• 터널과지하공간
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• 제28권3호
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• pp.277-291
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• 2018

이 논문에서는 재료의 단축하중 하에서의 응력-변형률 곡선을 예측하기 위하여 순환 신경망의 일종인 LSTM(Long Short-Term Memory) 알고리즘을 사용하였다. 석고와 규사를 혼합해 만든 재료에 일축압축시험을 수행하여 얻은 응력-변형률 데이터를 이용하였으며, 낮은 응력 구간의 초반 데이터를 활용해서 파괴 전까지의 거동을 예측하였다. 앞부분의 데이터를 활용하여 단계적으로 뒤쪽 구간의 값을 예측하는 LSTM 순환 신경망의 구조상 큰 응력에 대응하는 변형률을 예측할 경우에는 앞쪽 구간의 오차가 누적되어 실측값과 차이가 늘어났으나 전반적으로 높은 정확도로 응력-변형률 곡선을 예측하였다. 예측에 사용한 초기 데이터의 길이가 늘어나는 경우 정확도는 조금 증가했다. 그러나 접선을 이용한 단순 예측과의 성능 차이는 초기 데이터의 길이가 작은 경우에 두드러졌으며, 적은양의 데이터로도 응력-변형률 곡선 전체 구간의 예측을 가능하게 한다는 점으로부터 신경망 모델의 필요성을 확인하였다.

• 대한기계학회논문집A
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• 제26권4호
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• pp.677-682
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• 2002

Break-in is an intentional treatment to enhance the performance life of machinery parts and to maintain static friction behavior. Most studies on break-in have concerned only about surface conditions such as roughness or film formation. But the exact mechanism of break-in has not been found yet. Friction, scuffing behavior and wear of AISI 1045 were studied in relation to break-in and residual stress. The cylinder-on-disk type tribometer was used with the line-contact geometry. Scuffing tests were carried out using a constant load of 730N. In the break-in procedure the step load was applied from 100N to 200N. In this experiment, it was found that the break-in helps compressive residual stress to be formed well enough to enhance the scuffing life during the scuffing test. Specimens that had high compressive residual stress induced by shot-peening show better wear resistance than those were not shot-peened. Results of scuffing test, break-in procedure and wear amount in relation to residual stress have been discussed.

• KEPCO Journal on Electric Power and Energy
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• 제7권2호
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• pp.241-248
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• 2021

High cycle fatigue life for the cables with two different types of clamps is estimated comparatively through acceleration testing. The high cycle fatigue fracture of overhead lines is caused mainly by the aeolian vibration which is induced by vortex shedding. It is necessary to manage the integrity of cables continuedly considering that the aeolian vibration is unavoidable since it occurs in steady and relatively low wind velocity. Two types of clamps which are largely used for overhead lines of the distribution grids are selected and failure data are obtained by step stress testing with a electrodynamic shaker with them. The inverse power law is assumed to describe the stress-life relationship and the fatigue limit at any specified life is supposed to follow Weibull distribution. The life of the cable is defined as the number of cycles to the time that one of strands is completely broken. Finally, the fatigue limits of the cables with two clamp types are estimated at the reference life of 500 Mcycles and compared each other based on a bending vibration amplitude.

• Korea-Australia Rheology Journal
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• 제20권2호
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• pp.51-58
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• 2008

This paper describes a two-step Tikhonov regularization procedure for converting the steady shear data generated by parallel-disk viscometers, in the presence of wall slip, into a shear stress-shear rate function and a wall shear stress-slip velocity functions. If the material under test has a yield stress or a critical wall shear stress below which no slip is observed the method will also provide an estimate of these stresses. Amplification of measurement noise is kept under control by the introduction of two separate regularization parameters and Generalized Cross Validation is used to guide the selection of these parameters. The performance of this procedure is demonstrated by applying it to the parallel disk data of an oil-in-water emulsion, of a foam and of a mayonnaise.

