• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.324-337
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• 2010

For the development of load and resistance factor design, reliability analysis is required to calibrate resistance factors in the framework of reliability theory. The distribution of measured-to-predicted pile resistance ratio was constructed based on only the results of load tests conducted to failure for the assessment of uncertainty regarding pile resistance and used in the conventional reliability analysis. In other words, successful pile load test (piles resisted twice their design loads without failure) results were discarded, and therefore, were not reflected in the reliability analysis. In this paper, a new systematic method based on Bayesian theory is used to update reliability index of driven steel pile piles by adding more pile load test results, even not conducted to failure, into the prior distribution of pile resistance ratio. Fifty seven static pile load tests performed to failure in Korea were compiled for the construction of prior distribution of pile resistance ratio. Reliability analyses were performed using the updated distribution of pile resistance ratio and the total load distribution using First-order Reliability Method (FORM). The challenge of this study is that the distribution updates of pile resistance ratio are possible using the load test results even not conducted to failure, and that Bayesian update are most effective when limited data are available for reliability analysis or resistance factors calibration.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.157-166
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• 2021

This paper aims at the temperature and slenderness ratio effects on physical and mechanical properties of Beishan granite. A series of uniaxial compression tests with various slenderness ratios and temperatures were carried out, and the acoustic emission signal was also collected. As the temperature increases, the fracture aperture of intercrystalline cracks gradually increases, and obvious transcrystalline cracks occurs when T > 600℃. The failure patterns change from tensile failure mode to ductile failure mode with the increasing temperature. The elastic modulus decreases with the temperature and increases with slenderness ratio, then tends to be a constant value when T = 1000℃. However, the peak strain has the opposite evolution as the elastic modulus under the effects of temperature and slenderness ratio. The uniaxial compression strength (UCS) changes a little for the low-temperature specimens of T < 400℃, but a significant decrease happens when T = 400℃ and 800℃ due to phase transitions of mineral. The evolution denotes that the critical brittle-ductile transition temperature increases with slenderness ratio, and the critical slenderness ratio corresponding to the characteristic mechanical behavior tends to be smaller with the increasing temperature. Additionally, the AE quantity also increases with temperature in an exponential function.

• Clinical and Experimental Reproductive Medicine
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• v.30 no.2
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• pp.135-139
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• 2003

Objective: We investigated whether serum testosterone to estradiol ratio was decreased in infertile men and whether this condition can be corrected with oral aromatase inhibitor. Method: The serum testosterone to estradiol ratio of 26 men with testicular failure were compared with those of normal semen analysis parameter, 89 control reference group. All of 26 testicular failure group were diagnosed with the previous testicular biopsy. Then 46 men with oligospermia and/or asthenospermia were selected and treated with 1 mg of the aromatase inhibitor anastrozole ($Arimidex^{(R)}$) orally once daily for 3 months. Testosterone to estradiol ratio and semen analyses were evaluated during anastrozole therapy. Results: The testosterone level of testicular failure group was significantly lower and the testosterone to estradiol ratio was more decreased than normal semen parameter group. Forty six on-anastrozole group had significantly lower testosterone (4.6 versus 5.7 ng/ml, p<0.01) and higher estradiol (15.9 versus 23.4 pg/ml, p<0.01) than pre-anastrozole group, resulting in a decreased testosterone to estradiol ratio ($0.21{\pm}0.07$ versus $0.39{\pm}0.15$, p<0.01). Semen analyses before and during anastrozole treatment revealed significant increases in sperm count (35.5 versus 52.2 million sperm per ml, p<0.01) and motility (22.9% versus 29.3%, p<0.01). Conclusions: We identified infertile men with testicular failure had hormonal changes characterized by a decreased serum testosterone to estradiol ratio. The ratio can be corrected with aromatase inhibitor, resulting in a significant improvement in semen parameters.

