• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.386-390
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• 2007

At recent times, an essential issue in the replacement of the old analogue I&C to computer-based digital systems in nuclear power plants becomes the quantitative software reliability assessment. Software reliability models have been successfully applied to many industrial applications, but have the unfortunate drawback of requiring data from which one can formulate a model. Software that is developed for safety critical applications is frequently unable to produce such data for at least two reasons. First, the software is frequently one-of-a-kind, and second, it rarely fails. Safety critical software is normally expected to pass every unit test producing precious little failure data. The basic premise of the rare events approach is that well-tested software does not fail under normal routine and input signals, which means that failures must be triggered by unusual input data and computer states. The failure data found under the reasonable testing cases and testing time for these conditions should be considered for the quantitative reliability assessment. We presented the quantitative reliability assessment methodology of safety critical software for rare failure cases in this paper.

• Journal of Environmental Science International
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• v.17 no.11
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• pp.1295-1305
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• 2008

This study aims at the analyze of unsteady downstream flow due to dam failure along dam failure scenario and applied to Yeoncheon Dam which was collapsed August 1st 1999, using HEC-RAS simulation model. The boundary conditions of this unsteady flow simulation are that dam failure arrival time could be at 02:45 a.m. August 1st 1999 and failure duration time could be also 30 minutes. Downstream 19.5 km from dam site was simulated for unsteady flow analysis in terms of dam failure and non-failure cases. For the parameter calibration, observed data of Jeonkok station were used and roughness coefficient was applied to simulation model. The result of the peak discharge difference was 2,696 to $1,745\;m^3/sec$ along the downstream between dam failure and non-failure and also peak elevation of water level showed meanly 0.6m difference. Those results of these studies show that dam failure scenarios for the unknown failure time and duration were rational because most results were coincident with observed records. And also those results and procedure could suggest how and when dam failure occurs and downstream unsteady flow analyzes.

• Journal of Korean Dental Science
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• v.2 no.2
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• pp.24-30
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• 2009

Two component orthodontic C-implants have been introduced as intermaxillary fixation (IMF) screws in cases of periodontal problems with bone loss, severely damaged teeth, or short roots. This retrospective research sought to investigate the complications and risk factors associated with the failure of two-part C-implants for IMF cases and to show the possible indications compared to one-component mini-implants. The study sample consisted of 46 randomly selected patients who had a total of 203 implants. Pearson chi-square tests of independence were used to test for associations among categorical variables. At least 19 of the total 203 implants failed (9.3%). There was no significant difference in implant failure due to gender, oral hygiene, and placement, although a significant difference due to soft tissue characteristics and root contact was observed. The two-component design of the mini-implant is reliable for difficult IMF cases. Note, however, that the factors influencing implant failure were found to be age, root damage, and condition of soft tissues.

• Childhood Kidney Diseases
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• v.11 no.1
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• pp.112-117
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• 2007

Although juvenile nephronophthisis(NPHP) is one of the most frequent genetic causes of chronic renal failure, it has very rarely been reported in Korean children. Most NPHP patients are found to have chronic renal failure, since there are no distinct clinical symptoms for NPHP except polydipsia, polyuria and enuresis in the early stage of disease. Ten percent of NPHP patients manifest retinitis pigmentosa, called $Senior-L\ddot{o}ken$ syndrome. We experienced 2 cases of $Senior-L\ddot{o}ken$ syndrome that occurred in siblings(a 10 year-old boy and a 14-year-old girl) who were diagnosed with Leber's amaurosis. They were found to have severe renal impairment without polydipsia and polyuria. However, no large homogenous deletion of the NPHPI(2q13) gene was not identified in these patients. We report here on these cases and we review the literature to emphasize the association between Leber's amaurosis and the development of chronic renal failure.

• Journal of Chest Surgery
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• v.24 no.1
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• pp.1-7
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• 1991

This report describes our 10-year experience with intracardiac repair in 42 patients older than 16 year with tetralogy of Fallot. The mean age was 22.0$\pm$5.18 years[range 16~41]. The preoperative clinical manifestations were cyanosis & clubbing[93%], frequent URI [55%], anoxic spell[40%], pulmonary tuberculosis[21%], tuberculous empyema[7%], chronic renal failure[7%], congestive heart failure[7%] and subacute bacterial endocarditis [2%], etc. The previous shunt procedure for palliation had been performed in 7 patients. The type of VSD were typical perimembranous type[67%], total canal defect[28%] and combined type[5%]. The right ventricular outflow tract obstruction were combined type[69%], infundibular type[21%] and valvular type[10%]. Transannular patch was used in 50% of patients. Associated cardiovascular anomalies were ASD[33%], PFO[31%], Rt. aortic arch[10%], Lt. SVC[10%], single Rt. pulmonary artery, single Lt. coronary artery, ASI, proximal stenosis of Rt. pulmonary artery and anomalous systemic venous return, etc. Hospital mortality was 7.1%[3 cases]in overall. The causes of hospital deaths were revealed low cardiac output & acute renal failure[2 cases], postoperative bleeding[1 case]. There were 2 late deaths 3 & 68 months after surgery. Residual intracardiac shunt was detected in 2 patients. one patient was successfully reoperated and another patient had Qp /Qs ratio less than 1.5.

