• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1288-1296
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• 2012

A candidate hybrid satellite and terrestrial network architecture, MSS/ATC(Mobile Satellite Service/Ancillary Terrestrial Component), is proposed for utilizing efficiently the exist MSS bands. Studies on the adjacent channel interference from the existing terrestrial mobile services and MSS/ATC itself are important to allocate a new ATC service frequency in MSS band. In this paper, we have analyzed the minimum permission power of terrestrial base station and the capacity loss with parameters of ACIR, number of MS(mobile Station) and MES(Mobile Earth Station) in uplink, and also, the capacity performance based on 1 beam and 1 cell assumption for MSS/ATC in downlink. The ACIR requirements are estimated in two MSS/ATC frequency allocation scenarios for 5 MHz and 10 MHz guard band to share spectrum with adjacent systems, and according to these ACIR requirements the service coverage and the receiver filter for ATC system should be designed in near future.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.69-75
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• 2012

The purpose of this paper is to study comparative analysis of cable dome structures by reinforcement effect with bracing and fabric. Tensegrity systems are stable structures which are reticulated spatial structures composed of compressive straight members, struts, and cables. Tensegrity structures need to be introduced to the initial stress for the self-equilibrated system to have a stable state. In this paper, the effect of reinforcement resisting the in-plan twisting is investigated for the Geiger-type and Zetlin-type models reinforced by bracing and fabric. The effect of initial imperfection is also studied because the structural instabilitity phenomenon of shell-like structures is very sensitive according to the initial condition. We study a more exact analysis concerning the structural instability of tensegrity structures using nonlinear analysis program. Then, two types of tensegrity models will be analysed and compared.

• Journal of Intelligence and Information Systems
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• v.12 no.2
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• pp.167-183
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• 2006

Since data mining attempts to find unknown facts or rules by dealing with also vaguely-known data sets, it always suffers from high error rate. In order to reduce the error rate, many researchers have employed multiple models in solving a problem. In this research, we present a new type of multiple models, called DyMoS, whose unique feature is that it classifies the input data and applies the different model developed appropriately for each class of data. In order to evaluate the performance of DyMoS, we applied it to a real customer churn problem of an automobile insurance company, The result shows that the DyMoS outperformed any model which employed only one data mining technique such as artificial neural network, decision tree and case-based reasoning.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.1041-1043
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• 2013

As the mobile device supply is increasing currently, the era of N mobile devices per person has opened. Types of mobile devices and OS are increasing continuously. Samsung and Intel are developing TIZEN, the OS mobilized by UBUNTU of Linux is going to be released as well as the market share of Google's Android and Apple's IOS remains above 90%. However, it is a reality that there are not specific technologies or systems which can share files between different OS. Despite of technologies such as Bluetooth and WiFi Direct, constraints are shown in device compatibility and file formats. In this paper, we have studied how to share files between OS as well as mobile devices, and to share files in a wireless LAN environment of heterogeneous variety. Future research includes the mobile phone integration server system that provides services such as introduction, management, maintenance, and repair in one-touch Mobile Server that spread and building are easy.

• The KIPS Transactions:PartB
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• v.8B no.6
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• pp.657-668
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• 2001

It is difficult that web documents are classified with exact user intention because existing document classification systems are based on word frequency number using single keyword. To improve this defect, first, we use keyword, a query, domain knowledge. Like explanation based learning, first, query is analyzed with knowledge based information and then structured user intention information is extracted. We use this intention tree in the course of existing word frequency number based document classification as user information and constraints. Thus, we can classify web documents with more exact user intention. In classifying document, structured user intention information is helpful to keep more documents and information which can be lost in the system using single keyword information. Our hybrid approach integrating user intention information with existing statistics and probability method is more efficient to decide direction and range of document category than existing word frequency approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.901-911
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• 1994

