374 Matching Results

Search Results

Epitaxial Growth of Icosahedral Boride Semiconductors for Novel Energy Conversion Devices

Description: The chemical vapor deposition and properties of the boron-rich semiconductors B12As2 and B12P2 on 6H-SiC(0001) and silicon substrates were investigated. Crystalline, stoichiometric films were deposited between 1200 C and 1500 C using two types of reactants, hydrides (B2H6 and AsH3) for B12As2 and halides (BBr3 and PBr3) for B12P2. 6H-SiC proved to be the better substrate for B12As2 heteroepitaxy, in terms of the residual impurity concentrations. Films on Si substrates suffered from high concentrations of Si (up to 4at.%); in contrast, the Si and C concentrations in the B12As2 films deposited on 6H-SiC at 1300 C were at or below the detection limits of secondary ion mass spectrometry (SIMS). The deposition temperature was significant as films deposited at 1450 C contained high residual C and Si concentrations (>1020 cm-3), probably due to the decomposition of the substrate. The hydrogen concentration in all B12As2 films was relatively high, with a minimum concentration of 3x1019 cm-3 in undoped B12As2. SIMS measurements showed that the hydrogen concentration was directly proportional to and tracked the Si concentration, reaching values as high as 3 x 1020 cm-3. The structural properties of the B12As2 films were characterized by x-ray diffraction and transmission electron microscopy. The FWHM of typical high resolution x-ray rocking curves for the (333) peaks of the B12As2 films were 800 arcsec. The films are under tensile strain due the higher coefficient of thermal expansion for B12As2 than SiC. Rotational twins were present in B12As2 films deposited on (0001) oriented 6H-SiC substrates, as revealed by cross-sectional TEM and x-ray diffraction pole figures. While the c-plane 6H-SiC has six-fold rotational symmetry, rhombohedral B12As2 has only 3-fold symmetry (along its (111) axis), thus it randomly nucleates with two different in-plane orientations. The electrical properties of undoped and silicon-doped B12As2 deposited on semi-insulating 6H-SiC substrates were characterized ...
Date: January 3, 2006
Creator: Edgar, J.H.
Partner: UNT Libraries Government Documents Department

Clean Air Act Issues in the 109th Congress

Description: The courts and the executive branch face major decisions on clean air issues in 2006, with Congress more likely playing an oversight role. One focus is EPA's Jan. 17 2006 proposal to strengthen air quality standards for fine particles, which are estimated to cause tens of thousands of premature deaths annually. Whether the proposal is supported by the available science and what impact its implementation would have likely issues of concern. Other issues of continuing interest are EPA's 2005 decisions limiting interstate transport of air pollution and establishing cap-and-trade systems for emissions from coal-fired power plants, and the agency's proposed changes to New Source Review.
Date: May 3, 2006
Creator: McCarthy, James E.
Partner: UNT Libraries Government Documents Department

Investigation of the Rayleigh-Taylor and Richtmyer-Meshkov instabilities

Description: The present research program is centered on the experimental and numerical study of two instabilities that develop at the interface between two different fluids when the interface experiences an impulsive or a constant acceleration. The instabilities, called the Richtmyer-Meshkov and Rayleigh-Taylor instability, respectively, adversely affect target implosion in experiments aimed at the achievement of nuclear fusion by inertial confinement by causing the nuclear fuel contained in a target and the shell material to mix, leading to contamination of the fuel, yield reduction or no ignition at all. The laboratory experiments summarized in this report include shock tube experiments to study a shock-accelerated bubble and a shock-accelerated 2-D sinusoidal interface; and experiments based on the use of magnetorheological fluids for the study of the Rayleigh-Taylor instability. Computational experiments based on the shock tube experimental conditions are also reported.
Date: November 3, 2006
Creator: Bonazza, Riccardo; Anderson, Mark & Oakley, Jason
Partner: UNT Libraries Government Documents Department

Japan-U.S. Relations: Issues for Congress

Description: This report discusses the Japan - U.S. relations. The alliance, with its access to bases in Japan, where about 53,000 U.S. troops are stationed, facilitates the forward deployment of U.S. military forces in the Asia-Pacific, thereby undergirding U.S. national security strategy.
Date: May 3, 2006
Creator: Chanlett-Avery, Emma; Manyin, Mark E. & Cooper, William H.
Partner: UNT Libraries Government Documents Department

FY2006 Supplemental Appropriations: Iraq and Other International Activities; Additional Hurricane Katrina Relief

Description: This report discusses the two separate FY2006 supplemental appropriations requests submitted on February 16, 2006. The first, totaling $72.4 billion, would fund ongoing military operations in Iraq and Afghanistan ($67.9 billion), non-DOD intelligence operations ($0.3 billion), State Department operations in Iraq and various foreign aid programs, including additional assistance for Iraq ($4.2 billion), and other counter-terrorism funding for other agencies ($12 million). The other supplemental would provide $19.8 billion for recovery and reconstruction activities in hurricane affected Gulf Coast areas. Thus, Congress is to consider during the early months of 2006 a combined spending proposal of $92.2 billion.
Date: March 3, 2006
Creator: Irwin, Paul M. & Nowels, Larry
Partner: UNT Libraries Government Documents Department

