Ride quality and international standard ISO 2631 (Guide for the evaluation of human exposure to whole-body vibration)

The evolution of the standard, which is aimed at promoting research and production of more data, and providing some design guidance, is outlined and its contents summarized. Some of the assumptions and information on which it is based are analyzed. Its application to vehicle ride quality is considered in the context of the safety, efficiency and comfort of crew and passengers. The importance of establishing the precise criteria against which vibration limits are required is underlined, particularly the difficulties of first defining comfort and then postulating appropriate levels. Some current and future work related to improving the standard is outlined and additional suggestions offered

Electric welding torch Patent

Development of electric weeding torch with casing on one end to form inert gas shiel

Weakly nonlinear waves in magnetized plasma with a slightly non-Maxwellian electron distribution. Part 1, Stability of solitary waves

Weakly nonlinear waves in strongly magnetized plasma with slightly non-isothermal electrons are governed by a modified Zakharov–Kuznetsov (ZK) equation, containing both quadratic and half-order nonlinear terms, which we refer to as the Schamel–Korteweg–de Vries–Zakharov–Kuznetsov (SKdVZK) equation. We present a method to obtain an approximation for the growth rate, γ, of sinusoidal perpendicular perturbations of wavenumber, k, to SKdVZK solitary waves over the entire range of instability. Unlike for (modified) ZK equations with one nonlinear term, in this method there is no analytical expression for kc, the cut-off wavenumber (at which the growth rate is zero) or its corresponding eigenfunction. We therefore obtain approximate expressions for these using an expansion parameter, a, related to the ratio of the nonlinear terms. The expressions are then used to find γ for k near kc as a function of a. The approximant derived from combining these analytical results with the ones for small k agrees very well with the values of γ obtained numerically. It is found that both kc and the maximum growth rate decrease as the electron distribution becomes progressively less peaked than the Maxwellian. We also present new algebraic and rarefactive solitary wave solutions to the equation

Some efficient methods for obtaining infinite series solutions of n-th order linear ordinary differential equations

The use of the theta-operator method and generalized hypergeometric functions in obtaining solutions to nth-order linear ordinary differential equations is explained. For completeness, the analysis of the differential equation to determine whether the point of expansion is an ordinary point or a regular singular point is included. The superiority of the two methods shown over the standard method is demonstrated by using all three of the methods to work out several examples. Also included is a compendium of formulae and properties of the theta operator and generalized hypergeometric functions which is complete enough to make the report self-contained

Can Union Labor Ever Cost Less?

This paper examines the effect of unions on efficiency by estimating cost function systems over three different sets of construction projects. The results show that union contractors have greater economies of scale. This gives them a cost advantage in large commercial office buildings, but in school and hospital construction, nonunion contractors have lower costs at all output levels. Despite the cost differences, profits for nonunion contractors in school and hospital construction are no higher than those for union contractors because the burden of higher union costs is shifted to buyers.

Productivity Levels and Productivity Change Under Unionism

This paper examines how unions affect the rate of productivity change over time. The direction of union impact cannot be predicted from economic theory. Firms may tend to select more productive technologies to offset the cost of higher union wages or they may tend to select less productive technologies to keep union wage demands in line. Evidence from manufacturing indicates that unions have not affected productivity growth, but in the construction industry productivity growth has been much slower in areas where there is a high initial level of unionization or where unionization is growing.

Human Resource Policies and Union-Nonunion Productivity Differences

Many researchers in both economics departments and business schools recently have become interested in examining how much of an effect human resource decisions and policies have on firm performance. This paper surveys the literature on unionism and productivity and discusses its implications for future research on more general issues. The main focus is on (I) conclusions as to whether unions raise or lower productivity and (2) procedures used to identify the channels through which unions affect productivity. The studies of unions and productivity have documented large productivity differences between seemingly comparable union and nonunion establishments. In many cases unionism is associated with higher productivity, especially when unionized firms are in a competitive environment. However, the mechanisms responsible for union-nonunion productivity differences in each study remain poorly understood, either because detailed information on how unions affected company decisions was not available or because the available information produced inconclusive results. These conclusions suggest that human resource policies can have a very large effect on financial outcomes, but our ability to estimate the magnitude of that effect for a particular policy is currently very limited.

Self-acting lift-pad geometry for circumferential seals: A noncontacting concept

A segmented circumferential seal with lift pads for hydrodynamic action was analyzed over ranges of speed and sealed pressure. Performance predictions, which predicted noncontact operation for speeds as high as 600 revolutions per second at sealed pressures to 86 N/sq cm, are discussed. Performance tests were performed on the seals and compared with the performance predictions

Silicon sheet with molecular beam epitaxy for high efficiency solar cells

The capabilities of the new technique of Molecular Beam Epitaxy (MBE) are applied to the growth of high efficiency silicon solar cells. Because MBE can provide well controlled doping profiles of any desired arbitrary design, including doping profiles of such complexity as built-in surface fields or tandem junction cells, it would appear to be the ideal method for development of high efficiency solar cells. It was proposed that UCLA grow and characterize silicon films and p-n junctions of MBE to determine whether the high crystal quality needed for solar cells could be achieved

Self-acting geometry for noncontact seals

Performance ot two self acting seal designs for a liquid oxygen (LOX) turbopump was predicted over ranges of pressure differential and speed. Predictions were compared with test results. Performance of a radial face seal for LOX was predicted up to 448 N/cu cm and 147 m/sec. Performance of a segmented circumferential seal for helium was predicted up to 69 N/cu cm and 189 m/sec. Results confirmed predictions of noncontact operation. Qualitative agreement between test and analysis was found. The LOX face seal evidently operated with mostly liquid in the self acting geometry and mostly gas across the dam