• Korean Journal of Construction Engineering and Management
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• v.6 no.3 s.25
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• pp.120-127
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• 2005

This study examines the occurrence of accidents when workers were travelling on construction sites and the differences in risk involved in each occupation. An analysis of 750 fatal accident reports found that in 138 cases, the fatality occurred when the workers were travelling on site. The 138 cases were then divided according to occupation and were then examined to determine how the workers in each occupation had been affected by various hazardous situations. There were significant differences in accident occurrence between the occupations and in the various hazardous situations. The results imply that the cultural aspect of each occupation leads to a substantial difference in the possibility of fatal injuries or death and that such differences in risk should be taken into account when planning the workers' movements on site. The findings of this study aim to help workers to understand the risks entailed when travelling on site and also to assist managers in the planning of workers, movements on construction sites.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.167-174
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• 2008

Number of long-span bridge construction has been increased recently so that seismic consideration of design has become significant. To adapt such significance to design, seismic design in the newly revised 'Cable Steel Bridge Design Handbook' specifies some of wave travelling effect and local site effect. In this study, a cable-stayed bridge with main span of 500m is analysed having variables of uniform excitation, wave travelling effect, and wave travelling effect plus local site effect. Result shows that wave travelling effect in cable-stayed bridge affects considerably to its seismic response under weak soil condition even though the span length is relatively short. What's more, regardless of soil type, the seismic response has become higher for analysis with wave travelling effect and local site effect than with wave travelling effect only. Consequently, in seismic response analysis of long-span bridge, consideration should be given to application of wave travelling effect and local site effect.

• Computers and Concrete
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• v.18 no.2
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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.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.32 no.1
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• pp.53-62
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• 2014

Human has noticed a beautiful natural scenery and appreciated it as a scenic site by giving meaning to it and evaluating it. How the beautiful natural scenery was appreciated as a scenic site depends on natural features, social and cultural environments, and the current of the times. Mt. Jiri is the highest mountain in inland South Korea and keeps ancestors' history and culture intact. Joseon Dynasty literary men frequently mentioned Mt. Jiri as a tourist attraction where they could pursue and share their studies against its beautiful natural scenery. The countless literary men visited Mt. Jiri and some of them left their journeys as travelling records. This research aimed at apprehending travel routes of Chunwang Peak of Mt. Jiri based on the contents of travelling records and investigating the scenic site value of scenic resources as the literary men in Joseon Dynasty recognized. The scenic resources of Mt. Jiri were related to the change of the reason or motivation of person who climbed and it should be noted that there was a change of reason or motivation in climbing Mt. Jiri from a following of master's paths to discovery of a new trails. Thus, even if there was a difference in reason or purpose of natural scenic beauty, the concept of scenic sites of the past and the present day should be included into the extended meaning of scenic sites. This research aimed the routes of well-known literary men need to be developed as programs utilizing "the concept of ancient sages' footprints" and the development of these contents shall be used for vitalization and self-support of a regional economy.

• Structural Engineering and Mechanics
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• v.70 no.2
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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.

• Journal of Drive and Control
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• v.15 no.4
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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.

• Journal of the Korea Safety Management & Science
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• v.16 no.3
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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.

• Sleep Medicine and Psychophysiology
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• v.3 no.2
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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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• v.10 no.2
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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.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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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.