• Transactions of the Society of Information Storage Systems
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• v.9 no.2
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• pp.42-47
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• 2013

In this study, we have experimentally analyzed how the surface properties of transparent electrode layer influence the photovoltaic performance of bulk heterojunction organic solar cell by the contact angle measurement and X-ray photoelectron spectroscopy(XPS) observation. As a result, the power conversion efficiency of test devices improved from 0.64% to 1.83% and 2.15% by UV-ozone exposure and $O_2$ plasma treatment, respectively. Thus, we conclude that the surface activation process is very important for better performance and stability in addition to the cleaning process of carbonate residue on the surface.

• Composites Research
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• v.37 no.1
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• pp.32-39
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• 2024

Solid-state hydrogen storage is gaining prominence as a crucial subject in advancing the hydrogen-based economy and innovating energy storage technology. This storage method shows superior characteristics in terms of safety, storage, and operational efficiency compared to existing methods such as compression and liquefied hydrogen storage. In this study, we aim to evaluate the solid hydrogen storage performance on the nanotube surface by various structural design factors. This is accomplished through molecular dynamics simulations (MD) with the aim of uncovering the underlying ism. The simulation incorporates diverse carbon nanotubes (CNTs) - encompassing various diameters, multi-walled structures (MWNT), single-walled structures (SWNT), and boron-nitrogen nanotubes (BNNT). Analyzing the storage and effective release of hydrogen under different conditions via the radial density function (RDF) revealed that a reduction in radius and the implementation of a double-wall configuration contribute to heightened solid hydrogen storage. While the hydrogen storage capacity of boron-nitrogen nanotubes falls short of that of carbon nanotubes, they notably surpass carbon nanotubes in terms of effective hydrogen storage capacity.

• ETRI Journal
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• v.35 no.1
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• pp.69-79
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• 2013

For real-time interactive multimedia operations, such as video uploading, video play, fast-forward, and fast-rewind, solid state disk (SSD)-based storage systems for video streaming servers are becoming more important. Random access rates in storage systems increase significantly with the number of users; it is thus difficult to simultaneously serve many users with HDD-based storage systems, which have low random access performance. Because there is no mechanical operation in NAND flash-based SSDs, they outperform HDDs in terms of flexible random access operation. In addition, due to the multichannel architecture of SSDs, they perform similarly to HDDs in terms of sequential access. In this paper, we propose a new SSD-based storage system for interactive media servers. Based on the proposed method, it is possible to maximize the channel utilization of the SSD's multichannel architecture. Accordingly, we can improve the performance of SSD-based storage systems for interactive media operations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4063-4086
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• 2016

Cloud computing is a robust technology, which facilitate to resolve many parallel distributed computing issues in the modern Big Data environment. Hadoop is an ecosystem, which process large data-sets in distributed computing environment. The HDFS is a filesystem of Hadoop, which process data blocks to the cluster nodes. The data block placement has become a bottleneck to overall performance in a Hadoop cluster. The current placement policy assumes that, all Datanodes have equal computing capacity to process data blocks. This computing capacity includes availability of same storage media and same processing performances of a node. As a result, Hadoop cluster performance gets effected with unbalanced workloads, inefficient storage-tier, network traffic congestion and HDFS integrity issues. This paper proposes a storage-tier-aware Robust Data Placement (RDP) scheme, which systematically resolves unbalanced workloads, reduces network congestion to an optimal state, utilizes storage-tier in a useful manner and minimizes the HDFS integrity issues. The experimental results show that the proposed approach reduced unbalanced workload issue to 72%. Moreover, the presented approach resolve storage-tier compatibility problem to 81% by predicting storage for block jobs and improved overall data block placement by 78% through pre-calculated computing capacity allocations and execution of map files over respective Namenode and Datanodes.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.763-765
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• 2005

