• 한국기계가공학회지
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• 제11권1호
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• pp.88-94
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• 2012

An axle drive shaft with double joint shaft, cross kit and yoke has an important role by transferring power and changing steering angle between axle and wheel in power train system. It has been used widely in the heavy machinery requiring a high reliability in the power train system. At fatigue failures of the axle drive shaft with the long span, a relatively high stress concentration at a snap ring groove on the drive shaft brings to significant fatigue damages under repeated loading condition. As Peterson's suggestions on this study, a relief groove in the vicinity of the snap ring groove is applied by decreasing the stress concentration and improving the fatigue life of axle drive shaft. By using FEM analysis, the decreasing effect of the stress concentration and extended fatigue life are due to the change of design parameters related with size and location of the relief groove. The relief groove with the design parameters such as d/b=2.0 and r/h=1.2 enables to decrease the stress concentration of 22.3% and increase the fatigue life more than 3 times by comparing with no relief groove application.

• 한국정밀공학회지
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• 제18권6호
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• pp.59-66
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• 2001

Fatigue strength of the welding structure is governed by the residual stress at the weldment toe and static tensile overloads were known as relieving the residual stresses. In this study, static tensile overloads were applied to the welding structures which caused the relief of residual stresses. The amount of residual stress relief was found as proportional to the change of fatigue limit at the given conditions. Based on the fact of the proportionality between the change of fatigue limit and that of residual stress, simple measurement technique is proposed. Modified stress-life curves base on proposed technique gave good agreement with test results.

• Journal of Acupuncture Research
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• 제39권3호
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• pp.170-181
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• 2022

This review evaluated the efficacy of electroacupuncture (EA) for chronic fatigue syndrome. Randomized controlled trials (RCTs) using EA as an intervention for patients with chronic fatigue syndrome were identified in 6 databases (PUBMED, EMBASE, CNKI, J-STAGE, KMBASE, OASIS). Fatigue indicators were used as the primary outcome measures. The quality-of-life index, efficiency rate, and level of pain were used as secondary outcome measures. There were 408 patients from seven RCTs included in this study. Meta-analysis showed that EA was significantly associated with fatigue relief compared with the control group (n = 141 SMD = -1.55, 95% CI; -2.58 - -0.52, p = 0.003, I² = 92%). In addition, EA had a statistically significant improvement in quality of life compared with the control group (n = 176, SMD = -2.29, 95% CI; -3.68 - -0.90, p = 0.001, I² = 96%). One study reported ten cases of bleeding, however, no serious adverse events were reported in any of the included studies. This review determined that EA may have a greater clinical effect than the control group for fatigue relief and improved quality of life. However, there were several risks of bias identified. Not all of the RCTs accurately reported the research method, all studies were conducted in 1 country (China), and the number of studies included were small.

• 한국강구조학회 논문집
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• 제26권5호
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• pp.419-430
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• 2014

연구대상인 강바닥판교의 U-리브와 가로리브를 교차하는 접합부에 대한 연구는 지속적으로 이루어지고 있으나 아직까지는 현재 적용되고 있는 스캘럽 자체 또는 내부의 다이아프램 형상을 개발 이용하고 있는 정도이다. 근본적으로 문제가 되고 있는 교차부 U-리브 하단 부위의 피로손상을 줄이기 위해, 본 연구를 통하여 제시된 SRH, 즉, U-리브가 교차하는 가로리브의 적절한 위치에 적합한 크기의 원형의 구멍을 두는 방안에 대하여 검토하였다. 최종적으로 원형 SRH가 강바닥판교의 U-리브와 가로리브 교차부 응력집중을 충분히 완화시킬 수 있음을 확인하였고, 이 부위의 구조상세의 피로손상을 방지할 수 있는 방안 중 하나로 SRH를 제안할 수 있었다.

• Advances in nano research
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• 제14권1호
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• pp.17-25
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• 2023

Gold nanoparticles have recognized a promising drug carriers in many diseases. These nanoparticles could carry anti-inflammatory drugs in the case of muscle injury and for fatigue relief. On the other hand, specific surface of this kind of nanoparticles could be critical in amount of drug they could carry. Therefore, in this study, we explore different methodology and influencing parameters on the specific surface of gold nanoparticles. After specifying the main parameters, different machine learning and artificial neural network are adopted to model the effects of different parameters. Furthermore, response surface methodology is utilized to obtain a quadrilateral relationship between different parameters and specific surface. The results indicate that concentration of the gold salt solution is the most important parameter in increasing the size of gold nanoparticle and, as a consequence, increasing specific surface. Moreover, the ability of gold nanoparticles in prolonging retention of the drugs is discussed in detail.

