• Nuclear Engineering and Technology
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• 제39권5호
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• pp.591-602
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• 2007

The results of Reactivity-Initiated Accidents (RIA) experiments have been analysed and the main variables affecting the fuel failure propensity identified. Fuel burn-up aggravates the mechanical loading of the cladding, while corrosion, or better the hydrogen absorbed in the cladding as a consequence of corrosion, may under some conditions make the cladding brittle and more susceptible to failure. Experiments point out that corrosion impairs the fuel resistance for RIA transient occurring at cold conditions, whereas there is no evidence of important embrittlement effects at hot conditions, unless the cladding was degraded by oxide spalling. A fuel failure threshold correlation has been derived and compared with experimental data relevant for BWR and PWR fuel. The correlation can be applied to both cold and hot RIA transients, account taken for the lower ductility at cold conditions and for the different initial enthalpy. It can also be used for non-zero power transients, provided that a term accounting for the start-up power is incorporated. The proposed threshold is easy to use and reproduces the results obtained in the CABRI and NSRR tests in a rather satisfactory manner. The behaviour of advanced PWR alloys and of MOX fuel is discussed in light of the correlation predictions. Finally, a probabilistic approach has been developed in order to account for the small scatter of the failure predictions. This approach completes the RIA failure assessment in that after determining a best estimate failure threshold, a failure probability is inferred based on the spreading of data around the calculated best estimate value.

• 한국지반환경공학회 논문집
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• 제17권5호
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• pp.5-16
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• 2016

A rainfall induced slope failure is a common natural hazard in mountainous areas worldwide. Sudden and rapid failures which have a high possibility of occurrence in a steep slope are always the most dangerous due to their suddenness and high velocities. Based on a series of experiments this study aimed to determine a critical angle which could be considered as an approximate threshold for a sudden failure. The experiments were performed using 0.42 mm mean grain size sand in a 200 cm long, 60 cm wide and 50 cm deep rectangular flume. A numerical model was created by integrating a 2D seepage flow model and a 2D slope stability analysis model to predict the failure surface and the time of occurrence. The results showed that, the failure mode for the entire material will be sudden for slopes greater than $67^{\circ}$; in contrast the failure mode becomes retrogressive. There is no clear link between the degree of saturation and the mode of failure. The simulation results in considering matric suction showed good matching with the results obtained from experiment. A subsequent discarding of the matric suction effect in calculating safety factors will result in a deeper predicted failure surface and an incorrect predicted time of occurrence.

• 한국임상약학회지
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• 제16권2호
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• pp.113-122
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• 2006

Purpose: A retrospective study was performed to assess the efficacy and tolerance of ${\beta}-blocker$ administration in patients with heart failure and diabetes. Method: Records of 164 patients who were treated for the heart failure condition more than a year were studied retrospectively. Patients were divided into 4 groups based on their diabetes(DM) status and the administration of ${\beta}-blockers$ ($DM+{\beta}-blocker$ group: 14, DM w/o ${\beta}-blocker$: 19, No DM + ${\beta}-blocker$: 62, No DM + no ${\beta}-blocker$: 69). All patients had been receiving conventional therapy such as digoxin, ACE-I, ARB, diuretics, nitrates, aspirin, anticoagulants or lipid-lowering agents. The primary endpoints (death and hospital admission) were recorded during 1 year period and hemodynamic factors (HR, LVEF, SBP, DBP) were obtained from all patient groups before and after 12 months of ${\beta}-blocker$ treatment. To evaluate toxicity of ${\beta}-blocker$, SCr, BUN, AST, ALT and Alkaline phosphatase were obtained. Result: There were less death and hospital admission in DM + ${\beta}-blocker$ group than in DM without ${\beta}-blocker$ group (p=0.014). Relative risk of hospital admission for $DM+{\beta}-blocker$ group over no DM group was 1.17. Long term ${\beta}-blocker$ administration was associated with an improvement of heart rate in patients with DM (P< 0.02) with no significant improvement of LVEF, SBP, DBP. in DM patient. In patient without DM, ${\beta}-blocker$ was associated with improvement in LVEF, HR and DBP (P<0.01, P<0.03), but not in SBP. The incidence of toxicity was similar between the four group with no significant difference. Conculsion: Treatment of heart failure patients with ${\beta}-blocker$ appears to be beneficial in terms of hospital admission event and several hemodynamic factors. The toxicities of ${\beta}-blocker$ treatment were not significant and the treatment is generally well-tolerated in most of the heart failure patients.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.117-122
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• 2003

