Yoshikawa H.,Tohoku Gakuin University
Proceedings of 2016 International Symposium on Information Theory and Its Applications, ISITA 2016 | Year: 2016
Maximum a posteriori probability (MAP) decoding minimizes the symbol or bit error probability, however, few studies have performed an exact error performance evaluation, although the optimality does not require explanation. The MAP algorithm is much more complex than maximum likelihood decoding methods, therefore, suboptimal MAP algorithms are considered for practical systems. The Max-Log-MAP decoding algorithm is one of several near optimum algorithms that reduce decoding complexity. However, it is shown that turbo decoding with Max-Log-MAP has an error-performance degradation compared with MAP decoding. Log-MAP decoding can be realized using Max-Log-MAP decoding with a correction term, which corrects the error induced by maximum approximation. Constant Log-MAP decoding employs the constant correction term instead of the log-domain correction term. In this paper, analytical results of bit error probability of convolutional codes with constant Log-MAP decoding are shown. Furthermore, the analytical results are compared with the result of Max-Log-MAP decoding, and the improvement by the correction term which correct error induced by maximum approximation is presented, theoretically. The results show that the error performance of constant Log-MAP decoding is slightly better than Max-Log-MAP decoding. © 2016 IEICE.
Furuno Electrical Co. and Tohoku Gakuin University | Date: 2012-12-26
An underwater detection device (1) is provided. The device comprises a transceiver (10, 11, 121-124, 13) for transmitting underwater an ultrasonic signal and receiving an echo signal caused by the ultrasonic signal, and a detector (141, 142) for detecting, based on the echo signal, an incident angle of the ultrasonic signal with respect to an underwater moving body and a reflection intensity of the echo signal reflected on the underwater moving body.
Furuno Electrical Co. and Tohoku Gakuin University | Date: 2010-05-10
A method and device for displaying an underwater detection image is provided, in which an ultrasonic signal having a predetermined beam width is periodically transmitted underwater, receives a signal reflected on a detection target object which moves underwater, generates information on the detection target object based on the received signal, and displays the information on a display module. The method includes periodically detecting the detection target object and a position thereof based on the received signal, coupling the same detection target objects by associating the same based on the detection target object and the position periodically detected, and associating a displacement symbol corresponding to a change in a position of the detection target object with the coupled detection target object, and displaying the displacement symbol at the detected position of the detection target object at least on a two-dimensional position coordinates displayed in the display module.
Kazmi S.M.R.,Tohoku University |
Goto H.,Tohoku University |
Guo H.-J.,Tohoku Gakuin University |
Ichinokura O.,Tohoku University
IEEE Transactions on Industrial Electronics | Year: 2011
This paper proposes a novel solution to the problems that exist in the conventional hill climb searching (HCS) maximum power point tracking (MPPT) algorithm for the wind energy conversion system. The presented solution not only solves the tracking speed versus control efficiency tradeoff problem of HCS but also makes sure that the changing wind conditions do not lead HCS in the wrong direction. It intelligently adapts the variable step size to keep up with the rapid changes in the wind and seizes the perturbation at the maxima to yield 100% control efficiency. For this purpose, a novel peak detection capability has been devised which, in contrast with conventional peak detection, can work robustly under changing wind conditions. The proposed MPPT performs self-tuning to cope with the nonconstant efficiencies of the generatorconverter subsystemsa phenomenon quite rarely discussed in research papers so far. In addition, a smart speed-sensorless scheme has been developed to avoid the use of mechanical sensors. The experimental results confirm that the proposed algorithm is remarkably faster and more efficient than the conventional HCS. © 2006 IEEE.
