• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.8
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• pp.1210-1215
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• 2012

Traction motors for driving and power conversion devices using semiconductor switch are equipped with a transportation systems such as an electrical railway system. Power conversion devices have the possibility of malfunction by external electromagnetic waves. As a result, these could affect the safe operation of the railway. Moreover, the electromagnetic waves above safe limits will be harmful to the passengers inside the railway vehicles or anyone working around the rail-track. For this reason, the importance and need about the reliability check and complement of electromagnetic waves generated from the IPT(Inductive Power Transfer) system have been suggested for the safe application of the IPT system to the railway system. In this study, prediction for the electromagnetic wave properties was conducted through FEM(Finite Element Method) analysis of 5kW-class IPT system design model. Next, the 5kW IPT system prototype was made and then the small-scaled railway vehicle was made to mount the IPT system and the energy management system. Finally, the electromagnetic waves generated from the real small-scaled IPT system were measured and analyzed, and then the reliability check of predictions by FEM analysis were carried out.

• Coupled systems mechanics
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• v.2 no.3
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• pp.289-302
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• 2013

The piled raft is a geotechnical construction, consisting of the three elements-piles, raft and the soil, that is applied for the foundation of a tall buildings in an increasing number. The piled rafts nowadays are preferred as the foundation to reduce the overall and differential settlements; and also, provides an economical foundation option for circumstances where the performance of the raft alone does not satisfy the design requirements. The finite element analysis of the piled raft foundation is presented in this paper. The numerical procedure is programmed into finite element based software SAFE in order to conduct the parametric study wherein soil modulus and raft thickness is varied for constant pile diameter. The problems of piled raft for three different load patterns as considered in the available literature (Sawant et al. 2012) are analyzed here using SAFE. The results obtained for load pattern-I using SAFE are compared with those obtained by Sawant et al. (2012). The fair agreement is observed in the results which demonstrate the accuracy of the procedure employed in the present investigation. Further, substantial reduction in maximum deflections and moments are found in piled raft as compared to that in raft. The reduction in deflections is observed with increase in raft thickness and soil modulus. The decrease in maximum moments with increase in soil modulus is seen in raft whereas increase in maximum moments is seen in piled raft. The raft thickness and soil modulus affects the response of the type of the foundation considered in the present investigation.

• Journal of the Korean Society of Safety
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• v.34 no.3
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• pp.75-82
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• 2019

The purpose of this study was to evaluate the effectiveness of a vibration feedback system in improving two safe seating postures of office workers. In addition, the relative effectiveness of positive and negative feedback procedures was examined. Participants were four office workers. The dependent variables were the percentages of time participants spent in the safe sitting postures including shoulder, back, and overall body positions during the experimental sessions. A multiple-baseline design counterbalanced across participants was adopted. For two participants, the negative procedure was introduced first after baseline and positive procedure was introduced in the next phase. For the other two participants, the sequence of introducing the positive and negative feedback procedures was reversed. The result showed that the vibration feedback system, regardless of the type of the procedure, was effective in improving the safe sitting postures for all participants. However, the difference between the two procedures was not clearly shown. The benefits of the automated observation and vibration feedback system in workers' safety were discussed.

• Journal of the Ergonomics Society of Korea
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• v.35 no.1
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• pp.1-10
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• 2016

Objective: This study aimed to find good design for summer functional farm shoes under the agricultural environment and working characteristics, which can help safe farm work and further promote the efficiency of working. Background: Most accidents at farms were overturn accidents caused by slipping or falling, and it was found that the main factors which caused the overturn accidents were inappropriate work shoes for the working conditions. These inappropriate work shoes often cause overturn accidents in the rural areas with steep paths. Method: A survey on work shoes was conducted with 174 farmers, and the outcome of this survey was used to find problems of work shoes and improvement ideas for the design of work shoes which can be used at farms. Results: Regarding the form of farm shoes, the ankle height was set at 6 inches to prevent the bending of the ankle and the inflow of foreign substances. The size and groove of the pattern of the outsole were extended to prevent catching of foreign substances. In the upper part, polyurethane and cordura were used in combination to secure air permeability, which was pointed out as the reason for the discomfort during the work wearing existing work shoes. Conclusion: Since farmers felt discomfort with the shoes which they were currently wearing, this study suggested a design of farm shoes by analyzing the important matters of the work shoes in development in order to improve such discomfort. Application: This study can help develop farm shoes that would practically ease farmers' burden of working at farm worksites and keep them safe.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.9-13
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• 2011

The Performance-based fire protection design required to construct super high-rise building is the active measure for the evaluation of fire risks and the establishment of fire protection systems on the basis of engineering analysis, which is more efficient and proper than existing prescriptive-based design. This study applied time-line analysis of RSET is required safe egress time and ASET is available safe egress time with the fire and evacuation simulation to analyze. The result of this study showed the sprinkler system increased ASET and fire detection and alarm system reduced RSET efficiently. Reduced evacuation time influences to secure the life safety. Also it is essential to maintain the fire suppression system and fire detection & alarm system properly. Database of fire movement and evacuation action program are useful for the performance-based design.

