• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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• pp.9-12
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• 2010

Conventional apartment building projects have favored wall slab structure for the ease of construction and economic viability. However, wall slab structure, consisting of bearing walls, makes remodeling a difficult challenge. In addition, as the amendment to the Building Act in November, 2005 incentivized easy-to-remodel Rahmen structure design for apartment building in terms of floor area ratio and the number of stories, were are seeing more use of PC construct method in apartment building projects gradually. However, PC construction method requires complex connections between beams and columns, making it difficult to install and remove formwork. Furthermore, it is not possible to reuse forms after removal, generating lots of construction wastes, and it is necessary to install new forms again when the size of connection changes in line with modification of column cross-section. Researchers in Korea and elsewhere in the world have focused on structural performance of connection in PC construction method, with little attention to alternative approaches to improving connection forms for PC construction method. Accordingly, this research aims to study an approach to improving connection forms for PC construction method.

• 한국공작기계학회논문집
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• 제15권2호
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• pp.51-58
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• 2006

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding qualify is 1600W of the laser power, 0.85m/min of welding speed and $4{\ell}/min$ of pressure for shielding gas.

• Journal of Advanced Marine Engineering and Technology
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• 제22권2호
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• pp.210-218
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• 1998

Experimental results for forced convection condensationof Refrigerant-22 and ternary Refrigerant-407c(HFC-32/125/134a 23/25/52 wt%) considered as a substitute R-22 inside horizontal micor-fin tubes are presented. The test section was horizontal double-tubed counterflow condenser with a length 4000 mm micro-fin tube having 9.53 mm OD., 0.2 mm fin height and 60 fins. The refrigerants R-22 and R-407c were cooled by a coolant circulated in a surrounding annulus. The range of parameters of mass velocity was varied from 102.1 to 301.0kg/($\textrm{m}^{2}.s$) with inlet quality 1.0. Both refrigerant R-22 and its alternative refrigerant R-407c were tested within the same range of parameters. At the given experimental conditions for R-22 and R-407c the pressure drops for R-407c were considerably higher than those for R-22 at micro-fin tubes. Over the mass velocity range tested the PF(penalty factor)was lower than the increasing ratio of heat transfer area by fins. Based on the data correlation was proposed for predicting the frictional pressure drops for R-22 and R-407c for a duration of condensation inside a horizontal micro-fin tube.

• 한국국방경영분석학회지
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• 제3권1호
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• pp.83-96
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• 1977

The combustion chamber and nozzle of an end burning, small spherical rocket is designed. A spherical external shape has a number of advantages such as fixed center-of-gravity and minimum aerodynamic precession torques during flight and a better mass distribution for gyro-stabilization as contrasted to a conventional ogive rocket shape. It is shown that the cross-sectional variation of the end burning solid propellant with length is an exponential geometry to provide a constant thrust-weight ratio of the rocket device during the propellant burning period, and that the factors which affect the attainment of the constant relationship of thrust to weight in the design are the initial propellant area, initial weight of the rocket and propellant density. The measurement of the transient thrust in the ground static test using black powder propellant supports the predicted results. A wind tunnel having a $30{\times}30{\times}75cm$ test section and Mach number 0.11 is constructed, and a simple balance-type device is designed for the measurement of the drag of a spinning sphere. The experimental results indicate that the. spinning has no effect on the magnitude of the drag up to the Reynolds number $3{\times}10^5$. Numerical computation of the flight trajectories for various launching angles is presented, and the gyro-stabilization of spinning sphere is discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.17-18
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• 2006

Laser welding of metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for metals with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the butt welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1400W of the laser power, 0.8m/min, 0.9m/min of welding speed and $4{\ell}$ in of pressure for shielding gas.

• 소음진동
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• 제9권5호
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• pp.975-983
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• 1999

This paper describes the dynamic characteristics of the joint structures in case of using the simplified beam model in the F. E. analysis. The modeling errors, when replace the shell with the beam, are investigated through F. E. normal modes analysis. Normal mode analysis were performed to obtain the natural frequencies of the L and T shaped joints with various type of channels. The results were analyzed to access the effects of the models on the accuracy of F.E. analysis by identifying the geometric factors which cause the error. The geometric factors considered are joint angle, channel length, thickness and area ratio of the hollow section to the filled one. The joint stiffness evaluation technique is developed in this study using normal modes analysis with Lumped Mass. With this method, the progressively improved results of F. E. analysis are obtained using the simplified beam model. The static and normal modes analysis are performed with the joint stiffness values obtained by the Kazunori Shimonkakis' virtual stiffness method and the proposed method and these simplified modeling errors are compared.

