• Journal of Korean Neurosurgical Society
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• 제56권4호
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• pp.315-322
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• 2014

Objective : Posterior accessed lumbar interbody fusion (PALIF) has a clear objective to restore disc height and spinal alignment but surgeons may occasionally face the converse situation and lose lumbar lordosis. We analyzed retrospective data for factors contributing to a postoperative flat back. Methods : A total of 105 patients who underwent PALIF for spondylolisthesis and stenosis were enrolled. The patients were divided according to surgical type [posterior lumbar inter body fusion (PLIF) vs. unilateral transforaminal lumbar interbody fusion (TLIF)], number of levels (single vs. multiple), and diagnosis (spondylolisthesis vs. stenosis). We measured perioperative index level lordosis, lumbar lordosis, pelvic tilt, sacral slope, pelvic incidence, and disc height in standing lateral radiographs. The change and variance in each parameter and comparative group were analyzed with the paired and Student t-test (p<0.05), correlation coefficient, and regression analysis. Results : A significant perioperative reduction was observed in index-level lordosis following TLIF at the single level and in patients with spondylolisthesis (p=0.002, p=0.005). Pelvic tilt and sacral slope were significantly restored following PLIF multilevel surgery (p=0.009, p=0.003). Sacral slope variance was highly sensitive to perioperative variance of index level lordosis in high sacral sloped pelvis. Perioperative variance of index level lordosis was positively correlated with disc height variance ($R^2=0.286$, p=0.0005). Conclusion : Unilateral TLIF has the potential to cause postoperative flat back. PLIF is more reliable than unilateral TLIF to restore spinopelvic parameters following multilevel surgery and spondylolisthesis. A high sacral sloped pelvis is more vulnerable to PALIF in terms of a postoperative flat back.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.167-173
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• 2007

This study analyzed by simulation using TRNSYS as well as by experiment on the solar district heating system installed for the first time for the district heating system in Bundang. Simulation analysis using TRNSYS focused on the thermal behavior and long-term thermal efficiency of solar system. Experiment carried out for the reliability of simulation system. This solar system where the circuits of two different collectors, flat plate and vacuum tube collector, are connected in series by a collector heat exchanger, and the collection characteristics of each circuit varies. Therefore, these differences must be considered for the system's control. This system uses variable flow rate control in order to obtain always setting temperature of hot water by solar system. Specifically, this is a system that heats returning district heating water (DHW) at approximately $60^{\circ}C$ using a solar collector without a storage tank, up to the setting temperature of approximately $85{\sim}95^{\circ}C$ To realize this, a flat plate collector and a vacuum tube collector are used as separate collector loops. The first heating is performed by a flat plate collector loop and the second by a vacuum tube collector loop. In a gross collector area basis, the mean system efficiency, for 4 years, of a flat plate collector is 33.4% and a vacuum tube collector is 41.2%. The yearly total collection energy is 2,342GJ and really collection energy per unit area ($m^2$) is 1.92GJ and 2.37GJ respectively for the flat plate vacuum tube collector. This result is very important on the share of each collector area in this type of solar district heating system.

• 한국전산구조공학회논문집
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• 제27권2호
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• pp.121-128
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• 2014

본 논문에서는 새로운 형상의 GFRP 판으로 전단보강된 플랫 플레이트의 전단거동에 관하여 실험적으로 연구하였다. GFRP 판은 개구부가 있는 판의 형태로서 콘크리트와의 일체화 거동을 위하여 콘크리트에 매립하여 사용한다. 총 7개의 시험체에 대한 뚫림 전단실험을 수행하였고, 실험 변수로는 전단보강재의 종류와 전단보강량을 선택하였다. 실험결과를 시험체의 균열 및 파괴양상, 변형률, 하중변위곡선으로 분석하였다. 또한 GFRP 판으로 전단 보강된 플랫 플레이트의 ACI 318-11 기준식에 의한 계산값과 실험에 의한 결과값을 비교하였다. 실험 결과 GFRP 판이 플랫 플레이트의 전단보강재로써 뚫림 전단에 효과적으로 적용함을 확인하였다.

