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Aquaculture in high-energy areas poses significant challenges to traditional engineering tools, as the strong non-linear loads exerted on structures often require more refined numerical models. In this work, we carry out the numerical modelling of an aquaculture net made of copper alloy interacting with current, employing a Computational Fluid Dynamic (CFD) method. The numerical approach used in this work allows for the simulation of the direct interaction between the net and the fluid, without the need to use hydrodynamic coefficients to model the net, unlike traditional numerical approaches. The methodology used was validated at current velocities typical of high energy sea states and gave satisfactory results in the majority of cases analysed. The methodology presented here allows the evaluation of hydrodynamic forces on the numerical net, its displacement and deformation, and the fluid velocity field surrounding the net. The proposed methodology is based on the application of the Smoothed Particle Hydrodynamics (SPH) method. The net is modelled as a set of fluid-driven elements with spherical geometry connected with dynamic mooring lines, where the boundary particles that make up the fluid-driven elements interact with the particles that make up the fluid, providing the fluid-structure interaction. The numerical modelling of the net is executed through the coupling of DualSPHysics and MoorDyn+. DualSPHysics is an open-source, fully Lagrangian, meshless code based on weakly compressible SPH that addresses the fluid-structure interaction. On the other hand, MoorDyn+ is a dynamic mooring library that uses a lumped-mass numerical model to resolve tensions in the mooring lines and allows the connections between fluid-driven elements. Two cases of analysis were carried out and validated against experimental data. For the first case, the net was modelled in a fixed frame in currents and the drag forces on the net were evaluated. In the second case, the setup comprises a floating fish cage (scale 1:15) with a copper alloy net moored to a fixed point, modelled in currents. In this latest study, the loads on the fish cage measured at the mooring were evaluated. The numerical results showed a satisfactory agreement. [ABSTRACT FROM AUTHOR]

In this paper, the deformation of an isolated single two-dimensional droplet under simple shear flow is studied regarding the thixotropic behavior. In doing so, a modified consistent weakly compressible smoothed particle hydrodynamics method is employed. It is assumed that the thixotropic fluid obeys the Moore model, and the surface tension is modeled by the continuum surface tension (CST) method. After verifying the utilized paradigm, it is applied to novel cases in which one of the fluids exhibits thixotropic behavior. The effects of Moore's model constants are examined through several numerical simulations. It is shown that the drop deformation is dramatically affected by thixotropic behavior. Generally speaking, the deformation of the Newtonian droplet is decreased by increasing the destruction-to-rebuild ratio of the surrounding thixotropic liquid. The same trend is found when the thixotropic droplet is exposed to the shear flow of a Newtonian fluid. Also, it is demonstrated that the presence of another droplet in the vicinity of the first droplet could dramatically change the flow domain. To the best of the author's knowledge, the effect of thixotropy is investigated on droplet deformation for the first time. • The effects of thixotropy are investigated on droplet deformation in the simple shear flow by a consistent WC-SPH. • Two distinguishable cases are considered: Newtonian drop in thixotropic shear flow and vice versa. • The deformation is decreased by increasing b/a for both cases. The effects are more pronounced in the first case. • The threshold values of b/a for thixotropic behavior are about 0.01 and 0.1 for the first and second cases, respectively. • The presence of the second droplet could dramatically affect the flow field, especially in the intermediate times. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the applicability and suitability of the Smoothed Particle Hydrodynamics (SPH) method in modelling a flexible flat net in currents. SPH is a meshless Lagrangian method that discretises the system into particles, making it particularly suitable for modelling turbulent and highly nonlinear flows with the presence of a free surface. For the modelling of the flexible net, a methodology is proposed that uses fluid-driven elements (spheres) and dynamic links to discretise the geometry of the net within the SPH framework. This numerical approach allows the determination of the deformation of the net elements in the numerical model, the analysis of the fluid velocity field through the discrete elements and the calculation of the drag forces on the system under different flow regimes. The proposed method for the numerical modelling of the net is based on the coupling of DualSPHysics and MoorDyn+. DualSPHysics is a fully Lagrangian and meshless open-source code based on weakly compressible SPH that solves the fluid-structure interaction. MoorDyn+ is a dynamic library based on a lumped-mass numerical model, which solves tensions in the lines and allows the establishment of connections between the floating elements. In addition, an in-house algorithm is used to generate the configuration of the net in the numerical model, preserving the hydrodynamic and structural properties of the studied net. The proposed method for the discretisation of the net is validated by a comparative analysis of the drag forces obtained in the numerical model for a flat net fixed in a rigid frame, with different solidity values and those obtained by analytical solutions. Then, the method is applied to simulate a flexible flat net in steady currents with different velocities. The results are compared with those obtained from physical modelling tests and show a satisfactory agreement of the proposed method in the majority of the cases analysed, with a difference of less than 11%. • The application of the Smoothed Particle Hydrodynamics (SPH) method to the modelling and simulation of a flexible net in a constant velocity fluid flow is investigated. • A new methodology for modelling a flexible net in the SPH framework is presented. • The coupling of DualSPHysics and MoorDyn+ is used for the numerical modelling and simulation of the net in the SPH framework. [ABSTRACT FROM AUTHOR]

