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1
Singh, J. J., A. Eftekhari, and T. L. St. Clair. "Low Energy Positron Flux Generator for Microstructural Characterization of Thin Films." Materials Science Forum 105-110 (January 1992): 1985–88. http://dx.doi.org/10.4028/www.scientific.net/msf.105-110.1985.
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Singh, Jag J., Abe Eftekhari, and Terry L. St. Clair. "Low energy positron flux generator for lifetime studies in thin films." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 53, no. 3 (March 1991): 342–48. http://dx.doi.org/10.1016/0168-583x(91)95624-m.
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Wang, Qing Long, Min Tan, and Shu Ying Yang. "A Novel Sliding-Mode Observer for Doubly-Fed Induction Generator." Applied Mechanics and Materials 511-512 (February 2014): 1105–9. http://dx.doi.org/10.4028/www.scientific.net/amm.511-512.1105.
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This paper proposes a novel sliding-mode model reference adaptive system (MRAS) observers for speed observer in a sensorless controlled doubly fed induction generator (DFIG) aligned with the stator flux. In the strategy, two stator flux models with different structure are used. The stator flux voltage model without including rotor position item is used as reference model, and the stator flux current model including rotor position item as adjustable model. A slide-mode surface is formulated from the errors between the two models, and the rotor speed estimation can be obtained by a sliding mode algorithm. Meanwhile the one order inertial link is used to avoid suffering from integrator drift effects in voltage model. Simulation results confirm the validity of the approach.
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Wang, Qing Long, and Shu Ying Yang. "Sensorless Control of Doubly-Fed Induction Generator Based on Adaptive Sliding-Mode Observer." Advanced Materials Research 860-863 (December 2013): 337–41. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.337.
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In this paper, a rotor flux based variable-structure model reference adaptive system (MRAS) observers is proposed for speed observer in a sensorless controlled doubly fed induction generator (DFIG) aligned with the stator flux. In the strategy, two rotor flux models with different structure are used. The rotor flux voltage model without including rotor position item is used as reference model, and the rotor flux current model including rotor position item as adjustable model. A slide-mode surface is formulated from the errors between the two models, and the rotor speed estimation can be obtained by a sliding mode algorithm. Meanwhile the one order inertial link is used to avoid suffering from integrator drift effects in voltage model. Simulation results confirm the validity of the approach.
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Benamimour, Tariq, Amar Bentounsi, and Hind Djeghloud. "Study of Wind Turbine based Variable Reluctance Generator using Hybrid FEMM-MATLAB Modeling." International Journal of Electrical and Computer Engineering (IJECE) 7, no. 1 (February 1, 2017): 1. http://dx.doi.org/10.11591/ijece.v7i1.pp1-11.
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Based on exhaustive review of the state of the art of the electric generators fitted to Wind Energy Conversion System (WECS), this study is focused on an innovative machine that is a Variable Reluctance Generator (VRG). Indeed, its simple and rugged structure (low cost), its high torque at low speed (gearless), its fault-tolerance (lowest maintenance), allow it to be a potential candidate for a small wind power application at variable wind speed. For better accuracy, a finite element model of a studied doubly salient VRG is developed using open source software FEMM to identify the electromagnetic characteristics such as linkage flux, torque or inductance versus rotor position and stator excitation. The obtained data are then transferred into look-up tables of MATLAB/Simulink to perform various simulations. Performance of the proposed wind power system is analyzed for several parameters and results are discussed.
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Lahouel, D., D. Hedjazi, and R. Abdessemed. "Sizing inductors of an axial flux synchronous generator." International Journal of Applied Power Engineering (IJAPE) 8, no. 2 (August 1, 2019): 110. http://dx.doi.org/10.11591/ijape.v8.i2.pp110-119.
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<p>This given the outcome of environmental situations in recent years, it has become necessary to use other resolutions for the energy production we need, and among these wind power sources. Since the advent of windmills to the first wind turbines, the technology of aero-motors (or wind sensors) has evolved rapidly. This article presents a study of an axial flow generator, and this mechanism is based on the energy of the wind turbine, this structure solves the problem of the distribution of the magnetic field lines in the armature coils and the inductor of the generator, observing the influence on the voltage from the linear velocity, the density of the injected current and the position along its axis; and that by the method of Finite Elements and is used the computer aided design (CAD), and more particularly the software comsol multiphysics to obtain the results that the good operation of the generator.</p>
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He, Yu-Ling, Meng-Qiang Ke, Gui-Ji Tang, Hong-Chun Jiang, and Xing-Hua Yuan. "Analysis and Simulation on the Effect of Rotor Interturn Short Circuit on Magnetic Flux Density of Turbo–Generator." Journal of Electrical Engineering 67, no. 5 (September 1, 2016): 323–33. http://dx.doi.org/10.1515/jee-2016-0047.
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Abstract The intent of this paper is to investigate the effect of the interturn short circuit fault (ISCF) in rotor on the magnetic flux density (MFD) of turbo-generator. Different from other studies, this work not only pays attention to the influence of the faulty degrees on the general magnetic field, but also investigates the effect of the short circuit positions on the harmonic components of MFD. The theoretical analysis and the digital simulation through the FEM software Ansoft are performed for a QSFN-600-2YHG turbo-generator. Several significant formulas and conclusions drawn from the analysis and the simulation results are obtained to indicate the relation between the harmonic amplitude of the MFD and the faulty degree (via nm, the number of the short circuit turns), and the relation between the MFD harmonic amplitude and the faulty position (via αr, the angle of the two slots in which the interturn short circuit occurs). Also, the developing tendency of the general magnetic field intensity, the distribution of the magnetic flux lines, and the peak-to-peak value of MFD are presented.
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Chen, Xi, and Qing Jie Jiao. "Study on the Circular Fracture in MFCG Armatures Expansion." Key Engineering Materials 326-328 (December 2006): 1637–40. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1637.
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The high-speed photography and the non-linear dynamics engineering program LS-DYNA are conducted to research on Al and Cu armatures expansion process under the drive of pressed composite B explosive with the charge method of several-section. A special experiment system with an equipment of blocking off armature fracture flashing light is built, and a thorough analysis of the “circular fracture” phenomena has been made: For the air gap existence, there is a difference between the axial movement velocity of the armature joint position wall and other positions wall. The upward wall forces the joint position wall and then the “circular fracture” appears. Some conclusions about Magnetic Flux Compression Generator design are obtained.
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Singh, J. J. "Microstructural characterization of thin polymer films using the Langley low energy positron flux generator." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 79, no. 1-4 (June 1993): 349–52. http://dx.doi.org/10.1016/0168-583x(93)95361-8.
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Li, Bin, Liang Yan, and Wenping Cao. "An Improved LPTN Method for Determining the Maximum Winding Temperature of a U-Core Motor." Energies 13, no. 7 (March 28, 2020): 1566. http://dx.doi.org/10.3390/en13071566.
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In a traditional lumped-parameter thermal network, no distinction is made between the heat and non-heat sources, resulting in both larger heat flux and temperature drop in the uniform heat source. In this paper, an improved lumped-parameter thermal network is proposed to deal with such problems. The innovative aspect of this proposed method is that it considers the influence of heat flux change in the heat source, and then gives a half-resistance theory for the heat source to achieve the temperature drop balance. In addition, the coupling relationship between the boundary temperature and loading position of the heat generator is also added in the lumped-parameter thermal network, so as to amend the loading position and nodes’ temperature through iterations. This approach breaks the limitation of the traditional lumped-parameter thermal network: that the heat generator can only be loaded at the midpoint, which is critical to determining the maximum temperature in asymmetric heat dissipation. By adjusting the location of heat generator and thermal resistances of each branch, the accuracy of temperature prediction is further improved. A simulation and an experiment on a U-core motor show that the improved lumped-parameter thermal network not only achieves higher accuracy than the traditional one, but also determines the loading position of the heat generator well.
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Li, Yong Gang, and Bing Han. "Magnetic Field Finite Element Analysis of Generator with Rotor Inter-Turn Short-Circuit Fault." Applied Mechanics and Materials 707 (December 2014): 343–47. http://dx.doi.org/10.4028/www.scientific.net/amm.707.343.
