• Macromolecular Research
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• v.17 no.9
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• pp.658-665
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• 2009

This study examined the effects of the sodium salts of aliphatic dicarboxylic acids (DCAs) on the dynamic mechanical properties and morphology of two sets of poly(styrene-co-sodium methacrylate) (MNa) and poly(styrene-co-sodium styrenesulfonate) (SNa) ionomers. When the DCA content was relatively low, the ionic moduli of the MNa and SNa ionomers increased but the matrix and cluster glass transition temperature ($T_g$) did not change significantly. The increasing ionic modulus was almost independent of the type of the ionic groups of the ionomer, and the chain length of DCAs. When a large amount of the sodium succinate (DCA4) was added to the MNa and SNa ionomers, the ionic moduli of the two ionomers increased strongly but the matrix and cluster $T_g's$ increased slightly and significantly, respectively. In the case of sodium hexadecanedioate (DCA 16), DCA 16 increased the ionic moduli of the two ionomers. The addition of DCA16 changed the matrix and cluster $T_g's$ of the MNa ionomer slightly, but decreased the cluster $T_g$ of the SNa ionomer significantly with no change in the matrix $T_g$. In addition, the DCA-containing ionomers showed an X-ray diffraction peak indicating the presence of ordered domains of DC As in the ionomers. Hence, DCA4 acts mainly as a reinforcing filler in MNa and SNa systems. In the case of DCA 16, it initially behaved like a filler but also functioned as a preferential plasticizer for the clusters at high content.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.2
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• pp.23-40
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• 2013

The natural environment restoration industry has been newly included in the environment area of engineering technology. Accordingly, the enactment of a standard of estimate for determining the 'Cost plus Fixed Fee' method has become necessary for the implementation and vitalization of natural environment restoration projects. The purpose of this study is to determine the standards for which the prices for engineering projects are calculated with respect to the enactment of an engineering project standard of estimate in the natural environment restoration field. These include the scope of the technological work, standard area, manpower requirements by technical grade that are necessary for carrying out the technological tasks. Relevant laws and regulations, systems and precedent case studies were investigated and analyzed to establish a price calculation standard. The overall results of the analysis were used and applied to questionnaires, public hearings, and expert delphi techniques. The study showed the following results： The scope of the technological work was categorized into 'Biotopes', 'Eco-corridors' and 'Ecological restoration'. The standard area was set up as $1,000m^2$ for 'Biotopes' and $5,000m^2$ for 'Eco-corridors' and 'Ecological restoration'. The manpower requirements by technical grade that are necessary for carrying out the technological tasks were determined. The suitability of the costs, standard area, manpower requirements by technical grade of ordered engineering projects that are determined by applying the standard of estimate for natural environment restoration that may be enacted pursuant to this study may be effectively investigated and analyzed. Moreover, further studies on the calculation of standard prices that can ensure the stability of natural environment restoration projects will be necessary.

• Journal of Information Processing Systems
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• v.9 no.4
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• pp.511-537
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• 2013

Numerous data intensive applications demand the efficient processing of a new type of query, which is called a progressive query (PQ). A PQ consists of a set of unpredictable but inter-related step-queries (SQ) that are specified by its user in a sequence of steps. A conventional DBMS was not designed to efficiently process such PQs. In our earlier work, we introduced a materialized view based approach for efficiently processing PQs, where the focus was on selecting promising views for materialization. The problem of how to efficiently find usable views from the materialized set in order to answer the SQs for a PQ remains open. In this paper, we present a new index technique, called the Dynamic Materialized View Index (DMVI), to rapidly discover usable views for answering a given SQ. The structure of the proposed index is a special ordered tree where the SQ domain tables are used as search keys and some bitmaps are kept at the leaf nodes for refined filtering. A two-level priority rule is adopted to order domain tables in the tree, which facilitates the efficient maintenance of the tree by taking into account the dynamic characteristics of various types of materialized views for PQs. The bitmap encoding methods and the strategies/algorithms to construct, search, and maintain the DMVI are suggested. The extensive experimental results demonstrate that our index technique is quite promising in improving the performance of the materialized view based query processing approach for PQs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.10
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• pp.791-798
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• 2018

The CFAR algorithm is mainly used for target detection in radar systems. In particular, OS CFAR is used in a non-uniform noise environment. However, it requires a large amount of computation, because it should sort reference cells in ascending order. This makes it difficult to apply the radar system in real time. In this paper, we describe how to reduce the computational burden of OS CFAR. We compared the power of the test cell and reference cell to determine only the presence or absence of target detection. The common reference cells overlapping in the reference cells of the three test cells are obtained. We first compare the test cell with the highest power value among the three test cells to the common reference cells. Next, we compare each test cell to general reference cells, excluding the common reference cells. The computation time is shortened by reducing the power comparison computation amounts.

