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This paper presents a coherent approach to evaluate the roll damping derivatives for the standard Basic Finner Model. The study compares and analyses the results obtained through a range of techniques, including experimental testing, numerical simulations and semi-empirical models. The study aims to evaluate the reliability and accuracy of these methods and to identify the factors that contribute to their sensitivity. The paper concludes by summarizing the findings of the study and discussing the implications of the results for the design and operation of rockets. The experimental and numerical analysis used in this study provides a robust and comprehensive evaluation of the roll damping coefficient. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the behavior of a spherical absorber composed of two parts, an inner sphere and a supporting convex spherical dish in which the ball is placed. Considering only the planar behavior of the system, a set of governing nonlinear differential equations was derived and solved numerically. Firstly, the system is exposed to the harmonic excitation of the supporting bowl and its time response is analyzed for all time dependent variables. By gradually changing the angular frequency of the excitation, a resonance curve is obtained, which is examined in detail with respect to the changing amplitudes of the excitation force and the nonlinear behavior. The effect of internal damping and different settings of the absorber characteristics are also investigated. The effect of initial conditions without the presence of an external excitation force is also numerically analyzed by means of phase portraits for selected pairs of initial conditions. [ABSTRACT FROM AUTHOR]

In this paper, our aim is mathematical analysis and numerical simulation of a prey-predator model to describe the effect of predation between prey and predator with nonlinear functional response. First, we develop results concerning the boundedness, the existence and uniqueness of the solution. Furthermore, the Lyapunov principle and the Routh–Hurwitz criterion are applied to study respectively the local and global stability results. We also establish the Hopf-bifurcation to show the existence of a branch of nontrivial periodic solutions. Finally, numerical simulations have been accomplished to validate our analytical findings. [ABSTRACT FROM AUTHOR]

In this paper, our aim is mathematical analysis and numerical simulation of a prey-predator model to describe the effect of predation between prey and predator with nonlinear functional response. First, we develop results concerning the boundedness, the existence and uniqueness of the solution. Furthermore, the Lyapunov principle and the Routh–Hurwitz criterion are applied to study respectively the local and global stability results. We also establish the Hopf-bifurcation to show the existence of a branch of nontrivial periodic solutions. Finally, numerical simulations have been accomplished to validate our analytical findings. [ABSTRACT FROM AUTHOR]

Highlights • Constitutive equations for a vertical rod bundle are reviewed. • Dependence of distribution parameter on flow conditions is discussed. • 1D momentum equation by considering void fraction distribution is discussed. • Effect of channel size on interfacial area concentration is discussed. Abstract In view of the quality assurance of two-phase flow simulations, CSAU (Code Scalability, Applicability, and Uncertainty) methodology and code V & V (Verification and Validation) have been proposed. The estimation of simulation uncertainty is indispensable in using best-estimate computational codes. A key of successful two-phase flow simulations is to use the state-of-the-art constitutive equations to close the mathematical system used in two-phase flow analyses. The advanced constitutive equations should be developed based on “physics” behind phenomena and should consider scaling parameters which enable their application beyond test conditions used for a code validation. Two-phase flow simulations in a rod bundle is important in various industrial apparatuses such as heat exchangers and nuclear reactors. Constitutive equations for two-phase flows in a vertical rod bundles have been advanced in recent five years. In view of this, this paper provides a comprehensive review of most advanced constitutive equations for two-phase flow analyses in a vertical rod bundle. The constitutive equations of two-phase flow parameters reviewed in this paper are flow regime map, void fraction, void fraction covariance and relative velocity covariance, interfacial area concentration and wall friction. In addition, an exact formulation of one-dimensional momentum equation in two-fluid model considering void fraction distribution is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lattice beam model extended to self-healing in cementitious materials. • A new rate dependent discrete damage-healing model is presented. • Healing response derived from healing-agent chemo-physical properties. • Detailed information is provided on the size and disposition of cracking and healing zones throughout a transient analysis. • The model provides valuable information required for designing a self-healing system. • Model validated using experiments with healing under fixed and moving crack conditions. • Nature and extent of damage-healing zones determined numerically. This paper describes the development of a discrete lattice model for simulating structures formed from self-healing cementitious materials. In particular, a new approach is presented for simulating time dependent mechanical healing in lattice elements. The proposed formulation is designed to simulate the transient damage and healing behaviour of structures under a range of loading conditions. In addition, multiple and overlapping damage and healing events are considered. An illustrative example demonstrates the effects of varying the healing agent curing parameters on the computed mechanical response. The model is successfully validated using published experimental data from two series of tests on structural elements with an embedded autonomic self-healing system. The meso -scale model gives detailed information on the size and disposition of cracking and healing zones throughout an analysis time history. The model also provides an accurate means of determining the volume of healing agent required to achieve healing for all locations within a structural element. The importance of the information provided by the model for the design of self-healing cementitious material elements is highlighted. [ABSTRACT FROM AUTHOR]

