Angle Oscillations Research Articles

Using nonlinear finite element models to analyse stress distribution during subluxation and torque required for dislocation of newly developed total hip structure after prosthetic impingement.

Dislocation is a serious potential complication of total hip replacement. Previous studies have proposed a newly developed total hip structure that meets the required oscillation angle of 120°, for which the chamfer on the acetabular liner rim was designed to enable the neck to impinge on the chamfer over a large area after impingement occurs. This study adopted the finite element method to further analyse the torque limits leading to dislocation and the contact stresses at the impingement and egress sites of the liner during subluxation. The compressive stress-strain curve for ultra-high molecular weight polyethylene is nonlinear. The results reveal that an adequate chamfer angle of the acetabular cup liner can significantly increase dislocation torque and decrease contact stress on the liner rim. By means of the new design, when the head-neck ratio (HNR) is 2.5 or 3.0, the maximum torque value that a 36-mm head can withstand is 1.38 (8.7Nm/6.3Nm) or 1.47 (8.4Nm/5.7Nm) times that of a 22-mm head, while the maximum stress of a 36-mm head is 0.41 (14.58MPa/35.73MPa) or 0.70 (33.71MPa/47.90MPa) times that of a 22-mm head. When the head diameters are identical, the dislocation torque of the HNR=2.5 structure is slightly greater than that of the HNR=3.0 structure (3.3-10.5%); thus, the newly developed structure can disperse contact stress, and the structure of a large head with a low HNR exhibits a higher dislocation torque value and lower stress.

Energy flow of electric dipole radiation in between parallel mirrors

We have studied the energy flow patterns of the radiation emitted by an electric dipole located in between parallel mirrors. It appears that the field lines of the Poynting vector (the flow lines of energy) can have very intricate structures, including many singularities and vortices. The flow line patterns depend on the distance between the mirrors, the distance of the dipole to one of the mirrors and the angle of oscillation of the dipole moment with respect to the normal of the mirror surfaces. Already for the simplest case of a dipole moment oscillating perpendicular to the mirrors, singularities appear at regular intervals along the direction of propagation (parallel to the mirrors). For a parallel dipole, vortices appear in the neighbourhood of the dipole. For a dipole oscillating under a finite angle with the surface normal, the radiating tends to swirl around the dipole before travelling off parallel to the mirrors. For relatively large mirror separations, vortices appear in the pattern. When the dipole is off-centred with respect to the midway point between the mirrors, the flow line structure becomes even more complicated, with numerous vortices in the pattern, and tiny loops near the dipole. We have also investigated the locations of the vortices and singularities, and these can be found without any specific knowledge about the flow lines. This provides an independent means of studying the propagation of dipole radiation between mirrors.

Running Technique is an Important Component of Running Economy and Performance.

ABSTRACTDespite an intuitive relationship between technique and both running economy (RE) and performance, and the diverse techniques used by runners to achieve forward locomotion, the objective importance of overall technique and the key components therein remain to be elucidated.PurposeThis study aimed to determine the relationship between individual and combined kinematic measures of technique with both RE and performance.MethodsNinety-seven endurance runners (47 females) of diverse competitive standards performed a discontinuous protocol of incremental treadmill running (4-min stages, 1-km·h−1 increments). Measurements included three-dimensional full-body kinematics, respiratory gases to determine energy cost, and velocity of lactate turn point. Five categories of kinematic measures (vertical oscillation, braking, posture, stride parameters, and lower limb angles) and locomotory energy cost (LEc) were averaged across 10–12 km·h−1 (the highest common velocity < velocity of lactate turn point). Performance was measured as season's best (SB) time converted to a sex-specific z-score.ResultsNumerous kinematic variables were correlated with RE and performance (LEc, 19 variables; SB time, 11 variables). Regression analysis found three variables (pelvis vertical oscillation during ground contact normalized to height, minimum knee joint angle during ground contact, and minimum horizontal pelvis velocity) explained 39% of LEc variability. In addition, four variables (minimum horizontal pelvis velocity, shank touchdown angle, duty factor, and trunk forward lean) combined to explain 31% of the variability in performance (SB time).ConclusionsThis study provides novel and robust evidence that technique explains a substantial proportion of the variance in RE and performance. We recommend that runners and coaches are attentive to specific aspects of stride parameters and lower limb angles in part to optimize pelvis movement, and ultimately enhance performance.

