• New & Renewable Energy
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• v.16 no.4
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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.

• Journal of Power System Engineering
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• v.16 no.3
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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.

• Journal of Environmental Impact Assessment
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• v.4 no.2
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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.

• Journal of Engineering Education Research
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• v.19 no.1
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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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.115-118
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• 2009

Life time and number of use of liquid propellant rocket engine (LRE) should be carefully defined since those are crucial parameters affecting development costs and period. The present study surveyed the development and qualification records of LRE for space launch vehicles, especially concerning about test numbers and duration. It was shown that a single engine for expendable launch vehicle is tested with tens of ignition and several times duration of flight at least.

• Korean Security Journal
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• no.15
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• pp.243-264
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• 2008

Recently the private security industry is showing rapid growth compared with the different types of industry. However, it is not prepared the device for the system to verify the professional qualification of the security guards. To protect individual life and property, body and security guards have to be qualified professionally. For it the role of professional qualification systems is emphasized. The problem of the certification of the qualification about the security guard to play the role to protect a body / life of the individual and property are the part to need necessarily as the quality problem of the individual and the trust of the people. The settlement of the qualification system which is such system can induce the development of the security industry with social trust. The certified security certification is needed and how to control the security quality to get better service to the clients. The professional qualification system to be carrying out with America and Japan is fixed through the cooperation of the business world and steady research for the qualification system plan, these are giving the trial of the qualification system of a security of Korea full of the suggestion. This study will do this to the basis which a necessity about the qualification system of the security man emphasis and considerate professional qualification system concerning the private security development plan around the Bodyguard Qualifying Examination which are carried out at twice by the Korea Security Association and the Korean Institute of Security. In summary to meet the social demand professional qualification for the security guards will be drawn from the analyses of civil security qualification systems.

• Journal of Korean Society for Quality Management
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• v.39 no.1
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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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.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.2
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.397-403
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• 2015

This paper proposes the development of a method for assessing the system reliability of an unmanned control robot system for an excavator. It then shows the results of the reliability qualification test based on the proposed method. The robot system functions to ensure the safety of the workers who control excavators in dangerous working environments, and the system reliability was calculated by integrating the reliabilities of the system components. Thus, test equipment for the three key units of the robot system were constructed and used in accelerated life testing. From the life testing results, guaranteed mean time between failures for the chosen confidence level was estimated, and the reliability qualification testing method of the robot system using small sample sizes was proposed.