Optimization and surface charge sensitivity of high-voltageblocking structures with shallow junctions

The most commonly used high-voltage blocking and termination structures-floating field limiting rings (FLR), lateral charge control HVIC devices, and junction termination extension (JTE) structures-are very sensitive to positive silicon and silicon dioxide interface charges. These high-voltage termination structures specifically designed for 1000-V blocking capability lose 25 to 50% of their voltage-blocking capability under 5×10¹¹ cm^-2 net interface state density. In contrast, optimized multiple-zone JTE (MZ-JTE), and offset multiple field plated and field-limiting ring (OFP-FLR) structures will lose only 5% of their respective voltage blocking capabilities under the same surface-charge condition. These improved high-voltage blocking structures do not require additional passivation and process complexities     

Elliptic cylinder geometry for distinguishability analysis in impedance tomography

Electrical impedance tomography (EIT) is a technique that computes the cross-sectional impedance distribution within the body by using current and voltage measurements made on the body surface. It has been reported that the image reconstruction is distorted considerably when the boundary shape is considered to be more elliptical than circular as a more realistic shape for the measurement boundary. This paper describes an alternative framework for determining the distinguishability region with a finite measurement precision for different conductivity distributions in a body modeled by elliptic cylinder geometry. The distinguishable regions are compared in terms of modeling error for predefined inhomogeneities with elliptical and circular approaches for a noncircular measurement boundary at the body surface. Since most objects investigated by EIT are noncircular in shape, the analytical solution for the forward problem for the elliptical cross section approach is shown to be useful in order to reach a better assessment of the distinguishability region defined in a noncircular boundary. This paper is concentrated on centered elliptic inhomogeneity in the elliptical boundary and an analytic solution for this type of forward problem. The distinguishability performance of elliptical cross section with cosine injected current patterns is examined for different parameters of elliptical geometry.     

Effect of copper on boride layer of boronized ductile cast irons

GGG-50, GGG-60 and GGG-80 ductile cast irons containing 0.01, 0.3 and 0.98 wt% copper, respectively, were boronized in a salt bath and then analyzed using optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Increasing copper concentration in ductile cast irons resulted in formation of mono-phase boride layer (Fe₂B), decreased Si-ferrite zone and hindered the growth discontinuous graphite between boride layer and matrix.     

Effect of heat treatment in air on the thermal properties of SiC fibre-reinforced composite. Part 1: a barium osumilite (BMAS) matrix glass ceramic composite

The thermal properties have been studied on a glass ceramic composite comprised of a barium osumilite (BMAS) matrix reinforced with SiC (Tyranno) fibres which has been subjected to a heat treatment in air in the range of 700–1,200 °C. Microstructural studies were carried out especially on of the interface between fibre and matrix. The presence of a carbon thin layer in the interface is a typical observation in SiC fibre-reinforced glass ceramic matrix composite systems. The microstructural evaluation and thermal properties showed a degradation of interfacial layer occurred at low heat treatment temperatures, (700–800 °C) this was attributed to the fact that, at those heat treatment temperatures the carbon rich layer formed during processing was oxidised away leaving voids between fibre and matrix, which were linked by isolated silicon-rich bridges. After heat treatment at higher temperatures of 1,000–1,200 °C, the thermal properties were retained or even enhanced by leaving a thick interfacial layer.     

Investigation of thermoluminescence properties of metal oxide doped lithium triborate

In this study, lithium triborate (LiB₃O₅) doped with different metal oxides were investigated to explore its thermoluminescence properties. Solid-state reaction method was employed for the synthesis of the desired materials. The formation of the produced phases was confirmed by Powder X-Ray Diffraction (XRD), Infrared (IR), Differential Thermal Analysis (DTA) and Scanning Electron Microscopy (SEM) examinations. It was found that, CuO and Al₂O₃ doped lithium triborate samples exhibit very significant thermoluminescence glow curves to be promising dosimetric material.     

The existence and the determination of terminal equations for hybrid connected N-ports

A new procedure for the existence and the determination of terminal equations for the hybrid interconnection of two n-port networks is given. It is shown that this procedure generalizes the previous works of Duffin, Trapp and Mitra for the hybrid sum of terminal impedance matrices which are either Hermitian positive semi-definite (HSD) or arbitrary matrices with complex entries. For the application of the new procedure it is shown that each n-port need not be terminal solvable or well defined. In fact, even in the case of active RLC n-ports considered in sinusoidal steady-state, the previous results of Duffin, Mitra and Trapp established for HSD matrices or arbitrary complex matrices can still be utilized with the use of modified terminal equations, to obtain the terminal equations of the resulting n-port networks. It is also noted that the method introduced in this paper is independent of the choice of generalized inverses.     

Evidence of PAH production under lean combustion conditions

While it is common knowledge that PAH formation can be expected at rich combustion conditions, this paper presents experimental and computational evidence that PAH formation can also be expected under lean, or cool, combustion conditions. Experimental evidence for diesel engine operation at lean conditions, as well as the literature references related to waste tire and coal combustion, are cited as supportive evidence of conclusions drawn here. A computational model based on reaction mechanisms for three surrogate fuels: C₂H₂, C₇H₁₆ and C₁₄H₂₈, was validated against the available diesel engine data, and projected to both lean and rich combustion conditions. The finding was that for the adiabatic case, minimum production of PAHs occurs at equivalence of unity and increases as equivalence becomes either lean or rich; the latter observation being consistent with the common knowledge.     

Stress-strain response of a cast 319-T6 aluminum under thermomechanical loading

The stress-strain behavior of cast 319-T6 aluminum-copper alloys with three different secondary dendrite arm spacings (SDASs) was studied at high temperatures and under thermomechanical deformation, exposing marked cyclic softening. A two state-variable unified inelastic constitutive model proposed earlier was modified to describe the stress-strain responses of these alloys by considering the variation of hardening and recovery functions of back-stress and drag stress. The SDAS was incorporated in the model as a length-scale parameter, and the material constants were determined systematically from experiments on a cast 319-T6 aluminum with small and large SDASs. The capabilities of the constitutive model were checked by the comparisons of simulations to experiments in the small-strain regime (<0.005). The results show that the model provides successful simulations for material response after thermal exposure at high temperature and cyclic transient stress-strain behavior. The causes of mechanical behaviors at the macro scale are discussed based on microstructural changes during thermal exposure.