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排序方式: 共有1821条查询结果,搜索用时 15 毫秒
1.
Koji Morita Byung-Nam Kim Hidehiro Yoshida Keijiro Hiraga Yoshio Sakka 《Journal of the European Ceramic Society》2018,38(6):2588-2595
Carbon contamination from the carbon paper/dies during spark-plasma-sintering (SPS) processing was examined in the MgAl2O4 spinel. The carbon contamination sensitively changes with the heating rate during the SPS processing. At the high heating rate of 100 °C/min, the carbon contamination having organized structures occurred over almost the entire area from the surface to deep inside the SPSed spinel disk. In contrast, at the slow heating rate of 10 °C/min, the carbon contamination having disordered structures occurred only around the surface area. The carbon phases transform into high pressure CO/CO2 gases by post-annealing in air and lead to pore formation along the grain junctions. The pore formation significantly occurs at the high heating rate due to the large amount of the contaminant carbon phases. This suggests that if once the carbon contamination was formed in the materials, it is very difficult to remove the carbon phases from the materials. 相似文献
2.
Chou Y.C. Leung D. Lai R. Grundbacher R. Barsky M. Kan Q. Tsai R. Wojtowicz M. Eng D. Tran L. Block T. Liu P.H. Nishimoto M. Oki A. 《Electron Device Letters, IEEE》2003,24(6):378-380
The authors have investigated the reliability performance of G-band (183 GHz) monolithic microwave integrated circuit (MMIC) amplifiers fabricated using 0.07-/spl mu/m T-gate InGaAs-InAlAs-InP HEMTs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel on 3-in wafers. Life test was performed at two temperatures (T/sub 1/ = 200 /spl deg/C and T/sub 2/ = 215 /spl deg/C), and the amplifiers were stressed at V/sub ds/ of 1 V and I/sub ds/ of 250 mA/mm in a N/sub 2/ ambient. The activation energy is as high as 1.7 eV, achieving a projected median-time-to-failure (MTTF) /spl ap/ 2 /spl times/ 10/sup 6/ h at a junction temperature of 125 /spl deg/C. MTTF was determined by 2-temperature constant current stress using /spl Delta/G/sub mp/ = -20% as the failure criteria. The difference of reliability performance between 0.07-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel and 0.1-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with In/sub 0.6/Ga/sub 0.4/As channel is also discussed. The achieved high-reliability result demonstrates a robust 0.07-/spl mu/m pseudomorphic InGaAs-InAlAs-InP HEMT MMICs production technology for G-band applications. 相似文献
3.
Yamanaka N. Kawano R. Oki E. Yasukawa S. Okazaki K. 《Advanced Packaging, IEEE Transactions on》2002,25(1):65-72
A 640-Gb/s high-speed ATM switching system that is based on the technologies of advanced MCM-C, 0.25-μm CMOS, and optical wavelength-division-multiplexing (WDM) interconnection is fabricated for future broadband backbone networks. A 40-layer, 160×114 mm ceramic MCM forms the basic ATM switch module with 80-Gb/s throughput. It consists of 8 advanced 0.25-μm CMOS LSIs and 32 I/O bipolar LSIs. The MCM has a 7-layer high-speed signal line structure having 50-Ω strip lines, high-speed signal lines, and 33 power supply layers formed using 50-μm thick ceramic layers to achieve high capacity. A uniquely structured closed-loop-type liquid cooling system for the MCM is used to cope with its high power dissipation of 230 W. A three-stage ATM switch is made using the optical WDM interconnection between high-performance MCMs. For WDM interconnection, newly developed compact 10-Gb/s, 8-WDM optical transmitter and receiver modules are used. These modules are each only 80×120×20 mm and dissipate 9.65 W and 22.5 W, respectively. They have a special chassis for cooling, which contains high-performance heat-conductive plates and micro-fans. An optical WDM router based on an arrayed waveguide router is used for mesh interconnection of boards. The optical WDM interconnect has 640-Gb/s throughput and simple interconnection 相似文献
4.
A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitatite disaturated species
of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted
by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential
refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC.
The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chroamtograms obtained by
RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responsed in the same degree for different, authentic standards
of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human
lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those
reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis
among the molecular species containing disaturated species. 相似文献
5.
