• Title/Summary/Keyword: numerical testing

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A Numerical Study on the Effect of Blade Shapes on the Performance of the Propeller-type Submersible Mixers (날개형상이 프로펠러형 수중믹서의 성능에 미치는 영향에 관한 수치적 연구)

  • Choi, Y. S.;Lee, J. H.;Kim, S. I.
    • 유체기계공업학회:학술대회논문집
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    • 1999.12a
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    • pp.252-256
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    • 1999
  • In this research, the performance predictions of the submersible mixer were investigated. The variation of the performance characteristics by changing the impeller design parameters were discussed through the flow calculation results by using a commercial program, FLUENT. The performance of the submersible mixers is related to the velocity diffusion profiles downstream of the impeller and also the required input motor power to mix the fluid. In this study, the various design parameters such as the number of blade, the hub and tip diameters, the impeller blade profiles and revolution speed of the blades were taken for the fixed values. The blade sweep direction, the chord length distribution along with the radius of the blade and the inlet blade angle were changed to make different testing models. The flow calculation results show the effect of the changed design parameters on the performance of the submersible mixers and also give some helpful information for designing more efficient submersible mixers.

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Attenuation of Fundamental Longitudinal Cylindrical Guided Wave Propagating in Liquid-Filled Steel Pipes

  • NA WON-BAE;RYU YEON-SUN;KIM JEONG-TAE
    • Journal of Ocean Engineering and Technology
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    • v.19 no.5 s.66
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    • pp.26-33
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    • 2005
  • Attenuation of fundamental longitudinal guided wave propagating liquid-filled steel pipes is numerically investigated. Several liquids such as water, diesel oil, castor oil etc. are considered for the filing materials in the pipes. Sink is considered for numerical models for abandoning standing wave modes; hence the attenuation dispersion curves become much simpler. Those attenuation calculations can be utilized for guided-wave-based nondestructive testing of pipelines when one inspects pipelines, using monitoring sensors, which are installed outside pipes.

Nonparametric Estimation of the Survival Function under Progressively Random Censorship (점진적(漸進的) 임의중단법(任意中斷法)에서 생존함수(生存函數)의 비모수적(非母數的) 추정(推定)에 관한 연구(硏究))

  • Park, Byung-Gu;Lee, Kwang-Ho
    • Journal of the Korean Data and Information Science Society
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    • v.2
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    • pp.45-62
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    • 1991
  • In this paper we propose new nonparametric estimators of the survival function using spline function under the progressively random censoring scheme. This sampling scheme is applied in many practical situations such as clinical trials or the life testing problems. We also investigate the behaviors for some estimators in the proposed class and the performance of progressively random censoring scheme through the numerical examples and Monte Carlo simulation.

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Linear shell elements for active piezoelectric laminates

  • Rama, Gil;Marinkovic, Dragan Z.;Zehn, Manfred W.
    • Smart Structures and Systems
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    • v.20 no.6
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    • pp.729-737
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    • 2017
  • Piezoelectric composite laminates are a powerful material system that offers vast options to improve structural behavior. Successful design of piezoelectric adaptive structures and testing of control laws call for highly accurate, reliable and numerically efficient numerical tools. This paper puts focus onto linear and geometrically nonlinear static and dynamic analysis of smart structures made of such a material system. For this purpose, highly efficient linear 3-node and 4-node finite shell elements are proposed. Both elements employ the Mindlin-Reissner kinematics. The shear locking effect is treated by the discrete shear gap (DSG) technique with the 3-node element and by the assumed natural strain (ANS) approach with the 4-node element. Geometrically nonlinear effects are considered using the co-rotational approach. Static and dynamic examples involving actuator and sensor function of piezoelectric layers are considered.

Validation of the Reynolds Stress Turbulence Models in Turbulent Jet Diffusion Flames (난류분류확산화염에 대한 레이놀즈응력모델의 적용성 검토)

  • 한지웅;이태우;이근오;이창언
    • Journal of the Korean Society of Safety
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    • v.11 no.3
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    • pp.66-74
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    • 1996
  • Numerical simulations were carried out using standard Reynolds stress turbulence model(LRR model) and modified RSM(Janicka model ) to validate these models in combustion flow fields. Two flames were selected for use as a benchmark data for model testing. One is a conventional jet diffusion flame that has the effect of suppression of turbulence by combustion. The other is a triple jet diffusion flame that designed to give high turbulence to the periphery of the flame and to remove the low Reynolds-number flow fields. As a result, it was found that the modification of standard RSM model is indispensable in the modelling of flames with low turbulence region. And it is also necessary to improve the existing modified models for the universal use.

