• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.276-281
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• 2002

본 연구에서는 정밀 쇄미 선별 시스템을 개발하기 위하여 원통형 홈 쇄미 선별기의 시작품을 제작하고 이것의 설계인자와 운전인자에 따른 성능 분석을 수행한 결과는 다음과 같다. 1. 원통형 홈 쇄미 선별기의 시작품은 홈의 직경이 작은 선별원통을 상단에, 홈의 직경이 큰 선별원통을 하단에 장착하는 2단형으로 설계 제작하였다. 각 단의 trough에는 스크류 컨베이어를 설치하였으며, 원통의 회전 속도와 trough의 각도 및 원통의 수평각을 변경시킬 수 있도록 하였다. 홈의 크기가 작은 상단에서 쇄미를, 홈의 크기가 큰 하단에서 준완전립을 선별하도록 하였다. 2. 원통형 홈 쇄미 선별기의 원통 회전속도가 증가하면 처리 용량이 증가하며, 이 속도에 따른 최적의 trough 각이 존재하는데, 본 실험에서는 회전 속도 35rpm에서 trough 각 37$^{\circ}$, 45rpm에서 55$^{\circ}$, 55rpm에서 73$^{\circ}$로 분석되었다. 3. 원통형 홈 쇄미 선별기의 공급율이 증가할수록 선별효율과 수거율(준완전립+쇄미)은 급격히 감소하지만, 순도(준완전립+쇄미)는 완만히 증가하였고, 완전립의 수거율과 순도는 95%이상을 유지하며 일정한 경향을 보였다. 본 실험 범위에서는 원통형 홈 쇄미선별기의 선별효율은 각 공급율에서 공히 원통의 분당 회전수 35rpm, trough 각 37$^{\circ}$에서 최대치를 나타내었다. 이 최적 조건에서 공급을 400-800kg/h 범위의 선별효율 평균치는 70% 정도로 분석되었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.231-236
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• 2012

This work presents the application of the DFSS (Design for Six Sigma) methodology to optimizing both the linearity and the sensitivity of the output voltage of a Hall-effect rotary position sensor. To this end, the dimensions and relative positions of a permanent magnet with reference to a Hall sensor are selected as the design factors for a full factorial design. In order to evaluate the output voltage of the rotary position sensor at each run in the experimental design, analytical solutions to the magnetic flux density were obtained using the Biot-Savart law and the relations between the magnetic flux density and the output voltage intrinsic to a Hall sensor. Through measurements of the improved output voltage of the rotary position sensors manufactured using the optimized design factors, the proposed method is shown to be simple and practical.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.801-806
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• 2015

Journal bearings support rotors using fluid film between the rotor and the stator. Generally, journal bearings are used in large rotor systems such as turbines in a power plant, because even in high-speed and load conditions, journal bearing systems run in a stable condition. To enhance the reliability of journal-bearing systems, in this paper, we study health-diagnosis algorithms that are based on the supervised learning method. Specifically, this paper focused on defining the unit of features, while other previous papers have focused on defining various features of vibration signals. We evaluate the features of various lengths or units on the separable ability basis. From our results, we find that one cycle datum in the time-domain and 60 cycle datum in the frequency domain are the optimal datum units for real-time journal-bearing diagnosis systems.

• Journal of the Korean Orthopaedic Association
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• v.56 no.1
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• pp.61-67
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• 2021

Purpose: To evaluate the prognostic factors affecting poor functional outcomes in patients with retear after rotator cuff repair. Materials and Methods: From January 2013 to December 2018, among 631 patients who underwent arthroscopic repair of a rotator cuff tear, 42 patients, who could be followed-up for more than one year and showed a retear of the repaired cuff on magnetic resonance imaging (MRI), were collected retrospectively. The preoperative demographic data, range of motion, American Shoulder and Elbow Surgeons (ASES) score, fatty degeneration, and tear progression on postoperative MRI, as well as other factors that could affect the clinical outcomes, were analyzed. Patients who scored <80 points on the ASES score were allocated to the poor function group. The risk factors for poor clinical outcomes were compared with the group with ASES scores of 80 or above. Results: The postoperative functional results in the group with retear (n=42) after arthroscopic rotator cuff repair showed significant improvement. Univariate analysis revealed the preoperative visual analogue scale (VAS) score and tear progression to have associations with a poor shoulder function. In addition, subscapularis repair was found to be associated with a good shoulder function. The preoperative VAS score and tear progression except for subscapularis repair were independent factors associated with poor clinical outcomes according to multivariate logistic regression analysis. Conclusion: In patients with retear after rotator cuff repair, the preoperative VAS and tear progression in postoperative MRI are factors predicting a poor functional outcome.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.497-502
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• 2009