• Journal of the Korean Magnetics Society
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• v.19 no.5
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• pp.171-175
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• 2009

The magnetism of the Fe monolayer on Ir(001) substrate [Fe/Ir(001)] was investigated by the first-principles energy band method. For comparison, the Fe and Ir ordered-alloyed monolayer on Ir(001) [Fe$_{0.5}$Ir$_{0.5}$/Ir(001)] was also considered. The calculated magnetic moments for Fe atoms in Fe/Ir(001) system and Fe$_{0.5}$Ir$_{0.5}$/Ir(001) system are 2.95 and 2.83 bohr magnetons, respectively. The detailed aspects of the magnetism and electronic structures for these systems are discussed with the calculated denisty of states and spin densities. The optimized atomic sites for the overlayer Fe and Ir atoms were determined by the total energy and atomic force calculations. The Fe atoms in Fe/Ir(001) move closer to the substrate Ir layer than the Fe atoms in Fe$_{0.5}$Ir$_{0.5}$/Ir(001) do to the Ir substrate.

• Archives of Metallurgy and Materials
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• v.67 no.4
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• pp.1469-1473
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• 2022

Tungsten diselenide (WSe₂) is one of the promising transition metal dichalcogenides (TMDs) for nanoelectronics and optoelectronics. To enhance and tune the electronic performance of TMDs, chemical functionalization via covalent and van der Waals approaches has been suggested. In the present report, the electric and structural transition of WSe₂ oxidized by exposure to O₃ is investigated using scanning tunneling microscopy. It is demonstrated that the exposure of WSe₂/high-ordered pyrolytic graphite sample to O₃ induces the formation of molecular adsorbates on the surface, which enables to increase in the density of states near the valence band edge, resulting from electric structural modification of domain boundaries via exposure of atomic O. According to the work function extracted by Kelvin probe force microscopy, monolayer WSe₂ with the O₃ exposure results in a gradual increase in work function as the exposure to O₃. Therefore, the present report demonstrates the potential pathway for the chemical functionalization of TMDs to enhance the electric performance of TMDs devices.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4B
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• pp.620-629
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• 2010

The analogue radio broadcasting was proven to be a successful and efficient media of delivering information because of free content and wide availability of cheap receivers. But the competition was more dropped than any other media due to the limited amount of radio spectrum that is available. The risk of doing nothing is to miss the opportunity and to loss existing audiences in the long term, or to be locked into inefficient proprietary systems. That is the reason why it is important to act now. It is time for regulators and market participants to hone their strategies, by clearly establishing factors to adopt the digital radio and to facilitate its diffusion. The purpose of this study is to find adoption factors that affected to potential users of digital radio broadcasting. Former research based on diffusion of innovation theory showed that adoption of innovation is affected by demographic variables, media usage and consumer's attitude of innovation. In this study based on a consumer survey, we examined those factors and characteristics of each steps that suggested in diffusion of innovation theory. The findings of this study have implications to explore the suitable technologies and services of digital radio broadcasting.

• Journal of Service Research and Studies
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• v.11 no.3
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• pp.55-74
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• 2021

In the global era, the tourism industry is a major profitable business, and the state and local governments are making various efforts to provide quality tourism experiences. The purpose of this study in a variety of tourism contents is to study barrier-free subway services in line with the global era, and to expand from the existing rapid, safe, and ordered transportation to the provision of high-quality comfort and all-round service experiences. This study compared and analyzed the subway service systems of Korea, China and both countries through the service design method, and presented a barrier-free subway service system to improve the user's satisfaction with the subway service system by improving the user's service experience. As a result, research results showed that 20 attractive quality attributes in 17 fields, such as convenience facilities, language issues, security equipment, and riding environment, play an important role in improving the quality and experience of subway services. In addition, through the construction of a Service Spatial Scenario, an optimized subway service system can be visualized to help understand this so that it can be used as a reference for creating a strategic application.

• Journal of Intelligence and Information Systems
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• v.7 no.2
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• pp.51-63
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• 2001

In supervised machine learning, an induction algorithm, which is able to extract rules from data with learning capability, provides a useful tool for data mining. Practical induction algorithms are known to degrade in prediction accuracy and generate complex rules unnecessarily when trained on data containing superfluous features. Thus it needs feature subset selection for better performance of them. In feature subset selection on the induction algorithm, wrapper method is repeatedly run it on the dataset using various feature subsets. But it is impractical to search the whole space exhaustively unless the features are small. This study proposes a heuristic method that uses sensitivity analysis of neural networks to the wrapper method for generating rules with higher possible accuracy. First it gives priority to all features using sensitivity analysis of neural networks. And it uses the wrapper method that searches the ordered feature space. In experiments to three datasets, we show that the suggested method is capable of selecting a feature subset that improves the performance of the induction algorithm within certain iteration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.394-401
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• 2013

Recently there have been much interest in the performance improvement of maritime communication system. In the maritime communication system, the wireless channel is likely to be time-invariant and the retransmission scheme is not proper because it does not provide time diversity. For the improvement of reliability, we consider MIMO ARQ scheme using Alamouti-type signal which can provide space and time diversity. In this paper, we also propose the criterion of optimal retransmission order and provide its performance of error probability and packet throughput. The proposed MIMO ARQ scheme with optimal retransmission order has performance gain over random ordered MIMO ARQ and conventional Chase combining method. Therefore we expect that it can be adapted to the next generation maritime communication system.