• Journal of KIISE:Software and Applications
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• v.33 no.8
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• pp.668-680
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• 2006

Web services on the Internet are not always reliable in terms of service availability and performance. Dynamic service coordination capability of a system or an application invoking Web services is essential to cope with such unreliable situations. In dynamic service coordination, if a Web service does not respond within a specific time constraint, it is replaced with another Web service at run time for reliable invocation of Web services. In this paper, we develop an exception based dynamic service coordination framework for Web services. In the framework, all necessary information for dynamic service coordination is explicitly specified and summarized as a set of attributes. Then classes and workflows, supporting dynamic service coordination and invoking Web services, are automatically created based on these attributes. Developers of Web services client programs can make the invocations of Web services reliable by calling the methods of the classes. Some performance loss has been observed in the indirect invocation of a Web service. However, when we consider the flexibility and reliability gained from the method, the performance loss would be acceptable in many cases.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.116-125
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• 2019

The Dynamic Vehicle Routing Problem (DVRP) involves a combinatorial optimization problem where new customer demands become known over time, and old routes must be reconfigured to generate new routes while executing the current solution. We consider the high level of dynamism problem. An application of highly dynamic DVRP is the ambulance service where a patient contacts the service center, followed by an evaluation of case severity, and a visit by a practitioner/ ambulance is scheduled accordingly. This paper considers a variant of the DVRP and proposes a decentralized algorithm in which collaborators (Depot and Vehicle), both have only partial information about the entire system. The DVRP is modeled as a periodic re optimization of VRP using the proposed decentralized algorithm where collaborators exchange local information to achieve the best global objective for the current state of the system. We assume the existence of a dispatcher e.g., headquarter of the company who can communicate to vehicles in order to gather information and assigns the new visits to them. The effectiveness of the proposed decentralized coordination algorithm is further evaluated using benchmark data given in literature. The results show that the proposed method performed better than the compared algorithms which utilize the centralized coordination in 12 out of 21 benchmark problems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.61-77
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• 2017

The most challenging issues in the multi-channel MAC of the IEEE 1609.4 standard is how to handle the dynamic vehicular traffic condition with a high mobility, dynamic topology, and a trajectory change. Therefore, dynamic channel coordination schemes between CCH and SCH are required to provide the proper bandwidth for CCH/SCH intervals and to improve the quality of service (QoS). In this paper, we use a Markov model to optimize the interval based on the dynamic vehicular traffic condition with high mobility nodes in the multi-channel MAC of the IEEE 1609.4 standard. We evaluate the performance of the three-dimensional Markov chain based on the Poisson distribution for the node distribution and velocity. We also evaluate the additive white Gaussian noise (AWGN) effect for the multi-channel MAC coordination scheme of the IEEE 1609.4 standard. The result of simulation proves that the performance of the dynamic channel coordination scheme is affected by the high node mobility and the AWGN. In this research, we evaluate the model analytically for the average delay on CCHs and SCHs and also the saturated throughput on SCHs.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.3
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• pp.369-381
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• 2019

As tactical networks are gradually shifting toward IP-based flexible operation for diversified battlefield services, QoS(Quality-of-Service) coordination for service differentiation becomes essential to overcome the heterogeneous and scarce networking resources limitations. QoS coordination for tactical network traffic should be able to monitor and react the dynamic changes in underlying network topology and service priorities. In this paper, by adopting the emerging cloud-native service mesh concept into tactical network context, we study the feasibility of intelligent QoS coordination by employing tactical service mesh(TSM) as an additional layer to support enhanced traffic quality monitoring and control. The additional TSM layer can leverage distributed service-mesh proxies at tactical mesh WAN(Wide Area Network) nodes so that service-aware differentiated QoS coordination can be effectively designed and integrated with TSM-assisted traffic monitoring and control. Also, by validating the feasibility of TSM layer for QoS coordination with miniaturized experimental setup, we show the potential of the proposed approach with several approximated battlefield traffics over a simulated TSM-enabled tactical network.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.238-240
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• 2005

웹 서비스는 서비스 가용성(availability)과 성능(performance)연에서 신뢰성을 항상 보장해 주지 못한다. 동적 서비스 조정(Dynamic Service Coordination)은 웹 서비스를 호출하는 시스템이나 응용 프로그램 내에서의 비 신뢰적인 문제상황을 처리하는 기술이다. 이 환경 내에서의 웹 서비스는 제한된 시간내에 응답 하지 못하는 등의 문제가 발생 할 경우, 신뢰적인 웹 서비스의 호출을 위해 다른 웹 서비스로의 대체작업이 런타임(run-time)에 이뤄진다. 본 논문에서는 웹 서비스를 위한 동적 서비스 조정 프레임워크를 제안한다. 프레임워크 내에서 동적 서비스 조정의 지원 및 웹 서비스 호출을 담당하는 클래스와 워크플로우가 생성되고, 생성된 클래스 메소드를 호출함으로써 신뢰적인 웹 서비스 호출이 가능하다. 호출작업이 간접적으로 이뤄짐으로 인해 어느 정도의 성능적 손실이 발생하나, 이 방식을 통해 얻는 시스템 유연성과 신뢰성의 측면을 고려한다면, 충분히 감 수 될 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.24-33
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• 2007

