• Journal of the Korean Arthroscopy Society
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• v.7 no.2
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• pp.153-159
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• 2003

Purpose : The purpose of this study was to compare the pattern of displaced bucket-handle tear of lateral and medial menisci and the treatment modality and results from accompanying injury. Materials and Methods : Patients who were diagnosed for displaced bucket-handle tear of medial meniscus (group I: 52patients, 52cases) and lateral meniscus (group II: 31patients, 32cases) from September 1998 to December 2002. The mean ages were 25years $(16\~66)$ for Group I and 29years $(18\~63)$ for Group II, and the average follow-up period were 18months $(12\~44)$ and 13months $(6\~46)$, respectively. The zone of meniscus tear and the existence of accompanying injury were verified through intraoperative arthroscopy and discoid type meniscus was additionally examined for group II. The assessment was made according to the physical examination and clinical pattern at the postoperative last follow-up, and the 2nd look arthroscopy was performed in 19cases $(23\%)$ for the cases accompanying anterior cruciate ligament (ACL) injury in both groups. Results : There were 38cases $(73\%)$ in group I, 5cases $(16\%)$ in group II for associating ACL injury. We observed discoid type meniscus (19cases, $59\%$) in group II. At last follow-up clinical success in repair cases of group I and II are 22cases $(85\%)$, 2cases $(67\%)$, in resection cases are 26cases $(100\%)$, 26cases $(93\%)$ respectively. Reoperation is performed 2cases in repair cases of group I. One case is re-rupture, the other case is newly developed tear in white-white zone. Reoperation is performed 2cases due to remnant meniscal tear in resection cases of group II. All of 2cases are discoid type menisci. Conclusion : Displaced bucket-handle tear of medial & lateral menisci would be substantially different an aspect, considering on difference would help to select proper treatment modality.

• Journal of Energy Engineering
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• v.12 no.1
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• pp.17-22
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• 2003

The present study was conducted to obtain the fundamental knowledge on the manufacturing and operating characteristics of a small scale CPL (Capillary Pumped Loop) heat pipe. CPL heat pipes are able to transfer heat effectively at any orientation in a gravitational field over long distances. An experimental model with an evaporator of a circular plate shape was designed and manufactured and its operating performances were tested. A Bronze powder sintered metal plate of 3 mm thick and $\Psi$ 50 mm was used as wick and ethanol was used as working fluid. An experimental apparatus was set up to ascertain the operating conditions oi CPL at different heat load and an surrounding temperature at the condenser was maintained about 13$^{\circ}C$.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.370-376
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• 2011

Recently, the application range of plastic gears is widely expanding by the development of engineering plastics with good mechanical properties. Plastic gears have excellent performances such as light weight, water resistance and vibration absorbing ability for metallic gears. In this study, the optimization of injection molding process was done for the large disk type plastic gears of auto phoropter. Design Of Experiment (Taguchi method) was adopted to find a tendency of molding conditions that influence the flatness of disk type gear. Four main factors for molding conditions were selected based on injection temperature, filling time, packing pressure and mold temperature. Also, Filling, packing and cooling analyses were carried out to evaluate Z directional deflection of large disk type gear by using the simulation software (Moldflow) based on the DOE. From the results, it was found that the injection temperature and packing pressure are the most sensitive parameters for the Z directional deflection of large disk type gears.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.860-869
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• 2000

Numerical and experimental investigations are performed for the molecular transition and slip flows in pumping channels of a disk-type drag pump. The flow occurring in the pumping channel develops from the molecular transition to the slip flow traveling downstream. Two different numerical methods are used in this analysis: the first one is a continuum approach in solving the Navier-Stokes equations with slip boundary conditions, and the second one is a stochastic approach through the use of the direct simulation Monte Carlo method. In the experimental study, the inlet pressures are measured for various outlet pressures in the range of 0.1{\sim}4Torr. From the present study, the numerical results of predicting the performance, obtained by both methods, agree well with the experimental data for the range of Knudsen number $Kn{\leq}0.1$ (i.e., the slip flow regime). But the results from the second method only agree with the experimental data for Kn>0.1(i.e., the molecular transition regime)

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.816-821
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• 2003

The pumping characteristics of a disk-type drag pump (DTDP) from free molecular flow region to the slip flow region are calculated by the direct simulation Monte Carlo (DSMC) method. In this study, the pumping performance is studied numerically for several channel depths. The interaction between molecules is modeled by variable hard-sphere (VHS). The no time counter method is used as a collision sampling technique. The clearance between rotor and stator is considered an effect on performance. Spiral channels are cut on both upper and lower sides of rotating disks, and stationary disks are planar. A three-dimensional DSMC method for the analysis of steady rarefied flows in a single-stage DTDP has been developed. Velocity and density fields were obtained by the DSMC simulation in the rotor. The present experimental data in the outlet pressure range of $7.5{\times}10^{-3}{\sim}4$ Torr were compared with the DSMC results in the single-stage DTDP. Comparison between the experimental data and DSMC results showed good agreement.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.828-833
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• 2003

