Lin C.-K.,Naval Academy
Applied Soft Computing Journal
This paper presents a new adaptive critic controller to achieve precise position-tracking performance of induction motors using a radial basis function neural network (RBFNN). The adaptive controller consists of an associative search network (ASN), an adaptive critic network (ACN), a feedback controller and a robust controller. Due to the mechanical parameter drift, unmodelled dynamics, actuator saturation, and external disturbances, the exact model of an induction motor is difficult to be obtained. The ASN, which can approximate nonlinear functions, is employed to develop an RBFNN-based feedback control law to deal with the unknown dynamics. The ACN receives a reward from credit-assignment unit to generate an internal reinforcement signal to tune the ASN. Due to the inevitable approximation errors and uncertainties, a robust control technique is developed to reject the effects of the uncertainties. Moreover, the weight updating laws with projection algorithm can tune all parameters of the RBFNN and ensure the localized learning capability. By Lyapunov theory, the stability of the closed-loop system can be guaranteed. In addition, the effectiveness of the proposed RBFNN-based induction motor controller is verified by experimental results. © 2010 Elsevier B.V. All rights reserved. Source
Reeder D.B.,Naval Postgraduate School, Monterey |
Ma B.B.,University of Washington |
Yang Y.J.,Naval Academy
Very large subaqueous sand dunes were discovered on the upper continental slope of the northern South China Sea. The dunes were observed along a single 40. km long transect southeast of 21.93°N, 117.53°E on the upper continental slope in water depths of 160. m to 600. m. The sand dunes are composed of fine to medium sand, with amplitudes exceeding 16. m and crest-to-crest wavelengths exceeding 350. m. The dunes' apparent formation mechanism is the world's largest observed internal solitary waves which generate from tidal forcing on the Luzon Ridge on the east side of the South China Sea, propagate west across the deep basin with amplitudes regularly exceeding 100. m, and dissipate extremely large amounts of energy via turbulent interaction with the continental slope, suspending and redistributing the bottom sediment. While subaqueous dunes are found in many locations throughout the world's oceans and coastal zones, these particular dunes appear to be unique for two principal reasons: their location on the upper continental slope (away from the influence of shallow-water tidal forcing, deep basin bottom currents and topographically-amplified canyon flows), and their distinctive formation mechanism (approximately 60 episodic, extremely energetic, large amplitude events each lunar cycle). © 2010. Source
NORMAN — A University of Oklahoma-led team of physicists believes chip-based atomic physics holds promise to make the second quantum revolution—the engineering of quantum matter with arbitrary precision—a reality. With recent technological advances in fabrication and trapping, hybrid quantum systems are emerging as ideal platforms for a diverse range of studies in quantum control, quantum simulation and computing. James P. Shaffer, professor in the Homer L. Dodge Department of Physics and Astronomy, OU College of Arts and Sciences; Jon Sedlacek, OU graduate student; and a team from the University of Nevada, Western Washington University, The United States Naval Academy, Sandia National Laboratories and Harvard-Smithsonian Center for Astrophysics, have published research important for integrating Rydberg atoms into hybrid quantum systems and the fundamental study of atom-surface interactions, as well as applications for electrons bound to a 2-D surface. “A convenient surface for application in hybrid quantum systems is quartz because of its extensive use in the semiconductor and optics industries,” Sedlacek said. “The surface has been the subject of recent interest as a result of it stability and low surface energy. Mitigating electric fields near ‘trapping’ surfaces is the holy grail for realizing hybrid quantum systems,” added Hossein Sadeghpour, director of the Institute for Theoretical Atomic Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics. In this work, Shaffer finds ionized electrons from Rydberg atoms excited near the quartz surface form a 2-D layer of electrons above the surface, canceling the electric field produced by rubidium surface adsorbates. The system is similar to electron trapping in a 2-D gas on superfluid liquid helium. The binding of electrons to the surface substantially reduces the electric field above the surface. “Our results show that binding is due to the image potential of the electron inside the quartz,” said Shaffer. “The electron can’t diffuse into the quartz because the rubidium adsorbates make the surface have a negative electron affinity. The approach is a promising pathway for coupling Rydberg atoms to surfaces, as well as for using surfaces close to atomic and ionic samples.” A paper on this research was published in the American Physics Society’s Physical Review Letters. The OU part of this work was supported by the Defense Advanced Research Projects Agency Quasar program by a grant through the Army Research Office, the Air Force Office of Scientific Research and the National Science Foundation.