• Workflow incorporating image processing, patient-specific modelling and FSI simulation. • Automatic processing of clinically acquired cardiac magnetic resonance and 3D echocardiogram. • Image-derived patient-specific virtual model of the left heart and mitral valve. • Fluid–structure interaction simulations can reproduce mitral valve mechanics and function. The mechanics of the mitral valve (MV) are the result of the interaction of different anatomical structures complexly arranged within the left heart (LH), with the blood flow. MV structure abnormalities might cause valve regurgitation which in turn can lead to heart failure. Patient-specific computational models of the MV could provide a personalised understanding of MV mechanics, dysfunctions and possible interventions. In this study, we propose a semi-automatic pipeline for MV modelling based on the integration of state-of-the-art medical imaging, i.e. cardiac magnetic resonance (CMR) and 3D transoesophageal-echocardiogram (TOE) with fluid–structure interaction (FSI) simulations. An FSI model of a patient with MV regurgitation was implemented using the finite element (FE) method and smoothed particle hydrodynamics (SPH). Our study showed the feasibility of combining image information and computer simulations to reproduce patient-specific MV mechanics as seen on medical images, and the potential for efficient in-silico studies of MV disease, personalised treatments and device design. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The present work addresses the need for an efficient, versatile, accurate and open-source numerical tool to be used during the design stage of wave energy converters (WECs). The device considered here is the heaving point-absorber developed and tested by Sandia National Laboratories. The smoothed particle hydrodynamics (SPH) method, as implemented in DualSPHysics, is proposed since its meshless approach presents some important advantages when simulating floating devices. The dynamics of the power take-off system are also modelled by coupling DualSPHysics with the multi-physics library Project Chrono. A satisfactory matching between experimental and numerical results is obtained for: (i) the heave response of the device when forced via its actuator; (ii) the vertical forces acting on the fixed device under regular waves and; (iii) the heave response of the WEC under the action of both regular waves and the actuator force. This proves the ability of the numerical approach proposed to simulate accurately the fluid–structure interaction along with the WEC’s closed-loop control system. In addition, radiation models built from the experimental and WAMIT results are compared with DualSPHysics by plotting the intrinsic impedance in the frequency domain, showing that the SPH method can be also employed for system identification.

Submarine slide is the most serious threat on both local and regional scales. Tsunami phenomenon induced by submarine slide has put us on the challenge in understanding from generation mechanism to propagation and coastal inundation and mitigating the risk from submarine slide generated tsunami. This research presents the numerical simulation methodology by using Smooth Particle Hydrodynamics (SPH) to investigate all stages of tsunami waves with the aid of physical modeling. Results of tsunami generation, propagation, run-up, impact in experimental test are compared with the results from the numerical simulation. The comparisons of results have a slight difference. The conclusions may potentially be taken as guideline of mitigate the risk from tsunami wave.

