• 국제학술발표논문집
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• The 4th International Conference on Construction Engineering and Project Management Organized by the University of New South Wales
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• pp.52-57
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• 2011

Bridges are essential and valuable elements in road and rail transportation networks. Bridge remediation is a top priority for asset managers, but identifying the nature of true defect deterioration and associated remediation treatments remains a complex task. Nowadays Decision Support Systems (DSS) are used extensively to assist in decision-making across a wide spectrum of unstructured decision environments. In this paper a requirements-driven framework is used to develop a risk based decision support model which has the ability to quantify the bridge condition and find the best remediation treatments using Multi Attribute Utility Theory (MAUT), with the aim of maintaining a bridge within acceptable limits of safety, serviceability and sustainability.

• Earthquakes and Structures
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• 제13권3호
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• pp.267-277
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• 2017

Base-isolation is now being adopted as a retrofitting strategy to improve seismic behaviour of reinforced concrete (r.c.) framed structures subjected to far-fault earthquakes. However, the increase in deformability of a base-isolated framed building may lead to amplification in the structural response under the long-duration horizontal pulses of high-magnitude near-fault earthquakes, which can become critical once the strength level of a fire-weakened r.c. superstructure is reduced. The aim of the present work is to investigate the nonlinear seismic response of fire-damaged r.c. framed structures retrofitted by base-isolation. For this purpose, a five-storey r.c. framed building primarily designed (as fixed-base) in compliance with a former Italian seismic code for a medium-risk zone, is to be retrofitted by the insertion of elastomeric bearings to meet the requirements of the current Italian code in a high-risk seismic zone. The nonlinear seismic response of the original (fixed-base) and retrofitted (base-isolated) test structures in a no fire situation are compared with those in the event of fire in the superstructure, where parametric temperature-time curves are defined at the first level, the first two and the upper levels. A lumped plasticity model describes the inelastic behaviour of the fire-damaged r.c. frame members, while a nonlinear force-displacement law is adopted for the elastomeric bearings. The average root-mean-square deviation of the observed spectrum from the target design spectrum together with a suitable intensity measure are chosen to select and scale near- and far-fault earthquakes on the basis of the design hypotheses adopted.

• 한국전산구조공학회논문집
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• 제25권2호
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• pp.149-154
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• 2012

도로교설계기준 내진설계편은 붕괴방지수준의 확보를 설계절차에 의해 규정하고 있는 반면 기능수행수준의 확보에 대한 요구사항은 명확하게 제시하고 있지 않다. 붕괴방지수준의 확보를 위해 기본적으로 제시된 설계방법은 응답수정계수를 사용하는 스펙트럼해석법으로, 기능수행수준은 설계과정에 적용되는 위험도계수와 응답수정계수에 의해 결정 되어진다. 위험도계수는 교량의 중요도에 따라 단순하게 적용할 수 있으나 중약진지역에서의 응답수정계수 적용은 설계조건에 따라 다른 결과를 갖게 된다. 이 연구에서는 중약진지역의 일반 도로교량을 대상으로 내진설계를 수행하여 기능수행수준의 결정과정을 검토하고, 이 결과를 토대로 기능수행수준의 확보와 관련하여 내진설계편에 보완해야 하는 사항을 제시하였다.

• 항공우주시스템공학회지
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• 제13권3호
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• pp.32-39
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• 2019

항공기 외부에 장착되어 전술임무에 사용되는 센서 포드는 운용기간 동안 예상되는 하중 스펙트럼에 대한 피로수명이 확보되어야 한다. 센서 포드와 같은 임무장비는 해석의 효율성을 고려하여 동적 진동 환경조건을 적용한 주파수 영역의 피로수명 예측방법이 선호되어 왔다. 본 논문에서는 실제 비행체 하중 스펙트럼을 고려하여 정적 및 동적 하중에 의한 응력을 합성한 주파수 영역에서의 피로수명 예측방법을 제안하였다. 기존 해석방법과 비교한 결과 제안된 해석방법은 피로수명이 보수적으로 예측되었다. 그리고 제안된 방법으로 해석한 결과 설계된 센서 포드는 피로수명 요구조건을 만족하였다.

• Steel and Composite Structures
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• 제46권2호
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• pp.221-236
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• 2023

In order to study the seismic response of the main plant of steel reinforced concrete (SRC) structure of the CAP1400 nuclear power plant under the influence of different high-mode vibration, the 1/7 model structure was manufactured and its dynamic characteristics was tested. Secondly, the finite element model of SRC frame-bent structure was established, the seismic response was analyzed by mode-superposition response spectrum method. Taking the combination result of the 500 vibration modes as the standard, the error of the base reactions, inter-story drift, bending moment and shear of different modes were calculated. Then, based on the results, the influence of high-mode vibration on the seismic response of the SRC frame-bent structure of the main plant was analyzed. The results show that when the 34 vibration modes were intercepted, the mass participation coefficient of the vertical and horizontal vibration mode was above 90%, which can meet the requirements of design code. There is a large error between the seismic response calculated by the 34 and 500 vibration modes, and the error decreases as the number of modes increases. When 60 modes were selected, the error can be reduced to about 1%. The error of the maximum bottom moment of the bottom column appeared in the position of the bent column. Finally, according to the characteristics of the seismic influence coefficient αj of each mode, the mode contribution coefficient γj•Xji was defined to reflect the contribution of each mode to the seismic action.

