• Journal of Korean Society of Transportation
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• v.18 no.5
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• pp.7-16
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• 2000

This paper is focused on verifying time-space repetition of the highway accident and finding the their causes and deterrents. We classify all months into several seasonal groups, develop the model for each seasonal group and analyze the results of these models for Joong-bu highway. The existence of seasonal effect is verified by the analysis or self-organizing map and the accident indices. Agglomerative hierarchical cluster analysis which is used to decide the seasonal groups in accordance with accident patterns, winter group, spring-fall group. and summer group. The accident features of winter group are that the accident rate is high but the severity rate is low. while those of summer group are that the accident rate is low but the severity rate is high. Also, the regression model which is developed to identify the accident Pattern or each seasonal group represents that the season-related factors, such as the amount of rainfall, the amount of snowfall, days of rainfall, days of snowfall etc. are strongly related to the accident pattern of evert seasonal group and among these factors the traffic volume, amount of rainfall. the amount of snowfall and days of freezing importantly affect the local accident Pattern. So, seasonal effect should be considered to the identification of high-risk road section. the development of descriptive and Predictive accident model, the resource allocation model of accident in order to make safety management plan efficient.

• Journal of KIISE
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• v.44 no.12
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• pp.1296-1306
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• 2017

Recently, as the number of Internet of Things users has increased, IETF (Internet Engineering Task Force) has released the CoAP (Constrained Application Protocol). So Internet of Things have been researched actively. However, existing studies are difficult to adapt to streaming service due to low transmission rate that result from buffer underflow. In other words, one block is transmitted one block to client's one request according to the internet environment of limited resources. The proposed scheme adaptively adjusts the rate of CON(Confirmable) message among all messages for predicting the exact network condition. Based on this, the number of blocks is determined by using buffer occupancy rate and content download rate. Therefore it improves the quality of user experience by mitigating playback interruption. Experimental results show that the proposed scheme solves the buffer underflow problem in Internet of Things streaming environment by controlling transmission rate according to the network condition.

• Convergence Security Journal
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• v.19 no.5
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• pp.47-53
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• 2019

Network-based sharing of information has evolved into a cloud service environment today, increasing its number of users rapidly, but has become a major target for network-based illegal attackers.. In addition, IP spoofing among attackers' various attack techniques generally involves resource exhaustion attacks. Therefore, fast detection and response techniques are required. The existing detection method for IP spoofing attack performs the final authentication process according to the analysis and matching of traceback information of the client who attempted the connection request. However, the simple comparison method of traceback information may require excessive OTP due to frequent false positives in an environment requiring service transparency. In this paper, symmetric key cryptography based on traceback information is used as mutual authentication information to improve this problem. That is, after generating a traceback-based encryption key, mutual authentication is possible by performing a normal decryption process. In addition, this process could improve the overhead caused by false positives.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.265-275
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• 2004

In this paper, an OFDM-CDMA broadband system is considered for a possible candidate of fixed wireless broadband access network applications. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in OFDM-based multiple-antenna transmission systems. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be applied to the ETSI HlPERLAN/2 and IEEE-802.11a standards in the case of more than two transmit antennas. Also, an effect of diversity techniques on the performance of OFDM-CDMA based broadband wireless access networks is investigated and the maximum achievable diversity gain for a two-path Rayleigh fading environment is evaluated Simulation results show that the OFDM-CDMA system applying a space-time-frequency diversity with a full-rate full diversity code can give the diversity of D = 4 and D = 8 for both multi-user cases of maximum user and half user capacities, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.5
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• pp.34-40
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• 2001

In this paper, a narrowband active noise control system to reduce the noise in thermal power plants is proposed. The narrowband active noise control system contains rectangular wave generator and has a multi channel feed forward adaptive algorithms which uses the adjoint LMS algorithm. Although the effectiveness have been proven in the filtered-X LMS broadband active noise control system, this algorithm has much more computational complexity than that of narrowband active noise control system. The proposed active control system that uses the adjoint LMS algorithm, compared to the previous broadband active noise control system, not only is more effective in controlling narrowband noise but also has a more stable structure. Adaptive filter contains the FIR structure and IIR structure for primary and secondary path models. The simulation proves the effectiveness of the proposed algorithm.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2007.05a
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• pp.39-41
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• 2007

