• 한국음향학회지
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• 제19권8호
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• pp.47-53
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• 2000

수중에서 프로펠러에 의해 추진되는 추진체를 식별하기 위해 프로펠러의 추진력에 의하여 수중에 발생되는 cavitation의 비선형 음향학적 현상으로부터 발생되는 프로펠러의 shaft-rates와 blade-rates를 탐지하여 표적을 식별하기 위한 Maximum Likelihood Classifier를 유도하고, 시뮬레이션과 실험을 통한 검증을 수행하였고, 실제 해양에서 수집한 데이터에 대해 적용 가능함을 입증하였다.

• Tribology and Lubricants
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• 제9권2호
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• pp.29-35
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• 1993

The thermohydrodynamic(THD) performance of a large tilting pad journal bearing in laminar and turbulent flow regions is investigated experimentally. The continuous shaft surface temperature, and bearing surface temperature are measured along with the shaft speed and the bearing load for various flow rates. It is observed that the shaft surface temperature is constant in the circumferential direction and increases with the increase of shaft speed in both low and high shaft speed region, however, there exist transition region where the shaft surface temperature decreases with the increase of shaft speed. When the turbulence occurs in the lubricant film, both the inlet and maximum bearing surface temperature steeply increase and the temperature gradient in the circumferential direction decreases.

• 설비공학논문집
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• 제15권12호
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• pp.996-1006
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• 2003

The objective of this study is to find major variables which influence the performance of kitchen and bathroom exhaust systems in high-rise apartment buildings. For this purpose, the influencing factors on the exhaust airflow rates from the kitchen or bathroom are identified and in every cases, which are made of combinations between the influencing factors, the exhaust airflow rates are calculated through the simulations. The results of the simulation show that the exhaust airflow rates from the kitchen and bathroom mainly depends on outdoor air temperature, number of floors, airtightness of the building envelope, fan on ratio, vertically connected to same shaft, exhaust fan capacity for kitchen or bathroom, roof ventilator capacity and shaft area for kitchen or bathroom exhaust.

• Journal of Trauma and Injury
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• 제33권2호
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• pp.104-111
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• 2020

Purpose: Although exchange nailing is a standard method of treating femoral shaft nonunion, various rates of healing, ranging from 72% to 100%, have been reported. The purpose of this study was to evaluate the efficacy of exchange nailing in femoral shaft nonunion. Methods: We retrospectively reviewed 30 cases of aseptic femoral shaft nonunion after intramedullary nailing. The mean postsurgical period of nonunion was 66.8 weeks. A nail at least 2 mm larger in diameter was selected to replace the previous nail after reaming. Distal fixation was performed using at least two interlocking screws. The success of the procedure was determined by the finding of union on simple radiographs. Possible reasons for failure were analyzed, including the location of nonunion, the type of nonunion, and the number of screws used for distal fixation. Results: Of the 30 cases, 27 achieved primary healing with the technique of exchange nailing. The average time to achieve union was 23.1 weeks (range, 13.7-36.9 weeks). The three failures involved nonunion at the isthmic level (three of 15 cases), not at the infraisthmic level (zero of 15 cases). Of eight cases of oligotrophic nonunion, two (25%) failed to heal, and of 22 cases of hypertrophic nonunion, one (4.5%) failed to heal. Of 11 cases involving two screws at the distal fixation, two (18.2%) failed to heal, and of 19 cases involving three or more screws, one (5.3%) failed to heal. None of these findings was statistically significant. Conclusions: Exchange nailing may enable successful healing in cases of aseptic nonunion of the femoral shaft. Although nonunion at the isthmic level, oligotrophic nonunion, and weaker distal fixation seemed to be associated with a higher chance of failure, further study is needed to confirm those findings.

• 대한기계학회논문집A
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• 제31권6호
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• pp.701-709
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• 2007

To clarify the characteristics of surface damage due to fretting in press-fitted shaft, experimental methods were applied to small scale specimen with different bending load condition. Fatigue tests and interrupted fatigue tests of press-fitted specimen were carried out by rotate bending fatigue test. Macroscopic and microscopic characteristics were examined using scanning electron microscope (SEM), optical microscope or profilometer. It is found that small fatigue cracks are nucleated early in life regardless of bending stress, and thus the most portion of fatigue life on press fits can be considered to be crack propagation process. Most of surface cracks are initiated near the contact edge, and multiple cracks are nucleated and interconnected. Furthermore, the fretting wear rates at the contact edge are increased rapidly at the initial stage of total fatigue life. It is thus suggested that the fatigue crack nucleation and propagation process is strongly related to the evolution of surface profile by fretting wear in press fits.

