• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.2-3
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• 2005

Air gap control method using a conventional actuator for near field recording technology has been reported. To achieve good performance in the air gap servo and further experiments, the assembling between OL and SIL is the critical procedure. A lens set with NA 1.45 at 405 m has been assembled and tested by using a Twyman-Green interferometer. The tolerance of assembling is very tight and the designing and adjusting procedure must be carefully controlled.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.688-692
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• 2001

본 논문에서는 무선 통신로 환경에서 발생하는 페이딩 현상과 전자기기에서 방출되는 임펄스성 전자간섭파에 따른 MC DS-CDMA와 DS-CDMA 시스템의 성능을 비교 분석하였다. 결과에 의하면, 페이딩과 임펄스 전자간섭파에 의해 시스템에 심각한 영향을 미치게 되는데 특히, 직접파 성분이 존재하는 페이딩 보다는 임펄스 전자간섭파의 발생빈도와 크기에 따라 두 시스템 성능이 크게 좌우됨을 알 수 있었다. 이에 대한 성능개선 기법으로 다이버시티 기법과 BCH(15, 7) 부호화 기법을 적용하여 직접파가 존재하는 페이딩과 강한 임펄스 간섭 환경에서도 만족할 만한 성능을 얻을 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1998-2004
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• 1997

In this paper, we have analyzed the bit error performance ofthe chip-spreading OCDM system proposed in the previous papaer and compared the results, through computer simulations, with those of conventional DS/CDMA system which employs the maximal ration combining method. WE have shown, analytically, that the BER upper bound of the OCDM system coincides with that of the conventional DS/CDMA system and the lower bound exhibits much improved results. From the simulation results, we have confirmed that the BER curves of proposed OCDM system actually lie between the two theoretical bounds and its performance is superior to that of the DS/CDMA system.

• ETRI Journal
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• v.42 no.5
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• pp.799-804
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• 2020

Network security situation prediction is difficult due to its strong uncertainty, but DS evidence theory performs well in solving the problem of uncertainty. Based on DS evidence theory, this study analyzed the prediction of the network security situation, designed a prediction model based on the improved DS evidence theory, and carried out a simulation experiment. The experimental results showed that the improved method could predict accurately in the case of a large conflict, and had strong anti-jamming abilities as compared with the original method. The experimental results prove the effectiveness of the improved method in the prediction of the network security situation and provide some theoretical basis for the further application of DS evidence theory.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.603-610
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• 2008

In this paper, analytical methods for calculating the average probability of bit error of direct sequence pulse amplitude modulation ultra wideband (DS-PAM UWB) system and time hopping pulse position modulation ultra wideband (TH-PPM UWB) system are given. For the multi-user DS-PAM UWB system, the bipolar pulse amplitude modulation is used in order to achieve better performance. As we know, more attention is paid to the TH-PPM UWB systems recently. In this paper. we first introduce the accurate BER calculation methods of the multi-user DS-PAM UWB and TH-PPM UWB systems and then give the performance analysis over the ideal AWGN channel and a correlation receiver. Furthermore, we also introduce their applications in image transmission and data transmission and give the simulation results. The analytical method yields simple and exact formulas relating the performance to the system parameters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.500-508
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• 2008

Direct-sequence ultra-wideband(DS-UWB) system is being considered as one of promising transmission technologies for wireless personal area networks(WPANs). Due to relatively low spreading factors and huge bandwidth of transmit signal, a DS-UWB receiver needs to be equipped not only with a rake receiver but also with an equalizer, of which the equalizer is not required for traditional direct-sequence code division multiple access(DS-CDMA) systems. The number of rake fingers is limited in practice, influencing the performance of the subsequent equalizer. In this paper, we derive a decision feedback equalizer(DFE) for DS-UWB systems based on the minimum mean square error(MMSE) criterion, and investigate the impact of various parameters on the DFE performance in realistic scenarios. In particular, we propose an approach to improving the performance of the DFE using additional channel estimates for multipaths not combined in the rake receiver, and discuss how the accuracy of channel estimation affects desirable DFE configuration. Moreover, we present simulation results that show the impact of turbo equalization on the DFE performance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.5
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• pp.34-40
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• 2015

This paper presents an application of Differential Search (DS) meta-heuristic optimization algorithm for optimal operation of micro grid system. DS algorithm has the benefit of high convergence rate and precision compared to other optimization methods. The micro grid system consists of a wind turbine, a diesel generator, and a fuel cell. The simulation is applied to micro grid system only. The wind turbine generator is modeled by considering the characteristics of variable output. One day load data which is divided every 20 minute and wind resource for wind turbine generator are used for the study. The method using the proposed DS algorithm is easy to implement, and the results of the convergence performance are better than other optimization algorithms.

