• 대한기계학회논문집B
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• 제20권3호
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• pp.1106-1113
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• 1996

The phase criterion of the feedback cycle of low-speed edgetones has been obtained using the jet-edge interaction model which is based on the substitution of an array of dipoles for the reaction of the wedge to the impinging jet. The edgetone is produced by the feedback loop between the downstream-convected sinuous disturbance and upstream-propagating waves generated by the impingement of the disturbance on the wedge. By estimation of the phase difference between the downstream and the upstream disturbances, the relationship between the edge distance and the wavelength is obtained according to the phase-locking condition at the nozzle lip. With a little variation depending on the characteristics of jet-edge interaction, the criterion can be approximated as follows: h/.LAMBDA. + h/.lambda. = n - 1/4, where h is the stand-off distance between the nozzle lip and the edge tip, .LAMBDA. is the wavelength of downstream-convected wave, .lambda. is the wavelength of the upstream-propagating acoustic wave and n is the stage number for the ladder-like characteristics of frequency. The present criterion has been confirmed by estimating wavelengths from available experimental data and investigating their appropriateness. The above criterion has been found to be effective up to 90.deg. of wedge angle corresponding to the cavitytones.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1212-1218
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• 2003

A novel loading mechanism of wedge roller type has been developed. This type traction drive has long system life and high efficiency by changing the pre-load on a contact point. And this loading mechanism does not need precision machining. So it has, as opposed to the conventional loading mechanism, an advantage in saving manufacturing cost. In this paper, by analyzing pre-load generating mechanism, spring pre-load and the roller size are defined and the stress on the contact point by pre-load is calculated. On the basis of this analysis, the model of wedge roller type traction drive for the test is made and was carried out its performance test. It can transmit input torque up to 1.5 N m, with high efficiency over 91% up to 98%, with slip rate under 2.5%.

• International Journal of Concrete Structures and Materials
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• 제18권3E호
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• pp.191-198
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• 2006

The objective of this study is to examine fracture characteristics of concrete at early ages, i.g. critical stress intensity factor, critical crack-tip opening displacement, fracture energy, and bilinear softening curve based on the concepts of effective-elastic crack model and cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By experimenting with various strengths and ages, load-crack mouth opening curves were obtained, and the results were analyzed by linear elastic fracture mechanics and FEM(finite element method). The results from the test and analysis showed that critical stress intensity factor and facture energy increased while critical crack-tip opening displacement decreased with concrete aging from 1 day to 28 days. Four parameters of bilinear softening curve from 1 day to 28 days were obtained from a numerical analysis. The obtained fracture parameters and bilinear softening curves at early ages from this study are to be used as a fracture criterion and an input data for the finite element analysis of concrete at early ages.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1543-1546
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• 2008

The purpose of this study was to investigate factors affecting the change of tibial posterior slope and introduce a mathematical model which calculate, through 3-dimensional analysis of the proximal tibia, how the angle of the opening wedge along the anteromedial tibial cortex influences the tibial posterior slope and valgus correction when performing a medial open wedge osteotomy. This mathematical model with navigation system can be guidelines which provide surgeons on preoperative and intraoperative measurements to maintain or correct the tibial slope and to obtain the desired valgus correction of the lower limb during an opening wedge osteotomy.

• 대한방사선치료학회지
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• 제16권2호
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• pp.69-79
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• 2004

