• 열처리공학회지
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• 제27권3호
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• pp.121-126
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• 2014

High-nitrogen Fe-18Mn-18Cr-N austenitic steels with higher yield strength have been recently developed and used for generator retaining rings because they have non-magnetic, high strength, high ductility, and good corrosion resistance. In the present study, a high-nitrogen Fe-18Mn-18Cr-0.61N austenitic steel was fabricated and then tensile and Charpy impact tests were conducted on them in order to investigate the effect of cold working on the mechanical properties. Although the yield and tensile strengths usually increased with cold working, the ductility and impact toughness significantly decreased after cold working. On the other hand, the high-nitrogen austenitic steel exhibited a ductile-brittle transition due to unusual brittle fracture at low temperatures despite having a face-centered cubic structure. The ductile-brittle transition temperature obtained from Charpy impact tests could be remarkably increased by $60^{\circ}C$ after 20% cold working because of the enhanced cleavage-like brittle fracture.

• 한국산업보건학회지
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• 제33권4호
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• pp.447-454
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• 2023

Objective: This study aims to investigate the impact of changes in working conditions on job-related stress and musculoskeletal disorders using the results of seven surveys conducted at a single workplace from 2004 to 2022 regarding factors hazardous to the musculoskeletal system. Additionally, the study aims to propose alternative methods of investigating factors hazardous to the musculoskeletal system. Methods: A car parts manufacturing plant where the same survey was taken seven times from 2004 to 2022 was selected and the survey data was analyzed. The main contents of the survey were weekly working hours, Borg's scale, work intensity, job-related stress, and the prevalence of musculoskeletal symptoms. The statistical analysis was performed using SAS (version 9.4). Results: The results of this study are as follows. Firstly, changes in working conditions have an impact on job-related stress. Secondly, changes in working conditions have an impact on work intensity indicators. Thirdly, changes in working conditions have an impact on the prevalence of musculoskeletal symptoms. Fourthly, even with an increase in age and length of service, job-related stress and musculoskeletal symptoms were alleviated when working conditions were improved. Conclusions: In order for measures to reduce musculoskeletal disorders to be successful, working conditions must not deteriorate, and it is necessary to demand revisions to regulations, etc. to reflect these points in the investigation of hazardous factors to the musculoskeletal system.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2004년도 제5회 정기학술발표대회 논문집
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• pp.170-173
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• 2004

2004년 4월 23일부터 바닥충격음에 대한 법이 시행되어 신규설계에 반영되고 있다. 새롭게 제시된 법에 따르면 표준 바닥구조를 통해 최소 슬래브 두께가 180 mm로 제시되었으며 중량충격음에 대한 최소 기준도 함께 제시되었다. 또한 최소기준과는 별도로 경량 충격음에 대한 등급화가 제시되어 소비자의 요구를 수용할 수 있도록 하였다. 그러나 현장 시험을 통한 조사 결과 경량 충격음의 등급화 시공을 위한 방안이 제시되지 않음으로서 설계목표를 세우고도 이루지 못하는 문제가 예상되고 있다. 본 내용은 등급화 시공을 위해서 검토해야 할 내용을 정리하여 설계자와 건설사에 도움을 주고자 한 내용이다.

• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.39-46
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• 2016

A high frequency hydraulic rock drill drifter with sleeve valve is developed to use on arm of excavator. In order to ensure optimal working parameters of impact system for the new hydraulic rock drill drifter controlled by sleeve valve, the performance test system is built using the arm and the hydraulic source of excavator. The evaluation indexes are gained through measurement of working pressure, supply oil flow and stress wave. The relations of working parameters to impact system performance are analyzed. The result demonstrates that the maximum impact energy of the drill drifter is 98.34J with impact frequency of 71HZ. Optimal pressure of YZ45 rock drill is 12.8 MPa-13.6MPa, in which the energy efficiency reaches above 58.6%, and feature moment of energy distribution is more than 0.650.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.863-867
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• 2020

This study was conducted on financial data of 38 economic groups listed on Vietnam's stock market for the period 2009 - 2019 and it aims to provide an empirical evidence on the impact of working capital management policy on performance in all phases of the economic cycle of Vietnamese economic groups. The study uses FGLS estimation method with 2 dependent variables ROA, GOP, independent variables including INV, AR, AP, CCC, dummy variable representing different phases of the economic cycle, variables Control includes CAT, CR, LEV, SZ, GR. Research shows that the greater the level of investment by companies in liquid assets corresponding to a certain level of activity (shown by average days of inventory (INV), average days of collection. (AR), cash flow cycle (CCC)) the lower the rate of return on assets. The study also provides additional evidence of the negative effects of economic crisis on the performance of economic groups. The study also shows that the number of short-term asset cycles has a positive impact on operational efficiency, and the level of debt use has a negative impact on operational efficiency. This result implies that the managers of economic groups can increase the efficiency of businesses through a reasonable working capital policy.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.377-389
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• 2020

