• KNOM Review
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• v.22 no.1
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• pp.52-59
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• 2019

As the video streaming service are supported by various devices, the amount of usage increases and efforts to improve the service from the viewpoint of users have continued. When a user watches a video, a response time occurs from input to playback, and if this response time becomes longer, the user's service satisfaction decreases. In this paper, we are proposing a method prefetching each user's preference video data obtained by analyzing user's past history record to the device for reducing the response time. We will show the result that prefetching data can improve the response time to 41% at most. And we analyzed real-video streaming viewing record and got each user's preferred video list. We investigated the change of response time according to a hit-ratio and amount of overhead data that was prefetched to the device, but not viewed. It was shown that as the hit-ratio grows bigger, the improvement of response time becomes more effective.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.523-532
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• 2006

It is thought that the suggestion of efficient and rational design guideline based on the behavior evaluation of bridge structure system the included cross beam is necessary for the construction efficiency of two-I girder steel bridges. Therefore, in this study, the effects of influence parameters are investigated by the behavior analyses of the bridges, in which the influence parameters are location, spacing and rigidity of the cross beam. For this study, the existed two-I girder steel bridges firstly were selected with the model of case study and the FE analyses for some case models were performed to estimate the action of the cross beam in the bridge. From the analyses, it was estimated that if it consider local stress and load distribution of a floor system, shell and solid elements are compatible to modeling of the cross beams. Also, the efficient design guideline for the cross beam of two-I girder steel bridge was suggested from parameter studies used location, spacing and rigidity of the cross beam.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.527-536
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• 2005

A method of reinforcement using external tendons has been found to be one of the effective techniques of reinforcement and its application is increasing. In this paper, the method to calculate the initial tendon force is proposed for the improvement of load-carrying capacity in existing steel-concrete composite bridges. An equation for the increment of tendon force was derived for tendon configurations and live load types, and the effect of reinforcement in a composite beam was numerically studied. The method to calculate the number of tendon and initial tendon force was presented by proposing the new method to calculate the rating factor, which considers the increment of tendon force. The method was shown to be effective for an existing steel-concrete bridge.

• Journal of KIISE:Databases
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• v.32 no.4
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• pp.416-428
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• 2005

In the paper we propose an index method for XML streaming services, where a server broadcasts XML data to a lot of clients in wireless information systems. In order to control the access and tuning time of mobile clients, the proposed method constructs the XML stream through replicating partial index intermixed with parts of data. For this purpose, we propose a two-level tree structure for separating index and XML data into two parts: replicated vs. non-replicated. We analyze the performance of the proposed method with respect to access time and tuning time. With the analysis result, we derive the optimal level value.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.378-386
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• 2014

In this study, the characteristics of the current and wind forces acting on two floating bodies were numerically investigated using a commercial CFD software, STAR-CCM+. In the numerical analyses, LNGC was located right behind FSRU under uniform current or wind conditions. Steady calculations were carried out using a Reynolds averaged Navier-Stokes (RANS) solver and the realized k-epsilon model. First, the current coefficients of FSRU based only the CFD were compared with the model test data. Through this comparison, the present numerical models and mesh systems were indirectly verified. Next, computations for FSRU and LNGC in a uniform current were performed using different relative positions. It was found that the current coefficients were great affected by the longitudinal positions. Finally, the wind forces acting on FSRU and LNGC in tandem configurations were studied. The focus was on the shielding effects due to the aerodynamic interactions between FSRU and LNGC.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.3
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• pp.230-238
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• 2003

In this paper, Inverter drives adopting 2 phase space vector SRP-PWM (Separately Randomized Pulse Position PWM) with fixed switching frequency is proposed. The proposed 2 phase space vector SRP-PWM scheme is based on the 3 phase SRP-PWM. In the proposed SRP-PWM scheme, each of two phase pulses is located randomly in each switching interval. The experimental results show that the voltage and acoustic noise harmonics are spread to a wide band area. Also, the performance of the proposed 2 phase SRP-PWM and the conventional center aligned SVM are compared to each other. In result, the speed response is nearly similar to each other from the viewpoint of the v/f constant control.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.10
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• pp.2247-2256
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• 2011

In this paper, we propose a coordinator-based reader protocol that can avoid reader collisions in a passive RFID system. In a proposed protocol, unlike conventional protocols that a reader itself selects its own slot randomly to communicate with tags such as DCS, Colorwave, a coordinator reader allocates an unused slot to a reader to participate in the network and sends a current slot number. A reader allocated a slot can communicate with tags. The proposed protocol can adaptively modified to apply for multiple coordinator readers environment in a wide area. This causes reader collision problem, but can be alleviated partly by applying the frequency planning. In this way, we verifies that a RFID system using the proposed protocol is three to five times better than existing systems through the simulation.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.6
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• pp.11-18
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• 2005

In this paper, English pronunciation system and the methods of its notations which is used in the internet web sites or in electronic English dictionaries are analyzed and new font table and its key layout are presented to input it efficiently. By using this method, English pronunciation can be inputted to the spreadsheets, databases and presentations as well as word-processors, and each application program's data can have compatibility. Furthermore, it can have compatibility within another type of computers and increase inputting speed. In the result of experiments, every data can have the compatibility in all of application programs and inputting speed is increased highly compare with using the pre-existing functions of word-processors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.3
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• pp.49-55
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• 2003

This paper studied characteristics of surface discharge and tracking phenomena on the surface of solid insulators in Liquid Nitrogen(LN2) noticed as a cooling medium of high temperature superconductor. In order to investigate the bubble effect which have much influence on electric surface discharge in Liquid Nitrogen, knife type electrode and plane electrode were formed oppositely with A-mode, B-mode and C-mode configuration. It is considered that these result are fundamental data for electric insulation design of superconductor and cryogenic application machinery which will be studied and developed in the future.

• Journal of the Korea Society for Simulation
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• v.25 no.4
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• pp.1-12
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• 2016

The industry producing the parts of aircraft engines is a traditional order-made system with highly variety and small quantity, and the manufacturing system is the typical job shop with identical or non-identical multiple machines in a workstation. Furthermore, there are many alternative operations and alternative machines allowed in machining processes, and tremendous routings and assembly operations should be considered. Usually simulation is the most efficient technology to analyze such a complex system, and high modeling skills are required for developing the simulation models. In this paper, a case study on a company which produces the parts of aircraft engines is introduced, specially focused on simulation modeling methodologies for the complex system.