10,457 research outputs found
Hyoun-Chul Choi
No full text학위논문(박사)--아주대학교 일반대학원 :제어계측공학과,2006. 8Acknowledgments --- v
Table of Contents --- viii
List of Figures --- x
List of Tables --- xii
Abstract --- xiii
1 Introduction --- 1
1.1 Background and Motivation --- 1
1.2 Organization of the Thesis --- 4
2 Guaranteed Cost Control Using Linear Matrix Inequalities --- 6
2.1 Linear Matrix Inequalities --- 6
2.1.1 Useful Results in LMIs --- 8
2.1.2 Standard Problems Involving LMIs --- 10
2.2 Guaranteed Cost Control for Linear Systems --- 12
2.2.1 Guaranteed Cost Control for Nominal Linear Systems --- 13
2.2.2 Guaranteed Cost Control for Uncertain Linear Systems --- 15
3 Optimal Guaranteed Cost Control for Uncertain Systems with Actuator Saturation --- 17
3.1 Introduction --- 17
3.2 Problem Statements and Preliminary Results --- 20
3.3 Guaranteed Cost Controller Design --- 24
3.3.1 Sufficient Condition for Controller Design --- 24
3.3.2 Optimization --- 27
3.4 Illustrative Example --- 30
3.4.1 Case When Without Uncertainties --- 32
3.4.2 Case When With Constant Uncertainties --- 36
3.4.3 Case When With Sinusoidal Uncertainties --- 36
3.4.4 Case When With Sinusoidal Uncertainties --- 40
3.5 Summary --- 41
4 Adaptive Guaranteed Cost Control for Uncertain Systems with Hard Nonlinearities --- 49
4.1 Introduction --- 49
4.2 Problem Statements --- 51
4.3 Adaptive Guaranteed Cost Controller Design --- 53
4.3.1 Sufficient Condition for Controller Design --- 53
4.3.2 Optimization --- 55
4.4 Illustrative Example --- 57
4.5 Summary --- 59
5 Conclusions --- 62
5.1 Contributions of the Thesis --- 63
5.2 Directions for Future Research --- 64
Bibliography --- 65
Appendix. MATLAB Code --- 70
Abstract in Korean --- 76MasterIn this thesis, the problem of guaranteed cost control (GCC) for some classes of uncertain nonlinear systems is considered. In particular, the thesis considers two types of problems in this direction: the problem of GCC for uncertain systems subject to actuator saturation and the problem of adaptive GCC for a class of uncertain nonlinear systems which may include systems with hard nonlinearities such as the Coulomb friction. Based on LMI techniques, the thesis proposes new conditions for GCC design, which admit norm-bounded uncertainties and some classes of nonlinearities. The resulting LMI conditions are further used for solving convex optimization problems which minimize the upper-bounds of cost functions associated with the given systems. The solution for the first problem leads to a state-feedback controller that minimizes the upper-bound of the cost function in the presence of uncertainties and actuator saturation. The solution for the second problem leads to an adaptive state-feedback controller that compensates for the effects of uncertain nonlinearities while minimizing the upper-bound of the given cost function. The effectiveness and applicability of the proposed methods is illustrated by using simulation examples, in which an uncertain helicopter model in a vertical plane subject to actuator saturation is considered for the first problem and a 1-DOF mechanical oscillator subject to uncertain Coulomb friction is considered for the second problem
Choi, Jin-Chul
No full text학위논문(석사)--아주대학교 일반대학원 :전자공학과,2007. 2센싱, 데이터 가공, 통신이 가능한 소형의 센서 노드로 구성된 무선 센서 네트워크는 다양한 환경 변화를 측정할 수 있는 유용한 수단이다. 센서 노드에서 측정된 데이터는 모든 데이터를 수집, 처리하며 사용자에게 전달하는 기능을 가진 싱크 노드에 전송된다. 이러한 과정은 에너지 제약을 가진 센서 노드를 고려하여 설계되어야 한다. 일반적으로 인접한 센서 노드는 유사한 정보를 가지므로, 로컬 클러스터를 형성하고 클러스터 헤드에 의해 집약된 데이터를 싱크 노드에 전송하는 클러스터링 기법이 저전력 구동에 효과적이다. 자동 구성능력을 지닌 기존의 다중 홉 클러스터의 에너지 소비량 모델링 기법은 개별 센서 노드의 정확한 에너지 소비량을 예측할 수 없는 문제를 가지고 있다. 따라서 따라서 본 논문에서는 이러한 문제를 보완한 새로운 클러스터 에너지 소비량 모델링 기법을 제안한다. 제안된 모델링 기법은 센서 필드의 면적, 분포된 센서 노드의 수와 통신 범위를 이용하여 전체 네트워크의 에너지 소비량을 클러스터 헤드의 수에 따라 정량적으로 나타낸다. 본 모델링 기법을 통해 전체 네트워크의 에너지 소비량이 최소가 되는 클러스터의 수를 예측함으로써 저전력을 실현할 수 있다. 본 논문에서 제안하는 모델링 기법은 시뮬레이션을 통해 구성한 실제 네트워크의 에너지 소비량과 90% 이상의 정확도를 가지며, 기존 모델링의 60%대에 비춰볼 때 상당히 우수한 정확도를 지니고 있다.Ⅰ. Introduction = 1
Ⅱ. Related Work = 5
A. LEACH(Low-Energy Adaptive Clustering Hierarchy) = 6
B. EEHCA(Energy Efficient Hierarchical Clustering Algorithm) = 10
Ⅲ. A New Energy Model for the Multi-hop Clustered Wireless Sensor Network = 16
A. Clustering algorithm = 16
B. Assumption for the modeling = 17
C. Derivation of the energy model = 19
Ⅳ. Evaluation of the Model = 26
A. Simulation Setup = 26
B. Evaluation of the model = 27
Ⅴ. Conclusion = 33
References = 34
