• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2377-2379
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• 1999

In order to analyze failure rates of underground transmission power cable systems in Korea, the survey has been performed for the failure cases of cables, joints, and terminations in CV, OF and POF cable systems which occurred from 1983 to 1998. During 16 years, the failure cases due to trips of the systems were 47 among the total 108 cases, These 47 cases could be divided into internal reasons(manufacture/installation, corrosion and degradation) of 16 cases and external reasons (external mechanical damages, lightning, fire. etc.) of 31 cases. For the 154 kV cable systems during 12 years from 1987 to 1998, total failure rate was 0.0057 [case/100C-km/year] and internal reason failure rate was 0.0020 [case/100C-km/Year], which is similar to those of foreign countries. Also, the many cases of internal reason failures occurred in the early stage after the operations due to incorrect installations. This implies that the installation process is very important and some diagnostic tests such as PD measurement are needed besides after laying test.

• Geomechanics and Engineering
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• 제17권4호
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• pp.333-342
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• 2019

Geological dynamic hazards during coal mining can be caused by the failure of a composite system consisting of roof rock and coal layers, subject to different loading rates due to different advancing velocities in the working face. In this paper, the uniaxial compression test simulations on the composite rock-coal layers were performed using $PFC^{2D}$ software and especially the effects of loading rate on the stress-strain behavior, strength characteristics and crack nucleation, propagation and coalescence in a composite layer were analyzed. In addition, considering the composite layer, the mechanisms for the advanced bore decompression in coal to prevent the geological dynamic hazards at a rapid advancing velocity of working face were explored. The uniaxial compressive strength and peak strain are found to increase with the increase of loading rate. After post-peak point, the stress-strain curve shows a steep stepped drop at a low loading rate, while the stress-strain curve exhibits a slowly progressive decrease at a high loading rate. The cracking mainly occurs within coal, and no apparent cracking is observed for rock. While at a high loading rate, the rock near the bedding plane is damaged by rapid crack propagation in coal. The cracking pattern is not a single shear zone, but exhibits as two simultaneously propagating shear zones in a "X" shape. Following this, the coal breaks into many pieces and the fragment size and number increase with loading rate. Whereas a low loading rate promotes the development of tensile crack, the failure pattern shows a V-shaped hybrid shear and tensile failure. The shear failure becomes dominant with an increasing loading rate. Meanwhile, with the increase of loading rate, the width of the main shear failure zone increases. Moreover, the advanced bore decompression changes the physical property and energy accumulation conditions of the composite layer, which increases the strain energy dissipation, and the occurrence possibility of geological dynamic hazards is reduced at a rapid advancing velocity of working face.

• Journal of Gastric Cancer
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• 제10권4호
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• pp.155-161
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• 2010

Purpose: The purpose of this study was to investigate the reliability and the clinical applicability of the adenosine-triphosphate-based chemotherapy response assay (ATP-CRA) as a method of determining in vitro chemosensitivity in patients with gastric cancer. Materials and Methods: A total of 243 gastric cancer tissue samples were obtained from gastrectomies performed between February 2007 and January 2010. We evaluated the effectiveness of the ATP-CRA assay in determining the chemosensitivity of gastric cancer specimens using eleven chemotherapeutic agents - etoposide, doxorubicin, epirubicin, mytomicin, 5-fluorouracil, oxaliplatin, irinotecan, docetaxel, paclitaxel, methotraxate, and cisplatin - for chemosensitivity studies using ATP-CRA. We assessed the failure rate, the cell death rate, and the chemosensitivity index. Results: The failure rate of ATP-CRA was 1.6% (4/243). The mean coefficient of variation for triplicate ATP measurements was 6.5%. Etoposide showed the highest cell death rate (35.9%) while methotrexate showed the lowest (16.6%). The most active chemotherapeutic agent was etoposide, which most frequently ranked highest in the chemosensitivity test: 31.9% (51/160). Oxaliplatin was more active against early gastric cancers than advanced gastric cancers, whereas docetaxel was more active against advanced cancers. The lymph node negative group showed a significantly higher cell death rate than the lymph node positive group when treated with doxorubicin, epirubicin, and mitomycin. Conclusions: ATP-CRA is a stable and clinically applicable in vitro chemosensitivity test with a low failure rate. The clinical usefulness of ATP-CRA should be evaluated by prospective studies comparing the regimen guided by ATP-CRA with an empirical regimen.

