Passive dual spin misalignment compensators

A combination dual-spin gyroscopically stabilized device is described having a spinning rotor and a non-spinning platform. Two substantially lossless mechanical resonators, resonant at the spin frequency, are orthogonally positioned on the platform for compensation for the disturbing torque acting on the platform due to rotor misalignment

The intergenerational correlation in AFDC participation: Welfare trap or poverty trap?

Several recent studies have shown that daughters whose mothers have participated in the welfare program Aid to Families with Dependent Children (AFDC), are themselves more likely to participate in AFDC when they head their own household. Other studies have shown that the earnings of parents and their children are highly correlated across generations. This suggests that any variable correlated with income such as AFDC participation will also be correlated across generations. This paper uses data from the original and youth cohorts of the National Longitudinal Surveys to investigate the question of whether the link in mother-daughter welfare participation is a causal relationship, or whether it can be explained by the expected intergenerational correlation in earnings. Several reduced-form probit equations are estimated, and attention is directed to the potential endogeneity of key explanatory variables. The empirical findings suggest that much of the observed correlation in AFDC participation across generations can be explained by the intergenerational correlation of income and other family characteristics.

An empirical analysis of the welfare magnet debate using the NLSY

This paper examines the extent to which differences in welfare generosity across states lead to interstate migration. Using microdata from the National Longitudinal Survey of Youth between 1979 and 1992, we employ a quasi-experimental design that utilizes the categorical eligibility of the welfare system. The "treatment" group consists of all those in the survey who appear eligible to participate in Aid to Families with Dependent Children. The "control" group contains those who are poor but ineligible for other reasons. The pattern of cross-state moves among poor single women with children who are likely to be eligible for benefits (treatment-group members) is compared to the pattern among other poor households. We find little evidence indicating that welfare-induced migration is a widespread phenomenon.

An Empirical Analysis of the Welfare Magnet Debate Using the NLSY

This paper examines the extent to which differences in welfare generosity across states leads to interstate migration. Using microdata from the National Longitudinal Survey of Youth (NLSY) between 1979 and 1992, we employ a quasi-experimental design that utilizes the categorical eligibility of the welfare system. The pattern of cross-state moves among poor single women with children who are likely to be eligible for benefits is compared to the pattern among other poor households. We find little evidence indicating that welfare-induced migration is a widespread phenomenon.

The Effect of Medicaid Abortion Funding Restrictions on Abortions, Pregnancies, and Births

This paper considers whether state Medicaid abortion funding restrictions affect the likelihood of getting pregnant, having an abortion, and bearing a child. Aggregate, state-level data and microdata from the National Longitudinal Survey of Youth (NLSY) are applied in the empirical work. Changes in laws resulting from Supreme Court decisions create a natural experiment which is utilized to examine fertility behavior. Multivariate models controlling for state and, in the NLSY, personal characteristics are also estimated using alternative fixed effect specifications. We find that Medicaid funding restrictions are associated with a reduction in both the number of abortions and pregnancies, resulting in either no change or a reduction in births.

A cryocooler for applications requiring low magnetic and mechanical interference

A very low-power, low-interference Stirling cryocooler is being developed based on principles and techniques described in several previous publications over the last four years. It differs in several important details from those built previously. It uses a tapered displacer based upon an analytical optimization procedure. The displacer is driven by an auxiliary piston and cylinder (rather than by mechanical linkage) using some of the working fluid itself to provide the driving force. This provides smooth, vibration-free motion, and, more importantly, allows complete mechanical and spatial separation of the cryostat from the pressure-wave generator. Either of two different pressure-wave generators can be used. One is a non-contaminating, unlubricated ceramic piston and cylinder. The other is a compressed-air-operated rubber diaphragm with motor-driven valves to cycle the pressure between appropriate limits