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This paper presents a non-invasive methodology for structural health monitoring (SHM) integrated with inertial sensors and signal conditioning techniques. The proposal uses the signal of an IMU (inertial measurement unit) tri-axial accelerometer and gyroscope to continuously measure the displacements of a structure in motion due to seismic vibrations. A system, called the "Inertial Displacement Monitoring System" or "IDMS", is implemented to attenuate the signal error of the IMU with methodologies such as a Kalman filter to diminish the influence of white noise, a Chebyshev filter to isolate the frequency values of a seismic motion, and a correction algorithm called zero velocity observation update (ZVOB) to detect seismic vibrations and diminish the influence of external perturbances. As a result, the IDMS is a methodology developed to measure displacements when a structure is in motion due to seismic vibration and provides information to detect failures opportunely. [ABSTRACT FROM AUTHOR]

The seismic vibration measurement of reinforced concrete (RC) structures is an important aspect of post‐disaster reconstruction. Unfortunately, the existing method of installing sensors on walls and columns is prohibitively expensive, and the measurement signals are prone to loss during seismic vibration. In this paper, a marker‐free measurement method based on the Lucas‐Kanade (L‐K) optical flow algorithm for vibration measurements of RC structures under seismic vibration has been developed. In addition, to improve the accuracy of L‐K optical flow in dealing with the RC structure under seismic vibration, a new approach for selecting the feature point that is used to solve the restrictions of manual marking, as well as an adaptive matched window strategy that uses different sizes of matched window along the motion to replace the fixed matched window in the original L‐K algorithm, are proposed. The precision of the proposed method is first validated by comparing it to the original L‐K optical flow algorithm. Then, compare its precision and efficiency to the existing vision‐based methods, including feature matching (FM) and digital image correlation (DIC). Finally, the behaviors of RC structures during seismic vibration, such as inter‐story drift, frequency, and strain, are investigated. The results show that, when compared to the original L‐K optical flow algorithm and other vision‐based methods, the proposed method can accurately and efficiently measure motion without spraying speckle or high contrast markers on the structure's surface, and it enables the rapid diagnosis of structures affected by earthquakes. [ABSTRACT FROM AUTHOR]

The paper analyses an opportunity to develop predictive models for identification of parameters of seismic vibrations by applying statistical processing of measurement data. The calculations used measurement data arrays according to vectors E, N and Z obtained from four seismic stations (India EVBH, Indonesia LUWIBH, Italy CERABN and Turkey BNHBH). The Doppler method and the theory of covariance functions were applied for analysing the measurement data arrays. The trend of seismic vibration intensity vectors was estimated by applying the least-squares method. In addition, the said procedure partially eliminates random errors of the measurement data from the stations. Using the intensity variation of seismic vibration vectors E, N and Z on the timescale, the estimates of autocovariance and cross-covariance functions of seismic vibration vectors were calculated by changing the quantised interval on the time scale. The average values of parameter z in the Doppler formula were calculated according to the created formula by applying the expressions of cross-covariance functions of the algebraic addition of the relevant vectors and a single vector. By applying the values of parameter z from the Doppler formula, the approximate value of the velocity of reciprocal movement of seismic vectors was calculated. In the calculations, the software developed on the basis of the MATLAB program package operators was applied. [ABSTRACT FROM AUTHOR]

African elephants (Loxodonta africana) use many sensory modes to gather information about their environment, including the detection of seismic, or ground-based, vibrations. Seismic information is known to include elephant-generated signals, but also potentially encompasses biotic cues that are commonly referred to as 'noise'. To investigate seismic information transfer in elephants beyond communication, here we tested the hypothesis that wild elephants detect and discriminate between seismic vibrations that differ in their noise types, whether elephant- or human-generated. We played three types of seismic vibrations to elephants: seismic recordings of elephants (elephant-generated), white noise (human-generated) and a combined track (elephant- and human-generated). We found evidence of both detection of seismic noise and discrimination between the two treatments containing human-generated noise. In particular, we found evidence of retreat behaviour, where seismic tracks with human-generated noise caused elephants to move further away from the trial location. We conclude that seismic noise are cues that contain biologically relevant information for elephants that they can associate with risk. This expands our understanding of how elephants use seismic information, with implications for elephant sensory ecology and conservation management. [ABSTRACT FROM AUTHOR]