• Wind and Structures
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• 제35권5호
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• pp.309-322
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• 2022

Due to the complex terrain around high-speed railways, the windbreaks were established along different landforms, resulting in irregular windbreak transition regions between different subgrade infrastructures (flat ground, cutting, embankment, etc). In this paper, the effect of a windbreak transition on the wind flow around railways subjected to crosswinds was studied. Wind tunnel testing was conducted to study the wind speed change around a windbreak transition on flat ground with a uniform wind speed inflow, and the collected data were used to validate a numerical simulation based on a detached eddy simulation method. The validated numerical method was then used to investigate the effect of the windbreak transition from the flat ground to cutting (the "cutting" is a railway subgrade type formed by digging down from the original ground) for three different wind incidence angles of 90°, 75°, and 105°. The deterioration mechanism of the flow fields and the reasons behind the occurrence of the peak wind velocities were explained in detail. The results showed that for the windbreak transition on flat ground, the impact was small. For the transition from the flat ground to the cutting, the influence was relatively large. The significant increase in the wind speeds was due to the right-angle structure of the windbreak transition, which resulted in sudden changes of the wind velocity as well as the direction. In addition, the height mismatch in the transition region worsened the protective effect of a typical windbreak.

• 한국생산제조학회지
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• 제9권2호
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• pp.96-101
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• 2000

In machining with cutting tool inserts having complex chip groove shape the flow curl and breaking pattern of the chip are different than in flat-face inserts. In the present work an effort is made to understand the three basic phe-nomena occurring in a chip since its formation in machining with groove type and pattern type inserts. These are the ini-tial chip flow the subsequent development of up and side curl and the final chip breaking due to the development of tor-sional and bending stresses. in this paper chip flow angle in a groove type and pattern type inserts. The expres-sion for chip flow angle in groove type and pattern type inserts is also verified experimentally using high speed filming techniques.

• 한국해양환경ㆍ에너지학회지
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• 제4권4호
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• pp.3-11
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• 2001

조간대와 같은 연안지역에서 해수의 토양 이동이 가지는 의미는 육상으로부터 유입되는 오염물질의 토양 이동 및 생물농축, 저서생물들의 생존에 필수적인 플랑크톤, 박테리아, 유기쇄설물, 산소, 영양염, 유기물의 생물공급, 수질 정화량 산정의 중요한 단서가 된다는 점이다. 따라서, 본 연구에서는 폐쇄성 수역과 같이 파도에너지가 비교적 작은 조간대에서 파도에 의한 해수의 침투거동을 해석하고, 파도에너지와 사면 구배의 변화에 따른 해수의 침투량 변화를 파악하고, 그 결과를 바탕으로 실제 조간대에서의 해수 침투량을 개략적으로 산정하는 것을 목적으로 하여, 모의 조간대 실험장치를 이용하여 실험을 수행한 결과, 다음과 같은 결론을 얻을 수 있었다. 폐쇄성 수역과 같은 파도에너지가 작은 조간대에서는 파도에 의해서 해수가 반원형의 형태로 토양중으로 침투하는 semi-circular mechanism은 지금까지 알려지지 않았던 새로운 침투 거동임을 알 수 있었다. 구배 또는 쇄파파고가 높아짐에 따라서 해수의 침투량이 증가하는 것을 알 수 있었다. 또한, 해수는 쇄파파고 보다는 구배의 영향을 크게 받아서 토양중으로 침투한다는 사실을 알 수 있었다. 현장토양을 이용하여 해수의 침투량을 정량화 할 수 있었으며, 본 연구의 결과를 바탕으로 현장 조간대에서의 해수 침투량을 개략적으로 산정 할 수 있었다. 따라서, 본 연구 결과를 바탕으로 오염물질의 토양 이동 및 생물농축, 저서생물들의 먹이공급, 수질 정화량 산정에 관한 연구가 활발히 진행되기를 요망한다.

