N=2 gauge theories and degenerate fields of Toda theory

We discuss the correspondence between degenerate fields of the W_N algebra and punctures of Gaiotto's description of the Seiberg-Witten curve of N=2 superconformal gauge theories. Namely, we find that the type of degenerate fields of the W_N algebra, with null states at level one, is classified by Young diagrams with N boxes, and that the singular behavior of the Seiberg-Witten curve near the puncture agrees with that of W_N generators. We also find how to translate mass parameters of the gauge theory to the momenta of the Toda theory.Comment: 23 pages,v2: minor corrections,published versio

IGBT Avalanche Current Filamentaion Ratio: Precise Simulations on Mesh and Structure Effect

Current filamentaion effect with dynamic avalanche during turn-off transient in IGBT has been discussed for years. In the prior papers, the possibility of device failure has been reported based on TCAD simulation and simulation results have shown that variety of filamentation phenomena exist for conditions assumed in each simulation. It is discussed in this paper, for the first time, that the relationship of filamentation current concentration strength to device design parameters and categorizes filamentation phenomena, introducing current filamentation ratio (CFR). In the paper, guidelines for appropriate mesh pattern selection are also described to ensure the validity of simulation results.ISPSD 2016 28th International Symposium on Power Semiconductor Devices and ICs., Jun 12-16, 2016, Žofín Palace, Prague, Czech Republi

IGBT Avalanche Current Filamentaion Ratio: Precise Simulations on Mesh and Structure Effect

ISPSD 2016 28th International Symposium on Power Semiconductor Devices and ICs., Jun 12-16, 2016, Žofín Palace, Prague, Czech RepublicCurrent filamentaion effect with dynamic avalanche during turn-off transient in IGBT has been discussed for years. In the prior papers, the possibility of device failure has been reported based on TCAD simulation and simulation results have shown that variety of filamentation phenomena exist for conditions assumed in each simulation. It is discussed in this paper, for the first time, that the relationship of filamentation current concentration strength to device design parameters and categorizes filamentation phenomena, introducing current filamentation ratio (CFR). In the paper, guidelines for appropriate mesh pattern selection are also described to ensure the validity of simulation results

Novel 600 V Low Reverse Recovery Loss Vertical PiN Diode with Hole Pockets by Bosch Deep Trench

The performance of a novel diode with characteristic trench shape is predicted by TCAD simulation. A novel 600 V vertical PiN diode with hole pockets by the Bosch deep trench process is proposed for a better trade-off curve between reverse recovery loss and forward voltage. The reverse recovery loss is reduced to a half. In addition, the active chip size of the novel diode is reduced to two-thirds that of the conventional PiN diode in the same forward voltage. The novel diode structure is a strong candidate when the simple fabrication process under development is established.ISPSD 2016 28th International Symposium on Power Semiconductor Devices and ICs., Jun 12-16, 2016, Žofín Palace, Prague, Czech Republi

Formulation of Single Event Burnout Failure Rate for High Voltage Devices in Satellite Electrical Power System

Single-Event Burnout (SEB) is a catastrophic failure in the high voltage devices that is initiated by the passage of particles during turn-off state. Previous papers reported that SEB failure rate increases sharply when applied voltage exceeds a certain threshold voltage. On the other hand, the high voltage devices for the artificial satellite have been increasing. In space, due to increase flux of particle, it is predicted that SEB failure rate will be higher. In this paper, we proposed the failure rate calculation method for high voltage devices based on SEB cross section and flux of particles. This formula can calculate the failure rate at space level and terrestrial level depending on the applied voltage of the high voltage devices.2017 29th International Symposium on Power Semiconductor Devices and IC\u27s (ISPSD), May 28 2017-June 1 2017, Sapporo, Japa

High-performance vertical Si PiN diode by hole remaining mechanism

A novel diode with a unique trench shape is predicted by TCAD simulation to have high performance. The novel 600 V vertical PiN diode with hole pockets by the Bosch deep trench process shows a better trade-off curve between reverse recovery loss and forward voltage. The reverse recovery loss is reduced by half. In addition, the active chip size of the novel diode is reduced to two-thirds that of the conventional PiN diode in the same forward voltage. Thanks to the hole pockets with an electric field in the diagonal direction, the remaining hole suppresses the surge voltage with noise for high performance. In this paper, we specially focus on the analysis of phenomenon and the noise suppression mechanism during reverse recovery. The novel diode structure is a strong candidate when developing the fabrication process after silicon trench etching is established

Failure rate calculation method for high power devices in space applications at low earth orbit

This paper discusses the universal calculation method for space proton induced failure rate on high power device. High energetic particles can be the reason of power device failure in both terrestrial and space. T-CAD simulation result gives a threshold charge value for the device destruction which is triggered by energetic proton from space. The amount of threshold charge depends on applied voltage for high power device. The probability of charge generation in silicon due to proton penetration is considered as well. This probability function variation depends on the thickness of device and incident energy of proton which studied before at there. Last consideration on this paper is 3.3 kV PiN diode\u27s Single Event Upset Cross section and failure rate which was calculated by proposed method in Low earth orbit environment condition

Novel 600 V Low Reverse Recovery Loss Vertical PiN Diode with Hole Pockets by Bosch Deep Trench

ISPSD 2016 28th International Symposium on Power Semiconductor Devices and ICs., Jun 12-16, 2016, Žofín Palace, Prague, Czech RepublicThe performance of a novel diode with characteristic trench shape is predicted by TCAD simulation. A novel 600 V vertical PiN diode with hole pockets by the Bosch deep trench process is proposed for a better trade-off curve between reverse recovery loss and forward voltage. The reverse recovery loss is reduced to a half. In addition, the active chip size of the novel diode is reduced to two-thirds that of the conventional PiN diode in the same forward voltage. The novel diode structure is a strong candidate when the simple fabrication process under development is established

Increased predominance of the matured ventricular subtype in embryonic stem cell-derived cardiomyocytes in vivo

Accumulating evidence suggests that human pluripotent stem cell-derived cardiomyocytes can affect “heart regeneration”, replacing injured cardiac scar tissue with concomitant electrical integration. However, electrically coupled graft cardiomyocytes were found to innately induce transient post-transplant ventricular tachycardia in recent large animal model transplantation studies. We hypothesised that these phenomena were derived from alterations in the grafted cardiomyocyte characteristics. In vitro experiments showed that human embryonic stem cell-derived cardiomyocytes (hESC-CMs) contain nodal-like cardiomyocytes that spontaneously contract faster than working-type cardiomyocytes. When transplanted into athymic rat hearts, proliferative capacity was lower for nodal-like than working-type cardiomyocytes with grafted cardiomyocytes eventually comprising only relatively matured ventricular cardiomyocytes. RNA-sequencing of engrafted hESC-CMs confirmed the increased expression of matured ventricular cardiomyocyte-related genes, and simultaneous decreased expression of nodal cardiomyocyte-related genes. Temporal engraftment of electrical excitable nodal-like cardiomyocytes may thus explain the transient incidence of post-transplant ventricular tachycardia, although further large animal model studies will be required to control post-transplant arrhythmia