Abstract The paper presents a numerical investigation of an efficiency of a needle structure at a hypervelocity impact with a spherical projectile. A modeling was performed using a smoothed particle hydrodynamics method implemented in Ansys/Ls-Dyna explicit software and a verified model. We investigated hypervelocity impacts of the spherical projectile with needle structure at different initial velocities in the range of 4190–9200 m/s and both normal and oblique impact angle. The investigations revealed efficiency of a needle structure in comparison with a solid structure of the same mass at a normal impact angle. It was shown that the character of hypervelocity impact of the spherical projectile with needle structure did not change qualitatively when the impact angle changed, and the needle structure preserved its capability to resist a hypervelocity impact. [ABSTRACT FROM AUTHOR]

The natural phenomena hydraulic jump that is commonly used in spillways as an energy dissipater coupled to hydropower applications has been investigated with Smoothed Particle Hydrodynamics. A new approach was applied based on a periodic open boundary condition. The model consisted of a tank, a gate, a stilling basin and periodic open boundaries at each end of the computational domain. The tank provided a hydraulic head and in turn a specific flow through the gate, and a downstream condition in terms of a depth for the jump. The gate elevation had a major impact and was calibrated to ensure a correct and stable flow rate, when compared to experiments. With the proper flow rate, the position of the jump toe was significantly improved. The jump toe oscillated with a frequency in good agreement with experimental findings found in the literature and the oscillation amplitude increased with Froude number. However, for high Froude number cases the position was still too close to the gate but could be improved by including a correction based on the length of the jump. The depths in both the super- and subcritical zones was in good agreement with experiments and previous numerical studies. Furthermore, the Froude number was in-line with the definition of super- and subcritical flows. [ABSTRACT FROM AUTHOR]

We present a discrete particle based method capable of realistically representing the entire boiling process including nucleation, bubble formation, growth, bursting, vapour and steam formation at the fluid free surface. The underlying fluid simulation is based on the mesh-free Smoothed Particle Hydrodynamics method. Vapour bubbles are created at nucleation sites when they reach suitable superheat temperatures above the boiling point. Rising bubbles grow or shrink in the fluid depending on the local superheat of the fluid. The bubbles burst at the fluid free surface and create jets of steam particles and small sprays of liquid drops. This model contains significant bubble scale physics and allows the capturing of key processes that cannot be directly modeled by traditional methods. The method provides the visual artist control over several key aspects of the bubble nucleation, generation, growth and interaction with fluid and other species allowing a broader range of boiling behaviour to be realistically and easily animated. This is demonstrated by examples showing the variation in bubble creation, growth and distribution with temperature and nucleation density. The utility of this model for realistic animation is demonstrated by the boiling of some eggs in a water filled glass pot heated on a cook top. [ABSTRACT FROM AUTHOR]

The present work shows a novel phase-change concept for simulating landslides using the smoothed particles hydrodynamics (SPH) method. The idea is to initiate the simulation of a slope stability problem with a Solid Mechanics-based SPH, modeling the soil as an elastoplastic material at finite strain. Next, if a particle exceeds a certain level of plastic strain, such particle changes its phase to a fluid state with non-Newtonian rheology, which is then solved with a Fluid Dynamics-based SPH method. We use the total Lagrangian SPH (TLSPH) method to solve the Solid Mechanics phase to avoid problems related to particle distribution (such as the tensile instability), while the implicit incompressible SPH (IISPH) to solve the Fluid Dynamics part to avoid the restriction on time increment in relation to high values of viscosity. The coupling between the two phases is treated as a conventional fluid–solid interaction (FSI) problem. We verified the proposed TLSPH method with the triaxial compression problem and demonstrated the robustness of the proposed phase-change TLSPH–IISPH coupled method in the simulation of the Aso landslide. Specifically, it may be the first time to simulate the Aso landslide from its initiation to its propagation in a single numerical simulation. • The concept of phase-change is introduced to simulate landslides. • Total Lagrangian description for the nonlinear solid solves the tensile instability problem. • An elastoplastic constitutive model with the logarithmic strain was introduced. • Triaxial compression simulation with the modified Cam–Clay model shows high accuracy. • Aso landslide simulation from initiation to post-failure demonstrated the robustness of the proposed method. [ABSTRACT FROM AUTHOR]

