• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.5
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• pp.38-46
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• 1995

In this paper, an experimental study on the effects of the impact damage and the perforation characteristic of CFRP laminates with different fiber stacking orientation and ply number was done through an observation of interrelations between the impact energy vs. transmitted energy and the impact energy vs. absorbed energy per unit volume. The velocities of the ball before or after impact are measured by the high-speed camera. And when CFRP laminates are subjected to tranverse impact by a steel ball(${\phi}10$), the delamination shapes generated by impact damage are observed by using SAM (Scanning acoustic Microscope).

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.1-4
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• 2008

Fuel cells have the potential of providing several times higher energy storage densities than those possible using current state-of-the-art lithium-ion batteries, but current energy density of fuel cell system is not better than that of lithium-ion batteries. To achieve the high energy density, volume and weight of fuel cell system need to be reduced by miniaturizing system components such as stack, fuel tank, and balance-of-plant. In this paper, the thin flexible PCB (Printed circuit board) is used as a current collector to reduce the stack volume. Two end plates are made from light weight aluminum alloy plate. The plate surface is wholly oxidized through the anodizing treatment for electrical insulation. The opening rate of cathode plate hole is optimized through unit cell performance measurement of various opening rates. The performances are measured at room temperature and ambient pressure condition without any repulsive air supply. The active area of MEA is 10.08 $cm^2$ and active area per a unit cell is 1.68 $cm^2$. The peak power density is about 210 mW/$cm^2$ and the air-breathing planar stack of 2 Wis achieved as a small volume of 18 cc.

• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.103-109
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• 2007

This study was focused on the establishment of a fundamental DB(database) that is available in the building design process, so we performed the simulation analysis about the energy consumption on the various same volume buildings. Because energy consumption in building is affected by the exterior surface area, the ratio of long/short length in surface and the adjacent internal surface area etc.. For these purpose, we assumed the unit module and made a constructable 16 model buildings which are composed of the 16 unit modules. Then we analyzed the simulation using the TRNSYS 16 and the Seoul weather data. In results, energy consumption in building is more reduced that in case of the smaller exterior surface area, the lower stories building and the larger adjacent surface area etc.. Further study is to be required the sensitivity analysis on the various weather conditions, building shapes and window area etc..

• Magazine of the Korea Concrete Institute
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• v.2 no.3
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• pp.65-72
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• 1990

Theoretical expressions were dcrived for the numher of fibers per unit cross-sectional area in fiber reinforced concrete, with due consideration given to the effects of the surrounding boundaries. The number of fibers per unit cross-sectional area in steel fiber reinforced concrete was also measured experimentally for the specimens incorporating various volume fractions of fibers of different types. Statistical evaluation of the measured value was then performed in order to assess the differences in fiber concentration at different location on tbe cross section. Degree of reorientation of steel fibers in concrete occuring during vibration was examined by com¬paring the differences in the computed and measur'ed values of the number of fibers per unit cross-sectional area.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.146-156
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• 2003

A numerical algorithm is developed to analyze the performance of a Unit-injector (UI) System for a diesel engine. The fundamental theory of the algorithm is based on the continuity equation of fluid dynamics. The loss factors that should be seriously regarded on the continuity equation are the compressibility effect of liquid fuel, the wall friction loss in high-pressure fuel lines of the system, the kinetic energy loss of fuel in the system, and the leakage of fuel out of the control volume. For an evaluation of the developed simulation algorithm, the calculation results are compared with the experimental outputs provided by the Technical Research Center of Doowon Precision Industry Co. (DPICO) ； the maximum pressure in the plunger chamber (P$\_$p/) and total amount of fuel injected into a cylinder per cycle (Q$\_$f/) at each operational condition. The result shows that the average error rate (%) of P$\_$p/ and Q$\_$f/ are 2.90% and 4.87%, respectively, in the specified operational conditions. Hence, it can be concluded that the analytical simulation algorithm developed in this study can be reasonably applied to the performance prediction of newly designed UI system.

