• Korean Journal of Remote Sensing
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• v.27 no.6
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• pp.729-741
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• 2011

Wind speeds have long been estimated from C-band VV-polarized SAR data by using the CMOD algorithms such as CMOD4, CMOD5, and CMOD_IFR2. Some SAR data with HH-polarization without any observations in VV-polarization mode should be converted to VV-polarized value in order to use the previous algorithms based on VV-polarized observation. To satisfy the necessity of polarization ratio (PR) for the conversion, we retrieved the conversion parameter from full-polarized SIR-C SAR image off the east coast of Korea. The polarization ratio for SIR-C SAR data was estimated to 0.47. To assess the accuracy of the polarization ratio coefficient, pseudo VV-polarized normalized radar cross section (NRCS) values were calculated and compared with the original VV-polarized ones. As a result, the estimated psudo values showed a good agreement with the original VV-polarized data with an root mean square error by 0.99 dB. We applied the psudo NRCS to the estimation of wind speeds based on the CMOD wind models. Comparison of the retrieved wind field with the ECMWF and NCEP/NCAR reanalysis wind data showed relatively small rms errors of 1.88 and 1.91 m/s, respectively. SIR-C HH-polarized SAR wind retrievals met the requirement of the scatterometer winds in overall. However, the polarization ratio coefficient revealed dependence on NRCS value, wind speed, and incident angle.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.3
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• pp.234-239
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• 2015

This paper focuses on analyzing the modern warfare and weapon systems supported by improved GPS informations. The GPS capability was investigated through the real experimental test for verifying the most recent GPS features under its modernization processing. And then it was verified that such capabilities, accuracy and availability, of a typical L1, C/A code GPS receiver are equivalent to the military receiver's ones. It was also sure that the influence of GPS improved informations on NCW(Network-Centric Warfare), PGM(Precision Guided Munition) and C4SIR(Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance) should be increased and the modern warfare may be strongly dependent on GNSS informations.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.584-587
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• 2000

The invasion genes from Salmonella typhimurium were identified by the construction of a cosmid library and subcloning genes into a plasmid vector, pGEM-7Z. The 4.65 kb fragment of the invasion-conferring genomic region of the subclone, pSV6235 was sequenced in both direction. The three open reading frames, which were located at downstream of a promoter region, were designated as sir (Salmonella invasion region)A coding for the 36 amino acids, sirB coding for the 132 amino acids and sirC for the 82 amino acids, respectively. Interesingly, the genomic region of pSV6235 was highly homologous to Yersinia enterocolitica genomic DNA for a high pathogenicity island and Salmonella enteritidis insertion element IS1351 and IS200 DNA. These results show that there could be a significant relationship between S. typhimurium, Y. enterocolitica and S. enteritidis with respect to horizontal evolution process and acquisition of virulence determinants by means of transposon, plasmid or bacteriophage.

• Journal of Gastric Cancer
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• v.20 no.1
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• pp.81-94
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• 2020

Purpose: Duodenal stump leakage (DSL) is a potentially fatal complication that can occur after gastrectomy, but its underlying risk factors are unclear. This study aimed to investigate the risk factors and management of DSL after laparoscopic radical gastrectomy for gastric cancer (GC). Materials and Methods: Relevant data were collected from several prospective databases to retrospectively analyze the data of GC patients who underwent Billroth II (B-II) or Rouxen-Y (R-Y) reconstruction after laparoscopic gastrectomy from 2 institutions (Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, and HwaMei Hospital, University of Chinese Academy of Sciences). The DSL risk factors were analyzed using univariate and multivariate analysis regression. Results: A total of 810 patients were eligible for our analysis (426 with R-Y, 384 with B-II with Braun). Eleven patients had DSL (1.36%). Body mass index (BMI), elevated preoperative C-reactive protein (CRP) level, and unreinforced duodenal stump were the independent risk factors for DSL. DSL was diagnosed in 2-12 days, with a median of 8 days. Seven patients received conservative treatment, 3 patients received puncture treatment, and only 1 patient required reoperation. All patients recovered successfully after treatment. Conclusions: The risk factors of DSL were BMI ≥24 kg/㎡, elevated preoperative CRP level, and unreinforced duodenal stump. Nonsurgical treatments for DSL are preferred.

