Search

We provide an explicit algorithm to compute a lifted Massey triple product relative to a defining system for a smooth projective plane curve X defined by a homogeneous polynomial G (x ̲) over a field. The main idea is to use the description (due to Carlson and Griffiths) of the cup product for H 1 (X , ℂ) in terms of the multiplications inside the Jacobian ring of G (x ̲) and the Cech–deRham complex of X. Our algorithm gives a criterion whether a lifted Massey triple product vanishes or not in H 2 (X) under a particular nontrivial defining system of the Massey triple product and thus can be viewed as a generalization of the vanishing criterion of the cup product in H 2 (X) of Carlson and Griffiths. Based on our algorithm, we provide explicit numerical examples by running the computer program. [ABSTRACT FROM AUTHOR]

This paper presents an online maximum torque per ampere (MTPA) control that considers both magnetic saturation and cross-magnetization effects of interior permanent-magnet synchronous machines (IPMSMs). For IPMSM drives, especially in torque-controlled applications, torque accuracy and high-efficiency operations are important issues. They can be dealt as a constrained optimization problem to satisfy both torque reference tracking and loss-minimizing operation. In this paper, nonlinear simultaneous equations are derived from Lagrange multiplier method, which could be solved by numerical algorithms. Among them, Levenberg–Marquardt algorithm (LMA) is employed to guarantee a robust calculation of optimal current references. It is optimized to alleviate calculation burden while maintaining the stability of the proposed algorithm. In addition, a torque reference limiter is implemented to satisfy a current limit in real time. The feasibility of the proposed method is verified under various operating conditions by simulation and experimental results. Through the proposed algorithms, accurate MTPA control is achieved under not only unsaturated but also highly saturated operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, the theoretical analysis of the position estimation error in position-sensorless operation using pulsating square wave signal injection is presented. The purpose of this paper is to analyze the phenomenon that the position estimation performance varies depending on the injection frequency. Mathematical derivation supported by simulation and experimental results shows that, in no-load condition, the voltage distortion induces position estimation error with 3rd-order harmonics if the frequency of the injected square wave is the same to the switching frequency. While, if the frequency is a half of the switching frequency or heavier load condition in either injection frequency, the effect of nonideal characteristics of inverter disappears and there is no 3rd harmonics in the position estimation error. Therefore, only the effect of cross-coupling inductance is reflected in the estimation error. As the result, the position estimation error appears in the form of 6th-order harmonics due to the spatial harmonics of inductances, and the error is relatively small compared with the switching frequency injection case. The theoretical analysis was verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, new model-based sensorless control methods are proposed that include independent estimations of position and speed errors, and compatible position and speed estimators. Using the proposed position estimator, a unity transfer function can be achieved from the actual position to the estimated position, eliminating the effects of load disturbances. This implies that the position error would ideally be zero, even in a transient state. In addition, the effects of parameter and voltage synthesis errors on the steady-state position error are analyzed. Experimental results verify both the analysis and the effectiveness of the proposed methods under severe load disturbances such as speed transient (20 000 r/min/s) and load torque transient (10 p.u./s). With the proposed methods, position estimation errors are significantly reduced by more than 50% during speed and load torque transients at identical dominant-pole placements, verifying the enhanced tracking capability and robustness of the proposed methods against external load disturbances. [ABSTRACT FROM AUTHOR]

The purpose of the study was to investigate the influence of short-term weight loss on body shape, physical fitness, and blood variables in college ssireum (one of the Korean traditional martial art) athletes. Six college ssireum athletes participated as subjects. The weight loss program includes 50% of limited diet, 5.5 hr of physical and skill training. Body composition such as weight, body fat, muscle mass, and body mass index (BMI) was determined. Fitness test such as shuttle run, sit-up, trunk extension test, grip test, sitting reach test, and side step test was measured. Blood variables such as total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein, glucose, reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) were checked before and after the short-term weight reduction. The results revealed significant decrease in body composition such as weight, body fat, muscle mass, and BMI. Fitness test also showed significant decrease in sit-up, trunk extension test, and grip test. The results demonstrated positive significant change in side step test, shuttle run, and sitting reach test. The results of blood variables showed significant decrease in total cholesterol, LDL, glucose and SOD. In contrast, MDA revealed significant increase and no significant change was found in ROS. Finally, it is assumed that a proposal of weight loss without decrease of muscle mass, muscle force, and muscle endurance is necessary because of the negative effects on muscle force and muscle endurance which should be used during actual games., Competing Interests: CONFLICT OF INTEREST No potential conflict of interest relevant to this article was reported.