• Wind and Structures
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• 제12권5호
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• pp.457-474
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• 2009

Techniques for stabilising slender bridges under wind loads are presented in this article. A mathematically consistent description of the acting aerodynamic forces is essential when investigating these ideas. Against this background, motion-induced aerodynamic forces are characterised using a linear time-invariant transfer element in terms of rational functions. With the help of these functions, the aeroelastic system can be described in the form of a linear, time-invariant state-space model. It is shown that the divergence wind speed constitutes an upper bound for the application of the selected mechanical actuators. Even active control with full state feedback cannot overcome this limitation. The results are derived and explained with methods of control theory.

• Structural Engineering and Mechanics
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• 제40권3호
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• pp.335-346
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• 2011

This paper deals with the bifurcations of non-semi-simple eigenvalues at critical point of Hopf bifurcation to understand the dynamic behavior of the system. By using the Puiseux expansion, the expression of the bifurcation of non-semi-simple eigenvalues and the corresponding topological structure in the parameter space are obtained. The zero-order approximate solutions in the vicinity of the critical points at which the multiple Hopf bifurcation may occur are developed. A numerical example, the flutter problem of an airfoil in simplified model, is given to illustrate the application of the proposed method.

• Wind and Structures
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• 제14권2호
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• pp.133-151
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• 2011

For a detailed investigation of the dynamic behaviour of slender bridges under wind action especially the motion-induced fluid forces should be available not only for harmonic motions but also for more general ones. If linear transfer behaviour is assumed, the force-displacement relation for almost arbitrary motions can be handled in the frequency domain using aerodynamic transfer functions. In aerospace engineering as well as in bridge engineering, these functions are usually approximated by special kinds of complex-valued rational functions which depend on complex frequencies. The quality of this approximation is evaluated for several bridge cross sections in this article. It is shown that rational functions are for some sections scarcely suitable to realistically represent the transfer behaviour of motion-induced aerodynamic forces for arbitrarily complex frequencies.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.201-204
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• 1995

In this study, we proposed an algorithm for P-wave detection. It is essential to decide the existence of P-wave and to extract some parameter about P-wave in automated ECG interpreter. Especially this paper describes the detection and estimation of three case, artrial flutter, coupled and non-coupled, which are very crucial things in ECG diagnosis. The performance of algorithm is showed by applying it to CSE(Common Standards for Quantative Electrocardiography) database.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.113-116
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• 2006

In this paper, the fairing effects on the aerodynamics stability of basic plate-girder sections are investigated trough wind tunnel tests. As basis sections, two types of $\pi$-type shape sections with aspect ratios(D/B) of 1/5 and 1/10 are employed as the basic sections. And three types of triangular fairings are applied such as right-angled triangle(F1), inverted right-angled triangle(F2) and regular triangle(F3). The effects of attack angle on the dynamic response of each section are also investigated. As the results of experiments, fairings F2 is most effective to suppress flutter phenomenon or vortex induced vibration among three types of fairings.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.377-380
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• 2000

The collapsible phenomena of the circular tubes due to the excessive transmural pressure are investigated experimentally. Collapsible tubes are installed in the test section where the external pressure is applied to the test tubes by applying the hydrostatic head. The collapsible circular tubes are made of rubber, whose diameters are 6 and 4.2 mm, respectively. The hydrostatic water head of the upper reservoir is applied to the test section. Pressures at the upstream and downstream sides are measured by the pressure transducers. The collapsible phenomena are observed as the transmural pressure Increases, and also the flutter phenomenon occurs due to the critical transmural pressure.

• 대한기계학회논문집
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• 제19권3호
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• pp.615-622
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• 1995

It may be inefficient to conduct the aeroelastic analysis by using full-scale conventional finite-element analyses or experiments, from the initial design phase, for an aircraft wing which can be considered as the discontinuum complex structure with composite laminated skins. In this paper, therefore more efficient aeroelastic analysis has been conducted for a box-beam typed aircraft wing by using the equivalent continuum beam-rod model which is derived from the concept of energy equivalence. Equivalent structural properties of the continuum beam-rod model are obtained from the direct comparison of the finite-element matrices of continuum beam-rod model with those of box-beam typed aircraft wing. Numerical results by the continuum beam-rod model approach are compared with those by the conventional finite-element analysis approach to show that the continuum beam-rod model proposed herein is quite satisfactory as a simplified model of aircraft wing structure for aeroelastic analyses.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1653-1660
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• 2003

The use of frequency-dependent spectral element matrix (or exact dynamic stiffness matrix) in structural dynamics is known to provide very accurate solutions, while reducing the number of degrees-of-freedom to resolve the computational and cost problems. Thus, in the present paper, the spectral element model is formulated for the axially moving Timoshenko beam under a uniform axial tension. The high accuracy of the present spectral element is then verified by comparing its solutions with the conventional finite element solutions and exact analytical solutions. The effects of the moving speed and axial tension on the vibration characteristics, the dispersion relation, and the stability of a moving Timoshenko beam are investigated, analytically and numerically.

• 생약학회지
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• 제19권3호
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• pp.208-215
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• 1988

To investigate the experimental effects of Chunwangboshimdan which have been widely used for aterial or auricular flutter, neurosis, insomnia and disease caused by cardiac malfunction, we have done the effects on the central nervous and cardiovascular system. The result as follow; It inhibited the convulsion induced by caffeine, the writhing syndrome induced by acetic acid and the spontaneous movement. Furthermore it prolonged the sleeping time induced by thiopental-Na in mice. It also showed the negative inotropic action on the isolated heart of frog, the vasodilative action as to peripheral bloods of rabbit ear and the hypotensive action in the anesthetized rabbit.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.675-680
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• 2001

In this study, a fluid/structure coupled analysis system using computational fluid dynamics and computational structural dynamics has been developed. The unsteady flow fields are predicted using unstructured Euler code. Coupled time-integration method (CTIM) was applied to computer simulation of the flow-induced vibration phenomena. To investigate the interaction effect of shock motions, 2-DOF airfoil systems have been studied in the subsonic and transonic flow region. Also, aeroelastic analyses for the airfoil with an arbitrary object are performed to show the analysis capability and interference effects for the complex geometries. The present results show the flutter stabilities and characteristics of aeroelastic responses with moving shock effects.