• 한국안전학회지
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• 제26권3호
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• pp.69-74
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• 2011

Despite most of tasks in manufacturing, construction and agriculture, etc., were currently mechanized and automated, manual materials handling still existed in atypical working condition. In case of manual materials handling, repetitive work, inappropriate working posture, excessive force, contact stress might cause overload, which could lead to work-related musculoskeletal disorders and low back pains. On this basis, the goal of this study is to reveal the effects of various lifting postures of trunk angles and lower extremity postures on maximum holding time(MHT). Twenty two subjects were recruited from a university population. The experiment was designed by a combination of three trunk angle ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) and three lower extremity postures(straight, bent, kneeling). Before experimental trials, subjects performed MVC(maximum voluntary contraction) exertions in three trunk angles ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) to calculate 30%MVC at designated postures. In each trial, they were required to hold the handheld load(30%MVC) for a designated posture as long as they could. The results of MVC by trunk angles were measured in $0^{\circ}$ > $20^{\circ}$ > $60^{\circ}$ orders, but those of MHT measured in $20^{\circ}$ > $0^{\circ}$ > $60^{\circ}$ orders. These results showed that straight posture is the ideal working posture in work exerted a strong force for a short time, but the ability to work might be improved in the trunk angle $20^{\circ}$ in work required 30%MVC for a long time. Also, results of MVC and MHT by lower extremity postures measured in straight > bent > kneeling orders.

• 한국태양에너지학회 논문집
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• 제31권4호
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• pp.80-86
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• 2011

Investigation of the effective soil thermal conductivity(k) is the first step in designing the ground loop heat exchanger(borehole) of a geothermal heat pump system. Another important factor is the borehole thermal resistance($R_b$). Thermal response tests offer a good method to determine the ground thermal properties for the total heat transport in the ground. This is done by supplying a constant heat power into a borehole heat exchanger. There are two methods to supply a constant heat power. One is to employ the electricity provided by Korea Electric Power Corporation(KEPCO). The other is to use electricity generated by a generator. In this study, the power supply regulation was found to reduce when the electricity generated by the generator was used. This is because the generator evaluated with the power supply characteristically reduces the power supply regulation between an overload and a complex using. But it sometimes occurs a power supply regulation in In-situ thermal response test. In this case getting of k,$R_b$ requires delay times and restored normal state. However, the effect of the delay times and restored normal state on the soil thermal conductivity and borehole thermal resistance is very small. Therefore it is possible to use a generally accepted delay times and restored normal state in the analysis. In this work, it is also shown that an acceptable range of ${\Delta}k$, ${\Delta}R_b$ for normal state and regulation state might be approximately 0.01-0.16W/m k, and -0.004-0.007m K/W, respectively. Thus, restored normal state of power supply regulation is valuable to recommend.

• 문화기술의 융합
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• 제5권3호
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• pp.139-145
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• 2019

본 연구는 IT분야의 종사자 및 관련자를 대상으로 업무환경에 따른 직무스트레스 요인을 파악하고 이를 바탕으로 이러한 요인들이 종사자들의 직무몰입과 정서적 몰입에 미치는 영향 관계를 살펴보기 위하여 실시하였다. 연구대상자는 서울 경기지역의 IT관련 업체 중 15개의 업체 및 개인(프리랜서)으로 선정하였다. 자료 수집은 2019년 5월 27일부터 6월 28일까지 4주간 실시하였다. 총 400부를 배포하여 최종 유효한 설문지 352부를 분석에 사용하였다. 연구결과, IT분야 종사자의 직무스트레스 요인(역할과다, 역할모호성, 역할갈등) 중 '역할모호성'과 '역할갈등'의 2개의 요인이 직무몰입에 영향을 미치는 것으로 나타났다. 직무스트레스 요인이 정서적 몰입에 미치는 영향에 대한 분석에서는 직무스트레스의 역할과다, 역할모호성, 역할갈등의 모든 요인이 영향을 미치는 것으로 나타났다.