• Tribology and Lubricants
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• 제9권2호
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• pp.22-28
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• 1993

The experimental investigation on the inlet pressure of a large tilting pad journal bearing is studied. The continuous distribution of the film pressure and film thickness are measured along with the shaft speed and bearing load for various flow rates. Considerably large inlet pressure is observed at the entrance of each pad, especially lower pads. The inlet pressure increases with the increase of shaft speed as well as bearing load, but it is almost independent on the folw rate and the oil supply temperature. Because of the inlet pressure, the upper pads always keep up slight wedge film shape which are almost parallel to the journal surface, and spragging is not observed in the upper pads with no preload.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.27-36
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• 2004

A Numerical analysis has been used to predict the performance in the automotive water pump with double discharge single suction. The influence of parameters such as coolant flow rate, rotational speed, ratio of blade height and clearance has been investigated. Also, the prediction of hydraulic performances such as static pressure rise, shaft power, hydraulic power and pump efficiency is carried out on the water pump including an impeller and a volute casing. A full size water pump test bench has been developed to validate the CFD flow model. Discharge flow rate, suction pressure, discharge pressure, rotational speed and torque measurements are provided. Coolant temperature is 8$0^{\circ}C$, water tank pressure is 1 kgf/$\textrm{cm}^2$ and flow rates vary.

• Asian Pacific Journal of Cancer Prevention
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• 제13권2호
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• pp.737-742
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• 2012

To evaluate efficacy of microwave ablation in a primary clinical study, sixty patients (44 men, 16 women; mean age 53 years) with 96, 1-8 cm (mean $3.20{\pm}0.17$ cm) liver cancers were treated with 2,450-MHz internally cooled-shaft antenna. Complete ablation (CA) and local tumor progression (LTP) rates as well as complications were determined. CA rates in small (< 3.0 cm), intermediate (3.1-5.0 cm) and large (5.1-8.0 cm) liver cancers were 96.4% (54/56), 92.3% (24/26) and 78.6% (11/14), respectively. During a mean follow-up period of $17.17{\pm}6.52$ months, LTP occurred in five (5.21%) treated cases. There was no significant difference in the CA and LTP rates between the HCC and liver metastasis patient subgroups (P<0.05). Microwave ablation provides a reliable, efficient, and safe technique to perform hepatic tumor ablation.

• 대한기계학회논문집A
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• 제40권2호
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• pp.221-227
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• 2016

풍력발전기에서 메인 샤프트는 로터허브와 증속기를 연결하는 중요 부품 중 하나이며 주로 자유단조공법을 통하여 제조된다. 하지만 고 MW급 이상의 메인샤프트는 중량을 감소시키기 위하여 중공형 설계가 이루어지며 주조공법을 이용하여 제조되고 있다. 본 연구의 목적은 중공형 메인샤프트를 단조공법을 이용하여 생산할 수 있는 제조공정을 개발하는 것이다. 자유단조 공법의 공정설계 방법에 따라 중실형과 중공형 메인샤프트를 제조하기 위한 단조공정을 각각 설계하였다. 설계된 공정의 성형가능성을 확인하기 위하여 온도, 변형률 속도에 따른 유동응력을 열간압축실험을 통하여 구한 후 유한요소해석을 수행하였다. 유한요소해석을 통하여 단조업계에서 통상 행해지는 중실형 단조공법의 온도 및 변형률 등의 관리인자와 제안된 중공형단조공법의 인자를 비교하여 성형가능성을 예측하였다. 시제품 제작을 통하여 중공형 형상을 원소재회수율, 내부품질, 형상 및 치수 등에서 높은 생산성으로 제조가 가능함을 확인하였다.

• 한국정밀공학회지
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• 제21권2호
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• pp.108-115
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• 2004

Experiment and analytical studies on the oil supply characteristics of scroll compressor have been presented. For a scroll compressor, oil supply system consisting of individual lubricating element such as pumps, oil passages and sliding surfaces has been modeled by equivalent electric circuit. By solving the closed network equations of the model, oil flow rates at various lubrication elements could be obtained. Total amount of the oil flow rate drawn into the shaft has been measured and compared reasonably well with the prediction by the numerical simulation.