Measurement Of Dynamic Response Research Articles

Dynamic-Feature Extraction, Attribution, and Reconstruction (DEAR) Method for Power System Model Reduction

In interconnected power systems, dynamic model reduction can be applied to generators outside the area of interest (i.e., study area) to reduce the computational cost associated with transient stability studies. This paper presents a method of deriving the reduced dynamic model of the external area based on dynamic response measurements. The method consists of three steps, namely dynamic-feature extraction, attribution, and reconstruction (DEAR). In this method, a feature extraction technique, such as singular value decomposition (SVD), is applied to the measured generator dynamics after a disturbance. Characteristic generators are then identified in the feature attribution step for matching the extracted dynamic features with the highest similarity, forming a suboptimal “basis” of system dynamics. In the reconstruction step, generator state variables such as rotor angles and voltage magnitudes are approximated with a linear combination of the characteristic generators, resulting in a quasi-nonlinear reduced model of the original system. The network model is unchanged in the DEAR method. Tests on several IEEE standard systems show that the proposed method yields better reduction ratio and response errors than the traditional coherency based reduction methods.

Dynamic characterisation of a ballast layer subject to traffic impact loads using three-dimensional sensing stones and a special sensing sleeper

Spectral analyses, based on field measurement of dynamic response of the ballast layer subject to traffic loads, evaluated the dependency on frequency regarding attenuation effect and strength of ballast layer. The measurement was conducted by using high-performance three-dimensional acceleration sensors and a special sensing-sleeper, which was assembled to assess the dynamic response loads acting on the sleeper bottom at a wide frequency domain. The measured results confirmed that for impact-load components over 100Hz, the ballast layer resists because of its high rigidity and can reduce the impact loads substantially. However, the ballast layer is almost non-resistant to the low-frequency load components, which are not reduced enough. The finite element vibration analysis of the ballast aggregate, whose ballast stones are expressed as a polyhedron model using a three-dimensional discrete element method, examines frequency characteristics up to high-frequencies and clarifies the stress distribution of the ballast and the wave propagation of the ballast stone.

Experimental studies and micromagnetic simulations of electrodeposited Co nanotube arrays

Magnetic hollow nanotubes of cobalt forming close-packed arrays are synthesized by controlling the growth during electrodeposition in AAO template. Superconducting quantum interference device (SQUID) magnetometry is used to experimentally measure the static magnetization of the array of nanotubes. Excellent qualitative agreements of SQUID and micromagnetic simulations for static measurements are observed. This motivates us to evaluate dynamic response measurements via micromagnetic simulations. The coercivity simulated along the longitudinal axis of the nanotube is found increase with the length of isolated as well as for array of nanotubes. The effect of interactions is also clearly observed both in static as well as in dynamic evaluations. The interactions cause reduction in coercivity along with the switching which depends upon the length of the nanotubes. The calculation for FMR modes also indicates that propagation of the spin waves are greatly influenced by the hollow centre of nanotube as compare to nanowire and support to maintain the stable vortex configuration. For array of nanotubes, multiple peaks are found over larger number of frequencies which is anticipated due the interactions between nanotubes. Simulation for bias field and angular dependence of spin wave modes also yields a significant influenced by the presence of neighbouring nanotubes.

Novel Outlier-Resistant Extended Kalman Filter for Robust Online Structural Identification

AbstractStructural health monitoring (SHM) using dynamic response measurement has received tremendous attention over the last decades. In practical circumstances, outliers may exist in the measurements that lead to undesirable identification results. Therefore, detection and special treatment of outliers are important. Unfortunately, this issue has rarely been taken into systematic consideration in SHM. In this paper, a novel outlier-resistant extended Kalman filter (OR-EKF) is proposed for outlier detection and robust online structural parametric identification using dynamic response data possibly contaminated with outliers. Instead of definite judgment on the outlierness of a data point, the proposed OR-EKF provides the probability of outlier for the measurement at each time step. By excluding the identified outliers, the OR-EKF ensures the stability and reliability of the estimation. In the illustrative examples, the OR-EKF is applied to parametric identification for structural systems with time-varyin...

