• Bulletin of the Korean Chemical Society
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• 제32권12호
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• pp.4185-4190
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• 2011

The nucleophilic substitution reactions of ethylene phosphorochloridate (1c) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $5.0^{\circ}C$. The anilinolysis rate of 1c involving a cyclic five-membered ring is four thousand times faster than its acyclic counterpart (1a: diethyl chlorophosphate) because of great positive value of the entropy of activation of 1c (${\Delta}S^{\neq}=+30\;cal\;mol^{-1}K^{-1}$ compared to negative value of 1a (${\Delta}S^{\neq}=-45\;cal\;mol^{-1}K^{-1}$) over considerably unfavorable enthalpy of activation of 1c (${\Delta}H^{\neq}=27.7\;kcal\;mol^{-1}$) compared to 1a (${\Delta}H^{\neq}=8.3\;kcal\;mol^{-1}$). Great enthalpy and positive entropy of activation are ascribed to sterically congested transition state (TS) and solvent structure breaking in the TS. The free energy correlations exhibit biphasic concave upwards for substituent X variations in the X-anilines with a break point at X = 3-Me. The deuterium kinetic isotope effects are secondary inverse ($k_H/k_D$ < 1) with the strongly basic anilines and primary normal ($k_H/k_D$ > 1) with the weakly basic anilines and rationalized by the TS variation from a dominant backside attack to a dominant frontside attack, respectively. A concerted $S_N2$ mechanism is proposed and the primary normal deuterium kinetic isotope effects are substantiated by a hydrogen bonded, four-center-type TS.

• Journal of Microbiology and Biotechnology
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• 제10권5호
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• pp.643-650
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• 2000

A new aniline-utilizing microorganism, strain HY1 obtained from an orchard soil, was characterized by using the BIOLOG system, an analysis of the total cellular fatty acids, and a 16S rDNA sequence. Strain HY1 was identified as a Burkholderia species, and was designated Burkholderia sp. HY1. GC and HPLC analyses revealed that Burkholderia sp. HY1 was able to degrade aniline to produce catechol, which was subsequently converted to cis,cis-muconic acid through an ortho-ring fission pathway under aerobic conditions. Strain HY1 exhibited a drastic reduction in the rate of aniline degradation when glucose was added to the aniline media. However, the addition of peptone or nitrate to the aniline media dramatically accelerated the rate of aniline degradation. A fatty acid analysis showed that strain HY1 was able to produce lipids 16:0 2OH, and 11 methyl 18:1 ${\omega}7c$ approximately 3.7-, 2.2-, and 6-fold more, respectively, when grown on aniline media than when grown on TSA. An analysison the alignment of a 1,435 bp fragment. A phylogenetic analysis of the 16S rDNA sequence based on a 1,420 bp multi-alignment sowed of the 16s rDNA sequence revealed that strain HY1 was very closely related to Burkholderia graminis with 95% similarity based that strain HY1 was placed among three major clonal types of $\beta$-Proteobacteria, including Burkholderia graminis, Burkholderia phenazinium, and Burkholderia glathei. The sequence GAT(C or G)${\b{G}}$, which is highly conserved in several locations in the 16S rDNA gene among the major clonal type strains of $\beta$-Proteobacteria, was frequently replaced with GAT(C or G)${\b{A}}$ in the 16S rDNA sequence from strain HY1.

• 약학회지
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• 제40권1호
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• pp.102-111
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• 1996

LB10522 is a new parenteral broad spectrum cephalosporin with a catechol moiety at C-7 position of beta-lactam ring. This compound can utilize tonB-dependent iron transp ort system in addition to porin proteins to enter bacterial periplasmic space and access to penicillin-binding proteins (PBPs) which are the lethal targets of ${\beta}$-lactam antibiotics. The chelating activity of LB10522 to metal iron was measured by spectrophotometrically scanning the absorbance from 200 to 900nm. When $FeCl_3$ was added, optical density was increased between 450 and 800nm. LB10522 was more active against gram-negative strains in iron-depleted media than in iron-replete media. This is due to the increased expression of iron transport channels in iron-depleted condition. LB10522 showed a similar activity against E. coli DC2 (permeability mutant) and E. coli DCO (wild type strain) in both iron-depleted and iron-replete media, indicating a minimal permeaility barrier for LB10522 uptake. LB10522 had high affinities to PBP 3 and PBP 1A, 1B of E. coli. By blocking these proteins, LB10522 caused inhibition of cell division and the eventual death of cells. This result was correlated well with the morphological changes in E. coli exposed to LB10522. Although the in vitro MIC of LB10522 against P. aeruginosa 1912E mutant (tonB) was 8-times higher than that of the P. aeruginosa 1912E parent strain, LB10522 showed a similar in vivo protection efficacy against both strains in the mouse systemic infection model. This result suggested that tonB mutant, which requires a high level of iron for normal growth, might have a difficulty in surviving in their host with an iron-limited environment.

