Values Of Angular Velocity Research Articles

Pengaruh Model Sudu Overlap dan Helix pada Proses Inisiasi Putaran Turbin Savonius

This research proposes a new model of overlap and helix blade shape. The overlap shape of the blades gives room to the air flow shortly after pounding the blades. Air flow direction is strived to be able to push the next blade so that the process of the turbine blade rotation becomes more effective. While the helix model is expected to produce a more efficient turbine rotation due to its multilevel shape. The wind speeds tested were 2 m / s, 4 m / s, and 6 m / s. Turbine speed rotation data retrieval is carried out at each additional time. The overlap blade has a greater angular velocity value of 9.4 rad / s at 2 m / s wind speed, 21.9 rad / s at 4 m / s wind speed, and 29.8 rad / s at 6 m / s wind speed.Turbines with multilevel helix blades have a higher level of stability compared to overlap blades. This is because there are two levels of turbine blades which have an angle difference of 600 which can receive more stable wind collisions. However, due to the smaller cross-sectional area of the helix blade turbine (ie 50% of the overlap blade) the effective impact area on the blade is also getting smaller. So that the energy that can be converted is also relatively smaller than the overlapping blade.

Active arm swing and asymmetric walking leads to increased variability in trunk kinematics in young adults

Fall induced injuries are a leading cause for occupational injuries with the majority originating from challenging same-level walking surfaces. Despite current perturbation and fall prevention paradigms, occupational fall prevalence remains stable. Typically, these paradigms do not account for arm swing which has been demonstrated to affect the center of mass′ movement during walking. This study examined the effect of different arm swing on postural control during symmetric and asymmetric walking. Fifteen healthy young adults (age = 23.4 ± 2.8) walked symmetrically and asymmetrically with three arm motions (normal, held, and active) on a split-belt treadmill CAREN Extended-System (Motek Medical, Amsterdam, NL). Mean, standard deviation and maximal values of trunk linear and angular velocity, and whole-body angular momentum were calculated in all three axes; additionally, step length, time and width mean and Coefficient of Variation, Margin of Stability and Harmonic Ratios were calculated. Compared to normal and held conditions, active arm increased trunk linear and angular velocity standard deviation, max velocity values, mean step length and time, as well as the Coefficient of Variation for step length, time, and width. Furthermore, whole-body angular momentum increased as a function of arm swing amplitude. Active arm swing further reduced Harmonic Ratios in the mediolateral and anteroposterior directions. Asymmetric walking increased average step time, and width as well as increased the Coefficient of Variation for step length and time but reduced left average step length and step width Coefficient of Variation. Further, asymmetric walking increased mediolateral Margin of Stability and reduced anteroposterior and mediolateral Harmonic Ratios. Finally, results demonstrated that actively increasing arm swing increases trunk linear and angular velocity variability in healthy young adults during symmetric and asymmetric treadmill walking. Findings may be due to active arm swing and asymmetric walking causing a disproportional contribution to trunk and center of mass movement causing participants to modify their base of support to maintain stability.

Effect of rotation on wave propagation through a poroelastic wet bone with cavity

PurposeThe purpose of this paper is to investigate the wave propagation of wave in an infinite poroelastic cylindrical bone. The dynamic behavior of a wet long bone that has been modeled as a piezoelectric hollow cylinder of crystal class 6 is investigated.Design/methodology/approachAn exact closed form solution is presented by employing an analytical procedure. The frequency equation for poroelastic bone is obtained when the boundaries are stress free and is examined numerically.FindingsThe study of wave propagation over a continuous medium is of practical importance in the field of engineering, medicine and bio-engineering. Application of the poroelastic materials in medicinal fields such as orthopedics, dental and cardiovascular is well known. In orthopedics, wave propagation over bone is used in monitoring the rate of fracture healing. There are two types of osseous tissue, such as cancellous or trabecular and compact or cortical bone, which are of different materials, with respect to their mechanical behavior.Originality/valueThe frequencies are calculated for poroelastic bone for various values for different values of rotation, angular velocity and density. In wet bone little velocity dispersion was observed, in contrast to the results of earlier studies on wet bone. Large values of attenuation were observed. Such a model would in particular be useful in large-scale parametric studies of bone mechanical response.

Hiemenz stagnation-point flow impinging on a uniformly rotating plate

Abstract Planar stagnation-point flow normally impinging a rotating plate is studied. Symmetries show that along a circle of radius r , the radial velocity u r can be computed from results in one quadrant and the angular velocity u θ can be computed from results in two quadrants. The results of this study for various values of the dimensionless angular velocity σ are compared with axisymmetric Homann stagnation-point flow on a rotating plate first studied by Hannah.

