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HIV/AIDS-COVID-19 co-infection is a major public health concern especially in developing countries of the world. This paper presents HIV/AIDS-COVID-19 co-infection to investigate the impact of interventions on its transmission using ordinary differential equation. In the analysis of the model, the solutions are shown to be non-negative and bounded, using next-generation matrix approach the basic reproduction numbers are computed, sufficient conditions for stabilities of equilibrium points are established. The sensitivity analysis showed that transmission rates are the most sensitive parameters that have direct impact on the basic reproduction numbers and protection and treatment rates are more sensitive and have indirect impact to the basic reproduction numbers. Numerical simulations shown that some parameter effects on the transmission of single infections as well as co-infection, and applying the protection rates and treatment rates have effective roles to minimize and also to eradicate the HIV/AIDS-COVID-19 co-infection spreading in the community. [ABSTRACT FROM AUTHOR]

Coupler separation is among the serious accidents threatening the operation safety of heavy-haul trains. This paper reports a study on the formation mechanism and key influencing factors of middle coupler separation of a 20,000-tonne combined heavy-haul train during air-braking release by means of field investigation, theoretical analysis and numerical simulation. The interaction state between the connected coupler knuckles and the potential sensitive factors leading to the coupler separation are investigated based on field tests and theoretical analysis. The formation process of coupler separation and the related influencing factors are analysed through numerical simulations. The results show that the coupler separation between slave locomotives and connected wagons usually occurs in the switching process of the longitudinal coupler force from the buffing (compressive) state to the draw (tensile) state. The excessive initial height difference of connected coupler knuckles, dynamic braking force of locomotive, pitch angle of locomotive and wagon coupler as well as the too small friction coefficient of the coupler knuckles significantly increase the risk of coupler separation. [ABSTRACT FROM AUTHOR]

In this paper, motivated by considerations of server utilization and energy consumption in cloud computing, we investigate a homogeneous queueing system with a threshold-based workload control scheme. In this system, a virtual machine will be turned off when there are no tasks in its buffer upon the completion of a service by the machine, and turned on when the number of tasks in its buffer reaches a pre-set threshold value. Due to complexity of this system, we propose approximations to system performance measures by mean field limits. An iterative algorithm is suggested for the solution to the mean field limit equations. In addition, numerical and simulation results are presented to justify the proposed approximation method and to provide a numerical analysis on the impact of the system performances by system parameters, which suggests that the proposed system saves about (1 − λ μ) × 100 % of the energy consumption compared to the ordinary supermarket models. [ABSTRACT FROM AUTHOR]

This paper is devoted to study the dynamical behavior of a Belousov–Zhabotinsky reaction–diffusion system with nonlocal effect and find the essential difference between it and classical equations. First, we prove the existence of the solution by using the comparison principle and constructing monotonic sequences. Furthermore, the uniqueness is given by using fundamental solution and Gronwall's inequality. Then we obtain the uniform boundedness of the solution by means of auxiliary function. Finally, we investigate the states of the solution as the parameters change and show some new and interesting phenomena about nonlocal Belousov–Zhabotinsky reaction–diffusion system by using stability analysis and numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, we present an approach to study the electrical and spectral degradation properties of InxGa1-xAs (x = 0.2, 0.3, 0.53) solar cell under 150 keV proton irradiation based on numerical simulation. First, the structures of InxGa1-xAs solar cell were optimized by adjusting the doping concentration of base layer and modifying the thickness of base and emitter layer. The structural parameter related to providing higher conversion efficiency was figured out. Then, the degradation of electrical parameters such as short-circuit current density (Jsc), open-circuit voltage (Voc), maximum output power (Pmax), fill factor (FF), as well as the spectral response were obtained. The degradation correlation with radiation-induced defects was built to reveal the damage mechanism under 150 keV proton irradiation. This study provides constructive model of InxGa1-xAs to be applied in multi-junction solar cells, and the predicted degradation behavior could contribute to design the radiation-hardened space devices. [ABSTRACT FROM AUTHOR]

