Author: Walter Jackson LackeyPublisher:
ISBN:
Category : Chemical processes
Languages : en
Pages :
Book Description
Ultrafine Microstructure Composites Prepared by Chemical Vapor Deposition
Author: Walter Jackson LackeyPublisher:
ISBN:
Category : Chemical processes
Languages : en
Pages :
Book Description
Ultrafine Microstructure Composites Prepared by Chemical Vapor Deposition
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 33
Book Description
It is our goal to develop an analytical model which predicts the experimental conditions which permit the preparation of ultrafine microstructure ceramic composites by chemical vapor deposition (CVD). The model is to be based on classical thermodynamics, mass transport, kinetic, nucleation, and growth theory. The model will be validated for two dispersed phase composite systems. One system will be boron nitride plus aluminum nitride. The other will be hafnium diboride plus silicon carbide. The BN + AlN system is of interest for radomes, windows, and tribological applications while HfB2 + SiC offers potential as a high temperature oxidation resistant material including oxidation protective coatings for carbon-carbon composites. Thermodynamic analyses of the BN + AlN and the HfB2 + SiC systems have been completed. These computerized studies indicate that both composite systems can be prepared by codeposition using commercially available, conventional reagents.
Scientific and Technical Aerospace Reports
Author: Research Opportunities for Materials with Ultrafine Microstructures
Author: Publisher:
ISBN:
Category : Science
Languages : en
Pages : 138
Book Description
Materials with nanoscale structure (i.e. a structure of less than 100 nanometers in size) represent a new and exciting field of research. These materials can be produced in many ways, possess a number of unique properties compared with coarser-scaled structures, and have several possible applications with significant technological importance. Based on a state-of-the-art survey of research findings and commercial prospects, this new book concludes that much work remains to be done in characterizing these structures and their exceptional properties, and presents recommendations for the specific research and development activities needed to fill these gaps in our understanding.
Energy Research Abstracts
Author: Technical Reports Awareness Circular : TRAC.
Author: Use of Services for Family Planning and Infertility, United States, 1982
Author: Gerry E. HendershotPublisher:
ISBN: 9780840602220
Category : Birth control
Languages : en
Pages : 982
Book Description
The 1982 statistics on the use of family planning and infertility services presented in this report are preliminary results from Cycle III of the National Survey of Family Growth (NSFG), conducted by the National Center for Health Statistics. Data were collected through personal interviews with a multistage area probability sample of 7969 women aged 15-44. A detailed series of questions was asked to obtain relatively complete estimates of the extent and type of family planning services received. Statistics on family planning services are limited to women who were able to conceive 3 years before the interview date. Overall, 79% of currently mrried nonsterile women reported using some type of family planning service during the previous 3 years. There were no statistically significant differences between white (79%), black (75%) or Hispanic (77%) wives, or between the 2 income groups. The 1982 survey questions were more comprehensive than those of earlier cycles of the survey. The annual rate of visits for family planning services in 1982 was 1077 visits /1000 women. Teenagers had the highest annual visit rate (1581/1000) of any age group for all sources of family planning services combined. Visit rates declined sharply with age from 1447 at ages 15-24 to 479 at ages 35-44. Similar declines with age also were found in the visit rates for white and black women separately. Nevertheless, the annual visit rate for black women (1334/1000) was significantly higher than that for white women (1033). The highest overall visit rate was for black women 15-19 years of age (1867/1000). Nearly 2/3 of all family planning visits were to private medical sources. Teenagers of all races had higher family planning service visit rates to clinics than to private medical sources, as did black women age 15-24. White women age 20 and older had higher visit rates to private medical services than to clinics. Never married women had higher visit rates to clinics than currently or formerly married women. Data were also collected in 1982 on use of medical services for infertility by women who had difficulty in conceiving or carrying a pregnancy to term. About 1 million ever married women had 1 or more infertility visits in the 12 months before the interview. During the 3 years before interview, about 1.9 million women had infertility visits. For all ever married women, as well as for white and black women separately, infertility services were more likely to be secured from private medical sources than from clinics. The survey design, reliability of the estimates and the terms used are explained in the technical notes.
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