• Journal of computational fluids engineering
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• v.11 no.3 s.34
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• pp.52-58
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• 2006

A numerical investigation is made of air flow in a spinner equipment used for cleanning and drying flat display panels. A unique feature of the spinner under question is the placement of a torus plate cover over the rotating plate. The turbulent flow is driven by rotation of a large disk and suction by the exhaust system connected to vacuum chamber. The flow is modelled as an axisymmetric two-dimensional flow and computation is conducted by using the FLUENT package with a version of k-$\varepsilon$ turbulence model. The required capacity of the exhaust system is assessed numerically. The usefulness of the cover in controlling air flow circulation is examined. A computational trouble shooting is attempted to resolve the problem of panel rising which occurred in real experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1417-1427
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• 2000

A flow stabilizer, which is made of a honeycomb and three different mesh screens, is located downstream of a butterfly-type valve, for the reduction of flow disturbances behind the valve. Mean flow and turbulence measurements as well as flow visualizations are conducted in the downstream region of the deepens the non-uniformity of the streamwise velocity component and turbulence. The mesh screens considerably reduce the turbulence and enhance the uniformity of mean velocities. The combination of the honeycomb and the three mesh screens results in an efficient reduction in the flow disturbances. In addition, the flow stabilizer proves to have a good performance in the suppression of turbulence at a short distance.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.3
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• pp.19-28
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• 2009

Computer system performance has always had the possibility of affecting business profitability, but with the advent of the World Wide Web where customers interact directly with Web servers, response time can have a direct and dramatic impact on business revenue. This paper is written in the operation environment and system analysis of HTS(Home Trading System) running K Securities. This paper also shows the method for performance improvement through investigation and analysis for the overall systems resources whether HTS has an appropriate performance or not. Performance analysis includes specially CPU analysis, Memory analysis, Disk Input/Output analysis and application analysis. Besides providing more detailed server specification for expansion from now on, system performance can be maintained with effect in the future. Through this study it is possible to manage the performance of HTS more easily and to solve problems such as a bottleneck more quickly.

• Laser Solutions
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• v.7 no.2
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• pp.11-18
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• 2004

We propose a novel application of optical coherence tomography (OCT) to monitor pit formation in laser irradiated optical storage materials. A multilayer optical storage recordable compact disk, is composed of multiple layers, each of different structure. Disks were irradiated with aQ-Switched Nd:YAG laser with an energy of 373 mJ. Post-irradiated disks were evaluated by OCT and those images were compared with optical microscopy. Our results indicate that OCT is a useful instrument to investigate pit formation in multilayer optical storage disks and might also provide information to optimize optical memory technology.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.423-426
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• 2011

SSD는 HDD와 다른 물리적 특성으로 인해 새로운 I/O 스케줄러를 요구하고 있다. 본 논문은 기존 CFQ 스케줄러가 SSD에서 어떤 성능을 보이는지 다양한 설정값 하에서 실험하고, 그 결과를 분석하여 SSD에서의 I/O 스케줄링 성능의 특징을 알아보고자 한다. 대상 설정값으로는 역탐색 제한 설정, FIFO 큐 내의 I/O 요청에 대한 만료 시간, I/O 요청 큐 별 할당 시간, 동기적 요청 큐를 위한 대기 시간을 고려하였다. 이러한 설정값을 다양하게 변화시키며 여러 개의 I/O 벤치마크 프로세스를 동시에 수행한 결과, 역탐색 제한을 제거하면 처리량이 상승하지만 그 폭이 매우 적으며, I/O 요청 만료 시간에 대해서는 연관성을 찾지 못하였다. I/O 요청 큐 별 할당 시간과 동기적 요청 큐를 위한 대기 시간은 클수록 처리량이 상승함을 보였다. CFQ의 목표인 평등성은 항상 97% 이상 보장됨을 관찰할 수 있었다. 우리는 이러한 결과가 차후 평등성을 보장하는 새로운 SSD I/O 스케줄러의 연구를 위한 초석이 되리라 기대한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.240-247
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• 2002

The rolling wear behavior of SM55C is investigated under lubrication. This is a comparative tribological behavior of heat treatment effect for SM55C. Rolling wear test method is used for Ball-on-disk type. Specimens can be classified into two main groups: as-annealing and non-annealing. As result of wear behavior, flanking initial time of non-annealing specimen keep at retard but it have not under high normal load. One of the notable features of annealing specimen is steady flanking initial time for a normal load in this experiment. Failure mechanism of SM55C is due to the fatigue wear such like flanking, pitting etc.. Flanking leads to abruptly fracture of worn surface. Fracture mechanism has a connection with normal load and polishing direction of specimens.

• Transactions of Materials Processing
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• v.24 no.4
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• pp.272-279
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• 2015

The characteristics of the laser metal deposition parameters were studied to enhance the deposition efficiency using a diode pumped disk laser. STD61 hot tool steel plate and Fe based AISI M2 alloy were used as a substrate and powder for the laser metal deposition, respectively. Among the laser metal deposition parameters the laser power, track pitch and powder feed rate were used to estimate the deposition efficiency. From the experimental results, the deposition efficiency was shown to be excellent when 1.8kW laser power 500um track pitch and 10g/min of the powder feed rate were used. For this optimal condition the average hardness of the deposition track was approximately 830HV, and this value is 30~50% better than the hardness of the commercially produced tool steel after heat treatment.

• Journal of Energy Engineering
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• v.8 no.1
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• pp.110-118
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• 1999

In order to protect the nuclear reactor coolant system from corrosion, lithium is injected into the coolant from the chemical injection tank. The present study investigates the chemical injection characteristics of the injection tank using a low Reynolds number turbulence model. Laminar flow analysis showed very little diffusion of the jet and gave incorrect flow and concentration fields. A disk located near the inlet of the injection tank was effective in mixing the chemical additives in the top portion of the tank, and significant reduction in injection time was obtained.

• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.129-135
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• 1999

In this review article, in vivo and in vitro wear test methods which measure the wear of tooth and restorative material were discribed. In vivo test, the criteria of each test were reviewed. The merits and limitations were also commented. In vitro tests, three dimensional scanning methods which scan the occlusal tooth surface three dimensionally were described. Profilometer method, Pin on disk method, laser scanner method were reviewed and the limitations of each test were commented. Additionally, the structer of the three dimensional scanner which has been developed in Zurich university and has been reputated as the most accurate one was described. This study was partly supported by 1997 post-doctoral foreign study program.

• Journal of Environmental Science International
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• v.7 no.4
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• pp.481-486
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• 1998

This paper discussed about the effect of Zoogloea ramigera on the initial microorganism attachment and the biofilm growth. The additions of 5, 10 and 15%(w/w) of Zoogoea ramigera were facilitated for the initial attachment on the surface of the acryl disk. At biofilm growth, the more Zoogoea ramikera added to the activated sludge, the more biofilm dry weight was obtained. In order to get the stable blofllm and to mlnlmlze the start-up periods, Initial biofilm formation using activated sludge with floe forming microorganisms like Zoogloea ramigera was recommended rather than that without floe forming microorganisms.