• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7934-7940
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• 2015

The raise of the acceleration can be one of possible methods to increase the scheduled speed of the metropolitan railway system. It is possible to raise the acceleration to the some point by increasing the traction power of the motor. However, there is a limit of the acceleration because the traction power over some level related to the adhesion causes a slip, which prevents from accomplishing the target acceleration. The running resistance is also an important factor to consider. Both the adhesion and the running resistance as well as the traction power vary according to the velocity. Therefore, the standardization of the acceleration needs the analysis of these factors as a function of velocity. In this study, we focus on the advanced urban transit unit(AUTS) for the standardization. We derive a novel equation of the adhesion suitable for the AUTS by investigation of the traction and adhesion equation as well as the experiment data. And finally we propose the standard of the acceleration based on this analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.173-178
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• 2016

When a ballast track of a high-speed train is constructed on a bridge, the displacement of the bridge decks can occur because they are not fixed to the rails. Moreover, relative displacements occur between the bridge and rails caused by temperature changes and external loads. The current longitudinal resistance criteria (UIC Code 774-3, KR C-08080) on ballast tracks with continuous welded rails (CWRs) do not take into account the longitudinal movement of the bridge and the frictional force between the ballast and slabs. In addition, the magnitude of the longitudinal resistance, k, is calculated somewhat conservatively and, (therefore?) it acts as an unfavorable element in the design of long span and continuous railway bridges. Thus, in order to replicate the actual behavior more effectively, the longitudinal resistance of CWRs should take into account the additional rigidity between the slab and track. In this study, the longitudinal resistances of the ballasted track on the bridge were analyzed by carrying out an experimental study with a test setup designed to simulate the deck and bed track. In the test results, the maximum longitudinal resistances of the tests were similar to the resistances of the current codes, however, the measured longitudinal stiffness designed to limit the displacement of the tests were much smaller in comparison with the longitudinal stiffness on the codes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.709-716
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• 2016

Recently, the operating conditions of the various mechanical structures have become more severe and the running time has become longer as the development of plant equipment increases with the introduction of high technology. Thus, the reliability of the system and its accessories is becoming a problem. Normally, synthetic natural gas (SNG) plants use 1.25Cr-0.5Mo or 2.25Cr-1Mo heat resistant steel according to the operating conditions. In this study, a lab-scale reactor was set up using 1.25Cr-0.5Mo steel, in order to carry out corrosion tests for producing synthetic natural gas. The corrosive characteristics were investigated under 1st-methanator operating conditions and fundamental data about the durability and reliability were obtained by using the experimental test. The analysis of results obtained on the durability of the reactor under emission and injection compositions showed that the hydrogen embrittlement caused by hydrogen and the oxidation corrosion caused by H2O had the most effect on the durability of 1.25Cr-0.5Mo steel in the SNG reactor. However, the hydrogen embrittlement and oxidation corrosion occurred simultaneously under emission conditions, so that the corrosion of the material increased suddenly after a long operating time. Besides, the corrosion of the 1.25Cr-0.5Mo steel under the injection composition was faster than that under the emission composition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.696-701
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• 2016

Multi-stage deep drawing is a widely used industrial manufacturing process, and its applications are gradually expanding to both small products and large metallic products. The USB C-type socket used in smart phones, for example, is manufactured using oval multi-stage deep drawing. The socket is very small and slender and it requires precise manufacturing. The thickness distribution of the final product is guaranteed only if it is uniform throughout the overall process. Therefore, minimizing the height difference between long and short sidewalls after the first operation is important for this goal. An initial blank optimization was performed for an oval-type drawing process based on finite element simulations. The goal was to determine an initial blank geometry that can maintain uniform height and thickness after the first draw operation. The initial blank shape of the sheet metal was optimized, and the results show that it satisfied the conditions of minimal thickness reduction and even thickness distribution. The geometry from the optimized simulation was compared with experimental results, which showed good agreement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.599-615
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• 2022

In order to excavate underground tunnel most safely such as Han river, the slurry shield TBM method is applied to cope with face of high water pressure for many metro projects. In downtown subway project most of excavated soil is discharged externally whereas in road construction excavated soil is used as filling materials so it becomes important factor for success of the project. After excavated soil, weathered rock and soft rock are discharged with bentonite through discharge pipe to slurry treatment plant then those soils are separated in separation plant according to those size. Fine grained soil has been discarded together with filter cake but it is not toxic and can be mixed with coarse aggregate in proper ratio so this study is performed to find use of qualified filling material to meet quality standard. Therefore, in this study, legal standards and quality standards for the utilization of excavated soil of the slurry shield TBM method were examined and test was conducted to derive recycling way for filter cake and aggregate. And a plan for using it as a filling material for road construction was derived. Because bentonite is a clay composed of montmorillonite, and the excavated soil in the tunnel is also non-toxic, disposal of this material can waste social cost so it is expected to be helpful in the underground space development project that carries out the TBM project by recycling it as a valuable resource.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.594-600
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• 2021

