Article
Astronomy & Astrophysics
Olga O. O. Tsareva, Makar V. V. Leonenko, Elena E. E. Grigorenko, Helmi V. V. Malova, Victor Yu. Popov, Lev M. M. Zelenyi
Summary: Recent MMS observations have confirmed the existence of ultra-thin current sheets (STCSs) on electron scale. These sheets consist of magnetized and demagnetized electron populations. A self-consistent combined model was developed to study the influence of demagnetized electrons on STCSs. The presence of demagnetized electrons significantly increases the intensity and narrows the current density profile of the STCSs.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Geochemistry & Geophysics
A. Runov, V Angelopoulos, A. Artemyev, J. M. Weygand, S. Lu, Y. Lin, X-J Zhang
Summary: The formation of thin current sheets in Earth's magnetotail is crucial for magnetosphere dynamics, influencing magnetic reconnection and particle acceleration. Recent research utilizing multipoint observations and simulations has improved understanding of the structure and dynamics of thin current sheets, including ion kinetic physics. Global hybrid simulations have also provided insights into ion kinetics in thin current sheet physics.
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS
(2021)
Review
Astronomy & Astrophysics
Syun-Ichi Akasofu
Summary: The article reviews the progress of space physics from a personal perspective, emphasizing the importance of the electric current approach in studying auroral substorms and geomagnetic storms. It suggests that new generations of researchers are welcome to further explore this new way of studying space weather phenomena.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2021)
Article
Astronomy & Astrophysics
J. K. Sandhu, I. J. Rae, M-T Walach
Summary: The study investigates the spatial distribution and energy content variations of the ring current during geomagnetic storms, revealing large enhancements in the premidnight sector during the main phase and reductions in local time asymmetry and intensity during the recovery phase. Comparison with the Sym-H index shows a significant overestimation of energy content and a temporal discrepancy, with estimated maxima occurring 3-9 hours earlier than in-situ observations.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Tommaso Alberti, Davide Faranda, Giuseppe Consolini, Paola De Michelis, Reik Donner, Vincenzo Carbone
Summary: An accurate understanding of the differences in geomagnetic variability between quiet and disturbed periods can improve space weather diagnosis. This study uses dynamical system theory to investigate the co-variation and recurrence statistics of two geomagnetic indices, SYM-H and AL, that measure the intensity of different current systems. The number of active degrees of freedom in the phase space dynamics of these indices depends on the geomagnetic activity level. The results suggest that the near-Earth electromagnetic environment is a complex system that is far from equilibrium.
Article
Environmental Sciences
Tommaso Alberti, Paola De Michelis, Lucia Santarelli, Davide Faranda, Giuseppe Consolini, Maria Federica Marcucci
Summary: Using a dynamical systems approach, this study examines the persistence and predictability of geomagnetic perturbations at different latitudes and levels of geomagnetic activity. The analysis of the measured magnetic field data reveals that the instantaneous dimension of the horizontal strength of the magnetic field increases during disturbed periods, indicating external driving. During quiet times, the fluctuation of the instantaneous dimension values around the state-space dimension suggests a more stochastic and less predictable nature of the system.