News Article | March 8, 2016
Home > Press > Oxford Instruments unveils new generation 2016 Triton Cryofree dilution refrigerator: High power and enhanced sensitivity in quantum technologies and ultra low temperature physics Abstract: Oxford Instruments is unveiling its 2016 new generation Triton Cryofree® dilution refrigerator at a series of high-profile physics conferences this month. With over 220 systems installed worldwide, Triton is used in world-leading research across condensed matter physics, with a particular focus on advanced computing, quantum technologies, spintronics and optics. The new generation Triton system continues to provide market leading performance and reliability, with enhanced cooling power, ease of use, user access and experimental space. Dilution refrigerators are used by physicists to achieve ultra low temperatures below 10 milliKelvin that is, within 0.01 ◦C of absolute zero to observe, understand and control materials and devices at their fundamental limits in order to develop techniques and technologies of the future. Such ultra low temperature experiments now frequently extend well beyond the sample or device itself, to incorporate signal conditioning such as high frequency qubit read-write control lines, low radiation environments for quantum sensor detection, and ultra low vibration systems for pump-probe experiments. These all create growing demands for space, cooling power and performance, which the new generation Triton has been designed to answer. The new generation Triton system design gives far-reaching benefits. Latest 7th series high cooling power DU7 dilution units give enhanced sample cooling powers of 500 µW at 100 mK and 15 µW at 20 mK as standard, without increased volumes of costly 3He. Larger diameter plates at intermediate temperatures and the mixing chamber give greater capacity for wiring, filtering, signal attenuation and other RF signal chain components to be easily accommodated, while a range of larger, heavier and more complex integrated superconducting magnets are also made possible. The new high-rigidity support structure reduces low frequency modes and harmonics within the cryostat to provide ultra low vibration characteristics for sensitive measurement needs. Simplified single-user system assembly and a new system control rack are among the new ergonomic features. Oxford Instruments unique offering of both top- and bottom-loading mechanisms for rapid, protected sample exchange while preserving base temperature performance remains a key feature. We are excited to bring the new generation Triton to experimentalists in quantum computing, quantum technologies, and condensed matter physics, comments Dr John Burgoyne, Marketing Director at Oxford Instruments NanoScience. Together with our recent announcement on the Nanonis Tramea quantum transport measurement system, we are continuing our focused commitment to bring the highest possible experimental capabilities to our customers. Our technology team have done a fantastic job in pre-empting and incorporating our customers needs as well as innovative low temperature engineering into this new generation product. Oxford Instruments will be present to discuss the new 2016 Triton dilution refrigerator at a number of key physics conferences in March, including the DPG (Regensburg, Germany, 6-11 March), APS (Baltimore, MD, USA, 14-18 March), JPS (Tohoku Gakuin University, Japan, 19-22 March) and JSAP (Tokyo Institute of Technology, Japan, 19-22 March) Spring Meetings. More information on the 2016 new generation Triton can be found at www.oxford-instruments.com/triton2016. - ends - Issued for and on behalf of Oxford Instruments NanoScience About Oxford Instruments NanoScience Oxford Instruments NanoScience designs, supplies and supports market-leading research tools that enable quantum technologies, new materials and device development in the physical sciences. Our tools support research down to the atomic scale through creation of high performance, cryogen free low temperature and magnetic environments, based upon our core technologies in low and ultra-low temperatures, high magnetic fields and system integration, with ever-increasing levels of experimental and measurement readiness. Oxford Instruments NanoScience is a part of the Oxford Instruments plc group. About Oxford Instruments plc Oxford Instruments designs, supplies and supports high-technology tools and systems with a focus on research and industrial applications. Innovation has been the driving force behind Oxford Instruments' growth and success for over 50 years, and its strategy is to effect the successful commercialisation of these ideas by bringing them to market in a timely and customer-focused fashion. The first technology business to be spun out from Oxford University, Oxford Instruments is now a global company and is listed on the London Stock Exchange (OXIG). Its objective is to be the leading provider of new generation tools and systems for the research and industrial sectors with a focus on nanotechnology. Its key market sectors include nano-fabrication and nano-materials. The companys strategy is to expand the business into the life sciences arena, where nanotechnology and biotechnology intersect. This involves the combination of core technologies in areas such as low temperature, high magnetic field and ultra high vacuum environments; nuclear magnetic resonance; X-ray, electron, laser and optical based metrology; atomic force microscopy; optical imaging; advanced growth, deposition and etching. Oxford Instruments aims to pursue responsible development and deeper understanding of our world through science and technology. Its products, expertise, and ideas address global issues such as energy, environment, security and health. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Tohoku Gakuin University and Furukawa Electric Group | Date: 2013-12-16
An optical coupling structure optically coupling a plurality of core portions and a plurality of core portions includes a plurality of first core portions outputting a plurality of lights, a first lens focusing or collimating the plurality of lights outputted from the plurality of first core portions, a second lens focusing the plurality of lights focused or collimated by the first lens, a plurality of second core portions, the plurality of lights focused by the second lens being inputted into the second core portions respectively, and an optical functional component disposed between the first lens and the second lens, the plurality of lights being inputted into the optical functional component. At least one of the first lens and the second lens is configured by a lens or a lens group focusing or collimating the plurality of lights collectively.
