The Effects of Exposure to Social Media on Conspicuous Consumption and Posting Behavior: The Mediating Roles of Social Comparison, Materialism, and Fear of Missing Out

Dinh, Thi Cam Tu 영남대학교 대학원 2022 국내박사

소셜미디어가 소비자행동에 미치는 영향과 관련해 다양한 연구가 이루어지고 있다. 또한 소비자들의 과시적 소비에 영향을 미치는 요인들에 대한 연구 역시도 활발하게 수행되고 있는데, 아직까지 이 두가지 주제를 연결시킨 연구, 즉 소셜미디어의 활용이 소비자들의 과시적 소비에 어떤 영향을 주는 지와 관련한 연구는 부족하였다. 본 연구는 소비자들의 소셜미디어에 대한 노출 증가가 과시적 소비 및 과시적 소비 관련 내용을 소셜미디어에서 포스팅하는 행동에 미치는 영향을 설명할 수 있도록 사회적 비교, 물질주의, 그리고 소외에 대한 두려움(FOMO; fear of missing out)이 이들 간의 관계를 매개하는 연구모형을 제시하였다. 또한 과시적 소비를 수행한 뒤 과시적 소비와 관련된 포스팅 행동을 수행하는 데 있어 온라인 자기표현욕구와 사회적 네트워크 유형이 조절 역할을 수행할 것으로 판단하여 이를 조절변수로 연구모형에 포함하였다. 제시된 연구모형을 검증하기 위해 MTurk 플랫폼을 활용하여 385 명의 표본 데이터를 수집하여 분석에 활용하였다.152 연구결과 소비자들의 소셜미디어에 대한 노출이 증가할수록 다른 사람들과 자신을 더 많이 비교하게 되며, 물질주의 수준과 소외에 대한 두려움 인식이 높아지게 됨을 확인하였다. 그리고 사회적 비교와 물질주의, 소외에 대한 두려움 인식 증가는 소비자들의 과시적 소비 및 소셜미디어 내에서의 과시적 소비 관련 포스팅 활동에 영향을 주고 있음을 확인하였다. 또한 온라인 자기표현 욕구가 강하고, 사회적 네트워크 유형이 덜 친밀한 관계로 이루어져 있을 때 더 많은 과시적 소비 관련 포스팅을 수행하는 것으로 나타나, 온라인 자기표현욕구와 소셜미디어 상에서의 사회적 네트워크 유형이 과시적 소비와 과시적 소비 관련 포스팅 행동 사이의 관계를 조절하고 있음을 확인하였다. 본 연구의 결과는 소셜미디어의 맥락에서 과시적 소비와 관련한 소비자행동을 설명하는 데에 기여할 수 있을 것이며, 기존 소셜 미디어에 대한 연구와 더불어 사회적 비교, 소외에 대한 두려움, 물질주의, 과시적 소비, 관련 포스팅 행동 등과 관련한 연구들을 더욱 풍성하게 하는 데에도 기여할 수 있다. 본 연구는 소셜미디어 상에서의 과시적 소비 관련 소비자 행동에 대한 이해를 증진시킴으로써 소셜미디어 이용자를 대상으로 커뮤니케이션을 수행하는 마케터들이 효과적인 마케팅 캠페인을 수립하는데 실무적 함의를 제공할 수 있을 것이다. Although many studies have explored the impact of social media on customers’ behavior and the antecedents of conspicuous consumption, little effort has been made to connect these two phenomena to explain the customers’ underlying process. This study proposes a new model explaining the effect of social media exposure on conspicuous consumption, and then on posting such conspicuous goods on social media platform behavior. Social comparison, materialism, and FOMO are the mediators in this relationship. Online self-presentation and social network type play as moderators in the relationship between conspicuous consumption and conspicuous consumption-related posting behavior. Through the MTurk platform, 385 respondents were collected to test the proposed model and direct, indirect, and interaction effects. This study found that individuals exposed to social media are more likely to make social comparisons with others. The more they compare with people on social media, the more materialistic they are, the higher FOMO they feel. Thus, social comparison, materialism, and FOMO, under the influences of social media exposure, together affect conspicuous consumption and the conspicuous consumption related posting behavior on social media. This research also found that self-presentation and social network type have potent effects on the relationship between the purchase desire and the consumption-related posting behavior. Those findings contribute to the existing literature on social media, social comparison, FOMO, materialism, conspicuous consumption, posting behavior, self-presentation desire, and social network type. This study also provides an additional explanation of consumers’ behaviors in the social media context related to conspicuous consumption, which is a practical implication for social media users and marketers to develop effective marketing campaigns. Viết cho Cam Tu Dinh

