WorldWideScience

Sample records for current ramp-up phase

  1. Current ramp-up with lower hybrid current drive in EAST

    Science.gov (United States)

    Ding, B. J.; Li, M. H.; Fisch, N. J.; Qin, H.; Li, J. G.; Wilson, J. R.; Kong, E. H.; Zhang, L.; Wei, W.; Li, Y. C.; Wang, M.; Xu, H. D.; Gong, X. Z.; Shen, B.; Liu, F. K.; Shan, J. F.

    2012-12-01

    More economical fusion reactors might be enabled through the cyclic operation of lower hybrid current drive. The first stage of cyclic operation would be to ramp up the plasma current with lower hybrid waves alone in low-density plasma. Such a current ramp-up was carried out successfully on the EAST tokamak. The plasma current was ramped up with a time-averaged rate of 18 kA/s with lower hybrid (LH) power. The average conversion efficiency Pel/PLH was about 3%. Over a transient phase, faster ramp-up was obtained. These experiments feature a separate measurement of the L/R time at the time of current ramp up.

  2. Flux consumption, current ramp-up and current diffusion in Tore Supra non-inductive Lower Hybrid scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Kazarian, F.; Litaudon, X.; Moreau, D.; Arslanbekov, R.; Hoang, G.T.; Joffrin, E.; Peysson, Y.; Allibert, J.P.; Ane, J.M.; Bremond, S. [Association Euratom-CEA, Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    1995-12-31

    The main objective of the Lower Hybrid (LH) experiments performed on Tore Supra is to provide large flux savings for long pulse operation while controlling the plasma current density profile. This goal will be best achieved by applying LH wave directly during the current ramp-up phase. Experiments have been performed where a large fraction of the current is driven non-inductively during the ramp-up phase. A theoretical flux consumption scaling is presented and compared to experimental data. The time evolutions of the current density profiles are analysed with a new current diffusion code (CRONOS). In view to achieve fully non-inductive current drive discharges in a fast, systematic and reproducible way, experiments where the primary voltage is imposed have been carried out. In a complementary approach, an appropriate transformer flux feedback scheme has been also studied. (author) 6 refs.; 6 figs.

  3. Dynamic Optimization of Trajectory for Ramp-up Current Profile in Tokamak Plasmas

    CERN Document Server

    Ren, Zhigang; Ou, Yongsheng

    2016-01-01

    In this paper, we consider an open-loop, finite-time, optimal control problem of attaining a specific desired current profile during the ramp-up phase by finding the best open-loop actuator input trajectories. Average density, total power, and plasma current are used as control actuators to manipulate the profile shape in tokamak plasmas. Based on the control parameterization method, we propose a numerical solution procedure directly to solve the original PDE-constrained optimization problem using gradient-based optimization techniques such as sequential quadratic programming (SQP). This paper is aimed at proposing an effective framework for the solution of PDE-constrained optimization problem in tokamak plasmas. A more user-friendly and efficient graphical user interface (GUI) is designed in MATLAB and the numerical simulation results are verified to demonstrate its applicability. In addition, the proposed framework of combining existing PDE and numerical optimization solvers to solve PDE-constrained optimiz...

  4. Non-inductive Plasma Start-up and Current Ramp-up in NSTX-U

    Science.gov (United States)

    Raman, R.; Jarboe, T. R.; Jardin, S. C.; Kessel, C. E.; Mueller, D.; Nelson, B. A.; Poli, F.; Taylor, G.; NSTX Research Team; Princeton Plasma Physics Laboratory Team

    2013-10-01

    Results from NSTX Transient Coaxial Helicity Injection (CHI) experiments have demonstrated generation of 300 kA start-up currents, and when these discharges were coupled to induction they attained 1 MA of plasma current consuming 65% of the inductive flux of standard inductive-only discharges in NSTX. The NSTX-U device, which is now under construction at PPPL, will have numerous improvements to enhance transient CHI start-up. These are: (1) factor of two increase in toroidal field, (2) more than 2.5 times the injector flux, (3) increased CHI voltage, (4) full lithium coverage to reduce low-Z impurities and (5) 1 MW ECH system for increasing the electron temperature of CHI discharges to allow direct coupling to NBI current drive using a new second more tangential neutral beam system. In support of NSTX-U objectives for full non-inductive start-up and current ramp-up, the TSC code has been used for a full discharge simulation in which a transient CHI discharge is used as the front end of the non-inductive current ramp-up simulation. This work supported by U.S. DOE Contracts DE-AC02-09CH11466 and DE-FG02-99ER54519 AM08.

  5. Analysis of the EDIPO Temperature Margin During Current Ramp-Up

    CERN Document Server

    Marinucci, C; Calvi, Marco; Marinucci, Claudio; Cau, Francesca; Bottura, Luca

    2010-01-01

    The European dipole (EDIPO), currently under construction, will provide background magnetic fields of up to 12.5 T for tests of ITER high-current superconducting cables. The EDIPO winding consists of 7 x 2 double layers of Nb3SN cable-in-conduit conductors with forced flow cooling of supercritical helium. The performance limits of EDIPO during current ramp-up are analyzed analysed with the CryoSoft suite of codes, recently integrated into a customizable and flexible environment for the analysis of thermal hydraulic and electrical transients in superconducting magnetic systems. The simultaneous analysis of the cryogenic system and all 14 double layers shows that under all charging conditions the EDIPO temperature margin remains sufficiently high.

  6. Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

    Science.gov (United States)

    McKee, G. R.; Austin, M.; Boedo, J.; Bravenec, R.; Holland, C.; Jackson, G.; Luce, T. C.; Rhodes, T. L.; Rudakov, D.; Wang, G.; Yan, Z.; Zeng, L.; Zhao, Y.

    2017-08-01

    Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75  qualitative consistency with measured fluctuation levels, but calculations don’t exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. This indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.

  7. Lean Application to Manufacturing Ramp-Up

    DEFF Research Database (Denmark)

    Christensen, Irene; Rymaszewska, Anna

    2016-01-01

    product development process, that is, the ramp-up process, is a critical, early enabler of lean manufacturing. The manufacturing strategy literature conceptualizes a state of “leanness in operations,” which can consolidate both the concepts of lean and manufacturing ramp-up, providing a dual perspective......This article provides a theoretical overview of the concepts of lean and manufacturing ramp-up in an attempt to conceptualize the strategic areas in which lean philosophy and principles can be applied for continuous improvements. The application of lean principles during the final stage of a new....... Abstracting from the extant literature, the authors considered the competitiveness of manufacturing companies from two principal perspectives: the leanness of the ramp-up process and the new-value creation of quality managers. While much of the literature fails to acknowledge that the roots of lean actually...

  8. LHC Report: Ramp-up complete

    CERN Document Server

    Mike Lamont for the LHC Team

    2012-01-01

    The intensity ramp-up outlined in the last Bulletin continued more or less as planned, with some steady running with 1092 bunches followed by the final step-up to 1380 – the maximum number of bunches for the year.   Monday, 16 April was spent performing luminosity calibration. Under carefully controlled conditions and a special beam configuration, the experiments' luminosity measurements were calibrated against a measurement of the accelerator’s absolute luminosity obtained with Van der Meer scans. These scans give the beam sizes at the interaction point which, together with an accurate measurement of the beam and bunch currents (and other more subtle considerations), allow a precise measurement of the absolute luminosity. With the Van der Meer scans out of the way, the final step-up in the number of bunches to 1380 was made. This has resulted in an average peak luminosity of around 5.6x1033 cm-2s-1 in the general-purpose detectors (ATLAS and CMS have yet to publish th...

  9. LHC Report: Intensity ramp-up

    CERN Multimedia

    Mike Lamont for the LHC Team

    2012-01-01

    The first stable beams at 4 TeV were declared on Thursday, 5 April with 3 bunches per beam. This marked the start of the intensity ramp-up, which aims to get back up to 1380 bunches per beam as quickly as is safely possible.   The next couple of days saw fills with 47, 84 and 264 bunches per beam and on Sunday, 8 April the move was made to 624 bunches. With the squeeze to 60 cm in place, 624 bunches with reasonably high bunch intensities of around 1.3 to 1.4 x1011 protons per bunch have already yielded respectable peak luminosities of up to 2.5 x1033 cm-2s-1. Following a lot of hard work during the Christmas technical stop, machine availability is very good at the moment. The ramp-up in the number of bunches is accompanied by a series of checks aimed to make sure the machine protection systems and operational procedures are in a good enough shape to safely deal with the beam intensity. 624 bunches at 4 TeV already represents an energy over 50 MJ and serious damage potential. The next few days sh...

  10. Inter-Organisational Coordination in Ramp-Up Execution

    DEFF Research Database (Denmark)

    Christensen, Irene; Karlsson, Christer

    While fast product development with early prototyping and reduction of both cycle time and lead time are major concerns, there is little research on ramp up management. This paper examines the structural complexity of the ramp-up processes including the interactions with suppliers and analyses...

  11. Inter-Organisational Coordination in Ramp-Up Execution

    DEFF Research Database (Denmark)

    Christensen, Irene; Karlsson, Christer

    While fast product development with early prototyping and reduction of both cycle time and lead time are major concerns, there is little research on ramp up management. This paper examines the structural complexity of the ramp-up processes including the interactions with suppliers and analyses...... the degree of fragmentation in the process planning and execution. Resource dependence theory (RDT) is used as central explanatory framework for inter-organisational interdependencies formation throughout the planning and execution of the ramp-up activities and milestones. This study aims at exploring inter...

  12. LHC Report: intensity ramp-up – familiar demons

    CERN Multimedia

    Mike Lamont for the LHC team

    2015-01-01

    The first 2015 scrubbing run ended on Friday, 3 July and successfully delivered a well-scrubbed machine ready for operation with a 50 ns beam. This opened the way for the first phase of the so-called beam intensity ramp-up. The last couple of weeks have seen the number of bunches increase from 3 to 476 per beam via periods of 50, 144 and 300 bunches per beam.   The graph plots the rate of LHC beam dumps due to single-event effects (SEE) versus beam luminosity. It is an indication of the importance of tackling this issue.   To verify the full and proper functioning of all systems, operators need at least 3 fills and 20 hours of stable beams without significant problems. After 20 hours, an extensive checklist is signed off by the system experts before the next step up in the number of bunches. The systems involved include magnet protection, radio-frequency, beam instrumentation, collimation, operations, feedback, beam dump and injection. Increasing the total beam intensity poses a numb...

  13. Key Performance Indicators for the Impact of Cognitive Assembly Planning on Ramp-Up Process

    Directory of Open Access Journals (Sweden)

    Christian Buescher

    2012-01-01

    Full Text Available Within the ramp-up phase of highly automated assembly systems, the planning effort forms a large part of production costs. Due to shortening product lifecycles, changing customer demands, and therefore an increasing number of ramp-up processes, these costs even rise. So assembly systems should reduce these efforts and simultaneously be flexible for quick adaption to changes in products and their variants. A cognitive interaction system in the field of assembly planning systems is developed within the Cluster of Excellence “Integrative production technology for high-wage countries” at RWTH Aachen University which integrates several cognitive capabilities according to human cognition. This approach combines the advantages of automation with the flexibility of humans. In this paper the main principles of the system's core component—the cognitive control unit—are presented to underline its advantages with respect to traditional assembly systems. Based on this, the actual innovation of this paper is the development of key performance indicators. These refer to the ramp-up process as a main objective of such a system is to minimize the planning effort during ramp-up. The KPIs are also designed to show the impact on the main idea of the Cluster of Excellence in resolving the so-called Polylemma of Production.

  14. Experiencing Production Ramp-Up Education for Engineers

    Science.gov (United States)

    Bassetto, S.; Fiegenwald, V.; Cholez, C.; Mangione, F.

    2011-01-01

    This paper presents a game of industrialisation, based on a paper airplane, that mimics real world production ramp-up and blends classical engineering courses together. It is based on a low cost product so that it can be mass produced. The game targets graduate students and practitioners in engineering fields. For students, it offers an experiment…

  15. Effect of station-specific alerting and ramp-up tones on firefighters' alarm time heart rates.

    Science.gov (United States)

    MacNeal, James J; Cone, David C; Wistrom, Christopher L

    2016-11-01

    A number of long-term health effects are suffered by emergency responders, some influenced by psychological stress and fatigue. This study explored if stress and fatigue can be reduced by changing the method by which firefighters are alerted to emergency responses. Over several months, the method by which responders at a fire department were alerted was altered. Firefighter heart rates were measured first with standard alerting as a control (phase 1: all stations alerted simultaneously, with high-volume tones). The department then implemented station-specific (phase 2) and gradual volume ramp-up (phase 3) tone alerting, and heart rate increases were compared. The Fatigue Severity Score was used to examine firefighter fatigue, and the department administered a follow-up survey on personnel preferences. Individual heart rate increases (Δbpm) ranged from 2-48 bpm. Median increases were 7 bpm (IQR 4-11 bpm) during phase 1 (72.2% of alarms Δbpmalarms Δbpmalarms Δbpmalarms in phase 3 resulted in increases of Fatigue Severity Scale showed little variability: median scores 7 in phase 1, 8 in phase 2, and 7 in phase 3. Firefighters reported a strong preference for the "ramp-up" tones, and were roughly evenly divided between preferring alerting all stations simultaneously 24/7 (40% rating this 4 or 5 on a five-point Likert scale), station-specific alerting 24/7 (47.5%), or all stations during the day but station-specific at night (40%). Ramp-up tones were perceived as the best method to reduce stress during the day and overnight. Small but significant decreases in the amount of tachycardic response to station alerting are associated with simple alterations in alerting methods. Station-specific and ramp-up tones improve perceived working conditions for emergency responders.

  16. Modelling ramp-up curves to reflect learning: improving capacity planning in secondary pharmaceutical production

    DEFF Research Database (Denmark)

    Hansen, Klaus Reinholdt Nyhuus; Grunow, Martin

    2015-01-01

    are overestimated. We develop a new method, which captures ramp-up as a function of the cumulative production volume to better reflect the experience gained while producing the new product. The use of the more accurate and computationally effective approach is demonstrated for the case of secondary pharmaceutical...... production. Due to its regulatory framework, this industry cannot fully exploit available capacities during ramp-up. We develop a capacity planning model for a new pharmaceutical drug, which determines the number and location of new production lines and the build-up of inventory such that product...... availability at market launch is ensured. Our MILP model is applied to a real industry case study using three empirically observed ramp-up curves to demonstrate its value as decision support tool. We demonstrate the superiority of our volume-dependent method over the traditional time-dependent ramp...

  17. A Study of Energy Conversion Efficiency Versus Plasma Density by Lower Hybrid Current Drive in HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    丁伯江; 匡光力; 刘岳修; 刘登成; 单家方; 刘甫坤; 沈慰慈; 石跃江; 吴振伟; 林建安; 俞家文; 徐汉东; 商连全; 张晓东; 刘小宁; 赵燕平; 李建刚

    2002-01-01

    Ramp-up experiments by means of lower hybrid wave on HT-7 superconducting tokamak have been performed and analyzed. A ramp-up rate of over 300 kA/s is obtained and a conversion efficiency of over 10% has been achieved during the ramp-up phase. The study of the dependence of conversion efficiency on plasma density shows that the conversion efficiency is affected by the driven current, which is mainly dominated by the competition of impurity concentration with wave accessibility condition. In addition, the effect of current profile may play an important role in determining the conversion efficiency.

  18. A Study of Energy Conversion Efficiency Versus Plasma Density by Lower Hybrid Current Drive in HT—7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    丁伯江; 匡光力; 等

    2002-01-01

    Ramp-up experiments by means of lower hydrid wave on HT-7 superconducting tokamak have been performed and analyzed.A ramp-up rate of over 300kA/s is obtained and a conversion efficiency of over 10% has been achieved during the ramp-up phases.The study of the dependence of conversion efficiency on plasma density shows that the conversion efficiency is affected by the driven current,which is mainly dominated by the competition of impurity concentration with wave accessibility condition.In addition,the effect of current profile may play an important role in determining the conversion efficiency.

  19. Never the twain shall meet? : Simulating sales & operations planning ramp-up dynamics in IT-enabled service supply chains

    NARCIS (Netherlands)

    Akkermans, Henk; Voss, C.; van Oers, Roeland; Zhu, Quan

    2016-01-01

    In IT-enabled service supply chains offering services through a mix of manual and automated activities, volume ramp-ups are notoriously difficult. Especially difficult is the attempt to effectively balance the inherently conflicting objectives of the functions Sales, who want to increase output as

  20. Intensity ramp-up: 2011 experience - Limitations, mitigation, risks, strategy, pushing it in 2012, 1380 in 3 weeks?

    CERN Document Server

    Zerlauth, M; Wenninger, J

    2012-01-01

    This paper will discuss the experience with ramping up the beam intensities in the early days of the 2011 run and after the subsequent technical stops. Weak points and limitations are being identified and their possible mitigations evaluated. In view of the risks and drawbacks of a too aggressive approach, possible improvements of the applied strategy whilst maintaining the required validation points for the various equipment and machine protection systems (MPS) are being discussed.

  1. Current ramps in tokamaks: from present experiments to ITER scenarios

    NARCIS (Netherlands)

    Imbeaux, F.; Citrin, J.; Hobirk, J.; Hogeweij, G. M. D.; Kochl, F.; Leonov, V. M.; Miyamoto, S.; Nakamura, Y.; Parail, V.; Pereverzev, G.; Polevoi, A.; Voitsekhovitch, I.; Basiuk, V.; Budny, R.; Casper, T.; Fereira, J.; Fukuyama, A.; Garcia, J.; Gribov, Y. V.; Hayashi, N.; Honda, M.; Hutchinson, I. H.; Jackson, G.; Kavin, A. A.; Kessel, C. E.; Khayrutdinov, R. R.; Labate, C.; Litaudon, X.; Lomas, P. J.; Lonnroth, J.; Luce, T.; Lukash, V. E.; Mattei, M.; Mikkelsen, D.; Nunes, I.; Peysson, Y.; Politzer, P.; Schneider, M.; Sips, G.; Tardini, G.; Wolfe, S. M.; Zhogolev, V. E.

    2011-01-01

    In order to prepare adequate current ramp-up and ramp-down scenarios for ITER, present experiments from various tokamaks have been analysed by means of integrated modelling in view of determining relevant heat transport models for these operation phases. A set of empirical heat transport models for

  2. Review of the Mechanical Engineering Challenges associated with the SNS* Power Ramp Up

    Energy Technology Data Exchange (ETDEWEB)

    Murdoch, Graeme R [ORNL; Holding, Mike [ORNL; Ladd, Peter [ORNL; Potter, Kerry G [ORNL; Roseberry, Jr., R Tom [ORNL

    2008-01-01

    Since commissioning of the SNS in April 2006 the beam power has been steadily increasing towards the design intensity of 1.4 MW. Several areas of the accelerator have been shown to require modifications, upgrades or new designs of mechanical equipment to support the power ramp schedule. This paper presents mechanical engineering design work implemented since initial commissioning along with a review of current projects and discussion of mechanical engineering issues being addressed that are a direct result of design decisions made early in the project.

  3. CD uniformity optimization at volume ramp up stage for new product introduction

    Science.gov (United States)

    Kim, Jin-Soo; Ma, Won-Kwang; Kim, Young-Sik; Kim, Myoung-Soo; Kwon, Won-Taik; Park, Sung-Ki; Nikolsky, Peter; Otter, Marian; Marun, Maryana Escalante; Anunciado, Roy; Sun, Kyu-Tae; Storms, Greet; van West, Ewould

    2014-04-01

    In this paper we describe the joint development and optimization of the critical dimension uniformity (CDU) at an advanced 300 mm ArFi semiconductor facility of SK Hynix in the high volume device. As the ITRS CDU specification shrinks, semiconductor companies still need to maintain high wafer yield and high performance (hence market value) even during the introduction phase of a new product. This cannot be achieved without continuous improvement of the on-product CDU as one of the main drivers for yield improvement. ASML Imaging Optimizer is one of the most efficient tools to reach this goal. This paper presents experimental results of post-etch CDU improvement by ASML imaging optimizer for immature photolithography and etch processes on critical features of 20nm node. We will show that CDU improvement potential and measured CDU strongly depend on CD fingerprint stability through wafers, lots and time. However, significant CDU optimization can still be achieved, even for variable CD fingerprints. In this paper we will review point-to-point correlation of CD fingerprints as one of the main indicators for CDU improvement potential. We will demonstrate the value of this indicator by comparing CD correlation between wafers used for Imaging Optimizer dose recipe development, predicted and measured CDU for wafers and lots exposed with various delays ranging from a few days to a month. This approach to CDU optimization helps to achieve higher yield earlier in the new product introduction cycle, enables faster technology ramps and thereby improves product time to market.

  4. LHC Report: Start of intensity ramp-up before a short breather

    CERN Multimedia

    Mike Lamont for the LHC team

    2015-01-01

    The first Stable Beams on 3 June were followed, to the accompaniment of thunderstorms, by the start of a phase known as the “intensity ramp-up” which saw the LHC team deliver physics with 50 bunches per beam. Time was also taken for a special five-day run devoted principally to the LHCf experiment. This week (15-19 June) the beam-based programme of the machine and its experiments was stopped temporarily for regular maintenance work.   LHCf’s Arm1 detector. While the first stable colliding beams were delivered with only 3 nominal bunches per beam, the aim of last week’s operations was to start the process of increasing the number of bunches in the beam with an ultimate 2015 target of ~2400 bunches per beam. The number of bunches is gradually increased in well-defined steps. At each step – 3 bunches per beam, then 13, 40 and, finally, 50 – the machine protection team requests 3 fills and around 20 hours of Stable Be...

  5. Ramping up PCI production

    Energy Technology Data Exchange (ETDEWEB)

    Bergsma, D.; Kieftenbeld, B.; Bol, L. [Corus Strip Products IJmuiden (Netherlands). Blast Furnace Dept.

    2008-07-01

    This paper described the improvements at the Corus Strip Products IJmuiden coal preparation plant and injection facilities that have resulted in ultra high productivities and very low coke rates of the blast furnaces. Pulverized coal injection (PCI) began at the steelmaking plant 25 years ago. Since then, an increased coal preparation output has been realized each year. The capacity of the mills and the injection systems were increased from about 70 tons/h to over 200 tons/h, thereby allowing a steady decrease in coke rate per ton of hot metal with a considerable increase in hot metal production from the blast furnaces. Many modifications were in hardware, but much of the increase in productivity was due to increasing the aimed pulverized coal (PC) particle size, selecting different coals and improving process control in both milling and injection facilities. Depending on the coal variety, the specific PCI-rates could reach over 250 kg/thm. The excellent performance was made possible by improving key factors such as burden quality, burdening, cast house performance and installation reliability. The modifications also solved constraints in working pressure; uptake pulverized coal moisture content; inlet and outlet air temperature; and injection rate stability. Coal selection was based on handlability, chemical composition and economics. 1 tab., 9 figs.

  6. Ramping up on Fractions

    Science.gov (United States)

    Stephens, Ana C.; Bottge, Brian A.; Rueda, Enrique

    2009-01-01

    This article describes a technology-based and hands-on instructional intervention designed to advance middle school students' understandings of fractions. This problem-solving experience is based on the principles of Enhanced Anchored Instruction (EAI) and proved instructionally worthwhile and motivating to teachers and students in both inclusive …

  7. Lessons from the President's Emergency Plan for AIDS Relief: from quick ramp-up to the role of strategic partnership.

    Science.gov (United States)

    Simonds, R J; Carrino, Constance A; Moloney-Kitts, Michele

    2012-07-01

    In its first five years, the President's Emergency Plan for AIDS Relief (PEPFAR)--the largest commitment ever by any nation to combat a single disease--succeeded in getting 2.1 million people on antiretroviral treatment and 10.1 million people in care; prevented an estimated 237,600 HIV infections in infants; and saved an estimated 3.28 million adult years of life. Much of the global program's success can be attributed to early decisions to implement new structures and approaches designed to meet its ambitious targets quickly, overcome bureaucratic inertia, and ensure continued progress. A unified US government program was created with a single coordinator. There was a focus on quick ramp-up, strategic partnerships, and sustainable local ownership. Accountability and performance were emphasized. These new approaches played critical roles in translating the unprecedented resources and political support for PEPFAR into improved health for millions of people. Successful aspects of the way in which PEPFAR was organized and implemented, along with less successful or deficient ones, offer lessons for any large, complex international health initiative.

  8. Study of toroidal current penetration during current ramp in JIPP T-IIU with fast response Zeeman polarimeter

    Energy Technology Data Exchange (ETDEWEB)

    Kuramoto, H.; Hiraki, N. [Kyushu Inst. of Tech., Kitakyushu, Fukuoka (Japan); Toi, K. [and others

    1997-01-01

    The toroidal current penetration is studied in current ramp experiments of the JIPP T-IIU tokamak. The poloidal magnetic field profile in the peripheral region of a plasma (0.5 {<=} {rho} {<=} 1.0) has been measured directly with a newly developed fast response Zeeman polarimeter. The experimental results indicate that an obvious skin effect of toroidal current density is clearly observed during both the current ramp-up and ramp-down experiments. The experimentally obtained toroidal current density profiles are well described by the profiles calculated on the assumption of the neoclassical electrical conductivity. Quasi-linear {Delta}`-analysis of tearing modes for the measured current density profile is consistent with time behaviour of coherent MHD modes such as m=4/n=1 or m=3/n=1 (m: poloidal mode number, n: toroidal mode number) often observed during the current ramp-up phase. The effect of these MHD modes on current penetration during the current ramp-up discharges is studied. (author)

  9. Novel 3-Phase Inductive Fault Current Limiter

    Science.gov (United States)

    Kosa, Janos

    The paper describes the inductive three-phase fault current limiter. In this work I examine the novel arrangements of the perfect closed superconducting loop made of HTS wire. I applied one iron core with 3 limbs and special loops for uniform temperature of the superconducting wire. In this work I present the results of my experiments with this device. I present the static and dynamic measured results of this solution. It has got several advantages e. g. fast switching and less fault power for high-power electric machines. The advantage of the equipment is that in the case of single-phase short circuit the current will decrease in all the three phases. This can be an appropriate solution for high power machines. For example, in the case of high-power electric motor if there is a single-phase breaking or a single phase short circuit, we can decrease the current in the three phases.

  10. Capabilities of the ITER Electron Cyclotron Equatorial Launcher for Heating and Current Drive

    Directory of Open Access Journals (Sweden)

    Ramponi G.

    2012-09-01

    Full Text Available The ITER Electron Cyclotron Equatorial Launcher is designed to be one of the heating systems to assist and sustain the development of various ITER plasma scenarios starting with the very first plasma operation. Here the capabilities for Heating and Current Drive of this system are reviewed. In particular, the optimum launching conditions are investigated for two scenarios at burn, comparing toroidal and poloidal steering options. Then, the EC capabilities are investigated for different plasma parameters corresponding to various phases of the ITER plasma discharge, from current ramp-up up to burn, and for a wide range of magnetic field, focusing in particular on the EC potential for heating and for L to H-mode assist. It is found that the EC system can contribute to a wide range of heating scenarios during the ramp-up of the magnetic field, significantly increasing the applicable range as a function of magnetic field.

  11. Transient behaviour of a resistive joint in the ATLAS toroids during the magnet ramp-up and discharge

    CERN Document Server

    Volpini, G

    2000-01-01

    Several resistive joints are foreseen inside the coils of the ATLAS Barrel Toroid. Here we investigate the problems linked to nonstationary effects: during the magnet charge and dump discharge the magnetic field induces eddy-currents inside the joints, increasing the Joule dissipation and possibly exceeding the conductor's critical current. We have developed an electrical model of the joint to predict the current distribution under nonstationary conditions and consequent heat dissipation; this model allowed us to compute the optimum length of these joints in order to minimise the heat dissipation and the eddy-currents. (5 refs).

  12. Current fluctuations at a phase transition

    Science.gov (United States)

    Gerschenfeld, A.; Derrida, B.

    2011-10-01

    The ABC model is a simple diffusive one-dimensional non-equilibrium system which exhibits a phase transition. Here we show that the cumulants of the currents of particles through the system become singular near the phase transition. At the transition, they exhibit an anomalous dependence on the system size (an anomalous Fourier's law). An effective theory for the dynamics of the single mode which becomes unstable at the transition allows one to predict this anomalous scaling.

  13. CERN ramps up neutrino program

    CERN Multimedia

    2016-01-01

    Among the brambles of the French countryside is a workshop the size of an aircraft hangar bustling with activity. In a well-lit new extension, technicians cut through thick slices of steel with electric saws and blast metal joints with welding torches

  14. YBCO SQUIDs with unconventional current phase relation

    Energy Technology Data Exchange (ETDEWEB)

    Bauch, T. [Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-41296 Goeteborg (Sweden)], E-mail: Thilo.bauch@mc2.chalmers.se; Johansson, J.; Cedergren, K. [Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-41296 Goeteborg (Sweden); Lindstroem, T. [National Physical Laboratory, Teddington, Middlesex TW11 0LW (United Kingdom); Lombardi, F. [Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-41296 Goeteborg (Sweden)

    2007-10-01

    We have studied the dynamics of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) dc sperconducting quantum interference devices (SQUIDs) characterized by an unconventional Josephson current phase relation (CPR). We have focused on SQUID configurations with Josephson junctions where the lobe of the order parameter in one electrode is facing a node in the other electrode. This order parameter arrangement should enhance the appearance of a sin(2{phi}) term in the CPR. The response of the critical current of the dc SQUID, under the effect of an external magnetic field, has been measured in temperature, down to 20 mK. Our experimental data have been compared with numerical simulations of the SQUIDs dynamics by considering a CPR of a single junction of the form I({phi}) = I{sup I} sin({phi}) - I{sup II} sin(2{phi}) where I{sup I} and I{sup II} are, respectively, the first and second harmonic component. In our devices the values of the sin(2{phi}) term are such that the fundamental state of the SQUID is naturally double degenerate. This is of great relevance for applications of d-wave SQUIDs in quantum information processing.

  15. Sliding Mode Control of Induction Motor Phase Currents

    DEFF Research Database (Denmark)

    Hansen, R.B.; Hattel, T.; Bork, J

    1995-01-01

    Sliding mode control of induction motor phase currents are investigated through development of two control concepts.......Sliding mode control of induction motor phase currents are investigated through development of two control concepts....

  16. Sliding Mode Control of Induction Motor Phase Currents

    DEFF Research Database (Denmark)

    Hansen, R.B.; Hattel, T.; Bork, J

    1995-01-01

    Sliding mode control of induction motor phase currents are investigated through development of two control concepts.......Sliding mode control of induction motor phase currents are investigated through development of two control concepts....

  17. Equilibria and Stability of JET Discharges with Zero Core Current Density

    Energy Technology Data Exchange (ETDEWEB)

    B.C. Stratton; N.C. Hawkes; G.T.A. Huysmans; J.A. Breslau; L.E. Zakharov; B. Alper; R.V. Budny; C.D. Challis; R. Deangelis; V. Drozdov; C. Fenzi; C. Giroud; T.C. Hender; J. Hobirk; S.C. Jardin; E. Joffrin; P.J. Lomas; P. Lotte; J. Mailloux; W. Park; E. Rachlew; S. Reyes-Cortes; E. Solano; T. Tala; K-D. Zastrow; JET-EFDA Contributors

    2002-10-15

    Injection of Lower Hybrid Heating and Current Drive (LHCD) into the current ramp-up phase of JET [Joint European Torus] discharges can produce extremely reversed q-profiles characterized by a core region of near zero current density (within Motional Stark Effect diagnostic measurement errors). Non-inductive, off-axis co-current drive induces a back electromotive force inside the non-inductive current radius that drives a negative current in the plasma core. The core current density does not go negative, although current diffusion calculations indicate that there is sufficient LHCD to cause this. The clamping of the core current density near zero is consistent with n=0 reconnection events redistributing the core current soon after it goes negative. This is seen in reduced MHD simulations and in nonlinear resistive MHD simulations which predict that these discharges undergo n=0 reconnection events that clamp the core current near zero.

  18. Current Harmonics from Single-Phase Grid-Connected Inverters

    DEFF Research Database (Denmark)

    Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede

    2016-01-01

    is focused on the impacts of the power factor and the feed-in grid current level on the quality of the feed-in grid current from single-phase inverters. As a consequence, an internal model principle based high performance current control solution is tailor-made and developed for single-phase grid...... factor, or in the low voltage ride through mode with reactive current injection. In this paper, the mechanism of the harmonic current injection from grid-connected single-phase inverter systems is thus explored, and the analysis is conducted on single-phase PV systems. In particular, the analysis......-connected systems to produce high quality currents in different operation conditions, where a design procedure is also provided. The developed current controller in this paper can achieve a minimum steady-state error while maintaining a relatively fast transient response, and also being feasible in other single...

  19. Phase state dependent current fluctuations in pure lipid membranes

    CERN Document Server

    Wunderlich, B; Idzko, A-L; Keyser, U F; Wixforth, A; Myles, V M; Heimburg, T; Schneider, M F

    2009-01-01

    Current fluctuations in pure lipid membranes have been shown to occur under the influence of transmembrane electric fields (electroporation) as well as a result from structural rearrangements of the lipid bilayer during phase transition (soft perforation). We demonstrate that the ion permeability during lipid phase transition exhibits the same qualitative temperature dependence as the macroscopic heat capacity of a D15PC/DOPC vesicle suspension. Microscopic current fluctuations show distinct characteristics for each individual phase state. While current fluctuations in the fluid phase show spike-like behaviour of short time scales (~ 2ms) with a narrow amplitude distribution, the current fluctuations during lipid phase transition appear in distinct steps with time scales in the order of ~ 20ms. 1 We propose a theoretical explanation for the origin of time scales and permeability based on a linear relationship between lipid membrane susceptibilities and relaxation times in the vicinity of the phase transition.

  20. Eddy current pulsed phase thermography and feature extraction

    Science.gov (United States)

    He, Yunze; Tian, GuiYun; Pan, Mengchun; Chen, Dixiang

    2013-08-01

    This letter proposed an eddy current pulsed phase thermography technique combing eddy current excitation, infrared imaging, and phase analysis. One steel sample is selected as the material under test to avoid the influence of skin depth, which provides subsurface defects with different depths. The experimental results show that this proposed method can eliminate non-uniform heating and improve defect detectability. Several features are extracted from differential phase spectra and the preliminary linear relationships are built to measure these subsurface defects' depth.

  1. Experimental observation of direct current voltage-induced phase synchronization

    Indian Academy of Sciences (India)

    Haihong Li; Weiqing Liu; Qiongling Dai; Jinghua Xiao

    2006-09-01

    The dynamics of two uncoupled distinct Chua circuits driven by a common direct current voltage is explored experimentally. It was found that, with increasing current intensity, the dominant frequencies of these two Chua circuits will first vary at different speeds, approach an identical value for a certain current intensity and then separate. Techniques such as synchronization index and phase difference distribution were employed to analyze the phase coherence between these two Chua circuits.

  2. The current-phase relation in HTS Josephson junctions

    Science.gov (United States)

    Il'ichev, E.; Zakosarenko, V.; Ijsselsteijn, R. P. J.; Schultze, V.; Meyer, H.-G.; Hoenig, H. E.

    The current-phase relation of YBa2Cu3O7-x step-edge as well as 24° and 45° grain boundary Josephson junctions has been investigated experimentally. The junctions were incorporated into a washer-shaped superconducting ring with inductance L≈80-300 pH. The ring was inductively coupled to a tank circuit with a resonance frequency 9…40 MHz. The current-phase relation was obtained from the measurement of the impedance of the phase-biased junction. It is shown, that experimentally observed deviations from harmonic behavior of the apparent current-phase relation for step-edge and 24° grain boundary junctions can be explained by the influence of thermal noise. The current-phase relation of 45° grain boundary junctions was found to be extremely non-harmonic. The reasons of this unusual behavior are discussed.

  3. Lower hybrid heating and current drive design for ITER and application for present tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Froissard, P.; Rey, G.; Bibet, P.; Goniche, M.; Kazarian, F.; Portafaix, C.; Tonon, G. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Bosia, G.; Bruno, L. [ITER Joint Work Site, Garching (Germany); Kuzikov, S. [Inst. of Applied Physics, Nizhny Novgorod (Russian Federation); Wasastjerna, F. [VTT Energy (Finland)

    1998-07-01

    The lower Hybrid Heating and Current Drive (LHH and CD) System shall provide on ITER off-axis current profile control during burn, main contribution to the non-inductive current generation in the advanced Tokamak scenario, current profile tailoring during ramp up phase, heating and current drive during plasma shut-down, extension of the pulse duration during commissioning phase. The LHH and CD system operates at 5 GHz, this frequency being a trade-off between power absorption by alpha particles and klystron technology and couples a minimum of 50 MW using two ITER ports. This article describes the launcher plug and the transmission lines. Specific converters, such as the mode converters, RF windows and the hyper-guide have now been successfully tested at high power and long pulse duration.

  4. A uniform phase noise QVCO with a feedback current source

    Institute of Scientific and Technical Information of China (English)

    Zhou Chunyuan; Zhang Lei; Qian He

    2012-01-01

    A novel integrated quadrature voltage controlled oscillator (QVCO) with a feedback current source is presented in this paper.Benefiting from the current adjusting function of the feedback current source,the proposed QVCO exhibits a uniform phase noise over the entire tuning range.This QVCO is implemented in 65-nm CMOS technology.The measurement results show that it draws less than 3-mA average current from a 1.2-V supply and the phase noise is less than -110 dBc/Hz @1MHz offset over the entire tuning range.The fluctuation of phase noise @l MHz offset from the center frequency of 2 84-GHz to 3.27-GHz is less than 1 dBc/Hz,which validates the correctness of the proposed current source feedback technique.

  5. Current phase relation in nanowire based Josephson junctions

    Science.gov (United States)

    Szombati, Daniel; Nadj-Perge, Stevan; Geresdi, Attila; Mourik, Vincent; Zuo, Kun; Woerkom, David; Car, Diana; Bakkers, Erik; Kouwenhoven, Leo

    2015-03-01

    Junctions based on small band-gap nanowires are convenient platform for studying Josephson effect in the presence of strong spin-orbit coupling. As predicted by theory, due to the interplay between strong Zeeman interaction and large spin orbing coupling in these nanowires, the critical current and in particular current phase relation exhibits rich set of features in the presence of external magnetic field and electrostatic gating. We study supercurrent transport through Indium Antimonide nanowires contacted using Niobium-Titanium-Nitride leads using both current and phase bias measurements. Our results provide useful insights into superconductor/semiconductor hybrid systems capable of hosting Majorana fermions, potential building blocks for topological quantum computing.

  6. Distribution of current in nonequilibrium diffusive systems and phase transitions

    Science.gov (United States)

    Bodineau, T.; Derrida, B.

    2005-12-01

    We consider diffusive lattice gases on a ring and analyze the stability of their density profiles conditionally to a current deviation. Depending on the current, one observes a phase transition between a regime where the density remains constant and another regime where the density becomes time dependent. Numerical data confirm this phase transition. This time dependent profile persists in the large drift limit and allows one to understand on physical grounds the results obtained earlier for the totally asymmetric exclusion process on a ring.

  7. Eddy current pulsed phase thermography for subsurface defect quantitatively evaluation

    Science.gov (United States)

    He, Yunze; Pan, Mengchun; Tian, GuiYun; Chen, Dixiang; Tang, Ying; Zhang, Hong

    2013-09-01

    This Letter verified eddy current pulse phase thermography through numerical and experimental studies. During the numerical studies, two characteristic features, blind frequency and min phase, were extracted from differential phase spectra, and their monotonic relationships with defects' depth under different heating time were compared. According to the numerical studies, 100 ms was employed as heating time during the improved experimental studies. The experimental results agreed with the numerical results. Based on their linear relationship with defects' depths, both features can be used to measure the defect's depth.

  8. A Phase Current Reconstruction Approach for Three-Phase Permanent-Magnet Synchronous Motor Drive

    Directory of Open Access Journals (Sweden)

    Hao Yan

    2016-10-01

    Full Text Available Three-phase permanent-magnet synchronous motors (PMSMs are widely used in renewable energy applications such as wind power generation, tidal energy and electric vehicles owing to their merits such as high efficiency, high precision and high reliability. To reduce the cost and volume of the drive system, techniques of reconstructing three-phase current using a single current sensor have been reported for three-phase alternating current (AC control system using the power converts. In existing studies, the reconstruction precision is largely influenced by reconstructing dead zones on the Space Vector Pulse Width Modulation (SVPWM plane, which requires other algorithms to compensate either by modifying PWM modulation or by phase-shifting of the PWM signal. In this paper, a novel extended phase current reconstruction approach for PMSM drive is proposed. Six novel installation positions are obtained by analyzing the sampling results of the current paths between each two power switches. By arranging the single current sensor at these positions, the single current sensor is sampled during zero voltage vectors (ZVV without modifying the PWM signals. This proposed method can reconstruct the three-phase currents without any complex algorithms and is available in the sector boundary region and low modulation region. Finally, this method is validated by experiments.

  9. MAGNETIZING CURRENT INRUSH IN THREE PHASE POWER TRANSFORMERS DURING INCOMPLETE PHASE SWITCHING

    Directory of Open Access Journals (Sweden)

    V. I. Novash

    2005-01-01

    Full Text Available The paper provides investigation results of magnetizing current inrushes in three-phase transformer during one-phase switching. Numerical experiments have been carried out with the help of a mathematical model developed on the basis of the second dissipation theory. It is shown that a magnetizing current inrush in the phase to be switched with absence of a residual induction exceeds an analogous inrush values by 1.4…1.6-fold in the case of simultaneous switching of all three phases.

  10. Treadmill motor current value based walk phase estimation.

    Science.gov (United States)

    Ohki, Eiichi; Nakashima, Yasutaka; Ando, Takeshi; Fujie, Masakatsu G

    2009-01-01

    We have developed a gait rehabilitation robot for hemiplegic patients using the treadmill. A walk phase, which includes time balance of stance and swing legs, is one of the most basic indexes to evaluate patients' gait. In addition, the walking phase is one of the indexes to control our robotic rehabilitation system. However, conventional methods to measure the walk phase require another system such as the foot switch and force plate. In this paper, an original algorithm to estimate the walk phase of a person on a treadmill using only the current value of DC motor to control the treadmill velocity is proposed. This algorithm was verified by experiments on five healthy subjects, and the walk phase of four subjects could be estimated in 0.2 (s) errors. However, the algorithm had erroneously identified a period of time in the stance phase as swing phase time when little body weight loaded on the subject's leg. Because a period of time with little body weight to affected leg is often observed in a hemiplegic walk, the proposed algorithm might fail to properly estimate the walk phase of hemiplegic patients. However, this algorithm could be used to estimate the time when body weight is loaded on patient legs, and thus could be used as a new quantitative evaluation index.

  11. The current-phase relation in Josephson junctions

    NARCIS (Netherlands)

    Golubov, A.A.; Kupriyanov, M. Yu.; Il'ichev, E.

    2004-01-01

    This review provides a theoretical basis for understanding the current-phase relation (CPhiR) for the stationary (dc) Josephson effect in various types of superconducting junctions. The authors summarize recent theoretical developments with an emphasis on the fundamental physical mechanisms of the d

  12. Effect of counter current gas phase on liquid film

    Institute of Scientific and Technical Information of China (English)

    Shujuan LUO; Huaizhi LI; Weiyang FEI; Yundong WANG

    2009-01-01

    Liquid film flow is very important in many industrial applications. However, there are few reports about its characteristics on structured packings. Therefore, in this paper, liquid film phenomena were investigated experimentally to exploit new approaches for intensifying the performance of the structured packings. All experiments were performed at room temperature. Water and air were the working fluids. The effect of counter current gas phase on the liquid film was taken into consideration. A high speed camera, a non-intrusive measurement technique, was used. It is shown that both liquid and gas phases have strong effects on film characteristics. In the present work, liquid film width increased by 57% because of increasing liquid flow rate, while it decreased by 25% resulting from the counter current gas phase.

  13. A New PWM Modifying Technique for Reconstructing Three-phase Currents from DC Bus Current

    Science.gov (United States)

    Aoyagi, Shigehisa; Iwaji, Yoshitaka; Tobari, Kazuaki; Sakamoto, Kiyoshi

    Vector control is used to drive a DC brushless motor and generally needs current information. DC bus current detection is often adopted as a low cost method for reconstructing three-phase currents. PWM modifying techniques increase the DC pulse duration, thereby enabling easy detection of the DC bus current. However, these techniques have two problems: reducing a noise frequency and making the reconstructed current waveforms distorted by current ripple. In the techniques, modification signals are added to the three-phase voltage commands; the sum of the signals over a single cycle is zero. The authors examined several PWM modifying techniques from the points of view of noise and current distortion performance. One of the techniques had a good noise performance, and the frequency component of the noise was the same as the carrier frequency (fc). However, the reconstructed current waveforms were distorted. The total harmonic distortion (THD) varied from 1.7% to 4.1%. Another technique had a very poor noise performance, and the frequency component on the noise was one-fourth of fc. The authors developed a new PWM modifying method called “Half Pulse Shift”, which achieves the optimum noise and current distortion performance. The frequency component of the new method was two-thirds of fc, and the current waveforms were not distorted; the THD in the simulations and experiments was 0.5%-1.4% and 3.4%-3.6%, respectively.

  14. Spin-current probe for phase transition in an insulator

    Science.gov (United States)

    Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'diaye, Alpha T.; Tan, Ali; Uchida, Ken-Ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; Qiu, Z. Q.; Saitoh, Eiji

    2016-08-01

    Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is a flux of spin without an electric charge and its transport reflects spin excitation. We demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices.

  15. Wideband digital phase comparator for high current shunts

    CERN Document Server

    Pogliano, Umberto; Serazio, Danilo

    2011-01-01

    A wideband phase comparator for precise measurements of phase difference of high current shunts has been developed at INRIM. The two-input digital phase detector is realized with a precision wideband digitizer connected through a pair of symmetric active guarded transformers to the outputs of the shunts under comparison. Data are first acquired asynchronously, and then transferred from on-board memory to host memory. Because of the large amount of data collected the filtering process and the analysis algorithms are performed outside the acquisition routine. Most of the systematic errors can be compensated by a proper inversion procedure. The system is suitable for comparing shunts in a wide range of currents, from several hundred of milliampere up to 100 A, and frequencies ranging between 500 Hz and 100 kHz. Expanded uncertainty (k=2) less than 0.05 mrad, for frequency up to 100 kHz, is obtained in the measurement of the phase difference of a group of 10 A shunts, provided by some European NMIs, using a digit...

  16. Flooding in counter-current two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Ragland, W.A.; Ganic, E.N.

    1982-01-01

    Flooding is a phenomenon which is best described as the transition from counter-current to co-current flow. Early notice was taken of this phenomenon in the chemical engineering industry. Flooding also plays an important role in the field of two-phase heat transfer since it is a limit for many systems involving counter-current flow. Practical applications of flooding limited processes include wickless thermosyphons and the emergency core cooling system (ECCS) of pressurized water nuclear reactors. The phenomenon of flooding also is involved in the behavior of nuclear reactor core materials during severe accident conditions where flooding is one of the mechanisms governing the motion of the molten fuel pin cladding.

  17. Quasiparticle current and phase locking of intrinsic Josephson junctions

    Science.gov (United States)

    Seidel, P.; Grib, A. N.; Shukrinov, Yu. M.; Scherbel, J.; Hübner, U.; Schmidl, F.

    2001-09-01

    On the base of our experiments on thin film Josephson junctions in mesa geometry we discuss the quasiparticle branches of the intrinsic arrays within a tunnelling model using d-wave superconductor density of states. We find temperature dependent current contributions and a zero bias anomaly. The coherent behaviour is studied for intrinsic arrays with an additional side-wall shunt. The existence of thresholds of phase locking at small as well as at large inductances is demonstrated. We discuss the problems with experimental realisation of the shunts as well as with an alternative concept to enhance phase locking in such arrays towards application as oscillators in the frequency range up to some THz.

  18. Enhancement of the power supply systems in RFX-mod towards 2 MA plasma current

    Energy Technology Data Exchange (ETDEWEB)

    Novello, Luca, E-mail: luca.novello@igi.cnr.it [Consorzio RFX, Euratom-ENEA Association, Padova (Italy); Zamengo, Andrea; Ferro, Alberto; Zanotto, Loris; Barp, Marco; Cavazzana, Roberto; Finotti, Claudio; Recchia, Mauro; Gaio, Elena [Consorzio RFX, Euratom-ENEA Association, Padova (Italy)

    2011-10-15

    The recent start-up improvements brought to RFX-mod have allowed increasing the plasma current in the range 1.7-1.9 MA, but still they proved to be not sufficient to routinely and reliably reach higher values of plasma current that would be very useful for the present studies on enhanced confinement. The need for higher poloidal flux variation together with the overabundant available toroidal flux has led to the study of a rearrangement of the power supply system with the aim of increasing the first at the expenses of the latter. Thanks to the flexibility of the power supply system, composed of modular thyristor converters, the rearrangement has been easily obtained and the resulting enhanced poloidal flux capability scenario described in the paper allows a two step plasma current ramp-up. In order to increase as much as possible the plasma current up to the nominal value of 2 MA it is necessary to fully exploit the thyristor converter power capability, in particular in the first ramp-up phase. In the paper a detailed verification of their maximum performance is presented. The first results obtained after power supply reconfiguration are very good, with plasma current kept constant at about 2 MA for 100 ms. The enabled operation at very high plasma current requires also an optimization of the magneto hydro dynamics (MHD) mode coil power supplies that are required to provide higher current values. Therefore a dedicated study of their control system has been worked out, which allowed understanding how to increase as much as possible the output current without losing the dynamic performance, so keeping the efficiency in the control of dominant and secondary modes, which is essential to obtain good and reproducible discharges.

  19. Dynamic phase-control of a rising sun magnetron using modulated and continuous current

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Gutierrez, Sulmer, E-mail: sulmer.a.fernandez.gutierrez@intel.com [Intel Corporation, 2111 NE 25th Ave, Hillsboro, Oregon 97214 (United States); Browning, Jim [Department of Electrical and Computer Engineering, Boise State University, Boise, Idaho 83725 (United States); Lin, Ming-Chieh [Department of Electrical and Biomedical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Smithe, David N. [Tech-X Corporation, 5621 Arapahoe Ave, Boulder, Colorado 80303 (United States); Watrous, Jack [Confluent Sciences, LLC, Albuquerque, New Mexico 87111 (United States)

    2016-01-28

    Phase-control of a magnetron is studied via simulation using a combination of a continuous current source and a modulated current source. The addressable, modulated current source is turned ON and OFF at the magnetron operating frequency in order to control the electron injection and the spoke phase. Prior simulation work using a 2D model of a Rising Sun magnetron showed that the use of 100% modulated current controlled the magnetron phase and allowed for dynamic phase control. In this work, the minimum fraction of modulated current source needed to achieve a phase control is studied. The current fractions (modulated versus continuous) were varied from 10% modulated current to 100% modulated current to study the effects on phase control. Dynamic phase-control, stability, and start up time of the device were studied for all these cases showing that with 10% modulated current and 90% continuous current, a phase shift of 180° can be achieved demonstrating dynamic phase control.

  20. ITER (International Thermonuclear Experimental Reactor) current drive and heating physics

    Energy Technology Data Exchange (ETDEWEB)

    Nevins, W.M.; Lindquist, W. (Lawrence Livermore National Lab., CA (USA)); Fujisawa, N.; Kimura, H. (Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan)); Hopman, H.; Rebuffi, L.; Wegrowe, J.G. (Max-Planck-Institut fuer Plasmaphysik, Garching (Germany, F.R.). NET Design Team); Parail, V.; Vdovin, V. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow (USSR). Inst. Atomnoj Ehn

    1990-01-01

    The ITER Current Drive and Heating (CD H) systems are required for: Ionization and current initiation; Non-inductive current ramp-up assist; Heating of the plasma; Steady-state operation with full non-inductive current drive; Current profile control; and Burn control by modulation of the auxiliary power. Steady-state current drive is the most demanding requirement, so this has driven the choice of the ITER current drive and heating systems.

  1. Single-phase Multilevel Current Source Inverter with Reduced Device Count and Current Balancing Capability

    Directory of Open Access Journals (Sweden)

    MOALLEMI KHIAVI, A.

    2015-08-01

    Full Text Available Nowadays power converters play an important role in power system and industrial centers. One of the most important and widely used types of conversion is DC to AC conversion that is also called inverters. Generally inverters are divided to voltage source inverter (VSI and current source inverter (CSI. From another view the inverters are divided to two-level and multilevel types. The multilevel inverters are attractive because of their good output waveform quality. However, there has been less attention to multilevel current source inverter (MLCSI when compared with multilevel VSI. In this paper, a new topology for MLCSI is proposed. The proposed topology employs reduced number of switches to generate desired multilevel output current. The proposed MLCSI is capable of balancing the currents of the inductors that are used in the MLCSI structure. A multicarrier PWM based switching strategy is also proposed for the MLCSI. The simulation results using PSCAD/EMTDC as well as the experimental results from a single-phase 5-level CSI laboratory prototype demonstrate its validity.

  2. Methods, systems and apparatus for synchronous current regulation of a five-phase machine

    Science.gov (United States)

    Gallegos-Lopez, Gabriel; Perisic, Milun

    2012-10-09

    Methods, systems and apparatus are provided for controlling operation of and regulating current provided to a five-phase machine when one or more phases has experienced a fault or has failed. In one implementation, the disclosed embodiments can be used to synchronously regulate current in a vector controlled motor drive system that includes a five-phase AC machine, a five-phase inverter module coupled to the five-phase AC machine, and a synchronous current regulator.

  3. Preanalytical Phase – an updated review of the current evidence

    OpenAIRE

    Simundic, Ana-Maria

    2014-01-01

    European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working group for preanalytical phase (WG-PRE) has recently launched a series of conferences on preanalytical phase. First such meeting was held in Parma (Italy) in the spring of 2011 and the second one took place in Zagreb (Croatia) during 1-2 March 2013. The Zagreb audience had the opportunity to enjoy a focused and challenging scientific program as well as to participate actively in interactive e-voting sessions. S...

  4. Current distribution among layers of single phase HTS cable conductor

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Y.B., E-mail: yeaber@ncepu.edu.cn [Key Laboratory of HV and EMC Beijing, State Key Laboratory for Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, No. 2 Beinong Road, Changping District, Beijing 102206 (China); Wang, Y.S., E-mail: yswang@ncepu.edu.cn [Key Laboratory of HV and EMC Beijing, State Key Laboratory for Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, No. 2 Beinong Road, Changping District, Beijing 102206 (China); Pi, W., E-mail: ppiiwei@ncepu.edu.cn [Key Laboratory of HV and EMC Beijing, State Key Laboratory for Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, No. 2 Beinong Road, Changping District, Beijing 102206 (China); Ju, P., E-mail: jupeng-cool@153.com [Key Laboratory of HV and EMC Beijing, State Key Laboratory for Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, No. 2 Beinong Road, Changping District, Beijing 102206 (China); Wang, Y.S., E-mail: wangyixuan@epri.sgcc.com.cn [Power System Department, China Electric Power Research Institute, No. 15 Qinghexiaoying East Road, Haidian District, Beijing 100198 (China)

    2014-12-15

    Highlights: • A 1.5 m long HTS model cable with 4 layers designed by the uniform current principle has been built. • It is testified that the current distribution is influenced by the proximity effect. • The magnetic flux density and current density have been analyzed. • AC losses of tested current are larger than those of uniform current. - Abstract: High temperature superconducting (HTS) power cable shows high application prospect in modern power transmission, as it is superior over conventional transmission lines in high engineering current density and environmental friendliness. Its configuration is generally composed of several HTS layers designed with the principle of uniform current distribution, but there are few experimental results to verify the distribution. In this paper, a HTS cable model was designed based on the principle of uniform current, and the current distributions among layers in an HTS cable model were measured by Rogowski coils. The results provide an important basis for design of multi-layer HTS cable.

  5. Current distribution among layers of single phase HTS cable conductor

    Science.gov (United States)

    Zheng, Y. B.; Wang, Y. S.; Pi, W.; Ju, P.; Wang, Y. S.

    2014-12-01

    High temperature superconducting (HTS) power cable shows high application prospect in modern power transmission, as it is superior over conventional transmission lines in high engineering current density and environmental friendliness. Its configuration is generally composed of several HTS layers designed with the principle of uniform current distribution, but there are few experimental results to verify the distribution. In this paper, a HTS cable model was designed based on the principle of uniform current, and the current distributions among layers in an HTS cable model were measured by Rogowski coils. The results provide an important basis for design of multi-layer HTS cable.

  6. Computation of reduced energy input current stimuli for neuron phase models.

    Science.gov (United States)

    Anyalebechi, Jason; Koelling, Melinda E; Miller, Damon A

    2014-01-01

    A regularly spiking neuron can be studied using a phase model. The effect of an input stimulus current on the phase time derivative is captured by a phase response curve. This paper adapts a technique that was previously applied to conductance-based models to discover optimal input stimulus currents for phase models. First, the neuron phase response θ(t) due to an input stimulus current i(t) is computed using a phase model. The resulting θ(t) is taken to be a reference phase r(t). Second, an optimal input stimulus current i(*)(t) is computed to minimize a weighted sum of the square-integral `energy' of i(*)(t) and the tracking error between the reference phase r(t) and the phase response due to i(*)(t). The balance between the conflicting requirements of energy and tracking error minimization is controlled by a single parameter. The generated optimal current i(*)t) is then compared to the input current i(t) which was used to generate the reference phase r(t). This technique was applied to two neuron phase models; in each case, the current i(*)(t) generates a phase response similar to the reference phase r(t), and the optimal current i(*)(t) has a lower `energy' than the square-integral of i(t). For constant i(t), the optimal current i(*)(t) need not be constant in time. In fact, i(*)(t) is large (possibly even larger than i(t)) for regions where the phase response curve indicates a stronger sensitivity to the input stimulus current, and smaller in regions of reduced sensitivity.

  7. Extracting DC bus current information for optimal phase correction and current ripple in sensorless brushless DC motor drive

    Institute of Scientific and Technical Information of China (English)

    Zu-sheng HO; Chii-maw UANG; Ping-chieh WANG

    2014-01-01

    Brushless DC motor (BLDCM) sensorless driving technology is becoming increasingly established. However, op-timal phase correction still relies on complex calculations or algorithms. In finding the correct commutation point, the problem of phase lag is introduced. In this paper, we extract DC bus current information for auto-calibrating the phase shift to obtain the correct commutation point and optimize the control of BLDC sensorless driving. As we capture only DC bus current information, the original shunt resistor is used in the BLDCM driver and there is no need to add further current sensor components. Software processing using only simple arithmetic operations successfully accomplishes the phase correction. Experimental results show that the proposed method can operate accurately and stably at low or high speed, with light or heavy load, and is suitable for practical applications. This approach will not increase cost but will achieve the best performance/cost ratio and meet market expectations.

  8. Phase Current Differential Protection for Transformers in Wye-delta Mode

    Directory of Open Access Journals (Sweden)

    Zhe Zhang

    2012-10-01

    Full Text Available For the current transformers (CTs on the delta side measure the line current instead of the phase current, line current differential protection is adopted in transformers connected in wye-delta mode currently. However, the symmetry feature of inrush current in line current differential protection may invalidate the inrush current restrained criterion. A calculating method of current through delta windings according the measured current from CT is proposed in this paper. Using this calculated current, phase current differential protection can be realized. Based on the method an adaptive second harmonic restrained scheme for magnetizing inrush current is presented. The scheme not only adaptively adjusts the secondary harmonic ratio of restrained current but also guarantees the fast action when transformers with internal faults are no-load energized. Consequently the performance of transformer differential protection is greatly improved. Simulation results in Matlab/Simulink validate the proposed method.