본 연구는 직물 기반 바이오 모니터링 스마트 의류를 개발하기 위해 의복 소재의 신축성에 따른 심전도 신호 검출 성능과 착용 성능을 평가하여 직물 기반 심전도 의복을 위한 최적 범위를 제안하고자 한다. 이를 위해, 서로 다른 신축률의 편물을 얻기 위해 면/폴리에스테르에 스판덱스 함유율을 0%, 5%, 8%로 다르게 하여 제편하였다. 이 세 가지 소재로 심전도 측정을 위해 동일한 사이즈로 의복을 제작한 후, 금속사를 이용한 자수 기법으로 심전도 전극을 설치하였다. 심장 관련 병력이 없고 평균 BMI가 $20{\sim}24$인 정상 체중의 5명을 대상으로 Biopac MP150을 사용하여 심전도 신호를 검출한 후, 설문지를 사용하여 소재의 신축성에 따른 착용성 평가를 시행하여 신축성에 대한 만족감, 동작용이성, 전반적 쾌적함 등을 Likert 7점 척도로 평가하도록 하였다. 실험 결과, 심전도 신호 검출 성능 측면에서는 8% 라이크라 함유 소재가 가장 우수하였으나, 착용성 측면에서는 5% 소재가 가장 우수한 것으로 파악되었다. 향후 그 수요가 높아질 것으로 예상되는 바이오 모니터링 의복 소재 개발을 위해 기능성과 착용성을 모두 고려한 본 연구 결과가 유용하게 활용될 것이다.

• The Korean Journal of Applied Statistics
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• v.21 no.3
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• pp.413-427
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• 2008

In sample design, it is usually planned by purpose and the range of the announcing statistics from the survey. After survey, getting a proper and decent statistics, applying the proper weights on the results of survey is very important and necessary. Therefore in this study, three estimation methods which are raking, BLS and general linear regression method are compared with MSE, Coverage, CV, LE and NC.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.2
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• pp.75-82
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• 2000

In this paper, described is the comparison of performances based on the computer simulation under IMT-2000 environment between multicode and multicarrier CDMA system for the design of wireless systems using wideband CDMA technology. From simulation results, it can be concluded that both multicode and multicarrier CDMA scheme show comparable performances. Diversity scheme of RAKE receiver is indispensible for both multicode and multicarrier CDMA systems under IMT-2000 outdoor B and vehicular B channel environment. Either Hadamard matrix or PN sequence can be used as the orthogonal code as far as the orthogonality is kept. Finally, with increasing chip rate and less users, performance is getting better.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1510-1521
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• 1996

This paper presents acquisition algorithm and an improved detection technique for the DS/CDMA (direction sequence code division multiple access) RAKE receiver in multipath fading channel. The DS/CDMA systems use the RAKE receiver, an accurate code acquisition is required for the RAKE branches. The algorithmis able to findthe pseudonoise (PN) code delay estimates for the RAKE branches in a multipath fading channel. In this paper a numerical method and computer simulation simulation have been developed for the acquisition system. The detection probability and mean acquisition time are investigated asa performance measure of the system using the Monte Carlo method. And also in order to analyze the effect of the acquisition on the RAKE receiver this paper bring out the effect of integration time, doppler frequency, processing gain and the number of users on the acquired code phase.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.674-681
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• 2006

In this paper, a new receiver with low complexity for a DS-UWB system which can eliminate efficiently the multiple access interference and the detrimental effects caused by multi-paths is proposed. The performance of conventional DS-UWB receivers depends greatly on the types and lengths of spreading codes. Generally, as the length of spreading codes increases, the receiver performance improves. But, the receiver performance does not improve satisfactorily in a multi-paths fading environment. Through computer simulations, it can be shown that the proposed DS-UWB receiver eliminate the multi-paths effects efficiently in a multi-user, multi-paths fading environment, and the user capacity can be increased dramatically using the proposed receiver.