DVC에서 사이드 정보를 위한 해쉬 구조 연구

NGUYEN DINH TOAN 전남대학교 대학원 2008 국내석사

Distributed Video Coding (DVC) is a new video paradigm based on two information theorems: the Slepian-Wolf and Wyner-Ziv. In this new video paradigm, the source statistic is exploited at the decoder only so the complexity is shifted from the encoder to the decoder. Since the encoding requirement is much lower than that of conventional video codec, the DVC codec is very useful in some emerging applications such as wireless low-power surveillance systems, wireless PC cameras, multimedia sensor network and mobile camera phones. In DVC, the video sequence is divided into key frames and Wyner-Ziv (WZ) frames. Key frames are encoded and decoded by conventional intra-frame video codec such as H.26x or MPEG-x. To decode the WZ frames, the DVC decoder uses a part of parity bits produced from this WZ frame at the encoder and side information generated by applying motion compensation methods on decoded key frames at the decoder. The side information plays an important role in DVC. The more accurate of side information is generated, the less number of parity bits is needed to successfully decode the WZ frame. Since the decoder does not have any information about current WZ frame being decoded, it must use future decoded key frame to generate good side information. In the thesis, beside the bitstream resulting from the current WZ frame encoding process at the encoder, some extra information about current WZ frame is generated and transmitted to help the decoder generate good side information without future decoded key frame. Although the encoding complexity is increased a little and a small amount of buffer is needed at the encoder, the extra information may help improve the quality of side information and remove the system delay which is a result of using future decoded key frame. There are many hashes can be used as extra information. The main objective of the thesis is to design hashes together with motion estimators and lossless coding methods for them. We examine the impact of different hashes on the side information generated at the decoder. 분산 비디오 부호화(Distributed Video Coding : DVC)는 Slepian-Wolf와 Wyner-Ziv 가 제안한 정보이론에 근거한 새로운 비디오 부호화의 패러다임이다. 이러한 새로운 부호화 이론에서 (the source static)은 부호기에서 복호기로 이동하는 복잡한 구조에서 오직 복호기에 대해서만 적용한 것이다. 기존의 비디오 코덱은 매우 복잡한 부호화기 구조와 많은 처리량을 가지고 있는 반면에 DVC 코덱은 매우 규모가 큰 무선환경, 저전력 감시 시스템 또는 모바일 카메라폰에서 매우 유용한 프로그램이다. DVC에서 비디오 시퀀스는 키프레임과 Wyzer-Ziv(WZ) 프레임으로 나누어진다. 키프레임은 기존 코덱(H.26x, MPEG-x 등)에서 I 프레임(Intra frame)을 다루는 것처럼 부호화되고 복호화된다. 그리고 DVC 코덱에서 새롭게 정의된 WZ 프레임은 DVC 디코더에서 패리티 비트(Parity bit)로 사용하기 위해 부호화되며 추가적으로 생성되는 Side Information은 복호기에서 복호화된 키프레임에 대해서 모션 보상(Motion Compensation)을 적용하기 위하여 생성된다. 다시 말해서 Side Information은 DVC코덱에서 패리티 비트와 함께 WZ 프레임을 복화화하기 매우 중요한 역할을 수행하며 그런 이유로 매우 정밀하게 생성한다. 복호기는 현재 복호화된 WZ 프레임에 대한 어떤 정보도 가지고 있지 않으며 좋은 Side Information을 생성하기 위해 다음에 복호화될 키프레임에만 오직 사용되어진다. 이 이론에 의하면, 부호기에서는 현재 WZ 프레임 부호화 공정으로부터 초래한 비트스트림과 약간의 Extra Information이 생성되고 전송되는데 이것은 복호기에서 다음에 복호화될 키프레임 없이 좋은 Side Information을 생성하기 위함이다. 이러한 과정으로 인해 부호기의 복잡성이 크게 줄어들었고 버퍼공간도 조금 사용하게 되었다. 또한 Hash 기술은 Side Information의 Quality를 향상시켰고, 다음 복호화할 키프레임으로 인한 시스템 지연을 제거하였다. 결론적으로 Extra Information로서 사용할 수 있는 많은 Hash가 있다. 이 연구의 가장 중요한 목적은 무손실 부호화 방법과 모션 예측기와 함께 해쉬 코드를 설계하기 위함이다. 우리는 복호기에서 생성된 Side Information 상에서 서로 다른 해쉬들의 영향을 실험하여 확인하였다.