There exist many well-known analytical models for adhesive contact for spherical asperities. However, in many situations, the asperities are not spherical and may be better described by a power-law function. Thus, these well-known analytical models were extended to power-law-shaped axisymmetric asperities in the past decades. In this paper, numerical simulation is employed for the adhesive contact between a rigid power-law axisymmetric asperity and an elastic half-space. The realistic Lennard-Jones potential and the Derjaguin approximation are used for the surface traction. Numerical simulations are performed with different shape indexes and different Tabor parameters. The whole solution is obtained. Semi-empirical formulas for the pull-off forces, the contact radius at zero loads, the jump-in distance, and the pull-off distance are proposed. All these equations are both simple and as accurate as of the numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive generalised function projective synchronisation scheme of fractional-order chaotic systems with different dimensions and orders and fully unknown parameters is presented. On the basis of the Lyapunov method of fractional-order systems, a stability theorem of the fractional-order system with non-identical orders is proven. Using the fractional-order controller and adaptive control theory, sufficient conditions for synchronisation and unknown parameters update rules are obtained. Theoretical analysis and numerical simulations are provided to verify the validity of the proposed scheme. Moreover, synchronisation results are applied to secure communication via modified chaotic masking (MCM) method. The unpredictability of the scaling function matrix and the use of fractional-order systems with different orders can increase the security of the cryptosystem. The security analysis shows that the introduced algorithm has large key space, high sensitivity to encryption keys, higher security and the acceptable encryption speed. [ABSTRACT FROM AUTHOR]

This paper addresses the trajectory tracking control problem of a planar vertical take-off and landing (PVTOL) aircraft in the presence of position constraints and external disturbances. A novel robust constrained control approach is proposed by incorporating the barrier Lyapunov function (BLF) and nonlinear damping items within the framework of dynamic surface control design. The dynamic surface control is used to avoid the 'explosion of terms' problem of the traditional backstepping control. The tan-type BLF is utilised to preserve the position tracking errors always within the predefined position constraints. The nonlinear damping items are applied to handle the effect of external disturbances. The uniform ultimate boundedness of the resulting closed-loop system is rigorously proved through the Lyapunov's direct method. A distinct feature of the proposed control approach is that it is a general methodology for the trajectory tracking control of PVTOL aircraft with or without position constraints. Both theoretical analysis and numerical simulations illustrate the effectiveness and benefits of the proposed control approach. [ABSTRACT FROM AUTHOR]

When the tire of aircraft landing gear passes through the contaminated runway, besides the side water spray, the water spray between the multi-wheels will collide and form the pattern similar to the tail of the rooster. This kind of water spray is called the cock tail flow. In this paper, numerical analysis is used to study the formation process of the cock tail flow caused by the main aircraft tires, and the water is simulated by smoothed particle hydrodynamics (SPH) method. According to the results of numerical simulation, the pattern and velocity distribution of cock tail flow are analyzed. The effects of water depth, tire spacing and tire speed on the pattern and velocity distribution of cock tail flow are obtained, and the formation mechanism of cock tail flow is revealed. It is preliminarily verified that numerical simulation using SPH method can analyze the specific problems of the tire including different configurations. [ABSTRACT FROM AUTHOR]

Gradation is one of the crucially important features of aggregate blend. The objective of this paper is to present a review on the theory and design method of aggregate gradation, followed by its effect on asphalt pavement performance. The results indicate that, (i) Theory of maximum density curve, particle interfering theory and fractal theory are the main theories for aggregate gradation. (ii) The gradation design of asphalt mixture has two types by aggregate morphology-continuous and gap gradation, or three types by air voids of mixture-dense, open and semi-open gradation. However, the only constant principle of aggregate gradation design is to strictly follow the requirements of pavement performance. (iii) Aggregate gradation significantly influences almost all of the pavement performances. The performance-based design method for asphalt mixture should pay more attention on aggregate gradation. (iv) The variability of aggregate gradation cannot be eliminated due to its objective existence from aggregate production in quarry to mixture compaction in field. Several effective control measures are summarized to limit gradation variability under an acceptable range. (v) The latest developments and the trend for gradation analysis are numerical simulation based on virtual reconstruction, image-based modelling and computer-generated modelling. [ABSTRACT FROM AUTHOR]

