Acceleration Response Time Research Articles

Dynamic performance of concrete slabs reinforced with steel and GFRP bars under impact loading

Reinforced concrete slabs are common structural elements that could be exposed to impact loading. Although use of reinforced concrete slabs and utilization of Fiber Reinforced Polymer (FRP) as alternative to traditional steel reinforcement slabs are growing, but the influence of various parameters on their response under impact loads is not properly evaluated. This study investigated the effect of rebar’s material, amount and arrangement of reinforcements, concrete strength and slab thickness on dynamic behavior of reinforced concrete slabs using both laboratory experiments and numerical simulations. Performance of fifteen 1000 × 1000 mm concrete slabs, including two 75 mm thick plain slabs, five 75 mm thick steel reinforced concrete slabs, six 75 mm thick reinforced concrete slabs with Glass Fiber Reinforced Polymer (GFRP) bars and two 100 mm thick steel reinforced concrete slabs under drop weight impact loads was experimentally investigated. Failure mode, crack development, displacement-time, strain-time, and acceleration-time responses were studied and compared between various slabs. Finite element analyses and simulation of specimens were conducted using LS-DYNA explicit software. The results obtained from experiments and numerical models are in good agreement, and they indicate that increasing the reinforcement ratio or the slab thickness enhance the behavior of RC slabs under impact loads. By adjusting the amount and arrangement of GFRP, better performance in GFRP slabs than steel reinforced slabs can be achieved, which considering the corrosion resistance of this material, can make it an appropriate selection of reinforcement material.

8 - Supplementation with omega-3 fatty acids potentiates glutathione oxidation in human airway epithelial cells exposed to ozone

The health benefits of dietary fish oil consumption have been widely reported. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, two omega-3 fatty acids found in fish oil, have been associated with anti-inflammatory and pro-resolving effects through their metabolism to specialized pro-resolving mediators (SPMs) and displacement of arachidonic acid (AA). However, the 5 and 6 double bonds in EPA and DHA respectively are targets for lipid peroxidation by ozone (O3), a major photochemical pollutant to which millions of Americans are exposed. Products of unsaturated fatty acid peroxidation by O3 have been proposed to mediate functional and inflammatory effects of O3 exposure. Thus, cellular supplementation with omega-3s has the potential to both promote and help resolve inflammation during O3 exposure. To investigate this paradox, we supplemented 16-HBE human airway epithelial cells (HAEC) expressing the fluorogenic glutathione redox potential (EGSH) sensor roGFP overnight with EPA, DHA, the monounsaturated fatty acid oleic acid (OA), or the saturated fatty acid stearic acid (SA). Alterations in EGSH were monitored in real time using live-cell microscopy during exposure to O3. We found that supplementation with EPA and DHA, but not OA or SA, caused a marked potentiation of the O3-induced increases in EGSH, evident as both an accelerated response time and increase in the magnitude of response. Notably, the potentiation of GSH oxidation occurred at O3 concentrations as low as 0.08 ppm, the current National Ambient Air Quality Standard level. These results suggest that membrane fatty acid saturation is a determinant of the oxidative responses to O3 in HAEC. These findings may have implications for dietary recommendations for populations exposed to O3. This abstract does not necessarily reflect EPA policy.

Bayesian optimal estimation for output-only nonlinear system and damage identification of civil structures

This paper presents a new framework for output-only nonlinear system and damage identification of civil structures. This framework is based on nonlinear finite element (FE) model updating in the time-domain, using only the sparsely measured structural response to unmeasured or partially measured earthquake excitation. The proposed framework provides a computationally feasible approach for structural health monitoring and damage identification of civil structures when accurate measurement of the input seismic excitations is challenging (e.g., buildings with significant foundation rocking and bridges with piers in deep water) or the measured seismic excitations are erroneous and/or distorted by significant measurement error (e.g., malfunctioning sensors). Grounded on Bayesian inference, the proposed framework estimates the unknown FE model parameters and the ground acceleration time histories simultaneously, using the sparse measured dynamic response of the structure. Two approaches are presented in this study to solve the joint structural system parameter and input identification problem: (a) a sequential maximum likelihood estimation approach, which reduces to a sequential nonlinear constrained optimization method, and (b) a sequential maximum a posteriori estimation approach, which reduces to a sequential iterative extended Kalman filtering method. Both approaches require the computation of FE response sensitivities with respect to the unknown FE model parameters and the values of base acceleration at each time step. The FE response sensitivities are computed efficiently using the direct differentiation method. The two proposed approaches are validated using the seismic response of a 5-story reinforced concrete building structure, numerically simulated using a state-of-the-art mechanics-based nonlinear structural FE modeling technique. The simulated absolute acceleration response time histories of 3 floors and the relative (to the base) roof displacement response time histories of the building to a bidirectional horizontal seismic excitation are polluted with artificial measurement noise. The noisy responses of the structure are then used to estimate the unknown FE model parameters characterizing the nonlinear material constitutive laws of the concrete and reinforcing steel and the (assumed) unknown time history of the ground acceleration in the longitudinal direction of the building. The same nonlinear FE model of the structure is used to simulate the structural response and to estimate the dynamic input and system parameters. Thus, modeling uncertainty is not considered in this paper. Although the validation study demonstrates the estimation accuracy of both approaches, the sequential maximum a posteriori estimation approach is shown to be significantly more efficient computationally than the sequential maximum likelihood estimation approach.

