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Experimental and numerical studies have been made of the hydrodynamics of isothermal flows in a small-scale cyclone chamber (D = 0.21 m) with two-stage differently directed injection of tangentially blown air (with a cocurrent and countercurrent swirl). It has been established that the character of vortex flow with a countercurrent swire differs significantly from the structure of flow with a cocurrent swirl. The character of velocity and pressure distribution in the chamber′s volume has been revealed for the flows in question. Dimensionless dependences have been obtained for calculating the tangential velocity and pressure in the chamber. It has been shown that results of numerical modeling of vortex flows with the k–ω (SST) turbulence models for the concurrent and countercurrent air swirl are in satisfactory agreement with experimental data. [ABSTRACT FROM AUTHOR]

Ultrasonic structural health monitoring of cement paste is of great interest both scientifically and practically, because cement is a complex acoustic medium, whose structure affects the propagation of ultrasound, which offers a great wealth for structural monitoring in a non-viscous fluid. In this paper, the effect of water content on the ultrasonic signal of cement was studied. The immersion transmission technique is used to study the relationship between water content and durability of cement. Therefore, this experimental technique investigates the dispersion curves of cement paste prepared with different percentages of water, based on the ultrasonic signal transmitted through the cement paste recorded at different angular orientations, which allows the durability of the cement paste to be controlled by finding the critical angle in order to calculate the ultrasonic velocity. Overall, the result of this analysis shows that the water content has a significant effect on the ultrasonic velocity and durability of the cement paste. [ABSTRACT FROM AUTHOR]

Mathematical models of the nonlinear transversal oscillations for a beam moving along its axis have been studied. These models deal with the nonlinearity of body elastic properties and with the influence of physical–mechanical and kinematic parameters on the oscillation amplitude and frequency of the moving one-dimensional nonlinear systems as well. A procedure for studying both cases, non-resonance and resonance oscillation regimes, has been developed. The paper focuses on the influence of the longitudinal velocity, nonlinear elastic material properties, and external periodical perturbations on the dynamical process of beam transversal oscillation. The obtained mathematical model could be applied to describe the oscillation behavior of the different types of pipelines (liquid or gas). The proposed results allow the estimation of the influence of these parameters on the amplitude and frequency of the oscillations. Mathematical analysis realized by asymptotic methods enables the prediction of the resonance phenomena and proposal of a numerical algorithm to plan the most effective operation regime. Applications of this approach in engineering, particularly to construct the corresponding elements of industrial environments and pipelines, are also discussed. [ABSTRACT FROM AUTHOR]

The piers water resistance ratio is one of the main consideration indexes for determining the engineering scheme of river related bridge. In order to study the influence of piers water resistance ratio on velocity distribution in curved river, a plexiglass curved flume model was established. An experimental study was carried out to study the influence of piers with different water resistance ratio on the velocity distribution in curved river. Acoustic doppler velocimeter（ADV） was used to collect and analyze the longitudinal and transverse velocity within the curved test section. The results show that with the increase of water resistance ratio, the upstream and downstream mainstream positions near piers tends to be concentrated in the middle of the flume. Under the conditions of Fr=0.21 and Fr=0.28, the variance of longitudinal velocity in front of piers decreased, and the velocity distribution becomes more uniform. The variance of the longitudinal velocity behind piers increases, and the velocity distribution becomes more disordered. The distribution of transverse velocity in front of piers and behind pier is more disordered. The influence of piers water resistance ratio on longitudinal and transverse velocity distribution decreases with the increase of Fr. [ABSTRACT FROM AUTHOR]

In order to increase the accuracy of the path tracking, an improved model predictive control (IMPC) is proposed for autonomous vehicle under road conditions of large curvature, which can enhance the performances of the driving stability and safety. The controller design is implemented in four steps. First, the curvature of road ahead is derived and applied to determine the longitudinal velocity. Thus, the longitudinal velocity is not assumed to be constant, which is the salient feature of the proposed control. Second, the kinematic model of vehicle is established by the Ackermann steering principle. Third, the predictive model is constructed by linearization and discretization of the kinematic model. Fourth, the longitudinal velocity and the front steering angle are imposed on hard constraints, and the constrained objective function is designed and composed of the position deviation and the control increment. Then, we can obtain the optimal results of the longitudinal velocity and the front steering angle. Furthermore, experiment and simulation on the path tracking of an autonomous vehicle are presented. The results show that the proposed control can realize excellent tracking performance under the road conditions of large curvature. [ABSTRACT FROM AUTHOR]