• Progress in Superconductivity
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• 제14권1호
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• pp.66-70
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• 2012

Superconductor flywheel energy storage system (SFESs) is an electro-mechanical battery with high energy storage density, long life, and good environmental affinity. SFESs have been developed for application to a regenerative power of train, the storage of distributed power sources such as solar and wind power, and a power quality improvement. As superconductor bearing is completely passive, it is not necessary to control a system elaborately but accurate analysis in mechanical properties of the HTS bearing is very important for application to SFESs. Stiffness and damping properties are the main index for evaluation the capacity of HTS bearings and make it possible to adjust rotordynamic properties while operating the rotor-bearing system. The superconductor bearing consists of a stator containing single grain YBCO bulks, a ring-type permanent magnet rotor with a strong magnetic field that can reach the bulk surface, and a bearing support for assembly to SFESs frame. In this study, we investigated the stiffness and damping properties of superconductor bearings in 35 kWh SFESs. Finally, we found that 35 kWh superconductor bearing has uniform stiffness properties depend on the various orientations of rotor vibration. We discovered total damping coefficient of superconductor bearing is affected by not only magnetic damping in superconductor bulk but also external damping in bearing support. From the results, it is confirmed that the conducted evaluation can considerably improve energy storage efficiency of the SFESs, and these results can be used for the optimal capacity of superconductor bearings of the SFESs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1996년도 제11회 학술발표회 논문개요집
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• pp.40-41
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• 1996

Nitridation technique has been receiving much attention for the formation of a thin nitrided buffer layer on which high quality nitride films can be formedl. Particularly, gallium nitride (GaN) has been considered as a promising material for blue-and ultraviolet-emitting devices. It can also be used for in situ formed and stable passivation layers for selective growth of $GaAs_2$. In this work, formation of a thin nitrided layer is investigated. Nitrogen electron cyclotron resonance(ECR)-plasma is employed for the formation of thin nitrided layer. The plasma source used in this work is a compact ECR plasma gun3 which is specifically designed to enhance control, and to provide in-situ monitoring of plasma parameters during plasma-assisted processing. Microwave power of 100-200 W was used to excite the plasma which was emitted from an orifice of 25 rnm in diameter. The substrate were positioned 15 em away from the orifice of plasma source. Prior to nitridation is performed, the surface of n-type (001)GaAs was exposed to hydrogen plasma for 20 min at $300{\;}^{\circ}C$ in order to eliminate a native oxide formed on GaAs surface. Change from ring to streak in RHEED pattern can be obtained through the irradiation of hydrogen plasma, indicating a clean surface. Nitridation was carried out for 5-40 min at $RT-600{\;}^{\circ}C$ in a ECR plasma-assisted molecular beam epitaxy system. Typical chamber pressure was $7.5{\times}lO^{-4}$ Torr during the nitridations at $N_2$ flow rate of 10 seem.(omitted)mitted)

• Journal of the Korean Wood Science and Technology
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• 제41권4호
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• pp.346-357
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• 2013

본 연구에서는 국내 숲가꾸기산물을 이용하여 목재펠릿을 제조하고 품질을 분석하였다. 원료는 일본잎갈나무(Larix kaempferi C.)와 활엽수 혼합 수종을 사용하였으며, 말구직경 6 cm를 기준으로 침엽수와 활엽수로 구분하였다. 분쇄 후 건조된 원료를 이용하여 목재펠릿을 제조하였다. 분쇄와 건조공정을 동일 조건에서 수행하였음에도 불구하고, 원료의 물리 화학적 차이에 따라 생산되는 목재펠릿의 품질에 차이가 발생하였다. 활엽수 혼합수종으로 제조한 목재펠릿은 회분이 1.6% 이상으로 분석되었으며, 일본잎갈나무의 경우에는 직경 6 cm 이하의 소경목에서 회분이 1.0%를 초과하였다. 목재펠릿을 제조하기 이전의 원료 상태에서와 비교하여 제조 후에 회분함량이 0.01~0.1% 정도 상승하는 것을 확인하였다. 발열량에서는 일본잎갈나무가 활엽수 혼합 원료에 비해 약 198 kcal/kg 정도 높았으며, 모든 시료에서 4,300 kcal/kg 이상으로 목재펠릿 원료로 적합한 것으로 분석되었다. 또한, 원료 상태보다 목재펠릿 제조 후 발열량이 일부 상승하는 것을 확인하였다. 원료에 포함된 주요 무기물은 수종 및 분류에 관계없이 Ca, K, Mg, Mn, Fe 등이었으며, 장기 연속 운전을 위해서는 연소기 내 클링커 형성을 억제할 수 있는 연소 방법의 개발이 요구된다. 동일한 펠릿 제조 조건에서 원료에 의해 제품 간의 품질 편차가 크게 발생할 수 있으며, 이를 극복하고 생산성 및 품질 향상을 위해서는 원료에 따른 공정 최적화가 중요한 요소임을 확인하였다.