  9. A 6-switch single-phase 5-level current-source inverter

    Institute of Scientific and Technical Information of China (English)

    BAO Jian-yu; LI Yu-ling; ZHANG Zhong-chao

    2006-01-01

    The new 6-switch single-phase 5-level current-source inverter proposed in this paper was developed by properly simplifying the traditional 8-switch single-phase 5-level current-source inverter, and its operational principle was analyzed. Just like the problem of voltage-unbalance between different levels existing in voltage-source multilevel inverters, a similar problem of current-unbalance between different levels whether for the 8-switch single-phase 5-level current-source inverter, or for the new 6-switch 5-level current-source inverter also exists. A simple current-balance control method via DC current feedback is presented here to implement the current-balance control between different levels. And to reduce the output current harmonics, PWM control technique was used. Simulation and experimental results showed that this new 6-switch topology operates correctly and that the balance-inductor can almost equally distribute the total DC current.

  10. Analysis of the effects of asymmetric faults in three-phase superconducting inductive fault current limiters

    Science.gov (United States)

    Ferreira, R.; Pina, J. M.; Vilhena, N.; Arsénio, P.; Pronto, A. G.; Martins, J.

    2014-05-01

    Inductive fault current limiters of magnetic shielding type can be described in terms of the excursion in the plane defined by flux linked with primary and line current, and this methodology has been previously applied to single-phase devices. Practical applications, however, require three-phase limiters, which, for the sake of compactness, may be built by three legged cores, instead of three single phase units. This has the advantage of using well established methods of power transformers industry, but the performance of the devices depends on the type of fault, e.g. phase to ground or phase to phase. For instance, in a three legged core, a phase to ground fault affects healthy phases, and these are the most frequent faults in distribution grids, where such systems are envisaged. The effects of asymmetric faults are analysed in this paper, by means of measured excursions in the linked flux-current plane.

  11. Baryon currents in the C-broken phase of QCD

    CERN Document Server

    Lucini, B; Pica, C

    2007-01-01

    In a space with some sufficiently small compact dimension (with non-trivial cycles) and with periodic boundary conditions for the fermions, the charge conjugation (C), spatial parity (P), time reversal (T) and CPT symmetries are spontaneously broken in QCD. We have investigated what are the physical consequences of the breaking of these discrete symmetries, that is what local observables can be used to detect it. We show that the breaking induces the generation of baryon currents, propagating along the compact dimensions.

  12. Energy Efficiency Financing for Low- and Moderate-Income Households: Current State of the Market, Issues, and Opportunities

    Energy Technology Data Exchange (ETDEWEB)

    None

    2017-08-01

    Although the need is great, many LMI households may not be able to afford efficiency improvements or may be inhibited from adopting efficiency for other reasons. Decision-makers across the country are currently exploring the challenges and potential solutions to ramping up adoption of efficiency in LMI households, including the use of financing.

  13. Dynamical effects of an unconventional current-phase relation in YBCO dc SQUIDs.

    Science.gov (United States)

    Lindström, T; Charlebois, S A; Tzalenchuk, A Ya; Ivanov, Z; Amin, M H S; Zagoskin, A M

    2003-03-21

    The predominant d-wave pairing symmetry in high-temperature superconductors allows for a variety of current-phase relations in Josephson junctions, which is to a certain degree fabrication controlled. In this Letter, we report on direct experimental observations of the effects of a nonsinusoidal current-phase dependence in YBCO dc SQUIDs, which agree with the theoretical description of the system.

  14. PROTECTION OF HOUSEHOLD APPLIANCES INDUCTION MOTORS AGAINST OVERCURRENT TAKING INTO ACCOUNT NONLINEAR DISTORTION OF PHASE CURRENT

    Directory of Open Access Journals (Sweden)

    A.G. Sereda

    2015-06-01

    Full Text Available Purpose. Theoretical justification and engineering of induction motors heat protection method from overload currents taking into account nonlinear distortion of the phase current and implementation as a microprocessor device functioning algorithm. Methodology. To solve the problem used the theory of the representing complex harmonic oscillations analog signals expansion into the oscillation spectrum forming elementary harmonic components in order to compare their properties by applying the theory of discrete signals and systems, as well as methods of spectral analysis and discrete signals filtering. The harmonic analysis versatility is that any periodic signal may be synthesized from harmonic oscillation of certain amplitude, frequency and initial phase. A mathematical model for determining the phase current harmonic content of power supply networks with isolated neutral and non-linear loads types and, as a consequence, the distortion of sinusoidal phase current change is developed by multiplying the analog current in time dependency on the grate delta-function with different sampling intervals, in which the use of simple and widely used in relay protection units, in particular electronic overcurrent relays, mathematical operations of integration squares instantaneous current allows the most in harmony with the mathematical tools to build other network protection types. Findings. The necessity to increase the sensitivity of the induction motors heat protection from overload currents taking into account nonlinear distortion of the phase currents is proved. By nonlinear distortion harmonic analysis of the phase currents the motor protection reliability increasing provided by taking into account the higher harmonic components of the phase currents, which causes to additional losses and heating of the stator winding. It uses the simplest and widely used in protective relaying mathematical apparatus determining of most significant higher harmonics

  15. Enhanced Phase-Shifted Current Control for Harmonic Cancellation in Three-Phase Multiple Adjustable Speed Drive Systems

    DEFF Research Database (Denmark)

    Yang, Yongheng; Davari, Pooya; Zare, Firuz

    2017-01-01

    A phase-shifted current control can be employed to mitigate certain harmonics induced by the Diode Rectifiers (DR) and Silicon-Controlled Rectifiers (SCR) as the front-ends of multiple parallel Adjustable Speed Drive (ASD) systems. However, the effectiveness of the phase-shifted control relies on......-shifted current control is a cost-effective solution to multiple ASD systems in terms of harmonic cancellation.......A phase-shifted current control can be employed to mitigate certain harmonics induced by the Diode Rectifiers (DR) and Silicon-Controlled Rectifiers (SCR) as the front-ends of multiple parallel Adjustable Speed Drive (ASD) systems. However, the effectiveness of the phase-shifted control relies...... on the loading condition of each drive unit as well as the number of drives in parallel. In order to enhance the harmonic cancellation by means of the phase-shifted current control, the currents drawn by the rectifiers should be maintained almost at the same level. Thus, this paper firstly analyzes the impact...

  16. Three-phase diode rectifiers with low harmonics current injection methods

    CERN Document Server

    Pejovic, Predrag

    2007-01-01

    Presents results of numerous research papers in the area of current injection based rectifiers. This book discusses the principles of current injection, followed by an analysis of various magnetic current injection devices. It concludes with a chapter where the results are generalized to three-phase full-bridge thyristor rectifiers.

  17. Direct-current-like Phase Space Manipulation Using Chirped Alternating Current Fields

    Energy Technology Data Exchange (ETDEWEB)

    P.F. Schmit and N.J. Fisch

    2010-02-01

    Waves in plasmas can accelerate particles that are resonant with the wave. A dc electric field also accelerates particles, but without a resonance discrimination, which makes the acceleration mechanism profoundly different. Whereas wave-particle acceleration mechanisms have been widely discussed in the literature, this work discusses the direct analogy between wave acceleration and dc field acceleration in a particular parameter regime explored in previous works. Apart from the academic interest of this correspondence, there may be practical advantages in using waves to mimic dc electric fields, for example, in driving plasma current with high efficiency.

  18. Point discharge current measurements beneath dust devils

    Science.gov (United States)

    Lorenz, Ralph D.; Neakrase, Lynn D. V.; Anderson, John P.; Harrison, R. Giles; Nicoll, Keri A.

    2016-12-01

    We document for the first time observations of point discharge currents under dust devils using a novel compact sensor deployed in summer 2016 at the USDA-ARS Jornada Experimental Range in New Mexico, USA. A consistent signature is noted in about a dozen events seen over 40 days, with a positive current ramping up towards closest approach, switching to a decaying negative current as the devil recedes. The currents, induced on a small wire about 10 cm above the ground, correlate with dust devil intensity (pressure drop) and dust loading, and reached several hundred picoAmps.

  19. How to target inter-regional phase synchronization with dual-site Transcranial Alternating Current Stimulation

    DEFF Research Database (Denmark)

    Saturnino, Guilherme Bicalho; Madsen, Kristoffer Hougaard; Siebner, Hartwig Roman

    2017-01-01

    Large-scale synchronization of neural oscillations is a key mechanism for functional information exchange among brain areas. Dual-site Transcranial Alternating Current Stimulation (ds-TACS) has been recently introduced as non-invasive technique to manipulate the temporal phase relationship of local...... oscillations in two connected cortical areas. While the frequency of ds-TACS is matched, the phase of stimulation is either identical (in-phase stimulation) or opposite (anti-phase stimulation) in the two cortical target areas. In-phase stimulation is thought to synchronize the endogenous oscillations...... and hereby to improve behavioral performance. Conversely, anti-phase stimulation is thought to desynchronize neural oscillations in the two areas, which is expected to decrease performance. Critically, in- and anti-phase ds-TACS should only differ with respect to temporal phase, while all other stimulation...

  20. Leakage Current Elimination of Four-Leg Inverter for Transformerless Three-Phase PV Systems

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; He, Ran; Jian, Jiamin

    2016-01-01

    Eliminating the leakage current is one of the most important issues for transformerless three phase photovoltaic (PV) systems. In this paper, the leakage current elimination of a three-phase four-leg PV inverter is investigated. With the common mode loop model established, the generation mechanis...... the different modulation methods are implemented and tested on the TMS320F28335 DSP +XC3S400 FPGA digital control platform. The experimental results verify the effectiveness of the proposed solution....

  1. Asymmetric current-phase relation due to spin-orbit interaction in semiconductor nanowire Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, Tomohiro; Eto, Mikio [Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Nazarov, Yuli V. [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands (Netherlands)

    2013-12-04

    We theoretically study the current-phase relation in semiconductor nanowire Josephson junction in the presence of spin-orbit interaction. In the nanowire, the impurity scattering with strong SO interaction is taken into account using the random matrix theory. In the absence of magnetic field, the Josephson current I and phase difference φ between the superconductors satisfy the relation of I(φ) = –I(–φ). In the presence of magnetic field along the nanowire, the interplay between the SO interaction and Zeeman effect breaks the current-phase relation of I(φ) = –I(–φ). In this case, we show that the critical current depends on the current direction, which qualitatively agrees with recent experimental findings.

  2. Particle Confinement Improvement with Current Ramp in the HL-IM Tokamak

    Institute of Scientific and Technical Information of China (English)

    YAN Long-Wen; WANG En-Yao; QIAN Jun; CHEN Liao-Yuan; LIU Yong

    2003-01-01

    Particle confinement with current ramp is investigated in the HL-IM tokamak. The ratio of particle confinement time to energy confinement time is used to determine confinement improvement. It increases a factor of 3 after the current rises twofold. An optimization density range to improve particle confinement is (1.5-3.5) XlO19 m~3. Particle confinement improvement during current ramp-up is beneficial to the startup of fusion reactors.

  3. Burnout current density of bismuth nanowires

    Science.gov (United States)

    Cornelius, T. W.; Picht, O.; Müller, S.; Neumann, R.; Völklein, F.; Karim, S.; Duan, J. L.

    2008-05-01

    Single bismuth nanowires with diameters ranging from 100nmto1μm were electrochemically deposited in ion track-etched single-pore polycarbonate membranes. The maximum current density the wires are able to carry was investigated by ramping up the current until failure occurred. It increases by three to four orders of magnitude for nanowires embedded in the template compared to bulk bismuth and rises with diminishing diameter. Simulations show that the wires are heated up electrically to the melting temperature. Since the surface-to-volume ratio rises with diminishing diameter, thinner wires dissipate the heat more efficiently to the surrounding polymer matrix and, thus, can tolerate larger current densities.

  4. A Coordinate Control Strategy for Circulating Current Suppression in Multiparalleled Three-Phase Inverters

    DEFF Research Database (Denmark)

    Zhang, Xueguang; Wang, Tianyi; Wang, Xiongfei

    2017-01-01

    This paper addresses the zero-sequence circulating current control in the multiparalleled three-phase voltage-source inverters. The model of the zero-sequence circulating current in the N-paralleled (N ≥ 3) inverters is derived. It is shown that the circulating current is not only susceptible...... to the mismatches of circuit parameters, but it is also influenced by the interactions of circulating current controllers used by other paralleled inverters. To eliminate these adverse effects on the circulating current control loop, a coordinate control strategy for the N-paralleled inverter is proposed based...

  5. Eddy currents in the anisotropy of out-of-phase magnetic susceptibility measurement - A model study

    Science.gov (United States)

    Jezek, Josef; Hrouda, Frantisek

    2016-04-01

    Analytical solutions of Maxwell equations for eddy currents caused by AC field in a conductive sphere, known from 1950s, provide a general formula for magnetic susceptibility. It contains the parameters describing the sphere (its size, conductivity and permeability), surrounding medium (permeability) and the applied field (frequency). The formula is complex and without numerical evaluation it is difficult to distinguish the real (in-phase) and imaginary (out-of-phase) part of susceptibility. Representing all the parameters by only two, relative permeability (sphere vs. medium) and skin ratio (summarizing the effect of sphere size, conductivity and permeability, and frequency of the field), we derive approximate formulas for both phases and the phase angle. These are valid for a reasonable range of parameters (from rock magnetism point of view) and enable us to study their influence. The in-phase susceptibility depends very weakly on the fourth power of the skin ratio while the out-of-phase susceptibility depends more strongly on its second power. The coefficients of the dependence are expressed by means of relative permeability. The approximations of in-phase and out-of-phase susceptibilities provide a possibility to assess possible effects of eddy currents in rocks in case of low content of conductive minerals and solve problems of the type by which size one piece of a mineral in the measured sample can produce a phase shift that is observed by measurement. Examples of magnetite and pyrrhotite are given.

  6. Current loops, phase transitions, and the Higgs mechanism in Josephson-coupled multicomponent superconductors

    Science.gov (United States)

    Galteland, Peder Notto; Sudbø, Asle

    2016-08-01

    The N -component London U (1 ) superconductor is expressed in terms of integer-valued supercurrents. We show that the inclusion of interband Josephson couplings introduces monopoles in the current fields, which convert the phase transitions of the charge-neutral sector to crossovers. The monopoles only couple to the neutral sector, and leave the phase transition of the charged sector intact. The remnant noncritical fluctuations in the neutral sector influence the one remaining phase transition in the charged sector, and may alter this phase transition from a 3 D X Y inverted phase transition into a first-order phase transition depending on what the values of the gauge charge and the intercomponent Josephson coupling are. This preemptive effect becomes more pronounced with increasing number of components N , since the number of charge-neutral fluctuating modes that can influence the charged sector increases with N . We also calculate the gauge-field correlator, and by extension the Higgs mass, in terms of current-current correlators. We show that the onset of the Higgs mass of the photon (Meissner effect) is given in terms of a current loop blowout associated with going into the superconducting state as the temperature of the system is lowered.

  7. The targeted heating and current drive applications for the ITER electron cyclotron system

    Energy Technology Data Exchange (ETDEWEB)

    Henderson, M.; Darbos, C.; Gandini, F.; Gassmann, T.; Loarte, A.; Omori, T.; Purohit, D. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Saibene, G.; Gagliardi, M. [Fusion for Energy, Josep Pla 2, Barcelona 08019 (Spain); Farina, D.; Figini, L. [Istituto di Fisica del Plasma CNR, 20125 Milano (Italy); Hanson, G. [US ITER Project Office, ORNL, 1055 Commerce Park, PO Box 2008, Oak Ridge, Tennessee 37831 (United States); Poli, E. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany); Takahashi, K. [Japan Atomic Energy Agency (JAEA), Naka, Ibaraki 311-0193 (Japan)

    2015-02-15

    A 24 MW Electron Cyclotron (EC) system operating at 170 GHz and 3600 s pulse length is to be installed on ITER. The EC plant shall deliver 20 MW of this power to the plasma for Heating and Current Drive (H and CD) applications. The EC system is designed for plasma initiation, central heating, current drive, current profile tailoring, and Magneto-hydrodynamic control (in particular, sawteeth and Neo-classical Tearing Mode) in the flat-top phase of the plasma. A preliminary design review was performed in 2012, which identified a need for extended application of the EC system to the plasma ramp-up, flattop, and ramp down phases of ITER plasma pulse. The various functionalities are prioritized based on those applications, which can be uniquely addressed with the EC system in contrast to other H and CD systems. An initial attempt has been developed at prioritizing the allocated H and CD applications for the three scenarios envisioned: ELMy H-mode (15 MA), Hybrid (∼12 MA), and Advanced (∼9 MA) scenarios. This leads to the finalization of the design requirements for the EC sub-systems.

  8. Recent progress on lower hybrid current drive and implications for ITER

    CERN Document Server

    Hillairet, Julien; Goniche, M; Achard, J; Armitano, A; Beckett, B; Belo, J; Berger-By, G; Corbel, E; Delpech, L; Decker, J; Dumont, R; Guilhem, D; Kazarian, F; Litaudon, X; Magne, R; Marfisi, L; Mollard, P; Namkung, W; Nilsson, E; Park, S; Peysson, Y; Preynas, M; Sharma, P K; Prou, M

    2015-01-01

    The sustainment of steady-state plasmas in tokamaks requires efficient current drive systems. Lower Hybrid Current Drive (LHCD) is currently the most efficient method to generate a continuous additional off-axis toroidal plasma current as well as reduce the poloidal flux consumption during the plasma current ramp-up phase. The operation of the Tore Supra ITER-like LH launcher has demonstrated the capability to couple LH power at ITER-like power densities with very low reflected power during long pulses. In addition, the installation of eight 700kW/CW klystrons at the LH transmitter has allowed increasing the total LH power in long pulse scenarios. However, in order to achieve pure stationary LH sustained plasmas, some R\\&D are needed to increase the reliability of all the systems and codes, from the RF sources to the plasma scenario prediction. The CEA/IRFM is addressing some of these issues by leading a R\\&D program towards an ITER LH system and by the validation of an integrated LH modeling suite of...

  9. Qualitative modifications and new dynamic phases in the phase diagram of one-dimensional superconducting wires driven with electric currents

    Science.gov (United States)

    Kallush, Shimshon; Berger, Jorge

    2014-06-01

    After an initial transient period, the conduction regime in a one-dimensional superconducting wire that carries a fixed current is either normal, periodic, or stationary. The phase diagram for these possibilities was studied in Phys. Rev. Lett. 99, 167003 (2007), 10.1103/PhysRevLett.99.167003 for particular values of the length and the material parameters. We have extended this study to arbitrary length and to a range of material parameters that includes realistic values. Variation of the length leads to scaling laws for the phase diagram. Variation of the material parameters leads to new qualitative features and new phases, including a parameter region in which all three regimes are possible.

  10. Real-Time Method for Detecting Harmonic and Reactive Currents of Single-Phase Circuits

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiufeng; Ding Juxia

    2006-01-01

    According to the characteristics of single-phase circuits and demand of using active filter for real-time detecting harmonic and reactive currents, a detecting method based on Fryze's power definition is proposed. The results of theoretical analysis and simulation show that the proposed method is effective in real-time detecting of instantaneous harmonic and reactive currents in single-phase circuits. When only detecting the total reactive currents, this method does not need a phase-locked loop circuit, and it also can be used in some special applications to provide different compensations on the ground of different requirements of electric network. Compared with the other methods based on the theory of instantaneous reactive power, this method is simple and easy to realize.

  11. Eddy Current Transducer Dedicated for Sigma Phase Evaluation in Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Grzegorz Psuj

    2012-01-01

    Full Text Available The paper describes a new transducer dedicated for evaluation of a duplex stainless steel (DSS. Different phases which exist in DSS have influence on mechanical as well as on electrical properties. Therefore, an eddy current transducer was utilized. In order to achieve high sensitivity, a differential type of the transducer was selected. The performance of the transducer was verified by utilizing the samples which had a different amount of sigma phase.

  12. Energy content of stormtime ring current from phase space mapping simulations

    Science.gov (United States)

    Chen, Margaret W.; Schulz, Michael; Lyons, Larry R.

    1993-01-01

    We perform a phase space mapping study to estimate the enhancement in energy content that results from stormtime particle transport in the equatorial magnetosphere. Our pre-storm phase space distribution is based on a steady-state transport model. Using results from guiding-center simulations of ion transport during model storms having main phases of 3 hr, 6 hr, and 12 hr, we map phase space distributions of ring current protons from the pre-storm distribution in accordance with Liouville's theorem. We find that transport can account for the entire ten to twenty-fold increase in magnetospheric particle energy content typical of a major storm if a realistic stormtime enhancement of the phase space density f is imposed at the nightside tail plasma sheet (represented by an enhancement of f at the neutral line in our model).

  13. COLLABORATE©, Part IV: Ramping Up Competency-Based Performance Management.

    Science.gov (United States)

    Treiger, Teresa M; Fink-Samnick, Ellen

    The purpose of this fourth part of the COLLABORATE© article series provides an expansion and application of previously presented concepts pertaining to the COLLABORATE paradigm of professional case management practice. The model is built upon a value-driven foundation that: PRIMARY PRACTICE SETTING(S):: Applicable to all health care sectors where case management is practiced. As an industry, health care continues to evolve. Terrain shifts and new influences continually surface to challenge professional case management practice. The need for top-performing and nimble professionals who are knowledgeable and proficient in the workplace continues to challenge human resource departments. In addition to care setting knowledge, professional case managers must continually invest in their practice competence toolbox to grow skills and abilities that transcend policies and processes. These individuals demonstrate agility in framing (and reframing) their professional practice to facilitate the best possible outcomes for their clients. Therefore, the continued emphasis on practice competence conveyed through the performance management cycle is an essential ingredient to performance management focused on customer service excellence and organizational improvement. Professional case management transcends professional disciplines, educational levels, and practice settings. Business objectives continue to drive work process and priorities in many practice settings. However, competencies that align with regulatory and accreditation requirements should be the critical driver for consistent, high-quality case management practice. Although there is inherent value in what various disciplines bring to the table, this advanced model unifies behind case management's unique, strengths-based identity instead of continuing to align within traditional divisions (e.g., discipline, work setting, population served). This model fosters case management's expanding career advancement opportunities.

  14. Overseas Tech Firms Ramp Up Hiring In Silicon Valley

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Fpr years, U.S.high-tech executives have fretted about the loss of technology jobs to countries such as China and India.But there is a countervailing force: Foreign companies are leaning heavily on engineers they hire in Silicon Valley. Companies from Europe and Asia increasingly are using high-tech teams in the Bay Area to conduct long-range research and help design cutting-edge products for global markets.

  15. Carrier phase shifted SPWM based on current sourced multi-modular converter for active power filter

    Institute of Scientific and Technical Information of China (English)

    王立乔; 李建林; 张仲超

    2004-01-01

    A novel current-source active power filter(APF)based on multi-modular converter with carrier phase-shifted SPWM(CPS-SPWM)technique is proposed.With this technique,the effect of equivalent high switching frequency converter is obtained with low switching frequency converter.It is very promising in current-source APF that adopt superconducting magnetic energy storage component.

  16. Current Sensorless Control Algorithm for Single-Phase Three-Level NPC Inverter

    Directory of Open Access Journals (Sweden)

    Suzdalenko Alexander

    2014-12-01

    Full Text Available The current measurement is becoming a challenging task in power converters operating at high switching frequencies, moreover traditional control system requires two control loops - first (slow regulates DC-link voltage, second (fast controls the shape of current, that all together results in complicated transfer function and long transition periods. The current sensorless control (CSC allows neglecting the mentioned problems. This research for the first time presents the solution of CSC implementation in single-phase three-level neutral point clamped inverter. Mathematical equations were defined for inductor current peaks and transistor conduction time during discontinuous and continuous conduction modes, as well as major problem of current fitting between different voltage levels (consequently with different current peak-to-peak values was solved, providing two solutions - pre-fitting and post-fitting trajectories. The verification of our theoretical assumptions and analytical equations was confirmed by the simulation analysis. Challenges of real experiments are discussed in the conclusion.

  17. Plasma current start-up experiments without a central solenoid in the iron core STOR-M tokamak

    Science.gov (United States)

    Mitarai, O.; Tomney, G.; Rohollohi, A.; Lewis, E.; McColl, D.; Xiao, C.; Hirose, A.

    2015-06-01

    Reproducible plasma current start-up without a central solenoid (CS) has been demonstrated using the outer ohmic heating (OH) coils in the iron core STOR-M tokamak (Mitarai et al 2014 Fusion Eng. Des. 89 2467-71). Although the outer OH coil current saturates the iron core eventually, it has been demonstrated that the plasma current can be maintained during the iron core saturation phase. In this work, further studies have been conducted to investigate the effects of the turn number of the outer OH coils (N = 4 or N = 6) in the CS-less discharges and to evaluate the plasma stability with respect to the n-decay index of the vertical magnetic field. For the loose coupling of the iron core with N = 4 turns, the plasma current can be sustained after the additional third capacitor bank is applied near the iron core saturation phase, showing the slow transition from the unsaturated to the partially saturated phase. For the case of stronger coupling of N = 6 turns, the plasma current is increased at the same fast bank voltage, but the main discharge is shortened from 35 to 20 ms. As the magnetizing current is smaller due to stronger coupling between the OH coils and the plasma current, the transition from the unsaturated to the saturated phase is slightly difficult at present. The present experimental results suggest a feasible operation scenario in a future spherical tokamak (ST) at least using loose iron core coupling for smoother transition from the unsaturated to the saturated iron core phase. Thus, a reliable plasma current start-up by the outer OH coils and the current ramp-up to a steady state by additional heating power and vertical field coils could be considered as an operation scenario for future ST reactors with an iron core transformer.

  18. Industrial fuel gas demonstration plant program. Current working estimate. Phase III and III

    Energy Technology Data Exchange (ETDEWEB)

    1979-12-01

    The United States Department of Energy (DOE) executed a contract with Memphis Light, Gas and Water Division (MLGW) which requires MLGW to perform process analysis, design, procurement, construction, testing, operation, and evaluation of a plant which will demonstrate the feasibility of converting high sulfur bituminous coal to industrial fuel gas with a heating value of 300 +- 30 Btu per standard cubic foot (SCF). The demonstration plant is based on the U-Gas process, and its product gas is to be used in commercial applications in Memphis, Tenn. The contract specifies that the work is to be conducted in three phases. The Phases are: Phase I - Program Development and Conceptual Design; Phase II - Demonstration Plant Final Design, Procurement and Construction; and Phase III - Demonstration Plant Operation. Under Task III of Phase I, a Cost Estimate for the Demonstration Plant was completed as well as estimates for other Phase II and III work. The output of this Estimate is presented in this volume. This Current Working Estimate for Phases II and III is based on the Process and Mechanical Designs presented in the Task II report (second issue) and the 12 volumes of the Task III report. In addition, the capital cost estimate summarized in the appendix has been used in the Economic Analysis (Task III) Report.

  19. Interleaved Buck Converter with Variable Number of Active Phases and a Predictive Current Sharing Scheme

    DEFF Research Database (Denmark)

    Jakobsen, Lars Tønnes; Garcia, O.; Oliver, J. A.

    2008-01-01

    The efficiency of an interleaved Buck converter is typically low at light load conditions because of the switching losses in each of the switching stages. Improvements in the converter efficiency can be achieved by dynamically changing the number of active phases depending on the load current...

  20. Single phase cascaded H5 inverter with leakage current elimination for transformerless photovoltaic system

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; Jia, X.; Lu, Z.;

    2016-01-01

    Leakage current reduction is one of the important issues for the transformelress PV systems. In this paper, the transformerless single-phase cascaded H-bridge PV inverter is investigated. The common mode model for the cascaded H4 inverter is analyzed. And the reason why the conventional cascade H...

  1. Condition for the occurrence of phase slip centers in superconducting nanowires under applied current or voltage

    DEFF Research Database (Denmark)

    Michotte, S.; Mátéfi-Tempfli, Stefan; Piraux, L.;

    2004-01-01

    Experimental results on the phase slip process in superconducting lead nanowires are presented under two different experimental conditions: constant applied current or constant voltage. Based on these experiments we established a simple model which gives us the condition of the appearance of phas...

  2. A Transformerless Single Phase Inverter For photovoltaic Systems without Leakage Current

    DEFF Research Database (Denmark)

    Mostaan, Ali; Qu, Ying; Alizadeh, Ebrahim

    2017-01-01

    A new single phase inverter is introduced in this paper. In the proposed inverter, negative terminal of the DC source is common with the negative terminal of the grid. Therefore, the leakage current value is zero naturally and the safety is improved when the DC source is a photovoltaic module. In...

  3. Control of Josephson current by Aharonov-Casher phase in a Rashba ring

    Science.gov (United States)

    Liu, Xin; Borunda, M. F.; Liu, Xiong-Jun; Sinova, Jairo

    2009-11-01

    We study the interference effect induced by the Aharonov-Casher phase on the Josephson current through a semiconducting ring attached to superconducting leads. Using a one-dimensional model that incorporates spin-orbit coupling in the semiconducting ring, we calculate the Andreev levels analytically and numerically, and predict oscillations of the Josephson current due to the AC phase. This result is valid from the point-contact limit to the long channel-length case, as defined by the ratio of the junction length and the BCS healing length. We show in the long channel-length limit that the impurity scattering has no effect on the oscillation of the Josephson current, in contrast to the case of conductivity oscillations in a spin-orbit-coupled ring system attached to normal leads where impurity scattering reduces the amplitude of oscillations. Our results suggest a scheme to measure the AC phase with, in principle, higher sensitivity. In addition, this effect allows for control of the Josephson current through the gate-voltage-tuned AC phase.

  4. A PAC Based Current Feedforward Control for Three-Phase PWM Voltage-Type Converter

    Institute of Scientific and Technical Information of China (English)

    屈克庆; 陈国呈; 孙承波

    2004-01-01

    This paper presents a novel current feedforward control strategy for a three-phase pulse-width modulation (PWM) DC voltage-type converter based on phase and amplitude control (PAC). With right-angle triangle relation of phasors and principle of conservation of energy, a phasor adjustment method and the relevant low-frequency mathematical model of the system are analyzed in detail, both in rectification and regeneration modes for the converter, are discussed. For improving the traditional PAC dynamic performance, variable load current is detected indirectly by the change of the DC voltage, which is fed to the control system as an additional control variable to generate modulation index and phase angle. Also, the algorithm is derived and the system principle is introduced. Experimental results from a 3 kw laboratory device are included to demonstrate the effectiveness of the proposed control strategy.

  5. A Study on New Current Controller for 7-Phase BLDC Motor Drive System

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Surk; Jeon, Ywun Seok; Mok, Hyung Soo [Konkuk University (Korea); Kim, Duk Keun [Komotek Co., Ltd. (Korea)

    2001-04-01

    Recently, the demand of motor for industrial, household machinery is increasing. As Switching devices and control technology are progressing, so the use of BLDC Motor is increasing. But 3-phase BLCD Motor generally used has pulsating torque and speed variation in commutation, so the range of its application is limited to high speed operation. Especially, to solve these problems, it is necessary to increase phase of Motor, so study of Poly-Phase BLDC Motor is progressing. However, when hysteresis current controller is used, switching frequency is highly increasing. In this paper, 7-Phase BLDC Motor drive system is designed. Also MSTC (Minimum Switching Time Controller) is proposed and with simulation and experiment, their validities are verified. (author). 10 refs., 26 figs., 1 tab.

  6. A Smart Current Modulation Scheme for Harmonic Reduction in Three- Phase Motor Drive Applications

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2015-01-01

    harmonic mitigation methods have been developed over the years, the total cost and complexity has become the main obstacle in employing prior-art methods for motor drive systems. This paper presents a novel current modulation method based on the electronic inductor concept for three-phase ac-dc systems......Electric motor-driven systems consume considerable amount of the global electricity. Majority of three-phase motor drives are equipped with conventional diode rectifier and passive harmonic mitigation, being witnessed as the main source in generating input current harmonics. While many active...... to reduce input current harmonics. The obtained results at simulation and experimental levels confirm the effectiveness of the proposed approach....

  7. Frequency dependence of CA3 spike phase response arising from h-current properties

    Directory of Open Access Journals (Sweden)

    Melodie eBorel

    2013-12-01

    Full Text Available The phase of firing of hippocampal neurons during theta oscillations encodes spatial information. Moreover, the spike phase response to synaptic inputs in individual cells depends on the expression of the hyperpolarisation-activated mixed cation current (Ih, which differs between CA3 and CA1 pyramidal neurons. Here, we compared the phase response of these two cell types, as well as their intrinsic membrane properties. We found that both CA3 and CA1 pyramidal neurons show a voltage sag in response to negative current steps but that this voltage sag is significantly smaller in CA3 cells. Moreover, CA3 pyramidal neurons have less prominent resonance properties compared to CA1 pyramidal neurons. This is consistent with differential expression of Ih by the two cell types. Despite their distinct intrinsic membrane properties, both CA3 and CA1 pyramidal neurons displayed bidirectional spike phase control by excitatory conductance inputs during theta oscillations. In particular, excitatory inputs delivered at the descending phase of a dynamic clamp-induced membrane potential oscillation delayed the subsequent spike by nearly 50 mrad. The effect was shown to be mediated by Ih and was counteracted by increasing inhibitory conductance driving the membrane potential oscillation. Using our experimental data to feed a computational model, we showed that differences in Ih between CA3 and CA1 pyramidal neurons could predict frequency-dependent differences in phase response properties between these cell types. We confirmed experimentally such frequency-dependent spike phase control in CA3 neurons. Therefore, a decrease in theta frequency, which is observed in intact animals during novelty, might switch the CA3 spike phase response from unidirectional to bidirectional and thereby promote encoding of the new context.

  8. Verification of a thermal interpretation of BSCCO-2223/Ag current voltage hysteresis

    Science.gov (United States)

    Sastry, P. V. P. S. S.; Nguyen, D. N.; Usak, P.; Schwartz, J.

    2004-03-01

    The current-voltage characteristic hysteresis of Bi-2223 tape in a silver matrix cooled by liquid nitrogen (LN2) at 77 K can be interpreted thermally, i.e. while the ramping-up temperature of the tape is higher than the ramping-down temperature for the same current levels. The reason for this could be hysteresis of the heat transfer coefficient. The coefficient is smaller during ramping up and larger (better cooling) during ramping down. To verify or deny this concept we have measured the surface temperature of the tape at LN2 temperature with and without a thermal insulation sheet upon the tape during ramping up over Ic and ramping down back under Ic. Different ramping rates were applied. The amplitudes of E on the tape was under 0.5 mV cm-1. In spite of measurement error and thermal fluctuations, we observed a difference between the surface temperature curve branch during ramping up and the higher branch during ramping down for a non-insulated tape. Furthermore, the measurements showed that a positive current-voltage (I-V) hysteresis pattern (with the down branch shifted to higher currents and smaller voltages) was observed even with thermal insulation. Under these conditions, however, the down branch of the temperature curve clearly revealed a higher temperature with respect to the up branch of the temperature, contrary to expectations of the thermal interpretation of I-V hysteresis. According to this result, the thermal concept of positive I-V hysteresis under stable cooling conditions can be denied. On the other hand, an accidental voltage drop in the I-V curve was observed on one degraded sample accompanied by a corresponding drop in temperature. This proves the thermal interpretation of voltage drops in I-V curves of locally degraded tapes.

  9. Verification of a thermal interpretation of BSCCO-2223/Ag current-voltage hysteresis

    Energy Technology Data Exchange (ETDEWEB)

    Sastry, P V P S S [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Nguyen, D N [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Usak, P [Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravska cesta 9, Bratislava, Sk84239 (Slovakia); Schwartz, J [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States)

    2004-03-01

    The current-voltage characteristic hysteresis of Bi-2223 tape in a silver matrix cooled by liquid nitrogen (LN{sub 2}) at 77 K can be interpreted thermally, i.e. while the ramping-up temperature of the tape is higher than the ramping-down temperature for the same current levels. The reason for this could be hysteresis of the heat transfer coefficient. The coefficient is smaller during ramping up and larger (better cooling) during ramping down. To verify or deny this concept we have measured the surface temperature of the tape at LN{sub 2} temperature with and without a thermal insulation sheet upon the tape during ramping up over I{sub c} and ramping down back under I{sub c}. Different ramping rates were applied. The amplitudes of E on the tape was under 0.5 mV cm{sup -1}. In spite of measurement error and thermal fluctuations, we observed a difference between the surface temperature curve branch during ramping up and the higher branch during ramping down for a non-insulated tape. Furthermore, the measurements showed that a positive current-voltage (I-V) hysteresis pattern (with the down branch shifted to higher currents and smaller voltages) was observed even with thermal insulation. Under these conditions, however, the down branch of the temperature curve clearly revealed a higher temperature with respect to the up branch of the temperature, contrary to expectations of the thermal interpretation of I-V hysteresis. According to this result, the thermal concept of positive I-V hysteresis under stable cooling conditions can be denied. On the other hand, an accidental voltage drop in the I-V curve was observed on one degraded sample accompanied by a corresponding drop in temperature. This proves the thermal interpretation of voltage drops in I-V curves of locally degraded tapes.

  10. Improvement of multilayer graphene crystallinity by solid-phase precipitation with current stress application during annealing

    Science.gov (United States)

    Sahab Uddin, Md.; Ichikawa, Hiroyasu; Sano, Shota; Ueno, Kazuyoshi

    2016-06-01

    To improve the crystallinity of multilayer graphene (MLG) films by solid-phase precipitation, a new method by which current stress is introduced during annealing of a carbon-doped cobalt (Co-C) layer using cobalt (Co) as the catalyst has been investigated. The effects of current stress on the formation and crystallinity of MLG films were investigated by comparing the characteristics of the films annealed at the same temperature with and without current by taking into account the temperature rise due to Joule heating. The characteristics obtained by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) measurements revealed that the MLG films produced were crystalline in nature and their crystallinity increased with applied current stress at the same temperature. From SEM observations, beside Joule heating, enhancement of Co grain size by agglomeration induced by current stress may be the potential reason for the improvement of the crystallinity of MLG films. We have also improved the uniformity of MLG films by depositing an additional copper (Cu) capping layer over the Co-C layer. Current stress application can lead to low-temperature fabrication of MLG with higher crystallinity by solid-phase precipitation.

  11. Experimental Investigations on PV Powered SVM-DTC Induction Motor without AC Phase Current Sensors

    Directory of Open Access Journals (Sweden)

    T. Muthamizhan

    2014-05-01

    Full Text Available The paper presents a low-cost, phase-current reconstruction algorithm for space vector modulated direct torque controlled induction motor using the information obtained from only one shunt resistor which is in series with low side switches in a conventional three-phase inverter. The aim is to develop a low-cost high - performance induction motor drive. It uses the dc-link voltage and dc current to reconstruct the stator currents needed to estimate the motor flux and the electromagnetic torque. Photovoltaic arrays convert solar power to dc electric power; uses chopper and dc-ac inverter to fed three phase Induction Motor. The chopper used here is current fed full bridge boost dc-dc converter, which is preferred and extensively used in high voltage applications and advantageous over voltage fed converters. The inverter switches are controlled by PWM techniques obtained from SVM-DTC of IM. The experimental investigations are given to prove the ability of the proposed scheme of reproducing the performances of a SVM- DTC IM drive.

  12. Detection of stator winding faults in induction motors using three-phase current monitoring.

    Science.gov (United States)

    Sharifi, Rasool; Ebrahimi, Mohammad

    2011-01-01

    The objective of this paper is to propose a new method for the detection of inter-turn short circuits in the stator windings of induction motors. In the previous reported methods, the supply voltage unbalance was the major difficulty, and this was solved mostly based on the sequence component impedance or current which are difficult to implement. Some other methods essentially are included in the offline methods. The proposed method is based on the motor current signature analysis and utilizes three phase current spectra to overcome the mentioned problem. Simulation results indicate that under healthy conditions, the rotor slot harmonics have the same magnitude in three phase currents, while under even 1 turn (0.3%) short circuit condition they differ from each other. Although the magnitude of these harmonics depends on the level of unbalanced voltage, they have the same magnitude in three phases in these conditions. Experiments performed under various load, fault, and supply voltage conditions validate the simulation results and demonstrate the effectiveness of the proposed technique. It is shown that the detection of resistive slight short circuits, without sensitivity to supply voltage unbalance is possible.

  13. Analysis of Three-Phase Rectifier Systems with Controlled DC-Link Current Under Unbalanced Grids

    DEFF Research Database (Denmark)

    Kumar, Dinesh; Davari, Pooya; Zare, Firuz

    2017-01-01

    Voltage unbalance is the most common disturbance in distribution networks, which give undesirable effects on many grid connected power electronics systems including Adjustable Speed Drive (ASD). Severe voltage unbalance can force three-phase rectifiers into almost single-phase operation, which...... degrades the grid power quality and also imposes a significant negative impact on the ASD system. This major power quality issue affecting the conventional rectifiers can be attenuated by controlling the DC-link current based on an Electronic Inductor (EI) technique. The purpose of this digest...

  14. Methods, systems and apparatus for optimization of third harmonic current injection in a multi-phase machine

    Science.gov (United States)

    Gallegos-Lopez, Gabriel

    2012-10-02

    Methods, system and apparatus are provided for increasing voltage utilization in a five-phase vector controlled machine drive system that employs third harmonic current injection to increase torque and power output by a five-phase machine. To do so, a fundamental current angle of a fundamental current vector is optimized for each particular torque-speed of operating point of the five-phase machine.

  15. Fractionation of wheat gliadins by counter-current distribution using an organic two-phase system.

    Science.gov (United States)

    Truust, H; Johansson, G

    1998-06-26

    A liquid liquid two-phase system based on N,N-dimethylformamide and the two polymers, poly(ethyleneglycol) and Ficoll, useful for partitioning of hydrophobic proteins, has been developed. The system has been applied to a counter-current distribution process in 56 steps for analysing the heterogeneity of proteins extracted with N,N-dimethylformamide from wheat flour. The counter-current distribution patterns of proteins, extracted from eight kinds of wheat, have been analysed. The minimum number of hypothetical proteins necessary to describe the patterns was found to be seven. The relative amount of these hypothetical components varied among the wheats.

  16. New phases of D ge 2 current and diffeomorphism algebras in particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Tze, Chia-Hsiung.

    1990-09-01

    We survey some global results and open issues of current algebras and their canonical field theoretical realization in D {ge} 2 dimensional spacetime. We assess the status of the representation theory of their generalized Kac-Moody and diffeomorphism algebras. Particular emphasis is put on higher dimensional analogs of fermi-bose correspondence, complex analyticity and the phase entanglements of anyonic solitons with exotic spin and statistics. 101 refs.

  17. Purification of Active Myrosinase from Plants by Aqueous Two-Phase Counter-Current Chromatography

    Science.gov (United States)

    Wade, Kristina L.; Ito, Yoichiro; Ramarathnam, Aarthi; Holtzclaw, W. David; Fahey, Jed W.

    2014-01-01

    Introduction Myrosinase (thioglucoside glucohydrolase; E.C. 3.2.1.147), is a plant enzyme of increasing interest and importance to the biomedical community. Myrosinase catalyses the formation of isothiocyanates such as sulforaphane (frombroccoli) and 4-(α-l-rhamnopyranosyloxy)benzyl isothiocyanate (from moringa), which are potent inducers of the cytoprotective phase-2 response in humans, by hydrolysis of their abundant glucosinolate (β-thioglucoside N-hydroxysulphate) precursors. Objective To develop an aqueous two-phase counter-current chromatography (CCC) system for the rapid, three-step purification of catalytically active myrosinase. Methods A high-concentration potassium phosphate and polyethylene glycol biphasic aqueous two-phase system (ATPS) is used with a newly developed CCC configuration that utilises spiral-wound, flat-twisted tubing (with an ovoid cross-section). Results Making the initial crude plant extract directly in the ATPS and injecting only the lower phase permitted highly selective partitioning of the myrosinase complex before a short chromatography on a spiral disk CCC. Optimum phase retention and separation of myrosinase from other plant proteins afforded a 60-fold purification. Conclusion Catalytically active myrosinase is purified from 3-day broccoli sprouts, 7-day daikon sprouts, mustard seeds and the leaves of field-grown moringa trees, in a CCC system that is predictably scalable. PMID:25130502

  18. Structural Characterization of Phase Separation in Fe-Cr: A Current Comparison of Experimental Methods

    Science.gov (United States)

    Xu, Xin; Odqvist, Joakim; Colliander, Magnus Hörnqvist; Thuvander, Mattias; Steuwer, Axel; Westraadt, Johan E.; King, Stephen; Hedström, Peter

    2016-12-01

    Self-assembly due to phase separation within a miscibility gap is important in numerous material systems and applications. A system of particular interest is the binary alloy system Fe-Cr, since it is both a suitable model material and the base system for the stainless steel alloy category, suffering from low-temperature embrittlement due to phase separation. Structural characterization of the minute nano-scale concentration fluctuations during early phase separation has for a long time been considered a major challenge within material characterization. However, recent developments present new opportunities in this field. Here, we present an overview of the current capabilities and limitations of different techniques. A set of Fe-Cr alloys were investigated using small-angle neutron scattering (SANS), atom probe tomography, and analytical transmission electron microscopy. The complementarity of the characterization techniques is clear, and combinatorial studies can provide complete quantitative structure information during phase separation in Fe-Cr alloys. Furthermore, we argue that SANS provides a unique in-situ access to the nanostructure, and that direct comparisons between SANS and phase-field modeling, solving the non-linear Cahn Hilliard equation with proper physical input, should be pursued.

  19. On wind Turbine failure detection from measurements of phase currents: a permutation entropy approach

    CERN Document Server

    Ram, Sumit Kumar; Molinas, Marta

    2016-01-01

    This article presents the applicability of Permutation Entropy based complexity measure of a time series for detection of fault in wind turbines. A set of electrical data from one faulty and one healthy wind turbine were analysed using traditional FastFourier analysis in addition to Permutation Entropy analysis to compare the complexity index of phase currents of the two turbines over time. The 4 seconds length data set did not reveal any low frequency in the spectra of currents, neither did they show any meaningful differences of spectrum between the two turbine currents. Permutation Entropy analysis of the current waveforms of same phases for the two turbines are found to have different complexity values over time, one of them being clearly higher than the other. The work of Yan et. al. in has found that higher entropy values related to thepresence of failure in rotary machines in his study. Following this track, further efforts will be put into relating the entropy difference found in our study to possible...

  20. Determination of defect in rotor of induction machine by spectral analysis of stator phase current

    Directory of Open Access Journals (Sweden)

    Myrteza Braneshi

    2010-10-01

    Full Text Available Induction motors are important part of safe and efficient running of any industrial plant. These motors are often used in industrial applications thanks to their usability and their robustness. Faults and failures of induction machine can lead to excessive downtimes processes; generate large losses in revenues and long term maintenance. Early detection of motor abnormalities would help avoiding costly breakdowns. In this paper a diagnostic technique of induction motor broken rotor bars is presented. The applied method is the so-called Motor Current Signature Analysis (MCSA which utilized the results of spectral analysis of the stator current. The broken rotor bars and rings will cause twice slip frequency side bands around the supplying frequency. The fault detection method consists in monitoring of stator phase current spectrum. Twice slip frequency side bands around the main frequency detected by spectral analysis is an indicator of the broken bars. The experimental results show the efficiency of the method.

  1. Predictive Pulse Pattern Current Modulation Scheme for Harmonic Reduction in Three-Phase Multidrive Systems

    DEFF Research Database (Denmark)

    Davari, Pooya; Yang, Yongheng; Zare, Firuz

    2016-01-01

    of them can lead to the cancellation of specific harmonics. This paper proposes a new cost-effective harmonic mitigation solution for multi-drive systems using a predictive pulse pattern current modulation control strategy. The proposed technique applies suitable interaction among parallel drive units......The majority of the industrial motor drive systems are equipped with the conventional line-commutated front-end rectifiers, and being one of the main sources of harmonics in the power line. While a parallel combination of these drive units elevates current quality issues, a proper arrangement...... at the rectification stage to synthesize sinusoidal input currents. The input voltage sensing is avoided in order to minimize the number of required sensors, and the grid synchronization also has been implemented based on a common Phase-Locked-Loop (PLL) using the DC-link capacitor voltage ripple. Experimental results...

  2. Euler-Lagrange models with complex currents of three-phase electrical machines

    CERN Document Server

    Basic, Duro; Rouchon, Pierre

    2008-01-01

    A Lagrangian formulation with complex currents is developed and yields a direct and simple method for modeling three-phases permanent-magnet and induction machines. The Lagrangian is the sum of the mechanical kinetic energy and of the magnetic energy. This magnetic energy is expressed in terms of rotor angle, complex stator and rotor currents. Such Lagrangian setting is a precious guide for modeling space-harmonics and saturation effects. A complexification procedure is applied here in order to derive the Euler-Lagrange equations with complex stator and rotor currents. Such complexification process avoids the usual separation into real and imaginary parts and simplifies notably the calculations. Via simple modification of magnetic energies we derive non-trivial dynamical models describing permanent-magnet machines with both saturation and saliency, and induction machines with both saturation and space harmonics.

  3. Mechanics of the Separating Surface for a Two-Phase Co-current Flow in a Porous Medium

    DEFF Research Database (Denmark)

    Shapiro, Alexander A.

    2016-01-01

    A mechanical description of an unsteady two-phase co-current flow in a porous medium is developed based on the analysis of the geometry and motion of the surface separating the two phases. It is demonstrated that the flow should be considered as essentially three-dimensional, even if the phase ve...

  4. Third harmonic current injection into highly saturated multi-phase machines

    Directory of Open Access Journals (Sweden)

    Klute Felix

    2017-03-01

    Full Text Available One advantage of multi-phase machines is the possibility to use the third harmonic of the rotor flux for additional torque generation. This effect can be maximised for Permanent Magnet Synchronous Machines (PMSM with a high third harmonic content in the magnet flux. This paper discusses the effects of third harmonic current injection (THCI on a five-phase PMSM with a conventional magnet shape depending on saturation. The effects of THCI in five-phase machines are shown in a 2D FEM model in Ansys Maxwell verified by measurement results. The results of the FEM model are analytically analysed using the Park model. It is shown in simulation and measurement that the torque improvement by THCI increases significantly with the saturation level, as the amplitude of the third harmonic flux linkage increases with the saturation level but the phase shift of the rotor flux linkage has to be considered. This paper gives a detailed analysis of saturation mechanisms of PMSM, which can be used for optimizing the efficiency in operating points of high saturations, without using special magnet shapes.

  5. Strictly hyperbolic models of co-current three-phase flow withgravity

    Energy Technology Data Exchange (ETDEWEB)

    Juanes, Ruben; Patzek, Tadeusz W.

    2002-11-18

    We study the character of the equations in the traditional formulation of one-dimensional immiscible three-phase flow with gravity, in the limit of negligible capillarity. We restrict our analysis to co-current flow required for a displacement process; in cases of mixed co-current and counter-current flow, capillarity effects cannot be dropped from the formulation. The model makes use of the classical multiphase extension of Darcy's equation. It is well known that, if relative permeabilities are taken as fixed functions of saturations, the model yields regions in the saturation space where the system of equations is locally elliptic. We regard elliptic behavior as a nonphysical artifact of an incomplete formulation, and derive conditions on the relative permeabilities that ensure strict hyperbolicity of the governing equations. The key point is to acknowledge that a Darcy-type formulation is insufficient to capture all the physics of three-phase flow and that, consequently, the relative permeabilities are functionals that depend on the fluid viscosity ratio and the gravity number. The derived conditions are consistent with the type of displacements that take place in porous media. By means of an illustrative example, we show how elliptic behavior can be removed, even when using simplistic relative permeability models.

  6. The geometric effect and programming current reduction in cylindrical-shaped phase change memory

    Science.gov (United States)

    Li, Yiming; Hwang, Chih-Hong; Li, Tien-Yeh; Cheng, Hui-Wen

    2009-07-01

    This study conducts a three-dimensional electro-thermal time-domain simulation for numerical analysis of cylindrical-shaped phase change memories (PCMs). The influence of chalcogenide material, germanium antimony telluride (GeSbTe or GST), structure on PCM operation is explored. GST with vertical structure exhibits promising characteristics. The bottom electrode contact (BEC) is advanced to improve the operation of PCMs, where a 25% reduction of the required programming current is achieved at a cost of 26% reduced resistance ratio. The position of the BEC is then shifted to further improve the performance of PCMs. The required programming current is reduced by a factor of 11, where the resistance ratio is only decreased by 6.9%. However, the PCMs with a larger shift of BEC are sensitive to process variation. To design PCMs with less than 10% programming current variation, PCMs with shifted BEC, where the shifted distance is equal to 1.5 times the BEC's radius, is worth considering. This study quantitatively estimates the structure effect on the phase transition of PCMs and physically provides an insight into the design and technology of PCMs.

  7. Parasitic Currents in Diffuse-Interface Two-Phase Flow Simulations

    Science.gov (United States)

    Milani, Pedro; Mirjalili, Seyedshahabaddin; Mani, Ali

    2016-11-01

    Two phase flow phenomena are important in a wide range of applications, such as bubble generation in ocean waves and droplet dynamics in fuel injectors. Several methods can be used to simulate such phenomena. The focus of this study is the diffuse-interface method, in which the interface is described via a mixing energy and spans a few computational cells, while surface tension is modeled as a force density term on the right-hand side of the momentum equation. The advantages of this method include the ability to easily simulate complex geometries since it does not require special treatment around the interface, and to conserve mass exactly. However, this method suffers from parasitic currents, an unphysical velocity field generated close to the interface due to numerical imprecisions in the surface tension term. This can be a serious problem in low speed flows, where the parasitic currents are significant compared to the velocity scale of the problem. In this study, we consider a wide range of diffuse-interface schemes for two-phase flows, including different options for discrete representation of the surface tension force. By presenting an assessment of each method's performance in scenarios involving parasitic currents, we develop accuracy estimates and guidelines for selection among these models. Supported by the ONR.

  8. Modulation of auroral electrojet currents using dual HF beams with ELF phase offset

    Science.gov (United States)

    Golkowski, M.; Cohen, M.; Moore, R. C.

    2012-12-01

    The modulation of naturally occuring ionospheric currents with high power radio waves in the high frequency (HF, 3-10 MHz) band is a well known technique for generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) waves. We use the heating facility of the High Frequency Active Auroral Research Program (HAARP) to investigate the effect of using dual HF beams with an ELF/VLF phase offset between the modulation waveforms. Experiments with offset HF beams confirm the model of independent ELF/VLF sources. Experiments with co-located HF beams exhibit interaction between the first and second harmonics of the modulated tones when square and sine wave modulation waveforms are employed. Using ELF/VLF phase offsets for co-loacted beams is also shown to be a potential diagnostic for the D-region ionospheric profile.

  9. One-dimensional transport of interacting particles: currents, density profiles, phase diagrams, and symmetries.

    Science.gov (United States)

    Dierl, Marcel; Einax, Mario; Maass, Philipp

    2013-06-01

    Driven lattice gases serve as canonical models for investigating collective transport phenomena and properties of nonequilibrium steady states. Here we study one-dimensional transport with nearest-neighbor interactions both in closed bulk systems and in open channels coupled to two particle reservoirs at the ends of the channel. For the widely employed Glauber rates we derive an exact current-density relation in the bulk for unidirectional hopping. An approach based on time-dependent density functional theory provides a good description of the kinetics. For open systems, the system-reservoir couplings are shown to have a striking influence on boundary-induced phase diagrams. The role of particle-hole symmetry is discussed, and its consequence for the topology of the phase diagrams. It is furthermore demonstrated that systems with weak bias can be mapped onto systems with unidirectional hopping.

  10. Droplet entrainment correlation in vertical upward co-current annular two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, Pravin [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States)], E-mail: psawant@purdue.edu; Ishii, Mamoru [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States); Mori, Michitsugu [Tokyo Electric Power Co., Inc., R and D Center, 4-1 Egasaki-cho, Tsurumi-ku, Yokohama 230-8510 (Japan)], E-mail: michitsugu.mori@tepco.co.jp

    2008-06-15

    Upward annular two-phase flow in a vertical tube is characterized by the presence of liquid film on the tube wall and entrained droplet laden gas phase flowing through the tube core. Entrainment fraction in annular flow is defined as a fraction of the total liquid flow flowing in the form of droplets through the central gas core. Its prediction is important for the estimation of pressure drop and dryout in annular flow. In the following study, measurements of entrainment fraction have been obtained in vertical upward co-current air-water annular flow covering wide ranges of pressure and flow conditions. Comparison of the experimental data with the existing entrainment fraction prediction correlations revealed their inadequacies in simulating the trends observed under high flow and high pressure conditions. Furthermore, several correlations available in the literature are implicit and require iterative calculations. Analysis of the experimental data showed that the non-dimensional numbers, Weber number (We = {rho}{sub g}{sup 2}D/{sigma}({delta}{rho}/{rho}{sub g}){sup 1/4}) and liquid phase Reynolds number (Re{sub f} = {rho}{sub f}D/{mu}{sub f}), successfully collapse the data. In view of this, simple, explicit correlation was developed based on these non-dimensional numbers for the prediction of entrainment fraction. The new correlation successfully predicted the trends under the high flow and high pressure conditions observed in the current experimental data and the data available in open literature. However, in order to use the proposed correlation it is necessary to predict the maximum possible entrainment fraction (or limiting entrainment fraction). In the current analysis, an experimental data based correlation was used for this purpose. However, a better model or correlation is necessary for the maximum possible entrainment fraction. A theoretical discussion on the mechanism and modeling of the maximum possible entrainment fraction

  11. Effect of current quark masses on quark phase transitions in supernovae

    Institute of Scientific and Technical Information of China (English)

    LAI Xiang-Jun; LUO Zhi-Quan; LIU Hong-Lin

    2008-01-01

    The current quark mass model is adopted to study the phase transition of two-flavor quark matter to more stable three-flavor quark matter in the whole core of a supernova. It shows that the timescale of the process is shorter than 10-8 seconds, thatthe u- and d-quark masses can be neglected completely in this model, and that the temperature and the total neutrino energies in the core after the conversion increase nearly by 40% and 20% on the average compared with former results, respectively. The last result can further enhance the probability of success for a supernova explosion significantly.

  12. Single Phase Current-Source Active Rectifier for Traction: Control System Design and Practical Problems

    Directory of Open Access Journals (Sweden)

    Jan Michalik

    2006-01-01

    Full Text Available This research has been motivated by industrial demand for single phase current-source active rectifier dedicated for reconstruction of older types of dc machine locomotives. This paper presents converters control structure design and simulations. The proposed converter control is based on the mathematical model and due to possible interaction with railway signaling and required low switching frequency employs synchronous PWM. The simulation results are verified by experimental tests performed on designed laboratory prototype of power of 7kVA

  13. Design, Analysis and Implementation of a new topology of multi phase synchronous buck converter under current mode control

    Directory of Open Access Journals (Sweden)

    Nittala S K Sastry

    2012-06-01

    Full Text Available This paper presents a new PWM Multi phase DC-DC converter under current mode control with an auxiliary circuit which provides zero voltage switching in order to meet the power supply requirements of the processors of modern electronic equipments like laptops, mobiles, and PDAs etc which require more than 70 A current, lower voltage and better transient response.The multi phase topology benefits in high current, good efficiency and better current transient response. High current multi phase buck converters found applications in advanced data control, solid state lasers, communication equipment and Pentium processors etc. In this paper designed of three phase DC-DC converter 100W, 12V/1V under current mode control is discussed in detail and the simulation results are presented to support the theoretical analysis.

