Hyun Kyoo Park

Chung-Ang University, Sŏul, Seoul, South Korea

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Publications (6)1.66 Total impact

  • Hyun Kyoo Park, Min Hyuk Hwang, Sun Geon Kim
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    ABSTRACT: Industrial wastes that have calcium silicates as main ingredients include steelmaking slag, wasted cement, fly ashes and so on. We separated and/or re-crystallized calcium oxide and silica from these wastes. The concentration of acetic acid as an extract, extraction time, and extraction temperature had significant influence on the composition of the extract or the raffinate. We found that more silica was extracted with lower temperature, higher concentration of acetic acid and shorter extraction time. Under the same conditions of extraction, silica in the slag was more extractable than that in waste cement. In the former, extracted silica was gelated out of the extract while the recrystallized solids on the gel showed very low CO2 absorptivity. On the other hand, porous solids recrystallized from the latter was more active for the absorption. The absorptivity was kept almost constant in their repeated use.
    2009 AIChE Annual Meeting; 11/2009
  • Hyun Kyoo Park, Jin Hyun Son, Myoung Ho Kim
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    ABSTRACT: Recently, in moving object databases that mainly manage the spatiotemporal attributes, approximate query processing for the future location-based queries has deserved enormous attention. Histograms are generally used for selectivity estimation and approximate query answering in database environments. Because histograms’ static properties may, however make them inappropriate for application areas that treat dynamic properties such as moving object databases, it is necessary to develop several mechanisms that can be well applied to dynamic query processing.In this paper we present a new method to efficiently process the approximate answers for future location-based query predicates on demand by using spatiotemporal histograms. Based on the concepts of entropy and marginal distribution, we build spatiotemporal histograms for the movement parameters, which result in the avoidance of reconstructing histograms. Using spatiotemporal histograms, the approximate future query processing can be achieved efficiently. In addition, we clarify and evaluate our proposed method with several experiments.
    Information Sciences. 06/2005;
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    Hyun Kyoo Park, Jin Hyun Son, Myoung Ho Kim
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    ABSTRACT: Many location-based applications have arisen in various areas including mobile communications, traffic control and military command and control (C2) systems. And one of the important research issue in these areas is tracking and managing moving objects through spatiotemporal indexing for the efficient location-based services. However, managing exact geometric location information is difficult to be achieved due to continual changes of moving objects.Traditionally spatiotemporal index structures focus on optimizing the node accesses during construction and massive updates that do not refer on-line movement updates. In this paper we propose an indexing framework for future location queries based on space partitioning and the dual transformation. Our method provides a constraint database approach for constructing indexes to improve the efficiency of spatiotemporal query answering. In addition, the performance enhancement is achieved by our cost-based dynamic management algorithm that determines the appropriate index reorganization probabilistically induced by various mobility models and query cost functions. This approach can be applied for the predictive range queries on moving object's trajectories specifically in the mobile communication environments. We evaluate our method and compare the performance with the related spatiotemporal index structures in the simulated environments.
    Journal of Systems and Software. 01/2005;
  • Hyun Kyoo Park, Jin Hyun Son, Myoung-Ho Kim
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    ABSTRACT: The spatio temporal databases concern about the time-varying spatial attributes. And one of the important research areas is tracking and managing moving objects for the location-based services. Many location-aware applications have arisen in various areas including mobile communications, traffic control and military command and control (C2) systems. However, managing exact geometric location information is difficult to be achieved due to continual change of moving objects’ locations. In this paper we propose the B st -tree that utilizes the concept of multiversion B-trees. It provides an indexing method for future location queries based on the dual transformation. This approach can be applied for the range query on moving object’s trajectories specifically in the mobile communication systems. Also we present a dynamic management algorithm that determines the appropriate update interval probabilistically induced by various mobility patterns to guarantee the query performance.
    Mobile Data Management, 4th International Conference, MDM 2003, Melbourne, Australia, January 21-24, 2003, Proceedings; 01/2003
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    ABSTRACT: High-temperature CO2 sorbents were prepared by leaching and recrystallizing of calcium resources such as steel slag, tail-wollastonite, waste cement and fly ash. Alumina and small amount of silica in the sorbents were useful to maintain the CO2 sorption for more than 30 cycles. However, the silica, if included more than 10 mol% with respect to CaO, had negative effect on the sorption by more than its mole fraction. Thus, it was necessary to control Si dissolution for the resources composed of calcium silicate such as steel slag. The highest sorption of the sorbents from steel slag was 49% with 66% calcium utilization. On the other hand, if silica is in ‘free’ state, such as in waste cement, it hardly dissolves in the acid. Therefore, the sorbent could be prepared in core(SiO2)–shell(CaO) type by restructuring waste cement to show 100% utilization of the calcium in the shell.
    Chemical Engineering Journal. s 195–196:158–164.
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    ABSTRACT: Nanostructures of single crystallites of spinel LiMn2O4 (LMO) were prepared by the simple pyrolysis of aqueous solution of LiNO3 and Mn(NO3)2 in a confined space such as either droplets or mesopores. When the mixed nitrate solution was spray pyrolyzed at temperatures below 700 °C, 1-μm LMO spheres were obtained consisting of ~20-nm single crystallites randomly packed. Such LMO phase, once obtained, would sustain for further heat-treatment. Next, new spraying solution was prepared by adding the precursor for mesoporous silica (MPS) to the nitrates solution. By spray pyrolyzing such solution, LMO was impregnated inside pores of the MPS being structured. The silica could be removed by subsequent NaOH treatment to leave spherical LMO mesophase. The nitrates was also able to soak into the existing MPS having cylindrical pores and form short isolated LMO chains in the mesopores by the subsequent heating. After the same NaOH treatment, the LMO phase turned into bundles of very ‘long’, and often straight, chains, consisting of 8-nm LMO nanoparticles. This will be elucidated through further study.
    Journal of Sol-Gel Science and Technology · 1.66 Impact Factor