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Effect of Reinforcement Corrosion Sediment Distribution Characteristics on Concrete Damage Behavior
Full text linkReinforcement corrosion directly affects the mechanical behavior of reinforced concrete structures. An electric corrosion test was conducted on a reinforced concrete test specimen, and a finite element model of the reinforcement corrosion damage was established. In addition, the damage behavior of reinforced concrete under different corrosion sediment distribution characteristics and different corrosion rates was studied. It was noted that when corrosion sediments are in a “semiellipse+semicircle” distribution, the results of numerical calculation are consistent with those obtained experimentally, reflecting the damage characteristics of reinforced concrete test specimens. Further, the results showed that the distribution characteristics of corrosion sediments greatly influence the damage behavior of reinforced concrete. In particular, when the corrosion sediments demonstrate a “semiellipse” distribution, reinforced concrete members may easily suffer from reinforcement damages. In the case of “semiellipse+semicircle” and “circle” distributions, the cohesive force between the reinforcements and concrete decreases: With the same corrosion rate, the damaged area expands with the increase in the number of reinforcements, which indicates a reduction in the cohesive force and thus, a reduction in the damage in the reinforcement area. This paper analyzes in-depth the effects of reinforcement corrosion expansion on the concrete damage behavior, provides references for practical engineering
A Capacity Improving Scheme in Multi-RSUs Deployed V2I
Full text linkThe communication reliability and system capacity are two of the key performance indicators for Internet of Vehicles (IoV). Existing studies have proposed a variety of technologies to improve reliability and other performance, such as channel selection and power allocation in Vehicle-to-Infrastructure (V2I). However, these researches are mostly applied in a single roadside unit (RSU) scenario without considering inter-cell interference (ICI) of multi-RSUs. In this paper, considering the distribution characteristics of multi-RSUs deployment and corresponding ICI, we propose a reliable uplink transmission scheme to maximize the total capacity and decrease the interference of multi-RSUs (mRSU-DI) in condition of the uplink interruption performance. In the proposed mRSU-DI scheme, ICI is depressed by dynamic channel and power allocation algorithm. A heuristic algorithm based on penalty function is proposed to obtain the optimal power allocation solution of the model. In addition, we realize the scheme in both given conditions of channel state information (CSI) and channel state distribution, respectively. The results show that the proposed scheme can both improve the system capacity and guarantee the reliable transmission in both premises
Improved Enhanced Dbtma with Contention-Aware Admission Control to Improve the Network Performance in Manets
Full text linkDBTMA relies entirely on RTS/CTS dialogue for un-collided transmission of data. The purpose is to improve the QoS at MAC layer by developing it over 802.11e standard. However, DBTMA does not guarantee real-time constraints without efficient method for controlling the network loads. The main challenges in MANETs include prediction of the available bandwidth, establishing communication with neighboring nodes and predicting the consumption of bandwidth flow. These challenges are provided with solutions using Contention-Aware Admission Control (CACP) protocol. In this paper, the EDBTMA protocol is combined with CACP protocol that introduces bandwidth calculation using admission control strategy. The calculation includes certain metrics like: admission control and bandwidth consumption. To compute the bandwidth of channel, bandwidth utilization and traffic priority is distinguished through dual busy tone is proposed. This operates distinctly on its own packet transmission operation. This CACP mechanism defends the conventional traffic flows from new nodes and based on the measured status information of the channel, it QoS of the admitted flows is maintained. This ensures maximum amount of bandwidth flows accommodated by resources and determines the resources in a system meet the new flow requirements while maintaining existing bandwidth flow levels
Unified Dispersion Characteristics of Structural Acoustic Waveguides
No full textIn this article, we show with some formalism that infinite flexible structural acoustic waveguides have a general form for the dispersion equation. The dispersion equation of all such waveguides should conform to a generic form. This allows us to bring out the common features of structural acoustic waveguides. We take three examples to demonstrate this fact, namely, the rectangular, the circular cylindrical and the elliptical geometries. Where necessary, the equations are simplified for applicability to a particular frequency-regime before demonstrating the conformance to the generic form of the dispersion relation. It is then shown that the coupled wavenumber solutions of all these systems can be represented on a single schematic
Residual Stresses in Resistance Spot Welded AZ61 Mg Alloy
Full text linkThe use of magnesium alloys has been rapidly increased due to their ability to maintain high strengths at light weights. However weldability of steels and aluminum alloys by using resistance spot weld (RSW) process is a major issue, because it cannot be directly utilized for magnesium alloys. In this study, a structural-thermal-electrical finite element (FE) model has been developed to predict the distribution of residual stresses in RSW AZ61 magnesium alloy. Thermophysical and thermomechanical properties of AZ61 magnesium alloy have been experimentally determined, and have been used in FE model to increase the accuracy of the model. X-ray diffraction (XRD) technique has been utilized to measure the residual stresses in welded samples, and its results have been used to validate the FE model. Comparison study shows that the results obtained by using FE model have a good agreement with the experimental XRD data. In specific, the results show that the maximum tensile residual stress occurs at the weld center while decreases towards the nugget edge. In addition, the effects of welding parameters such as electrical current, welding time, and electrode force have been investigated on the maximum tensile residual stress. The results show that the tensile residual stress in welded joints rises by increasing the electrical current; however, it declines by prolonging the welding time as well as increasing the electrode force