  14. Bifurcation Diagram and Pattern Formation of Phase Slip Centers in Superconducting Wires Driven with Electric Currents

    Science.gov (United States)

    Rubinstein, J.; Sternberg, P.; Ma, Q.

    2007-10-01

    We provide here new insights into the classical problem of a one-dimensional superconducting wire exposed to an applied electric current using the time-dependent Ginzburg-Landau model. The most striking feature of this system is the well-known appearance of oscillatory solutions exhibiting phase slip centers (PSC’s) where the order parameter vanishes. Retaining temperature and applied current as parameters, we present a simple yet definitive explanation of the mechanism within this nonlinear model that leads to the PSC phenomenon and we establish where in parameter space these oscillatory solutions can be found. One of the most interesting features of the analysis is the evident collision of real eigenvalues of the associated PT-symmetric linearization, leading as it does to the emergence of complex elements of the spectrum.

  15. Detection of second harmonic of phase dependence of superconducting current in Nb/Au/YBCO heterojunctions

    CERN Document Server

    Komissinskij, F V; Ilichev, E V; Ivanov, Z G

    2001-01-01

    The results of the experimental study on the current phase dependence (CPD) of the heterotransitions, consisting of the niobium and the YBa sub 2 Cu sub 3 O sub x (YBCO) film with an additional interlayer from gold (Nb/Au/YBCO) are presented. The CPD measurement is carried out through the radiofrequency superconducting quantum interferometer. The CPD second harmonic is determined in the Nb/Au/YBCO heterotransitions. Possible causes of its appearance are discussed within the frames of the d +- s combined symmetry of the YBCO order parameter. One of the causes of the CPD second harmonic appearance is the twinning of the YBCO films (001). The second cause of existing the anomalously high critical current consists in the availability of the Nb/Au boundary with the transparence of approx 10 sup - sup 1 in the Nb/Au/YBCO

  16. High-frequency, three-phase current controller implementation in an FPGA

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, M.; Round, S. D.; Kolar, J. W.

    2008-07-01

    Three phase rectifiers with switching frequencies of 500 kHz or more require high speed current controllers. At such high switching frequencies analog controllers as well as high speed digital signal processing (DSP) systems have limited performance. In this paper, two high speed current controller implementations using two different field-programmable gate arrays (FPGA) - one for switching frequencies up to 1 MHz and one for switching frequencies beyond 1 MHz - are presented to overcome this performance limitation. Starting with the digital system design all the blocks of the signal chain, containing analog-to-digital (A/D) interface, digital controller implementation using HW-multipliers and implementation of a novel high speed, high resolution pulse width modulation (PWM) are discussed and compared. Final measurements verify the performance of the controllers. (author)

  17. A Smart Voltage and Current Monitoring System for Three Phase Inverters Using an Android Smartphone Application

    Science.gov (United States)

    Mnati, Mohannad Jabbar; Van den Bossche, Alex; Chisab, Raad Farhood

    2017-01-01

    In this paper, a new smart voltage and current monitoring system (SVCMS) technique is proposed. It monitors a three phase electrical system using an Arduino platform as a microcontroller to read the voltage and current from sensors and then wirelessly send the measured data to monitor the results using a new Android application. The integrated SVCMS design uses an Arduino Nano V3.0 as the microcontroller to measure the results from three voltage and three current sensors and then send this data, after calculation, to the Android smartphone device of an end user using Bluetooth HC-05. The Arduino Nano V3.0 controller and Bluetooth HC-05 are a cheap microcontroller and wireless device, respectively. The new Android smartphone application that monitors the voltage and current measurements uses the open source MIT App Inventor 2 software. It allows for monitoring some elementary fundamental voltage power quality properties. An effort has been made to investigate what is possible using available off-the-shelf components and open source software. PMID:28420132

  18. Random phase approximation with second-order screened exchange for current-carrying atomic states

    Science.gov (United States)

    Zhu, Wuming; Zhang, Liang; Trickey, S. B.

    2016-12-01

    The direct random phase approximation (RPA) and RPA with second-order screened exchange (SOSEX) have been implemented with complex orbitals as a basis for treating open-shell atoms. Both RPA and RPA+SOSEX are natural implicit current density functionals because the paramagnetic current density implicitly is included through the use of complex orbitals. We confirm that inclusion of the SOSEX correction improves the total energy accuracy substantially compared to RPA, especially for smaller-Z atoms. Computational complexity makes post self-consistent-field (post-SCF) evaluation of RPA-type expressions commonplace, so orbital basis origins and properties become important. Sizable differences are found in correlation energies, total atomic energies, and ionization energies for RPA-type functionals evaluated in the post-SCF fashion with orbital sets obtained from different schemes. Reference orbitals from Kohn-Sham calculations with semi-local functionals are more suitable for RPA+SOSEX to generate accurate total energies, but reference orbitals from exact exchange (non-local) yield essentially energetically degenerate open-shell atom ground states. RPA+SOSEX correlation combined with exact exchange calculated from a hybrid reference orbital set (half the exchange calculated from exact-exchange orbitals, the other half of the exchange from orbitals optimized for the Perdew-Burke-Ernzerhof (PBE) exchange functional) gives the best overall performance. Numerical results show that the RPA-like functional with SOSEX correction can be used as a practical implicit current density functional when current effects should be included.

  19. Design and control of the phase current of a brushless dc motor to eliminate cogging torque

    Science.gov (United States)

    Jang, G. H.; Lee, C. J.

    2006-04-01

    This paper presents a design and control method of the phase current to reduce the torque ripple of a brushless dc (BLDC) motor by eliminating cogging torque. The cogging torque is the main source of torque ripple and consequently of speed error, and it is also the excitation source to generate the vibration and noise of a motor. This research proposes a modified current wave form, which is composed of main and auxiliary currents. The former is the conventional current to generate the commutating torque. The latter generates the torque with the same magnitude and opposite sign of the corresponding cogging torque at the given position in order to eliminate the cogging torque. Time-stepping finite element method simulation considering pulse-width-modulation switching method has been performed to verify the effectiveness of the proposed method, and it shows that this proposed method reduces torque ripple by 36%. A digital-signal-processor-based controller is also developed to implement the proposed method, and it shows that this proposed method reduces the speed ripple significantly.

  20. A Smart Voltage and Current Monitoring System for Three Phase Inverters Using an Android Smartphone Application.

    Science.gov (United States)

    Mnati, Mohannad Jabbar; Van den Bossche, Alex; Chisab, Raad Farhood

    2017-04-15

    In this paper, a new smart voltage and current monitoring system (SVCMS) technique is proposed. It monitors a three phase electrical system using an Arduino platform as a microcontroller to read the voltage and current from sensors and then wirelessly send the measured data to monitor the results using a new Android application. The integrated SVCMS design uses an Arduino Nano V3.0 as the microcontroller to measure the results from three voltage and three current sensors and then send this data, after calculation, to the Android smartphone device of an end user using Bluetooth HC-05. The Arduino Nano V3.0 controller and Bluetooth HC-05 are a cheap microcontroller and wireless device, respectively. The new Android smartphone application that monitors the voltage and current measurements uses the open source MIT App Inventor 2 software. It allows for monitoring some elementary fundamental voltage power quality properties. An effort has been made to investigate what is possible using available off-the-shelf components and open source software.

  1. Direct evidence for local oscillatory current sources and intracortical phase gradients in turtle visual cortex.

    Science.gov (United States)

    Prechtl, J C; Bullock, T H; Kleinfeld, D

    2000-01-18

    Visual stimuli induce oscillations in the membrane potential of neurons in cortices of several species. In turtle, these oscillations take the form of linear and circular traveling waves. Such waves may be a consequence of a pacemaker that emits periodic pulses of excitation that propagate across a network of excitable neuronal tissue or may result from continuous and possibly reconfigurable phase shifts along a network with multiple weakly coupled neuronal oscillators. As a means to resolve the origin of wave propagation in turtle visual cortex, we performed simultaneous measurements of the local field potential at a series of depths throughout this cortex. Measurements along a single radial penetration revealed the presence of broadband current sources, with a center frequency near 20 Hz (gamma band), that were activated by visual stimulation. The spectral coherence between sources at two well-separated loci along a rostral-caudal axis revealed the presence of systematic timing differences between localized cortical oscillators. These multiple oscillating current sources and their timing differences in a tangential plane are interpreted as the neuronal activity that underlies the wave motion revealed in previous imaging studies. The present data provide direct evidence for the inference from imaging of bidirectional wave motion that the stimulus-induced electrical waves in turtle visual cortex correspond to phase shifts in a network of coupled neuronal oscillators.

  2. Tunable current-phase relation in double-dot Josephson junctions

    Science.gov (United States)

    Koch, Jens; Le Hur, Karyn

    2008-03-01

    The current-phase relation I() for a Josephson junction contains information about the microscopic nature of the Cooper pair transfer. In particular, junctions more complicated than the single tunnel junction exhibit characteristic non-sinusoidal forms. Here, we investigate the Josephson effect in a superconducting double dot device, similar to the devices studied experimentally by Y. A. Pashkin et al. [1] and E. Bibow et al. [2]. In the vicinity of a charge degeneracy line, the system reduces to a two-level system equivalent to a charge qubit. In this regime, we find that the interplay between sequential tunneling and cotunneling of Cooper pairs leads to a strongly non-sinusoidal current- phase relation, tunable via gate electrodes. We propose the measurement of I() in a SQUID configuration, analyze the implications of flux noise, and compare our results to different types of Josephson junctions such as single-dot systems and microbridges. [1] Y. A. Pashkin et al., Nature (London) 421 (2003), 823 [2] E. Bibow, P. Lafarge, L. L'evy, Phys. Rev. Lett. 88 (2002), 017003

  3. Current control of 6-phases 100kW interleaved buck/boost converter for railway application

    OpenAIRE

    2009-01-01

    The purpose of this paper is to present a 6-phases interleaved buck-boost converter of 100kW de-signed for a hybrid locomotive. The IGBT’s are working partially in continuous and discontinuous con-duction mode. Experiments show the effectiveness of the digital current control, current sharing and discontinuous-continuous transition with only one current sensor

  4. Study of internal transport barriers in the initial phase of Ohmic discharges in TUMAN-3M

    Energy Technology Data Exchange (ETDEWEB)

    Askinazi, L G [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Bulanin, V V [St Petersburg State Polytechnical University, 195251 (Russian Federation); Vildjunas, M I [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Golant, V E [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Gorokhov, M V [St Petersburg State Polytechnical University, 195251 (Russian Federation); Kornev, V A [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Krikunov, S V [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Lebedev, S V [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Petrov, A V [St Petersburg State Polytechnical University, 195251 (Russian Federation); Rozhdestvensky, V V [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Tukachinsky, A S [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation); Zhubr, N A [Ioffe Physico-Technical Institute, RAS, 194021, St Petersburg (Russian Federation)

    2004-05-01

    A regime with electron heat confinement improvement was recently found in the initial phase of discharges in the TUMAN-3M tokamak. An internal transport barrier (ITB) formation in this regime was confirmed by Thomson scattering measurements and by transport modelling. Two possible reasons for the ITB formation are discussed in the paper: by reduction of turbulent transport in the presence of low magnetic shear or by plasma sheared rotation. It is demonstrated that low magnetic shear formation is possible in the current ramp-up phase of the Ohmic discharge. The low magnetic shear does not seem to be the only reason for the transport reduction. Results of Doppler reflectometry measurements of poloidal rotation of density fluctuations are presented. It is found that core confinement improvement correlates with the appearance of sheared rotation of the density fluctuations and with a burst of the MHD activity. The ITB formation in the regime seems to be a result of a combined action of reduced magnetic shear and plasma sheared rotation.

  5. Modeling and Simulation of 3-Phase Voltage and Current Source Inverter using MATLAB/SIMULINK for Various Loads

    Directory of Open Access Journals (Sweden)

    Braj Kishor Verma

    2014-05-01

    Full Text Available In today’s world inverters are used to convert a single or multiple phase AC voltages from a DC supply source. Various types of inverters such as 1-phase inverters and 3-phase inverters are used for various industrial applications. Inverter comes in two categories which is voltage source inverter (VSI and current source inverter (CSI. In this paper work simulation of three phase VSI and CSI is performed using MATLAB/SIMULINK. THD is compared in voltage and current waveform and analyzed in different load conditions

  6. A SIMPLIFIED MODEL OF THREE-PHASE BANK OF CURRENT TRANSFORMERS IN THE DYNAMIC SIMULATION SYSTEM

    Directory of Open Access Journals (Sweden)

    I. V. Novash

    2015-01-01

    Full Text Available  The article presents and substantiates a simplified mathematical simulation model realization technique for a three-phase bank of current transformers (CT based on their nameplate data. The secondary windings and load of the current transformers form a Y-connected circuit with neutral conductor. Consistent with the presented technique the simplified mathematical simulation realizes in the dynamic-modeling environment of MatLab–Simulink–SimPowerSystems. This simulation allows obtaining the secondary current curve shape entering only the nameplate data of the CT being simulated. Thus, the simulation under consideration enables the assessment of technical feasibility of the CT from viewpoint of correct functioning of the relay protective devices during transient processes in the electric energy systems.Employing the model, the authors conduct computational experiments simulating the CT typical operating modes: short-circuit current passage with presence/absence of the direct component and short-circuit current passage with presence of the direct component and residual magnetic induction of the CT. The paper examines the modes of automatic re-closing failure at different stages of the breaker closure with oscillograms drawn illustrating each characteristic case.The authors compare two methods for the CT iron magnetization-curve assigning: manual approximation and the Ollendorf-formula approximation. Relying on this comparison they conclude on feasability of application of the magnetization-curve approximating function for the CT operating analysis during transient processes in the electric energy systems. An elaborated user-friendly graphic interface provides a means of visual assigning the CT nominal parameters, the residual magnetic induction, and the method of the transformer iron magnetization curve approximation. The results of conducted computational experiments prove feasibility of the CT-bank simulation model.

  7. Investigation of data retention under current bias for phase change memory

    Science.gov (United States)

    Lu, Yao-Yao; Cai, Dao-Lin; Chen, Yi-Feng; Wang, Yue-Qing; Wei, Hong-Yang; Huo, Ru-Ru; Song, Zhi-Tang

    2016-10-01

    With Phase-change memory (PCM), information can be stored as different resistance states even when not powered. In order to accurately characterize the reliability of PCM devices, data retention has to be tested carefully. In this paper, a new test method is applied to measure the data retention of T-shaped PCM devices. This method makes it possible to accelerate crystallization in the amorphous area by using current bias. The new method works based on the field-induced crystallization theory, and could be able to gather fast and detailed information about high-resistance state's failure process, and at the same time, it could avoid issues related to high temperature. Experimental data for T-shaped PCM devices based on Ge2Sb2Te5 are presented and analyzed. An exponential trend-line of failure time t versus reciprocal bias current 1/I shows only negligible deviation of the measured data points, enabling the extrapolation of the retention behavior for ten-year lifetime. A maximum disturb current value of 5.08 μA is extracted to guarantee the ten years data retention requirement for PCM applications.

  8. On the study of phase formation and critical current density in superconducting MgB2

    Indian Academy of Sciences (India)

    Suchitra Rajput; Sujeet Chaudhary; Subhash C Kashyap; Pankaj Srivastava

    2006-06-01

    Superconducting bulk MgB2 samples have been synthesized by employing sintering technique without using any additional process steps, generally undertaken in view of the substantial loss of magnesium, during heat treatment. Starting with Mg rich powders having different atomic ratios of Mg : B, as against the nominally required Mg : B = 1 : 2 ratio, we have obtained superconducting MgB2 samples of different characteristics. The effect of excess Mg in the starting mixture and processing temperature on the phase-formation, transition temperature (C) and critical current density (C) have been investigated by electrical transport and a.c. susceptibility measurements. The X-ray diffraction and X-ray photoelectron spectroscopic analyses of MgB2 bulk samples have been carried out to understand the role of excess Mg and the effect of processing temperature. It is established that MgB2 samples with high critical current density can be synthesized from a Mg rich powder having Mg : B in 2 : 2 ratio, at temperatures around 790°C. Critical current density has been found to vary systematically with processing temperature.

  9. A Single-Phase Multilevel Current-Source Converter using H-Bridge and DC Current Modules

    Directory of Open Access Journals (Sweden)

    Suroso Suroso

    2014-03-01

    Full Text Available This paper presents a different topology of H-bridge based multilevel current-source inverter (CSI. In this new topology, an H-bridge CSI is connected with a single or more current modules to generate a multilevel output current waveform with lower di/dt, and less distortion. Using the proposed multilevel CSI, the number of the power switching devices, and isolated gate drive circuits can be reduced. Moreover, chopper based DC current sources are presented to reduce the inductor size effectively to be in micro-Henry order, and ensure the balance of the intermediate current levels. The proposed topology is inherently able to reduce the inductor conduction losses if compared with the conventional multilevel CSIs and the H-bridge CSI. Seven-level PWM inverter configurations with non-isolated DC current sources and with a single DC power source are verified through computer simulations. Furthermore, laboratory prototypes of seven-level CSI is setup and tested. The results show that the inverter circuit works properly to generate the multilevel output current waveform with low harmonics currents, small inductors and with less conduction losses which proves feasibility of the proposed multilevel CSI. Normal 0 false false false EN-US X-NONE X-NONE

  10. Berry{close_quote}s phase and a possible new topological current drive in certain weak link superconducting systems

    Energy Technology Data Exchange (ETDEWEB)

    Gaitan, F.; Shenoy, S.R. [International Center for Theoretical Physics, P. O. Box 586, Miramare, 34100 Trieste (Italy)

    1996-06-01

    We examine the consequences of Berry{close_quote}s phase for the dynamics of Josephson junctions and junction arrays in which moving vortices are present. For both a large annular Josephson junction and a 2D junction array, Berry{close_quote}s phase produces a new current drive in the superconducting phase dynamics of these weak link systems. This Berry phase effect is shown to be physically inequivalent to a known effect in junction arrays associated with the Aharonov-Casher phase. {copyright} {ital 1996 The American Physical Society.}

  11. Transcranial Direct Current Stimulation combined with treadmill training in the subacute phase following stroke: case series

    DEFF Research Database (Denmark)

    Figlewski, Krystian; Nielsen, Jørgen Feldbæk; Blicher, Jakob

    Background Stroke is a common cause of gait impairment and regaining a normal gait is a major target in stroke rehabilitation. To facilitate motor recovery after stroke, a variety of experimental approaches have been tested. Recent developments include non-invasive brain stimulation techniques...... such as transcranial Direct Current Stimulation (tDCS). In neurophysiologic studies an imbalance of interhemispheric interactions has been demonstrated which is believed to interfere with the recovery process. This imbalance can be ameliorated by upregulation of the excitability in the lesioned hemisphere applying...... (Fig.3). No major side effects were reported. Conclusions This case series supports the feasibility of anodal tDCS combined with body weight support treadmill training and demonstrates that this type of intervention carries potential for strategy to improve gait recovery in early phase...

  12. Bispectrum of stator phase current for fault detection of induction motor.

    Science.gov (United States)

    Treetrong, Juggrapong; Sinha, Jyoti K; Gu, Fengshu; Ball, Andrew

    2009-07-01

    A number of research studies has shown that faults in a stator or rotor generally show sideband frequencies around the mains frequency (50 Hz) and at higher harmonics in the spectrum of the Motor Current Signature Analysis (MCSA). However in the present experimental studies such observations have not been seen, but any fault either in the stator or the rotor may distort the sinusoidal response of the motor RPM and the mains frequency so the MCSA response may contain a number of harmonics of the motor RPM and the mains frequency. Hence the use of a higher order spectrum (HOS), namely the bispectrum of the MCSA has been proposed here because it relates both amplitude and phase of number of the harmonics in a signal. It has been observed that it not only detects early faults but also indicates the severity of the fault to some extent.

  13. Current Status of the Pixel Phase I Upgrade in CMS: Barrel Module Production

    CERN Document Server

    Bartek, Rachel

    2015-01-01

    The silicon pixel detector is the innermost component of the CMS tracking system, providing high precision space point measurements of charged particle trajectories. Before 2018 the instantaneous luminosity of the LHC is expected to reach about 2~x~$10^{34}~\\rm{cm}^{-2}\\rm{s}^{-1}$, which will significantly increase the number of interactions per bunch crossing. To maintain a high tracking efficiency, CMS has planned to replace the current pixel system during phase I by a new lightweight detector, equipped with an additional 4th layer in the barrel, and one additional forward/backward disk. The present status of barrel modules production will be presented, including preliminary results from tests on the first production pixel modules of the new pixel tracker.

  14. Analytical Modeling Of The Steinmetz Coefficient For Single-Phase Transformer Eddy Current Loss Prediction

    Directory of Open Access Journals (Sweden)

    T. Aly Saandy

    2015-08-01

    Full Text Available Abstract This article presents to an analytical calculation methodology of the Steinmetz coefficient applied to the prediction of Eddy current loss in a single-phase transformer. Based on the electrical circuit theory the active power consumed by the core is expressed analytically in function of the electrical parameters as resistivity and the geometrical dimensions of the core. The proposed modeling approach is established with the duality parallel series. The required coefficient is identified from the empirical Steinmetz data based on the experimented active power expression. To verify the relevance of the model validations both by simulations with two in two different frequencies and measurements were carried out. The obtained results are in good agreement with the theoretical approach and the practical results.

  15. Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes

    KAUST Repository

    Li, Yiyang

    2014-09-14

    ©2014 Macmillan Publishers Limited. All rights reserved. Many battery electrodes contain ensembles of nanoparticles that phase-separate on (de)intercalation. In such electrodes, the fraction of actively intercalating particles directly impacts cycle life: a vanishing population concentrates the current in a small number of particles, leading to current hotspots. Reports of the active particle population in the phase-separating electrode lithium iron phosphate (LiFePO 4; LFP) vary widely, ranging from near 0% (particle-by-particle) to 100% (concurrent intercalation). Using synchrotron-based X-ray microscopy, we probed the individual state-of-charge for over 3,000 LFP particles. We observed that the active population depends strongly on the cycling current, exhibiting particle-by-particle-like behaviour at low rates and increasingly concurrent behaviour at high rates, consistent with our phase-field porous electrode simulations. Contrary to intuition, the current density, or current per active internal surface area, is nearly invariant with the global electrode cycling rate. Rather, the electrode accommodates higher current by increasing the active particle population. This behaviour results from thermodynamic transformation barriers in LFP, and such a phenomenon probably extends to other phase-separating battery materials. We propose that modifying the transformation barrier and exchange current density can increase the active population and thus the current homogeneity. This could introduce new paradigms to enhance the cycle life of phase-separating battery electrodes.

  16. Five-Phase Five-Level Open-Winding/Star-Winding Inverter Drive for Low-Voltage/High-Current Applications

    DEFF Research Database (Denmark)

    Padmanaban, Sanjeevi Kumar; Blaabjerg, Frede; Wheeler, Patrick

    2016-01-01

    This paper work proposed a five-phase five-level open-/star-winding multilevel AC converter suitable for low-voltage/high-current applications. Modular converter consists of classical two-level five-phase voltage source inverter (VSI) with slight reconfiguration to serve as a multilevel converter...

  17. Comparison between Phase-Shift Full-Bridge Converters with Noncoupled and Coupled Current-Doubler Rectifier

    Directory of Open Access Journals (Sweden)

    Cheng-Tao Tsai

    2013-01-01

    Full Text Available This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR or a coupled current-doubler rectifier (CCDR is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications.

  18. Influence of powder pre-annealing on the phase formation and critical current of Bi-2223/Ag tapes

    DEFF Research Database (Denmark)

    Chen, X.P.; Grivel, Jean-Claude; Li, M.Y.;

    2004-01-01

    the precursor with Ca2PbO4 phase (tape T1) had lower transformation rate of 2223 phase than tapes fabricated using the precursor with 3321 phase (tape T2). SEM results show that a large fraction of secondary phases with big particle size was formed in the tape T1 during the subsequent sintering, which might......The influence of precursor powders with different lead-rich phases, such as Ca2PbO4 and Pb-3(Sr,Bi)(3)Ca2CuOy (3 3 2 1), on the phase formation and critical current of Bi-2223/Ag tapes has been studied. Three precursors with different phase assemblages were prepared and used to make the tapes...

  19. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage circuits...

  20. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Low- and medium-voltage circuits serving three... STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit breakers...

  1. 100 kV/2A three-phase constant-current repetitive-rate charging equipment

    CERN Document Server

    Tan Yu Gang; Chen Li Dong; Guo Zhi Gang; Zou Xiao Bing; Luo Min; Cao Shao Yun; Chang An Bi

    2002-01-01

    A 100 kV/2A three-phase constant-current repetitive-rate charging equipment was designed and constructed. A three-phase L-C converter is adopted as constant-current power source. Six Insulated Gate Bipolar Transistors (IGBTs) are connected in parallel to control the stop of charge. A Programmable Logical Controller (PLC) is the central element of the control unit. The equipment is used in the repetitive-rate discharge features test of the switch. It works stably under the conditions of 2A charging current, 10 Hz operating voltage, 100 kV repetitive rate and 1 mu F capacitor

  2. New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

    OpenAIRE

    Yong-Jin Park; Ju-Young Cho; Min-Woo Jeong; Sekwon Na; Young-Chang Joo

    2016-01-01

    The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm2), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modu...

  3. A Current-Forced Line-Commutated Inverter for Single-Phase Grid-Connected Photovoltaic Generation Systems

    OpenAIRE

    2015-01-01

    A simple power electronic interface based on the line-commutated inverter (LCI) has been developed in order to inject sinusoidal current to the grid for single-phase grid-connected photovoltaic (PV) energy generation systems. The proposed inverter facilitates controlling the injecting/grid current with a controllable power factor in contrast to the conventional LCI system. It is achieved that the total harmonic distortion (THD) of the injecting currents for the different firin...

  4. First-principles-driven model-based current profile control for the DIII-D tokamak via LQI optimal control

    Science.gov (United States)

    Boyer, Mark D.; Barton, Justin; Schuster, Eugenio; Luce, Tim C.; Ferron, John R.; Walker, Michael L.; Humphreys, David A.; Penaflor, Ben G.; Johnson, Robert D.

    2013-10-01

    In tokamak fusion plasmas, control of the spatial distribution profile of the toroidal plasma current plays an important role in realizing certain advanced operating scenarios. These scenarios, characterized by improved confinement, magnetohydrodynamic stability, and a high fraction of non-inductively driven plasma current, could enable steady-state reactor operation with high fusion gain. Current profile control experiments at the DIII-D tokamak focus on using a combination of feedforward and feedback control to achieve a targeted current profile during the ramp-up and early flat-top phases of the shot and then to actively maintain this profile during the rest of the discharge. The dynamic evolution of the current profile is nonlinearly coupled with several plasma parameters, motivating the design of model-based control algorithms that can exploit knowledge of the system to achieve desired performance. In this work, we use a first-principles-driven, control-oriented model of the current profile evolution in low confinement mode (L-mode) discharges in DIII-D to design a feedback control law for regulating the profile around a desired trajectory. The model combines the magnetic diffusion equations with empirical correlations for the electron temperature, resistivity, and non-inductive current drive. To improve tracking performance of the system, a nonlinear input transformation is combined with a linear-quadratic-integral (LQI) optimal controller designed to minimize a weighted combination of the tracking error and controller effort. The resulting control law utilizes the total plasma current, total external heating power, and line averaged plasma density as actuators. A simulation study was used to test the controller's performance and ensure correct implementation in the DIII-D plasma control system prior to experimental testing. Experimental results are presented that show the first-principles-driven model-based control scheme's successful rejection of input

  5. Current limiting behavior in three-phase transformer-type SFCLs using an iron core according to variety of fault

    Science.gov (United States)

    Cho, Yong-Sun; Jung, Byung-Ik; Ha, Kyoung-Hun; Choi, Soo-Geun; Park, Hyoung-Min; Choi, Hyo-Sang

    To apply the superconducting fault current limiter (SFCL) to the power system, the reliability of the fault-current-limiting operation must be ensured in diverse fault conditions. The SFCL must also be linked to the operation of the high-speed recloser in the power system. In this study, a three-phase transformer-type SFCL, which has a neutral line to improve the simultaneous quench characteristics of superconducting elements, was manufactured to analyze the fault-current-limiting characteristic according to the single, double, and triple line-to-ground faults. The transformer-type SFCL, wherein three-phase windings are connected to one iron core, reduced the burden on the superconducting element as the superconducting element on the sound phase was also quenched in the case of the single line-to-ground fault. In the case of double or triple line-to-ground faults, the flux from the faulted phase winding was interlinked with other faulted or sound phase windings, and the fault-current-limiting rate decreased because the windings of three phases were inductively connected by one iron core.

  6. Generation of geometrical phases and persistent spin currents in 1-dimensional rings by Lorentz-violating terms

    CERN Document Server

    Casana, R; Mouchrek-Santos, V E; Silva, Edilberto O

    2015-01-01

    We have demonstrated that Lorentz-violating terms stemming from the fermion sector of the SME are able to generate geometrical phases on the wave function of electrons confined in 1-dimensional rings, as well as persistent spin currents, in the total absence of electromagnetic fields. We have explicitly evaluated the eigenenergies and eigenspinors of the electrons modified by the Lorentz-violating terms, using them to calculate the dynamic and the Aharonov-Anandan phases in the sequel. The total phase presents a pattern very similar to the Aharonov-Casher phase accumulated by electrons in rings under the action of the Rashba interaction. Finally, the persistent spin current were carried out and used to impose upper bounds on the Lorentz-violating parameters.

  7. Generation of geometrical phases and persistent spin currents in 1-dimensional rings by Lorentz-violating terms

    Directory of Open Access Journals (Sweden)

    R. Casana

    2015-06-01

    Full Text Available We have demonstrated that Lorentz-violating terms stemming from the fermion sector of the SME are able to generate geometrical phases on the wave function of electrons confined in 1-dimensional rings, as well as persistent spin currents, in the total absence of electromagnetic fields. We have explicitly evaluated the eigenenergies and eigenspinors of the electrons modified by the Lorentz-violating terms, using them to calculate the dynamic and the Aharonov–Anandan phases in the sequel. The total phase presents a pattern very similar to the Aharonov–Casher phase accumulated by electrons in rings under the action of the Rashba interaction. Finally, the persistent spin current were carried out and used to impose upper bounds on the Lorentz-violating parameters.

  8. Generation of geometrical phases and persistent spin currents in 1-dimensional rings by Lorentz-violating terms

    Energy Technology Data Exchange (ETDEWEB)

    Casana, R.; Ferreira, M.M., E-mail: manojr.ufma@gmail.com; Mouchrek-Santos, V.E.; Silva, Edilberto O.

    2015-06-30

    We have demonstrated that Lorentz-violating terms stemming from the fermion sector of the SME are able to generate geometrical phases on the wave function of electrons confined in 1-dimensional rings, as well as persistent spin currents, in the total absence of electromagnetic fields. We have explicitly evaluated the eigenenergies and eigenspinors of the electrons modified by the Lorentz-violating terms, using them to calculate the dynamic and the Aharonov–Anandan phases in the sequel. The total phase presents a pattern very similar to the Aharonov–Casher phase accumulated by electrons in rings under the action of the Rashba interaction. Finally, the persistent spin current were carried out and used to impose upper bounds on the Lorentz-violating parameters.

  9. Generation of geometrical phases and persistent spin currents in 1-dimensional rings by Lorentz-violating terms

    Science.gov (United States)

    Casana, R.; Ferreira, M. M.; Mouchrek-Santos, V. E.; Silva, Edilberto O.

    2015-06-01

    We have demonstrated that Lorentz-violating terms stemming from the fermion sector of the SME are able to generate geometrical phases on the wave function of electrons confined in 1-dimensional rings, as well as persistent spin currents, in the total absence of electromagnetic fields. We have explicitly evaluated the eigenenergies and eigenspinors of the electrons modified by the Lorentz-violating terms, using them to calculate the dynamic and the Aharonov-Anandan phases in the sequel. The total phase presents a pattern very similar to the Aharonov-Casher phase accumulated by electrons in rings under the action of the Rashba interaction. Finally, the persistent spin current were carried out and used to impose upper bounds on the Lorentz-violating parameters.

  10. Structural and phase transformations in zinc and brass wires under heating with high-density current pulse

    Science.gov (United States)

    Pervikov, A. V.

    2016-06-01

    The work is focused on revealing the mechanism of structure and phase transformations in the metal wires under heating with a high-density current pulse (the electric explosion of wires, EEWs). It has been demonstrated on the example of brass and zinc wires that the transition of a current pulse with the density of j ≈ 3.3 × 107 A/cm2 results in homogeneous heating of the crystalline structure of the metal/alloy. It has been determined that under heating with a pulse of high-density current pulse, the electric resistance of the liquid phases of zinc and brass decreases as the temperature increases. The results obtained allow for a conclusion that the presence of the particles of the condensed phase in the expanding products of EEW is the result of overheating instabilities in the liquid metal.

  11. Negative DC corona discharge current characteristics in a flowing two-phase (air + suspended smoke particles) fluid

    Science.gov (United States)

    Berendt, Artur; Domaszka, Magdalena; Mizeraczyk, Jerzy

    2017-04-01

    The electrical characteristics of a steady-state negative DC corona discharge in a two-phase fluid (air with suspended cigarette smoke particles) flowing along a chamber with a needle-to-plate electrode arrangement were experimentally investigated. The two-phase flow was transverse in respect to the needle-to-plate axis. The velocity of the transverse two-phase flow was limited to 0.8 m/s, typical of the electrostatic precipitators. We found that three discharge current modes of the negative corona exist in the two-phase (air + smoke particles) fluid: the Trichel pulses mode, the "Trichel pulses superimposed on DC component" mode and the DC component mode, similarly as in the corona discharge in air (a single-phase fluid). The shape of Trichel pulses in the air + suspended particles fluid is similar to that in air. However, the Trichel pulse amplitudes are higher than those in "pure" air while their repetition frequency is lower. As a net consequence of that the averaged corona discharge current in the two-phase fluid is lower than in "pure" air. It was also found that the average discharge current decreases with increasing suspended particle concentration. The calculations showed that the dependence of the average negative corona current (which is a macroscopic corona discharge parameter) on the particle concentration can be explained by the particle-concentration dependencies of the electric charge of Trichel pulse and the repetition frequency of Trichel pulses, both giving a microscopic insight into the electrical phenomena in the negative corona discharge. Our investigations showed also that the average corona discharge current in the two-phase fluid is almost unaffected by the transverse fluid flow up to a velocity of 0.8 m/s. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

  12. Laminar distribution of phase-amplitude coupling of spontaneous current sources and sinks

    Directory of Open Access Journals (Sweden)

    Roberto C Sotero

    2015-12-01

    Full Text Available Although resting-state functional connectivity is a commonly used neuroimaging paradigm, the underlying mechanisms remain unknown. Thalamo-cortical and cortico-cortical circuits generate oscillations at different frequencies during spontaneous activity. However, it remains unclear how the various rhythms interact and whether their interactions are lamina-specific. Here we investigated intra- and inter-laminar spontaneous phase-amplitude coupling (PAC. We recorded local-field potentials using laminar probes inserted in the forelimb representation of rat area S1. We then computed time-series of frequency-band- and lamina-specific current source density (CSD, and PACs of CSD for all possible pairs of the classical frequency bands in the range of 1–150 Hz. We observed both intra- and inter-laminar spontaneous PAC. Of 18 possible combinations, 12 showed PAC, with the highest measures of interaction obtained for the pairs of the theta/gamma and delta/gamma bands. Intra- and inter-laminar PACs involving layers 2/3–5a were higher than those involving layer 6. Current sinks (sources in the delta band were associated with increased (decreased amplitudes of high-frequency signals in the beta to fast gamma bands throughout layers 2/3–6. Spontaneous sinks (sources of the theta and alpha bands in layers 2/3 to 4 were on average linked to dipoles completed by sources (sinks in layer 6, associated with high (low amplitudes of the beta to fast-gamma bands in the entire cortical column. Our findings show that during spontaneous activity, delta, theta, and alpha oscillations are associated with periodic excitability, which for the theta and alpha bands is lamina--dependent. They further emphasize the differences between the function of layer 6 and that of the superficial layers, and the role of layer 6 in controlling activity in those layers. Our study links theories on the involvement of PAC in resting-state functional connectivity with previous work that

  13. Phase-field simulation of counter-current spontaneous imbibition in a fractured heterogeneous porous medium

    Science.gov (United States)

    Rokhforouz, M. R.; Akhlaghi Amiri, H. A.

    2017-06-01

    Spontaneous imbibition is well-known to be one of the most effective processes of oil recovery in fractured reservoirs. However, the detailed pore-scale mechanisms of the counter-current imbibition process and the effects of different fluid/rock parameters on this phenomenon have not yet been deeply addressed. This work presents the results of a new pore-level numerical study of counter-current spontaneous imbibition, using coupled Cahn-Hilliard phase field and Navier-Stokes equations, solved by a finite element method. A 2D fractured medium was constructed consisting of a nonhomogeneous porous matrix, in which the grains were represented by an equilateral triangular array of circles with different sizes and initially saturated with oil, and a fracture, adjacent to the matrix, initially saturated with water and supported by low rate water inflow. Through invasion of water into the matrix, oil drops were expelled one by one from the matrix to the fracture, and in the matrix, water progressed by forming capillary fingerings, with characteristics corresponding to the experimental observations. The effects of wettability, viscosity ratio, and interfacial tension were investigated. In strongly water-wet matrix, with grain contact angles of θ movement, water bridging, and oil drop detachment. It was notified that there was a specific grain contact angle for this simulated model, θ = π/4, above it, matrix oil recovery was negligible by imbibition, while below it, the imbibition rate and oil recovery were significantly increased by decreasing the contact angle. In simulated mixed wet models, water, coming from the fracture, just invaded the neighboring water-wet grains; the water front was stopped moving as it met the oil-wet grains or wide pores/throats. Increasing water-oil interfacial tension, in the range of 0.005-0.05 N/m, resulted in both higher rate of imbibition and higher ultimate oil recovery. Changing the water-oil viscosity ratio (M), in the range of 0

  14. Phase-to-intensity conversion of magnonic spin currents and application to the design of a majority gate

    Science.gov (United States)

    Brächer, T.; Heussner, F.; Pirro, P.; Meyer, T.; Fischer, T.; Geilen, M.; Heinz, B.; Lägel, B.; Serga, A. A.; Hillebrands, B.

    2016-12-01

    Magnonic spin currents in the form of spin waves and their quanta, magnons, are a promising candidate for a new generation of wave-based logic devices beyond CMOS, where information is encoded in the phase of travelling spin-wave packets. The direct readout of this phase on a chip is of vital importance to couple magnonic circuits to conventional CMOS electronics. Here, we present the conversion of the spin-wave phase into a spin-wave intensity by local non-adiabatic parallel pumping in a microstructure. This conversion takes place within the spin-wave system itself and the resulting spin-wave intensity can be conveniently transformed into a DC voltage. We also demonstrate how the phase-to-intensity conversion can be used to extract the majority information from an all-magnonic majority gate. This conversion method promises a convenient readout of the magnon phase in future magnon-based devices.

  15. Current Harmonics Cancellation in Three-Phase Four-Wire Systems by Using a Four-Branch Star Filtering Topology

    DEFF Research Database (Denmark)

    Rodriguez, Pedro; Candela, J. I.; Luna, A.;

    2009-01-01

    This paper presents a new solution for filtering current harmonics in three-phase four-wire networks. The original four-branch star (FBS) filter topology presented in this paper is characterized by a particular layout of single-phase inductances and capacitors, without using any transformer......, a specific implementation of a three-phase four-wire hybrid power filter is presented as an illustrative application of the filtering topology. An extensive evaluation using simulation and experimental results from a DSP-based laboratory prototype is conducted in order to verify and validate the good...

  16. Phase stability and grain growth in an Ag/Bi-2223 composite conductor prepared using fine-grained Bi-2223 as a precursor.

    Energy Technology Data Exchange (ETDEWEB)

    Merchant, N. N.

    1998-09-17

    We have investigated the stability and microstructural transformability of the Bi-2223 phase in a silver-sheathed monofilament composite tape fabricated using fine-grained Bi{sub 1.7}Pb{sub 0.3}Sr{sub 1.9}Ca{sub 2.0}-Cu{sub 3.0}O{sub y} (Bi-2223) as the precursor powder. The fully formed Bi-2223 precursor was prepared using established procedures. The purpose of this study was to explore the prospects for growing textured, large-grain-size Bi-2223 from the fine-grained precursor by process parameter perturbations. These perturbations included thermal ramp up variations, programmed heat treatment temperature and oxygen pressure fluctuations, and parameter manipulations during cool-down. Our results show that the types of heat treatments used in conventional oxide-powder-in-tube (OPIT) processing do not facilitate Bi-2223 grain growth when the precursor powder is preconcerted Bi-2223. We also observed that the Bi-2223 partially. decomposed during conventional thermal ramp-up in 0.075 atm O{sub 2}, but that this decomposition can be inhibited by ramping up in a reduced oxygen pressure. A pathway was found for back-reacting the fine-grained Bi-2223 (to Bi-2212, Bi-2201 and nonsuperconducting secondary phases), then reforming large-grained Bi-2223 in a colony microstructure having some distinct differences from that produced during conventional OPIT processing.

  17. Evaluation of the Current Status of the Combinatorial Approach for the Study of Phase Diagrams.

    Science.gov (United States)

    Wong-Ng, W

    2012-01-01

    This paper provides an evaluation of the effectiveness of using the high throughput combinatorial approach for preparing phase diagrams of thin film and bulk materials. Our evaluation is based primarily on examples of combinatorial phase diagrams that have been reported in the literature as well as based on our own laboratory experiments. Various factors that affect the construction of these phase diagrams are examined. Instrumentation and analytical approaches needed to improve data acquisition and data analysis are summarized.

  18. Pulse pattern modulated strategy for harmonic current components reduction in three-phase AC-DC converters

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2015-01-01

    Generated harmonic current as a consequence of employing power electronics converter is known as an important power quality issue in distribution networks. From industry point of view complying with international standards is mandatory, however cost and efficiency are two other important features......, which need to be considered in order to be competitive in the market. Therefore, having a flexibility to meet various requirements imposed by the standard recommendations or costumer needs is at most desirable. This makes the generated harmonic current mitigation a challenging task especially with three......-phase diode bridge rectifier, which still is preferred in many power electronic systems. This paper addresses a novel current modulation strategy using a single-switch boost three-phase diode bridge rectifier. The proposed method can selectively mitigate current harmonics, which makes it suitable...

  19. Pulse Pattern-Modulated Strategy for Harmonic Current Components Reduction in Three-Phase AC–DC Converters

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2016-01-01

    Generated harmonic current as a consequence of employing power electronics converter is known as an important power quality issue in distribution networks. From industry point of view complying with international standards is mandatory, however cost and efficiency are two other important features......, which need to be considered in order to be competitive in the market. Therefore, having a flexibility to meet various requirements imposed by the standard recommendations or costumer needs is at most desirable. This makes the generated harmonic current mitigation a challenging task especially with three......-phase diode bridge rectifier, which still is preferred in many power electronic systems. This paper addresses a novel current modulation strategy using a single-switch boost three-phase diode bridge rectifier. The proposed method can selectively mitigate current harmonics, which makes it suitable...

  20. Analysis of Three-Phase Rectifier Systems with Controlled DC-Link Current Under Unbalanced Grids

    DEFF Research Database (Denmark)

    Kumar, Dinesh; Davari, Pooya; Zare, Firuz

    2017-01-01

    Voltage unbalance is the most common disturbance in distribution networks, which give undesirable effects on many grid connected power electronics systems including Adjustable Speed Drive (ASD). Severe voltage unbalance can force three-phase rectifiers into almost single-phase operation, which de...

  1. Phase I and Phase II Therapies for Acute Ischemic Stroke: An Update on Currently Studied Drugs in Clinical Research

    Science.gov (United States)

    Reis, Cesar; Akyol, Onat; Ho, Wing Mann; Araujo, Camila; Huang, Lei; Applegate II, Richard

    2017-01-01

    Acute ischemic stroke is a devastating cause of death and disability, consequences of which depend on the time from ischemia onset to treatment, the affected brain region, and its size. The main targets of ischemic stroke therapy aim to restore tissue perfusion in the ischemic penumbra in order to decrease the total infarct area by maintaining blood flow. Advances in research of pathological process and pathways during acute ischemia have resulted in improvement of new treatment strategies apart from restoring perfusion. Additionally, limiting the injury severity by manipulating the molecular mechanisms during ischemia has become a promising approach, especially in animal research. The purpose of this article is to review completed and ongoing phases I and II trials for the treatment of acute ischemic stroke, reviewing studies on antithrombotic, thrombolytic, neuroprotective, and antineuroinflammatory drugs that may translate into more effective treatments. PMID:28286764

  2. Phase I and Phase II Therapies for Acute Ischemic Stroke: An Update on Currently Studied Drugs in Clinical Research.

    Science.gov (United States)

    Reis, Cesar; Akyol, Onat; Ho, Wing Mann; Araujo, Camila; Huang, Lei; Applegate, Richard; Zhang, John H

    2017-01-01

    Acute ischemic stroke is a devastating cause of death and disability, consequences of which depend on the time from ischemia onset to treatment, the affected brain region, and its size. The main targets of ischemic stroke therapy aim to restore tissue perfusion in the ischemic penumbra in order to decrease the total infarct area by maintaining blood flow. Advances in research of pathological process and pathways during acute ischemia have resulted in improvement of new treatment strategies apart from restoring perfusion. Additionally, limiting the injury severity by manipulating the molecular mechanisms during ischemia has become a promising approach, especially in animal research. The purpose of this article is to review completed and ongoing phases I and II trials for the treatment of acute ischemic stroke, reviewing studies on antithrombotic, thrombolytic, neuroprotective, and antineuroinflammatory drugs that may translate into more effective treatments.

  3. Phase I and Phase II Therapies for Acute Ischemic Stroke: An Update on Currently Studied Drugs in Clinical Research

    Directory of Open Access Journals (Sweden)

    Cesar Reis

    2017-01-01

    Full Text Available Acute ischemic stroke is a devastating cause of death and disability, consequences of which depend on the time from ischemia onset to treatment, the affected brain region, and its size. The main targets of ischemic stroke therapy aim to restore tissue perfusion in the ischemic penumbra in order to decrease the total infarct area by maintaining blood flow. Advances in research of pathological process and pathways during acute ischemia have resulted in improvement of new treatment strategies apart from restoring perfusion. Additionally, limiting the injury severity by manipulating the molecular mechanisms during ischemia has become a promising approach, especially in animal research. The purpose of this article is to review completed and ongoing phases I and II trials for the treatment of acute ischemic stroke, reviewing studies on antithrombotic, thrombolytic, neuroprotective, and antineuroinflammatory drugs that may translate into more effective treatments.

  4. Computation of a Single-phase Shell-Type Transformer Windings Forces Caused by Inrush and Short-circuit Currents

    Directory of Open Access Journals (Sweden)

    M. B.B. Sharifian

    2008-01-01

    Full Text Available This research studies the forces on the windings of transformer due to inrush current. These forces are compared with the corresponding forces due to short-circuit of the windings. Two-dimensional finite element computation of a single-phase shell-type transformer is carried out based on the maximum permissible inrush current value where its amplitude is the same as the rated short-circuit current. To verify the computation results, they are compared with those recently obtained using Artificial Neural Network (ANN.

  5. Magnetic resonance visualization of conductive structures by sequence-triggered direct currents and spin-echo phase imaging

    Energy Technology Data Exchange (ETDEWEB)

    Eibofner, Frank; Wojtczyk, Hanne; Graf, Hansjörg, E-mail: hansjoerg.graf@med.uni-tuebingen.de, E-mail: drGraf@t-online.de [Section on Experimental Radiology, University Hospital Tübingen, Tübingen D-72076 (Germany); Clasen, Stephan [Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen D-72076 (Germany)

    2014-06-15

    Purpose: Instrument visualization in interventional magnetic resonance imaging (MRI) is commonly performed via susceptibility artifacts. Unfortunately, this approach suffers from limited conspicuity in inhomogeneous tissue and disturbed spatial encoding. Also, susceptibility artifacts are controllable only by sequence parameters. This work presents the basics of a new visualization method overcoming such problems by applying sequence-triggered direct current (DC) pulses in spin-echo (SE) imaging. SE phase images allow for background free current path localization. Methods: Application of a sequence-triggered DC pulse in SE imaging, e.g., during a time period between radiofrequency excitation and refocusing, results in transient field inhomogeneities. Dependent on the additional z-magnetic field from the DC, a phase offset results despite the refocusing pulse. False spatial encoding is avoided by DC application during periods when read-out or slice-encoding gradients are inactive. A water phantom containing a brass conductor (water equivalent susceptibility) and a titanium needle (serving as susceptibility source) was used to demonstrate the feasibility. Artifact dependence on current strength and orientation was examined. Results: Without DC, the brass conductor was only visible due to its water displacement. The titanium needle showed typical susceptibility artifacts. Applying triggered DC pulses, the phase offset of spins near the conductor appeared. Because SE phase images are homogenous also in regions of persistent field inhomogeneities, the position of the conductor could be determined with high reliability. Artifact characteristic could be easily controlled by amperage leaving sequence parameters unchanged. For an angle of 30° between current and static field visualization was still possible. Conclusions: SE phase images display the position of a conductor carrying pulsed DC free from artifacts caused by persistent field inhomogeneities. Magnitude and phase

  6. Acute-phase reactants in periodontal disease: current concepts and future implications.

    Science.gov (United States)

    Archana, Vilasan; Ambili, Ranjith; Nisha, Krishnavilasam Jayakumary; Seba, Abraham; Preeja, Chandran

    2015-05-01

    Periodontal disease has been linked to adverse cardiovascular events by unknown mechanisms. C-reactive protein is a systemic marker released during the acute phase of an inflammatory response and is a prognostic marker for cardiovascular disease, with elevated serum levels being reported during periodontal disease. Studies also reported elevated levels of various other acute-phase reactants in periodontal disease. It has been reported extensively in the literature that treatment of periodontal infections can significantly lower serum levels of C-reactive protein. Therefore, an understanding of the relationship between acute-phase response and the progression of periodontal disease and other systemic health complications would have a profound effect on the periodontal treatment strategies. In view of this fact, the present review highlights an overview of acute-phase reactants and their role in periodontal disease. © 2014 Wiley Publishing Asia Pty Ltd.

  7. Peak current mode control of three-phase boost rectifiers in discontinuous conduction mode for small wind power generators

    Energy Technology Data Exchange (ETDEWEB)

    Carranza, O. [Escuela Superior de Computo, Instituto Politecnico Nacional (Mexico); Garcera, G.; Figueres, E. [Grupo de Sistemas Electronicos Industriales del Departamento de Ingenieria Electronica, Universidad Politecnica de Valencia (Spain); Gonzalez, L.G. [Departamento de Ingenieria Electronica y Comunicaciones, Universidad de los Andes (Venezuela)

    2010-08-15

    This paper presents a peak current mode control scheme of a boost rectifier with low distortion of the input current for wind power systems based on permanent magnet synchronous generators with variable speed operation. The three-phase boost rectifier is operated in discontinuous conduction mode (DCM), and power factor correction techniques are applied. It is shown that the DCM operation significantly reduces the total harmonic distortion of the currents in the permanent magnet synchronous generator, increasing the power factor of the system, so that the vibrations and mechanical stress of the generator are minimized. The characteristics of the DCM boost rectifier are studied considering: (1) the series resistance of the inductors; (2) the modeling and adjustment of peak current mode control yielding a stable loop; (3) the design of an input filter that reduces the switching noise in the currents of the generator. (author)

  8. Cross-Circulating Current Suppression Method for Parallel Three-Phase Two-Level Inverters

    DEFF Research Database (Denmark)

    Wei, Baoze; Guerrero, Josep M.; Guo, Xiaoqiang

    2015-01-01

    The parallel architecture is very popular for power inverters to increase the power level. This paper presents a method for the parallel operation of inverters in an ac-distributed system, to suppress the cross-circulating current based on virtual impedance without current-sharing bus...

  9. Linguistic Gender Sensitivity Strategies in Current South African Intermediate Phase English Workbooks: Feminisation or Degenderisation?

    Science.gov (United States)

    Sibanda, Jabulani; Sibanda, Lucy

    2016-01-01

    This study extends research on manifestations of gender insensitivity in learners' reading materials by shifting attention to the linguistic strategies that authors of current texts employ for the realisation of gender sensitivity. We analysed the content of 12 current (2014) English workbooks (Grade 4-6) used in South African government and…

  10. Linguistic Gender Sensitivity Strategies in Current South African Intermediate Phase English Workbooks: Feminisation or Degenderisation?

    Science.gov (United States)

    Sibanda, Jabulani; Sibanda, Lucy

    2016-01-01

    This study extends research on manifestations of gender insensitivity in learners' reading materials by shifting attention to the linguistic strategies that authors of current texts employ for the realisation of gender sensitivity. We analysed the content of 12 current (2014) English workbooks (Grade 4-6) used in South African government and…

  11. Elimination of the Inrush Current Phenomenon Associated with Single-Phase Offline UPS Systems

    Directory of Open Access Journals (Sweden)

    Syed Sabir Hussain Bukhari

    2016-02-01

    Full Text Available Critical load applications always rely on UPS systems to uphold continuous power during abnormal grid conditions. In case of any power disruption, an offline UPS system starts powering the load to avoid blackout. However, this process can root the momentous inrush current for the transformer installed before the load. The consequences of inrush current can be the reduction of output voltage and tripping of protective devices of the UPS system. Furthermore, it can also damage the sensitive load and decrease the transformer’s lifetime. To prevent the inrush current, and to avoid its disruptive effects, this research suggests an offline UPS system based on a current regulated inverter that eliminates the inrush current while powering the transformer coupled loads. A detailed comparative analysis of the conventional and proposed topologies is presented and the experiment was performed by using a small prototype to validate the performance, and operation of the proposed topology.

  12. Potential for using a six-phase alternating current power supply system for in situ vitrification

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, R.L.

    1991-09-01

    In situ vitrification (ISV) has been identified as a potential treatment technology for stabilizing underground tanks at Hanford and other US Department of Energy (DOE) sites. A key requirement for this application is an electrical system that can supply the power needed to vitrify a tank in a single setting. This paper describes an engineering-scale test conducted at the Pacific Northwest Laboratory (PNL) to assess the efficiency of a six-electrode, six-phase energy supply system in melting soil. The test was conducted with a 30-kW six-phase system. Based on the test results, a six-electrode, six-phase system shows potential for scaleup to larger systems. 5 refs., 5 figs., 2 tabs.

  13. Comparison of the current LHC Collimators and the SLAC Phase 2 Collimator Impedances

    CERN Document Server

    Day, Hugo; Metral, Elias; Salvant, Benoit; Jones, Roger

    2011-01-01

    One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.

  14. Comparison of the current LHC Collimators and the SLAC phase 2 Collimator impedances

    CERN Document Server

    Day, H A; Metral, E; Salvant, B; Jones, R M

    2011-01-01

    One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.

  15. Comparison of the current LHC Collimators and the SLAC Phase 2 Collimator Impedances

    CERN Document Server

    Day, Hugo; Metral, Elias; Salvant, Benoit; Jones, Roger

    2011-01-01

    One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.

  16. Interaction between Current Imbalance and Magnetization in LHC Cables

    CERN Document Server

    Bottura, L; Kuijper, A; den Ouden, A; ten Haken, B; ten Kate, H H J

    2001-01-01

    The quality of the magnetic field in superconducting accelerator magnets is associated with the properties of the superconducting cable. Current imbalances due to coupling currents DI, as large as 100 A, are induced by spatial variations of the field sweep rate and contact resistances. During injection at a constant field all magnetic field components show a decay behavior. The decay is caused by a diffusion of coupling currents into the whole magnet. This results in a redistribution of the transport current among the strands and causes a demagnetization of the superconducting cable. As soon as the field is ramped up again after the end of injection, the magnetization rapidly recovers from the decay and follows the course of the original hysteresis curve. In order to clarify the interactions between the changes in current and magnetization during injection we performed a number of experiments. A magnetic field with a spatially periodic pattern was applied to a superconducting wire in order to simulate the cou...

  17. 三相软开关PWM变流器电流极性检测与电流补偿方法%Current Polarity Detection and Current Compensation Strategy for PAC Based Three-Phase ZVS PWM Converter

    Institute of Scientific and Technical Information of China (English)

    屈克庆; 陈国呈; 孙承波

    2005-01-01

    A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching (ZVS) PWM converter based on phase and amplitude control (PAC), when saw-tooth carriers with alternate positive and negative slopes are adopted, the positive or negative slopes are chosen according to the phase current polarity. Since polarity reversal causes current distortion, current at the instant of reversal should be compensated for. Based on the characteristic of unity power factor converter in rectification and regeneration modes, a software implementation for current polarity detection is proposed.Distortion of current zero-crossing caused by using saw-tooth carriers with alternate positive and negative slopes is analyzed, and the relevant compensation method is proposed. Experimental study with a 1.5 kW device shows that phase current has a small harmonic content and power factor is high both in rectification and regeneration modes.

  18. High performance predictive current control of a three phase VSI: An experimental assessment

    Indian Academy of Sciences (India)

    Vikas Kumar; Prerna Gaur; A P Mittal

    2014-12-01

    Delay has a significant role to play in the implementation of the predictive current control scheme as large amount of calculations are involved. Compensating delay in the predictive current controller design can lead to an improved load current total harmonic distortion (THD) and also an increased switching frequency. Minimization of switching frequency while maintaining the lower value of load current THD requires multiple objective optimization which is achieved by optimizing a single objective function, constructed using weighting factors as a linear combination of individual objective function. The effect of weighting factor on the switching frequency minimization and the current tracking error with delay compensation for the two level voltage source inverter (VSI) are investigated in this paper. The outcomes of the predictive current control using an optimized weighting factor which is calculated using branch and bound algorithm with the delay compensation are compared with the PWM based current control scheme. The experimental tests are conducted on a 2.2 kW VSI to verify the simulation observations.

  19. Surface modification of polytetrafluoroethylene column for two-stationary phase separations by counter-current chromatography.

    Science.gov (United States)

    Quan, Kai-jun; Huang, Xin-yi; Li, Xiao-ting; Wang, Gao-hong; Liu, Yan-juan; Duan, Wen-da; Di, Duo-long

    2015-11-27

    To improve the separation capability of CCC, a novel solid-liquid two-stationary phases CCC (ASP-CCC) column was prepared employing graphene oxide (GO) conjugated poly-dopamine (PD) coating (GO/PD) as auxiliary stationary phase (ASP). The results of Scanning electron microscopy (SEM), contact angle and X-ray photoelectron spectroscopy (XPS) indicated that nanostructured GO and PD were successfully grafted on the inner wall of the PTFE column. Three alkaloid compounds were selected as the target analytes to evaluate the performance of the novel column. Because of the intermolecular force (hydrogen bond, electrostatic interaction and π-π interaction) between the ASP and model compounds, three analytes were well separated with this novel ASP-CCC column. Additionally, the novel column exhibited higher stationary phase retention ratio, about 8%, than original column without changing the chromatographic condition. Furthermore, the eluotropic sequence of analytes on novel column was in accordance with that in the original column. This suggested that the novel column is a CCC column with auxiliary stationary phase (ASP) in its own right, and the present separation mode is the combination of partition chromatography and adsorption chromatography.

