• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.127-127
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• 2010

Owing to many advantages on indirect intersubband absorption from the hole miniband to the electron miniband based on the type-II band alignment in InAs/GaSb strained-layer superlattice (SLS), InAs/GaSb SLS infrared photodetector (SLIP) has emerged as a promising system to realize high-detectivity quantum photodetector operating up to room temperature in the spectral range of mid-infrared (MIR) to far-infrared (FIR). In particular, n-barrier-n (n-B-n) structure designed for blocking the majority-carrier dark current makes it possible for MIR/FIR dual-band SLIP whose photoresponse (PR) band can be exclusively selected by the bias polarity. In this study, we present the MIR and FIR photoresponse (PR) mechanism identified by dual-band PR spectra and photoluminescence (PL) profiles taken from InAs/GaSb SLIP. In the MIR/FIR PR spectra measured by changing bias polarity, each spectrum individually shows a series of distinctive peaks related to the transitions from the hole subbands to the conduction one. The PR mechanism at each polarity is discussed in terms of diffusion current, and a superposition of MIR-PR in the FIR-PR spectrum is explained by tunnelling of electrons activated in MIR-SLS. The effective FIR-PR spectrum decomposed into three curves for HH1, LH1, and HH2 has revealed the edge energies of 120, 170, and 220 meV, respectively, and the temperature variation of the MIR-PR edge energies shows that the temperature behavior of the SLS systems can be approximately expressed by the Varshni empirical equation.

• 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.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.404-416
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• 2020

An analytical procedure for calculating the failure load of a V-shaped rock notch under two-dimensional stress conditions was developed based on the slip-line plastic analysis method. The key idea utilized in the development is the fact that the α-line, one of the slip-lines, extends from the rock notch surface to the horizontal surface outside the notch when the rock around the notch is in the plastic state, and that there exists an invariant which is constant along the α-line. Since the stress boundary condition of the horizontal surface outside the rock notch is known, it is possible to calculate the normal and shear stresses acting on the rock notch surface by solving the invariant equation. The notch failure load exerted by the wedge was calculated using the calculated stress components for the notch surface. Rock notch failure analysis was performed by applying the developed analytical procedure. The analysis results show that the failure load of the rock notch increases with exponential nonlinearity as the angle of the notch and the friction of the notch surface increase. The analytical procedure developed in this study is expected to have applications to the study of fracture initiation in rocks through wedge-shaped notch formation, calculation of bearing capacity of the rock foundation, and stability analysis of rock slopes and circular tunnels.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.156-161
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• 1999

new bearing concept, the wave journal bearing, has been developed to improve the static and dynamic performances of an air-lubricated hydrodynamic journal bearing. This concept features waves on bearing surface. In this study, we present the solution of the compressible Reynolds equation valid for arbitrary Knudsen numbers. Straight wave journal bearing is investigated numerically. The performances of straight wave bearing are compared to the plain journal bearing over relatively wide range of bearing number and eccentricity. The wave journal bearing offers better stability than the plain journal bearing under a13 bearing numbers covered in this study. The bearing load and stability characteristics are dependent on the geometric parameters such as the amplitude and the starting point of the wave relative to the applied load. Under the condition of Knudsen number)0.01, we can not ignore the effect of slip for journal bearing.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.17-22
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• 1991

An accurate and efficient analytical model describing the bond effect between reinforcing steel and concrete without taking the double nodes is presented. To increase the efficiency of the solution and reduce the number of degrees of freedom, the reinforcing bar elements are considered to be embedded in the connote elements. Relative douses of freedom accounting for the relative slip between reinforcing steel and concrete are condensed out during the stiffness formation phase. However, these degrees of freedom Can be taken into account explicitly by solving the constructed global equilibrium equation for each reinforcing steel. The usefulness of proposed model is established through the comparison with the experimental data subjected on push and push-pull loadings.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.443-448
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• 2001

This paper presents a bond characteristics of high strength steel reinforced concrete members. High strength steel is what yield strength is higher than that of normal strength steel. So, the amount of flexural steel needed in R.C. members can be decreased. In result, it is expected that the workability and structure quality can improve and man power can minimize. For this purpose, specimens were made and tested with experimental parameters, such as concrete strength, steel diameter and yield strength. The result showed that under same tensile force of steel, in case of substituting normal strength steel with high strength steel, maximum bond stress increased and development length didn't almost change. In addition, the governing equation of bond and bond stress verse slip relationship were derived and compared with test values such as maximum bond stress, slip and bond stiffness.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.341-344
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• 1988

This paper derives a condition foe constant voltage i constant frequency generation of doubly-fed induction generator. The condition is varied by the magnitude of output voltage, load current and its power factor, slip of the machine. Magnitude of output voltage is controlled by exiting voltage which is caculated by derived equation from operating condition. frequency of output voltage is controlled by injecting slip frequency to the rotor which is the difference between wanted output frequency and rotor frequency.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.42-47
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• 2015

This paper studies on the design of a servo controller for an antilock brake system(ABS) based on the car tire model. First, a nonlinear differential equation of the car tire is constructed and its linearization model is obtained by Taylor's series. Second, a servo controller based on the mathematical model is analytically designed to obtain the maximum brake force, where the tire velocity and the slip ratio of car tire are respectively controlled to the given command values. Third, it is theoretically shown that the proposed control algorithm has good usefulness in ABS.

• Tribology and Lubricants
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• v.17 no.1
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• pp.28-32
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• 2001

A new bearing concept, the wave journal bearing, has been developed to improve the static and dynamic performances of an air-lubricated hydrodynamic journal bearing. This concept features waves on bearing surface. In this study, we present the solution of the compressible Reynolds equation valid for arbitrary Knudsen numbers. Straight wave journal bearing is investigated numerically. The performances of straight wave bearing are compared to the plain journal bearing over relatively wide range of bearing number and eccentricity. The wave journal bearing offers better stability than the plain journal bearing under all bearing numbers covered in this study. The bearing load and stability characteristics are dependent on the geometric parameters such as the amplitude and the starting point of the wave relative to the applied load. Under the condition of Knudsen number＞0.01, we can not ignore the effect of slip for Journal bearing.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.475-482
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• 2002

A moment-curvature relationship to simulate the behavior of reinforced concrete (RC) columns under cyclic loading is introduced. Unlike previous moment4curvature models and the layered section approach, the proposed model takes into account the bond-slip effect by using a monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The pinching effect caused by axial force is considered with an assumption that the absorbing energy corresponding to any deformation level maintains constant regardless of the magnitude of applied axial lone. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. Finally, correlation studies between analytical result and experimental studies are conducted to establish the validity of the proposed model.