Smoothed Particle Hydrodynamics (SPH) is a particle-based Lagrangian numerical method, particularly suitable for modeling free surface flows of fluids with different constitutive equations. In this work, a SPH model is developed to solve flow problems of granular matter flowing in a dense regime, featuring a constitutive equation proposed by Pouliquen et al. (2006) [17] and Jop et al. (2006) [18]. The problem of resolving the flow close to static conditions has been solved by introducing a weak compressibility for the grains: this leads to a third order algebraic equations to be solved for computing granular material density. A new viscosity regularisation method, suitable for any visco-plastic fluid with varying yield stress has been developed, in order to reproduce stopping flow and static conditions. Validation of the model has been performed by solving the simple uniform granular flow problem, for which the solution is known analytically and by reproducing a set of experimental data on granular columns collapses by Lube et al. (2004) [19]. [ABSTRACT FROM AUTHOR]

A combined method blending the advantages of smoothed particles hydrodynamics (SPH) and the grid-characteristic method (GCM) is proposed for simulating elastoplastic bodies. Various grid methods, including the GCM, have long been used for the numerical simulation of elastoplastic media. This method applies to the simulation of wave processes in elastic media, including elastic impacts, in which case an advantage is the use of moving tetrahedral meshes. Additionally, fracture processes can be simulated by applying various fracture criteria. However, this is a technically complicated task with the accuracy of the results degrading due to the continual updating of the grid. A more suitable approach to the simulation of processes involving substantial fractures and deformations is based on SPH, which is a meshless method. However, this method also has shortcomings: it produces spurious modes, and the simulation of oscillations requires particle refinement. Thus, two families of methods are available that are optimal as applied to two different groups of problems. However, a realworld problem can frequently be a mixed one, which requires a substantial tradeoff in the numerical methods applied. Aimed at solving such problems, a combined GCM-SPH method is developed that blends the advantages of two constituting techniques and partially eliminates their shortcomings. [ABSTRACT FROM AUTHOR]

SUMMARY Wall boundary conditions in smoothed particle hydrodynamics (SPH) is a key issue to perform accurate simulations. We propose here a new approach based on a renormalising factor for writing all boundary terms. This factor depends on the local shape of a wall and on the position of a particle relative to the wall, which is described by segments (in two-dimensions), instead of the cumbersome fictitious or ghost particles used in most existing SPH models. By solving a dynamic equation for the renormalising factor, we significantly improve traditional wall treatment in SPH, for pressure forces, wall friction and turbulent conditions. The new model is demonstrated for cases including hydrostatic conditions for still water in a tank of complex geometry and a dam break over triangular bed profile with sharp angle where significant improved behaviour is obtained in comparison with the conventional boundary techniques. The latter case is also compared with a finite volume and volume-of-fluid scheme. The performance of the model for a two-dimensional laminar flow in a channel is demonstrated where the profiles of velocity are in agreement with the theoretical ones, demonstrating that the derived wall shear stress balances the pressure gradient. Finally, the performance of the model is demonstrated for flow in a schematic fish pass where both the velocity field and turbulent viscosity fields are satisfactorily reproduced compared with mesh-based codes. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Integrated Coastal Zone Management / Revista de Gestão Costeira Integrada is the property of Associacao Portuguesa dos Recursos Hidricos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vector fields analysis traditionally distinguishes conservative (curl-free) from mass preserving (divergence-free) components. The Helmholtz-Hodge decomposition allows separating any vector field into the sum of three uniquely defined components: curl free, divergence free and harmonic. This decomposition is usually achieved by using mesh-based methods such as finite differences or finite elements. This work presents a new meshless approach to the Helmholtz-Hodge decomposition for the analysis of 2D discrete vector fields. It embeds into the SPH particle-based framework. The proposed method is efficient and can be applied to extract features from a 2D discrete vector field and to multiphase fluid flow simulation to ensure incompressibility. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Water Resources / Recursos Hídricos is the property of Associacao Portuguesa dos Recursos Hidricos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present a discrete particle based method capable of creating very realistic animations of bubbles in fluids. It allows for the generation (nucleation) of bubbles from gas dissolved in the fluid, the motion of the discrete bubbles including bubble collisions and drag interactions with the liquid which could be undergoing complex free surface motion, the formation and motion of coupled foams and the final dissipation of bubbles. This allows comprehensive simulations of dynamic bubble behavior. The underlying fluid simulation is based on the mesh-free Smoothed Particle Hydrodynamics method. Each particle representing the liquid contains an amount of dissolved gas. Gas is transferred from the continuum fluid model to the discrete bubble model at nucleation sites on the surface of solid bodies. The rate of gas transport to the nucleation sites controls the rate of bubble generation, producing very natural time variations in bubble numbers. Rising bubbles also grow by gathering more gas from the surrounding liquid as they move. This model contains significant bubble scale physics and allows, in principle, the capturing of many important processes that cannot be directly modeled by traditional methods. The method is used here to realistically animate the pouring of a glass of beer, starting with a stream of fresh beer entering the glass, the formation of a dense cloud of bubbles, which rise to create a good head as the beer reaches the top of the glass. [ABSTRACT FROM AUTHOR]