Balancing and Transferring Controls of the Ridable Ballbot

PHAM DINH BA Kyung Hee University - Graduate School 2018 국내박사

This thesis focuses on the design and implementation of a ridable ballbot and application of control methodology to control the ridable ballbot. The control methods, which include linear double-loop control and the nonlinear control techniques, such as partial feedback linearization (PFL) and sliding mode control (SMC), are designed based on two versions of the mathematical models of the ridable ballbot system: one describes the two-dimensional (2D) motions of ridable ballbot and the other is extended for its two and half-dimensional (2.5D) motions. The performance and effectiveness of the proposed control methods and accuracy of the mathematical models are demonstrated by both simulation and experiment. The simulation is realized in the PC using Simulink Matlab. The real ridable ballbot is installed for experiment with Visual Studio C++. Generally, a ridable ballbot has a body that balances on top of a ball and forms an underactuated system. The robot has more degrees of freedom (DOF) than independent control inputs. The ridable ballbot accelerates by leaning, but cannot directly control its tilt angles. The body is kept upright at approximately its unstable equilibrium point by only maneuvering the ball, similar to controlling an inverted pendulum. The controllers are first designed for the planar ridable ballbot then improved for the spatial motion of ridable ballbot system. The proposed control scheme concurrently implements three main tasks: balancing, transferring, and rotating a ridable ballbot on the floor. Based on the application of multi-loop control, linear quadratic regulator (LQR), PFL, and SMC techniques, this study proposes one linear optimal double-loop controller and six types of nonlinear controllers represented as follows. (i) Linear double-loop control system with LQR outer-loop and proportional-integral(PI)-plus-feedforward inner-loop controllers. This study proposes a linear double-loop control system based on planar ridable ballbot models. These planar models are linearized around an equilibrium point where the ridable ballbot is in an upright position and stationary. The double-loop control system includes two controllers: one is a PI-plus-feedforward inner-loop controller and the other is an LQR outer-loop controller. The double-loop control system allows the ridable ballbot to overcome the hindrance caused by its heavy weight and bulk and eliminate most of the uncertainties of system parameters, modeling, friction and external disturbances. (ii) The PFL based controller for planar ridable ballbot motion and its extended version for spatial motion. The PFL controller is designed to control balancing and transferring of the ridable ballbot. The planar dynamics of the ridable ballbot is formulated with highly nonlinear second order differential equations. This planar dynamics involves the ball state and body state driven by only one torque input. First, its system dynamics should be divided into ball subsystem model and body subsystem model. Next, two PFL laws are proposed; one is determined by the ball subsystem and the remaining law is got from the feedback linearization of the body subsystem. Considering the body state as the primary system output, the PFL control input is proposed to balance and track the position of the ball to the desired reference trajectory. Because this nonlinear control law does not guarantee the convergence of the overall state variables, the structure of the controller should be modified to satisfy the stability condition of the full state variables. The modification is a linear combination of two components: one is received from feedback linearization of the ball dynamics and body dynamics. Then the proposed controller asymptotically pulls all system responses to the desired values. Improving the aforementioned proposed controller for the spatial ridable ballbot motion, another nonlinear controller is considered for the robot in the case of the most complicated tasks in which the ball, three omnidirectional wheels, and body motions are simultaneously operated. The control structure is designed based on the nonlinear feedback of the ball and body states. First, system dynamics of ridable ballbot composed of four highly nonlinear second-order differential equations are created. Because the ridable ballbot is a second-order underactuated system with non-holonomic velocity constraints and input coupling case, its system dynamics should be separated into ball and body subsystems. Next, the two sub-systems are linearized by using the nonlinear feedback technique. Afterward, considering states as system outputs, a nonlinear controller of the ball subsystem is proposed to track output positions of the ball on the floor to the desired path while another nonlinear controller of the body subsystem is proposed to keep the body at the vertical position. The stability analysis of the two subsystems