• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.869-879
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• 1995

The new field of learning control develops controllers that learn to improve their performance at executing a given task, based on experience performing this task. The simplest forms of learning control are based on the same concept as integral control, but operating in the domain of the repetitions of the task. In the previous paper, I had studied the use of such controllers in a decentralized system, such as a robot with the controller for each link acting independently. The basic result of the paper is to show that stability of the learning controllers for all subsystems when the coupling between subsystems is turned off, assures stability of the decentralized learning in the coupled system, provided that the sample time in the digital learning controller is sufficiently short. In this paper, we present two examples. The first illustrates the effect of coupling between subsystems in the system dynamics, and the second studies the application of decentralized learning control to robot problems. The latter example illustrates the application of decentralized learning control to nonlinear systems, and also studies the effect of the coupling between subsystems introduced in the input matrix by the discretization of the system equations. The conclusion is that for sufficiently small learning gain, and sufficiently small sample time, the simple learning control law based on integral control applied to each robot axis will produce zero tracking error in spite o the dynamic coupling in the robot equations. Of course, the results of this paper have much more general application than just to the robotics tracking problem. Convergence in decentralized systems is seen to depend only on the input and output matrices, provided the sample time is suffiently small.

• The Journal of the Korea Contents Association
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• v.9 no.2
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• pp.67-75
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• 2009

The growing need for the mobility supportable networks induces the IP-based mobility management protocols. Though HMIPv6 which manages the micro-mobility of mobile nodes using MAPs suggests an effective method for mobility-support for mobile nodes within the domain that is managed by MAP. There is a problem that traffic may be concentrated on MAPs. In this paper, therefore, we proposed a method that can effectively distribute the traffic which is concentrated on a MAP under phased Mobile IPv6. In our proposed method, two or more MAPs are required and classified as an 'Active MAP' or a 'Passive MAP'. In addition, we defined the state of transition events between Active MAP and Passive MAP and the operations among MAPs for load distribution when an overload condition is occurred at some MAPs by traffic congestion. We compared the performance of our proposed method with its phased Mobile IPv6 to prove the propriety of our proposed method. As a result, we showed that our proposed method can provide an enhanced performance by about 12 percentages in view of packet throughput at the node.

• Journal of Korea Multimedia Society
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• v.12 no.1
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• pp.16-25
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• 2009

In the car environment that the first priority is a safety problem, the large vocabulary isolated word recognition system with POI domain is required as the optimal HMI technique. For the telematics terminal with a highly limited processing time and memory capacity, it is impossible to process more than 100,000 words in the terminal by the general speech recognition methods. Therefore, we proposed phoneme recognizer using the phonetic GMM and also PDM Levenshtein distance with multi-layer architecture for the POI recognition of telematics terminal. By the proposed methods, we obtained high performance in the telematics terminal with low speed processing and small memory capacity. we obtained the recognition rate of maximum 94.8% in indoor environment and of maximum 92.4% in the car navigation environments.

• Journal of Advanced Navigation Technology
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• v.20 no.3
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• pp.196-202
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• 2016

In this paper, a stationary wavelet transform method is proposed for improving the altitude control performance of quadrotor UAV using an ultrasonic rangefinder. A ground tests are conducted using an ultrasonic rangefinder that is much used for vertical takeoff and landing. An ultrasonic rangefinder suffers from signal's spike due to specular reflectance and acoustic noise. The occurred spikes in short time span need to be analyzed at both sides time and frequency domain. It was known that stationary wavelet transform is the transferring solution to the problem occurred by down sampling from DWT also more efficient to remove noise than DWT. The analyzed spikes of the ultrasonic rangefinder using a stationary wavelet transform and experimental results show that it can effectively remove the spikes of the ultrasonic rangefinder.

• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.124-129
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• 2011

In the process of cooperation which can be the best proposals for resolving complex problems in computing domain, the way of team organizing is one of the most important aspects for succeeding the goal. Especially in ubiquitous computing environment, where the participants of a team are selected from the heterogeneous computing objects which are deployed by other providers for their own goals, finding the relevant teammate can be regarded as the most important factor for determining the success or failure of the given problem. In this paper, we propose a method of finding teammate and assigning a role, which is a sub task of cooperation, by comparing the attributes of the computing object and the requirement of the role such as capability of functions, loyalty for the given team, and harmony with other teammates. By considering the situationally changing weights of each attributes, this method can be suited for dynamic computing environment where the cooperation should be executed with dynamically in/out computing objects and satisfy the dynamically chaining constraints.