• 로봇학회논문지
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• 제5권1호
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• pp.14-22
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• 2010

Recently researches on the window cleaning robot are being conducted actively. Moving mechanismsof these window cleaning robots are divided into two categories, which are towed type and walking type. Towed type is focused on fast cleaning on the flat surface of building and walking type has priority on cleaning task on relatively complex surface with overcoming obstacles. Currently commercialized towed type window cleaning robot has weakness that it is hard to adhere closely with the wall and easy to be affected by wind. In case of walking type it has the problem that the position errors are continuously accumulated during motion. In this paper, we propose new towed and walking type mechanism which can compensate previous weaknesses. After that we estimate the performance of each proposed mechanism by simulation.

• Clinics in Shoulder and Elbow
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• 제2권1호
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• pp.35-40
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• 1999

Impingement syndrome is caused by a conflictual status between rotator cuff, subacromial bursa and anatomic and functional coracoacromial arch. The purpose of this study was to assessment the coracoacromial arch by MRI and to determine major factors among five components of coracoacromial arch. We analyzed forty-two cases of clinical impingement sign and test positive and postoperative confirmed diagnosed from March, 1991 to January, 1999. We evaluated acromial end abnormality according to the Bigliani acromial type and formation of osteophyte. Clavicular end abnormality classified flat, outward protrusion, inward protrusion to coracoacromial arch. Acromioclavicular joint abnormalities were advanced osteoarthritis and positive signal change. Coracoacromial ligament thickening was above 2 mm in oblique sagittal image. Coracoid process abnormality was inward protrusion to coracoacromial arch. All consecutive patients abnormalities were as follows: clavicular end osteophyte formation and inward protrusion to coracoacrmial arch were 30%, acromial end osteophyte formation was 28%, advanced acromioclavicular joint arthritis and osteophyte formation were 56%, coracoacromial ligament thickening was 24% and no coracoid process inward protrusion to coracoacromial arch. Impingement syndrome combined with rotator cuff tear group abnormalities were clavicular end(40%), acromial end(40%), acromioclavicular joint(20%), coracoacromialligament(20%) and coracoid process abnormality(0%) respectively. Only impingement syndrome group abnormalities were clavicular end(25%), acromial end(31%), acromioclavicular joint(62%), coracoacromial ligament(25%) and coracoid process(0%) respectively. Acromial type I(flat) were 6 cases, type II(curved) were 26 cases and type III(hooked) were 10 cases. We concluded that the most important contributing factors for impingement syndrome was acromial type and second was acromioclavicular joint arthritis and bony spur formation.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.100-106
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• 2006

The behavior of spray impinging on the inclined constant temperature flat plate was experimentally investigated. To clarify the wall effect of a high pressure DISI injector, a relative angle of the inclined wall to a spray axis was varied. Spray penetration along the wall was observed optically and it was compared with that of a Fan spray type and Swirl type spray. To evaluate various spray motion quantitatively, a spray path penetration which describe the development of a spray tip along the wall was newly introduced. To observe the structure of an impinging spray, it was visualized by a controlled stroboscope light and its visualized image was captured on an CCD camera. Using the digital image of impinging spray $H_x$ and $R_x$ was extracted to clarify the structure of impinging spray. The main parameter of the relative position of the wall was the inclined angle which was defined as the angle was varied from $0^{\circ}$ (vertical impingement) to $60^{\circ}$ at the same condition.

• 한국태양에너지학회 논문집
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• 제35권4호
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• pp.1-7
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• 2015

The operation of the natural circulation type solar heating systems with facade integrated collector was analyzed by experiment. Two different types of flat plate solar collectors were used for these experiments. One was for the normal flat plate solar collector with the size of 1m*2m and the other was for the large size solar collector with $4m^2$(1m*4m). The experiments were carried out to investigate the effect of the series or parallel connection method on the performance of the collectors. As a result, the solar thermal system which is installed on the wall or facade would be applicable for the natural circulation type if the system design reflects various parameters, including collector connecting method(series or parallel), to provide enough vertical height between collector and storage tank, and to reduce pressure loss due to collector and piping network, etc. The natural circulation type of solar thermal system as proposed in this study can increase the system reliability by removing or minimizing the use of the components such as pump, controller, sensors which may cause serious troubles of the system for a long-time operation