Article
Astronomy & Astrophysics
E. Yushkov, A. A. Petrukovich, A. Artemyev, R. Nakamura
Summary: This study combines datasets from Cluster and THEMIS missions to show similar characteristics of CS thinning in the magnetotail. The process cannot be directly associated with the increase of lobe magnetic pressure, and usually results in equatorial density increase and plasma temperature decrease.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
R. Nakamura, W. Baumjohann, T. K. M. Nakamura, E. Panov, D. Schmid, A. Varsani, S. Apatenkov, V. A. Sergeev, J. Birn, T. Nagai, C. Gabrielse, M. Andre, J. L. Burch, C. Carr, I. S. Dandouras, C. P. Escoubet, A. N. Fazakerley, B. L. Giles, O. Le Contel, C. T. Russell, R. B. Torbert
Summary: MMS and Cluster made a unique simultaneous observation of fast flows and associated current sheet disturbances in the near-Earth magnetotail before a small substorm onset on September 8, 2018. The current sheet thickened during the passage of a localized fast flow, but temporally thinned subsequently, possibly related to the flow bouncing process and/or the expansion/activation of reconnection. This study highlights the mesoscale and small-scale multipoint observations of the flow and current-sheet disturbances leading up to a substorm current wedge development.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
A. Artemyev, V Angelopoulos, X-J Zhang, A. Runov, A. Petrukovich, R. Nakamura, E. Tsai, C. Wilkins
Summary: This paper investigates the thinning process of the magnetotail current sheet during substorm growth phase. The study confirms previous concepts using low-altitude measurements and finds that the thinning process leads to a shrinking of the current sheet projection at low altitudes and a change in the tail magnetic field configuration. The findings suggest the importance of understanding the current sheet thinning and its relationship with magnetic reconnection during substorms.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Physics, Multidisciplinary
Alisa K. Galishnikova, Matthew W. Kunz, Alexander A. Schekochihin
Summary: The study demonstrates that turbulence in conducting plasma can amplify seed magnetic fields, leading to the formation of folded structures which become unstable to tearing during the nonlinear stage of dynamo. This disruption of folds by tearing increases the ratio of viscous-to-resistive dissipation.
Article
Physics, Applied
Justin M. Little, Gordon I. McCulloh, Cameron Marsh
Summary: This study investigates the formation of current sheets in inductive pulsed plasma thrusters (IPPTs). It finds that non-equilibrium ionization processes play an important role in the plasma impermeability to electromagnetic fields and propellant mass. The dynamics of electron heating during the early phase of the inductive current cycle are identified as the dominant contributors to current sheet formation.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Astronomy & Astrophysics
A. Runov, V Angelopoulos, J. M. Weygand, A. Artemyev, F. Beyene, V Sergeev, M. Kubyshkina, M. G. Henderson
Summary: This study investigates whether particles with relativistic energy can be injected directly into the inner magnetosphere through near-Earth reconnection during magnetic storms. By analyzing a series of observed events during a geomagnetic storm, the researchers found evidence of particle injection at a near-Earth reconnection site, indicating the possibility of such injection during magnetic storms.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Sobin Mathew, Shilpashree Narasimha, Johannes Reiprich, Theresa Scheler, Bernd Haehnlein, Sebastian Thiele, Jaqueline Stauffenberg, Vladislav Kurtash, Saadman Abedin, Eberhard Manske, Heiko O. Jacobs, Jorg Pezoldt
Summary: A method for synthesizing bulk tetrahedral MoS2 thin films using solid source chemical vapor deposition is presented. The study analyzes the time-dependent growth morphologies and combines the results into a growth model. Various techniques like optical, electron, atomic force microscopy, Raman spectroscopy, and X-ray diffraction are utilized to study the morphological and structural features of the tetrahedral MoS2 thin layers.
CRYSTAL GROWTH & DESIGN
(2022)
Article
Astronomy & Astrophysics
Robert L. McPherron
Summary: The coupling function between solar wind and geomagnetic activity is investigated. Magnetic indices provide measures of magnetospheric response. A study on over 100,000 negative bay onsets suggests that a pulse, either positive or negative, precedes 40% of all onsets, indicating that it triggers the onset. Positive pulses lead to stronger substorms than negative pulses.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Geosciences, Multidisciplinary
A. M. Keesee, N. Buzulukova, C. Mouikis, E. E. Scime
Summary: Mesoscale structures in Earth's magnetotail play a key role in particle transport to the inner magnetosphere during storms and substorms. Observations from ENA data, along with magnetohydrodynamics simulations, demonstrate a correlation between ion temperatures, ion flows, and FACs. Discrepancies in plasma heating intensity between observed data and simulated results suggest the model may be missing some heating processes.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Engineering, Electrical & Electronic
Fu-Sheng Pai, Yan-Zhen Huang, Po-Hsun Chen, Min-Fu Hsieh
Summary: This paper introduces a control strategy to enhance the operating efficiency of a Hybrid Energy Storage System (HESS) for an Interior Permanent Magnet Synchronous Motor (IPMSM) drive. By using an interleaved DC-DC converter to connect the battery and super-capacitor, an adjustable DC-link voltage is achieved to fit different motor operating conditions, resulting in improved efficiency and extended battery lifetime. Simulation and experimental studies confirm the feasibility and practicality of the proposed method for potential electric vehicle applications.