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Rotor inter-turn short-circuit is a common fault in generator and it is a research hotspot to identify the fault at its early stage. Considering the disadvantage of circuit analytical method, this paper establishes a 2D transient finite element electromagnetic-circuit coupling model, and calculates the magnetic field at normal and fault situations through the powerful post-processing function of ANSOFT, then magnetic flux density cloud pictures and air-gap magnetic flux density curves of different operating conditions are got. Using MATLAB to analyze and deal with the air-gap flux density cures, we can get the differences of faults in different levels and different positions, which provide a basis for further study of rotor inter-turn short-circuit fault.
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Brando, Gianluca, Adolfo Dannier, and Ivan Spina. "Performance Analysis of a Full Order Sensorless Control Adaptive Observer for Doubly-Fed Induction Generator in Grid Connected Operation." Energies 14, no. 5 (February 25, 2021): 1254. http://dx.doi.org/10.3390/en14051254.
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This paper focuses on the performance analysis of a sensorless control for a Doubly Fed Induction Generator (DFIG) in grid-connected operation for turbine-based wind generation systems. With reference to a conventional stator flux based Field Oriented Control (FOC), a full-order adaptive observer is implemented and a criterion to calculate the observer gain matrix is provided. The observer provides the estimated stator flux and an estimation of the rotor position is also obtained through the measurements of stator and rotor phase currents. Due to parameter inaccuracy, the rotor position estimation is affected by an error. As a novelty of the discussed approach, the rotor position estimation error is considered as an additional machine parameter, and an error tracking procedure is envisioned in order to track the DFIG rotor position with better accuracy. In particular, an adaptive law based on the Lyapunov theory is implemented for the tracking of the rotor position estimation error, and a current injection strategy is developed in order to ensure the necessary tracking sensitivity around zero rotor voltages. The roughly evaluated rotor position can be corrected by means of the tracked rotor position estimation error, so that the corrected rotor position is sent to the FOC for the necessary rotating coordinate transformation. An extensive experimental analysis is carried out on an 11 kW, 4 poles, 400 V/50 Hz induction machine testifying the quality of the sensorless control.
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PARK, MIN GYU, SANG KWANG BANG, SEONG HWAL SHIN, KI WOONG SEONG, and JYUNG HYUN LEE. "ALTERNATING MAGNETIC FIELD GENERATOR FOR THREE-DIMENSIONAL POSITION TRACKING OF MEDICAL TREATMENT EQUIPMENT FOR TRAINING." Journal of Mechanics in Medicine and Biology 21, no. 05 (April 21, 2021): 2140027. http://dx.doi.org/10.1142/s0219519421400273.
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In recent years, the incidence of cardiovascular disease is high due to the aging population and westernization of dietary habits, what encourages researching new methods. Most cardiovascular procedures use the catheter. In the procedure using a catheter, a long time of training is required to lower the procedure risk. So, a medical training simulator is being developed. In the actual procedure, the position of the catheter is confirmed by a C-arm using X-ray, but there is a risk of over exposure to radiation if the X-ray device is used until training. To solve this problem, in previous studies, the position of the catheter was tracked using a permanent magnet. However, the method of permanent magnet has a high error value due to the shape of the external magnetic flux density and the interference of environmental magnetic field. In this paper, an alternating magnetic field generator is proposed for 3D position tracking of medical equipment for training. An electromagnet with an optimal shape was designed through finite element analysis. The designed electromagnet is implemented and tested to confirm the performance. Through the location tracking experiment, an equation to estimate the distance between the electromagnet and the Hall sensor in 3D space was derived by linear regression recursive method. Through the derived equation, it was possible to track the position of the electromagnet at any position in the 3D space. Unlike previous studies using permanent magnets, the proposed alternating magnetic field generator has an isotropic shape with an external magnetic flux density according to the same distance. So, it is possible to reduce errors in position and distance, and minimize the effect of environmental magnetic fields by using an alternating magnetic field.
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Zeman, Andrej, K. Tuček, G. Daquino, L. Debarberis, and A. Hogenbirk. "Scoring Analysis of Design, Verification and Optimization of High Intensity Positron Source (HIPOS)." Materials Science Forum 733 (November 2012): 297–305. http://dx.doi.org/10.4028/www.scientific.net/msf.733.297.
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As part of an exploratory research project at the Institute for Energy (Joint Research Centre of the European Commission), a feasibility assessment was performed for the design and construction of a high-intensity positron facility (HIPOS) in a neutron beam tube, HB9, at the High Flux Reactor (HFR) in Petten. The full model of reactor core, reflector and reactor instrumentation at the neutron beam line HB9 were modeled and full neutronic and photonic calculations were carried out by MCNP4C3. The source file was generated in two formats: SDEF and WESSA. Consequently, two different codes were used for scoring analysis for the optimization of the concept and geometry of positron generator. The main concept including key design parameters have been evaluated independently by two computer codes, in particular MCNP-X and GEANT4. The parametric design analysis including the optimization of positron generator at the pre-selected neutron beam line is reported in this paper. The detailed assessment of the critical design parameters, specifically from technological point of view is summarised. The results of independent analysis confirmed that the best approach is to combine two concepts of positron generation, which are based on the exploiting of neutron and gamma radiation. The results verified that the proposed concept can reach the defined threshold of the positron yield and the positron beam can reach an intensity of 1013e+/sec (un-moderated). The details of completed work are reported in this paper.
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Kenne, Godpromesse, Clotaire Thierry Sanjong, and Eustace Mbaka Nfah. "Adaptive PI Control Strategy for a Self-Excited Induction Generator Driven by a Variable Speed Wind Turbine." Journal of Circuits, Systems and Computers 26, no. 02 (November 3, 2016): 1750024. http://dx.doi.org/10.1142/s0218126617500244.
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In this paper, an adaptive proportional-integral (API) control strategy is developed to extract the maximum power from a variable wind speed turbine and to regulate the DC-link voltage, rotor flux and AC load voltage in a three-phase grid-connected self-excited induction generator (SEIG) system. The resulting controller associated to the flux-oriented control technique can be easily implemented in practice since finite time estimators for the unknown time-varying rotor resistance, rotor flux (nonmeasurable signal) and stator electrical angular position required for the online implementation of the proposed algorithm are provided. Comparative results with a conventional nonadaptive proportional-integral regulator have shown the superiority of the proposed strategy in terms of robustness with respect to online variation of the rotor resistance (up to 100%) and large varying load condition. The computing results are obtained using relatively low wind speed profile. Thus, the generating system with the proposed control strategy is suitable for variable wind speed turbine installation for grid-connected and remote-area power supply where the wind speed profile is relatively low.
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Wang, Yu, and Zhi-Quan Deng. "A Position Sensorless Method for Direct Torque Control With Space Vector Modulation of Hybrid Excitation Flux-Switching Generator." IEEE Transactions on Energy Conversion 27, no. 4 (December 2012): 912–21. http://dx.doi.org/10.1109/tec.2012.2210718.
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Xi, Shibo, Lucas Santiago Borgna, and Yonghua Du. "General method for automatic on-line beamline optimization based on genetic algorithm." Journal of Synchrotron Radiation 22, no. 3 (April 2, 2015): 661–65. http://dx.doi.org/10.1107/s1600577515001861.
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It is essential but inconvenient to perform high-quality on-line optimization for synchrotron radiation beamlines. Usually, synchrotron radiation beamlines are optimized manually, which is time-consuming and difficult to obtain global optimization for all optical elements of the beamline. In this contribution a general method based on the genetic algorithm for automatic beamline optimization is introduced. This method can optimize all optical components of any beamline simultaneously and efficiently. To test this method, a program developed usingLabVIEWis examined at the XAFCA beamline of the Singapore Synchrotron Light Source to optimize the beam flux at the sample position. The results demonstrate that the beamline can be optimized within 17 generations even when the initial flux is as low as 4% of its maximum value.
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Yao, Tao, Yulong Wang, Zhihua Wang, and Can Qin. "Design and performance analysis of wave linear generator with parallel mechanism." Mechanical Sciences 12, no. 1 (April 14, 2021): 405–17. http://dx.doi.org/10.5194/ms-12-405-2021.