Every year in domestic slope failure caused by rainfall is happening frequently. Specially, causable failure accident by localized downpour accompanied when summer rainy season period and produces typhoon gets damage of large scale human life and property. Failure happened at slope of 121 places ranged whole country national highway by No.15 typhoon Rusa that strike whole country during 3 days from August 30, 2002. Slope failure that happen by typhoon are judged for major cause to effect of ground saturation and surface water by localized downpour. In this research, failure characteristic was analyzed to target 20 places attaining site investigation among failure slope. As a result, erosions by surface water was construed for major cause of failure and judged for direct relation in failure slope weathering and topography Also, result that analyze inclination of failure part, in the case of ripping rock, inclination of failure side is forming Incline of the lowest 40$^{\circ}$, because surface failure of depth 4m on or so scale happened, it is require that regulating plan gently design standard inclination of weathered rock and soil layer And it is considered that desirable preparation of design standard about measure that help smooth drainage of surface water and can restrain percolation in ground to reduce failure damage by rainfall.

• 상하수도학회지
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• 제10권1호
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• pp.96-111
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• 1996

The failure of water pipelines is progressed by several compound factors and the collection and analysis of data about pipeline failure are inevitable for effective pipeline rehabilitation. Data analysis of pipeline failure was already performed in USA and Europe. Based on such phenomena, failure characteristics about metropolitan pipelines in Korea were analyzed: The conclusions of this study are as followings. 1. The failure cause of pipelines can be classified into natural cause and artificial cause. Artificial cause is 32% of total causes, so artificial failure as several constructions happens frequently in Korea. Although the failure by old pipe is greatest of any other causes m classtfied cause, failure cause is not classified in detail now. 2. The damaged part of pipelines is affected by cities, distribution system inventory, bedding conditions, and so on. In this study, the failure of pipeline body(67%) is greater than the failure of pipeline joint(33%) in natural failure. 3. In regard to pipe materials, failure rate of DCIP(0.8456), PEP(0.7288), and GSP(0.6643) is greater than that of CIP(0.3985) and CWSP(0.2348). 4. Usually, faIlure rate is increased in proportion to diameter of pipeline. In this study, CIP, DCIP, and CWSP have clear trends. But the trends of PEP is reverse, the case of GSP, HP is obscure due to data shortage. 5. There are no direct relationships between burial age and failure rate of pipelines. 6. Annual breaks and winter(Nov.~Feb.) breaks of pipelines are investigated. As a result, WInter breaks to annual breaks of CIP is 51.3%(Seoul), 51.1%(Taegu),38.7%(Pusan). This phenomena have direct correlation with average winter temp. of cities.

• Journal of Chest Surgery
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• 제27권9호
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• pp.764-769
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• 1994

