• Elastomers and Composites
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• 제41권2호
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• pp.79-87
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• 2006

내소음성과 내균열성을 가진 고무재료의 개발을 목적으로 NBR에 oleamide와 아라미드를 첨가하여 함량에 따른 가황특성, 물리적 성질, 내열성, 내유성, 내마모성, 내균열성 및 내소음성을 조사하였다. 가황특성과 Mooney 점도를 측정한 결과, 미가황고무의 가황특성은 oleamide의 양이 증가할수록 torque가 감소하였다. oleamide의 함량이 3 phr까지 증가함에 따라 경도 및 모듈러스 값은 조금씩 감소하였고 신장률은 감소하는 경향을 나타내었으며 인장강도는 거의 변화가 없었다. 내열성 시험(70시간, $120^{\circ}C$) 및 내유성 시험(70시간, $40^{\circ}C$)을 수행한 결과. 인장강도와 신장률이 모두 감소하였으며, TGA/DSC 분석 결과 첨가제에 따른 배합고무재료의 열적특성은 변화가 없었다. 기본물성, 내마모성, 내소음성 및 내균열성을 종합한 결과, NBR 227001 고무재료에서 내마모성과 내소음성에 대한 oleamide의 최적배합비는 3 phr였으며, 내균열성에 대한 아라미드의 최적배합비는 1 phr로 나타났다.

• Molecules and Cells
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• 제42권3호
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• pp.237-244
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• 2019

Understanding the mechanisms of cancer drug resistance is a critical challenge in cancer therapy. For many cancer drugs, various resistance mechanisms have been identified such as target alteration, alternative signaling pathways, epithelial-mesenchymal transition, and epigenetic modulation. Resistance may arise via multiple mechanisms even for a single drug, making it necessary to investigate multiple independent models for comprehensive understanding and therapeutic application. In particular, we hypothesize that different resistance processes result in distinct gene expression changes. Here, we present a web-based database, CDRgator (Cancer Drug Resistance navigator) for comparative analysis of gene expression signatures of cancer drug resistance. Resistance signatures were extracted from two different types of datasets. First, resistance signatures were extracted from transcriptomic profiles of cancer cells or patient samples and their resistance-induced counterparts for >30 cancer drugs. Second, drug resistance group signatures were also extracted from two large-scale drug sensitivity datasets representing ~1,000 cancer cell lines. All the datasets are available for download, and are conveniently accessible based on drug class and cancer type, along with analytic features such as clustering analysis, multidimensional scaling, and pathway analysis. CDRgator allows meta-analysis of independent resistance models for more comprehensive understanding of drug-resistance mechanisms that is difficult to accomplish with individual datasets alone (database URL: http://cdrgator.ewha.ac.kr).

• 한국동물위생학회지
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• 제32권3호
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• pp.227-239
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• 2009

At the present study, it was aimed to detect virulence genes and antimicrobial resistance genes among 102 strains of 12 Salmonella serotypes isolated from pigs and cattle. In polymerase chain reaction (PCR), invA was detected from all strains of Salmonella spp., spvC was detected from Salmonella enterica serotype Enteritidis (S. Enteritidis) (100%), S. Bradenburg (75%), and S. Typhimurium (20.4%). Drug resistance related genes of 12 types were detected from all strains. TEM ($bla_{TEM}$) gene was detected from 51 (92.7%) of 55 $\beta$-lactams (54 ampicillin or 1 amoxicillin) resistance strains. 55 (100%) of 55 chloramphenicol resistance strains, 3 (100%) of 3 gentamicin resistance strains and 5 (100%) of 5 kanamycin resistance strains did contain cml, aadB, and aphA1-Iab, respectively. strB (89.9%), strA (88.4%), aadA2 (84.1%) and aadA1 (72.5%) were detected from 69 streptomycin resistance strains. sulII and dhfrXII were detected from 49 (100%) of 49 sulfamethoxazole/trimethoprim resistance strains, but sulI was not detected. tetA (97.9%) and tetB (21.6%) were detected from 97 tetracycline resistance strains. int gene was detected from 58 (56.9%) of 102 strains. 54 S. Typhimurium of 102 Salmonella spp. were attempted to detect drug resistance genes. TEM was detected from 44 (95.7%) of 46 $\beta$-lactams (45 ampicillin or 1 amoxicillin) resistance strains. cmlA was detected from 51 (100%) of 51 chloramphenicol resistance strains. aadA2 (100%), strA (100%), strB (100%), and aadA1 (79.6%) were detected from 54 streptomycin resistance strains. sulII (100%) and dhfrXII (100%) were detected from 49 sulfamethoxazole/trimethoprim resistance strains. tetA was detected from 54 (100%) of 54 tetracycline resistance strains. int gene was detected from 54 (100%) of 54 strains. The major drug resistance pattern and resistance gene profile were ampicillin, chloramphenicol, streptomycin, sulfamethoxazole/trimethoprim and tetracycline (ACSSuT) and TEM, cmlA, aadA1, aadA2, strA, strB, sulII, dhfrXII, tetA and int, respectively.

