• Journal of the Economic Geographical Society of Korea
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• v.12 no.1
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• pp.56-66
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• 2009

As the amount of information is rapidly growing, and the ubiquitous urban environments are emerging, the question which information type to provide and which communication media to support is a major challenge for commercial and public travel-information service providers. The current research reports the first findings of analyses of recent data, collected in metropolitan Seoul, about the acquisition of travel information and the communication media used. The study is based on the assumption that information acquisition and choice of communication medium is strongly context-driven. The study applies CHAID analysis to find homogeneous segments in information acquisition and use of communication media. Findings indicate that transport mode and activity are important determinant of information acquisition and choice of media. The type of travel information acquired co-varies strongly with transport mode and activity. In addition, we found evidence of time of day effects. Similarly, the choice of communication medium depends on the type of travel information searched for, transport mode and activity. The results suggest important implications of managerial and policy measures, in particular the dynamic, contextual market segmentation.

• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.143-155
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• 2009

A dynamic traffic assignment (DTA) has recently been implemented in many practical projects. The core of dynamic model is the inclusion of time scale. If excluding the time dimension from a DTA model, the framework of a DTA model is similar to that of static model. Similar to static model, with given exogenous travel demand, a DTA model loads vehicles on the network and finds an optimal solution satisfying a pre-defined route choice rule. In most DTA models, the departure pattern of given travel demand is predefined and assumed as a fixed pattern, although the departure pattern of driver is changeable depending on a network traffic condition. Especially, for morning peak commute where most drivers have their preferred arrival time, the departure time, therefore, should be modeled as an endogenous variable. In this paper, the authors point out some shortcomings of current DTA model and propose an alternative approach which could overcome the shortcomings of current DTA model. The authors substitute a traditional definition for time-dependent OD table by a new definition in which the time-dependent OD table is defined as arrival time-based one. In addition, the authors develop a new DTA model which is capable of finding an equilibrium departure pattern without the use of schedule delay functions. Three types of objective function for a new DTA framework are proposed, and the solution algorithms for the three objective functions are also explained.

• Journal of Internet Computing and Services
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• v.12 no.3
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• pp.27-36
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• 2011

The sensor nodes of sensor network system are capable of wireless communication with sink nodes. They also acquire and transmit sensor data in broad region where people cannot access easily. However, the transmission of redundant data from sensor nodes reduces the lifetime of the entire system and substantial amount of resulted data needs to be resorted before implementing them to the specific applications. In this paper, the mobile agent middleware to eliminate the redundant sensor data is designed and implemented. In the proposed system, the mobile agent visits the destination sensor nodes according to the migration list offered by the meta table in the name space of the naming agent, eliminates the redundant sensor data corresponding to user condition, and acquires and transmits sensor data according to the purpose and needs. Thus, the excess transmission of the sensor data is avoided and the lifetime of the entire system can be extended. Moreover, the experiments using the mobile agent middleware with the conditions and limitations that are possible in real situation ore done to verify the successful elimination of the redundant sensor data and the efficiency of the data acquisition. Also, we show the potential applicability of the mobile agent middleware in various active sensor networks through the active rule based mobile agent middleware or the interaction with the active rule system.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.3
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• pp.268-274
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• 2013

Any new method for controlling a nonlinear system has widely been reported. An inverted pendulum system has typically been used as a target system for demonstrating its usefulness. In this paper, we propose an algorithm to control a flexible joint cart based inverted pendulum system. Two carts are connected with a spring and one is a driving cart and the other is no driving cart with a pole. We here present a system modeling and a good fuzzy logic based control algorithm. We also introduce LQR (Linar Quadratic Regulator) technique for reducing the number of control variables. By using this technique, the number of input variables for a fuzzy logic controller is become only two not six. So the computational complexity is largely reduced. Moreover, a two-input fuzzy logic controller has a control rule table with a skew-symmetric property. And it will lead the design of a single-input fuzzy logic controller. In order to demonstrate the usefulness of the proposed method and prove the superiority of the proposed method, some computer simulations are presented.

