• 한국군사과학기술학회지
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• 제13권6호
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• pp.967-975
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• 2010

There have been a lot of efforts on the improvement for the ride comfort and handling stability of the combat vehicles. Especially most of vehicles for military purpose have bad inertial condition and severe operating condition such as the rough road driving, and need a high mobility in the emergency status. It is necessary to apply the controlled suspension system in order to improve the vehicle mobile stability and ride comfort ability of crews. A feasibility study is performed on the application of the semi-active suspension system with a magneto-rheological controlled shock absorber for a $6{\times}6$ combat vehicle. First, the dynamic simulation model of the vehicle including the control model for the semi-active suspension system was executed. Based on this model, a hardware-in-the-loop simulation(HILS) system which has a semi-active suspension controller hardware was constructed. After full vehicle simulations were performed in virtual proving courses with this system, the semi-active suspension system was proven to give better ride comfort and handling stability in comparison with the conventional passive suspension system.

• Wind and Structures
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• 제13권5호
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• pp.413-431
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• 2010

The focus of this article is on the assessment of vertical wind vector components and their aerodynamic impact on lattice framework, specifically two distinct sections of a guyed transmission tower. Thunderstorm winds, notably very localized events such as convective downdrafts (including downbursts) and tornadoes, result in a different load on a tower's structural system in terms of magnitude and spatial distribution when compared to horizontal synoptic winds. Findings of previous model-scale experiments are outlined and their results considered for the development of a testing rig that allows for rotation about multiple body axes through a series of wind tunnel tests. Experimental results for the wind loads on two unique experimental models are presented and the difference in behaviour discussed. For a model cross arm with a solidity ratio of approximately 30%, the drag load was increased by 14% when at a pitch angle of $20^{\circ}$. Although the effects of rotation about the vertical body axis, or the traditional 'angle of attack', are recognized by design codes as being significant, provisions for vertical winds are absent from each set of wind loading specifications examined. The inclusion of a factor to relate winds with a vertical component to the horizontal speed is evaluated as a vertical wind factor applicable to load calculations. Member complexity and asymmetric geometry often complicate the use of lattice wind loading provisions, which is a challenge that extends to future studies and codification. Nevertheless, the present work is intended to establish a basis for such studies.

• 대한기계학회논문집B
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• 제26권2호
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• pp.269-277
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• 2002

Experiments on the evaporation heat transfer and pressure drop in the brazed type plate heat exchangers were performed using refrigerants R410A and R22. To investigate the geometric effect, plate heat exchangers with the same pitch and height but different 45$^{\circ}$, 35$^{\circ}$and 20$^{\circ}$chevron angles are used. Tests were conducted fur the ranges of the mass flux of refrigerant from 13 kg/m$^2$s to 34 kg/m$^2$s, the evaporation temperatures of 15$^{\circ}C$, 1$0^{\circ}C$ and 5$^{\circ}C$, vapor quality from 0.15 to 0.95 and the heat flux from 2.5 kW/m$^2$to 8.5 kW/m$^2$. The evaporation heat transfer coefficients and pressure drops were measured. Most of flow patterns are in the chum flow regime and become close to the annular flow for increasing the mass flux and the vapor quality. The heat transfer coefficient increases with increasing the evaporation temperature at a given mass flux in all plate heat exchangers. Also, the pressure drop increases with increasing the mass flux and the quality and decreasing the evaporation temperature and the chevron angle.

• 항공우주시스템공학회지
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• 제13권5호
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• pp.32-38
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• 2019

높은 후퇴각을 갖는 둥근 앞전 날개 형상은 앞전 와류에 의해 복잡한 유동 현상이 나타난다. 불안정한 방향 안정성을 갖는 무미익 플라잉윙의 제어를 위해서 플래퍼론이 사용된다. 본 연구에서는 플래퍼론이 전개된 비세장형, 둥근 앞전의 플라잉윙 형상의 전산해석을 수행하였으며 옆미끄럼각 및 플래퍼론에 대한 영향을 분석하였다. 공력계수 분석을 통해 양력과 항력계수에 대한 옆미끄럼각의 영향은 적으며 측력 및 모멘트 계수는 옆미끄럼각의 영향을 크게 받음을 알 수 있었다. 정적 안정성 분석을 통해 플래퍼론이 전개된 플라잉윙의 가로안정성과 방향안정성이 좋아졌음을 확인하였다. 또한 압력계수분포, 표면 마찰선의 관찰을 통해 앞전 와류 구조 및 거동을 분석하였다.