The saturation input control problem of discrete-time networked systems via adaptive event-triggered communication scheme is discussed in this paper. The criteria are derived by utilising a new Lyapunov functional to guarantee that the considered networked system with randomly occurring infinite distributed delays, random packet losses and sensor saturation is exponentially stable in mean square sense. A novel adaptive event-triggered law is proposed, which is dependent on the exponentially stable index α. The effectiveness of our proposed method is illustrated by both theoretical analysis and numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, we present a mathematical model for the 3D △×n memristor-LC circuit network in the fractional-order sense. First, the impedance of the fractional-order 3D circuit network is derived using matrix transform method and difference equation model. Moreover, we extend the concept of saturation time across the memristor to the circuit network and attempt to explore the relationship between the generalized saturation time and the direct voltage across the network in fractional-order sense. In addition, the effects of the time-varying characteristics of the memristor on the fractional-order 3D circuit network are studied. Also, we propose some issues remaining to be addressed in the near future for the network model. Furthermore, the impedance characteristics are specifically analyzed with theoretical analyses and numerical simulations, where many interesting phenomena are discussed. Finally, sensitivity analysis is provided to carefully investigate the effects of various input parameters on the output response of the fractional-order 3D circuit network. [ABSTRACT FROM AUTHOR]

This paper reports the emergence of bi-stability in a third-order memristive Wien-bridge oscillator. By transforming the parallel RC feedback network into a series resistor and capacitor (RC) feedback network in the previous non-ideal voltage-controlled memristor emulator, an improved memristor emulator is proposed and its fingerprints are exhibited. And then through introducing the proposed emulator to replace the parallel resistor in the conventional Wien-bridge oscillator, an improved memristor-based third-order Wien-bridge oscillator is constructed. Based on its mathematical model, the initial condition-dependent dynamical behaviour is revealed by theoretical analyses and numerical simulations and further verified by hardware experiments, from which the emergence of bi-stability in the memristive oscillator is well demonstrated. [ABSTRACT FROM AUTHOR]

This paper describes the beneficial effects of multiple layers of rubber-sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM layers was granulated rubber, produced from waste tires. The optimum thickness of the RSM layer was determined to be approximately 0.4 times the footing diameter. By increasing the number of RSM layers, the bearing capacity of the foundation can be increased and the footing settlement reduced. The influence of the number of RSM layers on bearing capacity and settlement become almost insignificant beyond three layers of RSM, particularly at low settlement ratios. At a ratio of settlement to plate diameter of 4%, the values of bearing pressure for the installation with one, two, three and four layers of RSM were about 1.26, 1.47, 1.52 and 1.54 times greater, respectively, than that for the unreinforced installation. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. For example, at an applied footing pressure of 560 kPa, the transferred pressure at a depth of 570 mm was about 58, 45 and 35% for one, two and three layers of RSM, respectively, compared to the transferred stress in the unreinforced bed. By numerical analysis, it was found that the presence of soil-rubber layers resulted in expansion of passive zones in the foundation due to the effectiveness of the confinement provided by the rubber inclusions, and this tends to make the bed deflect less. On the basis of this study, the concept of using multiple RSM layers has not only been shown to improve the performance of foundations under heavy loading, but also, the environmental impacts of waste tires are attenuated by re-using their rubber as part of a composite soil material in civil engineering works. [ABSTRACT FROM AUTHOR]