Evaluation of the charge carriers’ transportation through the grown MgFe2O4 on the nanotextured silicon surface in the presence of hydrogen gases

Here, we report, for the first time, the solution growth of n-type MgFe2O4 spinel ferrite nanoparticles on nano-textured p-type silicon (100) substrate. Water soluble MgFe2O4 spinel ferrite nanoparticles are prepared by polyol technique. The MgFe2O4 spinel ferrite nanoparticles were characterized by transmission electron microscopy both at low and high resolution, selected area electron diffraction, energy dispersive spectroscopy, and Raman spectroscopy. The texturing of the surface of the Si(100) substrate to create well-organized nanopillar-like shapes was carried out by a nanosecond laser lithography technique. The water soluble MgFe2O4 spinel ferrite nanoparticles were deposited on the textured Si(100) substrate. The sample was characterized by scanning electron microscopy and X-ray diffraction. The charge carriers transport mechanism was discussed in terms of the variation of the barrier height under the exposure to various gases. A comparison between the MgFe2O4 spinel ferrite nanoparticles grown on planar and textured p-type Si(100) surfaces showed that the latter demonstrated an improvement of gas sensitivity and accelerated response time. These two characteristics, combined with high performance stability, make these sensors promising for practical applications.

ASSESS THE READINESS OF THE OUTPATIENT TREATMENT CENTERS OF SOCIAL SECURITY TO RUN SMART HEALTH CARD

Introduction: Smart card, microprocessor chip, facilitate providing e-health services in health center. Design and implementation of smart cards in the Social Security Organization as one of the health centers reduce costs, prevent abuses of medical insurance, increase productivity and accelerate response time. In this study, readiness of the outpatient treatment centers of social security to implement health smart card assessed.
 Methods: this practical and descriptive study was conducted in nine outpatient treatment center of Khorasan Razavi Social Security center in 2016-2017. Total proposed number of outpatient treatment center was reduced to 9 center because other centers did not take part in this review .A questionnaire with three areas of technical readiness, organizational culture and leadership and management was used. The data were analyzed using spss 19 software
 Results: Finding showed Average scores of technical and leadership and cultural organization readiness were ordinary in all centers. Leadership and cultural organization readiness in 4 center were more than others. Average scores of technical were more than of leadership and cultural organization readiness .Technical readiness had significant difference between the studied centers.
 Conclusion: Finding showed appropriate technical readiness in Social Security, therefore we suggest to implement smart cards, educating staff to enhance technology skills and to promote its use culture. Readiness of management and leadership scope is impressive in designing and implementing smart cards; So implementing smart cards should be organization`s strategy and the road map should be determined, and its benefits should be clearly explain for social security center managers.

Proactive personalized services through fog-cloud computing in large-scale IoT-based healthcare application

With the development of medical sensors and IoT, personalized service assisted elder and patient living is a critical service in IoT-based healthcare application. However, the scale and complexity of personalized service is increasing because of ubiquitous deployment of various kinds of medical sensors, which cause response time increase and resource waste. Therefore, leveraging the advantage of complex event processing (CEP) in data stream processing, we propose a hierarchical fog-cloud computing CEP architecture for personalized service to accelerate response time and reduce resource waste. Firstly, we introduce the proposed architecture, which includes sensor layer, fog layer and cloud layer. Secondly, we propose a series of optimizations for the architecture, there are a partitioning and clustering approach and a communication and parallel processing policy to optimize the fog and cloud computing. Finally, we implement a prototype system based on the architecture named FogCepCare. Experimental result shows that FogCepCare is superior to the traditional IoT-based healthcare application.

