• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.375-380
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• 2000

The purpose of this study is to verify the relations with the fatigue life and stress distribution on the screw thread for thoracic and lumbar spine. These screws are now developed for Korean in this research group. The fatigue life of single screw was found longer than that of up-left-screw, but shorter than that of up-right-screw. The fatigue life of screw used was associated with the angie between bending and thread direction. In the case of upper left and right screw were fractured in the region of one pitch and two pitch of the thread valley from the shank of pedicle screw, respectively.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.554-559
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• 2016

본 논문은 EDISON CFD를 사용하여 스포일러가 장착된 무미익 BWB UCAV에 대하여 이차원 유동해석을 수행하였다. 무미익 형상은 일반적인 항공기보다 롤과 요 방향의 안정성과 조성성에 있어 불리한 특징을 갖는데 특히 이 착륙 시 고 받음각의 영역에서 발생하는 Pitch-up 현상이 항공기 안정성에 문제를 야기한다. 수직 미익 부재와 pitch-up 현상으로 인한 BWB형상의 UCAV가 지니는 단점을 보완하기 위해서 스포일러가 장착된 형상이 적용되기도 한다 본 연구에서는 윗면과 아랫면에 스포일러가 장착된 경우에 대해 전산유동해석을 수행하였다. 해석결과 윗면의 스포일러는 양력의 감소와 항력의 증가를 야기했으며, 아랫면의 스포일러는 양력과 항력을 모두 증가시켰다. 피칭모멘트의 경우 아랫면의 스포일러가 저받음각에서 안정성을 증가시켰다.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.7-13
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• 2007

This study proposes a new screw measurement system that is capable of measuring the pitch or lead of a screw, which is one of the most important parameters representing the screw quality. There are various conventional methods for screw measurement including some mechanical and optical ones, but they can not be applied to measure the lead except the profiles or sizes. The newly suggested method is able to measure the pitch or lead directly. This is executed by scanning the thread with a digital probe while the target screw rotates. The devised measurement system is a integrated computer system which is composed of a stepping motor, a digital linear gauge and a chuck device for holding the measured screw. In order to operate the system effectively and conveniently, a computer program having graphical user interface facility is developed. Some experiments were done to prove the effectiveness of the system.

• 동력기계공학회지
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• 제18권1호
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• pp.22-31
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• 2014

This paper introduced the new calibration algorithm of a straight-type five-hole pressure probe necessary for calculating three-dimensional flow velocity components. The new velocity data reduction method using both a commercial two-dimensional curve-fitting program and the zone partition method of a calibration map was firstly introduced in this study. This new calibration method can be applied up to the wide flow angle of ${\pm}80^{\circ}$ despite of using a five-hole pressure probe because this data reduction method showed a comparatively good performance in calculating yaw and pitch angles from the calibration map.

• 태양에너지
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• 제19권3호
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• pp.93-100
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• 1999

The objective of this experimental study was to investigate the characteristics of heat transfer and air flow in two-dimensional impinging jet system, in which hybrid rods have been set up in front of heating surface in order to increase heat transfer. The shape of hybrid rods had a cross section made with a half of circular cross section and that of rectangular. This time, the clearance from hybrid rod to heating surface(C=1, 2, 4mm) and the pitch between each hybrid rods(P=30, 40, 50mm) changed for the transition region(H/B=10). And this result compared with the experimentation without hybrid rod. As a result, heat transfer performance was best under the condition of C=1mm, in case clearance changed, and as the pitch is 30mm, it is largely influenced by eddies and acceleration in case pitch of hybrid rod changed.

• 공업화학
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• 제29권6호
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• pp.677-681
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• 2018

본 연구에서는 탄소블럭의 고밀도화를 위하여 불소화 표면처리된 코크스와 바인더피치를 압축성형으로 탄소블럭을 제조하였다. 불소화 표면처리 후 코크스 표면에 불소원소는 XPS 분석을 통하여 최대 24.14 at%가 도입된 것을 확인하였다. 불소화된 코크스와 바인더피치의 젖음성을 반응온도에 따라 평가하였다. 접촉각 측정 결과로부터 불소원소가 코크스 표면에 도입될수록 바인더피치와의 젖음성이 약 64.7% 향상됨을 알 수 있었다. 또한, 불소가 가장 많이 도입된 탄소블럭의 밀도는 미처리된 코크스로부터 제조된 탄소블럭의 밀도 대비 최대 6.8% 증가하였다.