  20. Canada ocean energy atlas phase 1 : potential tidal current energy resources analysis background

    Energy Technology Data Exchange (ETDEWEB)

    Tarbotton, M.; Larson, M. [Triton Consultants Ltd., Vancouver, BC (Canada)

    2006-05-15

    This report was prepared as a background document for a preliminary tidal current resource inventory for Canadian waters. Energy calculations in the study were based on preliminary estimates of known tidal flows. The inventory was based on nautical charts, Canadian sailing directions, tide and tidal current constituent data, and numerical tidal modelling data. A finite element harmonic tidal model tool was used to provide tidal height and current velocities data for a varying number of tidal constituents. The study identified several major tidal current power resources throughout Canada. It was concluded that modelling studies should concentrate on Minas Basin in Nova Scotia; Georgia and Johnstone Straits in British Columbia; and Hudson's Strait and Ungava Bay. Modelling studies should provide estimates of extractable energy as well as provide initial assessments of the environmental impacts of tidal energy extraction in all 3 regions. 3 refs., 8 tabs., 16 figs.

  1. Enhanced Predictive Current Control of Three-Phase Grid-Tied Reversible Converters with Improved Switching Patterns

    Directory of Open Access Journals (Sweden)

    Zhanfeng Song

    2016-01-01

    Full Text Available A predictive current control strategy can realize flexible regulation of three-phase grid-tied converters based on system behaviour prediction and cost function minimization. However, when the predictive current control strategy with conventional switching patterns is adopted, the predicted duration time for voltage vectors turns out to be negative in some cases, especially under the conditions of bidirectional power flows and transient situations, leading to system performance deteriorations. This paper aims to clarify the real reason for this phenomenon under bidirectional power flows, i.e., rectifier mode and inverter mode, and, furthermore, seeks to propose effective solutions. A detailed analysis of instantaneous current variations under different conditions was conducted. An enhanced predictive current control strategy with improved switching patterns was then proposed. An experimental platform was built based on a commercial converter produced by Danfoss, and moreover, relative experiments were carried out, confirming the superiority of the proposed scheme.

  2. Current Limiting Performance of Three-Phase Concentric Transformer Type SFCL at Unbalanced Fault Conditions

    OpenAIRE

    Shirai, Yasuyuki; Noda, Syo; Yamabe, Kenta; Hattori, Keisuke; Baba, Jumpei; Nishihara, Taichi; Nitta, Tanzo; Kobayashi, Shinichi; Sato, Kenichi

    2013-01-01

    We have proposed a transformer type SFCL whose primary and secondary superconducting coils have rewound structure. The primary coil is connected to a power line. The secondary one is short-circuited and has fewer turns than the primary coil. For small fault current, only the secondary coil turns to normal state. Inductive component of impedance at the primary terminal mainly appears. For larger fault current, the primary coil also turns to normal state, resistive component additively appears....

  3. Removal of Direct Current Link Harmonic Ripple in Single Phase Voltage Source Inverter Systems Using Supercapacitors

    Science.gov (United States)

    2016-09-01

    current. In practice , SC bank voltage dropped as low as approximately 5.0 V before the BBC entered DCM and data became invalid. 44 B. LABORATORY...distribution is unlimited 12b. DISTRIBUTION CODE 13. ABSTRACT (maximum 200 words) For an Energy Management System (EMS)-controlled microgrid that... bank as the only DC energy storage device, the DC link voltage ripple causes a second-order harmonic ripple in battery current that leads to a

  4. Prediction of SFL Interruption Performance from the Results of Arc Simulation during High-Current Phase

    Science.gov (United States)

    Lee, Jong-Chul; Lee, Won-Ho; Kim, Woun-Jea

    2015-09-01

    The design and development procedures of SF6 gas circuit breakers are still largely based on trial and error through testing although the development costs go higher every year. The computation cannot cover the testing satisfactorily because all the real processes arc not taken into account. But the knowledge of the arc behavior and the prediction of the thermal-flow inside the interrupters by numerical simulations are more useful than those by experiments due to the difficulties to obtain physical quantities experimentally and the reduction of computational costs in recent years. In this paper, in order to get further information into the interruption process of a SF6 self-blast interrupter, which is based on a combination of thermal expansion and the arc rotation principle, gas flow simulations with a CFD-arc modeling are performed during the whole switching process such as high-current period, pre-current zero period, and current-zero period. Through the complete work, the pressure-rise and the ramp of the pressure inside the chamber before current zero as well as the post-arc current after current zero should be a good criterion to predict the short-line fault interruption performance of interrupters.

  5. Analysis and Minimization of Output Current Ripple for Discontinuous Pulse-Width Modulation Techniques in Three-Phase Inverters

    Directory of Open Access Journals (Sweden)

    Gabriele Grandi

    2016-05-01

    Full Text Available This paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used DPWMs, including positive and negative clamped (DPWM+ and DPWM−, and the four possible combinations between them, usually named as DPWM0, DPWM1, DPWM2, and DPWM3. The maximum and the average values of peak-to-peak current ripple are estimated, and a simple method to correlate the ripple envelope with the ripple rms is proposed and verified. Furthermore, all the results obtained by DPWMs are compared to the centered pulse-width modulation (CPWM, equivalent to the space vector modulation to identify the optimal pulse-width modulation (PWM strategy as a function of the modulation index, taking into account the different average switching frequency. In this way, the PWM technique providing for the minimum output current ripple is identified over the whole modulation range. The analytical developments and the main results are experimentally verified by current ripple measurements with a three-phase PWM inverter prototype supplying an induction motor load.

  6. Analysis of Peak-to-Peak Current Ripple Amplitude in Seven-Phase PWM Voltage Source Inverters

    Directory of Open Access Journals (Sweden)

    Gabriele Grandi

    2013-08-01

    Full Text Available Multiphase systems are nowadays considered for various industrial applications. Numerous pulse width modulation (PWM schemes for multiphase voltage source inverters with sinusoidal outputs have been developed, but no detailed analysis of the impact of these modulation schemes on the output peak-to-peak current ripple amplitude has been reported. Determination of current ripple in multiphase PWM voltage source inverters is important for both design and control purposes. This paper gives the complete analysis of the peak-to-peak current ripple distribution over a fundamental period for multiphase inverters, with particular reference to seven-phase VSIs. In particular, peak-to-peak current ripple amplitude is analytically determined as a function of the modulation index, and a simplified expression to get its maximum value is carried out. Although reference is made to the centered symmetrical PWM, being the most simple and effective solution to maximize the DC bus utilization, leading to a nearly-optimal modulation to minimize the RMS of the current ripple, the analysis can be readily extended to either discontinuous or asymmetrical modulations, both carrier-based and space vector PWM. A similar approach can be usefully applied to any phase number. The analytical developments for all different sub-cases are verified by numerical simulations.

  7. Eddy current pulsed phase thermography considering volumetric induction heating for delamination evaluation in carbon fiber reinforced polymers

    Science.gov (United States)

    Yang, Ruizhen; He, Yunze

    2015-06-01

    Anisotropy and inhomogeneity of carbon fiber reinforced polymers (CFRPs) result in that many traditional non-destructive inspection techniques are inapplicable on the delamination evaluation. This letter introduces eddy current pulsed phase thermography (ECPPT) for CFRPs evaluation considering volumetric induction heating due to small electrical conductivity, abnormal thermal wave propagation, and Fourier analysis. The proposed methods were verified through experimental studies under transmission and reflection modes. Using ECPPT, the influence of the non-uniform heating effect and carbon fiber structures can be suppressed, and then delamination detectability can be improved dramatically over eddy current pulsed thermography.

  8. Control for the Three-Phase Four-Wire Four-Leg APF Based on SVPWM and Average Current Method

    Directory of Open Access Journals (Sweden)

    Xiangshun Li

    2015-01-01

    Full Text Available A novel control method is proposed for the three-phase four-wire four-leg active power filter (APF to realize the accurate and real-time compensation of harmonic of power system, which combines space vector pulse width modulation (SVPWM with triangle modulation strategy. Firstly, the basic principle of the APF is briefly described. Then the harmonic and reactive currents are derived by the instantaneous reactive power theory. Finally simulation and experiment are built to verify the validity and effectiveness of the proposed method. The simulation results show that the response time for compensation is about 0.025 sec and the total harmonic distortion (THD of the source current of phase A is reduced from 33.38% before compensation to 3.05% with APF.

  9. Study of Co-Current and Counter-Current Gas-Liquid Two-Phase Flow Through Packed Bed in Microgravity

    Science.gov (United States)

    Revankar, Shripad T.

    2002-11-01

    The main goal of the project is to obtain new experimental data and development of models on the co-current and counter-current gas-liquid two-phase flow through a packed bed in microgravity and characterize the flow regime transition, pressure drop, void and interfacial area distribution, and liquid hold up. Experimental data will be obtained for earth gravity and microgravity conditions. Models will be developed for the prediction of flow regime transition, void fraction distribution and interfacial area concentration, which are key parameters to characterize the packed bed performance. Thus the specific objectives of the proposed research are to: (1) Develop experiments for the study of the gas liquid two-phase flow through the packed bed with three different flow combinations: co-current down flow, co-current upflow and counter current flow. (2) Develop pore scale and bed scale two-phase instrumentation for measurement of flow regime transition, void distribution and gas-liquid interfacial area concentration in the packed bed. (3) Obtain database on flow regime transition, pressure drop, void distribution, interfacial area concentration and liquid hold up as a function of bed characteristics such as bed particle size, porosity, and liquid properties such as viscosity and surface tension. (4) Develop mathematical model for flow regime transition, void fraction distribution and interfacial area concentration for co-current gas-liquid flow through the porous bed in gravity and micro gravity conditions.(4) Develop mathematical model for the flooding phenomena in counter-current gas-liquid flow through the porous bed in gravity and micro gravity conditions. The present proposal addresses the most important topic of HEDS-specific microgravity fluid physics research identified by NASA 's one of the strategic enterprises, OBPR Enterprise. The proposed project is well defined and makes efficient use of the ground-based parabolic flight research aircraft facility. The

  10. Energy-Regenerative Braking Control of Electric Vehicles Using Three-Phase Brushless Direct-Current Motors

    OpenAIRE

    Bo Long; Shin Teak Lim; Ji Hyoung Ryu; Kil To Chong

    2013-01-01

    Regenerative braking provides an effective way of extending the driving range of battery powered electric vehicles (EVs). This paper analyzes the equivalent power circuit and operation principles of an EV using regenerative braking control technology. During the braking period, the switching sequence of the power converter is controlled to inverse the output torque of the three-phase brushless direct-current (DC) motor, so that the braking energy can be returned to the battery. Compared with ...

  11. Hysteresis Current Control of the Single-Phase Voltage Source Inverter Using eMEGAsim Real-Time Simulator

    Directory of Open Access Journals (Sweden)

    BOTEZAN, A.

    2015-08-01

    Full Text Available The paper presents the hysteresis current control of the voltage source inverter. The eMEGAsim real-time simulator is developed by OPAL-RT. Real-time simulation is used in many cases because it allows the behavior of the industrial processes operation to be determined. Two research directions are developed in this case, Rapid Control Prototyping and Hardware-In-the-Loop. Using eMEGAsim simulator allows implementing the command and control strategy of a single-phase voltage source inverter. At this stage, the real-time behavior of operation is monitored, because the voltage source inverter will be the part of a single-phase shunt active filter. In order to command and control the voltage source inverter, the current and voltage signals are acquired, since these signals are necessary to estimate reference signal. Extension of the Instantaneous Reactive Power Theorem is used because this theorem is suitable for single-phase active filter control. To test the real-time command and control strategy implemented, it was used a low power single-phase voltage source inverter (full bridge.

  12. Comparison of Output Current Ripple in Single and Dual Three-Phase Inverters for Electric Vehicle Motor Drives

    Directory of Open Access Journals (Sweden)

    Jelena Loncarski

    2015-04-01

    Full Text Available The standard solution for the traction system in battery powered electric vehicles (EVs is a two-level (2L inverter feeding a three-phase motor. A simple and effective way to achieve a three-level (3L inverter in battery-supplied electric vehicles consists of using two standard three-phase 2L inverters with the open-end winding connection of standard three-phase ac motors. The 3L inverter solution can be usefully adopted in EVs since it combines several benefits such as current ripple reduction, increment of phase motor voltage with limited voltage ratings of the two battery banks, improvement in system reliability, etc. The reduction in current ripple amplitude is particularly relevant since it is a source of electromagnetic interference and audio noise from the inverter-motor power connection cables and from the motor itself. By increasing the inverter switching frequency the ripple amplitude is reduced, but the drive efficiency decreases due to the proportionally increased switching losses. In this paper the peak-to-peak ripple amplitude of the dual-2L inverter is evaluated and compared with the corresponding ripple of the single-2L inverter, considering the same voltage and power motor ratings. The ripple analysis is carried out as a function of the modulation index to cover the whole modulation range of the inverter, and the theoretical results are verified with experimental tests carried out by an inverter-motor drive prototype.

  13. Adaptive Hysteresis Band Current Control for Transformerless Single-Phase PV Inverters

    DEFF Research Database (Denmark)

    Vázquez, Gerardo; Rodriguez, Pedro; Ordoñez, Rafael

    2009-01-01

    Current control based on hysteresis algorithms are widely used in different applications, such as motion control, active filtering or active/reactive power delivery control in distributed generation systems. The hysteresis current control provides to the system a fast and robust dynamic response......, and requires a simple implementation in standard digital signal platforms. On the other hand, the main drawback of classical hysteresis current control lies in the fact that the switching frequency is variable, as the hysteresis band is fixed. In this paper a variable band hysteresis control algorithm...... will be presented. As it will be shown, this variable band permits overcoming the aforementioned problem giving rise to an almost constant switching frequency. The performance of this algorithm, together with classical hysteresis controls and proportional resonant (PR) controllers, has been evaluated in three...

  14. Application of PI Current Controller in Single Phase Inverter System Connected to Non Linear Load

    Science.gov (United States)

    Chai Anak Ajot, Tracy; Salimin, Suriana; Aziz, Roziah

    2017-08-01

    This study is concerned with the problem of network power quality when inverter systems are connected to a nonlinear load. Nonlinear loads are well known as one of the biggest source of harmonics in the power system. Besides that, inverter systems also have their nonlinearity characteristic because of the electronic components. As the inverter system is connected to nonlinear load, it resulting in harmonic distortion-related problem and draw non-sinusoidal currents in the system, thus reducing the power quality in the system. The application of Proportional Integral controller in this system is the main interest of this study. This current controller capable of reducing total harmonic distortion and improve the state of current waveform. This paper focuses on application of simple manual trial and error tuning technique to produce the optimum value for the gains. The result of study verifies the trial and error manual tuning of PI current controller in compensating harmonic distortions. Simulation and modelling of the system are successfully developed using Matlab/Simulink.

  15. Turbidity current flow over an obstacle and phases of sediment wave generation

    CERN Document Server

    Strauss, Moshe

    2011-01-01

    We study the flow of particle-laden turbidity currents down a slope and over an obstacle. A high-resolution 2D computer simulation model is used, based on the Navier-Stokes equations. It includes poly-disperse particle grain sizes in the current and substrate. Particular attention is paid to the erosion and deposition of the substrate particles, including application of an active layer model. Multiple flows are modeled from a lock release that can show the development of sediment waves (SW). These are stream-wise waves that are triggered by the increasing slope on the downstream side of the obstacle. The initial obstacle is completely erased by the resuspension after a few flows leading to self consistent and self generated SW that are weakly dependant on the initial obstacle. The growth of these waves is directly related to the turbidity current being self sustaining, that is, the net erosion is more than the net deposition. Four system parameters are found to influence the SW growth: (1) slope, (2) current ...

  16. ADVANCED SIMULATION CAPABILITY FOR ENVIRONMENTAL MANAGEMENT- CURRENT STATUS AND PHASE II DEMONSTRATION RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, R.

    2013-02-26

    The U.S. Department of Energy (USDOE) Office of Environmental Management (EM), Office of Soil and Groundwater, is supporting development of the Advanced Simulation Capability for Environmental Management (ASCEM). ASCEM is a state-of-the-art scientific tool and approach for understanding and predicting contaminant fate and transport in natural and engineered systems. The modular and open source high-performance computing tool facilitates integrated approaches to modeling and site characterization that enable robust and standardized assessments of performance and risk for EM cleanup and closure activities. The ASCEM project continues to make significant progress in development of computer software capabilities with an emphasis on integration of capabilities in FY12. Capability development is occurring for both the Platform and Integrated Toolsets and High-Performance Computing (HPC) Multiprocess Simulator. The Platform capabilities provide the user interface and tools for end-to-end model development, starting with definition of the conceptual model, management of data for model input, model calibration and uncertainty analysis, and processing of model output, including visualization. The HPC capabilities target increased functionality of process model representations, toolsets for interaction with Platform, and verification and model confidence testing. The Platform and HPC capabilities are being tested and evaluated for EM applications in a set of demonstrations as part of Site Applications Thrust Area activities. The Phase I demonstration focusing on individual capabilities of the initial toolsets was completed in 2010. The Phase II demonstration completed in 2012 focused on showcasing integrated ASCEM capabilities. For Phase II, the Hanford Site deep vadose zone (BC Cribs) served as an application site for an end-to-end demonstration of capabilities, with emphasis on integration and linkages between the Platform and HPC components. Other demonstrations

  17. The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

    Indian Academy of Sciences (India)

    S. D. Bao; G. X. Ai; H. Q. Zhang

    2000-09-01

    We compute the signs of two different current helicity parameters (i.e., best and ) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative best and 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameter shows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

  18. Study for the electric arc of alternative current at the single phase welding machine using the Matlab/Simulink environment

    Science.gov (United States)

    Baciu, I.; Ghiormez, L.; Vasar, C.

    2017-01-01

    In this paper is presented a mathematical model of the electric arc for an alternative current welding machine of low power. The electric arc model is based on dividing the voltage-current characteristic of the electric arc in many functioning zones. For the model of the entire welding machine are used real parameters as the ones of the proper welding machine. The voltage and current harmonics spectrum that is obtained during the welding process is presented. Also, the waveforms for the current and voltage of the electric arc plotted against time and the voltage-current characteristic of the electric arc are illustrated. The electric arc is considered as being supplied by alternative voltage from the electrical power network using a single phase transformer which has the output voltage of 80 volts. The model of the welding machine is developed in Simulink and the variations of some parameters of the electric arc are obtained by modifying of them in a Matlab function. Also, in this paper is presented the total harmonic distortion for the voltage and current of the electric arc obtained during simulation of the welding machine.

  19. Current mode pulse width modulation/pulse position modulation based on phase lock loop

    Science.gov (United States)

    Wisartpong, Pichet; Silaphan, Vorapong; Kurutach, Sunee; Wardkein, Paramote

    2017-05-01

    In this paper, the fully integrated CMOS current mode PLL with current input injects at the place of input or output of the loop filter without summing amplifier circuit. It functions as PPM and PWM circuit is present. In addition, its frequency response is an analysis which electronic tuning BPF and LPF are obtained. The proposed circuit has been designed with 0.18 μm CMOS technology. The simulation results of this circuit can be operated at 2.5 V supply voltage, at center frequency 100 MHz. The linear range of input current can be adjusted from 43 μA to 109 μA, and the corresponding duty cycle of pulse width output is from 93% to 16% and the normalized pulse position is from 0.93 to 0.16. The power dissipation of this circuit is 4.68 mW with the total chip area is 28 μm × 60 μm.

  20. Reduction of RESET current in phase change memory devices by carbon doping in GeSbTe films

    Science.gov (United States)

    Park, J. H.; Kim, S.-W.; Kim, J. H.; Wu, Z.; Cho, S. L.; Ahn, D.; Ahn, D. H.; Lee, J. M.; Nam, S. U.; Ko, D.-H.

    2015-03-01

    Phase Change Memory (PCM) has been proposed for use as a substitute for flash memory to satisfy the huge demands for high performance and reliability that promise to come in the next generation. In spite of its high scalability, reliability, and simple structure, high writing current, e.g., RESET current, has been a significant obstacle to achieving a high density in storage applications and the low power consumption required for use in mobile applications. We report herein on an attempt to determine the level of carbon incorporated into a GeSbTe (GST) film that is needed to reduce the RESET current of PCM devices. The crystal structure of the film was transformed into an amorphous phase by carbon doping, the stability of which was enhanced with increasing carbon content. This was verified by the small grain size and large band gap that are typically associated with carbon. The increased level of C-Ge covalent bonding is responsible for these enhancements. Thus, the resistance of the carbon doped Ge2Sb2Te5 film was higher than that for an undoped GST film by a factor of 2 orders of magnitude after producing a stable face-centered cubic phase by annealing. As a consequence, the PCM devices showed a significant reduction in RESET current as low as 23% when the carbon content was increased to 11.8 at. %. This can be attributed to the elevated SET resistance, which is proportional to the dynamic resistance of the PCM device, caused by the high resistance due to a carbon doped GST film.

  1. CONCEPTUAL ANALYSIS OF THE CURRENT PHASE DEVELOPMENT OF RELATIONS BETWEEN RUSSIA AND ISRAEL

    Directory of Open Access Journals (Sweden)

    Yuri B. Bocharov

    2013-01-01

    Full Text Available The article dedicated to analysis of Russian-Israeli international business relations by using of all the arsenal of modern methods. The article investigates the possibility of using the geo-political, geo-economic and geo-cultural approaches to definition of optimal ways of relations between the two countries' development. It demonstrates that due to the historical and cultural features of the nature of relations between those two countries, geo-cultural approach is more preferable. Also, the article shows that this approach of the analysis is not often used for the analysis of relations of Russia with other countries. The geo-cultural approach of analysis had used for elaboration of suggestions of new phase of development of business relations between Russia and Israel.

  2. Current Methodologies and Implications of Phase Identification of the Vertical Jump: A Systematic Review and Meta-analysis.

    Science.gov (United States)

    Eagles, Alexander Neale; Sayers, Mark Gregory Leigh; Bousson, Matthew; Lovell, Dale Ingham

    2015-09-01

    The vertical jump (VJ) is considered a key indicator of lower limb explosive strength. Previous research has established that rate of force development and time to peak force are linked closely to athletic ability and hence the ability to extract these accurately is of significance. The objectives of this study were to (1) review the literature to ascertain what methods are currently used to extract jump phases from the force platform data and (2) compare identified methods on neutral data. In Part 1, an electronic search was conducted using PubMed, Central, and EBSCO host (January 1965 to April 2014). Articles were included if they (1) detailed how VJ phases from the force platform data were identified and (2) used only force platform data in the analysis. Additionally, study design and quality was independently examined. In Part 2, the three common methodologies identified were used to analyze a neutral pool of data to determine if any variance existed. For Part 1, a total of 19 studies met the inclusion criteria. Meta-analysis determined three methods of phase identification used in the literature from which to extract force-time variables. In Part 2, a one-way analysis of variance and Scheffe's post-hoc tests showed significant differences (p < 0.01) for force-time variables (eccentric phase time, concentric phase time, time to peak force, rate of force development) between methods. The results demonstrate that three common methods exist for determination of the VJ phases from force platform data. Consequently, each produce different values for force-time variables when used on a neutral data pool. There is a clear need for a robust agreed method for VJ analysis.

  3. CO2 capture technologies: current status and new directions using supported ionic liquid phase (SILP) absorbers

    DEFF Research Database (Denmark)

    Kolding, Helene; Fehrmann, Rasmus; Riisager, Anders

    2012-01-01

    Current state-of-the-art techniques for CO2 capture are presented and discussed. Post-combustion capture of CO2 by absorption is the technology most easily retrofitted to existing installations, but at present this is not economically viable to install and run. Using ionic liquids instead...... candidate for CO2 absorption using SILP technology. Thus a solid SILP absorber comprised of 40 wt% [N6666][Pro] loaded on precalcined silica quantitatively takes up about 1.2 mole CO2 per mole of ionic liquid in consecutive absorption-desorption cycles in a flow-experiment performed with 0.09 bar of CO2 (9......% CO2 in He)....

  4. CO2 capture technologies: current status and new directions using supported ionic liquid phase (SILP) absorbers

    DEFF Research Database (Denmark)

    Kolding, Helene; Fehrmann, Rasmus; Riisager, Anders

    2012-01-01

    Current state-of-the-art techniques for CO2 capture are presented and discussed. Post-combustion capture of CO2 by absorption is the technology most easily retrofitted to existing installations, but at present this is not economically viable to install and run. Using ionic liquids instead...... candidate for CO2 absorption using SILP technology. Thus a solid SILP absorber comprised of 40 wt% [N6666][Pro] loaded on precalcined silica quantitatively takes up about 1.2 mole CO2 per mole of ionic liquid in consecutive absorption-desorption cycles in a flow-experiment performed with 0.09 bar of CO2 (9......% CO2 in He)....

  5. Phase development and critical current density of Bi-2223 tapes fabricated by groove rolling

    Science.gov (United States)

    Iyer, A. N.; Salib, S.; Vipulanandan, C.; Salama, K.; Balachandran, U.

    1999-07-01

    The powder-in-tube technique is the most widely used method for fabricating silver-clad Bi-2223 wires and tapes. In this method the silver billet containing the precursor material is transformed to the final shape using metallurgical deformation techniques such as wire drawing and flat rolling. In the present study, a modified version of the powder-in-tube technique was adopted where the silver billet was reduced in size by groove rolling instead of wire drawing. Microstructural analysis during the initial deformation stage revealed crack formation in the superconductor core. Stress conditions during groove rolling were analysed and appropriate changes were incorporated in the deformation process. After groove rolling the wires were flat rolled to a final thickness of 250 icons/Journals/Common/mu" ALT="mu" ALIGN="TOP"/>m. Subsequent thermomechanical treatment resulted in tapes with critical current density of icons/Journals/Common/approx" ALT="approx" ALIGN="TOP"/>19700 A cm-2 (critical current of icons/Journals/Common/approx" ALT="approx" ALIGN="TOP"/>40 A).

  6. Impact of Neutral Point Current Control on Copper Loss Distribution of Five Phase PM Generators Used in Wind Power Plants

    Directory of Open Access Journals (Sweden)

    ARASHLOO, R. S.

    2014-05-01

    Full Text Available Efficiency improvement under faulty conditions is one of the main objectives of fault tolerant PM drives. This goal can be achieved by increasing the output power while reducing the losses. Stator copper loss not only directly affects the total efficiency, but also plays an important role in thermal stress generations of iron core. In this paper, the effect of having control on neutral point current is studied on the efficiency of five-phase permanent magnet machines. Open circuit fault is considered for both one and two phases, and the distribution of copper loss along the windings are evaluated in each case. It is shown that only by having access to neutral point, it is possible to generate less stator thermal stress and more mechanical power in five-phase permanent magnet generators. Wind power generation and their applications are kept in mind, and the results are verified via simulations and experimental tests on an outer-rotor type of five-phase PM machine.

  7. An Optimal PR Control Strategy with Load Current Observer for a Three-Phase Voltage Source Inverter

    Directory of Open Access Journals (Sweden)

    Xiaobo Dou

    2015-07-01

    Full Text Available Inverter voltage control is an important task in the operation of a DC/AC microgrid system. To improve the inverter voltage control dynamics, traditional approaches attempt to measure and feedforward the load current, which, however, needs remote measurement with communications in a microgrid system with distributed loads. In this paper, a load current observer (LCO based control strategy, which does not need remote measurement, is proposed for sinusoidal signals tracking control of a three-phase inverter of the microgrid. With LCO, the load current is estimated precisely, acting as the feedforward of the dual-loop control, which can effectively enlarge the stability margin of the control system and improve the dynamic response to load disturbance. Furthermore, multiple PR regulators are applied in this strategy conducted in a stationary  frame to suppress the transient fluctuations and the total harmonic distortion (THD of the output voltage and achieve faster transient performance compared with traditional dual-loop control in a rotating dq0 frame under instantaneous change of various types of load (i.e., balanced load, unbalanced load, and nonlinear load. The parameters of multiple PR regulators are analyzed and selected through the root locus method and the stability of the whole control system is evaluated and analyzed. Finally, the validity of the proposed approach is verified through simulations and a three-phase prototype test system with a TMS320F28335 DSP.

  8. Simulating the Thinning Magnetotail Current Sheet During a Substorm Growth Phase with the Rice Convection Model-Equilibrium

    Science.gov (United States)

    Lemon, C. L.; Crabtree, C. E.; Chen, M.; Guild, T. B.

    2015-12-01

    Modeling the progression of the magnetotail configuration during a substorm growth phase is challenging because the current sheet becomes very thin, and is difficult to resolve while keeping the problem computationally tractable. Magnetohydrodynamics (MHD) models have dealt with this problem in various ways, and many claim to be driven by physical rather than numerical considerations. The Rice Convection Model-Equilibrium (RCM-E) is not an MHD model, and has advantages and disadvantages compared to MHD. The notable advantages are the characterization of the full energy distribution of the plasma (including the associated gradient/curvature drift), as well as its generally more comprehensive treatment of the electrodynamics of magnetosphere-ionosphere coupling. The disadvantages include the bounce-averaging of plasma drift, which limits the domain to closed field lines, and the assumption of slow flow relative to the Alfvén speed. The RCM-E has been used in the past to model a substorm growth phase, but its assumptions do not allow it to properly treat the onset mechanism or the formation of x-lines. It can simulate the approach to onset, but is limited by its ability to resolve the thinning current sheet. In this presentation, we present advances in the technique used to calculate the self-consistent magnetic field, which allows us to resolve thinner current sheets than were previously possible. We combine this with a generalized ballooning mode analysis of specific flux tubes in order to assess the stability of the magnetotail to substorm onset.

  9. A Current-Forced Line-Commutated Inverter for Single-Phase Grid-Connected Photovoltaic Generation Systems

    Directory of Open Access Journals (Sweden)

    UNLU, M.

    2015-05-01

    Full Text Available A simple power electronic interface based on the line-commutated inverter (LCI has been developed in order to inject sinusoidal current to the grid for single-phase grid-connected photovoltaic (PV energy generation systems. The proposed inverter facilitates controlling the injecting/grid current with a controllable power factor in contrast to the conventional LCI system. It is achieved that the total harmonic distortion (THD of the injecting currents for the different firing angles/power factors and reference currents is about 5% or less than 5%. Thus, the grid-connected standards for injecting current are satisfied without filter equipment unlike the conventional LCI system. The proposed system has been built in MATLAB/Simulink and examined experimentally on PV array of 160 W. The simulation and experimental results are better performance than the conventional line-commutated inverter methods reported in the literature. The proposed LCI has a simple and robust structure, and it can be easily synchronized with grid thanks to self-latching property of SCRs. Therefore, it is a good alternative for the power transferring from PV panels to the utility grid in grid-connected PV systems.

  10. GPS phase scintillation during the geomagnetic storm of March 17, 2015: The relation to auroral electrojet currents

    DEFF Research Database (Denmark)

    Prikryl, Paul; Ghoddousi-Fard, Reza; Connors, Martin

    and magnetometers. GPS phase scintillation index is computed for L1 signal sampled at the rate of 50 Hz by specialized GPS scintillation receivers of the Expanded Canadian High Arctic Ionospheric Network (ECHAIN). To further extend the geographic coverage, the phasescintillation proxy index is obtained from......-enhanced plasma density (SED) and in the auroral oval during energetic particle precipitation events, substorms and pseudo-breakups in particular. In this paper we examine the relation to auroral electrojet currents observed by arrays of ground-based magnetometers and energetic particle precipitation observed......Ionospheric irregularities cause rapid fluctuations of radio wave amplitude and phase that candegrade GPS positional accuracy and affect performance of radio communication and navigation systems. The ionosphere becomes particularly disturbed during geomagnetic storms caused by impacts of coronal...

  11. Feasibility study of current pulse induced 2-bit/4-state multilevel programming in phase-change memory

    Science.gov (United States)

    Liu, Yan; Fan, Xi; Chen, Houpeng; Wang, Yueqing; Liu, Bo; Song, Zhitang; Feng, Songlin

    2017-08-01

    In this brief, multilevel data storage for phase-change memory (PCM) has attracted more attention in the memory market to implement high capacity memory system and reduce cost-per-bit. In this work, we present a universal programing method of SET stair-case current pulse in PCM cells, which can exploit the optimum programing scheme to achieve 2-bit/ 4state resistance-level with equal logarithm interval. SET stair-case waveform can be optimized by TCAD real time simulation to realize multilevel data storage efficiently in an arbitrary phase change material. Experimental results from 1 k-bit PCM test-chip have validated the proposed multilevel programing scheme. This multilevel programming scheme has improved the information storage density, robustness of resistance-level, energy efficient and avoiding process complexity.

  12. Comparison of the quench and fault current limiting characteristics of the flux-coupling type SFCL with single and three-phase transformer

    Science.gov (United States)

    Jung, Byung Ik; Cho, Yong Sun; Park, Hyoung Min; Chung, Dong Chul; Choi, Hyo Sang

    2013-01-01

    The South Korean power grid has a network structure for the flexible operation of the system. The continuously increasing power demand necessitated the increase of power facilities, which decreased the impedance in the power system. As a result, the size of the fault current in the event of a system fault increased. As this increased fault current size is threatening the breaking capacity of the circuit breaker, the main protective device, a solution to this problem is needed. The superconducting fault current limiter (SFCL) has been designed to address this problem. SFCL supports the stable operation of the circuit breaker through its excellent fault-current-limiting operation [1-5]. In this paper, the quench and fault current limiting characteristics of the flux-coupling-type SFCL with one three-phase transformer were compared with those of the same SFCL type but with three single-phase transformers. In the case of the three-phase transformers, both the superconducting elements of the fault and sound phases were quenched, whereas in the case of the single-phase transformer, only that of the fault phase was quenched. For the fault current limiting rate, both cases showed similar rates for the single line-to-ground fault, but for the three-wire earth fault, the fault current limiting rate of the single-phase transformer was over 90% whereas that of the three-phase transformer was about 60%. It appears that when the three-phase transformer was used, the limiting rate decreased because the fluxes by the fault current of each phase were linked in one core. When the power loads of the superconducting elements were compared by fault type, the initial (half-cycle) load was great when the single-phase transformer was applied, whereas for the three-phase transformer, its power load was slightly lower at the initial stage but became greater after the half fault cycle.

  13. Compact ASD Topologies for Single-Phase Integrated Motor Drives with Sinusoidal Input Current

    DEFF Research Database (Denmark)

    Klumpner, Christian; Blaabjerg, Frede; Thoegersen, Paul

    2005-01-01

    A standard configuration of an Adjustable Speed Drive (ASD) consists of two separate units: an AC motor, which runs with fixed speed when it is supplied from a constant frequency grid voltage and a frequency converter, which is used to provide the motor with variable voltage-variable frequency...... needed to adjust the speed of the motor. The integrated motor drive concept is a result of merging the two units in order to achieve the following benefits [1-3]: reducing the design and the commissioning time in complex industrial equipments, no need for a cabinet to host the frequency converter......, no needfor shielded cables to reduce EM1 (Electro Magnetic Inteiference), no needfor cables for the speed transducers or for other sensorsfor industrial process control (e.g. pressure). This solution is currently available up to 7.5 kW being not used in the medium and high power range due to a low...

  14. Influence of tube voltage and current on in-line phase contrast imaging using a microfocus x-ray source

    Institute of Scientific and Technical Information of China (English)

    Li Zheng; Yu Ai-Min; Li Cheng-Quan

    2007-01-01

    In-line x-ray phase contrast imaging has attracted much attention due to two major advantages:its effectiveness in imaging weakly absorbing materials,and the simplicity of its facilities.In this paper a comprehensive theory based on Wigner distribution developed by Wu and Liu [Med.Phys.31 2378-2384(2004)] is reviewed.The influence of x-ray source and detector on the image is discussed.Experiments using a microfocus x-ray source and a CCD detector are conducted,which show the role of two key factors on imaging:the tube voltage and tube current.High tube current and moderate tube voltage are suggested for imaging.

  15. Energy-Regenerative Braking Control of Electric Vehicles Using Three-Phase Brushless Direct-Current Motors

    Directory of Open Access Journals (Sweden)

    Bo Long

    2013-12-01

    Full Text Available Regenerative braking provides an effective way of extending the driving range of battery powered electric vehicles (EVs. This paper analyzes the equivalent power circuit and operation principles of an EV using regenerative braking control technology. During the braking period, the switching sequence of the power converter is controlled to inverse the output torque of the three-phase brushless direct-current (DC motor, so that the braking energy can be returned to the battery. Compared with the presented methods, this technology can achieve several goals: energy recovery, electric braking, ultra-quiet braking and extending the driving range. Merits and drawbacks of different braking control strategy are further elaborated. State-space model of the EVs under energy-regenerative braking operation is established, considering that parameter variations are unavoidable due to temperature change, measured error, un-modeled dynamics, external disturbance and time-varying system parameters, a sliding mode robust controller (SMRC is designed and implemented. Phase current and DC-link voltage are selected as the state variables, respectively. The corresponding control law is also provided. The proposed control scheme is compared with a conventional proportional-integral (PI controller. A laboratory EV for experiment is setup to verify the proposed scheme. Experimental results show that the drive range of EVs can be improved about 17% using the proposed controller with energy-regeneration control.

  16. Scorpion toxin prolongs an inactivation phase of the voltage-dependent sodium current in rat isolated single hippocampal neurons.

    Science.gov (United States)

    Kaneda, M; Oyama, Y; Ikemoto, Y; Akaike, N

    1989-05-15

    The effects of scorpion toxin on the voltage-dependent sodium current (INa) of CA1 pyramidal neurons isolated from rat hippocampus were studied under the single-electrode voltage-clamp condition using a 'concentration-clamp' technique. The toxin increased the peak amplitude of INa and prolonged its inactivation phase in a time- and dose-dependent manner. Inactivation phase of INa proceeded with two exponential components in the absence (control) and presence of the toxin. In the toxin-treated neurons, both the time constant of slow component and its fractional contribution to the total current increased dose-dependently while the fractional contribution of the fast one decreased in a dose-dependent fashion without changing its time constant. Actions of scorpion toxin on the sodium channels of hippocampal pyramidal neurons were essentially similar to those of peripheral preparations. Therefore, it can be concluded that the sodium channels of mammalian brain neurons have structures and functions similar to peripheral channels.

  17. Total Eddy Currents Induced in Screens of a Symmetrical Three-Phase Single-Pole Gas-Insulated Transmission Line (GIL

    Directory of Open Access Journals (Sweden)

    Zygmunt Piatek

    2008-01-01

    Full Text Available In the paper we discuss the question of eddy currents induced in screens of a symmetrical three-phase singlepole gas-insulated transmission line (GIL. First, we determine the eddy currents induced in the tubular screen by the magnetic field of self-current of the phase conductor. Then the magnetic field in the external parallel phase conductor is presented by means of a vector magnetic potential as Fourrier series. In the non-conducting external and internal area of the screen we use Laplace equation for the magnetic field strength taking into account the reverse reaction of eddy currents induced in the screen. In the conducting screen we apply Helmholtz equation for eddy currents density. Using classical boundary conditions we determine the density of the currents. The solutions obtained are used to determine the total eddy currents induced in all the screens of the GIL under consideration.

  18. Holistic Investigation of Corona Discharge: Impulse Current Waveform and Phase-resolved Measurement, Analysis and Simulation%Holistic Investigation of Corona Discharge: Impulse Current Waveform and Phase-resolved Measurement, Analysis and Simulation

    Institute of Scientific and Technical Information of China (English)

    Suwarno

    2011-01-01

    Partial discharge(PD) is one of the most important phenomenon in high voltage insulations. In most cases, the appearance of partial discharges is related to insulation defects. Understanding partial discharges is important for diagnosis on insulation condition. Corona discharges appear when extremely high electric field appears on the conductor surface exceeding the electric field strength of the gas. The high electric field may occur at around protrusion with very sharp tip. This paper reported a holistic approach of corona discharge investigation. The needle--plane electrode system was used. The medium between the electrodes was air. The needle was made from steel with radius of curvature of 3 μm (Ogura needle). Sinusoidal as well as triangular applied voltages were used. The waveform of the corona discharges was measured using a digital oscilloscope. The corona discharge pulses were measured using a phase--re- solved PD measurement system. The system was able to measure the magnitude (q) and phase angle position (9) of each PD pulses, as well as the number of discharge pulses (n). The role of applied voltage was investigated using phase--resolved analysis of corona discharge pulses through pulse sequence, pulse magnitude and pulse number analy- sis. Experimental results indicated that corona discharge current waveform was an impulse with rise time of about several ns and the impulse width of about 100 ns. The Fast Fourier Transform analysis indicated that the corona discharge current waveform had several spectrum peaks at frequency of 7.8 MHz, 85.9 MHz, 109.4 MHz and 195.3 MHz. The experimental results also showed that discharge pulses were concentrated around the peak of applied voltage for both sinusoidal and triangular voltages. The discharge magnitude, as well as its probability of occurrence, was strongly dependent on the instantaneous applied voltage. The shape of φn, as well as φ-q-n PD patterns, were strongly reflected by the shape

  19. Three-Phase High-Power and Zero-Current-Switching OBC for Plug-In Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Cheng-Shan Wang

    2015-06-01

    Full Text Available In this paper, an interleaved high-power zero-current-switching (ZCS onboard charger (OBC based on the three-phase single-switch buck rectifier is proposed for application to plug-in electric vehicles (EVs. The multi-resonant structure is used to achieve high efficiency and high power density, which are necessary to reduce the volume and weight of the OBC. This study focuses on the border conditions of ZCS converting with a battery load, which means the variation ranges of the output voltage and current are very large. Furthermore, a novel hybrid control method combining pulse frequency modulation (PFM and pulse width modulation (PWM together is presented to ensure a driving frequency higher than 10 kHz, and this will reduce the unexpected inner resonant power flow and decrease the total harmonic distortion (THD of the input current under a light load at the end of the charging process. Finally, a prototype is established, and experiments are carried out. According to the experimental results, the conversion efficiency is higher than 93.5%, the THD about 4.3% and power factor (PF 0.98 under the maximum power output condition. Besides, a three-stage charging process is also carried out the experimental platform.

  20. A three-phase current-fed dc/dc converter with a three-leg high frequency transformer for fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Hanju [Department of Electrical Engineering, Chungnam National University, 220 Gung-dong Yuseong-gu, Daejeon 305-764 (Korea); Choi, Jungwan [National Fusion Research Institute, Daejeon (Korea); Enjeti, Prasad [Texas A and M University, College Station, TX 77843-3128 (United States)

    2008-07-15

    In this paper, a three-phase current-fed dc/dc converter with an active clamp is introduced, and a new three-phase three-leg high frequency transformer is proposed for the converter. The three-phase dc/dc converter transfers power through transformer leakage inductances in the discontinuous current mode; a single common active clamp branch is employed for zero-voltage switching (ZVS) in all active switches. Further, the converter's three-phase power configuration increases power transfer, and it reduces the rms current per phase, thus reduces conduction losses. Moreover, a delta-delta connection on the three-phase transformer provides parallel current paths and reduces conduction losses in the transformer windings. A three-phase transformer can be constructed by connecting three discrete single-phase transformers, but this process results in a higher volume and higher material costs. Therefore, a new three-phase three-leg high frequency transformer is designed with three discrete cores integrated into a single transformer core. The proposed transformer is analyzed according to the several operating modes of the converter, and its design rules are determined. Experimental results are obtained on a 500-W prototype unit; the design is fully verified and analyzed. (author)

  1. Degradation of Li/S Battery Electrodes On 3D Current Collectors Studied Using X-ray Phase Contrast Tomography.

    Science.gov (United States)

    Zielke, L; Barchasz, C; Waluś, S; Alloin, F; Leprêtre, J-C; Spettl, A; Schmidt, V; Hilger, A; Manke, I; Banhart, J; Zengerle, R; Thiele, S

    2015-06-04

    Lithium/sulphur batteries are promising candidates for future energy storage systems, mainly due to their high potential capacity. However low sulphur utilization and capacity fading hinder practical realizations. In order to improve understanding of the system, we investigate Li/S electrode morphology changes for different ageing steps, using X-ray phase contrast tomography. Thereby we find a strong decrease of sulphur loading after the first cycle, and a constant loading of about 15% of the initial loading afterwards. While cycling, the mean sulphur particle diameters decrease in a qualitatively similar fashion as the discharge capacity fades. The particles spread, migrate into the current collector and accumulate in the upper part again. Simultaneously sulphur particles lose contact area with the conducting network but regain it after ten cycles because their decreasing size results in higher surface areas. Since the capacity still decreases, this regain could be associated with effects such as surface area passivation and increasing charge transfer resistance.

  2. Phase, current, absorbance, and photoluminescence of double and triple metal ion-doped synthetic and salmon DNA thin films

    Science.gov (United States)

    Chopade, Prathamesh; Reddy Dugasani, Sreekantha; Reddy Kesama, Mallikarjuna; Yoo, Sanghyun; Gnapareddy, Bramaramba; Lee, Yun Woo; Jeon, Sohee; Jeong, Jun-Ho; Park, Sung Ha

    2017-10-01

    We fabricated synthetic double-crossover (DX) DNA lattices and natural salmon DNA (SDNA) thin films, doped with 3 combinations of double divalent metal ions (M2+)-doped groups (Co2+–Ni2+, Cu2+–Co2+, and Cu2+–Ni2+) and single combination of a triple M2+-doped group (Cu2+–Ni2+–Co2+) at various concentrations of M2+ ([M2+]). We evaluated the optimum concentration of M2+ ([M2+]O) (the phase of M2+-doped DX DNA lattices changed from crystalline (up to ([M2+]O) to amorphous (above [M2+]O)) and measured the current, absorbance, and photoluminescent characteristics of multiple M2+-doped SDNA thin films. Phase transitions (visualized in phase diagrams theoretically as well as experimentally) from crystalline to amorphous for double (Co2+–Ni2+, Cu2+–Co2+, and Cu2+–Ni2+) and triple (Cu2+–Ni2+–Co2+) dopings occurred between 0.8 mM and 1.0 mM of Ni2+ at a fixed 0.5 mM of Co2+, between 0.6 mM and 0.8 mM of Co2+ at a fixed 3.0 mM of Cu2+, between 0.6 mM and 0.8 mM of Ni2+ at a fixed 3.0 mM of Cu2+, and between 0.6 mM and 0.8 mM of Co2+ at fixed 2.0 mM of Cu2+ and 0.8 mM of Ni2+, respectively. The overall behavior of the current and photoluminescence showed increments as increasing [M2+] up to [M2+]O, then decrements with further increasing [M2+]. On the other hand, absorbance at 260 nm showed the opposite behavior. Multiple M2+-doped DNA thin films can be used in specific devices and sensors with enhanced optoelectric characteristics and tunable multi-functionalities.

  3. Phase-field modeling of switchable diode-like current-voltage characteristics in ferroelectric BaTiO3

    Science.gov (United States)

    Cao, Y.; Shen, J.; Randall, C. A.; Chen, L. Q.

    2014-05-01

    A self-consistent model has been proposed to study the switchable current-voltage (I-V) characteristics in Cu/BaTiO3/Cu sandwiched structure combining the phase-field model of ferroelectric domains and diffusion equations for ionic/electronic transport. The electrochemical transport equations and Ginzburg-Landau equations are solved using the Chebyshev collocation algorithm. We considered a single parallel plate capacitor configuration which consists of a single layer BaTiO3 containing a single tetragonal domain orientated normal to the plate electrodes (Cu) and is subject to a sweep of ac bias from -1.0 to 1.0 V at 25 °C. Our simulation clearly shows rectifying I-V response with rectification ratios amount to 102. The diode characteristics are switchable with an even larger rectification ratio after the polarization direction is flipped. The effects of interfacial polarization charge, dopant concentration, and dielectric constant on current responses were investigated. The switchable I-V behavior is attributed to the polarization bound charges that modulate the bulk conduction.

  4. Single-step metal-organic vapor-phase diffusion for low-dark-current planar-type avalanche photodiodes

    Science.gov (United States)

    Jun, Dong-Hwan; Jeong, Hae Yong; Kim, Youngjo; Shin, Chan-Soo; Park, Kyung Ho; Park, Won-Kyu; Kim, Min-Su; Kim, Sangin; Han, Sang Wook; Moon, Sung

    2016-10-01

    In this paper, a p-type diffusion process based literally on single-step metal-organic vapor-phase diffusion (MOVPD) employing diethyl zinc as the diffusion source in combination with the recessetching technique is developed to improve the dark-current characteristics of planar-type avalanche photodiodes (APDs). The developed single-step MOVPD process exhibits on excellent linear relationship between the diffusion depth and the square root of the diffusion time, which mainly results from maintaining constant source diffusion. The single-step MOVPD process without any additional thermal activation process achieves a surface doping concentration of 1.9 × 1018 cm -3, which is sufficient to form ohmic contact. The measured diffusion profiles of the APDs clearly reveal the presence of a two-dimensional diffusion front formed by the recess-etched and guard-ring regions. The impact of this p-type diffusion process on the performance of the APD devices has also been demonstrated by exhibiting improved dark-current characteristics for the fabricated APDs.

  5. Theory and experiments on RF plasma heating, current drive and profile control in TORE SUPRA

    Energy Technology Data Exchange (ETDEWEB)

    Moreau, D.

    1994-01-01

    This paper reviews the main experimental and theoretical achievements related to the study of RF heating and non-inductive current drive and particularly phenomena related to the current density profile control and the potentiality of producing stationary enhanced performance regimes: description of the Lower Hybrid (LH) and Ion Cyclotron Resonant Frequency (ICRF) systems; long pulse coupling performance of the RF systems; observation of the transition to the so-called ``stationary LHEP regime`` in which the (flat) central current density and (peaked) electron temperature profiles are fully decoupled; experiments on ICRF sawtooth stabilization with the combined effect of LHCD modifying the current density profile; diffusion of fast electrons generated by LH waves; ramp-up experiments in which the LH power provided a significant part of the resistive poloidal flux and flux consumption scaling; theory of spectral wave diffusion and multipass absorption; fast wave current drive modelling with the Alcyon full wave code; a reflector LH antenna concept. 18 figs., 48 refs.

  6. Flow regime, void fraction and interfacial area transport and characteristics of co-current downward two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Lokanathan, Manojkumar [School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907-2088 (United States); Hibiki, Takashi [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907-2017 (United States)

    2016-10-15

    Highlights: • Downward flow regime maps and models were studied for 25.4 to 101.6 mm pipe diameters. • Effect of flow inlet on flow transition, void & interfacial area profile were studied. • Bubble void profiles were associated with the interfacial forces for downward flow. • Flow regime pressure drop and interfacial friction factor were studied. • The most applicable and accurate downward drift-flux correlation was determined. - Abstract: Downward two-phase flow is observed in light water reactor accident scenarios such as loss of coolant accident (LOCA) and loss of heat sink accident (LOHS) due to loss of feed water or a secondary pipe break. Hence, a comprehensive literature review has been performed for the co-current downward two-phase flow with information on the flow regime transitions and flow characteristics for each regime in the downward flow. The review compares the experimental data of the flow regime map and the current available transition models. Objectivity of the data varies on the method utilized as a certain degree of subjectivity is still present in the most objective method. Nevertheless, experimental data through subjective methods such as direct visualization or analysis of a wire mesh sensor (WMS) data were still studied in this review. Despite the wide range of flow regime data for numerous pipe sizes, a consensus was not reached for the effect of pipe sizes on flow regime transition. However, it is known that a larger pipe results in greater degree of coalescence at lower gas flow rates (Hibiki et al., 2004). The introduction of a flow straightener at the inlet led to less coring and fluid rotation and inevitably, reduced bubble coalescence. This also resulted in the disappearance of the kinematic shock wave phenomenon, contrary to an inlet without a flow straightener. The effect of flow inlet, flow location, pipe diameter and bubble interfacial forces on the radial distribution as well as bubble coalescence and breakup rate

  7. Impact of sodium on the secondary phases and current pathway in Cu{sub 2}(Zn,Sn)Se{sub 4} thin film solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yi-Cheng, E-mail: ielinyc@cc.ncue.edu.tw [Department of Mechatronics Engineering, National Changhua University of Education, Changhua, Taiwan (China); Lai, Chien-Mu [Department of Mechatronics Engineering, National Changhua University of Education, Changhua, Taiwan (China); Hsu, Hung-Ru [Green Energy & Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan (China)

    2017-05-01

    In this study, we investigated the influence of Na content on secondary phases and current pathway in Cu{sub 2}(Zn,Sn)Se{sub 4} (CZTSe) thin film solar cells with the following structure: Ti/Mo:Na/Mo/CZTSe/CdS/i-ZnO/ZnO:Al/Al. The application of Na-doped Mo target as a source of sodium. Experimental results demonstrate that increasing the Na content leads to an increase in the quantity of secondary phase SnSe{sub 2} on the surface of the absorber layer; however, it did not appear to affect the secondary phases of Cu{sub 2}SnSe{sub 3} (CTSe) or ZnSe. Excessive quantities of Na were shown to have an adverse effect on device efficiency. Our results using conductive atomic force microscopy (C-AFM) revealed that an increase in the quantity of secondary phase SnSe{sub 2} can shift the current pathway on the surface of CZTSe from CZTSe grain boundaries (GBs) to the SnSe{sub 2} grains. The role of secondary phase SnSe{sub 2} of the CZTSe acted as a channel for the current flow, which results in high leakage current and low device efficiency. - Highlights: • Increasing the Na content leads to an increase in the quantity of secondary phase SnSe{sub 2}. • An increase of secondary phase SnSe{sub 2} can shift the current pathway from CZTSe grain boundaries to the SnSe{sub 2} grains. • The secondary phase SnSe{sub 2} acted as a channel for the current flow, which results in high leakage current.

  8. Performance enhancement of the single-phase series active filter by employing the load voltage waveform reconstruction and line current sampling delay reduction methods

    DEFF Research Database (Denmark)

    Senturk, O.S.; Hava, A.M.

    2011-01-01

    This paper proposes the waveform reconstruction method (WRM), which is utilized in the single-phase series active filter's (SAF's) control algorithm, in order to extract the load harmonic voltage component of voltage harmonic type single-phase diode rectifier loads. Employing WRM and the line...... current sampling delay reduction method, a single-phase SAF compensated system provides higher harmonic isolation performance and higher stability margins compared to the system using conventional synchronous-reference-frame-based methods. The analytical, simulation, and experimental studies of a 2.5 k......W single-phase SAF compensated system prove the theory....

  9. HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    G. Taylor, P.T. Bonoli, D.L. Green, R.W. Harvey, J.C. Hosea, E.F. Jaeger, B.P. LeBlanc, R. Maingi, C.K. Phillips, P.M. Ryan, E.J. Valeo, J.R. Wilson, J.C. Wright, and the NSTX Team

    2011-06-08

    30 MHz high-harmonic fast wave (HHFW) heating and current drive are being developed to assist fully non-inductive plasma current (I{sub p}) ramp-up in NSTX. The initial approach to achieving this goal has been to heat I{sub p} = 300 kA inductive plasmas with current drive antenna phasing in order to generate an HHFW H-mode with significant bootstrap and RF-driven current. Recent experiments, using only 1.4 MW of RF power (P{sub RF}), achieved a noninductive current fraction, f{sub NI} {approx} 0.65. Improved antenna conditioning resulted in the generation of I{sub p} = 650 kA HHFW H-mode plasmas, with f{sub NI} {approx} 0.35, when P{sub RF} {ge} 2.5 MW. These plasmas have little or no edge localized mode (ELM) activity during HHFW heating, a substantial increase in stored energy and a sustained central electron temperature of 5-6 keV. Another focus of NSTX HHFW research is to heat an H-mode generated by 90 keV neutral beam injection (NBI). Improved HHFW coupling to NBI-generated H-modes has resulted in a broad increase in electron temperature profile when HHFW heating is applied. Analysis of a closely matched pair of NBI and HHFW+NBI H-mode plasmas revealed that about half of the antenna power is deposited inside the last closed flux surface (LCFS). Of the power damped inside the LCFS about two-thirds is absorbed directly by electrons and one-third accelerates fast-ions that are mostly promptly lost from the plasma. At longer toroidal launch wavelengths, HHFW+NBI H-mode plasmas can have an RF power flow to the divertor outside the LCFS that significantly reduces RF power deposition to the core. ELMs can also reduce RF power deposition to the core and increase power deposition to the edge. Recent full wave modeling of NSTX HHFW+NBI H-mode plasmas, with the model extended to the vessel wall, predicts a coaxial standing mode between the LCFS and the wall that can have large amplitudes at longer launch wavelengths. These simulation results qualitatively agree with HHFW

  10. Three-phase solvent systems for the comprehensive separation of a wide variety of compounds from Dicranostigma leptopodum by high-speed counter-current chromatography.

    Science.gov (United States)

    Liu, Yanjuan; Chen, Xiaofen; Liu, JunXi; Di, Duolong

    2015-06-01

    A three-phase solvent system was efficiently applied for high-speed counter-current chromatography to separate secondary metabolites with a wide range of hydrophobicity in Dicranostigma leptopodum. The three-phase solvent system of n-hexane/methyl tert-butyl ether/acetonitrile/0.5% triethylamine (2:2:3:2, v/v/v/v) was selected for high-speed counter-current chromatography separation. The separation was initiated by filling the column with a mixture of intermediate phase and lower phase as a stationary phase followed by elution with upper phase to separate the hydrophobic compounds. Then the mobile phase was switched to the intermediate phase to elute the moderately hydrophobic compounds, and finally the polar compounds still retained in the column were fractionated by eluting the column with the lower phase. In this research, 12 peaks were eluted out in one-step operation within 110 min, among them, eight compounds with acceptable purity were obtained and identified. The purities of β-sitosterol, protopine, allocryptopine, isocorydione, isocorydine, coptisine, berberrubine, and berberine were 94.7, 96.5, 97.9, 86.6, 98.9, 97.6, 95.7, and 92.8%, respectively.

  11. Grain refinement, hardening and metastable phase formation by high current pulsed electron beam (HCPEB) treatment under heating and melting modes

    Energy Technology Data Exchange (ETDEWEB)

    Grosdidier, T., E-mail: Thierry.grosdidier@univ-metz.f [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Lab of Materials Modification by Laser, Ion and Electron Beams and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Zou, J.X. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Bolle, B. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), ENIM, Ile du Saulcy, 57045 Metz (France); Hao, S.Z.; Dong, C. [Lab of Materials Modification by Laser, Ion and Electron Beams and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)

    2010-08-15

    High current pulsed electron beam is a recently developed technique for surface modification. The pulsed electron irradiation introduces concentrated energy depositions in the thin surface layer of the treated materials, giving rise to an extremely fast heating and subsequent rapid cooling of the surface together with the formation of dynamic stress waves. Improved surface properties (hardness, corrosion resistance) can be obtained under the 'melting' mode when the top surface is melted and rapidly solidified (10{sup 7} K/s). In steels, this is essentially the result of nanostructures formed from the highly undercooled melt, melt surface purification, strain hardening induced by the thermal stress waves as well as metastable phase selections in the rapidly solidified melted layers. The use of the 'heating' mode is less conventional, combining effects of the heavy deformation and recrystallization/recovery mechanisms. A detailed analysis of a FeAl alloy demonstrates grain size refinement, hardening, solid-state enhanced diffusion and texture modification without modification of the surface geometry.

