• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.4
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• pp.306-314
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• 2012

Several numerical or analytical models have been proposed to analyze the thermal response of vertical ground heat exchangers (GHEX). However, most models are valid only after several hours of operation since they neglect the heat capacity of the borehole. Recently, the short time response of the GHEX became important in system simulation to improve efficiency. In this paper, a simple new method to evaluate the short time response of the GHEX by using an analogy model of electric circuit transient analysis was presented. The new transient heat exchanger model adopting the concept of thermal capacitance of the borehole as well as the steady-state thermal resistance showed the transient thermal resistance of the borehole. The model was validated by in-situ thermal response test and then compared with the DST model of the TRNSYS program.

• The KIPS Transactions:PartD
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• v.14D no.7
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• pp.753-762
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• 2007

Traceability has been held as an important factor in testing activities as well as model driven development. Vertical traceability affords us opportunities to improve manageability from models and test cases to code in testing and debugging phase. Traceability also makes overcome to difficulties of going up-and-down abstraction level to find out error spot of faults discovered by testing This paper represents a vertical test method which connects a system test level and an integration test level in a test stage by using UML. Experiment of how traceability works and how effective focus on error spots has been included using concrete examples of tracing from models to the code.

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.1-8
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• 2009

This study pertains to damping device to reduce vibrational responses and shocks in multi-directions. To enhance the capability of disk spring damper which works for vertical vibration and shock, a multi-directional damper is proposed, which contains wedge system as well as disk spring stack. Wedge system converts horizontal load into vertical load. A mathematical model is proposed and investigated for the nonlinear behaviors of the disc spring damper containing wedge system. The results accord with the experimental results. Equivalent viscous damping in vertical and horizontal directions are found based upon energy dissipated.

• Geomechanics and Engineering
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• v.21 no.4
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• pp.379-390
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• 2020

The behavior of a piled raft system in multi-layered soil subjected to vertical loading has been studied numerically using 3D finite element analysis. Initially, the 3D finite element model has been validated by analytically simulating the field experiments conducted on vertically loaded instrumented piled raft. Subsequently, a comprehensive parametric study has been conducted to assess the performance of a combined piled raft system in terms of optimum pile spacing and settlement of raft and piles, in multi-layered soil stratum subjected to vertical loading. It has been found that a combined pile raft system can significantly reduce the total settlement as well as the differential settlement of the raft in comparison to the raft alone. Two different arrangements below the piled raft with the same pile numbers show a significant amount of increase of load transfer of piled raft system, which is in line with the load transfer mechanism of a piled raft. A methodology for the factor of safety assessment of a combined pile raft foundation has been presented to improve the performance of piled raft based on its serviceability requirements. The findings of this study could be used as guidelines for achieving economical design for combined piled raft systems.

• Steel and Composite Structures
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• v.31 no.6
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• pp.591-600
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• 2019

Based on the energy-variational principle, a coupling vibration analysis model of high-speed railway simply supported beam bridge-track structure system (HSRBTS) was established by considering the effect of shear deformation. The vibration differential equation and natural boundary conditions of HSRBTS were derived by considering the interlayer slip effect. Then, an analytic calculation method for the natural vibration frequency of this system was obtained. By taking two simply supported beam bridges of high-speed railway of 24 m and 32 m in span as examples, ANSYS and MIDAS finite-element numerical calculation methods were compared with the analytic method established in this paper. The calculation results show that two of them agree well with each other, validating the analytic method reported in this paper. The analytic method established in this study was used to evaluate the natural vibration characteristics of HSRBTS under different interlayer stiffness and length of rails at different subgrade sections. The results show that the vertical interlayer compressive stiffness had a great influence on the high-order natural vibration frequency of HSRBTS, and the effect of longitudinal interlayer slip stiffness on the natural vibration frequency of HSRBTS could be ignored. Under different vertical interlayer stiffness conditions, the subgrade section of HSRBTS has a critical rail length, and the critical length of rail at subgrade section decreases with the increase in vertical interlayer compressive stiffness.

• Geomechanics and Engineering
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• v.19 no.3
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• pp.269-282
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• 2019

Due to top-coal and immediate roof as cushion layer connecting with support and overlying strata, it can make significant influence on strata behaviors in fully mechanical top-coal caving working face (TCCWF). Taking Qingdong 828 working face as engineering background, $FLAC^{3D}$ and $UDEC^{2D}$ were adopted to explore the influence of top-coal thickness (TCT), immediate roof thickness (IRT), top-coal elastic modulus (TCEM) and immediate roof elastic modulus (IREM) on the vertical stress and vertical subsidence of roof, caving distance, and support resistance. The results show that the maximum roof subsidence increases with the increase of TCT and IRT as well as the decrease of TCEM and IREM, which is totally opposite to vertical stress in roof-control distance. Moreover, although the increase of TCEM and IREM leading to the increase of peak value of abutment pressure, the position and distribution range have no significant change. Under the condition of initial weighting occurrence, support resistance has negative and positive relationship with physical parameters (e.g., TCT and IRT) and mechanical properties (e.g., TCEM and IREM), respectively.

