• 제목/요약/키워드: approximate frequency

검색결과 287건 처리시간 0.023초

A Numerically Efficient Full Wave Analysis of Circular Resonators Microbandes Stacked Involving Multimetallisations

  • Chebbara, F.;Fortaki, T.
    • Journal of Electrical Engineering and Technology
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    • 제10권1호
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    • pp.314-319
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    • 2015
  • The conventional geometry of a plate microstrip resonator is made up of a single metallic patch, which is printed on a monolayer dielectric substrate. Its arrangement is simple and easy to make, but it is limited in its functional abilities. Many searches have been realized to improve the bandwidth and the gain of the microstrip resonators. Among the various configurations proposed in the open literature, the stacked geometry seems to be very promising. By appropriate design, it is able to provide the operation in dual frequency mode, wide bandwidth enough and high gain. The theoretical investigations of structures composed of two stacked anti-reflection coatings, enhanced metallic coatings are available in the literature, however, for the stacked configurations involving three metallic coatings or more, not to exact or approximate analysis was conducted due to the complexity of the structure.

반해석적 방법에 의한 작은 변위를 가지는 얇은판의 자유진동해석 (Free Vibration of a Thin Plate with Small Deflections by Semi-Analytical Approach)

  • 최덕기
    • 대한기계학회논문집
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    • 제18권8호
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    • pp.1967-1973
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    • 1994
  • The free vibration of a thin plate with three different boundary conditions is discussed in this paper. A semi-analytical approach to the plate problems has been exploited using computer algebra system(CAS). The approximate solutions are assumed as algebraic polynomials that satisfy the appropriate boundary conditions. In order to solve problems, Galerkin method is used, which is known as an ineffective tool for practical engineering problems, being involved with a large number of multiple integration and differentiation. All the admissible functions used in this paper are generated automatically by CAS otherwise a tedious algebraic manipulations should be done by hand. One, six and fifteen-term solutions in terms of frequency parameters are presented and compared with exact solutions. Even using one-term solution, the comparison with existing data shows good agreement and accuracy of the present method.

구조특성확인기법에 의한 PC교의 내하력평가 (Load Carrying Capacity Evaluation of Composite PC Girder Bridges Based on the System Identification)

  • 김기대
    • 한국산업융합학회 논문집
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    • 제8권4호
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    • pp.205-212
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    • 2005
  • This paper presents the application of system identification approaches for the load carrying capacity evaluation of composite PCI girder bridges based on the result of field test. For these problems, the moment of inertia of cross-sectional area and the natural frequency of bridge were used as structural parameters, the SAP2000 program for the structural analysis and the SLP method for the minimum error. As a result, it is found that the proposed algorithm for this study appears applicable to real structures with reasonable complexity. It is shown that the introduction of approximate quadratic equations is more realistic and timesaving than the common methods.

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유압 제어계에서 서보밸브 모델링을 위한 새로운 선형화 방정식의 제안 (A New Linearized Equation for Modelling a Servovalve in Hydraulic Control Systems)

  • 김태형;이일영
    • 대한기계학회논문집A
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    • 제27권5호
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    • pp.789-797
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    • 2003
  • In the procedure of the hydraulic control system design, a linearized approximate equation described by the first order terms of Taylor series has been widely used. Such a linearized equation is effective just near the operating point, However, pressure and flowrate in actual hydraulic systems are usually not confined near an operating point. This study suggests a new linearized flow equation for a servovalve as a modified form of the conventional linearized flow equation. Subsequently, a procedure to determine effective operating point for the new linearized equation is proposed. From the evaluations of time responses and frequency responses obtained from simulations for a hydraulic control system, the effectiveness of the new linearized equation and the procedure to determine effective operating point is confirmed.

닻의 해저 충격력과 파주깊이에 관한 연구 (A Study on the Anchor′s Strike and Penetrating Depth)

  • 강성진;김동수;김창제
    • 해양환경안전학회지
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    • 제6권1호
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    • pp.77-83
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    • 2000
  • En coastal area, many submarine facilities such as pipes and cables are installed on/under the sea bed. Also, there are heavy traffic due to numerous vessels which call in ports or navigate passages in adjacent water. Therefore, the frequency of dropping anchors will be increased to avoid various dangerous situations. When an anchor is dropped from vessel on the sea bed, the anchor strikes on the sea bed, and then, the anchor penetrates to certain depth into the sea bed. In this case, sometimes submarine facilities on/under the sea bed may be damaged by the strike or the maximum penetrating depth of anchor. In this paper, some approximate equations on the strike and the penetrating depth of anchors have been derived on the basis of actual data, and the results are expected to use as basic design data of related facilities.