  12. The effects of surface tension on flooding in counter-current two-phase flow in an inclined tube

    Energy Technology Data Exchange (ETDEWEB)

    Deendarlianto [Department of Mechanical and Industrial Engineering, Faculty of Engineering, Gadjah Mada University, Jalan Grafika No.2 Yogyakarta 55281 (Indonesia); Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, P.O. Box 510 119, D-01314 Dresden (Germany); Ousaka, Akiharu [Department of Mechanical Engineering, The University of Tokushima, 2-1 Minami Josanjima, Tokushima 770-8506 (Japan); Indarto [Department of Mechanical and Industrial Engineering, Faculty of Engineering, Gadjah Mada University, Jalan Grafika No.2 Yogyakarta 55281 (Indonesia); Kariyasaki, Akira [Department of Chemical Engineering, Fukuoka University, 8-19-1, Jyonan-ku, Fukuoka 814-0180 (Japan); Lucas, Dirk; Vallee, Christophe [Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, P.O. Box 510 119, D-01314 Dresden (Germany); Vierow, Karen; Hogan, Kevin [Department of Nuclear Engineering Texas A and M University, 129 Zachry Engineering Center, 3133 TAMU College Station, TX 77843-3133 (United States)

    2010-10-15

    The purpose of the present study is to investigate the effects of surface tension on flooding phenomena in counter-current two-phase flow in an inclined tube. Previous studies by other researchers have shown that surface tension has a stabilizing effect on the falling liquid film under certain conditions and a destabilizing or unclear trend under other conditions. Experimental results are reported herein for air-water systems in which a surfactant has been added to vary the liquid surface tension without altering other liquid properties. The flooding section is a tube of 16 mm in inner diameter and 1.1 m length, inclined at 30-60 from horizontal. The flooding mechanisms were observed by using two high-speed video cameras and by measuring the time variation of liquid hold-up along the test tube. The results show that effects of surface tension are significant. The gas velocity needed to induce flooding is lower for a lower surface tension. There was no upward motion of the air-water interfacial waves upon flooding occurrence, even for lower a surface tension. Observations on the liquid film behavior after flooding occurred suggest that the entrainment of liquid droplets plays an important role in the upward transport of liquid. Finally, an empirical correlation for flooding velocities is proposed that includes functional dependencies on surface tension and tube inclination. (author)

  13. INFLUENCE OF VARIATIONS OF THE CONDUCTIVITY OF UPPER LAYER OF TWO-LAYER SAMPLE ON OF PHASE INTRODUCED ELECTROMOTIVE FORCE OF SUPERIMPOSED TRANSDUCER OF EDDY CURRENT THICKNESS METER

    Directory of Open Access Journals (Sweden)

    A. V. Chernyshev

    2017-01-01

    Full Text Available In carrying out eddy current thickness measurement of two-layer conductive objects one from the interfering factors is the presence of variations in the value of the electrical conductivity of the material of the upper layer (coating when moving from point to point on the surface of object of control or when passing from one object of control to another. The aim of this work is to evaluate the accuracy of determining the thickness of the conductive coating disposed on a conducting ferromagnetic basis, using the phase method of eddy current testing. The reason of the error is variation of the electrical conductivity of the material of coating.Determination of the error is based on calculations using known analytical expressions for the loop with current of sinusoidal form arranged over the infinite half space with a covering as a thin layer. Selected in calculating electromagnetic parameters of coating and substrate approximately correspond to the case -chromium layer on a nickel base. Calculations are performed for different frequencies of current passed through coil.It is shown that at reduction of frequency of the current passes through the coil the error is reduced. The value of the lowest possible operating frequency of the excitation current is determined by the condition of absence influence on the phase introduced into the superimposed transducer emf variations in the thickness of the basis.To reduce the indicated error it is proposed to determine, on the basis of phase method at a relatively high frequency transducer current excitation, conductivity of the material of coating. After this, at a low frequency excitation current and using phase method, the coating thickness is determined, taking into consideration the previously determined value of the conductivity of coating. Also discussed ways to improve the accuracy of phase measurements in the MHz region of the excitation current frequency. 

  14. Ramping up to the Biology Workbench: A Multi-Stage Approach to Bioinformatics Education

    Science.gov (United States)

    Greene, Kathleen; Donovan, Sam

    2005-01-01

    In the process of designing and field-testing bioinformatics curriculum materials, we have adopted a three-stage, progressive model that emphasizes collaborative scientific inquiry. The elements of the model include: (1) context setting, (2) introduction to concepts, processes, and tools, and (3) development of competent use of technologically…

  15. Laws of Attraction: To Ramp up Alumni Engagement, Give Graduates What They Want

    Science.gov (United States)

    Collins, Mary Ellen

    2013-01-01

    Developing an effective engagement strategy begins with an open mind and an outstretched hand. It requires alumni professionals to reconsider how alumni identify themselves within the institution, relinquish some control of the planning and execution of programs, and meet alumni where they are--on terra firma or online. But most of all, it…

  16. RAMP UP DA MAIOR INSTALAÇÃO DE MOINHOS VERTIMILL DO MUNDO

    Directory of Open Access Journals (Sweden)

    Douglas B. Mazzinghy

    2015-12-01

    Full Text Available O circuito de remoagem do projeto Minas-Rio é atualmente o maior do mundo utilizando moinhos verticais. O circuito possui 16 Vertimill VTM-1500 da Metso e 8 baterias de ciclones. O início das operações ocorreu no final de 2014 e os moinhos têm se mostrado bem robustos para a aplicação selecionada. O minério processado é um itabirito que é concentrado através de flotação reversa. O circuito de remoagem tem como objetivo reduzir a granulometria do concentrado final para facilitar o transporte através de um mineroduto com mais de 525 km de extensão. O presente trabalho apresenta os dados obtidos através de amostragens do circuito industrial além de testes em escala de laboratório para estimativa de consumo energético. Estes resultados também são comparados com os testes em escala de laboratório e piloto executados para dimensionamento do circuito de remoagem.

  17. Increasing flux rate to shorten leaching period and ramp-up production

    Science.gov (United States)

    Ngantung, Billy; Agustin, Riska; Ravi'i

    2017-01-01

    J Resources Bolaang Mongondow (JBRM) has operated a dynamic heap leach in its Bakan Gold Mine since late 2013. After successfully surpassing its name plate capacity of 2.6 MT/annum in 2014, the clayey and transition ore become the next operational challenge. The presence of transition and clayey ore requires longer leaching period, hence reducing the leach pad capacity which then caused reduced production. Maintaining or even increasing production with such longer leaching ore types can be done by expanding the leach pad area which means an additional capital investment, and/or shortening the leaching cycle which compromise a portion of gold extraction. JBRM has been successfully increasing the leach pad production from 2.6 MT/annum to 3.8 MT/annum, whilst improving the gold extraction from around 70% to around 80%. This was achieved by managing the operation of the leach pad which is shortening the leach cycle by identifying and combining the optimal flux rate application versus the tonne processed in each cell, at no capital investment for expanding the cell capacity.

  18. Ramping up the signal: promoting endurance training adaptation in skeletal muscle by nutritional manipulation.

    Science.gov (United States)

    Hawley, John A; Morton, James P

    2014-08-01

    Mitochondrial biogenesis in skeletal muscle results from the cumulative effect of transient increases in mRNA transcripts encoding mitochondrial proteins in response to repeated exercise sessions. This process requires the coordinated expression of both nuclear and mitochondrial (mt) DNA genomes and is regulated, for the most part, by the peroxisome proliferator-activated receptor γ coactivator 1α. Several other exercise-inducible proteins also play important roles in promoting an endurance phenotype, including AMP-activated protein kinase, p38 mitogen-activated protein kinase and tumour suppressor protein p53. Commencing endurance-based exercise with low muscle glycogen availability results in greater activation of many of these signalling proteins compared with when the same exercise is undertaken with normal glycogen concentration, suggesting that nutrient availability is a potent signal that can modulate the acute cellular responses to a single bout of exercise. When exercise sessions are repeated in the face of low glycogen availability (i.e. chronic training), the phenotypic adaptations resulting from such interventions are also augmented.

  19. Eliminating the effect of phase shift between injection current and amplitude modulation in DFB-LD WMS for high-precision measurement.

    Science.gov (United States)

    Wei, Wei; Chang, Jun; Liu, Yuanyuan; Chen, Xi; Liu, Zhaojun; Qin, Zengguang; Wang, Qiang

    2016-05-01

    Phase shift between the injection current and amplitude modulation due to the characteristics of diode lasers is discussed in this paper. Phase shift has no apparent regularity, but it has an obvious effect on measurement results, especially for high-precision measurement. A new method is proposed to suppress the influence of this phase shift. Water vapor is chosen as the target gas for experiment in this paper. A new detection system with the new method applied is presented and shows much better performance than the traditional wavelength modulation spectroscopy detection system. Phase shift fluctuation between the injection current and amplitude modulation is suppressed from 0.72 deg to 0.07 deg; accuracy is improved from 0.88 ppm to 0.16 ppm.

  20. Startup of Plasma Current in J-TEXT Tokamak Prompted by the Hα Line Emission Criterion

    Institute of Scientific and Technical Information of China (English)

    GAO Li; ZHUANG Ge; HU Xiwei; ZHANG Ming

    2009-01-01

    An Hα line-emission detection system was developed on the joint texas experimental tokamak (J-TEXT), which is used to determine the Hα emission level during the gas breakdown and hereafter to control the startup of the plasma current. The detector consists of an Hα in-terference filter, a focusing lens, a photodiode and a preamplifier. In the J-TEXT operation, the Hα emission is taken as a monitor signal which is highly sensitive to the generation of a plasma.Furthermore, the power supply control system using the above signal as an input is capable of de-termining whether and when to fire the Ohmic heating capacitor banks, which are applied to drive the plasma current ramp-up. The experimental results confirm that the Hα emission criterion is acceptable for controlling the plasma current promotion in the J-TEXT tokamak.

  1. Nonadiabatic Phase and Persistent Currents for System of Spin-1/2 Particles in Presence of Electromagnetic Fields and Spin-Orbit Interaction

    Institute of Scientific and Technical Information of China (English)

    LI Nian-Bei; MA Zhong-Shui

    2004-01-01

    We present a comprehensive view and details of calculations on Aharonov-Anandan phase for the charged particles in the external electric and magnetic fields for a nonadiabatic process. We derive, with consideration of a spin-orbit interaction and Zeemann Splitting, the persistent currents as a response to an Aharonov-Casher topological interference effect in one-dimensional mesoscopic ring. We also establish a connection to Berry adiabatic phase with deduced dynamical-nature dependence in the nonadiabatic process. The second quantization representation has also been employed in exhibition of persistent currents in the many-body case.

  2. Design and Simulation for Producing Two Amplitude Matched Anti-phase Sine Waveforms Using ±2.5 V CMOS Current-Mode Approach

    OpenAIRE

    Anil Kumar Sharma; Dipankar Pal

    2010-01-01

    In this paper the current mode approach called “Current Conveyor (CCII+)” has been incorporated to design and simulate the circuit for producing two amplitude matched anti-phase sine waveforms which are frequently used in various communication and instrumentation systems. PSpice simulation has been used to depict the output waveforms. The power supply used is ±2.5 V which can be easily incorporated with CMOS IC technology. The designed circuit has been simulated at variousfrequency ranges and...

  3. Transport of Spin-Polarized Current Through a Mesoscopic Ring with Two Leads Induced by Aharonov-Bohm and Aharonov-Casher Phases

    Institute of Scientific and Technical Information of China (English)

    GAO Ying-Fang; ZHANG Yong-Ping; LIANG Jiu-Qing

    2004-01-01

    @@ We study the transport of spin-polarized current induced by the Aharonov-Bohm and Aharonov-Casher phases in a mesoscopic ring with two leads in the presence of a cylindrically symmetric electric field and the magnetic flux at the centre of the same ring. An exact solution for the quantum transport is obtained. It is shown that the transport spin-polarized current and its polarizability can be controlled by the electric field and the magnetic flux as well.

  4. Improving the Performance of Phase-Change Perfluorocarbon Droplets for Medical Ultrasonography: Current Progress, Challenges, and Prospects

    Directory of Open Access Journals (Sweden)

    Paul S. Sheeran

    2014-01-01

    Full Text Available Over the past two decades, perfluorocarbon (PFC droplets have been investigated for biomedical applications across a wide range of imaging modalities. More recently, interest has increased in “phase-change” PFC droplets (or “phase-change” contrast agents, which can convert from liquid to gas with an external energy input. In the field of ultrasound, phase-change droplets present an attractive alternative to traditional microbubble agents for many diagnostic and therapeutic applications. Despite the progress, phase-change PFC droplets remain far from clinical implementation due to a number of challenges. In this review, we survey our recent work to enhance the performance of phase-change agents for ultrasound through a variety of techniques in order to provide increased efficacy in therapeutic applications of ultrasound and enable previously unexplored applications in diagnostic and molecular imaging.

  5. Analysis of torque-current characteristic of brushless DC motor driven by three-phase H-bridge

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Presents the simulation and analysis of the steady state characteristic of a brushless DC motor studies the torque-current characteristic of the motor as well and discusses the design of a current-measure circuit for torque controlling.

  6. A dual mode operated boost inverter and its control strategy for ripple current reduction in single-phase uninterruptible power supplies

    DEFF Research Database (Denmark)

    Tang, Y.; Yao, W.; Blaabjerg, Frede

    2015-01-01

    In single-phase uninterruptible power supply (UPS) applications, it is well known that the AC side instantaneous power is not constant by nature. The resulting input current from the DC source side will inevitably contain low frequency ripple components that may largely deteriorate the system...

  7. Eddy Current Modeling and Measuring in Fast-Pulsed Resistive Magnets

    CERN Document Server

    Arpaia, P; Gollucio, G; Montenero, G

    2010-01-01

    A method for modeling and measuring electromagnetic transients due to eddy currents in fast-pulsed resistive magnets is proposed. In particular, an equivalent-circuit model and a method for time-domain measurements of eddy currents are presented. The measurements are needed for an accurate control of the magnetic field quality to ensure adequate stability and performance of the particle beam in particle accelerators in dynamic conditions (field ramps up to about 700 T/s). In the second part, the results of experiments for model definition, identification, and validation are discussed. The tests were carried out on a quadrupole of Linac4, a new linear particle accelerator under construction at CERN (European Organization for Nuclear Research).

  8. Simulation of Phase-Change Random Access Memory with Ring-Type Contactor for Low Reset Current by Finite Element Modelling

    Institute of Scientific and Technical Information of China (English)

    GONG Yue-Feng; LING Yun; SONG Zhi-Tang; FENG Song-Lin

    2008-01-01

    A three-dimensional finite element models for phase change random access memory (PCRAM) is established to simulate thermal and electrical behaviours during RESET operation. The RESET behaviours of the conventional structure (CS) and the ring-type contact in bottom electrode (RIB) are compared with each other. The simulation results indicate that the RIB cell has advantages of high heat efficiency for melting phase change material in cell,reduction of contact area and lower RESET current with maintaining good resistance contrast. The RESET current decreases from 1.26mA to 1.2mA and the heat consumption in GST material during programming increases from 12% to 37% in RIB structure. Thus the RIB structure PCRAM cell is suitable for future device with high heat efficiency and smaller RESET current.

  9. Determination of torque speed current characteristics of a brushless DC motor by utilizing back-EMF of non-energized phase

    Science.gov (United States)

    Jang, G. H.; Yeom, J. H.; Kim, M. G.

    2007-03-01

    This paper presents a method to determine the torque constant and the torque-speed-current characteristics of a brushless DC (BLDC) motor by utilizing back-EMF variation of nonenergized phase. It also develops a BLDC motor controller with a digital signal processor (DSP) to monitor its current, voltage and speed in real time. Torque-speed-current characteristics of a BLDC motor are determined by using the proposed method and the developed controller. They are compared with the torque-speed-current characteristics measured by dynamometer experimentally. This research shows that the proposed method is an effective method to determine the torque constant and the torque-speed-current characteristics of the BLDC motor without using dynamometer.

  10. Determination of torque-speed-current characteristics of a brushless DC motor by utilizing back-EMF of non-energized phase

    Energy Technology Data Exchange (ETDEWEB)

    Jang, G.H. [Department of Mechanical Engineering, Hanyang University, 17 Haengdangdong, Seongdonggu, Seoul 133-791 (Korea, Republic of)]. E-mail: ghjang@hanyang.ac.kr; Yeom, J.H. [Department of Mechanical Engineering, Hanyang University, 17 Haengdangdong, Seongdonggu, Seoul 133-791 (Korea, Republic of); Kim, M.G. [Department of Mechanical Engineering, Hanyang University, 17 Haengdangdong, Seongdonggu, Seoul 133-791 (Korea, Republic of)

    2007-03-15

    This paper presents a method to determine the torque constant and the torque-speed-current characteristics of a brushless DC (BLDC) motor by utilizing back-EMF variation of nonenergized phase. It also develops a BLDC motor controller with a digital signal processor (DSP) to monitor its current, voltage and speed in real time. Torque-speed-current characteristics of a BLDC motor are determined by using the proposed method and the developed controller. They are compared with the torque-speed-current characteristics measured by dynamometer experimentally. This research shows that the proposed method is an effective method to determine the torque constant and the torque-speed-current characteristics of the BLDC motor without using dynamometer.

  11. 航空油泵电机的相电流畸变纠正控制%Phase current distortion correction control for aerospace fuel pump motor

    Institute of Scientific and Technical Information of China (English)

    匡敏驰; 朱纪洪; 吉敬华

    2015-01-01

    In order to improve current performance, a new control method is proposed to correct the distortion of phase current, in which the magnetic saturation and the nonlinear characteristic of inverters are considered. The amplitude fluctuation is eliminated by using feed forward current amplitude compensation. Meanwhile, based on iteration convergence control, the phase current is compulsorily corrected to a standard sinusoidal shape. Then, the problem of the phase current distortion is successfully solved. The experimental results show that the amplitude of phase current is reduced effectively, and the efficiency of motor system is improved.%考虑电枢反应中磁饱和现象和驱动器功率管非线性特性等因素的影响,为了解决航空油泵电机相电流谐波含量大、畸变较为严重的问题,提出一种新型的相电流畸变纠正控制方法. 该方法通过电流前馈幅值补偿能够基本消除各周期相电流幅值的波动,并通过迭代收敛控制,最终将相电流强制纠正为标准正弦波,从而解决了相电流畸变的难题.实验结果表明,所提出的相电流畸变纠正控制方法可以有效减少相电流幅值,提高电机系统的效率.

  12. 78 FR 76791 - Availability of Version 4.0 of the Connect America Fund Phase II Cost Model; Adopting Current...

    Science.gov (United States)

    2013-12-19

    ... provide additional protection from harsh weather. This version modifies the prior methodology used for..., which provides more detail on the current model architecture, processing steps, and data sources...

  13. Current control methods for grid-side three-phase PWM voltage-source inverter in distributed generation systems

    DEFF Research Database (Denmark)

    Lar, Ionut Andrei; Radulescu, Mircea; Ritchie, Ewen

    2012-01-01

    A comparison between two current control methods of grid side inverter, PI current control and Robust Forward control is made. PI control is implemented in d-q synchronous frame while Forward is implemented in abc stationary frames.The report contains both simulations and experimental test wich w...

  14. Toroidal current profile control during low confinement mode plasma discharges in DIII-D via first-principles-driven model-based robust control synthesis

    Science.gov (United States)

    Barton, Justin E.; Boyer, Mark D.; Shi, Wenyu; Schuster, Eugenio; Luce, Tim C.; Ferron, John R.; Walker, Michael L.; Humphreys, David A.; Penaflor, Ben G.; Johnson, Robert D.

    2012-12-01

    In order for ITER to be capable of operating in advanced tokamak operating regimes, characterized by a high fusion gain, good plasma confinement, magnetohydrodynamic stability and a non-inductively driven plasma current, for extended periods of time, several challenging plasma control problems still need to be solved. Setting up a suitable toroidal current density profile in the tokamak is key for one possible advanced operating scenario characterized by non-inductive sustainment of the plasma current. At the DIII-D tokamak, the goal is to create the desired current profile during the ramp-up and early flat-top phases of the plasma discharge and then actively maintain this target profile for the remainder of the discharge. The evolution in time of the toroidal current profile in tokamaks is related to the evolution of the poloidal magnetic flux profile, which is modelled in normalized cylindrical coordinates using a first-principles, nonlinear, dynamic partial differential equation (PDE) referred to as the magnetic diffusion equation. The magnetic diffusion equation is combined with empirical correlations developed from physical observations and experimental data from DIII-D for the electron temperature, the plasma resistivity and the non-inductive current drive to develop a simplified, control-oriented, nonlinear, dynamic PDE model of the poloidal flux profile evolution valid for low confinement mode discharges. In this work, we synthesize a robust feedback controller to reject disturbances and track a desired reference trajectory of the poloidal magnetic flux gradient profile by employing the control-oriented model of the system. A singular value decomposition of the static gain matrix of the plant model is utilized to identify the most relevant control channels and is combined with the dynamic response of system around a given operating trajectory to design the feedback controller. A general framework for real-time feedforward + feedback control of magnetic and

  15. COMPARISON OF CHARACTERISTICS OF THE CONVERTER-FED MOTOR AT SUPPLY FROM THE SINGLE-PHASE NETWORK AND FROM THE SOURCE OF THE DIRECT CURRENT

    Directory of Open Access Journals (Sweden)

    V.B. Finkelshtein

    2015-08-01

    Full Text Available Purpose. Now even more often in various cars and mechanisms converter-fed motors are used. Their comparative characteristics with motors which are supplied from a network of a direct current are necessary for definition of the specific moment of motors which are supplied from the single-phase alternating current main. Methodology. For the converter-fed motor with a ratio of teeth of the stator and a rotor 8/6 at supply from a single-phase network via the rectifier two groups of numerical experiments were carried out. Motor capacity with a constant frequency of rotation at various capacity of the capacitor at the exit of the rectifier and motor capacity at the current providing the most admissible excess of temperature of a winding are determined. Dependences of useful power on capacity size at the rectifier exit are received with a constant frequency of rotation, and also at invariable current. Results. On the basis of the made numerical experiment it is possible to conclude that due to fluctuation of tension (from 0 to 100 % at the rectifier exit at power supply of the converter-fed motor from the single-phase alternating current main in comparison with the corresponding sizes at supply from a source of a direct current: • motor capacity at preservation of capacity of the capacitor at the exit of the rectifier and frequency of rotation decreases on 60 – 63 %; • at almost acceptable increase in capacity of the capacitor (approximately twice power should be reduced by 50 %; • power deceleration at preservation of that size of current of the motor what took place at its food from a source of a direct current makes 40 % at preservation of size of capacity of the capacitor at the exit of the rectifier and 32 % at its doubling, the frequency of rotation decreases approximately on 13 – 15 %. Practical value. The specific moment can be determined by power sizes at single-phase supply, frequency of rotation and to the volume of a rotor, with

  16. A Component-Minimized Single-Phase Active Power Decoupling Circuit with Reduced Current Stress to Semiconductor Switches

    DEFF Research Database (Denmark)

    Tang, Yi; Blaabjerg, Frede

    2015-01-01

    component, e.g. inductors or film capacitors for ripple energy storage because this task can be accomplished by the dc-link capacitors, and therefore its implementation cost can be minimized. Another unique feature of the proposed topology is that the current stress of power semiconductors can be reduced...... inductor. With such a configuration, this leg can control the current going into the two output capacitors connected in series for power decoupling, and the other leg can control the line current according to active and reactive power requirement. The proposed topology does not require additional passive...

  17. Nonlinear current-voltage characteristics due to quantum tunneling of phase slips in superconducting Nb nanowire networks

    Energy Technology Data Exchange (ETDEWEB)

    Trezza, M.; Cirillo, C.; Sabatino, P.; Carapella, G.; Attanasio, C. [CNR-SPIN Salerno and Dipartimento di Fisica “E. R. Caianiello”, Università degli Studi di Salerno, Fisciano I-84084 (Italy); Prischepa, S. L. [Belarusian State University of Informatics and Radioelectronics, P. Browka 6, Minsk 220013 (Belarus)

    2013-12-16

    We report on the transport properties of an array of N∼30 interconnected Nb nanowires, grown by sputtering on robust porous Si substrates. The analyzed system exhibits a broad resistive transition in zero magnetic field, H, and highly nonlinear V(I) characteristics as a function of H, which can be both consistently described by quantum tunneling of phase slips.

  18. Analysis on the Current Phase Compensation in Differential Protection for Transformer%变压器差动保护相位补偿分析

    Institute of Scientific and Technical Information of China (English)

    谢珍贵; 黄兴平; 朱文强

    2013-01-01

    This paper analyzes the relationship between angle-connection phase compensation and the algorithm phase compensation using in the current phase compensation in differential protection forWiring two-winding transformer microcomputer, and the relationship between the two phase short circuit fault sensitivity and phase compensation in differential protection for transformer, and then concludes that whether the transformer neutral point grounds or not, phase compensation choosing the plan of low voltage is good for the dif erential protection sensitivity.%  分析了接线双绕组变压器微机差动保护相位补偿采用角接与算法相位补偿关系,变压器差动保护内部两相短路故障灵敏度与相位补偿关系,得出无论变压器中性点是否接地,相位补偿选择低压侧的方案对差动保护灵敏度有利。

  19. Leakage Current Paths in PV Transformer-Less Single-Phase Inverter Topology and Its Mitigation through PWM for Switching

    Directory of Open Access Journals (Sweden)

    M. N. H. Khan

    2015-03-01

    Full Text Available The Photovoltaic (PV is a part and parcel and well known for cost-effective and easy to operatefeatures when it is used with transformer-less inverter-based grid-tied distribution generation systems. It reduces the leakage current issue that actually occurs making paths from PV penal to ground. In this paper has been addressed this issue as main problem for reducing leakage current. Moreover, here iscompared the proposed topology’s results to AC and DC-based transformer-less topologies. The possibilities of larger number of leakage current paths indicatepower loss, which is the focus of work in this paper for different switching conditions. The results on leakage current paths using PSpice with different parasitic capacitance values from inverters of different topologies are compared with the simulation results of the topology proposed in this paper.

  20. Adaptive Fuzzy PID Based Control Strategy For 3Phase 4Wire Shunt Active Filter To Mitigate Current Harmonics Of Grid Interconnection Of Renewable Energy Based Distribution System

    Directory of Open Access Journals (Sweden)

    Kaleemullah

    2016-06-01

    Full Text Available This paper presents a new control strategy for controlling the shunt active power filter to compensate reactive power and to reduce the unwanted harmonics in the grid current. Shunt active filter act as a current source which is connected in parallel with a non-linear load and controlled to produce the required compensating current. The proposed control strategy is based on the fuzzy PID controller which is used for determining the reference compensating currents of the three-phase shunt active power filters. Simulations are carried out using MATLAB/SIMULINK to verify the performance of the proposed controller. The output shows the controller has fast dynamic response high accuracy of tracking DC voltage reference and robust to load parameters variations.

  1. The separation of flavonoids from Pongamia pinnata using combination columns in high-speed counter-current chromatography with a three-phase solvent system.

    Science.gov (United States)

    Yin, Hao; Zhang, Si; Long, Lijuan; Yin, Hang; Tian, Xinpeng; Luo, Xiongming; Nan, Haihan; He, Sha

    2013-11-01

    The mangrove plant Pongamia pinnata (Leguminosae) is well known as a plant pesticide. Previous studies have indicated that the flavonoids are responsible of the biological activities of the plant. A new high-speed counter-current chromatography (HSCCC) method for the separation of three flavonoids, karanjin (1), pinnatin (2), and pongaflavone (3), from P. pinnata was developed in the present study. The lower and intermediate phase (LP and IP) of a new three-phase solvent system, n-hexane-acetonitrile-dichloromethane-water, at a volume ratio of 5:5:1:5, were used as the stationary phases, while the upper phase (UP) was used as the mobile phase, and the volume ratio between the stationary phases in the CCC column could be tuned by varying the initial pumped volume ratio of the stationary phases. The CCC columns containing all three phases of the solvent system were considered combination columns. According to the theories of combination column, it is possible to optimize the retention time of the target compounds by varying the volume ratio of the stationary phases in the HSCCC combination columns, as well as the suitable volume ratios of the stationary phases for the separation of the target compounds were predicted from the partition coefficients of the compounds in the three-phase solvent system. Then, three HSCCC separations using the combination columns with initial pumped LP:IP volume ratios of 1:0, 0.9:0.1, and 0.7:0.3 were performed separately based on the prediction. Three target compounds were prepared with high purity when the initial pumped volume ratio of the stationary phases was 0.9:0.1. The baseline separation of compounds 2 and 3 was achieved on the combination column with an initial pumped volume ratio of 0.7:0.3. Furthermore, the three experiments clearly demonstrated that the retentions and resolutions of the target compounds increased with an increasing volume ratio of IP, which is consistent with the prediction for the retention times for the

  2. In operando neutron diffraction study of the temperature and current rate-dependent phase evolution of LiFePO4 in a commercial battery

    Science.gov (United States)

    Sharma, N.; Yu, D. H.; Zhu, Y.; Wu, Y.; Peterson, V. K.

    2017-02-01

    In operando NPD data of electrodes in lithium-ion batteries reveal unusual LiFePO4 phase evolution after the application of a thermal step and at high current. At low current under ambient conditions the LiFePO4 to FePO4 two-phase reaction occurs during the charge process, however, following a thermal step and at higher current this reaction appears at the end of charge and continues into the next electrochemical step. The same behavior is observed for the FePO4 to LiFePO4 transition, occurring at the end of discharge and continuing into the following electrochemical step. This suggests that the bulk (or the majority of the) electrode transformation is dependent on the battery's history, current, or temperature. Such information concerning the non-equilibrium evolution of an electrode allows a direct link between the electrode's functional mechanism that underpins lithium-ion battery behavior and the real-life operating conditions of the battery, such as variable temperature and current, to be made.

  3. Design and Simulation for Producing Two Amplitude Matched Anti-phase Sine Waveforms Using ±2.5 V CMOS Current-Mode Approach

    Directory of Open Access Journals (Sweden)

    Anil Kumar Sharma,

    2010-08-01

    Full Text Available In this paper the current mode approach called “Current Conveyor (CCII+” has been incorporated to design and simulate the circuit for producing two amplitude matched anti-phase sine waveforms which are frequently used in various communication and instrumentation systems. PSpice simulation has been used to depict the output waveforms. The power supply used is ±2.5 V which can be easily incorporated with CMOS IC technology. The designed circuit has been simulated at variousfrequency ranges and the waveforms are obtained after the circuit is optimized.

  4. Comprehensive separation of secondary metabolites in natural products by high-speed counter-current chromatography using a three-phase solvent system.

    Science.gov (United States)

    Yanagida, Akio; Yamakawa, Yutaka; Noji, Ryoko; Oda, Ako; Shindo, Heisaburo; Ito, Yoichiro; Shibusawa, Yoichi

    2007-06-01

    High-speed counter-current chromatography (HSCCC) using the three-phase solvent system n-hexane-methyl acetate-acetonitrile-water at a volume ratio of 4:4:3:4 was applied to the comprehensive separation of secondary metabolites in several natural product extracts. A wide variety of secondary metabolites in each natural product was effectively extracted with the three-phase solvent system, and the filtered extract was directly submitted to the HSCCC separation using the same three-phase system. In the HSCCC profiles of crude natural drugs listed in the Japanese Pharmacopoeia, several physiologically active compounds were clearly separated from other components in the extracts. The HSCCC profiles of several tea products, each manufactured by a different process, clearly showed their compositional difference in main compounds such as catechins, caffeine, and pigments. These HSCCC profiles also provide useful information about hydrophobic diversity of whole components present in each natural product.

  5. Small-Signal Modeling, Analysis and Testing of Parallel Three-Phase-Inverters with A Novel Autonomous Current Sharing Controller

    DEFF Research Database (Denmark)

    Guan, Yajuan; Quintero, Juan Carlos Vasquez; Guerrero, Josep M.

    2015-01-01

    active or reactive power, instead it uses a virtual impedance loop and a SFR phase-locked loop. The small-signal model of the system was developed for the autonomous operation of inverter-based microgrid with the proposed controller. The developed model shows large stability margin and fast transient......A novel simple and effective autonomous currentsharing controller for parallel three-phase inverters is employed in this paper. The novel controller is able to endow to the system high speed response and precision in contrast to the conventional droop control as it does not require calculating any...... response of the system. This model can help identifying the origin of each of the modes and possible feedback signals for design of controllers to improve the system stability. Experimental results from two parallel 2.2 kVA inverters verify the effectiveness of the novel control approach....

  6. Design, real-time modelling, simulation and digital implementation of phase-locked loop-based auto-synchronising current-sourced converter for an induction heating prototype

    Indian Academy of Sciences (India)

    MOLAY ROY; MAINAK SENGUPTA

    2017-06-01

    Induction heating (IH) converters operate just above resonant frequency, at near unity power factor (UPF), to supply power to the targeted work-piece. Some power electronic converter-fed IH systems use power control strategies based on dynamic tracking of the changing resonant frequency as the work-piece gets heated up (since inductance changes). Therefore, the correct in-process determination of the resonant frequency is essential. A method of dynamically detecting the resonant frequency is by calculating the phase-shift betweencurrent and voltage continuously during the process. In case of CSI- (and VSI-) fed IH, the phase-shift between voltage and current is zero at resonant frequency. Hence one way of identifying the resonant frequency is by varying the frequency until the phase-shift is zero. For controlling this phase-shift between current and voltage waveforms, most of the controllers use a phase-locked loop (PLL) IC. In this paper, a novel method for the dynamic tracking of resonant frequency is proposed and the practical implementation of the same, using a fieldprogrammable gate array (FPGA) based digital-PLL, is presented. The scheme is first simulated with generated off-line signal samples and then implemented on a real-time model of a CSI-fed IH application. Finally, thedigital-PLL logic is implemented on controller hardware and practically tested in a laboratory-made experimental set-up of 2 kW at a nominal frequency of 10 kHz. The switching frequency is auto-synchronising. This fact is practically verified both by varying (i) the geometric dimensions as also (ii) the initial temperature of the work-piece. It is practically observed in the oscillograms that the phase gets locked in few cycles (and hence ensures quick tracking of the dynamically changing resonant frequency for this set-up).

  7. Enhanced Lower Hybrid Current Drive Experiments on HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Effective Lower Hybrid Current Driving (LHCD) and improved confinement exper-iments in higher plasma parameters (Ip > 200 kA, ne> 2×1013 cm-3, Te ≥ 1 keⅤ) havebeen curried out in optimized LH wave spectrum and plasma parameters in HT-7 supercon-ducting tokamak. The dependence of current driving efficiency on LH power spectrum, plasmadensity ne and toroidal magnetic field BT has been obtained under optimal conditions. A goodCD efficiency was obtained at higher plasma current and higher electron density. The improve-ment of the energy confinement time is accompanied with the increase in line averaged electrondensity, and in ion and electron temperatures. The highest current driving efficiency reachedηCD = IpneR/PRF ≈ 1.05 × 1019 Am-2/W. Wave-plasma coupling was sustained in a good stateand the reflective coefficient was less than 5%. The experiments have also demonstrated the abilityof LH wave in the start-up and ramp-up of the plasma current. The measurement of the temporaldistribution of plasma parameter shows that lower hybrid leads to a broader profile in plasmaparameter. The LH power deposition profile and the plasma current density profile were modeledwith a 2D Fokker-Planck code corresponding to the evolution process of the hard x-ray detectorarray.

  8. Performance Improvement for Two-Stage Single-Phase Grid-Connected Converters Using a Fast DC Bus Control Scheme and a Novel Synchronous Frame Current Controller

    Directory of Open Access Journals (Sweden)

    Bingzhang Li

    2017-03-01

    Full Text Available Two-stage single-phase grid-connected converters are widely used in renewable energy applications. Due to the presence of a second harmonic ripple across the DC bus voltage, it is very challenging to design the DC bus voltage control scheme in single-phase grid-connected inverters. The DC bus voltage controller must filter the ripple and balance a tradeoff between low harmonic distortion and high bandwidth. This paper presents a fast DC bus voltage controller, which uses a second order digital finite impulse response (FIR notch filter in conjunction with input power feedforward scheme to ensure the steady-state and dynamic performance. To gain the input power without extra hardware, a Kalman filter is incorporated to estimate the DC bus input current. At the same time, a modulation compensation strategy is implemented to eliminate the nonlinearity of the grid current control loop, which is caused by the DC bus voltage ripple. Moreover, a novel synchronous frame current controller for single-phase systems is also introduced, and its equivalent model in stationary frame has been derived. Simulation and experimental results are provided to verify the effective of the proposed control scheme.

  9. Separation of chemical constituents from three plant medicines by counter-current chromatography using a three-phase solvent system at a novel ratio.

    Science.gov (United States)

    Wu, Xiaoyi; Chao, Zhimao; Wang, Chun; Yu, Li

    2015-03-01

    A solvent system of n-hexane, methyl acetate, acetonitrile, and water at a novel volume ratio of 4:3:4:4 forms three layers, i.e. upper phase (UP), middle phase (MP), and lower phase (LP), with a volume ratio of 1:1.20:1.42 at room temperature (25°C). All three two-phases from this three-phase solvent system were successfully used to separate some chemical constituents from three plant medicines with counter-current chromatography (CCC). Eight coumarins (B1-B8) were obtained from petroleum ether extract of fresh roots of Angelica dahurica (Baizhi) with a stationary phase of UP and a mobile phase of LP. Six diarylheptanoids (L1-L6) were obtained from petroleum ether extract of dried rhizomes of Alpinia officinarum (Liangjiang) with a stationary phase of UP and a mobile phase of MP. Three chemical constituents (Z1-Z3) were obtained from ethyl acetate extract of fresh rhizomes of Anemarrhena asphodeloides (Zhimu) with a stationary phase of MP and a mobile phase of LP. Preparative HPLC was used for further purification if necessary. Seventeen chemical constituents were identified as oxypeucedanin hydrate (B1), byakangelicin (B2), byakangelicol (B3), bergapten (B4), oxypeucedanin (B5), imperatorin (B6), phellopterin (B7), isoimperatorin (B8), 5-hydroxy-7-(4-hydroxy-3-methoxyphenyl)-1-phenyl-3-heptanone (L1), 7-(4-hydroxy-3-methoxyphenyl)-1-phenyl-4E-en-3-heptanone (L2), 5-hydroxy-1,7-diphenyl-3-heptanone (L3), 1,7-diphenyl-4E-en-3-heptanone (L4), 5-hydroxy-1,7-diphenyl-4E,6E-dien-3-heptanone (L5), isomers of 1,7-diphenyl-3,5-heptandione and 5-hydroxy-1,7-diphenyl-4E-en-3-heptanone (L6), mangiferin (Z1), timosaponin A-III (Z2), and 2,6,4'-trihydroxy-4-methoxy-benzophenone (Z3) by means of MS, (1)H and (13)C NMR studies. Five compounds of B3, L3, L5, L6, and Z3 were isolated by CCC for the first time.

  10. Current control methods for grid-side three-phase PWM voltage-source inverter in distributed generation systems

    DEFF Research Database (Denmark)

    Lar, Ionut Andrei; Radulescu, Mircea; Ritchie, Ewen

    2012-01-01

    A comparison between two current control methods of grid side inverter, PI current control and Robust Forward control is made. PI control is implemented in d-q synchronous frame while Forward is implemented in abc stationary frames.The report contains both simulations and experimental test wich...... were made at a reduced scale ( 2.2 kW). The constant power test showed that both method have good results which can respect existing grid codes. The constant power test showed that both method have good results which can respect existing grid codes....

  11. A three-phase model proposal for the evolution of scientific communication: from first print periodicals to current electronic communication system

    Directory of Open Access Journals (Sweden)

    Patrícia Bertin

    Full Text Available Scientific communication has undergone deep transformations, since the emergence of Internet. Aiming to provide further thought on the evolution of scientific communication, this paper features a historical overview of the scientific communication advances over the last twenty years through a three-phase model for the evolution of the electronic journal and the preprints services, and presents Brazilian contemporary panorama for scientific communication. The three-phase model presented in this work is an adaptation of that one proposed by Tenopir et al. (2003 to describe the patterns of journal use by scientists since 1990. The early evolutionary phase followed the emergence of the first digital journals and the creation of repositories in the Web for publishing preliminary versions of scientific literature on the author’s initiative; by that time, most academics reproved electronic publishing initiatives. From 1996 and forward, in the consolidation phase, electronic journals were commonly identical to their print counterparts; the acceptance of the electronic format began to increase, and preprint services got underway in several disciplines. The advanced evolutionary phase started with the world discussion on open access to scientific information. The comparison of the current electronic journal with that viewed by enthusiasts in the first years of the 1990s shows that some aspects still remain to be improved in electronic formal and informal communication, towards effective dissemination of scientific information.

  12. Leakage current analysis of a single-phase transformer-less PV inverter connected to the grid

    DEFF Research Database (Denmark)

    Ma, Lin; Tang, F.; Zhou, F.;

    2009-01-01

    Due to the large surface of the PV generator, its stray capacity with respect to the ground reaches values that can be quite high. When no transformer is used in a grid-connected PV system, common-mode current, which caused by the common mode voltage, can flow through the stray capacitance betwee...

  13. Removal of direct current link harmonic ripple in single-phase voltage source inverter systems using supercapacitors

    OpenAIRE

    Hernandez, Gabriel D.

    2016-01-01

    Approved for public release; distribution is unlimited For an Energy Management System (EMS)-controlled microgrid that uses a single-phase voltage source inverter (VSI) configuration to supply power for AC loads from DC energy storage devices, the DC link connecting the VSI to the DC energy storage devices experiences a voltage ripple that is a second-order harmonic of the AC frequency. When the EMS has a battery bank as the only DC energy storage device, the DC link voltage ripple causes ...

  14. Discrimination between Fatigue Cracking and Mechanical Damage in Aircraft Fastener Holes by Eddy-Current Phase Rotation

    Science.gov (United States)

    2016-08-01

    removal of the interference- fit fasteners or out-of-round hole geometry. These imperfections can lead to either (i) a high degree of ‘noise’ on the...cracks which initiated and grew either in service or while undergoing laboratory-based fatigue testing of the F/A-18 centre barrel. 2...is a well-established NDI method that employs the induced magnetic fields and electrical currents produced by a small probe coil to detect defects

  15. Thermal quasiparticle random-phase approximation with Skyrme interactions and supernova neutral-current neutrino-nucleus reactions

    Science.gov (United States)

    Dzhioev, Alan A.; Vdovin, A. I.; Martínez-Pinedo, G.; Wambach, J.; Stoyanov, Ch.

    2016-07-01

    The thermal quasiparticle random-phase approximation is combined with the Skyrme energy density functional method (Skyrme-TQRPA) to study the response of a hot nucleus to an external perturbation. For the sample nuclei 56Fe and 82Ge, the Skyrme-TQRPA is applied to analyze thermal effects on the strength function of charge-neutral Gamow-Teller transitions, which dominate neutrino-nucleus reactions at Eν≲20 MeV. For the relevant supernova temperatures we calculate the cross sections for inelastic neutrino scattering. We also apply the method to examine the rate of neutrino-antineutrino pair emission by hot nuclei. The cross sections and rates are compared with those obtained earlier from the TQRPA calculations based on the phenomenological quasiparticle-phonon model Hamiltonian. For inelastic neutrino scattering on 56Fe we also compare the Skyrme-TQRPA results to those obtained earlier from a hybrid approach that combines shell-model and RPA calculations.

  16. Proposed chiral texture of the magnetic moments of unit-cell loop currents in the pseudogap phase of cuprate superconductors.

    Science.gov (United States)

    Pershoguba, Sergey S; Kechedzhi, Kostyantyn; Yakovenko, Victor M

    2013-07-26

    We propose a novel chiral order parameter to explain the unusual polar Kerr effect in underdoped cuprates. It is based on the loop-current model by Varma, which is characterized by the in-plane anapole moment N and exhibits the magnetoelectric effect. We propose a helical structure where the vector N(n) in the layer n is twisted by the angle π/2 relative to N(n-1), thus breaking inversion symmetry. We show that coupling between magnetoelectric terms in the neighboring layers for this structure produces optical gyrotropy, which results in circular dichroism and the polar Kerr effect.

  17. Data integrity and electronic calibrations for the Neutral Current Detector phase measurement of the 8B solar neutrino flux at the Sudbury Neutrino Observatory

    Science.gov (United States)

    Cox-Mobrand, Gary A.

    The Sudbury Neutrino Observatory (SNO) is a heavy water Cherenkov detector that observed solar neutrinos via elastic-scattering, charge-current and neutral-current interactions. SNO was designed to measure the flux the total 8B solar neutrino flux in three separate phases, making each measurement under a different set of detector conditions and detection mechanisms. In the third phase, an array of 3He proportional counters was installed, called Neutral Current Detectors (NCDs), which detected neutrons liberated in the neutral-current interactions with deuterium. The neutrino flux can be measured in the NCD phase by identification of neutron capture events via pulse-shape analysis techniques. To accomplish this, the transformation of the neutron capture signals caused by the NCD electronics and data acquisition system (NCD DAQ) must be well known. The NCD DAQ electronics model was developed and quantified, resulting in a small contribution to the systematic uncertainties of neutron identification. Of the four currently proposed neutron identification methods, the parameters which characterize the logarithmic amplification of pulse shapes contribute 1.65%, 0.65%, 0.05% and 0.0% to the systematic uncertainty in the number of identified neutrons. A mechanical problem in two NCDs was discovered that caused the detectors to disconnect from the signal cable with little evidence of being disconnected. The work presented here identified two NCDs that suffered from this mechanical problem and estimated the amount of time that each NCD was disconnected. The remaining NCDs are shown to be unaffected by this problem and an upper limit on the amount of time disconnected was estimated. This was accomplished by an analysis of the rate of thermal noise triggers, an instrumental background noise event. The detected rates of background alphas were also measured to test for anomalously low rates. It was determined that these two NCDs should be removed from the final neutrino flux

  18. Observation of Transient Overcritical Currents in YBCO Thin Films using High-Speed Magneto-Optical Imaging and Dynamic Current Mapping

    Science.gov (United States)

    Wells, Frederick S.; Pan, Alexey V.; Golovchanskiy, Igor A.; Fedoseev, Sergey A.; Rozenfeld, Anatoly

    2017-01-01

    The dynamics of transient current distributions in superconducting YBa2Cu3O7−δ thin films were investigated during and immediately following an external field ramp, using high-speed (real-time) Magneto-Optical Imaging and calculation of dynamic current profiles. A number of qualitatively unique and previously unobserved features are seen in this novel analysis of the evolution of supercurrent during penetration. As magnetic field ramps up from zero, the dynamic current profile is characterized by strong peaks, the magnitude of which exceed the conventional critical current density (as determined from static current profiles). These peaks develop close to the sample edges, initially resembling screening currents but quickly growing in intensity as the external field increases. A discontinuity in field and current behaviour is newly observed, indicating a novel transition from increasing peak current toward relaxation behaviour. After this transition, the current peaks move toward the centre of the sample while reducing in intensity as magnetic vortices penetrate inward. This motion slows exponentially with time, with the current distribution in the long-time limit reducing to the expected Kim-model profile. PMID:28067331

  19. Observation of Transient Overcritical Currents in YBCO Thin Films using High-Speed Magneto-Optical Imaging and Dynamic Current Mapping.

    Science.gov (United States)

    Wells, Frederick S; Pan, Alexey V; Golovchanskiy, Igor A; Fedoseev, Sergey A; Rozenfeld, Anatoly

    2017-01-09

    The dynamics of transient current distributions in superconducting YBa2Cu3O7-δ thin films were investigated during and immediately following an external field ramp, using high-speed (real-time) Magneto-Optical Imaging and calculation of dynamic current profiles. A number of qualitatively unique and previously unobserved features are seen in this novel analysis of the evolution of supercurrent during penetration. As magnetic field ramps up from zero, the dynamic current profile is characterized by strong peaks, the magnitude of which exceed the conventional critical current density (as determined from static current profiles). These peaks develop close to the sample edges, initially resembling screening currents but quickly growing in intensity as the external field increases. A discontinuity in field and current behaviour is newly observed, indicating a novel transition from increasing peak current toward relaxation behaviour. After this transition, the current peaks move toward the centre of the sample while reducing in intensity as magnetic vortices penetrate inward. This motion slows exponentially with time, with the current distribution in the long-time limit reducing to the expected Kim-model profile.

  20. Observation of Transient Overcritical Currents in YBCO Thin Films using High-Speed Magneto-Optical Imaging and Dynamic Current Mapping

    Science.gov (United States)

    Wells, Frederick S.; Pan, Alexey V.; Golovchanskiy, Igor A.; Fedoseev, Sergey A.; Rozenfeld, Anatoly

    2017-01-01

    The dynamics of transient current distributions in superconducting YBa2Cu3O7‑δ thin films were investigated during and immediately following an external field ramp, using high-speed (real-time) Magneto-Optical Imaging and calculation of dynamic current profiles. A number of qualitatively unique and previously unobserved features are seen in this novel analysis of the evolution of supercurrent during penetration. As magnetic field ramps up from zero, the dynamic current profile is characterized by strong peaks, the magnitude of which exceed the conventional critical current density (as determined from static current profiles). These peaks develop close to the sample edges, initially resembling screening currents but quickly growing in intensity as the external field increases. A discontinuity in field and current behaviour is newly observed, indicating a novel transition from increasing peak current toward relaxation behaviour. After this transition, the current peaks move toward the centre of the sample while reducing in intensity as magnetic vortices penetrate inward. This motion slows exponentially with time, with the current distribution in the long-time limit reducing to the expected Kim-model profile.

  1. Current Compensation with Reduced Rating VSC and A ZIG – ZAG Transformer an A Three Phase Four-Wire Distribution System

    Directory of Open Access Journals (Sweden)

    P.Narasimhulu

    2014-09-01

    Full Text Available A reduced rating voltage-source converter with a zig-zag transformer as a distribution static compensator is proposed for power-quality improvement in the three-phase four-wire distribution system. The source voltages in the distribution systems are also experiencing power quality problems, such as harmonics, unbalance, flicker, sag, swell, etc. The distribution static compensator (DSTATCOM is proposed for compensating power quality problems in the current, and the dynamic voltage restorer (DVR is used for mitigating the power quality problems in the voltage. The zig-zag transformer is used for the neutral current compensation. Distribution systems are facing severe power-quality (PQ problems, such as poor voltage regulation, high reactive power and harmonics current burden, load unbalancing, excessive neutral current, etc. The zig-zag transformer is used for providing a path to the zero-sequence current. The DSTATCOM is used to improve the quality of power to the non linear loads. By using both zig-zag transformer and DSTATCOM in the distribution system the rating of the voltage source converter can be reduced. Hence it can be also called reduced rating device. The performance of the DSTATCOM is validated through extensive simulations using MATLAB software with its Simulink and power system block set toolboxes.

  2. 无刷直流电动机不导通相电流分析%Analysis of Floating Phase Current in Brushless DC Motor

    Institute of Scientific and Technical Information of China (English)

    王璞; 解恩; 翟猛

    2012-01-01

    分析了无刷直流电动机在三相六状态及不同的PWM方式下,绕组续流期间不导通相电流,并且指出各有不同.对常用的各种PWM方式通过原理分析及数学推导,得出不导通相电流存在的时段和幅值趋势.并通过实验测试,验证了分析结果.%The floating phase current during the free-wheeling and the difference of the brushless DC motor operating in three-phase-six-states and different PWM modes were analysed. The conclusion of existing time and amplitude trend were achieved by theory analysis and mathematical deduction of common PWM modes. The result was verified through the experiment test.

  3. High-Quality Single Crystalline Ge(111) Growth on Si(111) Substrates by Solid Phase Epitaxy

    Institute of Scientific and Technical Information of China (English)

    SUN Bing; CHANG Hu-Dong; LU Li; LIU Hong-Gang; WU De-Xin

    2012-01-01

    Heterogeneous integration of crystalline Ge layers on cleaned and H-terminated Si(111) substrates are demonstrated by employing a combination of e-beam evaporation and solid phase epitaxy techniques. High-quality single crystalline Ge(111) layers on Si(111) substrates with a smooth Ge surface and an abrupt interface between Ge and Si are obtained.An XRD rocking curve scan of the Ge(111) diffraction peak shovs a FWHM of only 260 arcsec for a 50-nm-thick Ge layer annealed at 600℃ with a ramp-up rate of 20℃/s and a holding time of 1 min. The AFM images exhibit that the rms surface roughness of all the crystalline Ge layers are less than 2.1 nm.

  4. Currents as seen by the protection of a substation three phase short-circuits; Correntes vistas pela protecao nos curtos-circuitos trifasicos de uma subestacao

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, Monaco [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    1998-07-01

    In this paper, is presented a method to determine the currents that are seen by overcurrent protecting devices of the substations feeders and branches used in the petroleum and by products storage and transportation facilities, when a three phase fault occurs in bit bus bar or at motors terminals. This method was based on the theoretical approach developed for the ASYMMETRIC SHORT-CIRCUIT calculations of large electric systems, according to a new configuration for power transformers - which was enable the elaboration of a single software all the studies on short-circuit. (author)

  5. Neutral current and day night measurements from the pure D{sub 2}O phase of SNO

    Energy Technology Data Exchange (ETDEWEB)

    Hallin, A.L.; Beier, E.W.; Biller, S.D.; Boulay, M.G.; Bowler, M.G.; Bowles, T.J.; Brice, S.J.; Bullard, T.V.; Cameron, J.; Chan, Y.D.; Chen, X.; Chen, M.; Cleveland, B.T.; Cox, G.A.; Dai, X.; Dalnoki-Veress, F.; Doe, P.J.; Doucas, G.; Dragowsky, M.R.; Duba, C.A.; Duncan, F.A.; Dunford, M.; Dunmore, J.A.; Earle, E.D.; Elliott, S.R.; Evans, H.C.; Ewan, G.T.; Farine, J.; Fergani, H.; Formaggio, J.A.; Fowler, M.M.; Frame, K.; Frati, W.; Gagnon, N.; Graham, K.; Grant, D.R.; Hahn, R.L.; Hallman, E.D.; Hamer, A.S.; Handler, W.B.; Hargrove, C.K.; Harvey, P.J.; Hazama, R.; Heeger, K.M.; Heintzelman, W.J.; Heise, J.; Helmer, R.L.; Hime, A.; Howe, M.; Jagam, P.; Jelley, N.A.; Kazkaz, K.; Keener, P.T.; Klein, J.R.; Kutter, T.; Kyba, C.C.M.; Law, J.; Lawson, I.T.; Lesko, K.T.; Leslie, J.R.; Levine, I.; Luoma, S.; Majerus, S.; Mak, H.B.; Maneira, J.; Manor, J.; Marino, A.D.; McCauley, N.; McDonald, A.B.; McGregor, G.; Miller, G.G.; Nally, C.W.; Noble, A.J.; Norman, E.B.; Okada, C.E.; Orrell, J.L.; Oser, S.M.; Poon, A.W.P.; Robertson, B.C.; Robertson, R.G.H.; Rosendahl, S.S.E.; Rusu, V.L.; Schaffer, K.K.; Schwendener, M.H.; Simpson, J.J.; Sims, C.J.; Sinclair, D.; Skensved, P.; Smith, M.W.E.; Spreitzer, T.; Starinsky, N.; Stokstad, R.G.; Stonehill, L.C.; Tafirout, R.; Tagg, N.; Van Berg, R.; Van de Water, R.G.; Virtue, C.J.; Waltham, C.E.; Wark, D.L.; West, N.; Wilhelmy, J.B.; Wilkerson, J.F.; Wilson, J.R.; Wittich, P.; Wouters, J.M.; Yeh, M

    2003-04-01

    The Sudbury Neutrino Observatory is a 1000 T D{sub 2}O Cerenkov detector that is sensitive to {sup 8}B solar neutrinos. The energy, radius, and direction with respect to the sun is measured for each neutrino event; these distributions are used to separately determine the rates of the charged current, neutral current and electron scattering reactions of neutrinos on deuterium. Assuming an undistorted {sup 8}B spectrum, the {nu}{sub e} component of the {sup 8}B solar flux is phi{sub e} = 1.76{sup +0.05}{sub -0.05}(stat.){sup +0.09}{sub -0.09} (syst.) x 10{sup 6} cm{sup -2}s{sup -1} based on events with a measured kinetic energy above 5 MeV. The non-{nu}{sub e} component is phi{sub {mu}}{sub {tau}} 3.41{sup +0.45}{sub -0.45}(stat.){sup +0.48}{sub -0.45} (syst.) x 10{sup 6} cm{sup -2}s{sup -1}, 5.3{sigma} greater than zero, providing strong evidence for solar {nu}{sub e} flavor transformation. The total flux measured with the NC reaction is phi{sub NC} = 5.09{sup +0.044}{sub -0.43}(stat.){sup +0.46}{sub -0.43} (sy st.) x 10{sup 6} cm{sup -2}s{sup -1}, consistent with solar models. The night minus day rate is 14.0% {+-} 6.3%{sup +1.5}{sub -1.4}% of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the {nu}{sub e} asymmetry is found to be 7.0% {+-} 4.9%{sup +1.3}{sub -1.2}%. A global solar neutrino analysis is terms of matter-enhanced oscillations of two active flavors strongly favors the Large Mixing Angle (LMA) solution.

  6. Plasma current start-up experiments using outboard- and top-launch lower hybrid wave on the TST-2 spherical tokamak

    Science.gov (United States)

    Shinya, T.; Takase, Y.; Yajima, S.; Moeller, C.; Yamazaki, H.; Tsujii, N.; Yoshida, Y.; Ejiri, A.; Togashi, H.; Toida, K.; Furui, H.; Homma, H.; Nakamura, K.; Roidl, B.; Sonehara, M.; Takahashi, W.; Takeuchi, T.

    2017-03-01

    Non-inductive plasma current start-up experiments were performed using the lower hybrid wave (LHW) on the TST-2 spherical tokamak. The density limit, observed in previous experiments using the outboard-launch antenna, disappeared after changing the plasma condition in the scrape-off layer, and the plasma current reached about 20 kA. In order to improve the LHW power deposition in the plasma core through an up-shift of the parallel wavenumber during the first pass through the plasma, a new top-launch antenna was designed, fabricated and installed. The plasma current ramp-up to 12 kA was achieved using the top-launch antenna alone in a preliminary experiment. Ray-tracing calculations using the measured plasma parameters showed a large up-shift during the first pass, satisfying the strong electron Landau damping condition in the plasma core.

  7. Infrared gas phase study on plasma-polymer interactions in high-current diffuse dielectric barrier discharge

    Science.gov (United States)

    Liu, Y.; Welzel, S.; Starostin, S. A.; van de Sanden, M. C. M.; Engeln, R.; de Vries, H. W.

    2017-06-01

    A roll-to-roll high-current diffuse dielectric barrier discharge at atmospheric pressure was operated in air and Ar/N2/O2 gas mixtures. The exhaust gas from the discharge was studied using a high-resolution Fourier-transform infrared spectrometer in the range from 3000 to 750 cm-1 to unravel the plasma-polymer interactions. The absorption features of HxNyOz, COx, and HCOOH (formic acid) were identified, and the relative densities were deduced by fitting the absorption bands of the detected molecules. Strong interactions between plasma and polymer (Polyethylene-2,6-naphthalate, or PEN) in precursor-free oxygen-containing gas mixtures were observed as evidenced by a high COx production. The presence of HCOOH in the gas effluent, formed through plasma-chemical synthesis of COx, turns out to be a sensitive indicator for etching. By adding tetraethylorthosilicate precursor in the plasma, dramatic changes in the COx production were measured, and two distinct deposition regimes were identified. At high precursor flows, a good agreement with the precursor combustion and the COx production was observed, whereas at low precursor flows an etching-deposition regime transpires, and the COx production is dominated by polymer etching.