Congressional Oversight

Description: Congressional oversight of policy implementation and administration, which has occurred throughout the U.S. government experience under the Constitution, takes a variety of forms and utilizes various techniques. These range from specialized investigations by select committees to annual appropriations hearings, and from informal communications between Members or congressional staff and executive personnel to the use of extra congressional mechanisms, such as offices of inspector general and study commissions. Oversight, moreover, is supported by a variety of authorities—the Constitution, public law, and chamber and committee rules—and is an integral part of the system of checks and balances between the legislature and the executive
Date: January 3, 2006
Creator: Kaiser, Frederick M.
Partner: UNT Libraries Government Documents Department

Foreign Science and Engineering Presence in U.S. Institutions and the Labor Force

Description: The increased presence of foreign students in graduate science and engineering programs and in the scientific workforce has been and continues to be of concern to some in the scientific community. Enrollment of U.S. citizens in graduate science and engineering programs has not kept pace with that of foreign students in those programs. In addition to the number of foreign students in graduate science and engineering programs, a significant number of university faculty in the scientific disciplines are foreign, and foreign doctorates are employed in large numbers by industry. This report examines these issues and discusses their policy implications.
Date: January 3, 2006
Creator: Matthews, Christine M.
Partner: UNT Libraries Government Documents Department

Clean Air Act Issues in the 109th Congress

Description: Major amendments to the Clean Air Act were among the first items on the agenda of the 109th Congress, with S. 131 (the Clear Skies Act) scheduled for markup by the Senate Environment and Public Works Committee March 9. The most prominent air quality issues discussed in this report are; Clear Skies / Multi-Pollutant Legislation, Mercury from Power Plants, New Source Review (NSR), MTBE and Ethanol, Ozone Nonattainment Area Deadlines, Conformity of Transportation Plans and SIPs, Hurricanes Katrina and Rita.
Date: January 3, 2006
Creator: McCarthy, James E.
Partner: UNT Libraries Government Documents Department

Federal Student Aid Need Analysis System: Background, Description, and Legislative Action

Description: A federal need analysis system underlies the annual allocation of billions of dollars (more than $73 billion in FY2005) in student financial aid supported by Title IV of the Higher Education Act (HEA) (P.L. 89-329, as amended). The system has regularly been characterized by many as too complex, creating a barrier for students seeking financial assistance, especially low-income students. This report provides an overview of the federal need analysis system, including a discussion of recent legislative changes and proposals.
Date: February 3, 2006
Creator: Mercer, Charmaine
Partner: UNT Libraries Government Documents Department

Jamaica: Political and Economic Conditions and U.S. Relations

Description: Although Jamaica has a stable parliamentary democracy and is a middle-income developing country, the government of Prime Minister P.J. Patterson faces several significant challenges. These include a violent crime wave fueled by gangs and drug trafficking; high external debt, estimated at 135% of gross domestic product, that could constrain the government’s social expenditures; and an adult HIV/AIDS infection rate of over 1%. This report discusses U.S. relations with Jamaica, which are close and characterized by significant economic linkages and cooperation on such bilateral issues as anti-drug trafficking measures, hurricane reconstruction support, and efforts to combat the AIDS epidemic.
Date: February 3, 2006
Creator: Sullivan, Mark P.
Partner: UNT Libraries Government Documents Department

HIV/AIDS International Programs: Appropriations, FY2003-FY2006

Description: This report briefly discusses appropriations for international HIV/AIDS programs. FY2006 Appropriations for Foreign Operations (P.L. 109-102), Labor/HHS/Education (H.Rept. 109-300), Defense, and Agriculture (P.L. 109-97) provide more than $3.4 billion for international HIV/AIDS, tuberculosis (TB), and malaria initiatives. The largest portion of the funds is provided through P.L. 109-102, which directs more than $2.8 billion to fighting the three diseases.
Date: January 3, 2006
Creator: Salaam-Blyther, Tiaji
Partner: UNT Libraries Government Documents Department

CFTC Reauthorization in the 109th Congress

Description: This report provides brief summaries of the issues in the 2005 reauthorization legislation, including (1) the market in security futures, or futures contracts based on single stocks, which were authorized by the CFMA, but trade in much lower volumes than their proponents had hoped, (2) regulation of energy derivatives markets, where some see excessive price volatility and a lack of effective regulation, and (3) the legality of futures-like contracts based on foreign currency prices offered to retail investors.
Date: January 3, 2006
Creator: Jickling, Mark
Partner: UNT Libraries Government Documents Department