Search results

The purpose of this paper is to propose a statistical approach, which enables the prediction of the risk of the appearance of discharge bearing currents in a given drive that can damage the motor bearings. Using such an approach, the drives for the decisive but expensive, long‐term destructive investigations can be selected. A comparative analysis is presented to show the applicability of the presented statistical model.

In the paper, a statistical approach to large data sets of measured bearing currents is presented. Weibull distribution has been chosen to describe the amplitudes of bearing currents, whereas exponential distribution is used for the approximation of the awaiting times to puncture. In order to check the hypothesis that these distributions are independent two tests has been conducted: F‐Snedecor, to check equality of mean values and Bartlett's to check variance equality. On this basis, joint distribution is expressed as the product of independent marginal distributions.

The comparative analyses show that special caution is required for a proper selection of EMI filters. The additional inductance of the filter in a common mode (CM) current path decreases the damping factor of the circuit and significantly increases the risk of bearing damage caused by electric discharge machining currents. The CM transformer is a cheap and effective solution that reduces CM current without increasing the rate and the amplitudes of bearing currents.

This paper presents a new approach to bearing currents that allows prediction of the risk of bearing damage in a given drive.

The purpose of this paper is to evaluate the conditions in which a saturation of the common mode (CM) choke might appear to be essential for proper design of the CM voltage filters. This paper presents a method for the determination of a CM choke flux density produced by multilevel inverters with carrier‐based modulations.

The proposed combination of secant and tangent methods allows efficient and high‐resolution determination of the CM voltage waveforms produced at the output of the multilevel inverters with commonly used carrier‐based modulations.

The presented results show that the application of a five‐level inverter with specific modulation causes a decrease of the maximum flux density, down to 15 per cent of the maximum level of the flux density reached in a two‐level inverter. The proposed, dedicated approximation method provides an accuracy of the root estimation better by about three orders for a comparable number of the function calls in comparison with Brent's method.

The presented theoretical evaluations make possible the determination of the maximum expected value of the flux density produced by multilevel inverters with various types of carrier‐based modulations, which allows a reduction in dimensions, weight and cost of CM chokes applied in CM voltage compensators.

In the paper, the new formulas that describe the placement of triangular carrier functions for commonly used multilevel inverters have been presented. In order to avoid accumulation of the estimation error, during determination of the CM voltage time integral, a dedicated, efficient method of roots approximation has been developed.

The problems involved in trying to measure the effect of the budget on the distribution of lifetime income are reviewed. A comparison is made of the likely differences between the stylised facts of annual incidence studies and the possible lifetime impact of the budget. Annual studies show that redistribution to the poor occurs, primarily as a result of pensions. It is likely that the lifetime incidence of the budget is broadly neutral since pensions will not accrue mainly to the lowest deciles when a lifetime income perspective is taken.

An analysis of community health, its history, successes and failures, depends on an understanding of its scope, but there is little consensus as to precisely what the discipline entails. Some view it as a strict scientific discipline, others see it as a social movement, and still others conceive of it as a conglomerate of various disciplines. It is useful initially to identify the medical components of community health, and then to approach its interdisciplinary aspects. Community health, strictly defined, includes such fields as disease control, environmental sanitation, maternal and child care, dental health, nutrition, school health, geriatrics, occupational health, and the treatment of drug and alcohol abuse. This limited definition, though accurate, does not differentiate the field from the much older area of public health. Within community health, the disease focus of traditional public health epidemiology, the total health focus of community medicine, and the outcome focus of health services research are interconnected. Community health combines the public health concern for health issues of defined populations with the preventive therapeutic approach of clinical medicine. An emphasis on personal health care is the result of this combination. Robert Kane describes the field accurately and succinctly: “We envision community medicine as a general organizational framework which draws upon a number of disciplines for its tools. In this sense, it is an applied discipline which adopts the knowledge and skills of other areas in its effort to solve community health problems. The tools described here include community diagnosis (which draws upon such diverse fields as sociology, political science, economics, biostatistics, and epidemiology), epidemiology itself, and health services research (the application of epidemiologic techniques on analyzing the effects of medical care on health).”

