Operation of the quasi-optical gyrotron at harmonics of the gyrofrequency

This paper investigates the performance of a quasioptical gyrotron, when the electron beam interacts with the radiation fields at harmonics of the gyrofrequency. The nonlinear equations of motion are obtained in the slow-timescale. The expression for the linear gain is derived and the conditions for excitation are given (frequency threshold, optimal operating point, bean current and resonator quality thresholds). In the nonlinear regime, it is shown that maximum efficiencies comparable to those at the fundemental (～50%) are possible, albeit at a prohitively high radiation field amplitude, while realistically feasible field amplitudes can give somewhat smaller, but nevertheless still high efficiencies (～15%). Finally, the results are suplemented by empirical scaling laws, useful for experimental designs.     

Production of cocoa butter-like fat from interesterification of vegetable oils

Cocoa butter-like fat was prepared from completely hydrogenated cottonseed and olive oils by enzymatic interesterification. The optimum reaction time to produce the major-component of cocoa butter, 1(3)-palmitoyl-3(1)-stearoyl-2-monoolein (POS), was 4 hr. The cocoa butter-like fat was isolated from the reaction mixture by two filtration steps. The yield of cocoa butter-like fat was 19%, based on the weight of the original oils. Chromatographic analysis of the product by reversephase high-performance liquid chromatography (HPLC) has shown it contains triglyceride components similar to those of cocoa butter, but that it has slightly more diglycerides. The melting point of this product, as measured by a differential scanning calorimeter, is 39°C, which compares well to the 36°C melting point of natural cocoa butter. Presented in part at the AOCS meeting in Cincinnati, Ohio, in 1989.     

Filler cement: The effect of the secondary component on the hydration of Portland cement: Part 2: Fine hydraulic binders

In Part 1 of this paper, it was shown that enhanced hydration was achieved by blending a fine non-hydraulic filler into an ordinary Portland cement. This enhancement was considered to be a particle size effect and associated with the presence of fine particles of filler which provided the additional nucleation sites. The filler, rutile, had a variable cement equivalence and reached a maximum value of 0.9kg/kg after hydration had proceeded for three days. In this second part, the same Portland cement was blended seperately with latent hydraulic binders (two pulverized fuel ashes and a ground granulated blastfurnace slag, a Lurgi slag and a volatilized silica). The apparent overall reactivity of these binders was seen to have two components, the first being the particle size effect with its influence on the hydration of the Portland cement and the second the inherent hydraulicity of the secondary material.     

Embryonic fatty acid composition as a function of yolk fatty acid composition in eggs of the lesser spotted dogfish (Scyliorhinus canicula L.)

Yolk and embryonic total lipids were extracted from spotted dogfish eggs at two developmental stages. Total lipids were fractionated into neutral lipids (NL) and polar lipids (PL), and the fatty acid composition of each group was determined. Yolk lipid composition was found to be quantitatively different (NL/PL≊1) from embryo lipid composition (NL/PL≊0.5), for both stages of development. However, individual fatty acid composition did not differ from younger to older eggs for either yolk or embryo. There were significant differences (p<0.05) in major fatty acid groups from yolk and embryonic PL for saturated fatty acids, monounsaturated fatty acids (MUFA) and n−3 polyunsaturated fatty acids (PUFA) for younger eggs, and for MUFA and n−3 PUFA for older eggs. For NL, only MUFA composition from the oldest eggs showed differences between yolk and embryo. Results are discussed in terms of embryonic needs for highly unsaturated fatty acid (HUFA) biosynthesis, as well as to provide some explanations for the unusually high levels of 20∶4n−6 in both yolk and embryonic neutral lipids and polar lipids.     

Construction of validated, non-redundant composite protein sequence databases

A strategy has been developed for the construction of a validated,comprehensive composite protein sequence database. Entries areamalgamated from primary source data bases by a largely automatedset of processes in which redundant and trivially differententries are eliminated. A modular approach has been adoptedto allow scientific judgement to be used at each stage of databaseprocessing and amalgamation. Source databases are assigned apriority depending on the quality of sequence validation andcommenting. Rejection of entries from the lower priority database,in each pairwise comparison of databases, is carried out accordingto optionally defined redundancy criteria based on sequencesegment mismatches. Efficient algorithms for this methodologyare embodied in the COMPO software system. COMPO has been appliedfor over 2 years in construction and regular updating of theOWL composite protein sequence database from the source databasesNBRF-PIR, SWISS-PROT, a GenBank translation retrieved from thefeature tables, NBRF-NEW, NEWAT86, PSD-KYOTO and the sequencescontained in the Brookhaven protein structure databank. OWLis part of the ISIS integrated data resource of protein sequenceand structure [Akrigg et al. (1988) Nature, 335, 745–746].The modular nature of the integration process greatly facilitatesthe frequent updating of OWL following releases of the sourcedatabases. The extent of redundancy in these sources is revealedby the comparison process. The advantages of a robust compositedatabase for sequence similarity searching and information retrievalare discussed.     

