• Title/Summary/Keyword: critical parameters

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Stability Assessment of a Bi8h Speed Train via Optimal Design (고속전철 현가장치의 민감도해석을 통한 최적설계)

  • 탁태오;윤순형
    • Proceedings of the KSR Conference
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    • 1999.11a
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    • pp.542-549
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    • 1999
  • The purpose of this study is to investigate stability of a high speed train and to propose optimal design using sensitivity analysis of suspension design parameters. A form of equations of motion in tangent track and curve track is obtained based on each creep force. Tangent track and curve track equations include lateral, rolling and yawing motions of wheel sets, bogies, and carbodies. Three track cases have been chosen to stability assesment of a high speed train analysis. Sensitivity equations are set up by directly differentiating the equations of motion. This study def'.led Stability performance index of a high speed train in tangent track and curve track. The relative magnitude of the effect of suspension parameters on the critical speed is computed, and by adjusting these parameters, the increase of the critical speed is achieved.

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A methodology for uncertainty quantification and sensitivity analysis for responses subject to Monte Carlo uncertainty with application to fuel plate characteristics in the ATRC

  • Price, Dean;Maile, Andrew;Peterson-Droogh, Joshua;Blight, Derreck
    • Nuclear Engineering and Technology
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    • v.54 no.3
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    • pp.790-802
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    • 2022
  • Large-scale reactor simulation often requires the use of Monte Carlo calculation techniques to estimate important reactor parameters. One drawback of these Monte Carlo calculation techniques is they inevitably result in some uncertainty in calculated quantities. The present study includes parametric uncertainty quantification (UQ) and sensitivity analysis (SA) on the Advanced Test Reactor Critical (ATRC) facility housed at Idaho National Laboratory (INL) and addresses some complications due to Monte Carlo uncertainty when performing these analyses. This approach for UQ/SA includes consideration of Monte Carlo code uncertainty in computed sensitivities, consideration of uncertainty from directly measured parameters and a comparison of results obtained from brute-force Monte Carlo UQ versus UQ obtained from a surrogate model. These methodologies are applied to the uncertainty and sensitivity of keff for two sets of uncertain parameters involving fuel plate geometry and fuel plate composition. Results indicate that the less computationally-expensive method for uncertainty quantification involving a linear surrogate model provides accurate estimations for keff uncertainty and the Monte Carlo uncertainty in calculated keff values can have a large effect on computed linear model parameters for parameters with low influence on keff.

Critical State of Crushable Jeju Beach Sand (파쇄성이 큰 제주해사의 한계상태 특성)

  • Lee, Moon Joo;Bae, Kyung Doo;An, Sung Mo;Lee, Woo Jin
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2C
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    • pp.133-140
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    • 2010
  • A series of triaxial test was performed in order to determine critical state parameters of calcareous Jeju sand, which comprises angular shape particles with many pores in the surface. It is observed that Jeju sand mainly shows the contractive behavior during triaxial shear due to high extreme void ratios and large compressibility. The peak friction angle of Jeju sand decreases slightly with increasing mean effective stress due to the particle crushing of carbonate materials. However, the peak friction angle of Jeju sand is higher than that of other silica sands because of the more angular particle shape. The critical state friction angle of Jeju sand gradually decreases when the mean effective stress at a critical state increases. Whereas, there is not a clear influence of void ratio on the critical state friction angle. Critical state parameters of Jeju sand are similar to those of calcareous sands, but significantly larger than those of common sands.

Stability analysis of bimodular pin-ended slender rod

  • Yao, Wenjuan;Ma, Jianwei;Hu, Baolin
    • Structural Engineering and Mechanics
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    • v.40 no.4
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    • pp.563-581
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    • 2011
  • Many novel materials, developed in recent years, have obvious properties with different modulus of elasticity in tension and compression. The ratio of their tensile modulus to compressive modulus is as high as five times. Nowadays, it has become a new trend to study the mechanical properties of these bimodular materials. At the present stage, there are extensive studies related to the strength analysis of bimodular structures, but the investigation of the buckling stability problem of bimodular rods seems to cover new ground. In this article, a semi-analytical method is proposed to acquire the buckling critical load of bimodular slender rod. By introducing non-dimensional parameters, the position of neutral axis of the bimodular rod in the critical state can be determined. Then by combining the phased integration method, the deflection differential equation of bimodular pin-ended slender rod is deduced. In addition, the buckling critical load is obtained by solving this equation. An example, which is conducted by comparing the calculation results between the three of the methods including the laboratory tests, numerical simulation method and the method we developed here, shows that the method proposed in the present work is reliable to use. Furthermore, the influence of bimodular characteristics on the stability is discussed and analyzed.

