Reliability Predictions and System Support Costs

A case study demonstrates that spares requirements based on operational reliability predictions result in the system being undersupported during its burn-in and useful-life phases by average factors of 42.2 and 4.22, respectively. However, systems spares requirements based on logistics estimates result in the system being oversupported during its burn-in phase by an average factor of 4.26 with this factor probably increasing as the system enters the useful-life phase of its life cycle. Adequate system support within predetermined cost estimates will be achieved only when reliability predictions are accurate and when systems spares requirements are computed separately for the equipment burn-in phase and useful-life phase.     

The use of ethylenediaminetetraacetic acid or nitrilo-triacetic acid as masking agents in the determination of palladium with dimethylglyoxime or quinaldic acid

The use of complexing agents to mask interference in the gravimetric determination of palladium has been studied. Ethylenediaminetetraacctic acid was used to complex interfering ions in the determination of palladium with dimethylglyoxime, and nitrilotriacetic acid has been employed as a masking agent in the determination of palladium with quinaldic acid. From 15 to 150 mg of palladium were determined. All the metals tested do not interfere with the exception of gold which s reduced by the complexing agents and has to be removed prior to the determination. The procedures are rapid, simple and accurate.     

Gunshot residue analysis: An applicability study

Test firings were performed using 20 handguns and 20 ammunitions of various calibers and types to show the degree of reliability in the gunshot residue procedures described by D. B. Dahl and P. F. Lott (Microchem. J., 1987, 35, 347–359). The procedure entails analysis of a collected swab for gunpowder stabilizers by HPLC with electrochemical detection and analysis of the metallic content by graphite furnace atomic absorption.     

Undergraduate research opportunities in neutron activation analysis for local,regional and international students

Neutron activation analysis (NAA) remains an excellent technique to introduce undergraduate students to nuclear science and engineering coming from different academic areas. The NAA methods encompass an appreciation of basic reactor engineering concepts, radiation safety, nuclear instrumentation and data analysis. At the Nuclear Engineering Teaching Lab at the University of Texas at Austin we have continued to provide opportunities through outreach programs to Huston-Tillotson University in Austin and Florida Memorial University in Miami Gardens, both Historically Black Colleges and Universities, and Southwestern University in Georgetown, Texas. Furthermore, in the past four years we have established a strong educational collaboration with the école Nationale Supérieure d’Ingénieurs de Caen (ENSICAEN), France. Undergraduate students at ENSICAEN are required to have an internship outside of France. While many of the students stay in neighboring European countries others have chosen the United States. The cornerstone of these programs is to secure a relationship with each institution through clear educational and research objectives and goals.     

Matrices of 960-nm vertical-cavity surface-emitting lasers

Matrices of vertical-cavity surface-emitting lasers with individual addressing of elements and radiation output through a gallium arsenide substrate are implemented. Individual laser emitters with a current aperture diameter of 6–7 μm exhibit continuous-wave room-temperature lasing at a wavelength of 958–962 nm with threshold currents of 1.1–1.3 mA, differential efficiency of 0.5–0.8 mW/mA, and a maximum output power of 7.5–9 mW. The parameter variation of individual emitters within a matrix chip containing 5 × 7 elements does not exceed ±20%.     

3patial Load Balancing in Nide-Area Wireless Networks

Load balancing is typically used in the frequency domain of cellular wireless networks to balance paging, access, and traffic load across the available bandwidth. In this paper, we extend load balancing into the spatial domain, and we develop two approaches-network load balancing and single-carrier multilink-for spatial load balancing. Although these techniques are mostly applied to cellular wireless networks and Wi-Fi networks, we show how they can be applied to EV-DO, a 3G cellular data network. When a device has more than one candidate server, these techniques can be used to determine the quality of the channel between a server and the device and to determine the load on each server. The proposed techniques leverage the advantages of existing EV-DO network architecture and are fully backward compatible. Network operators can substantially increase network capacity and improve user experience by using these techniques. Combining load balancing in the frequency and spatial domains improves connectivity within a network and allows resources to be optimally allocated according to the p-fair criterion. Combined load balancing further improves performance.     

An antenna diversity MMIC vector modulator for HIPERLAN with lowpower consumption and calibration capability

The design and performance of a vector-modulator-based phase shifter for high-performance radio local area networks at 5.2 GHz is presented in this paper. Low power consumption is achieved using a 0.6-μm GaAs MESFET process. At a voltage supply of 1.4 V and with a current consumption between 3.5-7 mA, the gain is 0.6 dB and the 1-dB input compression point is -9 dBm. A full 360° phase control range is achieved by combining two of the three vectors, which have phase offsets of 120°, with variable amplitude. Chip size is only 1.3 mm ². The proposed vector modulator applies a new circuit configuration of variable-gain amplifiers to compensate their transmission phase errors. Within a gain control range of 20 dB, the phase error can be reduced to ±3°, which is about a factor of eight better than the results obtained by single FET amplifiers. A simple calibration procedure for the proposed vector modulators is presented to improve the manufacturing yield and to decrease the impact due to temperature changes and aging. A maximum gain error of ±0.8 dB and a maximum phase error of ±7° have been measured after applying this calibration to the designed vector modulator     

Strained quantum well modulation-doped ingasb/algasb structures grown by molecular beam epitaxy

Strained single quantum well InGaSb/AlGaSb structures for field-effect transistor applications have been grown by molecular beam epitaxy. Modulation-doped p-type structures have been characterized by a variety of techniques, including Hall effect, Shubnikov-de Haas measurements, and cyclotron resonance. These structures exhibit improved hole transport in comparison to similar GaSb/ AlGaSb structures as a result of strain-splitting of the valence band. P-channel field-effect transistors fabricated in this system exhibited a maximum transconductance of 51 and 161 mS/mm at 300 and 77K, respectively, for a 1.2 μm gate-length device.