• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.418-425
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• 2002

Bluetooth is an emerging technology expected to provide users with short range, low cost, pico-cellular wireless connectivity. The access to the medium for Bluetooth is based on a Master driven Time Division Duplexing (TDD) scheme. A slave transmits packets in the reverse slot only after the master polls the slave (or transmits a packet to the slave) in a forward slot. The master transmits packets to a slave in even slots while the slave transmits packets to the master in an odd slot. The way in which the master schedules packets transmission to slaves or polls them determines system performance. In this paper. we propose a traffic adaptive MAC scheduling scheme for Bluetooth. The proposed scheme adopts the ISAR (Intelligent Segmentation and Reassembly) policy, which adjusts the packet size to the traffic patterns, to adapt the polling frequency to the traffic conditions. Also for achieving fairness among master-slave connections our scheme includes a priority policy assinging prioritised service tlimes to each connection. By considering a scenario where a Bluetooth master is used as wireless access point to the Internet, we show that our scheme improve the system throughput and average queue delay with regard to a naive Round Robin (RR) scheme.

• Electronics and Telecommunications Trends
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• v.33 no.5
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• pp.24-32
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• 2018

With the advent of new convergence services, the requirements of 5G mobile communication systems are being newly derived. The 5G mobile communication system has been evolving to solve requirements that cannot be satisfied with existing 4G mobile communication systems, such as a high user experience transmission rate, short transmission delay, and high connection density. The evolution of a 5G mobile communication system to meet the new requirements is expected to be dominated by the UDN environment in which a number of small cells are concentrated. The 5G wireless backhaul system, which has advantages in terms of initial installation and operation cost, is expected to be an indispensable choice for connecting many small cells and core networks. This paper therefore looks at the frequency band characteristics and requirements applicable to 5G wireless backhaul systems that can accommodate new situations, and introduces key related technologies that can satisfy the 5G wireless backhaul requirements.. In addition, we describe the research and development trends of a 5G wireless backhaul system that is currently under development.

• Journal of the Korean housing association
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• v.18 no.2
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• pp.83-92
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• 2007

The past concept of constructing houses was focused on how to overcome the limitation of consuming natural resources such as energy and materials, which increased the official cost and the environmental pollution. On the other hand, the echo-friendly concept has considered the harmony between human being and nature more critically and has applied the characteristics of natural environment into a unique dwelling design by developing constructs and materials adjusted to the particular climate, making them into a unit of impacting positively the complicated system. The current environmental issue is how a dwelling adapts into a given climate in which the design is applied by ecology without damaging the natural environment. In another word, the main issue in the twenty first century will be how we meet the human needs to dwellings applied by the residential environment. Therefore, we have to provide a hospitable place for residents' mental and physical health through "Green Design", emerging as the critical design of urban collective dwellings. Based on these conceptions, the purpose of this study is to suggest the way of designing the urban collective dwelling applied by ecology, proffering wealthy life style to residents with the preservation of natural environment as applying an ecological concept into the design of collective dwellings that represent a contemporary housing type for urban residents.

• International Commerce and Information Review
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• v.8 no.1
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• pp.125-141
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• 2006

It is no unnecessary to tell the importance of foreign trade in Korea economics. Nevertheless, government's direct support is impossible owing to WTO's regulation. Accordingly, government have brought focus into trade facilitation as paperless trade. e-Trade document repositary building by government's budget and private sector's cooperation is a part of e-Trade platform and necessary function in connection with relay and certification of e-Trade document. This study examined the estimated operational problems of e-Trade document repositary as compared Licensed Electronic Document Repositary. Firstly, the operator of e-Trade document repositary undertake multiple role and function as Licensed Certification Authorities(e-sign Act), Licensed Electronic Document Repositary(Framework Act on Electronic Transaction) etc. Secondly, sufficient levy that meet operating cost of the e-trade document is the key point of e-Trade document repositary's success, because additional budget invest in that operation is too hard to do. Thirdly, the operator of the e-Trade document repositary have to keep fairness, objectivity and transparency because the operational right is exclusive.

