• Structural Engineering and Mechanics
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• v.43 no.4
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• pp.449-458
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• 2012

Finite element buckling analysis of insulated transition flue ducts is carried out to determine the critical buckling load multipliers when subjected to axial compression for design process. Through this investigation, the results of numerical computations to examine the buckling strength for different possible duct shapes (cylinder, and circular-to-square) are presented. The load multipliers are determined through detailed buckling analysis taking into account the effects of geometrical construction and duct plate thickness which have great influence on the buckling load. Enhancement in the buckling capacity of such ducts by the addition of horizontal and vertical stiffeners is also investigated. Several models with varying dimensions and plate thicknesses are examined to obtain the linear buckling capacities against duct dimensions. The percentage improvement in the buckling capacity due to the addition of vertical stiffeners and horizontal Stiffeners is shown to be as high as three times for some cases. The study suggests that the best location of the horizontal stiffener is at 0.25 of duct depth from the bottom to achieve the maximum buckling capacity. A design equation estimating the buckling strength of geometrically perfect cylindrical-to-square shell is developed by using regression analysis accurately with approximately 4% errors.

• Journal of Communications and Networks
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• v.11 no.1
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• pp.42-46
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• 2009

Superimposed training (SIT) design for estimating of time-varying multipath channels is investigated for mobile orthogonal frequency division multiplexing (OFDM) systems. The design of optimum SIT consists of two parts: The optimal SIT sequence is derived by minimizing the channel estimates' mean square error (MSE); the optimal power allocation between training and information data is developed by maximizing the averaged signal to interference plus noise ratio (SINR) under the condition of equal powered paths. The theoretical analysis is verified by simulations. For the metric of the averaged SINR against signal to noise ratio (SNR), the theoretical result matches the simulation result perfectly. In contrast to an interpolated frequency-multiplexing training (FMT) scheme or an SIT scheme with random pilot sequence, the SIT scheme with proposed optimal sequence achieves higher SINR. The analytical solution of the optimal power allocation is demonstrated by the simulation as well.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.270-273
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• 2003

The design, fabrication, and measured result of a 4.7 GHz differential VCO (Voltage Controlled Oscillator) for a 5.2 GHz WLAN (Wireless Local Area Network) applications is presented. The circuit is designed in a 0.35 mm technology employing three metal layers. The design is based on a fully integrated LC tank using spiral inductors. Measured tuning range is 10% of oscillation frequency with a control voltage from 0 to 3.0 V. Oscillation power of $\square$ 2.3 dBm at 4.63 GHz is measured with 21 mA DC current at 3V supply. The phase noise is $\square$ 104.17 dBc/Hz at 1 MHz offset.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.415-420
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• 2009

Selective Catalytic Reduction(SCR) has been used for the reduction of $NO_x$ in a steam supply boiler. Recently, the reduction of $NO_x$ becomes an important research field because of its negative effect on an environment. Shape optimization of circular poles installed in the chamber, which is located in upstream of a SCR, has been performed using response surface method and three-dimensional Navier-Stokes analysis to enhance gas flow uniformity. Three design parameters, diameter, arranging angle and stretching ratio of circular poles, are considered in the present study. Throughout the shape optimization of a circular pole, gas flow uniformity is successfully increased by decreasing local recirculation flow in a square duct chamber. Recirculation flow observed in the corner of the square duct can be reduced by proper installation of a guide vane or a blunt body. Detailed flow characteristics are also analyzed and discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.19-24
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• 1997

The weld line location and the weld line movement in stamping with laser-tailor welded blanks(TWB) were investigated through square cup deep drawing tests. The step blank holder was introduced to form TWB of different thicknesses without wrinkling, and the non-uniform blank holding force(BHF) was enforced to control weld line movement. Test results of the blanks with shifted weld lines showed that the large portion of the thinner area could result in a large weld line movement. Careful selection of the weld line location and the BHF control should be adapted in TWB design to avoid failures and to ensure its formability.

• Wind and Structures
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• v.16 no.3
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• pp.241-248
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• 2013

The wind turbine blade is a very important part of the rotor. Extraction of energy from wind depends on the design of blade. In this work, the analysis is done on a blade of length 38.95 m which is designed for V82-1.65 MW horizontal axis wind turbine (supplied by Vestas). The airfoil taken for the blade is NACA 634-221 which is same from root to tip. The analysis of designed blade is done in flap-wise loading. Two shapes of the spar are taken, one of them is of square shape and the other one is combination of square and cross shape. The blade and spar are of the same composite material. The Finite element analysis of designed blade is done in ANSYS. This work is focused on the two segments of blade, root segment and transition segment. Result obtained from ANSYS is compared with the experimental work.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.753-758
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• 2000

Heat engine and fluid machinery in the plant have to linked with various ducts network and the corresponding design have to be concerned about effectiveness and stability of system of plant. To optimum control and design system concerning stability, economization, operating effectiveness we have to exact analysis flow properties of a duct applying to fluid machinery, heat exchanger, cooling machine, air conditioning equipment. therefore, it is necessary to research the duct, heat transfer equipment, for increasing overall effectiveness of air conditioning system by suggesting basic data of the duct resulting from organic research. So we can contribute to technical development of the duct. In case of speeding up the flow rate of the duct, lots of wave velocity components are occurred the value of boundary layer resulting from developing the boundary layer at both walls of duct.

• Design & Manufacturing
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• v.2 no.1
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• pp.1-5
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• 2008

Restriking method is to add to process in order to get the correct size and high precision accuracy of product which is formed in pre-process. This method is widely used at bending work and drawing work. Restriking die is particularly design and used as restriking process is performed. Therefore, production cost is increasing as one process or a two process are added. In this paper, punches and die block of square shell drawing die which could be performed drawing work and restriking process by using only one die are designed in order to solve these factors. The structure of sectional die which can integrate drawing die and restriking die was developed.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.95-99
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• 2008

Applications of composite materials in various engineering fields have been extended significantly. For being useful composite materials, we could modify the rigidity and strength characteristics of composite material according to structures and material direction. In this study, CFRP, which has been widely used in space leisure and general structural applications due to the weight, elasticity coefficient, high fatigue strength and lower thermal transformation ect, was selected. As the CFRP is an anisotropic material whose mechanical properties change with its stacking sequence or angle, special attention was given to the effects of the fiber orientation angle on the bending characteristics of CFRP fiat and CFEP square members. It's different on the each result of strength and rigidity of CFRP flat and CFRP square members.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.169-173
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• 2011

Crash box is introduced to vehicle design to improve the impact performance and reduce the damage of vehicle body at impact speed. The crash box behind bumper can absorb impact energy effectively to improve vehicle safety. Repair cost at collision accident can be cut down by use of this box. The configuration of car body must be designed by considering the characteristic of material due to the deformation of car body happened at impact. Many papers have been published about material of crash box all over the world. The study of crash box with tube expansion type has been going on Korea. This study is done by the simulation analysis about front collisions against 5 kinds of aluminum crash boxes with the basic structure of square section.