• BMB Reports
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• 제54권9호
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• pp.476-481
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• 2021

Liver receptor homolog-1 (LRH-1) has emerged as a regulator of hepatic glucose, bile acid, and mitochondrial metabolism. However, the functional mechanism underlying the effect of LRH-1 on lipid mobilization has not been addressed. This study investigated the regulatory function of LRH-1 in lipid metabolism in maintaining a normal liver physiological state during fasting. The Lrh-1^f/f and LRH-1 liver-specific knockout (Lrh-1^LKO) mice were either fed or fasted for 24 h, and the liver and serum were isolated. The livers were used for qPCR, western blot, and histological analysis. Primary hepatocytes were isolated for immunocytochemistry assessments of lipids. During fasting, the Lrh-1^LKO mice showed increased accumulation of triglycerides in the liver compared to that in Lrh-1^f/f mice. Interestingly, in the Lrh-1^LKO liver, decreases in perilipin 5 (PLIN5) expression and genes involved in β-oxidation were observed. In addition, the LRH-1 agonist dialauroylphosphatidylcholine also enhanced PLIN5 expression in human cultured HepG2 cells. To identify new target genes of LRH-1, these findings directed us to analyze the Plin5 promoter sequence, which revealed -1620/-1614 to be a putative binding site for LRH-1. This was confirmed by promoter activity and chromatin immunoprecipitation assays. Additionally, fasted Lrh-1^f/f primary hepatocytes showed increased co-localization of PLIN5 in lipid droplets (LDs) compared to that in fasted Lrh-1^LKO primary hepatocytes. Overall, these findings suggest that PLIN5 might be a novel target of LRH-1 to mobilize LDs, protect the liver from lipid overload, and manage the cellular needs during fasting.

• 한국ITS학회 논문지
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• 제19권6호
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• pp.74-87
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• 2020

과적차량은 도로 주행환경의 안전을 위협하고 도로구조물의 수명단축에 직접적인 영향을 주는 주요 원인이다. 자중계는 화물차량에 탑재하여 중량을 측정할 수 있는 유일한 장비로, 운전자는 스스로 과적상태를 확인하고 운행 전 상차 시 적재중량을 조절하여 과적을 사전에 예방할 수 있다. 본 연구에서는 과적 적재물 중 골재 및 토사가 전체의 36.55%로 주요 과적적재물로 나타나 이를 주로 운송하는 30대의 건설폐기물 수집·운반차량을 선정하였으며, 자중계의 시범설치 및 원격 모니터링을 수행하여 운행데이터를 수집하였다. 운전자에게 중량을 인지할 수 있는 중량표시 앱을 배포하기 전 1달과 배포한 후 1달 동안 운행데이터를 비교하여 과적 예방효과를 분석하였다. 자중계로부터 제공받은 적재중량을 인지함으로써 과적운행이 6.1%가 감소한 것을 확인하였으며, 운송량을 극대화하면서 단속을 우려하여 원거리로 우회 주행을 할 필요가 없어 운송거리와 시간이 줄어 운송 효율이 높아진 것을 확인하였다.

• 한국건설순환자원학회논문집
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• 제8권4호
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• pp.444-449
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• 2020

본 연구에서는 건설폐기물의 발생에서부터 수집·운반 및 중간처리 또는 최종처리까지의 모든 단계에서의 폐기물의 중량을 모니터링 하기 위하여 차량탑재형 중량표시기(이하 자중계)를 운송차량에 설치하고, 여기서 얻어진 실시간 중량/위치정보를 활용하여 효율적으로 건설폐기물의 총량 및 재활용량을 관리할 수 있는 관제기술의 사례연구를 수행하였다. 연구결과 건설폐기물의 총량을 실시간으로 모니터링 할 수 있으며, 운송차량의 실시간 운송량, 운송거리, 운송시간 등을 관리하여 운행패턴 분석을 통한 물류운송 효율화 방안을 도출할 수 있음을 확인하였으며, 과적의 발생 시 적재를 제어함으로써 사전에 과적운행을 예방할 수 있음을 확인하였다.