• Current Applied Physics
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• v.18 no.12
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• pp.1540-1545
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• 2018

SiGe alloy is widely used thermoelectric materials for high temperature thermoelectric generator applications. However, its high thermoelectric performance has been thus far realized only in alloys synthesized employing mechanical alloying techniques, which are time-consuming and employ several materials processing steps. In the current study, for the first time, we report an enhanced thermoelectric figure-of-merit (ZT) ~ 1.1 at $900^{\circ}C$ in ntype $Si_{80}Ge_{20}$ nano-alloys, synthesized using a facile and up-scalable methodology consisting of rapid solidification at high optimized cooling rate ${\sim}3.4{\times}10^7K/s$, employing melt spinning followed by spark plasma sintering of the resulting nano-crystalline melt-spun ribbons. This enhancement in ZT > 20% over its bulk counterpart, owes its origin to the nano-crystalline microstructure formed at high cooling rates, which results in crystallite size ~7 nm leading to high density of grain boundaries, which scatter heat-carrying phonons. This abundant scattering resulted in a very low thermal conductivity ${\sim}2.1Wm^{-1}K^{-1}$, which corresponds to ~50% reduction over its bulk counterpart and is amongst the lowest reported thus far in n-type SiGe alloys. The synthesized samples were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy, based on which the enhancement in their thermoelectric performance has been discussed.

• Journal of the Korean earth science society
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• v.31 no.5
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• pp.475-487
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• 2010

Sea surface wind field was retrieved from high-resolution SIR-C SAR data by using CMOD algorithms off the east coast of Korea. In order to extract wind direction information from SAR data, a two-dimensional spectral analysis method was applied to the normalized radar cross section of the image. An $180^{\circ}$-ambiguity problem in the determination of wind direction was solved by selecting a direction nearest to the wind vector of the ECMWF reanalysis data. Comparison of the wind retrieval patterns with the ECMWF and NCEP/NCAR dataset showed RMS errors in the range of 1.30 to $1.72\;ms^{-1}$. In contrast, comparison of wind directions revealed large errors of greater than $60^{\circ}$, which is enormously higher than the permitted limit of about $20^{\circ}$ for satellite scatterometer winds. Compared with wind speed results from different algorithms, wind vectors based on commonly-used CMOD4 algorithm showed good agreement with those derived by other algorithms such as CMOD_IFR2 and CMOD5, particularly at medium winds from 4 to $8\;ms^{-1}$. However, apparent discrepancy appeared at low winds (< $4\;ms^{-1}$). This study also addressed an importance of accurate wind direction data to improve the accuracy of wind speed retrieval and discussed potential causes of wind retrieval errors from SAR data.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.2
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• pp.1043-1047
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• 2013

Although there have been many studies investigating possible associations between the C1653T mutation and risk of HCC, the results have been inconsistent. We conducted searches of the published literature in Pubmed and Embase databases up to January 2013. Seventeen studies with a total of 1,085 HCC cases and 1,365 healthy controls were retrieved. We found a significant association between the C1653T mutation and HCC risk (OR = 2.01, 95%CI= 1.49-2.70). In the subgroup analysis by ethnicity, a significant association was also found in Asians (OR = 2.07, 95%CI= 1.71-2.51). In subgroup analysis by HBV genotype, B and C were linked with development of HCC (B:OR = 2.21, 95%CI= 1.13-4.34; C:OR = 2.26, 95%CI= 1.61-3.16). However, no significant association was found between the C1653T mutation and HCC risk in HBeAg positive cases. In conclusion, this meta-analysis suggests that the C1653T mutation may be associated with susceptibility to HCC.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.370-382
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• 2013

