• 신재생에너지
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• 제16권4호
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• pp.49-64
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• 2020

Photovoltaic and Thermal collector (PV/T) systems are renewable energy devices that can produce electricity and heat energy simultaneously using solar panels and heat exchangers. Since PV/T systems are exposed to the outdoors, their reliability is affected by various environmental factors. This paper presents a reliability test for a PV/T system and evaluates the test results. The reliability assessment entails performance, environment, safety, and life tests. The factor that had the greatest influence on the life of the system was the hydraulic pressure applied to the heat exchanger. A test was conducted by repeatedly applying pressure to the PV/T system, and a reliability analysis was conducted based on the test results. As a result, the shape parameter (β) value of 5.6658 and the B10life 308,577 cycles at the lower 95% confidence interval were obtained.

• 동력기계공학회지
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• 제16권3호
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• pp.44-50
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• 2012

The reliability qualification test is essential in order to ensure the life time of the product under the normal operation conditions when a new product is developed. The reliability qualification test period has an important impact on the development time of new product. Therefore, some researches to reduce the test time of reliability qualification test have been actively studied. Generally, accelerated life test is well known as one method that can save the test time of the reliability qualification test. This test is conducted under the higher stress condition than normal condition. So we need to investigate what factor affects to the higher stress condition. This paper shows the relationship between the acceleration factor and reliability qualification test period. Especially, we focused on the method to obtain effective acceleration factors under the high temperature condition. Through some experiments for a refrigerator's compressor, we were able to confirm how to increase acceleration factors and how to reduce the reliability qualification test period with minimum samples.

• 환경영향평가
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• 제4권2호
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• pp.123-130
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• 1995

The equipment composed of many complicated electronic stuffs undergoes diverse stresses caused by mechanical vibrations during its service. Thus, to ensure its proper operation in the field a simulated vibration test has to be carried out in the laboratory with the Vibration Qualification Level, the test specification, which can include the real environment. In this paper we intent to deal with method and procedure for determining the Vibration Qualification Level so as to estimate the vibration-endurance for the equipment precisely.

• 공학교육연구
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• 제19권1호
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• pp.47-53
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• 2016

New occupational qualification system built on NCS(National Competency Standard) aimed to induce industries, the final appliers of qualification, to play a leading role in designing qualification and to spontaneously apply such qualification standard to employment and promotion so as to reinforce universality of qualification. In this study, we verified the validity of NCS level of qualification categories for 130 occupational fields by redesigning NCS-based new occupational qualification system with a focus on 7 major areas, including mechanical field, which were found to have wide-ranging social ripple effect throughout society and high acceptability in 2014. The results of study on suitability at qualification level suggested the followings: First, there is a difference in number of competency units for each qualification category, depending on area. New qualification covering 7 major areas included 15.3 competency units for each qualification category, which exceeds the number of competency units(about 10 units) in subdivided NCS. By field, some difference was found with 7.9 competency units for cultural field and 22.6 competency units for information and communication area. Second, preference above normal level was observed in the criteria, procedure and method for determining qualification redesigning. However, preference below normal level was exhibited in connection with possibility of linkage with overseas qualifications, although preference was above normal level in relation to the suitability of design/qualification level and qualification categories based on lifelong career development path within scope of NCS as the criteria for determining the redesign of qualification categories. Second, we compared NCS level and SC(Sector Council level, and the results showed that NCS level was found to be somewhat well-defined. For the qualifications with different definitions, it was deemed difficult to determine superiority between NCS level and SC level. However, majority opinion indicated that it would be desirable to follow NCS level because NCS was created through collection of opinions for a prolonged period.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.115-118
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• 2009

엔진 1기당 연소시험 횟수나 시험시간은 엔진 개발 초기에 시스템이나 구성품 개발의 설계/개발 요구조건을 설정하는 데 중요한 인자이다. 해외 액체로켓엔진의 개발 및 인증 시험 이력을 통해 우주 발사체용 액체로켓엔진에 요구되는 수명에 대해 조사하였다. 소모성 발사체에 장착되는 엔진도 개발과정에서 수십회의 점화와 비행시간 대비 수배 이상의 연소 시험을 거치는 것이 확인되었다.

