• Structural Engineering and Mechanics
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• v.38 no.5
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• pp.549-571
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• 2011

This paper presents analytical solutions for skewed thick plates under transverse loading that have previously been unreported in the literature. The thick plate solution is obtained in a framework of an oblique coordinate system. The governing equation is first derived in the oblique coordinate system, and the solution is obtained using deflection and rotation as partial derivatives of a potential function developed in this research. The solution technique is applied to three illustrative application examples, and the results are compared with numerical solutions in the literature and those derived from the commercial finite element analysis package ANSYS 11. These results are in excellent agreement. The present solution may also be used to model skewed structures such as skewed bridges, to facilitate efficient routine design or evaluation analyses, and to form special elements for finite element analysis. At the same time, the analytical solution developed in this research could be used to develop methods to address post-buckling and dynamic problems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5522-5540
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• 2018

Vehicular license plate (LP) recognition system has risen as a significant field of research recently because various explorations are currently being conducted by the researchers to cope with the challenges of LPs which include different illumination and angular situations. This research focused on restricted conditions such as using image of only one vehicle, stationary background, no angular adjustment of the skewed images. A real time vehicular LP recognition scheme is proposed for the skewed images for detection, segmentation and recognition of LP. In this research, a polar co-ordinate transformation procedure is implemented to adjust the skewed vehicular images. Besides that, window scanning procedure is utilized for the candidate localization that is based on the texture characteristics of the image. Then, connected component analysis (CCA) is implemented to the binary image for character segmentation where the pixels get connected in an eight-point neighbourhood process. Finally, optical character recognition is implemented for the recognition of the characters. For measuring the performance of this experiment, 300 skewed images of different illumination conditions with various tilt angles have been tested. The results show that proposed method able to achieve accuracy of 96.3% in localizing, 95.4% in segmenting and 94.2% in recognizing the LPs with an average localization time of 0.52s.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.815-826
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• 1994

Skew bridges are found frequently in new bridge construction due to geographical conditions when new constructing bridges are put across the existing highways, railroads or rivers. This study is to investigate the static behaviors of the steel deck plates of skew bridges which are increasingly used in bridges due to outstanding quality of structural steels, development of welding techniques, in order to reduce dead loads and period of constructions. The static behaviours of steel deck plates are analyzed using general purpose FE code SAP90 by modeling the skewed deck plates with rigorous finite elements, as the skew angles vary. The results of finite element analysis for the behaviors of steel deck plates and concrete slabs in acute, obtuse corners and center of decks are compared and discussed as the skew angles vary from $90^{\circ}$ to $30^{\circ}$. Two types of decks are treated, as isotropic plates and orthotropic plates, respectively. From the results of finite element analysis, it is found that more moments, reactions, and deflections occur at the obtuse corners than at the center of skewed decks regardless of isotropy or orthotropy. Especially, in case of the skewed deck plates with skew angles less than 45 degrees, significantly large discrepancies for the values of those internal forces are shown between the skewed and right deck plates. This study estimates the characteristics of deck behaviors according to skew angles, and proposes limitations of skew angles and the ciritical regions of decks.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.243-252
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• 1992

A mixed convection heat transfer from two vertical parallel plates has been studied numerically by the finite difference method. Effects of the Grashof number, the relative length, $L_2/L_1$. the dimensionless temperature ratio, ${\Phi}_2/{\Phi}_1$ and the dimensionless plate spacing, $b/L_1$ are examined for the heat transfer. Independent of the Grashof numbers and $L_2/L_1$, the dimensionless vertical velocity distributions skewed on the left plate as ${\Phi}_2/{\Phi}_1$ decreased. The dimensionless vertical velocity distribution for $Gr/Re^2=1$ and ${\Phi}_2/{\Phi}_1=1.0$ is skewed to the right plate $L_2/L_1=0.5$, symmetric at $L_2/L_1=1.0$ and skewed to the left plate at $L_2/L_1=1.5$. But for $Gr/Re_2=10.0$ and ${\Phi}_2/{\Phi}_1=1.0$ reversed velocity patterns are obtained. Regardless of the Grashof numbers and $L_2/L_1$, the mean Nusselt nembers on the inside surface of the left plate decreases and those of the right inside surface increases as ${\Phi}_2/{\Phi}_1$ increases. Temperature, velocity and mean Nusselt number distributions are apparently not affected by $L_2/L_1$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.1-7
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• 1995

The problem of amplitude-and frequency-modulated waveforms is analyzed when a linearly polarized electromagnetic wave is scattered by a slowly rotating rotor with metal plates. ECM in conjunction with a quasi-stationary method is used to analyze the modulated waveforms. The modulated waveforms depend on the orientation and dimension of the object. its rotation speed, and very strongly on the incident and scattering directions. The modulate waveforms of a rotating non-skewed metal plate and a rotor with two blades are functions of twice the rotating frequency of those. Similar results are discussed for a rotating skewed metal plate, but the modulated waveforms is a function of the rotating frequency. Numerical results based on our ECM are presented and compared with those of Sikta's and PO solution.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.363-374
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• 2000

