• KIISE Transactions on Computing Practices
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• v.23 no.2
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• pp.122-127
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• 2017

The data link layer operates reliable internode communication in the OSI reference model. Generally, the forward error correction (FEC) method is used in the data link layer of the wireless sensor network (WSN) environment that has a high frequency of errors. However, the FEC method consumes a significant amount of energy due to its high error correction rate, which negatively affects the networks' lifespan. In contrast with battery-based technology, energy is regularly recharged in the solar-powered WSN to meet higher energy needs than required for basic operation of existing nodes. By efficiently utilizing this surplus energy, the proposed energy-aware FEC method can reduce the data loss rate with no decrement of the network lifetime. The method employs a trade-off relationship between the energy and data loss rate by adjusting the parity length in the FEC method to the energy state in each node. The performance of the proposed scheme was verified through a simulation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.599-602
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• 2011

A propulsion controller for one-time flight vehicles should be designed robustly so that it can complete its missions even in case sensor failures. These vehicles improve their fault tolerance by back-up sensors prepared for the failure of major sensors, which raises the total cost. This paper presents the NARX model which substitutes vehicles' velocity sensors, and detects failure of sensor signals by using model based fault detection. The designed NARX model and fault detection algorithm were optimized and installed in TI's TMS320F2812 so that they were linked to HILS instruments in real-time. The designed propulsion controller made the vehicle to have better fault tolerance with fewer sensors and to complete its missions under a lot of complicated failure situations. The controller's applicability was finally confirmed by tests under the HILS environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1412-1418
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• 2005

Recently, more and more portable terminals probably have multiple interfaces to be connected to different access technologies. Each technology has its specific characteristics in terms of coverage area, bandwidth, reliability, etc. For example, the mobile node is equipped with three heterogeneous interfaces; IEEE 802.1lb MLAM link, CDMA Cellular link, and 802.16 WiMAX link These mobile nodes may be reachable through different links at the same time or use each interface alternately depending on the network environment. As like this, the portable terminal equipped multiple interfaces can have many benefits; it should be connect to Internet through other interface in case of occurring to failure for currently activate interface, and it should share a mount of traffic efficiently per interface etc. This environment is called end node Multihoming. However, current most Internet protocols are designed originally with single interface in mind. So these potocols do not provide methods for supporting simultaneous diffentiated use of multiple access technologies. In this paper, firstly we have to refer technical consideration items to use multiple interfaces based on IPv6 simultaneously. And we should propose extended registration mechanism for multiple addresses being acquired from interfaces to support reliable accessibility and vertical handover.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.467-474
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• 2007

MB-OFDM (Multiband-orthogonal frequency division multiplexing) UWB (ultra wide band) system uses DCM (dual carrier modulation) scheme to achieve high-data rate transmission. The basic idea of DCM is that to transmit the 4 bits more reliably two 16-QAM (quadrature amplitude modulation) symbols are used and the two 16-QAM sysmbols are allocated to each subcarrier of OFDM with maximum-distance. In the case of using the DCM, if one 16-QAM symbol is broken by deep fadding channel, a receiver can detect the transmitted signal by using another 16-QAM symbol. In the conventional ML(maximum likelihood) decision scheme, since the receiver does not use the CSI (channel state information), loss in diversity can not be reduced. In this paper, we propose improved soft-decision scheme with CSI for higher performance of MB-OFDM UWB systemn.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.9
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• pp.861-868
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• 2017

In this study, a novel magnetic field generator, using a shielding effect for controlling the dynamic stiffness and damping of magnetorheological gels, is proposed. A magnetorheological gel is a smart material that can alter its stiffness and damping, and it can be used as a vibration absorber and in vehicle suspension. It is necessary to control the magnetic field to use magnetorheological gels in various applications. There are two types of magnet field generators, namely the electromagnet and permanent magnet, and the electromagnet is generally used in practical applications. However, owing to its limitations, the electromagnet is not suitable for long-term use. Therefore, in this paper, a novel magnetic field generator is proposed to address such problems for use in real applications.