To this day, the petroleum industry is still searching for alternative ways to improve the recovery of hydrocarbon from the reservoir. The residual oil blotches may consist of about 30%–40% or more of a volume fraction. Seismic stimulation has great potential for IOR (improved oil recovery), because of its advantages on low cost, high effectivity, and environment-friendly as they introduce no formation damage, etc. The investigation and application of seismic stimulation have been launched for over 70 years. In this study, a literature review on the mechanism for IOR, including laboratory and theoretical modeling work, and oilfield application, is present here. Firstly, four different manners of vibration are introduced, and the seismic vibration with 1 Hz–100 Hz (frequency) and 1 μm–100 μm (amplitude) is the commonly used; Secondly, the mechanisms of IOR by seismic stimulation are summarized as: effect on capillary pressure, pore deformation, relative permeability, thermal and degassing effects, however, further tests and understanding of the mechanisms are necessary. Thirdly, the reviews of experimental research and mathematical modeling based on the published literature are made. Especially, the mathematical modeling of seismic vibration for the real reservoir development (such as non-Darcy flow, low permeability reservoirs, the coupling of non-Newtonian fluid, etc.) is still insufficient. Finally, some successful oilfield applications (in Russia, North America, and China) and prospects are proposed in this work. It will be more efficient to stimulate the reservoirs if the seismic wave is at the formation's resonant frequency. In our work, we don't expect to provide an exhaustive review of the work presented. On the contrary, we hope that our work can provide an introduction for other researchers to get a brief understanding of the seismic stimulation technology and possible results under which conditions the seismic stimulation works well. • Mechanisms of seismic stimulation based on the published literature are introduced. • Reviews of experiments and mathematical modeling on seismic stimulation are made. • Mathematical modeling of seismic vibration for real reservoir is insufficient. • Seismic wave at the formation's resonant frequency can efficient stimulate reservoir. • Seismic stimulation can work together with some chemical-based EOR methods. [ABSTRACT FROM AUTHOR]

In this paper, a new adaptive viscous damper (AVD) is proposed and required equations are developed to describe its mechanical behavior. As opposed to conventional adaptive devices, the proposed damper is capable of adapting its own mechanical properties without any need for other devices such as sensors, processing unit, actuators, energy supplies, and wired or wireless connections. Eliminating such equipment not only reduces costs, but also removes related time lag and improves the efficiency of the control system. The proposed AVD includes a cylinder filled with viscous fluid and a piston with a nozzle at its head. The passing area of the nozzle is variable and as a result, the device can cover a range of damping coefficients. For non-extreme excitations, the damping coefficient is relatively small and consequently the damping force is reduced. Conversely, when extreme movements occur, the nozzle contracts a bit and generates relatively large control forces in order to protect the main structure efficiently. The mechanical model of the AVD is created in OpenSees and the damper is implemented in a two-story building example subjected to different earthquake records. The results show that compared to a typical viscous device, the proposed AVD can reduce the mean values of displacement, acceleration, and base shear by up to 52.5, 62.9, and 44.4% and increase the energy dissipation by up to 94.3% for extreme cases. Moreover, for non-extreme cases, the AVD shows a more flexible behavior and reduces the unfavorable damping forces. [ABSTRACT FROM AUTHOR]

This paper considers the problem of designing a state-feedback controller with both passive base isolation (PBI) and active structural control (ASC). In order to improve control performance, state-feedback gains are designed based on the linear quadratic regulator (LQR) method that optimizes a new performance index containing absolute acceleration, and inter-story drifts and velocity. Simulations on a model of an eleven degree-of-freedom shear building for four earthquake accelerograms are used to verify this method. Comparison studies show that, compared with PBI, the combination of PBI and ASC improves control performance; and this method yields better control results than the conventional ASC, which considers relative displacement and relative velocity of each story. The results are also discussed from the viewpoint of control system structure regarding the location of system zeros. In addition, the effect of weights in the LQR on control performance is discussed. A method for selecting the weights is presented by using the infinity norm of a system as a criterion to visualize their effect. [ABSTRACT FROM AUTHOR]