INTERNATIONAL JOURNAL OF ELECTRONICS
(2021)
Article
Engineering, Electrical & Electronic
Duc-Kien Ngo, Min-Fu Hsieh, Tien Dung Le
Summary: This article analyzes the field weakening capability of a flux intensifying synchronous motor with a small quantity of inset permanent magnets on the rotor surface. By adjusting the permanent magnet dimensions, more flexibility in rotor design is provided, and the influence of the added permanent magnets on various parameters is analyzed to enhance motor performance and field weakening capability. Experiments validated the simulation results.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Engineering, Electrical & Electronic
Thanh Anh Huynh, Jun-Xian Peng, Min-Fu Hsieh, Po-Wei Huang
Summary: This study investigates the effect of different design parameters of permanent magnets and flux barriers on the anti-demagnetization ability of IPM motors for electric scooters. The results show that proper design of flux barriers can greatly improve the anti-demagnetization ability without significantly affecting the characteristic current of the motor.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Computer Science, Information Systems
Min-Fu Hsieh, Duc-Kien Ngo, Nguyen Gia Minh Thao
Summary: This paper investigates the flux intensifying feature of permanent magnet assisted synchronous reluctance motor to achieve high torque density. A comparison with other motors and an analysis on partial demagnetization and torque density are conducted to demonstrate its advantages.
Article
Energy & Fuels
Yin-Hui Lee, Min-Fu Hsieh
Summary: This paper investigates the application of anisotropic low-coercive force magnets to a novel variable-flux spoke-type permanent magnet synchronous motor for electrical vehicles. The feasibility of swiveling the magnetization direction of anisotropic magnets is confirmed through experiments. Different topologies and rotor configurations are compared to determine critical sizing factors. The proposed topology improves torque or flux adjustment ability compared to isotropic magnets.
Article
Chemistry, Multidisciplinary
That-Dong Ton, Min-Fu Hsieh
Summary: This paper proposes a new control scheme for interior permanent magnet synchronous machines (IPMSM) called deadbeat stator current and flux linkage vector control (DB-CFVC). The control structure is simplified by implementing the proposed flux linkage vector control method in the alpha-beta stationary coordinate. Unlike conventional deadbeat methods, the proposed DB-CFVC can enhance dynamic performance while avoiding voltage command saturation and over output current. By predicting stator flux linkage and current in the stationary coordinate and developing a practical and robust hybrid flux linkage observer, the proposed DB-CFVC method works more reliably and effectively than conventional methods.
APPLIED SCIENCES-BASEL
(2022)
Article
Engineering, Electrical & Electronic
Kai-Jung Shih, Min-Fu Hsieh, Bo-Jia Chen, Shih-Feng Huang
Summary: This study presents an approach using machine learning to detect inter-turn short-circuit faults in permanent magnet synchronous motors. Support vector machines and convolutional neural networks are employed for fault diagnosis and classification, achieving preventive maintenance and ensuring safe operations.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Engineering, Electrical & Electronic
Thanh-Anh Huynh, Po-Hsun Chen, Min-Fu Hsieh
Summary: This paper proposes a novel traction unit for electric vehicles that combines different types of motors to improve traction performance and energy efficiency while reducing cost. The characteristics of three different traction units are analyzed and compared, and the operational characteristics of each motor to achieve a wide constant power speed range are investigated. The evaluation using the Urban Dynamometer Driving Schedule shows that the proposed traction unit has higher efficiency compared to other configurations. The advantages and drawbacks of the proposed unit are also investigated, and experiments are conducted to validate the analysis.
