A Unifying Version Model for Objects and Schema in Object-Oriented Database System

There have been a number of different versioning models proposed. The research in this area can be divided into two categories: object versioning and schema versioning. In this dissertation, both problem domains are considered as a single unit. This dissertation describes a unifying version model (UVM) for maintaining changes to both objects and schema. UVM handles schema versioning operations by using object versioning techniques. The result is that the UVM allows the OODBMS to be much smaller than previous systems. Also, programmers need know only one set of versioning operations; thus, reducing the learning time by half. This dissertation shows that UVM is a simple but semantically sound and powerful version model for both objects and schema

Ubiquitous Health Management System with Watch-Type Monitoring Device for Dementia Patients

For patients who have a senile mental disorder such as dementia, the quantity of exercise and amount of sunlight are an important clue for doses and treatment. Therefore, monitoring daily health information is necessary for patients’ safety and health. A portable and wearable sensor device and server configuration for monitoring data are needed to provide these services for patients. A watch-type device (smart watch) that patients wear and a server system are developed in this paper. The smart watch developed includes a GPS, accelerometer, and illumination sensor, and can obtain real time health information by measuring the position of patients, quantity of exercise, and amount of sunlight. The server system includes the sensor data analysis algorithm and web server used by the doctor and protector to monitor the sensor data acquired from the smart watch. The proposed data analysis algorithm acquires the exercise information and detects the step count in patients’ motion acquired from the acceleration sensor and verifies the three cases of fast pace, slow pace, and walking pace, showing 96% of the experimental results. If developed and the u-Healthcare System for dementia patients is applied, higher quality medical services can be provided to patients

Active contour configuration model for estimating the posterior ablative margin in image fusion of real-time ultrasound and 3D ultrasound or magnetic resonance images for radiofrequency ablation: an experimental study

Purpose The purpose of this study was to evaluate the accuracy of an active contour model for estimating the posterior ablative margin in images obtained by the fusion of real-time ultrasonography (US) and 3-dimensional (3D) US or magnetic resonance (MR) images of an experimental tumor model for radiofrequency ablation. Methods Chickpeas (n=12) and bovine rump meat (n=12) were used as an experimental tumor model. Grayscale 3D US and T1-weighted MR images were pre-acquired for use as reference datasets. US and MR/3D US fusion was performed for one group (n=4), and US and 3D US fusion only (n=8) was performed for the other group. Half of the models in each group were completely ablated, while the other half were incompletely ablated. Hyperechoic ablation areas were extracted using an active contour model from real-time US images, and the posterior margin of the ablation zone was estimated from the anterior margin. After the experiments, the ablated pieces of bovine rump meat were cut along the electrode path and the cut planes were photographed. The US images with the estimated posterior margin were compared with the photographs and post-ablation MR images. The extracted contours of the ablation zones from 12 US fusion videos and post-ablation MR images were also matched. Results In the four models fused under real-time US with MR/3D US, compression from the transducer and the insertion of an electrode resulted in misregistration between the real-time US and MR images, making the estimation of the ablation zones less accurate than was achieved through fusion between real-time US and 3D US. Eight of the 12 post-ablation 3D US images were graded as good when compared with the sectioned specimens, and 10 of the 12 were graded as good in a comparison with nicotinamide adenine dinucleotide staining and histopathologic results. Conclusion Estimating the posterior ablative margin using an active contour model is a feasible way of predicting the ablation area, and US/3D US fusion was more accurate than US/MR fusion

