• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.7
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• pp.1-6
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• 2004

For MOSFET devices with nanometer range gate length, accurate extraction of effective gate length is highly important because transistor characteristics become very sensitive to effective channel length. In this paper, we propose a new approach to extract the effective channel length of nanometer range MOSFET by Capacitance Voltage(C-V) method. The effective channel length is extracted using gate to source/drain capacitance( $C_{gsd}$). It is shown that 1/$\beta$ method, Terada method and other C-V method are inadequate to extract the accurate effective channel length. Therefore, the proposed method is highly effective for extraction of effective channel length of 100nm CMOSFETs.s.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.242-245
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• 2009

The effect of fuel composition on flame length was studied in a non-premixed turbulent diluted hydrogen jet with coaxial air. The observed flame length was expressed as a function of the ratio of coaxial air to fuel jet velocity and compared with a theoretical prediction based on the velocity ratio. Four cases of fuel mixed by volume were determined. In the present study, we derived a scaling correlation for predicting the flame length in a simple jet with coaxial air using the effective jet diameter in the near-field concept. The experimental results showed that visible flame length had a good relation with the theoretical prediction. The scaling analysis is also valid for diluted hydrogen jet flames with varied fuel composition.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.169-179
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• 2005

An improved method for evaluating effective buckling lengths of beam-column members in plane frames is newly proposed based on system inelastic buckling analysis. To this end, the tangent stiffness matrix of be am-column elements is first calculated using stability functions and then the inelastic buckling analysis method is presented. The scheme for determining effective length of individual members is also addressed. Design examples and numerical results ?uc presented to show the validity of the proposed method.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.199-207
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• 2007

Strut-and-tie models for noncontact lap splices are presented and parameters affecting the effective lap length $(l_p)$ and the splice strength are discussed in this paper. The effective lap length along which bond stress is developed is shorter than the whole lap length. The effective lap length depends on the transverse reinforcement ratio $({\Phi})$ and the ratio of spacing to lap length $({\alpha})$. As the splice-bar spacing becomes wider, the effective lap length decreases and, therefore, the splice strength decreases. The influence of the ratio ${\alpha}$ on the effective lap length becomes more effective when the transverse reinforcement ratio is low. Because the slope of the strut developed between splice-bars becomes steeper as the ratio ${\Phi}$ becomes lower, the splice-bar spacing significantly affects the effective lap length. The proposed strut-and-tie models for noncontact lap splices are capable of considering material and geometric properties and, hence, providing the optimal design for detailing of reinforcements. The proposed strut-and-tie model can explain the experimental results including cracking patterns and the influence of transverse reinforcements on the splice strength reported in the literature. From the comparison with the test results of 25 specimens, the model can predict the splice strengths with 11.1% of coefficient of variation.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.129-137
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• 2007

In this study, the elastic out-of-plane buckling load and the effective length factor of X-bracing systems were studied. Points of the intersection of diagonals were modeled as a rigid connection or a pinned connection depending on the connection method of diagonals. The boundary condition of the intersection influences the buckling load of X-bracing systems. For each boundary condition of the intersection, effective out-of-plane length factors of X-bracing systems were derived as a function of the length ratio of tension and compression diagonals $L_P$/$L_T$, the applied force ratio of tension and compression diagonals T/P, and the Euler buckling load ratio of tension and compression diagonals $P_{ET}$/$P_{EP}$. The proposed effective out-of-plane length factors of X-bracing systems were compared with the results of previous researchers and those of the finite element analysis and their properties were verified. Finally, the effects of the boundary condition of the intersection on the out-of-plane buckling load of X-bracing systems were investigated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.81-92
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• 2010

In design of steel frames, it is generally believed that elastic system buckling analysis cannot predict real behaviors of structures, while inelastic system buckling analysis can give informative buckling behaviors of individual members considering inelastic material behavior. However, the use of Euler buckling equation with these system buckling analyses have the inherent problem that the methods evaluate unexpectedly large effective lengths of members having relatively small axial forces. This paper proposes a new method of obtaining elastic and inelastic effective lengths of all members in steel frames. Considering a fictitious axial force factor for each story of frames, the proposed method determines the effective lengths using the inelastic stiffness reduction factor and the iterative eigenvalue analysis. In order to verify the validity of the proposed method, the effective lengths of example frames by the proposed method were compared to those of previously established methods. As a result, the proposed method gives reasonable effective lengths of all members in steel frames. The effect of inelastic material behavior on the effective lengths of members was also discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.107-115
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• 2011

