Rotations and oscillations of a neutron star

Rotations and oscillations of neutron sta

Design of a novel phase-decoupling permanent magnet brushless ac motor

This paper presents a phase-decoupling permanent magnet brushless ac motor which can offer better controllability, faster response, and smoother torque than its counterparts. The key is due to its different motor configuration and simple scalar control. The motor configuration is so unique that it inherently offers the features of phase decoupling, flux focusing, and flux shaping, hence achieving independent phase control, fast response, and smooth torque. The scalar control is fundamentally different from the complicated vector control. It can achieve direct torque control through independent control of the phase currents. The proposed motor is prototyped and experimentally verified. © 2005 American Institute of Physics.published_or_final_versio

Flavor SU(3) symmetry and QCD factorization in B→PPB \to PP and PVPV decays

Using flavor SU(3) symmetry, we perform a model-independent analysis of charmless $\bar B_{u,d} (\bar B_s) \to PP, ~PV$ decays. All the relevant topological diagrams, including the presumably subleading diagrams, such as the QCD- and EW-penguin exchange diagrams and flavor-singlet weak annihilation ones, are introduced. Indeed, the QCD-penguin exchange diagram turns out to be important in understanding the data for penguin-dominated decay modes. In this work we make efforts to bridge the (model-independent but less quantitative) topological diagram or flavor SU(3) approach and the (quantitative but somewhat model-dependent) QCD factorization (QCDF) approach in these decays, by explicitly showing how to translate each flavor SU(3) amplitude into the corresponding terms in the QCDF framework. After estimating each flavor SU(3) amplitude numerically using QCDF, we discuss various physical consequences, including SU(3) breaking effects and some useful SU(3) relations among decay amplitudes of $\bar B_s \to PV$ and $\bar B_d \to PV$.Comment: 47 pages, 3 figures, 28 table

A linear stator permanent magnet vernier HTS machine for wave energy conversion

published_or_final_versio

Design and analysis of linear stator permanent magnet vernier machines

In Poster Session GP: Permanent Magnet Motor II: poster no. GP-10This paper presents a new class of linear permanent magnet (PM) vernier machines which is suitable for low speed and high thrust force applications. The machine is composed of a tubular stator and a tubular translator. The stator consists of an iron core with salient teeth wound with 3-phase armature windings and PMs mounted on the surface of stator teeth. The translator is designed as a simple tubular iron core with salient teeth so that it is very robust to transmit high thrust force. By using the finite element method, the characteristics and performances of the proposed machine are analyzed and verified. © 2011 IEEE.published_or_final_versionThe IEEE International Magnetic Conference (INTERMAG2011), Taipei, Taiwan, 25-29 April 2011. In IEEE Transactions on Magnetics, 2011, v. 47 n. 10, p. 4219-422

Design of doubly salient permanent magnet motors with minimum torque ripple

This paper presents a design approach for doubly salient permanent magnet (DSPM) motors, aiming to minimize the torque ripple. The key is to propose the design criteria that the reluctance of all magnetic paths is the same, and the armature windings can be artfully connected to compensate the variation of self-inductance. Based on these criteria, the magnetic characteristics become symmetric, and the variation of self inductance is suppressed. Thus, the resulting torque ripple can be minimized. By using the time-stepping finite element method, the proposed DSPM motor and the existing DSPM motor are quantitatively compared in terms of their back-EMFs, self-inductances, and torque ripples, hence confirming the validity of the proposed design approach. © 2009 IEEE.published_or_final_versio

Scalar control of a new phase-decoupling permanent magnet synchronous motor for servo application

This paper presents a new scalar-controlled phase-decoupling permanent magnet synchronous motor (PD-PMSM) which takes the advantages of smooth torque, fast response and good controllability for servo applications. Because of the PD nature, the proposed scalar control strategy can simply adjust the phase current amplitude and its angle with respect to the back EMF to achieve direct torque control. Experimental results are given to verify the advantages of the proposed scalar-controlled PD-PMSM. © 2005 IEEE.published_or_final_versio

Analytical calculation of magnetic field in surface-inset permanent magnet motors

This paper presents an analytical approach to calculate the magnetic field distribution in surface-inset permanent magnet motors. A series-slot analytical model is newly proposed to describe the magnetic field behavior by a set of partial differential equations in terms of scalar magnetic potentials. The field solutions are determined by considering the boundary constraints. Then, the cogging torque characteristic is deduced by calculating the Maxwell tensors. The accuracy of the proposed analytical calculation is verified by comparing the field distribution and cogging torque results with those obtained from the finite element method. © 2009 IEEE.published_or_final_versio

Analysis of doubly salient memory motors using preisach theory

With the introduction of doubly salient memory (DSM) motors, the flux controllability and hence the speed range of permanent magnet (PM) motors have reached a new height. This paper presents a new method to accurately analyze the DSM motor. The key is to incorporate the general expressions of the Preisach hysteresis model (PHM) of the AlNiCo-PM into the time-stepping finite element method (TS-FEM). Based on the proposed PHM-TS-FEM, both static and transient performances of the DSM motor are successfully simulated. Finally, the validity and accuracy of the proposed method are verified by experimental results. © 2009 IEEE.published_or_final_versio

Incorporating Inertia Into Multi-Agent Systems

We consider a model that demonstrates the crucial role of inertia and stickiness in multi-agent systems, based on the Minority Game (MG). The inertia of an agent is introduced into the game model by allowing agents to apply hypothesis testing when choosing their best strategies, thereby reducing their reactivity towards changes in the environment. We find by extensive numerical simulations that our game shows a remarkable improvement of global cooperation throughout the whole phase space. In other words, the maladaptation behavior due to over-reaction of agents is removed. These agents are also shown to be advantageous over the standard ones, which are sometimes too sensitive to attain a fair success rate. We also calculate analytically the minimum amount of inertia needed to achieve the above improvement. Our calculation is consistent with the numerical simulation results. Finally, we review some related works in the field that show similar behaviors and compare them to our work.Comment: extensively revised, 8 pages, 10 figures in revtex