• 설비공학논문집
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• 제16권1호
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• pp.62-69
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• 2004

Thermoelectric module is a device that can produce cooling in a direct manner using the electrical energy. The purpose of this study is to investigate the performance of thermoelectric module and cooling system equipped with the thermoelectric module. The performance of a thermoelectric module is estimated using two methods; theoretical analysis based on one-dimensional energy equations and experimental tests using heat source, heat sink and brass conduction extenders. For the thermoelectric cooling system, the temperatures in the chamber are recorded and then compared with those of lumped system analysis. The results show that the cooling capacity and COP of the thermoelectric module increases as the temperature difference between hot and cold surface decreases, and there is particular current at which cooling capacity reaches its maximum value. The experimental results for the thermoelectric cooling system are similar to those of lumped system analysis.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.803-809
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• 2005

This paper presents the theoretical model to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Foil deflection is restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. This point give the difference from Heshmat's frictionless and simple compliance bump model. The fluid is modeled with the compressible Reynolds equation. A perturbation approach is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. The analysis result shows that the static and dynamic performance is enhanced by bump friction. This analysis technique would be extended to development of a high performance bearing.

• 한국유체기계학회 논문집
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• 제9권1호
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• pp.47-55
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• 2006

This paper presents the theoretical model to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Foil deflection is restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. This point give the difference from Heshmat's frictionless and simple compliance bump model. The fluid is modeled with the compressible Reynolds equation. A perturbation approach is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. The analysis result shows that the static and dynamic performance is enhanced by bump friction. This analysis technique would be extended to development of a high performance bearing.

• Steel and Composite Structures
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• 제50권3호
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• pp.265-280
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• 2024

The collapse behavior observed in single-story beam-column assembly (SSBCA) do not accurately represent the actual overall stress characteristic of multi-story frame structure (MSFS) under column loss scenario owing to ignoring the interaction action among different stories, leading to a disconnection between the anti-collapse behaviors of "components" and "overall structures", that is, the anti-collapse performance of frame structures with two different structural scales has not yet formed a combined force. This paper conducts a numerical and theoretical study to explore the difference of the collapse behaviors of the SSBCA and MSFS, and further to reveal the internal force relationships and boundary constraints at beam ends of models SSBCA and MSFS. Based on the previous experimental tests, the corresponding refined numerical simulation models were established and verified, and comparative analysis on the resistant-collapse performance was carried out, based on the validated modeling methods with considering the actual boundary constraints, and the results illustrates that the collapse behaviors of the SSBCA and MSFS is not a simple multiple relationship. Through numerical simulation and theoretical analysis, the development laws of internal force in each story beam under different boundary constraints was clarified, and the coupling relationship between the bending moment at the most unfavorable section and axial force in the composite beam of different stories of multi story frames with weld cover-plated flange connections was obtained. In addition, considering the effect of the yield performance of adjacent columns on the anti-collapse bearing capacities of the SSBCA and MSFS during the large deformation stages, the calculation formula for the equivalent axial stiffness at the beam ends of each story were provided.

• Steel and Composite Structures
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• 제37권3호
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• pp.259-272
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• 2020

In this study a new hysteretic damper for seismic retrofit of soft-first story structures is proposed and its seismic retrofit effect is evaluated. The damper consists of one steel column member and two flexural fuses at both ends made of steel plates with reduced section, which can be placed right beside existing columns in order to minimize interference with passengers and automobiles in the installed bays. The relative displacement between the stories forms flexural plastic hinges at the fuses and dissipate seismic energy. The theoretical formulation and the design procedure based on plastic analysis is provided for the proposed damper, and the results are compared with a detailed finite-element (FE) model. In order to apply the damper in structural analysis, a macromodel of the damper is also developed and calibrated by the derived theoretical formulas. The results are compared with the detailed FE analysis, and the efficiency of the damper is further validated by the seismic retrofit of a case study structure and assessing its seismic performance before and after the retrofit. The results show that the proposed hysteretic damper can be used effectively in reducing damage to soft-first story structures.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.253-271
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• 2017

In this paper, considering that perfect channel state information (CSI) is hard to achieve in practice, the downlink capacity of distributed antenna systems (DAS) with imperfect CSI and multiple receive antennas is investigated over composite Rayleigh fading channel. According to the performance analysis, using the numerical calculation, the probability density function (PDF) of the effective output SNR is derived. With this PDF, accurate closed-form expressions of ergodic capacity and outage probability of DAS with imperfect CSI are, respectively, obtained, and they include the ones under perfect CSI as special cases. Besides, the outage capacity of DAS in the presence of imperfect CSI is also derived, and a Newton's method based practical iterative algorithm is proposed to find the accurate outage capacity. By utilizing the Gaussian distribution approximation, another approximate closed-form expression of outage capacity is also derived, and it may simplify the calculation of accurate outage capacity. These theoretical expressions can provide good performance evaluation for downlink DAS for both perfect and imperfect CSI. Simulation results verify the effectiveness of the theoretical analysis, and the system capacity can be improved by increasing the receive antennas, and decreasing the estimation error or path loss. Moreover, the system can tolerate the estimation error variance up to about 0.01 with a slight degradation in the capacity.

