New approach to determine the critical capacitance for self-excitedinduction generators

This paper presents a new simple approach for computing the minimum value of capacitance necessary to initiate the self-excitation process in three-phase isolated induction generators. The method proposed in this paper is based on the analysis of the complex impedance matrix of the induction generator when loaded with a general inductive load. The advantage of this method is its simplicity since it involves simple algebraic equations and only one equation is solved iteratively to get the value of minimum capacitance. A simple computer algorithm has been developed to predict the minimum value of capacitance necessary for the onset of self-excitation. Using the same approach, the algorithm is modified to predict the minimum value of capacitance necessary to maintain the generator terminal voltage at a preset value under specific load and speed conditions. Computer simulations obtained using the proposed method are compared with those obtained experimentally to confirm the validity and accuracy of the proposed method     

Simple lossless feed networks for array antennas

For a given array, describable as an n-port network for feed considerations, it is shown that, with a class of very simple lossless feed networks, it is possible to realise an arbitrarily specified voltage or current excitation at the array ports.     

The aperture admittance of a circumferential slot in a circularcylinder

A circumferential slot in an infinitely long cylinder when fed with a tangential electric field is considered. Parseval's theorem, in which Fourier integrals appear, is used to express the aperture admittance as the integral from zero to infinity of an infinite series. Recognizing that the first two terms of this infinite series have a nonintegrable singularity when the variable of integration w is equal to the wavenumber k, the authors distort slightly the contour of integration to avoid k. The terms of the infinite series are then approximated when w is close to k. A combination of numerical and analytical schemes employing both large and small argument approximations of Hankel functions is used to perform the integration. It has been found that these integration schemes work very well, and a simple and fast algorithm has resulted     

Control of radar scattering by reactive loading

A method for obtaining a desired radar scattering pattern by reactively loading a conducting body is given. The theory uses the concept of characteristic modes of a loaded body. Any desired real current can be resonated by reactive loads to make it the dominant mode current of that body. If no other mode is near resonance, the radar scattering pattern becomes nearly the same as the radiation pattern of the resonated current. A quality factorQis defined as a measure of the broadband behavior of a scatterer. Procedures for computing the real currents having minimumQand maximum gain-quality ratio are given. A pattern synthesis procedure is developed for obtaining the real current whose radiation field pattern is the least mean-square approximation to a desired field pattern. Numerical examples are given for each procedure discussed.     

Diagnosis and pathophysiology of paradoxical embolism

A review of the experience with 134 consecutive patients with germinal cell testicular neoplasia indicates that definitively accurate staging of the malignancy at presentation is the single most important prognostic factor. Nearly two-thirds of the patients with all types of germinal malignancies survived or died of other causes and the highest survival rates were seen among patients with earlier stages of seminoma. In recent years patients with all types of germinal malignancies of the testis have been treated by radical retroperitoneal lymphadenectomy with enhancement of survivals. Patients with seminoma and non-seminomatous tumors exhibited increased survival rates with node dissection. In 66 consecutive lymphadenectomies the complication rate was less than 14 per cent, with only 1 death related to the operation. Retroperitoneal lymphadenectomy not only affords therapeutic advantage but also provides an opportunity for accurate surgical staging of disease and allows for rational decision relative to additional treatment, radiation therapy or chemotherapy.     

Are adult children of dysfunctional families with alcoholism different from adult children of dysfunctional families without alcoholism? A look at committed, intimate relationships.

Investigating the validity of classifying adult children of dysfunctional families with alcoholism (ACDFAs) as a unique population, this study compared ACDFAs with adult children of dysfunctional families without alcoholism (ACDFs) and adult children of functional families (ACFFs) on current relationship satisfaction. Participants (N ?=?126) were from a community sample. No significant difference between the ACDFAs and ACDFs was found; however, both ACDFAs and ACDFs displayed significantly more difficulty with problem-solving communication than the ACFFs. Regression results indicated that dysfunction in the family of origin is significantly related to global distress and difficulties with problem-solving communication in current intimate relationships. Results do not lend support to the utility of classifying ACDFAs as a unique population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Negotiation in a knowledge-based concurrent engineering design environment

Abstract: Computational support for concurrent engineering design presents a number of issues in the design of knowledge-based systems. A fundamental concern is the need to provide the life-cycle perspective in recommending design alternatives. It is argued that such a complex knowledge-based system should be distributed, due to the inherent problems with large knowledge bases and the maintenance of consistency. Inconsistent local views of a problem and different priorities on design issues are expected between different knowledge-based design perspectives. These inconsistencies and different priorities will lead inherently to conflict which has to be resolved. This paper addresses the issues and key variables in conflict resolution and presents a strategy that can be applied for managing the conflict resolution process. We propose negotiation as the method of analysing a conflict situation, applying an appropriate conflict resolution strategy and monitoring its performance. We present an overview of the nature of conflict and some conflict resolution strategies, and see in what situations certain strategies are appropriate.     

Nuclear estradiol receptor in the adult rat uterus: a new exchange assay

A protamine exchange assay has been developed to measure uterine nuclear estrogen receptor in mature rats exposed to estradiol (E). After ovariectomized-adrenalectomized mature rats are injected with E, estrogen receptor (RnE) is extracted from uterine nuclei with 0.6 M potassium chloride, diluted, and quantitatively precipitated with protamine sulfate. The precipitate is subjected to a ligand exchange with radiolabeled estradiol (E), with or without unlabeled diethylstilbesterol, to determine nonspecific binding. At 37 degrees C complete exchange of E for E in RnE is observed at 2.5 h; virtually no receptor degradation occurs up to at least 5 h. Exchange does not occur at 4 degrees C. Using the protamine assay, the depletion of cytoplasmic estrogen receptor (Rc) and the accumulation of RnE were studied at various doses of E at specific time points. Increasing doses of E result in a decrease of Rc with an equal increase of RnE. At the highest dose of E (10 mug) Rc is completely depleted within 10 min, by 6 h it is 25% replenished, and by 24 h returns to slightly above control levels. Within 10 min after the injection, RnE increases to 80-90% of the original cytoplasmic level of receptor (approximately 2-3 pmol/mg of DNA or approximately 1.5 pmol/100 mg of uterus). At 6 h RnE is 75% depleted and it is completely absent at 24 h. The protamine assay permits precise quantitative studies of nuclear estrogen receptor and avoids the problems of receptor degradation and excessive nonspecific binding often found in exchange reactions at elevated temperatures.     

The inductance matrix of a multiconductor transmission line inmultiple magnetic media

A simple relationship between the inductance matrix and the auxiliary capacitance matrix is given. For a multiconductor transmission line consisting of N_c conducting cylinders in inhomogeneous media consisting of N_d homogeneous regions with permeabilities μ_i and permittivities ϵ _i, the inductance matrix [L] for the line is obtained by solving the magnetostatic problem of N_c conductors in N_d regions with permeabilities μ _i. The capacitance matrix [C] for the line is obtained by solving the electrostatic problem of N_c conductors in N_d regions with permittivities ϵ _i. It is shown that [L]=μ₀ϵ₀[C^'] ^-1, where [C^'] is the capacitance matrix of an auxiliary electrostatic problem of N_c conductors in N_d regions with relative permittivities set equal to the reciprocals of the relative permeabilities of the magnetostatic problem, i.e. ϵ^' _i/ϵ₀=μ₀/μ_i