The wastewater treatment by photocatalyst decomposes pollutants directly in water, and it is easy to decompose indecomposable organics and inorganic. and Especially, it has an advantage that there is no secondary production of pollutants. However, there will be many problems which are generated depending on the type of photocatalyst. The type of rotating photocatalyst minimizes previous problems, and advanced oxidation processes is possible by the application of rotating disc method. The consideration of the characteristics about various designs and operation factors is needed for the application of rotating photocatalyst system. In this study, rotating photocatalyst was manufactured for rotating disc method by fixing of $TiO_2$. The operation factors were derived for the wastewater treatment by the reaction of rotating photocatalyst. The contained quantity of $TiO_2$ was limited about 70%. The more the contained quantity of $TiO_2$ was increased, the more the treatment rate was continually increased. The optimum rotating photocatalyst was R4, and the contained quantity of $TiO_2$ was 36.8%. The more the exposed amount of UV is increased, the more the decomposition effect of TCODcr was continually increased. However, the adequate strength of light source must be determined by the consideration of economical efficiency. The more the speed of rotating photocatalyst is increased, the more treatment efficiency was increased. When UV lamp was not submerged in reactor, the wastewater treatment was efficient in the order of the depth of water 50%, 30%, 10%, 70%, 100%. This study is a basic research for the development of a system which treats organics in solar light.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.73-76
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• 2002

최근 링 정방기의 생산속도 증가로 인해 사절 및 사물성에 큰 영향을 미치는 정방장력의 중요성이 더욱 커지고 있다. 링 정방장력은 스핀들 회전수, 트래블러 중량, 링직경, 콥 직경 등과 같은 공정인자와 링 레일 상하운동에 따른 벌룬 높이, 얀 가이드에서의 실 굴절각도, 콥의 권취 반경 및 공기저항 등에 의해서도 영향을 받게 된다[1]. 이와 관련하여 링 정방장력 해석[2], 정방 공정인자가 정방장력에 미치는 영향[3] 및 정방 공정인자가 방적사 물성에 미치는 영향[4] 등의 연구가 많이 이루어져 왔다. (중략)

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2002.03a
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• pp.107-108
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• 2002

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2009.03a
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• pp.212-213
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• 2009

• Journal of Energy Engineering
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• v.10 no.4
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• pp.335-341
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• 2001

Pressure pulsations generated by the blade-tongue interaction induce vibration of the piping systems and the structure connected to pumps, resulting in the severe noise and fatigue fracture. Experiments were made on the natural frequencies of liquid columns in piping systems with a single suction, single stage, centrifugal volute pump. Experimental results show that the natural frequencies of the liquid columns in the pump piping systems depend on the dimensions of the pipes and the impeller shapes, and are not affected substantially by the rate of discharge and the rotating speed of the pump.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.13-17
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• 1992

최근 정보, 통신 광산업 등 첨단산업의 발달과 함께 부품의 초정밀가공및 특정에 대한 필요성이 높아지고 있다. 이에 따라 초정밀 가공기 및 초정밀계측기기등의 개발이 활발히 이루어지고 있으며, 이들에는 공기베어링두축이 널리 사용되고있다. 이 같이 초정밀 기기의 주축으로 공기베어링이 주로 이용되는 이유는 다른 베어링에 비해 윤활특성상 운동정도가 높고, 저 마찰특성 등의 장점을 가지고있기 때문이다. 본 연구에선 실험적으로 초정밀가공기용 공기베어링주축의 회전정도에 영향을 미치는 인자들의 상관관계를 파악하여 주축설계 및 제작시의 성능향상방법과 이론적 해석의 기초자료를 제시하고자 한다. 또한 공기베어링주축의 구조에 따른 정적 강성 및 회전정도를 비교하여 구조특성에 따른 차이점을 살펴보고, 주축의 강성과 불평형질량(unbalance mass)에 따른 회전 정도의 변화를 측정하였다.