This paper presents a new macroscopic mesh-free particle method in which Darcy's and Forchheimer's terms are introduced into the governing equation to ensure the capacity of the particle method in simulating laminar and turbulent porous medium flows. A developed interfacial condition and inflow boundary condition are implemented in the macroscopic particle method to improve the stability of the Particle-based model. The comparisons of channel flow over and within porous bed among the present method, previous mesh-based method, and experimental data show that the macroscopic particle method is capable of simulating flows in both the clear flow region and porous flow region. Finally, two cases of flow over a rigid box and a cylinder lying on porous bed are simulated, and the numerical results are in good agreement with the measured data. The analysis and comparisons indicate that the newly developed particle-based method is reliable and has been successfully extended to macroscopic porous medium simulation. [ABSTRACT FROM AUTHOR]

In this paper, the authors study the forward and inverse problems for a fractional boundary value problem with Dirichlet boundary conditions. The existence and uniqueness of solutions for the forward problem is first proved. Then an inverse source problem is considered. [ABSTRACT FROM AUTHOR]

Multiplexed model predictive control (MMPC) is a recently proposed efficient model predictive control (MPC) algorithm, which can effectively reduce the computational burden of the online optimisation in MPC implementation by updating the control inputs in an asynchronous manner. This paper investigates the application of MMPC in active vehicle suspension design. An MMPC controller integrated with soft constraints and a Kalman filter is proposed based on a full-car model. Ride comfort, roadholding and suspension deflection are considered in this paper, where ride comfort and roadholding are formulated as a quadratic cost function in terms of sprung mass accelerations and tyre deflections, while suspension deflection performance is formulated as a hard constraint. The saturation of the actuator force is also considered and formulated as a hard constraint as well. Numerical simulation is performed with respect to different choices of weighting factors, vehicle speeds and control horizons. The results show that the overall performance of ride comfort and roadholding can be improved significantly by employing MMPC and the average time taken by MMPC to solve the individual quadratic programming problem is considerably smaller than that of the conventional MPC, which effectively demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Block pavements are an attractive alternative to asphalt and concrete pavements, especially in communal areas. Architects and urban planners would like to take advantage of various shapes, colours and textures of paving blocks in order to achieve a higher quality of urban space if the performance of block pavements could be better predicted to avoid large horizontal displacements of chipped stone corners and rutting. Unfortunately, the computational performance prediction of paving block structures is more complex than that for flexible pavements with homogeneous surface layers of asphalt concrete. The influence of the large number of vertical joints between paving blocks on the overall mechanical performance has not been considered sufficiently within computational tools yet. The proposed numerical simulation tool is able to take into account the complex mechanical behaviour of sand-filled joints as well as the non-linear mechanical behaviour of the underlying base courses. Joints are modelled using a Mohr-Coulomb-type friction model with the normal stresses non-linearly related with joint opening. Three different experimental set-ups were developed for the identification of the model parameters. The base behaviour was modelled using the Drucker-Prager cap model. The paper shows that the proposed tool predicts reasonable deformations and stresses in block pavements. The results of the simulations were compared with measured stresses from the full-scale accelerated pavement testing and a good agreement was observed. [ABSTRACT FROM AUTHOR]

Numerical simulations of the tandem-system flow are widely conducted because of the complex interactions of the configuration. The cavitation phenomenon is an important factor that affects the hydrofoil in tandem. In this paper, we developed a new parameter for the Kunz preconditioner based on the local cavitation volume fraction. To assess this parameter, a type of Fourier footprint analysis and numerical test of the hydrofoil are adopted. The preconditioning method is also conducted in hydrofoil turbulent cavitation flows with RANS turbulence models, to prove that this method has good stability and convergence. Based on this, a tandem Clark-Y hydrofoil configuration is investigated. The results show that the distance of components has a strong influence on the cavitation and lift coefficient of the tandem hydrofoils. Therefore, the purpose of this study is to provide guidance on the design of marine vehicles that have tandem configurations. [ABSTRACT FROM AUTHOR]

