• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.558-567
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• 2019

When used for broadcasting, multipurpose halls need to accommodate various types of programs such as speeches, Korean traditional music, musicals, pop music, and concerts. Therefore, multipurpose halls must meet a wide range of electric and architectural acoustic demands. However, there are few ways to alter acoustic environments for multipurpose halls, given these different demands. The current study investigates the effects of banners on acoustic environments in the presence of an acoustic shell or electric acoustic system. The results indicate that the installation of a 15% banner of wall area could vary the range of reverberation time ($T_{30}$) by 0.12 s, EDT (Early Decay Time) by 0.15 s, clarity of music ($C_{80}$) by 0.76 dB, and clarity of speech ($D_{50}$) by 6.43 % under different measurement circumstances. A computer simulation that enlarges the banner size to 40 % of the wall area varies the reverberation time from 0.11 s to 0.55 s depending on the room environment.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.83-90
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• 2009

Since traffic is aggregated to a MPP that acts as an Internet gateway, if traffic load is not balanced among the MPPs in a WMN, the overall performance of a WMN becomes poor even though the total traffic load is far below the capacity of the WMN. Therefore, in this paper, we propose a stochastic load balancing scheme where each MP (Mesh Point) probabilistically selects its serving MPP according to the congestion levels of MPPs. Through extensive simulations using ns-2, we have verified that our scheme can stabilize a WMN fast when congestion occurs and reduce packet loss rate by distributing traffic load of a congested MPP to multiple MPPs in the inverse proportional to their congestion levels. Compared to queue-based load balancing scheme, our method can decrease network stabilization time by 34 seconds, and reduce packet loss rate by 7.6%. Since the proposed scheme can reduce network stabilization time by efficiently using network resource, it is expected to contribute to the reliable operation of a WMN.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.1
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• pp.1-10
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• 1992

In the already presented paper, the performance analysis of SMUX was need a lot of time bacause of recussive method, So this paper proposed the new mathematical method for the SMUX's performance. And it is constructed and analyzed the queueing model for SMUX based on the Go-back N retransmission ARQ model. It is assumed that it has the infinite buffer and a single server. It is analzied the parameters that have influence on the byffer and a single server. It is analzied the parameters that have influence on the buffer behaviour of statistical multiplexer overflow probabilities. maximum buffer size. mean wating time and mean buffer size, and these relationship are represented the graphs and datas which provided a guide to the buffer design problem. As these results. it is efficient when the SMUX is apphed that the traffic density is below 0.5 and transmission error probabilities is below 10­$^3$. So this paper can be applied to the basic and theoretical background prior to the implementation of SMUX.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.12
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• pp.1163-1170
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• 2008

A mission scheduling optimization algorithm according to the purpose of satellite operations is developed using genetic algorithm. Satellite mission scheduling is making a timetable of missions which are slated to be performed. It is essential to make an optimized timetable considering related conditions and parameters for effective mission performance. Thus, as important criterions and parameters related to scheduling vary with the purpose of satellite operation, those factors should be fully considered and reflected when the satellite mission scheduling algorithm is developed. The developed algorithm in this study is implemented and verified through a comprehensive simulation study. As a result, it is shown that the algorithm can be applied into various type of the satellite mission operations.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.5
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• pp.561-565
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• 2010

Many methods have been researched to prolong sensor network lifetime using mobile technologies. In the mobile sink research, there are the track based methods and the anchor points based methods as representative operation methods for mobile sinks. However, the existing methods decrease Quality of Service (QoS) and lead the routing hotspot in the vicinity of the mobile sink. The reason is that they use static mobile paths that are not concerned about the network environments such as the query position and the data priority. In this paper, we propose the novel mobile sink operation method that solves the problems of the existing methods. In our method, the probing priority of the mobile sink is determined with the data priorities for increasing the QoS and the mobile features are used for reducing the routing hotspot. The experimental results show that the proposed method reduces query response time and improves network lifetime over the existing methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5B
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• pp.247-252
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• 2005