News Article | October 4, 2016
More than a decade ago, Ralph Hollis invented the ballbot, an elegantly simple robot whose tall, thin body glides atop a sphere slightly smaller than a bowling ball. The latest version, called SIMbot, has an equally elegant motor with just one moving part: the ball. The only other active moving part of the robot is the body itself. The spherical induction motor (SIM) invented by Hollis, a research professor in Carnegie Mellon University's Robotics Institute, and Masaaki Kumagai, a professor of engineering at Tohoku Gakuin University in Tagajo, Japan, eliminates the mechanical drive systems that each used on previous ballbots. Because of this extreme mechanical simplicity, SIMbot requires less routine maintenance and is less likely to suffer mechanical failures. The new motor can move the ball in any direction using only electronic controls. These movements keep SIMbot's body balanced atop the ball. Early comparisons between SIMbot and a mechanically driven ballbot suggest the new robot is capable of similar speed—about 1.9 meters per second, or the equivalent of a very fast walk—but is not yet as efficient, said Greg Seyfarth, a former member of Hollis' lab who recently completed his master's degree in robotics. Induction motors are nothing new; they use magnetic fields to induce electric current in the motor's rotor, rather than through an electrical connection. What is new here is that the rotor is spherical and, thanks to some fancy math and advanced software, can move in any combination of three axes, giving it omnidirectional capability. In contrast to other attempts to build a SIM, the design by Hollis and Kumagai enables the ball to turn all the way around, not just move back and forth a few degrees. Though Hollis said it is too soon to compare the cost of the experimental motor with conventional motors, he said long-range trends favor the technologies at its heart. "This motor relies on a lot of electronics and software," he explained. "Electronics and software are getting cheaper. Mechanical systems are not getting cheaper, or at least not as fast as electronics and software are." SIMbot's mechanical simplicity is a significant advance for ballbots, a type of robot that Hollis maintains is ideally suited for working with people in human environments. Because the robot's body dynamically balances atop the motor's ball, a ballbot can be as tall as a person, but remain thin enough to move through doorways and in between furniture. This type of robot is inherently compliant, so people can simply push it out of the way when necessary. Ballbots also can perform tasks such as helping a person out of a chair, helping to carry parcels and physically guiding a person. Until now, moving the ball to maintain the robot's balance has relied on mechanical means. Hollis' ballbots, for instance, have used an "inverse mouse ball" method, in which four motors actuate rollers that press against the ball so that it can move in any direction across a floor, while a fifth motor controls the yaw motion of the robot itself. "But the belts that drive the rollers wear out and need to be replaced," said Michael Shomin, a Ph.D. student in robotics. "And when the belts are replaced, the system needs to be recalibrated." He said the new motor's solid-state system would eliminate that time-consuming process. The rotor of the spherical induction motor is a precisely machined hollow iron ball with a copper shell. Current is induced in the ball with six laminated steel stators, each with three-phase wire windings. The stators are positioned just next to the ball and are oriented slightly off vertical. The six stators generate travelling magnetic waves in the ball, causing the ball to move in the direction of the wave. The direction of the magnetic waves can be steered by altering the currents in the stators. Hollis and Kumagai jointly designed the motor. Ankit Bhatia, a Ph.D. student in robotics, and Olaf Sassnick, a visiting scientist from Salzburg University of Applied Sciences, adapted it for use in ballbots. Getting rid of the mechanical drive eliminates a lot of the friction of previous ballbot models, but virtually all friction could be eliminated by eventually installing an air bearing, Hollis said. The robot body would then be separated from the motor ball with a cushion of air, rather than passive rollers. "Even without optimizing the motor's performance, SIMbot has demonstrated impressive performance," Hollis said. "We expect SIMbot technology will make ballbots more accessible and more practical for wide adoption.