and the overall system is given to prove the convergence of the system states. Finally, the performance of the proposed nonlinear control method is simulated and experimentally tested for self-balancing and station-keeping, transferring, and robustness against external disturbances. (iii) The hierarchical SMC based controller for the planar motion of the ridable ballbot and its extended version for the spatial motion. SMC is a robust technique applied widely in nonlinear systems to implement and insensitive with external disturbances and uncertainties of system parameters, friction, and modeling. It is especially suitable for underactuated systems, such as ballbot system. The goal of SMC approach is to determine an asymptotically stable surface so that all state trajectories are attracted to this surface and slide along until reaching their desired values. As mentioned, the ridable ballbot is an underactuated system containing uncertain components, such as system parameters, friction factors, and model. Therefore, SMC technique is a proper selection in this study. Two hierarchical SMC schemes are discussed. One is for the planar motion of the ridable ballbot system and the other is improved for the spatial ridable ballbot system. Based on this physical structure, the hierarchical structure of the sliding mode surfaces (SMS) is designed as follows. At first, the SMS of every subsystem is defined. Then the SMS of one subsystem is defined as the first layer SMS. The first layer SMS is used to construct the second layer SMS with the SMSs of another subsystem. This process continues till the SMSs of the entire subsystems are included. According to the hierarchical structure, the total control law is deduced by the Lyapunov theorem. In theory, the asymptotic stability of the entire system of SMSs is proven and the parameter boundaries of the subsystem SMSs are given. (iv) PFL and SMC combination based control scheme for the planar and spatial motion of the ridable ballbot. An improved nonlinear control scheme for the planar motion of the ridable ballbot is proposed applying a combination of two nonlinear control techniques. The first step in combined control design is to decompose the ridable ballbot system into ball and body subsystems. Next, using the PFL technique, the body subsystem control is constructed to control balancing of the robot. The ball transferring control is designed based on the SMC technique and ball subsystem. In the final step, the balancing and transferring control laws are merged to stabilize overall state variables of the ridable ballbot system. Improving the aforementioned controller for the spatial motion of the ridable ballbot, the control scheme is divided into two parts in which each of them implements a particular duty. PFL controls the balance of the body while SMC controls the position of the ball on the floor. A combined nonlinear controller is proposed by integrating PFL based scheme into SMC based structure.

Micro-texturing technology on cylindrical stainless steel surface for biomedical applications

Truong, Dinh Sy Kangwon National Univ 2013 국내석사

Evaluation of micro-texturing technology on biomedical material has been developing in recent decades. In particular, increase or reduction of friction force on surgical equipment has fascinated a larger number of researchers. In this study, we evaluated the micro-texturing technique that changed the needle surface's structure. The results lead to orientation how to minimize pain and damage during injection process or improve the biocompatibility for implantable devices. Biomedical biopsy needles were made from stainless steel 316L. Stainless steel 316L contains Iron, Molybdenum, Chromium and Nickel as main compositions. In general, Chromium helps to prevent corrosion and scratch, Nickel provides smooth and Molybdenum helps to have a greater hardness and maintains a cutting edge. Furthermore, in order to measure friction force, the material that is identical human tissue called phantom tissue was utilized. After that, the textured biopsy needle will be injected through the tissue for calculating friction force. Also, we designed a surface friction measuring system that includes movement and fix part. The movement part brings tissue and move in vertical direction. The fix part helps to keep needle. In order to texture the surface of biopsy needles, a PDMS mold was design as hexahemispherical shape with the pitch of 30?m. Before rolling needles for fabricating patterns, AZ 4620 (PR-photoresist) was poured upon the PDMS mold and carried out doctoring step. After this, PR patterned needles were dipped into etchant solution for etching process, leading to micro-texturing surface. The solution contains FeCl3: HCl: HNO3 = 10:10:5 in weight ratio. The etching stage implemented at 40℃ and etching time interval ranged from 10 seconds to 60 seconds. In general, the results of experiments will provide the influences of pattern depth, pattern diameter as well as velocity of injection.

