• Smart Structures and Systems
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• 제30권6호
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• pp.687-701
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• 2022

Inevitable response loss under complex operational conditions significantly affects the integrity and quality of measured data, leading the structural health monitoring (SHM) ineffective. To remedy the impact of data loss, a common way is to transfer the recorded response of available measure point to where the data loss occurred by establishing the response mapping from measured data. However, the current research has yet addressed the structural condition changes afterward and response mapping learning from a small sample. So, this paper proposes a novel data driven structural response reconstruction method based on a sophisticated designed generating adversarial network (UAGAN). Advanced deep learning techniques including U-shaped dense blocks, self-attention and a customized loss function are specialized and embedded in UAGAN to improve the universal and representative features extraction and generalized responses mapping establishment. In numerical validation, UAGAN efficiently and accurately captures the distinguished features of structural response from only 40 training samples of the intact structure. Besides, the established response mapping is universal, which effectively reconstructs responses of the structure suffered up to 10% random stiffness reduction or structural damage. In the experimental validation, UAGAN is trained with ambient response and applied to reconstruct response measured under earthquake. The reconstruction losses of response in the time and frequency domains reached 16% and 17%, that is better than the previous research, demonstrating the leading performance of the sophisticated designed network. In addition, the identified modal parameters from reconstructed and the corresponding true responses are highly consistent indicates that the proposed UAGAN is very potential to be applied to practical civil engineering.

• Smart Structures and Systems
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• 제15권1호
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• pp.15-40
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• 2015

This paper proposes a structural damage identification approach based on the power spectral density transmissibility (PSDT), which is developed to formulate the relationship between two sets of auto-spectral density functions of output responses. The accuracy of response reconstruction with PSDT is investigated and the damage identification in structures is conducted with measured acceleration responses from the damaged state. Numerical studies on a seven-storey plane frame structure are conducted to investigate the performance of the proposed damage identification approach. The initial finite element model of the structure and measured acceleration measurements from the damaged structure are used for the identification with a dynamic response sensitivity-based model updating method. The simulated damages can be identified accurately without and with a 5% noise effect included in the simulated responses. Experimental studies on a steel plane frame structure in the laboratory are performed to further verify the accuracy of response reconstruction with PSDT and validate the proposed damage identification approach. The locations of the introduced damage are detected accurately and the stiffness reductions in the damaged elements are identified close to the true values. The identification results demonstrated the accuracy of response reconstruction as well as the correctness and efficiency of the proposed damage identification approach.

• 한국음향학회지
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• 제20권6호
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• pp.9-16
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• 2001

본 논문에서는 음파를 이용하여 덕트 내 길이 방향으로의 불균일 단면적을 역문제적으로 측정하는 방법에 대해서 연구하였다. 음파를 사사용하여 덕트 단면적을 구하는 이론 및 실험방법 등에 대해서 많은 연구가 되어왔으나, 본 연구에서는 덕트 내 충격응답을 구하고 이를 재구성 알고리즘에 대입하여 덕트 내 단면적을 구하는 방법을 채택하였다. 충격 가진을 통하여 덕트 내 충격응답을 구하는 기존 방법의 문제점을 살펴보았고, 광대역 가진 방법을 새로 제안하였다. 실험 및 이론적 고찰을 통하여 새로운 방법이 기존의 방법보다 면적 재구성 오차가 적음을 보였다. 덕트 단면적을 재구성 할 때의 오차 원인과 불규칙 잡음에 의한 오차범위를 파악하기 위하여 오차해석을 수행하여 음파를 이용한 면적 재구성 방법의 적용범위 및 대상을 명확히 하였다.

• 제어로봇시스템학회논문지
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• 제11권10호
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• pp.870-879
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• 2005

This paper presents that a transient response can be characterized by certain parameters which are correlated to characteristic polynomial coefficients. These are characteristic ratios and characteristic pulsatances by P. Naslin [4]. We have developed an approach to control directly the transient response. Firstly, speed of the response can be controlled by reconstruction form via multipliable characteristic pulsatances. Secondly, overshoot is controlled by reconstruction form via multipliable characteristic ratios. These formulas can be independently characterized by the system overshoot and the response time to a step input.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1587-1592
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• 2023

Time-encoded imagers (TEI) are important class of instruments to search for potential radioactive sources to prevent illicit transportation and trafficking of nuclear materials and other radioactive sources. The energy of the radiation cannot be known in advance due to the type and shielding of source is unknown in practice. However, the response function of the time-encoded imagers is related to the energy of neutrons or gamma-rays. An improved image reconstruction method based on MLEM was proposed to correct for the energy induced response difference. In this method, the count vector versus time was first smoothed. Then, the preset response function was adaptively corrected according to the measured counts. Finally, the smoothed count vector and corrected response were used in MLEM to reconstruct the source distribution. A one-dimensional dual-particle time-encode imager was developed and used to verify the improved method through imaging an Am-Be neutron source. The improvement of this method was demonstrated by the image reconstruction results. For gamma-ray and neutron images, the angular resolution improved by 17.2% and 7.0%; the contrast-to-noise ratio improved by 58.7% and 14.9%; the signal-to-noise ratio improved by 36.3% and 11.7%, respectively.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.923-928
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• 2022

