• 한국재료학회지
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• 제17권11호
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• pp.580-586
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• 2007

To enhance the reliability of a newly designed reciprocating compressor applied in a domestic compressor, accelerated life tests were developed using new definitions of the sample size and the $B_1$ life index. In $1^{st}$ accelerated life testing, the compressor was locked due to the fracture of the suction reed valve. The failure modes and mechanisms of the suction reed valve in the accelerated tests were found to be similar to that of the failed product in the field. The root cause of the failure was the overlap between the suction reed valve and the valve plate in the suction port. The missing parameters in the design phase were modified by expanding the trespan size, introducing tumbling process, changing the material and thickness for the valve, introducing a ball peening and brushing process for the valve plate. In $2^{nd}$ accelerated life testing, the compressor was locked due to the interference between the crank shaft and thrust washer. The corrective plan was to heat treat the crank shaft. The $B_1$ life of the compressor improved from 1.5 to 12.9 years.

• 한국산업정보학회논문지
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• 제27권6호
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• pp.1-12
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• 2022

음원 스트리밍 서비스와 Hi-Fi 시장이 성장함에 따라 다양한 음향기기들이 출시되고 있다. 이로 인해 소비자들의 제품 선택에 대한 폭은 넓어졌지만 자신의 음악적 취향과 일치하는 제품을 찾기는 더욱 어려워졌다. 본 연구에서는 사용자가 선호하는 음원으로부터 보컬 성분을 추출하고 이를 토대로 사용자에게 가장 적합한 음향기기를 추천하는 시스템을 제안하였다. 이를 위해 먼저 원본 음원을 Python의 Spleeter Library를 통해 분리하여 보컬 음원을 추출하고 제조사의 음향기기의 주파수 대역 데이터를 수집한 결과를 각각 격자 그래프로 나타내었다. 추출한 보컬 음원의 주파수 대역과 음향기기의 주파수 대역 측정치 데이터를 비교하기 위한 지표로서 Matching Gap Index(MGI)를 제안하였다. 산출된 MGI 값을 토대로 사용자 선호와의 유사도가 가장 높은 음향기기를 추천한다. 추천 결과는 음향 전문업체에서 제공하는 장르별 Equalizer 데이터를 이용하여 검증하였다.

• 유통과학연구
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• 제13권11호
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• pp.39-46
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• 2015

Purpose - In Korea, there has been a recent trend that shows housing prices have risen rapidly following the International Monetary Fund crisis. The rapid rise in housing prices is spreading recognition of this as a factor in housing price volatility. In addition, this raises the expectations of housing prices in the future. These expectations are based on the assumption that a relationship exists between the current housing prices and expected housing prices in the real estate industry. By performing an empirical analysis on the validity of the claim that an increase in current housing prices can be correlated with expected housing prices, this study examines whether a long-term equilibrium relationship exists between expected housing prices and existing housing prices. If such a relationship exists, the recovery of equilibrium from disequilibrium is analyzed to derive related implications. Research design, data, and methodology - The relationship between current housing prices and expected housing prices was analyzed empirically using the Vector Error Correction Model. This model was applied to the co-integration test, the long-term equilibrium equation among variables, and the causality test. The housing prices used in the analysis were based on the National Housing Price Trend Survey released by Kookmin Bank. Additionally, the Index of Industrial Product and the Consumer Price Index were also used and were obtained from the Bank of Korea ECOS. The monthly data analyzed were from January 1987 to May 2015. Results - First, a long-term equilibrium relationship was established as one co-integration between current housing price distribution and expected housing prices. Second, the sign of the long-term equilibrium relationship variable was consistent with the theoretical sign, with the elasticity of housing price distribution to expected housing price, the industrial production, and the consumer price volatility revealed as 1.600, 0.104,and 0.092, respectively. This implies that the long-term effect of expected housing price volatility on housing price distribution is more significant than that of the industrial production and consumer price volatility. Third, the sign of the coefficient of the error correction term coincided with the theoretical sign. The absolute value of the coefficient of the correction term in the industrial production equation was 0.006, significantly larger than the coefficients for the expected housing price and the consumer price equation. In case of divergence from the long-term equilibrium relationship, the state of equilibrium will be restored through changes in the interest rate. Fourth, housing-price volatility was found to be causal to expected housing price, and was shown to be bi-directionally causal to industrial production. Conclusions - Based on the finding of this study, it is required to relieve the association between current housing price distribution and expected housing price by using property taxes and the loan-to-value policy to stabilize the housing market. Further, the relationship between housing price distribution and expected housing price can be examined and tested using a sophisticated methodology and policy variables.

