• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.2
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• pp.62-68
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• 2007

This paper proposes an efficient integer division algorithm for high speed FPGAs' which support built-in RAMs' and multipliers. The integer division algorithm is iterative with RAM-based LUT and multipliers, which minimizes the usage of logic fabric and connection resources. Compared with some popular division algorithms such as division by subtraction or division by multiply-subtraction, the number of iteration is much smaller, so that very low latency can be achieved with pipelined implementations. We have implemented our algorithm in the Xilinx virtex-4 FPGA with VHDL coding and have achieved 300MSPS data rate in 17bit integer division. The algorithm used less than 1/6 of logic slices, 1/4 of the built-in multiply-accumulation units, and 1/3 of the latencies compared with other popular algorithms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.9
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• pp.875-881
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• 2010

During the lunar mission, spacecraft are subject to various unexpected disturbance sources such as third body attraction, solar pressure and operating impulsive maneuver error. Therefore, efficient trajectory correction maneuver (TCM) strategy must be required to follow the designed mission trajectory. In the early days of space exploration, the mission trajectory has been designed by using patched conic approach based on two-body dynamics for the lunar mission. Thus the TCM based on two-body dynamics has been usually adopted. However, with the advanced in computing power, the mission trajectory based on three-body dynamics is attempted recently. Thus, these approaches based on two-body dynamics are essentially different from real environment and large amount of energy for the TCM is required. In this work, we study the trajectory correction maneuver based on three-body dynamics.

• Journal of KIISE
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• v.41 no.11
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• pp.878-884
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• 2014

File I/O buffer cache plays an important role in narrowing the wide speed gap between the main memory and the secondary storage. However, data loss or inconsistencies may occur if the system crashes before the data that has been updated in the buffer cache is flushed to storage. Thus, most operating systems adopt a daemon that periodically flushes dirty data to the secondary storage. In this study, we show that periodic flushes account for 30-70% of the total write traffic to storage and remove this inefficiency by implementing a small, non-volatile buffer cache. Specifically, we present space-efficient management techniques, such as delta-write and fragment-grouping, and show that the storage write traffic and throughput can be improved by a margin of 44.2% and 23.6%, respectively, with only a small NVRAM.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.13-18
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• 2008

The global warming due to greenhouse gases is now the hottest issue all over the world. The world has been under $CO_2$ war since the Kyoto Protocol was opened for signature on December 11, 1997 in Kyoto, Japan. The Kyoto Protocol now covers more than 164 countries globally as of July 2006. Countries that ratify this protocol commit to reduce their $CO_2$ emissions, or engage in emissions trading. Korea is also expected to obey the Protocol starting in 2013, which will give a serious shock especially to the electric power industry. The power plants burning the fossil fuel produce more than 20 percent of national total $CO_2$ emission. This paper resents the calculation of the amount and cost of $CO_2$ emission w.r.t. generator MW output and its application to power system operation. The $CO_2$ emission function is derived using the input-output coefficients of the thermal power plants. The optimal power system operation considering $CO_2$ emission and its cost is demonstrated on a five-bus sample power system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.30-36
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• 2016

In this paper, an Rx-ordering aided sphere decoding algorithm for generalized spatial modulation (GSM) systems is proposed. In the proposed sphere decoding algorithm, to efficiently reduce the search region, the received signals are optimally ordered, which results in the reduction of computational complexity. To evaluate the performance and the computational complexity of the proposed Rx-ordered sphere decoding algorithm, the simulations are performed. In the simulation results, it is observed that in GSM systems, the proposed decoding algorithm achieves the same error performance with the conventional SD, whereas it efficiently decreases the computational complexity for symbol detection.

• The KIPS Transactions:PartD
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• v.10D no.3
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• pp.531-540
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• 2003

Because of the rapid increase of energy consumption, we have some problems such as environmental pollution, global warming, the oil shocks, and so on. To solve these problems, concern about renewable energy such as solar energy, wind force, and water energy is continuously increasing. America, Europe, and Japan have developed a system that manage and utilize the information of the renewable energy resources. However, in the domestic, renewable energy information system was not effectively built yet. Therefore, in this paper, we propose a renewable energy information system, which store and manage solar radiation energy data. We implemented the system using ArcView GIS. Also the system is able to retrieve the information from the energy database through various spatiotemporal queries. In addition, user can identify the results of summary data in the form of chart, graph, and counter line. The implemented system is supplied to the user through the web by ArcIMS.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.467-476
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• 2016

With the development of information technology, Small office Home office(SOHO) is picking up. SOHO generally uses Wi-Fi. The wireless LAN environment using 802.11 protocol is easily affected by DoS attacks. To deal with these threats, there is Wireless Intrusion Detection System(WIDS). However, legacy products of WIDS cannot be easily used by SOHO because they are expensive and require management burden. In this paper, Smart WIDS for SOHO is proposed and implemented on Raspberry Pi2. And, it provides the interface for attack detection notice to android smart phone. Smart WIDS detects Masquerading DoS and Resource Depletion DoS based on IEEE 802.11 so that we notice the attempt of cracking Pre-shared Key(PSK), Man-In-The-Middle(MITM), and service failure.

• The Journal of the Korea Contents Association
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• v.18 no.4
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• pp.178-185
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• 2018

Recently, demands for computer systems with multicore CPUs and high-performance flash-based storage devices (i.e., flash SSD) have rapidly grown in cloud computing, surer-computing, and enterprise storage/database systems. Journaling file systems running on high-performance systems do not exploit the full I/O bandwidth of high-performance SSDs. In this article, we evaluate and analyze the performance of the Linux EXT4 file system with high-performance SSDs and multicore CPUs. The system used in this study has 72 cores and Intel NVMe SSD, and the flash SSD has performance up to 2800/1900 MB/s for sequential read/write operations. Our experimental results show that checkpointing in the EXT4 file system is a major overhead. Furthermore, we optimize the checkpointing procedure and our optimized EXT4 file system shows up to 92% better performance than the original EXT4 file system.

• Journal of KIISE:Software and Applications
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• v.37 no.2
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• pp.120-128
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• 2010

A hypernetwork is a generalized hypo-graph and a probabilistic graphical model based on evolutionary learning. Hypernetwork models have been applied to various domains including pattern recognition and bioinformatics. Nevertheless, conventional hypernetwork models have the limitation that they can manage data with categorical or discrete attibutes only since the learning method of hypernetworks is based on equality comparison of hyperedges with learned data. Therefore, real-valued data need to be discretized by preprocessing before learning with hypernetworks. However, discretization causes inevitable information loss and possible decrease of accuracy in pattern classification. To overcome this weakness, we propose a novel feature-wise L1-distance based method for real-valued attributes in learning hypernetwork models in this study. We show that the proposed model improves the classification accuracy compared with conventional hypernetworks and it shows competitive performance over other machine learning methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1035-1041
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• 2004

Currently users are tend to use multimedia data types in their applications. Main features of multimedia data types are large amount of data compared to conventional data types. In this reason, it's hard to load data into main memory and to search. That is the cause of occur disk input and output frequently, and decrease the system performance. In this paper, we describe to have fast and efficient access to multimedia data using index technique. Index method presented by paper consists of two parts : one is index file part for keywords and the other is posting file part for the list of file names. Of course, we use keyword. But user is not charge of memory for the keywords. Users just use natural language to insert, delete and search data what he or she wants. Internally, System makes keywords from natural language to get access to multimedia data. It provides convenience to users. Using this study to develop one's application for multimedia, one may have a chance for advanced performance of a system and getting a result speedily.