This research studies the behavior of the FRP-concrete interface subjected to two environmental substances. Frist is to investigate the behavior by the application of different bonding materials at the interface between FRP and concrete, second is to understand a long-term performance at the interface by Freeze-thaw actions. The parameters considered in this research are the maximum bonding strength and the effective bonding length at the FRP-concrete interface. In the first experimental phase, three types of specimens are fabricated and tested considering the number of applied bonding materials and the Freeze-thaw tests are performed to evaluate the behavior of the interface in the cycle range of 0 to 300 cycles. Finally, it is known that there is a 5~7% difference of the effective bonding length between applied bonding materials and the values for the maximum stress and the effective length under Freeze-thaw action are varied randomly as the freeze-thaw cycle is increased even though initial reduction of their capacities are occurred.

• Journal of the Korean GEO-environmental Society
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• v.8 no.4
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• pp.27-39
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• 2007

This paper investigates numerically characteristics of the fluid flow in spatially correlated variable-aperture fractures under effective normal stress conditions. Spatially correlated aperture distributions are generated by using the geostaistical method (i.e. Turning Bands algorithm). In order to represent a nonlinear relationship between the effective normal stress and the fracture aperture, a simple mechanical formula is combined with a local flow model. Obtained numerical results indicate that the fluid flow is significantly affected by the geometry of aperture distribution varying according to the applied effective normal stress as well as the spatial correlation length of aperture distribution. Moreover, by using results simulated in this study, the modified Louis formula representing the relationship between the effective normal stress and the effective permeability of fracture is proposed.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.9-13
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• 2017

본 연구에서는 실내실험을 통하여 보의 경사변화에 따른 흐름특성과 보 상류에서 유사의 퇴적과정을 정량적으로 분석하고, 보 하류에서 세굴 및 지형변화 과정을 분석하였다. 보의 설치각도가 커질수록 보에 의항 굴절되는 유선의 각도가 증가하며, 하류에서 수충부가 형성되고 사수역의 크기가 증가한다. 즉, 보의 길이 대 수로 폭의 비로 정의되는 무차원 수로폭이 증가할수록 무차원 유효길이는 감소하였다. 보 상류에서는 보에 의하여 형성된 배수의 영향이 끝나는 지점에서 delta가 형성되며, 보 하류에서는 흐름이 집중되어 보 직하류 하상은 세굴되고 반대쪽에서는 이동성이 없는 교호사주가 형성되었다. 또한 충부에서는 깊게 세굴되었으며, 보의 설치 각도가 커질수록 수충부가 집중되면서 깊게 세굴되고, 세굴범위는 좁게 나타났다. 무차원 하상고가 증가할수록 유속과 delta의 이동속도의 비인 무차원 속도는 감소하며, 무차원 보의 길이가 증가함에 따라, 무차원 사주의 파장이 감소하였다. 무차원 보의 길이가 증가함에 따라 보에 의하여 굴절되는 흐름의 각이 크므로, 흐름이 집중되어 하상이 깊게 세굴되고 무차원 사주의 파고가 증가하였다.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.641-648
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• 2009

Concrete structures become more common in railway systems with an advancement of high speed train technologies. As the service life of concrete structures increases, structural strengthening for concrete structures may be necessary. There are several typical strengthening techniques using steel plate and fiber reinforced polymer (FRP) materials, which have their own inherent shortcomings. In order to enhance greater durability and resistance to fire and other environmental attacks, basalt fiber material attracts engineer's attention due to its characteristics. This study investigates bonding performance of basalt fiber sheet as a structural strengthening material. Experimental variables include bond width, length and number of layer. From the bonding tests, there were three different types of bonding failure modes: debonding, rupture and rip-off. Among the variables, bond width indicated more significant effect on bonding characteristics. In addition the bond length did not contribute to bond strength in proportion to the bond length. Hence this study evaluated effective bond length and effective bond strength. The effective bond strength was compared to those suggested by other researches which used different types of FRP strengthening materials such as carbon FRP.