• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.155-160
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• 2004

This paper presents a study on the permittivities of the carbon black/epoxy composite at microwave frequency. The measurements were performed at the frequency band of $1 GHz\~18GHz$. The results show that the complex permittivities of composites depend strongly on the natures and concentrations of the carbon black dispersion. The frequency spectrums of dielectric constants and ac conductivities of composites show the good conformities with descriptions of the percolation theory. The carbon black concentration dependencies do not have conformities with the descriptions of percolation theory and there is no peculiar concentration like percolation threshold, on that concentration, the conductivity of composite jumps up. A new scheme, that is a branch of Lichtenecker-Rother formula, is proposed to obtain a mixing law to describe the complex permittivities of the composites as function frequency and concentration of carbon black.

• Proceedings of the Korea Society for Simulation Conference
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• 한국시뮬레이션학회 2000년도 추계학술대회 논문집
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• pp.165-173
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• 2000

Analytic models have been developed to solve integrated production-distribution problems in supply chain management (SCM). As one of major constraints in analytic models, capacity, which is the total operation time in this paper has mostly been known or disregarded assuming infinite capacity. Also, as major factors, machine processing time to fabricate or assemble a part or product at a certain machine center in production system and vehicle processing time to deliver a product to a customer by a certain vehicle in distribution system have been fixed and regarded as a static factor, But in the real systems significant differences exit between capacity and the required time to achieve the production-distribution plan and between processing time and consumed time to process a part or product. In this paper, capacity and processing times in the analytic model are considered as dynamic factors and adjusted by the results from independently developed simulation model, which includes general production-distribution characteristics. Through experiments, we obtain the more realistic solutions reflecting stochastic natures by performing the iterative analytic-simulation procedure.

• Proceedings of the KSR Conference
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.623-629
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• 2005

A technical road map is one of critical research methods which include mid/long term strategies and objectives. There are many of projects conducted using this road map. A technical tree is used at the step of planning of the projects. This research was aimed at reviewing previous systems for conducting researches for and a basis required for improving railway safety in the future by finding out inconsistency arising from physical WBS, which is methodology of defining in existing railway technical trees. In the process of this research, we considered differences between systems safety and prevention as well as natures of them using the established technical tree, and set up plans for improving technical tree to secure railway safety as an integrated system.

• Proceedings of the KSR Conference
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.630-636
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• 2005

A safety management system is a information system. This system finds out hazards which could occur during safety management activities, and analyze and evaluate their natures, and then plan to take measures. Therefore accidents could be prevented. To establish the information system, robust architectures are required. A purpose of this research is to derive procedure of establishment in relation to developing safety management systems, which is needed to be advanced. To accomplish it, we reviewed a movement of architectures to establish electronic information and a movement of technology development And then we led definitions of requirements and architectures development process from those that are based on review of the trends.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.121-127
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• 2013

New types of monocyclic ${\beta}$-lactams constitute an important class of compounds due to their unique structures and natures. Here, the design and synthesis of new 4-alkylthio monocyclic ${\beta}$-lactams 2a and 3a are reported. Significantly, compounds 2a and 3a, while keeping a monocyclic system, were designed to contain all of the substructures provided by the cleavage of C(2)-C(3) bond in penicillins. Efficient synthetic pathways for compounds 2a and 3a were established based on two different strategies. Compound 2a was synthesized from raw materials, using 4-acetoxyazetidin-2-one as a key intermediate, through a ten-step synthetic sequence in 3% overall yield. Compound 3a was synthesized from potassium salt of penicillin G (17), using the degraded product 20 as a key intermediate, through a six-step synthetic sequence in 11% overall yield. 4-Alkylthioazetidin-2-one derivatives, introduced in this study, could serve as valuable intermediates for the development of new monocyclic ${\beta}$-lactams.

• Journal of Fisheries and Marine Sciences Education
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• 제17권3호
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• pp.281-292
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• 2005

Information on maritime boundaries is essential to manage ocean and fisheries effectively in the era of the UN Convention on the Law of the Sea. With various information regarding to maritime boundaries analysed and reviewed, maritime boundaries are mainly divided into two categories such as international and domestic boundaries and also sub-divided into two aspects such as administrative and other boundaries. After clarification of boundary information, the geographical natures of boundaries, for instance datum, projection, line types, are reviewed. The Geographic Information Systems (GIS) is used for the establishment, management and utilization of boundary information due to its strong function in database, analysis, visualization, etc.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제62권1호
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• pp.95-100
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• 2013

This paper presents a new state feedback control approach for communication networks based control systems in which control input and output observation time-delay natures are generally occurred in practice. We first establish a generic state feedback control framework based on well-known linear system theory. A maximum time-delay value which allows critical stability of whole control system are defined to make a positive definite Lyapunov function which is mathematically composed of controlled system states. We analytically derive its control parameters by using a steepest descent optimization method in order to guarantee a stability condition through Lyapunov theory. Computer simulation is numerically carried out for demonstrating reliability of the proposed NCS algorithm and a comparative study is accomplished to prove its superiority for which the traditional control approach for NCS is made use of under same simulation scenarios.

• Journal of Pharmaceutical Investigation
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• 제23권4호
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• pp.187-206
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• 1993

Since the advent of recombinant DNA technology coupled with other biotechnology a variety of therapeutically effective proteins and peptides have been extensively invesitigated and many of them are now on clinical trial. They, however, suffer from some problems such as immunogenicity, antigenicity, instability and short half-life in circulation due to their proteinous natures. These drawbacks can be overcome successfully by conjugating proteins and peptides with hydrophilic polymers such as polyethylene glycol (PEG), albumin or dextran. The resulting soluble conjugates showed reduced antigenicity and immunogenicity, increased circulatory half-life, enhanced stability against proteolytic degradation. Comparing with the unmodified proteins and peptides, the therapeutic potential of conjugates is greatly enhanced. Clinical applications of these conjugates have shown promising results for the future use.

• East Asian Economic Review
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• 제18권4호
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• pp.339-366
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• 2014

This paper examines the impact of internationalization on the product, process and organizational innovations of Korean service firms. Despite the increasing importance of the service sector and the discrepancies in the natures of the manufacturing and service industries, the internationalization-innovation link in the context of service firms has rarely been examined empirically on a large sample. Based on the results of the logistic regressions using the 2006 Korean Innovation Survey data, we found that Korean service firms' international expansion is significantly and positively associated with their product and organizational innovations. In addition, the magnitude of the estimates in our models revealed that internationalization has a greater impact on product innovation than on process or organizational innovation.

• Communications of Mathematical Education
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• 제20권1호
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• pp.87-101
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• 2006

Gifted students in elementary, middle and high schools require a specialized curriculum to foster their mathematically gifted natures. Questions that stimulate the teacher's intellectual curiosity, student reactions and methods pertaining to content organization and problem formation are the main foci.