This study deals with the capabilities of artificial neural networks in learning to control water towers of different structural properties that are subjected to earthquakes. To this end, water towers were considered as single-degree-of-freedom systems. First, a number of water towers of different structural properties were controlled by the predictive optimal control method, and then the data collected through this control were used in the training of a general neural network controller, called the general neurocontroller. Capabilities of the general neurocontroller were tested in the control of a number of water towers with structural parameters different from, but in the range of, those used in its training. One of the aims of this study was the introduction of general neurocontrollers as ready-to-use devices that may be used in the design of actively controlled structures, in this case, water towers. Results of this numerical study were promising. 相似文献
This paper proposes a new low-power MOS parametric integrator (MPI) for the design of wideband discrete time sigma-delta (ΣΔ) modulators. The MPI is implemented with MOS capacitors, which provide the required gain by switching from inversion in the sampling phase into depletion in the amplification phase. Analysis along with simulation results illustrate that MPI consumes very low power dissipation compared to the conventional active integrators with some negligible performance changes. To verify this, the MPI is used in two wideband ΣΔ modulators, one with 8-bit resolution and the other with 13-bit resolution with input bandwidth and sampling frequency of 12.5 and 200 MHz, respectively. The first one is a second order single stage ΣΔ modulator and the second one is a MASH 2-2 modulator, both implemented in 0.18-μm CMOS technology. Simulation results indicate that these modulators save a significant amount of power consumption when their second integrator is replaced by MPI. 相似文献
Reservoir operation cannot be carried out without due heed to surface water and groundwater resources, since neglecting either will have irreversible consequences. Optimal operation of the Zayandehrood Dam which supplies water into the Zayandehrood River basin in the central plateau of Iran is a case in point which warrants due consideration paid to both dam operation and the climate conditions in the region suffering from a history of successive droughts. The main objective of the present research is to develop operation rules for the Zayandehrood reservoir through a combined perspective of both surface and ground water resources using the fuzzy inference system, and adaptive neuro-fuzzy inference system. The objective is to determine the share of the Zayandehrood reservoir in meeting downstream water demands. For this purpose, the water shortage and the dramatic groundwater drawdown in the Zayandehrood River basin faced with in recent years have been studied in an attempt to develop operation models capable of controlling groundwater drawdown. The models indicate that not only can groundwater drawdown be controlled, but that it is also possible to establish a greater sustainability. Different operation models have been compared in terms of their operation criteria. Results show that the ANFIS model composed of optimal data enjoys a higher sustainability compared to others. 相似文献
In the present study, finite element formulation based on higher order shear deformation plate theory is developed to analyze nonlinear natural frequencies, time and frequency responses of functionally graded plate with surface-bonded piezoelectric layers under thermal, electrical and mechanical loads. The von Karman nonlinear strain–displacement relationship is used to account for the large deflection of the plate. The material properties of functionally graded material (FGM) are assumed temperature-dependent. The temperature field has uniform distribution over the plate surface and varies in the thickness direction. The considered electric field only has non-zero-valued component Ez. Numerical results are presented to study effects of FGM volume fraction exponent, applied voltage in piezoelectric layers, thermal load and vibration amplitude on nonlinear natural frequencies and time response of FGM plate with integrated piezoelectric layers. In addition, nonlinear frequency response diagrams of the plate are presented and effects of different parameters such as FGM volume fraction exponent, temperature gradient, and piezoelectric voltage are investigated. 相似文献
This paper reports the development of a high-impact epoxy nanocomposite toughened by the combination of poly(acrylonitrile-co-butadiene-co-styrene) (ABS) as thermoplastic, clay as layered nanofiller, and nano-TiO2 as particulate nanofiller. Response surface methodology (RSM) was applied for optimization and modeling of the impact strength
of epoxy/ABS/clay/TiO2 quaternary nanocomposite. A second-order mathematical model between the response (impact strength) and variables (ABS, clay
and nano-TiO2 contents) was derived. Analysis of variance (ANOVA) showed a high coefficient of determination value (R2 = 98%). Under optimum conditions, maximum impact strength of 29.2 KJ/m2 with 197% increase compared to neat epoxy was experimentally obtained. Also correlation between morphology and impact strength
of the nanocomposite was investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). A dispersion of
exfoliated clay platelets, TiO2 nanoparticles with low agglomeration and ABS nanoparticles was obtained as morphology of the nanocomposite. A new and more
effective method for impact toughening of epoxy was introduced. This study clearly showed that the addition of the combination
of layered and particulate nanofillers along with ABS as thermoplastic has a considerable enhancement effect on impact strength
of epoxy. 相似文献
