• 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.

• 한국군사과학기술학회지
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• 제19권1호
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• pp.35-42
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• 2016

Modern aircraft is facing the increase of power demands and thermal challenges. In accordance with the application of more electric technology and advanced mission requirement, aircraft system requires increase of power generation and it cause increase of internal heat generation. Simultaneously, restrictions have significantly been imposed to the thermal management system. Modern aircraft must maintain low radar observability and infra-red signature. In addition, new composite aircraft skins have reduced the amount of heat that can be rejected to the environment. The combination of these characteristics has increased the challenges faced by thermal management. In order to mitigate the thermal challenges, the concept of system level thermal management should be applied and new modeling and simulation tools need to be developed. To develop and utilize system level thermal management technology, three key points are considered. Firstly, the performance changes of subsystems and components must be assessed at an integrated thermal system. It is because that each subsystem and component interacts with other subsystems or components and it can directly effects on overall system performance. Secondly, system level thermal management requirements and solutions must be evaluated early in conceptual design process as vehicle and propulsion system configuration decisions are being made. Finally, new component level thermal management technologies must focus on reducing heat generation and increasing the availability of heat sinks.

• 한국항해항만학회지
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• 제34권1호
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• pp.77-82
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• 2010

오늘날 해안의 인구 증가와 산업화로 인하여 해안의 수질오염이 날로 증가하고 있으며, 이로 인한 생태계가 파괴됨으로써 수산물 양식업에 많은 문제를 발생시키고 있다. 이러한 문제를 해결하기 위해 해상 양식장이 육상 양식장으로 이동하고 있다. 본 논문은 육상 양식장에서의 자동 먹이 공급 시스템에 관하여 설명하고자 한다. 현재의 자동 먹이 공급 장치는 먹이양의 정확도가 떨어지고 먹이 공급 모터에 의해 먹이가 부서지는 단점을 지닌다. 그러나 제안하는 시스템은 현재의 시스템과 비교했을 때 로드 셀과 밸브의 조합을 사용하여 제어함으로써 높은 정확도를 가지고 먹이를 공급할 수 있으며, 먹이를 육상 양식 수조에 안전하게 공급할 수 있다. 실제 시스템을 통한 실험을 수행함으로써 모든 상황에서 육상 양식장 수조에 먹이를 공급할 수 있음을 입증한다.

• 한국산업보건학회지
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• 제5권1호
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• pp.68-86
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• 1995

This study was conducted at five Ethylene Oxide(EO) sterilizing processes in hospitals located in Seoul from August 8 to August 30, 1994. The main purposes of this study were to assess the TWA(Time Weighted Average) and short term exposures to EO and to evaluate factors affecting EO concentrations in sterilizing room. Results are summarized as follows. 1. The TWA concentrations of the sterilizing operators ranged from <0.005ppm to 3.04ppm and those of two sterilizing rooms out of five exceeded 1ppm, the Korean and ACGIH standards. 2. When the door of the sterilizer is opened at the end of the sterilization cycle, the short term concentrations of operators ranged from <0.005ppm to 11.4ppm, and those of three sterilizing room out of five exceeded 5ppm, the ACGIH short term exposure limit(STEL). The short term concentrations of area samples ranged from 0.24ppm to 49.2ppm and those of four sterilizing room out of five exceeded 5ppm. 3. Factors affecting EO exposure level were aeration type, the location of storage site for sterilized item, amount of gas, use period of sterilizer(p<0.005). 4. Following recommendations are suggested to minimize exposure to EO. The use of EO gas should be reduced by using another available sterilization methods, and the sterilizers and gas tank storage site should be isolated from, other work areas. Combination of local and general ventilation system should be installed. Metal carts or baskets for sterilization load should be used, and work environment and medical monitoring should be performed regularly.

• 한국시뮬레이션학회논문지
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• 제25권4호
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• pp.53-63
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• 2016

본 연구는 컴퓨터 해석프로그램 SimulationX로 압력 유량 제어형 사판식 피스톤 펌프의 해석모델을 개발하여 설계의 타당성을 검증하는 것을 다룬다. 설계도면의 제원을 바탕으로 해석모델을 개발하게 되면 프로토타입 제작 이전에 설계의 유효성을 미리 판단할 수 있고 이로 인해 제작상의 반복적 오류를 범하지 않기 때문에 개발비 절감의 효과를 가져올 수 있다. 해석모델 개발의 진행순서는 다음과 같다. 먼저 동역학적 요소가 포함된 밸브, 회전부 등의 각 부품의 구조를 분석하고 도면의 제원을 반영하여 단품 모델링을 한다. 각각의 해석모델을 조합하여 펌프 어셈블리 모델링을 하고 이것이 설계의도에 맞게 부하조건에 따른 압력 유량제어 기능을 원활히 수행할 수 있는지 파악한다. 모델링 절차의 마지막에는 예상했던 메카니즘대로 부품들이 움직이는 모습을 보여줌으로서 설계의 타당성을 검증한다.

• 한국안전학회지
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• 제34권5호
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• pp.15-21
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• 2019

A rack-type warehouse has the advantage of storing a large amount in a small area by loading goods vertically. But in terms of fire risk, the fire load is very high, which can cause massive damage in the event of a fire. In the United States, research has been actively conducted to minimize the spread of vertical fires, and relevant standards have been established and operated. In Korea, research and related standards are insufficient to prevent the vertical spread of rack-type warehouse fires. In this study, an experimental study was conducted to prevent the vertical spread of a rack-type warehouse fire using a horizontal barrier and in-rack sprinklers. As a result of the test, the horizontal barrier considering the continuous flame prevented the vertical spread of the flame for a certain time. However, the horizontal barrier with continuous flame did not show the effect of preventing continuous flame. The combination of the horizontal barrier and the in-rack sprinkler prevented the vertical spread of fire effectively. In addition, the heat collecting effect through the horizontal barrier was shown and helped the early operation of the in-rack sprinklers.