• Tuberculosis and Respiratory Diseases
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• 제40권3호
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• pp.267-273
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• 1993

연구배경 : Airway resistance 측정시 panting 방법은 비정상적인 호흡패턴으로 환자에 따라서는 수행이 어렵고 quiet breathing 방법은 더욱 생리적인 호흡상태하에서 측정이 가능하다. 과거에는 주로 panting을 이용하였으나 최근에는 quiet breathing을 이용하는 추세로 본 연구에서는 panting 및 quiet breathing시에 airway resistance를 측정하여 이를 비교하였다. 방법 : 정상대조군 및 호흡기질환군을 대상으로 유량기량곡선을 측정하고, body plethysmograph를 이용하여 airway resistance를 quiet breathing과 panting시에 각각 측정하였다. 결과: 1) Quiet breathing과 panting시 측정한 airway resistance는 높은 상관관계를 보였다(Raw tot; 0.887, Raw 0.5; 0.921, p<0.05). 2) Panting시 quiet breathing에 비하여 Raw tot는 21.2%. Raw 0.5는 22.1%의 감소율을 보였으며, Inspiratory와 expiratory Resistance의 측정이 가능하였던 경우 Raw insp은 29.3%, Raw exp은 40.6%의 감소율을 보였다. 3) Panting시 airway resistance의 감소율은 호흡기질환군보다 대조군에서 더 컸다. 4) Panting시 specific airway conductance가 유의하게 증가되었으므로 airway resistance의 감소는 thoracic gas volume의 차이와는 관련이 없었다. 5) Panting시 quiet breathing에 비하여 airway resistance가 감소하지 않는 환자는 비교적 airway resistance가 커서 panting을 잘 수행하지 못하는 환자로 추정된다. 결론 : Airway resistance 측정시 환자의 수행능력에 따라 quiet breathing 혹은 panting 방법을 이용할 수 있으나 panting시 quiet breathing보다 결과가 약 20% 감소됨을 고려하여야 하며, 정상군 및 폐질환군에서 panting보다 quiet breathing이 airway resistance를 측정하는 더 좋은 방법으로 생각된다.

• 한국지반공학회논문집
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• 제30권11호
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• pp.51-60
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• 2014

한계상태설계법의 하나인 하중저항계수설계법의 이용이 북미를 중심으로 점차 확산되고 있는 가운데, 국내에서도 이에 대한 연구가 활발하게 진행되고 있다. 하지만, 국내에서는 자료가 충분히 확보되지 못하여 기초구조물의 설계에 AASHTO에서 제안한 저항계수를 설계에 이용하고 있다. AASHTO에서 제안하고 있는 저항계수는 북미에 보편적으로 존재하는 암반조건을 이용하여 결정된 저항계수로서, 국내지반에 적합한 저항계수를 독자적으로 개발할 필요가 있다. 또한, 기존의 신뢰성 분석 기법에서는 하중저항계수를 결정할 때, 저항의 최소값을 0으로 가정하는 일반적인 대수정규 분포를 이용하기 때문에, 이로부터 산정한 파괴확률은 비현실적이라고 알려져 있다. 따라서, 이를 개선하기 위하여 저항계수를 산정할 때 저항의 하한값이 0이 아닌, 현실적으로 의미가 있는 하한지지력을 이용하는 방법이 최근에 고안되었다. 따라서, 본 연구에서는 국내에서 수행된 현장타설말뚝 13본에 대한 재하시험자료를 면밀히 분석하여 저항계수를 산정한 다음, 현실성 있는 하한지지력을 산정하여 저항계수 값을 보정하였다. 그 결과, 목표신뢰도지수가 3.0일때, 기존의 신뢰성 분석 기법으로부터 산정된 주면저항계수와 선단저항계수는 각각 0.13-0.32, 0.19-0.29 이었으며, 하한지지력을 보정하여 구한 주면저항계수와 선단저항계수는 Carter & Kulhawy 공식의 경우 각각 8%와 13% 증가하였다.

• 충청수학회지
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• 제26권1호
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• pp.243-248
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• 2013

In this paper, we introduce the mathematical resistance and examine its properties and consider the applications of mathematical resistance to conformal mappings. We obtain the theorems in the connection with "the mathematical resistance zero" and "the fundamental sequences".

