• Journal of Welding and Joining
• /
• 제29권4호
• /
• pp.11-20
• /
• 2011

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
• /
• pp.824-829
• /
• 1998

In regard to the very stringent-going requirements applied to power supply systems is nowadays applications, the reliability of typical UPS redundency systems are investigated. Several resonable assumptions are made to build up the probability models. The reliabilities of the typical UPS redundency systems are analysed. Their relating Relaibility and MTTF (Mean Time To Faults) are evaluated. It is resulted in that the MTTF of today's UPS redundency systems is unlikely to be beyond 1,000,000 hours.

• 한국전기전자재료학회논문지
• /
• 제28권12호
• /
• pp.843-846
• /
• 2015

In this paper, the failure mechanism of PTC heater were examined closely by failure analysis and based on it, accelerated life test were conducted. Finally, life distribution and acceleration model were established. The failure mechanism of PTC heater such as crack, increase of resistance due to heating were identified. Two acceleration factors such as temperature, humidity were chosen with two levels each and accelerated life test were done. Life distribution were identified as Weibull distribution with shape parameter 5.4 and Temperature-Humidity model was fitted as an acceleration model.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2003년도 추계학술대회 논문집
• /
• pp.159-162
• /
• 2003

Cooling with easy, reliable cryocooler is highly desirable for the commercial and military application The pulse tube refrigerator has no moving parts at the cold end, so that the mechanical vibration and magnetic noise can be reduced to the low level with higher relaibility and longer lifetime than the Stilting cryocooler. The inertance tube improve the performance of pulse tube refrigerator by providing optimal phase shift between pressure and amss flow rate, and it is easiest to implement at large cooling capacity and high operating frequency. In this study, the performance of the inertance pulse tube refrigerator was investigated by analysis. The results show the influence of the diameter and length of the inertance tube on the performance of the refrigerator.

• 한국자동차공학회논문집
• /
• 제7권7호
• /
• pp.242-249
• /
• 1999

Spot welding is very important and useful technology in fabrication of an automobile body structure. Because fatigue strength of the spot welding point is however considerably lower than parent metal due to stress concentration at the nugget edge, accurate stress analysis and fatigue stength evaluation of spot welded lap joint are very important to valuate the reliability and durability of automobile body structure and to establish a criterion of long life fatigue design. Many invetigators have studied so far onsystematic fatigue strength evaluation with various methods. It is however necessary to verify their reliability and abailability for practical application to fatigue design of spot welded structure, Thus,in this study, fatigue strength evaluation methods of spot welded lap joint. which are the maximum principal stress method. the fracture and availability with the Weibull probability distribution. From the results, it was found that reliability and availability withe the Weibull probaility distribution. From the results, it was found that reliability and availability of the suggest fatigue strength estimation methods methods were higher than $\Delta$P-$N_f$ relation. However, among them , reliability of the maximum pricipal stress method was the highest.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제49권9호
• /
• pp.504-511
• /
• 2000

The reliability of system is to become a important concern in developed industry. The controller based on the reliability is so important position. PPC(Plant Protection Controller) is for plant protection and human life by fault detection and control action against the transient condition of plant. The protection system of the nuclear reactor and chemical reactor are representative of PPC. This paper presents analysis of PPC relaibility formal problem statement of optimal redundancy based on the reliability for PPC. And the problem is optimized by genetic algorithm, The genetic algorithms is useful algorithm in case of large searching complex gradient existence local minimum. The genetic algorithms is useful algorithm is case of large searching complex gradient existence local minimum. The ability and effectiveness of the proposed optimization is demonstrated by the target reliability of one channel. PPC. using the failure rate based on the MIL-HDBK-217

• 한국세라믹학회지
• /
• 제35권2호
• /
• pp.172-179
• /
• 1998

Valve lifter namely tappet is supported by lifter hole which is located upper side of camshaft in cylinder block transforms rotatic mvement of camshaft into linear movement and helps to open and shut the en-gine valve as an engine parts. The face of valve lifter which is continuously contacting with camshaft brings about abnormal wears such as unfair wear and early wear because it is severely loaded in the valve train system. These wears act as a defect like over-clearance and cause imperfect combustion of fuel during the valve lifting in the combustion chamber. Consequently this imperfect combustion makes the engine out-put decrease and has cause on air pollution. To prevent these wears therefore The valve lifter cast in me-tal developed into SiC ceramics valve lifter which has an excellence in wear and impact resistance As a results the optimum process conditions like injection condition mixture ratio and debonding process could be established. After sintering fine-sinered dual microstructure in which prior ${\alpha}$-SiC matches well with new SiC(${\beta}$-SiC) produced by reaction among the ${\alpha}$-SiC carbon and silicon was obtained. Based on the study it is verified that mechanical properties of SiC valve lifter are excellent in Vickers hardness 1100-1200 bending strength (300-350 Pa) fracture toughness(1.5-1.7 Mpa$.$m1/2) Through engine dynamo test-ing SiC valve lifter and metal valve lifter are examined and compared into abnormal phenomena such as early fracture unfair and early wear. It is hoped that this research will serve as an important springboard for the future study of heavy duty diesel engine parts developed by ceramics which has a good wear resis-tance relaibility and lightability.