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Abstract. Considering the irregularity of wave motion, a wave energy converter (WEC) based on 6-UCU parallel mechanism has been investigated. A buoy connected to moving platform is used to harvest wave energy. Each chain is equipped with the linear generator of the same structure, which can convert the absorbed wave energy into electrical energy. Based on the inverse kinematics analysis of parallel mechanism, the position of the parallel mechanism is solved by using the space closed-loop vector method; the relative motion of stator and translator is obtained. Through electromagnetic numerical simulations, the influences of linear generator parameters such as magnetization mode, air gap, and yoke shape on electromagnetic performance were evaluated. Numerical results show axial magnetization and Halbach magnet array can increase magnetic flux intensity more than radial mode. Furthermore, the rule of electromagnetic resistance is discussed with the change of the speed amplitude and the angle frequency. For a case, dynamic differential equation of the whole system is established. The conversion rate of wave energy is derived.
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Karthikeyan, A., and C. Nagamani. "Decoupled Power Control of Doubly-Fed Induction Generator Based on an Implicit Position and Speed Estimation Algorithm without the Flux Computation." Wind Engineering 35, no. 6 (December 2011): 757–76. http://dx.doi.org/10.1260/0309-524x.35.6.757.
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Pedersen, Jan Skov. "A flux- and background-optimized version of the NanoSTAR small-angle X-ray scattering camera for solution scattering." Journal of Applied Crystallography 37, no. 3 (May 11, 2004): 369–80. http://dx.doi.org/10.1107/s0021889804004170.
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A commercially available small-angle X-ray scattering camera, NanoSTAR from Bruker AXS, has been modified to optimize its use for weakly scattering solution samples. The original NanoSTAR is a pinhole camera with two Göbel mirrors for monochromating and making the beam parallel, and with a two-dimensional position-sensitive gas detector (HiSTAR) for data collection. The instrument has one integrated vacuum. It was constructed for position-resolved studies and thus has a small beam size at the sample position. In the present work, the instrumental configuration has been optimized by numerical calculations based on phase-space analysis and Monte Carlo simulations in order to obtain a higher flux. This has led to a setup in which the beam at the sample is larger and the collimation part of the instrument is longer, so that divergence of the beam is similar to that of the original camera. An extra pinhole is included after the Göbel mirrors to make the beam size well defined after the mirrors. The camera thus has genuine three-pinhole collimation. The use of electron-microscope pinholes minimizes parasitic scattering. At the University of Aarhus, the modified camera is installed on a powerful rotating-anode X-ray source (MacScience 6 kW Cu with a 0.3 × 0.3 mm effective source size). Measurements have been performed on a wide variety of weakly scattering samples, such as surfactant micelles, homopolymer solutions, block copolymer micelles, proteinsetc. The data are routinely converted to absolute scale using the scattering from water as a primary standard. The standard configuration covers the range of scattering vectors from 0.01 to 0.35 Å−1with a flux of 1.7 × 107photons s−1for CuKα radiation at a generator power of 4.05 kW. The camera is easily converted to a high-resolution version covering 0.0037 to 0.22 Å−1with a loss of flux of about a factor of 10, as well as to a position-resolved version.
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Sahri, Younes, Salah Tamalouzt, and Sofia Belaid Lalouni. "Enhanced Direct Power Control Strategy of a DFIG-Based Wind Energy Conversion System Operating Under Random Conditions." Periodica Polytechnica Electrical Engineering and Computer Science 65, no. 3 (June 7, 2021): 196–206. http://dx.doi.org/10.3311/ppee.16656.
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The main objective of this paper is the performances analysis of an Enhanced Direct Power Control (EDPC), applied to Doubly Fed Induction Generator (DFIG) driven by variable speed Wind Turbine (WT). This control strategy uses hysteresis regulators and switching table for active and reactive powers control. These latter are estimated using rotor currents and grid voltages instead of a traditional measurement of stator currents. In addition, the EDPC switching table is based on the position of the rotor flux instead of the stator flux in order to have better regulation accuracy because the rotor voltage vector directly influences the rotor flux and has a proportional relationship with the active and reactive powers. All the operating modes (sub-synchronous, super-synchronous, synchronous and over-speed) of the variable speed WT-DFIG system and the possibility of local reactive power compensation are reported and discussed in this paper. Depending on the operating zone of the WT, Maximum Power Point Tracking (MPPT) technique and pitch angle control are considered to optimize the wind energy efficiency. The validation of the proposed EDPC strategy has been performed through simulation tests under MATALB/Simulink, the obtained results show robustness and good performances with low THD of the generated currents.
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Abdelrahem, Mohamed, Christoph M. Hackl, José Rodríguez, and Ralph Kennel. "Model Reference Adaptive System with Finite-Set for Encoderless Control of PMSGs in Micro-Grid Systems." Energies 13, no. 18 (September 16, 2020): 4844. http://dx.doi.org/10.3390/en13184844.
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In micro-grid systems, wind turbines are essential power generation sources. The direct-driven surface-mounted permanent-magnet synchronous generators (SMPMSGs) in variable-speed wind generation systems (VS-WGSs) are promising due to their high efficiency/power density and the avoidance of using a gearbox, i.e., regular maintenance and noise are averted. Usually, the main goal of the control system for SMPMSGs is to extract the maximum available power from the wind turbine. To do so, the rotor position/speed of the SMPMSG must be known. Those signals are obtained by the help of an incremental encoder or speed transducer. However, the system reliability is remarkably reduced due to the high failure rate of these mechanical sensors. To avoid this problem, this paper presents a model reference adaptive system with finite-set (MRAS-FS) observer for encoderless control of SMPMSGs in VS-WGSs. The motif of the presented MRAS-FS observer is taken from the direct-model predictive control (DMPC) principle, where a certain number of rotor position angles are utilized to estimate the stator flux of the SMPMSG. Subsequently, a new optimization criterion (also called quality or cost function) is formulated to select the best rotor position angle based on minimizing the error between the estimated and reference value of the stator flux. Accordingly, the traditional fixed-gain proportional-integral regulator generally employed in the classical MRAS observers is not needed. The proposed MRAS-FS observer is validated experimentally, and its estimation response has been compared with the conventional MRAS observer under different conditions. In addition to that, the robustness of the MRAS-FS observer is tested at mismatches in the parameters of the SMPMSG.
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Kolpakhchyan, P. G., and D. V. Olkhovatov. "Sensorless control of the high-speed switched reluctance generator of the micro power plant." Vestnik of Don State Technical University 19, no. 4 (January 3, 2020): 357–65. http://dx.doi.org/10.23947/1992-5980-2019-19-4-357-365.
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Introduction. In the distributed and autonomous generation systems using renewable energy sources, low-power generating units (not more than 100-200 kW) based on microturbines function. Microturbines operate most efficiently at high rotational speeds. In this regard, the generator running with a microturbine must also be a high-speed one. A generator is a switched reluctance electric machine (EM) that needs information on the rotor position. It is difficult to use a position sensor in such mechanisms at high speeds. This paper discusses the issues of sensorless control of a high-speed switched reluctance electric generator in conjunction with a steam microturbine.Materials and Methods. So, it is required to evaluate the proof-of-principle developed to control a high-speed switched reluctance EM. For this purpose, a mathematical model has been created including models of the investigated EM, an electric power converter, and a control system. For the EM under consideration, the active resistance is determined, as well as the dependence of the phase flux linkage on the current flowing through it and the position of the moving element. The method used involves probing the idle phase of an electric machine with short voltage pulses of equal duration, and measuring the current in this phase. If the voltage pulse length is much shorter than the phase time constant, then the current pulse amplitude is inversely proportional to the inductance. Thus, registering the maximum current pulse amplitude, it is possible to determine the rotor passage through an uncoordinated position for the probed phase. This information is used to form control actions by other phases. Moreover, the length of the test voltage pulses, required to obtain current pulses sufficient for measuring the value, is of significance versus the duration of the pulsing time. Hence, with an increase in the rotational speed, the number of test pulses is insufficient for measuring the position with the accuracy required for the control goals. This reduces drastically the precision of determining the rotor position; therefore, at high speeds, the application of this method is limited without further refinement of the rotor position. In this case, to increase the precision of measurements, it is necessary to evaluate the rate of current rise when applying the basic voltage pulse or the voltage pulse rate forming the phase current before switching to a single-pulse control mode. Research Results. Two conclusions important for correcting the estimation of the rotor position in a single-pulse operation mode of a reluctance EM are proved. The first conclusion is on the efficiency of the proposed technique of filtering phase current measurement data, the second one concerns the applicability of the identified information criteria. The analysis results of the processes in the switched reluctance EM using sensorless control that implements the described principles for determining the rotor position are presented.Discussion and Conclusions. To correct the estimation of the rotor position, the following information criteria can be used: the presence of a pause between the excitation pulse and the start of the generation process; the decrease in current by the time the generation begins. To refine the estimate, the following fact can be used: on the generation interval, the current curve knee corresponding to the maximum phase inductance is observed at the same rotor position.
