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Alginate Composite Hydrogel Bead with Multilayer Flake Structure for Dye Adsorptions
No full textWith the rapid development of textile industry, a large amount of dye-contaminated effluents was produced and caused serious environmental problem. To remove the dye from effluents, adsorption materials have been applied because of their relatively cheap, high efficiency, and easy handling. In this study, a novel composite hydrogel bead with unique multilayer flake structure was fabricated by alginate, acrylamide and attapulgite for dye adsorption. Acrylamide was grafted polymerization onto alginate to obtain alginate-g-poly(acrylamide). Then alginate-g-poly(acrylamide) was cross-linked by Ca2+ ions in present of attapulgite to form composite hydrogel bead. Scanning electron microscopy (SEM) results show that the freeze dried composite hydrogel bead has multilayer flake structure incorporating attapulgite. Fourier transform infrared spectroscopy (FTIR) and Thermo-gravimetric analysis (TGA) results indicate that acrylamide has been successfully grafted polymerization on sodium alginate. Grafting polymerization of acrylamide onto sodium alginate obviously enhances the swelling of hydrogel bead. Incorporating of attapulgite into hydrogel bead effectively enhances the adsorption capacity to methylene blue and the maximum adsorption capacity is 155.7 mg g-1. Multilayer flake structure increases the adsorption area for methylene blue, but hinders the diffusion of methylene blue into the inner of composite hydrogel bead. High pH solution is beneficial to the adsorption. Pseudo-second order model and Fraundlinch model best describe the adsorption kinetic and isotherm, respectively. These results indicate that composite hydrogel bead is a promising adsorption material for dye-contaminated water treatment
A Hybrid of Interval Wavelets and Wavelet Finite Element Model for Damage Detection in Structures
No full textDamages occurred in a structure will lead to changes in modal parameters (natural frequencies and modal shapes). The relationship between modal parameters and damage parameters (locations and depths) is very complicated. Single detection method using natural frequencies or modal shapes can not obtain robust damage detection results from the inevitably noise-contaminated modal parameters. To eliminate the complexity, a hybrid approach using both of wavelets on the interval (interval wavelets) method and wavelet finite element model-based method is proposed to detect damage locations and depths. To avoid the boundary distortion phenomenon, Interval wavelets are employed to analyze the finite-length modal shape to decompose into approximation and detailed signals. Damage locations will be detected by showing some peaks on the figures of detailed signal. To detect damage depths, the relationship between natural frequencies and damage depths (the damage depth detection database) is constructed using wavelet finite element method. Several natural frequencies obtained by experimental modal analysis are employed as inputs to the constructed database using particle swarm optimization (PSO) to search for damage depths. Numerical examples of beam and plate structures show that the new approach is robust to boundary distortion phenomenon and environment noise
Equivalence of Ratio and Residual Approaches in the Homotopy Analysis Method and Some Applications in Nonlinear Science and Engineering
Full text linkA ratio approach based on the simple ratio test associated with the terms of homotopy series was proposed by the author in the previous publications. It was shown in the latter through various comparative physical models that the ratio approach of identifying the range of the convergence control parameter and also an optimal value for it in the homotopy analysis method is a promising alternative to the classically used h-level curves or to the minimizing the residual (squared) error. A mathematical analysis is targeted here to prove the equivalence of both the ratio approach and the traditional residual approach, especially regarding the root-finding problems via the homotopy analysis method. Examples are provided to further justify this. Moreover, it is conjectured that every nonlinear differential equation can be considered as a root-finding problem by plugging a parameter in it from a physical viewpoint. Two examples from the boundary and initial and value problems are provided to verify this assertion. Hence, besides the advantages as deciphered in the previous publications, the feasibility of the ratio approach over the traditional residual approach is made clearer in this paper
Real-Time Hybrid Simulation of Seismically Isolated Structures with Full-Scale Bearings and Large Computational Models
Full text linkHybrid simulation can be a cost effective approach for dynamic testing of structural components at full scale while capturing the system level response through interactions with a numerical model. The dynamic response of a seismically isolated structure depends on the combined characteristics of the ground motion, bearings, and superstructure. Therefore, dynamic full-scale system level tests of isolated structures under realistic dynamic loading conditions are desirable towards a holistic validation of this earthquake protection strategy. Moreover, bearing properties and their ultimate behavior have been shown to be highly dependent on rate-of-loading and scale size effects, especially under extreme loading conditions. Few laboratory facilities can test full-scale seismic isolation bearings under prescribed displacement and/or loading protocols. The adaptation of a full-scale bearing test machine for the implementation of real-time hybrid simulation is presented here with a focus on the challenges encountered in attaining reliable simulation results for large scale dynamic tests. These advanced real-time hybrid simulations of large and complex hybrid models with several thousands of degrees of freedom are some of the first to use high performance parallel computing to rapidly execute the numerical analyses. Challenges in the experimental setup included measured forces contaminated by delay and other systematic control errors in applying desired displacements. Friction and inertial forces generated by the large-scale loading apparatus can affect the accuracy of measured force feedbacks. Reliable results from real-time hybrid simulation requires implementation of compensation algorithms and correction of these various sources of errors. Overall, this research program confirms that real-time hybrid simulation is a viable testing method to experimentally assess the behavior of full-scale isolators while capturing interactions with the numerical models of the superstructure to evaluate system level and in-structure response
Numerical Simulation of a New 3D Isolation System Designed for a Facility with Large Aspect Ratio
