• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.170-175
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• 2009

Shock focusing is related with explosive release of shock wave energy on a narrow spot in a short duration of time triggering a spontaneous high pressure near the focal point. It is well known that reflection of planar incident shock wave from the metallic concave mirror such as ellipsoidal, paraboloidal or hemispherical cavities will focus on a focal point. We intend to improve the computational results using a wave propagation algorithm and to resolve the mushroom-like structure. For computation of the concave cavity flow, it is not easy to use a single-block mesh because of the many singular points in geometry and coordinates. We have employed a uniform Cartesian-grid method for the wave propagation algorithm.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.3
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• pp.141-148
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• 1999

The magnitude of breaking wave forces given by plunging breakers incident on a pile structure is much greater than the forces calculated by Morison's formula, but those forces may act on pile for very short duration in the range of a few multiples of 0.01 second. Hence, a dynamic analysis for the impact forces of breaking waves may be necessary for the accurate determination of pile displacements in the first stage of design. The time series of the impact force along the pile length is thus required, which may be estimated from the pressure distribution. In the present study, breaking wave pressures are measured for a vertical pile at real field which is easily subjected to plunging breakers in stormy weather conditions. The measured data are analyzed and compared with other results to quantify the characteristics of breaking wave pressures in real fields.

• International Journal of Safety
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• v.10 no.2
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• pp.21-26
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• 2011

In 2001, an independent official board was constituted in Japan to investigate aircraft and railway accidents. In the past 10 years, many accidents and serious incidents have been investigated and these official reports were published by the board, on which the author had sat for 9 years as boarding member. In the interim, there were several train disasters which mocked our trust in railways and also many apparent trivial incidents. In recent years, serious incidents, which a door of running rail cars opens suddenly with some trouble, happen 2 or 3 times in a year. For the past 10 years, such incidents have happened 14 times and 13 cases of them were closed by the board mentioned above. In these 13 cases, no one fell off the rail car, so that the death toll was none luckily. In this paper, these 13 serious incidents are picked up among all the reports published by the board and outlined using some tables. Especially, fall accidents of passengers are discussed mainly from the view point of impact force and duration time. Then, the equation of HIC (Head Injury Criteria) and the risk curves in terms of the HIC are dealt with properly.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.516-516
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• 2022

Agricultural reservoirs are critical water resources structures to ensure continuous water supplies for rice cultivation in Korea. Climate change has increased the risk of reservoir failure by exacerbating discrepancies in upstream runoff generation, downstream irrigation water demands, and evaporation losses. In this study, the variations in water balance components of 400 major reservoirs during 1973-2017 were examined to identify the reservoirs with reliable storage capacities and resilience. A conceptual lumped hydrological model was used to transform the incident rainfall into the inflows entering the reservoirs and the paddy water balance model was used to estimate the irrigation water demand. Historical climate data analysis showed a sharp warming gradient during the last 45 years that was particularly evident in the central and southern regions of the country, which were also the main agricultural areas with high reservoir density. We noted a country-wide progressive increase in average annual cumulative rainfall, but the forcing mechanism of the rainfall increment and its spatial-temporal trends were not fully understood. Climate warming resulted in a significant increase in irrigation water demand, while heavy rains increased runoff generation in the reservoir watersheds. Most reservoirs had reliable storage capacities to meet the demands of a 10-year return frequency drought but the resilience of reservoirs gradually declined over time. This suggests that the recovery time of reservoirs from the failure state had increased which also signifies that the duration of the dry season has been prolonged while the wet season has become shorter and/or more intense. The watershed-irrigated area ratio (W-I_ratio) was critical and the results showed that a slight disruption in reservoir water balance under the influence of future climate change would seriously compromise the performance of reservoirs with W-I_ratio< 5.

• Physical Therapy Rehabilitation Science
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• v.6 no.3
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• pp.134-139
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• 2017

Objective: Dual-task interference is defined as decrements in performance observed when people attempt to perform two tasks concurrently, such as a verbal task and walking. The purpose of this study was to investigate the changes of gait ability according to the dual task interference in chronic stroke survivors. Design: Cross-sectional study. Methods: Ten chronic stroke survivors (9 male, 1 female; mean age, 55.30 years; mini mental state examination, 19.60; onset duration, 56.90 months) recruited from the local community participated in this study. Gait ability (velocity, paretic side step, and stride time and length) under the single- and dual-task conditions at a self-selected comfortable walking speed was measured using the motion analysis system. In the dual task conditions, subjects performed three types of cognitive tasks (controlled oral word association test, auditory clock test, and counting backwards) while walking on the track. Results: For velocity, step and stride length, there was a significant decrease in the dual-task walking condition compared to the single walking condition (p<0.05). In particular, higher reduction of walking ability was observed when applying the counting backward task. Conclusions: Our results revealed that the addition of cognitive tasks while walking may lead to decrements of gait ability in stroke survivors. In particular, the difficulty level was the highest for the calculating task. We believe that these results provide basic information for improvements in gait ability and may be useful in gait training to prevent falls after a stroke incident.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.68
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• pp.89-121
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• 2015