Label-free cell-based assay with spectral-domain optical coherence phase microscopy

Quantitative measurement of dynamic responses of unstained living cells is of great importance in many applications ranging from investigation of fundamental cellular functions to drug discoveries. Conventional optical methods for label-free cell-based assay examine cellular structural changes proximal to sensor surfaces under external stimuli, but require dedicated nanostructure-patterned substrates for operation. Here, we present a quantitative imaging method, spectral-domain optical coherence phase microscopy (SD-OCPM), as a viable optical platform for label-free cell-based assay. The instrument is based on a low-coherence interferometric microscope that enables quantitative depth-resolved phase measurement of a transparent specimen with high phase stability. We demonstrate SD-OCPM measurement of dynamic responses of human breast cancer cells (MCF-7) to 2-picolinic acid (PA) and histamine.

Frequency response function based damage identification using principal component analysis and pattern recognition technique

Pattern recognition is a promising approach for the identification of structural damage using measured dynamic data. Much of the research on pattern recognition has employed artificial neural networks (ANNs) and genetic algorithms as systematic ways of matching pattern features. The selection of a damage-sensitive and noise-insensitive pattern feature is important for all structural damage identification methods. Accordingly, a neural networks-based damage detection method using frequency response function (FRF) data is presented in this paper. This method can effectively consider uncertainties of measured data from which training patterns are generated.The proposed method reduces the dimension of the initial FRF data and transforms it into new damage indices and employs an ANN method for the actual damage localization and quantification using recognized damage patterns from the algorithm. In civil engineering applications, the measurement of dynamic response under field conditions always contains noise components from environmental factors. In order to evaluate the performance of the proposed strategy with noise polluted data, noise contaminated measurements are also introduced to the proposed algorithm. ANNs with optimal architecture give minimum training and testing errors and provide precise damage detection results. In order to maximize damage detection results, the optimal architecture of ANN is identified by defining the number of hidden layers and the number of neurons per hidden layer by a trial and error method. In real testing, the number of measurement points and the measurement locations to obtain the structure response are critical for damage detection. Therefore, optimal sensor placement to improve damage identification is also investigated herein.A finite element model of a two storey framed structure is used to train the neural network. It shows accurate performance and gives low error with simulated and noise-contaminated data for single and multiple damage cases. As a result, the proposed method can be used for structural health monitoring and damage detection, particularly for cases where the measurement data is very large. Furthermore, it is suggested that an optimal ANN architecture can detect damage occurrence with good accuracy and can provide damage quantification with reasonable accuracy under varying levels of damage.

An optical instrument based on defocusing for dynamic response model testing in water or wind tunnels

The design and performance of an optical measurement system that can be used for studying the three-dimensional dynamic response of flexibly mounted rigid or elastic bodies in laboratory facilities is presented. The photogrammetric technique implemented on the instrument is based on the defocusing principle, which was first introduced for three-dimensional (3D) robotic vision applications. The technique was later on applied for the measurement of seeded 3D flow velocity fields. The emphasis of this work is given to the design of the tool itself as well as to its validation by using an application that involves the dynamics of a spar floater in a water tank. The final purpose of this work is to produce a non-intrusive and accurate instrument for measuring the fluid-induced responses or deformations of bodies in laboratory facilities. The result is an optical tool that provides an accurate and better alternative to other traditional dynamic response measurement techniques used to study vortex-induced vibrations (VIV), wave-induced motions (WIM), etc. in water or wind tunnels.

Integrating a hive triangle pattern with subpixel analysis for noncontact measurement of structural dynamic response by using a novel image processing scheme.

This work presents a digital image processing approach with a unique hive triangle pattern by integrating subpixel analysis for noncontact measurement of structural dynamic response data. Feasibility of proposed approach is demonstrated based on numerical simulation of a photography experiment. According to those results, the measured time-history displacement of simulated image correlates well with the numerical solution. A small three-story frame is then mounted on a small shaker table, and a linear variation differential transformation (LVDT) is set on the second floor. Experimental results indicate that the relative error between data from LVDT and analyzed data from digital image correlation is below 0.007%, 0.0205 in terms of frequency and displacement, respectively. Additionally, the appropriate image block affects the estimation accuracy of the measurement system. Importantly, the proposed approach for evaluating pattern center and size is highly promising for use in assigning the adaptive block for a digital image correlation method.

