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991.
Eung Sup Lee Jae Yeon Park Sung Ho Yeom Young Je Yoo 《Korean Journal of Chemical Engineering》2008,25(1):139-143
For effective toluene degradation, the effects of a nitrogen source were studied with Pseudomonas putida BZ912, which was isolated from crude oil contaminated soil and is capable of degrading VOC. Two nitrogen sources, ammonia
and nitrate, showed different effects on specific growth rates (0.25 hr−1 and 0.12 hr−1, respectively), biomass yields (0.56 vs. 0.39) and specific toluene degradation rates (0.51 hr−1 vs. 0.26 hr−1). Under the resting cell conditions, the cells pre-cultured in the ammonia-containing medium showed higher specific toluene
degradation rate than that in nitrate-containing medium (0.045 hr−1 vs. 0.038 hr−1). Ammonia as a nitrogen source was effective for degradation in high toluene concentration because high cellular biomass
was accomplished. Nitrate showed slow growth rate compared to ammonia. The resting cell conditions demonstrated that it was
able to degrade toluene efficiently without increasing biomass. These conditions could be a solution for degrading VOC after
high cellular biomass was obtained in a biofilter. By changing the nitrogen source and the growth conditions according to
the toluene concentration, the control of cell biomass and the desired removal capacity were accomplished. 相似文献
992.
Jin Joo Kim Kyong Hon Kim Min-Hee Lee Hyun Sik Lee El-Hang Lee O-Kyun Kwon Jay Roh Byueng-Su Yoo 《Photonics Technology Letters, IEEE》2007,19(5):297-299
We report, for the first time, a successful 2.5-Gb/s transmission performance of a 1.5-mum emission monolithic vertical-cavity surface-emitting laser (VCSEL) over hybrid links composed of 25-km-long conventional single-mode fibers (SMFs) and a 2.2-km-long 50-mum core multimode fibers (MMFs). This result suggests that 1.5-mum wavelength VCSELs can be effectively used for multigigabit-per-second transmission over hybrid links interconnecting SMF-based long-distance and (or) subscriber network lines with MMF-based local-area network lines in the future ubiquitous network era 相似文献
993.
Novel isodideoxy nucleosides with exocyclic methylene were synthesized starting from L-xylose utilizing anomeric demethoxylation, Wittig reaction and Mitsunobu reaction as key steps and evaluated for antiviral activity. 相似文献
994.
995.
Sung-Hoon Hong Sang-Jo Yoo Si-Woong Lee Hyun-Soo Kang Sung Yong Hong 《Broadcasting, IEEE Transactions on》2003,49(1):1-13
We propose a rate control scheme using a rate-distortion (R-D) estimation model, which produces a consistent picture quality between consecutive frames. Our R-D estimation method offers a closed-form mathematical model that enables us to predict the bits and the distortion generated from a frame encoded at a given quantization parameter (QP) and vice versa. Its most attractive feature is its low computational complexity. Furthermore, it is accurate enough to be applied to practical video coding. In our simulation, the estimation errors for rate and distortion are less than 2.5% and 1.5%, respectively. Therefore, the proposed rate control scheme is appropriate for applications requiring low delay, low complexity, and the ability to control output bit-rate and quality accurately. Our scheme ensures that the video buffers do not underflow or overflow by satisfying the buffer constraint, and it also prevents quality difference between consecutive frames from exceeding a certain demanded level by adopting a distortion constraint. In addition, a consistent picture quality is maintained within a frame, and error propagation, caused by quality degradation of anchor frames, is reduced by differentiating the control procedure for anchor frames from that for nonanchor frames. Simulation results show that our control scheme achieves 0.52-1.84 dB peak signal-to-noise ratio (PSNR) gain over MPEG-2 Test Model 5 (TM5) rate control and maintains very consistent quality within a frame as well as between frames. 相似文献
996.
Numerical simulations of three dimensional turbulent incompressible flows through linear cascades of turbine rotor blades
with high turning angles have been performed using a generalized k−ɛ model which is a high Reynolds number form and derived by RNG (renormalized group) method to account for the variation
of the rate of strain. The convective terms are approximated by using a second order upwind scheme to suppress numerical diffusion.
