• Journal of The Korean Astronomical Society
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• v.32 no.2
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• pp.137-147
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• 1999

Recent studies show the importance of understanding three-dimensional magnetic reconnect ion on the solar surface. For this purpose, I consider non-coplanar magnetic reconnection, a simple case of three-dimensional reconnect ion driven by a collision of two straight flux tubes which are not on the same plane initially. The relative angle e between the two tubes characterizes such reconnection, and can be regarded as a measure of magnetic shear. The observable characteristics of non-coplanar reconnection are compared between the two cases of small and large angles. An important feature of the non-coplanar reconnect ion is that magnetic twist can be produced via the re-ordering of field lines. This is a consequence of the conversion of mutual helicity into self helicities by reconnection. It is shown that the principle of energy conservation when combined with the production of magnetic twist puts a low limit on the relative angle between two flux tubes for reconnect ion to occur. I provide several observations supporting the magnetic twist generation by reconnection, and discuss its physical implications for the origin of magnetic twist on the solar surface and the problem of coronal heating.

• Communications for Statistical Applications and Methods
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• v.10 no.2
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• pp.507-517
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• 2003

Self-organizing map (SOM) has been developed mainly by T. Kohonen and his colleagues as a unsupervised learning neural network. Because of its topological ordering property, SOM is known to be very useful in pattern recognition and text information retrieval areas. Recently, data miners use Kohonen´s mapping method frequently in exploratory analyses of large data sets. One problem facing SOM builder is that there exists no sensible criterion for evaluating goodness-of-fit of the map at hand. In this short communication, we propose valid evaluation procedures for the Kohonen SOM of any size. The methods can be used in selecting the best map among several candidates.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.11
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• pp.753-761
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• 1988

Partial Matrix Refactorization (PR) has been available for refactorization repeatedly. But this paper aims to present Modified PR(MPR), which is faster in (re) factorization speed and simpler in program than PR, but storage is almost as big as that of PR. MPR substitutes refactorization process of PR1 for Modifide Trifactortzation (MT) and, instead of PR 2, adds to PR1 the algoritm that calculates modified element values of modified row / cols. MT, which is subalgorithm for MPR, simplifies the algorithm by applying information vectors to currently used Trifactorization, and trifactorizes and refactorizes in high speed. The test results of Fast Decoupled Load Flow (FDLF) and Contingency Analysis useing Indexing Scheme and Optimal Ordering also prove that MPR is faster than PR.

• Journal of KIISE:Databases
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• v.29 no.1
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• pp.44-57
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• 2002

Multiple spatial queries are defined as two or more spatial range queries to be executed at the same time. The primary processing of internet-based map services is to simultaneously execute multiple spatial queries. To improve the throughput of multiple queries, the time of disk I/O in processing spatial queries significantly should be reduced. The declustering scheme of a spatial dataset of the MIMD architecture cannot decrease the disk I/O time because of random seeks for processing multiple queries. This thesis presents query scheduling strategies to ease the problem of inter-query random seeks. Query scheduling is achieved by dynamically re-ordering the priority of the queued spatial queries. The re-ordering of multiple queries is based on the inter-query spatial relationship and the latency of query processing. The performance test shows that the time of multiple query processing with query scheduling can be significantly reduced by easing inter-query random seeks as a consequence of enhanced hit ratio of disk cache.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.519-536
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• 2007

In this paper, we combine the Hybrid-Automatic Repeat reQuest (HARQ) algorithm with joint Tx and Rx antenna selection based on the reliability of the individual antennas links. The cyclic redundancy check (CRC) is applied on the data before being encoded using the Turbo encoder. In the receiver the CRC is used to detect errors of each antenna stream and to decide whether a retransmission is required or not. The receiver feeds back the transmitter with the Tx antennas ordering and the acknowledgement of each antenna (ACK or NACK). If the number of ACK antennas is higher than the NACK antennas, then the retransmission takes place from the ACK antennas using the Chase Combining (CC). If the number of the NACK antennas is higher than the ACK antennas then the ACK antennas are used to retransmit the data streams using the CC algorithm and additional NACK antennas are used to retransmit the remaining streams using Incremental Redundancy (IR, i.e. the encoder rate is reduced). Furthermore, the HARQ is used with the I-BLAST (Iterative-BLAST) which grantees a high transmission rate.