Full text linkThis paper proposes a novel three-dimensional (3D) isolation system for facilities and presents the numerical simulation approach for the isolated system under earthquake excitations and impact effect using the OpenSees (Open System for Earthquake Engineering Simulation) software frame work. The 3D isolators combine the quasi-zero stiffness (QZS) system in the vertical direction and lead rubber bearing in the horizontal direction. Considering the large aspect ratio of the isolated facility, linear viscous dampers are designed in the vertical direction to diminish the overturning effect. The vertical QZS isolation system is characterized by a cubic force-displacement relation, thus, no elements or materials can model this mechanic behavior in the existing finite element software. This study takes advantage of the open source feature of the OpenSees to create a new material to represent the mechanic properties of the QZS system. Then the user-defined material is combined with the rubber isolator element to model the 3D isolator. Considering different soil types and input magnitudes, six sets of natural seismic records and artificial waves and half sine pulses are selected as the input excitations. A finite element model for the 3D isolated facility is established based on the combined element and the simulation is performed to calculate the time history response. The numerical simulation reveals the flexibility of the OpenSees to deal with new engineering problems, and the results prove that the new 3D isolation system can have an optimal isolation effect in both horizontal and vertical directions. The maximum acceleration response at the top of the facility is below the target limit, and the maximum deformation and the overturning motion of the isolation system can be controlled in a safe range
Rotational Friction Damper’s Performance for Controlling Seismic Response of High Speed Railway Bridge-Track System
Full text linkCRTS-II slab ballastless track on bridge is a unique system in China high speed railway. The application of longitudinal continuous track system has obviously changed dynamic characteristics of bridge structure. The bridge system and CRTS-II track system form a complex nonlinear system. To investigate the seismic response of high speed railway (HSR) simply supported bridge-track system, nonlinear models of three-span simply supported bridge with piers of different height and CRTS-II slab ballastless track system are established. By seismic analysis, it is found that shear alveolar in CRTS-II track system is more prone to be damaged than bridge components, such as piers, girders and bearings. The result shows that the inconsistent displacement of bridge girders is the main cause of the CRTS-II track system’s damage. Then the rotational friction damper (RFD) is adopted, which utilizes the device’s rotation and friction to dissipate seismic energy. The hysteretic behavior of RFD is studied by numerical and experimental methods. Results prove that RFD can provide good hysteretic energy dissipation ability with stable performance. Furthermore, the analysis of RFD’s influence on seismic response of HSR bridge-track system shows that RFD with larger sliding force is more effective in controlling excessive inconsistent displacement where RFD is installed, though response of other bridge spans could slightly deteriorated
Application of Image Compression to Multiple-Shot Pictures Using Similarity Norms With Three Level Blurring
Full text linkImage compression is a process based on reducing the redundancy of the image to be stored or transmitted in an efficient form. In this work, a new idea is proposed, where we take advantage of the redundancy that appears in a group of images to be all compressed together, instead of compressing each image by itself. In our proposed technique, a classification process is applied, where the set of the input images are classified into groups based on existing technique like L1 and L2 norms, color histograms. All images that belong to the same group are compressed based on dividing the images of the same group into sub-images of equal sizes and saving the references into a codebook. In the process of extracting the different sub-images, we used the mean squared error for comparison and three blurring methods (simple, middle and majority blurring) to increase the compression ratio. Experiments show that varying blurring values, as well as MSE thresholds, enhanced the compression results in a group of images compared to JPEG and PNG compressors
A Quantum Authorization Management Protocol Based on EPR-Pairs
Full text linkQuantum authorization management (QAM) is the quantum scheme for privilege management infrastructure (PMI) problem. Privilege management (authorization management) includes authentication and authorization. Authentication is to verify a user’s identity. Authorization is the process of verifying that a authenticated user has the authority to perform a operation, which is more fine-grained. In most classical schemes, the authority management center (AMC) manages the resources permissions for all network nodes within the jurisdiction. However, the existence of AMC may be the weakest link of the whole scheme. In this paper, a protocol for QAM without AMC is proposed based on entanglement swapping. In this protocol, Bob (the owner of resources) authenticates the legality of Alice (the user) and then shares the right key for the resources with Alice. Compared with the other existed QAM protocols, this protocol not only implements authentication, but also authorizes the user permissions to access certain resources or carry out certain actions. The authority division is extended to fin-grained rights division. The security is analyzed from the four aspects: the outsider’s attack, the user’s attack, authentication and comparison with the other two QAM protocols
Stream-Based Data Sampling Mechanism for Process Object
Full text linkProcess object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object
An Auto-Calibration Approach to Robust and Secure Usage of Accelerometers for Human Motion Analysis in FES Therapies
Full text linkA Functional Electrical stimulation (FES) therapy is a common rehabilitation intervention after stroke, and finite state machine (FSM) has proven to be an effective and intuitive FES control method. The FSM uses the data information generated by the accelerometer to robustly trigger state transitions. In the medical field, it is necessary to obtain highly safe and accurate acceleration data. In order to ensure the accuracy of the acceleration sensor data without affecting the accuracy of the motion analysis, we need to perform acceleration big data calibration. In this context, we propose a method for robustly calculating the auto-calibration gain using redundant acceleration vectors, and then calibrating the data generated by the accelerometer based on the calculated gain. The selection of the acceleration vector involved in the gain calculation is demonstrated by different experiments. The results show that the auto-calibration gain calculated after calibration is very close to 1, and the error is significantly less than before calibration, which indicates that the accelerometer unit is well calibrated