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최대한,이상구,박찬우,김우경 대한척추신경외과학회 2011 Neurospine Vol.8 No.3
Objective: Since the 1990s, due to postoperative loss of mobility and adjacent segmental disease after anterior cervical fusion, many different types of cervical artificial discs have been developed as alternative implants. The purposes of this study are investigation and comparison of radiographic and clinical outcomes between two different types of prostheses, BryanⓇ and Mobi-CⓇ. Methods: We retrospectively evaluated 33 patients who were treated for cervical degenerative disc disease that resulted in radiculopathy and/or myelopathy between May 2004 and April 2009. Seventeen patients underwent BryanⓇ cervical disc arthroplasty and sixteen patients underwent Mobi-CⓇ arthroplasty. The radiographic outcomes were assessed by measuring the cervical lordosis, segmental lordosis, range-of-motion (ROM) of the cervical spine (C2-7), functional segmental unit (FSU), prosthesis’ shell and the upper adjacent segment. The clinical results were evaluated according to the Visual Analogue Scale (VAS) for axial pain and radiculopathy, Odom’s criteria, and the modified Prolo’s economic and functional outcome rating scale. Results: The age of the study population ranged from 24 to 69 years with a mean age of 48 years vs. 46 years in the BryanⓇ and Mobi-CⓇ groups, respectively. The mean duration of follow-up was 23.7 months in the BryanⓇ group and 11.3 months in the Mobi-CⓇ group. The changes of overall cervical sagittal angle were not significantly different between two groups,but the increase of segmental sagittal angle (0.85° in BryanⓇ, 8.04° in Mobi-CⓇ), ROM of the FSU(-0.51° in BryanⓇ, 2.47° in Mobi-CⓇ) and ROM of the shell (1.77° in BryanⓇ, 5.28° in Mobi-CⓇ) were significantly higher in Mobi-CⓇ group than in BryanⓇ group (p<0.05). The clinical results were not significantly different between two groups. Conclusion: The Mobi-CⓇ prosthesis showed more favorable radiographic results than that of the BryanⓇ prosthesis, however, the clinical outcomes were similar in both groups. Large-scale and long-term follow-up studies are needed to confirm our results.
응력부식균열성장을 고려한 105 mm 전차 포신 파단 신뢰성 분석
최대한,이두열 대한기계학회 2023 大韓機械學會論文集A Vol.47 No.2
The reliability considering the nucleation and growth of stress corrosion cracks in the 105-mm gun barrel is analyzed using data-driven and physics-based models. Based on the actual fracture data and non-defective data obtained during operation, the life distribution of the gun barrel is estimated using Weibull analysis. The crack length at the time of inspection is predicted using a stress corrosion crack growth linear model to consider the effect of periodic inspections. The detection probability corresponding to the predicted crack length is calculated to determine whether the crack is detected. The probability of the detection curve is calculated based on the result of the inspection performed using the inspection robot for the actual gun barrels. The inspection results are binary with detection and non-detection based on video images and converted into detection probability through logistic regression analysis. A risk analysis framework that incorporates the data-driven and physics-based models through Monte Carlo simulation is presented. The expected number of fracture failures of the 105-mm gun barrel is predicted, and risk-based inspection and maintenance optimization is demonstrated. 105 mm 포신의 응력부식균열 생성 및 성장에 따른 신뢰성을 데이터 기반 모델과 물리모델을 함께 사용하여 분석하였다. 실제 파단 결함 데이터와 운용 중 획득된 비결함 데이터를 바탕으로 와이블 분석을 통해 포신의 수명분포를 추정하였다. 주기적인 검사의 효과를 고려하기 위해 검사시점에서의 균열길이를 응력부식균열성장 선형모델을 사용하여 예측하였다. 예측된 균열길이에 해당하는 탐지확률을 구하여 검사 중 탐지 여부를 판단하였다. 이때 사용한 탐지확률모델은 실제 포신을 대상으로 검사로봇을 사용하여 수행한 검사의 결과를 바탕으로 산출하였다. 검사는 비디오 영상을 기반으로 탐지와 비탐지의 이진 결과를 나타내고, 이를 로지스틱 회귀분석을 통해 탐지확률로 변환하였다. 몬테카를로 시뮬레이션을 통해 데이터 기반 모델과 물리모델을 융합하는 신뢰성 분석 프레임워크를 제시하였다. 이를 통해 예상되는 105 mm 포신의 파단건수를 예측하였고, 최적의 포신 검사주기를 제시하는데 사용할 수 있음을 보였다.
3D 스토리텔링 증강현실에서 효과적인 객체 추적을 위한 학습 방법
최대한,한우리,이용환,김영섭 한국반도체디스플레이기술학회 2016 반도체디스플레이기술학회지 Vol.15 No.3
Recently, Depending on expectancy effect and ripple effect of augmented reality, the convergence between augmented reality and culture & arts are being actively conducted. This paper proposes a learning method for effective object tracking in 3D storytelling augmented reality in cultural properties. The proposed system is based on marker-less tracking, and there are four modules that are recognition, tracking, detecting and learning module. Recognition module is composed of SURF and LSH, and then this module generates standard object information. Tracking module tracks an object using object tracking based on reliability. This information is stored in Learning module along with learned time information. Detecting module finds out the object based on having the best possible knowledge available among the learned objects information, when the system fails to track. Also, it proposes a method for robustly implementing a 3D storytelling augmented reality in cultural properties in the future.
실시간 시뮬레이션을 위한 기호연산기법의 유용성 검증에 관한 연구
최대한,유완석,Choe, Dae-Han,Yu, Wan-Seok 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.7
In multibody dynamic analysis, one of the most important problems is to reduce computation times for real time simulation. In this paper, a symbolic computation method is implemented and tested for each dynamic analysis step. Applying symbolic formulations to the vehicle dynamics program AutoDyn7, the effectiveness of the symbolic computation method is verified.