• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1042-1048
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• 2008

Disc brake noise is an important customer satisfaction and warranty issue for many manufacturers as indicated by technical literature regarding the subject coming from Motor Company. This research describes results of a study to assess disk brake squeal propensity using finite element methods and optimal technique (Kriging). In this study, finite element analysis has been performed to determine likely modes of brake squeal. This paper deals with friction-induced vibration of disc brake system under contact friction coefficient. A linear, finite element model to represent the floating caliper disc brake system is proposed. The complex eigen-values are used to investigate the dynamic stability and in order to verify simulations which are based on the FEM model. In this paper, Kriging from among the meta-modeling techniques is proposed for an optimal design scheme to reduce the brake squeal noise.

• 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.

• Journal of Korea Society of Industrial Information Systems
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• v.5 no.4
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• pp.39-46
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• 2000

New products often have in-service reliability problem despite an intensive development program. Therefore reliability data must be collected and analyzed, and improvements designed and implemented. A type of reliability incentive contract which has recently attracted a lot of attention is reliability improvement warranty(RIW). It has been employed by military, airlines, telecommunication systems, and public utilities. An RIW contract requires that the supplies carries out all repairs, modify the equipment to improve its reliability, and provides all spates needed, for a fixed period, for once-off fee. This paper presents the reliability growth analysis and management methods for in-service MC68 microprocessor, which is the main component of the base station controller in PCS(Personal Communication Service) telecommunication system. The methods will provide guidelines to monitor reliability program in planning RIW contract.

• Journal of Korean Society for Quality Management
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• v.19 no.2
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• pp.158-165
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• 1991

The Q-cost has been used in the manufacturing company to decide the optimal level of company's product quality, and to evaluate the effect of company's quality control system since the advent of Q-cost theory. In spite of the following costs are generated in the user side, owing to an unsuitable level of product quality and inadequacy of company's quality control system, these costs are not usually included in the company's Q-cost : (1) the cost generated in relation to a claim proposal as traffic expeneses and transpotation of the product. (2) the cost of maintenance through the useful life of the product, especially accured after quality warranty period. (3) the cost related to the economical efficiency in using the product. (4) the cost ralated to a customer dissatisfaction for the product quality. In this point of view, the contents of user side Q-cost, and the relations between the user side Q-cost and the level of company's product quality are discussed. And then the importance of user side Q-cost in order to determine the optimal quality level is discussed.

• Journal of the Korea Safety Management & Science
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• v.17 no.3
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• pp.307-317
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• 2015

This study was to identify the effect of the satisfaction of certification, the educational use of the company offering certificate, the system of confirmation of the same model and the demographic aspect on the companies to see if compulsory certification(KC certificate) has negative effects on company management. First, the satisfaction of certification could reflect positive influences on company management. Second, there is no statistical significance in the education from the company offering certificate as a result of analyzing relationships but education is required and has an effect on improving quality according to the result of frequency analysis. Last, the system to declare by identifying the same model has a difference in significance in sales account, the development of products and warranty service for products.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.1
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• pp.44-49
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• 2021

Recently, infrared (IR) and near-infrared (NIR) light-emitting diodes (LEDs) were widely used for home medical applications owing to its low output power and wide exposed area for curing. For deep penetration of the light under the skin, multiple LEDs with wavelengths of 700~10,000 nm were located on a flexible printed circuit board. When multiple wavelengths of LEDs were soldered on a circuit board, the lifetime of LED module highly depends on LEDs with a short lifetime. The mean time to failure (MTTF) was able to calculate with the experimental results under high temperature and the Arrhenius model. The results of this study could help companies to approve the warranty of LED modules and its product.

• KIEAE Journal
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• v.14 no.6
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• pp.53-58
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• 2014

Residental photovoltaic power system achieved remarkable results in distribution and activation through 'One Million Green Homes Program' led by the government. However, system maintenance and management after installation are relative unsatisfactory. Thus, problems, such as malfunctioning, decrease in efficiency, breakage, etc, are occurring in succession which means that expensive facilities are not used effectively. This study attempted to propose a more preferred alternative to the photovoltaic power system currently applied and installed to the housing by investigating and analyzing the said system, identifying management practices, and deriving problems. For this study, 48 houses equipped with photovoltaic systems in J City were chosen and they were analyzed after preliminary research and field investigation. The results revealed that most of the surveyed systems in J City are still in fairly good conditions. But the instruction and information regarding the appropriate operational management of those surveyed systems have not been delivered to the owner. Therefore, promotion education and related manual deployment should be done by the contractor. In terms of installation, inadequate system location and some warranty services are required to be improved, which are usually caused by a lack of careful planning and construction. In addition, the follow-up management needs to be provided about five years later after installation considering system deterioration.

• Journal of Applied Reliability
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• v.17 no.4
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• pp.332-342
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• 2017

Purpose: In this study, the lifetime distribution of a k-out-of-n system with heterogeneous components is suggested as Markov model, and the time-to-failure (TTF) distribution of each component is considered as phase-type distribution (PHD). Furthermore, based on the model, a redundancy allocation problem with a mix of components (RAPMC) is proposed. Methods: The lifetime distribution model for the system is formulated by the structured Markov chain. From the model, the various information on the system lifetime can be ascertained by the matrix-analytic (or-geometric) method. Conclusion: By the generalization of TTF distribution (PHD) and the consideration of heterogeneous components, the lifetime distribution model can delineate many real systems and be exploited for developing system operation policies such as preventive maintenance, warranty. Moreover, the effectiveness of the proposed RAPMC is verified by numerical experiments. That is, under the equivalent design conditions, it presented a system with higher reliability than RAP without component mixing (RAPCM).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.5
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• pp.523-529
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• 2009

Smart sensor is known as intelligent sensor, it is different with other conventional sensors in the case of intelligent system embedded on it. Smart sensor has many benefits e.g. low-cost in usage, self-decision and self-diagnosis abilities. This sensor consists of perception element(sensing element), signal processing and technology of communication. In this work, a bridge and structure of smart sensor has been investigated to be capable to condition monitoring routine. This investigation involves low power consumption, software programming, fast data acquisition ability, and authoritativeness warranty. Moreover, this work also develops smart sensor to be capable to perform high sampling rate, high resolution of ADC, high memory capacity, and good communication for data transfer. The result shows that the developed smart sensor is promising to be applied to various industrial fields.

• Journal of the Korean Professional Engineers Association
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• v.34 no.4
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• pp.69-73
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• 2001

Due to the rapid increase of automobiles and daily driving distances, air pollution by automobiles is still dominant problem of large city in spite of strict emission refutation and development of reduction technologies. Among the air pollution resources of automobile , industry. electricity generation and heating. automobile keeps 51% of total nationwide air pollution in 1998 and this proportion Is increasing in large cities from 65% to 85%. To reduce these air pollution. catalytic converter and electronic engine control, exhaust gas re-circulation and evaporative emission control system have continuously developed and applied to automobiles since 1987. Also strong emission standards and emission durability warranty have enforced and monitored annually by sampling several vehicle models. But technologies and regulations are incomplete, driver should participate in reducing air pollution for himself by planning driving, avoiding unnecessary idle and air conditioning, keeping periodic maintenance and using mass transportation.