• Journal of the Korean Chemical Society
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• v.26 no.4
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• pp.229-234
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• 1982

Using solution technique, sulfur in the sulfide ore was indirectly determined by X-ray fluorescence spectrometry. The sample was dissolved with the mixed solution of B$r_2$ and HN$O_3$, and Si$O_2$, a major constituent, was repelled from the solution by HF treatment several times, B$a^{2+}$ solution was added to the solution to precipitate the S$O^4_{2-}$ ion as BaS$O_4$. Measuring the fluorescent X-ray intensity of excess Ba2+ ion in the filtrate, the content of sulfur in the original ore was back-calculated. Comparing the results by this method with the gravimetric method, the mean difference was ${\pm}1.7%$ in the range of 20 to 40% of sulfur content and the method was tolerably reproducible.

• Journal of the Korea Society of Computer and Information
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• v.20 no.4
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• pp.95-102
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• 2015

This paper proposes a simple algorithm for circuit minimization. There are currently two effective heuristics for circuit minimization, namely manual Karnaugh maps and computable Quine-McCluskey algorithm. The latter, however, has a major defect: the runtime and memory required grow $3^n/n$ times for every increase in the number of variables n. The proposed algorithm, however, extracts the prime implicants (PI) that cover minterms of a given Boolean function by deriving an implicants table based on frequency. From a set of the extracted prime implicants, the algorithm then eliminates redundant PIs again based on frequency. The proposed algorithm is therefore capable of minimizing circuits polynomial time when faced with an increase in n. When applied to various 3-variable and 4-variable cases, it has proved to swiftly and accurately obtain the optimal solutions.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.571-582
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• 2010

Typically nondestructive inspection methods of the large gear units are applied to penetrate non-destructive inspection. Nondestructive penetrating inspection put into the small openings of the defect to penetration liquid, remove to excess penetration liquid on the surface of the gear units, spread with developing solution and we can find the small defect by coating with penetration liquid. However, this method has so many issues because of penetrate nondestructive tests on the gear assembly. The steep angle of screw is hard to achieved full penetration and has the problem to remove the excess. In contrast, the magnetic nondestructive inspection is easy to detect subsurface defects and subtle defects. According to the inspection results the stress concentrates in gear surface, some internal defects and microscopic flaws exist on the gear units are not found to penetrate the nondestructive inspection, but magnetic nondestructive inspection could have found many defect. Therefore, a reasonable method of nondestructive inspection for the large gear units is suitable to magnetic nondestructive inspection.

• The Korean Journal of Applied Statistics
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• v.23 no.5
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• pp.835-844
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• 2010

Tools for statistical analysis of extreme values include the classical annual maximum method, the modern threshold method and variants improving the second one. While the annual maximum method is to t th generalized extreme value distribution to the annual maxima of a time series, the threshold method is to the generalized Pareto distribution to the excesses over a high threshold from the series. In this paper we deal with the Poisson-GPD method, a variant of the threshold method with a further assumption that the total number of exceedances follows the Poisson distribution, and apply it to the daily percentage increases and decreases computed from the spot prices of West Texas Intermediate, which were collected from January 4th, 1988 until December 31st, 2009. According to this analysis, the distribution of daily percentage increases as well as decreases turns out to have a heavy tail, unlike the normal distribution, which coincides well with the general phenomenon appearing in the analysis of lots of nowaday nancial data.

• Communications for Statistical Applications and Methods
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• v.16 no.5
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• pp.803-812
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• 2009

The application of extreme value theory to financial data is a fairly recent innovation. The classical annual maximum method is to fit the generalized extreme value distribution to the annual maxima of a data series. An alterative modern method, the so-called threshold method, is to fit the generalized Pareto distribution to the excesses over a high threshold from the data series. A more substantial variant is to take the point-process viewpoint of high-level exceedances. That is, the exceedance times and excess values of a high threshold are viewed as a two-dimensional point process whose limiting form is a non-homogeneous Poisson process. In this paper, we apply the two-dimensional non-homogeneous Poisson process model to daily losses, daily negative log-returns, in the data series of KBW/USD exchange rate, collected from January 4th, 1982 until December 31 st, 2008. The main question is how to estimate extreme quantiles of losses such as the 10-year or 50-year return level.