POD 축소기법을 이용한 유연 다물체 보 구조물의 동역학적 해석

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 8. 조맹효.유연 다물체 동역학 연구는 1970년대부터 활발히 연구가 진행되었다. 약 50년이라는 세월이 흘렀음에도 불구하고, 여전히 계산에 많은 전산 자원을 필요로 한다. 유연 다물체 동역학에서는 절대 좌표계와 상대 좌표계를 함께 사용하는 FFRF(Floating Frame Reference Formulation)가 가장 많이 사용된다. FFRF에서는 질량행렬을 구성하는 과정에서 원심력과 코리올리 힘이 나타난다. 반면에 절대절점 좌표계에서는 절대 절점 좌표만을 사용하기 때문에 이 힘들이 나타나지 않고 내력이 비선형으로 나타난다. 따라서 구조 비선형 방정식과 같은 모양을 만들 수 있고 일반적인 비선형 구조해석에 사용할 수 있는 축소기법들의 적용이 가능하다. 이에 본 논문에서는 모드 축소기법 중 하나인, POD(Proper Orthogonal Decomposition) 축소 기법을 이용하여 절대 절점 좌표계를 갖는 유연 다물체 동역학 문제에 적용했다. 절대 절점 좌표계로 이루어진 유연 다물체 동역학 문제에 POD 축소기법을 적용하여, 전체시스템에서 문제와 결과를 비교하여 그 효율을 검증하였다.1. 서론 1 2. 절대 절점 좌표계 3 2.1 좌표계 정의 3 2.2 질량행렬 및 강성행렬 구성 6 2.3 운동방정식 9 3. POD 축소기법 9 3.1 특정 구속조건이 없는 모델에서의 POD 축소 10 3.2 특정 구속조건이 있는 모델에서의 POD 축소 11 4. 수치예제 15 4.1 진자 모델 15 4.2 4절 링크가 포함된 보 구조물 18 5. 결론 21 참고 문헌 21 Abstract 24Maste

Factors affecting determination of the optimal ketamine dose for pediatric sedation

OBJECTIVE: Children are sedated before undergoing diagnostic imaging tests in emergency medicine or pediatric sedation anesthesia units. The aim of this study was to identify variables potentially affecting the dose of ketamine required for induction of sedation in pediatric patients undergoing diagnostic imaging. METHODS: This retrospective study included children aged 0 to 18 years who underwent sedation with ketamine for computed tomography or magnetic resonance imaging in the pediatric sedation anesthesia unit of a tertiary medical center between January 2011 and August 2016. The children's hemodynamic status and depth of sedation were monitored during the examination. We recorded data on demographics, categories of imaging tests, ketamine doses administered, adverse events, respiratory interventions, and duration of sedation. Data for patients who experienced adverse events were excluded. RESULTS: Sixty-six patients were included in the final analysis. Univariate linear regression analysis revealed that patient age, height, and body surface area (BSA) affected the sedative dose of ketamine administered. These three variables showed multicollinearity in multivariate linear regression analysis and were analyzed in three separate models. The model with the highest adjusted R-squared value suggested the following equation for determination of the dose of ketamine required to induce sedation: ketamine dose (mg)=-1.62+0.7×age (months)+36.36×BSA (m2). CONCLUSION: Variables such as age and BSA should be considered when estimating the dose of ketamine required for induction of sedation in pediatric patients.ope

Adequate interval for the monitoring of vital signs during endotracheal intubation

BACKGROUND: In the perioperative period, it may be inappropriate to monitor vital signs during endotracheal intubation using the same interval as during a hemodynamically stable period. The aim of the present study was to determine whether it is appropriate to use the same intervals used during the endotracheal intubation and stable periods to monitor vital signs of patients under general anesthesia. METHODS: The mean arterial pressure (MAP) and heart rate (HR) were continuously measured during endotracheal intubation (15 min after intubation) and hemodynamically stable (15 min before skin incision) periods in 24 general anesthesia patients. Data was considered "unrecognized" when continuously measured values were 30% more or less than the monitored value measured at 5- or 2.5-min intervals. The incidence of unrecognized data during endotracheal intubation was compared to that during the hemodynamically stable period. RESULT: There were significantly more unrecognized MAP data measured at 5-min intervals during endotracheal intubation than during the hemodynamically stable period (p value <0.05). However, there was no difference in the incidence of unrecognized MAP data at 2.5 min intervals or HR data at 5 or 2.5 min intervals between during the endotracheal intubation and hemodynamically stable periods. CONCLUSION: A 5-min interval throughout the operation period was not appropriate for monitoring vital signs. Therefore, , a 2.5-min interval is recommended for monitoring the MAP during endotracheal intubation.ope

Echocardiographic evaluation of pulmonary venous blood flow and cardiac function changes during one-lung ventilation