In this paper, two different dynamic cell coordination strategies for frequency flat and selective fading are proposed for efficient subcarrier allocation in the joint consideration of adaptive modulation and variable frequency reuse in the channel-aware OFDMA downlink multicellular environment. Compared to a conventional OFDMA system without cell coordination, where system throughput may become degraded due to the persistent interference from other cells, the proposed system dynamically allows RNC to apply different reuse factors on each subchannel and scheduling in consideration of channel and interference conditions of individual users so as to increase the system throughput and guarantee QoS of each user. In a frequency flat fading, the dynamic scheme with the proposed scheduling achieves on average three times larger throughput than the conventional dynamic scheme [8]. In a selective fading channel, the proposed schemes showed 2.6 times as large throughput as that of a single reuse factor of one for all subchannels.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.2
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• pp.140-150
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• 2008

Point Coordination Function (PCF) of the IEEE 802.11 protocol providing a centrally-controlled polling-based multiple access to a wireless channel is very efficient in high load conditions. However, its performance degrades with increasing the number of terminals and decreasing the load, because of wastes related to unsuccessful polling attempts. To solve the problem, we propose and study analytically the generic dynamic polling policy using backoff concept. For this aim, we develop Markov models describing the network queues changes, what allows us to estimate such performance measures as the average MAC service time and the average MAC sojourn time, to show the dynamic polling efficiency and to tune optimally the backoff rule.

• Journal of the Korean Society of Food Culture
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• v.20 no.2
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• pp.261-272
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• 2005

The color and its coordination should intensify the customer's memory and awareness in a brand website, through the consistent communication strategy by which a variety of brand identification in the offline could be expressed efficiently. We evaluated top 5 brand-valuable family restaurants in this study, how they made the best use of the website as a new communication channel, and how they constructed the brand identification by the coloring of a website. We found out that they employed colors with a dynamic and lilting feelings matching the concept of a family restaurant. In addition, A color scheme was well designed for the specific character of a brand, though web-safe colors were seldom employed. This report can be a guide to a corporation for the color and its coordination in the website, when existing brand images need to be intensified and enhanced, or when a new brand image need to be constructed.

• Smart Media Journal
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• v.8 no.2
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• pp.29-38
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• 2019

With the advancement of information and communication technology, tactical networks are continuously being converted to All-IP future tactical networks that integrate all application services based on Internet protocol. Futuristic tactical mesh network is built with tactical WAN (wide area network) nodes that are inter-connected by a mesh structure. In order to guarantee QoS (quality of service) of application services, tactical service mesh (TSM) is suggested as an intermediate layer between infrastructure and application layers for futuristic tactical mesh network. The tactical service mesh requires dynamic QoS monitoring and control for intelligent QoS coordination. However, legacy networking nodes used for existing tactical networks are difficult to support these functionality due to inflexible monitoring support. In order to resolve such matter, we propose a tactical mesh WAN node as a hardware/software co-designed networking node in this paper. The tactical mesh WAN node is conceptually designed to have multi-access networking interfaces and virtualized networking switches by leveraging the DANOS whitebox server/switch. In addition, we explain how to apply eBPF-based traffic monitoring to the tactical mesh WAN node and verify the traffic monitoring feasibility for supporting QoS coordination of tactical-mesh traffic.

• Korean Journal of Social Welfare
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• v.47
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• pp.148-177
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• 2001

Service learning usually has two aspects. One aspect is associated with applying class learning to related fields. The other aspect is associated with challenging and dynamic volunteering experiences. This study examined experiences of 70 social work students who took service learning courses at a university. After the courses, these students were asked regarding (1) evaluation and satisfaction of overall service learning experiences, (2) evaluation of service learning contents and the following activities, (3) the process of volunteering activities, and (4) the differences between service learning courses and other regular courses. Results were as follows: students generally regarded service learning experiences as positive; students reported understanding of social work practice and learning of professional skills; however, the service learning courses seemed to be very demanding in time and adjusting personal schedules; teamwork among students seemed to be good, especially in cooperation and emotional support; however, some students reported struggling experiences in allocating roles among team members; finally, the relationship between students and social workers at the agencies and the coordination of community resources seemed to be weak. In order for service learning courses to be more effective, this study presented some suggestions in the conclusion.