When a wheeled mobile robot is travelling at high longitudinal velocities and turning, it may sideslip. Except for a few researchers, this issue has not received much attention. However, there is a high possibility that sideslip may cause danger, so the authors think this problem needs to be solved urgently. The mechanism of preventing sideslip is simple, which is to reduce the longitudinal velocity of the robot when turning. But, how to slow down is a question worth studying. To this end, they have proposed two schemes, but these two schemes have poor real‐time performance and poor robustness to positioning errors, respectively. In order to solve the above problems, considering that the real‐time and robustness of fuzzy control are very good, they propose a controller by combining robust control and model predictive control in this Letter. The fuzzy control is used to adjust the longitudinal velocity according to the state of the robot, and the model predictive control is used to achieve path tracking. According to the simulation results, the proposed fuzzy model predictive controller does have small errors, small sideslip, good real‐time performance, and good robustness to positioning errors. [ABSTRACT FROM AUTHOR]

Numerical simulation was carried out in three-dimensional and axisymmetric formulations for the hydrodynamics and mixing of bottom- and tangentially blown air with different temperatures in a cyclone chamber with local supply of tangentially blown air. To calculate vortex flows in the chamber, use was made of the most popular turbulence models k-ε, k-ω, and SA. It has been established that the best correspondence between the results of calculation and experimental data on hydrodynamic parameters (velocity and pressure) and air mixing under nonisothermal conditions is furnished by the k-ε and k-ω models of turbulence. Good agreement of the results of numerical simulation of vortex flows in the indicated chamber in three-dimensional and axisymmetric formulations has been obtained. [ABSTRACT FROM AUTHOR]

Due to the fact that most of the cities and villages are built on the banks of the rivers, the hydraulic characteristics of water flow always undergo changes during floods, so it is necessary to study the interaction of the flood flows of meandering compound channel in these areas. In this paper, the effect of building arrangement on the flow characteristics in meandering compound channels was investigated by using laboratory models. For this purpose, a smooth floodplain (without building) and three different types of building arrangement on the floodplain including structural obstacles perpendicular and parallel to the floodplain flow and checkered structural obstacles have been used. The tests have been conducted at three relative depths of 0.29, 0.39 and 0.49 and the corresponding discharges. All experiments were performed under a quasi-uniform and fully developed flow condition. The measurement data were recorded at different sections along the meandering main channel. Stage-discharge curves, Manning's n , velocity distribution, boundary shear stress and Darcy-Weisbach friction factor are determined over 12 test runs. The results of this research show that the arrangement of buildings has a great effect on the longitudinal velocity of the main channel. At a relative depth of 0.49, in a meandering compound channel with the arrangement of structural obstacles perpendicular to the floodplain flow, the dimensionless longitudinal velocity of the main channel compared to the smooth floodplain increases by 113%, but with the arrangement of structural obstacles parallel to the floodplain flow, the dimensionless longitudinal velocity increases by 27%. Also, the building arrangement is effective in reducing the discharge capacity of the meandering compound channel, so that in a building density of 18.5%, structural obstacles perpendicular to the floodplain flow reduce the discharge capacity of the channel by 50% compared to the smooth floodplain. In the channel with structural obstacles arranged perpendicular to the floodplain flow, Manning's roughness coefficient increases sharply with increasing the relative depth, but in the channel with the structural obstacles parallel to the floodplain flow, Manning's roughness coefficient decreases with increasing the relative depth. In the channel with the arrangement of structural obstacles perpendicular to the floodplain flow, the bed shear stress of the main channel is higher than the other building arrangements, so that at the relative depth of 0.49, the average maximum bed shear stress in all sections increases by 42% compared to the smooth floodplain. • The effect of building arrangement on the flow characteristics in meandering compound channels was investigated by using laboratory models. • Building arrangement in floodplains has a significant effect on flow behaviors in the main channel. • In the arrangement of structural obstacles perpendicular to the floodplain flow (the most critical case), the average flow transfer capacity is reduced by 50% compared to the smooth floodplain. • In case with the arrangement of structural obstacles parallel and perpendicular to the floodplain flow, Manning roughness coefficient decreases and increases, respectively. • The dimensionless longitudinal velocity in case of the arrangement of structural barriers perpendicular to the floodplain flow increases 113% compared to the condition of the smooth floodplain. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model of longitudinal dynamics of Gatimaan Express. It has one locomotive class WAP5, two generator vans, eight second class chair cars and two executive chair cars respectively. Forces associated with longitudinal dynamics of model are developed in Matlab/Simulink. Longitudinal and coupler forces as well longitudinal velocities are studied during the failure of coupler of 3rd (coach of middle train) second class chair. Validation of longitudinal velocity of the model is done by comparing simulated results with measured field data provided by Research Designs Standards Organization (RDSO), Lucknow, India. [ABSTRACT FROM AUTHOR]

