• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.849-855
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• 2011

Emergency batteries on board are used for stairs, pathway lights, and emergency communications during alternator black-out. In addition, there are engine start-up batteries in lifeboats. Typically, these batteries are installed under the Classification Rules. However, Since batteries inside life boats are installed in a confined narrow space, it is difficult to perform regular maintenances. Also, even though there are air vents in the life boat, the temperature inside the life boat often reaches above $65^{\circ}C$, which is much higher than the regulation temperature, $45^{\circ}C$. In this paper, we will summarize the accident of battery explosion occurred in MMU training ship, and possible causes. We will propose preventive measures of battery explosions as well as the revision of the regulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3C
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• pp.69-76
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• 2005

In this paper, we propose a biorthogonal modulation employing a constant-amplitude transmission of multi-code signals by introducing a simple constant-amplitude coding scheme with redundant bits. The proposed constant-amplitude biorthogonal multi-code (CABM) modulation can provide high spectral efficiency compared with a conventional direct sequence/spread spectrum (DS/SS) modulation. Nevertheless the proposed CABM modulation can keep up a constant-amplitude signal. Additionally, we propose various types of demodulation structures for the CABM modulation. Simulation results show that bit error rate (BER) performance and hardware complexity of the proposed CABM modulation are highly improved in comparison with those of a constant-amplitude orthogonal multi-code (CAOM) modulation.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.201-206
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• 2006

As the seriousness of the global environment is gaining increasing our attention recently, studies on application of LCA(Life Cycle Assesment) to ship are being carried dynamically in various industry fields. This study examined general outline about local and international application cf LCA to ship. First of all, international background for the appearance of LCA and its general meaning are introduced. The state-of-the-art for its application to ship will be also explained. Finally, domestic study methodology for application of LCA to ship were suggested.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.85-88
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• 2001

High oxygen pressure has been applied for a floating zone (FZ) crystal grower in order to grow high quality $TiO_2$(rutile) single crystals suitable for optical application. The $TiO_2$ crystals, grown under 0.3, 0.4, 0.5, and 0.8MPa oxygen pressure respectively, are all transparent and dark blue. The degree of the presence of sub-grain boundary in the crystal differs from the applied oxygen pressure. In particular, $TiO_2$ single crystals grown under0.5 MPa showed sub-grain boundary-free and estimated good for optical devices.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.394-402
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• 2008

In this paper, we propose a novel soft output generation method for spatially multiplexed MIMO systems. The receiver complexity of spatially mutiplexed MIMO system is in proportion to the number of candidate vectors. The ML signal detection method considers all possible vectors as candidates, thereby achieving a high performance, however, its complexity is very high. Low complexity receiver techniques involving a small number of candidate vectors, provide soft output values of low reliability. In this paper, we propose a method to improve reliability of the soft output values obtained using a small number of candidate vectors.

• Journal of Internet of Things and Convergence
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• v.2 no.1
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• pp.17-21
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• 2016

The rapid development of IoT leads new kinds of services which does not existed. And, it requires several changes on existing network. Software Defined Network is one of the future network technology which can deal with problems from these kinds of changes. The strong point of Software Defined Network is flexibility and scalability. However, In some cases, these factors could be the security vulnerabilities. In this paper, we present adaptation of F(I)MEA technique for the security analysis on Software Defined Network Technology for IoT services.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2347-2352
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• 2012

In this paper, a new alternating equalizer and its differential adjustment algorithm are proposed. The proposed alternating equalizer achieves equalization effectively using an algorithm performing symbol decisions based on soft/hard decision. In addition, it is possible to improve the initial blind convergence speed and steady-state error performance simultaneously by adjusting the equalizer differentially according to the relative reliability of the symbol decisions by soft/hard decision devices. The simulation results on 16/64-QAM constellations under multipath propagation channel and additive noise conditions confirmed to support usefulness of the proposed method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.562-571
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• 2010

Forward error correction (FEC) coding schemes using iterative soft decision detection (SDD) information are mandatory in most of the next generation wireless communication system, in order to combat inevitable channel imparirnents. At the same time, space-time block coding (STBC) schemes are used for the diversity gain. Therefore, SDD information has to be fed into FEC decoder. In this paper, we propose efficient SDD methods for turbo-coded STBC system using high order modulation such as QAM. We present simulation results of various SDD schemes for turbo-coded STBC systems, and show that the proposed methods can provide almost approximating performance to maximum likelihood detection with much less computational load.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.416-422
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• 2011

In this paper, we use hard decision method for cooperative spectrum sensing. Sensing performance adopting hard decision is lower than soft decision but system load is low and the process is relatively simple when the combining scheme is hard decision compared to soft decision. In order to improve sensing performance, we propose optimal hard decision method applying weight that is based on a probability of individual sensing. Unlike conventional hard decision, we try to improve sensing performance applying weight and show the performance of the proposed method from the simulation results and performance analysis. The signal of licensed user is OFDM signal and the wireless channel between a licensed user and CR systems is modeled as Gaussian channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2035-2042
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• 1997

We consider the design of soft decision functions for each stage of multistage detection for coherent demodulation in an asynchronous code-division multiple-access(CDMA) system. In particular, the sigmoid function, which is shown to be optimal under the mean square error(MSE) criterion, andmultilevel quantizers that best approximate the sigmoid function are derived. At each stage of multistage detection, the parameters of these decision functions are adjusted depending on estimated input statistics. Computer simulation results demonstrate that multistage detectors employing these soft decision functions perform considerably better than those with hard decision.