• Safety and Health at Work
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• 제11권3호
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• pp.335-346
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• 2020

Background: Nursing service is a nonroutine work with an excessive physical load and diverse tasks. This study derived representative common tasks based on the frequently occurring tasks with a high physical load in the nursing workers' daily work and developed indicators to evaluate the work risk by reflecting the characteristics of nonroutine work. Methods: Common tasks were classified through the following stages: literature review, first focus group interview (FGI) with experts, first classification of common tasks, second FGI with hospital health managers, a survey of nursing service workers, and the final classification of common tasks for each task type. To develop an objective risk index for physical load assessment, we investigated the frequency and duration of the derived common tasks via survey. Results: Nursing common tasks were categorized into six task types and 56 subtasks. To evaluate the risks of various tasks in nonroutine works, three frequencies and three working time levels were defined by examining the task frequency and working hours. Exposure time was defined to reflect the characteristics of a nonroutine job. The final risk assessment was the product of the exposure time level and job intensity level. From this, four risk action levels were derived. Conclusion: This study has the advantage of solving the problem of focusing on some tasks in evaluating the physical load. It was meaningful in that a new risk assessment index based on exposure time was proposed based on the development of an evaluation scale for frequency and time by reflecting the characteristics of nonroutine work.

• 한국연초학회지
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• 제28권1호
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• pp.36-42
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• 2006

The papermaking process for a reconstituted tobacco sheet (RECON) has been preferred more because of the various merits such as a wide range of Recon products with better quality. The screw press is one of the very important process in RECON making process which divides the mixed raw materials into the soluble material and the insoluble material and could greatly affect the productivity and product quality. In this study, the characteristics of the screw press process in a Recon making mill were evaluated for two different RECON products. Three different efficiency index were proposed for the more detailed analysis of the screw press process. The result showed that the difference in the raw material might result in the difference in the efficiency and the properties of the extracts and the filter cake, especially in the HWS. The washing technique which applied in this experiment showed the amount of residual HWS in the fiber portion were not much changed by the each steps of the screw press.

• 산경연구논집
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• 제10권11호
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• pp.49-56
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• 2019

Purpose: Corporate social responsibility is a self-regulating business model that helps a firm be socially accountable to the public. By practicing corporate social responsibility, firms can be conscious of the kind of impact they are having on all aspects of society, including economic, social, and environmental. Corporate social responsibility activities are not directly linked to increasing corporate performance and corporate value, but rather involve spending expenses. Based on these facts, this study verifies whether the effects of corporate social responsibility activities differ depending on the firm's situation. Research design, data and methodology: This study analyzed the effect of market competition on corporate social responsibility activities using logistic regression analysis on listed companies in the KOSPI and KOSDAQ for fiscal years 2014 through 2016. In this study, market competition was measured using the Herfindahl-Herschman Index(HHI). Higher HHI value can be interpreted as a lower degree of market competition. We also measured corporate social responsibility activities using the KEJI Index published by the Korea Economic Justice Institute (KEJI). If a firm-year is included in the top 200 companies of the KEJI Index, it is classified as a good corporate social responsibility activity firm. Results: We find that companies in less competitive market were not included in the KEJI Index. This result indicates that firms in the market with lower market competition perform less corporate social responsibility activities that incur costs. An additional analysis showed that there was a significant negative relationship between the market competition and the corporate social responsibility activity scores published by the KEJI Index. These result adds robustness to the result of the hypothesis that firms that have a monopolistic place in the market practice passive corporate social responsibility activities. Conclusions: The results show that managers of a firm in the lower market competition have a lower incentive to use limited resources for projects that are not directly related to revenue. The results of this study imply that corporate social responsibility activities vary according to the position of the business. Therefore, this study suggests that market investors should consider the degree of competition in the market when they evaluate corporate social responsibility activities.

