• Journal of the Korea Safety Management & Science
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• v.17 no.1
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• pp.93-101
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• 2015

The demand from customers on better products and systems seems to be ever increasing. To meet the demand, the systems are becoming more and more complicated in terms of both scale and functionality, thereby requiring enormous effort in the development. One bright spot of this trend is that such effort has been the driving forces of the remarkable advancement in modern systems development. On the other hand, safety issues appear to be critical in many large-scale systems such as transportation and weapon systems including high-speed trains, airplanes, ships, missiles/rockets launchers, and so on. Such systems turn out to be prone to a variety of faults and thus the resultant failure can cause disastrous accidents. For the reason, they can be referred to as safety-critical systems. The systems failure can be attributed to either random or systemic factors (or sometimes both). The objective of this paper is on how to reduce potential systemic failure in safety critical systems. To do so, a proper system design is pursued to minimize the risk of systemic failure. A focus is placed on the fact that complex systems have a lot of complicated interfaces among the system elements. To effectively handle the sources of hazards at the complicated interfaces and resultant failure, a method is developed by utilizing a design structure matrix. As a case study, the developed method is applied in the design of train control systems.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.5
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• pp.537-542
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.641-648
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• 2009

Concrete structures become more common in railway systems with an advancement of high speed train technologies. As the service life of concrete structures increases, structural strengthening for concrete structures may be necessary. There are several typical strengthening techniques using steel plate and fiber reinforced polymer (FRP) materials, which have their own inherent shortcomings. In order to enhance greater durability and resistance to fire and other environmental attacks, basalt fiber material attracts engineer's attention due to its characteristics. This study investigates bonding performance of basalt fiber sheet as a structural strengthening material. Experimental variables include bond width, length and number of layer. From the bonding tests, there were three different types of bonding failure modes: debonding, rupture and rip-off. Among the variables, bond width indicated more significant effect on bonding characteristics. In addition the bond length did not contribute to bond strength in proportion to the bond length. Hence this study evaluated effective bond length and effective bond strength. The effective bond strength was compared to those suggested by other researches which used different types of FRP strengthening materials such as carbon FRP.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.165-178
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• 2000

The simplified model for 3-dimensional analysis of vehicle-bridge interactions is presented in this study. By using the analysis model which includes the eccentricity of axle loads and the effect of the torsional forces acting on the bridge, the more accurate analysis results of the behavior of the bridge can be obtained. The equations of kinetic energy, potential energy and damping energy are expressed by degrees of freedom of the vehicle and the bridge. And then by applying Lagrange's equations of motion, the equations of motion of the vehicle and the bridge are obtained. By deriving the equations of forces acting on the bridge considering the vehicle-bridge vertical interactions and also by identifying the position of vehicle as time goes by, mass matrix, stiffness matrix, damping matrix and load vector of vehicle-bridge system are constructed in accordance with the position of vehicles. Then using Newmark's β-method(average acceleration), the equations of motion for the total vehicle bridge system are solved.

• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.589-594
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• 2010

Superimposition of horizontal and vertical curves may hamper the ride comfort and running stability of train and largely affect the maintenance costs. However, in many cases, it is not easy to make a track alignment plan because of the geographic conditions or undesirable environmental factors. In this paper, a comparative study on the effect of superimposition of vertical and horizontal curve on the ride comfort and optimum horizontal curve conditions was performed. That is, optimal cant and ride comfort analysis with and without a vertical curve superimposed on the horizontal curve were evaluated. Also the superimposition effect on ride comfort and alignment conditions in high speed zone were evaluated. From the analysis results, it was found that the ride comfort is similar to that at the only horizontal curves when applying the compensation cant for the superimposed site.

• Smart Structures and Systems
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• v.18 no.2
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• pp.197-216
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• 2016

The increased speed of a train causes increased loads that act on the track substructures. To ensure the safety of the track substructures, proper maintenance and repair are necessary based on an accurate characterization of strength and stiffness. The objective of this study is to develop and apply a cone penetrometer incorporated with the dynamic cone penetration method (CPD) for investigating track substructures. The CPD consists of an outer rod for dynamic penetration in the ballast layer and an inner rod with load cells for static penetration in the subgrade. Additionally, an energy-monitoring module composed of strain gauges and an accelerometer is connected to the head of the outer rod to measure the dynamic responses during the dynamic penetration. Moreover, eight strain gauges are installed in the load cells for static penetration to measure the cone tip resistance and the friction resistance during static penetration. To investigate the applicability of the developed CPD, laboratory and field tests are performed. The results of the CPD tests, i.e., profiles of the corrected dynamic cone penetration index (CDI), profiles of the cone tip and friction resistances, and the friction ratio are obtained at high resolution. Moreover, the maximum shear modulus of the subgrade is estimated using the relationships between the static penetration resistances and the maximum shear modulus obtained from the laboratory tests. This study suggests that the CPD test may be a useful method for the characterization of track substructures.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.466-473
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• 2014