News Article | April 18, 2016
I returned from the Nuclear Energy Insider International Advanced Reactor and SMR Summit with revived energy, optimism and passion for participating in an expanding effort to smooth and straighten the tortuous path associated with producing increased quantities of clean energy from atomic fission. The effort isn’t small, it isn’t narrowly focused, and it isn’t–by any means–limited to the United States. It is exciting, potentially paradigm busting, wide ranging and the right thing to do. I can’t think of a better investment of the time I cannot spend with my family, especially my ever-entertaining young grandchildren. While at the event, I asked a few questions. (Some who attended might quibble with my use of the word “few.”) One question apparently intrigued people enough that the speakers began answering it before I even had a chance to ask it. There were several versions of the question, but they all boiled down to the following, generally asked of company business and technical leaders. Maybe this question and the answers can spread to become a meme with legs that helps the public gain a better appreciation of the nuclear energy’s proven benefits. It might help stimulate a curiosity about atomic energy’s potential to make their own lives more comfortable and prosperous while also helping human society achieve a more sustainable development path. The idea came during a talk by Harlen Bowers, president of X-Energy, a company that Atomic Insights has covered in the past (X-Energy introduced its company and first product to Virginia chapter of ANS and Atomic Show #248 – Dr. Pete Pappano, VP Fuel Production X-Energy. Bowers began by pointing to Elon Musk’s success in generating excitement for the Tesla 3, a car that will not even enter production for at least a year. Despite the fact that no one has seen an actual car or been able to test drive one, approximately 300,000 people have put down a $1,000 deposit to place an advanced order. Bowers stated that this show of interest provides evidence that there are people that care so much about climate change that they are willing to pay more for products that make a contribution. Bowers talk included strong admonitions to advanced reactor companies about coming together as a community to communicate the value of their technology in terms of flexibility, siting options and as a vital contributor to the fight against climate change. He told the assembled audience that we need to be willing to take the “spears and arrows” that will be thrown our way if we put ourselves into the public spotlight to make the case of for the importance of building new nuclear power sources. Then he said something that stimulated my question about building plants in our own backyards. Bowers concluded his talk as follows, “Reach out, communicate early and often and envision us as the Teslas of the nuclear industry.” Here is the question as I first asked it. (Note: X-Energy was founded and is funded by Dr. Kam Ghaffarian, an entrepreneur whose financial resources came from prior successes in the aerospace and defense industry.) Maybe one of the best ways to convince everybody, or almost everybody, is for Kam to buy himself a nice rural estate and put an X-Energy reactor in his backyard. Seriously, if he, or you or me or others in the industry say, “I’ll show you how confident I am. I’ll put it in my backyard. I’ll raise my children here, I’ll bring my grandchildren and show that it’s safe. We’ve seen the testing data, we understand it, but it’s hard to convince people using terms like “design basis accident” and “source term.” What I did not say, but wish I had, is that Kam, or other industry leaders deciding to adopt this strategy should make a big splash with the announcement and sell the idea hard to neighbors by helping them understand the benefits that such a machine could provide to the whole community. When I get more time, I will put together an audio file of some of the responses I received during the rest of day two of the summit as I asked several other company leaders, industry advocates or technical experts versions of the question. I know it is easy to say and easy to attempt to dismiss it as the empty promise of an overly enthusiastic sales guy, but I really want to eventually power and heat my home and my community with a nearby nuclear power source. I would need a couple of cooperating neighbors as partners, but the field behind our houses might be big enough. My ideal installation would be an Adams Engine, but the Xe-100 is reasonably close in concept and technology. There are other entries in the field of advanced small reactors that would also be acceptable as my next door neighbor. I’ve a lot more content from the summit to share with you, but it’s getting too close to departure time for my next research trip. This one is back in my old stomping grounds in Annapolis, MD. It will be a little like deja vu all over again to sit in a Rickover Hall auditorium for the opening plenary of a Technical Meeting on Nuclear Energy and Cyber Security. This meeting is in recognition of the first Naval Academy graduating classes for the Nuclear Engineering and Cyber Security majors. PS: After recent meetings in Washington, New York City, Atlanta and the coming meeting in Annapolis, the Atomic Insights travel account is shrinking. If you like having a vocal representative at these meetings who–eventually–provides you useful reports, please consider providing your financial support.
Vice Adm. Ted Carter made the announcement at the academy's "Athena Conference: Heroines of the past, present and future," which is marking the 40th anniversary of women's admission to the academy. The cyber facility, which will be called Hopper Hall, will be the first building named after a woman at the three main service academies. Often referred to as "Amazing Grace" and the mother of computing, Hopper joined the U.S. Navy Reserve during World War II. She later worked on a team to develop the UNIVAC computer and convert mathematic code into language. That led to developing the first compiler in 1952, which led to the creation of COBOL. Carter said Hopper also wanted to be known for training men and women in the Navy. "So today, her vision, her legacy, will follow through in this field of dreams of cyber for the admiral of the cyber seas—Adm. Grace Hopper," Carter said. A group of women who were the first females to graduate from the academy in 1980 were on hand to applaud the announcement. It meant a lot to Midshipman Frances Kratz, who said she "teared up a little bit" when she heard the building would be named for a Navy woman who inspired her. The sophomore computer science major said Hopper was a big influence on her decision to study computers at the academy. "I just really think that she was so influential, for not only the women in the Navy, but for computer science," Kratz, of Tampa, Florida, said. "Obviously, she was such a leader in that field, and I'm just so excited that it's going to be named after her." Carter noted Hopper Hall will likely be the last major academic building constructed on school grounds, which is tight for space along the Severn River. Groundbreaking is set for Oct. 21 on the 206,000-square-foot building. The academy hopes to have the $106 million facility operational by 2019. It will be built between the Nimitz Library and Rickover Hall. The academy requires all students to take two cyber security classes in a field of increasing importance to national security and civilian computer networks. The school graduated its first cyber security majors this year. Next year, it hopes to become the nation's first college to have a cyber major accredited by ABET, a leading nonprofit accrediting agency for the disciplines of applied science, computing and engineering. "It will be a first for a cyber program nationwide, but we expect to do pretty well. We've been planning this for three years," said Andrew Phillips, the academy's academic dean and provost. Explore further: Naval Academy should be center for study of cybersecurity, new superintendent says © 2016 The Associated Press. All rights reserved.