• Journal of computational fluids engineering
• /
• v.13 no.2
• /
• pp.20-26
• /
• 2008

A numerical study is carried out to analyze the steady three-dimensional turbulent flow and convective heat transfer in a staggered pin-fin array with diamond shaped elements at various geometrical configurations. Steady Reynolds-averaged Navier-Stokes equations and energy equation are solved using a finite volume based solver. Shear stress transport (SST) model is used as turbulence closure. The computational domain is composed of one pitch of pin-fin displacement with periodic boundary conditions on the surfaces normal to the streamwise direction and the cross-streamwise direction. The numerical results for Nusselt number and friction factor are validated with experimental results. The effects of pin angle, pin height and pitch on Nusselt number, friction factor and efficiency index are investigated.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.228-235
• /
• 2002

As the response spectrum method generally used in the earthquake resistant design is a linear method, the nonlinear behavior of a structure is to be reflected with a specific factor. Such factors are provided in the "Design Criteria for Roadwaybridges"as response modification factors and in the Eurocode 8, Part 2 as behavior factors. In this study a 5-span steel box bridge with single column piers is selected and the behavior factor is determined. The linear time history analyses are carried out with a simple linear model, where the nonlinear behavior of piers leading to the ductile failure mechanism is considered as predetermined characteristic curves.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.52 no.5
• /
• pp.203-210
• /
• 2003

This paper describes high voltage and high energy density capacitor developed for pulsed power applications. The rated voltage of the developed capacitor is DC 22 [kV], the capacitance is 206 [$\mu$F] and the energy density is about 0.7 [kJ/kg]. Polypropylene film and kraft paper were used as the dielectrics. The ratio of the thickness of each dielectric material which consists of the composite dielectric structure, stacking factor and the termination method were determined by the charging and discharging tests on model capacitors. In terms of energy density, the developed capacitor has higher energy density compared with the products of foreign leading companies. In addition, it has been proved that the life expectancy can be more over 2000 shots through the charging and discharging test. The voltage reversal factor was 20%. This capacitor can be used as numerous discharge applications such as military, medical, industrial fields.

• Proceedings of the KIEE Conference
• /
• 1996.07a
• /
• pp.564-566
• /
• 1996

New simple control method of power factor correcting(PFC) boost convertor without instantaneous measurement of input current is proposed. Using the averaged model, the power factor correction scheme is presented. With the measurements of input voltage and output voltage, the control signal is generated to make the shape of the line current same as the input voltage. The validity of the controller is verified through the computer simulations.

• Proceedings of the KIEE Conference
• /
• 2003.10b
• /
• pp.161-165
• /
• 2003

In this paper, A new controller for power factor and harmonics compensation of a single-phase PWM converter is described. The proposed controller requires only the dc voltage sensor and the at current sensor to compensate the power factor and harmonics. Detail simulation model with EMTBC (Electro-Magnetic Transient program for DC transmission) including power circuit and controller was developed to verify the operation of proposed controller. The application feasibility of the proposed controller was verified through experimental works with a prototype. The proposed controller has a simple structure in the point of hardware implementation, and shows excellent performance in normal operation as well as in sudden load change.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.22 no.3
• /
• pp.569-578
• /
• 1998

The mode I and II stress intensity factors have been calculated theoretically for the cracked plate reinforced with a plate by symmetric spot welding under remote mixed mode loading. This is the extension of authors' previous work for the reinforced cracked plate under remote normal stress. Regardless of loading types, the reinforcement effect gets better as one joining spot is closer to the crack tip and the others are closer to the crack surface, and optimum number of the joining spots can be existed. For the present model, the remote loading parallel to crack surface produces the mode I stress intensity factor.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.101-104
• /
• 2000

The general solution of the anti-plane shear problem for the curved interfacial crack between viscoelastic foam and composites was investigated with the complex variable displacement function and Kelvin-Maxwell model. The Laplace transform was applied to treat the viscoelastic characteristics of foam in the analysis. The stress intensity factor near the interfacial crack tip was predicted by considering both anisotropic and viscoelastic properties of two different materials. The results showed that the stress intensity factor increased with increasing the curvature of the curved interfacial crack and it also increased and eventually converged to a specific value with increasing time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.5
• /
• pp.511-518
• /
• 2000

The present experimental study investigates the impact of porous fins on the pressure drop and heat transfer characteristics in plate-fin heat exchangers. Systematic experiments have been carried out in a simplified model of a plate-porous fin heat exchanger at a controlled test environment. Comparison of performance between the porous fins and the conventional louvered fins has been made. The experimental results indicate that friction and heat transfer rate are significantly affected by permeability as well as porosity of the porous fin. The porous fins used in the present study show a similar air-side performance to the louvered fin. The correlations of friction and modified j-factor are also given for the design of the plate-porous fin heat exchanger.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.18 no.2
• /
• pp.261-268
• /
• 1996

An experimental study was performed to evaluate the efficacy of nerve growth factor(NGF) on inferior alveolar nerve in a rabbit model. In 20 New Zealand white rabbits, 14mm of bilat eral alveolar nerve were resected and the defects were repaired with the 17mm silicone conduits. In group I, 5mm autologous nerve segment were located centrally in the left side after tubulization and NGF solution(Sigma chemical 0.1 mg/mL) was instilled into each conduit. In group II, nerve repair modality was the same but no NGF solution was instilled into the conduits. On 2 months and 6 months postoperatively, the results were evaluated by clinical and hist omorphometric assessment. The result was that autologous nerve segment group show the best nerve regeneration effect and NGF instilled group the worst.

• Journal of the Korean housing association
• /
• v.10 no.2
• /
• pp.247-257
• /
• 1999

This study is aimed to propose the evaluation model of forecasting visual quality of apartment buildings, which would be a useful tool to make the architectural concepts corresponding to user needs. This study was carried out through the four-step experiments as follows. The first step is to take the user's visual evaluation construct. To do this, the 22 adjective phrases were extracted, which were applicable to all apartment buildings. The second step is to analyze the user's visual preference, which is measured by the user's psychological quantity on the apartment buildings by S. D.(Semantic Differential) Method. The third step is to analyzethe five psychological-factors obtained from the Factor Analysis. The perceptual images on the 41 experimental subjects were checked up through evaluating and analyzing the factor scores of each subjects for each psychological-factor. The fourth step is to analyze, the similarity of various characters in a building, which is mirrored on the user's psychological quantity and how buildings are grouped by it.