In the area of remote sensing, an immense number of images are continuously generated by various remote sensing systems. These images must then be managed by a database system efficient storage and retrieval. There are many types of image database systems, among which the content-based image retrieval (CBIR) system is the most advanced. CBIR utilizes the metadata of images including the feature data for indexing and searching images. Therefore, the performance of image retrieval is significantly affected by the storage method of the image metadata. There are many features of images such as color, texture, and shape. We mainly consider the shape feature because shape can be identified in any remote sensing while color does not always necessarily appear in some remote sensing. In this paper, we propose a metadata representation and storage method for image search based on shape features. First, we extend MPEG-7 to describe the shape features which are not defined in the MPEG-7 standard. Second, we design a storage schema for storing images and their metadata in a relational database system. Then, we propose an efficient storage method for managing the shape feature data using a Wavelet technique. Finally, we provide the performance results of our proposed storage method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.341-346
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• 2005

The simplification of solar thermal systems reduces the possibility of operating trouble and lowers the cost of the initial investment and maintenance. This also leads to increased competitiveness in the energy market. We proposed a spiral-jacketed storage tank that functions both as a heat exchanger and expansion tank, which removes the secondary piping and markedly simplifies the entire system. The new storage tank was designed and manufactured to maintain the same performance as the conventional system and the exiting system was remodelled by adopting the newly proposed storage tank. This experiment was conducted under real conditions over a period of several months. The retrofitted system with the spiral-jacketed storage tank showed good performance that is on a similar level as the previous system having a typical storage tank and heat exchanger.

• Transactions of the Society of Information Storage Systems
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• v.3 no.1
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• pp.5-12
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• 2007

This paper investigates the design of disturbance observer for rotational vibration suppression in disk drive systems. The design aims to provide an optimal controller which satisfies both vibration performance and robust stability. It consists of an inversion method, a special filter, and optimization scheme. Firstly a new inversion method is introduced, which provides more accurate inversion compared to conventional zero phase error method. The inversion is to deal with unstable zeros in the plant model. Secondly a special filter for disturbance selection is given, which features adjustable gain and band pass characteristics so that it enables flexible shaping of the loop considering the trade-off between performance and stability margins. And finally the parameters of disturbance observer are optimized in conjunction with external disturbance model. Simulation and experiment on commercial hard disk drives confirm that the design is very effective to such disturbance which is hard to be handled by conventional approach.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.

• Journal of the Korean Solar Energy Society
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• v.35 no.6
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• pp.25-33
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• 2015

In this study, heating performance of the air-cooled heat pump with vapor-injection (VI) cycles, re-heater and solar heat storage tank was investigated experimentally. Devices used in the experiment were comprised of a VI compressor, re-heater, economizer, variable evaporator, flat-plate solar collector for hot water, thermal storage tank, etc. As working fluid, refrigerant R410A for heat pump and propylene glycol (PG) for solar collector were used. In this experiment, heating performance was compared by three cycles, A, B and C. In case of Cycle B, heat exchange was conducted between VI suction refrigerant and inlet refrigerant of condenser by re-heater (Re-heater in Fig. 3, No. 3) (Cycle B), and Cycle A was not use re-heater on the same operating conditions. In case of Cycle C, outlet refrigerant from evaporator go to thermal storage tank for getting a thermal energy from solar thermal storage tank while re-heater also used. As a result, Cycle C reached the target temperature of water in a shorter time than Cycle B and Cycle A. In addition, it was founded that, as for the coefficient of heating performance($COP_h$), the performance in Cycle C was improved by 13.6% higher than the performance of Cycle B shown the average $COP_h$ of 3.0 and by 18.9% higher than the performance of Cycle A shown the average $COP_h$ of 2.86. From this results, It was confirmed that the performance of heat pump system with refrigerant re-heater and VI cycle can be improved by applying solar thermal energy as an auxiliary heat source.

• Journal of Internet Computing and Services
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• v.4 no.1
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• pp.53-65
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• 2003

I/O processing speed of relatively sluggish storage devices incurs overall performance degradation in computer systems. As a solution to improve the situation, SAN(Storage Area Network) has been proposed. In order to utilize a SAN system more effectively, where storage devices are directly connected with a high speed network such as Fibre Channel, a proper management tool is needed. In this paper, we present a design and implementation of a performance monitoring and configuration management tool for the SANtopia system which supports global file sharing in the SAN environment The developed tool is to monitor the performance of the Linux hosts composing the SANtopia system and to manage the configuration of the hosts and storage devices. It also supports GUI(Graphic User Interface) environment using the JAVA programming language.