The purpose of the study is to clarify the mechanism of interatomic interaction in the model of Ya.I. Frenkel and to link this process with the propagation of ultrasound in the crystal lattice of metals, as well as with the velocity of propagation of ultrasound in rods from different materials taken as standard samples for determining the Yung's modulus. An analysis of the mechanism of interatomic interaction in the diatomic model Ya.I. Frenkel is made. A model that linked the process of interaction of the electron shells of atoms with the speed of sound propagation was created, taking into account the structure of the metal crystal lattice. The new model allows the theoretical calculation of the ultrasound velocity in different crystal lattices of metals. In the result of the research, it was found that the theoretically calculated values of the ultrasound velocities with a sufficiently high accuracy coincided with the experimentally obtained values of its propagation, which makes it possible to correlate the rate indicator with the strength properties of metals. [ABSTRACT FROM AUTHOR]

The paper is concerned with the study of longitudinal motion of a lightweight wheeled mobile robot on soft ground. The study is focused on the influence of the desired longitudinal velocity of a robot on both the longitudinal slip of the wheels and the ratio of wheel-terrain contact angles. Design of the four-wheeled skid-steered robot and research environment are described. Experimental investigations were conducted on a dedicated test stand with dry sand. A dynamics model of the robot-ground system taking into account properties of soft ground is presented. The classical terramechanics models of Bekker and Janosi-Hanamoto are used. Results of simulation research of robot motion and of the analogous experimental investigations are presented. Actual motion parameters of the robot and the values of longitudinal slip ratio of the wheels are determined. The results of simulation and experimental investigations are compared and discussed. A formula to describe front-to-back wheel-terrain contact angle ratio dependency on the desired velocity is proposed. [ABSTRACT FROM AUTHOR]

This study investigates nonlinear dynamic thermoelastic response of functionally graded material (FGM) plates with longitudinal velocity for the first time. The large amplitude motion of FGM plates is considered so that the present model includes both geometry and material nonlinearities. Based on the D'Alembert's principle, the out-of-plane equation of motion of the system is obtained by considering the thermal effect and the longitudinal velocity. After that, the Galerkin method is employed to discretize the partial differential equation of motion to a set of ordinary differential equations. The method of harmonic balance is used to solve analytically the time-varying set of ordinary differential equations. The approximately analytical solutions are verified by numerical solutions utilizing an adaptive step-size fourth-order Runge-Kutta technique. Furthermore, the stability of steady-state response is analyzed for the approximately analytical solutions. The linear frequency characteristics and nonlinear frequency-response characteristics are both presented for the system. The nonlinear frequency-response relationships demonstrate strong hardening-type behavior of the system. Results are shown to examine the influences of different parameters including longitudinal velocity, temperature, constituent volume distribution, in-plane pretension, damping and force amplitude on the nonlinear dynamic thermoelastic response of FGM plates with longitudinal velocity. [ABSTRACT FROM AUTHOR]