Non-contact critical current measurement using hall probe (Hall probe를 이용한 비접촉 임계전류 측정)

  • Kim, Ho-Sup;Lee, Nam-Jin;Ha, Dong-Woo;Baik, Seung-Kyu;Kim, Tae-Hyung;Ko, Rock-Kil;Ha, Hong-Soo;Oh, Sang-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.05a
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    • pp.7-8
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    • 2009
  • Non-contact critical current measurement apparatus was developed using hall probe which measures the magnetic field distribution across the width of superconducting tape. The hall probe consists of 7 independent hall sensors which lie in a line 600 ${\mu}m$. The difference between maximum and minimum magnetic field in the magnetic filed distribution is a main parameter to determine the critical current. As preliminary research, we calculated the magnetic field intensity at the middle sensor, which is a minimum magnetic field and generated by the circular shielding current modeled by Bean model. We confirmed that there are some parameters that affect on the minimum magnetic field; the distance between superconducting layer and hall sensor, the width of superconducting tape, and the critical current distribution across the width of superconducting tape. Among these parameters, the distance between superconducting layer and hall sensor highly influences on the minimum magnetic field.

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A Study on the Optimum Design of Rail Vehicle Suspension Characteristics (철도차량 현가특성의 최적설계에 관한 연구)

  • 조동현;임진수
    • Proceedings of the KSR Conference
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    • 1998.11a
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    • pp.413-420
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    • 1998
  • In this study, optimum design methodology for rail vehicle suspension characteristics is suggested. Three parameters, primary lateral/longitunal stiffness and secondary lateral stiffness, are selected as design parameters. critical speed, suspension stroke trade-off and derailment coefficient are selectee as performance constraints. The optimum parameters to maximize ride quality are evaluated under the constraints. Steady-state curiving model to be able to evaluate derailment coefficient is developed. The combined design procedure is developed to evaluate Three parameters at the same time.

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The buckling of a cross-ply laminated non-homogeneous orthotropic composite cylindrical thin shell under time dependent external pressure

  • Sofiyev, A.H.
    • Structural Engineering and Mechanics
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    • v.14 no.6
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    • pp.661-677
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    • 2002
  • The subject of this investigation is to study the buckling of cross-ply laminated orthotropic cylindrical thin shells with variable elasticity moduli and densities in the thickness direction, under external pressure, which is a power function of time. The dynamic stability and compatibility equations are obtained first. These equations are subsequently reduced to a system of time dependent differential equations with variable coefficients by using Galerkin's method. Finally, the critical dynamic and static loads, the corresponding wave numbers, the dynamic factors, critical time and critical impulse are found analytically by applying a modified form of the Ritz type variational method. The dynamic behavior of cross-ply laminated cylindrical shells is investigated with: a) lamina that present variations in the elasticity moduli and densities, b) different numbers and ordering of layers, and c) external pressures which vary with different powers of time. It is concluded that all these factors contribute to appreciable effects on the critical parameters of the problem in question.

The Elastic Critical Loads of Sinusolidally Tapered Symmetric Compression Members (정현상 대칭으로 Taper진 변단면 압축재의 임계하중)

  • 오금열;홍종국;김순철;이수곤
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2000.04b
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    • pp.27-34
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    • 2000
  • The elastic critical loads of prismatic compression members can be easily determined by the conventional analytic method. In the cases of sinusoidally tapered members, however, the determination of elastic critical loads become impossible when one relies on the analytic method. In this paper, the critical loads of sinusoidally tapered members were determined by finite element method. Generally the output or results of numerical analysis are valid only when the governing parameters of a given system(or problem) have particular values. To make the practical applications easy, the critical loads determined by finite element method are expressed by some algebraic equations. The constants contained in the algebraic equations were determined by regression technique. The elastic critical loads estimated by the proposed algebraic equations coincide well with those by finite element method.

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The effect of nanoparticle in reduction of critical fluid velocity in pipes conveying fluid

  • Ghaitani, M.M.;Majidian, A.;Shokri, V.
    • Advances in concrete construction
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    • v.9 no.1
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    • pp.103-113
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    • 2020
  • This paper deal with the critical fluid velocity response of nanocomposite pipe conveying fluid based on numerical method. The pressure of fluid is obtained based on perturbation method. The motion equations are derived based on classical shell theory, energy method and Hamilton's principle. The shell is reinforced by nanoparticles and the distribution of them are functionally graded (FG). The mixture rule is applied for obtaining the equivalent material properties of the structure. Differential quadrature method (DQM) is utilized for solution of the motion equations in order to obtain the critical fluid velocity. The effects of different parameters such asCNT nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios and internal fluid are presented on the critical fluid velocity response structure. The results show that with increasing the CNT nanoparticles, the critical fluid velocity is increased. In addition, FGX distribution of nanoparticles is the best choice for reinforcement.

Fast iterative algorithm for calculating the critical current of second generation high temperature superconducting racetrack coils

  • Huang, Xiangyu;Huang, Zhen;Xu, Xiaoyong;Li, Wan;Jin, Zhijian
    • Progress in Superconductivity and Cryogenics
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    • v.21 no.4
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    • pp.53-58
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    • 2019
  • The critical current is one of the key parameters of high temperature superconducting (HTS) racetrack coils. Therefore, it is significant to calculate critical currents of HTS coils. This paper introduces a fast iterative algorithm for calculating the critical current of second generation (2G) HTS coils. This model does not need to solve long charging transients which greatly reduced the amount of calculation. To validate this model, the V-I curve of four 2G HTS double racetrack coils are measured. The effect of the silicon steel sheet on the critical current of the racetrack coil is also studied based on this algorithm.