This paper proposes a new set-point control method for a musculoskeletal arm by combining muscular internal force feedforward control with feedback control including a large time delay. The proposed method accomplishes robust and rapid positioning with a relatively small muscular force. In the positioning by the muscular internal force feedforward controller, a large muscular force is required to achieve good performance. On the other hand, in the positioning by the feedback controller including the large time delay, the system can easily fall into an unstable state. A simple linear combination of these two controllers makes it possible to improve the control performance and to overcome the drawbacks of each controller in a complementary manner. First, a two-link six-muscle arm model is considered as a musculoskeletal system in this study. Second, the new set-point control method, which consists of the feedforward control signal and the feedback control signal including the time delay, is designed. Third, the stability of the proposed method is investigated using the Lyapunov-Razumikhin method. Finally, the results of numerical simulations and experiments are presented to demonstrate the advantages of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper a method based on Sinc approximation is developed for the numerical solution of a nonlinear fractional pantograph equation. In order to use Sinc approximation, the problem needs to have an analytic solution. So we investigated the existence and uniqueness of analytic solutions in the proposed domain. Single and double exponential transformations are used to approximate the solution. Some test problems are given to demonstrate the efficiency and applicability of the methods. The results are compared with some other existing numerical methods to show the performance and good accuracy of the methods. The numerical orders of convergence show that the method has exponential rate of convergence. [ABSTRACT FROM AUTHOR]

In this paper, the synchronisation problems of multi-agent systems with asynchronous and synchronous event-triggered control under a novel event-triggered condition are solved. Our event-triggered control protocols only require each agent to send its state information to its neighbouring agents when an event-triggered condition is satisfied. Such control protocols substantially reduce the cost of communication. It is worth mentioning that the proposed protocols also ensure that the synchronisation of the multi-agent system with asynchronous and synchronous event-triggered can be achieved asymptotically without Zeno-behaviour. Meanwhile, an ultimate synchronisation trajectory is given. Moreover, our results are applied to solve the formation control problem. Some numerical simulations are presented to illustrate the effectiveness of our protocols. [ABSTRACT FROM AUTHOR]

This paper studies the distributed consensus problem in sampled-data multi-agent systems with directed network topologies subject to a quantisation constraint. Different from the widely used consensus protocol which exploits current information, we adopt a distributed proportional-differential (PD)-like protocol. First, we provide a necessary and sufficient condition of control gains which guarantee the consensus with the assumption that real-valued communication information can be obtained. Next, we analyse the quantisation effects in system performances under the proposed protocol; it is proved that the quantised consensus can be achieved. Finally, by providing numerical examples, we show that with appropriate parameters, the consensus can be achieved and the quantisation noises can be attenuated effectively. [ABSTRACT FROM AUTHOR]

This paper addresses the installation effects of stone columns in soft soils. Focus is made on the lateral expansion of stone material using the vibro displacement and substitution techniques by means of numerical simulations. The behaviour of reinforced soil after stone column installation is investigated to show how the properties of soft soils can be improved prior to final loading. The effect of such an improvement on the prediction of reinforced soil settlement is evaluated. The axisymmetric unit cell model (UCM) served for the comparison between numerical predictions made by the Mohr-Coulomb and hardening soil constitutive laws adopted for the soft soil. An equivalent group of end bearing columns model was investigated in the axisymmetric condition to predict the settlement of reinforced soil by adopting the Mohr-Coulomb constitutive model for soft clay. The reduction of settlements predicted by the unit cell and group of columns models, due the improvement of the Young’s modulus of soft clay, were compared. It is concluded that a significant reduction of settlement is expected when the group of columns model is considered. [ABSTRACT FROM AUTHOR]

This paper presents a numerical analysis of the migration and transformation mechanism of petroleum hydrocarbons (PHs) pollutants in soil. The mathematical model of the solute migration and plant–microbial remediation for PH polluted soil was established. The model was verified by field experimental data. Then, the software Hydrus-1D was employed to simulate the processes of diffusion, adsorption, desorption, microbial degradation, and plant adsorption of PHs in the soil–water system. The process of plant–microbial remediation for PH-contaminated soil was also simulated. The space-time change of PHs in soil was obtained, and the fate and remediation efficiency of PHs in soil were revealed in different remediation conditions. The results indicated that the Hydrus-1D model can adequately simulate the process of plant–microbial remediation. Plant–microbial remediation appears to be more efficient than the application of bacteria orSuaeda salsa. The majority of PH pollutants are degraded in the upper soil levels. For long-chain petro-alkane-contaminated soil, plant–microbial remediation is a more efficient method. A suitable moisture level in soil is important for improving the bioremediation effect of plant–microbial remediation technology. [ABSTRACT FROM AUTHOR]