  8. Effects of Y211 phase contents on the critical current density Jc and microstructural analysis in YBCO bulk superconductors

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    YBCO bulk superconductors were prepared by the solid state reaction and top-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, the critical transition temperature Tc of samples is 91.5 K for the highest value, and the transition width ?Tc is less than 1 K. The highest magnetization critical current densities Jc achieved 106 A/cm2 under 5 T at 10 K and 1.35?104 A/cm2 under 2 T at 70 K (H//c), respectively. The results combining the SEM observation indicate that doping of Y211 particles is more effective in improving the growth quality of melt-textured YBCO superconductor and in reducing the micro-cracks of specimens. Doping of Y2O3 powder forms the rod-shaped Y211 particles, but doping of Y211 particles directly to matrix materials forms the spherical Y211 particles mainly. Combining the microstructures with Jc measurements shows that the interfaces are most important on flux bundle pinning, in which the gradient of free energy is larger than that of other place between the Y211 particles and the Y123 matrix materials.

  9. CFD studies on the phenomena around counter-current flow limitations of gas/liquid two-phase flow in a model of a PWR hot leg

    Energy Technology Data Exchange (ETDEWEB)

    Deendarlianto, E-mail: deendarlianto@ugm.ac.id [Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Safety Research, P.O. Box 510 119, D-01314 Dresden (Germany); Department of Mechanical and Industrial Engineering, Faculty of Engineering, Gadjah Mada University, Jalan Grafika No. 2, Yogyakarta 55281 (Indonesia); Hoehne, Thomas; Lucas, Dirk; Vallee, Christophe [Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Safety Research, P.O. Box 510 119, D-01314 Dresden (Germany); Zabala, Gustavo Adolfo Montoya [Department of Chemical Engineering, Simon Bolivar University, Valle of Sartenejas, Caracas 1080 (Venezuela, Bolivarian Republic of)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer We modelled CCFL in a PWR hot leg using Algebraic Interfacial Area Density model. Black-Right-Pointing-Pointer The model is able to distinguish the local flow morphologies. Black-Right-Pointing-Pointer Test fluids are air-water and steam-water. Black-Right-Pointing-Pointer Calculated CCFL and water level are in good agreement with experimental data. - Abstract: In order to improve the understanding of counter-current two-phase flow and to validate new physical models, CFD simulations of a 1/3rd scale model of the hot leg of a German Konvoi pressurized water reactor (PWR) with rectangular cross section were performed. Selected counter-current flow limitation (CCFL) experiments conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX using the multi-fluid Euler-Euler modelling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a shear stress transport (SST) turbulence model. In the simulation, the drag law was approached by a newly developed correlation of the drag coefficient in the Algebraic Interfacial Area Density (AIAD) model. The model can distinguish the bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicate also a quantitative agreement between calculations and experimental data for the CCFL characteristics and the water level inside the hot leg channel.

  10. Optimization of BaZrO3 concentration as secondary phase in superconducting YBa2Cu3O7 for high current applications

    Science.gov (United States)

    Malik, Bilal A.; Malik, Manzoor A.; Asokan, K.

    2016-04-01

    We report the superconducting state properties of YBa2Cu3O7 (YBCO) on introduction of BaZrO3 (BZO) as a secondary phase. YBCO+xBZO (x= 0, 2, 4, 6, and 10 wt%) composite samples were prepared by solid state reaction method and characterized for structural, morphological and superconducting properties. X-ray diffraction confirms the increased crystallinity and images of scanning electron microscopy measurement show an increase in both grain size and grain connectivity on addition of BZO in YBCO. These effects are well pronounced in an applied magnetic field. Critical current density, JC, as well as the pinning force peaks at 4% of BZO concentration showed significant difference. A three-fold enhancement in JC and a six-fold enhancement in pinning force were observed at this optimum BZO concentration. This has been attributed to the pinning of flux lines in YBCO due to introduction of BZO as a secondary phase. These results show that this composite has potential application in high current applications.

  11. Optimization of BaZrO3 concentration as secondary phase in superconducting YBa2Cu3O7 for high current applications

    Directory of Open Access Journals (Sweden)

    Bilal A. Malik

    2016-04-01

    Full Text Available We report the superconducting state properties of YBa2Cu3O7 (YBCO on introduction of BaZrO3 (BZO as a secondary phase. YBCO+xBZO (x= 0, 2, 4, 6, and 10 wt% composite samples were prepared by solid state reaction method and characterized for structural, morphological and superconducting properties. X-ray diffraction confirms the increased crystallinity and images of scanning electron microscopy measurement show an increase in both grain size and grain connectivity on addition of BZO in YBCO. These effects are well pronounced in an applied magnetic field. Critical current density, JC, as well as the pinning force peaks at 4% of BZO concentration showed significant difference. A three-fold enhancement in JC and a six-fold enhancement in pinning force were observed at this optimum BZO concentration. This has been attributed to the pinning of flux lines in YBCO due to introduction of BZO as a secondary phase. These results show that this composite has potential application in high current applications.

  12. Lattice Boltzmann simulations of 3D crystal growth: Numerical schemes for a phase-field model with anti-trapping current

    CERN Document Server

    Cartalade, Alain; Plapp, Mathis

    2016-01-01

    A lattice-Boltzmann (LB) scheme, based on the Bhatnagar-Gross-Krook (BGK) collision rules is developed for a phase-field model of alloy solidification in order to simulate the growth of dendrites. The solidification of a binary alloy is considered, taking into account diffusive transport of heat and solute, as well as the anisotropy of the solid-liquid interfacial free energy. The anisotropic terms in the phase-field evolution equation, the phenomenological anti-trapping current (introduced in the solute evolution equation to avoid spurious solute trapping), and the variation of the solute diffusion coefficient between phases, make it necessary to modify the equilibrium distribution functions of the LB scheme with respect to the one used in the standard method for the solution of advection-diffusion equations. The effects of grid anisotropy are removed by using the lattices D3Q15 and D3Q19 instead of D3Q7. The method is validated by direct comparison of the simulation results with a numerical code that uses t...

  13. Estimation of phase signal change in neuronal current MRI for evoke response of tactile detection with realistic somatosensory laminar network model.

    Science.gov (United States)

    BagheriMofidi, Seyed Mehdi; Pouladian, Majid; Jameie, Seyed Behnamedin; Abbaspour Tehrani-Fard, Ali

    2016-09-01

    Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000 PNs of simulated network were positioned randomly in a voxel. Biot-savart law applied to calculate neuronal magnetic field and additional phase. The procedure repeated for eleven neuronal arrangements in the voxel. PSC signal variation with the echo time and voxel size was assessed. The simulated results show that PSC signal increases with echo time, especially 100/80 ms after stimulus for gradient echo/spin echo sequence. It can be up to 0.1 mrad for echo time = 175 ms and voxel size = 1.48 × 1.48 × 2.18 mm(3). With echo time less than 25 ms after stimulus, it was just acquired effects of physiological noise on PSC signal. The absolute value of the signal increased with decrease of voxel size, but its components had complex variation. External field orthogonal to local surface of cortex maximizes the signal. Expected PSC signal for tactile detection in the somatosensory cortex increase with echo time and have no oscillation.

  14. Time-Domain Minimization of Voltage and Current Total Harmonic Distortion for a Single-Phase Multilevel Inverter with a Staircase Modulation

    Directory of Open Access Journals (Sweden)

    Milan Srndovic

    2016-10-01

    Full Text Available This paper presents the optimization technique for minimizing the voltage and current total harmonic distortion (THD in a single-phase multilevel inverter controlled by staircase modulation. The previously reported research generally considered the optimal THD problem in the frequency domain, taking into account a limited harmonic number. The novelty of the suggested approach is that voltage and current minimal THD problems are being formulated in the time domain as constrained optimization ones, making it possible to determine the optimal switching angles. In this way, all switching harmonics can be considered. The target function expression becomes very compact and existing efficient solvers for this kind of optimization problems can find a solution in negligible processor time. Current THD is understood as voltage frequency weighted THD that assumes pure inductive load—this approximation is practically accurate for inductively dominant RL-loads. In this study, the optimal switching angles and respective minimal THD values were obtained for different inverter level counts and overall fundamental voltage magnitude (modulation index dynamic range. Developments are easily modified to cover multilevel inverter grid-connected applications. The results have been verified by experimental tests.

  15. Experimental study on the effects of surface gravity waves of different wavelengths on the phase averaged performance characteristics of marine current turbine

    Science.gov (United States)

    Luznik, L.; Lust, E.; Flack, K. A.

    2014-12-01

    There are few studies describing the interaction between marine current turbines and an overlying surface gravity wave field. In this work we present an experimental study on the effects of surface gravity waves of different wavelengths on the wave phase averaged performance characteristics of a marine current turbine model. Measurements are performed with a 1/25 scale (diameter D=0.8m) two bladed horizontal axis turbine towed in the large (116m long) towing tank at the U.S. Naval Academy equipped with a dual-flap, servo-controlled wave maker. Three regular waves with wavelengths of 15.8, 8.8 and 3.9m with wave heights adjusted such that all waveforms have the same energy input per unit width are produced by the wave maker and model turbine is towed into the waves at constant carriage speed of 1.68 m/s. This representing the case of waves travelling in the same direction as the mean current. Thrust and torque developed by the model turbine are measured using a dynamometer mounted in line with the turbine shaft. Shaft rotation speed and blade position are measured using in in-house designed shaft position indexing system. The tip speed ratio (TSR) is adjusted using a hysteresis brake which is attached to the output shaft. Free surface elevation and wave parameters are measured with two optical wave height sensors, one located in the turbine rotor plane and other one diameter upstream of the rotor. All instruments are synchronized in time and data is sampled at a rate of 700 Hz. All measured quantities are conditionally sampled as a function of the measured surface elevation and transformed to wave phase space using the Hilbert Transform. Phenomena observed in earlier experiments with the same turbine such as phase lag in the torque signal and an increase in thrust due to Stokes drift are examined and presented with the present data as well as spectral analysis of the torque and thrust data.

  16. Stress controlled pulsed direct current co-sputtered Al1−xScxN as piezoelectric phase for micromechanical sensor applications

    Directory of Open Access Journals (Sweden)

    Simon Fichtner

    2015-11-01

    Full Text Available Scandium alloyed aluminum nitride (Al1−xScxN thin films were fabricated by reactive pulsed direct current co-sputtering of separate scandium and aluminum targets with x ≤ 0.37. A significant improvement of the clamped transversal piezoelectric response to strain e31,f from −1.28 C/m2 to −3.01 C/m2 was recorded, while dielectric constant and loss angle remain low. Further, the built-in stress level of Al1−xScxN was found to be tuneable by varying pressure, Ar/N2 ratio, and Sc content. The thus resulting enhancement of the expectable signal to noise ratio by a factor of 2.1 and the ability to control built-in stress make the integration of Al1−xScxN as the piezoelectric phase of micro-electro-mechanical system sensor applications highly attractive.

  17. Phase-field modeling of switchable diode-like current-voltage characteristics in ferroelectric BaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Y., E-mail: yxc238@psu.edu; Randall, C. A.; Chen, L. Q. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Shen, J. [Department of Mathematics, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-05-05

    A self-consistent model has been proposed to study the switchable current-voltage (I-V) characteristics in Cu/BaTiO{sub 3}/Cu sandwiched structure combining the phase-field model of ferroelectric domains and diffusion equations for ionic/electronic transport. The electrochemical transport equations and Ginzburg-Landau equations are solved using the Chebyshev collocation algorithm. We considered a single parallel plate capacitor configuration which consists of a single layer BaTiO{sub 3} containing a single tetragonal domain orientated normal to the plate electrodes (Cu) and is subject to a sweep of ac bias from −1.0 to 1.0 V at 25 °C. Our simulation clearly shows rectifying I-V response with rectification ratios amount to 10{sup 2}. The diode characteristics are switchable with an even larger rectification ratio after the polarization direction is flipped. The effects of interfacial polarization charge, dopant concentration, and dielectric constant on current responses were investigated. The switchable I-V behavior is attributed to the polarization bound charges that modulate the bulk conduction.

  18. Phase equilibria of a low S and C lunar core: Implications for an early lunar dynamo and physical state of the current core

    Science.gov (United States)

    Righter, K.; Go, B. M.; Pando, K. A.; Danielson, L.; Ross, D. K.; Rahman, Z.; Keller, L. P.

    2017-04-01

    Multiple lines of geochemical and geophysical evidence suggest the Moon has a small metallic core, yet the composition of the core is poorly constrained. The physical state of the core (now or in the past) depends on detailed knowledge of its composition, and unfortunately, there is little available data on relevant multicomponent systems (i.e., Fe-Ni-S-C) at lunar interior conditions. In particular, there is a dearth of phase equilibrium data to elucidate whether a specific core composition could help to explain an early lunar geodynamo and magnetic field intensities, or current solid inner core/liquid outer core states. We utilize geochemical information to estimate the Ni, S and C contents of the lunar core, and then carry out phase equilibria experiments on several possible core compositions at the pressure and temperature conditions relevant to the lunar interior. The first composition is 0.5 wt% S and 0.375 wt% C, based on S and C contents of Apollo glasses. A second composition contains 1 wt% each of S and C, and assumes that the lunar mantle experienced degassing of up to 50% of its S and C. Finally a third composition contains C as the dominant light element. Phase equilibrium experiments were completed at 1, 3 and 5 GPa, using piston cylinder and multi-anvil techniques. The first composition has a liquidus near 1550 °C and solidus near 1250 °C. The second composition has a narrower liquidus and solidus temperatures of 1400 and 1270 °C, respectively, while the third composition is molten down to 1150 °C. As the composition crystallizes, the residual liquid becomes enriched in S and C, but S enrichment is greater due to the incorporation of C (but not S) into solid metallic FeNi. Comparison of these results to thermal models for the Moon allow an evaluation of which composition is consistent with the geophysical data of an early dynamo and a currently solid inner and liquid outer core. Composition 1 has a high enough liquidus to start crystallizing

  19. Neuroplastic effects of transcranial direct current stimulation on painful symptoms reduction in chronic Hepatitis C: a phase II randomized, double blind, sham controlled trial

    Directory of Open Access Journals (Sweden)

    Aline Patricia Brietzke

    2016-01-01

    Full Text Available Introduction: Pegylated Interferon Alpha (Peg-IFN in combination with other drugs is the standard treatment for chronic hepatitis C infection (HCV and is related to severe painful symptoms. The aim of this study was access the efficacy of transcranial direct current stimulation (tDCS in controlling the painful symptoms related to Peg-IFN side effects. Material and Methods: In this phase II double-blind trial, twenty eight (n=28 HCV subjects were randomized to receive either five consecutive days of active tDCS (n=14 or sham (n=14 during five consecutive days with anodal stimulation over the primary motor cortex region using 2 mA for 20 minutes. The primary outcomes were visual analogue scale (VAS pain and brain-derived neurotrophic factor (BDNF serum levels. Secondary outcomes were the pressure-pain threshold (PPT, the Brazilian Profile of Chronic Pain: Screen (B-PCP:S and drug analgesics use. Results: tDCS reduced the VAS scores (P<0.003, with a mean pain drop of 56% (p<0.001. Furthermore, tDCS was able to enhance BDNF levels (p<0.01. The mean increase was 37.48% in the active group. Finally, tDCS raised PPT (p<0.001 and reduced the B-PCP:S scores and analgesic use (p<0.05. Conclusions: Five sessions of tDCS were effective in reducing the painful symptoms in HCV patients undergoing Peg-IFN treatment. These findings support the efficacy of tDCS as a promising therapeutic tool to improve the tolerance of the side effects related to the use of Peg-IFN. Future larger studies (phase III and IV trials are needed to confirm the clinical use of the therapeutic effects of tDCS in such condition. Trial registration: Brazilian Human Health Regulator for Research with the approval number CAAE 07802012.0.0000.5327

  20. Totally solution-processed CuInS2 solar cells based on chloride inks: reduced metastable phases and improved current density

    Science.gov (United States)

    Dehghani, Mehdi; Behjat, Abbas; Tajabadi, Fariba; Taghavinia, Nima

    2015-03-01

    Planar superstrate CuInS2 (CIS) solar cell devices are fabricated using totally solution-processed deposition methods. These Cd-free devices are structured by FTO/TiO2/In2S3/CIS/carbon, where TiO2 and In2S3 are deposited by spray pyrolysis, and a CIS film is deposited using spin-coating followed by annealing at 250 °C. The pasted carbon layer is utilized as the anode. No further sulfurization or selenization is employed. The Cu/In ratio in the ink is found as a critical factor affecting the morphology and crystallinity of the film as well as the photovoltaic performance of the device. An optimum Cu/In = 1.05 results in large-grain films with sharp diffraction peaks and, subsequently, optimal series resistance and shunt conductance. It is also found that the chloride-based ink results in CIS films with considerably reduced metastable phases, compared to the conventional acetate-based inks. A current density of 23.6 mA cm-2 is obtained for the best devices, leading to a conversion efficiency of 4.1%.

  1. Stress controlled pulsed direct current co-sputtered Al{sub 1−x}Sc{sub x}N as piezoelectric phase for micromechanical sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Fichtner, Simon, E-mail: sif@tf.uni-kiel.de [Institute of Material Science, Christian-Albrechts-Universität, Kaiserstr. 2, 24143 Kiel (Germany); Reimer, Tim; Chemnitz, Steffen; Wagner, Bernhard [Institute of Material Science, Christian-Albrechts-Universität, Kaiserstr. 2, 24143 Kiel (Germany); Fraunhofer Institute for Silicon Technology, Fraunhoferstr. 1, 25524 Itzehoe (Germany); Lofink, Fabian [Fraunhofer Institute for Silicon Technology, Fraunhoferstr. 1, 25524 Itzehoe (Germany)

    2015-11-01

    Scandium alloyed aluminum nitride (Al{sub 1−x}Sc{sub x}N) thin films were fabricated by reactive pulsed direct current co-sputtering of separate scandium and aluminum targets with x ≤ 0.37. A significant improvement of the clamped transversal piezoelectric response to strain e{sub 31,f} from −1.28 C/m{sup 2} to −3.01 C/m{sup 2} was recorded, while dielectric constant and loss angle remain low. Further, the built-in stress level of Al{sub 1−x}Sc{sub x}N was found to be tuneable by varying pressure, Ar/N{sub 2} ratio, and Sc content. The thus resulting enhancement of the expectable signal to noise ratio by a factor of 2.1 and the ability to control built-in stress make the integration of Al{sub 1−x}Sc{sub x}N as the piezoelectric phase of micro-electro-mechanical system sensor applications highly attractive.

  2. Phase Equilibrium Experiments on Potential Lunar Core Compositions: Extension of Current Knowledge to Multi-Component (Fe-Ni-Si-S-C) Systems

    Science.gov (United States)

    Righter, K.; Pando, K.; Danielson, L.

    2014-01-01

    Numerous geophysical and geochemical studies have suggested the existence of a small metallic lunar core, but the composition of that core is not known. Knowledge of the composition can have a large impact on the thermal evolution of the core, its possible early dynamo creation, and its overall size and fraction of solid and liquid. Thermal models predict that the current temperature at the core-mantle boundary of the Moon is near 1650 K. Re-evaluation of Apollo seismic data has highlighted the need for new data in a broader range of bulk core compositions in the PT range of the lunar core. Geochemical measurements have suggested a more volatile-rich Moon than previously thought. And GRAIL mission data may allow much better constraints on the physical nature of the lunar core. All of these factors have led us to determine new phase equilibria experimental studies in the Fe-Ni-S-C-Si system in the relevant PT range of the lunar core that will help constrain the composition of Moon's core.

  3. Insights from Smart Meters. Ramp-up, dependability, and short-term persistence of savings from Home Energy Reports

    Energy Technology Data Exchange (ETDEWEB)

    Todd, Annika [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Perry, Michael [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Smith, Brian [Pacific Gas and Electric Co., San Francisco, CA (United States); Sullivan, Michael [Nexant, San Francisco, CA (United States); Cappers, Peter [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Goldman, Charles A. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-04-21

    Smart meters, smart thermostats, and other new technologies provide previously unavailable high-frequency and location-specific energy usage data. Many utilities are now able to capture real-time, customer specific hourly interval usage data for a large proportion of their residential and small commercial customers. These vast, constantly growing streams of rich data (or, “big data”) have the potential to provide novel insights into key policy questions about how people make energy decisions. The richness and granularity of these data enable many types of creative and cutting-edge analytics. Technically sophisticated and rigorous statistical techniques can be used to pull useful insights out of this high-frequency, human-focused data. In this series, we call this “behavior analytics.” This kind of analytics has the potential to provide tremendous value to a wide range of energy programs. For example, disaggregated and heterogeneous information about actual energy use allows energy efficiency (EE) and/or demand response (DR) program implementers to target specific programs to specific households; enables evaluation, measurement and verification (EM&V) of energy efficiency programs to be performed on a much shorter time horizon than was previously possible; and may provide better insights into the energy and peak hour savings associated with EE and DR programs (e.g., behavior-based (BB) programs). The goal of this series is to enable evidence-based and data-driven decision making by policy makers and industry stakeholders, including program planners, program administrators, utilities, state regulatory agencies, and evaluators. We focus on research findings that are immediately relevant.

  4. Insights from Smart Meters: Ramp-Up, Dependability, and Short-Term Persistence of Savings from Home Energy Reports

    Energy Technology Data Exchange (ETDEWEB)

    Todd, A. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Perry, M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Smith, B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sullivan, M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Cappers, P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Goldman, C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-04-01

    Smart meters, smart thermostats, and other new technologies provide previously unavailable high-frequency and location-specific energy usage data. Many utilities are now able to capture real-time, customer-specific hourly interval usage data for a large proportion of their residential and small commercial customers. These vast, constantly growing streams of rich data (or big data) have the potential to provide novel insights into key policy questions about how people make energy decisions.

  5. Plasma current start-up using the lower hybrid wave on the TST-2 spherical tokamak

    Science.gov (United States)

    Takase, Y.; Ejiri, A.; Inada, T.; Moeller, C. P.; Shinya, T.; Tsujii, N.; Yajima, S.; Furui, H.; Homma, H.; Imamura, K.; Nakamura, K.; Nakamura, K.; Sonehara, M.; Takeuchi, T.; Togashi, H.; Tsuda, S.; Yoshida, Y.

    2015-12-01

    Non-inductive plasma current start-up, ramp-up and sustainment by waves in the lower hybrid wave (LHW) frequency range at 200 MHz were investigated on the TST-2 spherical tokamak (R0 ≤ 0.38 m, a ≤ 0.25 m, Bt0 ≤ 0.3T, Ip ≤ 0.14 MA). Experimental results obtained using three types of antenna were compared. Both the highest plasma current (Ip = 18 kA) and the highest current drive figure of merit ηCD≡n¯eIpR0/PRF=1.4 ×1017 A/W/m2 were achieved using the capacitively-coupled combline (CCC) antenna, designed to excite the LHW with a sharp and highly directional wavenumber spectrum. For Ip greater than about 5 kA, high energy electrons accelerated by the LHW become the dominant carrier of plasma current. The low value of ηCD observed so far are believed to be caused by a rapid loss of energetic electrons and parasitic losses of the LHW energy in the plasma periphery. ηCD is expected to improve by an order of magnitude by increasing the plasma current to improve energetic electron confinement. In addition, edge power losses are expected to be reduced by increasing the toroidal magnetic field to improve wave accessibility to the plasma core, and by launching the LHW from the inboard upper region of the torus to achieve better single-pass absorption.

  6. Growth of nanocrystalline TiO{sub 2} thin films and crystal anisotropy of anatase phase deposited by direct current reactive magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Sarma, Bimal K., E-mail: sarmabimal@gmail.com [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Paschim Boragaon, Guwahati 781035 (India); Department of Physics, Gauhati University, Gopinath Bordoloi Nagar, Guwahati 781014 (India); Pal, Arup R.; Bailung, Heremba; Chutia, Joyanti [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Paschim Boragaon, Guwahati 781035 (India)

    2013-05-15

    This work describes the growth and elastic anisotropy of nanocrystalline TiO{sub 2} films deposited by direct current reactive magnetron sputtering. The films are nanocrystalline in the gas pressure range 0.4–1.0 Pa even in the absence of substrate bias and substrate heating. It has been observed that gas pressure has a considerable effect on the phase evolution of TiO{sub 2} and at a higher pressure, nanocrystalline anatase can be produced with a greater crystallinity and dense surface. X-ray diffraction line profile analysis of anatase TiO{sub 2} has been performed and the integral breadth expressions of line broadening due to the domain size and lattice microstrain are combined on the basis of the Williamson–Hall (WH) method. The Miller indices dependence of Young's modulus is estimated on the basis of the Reuss approximation for polycrystalline aggregates. Young's modulus shows strong anisotropy. The anisotropic nature of the elastic medium has been introduced in the classical WH plot under the uniform stress deformation model (USDM) and uniform deformation energy density model (UDEDM). USDM represents the better fit of the experimental data. - Highlights: ► Growth of nanocrystalline TiO{sub 2} films prepared by reactive magnetron sputtering. ► Anatase grains grow much faster than rutile grains. ► Near band edge luminescence of TiO{sub 2} due to oxygen vacancies. ► Facile X-ray line profile analysis for nanocrystalline thin films. ► Elastic anisotropy causes X-ray diffraction line broadening of anatase TiO{sub 2}.

  7. Three-phase PFC rectifier with current control for PMSG wind generation systems%永磁风力发电机三相PFC整流器控制策略

    Institute of Scientific and Technical Information of China (English)

    孙旭东; 马颖涛; 柴建云; 翟庆志

    2011-01-01

    A synchronous proportional integral(PI) current control strategy was developed based on a three-phase power factor correction(PFC) rectifier consisting of three single-phase PFC circuits for each phase of a permanent magnetic synchronous generator(PMSG).The current control keeps the stator phase current and voltage in phase.The stator alternating currents are transformed to direct currents in the synchronously rotating reference frame,so the PI regulators give zero steady-state error in the fundamental currents.Simulations and experiments verify that the steady DC output voltage and the sinusoidal AC currents are in phase with the fundamental voltages of the PMSG with this control technique.%针对用于变速恒频风力发电的永磁同步发电机(PMSG),采用每相定子绕组由一个单相功率因数校正(PFC)电路进行整流的拓扑结构,提出了一种同步比例积分(PI)控制策略。根据PMSG运行工况和PFC主电路拓扑结构的特点,选取整流控制目标为发电机定子电流与端电压同相位,并依此设计了控制系统。利用同步旋转坐标变换将电机定子电流变换为直流量进行控制,消除了传统方法中各相PFC电路分别使用一个PI调节器对交流电流进行调节所存在的稳态误差。仿真和实验表明:该控制策略既能稳定直流输出电压,亦能保持发电机三相电流波形正弦,

  8. Analysis of Limiting Measures of Three-phase Short-circuit Current of 500kV Intensive Receiving-end Power Grid in the Early Stage of UHV Construction

    Directory of Open Access Journals (Sweden)

    Zhang Xiao Hang

    2016-01-01

    Full Text Available This paper took the intensive receiving-end power grid as the research object and analysed the problems of three-phase short-circuit current over-limited of 500kV intensive power grid in the early stage of UHV construction. Firstly, this paper analysed the influence factors of the short-circuit current based on self-impedance analysis model of two-port network theory and the equivalent model of UHV power grid. Then, the applicable current-limiting measures were put forward. Finally, this paper proposed one scheme to solve the problems of three-phase short-circuit current over-limited of 500kV buses in one practical receiving-end power grid and verified the feasibility of this scheme from three different aspects. Aiming at the over-limited influential factors, the applicable current-limiting measures can be taken as follows: separating the 500kV bus at UHV substation, lapping the lines outside the substation and decentralizing the power supplies. The proposed measures can effectively solve the problems of short-circuit current over-limited in the early stage of UHV construction and provide reference for other power grid.

  9. 三相电压型PWM整流器无电流传感器控制策略研究%Study on the Sensorless Current Control Strategy of Three- Phase Voltage- Source PWM Rectifier

    Institute of Scientific and Technical Information of China (English)

    毛鸿; 吴兆麟; 王毅; 刘树林

    2001-01-01

    三相电压型PWM整流器有间接电流控制和直接电流控制两种方式,两种控制方式各有优点。根据三相电压型PWM整流器的高频动态数学模型,提出了基于开关函数检测的无电流传感器控制策略。该控制策略兼有间接电流控制结构简单,成本低和直接电流控制动态响应速度快、限流容易、控制精度高等优点。实验结果验证了控制策略的可行性。%There are two basic control schemes for three-phase voltage-source PWM rectifier: the direct current control and indirect current control. The direct current control scheme achieves better dynamic and steady state performance, but its control cost is much higher than the indirect current control. Based on the dynamic high frequency mathematical model of three-phase voltage-source PWM rectifier, a novel sensorless current control strategy is presented for the first time, which is implemented by estimating the variables of the three-phase input current via other variables. The control strategy has super characters such as simple structure, low cost, good dynamic and steady state performance and ability to limit the input currents. A simple hardware implementation is proposed and the good experimental results are reported to confirm the quality of the presented strategy.

  10. Transformer excitation inrush current recognition based on the phase space reconstruction%基于相空间重构的变压器励磁涌流识别

    Institute of Scientific and Technical Information of China (English)

    宋晓; 李平; 徐公林

    2012-01-01

    For the problem that transformer excitation inrush current can cause differential protection maloperation, based on the phase space reconstruction theory, phase spaces of transformer excitation inrush current and different internal fault current series are reconstructed from one-dimensional time series to high-dimensional phase space. Through the research of high dimensional phase space attractor's distribution and movement characteristics, dynamic characteristics are obtained form the original time series. And the characteristic of attractor, namely the correlation dimension is calculated to differentiate transformer excitation inrush current from internal fault current. Experimental analysis results indicate that the value of correlation dimension corresponding with current series of excitation inrush current is greater than 2, but the value of correlation dimension corresponding with current series of internal fault is between 1 and 2. Therefore, they are obviously different. So correlation dimension can serve as a kind of new features criterion to identify transformer excitation inrush current%针对变压器励磁涌流会引起差动保护误动的问题,应用相空间重构理论,对变压器励磁涌流和不同内部故障时的电流序列进行相空间重构,将一维的时间序列重构到高维相空间,通过研究高维相空间吸引子的分布规律和运动特点,获取原始时间序列的动力学特性.计算吸引子的特征量——关联维数来区分变压器励磁涌流与内部故障电流.实验分析结果表明:励磁涌流时电流序列对应的关联维数大于2,而内部故障时电流序列对应的关联维数在1和2之间,两者明显不同.因此关联维数可以作为一种新的特征判据来识别变压器励磁涌流.

  11. Analysis of neutral current in three-phase systems with harmonic pollution; Analisis de la corriente de neutro en sistemas trifasicos con polucion armonica

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, J.A.; Mauro, G.F. di; Dimenna, C.; Anaut, D.; Aguero, C. [Universidad Nacional Mar del Plata (Argentina). Fac. de Ingenieria. Grupo LAT], e-mail: lat@mdp.edu.ar

    2009-07-01

    This paper analyzes potential variables that affect the neutral current when connected receivers presents nonlinear characteristics. Were simulated scenarios in the Alternative Transients Program combining the type and number of units loads, fed on sinusoidal voltages, symmetrical, balanced, asymmetrical and unbalanced. Also has been studied the effect of voltage harmonics. As a result of simulations with asymmetric and unbalanced sources was found variations in the neutral current up to 5%. Analysis of diversity effects and attenuation reported significant variances: 10% and 20% respectively. The results achieved show that asymmetries and imbalances in power have a slight impact on the neutral current, while the more prominent were the diversity and attenuation effects.

  12. It does not always have to be three-phase current. Digitalisation makes dc drives still attractive. Es muss nicht immer Drehstrom sein. Digitalisierung macht Gleichstromantriebe weiter attraktiv

    Energy Technology Data Exchange (ETDEWEB)

    Heinrich, W. (ABB Antriebstechnik GmbH, Lampertheim (Germany))

    1992-01-31

    The stormy development of three-phase drives has replaced the dc systems in mechanical engineering and plant engineering partially, but the dc drive has managed to preserve its attractivity. Digitalisation sees to it. The progress made here is proved by the example a digital compact power converter of the second generation. (orig.).

  13. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  14. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  15. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  16. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  17. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  18. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  19. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  20. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  1. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  2. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  3. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  4. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  5. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  6. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in Ventura County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  7. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in Orange County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  8. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in Los Angeles County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  9. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  10. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  11. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in San Diego County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  12. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in Orange County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  13. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  14. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  15. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in Orange County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  16. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  17. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in Ventura County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  18. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in Ventura County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  19. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  20. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 1-year storm in Ventura County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  1. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in Orange County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  2. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: average conditions in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  3. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 20-year storm in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  4. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 2 ocean-currents projections: 100-year storm in Santa Barbara County

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. The Coastal Storm Modeling System...

  5. Derivation of linearized transfer functions for switching-mode regulations. Phase A: Current step-up and voltage step-up converters

    Science.gov (United States)

    Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.

    1981-01-01

    Small-signal models are derived for the power stage of the voltage step-up (boost) and the current step-up (buck) converters. The modeling covers operation in both the continuous-mmf mode and the discontinuous-mmf mode. The power stage in the regulated current step-up converter on board the Dynamics Explorer Satellite is used as an example to illustrate the procedures in obtaining the small-signal functions characterizing a regulated converter.

  6. Region-specific regulation of voltage-gated intrinsic currents in the developing optic tectum of the Xenopus tadpole.

    Science.gov (United States)

    Hamodi, Ali S; Pratt, Kara G

    2014-10-01

    Across the rostrocaudal (RC) axis of the Xenopus tadpole optic tectum exists a developmental gradient. This gradient has served as a useful model to study many aspects of synapse and dendrite maturation. To compliment these studies, we characterized how the intrinsic excitability, the ease in which a neuron can fire action potentials, might also be changing across the same axis. Whole-cell recordings from tectal neurons at different points along the RC axis revealed a graded increase in intrinsic excitability: compared with neurons at the caudal end of the tectum, neurons at the rostral end fired more action potentials in response to current injection and expressed greater peak Na⁺ and K⁺ currents, the major intrinsic currents in these neurons that underlie the action potential. We also observed, along the same axis and in the same direction, a previously described increase in the amount of synaptic drive received by individual neurons (Wu GY, Malinow R, Cline HT. Science 274: 972-976, 1996). Thus as synaptic activity ramps up across the RC axis, so does intrinsic excitability. The reduction of overall circuit activity induced a compensatory scaling up of peak Na⁺ and K⁺ currents only in the caudal portion of the tectum, suggesting a region-specific, compensatory form of plasticity.

  7. Polarity, selectivity and performance of hydrophilic organic/salt-containing aqueous two-phase system on counter-current chromatography for polar compounds.

    Science.gov (United States)

    Liu, Dan; Hong, Zhilai; Gao, Mingzhe; Wang, Zhixin; Gu, Ming; Zhang, Xiaozhe; Xiao, Hongbin

    2016-05-27

    The essential attributes of a solvent system for separation polar compounds on CCC are polarity, selectively and performance. Here, hydrophilic organic/salt-containing aqueous two-phase system (HO/S TPS) was evaluated as an alternative solvent system for CCC separation of polar compounds. Polarity measurements based on Rohrschneider-Snyder parameter was developed as quantitative assessing the polarity of HO/S TPS and comparing with an organic/aqueous system. All investigated 1-butanol/ethanol/saturated ammonium sulfate solution/water (BEAsWat) and 1-butanol/ethanol/saturated dipotassium hydrogen phosphate solution/water (BEDhpWat) systems with polarity values of organic phase from 4.5 to 6.8, were more polar than chloroform/methanol/water (1/1/1). The considerable water content of BEAsWat and BEDhpWat (0/1/1/1/) was 45.4 and 42.6% (w%) of hydrophilic organic phase, and 66.4 and 51.2% (w%) of salt-containing aqueous phase, respectively, closed to conventional aqueous two-phase system. Therefore, the polarity of HO/S TPS is in the middle of organic/aqueous and aqueous two-phase system. The LogKC values of twenty four polar compounds as model mixture confirmed that the polarities of HO/S TPSs were matched to that of the polar compounds and shown to be a very selective technique capable of separating positional isomers. Moreover, BEAsWat and BEDhpWat systems can be easily retained in CCC column with suitable elution mode. The hydrodynamic behavior reversion of HO/S TPS on hydrodynamic CCC was observed and was tentatively explained based on the density difference. Finally, caffeoylquinic acid isomers and dihydroxybenzoic acid isomers were successfully separated with HO/S TPS on CCC, respectively. Those results demonstrate that HO/S TPS on CCC is a performant and stable way to separate polar compounds from natural products.

  8. Laser and electrical current induced phase transformation of In{sub 2}Se{sub 3} semiconductor thin film on Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Chih-Yuan [Intel Corporation, Hillsboro, OR (United States); Shamberger, Patrick J.; Ohuchi, Fumio S. [University of Washington, Department of Materials Science and Engineering, Seattle, WA (United States); Yitamben, Esmeralda N.; Olmstead, Marjorie A. [University of Washington, Department of Physics, Seattle, WA (United States); Beck, Kenneth M. [W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA (United States); Joly, Alan G. [Fundamental and Computational Sciences, Pacific Northwest National Laboratory, Richland, WA (United States)

    2008-10-15

    Phase transformation of thin film ({proportional_to}30 nm)In{sub 2}Se{sub 3}/Si(111) (amorphous{yields}crystalline) was performed by resistive annealing and the reverse transformation (crystalline{yields}amorphous) was performed by nanosecond laser annealing. As an intrinsic-vacancy, binary chalcogenide semiconductor, In{sub 2}Se{sub 3} is of interest for non-volatile phase-change memory. Amorphous In{sub x}Se{sub y} was deposited at room temperature on Si(111) after pre-deposition of a crystalline In{sub 2}Se{sub 3} buffer layer (0.64 nm). Upon resistive annealing to 380 C, the film was transformed into a {gamma}-In{sub 2}Se{sub 3} single crystal with its {l_brace}0001{r_brace} planes parallel to the Si(111) substrate and (11 anti 20) parallel to Si(1 anti 10), as evidenced by scanning tunneling microscopy, low energy electron diffraction, and X-ray diffraction. Laser annealing with 20-ns pulses (0.1 millijoules/pulse, fluence {<=}50 mJ/cm{sup 2}) re-amorphized the region exposed to the laser beam, as observed with photoemission electron microscopy (PEEM). The amorphous phase in PEEM appears dark, likely due to abundant defect levels inhibiting electron emission from the amorphous In{sub x}Se{sub y} film. (orig.)

  9. Laser and Electrical Current Induced Phase Transformation of In2Se3 Semiconductor thin film on Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Chih-Yuan [Intel Corporation, Hillsboro, OR (United States); Shamberger, Patrick J. [Univ. of Washington, Seattle, WA (United States); Yitamben, Esmeralda N. [Univ. of Washington, Seattle, WA (United States); Beck, Kenneth M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joly, Alan G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Olmstead, Marjorie A. [Univ. of Washington, Seattle, WA (United States); Ohuchi, Fumio S. [Univ. of Washington, Seattle, WA (United States)

    2008-07-25

    Phase transformation of thin film (~30 nm) 2Se3 /Si(111) (amorphous → crystalline) was performed by resistive annealing and the reverse transformation (crystalline → amorphous) was performed by nanosecond laser annealing. As an intrinsic-vacancy, binary chalcogenide semiconductor, 2Se3 is of interest for non-volatile phase-change memory. Amorphous InxSey was deposited at room temperature on Si(111) after pre-deposition of a crystalline 2Se3 buffer layer (6.4 Å). Upon resistive annealing to 380°C, the film was transformed into a y-2Se3 single crystal with its {0001} planes parallel to the Si (111) substrate and parallel to Si , as evidenced by scanning tunneling microscopy, low energy electron diffraction, and x-ray diffraction. Laser annealing with 20 nanosecond pulses (0.1 milliJoules/pulse) re-amorphized the region exposed to the laser beam, as observed with photoemission electron microscopy (PEEM). The amorphous phase in PEEM appears dark, likely due to abundant defect levels inhibiting electron emission from the amorphous InxSey film.

  10. Modulation of auroral electrojet currents using dual modulated HF beams with ELF phase offset, a potential D-region ionospheric diagnostic

    Science.gov (United States)

    GołKowski, M.; Cohen, M. B.; Moore, R. C.

    2013-05-01

    Experiments at the ionospheric heating facility of the High Frequency Active Auroral Research Program (HAARP) are performed employing dual HF beams amplitude modulated at ELF/VLF with a phase offset between the two modulation waveforms. The amplitude of the observed ELF/VLF waves is strongly dependent on the imposed ELF/VLF phase offset, the modulation waveform, and the orientation of the HF beams. Data from two ground stations are interpreted using simulations of modulated heating power envelopes as well as a comprehensive model of ionospheric ELF/VLF generation. It is found that two colocated vertical beams HF beams excite a single ionospheric ELF/VLF source, but independent ELF/VLF sources can be induced in the ionospheric region above the heater if the HF beams are offset from zenith to intersect at their 3 dB points. Furthermore, the use of two vertical HF beams with ELF phase offset is found to be a potential diagnostic method for the ionospheric D region.

  11. An Adaptive Secondary Harmonic Split-phase Restrained Scheme for Magnetizing Inrush Current in Transformers%变压器励磁涌流的自适应二次谐波分相制动方案

    Institute of Scientific and Technical Information of China (English)

    李贞; 张明珠; 倪传坤; 邹欣洁

    2013-01-01

    Yd接线方式的大型变压器由于无法测量三角形绕组环流而采用线电流差动保护,可能出现对称性涌流导致涌流制动判据失效.文中提出一种利用变压器两侧电流互感器测量线电流计算三角形绕组电流的方法,通过计算得到的三角形绕组电流实现相电流差动保护,基于该方法形成一种Yd接线方式的变压器励磁涌流的自适应二次谐波分相制动方案,既可以自适应调整二次谐波制动比,又保证了空合于故障时的差动保护的动作速度,大大提高了变压器差动保护的性能.MATLAB/Simulink仿真结果验证了所提出方案的正确性和有效性.%Currents through delta windings of transformers connected in wye-delta mode cannot be measured directly therefore line differential current is used to realize differential protection. The symmetry inrush current resulted from line differential current may invalidate the restrained criterion for inrush current. A method for calculating the current through delta windings utilizing the measured current from current transformers is proposed. With this calculated current the phase differential current can be obtained. Based on the method an adaptive secondary harmonic split-phase restrained scheme for magnetizing inrush current for transformers connected in wye-delta mode is presented. The scheme can greatly improve the performance of transformer differential protection because it can adaptively adjust the secondary harmonic ratio of restrained current, and guarantee the fast action when transformers with internal faults are no-load energized. Simulation results in MATLAB/ Simulink validate the proposed scheme.

  12. Circuit Design on Three-phase Current Unbalance of Electric Vehicle Motor Controller%电动汽车用电机控制器三相电流不平衡检测电路设计

    Institute of Scientific and Technical Information of China (English)

    赵圣宝; 吴成加

    2015-01-01

    In order to improve the reliability and stability of the electric vehicle motor controller, the authors design a type of three-phase current unbalance circuit, including the selection of the current sensor, the circuit of three-phase filter, the inverting summing circuit of three-phase current, the comparator circuit of upper and lower limits and the light-emitting diode warning. Through simulation experiments, the results verify the detection circuit is correct and feasible.%为提高电动汽车电机控制器的可靠性和稳定性,设计一种三相电流不平衡检测电路,包括电流传感器选型及电路、三相滤波电路、三相电流反相求和电路,上/下限比较电路及发光二极管报警电路。通过仿真试验,验证该检测电路是正确和可行的。

  13. High-performance control of a three-phase voltage-source converter including feedforward compensation of the estimated load current

    Energy Technology Data Exchange (ETDEWEB)

    Leon, Andres E.; Solsona, Jorge A.; Busada, Claudio; Chiacchiarini, Hector [Instituto de Investigaciones en Ingenieria Electrica (IIIE) UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, Bahia Blanca 8000 (Argentina); Valla, Maria Ines [Laboratorio de Electronica Industrial, Control e Instrumentacion (LEICI) and CONICET, Facultad de Ingenieria, Universidad Nacional de La Plata, La Plata 1900 (Argentina)

    2009-08-15

    In this paper a new control strategy for voltage-source converters (VSC) is introduced. The proposed strategy consists of a nonlinear feedback controller based on feedback linearization plus a feedforward compensation of the estimated load current. In our proposal an energy function and the direct-axis current are considered as outputs, in order to avoid the internal dynamics. In this way, a full linearization is obtained via nonlinear transformation and feedback. An estimate of the load current is feedforwarded to improve the performance of the whole system and to diminish the capacitor size. This estimation allows to obtain a more rugged and cheaper implementation. The estimate is calculated by using a nonlinear reduced-order observer. The proposal is validated through different tests. These tests include performance in presence of switching frequency, measurement filters delays, parameters uncertainties and disturbances in the input voltage. (author)

  14. Discovery of Dihydrobenzoxazepinone (GS-6615) Late Sodium Current Inhibitor (Late INai), a Phase II Agent with Demonstrated Preclinical Anti-Ischemic and Antiarrhythmic Properties.

    Science.gov (United States)

    Zablocki, Jeff A; Elzein, Elfatih; Li, Xiaofen; Koltun, Dmitry O; Parkhill, Eric Q; Kobayashi, Tetsuya; Martinez, Ruben; Corkey, Britton; Jiang, Haibo; Perry, Thao; Kalla, Rao; Notte, Gregory T; Saunders, Oliver; Graupe, Michael; Lu, Yafan; Venkataramani, Chandru; Guerrero, Juan; Perry, Jason; Osier, Mark; Strickley, Robert; Liu, Gongxin; Wang, Wei-Qun; Hu, Lufei; Li, Xiao-Jun; El-Bizri, Nesrine; Hirakawa, Ryoko; Kahlig, Kris; Xie, Cheng; Li, Cindy Hong; Dhalla, Arvinder K; Rajamani, Sridharan; Mollova, Nevena; Soohoo, Daniel; Lepist, Eve-Irene; Murray, Bernard; Rhodes, Gerry; Belardinelli, Luiz; Desai, Manoj C

    2016-10-03

    Late sodium current (late INa) is enhanced during ischemia by reactive oxygen species (ROS) modifying the Nav 1.5 channel, resulting in incomplete inactivation. Compound 4 (GS-6615, eleclazine) a novel, potent, and selective inhibitor of late INa, is currently in clinical development for treatment of long QT-3 syndrome (LQT-3), hypertrophic cardiomyopathy (HCM), and ventricular tachycardia-ventricular fibrillation (VT-VF). We will describe structure-activity relationship (SAR) leading to the discovery of 4 that is vastly improved from the first generation late INa inhibitor 1 (ranolazine). Compound 4 was 42 times more potent than 1 in reducing ischemic burden in vivo (S-T segment elevation, 15 min left anteriorior descending, LAD, occlusion in rabbits) with EC50 values of 190 and 8000 nM, respectively. Compound 4 represents a new class of potent late INa inhibitors that will be useful in delineating the role of inhibitors of this current in the treatment of patients.

  15. Inter-machine comparison of the termination phase and energy conversion in tokamak disruptions with runaway current plateau formation and implications for ITER

    Science.gov (United States)

    Martín-Solís, J. R.; Loarte, A.; Hollmann, E. M.; Esposito, B.; Riccardo, V.; FTU; DIII-D Teams; EFDA Contributors, JET

    2014-08-01

    The termination of the current and the loss of runaway electrons following runaway current plateau formation during disruptions have been investigated in the JET, DIII-D and FTU tokamaks. Substantial conversion of magnetic energy into runaway kinetic energy, up to ˜10 times the initial plateau runaway kinetic energy, has been inferred for the slowest current terminations. Both modelling and experiment suggest that, in present devices, the efficiency of conversion into runaway kinetic energy is determined to a great extent by the characteristic runaway loss time, τdiff, and the resistive time of the residual ohmic plasma after the disruption, τres, increasing with the ratio τdiff/τres. It is predicted that, in large future devices such as ITER, the generation of runaways by the avalanche mechanism will play an important role, particularly for slow runaway discharge terminations, increasing substantially the amount of energy deposited by the runaways onto the plasma-facing components by the conversion of magnetic energy of the runaway plasma into runaway kinetic energy. Estimates of the power fluxes on the beryllium plasma-facing components during runaway termination in ITER indicate that for runaway currents of up to 2 MA no melting of the components is expected. For larger runaway currents, minimization of the effects of runaway impact on the first wall requires a reduction in the kinetic energy of the runaway beam before termination and, in addition, high plasma density ne and low ohmic plasma resistance (long τres) to prevent large conversion of magnetic into runaway kinetic energy during slow current terminations.

  16. Single-Phase LLCL-Filter-based Grid-Tied Inverter with Low-Pass Filter Based Capacitor Current Feedback Active damper

    DEFF Research Database (Denmark)

    Liu, Yuan; Wu, Weimin; Li, Yun

    2016-01-01

    The capacitor-current-feedback active damping method is attractive for high-order-filter-based high power grid-tied inverter when the grid impedance varies within a wide range. In order to improve the system control bandwidth and attenuate the high order grid background harmonics by using the quasi....... In this paper, a low pass filter is proposed to be inserted in the capacitor current feedback loop op LLCL-filter based grid-tied inverter together with a digital proportional and differential compensator. The detailed theoretical analysis is given. For verification, simulations on a 2kW/220V/10kHz LLCL...

  17. Zero-sequence current decoupling control of three-phase four-wire active power filter%四桥臂有源滤波器零序电流解耦预测电流控制

    Institute of Scientific and Technical Information of China (English)

    王晓刚; 张杰

    2016-01-01

    针对应用于三相四线制系统中的三相四桥臂有源电力滤波器的特点,研究了一种基于零序电流解耦的预测电流控制方法,分析了零序电流解耦的原理,设计了控制系统。该方法有效地解除了第四桥臂和前三桥臂的耦合,对中线电流进行独立补偿,与三相三桥臂的控制方法兼容,简单易行,易于对三桥臂有源电力滤波器进行改造后应用于三相四线系统。仿真分析表明,与其他方法相比,基于零序电流解耦的预测电流控制可使有源电力滤波器获得更好的补偿性能,电源电流总谐波畸变率和中线电流正负峰值均达到最小。%Zero-sequence current decoupling based predictive current control of three-phase four-wire active power filter (APF)is studied based on the characteristics of three-phase four-leg APF.The principle of zero-se-quence decoupling is analyzed and the control system is designed.The control method eliminates the coupling between the first three legs and the fourth leg,and the neutral current is compensated independently.The meth-od is compatible with the control of three-phase three-leg APF and is simple to implement.It is easy to upgrade the three-leg APF to meet the three-phase four wire applications.Simulation analyses show that zero-sequence current decoupling based predictive current control achieves better compensation performance than other meth-ods,total harmonic distortion of supply currents and positive /negative amplitudes of neutral current are both with minimum.

  18. 5kW phase-shifted full-bridge converter with current doubler using normally-off SiC JFETs designed for 98% efficiency

    DEFF Research Database (Denmark)

    Török, Lajos; Beczkowski, Szymon; Munk-Nielsen, Stig

    2013-01-01

    In this paper a 5kW step-down converter for low-voltage high-current application is presented using normally-off SiC JFETs as high voltage power switches, operating with efficiency close to 98%. Different low voltage side rectification solutions and loss estimations are also presented. As results...

  19. Discussion on the no-load current of three-phase asynchronous motor%浅论三相异步电动机的空载电流

    Institute of Scientific and Technical Information of China (English)

    杨立峰; 郭宗跃; 牛玉敏

    2015-01-01

    该文对以往利用空载电流判断电动机修理质量的方法进行了分析,提出了根据功率因数cosφ和效率η之积的经验值进行经验额定电流计算的方法。并根据长期现场工作经验,针对不同类型的电动机,计算出的经验额定电流和实测的空载电流,给出了鉴定电动机修理质量的具体判断依据。%In this paper, we analysis the conventional method of using the no-load current to judge the quality of motor repairs. Presents mehtod according to the product empirical value of the power factor cosφand efifciencyηto caculate experience rated current.. Based on the long-term ifeld experience, for different types of motor, according to the experience rated current calculated and load current measured, eventually give a speciifc identiifcation basis for motor repair quality.

  20. Abc-frame complex-coefficient filter and controller based current harmonic elimination strategy for three-phase grid connected inverter

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; Guerrero, Josep M.

    2016-01-01

    inverter. Different from the traditional method, our proposal utilizes the unique abc-frame complex-coefficient filter and controller to achieve the balanced, sinusoidal grid current. The main feature of the proposed method is simple and easy to implement without any frame transformation. The theoretical...... analysis and experimental test are presented. The experimental results verify the effectiveness of the proposed control strategy....

  1. An application of the time-step topological model for three-phase transformer no-load current calculation considering hysteresis

    Science.gov (United States)

    Carrander, Claes; Mousavi, Seyed Ali; Engdahl, G. öran

    2017-02-01

    In many transformer applications, it is necessary to have a core magnetization model that takes into account both magnetic and electrical effects. This becomes particularly important in three-phase transformers, where the zero-sequence impedance is generally high, and therefore affects the magnetization very strongly. In this paper, we demonstrate a time-step topological simulation method that uses a lumped-element approach to accurately model both the electrical and magnetic circuits. The simulation method is independent of the used hysteresis model. In this paper, a hysteresis model based on the first-order reversal-curve has been used.

  2. A 3.2-GHz fully integrated low-phase noise CMOS VCO with self-biasing current source for the IEEE 802.11a/hiperLAN WLAN standard

    Science.gov (United States)

    Quemada, C.; Adin, I.; Bistue, G.; Berenguer, R.; Mendizabal, J.

    2005-06-01

    A 3.3V, fully integrated 3.2-GHz voltage-controlled oscillator (VCO) is designed in a 0.18μm CMOS technology for the IEE 802.11a/HiperLAN WLAN standard for the UNII band from 5.15 to 5.35 GHz. The VCO is tunable between 2.85 GHz and 3.31 GHz. NMOS architecture with self-biasing current of the tank source is chosen. A startup circuit has been employed to avoid zero initial current. Current variation is lower than 1% for voltage supply variations of 10%. The use of a self-biasing current source in the tank provides a greater safety in the transconductance value and allows running along more extreme point operation The designed VCO displays a phase noise and output power of -98dBc/Hz (at 100 KHz offset frequency) and 0dBm respectively. This phase noise has been obtained with inductors of 2.2nH and quality factor of 12 at 3.2 GHz, and P-N junction varactors whose quality factor is estimated to exceed 40 at 3.2 GHz. These passive components have been fabricated, measured and modeled previously. The core of the VCO consumes 33mW DC power.

  3. Research on Characteristics of Transformer Differential Current for Different Phase Compensation Methods%不同相位补偿方式下变压器差流特性研究

    Institute of Scientific and Technical Information of China (English)

    孙向飞; 束洪春

    2013-01-01

    研究了励磁涌流条件下,不同相位补偿方式对变压器差动保护差流二次谐波含量的影响.从推导空载合闸磁链表达式出发,分析影响励磁涌流的因素,理论分析了y→△与△→Y两种相位补偿方式对变压器差动保护中差流的二次谐波含量影响的差异,并重点分析了出现对称性涌流情况下的二次谐波含量.在此基础上,对比研究了这两种电流相位补偿方式对二次谐波比励磁涌流识别判据的影响.根据现场录波数据,通过实际数据分别计算分析了相电流及两种相位补偿方式下所得差流的二次谐波比.理论分析和实际计算表明,经Y→△相位补偿后出现的对称性涌流,其二次谐波含量并不低;△→Y相位补偿方式下采用分相闭锁保护也存在问题,也不宜利用未经补偿的相电流计算闭锁判据中的二次谐波比.%The influence of different phase compensation methods on the ratio of second harmonic in differential current for transformer is investigated under magnetizing inrush.Firstly,the flux linkage expression of switching on without load is deduced and influencing factors of inrush current are analyzed.Then this paper compares the differences between two phase compensation methods of Y→ △ and △→Y,with an emphasis on the analysis of the ratio of second harmonic of symmetric inrush.Using inrush waveform of a real transformer,the ratio of second harmonic of phase current and that of differential current under two kinds of phase compensation methods are calculated respectively.Furthermore,based on the calculation results,the effect of two kinds of phase compensation methods on the inrush current identification is proved.The analysis and calculation results show that the ratio of second harmonic of symmetric inrush caused by phase compensation methods,from star to delta,is not low.Moreover,the split-phase blocking scheme should not be adopted for differential protection of from delta

  4. A stable route to high-{beta}{sub p} plasmas with non-monotonic q-profiles

    Energy Technology Data Exchange (ETDEWEB)

    Soeldner, F.X.; Baranov, Y.; Bhatnagar, V.P.; Bickley, A.J.; Challis, C.D.; Fischer, B.; Gormezano, C.; Huysmans, G.T.A.; Kerner, W.; Rimini, F.; Sips, A.C.C.; Springmann, R.; Taroni, A. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Goedbloed, J.P.; Holties, H.A. [Institute for Plasmas Physics, Nieuwegein (Netherlands); Parail, V.V.; Pereverzev, G.V. [Kurchatov Institute of Atomic Energy, Moscow (Russian Federation)

    1994-07-01

    Steady-state operation of tokamak reactors seems feasible in so-called Advanced Scenarios with high bootstrap current in high-beta{sub p} operation. The stabilization of such discharges with noninductive profile control will be attempted on JET in pursuit of previous high bootstrap current studies. Results of modelling studies of full noninductive current drive scenarios in JET and ITER are presented. Fast Waves (FW), Lower Hybrid (LH) Waves and Neutral Beam Injection (NBI) are used for heating and current drive, alternatively or in combination. A stable route to nonmonotonic q-profiles has been found with a specific ramp-up scenario which combines LH-current drive (LHCD) and a fast Ohmic ramp-up. A hollow current profile with deep shear reversal over the whole central region is thereby formed in an early low-beta phase and frozen in by additional heating. (authors). 5 refs., 4 figs.

  5. Detecting Techniques of Harmful Currents in ThreePhase Balanced and Unbalanced Systems%三相平衡和不平衡系统中有害电流的检测技术

    Institute of Scientific and Technical Information of China (English)

    秦梅; 周林; 叶一麟

    2000-01-01

    有源电力滤波器是一种对有害电流进行动 态补偿的装置,其有害电流检测电路是决定补偿性能好坏的关键环节。对其补偿电流在三相 平衡和不平衡系统下的检测技术进行分析和比较。%Active power filter is a kind of device used for dynamic compensation of harmful current.Harmful currents detecting circuits are essential and indispensable parts of active power filters that determine their compensating characters.This paper analyses and compares detecting techniques of compensating currents in threephase balanced and unbalanced systems.

  6. Stationary Frame Current Control Evaluations for Three-Phase Grid-Connected Inverters with PVR-based Active Damped LCL Filters

    DEFF Research Database (Denmark)

    Han, Yang; Shen, Pan; Guerrero, Josep M.

    2016-01-01

    under highly distorted grid conditions. In this paper, a synchronous reference frame equivalent proportional-integral (SRF-EPI) controller in αβ stationary frame using the parallel virtual resistance-based active damping (PVR -AD) strategy for grid-interfaced distributed generation (DG) systems...... to suppress the LCL resonance is proposed. Although both proportional-resonant (PR) controller in αβ stationary frame and PI controller in dq synchronous frame achieve zero steady-state error, the amplitude- and phase-frequency characteristics differ greatly from each other except for the reference tracking...... at fundamental frequency. Therefore, an accurate SRF-EPI controller in αβ stationary frame is established to achieve precise tracking accuracy. Moreover, the robustness, harmonic rejection capabilities, and influence of control delay are investigated by the Nyquist stability criterion when the PVR-based AD...