Seismic response of concrete-rockfill combination dam using large-scale shaking table tests

Concrete-rockfill combination dam (CRCD), a new type of dam, is mainly composed of an upstream concrete wall and a downstream inclined rockfill body. It is not in direct contact with the bedrock foundation but a water stop, which is different from conventional concrete gravity dam. The dynamic characteristics of CRCD are not quite fully understood yet. In this paper, large-scale models of CRCD were constructed and key parameters, such as acceleration-time response, dynamic earth pressure, deformation and failure pattern of slope were monitored. Results showed that the amplification factors in the upper part (0.6H) increased with the height. The model dam showed obvious concentration and amplification effect on the low frequency component. The total earth pressure acting on the back face of the wall varied approximately nonlinear along the wall height when the PGA exceeded 0.4g. In addition, the CRCD model exhibited good seismic performance with small residual deformation under earthquake. A shallow sliding mode of failure at a height of 0.8H was measured from the base on the downstream slope. Therefore, it was prudent to undertake some aseismatic reinforcement measurements at the top 1/5 thickness zone of the slope. These model test results could provide a certain reference value for preliminary understanding and qualitative analysis of a prototype CRCD.

Experimental study on damping characteristics of soil-structure interaction system based on shaking table test

Soil-structure interaction (SSI) system is composed of soil and structure that are two materials with quite different damping behaviors and it is regarded as non-classical damping system in conventional concept. Based on the analysis of motion state of SSI system, the paper presents the damping characteristic of SSI system via shaking table test. The results of transfer function, acceleration response time histories and equivalent viscous damping ratio and so on indicate that under certain conditions, SSI system shows approximate classical damping characteristic. In practical projects, dynamical analysis of SSI system can be viewed as approximately classical damping system once the synergistic effect of soil is considered.

Tetra-Sensitive Graft Copolymer Gels as Active Material of Chemomechanical Valves.

Stimuli-responsive hydrogels combine sensor and actuator properties by converting an environmental stimulus into mechanical work. Those materials are highly interesting for applications as a chemomechanical valve in microsystem technologies. However, studies about key characteristics of hydrogels for this application are comparatively rare, and further research is needed to emphasize their real potential. The first part of this study depicts the synthesis of grafted hydrogels based on a poly(N-isopropylacrylamide) backbone and pH-sensitive poly(acrylic acid) graft chains. The chosen approach of grafted hydrogels provides the preparation of multiresponsive hydrogels, which retain temperature sensitivity besides being pH-responsive. A pronounced salt and solvent response is additionally achieved. Key characteristics for an application as a chemomechanical valve of the graft hydrogels are revealed: (1) independently addressable response to all stimuli, (2) significant volume change, (3) sharp transition, (4) reversible swelling-shrinking behavior, and (5) accelerated response time. To prove the concept of multiresponsive hydrogels for flow control, a net-poly(N-acrylamide)-g-poly(acrylic acid) hydrogel containing 0.6 mol % poly(acrylic acid)-vinyl is employed as active material for chemomechanical valves. Remarkably, the chemomechanical valve can be opened and closed in a fluidic platform with four different stimuli.

A reduced modal parameter based algorithm to estimate excitation forces from optimally placed accelerometers

This paper presents a time domain technique for estimating dynamic loads acting on a structure from acceleration time response measured experimentally at a finite number of optimally placed accelerometers on the structure. The technique utilizes model reduction to obtain precise load estimates. The structure essentially acts as its own load transducer. The approach is based on the standard equilibrium equations of motion in modal coordinates. The modal parameters of a system – natural frequencies, mode shapes and damping factors – can be estimated experimentally from measured data, analytically for simple problems, or using the finite element method. For measurement of the acceleration response, there can be a large number of locations on the structure where the accelerometers can be mounted, and the precision with which the applied loads are estimated from measured acceleration response may be strongly influenced by the locations selected for accelerometer placements. A solution approach, based on the construction of D-optimal designs, is presented to determine the number and optimum locations of accelerometers that will provide the most precise load estimates. An improvement in the algorithm, based on reduced modal matrix, is further proposed to reconstruct the input forces accurately. Numerical examples that help understand the main characteristics of the proposed approach are also presented. The numerical results illustrate the effectiveness of the proposed technique in accurately recovering the loads imposed on discrete as well as continuous systems.

