• 한국건설관리학회논문집
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• 제6권3호
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• pp.120-127
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• 2005

건설현장에서 발생하는 재해의 상당부분은 근로자가 작업과관련하여 이동하는 과정에서 발생한다. 본 연구는 건설현장에서 근로자들이 이동하는 과정에서 발생한 재해의 예방과 저감을 위하여 최근 3년간의 중대재해보고서에서 근로자가 이동시 발생한 재해를 대상으로 하여 직종별로 어떠한 위험요인에 의해 재해가 발생했는지 분석하였다. 그 결과 직종과 위험상황에 따라 의미 있는 차이점이 있음이 파악되었으며, 결과적으로 각 직종별로 이동과정에서의 리스크의 강도가 다르다는 것을 알 수 있었다. 따라서 근로자들이 이동하는 과정에서 발생하는 재해를 줄이기 위해서는 이러한 직종별 리스크 특성을 고려하여 작업진도계획 및 안전계획을 수립하고 이를 관리과정에서 반영해야 할 것으로 판단된다. 본 연구에서 제시된 결과는 건설현장 근로자과 안전관리자에게 이동작업시의 위험성을 이해하는데 도움을 주고 공사계획 및 관리에 활용될 수 있을 것으로 기대된다.

• 한국구조물진단유지관리공학회 논문집
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• 제12권1호
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• pp.167-174
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• 2008

최근 국내에서 장대교량의 건설이 증가함에 따라 그에 대한 내진설계의 중요성도 증대되고 있다. 이와같은 여건을 반영하여 새로 개정된 케이블 강교량 설계지침(안)의 내진설계편에서 지진파의 파동전달효과와 지반특성효과를 일부 반영하였다. 본 연구에서는 국내 설계규정에 따라 사장교(주경간500m)의 다양한(균등입력, 파동전달효과, 파동전달효과+지반특성효과) 지진응답해석을 수행하여 설계적용시 문제점에 대하여 검토해 본 결과 장대교의 파동전달효과는 지지점간 거리가 짧은 경우에도 지반이 연약한 경우 큰 영향을 받는 것으로 나타났다. 한편 지반의 종류에 상관없이 파동전달효과와 함께 지점별로 지반특성을 고려한 해석이 그렇지 않은 해석결과보다 큰 값이 산출되었다. 따라서 장대교의 지진응답해석시 파동전달효과 및 지반특성효과의 적용에 대한 세심한 고려가 필요한 것으로 판단된다.

• Computers and Concrete
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• 제18권2호
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• pp.179-199
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• 2016

The aim of this study is to investigate arrival direction effects of travelling waves on non-linear seismic response of arch dams. It is evident that the seismic waves may reach on the dam site from any direction. Therefore, this study considers the seismic waves arrive to the dam site with different angles, ${\theta}=0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$, and $90^{\circ}$ for non-linear analysis of arch dam-water-foundation interaction system. The N-S, E-W and vertical component of the Erzincan earthquake, on March 13, 1992, is used as the ground motion. Dam-water-foundation interaction is defined by Lagrangian approach in which a step-by-step integration technique is employed. The stress-strain behavior of the dam concrete is idealized using three-dimensional Drucker-Prager model based on associated flow rule assumption. The program NONSAP is employed in response calculations. The time-history of crest displacements and stresses of the dam are presented. The results obtained from non-linear analyses are compared with that of linear analyses.

• 한국전통조경학회지
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• 제32권1호
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• pp.53-62
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• 2014

인간은 경치가 좋기로 이름난 자연경승지에 주목하고, 그 자연대상지에 의미를 부여하며 가치를 매기는 행위를 통해 명승(名勝)으로 인식해왔다. 자연이 어떻게 명승으로 인식되어 가는가 하는 것은 자연풍토, 사회, 문화, 시대흐름 등에 의해 달라지기 마련이다. 지리산(智異山)은 남한 내륙에서 가장 높고, 가장 넓은 산인만큼 옛 선조들의 역사와 문화를 고스란히 간직하고 있다. 조선시대 문인들은 수려한 풍광을 배경으로 학문을 수양하거나 학식을 나눌 수 있는 유람처(遊覽處)의 성격으로 지리산을 자주 거론하였다. 조선시대에 지리산을 찾은 문인 학자들의 수는 헤아릴 수 없으며, 이 중에 일부는 자신의 여정을 유람록(遊覽錄)으로 남겼다. 이에 본 연구는 지리산 유람을 즐기며 기록되었던 유람록의 내용을 중심으로 지리산 천왕봉 유람경로의 위치를 파악하고, 당시 조선시대 문인들의 시각에 보여졌던 경관자원의 가치를 알아보자 하였다. 지리산의 경관자원은 산을 이용하는 사람들의 동기나 욕구의 변화와 관련이 있고, 이러한 변화는 더이상 선인들이 다녔던 길의 답습의 개념이 아닌 새로운 탐방로의 개척과 편리성에 주목할 필요가 있다. 따라서 과거와 현재 사람들이 생각하는 명승의 개념은, 이용하려는 동기와 목적에서 차이를 보이더라도 넓은 의미의 명승의 범주에 포함되어야 할 것이다. 본 연구에서 분석된 유람경로와 경관자원 중 인물사적으로 인지도가 높은 문인의 경로는 '선현(先賢)들의 발자취 개념'을 응용한 프로그램 개발이 필요하며, 이러한 문화관광콘텐츠 개발을 통해 지역의 활성화 및 경제적 자립도 향상에 활용되어야 할 것이다.