Lasers having sub-Hz linewidth and long-term stability better than a few parts in 1 0 16 is an unavoidable requisite to achieve unprecedented accuracy in the optical atomic clocks, intercomparing distributed atomic clocks and their networking, establishing coherent optical fibres, precision time & frequency transfer, production of optical qubits, and many more. For these wide ranges of applications, ultrastable Fabry–Pérot (FP) cavities, which act as the reference optical resonator, have got lots of attention. Designing such a FP cavity is a challenge due to the requirements of suppressing instabilities from all the thermo-mechanical noise sources at the highest degree. In this article, we report a comprehensive study to elucidate detailed design steps and associated numerical analysis procedures to build such a FP cavity. For this, we considered all sources of noises arising from: improper optical and opto-mechanical settings, ground vibrations transmitted to the cavity, deformations due to self-weight as it worsens the stability due to acoustic noise coupled to it, and temperature fluctuation. We present quantitative assessments of the instabilities for different shapes, geometries, and constituent materials of the cavities. In order to model the vibration-induced instability, we developed a novel forced-vibration based technique for accurate estimation of the instabilities, that reciprocates the experimental results reported in the literature, and the method is found to be superior compared to the other approaches, therefore estimating the overall cavity stability more accurately. We found in short term (¡ 10 s), the instability of the cavity is limited by temperature fluctuation, and in the long term (¿ 10 s), Brownian noise dominates the instability, therefore demands adequate precautions to reach the desired level of stability. Through systematic simulations, we have identified the best criteria for minimization of all these noises and obtain stabilities of 8. 5 × 1 0 − 17 and 5. 1 × 1 0 − 17 using dielectric and crystalline mirror coatings, respectively, which are similar to the best-reported results among its homologue cavities. [Display omitted] • Stabilities of 8. 5 × 1 0 − 17 and 5. 1 × 1 0 − 17 using the dielectric and crystalline mirrors are useful for cutting edge research & technologies. • A comprehensive and systematic presentation for designing a room-temperature ultrastable Fabry–Perot cavity. • Guidance for selecting the constituent materials, shapes, geometries, and mounting structure to cover different applications of such cavity. • Instability estimation for thermo-mechanical and instrumentation noises together with their methodologies are described. • A novel approach for accurate calculation of the vibration-induced instability is presented. [ABSTRACT FROM AUTHOR]

A new method of active structural control, which suppresses vibrations in civil structures due to seismic shocks, has been developed. It is based on the equivalent-input-disturbance (EID) approach, which estimates the effect of a seismic shock and produces an equivalent control signal on the control input channel to compensate for it. A system designed by this method can be viewed as a conventional state-feedback control system with an EID estimator plugged in. Unlike conventional control systems, this one has two degrees of freedom, which yields better control performance. Simulations on a model of a ten-degree-of-freedom building demonstrated the validity of the method. In addition, the effect of the parameters of the low-pass filter in the EID estimator on the vibration suppression performance was examined. A comparison revealed that this method is superior to a linear-quadratic regulator and sliding-mode control. [ABSTRACT FROM AUTHOR]

The optimum design of base isolation system to control seismic vibration considering uncertain system parameters are usually performed by minimizing the unconditional expected value of mean square response of a structure without any consideration to the variance of such responses due to system parameter uncertainty. However, the unconditional mean square response based designed may have larger variance of responses due to uncertainty in system parameters and the overall system performance may be sensitive. But, it is desirable that the optimum design should reduce both the mean and variance of dynamic performance measure under system parameter uncertainty. The present study deals with robust design optimization (RDO) of base isolation system considering random system parameters characterizing the structure, isolator and ground motion model. The RDO is performed by minimizing the weighted sum of the expected value of the maximum root mean square acceleration of the structure as well its standard deviation. A numerical study elucidates the importance of the RDO procedure for design of base isolation system by comparing the proposed RDO results with the results obtained by the conventional stochastic structural optimization procedure and the unconditional response based optimization. [ABSTRACT FROM AUTHOR]

The optimum design of a base isolation (BI) system in the framework of total probability theory cannot be applied in many real situations when the required detailed information about the uncertain parameters are limited and the maximum possible ranges of variations are only known and can be modeled as an uncertain but bounded type. The interval analysis based bounded design optimization usually applied in such cases are the worst case measures and unsuitable for practical design. Moreover, such a design method does not consider the variation of the performance of an isolated system due to uncertainty and may not correspond to an optimum design yielding maximum performance with its minimum dispersion. The robust optimization requiring only the bounds on the magnitude of the uncertain parameters will be a viable alternative in such situations. The present study deals with the robust optimization of BI system for seismic vibration mitigation of structures characterized by bounded uncertain parameters. The robust optimization is performed by using a two-criteria equivalent optimization problem, where the weighted sum of the nominal value of the maximum root mean square acceleration of the superstructure and its dispersion is optimized. The bounded design optimization is also performed to demonstrate the effectiveness of the proposed robust optimization approach. A five-storied building frame with attached isolator elucidates the effectiveness and importance of the proposed design approach by comparing the present robust optimization results with the results obtained by the bounded design optimization procedure. [ABSTRACT FROM PUBLISHER]