Recently, there is has been significant interest in the allocation systems of rail track capacities with considerations of the multiple train operating companies. The system indicates both a well-defined procedure and an algorithmic method to allocate the rail track capacities. Among them, this study considers the algorithmic method to derive the optimal timetable for the trains, which the companies propose together with their arrival and departure times at each station. However, most studies have focused on the adjustment of the departure and arrival times without conflicts, which could result in incompatible allocations with the line plan, which would result in an insufficient number of trains on each line to satisfy the demands. Our study presents a new optimization model and algorithm for the allocation problem in order to reflect the predetermined line plan. Furthermore, we provide the experimental results that were applied to the Korean high-speed railway network including the Suseo lines.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6214-6220
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• 2015

A track circuit has used stably more than 100 years for detecting train position, but solution of track circuit sort circuit incapacity due to a rust is necessary for side line in station yard, coast line and level crossing for conventional line in rural line. Domestically, Axle Counter System(ACS) has partially used for Hot Box System for high speed line and turnout for CBTC system. In contrast, most of countries has used ACS not only trunk line but also rural line and its application has increased for metro, electric car and industrial railway. In this paper, we has verified the operating status of ACS which installed with existing track circuit through log analsis to implement pilot application in mail track and turnout in station yard. And interface test with interlocking system has conducted at Obong shunting yard, as well as Cheongju station and has analyzed test result. Based on a test result, we made fail safe design, manufacturing skill and established system requirement specification for the smooth operation and maintenance.

• Korean Journal of Applied Biomechanics
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• v.23 no.2
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• pp.117-123
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• 2013

The purpose of this study was to provide data to increase the success rate of penalty kicks through quantifying the shape of skilled kicks by performing a kinematic analysis on the change of movement during the kicking phase which the goalkeeper uses as a vital clue. Three high definition video cameras(GR-HD1KR, JVC, Japan) were used for the study and 18 reflective markers were attached to the body joints. Corners of the goal, difficult for goalkeepers to block, were set as aims and 1 m by 1.2 m targets were installed. Each subject had five sets of kicks at random, and the analysis was done on the movements that hit the target. Time, speed of the right lower limb's center of mass, joint angle, and angular velocity were chosen as factors and the results of the analysis showed statistical significance. The player taking a penalty kick should train to avoid leaning one's body towards the kicking direction and change the angle of the right foot right before the impact to decide the direction of the ball. The goalkeeper can increase the save success rate by studying the angle of the kicker's body and the right foot as well as the timing of the kick.

• Health Policy and Management
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• v.20 no.4
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• pp.19-44
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• 2010

This study was conducted to investigate the changes in patterns of Daegu- and Gyeongbuk-based patients' use of medical care facilities located in Seoul. The 'Patient Survey' data issued by the Ministry of Health and Welfare for 2002, 2005, and 2008 were used. Among all discharged patients residing in Daegu and Gyeongbuk, 133,456 who used medical facilities in Daegu, Gyeongbuk, and Seoul were selected. Among patients residing in Daegu, 2.2% used medical facilities in Seoul in 2002, 3.7% in 2005, and 3.5% in 2008. The corresponding rates among patients living in Gyeongbuk were 5.6%(2002), 7.1%(2005), and 7.3%(2008). Regarding the ICD-10 disease groups, the use of medical facilities in Seoul by patients residing in either Daegu or Gyeongbuk increased in 2005 right after the introduction of the KTX high-speed train service, covering various disease groups, but decreased again in 2008. 'Neoplasm' cases, however, showed a progressive rising trend during the years studied. Multivariate data analysis for the three years showed that sex, age, payment type, hospital type, residence, year, and disease groups were all significantly associated with the utilization of medical facilities in Seoul. The major results are : First, use of medical facilities in Seoul by Gyeongbuk patients was 2.4-fold higher than that by Daegu patients, but with respect to 2005 and 2008 vs. 2002, use of medical facilities in Seoul by Daegu resident patients' showed a larger increase than that by Gyeongbuk's patients. Second, for patients residing in the two regions, use of medical facilities in Seoul was highest for 'congenital malformations, deformations and chromosomal abnormalities', followed by 'neoplasms'. Third, for patients residing in the two regions, general hospitals comprise the primary factor in the use of medical facilities in Seoul. The study shows that local medical facilities should individually exert more efforts to improve the quality of their medical services. Relevant authorities should likewise help these facilities develop their own unique services and respective specialization.