Numerical modeling of optical wave propagation in atmospheric turbulence is traditionally performed with using the so-called “split”-operator method, when the influence of the propagation medium’s refractive index inhomogeneities is accounted for only within a system of infinitely narrow layers (phase screens) where phase is distorted. Commonly, under certain assumptions, such phase screens are considered as mutually statistically uncorrelated. However, in several important applications including laser target tracking, remote sensing, and atmospheric imaging, accurate optical field propagation modeling assumes upper limitations on interscreen spacing. The latter situation can be observed, for instance, in the presence of large-scale turbulent inhomogeneities or in deep turbulence conditions, where interscreen distances become comparable with turbulence outer scale and, hence, corresponding phase screens cannot be statistically uncorrelated. In this paper, we discuss correlated phase screens. The statistical characteristics of screens are calculated based on a representation of turbulent fluctuations of three-dimensional (3D) refractive index random field as a set of sequentially correlated 3D layers displaced in the wave propagation direction. The statistical characteristics of refractive index fluctuations are described in terms of the von Karman power spectrum density. In the representation of these 3D layers by corresponding phase screens, the geometrical optics approximation is used. [ABSTRACT FROM AUTHOR]

In this paper, finite-time multi-agent consensus problems are considered under networks associated with signed graphs whose edge weights can be not only positive but also negative. A nonlinear consensus protocol is proposed to guarantee the states of all agents to converge in a finite time. If the signed graph is structurally balanced, then the final consensus states of all agents are the same in modulus but not in sign. Otherwise, if the signed graph is structurally unbalanced, then the states of all agents converge to zero. Moreover, the final consensus states of agents can be provided uniformly regarding a signed-average quantity that depends on both the initial states of agents and the topology structure of the whole multi-agent network. Numerical simulations illustrate that the protocol is effective in achieving the finite-time consensus of agents under signed graphs and can particularly solve the finite-time average consensus problem of agents when their associated graph has all positive edge weights. [ABSTRACT FROM AUTHOR]

The Voraxial Separator (VAS) has attracted increasing attention in recent years because it can separate large volumes of oily water efficiently within a tubular compact structure. However, there is a lack of systematic research into the working mechanism and validation of the design theory of the separation technology. In this paper, the key factors influencing the separation efficiency of the VAS were analyzed, the theoretical model of this new separation technology was established, and a pilot VAS was designed. The velocity field in the pilot VAS was also analyzed by numerical simulation, which could provide a useful reference for the theoretical research. The results show that the tangential velocity distribution at the swirler end is in accordance with the pattern of Solid Body vortex, and there exists a low pressure region along the central longitudinal flowline which can be proved by the distribution of axial velocity. The maximum separation efficiency of the pilot VAS can achieve is up to 93%, which occurs when the back-flow ratio is 2.9-11.4%. [ABSTRACT FROM PUBLISHER]

We focus in this paper on the effect of the resolution of direct numerical simulations (DNS) on the spatio-temporal development of the turbulence downstream of a single square grid. The aims of this study are to validate our numerical approach by comparing experimental and numerical one-point statistics downstream of a single square grid and then investigate how the resolution is impacting the dynamics of the flow. In particular, using theQ–Rdiagram, we focus on the interaction between the strain-rate and rotation tensors, the symmetric and skew-symmetric parts of the velocity gradient tensor, respectively. We first show good agreement between our simulations and hot-wire experiment for one-point statistics on the centreline of the single square grid. Then, by analysing the shape of theQ–Rdiagram for various streamwise locations, we evaluate the ability of under-resolved DNS to capture the main features of the turbulence downstream of the single square grid. [ABSTRACT FROM AUTHOR]