• 융합경영연구
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• 제9권5호
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• pp.1-13
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• 2021

Purpose: Purpose - This study investigates and aims to discuss regarding the employee's work stress and its relationship with employee's workability based on literature content analysis. Finally, this study will provide how employees can manage it and coexist while enjoying the benefits of a stress-free working environment. Research design, data, and methodology - The author collected many textual contexts from mostly peer-reviewed academic journals, which means that academic comprehensive integrity can be obtained by qualitative approach for this study with discussing and following a constructive review analysis. The content analysis aims to determine a textural dataset in the longtime frame from the newest textural information. Result - There is little doubt that this study was significant and relevant to the relationship between employee work stress and workability, indicating how organizations that manage their employees in a stress-free working environment. the present researcher separate the solutions into five categories according to the person or body responsible for the answers. Conclusion - The numerous solutions on how to deal with various stresses, the theoretical aspect of the solutions involving the theories developed by multiple past articles on how to solve work stress. In general, workability and work stress is a very large field of study. Another consideration is the numerous professionalisms in the world, and each has different ways stress is induced in the organization.

• 디지털융복합연구
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• 제14권10호
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• pp.183-193
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• 2016

최근 팀 프로젝트에서 모바일 커뮤니케이션 서비스(MCS: mobile communication services)를 활용한 협업이 활발히 진행되고 있다. 본 연구에서는 MCS를 활용한 협업이 팀 프로젝트 성과에 미치는 영향을 살펴보았다. 조직 측면에서 팀 몰입과 팀 신뢰가 팀 프로젝트 성과 형성에 핵심적인 역할을 담당할 것으로 예상하였으며, MCS 유용성의 영향에 대해서도 살펴보았다. MCS 유용성을 형성하는 주요 특성으로 유비쿼티, 복합적 사용, 사용 용이성을 고려하였다. 팀 프로젝트 수행 시 IT 서비스를 자주 활용하는 116명의 대학생들을 대상으로 연구 모형을 검증하였으며, PLS를 활용하였다. 연구 모형 분석 결과, 팀 신뢰는 팀 몰입과 팀 프로젝트 성과에 긍정적으로 유의한 영향을 미쳤다. 하지만, MCS 유용성은 팀 몰입에 유의한 영향을 미치지 않았고, 팀 프로젝트 성과에만 유의한 영향을 미쳤다. MCS 특성 가운데 사용 용이성만 MCS 유용성 형성에 도움을 주는 것으로 밝혀졌으며, 유비퀴티와 복합 사용성은 MCS 유용성에 유의한 영향을 미치지 않았다.

• Journal of Magnetics
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• 제22권1호
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• pp.133-140
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• 2017

Split magnetic fluid sealing is a combination of magnetic fluid rotary and plane sealing. Using the theory of equivalent magnetic circuit design as basis, the author theorized the pressure resistance performance of magnetic fluid plane sealing. To determine the pressure resistance of magnetic fluid plane sealing, the author adopted the method of finite element analysis to calculate the magnetic field intensity in the gap between plane sealing structures. The author also analyzed the effect of different sealing gaps, as well as different ratios between the sealing gap and tooth and solt width, on the sealing performance of split magnetic fluid. Results showed that the wider the sealing gap, the lower the sealing performance. Tooth width strongly affects sealing performance; the sealing performance is best when the ratio between tooth width and sealing gap is 2, whereas the sealing performance is poor when the ratio is over 8. The sealing performance is best when the ratio between the solt width and sealing gap is 4, indicating a slight effect on sealing performance when the ratio between the solt width and sealing gap is higher. Theoretical analysis and simulation results provide reference for the performance evaluation of different sealing equipment and estimation of critical pressure at interface failure.

• ETRI Journal
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• 제22권4호
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• pp.1-12
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• 2000

Designing a reliable multicast-based network that scales to the size of a multicast group member is difficult because of the diversity of user demands. The loss inferences of internal nodes by end-to-end measurements do not require the use of complete statistics because of the use of maximum likelihood estimation. These schemes are very efficient and the inferred value converges fast to its true value. In the theoretical analysis, internal delay estimation is possible but the analysis is very complex due to the continuity property of the delay. In this paper, we propose the use of a bottleneck location estimator. This can overcome the analytical difficulty of the delay estimation using the power spectrum of the packet interarrival time as the performance metric. Both theoretical analysis and simulation results show that the proposed scheme can be used for bottleneck location inference of internal links in scalable multicasting.