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Douçot, Benoit, Franco Nori, and R. Rammal. "FILLING LANDAU LEVELS: FERMI SEA GROUND STATE ENERGY, COMPETING INTERACTIONS AND MARGINAL DISPERSIONS IN GENERALIZED FLUX PHASES." International Journal of Modern Physics B 06, no. 05n06 (March 1992): 563–83. http://dx.doi.org/10.1142/s0217979292000347.
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ABSTRACT: We review recent studies on the energetics of fermions confined to a two dimensional square lattice, and the relations of these results to mean-field approaches to the t−J model. Our goal has been to compute the kinetic energy of the Fermi sea of the spinless fermions for any value of the (1) fermion concentration, (2) magnetic flux, and (3) frustration. For the unfrustrated case, we confirm that the ground state energy, χ(Φ), is a minimum for Φ=π(1−δ), which corresponds to one flux quantum per spinless fermion. We then proceed to do a systematic study of frustration effects, coming from longer range couplings, which modify the picture obtained for the unfrustrated case. The frustrating influence of the kinetic energy of the holes (e.g., by breaking magnetic bonds and suppressing the long-range order present in the undoped systems) is the main focus of this work. We find that, in general, E(Φ) always exhibits cusp-like minima which position moves linearly as a function of the fermion density x. Frustration can induce a competition between different local minima. By first considering the local minima for one particle only, we can understand most of the qualitative features of E(Φ). These local minima occur at simple rational fractions of Φ0, and when the flux slightly deviates from these values a one-particle Landau level structure develops. It is precisely such a spectrum that generates a family of cusps that “move away” from the original flux value as x is increased. Every cusp corresponds to an integer number of filled Landau levels, and the minimum energy cusp corresponds to the one level case. Furthermore, we use perturbation theory, valid for low fermion density x, in order to analyze quantitatively the behavior of the cusp-like energy minima; which originate from the Landau level structure when the flux is close to a rational value. If the flux is slightly away from a given rational value [Formula: see text] each of the q subbands generates a secondary Landau level structure. We have derived a t2−t3 phase diagram indicating regions of similar behavior (i.e., adiabatic continuations can be performed with each region, preserving the E(Φ) structure) and the boundaries between them. We have studied several points belonging to those boundaries and found that anomalous behavior, (e.g., cancelation of the k2 term in the dispersion relation) induced by frustration, can occur.
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Veneva, Ivanka, Bram Vanderborght, Dirk Lefeber, and Pierre Cherelle. "PROPULSION SYSTEM WITH PNEUMATIC ARTIFICIAL MUSCLES FOR POWERING ANKLE-FOOT ORTHOSIS." Journal of Theoretical and Applied Mechanics 43, no. 4 (December 1, 2013): 3–16. http://dx.doi.org/10.2478/jtam-2013-0029.
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Abstract The aim of this paper is to present the design of device for control of new propulsion system with pneumatic artificial muscles. The propulsion system can be used for ankle joint articulation, for assisting and rehabilitation in cases of injured ankle-foot complex, stroke patients or elderly with functional weakness. Proposed device for control is composed by microcontroller, generator for muscles contractions and sensor system. The microcontroller receives the control signals from sensors and modulates ankle joint flex- ion and extension during human motion. The local joint control with a PID (Proportional-Integral Derivative) position feedback directly calculates desired pressure levels and dictates the necessary contractions. The main goal is to achieve an adaptation of the system and provide the necessary joint torque using position control with feedback.
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Abdalla, Turki, Haroution Hairik, and Adel Dakhil. "Minimization of Torque Ripple in DTC of Induction Motor Using Fuzzy Mode Duty Cycle Controller." Iraqi Journal for Electrical and Electronic Engineering 7, no. 1 (June 1, 2011): 42–49. http://dx.doi.org/10.37917/ijeee.7.1.8.
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Among all control methods for induction motor drives, Direct Torque Control (DTC) seems to be particularly interesting being independent of machine rotor parameters and requiring no speed or position sensors. The DTC scheme is characterized by the absence of PI regulators, coordinate transformations, current regulators and PWM signals generators. In spite of its simplicity, DTC allows a good torque control in steady state and transient operating conditions to be obtained. However, the presence of hysterics controllers for flux and torque could determine torque and current ripple and variable switching frequency operation for the voltage source inverter. This paper is aimed to analyze DTC principles, and the problems related to its implementation, especially the torque ripple and the possible improvements to reduce this torque ripple by using a proposed fuzzy based duty cycle controller. The effectiveness of the duty ratio method was verified by simulation using Matlab/Simulink software package. The results are compared with that of the traditional DTC models.
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Tsai, Ming-Fa, Chung-Shi Tseng, and Bor-Yuh Lin. "Phase Voltage-Oriented Control of a PMSG Wind Generator for Unity Power Factor Correction." Energies 13, no. 21 (October 30, 2020): 5693. http://dx.doi.org/10.3390/en13215693.
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This paper presents the power factor control of a permanent magnet synchronous wind generator (PMSG) wind turbine using a phase voltage-oriented control (PVOC) scheme, which is different from the conventional rotor flux-oriented control (RFOC) method and without using a rotor position sensor or sensorless estimator. The proposed control system is operated in two separately synchronously rotating d-q frames. One is for a phase-locked loop (PLL) and the other is for the PVOC current control loop. A PI controller functioned as a low-pass filter in the PLL loop is designed for extracting the phase voltage angle for the coordinate transformation between the stationary α-β frame and the synchronously rotating d-q frame in the PVOC control loop. The d-q modeling of the PMSG with the three-phase voltage vector aligned on the d-axis is then derived and based on which an another PI controller followed by decoupling control is designed, so that the three-phase currents are in phase with the three-phase output voltages of the wind generator for unity power factor correction. The simulation results in PSIM show the performance of the proposed control system which is also experimentally verified by using a TI TMS320F28335 digital control chip.
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Abedinzadeh, Taher, and Sajjad Tohidi. "A comprehensive sensorless control of DFIG-based wind turbines." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 35, no. 1 (January 4, 2016): 27–43. http://dx.doi.org/10.1108/compel-09-2014-0236.
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Purpose – The purpose of this paper is to present an improved approach for estimation of the rotor position and speed of doubly fed induction generator, which can be used in vector control and direct torque control (DTC) schemes. Design/methodology/approach – Some novel equations are developed for calculation of the rotor position and rotor speed. Such equations do not need to the value of stator flux linkage and just, measured values of the stator voltage and currents as well as rotor current are required to be known. Findings – The simulation results verify the satisfactory steady-state and dynamic performance of proposed approach with both the vector control and DTC schemes. The results show that the proposed estimation approach benefits from the starting on the fly, robustness against the variations of the most of the stator and rotor parameters and immunity against the noise. Originality/value – The proposed estimation approach is novel and the outcome of the research of authors. It is simple and effective and, no approximation is made in the calculations. The simulation results demonstrate that the proposed scheme can be successfully implemented in various control strategies, e.g. DTC and vector control.
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Ogata, Y., N. Ishigure, S. Mochizuki, K. Ito, K. Hatano, J. Abe, H. Miyahara, et al. "Estimation of thermal neutron flux in pet cyclotron rooms by means of radioactive analysis of bolts in the rooms." Proceedings in Radiochemistry 1, no. 1 (September 1, 2011): 55–61. http://dx.doi.org/10.1524/rcpr.2011.0009.
