• Earthquakes and Structures
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• 제17권3호
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• pp.271-282
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• 2019

Knowing the response of buildings to earthquakes is very important in order to ensure that a structure is able to withstand a given level of ground shaking. Thus, nonlinear dynamic earthquake engineering analyses are unavoidable and are preferable procedure in the seismic assessment of buildings. In order to estimate seismic performance on the basis of the hazard at the site where the structure is located, the selection of appropriate seismic input is known to be a critical step while performing this kind of analysis. In this paper, seismic analysis is performed for a four-story reinforced concrete ISPRA frame structure which is designed according to Eurocode 8 (EC8). A total of 90 different earthquake scenarios were selected, 30 for each of three target spectrums, EC8 spectrum, Uniform Hazard Spectrum (UHS), and Conditional Mean Spectrum (CMS). The aim of this analysis was to evaluate the average maximum Inter-story Drift Ratio (IDR) for each target spectrum. Time history analysis for every earthquake record was obtained and, as a result, IDR as the main measure of damage were presented in order to compare with defined performance levels of reinforced concrete bare frames.

• 한국위성정보통신학회논문지
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• 제12권4호
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• pp.141-145
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• 2017

스펙트럼 센싱은 인지무선 (cognitive radio) 시스템을 동작시키기 위한 주요한 기법이며 인지무선 시스템을 통해 최근 주목받고 있는 무선에너지하비스팅 시스템에 에너지 하비스팅 효율을 개선할 수 있다. 최근 스펙트럼 센싱을 위한 다양한 기술이 연구되었는데, 그 중에서 가장 널리 쓰이고 있는 에너지 검출 (energy detection) 기술이 있다. 그러나 2차 유저 (secondary user; SU) 가 주파수 페이딩 (frequency fading) 및 쉐도잉 (shadowing)에 의해 영향을 받을 수 있기 때문에, 에너지 검출은 실제 무선 통신에서 숨겨진 단말기 문제 (hidden terminal problem)를 갖는다. 협력 스펙트럼 센싱 (cooperative spectrum sensing)은 SU의 공간적 다양성을 이용하여 이 문제를 해결할 수 있습니다. 그러나 다중 보조를 처리하여 데이터를 증가시키는 문제가 있기 때문에 우리는 적응형 스펙트럼 센싱 알고리즘을 사용하는 시스템 모델을 제안하고 성능을 시뮬레이션 한다. 이 알고리즘은 기본 사용자 (primary user; PU)의 수신 신호의 신호 대 잡음비 (signal to Noise Ratio; SNR)에 따라 단일 에너지 검출과 협동 에너지 사이의 감지 방법을 선택하는 방법을 이용한다. 시뮬레이션 결과를 통해 적응형 스펙트럼 센싱이 인지무선 시스템에서 더 효율적이라는 것을 확인한다.

• 한국해양공학회지
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• 제19권3호
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• pp.25-30
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• 2005

To predict rolling performance for a barge-type FPSO, the evaluation of correct nonlinear roll damping is critical. The square section of FPSO causes a considerable viscous damping effect. Free roll decay tests were carried out to estimate nonlinear roll damping for a barge-type FPSO, under three different conditions. The roll motion RAO was deduced from model tests in the wave condition of the wideband spectrum. In numerical calculation, the quadratic damping was considered as equivalent linear damping, using the results of free roll decay test. Tested roll performance in the JONSWAP wave spectrum was compared with numerical results. These two results shaw good agreement, in spite of the proximity of peak wave period and roll natural period.

• 전자공학회논문지B
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• 제31B권12호
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• pp.51-58
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• 1994

Mathematical morphology based on set theory is easy to be implemented in parallel and can be applied to various fields in image analysis. Particularly mophological pattern spectrum can detect critical scales in an image object and quantify various aspects of the shape-size content. In this paper, texture classification using pattern spectrum based on morphological subband decomposition is porposed. The low-low band extracts pattern spectrum features, and the high-low, low-high, and high-high bands extrack the structural information. This approach has the advantages of efficient information extraction, less time-consuming, high accuacy, less computation, and parallel implementation.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.141-148
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• 2006

This study describes a generation of artificial earthquake wane compatible with seismic design spectrum. In seismic response analysis of building structures, the input ground accelerations have considerable effect on dynamic characteristics of structures. Therefore, it is important to properly select input ground motions for seismic response analysis. In this paper, the artificial earthquake wave are generated according to previously recorded earthquake waves in past earthquake events. The artificial wave have identical phase angles to the recorded earthquake wane, and their overall response spectra are compatible with seismic design spectrum with 5% of critical viscous damping. Each simulated earthquake wave has a identical phase angles to the original recorded ground acceleration, and match to design response spectra in the range of period from 0.02 to 10.0 seconds. It is concluded that the artificial earthquake waves simulated in this paper ate applicable as input ground motions for a seismic response analysis of building structures.