Improvement of Stability in Solar Energy Based Power System Using Hybrid PSO-GS Based Optimal SVC Damping Controller

Abstract This paper presents a dynamic stability study in a solar energy based power system connected to infinite bus based on optimal design of a Static Var Compensator (SVC). In the proposed study, SVC is incorporated in order to improve the rotor angle and voltage oscillations because of different disturbances created in the power system. A new computational hybrid optimization approach using Particle Swarm Optimization (PSO) and Gravitational Search (GS) technique is considered for designing an optimal SVC damping controller for an improved dynamic performance. The optimization technique is used for tuning the gains of proportional integral derivative (PID) controller. Transient oscillation results for conventional PID, PSO optimized PID and PSO-GS based PID are compared analytically as well as quantitatively. It is observed that the proposed PSO-GS based PID controller is robust and effective in minimizing the oscillations in the system as compared to the other two and thus improves the stability.

G-JITTER EFFECTS ON THE MIXED CONVECTION FLOW OF NANOFLUID PAST AN INCLINED STRETCHING SHEET

Mixed convection flows of nanofluid past an inclined stretching sheet with g-jitter is studied in this paper. Water based nanofluid containing copper, copper oxide, aluminium oxide and silver nanoparticles are concerned. Coupled nonlinear partial differential equations are solved numerically using an implicit finite difference scheme. The effect of solid nanoparticles volume fraction parameter, amplitude of modulation, frequency of oscillation, mixed convection and inclination angle parameter on the fluid flow and heat transfer characteristics are graphically presented. The reduced skin friction and heat transfer coefficient are decreased when inclination angle and solid nanoparticles volume fraction parameters are increased.

Analysis of Underactuated Dynamic Locomotion Systems Using Perturbation Expansion: The Twistcar Toy Example

Underactuated robotic locomotion systems are commonly represented by nonholonomic constraints where in mixed systems, these constraints are also combined with momentum evolution equations. Such systems have been analyzed in the literature by exploiting symmetries and utilizing advanced geometric methods. These works typically assume that the shape variables are directly controlled, and obtain the system’s solutions only via numerical integration. In this work, we demonstrate utilization of the perturbation expansion method for analyzing a model example of mixed locomotion system—the twistcar toy vehicle, which is a variant of the well-studied roller-racer model. The system is investigated by assuming small-amplitude oscillatory inputs of either steering angle (kinematic) or steering torque (mechanical), and explicit expansions for the system’s solutions under both types of actuation are obtained. These expressions enable analyzing the dependence of the system’s dynamic behavior on the vehicle’s structural parameters and actuation type. In particular, we study the reversal in direction of motion under steering angle oscillations about the unfolded configuration, as well as influence of the choice of actuation type on convergence properties of the motion. Some of the findings are demonstrated qualitatively by reporting preliminary motion experiments with a modular robotic prototype of the vehicle.

草刈ロボット用首振り草刈装置の特性評価

In our laboratory, we have developed a remote controlled mower robot, AMR-D01. However, it has several weak point such as it takes time to work, grass which is not mowed hit against front body because its blade diameter is small. In this paper, an oscillating mower mechanism for mower robot is proposed in order to increase the swath of the robot. This mechanism is based on Lever-crack mechanism, which has a rotary link, a transmission link, an oscillation link, a fixed link. Characteristics of the mechanism, such as angle of oscillation and quick return ratio of the oscillation link, required torque of the rotary link, with ratio patterns of length of each link is evaluated by simulating. From the results, proper design and parameters are selected. Proposed mower robot have the advantages of reduced mowing time and costs using the oscillating mower mechanism.

Long-period oscillations of active region patterns: least-squares mapping on second-order curves

Active regions (ARs) are the main sources of variety in solar dynamic events. Automated detection and identification tools need to be developed for solar features for a deeper understanding of the solar cycle. Of particular interest here are the dynamical properties of the ARs, regardless of their internal structure and sunspot distribution. We studied the oscillatory dynamics of two ARs: NOAA 11327 and NOAA 11726 using two different methods of pattern recognition. We developed a novel method of automated AR border detection and compared it to an existing method for the proof-of-concept. The first method uses least-squares fitting on the smallest ellipse enclosing the AR, while the second method applies regression on the convex hull.} After processing the data, we found that the axes and the inclination angle of the ellipse and the convex hull oscillate in time. These oscillations are interpreted as the second harmonic of the standing long-period kink oscillations (with the node at the apex) of the magnetic flux tube connecting the two main sunspots of the ARs. In both ARs we have estimated the distribution of the phase speed magnitude along the magnetic tubes (along the two main spots) by interpreting the obtained oscillation of the inclination angle as the standing second harmonic kink mode. After comparing the obtained results for fast and slow kink modes, we conclude that both of these modes are good candidates to explain the observed oscillations of the AR inclination angles, as in the high plasma $\beta$ regime the phase speeds of these modes are comparable and on the order of the Alfv\'{e}n speed. Based on the properties of the observed oscillations, we detected the appropriate depth of the sunspot patterns, which coincides with estimations made by helioseismic methods. The latter analysis can be used as a basis for developing a magneto-seismological tool for ARs.