• Structural Engineering and Mechanics
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• 제70권2호
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• pp.143-152
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• 2019

In this study, stochastic responses of a cable-stayed bridge subjected to the spatially varying earthquake ground motion are investigated for variable local soil cases and wave velocities. Quincy Bay-view cable-stayed bridge built on the Mississippi River in Illinois, USA selected as a numerical example. The bridge is composed of two H-shaped concrete towers, double plane fan type cables and a composite concrete-steel girder deck. The spatial variability of the ground motion is considered with the coherency function, which is represented by the components of incoherence, wave-passage and site-response effects. The incoherence effect is investigated by considering Harichandran and Vanmarcke model, the site-response effect is outlined by using hard, medium and soft soil types, and the wave-passage effect is taken into account by using 1000, 600 and 200 m/s wave velocities for the hard, medium and soft soils, respectively. Mean of maximum response values obtained from the analyses are compared with those of the specific cases of the ground motion model. It is concluded that the obtained results from the bridge model increase as the differences between local soil conditions cases of the bridge supports change from firm to soft. Moreover, the variation of the wave velocity has important effects on the responses of the deck and towers as compared with those of the travelling constant wave velocity case. In addition, the variability of the ground motions should be considered in the analysis of long span cable-stayed bridges to obtain more accurate results in calculating the bridge responses.

• 드라이브 ㆍ 컨트롤
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• 제15권4호
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• pp.81-90
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• 2018

Indoor construction site such as building demolition sites, tunnel, vinyl house, and cattle shed are subject to various risk factors such as falling stones, soot and bad odors. However, most of the mini excavators have no cabin that can protect the driver from such risk factors. Therefore, researches on remote control technology of construction equipment are actively conducted as a method for protecting the driver from the risk factors occurring in the working environment. For effective remote control, it is necessary to be able to control the travelling and work using a portable small transmitter. However, due to the limitation of the size of the transmitter, complex operation control is required to control two or more actuators with a single joystick. Also, it is essential to check how remote control characteristics change in various environments such as distance, signal strength, obstacle. Therefore, in this study, an algorithm that can control two actuators simultaneously with a single joystick signal was developed, and a communication method suitable for indoor and outdoor mini construction equipment by analyzing experimentally how the remote control characteristics vary according to various work environments and telecommunication methods proposed.

• 대한안전경영과학회지
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• 제16권3호
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• pp.45-54
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• 2014

The average injury rate in sawmilling industry for the last 5 years is 4.99%, which means that more than 200 injuries have occurred in that industry every year. Because the first step in risk assessment is the hazard identification, it is very important to know how to define the hazard and nature of harm. We analyzed 643 accident records of three years(2010-2012) and carried out site survey for the same cases. As a result, the most common types of work at the time of injury in sawmilling industry were removing jammed wood 81(12.8%), wood carrying task 52(8.1%), wood cutting 49(7.6%), travelling table log band saw 41(6.4%), maintenance 37(5.8%) etc. In addition, there were statistically significant differences in some analysis factors such as injured body parts, employment size, and handling material among different working places. Therefore, it is concluded that differentiated prevention efforts are necessary in each workplace.