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2022)
Article
Engineering, Multidisciplinary
Thanh-Anh Huynh, Viet-Hoa Che, Min-Fu Hsieh
Summary: This research focuses on optimizing the efficiency range of a spoke-type permanent magnet motor for E-bikes. By reducing copper and iron losses and using a new motor constant, the torque density is improved and power losses are minimized. The Genetic Algorithm is employed to maximize the high-efficiency operating range. The results show that the optimized motor achieves higher torque density and a broader high-efficiency range.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS
(2023)
Article
Engineering, Multidisciplinary
Ding-Cheng Hsiao, Min-Fu Hsieh
Summary: This paper develops a coreless-stator permanent magnet synchronous motor for reaction wheels applied to satellite attitude control. A comprehensive analysis for various design factors is conducted to minimize the power loss of the reaction wheel, taking the satellite operation scenarios into account. A lightweight and low-loss reaction wheel motor is designed and simulated, and experiments are conducted to validate the design and analysis.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS
(2023)
Article
Engineering, Electrical & Electronic
Hsien-Yuan Hsu, Tzu-Yang Lo, Min-Fu Hsieh
Summary: A fast and reliable interturn short circuit diagnosis system is developed based on signal extraction for permanent magnet synchronous motors. This technique utilizes the second-order harmonic components in dq-axis current to detect the fault, making it suitable for low-cost and remote applications.
INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS
(2023)
Article
Engineering, Electrical & Electronic
Hsien-Yuan Hsu, Min-Fu Hsieh
Summary: This study proposes a search coil design that uses a single strand of the motor winding from each phase terminal to derive the three-phase stator flux linkage. The flux linkage is transformed into the alpha-beta frame to determine the stator flux linkage angle, which is then used to determine the corresponding motor rotor angle. Experimental trials using a commercial 3.7 kW motor show that the proposed search coil provides accurate position estimation results under various speed and load conditions. The proposed search coil offers a simple, noninvasive, and reliable means of estimating the rotor angle, making it a suitable choice for a wide range of motor types.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2023)
Article
Computer Science, Information Systems
Ding-Cheng Hsiao, Min-Fu Hsieh
Summary: This article presents a novel compact-design homopolar magnetic bearing system for reaction wheels in satellite applications. The magnetic bearings, with low core loss, can increase the designed speed of the reaction wheel, thereby reducing the rotor inertia and wheel mass required to achieve attitude control. The proposed magnetic bearings are capable of producing both radial and axial suspension forces using a simple L-shaped core structure. The magnetic bearings simplify the control logic and enable independent control of the radial and axial forces. A magnetic circuit model of the proposed bearing system is derived and validated through finite element simulations, and the practical feasibility is confirmed experimentally using a prototype reaction wheel designed based on the developed magnetic circuit model.
Article
Engineering, Multidisciplinary
Pey Shey Wu, Min-Fu Hsieh, Yong En Lu, Wei Ling Cai, Shyy Woei Chang
Summary: This study proposes the use of rotating thermosyphon loops in the rotor of an electric motor to improve its cooling performance and increase the power-to-weight ratio. By measuring the thermal conductivity and heat-transfer rate of the thermosyphon loop, the thermal boundary conditions for simulating the temperature fields of the electric motors are defined. The combination of the high thermal conductivity of the thermosyphon loop and the heat convection enhancement in the air chamber effectively improves the heat transmission and reduces the temperature gradients in the rotor. At specific rotor speeds and electrical currents, the thermosyphon loops can significantly reduce the maximum temperatures in the rotor, demonstrating the effectiveness of the phase-change cooling device.
Article
Computer Science, Information Systems
Yin-Hui Lee, Minfu Hsieh, Po-Hsun Chen
Summary: This article proposes a novel variable-flux spoke-type permanent magnet synchronous motor, which adjusts the air gap flux density by swiveling magnetic pole directions in the permanent magnet. It has a wide flux regulation range, excellent on-load demagnetization-resisting capability, and safe working characteristics of low-coercivity magnet.