OBJECTIVES: The intra-pulmonary shunt induced by one-lung ventilation (OLV), is alleviated by increased pulmonary blood flow by gravitational redistribution and hypoxic pulmonary vasoconstriction. We investigated the changes of pulmonary venous blood flow (PVBF) and biventricular function during OLV with echocardiography. And the correlation between PVBF and intra-pulmonary shunt fraction (Qs/Qt) was evaluated. METHODS: PVBF of the left upper pulmonary vein and cardiac function were measured with echocardiography in twenty-five patients who underwent elective thoracic surgery in left lateral decubitus. Qs/Qt and PaO2 were measured with blood gas analysis. Data was obtained at 10 min after two-lung ventilation in supine (TLV-S) and lateral decubitus position (TLV-L), and at 10, 20 and 30 min after OLV in lateral decubitus position (OLV-10, -20 and -30). RESULTS: There were significant changes in PVBF among TLV-S, TLV-L and OLV-10 (959.5±280.8, 1416.9±489.7 and 1999.9±670.5 ml/min; P<0.05, respectively). There were not differences in PVBF, Qs/Qt and PaO2 among OLV-10, -20 and -30. There were an inverse correlation between percent change of PVBF and change of Qs/Qt (r(2) = 0.5; P<0.0001) and positive correlations between the percent change of PVBF and change of PaO2 (r(2) = 0.4; P<0.0001) during OLV over TLV-L. No significant changes in biventricular systolic and diastolic function were observed during positional change and OLV. CONCLUSIONS: A remarkable change of PVBF relevant to gravitational distribution and hypoxic pulmonary vasoconstriction was proved by echocardiography. And PVBF changes could represent the changes of Qs/Qt and PaO2 during OLV. However, biventricular function was not impaired during OLV.ope

소 난관상피세포 배양액 유래 배발달촉진인자의 정제와 소 수정란 체외배양시 발달에 미치는 효과에 관한 연구

Thesis (master`s)--서울대학교 대학원 :수의학과 수의산과학전공,1997.Maste

국내 분리 돼지생식기호흡기증후군 바이러스의 유전학적 다양성 및 불활화백신의 면역원성 분석 연구

Thesis(doctors) --서울대학교 대학원 :수의학과,2010.2.Docto

다개체의 무충돌 속도 계획을 위한 충돌맵 위의 랜덤 트리 생성기

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2018. 8. 이범희.This thesis proposes collision - avoidance control technique of robots operating in a multi-agent environment. This thesis proposes a random tree generator on the collision map as a key algorithm for driving control. The random tree generator method relates to generating a random tree on a collision map that reflects the SCC (Simple continuous-curvature) path model and generating a suitable velocity profile. Until now, the collision avoidance algorithm of the robot on the collision map did not consider the change of the velocity and the acceleration constraints in the path. However, there is a curved path as well as a straight path in the case of the actual robot system. The robot has a velocity and an acceleration range smaller than the maximum possible linear path to travel stably in a curved path. Therefore, it is necessary to reflect the velocity and acceleration changes according to the property of the path on the collision map to realize the near real speed plan. The conventional collision avoidance algorithm on collision map uses a time delay method or a minimum time delay method. However, when using the time delay method in the multi-agent environment, it can be confirmed that the accumulation effect of time delay rises as the number of robots increases. Therefore, there is a need for an algorithm that finds a velocity profile that can avoid the collision without delaying time on the collision map. According to the necessity of the new collision avoidance method, a random tree method designed to find the path on the map is modified and applied on the collision map. The random tree method is a method of locating the route to the destination by randomly generating trees from the origin on the map. We propose a random tree generator for collision avoidance by applying this method to collision map space which is time and distance space. A simulator of a multi-agent environment was created and compared with the conventional collision avoidance algorithm to verify the validity of the proposed algorithm. First, we modeled robots with SCC path model and created velocity and acceleration constraint conditions in each path. To construct multi-agent environment, we set priority, origin, destination, route, and the speed and acceleration limit conditions according to the path of 12 robots. To avoid a collision between robots, we used existing extended collision map method. Moreover, we applied the existing collision avoidance algorithms and proposed random tree generator method to the simulator. The results show that the proposed method generates the velocity profile on the collision map of each robot. The characteristics of the tree generation step considering the SCC path model are analyzed. Moreover, we compare the arrival time of the proposed method with the arrival time of the conventional time - delay algorithm. Then, we confirmed that the time - accumulation effect does not appear when we applied the random tree generator method to the multi-agent environment. Therefore, we confirmed that the proposed method is a time efficient method. In conclusion, we can apply the random tree generator method to the collision map with various velocity and acceleration constraints. Moreover, we can solve the accumulative time delay effect by using the random tree generator method. We expect that not only mobile robot such as unmanned car but also multi-agent robot systems such as airport surveillance system and hospital support robot system use the proposed method as a speed planning method to avoid a collision between each other.1 Introduction 1 1.1 Motivations 1 1.2 Contributions 3 1.3 Organization 4 2 Related Work 5 2.1 Path Planning 5 2.2 Collision map theory 9 2.3 Extended collision map 16 3 Problem Formulation 19 3.1 SCC path model 19 3.2 External constraints in SCC path model 21 3.3 Internal constraints in SCC path model 21 3.4 Speed planning using random tree 24 4 Random Tree Generator 25 4.1 Proposed method 25 4.2 Generation of the first tree and the second tree 27 4.3 Local planner 29 5 Multi-agent Motion Planning 57 5.1 Structure 57 6 Simulation 62 6.1 Environment 62 6.2 Generation process of random tree 68 6.3 Comparison with conventional algorithms 73 7 Conclusion 80 Reference 82Maste

(The)Impact of foot-and-mouth disease on the prices of livestock commodities

학위논문(석사)--서울대학교 대학원 :농경제사회학부,2005.Maste

Nuough multi-passage axial compressors

Maste