• Title/Summary/Keyword: Technical parameter

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Dynamic interaction effects of buried structures on seismic response of surface structures

  • Sisman, Rafet;Ayvaz, Yusuf
    • Earthquakes and Structures
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    • v.19 no.1
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    • pp.1-16
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    • 2020
  • This study presents an investigation of the dynamic interactions between a surface structure lying on two different soil deposits and a square-shaped buried structure embedded in the soil. To this end, a large number of numerical models are generated by using a well-known Finite Element Method software, i.e., OpenSEES. The interaction phenomenon is assumed to be affected by six different parameters. In the parametric study, these parameters are assumed to have various values in accordance with the engineering practices. A total of 1620 possible combinations of the parameter values are addressed in this study. 30 different numerical models are also generated as the 'free-field cases' to set a reference. The surface structure drift and acceleration amplifications are used as a measure to evaluate the dynamic interactions. The response (i.e., drifts and accelerations) amplifications are calculated as the ratio of the maximum surface structure response in any 'case' to the maximum surface structure response in corresponding free-field case. Variation of the response amplifications with any of the investigated parameters is addressed in this paper. The results obtained from the numerical analyses clearly reveal that the presence of a buried structure in the vicinity of a surface structure can cause both amplification and de-amplification of the surface structure responses, depending on the case parameters.

Decoupling of the Secondary Saliencies in Sensorless PMSM Drives using Repetitive Control in the Angle Domain

  • Wu, Chun;Chen, Zhe;Qi, Rong;Kennel, Ralph
    • Journal of Power Electronics
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    • v.16 no.4
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    • pp.1375-1386
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    • 2016
  • To decouple the secondary saliencies in sensorless permanent magnet synchronous machine (PMSM) drives, a repetitive control (RC) in the angle domain is proposed. In this paper, the inductance model of a concentrated windings surface-mounted PMSM (cwSPMSM) with strong secondary saliencies is developed. Due to the secondary saliencies, the estimated position contains harmonic disturbances that are periodic relative to the angular position. Through a transformation from the time domain to the angle domain, these varying frequency disturbances can be treated as constant periodic disturbances. The proposed angle-domain RC is plugged into an existing phase-locked loop (PLL) and utilizes the error of the PLL to generate signals to suppress these periodic disturbances. A stability analysis and parameter design guidelines of the RC are addressed in detail. Finally, the proposed method is carried out on a cwSPMSM drive test-bench. The effectiveness and accuracy are verified by experimental results.

Wave propagation in a microbeam based on the modified couple stress theory

  • Kocaturk, Turgut;Akbas, Seref Doguscan
    • Structural Engineering and Mechanics
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    • v.46 no.3
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    • pp.417-431
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    • 2013
  • This paper presents responses of the free end of a cantilever micro beam under the effect of an impact force based on the modified couple stress theory. The beam is excited by a transverse triangular force impulse modulated by a harmonic motion. The Kelvin-Voigt model for the material of the beam is used. The considered problem is investigated within the Bernoulli-Euler beam theory by using energy based finite element method. The system of equations of motion is derived by using Lagrange's equations. The obtained system of linear differential equations is reduced to a linear algebraic equation system and solved in the time domain by using Newmark average acceleration method. In the study, the difference of the modified couple stress theory and the classical beam theory is investigated for the wave propagation. A few of the obtained results are compared with the previously published results. The influences of the material length scale parameter on the wave propagation are investigated in detail. It is clearly seen from the results that the classical beam theory based on the modified couple stress theory must be used instead of the classical theory for small values of beam height.

Response of a finite beam on a tensionless Pasternak foundation under symmetric and asymmetric loading

  • Coskun, Irfan;Engin, Hasan;Ozmutlu, Aydin
    • Structural Engineering and Mechanics
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    • v.30 no.1
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    • pp.21-36
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    • 2008
  • The static response of a finite beam resting on a tensionless Pasternak foundation and subjected to a concentrated vertical load is assessed in this study. The concentrated vertical load may be applied at the center of the beam, or it may be offset from the center. The tensionless character of the foundation results in the creation of lift-off regions between the beam and the foundation. An analytical/ numerical solution is obtained from the governing equations of the contact and lift-off regions to determine the extent of the contact region. Although there is no nonlinear term in the equations, the problem shows a nonlinear character since the contact region is not known in advance. Due to that nonlinearity, the essentials of the problem (the coordinates of the lift-off points) are calculated numerically using the Newton-Raphson technique. The numerical results are presented in figures to illustrate the behaviours of the free-free and pinned-pinned beams under symmetric or asymmetric loading. The figures illustrate the effects of the shear foundation parameter and the symmetric and asymmetric loading options on the variation of the contact lengths and the displacement of the beam.

A hybrid DQ-TLBO technique for maximizing first frequency of laminated composite skew plates

  • Vosoughi, Ali R.;Malekzadeh, Parviz;Topal, Umut;Dede, Tayfun
    • Steel and Composite Structures
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    • v.28 no.4
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    • pp.509-516
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    • 2018
  • The differential quadrature (DQ) and teaching-learning based optimization (TLBO) methods are coupled to introduce a hybrid numerical method for maximizing fundamental natural frequency of laminated composite skew plates. The fiber(s) orientations are selected as design variable(s). The first-order shear deformation theory (FSDT) is used to obtain the governing equations of the plate. The equations of motion and the related boundary conditions are discretized in space domain by employing the DQ method. The discretized equations are transferred from the time domain into the frequency domain to obtain the fundamental natural frequency. Then, the DQ solution is coupled with the TLBO method to find the maximum frequency of the plate and its related optimum stacking sequences of the laminate. Convergence and applicability of the proposed method are shown and the optimum fundamental frequency parameter of the plates with different skew angle, boundary conditions, number of layers and aspect ratio are obtained. The obtained results can be used as a benchmark for further studies.