• 예술인문사회 융합 멀티미디어 논문지
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• 제7권1호
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• pp.177-186
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• 2017

최근 무인자동차가 큰 관심을 받고 있다. 세계 최대 규모의 온라인 쇼핑 서비스업체인 아마존은 드론을 활용한 배송시스템을 개발하고 있다. 이러한 플랫폼의 항법을 위해서는 정확한 자세정보가 필요하다. 본 논문에서는 저가형 관성센서를 활용한 AHRS 구조 설계를 제안하였다. 쿼터니언기반의 운동방정식, 바이어스가 제거된 자이로 측정치, MEMS 가속도계와 지자기 센서를 이용하여 자세를 추정하는 칼만 filter를 설계하였다. MEMS 자이로의 바이어스를 제거하기 위하여 자이로 측정치와 자세 추정치를 이용하는 자이로 바이어스 제거용 칼만 filter를 추가하였다. 구현한 AHRS의 성능을 고가의 상용 Microstrain사의 3DM-GX3-25 AHRS와 비교 실험을 통하여 칼만 filter가 자이로의 바이어스 오차를 0.0001[deg/s]이하로 추정함을 볼 수 있었다. 또한 최종적으로 구해진 자세에서 롤각과 피치각은 0.2, 0.3[deg]이내의 오차를 보여주었다. 요 각은 6[deg] 이하의 오차가 발생하였다.

• 대한방사선치료학회지
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• 제28권2호
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• pp.109-121
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• 2016

ExacTrac 6D couch를 이용한 영상유도 방사선 치료의 정확도를 검증하기 위하여 여섯 개의 방향의 오차 값을 임의로 부여하여 교정 한 후 CBCT 이미지와 비교 분석하여 ExacTrac의 정확도를 평가 하고자 하였다. Rando head Phantom의 치료좌표 값을 X, Y, Z 방향으로 이동시킨 Translationgroup과 pitch, Roll, Yaw방향으로 이동시킨 Rotationgroup으로 나누어 교정하였다. 교정 수치는 couch의 여섯 개의 방향으로 복합적으로 상호 작용하여 이동 하였다. 교정 값은 최소 1mm, 최대 23mm까지 다양하게 나타났다. 치료좌표로 수정된 Phantom를 CBCT 촬영한 이미지와 3D/3D matching 오차 값의 분석에서는 Rotation group에서 높은 오차 값이 나타났다. CBCT로 교정된 치료좌표 오차 값에 대한 선량분포의 비교에서는 정상조직에 선량 제한치 값은 처방선량에 충족되었으며 종양조직의 선량 균질성 지표인 PHI, PCI 값은 Rotation group에서 저 선량 분포영역이 다소 높음으로 나타났다. 본 연구에서는 ExacTrac 6D couch 의 정확도에 대한 평가를 CBCT를 이용하여 검증해 보았다. 단편적인 이동에 대한 오차 값은 비교적 정확한 교정 능력을 갖추고 있었지만, couch에 각이 들어가는 이동에서는 부정확한 교정 수치를 보였다. 환자의 체위가 Rotation방향으로 많은 변화가 예상되어지거나 ExacTrac 교정하였을 때 pitch, Roll, Yaw값의 오차가 크게 나타나면 CBCT 영상유도를 시행하여 정확히 치료 좌표를 교정하여 예상치 못한 부작용을 최소화해야 된다고 여겨진다.

• 대한족부족관절학회지
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• 제18권2호
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• pp.62-67
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• 2014