Boundary-fitted coordinates are adopted to represent the complex cascade geometry accurately. For the case without tip clearance,
secondary flows and flow losses are shown to be in good agreement with previous experimental results. For the case with tip
clearance, the effects of the passage vortex and tip clearance flow on the total pressure loss as well as their interactions
are discussed. The flow within the tip clearance has been analyzed to illustrate the existences of the tip clearance vortex
and vena contracta. 相似文献
997.
998.
Kim J.-Y. Cho S. Lee J. Kim G. B. Lim S.-J. Yoo J. Kim K.-S. Lee S.-M. Shim J. Kim T. Park Y. 《Photonics Technology Letters, IEEE》2006,18(23):2496-2498
We investigate the effect of relative wavelength difference between material gain and resonance peaks on lasing performance in vertical-external-cavity surface-emitting lasers (VECSELs). We propose a measurement method of the wavelength-dependent modal gain profiles by inserting a birefringent filter inside a cavity in order to modulate the optical loss according to the wavelength. With knowledge of the detailed gain profiles, we achieve a stable green output power of 3.3 W and a power conversion efficiency (= green output power/pump input power) of 17% in VECSEL with a LiB3O5 crystal as an intracavity frequency doubler 相似文献
999.
PS Kim SA Hossain YN Park I Lee SE Yoo P Arvan 《Canadian Metallurgical Quarterly》1998,95(17):9909-9913
Newly synthesized thyroglobulin (Tg), the major secretory glycoprotein of the thyroid gland, folds and homodimerizes in the endoplasmic reticulum (ER) before its export to the site of iodination, where it serves as the precursor for thyroid hormone synthesis. In families with defective Tg export, affected individuals suffer from a thyroidal ER storage disease characterized by a distended thyrocyte ER containing misfolded Tg, along with induced ER molecular chaperones. Inherited as an autosomal recessive trait, deficient Tg causes congenital hypothyroidism in newborns that, if untreated, results in goiter along with serious cognitive and growth defects. Recently, a similar phenotype has been observed in inbred cog/cog mice, although the precise molecular defect has remained undefined. Here, we have isolated and cloned a full-length 8.5-kb Tg cDNA from cog/cog mice and unaffected isogenic AKR/J mice. Comparison of the complete sequences reveals that cog/cog mice express a Leu-2263 --> Pro missense mutation in the acetylcholinesterase-homology domain of Tg. Heterologous expression studies in COS cells indicate that cog Tg exhibits a severe defect in exit from the ER. Site-directed mutagenesis of cog Tg to convert the single amino acid back to Leu-2263 restores normal Tg secretion. We conclude that the cog mutation in Tg is responsible for this ER storage disease that causes thyroid dyshormonogenesis. 相似文献
1000.
Seong-Jun Song Sung Min Park Hoi-Jun Yoo 《Solid-State Circuits, IEEE Journal of》2003,38(7):1213-1219
A 4-Gb/s clock and data recovery (CDR) circuit is realized in a 0.25-/spl mu/m standard CMOS technology. The CDR circuit exploits 1/8-rate clock technique to facilitate the design of a voltage-controlled oscillator (VCO) and to eliminate the need of 1:4 demultiplexer, thereby achieving low power consumption. The VCO incorporates the ring oscillator configuration with active inductor loads, generating four half-quadrature clocks. The VCO control line comprises both a programmable 6-bit digital coarse control and a folded differential fine control through a charge-pump and a low pass filter. Duty-cycle correction of clock signals is obtained by exploiting a high common-mode rejection ratio differential amplifier at the ring oscillator output. A 1/8-rate linear phase detector accomplishes the phase error detection with no systematic phase offset and inherently performs the 1:4 demultiplexing. Test chips demonstrate the jitter of the recovered clock to be 5.2 ps rms and 47 ps pk-pk for 2/sup 31/-1 pseudorandom bit sequence (PRBS) input data. The phase noise is measured to be -112 dBc/Hz at 1-MHz offset. The measured bit error rate is less than 10/sup -6/ for 2/sup 31/-1 PRBS. The chip excluding output buffers dissipates 70 mW from a single 2.5-V supply. 相似文献