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Measurement and Explanation of DC/RF Power Loci of an Active Patch Antenna

  • Mcewan, Neil J.;Ali, Nazar T.;Mezher, Kahtan A.;El-Khazmi, Elmahdi A.;Abd-Alhameed, Raed A.
    • ETRI Journal
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    • 제33권1호
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    • pp.6-12
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    • 2011
  • A case study of an active transmitting patch antenna revealed a characteristic loop locus of DC power versus RF output power as drive frequency was varied, with an operational bandwidth substantially smaller than the impedance bandwidth of the radiator. An approximate simulation technique, based on separation of the output capacitance of the power transistor, yielded easily visualized plots of power dependence on internal load impedance, and a simple interpretation of the experimental results in terms of a near-resonance condition between the output capacitance and output packaging inductance.

유연보의 과도 진동 감쇠를 위한 점탄성 재료의 최적 분포 (Optimal Distribution of Viscoelastic Material for Transient Vibration Suppression of a Flexible Beam)

  • 김태우;김지환
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2002년도 추계학술대회논문집
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    • pp.605-610
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    • 2002
  • Eigenvalues are taken as performance criteria for structural damping design using viscoelastic material. Given material properties, optimal distribution of damping material is sought based on eigenvalue sensitivity. For eigenanalysis of frequency dependent viscoelastic material treated structures, Golla-Mushes-McTavish (GHM) model is used and some dominant modes are chosen for consideration. To avoid the intensity of computation caused by increased problem size, an alternative approximate method is proposed which uses elastic modes and can be applied under small damping assumption. A cantilever beam treated with unconstrained viscoelastic layer is tested and optimal distribution of thickness of the layer is illustrated. Partial coverage configurations are compared with the one-sided full coverage case.

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외부 음향과 구조의 연동 현상 고려한 근사 모델 (Approximation Models for Structure-External Acoustic Interaction)

  • 이문석;박윤식;박영진;박광춘
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2007년도 춘계학술대회논문집
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    • pp.1191-1195
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    • 2007
  • Many approximate models for interaction between a flexible structure and an infinite external acoustic medium have been developed for a long time. Among them, Doubly Asymptotic Approximations (DAAs) are very well known approximations. But, it has shortcomings in intermediate frequency range and can't fully describe the acoustic medium. So, this paper presents the modified approximation by applying the retarded and advanced potentials to Kirchhoff's formula. It describes the external acoustic medium more in detail and shows a good result in early time transient responses when it was applied to a spherical shell. Through a spherical shell interacting with external acoustic medium, the transient responses for the proposed model is compared to Huang's exact solution and DAA2.

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압력파동에 대한 고체추진제의 연소응답함수 측정 및 응용 (Measurement and Application of Pressure-Coupled Combustion Response of Solid Propellant with T-Burner)

  • 이길용;임지환;윤웅섭;유지창
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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    • pp.268-271
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    • 2006
  • 고체추진 로켓엔진의 자발성 음향불안정 특성 예측 및 평가를 위해 대상 고체추진제의 연소응답함수를 측정하였다. Pulsed DB/AB 방법에 기초한 T-버너 실험을 통해 특정 주파수에서의 연소응답함수를 구하였다. 연소응답함수 계산식은 근사해석법에 기초한 연소불안정 이론으로부터 유도 적용하였다. 추진제 동시점화 및 시편 동시점화 등 연소응답의 측정에 관련된 문제들에 대해 해결방안을 제시하였다.

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Effect of road surface roughness on the response of a moving vehicle for identification of bridge frequencies

  • Yang, Y.B.;Li, Y.C.;Chang, K.C.
    • Interaction and multiscale mechanics
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    • 제5권4호
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    • pp.347-368
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    • 2012
  • Measuring the bridge frequencies indirectly from an instrumented test vehicle is a potentially powerful technique for its mobility and economy, compared with the conventional direct technique that requires vibration sensors to be installed on the bridge. However, road surface roughness may pollute the vehicle spectrum and render the bridge frequencies unidentifiable. The objective of this paper is to study such an effect. First, a numerical simulation is conducted using the vehicle-bridge interaction element to demonstrate how the surface roughness affects the vehicle response. Then, an approximate theory in closed form is presented, for physically interpreting the role and range of influence of surface roughness on the identification of bridge frequencies. The latter is then expanded to include the action of an accompanying vehicle. Finally, measures are proposed for reducing the roughness effect, while enhancing the identifiability of bridge frequencies from the passing vehicle response.