Sepehri-Amin H.,Japan National Institute of Materials Science |
Ohkubo T.,Japan National Institute of Materials Science |
Shima T.,Tohoku Gakuin University |
Hono K.,Japan National Institute of Materials Science
Acta Materialia | Year: 2012
The compositions of grain boundaries (GBs) and other interfaces surrounding Nd 2Fe 14B grains in commercial Nd-Fe-B sintered magnets have been investigated by laser-assisted three-dimensional atom probe to understand the mechanism of the coercivity enhancement by post-sinter annealing. While only a slight segregation of Nd and Pr to the GBs was confirmed in the as-sintered sample, a thin Nd-rich amorphous phase layer was observed along the GBs with Cu segregation to the interfaces in the annealed sample. The segregation of Cu to NdO x/Nd 2Fe 14B interfaces was also found, suggesting that the Nd 2Fe 14B grains are enveloped by a Cu-enriched layer after the annealing. The concentration of Fe + Co in the thin GB layer was found to be as high as 65 at.%, and a model amorphous film processed by sputtering with the same composition as the thin GB layer was found to be ferromagnetic. Ferromagnetic behavior of the thin GB layer suggested that Nd 2Fe 14B grains are magnetically coupled. The coercivity mechanism of the sintered magnets is discussed based on these new findings. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Matsuo I.,Tohoku Gakuin University
Journal of the Acoustical Society of America | Year: 2013
Bats use frequency-modulated echolocation to identify and capture moving objects in real three-dimensional space. Experimental evidence indicates that bats are capable of locating static objects with a range accuracy of less than 1 μs. A previously introduced model estimates ranges of multiple, static objects using linear frequency modulation (LFM) sound and Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates. The delay time for a single object was estimated with an accuracy of about 1.3 μs by measuring the echo at a low signal-to-noise ratio (SNR). The range accuracy was dependent not only on the SNR but also the Doppler shift, which was dependent on the movements. However, it was unclear whether this model could estimate the moving object range at each timepoint. In this study, echoes were measured from the rotating pole at two receiving points by intermittently emitting LFM sounds. The model was shown to localize moving objects in two-dimensional space by accurately estimating the object's range at each timepoint. © 2013 Acoustical Society of America.
Kumagai M.,Tohoku Gakuin University
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2016
Spherical motors are classified as multi-degrees-of-freedom actuators. Several types of spherical motors are under investigation in the world because they will be useful for robots that currently use combination of 2 or 3 one-degree-of-freedom motors. However, most of the previous works mainly demonstrated how the motors rotate or how they output torque without giving enough specifications. Torque, velocity, efficiency, controllability, and response are important issues to determine how they can be used for robots or practical mechatronic systems. The objective of this paper is to propose a method to measure three-degrees-of-freedom torque of spherical motors while they rotate with arbitrary angular velocity, which can evaluate torque in practical situations and can be used to derive efficiency of the motor. These measurements are important for comparison among the implementations and improvement of the systems. The idea consists of two parts. One is torque measurement using a 6-axis force/torque sensor. It enables off-axis simultaneous measurement of torque. The other is an external 3-degrees-of-freedom rotor driver using wheels for omnidirectional mobile robots, which is installed between the rotor and the sensor. Detailed principles and a set of experimental measurements of our spherical induction motor demonstrating usefulness of the proposed method are described in this paper. © 2016 IEEE.