• 한국항공우주학회지
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• 제30권5호
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• pp.127-133
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• 2002

항공기 구조 개발에 관련된 MIL-STD-1530A에는 구조 건전성을 확보하기 위한 요구사항이 기술되어 있다. 기체 구조의 내구성 및 손상허용성은 요구사항 중의 하나로서 관련 규격서의 요구조건과 절차에 따라 해석 및 시험을 통하여 입증되어야 한다. 본 논문에서는 기본 훈련기의 안전성 및 내구성 평가를 위한 실기체 내구성시험에 대하여 소개하였다. 내구성시험은 미군사규격서의 요구조건 및 절차에 따라 수행되었다. 내구성시험의 시험하중은 비행대비행 하중 스펙트럼으로 기본 훈련기의 피로하중 기준에 의거하여 개발되었다. 4배 설계수명 동안의 내구성시험을 성공적으로 완료하였으며, 기본훈련기 구조가 내구성 요구조건을 만족하고 있음을 확인하였다.

• 국제초고층학회논문집
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• 제1권4호
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• pp.271-281
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• 2012

Tianjin Goldin Finance 117 tower has an architectural height of 597 m, total of 117 stories, and the coronation of having the highest structural roof of all the buildings under construction in China. Structural height-width ratio is approximately 9.5, exceeding the existing regulation code significantly. In order to satisfy earthquake and wind-resisting requirements, a structure consisting of a perimeter frame composed of mega composite columns, mega braces and transfer trusses and reinforced concrete core containing composite steel plate wall is adopted. Complemented by some of the new requirements from the latest Chinese building seismic design codes, design of the super high-rise building in high-intensity seismic area exhibits a number of new features and solutions to professional requirements in response spectrum selection, overall stiffness control, material and component type selection, seismic performance based design, mega-column design, anti-collapse and stability analysis as well as elastic-plastic time-history analysis. Furthermore, under the prerequisite of economic viability and a series of technical requirements prescribed by the expert review panel for high-rise buildings exceeding code limits, the design manages to overcome various structural challenges and realizes the intentions of the architect and the client.

• 설비공학논문집
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• 제7권1호
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• pp.1-12
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• 1995

In order to seek various relationships among many design parameters employed in the design of the axial-flow fans the program which generates acoustic spectrum has been developed and its validity verified. Outputs of the program, with other outputs from a formerly developed performance prediction program, have been used to form a multi-objective function, for which an optimal design process was carried out. The present analysis shows that overall noise level and efficiency has contrasting trends, and the chord length turns out to be the most critical design variable. In the chosen design case of requirements $Q=2000m^2/min$, ${\Delta}P_s=67mmAq$, D=1.4m, the chord length of 0.2059m minimizes the overall noise level, while chord length of 0.1254m maximizes the efficiency. The resulting chord length in the balanced optimization is 0.1809m.

• Journal of information and communication convergence engineering
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• 제2권2호
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• pp.76-79
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• 2004

The DS-SS (Direct Sequence Spread Spec1nun) transmitter is part of a low data rate (∼150 kbps - burst rate and 64 bps - average data rate) wireless communication system. It is traditionally implemented using Digital Signal processing chip (DSP). However, with rapid increase in variety of services through cell phones, such as, web access, video transfer, online games etc. demand for higher rate is increasing steadily. Since the chip rate and thereby the sampling rate requirements of the system are fairly high, the transmitter should implemented using Field programmable Gate Arrays FPGAs instead of a DSP. This paper shows the steps taken to get a working prototype of the transmitter unit on a FPGA based platform.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.4034-4053
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• 2015

In order to meet various requirements for transmission quality of both primary users (PUs) and secondary users (SUs) in cognitive radio networks, we introduce a channel bonding mechanism for PUs and a channel reservation mechanism for SUs, then we propose a novel spectrum allocation strategy. Taking into account the mistake detection and false alarm due to imperfect channel sensing, we establish a three-dimensional Markov chain to model the stochastic process of the proposed strategy. Using the method of matrix geometric solution, we derive the performance measures in terms of interference rate of PU packets, average delay and throughput of SU packets. Moreover, we investigate the influence of the number of the reserved (resp. licensed) channels on the system performance with numerical experiments. Finally, to optimize the proposed strategy socially, we provide a charging policy for SU packets.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2019년도 춘계학술발표대회
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• pp.86-88
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• 2019