The testing tools implemented up to now for the LDAP(Light-weight Directory Access Protocol) interoperability tests are not easy to modify or add new test items since their source codes are not open. The object-oriented approach, therefore, is required to implement such a testing tool which can be easily modified or add new test items. Thus we designed the architecture for the testing tool applying the object-oriented approach. Java language, appropriate for the object-oriented approach, was used to implement the testing tool. The newly implemented testing tool can modify partly to adapt to the already stored data in the test suite information even during tests. Five LDAP servers can be tested simultaneously with the same configuration setup. Actual testing for the two LDAP servers validates the usefulness of the designed architecture with the proper working of the implemented testing tool according to the architecture.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.448-454
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• 2020

This study aims to determine the cause of structural defects occurring during aircraft operations and to verify the structural integrity of the improved features. The fracture plane was analyzed to verify the characteristics of the cracks and the fatigue failure leading to the final fracture was determined by the progress of the cracks by the repeated load. During aircraft operations, the comparative analysis of the load measurement data at the cracks with the aircraft design load determined that the measured load was not at the level of 30% of the design to be capable of being damaged. A gap analysis resulted in a significant stress of approximately 32 ksi at the crack site. Pre-Load testing also confirmed that the M.S. was reduced by more than 50% from +0.71 to +0.43, resulting in a sharp increase in aircraft load and the possibility of cracking when combined. Thus, structural reinforcement and the removal of the gap for aircraft cracking sites improved the defect. Based on the structural strength analysis of the improvement features, the bulkhead has a margin of about +0.88 and the fitting feature is about +0.48 versus allowable stress. In addition, the life analysis results revealed an improvement of approximately 84000 hours.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.610-611
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• 2011

전력 계통의 운용 계획을 최적화하기 위해서 연간 최대전력수요와 시간별 전력수요에 대한 장단기간의 수요 예측에 관한 연구가 활발하게 진행 중이다. 특히, 단기 수요 예측은 발전비용과 신뢰도에 크게 영향을 주며, 전력계통의 제어 및 단기계획, 경제급전, 전력조류계산 등의 입력 자료로 활용된다. 많은 예측 문제에 폭넓게 사용되고 있는 인공신경회로망은 전력수요 예측에도 자주 쓰이는 기법이다. 본 논문에서는 이를 보다 정확히 하기 위해 기존의 인공신경회로망 기법을 개선하여 보다 정확한 예측을 보였다.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.470-472
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• 2012

전파 지연이 큰 무선 네트워크 환경에서 Time Division Multiple Access(TDMA) 기법은 충돌을 방지하기 위해서 가드 타임을 고려한 슬롯을 운용해야 한다. 이 때, 가드 타임의 길이는 시스템의 통신 반경을 고려한 최대 전파 지연으로 하는 것이 일반적이다. 그러나 실제 환경에서는 노드 간의 거리가 대부분 통신 반경보다 짧기 때문에, 가드 타임의 낭비가 발생할 수 있다. 본 논문에서는 AGT-TDMA(TDMA with Adaptive Guard Time)을 제안하였다. AGT-TDMA는 노드 간의 거리에 따라 가드 타임을 유동적으로 조정함으로써 낭비되는 가드 타임을 최소화하였다. OPNET 시뮬레이션 결과를 통해 AGT-TDMA가 기존 TDMA보다 처리량이 향상되었고, 지연 시간이 단축되었음을 확인하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1035-1042
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• 2017

In this paper, we implement a public address system using power line communication in order to operate, extend, and expand the complicated public address devices and cables easily. Power line communication based public address system implemented consists of a public address control board and public address speaker boards which are suitable to digital streaming modulation. It can be noticed that we met satisfied results from performance measurement such as maximum audio output, audio channel response time, audio output SNR, and audio output THD+N.