• Proceedings of the Safety Management and Science Conference
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• 2006.11a
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• pp.373-383
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• 2006

Logistics is one of the most important factors to manage a stream of materials in economic environment. Establishing effective logistics system needs to consider some constraints which are fluctuation of materials volume, a long distance between makers and consumers, one way logistics and small quantity batch production. It is estimated that Unit Load System should be a powerful method to cope with those problems. It helps to realize the key issues which are Standardization and Logistics Pool System The Material Unification of Logistics System is able to participate in all kinds of industries including manufacturing, distribution and logistics. This system has some merits which are a long distance transportation cost down, product recovery, and treatment in the unbalance of demand and supply caused by unstable materials volume. Four strategies of Material Logistics Model are Packing Rationalization, Logistics Pool System, JIT System application and establishing effective infrastructure. The Material Unification Of Logistics System based on Unit Load System achieves efficiency of logistics and largely decreases moving cost.

• Transactions of Materials Processing
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• v.21 no.4
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• pp.234-239
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• 2012

This study examines the forming properties and forming loads needed to increase the edge thickness on the external face of a plate using finite element analysis(FEA). Recently, forming optimization techniques within FEA are being extensively used in designing the optimal forming conditions for processes like forging, extrusion, rolling, and spinning. Most of these existing forming operations involve reducing the volume per unit length, but research for increasing volume per unit length is not very extensive. For this study we chose an automotive engine flywheel which is a welded assembly of a plate and a gear with each component having a different thickness. We considered a forming technique to increase the thickness in order to allow the machining of the gear directly on the external face of plate alleviating the need for a weld. To study various forming techniques, we used the finite element method with the flow stress of material and incremental forming steps. We conclude from this study that the analysis of forming properties and forming loads by using the finite element analysis and testing is useful as a method to increase the thickness per unit length.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.434-442
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• 2006

In a two-stage compression $CO_2$ transcritical cycle, application of a scroll expander-compressor unit has been considered in order to improve the cycle COP. For both expander and 1st stage compressor, scroll wrap profile which was originally designed for a R410A air-conditioning cycle mechanism was used with minor modifications: wrap height and involute end angle were adjusted for required displacement volume and built-in volume ratio. For pressure condition of 10 Mpa/3.5 MPa and expander inlet temperature of $35^{\circ}C$, 25% improvement in COP was obtained by using expander-compressor unit. As evaporator pressure increased, COP improvement was lowered mainly due to decreasing compressor peformance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.11 no.2 s.23
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• pp.103-108
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• 2005

For the development of a disk type oil skimmer for a tank lorry, a basic study on comparison of oil recovery performance between disk materials of oil skimmer was conducted. The experiment results are summarized as follows: In all the disks, the volume of recovery of bunker-A oil was greater than diesel oil. In light oil, there was nearly no differences in the volume of oil recovery by disk material, but in the case of bunker A oil, recovery efficiency showed big differences depending on the disk materials. For diesel oil, the differences in the volume of oil recovery per unit of operation time from the initial time zone were hardly shown. However, the volume of recovery of bunker-A oil linearly increased from the initial operation time in all the disks and the increase showed a slew moving trend as time. went on; therefore, the volume of oil recovery per unit of operation time showed differences depending on time. This result shows that oil viscosity has an effect on the disk recovery efficiency. When comparing the mass of pure oil recovery and the volume of water recovery in the total mass of recovery by bunker-A oil, there was no difference in the volume of oil recovery between the window-aluminum material disk and the disks consisting of other materials, but the volume of water recovery of the former was relatively very small This shows the most ideal result in view of oil recovery efficiency that considers the volume of water recovery. In conclusion, it was found that aluminum is the most advantageous as the material for tank lorry oil skimmer disk.

• Journal of the Korea Computer Graphics Society
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• v.26 no.4
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• pp.17-26
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• 2020

We present a real-time GPU(Graphic Processing Unit) marching tetrahedra technique that extracts isosurfaces in the indexed mesh format from BCC(Body Centered Cubic) volume datasets. Compared to classical marching tetrahedra, our method shows better performance with little memory overhead. Our technique is composed of five stages. In the first stage, which needs to be done only once, we build min/max blocks that is to be used for empty space skipping to boost the performance. Next, we extract active blocks that contain the current isovalue. In the next two stages, we extract the edges and cells that contain the isosurface and then the final triangular mesh is generated in the last stage. When applied 512³ or higher resolution volume dataset, our technique shows up to 5 times speed improvement compared to the classical marching tetrahedra algorithm.