• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.262-269
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• 2016

Subway station scales are determined by peak predictions. In this study, the purpose behind the installation of a subway is public transportation convenience and public interest, but economic validity is also important. By proving that the scale of the station is excessive with regard to the target station size for Seoul subway Line 5-8, a reasonable plan. can be sought. According to station installation standards, the area of the station under investigation here is out of the service levels by six stages (A~F), and it must be four or more levels (D). The Actual level for the B level is a two-step design. The Actual ratio for over- Peak predictions is only 17.8% on average. The results of measurements of the excess area and determination of the excessive costs were analyzed by subdividing the area and by calculating it based on the B level, finding that it is possible to provide benefits for customers only in the current design, with an area ratio of 16.3%. Given the weight, it was estimated that current conditions can meet the needs of only 18.6% of the current area. Simplifying the scale calculation method of the station, it is convenient, safe, and advantageous to move citizens only if the scale can be streamlined. Then, with a reduced initial investment, maintenance costs during the operation can be reduced.

• Journal of Korea Water Resources Association
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• v.53 no.11
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• pp.1025-1037
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• 2020

This study attempted to evaluate the spatial characteristics and applicability of the predicted ensemble rainfall data used for heavy rain alarms. Limited area ENsemble prediction System (LENS) has 13 rainfall ensemble members, so it is possible to use a probabilistic method in issuing heavy rain warnings. However, the accessibility of LENS data is very low, so studies on the applicability of rainfall prediction data are insufficient. In this study, the evaluation index was calculated by comparing one point value and the area average value with the observed value according to the heavy rain warning system used for each administrative district. In addition, the accuracy of each ensemble member according to the LENS issuance time was evaluated. LENS showed the uncertainty of over or under prediction by member. Area-based prediction showed higher predictability than point-based prediction. In addition, the LENS data that predicts the upcoming 72-hour rainfall showed good predictive performance for rainfall events that may have an impact on a water disaster. In the future, the predicted rainfall data from LENS are expected to be used as basic data to prepare for floods in administrative districts or watersheds.

• Membrane Journal
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• v.19 no.4
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• pp.291-301
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• 2009

Double-layered polymer electrolyte membranes were prepared from two different sulfonated poly(aryl ether sulfone) copolymers by the two-step solution casting method for direct methanol fuel cells (DMFC). Sulfonation degrees were adjusted 10% (SPAES-10) and 50% (SPAES-50) by controlling monomer ratios, and the weight ratios of SPAES-10 copolymer were varied in the range of 5~20% to investigate the effect of thickness of coating layers on the membranes. Proton conducting layers were fabricated from SPAES-50 solutions of N-methyl-2-pyrrolidone (NMP) by a solution casting technique, and coating layers formed on the semiliquid surface of the conducting layer by pouring of SPAES-10-NMP solutions onto. It was found that double-layered polymer electrolyte membrane could significantly reduce the methanol crossover through the membrane and maintain high proton conductivities being comparable to single-layered SPAES-50 membrane. The maximum power density of membrane-electrolyte assembly (MEA) at the condition of $60^{\circ}C$ and 2 M methanol-air was $134.01\;mW/cm^2$ for the membrane prepared in the 5 wt-% of SPAES-10 copolymer, and it was corresponding to the 105.5% of the performance of the commercial Nafion 115 membrane.

• Journal of the Korean Geotechnical Society
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• v.29 no.2
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• pp.15-21
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• 2013

The analysis of long-term performance of pavement sections under wheel loads is normally conducted in two separated steps. First the resilient behavior of the pavement is calculated assuming the pavement is a layered or discrete elastic medium, and then the permanent deformation is evaluated based on empirical permanent displacement equations. Material properties required in both steps can be obtained from cyclic triaxial tests, in other words, resilient and permanent deformation tests. While this analytical approach is simple and convenient, it does not consider the modulus degradation caused by cyclic loads, and some types of reinforcements such as geosynthetic cannot be modeled in this type of analysis. A model for degraded secant modulus is proposed and suggested to be used for the analysis of permanent behavior of unpaved roadway sections. The parameter for suggested model can be obtained from cyclic triaxial tests, regular practice in pavement engineering. Examples to estimate the model parameters are presented based on both laboratory permanent deformation test and large-scale plate load test.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.231-237
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• 2008

This study was performed to evaluate joint behavior of prestressed concrete(PSC)-steel mixed girders through the flexural test of 14 beams according to embedded length, amount of reinforcing steel, stud arrangement, and prestressing force. All test beams were failed by turns of desertion of reinforcing steel, stud, and steel plate. From test results, prestressing force was more effective on performance of connection than stud arrangement and reinforcing steel. And the spacing of stud is also more effective than embedding length. This paper also presented 3D nonlinear analysis considering the slip of composite section as well as the static load tests of PSC-steel mixed girders. According to the slip modulus, the nonlinear analysis showed that the behavior of hybrid girders could be divided into three parts as full-composite, partial-composite and non-composite. However, the experimental results showed that the PSC-steel hybrid girders with shear connectors took the part of partial composite action in ultimate load stage. In addition, it was founded that stud shear connectors and welded reinforcements were contributed to improve the ultimate strength of hybrid girders for about 20%.