Reaction of Iradium with Metal Carbides in the Temperature Range of 1923 to 2400 K

The reactions of titanium carbide and hafnium carbide with iridium have been studied in thin film couples fabricated by vapor deposition processes. The reaction product layers after exposure in the temperature range of 1923 to 2400 K are dependent on the stoichiometry of the metal carbide layers and range from simple solid solutions to MIr_x compounds. The observed microstructures are predictable from available thermochemical data. The morphology of residual carbon in the reacted metal carbide-iridium product layer varies from interfacial deposits to uniform carbon dispersion and depends upon exposure temperature and metal carbide stoichiometry.     

Effect of Water Content on the Electrical Conductivity of Sodium Trisilicate Glasses

The effect of variations in water content on the direct-current electrical conductivity of Na₂O · 3SiO₂ glass was measured. Increasing the water content of this glass from 10 to 500 wt ppm of H₂O results in an increase in the resistivity of a factor of 2 to 3. The increase in resistivity is accompanied by an increase in the activation energy for conduction. Increasing resistivity with increasing water content is attributed to decreasing molar volume. Under identical annealing conditions, "wetter" glasses relax to a smaller molar volume (greater density) because of the presence of a larger number of "terminal" hydroxyl species that allow structural relaxation to continue to lower temperatures.     

Memory Fault Modeling Trends: A Case Study

In recent years, embedded memories are the fastest growing segment of system on chip. They therefore have a major impact on the overall Defect per Million (DPM). Further, the shrinking technologies and processes introduce new defects that cause previously unknown faults; such faults have to be understood and modeled in order to design appropriate test techniques that can reduce the DPM level. This paper discusses a new memory fault class, namely dynamic faults, based on industrial test results; it defines the concept of dynamic faults based on the fault primitive concept. It further shows the importance of dynamic faults for the new memory technologies and introduces a systematic way for modeling them. It concludes that current and future SRAM products need to consider testability for dynamic faults or leave substantial DPM on the table, and sets a direction for further research.     

Traffic Models and Blocking Probabilities for Two-Fold and Three-Fold SDMA Communication Systems

Spectrum efficiency is a constant challenge in the design of wireless networks. Space-division-multiple-access (SDMA) is a promising approach to achieve higher spectral efficiency which reuses bandwidth via multiplexing signals based on their spatial signature. Several different studies have shown that SDMA can effectively improve system capacity in a mobile environment. In this paper, we present a new Markov chain traffic model for a duplicate-at-last (DL) approach [IEE Proceedings on Communication 146 (1999) 303] in two-fold and three-fold SDMA systems. Simplified blocking probability formulations for two-fold and three-fold SDMA are also derived. Simulations based on a common method of spatial separation check for channel allocation in SDMA are presented to evaluate the probability of successfully creating two-fold and three-fold SDMA channels. The simulation, as well as analytical, results indicate that the SDMA system can reduce the blocking probability of the calls and result in more traffic loading than a traditional cellular system. The results also show that our simplified approaches not only can reduce the computational complexity, but can also accurate approximate two-fold and three-fold SDMA performance. Wen-Jye Huang received the B.S. degree in electrical engineering from Tatung Institute of Technology, Taipei, Taiwan, in 1991, the M.S. degree in electrical engineering from Ohio University, Athens, OH, in 1997, and the Ph.D. degree in electrical engineering from The Pennsylvania State University, University Park, PA, in 2001. Since 2002, he joined the Department of Electrical Engineering, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan, as an assistant professor. His research activities include smart antenna, SDMA, and MC-CDMA techniques. John F. Doherty received the B.S. degree (with honors) in engineering science from the College of Staten Island, City University of New York, in 1982, the M.Eng. degree in electrical engineering from Stevens Institute of Technology, Hoboken, NJ, in 1985, and the Ph.D. degree in electrical engineering from Rutgers University, New Brunswick, NJ, in 1990. He was an integrated circuit reliability engineer with IBM, from 1982 to 1984. From 1985 to 1988, he was member of the technical staff at AT&T Bell Laboratories, working in sonar signal processing. In 1990, he joined the Electrical and Computer Engineering Department, Iowa State University, Ames, as an assistant professor and Harpole Entair fellow. He is currently an associate professor of electrical engineering with The Pennsylvania State University, University Park. His current research activities include interference rejection in wireless communication systems, spatial-division multiple-access techniques, and radar target detection techniques. He is a former AFOSR summer faculty research fellow at the Rome Laboratory, Rome, NY, and an Army Research Office Young Investigator.     

Exploiting the Terahertz Band for Radionavigation

This paper demonstrates the feasibility of GPS-like ranging at terahertz (THz) frequencies. It is well established that GPS carrier signals are vulnerable to jamming via radio-frequency interference (RFI). As a result, there is a need for alternative radionavigation systems. THz signals offer a compelling option. Because of their high frequency (roughly ×100 higher than GPS), THz signals can be used to make highly precise range measurements. In addition, the large separation between the GPS and THz frequencies means that interference at GPS frequencies is very unlikely to impact the THz band. This paper lays the groundwork for a GPS-like ranging capability at THz frequencies. To this end, we identify key differences between THz hardware and GPS (radio frequency) hardware; we experimentally evaluate performance of a 0.30-THz system on a compact outdoor test range, and we introduce a measurement error model that highlights the distinctive role that multipath interference plays at THz frequencies.