• Korean Journal of Plant Resources
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• v.29 no.4
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• pp.479-494
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• 2016

The aim of this study is to select the superior resources of high yield, high content of functional material optimal to mechanical harvesting by the evaluation of crop growth and yield characteristics in sorghum germplasm. One hundred accessions of sorghum germplasm were used in this experiment. Days from seeding to heading date showed the range from 68 to 94 days with the highest frequency proportion was the group from 80 to 85 days, which occupied 34% (34 plant resources) of 100 germplasm. Ear types of 100 sorghum germplasm could be classified as 7 types of broom-tillering, half broom-tillering, extreme open-loose type, open-loose type, intermediate type, compact type, extreme-compact type of which intermediate type was the highest ratio of 28% (28 plant resources) of 100 germplasm. Yield showed the range from 106 to 365 ㎏/10a with the highest frequency proportion of it was the group from 150 to 200 ㎏/10a, which occupied 44% (44 plant resources) of 100 germplasm. Among 100 sorghum germplasm, 18 ideal resources of high yield and short plant height appropriate for mechanical harvesting were selected. In order to evaluate high content of functional substance, selected 18 resources were analyzed for total polyphenol content, DPPH radical scavenging activity and total anthocyanin content. Finally, we selected 5 resources of short plant height, high yield, high content of total polyphenol and high DPPH radical scavenging activity among 18 genetic resources.

• Journal of the Korea Society of Computer and Information
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• v.16 no.5
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• pp.79-91
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• 2011

In this paper, a DS (Data Synchronization) server for mobile communication environments is constructed and the suitability and the performance of its operations are validated. The DS server provides a way to update the newest data and keep data consistency for clients (mobile devices). In addition, the DS server constructed in this paper supports various synchronization types, and detects all changes and conflicts. In case of data conflicts, the DS server resolves the conflicts according to the several policies implemented in this work. The DS server conforms to the OMA(Open Mobile Alliance) DS standard protocol for interoperability with other mobile devices and servers. In addition to the transmission-by record scheme proposed by the OMA DS standard protocol, the DS server constructed in this paper also provides the transmission-by field scheme for the enhancement transmission performance between the server and clients. In order to validate its operations, data synchronization between the DS server and the SCTS (SyncML Conformance Test Suit), the suitability validation tool provided by the OMA, is performed. The validation results show that the DS server constructed in this paper satisfies all of the test cases except the Large Object function. The Large Object function will be implemented later because the function is not needed for the personal information synchronization process which this paper aims for. Also, synchronization times of the DS server are measured while increasing the number of data and clients. The results of the performance evaluations demonstrate that the DS server is scalable, in the sense that it has not suffered from any serious bottlenecks with respect to the number of data and clients. We expect that this work will provide a framework for various studies in the future for improving mobile DS operations.

• Journal of Pharmaceutical Investigation
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• v.27 no.1
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• pp.11-14
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• 1997

This laboratory has recently reported the solubility and in vivo absorption enhancement of diclofenac sodium by ${\beta}-cyclodextrin$ complexation. The acute gastroduodenal mucosa injury provoked by administration of 34 mg/kg and 68 mg/kg of a diclofenac sodium (DS) and equivalent dose of new formulation [diclofenac sodium-beta-cyclodextrin complexation$(DS-{\beta}-CD)$] was evaluated and compared. Microscopic examinations, performed after 18-hrs treatment, demonstrated that $DS-{\beta}-CD$ was less gastrolesive than DS. The drop in gastrophy after a single dose of the assigned drug was considerably greater for DS than for $DS-{\beta}-CD$, which registered similar values to control. Since gastrophy is an expression of the anatomy-functional integrity of the gastric barrier, the results indicate that $DS-{\beta}-CD$ exerts less direct acute damage on the gastric mucosa. Therefore, when administered short-term, $DS-{\beta}-CD$ appears to be less gastrolesive than the standard DS formulation.