• 소성∙가공
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• 제21권6호
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• pp.372-377
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• 2012

In this study, the plastic flow behaviors of extra deep drawing quality (EDDQ) steel subjected to non-proportional strain paths were investigated. Two-step uniaxial tension tests, in which the first step was performed in the rolling direction (RD) and the subsequent test in different directions in $15^{\circ}$ increments from the RD, were conducted. The experiments clearly showed that stress overshooting and strain hardening stagnation were the dominant features, which were captured reasonably well using a recently proposed distortional hardening model.

• 한국응급구조학회지
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• 제13권1호
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• pp.35-48
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• 2009

Purpose: Firefighters were subjected to be exposed to 24-hour shiftwork and high level of job stress, but there is little study of fire fighters about between Job Stress and Psychological stress in Korea. This study was performed to evaluate job stress of fire fighters grouped by different job types and analyze the health effect of job stress by using a PWI-SF(Psycho-social Well-being Index, Short Form). Methods : This study was to measure the degree of job stress and socio-psychological stress of firefighters working at 119 safety center and analyze the relationship between job stress and mental health, through self-administered questionnaire survey on 918 fire fighters working at fire department located in Korea, during October in 2008. Question items of the questionnaire consist of general characteristics, job stress, and socio-psychological stress. Job Stress Measurement Scale for Koreans was used to measure job stress, while PWI-SF used for socio-psychological stress. Collected data was analyzed through frequency analysis, ${\chi}^2$ test, one-way ANOVA, correlation analysis, multi-regression analysis using a statistic program, SPSS/10.0 Ver for Windows, and statistical significance level was 0.05. Result : Accordingly, this paper is written for the purpose of scrutinizing the reason of 119 rescuers' job stress and Socio-Psychological stress. This thesis tries to analyze a problem and provide contents through many variables concerned and theoretical investigation with the actual research of questionnaire. The results of the study are summarized as follows : Fire fighters feel relatively high stressful in their performance. Job stress, organizational commitment and burnout did not have been influence upon by individual cases such as economic condition, regular exercise etc. Finally, as a result of step by step regression analysis, the variable that can explain Socio-Psychological stress the best was negative emotion scale(NE). Conclusions : It is necessary to conduct repeated studies in the future, since the study implied that there was a contrary relationship between job stress and socio-psychological stress. In order to reduce job stress and maintain better mental health, it is more important than anything else to help firefighters have willingness and efforts to sustain a healthy life, so the development of various programs and education to raise their awareness should be implemented.

• 근관절건강학회지
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• 제24권3호
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• pp.196-204
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• 2017

Purpose: This study was conducted to explore the mediating effect of resilience in the relationship between stress and therapeutic compliance in patients with systemic lupus erythematosus. Methods: The subject (N=145) was a systemic lupus erythematosus patient who visited the D Hospital in B city. Data collection was conducted from January 2016 to August 2016. Twenty-five resilience measurement tools, 20 stress measurement tools, 39 therapeutic compliance measurement tools used to measure resilience, stress and therapeutic compliance levels. The collected data were analyzed using descriptive analysis, Pearson correlation, 3-step regression analysis of Baron and Kenny, and Sobel test in SPSS/WIN 21.0. Results: There was a significant negative correlation between stress and therapeutic compliance, a significant negative correlation between stress and resilience, and significant positive correlation between resilience and therapeutic compliance. Resilience showed a direct effect on therapeutic compliance through stress as a mediating variable. Conclusion: It is necessary to develop appropriate resilience enhancement program to improve therapeutic compliance with systemic lupus erythematosus.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.66-73
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• 2004

Prototype crushed-stone compaction pile(${\Phi}=700mm$) were constructed on specific test site. Static loading tests for crushed-stone compaction piles were performed. Based on the static loading test results, finite element analysis was performed using software PENTAGON 3D. Numerical analysis were done for the area replacement ratio($a_s$) of $20{\sim}70%$ and $a_s$ was varied as a step of 10%. In the single crushed-stone compaction pile, settlement was decreased as $a_s$ was increased. In the group pile, this tendency was similar. In the in-sit test and numerical analysis, as $a_s$ increased, the stress concentration ratio was increased. But $a_s$ in the numerical analysis were more than that of in-situ test, greatly.