• 한국공간구조학회논문집
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• 제17권2호
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• pp.21-32
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• 2017

The objective of this study is to analysis the mechanical characteristics on the geometric nonlinear behavior of radial cable roof systems for long span retractable cable roof structures. The retractable roof is designed as a full control system to overcome extreme outdoor environments such as extreme hot or cold weather, strong wind or sunlight, and the cable roof greatly can reduce roof weight compared to other rigid structural system. A retractable cable roof system is a type of structures in which the part of entire roof can be opened and closed. The radial cable roof is an effective structural system for large span retractable roofs, the outer perimeter of the roof is a fixed membrane roof and the middle part is a roof that can be opened and closed. The double arrangement cables of a radial cable truss roof system with reverse curvature works more effectively as a load bearing cables, the cable system can carry vertical load in up and downward direction. In this paper, to analyze the mechanical characteristics of a radial cable roof system with central posts, the authors will investigate the tensile forces of bearing cables, stabilized cables, ring cables, and the deflection of roof according to the height of the post or hub that affects the sag ratio of cable truss. The tensile forces of the cables and the deflection of the roof are compared for the cases when the retractable roof is closed and opened.

• 대한전자공학회논문지TC
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• 제45권12호
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• pp.139-145
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• 2008

본 연구에서는 여파성 표면(FSS : frequency Selective Surface)을 가지는 마이크로스트립 표면파안테나(SWA : Surface Wave Antenna)를 설계 제작하여 그 특성을 실험적으로 고찰한다. 표면파 안테나는 마이크로스트립을 이용하여 박막, 경량, 간단한 제조와 고주파 집적회로에 적합하며 모노폴 안테나와 유사한 방사패턴을 가진다. 여파성 표면을 가지는 마이크로스트립 표면파 안테나는 표면파의 여기를 위한 중앙급전 방식의 마이크로스트립 패치와 표면파의 방사를 위한 주기적인 구조의 패치를 적층하여 구성한다. 광대역 특성을 얻기 위하여 링 모양의 기생 패치를 추가하였고, FSS 단위소자로 원형의 패치를 선택하였다. 실험결과, 공진 주파수는 5.9GHz이고, 대역폭은 12%이며, 5.6dBi의 이득을 나타내었다.

• 대한전자공학회논문지SD
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• 제45권2호
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• pp.130-134
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• 2008

본 논문에서는 1/4-레이트 기법을 사용한 클록 데이터 복원회로를 제안하였다. 제안한 클록 데이터 복원회로를 사용함에 따라 VCO의 발진 주파수를 낮추므로 고속 동작에 유리하다. 제안된 클록 데이터 복원회로는 기존 클록 데이터 복원회로 보다 낮은 지터 특성과 넓은 풀인(pull-in) 범위를 갖는다. 제안된 클록 데이터 복원회로는 1/4-레이트 뱅-뱅 형태의 오버샘플링 위상 검출기, 1/4-레이트 주파수 검출기, 2개의 전하펌프 회로와 저역 통과 필터 그리고 링 VCO회로로 구성되어 있다. 제안된 클록 데이터 복원회로는 $0.18{\mu}m$ 1P6M CMOS 공정으로 설계되었고, 칩 면적과 전력 소모는 $1{\times}1mm^2$, 98 mW 이다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.939-940
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• 2015

본 논문에서는 UHF 대역에 적합한 준-야기 안테나 설계방법에 대해 연구하였다. 코플래너 스트립으로 급전되는 평면 다이폴과 그에 근접하는 도체 스트립 도파기는 상호결합에 의해 광대역 다이폴 특성을 갖는다. 접지면 반사기는 저주파 대역의 이득을 개선할 수 있고, 반사기를 접어서 안테나 크기를 감소시킬 수 있다. 마이크로스트립과 코플래너 스트립 간 밸런은 마이크로스트립 선로 종단을 코플래너 스트립에 단락 핀으로 연결하여 구성하였으며, 코플래너 스트립 선로와 반사기를 원형 링도체로 연결하였다. 안테나의 여러 가지 파라미터들과 밸런이 안테나 특성에 미치는 영향을 관찰하였다. 제안된 구조의 안테나를 지상파 DTV 방송 주파수대역인 470-806 MHz 대역에서 동작하도록 설계하였다.