This work analyzes the effects of the independent variation of different geometric dimensions of compressor valves on the effective flow and force areas using a circular valve plate, such as different geometry of the valve seat, and the valve reed is opened and closed by pressure pulsation, the flow characteristic of the refrigerant passing the valve is very important. In the present study, a circular disk with inclination is assumed to be the valve reed of a reciprocating compressor and numerical analysis of three dimensional velocity fields are performed for theradial flow through the valve model. The effective flow and force area which are required to predict the efficiency of the valve are required to predict the efficiency of the valve are measured and compared with the numerical analysis in this research.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1703-1708
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• 2004

In this study, we are investigated experimentally the pumping characteristics about the pumping channel shapes of disk-type drag pump (DTDP). We are experimented the pumping performance about the rotors which have channel or do not exist. The channel disk-type rotor has spiral channels both upper and lower part, and stator is planar. The planar disk-type rotor hasn't channel and stator has spiral channels both upper and lower part. The flow-meter method is adopted to calculate the pumping speed. Compression ratio and pumping speeds for the nitrogen gas are measured under the inlet pressure range of 0.001 ${\sim}$ 4 Torr. The maximum of compression ratio was about 3300 for three-stage DTDP (channel disk-type rotor), 1000 for four-stage (planar disk-type rotor) and two-stage DTDP (channel disk-type rotor) at zero throughput. The ultimate pressure was $1.6{\times}10^{-6}$ Torr for three-stage DTDP (channel disk-type rotor), $2.5{\times}10^{-6}$ Torr for four-stage DTDP (planar disk-type rotor).

• Korean Journal of Microbiology
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• v.28 no.4
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• pp.337-344
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• 1990

Slime sampless from 10 ratating biological contactor (RBC) plants in New Jersey were microscopically examined. Filamentous bacteria such as Type 1701, Type 0041, Type 021N, Nocardia, Beggiatoa, and Sphaerotilus, which are commonly present as suspended forms also were found in RBC slimes growing as attached forms. However, the abundance wwas much different from that of activated sludge. In RBC slimes, Beggiatoa was most frequently observed filamentous bacteria and Sphaerotilus, Type 0041, Type 1701, Type 021N and Nocardia were present in decreasing order of abundance. There were morphologically two different types of Behhiatia in RBC slimes. The statistical anaysis shows that filamentous bacterial poulations between the 100 cm inside and the outside the RBC were different in most cases with significant interactions between the location and stage.

• Membrane Journal
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• v.16 no.1
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• pp.51-58
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• 2006

The permeation experiments were carried out for the submerged membrane module equipped with self-designed rotating disks in order to determine the effect of fouling reduction and the optimum operating conditions as a function of operating time. Kaolin and bentonite particles were used to prepare various concentrations of feed solution. Every experiment was continued until 60 minutes at various rotating disk speeds up to 120 rpm. The suction pressure for kaolin solutions decreased to 28% by using rotating disk to decrease the fouling. Also, the optimum permeation flux decreased as kaolin concentration increased, and became 60 to 70 LMH for 0.4 wt% of kaolin solution. The suction pressure for bentonite experiment approached to 0 mmHg at 30 LMH and above 80 rpm rotating disk speed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1990.11a
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• pp.69-72
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• 1990

최근의 전자및 광학기기 분야에 있어서의 준부신 발전은 다면경 가공기나 초정밀 절삭, 연삭기와 같은 초정밀 가공기계의 개발과 실용화에 힘입은 바 크다. 이러한 초정밀 가공기의 성능을 좌우하는 핵심 요소로서 주축계를 들 수 있으며, 비교적 소형 경량의 공작물을 가공하는 기계의 주축용 베어링으로는 볼 베어링이나 오일 베어링을 대신하여 공기베어링이 점차 널리 사용되고 있다. 일반적으로 주축으로 사용되는 베어링은 원통형 레이디얼 베어링과 원판형 스러스트 베어링이 결합된 형식이 주류를 이루나 이러한 베어링은 스러스트 판과 축의 직가곧 가공오차가 존재하기 때문에 가공하기는 쉬우나 회전시에 의의 영향에 의해 회전 정밀도 유지가 어렵다는 단점을 지니고 있다. 이러한 단점을 보완하기 위하여 사용되는 베어링에는 원추형(conical) 베어링과 구면형(spherical) 베어링이 쓰이고 있다. 이러한 원추형 베어링과 구면형 베어링은 가공오차를 베어링과 축의 현압 연마로써 없애줄 수 있으며 베어링이 축방향 하중과 경방향 하중을 동시에 지지하여 줌으로써 기계 전체의 부피를 줄이고 회전 정밀도를 향상시켜 주는 것으로 알려져 있다. 그러나 구면의 베어링 간극을 정확히 가공하기 어려운 단점이 있어 축과 베어링을 현압연마하여 가공한 후에 두부품을 중심선상에서 분리시키므로써 요구되는 간극을 얻을 수 있는 원추형 베어링이 많이 쓰이고 있다. 본 연구에서는 직접 수치 해법을 이요하여 원추형 베어링의 유막내의 압력 분포를 계산하고 이 합력인 하중지지 용량이 축방향 하중과 경방향 하중을 지지하는 특성을 이론적으로 검토하여 외부 가압 원추형 베어링으 특성수를 파악하여 설계자료를 제시하고자 한다.