  7. Study on phase current reconstruction of inverter compressor based on single-resistor sampling%基于单电阻的变频压缩机相电流重构方法

    Institute of Scientific and Technical Information of China (English)

    李岳; 徐鸣; 黄跃进; 顾江萍; 沈希

    2013-01-01

    为了提高直流变频压缩机的控制效率,降低运行成本,需要对其电动机的定子相电流的精确采样.针对电机三相相电流与直流母线电流及逆变器开关状态的关系,结合压缩机电机的数学模型,采用了一种基于单电阻采样母线电流的电机相电流重构方法.首先,结合永磁同步电机(PMSM)的数学模型,对单电阻电流采样重构三相电流技术及其难点进行了原理上的分析;然后,在空间矢量PWM调制过程中的中、高频调制区的非观测区域采用了预测状态观测器的数学方法,正确、有效地完成了三相电流的重构;最后,基于STM32芯片设计了一套无传感器直流变频压缩机控制的平台.实验结果表明,该方法能够实现正确重构相电流,在低成本的变频冰箱领域具有很高的实际应用价值.%In order to improve the control efficiency of the DC inverter compressor and reduce cost, the phase current of motor stator should be sampled. Aiming at the relationship between the motor three-phase current, DC bus current and inverter switch states, three-phase current reconstruction using only a single-resistor in the inverter DC link was proposed. Firstly, based on the mathematical model of permanent magnet synchronous motor (PMSM) , the key technology and difficulties in reconstructing three-phase current by single-resistor sensor were analyzed. Then, a mathematical method of using predictive state observer to the non-observable regions of the middle and high frequency modulation region in the process of space vector PWM modulated was adopted. The three-phase current was constructed effectively and accurately. Finally,based on STM32 chip,a system of senseless DC inverter compressor control was designed. The hardware circuit of the single-resistor sensor was given. The results indicate that this method can correctly reconstruct the phase current and has a high practical value in the field of low-cost frequency

  8. Second Order Generalized Integrator Based Reference Current Generation Method for Single-Phase Shunt Active Power Filters Under Adverse Grid Conditions

    DEFF Research Database (Denmark)

    Golestan, Saeed; Monfared, Mohammad; Guerrero, Josep M.

    2013-01-01

    design procedure based on the pole-zero cancellation, and the extended symmetrical optimum theory is proposed. During the design procedure, the effects of grid frequency variations and the presence of distortion in the grid voltage are taken into account. Finally, to confirm the effectiveness......The reference current generation (RCG) is a crucial part in the control of a shunt active power filter (APF). A variety of RCG techniques have been proposed in literature. Among these, the instantaneous reactive power theory, called pq theory, is probably the most widely used technique. The pq...

  9. Two-phase flow experiments on Counter-Current Flow Limitation in a model of the hot leg of a pressurized water reactor (2015 test series)

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Matthias; Lucas, Dirk; Pietruske, Heiko; Szalinski, Lutz

    2016-12-15

    Counter-Current Flow Limitation (CCFL) is of importance for PWR safety analyses in several accident scenarios connected with loss of coolant. Basing on the experiences obtained during a first series of hot leg tests now new experiments on counter-current flow limitation were conducted in the TOPFLOW pressure vessel. The test series comprises air-water tests at 1 and 2 bar as well as steam-water tests at 10, 25 and 50 bar. During the experiments the flow structure was observed along the hot leg model using a high-speed camera and web-cams. In addition pressure was measured at several positions along the horizontal part and the water levels in the reactor-simulator and steam-generator-simulator tanks were determined. This report documents the experimental setup including the description of operational and special measuring techniques, the experimental procedure and the data obtained. From these data flooding curves were obtained basing on the Wallis parameter. The results show a slight shift of the curves in dependency of the pressure. In addition a slight decrease of the slope was found with increasing pressure. Additional investigations concern the effects of hysteresis and the frequencies of liquid slugs. The latter ones show a dependency on pressure and the mass flow rate of the injected water. The data are available for CFD-model development and validation.

  10. On the interaction of Taylor bubbles rising in two-phase co-current slug flow in vertical columns: turbulent wakes

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, A.M.F.R.; Campos, J.B.L. [Centro de Estudos de Fenomenos de Transporte, Universidade do Porto Rua (Portugal); Coelho Pinheiro, M.N. [Dept. de Engenharia Quimica, Politecnico de Coimbra (Portugal)

    2001-12-01

    An experimental study on the interaction between Taylor bubbles rising through a co-current flowing liquid in a vertical tube with 32 mm of internal diameter is reported. The flow pattern in the bubble's wake was turbulent and the flow regime in the liquid slug was either turbulent or laminar. When the flow regime in the liquid slug is turbulent (i) the minimum distance between bubbles above which there is no interaction is 5D-6D; (ii) the bubble's rising velocity is in excellent agreement with the Nicklin relation; (iii) the experimental values of the bubble length compare well with theoretical predictions (Barnea 1990); (iv) the distance between consecutive bubbles varied from 13D to 16D and is insensitive to the liquid Reynolds number. When the flow regime in the liquid slug is laminar (i) the wake length is about 5D-6D; (ii) the minimum distance between bubbles above which there is no interaction is higher than 25D; (iii) the bubble's rising velocity is significantly smaller than theoretical predictions. These results were explained in the light of the findings of Pinto et al. (1998) on coalescence of two Taylor bubbles rising through a co-current liquid. (orig.)

  11. Design and simulation of control algorithms for stored energy and plasma current in non-inductive scenarios on NSTX-U

    Science.gov (United States)

    Boyer, Mark; Andre, Robert; Gates, David; Gerhardt, Stefan; Menard, Jonathan; Poli, Francesca

    2015-11-01

    One of the major goals of NSTX-U is to demonstrate non-inductive operation. To facilitate this and other program goals, the center stack has been upgraded and a second neutral beam line has been added with three sources aimed more tangentially to provide higher current drive efficiency and the ability to shape the current drive profile. While non-inductive start-up and ramp-up scenarios are being developed, initial non-inductive studies will likely rely on clamping the Ohmic coil current after the plasma current has been established inductively. In this work the ability to maintain control of stored energy and plasma current once the Ohmic coil has been clamped is explored. The six neutral beam sources and the mid-plane outer gap of the plasma are considered as actuators. System identification is done using TRANSP simulations in which the actuators are modulated around a reference shot. The resulting reduced model is used to design an optimal control law with anti-windup and a recently developed framework for closed loop simulations in TRANSP is used to test the control. Limitations due to actuator saturation are assessed and robustness to beam modulation, changes in the plasma density and confinement, and changes in density and temperature profile shapes are studied. Supported by US DOE contract DE-AC02-09CH11466.

  12. Current challenges for pre-earthquake electromagnetic emissions: shedding light from micro-scale plastic flow, granular packings, phase transitions and self-affinity notion of fracture process

    Directory of Open Access Journals (Sweden)

    K. Eftaxias

    2013-10-01

    Full Text Available Are there credible electromagnetic (EM potential earthquake (EQ precursors? This a question debated in the scientific community and there may be legitimate reasons for the critical views. The negative view concerning the existence of EM potential precursors is enhanced by features that accompany their observation which are considered as paradox ones, namely, these signals: (i are not observed at the time of EQs occurrence and during the aftershock period, (ii are not accompanied by large precursory strain changes, (iii are not accompanied by simultaneous geodetic or seismological precursors and (iv their traceability is considered problematic. In this work, the detected candidate EM potential precursors are studied through a shift in thinking towards the basic science findings relative to granular packings, micron-scale plastic flow, interface depinning, fracture size effects, concepts drawn from phase transitions, self-affine notion of fracture and faulting process, universal features of fracture surfaces, recent high quality laboratory studies, theoretical models and numerical simulations. We try to contribute to the establishment of strict criteria for the definition of an emerged EM anomaly as a possibly EQ-related one, and to the explanation of potential precursory EM features which have been considered as paradoxes. A three-stage model for EQ generation by means of pre-EQ fracture-induced EM emissions is proposed. The claim that the observed EM potential precursors may permit a real-time and step-by-step monitoring of the EQ generation is tested.

  13. Terahertz and direct current losses and the origin of non-Drude terahertz conductivity in the crystalline states of phase change materials

    Science.gov (United States)

    Shimakawa, Koichi; Wagner, Tomas; Frumar, Miloslav; Kadlec, Filip; Kadlec, Christelle; Kasap, Safa

    2013-12-01

    THz and DC losses in crystalline states of GeSbTe and AgInSbTe phase-change material systems are re-examined and discussed. Although a simple free carrier transport has been assumed so far in the GeSbTe (GST) system, it is shown through recent experimental results that a series sequence of intragrain and intergrain (tunneling) transport, as recently formulated in Shimakawa et al., "The origin of non-Drude terahertz conductivity in nanomaterials," Appl. Phys. Lett. 100, 132102 (2012) may dominate the electronic transport in the commercially utilized GST system, producing a non-Drude THz conductivity. The extracted physical parameters such as the free-carrier density and mobility are significantly different from those obtained from the Drude law. These physical parameters are consistent with those obtained from the DC loss data, and provide further support for the model. Negative temperature coefficient of resistivity is found even in the metallic state, similar to amorphous metals, when the mean free path is short. It is shown that the concept of minimum metallic conductivity, often used in the metal-insulator transition, cannot be applied to electronic transport in these materials.

  14. Terahertz and direct current losses and the origin of non-Drude terahertz conductivity in the crystalline states of phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Shimakawa, Koichi [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice (Czech Republic); Department of Electrical Engineering, Gifu University (Japan); Wagner, Tomas; Frumar, Miloslav [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice (Czech Republic); Kadlec, Filip; Kadlec, Christelle [Institute of Physics, Academy of Sciences of the Czech Republic, Prague (Czech Republic); Kasap, Safa [Department of Electrical Engineering, University of Saskatchewan, Saskatoon SK S7N 5A9 (Canada)

    2013-12-21

    THz and DC losses in crystalline states of GeSbTe and AgInSbTe phase-change material systems are re-examined and discussed. Although a simple free carrier transport has been assumed so far in the GeSbTe (GST) system, it is shown through recent experimental results that a series sequence of intragrain and intergrain (tunneling) transport, as recently formulated in Shimakawa et al., “The origin of non-Drude terahertz conductivity in nanomaterials,” Appl. Phys. Lett. 100, 132102 (2012) may dominate the electronic transport in the commercially utilized GST system, producing a non-Drude THz conductivity. The extracted physical parameters such as the free-carrier density and mobility are significantly different from those obtained from the Drude law. These physical parameters are consistent with those obtained from the DC loss data, and provide further support for the model. Negative temperature coefficient of resistivity is found even in the metallic state, similar to amorphous metals, when the mean free path is short. It is shown that the concept of minimum metallic conductivity, often used in the metal-insulator transition, cannot be applied to electronic transport in these materials.

  15. Random instabilities of current-voltage curves of BSCCO-2223/Ag multifilamentary tapes in LN2 at 77 K

    CERN Document Server

    Usak, P

    2003-01-01

    The measurement of the current-voltage (I-V) characteristics of BSCCO-2223/Ag multifilamentary tapes in a silver matrix has been performed on short samples (of several centimetres) as well as on long tape (1 m), wound in the form of a helical one-layer coil. Measurements at 77 K and in zero external magnetic field have revealed good reproducibility of the I-V hysteresis in most runs. Nevertheless, strange irregularities have sometimes been observed in the I-V curve behaviour during current ramping up and down. Quasi-reproducible drops from the ascending hysteretic branch in the direction of the descending one have been measured at higher voltage levels (approx 1 mV cm sup - sup 1) on the curve measured on the helical coil. These have recently been explained by a sudden change in the heat transfer coefficient [1]. Rarely and non-reproducibly we have also observed these drops on short samples at E approx 1 x 10 sup - sup 2 V m sup - sup 1 , (and even under 1 x 10 sup - sup 3 V m sup - sup 1). The accidental dro...

  16. Partition efficiencies of newly fabricated universal high-speed counter-current chromatograph for separation of two different types of sugar derivatives with organic-aqueous two-phase solvent systems.

    Science.gov (United States)

    Shinomiya, Kazufusa; Sato, Kazuki; Yoshida, Kazunori; Tokura, Koji; Maruyama, Hiroshi; Yanagidaira, Kazuhiro; Ito, Yoichiro

    2013-12-27

    A new design of universal high-speed counter-current chromatograph (HSCCC) was fabricated in our laboratory. It holds a set of four column holders symmetrically around the rotary frame at a distance of 11.2cm from the central axis. By engaging the stationary gear on the central axis of the centrifuge to the planetary gears on the column holder shaft through a set of idle gears, two pairs of diagonally located column holders simultaneously rotate about their own axes in the opposite directions: one forward (type-J planetary motion) and the other backward (type-I planetary motion) each synchronously with the revolution. Using the eccentric coil assembly, partition efficiencies produced by these two planetary motions were compared on the separation of two different types of sugar derivatives (4-methylumbelliferyl and 5-bromo-4-chloro-3-indoxyl sugar derivatives) using organic-aqueous two-phase solvent systems composed of n-hexane/ethyl acetate/1-butanol/methanol/water and aqueous 0.1M sodium tetraborate, respectively. With lower phase mobile, better peak resolution was obtained by the type-J forward rotation for both samples probably due to higher retention of the stationary phase. With upper phase mobile, however, similar peak resolutions were obtained between these two planetary motions for both sugar derivatives. The overall results indicate that the present universal HSCCC is useful for counter-current chromatographic separation since each planetary motion has its specific applications: e.g., vortex CCC by the type-I planetary motion and HSCCC by the type-J planetary motion both for separation of various natural and synthetic products.

  17. Analysis on Common Mode Current of Single-Phase Grid-Connected PV System%单相光伏并网系统共模电流分析

    Institute of Scientific and Technical Information of China (English)

    杨秋霞; 高金玲; 荣雅君; 任玉艳

    2011-01-01

    Common mode current problem is very important to grid-connected photovoltaic (PV) system and in German standard DIN VDE 0126-1-1, the stipulations related to the common mode current are specified. When common mode current exceeds specified value, the connected PV generation system should be cut off within the stipulated time.Considering the importance of common mode current to the connection of photovoltaic generation to power grid, a common mode current is built. It is known throuth the analysis that common mode current is related to modulation technology and the position where the inductance locates. In allusion to above-mentioned features, a new single-phase grid-connected PV system that can suppress common mode current is designed.The designed system is a full-bridge single-phase gridconnected PV system with AC bypass circuit and in which inductances are symmetically arranged at both phase line and neutral line. Comparing with traditional full-bridge inverter systems adopting unipolar or bi-polar modulation technology,the structure of the proposed single-phase grid-connected PV system not only can eliminate common mode current produced in the grid-connected PV system, but also improve system efficiency and quality of current sent into power grid, thus the overall performance of the grid-connected PV system is improved. Results from theoretical analysis and simulation show that the proposed model and system are correct and available.%共模电流问题是光伏并网系统中的一个重要问题,德国DIN VDE 0126-1-1对共模电流做出了相关规定.当共模电流超过规定值时,系统必须在规定的时间内断开.考虑到共模电流在光伏并网系统中的重要性,建立了共模模型.通过分析可知,共模电流与调制技术和电感的安放位置相关.针对上述特点,设计了能够抑制共模电流的新型单相光伏并网系统,即带有交流旁路且电感对称分布在相线和中线上的全桥光伏并网系统.与传

  18. Design of a coil satellite centrifuge and its performance on counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives with polar organic-aqueous two-phase solvent systems.

    Science.gov (United States)

    Shinomiya, Kazufusa; Tokura, Koji; Kimura, Emiru; Takai, Midori; Harikai, Naoki; Yoshida, Kazunori; Yanagidaira, Kazuhiro; Ito, Yoichiro

    2015-05-01

    A new high-speed counter-current chromatograph, named coil satellite centrifuge (CSC), was designed and fabricated in our laboratory. The CSC apparatus produces the satellite motion such that the coiled column simultaneously rotates around the sun axis (the angular velocity, ω1), the planet axis (ω2) and the satellite axis (the central axis of the column) (ω3). In order to achieve this triplicate rotary motion without twisting of the flow tube, the rotation of each axis was determined by the following formula: ω1=ω2+ω3. This relation enabled to lay out the flow tube without twisting by the simultaneous rotation of three axes. The flow tube was introduced from the bottom side of the apparatus into the sun axis of the first rotary frame reaching the upper side of the planet axis and connected to the column in the satellite axis. The performance of the apparatus was examined on separation of 4-methylumbelliferyl (MU) sugar derivatives as test samples with organic-aqueous two-phase solvent systems composed of ethyl acetate/1-butanol/water (3:2:5, v/v) for lower phase mobile and (1:4:5, v/v) for upper phase mobile. With lower phase mobile, five 4-MU sugar derivatives including β-D-cellobioside (Cel), β-D-glucopyranoside, α-D-mannopyranoside, β-D-fucopyranoside and α-L-fucopyranoside (α-L-Fuc) were separated with the combined rotation around each axis at counterclockwise (CCW) (ω1) - CCW (ω2) - CCW (ω3) by the flow tube distribution. With upper phase mobile, three 4-MU sugar derivatives including α-L-Fuc, β-D-galactopyranoside and Cel were separated with the combined rotation around each axis at clockwise (CW) (ω1) - CW (ω2) - CW (ω3) by the flow tube distribution. A series of experiments on peak resolution and stationary phase retention revealed that better partition efficiencies were obtained at the flow rate of 0.5 mL/min (column 1) and 0.8 mL/min (column 2) for lower phase mobile and 0.2 mL/min (column 1) and 0.4 mL/min (column 2) for upper phase

  19. Three-phase Four-wire Unbalanced Current Compensation Based on Steinmetz Theory%基于Steinmetz理论的三相四线制不平衡电流补偿

    Institute of Scientific and Technical Information of China (English)

    王江彬; 田铭兴; 陈敏; 赵远鑫

    2016-01-01

    由于零序分量的存在,三相四线制电路的不平衡补偿问题较三相三线制电路更复杂。该文基于Steinmetz理论的对称分量分析法考虑三相三线制系统负荷的平衡化补偿思路给出了三相四线制系统负荷不平衡电流的补偿方法,并给出3种约束方程下的补偿电纳模型。在三相四线制系统中,在已找到的3种约束方程条件下,对Y型联接的负荷进行零、负序电流补偿,并使系统功率因数提高到1。最后通过Matlab仿真表明,所提补偿理论不仅能实现不平衡电流的平衡化,还能使系统总功率因数接近于1,证明了所提补偿理论的正确性。%Because of the existence of zero sequence components,the unbalanced compensation of three-phase four-wire system is more complicated than that of three-phase three-wire system. The compensation method of symmetrical component analysis method based on Steinmetz theory in three-phase three-wire system load balancing compensation is considered in the three-phase four-wire system unbalanced load current compensation. Moreover,the compensation mod⁃el of three kinds of constraint equations is given. In the three-phase four-wire system with the three above constraint equations,attempts are made to compensate the zero sequence and negative sequence current for star-connected load, and increase the system power factor to 1. Finally,the Matlab simulation results show that the proposed compensation theory can not only keep the unbalanced current balanced,but also make the power factor of total system be equal to 1 approximately,which proves the correctness of the proposed compensation theory.

  20. 基于涡流脉冲相位热成像的金属材料裂纹检测%Crack detection for metallic materials based on eddy-current pulsed-phase thermography

    Institute of Scientific and Technical Information of China (English)

    胡德洲; 左宪章; 李伟

    2014-01-01

    涡流热成像可以对金属材料表面、近表面缺陷进行快速准确的检测。采用涡流热成像与脉冲相位分析相结合的方法,针对裂纹附近相位谱的分布规律及温度场对相位谱的影响关系问题,分别对带有上表面裂纹和下表面裂纹的45#钢料进行感应加热仿真和实验分析。结果表明,相位谱分布与温度大小无关,只与温度变化趋势有关,相位谱图对不均匀加热有很好的抑制作用,可以扩大裂纹的检测范围,当频率低于12.5 H z时能够清晰地识别裂纹。结合实验验证了仿真结论的正确性,为下一步利用相位信息实现缺陷的定量检测提供参考。%T he surface and near surface crack of metallic materials can be detected efficiently and accurately by eddy current thermography .In this paper ,combining with eddy current ther-mography and pulsed phase analysis ,45# steel with surface and subsurface cracks were studied by inductive heating simulation and experiments ,which were aimed to solve the problem of the phase spectrum distribution and the influence of temperature distribution on the phase spec-trum .It shows that ,the phase spectrum distribution has nothing to do with temperature val-ue ,but is closely related to temperature trend .T he phase image has good suppression to inho-mogeneous heating ,and can also broaden the detection range .Crack can be easily detected when frequency is below 12 .5 Hz .The conclusions are experimentally verified ,in order to pro-vide guidance for quantitative crack detection with the phase information in the future study .

  1. The reporting of adverse events in oncology phase III trials: a comparison of the current status versus the expectations of the EORTC members.

    Science.gov (United States)

    Maillet, D; Blay, J Y; You, B; Rachdi, A; Gan, H K; Péron, J

    2016-01-01

    Determination of drug safety and tolerability is usually based on the frequency of certain key adverse events (AEs) rather than the frequency of all-grade toxicities. We assessed the reporting of key AEs in oncology randomized, controlled trials (RCTs) and compared that with the expectations of the European Organization for Research and Treatment of Cancer (EORTC) membership. RCTs reports published between 2007 and 2011 were reviewed regarding the reporting of key AEs, namely: grade 3/4 AEs, grade 5 AEs, and AEs resulting in study withdrawal or in dose reduction. Study characteristics associated with better reporting of key AEs were investigated. Finally, a survey was conducted among the EORTC membership to determine their expectations on key AEs reporting. Although the frequency of grade 3/4 was reported in most reports (96%), only 17% of them described the reporting threshold above which grade 3/4 AEs were included for reporting, raising the possibility that important but less frequent grade 3/4 AEs might be underreported. Frequency and nature of grade 5 AEs were adequately reported in 161 (50%) of manuscripts; AEs leading to study withdrawal in 61 manuscripts (19%); and AEs leading to dose reduction in 43 manuscripts (13%). In contrast, most EORTC members expected a comprehensive reporting of grade 5 AEs (96% of EORTC member's responses), AEs leading to study withdrawal (86%) and AEs leading to dose reduction (70%). In multivariate analysis, frequencies of grade 5 AEs were less frequently reported in European trials (P = 0.004). Frequencies of AEs leading to withdrawals were more frequently reported in trials funded by industry (P = 0.005) and in trials including patients with breast or urological cancers (P = 0.006). These findings suggest that current practice of key AEs reporting remains highly variable and sometimes inadequate in oncology RCTs reports. Current standards for safety reporting in RCTs should be revised to emphasize the importance of key AEs

  2. Brief Analysis on the Theory of Fault Line Selection of Single Phase Grounding in Small Current Neutral Grounding System%浅析小电流接地系统单相接地故障选线原理

    Institute of Scientific and Technical Information of China (English)

    邢威

    2015-01-01

    文章纵观小电流接地选线的发展历史,简要概括了小电流接地系统发生单相接故障时系统基本特征,分析了几种选线原理的特点,提出了尚需解决的问题,最后给出了分析结论。%In the view of the history of small current grounding fault line selection, the basic features of small current grounding system when single phase grounding failure occurs were briefly summarized, and several characteristics of fault line selection were analyzed, the problems need to be solved were proposed, and the analysis of ifndings was given.

  3. Double hysteresis SVPWM current control method for single-phase three-level rectifiers%单相三电平整流器双滞环SVPWM电流控制方法

    Institute of Scientific and Technical Information of China (English)

    袁洁; 王耀南

    2014-01-01

    Based on the principle of voltage space vector analysis, a kind of double hysteresis current SVPWM control method for a mixed single-phase three-level rectifier is proposed. This paper analyzes the working mode of a single-phase three-level rectifier, puts forward a double hysteresis comparator to control the current inner ring. Four state values will be output from the comparator according to the value of error current. Combined with the area of the command voltage vector which is calculated by the electromotive force and the forcasted current from discretizing, the best output vector of switch is chosen to make the current error be within the scope of the system requirements. Through MATLAB simulation, this paper compares three kinds of control methods, named the tracking voltage vector and two-state hysteresis, four-state double hysteresis SVPWM current. The superiority of the four-state double loop hysteresis controller is verified by the results. The reliability of double hysteresis current control algorithm is testified by the experiment of low power prototype.%基于电压空间矢量分析原理,提出了一种适用于开关管钳位混合单相三电平整流器的双滞环SVPWM电流控制方法。分析了单相三电平整流器的工作模式,提出了一种四态双滞环比较器来控制电流内环。根据输入比较器的误差电流大小,输出四种状态值,结合由电动势与预测电流离散化计算得到的指令电压矢量的所在区域,选择最佳开关输出矢量,使得电流误差控制在系统要求范围内。通过Matlab仿真,比较了跟踪电压矢量、两态单滞环、四态双滞环SVPWM电流三种控制方法,仿真结果验证了四态双滞环电流控制的优越性,通过小功率样机实验验证了双滞环控制算法的可靠性。

  4. 感应电机软启动初始两相瞬态电流解析与控制%Analysis and Control of Initial Two-phase Transient Current During Soft-starting of Induction Motor

    Institute of Scientific and Technical Information of China (English)

    周振华; 崔学深; 王月欣; 付永长

    2012-01-01

    针对三相感应电机调压软启动初始时刻不对称过渡过程及电流冲击问题,给出了求解时域电流解析表达式的方法.该方法根据感应电机两相导通时的数学模型,通过频域和时域变换,得到了感应电机初始两相导通时定子电流与电机参数和晶闸管触发角之间的关系,并分析了不同的初始触发角对感应电机定子电流的影响,进而达到精确控制定子电流首半波峰值的目的.以一台2.2kW感应电机为例进行了实测和MATLAB仿真分析对比,验证了电流解析解的正确性.%A method to solve the time-domain current analytical expression is proposed as to the asymmetry of the transition process and the inrush current at the initial time when three-phase induction motor soft-started by an AC voltage controller. Based on the mathematical model when induction motor is switched on two-phase electrical source, through frequency-domain and time-domain transforming, the relationship between stator current and motor parameters, thyristor triggering angle is obtained, and the impact of different triggering angle on stator current of induction motor is analyzed to precisely control its initial half-wave peak value. At the same time, with a 2. 2kW induction motor as an example, the correctness of the analytical solution is verified by comparing experiments data with MATLAB simulation results.

  5. MHD instabilities and their control in high-beta plasmas in KSTAR

    Energy Technology Data Exchange (ETDEWEB)

    In, Yongkyoon

    2013-02-06

    We established 3 specific tasks as follows: Task 1 - Investigate the MHD activity during the current ramp-up phase with shaped plasmas; Task 2 - Develop a theoretical model that may show the hollowness dependent instability; Task 3 - Explore the beta-limiting instabilities. To address each task, FAR-TECH actively participated in the 2012 KSTAR run-campaign, which helped us make productive progress. Specifically, the shaping dependence of MHD activity during current ramp-up phase was investigated using dedicated run-time in KSTAR (October 4 and 9, 2012), which was also attempted to address the hollowness of temperature (or pressure) profiles. Also, a performance-limiting disruption, which occurred in a relatively high intermediate beta plasma (shot 7110) in KSTAR ({beta}{sub N} ~ 1.7), was studied, and the preliminary analysis shows that the disruption might not be stability-limited but likely density-limited.

  6. Quantitative evaluation of difference in impact of grounding accident on zero-phase voltage and zero-phase current in 6kV distribution system. Results of EMTP simulation; 6kV haiden keito deno chiraku jiko yoso no reiso den`atsu, reiso denryuha eno eikyo ni kansuru teiryoteki hyoka. EMTP (Electro Magnetic Transients Program) simulation kekka

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, K. [Kansai Electric Power Co. Inc., Osaka (Japan)

    1997-10-10

    EMTP (electromagnetic transients program) analysis using accident spot models is conducted to disclose the different effect exerted on the zero-phase voltage and zero-phase current by different grounding accidents. An accident spot producing a near-delta waveform is represented by an equivalent circuit model No. 1 in which a switch simulating a discharge gap and the accident spot resistance are connected in series. In the case of an accident presenting a near-needle waveform, since it is supposed that the discharge is caused to be intermittent because the gap discharge start voltage is high and the accident spot resistance is low, it is presented by an equivalent circuit similar in configuration to model No. 1 with the constants altered. A leak-suggesting waveform with a current flowing even in the neighborhood of the zero cross point is represented by model No. 1 with a leak resistor added in parallel thereto, which circuit is shown as model No. 2. In the accidents represented by model No. 1, zero-phase current waveforms are grouped into three types, and the relations between the switch on-off circuit/grounding resistance and waveform configuration are disclosed. As for the accidents represented by model No. 2, it is found that the leak resistance values fall somewhere in the 200-2000 ohm range. 2 refs., 6 figs., 2 tabs.

  7. Towards a phoenix phase in aeolian research: shifting geophysical perspectives from fluvial dominance

    Energy Technology Data Exchange (ETDEWEB)

    Whicker, Jeffrey J [Los Alamos National Laboratory; Field, Jason P [UNIV OF ARIZONA; Breshears, David D [UNIV OF ARIZONA

    2008-01-01

    Aeolian processes are a fundamental driver of earth surface dynamics, yet the importance of aeolian processes in a broader geosciences context may be overshadowed by an unbalanced emphasis on fluvial processes. Here we wish to highlight that aeolian and fluvial processes need to be considered in concert relative to total erosion and to potential interactions, that relative dominance and sensitivity to disturbance vary with mean annual precipitation, and that there are important scale-dependencies associated with aeolian-fluvial interactions. We build on previous literature to present relevant conceptual syntheses highlighting these issues. We then highlight the relative investments that have been made in aeolian research on dust emission and management relative to that in fluvial research on sediment production. Literature searches highlight that aeolian processes are greatly understudied relative to fluvial processes when considering total erosion in different environmental settings. Notably, within the USA, aeolian research was triggered by the Dust Bowl catastrophe of the 1930s, but the resultant research agencies have shifted to almost completely focusing on fluvial processes, based on number of remaining research stations and on monetary investments in control measures. However, numerous research issues associated with intensification of land use and climate change impacts require a rapid ramping up in aeolian research that improves information about aeolian processes relative to fluvial processes, which could herald a post-Dust Bowl Phoenix phase in which aeolian processes are recognized as broadly critical to geo- and environmental sciences.

  8. Ivabradine prolongs phase 3 of cardiac repolarization and blocks the hERG1 (KCNH2) current over a concentration-range overlapping with that required to block HCN4.

    Science.gov (United States)

    Lees-Miller, James P; Guo, Jiqing; Wang, Yibo; Perissinotti, Laura L; Noskov, Sergei Y; Duff, Henry J

    2015-08-01

    In Europe, ivabradine has recently been approved to treat patients with angina who have intolerance to beta blockers and/or heart failure. Ivabradine is considered to act specifically on the sinoatrial node by inhibiting the If current (the funny current) to slow automaticity. However, in vitro studies show that ivabradine prolongs phase 3 repolarization in ventricular tissue. No episodes of Torsades de Pointes have been reported in randomized clinical studies. The objective of this study is to assess whether ivabradine blocked the hERG1 current. In the present study we discovered that ivabradine prolongs action potential and blocks the hERG current over a range of concentrations overlapping with those required to block HCN4. Ivabradine produced tonic, rather than use-dependent block. The mutation Y652A significantly suppressed pharmacologic block of hERG by ivabradine. Disruption of C-type inactivation also suppressed block of hERG1 by ivabradine. Molecular docking and molecular dynamics simulations indicate that ivabradine may access the inner cavity of the hERG1 via a lipophilic route and has a well-defined binding site in the closed state of the channel. Structural organization of the binding pockets for ivabradine is discussed. Ivabradine blocks hERG and prolongs action potential duration. Our study is potentially important because it indicates the need for active post marketing surveillance of ivabradine. Importantly, proarrhythmia of a number of other drugs has only been discovered during post marketing surveillance.

  9. Single-phase to three-phase power conversion interface

    Science.gov (United States)

    Wu, Jinn-Chang; Wang, Yung-Shan; Jou, Hurng-Liahng; Lu, Wei-Tso

    2016-07-01

    This study proposes a single-phase to three-phase power conversion interface which converts the power from a single-phase utility to three-phase power for a three-phase load. The proposed single-phase to three-phase power conversion interface comprises a bridge-type switch set, a set of three-phase inductors, a transformer set and a set of three-phase capacitors. A current-mode control controls the switching of bridge-type switch set, to generate a set of nonzero-sequence (NZS) currents and a set of zero-sequence (ZS) currents. The transformer set is used to decouple the NZS currents and the ZS currents. The NZS currents are used to generate a high-quality three-phase voltage that supplies power to a three-phase load. The ZS currents flow to the single-phase utility so that the utility current is sinusoidal and in phase with the utility voltage. Accordingly, only a bridge-type switch set is used in the single-phase to three-phase power conversion interface to simply the power circuit. A prototype is developed and tested to verify the performance of the proposed single-phase to three-phase power conversion interface.

  10. Energy Efficiency Financing for Low- and Moderate-Income Households: Current State of the Market, Issues, and Opportunities

    Energy Technology Data Exchange (ETDEWEB)

    Leventis, Greg [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kramer, Chris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Schwartz, Lisa [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-08-09

    Ensuring that low- and moderate-income (LMI) households have access to energy efficiency is equitable, provides energy savings as a resource to meet energy needs, and can support multiple policy goals, such as affordable energy, job creation, and improved public health. Although the need is great, many LMI households may not be able to afford efficiency improvements or may be inhibited from adopting efficiency for other reasons. Decision-makers across the country are currently exploring the challenges and potential solutions to ramping up adoption of efficiency in LMI households, including the use of financing. The report’s objective is to offer state and local policymakers, state utility regulators, program administrators, financial institutions, consumer advocates and other LMI stakeholders with an understanding of: -The relationship between LMI communities and financing for energy efficiency, including important considerations for its use such as consumer protections -The larger programmatic context of grant-based assistance and other related resources supporting LMI household energy efficiency -Lessons learned from existing energy efficiency financing programs serving LMI households -Financing products used by these programs and their relative advantages and disadvantages in addressing barriers to financing or to energy efficiency uptake for LMI households

  11. 三相变压器励磁涌流的MATLAB仿真与分析%Simulation and Analysis for Magnetizing Inrush Current of Three Phase Power Transformer by MATLAB

    Institute of Scientific and Technical Information of China (English)

    孙浩; 黄巍; 窦增

    2015-01-01

    Magnetizing inrush current model of three phase transformer was established on the simulation platform ,in the two cases of no-load input and removed external fault, inrush current waveforms were obtained , and which were carried out the Fast Fourier Transform , and wave shape characteristics of magnetizing inrush current were verified, The simulation results are consistent with the theoretical analysis, and the simulation shows that the software of MATLAB is a good tool to be used to transformer protection research and theoretical teaching.%在Simulink仿真平台上建立三相变压器励磁涌流仿真模型,对变压器空载合闸投入和外部故障切除后两种情况进行仿真,得出励磁涌流波形,并对其进行快速傅里叶变换(FFT),验证了励磁涌流的波形特点,仿真结果与理论相一致,表明MATLAB软件具有强大的仿真功能,是变压器保护研究和理论教学非常重要的工具.

  12. Harmonic and Reactive Currents Detection Method of Unbalanced Three-Phase Voltage System%三相电压不对称系统的谐波和无功电流检测

    Institute of Scientific and Technical Information of China (English)

    杨浩; 叶明佳; 张楠

    2012-01-01

    When three-phase voltages are unbalanced, the circuit structure and mathematical operation of traditional dq harmonic and reactive currents detection method are both comparatively complicated so that the real-time performance and accuracy will be decreased. A novel detection method of unbalanced three—phase voltage system was proposed. The symmetry of fundamental positive-sequence current or fundamental positive - sequence active (reactive) current is comparatively better and its frequency is the same as the voltage' s,so it is used as the input of PLL rather than the voltage to get the sine and cosine signal that dq transformation needs, thus avoiding the problems that unbalanced three-phase voltages cause. This method was built into model and simulated by MATLAB/SIMULINK. Simulation results prove that this improved method raises the detection accuracy and real—time performance, and it has good dynamic response speed, as well as tracking characteristic, and can be implemented simply and applied flexibly.%三相电网电压不对称时存在相位差,会影响电网运行的安全.为了对谐波的实时性及精度进行检测.提出一种改进的dq坐标变换的谐波和无功电流检测法:即用得到的对称性较好且频率与电网电压相同的基波正序电流或基波正序有功(无功)电流代替电网电压进行锁相得到dq变换所需的正余弦信号,避免了三相电压不对称带来的检测精度和实时性问题.利用MATLAB/SIMULINK仿真软件进行建模仿真,仿真结果表明,提出的方法提高了检测的精度和实时性,同时具有良好的动态响应速度及跟踪性能且实现简单、运用灵活.

  13. High-Current Betatron, Phase I.

    Science.gov (United States)

    1982-04-16

    equivalent to the energy imparted by Ionizing radiation to a mass and corresponds to one joule/kilogram. tThe becquerel (Bq) is the SI unit of...resonances. *b. Negative mass instability. C. Resistive wall/negative energy wave insta- bilities. This work was carried out during the period...D. Daugherty, J. Eninger , and G. S. James, Avco Everett Research Report 375, October 1971. 10. W. Clerk, P. Korn, A. Mondelli, and N. Rostoker, Phys

  14. Study on three-phase photovoltaic grid-connected inverter based on current deadbeat control%基于电流无差拍控制的三相光伏并网逆变器的研究

    Institute of Scientific and Technical Information of China (English)

    黄天富; 石新春; 魏德冰; 孙玉巍; 王丹

    2012-01-01

    In order to make the photovoltaic (PV) grid-connected power generation system output high-quality electric power, the paper proposes a three-phase photovoltaic grid-connected inverter current deadbeat control PWM algorithm based on the principle of deadbeat control, and presents an overall control strategy based on current deadbeat control of double-stage photovoltaic grid-connected inverter. This control strategy includes MPPT (Maximum Power Point Tracking) loop, DC voltage loop and AC voltage loop. Simulative results verity the efficacy of current deadbeat control based on Matlab/Simulink. Finally, the proposed control strategy is applied to 10 kW photovoltaic grid-connected inverter, and the experimental results verify the accuracy and validity of grid-connected control strategy and the good dynamic and steady-state characteristics of the PV power generation system. The experimental results also show that the three-phase current total distortion rate is less than 3%, which is better than the data provided in the national standard, and net power factor is equal to 1.%为了使光伏并网发电系统输出高质量的电能,在分析无差拍控制工作原理的基础上,推导了一种三相光伏并网逆变器电流无差拍控制PWM算法,提出了一种基于电流无差拍控制的两级式光伏并网逆变器的总体控制策略.该控制策略包括MPPT(Maximum Power Point Tracking)环、直流电压环和交流电流环.Matlab/Simulink仿真验证了电流无差拍控制的有效性.最后将提出的控制策略应用到10 kW光伏并网逆变器中,实验结果验证了该并网控制策略的正确性和有效性,系统具有良好的动态特性和稳态特性.实验结果所得的三相并网电流总畸变率均在3%以内,优于国标规定值;并网功率因数为1.

  15. 油田电力系统小电流单相接地故障选线研究%Study on Small Current Single-Phase Earth Fault Line-Selection Principle to Oilfield Power System

    Institute of Scientific and Technical Information of China (English)

    阚哲; 王晓蕾; 李庆华; 李成志

    2013-01-01

    In small current grounding system,determining single phase grounding fault lines is quick a key question for realizing protection of power distribution net.Studies at the paper as follows was outspreads:a method of malfunction lineselection using the size and direction of zero sequence full current was advanced in neutral point indirect grounding system on the base of studying malfunction line-selection methods.Besides,a new method of line-selection using zero sequence transient electric charges for identifying single-phase grounding fault was put forward.This method is suit for neutral point to the ground via arc-suppression coil system.Computer simulation results indicate that the method has the merit of high lineselection accuracy rate and is propitious to implement microcomputer line-selection devices.%在小电流接地系统中,迅速判定单相接地故障线路是实现配电网保护的关键问题.在分析研究现有故障选线方法的基础上,提出了利用零序全电流的大小和方向进行故障选线的方法.在此研究的基础上,提出了利用零序暂态电荷实现故障选线的新方法,此方法适用于主变中性点经消弧线圈接地系统.经计算机仿真验证,此方法具有选线准确率高、利于微机选线装置实现的优点.

  16. Performance Analysis and Implementation of Six-phase Induction Machine Based on Trapezoidal Phase Current Waveform Control%基于梯形波相电流控制的六相感应电机性能分析与实现

    Institute of Scientific and Technical Information of China (English)

    艾永乐; 牛联波; 艾宝

    2009-01-01

    With the characteristic which the control of the muhiphase machine is more complex compared with three-phase AC machine, proposed a novel control method in this paper, namely six-phase motor trapezoidal wave phase current control. By using the trapezoidal phase current wavefonn, the stator winding was separated into the field winding and the torque winding. The function which was about the field and torque control in directed and separated mode can be realized without the complex Park transfor-marion. The paper carried on the theoretical analysis, the computation of the air gap magnetomotive force (MMF), the electromagnetism torque and MMF decoupling parameter k. And these results were validated by the experiment. It is shown from the theoretical analysis computation and experiment result that it is possible for the control strategy proposed in this paper and it is also of some advantages not only in the control method but also for motor control performance.%针对传统多相电机控制模式复杂性的特点,提出一种六相感应电机新颖的控制方式,即梯形波相电流控制.把定子绕组分为励磁绕组和转矩绕组,从而实现励磁磁场和转矩磁场的直接控制而不需要复杂的派克变换.对六相电机气隙磁动势、电磁转矩和磁势解耦参数k进行了理论分析和计算,并通过实验进行验证.理论分析和实验结果表明,控制策略是可行的,且还具有其它一些优势.

  17. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2012-01-01

    In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.

  18. Simulation of an active filter for compensation of reactive power and suppression of harmonic currents in the phases and in the neuter of an unbalanced three-phase system of 4 wires; Simulacion de un filtro activo para compensacion de potencia reactiva y supresion de corrientes armonicas en las fases y en el neutro de un sistema trifasico de 4 kilos desbalanceado

    Energy Technology Data Exchange (ETDEWEB)

    Mino Aguilar, Gerardo

    1999-05-01

    In here it is presented a brief review of the state of art of power active filters used in the common coupling points between AC sources and nonlinear loads formed by static converters of AC/DC, for the suppression of harmonic currents and instantaneous compensation of the reactive power. Starting off from the active filters that affect only the three balanced currents of the three-phase systems of 3 wires, it is arrived at the subject of this thesis, whose objective is to solve the problem of the reactive compensation and suppression of harmonic currents in the three phases as well as in the neuter of the three-phase systems of 4 wires. The main contribution of this thesis is the design, analysis and simulation of an active filter that besides of suppressing the harmonic currents and compensating the power factor in the three phases of an unbalanced three-phase system, also has the capacity of removing the current that circulates in the neuter due to the unbalance of the phase currents. This design is based on the extension of the theory of the instantaneous reactive power that includes the existence of the zero sequence components of in the phase currents. It is set out in the thesis a novel filter based on an three-phase inverter of 4 branches, 3 branches of phase and one branch of neuter, that to the best knowledge of the author it has not been reported in the literature. Use is made of an extensive number of simulation results to prove the validity of this filter, whose behavior is superior to the filters for suppression of currents in the neuter existing in the literature, of which also a comparative study is presented. The thesis also includes a mathematical and graphical analysis of the symmetrical components in balanced and unbalanced systems in order to know the nature of the harmonic currents of zero sequence. It is included a section on causes and effects of the harmonic contamination problem. [Spanish] Se presenta un breve revision del estado del

  19. The Alternating Current Phase Tracking Homodyne Compensation Method and Its Implementation Using CORDIC%基于CORDIC的交流相位跟踪零差补偿方法及其实现

    Institute of Scientific and Technical Information of China (English)

    伯恩; 段发阶; 吕昌荣; 张甫恺; 冯帆; 梁春疆

    2014-01-01

    为了消除温度、振动等环境因素在光纤干涉测量中的影响,发展了一种基于交流相位跟踪零差补偿( PTAC)的干涉条纹相位稳定技术。利用马赫-泽德光纤干涉仪结构和杨氏双孔干涉原理实现高密度的余弦分布干涉条纹投射。光纤端面菲涅尔反射与光纤耦合器构成迈克尔逊干涉结构,光电探测器检测迈克尔逊干涉仪的输出信号。相位稳定子系统采用相位生成载波( PGC)方法提取环境因素引起的光纤干涉臂相位差,结合坐标旋转数字式计算机( CORDIC)求解相位差,并生成补偿信号反馈给压电陶瓷(PZT)驱动器,实现条纹相位的稳定。该系统相位解调精度达2.75 mrad,环境因素对干涉条纹相位的影响低于53.43 mrad。实验结果验证了该相位稳定方法的可行性。%In order to eliminate the effection of the environmental factors,such as temperature and vibration,a phase stabilization method of interference fringe map based on the Alternating Current Phase Tracking homodyne compensation( PTAC) is developed. The system makes use of the Mach-Zehnder interferometer structure and Young’s double pinhole interference principle to achieve the high-density interference fringe projection of cosine distribution. The Fresnel reflection on its fiber end face and optical fiber coupler make up a Michelson interferometer structure,the photodetector detects the interference signal. The Phase Generated Carrier ( PGC) method is utilized to achieve the phase difference between interference arms,and the Coordinated Rotation Digital Computer( CORDIC) counts out it. The compensation signal acts as a feedback to the Piezoelectric Transducer(PZT)driver,and a well stability of the fringe phase is achieved. The demodulated phase can be measured with a precision of 2. 75 mrad,the environmental disturbance can be reduced to 53. 43 mrad for the fringe map. The experiment result has verified the availability of the phase

  20. The dynamics of vortex structures and states of current in plasma-like fluids and the electrical explosion of conductors; 1, the model of a non-equilibrium phase transition

    CERN Document Server

    Volkov, N B

    1993-01-01

    A set of equations according to which the conducting medium consists of two fluids - laminar and vortex, has been obtained in the present paper by transforming MHD equations. In a similar way, an electronic fluid is assumed to consist of a laminar and a vortex fluid. This system allows one to study the formation and the dynamics of large-scale hydrodynamic fluctuations. From this model a model of a non-equilibrium phase transition belonging to a class of the Lorenz-type models has been developed [Lorenz E N 1963 J. Atmos. Sci. {\\bf 20} 130]. Vortex structures resulting in the increase in an effective resistance of the conducting medium and the interruption of current have been shown to appear even at constant transport coefficients in a laminar electronic fluid. Critical exponents of the parameters of an order (amplitudes), which for a direct current coincide with the critical exponents in the Lorenz model, have been found. A spatial scale of the structure described by the theory is in good agreement with exp...

  1. Phases and Phase Transitions

    Science.gov (United States)

    Gitterman, Moshe

    2014-09-01

    In discussing phase transitions, the first thing that we have to do is to define a phase. This is a concept from thermodynamics and statistical mechanics, where a phase is defined as a homogeneous system. As a simple example, let us consider instant coffee. This consists of coffee powder dissolved in water, and after stirring it we have a homogeneous mixture, i.e., a single phase. If we add to a cup of coffee a spoonful of sugar and stir it well, we still have a single phase -- sweet coffee. However, if we add ten spoonfuls of sugar, then the contents of the cup will no longer be homogeneous, but rather a mixture of two homogeneous systems or phases, sweet liquid coffee on top and coffee-flavored wet sugar at the bottom...

  2. Practical Calculation Model of Three-phase Short-circuit Current for Doublyˉfed Induction Generator%双馈感应发电机三相短路电流解析计算模型

    Institute of Scientific and Technical Information of China (English)

    石一辉; 鲁宗相; 闵勇; 乔颖; 陈惠粉

    2011-01-01

    The power system short-circuit capacity grows with the increasing of penetration* power from wind farm based on doubly-fed induction generator (DFIG). Thus, it is important to analyze the short-circuit current from wind farm quantitatively in relay setting and breaker switching. Based on the analysis of physical processes following the short-circuit fault of DFIG, the balance circuit of initial fluxes, components of frequencies and the dependent relationship between stator current and rotor current are studied. By solving the flux circuits, an analytic expression and practical calculation method for the short-circuit current are obtained and the perspectives on frequency components, decay time constants, amplitude and initial phase are unified. The practical model simulation results compared with detail model show that the practical model can accurately describe the short circuit current for DFIG.%电网电压跌落在双馈感应发电机(DFIG)定、转子绕组中激发的电磁暂态过程是影响DFIG和电网安全的重要因素,因此,定量分析电压跌落后DFIG的电磁暂态过程具有重要意义.以DFIG电压完全跌落后的物理过程分析为基础,研究了DFIG在三相短路后的磁链初值平衡电路、电流频率特性以及定、转子电流中各频率成分之间的依存关系.根据磁链平衡电路,求解得到了三相短路电流的解析表达式,提出了DFIG三相短路电流的解析计算模型,统一了三相短路过程中频率成分、衰减时间常数、幅值和初相位的分析结论,并通过解析模型与DFIG经典模型的仿真对比验证了模型的有效性.

  3. Study of the active filter for the cancellation of currents of the neutral in three-phase systems; Estudio del filtro activo para la cancelacion de corrientes de neutro en sistemas trifasicos

    Energy Technology Data Exchange (ETDEWEB)

    Diaz Saldierna, Luis Humberto

    2004-05-15

    The proliferation of the so called nonlinear loads has increased in a considerable way in the last years. These loads generate non sine waveforms in the current that consume, producing effects such as low power factor, generation of reactive power and harmonics, to mention some of them. Another problem shows up when an unbalance of loads exists in the three-phase systems with connection to the neutral (star connection); the unbalance generates circulation of currents through the neutral conductor, which can get to be of equal to greater magnitude than the phase currents; these are problems that degrade the quality of the supply and the consumption of electrical energy. Solutions such as the passive filters and active filters are used to face this kind of problems. The passive filters are used to attenuate the harmonics of current of more significant magnitude in three-phase systems non-connected to the neutral (delta connection), nevertheless the passive filters have considerable limitations, because they cannot compensate unbalance, and it is necessary a filter for every harmonic and its performance is adequate for constant loads. The active filters can be used to correct the power factor, since they can get to filter most of the LF harmonics, compensate the loads unbalance and the reactive power flow. In this work a study is made on the neutral currents associated to the active power and harmonic currents in the three-phase systems of four wires, the most active filters are chosen as a solution. The objective of the thesis is to analyze and to construct an active filter of current for the attenuation of current harmonics and the compensation of the load unbalance existing in a three-phase of four wires. The thesis document comprises five chapters and three appendixes, as it is next described: In chapter I a short introduction is presented on the problems and possible solutions of the same ones. In chapter II an analysis is made on the harmonic distortion and the

  4. One-step separation and purification of two chromones and one pyrone from Aloe barbadensis Miller: a comparison between reversed-phase flash chromatography and high-speed counter current chromatography.

    Science.gov (United States)

    Zhong, Jia-Sheng; Wan, Jin-Zhi; Ding, Wen-Jing; Wu, Xiao-Fang; Xie, Zhi-Yong

    2014-01-01

    Chromones and pyrones are the major secondary metabolites of Aloe barbadensis Miller. As they are minor components of the plant, an efficient purification procedure for them is of great importance for promoting their pharmacological studies. To develop efficient methods for one-step separation and purification of two chromones (5-((S)-2'-oxo-4'-hydroxypentyl)-2-hydroxymethylchromone (1) and 5-((4E)-2'-oxo-pentenyl)-2-hydroxymethylchromone (3)) and one pyrone (aloenin aglycone (2)) from A. barbadensis via reversed-phase flash chromatography (RP-FC) and high-speed counter current chromatography (HSCCC). The RP-FC separation was performed using methanol:water (26:74, v/v) as the mobile phase at a flow rate of 20 mL/min. A solvent system composed of dichloromethane:methanol:water (3:1.5:1, v/v/v) was used for the HSCCC separation, at a flow rate of 2.0 mL/min. A one-step RP-FC operation within 110 min was successfully used for the purification of compounds 1 (27.9 mg, 96.5%), 2 (32.4 mg, 98.2%) and 3 (4.1 mg, 99.0%) from 129 mg of crude sample, and a one-step HSCCC separation within 95 min was successfully implemented for the purification of compounds 1 (31.1 mg, 97.6%), 2 (35.8 mg, 96.7%) and 3 (2.7 mg, 98.1%) from 134 mg of crude sample. The developed procedures were efficient, with low cost and high yield, which would afford sufficient amounts of high-purity compounds for chromatographic purposes and pharmacological activity screening. Copyright © 2014 John Wiley & Sons, Ltd.

  5. Current limiters

    Energy Technology Data Exchange (ETDEWEB)

    Loescher, D.H. [Sandia National Labs., Albuquerque, NM (United States). Systems Surety Assessment Dept.; Noren, K. [Univ. of Idaho, Moscow, ID (United States). Dept. of Electrical Engineering

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  6. Ontology matchmaking of product ramp-up knowledge in manufacturing industries - How to transfer a cake-baking recipe between bakeries

    OpenAIRE

    2016-01-01

    von Roland Willmann Arbeit an der Bibliothek noch nicht eingelangt - Daten nicht geprueft Abweichender Titel nach Übersetzung der Verfasserin/des Verfassers Technische Universität Wien, Univ., Dissertation, 2016

  7. Sound exposure changes European seabass behaviour in a large outdoor floating pen: Effects of temporal structure and a ramp-up procedure

    NARCIS (Netherlands)

    Neo, Y.Y.; Hubert, J.; Bolle, L.J.; Winter, Hendrik V.; Cate, ten C.; Slabbekoorn, H.

    2016-01-01

    Underwater sound from human activities may affect fish behaviour negatively and threaten the stability of fish stocks. However, some fundamental understanding is still lacking for adequate impact assessments and potential mitigation strategies. For example, little is known about the potential contri

  8. Single-Phase Photovoltaic Grid-Connected Inverter under Constant-Frequency Hysteresis Current Control%恒频滞环电流控制的单相光伏并网逆变器

    Institute of Scientific and Technical Information of China (English)

    刘俊杰; 张新燕

    2012-01-01

    Based on the mathematical models of photovoltaic module practical in engineering,the module simulation model is established in PSIM software for the output quickly and dynamically changing with light intensity and temperature, and the output electrical characteristics of the PV module is analyzed by simulation.Meanwhile an algorithm is proposed to achieve MPPT,and its validity has been verified.Grid-connected inverter is a key electrical element of grid-connected PV system,influencing power quality and system stability.The grid-connected inverter under constantfrequency hysteresis current control is adopted,and the dynamic simulation model is built for the grid-connected singlephase PV system.The simulation results verify that the single-phase PV grid-connected inverter under constant-frequency hysteresis current control can track public grid quickly and effectively,output grid-connected current with low harmonic distortion rate,and enhance the stability and dynamism of grid-connected PV system,as well as its output efficiency.%基于符合工程实际的光伏模块数学模型,在PSIM软件中建立输出能快速动态随光照强度与温度变化的模块仿真模型,通过仿真分析光伏模块的输出电气特性。同时提出一种实现模块最大功率跟踪算法,并验证其有效性。光伏并网发电系统中的关键部件并网逆变器,影响电能质量与系统稳定。采用恒频滞环电流跟踪控制下的并网逆变器,建立单相光伏并网发电系统的动态仿真模型,仿真结果验证了恒频滞环电流控制光伏并网逆变器能够快速有效地跟踪公共电网,输出谐波畸变率低的并网电流,改善并网系统稳定性与动态性,提高光伏系统输出效率。

  9. 基于低压电力载波通信的单相智能电表的设计%Design of Single-phase Smart Meter Based on low Voltage Power Line Carrier-Current Communication

    Institute of Scientific and Technical Information of China (English)

    宋树祥; 韦正丛; 梁承福; 何婷婷

    2012-01-01

    In order to remote real-time monitoring and management of single-phase smart meters, a single-phase smart meters has been designed based on carrier chip PL3201 and metering chip 90E24. This design used the low-voltage power line carrier communication, by the direct sequence spread spectrum communication technology, making the system's anti - jamming capability improved significantly. Meanwhile, the design uses the IDT's latest high - precision chip 90E24, the measurement accuracy is better than current industry standards, in a considerable time, the power sector to meet national requirements for measurement accuracy. Practical results show that the design is not only Low-cost, simple, and the measurement of high precision, strong anti -interference, for low carrier concentration meter reading system.%为了对单相智能电表进行远程实时监控管理,设计了一种基于载波芯片PL3201和计量芯片90E24的单相智能电表;该设计把直接序列扩频通信技术应用于低压电力线载波通信,使得系统的抗干扰能力得到显著提升;同时,该设计采用了IDT公司最新推出的高精度计量芯片90E24进行计量,其计量精度优于目前业内水平,能在相当时间内满足国家电力部门对计量精度的要求;实践结果表明,该设计不仅成本低廉、方法简单,且计量精度高、扰干扰能力强,适用于低压载波集中抄表系统.

  10. Current Titles

    Energy Technology Data Exchange (ETDEWEB)

    Various

    2006-06-01

    This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Jane Cavlina, Administrator, at 510/486-6036.

  11. Study of the generation of non-inductive current in Tore Supra and application to operational scenarios of a continuous tokamak; Etude de la generation de courant non inductive dans Tore Supra et application aux scenarios operationnels d`un tokamak continu

    Energy Technology Data Exchange (ETDEWEB)

    Kazarian-Vibert, F.

    1996-07-05

    Lower Hybrid Current Drive in tokamak plasma allows to obtain continuous operations, which constitute a necessary step towards a definition of a thermonuclear fusion reactor. The objectives of this work is to define and study fully non inductive steady-state scenarios on Tore Supra. The current diffusion equation is solved to determined precisely the inductive and non inductive current density profiles and their influence on the time evolution of a discharge. Then, a new operation mode is studied theoretically and experimentally. In this scenario, the transformer primary circuit voltage is controlled in such a way that the flux consumption vanishes. It allows to achieve full steady-state discharges in a fast and reproducible manner. A theoretical flux consumption scaling law during plasma current ramp-up assisted by Lower Hybrid waves is presented and validated by experimental data, in view to minimized this consumption. The influence of a non monotonic current density profile on the confinement and the transport of energy in the plasma is also clearly illustrated by experiments. (author). 155 refs.

  12. Study of the non inductive current generation in Tore Supra and application to the operational scenario of a continuous tokamak; Etude de la generation de courant non inductive dans Tore Supra et application aux scenarios operationnels d`un tokamak continu

    Energy Technology Data Exchange (ETDEWEB)

    Kazarian-Vibert, F.

    1996-07-05

    Lower Hybrid Current Drive in tokamak plasmas allows to obtain continuous operations, which constitute a necessary step towards a definition of a thermonuclear fusion reactor. The objectives of this work is to define and study fully non inductive steady-state scenarios on Tore Supra. The current diffusion equation is solved to determined precisely the inductive and non inductive current density profiles and their influence on thee time evolution of a discharge. Then, a new operation mode is studied theoretically and experimentally. In this scenario, the transformer primary circuit voltage is controlled in such a way that the flux consumption vanishes. It allows to achieve full steady-state discharges in a fast and reproducible manner. A theoretical flux consumption scaling law during plasma current ramp-up assisted by Lower-Hybrid waves is presented and validated by experimental data, in view to minimized this consumption. The influence of a non monotonic current profile on the confinement and the transport of energy in the plasma is also clearly illustrated by experiments. (author). 138 refs., 16 figs., 1 tab.

  13. Comparison of the peak resolution and the stationary phase retention between the satellite and the planetary motions using the coil satellite centrifuge with counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives.

