• Title, Summary, Keyword: Quasi-static

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Accurate Non-Quasi-Static Gate-Source Impedance Model of RF MOSFETs

  • Lee, Hyun-Jun;Lee, Seonghearn
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.13 no.6
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    • pp.569-575
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    • 2013
  • An improved non-quasi-static gate-source impedance model including a parallel RC block for short-channel MOSFETs is developed to simulate RF MOSFET input characteristics accurately in the wide range of high frequency. The non-quasi-static model parameters are accurately determined using the physical input equivalent circuit. This improved model results in much better agreements between the measured and modelled input impedance than a simple one with a non-quasi-static resistance up to 40GHz, verifying its accuracy.

Quasi-static cyclic displacement pattern for seismic evaluation of reinforced concrete columns

  • Yuksel, E.;Surmeli, M.
    • Structural Engineering and Mechanics
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    • v.37 no.3
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    • pp.267-283
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    • 2011
  • Although earthquakes generate random cyclic lateral loading on structures, a quasi-static cyclic loading pattern with gradually increasing amplitude has been commonly used in the laboratory tests because of its relatively low cost and simplicity compared with pseudo-dynamic and shake table tests. The number, amplitudes and sequence of cycles must be chosen appropriately as important parameters of a quasi-static cyclic loading pattern in order to account for cumulative damage matter. This paper aims to reach a new cyclic displacement pattern to be used in quasi-static tests of well-confined, flexure-dominated reinforced concrete (RC) columns. The main parameters of the study are sectional dimensions, percentage of longitudinal reinforcement, axial force intensity and earthquake types, namely, far-fault and near-fault.

Laminate composites behavior under quasi-static and high velocity perforation

  • Yeganeh, E. Mehrabani;Liaghat, G.H.;Pol, M.H.
    • Steel and Composite Structures
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    • v.22 no.4
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    • pp.777-796
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    • 2016
  • In this paper, the behavior of woven E-glass fabric composite laminate was experimentally investigated under quasi-static indentation and high velocity impact by flat-ended, hemispherical, conical (cone angle of $37^{\circ}$ and $90^{\circ}$) and ogival (CRH of 1.5 and 2.5) cylindrical perforators. Moreover, the results are compared in order to explore the possibility of extending quasi-static indentation test results to high velocity impact test results in different characteristics such as perforation mechanisms, performance of perforators, energy absorption, friction force, etc. The effects of perforator nose shape, nose length and nose-shank connection shapes were investigated. The results showed that the quasi-static indentation test has a great ability to predict the high velocity impact behavior of the composite laminates especially in several characteristics such as perforation mechanisms, perforator performance. In both experiments, the highest performance occurs for 2.5 CRH projectile and the lowest is related to blunt projectiles. The results show that sharp perforators indicate lower values of dynamic enhancement factor and the flat-ended perforator represents the maximum dynamic enhancement factor among other perforators. Moreover, damage propagation far more occurred in high velocity impact tests then quasi-static tests. The highest damage area is mostly observed in ballistic limit of each projectile which projectile deviation strongly increases this area.

Strength and stiffness of cold-formed steel portal frame joints using quasi-static finite element analysis

  • Mohammadjani, Chia;Yousefi, Amir M.;Cai, Shu Qing;Clifton, G. Charles;Lim, James B.P.
    • Steel and Composite Structures
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    • v.25 no.6
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    • pp.727-734
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    • 2017
  • This paper describes a quasi-static finite element analysis, which uses the explicit integration method, of the apex joint of a cold-formed steel portal frame. Such cold-formed steel joints are semi-rigid as a result of bolt-hole elongation. Furthermore, the channel-sections that are being connected have a reduced moment capacity as a result of a bimoment. In the finite element model described, the bolt-holes and bolt shanks are all physically modelled, with contact defined between them. The force-displacement curves obtained from the quasi-static analysis are shown to be similar to those of the experimental test results, both in terms of stiffness as well as failure load. It is demonstrated that quasi-static finite element analysis can be used to predict the behavior of cold-formed steel portal frame joints and overcome convergence issues experienced in static finite element analysis.