데이터 분석 기반 복합소재 박판 보의 유한요소 모델 개발

학위논문(박사)--서울대학교 대학원 :공과대학 기계항공공학부(멀티스케일 기계설계전공),2019. 8. 김윤영.To analyze the behavior of the thin-walled beams using one-dimensional beam finite elements, considering complex cross-sectional deformations happening on the beam section is important. When it comes to composite thin-walled beams, the accurate definition of shape functions that describe local cross-sectional deformation becomes more critical. It is because anisotropic and laminate effects produce more complicated deformation patterns that do not appear in isotropic beams. This dissertation deals with identifying shape functions required for composite thin-walled beams and expand the higher-order beam theory which was limited to isotropic thin-walled beams before. Here, a data-driven approach was conducted to extract the shape functions required for general composite thin-walled beams consist of various cross-sections, ply orientations and stacking sequences. From the shell-based static analysis results of composite beams, big data representing cross-sectional deformations were obtained and then the principal component analysis was performed to identify shape functions. Compared with previous researches deriving shape functions of composite thin-walled beams, proposed approach identified them without various kinematic assumptions. Also, the shape functions were derived generally without considering a specific condition of ply orientation or stacking sequence. The higher-order beam elements using these shape functions deal with static, vibration and buckling analysis of composite thin-walled beams under general conditions. This dissertation demonstrates that the present results agree well with those obtained by shell analysis results by numerical examples. The proposed research is expected to be applied at various industrial fields requiring composite thin-walled beam models.일 차원 유한요소를 가지고 박판 보의 거동을 해석하기 위해서는 보의 단면에서 발생하는 복잡한 단면 변형을 고려해야 한다. 보 단면에서의 국부적인 변형들을 기술하는 형상 함수들의 엄밀한 정의는 복합소재로 만들어진 박판 보를 해석할 때 더욱 중요해진다. 등방성 물질로 구성된 보에서는 고려되지 않는 이방성 특성과 적층 특성들이 보의 단면에서 발생하는 변형을 더 복합하게 만들기 때문이다. 이 논문에서는 복합소재 박판 보를 다루기 위한 형상 함수들을 정의하고, 이를 활용하여 기존에 등방성 물질로 구성된 박판 보 해석에 한정되어 있었던 고차 보 이론 연구를 확장한다. 본 연구에서는 데이터 분석 기반 접근을 통하여 일반적인 플라이 각도 및 적층 순서를 포괄하는 다양한 단면의 복합소재 박판 보 해석에 필요한 형상 함수들을 구하였다. 복합소재 박판 보의 쉘 모델 기반 해석 결과들을 통하여 단면 변형들을 대표하는 빅 데이터를 확보하고, 이에 대한 주성분 분석을 수행하여 형상 함수들을 정의하였다. 제안하는 방법론을 통하여 기존의 복합소재 박판 보 해석 연구들에서 요구하였던 보 단면 형상에 대한 특정 기구학적 가정 없이 형상 함수들을 식별할 수 있었다. 또한, 형상 함수들이 특정 플라이 각도나 적층 순서에 제한되지 않고 일관되도록 정의할 수 있었다. 복합소재 박판 보 해석으로 확장한 고차 보 요소들은 확보한 데이터 분석 기반의 형상 함수들을 기반으로 정의되었으며, 제안한 보 요소를 활용하여 다양한 조건에서의 복합소재 박판 보의 정적, 진동 및 좌굴 해석을 수행하였다. 본 논문에서는 다양한 수치 예제들을 통해, 제안하는 일 차원 보 해석 모델이 기존의 이차원 쉘 해석 모델들에 준하는 해석을 수행할 수 있음을 입증하였다. 제안하는 연구는 복합소재 박판 보 해석 모델을 요구하는 다양한 산업 분야에 활용될 것으로 기대된다.CONTENTS ABSTRACT i CONTENTS iii LIST OF TABLES vi LIST OF FIGURES viii CHAPTER 1. INTRODUCTION 1 1.1 Motivation 1 1.2 Previous works 5 1.3 Research objectives 10 1.4 Outline of thesis 12 CHAPTER 2. Higher-order beam formulation 16 2.1 Overview 16 2.2 Theoretical review: Higher-order beam theory for isotropic thin-walled beam 17 2.3 Higher-order beam theory for composite thin-walled beam 20 2.4 Higher-order beam finite element formulation 22 2.4.1 Formulation for static analysis 22 2.4.2 Formulation for vibration analysis 24 2.4.3 Formulation for buckling analysis 25 CHAPTER 3. Data-driven approach for deriving shape functions of composite thin-walled beams 29 3.1 Overview 29 3.2 Preparing cross-sectional deformation big data 30 3.2.1 Cross-sectional deformation data required for isotropic materials or a certain composite 30 3.2.2 Cross-sectional deformation data required for general composites 32 3.3 Pre-process of cross-sectional deformation data 37 3.4 Data-driven analysis for obtaining principal cross-sectional deformations 39 3.5 Post-process required for defining shape functions. 41 CHAPTER 4. Numerical examples and discussions 49 4.1 Overview 49 4.2 Examples using data-driven shape functions for isotropic thin-walled beams 50 4.2.1 Verification of static, vibration and buckling analysis 52 4.2.2 Examples dealing with the validation of the data-driven approach 57 4.3 Examples using data-driven shape functions for composite thin-walled beams 62 4.3.1 Verification of static, vibration and buckling results 64 4.3.2 Examples dealing with special issues in a composite thin-walled beam under the data-driven approach 69 CHAPTER 5. Conclusions 110 APPENDIX A. Physical approach for deriving shape functions of composite thin-walled box beams 113 A.1 Overview 113 A.2 Cross-sectional deformations derived by plane stress assumption 115 A.3 Definition of sectional shape functions for degrees of freedom 127 A.4 Examples 131 REFERENCES 151 ABSTRACT (KOREAN) 161Docto