목적 : 10MV 이상의 고 에너지를 사용할 경우 X선에 의해 광중성자(Photoneutron)가 발생되고 이 중성자는 주변 물질을 방사화(Activation)시켜 Beam-off기간에도 방사화된 물질의 유도 방사선(Induced radiation)에 의해 작업자의 피폭을 유발할 수 있다. 특히, 방사화된 물질중 방사선 치료시 작업자가 직접 손으로 접촉하는 wedge filter의 방사화를 알아보기 위해 10MV Siemens 가속기와 15MV Siemens 가속기에서 5Gy 조사 후 wedge filter에서 방사선량을 측정하여 방사선 발생 메커니즘을 확인하고, 선량측정을 통해 방사선 작업종사자의 작업환경에 미치는 영향을 평가하고자 한다. 대상 및 방법 : 본 연구에서 사용한 방사선 치료용 선형가속기는 Siemens사의 10MV Primus, Siemens사의 15MV Primus를 사용하였다. Siemens사의 Wedge filter를 사용하였으며, Wedge의 재질은 Fe, Wedge holder는 Al이다. 선량측정은 GM-측정기인 RDS-110 Model을 이용하였다. 본 실험에 사용된 GM-측정기는 $50keV{\sim}1.25MeV$의 X-ray가 측정가능하며, $0.05{\mu}Sv/hr{\sim}100mSv/hr$까지 측정이 가능하다. GM survey meter를 사용하여 환자 대기실과 건물 밖, 두 지점의 자연 방사선량을 측정하여 background값으로 사용하였다. 광중성자를 발생시키고, 또한 방사화를 진행시키기 위해 wedge를 장착한 상태에서 10MV X선, 15MV X선을 5Gy(500MU)를 조사하였고, beam-off직후 wedge filter를 가속기로부터 분리시켜 GM survey meter를 이용하여 wedge filter 중심부분에서 30초 단위로 방사선량을 측정하였다. 결과 : Primus 10MV의 경우 H병원에서 측정을 수행했으며, $0{\times}0cm^2,\;5{\times}5cm^2,\;25{\times}25cm^2$ Field size에 대하여 500MU 조사 후 방사선량의 측정결과 Field size의 영향은 거의 존재하지 않았으며, beam off 후 $1{\sim}2$분 뒤 측정 시작 시점에서 대략 $1{\mu}Sv/hr$를 나타냈으며, 반감기는 약 $3{\sim}4$분인 것으로 측정되었다. Primus 15MV의 경우 S병원에서 측정을 수행하였으며, $25{\times}25cm^2$ Field size에 대하여 500MU 조사 뒤 방사선량을 측정한 결과, beam off후 $1{\sim}2$분 뒤 측정시점에서 대략 $3.26{\mu}Sv/hr$를 나타냈으며 10MV X선보다 대략 3.3배 큰 값을 나타내었다. 결과 : 일일 치료환자가 $20{\sim}50$명이고, 환자 1인당 Wedge filter의 교체작업이 $1{\sim}2$회일 때 10MV의 경우 연간선량이 $0.08{\sim}0.4mSv$로 평가되었으며, 15MV의 경우 $0.27{\sim}1.36mSv$로 평가되어 작업종사자의 연간 허용선량인 20mSv에 비해 안전한 것으로 평가되었다.

• 대한의용생체공학회:의공학회지
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• 제31권1호
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• pp.56-66
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• 2010

The various total replacement artificial discs have developed because spinal fusion has shown a lesser mobility of an operated segment and an accelerated degeneration at adjacent discs. But almost artificial discs have not yet been reached on the substitute surgery of fusion because many problems such as those clinical success rates were not more than them of fusion have not solved. In this paper, vertically inserted assemble-screw fixture in vertebrae was proposed to improve the fixed capability of artificial disc. And also, to evaluate the design suitability of newly designed screw-type, including fixtures of commercial discs such as wedge and plate type, the 1/4 finite element model with a vertebra and various implanted fixtures were generated, and next, 3 bending motions such as flexion, bending and twisting under the moment of 10Nm and compression under the force of 1000N were considered, respectively and finally, FE analyses were performed. Results of three fixture types were compared, such as Range of Motion and maximal stress, and so on. For ROM, the screw type was average 58% less than the wedge type and was average 42% less than the plate type under all loading conditions. For average stress ratio at closer nodes between vertebra and each fixture, the wedge type was the lowest as minimum 0.02 in twisting, screw types were the highest as maximum 0.28 in compression. As the results of using cement material, it was predicted that the instability problem of the wedge type was better solved. The screw type which could be increased by implanting depth according to the number of assembling mid screws, showed that the decreased tendency of ROMs and maximal cancellous bone stresses. In further study, controlling the number of assembling screws that was suitable for a patient's bone quality, development of surgical tools and keeping on design supplementations, which will be able to develop the competitive artificial disc.