Thermally affected high-speed spindle system with angular contact ball bearings

DINH SY TRUONG University of Science and Technology, Daejeon, Rep 2020 국내박사

Failure and vibration of high-speed spindles in machine tools have been the common issues during the machining process. Investigating the vibration of spindles helps engineers to predict the performance of machining elements before manufacturing. As the rotational velocity increases, the spindle performance is affected by a variety of mechanical determinants of bearings such as stiffness, contact loads, contact angle, axial displacement, bearing configurations, and thermal effects. Stiffness of the bearings directly influences the dynamic properties of a high-speed spindle system and plays a significant function with respect to precision manufacturing quality. In this thesis, a new approach is developed to predict the thermal behavior of a high-speed spindle, estimate the thermal expansion and generate stiffness matrices of the bearings for angular contact ball bearings. The heat convection of the balls in the lubricant, bearing inner ring surfaces, the spindle shaft in quiescent air, and spindle housing in the room temperature was calculated. Heat sources such as the heat generated by the embedded motor, and bearing friction, were simulated and utilized in a steady-state thermal model built in ANSYS. The heat effects were incorporated into a static structural model. Ball thermal expansion was determined based on changes in the coordinates of nodal points on the surface of the ball. Also, radial thermal expansion coefficients of the couplings between the bearing inner ring-shaft, and outer ring-housing are included for generating the front and rear bearing stiffness matrices. By applying the Newton-Raphson technique, the matrices of bearing stiffness under thermal effects were produced in five by five. Declines in the coupling stiffness, axial, radial, and angular stiffness values were determined as rotational spindle speed increased. The coefficients of stiffness were increased significantly due to the thermal effects. The bearing stiffness was compared to the one measured using an earlier thermal network method for validation. Also, the thermally affected stiffness matrices of the bearings are generated without the effects of centrifugal expansions. These stiffness matrices were used as inputs for a finite element model generated in the ANSYS Workbench environment, in which the bearings were simulated as bushing joints with five degrees of freedom, to numerically compute the acceleration spindle frequency responses. The findings showed that the spindle natural frequencies are decreasing with the spindle system rising temperature. This was because of reductions in the coefficients of the bearing stiffness, caused by decreases in the bearing inner ring loads. An experimental system was set up to measure the acceleration frequency response function, and the results showed good agreement with the simulations.

(A) study on the RTDS-based design and analysis of novel protection schemes for transmission systems equipped with advanced power devices