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Economic Constant Stress Plans for Accelerated Life Testing (가속수명시험을 위한 경제적 일정스트레스 계획의 개발)

  • Seo, Sun-Keun;Kim, Kap-Seok
    • Journal of Korean Institute of Industrial Engineers
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    • v.25 no.4
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    • pp.517-526
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    • 1999
  • This paper deals with two economic optimal designs of constant-stress accelerated life test(ALT) where failure distribution follows one of location-scale family, i. e., exponential, Weibull, and lognormal distributions which have been ones of the popular choices of failure distributions. Two optimization criteria to develop ALT plans are the statistical efficiency per unit expected cost which consists of the fixed test cost, cost being proportional to the number of test units, and variable test cost depending on test period and stress level, and the expected loss which combines Taguchi's quadratic loss function and expected test cost. Optimum plan determines the low stress level, test units allocated to each stress, and censoring times at two stress levels under Type I censoring. The proposed ALT plans are illustrated with a numerical example and sensitivity analyses are conducted to study effects of pre-estimates of design parameters.

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Numerical Analysis of Through Transmission Pulsed Eddy Current Testing (투과형 펄스와전류 탐상의 수치해석)

  • Shin, Young-Kil;Choi, Dong-Myung;Lee, Chang-Jun
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.2034-2035
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    • 2007
  • 투과형 펄스와전류(Pulsed Eddy Current; PEC) 탐상을 대상으로 수치해석 방법을 사용하여 펄스와전류 탐상신호를 예측하고, 펄스의 폭이 신호에 미치는 영향을 조사하였다. 그 결과 전도도나 두께가 증가하면 PEC 신호의 최대값이 작아지며 최대값 발생시간이 지연됨을 관찰할 수 있었고, 전도도나 두께를 측정할 때 펄스의 폭이 좁으면 신호의 최대치를 사용하는 것이 유리하고, 펄스의 폭이 넓으면 최대치가 나타나는 시간을 사용하는 것이 판별에 유리하다는 것을 알 수 있었다. 또한, lift-off가 커질수록 PEC 신호의 최대값은 작아지지만, 두 코일 사이의 간격만 일정하면 피검사체가 어디에 위치해도 신호는 거의 동일하며, 같은 두께에서 서로 다른 lift-off 변화는 PEC 신호를 한 점에서 만나게 하는 것을 알 수 있었다.

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A Study on Nonlinear Analysis of Circular Concrete Beams Confined by Carbon Sheet Tube Using Solid element (Solid Element를 이용한 Carbon Sheet Tube로 구속된 원형 콘크리트 보의 비선형 해석적 연구)

  • 박연호;박진영;이경훈;홍원기;김희철
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2003.09a
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    • pp.147-154
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    • 2003
  • The purpose of this study is to investigate analytically the flexural behavior characteristics of Circular concrete beams confined by carbon sheet. Nonlinear analysis method is presented to simulate the structural behavior beam models. The proposed analytical hardening models were considered the confinement effect of concrete and the tensile effect of carbon sheet in tensile region of concrete. Prandtl-Reuss numerical formula was used to nonlinear analysis of finite element models. Comparisons analytical models with experimental data obtained from flexural testing in the laboratory were presented. Analytical and experimental models show similar behavior.

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Development of Design Static Property Analysis of Mooring System Caisson for Offshore Floating Wind Turbine

  • Dodaran, Asgar Ahadpour;Park, Sang-Kil
    • International Journal of Ocean System Engineering
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    • v.2 no.2
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    • pp.97-105
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    • 2012
  • A all floating structures operating within a limited area require, stationkeeping to maintain the motions of the floating structure within permissible limits. In this study, methods for selecting and optimizing the mooring system Caisson for floating wind turbines in shallow water are investigated. The design of the mooring system is checked against the governing rules and standards. Adequately verifying the design of floating structures requires both numerical simulations and model testing, the combination of which is referred to as the hybrid method of design verification. The challenge in directly scaling moorings for model tests is the depth and spatial limitations of wave basins. It is therefore important to design and build equivalent mooring systems to ensure accurate static properties (global restoring forces and global stiffness).

Extension of the variational theory of complex rays to orthotropic shallow shell structures

  • Cattabiani, Alessandro;Barbarulo, Andrea;Riou, Herve;Ladeveze, Pierre
    • Advances in aircraft and spacecraft science
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    • v.3 no.3
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    • pp.317-330
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    • 2016
  • Nowadays, the interest of aerospace and automotive industries on virtual testing of medium-frequency vibrational behavior of shallow shell structures is growing. The development of software capable of predicting the vibrational response in such frequency range is still an open question because classical methods (i.e., FEM, SEA) are not fully suitable for the medium-frequency bandwidth. In this context the Variational Theory of Complex Rays (VTCR) is taking place as an ad-hoc technique to address medium-frequency problems. It is a Trefftz method based on a weak variational formulation. It allows great flexibility because any shape function that satisfies the governing equations can be used. This work further develops such theory. In particular, orthotropic materials are introduced in the VTCR formulation for shallow shell structures. A significant numerical example is proposed to show the strategy.