• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.175-182
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• 1997

The purpose of this study is to investigate the effects of intake manifold shapes to improve the engine performance in a 3-cylinder LPG engine with a closed loop fuel supply system. To know the flow resistance of intake manifolds with shape, the intake negative pressure of each runner in intake manifolds were measured by using the digital pressure meter at each driving condition. And, the engine torque and power have been measured with an engine dynamometer while adjusting the optimal fuel consumption ratio with a solenoid driver. As 속 results form this experiment, the torque characteris- tics were more improved with the plenum chamber(B type intake manifold) than with the banana type(A type intake manifold). The torque characteristics were improved at mid-engine speed(rpm) range as the inner diameter of the intake manifold became smaller. And also the optimum volume among the examined plenum chamber volume was 0.74 times(590cc) the displacement of the test engine.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.4
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• pp.169-175
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• 2001

Ozone has been widely applied to many industrial fields because of its strong oxidation power, Therefore, the studies have been carried out for the methods on an effective and high concentration ozone generation. The silent or surface discharge type ozone generators have been mainly used for high concentration ozone generation in many fields of applications. But these two types of ozone generators have shortcomings to be improved. In this study, the ozone generator which improved the shortcomings of above ozone generators was proposed and fabricated for the high concentration ozone generation. And the proposed ozone generator could generate the surface and barrier discharge simultaneously. For this purpose, a mesh type discharge electrode was proposed and studied as a function of the widths output maximum ozone concentration of 2.96[vol%] was obtained at 5.6[kV], 830[mA], for 0.3[mm] width and 0.8[mm] vacancy of the mesh electrode and gap spacing of 0.65[mm] respectively.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.48-52
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• 2001

In this paper presents an accurate AFM used that is free from the Z-directional distortion of a servo actuator is described. Two mathematical correction methods by the in-situ self-calibrationare employed in this AFM. One is the method by the integration, and the other is the method by inverse function of the calibration curve. The in situ self-calibration method by the integration, the derivative of the calibration curve function of the PZT actuator is calculated from the profile measurement data sets which are obtained by repeating measurements after a small Z-directional shift. Input displacement at each sampling point is approximately estimated first by using a straight calibration line. The derivative is integrated with reference to the approximate input to obtain the approximate calibration curve. Then the approximation of the input value of each sampling point is improved using the obtained calibration curve. Next the integral of the derivative is improved using the newly estimated input values. As a result of repeating these improving process, the calibration curve converges to the correct one, and the distortion of the AFM image can be corrected. In the in situ self-calibration through evaluating the inverse function of the calibration curve, the profile measurement data sets were used during the data processing technique. Principles and experimental results of the two methods are presented.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.381-390
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• 2001

In this paper, a new improved crack analysis technique by Element-Free Galerkin(EFG) method is proposed, in which the singularity and the discontinuity of the crack successfully described by adding enrichment terms containing a singular basis function to the standard EFG approximation and a discontinuity function implemented in constructing the shape function across the crack surface. The standard EFG method requires considerable addition of nodes or modification of the model. In addition, the proposed method significantly decreases the size of system of equation compared to the previous enriched EFG method by using localized enrichment region near the crack tip. Numerical example show the improvement and th effectiveness of the previous method.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.141-152
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• 1999

Precast prestressed double-tee slab may be designed by the PCI Design Handbook. It is based on the bridge construction and is required for reorganization for the use of buildings in the domestic construction environments. Much enhanced sections are developed from the reforming process on the determined design factors in the previous experimental works on double tees. Pre-determined shape, reinforcement detail, and 5000 psi concrete strength can not be expected as the best solution for the domestic construction requirements because large amount of use on that systems are anticipated. Flexural tests are performed on four full-scale 12.5m proto-type models, "least depth double tee", which are resulted from the optimization process. Domestic superimposed live load regulation, domestic material properties which is available to product, building design requirements and economy in construction are considered as the main factors to establish. the first two sections are double tee section for 1.2 ton/$\m^2$ market live load with straight and one-point depressed strands and the second two are for 0.6 ton/$\m^2$ parking live load with those strand types. All of the specimens tested fully comply with the flexural strength requirements as specified by ACI 318-95. However, the research has shown that following improved considerations are needed for better result in practice. The locations and method of connection for the lowest bottom mild bar, connection method between precast and cast-in-place concrete, and dap-end reinforcement are need to be improved.

• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.379-385
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• 2010

We developed a high-efficiency, wide-operating-range centrifugal blower stage to meet the demand for reduced total energy-consumption in sewage treatment plants. We improved the efficiency of the two-dimensional impeller using a shape optimization tool and one-dimensional performance prediction tool. A limit of the throat deceleration ratio was set to maintain the stall-margin of the impeller. The low solidity vaned diffuser and return channel were designed using a sensitivity analysis with orthogonal arrays and three-dimensional steady flow simulations. The low solidity diffuser was designed in order to improve the performance in the low-flow-rate region. The return channel was designed so that the total pressure loss in the return channel was minimized. Model tests of both the conventional and optimized blower stages were carried out, and the efficiency and operating range of both stages were compared. The optimized blower stage improved in stage efficiency by 3% and in operating range by 5% compared with the conventional blower stage.

• Journal of Pharmaceutical Investigation
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• v.32 no.1
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• pp.41-45
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• 2002

The purpose of this study is to microencapsulate a highly hygroscopic drug, pyridostigmine bromide (PB), with a waterproof wall material, in order to increase the flowability of the drug particles. Polyvinylacetaldiethylaminoacetate (AEA), Eugragit E and Eugragit RS were examined as the wall materials. Microcapsules containing PB were prepared by the evaporation technique in an acetone/liquid paraffin system using aluminum tristearate as a core material, and evaluated for drug encapsulation efficiency, surface morphology, particle size and drug dissolution. The encapsulation of PB in the wall material was almost complete. Among the wall materials examined, AEA exhibited the most excellency in shape, surface texture, flowability, size distribution of microcapsules. Above results suggest that AEA would be a potential wall material for microcapsulation of highly hygroscopic drugs, such as PB. Through microencapsulation with AEA, inconvenience of handling of PB powders encountered in the process of weighing and packing the powders to tableting die or capsule body could be greatly improved.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.237-243
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• 2012

In this paper, a magnetic analysis of SRM(Switched Reluctance Motor) using 3d finite element method considering end-coil effect is presented. SRM models with different stator pole shapes are taken into consideration for the analysis of magnetic characteristics. It is observed that a stator pole shape model having a pole shoe depth is the most suitable one for railway traction application because it gives an improved inductance and torque characteristic. For a speed control of SRM, the PI and sliding mode controllers are applied to designed SRM with magnetic characteristic data obtained from the magnetic analysis. The simulations are carried out using Matlab-Simulink and the control performance is analyzed. By employing the sliding mode controller, the transient response as well as the steady-state error are much improved under a load variation of railway resistance under operation.

• Journal of ILASS-Korea
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• v.28 no.3
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• pp.126-133
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• 2023

This study analyzes the flow characteristics and sponge ball recovery performance in a ball strainer according to vortex promoter design variables through flow-particle analysis based on actual experiments to derive a method for improving the recovery rate of cleaning sponge balls of CTCS applied to existing power plants. Based on the ball strainer in CTCS used in the power plant, the experiment was conducted by changing the design factor of the improved shape. In addition, flow and particle analysis were performed under the same conditions as the experiment to numerically the flow characteristics and recovery rate in the ball strainer according to the design factor of the vortex promoter. As a result of the study, it was confirmed that the recovery performance was improved by about 3% by changing the design height of the Vortex promoter. And when comparing the difference between maximum and minimum recovery rate, it was found that the effect on the recovery performance increased slightly according to the distance condition compared to the vortex promoter design height condition.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.72-79
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• 1996

In a BAF(Batch Annealing Furnace), various studies have been pursued in order to reduce energy consumption rate to improve productivity and to stabilize the properties of products. The purpose of this study was to investigate the effects of both the atmospheric gas and convector plate shapes on the augmentation of heat transfer. The use of hydrogen instead of nitrogen as an atmospheric gas, combined with high convection in the BAF, has shown that considerable increases in furnace out put and significantly improved material quality are attainable. Because convector plate shapes make the atmosheric gas easily flow density, high diffusivity and reducing character of hydrogen, a better heat transfer rates resulting in uniform material temperature distribution and improved coil surface quality can be achieved. Also, it was found that the closed convector plate took more time for the annealing cycle time than the other plate type(open-type)by about ten hours.