• 경영정보학연구
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• 제19권1호
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• pp.49-74
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• 2017

스마트 기기의 발전은 종사자들의 업무환경뿐만 아니라 생활에도 많은 영향을 주었다. 스마트 기기는 업무 방식이나 절차를 간편하게 만들었으며, 언제 어디서든 팀원들과 자료를 공유할 수 있게 하는 등 많은 이점을 가져다주었지만, 한편으로는 업무의 과부화, 역할 모호성 등 많은 문제점 역시 야기하였다. 따라서 본 연구에서는 업무 종사자들의 테크노스트레스가 업무 간 지속적인 기기활용에 미치는 영향에 대해 알아보고자 하였으며, 이 과정에서 스트레스 대처방식이 어떻게 매개하는지를 알아보고자 하였다. 본 연구에서는 317명의 중소기업 종사자들을 대상으로 구조방정식 모델을 검증하였다. 그 결과 테크노스트레스 선행요인 중 역할 모호성, 기술적 한계만이 테크노스트레스에 영향을 미치는 요인임을 알 수 있었고, 종사자들이 테크노스트레스를 느낄 때 정서 중심적 대처를 통해 스트레스를 해소한다는 것을 알 수 있었다.

• 대한치과보철학회지
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• 제40권5호
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• pp.507-524
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• 2002

Load transfer of implant overdenture varies depending on anchorage systems that are the design of the superstructure and substructure and the choice of attachment. Overload by using improper anchorage system not only will cause fracture of the framework or screw but also may cause failure of osseointegration. Choosing anchorage system in making prosthesis, therefore, can be considered to be one of the most important factors that affect long-term success of implant treatment. In this study, in order to determine the effect of anchorage systems on load transfer in mandibular implant overdenture in which 4 implants were placed in the interforaminal region, patterns of stress distribution in implant supporting bone in case of unilateral vertical loading on mandibular left first molar were compared each other according to various types of anchorage system using three-dimensional photoelastic stress analysis. The five photoelastic overdenture models utilizing Hader bar without cantilever using clips(type 1), cantilevered Hader bar using clips(type 2), cantilevered Hader bar with milled surface using clips(type 3), cantilevered milled-bar using swivel-latchs and frictional pins(type 4), and Hader bar using clip and ERA attachments(type 5), and one cantilevered fixed-detachable prosthesis(type 6) model as control were fabricated. The following conclusions were drawn within the limitations of this study, 1. In all experimental models. the highest stress was concentrated on the most distal implant supporting bone on loaded side. 2. Maximum fringe orders on ipsilateral distal implant supporting bone in a ascending order is as follows: type 5, type 1, type 4, type 2 and type 3, and type 6. 3. Regardless of anchorage systems. more or less stresses were generated on the residual ridge under distal extension base of all overdenture models. To summarize the above mentioned results, in case of the patients with unfavorable biomechanical conditions such as not sufficient number of supporting implants, short length of the implant and unfavorable antero-posterior spread. selecting resilient type attachment or minimizing distal cantilever bar is considered to be appropriate methods to prevent overloading on implants by reducing cantilever effect and gaining more support from the distal residual ridge.

• Toxicological Research
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• 제28권1호
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• pp.39-49
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• 2012