Calculating the mechanical characteristics of the asynchronous motor having a minimal moment in it

Problem Asynchronous electric motors (AEs) are the most common among all electric motors. This is due to the simplicity of design, high reliability, relatively low cost, better weight and overall performance, etc. The asynchronous electric drive, which has a vector control based on modern static converters with microprocessor controllers, is especially widespread now. One of the most important characteristics of the engine is its mechanical characteristics. Based on the knowledge of the dependence of the moment on the electric motor shaft on its speed of rotation in various modes of operation, it is possible to implement high-quality and efficient control. Goal. The goal is conducting the analysis of operating modes of the asynchronous motor with the calculation of its mechanical characteristics in the presence of a minimal moment in it. Methodology. Analytical methods of research, methods of the theory of electric machines and electric drives are used, as well as methods of calculating electric circuits. The method of calculating the mechanical characteristics of AE in the presence of a site with a clearly expressed minimum torque is considered. Results. The analysis of the AE is based on its G-shaped replacement scheme. The mechanical characteristics of AE in different modes of operation were considered and analyzed in details. The mechanical characteristics of the AE were calculated in the presence of a minimal moment in it. It is determined that the value of the critical slip depends on the value of the active resistance of the rotor circle. Since the current of the motor is proportional to the voltage in the first stage, and the moment is the supply voltage squared, therefore, the characteristics of the voltage drop change both qualitatively and quantitatively. Originality. The current value of the moment of the AE depends on the square of the supply voltage, the active and inductive resistance of the windings of the rotor and the stator with the given values of slip and synchronous angular velocity. For all values of the voltage, the critical velocity (critical slip) does not change, that is, it does not depend on the voltage value. The magnitude of the moment varies significantly with the change in voltage. Practical value. In real conditions, all industrial networks may be subject to voltage, therefore, it is necessary to continuously monitor how significant it is to reduce the maximum and starting moments of the drives when reducing the voltage and how much they meet the demands of the technological process. If the control of a traction electric drive based on an electric motor is considered, the fact that the voltage from the energy storage will vary with the discharge should also be taken into account. Consequently, there will be a change in both the starting and the maximum moment that this drive can develop.Keywords: asynchronous motor; mechanical characteristic; minimum torque; Clause formula; traction electric drive; electric car; electric drive system.

About possibility of immediate evaluation of technical condition of mining equipment using signal value of acoustic emission friction

An experiment was conducted to confirm the reliability of the evaluation of the technical condition of transmission elements during operation in terms of the magnitude and nature of the acoustic emission signal, while completing the negative effect of the artificial environment on the durability of the transmission elements. Thus, the results of the experiment are presented where the acoustic emission signal in the friction pair was changed depending on the pressure value in the contacting pair and the angular velocity value. The possibility of obtaining an estimate of the technical state of the transmission elements during its operation in terms of acoustic and emission characteristics has been experimentally confirmed.

Optimization of angular velocity of drum mixers

Drum mixers ensure a high level of uniformity when mixing the components of feed additives. However, the issues on theoretical and experimental substantiation of the structural and kinematic parameters of drum mixers have not been scientifically explored in detail. The aim of this study is to improve the efficiency of producing feed mixtures by ensuring the optimal angular rotation velocity of a drum mixer.To determine the radial speed of a particle’s motion along a drum blade, we solved a homogeneous differential equation. The numerical value for angular velocity was determined by a computer simulation method. We experimentally studied the uniformity of redistribution of feed components in a mixture of fodder using the designed experimental drum mixer. The mixer included a chamber, a rectangular frame, a supporting frame, and a drive. The mixing chamber included a loading/unloading window with a closed lid. Radial blades were installed inside the chamber along its entire length and evenly along the perimeter.Experiments were conducted using a drum mixer with a drum radius of 0.17 m, which included radial blades with a width of 25 mm, with a chamber’s fill factor of 0.5. It was established that the drum mixer ensures the maximum scattering of a material’s particles on the surface of the working segment at the drum’s angular rotation velocity of 9.69 rad/s.The results of experimental research have established that at rotation frequency of the laboratory plant’s drum of 9.42 rad/s the uniformity of mixture is 92.5‒93 %, which meets acting zootechnical requirements for all types of mixed fodder. In this case, a maximum deviation of the theoretical and experimental data was about 9 %. The results obtained suggest the possibility of determining a numerical value for the angular velocity of drum mixers by using the proposed method of computer simulation.