The possibility of controlling two modes of structural vibration due to earthquake excitation by considering the sloshing action in the vertical limbs of the liquid column vibration absorber (LCVA) has been explored in this paper. The structure has been modeled as a linear, viscously damped multi-degree-of-freedom (m.d.f.) system. The governing differential equations of motion for the damper liquid and for the coupled structure-LCVA system have been derived from dynamic equilibrium. The nonlinear orifice damping in the LCVA has been linearized by a stochastic equivalent linearization technique. A displacement transfer function formulation for the structure-LCVA system has been presented. The study has been carried out on a 2-d.f. example structure for which both the modes have significant contribution to the total response. The performance of the LCVA has been evaluated in the frequency domain with the base input characterized by a white noise power spectral density function and through a simulation study by subjecting the example structure-LCVA system to a recorded accelerogram. The results are compared with that of the liquid column damper and indicate superior performance of the LCVA. Furthermore, an LCVA has been designed for the example structure. [ABSTRACT FROM PUBLISHER]

The paper presents a study on the effects of soil-structure-interaction (SSI) on the performance of the compliant liquid column damper (CLCD) for the seismic vibration control of short period structures. The frequency-domain formulation for the input-output relation of a flexible-base structure with CLCD has been derived. The superstructure has been modeled as a linear, single degree-of- freedom (SDOF) system. The foundation has been considered to be attached to the underlying soil medium through linear springs and viscous dashpots, the properties of which have been represented by complex valued impedance functions. By using a standard equivalent linearization technique, the nonlinear orifice damping of the CLCD has been replaced by equivalent linear viscous damping. A numerical stochastic study has been carried out to study the functioning of the CLCD for varying degrees of SSI. Comparison of the damper performance when it is tuned to the fixed-base structural frequency and when tuned to the flexible-base structural frequency has been made. The effects of SSI on the optimal value of the orifice damping coefficient of the damper has also been studied. A more convenient approach for designing the damper while considering SSI, by using an established model of a replacement oscillator for the structure-soil system has also been presented. Finally, a simulation study, using a recorded accelerogram, has been carried out on the CLCD performance for the flexible-base structure. [ABSTRACT FROM AUTHOR]

The purpose of blasting operations is rock fragmentation. Blasting is a key component in the overall rock fragmentation system - the first element of the ore extraction process. It provides appropriate rock material granulation or size that is suitable for loading and transportation. However, in spite of many advantages explosives have, their usage may cause environmental problem such as seismic vibration. One of the solutions to this particular problem may be application of an artificial screen as a barrier to the seismic wave path. The results of experimental research on the artificial screen concept, its characteristics and role in attenuation of seismic effects generated by blasting are presented. The experiment is based on two physical phenomena: (1) the size and degree of discontinuity and (2) the reflection and refraction of seismic waves. More than 1,500 laboratory measurements were conducted with different combinations of screen sizes, positions of the screen to blasting source, and intensities of blasting impulses. The results of the study show reduction of generated vibrations up to 58% by employment of artificial screens. [ABSTRACT FROM AUTHOR]

• The interfacial parameters in boiling flow were measured by four-sensor conductivity probe under static and vibration conditions. • The time-averaged local parameters under vibration conditions were analyzed. • The instaneous change of local void fraction was analyzed by adopting the phase partitioning method. • The additional forces induced by mechanical vibration were calculated and compared with each other. • The effect of vibration frequency on local void fraction was studied. In this paper, the subcooled boiling flow experiments in a vertical annulus were conducted to study the effect of vibration on local interfacial characteristics. The local interfacial parameters including void fraction, bubble velocity, interfacial area concentration and Sauter mean diameter were measured by four-sensor conductivity probe. The time-averaged local parameters under vibration conditions were firstly measured and analyzed. It is found that the effects of vibration on time-averaged void fraction and interfacial area concentration are very limited. Therefore, we have developed the phase partitioning method to obtain the instantaneous variation of void fraction for further investigation. The instantaneous void fraction along the radial direction varies periodically with the vibration phase. The additional forces induced by vibration are analyzed and compared with each other. Among them, the tangential force is the dominant, which can account for the change tendency of void fraction under vibration. Besides, the variations of void fraction depend on different working conditions. The change tendencies of void fraction near the inner wall and outer wall are opposite in relatively low averaged void fraction regime while those in relatively high averaged void fraction regime are consistent. [ABSTRACT FROM AUTHOR]