A preliminary Monte-Carlo analysis of the reflection of an imploding hemispherical shock wave similar to that generated in the UTIAS implosion driven hypervelocity launcher or shock tube

Cold wall and multibody collision effects on reflection of imploding shock waves using Monte Carlo method and molecular dynamic

When Will the Gender Gap in Retirement Income Narrow?

Among recent retirees, women receive substantially less retirement income from Social Security and private pensions than men. Increases in women's labor market attachment and earnings relative to men over the past 50 years provide some optimism for an improvement in female retirement income, particularly for married women. This study shows that women's income from Social Security and private pensions has improved only slightly relative to men over the past 25 years. Using data on people approaching retirement age over the next 20 years, prospects for future improvement are investigated. One of the main conclusions is that pension income among women (particularly married women) will rise sharply relative to men's over the next few decades, but a substantial gap could remain even if women close the gap in experience and salaries.

Wages, racial composition, and quality sorting in labor markets

This paper examines the relationship between wage rates and the racial composition of jobs, using large cross-sectional and longitudinal samples constructed from monthly Current Population Surveys for 1983-92. Support is found for a "quality sorting" model that posits an equilibrium in which the racial composition of jobs serves as a skill index of unmeasured labor quality. Estimation of standard wage-level equations shows that wages of both black and white workers are substantially lower in occupations with a high density of blacks. Consistent with the quality sorting hypothesis, the magnitude of the relationship is reduced sharply after accounting for occupational skill measures. Longitudinal wage-change estimates controlling for person-specific quality indicate little if any causal effect of racial composition on wages. Estimates of racial discrimination are reduced only moderately after accounting for racial composition; unexplained differentials occur within occupations or reflect inter-occupational differences uncorrelated with racial composition and occupational skill measures.

Determinants and Effects of Employer Matching Contributions in 401(k) Plans

This paper uses data from the April 1993 Pension Supplements to the Current Population Survey to investigate the impact of employer matching and employee tenure on participation levels in 401(k) plans. While earlier studies examine similar issues, this study makes several advances. First, consistent with the theory that employers may use matching contributions to satisfy nondiscrimination rules, the study shows that correcting for the endogeneity of employer matching substantially increases the estimated effect of matching on participation levels. Second, the study provides evidence that the large positive association between employee tenure and 401(k) participation is because 'stayers' tend to be 'savers'.

The Impact of Rising 401(k) Pension Coverage on Future Pension Income

Using data from the 1992 Health and Retirement Survey and the 1992 Survey of Consumer Finances, this study compares the level of benefits in 401(k), non-401(k) defined contribution (DC), and defined benefit (DB) plans. Based on current pension information regarding pension contribution rates or benefit formulas, it is shown that a shift to 401(k) plans will reduce the average level of pension benefits for low income workers but have relatively small effects on middle and high income workers. A shift to 401(k) plans would also increase the variance of benefits among low income workers, though the effect would be negligible for middle and high income workers.pension plan; defined benefit; defined contribution

The Growth of Participant Direction in Defined Contribution Plans

Since 1990, most pension plans have shifted the responsibility for directing pension assets to the employee. This study summarizes some of the possible explanations for this rapid shift toward participant direction and uses IRS Form 5500 data to investigate the effect of worker and plan characteristics on the likelihood of making a switch. The study also estimates the effect of a switch to participant direction on employee contribution and asset allocation behavior. The analysis reveals that collective bargaining and pension investments in employer stock reduce the chance of a switch to participant direction, whereas below average return performance increases the chance. Also, a switch to participant direction increases employee contributions to the pension and reduces the share of assets invested in employer securities.participant direction, pensions, employer stock

Some aspects of analytical chemistry as applied to water quality assurance techniques for reclaimed water: The potential use of X-ray fluorescence spectrometry for automated on-line fast real-time simultaneous multi-component analysis of inorganic pollutants in reclaimed water

The potential use of isotopically excited energy dispersive X-ray fluorescence (XRF) spectrometry for automated on line fast real time (5 to 15 minutes) simultaneous multicomponent (up to 20) trace (1 to 10 parts per billion) analysis of inorganic pollutants in reclaimed water was examined. Three anionic elements (chromium 6, arsenic and selenium) were studied. The inherent lack of sensitivity of XRF spectrometry for these elements mandates use of a preconcentration technique and various methods were examined, including: several direct and indirect evaporation methods; ion exchange membranes; selective and nonselective precipitation; and complexation processes. It is shown tha XRF spectrometry itself is well suited for automated on line quality assurance, and can provide a nondestructive (and thus sample storage and repeat analysis capabilities) and particularly convenient analytical method. Further, the use of an isotopically excited energy dispersive unit (50 mCi Cd-109 source) coupled with a suitable preconcentration process can provide sufficient sensitivity to achieve the current mandated minimum levels of detection without the need for high power X-ray generating tubes

A comparison of surface sensible and latent heat fluxes from aircraft and surface measurements in FIFE 1987

Surface fluxes of sensible and latent heat over a tall-grass prairie in central Kansas, as measured by 22 surface stations during FIFE 1987, are compared with values gained indirectly by linear extrapolation of aircraft-measured flux profiles to the surface. The results of 33 such comparisons covering the period 26 June to 13 October 1987 indicate that the sensible heat flux profiles were generally more linear with less scatter in the measurements at each level than were the latent heat flux profiles, the profile extrapolations of sensible heat flux in general underestimate the surface averages by about 30 percent, with slightly better agreement during periods of small flux, and the profile extrapolations of latent heat flux in general underestimate the surface averages by about 15 percent, with overestimates during periods of small fluxes (dry conditions) and overestimates during periods of large fluxes (moist conditions). Possible origins of the differences between the two sets of measurements are discussed, as directions for further research