Analyzing media discourse on the development of the National English Ability Test (NEAT) in South Korea

Abstract The purpose of this study is to analyze newspaper articles from three publications (Chosun Ilbo, Donga Ilbo, and JoongAng Ilbo) regarding a newly developed high-stakes English test in South Korea, the National English Ability Test (NEAT), from the viewpoint of critical discourse analysis. All of the articles were collected from online archives, and most were published between 2007 and 2012. The events surrounding the development of the test were analyzed from three dimensions: textual, discursive, and social. It was found that NEAT-related media discourse was formulated in terms of technology-focused, economic (private education expenditure), or utilitarian (the benefits of a domestic “Korean” test) practice. These discursive events were implicitly connected to the cultures of “technopoly” and “teach-to-the-test,” both of which were exploited to silence the voices of diverse groups in the English language education community

Nonlinear Vibration Analysis of a Rotor-Hydrodynamic Bearing System: Gear and Thermal Bow-Induced Vibration

This dissertation presents a novel approach for modeling and analyzing a geared rotor-bearing system including nonlinear forces in the gear set and the supporting fluid film journal bearings. Co-existing, steady-state, autonomous and non-autonomous responses are obtained in an accurate and computationally efficient manner utilizing the multiple shooting and continuation algorithms. The results reveal a dependence of the gear set contact conditions and system nonlinear response characteristics, i.e. jump, coexisting responses, subharmonic resonances and chaos on the choice of journal bearing parameters. The Morton effect is caused by uneven viscous heating of the journal in a fluid film bearing, which causes thermal bending, especially in rotors with an overhung disc or coupling weight. This work investigates the influence of misaligned journal bearing effects on the thermally induced rotor instability problem. The simulation results indicate that the amplitude of the misalignment angle affects the instability speed range caused by the Morton effect under certain conditions. This work also treats the unconventional application of the SFD for the mitigation of ME-induced vibration. Installing a properly designed squeeze film damper may change the rotor’s critical speed location, damping and deflection shape, and thereby suppress the vibration caused by the ME. The effectiveness of the SFD on suppressing the ME is tested via linear and nonlinear simulation studies. The influence of SFD cage stiffness is evaluated. The influence of tilting pad journal bearing’s pivot design on the severity and instability speed range of the ME vibration was investigated. The friction between pad and pivot, which only exists in the spherical pivot, is taken into account and its impact on the ME is also tested. Nonlinear transient simulations are carried out for a wide operating speed range with varying pivot design parameters. Simulation results indicate that the predicted ME instability is sensitive to the pivot shape, pivot flexibility, and padpivot friction. The Morton effect test rig was built, and its vibration test results are presented. The vibration increases of the rotor at constant operating speed reveals that the existence of the Morton effect in the designed rotor-bearing test rig