Purpose: Reconstructive surgeries for equinocavovarus foot deformities are quite variable, including hind-midfoot osteotomy or arthrodesis, soft tissue procedure, tendon transfers, etc. Comprehensive evaluation of the deformity and its etiology is mandatory for achievement of successful deformity correction. Few studies in this field have been reported. We report on the clinical and radiographic outcome of reconstruction for cavovarus foot deformities. Materials and Methods: The study is based on 16 feet with cavovarus foot deformities that underwent bony and soft tissue reconstructive surgery from 2004 to 2008. We evaluated the etiologies, varieties of surgical procedures performed, pain score, functional scores, and patient satisfaction and measured the radiographic parameters. Results: The average age at the time of surgery was 39.4 years old, with a male/female ratio of 9/4 and an average follow-up period of 23.9 months (range, 12~49 months). The etiologies of the cavovarus deformity were idiopathic 7 feet, residual poliomyelitis 5 feet, Charcot-Marie-Tooth disease 2 feet, and Guillain-Barre syndrome and hemiplegia due to cerebrovascular accident sequela 1 foot each. Lateral sliding calcaneal osteotomies were performed in 12 feet (75%), followed by Achilles tendon lengthening and plantar fascia release in 11 feet (69%), and first metatarsal dorsiflexion osteotomy/arthrodesis and tendon transfer in 10 feet (63%). Visual analogue scale pain score showed improvement, from an average of 4.2 to 0.5 points. American Orthopaedic Foot and Ankle Society ankle-hindfoot score showed significant improvement, from 47.8 to 90.0 points (p<0.05). All patients were satisfied. Ankle range of motion improved from $27.5^{\circ}$ to $46.7^{\circ}$. In radiographic measurements, calcaneal pitch angle improved from $19.1^{\circ}$ to $15.8^{\circ}$, Meary angle from $13.0^{\circ}$ to $9.3^{\circ}$, Hibb's angle from $44.3^{\circ}$ to $37.0^{\circ}$, and tibio-calcaneal axis angle from varus $17.5^{\circ}$ to varus $1.5^{\circ}$ Conclusion: We achieved successful correction of cavovarus foot deformities by performing appropriate comprehensive reconstructive procedures with improved functional, radiographic measures and high patient satisfaction.

• 한국항공우주학회지
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• 제49권3호
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• pp.221-231
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• 2021

본 연구에서는 덕트 팬-상/하부 베인의 제자리 비행 공력 특성에 관한 수치적 연구를 수행하였다. 일정한 회전 속도, 블레이드 콜렉티브 피치각에서 상부 베인 꺾임각 변화에 따른 시스템 구성 요소별 공력 민감도를 분석하였다. 개별 베인 작동 메커니즘과 덕트-베인 공력 상호 간섭의 물리적 특성을 파악하고자 베인의 조종 성능과 덕트 공력하중 분포를 상세히 분석하였다. 마지막으로, 전기체의 조종 성능 개선을 위해 상부 베인의 새로운 작동 메커니즘을 제안하였다. 상부 베인 꺾임각 변화에 따라 상부 베인 측력과 롤링 모멘트는 선형 증가하였으나, 전기체 측력은 덕트에서 작용하는 반력에 의해 현저히 낮게 나타났다. 또한 덕트 수축부 가까이 위치한 상부 베인이 조종 성능 변화에 가장 큰 역할을 하였다. 덕트와 상부 베인 흡입면의 공력 상호 간섭에 의해 덕트의 음압이, 덕트와 상부 베인의 압력면 공력 상호 간섭에 의해 압력 회복이 발생하여 덕트의 비대칭 공력 증가의 원인이 되었다. 4개의 상부 베인을 0°로 고정시키거나 제거했을 때, 덕트의 비대칭 공력은 감소하고, 전기체의 롤링 모멘트는 80%까지 증가하여 공력 성능이 개선되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2384-2389
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• 2007

The 2nd order response surface method (RSM) has been carried out to get optimum thermal design for enhanced heat transfer on square channel with bleed holes. The RSM was used as an optimization technique with Reynolds-averaged navier-stokes equation. Turbulence model for heat transfer analysis used RNG k-epsilon model. The wall function used enhanced wall function. Numerical local heat transfer coefficients were similar to the experimental tendency. Two design variables such as attack angle of rib (${\alpha}$), rib pitch-to-rib height ratio (p/e) were chosen. Operation condition considered bleeding ratio per bleed hole ($BR_{hole}$). A response surface were constructed by the design variables and operation condition. As a result, adjusted $R^2$ was more than 0.9. Optimization results of various objective function were similar to heat transfer in channel with and without bleed flow. But friction factor was lower than channel without bleed flow.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2004년도 춘계학술발표회논문집
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• pp.15-26
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• 2004

The calibration for systematic error in LiDAR is crucial for the accuracy of airborne laser scanning. The main error is the misalignment of platforms between INS(Inertial Navigation System) and Laser scanner For planimetrical calibration of LiDAR, the building is good feature which has great changes in height and continuous flat area in the top. The planimetry error(pitch, roll) is corrected by adjustment of height which is calculated from comparing ground control points(GCP) of building to laser scanning data. We can know scale correction of laser range by the comparison of LiDAR data and GCP is arranged at the end of scan angle where maximize the height error. The area for scale calibration have to be large flat and have almost same elevation. At 1000m for average flying height, The Accuracy of laser scanning data using LiDAR is within 110cm in height and ${\pm}$50cm in planmetry so we can use laser scanning data for generating 3D terrain surface, expecically digital surface model(DSM) which is difficult to measure by aerial photogrammetry in forest, coast, urban area of high buildings