Investor-State Dispute Settlement(ISDS) grants a foreign investor the right to access an international arbitrator, if he believes actions taken by a host government are in breach of commitments made in an investment agreement or an investment treaty. The arbitration procedure of ICSID is made specifically to resolve investment disputes, so most of investment disputes have been settled in accordance with the procedure. Owing to limitation of dispute settlements through the ICSID arbitration procedure, several investment dispute conciliation schemes have been emerged as alternatives. In the case of a conciliation, the conciliation procedure will be in progress based on arbitrary agreement between parties, and if both parties agree on a conciliation program, then the arbitrary execution rate is relatively higher than that of arbitration procedures. In addition, it is evaluated that the time duration of conducting a conciliation procedure is in general rather short in 8 to 24months, and its incumbent cost is also rather inexpensive. Most of all, through amicable settlement of a dispute between a foreign investor and a host state, the foreign investor may continue his investment activities without a hitch, while the host state may invite more investment without any risk of losing its external credibility. In conclusion, it is desirable to lead any investment dispute between a foreign investor and a host state settle in accordance with the dispute settlement procedure as specified in the relevant investment agreement. In addition, to make the foreign investor continue his investment activities, it will be necessary to provide a separate investment dispute conciliation system aside from such arbitration procedures to cope any unexpected incident flexibly.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.235-241
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• 2018

The internal pressure is a critical parameter for designing a pressure vessel. The static pressure that a pressure vessel must withstand is usually determined according to the various codes and standards with simple formula or numerical simulations considering the geometric parameters such as diameter and thickness of a vessel. However, there is no specific codes or technical standards we can use practically for designing of pressure vessels which have to endure the detonation pressure. Detonation pressure is a kind of dynamic pressure which causes an impulsive pressure on the vessel wall in a extremely short time duration. In addition, it is known that the magnitude of reflected pressure at the vessel wall due to the explosion can be over twice the incident pressure. Therefore, if we only consider the reflected pressure, the design of the pressure vessel can be too conservative from the economical point of view. In this study, we suggest a practical method to evaluate the magnitude of maximum allowable pressure that the pressure vessel can withstand against the detonation inside a vessel. As an example to validate the proposed method, we consider the pressure vessel containing hydrogen gas.

• The Korean Journal of Emergency Medical Services
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• v.9 no.2
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• pp.55-78
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• 2005

The purpose of this study was to provide basic data for the improvement of the guidelines and training programs regarding the cardiopulmonary resuscitation performance of bystanders who can respond to the incidents in earlier times as the first responder of the cardiac arrest incident, by reviewing the performance of basic CPR and the influencing factors after providing 70 students of Department of Emergency Medical Technology with the CPR training. For the purpose of the study, the collected data were computerized and analyzed by SPSS-WIN program(ver. 10.1). The results for this study were as follows The duration of session between the groups in the BLS CPR were 3 minutes and 36 seconds, 2 minutes and 32 seconds respectively. The average compression number per minute were 24.3 times and 33,2 times respectively(p=.000), and the average compression rate per minute were 112 times and 122 times respectively(p=.000). The average ventilation number per minute were 3.54 times and 5.1 times respectively(p=.000). The errors in compression "Too shallow" were 20.73 times(34.6%) and 23,23 times(38,7%) out of 60 times in 4 cycles with the standard of 38 nun. In CPR performance results according to gender in the first episode, males showed better results in compression depth as 41.5 mm comparing to females average 38.2 mm(p=.015). When ventilation results were compared according to the use of FS, the average ventilation number per minute, total ventilation per minute and the average volume per episode were significantly higher when FS was not used(<.040), There was no significant difference in ventilation accuracy between two groups. According to the results, we need to improve and distribute portable barrier devices, and to be familiar with those devices. We need to enforce ventilations as well as to include compressions so that faster and more accurate CPR can be performed. Additionally, we need to exclude ventilation only cases, minimize the interference time of chest compression due to inaccurate ventilation, simplify or minimize the complicatedness of CPR performance and responding time related to breathing, provide first responders with various training programs such as initial assessment and ventilations only, or initial assessment and chest compression-only CPR and than provide advanced training with AHA BLS education including CPR for more than two people according to CPR skills and target characteristics.