Accurate information on vehicle longitudinal and lateral velocities is vital for the efficient operation of many vehicle control systems. In this paper, an estimation structure to simultaneously estimate vehicle velocities in longitudinal and lateral directions is developed and experimentally validated. This structure includes two parallel estimators: The first estimator is a kinematic-based observer for longitudinal velocity estimation, and the second is a combination of a kinematic-based observer and an inverse tire model to estimate vehicle lateral velocity. The proposed structure can effectively handle the additive biases, which are common in a vehicle's stock accelerometers' signals, and provide an accurate estimate of vehicle velocities when one (or more than one) wheel experiences excessive slippage. Additionally, the proposed structure is not sensitive to changes in parameters of the tire model and vehicle mass. The performance of this estimation structure is validated by experimental studies. [ABSTRACT FROM PUBLISHER]

The effect of the vehicular blockage in a tunnel under longitudinal ventilation smoke control was systematically studied using a small-scale tunnel (1:30 of a standard tunnel section) with a helium-air mixture as the buoyant plume. The experimental results showed excellent agreement with full-scale data and reference correlations from former studies. When there are vehicular obstacles in the tunnel, the critical velocity decreased as a function of the blockage ratio. Notwithstanding, it was found that the relative size of the vehicular obstacle and the relative location of the fire source can have a reversed effect, inasmuch as the presence vehicular obstacle exerted an influence on the critical and confinement velocities. Moreover, the backlayering distance was evidently affected by the vehicular blockage. A parallel analysis was carried out for the backlayering distance for lower and upper regimes of the dimensionless heat release rate, where the current data was compared against data from other studies. The method and experimental set-up proved their ability to reproduce several phenomena and thus also their capability to supply relevant and valuable information on the effect of the vehicular blockage on tunnel fire dynamics. [ABSTRACT FROM AUTHOR]

A numerical investigation of flows in a cyclone chamber has been carried out at the fraction of bottom blast φ =0-0.5, at the values of the dimensionless pinch diameter d/D =0.7 with different locations and configurations of nozzles for air intake. In the simulation of swirling flows, the well-known k-ε and k-ω turbulence models, as well as the laminar flow model, were used. A satisfactory agreement between the results of numerical simulation and experimental data at d/D =0.5-0.7 is obtained. For a chamber with a relative pinch diameter d/D =0.3 the calculated flow parameters differ substantially from experimental values. [ABSTRACT FROM AUTHOR]

Abstract: Early thermal damage in 2205 duplex stainless steel which is caused by the precipitation of second phases during a short term exposure to high temperature (700°C) is investigated. Nonlinear ultrasonic measurements are performed and their results are compared with those from ultrasonic velocity and attenuation measurements. Experimental results show that the measured acoustic nonlinearity parameter is more sensitive than the ultrasonic longitudinal velocity and attenuation to the precipitation of chi and sigma phases early in the aging treatments. The results from the nonlinear ultrasonic measurements are also supported with those from the scanning electron microscopy (SEM), Rockwell C hardness and Charpy impact test. Especially notable is the close correlation between the hardness and the nonlinearity parameter. This research therefore proposes the nonlinear ultrasonic method as a nondestructive assessment means for early detection of thermal degradation of mechanical properties in 2205 duplex stainless steel. [Copyright &y& Elsevier]

Swirling flows in a vortex chamber of diameter 0.393 m with a granular bed on a gas-distribution grate and a bottom blow were experimentally investigated. The structure of a swirling flow and the influence of a granular bed on this flow were determined. Equations for calculating the main characteristics of a swirling air flow in the indicated chamber with an immovable granular bed and a bottom blow have been derived. [ABSTRACT FROM AUTHOR]

Abstract: The ultrasonic reflection coefficient amplitude spectrum (URCAS) has been extended to obtain the coating thickness and its longitudinal velocity at the same time on thick substrates. A model was set up first to represent the ultrasonic waves reflected from a coating system at normal incident, and the expression of URCAS was derived in order to obtain the coating thickness and velocity. Then, an inverse algorithm based on the Gauss–Newton method was introduced to determine the thickness and velocity by comparing the theoretical and measured URCAS. Experimental validation was conducted on the homogeneous epoxy coatings on the aluminum substrates and inhomogeneous ZrO2−7wt%Y2O3 (YSZ) coatings on the superalloy substrates. The relative errors of the thickness and velocity measurement were in the ranges of 2.15–2.35% and 2.67–4.40% for epoxy coatings, and between 5.33–5.96% and 8.95–9.66% for YSZ coatings. It is concluded that the URCAS combined with inversion technique can be applied to obtain the thickness and longitudinal velocity of coatings simultaneously. [ABSTRACT FROM AUTHOR]