Solid particle erosion inevitably occurs if a gas–solid or liquid–solid mixture is in contact with a surface, e.g., in pneumatic conveyors. Having a good understanding of this complex phenomenon enables one to reduce the maintenance costs in several industrial applications by designing components that have longer lifetimes. In this paper, we propose a methodology to numerically investigate erosion behavior of ductile materials. We employ smoothed particle hydrodynamics that can easily deal with large deformations and fractures as a truly meshless method. In addition, a new contact model was developed in order to robustly handle contacts around sharp corners of the solid particles. The numerical predictions of erosion are compared with experiments for stainless steel AISI 304, showing that we are able to properly predict the erosion behavior as a function of impact angle. We present a powerful tool to conveniently study the effect of important parameters, such as solid particle shapes, which are not simple to study in experiments. Using the methodology, we study the effect of a solid particle shape and conclude that, in addition to angularity, aspect ratio also plays an important role by increasing the probability of the solid particles to rotate after impact. Finally, we are able to extend a widely used erosion model by a term that considers a solid particle shape. [ABSTRACT FROM AUTHOR]

This article presents an analysis of the effectiveness of available numerical techniques in mapping the characteristic behavior of ballistic ceramics under projectile impact conditions. As part of the work, the ballistic tests were performed on the layered ceramic/steel composite armor and tested with the 7.62 × 39 mm, armor-piercing incendiary (API) BZ projectile. The experimental tests were then mapped using computer simulations. In numerical analyses, four different techniques were used to describe cubic ceramic tiles Al2O3 placed on the ARMOX 500T steel backing plate, i.e.,: the Finite Element Method without Erosion (FEM), Finite Element with erosion (FEM + Erosion), Smoothed Particles Hydrodynamics (SPH) and a hybrid method that converts finite elements to SPH particles after exceeding the defined failure criteria (FEM to SPH conversion). The effectiveness of the individual methods was compared in terms of quality (mapping of characteristic phenomena occurring during the penetration process), quantity (bulge height of the backing plate) and time needed to complete the calculations. On the basis of the results of the experiments and numerical simulations, it was noticed that the most accurate reproduction of the phenomenon of ballistic impact of AP projectiles on ceramic/steel composite armor can be obtained by using a hybrid method, incorporating the conversion of finite elements into SPH particles. This method should be used in cases where accuracy of the results is more important than the time required to complete the calculations. In other situations where the purpose of the calculation is not to determine, for example, the exact value of penetration depth but only to observe a certain trend, the FEM method with defined erosion criteria (variant 2), which is more than 10 times faster, can be successfully used. [ABSTRACT FROM AUTHOR]

Solid particle erosion inevitably occurs if a gas-solid or liquid-solid mixture is in contact with a surface, e.g., in pneumatic conveyors. Having a good understanding of this complex phenomenon enables one to reduce the maintenance costs in several industrial applications by designing components that have longer lifetimes. In this paper, we propose a methodology to numerically investigate erosion behavior of ductile materials. We employ smoothed particle hydrodynamics that can easily deal with large deformations and fractures as a truly meshless method. In addition, a new contact model was developed in order to robustly handle contacts around sharp corners of the solid particles. The numerical predictions of erosion are compared with experiments for stainless steel AISI 304, showing that we are able to properly predict the erosion behavior as a function of impact angle. We present a powerful tool to conveniently study the effect of important parameters, such as solid particle shapes, which are not simple to study in experiments. Using the methodology, we study the effect of a solid particle shape and conclude that, in addition to angularity, aspect ratio also plays an important role by increasing the probability of the solid particles to rotate after impact. Finally, we are able to extend a widely used erosion model by a term that considers a solid particle shape.

