Low-temperature CV dispersion in MOS devices

A study is reported of the dispersion seen in the accumulation and depletion regions, of the C-V curve in n-channel MOS devices in the temperature range 30-45 K. It is concluded that the dispersion observed in these experiments is caused by time-constant effects, due to the substrate resistance and not caused by dopant atom emission time constant effects. From the measured admittance as a function of temperature and frequency, the acceptor energy level is determined to within ±0.4 meV     

Influence of production method on direction of processing heavy Ashal'chinsk crude

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 6, pp. 7–9, June, 1992.     

Finding nondegenerate Hopf bifurcation points for four-dimensional two-parametric systems

We establish a numerically feasible algorithm to find a simplicial approximation A to a certain part of the boundary of the set of stable (or Hurwitz) polynomials of degree 4. Moreover, we have that . Using this, we build an algorithm to find a piecewise-linear approximation to the intersection curve of a given surface contained in ⁴ with . We have also devised an efficient computer program to perform all these operations. The main motivation is to find the curve of nondegenerate bifurcation points in parameter space for a given 2-parametric Hopf bifurcation problem of dimension 4.     

Association of Escherichia coli O157:H7 with preharvest leaf lettuce upon exposure to contaminated irrigation water.

Recent foodborne outbreaks have linked infection by enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 to the consumption of contaminated lettuce. Contamination via food handler error and on-the-farm contamination are thought to be responsible for several outbreaks. Though recent studies have examined the application of EHEC to store-bought lettuce, little is known about the attachment of EHEC to growing plants. We investigated the association of lettuce seedlings with EHEC O157:H7 strains implicated in lettuce or fruit outbreaks using hydroponic and soil model systems. EHEC strains that express the green fluorescent protein were observed by stereomicroscopy and confocal laser scanning microscopy to determine adherence patterns on growing lettuce seedlings. Bacteria adhered preferentially to plant roots in both model systems and to seed coats in the hydroponic system. Two of five nonpathogenic E. coli strains showed decreased adherence to seedling roots in the hydroponic system. EHEC was associated with plants in as few as 3 days in soil, and contamination levels were dose-dependent. EHEC levels associated with young plants inoculated with a low dose suggested that the bacteria had multiplied. These data suggest that preharvest crop contamination via contaminated irrigation water can occur through plant roots.     

Hydrogen and Calcium Ion Concentrations Affect Volume of CO2 Puffed Diced Green Bell Peppers

Diced green bell peppers were soaked in a solution of hydrochloric acid or calcium chloride, air-dried to 50% moisture, held in CO₂ at 5.8 MPa for 1, 3 or 5 min, and puffed by abruptly releasing the CO₂ pressure. Treatment with 1% CaCl₂ increased the size of puffed-dried products as compared to a control; however, HCl treatments did not. The treatment with 1 or 2% CaCl₂ reduced shrinkage as compared to the control. The 1% CaCl₂ treatment may have increased the CO₂ saturation rate.     

The influence of sulfur pressure on Sulfidation behaviour of NiCoCrAl(Y) alloys at high temperature

Sulfidation of alloy having nominal composition Ni-23Co-19Cr-12Al (wt%) with and without the addition of 0.6% yttrium was studied at temperatures 1073–1273 K in sulfur vapor at atmospheric pressure and in H₂/H₂S gas mixtures at sulfur pressure of 10^?3 and 10^?1.5 Pa. Sulfidation runs were followed thermogravimetrically. Phase and chemical composition of sulfide scales and scale morphologies were determined by means of XRD, EDX, EPM and SEM analyses. After certain initial period sulfidation of both materials followed approximately a parabolic rate law. The estimated sulfidation rates for each alloy increased with sulfur pressure and temperature. The sulfide scales on both materials showed complex microstructures and compositions, depending on sulfidation conditions, with several sulfide and sulfospinel phases present, such as (Ni,Co)S, (Ni,Co)₃S₄, (Ni,Co)Cr₂S₄, (Cr,Ni,Co)Al₂S₄ or (Cr,Ni,Co)S and (Cr,Ni,Co)₃S₄. There was no evidence of yttrium segregation either to the grain boundary regions in the scale or to the alloy/scale interface. Yttrium dissolved in the sulfide phases and accelerated the sulfidation process. This behaviour was ascribed to the doping effect.     

An isolated ZVS/ZCS flyback converter using the leakage inductanceof the coupled inductor

This paper describes a simple and effective way to modify an existing hard-switched flyback power converter into a circuit with zero-voltage switching (ZVS) and zero-current switching (ZCS). The key improvement is to turn the unattractive features of the coupled inductor leakage inductance and snubber capacitor into attractive ones. The coupled inductor leakage inductance and snubber are used to form a quasi-resonant circuit to facilitate ZVS/ZCS of all power devices. The operating principles of the power converter and experimental results are presented