• Steel and Composite Structures
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• v.33 no.2
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• pp.209-224
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• 2019

This paper describes a study of the mapping relationship between the vertical deformation of bridge structures and rail deformation of high-speed railway, taking the interlayer interactions of the bridge subgrade CRTS II ballastless slab track system (HSRBST) into account. The differential equations and natural boundary conditions of the mapping relationship between the vertical deformation of bridge structures and rail deformation were deduced according to the principle of stationary potential energy. Then an analytical model for such relationship was proposed. Both the analytical method proposed in this paper and the finite element numerical method were used to calculate the rail deformations under three typical deformations of bridge structures and the evolution of rail geometry under these circumstances was analyzed. It was shown that numerical and analytical calculation results are well agreed with each other, demonstrating the effectiveness of the analytical model proposed in this paper. The mapping coefficient between bridge structure deformation and rail deformation showed a nonlinear increase with increasing amplitude of the bridge structure deformation. The rail deformation showed an obvious "following feature"; with the increase of bridge span and fastener stiffness, the curve of rail deformation became gentler, the track irregularity wavelength became longer, and the performance of the rail at following the bridge structure deformation was stronger.

• The Magazine of the IEIE
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• v.24 no.6
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• pp.38-49
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• 1997

0.4mm Resign Rule의 Super Low Power Dissipation, Low Voltage. Operation-5- Full CMOS SRAM Cell을 개발하였다. Retrograde Well과 PSL(Poly Spacer LOCOS) Isolation 공정을 사용하여 1.76mm의 n+/p+ Isolation을 구현하였으며 Ti/TiN Local Interconnection을 사용하여 Polycide수준의 Rs와 작은 Contact저항을 확보하였다. p-well내의 Boron이 Field oxide에 침적되어 n+/n-well Isolation이 취약해짐을 Simulation을 통해 확인할 수 있었으며, 기생 Lateral NPN Bipolar Transistor의 Latch Up 특성이 취약해 지는 n+/n-wellslze는 0.57mm이고, 기생 Vertical PNP Bipolar Transistor는 p+/p-well size 0.52mm까지 안정적인 Current Gain을 유지함을 알 수 있었다. Ti/TiN Local Interconnection의 Rs를 Polycide 수준으로 낮추는 것은 TiN deco시 Power를 증가시키고 Pressure를 감소시킴으로써 실현할 수 있었다. Static Noise Margin분석을 통해 Vcc 0.6V에서도 Cell의 동작 Margin이 있음을 확인할 수 있었으며, Load Device의 큰 전류로 Soft Error를 개선할수 있었다. 본 공정으로 제조한 1M Full CMOS SRAM에서 Low Vcc margin 1.0V, Stand-by current 1mA이하(Vcc=3.7V, 85℃기준) 를 얻을 수 있었다.

• Journal of Korean Port Research
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• v.9 no.1
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• pp.45-56
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• 1995

Investigation of the physical behavior of dredged material disposal in coastal water includes estimations of water column concentration in the receiving water, exposure time, the initial deposition pattern as well as thickness of material at the dumping fields near the estuary area. Calculation based on vertical setting and horizontal advection of single particles ignore the effects of bulk properties of the disposed material, vertical and horizontal diffusion, and material dilution due to the entrainment of ambient water during descent. This paper focuses on the spatial and temporal changes in the dumping fields for the water column and bottom at a hypothetically confined coastal water, where the ambient time-invariant velocity and density profiles are applied, within the initial time period following the instantaneous release of the dredged material. This model accounts the behavior of material after release divided into three phases: convective descent, dynamic collapse and long-term passive dispersion

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.111-116
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• 2003

Instrumentation system in Concrete Face Rockfill Dam(CFRD) can give special attention to the deformation characteristics of the rockfill and behavior of the concrete membrane during construction, reservoir filling and subsequent phase of operation. It also contains data about vertical and transversal compressibility moduli of the rockfill, deflections in the concrete slab, and draws comparisons with other concrete face rockfill dams of recent construction. In this paper, the internal deformation data from D dam monitored by means of hydrostatic settlements cells are analyzed. Observations cover the construction stage, reservoir filling and up to March 1991. The above method can be concluded D dam was well constructed and maintained.