Wildfire disasters in the United States impact lives and livelihoods by destroying private homes, businesses, community facilities, and infrastructure. Disaster victims suffer from damaged houses, inadequate shelters, inoperable civil infrastructure, and homelessness coupled with long-term recovery and reconstruction processes. Cities and their neighboring communities require an enormous commitment for a full recovery for as long as disaster recovery processes last. State, county, and municipal governments inherently have the responsibility to establish and provide governance and public services for the benefit and well being of community members. Municipal governments' comprehensive and emergency response plans are the artifacts of planning efforts that guide accomplishing those duties. Typically these plans include preparation and response to natural disasters, including wildfires. The standard wildfire planning includes and outlines (1) a wildfire hazard assessment, (2) response approaches to prevent human injury and minimize damage to physical property, and (3) near- and long-term recovery and reconstruction efforts. There is often a high level of detail in the assessment section, but the level of detail and specificity significantly lessons to general approaches in the long-term recovery subsection. This paper aims to document the extent of wildfire preparedness at the county level in general, focusing on the long-term recovery subsections of municipal plans. Based on the identified challenges, the researchers provide recommendations for better longer-term recovery and reconstruction opportunities: 1) building permit requirements, 2) exploration of the use of modular construction, 3) address through relief from legislative requirements, and 4) early, simple, funding, and the aid application process.

• Earthquakes and Structures
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• 제2권4호
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• pp.323-336
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• 2011

The problem of reconstruction of complete building response from a limited number of response measurements is considered. The response at the intermediate degrees of freedom is reconstructed by using piecewise cubic Hermite polynomial interpolation in time domain. The piecewise cubic Hermite polynomial interpolation is preferred over the spline interpolation due to its trend preserving character. It has been shown that factorization of response data in variable separable form via singular value decomposition can be used to derive the complete set of normal modes of the structural system. The time domain principal components can be used to derive empirical transfer functions from which the natural frequencies of the structural system can be identified by peak-picking technique. A reduced-rank approximation for the system flexibility matrix can be readily constructed from the identified mass-orthonormal mode shapes and natural frequencies.

• 융합보안논문지
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• 제22권4호
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• pp.25-34
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• 2022

본 논문은 군집 드론, 무인기 편대 운용 시 자율적인 통신망 구축을 위해 활용 가능한 FANET(Flying Ad-Hoc Network)에 적용할 비밀분산 기반의 신속한 노드 인증 기법을 제안한다. FANET 환경에서 운용되는 각 노드는 필드에 전개되기 이전에 지수 분산비밀(share), 지수 원본비밀(secret) 및 PUF CRP(Challenge-Response Pair) 테이블 중 일부분을 저장한다. 필드에 배치된 이후 네트워크 형성 초기 단계에서 각 노드는 ID, 지수 분산비밀과 자신의 PUF Response 및 의사난수가 결합되어 해시 된 값을 네트워크로 브로드캐스트한다. 개별 노드는 이웃 노드들로부터 전송받은 지수 분산비밀을 이용, 지수 원본비밀의 복원 연산을 수행한다. 지수 원본비밀이 복원되면 연산에 사용된 지수 분산비밀을 전송한 모든 노드에 대한 동시 인증이 완료된다. 잘못된 지수 분산비밀을 전송하여 인증과정에서 원본비밀 복원을 방해하는 노드는 원본비밀 복원 연산을 수행하기 이전에 PUF 값을 검증하여 탐지하고, 복원 연산에서 배제한다.

• 제어로봇시스템학회논문지
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• 제8권4호
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• pp.308-312
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• 2002

To determine the natural frequencies and damping ratios of composite laminated plates, we present an officient modal parameter estimation technique by developing residual spectrum based structural system reconstruction. The modal parameters can be estimated from poles and residues of the system transfer functions, derived from the state space system matrices. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios can be estimated using the modal coordinates of the structural dynamic system reconstructed from the experimental frequency response functions. These results are compared with those of finite element analysis and single-degree-of-freedom curve fitting.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.150-150
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• 2000

We as modal parameter estimation technique by developing a residual based system reconstruction and using the system matrix coordinate transformation. The modal parameters can be estimated from and residues of the system transfer functions expressed in modal coordinate basis, derived from the state space system matrices. However, for modal parameter estimation of multivariable and order structural systems over broad frequency bands, this non-iterative algorithm gives high accuracy in the natural fre- and damping ratios. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios on be estimated using tile coordinates of the structural system reconstructed fro the experimental frequency response. These results are compared with those of finite element analysis and single-degree-of-freedom curve-fitting.