Extracting Modal Parameters of a Layered Stone Pagoda Using TDD Technique

This work introduces a modal testing and analysis results of the mock-up for a layered stone pagoda. The pagoda has been horizontally excited by an impact hammer. As to the measured acceleration time responses, the first five lower mode shapes and natural frequency are extracted by the TDD technique. It is observed that the time delay of a shear wave occurs through friction surfaces. Such phenomena cannot be described by using the traditional analytical models such as a continuum cantilever beam model or a discrete shear building model. However, the time delay typically affects only the phases of the pagoda system. The frequencies of the pagoda system are not affected by such time delay. It is found in the first time that the layered stone pagoda system has a set of closely placed modes in near of natural frequency. It is believed that such modes are due to the friction characteristics in friction surfaces. Based on the stick-slip friction model, it seems that the one of the closely placed mode can be a self-excited one.

The Effect of Using Current Stabilizer to the Dynamic Characteristic of a Regenerative Shock Absorber

Most of the energy from the vehicle is wasted in the form of heat energy and vibration. On vehicles, the largest vibration occurs in the suspension system. The development of a mechanism which can recover the vibration energy and convert it into electrical energy, named Regenerative Shock Absorber (RSA), will be detailed in this paper. The prototype of RSA which consist of gear transmission and an electromagnetic type electric generator was studied and analyzed. Electrical circuit signal conditioner / stabilizer is added into the RSA system to stabilize the output current of the generator so that the generated electrical energy can be stored in the battery of 6 volts. The characteristics of the RSA are obtained by testing the value of the damping coefficient, the energy absorbtion capacity, and the generated electrical energy before and after going through a series of signal conditioner. Experiment was also performed by measuring the acceleration response time of the sprung and un-sprung suspension system that uses RSA with damping ratio value of 0.6. From this research, it is found that RSA design with stabilizer circuit can produce more stable electric current and voltage. The measurement results show the value of the electrical voltage output through the generator is fluctuating with an average value of 15 volts and a constant 6 volts output is obtained through the signal conditioning circuit. Furthermore, the dynamic response is obtained in the form of acceleration time-value of less than 0.2 m/s2 in a corresponding ISO 2631 standard is stated very comfortable.

Reinforced Concrete Frame Structure Dynamic Analysis Based on SAP2000

Structure under long-term load, environmental erosion, material aging, especially under the seismic action can cause damage accumulation and bearing capacity decrease. In order to make sure its safety and reliable, avoid extreme cases of catastrophic accident, it is necessary to carry out the engineering structural health diagnosis. Using SAP2000 software, seismic response analysis for a two layer reinforced concrete frame structure is carried out. The laws of the acceleration response time history and spectrum under different seismic action were found out by discussing structure in no damage and different damages. The results showed that no matter where the damage located, the top node response increment is bigger than the middle node, the peak of acceleration response spectrum changes little with the beam damage degrees changing. Selecting the acceleration response peak of the top node as a structural damage index is feasible in the damage detection and identification of engineering structures, but analyzing the response spectrum for damage detection is unpractical.

A catalytic combustion-type CO gas sensor incorporating aluminum nitride as an intermediate heat transfer layer for accelerated response time

Abstract. A catalytic combustion-type carbon monoxide gas sensor exhibiting good sensing performance even at moderate temperatures was previously developed by employing a Pt loaded CeO2–ZrO2–SnO2 solid solution as the CO oxidizing catalyst. The addition of aluminum nitride as an intermediate heat transfer layer between the Pt coil and the CO oxidizing catalyst drastically accelerated the response of this device to CO at temperatures as low as 70 °C.

Train-induced vibration on elevated railway station

Results of in-situ vibration measurement carried out at Tianjin West Elevated Railway Station which has the trains running on the station structure were reported. The main excitation source is the train passing through the station. Vibration measurements were recorded in the vertical direction of the supporting track beam, the platform and the steel truss beam of the waiting hall, as well as in the vertical, longitudinal and transverse directions of the roof arch base of the station. Acceleration time responses were obtained. The maximum value, vibration level and one-third octave band RMS spectra of the measured accelerations were studied. The propagation of vibration in different structural floors was discussed. The influence of train speed, distance to the vibration source and the type of train on the structural vibration were analyzed. Results show that the vibration level increases with the train speed, while it attenuates with the distance to the track. Furthermore, the vibration responses of different structural floors were compared, and it is noted that the vertical vibration of the bottom slab of the platform is most severe and the transverse vibration of the roof arch base is the smallest. The results provide reference on the vibration characteristics and vibration energy distribution of this type of “Train on building frame” system used as an elevated railway station.