This paper studies the sampled-data consensus problem of first-order and second-order multi-agent systems (MASs) with logarithmic quantised information transmission. Both undirected and directed communication topologies are considered. Under the undirected connected communication topology, we adopt for each agent the standard consensus protocols based on the logarithmic quantised relative states between neighbouring agents. Under the directed communication topology, so as to preserve the weighted average of agents’ states, we utilise the encoding/decoding strategy to transmit quantised information and estimate neighbouring agents’ states, and then, distributed control laws based on the state estimates are employed for each agent. Under both kinds of communication topologies, we prove that, for any given sampling period, by designing appropriate control gains, first-order MASs can reach consensus for any given quantiser accuracy, while second-order MASs can reach consensus if the quantiser accuracy is small enough. In all cases, the consensus states are presented explicitly. Finally, four numerical examples are given to illustrate the effectiveness of our results. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of containment control for coupled harmonic oscillators with multiple leaders under directed topology. Using tools from matrix, graph and stability theories, necessary and sufficient conditions are obtained for coupled harmonic oscillators under continuous-time and sampled-data-based protocols, respectively. When the continuous-time protocol is used, it is proved that every follower will ultimately converge to the convex hull spanned by the leaders if and only if there exists at least one leader that has a directed path to that follower at any time. When the sampled-data-based protocol is used, it is shown that the containment can be achieved if and only if: (1) an appropriate sampling period is chosen and (2) for every follower, there exists at least one leader that has a directed path to that follower at any time. And we also give the containment conditions for coupled harmonic oscillators under undirected topology as a special case. Finally, numerical simulations are presented to illustrate the theoretical findings. [ABSTRACT FROM AUTHOR]

This paper considers the effect of artificial viscosity in smoothed particle hydrodynamics (SPH) computations of six different regular waves. The purpose is to improve the modelling of physically real effects and thereby make SPH a more attractive modelling option. The essence of the proposed method is to avoid running the simulation with different values of the empirical coefficient used in artificial viscosity in order to find the optimum value of this parameter for a given problem. Thorough calibration of the SPH's numerical parameters is performed through the comparison between numerical and experimental data. Among the various parameters involved, the smoothing length and the particle resolution are important in shaping the results. The analysis confirms that when the ratio of particle spacing to smoothing length and the particle resolution useful for different computational domains have been defined, the empirical coefficient depends only on the type of wave breaking in term of the Irribarren number. [ABSTRACT FROM AUTHOR]

Unreinforced soft-brick masonry structures comprise a large portion of buildings in earthquake prone regions of India. Recent earthquakes have extensively damaged such structures. Experimental and numerical studies on soft brick unreinforced masonry structures are scarce in literature. In this paper, numerical simulation of soft brick unreinforced masonry panels subjected to lateral loads is performed. At the panel level, the masonry structure is modelled using the micro modelling approach within a finite element framework. Monotonic load envelope curve is generated through a pushover analysis of the finite element model. The in-plane failure modes are identified, and the effect of aspect ratio and axial stress on failure is examined. Cyclic load analyses are performed on the finite element model to understand the complex hysteretic behaviour of unreinforced soft-brick masonry walls. [ABSTRACT FROM AUTHOR]

A numerical model has been proposed to predict the material removal of electric discharge machining process while it is machining a particulate reinforced aluminium 6061 with 10 vol.-% Al2O3. The heating effect of an electric discharge machining spark on the temperature field of the workpiece was analysed using ANSYS software. According to the simulated temperature field profiles, the diameter, depth and volume of the crater created by a single electric discharge machining pulse can all be obtained. The influence of pulse duration and discharge current on the material removal mechanism was theoretically and experimentally investigated. It was found that the experimental results agreed well with the simulated results. The average percentage errors of the crater volume were found to be 3·2% at different discharge current conditions, and 2·5% at different pulse duration conditions. [ABSTRACT FROM AUTHOR]