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Abstract Short-lived radionuclides for positron emission tomography (PET) examinations in medicine are produced mainly using on site small cyclotrons. The operation of the cyclotron generates a significant quantity of neutrons, which will activate the cyclotron and surrounding materials. A new technique is proposed to estimate the neutron fluxes in the cyclotron rooms, in which small bolts in the cyclotron rooms were used as surrogates for neutron detectors. The measurements were carried out at four PET cyclotrons. The induced radioactivity of the bolts was analyzed by gamma-ray spectroscopy and elemental analysis. A gold foil activation method was applied to compare the results. The neutron fluxes in the PET cyclotron rooms were in the range of 105∼106 cm−2 s−1 during 18F production. In the brass bolts, 69mZn, 65Zn, 64Cu, 58Co, and 60Co were detected. In the iron bolts, 56Mn, 54Mn, 59Fe, 60Co, 69mZn, and 65Zn were detected. In the stainless steel bolts, 58Co, 60Co, 56Mn, 54Mn, and 59Fe were detected. Neutron fluxes estimated from the activities of 56Mn agreed well with those by the Au foil method. The feasibility of estimating the neutron fluxes in cyclotron rooms by means of radioactive analysis of bolts in the rooms was proven.
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Uhlář, Radim, and Petr Alexa. "MCNP APPROACHES FOR DOSE RATES MODELING IN LABORATORY FOR NEUTRON ACTIVATION ANALYSIS AND GAMMA SPECTROMETRY AT OSTRAVA." Radiation Protection Dosimetry 185, no. 1 (December 1, 2018): 116–23. http://dx.doi.org/10.1093/rpd/ncy209.
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Abstract The Laboratory for Neutron Activation Analysis and Gamma Spectrometry at the VŠB-Technical University of Ostrava was equipped with the neutron generator MP320 operating on the principle of the deuterium–tritium fusion and producing 108 neutrons/s at maximum. To ensure radiation protection of radiation workers and public outside the laboratory, the concrete shielding was designed and its protection efficiency was validated by MCNP simulations. Three approaches to calculate the dose rates were compared. The dose rates were estimated for the ORNL MIRD phantom located at the relevant positions (Tally F6 and *F8) and using the MCNPX mesh tally feature with the new ICRP Publication 116 flux-to-dose conversion factors. It was proven that the Approach II in which the absorbed dose rates due to neutrons for all organs are computed using the cell tally F6 and the photon dose calculation is performed by the *F8 energy deposition tally is the most valuable one.
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Frigon, Alain, Jennifer Sirois, and Jean-Pierre Gossard. "Effects of Ankle and Hip Muscle Afferent Inputs on Rhythm Generation During Fictive Locomotion." Journal of Neurophysiology 103, no. 3 (March 2010): 1591–605. http://dx.doi.org/10.1152/jn.01028.2009.
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Hip position and loading of limb extensors are major sensory cues for the initiation and duration of different phases during walking. Although these inputs have pathways projecting to the locomotor rhythm generator, their effects may vary in different parts of the locomotor cycle. In the present study, the plantaris (Pl), sartorius (Sart), rectus femoris (RF), and caudal gluteal (cGlu) nerves were stimulated at group I and/or group II strength during spontaneous fictive locomotion in 16 adult decerebrate cats. These nerves supply muscles that extend the ankle (Pl), flex the hip (Sart, RF), or extend the hip (cGlu). Stimuli were given at six epochs of the locomotor cycle to evaluate when they access the rhythm generator. Group I afferents from Pl nerve always reset the locomotor rhythm; stimulation during extension prolonged cycle period and extension phase duration, while stimulation during flexion terminated flexion and initiated extension. On the other hand, stimulating RF and cGlu nerves only produced significant effects on the rhythm in precise epochs, particularly during mid-flexion and/or mid- to late extension. Stimulating the Sart nerve produced complex effects on the rhythm that were not distributed evenly to all extensor motor pools. The most consistent effect was reduced flexion phase duration with stimulation during flexion, particularly at group II strength, and prolongation of the extension phase but only in late extension. That hip muscle afferents reset the rhythm in only specific epochs of the locomotor cycle suggests that the rhythm generator operates with several subdivisions to determine phase and cycle durations.
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Chen, Long, Haoxiang Wang, Xiaodong Sun, Yingfeng Cai, Ke Li, Kaikai Diao, and Jiangling Wu. "Development of a digital control system for a belt-driven starter generator segmented switched reluctance motor for hybrid electric vehicles." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 234, no. 9 (July 15, 2020): 975–84. http://dx.doi.org/10.1177/0959651820938945.
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A novel four-phase 16/10 belt-driven starter generator segmented switched reluctance motor has been proposed in a previous work to reduce torque ripple and increase the fault tolerance ability. Based on the previous research, the segmented switched reluctance motor digital control system is designed and presented. The digital control system including a power converter, detection circuits, and protection circuits is introduced in detail. For detection circuits, the half-detection method is employed to decrease the cost of the system. In addition, based on MicroAutoBox DS1401, a rapid control prototype platform is established. With this software system, it is easy to transfer control models and realize real-time control directly. Then, the speed closed closed-loop control for the segmented switched reluctance motor is applied to verify the proposed system. It contains current chopper control at a low speed and angle position control at a high speed. The simulation results are given, including the flux, current, torque, and efficiency range over the entire speed range of the segmented switched reluctance motor. Finally, the experimental results are presented to verify the simulation results and the effectiveness of the system. It can be found that the simulation and experimental results are consistent and acceptable, which means that the proposed digital system can operate naturally and accurately under speed closed loop control. Hence, the proposed digital system has high compatibility and practicability.
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He, Yu-Ling, Wei-Qi Deng, Gui-Ji Tang, Xiao-Ling Sheng, and Shu-Ting Wan. "Impact of Different Static Air-Gap Eccentricity Forms on Rotor UMP of Turbogenerator." Mathematical Problems in Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/5284815.
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Theoretical analysis and numerical FEM calculations, together with segmental experiment studies, are used to study the impact of the static air-gap eccentricity forms on the rotor unbalanced magnetic pull (UMP) of turbogenerator. The universal expression of the magnetic flux density under different forms of SAGE is firstly deduced, based on which the detailed UMP formulas for the normal condition and three SAGE cases are obtained, respectively. Then the exciting characteristics of the UMP for each SAGE form to generate vibrations are analyzed. Finally, numerical FEM calculations and segmental experiments are carried out to investigate the effect of SAGE forms on the rotor UMP, taking the SDF-9 type non-salient-pole fault simulating generator as the object. It is shown that, no matter what kind of SAGE occurs, amplitude increments at each even harmonic component of the UMP and the rotor vibration, especially the 2nd harmonic component, will be brought in. Meanwhile, the UMP keeps directing to the very position where the minimum radial air-gap is. Among the different SAGE forms, the rotor offset has the most sensitive effect on the rotor UMP and vibration, while the stator ellipse deformation has the weakest impact.
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He, Yu-Ling, Wei-Qi Deng, and Gui-Ji Tang. "Analysis and Simulation on UMP and EMT Characters of Turbogenerator under Axial Air-Gap Eccentricity." International Journal of Rotating Machinery 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/825835.
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The purpose of this paper is to investigate the effect of the axial air-gap eccentricity (AAGE) on the electromagnetic characters such as the axial unbalanced magnetic pull (UMP) and the electromagnetic torque (EMT). Firstly, the theoretical model of AAGE is set up, and the formulas of the axial UMP and EMT are deduced. Then the simulation study of a SDF-9 nonsalient pole synchronous generator is taken with Ansoft Maxwell to calculate the detailed axial UMPs and EMTs under normal condition and five AAGE conditions, respectively, with 2 mm to 10 mm rotor displacements. It is shown that an apparent axial UMP will be produced due to AAGE, while EMT and the phase current will be decreased. In addition, the magnetic flux density (MFD) on the stator end and the rotor end, which are more far from the center position of the stator core in the axial direction, will be decreased, while the MFD on the other ends will be generally kept stable. As AAGE develops, the axial UMP will be increased, while EMT and the phase current will be decreased. The proposed work offers a reference for the fault diagnosis and monitoring on AAGE.
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Aman, Holger. "The Legal Information Landscape: Change is the New Normal." Legal Information Management 19, no. 02 (June 2019): 98–101. http://dx.doi.org/10.1017/s1472669619000227.