• 한국식품영양학회지
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• 제6권3호
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• pp.178-188
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• 1993

This research was attempted to investigate changes in physicochemical properties of rice extrudate with added ginger powder extruded by single screw extruder. Graphic three dimensional analysis on response surface regression was used to evaluate effects of extrusion variables on quality factors of the extrudate according to two independent variables, ginger consent 0∼12%, moisture content 14∼26%. The summarized results are as follows : 1) Regarding proximate composition of rice extrudate with added ginger powder, as ginger powder content of raw material Increased, crude tat, crude protein, crude ash and crude fiber increased, while soluble nitrogen free extract decreased. 2) Graphic three dimensional analysis on response surface regression was conducted for each dependent variable which revealed statistically significant relationship with independent variables, 0∼120A ginger and 14∼26% moisture content. Expansion ratio had a critical point as moisture content changed. As ginger and moisture content Increased, bulk density, break strength and water absorption Index Increased, while water solubility Index decreased. The predicted maximum degree of gelatinization in 6.15% ginger and 15.56% moisture content is 88.27%, and lightness decreased as ginger content Increased. According to the microstructure for the cross section of extrudate obsorbed with image analyzer, air cell number and perimeter revealed saddle point, meanwhile total area and fractarea of air cell had critical points as moisture content changed. In view of the results, quality of rice extrudate with added ginger powder was optimum when rice flour was fed to the extruder with 2∼7% singer powder and 15∼20% moisture content.

• 대한조선학회지
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• 제25권2호
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• pp.19-30
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• 1988

Sectional added masses of an elastic beam vibrating vertically on the free surface in higher harmonic modes are evaluated. Hydrodynamic interactions between neighboring sections, which strip theory ignores, are considered for modal wave lengths of the order of magnitude of cross-sectional dimensions of the body. An approximate solution of modified Helmholtz equation which becomes a singular perturbation problem at small wave lengths is secured to get an analytic expression for added masses attending higher harmonic modes. As a bound of the present theory, the modified Helmholtz equation is solved for the long flat plate vibrating at high frequency on the water surface without any limitations on modal frequency. Finally, extensive series of numerical calculations are carried out for ship-like forms. It is found that when modal wave length is comparable to or shorter than a typical cross-sectional dimension of a body, sectional interaction effects are large which result in considerable reductions in added masses. For a fuller section, the ratio of added mass reduction is greater. In the limit of vanishing sectional area, the added masses approach to that of flat plate of equal beam. It is shown that the added mass distribution for a Legendre modal from can be determined form the present theory and that the results agree with the extensive three-dimensional determination of Vorus and Hilarides.

• Coupled systems mechanics
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• 제1권3호
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• pp.285-295
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• 2012

In this paper, two types of porous burners with radial and axial flow have been modeled numerically and compared. For this purpose, governing equations were solved one-dimensionally for methane-air premix gas. The mechanism used in simulating combustion phenomenon was 15 stage reduced mechanism based on GRI3.0. In order to compare the two burners, the inlet flow rate and fuel-air ratio have been assumed equal for the two burners. The results of the study indicated that reduction in speed and increase in cross-section area in the direction of flow have a considerable influence on the behavior of radial burner in comparison to axial burner. Regarding temperature distribution inside the burner, it was observed that the two above mentioned factors can be influential in temperature of flame propagation region. Also, regarding distribution of CO and NO emission, the results indicate that the porous radial burner has lower emissions in comparison to the axial once. The output radiative heat transfer efficiency of the two burners was also compared and in this case also even the radial porous burner was found to be preferable.

• Steel and Composite Structures
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• 제34권1호
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• pp.53-73
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• 2020

A novel all-steel miniature bar-type structural fuse (MBSF) with cold formed bolted connections is developed in this study, which consists of a central energy dissipation core cut from a smooth round bar, an external confining tube and nuts. Three types of cross sections for the central energy dissipation core, i.e., triple-cut, double-cut and single-cut cross sections, were studied. Totally 18 specimens were axially tested under either symmetric or asymmetric cyclic loading histories, where the parameters such as cut cross sectional area ratio, length of the yielding portion and cross sectional type were investigated. Numerical simulation of 2 representative specimens were also conducted. An analytical model to evaluate the bending failure at the elastic portion was proposed, and a design method to avoid this failure mode was also presented. The experimental results show that the proposed MBSFs exhibit satisfactory hysteretic performance under both the two cyclic loading histories. Average strain values of 8% and 4% are found to be respectively suitable for designing the new MBSFs as the ultimate strain under the symmetric and asymmetric cyclic loadings.