• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.461-468
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• 2001

Large-scale distributed applications based on Internet and client/server applications have to deal with series of problems such as load balancing, unpredictable communication delays, partial errors, and networking failures. Therefore, sophisticated applications such as teleconferencing, video-on-demand, and concurrent software engineering require an abstracted communication. In this paper, we present our design, implementation and performance analysis of group communication using the CORBA ORB, JAVA RMI, Socket based on distributed computing. We anticipate our study may apply to the various field of applications such as fault-tolerant client/server system, groupware, scalable text retrieval system, and financial information systems.

• Korean Journal of Community Nutrition
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• v.23 no.3
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• pp.202-215
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• 2018

Objectives: We conducted a qualitative study to explore the feasibility of mobile applications for self-monitoring of diet. Methods: We conducted in-depth and focus group interviews with eight laymen who had used mobile dietary applications and eight experts. Interviews were audio-recorded and analyzed using an open coding method. Results: The qualitative data of our study revealed two key themes: (1) perceptions, opinions and attitudes towards mobile applications of self-monitoring of diet and (2) future directions to improve mobile applications. Conclusions: Our qualitative study suggested the potential use of mobile applications as a food-tracking and dietary monitoring tool and the need for improved mobile applications for self-monitoring of diet. The results of our study may provide insights into how to technically improve mobile applications for self-monitoring of diet, how to utilize dietary data generated through mobile applications, and how to improve individual's health though mobile applications.

• ETRI Journal
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• v.20 no.2
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• pp.149-170
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• 1998

Between a wide range of distributed applications, this work is particularly focused on those applications which allow a group of persons, who are geographically distributed, to interact and cooperate exchanging different kind of information in order to realize group activities in a common work environment. In this paper we realized a study of this kind of applications to identify general and functional characteristics which will then enable us to determine their communication requirements. Also, we analyzed the existent support architectures to examine whether they support multimedia cooperative applications. Based on the results of analysis, we proposed a set of communication functions needed additionally to support these applications, using the ODP(Open Distributed Processing) modelling concepts, rules and view points as our global design methodology.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.535-538
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• 2005

Today, most fixed-wing aircrafts are equipped with the antiskid brake system. It can modulate braking moments in the wheels optimally, when an aircraft is landing. So it can reduce landing distance and increase safeties. The antiskid brake system for an aircraft are mainly composed of braking moment modulators (hydraulic control valves) and brake control unit. In this paper, a Mark IV type - fully digital - brake controller is studied. For the development of its control algorithms, a 5-DOF (Degree of Freedom) aircraft landing model is composed in the form of matlab/simulink model at first. Then, braking moment control algorithms using wheel decelerations and slips are made. The developed algorithms are tested in software simulations using state-flow toolboxes in matlab/simulink model. Also, a real-time simulation systems are made, which use hydraulic brake systems of a real aircraft, pressure control valves and its controller as hardware components of HIL(Hardware In-the-Loop) simulation. Algorithms tested in software simulations are coded into the controller and the real-time landing simulations are made in very severe road conditions. The real-time simulation results are presented.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2320-2322
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• 2004

전자제어식 미끄럼방지 제동장치 (ABS, Antilock Brake System)는 차량의 급제동시 발생할 수 있는 바퀴의 슬립을 방지하여 차량의 제동거리를 단축시키고 주행 성능을 향상시키는 차량 내 안전장치이다. 지난 몇 년 동안 공압식 제동시스템을 사용하는 대형차량에 적합한 미끄럼방지 제동 제어기를 연구해 왔다. 이 제어기는 바퀴의 슬립율과 그 변화량을 이용한 제어 법칙을 유도하여, 제어 파라미터로 사용하고 있다. 이러한 제어 파라미터의 튜닝에는 맡은 반복적인 실험이 요구된다. 이러한 요구에 부응하기 위하여 차량의 제동을 실시간으로 모사 할 수 있는 HILS (Hardware In-the Loop Simulation) 시스템을 개발, 구축하였다. 개발 HILS는 공압식 브레이크 시스템 및 14 자유도를 가지는 차량 동역학 모델 및 타이어-바퀴 동역학을 소프트웨어 모델로 사용하고, 개발 중인 전자제어식 미끄럼 방지 제동 제어기를 하드웨어로 사용하여, 바퀴속도 센서 신호 모의 장치 및 공압 엑추에이터 모의 신호등의 인터페이스 장치를 사용하여 제동중인 차량의 상태를 실시간으로 시뮬레이션 및 감시할 수 있다. 이 개발 HILS를 이용하여 제동 제어기의 제어 파라미터의 튜닝을 짧은 시간에 성공적으로 끝낼 수 있었을 뿐만 아니라, HILS 실험을 마친 제어기는 미끄럼 방지 제동 시험장에서 실차 주행 시험을 무사히 마침으로써, 개발 기간과 비용을 절감할 수 있는 하드웨어를 이용하는 시뮬레이션의 효용성을 간접적으로 증명하였다.