• Journal of Broadcast Engineering
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• v.20 no.6
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• pp.921-927
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• 2015

In this paper, we propose a novel design scheme for the operation of Decoded Picture Buffer (DPB) including reference picture re-ordering, marking process, and reference picture list construction to perform an efficient scalable multi-view video coding. Extensive simulations show that the proposed method can provide improved compression efficiency and improved video quality measured in terms of BD-Rate and BD-PSNR for the scalable multi-view video coding.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.4
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• pp.291-297
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• 2014

A Design of Experiments(DOE) approach to an experimental study of fuselage drag and stability characteristics of a helicopter configuration was applied to achieve an accuracy improvement in the wind tunnel testing. The impact of blocking the test was assessed by comparing the ANOVA table for the blocked and unblocked cases. For a second-order response model, the role of blocking resulted in a substantial increase in the accuracy of test results. These accuracy improvement could be achieved through randomization, blocking, and replication of the data points i.e. a re-ordering of the test sequence where the data were acquired.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.565-565
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• 2004

Due to limitation of resources and increasing concerns about environment, reverse logistics has received growing attention in recent years. In this paper, we propose three types of reverse logistics networks based on reuse of returnable containers, materials recycling process and remanufacturing for parts reuse. First, the sender in the re-usable item network supplies containers for the recipient and orders either new containers from external supplier or returnable containers cleaned from the container depot. Second, the recycling center in the proposed recycling network collects either end of life products from customer or faulty goods from manufacturer, collected products are dismantled into materials and materials go into recycling process. Finally, the manufacturer in the proposed remanufacturing network has two alternatives for supplying parts: either ordering the required parts to external supplier or overhauling disassembled parts and bringing them back 'as new' conditions. In this product recovery environment, we build optimal order quantity models to minimize the total logistics costs related to reverse logistics network. The validity of the proposed model is investigated through comprehensive computational experiments.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.200-203
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• 2003

By minimizing the burst error of data and correcting the error, we can define the convolution coding and interleaving in IEEE 802.11a wireless tan system. Two step block interleaver was decided by coded bits per OFDM symbol and due to this it comes to the delay time in IEEE 802.11a. This is the point of the question which we must consider. We try to decrease the delay time by all 48-clock from interleavings, and we have proposed a way carried out the interleaving outputs per symbol. So in comparison with the existing interleaver, we can decrease the delay time in reading and writing data, as well as reduce the delay time of bit re-ordering per symbol. Also this scheme is apply in all x-QAM cases.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1190-1193
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• 2009

최근 무선네트워크의 급격한 발달로 이동 중에도 통신을 할 수 있는 요구사항에 IETF에서는 Mobile IPv6(MIPv6)라는 기술을 제안하였다. MIPv6는 IPv6환경에서 모바일 노드(모바일 노드)가 이동을 하면서도 통신을 할 수 있는 기술인데, 실제 상용망에서는 사용되지 않고 있다. 그 이유는 모바일 노드에 이동성을 제공하는 모바일 스택의 탑재가 높은 오버헤드를 가지고 있고, 시그널링 비용이 많이 들기때문이다. 이와 같은 문제를 해결하기 위해서 지난 해 Proxy Mobile IPv6(PMIPv6)가 표준화 되었다. PMIPv6는 모바일 노드에 이동성을 제공하는 모바일 스택을 올리지 않고 네트워크 엔티티가 대신 모바일 스택을 가지고 시그널링을 처리하기 때문에 결과적으로 시그널링 비용을 줄였다. 하지만 PMIPv6에서는 인접한 네트워크 사이에서 패킷을 전송할 때 MAG간의 통신이 가능하지 않고, 오직 LMA를 통하여 대응 노드(대응 노드)에게 패킷을 전송할 수 있다. 게다가 같은 서브넷에 있는 대응 노드에게 패킷을 전송할 때도 LMA를 거치게 되는 불필요한 과정이 발생한다. 게다가 LMA를 통하여 패킷을 전송하는 방식은 지연과 리오더링(Re-Ordering)을 발생시켜본 패킷 재전송을 유발하여 전송 품질을 떨어뜨리게 된다. 본 논문에서는 인접한 MAG간의 통신, 또는 같은 서브넷 내에서의 통신에서 LMA를 거치지 않고 통신을 할 수 있는 방안으로 블룸 필터를 이용한 통신 기법을 제안한다.