Numerical Study of Savonius Wind Turbine with Fluid-Rotor Interactions

Previous numerical studies in the Savonius wind turbine mostly used constant angular velocity as input data, where the values were obtained from experiments. This process cannot be used in the design optimization of the turbine, in which the angular velocity of the modified turbine is not known a priority. In numerical simulation, the use of loading system to get constant angular velocity to control the tip speed ratio (TSR), tends to have fluctuating value on output data. Moreover, the values of angular velocity shall be the results from freestream flow and Savonius rotor interaction. This condition can be simulated by using fluid structure interaction (FSI) method. Three dimensional Savonius S wind turbine is simulated using unsteady Reynolds Averaged Navier Stokes (RANS). Inlet velocity and wind turbine inertia are used as input data. The flow is assumed to be incompressible, viscous, and uniform at the inlet. The turbulence model used is the Eddy Viscosity k-ω SST, with y+ < 1. The domain consists of a sliding mesh, which rotates in the overset mesh region. Simulation results Power Coefficient (CP) and angular velocity and compared with experimental result. This study is resulted a standard method for the Savonius wind turbine numerical study

Bifurcation analysis of the rotating axially compressed nano‐rod with imperfections

AbstractStatic stability problem for axially compressed rotating nano‐rod clamped at one and free at the other end is analyzed by the use of bifurcation theory. It is obtained that the pitchfork bifurcation may be either super‐ or sub‐critical. Considering the imperfections in rod's shape and loading, it is proved that they constitute the two‐parameter universal unfolding of the problem. Numerical analysis also revealed that for non‐locality parameters having higher value than the critical one interaction curves have two branches, so that for a single critical value of angular velocity there exist two critical values of horizontal force.

On gravitational echoes from ultracompact exotic stars

At the dawn of a golden age for gravitational wave astronomy, we must leave no stone unturned in our quest for new phenomena beyond our current understanding of General Relativity (GR), particle physics and nuclear physics. In this paper we discuss gravitational echoes from ultracompact stars. We restrict our analysis to exact solutions of Einstein field equations in GR that are supported by an isotropic fluid with a physically motivated equations of state (EoS), and in particular we impose the constraint of causality. Our main conclusion is that ultracompact objects belonging to this category are not able to generate gravitational echoes like those that characterize the relaxation phase of a putative black hole mimicker. Nevertheless, we identify a class of physical exotic objects that are compact enough to accommodate the presence of an external unstable light ring, thus opening the possibility of trapping gravitational radiation and affecting the ringdown phase of a merger event. Most importantly, we show that once rotation is included these stars—contrary to what usually expected for ultracompact objects—are not plagued by any ergoregion instability. We extend our analysis for arbitrary values of angular velocity up to the Keplerian limit, and we comment about potential signals relevant for gravitational wave interferometers.

Measurement of Angular Parameters and Velocities of the Upper Limb Segments in Tennis Using Inertial Motion Sensors for the Purposes of the Didactic Process

The aim of the study is to show differences in accurate and missed forehand and backhand strokes in tennis, as a feedback for coaches, teachers and players. The main assumptions of the study are to show the values of angular parameters and velocity, as well as to analyse every phase of a stroke. The priority in the study is to show how the abovementioned parameters affect the accuracy and velocity of forehand and backhand strokes. Material and research methods: A professional tennis player was tested using the individual case method and kinematic analysis. The motion capture system (MCS) was used for research purposes using inertial motion sensors. Results: Strokes were analysed to demonstrate the angular parameters and velocities of selected upper limb segments. Three upper limb segments were taken into account, i.e. the right hand, the right forearm and the right shoulder. The results of the angles and velocities achieved by individual segments were analysed in three axes of the body: X, Y, Z. The results concern the beginning of the acceleration phase, the end of the acceleration phase, i.e. the moment of impact, and the final, follow-through phase. Conclusion: The results show that a stroke can be accurate despite a significant change in angle and velocity. This situation applies to both forehand and backhand strokes.

Disturbance Observer‐Based Robot End Constant Contact Force‐Tracking Control

A disturbance observer‐based hybrid sliding mode impedance control method is proposed in this paper, which is able to achieve robot end constant contact force‐tracking control without force/torque sensors. The method requires only the values of joint torque, joint angle, and joint angular velocity, which are converted by robot servo motor signals, to implement the control. The control scheme consists of two parts: one is a disturbance observer and the other is a hybrid sliding mode impedance controller. The disturbance observer, which takes robot internal signals mentioned above as the inputs to estimate the robot end contact force, is designed based on generalized momentum, thus improving the estimation accuracy. The hybrid sliding mode impedance controller, which uses the values estimated by the disturbance observer and the robot internal signals as the inputs to calculate the corresponding position adjustment, integrates both the impedance control and sliding mode control, thus improving the force‐tracking performance and robustness. Experimental results show that the proposed disturbance observer‐based hybrid sliding mode impedance control method possesses high control precision.