The existing experimental methods and numerical models were difficult to get accurate aerodynamic characteristics of the anti-torque system of a NOTAR under rotor wake. To solve this problem, a new three-dimensional aerodynamic model with momentum source based on finite volume method was proposed in this paper. By means of time domain equalization and spatial interpolation, the complicated dynamic meshes on blade were replaced by the nonblade fixed rotor domain with momentum source. And the model was calculated by steady, compressible and three-dimensional Reynolds averaged N-S equation. In this paper, a typical NOTAR was took for research, the aerodynamic characteristics including flow field and variation regularity of lateral force with momentum coefficient of anti-torque system during hover condition was obtained by applying the above computational model, and the accuracy of which was verified by corresponding experimental data. In addition, the model was also used to analyze the key factors that influence working condition of the tail boom, including length of tail boom, area of nozzle and fan pressurization. And the curves of variation regularity were given. The model and work in this paper could provide reference for further research and design on anti-torque system for NOTAR. [ABSTRACT FROM AUTHOR]

To improve the interception performance in missile guidance applications, this paper proposes a novel control strategy for the integrated guidance and control design subject to input constraints. The system constraints are translated into a restriction in an invariant set, which is then enforced by manipulating the derivative of the applied reference. For the integrated system in the presence of disturbances and parametric uncertainties, disturbance observers are applied to estimate the lumped disturbances existing in each loop. The quadratic stability via dynamic surface control is guaranteed, and an ellipsoidal approximation of the invariant set is obtained, which can be enlarged to allow some degree of the input saturation. The effectiveness of the proposed scheme is illustrated using numerical simulations against a maneuvering target. [ABSTRACT FROM AUTHOR]

Numerical models for vibro-acoustic analyses of complex mechanical systems are becoming more and more popular, in particular in the field of virtual product development. Therefore, reliable, comprehensive, and validated modeling methodologies remain crucial. However, system characteristics such as elasticities of the drive train components and nonlinear characteristics can lead to complex, and costly numerical models with a huge number of degrees of freedom. This may raise not only the need for novel and reasonable modeling strategies, but also exacerbates validation process, due to the wide scope in terms of operating conditions. In practice, structure-borne noise signals, for example, from accelerometers, are often used for the validation of mechanical systems. By choice of a sufficient number of measurement points, the interpretation becomes more complex. A lot of vibration response curves then need to be compared and interpreted over a wide operating range. In general, the interpretation focuses on deviations in quality and quantity. In this paper, to overcome these mentioned challenges, a validation methodology is proposed allowing a fast and transparent check of a number of captured signals. Therefore, it is shown how the original information can be reduced in a meaningful manner, making it possible to run a fast and accurate validation. The method is demonstrated on a real application with high mechanical complexity and it is shown that the chosen parameters are reliable. [ABSTRACT FROM AUTHOR]

The main focus of this paper is to investigate the dynamics of the competition between rural and commercial bank with in the framework of fractal–fractional Atangana–Baleanu derivative sense. Initially, we take a model from literature and then utilize the real data since 2004–2014. We estimate effectively the parameters for the competition fractal–fractional model. Then, we provide a novel numerical technique for fractal–fractional model with many graphical results. We show graphical results for data fitting with the suggested operators and show that these two operators give the same results for the data fitting but varying both the values of the fractal and fractional order we have reasonable results. The results of the data fitting with these two operators are reliable and good are shown. Moreover, we present by comparing these two operators for many values of the fractal and fractional order parameters θ and α. [ABSTRACT FROM AUTHOR]

In this paper, a novel finite-time nonlinear extended state observer (NLESO) is proposed and employed in active disturbance rejection control (ADRC) to stabilize a nonlinear system against system's uncertainties and discontinuous disturbances using output feedback based control. The first task was to aggregate the uncertainties, disturbances, and any other undesired nonlinearities in the system into a single term called the "generalized disturbance". Consequently, the NLESO estimates the generalized disturbance and cancel it from the input channel in an online fashion. A peaking phenomenon that existed in linear ESO (LESO) has been reduced significantly by adopting a saturation-like nonlinear function in the proposed nonlinear ESO (NLESO). Stability analysis of the NLEO is studied using finite-time Lyapunov theory, and the comparisons are presented over simulations on permanent magnet DC (PMDC) motor to confirm the effectiveness of the proposed observer concerning LESO. [ABSTRACT FROM AUTHOR]

This paper presents a framework of incremental 3D cuboid modeling by using the mapping results of an RGB-D camera based simultaneous localization and mapping (SLAM) system. This framework is useful in accurately creating cuboid CAD models from a point cloud in an online manner. While performing the RGB-D SLAM, planes are incrementally reconstructed from a point cloud in each frame to create a plane map. Then, cuboids are detected in the plane map by analyzing the positional relationships between the planes, such as orthogonality, convexity, and proximity. Finally, the position, pose, and size of a cuboid are determined by computing the intersection of three perpendicular planes. To suppress the false detection of the cuboids, the cuboid shapes are incrementally updated with sequential measurements to check the uncertainty of the cuboids. In addition, the drift error of the SLAM is compensated by the registration of the cuboids. As an application of our framework, an augmented reality-based interactive cuboid modeling system was developed. In the evaluation at cluttered environments, the precision and recall of the cuboid detection were investigated, compared with a batch-based cuboid detection method, so that the advantages of our proposed method were clarified. [ABSTRACT FROM AUTHOR]