Kyu Min Lee

Yonsei University, Sŏul, Seoul, South Korea

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Publications (17)9.96 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: We report on the anisotropic properties of solution-processed thin-film transistors (TFTs) fabricated by the vertical flowing of the viscous 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and isotactic (i-) poly-(methyl methacrylate) (PMMA) blend. During film formation processes, lateral crystalline growth of TIPS-pentacene and TIPS-pentacene/i-PMMA phase-separation were observed. Such anisotropic crystallization of TIPS-pentacene channel caused anisotropic mobility with respect to the channel orientation, so that it could be used for composing of a logic inverter where two TFTs with different channel orientations were serially connected.
    Organic Electronics 07/2012; 13(7):1250–1254. · 3.84 Impact Factor
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    ABSTRACT: Ag-doped and un-doped Sb-rich GeSb thin films were deposited by DC magnetron co-sputtering. The electrical, structural, and optical properties of the thin films phase change were investigated using 4-point probe measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), and a static tester. With increasing Ag doping content, the crystallization temperature and sheet resistance of crystalline state decreased from 325°C to 283°C and from 187.33Ω/□ to 114.62Ω/□, respectively. XRD patterns of the films showed a Sb hexagonal structure, and the calculated grain size increased from 13.9nm to 17nm as the Ag concentration increased. Grain sizes of the Ag-doped thin films were larger than the grain sizes of un-doped thin films, as determined by TEM images. A static tester verified the decreased crystallization speed and optical contrast. Un-doped GeSb crystallization took 160ns and 16at.% Ag-doped GeSb crystallization took 200ns when the laser power was 13mW. Based on a power–time-effect diagram, the 12.6at.% Ag-doped GeSb showed good thermal stability in a crystalline state.
    Thin Solid Films 01/2011; 519(16):5323-5328. · 1.60 Impact Factor
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    ABSTRACT: β-Silicon carbide (β-SiC) whiskers were synthesized on carbon fiber substrates using a chemical vapor infiltration (CVI) vapor–solid (VS) growth mechanism. An additional SiC surface coating process was utilized after whisker deposition by controlling the input gas ratio of the source gas flow and changing the H2 (hydrogen) diluent gas to N2 (nitrogen) under the same deposition temperature of 1,300°C. As the surface coating deposition time increased, whiskers thickness and spherical blunt tips which were seen at the top edge of the whiskers went thicker. Observing the microstructure of the resulting tips by transmission electron microscopy (TEM) revealed that uncoated whiskers showed few stacking faults, whereas surface-coated whiskers were completely filled with stacking faults. The effect of surface coating deposition time was also evaluated by measuring the properties of a filtration system. Specifically, as the surface coating deposition time increased, gas permeability decreased; however, even at 30min, the gas permeability of the thickest surface coated whisker filters was five times higher than that of cordierite honeycomb, which is currently used in commercial diesel particulate filter (DPF) devices. A specimen that had been surface coated for more than 20min almost completely maintained its prime line density under high-pressure (5MPa) gas. Moreover, we confirmed that SiC surface coating on whiskers and carbon fiber substrates enhanced oxidation resistance and filtration efficiency.
    Ceramics International - CERAM INT. 01/2011; 37(4):1307-1312.
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    ABSTRACT: The authors report on the high current density n-ZnO/p-Si heterojunction diode that has been fabricated by atomic layer deposition (ALD) of 70 nm thin ZnO on a p-Si substrate. While the diode was formed at four different ALD temperatures of 80, 100, 150 and 200 °C, the 100 °C processed diode showed an optimal behaviour of an on-off ratio over 3.3 × 103 and a high forward current density, ~300 A cm-2 at 3 V. Although the highest film conductance appeared from the 200 °C deposited ZnO layer, nanometre thin SiOx was also revealed at the ZnO/p-Si interface; it might cause a high reverse leakage current level. Our high current density diode also demonstrates a fast switching performance without any reverse recovery delay, which is often observed at a usual Si p-n diode.
    Journal of Physics D Applied Physics 01/2010; 43(34). · 2.53 Impact Factor
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    ABSTRACT: Multi-agent technologies for ubiquitous environment became recently attractive for many peoples. According to these interests, agent technologies have been researched by various researchers and laboratories. In this multi-agent environment, each of these agents has its own services and stores the service descriptions in the service repository of the multi-agent system. From this repository, the user agent can search the specific descriptions which the user wants to find. In this paper, we proposed the efficient service repository architecture which can improve the existing directory facilitator as service repository. An advantage of using this architecture is that searching for suitable services can be faster than the old one.
    Advanced Communication Technology, The 9th International Conference on; 03/2007
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    ABSTRACT: Multi-agent technologies are essential in realizing ,the upcoming ubiquitous environment. In the multi-agent environment, each agent has its own set of services,and stores these services in the service repository of the,multi- agent system. By using this repository, the user can retrieve the most appropriate service. In this paper, we propose an efficient service repository architecture that can ,improve ,the ,existing repository by using ,context inferencing, context filtering, user-predefined policies, and the categorized tree. Anadvantage,of the ,proposed ,architecture is that the user can obtain more suitable services than existing approaches about service discovery. Keywords: yellow page, service repository, DF, agent, context aware.