Caloric test and video head impulse test sensitivity as vestibular impairment predictors before cochlear implant surgery

OBJECTIVES:Currently, cochlear implant procedures are becoming increasingly broad and have greatly expanded. Bilateral cochlear implants and cochlear implants are more frequently applied in children. Our hypothesis is that the video head impulse test may be more sensitive than the caloric test in detecting abnormal vestibular function before cochlear implant surgery. The objective of this study was to compare the video head impulse test and caloric test results of patients selected for cochlear implant procedures before surgery.METHODS:The patients selected for cochlear implant surgery were submitted to a bithermal caloric test and video head impulse test.RESULTS:By comparing angular slow phase velocity values below 5° in the bithermal caloric test (hypofunction) and video head impulse test with a gain lower than 0.8, we identified 37 (64.9%) patients with vestibular hypofunction or canal paresis and 21 (36.8%) patients with abnormal video head impulse test gain before the cochlear implant procedure. Of the 37 patients with caloric test vestibular hypofunction, 20 (54%) patients exhibited an abnormal gain in the video head impulse test.CONCLUSION:The caloric test is more sensitive than the video head impulse test (Fisher's exact test, p=0.0002) in detecting the impaired ear before cochlear implant delivery. The proportion of caloric test/video head impulse test positive identification of abnormal vestibular function or caloric test/video head impulse test sensitivity was 1.8:1.

Investigation of the non-stationary temperature field of a two-layer cylinder at different angular velocities of motion of normally distributed stream of heat

A three-dimensional non-stationary heat conduction problem for a two-layer cylinder heated by normally distributed heat stream moving on the external surface along the cylinder guide is considered. On the basis of the solution obtained through the Green's functions for the corresponding heat conductivity problem the temperature fields for different values of angular velocity are investigated. Cite as: B. V. Protsiuk, V. M. Syniuta, “Investigation of the non-stationary temperature field of a two-layer cylinder at different angular velocities of motion of normally distributed stream of heat,” Prykl. Probl. Mekh. Mat. , Issue 16, 91–97 (2018) (in Ukrainian), http://doi.org/10.15407/apmm2018.16.91-97

The nonlinear vibrations of orthogonal mechanism of vibrating table in view of friction

Abstract. In dynamics of the orthogonal mechanism of vibrating table main attention is paid to the effect of friction on vibrational process when it is interacting with non-ideal energy source. As a result of analysis of numerical solutions of nonlinear equation of motion, it is established that in general, for the period of rotation, both sliding friction and rotational friction increase the difference between the maximum and minimum angular velocity values of the driving link (engine shaft) when its average value is constant; both increase the coefficient of non-uniformity of rotation. When there is a cargo of significant mass in the working link, the effect of sliding friction impacts more on the amplitude and frequency of the angular velocity oscillations of the driving link (engine shaft) and on the frequency of the coordinate changes, as well as on the frequencies and maximum and minimum values of the projections of the velocity and acceleration of the hinge linking the work platform to coupler. Similarly, the larger of the load mass, the stronger the effect of rotational friction on the amplitude and frequency of angular velocity oscillations of the driving link (engine shaft).

Dynamics of sedimentation of particle in a viscous fluid in the presence of two flat walls

The model problem of sedimentation of a solid spherical particle in a viscous fluid bordering two solid planar surfaces is considered. To find the solution of the hydrodynamic equations in the approximation of small Reynolds numbers with boundary conditions on a particle and on two planes, a procedure developed for numerical simulation of the dynamics of a large number of particles in a viscous fluid with one plane wall is used. The procedure involves usage of fictive particles located symmetrically to real ones with respect to the plane. To solve the problem of the real particle’s sedimentation in the presence of two planes, a system of fictive particles is introduced. An approximate solution was found using four fictive particles. Basing on this solution, numerical results are obtained on dynamics of particle deposition for the cases of planes oriented parallel and perpendicular to each other. In particular, the values of linear and angular velocities of a particle are found, depending on the distance to each plane and on the direction of gravity. In the limiting case, when one of the planes is infinitely far from the particle, we obtain known results on the dynamics of particle sedimentation along and perpendicular to one plane.

