원심압축기의 선회실속특성에 관한 연구

모양우,나기대,유영태,김지환 朝鮮大學校 機械技術硏究所 2003 機械技術硏究 Vol.6 No.2

In the present study, the performance characteristics and the number of stall cell during rotating stall of a centrifugal air compressor were experimentally investigated. Rotating stall in the vaneless diffuser were investigated by measuring unsteady pressure fluctuations at several different diffuser radius using a high frequency pressure transducer. The number of stall cell and their rotational speeds are distinctive features of the rotating stall phenomenon. The present study is mainly forced on the analysis for the stall cell number and its propagation speed unstable operating region of the compressor. The interpretation method of visualization is based on the pressure distribution in the circumference pressure fields while plotting the pressure and its harmonics variations in time in polar coordinates. To obtain the visualize the existence rotating stall, auto-correlation function and the frequency spectra of the pressure fluctuations were measured at rh-2 = 1.52. When the flow coefficient is lower than 0.150, the static pressure at impeller inlet is higher than that at inlet duct of the Compressor. And the flow coefficient is lower than 0.086, several stall cell groups of discrete frequencies are observed.

압박 고 나사로 치료한 대퇴골 전자부 골절 : 고정 실패의 인자에 대한 분석 Analysis of Factors associated with Failure of Fixation

유찬훈,김홍태,변영수,남준모,조영호,문성건 대한골절학회 2002 대한골절학회지 Vol.15 No.4

목 적 : 압박 고 나사로 치료한 대퇴골 전자부 골절의 고정 실패에 영향을 미치는 요소에 대하여 분석하고자 하였다. 대상 및 방법 : 1995년 5월부터 2000년 7월까지 대퇴골 전자부 골절을 압박 고 나사를 이용하여 치료하고 1년 이상 추시가 가능했던 97예를 대상으로 하였다. 골절의 분류는 Jensen 분류법을, 골다공증의 정도는 Singh 지수를 이용하였다. 술후 방사선 검사에서 경체각, 정복 상태, 지연 나사의 대퇴골 두 내 위치, tip-apex distance(TAD) 및 지연 나사의 활강 거리를 측정하였고 고정 실패에 미치는 영향을 통계학적으로 분석하였다. 결 과 : 97예 중 17예(17%)에서 고정 실패가 발생하였고 그 중 지연 나사의 과도한 활강으로인한 경우가 15례(15.4%), 골두 천공 1얘, 10도 이상의 외반 변형 1예였다. 고정 실패의 발생과 80세 이상의 고령, 불안정성 골절, telescoping 정복, 원위 골편의 내측 혹은 전방 전위, 대퇴골 두 내 지연 나사의 위치와 밀접한 관계가 있었다. 결 론 : 압박 고 나사를 이용한 대퇴골 전자부 골절의 치료에서 고정 실패를 방지하기 위해서는 정확한 정복이 필요하고 대퇴골 두 내에서 지연 나사의 전방 위치를 피하는 것이 좋을 것으로 사료된다. Purpose : This study was performed to analyze the significant factors that may affect failure of fixation in trochanteric fractures of the femur treated with the compression hip screw. Materials and Methods : From May 1995 to July 2000, the authors analyzed 97 cases of trochanteric fracture of the femur treated with the compression hip screw and followed more than one year. We classified the fracture type by Jensen's method. We used Singh index for the degree of osteroporosis. In the post-operative radiograph, we checked neck-shaft angle, state of reduction, position of the lag screw within the femoral head, tip-apex distance, and sliding distance of the lag screw. The relationship between these factors and failure of fixation was statistically analyzed. Results : There were 17 cases(17.5%) of failure of fixation ; 15 cases(15.4%) of excessive sliding of the lag screw, 1 case (1%) of cutting out of the lag screw, and 1 case (1%) of valgus malunion. There were significant relationship between failure of fixation and old age over 80 , unstable fracture, telescoping reduction, anterior or medial displacement of the distal fragment, and anterior placement of the lag screw within the femoral head. Conclusion : Accurate reduction and avoidance of the placement of the lag screw in the anterior part of the femoral head were important factors to prevent failure of fixation in trochanteric fractures of the femur treated with the compression hip screw.

