Shingo Hiruma

This article introduces novel hybridization of parameter optimization (PO) and topology optimization (TO) methods. The proposed method is applied to the optimization of a permanent magnet motor. The magnet shape and topology of the flux barrier of the rotor core are optimized by performing PO and TO simultaneously. In the optimization, automatic mesh generation is adopted to improve the resolution of the shape representation. It is shown that the increase in the average torque resulting from the

A new method is introduced to evaluate the macroscopic permeability of a litz wire which is composed of stranded conductors. In this method, an integral equation is solved for the complex magnetization in the litz wire generated due to the proximity effect. The macroscopic permeability computed from the magnetization is used in the homogenization-based finite-element analysis of eddy currents in a litz-wire coil. It is shown that the wire twist has a little effect on the complex permeability.

Eddy current loss in a litz wire which has 3-D structure is analyzed using the integral equation method considering the proximity effect. In the present method, each wire is modeled as a polygonal line. 1-D integral equation is solved for the dipole magnetization generated by the anti-parallel eddy currents in the wire. The discretized integral equation can effectively be solved using an iterative method solver to compute the eddy current distribution in the wire due to the proximity effect.

This article introduces a new model order reduction method for a linear time-invariant system with symmetric positive-definite matrices. The proposed method allows the construction of a reduced model, represented by a Cauer-equivalent circuit, from the original system. The method is developed by extending the Cauer ladder network method for the quasi-static Maxwell's equations, which is shown to be regarded as the Lanczos algorithm with respect to a self-adjoint matrix. As a numerical example, a

Rat is susceptible whereas hamster is resistant to aflatoxin B1 (AFB1) hepatocarcinogenesis. Effect of cell proliferation on AFB1-induced glutathione S-transferase placental form (GST-P) positive foci has been examined in these two species after a single i.p. dose of AFB1 and phenobarbital (PB) as a promoter in a 3 week period. Bromodeoxyuridine incorporation as a measure of cell proliferation and GST-P hepatic foci were analyzed by immunohistochemical methods. Hepatic cell proliferation was max

This article proposes a novel homogenization method based on the unit cell approach which provides the continued fraction and, equivalently, the Cauer circuit representation of the complex permeability of fine structure materials. The proposed method makes it possible to perform the homogenization analysis in time domain. It is shown that the proposed method provides a more accurate resistance factor in comparison to the Dowell method and other classical methods.

Consistently reproducible experimental trauma was inflicted on the rat spinal cord (L3-L4) employing a controlled cortical impact device. The spinal cord was injured with one of three sizes of chips; thick (3 mm diameter), medium (2 mm diameter), thin (1 mm diameter). Each chip was applied at 1, 2 and 3 mm deformation depths. The correlations of the magnitude of the primary trauma were examined histopathologically. It was found that the extent and intensity of the trauma could be changed by alte

The Cauer ladder network (CLN) method enables to construct a reduced-based circuit model of analytical or numerical models, e.g., finite-element (FE) model, under quasistatic approximation. This article proposes an estimator that provides guaranteed upper bounds of the truncation error due to the CLN method. The error estimator is tested on an analytical model and an FE model to validate the approach.

The immunoreactivity of ciliary neurotrophic factor (CNTF) and S100 was studied in the degenerating and regenerating intramuscular nerves after the sciatic nerve was severed. The sciatic nerves of male Wistar rats were transected at the midpoint of the thigh, and silicone tubing was used to obtain effective reinnervation. The strong immunoreactivity of CNTF and S100 was observed in the Schwann cell cytoplasm of intramuscular nerves (IMN) and at the neuromuscular junction (NMJ) on the control sec

The quasi-static approximation that considers inductive–capacitive–resistive effects is referred to as the Darwin model of Maxwell’s equation. However, numerical analysis of the Darwin model is computationally expensive on account of large ill-conditioned equations. In this article, we proposed a new model order reduction technique for the Darwin model of Maxwell’s equations to drastically reduce the computational cost. In this method, four symmetric non-gauged equations were solved to obtain th

This article presents a new method for time-domain analysis based on the homogenized finite-element method (FEM). The permeability in the homogenized domain is expressed by the Cauer-equivalent circuit. The auxiliary unknowns relevant to the Cauer circuit are then eliminated using the finite-difference method. The homogenized finite-element (FE) equation without the auxiliary unknowns can be effectively solved.

The extended finite element method (XFEM) is used for calculating eddy currents at high frequencies, which reduces the number of unknowns in conductive materials. In this study, 2-D and 3-D models are analyzed numerically, and the solutions are compared with the solution obtained using the conventional FEM (CFEM). The proposed method is shown to give the accurate eddy current distribution and Joule losses for a wide range of frequencies even when the skin depth is smaller than the size of elemen

The extended finite element method (XFEM) is utilized for high-frequency eddy current analysis. However, when a conductor with a curved surface is involved, the geometric approximation tends to degrade due to the coarse mesh used in XFEM. To enhance the approximation accuracy, exact boundary representation (EBR) methods are employed within XFEM for eddy current analysis. The proposed method is validated using a round conductor model, demonstrating a substantial reduction of error in global quant