Curved beam structures are generally used as components in structures such as railroad bridges and vehicles. The stability analysis of curved beams has been studied by a large number of researchers. Due to the complexities of structural components, it is difficult to obtain an analytical solution for any boundary conditions. In order to overcome these difficulties, the differential quadrature method (DQM) has been applied for a large number of cases. In this study, DQM was used to solve the complicated partial differential equations for buckling analysis of curved beams. The governing differential equation was deduced and solved for beams subjected to uniformly distributed radial loads. Critical loads were calculated with various opening angles, boundary conditions, and parameters. The results of the DQM were compared with exact solutions for available cases, and the DQM gave outstanding accuracy even when only a small number of grid points was used. Critical loads were also calculated for the in-plane inextensional buckling of the asymmetric curved beams, and two theories were compared. The study of a beam with extensibility of the arch axis shows that the effects on the critical loads are significant.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.14 no.1
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• pp.17-32
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• 2019

Sales representatives of automobile company play a key role in the circulation system. Given the characteristics of the good, consumers demand high-quality information and guides from the salespersons when they decide to purchase an automobile. Sales representatives provide service to the customers in accordance with their needs to help purchase decision-making process. Therefore, a sales representative's personal competence have a significant effect on sales performance. Based on this hypothesis, we assumed that personal competence of a salesperson has a positive correlation with sales performance. An empirical analysis was conducted to test the hypothesis. This study classifies personal competence into 4 independent variables((1) sales technique professionalism (2) salesperson's attitude and relationship with customers (3) emotion utilization (4) emotion control) and measures the correlation with the dependent variable(sales performance). To verify the relationship, we set and modified the hypothesis based on the precedent studies and researches. In addiction, a survey was conducted targeting 300 local salespersons from Gyeonggi-Gangwon region. 268 valid samples were used and analyzed with SPSS WIN24.0 statistical program. As a result of an empirical analysis, it turned out that sales technique professionalism and emotion utilization have positive correlation with sales performance. However, the result failed to support the assumption that sales representative's attitude and relationship with customers and emotion control have positive correlation with sales performance. At last the result revealed that personal competence should be considered as an important determinant of recruitment specification for sales representatives.

• Journal of Software Engineering Society
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• v.24 no.1
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• pp.9-17
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• 2011

Software reuse the concept of developing software by using existing software assets, rather than developing it from scratch. Developers may face difficulties of reusing existing software assets because existing assets are normally developed by other developers for different purposes. Developers tend to seek appropriate knowledge about effectively reusing software assets from the developers who have faced and solved similar problems in reusing software assets previously. In other words, the reuse-related knowledge of domain experts or other developers usually provides important clues to solve reuse-related problems. Such reuse-relalted knowledge can help developers to reduce the time and effort to identify and solve the difficulties and problems that may arise in reusing software assets and in minimizing the risks of reusing them by allowing them to reuse reliable software assets in an appropriate way and by recognizing similar requirements or constraints of resuing the assets. In this paper, we describe a model to represent reuse-related knowledge in a formal way, and explain the architecture and a prototype implementation of Software Reuse Wiki (SRW) that enables collaborative organization and sharing of software reuse-related knowledge. We have conducted an experiment pertaining to problem solving in reusing assets based on reuse-related knowledge. We also discuss about our evaluation plan for showing the benefits and contributions of reuse knowledge representation model and management methods in SRW. We expect that SRW can contribute to facilitate users' participations and make efficient sharing and growing of reuse-related knowledge. In addition, the representation model of reuse-related knowledge and management methods can make developers acquire more reliable and useful reuse-related knowledge in a straightforward manner without spending additional efforts to find solutions to solve reuse-related problems.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.35-44
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• 2019

One of the key factors of a safe workplace is to communicate with the workers about safety. For this, natural gas workplace is developing and operating related programs or communication activities. But, if there are silence behavior of the workers on the safety issues in this process, no positive outcomes could be expected for the workplace. The purpose of this study is to examine how safety silence motives, silence behavior, and safety communication influence each other. A total of 233 questionnaires based on the workers of natural gas workplace (in Seoul and Gyeonggi) were analyzed. The confidence analysis is to check consistency of the questions, analysis of the correlations between factors, and regression analysis to verify the hypotheses. As a result, the safety silence motives affected safety communication more seriously than the silence behavior did. Safety communication influenced safety silence motives more significantly than the silence behavior. The safety silence motives can be one of the reasons for safety communication to fail, and it was confirmed that a good safety communication does not necessary mean that there is no safety silence motivation. Based on such results, it is expected that improving and developing the safety communication activities of the workplace, it would improve safety in workplace in general.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.577-584
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• 2019

Recently, CSB(Cable-Stayed Bridge) have been attempted to be atypical forms for landscape elements in Korea. CSB with new geometry need to analyze their characteristics clearly to ensure structural safety. This study's bridge is the S-shaped curved pedestrian CSB that has a girder with S-shape plane curve and reverse triangular truss cross section, inclined independent pylon, modified Fan type main cable and vertical backstay cable. Curved CSB can have excessive lateral displacement and moment when the tension is adjusted, focusing only on longitudinal behavior, such as a straight CSB. In order to analyze the effect of the cable on the lateral behavior of bridges, the cable is divided into two groups according to the lateral displacement direction of the pylon due to tension. The influence of the combination ratio of GR1 and GR2 on the girder, bearing, pylon, and vertical anchor cable was analyzed. When the tension applied to the bridge is 1.0GR1 plus 1.0GR2, In the combination of 1.2GR1 plus 0.8GR2, the stress on the left and right upper member of the truss girder and the deviation of the both were minimized. In addition, the horizontal force of the bearing, the lateral displacement and moment of the pylon, and the tension of the vertical backstay cable also decreased. This study is expected to be used as basic data for determination of tension of CSB with similar geometry.