Using data from the linked National Health Interview Survey National Death Index (NHIS‐NDI), a new and unique data set, we examine the interaction of age and self‐rated health as a predictor of overall and cause‐specific mortality. Proponents of wear and tear theories argue that as the body ages, it begins to degenerate, leaving the aged in poor health and vulnerable to their ultimate mortality. We find that although the majority of the elderly rate their health as good or better, low levels of education and income contribute to poor perceived health, and the effect of age on mortality varies by level of perceived health. While the oldest old who report the poorest health experience greater risks of mortality, elders who report good health experience much lower risks. As a larger share of our population survives into old age, it is important to emphasize preventive health care policy, as well as strong economic and health care safety nets, not only to promote health but also to lengthen life.

This paper is an exploratory study of one approach to incorporating situational information into information retrieval systems, drawing on principles and methods of discourse linguistics. A tenet of discourse linguistics is that texts of a specific type possess a structure above the syntactic level, which follows conventions known to the people using such texts to communicate. In some cases, such as literature describing work done, the structure is closely related to situations, and may therefore be a useful representational vehicle for the present purpose. Abstracts of empirical research papers exhibit a well‐defined discourse‐level structure, which is revealed by lexical clues. Two methods of detecting the structure automatically are presented: (i) a Bayesian probabilistic analysis; and (ii) a neural network model. Both methods show promise in preliminary implementations. A study of users' oral problem statements indicates that they are not amenable to the same kind of processing. However, from in‐depth interviews with users and search intermediaries, the following conclusions are drawn: (i) the notion of a generic research script is meaningful to both users and intermediaries as a high‐level description of situation; (ii) a researcher's position in the script is a predictor of the relevance of documents; and (iii) currently, intermediaries can make very little use of situational information. The implications of these findings for system design are discussed, and a system structure presented to serve as a framework for future experimental work on the factors identified in this paper. The design calls for a dialogue with the user on his or her position in a research script and incorporates features permitting discourse‐level components of abstracts to be specified in search strategies.

This paper describes a thermal and electrical model, used at Robert Bosch GmbH for the design of an innovative motor for a water‐pump. In addition, it offers an example of a highly integrated mechatronic system. A bonded‐ferrite inner rotor has been developed with an integrated front centrifugal impeller which is driven by the magnetic interaction of a rotating field created by claw‐poles. The two phase unipolar coil arrangement is fed by an internal circuit using two MOSFETS controlled by the commutation signal from a bipolar Hall‐IC. This is the first mass‐production example of an electrical machine for an automotive application where the claw pole topology is used to realise the armature of the motor (i.e. the rotating field) and not the excitation field.

A tax based on land value is in many ways ideal, but many economists dismiss it by assuming it could not raise enough revenue. Standard sources of data omit much of the potential tax base, and undervalue what they do measure. The purpose of this paper is to present more comprehensive and accurate measures of land rents and values, and several modes of raising revenues from them besides the conventional property tax.

The paper identifies 16 elements of land's taxable capacity that received authorities either trivialize or omit. These 16 elements come in four groups.

In Group A, Elements 1‐4 correct for the downward bias in standard sources. In Group B, Elements 5‐10 broaden the concepts of land and rent beyond the conventional narrow perception, while Elements 11‐12 estimate rents to be gained by abating other kinds of taxes. In Group C, Elements 13‐14 explain how using the land tax, since it has no excess burden, uncaps feasible tax rates. In Group D, Elements 15‐16 define some moot possibilities that may warrant further exploration.

This paper shows how previous estimates of rent and land values have been narrowly limited to a fraction of the whole, thus giving a false impression that the tax capacity is low. The paper adds 14 elements to the traditional narrow “single tax” base, plus two moot elements advanced for future consideration. Any one of these 16 elements indicates a much higher land tax base than economists commonly recognize today. Taken together they are overwhelming, and cast an entirely new light on this subject.