• Archives of Reconstructive Microsurgery
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• v.5 no.1
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• pp.70-79
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• 1996

From January 1980 to May 1995, ninety-six patients had been treated by free-flap transfer for the soft tissue defects of the extremities. Ninety-eight cases of free-tissue transfer were reviewed to evaluate the clinical reliability in terms of survival and quality of long-time function after reconstructive surgery. Among these 98 cases(27 cases in latissimus dorsi myocutaneous flap, 25 in dorsalis pedis flap, 20 in forearm fasciocutaneous flap, 9 in groin flap, 7 in gracilis myocutaneous flap, 6 in 1st web space flap of foot and 4 cases in tensor fascia lata flap), 92 cases of then were survived. 7 cases were performed with vein grafts. We ananalyzed the reconstruction of the extremities on 98 cases with the soft tissue defects which had been reconstructed free-flap transfer and followed for minimum 1 year period at Korea University Hospital. 1. 92 cases(93.9%) of the total 98 cases were successful and can be obtained the excellent results in soft tissue free-flap transfer. 2. While there were no clinically significant differences in survival rate of flaps transferred from different potential flap donor sites,3 cases of 9 groin flaps were showed higher failure rate due to the complications such as arterial thrombosis, infection and anatomical variation of vessels. 3. Postoperative thrombectomy was performed in 30 cases to be occured in the arterial and venous thrombosis. The revision was failed in 2 cases due to persistent arterial thrombosis and infection, then treated with skin graft. 4. Vein graft was frequently required in severely compromised-soft tissue defects resulted from high-energy trauma. The vein graft was not stitistically significant on the frequency of flap failure rate(P<0.04). 5. Meticulous monitoring, careful planning, early revision and technical considerations will provide for a high clinical success of the free-flap transfer.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.436-449
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• 2017

In this paper, the damage and failure behavior of triaxially braided textile composites was studied using progressive failure analysis. The analysis was performed at both micro and meso-scales through iterative cycles. Stress based failure criteria were used to define the failure states at both micro- and meso-scale models. The stress-strain curve under uniaxial tensile loading was drawn based on the load-displacement curve from the progressive failure analysis and compared to those by test and computational results from reference for verification. Then, the detailed failure initiation and propagation was studied using the verified model for both tensile and compression loading cases. The failure modes of each part of the model were assessed at different stages of failure. Effect of ply stacking and number of unit cells considered were then investigated using the resulting stress-strain curves and damage patterns. Finally, the effect of matrix plasticity was examined for the compressive failure behavior of the same model using elastic, elastic - perfectly plastic and multi-linear elastic-plastic matrix properties.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.143-146
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• 2005

The software reliability growth depends on the testing time because the failure rate varies whether it is long or not. On the other hand, it might be difficult to reduce failure rate for most of the cases are not available for debugging during operational phase, hence, there are some literatures to study that the failure rate is uniform throughout the operational time. The failure rate reduces and the reliability grows with time regardless of debugging. As a result, the products reliability varies with the time duration of these products in point of customer view. The reason of this is that it accumulates the products experience, studies the exact operational method, and then finds and takes action against the fault circumstances. I propose the simple model to represent this status in this paper.

• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.81-94
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• 2018

This paper uses the finite element method (FEM) considering geometrically nonlinear strains to study the first ply failure of laminated composite skewed hypar shell roofs through well-established failure criteria along with the serviceability criterion of deflection. Apart from validating the approach through solution of benchmark problems, skewed hypars with different practical parametric variations are studied for failure loads and tendencies. First ply failure zones are also identified to suggest design and non-destructive monitoring guidelines to the practising engineers. Recommendation tables regarding the design approaches to be adopted in specific cases and factor of safety values needed to be imposed on first ply failure load values for varying shell curvatures are also suggested in this paper. Providing practical inputs to design engineers is the main achievement of the present study.

• Journal of Korean Institute of Industrial Engineers
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• v.26 no.2
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• pp.128-135
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• 2000

This paper considers a consecutive k-out-of-n:F system when the failure of a component in the system induces higher failure rate of the preceding survivor. The reliability, mean time to failure(MTTF), and average failure number of a consecutive k-out-of-n:F system are obtained, when the failure of a component increases the failure rate of the survivor which is working just before the failed component. Then the optimal number of consecutive failed components to minimize this long run average cost rate can be obtained. An example is considered to calculate the reliability, MTTF and average failure number of the system. And two procedures that find the optimal number of consecutive failed components are studied. Then, various cases of system parameters are also studied.