Seismic hazard and design earthquakes for the central archaeological area of Rome

In order to evaluate the seismic input suitable to be used for the microzonation of the central archaeological area of Rome, two different approaches were used: Probabilistic and Deterministic Seismic Hazard Assessment (PSHA, DSHA). For PSHA, three Uniform Hazard Spectra and three design spectra, derived from the literature and the Italian regulations, were considered. For DSHA two possible design earthquakes were selected: one having a magnitude 5.5 and a distance 20 km and the other having a magnitude 7 and a distance 85 km. The choice of these two scenarios was supported by the analysis of historical and instrumental seismicity, by the study of the surrounding faults, and by the disaggregation of the seismic hazard. The standard PSHA, based on seismogenic zones with uniformly distributed seismicity used for the Italian hazard map and building code, results in higher values with respect to DSHA (PGA of about 0.12 g and spectral maximum of around 0.35 g), unless an appropriate fraction of the standard deviation of the attenuation relationship is considered in the deterministic analysis. Recorded accelerograms, corresponding to the magnitude-distance couples selected using the DSHA were also included in the analysis. The seismic input was represented in terms of acceleration response spectra and time histories.

Dynamic Response Control of a Building Model using Bracings

Abstract Construction of tall and flexible structures has become easier now-a-days because of advances in analytical techniques and availability of more efficient materials. However, these structures are more sensitive towards dynamic loadings. Dynamic response of such structures under various excitations can be quantified by displacement and acceleration response time history. Excessive dynamic response of structure leads to substantial damage to the structural components and hence it need to be controlled. Passively, this is achieved by adding either mass or stiffness or both of them. This paper covers experimental study on controlling dynamic response of a building model using two types of bracings, namely, Concentric- and Eccentric bracing. A building model is fabricated using aluminum flats and plates and bracings are fabricated using linear springs of moderate stiffness. A model represented as Single Degree of Freedom (SDOF) system is subjected to sinusoidal excitations of various frequencies through small scale shake table. Acceleration response of a uncontrolled building model (model without bracings) is obtained using accelerometers and Data Acquisition System (DAQ) – LabVIEW 8.0. Displacement response is derived through numerical integration from acceleration response using LabVIEW. Acceleration and displacement response of controlled building model (model with bracings) are extracted and compared with uncontrolled system. Dynamic properties like Natural Time Period and Damping Ratio for both types of bracing systems are obtained and comparisons are made among them. It is found that natural time period and damping ratio of controlled building model is increased as compared to uncontrolled system due to stiffness addition. Displacement and Acceleration response are reduced appropriately for controlled system as compared to uncontrolled system.

The Analysis of Test of the Seismic Response for the Metro Station Structure Considering Soil-Structure Interaction

In this paper, the subway station structure seismic response of large-scale three-dimensional shaking table model test is analysis, the model system acceleration response time, the stress response of the model structure of the schedule and structure of the surface of the earth pressure time is obtained, which has been the subway underground structure seismic response of the general law, the conclusion can provide a reliable basis and guidance for the seismic design of the MTR underground structures in the general venue.

Shock testing accelerometers with a Hopkinson pressure bar

The electronic industry continues to dramatically reduce the size of electrical components. Many of these components are now small enough to allow shock testing with Hopkinson pressure bar techniques. However, conventional Hopkinson bar techniques must be modified to provide a broad array of shock pulse amplitudes and durations. For this study, we evaluate the shock response of accelerometers that measure large amplitude pulses, such as those experienced in projectile perforation and penetration tests. In particular, we modified the conventional Hopkinson bar apparatus to produce relatively long duration pulses. The modified apparatus consists of a steel striker bar, annealed copper pulse shapers, an aluminum incident bar, and a tungsten disk with mounted accelerometers. With these modifications, we obtained accelerations pulses that reached amplitudes of 10kG and durations of 0.5ms. To evaluate the performance of the accelerometers, acceleration-time responses are compared with a model that uses data from a quartz stress gage. Comparisons of data from both measurements are in good agreement.

Experimental Research on the Effect of Sinusoidal Excitation on Dynamic Wheel Load of Hydro-Pneumatic Suspension Vehicle

Based on the mathematical model of quarter car body model being put forward, the indoor platform experiment of quarter car body with hydro-pneumatic suspension system was done. During test, the parameters of dynamic wheel load along with the change of vibration amplitude and frequency were investigated. The results show that: the cycle of acceleration of sprung mass has half cycle lag than unsprung mass, and the main parameters of dynamic wheel load has increased significantly along with the increase of vibration amplitude and frequency. At the same time, through analysis the acceleration time responses of sprung and unsprung mass, it can be shown that hydro-pneumatic suspension has good anti-vibration performance.