Abstract: A series of multiferroic materials with the compositional formula, RMnO3 (where R=Sm, Eu, Gd, Dy) were prepared by the well-known citrate sol–gel technique. After characterizing the samples structurally, a systematic investigation of elastic behavior has been undertaken and it has been found that the elastic moduli are increasing continuously with decreasing ionic radii of the dopant ion. Variation of longitudinal velocity with temperature for all the samples, over a temperature range 80–300K has also been studied and the observed experimental behavior is explained using four theoretical models. It has been concluded that Lakkad''s model explains the variation of Young''s modulus with temperature in a better way than the other ones. [Copyright &y& Elsevier]

Using physical (acoustical engineering mechanics and scanning electron microscope) and other technical methods, is study makes a comprehensive analysis of the structural characteristics and engineering mechanics properties of sediments, the sediment structure, microstructure and their classification characteristics and in the light of the physical-mechanical characteristic parameters, the relations between the grain contact, grain accumulation, and porosity with the physical-mechanical characteristics of sediment, and reports the relationship between the acoustic physical parameters and the stress-strain properties of sediment. Results show that there are six structural types in the shelf seabed sediment of the northern South China Sea, among which, the mixed contact structural type sediment has a higher compressive strength and a higher sound velocity than others, and that in the shallow seabed there exists a mesoscale structure with high and low velocity layers. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine the mechanical properties of bovine bones. An ultrasonic method was used to determine acoustical parameters such as the longitudinal and transverse velocities in the longitudinal and two radial directions of compact bone, i.e., in all directions of the plane. Waves propagating through bovine femoral bones were studied using an ultrasonic scanner for linear and sectorial scanning. The mechanical parameters of compact bone, such the Young''s modulus and Poisson''s ratio in the orthotropic case, were then determined from the measured velocities. The results are in line with those in the literature. [Copyright &y& Elsevier]

• Effects of the longitudinal ventilation on the upstream spreading smoke is studied. • A theoretical model for calculating the mass flow rate of upstream smoke is proposed. • The ration of mass flow rates is deduced from ceiling temperatures distribution. • The influences of tunnel length on the ratio of the mass flow rates are considered. Experimental investigation on the fire plume mass flow rate distribution in the upstream and downstream direction of fire is performed. Series of tests were conducted in a reduced-scale tunnel model with longitudinal ventilation. The ceiling temperatures along the tunnel were measured under different heat release rate of the fire source and longitudinal velocity. Based on the ceiling temperature decay coefficients, the ratios of the upstream fire plume mass flow rate to the total fire plume mass flow rate released by the fire, δ = m ̇ up m ̇ 0 , were calculated. The results show that the value of δ is significantly affect by the longitudinal velocity (V a). When V a is smaller than 0.50 V c (V c is the velocity at which the fire smoke is fully confined at the impinging point.), that is V a ≤ 0.50 V c , δ would attain constant value, being 0.5. When V a > 0.50 V c , δ would decrease with longitudinal velocity. Once V a excesses V c , δ will be zero in terms of no fire smoke presence in the upstream side of the fire. Thus a correlation between δ and V a is obtained. A verification of the correlation is also presented at last by comparing to other experimental data. [ABSTRACT FROM AUTHOR]

Abstract: The detailed spatial distributions of longitudinal ultrasonic velocity in cortical bone specimens obtained from three bovine femoral diaphysis were experimentally investigated using a pulse-echo system. The relationship between velocity, density, bone mineral density (BMD) and microstructure was investigated. Velocity was found to vary as a function of the direction of propagation and the location of the measured specimens in the bone diaphysis. A significant correlation was found between density and velocity, and between density and BMD. In some parts with plexiform structure, clear variations in velocity anisotropy were found despite no significant difference in density, BMD and microstructure. [Copyright &y& Elsevier]