• Computers and Concrete
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• 제23권1호
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• pp.61-68
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• 2019

This paper presents a computational rational model to predict the ultimate and optimized load capacity of reinforced concrete (RC) beams strengthened by a combination of longitudinal and transverse fiber reinforced polymer (FRP) composite plates/sheets (flexure and shear strengthening system). Several experimental and analytical studies on the confinement effect and failure mechanisms of fiber reinforced polymer (FRP) wrapped columns have been conducted over recent years. Although typical axial members are large-scale square/rectangular reinforced concrete (RC) columns in practice, the majority of such studies have concentrated on the behavior of small-scale circular concrete specimens. A high performance concrete, known as polymer concrete, made up of natural aggregates and an orthophthalic polyester binder, reinforced with non-metallic bars (glass reinforced polymer) has been studied. The material is described at micro and macro level, presenting the key physical and mechanical properties using different experimental techniques. Furthermore, a full description of non-metallic bars is presented to evaluate its structural expectancies, embedded in the polymer concrete matrix. In this paper, the mechanism of mechanical interaction of smooth and lugged FRP rods with concrete is presented. A general modeling and application of various elements are demonstrated. The contact parameters are defined and the procedures of calculation and evaluation of contact parameters are introduced. The method of calibration of the calculated parameters is presented. Finally, the numerical results are obtained for different bond parameters which show a good agreement with experimental results reported in literature.

• 한국건설순환자원학회논문집
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• 제9권1호
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• pp.100-108
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• 2021

이 연구의 목적은 최근 국내에서 개발된 섬유보강 고강도 콘크리트 설계지침(안)의 저감계수를 적용하여 확보하는 설계의 신뢰도지수를 분석하는 것이다. 설계지침(안) 개발을 위하여 수행된 재료실험 및 부재실험 데이터를 수집하여 재료강도 통계특성 및 부재강도 해석식에 대한 통계특성을 구한다. 재료통계특성과 설계지침(안)의 부재 해석식을 적용한 시뮬레이션을 수행하고 해석식의 통계특성과 종합하여 단면강도에 대한 통계특성을 산출한다. 국내 도로교설계기준과 콘크리트구조기준의 하중조합을 적용한 신뢰도분석을 수행하였으며, 설계지침(안)에서 제시한 재료 및 부재에 대한 저감계수를 적용한 설계는 목표신뢰도 지수를 만족함을 확인하였다.

• 대한물리치료과학회지
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• 제29권1호
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• pp.47-54
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• 2022

Background: Plyometric exercise is an exercise exerting forceful power in a brief period using isotonic activation. It is effective to improve reaction of muscle, agility, endurance and athletics performance. Weight training is an exericse improving muscular strength, endurance and respirating ability applying diversely in frequency and load of exercise Plyometric exercise and Weight training is to facilitate the athletics performance though improving the function of lower limb muscle, there is a difference that Plyometic jump squats is the way to improve agility and Weight training is the way to improve muscular strength. Therefore, it is necessary to know how this difference effects on athletics performance as measuring ankle, ROM, and jumping ability. Design: Randomized controlled trial. Method: This study was conducted with the voluntary participation of 40 university students, who were randomly assigned to jump squat and calf raise groups (n=20 per group). For each subject, we measured the range of motion of the ankle joint before and after exercise, as well as a standing broad jump and vertical jump test performance. We compared the performance indices before and after exercises using paired t-tests, and between groups using independent-samples t-tests. Conclusions: Both jump squat and calf raise exercises improved ankle joint dorsiflexion and plantar flexion, as well as standing broad jump and vertical jump height performance. However, there were no significant differences before versus after exercise, or between exercise types. Although jump squats and calf raises have different purposes, it is thought that, in combination, these exercises improve performance more effectively than either alone, and that such a combined exercise program improves the quality of training in both the general public and athletes in various sports.

• 한국콘텐츠학회논문지
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• 제22권4호
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• pp.70-82
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• 2022

4단계 이전의 자율주행은 반자율주행 단계로 차량이 주행을 하다가 운전자에게 빠르게 제어권을 넘겨야 하는 상황이 반복적으로 벌어진다. 하지만 지금의 자율주행 차량은 제어권을 넘길 때 일괄적으로 간단한 메시지와 경고음만을 사용해 운전자에게 알림을 주고 있어 개개인의 특성에 대한 고려나 다양한 위급 상황에 대한 설명을 제대로 전달하지 못하고 있다. 본 연구에서는 자율주행 차량의 판단에 대한 시·청각 정보 제공 정도와 운전자의 운전 효능감이 제어권 전환 요청 상황에서 운전자의 판단과 행동에 미치는 영향을 살펴보았다. 연구 결과 제어권 전환 요구 시 제공된 시·청각 정보 조합 방식에 따른 운전자의 인지 부하, 신뢰도, 안전감, 사용성 및 유용성의 설문 항목에서 조건에 따라 유의한 차이가 있는 것을 확인할 수 있었다. 본 연구를 통해 운전자의 운전 효능감에 따라 제어권 전환 상황에서 요청을 전달하는 효율적인 정보 제공 방식이 달라진다는 인사이트를 발견할 수 있었다. 급박한 제어권 전환 상황에서 운전자의 특성을 고려한 요청이 이루어져야 한다는 본 연구의 결과는 보다 안전하고 효율적으로 운전자와 소통할 수 있는 자율주행 차량을 설계하는데 도움을 줄 수 있을 것으로 기대한다.