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排序方式: 共有1866条查询结果,搜索用时 15 毫秒
21.
Pramod K. Singh B. Bhattacharya R.K. Nagarale Kang-Wook Kim Hee-Woo Rhee 《Synthetic Metals》2010,160(1-2):139-142
Biopolymer composite membranes based on chitosan doped with an ionic liquid (IL) 1-ethyl 3-methylimidazolium thiocyanate (EMImSCN) have been developed and characterized. The doped ionic liquid films show remarkable enhancement in ionic conductivity (σ). The Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and X-ray diffraction studies (XRD) affirmed the composite nature, good incorporation of ionic liquid and reduction in crystallinity of films, respectively. The interaction between ionic liquid, chitosan and iodide polymer electrolyte matrix was evaluated by cyclic voltammetry. The fabricated dye sensitized solar cell (DSSC) using this new biopolymer electrolyte membranes shows promising performance. 相似文献
22.
Twelve percent of high-oleic sunflower oil (HOSO) was incorporated into a swine diet to replace substantial amounts of saturated fatty acids (S) in pork by monounsaturated fatty acids (M). Pork loin chops (longissimus dorsi), cooked to 74°C, and eye of round roasts (semitendinosus), cooked to 77°C, from animals on the HOSO diet were 49% and 66%, respectively, higher in the M/S ratio as compared to their counterparts from animals on the control diet. Cooking had little effect on relative differences in the M/S ratio between HOSO and control samples. Cooking loss and sensory properties were not adversely affected by the changes in fatty acid composition. However, cooked chops and roasts from the HOSO group had lower thiobarbituric acid values during storage at 4°C. 相似文献
23.
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
24.
JW Rhee 《The Journal of communication》1997,47(3):26-48
This study examines how news frames in campaign coverage affect individuals' interpretation of campaigns. Framing effects are conceptualized in terms of the process by which textual features in news stories set limits on knowledge use in the construction of a discourse model - a mental model constructed through the interaction between news frames and the interpreter's social knowledge. Examining message structures in campaign news stories led to identifying two major frames in campaign coverage: strategy and issue. Narrative data collected from two field experiments were analyzed. The findings suggest that both strategy-framed and issue-framed print news stories are effective in influencing campaign interpretation. 相似文献
25.
S. Kim S. J. Rhee X. Li J. J. Coleman S. G. Bishop P. B. Klein 《Journal of Electronic Materials》1998,27(4):246-254
Site-selective photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies carried out at 6K on the ∼1540
nm 4I13/2→4I15/2 emissions of Er3+ in Er-implanted GaN have revealed the existence of four different Er3+ sites and associated PL spectra in this semiconductor. Three of these four sites are excited by below-gap, impurity- or defect-related
absorption bands, with subsequent nonradiative energy transfer to the Er3+ 4f electrons; a fourth site is excited by direct Er3+ 4f shell absorption. PLE spectra obtained by selectively detecting Er3+ PL from each of the three sites pumped by broad below-gap absorption bands are compared with the PLE spectra of broad PL
bands attributed to implantation damage-induced defects in the Er-implanted GaN. This comparison enables us to distinguish
broad-band, below-gap optical excitation processes for Er3+ emission that are attributable to (1) absorption due to implantation damage-induced defects; (2) absorption due to defects
or impurities characteristic of the as-grown GaN film; and (3) an Er-specific absorption band just below the band gap which
may involve the formation of an Er-related isoelectronic trap. The two sites excited by impurity-or defect-related absorption
bands are also strongly pumped by above-gap excitation, while the sites pumped by the Er-related trap and direct 4f shell
absorption are not. This observation indicates that excitation of Er3+ luminescence in crystalline semiconductor hosts by either optical or electrical injection of electron-hole pairs is dominated
by trap-mediated carrier capture and energy transfer processes. These trap-mediated processes may also control the thermal
quenching of Er3+ emission in semiconductors. 相似文献
26.
