A Simple Inverter-Motor System to Improve Energy Consumption and Maximum Torque

A new inverter-AC motor system having four power source lines, which can control each coil current independently, is compared to an ordinary inverter-AC motor system using a Y-type coil connection and three power lines. In this paper, three-phase rectangular-type currents are generated by the inverter made of simple ICs. In a previous paper[1], similar comparison experiments were executed using a high-speed DSP board. The board can calculate the three-phase currents to generate a rotating, resultant, magnetic flux with a precise constant strength and phase. It was verified by experiments that an energy consumption of 15% can be saved by using the proposed independent, motor-coil currents. However, it requires high speed and high cost DSP or CPU. In this paper, it is verified by using a new inverter-AC motor system that an energy consumption of 15% can be saved, and also the maximum torque increases 10%.

Estimations of the remainder of spherical harmonic series

An asymptotic estimate is obtained for the error in approximation of functions by partial sums of spherical harmonic expansions. The precise constant in the main term is found and the order of growth of the remainder term is given.

Experimental Study of Springback in Draw Bend Test of AZ31B Magnesium Alloy Sheet

Springback has been measured under various process conditions corresponding to those found in real press-stamping operations. The draw bend tests originally developed at Ohio State University (Carden et al., 2002 [1]) were conducted using a range of tool radii, direct controlled constraining forces, and friction conditions. Especially, the draw-bend test was able to apply precise constant restraining force and almost negligible friction by rotating the cylindrical tool with the same speed of drawn sheet strip. Springback angle changes were measured for the bending and sidewall curl regions to find the dependence on the process variables. As expected, tensile restraining force dominates the springback sensitivity, with higher forces reducing springback. The measured springback angles and curvatures were reported for use in modeling of springback of higly anisotropic and asymmetric magnesium alloy sheets.

Sharp constants in higher-order heat kernel bounds

We consider a space X of polynomial type and a self-adjoint operator on L2(X) which is assumed to have a heat kernel satisfying second-order Gaussian bounds. We prove that any power of the operator has a heat kernel satisfying Gaussian bounds with a precise constant in the Gaussian. This constant was previously identified by Barbatis and Davies in the case of powers of the Laplace operator on RN. In this case we prove slightly sharper bounds and show that the above-mentioned constant is optimal.