Simulation Analysis on Quasistatic Characteristics of Multistage Face Gears with Double Crown Surface
Full text linkThe multistage face gears are the core component of the planetary gear train, which is symmetrically meshed by multiple single-stage face gear and multiple cylindrical gears. However, it is difficult to synchronize the contact between face gears and cylindrical gear due to the tooth number differences. Thus, the interference problems between two stages and big stress concentration are obvious. The crown surface configuration technology and structure design were introduced to optimize the meshing condition. To improve the double crown design feasibility and meshing stability, it is necessary to establish a reasonable multistage face gears pair simulation model to evaluate various influence factors on the contact condition and quasi-static characteristics of multistage face gears structure. The relevant scatter plots are fitted by comparing the contact results with different crown quantities and friction coefficients to intuitively obtain the variation regularity of maximum deformation, maximum strain, maximum stress and maximum strain energy. The natural frequency and mode coefficient are also determined by modal analysis under these two conditions. All the above mentioned studies verified the contact conjugate properties of double crown surface configuration were suitable. The results can provide a foundation for structure optimization and transmission reliability of multistage face gears
Blending Basic Shapes By C-Type Splines and Subdivision Scheme
Full text linkIn this article, we adopt the C-type spline of degree 2 to model and blend basic shapes including conics and circle arcs. The C-type spline belongs to the ωB-spline category of splines that are capable of blending polynomial, trigonometric and hyperbolic functions. Commonly used basic shapes can be exactly represented by these types of splines. We derive explicit formulas for the convenience of modeling the basic curves. The entire blending curve is C1-continuous. In comparison with the existing best blending method by rational G2 splines, which are rational splines of degree 3, the proposed method allows simpler representation and blending of the basic curves, and it can represent numerous basic shapes including the hyperbolic types. We also design a subdivision method to generate blending curves; this method is precise for the basic curves and approximate for the blending sections. The subdivision process is efficient for modeling and rendering. It has also proven to be C1-continuous by the asymptotically equivalent theory and the continuity of stationary subdivision method. In addition, we extend the proposed methods to cases involving the modeling and blending of basic surfaces. We provide many examples that illustrate the merits of our methods
Numerical Validations of the Tangent Linear Model for the Lorenz Equations
Full text linkThe validity of the tangent linear model (TLM) is studied numerically using the example of the Lorenz equations in this paper. The relationship between the limit of the validity time of the TLM and initial perturbations for the Lorenz equations is investigated using the Monte Carlo sampling method. A new error function between the nonlinear and the linear evolution of the perturbations is proposed. Furthermore, numerical sensitivity analysis is carried to establish the relationship between parameters and the validity of the TLM, such as the initial perturbation, the prediction time, the time step size and so on, by the method of mathematical statistics
Numerical Treatment for Stochastic Computer Virus Model
Full text linkThis writing is an attempt to explain a reliable numerical treatment for stochastic computer virus model. We are comparing the solutions of stochastic and deterministic computer virus models. This paper reveals that a stochastic computer virus paradigm is pragmatic in contrast to the deterministic computer virus model. Outcomes of threshold number C∗ hold in stochastic computer virus model. If C∗ ∗ > 1 shows virus persists in the computer population. Unfortunately, stochastic numerical methods fail to cope with large step sizes of time. The suggested structure of the stochastic non-standard finite difference scheme (SNSFD) maintains all diverse characteristics such as dynamical consistency, boundedness and positivity as defined by Mickens. The numerical treatment for the stochastic computer virus model manifested that increasing the antivirus ability ultimates small virus dominance in a computer community
Effects of Deformation Rate on the Unbinding Pathway of the MMP8-Aggrecan_IGD Complex in Cartilage
Full text linkMechanical force plays a critical role in the remodeling and degradation of cartilage tissues. The cartilage tissue generates, absorbs, and transmits mechanical force, enabling specific biological processes in our body. A moderate intensity mechanical force is necessary for cartilage tissue remodeling and the adaptation of biomechanical properties, but a high intensity mechanical force can lead to pathological degradation of cartilage tissue. However, the molecular mechanism of cartilage degradation is still unclear. We use full atomistic simulations with SMD simulations to investigate whether the magnitude of mechanical force affects the unbinding pathway of the MMP8-Aggrecan_IGD complex. We find that when the pulling velocity is slow, the mechanical force required to unbind the Aggrecan_IGD from MMP8 is higher, and a three-step unbinding pathway is observed. On the other hand, when the pulling velocity is fast, the mechanical force required to unbind the Aggrecan_IGD from MMP8 is lower, and a two-step unbinding pathway is observed. Our results help us to understand how the magnitude of the mechanical force affects the unbinding pathway of the enzyme-ligand complex in cartilage tissue at the molecular level