    Agent and Multi-Agent Systems: Technologies and Applications, First KES International Symposium, KES-AMSTA 2007, Wroclaw, Poland, May 31- June 1, 2007, Proceedings; 01/2007
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    ABSTRACT: Although current service discovery protocols provide the same basic function of service discovery, they differ significantly in architecture, message exchange pattern, expected operating environment and service representation/description. These differences prevent service interoperability among protocols. To solve this problem, we propose a web-based integrated service discovery mechanism, using an agent platform to guarantee scalability of scope of available services without modifying existing service discovery protocols. The proposed web-based integrated service discovery mechanism provides users with a wider selection of services, and convenient search methods.
    Computational Science - ICCS 2007, 7th International Conference, Beijing, China, May 27 - 30, 2007, Proceedings, Part II; 01/2007
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    ABSTRACT: Nowadays, the field of healthcare becomes more grew and sophisticated. The purpose of these u-healthcare technologies is to provide convenient healthcare service to both caregivers and patients, and to make it easy to diagnose user's health condition by caregiver. In this paper, we design a ubiquitous-healthcare system that can consider user's context information dynamically by rule engine.
    Optical Internet and Next Generation Network, 2006. COIN-NGNCON 2006. The Joint International Conference on; 08/2006
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    ABSTRACT: The purpose of service discovery techniques is to minimize the cost of detecting services and provide users with convenience, even though various devices and services exist. For more dynamic and useful service discovery, middleware for context-aware service discovery is required. In this paper, a middleware system is designed and implemented, based on the agent platform for context-aware service discovery. When a service is detected, context information relating to the user and environment is used. As a policy-based system, our middleware does not only use context information, but also use predefined policy. In other words, user preference can be considered. Also, it has authentication module, so users having authority can only access the middleware. Near the conclusion of this paper, a hospital scenario is composed and implemented, by applying the proposed middleware solution.
    05/2006: pages 483-490;
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    ABSTRACT: This paper discusses a multi-agent system (MAS) based efficient healthcare system, which is comprised of medical sensor modules in conjunction with wireless communication technology. In particular, the proposed system supports a wide range of services including mobile telemedicine, patient monitoring, emergency management and information sharing between patients and doctors or among the healthcare workers involved. For this purpose, the proposed system provides not only a systematic computing environment between the BAN (body area network) and the subsystem within the hospital, but also participates in an agent network with the BAN's PDAs through peers. Information within the hospital is shared under a MAS environment. The tool used to develop the MAS is called JADE, a FIPA-compliant development framework. The ultimate goal of our system is to manage and monitor the patient's medical information and to support efficient medical service through the medical staff's cooperation
    Advanced Communication Technology, 2006. ICACT 2006. The 8th International Conference; 03/2006
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    ABSTRACT: Service discovery is becoming a hot topic as it becomes more widespread through the Internet. In pervasive environments, there are various services, and users use a service discovery protocol for finding the most appropriate service among them. Thus, over the past few years, many service discovery protocols have been proposed. Even though they provide convenient service discovery functionality with users, complexity is increased because they have different message exchange pattern and architecture. In this paper, we propose a novel middleware based on agent platform for interoperability among heterogeneous services. This has the Discovery Agent for each service discovery protocols and it can detect service advertisement messages for registration, so the services are registered in agent platform. Finally, user can use them. The key point of this is not to require modification of existing service discovery protocols. Near the conclusion of this paper, this is implemented.
    Computational Science - ICCS 2006, 6th International Conference, Reading, UK, May 28-31, 2006, Proceedings, Part III; 01/2006
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    ABSTRACT: There is a high interest on service discovery techniques, which minimize the cost of detecting services and provide users with convenience. For more dynamic and useful service discovery, middleware for context-aware service discovery is required. This paper proposes an intelligent middleware architecture for context-aware service discovery that is based on JADE, which is a FIPA-compliant agent platform. The proposed middleware provides not only service scalability among heterogeneous domains, but also modules processing context information. When a service is detected, context information relating to the user and environment is used. As a policy-based system, the proposed middleware also use predefined policy. In other words, user preference can be considered. Near the conclusion of this paper, we discuss future works.
    Computational Science - ICCS 2006, 6th International Conference, Reading, UK, May 28-31, 2006, Proceedings, Part III; 01/2006
  • Shi Shuo, Kyu Min Lee, Dong Ryeol Shin