• Journal of the Korea Institute of Building Construction
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• v.10 no.6
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• pp.117-126
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• 2010

As one of the key IT applications, the project management information system (PMIS) has played a significant role in construction management processes. This is because PMIS is an information system that gathers, integrates, and disseminates the output of project management processes among project participants, and is used to support all aspects of a project, from initiation through closing. This paper aims to identify the CSFs(Critical Success Factor) of Project Management and quality associated with Project Management Information System (PMIS) in construction projects, to analyze the Effect of PMIS quality on Project Management Success. The CSFs of Project Management and the quality components for PMIS are identified through a review of the literature, and consolidated through interviews with professionals in the construction industry. A questionnaire instrument was sent out to experienced users (Construction Manager and Constructor), and 253 completed questionnaires were retrieved. To increase the applicability of the results, the respondents consisted of workers spread across various parts of the construction site. Using SPSS 12.0, the data was used to analyze the relationship between PMIS Quality and Project Management Success through multiple regression analysis. These findings help to clarify what the highly prioritized factors are, and could also be used as an assessment tool to evaluate the performance of PMIS and thus help to identify areas for improvement.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.172-177
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• 2010

This study reports the high-temperature oxidation kinetics, ASR(area specific resistance), and interfacial microstructure of metallic interconnects coated with conductive oxides in oxidation atmosphere at $800^{\circ}C$, The conductive material LSC($La_{0.8}Sr_{0.2}CoO_3$, prepared by Solid State Reaction) was coated on the Crofer22APU. The contact behavior of coating layer/metal substrate was increased by sandblast. The electrical conductivity of the LSC coated Crpfer22APU was measured by a DC two probe four wire method for 4000hr, in air at $800^{\circ}C$. Microstructure and composition of the coated layer interface were investigated by SEM/EDS. These results show that a coated LSC layer prevents the formation and growth of oxide scale such as $Cr_2O_3$ and enhances the long-term stability and electrical performance of metallic interconnects for SOFCs.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.10 no.2
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• pp.7-12
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• 2014

Government has recently restricted heating and cooling set temperatures for the commercial and public buildings due to increasing national energy consumption. The goal of this paper is to visualize a future two way indoor set temperature control impact on building energy consumption by using TRNSYS simulation modeling. The building was modelled based on the twin test cell with the same dimension. Air source ground coupled heat pump performance data has been used for modeling by TRNSYS 17. Daejeon weather data has been used from Korea Solar Energy Society. The heating set temperature in the reference room is $24^{\circ}C$ as well as the target room set temperature are $23^{\circ}C$, $22^{\circ}C$, $21^{\circ}C$ and $20^{\circ}C$. The cooling set temperature of the reference room is also $24^{\circ}C$ as well as the target room set temperature of $25^{\circ}C$, $26^{\circ}C$, $27^{\circ}C$ and $28^{\circ}C$. For the air source heat pump system, heating season energy consumption is $35.52kWh/m^2y$ in the reference room. But the heating energy consumption in the target room is reduced to 7.5% whenever the set temperature decreased every $1^{\circ}C$. The cooling energy consumption in the reference room is $4.57kWh/m^2y$. On the other hand, the energy consumption in the target room is reduced to 22% whenever the set temperature increased every $1^{\circ}C$ by two way controller. For the geothermal heat pump system, heating energy consumption in the reference room is reduced to 20.7%. The target room heating energy consumption is reduced to 32.6% when the set temperature is $22^{\circ}C$. The energy consumption in the target room is reduced to 59.5% when the set temperature is $26^{\circ}C$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.953-960
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• 2019

The Miller cycle is a diesel engine that has been developed in recent years that it can reduce NOx and improve fuel consumption by reducing the compression ratio through intake valve closing (IVC) time control. The Miller cycle can be divided into the early Miller method of closing the intake valve before the bottom dead center (BDC) and the late Miller method of closing the intake valve after the BDC. At low speeds, the late Miller method is advantageous as it can increase the volumetric efficiency; while at medium and high speeds, the early Miller method is advantageous because of the high internal temperature reduction effect due to the expansion of the intake air during the piston lowering from IVC to BDC. Therefore, in consideration of the ef ects of the early and late Miller methods, it is necessary to adopt the most suitable Miller method for the operating conditions. In this study, a two-stage turbo charge system was applied to four-stroke engines and the process of enhancing the Miller effect through a reduction of the intake and exhaust valve overlap as well as the valve change adjustment mechanism were considered. As a result, the ef ects of fuel consumption and Tmax reduction were confirmed by adopting the Miller cycle with a two-stage supercharge, a reduction of valve overlap, and an increase of suction valve lift.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.43-50
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• 2009

Although thin PCBs(Printed Circuit Boards) have recently been required for high density interconnection, high electrical performance, and low manufacturing cost, the utilization of thin PCBs is severely limited by warpage and reliability issues. Warpage of the thin PCB leads to failure in solder-joints and chip. The $B^2it$(Buried Bump Interconnection Technology) for PCB has been developed to achieve a competitive manufacturing price. In this study, chip temperature, package warpage, chip stress and solder-joints stress characteristics of the PCB prepared with $B^2it$ process have been calculated using thermo-mechanical coupled analysis by the FEM(Finite Element Method). FEM computation was carried out with the variations in bump shapes and kinds of materials under 1.5W power of chip and constant convection heat transfer. The results show that chip temperature distribution reached more quickly steady-state status with PCB prepared with $B^2it$ process than PCB prepared with conventional via interconnection structure. Although $B^2it$ structures are effective on low package warpage and chip stress, with high strength bump materials arc disadvantage for low stress of solder-joints. Therefore, it is recommended that optimized bump shapes and materials in PCB design should be considered in terms of reliability characteristics in the packaging level.