• The Journal of the Acoustical Society of Korea
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• 제25권2E호
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• pp.60-68
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• 2006

High-frequency bistatic scattering measurements from a corrugated surface were made in an acoustic water tank. First the azimuthal scattering pattern was measured from an artificially corrugated surface which has varying impedance. The corrugated surface was installed both transverse to the direction of incident wave and longitudinal to the direction of incident wave. The angle between the corrugated surface and the direction of the incident wave was about $45^{\circ}$. Second, the scattering strengths were measured from the flat sediment and the corrugated sediment. A critical angle of about $37^{\circ}$ was calculated in the acoustic water tank. The measurements were made at three fixed grazing angles: $33^{\circ}$ (lower than critical angle), $37^{\circ}$ (critical angle), and $41^{\circ}$ (higher than critical angle). The scattering angle and the grazing angle are equal in each measurement. Frequencies were from 50 kHz to 100 kHz with an increment of 1 kHz. The corrugated sediment was made transverse to the direction of the incident wave. The first measurement indicates that the scattering patterns depend on the relations between the corrugated surface and the direction of the incident wave. In the second measurement, the data measured from the flat sediment were compared to the APL-UW model and to the NRL model. The NRL model's output shows more favorable comparisons than the APL-UW model. In case of the corrugated sediment, the model and the measured data are different because the models used an isotropic wave spectrum of sediment roughness in the scattering calculations. The isotropic wave spectrum consists of $w_2$ and ${\gamma}_2$. These constants derived from sediment names or bulk size. The model which used the constants didn't consider the effect of a corrugated surface. In order to consider a corrugated surface, the constants were varied in the APL-UW model.

• 정보과학회 논문지
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• 제43권12호
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• pp.1412-1419
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• 2016

인지 무선 센서 네트워크 (CRSNs)에서 보조 사용자가 (SUs) 주 사용자 (PUs)에 간섭을 주지 않고 기회주의적 방식으로 라이선스 대역을 사용할 수 있다. SUs가 스펙트럼 센싱을 통해 PU의 존재 여부를 확인할 수 있다. 그리고 센싱 시간은 스펙트럼 센싱의 중요한 파라미터이다. 센싱 시간은 센싱 성능과 스루풋 간의 균형을 얻을 수 있다. 본 논문에서는 다른 관점에서 이 균형을 탐구하기를 통해 스펙트럼 센싱을 위한 새로운 기법을 제안한다: a) PU의 검출 (SSPD)과 b)스루풋(SSST)을 극대화을 위한 스펙트럼 센싱이다. 제안한 기법에서 현재 프레임의 첫 번째 센싱 결과에 따라 동적인 두 번째 스펙트럼 센싱을 수행한다. CRSNs에서 에너지 제약을 때문에 네트워크 에너지 효율도 센싱 시간의 최적화를 통해 최대화된다. 시뮬레이션 결과를 통하여 제안된 SSPD과 SSST가 각각의 에너지 효율과 스루풋의 성능을 향상시킬 수 있음을 검증하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제17권4호
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• pp.112-118
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• 2013

성능기반 내진설계 및 평가의 정밀도 향상에 있어서 적절한 지반운동 데이터 선정과 이를 합리적으로 수정하는 것에 대한 중요성이 부각되고 있다. 지반운동 데이터를 수정하는 방법으로 단일 진폭수정법 (Amplitude scaling)이 널리 사용되고 있으나, 단일 진폭수정법에서 는 단 하나의 주기, 특히 구조물의 고유주기에서만 그 응답스펙트럼 값이 설계스펙트럼의 값과 일치하도록 수정되므로 특정 지역의 지진 재해도에 대해 일관성 있는 구조 해석 결과를 기대하기 어렵다. 따라서 이에 대해 여러 가지 대안 수정법들이 제시되고 있으나 이들의 타당성을 평가할 수 있는 방안이 마련되어 있지 않다. 본 논문에서는 단일 진폭수정법의 문제점을 설명하고, 대안 수정법과 비교 평가하기 위한 구조 응답에 대한 회귀 모델을 제시하는데 목표를 두었다. 대안 수정법으로써 전체 주기 범위에서 지반운동의 응답스펙트럼이 설계스펙트럼의 값과 일치하도록 수정하는 다중 스펙트럼 수정법을 고려하였다. 설계스펙트럼은 ASCE7-05에 따라 구하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.567-572
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• 2008

This paper's purpose is to improve determining of the critical response of curved bridge to multi-component seismic motion. There are several methods to combine responses by multi-component excitation response, 30%, 40% rules and square-root-of-sum (SRSS). These combination rules determine same value of critical response in straight bridges. However, each method has critical response value of different magnitude in curved bridges. Thus a study about critical response of curved bridges is required. This paper presents comparison critical responses value as each combination rule, 30%, 40% rules and SRSS on curved bridges with the different radiuses of curvature. This study was carried out by response spectrum analysis of OO IC steel box girder bridge using SAP2000. It is concluded as follows: 1) In curved bridges, 30% and 40% rules tend to underestimate the critical response relatively to SRSS. 2) When bridges have smaller radiuses than 100m, difference between SRSS and 30% or 40% rules let run errors up as radiuses of curvature decreased.

• 항공우주시스템공학회지
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• 제1권2호
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• pp.27-36
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• 2007

The Damage Tolerant Design is developed to help alleviate structural failure and cracking problems in aerospace structures. Recently, the Damage Tolerant Design is required and recommended for most of aircraft design. In this paper, the damage tolerant design is applied to tilt rotor UAV. First of all, the fatigue load spectrum for the tilt rotor UAV is developed and fatigue analysis is performed for the flaperon joint which has FCL (fatigue critical location). Tilt rotor UAV has two modes: helicopter mode when UAV is taking off and landing; fixed wing mode when the tilt rotor UAV is cruising. To make fatigue load spectrum, FELIX is used for helicopter mode. TWIST is used for fixed wing mode. Fatigue analysis of flaperon joint is performed using fatigue load spectrum. E-N curve approach is used for picking crack initiation point. The LEFM(Linear Elastic Fracture Method) is considered for analyzing crack growth or propagation. Finally, including the crack initiation and propagation, the fatigue life is evaluated. Therefore the Damage Tolerant Design can be done.