The error performance of a modulation code over a channel depends on several distance parameters and the path multiplicity of the code. For the AWGN channel, the error performance of a modulation code depends mainly on its minimum squared Euclidean distance and path multiplicity. For the Rayleigh fading channel, however, the error performance of a modulation code depends strongly on its minimum symbol distance, minimum product distance, and path multiplicity. It depends on the minimum squared Euclidean distance in a lesser degree. This paper is concerned with the construction of block and trellis MPSK modulation codes for the Rayleigh fading channel. In each construction, the distance parameters are chosen to achieve good error performance with reduced decoding complexity 相似文献
27.
Transparent ultra-long-haul DWDM networks with "broadcast-and-select" OADM/OXC architecture 总被引:2,自引:0,他引:2
Vasilyev M. Tomkos I. Mehendale M. Rhee J.-K. Kobyakov A. Ajgaonkar M. Tsuda S. Sharma M. 《Lightwave Technology, Journal of》2003,21(11):2661-2672
We describe an experimental realization of ultra-long-haul (ULH) networks with dynamically reconfigurable transparent optical add-drop multiplexers (OADMs) and optical cross-connects (OXCs). A simple new approach to dispersion management in ULH dense-wavelength-division-multiplexing (DWDM) transparent optical networks is proposed and implemented, which enables excellent transmission performance while avoiding dispersion compensation on a connection-by-connection basis. We demonstrate "broadcast-and-select" node architectures that take full advantage of this method. Our implementation of signal leveling ensures minimum variations of path-averaged power among the wavelength-division-multiplexing (WDM) channels between the dynamic gain-equalizing nodes and results in uniform nonlinear and spontaneous-emission penalties across the WDM spectrum. We achieve 80/spl times/10.7-Gb/s DWDM networking over 4160 km (52 spans/spl times/80 km each) of all-Raman-amplified symmetric dispersion-managed fiber and 13 concatenated OADMs or 320/spl times/320 wavelength-port OXCs with 320-km node spacing. The WDM channels use 50-GHz grid in C band and the simple nonreturn-to-zero (NRZ) modulation format. The measured Q values exhibit more than a 1.8-dB margin over the forward-error correction threshold for 10/sup -15/ bit-error-rate operation. We compare these results with point-to-point transmission of 80/spl times/10-Gb/s NRZ WDM signals over 4160 km without OADM/OXC and provide detailed characterization of penalties due to optical signal-to-noise-ratio degradation, filter concatenation, and crosstalk. 相似文献
28.
A 2.5-GHz/900-MHz dual fractional-N/integer-N frequency synthesizer is implemented in 0.35-μm 25-GHz BiCMOS. A ΔΣ fractional-N synthesizer is employed for RF channels to have agile switching, low in-band noise, and fine frequency resolution. Implementing two synthesizers with an on-chip ΔΣ modulator in a small package is challenging since the modulator induces substantial digital noise. In this work, several design aspects regarding noise coupling are considered. The fractional-N synthesizer offers less than 10-Hz frequency resolution having the in-band noise contribution of -88 dBc/Hz for 2.47-GHz output frequency and -98 dBc/Hz for 1.15-GHz output frequency, both measured at 20-kHz offset frequency. The prototype dual synthesizer consumes 18 mW with 2.6-V supply 相似文献
29.
30.
Sung-Chan Kim Baek-Seok Ko Tae-Jong Baek Byeong-Ok Lim An D. Dong-Hoon Shin Jin-Koo Rhee 《Microwave and Wireless Components Letters, IEEE》2005,15(10):652-654
The hybrid ring coupler was designed and fabricated on a GaAs substrate using surface micromachining techniques, which adopted dielectric-supported air-gapped microstrip line (DAML) structure. The fabrication process of DAML is compatible with the standard monolithic microwave integrated circuit (MMIC) techniques, and the hybrid ring coupler can be simply integrated into a plane-structural MMIC. The fabricated hybrid ring coupler shows wideband characteristics of the coupling loss of 3.57 /spl plusmn/ 0.22dB and the transmission loss of 3.80 /spl plusmn/ 0.08dB across the measured frequency range of 85 to 105GHz. The isolation characteristics and output phase differences are -34dB and 180/spl plusmn/1/spl deg/, at 94GHz, respectively. 相似文献