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排序方式: 共有1543条查询结果,搜索用时 15 毫秒
61.
Sung Chan Kim An D. Byeong Ok Lim Tae Jong Baek Dong Hoon Shin Jin Koo Rhee 《Electron Device Letters, IEEE》2006,27(1):28-30
We reported 94-GHz, low conversion loss, and high isolation single balanced active gate mixer based on 70-nm gate length InGaAs/InAlAs metamorphic high-electron mobility transistors (MHEMTs). This mixer showed that the conversion loss and isolation characteristics were 2.5/spl sim/3.5 dB and under -29 dB in the range of 92.95/spl sim/94.5 GHz, respectively. The low conversion loss of the mixer is mainly attributed to the high-performance of the MHEMTs exhibiting a maximum drain current density of 607 mA/mm, an extrinsic transconductance of 1015 mS/mm, a current gain cutoff frequency (f/sub t/) of 330 GHz, and a maximum oscillation frequency (f/sub max/) of 425 GHz. High isolation characteristics are due to hybrid ring coupler which adopted dielectric-supported air-gapped microstrip line structure using surface micromachined technology. To our knowledge, these results are the best performance demonstrated from 94 GHz single balanced mixer utilizing GaAs-based HEMTs in terms of conversion loss as well as isolation characteristics. 相似文献
62.
Micromachined jets for liquid impingement cooling of VLSI chips 总被引:2,自引:0,他引:2
Wang E.N. Lian Zhang Linan Jiang Jae-Mo Koo Maveety J.G. Sanchez E.A. Goodson K.E. Kenny T.W. 《Journal of microelectromechanical systems》2004,13(5):833-842
Two-phase microjet impingement cooling is a potential solution for removing heat from high-power VLSI chips. Arrays of microjets promise to achieve more uniform chip temperatures and very high heat transfer coefficients. This paper presents the design and fabrication of single-jets and multijet arrays with circular orifice diameters ranging from 40 to 76 /spl mu/m, as well as integrated heater and temperature sensor test devices. The performance of the microjet heat sinks is studied using the integrated heater device as well as an industry standard 1 cm/sup 2/ thermal test chip. For single-phase, the silicon temperature distribution data are consistent with a model accounting for silicon conduction and fluid advection using convection coefficients in the range from 0.072 to 4.4 W/cm/sup 2/K. For two-phase, the experimental results show a heat removal of up to 90 W on a 1 cm/sup 2/ heated area using a four-jet array with 76 /spl mu/m diameter orifices at a flowrate of 8 ml/min with a temperature rise of 100/spl deg/C. The data indicate convection coefficients are not significantly different from coefficients for pool boiling, which motivates future work on optimizing flowrates and flow regimes. These microjet heat sinks are intended for eventual integration into a closed-loop electroosmotically pumped cooling system. 相似文献
63.
The decomposition of CHF3 in a mixture with O2 and Ar was investigated in a coaxial dielectric barrier discharge at atmospheric pressure. CHF3 decomposition increased linearly in regard to specific energy input (SEI), whereas energy efficiency decreased. The main product was CO2, and its selectivity increased with high SEI and the presence of O2 in the feed, but an increase of O2 in the feed led to a decrease in decomposition rate. An increase in total flow rate led to an increase of the absolute amount of CHF3 decomposition and energy efficiency; however, the decomposition of CHF3 decreased. A complete CHF3 decomposition occurred under an SEI of 1.54 kJ/L with the selectivity of CO2 and CO as 89.87% and 7.00%, respectively. Optical emission spectroscopic analysis could explain the available reaction pathways for CHF3 decomposition in the CHF3/O2/Ar atmospheric plasma and show the possibility of F2 and HF formation. 相似文献
64.
65.
Seung Koo Lee Myung Shin Han Ching‐Hsuan Tung 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(21):3315-3320
A long‐lasting particle‐based fluorescent label is designed for extended cell imaging studies. This onion‐like nanoprobe is constructed through layer‐by‐layer fabrication technology. The nanoprobes are assembled with multiple layers of optically quenched polyelectrolytes, the fluorescence signal of which can be released later by intracellular proteolysis. Upon incubation with cells, the assembled nanoprobes are taken up efficiently. The tight packing and layered assembly of the quenched polyelectrolytes slow subsequent intracellular degradation, and then result in a prolonged intracellular fluorescence signal for up to 3 weeks with no noticeable toxicity. 相似文献
66.
For elevated temperature design evaluations by the ASME-NH rules, the most important material data is the isochronous stress-strain
curves, which can provide design creep information. The main purpose of this paper is to investigate appropriate formulations
to be able to generate the isochronous stress-strain curves and implement it to the computer program which is coded the ASME-NH
design evaluation procedures. To do this, formulations by the strain-time relationship are investigated in detail and the
sensitivity studies for rapid initial transient creep contributions, slower and longer transient creep contribution, and secondary
creep contributions are carried out for type 316 austenitic stainless steel. From the results of this study, it is found that
the strain-time relationship formulations can well describe the isochronous stress-strain curves with the transient creep
contributions. 相似文献
67.
A continuous screening procedure interchangeably using the performance and surrogate variables is proposed. At the start of the inspection, the performance variable is measured for all items. As soon as i consecutive items are found to be free of defects, the surrogate variable is measured instead of the performance variable. If an item is rejected, the inspection based on the performance variable is resumed. All non-conforming items found in the inspection are either reworked or replaced with conforming items. The average outgoing quality (AOQ) expression is derived, and methods of finding the inspection procedure with a specified average outgoing quality limit (AOQL) are presented. 相似文献
68.
69.
You Jeong Eum Jungho Ryu Chang Young Koo Jung Min Park Jai-Yeoul Lee Hee Young Lee 《Ceramics International》2021,47(5):6371-6375
Magnetoelectric (ME) property modulation in heterostructured (Ni0.5Zn0.5)Fe2O4/Pt/Pb(Zr0.3Ti0.7)O3 (NZFO/Pt/PZT) thin films on platinized Si substrate by thermal annealing condition variation was studied. In an attempt to prevent interfacial reaction between NZFO and PZT layers during high temperature annealing, thin Pt layer was deposited which can serve as inter-diffusion barrier as well as electrode. The ferroelectric, magnetic, and ME properties of the heterostructured film were noticeably modulated due to microstructural evolution and clamping relaxation developed during thermal annealing process. Room temperature ME voltage coefficient of the heterostructured thin films was enhanced with increasing annealing temperature and reached to 29 mV/cm·Oe when annealed at 650 °C. 相似文献
70.
The purpose of this study was to assess the microbial community in ground beef purchased from local stores in the north central area of South Korea. A total of 31 ground beef samples showed 3.77 ± 5.16 × 105 CFU/g on aerobic plate counts, and PCR-based denaturing gradient gel electrophoresis was performed to assess the microbial community, which revealed a diverse profile among the products. Four of these samples were selected for further analyses via 454 pyrosequencing. Pseudomonas was the most frequently identified genus in terms of relative abundance (4.54–73.8%), and other bacteria such as Lactobacillus, Acinetobacter, and Carnobacterium were also identified in the ground beef. The presence of bacteria can affect the spoilage of ground beef products depending on the microbial populations, and understanding these populations may help limit spoilage and/or foodborne illness. This study illustrates the microbial diversity occurring among Korean ground beef products, even within a local region, and provides a molecular approach for potential ground beef microbial quality assessment. 相似文献