We investigated the effect of zinc on the formation of colonic aberrant crypt foci induced by azoxymethane (AOM) followed by dextran sodium sulfate (DSS) in mice with high iron diet (HFe; 450 ppm iron). Sixweek old ICR mice were fed on high iron diets with combination of three different levels of zinc in diets, low-zinc (LZn; 0.01 ppm), medium-zinc (MZn; 0.1 ppm), and high-zinc (HZn; 1 ppm) for 12 weeks. Animals were received weekly intraperitoneal injections of AOM (10 mg/kg B.W. in saline) for 3 weeks followed by 2% DSS (molecular weight 36,000~50,000) in the drinking water for a week. To confirm the iron storage in the body, the hepatic iron concentration has been determine chemically and compared with histological assessment visualized by Prussian blue reaction. Aberrant crypt (AC) and aberrant crypt foci (ACF) were analyzed in the colonic mucosa of mouse fed high dietary iron. Superoxide dismutase (SOD) activity and thiobarbituric acid-reactive substances (TBARS) level were also investigated. Apoptosis in the preneoplastic lesion was determined by terminal deoxynucleotidyl transferase-mediated dUTP nickend labeling (TUNEL). In addition, immunohistochemistry of ${\beta}$-catenin was also performed on the mucous membrane of colon. The number of large ACF (${\geq}4$ AC/ACF), which possess greater tumorigenic potential, was significantly lower in MZn and HZn groups compared with LZn group. Cytosolic SOD activity in the liver was significantly higher in HZn group compared with LZn group. Hepatic MDA level was decreased significantly in HZn group compared with MZn and LZn groups. Apoptotic index was significantly higher in HZn group. Taken together, these findings indicate that dietary zinc might exert a protective effect against colonic preneoplastic lesion induced by AOM/DSS in ICR mice with high iron status, and suggest that dietary supplement of zinc might play a role in suppressing colon carcinogenesis in mice.

• 대한한의학회지
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• 제23권4호
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• pp.161-168
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• 2002

Objectives: Hwangryunhaedok-tang (Huang-lian-jie-du-tang, HRHDT, 黃連解毒湯) is a traditional Korean herbal medicine that is formulated with Coptidis Rhizoma, Phellodendri Cortex, Scutellariae Radix and Gardeniae Fructus. HRHDT is cold (寒) and bitter (苦) in nature and has general properties of clearing heat and detoxifying (淸熱解毒), strengthening the stomach and settling the liver (健胃平肝), and reducing inflammation, fever and swelling. This formula can prevent and treat artherosclerosis, hyperplasia of the endothelium, cerebral fluid circulation, cerebral vascular deterioration through aging, impairment of neurotransmitters, or disruption of the functioning of the cerebral cortex following infection or trauma. The purpose of the study reported here was to determine the neuroprotective effect of HRHDT on global ischemia induced by 4-vessel occlusion in Wistar rats. Methods: HRHDT extract was lyophilized after extraction with 85% methanol and 100% water. Rats were induced to 10 minutes of forebrain ischemia by 4-vessel occlusion (4-VO) and reperfused again. HRHDT was administered with a dose of 100 mg/kg, and 500 mg/kg of 85% methanol extracts and 100 mg/kg of 100% water extracts, respectively, at 0 min and 90 min after 4-VO. Rats were killed at 7 days after ischemia and the number of CA1 pyramidal neurons was counted in hippocampal sections stained with cresyl violet. Results: Body temperature of animals showed no significant difference between saline-treated groups and HRHDT extracts-treated groups until 5 hours of reperfusion. This result indicated that neuroprotective effects of HRHDT extracts were not due to hypothermic effects. The administration of HRHDT showed a significant neuroprotective effect on hippocampal CA1 neurons at 7 days after ischemia compared to the saline-treated group (P<0.001). HRHDT methanol extracts of 100 mg/kg, 500 mg/kg and HRHDT water extracts of 100 mg/kg showed 88.5%, 98.3% and 95.1 % neuroprotection, respectively. Conclusions: The results of this study demonstrate that administration of HRHDT is highly effective in reducing neuronal damage in response to transient global cerebral ischemia. HRHDT may involve many mechanisms that might account for its high degree of efficacy. A number of factors including free radicals, glutamate, calcium overload, NO, and various cytokines have been proposed to have an important role in causing neuronal death after short periods of global ischemia. Further studies are needed to know the neuroprotective mechanisms of HRHDT.