• 천문학논총
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• 제15권1호
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• pp.61-86
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• 2000

Radio astronomy, on its part, requires 'quiet zones' to be able to receive incoming cosmic signals unaffected by interference to enable astronomers and others learn about universe. The agenda item 1.16 of WRC-2000 contains a number of issues relevant for radio astronomy, but some of them are more important than others. The preparations for WRC-2000 have reached a close-to-final stages, with a number of proposals to this agenda item submitted to the ITU by many countries and groups of countries, like APT, CEPT and CITEL. There is no clear preference to anyone of these proposals since their differences are only minor. However, several points remain to be solved in the APT and CITEL. Fortunately, the preparation went very well, and consensus was reached on allocations above 71 GHz and three resolutions. The radio astronomy has obtained about 100 GHz of new spectrum allocations in bands above 71 GHz. In addition, a new resolution was approved by plenary meeting of WRC-2000. It deals with the consideration by a future WRC of sharing and compatibility issues between passive and active services in adjacent bands particularly with the space services (downlinks) into radio astronomy above 71 GHz. Therefore, in future, there should be a need for studies to be made to determine if and under what conditions sharing is possible, given that modifications were made on the basis of requirements known now and that little was known of requirements and implementation plans for active services in bands above 71 GHz.

• 한국음향학회지
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• 제10권4호
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• pp.38-47
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• 1991

음성인식에 있어서 문제점의 하나는 발성자에 따른 주파수 변동문제이다. 본 논문에서는 이러한 음성 신호의 주파수 특성의 변동에 따른 영향을 해결하기 위하여 fuzzy 이론을 도입하였다. 여기서 표준패턴은 음성신호의 대표적인 특징들을 포함하고 있어야 하므로, 먼저 여러 화자가 발성한 단어들을 벡터 양자화한 코드북을 생성하였으며, 이코드북으로 부터 추출한 피크 주파수와 피크 에너지를 fuzzy화 패턴으로 작성하였다. 입력 음성신호로 부터 추출한 특징량인 스펙트럼의 피크 주파수와 피크에너지를 각각 멤버쉽 함수로 표현하여 fuzzy 추론에 의한 단어인식을 하였다. 실제 확신도 계산에 있어서는 계산량을 줄이기 위하여 fuzzy 값의 차만으로 확신도를 구하는 개선 확신도를 제안하여 사용하였다. 한국어 숫자음을 인식 실험한 결과 주파수 특성의 변동에 따른 영향을 해결할 수 있음을 확인하였으며, 제안된 개선 확신도 계산방법에 의해서 기억용량과 계산량을 감소 시킬 수 있었다.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.575-580
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• 2020

We have developed a position-sensitive Parallel Plate Avalanche Counter (PPAC) to detect the fission fragments and reconstruct the fission reaction plane in the experiment of studying nuclear equation of state (nEOS) by means of heavy ion collision (HIC). This experiment put forward high requirements for the performances of PPAC, such as the time resolution, efficiency and position resolution. According to these requirements we designed the PPAC with an active area of 240 mm × 280 mm working at low gas pressure. The results show that time resolution could be less than 300 ps. Position resolution is consistent with the theoretical calculation about 1.35 mm. Detection efficiency could be approaching 100% gradually with the voltage increasing in different gas pressures. The performances of PPAC have also been verified in beam experiment. Each set of anode wires can be accurately separated in the position spectrum. In the beam experiment, we also got the back-to-back correlation of fission fragments which is one of the direct signals characterizing binary decay.

• Journal of Communications and Networks
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• 제7권2호
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• pp.115-125
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• 2005

This paper discusses how to effectively design a next-generation wireless communication system that can possibly provide very high data-rate transmissions and versatile quality services. In order to accommodate the sophisticated user requirements and diversified user environments of the next-generation systems, it should be designed to take an efficient and flexible structure for multiple access and resource allocation. In addition, the design should be optimized for cost-effective usage of resources and for efficient operation in a multi-cell environment. As orthogonal frequency division multiple access (OFDMA) has turned out in recent researches to be one of the most promising multiple access techniques that can possibly meet all those requirements through efficient radio spectrum utilization, we take OFDMA as the basic framework in the next-generation wireless communications system design. So, in this paper, we focus on introducing an OFDMA-based downlink system design that employs the techniques of hybrid multiple access (HMA) and frequency group (FG) in conjunction with intra-frequency group averaging (IFGA). The HMA technique combines various multiple access schemes on the basis of OFDMA system, adopting the multiple access scheme that best fits to the given user condition in terms of mobility, service, and environment. The FG concept and IFGA technique help to reduce the feedback overhead of OFDMA system and the other-cell interference (OCI) problem by grouping the sub-carriers based on coherence band-widths and by harmonizing the channel condition and OCI of the grouped sub-carriers.

• 한국전자파학회논문지
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• 제23권11호
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• pp.1288-1296
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• 2012

최근 기존의 MSS(Mobile Satellite Service) 대역에 지상망과 위성망의 하이브리드 형태인 ATC(Ancillary Terrestrial Component) 서비스 도입이 추진되고 있다. 새로운 MSS/ATC 서비스 주파수 할당을 위해서는 기존의 지상망에 의한 인접 채널 간섭뿐만 아니라 시스템 자체 내의 인접 채널 간섭 분석이 중요하다. 이에 본 논문에서는 인접 채널 간섭에 의한 ACIR(Adjacent Channel Interference Ratio), 지상 이동국 및 위성 이동 지구국의 수를 파라미터로 하여 업링크에서는 지상 기지국 최소 허용 전력 및 시스템 용량(capacity) 손실, 다운링크에서는 1 빔(beam) 당 1 셀(cell)을 가정하여 MSS/ATC 시스템 용량 손실에 대한 시스템 성능을 평가하였다. MSS/ATC 서비스 주파수 배치에 따른 주파수 공유를 위해 두 가지 시나리오 즉, 5 MHz 및 10 MHz 주파수 간격에 대한 ACIR 기준값을 평가하였으며, 향후 이 기준값에 따른 ATC 서비스 커버리지 및 수신 필터 설계 등이 요구된다.