The error performance of M-ary differential phase shift keying (MDPSK) through m-distribution fading channel in hybrid direct sequence/slow frequency hopped spread spectrum multiple access (DS/SFH-SSMA) systems has been evaluated, and also the error probability has been evaluate when adopting diversity technique and coding technique. From the results, we know that the error performance more deteriorates as depth of fading becomes deeper. In Rayleigh fading environment (m=1), increasing of the number of frequency hopping (q) reduces the effect of multiple access interference, because it decreases the probability a hit. When q is much larger than the number of user (K), the probability of error in high E/N region is dominated by the multipath interference while the multiple access interference is negligible. In lower E/N region, the probability of error is independent of q because the effect of gaussian noise becomes dominat.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.441-451
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• 2002

Recently, Increasing residential-commercial buildings are composed of upper wall and lower frame type. As structural fragility, a large numbers of researchers have tried to develope the efficient analysis methods. But these studies were too theoretical and were not considered the lateral load which was required in analysing the transfer level in addition to being used nonlinear program which was difficult to use for practical design. thus, results of these studies we not appropriate to apply practical design, therefore, in this paper, the procedure of the current design practice were compared with that of used FEM method and presented new modeling method. in particular, an efficient analytical model which can be used in practical design of residential-commercial buildings for vortical and seismic loads was proposed and the usefulness of proposed model was verified.

• Ocean Systems Engineering
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• v.7 no.2
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• pp.143-155
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• 2017

For complex flexible structures such as nets, the determination of drag forces and its deformation is a challenging task. The accurate prediction of loads on cages is one of the key steps in designing fish farm facilities. The basic physics with a simple cage, can be addressed by the use of experimental studies. However, to design more complex cage system for various environmental conditions, a reliable numerical simulation tool is essential. In this work, the current load on a cage is calculated using a Morison-force model applied at instantaneous positions of equivalent-net modeling. Variations of solidity ratio ($S_n$) of the net and current speed are considered. An equivalent array of cylinders is built to represent the physical netting. Based on the systematic comparisons between the published experimental data for Raschel nets and the current numerical simulations, carried out using the commercial software OrcaFlex, a new formulation for $C_d$ values, used in the equivalent-net model, is presented. The similar approach can also be applied to other netting materials following the same procedure. In case of high solidity ratio and current speed, the hybrid model defines $C_d$ as a function of Re (Reynolds number) and $S_n$ to better represent the corresponding weak diffraction effects. Otherwise, the conventional $C_d$ values depending only on Re can be used with including shielding effects for downstream elements. This new methodology significantly improves the agreement between numerical and experimental data.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.471-480
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• 2015

Reliance on road transport in domestic logistics can lead to intensified congestion and greenhouse gas emissions due to the rise in oil prices, any increase in logistics costs can have a high social cost. The government policy on Low Carbon Green Growth is seeking to take advantage of the railway system. However, existing railway transport logistics systems, for reasons such as low speed, low track capacity constraints, and the impossibility of implementing a Door to Door system, make it difficult to activate a railway logistics program. As a result of this study, a national R&D project to develop a High-Speed Passenger/Baggage Mixed Train(Hy-SoBex) utilizing the rail capacity constraints to overcome the difficulties of linking an air cargo and freight railway logistics system, we propose a variety of service models and select the optimal service model.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.110-124
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• 1993

A Nonlinear model-based Hybrid Controller (NHC) is developed which consists of the adaptive proportional-integral-feedforward (PIF) gains and variable structure controller. The controller has the robustness against modeling uncertainty and is applied to the trajectory tracking control of single-input, single-output nonlinear systems. The essence of the scheme is to divide the control into four different terms. Namely, the adaptive P-I-F gains and variable structure controller are used to accomplish the specific control actions by each terms. The robustness of the controller is guaranteed by the feedback of estimated uncertainty and the performance specification given by the adaptation of PIF gains using the second method of Lyapunov. The variable structure controller is incorporated to regulate the initial peak of the tracking error during the parameter adaptation is not settled yet. The newly developed NHC method is applied to the power tracking control of a nuclear reactor and the simulation results show great improvement in tracking performance compared with the conventional model-based control methods.