An accurate method is presented for vibrations of rhombic plates having three different combinations of clamped, simply supported, and free edge conditions. A specific feature here is that the analysis explicitly considers the moment singularities that occur in the two opposite corners having obtuse angles of the rhombic plates. Stationary conditions of single-field Lagrangian functional are derived using the Ritz method. Convergence studies of frequencies show that the corner functions accelerate the convergence rate of solutions. In this paper, accurate frequencies and normalized contours of the vibratory transverse displacement are presented for highly skewed rhombic plates, so that a significant effect of corner stress singularities nay be understood.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.241-245
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• 2004

An analytical study was conducted to characterize the fatigue crack growth behavior of pre-cracked aluminum plates repaired with asymmetric bonded composite patch. For single-sided repairs, due to the asymmetry and the presence of out-of-plane bending, crack front shape would become skewed curvilinear started from a uniform through-crack profile, as observed from previous studies. In this study, the fatigue analysis of single-sided repairs considering crack front shape development was conducted by implementing three-dimensional successive finite element method coupled with linear elastic fracture mechanics (LEFM) concept, which enables the growing crack front to be directly traced and modeled in a step by step way. Through conducting present analysis technique, crack path of the patched plate as well as the fatigue life was evaluated with sufficient accuracy. The analytical predictions of both the crack front shape evolution and the fatigue life were in good agreement with the experimental observations.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.1
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• pp.1-7
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• 2013

The high-skewed and/or composite propellers of current interests to reduce the ship vibration and to increase the acoustic performance are likely to be exposed to the unexpected structural problems. One typical example is that the added mass effect on the propellers working in the non-uniform wake field reduces the natural frequency of the propeller leading to the resonance with the low-frequency excitation of the external forces. To avoid this resonance problem during the design stage, the technique of fluid-structure interaction has been developed, but the higher-order effect of the blade geometry deformation is not yet considered in evaluating the added mass effects. In this paper the fluid boundary-value problem is formulated by the potential-based panel method in the inviscid fluid region with the velocity inflow due to the body deformation, and the structural response of the solid body under the hydrodynamic loading is solved by applying the finite element method which implements the 20-node iso-parametric element model. The fluid-structure problem is solved iteratively. A basic fluid-sturcture interaction study is performed with the simple rectangular plates of thin thickness with various planform submerged in the water of infinite extent. The computations show good correlation with the experimental results of Linholm, et al. (1965).

• Structural Engineering and Mechanics
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• v.17 no.1
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• pp.113-140
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• 2004

A mixed eight-node hexahedral element formulated via the Hu-Washizu principle as well as the field extrapolation technique is presented. The mixed element with only three translational degrees of freedom at each node can provide extremely accurate and reliable performance for popular benchmark problems such as spacial beams, plates, shells as well as general three-dimensional elasticity problems. Numerical calculations also show that when extremely skewed and coarse meshes and nearly incompressible materials are used, the proposed mixed element can still possess excellent behaviour. The mixed formulation starts with introduction of a parallelepiped domain associated with the given general eight-node hexahedral element. Then, the assumed strain field at the nodal level is constructed via the Hu-Washizu variational principle for that associated parallelepiped domain. Finally, the assumed strain field at the nodal level of the given hexahedral element is established by using the field extrapolation technique, and then by using the trilinear shape functions the assumed strain field of the whole element domain is obtained. All matrices involved in establishing the element stiffness matrix can be evaluated analytically and expressed explicitly; however, a 24 by 24 matrix has to be inverted to construct the displacement extrapolation matrix. The proposed hexahedral element satisfies the patch test as long as the element with a shape of parallelepiped.

• Composites Research
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• v.17 no.4
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• pp.68-73
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• 2004

An analytical study was conducted to characterize the fatigue crack growth behavior of pre-cracked aluminum plates repaired with asymmetric bonded composite patch. For single-sided repairs, due to the asymmetry and the presence of out-of$.$plane bending, crack front shape would become skewed curvilinear started from a uniform through-crack profile, as observed from Previous studies. Therefore, for the accurate investigation of fatigue behavior, it is necessary to predict the actual crack front evolution and take it into consideration in the analysis. In this study, the fatigue analysis of single-sided repairs considering crack front shape development was conducted by implementing three-dimensional successive finite element method coupled with linear elastic fracture mechanics (LEFM) concept, which enables the growing crack front to be directly traced and modeled in a step by step way. Through conducting present analysis technique, crack path of the patched plate as well as the fatigue life was evaluated with sufficient accuracy. The analytical predictions of both the crack front shape evolution and the fatigue life were in good agreement with the experimental observations.