Dinh, Minh-Chau 창원대학교 2016 국내박사

전력수요의 증가에 따라, 발전 설비의 설치 또한 지속적으로 증가하고 있다. 이와 함께, 전력 시스템의 송전 용량의 확충도 요구되고 있다. 이를 위한 방안으로, 송전 계통 내 새로운 전력기기의 도입 및 송전 선로의 증설과 같이 크게 두가지로 나뉠 수 있다. 송전 용량을 증가시키기 위하여 송전조류 제어장치(TCSC) 및 초전도 전력 케이블과 같은 전력기기의 도입이 국내에서 추진되고 있다. 송전조류 제어장치는 송전 선로와 직렬로 연결되는 전력기기이고, 이는 내부 임피던스의 제어를 통해 송전 선로의 임피던스를 가변하는 역할을 하며, 초전도 전력 케이블은 기존 전력 케이 블과 비교하여 동일 전압 혹은 더 낮은 전압에서 더 큰 송전 용량을 가진다. 전력수요와 공급의 증가는 고장 전류의 증가라는 또다른 문제점을 야기한다. 송전 선로에서의 고장 전류 증가는 차단기의 허용 용량을 초과할 때 그 문제점이 두드러지게 된다. 이를 위한 방안으로, 계통의 고장시에만 송전 선로의 임피던스를 증가시켜 고장 전류를 제한하는 초전도 한류기의 도입이 추진되고 있다. 그러나, 가변 임피던스 특성을 갖는 송전조류 제어장치, 초전도 전력 케이블 및 초전도 한류기는 송전 선로 보호를 위한 보호 협조 시스템에 문제를 야기 할 수 있다. 송전 선로를 위한 보호 시스템은, 차동 계전요소 기반의 주 보호와 거리 계전요소 기반의 후비 보호로 구성되어, 상호 협조하에 운전된다. 이중, 전력기기의 가변 임피던스 특성은 거리 계전요소에 영향을 주게 되며, 이에 대한 해결책이 요구되고 있다. 본 논문에서는 가변 임피던스 특성을 가지는 전력기기들의 계통 적용에 따른 문제점에 대한 새로운 보호 협조 방안들을 제안하였다. 먼저, 계통 전압 신호에 대한 보상을 통해 송전조류 제어장치의 임피던스 영향을 상쇄할 수 있는 방안에 대해 제안하였고, 두번째로, 임피던스 특성을 그룹으로 나누어 전력기기 및 시스템의 거동에 맞게 동작하는 보호 협조 방안을 제안하였다. 실시간 계통 모의 장치(RTDS)를 기반으로 하여, 가변 임피던스 특성을 갖는 전력기기들의 계통 적용에 따른 거리 계전요소의 동작 특성에 대해 분석하였고, 기존 거리 계전요소의 보호 협조 방안과 본 논문에서 제안된 보호 협조 방안에 대해 비교 분석하였다. 분석 결과를 통하여, 제안된 전압 보상 및 임피던스 그룹 지정을 통한 방안들은 가변 임피던스에 의한 거리 계전요소의 오동작에 대한 적절한 해결책이 됨을 확인하였다. 본 결과들은 차세대 전력기기들이 적용된 전력 계통에서의 보호 협조 시스템을 구성하는데 활용 될 것이다. 주제어 송전조류 제어장치(TCSC), 초전도 전력 케이블, 초전도 한류기, 차동 계전요소, 보호 협조 방안, 실시간 계통 모의 장치 (RTDS)

Preparation of Y2O3:Bi3+,Eu3+@SiO2/EVA film for application in solar cells

Dinh Thi Thuy Duong University of Science and Technology 2017 국내석사

In designing the light converting layers for solar cells, high conversion efficiency and excellent transparency are the dominant goals. In this study, the facile method was presented to prepare homogeneous downconversion (DC) nanoparticles by the urea precipitation. In order to adjust the absorption maximized to the solar radiation, Eu3+dopant was sensitized by Bi3+dopant in Y2O3 host materials. The phosphor nanoparticles were further coated with silica shell to enhance transparence and miscibility with polymer materials. The core-shell phosphors were incorporated into poly-ethylene vinyl acetate (EVA) film in different concentrations. The optical properties of the nanocomposite films were investigated by photoluminescence (PL) and UV-Vis absorption spectra. It was demonstrated that the phosphors/EVA films have the broad absorption in UV range and the strong emission in red light (613 nm) which is close to effective response region of the Si solar cell. In addition, it was found that the nanocomposite films have highly transparent in visible and near-infrared range (≥ 90%). Meanwhile, these films have strong absorption in low wavelength which is advantageous in shielding harmful UV range. This behavior is important for prolonging the lifetime of photovoltaic cells. The efficiency enhancement in solar cell was measured with Si solar cell and it showed that the Y2O3:BiEu@SiO2/EVA films are potential spectral converters in the field of photovoltaics.

