• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.488.1-488.1
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• 2014

As the society demands the high performance energy storage devices, development of efficient and renewable energy storage materials has been a topic of interest. Here, we report pseudocapacitive behaviors of biopolymer (lignin) that was confined onto reduced graphene oxides (RGOs) for a renewable energy storage system. The strong surface confinement of quinone groups onto the electroconductive RGOs created the renewable hybrid electrodes for supercapacitors (SCs) with fast and reversible redox charge transfer. As a result, the pseudocapacitors fabricated with the hybrid electrodes of lignin and RGO presented the outstanding electrochemical performances of remarkable rate and cyclic performances:~4% capacitance drop after 3000 cycles and a maximum capacitance of 432 F g-1.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5290-5304
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• 2016

With the growth of the massive amount of data, the failure probability of the cloud storage node is becoming more and more big. A single fault tolerance strategy, such as replication and erasure codes, has some unavoidable disadvantages, which can not meet the needs of the today's fault tolerance. Therefore, according to the file access frequency and size, an adaptive hybrid redundant fault tolerance strategy is proposed, which can dynamically change between the replication scheme and erasure codes scheme throughout the lifecycle. The experimental results show that the proposed scheme can not only save the storage space(reduced by 32% compared with replication), but also ensure the fast recovery of the node failures(increased by 42% compared with erasure codes).

• Journal of Information Processing Systems
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• v.15 no.6
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• pp.1265-1276
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• 2019

Data deduplication is a common method to improve cloud storage efficiency and save network communication bandwidth, but it also brings a series of problems such as privacy disclosure and dictionary attacks. This paper proposes a secure deduplication scheme for cloud storage based on Bloom filter, and dynamically extends the standard Bloom filter. A public dynamic Bloom filter array (PDBFA) is constructed, which improves the efficiency of ownership proof, realizes the fast detection of duplicate data blocks and reduces the false positive rate of the system. In addition, in the process of file encryption and upload, the convergent key is encrypted twice, which can effectively prevent violent dictionary attacks. The experimental results show that the PDBFA scheme has the characteristics of low computational overhead and low false positive rate.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.248-254
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• 2010

This paper deals with implementation of the laboratory-scale microgrid using energy storage system. Also, this paper develops a simulation model of the microgrid with same parameters on the laboratory-scale microgrid using PSCAD/EMTDC. The experimental results show good agreement with the simulation results. This shows the validity of the simulation model. A valve regulated lead acid (VRLA) battery is used to store energy. Energy storage system with fast response is able to maintain power quality of sensitive load within the microgrid.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.25-31
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• 2021

This paper describes the design of a power cell-based pulsed power modulator with fast rise times. The pulse-generating section of the pulse power modulator is a series stack of power cells. Each power cell is composed of a storage capacitor, a pulse switch, and a bypass diode. When the pulse switches are turned on, the capacitors are connected in series and the sum of voltages is applied to the load. For output pulses with fast rise times, an IGBT with fast turn-on characteristics is adopted as a pulse switch and the optimized gate driving method is used. Pspice simulation is performed to account for the gate driving method. A 10 kV, 12-power cell-based pulsed power modulator is tested under resistive load and plasma reactor load. The rise times of output pulses less than 20 ns are confirmed, showing that the pulsed power modulator can be effectively applied to pulsed power applications with fast rise times.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.51-56
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• 2009

Flash memory has rapidly deployed as data storage. However, the flash memory has a major disadvantage that recorded data cannot be dynamically overwritten. In order to solve this "erase-before-write" problem, the log block buffer scheme used Flash memory file system. however, the current managements of the log buffer, in case random write pattern, BAST technique have problem of frequent merge operation, but FAST technique don't consider merge operation by frequently updated data. Previous methods not consider merge operation cost and frequently updated data. In this paper, we propose a new log buffer management scheme, called JBB. Our proposed method evaluates the worth of the merge of log blocks, so we conducts the merge operation between infrequently updated data and its data blocks, and postpone the merge operation between frequently updated data and its data blocks. Through the method, we prevent the unnecessary merge operations, reduce the number of the erase operation, and improve the utilization of the flash memory storage. We show the superiority of our proposed method through the performance evaluation with BAST and FAST.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.336-341
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• 2010

The burning interruption between the initiator and the delay column in a Zr-Ni K1 delay system used for a K510 fuze occurs with long-time storage. About 10 % failure probability of 15-years stored delay systems shows the failure mode in open literature. This paper shows storage lifetime improvement results for the delay system through changing the single-base delay column into double-base ones and controlling the manufacturing processes especially the initial inclusion of humidity. The double-base delay columns was implemented by inserting one delay column of fast burning rates between the initiator and the previous delay column of slow burning rates. Accelerated aging tests of the delay systems with double-base columns, and then the firing tests were performed to evaluate the improved lifetime. The double-base delay columns shows improved storage lifetime of the delay system through preventing the failure mode.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.9
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• pp.8-12
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• 2015

A Holographic data storage has some advantage of fast transmission, short access time and high storage capacity. However, it has several problems such as inter-symbol interference, inter-page interference and misalignment. Especially, for multi-level holographic data storage system, since one pixel contains more than 1bit, the system is more vulnerable to the error. In this paper, we propose a 3/4 modulation code which mitigate inter-symbol interference for 4-level holographic data storage.

• Korean journal of food and cookery science
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• v.21 no.2 s.86
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• pp.217-224
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• 2005

The storage characteristics of frozen soy yogurt prepared with hydrolyzed soy protein isolates were evaluated. In order to facilitate lactic fermentation bacteria grow and produce lactic acid as fast rate as possible, soy protein isolate(SPI) was hydrolyzed using two kinds of proteases; bromelain and a-chymotrypsin. The cultural systems employed thereafter for lactic fermentations were Bifidobacterium bifidum or B. bifidum and Lactobacillus bulgaricus. The viable cell counts, normal- and bile acid tolerances from the mixed cultures of B. bifidum and L. bulgaricus decreased sharply during the initial first 3 days of frozen storage and then showed a gradual decrease thereafter. Melt-down percent of the all frozen products have been favorably affected as was shown by less melting at raised testing temperature during 28 days of frozen storage except for the initial 3 days during which a minor change has been observed. Among the various volatile flavor components, the contents of acetaldehyde, acetone, diacetyl and methanol generally increased during the frozen storage. In sensory test, the frozen soy yogurt prepared with a-chymotrypsin and mixed culture of B. bifidum and L. bulgaricus was the most desirable, the highest scores in sourness, bitterness and mouthfeel.

• The Journal of the Korea Contents Association
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• v.5 no.1
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• pp.217-227
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• 2005

In this paper, we present the result of an efficient implementation of DirectX-based multichannel visual monitoring system and the performance analysis of it. Our proposed system mainly consists of three subsystems: display, storage, and retrieval/playback. The display subsystem is designed to utilize efficiently H/W acceleration, overlay and flip of DirectX for faster real-time display, display synchronization among channels, and improvement of tearing artifact. For the performance improvement of storage speed, the storage subsystem is designed and implemented in DirectShow Filter-based multithreading architecture so that it can store multichannel video streams efficiently in each channel with minimizing data bottleneck among channels. In the retrieval and playback subsystem, efficient index file architecture and video data storage architecture, efficient playback architecture which can make playback be processed parallel among channels are designed and implemented for faster retrieval and playback,. Through experiments, our proposed system is shown to be maximally 2 times as fast in storaging speed and maximally 3.5 times as fast in retrieval and playback speed as the previous system.