• 수면정신생리
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• 제3권2호
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• pp.18-31
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• 1996

Jet-lag can be defined as the cumulative physiological and psychological effects of rapid air travel across multiple time zones. Many reports have suggested that age-related changes in sleep reflect fundamental changes in the circadian system and in significant declines in slow wave sleep. Jet lag is a dramatic situation in which the changes of the phase of circadian process and homeostatic process of sleep occur. Thus the authors evaluatead the changes of sleep-wake cycle from jet lag by age. Thirty-eight healthy travellers were studied for 3 days before and 7 days after jet-flights across seven to ten time zone. They were aged 19-70, They trareled eastbound, Seoul to North America (USA, Canada). Sleep onset time, wake-up time, sleep latency, awakening frequency on night sleep, awakening duration on night sleep, sleepiness at wake-up and nap length were evaluated. Our results suggest that by the 7 to 10 time zone shift, the old age group was significantly influenced in sleep-wake cycles. The date on which subjective physical condition was recovered was $6.23{\pm}83$ day after arrivals for old age group, while for young and middle age group, $4.46{\pm}1.50$ day and $4.83{\pm}1.52$ day, respectively. In old age group, sleep onset time was later than baselines and could not recover untill 7th day. But in other groups, the recovery was within 5th day. Nap dura fion was longer in old age group through jet lag than younger age group. In other parameters, there was no definite difference among three age groups. Our results suggested that the old age was significantly influenced by the disharmony between internal body clock and sleep-wake cycle needed at the travel site. Thus we proved that recovery ability from jet lag was age-dependent as well as travelling direction-dependent. To demonstrate more definite evidence, EEG monitoring and staging of sleep were funthun encouraged.

• International Journal of Fluid Machinery and Systems
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• 제10권2호
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• pp.119-137
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• 2017

Although the stall stagnation phenomena have often been experienced in site and also analytically in numerical experiments in surges in systems of compressors and flow paths, the fundamental causes have not been identified yet. In order to clarify the situations, behaviours of infinitesimal disturbance waves superposed on a main flow were studied in a simplified one-dimensional flow model. A ratio of the amplifying rate of the system instability to the characteristic slope of the compressor element was surveyed as the instability enhancement factor. Numerical calculations have shown the following tendency of the factor. In the situation where both the sectional area ratio and the length ratio of the delivery flow-path to the suction duct are sufficiently large, the enhancement factors are greater in magnitude, which means occurrence of ordinary deep surges. However, in the situation where the area ratio and/or the length ratio is relatively smaller, the enhancement factor tends to lessen significantly, which situation tends to suppress deep surges for the same value of the characteristic slope. It could result in the stall stagnation condition. In the domain of area ratio vs. length ratio of the delivery duct to the suction duct, contour-lines of the enhancement factor behave qualitatively similar to those of the stall stagnation boundaries of a fan analytically obtained, suggesting that a certain range of the enhancement factor values could specify the stagnation occurrence. The significant decreases in the factors are observed to accompany appearances of phase lags and travelling waves in the wave motions, which macroscopically suggests breaking down of the complete surge actions of filling and emptying of the air in the delivery duct. The strength of the action is deeply related with acoustic interferences and is evaluated in terms of the volume-modified reduced resonance frequency proposed by the author. These observations have shown the fundamental cause and the sequence of the stall stagnation in principle.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 추계학술발표회
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• pp.44-52
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• 2002

Low temperature thermal desorption (LTTD) has become one of the cornerstone technologies used for the treatment of contaminated soils and sediments in the United States. LTTD technology was first used in the mid-1980s for soil treatment on sites managed under the Comprehensive Environmental Respones, Compensation and Liability Act (CERCLA) or Superfund. Implementation was facilitated by CERCLA regulations that require only that spplicable regulations shall be met thus avoiding the need for protracted and expensive permit applications for thermal treatment equipment. The initial equipment designs used typically came from technology transfer sources. Asphalt manufacturing plants were converted to direct-fired LTTD systems, and conventional calciners were adapted for use as indirect-fired LTTD systems. Other innovative designs included hot sand recycle technology (initially developed for synfuels production from tar sand and oil shale), recycle sweep gas, travelling belts and batch-charged vacuum chambers, among others. These systems were used to treat soil contaminated with total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), pesticides, polychlorinated biphenyls (PCBs) and dioxin with varying degrees of success. Ultimately, performance and cost considerations established the suite of systems that are used for LTTD soil treatment applications today. This paper briefly reviews the develpoment of LTTD systems and summarizes the design, performance and cost characteristics of the equipment in use today. Designs reviewed include continuous feed direct-fired and indirect-fired equipment, batch feed systems and in-situ equipment. Performance is compared in terms of before-and-after contaminant levels in the soil and permissible emissions levels in the stack gas vented to the atmosphere. The review of air emissions standards includes a review of regulations in the U.S. and the European Union (EU). Key cost centers for the mobilization and operation of LTTD equipment are identified and compared for the different types of LTTD systems in use today. A work chart is provided for the selection of the optmum LTTD system for site-specific applications. LTTD technology continues to be a cornerstone technology for soil treatment in the U.S. and elsewhere. Examples of leading-edge LTTD technologies developed in the U.S. that are now being delivered locally in global projects are described.