고출력 레이저에 의한 이종금속 용접시험평가에 관한 연구

유영태,신호준,송성욱,모양우 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.1

Laser welding techniques have been characterised for various materials. In this paper. the laser weldability of STS304 stainless steel and Inconel 600 at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. Inconel 600 is being used in a steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion. Stress corrosion cracking can occur on this material. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser were tested.

유압관로에서 맥동유동의 유량특성

유영태,모양우,김지환 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.2

The measurement of unsteady flow rate is importance to clarify and improve the dynamic characteristics in pipeline, hydraulic components and systems. There is also demand for a real time flow at the sensor in order to measure unsteady flow rate with high accuray and fast response to realize feedback control of flow rate in fluid power systems therefore We propose an approch for estimating unsteady flow rate through a pipeline and dynamic characteristics of pulsting flow rate components under high pressure condition. Unsteady flow rate is estimated by using semiconductor type pressure transducers and the measured pressure values at two distant points along the pipeline.

고출력레이저에 의한 인코넬600의 맞대기용접 시험 평가

유영태,신호준,모양우 조선대학교 에너지.자원신기술연구소 2004 에너지·자원신기술연구소 논문지 Vol.26 No.1

Welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were position of focus, laser power, travel speed. The gap and offset maintained as small as possible. Optical microscope were used to investigate the microstructures of the welded zone. This study shows the result of the tension experiments. And then this paper used the Electronic Speckle Pattern Interferometry to present the welding residual stress in welds. The follow conclusions can be drawn the laser power and travel speed have a pronounced effect the fusion zone size and shape.

유압관로의 임피던스 전달특성

유영태,나기대,모양우,김지환 朝鮮大學校 機械技術硏究所 2003 機械技術硏究 Vol.6 No.2

Design for quite operation of fluid power system requires t h understanding of noise and vibration characteristics of t h system This paper presents a dynamic response of design of hydraulic circuit. Experimental investigations on the attenuation characteristics of pressure ripple in automotive power steering hydraulic pipe with dynamic response of hydraulic pipe line is examined.

정사각 덕트의 출구 영역에서 속도분포에 대한 실험적 연구

유영태,모양우,나기대,임인호 朝鮮大學校 機械技術硏究所 2002 機械技術硏究 Vol.5 No.2

A numerical simulation has been performed with the non-linear turbulence model proposed by Speziale(1987) coupled with the k-ε equations coming from the renormalization group theory(RNG) derived by Yakhot et al(1992). The fully developed turbulent flow through a straight square duct, involing secondary motion is simulated. This paper represent computations of the interaction between measurement and numerical computation of turbulent flow on velocity distribution of outlet region in a square duct. RNG turbulent model was adapted and compared with the experimental data and the result of Standard k-ε turbulent model. The predictions obtained with the RNG k-ε model show improvements when compared with the Standard k-ε model. Mean velocity, turbulence kinetic energy and Reynolds shear stresses are in quantitiative agreement with the experimental data. We feel that the RNG k-ε model suggested in this paper can be a useful turbulence model for practical engineering

유압관로의 비정상유동에 따른 임피던스 전달특성

모양우,유영태,나기대,김지환 한국공작기계학회 2004 한국생산제조학회지 Vol.13 No.6

Design for quite operation of fluid power system requires the understanding of noise and vibration characteristics of the system. This paper presents a dynamic response of design of hydraulic circuit. Experimental investigations on the attenuation of pressure ripple in automotive power steering hydraulic pipe line is examined. Also, a mathematical model of hydraulic pipe is proposed to support a design of the hydraulic circuit. and the impedance characteristics of pressure ripple is analyzed. It is experimentally shown that power steering hydraulic pipe attenuates pressure ripple with high frequency.