• 디지털융복합연구
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• 제15권12호
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• pp.615-623
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• 2017

본 연구는 중년 남성 근로자의 수면의 질에 미치는 영향 요인을 파악하기 위한 목적으로 시도된 서술적 조사연구이다. 본 연구의 대상자는 전남지역 사업장의 중년 남성 근로자 127명이며, 자료 조사는 구조화된 설문지를 이용한 자가 보고식으로 이루어졌다. 자료 분석은 t-test, one-way ANOVA, Pearson correlation coefficient 와 step wise multiple regression 으로 SPSS/WIN 18.0을 사용하여 분석하였다. 연구결과, 수면의 질과 관련 변인들 간의 관계를 살펴보면 직무 스트레스는 양의 상관관계를 보였고, 직무만족도는 음의 상관관계를 보였다. 직무스트레스 중 하위영역 직무요구, 직장문화와 직무만족 중 하위영역 직무자체가 수면의 질을 24.5% 설명하였다. 이에 중년 남성 근로자들의 수면의 질을 향상하기 위한 간호중재 전략과 직업만족도를 높이고 직업스트레스를 줄이는 전략을 강구해야 할 것이다. 더불어 대상자의 수면의 질 향상을 위해 과도한 업무량을 줄일 수 있는 제도적 방안 마련과 건전한 직장문화를 확립할 수 있도록 구성원 간의 노력이 필요할 것으로 생각된다.

• 대한치과기공학회지
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• 제31권3호
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• pp.67-85
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• 2009

This study aims to provide the research for dental technician's stress prevention and management with basic materials by understanding dental technician's psychosocial stress level and examining relevant factors. The subject of this study is 255 dental technologists who work mainly in Seoul Gyeonggi district for a month of April of 2009 and I conducted cross-sectional study through self administered survey. The contents of survey include general feature, occupational feature, health behavior feature. I used Karasek's Job Content Questionnaire, JCQ and Psychosocial well-being index, PWI-SF as means of measurement. To compare the level of dental technician's psychosocial stress, I conducted t-test and ANOVA and I measured the factors that are related with psychosocial stress symptom with step by step multiple regressive analysis. According to the result of Cronbach's a value which is yielded to verify the reliability of means of measurement, the reliability of concept is sufficient. The detailed result of this study is as follows. 1. According to the result of analyzing the stress symptom in accordance with general feature and occupational feature, those dental technologists who are older and not married, graduate from junior college, have lower position, work at university hospital or general hospital show lower stress(p<0.05). There is no difference in the level of psychosocial stress with regard to duty related feature, period of service, daily average working hours, monthly average pay. 2. With regard to health behavior feature, those dental technologists who control weight better and have meal more regularly show lower stress(p<0.05). Those dental technicians who smoke, drink liquid and take a suitable sleep show low stress but the difference does not have significance statistically. 3. With regard to the factors of stress in the workplace, those dental technicians who have lower duty related requirement, have higher duty related control ability, have higher social support, have less instability of employment and have less workload and physical burden show lower stress(p<0.05). 4. According to the result of analyzing the factors that influence dental technologist's stress symptom, social support has the most enormous influence on stress symptom. Unstable employment, regular exercise, regular eating, daily average sleeping hours and technological capacity are also important in this order. According to the result of this study, those dental technicians who have higher social support, less instability of employment, do exercise more regularly, take enough sleep more soundly and have higher technological capacity show lower psychosocial stress symptom. Therefore, to adjust appropriately the dental technician's stress and properly maintain and improve the dental technician's mental health, effective management plan that enables dental technicians to maintain smooth human relationships for dental technicians should be sought. In addition, heath education and health management for dental technicians should be given more thoroughly so that they can establish desirable health behavior in daily life.