• Tuberculosis and Respiratory Diseases
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• 제50권6호
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• pp.686-692
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• 2001

배 경 : 다제내성 폐결핵의 발생은 약제선택의 제한성과장기간의 항결핵제의 복용으로 인한 부작용 등으로 인하여 치료 성공율을 감소시킨다. 본 연구는 치료 실패인자들을 알아내어 다제내성 폐결핵의 치료 성공율을 향상시키는데 기초자료로 삼고자 하였다. 대상 및 방법 : 1996년 1월부터 1998년 12월까지 입원치료를 시행한 다제내성 폐결핵 환자 111명을 대상으로 하였다. 다제내성 폐결핵 치료의 실패에 관계되는 인자들을 분석하기 위하여 치료에 성공한 군(I군)과 실패한 군(II군)으로 나누어 각 인자들을 독립표본 T-검정, $X^2$ 검정 그리고 Fisher의 정확확률 검정으로 비교 분석하였다. 결 과 : I군과 II군을 비교한 결과, 폐결핵 과거력의 유무, 흉부방사선 검사상 공동이 있는 경우와 과거의 치료 횟수, 내성 약제의 개수 그리고 치료약제의 개수에서 통계적 유의성을 관찰할 수 있었다(p<0.05). 결 론 : 다제내성 폐결핵 치료 실패의 위험인자는 과거의 치료력, 흉부방사선상 공동이 있는 경우, 내성약제의 개수가 많은 것임을 알 수 있었다. 따라서 다제내성 폐결핵의 치료 효과를 향상시키기 위하여 초치료 폐결핵관리를 보다 철저히 하여 항결핵제에 대한 약제 내성발생을 억제하는데 노력을 하여야 할 것으로 생각된다.

• 품질경영학회지
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• 제34권3호
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• pp.19-30
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• 2006

For highly reliable products, it is difficult to assess the lifetime of the products with traditional life tests. Accordingly, a recent approach is to observe the performance degradation of product during the test rather than regular failure time. This study compares performances of three methods(i.e. the approximation, analytical and numerical methods) to estimate the parameters and quantiles of the lifetime when the time-to-failure distribution follows Weibull and lognormal distributions under a random coefficient degradation rate model. Numerical experiments are also conducted to investigate the effects of model error such as measurements in a random coefficient model.

• 한국신뢰성학회지:신뢰성응용연구
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• 제4권1호
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• pp.15-26
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• 2004

Life test is performed to set a confidence (lower) limit on the mean or median life of items if the number of failures at the end of the fixed time t does not exceed a given number c. Gupta(1962) propose a sampling plan for truncated life tests when the life distribution of an item is normal or lognormal distribution. In this paper, based on the result of Gupta(1962), we propose a sampling plan for failure rate test when an item has normal or lognormal life distribution. We assume that the shape parameter is known while the location parameter is unknown.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권3호
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• pp.259-274
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• 2009

Printed circuit boards for RAM are widely used in modern electronics such as computers, artificial satellites and consumer durables. They are exposed to a very diverse environment and consists of many complicated components and therefore needs careful approach to the enhancement and assessment of reliability of the item. In this article reliability standards for PCBs for RAM are established in terms of quality certification tests and failure rate tests.

• 한국정보통신학회논문지
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• 제10권1호
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• pp.7-14
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• 2006

비동질적인 포아송 과정에 기초한 모형들에서 잔존 결함 1개 당 고장 발생률은 일반적으로 상수, 혹은 단조증가 및 단조 감소 추세를 가지고 있다. 본 논문에서는 잔존 결함 1개당 고장 발생률이 증가추세를 가진 어랑 분포를 이용한 어랑 모형을 제안하였다. 고장 간격시간으로 구성된 실측자료를 이용하여 기존의 모형과 어랑 모형의 모수 추정을 실시하였다. 어랑 모형의 형상모수를 선택하기 위하여 (누적)분포적합도 검정을 사용하였고 이 자료들에서 어랑 모형의 제안과 비교를 위하여 산술적 및 라플라스 검정, 적합도 검정, 편의 검정 등을 이용하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.209-213
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• 2001

The reliability data analysis for components of CNC machining center is studied in this paper. The failure data of mechanical part is analyzed by Exponential, Weibull, and Log-normal distributions. And then, the optimum failure distribution model is selected by goodness of fit test. The reliability data analysis program is developed with ASP language to use on the Internet. The failure rate, MTBF, life, and failure mode of mechanical parts are estimated and searched by this program. The failure data and analysis results are stored in the database.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.507-517
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• 2018

In this research the effect of bedding layer angle and bedding layer thickness on the shear failure mechanism of concrete has been investigated using PFC3D. For this purpose, firstly calibration of PFC3d was performed using Brazilian tensile strength. Secondly punch shear test was performed on the bedding layer. Thickness of layers were 5 mm, 10 mm and 20 mm. in each thickness layer, layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $25^{\circ}$. Totally 15 model were simulated and tested by loading rate of 0.016 mm/s. The results show that when layer angle is less than $50^{\circ}$, tensile cracks initiates between the layers and propagate till coalesce with model boundary. Its trace is too high. With increasing the layer angle, less layer mobilizes in failure process. Also, the failure trace is very short. It's to be note that number of cracks decrease with increasing the layer thickness. The minimum shear punch test strength was occurred when layer angle is more than $50^{\circ}$. The maximum value occurred in $0^{\circ}$. Also, the shear punch test tensile strength was increased by increasing the layer thickness.