Development of Technique Predicting of the Wear of DCI Roll Using Carbon Steel in Hot Rod Rolling Process (탄소강 선재 압연공정의 DCI 롤 마멸 예측 기술의 개발)

  • Kim, Dong-Hwan;Kim, Byeong-Min;Lee, Yeong-Seok;Yu, Seon-Jun;Ju, Ung-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.9
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    • pp.1736-1745
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    • 2002
  • The objective of this study is to predict the roll wear in hot rod rolling process. In this study hot rod rolling process for round and oval passes has been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental form and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the thermal softening of DCI (Ductile Cast Iron) roll according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering parameter curve. 3D wear program developed in this study might be used for adjusting the gap of rolls to set up a suitable rolling schedule for keeping dimensional tolerance of the product.

Modal parameter identification of in-filled RC frames with low strength concrete using ambient vibration

  • Arslan, Mehmet E.;Durmus, Ahmet
    • Structural Engineering and Mechanics
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    • v.50 no.2
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    • pp.137-149
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    • 2014
  • In this study, modal parameters such as natural frequencies, mode shapes and damping ratios of RC frames with low strength are determined for different construction stages using ambient vibration test. For this purpose full scaled, one bay and one story RC frames are produced and tested for plane, brick in-filled and brick in-filled with plaster conditions. Measurement time, frequency span and effective mode number are determined by considering similar studies and literature. To obtain experimental dynamic characteristics, Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques are used together. It is shown that the ambient vibration measurements are enough to identify the most significant modes of RC frames. The results indicate that modal parameters change significantly depending on the construction stages. In addition, Infill walls increase stiffness and change the mode shapes of the RC frame. There is a good agreement between mode shapes obtained from brick in-filled and in-filled with plaster conditions. However, some differences are seen in plane frame, like expected. Dynamic characteristics should be verified using finite element analysis. Finally, inconsistency between experimental and analytical dynamic characteristics should be minimize by finite element model updating using some uncertain parameters such as material properties, boundary condition and section properties to reflect the current behavior of the RC frames.

Molecular Diffusion of Water in Paper(III) -Theoretical analysis on vapor sorption properties of fiber surface - (종이내 수분확산 (제3보) -종이 표면의 수증기-흡습성에 관한 이론적 고찰-)

  • Yoon, Sung-Hoon;Jeon, Yang;Park, Jong-Moon
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.31 no.1
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    • pp.61-71
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    • 1999
  • The study aimed at the theoretical analysis of vapor sorption properties of, pp.rmaking fibers. Water vapor affinity and sorption thermodynamic properties of fiber constituents were evaluated based on Henry's law and Hildebrand's solubility theory. Theoretical equilibrium moisture content(ThEMC) on fiber surface was estimated using functional group contribution. Crystallinity of cellulose in fiber significantly controlled the water vapor solubility. Comparisons of the measured equilibrium moisture content data and the estimated ThEMC data coincidently suggested the fact that crystallinity of cellulose in fibers was around 60% to 70%. Carbohydrates constituents including amorphous cellulose and hemicellulose in fibers showed higher vapor solubility than lignin molecules. High correlation existed between ThEMC and vapor solubility as well as between ThEMC and solubility parameter. In the thermodynamic analysis on water-vapor sorption process in fibers, the sorption enthalpy increased as RH increased, whereas sorption entropy and free energy decreased with increasing RH.

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Absorption of Carbon Dioxide into Polar Solvents of 2-Amino-2-Methyl-1-Propanol (2-Amino-2-Methyl-1-Propanol이 용해한 극성 용매에서 이산화탄소의 흡수)

  • Son, Young-Sik;Heo, Nam-Hwan;Lee, Sung-Su;Park, Sang-Wook
    • Korean Chemical Engineering Research
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    • v.47 no.3
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    • pp.380-385
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    • 2009
  • The absorption rate of carbon dioxide with 2-amino-2-methyl-1-propanol(AMP) was measured in such non-aqueous solvents as methanol, ethanol, n-propanol, n-butanol, ethylene glycol, propylene glycol, and propylene carbonate, and in water at 298 K and 101.3 kPa using a semi-batch stirred tank with a plane gas-liquid interface. The overall reaction rate constant, obtained under the condition of fast reaction regime, from the measured rate of absorption was used to get the elementary reaction rate constants in complicated reactions represented by reaction mechanism of carbamate formation and the order of overall reaction of $CO_2$ with amine. The correlation between the elementary reaction rate constant and the solubility parameter of the solvent was also presented.

Replication of Automotive Vibration Target Signal Using Iterative Learning Control and Stewart Platform with Halbach Magnet Array (반복학습제어와 할바흐 자석 배열 스튜어트 플랫폼을 이용한 차량 진동 신호 재현)

  • Ko, Byeongsik;Kang, SooYoung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.5
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    • pp.438-444
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    • 2013
  • This paper presents the replication of a desired vibration response by iterative learning control (ILC) system for a vibration motion replication actuator. The vibration motion replication actuator has parameter uncertainties including system nonlinearity and joint nonlinearity. Vehicle manufacturers worldwide are increasingly relying on road simulation facilities that put simulated loads and stresses on vehicles and subassemblies in order to reduce development time. Road simulation algorithm is the key point of developing road simulation system. With the rapid progress of digital signal processing technology, more complex control algorithms including iterative learning control can be utilized. In this paper, ILC algorithm was utilized to produce simultaneously the six channels of desired responses using the Stewart platform composed of six linear electro-magnetic actuators with Halbach magnet array. The convergence rate and accuracy showed reasonable results to meet the requirement. It shows that the algorithm is acceptable to replicate multi-channel vibration responses.