• Journal of KIISE:Databases
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• v.30 no.5
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• pp.451-463
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• 2003

Recently, there have been various research efforts to develop strategies for accelerating OLAP operations on huge amounts of spatio-temporal data. Most of the work is based on multi-tree structures which consist of a single R-tree variant for spatial dimension and numerous B-trees for temporal dimension. The multi~tree based frameworks, however, are hardly applicable to spatio-temporal OLAP in practice, due mainly to high management cost and low query efficiency. To overcome the limitations of such multi-tree based frameworks, we propose a new approach called Hilbert Cube(H-Cube), which employs fractals in order to impose a total-order on cells. In addition, the H-Cube takes advantage of the traditional Prefix-sum approach to improve Query efficiency significantly. The H-Cube partitions an embedding space into a set of cells which are clustered on disk by Hilbert ordering, and then composes a cube by arranging the grid cells in a chronological order. The H-Cube refines cells adaptively to handle regional data skew, which may change its locations over time. The H-Cube is an adaptive, total-ordered and prefix-summed cube for spatio-temporal data warehouses. Our approach focuses on indexing dynamic point objects in static spatial dimensions. Through the extensive performance studies, we observed that The H-Cube consumed at most 20% of the space required by multi-tree based frameworks, and achieved higher query performance compared with multi-tree structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6360-6367
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• 2015

The location selection of the element that should guarantee easy visual perception, like the landmark, is the a topic that appears much in the design process. Recently, a graph analysis technique using computers has been applied in order to evaluate the visibility of the visual element, but the analytic frame is flat and the setting of the visual pont and the matrix are fixed so there were great limitations in obtaining the results of the practical analysis. Thus, this study presented Nondirectional Multi-Dimensional Calculation (MDVC-N), an analytic methodology available for the analysis of the dynamic visual point in the 3D environment. It thus attempted to establish the analytic application using the 3D computer graphics technology and designed a script structure to set the visual point and the matrix. In addition to that, this study tried to verify the analytic methodology by applying the complex land as an example model, where buildings in various heights of terrains with a high-differences are located, verifying the same analytic methodology. It thus tried to identify the visual characteristics of each alternative location. The following results were gained from the study. 1) The visibility can be measured quantitatively trough the application of the 6-alternatives. 2) Using the 3dimensional graph, intuitive analysis was possible. 3) It attempted to improve the analytic applicability by calculating the results corrected as a variable behavior from the local integration variable of the space syntax.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1844-1866
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• 2011

In a home network system, each customer electronic device has the control data format chosen by its manufacturing company and there are various types of digital devices and protocols. Besides the mutual operating environments among the various devices are dissimilar. Affected by the characteristics explained above, home network systems can hardly support the crucial functions, such as data compatibility, concurrency control, and dynamic plug-in. Thus, the home network system shows relatively poor reusability. In this paper, we suggest design technique of configurable framework, which can widely support the variability, to increase the reusability of the home network system. We extract the different parts of the home network system as variation points, and define them as the variability types. We design a structure of configurable framework, and suggest customization technique of configurable framework through selection technique and plug-in technique. Also, we prove the reusability by applying the proposed framework and it methods to real-world home network systems and analyzing the measurement results of these case studies using software metrics. We can expect the proposed approach provides better reusability than the existing them by analyzing those measurement results.

• Journal of Biomedical Engineering Research
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• v.24 no.6 s.81
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• pp.515-522
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• 2003

Pharynx is a system transporting foods by peristaltic motion(contraction and expansion movement! into the esophagus and functioning as airway passages. In this study, structural changes of pharyngeal dysfunction are analyzed by biomechanical model using CT and FEM(finite clement method). Loading condition was assumed that equal pressure was loaded sequentially to inside of pharyngeal tissue. In order to analyze the pharyngeal muscular dysfunction by biomechanical model. the pharyngeal dysfunctions was classified into 3 cases. Taking into account the clinical complication by neuromuscular symptoms such as pharyngeal dysfunction after stroke. we assumed that a change of material property is caused by muscular tissue stiffness. A deformation of cross sectional area of the pharynx is analyzed increasing the stiffness $25\%,\;50\%,\;75\%$ in each case on the basis of stress-strain relationship. Based on three-dimensional reconstruction of pharyngeal structure using limited factor - techniques and the optimization procedure by means of inverse dynamic approach. the biomechanical model of the human pharynx is implemented. The results may be used as clinical index illustrating the degree of pharyngeal muscular dysfunction. This study may be used as useful diagnostic model in discovering early deglutitory impediment caused by physiological or pathological pharyngeal dysfunction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.86-92
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• 2016

A high-capacity battery installed in a hybrid vehicle or electric vehicle is used to power, or as a power supply for, electric sub-assemblies. In order to use a high-capacity battery as a power supply for electric sub-assemblies, such as an electronic control unit or for lighting, radio, and navigation, there is a need for a DC converter that changes a high voltage of 240-400V to a low voltage of 12-14V, which is done with a low-voltage DC-DC converter (LDC). An LDC undergoes long-term aging so as to reduce latent defects in the production process. With regard to the usual aging method, an LDC is a DC-DC converter. So, a DC power supply is connected and used as input, and a programmable DC electronic load is the output. For stable operation, a product having a larger capacity by 10% (compared to an LDC) is used, and has a structure where electric power is dissipated into 100% heat. So, there is a problem with volume, based on the use of two pieces of equipment to test the LDC, and another problem based on the generation of heat in the programmable DC electronic load. Hence, this paper suggests a load test method as a way of recycling, where a significant portion of the electricity dissipated as heat in a load tester is returned as input. The method realizes savings of 80% or more in the electricity dissipated as heat through improvement in the efficiency of the recycling load tester.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.59-65
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• 1998

