• 대한수학회보
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• 제46권1호
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• pp.107-116
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• 2009

We consider a single server multi-class queueing model with Poisson arrivals and relative priorities. For this queue, we derive a system of equations for the transform of the queue length distribution. Using this system of equations we find the moments of the queue length distribution as a solution of linear equations.

• Journal of information and communication convergence engineering
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• 제9권6호
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• pp.738-742
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• 2011

This paper has studied drain induced barrier lowering(DIBL) for Double Gate MOSFET(DGMOSFET) using analytical potential model. Two dimensional analytical potential model has been presented for symmetrical DGMOSFETs with process parameters. DIBL is very important short channel effects(SCEs) for nano structures since drain voltage has influenced on source potential distribution due to reduction of channel length. DIBL has to be small with decrease of channel length, but it increases with decrease of channel length due to SCEs. This potential model is used to obtain the change of DIBL for DGMOSFET correlated to channel doping profiles. Also device parameters including channel length, channel thickness, gate oxide thickness and doping intensity have been used to analyze DIBL.

• 대한기계학회논문집B
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• 제30권2호
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• pp.161-169
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• 2006

The spray characteristics of liquid jet in cross flow with variation of injection angle are numerically studied. Numerical analysis was carried out using KIVA code, which was modified to be suitable for simulating liquid jet ejected into cross flow. Wave model and Kelvin-Helmholtz(KH)/Rayleigh-Taylor(RT) hybrid model were used for the purpose of analyzing liquid column, ligament, and the breakup of droplet. Numerical results were compared with experimental data in order to verify the reliability of the physical model. Liquid jet penetration length, volume flux, droplet velocity profile and SMD were obtained. Penetration length increases as flow velocity decreases and injection velocity increases. From the bottom wall, the SMD increases as vertical distance increases. Also the SMD decreases as injection angle increases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.873-878
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• 2007

Stability of high-speed roll-to-roll printing machines is one of the most important factors that are required for the printing machines to operate properly and to obtain reasonable printing performance. This paper proposes a new model for the web-tension system of a high-speed gravure printing machine considering span-length variations due to dancer rollers, and analyzes the stability of plant dynamics of the printing machine using the proposed model. Span-length variations due to dancer motions are considered for the modeling of plant dynamics in two ways; one is to include the effect of span-length variations without considering dancer inertias and viscous frictions, and the other is to include the effect of span-length variations with considering dancer inertias and viscous frictions. The stability of the plant model is analyzed for various web-speeds using the eigenvalues of the linearized model about operating points.

• 대한의용생체공학회:의공학회지
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• 제29권3호
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• pp.222-230
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• 2008

This paper introduces a method of estimating the knee joint moment developed during MVC. By combining the Hill-type muscle model and analytic results on moment arm and musculotendon length change as a function of hip and knee joint angle, the knee joint moment at a specific knee joint angle during MVC is determined. Many differences between the estimated results and the experimental data are noted. It is believed that these differences originate from inaccurate information on the muscle-tendon parameters. The establishment of exact values for the subject's muscle parameters is almost impossible task. However, sensitivity analysis shows that the tendon slack length is the most critical parameter when applying the Hill-type muscle model. The effect of a change of this parameter on the muscle length force relationship is analyzed in detail.

• 한국초전도ㆍ저온공학회논문지
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• 제19권3호
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• pp.8-12
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• 2017

If the part of the HTS magnet is exposed to the outside of the cryogenic coolant due to the fluctuation of the height of the cooling liquid or the vapor generation, the uncooled part becomes very unstable. In this paper, the unstable equilibrium temperature distribution of the uncooled part of a superconductor is obtained, and the maximum temperature and energy are calculated as a function of the uncooled length. Similar to the superconductor stability problem, the current sharing model was applied to derive the theoretical formula and calculated by numerical integration. We also applied a jump model, which assumes that joule heat is generated in all of the uncooled segment, and compares it with the current sharing model results. As a result of the analysis, the stable equilibrium state and the critical uncooled length in the jump model are not shown in the current sharing model. The stability of the conductors to external disturbances was discussed based on the obtained temperature distribution, maximum temperature, and energy.

• Structural Engineering and Mechanics
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• 제26권2호
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• pp.211-229
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• 2007

An experimental investigation to determine the transfer length of a seven-wire prestressing strand in different concretes is presented in this paper. A testing technique based on the analysis of bond behaviour by means of measuring the force supported by the prestressing strand on a series of specimens with different embedment lengths has been used. An analytical bond model to calculate the transfer length from an inelastic bond stress distribution along the transfer length has been obtained. A relationship between the plastic bond stress for transfer length and the concrete compressive strength at the time of prestress transfer has been found. An equation to predict the average and both the lower bound and the upper bound values of transfer length is proposed. The experimental results have not only been compared with the theoretical prediction from proposed equations in the literature, but also with experimental results obtained by several researchers.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.579-584
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• 1999

In evaluating the ultimate strength of a section for a concrete flexural member, the effect of member length is not usually considered, even though the strength tends to decrease with increase of member length. In this paper the influence of specimen length on flexural compressive strength of concrete was evaluated. For this purpose, a series of C-shaped specimens subjected to axial compression and bending moment were tested using four different length-to-depth ratios(from 1, 2, 3 and 4) of specimens with compressive strength of 58 MPa. Results indicate that the reduction in flexural compressive strength with increase of length-to-width ratios was apparent. A model equation was derived using regression analyses on the experimental data. It was also founded that the effect of specimen length on ultimate strain was negligible, but its effect of the ultimate load and the displacement at center of specimen was distinct. Finally more general model equation is also suggested.

• 대한소아치과학회지
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• 제47권2호
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• pp.176-187
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• 2020

이 연구는 모델 스캐너로 석고 모형을 스캔한 디지털 모형(Model scanned digital model, MSD)과 구내 스캐너로 구강을 스캔한 디지털 모형(Intraoral scanned digital model, ISD)에서 계측한 치아 근원심 폭경(Tooth width, TW)과 치열궁 길이(Arch length, AL)의 신뢰도와 재현성, 치열궁 길이 편차(Arch length discrepancy, ALD) 분석의 타당도를 평가하였다. 만 12 - 18세의 남, 여 30명에게 석고 모형, MSD, ISD를 획득하고, 2번 계측한 TW, AL의 신뢰도는 Pearson 상관 분석, 4명의 재현성은 군간 상관 분석 그리고 TW, AL 및 ALD의 타당도는 대응표본 t검정으로 평가하였다. 결과적으로 모든 군에서 계측한 TW, AL는 높은 신뢰도와 재현성을 보였고 MSD군의 ALD분석은 적절한 타당도를 보였다. ISD 군의 TW는 가장 높은 타당도를 보인 반면에, AL와 ALD분석은 유의미하게 짧게 측정되어 낮은 타당도를 보였으므로 임상가는 디지털 모델을 이용하여 공간 분석 시행 시 이를 고려해야 할 것이다.

• 한국정밀공학회지
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• 제22권3호
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• pp.61-67
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• 2005

A dynamic model for flexure hinge-based compliant mechanisms is derived. The dynamic model of the previous works do not well describe the behaviors of rigid bodies in the compliant mechanism when the length of the flexure hinge is long. In this study, the effect on the length of the flexure hinge is pointed out and then the dynamic model is derived to overcome the length effect. For verification, modal analyses are carried out using the proposed dynamic model and FEM (Finite Element Method). Finally they are compared by the terms of modal frequency. As the result, the proposed dynamic model can be used in design and analysis of the compliant mechanism.