• Journal of Chest Surgery
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• v.31 no.5
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• pp.494-501
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• 1998

From May 1, 1993 to May 31 1995, the authers studied retrospectively 211 patients who underwent cardiovascular operation with cardiopulmonary bypass(CPB). Because we were interested in new development of ARF(prevalence, mortality rate, and main risk factors), we performed a multivariate statistical analysis about data of patients with preoperative serum creatinine values of less than 1.5 mg/dL. Normal renal function before operation(serum creatinine level less than 1.5 mg/dL) was registered in 198(74%) patients. Of these, 27(14%) patients showed postoperative renal complication, including 20(10%) patients classified as renal dysfunction(serum creatinine level between 1.5 and 2.5 mg/dL) and 7(4%) patients as acute renal failure(serum creatinine level higher than 2.5 mg/dL). The mortality rate was 5.8% in normal patients, 5% in patients with renal dysfunction, and 43% when acute renal failure developed(p=0.036). Indeed, the renal impairment proved to be an independent predictor of mortality(odd ratio 2.52∼11.25), along with cardiovascular(odd ratio 4.20) and respiratory(odd ratio 2.18) complications. Multivariate analysis identified the following variables as independent risk factors for postoperative renal impairment : advanced age(odd ratio 1), need for emergency operation(odd ratio 3.78), low-output syndrome(odd ratio 3.66), respiratory complication(odd ratio 1.30), need for deep hypothermic circulatory arrest(odd ratio 1.4). The 13 patients(7%) with preoperative renal failure showed a significantly higher morbidity and mortality rate than those without renal complications before operation. We concluded that the likelihood of severe renal complications is resonably low in the patients undergoing cardiac operation without preexisting renal dysfunction, but associated mortality remains high. A prominant role of hemodynamic factor in the development of postoperative acute renal failure must be recognized during preoperative, intraoperative, and postoperative periods.

• Structural Engineering and Mechanics
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• v.29 no.2
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• pp.187-201
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• 2008

Earthquake induced hysteretic energy demand for a structure can be used as a limiting value of a certain performance level in seismic design of structures. In cases where it is larger than the hysteretic energy dissipation capacity of the structure, failure will occur. To be able to select the limiting value of hysteretic energy for a particular earthquake hazard level, it is required to define the variation of hysteretic energy in terms of probabilistic terms. This study focuses on the probabilistic evaluation of earthquake induced worst failure probability and approximate confidence intervals for inelastic single-degree-of-freedom (SDOF) systems with a typical steel moment connection based on hysteretic energy. For this purpose, hysteretic energy demand is predicted for a set of SDOF systems subject to an ensemble of moderate and severe EQGMs, while the hysteretic energy dissipation capacity is evaluated through the previously published cyclic test data on full-scale steel beam-to-column connections. The failure probability corresponding to the worst possible case is determined based on the hysteretic energy demand and dissipation capacity. The results show that as the capacity to demand ratio increases, the failure probability decreases dramatically. If this ratio is too small, then the failure is inevitable.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.73-78
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• 2000

This paper describes the effect of span-to-depth ratio, which describes aspect of cell formed with top diaphragm steel plate, on capacity in composite steel-concrete structure of sandwich system. The span-to-depth ratio \ulcorner load-carrying mechanism and load-distribution capacity of structure. Therefore, stress levels of members and load-resis\ulcorner of system vary according to span-depth ratio. In this study, numerical nonlinear analysis was performed to various ratio for two types(MA, MB) composite structure of sandwich system to analyze the influence of span-to-depth ratio or, behavior. The difference of load-carrying mechanism and stress of members results from analysis results, then bas\ulcorner differences, the effects of span-to-depth ratio on shear capacity, flexural capacity and load-resistance capacity were analyze effects on failure mode and ductility were briefly. As a results of this study, as span-to-depth ratio increases, \ulcorner bottom steel plate and concrete lower. This implies an increase in effective flexural and shear capacity. Therefore lo\ulcorner capacity of structure improves as span-to-depth ratio increases, Especially, the effect is greate in shear than flexural span-to-depth ratio increases, this difference between flexural and shear capacity may change failure mode and ductility. span-to-depth ratio increases capacity increases more than flexural capacity, we should expect that structural behavior mode gradually change from shear to flexural and ductility of structure gradually improves.