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AbstractThe legal information landscape has always been one of instability and change. The rate of these changes seems to be speeding up as societal and technological changes interact and impact our lives. In the face of this volatility, we should remain constant by being the human factor between information and our clients. We are the interface between new technology and the changing information usage behaviours of our clients. We must understand both aspects to ensure the best outcomes. Our client centric attitude positions us perfectly to be leaders when exploring, and perhaps even creating, new solutions. We are best placed to bring them back to our institutions and provide the human touch to ensure they are implemented in a way that will succeed and add value. It is important to embrace this constant state of flux and find our value in being supportive change agents, while also ensuring that we can ensure, and advocate for, the importance of safeguarding legal information for generations to come.
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Eitzen, Zachary A., and David A. Randall. "Numerical Simulations of Interactions between Gravity Waves and Deep Moist Convection." Journal of the Atmospheric Sciences 62, no. 5 (May 1, 2005): 1480–96. http://dx.doi.org/10.1175/jas3418.1.
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Abstract This study uses a numerical model to simulate deep convection both in the Tropics over the ocean and the midlatitudes over land. The vertical grid that was used extends into the stratosphere, allowing for the simultaneous examination of the convection and the vertically propagating gravity waves that it generates. A large number of trajectories are used to evaluate the behavior of tracers in the troposphere, and it is found that the tracers can be segregated into different types based upon their position in a diagram of normalized vertical velocity versus displacement. Conditional sampling is also used to identify updrafts in the troposphere and calculate their contribution to the kinetic energy budget of the troposphere. In addition, Fourier analysis is used to characterize the waves in the stratosphere; it was found that the waves simulated in this study have similarities to those observed and simulated by other researchers. Finally, this study examines the wave energy flux as a means to provide a link between the tropospheric behavior of the convection and the strength of the waves in the stratosphere.
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Huang, Lilian, Wenju Yao, Jianhong Xiang, and Zefeng Zhang. "Heterogeneous and Homogenous Multistabilities in a Novel 4D Memristor-Based Chaotic System with Discrete Bifurcation Diagrams." Complexity 2020 (April 25, 2020): 1–15. http://dx.doi.org/10.1155/2020/2408460.
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In this paper, a new 4D memristor-based chaotic system is constructed by using a smooth flux-controlled memristor to replace a resistor in the realization circuit of a 3D chaotic system. Compared with general chaotic systems, the chaotic system can generate coexisting infinitely many attractors. The proposed chaotic system not only possesses heterogeneous multistability but also possesses homogenous multistability. When the parameters of system are fixed, the chaotic system only generates two kinds of chaotic attractors with different positions in a very large range of initial values. Different from other chaotic systems with continuous bifurcation diagrams, this system has discrete bifurcation diagrams when the initial values change. In addition, this paper reveals the relationship between the symmetry of coexisting attractors and the symmetry of initial values in the system. The dynamic behaviors of the new system are analyzed by equilibrium point and stability, bifurcation diagrams, Lyapunov exponents, and phase orbit diagrams. Finally, the chaotic attractors are captured through circuit simulation, which verifies numerical simulation.
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Cheng, Wayland W. L., Decha Enkvetchakul, and Colin G. Nichols. "KirBac1.1: It's an Inward Rectifying Potassium Channel." Journal of General Physiology 133, no. 3 (February 9, 2009): 295–305. http://dx.doi.org/10.1085/jgp.200810125.
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KirBac1.1 is a prokaryotic homologue of eukaryotic inward rectifier potassium (Kir) channels. The crystal structure of KirBac1.1 and related KirBac3.1 have now been used extensively to generate in silico models of eukaryotic Kir channels, but functional analysis has been limited to 86Rb+ flux experiments and bacteria or yeast complementation screens, and no voltage clamp analysis has been available. We have expressed pure full-length His-tagged KirBac1.1 protein in Escherichia coli and obtained voltage clamp recordings of recombinant channel activity in excised membrane patches from giant liposomes. Macroscopic currents of wild-type KirBac1.1 are K+ selective and spermine insensitive, but blocked by Ba2+, similar to “weakly rectifying” eukaryotic Kir1.1 and Kir6.2 channels. The introduction of a negative charge at a pore-lining residue, I138D, generates high spermine sensitivity, similar to that resulting from the introduction of a negative charge at the equivalent position in Kir1.1 or Kir6.2. KirBac1.1 currents are also inhibited by PIP2, consistent with 86Rb+ flux experiments, and reversibly inhibited by short-chain di-c8-PIP2. At the single-channel level, KirBac1.1 channels show numerous conductance states with two predominant conductances (15 pS and 32 pS at −100 mV) and marked variability in gating kinetics, similar to the behavior of KcsA in recombinant liposomes. The successful patch clamping of KirBac1.1 confirms that this prokaryotic channel behaves as a bona fide Kir channel and opens the way for combined biochemical, structural, and electrophysiological analysis of a tractable model Kir channel, as has been successfully achieved for the archetypal K+ channel KcsA.
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Yücel, Haluk, R. Bora Narttürk, Senem Zümrüt, Gizem Gedik, and Mustafa Karadag. "Investigation of thermal neutron detection capability of a CdZnTe detector in a mixed gamma-neutron radiation field." Nukleonika 63, no. 3 (September 1, 2018): 59–64. http://dx.doi.org/10.2478/nuka-2018-0007.
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Abstract The aim of this study was to investigate the thermal neutron measurement capability of a CdZnTe detector irradiated in a mixed gamma-neutron radiation field. A CdZnTe detector was irradiated in one of the irradiation tubes of a 241Am-Be source unit to determine the sensitivity factors of the detector in terms of peak count rate (counts per second [cps]) per neutron flux (in square centimeters per second) [cps/neutron·cm−2·s−1]. The CdZnTe detector was covered in a 1-mm-thick cadmium (Cd) cylindrical box to completely absorb incoming thermal neutrons via 113Cd(n,γ) capture reactions. To achieve, this Cd-covered CdZnTe detector was placed in a well-thermalized neutron field (f-ratio = 50.9 ± 1.3) in the irradiation tube of the 241Am-Be neutron source. The gamma-ray spectra were acquired, and the most intense gamma-ray peak at 558 keV (0.74 γ/n) was evaluated to estimate the thermal neutron flux. The epithermal component was also estimated from the bare CdZnTe detector irradiation because the epithermal neutron cutoff energy is about 0.55 eV at the 1-mm-thick Cd filter. A high-density polyethylene moderating cylinder box can also be fitted into the Cd filter box to enhance thermal sensitivity because of moderation of the epithermal neutron component. Neutron detection sensitivity was determined from the measured count rates from the 558 keV photopeak, using the measured neutron fluxes at different irradiation positions. The results indicate that the CdZnTe detector can serve as a neutron detector in mixed gamma-neutron radiation fields, such as reactors, neutron generators, linear accelerators, and isotopic neutron sources. New thermal neutron filters, such as Gd and Tb foils, can be tested instead of the Cd filter due to its serious gamma-shielding effect.
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Psiuk, Rafael, Alisa Artizada, Daniel Cichon, Hartmut Brauer, Hannes Toepfer, and Albert Heuberger. "Modeling of an inductively coupled system." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 37, no. 4 (July 2, 2018): 1500–1514. http://dx.doi.org/10.1108/compel-08-2017-0351.
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Purpose This paper aims to provide a flexible model for a system of inductively coupled loops in a quasi-static magnetic field. The outlined model is used for theoretical analyses on the magnetic field-based football goal detection system called as GoalRef, where a primary loop generates a magnetic field around the goal. The passive loops are integrated in the football, and a goal is deduced from induced voltages in loop antennas mounted on the goal frame. Design/methodology/approach Based on the law of Biot–Savart, the magnetic vector potential of a primary current loop is calculated. The induced voltages in secondary loops are derived by Faraday’s Law. Expressions to calculate induced voltages in elliptically shaped loops and their magnetic field are also presented. Findings The induced voltages in secondary loops close to the primary loop are derived by either numerically integrating the primary magnetic flux density over the area of the secondary loop or by integrating the primary magnetic vector potential over the boundary of that loop. Both approaches are examined and compared with respect to accuracy and calculation time. It is shown that using the magnetic vector potential instead of the magnetic flux density can decrease the processing time by a factor of around 100. Research limitations/implications Environmental influences like conductive or permeable obstacles are not considered in the model. Practical implications The model can be used to investigate the theoretical behavior of inductively coupled systems. Originality/value The proposed model provides a flexible, fast and accurate tool for calculations of inductively coupled systems, where the loops can have arbitrary shape, position and orientation.
