진동기구가 Bulk-Fill 복합 레진의 내부 적합도와 기포 생성에 미치는 영향

학위논문(박사) -- 서울대학교대학원 : 치과대학 치의과학과, 2022. 8. 백승호.Objectives. The aim of this study was to investigate the effects of vibration on internal adaptation and void formation of bulk-fill composite resin, according to different frequencies of vibration devices and layering thickness of composite resin. Methods. The change of complex viscosity when oscillating shear was applied to the Filtek Bulk Fill (FB) composite resin was measured using a rotational rheometer. The frequency and amplitude of two vibration devices (COMO and SONICflex) were measured using a scanning laser doppler vibrometer (SLDV). After preparing cylindrical class I cavities on CAD/CAM hybrid composite blocks, FB was filled using different layering thicknesses (2 mm, 4 mm) and vibration methods (No vibration, COMO, SONICflex) (n = 10). The internal adaptation (2D void area % at the bottom surface) and void formation (3D void volume %) were measured using micro-computed tomography. The median values of the 2D void area (%) and 3D void volume (%) were analyzed using the Kruskal-Wallis test, followed by post-hoc Mann-Whitney U test. Results. Complex viscosity of FB decreased with increasing frequency of applied oscillation. The frequency and amplitudes of COMO were 149.1 Hz and, 50.5 µm (vertical), 26.4 µm (horizontal) while those of SONICflex were 4,818.9 Hz and 52.1 µm (vertical), 23.3 µm (horizontal). With 2 mm incremental layering, vibration methods demonstrated significantly lower bottom surface void area and lower total void volume than no vibration methods (p 0.05). Both vibration devices with different frequencies showed no significant difference in internal adaptation and void volume. Conclusion. Using vibration devices with 2 mm incremental layering can enhance the internal adaptation and reduce the void volume of bulk-fill composite resin.1. 연구 목적 본 연구의 목적은 Bulk-Fill 복합 레진 수복 시 진동기구의 사용과 적층 두께가 복합 레진의 내부 적합도와 기포 생성에 미치는 영향을 알아보고자 하는 것이다. 2. 재료 및 방법 회전형 점성계를 이용하여 Filtek Bulk Fill (FB) 복합 레진에 진동 전단을 가했을 때의 복소 점도 변화를 측정하였다. 두 가지 진동기구(COMO, SONICflex)의 진동수와 진폭을 스캐닝 레이져 도플러 진동계(SLDV)를 이용하여 측정하였다. CAD/CAM 용 하이브리드 컴포짓 블록에 실린더 형태의 1급 와동을 형성한 후 적층 두께 (2 mm, 4 mm) 및 진동 방법 (No vibration, COMO, SONICflex)을 달리하여 복합 레진을 수복하였다 (n=10). 수복된 복합 레진의 내부 적합도 (2D 바닥면의 기포 면적 %) 및 기포 생성 (3D 기포 부피 %)을 마이크로 CT를 이용하여 측정하였다. Kruskal-Wallis 와 Mann-Whitney U test 로 진동 기구 및 적층 방법이 복합레진의 적합도 및 기포 생성에 미치는 영향을 분석하였다. 3. 결과 FB 복합 레진의 복소 점도는 가해지는 진동의 진동수가 커짐에 따라 감소하였다. 측정된 COMO의 진동수 및 진폭은 149.1 Hz, 50.5 µm (수직), 26.4 µm (수평), SONICflex의 진동수 및 진폭은 4818.9 Hz, 52.1 µm (수직), 23.3 µm (수평)이었다. 2 mm 적층 수복 시, 복합 레진에 진동을 가하였을 때 통계적으로 유의하게 바닥면의 기포 면적 감소 및 전체 기포 부피가 감소하였다 (p 0.05). 서로 다른 진동수의 두 진동 기구 사이에는 적합도와 기포 생성에 통계적으로 유의한 차이를 보이지 않았다. 4. 결론 진동기구를 사용하여 2 mm 적층 수복을 하였을 때 bulk-fill 복합 레진의 내부 적합도 증가하였고 기포가 감소하였다.1. Introduction 1 2. Materials and Methods 5 3. Results 12 4. Discussion 17 5. Conclusion 23 6. References 24 Tables and Figures 30 Abstract in Korean 41박

Design of a Robust Water Level Controller for Coupled Tank System Using Fuzzy Gain Scheduling