Recent research and applications of numerical simulation for dynamic response of long-span bridges subjected to multiple loads.

Many long-span bridges have been built throughout the world in recent years but they are often subject to multiple types of dynamic loads, especially those located in wind-prone regions and carrying both trains and road vehicles. To ensure the safety and functionality of these bridges, dynamic responses of long-span bridges are often required for bridge assessment. Given that there are several limitations for the assessment based on field measurement of dynamic responses, a promising approach is based on numerical simulation technologies. This paper provides a detailed review of key issues involved in dynamic response analysis of long-span multiload bridges based on numerical simulation technologies, including dynamic interactions between running trains and bridge, between running road vehicles and bridge, and between wind and bridge, and in the wind-vehicle-bridge coupled system. Then a comprehensive review is conducted for engineering applications of newly developed numerical simulation technologies to safety assessment of long-span bridges, such as assessment of fatigue damage and assessment under extreme events. Finally, the existing problems and promising research efforts for the numerical simulation technologies and their applications to assessment of long-span multiload bridges are explored.

Study on dynamic response measurement of the submarine pipeline by full-term FBG sensors.

The field of structural health monitoring is concerned with accurately and reliably assessing the integrity of a given structure to reduce ownership costs, increase operational lifetime, and improve safety. In structural health monitoring systems, fiber Bragg grating (FBG) is a promising measurement technology for its superior ability of explosion proof, immunity to electromagnetic interference, and high accuracy. This paper is a study on the dynamic characteristics of fiber Bragg grating (FBG) sensors applied to a submarine pipeline, as well as an experimental investigation on a laboratory model of the pipeline. The dynamic response of a submarine pipeline under seismic excitation is a coupled vibration of liquid and solid interaction. FBG sensors and strain gauges are used to monitor the dynamic response of a submarine pipeline model under a variety of dynamic loading conditions and the maximum working frequency of an FBG strain sensor is calculated according to its dynamic strain responses. Based on the theoretical and experimental results, it can be concluded that FBG sensor is superior to strain gauge and satisfies the demand of dynamic strain measurement.

S1910202 回収カプセル着水時の動的応答計測と簡易解析([S191-02]大気突入・減速技術(2),宇宙工学部門)

S1910202 回収カプセル着水時の動的応答計測と簡易解析([S191-02]大気突入・減速技術(2),宇宙工学部門)

Running Behavior of a High-Speed Spindle Using a Micro-Mist Lubrication System

This work investigates the effect of lubrication parameter on the operation performance of a high-speed spindle using a micro-mist lubrication system. Experiments are conducted through a long-time spindle test under different combinations of oil-supply parameter and rotating speed for a micro-mist lubricated spindle. The correspondent relationships among temperature rise, vibration, oil-supply parameter and rotating speed are established through the experiments under moderate oil-supply. The results show that the better oil-supply parameter combinations exist under different spindle rotating speeds, which could ensure the sufficient and adequate lubricating oil film to be formed and a stable elasto-hydro-dynamic lubrication could be further created during the operation period. The minimization of the temperature rise in bearings may be attained. Increasing air pressure contributed to the reduction in bearing temperature, but saturation might be appeared after the pressure level reached to a certain extent. The dynamic response measurement shows that this prototype spindle has an overly large vibration and rotation unbalance on the radial plane, which highlights the unstable operation problem of the spindle. Therefore, it is necessary to improve the constructed procedures, such as design, manufacture, and assembly for further use, to enhance the operation performance of the spindle. The analysis, measurement and diagnosis procedures established in this study could be helpful to uplift the related techniques for precision machinery industry.