    Science.gov (United States)

    Shinomiya, Kazufusa; Zaima, Kazumasa; Harada, Yukina; Yasue, Miho; Harikai, Naoki; Tokura, Koji; Ito, Yoichiro

    2017-01-20

    Coil satellite centrifuge (CSC) produces the complex satellite motion consisting of the triplicate rotation of the coiled column around three axes including the sun axis (the angular velocity, ω1), the planet axis (ω2) and the satellite axis (the central axis of the column) (ω3) according to the following formula: ω1=ω2+ω3. Improved peak resolution in the separation of 4-methylumbelliferyl sugar derivatives was achieved using the conventional multilayer coiled columns with ethyl acetate/1-butanol/water (3: 2: 5, v/v) for the lower mobile phase at the combination of the rotation speeds (ω1, ω2, ω3)=(300, 150, 150rpm), and (1:4:5, v/v) for the upper mobile phase at (300:100:200rpm). The effect of the satellite motion on the peak resolution and the stationary phase retention was evaluated by each CSC separation with the different rotation speeds of ω2 and ω3 under the constant revolution speed at ω1=300rpm. With the lower mobile phase, almost constant peak resolution and stationary phase retention were yielded regardless of the change of ω2 and ω3, while with the upper mobile phase these two values were sensitively varied according to the different combination of ω2 and ω3. For example, when ω2=147 or 200rpm is used, no stationary phase was retained in the coiled column while ω2=150rpm could retain enough volume of stationary phase for separation. On the other hand, the combined rotation speeds at (ω1, ω2, ω3)=(300, 300, 0rpm) or (300, 0, 300rpm) produced insufficient peak resolution regardless of the choice of the mobile phase apparently due to the lack of rotation speed except at (300, 0, 300rpm) with the upper mobile phase. At lower rotation speed of ω1=300rpm, better peak resolution and stationary phase retention were obtained by the satellite motion (ω3) than by the planetary motion (ω2), or ω3>ω2. The effect of the hydrophobicity of the two-phase solvent systems on the stationary phase retention was further examined using the n

  14. Current barriers to confine high frequency common mode currents

    NARCIS (Netherlands)

    Moonen, Dominicus Johannes Guilielmus; Buesink, Frederik Johannes Karel; Leferink, Frank Bernardus Johannes

    2016-01-01

    A commercially produced three phase power line filter is submitted to a Current Barrier (CB) Electro-Magnetic Compatibility (EMC) zoning strategy as an attempt to confine high frequency common mode currents. The intent of the paper is not to show how to build a ’perfect’ filter, since this is known.

  15. Current titles

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-07-01

    This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Gretchen Hermes at (510) 486-5006 or address below for a User`s Guide. Copies of available papers can be ordered from: Theda Crawford National Center for Electron Microscopy, Lawrence Berkeley Laboratory, One Cyclotron Rd., MS72, Berkeley, California, USA 94720.

  16. Generalized phase contrast:

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin

    Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast...... (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than...... efficiency. Optimization can address practical issues, such as finding an optimal spatial filter for the chosen application, and can even enable a Reverse Phase Contrast mode where intensity patterns are converted into a phase modulation....

  17. Generalized Phase Contrast

    CERN Document Server

    Glückstad, Jesper

    2009-01-01

    Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than the restrictive assumptions of conventional Zernike phase contrast analysis and achieves an expanded range of validity beyond weak phase perturbations. The generalized analysis yields design criteria for tuning experimental parameters to achieve optimal performance in terms of accuracy, fidelity and light efficiency. Optimization can address practical issues, such as finding an optimal spatial filter for the chosen application, ...

  18. Generalized phase contrast:

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin

    Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast...... (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than...... the restrictive assumptions of conventional Zernike phase contrast analysis and achieves an expanded range of validity beyond weak phase perturbations. The generalized analysis yields design criteria for tuning experimental parameters to achieve optimal performance in terms of accuracy, fidelity and light...

  19. Current ornithology

    CERN Document Server

    1983-01-01

    The appearance of the first volume of a projected series is the occasion for comment on scope, aims, and genesis of the work. The scope of Current Ornithology is all of the biology of birds. Ornithology, as a whole-organism science, is concerned with birds at every level of bi­ ological organization, from the molecular to the community, at least from the Jurassic to the present time, and over every scholarly discipline in which bird biology is done; to say this is merely to expand a dic­ tionary definition of "ornithology. " The aim of the work, to be realized over several volumes, is to present reviews or position statements con­ cerning the active fields of ornithological research. The reviews will be relatively short, and often will be done from the viewpoint of a readily­ identified group or school. Such a work could have come into being at any time within the past fifty years, but that Current Ornithology appears now is a result of events that are only seven to eight years old. One important event wa...

  20. Phase I of The National Beef Quality Audit-2011: quantifying willingness-to-pay, best-worst scaling, and current status of quality characteristics in different beef industry marketing sectors.

    Science.gov (United States)

    Igo, J L; VanOverbeke, D L; Woerner, D R; Tatum, J D; Pendell, D L; Vedral, L L; Mafi, G G; Moore, M C; McKeith, R O; Gray, G D; Griffin, D B; Hale, D S; Savell, J W; Belk, K E

    2013-04-01

    The National Beef Quality Audit (NBQA)-2011 benchmarked the current status of and assessed progress being made toward quality and consistency of U.S. cattle, carcasses, and beef products after the completion of the first NBQA in 1991. Unlike previous NBQA, objectives of the 2011 Phase I study were to determine how each beef market sector defined 7 quality categories, estimate willingness-to-pay (WTP) for the same quality categories by market sector, and establish a best-worst (B/W) scaling for the quality categories. Structured face-to-face interviews were conducted and responses were recorded using dynamic routing software over an 11-mo period (February to December 2011) with decision makers in each of the following beef market sectors: Feeders (n = 59), Packers (n = 26), Food Service, Distribution, and Further Processors (n = 48), Retailers (n = 30), and Government and Allied Industries (n = 47). All respondents participated in a structured interview consisting of WTP and B/W questions that were tied to 7 quality categories and then were asked to "define" each of the 7 categories in terms of what the category meant to them, resulting in completely unbiased results. The 7 quality categories were a) how and where the cattle were raised, b) lean, fat, and bone, c) weight and size, d) cattle genetics, e) visual characteristics, f) food safety, and g) eating satisfaction. Overall, "food safety" and "eating satisfaction" were the categories of greatest and second most importance, respectively, to all beef market sectors except for Feeders. Feeders ranked "how and where the cattle were raised" and "weight and size" as the most important and second most important, respectively. Overall, "how and where the cattle were raised" had the greatest odds of being considered a nonnegotiable requirement before the raw material for each sector would be considered for purchase and was statistically more important (P market sectors were considered, "eating satisfaction" was shown to

  1. 基于STC90C58的单相交流供电线路漏电流监测装置%STC90C58-based Device to Monitor Leakage Current of Single-phase AC Power Line

    Institute of Scientific and Technical Information of China (English)

    关旭俊; 谢力扬

    2014-01-01

    基于STC90C58设计了一种监测单相交流供电线路漏电流的装置。采用了微控制器和电能计量器件,可同时采集并显示单相交流供电线路相线电流、中性线电流和相线对地漏电流的幅值。可为判断漏电性质和排查漏电点提供数据支持,对提高漏电保安器的投入率、提高用电安全性、降低线损有一定的积极意义。%A device based on STC90C58 to monitor the leakage current of single-phase AC power line is designed .The device uses a micro-controller and a power energy IC ,it can simultaneously capture and display the amplitudes of the phase line current ,the neutral current and the phase-to-ground leakage current of the single-phase AC supply line .The device can determine the nature of leakage points and provide data to support the investigation ,it will have some positive significance to improve the input rate of leakage protectors and improve the security for using electricity and reduce line losses .

  2. 一种基于幅相控制方式电流前馈控制的三相PWM电压型变注器%A PAC Based Current Feedforward Control for Three-Phase PWM Voltage-Type Converter

    Institute of Scientific and Technical Information of China (English)

    屈克庆; 陈国呈; 孙承波

    2004-01-01

    This paper presents a novel current feedforward control strategy for a three-phase pulse-width modulation (PWM) DC voltage-type converter based on phase and amplitude control (PAC).With right-angle triangle relation of phasors and principle of conservation of energy, a phasor adjustment method and the relevant low-frequency mathematical model of the system are analyzed in detail, both in rectification and regeneration modes for the converter, are discussed.For improving the traditional PAC dynamic performance, variable load current is detected indirectly by the change of the DC voltage, which is fed to the control system as an additional control variable to generate modulation index and phase angle.Also, the algorithm is derived and the system principle is introduced.Experimental results from a 3 kw laboratory device are included to demonstrate the effectiveness of the proposed control strategy.

  3. Moon Phases

    Science.gov (United States)

    Riddle, Bob

    2010-01-01

    When teaching Moon phases, the focus seems to be on the sequence of Moon phases and, in some grade levels, how Moon phases occur. Either focus can sometimes be a challenge, especially without the use of models and observations of the Moon. In this month's column, the author describes some of the lessons that he uses to teach the phases of the Moon…

  4. Modeling of Current Transformers Under Saturation Conditions

    Directory of Open Access Journals (Sweden)

    Martin Prochazka

    2006-01-01

    Full Text Available During a short circuit the input signal of the relay can be distort by the magnetic core saturation of the current transformer. It is useful to verify the behavior of CT by a mathematical model. The paper describes one phase and three phase models and it presents some methods of how to analyze and classify a deformed secondary current

  5. CrowdPhase: crowdsourcing the phase problem.

    Science.gov (United States)

    Jorda, Julien; Sawaya, Michael R; Yeates, Todd O

    2014-06-01

    The human mind innately excels at some complex tasks that are difficult to solve using computers alone. For complex problems amenable to parallelization, strategies can be developed to exploit human intelligence in a collective form: such approaches are sometimes referred to as `crowdsourcing'. Here, a first attempt at a crowdsourced approach for low-resolution ab initio phasing in macromolecular crystallography is proposed. A collaborative online game named CrowdPhase was designed, which relies on a human-powered genetic algorithm, where players control the selection mechanism during the evolutionary process. The algorithm starts from a population of `individuals', each with a random genetic makeup, in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals. A user-friendly interface, a training stage and a competitive scoring system foster a network of well trained players who can guide the genetic algorithm towards better solutions from generation to generation via gameplay. CrowdPhase was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30° phase error range and corresponding molecular envelopes showing agreement with the low-resolution models. The successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it possible to extract meaningful information in cases where limited resolution might otherwise prevent initial phasing.

  6. HLS bunch current measurement system

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Bunch current is an important parameter for studying the injection fill-pattern in the storage ring and the instability threshold of the bunch, and the bunch current monitor also is an indispensable tool for the top-up injection. A bunch current measurement (BCM) system has been developed to meet the needs of the upgrade project of Hefei Light Source (HLS). This paper presents the layout of the BCM system. The system based on a high-speed digital oscilloscope can be used to measure the bunch current and synchronous phase shift. To obtain the absolute value of bunch-by-bunch current, the calibration coefficient is measured and analyzed. Error analysis shows that the RMS of bunch current is less than 0.01 mA when bunch current is about 5 mA, which can meet project requirement.

  7. Power quality issues current harmonics

    CERN Document Server

    Mikkili, Suresh

    2015-01-01

    Power Quality Issues: Current Harmonics provides solutions for the mitigation of power quality problems related to harmonics. Focusing on active power filters (APFs) due to their excellent harmonic and reactive power compensation in two-wire (single phase), three-wire (three-phase without neutral), and four-wire (three-phase with neutral) AC power networks with nonlinear loads, the text:Introduces the APF technology, describing various APF configurations and offering guidelines for the selection of APFs for specific application considerationsCompares shunt active filter (SHAF) control strategi

  8. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 1.5 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  9. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 0.0 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  10. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 0.5 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  11. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 1.0 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  12. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 0.5 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  13. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 2.0 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  14. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 1.5 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  15. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 0.0 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  16. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 1.0 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  17. CoSMoS (Coastal Storm Modeling System) Southern California v3.0 Phase 1 (100-year storm) sea-level rise 2.0 m: ocean currents projections

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Projected Hazard: Model-derived ocean current velocities (in meters per second) for the given storm condition and sea-level rise (SLR) scenario. Model Summary: The...

  18. Stability analysis of direct current control in current source rectifier

    DEFF Research Database (Denmark)

    Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Current source rectifier with high switching frequency has a great potential for improving the power efficiency and power density in ac-dc power conversion. This paper analyzes the stability of direct current control based on the time delay effect. Small signal model including dynamic behaviors...... of dc link is developed to identify the control plants of grid ac current control and dc current control. Analysis on the poles and zeros under dq frame is carried out. Base on this model, it turns out that the phase lag caused by the time delay can stabilized the grid ac current control while reduces...... the stable region for dc current control. Simulation and experimental results are presented to validate the theoretical analysis....

  19. Phase Referencing in Optical Interferometry

    OpenAIRE

    Mercedes E. Filho; Garcia, Paulo; Duvert, Gilles; Duchene, Gaspard; Thiebaut, Eric; Young, John; Absil, Olivier; Berger, Jean-Phillipe; Beckert, Thomas; Hoenig, Sebastian; Schertl, Dieter; Weigelt, Gerd; Testi, Leonardo; Tatuli, Eric; Borkowski, Virginie

    2008-01-01

    One of the aims of next generation optical interferometric instrumentation is to be able to make use of information contained in the visibility phase to construct high dynamic range images. Radio and optical interferometry are at the two extremes of phase corruption by the atmosphere. While in radio it is possible to obtain calibrated phases for the science objects, in the optical this is currently not possible. Instead, optical interferometry has relied on closure phase techniques to produce...

  20. Simulation on relationship b etween p ower/phase stability of low frequency oscillatory p otentials and activity of dip ole current%低频振荡电位的能量和相位稳定性与偶极子电流活动相关性的仿真∗

    Institute of Scientific and Technical Information of China (English)

    葛曼玲; 魏孟佳; 师鹏飞; 陈营; 付晓璇; 郭宝强; 张惠娟

    2015-01-01

    能量和相位是分析脑节律的重要物理量,虽有许多研究,但其与脑组织电特性和脑节律源的关系尚不完全清楚,弄清这一问题有助于脑电测量及脑功能和疾病的分析。为此,借鉴脑电正问题研究方法,大脑可看作均匀球,脑组织电特性用导体各向同性和各向异性电导率来表示,脑节律源用准静态偶极子电流来模拟,其活动表达为较低频率的正弦振荡,在改变该活动的振幅和相位时程时,用球表面剖分网格的振荡电位仿真脑节律,提取节律的能量和相位,计算源和节律的窄带相位稳定性。结果表明:仿真节律的能量随电导率增大而减小,受网格位置、电导率各向异性、偶极子电流幅值和偏心位置影响较大;但仿真节律的相位稳定性只与自身的相位时程有关。说明能量与相位稳定性电学意义无交集,同时用来分析脑节律可提供更多神经信息;能量的电学意义更复杂,取决于包括测量条件在内的多种因素;相位稳定性的优势在于它仅与脑节律相位时程直接相关,可预测的是脑的非线性导致的相位时程越离散,则相位稳定性越差。%The physical parameters, e.g. power and phase, are usually employed in the neural analysis of brain rhythms, which are important in brain function and disease diagnosis. Though there has been extensive work, how both parameters are related to the electrical properties of brain tissue and the sources of brain rhythms has not been fully understood. To address the issue, a simulation is done based on the theory of dipole current. When referring to the solution to the forward problem in electroencephalograph, the brain is regarded as a ho-mogenous sphere model, the electrical features of brain tissue are described by an isotropic electrical conductivity. The source of brain rhythms is simulated by the quasi-static dipole current whose activity is described

  1. 变压器三相涌流波形特征分析及判别方法研究%Analysis and Assessment Methods of Waveform Characteristics of Three-Phase Transformer Inrush Current

    Institute of Scientific and Technical Information of China (English)

    卓元志; 李康; 赵斌; 韩斌; 赵雪沉璎

    2012-01-01

    With two big waveform characteristics of the transformer excitation inrush current revealed, this paper makes full use of the waveform characteristics,and then proposes a method of distinguishing the transformer excitation inrush current and internal fault current. This method is based on the assumption that the inrush current waveform presents the spire concave arc characteristics and fault current presents the sine waveform characteristics, and in half a cycle samples values can find the extreme value point,frequency, forming the corresponding virtual sine wave. Judging the similarity between the closing current and the tectonic waveform in half-wave cycle can distinguish between the excitation inrush current and fault current. The simulation results show that this method can effectively and quickly remove the internal faults of the transformer, and is not influenced by the aperiodic current components.%在揭示变压器励磁涌流两大波形特征的基础上,充分利用波形特征,提出一种利用波形特征区分变压器励磁涌流和内部故障电流的方法,该方法基于涌流波形呈现出尖顶波的凹弧特征,而故障电流基本保持正弦波形特征,在半波周期内找到采样值的极值点及频率,构造出与之对应的虚拟正弦波形,通过判断合闸电流与构造波形在半波周期内的相似程度来区分励磁涌流和故障电流.仿真结果表明,该方法能够有效、快速切除变压器内部故障,并且不受电流非周期分量的影响.

  2. Soft-start mechanism with coefficients Ki optimization for DC-DC power converters

    Science.gov (United States)

    Wang, Qian; Hu, Jiajun; Chen, Houpeng; Li, Xi; Fan, Xi; Miao, Jie; Song, Zhitang

    2016-10-01

    This paper presents a fully digital-control soft start mechanism with coefficients Ki optimization for DC-DC power converters. During the soft start phase, a ladder reference voltage steps up gradually to make inductor current ramp up smoothly and overshoot voltage is minimized with the proposed coefficients Ki distribution. Simulation results show that massive inductor current can be well avoided during the soft start process with the proposed soft start mechanism, which only occupies a chip area of 300um×120um.

  3. Nine-Phase Induction Motor Vector Control System Based on the Harmonic Current Closed-Loop Control Strategy%基于谐波电流闭环控制的九相感应电机矢量控制系统

    Institute of Scientific and Technical Information of China (English)

    梅柏杉; 冯江波; 吴迪

    2014-01-01

    采用转子磁链定向矢量控制方法,对九相感应电机矢量控制系统的转矩动静态响应进行了研究。针对应用传统的谐波电流开环控制策略时定子电流谐波含量较大的问题,使用了谐波电流闭环控制策略以抵制各高次谐波对定子电流的影响。以一台九相集中整距绕组感应电机为例,在MATLAB的Simulink工具箱中搭建了完整的九相感应电机矢量控制系统模型。仿真结果表明,系统可以有效抑制定子的谐波电流,且具有较好的动态性能。%Based on the rotor field oriented control method, the dynamic and static torque response of a nine-phase induction motor vector control system was studied. To solve the problem of high harmonic content in the stator current in the conventional harmonic currents open-loops control strategy,the harmonic currents closed-loops control method was used to resist the higher harmonic currents’ s effect on the stator currents . Taking a nine phase concen-trated winding induction motor for example,a complete nine-phase induction motor vector control system model was built in MATLAB/Simulink toolbox. The simulation results show that the system can effectively restrain the stator har-monic current, and has good dynamic performance.

  4. Amplification of the discharge current density of lithium-ion batteries with spinel phase Li(PtAu)0.02Mn1.98O4 nano-materials

    CSIR Research Space (South Africa)

    Ross, N

    2014-05-01

    Full Text Available capacity retention of 99% after 50 cycles. Faster charge transportation at high current rates proved to prevent the pronounced pile-up of Li(sup+) ions and undesired Mn(sup3+) ions on the surfaces. The electrochemical impedance spectroscopy (EIS) results...

  5. Phase II clinical study of boron neutron capture therapy combined with X-ray radiotherapy/temozolomide in patients with newly diagnosed glioblastoma multiforme-Study design and current status report

    Energy Technology Data Exchange (ETDEWEB)

    Kawabata, Shinji, E-mail: neu046@poh.osaka-med.ac.jp [Department of Neurosurgery, Osaka Medical College, 2-7 Daigaku-Machi, Takatsuki, Osaka 569-8686 (Japan); Miyatake, Shin-Ichi; Hiramatsu, Ryo; Hirota, Yuki; Miyata, Shiro; Takekita, Yoko; Kuroiwa, Toshihiko [Department of Neurosurgery, Osaka Medical College, 2-7 Daigaku-Machi, Takatsuki, Osaka 569-8686 (Japan); Kirihata, Mitsunori [Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8931 (Japan); Sakurai, Yoshinori; Maruhashi, Akira; Ono, Koji [Kyoto University Research Reactor Institute, 2 Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan)

    2011-12-15

    Recently, we reported our clinical experiences of boron neutron capture therapy (BNCT) for the newly diagnosed glioblastoma. The major differences of our protocol from the other past studies were simultaneous use of both sodium borocapate and boronophenylalanine, and combination with fractionated X-ray irradiation. These results showed the efficacy of combination therapy with external beam X-ray irradiation and BNCT. For our future study, we planned the multi-centric phase II clinical study for newly diagnosed glioblastoma patients in Japan (OSAKA-TRIBRAIN0902, NCT00974987).

  6. UPVG phase 2 report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-08-01

    The Utility PhotoVoltaic Group (UPVG), supported by member dues and a grant from the US Department of Energy, has as its mission the acceleration of the use of cost-effective small-scale and emerging large-scale applications of photovoltaics for the benefit of electric utilities and their customers. Formed in October, 1992, with the support of the American Public Power Association, Edison Electric Institute, and the National Rural Electric Cooperative Association, the UPVG currently has 90 members from all sectors of the electric utility industry. The UPVG`s efforts as conceived were divided into four phases: Phase 0--program plan; Phase 1--organization and strategy development; Phase 2--creating market assurance; and Phase 3--higher volume purchases. The Phase 0 effort developed the program plan and was completed early in 1993. The Phase 1 goal was to develop the necessary background information and analysis to lead to a decision as to which strategies could be undertaken by utilities to promote greater understanding of PV markets and achieve increased volumes of PV purchases. This report provides the details of the UPVG`s Phase 2 efforts to initiate TEAM-UP, its multiyear, 50-MW hardware initiative.

  7. Method and apparatus for current-output peak detection

    Energy Technology Data Exchange (ETDEWEB)

    De Geronimo, Gianluigi

    2017-01-24

    A method and apparatus for a current-output peak detector. A current-output peak detector circuit is disclosed and works in two phases. The peak detector circuit includes switches to switch the peak detector circuit from the first phase to the second phase upon detection of the peak voltage of an input voltage signal. The peak detector generates a current output with a high degree of accuracy in the second phase.

  8. Turbulent lock release gravity current

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The time evolution of a turbulent lock release gravity current, formed by a finite volume ofhomogeneous fluid released instantaneously into another fluid of slightly lower density, was studied byexperimental measurements of the density structure via elaborate digital image processing and by a nu-merical simulation of the flow and mixing using a two-equation turbulence model. The essential fact thatthe gravity current passes through an initial slumping phase in which the current head advances steadilyand a second self-similar phase in which the front velocity decreases like the negative third power of thetime after release is satisfactorily presented by the laboratory observation. An overall entrainment ratioproportional to the distance from the release point is found by the numerical simulation. The renormal-ization group (RNG) k- ε model for Reynolds-stress closure is validated to characterize the gravitycurrent with transitional and localized turbulence.

  9. A New Three-level Hysteresis Current Controlled Single-phase H-bridge Voltage Source Inverters%一种单相H桥电压型逆变器三电平滞环电流跟踪控制方法

    Institute of Scientific and Technical Information of China (English)

    毛惠丰; 孔德鹏; 陈增禄; 杨旭; 王兆安

    2015-01-01

    提出了一种单相 H 桥电压型逆变器三电平滞环电流跟踪控制方法。该控制方法具有载波移相PWM调制效果以及无死区效应的特点。在稳态条件下,误差电流被严格限制在内环中。当指令电流发生突变并且达到外环的上或下阈值时,逆变器输出最高或最低电平以使误差电流以最快速度趋近于0。与传统的三电平滞环电流控制方法相比,该控制方法能进一步改善逆变器输出电流的波形。通过仿真和实验结果验证了该方法的有效性。%ABSTRACT:A new three-level hysteresis current controller for single-phase H-bridge voltage source inverters (VSI) is proposed here. The proposed hysteresis current controller has successfully combined the advantage of the symmetrical unipolar carrier-based PWM and no dead-time effects. Under steady-state conditions, the current error will be confined within the inner band. When the commanded current step changes so that the current error exceeds the outer hysteresis band, the extreme voltage level is selected to force the current error towards zero quickly. Compared with the conventional three-level hysteresis current controller, the proposed hysteresis current controlled single-phase H-bridge voltage source inverters can further improve the inverter output current waveform. Simulated and experimental results have been given to demonstrate the validity and features of the novel hysteresis current controller with the improved switching scheme.

  10. Characteristics of electron cyclotron resonance plasma formed by lower hybrid current drive grill antenna

    Indian Academy of Sciences (India)

    P K Sharma; S L Rao; K Mishra; R G Trivedi; D Bora

    2008-03-01

    A 3.7 GHz system, which is meant for LHCD experiments on ADITYA tokamak, is used for producing ECR discharge. The ECR discharge is produced by setting the appropriate resonance magnetic field of 0.13 T, with hydrogen at a fill pressure of about 5 × 10-5 Torr. The RF powe r, up to 10 kW (of which ∼ 50% is reflected back), with a typical pulse length of 50 ms, is injected into the vacuum chamber of the ADITYA tokamak by a LHCD grill antenna and is used for plasma formation. The average coupled RF power density (the RF power/a typical volume of the plasma) is estimated to be ∼ 5 kW/m3. When the ECR appears inside the tokamak chamber for the given pumping frequency ( = 3.7 GHz) a plasma with a density () ∼ 4 × 1016 m-3 and electron temperature ∼ 8 eV is produced. The density and temperature during the RF pulse are measured by sets of Langmuir probes, located toroidally, on either side of the antenna. signals are also monitored to detect ionization. An estimate of density and temperature based on simple theoretical calculation agrees well with our experimental measurements. The plasma produced by the above mechanism is further used to characterize the ECR-assisted low voltage Ohmic start-up discharges. During this part of the experiments, Ohmic plasma is formed using capacitor banks. The plasma loop voltage is gradually decreased, till the discharge ceases to form. The same is repeated in the presence of ECR-formed plasma (RF pre-ionization), formed 10 ms prior to the loop voltage. We have observed that (with LHCD-induced) ECR-assisted Ohmic start-up discharges is reliably and repeatedly obtained with reduced loop voltage requirement and breakdown time decreases substantially. The current ramp-up rates also decrease with reduced loop voltage operation. These studies established that ECR plasma formed with LHCD system exhibits similar characteristics as reported earlier by dedicated ECR systems. This experiment also addresses the issue of whether ECR plasma

  11. Discussion on Current Situation of Volunteers Who Involved in Volunteer Screening for Phase I Clinical Trials Yu%I期药物临床试验筛选健康志愿者现状浅析

    Institute of Scientific and Technical Information of China (English)

    于伟越; 李鹏飞; 张丽荣; 刘洪川; 张茜; 刘丽宏; 彭军

    2015-01-01

    ObjectiveThe situations of volunteers who involved in volunteer screening for Phase I clinical trials in 2012 were analyzed to provide reference for the development of volunteer screening criteria for phase I clinical trials. Methods 98 volunteers, who participated volunteer screening from May 2012 to September 2012, were analyzed. Retrospective pooled analysis was used for their general conditions, physical examinations, vital signs, electrocardiograms, chest radio graphs and laboratory check.Results A total of 98 volunteers, male 78, female 20. The abnormal BMI takes 5 cases, 2 cases with hypertension, 2 cases with heart murmur, 3 cases with tachycardia, 20 cases with abnormal laboratory test results, 2 cases with chest-ray abnormalities, 16 cases with poor compliance, 48 cases actually participated in Phase I clinical trial. ConclusionThe proportion of unqualified volunteers involved in screening for phase I clinical trials is very high, because in addition to the volunteers themselves substandard physical fitness, but also accounted for the main reason for compliance. So researchers should take a variety of methods to improve the compliance of volunteers such as learning more about volunteer's personal circumstances, affinity attitude and proper communication skills et al.%目的:对参与2012年I期药物临床试验筛选的志愿者一般状况进行分析,为制定I期药物临床试验受试者的筛选标准提供参考依据。方法对2012年5月-2012年9月在某院I期药物临床试验研究室参加临床试验筛选的98名志愿者的一般资料、体格检查、生命体征、心电图、胸部正位片以及实验室检查进行回顾性汇总分析。结果参加筛选的共有98人,男性78人,女性20人。其中体重指数不合格5人,高血压2人,心脏杂音2人,心动过速3人,实验室检查结果异常20人,胸片异常2人,依从性差者16人,实际可参加试验的志愿者为48人。结论参与I期药

  12. 中医药治疗出血性中风急性期研究现状%Current status of traditional Chinese medicine in the treatment of hemorrhagic stroke at acute phase

    Institute of Scientific and Technical Information of China (English)

    王家艳; 康宁; 黄宏敏

    2015-01-01

    Hemorrhagic stroke at acute phase is a common dangerous critical disease. A lot of researches in traditional Chinese medicine are documented. By reading ancient books and a decade of clinical research in the treat-ment of hemorrhagic stroke at acute phase, we sum up main treatment methods and achievements in this article. Learn-ing and innovation help generate good therapeutic effect and new methods and also improve the quality of scientific re-search. However, there are still some problems such as lack of high-quality research results, which arouse us that more careful design and unified platform in future clinical studies are needed.%出血性中风急性期是临床常见急危重症,相关的中医药研究不断,本文通过查阅古籍,阅读近十年临床研究文献百余篇,将主要治疗方法及成果进行总结。在治疗上,经验传承加理论创新,多有不错的疗效;在研究中,引入了先进的研究方法,提高了科研质量。目前还存在一定问题,如研究结果的循证医学证据质量较低,在将来的临床研究中需要更严谨的设计及规范统一的平台。

  13. Unparticle phase effects

    CERN Document Server

    Chen, Chuan-Hung

    2007-01-01

    Unparticles proposed by Georgi carry CP conserving phases in their propagators. We demonstrate that these peculiar phases have an important impact on CP violation. Without including the strong QCD phases, we study the unparticle phase effects on the direct CP asymmetries in the exclusive decays of $\\bar B_d\\to \\pi^{+} \\pi^{-}$ and $B\\to \\pi K$, in which the flavor changing neutral currents are forbidden at tree level but induced by one-loop diagrams. Interesting and consistent results comparing to the data are obtained. In addition, we find that unparticles will significantly enhance the differential branching ratio of $b\\to s \\ell^{+} \\ell^{-}$ at the small invariant mass of $\\ell^{+} \\ell^{-}$. The forward-backward asymmetries for $b\\to s \\ell^{+} \\ell^{-}$ due to unparticles are also explored.

  14. Now entering phase two...

    CERN Multimedia

    Katarina Anthony

    2012-01-01

    Building on the success of their feasibility phase, the CLIC test facility, CTF3, has just launched into a five-year project development phase. This will involve detailed performance optimisation studies, marking the project’s transition from pure research and development to prototyping and construction.   CLIC accelerator modules under construction at CERN. “With the feasibility phase now complete, we have established that CLIC can be built,” says Roberto Corsini, CLIC Collaboration spokesperson. “Now we want to be sure that it can provide the luminosity and energy performance needed. We will be looking at the engineering, performance and cost of a real CLIC machine also seeing if we can reduce it.” CTF3’s second phase will focus on selected performance-related research areas for further investigation. The largest of these involves the construction and testing of several authentic CLIC accelerator modules that are currently being ...

  15. A combination strategy for extraction and isolation of multi-component natural products by systematic two-phase solvent extraction-(13)C nuclear magnetic resonance pattern recognition and following conical counter-current chromatography separation: Podophyllotoxins and flavonoids from Dysosma versipellis (Hance) as examples.

    Science.gov (United States)

    Yang, Zhi; Wu, Youqian; Wu, Shihua

    2016-01-29

    Despite of substantial developments of extraction and separation techniques, isolation of natural products from natural resources is still a challenging task. In this work, an efficient strategy for extraction and isolation of multi-component natural products has been successfully developed by combination of systematic two-phase liquid-liquid extraction-(13)C NMR pattern recognition and following conical counter-current chromatography separation. A small-scale crude sample was first distributed into 9 systematic hexane-ethyl acetate-methanol-water (HEMWat) two-phase solvent systems for determination of the optimum extraction solvents and partition coefficients of the prominent components. Then, the optimized solvent systems were used in succession to enrich the hydrophilic and lipophilic components from the large-scale crude sample. At last, the enriched components samples were further purified by a new conical counter-current chromatography (CCC). Due to the use of (13)C NMR pattern recognition, the kinds and structures of major components in the solvent extracts could be predicted. Therefore, the method could collect simultaneously the partition coefficients and the structural information of components in the selected two-phase solvents. As an example, a cytotoxic extract of podophyllotoxins and flavonoids from Dysosma versipellis (Hance) was selected. After the systematic HEMWat system solvent extraction and (13)C NMR pattern recognition analyses, the crude extract of D. versipellis was first degreased by the upper phase of HEMWat system (9:1:9:1, v/v), and then distributed in the two phases of the system of HEMWat (2:8:2:8, v/v) to obtain the hydrophilic lower phase extract and lipophilic upper phase extract, respectively. These extracts were further separated by conical CCC with the HEMWat systems (1:9:1:9 and 4:6:4:6, v/v). As results, total 17 cytotoxic compounds were isolated and identified. In general, whole results suggested that the strategy was very

  16. 光伏并网逆变器空间电压矢量双滞环电流控制新策略%A novel double hysteresis loop current control method for three-phase PV grid-connected inverter with voltage space vector

    Institute of Scientific and Technical Information of China (English)

    王新勇; 许炜; 汪显博; 范波

    2011-01-01

    提出了一种适用于三相光伏并网逆变器的双滞环电流控制改进算法.根据逆变器线电流与功率器件开关状态的关系,对线电流实行解耦控制,利用双滞环来判断参考空间电压矢量的位置,结合锁相环电路对输出的开关状态进行检测,构成频率闭环控制.最后利用Matlab/Simulink工具箱和3 kW实验平台对双滞环控制算法进行验证.结果表明,该算法保留了传统滞环控制电流跟踪响应快、有限流能力的优点,同时也有效地克服了开关频率变化不固定、开关损耗较大等问题.%An improved algorithm of double hysteresis loop current control method for three-phase PV grid-connected inverter is proposed. The decoupling control of the line current is realized under the relationship between inverter line current and switch status of power instrument The position of reference space voltage vector can be judged by double hysteresis loop. Output switch state can be detected by phase-lockod loop circuit, thus the frequency closed-loop control is constructed. At last, the algorithm is simulated in Matlab/Simulink toolbox and verified on 3 kW experimental platform. The results show that the improved algorithm remains the fast response and limiting current capacity of traditional hysteresis current tracking control, also effectively overcomes the non-fixed switching frequency and the larger switching loss.

  17. 750kV同塔同窗同相序双回紧凑型线路的潜供电流和感应电压%Research on Secondary-Arc Currents and Induced Voltages for 750 kV Compact Double-Circuit Transmission Lines on the Same Tower With the Same Phase Sequence in the Same Tower Window

    Institute of Scientific and Technical Information of China (English)

    王晓彤; 班连庚; 朱普轩; 郑彬

    2011-01-01

    A model of 750kV compact double-circuit transmission lines on the same tower with the same phase sequence in the same tower window is built by use of electromagnetic transient program (EMTP). The problems of secondary-arc currents and recovery voltages, induced voltages and induced currents are studied when the structure of double-circuit compact transmission lines on the same tower with the same phase sequence in the same tower window are applied to full or partial length of the project. Research results show that in the viewpoint of suppressing secondary arc current, recovery voltage, induced voltage and induced current, it is not suitable to adopt such a line structure, i.e., double-circuit transmission lines on the same tower with the same phase sequence in the same tower window, to full length of the project while high voltage shunt reactors are configured. For this reason, following scheme that conventional type is used for the main part of this project and the structure of compact double-circuit transmission lines on the same tower with the same phase sequence in the same tower window is only applied in the sections where the land for line corridors is undersupplied. If the length of the section where the compact double-circuit transmission lines on the same tower with the same phase sequence in the same tower window is applied is short enough, the values of secondary arc current and induced voltages can be suppressed into a rational level. For short transmission lines where the high voltage shunt reactors are not to be configured, if the problem of switching-off induced currents can be solved, it is worthy of consideration to adopt the structure of compact double-circuit transmission lines on the same tower with the same phase sequence in the same tower window to the full lengths of transmission lines.%使用电磁暂态程序(electromagnetic transient program,EMTP),建立了750kV同塔同窗同相序双回紧凑型线路模型.研究了全线或部分采

  18. Variation of fibrinogen oligosaccharide structure in the acute phase response: Possible haemorrhagic implications

    Directory of Open Access Journals (Sweden)

    Stephen O. Brennan

    2015-06-01

    Conclusions and implications: The failure of incorporation Gal excludes the possibility of the hepatic NAcNeu Gal transferase capping the oligosaccharides with sialic acid. This has two desirable haemostatic outcomes: fibrin monomers will polymerise and form clots more rapidly, and two galactose residues can never be exposed diminishing uptake of the protein by the asialoglycoprotein receptor and ramping up concentration at a time of challenge.

  19. Phase transitions

    CERN Document Server

    Solé, Ricard V

    2011-01-01

    Phase transitions--changes between different states of organization in a complex system--have long helped to explain physics concepts, such as why water freezes into a solid or boils to become a gas. How might phase transitions shed light on important problems in biological and ecological complex systems? Exploring the origins and implications of sudden changes in nature and society, Phase Transitions examines different dynamical behaviors in a broad range of complex systems. Using a compelling set of examples, from gene networks and ant colonies to human language and the degradation o

  20. Realizing and optimizing an atomtronic SQUID

    Science.gov (United States)

    Mathey, Amy C.; Mathey, L.

    2016-05-01

    We demonstrate how a toroidal Bose-Einstein condensate with a movable barrier can be used to realize an atomtronic SQUID. The magnitude of the barrier height, which creates the analogue of an SNS junction, is of crucial importance, as well as its ramp-up and -down protocol. For too low of a barrier, the relaxation of the system is dynamically suppressed, due to the small rate of phase slips at the barrier. For a higher barrier, the phase coherence across the barrier is suppressed due to thermal fluctuations, which are included in our Truncated Wigner approach. Furthermore, we show that the ramp-up protocol of the barrier can be improved by ramping up its height first, and its velocity after that. This protocol can be further improved by optimizing the ramp-up and ramp-down time scales, which is of direct practical relevance for on-going experimental realizations.

  1. 基于ZPETC的雕刻机直流伺服控制系统设计%Direct Current Servo Controller Design for Engraving Machine Based on Zero Phase Error Tracking Control

    Institute of Scientific and Technical Information of China (English)

    张后来; 李红梅

    2012-01-01

    In order to improve tracking performance and orientation precision for an engraving machine, a zero phase error-tracking controller was firstly introduced for its DC servo control system. Due to the drawbacks such as sensitive dependence on the system's modeling error and parameters change for ZPETC, overcome them by making use of model identification, nonlinear friction compensation and disturbance observer's design. Based on abovementioned researches, a TMS320F2812 type DSP was adopted to design the DC servo control system comprised of ZPETC, PD controller and disturbance observer. Experiment results validate that the designed DC servo controller for the engraving machine has the merits of robust stability and anti-interference , nicer tracking performance and orientation precision.%为了提高雕刻机的跟踪性能和定位精度,首先在其直流伺服控制系统设计中引入了零相位误差跟踪控制器(ZPETC),然后通过模型辨识、非线性摩擦补偿及干扰观测器的设计来克服ZPETC存在的对系统建模误差和参数变化敏感的缺点.在上述研究的基础上,采用TMS320F2812型DSP设计了集ZPETC、PD控制器及干扰观测器一体的直流伺服控制系统.实验结果表明:为雕刻机所设计的直流伺服控制系统不仅有鲁棒性强和抗干扰能力强的特点,而且有良好的定位精度和跟踪性能.

  2. Acoustoelectric current for composite fermions

    Science.gov (United States)

    Bergli, J.; Galperin, Y. M.

    2001-07-01

    The acoustoelectric current for composite fermions in a two-dimensional electron gas (2DEG) close to the half-filled Landau level is calculated in the random phase approximation. The Boltzmann equation is used to find the nonequilibrium distribution of composite fermions to second order in the acoustic field. It is shown that the oscillating Chern-Simons field created by the induced density fluctuations in the 2DEG is important for the acoustoelectric current. This leads to a violation of the Weinreich relation between the acoustoelectric current and acoustic intensity. The deviations from the Weinreich relation can be detected by measuring the angle between the longitudinal and the Hall components of the acoustoelectric current. This departure from the Weinreich relation gives additional information on the properties of the composite fermion fluid.

  3. Current status of iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kamihara, Yoichi, E-mail: kamihara_yoichi@appi.keio.ac.jp [Keio University, Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology (Japan)

    2012-03-15

    Current status of iron-based superconductors is summarized. Although short range magnetic ordering and magnetic phase separation of Fe are controversial, (long range) magnetic and electronic phase diagrams of iron based superconductors can be classified into two-type. Antiferromagnetic ordering of itinerant Fe does not coexist with superconducting phase of SmFeAsO{sub 1 - x}F{sub x}. The very large H{sub c2} of iron-based superconductors attract us to attempts at applications.

  4. Current status of iron-based superconductors

    Science.gov (United States)

    Kamihara, Yoichi

    2012-03-01

    Current status of iron-based superconductors is summarized. Although short range magnetic ordering and magnetic phase separation of Fe are controversial, (long range) magnetic and electronic phase diagrams of iron based superconductors can be classified into two-type. Antiferromagnetic ordering of itinerant Fe does not coexist with superconducting phase of SmFeAsO1 - xFx. The very large H c2 of iron-based superconductors attract us to attempts at applications.

  5. Current detection method based on no phase-locked loop for electrified railway power balance device%基于无锁相环的电气化铁道功率平衡装置电流检测方法的研究

    Institute of Scientific and Technical Information of China (English)

    田铭兴; 阎宏; 赵雨欣

    2013-01-01

      针对平衡变压器供电方式下,高速电气化铁道谐波、负序电流引起的电压畸变,指令电流检测过程复杂、延时较长,结果含有误差的缺点,提出了一种无需锁相环电路快速准确地提取指令电流的方法。该方法通过简单的数乘运算提取基波电压,运用同步检测法来准确地检测出指令电流信号的方法,使两供电臂功率平衡,电流对称且与供电臂基波电压同相位,消除无功、谐波及负序电流对三相电力系统的影响。相比传统的带锁相环,基于鉴相原理和瞬时无功功率理论的检测方法,该方法更加简便易行,运算速度更快,且不受电网畸变条件的影响。通过仿真分析,验证了该检测方法在电气化牵引供电系统电压畸变条件下运用的正确性和可行性。%Aiming at the shortcoming of voltage distortion caused by high-speed electrified railway harmonic and negative sequence current and the complexity and longer delay of command current detection process leading to results containing error under balance transformer power supply, this paper proposes a fast and accurate method to extract the instruction current without phase-locked loop circuit. The method extracts fundamental voltage by a simple number multiplication, and uses synchronous detection method to accurately detect the command current signal and to balance the power of two supply arms, make current symmetrical and phased with fundamental voltage of the supply arm, eliminating the effects of reactive power, harmonic and negative-sequence current on three-phase power system. Compared with traditional detection method with phase-locked loop based on principle of phase and instantaneous reactive power theory, this method is simpler and faster, and not subject to the effect of grid distortion. Simulation analysis verifies the correctness and feasibility of the detection method in the electrified traction power supply

  6. Phase Referencing in Optical Interferometry

    CERN Document Server

    Filho, Mercedes E; Duvert, Gilles; Duchene, Gaspard; Thiebaut, Eric; Young, John; Absil, Olivier; Berger, Jean-Phillipe; Beckert, Thomas; Hoenig, Sebastian; Schertl, Dieter; Weigelt, Gerd; Testi, Leonardo; Tatuli, Eric; Borkowski, Virginie; de Becker, Michael; Surdej, Jean; Aringer, Bernard; Hron, Joseph; Lebzelter, Thomas; Chiavassa, Andrea; Corradi, Romano; Harries, Tim

    2008-01-01

    One of the aims of next generation optical interferometric instrumentation is to be able to make use of information contained in the visibility phase to construct high dynamic range images. Radio and optical interferometry are at the two extremes of phase corruption by the atmosphere. While in radio it is possible to obtain calibrated phases for the science objects, in the optical this is currently not possible. Instead, optical interferometry has relied on closure phase techniques to produce images. Such techniques allow only to achieve modest dynamic ranges. However, with high contrast objects, for faint targets or when structure detail is needed, phase referencing techniques as used in radio interferometry, should theoretically achieve higher dynamic ranges for the same number of telescopes. Our approach is not to provide evidence either for or against the hypothesis that phase referenced imaging gives better dynamic range than closure phase imaging. Instead we wish to explore the potential of this techniq...

  7. Overview of Current Activities in Combustion Instability

    Science.gov (United States)

    2015-10-02

    9/23/2015 14. ABSTRACT Briefing Charts/Viewgraph 15. SUBJECT TERMS N/A 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18...CSTD Approved for public release; distribution unlimited 14 ALREST phase II Multifidelity Tools and Methodologies Phase I VISP SPACE Current gen  HF ...Current gen  HF ,  productional Next gen  HF F i d e l i t y High fidelity Cost  ALREST phase II Experiments  Approved for public release

  8. Record critical current densities in IG processed bulk YBa{sub 2}Cu{sub 3}O{sub y} fabricated using ball-milled Y{sub 2}Ba{sub 1}Cu{sub 1}O{sub 5} phase

    Energy Technology Data Exchange (ETDEWEB)

    Muralidhar, Miryala; Kenta, Nakazato; Murakami, Masato [Department of Materials Science and Engineering, Superconducting Materials Laboratory, Shibaura Institute of Technology, Tokyo (Japan); Zeng, XianLin; Koblischka, Michael R. [Institute of Experimental Physics, Saarland University, Saarbruecken (Germany); Diko, Pavel [Institute of Experimental Physics, Material Physics Laboratory, Slovak Academy of Sciences, Kosice (Slovakia)

    2016-02-15

    The infiltration-growth (IG) technique enables the uniform and controllable Y{sub 2}BaCuO{sub 5} (Y211) secondary phase particles formation within the YBa{sub 2}Cu{sub 3}O{sub y} (Y123) matrix. Recent results clarified that the flux pinning performance of the Y123 material was dramatically improved by optimizing the processing conditions during the IG process. In this paper, we adapted the IG technique and produced several samples with addition of nanometer-sized Y211 secondary phase particles, which were produced by a ball milling technique. We found that the performance of the IG processed Y123 material dramatically improved in the low field region for a ball milling time of 12 h as compared to the samples without a ball milling step. Magnetization measurements showed a sharp superconducting transition with an onset T{sub c} at around 92 K. The critical current density (J{sub c}) at 77 K and zero field was determined to be 224 022 Acm{sup -2}, which is higher than the not ball-milled sample. Furthermore, microstructural observations exhibited a uniform microstructure with homogenous distribution of nanosized Y-211 inclusions within the Y-123 matrix. The improved performance of the Y-123 material can be understood in terms of fine distribution of the secondary phases. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Extreme geomagnetically induced currents

    Science.gov (United States)

    Kataoka, Ryuho; Ngwira, Chigomezyo

    2016-12-01

    We propose an emergency alert framework for geomagnetically induced currents (GICs), based on the empirically extreme values and theoretical upper limits of the solar wind parameters and of d B/d t, the time derivative of magnetic field variations at ground. We expect this framework to be useful for preparing against extreme events. Our analysis is based on a review of various papers, including those presented during Extreme Space Weather Workshops held in Japan in 2011, 2012, 2013, and 2014. Large-amplitude d B/d t values are the major cause of hazards associated with three different types of GICs: (1) slow d B/d t with ring current evolution (RC-type), (2) fast d B/d t associated with auroral electrojet activity (AE-type), and (3) transient d B/d t of sudden commencements (SC-type). We set "caution," "warning," and "emergency" alert levels during the main phase of superstorms with the peak Dst index of less than -300 nT (once per 10 years), -600 nT (once per 60 years), or -900 nT (once per 100 years), respectively. The extreme d B/d t values of the AE-type GICs are 2000, 4000, and 6000 nT/min at caution, warning, and emergency levels, respectively. For the SC-type GICs, a "transient alert" is also proposed for d B/d t values of 40 nT/s at low latitudes and 110 nT/s at high latitudes, especially when the solar energetic particle flux is unusually high.

  10. 单相变压器空载合闸励磁涌流暂态特性建模与实验%Modeling and experiment investigation of the transient characteristics of magnetizing inrush current in the switch-on of unloaded single phase transformer

    Institute of Scientific and Technical Information of China (English)

    潘洋; 来磊; 石雷兵; 邵海明; 朱力

    2012-01-01

    The primary winding of the transformer will generate large inrush current due to the saturation of iron core when an unloaded transformer is switched-on. The inrush current not only causes mechanical interaction force due to which the windings are damaged, but also induces the differential protection relays to operate incorrectly. In this paper, the mathematical model of unloaded single phase transformer in switeh-on is analyzed; the computation formulas of the inrush current and its interruption angle are presented. The experiment investigation of single phase transformers with different capacities shows that the inrush current measurement result is consistent with theoretical analysis. The inrush current waveform is typically a steeple top waveform with high order harmonics and damping in one direction. In the same condition, large inrush current amplitude will be induced with smaller switching angle, larger residual flux and smaller staturation flux.%变压器在空载合闸时,由于铁芯饱和导致在变压器的一次绕组内会产生很大的励磁涌流.励磁涌流一方面会引起变压器差动保护装置的误动作;另一方面励磁涌流会导致绕组之间产生机械力作用而损伤绕组.通过分析单相变压器空载合闸的数学模型得出了励磁涌流及其间断角的计算公式.采用分流器和数字示波器对不同容量的单相变压器进行测量后得到了与理论分析一致的涌流波形.理论和实验结果表明励磁涌流是含有高次谐波的单侧衰减尖顶波.在相同条件下,合闸角越小、铁芯剩磁越大、饱和磁通越小,都会导致产生更大的励磁涌流幅值.

  11. Direct Torque Control for Six-phase Permanent Magnet Synchronous Motor With Zero-sequence Current Self-adjust%具有零序电流自矫正的六相永磁同步电机直接转矩控制

    Institute of Scientific and Technical Information of China (English)

    周扬忠; 程明; 熊先云

    2015-01-01

    逆变器死区、功率管导通压降及开关过渡过程等非线性因素易导致直接转矩控制(direct torque control,DTC)多相永磁同步电机定子电流严重畸变。该文针对六相对称偏置60°定子绕组永磁同步电机提出一种DTC策略。首先,基于零序电流等于零思想进行电压矢量重构,并由此提出理想DTC;其次,基于死区补偿原理对实际电压矢量作用时间进行离散补偿;最后,利用 PI 调节器对电压矢量作用时间进行连续补偿,实现零序电流等于零目的。实验结果表明该文提出的驱动控制系统具有快速的转矩动态响应特性;同时零序电流基本等于零,定子电流总谐波含量较低。%There may be serious distortion in stator currents of multi-phase permanent magnet synchronous motor with direct torque control (DTC) because of the nonlinear factors such as inverter dead-zone, power switch voltage drop and switching transition. A novel DTC was proposed for six-phase symmetric winding phase-shifted by a 60 degree permanent magnet synchronous motor. Firstly, the synthesized voltage vectors were determined to achieve the zero-sequence current, and the ideal DTC strategy was proposed based on the synthesized vectors. Secondly, the factual voltage vector operating time was compensated according to the principle of dead-zone compensation. At last, the voltage vector operating time was regulated continuously by a proportion-integral controller aiming at zero zero-sequence current. The experimental results show that the presented DTC has fast response of torque and the total harmonics is very small due to very lower zero-sequence current.

  12. Phase-field simulation of liquid phase migration in the WC-Co system during liquid phase sintering

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Kaiming; Zhang, Lijun; Du, Yong [Central South Univ., Changsha (China). State Key Lab. of Powder Metallurgy; Schwarze, Christian; Steinbach, Ingo [Bochum Univ. (Germany). Interdisciplinary Centre for Advanced Materials Simulation

    2016-04-15

    Liquid phase sintering is a process for forming high performance, multiple-phase components from powders. The process includes very complex interactions between various mass transportation phenomena, among which the liquid phase migration represents an important one in the aspect of forming a gradient structure in cemented carbide. In the present work, phase-field simulation of the liquid phase migration phenomenon during liquid phase sintering is performed in the WC-Co based cemented carbide. The simulation results are analyzed and compared with the experimentally determined key factors of microstructural evolution, such as contiguity and liquid phase migration rate. The diffusion-controlled solution-precipitation mechanism of the liquid phase migration process in the cemented carbide system is confirmed from the current simulation result, which provides deeper understanding of the microstructural evolution during the liquid phase migration process. These simulations can offer guidance in preventing the liquid phase migration process during liquid phase sintering of cellular cemented carbide.

  13. Computational thermodynamics in electric current metallurgy

    DEFF Research Database (Denmark)

    Bhowmik, Arghya; Qin, R.S.

    2015-01-01

    A priori derivation for the extra free energy caused by the passing electric current in metal is presented. The analytical expression and its discrete format in support of the numerical calculation of thermodynamics in electric current metallurgy have been developed. This enables the calculation...... of electric current distribution, current induced temperature distribution and free energy sequence of various phase transitions in multiphase materials. The work is particularly suitable for the study of magnetic materials that contain various magnetic phases. The latter has not been considered in literature....... The method has been validated against the analytical solution of current distribution and experimental observation of microstructure evolution. It provides a basis for the design, prediction and implementation of the electric current metallurgy. The applicability of the theory is discussed in the derivations....

  14. Phase Vocoder

    Directory of Open Access Journals (Sweden)

    J.L. Flanagan

    2013-08-01

    Full Text Available A vocoder technique is described in which speech signals are represented by their short-time phase and amplitude spectra. A complete transmission system utilizing this approach is simulated on a digital computer. The encoding method leads to an economy in transmission bandwidth and to a means for time compression and expansion of speech signals.

  15. IVA Ultrasonic and Eddy Current NDE for ISS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Phased array ultrasonic testing (PAUT) instruments and array eddy current testing instruments were tested on hypervelocity impact damaged aluminum plates simulating...

  16. A Study of Characteristic of Short-Circuit Current Contributed by DC Systems With Single-Phase Short-Circuit Fault on AC Side%交流侧单相短路时直流系统提供短路电流的特性分析

    Institute of Scientific and Technical Information of China (English)

    王铁柱; 万磊; 张彦涛; 卜广全

    2016-01-01

    随着直流输电系统的迅速发展,能否忽略直流系统对短路电流的贡献成为一个亟待研究的问题。文章基于实际直流工程的详细电磁暂态模型,对交流侧发生单相短路故障时直流系统提供短路电流的特性进行研究。通过分析故障后直流输电系统的暂态特性,提出针对短路电流计算关键值,提取并分析直流系统提供短路电流的对应分量;通过对大量仿真结果的统计分析,明确了直流系统提供短路电流的特性及其对短路电流计算的影响,得出结论:直流系统提供的短路电流会使短路电流计算中的工频短路电流初始值、对称开断短路电流的幅值减小,而短路电流峰值增大,且工程应用中短路电流计算可以不考虑直流系统。通过基于实际电网的短路电流对比计算,验证了以上结论。%With rapid development of HVDC systems, it has become important to determine whether DC system contribution can be ignored in short-circuit (SC) current calculation. This paper studies characteristic of SC current contributed by DC systems with single-phase SC fault on AC Side, based on a detailed electromagnetic transient model. By analyzing transient process of a DC system during fault, it is proposed that certain components of SC current contributed by DC systems should be extracted and analyzed, corresponding to critical value of SC current calculation. Based on statistical analysis of a large number of simulation results, features of SC current contributed by DC systems are proposed, as well as its impact on SC current calculation. It is concluded that, SC current contributed by DC systems will decrease amplitude of initial symmetrical SC current and symmetrical breaking SC current, but will increase SC peak current, and that for engineering applications, DC system can be ignored in SC current calculation. Comparative calculation of SC current based on actual grid verifies above

  17. Current measurement apparatus

    Science.gov (United States)

    Umans, Stephen D.

    2008-11-11

    Apparatus and methods are provided for a system for measurement of a current in a conductor such that the conductor current may be momentarily directed to a current measurement element in order to maintain proper current without significantly increasing an amount of power dissipation attributable to the current measurement element or adding resistance to assist in current measurement. The apparatus and methods described herein are useful in superconducting circuits where it is necessary to monitor current carried by the superconducting elements while minimizing the effects of power dissipation attributable to the current measurement element.

  18. Study of transient zero-module current measurement of single-phase earth fault in neutral non-effective grounding system%中性点非有效接地系统单相接地故障暂态零模电流获取方法研究

    Institute of Scientific and Technical Information of China (English)

    季涛; 孙波; 苑倩倩

    2011-01-01

    提出利用空间磁场感应原理获取中性点非有效接地系统架空线路单相接地故障暂态零模电流分量.详细分析了单相接地故障时架空线路周围故障磁场的特征,分析发现,架空线路下方磁场与零模电流基本成线性关系,通过感应该处的磁场变化就可以获取单相接地故障暂态零模电流分量.提出利用霍尔传感器感应架空线路周围空间磁场,并阐述了实际应用中诸多关键技术问题的解决办法.最后通过仿真及实验验证了上述方法可行有效.%A new method using magnetic field induction to measure transient zero-module current of single phase earth fault in neutral non-effective grounding system overhead lines is proposed. The paper analyses the characteristics of magnetic field around the overhead lines in detail, and the results show that the relationship of magnetic field under overhead lines and the transient zero-module current is linear, so transient zero-module current can be measured by inducting the magnetic field. Using a Hall probe magnetometer to induct magnetic field for fault transient current measurements is proposed, and some key techniques of practical application are expatiated. Simulation and experimental tests verify the correctness and feasibility of the proposed method.

  19. Cryogenic current leads

    Energy Technology Data Exchange (ETDEWEB)

    Zizek, F.

    1982-01-01

    Theoretical, technical and design questions are examined of cryogenic current leads for SP of magnetic systems. Simplified mathematical models are presented for the current leads. To illustrate modeling, the calculation is made of the real current leads for 500 A and three variants of current leads for 1500 A for the enterprise ''Shkoda.''

  20. 关于秦山一期棒控系统电流调节回路软件化的设想%The Assumption of the Current Regulating Circuit of Control rod Control System in Qin Shan Nuclear Power Plant Phase I Achieved by Software

    Institute of Scientific and Technical Information of China (English)

    谭平; 黄程

    2016-01-01

    The paper takes the control rod control system of Qin Shan nuclear power phase I as anexample, describe thecontrol rod driven mechanism、the principle of current regulating circuit and control scheme briefly, discuss the function of theset point function module, currentregulating module,phase shift trigger module, anddo the software requirement analysis for them. The paper is based on the C8051F(micro control unit)toachieve the function of these three module,improving the integrity of the current regulating circuit, saving the space of cabinet, conforming to the Miniaturized design.%本文以秦山一期棒控系统为例,简要介绍了秦山一期控制棒控制系统(下述简称棒控系统)的控制对象控制棒驱动机构、电流调节回路原理及控制方案,论述了棒控系统定值、电流调节、移相触发器组件的功能,并对这三类模块功能进行软件分析。本文采用以C8051F单片机为控制核心,将原来采用硬件实现的功能改由软件实现,提高了电流调节回路的集成度,节省机柜空间,符合微型化设计理念。