Even though lots of the modern control theories are developed, the PID control is the most widely used in real industrial field which is familiar to control engineer. It offers satisfactory control performance in most case of industrial applications. However, traditional PID control has fixed gain for particular operating conditions, thus the conventional unique PID strategy would be unsatisfactory when the system parameters have changed due to the change of operating condition, aging, etc. of the controlled plants. The Fuzzy Gain Scheduling strategy, which changes the controller parameters for operating condition variation, could be a solution of these problems. Water level control systems are applied to the many industrial plants like chemical reaction process, but it is known very difficult to control precisely the tank level without any overflow and shortageBecause of its complicate dynamic characteristics, it's impossible to realize the accurate control using the mathematical model which can be applied to the various operation modes. In this paper, the author designed the PID controller for the various operating conditions like different water level points and different magnitude of step change, and verified the performance of these controllers by experiments as well as simulations. It is noticed that the PID controller with fixed gains does not meet the requirements of control performance with large overshoot or late convergence, with varying the magnitude of step change. To improve this problem, three kinds of PID gain were scheduled under Fuzzy Gain Scheduling strategy and simulated and experimented under those operating conditions. The Fuzzy gain scheduled PID controller made satisfactory performance which fixed gain PID controller couldn't make to the various magnitude of step change command.Abstract ⅲ Nomenclature ⅴ 제 1 장 서론 1 1.1 연구배경 1 1.2 연구동향 1 1.3 연구내용과 구성 2 제 2 장 이중수조 시스템의 모델링 4 2.1 이중수조 시스템 4 2.2 모델링 5 2.2.1 펌프 5 2.2.2 이중수조 5 2.2.3 센서 7 2.3 시스템 파라미터 10 제 3 장 퍼지 게인 스케쥴링에 의한 제어기 설계 12 3.1 PID 제어 12 3.1.1 제어동작 특성 12 3.1.2 PID 제어기 파라미터 동조 17 3.2 퍼지제어 21 3.2.1 퍼지제어의 특징 21 3.2.2 퍼지제어기 22 3.3 PID 제어기의 설계 35 3.4 퍼지 게인 스케쥴링 38 제 4 장 시뮬레이션 및 고찰 41 4.1 PID 제어기의 계단응답 41 4.1.1 동작구간의 변화에 따른 계단응답 41 4.1.2 계단입력의 크기에 대한 응답 47 4.2 퍼지 게인 스케쥴링에 의한 시뮬레이션 50 제 5 장 실험 및 비교 53 5.1 실험장치 및 실험방법 53 5.1.1 실험장치의 구성 53 5.1.2 실험방법 54 5.2 실험결과 55 5.2.1 동일한 크기의 계단입력에 대한 응답 55 5.2.2 계단입력의 크기 변화시 응답실험 58 제 6 장 결론 61 참고문헌 6

Preventive Measures against Plague and the Control of Chinese Coolies in Colonial Korea

This paper aims to examine the preventive measures taken against the plague in colonial Korea, particularly as applied to the control of Chinese coolies in 1911, soon after the annexation. The Government General of Korea began preventive measures with a train quarantine in Shin'uiju and Incheon in response to the spread of the plague to the Southern Manchuria. Shin' uiju had become urbanized due the development of the transportation network, and the seaport of Incheon was the major hub for traffic with China. Examining the transportation routes for the entry and exit of Chinese to and from Korea makes clear the reason why the Korea Government General initiated preventive measures in mid-January, 1911. The Government General of Korea tried to block the entry of Chinese through the land border crossing with China and through ports of entry, primarily Incheon. During the implementation of the preventive measures, quarantine facilities were built, including a quarantine station and isolation facility in Incheon. It was also needed to investigate the population and residential locations of Chinese in Korea to prevent the spread of plague. A certificate of residence was issued to all Chinese in Korea, which they needed to carry when they travelled. The preventive measures against plague which broke out in Manchuria were removed gradually. However, there was no specific measures against Chinese coolies, those who had migrated from China to work in the spring in Korea. Still the Government General of Korea had doubt about an infection of the respiratory system. As a result, the labor market in colonial Korea underwent changes in this period. The Government General recruited Korean laborers, instead of Chinese coolies whose employment had been planned. This move explains the Government General's strong preventive measures against plague and uncertainty in the route of plague infection, which influenced subsequent regulations on the prohibition of Chinese coolies working on the public enterprise sites and the improvement of labor conditions for Korean laborers.ope

"Byoin" in Modern Japan: Focusing on the Terminological Introduction of "Hospital" and the Complex Formation of Its Concept