This research focuses on identifying and measuring key personality factors affecting the job performance of salesperson working in the machinery industry in Vietnam. A total number of 218 salesperson working in machinery industry were surveyed. After evaluating Cronbach's Alpha and using the regression analysis technique, the results show the impact level of personality trait factors affecting the job performance of salesperson working in machinery industry. Ordered from the highest to the lowest effects on job performance, these factors are: agreeableness, openness to experience, conscientiousness, extraversion, and neuroticism. Five research hypotheses are accepted. Specifically, openness to experience, conscientiousness, extraversion, and agreeableness have positive impacts on job performance of salesperson working in machinery industry in Vietnam. However, neuroticism has a negative impact on job performance of salesperson. This research results indicate the level of impact of personality traits on the sales staff performance in machinery industry. Many people apply to this profession as a career choice. Each occupation is suitable for certain personality trait, which changes very little during adulthood. Research also shows that each personality trait always has its strengths and weaknesses. The educational environment should create conditions for learners to develop their character in a natural way.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.91-94
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• 1995

A newly developed discrete-time control design method for impact machines is proposed. It is composed of identification and control using neural networks, where the optimal controller with saturationn and no use of velocity measurements is obtained. By computer simulation, the proposed method is demonstrated to be effective: as the training progresses, the cost function becomes smaller, the proposed control is superior to PID control tuned with Ziegler-Nichols (Z-N) parameters; robust performance with respect to uncertainty, disturbances and working time is so good.

• 융합경영연구
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• 제2권1호
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• pp.18-28
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• 2014

In this research we investigate the effect return on assets, return on equity, profit margin and earnings per share on working capital management. Current ratio and quick ratio used as proxies for working capital management. The research sample includes 451 year -firm of Tehran Stock Exchange (TSE) listed companies for period 2007-10. The multiple linear regressions were applied to test the research hypotheses. The results showed that, return on assets and earnings per share have a negative impact on working capital management. The results also show that earnings per share and profit margin positively associated with the firm performance.

• 한국치위생학회지
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• 제15권3호
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• pp.539-546
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• 2015

Objectives: The purpose of the study is to investigate the impact of working environment on the subjective health symptoms in the dental hygienists. Methods: The subjects were 220 dental hygienists in Gwangju and Jeonnam. A self-reported questionnaire was completed from September 9 to 22, 2012. The questionnaire was adapted and modified from building symptom index of workers in large buildings by O. The questionnaire consisted of eight questions of the general characteristics of the subjects, 19 questions of working environment and job satisfaction, nine questions of working environment characteristics, and six questions of subjective health symptoms. The questionnaire was measured by Likert 4 scale. Cronbach's alpha in this study was 0.826. Except incomplete answers, 192 data were analyzed using SPSS 19.0 program including t-test, ANOVA, and multiple regression. Results: The health symptoms were statistically and significantly different in glasses wearer and contact lens wearer, working hour satisfaction, and indoor environment(p<0.05). The subjective health symptoms were statistically different from the salary satisfaction, human relations satisfaction, office air environment, indoor environmental awareness score(p<0.05). Conclusions: It is necessary to improve the pleasant indoor working environment by providing the efficient working environment for the health care providers.

• 한국컴퓨터정보학회논문지
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• 제22권6호
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• pp.149-156
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• 2017

In this paper, we propose to enhance a Physical working conditions to decrease absence from work. we demonstrated the correlation of worker's absence with various environmental factors in workplace by surveying 6,962 workers. As result, first, concerning exposure to physical work factors, most of them complained of vibration, and concerning exposure to improper working posture, most of them complained of repetitive arm and hand motions. Second, the absence experience had correlations with age, monthly income, smoking, number of employees, long term working, and shift work, and of the physical factors, hand vibration, noise, high temperature, low temperature and improper working posture had correlations with physical pain posture, movement of people and carrying heavy materials. Third, experience of exposure to hand vibration, noise and low temperature of the physical factors had impact on absence, and of the improper working posture, physical pain posture and carrying heavy stuff had impacts on absence. Through this study, it was found that of the work factors of Korean workers, physical factors and improper working posture had impacts on absence. The results of this study confirmed that physical factors and inappropriate working posture among work factors influenced the absenteeism. Therefore, it is required to improve the work environment regarding physical risk factors and prepare a systematic management plan.