• 한국기계가공학회지
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• 제17권3호
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• pp.16-21
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• 2018

The effect of heat treatment on the fatigue crack growth behavior in welded joints between the heat-affected zone (HAZ) of SA 508 Cl.3 low-alloy steel and HAZ of AISI 316L stainless steel is investigated. When the crack propagates across SA 508 Cl.3 or AISI 316L SS and HAZ into the weldment, the fatigue crack growth rate (FCGR) in the HAZ region does not change or decrease despite the increase in stress intensity factor ${\Delta}K$. The residual stress at the HAZ region is more compressive than that at the base Δ materials and weldment. The effect of the welding residual stress on the crack growth behavior is determined by performing a residual stress relief heat treatment at $650^{\circ}C$ for 1h and subsequent furnace cooling. The FCG behavior in the HAZ region in the as-welded specimen and the residual stress relief heat-treated specimen is discussed in terms of the welding residual stress.

• 한국강구조학회 논문집
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• 제25권5호
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• pp.451-461
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• 2013

강교량에는 외력에 대해 저항하는 부재의 좌굴 등의 변형을 구속시키기 위한 여러 상세부들이 존재한다. 이들 상세부는 상호 교차하는 부재들로 구성되고 제작의 용이성, 용접결함의 원천적 배제 및 응력집중을 완화시키기 위해 스켈럽을 이용해 왔다. 본 연구에서는 교차부에 발생되는 응력집중으로 상세범주 D등급 이하를 갖게 되는 강교량 상세부의 피로저항 능력을 상세범주 C등급 이상으로 개선시키는 방안으로 응력완화홀(SRH)을 제안하였다. 적절한 크기 및 위치의 SRH 효과를 확인하고 이를 강바닥판교의 U-rib와 가로보 교차부에 작용시켜 SRH에 의한 피로저항능력 개선 가능성을 확인하였다.

• 대한조선학회논문집
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• 제48권3호
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• pp.238-245
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• 2011

Welding inevitably introduces the residual stresses which affect the fatigue strength of the joint structure. The mitigation of fatigue strength depends on the residual stress magnitude and distribution. Stress relief analyses are of practical interest for all cyclic loaded welded structures, such as ships and offshore structures. In order to estimate the effects of relaxation of residual stresses in the welded structure, this paper presents a finite element analysis procedure and experimental results for the welded structure. Cruciform specimens joint by MAG welding have been tested to measure the released stress. Relieved welding residual stresses obtained by finite element analysis are compared with those measured by experiment.

• 한국생산제조학회지
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• 제25권1호
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• pp.21-29
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• 2016

To overcome the large ring gear manufacturing problems seen in slewing bearings and girth gears, pin gear drive units have been developed. Among them, a novel slewing bearing with an internal pinwheel gear set (i-PGS) is introduced in this paper. First, we consider the exact cam pinion profile of i-PGS with the introduction of a profile shift coefficient. Furthermore, a new root relief profile modification for the i-PGS cam pinion is presented. Then, the contact stresses are investigated to determine the characteristics of the surface fatigue by varying the shape design parameters. The results show that the contact stresses of i-PGS can be reduced significantly by increasing the profile shift coefficient. In addition, the contact ratio, a measure of teeth overlapping action, decreases with the decrease of the allowable pressure angle.

• 한국산학기술학회논문지
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• 제19권4호
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• pp.229-238
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• 2018

본 연구의 목적은 자살시도를 한 중학생의 스트레스 인자와 주관적 행복감의 관계에서 잠으로 피로회복, 주관적 건강인지를 이용하여 다중매개효과 차이를 파악하고자 함이다. 2016년(제 12차) 청소년건강형태온라인조사 원시자료에서 최근 12개월 동안 자살시도를 한 적이 있는 중학생 820명을 대상으로 IBM SPSS 23과 IBM SPSS AMOS 23 프로그램을 이용하여, 경로분석, 부트스트래핑, 팬텀변수, 다중집단분석으로 분석하였다. 연구결과 스트레스 인지와 주관적 행복감의 관계에서 잠으로 피로회복과 주관적 건강인지는 간접효과(${\beta}=-.12$, p=.003)가 통계적으로 유의하였다. 스트레스 인지와 주관적 행복감의 관계에서 잠으로 피로회복 간접효과는 -.05(p=.004), 주관적 건강인지 간접효과는 -.09(p=.004)로, 두 변수의 간접효과 크기 차이는 주관적 건강인지가 잠으로 피로회복보다 -.02(p=.028) 효과크기가 큰 것으로 나타났다. 남 여 중학생 집단별 경로 간 효과 크기의 차이를 본 결과 남학생집단(${\beta}=.44$, p<.001)이 여학생집단(${\beta}=.23$, p<.001) 보다 효과가 큰 것으로 나타났다. 연구결과를 바탕으로 자살시도 중학생의 행복감 증진에 도움이 되는 스트레스인지, 잠으로 피로회복, 주관적 건강인지 내용이 포함된 교육 프로그램의 개발 및 적용되어야 할 것이다.