• 산업경영시스템학회지
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• 제40권3호
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• pp.1-6
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• 2017

Process capability is well known in quality control literatures. Process capability refers to the uniformity of the process. Obviously, the variability in the process is a measure of the uniformity of output. It is customary to take the 6-sigma spread in the distribution of the product quality characteristic as a measure of process capability. However there is no reference of process capability when maximum material condition is applied to datum and position tolerance in GD&T (Geometric Dimensioning and Tolerancing). If there is no material condition in datum and position tolerance, process capability can be calculated as usual. If there is a material condition in a feature control frame, bonus tolerance is permissible. Bonus tolerance is an additional tolerance for a geometric control. Whenever a geometric tolerance is applied to a feature of size, and it contains an maximum material condition (or least material condition) modifier in the tolerance portion of the feature control frame, a bonus tolerance is permissible. When the maximum material condition modifier is used in the tolerance portion of the feature control frame, it means that the stated tolerance applies when the feature of size is at its maximum material condition. When actual mating size of the feature of size departs from maximum material condition (towards least material condition), an increase in the stated tolerance-equal to the amount of the departure-is permitted. This increase, or extra tolerance, is called the bonus tolerance. Another type of bonus tolerance is datum shift. Datum shift is similar to bonus tolerance. Like bonus tolerance, datum shift is an additional tolerance that is available under certain conditions. Therefore we try to propose how to calculate process capability index of position tolerance when maximum material condition is applied to datum and position tolerance.

• 산업경영시스템학회지
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• 제42권3호
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• pp.95-108
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• 2019

Quality management has become an pervasive philosophy in most sectors of business. Specific movements such as statistical quality control, quality circle, total quality management, and quality management system have become embedded in business organizations. Only the companies with competitive edge can survive in the competition in global market. KSA(Korean Standards Association) established in 1962 has launched all kinds of quality education, quality standard certification service for business, and KNQA(Korean National Quality Award) system. This article considers quality competitiveness excellent company award among KNQA. We performed a statistical analysis of audit data for quality competitiveness excellent company for three years, from 2015 to 2017. By using ANOVA and two sample t-tests, the average scores of 13 evaluation fields were significantly different depending on company size and type. We proposed ways to improve the current hall of fame system. We discovered that the average scores of 13 evaluation fields in the audit data according to years and hall of fame status were not significantly different. We also showed linear relationships among 13 evaluation fields by correlation analysis and obtained an estimated linear regression equation : Business Performance, which is a comprehensive index, as a dependent variable was significantly related to Customer Focus and Product Liability as regressor variables among 13 evaluation fields by regression analysis.

• 산업경영시스템학회지
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• 제44권1호
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• pp.45-50
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• 2021

Machines and facilities are physically or chemically degenerated by continuous usage. The representative type of the degeneration is the wearing of tools, which results in the process mean shift. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore, a preventive maintenance is necessary at some point. The problem of determining the maintenance period (or wear limit) which minimizes the total cost is called the 'process mean shift problem'. The total cost includes three items: maintenance cost (or adjustment cost), non-conforming cost due to the non-conforming products, and quality loss cost due to the difference between the process target value and the product characteristic value among the conforming products. In this study, we set the production volume as a decreasing function rather than a constant. Also we treat the process variance as a function to the increasing wear rather than a constant. To the quality loss function, we adopted the Cpm+, which is the left and right asymmetric process capability index based on the process target value. These can more reflect the production site. In this study, we presented a more extensive maintenance model compared to previous studies, by integrating the items mentioned above. The objective equation of this model is the total cost per unit wear. The determining variables are the wear limit and the initial process setting position that minimize the objective equation.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.545-551
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• 2011

최근 고품질의 수돗물에 대한 소비자의 요구가 상승함에 따라 상수도 배급수관의 내부 부식에 의한 수질악화 및 부식제어 연구에 대한 관심이 높아지고 있다. 이에 따라 노후 관 교체 사업을 대신하여 수질 관리를 위한 부식 제어 수단을 강구하지 않고서는 근본적인 문제 해결이 이루어질 수 없는 실정이다. 본 연구에서는 수질안정화 약품 주입에 의한 상수도관 내부 부식제어 효율을 평가하기 위해 Pilot Plant 실험을 실시하였으며, 부식성제어 효율은 물의 부식성을 나타내는 LSI(Langelier Saturation Index)값에 의해 평가되었다. 실험결과, Pilot Plant에 의해 제조된 반응수는 수질안정화 약품인 액상소석회($Ca(OH)_2$, liquid lime)의 주입으로 부식성이 개선되어 철 용출이 억제되는 효과가 확인되었다. 강관과 동관을 절단하여 제작한 시편의 부식도 측정을 통해 각각 35.4, 44.5%의 부식제어 효과가 있음을 확인하였고 수질안정화 약품이 주입된 Sample관이 더 두터운 부식 생성물 층을 갖고 있는 것으로 밝혀졌으며, 결과적으로 수질안정화 약품을 투입한 배관이 부식 방지 측면에서 안정한 수질을 갖고 있음을 알 수 있었다.