• 한국해양공학회지
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• 제14권2호
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• pp.112-116
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• 2000

To determine a preliminary hull form with a minimum viscous resistance this study considers the systematic variations of full form and calculations of the viscous resistance for varied hull forms. A preliminary hull form can be determined from a parametric study of viscous resistance.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.5.1-5.1
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• 2009

Organic photovoltaic (OPV)cells have attracted considerable attention due to their potential for flexible, lightweight, and low-cost application of solar energy conversion. Since a 1% power conversion efficiency (PCE) OPV based on a single donor-acceptor heterojunction was reported by Tang, the PCE has steadily improved around 5%. It is well known that a high parallel (shunt)resistance and a low series resistance are required simultaneously to achieve ideal photovoltaic devices. The device should be free of leakage current through the device to maximize the parallel resistance. The series resistance is attributed to the ohmic loss in the whole device, which includes the bulk resistance and the contact resistance. The bulk resistance originated from the bulk resistance of the organic layer and the electrodes; the contact resistance comes from the interface between the electrodes and the active layer. Furthermore, it has been reported that the bulk resistance of the indium tin oxide (ITO) of the devices dominates the series resistance of OPVs for a large area more than $0.01\;cm^2$. Therefore, in practical application, the large area of ITO may significantly reduce the device performance. In this work, we investigated the effect of sheet resistance ($R_{sh}$) of deposited ITO on the performance of OPVs. It was found that the device performance of polythiophene-fullerene (P3HT:PCBM) bulk heterojunction OPVs was critically dependent on Rsh of the ITO electrode. With decreasing $R_{sh}$ of the ITO from 39 to $8.5\;{\Omega}/{\square}$, the fill factor (FF) of OPVs was dramatically improved from 0.407 to 0.580, resulting in improvement of PCE from $1.63{\pm}0.2$ to $2.5{\pm}0.1%$ underan AM1.5 simulated solar intensity of $100\;mW/cm^2$.

• Steel and Composite Structures
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• 제8권6호
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• pp.491-510
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• 2008

This paper presents a plan and guidelines that were drawn for Korean based research carried out on the fire-resistance of CFT columns. This research was carried out by reviewing the Korean regulations related to the fire-resistance of CFT columns and examining studies which had been made in Korea as well as overseas. The first phase of the study plan was to compare the fire-resistance of square CFT columns without fire protection (obtained through fire-resistance tests and numerical analyses) with estimated values (obtained through fire-resistance design formulas proposed in Korea and overseas). This comparison provided conclusions as outlined below. Fire-resistance tests conducted in this study proved that, when the actual design load is taken into consideration, square CFT columns without fire protection are able to resist a fire for more than one hour. A comparison was made of test and analysis results with the fire-resistance time based on the AIJ code, the AISC design formula and the estimation formula suggested for Korea. The results of this comparison showed that the test and analysis results for specimens SAH1, SAH2-1, SAH2-2 and SAH3 were almost identical with the AIJ code, the AISC design formula and estimation formula. For specimens SAH4 and SAH5, the estimation formula was more conservative than the AIJ code and the AISC design formula. It was necessary to identify the factors that have an influence on the fire-resistance of CFT columns without fire protection and to draw fire-resistance design formulas for these columns. To achieve this, it is proposed that numerical analyses and tests be conducted in order to evaluate the fire-resistance of circular CFT columns, the influence of eccentricity existing as an additional factor and the influence of the slenderness ratio of the columns. It is also suggested that the overall behavior of CFT structures without fire protection within a fire be evaluated through analysis simulation.

• 한국동물위생학회지
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• 제35권1호
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• pp.1-8
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• 2012

To detect the virulence genes (invA and spvC) and antimicrobial resistance genes, polymerase chain reaction (PCR) was carried out using total 67 strains of S. Schwarzengrund isolated from pigs. As results, invA was detected from all 67 strains of S. Schwarzengrund, however, spvC was not at all. All 12 strains with ampicillin resistance, 15 strains with chloramphenicol resistance, 9 strains with kanamycin resistance, 1 strain with sulfamethoxazole/trimethoprim resistance, and 66 (98.5%) of 67 strains with tetracycline resistance carried TEM (${\beta}$-lactamase $bla_{TEM}$), cmlA (nonenzymatic chloramphenicol resistance), aphA1-Iab (aminoglycoside phosphotransferase), sulII (dihydropteroate synthase), and tetA (class A tetracycline resistance), respectively. All 63 strains with streptomycin resistance carried 3 aminoglycoside resistance genes, including aadA (aminoglycoside adenyltransferase), strA, and strB (streptomycin phosphotransferase). With respect to prevalence of antibiotic resistance genes occurred in S. Schwarzengrund, genes for strB (46.0%); strA and strB (30.2%); aadA, strA, and strB (9.5%); strA (7.9%); aadA and strB (3.2%); and aadA (3.2%) were detected by PCR.