• Journal of Applied Reliability
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• v.15 no.1
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• pp.44-51
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• 2015

In this study, we propose reliability prediction of a satellite by function analysis. To do so, the intended functions of the satellite are derived from using function structure block diagram, and defined as main, sub, and detailed functions. Furthermore, in order to generate function and reliability structure table, reliability model rule, duty cycle, and types of switch are assigned to the classified functions. This study also establishes reliability block diagram and mathematical reliability models to schematize the relationship among the functions. The reliability of the classified function is estimated by calculating the failure rate of parts comprising them. Finally, we apply the proposed method to a small satellite as a case study. The result shows that the reliability for the detailed function and the sub function as well as the main function could be predicted quantitatively and accurately by the proposed approach.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.70-75
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• 2014

Super-resolution near-field structure (super-RENS) read-out samples are affected by a nonlinear and noncausal channel, which results in inter-symbol interference (ISI). In this study, we investigate asymmetry or domain bloom in super-RENS in terms of equalization. Domain bloom is caused by writing process in optical recording. We assume in this work that the asymmetry symbol conversion scheme is to generate asymmetric symbols, and then a linear finite impulse response filter can model the read-out channel. For equalizing this overall nonlinear channel, the read-out signals are deconvolved with the finite impulse response filter and its output is decided based on the decision rule table that is developed from the asymmetry symbol conversion scheme. The proposed equalizer is investigated with the simulations and the real super-RENS samples in terms of raw bit error rate.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.8
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• pp.39-47
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• 1999

This paper describes on-line retrainable RBF network in order to control the coiling temperature for a hot coil strip at Pohang Iron & Steel Company(POSCO). The proposed neural network can be used for improving conventional rule-based lookup table, which generates a heat transmission coefficient. To cope with time-varying characteristics of hot coil process, additional synaptic weights for on-line retraining purposes are introduced to hidden-to-output weights of conventional RBF network. Those weights are locally adjusted to newly incoming test data while preserving old information trained with off-line past data. Hence the effect of catastrophic interference can be greatly alleviated with the proposed network. In addition, rejection scheme is introduced for reliability concerns. From the experimental results applied to the actual process, it is noticed that overall control performance represents about 2.2% increase compared to the conventional one.

• KEPCO Journal on Electric Power and Energy
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• v.3 no.2
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• pp.89-97
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• 2017

The substation is a critical node in the power network where power is transformed in the power generation, transmission and distribution system. The IEC 61850 is a global standard which proposes efficient substation automation by defining interoperable communication and data modelling techniques. In order to achieve this level of interoperability and automation, the IEC 61850 (Part 6) defines System Configuration description Language (SCL). The SCL is an XML based file format for defining the abstract model of primary and secondary substation equipment, communications systems and also the relationship between them. It enables the interoperable exchange of data during substation engineering by standardizing the description of applications at different stages of the engineering process. To achieve the seamless interoperability, multi-vendor devices are required to adhere completely to the IEC 61850. This paper proposes an efficient algorithm required for verifying the interoperability of multi-vendor devices by checking the adherence of the SCL file to specifications of the standard. Our proposed SCL validation algorithm consists of schema validation and other functionalities including information model validation using UML data model, the Vendor Defined Extension model validation, the User Defined Rule validation and the IED Engineering Table (IET) consistency validation. It also integrates the standard UCAIUG (Utility Communication Architecture International Users Group) Procedure validation for quality assurance testing. Our proposed algorithm is not only flexible and efficient in terms of ensuring interoperable functionality of tested devices, it is also convenient for use by system integrators and test engineers.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.1-13
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• 1992

The objective of this study is to develop knowledge-based system for the preliminary design and midship section design of bulk carrier and to enhance the applicability of knowledge engineering in the field of Naval Architecture. First, expert system shell called E.1 is developed in C language. E.1 supports backward-chaining, automatic iteration procedure and reiterative inference mechanism for efficient application of knowledge-based system in structural design. Knowledge representation in E.1 includes IF-THEN rules, 'facts'and 'tables'. Second, knowledge bases for the principal particulars and midship section design are developed by experimental formula, design standard and experiential knowlege. Third, hybrid system combined this knowledge-based system with the optimization program of midship section is developed. Finally, the simplified design method utilizing the regression analysis of the optimum results of stiffened plate is developed for facilitating the design process. Using this knowledge-based system, the design process and results for Bulk carrier and stiffened plates are discussed. It is concluded that knowledge-based system is efficient for preliminary design and midship section design of the ship. It is expected that the performance of the CAD system would be enhanced if the better knowledge-base is accumulated in the E.1 tool.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.245-257
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• 2012

As one of the most challenging tasks in designing the Internet routers, packet classification is required to achieve the wire-speed processing for every incoming packet. Packet classification algorithm which applies binary search on trie levels to the area-based quad-trie is an efficient algorithm. However, it has a problem of unnecessary access to a hash table, even when there is no node in the corresponding level of the trie. In order to avoid the unnecessary off-chip memory access, we proposed an algorithm using Bloom filters along with the binary search on levels to multiple disjoint tries. For ACL, FW, IPC sets with about 1000, 5000, and 10000 rules, performance evaluation result shows that the search performance is improved by 21 to 33 percent by adding Bloom filters.