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    ABSTRACT: In this paper, we propose SDRP: a new service discovery protocol combined with routing policies in MANETs. The protocol is performed upon a distributed network. We describe a service by a unique ID number and use a group-cast routing policy in advertisement and request. In addition, the nodes included in the reply path also cache the advertisement information. We compare SDRP with both Flood and MAODV in terms of overload, and average delay. Simulation results show SDRP can spend less response time and accommodate even high mobility network environments.
    IEICE Transactions. 01/2006; 89-A:1746-1748.
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    ABSTRACT: Traditional service discovery mechanisms propose efficient and fast searching schemes for service discovery. And their schemes do not consider interoperability among discovery protocols. In this paper, we design an agent platform (AP) modifying FIPA-OS (Foundation for Intelligent Physical Agents Open Source) based on FIPA specifications. FIPA (Foundation for Intelligent Physical Agents) is a nonprofit organization aimed at producing standards for the interoperation of heterogeneous software agents. Until now FIPA specifications have not been considering mobile ad hoc networks. In such environments, agents can 7 find services offered by other service discovery engines in heterogeneous networks. We can guarantee scalability, by adding DM (discovery middleware) modules in the AP. The DM helps agents find and use services exploiting existing service discoveries under ad hoc networks. We chose UPnP (universal plug and play) and LSD (lightweight service discovery protocol) as DMs among various service discovery technologies. UPnP is a set of protocols for service discovery under development by the UPnP forum and LSD is a new discovery protocol for mobile ad hoc networks emphasizing on cache management that we designed. On our AP, we can use the services which devices of UPnP and LSD provide.
    Computer and Information Science, 2005. Fourth Annual ACIS International Conference on; 02/2005
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    ABSTRACT: Service discovery middleware allows users to find and use services through service discovery protocols without previous knowledge of the locations or characteristics of the services with minimum manual efforts in heterogeneous and ubiquitous environments. For this reason, many researchers have carried out studies related to service discovery middleware and many papers dealing with this field have been published. However, when a number of service consumers request services from middle agents (e.g. matchmaker, broker, yellow page, blackboard, etc.) within the service discovery middleware, the middle agent does not guarantee efficient and rapid matching results because they only use a simple matching algorithm. In this paper, we address the issues of existing matching algorithms, and then propose a new matchmaking algorithm based on the marriage matching algorithm of ATM networks (Gusfield and Irving, 1989) to improve middle agents' performance, complementing shortcomings of existing matching algorithms. We also add priority based matching to the new algorithms. Through this priority, important service request messages are processed faster than request messages that have low priorities. We expect the proposed matchmaking mechanism to increase users' satisfaction in dynamic environments.
    Computer and Information Science, 2005. Fourth Annual ACIS International Conference on; 02/2005
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    ABSTRACT: Service discovery middleware allows users to find and use services through service discovery protocols in heterogeneous and ubiquitous environments without previous knowledge of the specific service location or characteristics, and with minimum manual effort. For this reason, in recent years, a number of researchers have studied service discovery middleware and many of papers dealing with this field have been published. However, when a number of service consumers request services from middle agents (e.g. matchmaker, broker, yellow page, blackboard, lookup server, etc) within the service discovery middleware, the middle agents do not guarantee efficient and rapid matching results because they use only a simple matching algorithm based on set theory for match processing. In this paper we address issues of existing matching algorithms, and propose a new matchmaking method adopting the marriage matching algorithm of the ATM network [1] to improve middle agent performance, complementing shortcomings of the existing matching algorithms. Furthermore, we use traffic type (e.g. voice/video applications, data-sharing applications, convenience applications, and so on) priority information for providing application-oriented QoS.
    E-Commerce and Web Technologies: 6th International Conference, EC-Web 2005, Copenhagen, Denmark, August 23-26, 2005, Proceedings; 01/2005
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    ABSTRACT: Thermal stress according to growth temperature and surface region of single crystal SiC was analyzed using ABAQUS simulation. Three 6H SiC single crystal wafers grown with the PVT method under the same growth conditions by different companies were used to analyze the changes in properties caused by thermal stress. All three wafers differed in diffraction distance. The wafer with the higher tensile stress from thermal stress showed a larger diffraction distance. Also the impact of thermal stress on crystallinity and defect density was analyzed. Our results showed that the wafer with the higher thermal stress had lower crystallinity and more defects, and we also confirmed that the wafer had a lower thermal conductivity and bandgap.
    Thermochimica Acta 542:6–10. · 1.99 Impact Factor

Publication Stats

18 Citations
7 Downloads
643 Views
9.96 Total Impact Points

Institutions

  • 2010–2012
    • Yonsei University
      • Department of Materials Science and Engineering
      Sŏul, Seoul, South Korea
  • 2005–2006
    • Sungkyunkwan University
      • Department of Computer Engineering
      Seoul, Seoul, South Korea