Quasi-static Characteristics in Radial Direction of 100 kWh Class Superconductor Bearing (100 kWh급 초전도 베어링의 지름방향 준정적 특성)

  • Jung, S.Y.;Park, B.J.;Han, Y.H.;Park, B.C.;Lee, J.P.;Han, S.C.
    • Progress in Superconductivity
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    • v.12 no.1
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    • pp.27-31
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    • 2010
  • A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. Many aspects of the quasi-static behavior of flywheel rotors still need to be studied closely, and the rotors require a stable and highly efficient supporting system such as high temperature superconductor (HTS) bearings, which offer dynamic stability without the use of active control. Quasi-static properties of HTS bearings in the radial direction provide data to solve problems which may occur in a running system. Since stiffness in countering rotor vibration is the main parameter for designing an HTS bearing system, we investigated the quasi-static properties of the magnetic force between permanent magnets(PMs) and HTS bulks in the radial direction. We measured radial stiffness, and discovered that bearing stiffness varied greatly depending on the number of active HTS bulks. This is valuable data for predicting the change in stiffness during partial HTS bearing failure. The quasi-static test results are used for optimal design and performance prediction for the 100 kWh class superconductor bearing.

A Study on Residual Strength of Carbon/Epoxy Face Sheet and Honeycomb Core Sandwich Composite Structure after Quasi Static Indentation Damage (탄소섬유/에폭시 면재, 알루미늄 허니컴 코어 샌드위치 복합재 구조의 압입 손상에 의한 잔류강도 연구)

  • Kong, Chang-Duk;Park, Hyun-Bum;Lee, Seoung-Hyun
    • Composites Research
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    • v.22 no.2
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    • pp.24-29
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    • 2009
  • This study aims to investigate the residual strength of sandwich composites with Al honeycomb core and carbon fiber face sheets after the quasi-static indentation damage by the experimental investigation. The 3-point bending test and the edge-wise compressive strength test were used to find the mechanical properties, and the quasi-static point load was applied to introduce the simulated damage on the specimen. The damaged specimens were finally assessed by the 3-point bending test and the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the quasi-static indentation. The both test results showed that the residual strength of the damaged specimen was decreased according to increases of the damaged depth.

QUASI-STATIC THERMOELASTIC PROBLEM OF AN INFINITELY LONG CIRCULAR CYLINDER

  • Gaikwad, Kishor R.;Ghadle, Kirtiwant P.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.14 no.3
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    • pp.141-149
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    • 2010
  • The aim of this work is to determine the quasi-static thermal stresses of an infinitely long circular cylinder having constant initial temperature under steady-state field. The arbitrary heat flux is applied on the lower surface and the upper surface of the cylinder is at initial temperature. The fixed circular edge is thermally insulated. The results are obtained in series form in terms of Bessel's functions. These have been computed numerically and illustrated graphically.

The Analysis of SAW IDT Characteristics Using Quasi-Static Approximation (준정근사계산법을 이용한 탄성표면파 변환기의 특성 해석)

  • 이동도;정영지;이재경;황금찬
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.30A no.11
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    • pp.88-98
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    • 1993
  • In this paper, the effective permittivity in the piezoelectric material is numerically obtained and greens function is derived from that. It is shown that the admittance and the transfer function of an interdigital transducer is represented by electrostatic charge distribution using Quasi-static approximation. To prove the validity of the quasi-static approximation, numerical results for the uniform IDT of a filter mounted on 128 $^{\circ}$ rotated Y-cut X-propagating Lithium Niobate are compared with the measured ones.

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Boundary element characterization of coplanar waveguide discontinuities by quasi-static approximation (Quasi-static 근사에 의한 코플래너 도파로 불연속의 경계요소 해석)

  • 강연덕;이택경
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.34D no.6
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    • pp.1-10
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    • 1997
  • By using the boundary element method, the cahracterization and the circuit modelling of the coplanar waveguide (CPW) discontinuities are performed bvia quasi-static approximation. The capacitive equivalent circuits are obtained by developing the 3-D boundary element method with collocation method. On the triangular patch, the numerical scheme employed the linear basis functions and the analytic solutions of the integrals on the singular points. The capacitive discontinuities of gaps, end-gaps, and open-ends are characterized and the results compared with the conductor backed coplanar waveguides.

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