Optical characteristics of silicon semiconductor bridges under highcurrent density conditions

The optical emission spectra (180-700 nm) of plasma produced by a semiconductor bridge (SCB) with aluminum or tungsten electrodes have been measured and analyzed. The spatially and temporally resolved emission spectra of the SCB device have provided insights into the dynamic discharge of the bridge. The plasma electron temperature of the SCB device was measured using the comparison of the continuum emission of the bridge with the calculated optical emission spectra for a gray body source. Measured electron temperatures in the plasma produced by the bridges are related to the capacitor discharging voltage. The best estimates indicate that 4100-5500 K was measured for Al-electrode SCB device and 5650-6000 K for W-electrode SCB device     

Novel design for high-power single-lateral-mode lasers

A new laser design for single-mode high-power applications is reported. The waveguide is a laterally flaring and transversely tapering GaAs buried ridge fabricated by selective area epitaxy. Single-lateral-mode powers of 200 mW were achieved     

Effects of cooking methods on starch hydrolysis kinetics and digestion-resistant fractions of rice and soybean

In this study, we investigated the effects of cooking methods and digestion-resistant fractions on the starch hydrolysis kinetics of rice and soybeans. The RS1 contents in unheated rice and soybeans were found to be high at 5.3 and 4.9%, respectively. After heating, the RS1 levels of the rice and soybeans were significantly reduced to 0.4 and 2.4%, respectively. The total nonstarch polysaccharide (NSP) content was not significantly different according to heat treatment, but the heat treatments affected the amounts of water insoluble nonstarch polysaccharides (WISNSP) and water soluble nonstarch polysaccharides (WSNSP). The level of WISNSP in the unheated samples was higher than the WSNSP of both samples; however, the WISNSP level showed a reducing trend after heating. Also, total pentosan and water soluble pentosan contents showed similar trends with total NSP and WSNSP. The hydrolysis indices (HI) of the unheated rice and soybeans were low (36.2 and 40.3%), while the heated group had high levels (89.5 and 45.0%). Among the cooking methods, the highest kinetic constants (0.284 and 0.199) were found with autoclaving for both rice and soybeans, followed by electric cooker (0.282 and 0.170), microwave oven (0.256 and 0.155), and stone pot (0.238 and 0.167). Particularly, all soybean samples appeared to have lower starch hydrolysis kinetics than the rice samples. The RS contents of the rice and soybeans were highest in the samples that were cooked in the stone pot, at 1.2 and 3.8%, respectively.     

Channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories

The channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories is investigated. While the trapped charge profile-dependent overerasure is observed in 10-μm-wide device, it is suppressed in 0.22-μm-wide device. Both the overerasure suppression and gradual positive threshold voltage shift in narrow device are explained as an elevated hot hole injection efficiency followed by more pronounced redistribution of the hole profile in the channel-center and the suppression of the lateral migration of injected holes in the channel-edge, by combining the measured endurance characteristics and TCAD simulation results. Main physical mechanisms are three-dimensional distribution of the electric field by gate/drain voltage, increasing interface states, and their trapped charge with cycling in the channel-edge.     

Efficient geocasting with multi-target regions in mobile multi-hop wireless networks

Geocasting, a variation on the notion of multicasting, is a mechanism to deliver messages of interest to all nodes within a certain geographical target region. Although several geocasting protocols have already been proposed for multi-hop wireless networks, most of these algorithms consider a “single” target region only. Here, when more than one target regions need to receive the same geocast messages, multiple transmissions need to be initiated separately by the message source. This causes significant performance degradation due to redundant packet transmissions, and it becomes more severe as the number of target regions increase. To solve this problem, we propose a basic scheme and its variations which utilize the geometric concept of “Fermat point” to determine the optimal junction point among multiple geocast regions from the source node. Our simulation study using ns-2 shows that the proposed schemes can effectively reduce the overhead of message delivery while maintaining a high delivery ratio in mobile multi-hop wireless networks.     