• Journal of Korean Association for Spatial Structures
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• v.14 no.2
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• pp.69-78
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• 2014

The purpose of this study is to increase applicability of high strength steel, HSA800 to the structure. Selected study of structure is to consider high strength steel, and following parts, 1) Tensile member with no consider of buckling, 2) Truss existing both tension and compression members with small slenderness ratio. This studied structure is included tension column hang on to the upper bridge truss. The structure element quantity with apply HSA800 instead of SM570 is reduced about 38.9% of tension column and 29.7% of bridge truss. In addition, the number of element's division is reduced about two sections due to reduction of self weight that the crane is able to lift up. This improves to reduce erection sequence and construction period which can save about a month. All connections are reviewed as welding and bolt. Also, the cost of welding is reduced about 41.3% due to apply HSA800. In conclusion, applying HSA800 to the hanging structure aggressively can secure economic and constructability.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.1005-1008
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• 1993

Supervised learnmg 01 recurrent neural networks (RNNs) is discussed. First, we review the present state of art, featuring their major properties in contrast of those of the multilayer neural networks. Then, we concisely describe one of the most practical learning algorithms, i.e. backpropagation through time. Revising the basic formulation of the learning algorithms, we derive a general formula to solve for the exact solution(s) of the whole connection weights w of RNNs. On this basis we introduce a novel interpretation of the supervised learning. Namely, we define a multidimensional Euclidean space, by assigning the cost function E(w) and every component of w to each coordinate axis. Since E=E(w) turns up as a hyper surface in this space, we refer to the surface as learning surface. We see that topological features of the learning surface are valleys and hills. Finally, after explicating that the numerical procedures of learning are equivalent to descending slopes of the learning surface along the steepest gradient, we show that a minimal value of E(w) is the intersection of curved valleys.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.198-209
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• 2007

This paper provides a thorough study on shared segment protection (SSP) for mesh communication networks in the complete routing information scenario, where the integer linear program (ILP) in [1] is extended such that the following two constraints are well addressed: (a) The restoration time constraint for each connection request, and (b) the switching/merging capacity constraint at each node. A novel approach, called SSP algorithm, is developed to reduce the extremely high computation complexity in solving the ILP formulation. Basically, our approach is to derive a good approximation on the parameters in the ILP by referring to the result of solving the corresponding shared path protection (SPP) problem. Thus, the design space can be significantly reduced by eliminating some edges in the graphs. We will show in the simulation that with our approach, the optimality can be achieved in most of the cases. To verify the proposed formulation and investigate the performance impairment in terms of average cost and success rate by the additional two constraints, extensive simulation work has been conducted on three network topologies, in which SPP and shared link protection (SLP) are implemented for comparison. We will demonstrate that the proposed SSP algorithm can effectively and efficiently solve the survivable routing problem with constraints on restoration time and switching/merging capability of each node. The comparison among the three protection types further verifies that SSP can yield significant advantages over SPP and SLP without taking much computation time.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.72-75
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• 2001

The solar energy is purity and infinity. Solar power converter were used to convert the electrical energy from the solar arrays to a stable and reliable power source. So much country research this solar energy system. The photovoltaic system is construct many solar cell array, In this paper, new implementation solar system was showed buck converter that V-I curve produced. This system can be used to study the short-term and long-term performances of solar cell and efficiency. This system is a far more cost effective and reliable replacement for field and outdoor flight testing. Study of buck converter, analysis and control shun t$\cdot$series connection characteristics of solar cell array.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.135-143
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• 2018

Sony has recently launched a remote play service that connects PC and PlayStation4 using the Internet. This service enables the network connection between the external network and PS4 network. After the service released, additional security threats may arise in remote environments with new services. Therefore, those threats should have been analyzed. In this paper, as applying threat modeling to remote play system, threats have been analyzed and identified. After cost-effective and usability analysis, finally, reasonable security measure of each threat has been suggested.

• Journal of the Korean Institute of Navigation
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• v.8 no.1
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• pp.17-48
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• 1984

The economy of ship's size and speed is affected by the freight rates, sailing distances, cargo handling rates, fuel oil prices and even interest rates of the borrowed funds. It can be a step more powerful measures if the economic evaluation model takes in a cargo lot size which prevails in the shipping markets. This paper has dealt with hypothetical cargo lots which happen to the market with uniform distribution in probability. The evaluation models are either profit maximization method or cost minimization method. The former compares among different voyages in profitability to the invested funds, the later defines the transportation efficiency in ton-mile unit and be used in comparing two or more transportation means. This paper adopted both of above methods to derive out ships economical evaluation contours for the various ship's speed and deadweight for certain cargo lot sizes, which can be used as important managerial decision data in purchasing ships or selecting a most profitable one among the proposed voyages. This evaluation contours will also be efficiently used in appraising so called "handy size ships" in connection with port water depth and conditions of voyage tracks.ge tracks.