This article presents an analysis of the effectiveness of available numerical techniques in mapping the characteristic behavior of ballistic ceramics under projectile impact conditions. As part of the work, the ballistic tests were performed on the layered ceramic/steel composite armor and tested with the 7.62 × 39 mm, armor-piercing incendiary (API) BZ projectile. The experimental tests were then mapped using computer simulations. In numerical analyses, four different techniques were used to describe cubic ceramic tiles Al 2 O 3 placed on the ARMOX 500T steel backing plate, i.e.,: the Finite Element Method without Erosion (FEM), Finite Element with erosion (FEM + Erosion), Smoothed Particles Hydrodynamics (SPH) and a hybrid method that converts finite elements to SPH particles after exceeding the defined failure criteria (FEM to SPH conversion). The effectiveness of the individual methods was compared in terms of quality (mapping of characteristic phenomena occurring during the penetration process), quantity (bulge height of the backing plate) and time needed to complete the calculations. On the basis of the results of the experiments and numerical simulations, it was noticed that the most accurate reproduction of the phenomenon of ballistic impact of AP projectiles on ceramic/steel composite armor can be obtained by using a hybrid method, incorporating the conversion of finite elements into SPH particles. This method should be used in cases where accuracy of the results is more important than the time required to complete the calculations. In other situations where the purpose of the calculation is not to determine, for example, the exact value of penetration depth but only to observe a certain trend, the FEM method with defined erosion criteria (variant 2), which is more than 10 times faster, can be successfully used.

The present work addresses the need for an efficient, versatile, accurate and open-source numerical tool to be used during the design stage of wave energy converters (WECs). The device considered here is the heaving point-absorber developed and tested by Sandia National Laboratories. The smoothed particle hydrodynamics (SPH) method, as implemented in DualSPHysics, is proposed since its meshless approach presents some important advantages when simulating floating devices. The dynamics of the power take-off system are also modelled by coupling DualSPHysics with the multi-physics library Project Chrono. A satisfactory matching between experimental and numerical results is obtained for: (i) the heave response of the device when forced via its actuator; (ii) the vertical forces acting on the fixed device under regular waves and; (iii) the heave response of the WEC under the action of both regular waves and the actuator force. This proves the ability of the numerical approach proposed to simulate accurately the fluid–structure interaction along with the WEC's closed-loop control system. In addition, radiation models built from the experimental and WAMIT results are compared with DualSPHysics by plotting the intrinsic impedance in the frequency domain, showing that the SPH method can be also employed for system identification. [ABSTRACT FROM AUTHOR]

Numerical simulation is a significantly important method for the dynamic analysis of coal-bed methane reservoir and gas production. This paper proposed a stress-seepage hydro-mechanical model for coal-bed methane reservoir that was considered as dual permeability media of matrix pore and fracture. At the same time, the influence of the deformation of coal-bed on the gas seepage field was considered. The model involved the effects of coal-bed methane’s adsorption and desorption, the coupling of stress-seepage, and other factors on the coal bed methane extraction. SPH (Smoothed Particles Hydrodynamics) method was used to discretize the governing equations, and thus corresponding SPH code was made. A numerical example was presented using the proposed model and field coal bed parameters. The model is used to solve and analyze the process of coal bed methane desorption and the change of permeability. The SPH method can be applied to the study of coalbed methane desorption and seepage process and the dynamic analysis of coalbed gas reservoir. Results show that the matrix permeability and fracture permeability are influenced obviously by effective stress. Considering the adsorption and desorption of coal-bed methane are more realistic in the process of the coal-bed methane seepage, which is needed in the reasonable estimation of the amount of gas emission during the actual gas production process. [ABSTRACT FROM AUTHOR]