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

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

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.

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

The Value of Phased Retirement

This paper examines how phased retirement plans in higher education create value for both the institution and individual faculty, based upon evidence from the Survey of Changes in Faculty Retirement Policies and an in-depth case study of the University of North Carolina system. Faculty benefit by receiving improved opportunities for part-time work and by having the ability to make a smoother transition to retirement. The policy is clearly of great value to the 25 to 35 percent of UNC faculty who opt for phased over full retirement. The biggest payoff to the university is an increase in the odds that low-performing faculty will start the retirement process earlier. Universities also anticipate increased flexibility in managing faculty employment and compensation; phased retirement is most likely to be observed on campuses where a high percentage of faculty has tenure.

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

Declining Unionization in Construction: The Facts and the Reasons

This paper documents and examines the forces behind the decline of unionization in the construction industry. The proportion of construction workers belonging to unions has dropped from slightly less than one-half in 1966 to less than one-third in 1984. The employment share of union contractors has declined even further because of the fraction of union members working in the open shop rose from 29 to 46 percent between 1973 and 1981. Initially, an important factor in the initial decline in percentage unionized was the growth in the union-nonunion wage gap between 1967 and 1973. However, the gap did not widen any further after 1973 and actually has narrowed substantially since 1978. A key subsequent factor has been the erosion of the productivity advantage of union contractors, which dropped substantially between 1972 and 1977 and vanished by 1982. The decline of unionization is unrelated to changes in worker characteristics or changes in the mix and location of construction activity.

A note on muscle composition and colour of Holstein-Friesian, Piedmontese × Holstein-Friesian and Romagnola × Holstein-Friesian steers.

peer-reviewedHolstein-Friesian (HF), Piedmontese × Holstein-Friesian (PM) and Romagnola × Holstein-Friesian (RO) steers were compared for muscle composition and colour. A total of 120 steers in a 3 breed types (HF, PM and RO) × 2 feeding levels (low and high) × 2 finishing periods (short, S and extended, E) factorial experiment were used. Three samples of m. longissimus were taken for chemical analysis, measurement of drip loss and Hunterlab colour measurements. Muscle moisture and protein concentrations were lower, and lipid concentration was higher for HF than for PM and RO, which were similar. There were no effects of feeding level on chemical composition, but after blooming all colour values except hue were lower for the higher feeding level. The E finishing period reduced moisture, protein, drip-loss, L (lightness), a (redness) and chroma values. It is concluded that PM and RO had similar muscle composition but HF had a higher lipid concentration. Feeding level had few effects on muscle composition, but extended finishing increased all measures of fatness and reduced colour values

Ecology of fishes in Upper Newport Bay, California: seasonal dynamics and community structure

A total of 366 bimonthly (January 1978-January 1979) samples taken with six types of gear (otter trawl, gill net, bag seine, small seine, drop net, square enclosure - all with replication except the gill net) at four stations in upper Newport Bay, California yielded 51,816 fishes belonging to 46 species and weighing over 353 kg. Atherinops affinis (topsmelt) was the most abundant species accounting for 76% of total individuals. Seven species, all of low trophic levels, made up over 97% of the total catch. Mugil cephalus (striped mullet) ranked first in biomass (= 36% of the total) with six species accounting for more than 80% of the total biomass. The largest number of individuals (71%) was collected with the bag seine, the greatest number of species (35) was captured with the otter trawl and the largest percentage of the biomass (56%)was obtained with the gill net. Species richness, number of individuals and biomass were lowest in January (1978 or 1979) or March and highest in July (numbers, biomass) or September (species). Bimonthly diversity (H') values ranged from 0.48 to 2.17 (overall value 1.05) and tended to be inversely related to abundance levels. Species richness was greatest at Station 4 (the lowermost station) and least at Station 1 (the uppermost station). Numbers of individuals and biomass peaked at Station 2 and reached lowest levels at Station 1. Length-frequency analysis of six of the most abundant species indicated utilization of the upper bay by two or more stages in the life history of these species. More than 92,000 eggs belonging to seven taxa and an unknown category and 426 larvae from 20 taxa were collected with a 0.5 m net mounted on an epibenthic sled during the same bimonthly periods and at the same stations as the juvenile/adult samples. Most of the eggs were collected at Station 2 in May with the numbers overwhelmingly dominated by those of Anchoa compressa (deepbody anchovy) (99.7% of total numbers). The most abundant larva was that of Clevelandia ios (arrow goby). Nearly 60% of the total larval catch was made up of members of the family Gobiidae. Larval taxa and individuals were fewest in January (1978). The number of taxa was highest in March, September and January (1979) whereas larval numbers peaked in May. The number of taxa and of individual larvae varied only slightly among the four stations. Asymptotic species accumulation curves indicated adequate sampling of juvenile/adult fishes. Cluster analysis produced eight species groups of resident and periodic species that variously utilize the three main habitats (channel, inshore, pannes) in the upper bay. Species richness and abundance were positively correlated with both temperature and salinity. Temperature, salinity and depth of capture were frequently correlated with individual species abundances and were used in combination to partially explain the spatial utilization of species and species groups. The upper bay fish community is important and worthy of preservation for at least three reasons: 1) it contains species assemblages not duplicated in any other coastal environment; 2) it contains life history stages of a variety of coastal fish species; and 3) it contains large populations of small, low-trophic level species and juveniles of other species which serve as forage for larger, predatory species that are frequently of economic importance. Members of the fish community respond noticeably to altered environmental conditions such as the heavy rainfall (and accompanying low salinity and high turbidity) that occurred during the early months of 1978. The short and long term, as yet often unpredictable, fluctuations in the populations emphasize the need for periodic monitoring and for the development of a mathematical model of the fish community if it is to be thoroughly understood and properly managed. (102pp.