Kinetics of Intermetallic Compound Formation at the Interface Between Sn-3.0Ag-0.5Cu Solder and Cu-Zn Alloy Substrates

The growth kinetics of an intermetallic compound (IMC) layer formed between Sn-3.5Ag-0.5Cu (SAC) solders and Cu-Zn alloy substrates was investigated for samples aged at different temperatures. Scallop-shaped Cu₆Sn₅ formed after soldering by dipping Cu or Cu-10 wt.%Zn wires into the molten solder at 260°C. Isothermal aging was performed at 120°C, 150°C, and 180°C for up to 2000 h. During the aging process, the morphology of Cu₆Sn₅ changed to a planar type in both specimens. Typical bilayer of Cu₆Sn₅ and Cu₃Sn and numerous microvoids were formed at the SAC/Cu interfaces after aging, while Cu₃Sn and microvoids were not observed at the SAC/Cu-Zn interfaces. IMC growth on the Cu substrate was controlled by volume diffusion in all conditions. In contrast, IMC growth on Cu-Zn specimens was controlled by interfacial reaction for a short aging time and volume diffusion kinetics for a long aging time. The growth rate of IMCs on Cu-Zn substrates was much slower due to the larger activation energy and the lower layer growth coefficient for the growth of Cu-Sn IMCs. This effect was more prominent at higher aging temperatures.     

Distribution and removal of added mercury in milk.

Distribution patterns of added mercury in raw whole milk after equilibration for 30 min and 2 h at 37 C showed a distribution among acid casein, whey proteins, fat globule membrane, and soluble fat globule membrane of 33, 28, 16, and 2%. On the basis of protein content, the fat globule membrane had the highest amount of mercury. Mercury added to milk as mercuric chloride was removed by treatment with thiolated aminoethyl celluloses and reduced human hair. In a 5 min treatment, 70, 43, and 41% of the mercury was removed by thiosuccinylated aminoethyl cellulose, thionitrocarboxyphenylated aminoethyl cellulose, and reduced human hair, respectively, from whole milk initially containing 1 ppm mercury and equilibrated for 2 h at 37 C prior to treatment. After treatment for 60 min, 82, 52, and 64% of the mercury was removed by thiosuccinilated aminoethyl cellulose, thionitrocarboxyphenylated aminoethyl cellulose, and reduced hair, respectively. However, increasing incubation temperature and time prior to treatment decreased the removal efficiencies. Thiosuccinilated aminoethyl cellulose and reduced human hair showed increasing efficiency directly with pH, while thionitrocarboxyphenylated aminoethyl cellulose showed the opposite effect and had higher affinity for mercury at pH 5.5 than at pH 7.5. Moreover, the rate of removal of mercury at 4 C compared to 37 C was much slower. The removal of mercury from soluble casein and soluble whey proteins was more efficient than from micellar casein. Protein, lactose content, and pH of milk were not changed by the polymer treatments.     

Effect of material properties of impact limiter steel on drop accident of spent nuclear fuel transport cask

In this study, the sensitivity of the drop response according to changes in material properties was analyzed to determine the material properties that have a dominant influence on energy absorption performance. Parametric analyses were performed using a spent nuclear fuel (SNF) transport cask as an example, wherein the parameters were the material properties related to the stiffness of the steel (the elastic modulus, yield strength, and tangent modulus) that constitutes an impact limiter installed in the SNF transport cask. On the basis of the analysis results, the absorbed impact energy and transmitted energy were quantitatively calculated and the variations in the structural response were identified. In addition, changes in the structural safety of the SNF transport cask were investigated. The results of this study suggest that material properties must be considered to effectively design a structure that absorbs impact energy.

     

Multiple defect diagnostics of gas turbine engine using SVM and RCGA-based ANN algorithms

An artificial neural network (ANN) based on the real coded genetic algorithm (RCGA) has been used with the support vector machine (SVM) for developing the defect diagnostics of the turbo-shaft engine of an aircraft. Nonlinearity increases due to the ascending number of input data in the off-design region. If the ANN algorithm is used by itself to determine defects under this condition, the possibility of falling in the local minima becomes high because of the large amount of learning data. To solve this problem, the expanded multi-class SVM has been used to reduce nonlinearity of input data. The RCGA, which is effective to search the global minima, has been applied to the ANN algorithm to obtain the magnitude of defects. As results, the number of learning data has been decreased and convergence and accuracy have been improved.