Abstract A016: Electrical impedance assessment of the effect of LBH589 on the cellular behavior and migratory potential of breast cancer cells

Abstract We have previously shown histone deacetylase inhibitor, LBH589 (Panobinostat), to increase E-cadherin expression and alter mesenchymal MDA-MB-231 cell morphology to a more epithelial phenotype suggestive of the reversal of EMT (epithelial-to-mesenchymal transition). As EMT has been linked to enhanced cell motility, we examined the effects of LBH589 on breast cancer cells in vitro. Electrical Cell-substrate Impedance Sensing (ECIS) allows for real-time, noninvasive measurement of cell behavior and reproducible wounding by lethal electroporation of the cell monolayer for migration studies. Method: A 1 uA, 4kHz AC current applied across surface electrodes (250-μm diameter) provided electrical impedance monitoring capability, as MBA-MB-231 or MCF-7 breast cancer cells attached, spread, proliferate on the substrate. Measurements were reported as calculated resistance and capacitance. As cells grow on the substrate, the cell-electrode interaction is such that the current is forced to flow underneath and between cells. At 64 kHz, the capacitance is an indicator of electrode surface coverage. At 1 kHz, the resistance is an indicator of tight-junction formation between adjacent cells. As a monolayer develops, a decrease in capacitance and increase in resistance is observed. Upon visual confirmation of established cell monolayers, cells were treated with the LBH589 and cellular response was measured for 24 hrs. Afterwards, an elevated current (1 mA, 40 kHz, duration >200 ms) was applied to the surface electrode, permanently damaging cell plasma membranes directly above the electrode and creating a defined gap in the monolayer or ‘wound’. Repopulation of the ‘wound’ was then monitored for 24 hrs. Results: Cells were successfully grown and electrically monitored on the ECIS arrays. Micrographs show that proliferating MCF-7 and MDA-MB-231 cells gradually covered the electrode surface. MCF-7 cells arranged into a ‘cobblestone’ monolayer without gaps between adjacent cells, whereas MDA-MB-231 cells formed a loose monolayer with spaces between neighboring cells. At 22 hrs, the capacitance values for MCF-7 and MDA-MB-231 cells were observed to stabilize at ~1.3 nF and ~7.5 nF, respectively. The corresponding resistance values were ~40,000 Ohm and ~2,100 Ohm, respectively. LBH589 exposure did not affect MCF-7 morphology, as capacitance or resistance values remained nearly constant at ~1.5 nF and ~40,000 Ohm, respectively. However, LBH589 appears to have a gradual effect on MDA-MB-231 cell monolayers, decreasing the capacitance value to ~3.5 nF and resistance to ~3,400 Ohm. Micrograph images taken after exposure indicate morphological changes in MDA-MB-231 cells from spindle-shaped to a more epithelial phenotypes. In situ lethal electroporation introduced a ‘wound’ in the monolayer, generating a migration assay with a circular gap 250 μm in diameter. Live/dead staining performed 30 mins after electroporation indicated that cells on the electrode were dead. The corresponding resistance and capacitance values dropped to baseline (cell-free media) levels prior to recovery to control levels (non-electroporated cells). Based on measured resistance, the time to recovery for both LBH589-treated and untreated MCF-7 cells was ~7 hrs (radial migration rate of 17.9 μm/hr). Similarly, the time to recovery for treated MDA-MB-231 cells was ~2 hrs (62.5 μm/hr). Conclusion: LBH589 appears to have an effect the morphology and the migration of MDA-MB-231, but not MCF-7, cells, as monitored by electrical measurements. ECIS provides a powerful tool to measure real-time functional cellular behavior, as well as a robust and reproducible method for assessing the migration potential of cancer cells. Measurement of dynamic cellular response following drug treatment could lead to more accurate evaluation of drug treatment against cancer. Citation Format: Theresa B. Phamduy, Lyndsay V. Rhodes, Matthew E. Burow, Douglas B. Chrisey. Electrical impedance assessment of the effect of LBH589 on the cellular behavior and migratory potential of breast cancer cells. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr A016.