From november, 1985 to May, 1993, 222 arteriovenous fistulae were made in 201 patients with chronic renal failure. Among them, a total of 183 arteriovenous fistulae in 173 patients were reviewed to evaluate the factors influencing patency rate of the vascular access. The results were revealed as follows: There were 102 men and 71 women,aged 10 to 76 years [mean = 45.7 years]. Sixteen patients of them had previous shunts. The procedures included establishment of 214 radiocephalic or brachioocephalic fistulae, 203 side to end, 9 side to side, 2 end to end, 2 autologous saphenous vein grafts, 6 Gore-Tex grafts. There were 28 early shunt failures[12%] due to use of 23 inadequate veins and 5 thrombosis.There were 32 late complications[14%]; 19 thrombosis, 4 aneurysm, 4 venous hypertension, 3 steal syndrome, 2 infections. There were 32 diabetic patients [17 %]. No significant differences in graft patency were noted between diabetic and nondiabetic individuals. There were no significant difference in graft patency between male and female. Overall shunt patency in 183 cases with chronic renal failure was 96% at I month, 95% at 3 months, 93% at I year, 91% at 2 years, 84% at 3 years, 56% at 5years.This Study showed that early postoperative thrombosis and diabetic vasculopathy were most causes of the vascular access failure and suggested that prevention of thrombi and well control of diabetes mellitus were most important to enhance patency rates of the vascular access.

• 대한한의학회지
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• 제21권4호
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• pp.276-285
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• 2000

Paraquat is a very potent herbicide which causes fatal toxicity when ingested, and there is no specific antidote against it. Human ingestion induces acute renal failure, hepatic dysfunction and progressive respiratory failure with high mortality rate. Clinical investigation and medical treatment were done on two cases of acute renal failure caused by paraquat poisoning admitted to the Department of Internal Medicine, Wonkwang University Oriental Chonju Medical Hospital. We report two cases of patients who survived after acute paraquat intoxication, by means of oriental medicine such as Gamdutang, a typical antidote of toxins, chinese ink as an absorbent and burned powder of Rhei Radix et Rhizoma for laxative and so on, western medicine such as gastric lavage, diuretics and fluid therapy. We suggest more experiments and studies related to such treatment for paraquat poisoning be conducted.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.617-621
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• 2003

The purpose of this paper is to analyze piping failure trend of safety pipings In domestic nuclear power plants. First, database for the piping failure was constructed with 105 data fields. The database includes plant population data, event data, and service history data. 7 kinds of piping failures in domestic NPPs were investigated. Among the 7 cases, detailed root causes were investigated for 3 cases. The first one is pipe wall thinning in main feedwater pipings of Westinghouse 3 loop type plants. The root cause of the wall thinning was flow accelerated corrosion near welding area. The next one is leak event in chemical and volume control system(CVCS) due to vibration. Some cracks occurred in socket welding area. The events showed that the integrity or socket weld is very vulnerable to vibration. The last one is also a leak event in primary sampling line in Korean standard reactor due to thermal fatigue. Although the structural integrity was not maintained by the events, there was no effect on nuclear safety in the above 3 piping failure eases.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.174-178
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• 1999

This paper describes an investigation on bearing failure due to spragging that has been continuously occurred in turbine hearings. The spragging is defined as the damage found on the leading edge of unloaded pads in the tilting pad journal bearing, In general, the damage mechanism by spragging is classified into fatifgue failure, The principle cause of spragging could be thought as the self-excited vibration by the absence of a stable static equilibrium position of upper pads with no preload. Because of serious consequences of system breakdowns due to bearing failures, determination ar the causes of failure and effective method for countermeasures are very important. This paper describes both the causes of spragging and countermeasures for prevention of such failure, which are taken place in the electric power plants.

• Journal of Chest Surgery
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• 제24권7호
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• pp.656-662
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• 1991

endocarditis, 1.475% /pt-yr, overall valve failure, 3.319% /pt-yr; and primary tissue failure, 1.475% /pt-yr. The actuarial probability of survival was 94.3$\pm$3.6% and the probability of freedom from thromboembolism 90.6$\pm$4.6% at 11 years after surgery respectively. And, the probability of freedom from primary tissue failure was 60.4$\pm$16.9% also at 11 years The evidence of possible premature and accelerated failure of the pericardial valve in the aortic position among the young population was not clear on the age-related analysis of the structural failure, and no suggestion could be made to indicate age limit when the use of the pericardial valve would better be avoided.