흉요추부 굴곡-신연 손상에서 척추체의 골절 양상

고영도,김종오,윤여헌,유재두,정준모 대한골절학회 2003 대한골절학회지 Vol.16 No.2

목적 : 흉요추부 굴곡-신연 손상에 동반되는 척추체의 골절 양상을 알아 보고자 하였다. 대상 및 방법 : 흉요추부 굴곡 - 신연 손상 21례의 방사선 검사를 검토하여 골절된 척추체의 위치, 전후방 추체 높이, 손상된 분절의 후만각, 척추체 골편의 척추관내 침범 정도 및 척추체의 분쇄 정도를 관찰하였다. 결과 : 총 21례 중 압박 골절이 11례, 방출성 골절이 9례 있었다. 척추체 골절은 85%에서 굴곡-신연 손상된 분절내에서 하부 척추체에 위치하였다. 전방 추체 높이는 평균 27% 감소하였고, 압박 골절이 동반된 경우 18%, 방출성 골절이 동반된 경우 40% 감소하였다. 후방 추체 높이는 평균 1% 감소하였고, 압박 골절이 동반된 경우 1% 증가하였으며, 방출성 골절이 동반된 경우 4% 감소하였다. 손상된 분절의 후만각은 평균 19.5도이었고, 압박 골절이 동반된 경우는 15.4도, 방출성 골절이 동반된 경우는 26.8도이었다. 방출성 골절이 동반된 9례 중 골편의 척추관내 침범은 평균 27%이었으며, 척추체의 분쇄 정도는 71.4%에서 경미하였다, 결론 : 흉요추부 굴곡-신연 손상에서 척추세의 골절은 매우 흔하며 분절내 하부 척추체에 호발하였다. 가해진 힘에 비하여 전후방 추체 높이의 감소, 척추관내 침범 및 분쇄 정도가 적었으며, 이는 굴곡력이나 축성 부하의 효과가 신연력에 의해 일부 상쇄되었기 때문이다. Purpose : To evaluate the configuration of vertebral body fractures in flexion-distraction injuries of thoracolumbar spine. Materials and Method : We investigated the location of fractures, anterior or posterior vertebral body height, kyphotic angle of injured segments, canal encreachment and severity of comminution on radiologic examinations of 21 cases. Result : There were 11 compression fractures and 9 burst fractures. 85% of fractures were located in the inferior vertebrae of injured segments. Anterior vertebral height decreased by 27% on average with decrease of 18% in compression fractures and 40% in burst fractures. Posterior height decreased by 1% on average with increase of 1% in compression fractures and decrease of 4% in burst fractures. The average kyphotic angle of injured segments was 19.5˚ with 15.4˚ in compression fractures and 26.8˚ in burst fractures. The canal encreachment in 9 burst fractures was 27% on average, and the comminution of vertebral body was mild in 74%. Conclusion : The fracture of vertebral body in flexion-distraction injuries of thoracolumbar spine was very common, and located on the inferior vertebare of injured segment. The decrease of vertebral height, canal encreachment and severity of comminution was relatively less than the estimated from mechanism of injury, with offset effect of distraction force.

Finn Chamber Occlusion 과 Histometry 를 사용한 수종 스테로이드제의 표피 위축에 대한 관찰

천영일(Young Il Chun),양준모(Joon Mo Yang),서명수(Myoung Soo Suh),은희철(Hee Chul Eun),이유신(Yoo Shin Lee) 대한피부과학회 1986 大韓皮膚科學會誌 Vol.24 No.5

The aim of this stud y was to compare the epidermal thinning properties of four corticosteroid ointments applied under occlusion, using histology and histometry. The results were surnmerized as follows: 1.The stratum corneurn was dramatically thinned, appearing as a wispy layer of horny cells as apposed to the norrnal basket-weave configuration. this effect was prominent at sites treated with clobestasol propionate, fluocinonide, and fluocinolone acetonide. 2. With the histometry, visible epidermal thickness wa.s markedly reduced. This effect w is prominent in the following ascending order: fluocinolone acetonide, fluocienonide, clobestasol-17-propionate. Hydrocortisone was the least atrophogenic. 3. Clohestasol-17-propionate and fluocinonide caused significant flattening of der- mo-epidermal junction, Fluocinolone acetonide and hydrocortisone caused less pronounced cbanges. 4. Marked capillary dilation af papilly dermis is caused by clobestasol-17-propionate, fluocinonide and fluocinolone acetonide.