Low-Cost Tower Root Fatigue Load Estimation for Structural Health Monitoring of Grouted Connections in Offshore Wind Turbines

The sinking of wind turbines (WTs) with monopile foundations is one of the major issues in the offshore wind industry nowadays. Dynamic wind and wave loads act on the WTs causing vibrations of the structure. However, grouted connections in the monopiled WTs are not designed well enough to transfer bending moments from the wind loading. When the load capacity of the grouted connection is reached, stress cracks appear in the grout causing transition piece to slide down. Direct measuring of the fatigue load, called the tower bending moment, causing fatigue failures and sinking of the WTs is expensive and practically unfeasible. This paper suggests a low-cost, model-based algorithm for indirect measuring of the tower bending moments from the WT dynamic response measurements. The bending moment is estimated recursively using well-known Kalman filter theory. The method is validated using WT simulated data, assuming different measurement noise levels.

Characterization of the Nonlinear Thermal Resistance and Pulsed Thermal Dynamic Behavior of AlGaN–GaN HEMTs on SiC

A laboratory setup, along with a set of measurement and identification procedures, have been developed expressly for the characterization of the thermal behavior of AlGaN/GaN HEMTs, suitable for microwave high power amplifier (HPA) design. The setup allows the measurement of the drain current time-domain dynamic response to positive drain bias pulses, performed at different temperatures and different dissipated power densities. The proposed measurement conditions discriminate thermal phenomena from electrical dispersive effects for this particular technology. Both the thermal resistance and the “transient thermal resistance” are identified for a single-cell 1-mm device and for a 4-mm power-bar composed of four devices, designed to be used as the final stage of a monolithic $C$ -band HPA for pulsed radar application. Transient data allow to compute the device operative channel temperature as a function of the pulsewidth and duty cycle, which is a crucial feature for pulsed HPA applications, typical for the GaN technology. The measured thermal data point out the nonlinearity of the thermal resistance versus dissipated power and base-plate temperature and the consequent critical thermal issue inherent in physically packing together such devices.

Identification of the nonlinear properties of rubber-bearings in base-isolated buildings with limited seismic response data

Seismic behaviors of base-isolated structures are highly affected by the nonlinear characteristics of the isolated systems. Most of the currently available methods for the identification of nonlinear properties of isolator require either the measurements of all structural responses or the assumptions of the proper mathematic models for the rubber-bearings. In this paper, two algorithms are proposed to identify the nonlinear properties of rubber-bearings in base-isolated buildings using only partial measurements of structural dynamic responses. The first algorithm is applicable to the case that proper mathematical models are available for the base isolators. It is based on the extended Kalman filter for the parametric identification of nonlinear models of rubber-bearing isolators and buildings. For the general case where it is difficult to establish a proper mathematical model to describe the nonlinear behavior of a rubber-bearing isolator, another algorithm is proposed to identify the model-free nonlinear property of rubber-bearing isolated system. Nonlinear effect of rubber-bearing is treated as ‘fictitious loading’ on the linear building under severe earthquake. The algorithm is based on the sequential Kalman estimator for the structural responses and the least-squares estimation of the ‘fictitious loading’ to identify the nonlinear force of rubber-bearing isolator. Simulation results demonstrate that the proposed two algorithms are capable of identifying the nonlinear properties of rubber-bearing isolated systems with good accuracy.

Rutting Mechanism Analysis of Heavy-duty Asphalt Pavement Based on Pavement Survey, Finite Element Simulation, and Instrumentation

Abstract The vertical strain of an asphalt layer is essentially important when identifying rutting mechanisms or causes in asphalt pavement with a semi-rigid base course, which is a typical pavement structure in China. As a result, three directional strain measurements (longitudinal, transverse, and vertical strain) in the field, together with a pavement rutting survey and finite element simulation, were carried out in order to clarify the causes of rutting happening in Beijing heavy-duty expressways. First, the basic principal of a fiber Bragg grating sensor is explained, followed by the introduction of sensor installation in the field. Then, a three-dimensional finite element pavement model subjected to a non-uniform moving load was established to validate the dynamic response measurement on site. Finally, based on a comprehensive analysis including a pavement condition survey, numerical simulation, and strain measurement, the rutting mechanism of heavy-duty asphalt pavement in Beijing is discussed. The results show that the occurrence of shear deformation within asphalt layers results in the rutting development, in which material weakness, modulus mismatch of asphalt layers, and heavy-duty characteristics play important roles. Optimizing asphalt layers’ moduli, i.e., making them match, might make pavement bear the applied loading with integrity, thus averting the occurrence of excessive local strain, i.e., rutting.

