Study of catalyst cured LaRC-160/Celion 6000 composites

LaRC 160 polyimide was modified with a high temperature peroxide catalyst, USP-138, in an attempt to reduce the final cure temperature to below 316 C. This effort was directed at obtaining a material for 177 C use that would cure at similar temperatures to a high performance epoxy while still maintaining the good moisture resistance of a polymide material. Attempts to prepare a laminate made from Celion 6000 fiber and 5% catalyzed LaRC 160 resin gave a material with minimal properties after curing at 193 C. Acceptable properties were not obtained until a final cure temperature of 260 C was used. A control laminate containing no catalyst and cured under the same conditions had only half the level of shear strength. The catalyzed LaRC 160 prepreg was also used to examine the possibility of shortening the conventional LaRC 160 cure at 316 C. Maximum properties were obtained using a 2.5% catalyzed product with a final cure temperature of 316 C held for fifteen minutes. Differences in properties between catalyzed and uncatalyzed product disappeared, however, when the cure time at 316 C was extended to 45 minutes

The effect of mixing, radiation, and finite rate combustion upon the flow field and surroundings of the exhaust plumes of rocket engines burning RP1 /kerosene/ and liquid oxygen

Shear layer mixing, hydrocarbon oxidation, and carbon cloud radiation models for liquid rocket engine exhaust plume analysi

Cooperatives: A Competitive Yardstick for Health Care

�As the national debate over health care reform continues, consideration is increasingly being given to the use of consumer-focused health care cooperatives as a key strategy for providing access to affordable health care and insurance for the millions of consumers and small businesses not presently able to afford or obtain adequate health care. Historically in many other sectors, the cooperative form of business has been successfully adapted by farmers, consumers, businesses, and public bodies as an effective strategy for attaining scale, lowering costs, improving incomes, providing services, and creating a better functioning marketplace. Reasons for forming cooperatives and analysis of cooperative movements can typically be traced to presence of a market failure (Schrader). Thus, as this nation seeks to remedy the plight of millions of uninsured urban and rural residents, cooperative models are properly on the table,

Process development of shaped magnesium- lithium castings

Casting process development for ternary magnesium- lithium-silicon allo

Application of advanced on-board processing concepts to future satellite communications systems: Bibliography

Abstracts are presented of a literature survey of reports concerning the application of signal processing concepts. Approximately 300 references are included

Review of alternative fuels data bases

Based on an analysis of the interaction of fuel physical and chemical properties with combustion characteristics and indicators, a ranking of the importance of various fuel properties with respect to the combustion process was established. This ranking was used to define a suite of specific experiments whose objective is the development of an alternative fuels design data base. Combustion characteristics and indicators examined include droplet and spray formation, droplet vaporization and burning, ignition and flame stabilization, flame temperature, laminar flame speed, combustion completion, soot emissions, NOx and SOx emissions, and the fuels' thermal and oxidative stability and fouling and corrosion characteristics. Key fuel property data is found to include composition, thermochemical data, chemical kinetic rate information, and certain physical properties

Analytical Study of Gravity Effects on Laminar Diffusion Flames

A mathematical model is presented for the description of axisymmetric laminar-jet diffusion flames. The analysis includes the effects of inertia, viscosity, diffusion, gravity and combustion. These mechanisms are coupled in a boundary layer type formulation and solutions are obtained by an explicit finite difference technique. A dimensional analysis shows that the maximum flame width radius, velocity and thermodynamic state characterize the flame structure. Comparisons with experimental data showed excellent agreement for normal gravity flames and fair agreement for steady state low Reynolds number zero gravity flames. Kinetics effects and radiation are shown to be the primary mechanisms responsible for this discrepancy. Additional factors are discussed including elipticity and transient effects

A Comparison of Attitudes about Aggression, Sexuality and Social Support in the Peer Relationships of Sexually Abused and Nonabused Female Adolescents

There is a paucity of research examining whether adolescents with a history of sexual abuse develop different norms or standards for acceptable behavior in their peer relationships. The trauma literature suggests that intervening variables such as perceived social support, interpretations of violence, and interpersonal attitudes may be relevant to the study of sexual abuse. The goal of this study was to examine the relationship between a history of sexual abuse, relational attitudes about aggression and sexuality, and the interpersonal factors of social support and negative interaction in adolescent peer relationships. Two groups of female subjects between 13 and 17 years of age participated in the study: 28 had experienced sexual abuse; 33 had no known history of abuse and served as the control group. Information on the sexually abused group was obtained using initial assessment data from a child abuse treatment facility. Subjects for the control group were recruited from a medical clinic. Evaluation of both groups included the measurement of the study variables using the Network of Relationship Inventory (NRI) and the Relationship Attitudes Survey for Adolescents (RASA). Analysis of Variance (ANOVA), Analysis of Covariance (ANCOVA), and Semipartial and Pearson Correlations were conducted on the data. The major finding of this study revealed a difference in levels of dysfunctional sexual attitudes between the sexually abused and nonabused groups: results from an ANCOVA analysis showed a significant effect for abuse history (

Multiple-scale turbulence modeling of boundary layer flows for scramjet applications

As part of an investigation into the application of turbulence models to the computation of flows in advanced scramjet combustors, the multiple-scale turbulence model was applied to a variety of flowfield predictions. The model appears to have a potential for improved predictions in a variety of areas relevant to combustor problems. This potential exists because of the partition of the turbulence energy spectrum that is the major feature of the model and which allows the turbulence energy dissipation rate to be out of phase with turbulent energy production. The computations were made using a consistent method of generating experimentally unavailable initial conditions. An appreciable overall improvement in the generality of the predictions is observed, as compared to those of the basic two-equation turbulence model. A Mach number-related correction is found to be necessary to satisfactorily predict the spreading rate of the supersonic jet and mixing layer

A mathematical model for jet engine combustor pollutant emissions

Mathematical modeling for the description of the origin and disposition of combustion-generated pollutants in gas turbines is presented. A unified model in modular form is proposed which includes kinetics, recirculation, turbulent mixing, multiphase flow effects, swirl and secondary air injection. Subelements of the overall model were applied to data relevant to laboratory reactors and practical combustor configurations. Comparisons between the theory and available data show excellent agreement for basic CO/H2/Air chemical systems. For hydrocarbons the trends are predicted well including higher-than-equilibrium NO levels within the fuel rich regime. Although the need for improved accuracy in fuel rich combustion is indicated, comparisons with actual jet engine data in terms of the effect of combustor-inlet temperature is excellent. In addition, excellent agreement with data is obtained regarding reduced NO emissions with water droplet and steam injection