• 시큐리티연구
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• 제15호
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• pp.243-264
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• 2008

민간시큐리티산업의 급속한 성장과 함께 이에 걸맞는 시큐리티요원에 대한 전문자격에 대한 제도적인 장치가 정착되어 있지 않다. 개인의 생명 신체 및 재산을 보호하는 역할을 하는 시큐리티요원에 대한 자격제도는 국민의 신뢰와 요원의 자질을 향상시키는 문제로서 반드시 필요한 부분이다. 양질의 시큐리티서비스를 제공하기 위해서는 업무수행에 필요한 요원의 전문성을 갖추는 것이 필요하다. 이를 위한 제도적인 시큐리티자격의 정착은 개인의 사회적인 신뢰와 시큐리티산업의 발전을 유도할 수 있다. 미국과 일본 등에서 시행하고 있는 자격제도는 시큐리티자격제도 마련을 위한 꾸준한 연구와 실무계의 협력을 통해 정착됐는데, 이들은 한국의 시큐리티자격제도 시행에 많은 시사점을 주고 있다. 본 논문에서는 시큐리티요원의 자격제도에 대한 필요성을 강조하고 한국 시큐리티자격제도의 실태를 살펴보고 이와 더불어 한국경비협회가 주관하여 한국시큐리티자격평가원이 제2차에 걸쳐 시행한 신변보호사 자격시험을 중심으로 시행상 도출된 문제점을 분석하여 시큐리티관련 민간경비자격제도의 발전방안을 고찰한다.

• 품질경영학회지
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• 제39권1호
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• pp.71-77
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• 2011

In the fields of reliability application, the most commonly used test methods for reliability qualification are zero failure tests since they require fewer test samples and less test time compared to other test methods that guarantee the same reliability with a given confidence level. An economic zero failure test plan is developed that minimizes the total cost related to perform a life test to guarantee a specified reliability of a product with a given confidence level and a numerical example is provided to illustrate the use of the proposed test method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.143-146
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• 2005

In modern automotive control modules, mechanical failures of surface mounted electronic components such as microprocessors, crystals, capacitors, transformers, inductors, and ball grid array packages, etc., are mai or roadblocks to design cycle time and product reliability. This paper presents a general methodology of failure analysis and fatigue prediction of these electronic components under automotive vibration environments. Mechanical performance of these packages is studied through finite element modeling approach fur given vibration environments in automotive application. Using the results of vibration simulation, fatigue lift is predicted based on cumulative damage analysis and material durability information. Detailed model of solder/lead joints is built to correlate the system level model and obtain solder strains/stresses. The primary focus in this paper is on surface-mount interconnect fatigue failures and the critical component selected for this analysis is 80 pin plastic leaded microprocessor.

• 마이크로전자및패키징학회지
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• 제22권2호
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• pp.1-4
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• 2015

Qualification includes all activities to demonstrate that a product meets and exceeds the reliability goals. Manufacturers need to spend time and resources for the qualification processes under the pressure of reducing time to market, as well as offering a competitive price. Failure to qualify a product could result in economic loss such as warranty and recall claims and the manufacturer could lose the reputation in the market. In order to provide valid and reliable qualification results, manufacturers are required to make extra effort based on the operational and environmental characteristics of the product. This paper discusses optimal interval censoring design for reliability prediction of electronic packages under limited time and resources. This design should provide more accurate assessment of package capability and thus deliver better reliability prediction.

• 대한기계학회논문집A
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• 제39권4호
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• pp.397-403
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• 2015

본 논문은 개발 중에 있는 굴삭기 무인조종 로봇을 대상으로 시스템 신뢰도 평가 방법을 제안하고, 제안한 방법을 이용하여 수행한 신뢰도 보증시험에 대한 결과를 나타낸다. 로봇 시스템은 위험한 작업환경에서 작업자의 안전을 위하여 개발되었으며 전체 시스템의 신뢰도는 각 구성품의 신뢰도로부터 계산될 수 있다. 따라서 세 가지 주요 구성품 각각에 대한 전용 시험 장비를 제작하여 가속수명시험에 사용하였다. 가속수명시험 결과를 이용하여 신뢰수준에 따른 보증할 수 있는 평균수명을 추정하고, 적은 시료 수를 사용하는 시스템 신뢰도 보증 시험법을 제안하였다.