Identification of Nonlinear Parameters of Rubber-Bearing in Base-Isolated Building

The research about base isolation in building construction in the region of medium risk seismicity has now received great attention. Seismic behavior of base-isolated structures is highly dependent on the nonlinear properties of the rubber-bearing isolated system. Thus, it’s very necessary and significant to identify the nonlinear properties of the rubber-bearing exactly with suitable method. In this paper, a data-based method solely using the time series of structural dynamic response and excitation measurements is proposed to identify the nonlinear parameters of rubber-bearing isolated system. The method is based on the sequential application of extended Kalman estimator for the nonlinear structural parameters. A numerical simulation results demonstrate that the proposed method is capable of identifying the nonlinear parameters of rubber-bearing isolated system with good accuracy.

Sub-cellular Dynamic Mechanical Response Measurements of Live Human Pulmonary Artery Endothelial Cells with Atomic Force Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

고층건물의 자연 진동실험 및 시스템판별

구조물의 특성치를 결정하기 위하여 18층 규모의 사무용 건물 3동에 대하여 자연진동 조건하에서 동적계측실험을 수행하였다. 대상건물은 기본적으로 보-기둥 골조시스템에 횡하중을 보다 효율적으로 지지하기 위하여 추가적으로 코아가 배치된 혼합 구조형식을 나타낸다. 매층 마다 측정한 일련의 진동기록으로부터 고유진동수, 모드형태 및 감쇠율 등과 같은 모달계수를 추출하기 위하여 최신 주파수- 및 시간영역-기반 응답의존 시스템판별법인 FDD, pLSCF 및 SSI를 적용하였다. 3방법에 의하여 추출한 결과는 대체로 일치하였으나, 초기 FE 해석결과와 비교하여 저차 3개 고유진동수는 대략 1.2~1.7배나 되는 단단한 거동을 나타냈다. 진동응답으로부터 추출된 값, 기준에서 제시하는 약산식 및 FE해석에 의하여 산정된 고유주기를 비교하여 보면, FE결과가 가장 유연한 거동을 예측하였으며, 높이를 변수로 하는 약산식이 추출된 값에 가장 근접한 결과를 나타냈다. 이러한 차이는 현재의 실험 추출치에는 콘크리트 균열 등과 같은 강성저감 요인을 포함하고 있지 않으며, 또한 FE 해석치는 비구조체 및 사용된 재료의 실제성능 등과 관련된 강성증가 요소를 포함하고 있지 않기 때문이다. Dynamic response measurements from natural excitation were carried out for three 18-story office buildings to determine their inherent properties. The beam-column frame system was adopted as a typical structural form, but a core wall was added to resist the lateral force more effectively, resulting in a mixed configuration. To extract modal parameters such as natural frequencies, mode shapes and damping ratios from a series of vibration records at each floor, the most advanced operational system identification methods based on frequency- and time-domain like FDD, pLSCF and SSI were applied. Extracted frequencies and mode shapes from the different identification methods showed a greater consistency for three buildings, however the three lower frequencies extracted were 1.2 to 1.7 times as stiff as those obtained using the initial FE models. Comparing the extracted fundamental periods with those estimated from the code equations and FE analysis, the FE analysis results showed the most flexible behavior, and the most simple equation that considers the building height as the only parameter correlated fairly well with test results. It is recognized that such a discrepancy arises from the fact that the present tests exclude the stiffness decreasing factors like concrete cracking, while the FE models ignore the stiffness increasing factors, such as the contribution of non-structural elements and the actual material properties used.