Dynamics of sedimentation of particle in a viscous fluid in the presence of two flat walls

The model problem of sedimentation of a solid spherical particle in a viscous fluid bordering two solid planar surfaces is considered. To find the solution of the hydrodynamic equations in the approximation of small Reynolds numbers with boundary conditions on a particle and on two planes, a procedure developed for numerical simulation of the dynamics of a large number of particles in a viscous fluid with one plane wall is used. The procedure involves usage of fictive particles located symmetrically to real ones with respect to the plane. To solve the problem of the real particle’s sedimentation in the presence of two planes, a system of fictive particles is introduced. An approximate solution was found using four fictive particles. Basing on this solution, numerical results are obtained on dynamics of particle deposition for the cases of planes oriented parallel and perpendicular to each other. In particular, the values of linear and angular velocities of a particle are found, depending on the distance to each plane and on the direction of gravity. In the limiting case, when one of the planes is infinitely far from the particle, we obtain known results on the dynamics of particle sedimentation along and perpendicular to one plane.

Effect of rotating magnetic field on orientational dynamics of ferrocholesteric liquid crystals

We present numerical and analytical results describing the dynamics of a helical orientational structure of a ferrocholesteric liquid crystal, i.e., dilute suspension of ferromagnetic nanoparticles in a cholesteric liquid crystal, under the action of a rotating magnetic field. We employ the continuum theory to show how rotating magnetic field can untwist the helical ferrocholesteric structure and induce a ferrocholesteric–ferronematic transition. We analyze the non-stationary and stationary rotation regimes of the helical structure of a ferrocholesteric in a magnetic field. For weak fields, small and large rotational velocities the analytical expressions are obtained for the pitch of the ferrocholesteric helix. In the stationary rotational regime the orientational phase diagram of the ferrocholesteric–ferronematic transition is constructed for different values of magnetic field and angular velocities. It is shown that with increasing these parameters the transition field decreases. The dependence of a ferrocholesteric pitch on the magnetic field and its angular velocity at various material parameters is numerically obtained. We derive the analytical expression describing the divergence law for the pitch of a helix in the pre-transition region.

Divide-and-conquer muscle synergies: A new feature space decomposition approach for simultaneous multifunction myoelectric control

Abstract Simultaneous multifunctional control based on surface electromyography (sEMG) is a key issue for natural and intuitive use of upper-limb prostheses in clinical and commercial applications. However, muscle synergies make simultaneous multifunctional control technologically challenging. In this study, we proposed a new feature space decomposition approach to alleviate the difficulty brought by muscle synergies for simultaneous control of hand and wrist movements. In the feature space decomposition approach, Gaussian mixture modeling (GMM) clustering is used to split the whole feature space into a set of Gaussian clusters, each consisting of samples with similar characteristics, to “divide-and-conquer” the complex muscle synergies. Then, a hybrid simultaneous control strategy, which consists of switch control of hand movements and proportional control of wrist movements, is performed in each cluster, instead of in the whole feature space. In the experimental study, sEMG signals were recorded during static and dynamic muscle contraction involving 2-dimensional wrist rotation (flexion-extension and radial-ulnar deviation) and 3 basic hand movement patterns (relaxing, fisting and grasping). Results show that, the new feature space decomposition approach can increase the accuracy for switch control of hand movement patterns from 90.10% to 96.62%, and can improve the correlation between true and predicted values of wrist rotation angular velocity from 0.71 to 0.84 (for wrist flexion-extension) and from 0.67 to 0.82 (for wrist radial-ulnar deviation) for proportional control of wrist. The proposed feature space decomposition approach has the potential to yield simultaneous multifunctional control for sEMG-based upper-limb prosthesis.

On the inertio-elastic instability of variable-thickness functionally-graded disks

Instability is observed at certain speeds for rotating disks when the radial displacement in the centrifugal force is taken into consideration. The critical angular velocity values which cause unbounded displacement and stresses will be determined. Analysis of functionally-graded variable-thickness disks requires solving variable-coefficient governing differential equations. Analytical solutions of such equations can be obtained only for certain material grading functions and uniform thickness profiles. In the present study, disks with non-uniform thickness profiles and heterogeneous material properties graded in the radial direction are considered. Solution of the resulting variable-coefficient governing equation of displacement requires the implementation of numerical methods. To this end, a novel approach, Complementary Functions Method is employed as the solution scheme. Complementary Functions Method provides an accurate and efficient solution procedure by reducing the two-point boundary value problem to a system of initial value problems. It is applicable for any continuous material grading functions and thickness profiles. The presented method is validated using a benchmark disk problem with uniform-thickness and material properties graded by a simple power function. Also, the efficiency of the solution scheme is demonstrated by comparing the results with those of finite element method (ANSYS).