Westinghouse Electric

About: Westinghouse Electric is a company organization based out in Cranberry Township, Pennsylvania, United States. It is known for research contribution in the topics: Brake & Signal. The organization has 27959 authors who have published 38036 publications receiving 523387 citations.

A unified analysis of MMIC power amplifier stability

Abstract: The author develops the mathematical framework and techniques for predicting possible oscillations for all n modes in order to ensure MMIC monolithic microwave integrated circuit stability. Although the analysis is applicable to any number of combined devices, only the cases for n=2 and 4 are discussed. These two cases illustrate the special considerations that apply for small numbers of combined devices (n=2) and the difficulties in analyzing larger numbers of combined devices (n=4). It was shown that the stability of the amplifier for all modes (even and odd) can be checked using small signal analysis software. >

Approximations for the ac Impurity Hopping Conduction

Abstract: A previous approximation of the ac impurity hopping conduction in the high-temperature, low-concentration limit is extended to low temperatures and to highly compensated material. Only the real part of the conductivity is considered, and random distribution is assumed. The lengths ${r}_{D}\ensuremath{\equiv}{r}_{\mathrm{maj}}={(\frac{4\ensuremath{\pi}{N}_{D}}{3})}^{\frac{\ensuremath{-}1}{3}}$, ${r}_{T}=\frac{{e}^{2}}{4\ensuremath{\pi}\ensuremath{\kappa}\mathrm{kT}}$ ($\ensuremath{\kappa}$ is the dielectric constant) and ${r}_{\ensuremath{\omega}}$ are defined for the sake of simple expressions. The latter is a distance characteristic of the frequency, proportional to the radius $a$ of the localized impurity state and only weakly dependent on other parameters. All the expressions for $\ensuremath{\sigma}$, written as functions of these variables, are explicitly proportional to $a$, to the imaginary conductivity $\ensuremath{\kappa}\ensuremath{\omega}$, and for low compensations, to ${N}_{A}={N}_{min}$. In addition to the distribution of spacings between impurities already considered in the high-temperature limit, the distribution in energies is now taken into account. The low-temperature treatment holds in the region where $\ensuremath{\sigma}$ can be expanded in $\frac{{r}_{D}}{{r}_{T}}$ and $\frac{{r}_{\ensuremath{\omega}}}{{r}_{T}}$. Due to the existence of a zero-order term, $\ensuremath{\sigma}$ is almost independent of temperature at very low temperatures. At extremely low temperatures, however, where $\mathrm{kT}$ is much smaller than the resonance energy for a separation ${r}_{\ensuremath{\omega}}$, $\ensuremath{\sigma}$ is proportional to the temperature. The low-compensation and high-compensation results are basically identical at high temperatures. At very low temperatures, they differ mainly in the concentration dependence. At intermediate temperatures, the high-compensation case is expected to interpolate smoothly between the two temperature extremes; the low-compensation case is not. For both cases, the frequency dependence at very low temperatures is slightly more pronounced than at high temperatures, as is borne out by experiments. The following additional results are of interest for low compensation. At very low temperatures, the previously reported experimental result, that $\ensuremath{\sigma}$ is practically independent of ${N}_{D}$, is accounted for. The magnitudes of the calculated and measured conductivities are in very satisfactory agreement, particularly when compensated for the experimentally found $N_{A}^{}{}_{}{}^{0.85}$ dependence. It is shown that the results are valid up to much higher concentrations than the previous high-temperature treatment. At higher temperatures, the situation is less satisfactory. A tendency for pairing and an alteration of the radii $a$ from those calculated by Miller and Abraham is necessary to get reasonable agreement. The radii have to be altered so as to make $\frac{{a}_{P}}{{a}_{{A}_{s}}}=1.14$ instead of 1.05. To test the validity of the previously described model at intermediate temperatures, similarity relations based on statistical equivalence are developed. Comparison with data again necessitates the assumption $\frac{{a}_{P}}{{a}_{{A}_{s}}}=1.14$. The results on the heavy compensation cannot be evaluated because of lack of experimental data.

Maggot therapy in "lower-extremity hospice" wound care: fewer amputations and more antibiotic-free days.

Abstract: We sought to assess, in a case-control model, the potential efficacy of maggot debridement therapy in 60 nonambulatory patients (mean ± SD age, 72.2 ± 6.8 years) with neuroischemic diabetic foot wounds (University of Texas grade C or D wounds below the malleoli) and peripheral vascular disease. Twenty-seven of these patients (45%) healed during 6 months of review. There was no significant difference in the proportion of patients healing in the maggot debridement therapy versus control group (57% versus 33%). Of patients who healed, time to healing was significantly shorter in the maggot therapy than in the control group (18.5 ± 4.8 versus 22.4 ± 4.4 weeks). Approximately one in five patients (22%) underwent a high-level (above-the-foot) amputation. Patients in the control group were three times as likely to undergo amputation (33% versus 10%). Although there was no significant difference in infection prevalence in patients undergoing maggot therapy versus controls (80% versus 60%), there were significantly more antibiotic-free days during follow-up in patients who received maggot therapy (126.8 ± 30.3 versus 81.9 ± 42.1 days). Maggot debridement therapy reduces short-term morbidity in nonambulatory patients with diabetic foot wounds. (J Am Podiatr Med Assoc 95(3): 254-257, 2005)

A One-Step Finite Element Method for Multiconductors Skin Effect Problems

Abstract: A one-step procedure is developed to solve the skin effect problem in multiconductor busbars. The procedure differs from previous solutions in that it treats the source (or quasi-static) current density in each conductor as an unknown. It couples the solution of the diffusion equation to Ampere's law, and allows for the finite element solution of skin effect problems to be obtained directly in one step from the currents imposed by the power system in each conductor.

Minimal structural response under random excitation using the vibration absorber

Abstract: The equations of motion are derived for the first mode response of a linear multistorey structure having a linear vibration absorber attached to the roof. Furthermore, the variance of the first mode response to a gaussian white noise lateral base acceleration (as a model of earthquake excitation) is determined. Smallest possible values of the variance of the response along with corresponding absorber parameters are established using an optimization program. It is demonstrated that the absorber is quite effective in reducing first mode response for 5- and 10-storey structures even with relatively small values of the absorber mass. Moreover, minimal responses for the randomly excited single-degree-of-freedom system have been determined, and a design example is presented. The absorber system has potential application not only in earthquake engineering but also in aerospace and terrestrial vehicle design.