This paper aims to clarify when the term of Byoin (病院, hospital) was introduced and how its concept was developed in modern Japan. The word “Byoin” was introduced in Japan in 1787 for the first time, but it had not been in use until early 1860s. Instead, various medical institutions performing the functions of modern medical facilities, such as Yojosho (養生所, A place for preserving health), Shijuku (私塾, private school), called by traditional names as ever. Japanese intellectuals already adopted the word Byoin and the concept of western hospital in early 1860s when their national delegates were dispatched to Europe to revise the treaties forged with western powers. Japanese translations of hospital appeared in English-Japanese/Japanese-English dictionaries published in the 1860s. For instance, the word Byoin (hospital in Japanese) was first published in a dictionary published in 1867 and unclearly connected to the words, hospital, infirmary. This paper will argue that the concept of Byoin was sophisticated through Meiji government's efforts to implement reforms distinguishing medical facilities based on their capacity of inpatients and quality. The first medical law (醫制, Isei) proclaimed by the Meiji government in 1874 articulated regulations for a hospital in eight different articles. The government established hospitals in various parts of the country, following its newly established modern medical care policies. However, in this process, Iin (醫院, hospital/clinic), another term for “hospital” appeared. Regional differences and financial issues made standardizing the concept of a hospital even more difficult. In response to the widely embedded confusion, the Japanese government made an effort to clarify the concept of a hospital, setting up provisions regarding the size of medical facilities. As a result, the word Byoin finally came to be used for a hospital with more than ten beds, while a clinic with beds below ten was called Shinryojo (診療所, clinic). On the other hand, Iin meant a medical facility less qualified than a hospital since 1933 when Japanese government made a harder restriction on the usage of Byoin.ope

Management of Wound Infection after Lumbar Spine Fusion with Instruments

Objective :This study is performed to evaluate the risk factors, clinical manifestations, treatments, and prognostic factors among patients with postoperative wound infection after spinal instrumentation. Methods :The records and radiologic data of 28 patients diagnosed as postoperative wound infection from Jan. 1991 to Oct. 2002 who had underwent spinal instrumentation initially were retrospectively evaluated. Results :All patients(mean age, 50.4 yrs) diagnosed as postoperative wound infection and subsequently received IV antibiotics and continuous irrigation system. The 13 among 28 cases had significant preoperative risk factors(for example, diabetes mellitus, obesity, alcoholism, long-term corticosteroid usage, and chronic renal failure). Infection was diagnosed at an average of 15.9 days after operation. The most common presenting features were local heating, fever, and wound discharge. All patients could be discharged after infection control. At follow up evaluation, 21 case(75%) have not shown recurrence but, the recurrence was developed among 7 cases. The C-reactive protein(CRP) was more correlated with clinical outcomes than other laboratory findings and the recurred group exhibited sign ificant(p<0.05) higher CRP level, compared with the non-recurred group, from 7 days to 21 days after operation. Conclusion :Without removal of instruments, surgical removal of infective tissues and continuous irrigation with susceptible antibiotics can be effective in the treatment of postoperative wound infection after spinal instrumentation. CRP level can be an effective parameter of infection treatment and prognosis.ope

Excess Cancer Risk and Its Damage Cost due to Indoor Air Pollution in Seoul

We gathered exposure data on indoor air pollution, and investigated the dose-response slope factor for indoor air pollutants, such as volatile organic compounds, aldehydes and radon. Population cancer risks (that is the theoretical cancer deaths) were estimated from exposure to the pollutants. In addition, the damage costs, due to their risks, were estimated using WTP (willingness to pay) and VSL (value of a statistical life), which were investigated by a dichotomous contingent valuation method (DCVM). As a priority for human health risks and damage costs, management strategies are required for both radon and formaldehyde as indoor air pollutants. When the numeric results of human risks and damage costs are applied for other purposes, some assumptions and uncertainties have to be considered to use the results as useful screening tools for the administration of practical risk-based priorities.ope

Degenerative Spondylolisthesis in Thoracic Spine

A 66 year-old woman was admitted to our hospital for progressive weakness of both lower extremities since a month ago. Imaging study, based on plain X-ray, computed tomography and magnetic resonance image revealed spinal stenosis owing to anterior slipping of T10/11 segment. Degenerative spondylolisthesis is common in the lumbar spine and rarely occurs in the cervical spine2,5). But there was no report of degenerative spondylolisthesis in thoracic spine. The authors experienced a case of degenerative spondylolisthesis in the thoracic spine. And we achieved a satisfactory result with posterior decompressive laminectomy alone.ope

The result of Posterior Microforaminotomy for Posterolateral Herniation of Cervical Discs

