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On the Tactile Sensing Based on the Smart Materials
Get PDFA flexible finger with muscles made of Nitinol wires and the skin made of auxetic material is analyzed from the tactile sensing point of view. The recognizing of the shape and texture of 3D objects is performed by simulation the action of an array of nanopiezotronic transistors integrated into the skin. The array of nanopiezotronic transistors makes possible the detection of the pressure-induced changes in the auxetic skin. The shape and texture of the objects is best estimated by determining the surface and texture as an n-ellipsoid defined by 12 parameters. An inverse problem is solved in order to find these parameters from the condition that the n-ellipsoid best fits the set of data points probed by touch with the finger
Simple Efficient Smart Finite Elements for the Analysis of Smart Composite Beams
Get PDFThis paper is concerned with the development of new simple 4-noded locking-alleviated smart finite elements for modeling the smart composite beams. The exact solutions for the static responses of the overall smart composite beams are also derived for authenticating the new smart finite elements. The overall smart composite beam is composed of a laminated substrate conventional composite beam, and a piezoelectric layer attached at the top surface of the substrate beam. The piezoelectric layer acts as the actuator layer of the smart beam. Alternate finite element models of the beams, based on an “equivalent single layer high order shear deformation theory”, and a “layer-wise high order shear deformation theory”, are also derived for the purpose of investigating the required number of elements across the thickness of the overall smart composite beams. Several cross-ply substrate beams are considered for presenting the results. The responses computed by the present new “smart finite element model” excellently match with those obtained by the exact solutions. The new smart finite elements developed here reveal that the development of finite element models of smart composite beams does not require the use of conventional first order or high order or layer-wise shear deformation theories of beams. Instead, the use of the presently developed locking-free 4-node elements based on conventional linear piezo-elasticity is sufficient
Prediction of Concrete Cubic Compressive Strength Using ANN Based Size Effect Model
Get PDFSize effect is a major issue in concrete structures and occurs in concrete in any loading conditions. In this study, size effect on concrete cubic compressive strength is modeled with a back-propagation neural network. The main advantage in using an artificial neural network (ANN) technique is that the network is built directly from experimental data without any simplifying assumptions via the self-organizing capabilities of the neural network. The proposed ANN model is verified by using 27 experimental data sets collected from the literature. For the large specimens, a modified ANN is developed in the paper to further improve the forecast accuracy. The results demonstrate that the ANN-based size effect model has a strong potential to predict the cubic compressive strength of concret
Small-Scale Effect on the Static Deflection of a Clamped Graphene Sheet
Get PDFSmall-scale effect on the static deflection of a clamped graphene sheet and influence of the helical angle of the clamped graphene sheet on its static deflection are investigated. Static equilibrium equations of the graphene sheet are formulated based on the concept of nonlocal elastic theory. Galerkin method is used to obtain the classical and the nonlocal static deflection from Static equilibrium equations , respectively. The numerical results show that the static deflection and small-scale effect of a clamped graphene sheet is affected by its small size and helical angle. Small-scale effect will decrease with increase of the length and width of the graphene sheet, and small-scale effect will disappear when the length and the width of graphene sheet are both larger than 200 um
Meshless Local Petrov-Galerkin Method for Rotating Euler-Bernoulli Beam
Get PDFFree vibration problem of a rotating Euler-Bernoulli beam is solved with a truly meshless local Petrov-Galerkin method. Radial basis function and summation of two radial basis functions are used for interpolation. Radial basis function satisfies the Kronecker delta property and makes it simpler to apply the essential boundary conditions. Interpolation with summation of two radial basis functions increases the node carrying capacity within the sub-domain of the trial function and higher natural frequencies can be computed by selecting the complete domain as a sub-domain of the trial function. The mass and stiffness matrices are derived and numerical results for frequencies are obtained for a fixed-free beam and hinged-free beam simulating hingeless and articulated helicopter blades. Stiffness and mass distribution suitable for wind turbine blades are also considered. Results show an accurate match with existing literature
Numerical Simulation of An Experienced Farmer Lifting Tubers of Cassava for Designing A Bionic Harvester
Get PDFHarvesting is the most difficult and costly operation in cassava production. Currently, most cassava harvest still depends on manual tools. Effective mechanized harvesters are necessary to improve harvesting quality and reduce production cost. Therefore, it is very important to figure out key information for designing an effective tuber lifting system used in bionic “dig-pull” harvesters. A numerical simulation model of human-stem-tuber-soil system was developed to carry out numerical simulation of manually pulling tuber. Coupling algorithm of Lagrange and smoothed particle hydrodynamics (SPH) was used in the model. Lifting mechanism of experienced farmer was studied at a micro level. Influence of lifting velocities was discussed. The results show that when the soil volume was compressed by 5% in the lifting direction, a ring sheared surface of soil occurs. The soil is gradually sheared and fractured along with the surface during lifting. After that, the soil falls down on ground due to tuber jittering and completely detaches from the tuber. Large lifting velocity, resulting in high harvesting efficiency, but consumption of energy also increases. Before the height achieves 75 mm, higher velocity is beneficial for improving efficiency, but after that, lifting velocity should be appropriate to avoid tuber broken and lost
