An evaluation of the relative fire hazards of jet A and jet B for commercial flight

The relative fire hazards of Jet A and Jet B aircraft fuels are evaluated. The evaluation is based on a consideration of the presence of and/or the generation of flammable mixtures in fuel systems, the ignition characteristics, and the flame propagation rates for the two fuel types. Three distinct aircraft operating regimes where fuel type may be a factor in fire hazards are considered. These are: (1) ground handling and refueling, (2) flight, and (3) crash. The evaluation indicates that the overall fire hazards for Jet A are less than for Jet B fuel

Caging Mechanism for a drag-free satellite position sensor

A disturbance compensation system for satellites based on the drag-free concept was mechanized and flown, using a spherical proof mass and a cam-guided caging mechanism. The caging mechanism controls the location of the proof mass for testing and constrains it during launch. Design requirements, design details, and hardware are described

Elastic suspension of a wind tunnel test section

Experimental verification of the theory describing arbitrary motions of an airfoil is reported. The experimental apparatus is described. A mechanism was designed to provide two separate degrees of freedom without friction or backlash to mask the small but important aerodynamic effects of interest

Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets

A photomicrographic technique for investigating eupercooled. water droplets has been devised and. used. to determine the spontaneous freezing temperatures of eupercooled. water droplets of the size ordinarily found. in the atmosphere. The freezing temperatures of 4527 droplets ranging from 8.75 to 1000 microns in diameter supported on a platinum surface and 571 droplets supported on copper were obtained. The average spontaneous freezing temperature decreased with decrease in the size of the droplets. The effect of size on the spontaneous freezing temperature was particularly marked below 60 microns. Frequency-distribution curves of the spontaneous freezing temperatures observed for droplets of a given size were obtained. Although no droplet froze at a temperature above 20 0 F, all droplets melted at 32 F. Results obtained with a copper support did not differ essentially from those obtained with a platinum surface

The Puzzle of the Antebellum Fertility Decline in the United States: New Evidence and Reconsideration

All nations that can be characterized as developed have undergone the demographic transition from high to low levels of fertility and mortality. Most presently developed nations began their fertility transitions in the late nineteenth or early twentieth centuries. The United States was an exception. Evidence using census-based child-woman ratios suggests that the fertility of the white population of the United States was declining from at least the year 1800. By the end of the antebellum period in 1860, child-woman ratios had declined 33 percent. There is also indication that the free black population was experiencing a fertility transition. This transition was well in advance of significant urbanization, industrialization, and mortality decline and well in advance of every other presently developed nation with the exception of France. This paper uses census data on county-level child-woman ratios to test a variety of explanations on the antebellum American fertility transition. It also uses micro data from the IPUMS files for 1850 and 1860. A number of the explanations, including the land availability hypothesis, the local labor market-child default hypothesis, and the life cycle saving hypothesis, are consistent with the data, but nuptiality, not one of the usual explanations, emerges as likely very important.

American Indian Mortality in the Late Nineteenth Century: The Impact of Federal Assimilation Policies on a Vulnerable Population

Under the urging of late nineteenth-century humanitarian reformers, U.S. policy toward American Indians shifted from removal and relocation efforts to state-sponsored attempts to "civilize" Indians through allotment of tribal lands, citizenship, and forced education. There is little consensus, however, whether and to what extent federal assimilation efforts played a role in the stabilization and recovery of the American Indian population in the twentieth century. In this paper, we rely on a new IPUMS sample of the 1900 census of American Indians and census-based estimation methods to investigate the impact of federal assimilation policies on childhood mortality. We use children ever born and children surviving data included in the censuses to estimate childhood mortality and [responses to] several questions unique to the Indian enumeration [including tribal affiliation, degree of "white blood", type of dwelling, ability to speak English, and whether a citizen by allotment] to construct multivariate models of child mortality. The results suggest that mortality among American Indians in the late nineteenth century was very high - approximately 62% [standardize as % or percent throughout] higher than that for the white population. The impact of assimilation policies was mixed. Increased ability to speak English was associated with lower child mortality, while allotment of land in severalty was associated with higher mortality. The combined effect was a very modest four percent [as above] decline in mortality. As of 1900, the government campaign to assimilate Indians had yet to result in a significant decline in Indian mortality while incurring substantial economic and cultural costs.

Nurturant and Provider Role Saliency of Fathers in Traditional and Non-Traditional Families

Although identity theory, out of symbolic interactionism, has been suggested to be the most useful framework for understanding the changing roles of fathers, little systematic research has been done to apply this framework to fathering roles, and especially the specific roles of provider and nurturer. In this study, seven fathers, four in economically traditional families and three in economically non-traditional families, were interviewed using a structured interview schedule. This interview focused on the saliency of the roles of provider and nurturer for fathers and the strain in fulfilling aspects of both as predicted by identity theory. The content analysis revealed how fathers are experiencing role conflict and how this conflict varies for economically traditional and nontraditional fathers. Implications for social workers as they strive to understand and serve fathers and their families are discussed. As this study is exploratory, future research could extend an identity theory understanding of fatherhood