Simulation of the transient temperature distribution in a high-power semiconductor device cooling apparatus using heat pipes

This study describes the transient temperature distributions in a cooling apparatus for high-power semiconductor devices used in electric-railcar drive systems. The cooling apparatus is composed of heat pipes, air-cooled fin arrays, and a metal block which is used for attaching several semiconductor packages, In our numerical simulation model, we substituted solid elements for the heat pipes, and determined their thermal properties by experiment. As a result, we could obtain transient temperature distributions for the cooling apparatus through a heat conduction analysis. Calculated results showed that when the amount of heat generated in the devices changes, the temperature of the cooling apparatus changes more slowly than that of the devices. A comparison between the transient-temperature distribution calculations and the experiments confirmed the accuracy of the modeling and prediction method. Thus, these calculations can be used to provide data for packaging design, especially concerning thermal stress and fatigue in the packages. © 1998 Scripta Technica, Inc. Heat Trans Jpn Res, 26(2): 107–115, 1997     

Microstructure and Wear Behavior of Cermet/Iron Alloy Cladding Layers on A6061 Alloy Coated by Resistance Seam Welding Method

Cermet/iron alloy cladding layers were coated on the surface of Al–Mg–Si alloy(A6061) plates by resistance seam welding method with tungsten carbide(WC) and high-carbon iron alloy(SHA) powders.The cladding layer consisted of WC reinforcement,SHA binder,A6061 and Fe Al3.The effect of WC ratio(30 wt%,50 wt% and 70 wt%) on the microstructure and wear behavior of the cladding layers was investigated in detail.Abrasive wear test was performed under two kinds of load condition by using a rubber wheel apparatus to evaluate wear resistance.The results showed that the wear resistance of the cladding layer was improved by 3.5–5 times than that of the substrate.At lower load,the wear resistances of the samples 30% and 70% WC were nearly the same,which suggested that Fe Al3 played an important role in improvement of the wear resistance instead of WC.While at higher load,the amount of WC determined the wear resistance of the cladding layer.Furthermore,wear behavior of these cladding layers was explained with reference to the observed microstructure of the worn surface.     

Tunable plasmon resonances in a metallic nanotip-film system

Tip-enhanced Raman spectroscopy (TERS) has emerged as a powerful tool for optical imaging at nanoscale spatial resolution, and for investigating the vibrational properties of molecules adsorbed on a substrate. Plasmonic enhancement of the electromagnetic fields near a metallic nanostructure plays a very important role in TERS, where resonant excitation of plasmons is crucial. When two metallic nanostructures are placed at a gap of nanometric distance, their plasmons can interact with one other and result in hybridized shifted plasmon modes. Here, we apply this idea to TERS and demonstrate a significant tunability of the plasmon resonance enabling large electric field enhancement at a desired excitation wavelength. This finding paves the way for efficient optimization of TERS in imaging and spectroscopy applications.     

A flexible full‐color AMOLED display driven by OTFTs

Abstract— Organic thin‐film‐transistor (OTFT) technologies have been developed to achieve a flexible backplane for driving full‐color organic light‐emitting diodes (OLEDs) with a resolution of 80 ppi. The full‐color pixel structure can be attained by using a combination of top‐emission OLEDs and fine‐patterned OTFTs. The fine‐patterned OTFTs are integrated by utilizing an organic semiconductor (OSC) separator, which is an insulating wall structure made of an organic insulator. Organic insulators are actively used for the OTFT integration, as well as for the separator, in order to enhance the mechanical flexibility of the OTFT backplane. By using these technologies, active‐matrix OLED (AMOLED) displays can be driven by the developed OTFT backplane even when they are mechanically flexed.     

Development of discharge plasma waveguide with external magnetic field for laser plasma acceleration

To improve the acceleration length in laser plasma acceleration, we investigate the discharge plasma waveguide with a magnetic field. The discharge circuit consists of two pulsed‐power circuits for preionization and main discharge. Discharges were repeated through the circuit using high‐power semiconductor switches. Laser propagation characteristics of discharge plasma waveguide with the external magnetic field were observed. The results show that the reproducibility of waveguide with the external magnetic field is relatively high compared to that without magnetic field. The laser intensity gradually decreases with the strength of external magnetic field. These results suggest that the electron density profile is possible to control using the discharge plasma waveguide with an external magnetic field.     

Chemical Evaluation of Eumelanin Maturation by ToF-SIMS and Alkaline Peroxide Oxidation HPLC Analysis

Residual melanins have been detected in multimillion-year-old animal body fossils; however, confident identification and characterization of these natural pigments remain challenging due to loss of chemical signatures during diagenesis. Here, we simulate this post-burial process through artificial maturation experiments using three synthetic and one natural eumelanin exposed to mild (100 °C/100 bar) and harsh (250 °C/200 bar) environmental conditions, followed by chemical analysis employing alkaline hydrogen peroxide oxidation (AHPO) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Our results show that AHPO is sensitive to changes in the melanin molecular structure already during mild heat and pressure treatment (resulting, e.g., in increased C-C cross-linking), whereas harsh maturation leads to extensive loss of eumelanin-specific chemical markers. In contrast, negative-ion ToF-SIMS spectra are considerably less affected by mild maturation conditions, and eumelanin-specific features remain even after harsh treatment. Detailed analysis of ToF-SIMS spectra acquired prior to experimental treatment revealed significant differences between the investigated eumelanins. However, systematic spectral changes upon maturation reduced these dissimilarities, indicating that intense heat and pressure treatment leads to the formation of a common, partially degraded, eumelanin molecular structure. Our findings elucidate the complementary nature of AHPO and ToF-SIMS during chemical characterization of eumelanin traces in fossilized organismal remains.     

