• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.289-298
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• 2000

In order to minimize the impact of water hammer In a pipeline, a determination of optimum position of hydraulic structures with best operation of pressure relief valve was explored at the Seobyun pumping station. Method of characteristics is used to simulate a surge impact originating from abrupt stop of pumping operation in a pipeline. Genetic algorithm shows a powerful capability in searching a global solution, especially for a nonlinear problem The application results suggests that the maximum positive pressure can be relaxed by decreasing the opening time of pressure relief valve, meanwhile the maximum negative pressure can be relaxed by increasing the opening time of pressure relief valve. This study shows that the integration of a genetic algorithm with a transient analysis technique such as method of characteristic can improve the design of hydraulic structure in a pipe network.

• Journal of Energy Engineering
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• v.29 no.1
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• pp.44-51
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• 2020

The importance of ESS has been emphasized due to stabilization of power demand due to deterioration of network reliability and expansion of renewable energy sources. ESS (Energy Storage System) stores the remaining power and uses it when necessary to meet the power demand, and build the ESS system mainly in conjunction with solar and wind power. In this paper, we propose a home PV Charging Module using the Master-Slave method which is effective for low insolation. After designing the module, Fast MPPT algorithm is applied to generate the maximum output from the nonlinear output characteristics of the PV modules. The average power value for the input of PV Charging Module was 296.90 W and the output power was 289.60 W, which averaged 97.54%.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.4
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• pp.169-175
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• 2005

In recent, implementation of the embedded system is gradually in the spotlight of world-wide by information technology(IT) engineers. By this time, an implementation of real time system is limited on image acquisition and processing system in practical. In this paper, the USB camera interface system based on the embedded linux OS is implemented using USB 2.0 camera with low cost. This system can obtain image signals into the memory via X-hyper255B processor from USB camera. It is need to initialize USB camera by the Video4Linux for the kernel device driver. From the system image capturing and image processing can be performed. It is confirmed that the image data can be transformed to packet of Network File System(NFS) and connected to the internetwork, then the data can be monitored from the client computer connected to the internetwork.

• The Journal of the Korea Contents Association
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• v.12 no.9
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• pp.16-26
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• 2012

A path generation method considering the tendencies of users is required because users has the preferred routes through the properties such as time, distance, and congest. The existing method must input the additional information about user's tendency to generate path considering moving tendencies. However, mobile device have the inconvenient interface. Therefore users are reluctant to input additional information for path generation. In this paper, we propose the path generation method considering the tendencies of users without additional input of users tendencies. To show the superiority of the proposed method, we compared it with shortest distance or time path through performance evaluation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8B
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• pp.507-513
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• 2005

As the rapid increasement of the number of internet users has occured recently, many multimedia application services have been emerging. To improve quality of service, traffic can be suggested to be classified with priority in EPON(Ethernet Passive Optical Network), which is supporting the multimedia application services. In this paper, multimedia application services treat bandwidth classifying device in serving both delay sensitive traffic for real-time audio, video and voice data such as Von(Voice over Internet Protocol), and for real-time traffic such as BE(Best Effort). With looking through existing mechanisms, new mechanism to improve the quality will be suggested. The delay performances and packet losses of traffic achieved by supporting bandwidth allocation of upstream traffic in suggested mechanism will be analized with simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12B
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• pp.1236-1243
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• 2010

The perimeter defense system was created and its characteristics were evaluated. It was designed to utilize the fiber sensing device, namely OTDR(Optical Time Domain Reflectometer) which has been used for the maintenance of the optical communication network. An OTDR was constituted by a pulse laser with the nature of 1310nm, +15dBm for the observation of 400 meter optical fence. The high-speed 32-bit processor(S3C2440) has applied to MPU(Main Processor Unit) which helps to improve the performance of OTDR algorithms. Consequently, the maximum error was 0.84 meter on the performance test of the 10km monitoring and the pass criteria of ${\pm}1m$ satisfied in all the sections. The alarm delay time was under 3 sec after detecting the disorder. For the case of secondary trespassing after primary trespassing, the optical switch was installed in OTDR to monitor the secondary trespassing and to measure the multi-point detection. Therefore, this paper shows that the detections of secondary trespassing and multi-point is possible by means of optical switch.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.2
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• pp.47-54
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• 1990

In this paper, we design the 4-bit phase shifter which have $22.5^{\circ},45^{\circ},90^{\circ}$ and $180^{\circ}$ phase shift by applying the loaded line and switched network phase shifter. Its phase shift is variable with changing of the stub and passive device parameters. The experiments show the 6.5 dB average insertion loss and $10^{\circ}$ average phase error at center frequency, 6GHz. The results of experiment agree well with the theories except $180^{\circ}$ phase shifter.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.183-195
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• 2014

This study aims at identifying and prioritizing the application areas for business development of IoT(Internet of Things). In specific, we collected the opinions of the experts on IoT in Korea through the survey based on pairwise comparison, and then we analyzed them using AHP(analytic hierarchy process). As a result, we found that 'Public Safety & Security', 'Automotive & Transportation', and 'Utility & Energy' are the most promising area in realizing IoT-related businesses. Also, we found that the experts had different views according to the positions of their industry in IoT value chain. The analysis showed that the device industry prioritizes 'Public Safety & Security', whereas the network industry does 'Automotive & Transportation'. The experts from the service industry were found to regard 'Utility and Energy' as the most promising commercialization area of IoT.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.324-327
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• 2013

Recently, due to evolving cloud computing technology, we can easily and transparently utilize both local computing resource and remote computing resource in real life. Especially, enhancing smart device technologies and network infrastructures promote an increase of needs to share files between local smart devices and cloud storages. However, since smart devices have a limited storage space, storing files on cloud storage causes a starvation problem of local storage. It means that users can face a storage-lack problem even a cloud storage service provide a huge file storing space. In this research, we propose a method to manage files between smart devices and cloud storages. Our approach calculate file usage pattern based on recently used date, and then this approach determines local files being migrated. As a result, our approach is sufficient for handling data synchronization between big data storage farm and local thin client which contains limited storage space.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.5
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• pp.39-43
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• 2020

In this paper, we propose the multi-channel interference cancellation algorithm for visible light communication (VLC) in smart building. The VLC system is communication technology using visible rays that come out in Light Emitting Diode (LED) device. It has energy curtailment effect and possible to use in ubiquitous network service applications. When a large number of users communicate indoors, the performance can be reduced due to channel interference. To remove interference, at the first, the minimum mean square error (MMSE) scheme as interference cancellation methods used, and then the successive interference cancellation (SIC) is applied to obtain additional diversity gain and improve interference cancellation performance. Indoor VLC channel model is employed. The performance is evaluated in terms of bit error rate (BER). From the simulation results, it is confirmed that the proposed scheme has better BER performance compared to the previous systems. As a result, the proposed interference cancellation improves the signal quality of VLC systems by effectively removing the channel noise. The results of the paper can be applied to VLC for smart building and general communication systems.