• 한국군사과학기술학회지
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• 제10권4호
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• pp.138-144
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• 2007

This paper introduces the design techniques of an IR module using the 2-D array un-cooled type infrared detector which is applied to the individual combat weapon. Considering the size and weight of the hand carried weapon system, we used a very small-sized detector and applied an adaptive temperature control algorithm so that the operation consumed with low power can be possible. We applied the AR(Auto Regressive) filter to improve the signal-to-noise ratio in a thermal image processing step. We also applied the plateau equalization and boundary enhancement techniques to improve the visibility for human visual system.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.140-148
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• 1993

When a large automobile sheet metal part is formed in a draw die, the binder wrap is first calculated to predict the initial punch contact location for avoiding wrinkles and severe stretching of its thin blank sheet. Since the boundary of a pseudo blank in calculating a binder wrap by means of a geometrically nonlinear finite element method is unknown in advance, an iteration method is generally used. This paper presents an effective iteration method for correction of the pseudo blank in a binder wrap calculation. For the performance test, two examples are adopted. The calculated results for both examples show the good convergence which wasted solutions are obtained in the second iteration step.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권1호
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• pp.31-40
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• 2009

In the present work transformation of dimensionless heat diffusion equation for the solution of moving boundary problems have been formulated. The formulation is based on 1-D, 2-D and 3-D, unsteady heat diffusion equations. These equations are rst turned int dimensionless form by using dimensionless quantities and their transformation was formulated in liquid and solid phases. The salient feature of this work is that during the transformation of dimensionless heat diffusion equation there arises a convective term $\tilde{v}$ which is responsible for the motion of interface in liquid as well as solid phase. In the transformed heat equation, a correction factor $\beta$ also arises naturally which gives the correct transformed flux at interface.

• Wind and Structures
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• 제23권6호
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• pp.543-558
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• 2016

The response of functionally graded ceramic-metal plates is investigated using theoretical formulation, Navier's solutions, and a new displacement based on the high-order shear deformation theory are presented for static analysis of functionally graded plates. The theory accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The plates are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. Numerical results of the new refined plate theory are presented to show the effect of the material distribution on the deflections, stresses and fundamental frequencies. It can be concluded that the proposed theory is accurate and simple in solving the static and free vibration behavior of functionally graded plates.

• Earthquakes and Structures
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• 제19권2호
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• pp.91-101
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• 2020

This work presents an efficient and original hyperbolic shear deformation theory for the bending and dynamic behavior of functionally graded (FG) beams resting on Winkler - Pasternak foundations. The theory accounts for hyperbolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. Based on the present theory, the equations of motion are derived from Hamilton's principle. Navier type analytical solutions are obtained for the bending and vibration problems. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions. It can be concluded that the present theory is not only accurate but also simple in predicting the bending and vibration behavior of functionally graded beams.

• Steel and Composite Structures
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• 제19권4호
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• pp.829-841
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• 2015

In this paper, a refined exponential shear deformation beam theory is developed for bending analysis of functionally graded beams. The theory account for parabolic variation of transverse shear strain through the depth of the beam and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. Contrary to the others refined theories elaborated, where the stretching effect is neglected, in the current investigation this so-called "stretching effect" is taken into consideration. The material properties of the functionally graded beam are assumed to vary according to power law distribution of the volume fraction of the constituents. Based on the present shear deformation beam theory, the equilibrium equations are derived from the principle of virtual displacements. Analytical solutions for static are obtained. Numerical examples are presented to verify the accuracy of the present theory.

• Structural Engineering and Mechanics
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• 제66권6호
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• pp.693-701
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• 2018

This paper develops a nonlocal strain gradient plate model for vibration analysis of graphene sheets under thermal environments. For more accurate analysis of graphene sheets, the proposed theory contains two scale parameters related to the nonlocal and strain gradient effects. Graphene sheet is modeled via a two-variable shear deformation plate theory needless of shear correction factors. Governing equations of a nonlocal strain gradient graphene sheet on elastic substrate are derived via Hamilton's principle. Differential quadrature method (DQM) is implemented to solve the governing equations for different boundary conditions. Effects of different factors such as temperature rise, nonlocal parameter, length scale parameter, elastic foundation and aspect ratio on vibration characteristics a graphene sheets are studied. It is seen that vibration frequencies and critical buckling temperatures become larger and smaller with increase of strain gradient and nonlocal parameter, respectively.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.780-785
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• 1987

The measuring point data of clay model are widely used to design parts whose external features are important design factor such as automobiles and general die products. This paper presents a method for improving the process to generate smooth surfaces from the measuring point data using turnkey CAD/CAM system. The process of smooth-surface generation involves several steps: styline finding, curve fairing, surface generation and filleting. The process is improved by automatic curve fairing, local correction of surface and multi-boundary surface treatment. An automobile bumper and a telephone receiver are measured and modeled to test the new method. Significant time saving is resulted by changing interactive mode to automatic mode and eliminating inefficient loop of surface generation process.

• 전자공학회논문지S
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• 제34S권11호
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• pp.16-24
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• 1997

In order to prevent the presence of the residual phase difference at the discriminator output by the existing AFC techniques, we propose a new automatic frequency control(AFC) tracking algorithm for QPSK demodulation at the digital direct broadcasting satellite(DBS) receiver, which we call a rotational decision-directed AFC(RDDAFC). The RDDAFC rotates the decision boundary for the kth received symbol by the frequency deterctor output of the (k-1)th received symbol. Tracking performances of carrier frequency offset by the proposed RDDAFC algorithm are evaluated through computer simulations under the practical DBS channel conditions with a carrier frequency offset of 2.3MHz when S/N equals 2dB. Test results show that the total pull-in time of the RDDAFC is 1.697msec for 10$^{-3}$ SER before forwared error correction at the receiver.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.475-480
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• 2001

The flowfield of transverse jet in a supersonic air stream subjected to shock wave turbulent boundary layer interactions is simulated numerically by Generalized Taylor Galerkin(GTG) finite element methods. Effects of turbulence are taken into account with a two-equation $(k-\varepsilon)$ model with a compressibility correction. Injection pressures and slot widths are varied in the present study. Pressure, separation extents, and penetration heights are compared with experimental data. Favorable comparisons with experimental measurements are demonstrated.