Preparation of polyimide-epoxy composites 总被引:2,自引:0,他引:2
Kevin Gaw Mitsutoshi Kikei Masa-aki Kakimoto Yoshio Imai 《Reactive and Functional Polymers》1996,30(1-3):85-91
The formation of a three dimensional network of crosslinked epoxy leads all unmodified epoxies to have inherent brittleness and relatively low degradation temperatures. Polyimides, on the other hand, are widely used for applications that require high degrees of flexibility and thermal resistance. Here, we have focused on the preparation of epoxy systems cured with polyamic acids instead of traditional amino-group-containing hardening agents. The cure behavior and potential reaction mechanisms of EPON 828 resin and polyamic acid mixtures were evaluated by DSC and TGA. Thermal analysis showed a complex reaction sequence taking place in the mixture and also determined the extent of reaction of the polyamic acid with itself and the competitive reaction of the polyamic acid with the epoxy. The compositions of the mixtures were varied to see the dependence of the cure behavior on component concentrations. Solutions of the two components did not phase separate and also phase separation was not apparent either optically or microscopically in the cured samples. This phase behavior was attributed to a unique in situ reaction. A novel solvent system for the polyamic acid precursor was also used. 相似文献
6.
It seems clear that, for whatever reasons, the dementia of the Alzheimer type patient group (as well as other patient groups) exhibits behavior that is different from the normal control group. G. Storms, T. Dirikx, J. Saerens, S. Verstraeten, and P. P. De Deyn (2003) rightfully argue that the observed behavior (similarity judgments) does not tell us the source (cause) of the differences between the 2 groups. Rather, the focus of the study should be placed more on finding the ways the 2 groups are different. They also point out various methodological problems in some of the previous attempts to characterize the nature of the differences. Further methodological issues in G. Storms et al.'s study are examined. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Streit D.C. Hafizi M.E. Umemoto D.K. Velebir J.R. Tran L.T. Oki A.K. Kim M.E. Wang S.K. Kim C.W. Sadwick L.P. Hwu R.J. 《Electron Device Letters, IEEE》1991,12(5):194-196
The authors have fabricated n-p-n GaAs/AlGaAs heterojunction bipolar transistors (HBTs) with base doping graded exponentially from 5×1019 cm-3 at the emitter edge to 5×1018 cm-3 at the collector edge. The built-in field due to the exponentially graded doping profile significantly reduces base transit time, despite bandgap narrowing associated with high base doping. Compared to devices with the same base thickness and uniform base doping of 1×1019 cm-3 , the cutoff frequency is increased from 22 to 31 GHz and maximum frequency of oscillation is increased from 40 to 58 GHz. Exponentially graded base doping also results ill consistently higher common-emitter current gain than uniform base doping, even though the Gummel number is twice as high and the base resistance is reduced by 40% 相似文献
8.
Hideaki Katayama Tsutomu Tawa Shinzaburo Ito Masahide Yamamoto Yoshio Wada 《Polymer Bulletin》1992,29(3-4):365-367
Summary The effect of side chain length on intramolecular triplet energy migration of naphthalene containing polymers was investigated by a delayed fluorescence (DF) spectroscopy for the solid solution of the polymers. The degree of triplet energy migration depends strongly on whether the chromophores are directly attached to the main chain or not. 相似文献
9.
Rong-Jun Xie Mamoru Mitomo Kyota Uheda Fang-Fang Xu Yoshio Akimune 《Journal of the American Ceramic Society》2002,85(5):1229-1234
Rare-earth-doped oxynitride or nitride compounds have been reported to be luminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, we report the photoluminescence (PL) spectra of europium-, terbium-, and praseodymium-doped Ca-α-SiAlON ceramics. The highly dense ceramics were prepared by hot pressing at 1750°C for 1 h under 20 MPa in a nitrogen atmosphere. Europium-doped Ca-α-SiAlON displayed a single broad emission band peaking at λ= 550–590 nm depending on the europium concentration. The emission bands in the spectra of europium-doped Ca-α-SiAlONs were assigned to the allowed transition of Eu2+ from the lowest crystal field component of 4 f 6 5 d to 8 S7/2 (4 f 7 ) ground-state level. The emission spectra of terbium- and praseodymium-doped Ca-α-SiAlON ceramics both consisted of several sharp lines, which were attributed to the 5 D4 →7 F j ( j = 3, 4, 5, 6) transitions of Tb3+ and 3 P0 →3 H j ( j = 3, 4, 5) transitions of Pr3+ , respectively. In particular, the terbium-doped α-SiAlON ceramics showed a strong green emission among these phosphors. 相似文献
10.
K-S. Park S-H. Park Y-K. Sun K-S. Nahm Y-S. Lee M. Yoshio 《Journal of Applied Electrochemistry》2002,32(11):1229-1233
The structural and electrochemical properties of LiNiO2 powders were investigated as a function of the oxygen flow rate employed in the preparation of lithium nickel oxide. It was found that oxygen played an important role in the synthesis of highly crystallized LiNiO2(R3¯m). In the crystallization process of LiNiO2, a deficiency of oxygen in the calcination reactor induced the formation of impurities and cubic rock-salt structure (Fm3m) in LiNiO2 powders. For LiNiO2 prepared at higher oxygen flow rates, the electrode delivered high discharge capacities with relatively good retention rates. But very low electrode capacity was obtained from LiNiO2 prepared at lower oxygen flow rates. 相似文献