• Journal of Aerospace System Engineering
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• v.13 no.4
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• pp.50-59
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• 2019

The design of the main control valve, which is the main component of the flap control system, was based on actual manufacturing experience on the basis of trial and error method. In this paper, a model-based part design method is proosed. The flap control system consists of a main control valve, fail-safe valve, solenoid valve, LVDT and force motor. The main control valve consists mainly of a spool and slot. The important design parameters of the main control valve are the slot width, overlap and clearance. AMESim is linked to the model and it analyzes the flow path of the main control valve. Applying the proposed design procedure, it was confirmed that the required performance was satisfied within the allowable machining error range.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.131-134
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• 1997

McT는 MOS-게이트형 사이리스터로써 MOS-게이트형 턴-온 및 턴-오프 특성과 낮은 도통 전압을 나타내는 소자이다. 그러나 SOA(Safe Operation Area)가 상대적으로 작기 때문에 스너버 회로를 필요로 한다. 본 논문에서는 간단한 MCT PSPICE 모델을 사용하여 스위칭 특성과 RCD 스너버의 특성을 분석하였고 스너버 회로 설계방식을 제안하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.2
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• pp.101-113
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• 2003

Nowadays, the construction of new ground structures, which can influence the stability of existing underground structures, is increasing. Consequently, many technical problems occur during the design and construction stage of the new structures. In constructing a neighboring structure, reasonable design and construction is strongly required to balance between the stability of the existing underground structures and the economy of construction of the new structure in terms of the importance of the existing underground structures. Many researches have been performed to estimate the safe region and behavior of underground structures. Constructing a new ground structure above the existing underground structure, external loads are to be applied to the existing underground structure. In this study, therefore, the stability and safe region of the existing underground structure was re-established with respect to the relative location of the new ground structure with the underground structure, the depth from surface to top of the underground structures, and ground conditions.

• Smart Structures and Systems
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• v.22 no.4
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• pp.481-493
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• 2018

Ultrasonic guided waves have attracted increasing attention for non-destructive testing (NDT) and structural health monitoring (SHM) of bridge cables. They offer advantages like single measurement, wide coverage of acoustical field, and long-range propagation capability. To design defect detection systems, it is essential to understand how guided waves propagate in cables and how to select the optimal excitation frequency and mode. However, certain cable characteristics such as multiple wires, anchorage, and polyethylene (PE) sheath increase the complexity in analyzing the guided wave propagation. In this study, guided wave modes for multi-wire bridge cables are identified by using a semi-analytical finite element (SAFE) technique to obtain relevant dispersion curves. Numerical results indicated that the number of guided wave modes increases, the length of the flat region with a low frequency of L(0,1) mode becomes shorter, and the cutoff frequency for high order longitudinal wave modes becomes lower, as the number of steel wires in a cable increases. These findings were used in design of transducers for defect detection and selection of the optimal wave mode and frequency for subsequent experiments. A magnetostrictive transducer system was used to excite and detect the guided waves. The applicability of the proposed approach for detecting and locating wire breakages was demonstrated for a cable with 37 wires. The present ultrasonic guided wave method has been found to be very responsive to the number of brokenwires and is thus capable of detecting defects with varying sizes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.2
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• pp.343-350
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• 2010

In the existing design of web server architecture, data encryption technique is used to keep the reliability, stability, and safety of web service. But the use of data encryption technique wastes the work of cpu while decreasing throughput of web server and increasing average response time so that it shows negative effect on the capacity of web application server. Also, the latest web applications require security and safety for the safe internet communication. Therefore, this paper suggests the improved web server which uses thread pool and Non-blocking I/O adding new web service modules to the existing web server for the safe web service, provides reliability and safety to show the safe web service capacity. And we compare and evaluate the safety and capacity through experiment on the existing traditional Tomcat based web server and the proposed system to evaluate the safety and capacity of the proposed web server system.