Abstract = 36MasterWireless Sensor Networks consisting of a number of small sensor nodes with limited battery power are deployed to collect useful information from the field. Since neighboring sensor nodes generally have the data of similar information, duplicate transmissions of similar information are usual. In order to prevent energy wastes by duplicate transmissions, it is advantageous to organize sensor nodes into clusters and have the cluster-head node to aggregate the collected data and transmit the data on behalf of its cluster. However, the performance of the clustering scheme is influenced by the method of cluster-head election and the size or the number of clusters. Thus, we should optimize these factors to maximize the energy efficiency of the clustering scheme. In this paper, we propose the analytic model of energy consumed by the sensor nodes in the multi-hop clustered sensor networks. From the model, we can estimate the optimal number of clusters which minimize the energy consumption in the system. The evaluation shows that our model is well matched with the result of the simulation
Characteristics of radial tears in the posterior horn of the medial meniscus compared to horizontal tears
No full textBACKGROUND: The clinical and radiologic features of radial tears of the medial meniscus posterior horn were compared with those of horizontal tears.
METHODS: From January 2007 to December 2008, 387 consecutive cases of medial meniscal tears were treated arthroscopically. Among these, 91 were radial tears in the medial meniscus posterior horn, and 95 were horizontal tears in the posterior segment of the medial meniscus. The patients' data (age, gender, duration of symptom, body mass index, and injury history), radiographic findings (Kellgren and Lawrence score, posterior tibial slope, and femorotibial angle), and chondral lesions were recorded.
RESULTS: The patient factors of age, gender, and body mass index were related to radial tears of the medial meniscus posterior horn. Radial tears were significantly correlated with Kellgren and Lawrence score, varus alignment, posterior tibial slope, and severity of the chondral lesion.
CONCLUSIONS: Radial tears of the medial meniscus posterior horn are a unique clinical entity that are associated with older age, females and obesity, and are strongly associated with an increased incidence and severity of cartilage degeneration compared to horizontal tears.ope
Genetically engineered human interleukin-6 variant with enhanced stability
No full textA recombinant human interleukin-6 mutant with enhanced conformational stability toward denaturant was obtained by site-specific mutagenesis. The clone was identified as having a single amino acid substitution of Lys70 → Glu. When urea-induced denaturation was monitored by the change in fluorescence intensity at 360 nm, Lys70 → Glu mutation shifted the midpoint of unfolding transition from 5.8 M (wild type) to 6.6 M urea. This mutation did not impair the biological activity.open
Molecular epidemiology of Streptococcus equi subsp. Zooepidemicus isolated from thoroughbred horses using multi locus sequence typing (MLST) in Korea
No full textBackground: Multi Locus Sequence Typing (MLST) is a new global molecular typing method used for analyzing the DNA polymorphisms in bacteria. In this study, using MLST, we analyzed the sequence profiles of Streptococcus (S.) zooepidemicus isolates from the Jeju and Jangsu provinces in South Korea. Objective: This study characterized the molecular epidemiology of S. zooepidemicus infection in Thoroughbred horses using MLST with an aim to control and prevent bacterial endometritis in mares. Methods: A total of 79 S. zooepidemicus isolates were included in this study. Sequencing of the 7 loci for the MLST analysis was performed as described in the MLST website manual (http:// pubmlst.org/szooepidemicus/) with some modifications. For each locus, every unique sequence was assigned a distinct allele number, and each Sequence Type (ST) was defined by a series of 7 integers (the allelic profile) corresponding to the alleles at the 7 loci (arcC, nrdE, proS, spi, tdk, tpi, and yqiL) using the MLST module in the Main Workbench. Results: Among the 79 isolates, 73 different MLST patterns were identified, each corresponding to 1-3 strains. The genetic relationships between the 79 isolates are presented in a dendrogram, and they diverged by up to 11% homology. At 11% homology, three MLST groups, M1, M2, and M3, were identified, and at 26% homology, five subgroups, L1-L5, were observed. We observed various MLST patterns in the strains isolated from Jeju and Jangsu. In addition, by estimating the epidemiological relationships among the strains isolated from Jangsu in 2007 and Jeju in 2009, which had similar MLST patterns, we determined that some strains from Jangsu may have been transported to Jeju. Conclusion: MLST can be used as a framework for determining the epidemiological relationships that form the genetic basis of host and infection site selection. © 2019 Choi et al.1