In a complex geographical environment, communication quality of communication equipment is being seriously challenged. Secondary Users(SUs) must make the best possible use the idle spectrums that Primary Users(PUs) do not use and change spectrum frequently. Using the relevance vector machine(RVM) to establish a signal noise Ratio(SNR) Model for interference information and bit error rate(BER). Through the model and real-time interference information, the minimum channel SNR meeting the BER requirements of communication equipment can be predicted, and we can also calculate the minimum transmitted power. According to the simulation results, this method has better performance for selecting available channel and restraining interference.

• 스마트미디어저널
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• 제1권1호
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• pp.17-26
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• 2012

무선인지 네트워크에서 비면허 사용자는 면허 스펙트럼 대역을 감지하여 가회가 있을 때마다 면허 사용자에 간섭을 일으키지 않고 매체에 접근한다. 특히 애드혹 네트워크에서는 MAC 계층이 비면허 사용자들간 스펙트럼 접근을 조정하는 중요한 역할을 수행한다. 이에 따라 최근 많은 MAC 프로토콜이 연구되고 있다. 본 논문에서는 무선인지 애드혹 네트워크에서의 MAC 프로토콜을 비교 분석한다. 먼저 프로토콜들을 공통 제어 채널을 기준으로 분류하고 각 종류별 주요 프로토콜을 분석한다. 그리고 나서 프로토콜들을 고유 특성과 성능 측면에서 정성적으로 비교한다.

• 한국통신학회논문지
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• 제25권1B호
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• pp.175-182
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• 2000

적외선을 이용한 수/발광 다이오드에 집적소자를 혼합한 Hybrid형 단거리 광무선 통신용 원칩모듈을 개발하였다. 발광다이오드는 850nm 의 적외선파장을 30$^{\circ}$지향각을 갖는 AlGaAs계 고속신호용으로서 전파지연이 60 ns 이며, PIN 포토다이오드는 Si계 반도체 수광소자로써 450-1050nm의 파장대에서 수광 흡수율이 양호하고 필터겸용 블록 에포시렌즈를 750nm 파장 저역대를 여과시켰다. 데이터 전송속도는 115.2 kbps이며 IrDA1.0 SIR 표준조건에서 동작이 양호함을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2037-2051
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• 2012

Cognitive radio (CR) is envisioned as a promising paradigm of exploiting intelligence for enhancing efficiency of underutilized spectrum bands. In CR, the main concern is to reliably sense the presence of primary users (PUs) to attain protection against harmful interference caused by potential spectrum access of secondary users (SUs). In this paper, evolutionary algorithms, namely, particle swarm optimization (PSO) and genetic algorithm (GA) are proposed to minimize the total sensing decision error at the common soft data fusion (SDF) centre of a structurally-centralized cognitive radio network (CRN). Using these techniques, evolutionary operations are invoked to optimize the weighting coefficients applied on the sensing measurement components received from multiple cooperative SUs. The proposed methods are compared with each other as well as with other conventional deterministic algorithms such as maximal ratio combining (MRC) and equal gain combining (EGC). Computer simulations confirm the superiority of the PSO-based scheme over the GA-based and other conventional MRC and EGC schemes in terms of detection performance. In addition, the PSO-based scheme also shows promising convergence performance as compared to the GA-based scheme. This makes PSO an adequate solution to meet real-time requirements.

• 한국통신학회논문지
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• 제37A권10호
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• pp.858-864
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• 2012

국내에서도 효율적이고 체계적인 재난대응을 위해 정부는 국가차원의 재난안전무선통신망을 2015년까지 구축할 예정이다. 이를 위해 행정안전부가 재난용 신규 주파수 지정을 요청함에 따라 방송통신위원회에서는 TETRA와 WiBro 기술방식을 대상으로 주파수 할당 여부에 대해 검토하고 있다. 따라서 본 논문에서는 ITU-R M.2033에서 권고한 주파수 산출 방법론을 기반으로 하여 국내 재난안전무선통신망을 위한 기술적 파라미터를 정의하고 TETRA-TRS에서 요구되는 주파수 소요량을 산출하였다.