• 한국CDE학회논문집
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• 제18권6호
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• pp.385-398
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• 2013

Opening wedge high tibial osteotomy (OWHTO) is widely used to treat unicompartmental osteoarthritis of the knee caused by degenerative deformations of the anatomical axes of the leg. However, since it is difficult to accurately plan the surgical degrees of adjustment such as coronal correction angle and tibial posterior slope angle to align the axes before the actual procedure, a number of studies have proposed analytical models to solve this problem. While previous analytical models for OWHTO were limited to specific cases, this study proposes an analytical osteotomy model (AOM) and a surgical planning system (SPS) that are suitable for a wide range of tibial morphologies and tibia conditions. The validity and generality of the model were verified in a total of 60 OWHTO cases. Results of the test showed that, as predicted, surgical degrees are affected quite significantly by tibia shape and slope of the resected surface. Comparison of the required surgical degrees and the degrees estimated from virtual surgery simulations using AOM showed a very small average difference of $0.118^{\circ}$. SPS, based on AOM, allows the operating surgeon to easily calculate surgical parameters needed to treat a patient.

• 대한조선학회논문집
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• 제57권1호
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• pp.23-34
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• 2020

This paper covers the development of prediction techniques for ice load on ice-breakers operating in continuous ice-breaking under level ice conditions using particle-based continuum mechanics. Ice is assumed to be a linear elastic material until the fracture occurs. The maximum normal stress theory is used for the criterion of fracture. The location of the crack can be expressed using a local scalar function consisting of the gradient of the first principal stress and the corresponding eigen-vector. This expression is used to determine the relative position of particle pair to the new crack. The Hertz contact model is introduced to consider the collisions between ice fragments and the collisions between hull and ice fragments. In order to verify the developed technique, the simulation results for the three-point bending problems of ice-specimen and the continuous ice-breaking problem around a wedge-type model ship with bow angle of 20° are compared with the experimental results carrying out at Korea Research Institute of Ships and Ocean Engineering (KRISO).

• 대한토목학회논문집
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• 제9권1호
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• pp.53-62
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• 1989

점변일차원이층류(漸變一次元二層流)모델로서의 염수(塩水)쐐기형상(形狀)의 계산(計算)을 행함에 있어서 필요(必要)한 계면저항계수(界面低抗係數)의 평가수단(評價手段)에 대(對)하여 논(論)한다. 예(例)를 들면, 폭(幅)이 좁은 실험수로(實驗水路)에서 얻어진 염수(塩水)쐐기의 형상(形狀)에 의해 계면저항계수(界面低抗係數)를 역산(逆算)하는 경우는 실제(實際)의 하천(河川)에서는 무시(無視)할 수 있는 수로(水路)의 측벽(側壁)의 영향(影響)을 보정(補正)하지 않으면 안된다. 본연구(本硏究)에서는 이러한 점(點)을 고려(考慮), 정상(定常) 염수(塩水)쐐기의 형상(形狀) 및 계면저항계수(界面低抗係數)에 미치는 수로(水路)의 측벽(側壁)의 영향(影響)을 밝힌다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.215-220
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• 2001

The objective of this study is to examine the fracture characteristics of concrete at early ages such as critical stress intensity factor, critical crack-tip opening displacement, fracture energy based on the concepts of the effective-elastic crack model and the cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By varying strength and age, load-crack mouth opening displacement curves were obtained and the results were analyzed by linear elastic fracture mechanics. The results from the test and analysis showed that critical stress intensity factor and fracture energy increased, and critical crack-tip opening displacement decreased with concrete age from 1 day to 28 days. The obtained fracture parameters at early ages may be used as a fracture criterion and an input data for finite element analysis of concrete at early ages.