Distributed massive MIMO systems, which have high bandwidth efficiency and can accommodate a tremendous amount of traffic using algorithms such as zero-forcing beam forming (ZFBF), may be deployed in large public venues with the antennas mounted under-floor. In this case the channel gain matrix H can be modeled as a multi-banded matrix, in which off-diagonal entries decay both exponentially due to heavy human penetration loss and polynomially due to free space propagation loss. To enable practical implementation of such systems, we present a multi-banded matrix inversion algorithm that substantially reduces the complexity of ZFBF by keeping the most significant entries in H and the precoding matrix W. We introduce a parameter p to control the sparsity of H and W and thus achieve the tradeoff between the computational complexity and the system throughput. The proposed algorithm includes dense and sparse precoding versions, providing quadratic and linear complexity, respectively, relative to the number of antennas. We present analysis and numerical evaluations to show that the signal-to-interference ratio (SIR) increases linearly with p in dense precoding. In sparse precoding, we demonstrate the necessity of using directional antennas by both analysis and simulations. When the directional antenna gain increases, the resulting SIR increment in sparse precoding increases linearly with p, while the SIR of dense precoding is much less sensitive to changes in p.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.78-84
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• 2001

In the present study, SiCSi-$Si_3 N_4$-SiC ceramic composites that contained up to 30 wt% of dispersed SiC particles were fabricat-ed cia hot-pressing with an oxynitride glass. The microstructure, the mechanical properties and the cutting performance of resulting ceramic composites were investigated. By fixing the composition as $Si_3 N_4$-20wf%SiC, the effect of sintering time on the microstructure, the mechanical properties and the cutting performance were also investigated. The longer sir-tering time is, the bigger the grain size of SiC is. The fracture toughness(-$K_k$) of the $Si_3 N_4$-SiC ceramic composites increased with the increase of gain size, while the flexural strengthh($\sigma$) decreased. For machining SCM440, the insert with 20wt%r SiC sintered for 8 hours showed the longest tool life while the insert with 20wt% SiC sintered for 12 hours showed the longest tool life for machining gray cast iron.

• Journal of Ecology and Environment
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• v.36 no.4
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• pp.223-233
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• 2013

Acid deposition is one of the most serious environmental problems in ecosystems. The present study surveyed the effects of simulated acid rain on leaf litter mass loss and microbial community in the decomposing leaf litter of Sorbus anifolia in a microcosm at $23^{\circ}C$ and 40% humidity. Microbial biomass was measured by substrate-induced respiration (SIR) and phospholipid fatty acids (PLFAs), and the microbial community structures were determined by composition of PLFAs at each interval of decomposition in litter sample and at each pH treatment. The microbial biomass showed peaks at mid-stage of decomposition, decreasing at the late stage. The leaf litter mass loss of S. anifolia decreased with decreasing pH during early and mid-decomposition stages; however the mass loss becomes similar between pH treatments at late-decomposition stage. The acidification remarkably lowers the microbial biomass of bacteria and fungi; however, microbial diversity was unchanged between pH treatments at each stage of litter decomposition. With changes of decomposition stage and pH treatment there were considerable differences in replacement and compensation of microbial species. Fungi/bacteria ratio was considerably changed by pH treatment. The PLFA profile showed significantly larger fungi/bacteria ratio at pH 5 than pH 3 at the early stage of decomposition, and the difference becomes smaller at the later decomposition stage. At low pH, pH 3 and pH 4, the fungi/bacteria ratios were stable according to the litter decomposition stages. Simulated acid rain caused decreases of 10Me17:0, 16:1${\omega}$7c, 18:1${\omega}$7, 15:0, but increase of 24:0. In addition, litter mass loss showed significant positive correlation with microbial biomass measured by SIR and PLFA on the decomposing leaf litter.