• 대한한의진단학회지
• /
• 제11권2호
• /
• pp.27-44
• /
• 2007

Background: Eight-Constitution Medicine (ECM) classifies the human body into eight constitutions. Diagnosis of discrimination of the eight constitutions depends on a unique pulse diagnosis. However, pulse diagnosis is subjective and requires vigorous training. Objectives: This study aims to analyze the validity and reliability of the Eight-Constitution Questionnaire as a diagnostic method. Methods: Participants of this study were outpatients in six ECM clinics located in Seoul. The resources were collected from 409 patients who were classified into one of the eightconstitutions according to their pulse types and their responses to constitution-acupuncture therapy. SPSS 13.0 for Windows was used for statistical analysis: factor analysis, reliability analysis, independent sample t-test, and multinomial logistic regression were used to verify the results. Results and Conclusions: 1. The proportion of participants' constitutions is in the order of Pancreotonia (23.7%), Colonotonia (19.8%), Pulmotonia (18.1%), Hepatonia (16.9%), Vesicotonia (8.1%), Cholecystotonia (7.3%), Renotonia (5.3%) and Gastrotonia (0.7%). 2. Sevencomponents and 74 items were selected through factor factor and relaibility analysis performed on about 251 items. 3. The firstcomponent's mean is significantly higher in Pancreotonia than that in other constitutions (p<0.05). The second is in Pulmotonia and Colonotonia, whereas the third is in Hepatonia and Cholecystotonia. Fifth is in Vesicotonia, the sixth is in Colonotonia, and the fourth and seventh are not significant in specific constitutions. 4. The percentage that Pancreotonia is correctly predicted is 96.9%, Pulmotonia is 91.9%, Colonotonia is 91.4%, Hepatonia is 88.4%, Vesicotonia is 81.8%, Gastrotonia is 66.7%, Renotonia is 66.7%, Choleeystotonia is 30.0%, and the total percentage is 85.3%.

• 대한간호학회지
• /
• 제26권3호
• /
• pp.531-543
• /
• 1996

This study was done to develop a Maternal Identity Scale for Pregnant Women and to test the validity and reliability of the scale. A convenience sample of 161 pregnant women were asked to complete the MISP questionnaire which consisted of 45 item, this was done from December 20, 1995 to January 15, 1996. The research procedure were as follows. The first step was to identify a conceptual definition of maternal identity using Robin(1984)'s maternal identity and maternal experience during pregnancy. The second step was to operationalize the maternal identity, that is, perception of image possible of selves as mother, maternal role play by imagination, and the experiences of various emotional responses which are embedded in the mother-fetus dyad. The third step was item development which resulted in 45 items as appropriate measurement of maternal identity are except for the perception of image possible of selves as mother. The result findings were as follows : 1) Four factors for MISP (finally 40 items) were extracted through the principal component analysis and varimax rotation, and these contributed 49.3% of the variance in the total score. All 40 items in the scale loaded above .43 on one of 4 factors. 2) Each factor was named : factor 1 was named maternal role imagery and has 10 items, factor 2 was named happiness and has 11 items, factor 3 was named maternal fetal interaction and has 10 items, and the last factor 4 was named negative emotion and has 9 items. 3) Cronbach's -alpha coefficient for internal consistsncy was .92 for the total 40 items and .89, .90, .86, .78 for the four subscales in that order. Recommendations are suggested below : 1) The developed MISP be used to assess maternal readiness in pregnancy. 2) Replication study be done to test validity and relaibility. 3) For the overall measure of Maternal Identity in Pregnancy, scale for the perception of image possible of selves as mother, and cognitive domain be reorganized for the maternal identity in pregnancy. 4) It is necessary to identify variables that influences maternal pregnancy. 5) It Is necessary to identify that maternal identity in pregnancy is a reliable index of motherhood, to do correlation studies on maternal identity and major maternal variables in maternal transition period, to reoperationalize the maternal identity in postpartum, and finally to designate a longitudinal study of the maternal identity changes or stabilities.

• 한국산학기술학회논문지
• /
• 제14권3호
• /
• pp.1228-1233
• /
• 2013

본 연구는 한국판 만성 뇌졸중 환자의 신경심리학적 평가도구를 결정하기 위하여 한국판 몬트리올인지평가 및 한국판 간이정신상태검사의 신뢰도를 알아보고, 두 평가도구의 상관관계를 알아보았다. 연구대상자는 만성뇌졸중환자 52명을 대상으로 하였으며, 인지손상 진단 여부에 따라서 정상인지 뇌졸중군(20명)과 인지손상 뇌졸중군(32명)으로 구분하였다. 연구대상자는 한국판 몬트리올인지평가 및 한국판 간이정신상태검사를 평가받았으며, 연구기간은 2012년 10월 2일부터 2012년 11월 30일까지 이었다. 연구결과 정상인지 뇌졸중군은 한국판 몬트리올인지평가에서 중등도 이상의 신뢰도를 보여주었으며, 한국판 간이정신상태검사에서 중등도의 신뢰도를 보여주었다. 인지손상 뇌졸중군은 한국판 몬트리올인지평가 및 한국판 간이정신상태검사에서 모두 중등도 이상의 신뢰도를 보여주었다. 또한 정상인지 뇌졸중군과 인지손상 뇌졸중군은 한국판 몬트리올인지평가의 점수가 높을수록 한국판 간이정신상태검사의 점수도 높은 양의 상관관계를 보여주었다. 본 연구의 결과는 한국판 몬트리올인지평가 및 한국판 간이정신상태검사 모두 뇌졸중으로 인한 인지손상을 진단하는데 적합하다고 사료되어, 연구 및 임상환경에서 신경심리학적 평가도구로 사용할 것을 제언한다.