• Journal of radiological science and technology
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• v.22 no.2
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• pp.33-39
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• 1999

This paper included a data analysis of the unit of medical devices using mainternance recording card that had medical devices of unit failure mode, hospital of failure mode and MTBF. The results of the analysis were as follows : 1. Medical devices of unit failure mode was the highest in QC/PM such A hospital as 33.9%, B hospital 30.9%, C hospital 30.3%, second degree was the Electrical and Electronic failure such A hospital as 23.5%, B hospital 25.3%, C hospital 28%, third degree was mechanical failure such A hospital as 19.5%, B hospital 22.5%, C hospital 25.4%. 2. Hospital of failure mode was the highest in Mobile X-ray device(A hospital 62.5%, B hospital 69.5%, C hospital 37.4%), and was the lowest in Sono devices(A hospital 16.76%, B hospital 8.4%, C hospital 7%). 3. Mean time between failures(MTBT) was the highest in SONO devices and was the lowest in Mobile X-ray devices which have 200 - 400 failure hours. 4. Anverage failure ratio was the highest in Mobile X-ray devices(A hospital 31.3%, B hospital 34.8%, C hospital 18.7%), and was the lowest in Sono(Ultrasound) devices (A hospital 8.4%, B hospital 4.2%, C hospital 3.5%). 5. Failure ratio results of medical devices according to QC/PM part of unit failure mode were as follows ; A hospital was the highest part of QC/PM (50%) in Mamo X-ray device and was the lowest part of QC/PM(26.4%) in Castro X-ray. B hospital was the highest part of QC/PM(56%) in Mobile X-ray device, and the lowest part of QC/PM(12%) in Gastro X-ray. C hospital was the highest part of QC/PM(60%) in R/F X-ray device, and the lowest a part of QC/PM(21%) in Universal X-ray. It was found that the units responsible for most failure decreased by systematic management. We made the preventive maintenance schedule focusing on adjustement of operating and dust removal.

• Geotechnical Engineering
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• v.12 no.3
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• pp.5-16
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• 1996

Based on many experimental results on fine silica sands, the strength relation between triaxial and plane strain tests is expressed as a function of both density and mean effective principal stress at failure. Stress ratio of mean normal stress to deviatoric stress at failure is a well defined function of shear angle of friction, This ratio decreases with increasing shear angle of friction. Intermediate principal stress is also expressed in terms of major and minor principal stresses and a relatively good agreement between theoretical and observed angles of failure plane in plane strain test is confirmed.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.471-474
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• 2005

Reliability-based durability model was developed to consider the uncertainty of analysis variables in durability model for harbor concrete structures. The durability analysis program based on Finite Element Method (FEM) was modified adopting the reliability concept to estimate the probability of durability failure. Water-cement ratio in the durability analysis is the most important factor influencing chloride diffusion coefficient, evaporable water, etc. The probability distribution of water-cement ratio was calculated converting standard deviations of compressive strength in Concrete Standard Code to those of water-cement ratio. Based on the Monte Carlo Simulation, the probabilities of penetration depth and durability failure were calculated.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.269-276
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• 2000

Granular compaction piled raft systems have been effectively used in soft ground foundation to improve not only settlement but also bearing capacity. In the present study, to examine the behavior characteristics and bulging failure zone on granular compaction piled raft system, carbon rod tests have been performed. The test results are compared with the zone of bulging failure and the effects of pile-pile interaction obtained from the analytical approaches. In addition, parametric studies are peformed with considering pile slenderness ratio, Poisson's ratio and load sharing ratio.