• 상하수도학회지
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• 제24권3호
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• pp.277-285
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• 2010

We examined the optimal shape of blades and efficiency of a self-power generator when the self-power generator using flow of the water in pipe as the power source was installed. Selected factors were the shape of blades, the number of blades, pitch angle, and the existence of separator. GAMBIT2.4 was used as a modeling program, FLUENT6.3, which is computational fluid dynamics simulation program, was used as an analytical model. In the case of a viscous model, k-epsilon standard model was chosen. As a result, when the number of blades was increased, the efficiency and maximum moment were enhanced slightly. The pitch of blades went up, and maximum moment was also increased. The optimal pitch of blade was 62.5 degree and the efficiency was increased by 30%. The efficiency was also increased when a separator was installed.

• 한국항공우주학회지
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• 제34권5호
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• pp.65-73
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• 2006

위성이 발사체로부터 분리될 때 초기 각속도가 발생한다. B-dot 로직은 일반적으로 위성의 초기각속도 제어에 사용되나, 상대적으로 제어시간이 많이 소요된다는 단점이 있다. 이런 문제를 해결하기 위해 본 논문에서는 피치 바이어스 모멘텀 방식을 사용하는 초소형 위성에 적용 가능한 디텀블링(detumbling) 방식을 새롭게 제안하였다. 제안된 디텀블링 방식은 제어시간이 약 20분 이내로 기존의 방식에 비해 상당한 시간을 줄일 수 있다. 본 논문에서 제안한 디텀블링 방식을 사용할 경우 기존의 모멘텀 휠 초기구동 방식을 사용할 수 없다. 따라서 휠의 속도를 안정적으로 공칭 속도까지 증가시키는 방식을 제안하고 시뮬레이션을 통해 비교, 검증하였다. 시뮬레이션 결과 기존의 방식과 비교했을 때 제어시간을 단축할 수 있었으며 휠의 공칭 속도와 3축 안정화를 이룰 수 있었다.

• 대한족부족관절학회지
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• 제12권2호
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• pp.117-121
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• 2008

Purpose: To determine the clinical and radiographic results of arthroereisis using the $Kalix^{(R)}$ implant (Newdeal, Lyon, France) for the treatment of flexible flatfoot deformity. Materials and Methods: From February 2005 to February 2007, we performed the subtalar arthroereisis on 8 patients (9 feet) of symptomatic flexible flat feet after more than 6 months of conservative treatment. Average age was 14.5 years ($11{\sim}29$ years) old. We checked the functional status with AOFAS functional score pre-operatively and at final follow-up. Radiologically, we took weight bearing anterior to posterior and lateral view of the feet, and measured the talo-first metatarsal angle, calcaneal pitch angle in pre-operatively and at final follow-up. Results: Mean follow up period was 34.4 months. Average AOFAS score improved from preoperatively 65.6 to postoperatively 94.8. Average lateral talo-first metatarsal angle reduced from $12.8^{\circ}$ preoperatively to $1.6^{\circ}$ at final follow-up. Average anterior to posterior talo-first metatarsal angle was reduced from $15.1^{\circ}$ preoperatively to $8.3^{\circ}$ at final follow-up. Average calcaneal pitch angle was increased from $9.5^{\circ}$ preoperatively to $12.0^{\circ}$ at final follow-up. Conclusions: Subtalar arthroereisis with Kalix$K^{(R)}$ implant can be considered to be one of treatment options symptomatic flatfoot deformity patients.

• 대한족부족관절학회지
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• 제10권2호
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• pp.218-222
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• 2006

Purpose: We evaluate the results of subtalar arthroereisis with $Kalix^{(R)}$ implant (Newdeal, Lyon, France) that were performed in painful flatfoot deformity. Materials and Methods: We performed the subtalar arthroereisis on 16 feet of children symptomatic flexible flat feet after more than 6 months of conservative treatment. Average age was 11 years (8-14 years) old. We checked the functional status with AOFAS functional score in pre-operatively and at final follow-up. Radiologically, we took weight bearing anterior to posterior and lateral view of the feet, and measured the talo-$1^{st}$ metatarsal angle, calcaneal pitch angle, cuboid-surface height. Finally, we asked to patient's parents for satisfaction of the surgery. Results: Mean follow up period was 34.1 months. Average AOFAS score improved from preoperatively 71.9 to postoperatively 91.3. Only one patient has subtalar pain. Average lateral $1^{st}$ metatarsal angle reduced from $-18.2^{\circ}$ preoperatively to $-4.6^{\circ}$ at final follow-up. Average anterior to posterior $1^{st}$ metatarsal angle was reduced from $18.9^{\circ}$ preoperatively to $6.5^{\circ}$ at final follow-up. Average calcaneal pitch angle was increased from $8.6^{\circ}$ preoperatively to $12.6^{\circ}$ at final follow-up. Average cuoboid-surface height was improved from 12.1 mm preoperatively to 16.0 mm at final follow-up. All patients had excellent or good satisfaction. Conclusions: Subtalar arthroereisis with $Kalix^{(R)}$ implant is a viable surgical alternative for painful flatfoot deformity of children.