Editorial: Neurobiological perspectives in behavioral addiction
No full textAbstract not availableJung-Seok Choi, Daniel Luke King and Young-Chul Jun
Transient Self-assembly Processes Operated by Gaseous Fuels under Out-of-Equilibrium Conditions
No full text© 2020 Wiley-VCH GmbH. Herein we report transient out-of-equilibrium self-assembly of molecules operated by gaseous fuel mixtures. The combination of an active gaseous chemical fuel and an inert gas or compressed air, which assists the degassing of the gaseous fuel from the solution, drives the transient self-assembly process. The gaseous nature of the fuel as well as the exhaust helps in their easy removal and thereby prevents their accumulation within the system and helps in maintaining the efficiency of the transient self-assembly process. The strategy is executed with a rather simple experimental set up and operates at ambient temperatures. Our approach may find use in the development of smart materials suitable for applications such as temporally active gas sensing and sequestration11sciescopu
Umbrales culturales en la dramaturgia del coreano Choi In-Hun
No full textEn este artículo se analiza la dramaturgia de Choi In-Hun en su trilogía Tres obras de teatro (2007), desde los planteamientos de Byung-Chul Han para colocarnos en los umbrales de lo des/conocido a través del análisis textual que atiende al concepto de hipertextualidad como una estructura libertaria para quien se coloca en los umbrales culturales. En referencia a la cultura coreana, la dramaturgia de esta región y la de Choi In-Hun desde la deixis que nos construye de acuerdo con la mirada occidentalizada que predomina en Latinoamérica, este trabajo destaca cómo los textos estudiados ofrecen la posibilidad de re/conocer la fuerza de los rituales que estructuran las obras Choi In-Hun, la capacidad de los pueblos para resistir a la desaparición de su diversidad, y el acercamiento que las letras coreanas permiten a la complejidad sociocultural al evidenciar la diversidad en las relaciones humanas
Evolution of hardness, microstructure, and strain rate sensitivity in a Zn-22% Al eutectoid alloy processed by high-pressure torsion
No full textSevere plastic deformation (SPD) is an attractive processing method for refining microstructures of metallic materials to give ultrafine grain sizes within the submicrometer to even the nanometer levels. Experiments were conducted to discuss the evolution of hardness, microstructure and strain rate sensitivity, m, in a Zn-22% Al eutectoid alloy processed by high- pressure torsion (HPT). The data from microhardness and nanoindentation hardness measurements revealed that there is a significant weakening in the Zn-Al alloy during HPT despite extensive grain refinement. Excellent room-temperature (RT) plasticity was observed in the alloy after HPT from nanoindentation creep in terms of an increased value of m. The microstructural changes with increasing numbers of HPT turns show a strong correlation with the change in the m value. Moerover, the excellent RT plasticity in the alloy is discussed in terms of the enhanced level of grain boundary sliding and the evolution of microsturucture.<br/
A Review of Recent Research on Nanoindentation of High-Entropy Alloys Processed by High-Pressure Torsion
No full textHigh entropy alloys (HEAs) are a novel class of materials that have emerged as potential candidates for various industrial applications due to their excellent mechanical properties at cryogenic, ambient, elevated temperatures, and even under a hydrogen environment. The incorporation of nanocrystalline (nc) structure into HEAs has attracted significant attention for the further enhancement of their exceptional properties, as exceptional grain refinement usually results in enhanced strength without a large expense of ductility. High-pressure torsion (HPT) is often considered one of the most efficient methods for nanocrystallization, and this also holds true for HEAs. Recently, nanoindentation technique has been widely utilized to explore the relationship between HPT-induced grain refinement and mechanical behavior due to the inhomogeneous microstructure within the HPT disk. In this report, recent nanoindentation studies performed on HPT-processed HEAs are comprehensively reviewed with special emphasis on the nanomechanical behavior of nc HEAs
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