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Vellinga, Michael, and Peili Wu. "Low-Latitude Freshwater Influence on Centennial Variability of the Atlantic Thermohaline Circulation." Journal of Climate 17, no. 23 (December 1, 2004): 4498–511. http://dx.doi.org/10.1175/3219.1.
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Abstract Variability of the thermohaline circulation (THC) has been analyzed in a long control simulation by the Met Office's Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3). It is shown that internal THC variability in the coupled climate system is concentrated at interannual and centennial time scales, with the centennial mode being dominant. Centennial oscillations of the THC can impact surface climate via an interhemispheric SST contrast of 0.1°C in the Tropics and more than 0.5°C in mid- and high latitudes. A mechanism is proposed based on detailed process analysis involving large-scale air–sea interaction on multidecadal time scales. Anomalous northward ocean heat transport associated with a strong phase of the Atlantic THC generates a cross-equatorial SST gradient. This causes the ITCZ to move to a more northerly position with increased strength. The extra rainfall resulting from the anomalous ITCZ imposes a freshwater flux and produces a salinity anomaly in the tropical North Atlantic. Such sustained salinity anomalies slowly propagate toward the subpolar North Atlantic at a lag of 5–6 decades. The accumulated low-salinity water lowers upper-ocean density, which causes the THC to slow down. The oscillation then enters the opposite phase.
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Wang, Shih-Yu, Tsing-Chang Chen, and S. Elwynn Taylor. "Evaluations of NAM Forecasts on Midtropospheric Perturbation-Induced Convective Storms over the U.S. Northern Plains." Weather and Forecasting 24, no. 5 (October 1, 2009): 1309–33. http://dx.doi.org/10.1175/2009waf2222185.1.
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Abstract In the U.S. northern plains, summer progressive convective storms that occur in weakly forced environments are often coupled with short-wave perturbations that are embedded in the midlevel northwesterly flow. These midtropospheric perturbations (MPs) are capable of inducing propagating convection that contributes to a majority of the rainfall over the northern plains during July and August. There is a possibility that the difficulties of numerical weather prediction models in forecasting summer convective rainfall over the northern plains are partly attributed to their deficiency in forecasting MPs. The present study tests this possibility through examining operational forecasts by the North American Mesoscale (NAM) model during the summers of 2005 and 2006. Forecasted MPs exhibit slower propagation speeds and weaker relative vorticity than the observations leading to systematic position errors. Underpredicted vorticity magnitudes weaken horizontal vorticity advection that influences the vorticity tendency throughout the MP life cycle and, in turn, slows the propagation speed of MPs. Moreover, biases of weak ambient flow speed and vortex stretching contribute to the magnitude and propagation speed errors of MPs. Skill scores of precipitation forecasts associated with MPs are low, but can be considerably improved after removing the MP position error that displaces the rainfall pattern. The NAM also tends to underpredict precipitation amounts. A modified water vapor budget analysis reveals that the NAM insufficiently generates atmospheric humidity over the central United States. The shortage of moisture in the forecast reduces the water vapor flux convergence that is part of the precipitation process. The precipitation bias may feed back to affect the MP growth through the bias in heating, thus further slowing the perturbation.
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Chaisan, Jirod, Somchai Maneewan, and Chantana Punlek. "Thermal Resistance by Phase Change Materials of the Double Roof System." Advanced Materials Research 807-809 (September 2013): 2784–87. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.2784.
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This research studies about the possibility of Phase change materials for development with the double roof system which uses the Radiant barrier to reduce the heat into the house and to reduce load of the air conditioner. The experiment was divided into 4 patterns. The Radiant barrier and the Phase change materials are on top of the air passage (model 1). The Phase change materials and the Radiant barrier are on top of the air passage (model 2). The Radiant barrier is under the roof and the Phase change materials is under the air passage is (model 3). The Radiant barrier is under the air passage and the Phase change materials is under the roof (model 4). By building the test room sizes 90x90 cm2 and the air passage sizes 10 cm. The heat source from the heat generator in temperature is 45, 50, 60. The results revealed that if the Radiant barrier is under the roof and the Phase change materials is under the air passage, temperature will tend to decrease by the heat transmission into the house decrease about 3-5 in the experiment. The above-mentioned decrease of the temperature, the calculation of the thermal energy per unit area in (model 3) can decrease the most quantity of heat flux more than the other patterns by average at 19.66, 22.5 and 29.14 W/m2 respectively. From the experiment was found that (model 3) has the appropriate position for development more than the other patterns.
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Tungol, Mary Widmark. "Infrared Microscopy As A Failure Analysis Tool In The Thermal Inkjet Cartridge Industry." Microscopy and Microanalysis 5, S2 (August 1999): 62–63. http://dx.doi.org/10.1017/s1431927600013635.
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Four major components comprise an inkjet cartridge (Fig.lA): (1) the pen body which contains the ink and positions the cartridge in the printer; (2) an ink delivery system which supplies ink at the correct backpressure and flow rate; (3) a flex circuit which provides the electrical interconnect to the printer; and (4) the printhead which generates and directs the drops. Because of its complexity and small critical dimensions, the printhead poses the greatest analytical challenge for many failure analysis problems. Each printhead may contain as many as 300 firing chambers (Fig. IB). Each chamber consists of a resistor surrounded by a polymer-based barrier material which forms a cavity into which ink flows from the ink delivery system. The chamber is capped by a metal or polymer orifice-containing plate. Printing occurs when the resistor is heated to form an ink vapor bubble which subsequently ejects a droplet of ink though the orifice onto the paper.
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Menzhinski, A. B. "Coordination of forces of mechanical and electric subsystems of power plant with free piston engine and electric generator of reciprocating type." Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series 64, no. 3 (October 6, 2019): 304–20. http://dx.doi.org/10.29235/1561-8358-2019-64-3-304-320.
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Autonomous power supply system of modern mobile special-purpose equipment requires the development of electromechanical energy converters with high energy and minimum weight- and size indicators. In industrialized countries, the system “free piston engine – reciprocating electric generator of transverse type” is considered as a promising power plant. The main feature of this kind of power plant is the lack of crank mechanism in the engine design. This allows: increasing the efficiency of the engine up to 50–60 % and overall power by 2.5–3 times while reducing the specific gravity and metal consumption compared to traditional engines; reducing the specific fuel consumption of the engine up to 30 %; increasing the resource to overhaul by 30–50 thousand hours; implementing a modular structure. The main drawbacks of this kind of power plant are high probability of failure when passing the ignition of the working mixture and instability of work with significant load fluctuations. The noted drawbacks are due to the inconsistency of the forces of the electrical and mechanical subsystems of the power plant throughout the operating cycle. The solution for the problem of matching the forces of the electrical and mechanical subsystems of the power plant in the extreme positions of the piston group of the free piston engine is of particular complexity. In this regard, a method for solving the problem of matching the forces of the mechanical and electrical subsystems of the power plant with a free-piston engine throughout the operating cycle was developed, characterized by the use of an electromechanical reciprocating energy converter with transverse- and longitudinal nonlinear changes in the magnetic flux in the electrical subsystem. Coordination of the forces of mechanical and electrical subsystems of the power plant on the entire operating cycle makes it possible to fulfill the conditions of continuous electromechanical energy conversion at all work cycle and to reduce the specific gravity of the electrical subsystems of the plant while improving efficiency.
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Baïri, Abderrahmane, and Najib Laraqi. "Natural convective heat transfer in a hemispherical cavity filled with ZnO–H2O nanofluid saturated porous medium." International Journal of Modern Physics C 29, no. 10 (October 2018): 1850097. http://dx.doi.org/10.1142/s0129183118500973.
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This three-dimensional (3D) numerical work based on the volume control method quantifies the convective heat transfer occurring in a hemispherical cavity filled with a ZnO–H2O nanofluid saturated porous medium. Its main objective is to improve the cooling of an electronic component contained in this enclosure. The volume fraction of the considered monophasic nanofluid varies between 0% (pure water) and 10%, while the cupola is maintained isothermal at cold temperature. During operation, the active device generates a heat flux leading to high Rayleigh number reaching [Formula: see text] and may be inclined with respect to the horizontal plane at an angle ranging from 0[Formula: see text] to 180[Formula: see text] (horizontal position with cupola facing upwards and downwards, respectively) by steps of 15[Formula: see text]. The natural convective heat transfer represented by the average Nusselt number has been quantified for many configurations obtained by combining the tilt angle, the Rayleigh number, the nanofluid volume fraction and the ratio between the thermal conductivity of the porous medium’s solid matrix and that of the base fluid. This ratio has a significant influence on the free convective heat transfer and ranges from 0 (without porous media) to 70 in this work. The influence of the four physical parameters is analyzed and commented. An empirical correlation between the Nusselt number and these parameters is proposed, allowing determination of the average natural convective heat transfer occurring in the hemispherical cavity.
