOF material. In a real-world setting whether for air-conditioning or water capture, the MOF would need to be part of a device that uses heat to release water and regenerate it. For instance, another research team recently reported a water harvesting device that used solar energy to regenerate the MOF (C&EN, April 17, page 8). The MIT team predicts that if used in the same device, the cobalt MOF would be able to deliver almost three times as much water per cycle. They are now working to test their MOFs in this context, Rieth said.


Wei H.,Beijing Institute of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

Recently, Geng et al. proposed to allow a non-minimal coupling between quintessence and gravity in the framework of teleparallel gravity, motivated by the similar one in the framework of General Relativity (GR). They found that this non-minimally coupled quintessence in the framework of teleparallel gravity has a richer structure, and named it "teleparallel dark energy". In the present work, we note that there might be a deep and unknown connection between teleparallel dark energy and Elko spinor dark energy. Motivated by this observation and the previous results of Elko spinor dark energy, we try to study the dynamics of teleparallel dark energy. We find that there exist only some dark-energy-dominated de Sitter attractors. Unfortunately, no scaling attractor has been found, even when we allow the possible interaction between teleparallel dark energy and matter. However, we note that w at the critical points is in agreement with observations (in particular, the fact that w=-1 independently of ξ is a great advantage). © 2012 Elsevier B.V.

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