Control of a 2-DOF Omnidirectional Mobile Inverted Pendulum

Tuan, Dinh Viet The Graduate School, Pukyong National University 2012 국내박사

Nowadays, simple and executable controllers that can control many complex processes are more popular, remarkable and justifiable. Studying and designing such controllers for an inverted pendulum system is a suitable way to prove the controllers performance. The reason to study the pendulum intensively relies on the fact that many important engineering systems can be approximately modeled as a pendulum. For example, in thrust vectored rocket control, the pitch dynamics of a rocket can be approximated by a simple pendulum. In robot systems, their dynamics can be modeled as the inverted pendulum systems. In biomechanics, the pendulum is used to model bipedal dynamic walking. The pendulums are also used in the study of wheeled motion and balancing mechanisms. Many challenging control algorithms have been tested with the inverted pendulum system. These controllers are from classical control theories to intelligent control algorithms. An 2-degrees-of-freedom (2-DOF) omnidirectional mobile inverted pendulum (OM-IP) is made of a 2-DOF inverted pendulum (IP) based on omnidirectional mobile platform (OMP) to take advantage of the convenient characteristics of omnidirectional wheels to balance the IP which is mounted on the OMP. Until now, there are little researches about this system with disturbance and friction. It is difficult to derive the dynamic modeling of an OMP with disturbance and friction and control it. Moreover, it is also difficult to derive the dynamic modeling of a 2-DOF OM-IP with an assumption that the distance from the center of gravity of the inverted pendulum to the rotary point on the OMP is unknown and how to control to keep the IP balance. So obtaining modeling and motion control of the 2-DOF OM-IP are deeply needed. Objective of this dissertation is to present modeling and controlling the balance of the IP mounted on the OMP with disturbance and friction by using adaptive backstepping technique. The OM-IP is separated into two subsystems, the OMP and the 2-DOF inverted pendulum. To control the motion of the OMP, two controllers are designed for the OMP to track a desired path with a desired velocity, and an adaptive backstepping controller to balance the IP which is mounted on the OMP. Therefore, the following tasks are implemented in this dissertation. First, the structure of the OM-IP used for experiment is proposed. Hardware configuration of the proposed system is implemented. A control system is developed based on PIC18F452 microcontroller technology. One PIC18F452 is used as a master unit, and other PIC18F452s are used as slave units. The master unit is connected with other slave units through I2C communication. The master unit receives data from the sensors that are used for main controller, and then it sends the commands to the slave controllers via I2C communication, respectively. The slave controller integrates PIC18F452 with motor drivers, LMD18200, for the DC motor control. Second, an OMP with three driving omnidirectional wheels in the presence of disturbance and friction is presented. A kinematic modeling of the OMP is presented, and a dynamic modeling of the OMP with disturbance and friction is derived based on the Newton’s second law of motion. Based on the modeling of the system, controllers are designed to control the OMP to track a desired path. Third, dynamic modeling for the 2-DOF OM-IP is presented. The IP is a rod that rotating around a universal joint structure with 2-DOF. The motions of the OMP are separated into two independent motions: motion in plane and motion in plane, so the 2-DOF inverted pendulum is decoupled into two subsystems of 1-DOF inverted pendulum. By applying the Newton’s second law at the center of gravity of the pendulum, the nonlinear mathematical modeling equations of the 1-DOF inverted pendulum in plane and plane are obtained. Fourth, based on the dynamic modeling, a backstepping controller is designed to stabilize the OMP to follow a desired path. The controller is designed based on a backstepping control theory. It includes two steps: firstly, a virtual state and a stability function are introduced. Secondly, Lyapunov functions for the system are chosen and an equation for the virtual control that makes the system stabilisable is obtained. The system stability is guaranteed by the Lyapunov stability theory. The simulation and experimental results are presented to illustrate the effectiveness of the proposed tracking controller. Fifth, based on the dynamic modeling of the OMP system with disturbance and friction, an adaptive backstepping controller is designed to stabilize the OMP with parameter variations and uncertainties caused by friction and slip to follow a desired path. The controller and update laws are designed based on an adaptive backstepping control theory. The system stability is guaranteed by the Lyapunov stability theory. The simulation and experimental results are presented to demonstrate the effectiveness of the proposed controller and update laws. After that, the controllers in chapter 4 and chapter 5 are compared by simulation and experimental results in the same conditions. The concepts of two controllers in Chapter 4 and 5 are applied to control the OM-IP in Chapter 6, respectively. Finally, from the dynamic equation of the OM-IP system, an adaptive backstepping control method is proposed to keep the inverted pendulum balance with an assumption that the distance from the center of gravity of the rod to the rotary point on the OMP is unknown. The stability and the convergence properties of OM-IP is guarantee by Lyapunov function. The effectivenesses of the proposed system are shown through simulation and experimental results. So the system can be applicable and implemented in the applications. Keywords: Inverted Pendulum Omnidirectional Mobile (OM-IP), 2 degrees of freedom (2-DOF), Omnidirectional Mobile Platform (OMP), Inverted Pendulum (IP), Lyapunov Function Candidate, Backstepping Method (BC), Adaptive Backstepping Controller (ABC).