Modification of SiO2 nanoparticles by salicylaldiminepropyl results in efficient adsorbents for removal of Th4+, UO22+ and Eu3+ ions from aqueous solutions. The effect of parameters influencing the adsorption efficiency such as aqueous phase pH, contact time, initial metal ions concentration, adsorbent dosage and temperature dependency of the process was verified and discussed. Under optimal conditions (pH 5.5, adsorbent dosage 0.05 g, contact time 30 min. and 25 °C), thorium and uranyl ions (initial concentration 20 mg/l) were quantitatively removed from 20 ml of sample solution. Under such conditions 85% of europium ions was removed. Comparison of the adsorption efficiency of the studied modified nano-particles with those unmodified ones shows a shift for uptake of the metal ions vs. pH curves towards lower pH values by applying the modified adsorbents. In addition, a significant improvement of europium ions adsorption was observed by using the modified nanoparticles. Kinetics of the process was studied by considering a pseudo second-order model. This model predicts chemisorption for the adsorption mechanism. Freundlich, Langmuir and Temkin models were suitable for describing the equilibrium data of Th4+, UO22+ and Eu3+ adsorption process, respectively. Thermodynamic investigation reveals the adsorption process of the studied ions is entropy driven. 相似文献
Mixed-model synchronous assembly line (MMSAL) is a type of assembly line that can be found in the production of large household appliances (e.g., washing machines, dryers, etc.). In this assembly line, products that are simultaneously processed on the line are transferred to the next station at the same time. In this paper, the sequencing problem of MMSAL with three objectives: (1) total idle cost, (2) total production rate variation cost, and (3) total setup cost is simultaneously studied. These three objectives are first weighted by their relative importance weights and a mathematical model is proposed for the problem. Since this problem is well known as non-deterministic polynomial-time hard class, a meta-heuristic algorithm based on simulated annealing is proposed to solve it. Performance of the proposed algorithm is compared against the Lingo 9 software. The computational results validate the efficiency and effectiveness of the proposed algorithm. 相似文献
Biomass has a direct relationship with agricultural production and may help to predict crop yield. Earth observation technology can contribute significantly to monitoring given the availability of temporally frequent and high-resolution radar or optical satellite data. Polarimetric Synthetic Aperture Radar (PolSAR) has several advantages for operational monitoring given that at these longer wavelengths atmospheric and illumination conditions do not affect acquisitions and considering the sensitivity of microwaves to the structural properties of targets. Therefore, SARs are a promising source of data for crop mapping and monitoring. With increasing access to SARs the development of robust methods to monitor crop productivity is timely.
In this paper, we examine the use of machine learning and artificial intelligence approaches to analyze a time series of Polarimetric parameters for crop biomass estimation. In total, 14 polarimetric parameters from a time series of Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) airborne L-band data were used for biomass estimation for an intensively cropped site in western Canada. Then, Multiple linear regression (MR) and artificial neural network (ANN) models were developed and evaluated to estimate the biomass for canola, corn, and soybeans. According to the experimental results, the ANN provided more accurate biomass estimates compared to MR.
Canola biomass, in general, showed less sensibility to almost all the polarimetric parameters. Nevertheless, Freeman-Double combined with vertical-vertical backscattering (VV) delivered the correlation coefficient (r) of 0.72, and the root mean square error (RMSE) of 56.55 g m?2of canola biomass. For corn, the highest correlation was observed between a pairing of horizontal- horizontal backscattering (HH) with Entropy (H) for biomass estimation yielding an r of 0.92 and RMSE of 196.71 g m?2. Horizontal-vertical backscattering (HV) and Yamaguchi-Surface (OY) delivered the highest sensitivity for soybeans (r of 0.82 and RMSE of 13.48 g m?2). If all crops are pooled, H combined with OY provided the most accurate estimates of biomass (r of 0.89 and RMSE of 135.31 g m?2). These results demonstrated that models which make use of polarimetric parameters that characterize the multiple sources of scattering typical of vegetation canopies can be used to estimate crop biomass accurately. Such results bode well for agricultural monitoring considering the increasing number of satellite SAR sensors with various frequencies, imaging modes and revisit times. As such, the time series analysis and methods proposed in this study could be used to monitor crop development and productivity using SAR space technologies. 相似文献
This paper proposes a methodology for developing earthquake‐resilient structures (ERSs). This is achieved by following principles of full cycle performance control and embracing a holistic approach to design led analysis (DLA) of ERS. Collapse prevention (CP) and postearthquake realignment and repairs (PERRs) are the basic traits of ERS. Despite the availability of several systems involving combinations of gap opening link beams (GOLBs), rigid rocking cores, buckling‐restrained braces, replaceable energy dissipating moment connections, and so forth, neither CP nor PERR are addressed in any code of practice. Although most of these devices have passed several tests of experiments and time–history analysis they have rarely been examined as integral parts of actual buildings. Real buildings cannot be ideally recentered unless specifically designed and detailed for CP and PERR. Almost all simple beam–column joints, especially standard hinged supports absorb small but sufficient amounts of residual strains that hinder PERR. The proposed methodology is introduced by way of developing an earthquake‐resilient rocking core‐moment frame, as the lateral resisting component of a gravity resisting structure that has been detailed not to develop residual effects while sustaining large lateral deformations. 相似文献