A New Minimax Probabilistic Approach and Its Application in Recognition the Purity of Hybrid Seeds
Get PDFMinimax probability machine (MPM) has been recently proposed and shown its advantage in pattern recognition. In this paper, we present a new minimax probabilistic approach (MPA),which can provide an explicit lower bound on prediction accuracy. Applying the Chebyshev-Cantelli inequality, the MPA is posed as a second order cone program formulation and solved effectively. Following that, this method is exploited directly to recognize the purity of hybrid seeds using near-infrared spectroscopic data. Experimental results in different spectral regions show that the proposed MPA is competitive with the existing minimax probability machine and support vector machine in generalization, while requires less computational time than them. These results illustrate the feasibility and effectiveness of the proposed approach in recognition the purity of hybrid seeds
Optimal Adaptive Genetic Algorithm Based Hybrid Signcryption Algorithm for Information Security
Get PDFThe functions of digital signature and public key encryption are simultaneously fulfilled by signcryption, which is a cryptographic primitive. To securely communicate very large messages, the cryptographic primitive called signcryption efficiently implements the same and while most of the public key based systems are suitable for small messages, hybrid encryption (KEM-DEM) provides a competent and practical way. In this paper, we develop a hybrid signcryption technique. The hybrid signcryption is based on the KEM and DEM technique. The KEM algorithm utilizes the KDF technique to encapsulate the symmetric key. The DEM algorithm utilizes the Adaptive Genetic Algorithm based Elliptic curve cryptography algorithm to encrypt the original message. Here, for the security purpose, we introduce the three games and we proved the attackers fail to find the security attributes of our proposed signcryption algorithm. The proposed algorithm is analyzed with Daniel of Service (DOS), Brute Force attack and Man In Middle (MIM) attacks to ensure the secure data transaction
Analysis and Numerical Simulation of Hydrofracture Crack Propagation in Coal-Rock Bed
Get PDFIn underground coal mines, hydrofracture can cause the increase of breathability in the fractured coal bed. When the hydrofracture crack propagates to the interface between the coal bed and the roof-floor stratum, the crack may enter roof-floor lithology, thus posing a limit on the scope of breathability increase and making it difficult to support the roof and floor board for subsequent coal mining. In this work, a two-dimensional model of coal rock bed that contains hydrofracture crack was constructed. Then an investigation that combines the fracture mechanics and the system of flow and solid in rock failure process analysis (RFPA2D-Flow) were carried out to study the failure mechanism at the interface between rocks and coals, and critical water pressure that hydrofracture crack propagates. The results indicated that the main factors that affect the direction of hydrofracture crack propagation are the angle of intersection between coal-rock interface and horizontal section, horizontal crustal stress difference, tension-shear mixed crack fracture toughness in coal-rock interface and differences in elasticity modulus of coal-rock bed.The possibility of crack directly entering coal-rock interface would increase with the increase in angle of intersection or horizontal crustal stress difference. The trend that crack propagates along the coal-rock interface will become stronger with the decrease of the fracture toughness at the coal-rock interface and the increase of the elasticity modulus difference between the coal bed and the roof strata. The results of this study was to put forward a method of controlling hydrofracture crack, optimize the fracturing well location provides a certain theoretical basis
Hemodynamic Based Surgical Decision on Sequential Graft and Y-Type Graft in Coronary Artery Bypass Grafting
Get PDFPurpose: Sequential graft and Y-type graft are two different surgical procedures in coronary artery bypass grafting (CABG). The hemodynamic environment of them are different, that may cause different short-term surgical result and long-term patency. In this study, the short-term and long-term result of sequential and Y-type graft was discussed by comparing the hemodynamics of them. Materials and Methods: Two postoperative 3-dimensional (3D) models were built by applying different graft on a patient-specific 3D model with serious stenosis. Then zero-dimensional (0D)/3D coupled simulation was carried out by coupling the postoperative 3D models with a 0D lumped parameter model of the cardiovascular system.
Results: The flow rate of native coronary arteries and grafts are all calculated and illustrated in this paper. No significant difference of the native coronary arteries flow and graft flow exists between two surgical procedures. The wall shear stress (WSS) and streamline were also depicted. The graft WSS of sequential graft is 19.1% higher than Y-type graft. While flow separation appears at the bifurcation of Y-type graft.
Conclusion: The short-term outcomes of sequential graft and Y-type graft are almost the same. But it can be found from the hemodynamics factors that the longterm patency of the sequential graft is better