(An)Efficient Method for Text Detection in Video Based on Stroke Width Similarity

Dinh Viet Cuong 고려대학교 대학원 2007 국내석사

Text appearing in video provides semantic knowledge and significant information for video indexing and retrieval system. This paper proposes an effective method for text detection in video possibly with complex background. First, an edge detection method with local adaptive threshold algorithm is applied to significantly reduce the number of non-text pixels. The threshold algorithm is based on the observation that text regions in video frames can be characterized by the similarity in stroke width of text. Second, text region candidates are roughly localized by employing a two-level projection technique. Third, a multi-frame verification method is used to verify the validity of each candidate and then refine the location of each true text region. Experimental results show that our proposed method is not only robust to different levels of background complexity, but also effective to different fonts (size, color) and languages of text.

Anti-Nucleic Acid Antibody-Mediated Cross Presentation of An Antigen and Its CD8+ T Cell Activation : 항-핵산 항체의 교차항원제시 및 항원 특이 T 세포의 활성화 기전연구

Dinh-Chuong Pham 아주대학교 대학원 2013 국내박사

Cross-presentation is important for initiating cytotoxic T lymphocyte (CTL) responses against tumors. Delivery of exogenous antigens to the cross-presentation pathway in dendritic cells using a number of different carriers has been attempted to further understand the mechanisms underlying cross-presentation and to develop therapeutic tumor vaccines. The present study reports a new antigenic carrier molecule: a single chain variable region fragment (scFv) of a nucleic acid-hydrolyzing antibody, 3D8. As the CD8-T cell epitopes, chicken ovalbumin amino acid 257-264 (OVA257-264-SIINFEKL) and 250-264 (OVA250-264-SGLEQLESIINFEKL) were used for 3D8 scFv fusion partners. Purified 3D8 scFv-OVA fusion proteins with ~95% purity retained DNA-binding, DNA-hydrolyzing, cell-penetrating, and cytotoxic activity comparable to 3D8 scFv. Although 3D8-OVA proteins induced B16 and MO5 melanoma cancer cell death up to 80%, they just had little effect on the viability of DC2.4 dendritic cells. Both 3D8-OVA257-264 and 3D8-OVA250-264 showed OVA-specific CD8 T cell stimulatory effect but the activity of 3D8-OVA250-264 was higher than that of 3D8-OVA257-264. Furthermore, 3D8-OVA250-264 stimulated OVA-specific CD8 T cells through cross-presentation by dendritic cells via a proteasome dependent, brefeldin- and cycloheximide-sensitive, chloroquine- and primaquine-insensitive pathway, resulting in loading of the CTL epitope onto H-2Kb. In vivo cross-presentation and cross-priming was efficient, even without adjuvant; injection of mice with 3D8 scFv-OVA250-264 induced cross-presentation of the CTL epitope by draining lymph node CD11c+ B7.1+ MHC class IIhigh dendritic cells, elicited a CTL response, and suppressed the growth of tumors expressing the OVA epitope. This is the first report of an anti-nucleic acid antibody used to deliver exogenous antigen to the cross-presentation pathway and inhibit in vivo tumor growth.