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Hirata, Kunio, Yoshiaki Kawano, Keitaro Yamashita, Go Ueno, Takaaki Hikima, Hironori Murakami, Kazuya Hasegawa, Seiki Baba, Takashi Kumasaka, and Masaki Yamamoto. "Current status of protein micro-crystallography at SPring-8." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C333. http://dx.doi.org/10.1107/s2053273314096661.
Full textAbstract:
Protein micro-crystallography is one of the most advanced technologies for protein structure analysis. In order to realize this, an undulator beamline, named BL32XU, was constructed at SPring-8. The beamline can provide beam with size of 0.9 x 0.9 µm and photon flux of 6E10 photons/s. The beam size can be easily changed by users from 1 to 10 µm square with the same flux density. Through three years user operation, we have established several key systems for efficient protein micro-crystallography. One of them is the software for precise positioning of micro-crystals in `raster scan'. SHIKA is a program with GUI which searches diffraction spots in a plenty of low dose diffraction images obtained in raster scan. Finally, it generates 2D map of crystal positions based on the number of spots or spot intensities. Parameters and thresholds in peak search have been empirically optimized for LCP crystals and it provides robust results. Another system is for the data collection strategy. Almost all successful data collections were conducted via `helical data collection' on BL32XU using the line-focused beam. The GUI software, named KUMA, enables estimation of an accumulated dose and suggests suitable experimental conditions for helical data collection. The system is proven to be useful for experimental phasing using tiny LCP crystals of membrane proteins[1-3]. Based on them, the rapid and automatic data collection system using protein micro-crystals is under development. The new CCD detector, Rayonix MX225HS, was installed for faster data acquisition in 10 Hz with the pixel size of 78 µm square. The new SHIKA using GPUs is under development for faster and more accurate crystal alignment. Following this step, KUMA system can suggest experimental conditions for each crystal found on the loop. We also report about the effects of higher dose rate in protein crystallography up to the order of 100 MGy/s. This work was supported by Platform for Drug Discovery, Informatics, and Structural Life Science from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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Tapper, Janne. "Modalities or Surfaces." Nordic Theatre Studies 26, no. 1 (May 1, 2014): 56–67. http://dx.doi.org/10.7146/nts.v26i1.109741.
Full textAbstract:
This article will examine the playing with aesthetical surfaces in postmodern theatre and how itreflects the poetics and the cultural logic of late capitalism. Surfaces are examined as aestheticelements of the postmodern culture of the image. This culture is not neutral as it seems toreject the modern spiritual depth, for instance, sense of history and hermeneutic depth. Thearticle examines the riddle concerning how the absence of these aspects of human thought insurfaces generates the spectators' need to produce coherent individual activities, trajectories,and eventually acoherent culture. This reflexive mechanism of surfacesis analyzed within theframework of Donald Norman's (2005) cognitive principles of design. Starting from thepremise of Gilles Deleuze's and Felix Guattari's (1987) and Lev Vygotsky's (1978) notions ofplay, it is interpreted that postmodern stage and culture works, metaphorically, like the plane ofimmanence, the way of thinking in which an agent is able to move, make transitions andcrossings in a revolutionary way without restrictions of reality's conditions. However,culturally the blurring of boundaries between play and reality may lead to delirium andill-founded practices. Theatre and art examine these ill-founded practices but involve in theirpoetics a strong dimension of reflexive level of human cognition. This reflexive level is anexplanatory perspective, which helps spectators examine theatre's mechanisms as metaphors ofcultural logic, to achieve a critical position extrinsic from the flux of postmodern culture. Thispoetics is examined in several cases of theatrical representation including Sofia Coppola's filmThe Bling Ring (2013), The Need Company's production The Lobster Shop (2006), KristianSmeds' production The Unknown Soldier (2007) and in several casesof postmodern art and stagedesign.
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Wiaux, F., K. Van Oost, and M. Vanclooster. "Quantitative estimation and vertical partitioning of the soil carbon dioxide fluxes at the hillslope scale on a loess soil." Biogeosciences Discussions 11, no. 9 (September 22, 2014): 13699–737. http://dx.doi.org/10.5194/bgd-11-13699-2014.
Full textAbstract:
Abstract. Both modelling and experimental approaches have been applied to assess C exchange fluxes at large spatial scales. Yet, these approaches are subjected to substantial limitations and uncertainties. Here, we aim to highlight two key mechanisms able to improve the estimation of the hillslope aggregated CO2 fluxes: (i) the persistence of soil organic carbon (OC) in deep colluvium deposits; and (ii) the physical controls on CO2 fluxes along soil profiles. This study focuses on a sloping cropland in the central loess belt of Belgium. On two contrasted soil types along the studied hillslope, we recorded time-series of CO2 concentration, water content and temperature along 1 m long soil profiles during two periods of 6 months. Then, we calculated profiles of CO2 fluxes using the gradient method. To extrapolate these fluxes to entire yearly periods (2011–2013), we performed simulation using the SOILCO2RothC model. The vertical partitioning of the soil CO2 fluxes shows that ca. 90 to ca. 95% of the surface CO2 fluxes originates from the 10 first centimeters of the soil profile at the footslope. We show that high water filled pore space at this slope position disables the transfer of biotic CO2 along the soil profile. However, the total annual flux averaged along 3 years of simulation show that the top soil layer (0–10 cm) of the footslope generates CO2 fluxes (870 ± 64 CO2-C m−2 year−1 which exceed those observed at the summit position (583 ± 61 CO2-C m−2 year−1. Hence, our results reconcile two seemingly contradictory hypotheses, i.e. (i) these support that soil OC at such a footslope is stored along the main part of the soil profile and submitted to a long-term stabilization, and (ii) at the same time these support that the depositional footslope profile emits more CO2 than the summit, due to its high amount and quality of OC. Our results support the need to consider slopes when modeling soil-atmosphere C exchanges. If landscapes dynamic processes are not accounted for, we pointed out a risk to under-estimate annual soil-atmosphere CO2 exchanges by ca. 20%.
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Lemon, Alaina. "Roma (Gypsies) in the Soviet Union and the Moscow Teatr ‘Romen’." Nationalities Papers 19, no. 3 (1991): 359–72. http://dx.doi.org/10.1080/00905999108408208.
Full textAbstract:
The Moscow Teatr “Romen,” dating back to 1931, is famous throughout the Soviet Union, and its performers have been some of the country's best-known. The Teatr “Romen” connects Roma from all over the country, and many who work there are related; three generations of a family may appear on the stage at one time. These families, along with Roma working as professionals, make up an lite within the Romani community in Moscow. They are the most outwardly assimilated (wearing European dress, etc.), most fluent and literate in Russian as well as Romani. These families usually move in different spheres than do Roma who live in villages around Moscow and work in cooperatives or as independent merchants, although extended family networks may include Roma of all spheres. Most studies of Gypsies (including those of non-Roma, such as Irish Travellers in the United Kingdom) assume a certain homogeneity of culture and of class: The refusal to acknowledge Gypsy upward mobility in the context of a dominant society has also prevented research of class difference within Gypsy groups and created a sense of marginalized homogeneity that does not reflect reality.The Teatr “Romen” is a case that demands such acknowledgment. Yet, in a sense, these élite performers are doubly marginal, both as performers and as ethnic outsiders who “threaten the rhetoric and narratives of nationalism.” Currently in the USSR, such narratives are in flux, as many national minorities demand greater cultural and political autonomy. Roma, however, are not demanding their own republic, and requests for schools and radio shows are often tempered by the assertion that, “this country has been kind to Gypsies.” Roma élites are also in a peculiar position: charged with representing Roma to outsiders, they are also concerned about maintaining the integrity of the urban community as Roma. Because of this, they must negotiate the interstitial area between cultures.