Morphology and thermal properties of polyurethane synthesized from 4,4'-diphenylmethane diisocyanate (MDI), polyester polyol, and 1,4-butane diol are investigated using fourier transform infrared spectroscopy (FT-IR), differential scanning calorimeter (DSC), and dynamic mechanical thermal analysis (DMTA). From the FT-IR study, it is found that the stretching peaks of hydrogen bonded N-H and C=O are shifted to the low frequencies with the increase of hard segment content of the polyurethanes. The shift of the stretching peaks of hydrogen bonded N-H and C=O indicates that the degree of hydrogen bonding is increased. From the DSC study, it appears that the glass transition temperature ($T_g$) of the polyurethanes is increased with the increase of the hard segment content. Also, it is found that the polyurethanes investigated in this study have the homogeneous network structure due to the high functionality of the MDI. From the DMTA study, transition of the soft segment was not found. Therefore it is concluded that the polyurethanes investigated in this study have the one-phase morphology which is consistent with the DSC results.

• Journal of the Korean Institute of Gas
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• v.2 no.4
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• pp.18-24
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• 1998

Polyurethane (PU) synthesized from 4,4'-diphenylmethane diisocyanate having high functionality (f=2.9) and polyester polyol have been investigated by differential scanning calorimeter (DSC), dynamic mechanical thermal analyzer (DMTA), and Fourier transform infrared spectroscope (FT-IR). From the DSC measurement of polyurethane, a single transition temperature ($T_g$) was observed. This result indicates that polyurethanes synthesized in this work have homogeneous network structure due to high functionality of diisocyanate. It was also found that the $T_g$ of polyurethane was increased as hard segment content was increased. The results from DMTA measurement are consistent with DSC results. In order to investigate the effect of thermal annealing on the $T_g$ of polyurethane, the samples were annealed at various annealing conditions. $T_gs$ of polyurethanes were found to increased with annealing temperature. From swelling experiment and FT-IR studies, it was found that the $T_g$ was increased as crosslinking density of polyurethane was increased.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.509-515
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• 2021

In this study, poly lactic-co-glycolic acid (PLGA) nanoparticles (PNP) were prepared through double (w/o/w) emlusion and emulsifying solvent-evaporation technique using PLGA, which has biocompatibility and biodegradability. To maximize stability and bioavailability of the particles, chitosan-coated PLGA nanoparticles (CPNP) were prepared by charge interaction between PNP and chitosan. We demonstrated that CPNP can be utilized as a drug carrier of oral administration. The chemical structure of CPNP was analyzed by ¹H-NMR and FT-IR, and all characteristic peaks appeared, confirming that it was successfully prepared. In addition, particle size and zeta potential of CPNP were analyzed using dynamic light scattering (DLS) while morphological images were obtained using transmission electron microscope (TEM). Thermal decomposition behavior of CPNP was observed through thermogravimetric analysis (TGA). In addition, the cytotoxicity of CPNP was confirmed by MTT assay at HEK293 and L929 cell lines, and it was proved that there is no toxicity confirmed by the cell viability of above 70% at all concentrations. These results suggest that the CPNP developed in this study may be used as an oral drug delivery carrier.

• Journal of Family Resource Management and Policy Review
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• v.25 no.1
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• pp.47-61
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• 2021

The purpose of this study is to analyze the trend of changes in household labor among middle-aged generations who are facing dynamic changes in the middle of their life cycle. The research method is a literature study that examines and analyzes related data. Specifically, it aims to analyze the basic characteristics of middle-aged generations and trends in household labor, which are revealed through Time Use Survey, market trend reports, newspaper articles, and books. From the perspective of family resource management, housework is an unpaid activity performed by and for family members, and is an activity that can be replaced by purchasing goods or services from the market. This study focuses on the rapid growth of the home appliance market that replaces housework with the development of technology after industrialization, and how the change of technology affected the efficiency of housework. In addition, the composition and characteristics of middle-aged generations greatly changed according to changes in family structure, form, and family value. Examining the current state of housework and changing trends of middle-aged generations, which have different characteristics from previous generations, is significant in that it can predict future market trends and suggest implications for family policies that support the improvement of the quality of life of middle-aged generations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.4
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• pp.83-91
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• 2021

In this study, to improve the connection performance between the existing reinforced concrete (R/C) frame and the strengthening member, we proposed a new H-section steel frame with elastic pad (HSFEP) system for seismic rehabilitation of existing medium-to-low-rise reinforced concrete (R/C) buildings. This HSFEP strengthening system exhibits an excellent connection performance because an elastic pad is installed between the existing structure and reinforcing frame. The method shows a strength design approach implemented via retrofitting, to easily increase the ultimate lateral load capacity of R/C buildings lacking seismic data, which exhibit shear failure mechanism. Two full-size two-story R/C frame specimens were designed based on an existing R/C building in Korea lacking seismic data, and then strengthened using the HSFEP system; thus, one control specimen and one specimen strengthened with the HSFEP system were used. Pseudodynamic tests were conducted to verify the effects of seismic retrofitting, and the earthquake response behavior with use of the proposed method, in terms of the maximum response strength, response displacement, and degree of earthquake damage compared with the control R/C frame. Test results revealed that the proposed HSFEP strengthening method, internally applied to the R/C frame, effectively increased the lateral ultimate strength, resulting in reduced response displacement of R/C structures under large scale earthquake conditions.