Objective：To evaluate the effectiveness of posterior microforaminotomy in treatment of posterolateral cervical disc herniation, the authors retrospectively analyzed the result of posterior microforaminotomy in our institute. Patients and Methods：Ten patients with radiculopathy due to posterolateral cervical disc herniation have been treated with posterior microforaminotomy from August 1996 to July 2000. We analyzed clinical results in all patients who were followed up for an average of 10 months. Results：The mean age was 47.2 years and all patients were treated with posterior microforaminotomy as primary treatment. one patient was received anterior cervical interbody fusion with iliac bone 12 years before. Clinical improvement in the last follow-up were seen in all patients and there were no complications. Conclusion：Microcervical foraminotomy is considered useful operative method for posterolateral soft disc herniation. We conclude that the posterior microforaminotomy for radiculopathy due to soft posterolateral cervical disc herniation seems to be safe and effective in selective patients.ope

서비스 로봇 주행 플랫폼을 위한 2-자유도 변형 바퀴 메커니즘

학위논문(박사)--서울대학교 대학원 :공과대학 기계항공공학부,2019. 8. 김종원.This thesis presents a new 2-degree of freedom (DOF) transformable wheel mechanism for service robot mobile platforms. On flat grounds, conventional wheel is a simple and effective structure for the mobile platforms. However, it is difficult for the mobile platforms with conventional wheels to overcome obstacles in human living environment due to high required friction and large fluctuations on main body while overcoming obstacles. By 2-DOF transformation, the wheel can effectively reduce friction dependency as the transformed wheel maintain contact only with a bottom surfaces of various obstacles. Also, bottom surface contact condition allows the platform to climb various obstacles regardless of the existence of vertical surfaces of obstacles. In addition, fluctuation of a main body while overcoming various obstacles is also reduced by the effect of the curved shaped transformed wheel. Consequently, the platform with 2-DOF transformable wheel can overcome various obstacles in human environment at high speed up to 40 m/min which is average walking speed of adult human. The concept and required functions of 2-DOF transformable wheel was defined and a preliminary simulation and experiments were performed to verify performance of transformed wheel shape. 36 Types of 2- DOF transformable were explored by type synthesis of 2-bar serial and 5-bar parallel mechanisms. By excluding mechanisms that do not satisfy kinematic requirements, and by applying mechanisms synchronizing 3 lobes, five different types of design alternative mechanisms were created. Through the step overcoming simulation, kinematic characteristics analysis and evaluation of design alternatives was performed in terms of range of transformation, interference, and singularity. 5-bar mechanism with two P joint at base (PRRRP) was selected as an optimal mechanism. To achieve both control simplicity and design simplicity, a pair of RRPP 4-bar mechanism was synthesized to the selected PRRRP mechanism to ensure independencies between wheel rotation DOF and transformation DOFs. The design variables were selected to satisfy the required transform range through kinematic analysis, and power transmission parts were designed based on static analysis. Selected mechanism based mobile platform STEP was designed and fabricated. The size and the weight of the platform is 1150 mm x 250 mm x 420 mm and 18 kg respectively. CompactRio was used as the main controller, and was controlled by the PC's labview wirelessly. The performance of the 2 DOF wheel based mobile platform was verified by experiments on step obstacles of various heights (70 mm, 110 mm) and stair obstacles of various sizes (300 mm x 100 mm, 320 mm x 140 mm, 300 mm x 160 mm). In addition, field tests had been performed on actual stairs in our living environment. As a result, the platform could overcome various obstacles at high speed up to 40 m/min. The transformable wheel based mobile platform STEP that is proposed in this study can be used as a mobile platform of service robots so that the service robots could expand their applications by increasing their range of activity.