• Journal of KIISE:Software and Applications
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• v.26 no.9
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• pp.1095-1104
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• 1999

객체지향 시스템의 개발은 클래스를 통해서 이루어진다. 즉, 문제 영역에 존재하는 중요한 대상 또는 개념을 클래스로 모델링하고, 이로부터 생성된 객체들 사이의 메시지 교환을 통해서 시스템은 구축된다. 또한, 클래스는 정보 은닉을 제공함으로써, 객체지향 시스템의 재사용성과 유지보수성에 상당한 기여를 한다. 그러나, 설계 단계에서 실세계의 대상을 부적절하게 모델링하거나, 또는 유지보수 단계에서 클래스에 무분별한 변경을 가하는 경우 클래스의 품질은 악화될 수 있고, 이는 결국 시스템을 유지보수 하거나 확장하는데 상당한 장애를 초래한다.응집도는 모듈의 구성 요소들 사이의 연관성 정도를 나타내는 척도로서 전통적으로 모듈의 품질을 평가하기 위한 기준으로 사용되어 왔다. 이 논문에서는 클래스의 품질을 평가하는 방법으로서의 클래스 응집도를 제안한다. 즉, 클래스가 실세계의 대상을 적절하게 모델링한다면, 그 구성요소들 사이에 밀접한 관련이 있고 결국 높은 응집도를 가지게 될 것이다. 반대로 실세계의 대상에 대한 적절한 모델이 아니라면, 그 클래스의 구성 요소들 사이에는 밀접한 관련성이 없을 것이고 따라서 낮은 응집도를 보일 것이다.Abstract Object-oriented systems are developed by means of classes; that is, classes captures the essential entities or concepts in the problem domain, and the system is embodied by the interactions of objects instantiated from the classes. In addition to the basic units of object-oriented systems, classes serves as the units of encapsulation, which considerably promote the modifiability and the extensibility of them. However, improper modeling in the design phase or uncontrolled changes during the maintenance phase can degrade the quality of classes, which leads to systems cumbersome to maintain and extend.Cohesion refers to the degree of connectivity among the elements of a single module, and is being used as a factor which characterizes the quality of a module. In this paper, we propose a new cohesion metric for assessing the quality of classes. If a class captures properly the essential features of objects, the members of the class surely have strong relationship among them. On the contrary, the poor relationship among class members can indicate that the class is not a proper model of objects.

• Journal of KIISE:Software and Applications
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• v.33 no.5
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• pp.460-469
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• 2006

To integrate heterogeneous distributed systems, there exist various researches and developments for the purpose of its adoption into enterprise environment. However, when web service technologies are applied, it is difficult to adopt directly existing software system development methodologies, because of the peculiar architecture of web services, such as service provider, service requester, and service repository. M4WSD(Method for Wes Services Development) is a web service development process model and involves procedures and guidelines to develop web services based on a Use Case model that is elicited from a business domain in requirement analysis. In this paper, we focus on how to determine key realization decisions for each service. The assessment guidelines help you to structure the problem of determining implementation strategy.

• Journal of Biomedical Engineering Research
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• v.10 no.3
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• pp.253-260
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• 1989

The time domain methods of estimating the attenuation coefficient are generally based on the analysis of statisical properties of the reflected echoes form an attenuating medium. Hence, it is often required to have a large number of data samples in order to obtain a statistically stable estimation result. In the attenuation estimation problem, this means that many different speckle patterns are required in the spatial resolution volume of an attenLlation image. In this paper, by using the fact that the speckle pattern Is sensitive to the point spread function of the ultrasound beam, we suggest a method to generate the statiscally uncorrelated or slightly correlated data samples in a given region by rotating a linear transducer and carrying out lateral scans for all rotating angles. This technique is applied to the entropy method for attenuation estimation proposed recently by the authors where the performance is verified by experiments using a tissue equivalent phantom.

• The Transactions of the Korea Information Processing Society
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• v.6 no.1
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• pp.11-20
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• 1999

Because conventional spatial databases process the spatial information that is valid at current time, it is difficult to manage historical information efficiently which has been changed from the past to current. Recently, there are rapid increasing of interest to solve this problem so that makes databases to support historical information as well as spatial management at the same time. It can be eventually used in a various application areas. The formal semantics in a database is used to represent database structures and operations in order to prove the correctiveness of them in terms or mathematics. It also plays an important role in database to design a database and database management system. So in this paper, we suggest spatiotemporal domain, object, data, and spatiotemporal geometric/topological operations. And we not only formalize relational algebra/calculus using formal semantics for a spatiotemporal data model, but also show the example of real orld with them.

• Journal of KIISE:Software and Applications
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• v.36 no.3
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• pp.200-207
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• 2009

U-Healthcare is more efficient as a solving method for health problems rather than visiting the hospital. Recently, systems have been studied to offer appropriate service to user, which gather and analyze biological signals of a user and context information around the user from a variety of sensors. The existing systems for U-Healthcare are based on domain specific service so it is difficult to expand and link to other systems. Also, they lack services focusing on the specific quality of the user, because they offer a general service which targets a lot of users. To address this problem, we expand an extensibility of system using the context-awareness agent based on multi-agents. Also, we provide the suitable services which match with the context information of user to each user using the modeling toolkit JaUCE based on GUI. We design and implement U-Silvercare service to demonstrate the effectiveness of the proposed context-awareness agent and modeling toolkit.