Improvement of Jc and Grain Alignment of Bi-2212/Ag Multilayer Tapes by Pre-Annealing and Intermediate Rolling Process

The high transport critical current density (J _c ) > 500 kA/cm ² at 4.2 K, 10 T is obtained in the Bi-2212/Ag multilayer tapes fabricated by using PAIR (Pre-Annealing and Intermediate Rolling) and melt-solidification process. This J _c value is twice higher than existing high-quality Bi-2212/Ag tapes (250 kA/cm ² ). By applying PAIR process to Bi-2212/Ag tapes, Bi-2212 grain alignment is much improved and a large J _c enhancement is achieved. J _c has been increased strongly by performing pre-annealing at 840°C in oxygen (1 atm) and intermediate rolling with 25% deformation.     

Salmon Protamine Decreases Serum and Liver Lipid Contents by Inhibiting Lipid Absorption in an In Vitro Gastrointestinal Digestion Model and in Rats

Protamine has been used as an antiheparin drug and a natural preservative in various food products. However, limited studies have evaluated the physicochemical and functional properties of protamine. Hence, we assessed the mechanisms underlying the inhibition of lipid absorption following salmon protamine intake in in vitro and in vivo studies. In initial experiments, a salmon protamine hydrolyzate (PH) was prepared using in vitro simulated gastrointestinal digestion suppressed pancreatic lipase activity and micellar cholesterol solubility. This PH had higher bile acid‐binding capacity and emulsion breakdown activity than casein hydrolyzate and l ‐arginine. However, the hypolipidemic functions of protamine were dramatically reduced by pancreatin digestion. In further experiments, groups of male Wistar rats were fed an AIN‐93G diet containing 5% (wt/wt) salmon protamine or a protamine amino acid mixture. After 4 wk of feeding with experimental diets, reductions in serum and liver triacylglycerol (TAG) and cholesterol contents were observed in the presence of protamine, reflecting inhibition of TAG, cholesterol, and bile acid absorption. These data suggest that the formation of insoluble PH–bile acid complexes is critical before the bile acid‐binding capacity is reduced. Therefore, dietary salmon protamine may ameliorate lifestyle‐related diseases such as hyperlipidemia and obesity.     

Concentrations and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans in soils from Korea

Soil samples were collected from Changwon and Masan Cities, Korea, and analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs). Nearly all tetra- through octachlorinated PCDDs/DFs including the 17 2,3,7,8-substituted PCDDs/DFs were detected in all samples. Total concentrations of PCDDs/DFs and of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TeCDD) equivalents (TEGs) in soils ranged from 35 to 121,400 pg/g, dry weight, and from 0.2 to 3720 pg of I-TEQ/g, respectively. On the basis of guidelines for TEQ concentrations established in Germany and the United States, 9 of 23 soil samples (39% of the total samples analyzed) could not be expected to pose human health hazards. The rest of 61% of soils need measures such as investigations of source identification, soil decontamination, and/or soil removal. Total concentrations of PCDDs/DFs were greater at or near four industrial sites, which are concerned with the steel industry, petrochemical-related industry, and industrial waste incineration, than other areas. This indicates the presence of potential source areas. Soil collected from a site 50 m from an open-burning industrial waste incinerator in an industrial complex was heavily contaminated, containing a total concentration of PCDDs/DFs of 121,400 pg/g, dry weight. PCDDs/DFs were also detected in soils from the top of a 200 m mountain indicating a wide dispersal of PCDDs/DFs by atmospheric transport from point source areas. The congener pattern and relative proportions of PCDFs in soils suggest that commercial PCB preparations such as Kanechlors may be one of the sources. The wide range of PCDD/DF isomers detected in soils from many locations also suggests a multitude of sources, in addition to commercial PCBs, such as incineration of industrial wastes such as car tires, scrap wires, plastics, papers, and emission of automobile exhaust.     

Mechanism of lower oxidizability of eicosapentaenoate than linoleate in aqueous micelles

The aerobic oxidation kinetics of methyl eicosapentaenoate (20:5n-3) and methyl linoleate (18:2n-6) were compared in homogeneous chlorobenzene solution and in Triton X-100 aqueous micelles at 37°C. The rate of disappearance of 20:5n-3 was two times faster than that of 18:2n-6 in chlorobenzene, while the former was five times slower than the latter in aqueous micelles. It was also observed that ΔO₂=Δ18:2n-6 and ΔO₂=2Δ20:5n-3 in aqueous micelles. In the oxidation of a 1∶1 mixture of 20:5n-3 and 18:2n-6 in micelles, the rate of disappearance of 20:5n-3 was 3.6 times faster than that of 18:2n-6, and the rate of total substrate disappearance was reduced by a factor of 5 as compared with 18:2n-6 oxidation. These data suggest that the peroxyl radical derived from 20:5n-3 is more polar than that from 18:2n-6, and the former is likely to diffuse from the core to the micelle surface. This lowers the oxidizability for 20:5n-3 in aqueous micelles by enhancing the termination reaction rate for peroxyl radicals and by reducing the rate of propagation since there may be more 20:5n-3 peroxyl radicals at the surface than in the micelle core.