본 논문은 새로운 2-자유도 변형 바퀴 기반의 주행 플랫폼(STEP)에 관한 연구이다. 기존의 원형 바퀴는 구조가 단순하고 구동이 간단하여 평지 주행에 효과적인 대안이지만 인간 생활 환경에 존재하는 다양한 장애물을 극복하기엔 마찰력에 대한 의존도가 높으며 흔들림이 크다는 한계가 존재한다. 본 논문에서는 2-자유도의 변형 메커니즘을 제안하여, 변형된 바퀴가 바닥 면과의 접촉만을 유지하게 함으로써 장애물 극복 시 마찰력에 대한 의존도를 효과적으로 감소시킨다. 또한 변형된 곡선 형상의 바퀴를 통해 본체의 흔들림도 감소시켜, 결과적으로는 사람이 걷는 속도인 40 m/min 의 주행 속도에서도 안정적으로 다양한 크기의 장애물 극복이 가능하다. 본 연구에서는 기구학을 기반으로 2-자유도 변형 바퀴의 개념 및 기구학적 요구조건을 정의하였다. 변형된 바퀴 형상을 3D 프린팅을 통해 제작하였으며, 예비 실험 및 해석을 통해 계단 장애물 극복 성능을 검증하였다. 2-자유도의 변형 기능을 수행할 수 있는 직렬 2절 링크 및 병렬 5절 링크 메커니즘이 총 36가지 탐색 되었다. 요구조건을 만족하지 못하는 메커니즘을 제외하고, 동기화 메커니즘을 결합하여 최종적으로 다섯 가지 유형의 설계 대안 메커니즘을 도출하였다. 설계대안들은 장애물 극복 과정의 기구학 시뮬레이션 및 변형 범위, 간섭 및 특이점 회피 여부를 통해 평가가 수행되었으며, 최종적으로 3R2P 5절 링크 메커니즘이 선정되었다. 설계를 단순화하면서 바퀴의 회전에 대해 바퀴의 변형 자유도를 독립시키기 위해, 한 쌍의 4절 RRPP 메커니즘을 합성하였다. 최종 변형 메커니즘의 기능 및 주행 플랫폼의 성능을 검증하기 위해, 모바일 플랫폼 STEP 이 설계되고 제작되었다. 설계 변수는 기구학 해석을 통해 필요한 변형 범위를 충족하도록 선정되었으며, 모터 선택 및 보강 설계는 정적 해석을 통해 수행되었다. 제작된 플랫폼의 크기는 1150 mm x 250 mm x 420 mm 이며 무게는 18 kg 이다. 주 제어기로 CompactRio 가 사용되었으며, PC 의 labview 로 무선으로 구동되었다. 2-자유도 변형 바퀴 기반 모바일 플랫폼 STEP 의 주행 성능은 다양한 크기의 계단 장애물 (300 mm x 100 mm, 320 mm x 140 mm, 300 mm x 160 mm)과 턱 장애물에 대한 실험을 통해 검증되었다.1. Introduction 1 1.1. Mobile platform for service robots 1 1.2. Limitations of wheeled mobile platforms 1 1.3. Previous researches 4 1.3.1. Wheel linkage mechanisms 4 1.3.2. Transformable wheel mechanisms 6 1.4. Performance indices for mobile platforms 9 1.4.1. Required friction coefficient 9 1.4.2. Trajectory smoothness 10 1.5. Research objevtices 12 2. The Concept Transformable Wheel 13 2.1. The Concept of 2-DOF transfomable wheel 13 2.1.1. Definition of transformable wheel 13 2.1.2. Objective obstacles in human environment 15 2.1.3. Necessity of 2-DOF transformation 17 2.2. Obstacle overcoming process of transformable wheel 18 2.3. Preliminary experiments with curved wheel 19 2.3.1. Trajectory analysis 19 2.3.2. Required friction coefficient 23 2.3.3. Preliminary experiments results 26 3. Type Synthesis of 2-DOF Transform Mechanism 29 3.1. Requirements of transform mechanisms 29 3.2. Exploration of 2-dof mechanisms 33 3.2.1. Systematic process of developing design alternative mechanisms 33 3.2.2. Exploration of 2-dof mechanisms 34 3.2.3. Exclusion of alternatives with passive prismatic joints 37 3.2.4. Design alternatives by combining synchronization mechanism 39 3.3. Characteristic analysis of alternative mechanisms 40 3.4. Step overcoming simulation and evaluation 47 3.4.1. Simulation conditions 47 3.4.2. Inverse kinematics of alternatives 48 3.4.3. Simulation results 48 3.4.4. Analysis and evaluations 51 3.5. 5-bar 3R2P mechanism 55 4. Design of the STEP Platform 56 4.1. Concept design of the STEP platform 56 4.1.1. Issues of actuator location 56 4.1.2. Final concept of the mobile platform STEP 57 4.2. Design of the STEP platform 60 4.2.1. Description of mechanical parts 61 4.2.2. Kinematics based parameter selection 66 4.2.3. Static analysis 69 4.3. Fabricated STEP Platform 75 4.4. Design modifications 80 4.4.1. Link supporting ball roller 80 4.4.2. Clearance of a screw axis 81 4.4.3. Gap between motor-boxes 82 4.4.4. Timing belt deviation 83 5. Experiments 84 5.1. Experimental setup 84 5.1.1. Testbench : various sizes of stairs and steps 84 5.1.2. Active supporter 86 5.1.3. Initial condition 87 5.1.4. Guide to constrain pitch motion & trajectory 87 5.2. Transformation tests 89 5.3. Tests on flat surfaces 90 5.4. Stair overcoming experiments 91 5.5. Step overcoming experiments 98 5.6. Size varying stairs overcoming experiments 100 5.7. Field tests 102 6. Conclusion 104Docto