• Progress in Superconductivity
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• v.10 no.1
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• pp.45-49
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• 2008

For the development of superconducting fault current limiters (SFCLs), fault current limiting elements were fabricated out of Bi-2212 bulk tubes and tested. The SFCL elements consisted of tube shaped Bi-2212 bulks and metal shunts for the stabilizers. Firstly, the Bi-2212 bulk tubes were processed based on a design of monofilar coils in order to acquire large resistance and high voltage rating. 300 mm-long Bi-2212 tubes were designed to have the current path of 410 cm in length with 24 turns and 41 mm in diameter. The processed monofilar coil, as designed, had 300 A $I_c$ at 77 K. The fabricated superconducting monofilar coils were affixed to Cu-Ni alloy as that of stabilizers. The Cu-Ni alloys were processed to have the same shape of the superconducting monofilar coils. The Cu-Ni coil had resistivity of 32 ${\mu}{\Omega}$-cm at 77 K and 37 ${\mu}{\Omega}$-cm at 300 K. The metal shunts were attached to the outside of the Bi-2212 monofilar coil by a soldering technique. After the terminals made of copper were attached to both ends of the superconductor-metal shunt composite, the gap between the turns and the surface of the elements was filled with an epoxy and a dense mesh made of FRP in order to enhance the mechanical strength. The completed SFCL elements went through fault tests, and we confirmed that the voltage rating of 143 $V_{rms}$ (E =0.35 $V_{rms}$/cm) could be accomplished.

• Journal of the Korea Society of Computer and Information
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• v.11 no.2 s.40
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• pp.285-294
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• 2006

The requirements of Computer Supported Cooperative Work supporting efficient cooperative or collaborative works between multi-users have been increasing in distributed environments. The various technical sections such as group communication technology and distributed processing technology should be provided in Cooperative Work. The replicated development of Cooperative Work applications of a number of common requirements increases development costs enormously and duplicated investment parts. Therefore, systematical development environments are required to develop these common requirements and applications efficiently in Cooperative Work applications development. In this study, we propose the hierarchical role-based coordination model that improves the coordination model of legacy mobile agent to be appropriate in Cooperative Work applications, and design the development environment for Cooperative Work applications based on mobile agent. The proposed hierarchical role-based coordination model provides multi-layered group concepts of mobile agent, and enables implementation of efficient coordination policy per group. Additionally, it supports efficient Cooperative Work application development by role assignment per group unit.

• Knowledge Management Research
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• v.15 no.3
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• pp.13-36
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• 2014

Recently, with the increasing popularity of smartphones, mobile applications have been being used in various sectors. In these environments, some mobile applications are being made for special purposes. The mobile campus application is one exemplary type of such special-purpose mobile applications, which have unique characteristics that allow only designated users, belonging to a specific group, to access and use relevant knowledge. The aim of this study is to identify and investigate critical success factors of mobile campus applications based on the DeLone & McLean's information systems (IS) success model and to find unique characteristics of mobile campus applications, compared to general-purpose mobile applications. In order to empirically test our research model, 199 samples were collected from students who actually had experience of using the mobile campus application of A university at least once. The findings of the structural equation modeling using SmartPLS 2.0 confirmed the DeLone & McLean's IS success model, with the exception for relationships between service quality and user satisfaction/intention to use. Moreover, the moderating role of sense of belonging to school on the relationships between quality-related factors (i.e., information, system, and service qualities) and success-related factors (i.e., user satisfaction and intention to use) was examined.

• Journal of Korea Multimedia Society
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• v.20 no.8
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• pp.1369-1378
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• 2017

Pub/Sub (Publish/Subscribe) paradigm is a simple and easy to use model for interconnecting applications in a distributed environment. In general, subscribers register their interests in a topic or a pattern of events and then asynchronously receive events matching their interest, regardless of the events' publisher. In order to build a low latency lightweight pub/sub system for Internet of Things (IoT) services, we propose a GQSFPS (Group Quorum System-based Fog Pub/Sub) system that is a core component in the event-driven service oriented architecture framework for IoT services. The GQSFPS organizes multiple installed pub/sub brokers in the fog servers into a group quorum based P2P (peer-to-peer) topology for the efficient searching and the low latency accessing of events. Therefore, the events of IoT are cached on the basis of group quorum, and the delay-sensitive IoT applications of edge devices can effectively access the cached events from group quorum fog servers in low latency. The performance of the proposed GQSFPS is evaluated through an analytical model, and is compared to the GQPS (grid quorum-based pud/sub system).

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1062-1072
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• 2000

The applications developing in distributed object computing enviroments are faced with the difficulties for managing various lots of distributed objects. Also, because the most multimedia service, like video, audio, and so forth, must be satisfied itself with real-time constraints, the users also are feeling with necessary to apply real-time mechanisms to distributed multimedia services. The goal of this paper is to solve the problems for managing distributed objects, and to be easy to develop complex applications that can provide real-time services. To do this, we designed and implemented a real-time object group platform that can be placed between applications and CORBA. This platform is extended the existing object group model[13,14] added to the scheduler and timer object components for supporting real-time concept. We designed the components for platform by using James Rumbaugh object modeling technology that consists of object, function, and dynamic model. And then we described the detailed interfaces of the components by IDL, and implemented our real-time object group's platform using OrbixMT 22 which is the IONA Technologies' ORB product. Finally, we showed the execution procedures of the schduler object of each components in a real-time object group platform.