Matched pitch rate extensions to dynamic stall on rotor blades

Dynamic stall on both horizontal axis and vertical axis wind turbine blades is accompanied by simultaneous changes in pitch and surge, but this simultaneous effect has never been documented. Using a unique unsteady wind tunnel, synchronous oscillations in angle of attack and flow speed were considered on two prototypical wind turbine blades. At a steady freestream, the concept of matched pitch rate was observed to be valid for large positive and negative pitch angles. In the presence of an unsteady stream, matching the flow speed as well as the pitch angle and its time derivative during pitch-up produced excellent correspondence between lift, drag and moment coefficients throughout the entire dynamic stall event.

Modelling of dynamic cutting force coefficients and chatter stability dependent on shear angle oscillation

Productivity of high-speed turning operations is limited by the onset of self-excited vibrations known as chatter. Unless avoided, chatter vibrations may cause large dynamic loads damaging the machine spindle, cutting tool or workpiece and leave a poor surface finish behind. Cutting force magnitude is proportional to the thickness of the chip removed from the workpiece. This paper presents a new procedure to determine dynamic cutting force coefficients (DCFC) required for process simulation by mechanistic modelling. In this study, a two degree of freedom complex dynamic model of turning with an orthogonal cutting system is considered. The complex dynamic system consists of a dynamic cutting system force model based on shear angle (φ) oscillations and penetration forces caused by the tool flank’s contact with the wavy surface. The dynamic cutting force coefficients are identified by operating a series of cutting tests at the desired frequency, while changing φ oscillations and penetration forces. It is shown that the process damping coefficient increases as the tool is worn, which increases the chatter stability limit in cutting. The chatter stability of a dynamic cutting process is solved using the Nyquist law and time domain simulation (TDS) techniques and compared favourably against experimental results at low cutting speeds. Finally, comparisons among the proposed mechanistic model and experimental results show a good agreement with the analytically established SLD and, thus, validate the effectiveness of the proposed model.

In plane oscillation of a bifilar pendulum

The line tensions, the horizontal and vertical accelerations as well as the period of large angle oscillations parallel to the plane of a bifilar suspension are presented and have been experimentally investigated using strain gauges and a smart phone. This system has a number of advantages over the simple pendulum for studying large angle oscillations, and for measuring the acceleration due to gravity.

Rotating pendulum with smooth and discontinuous dynamics

This paper focuses on a novel rotating pendulum system which is derived from the coupling rotational model of simple pendulum and mass-spring oscillator. The remarkable feature of the proposed system is a cylindrical dynamical system with strongly irrational nonlinearity exhibiting smooth and discontinuous characteristics due to the geometry configuration. The equilibrium stability and bifurcations of the unperturbed system are explored showing the subcritical pitchfork bifurcation, supercritical pitchfork bifurcation and saddle-node bifurcation. Furthermore, the complex transitions of multiple well dynamics and various kinds of singular orbits are demonstrated by using nonlinear dynamical technique in both smooth and discontinuous case. For the perturbed system, the primary resonance of small angle oscillation is investigated analytically by introducing the complete Jacobian elliptic integrals. Finally, complicated resonant structures of period, quasi-period and stochastic phenomena are presented for the system with unique harmonic perturbation. Bifurcation diagram, Poincaré section and basin analysis are carried out to demonstrate the co-existing different types of periodic motion and the transitions of chaotic motion between smooth and discontinuous case.

Simulation research of the tire Basic Relaxation Model in conditions of the wheel cornering angle oscillations

- A description of the tire Basic Relaxation Model (BRM) is presented in this paper. Simulation research of the tire BRM model in conditions of oscillatory changes of the wheel cornering angle were performed. During the simulation tests the courses of changes in the value of lateral reaction force, transmitted by the wheel, as a response to the sinusoidal changes in the value of the wheel cornering angle have been presented. There have been compared the simulation results obtained for the model of tire-road interaction in two modes: including and not including the BRM. The simulation results allowed to verify prepared BRM and also to determine the influence of the tire relaxation process on the tire behavior in conditions of dynamic changes of the wheel cornering angle.

Fan Response to Boundary-Layer Ingesting Inlet Distortions

The modeling capabilities of TURBO, an existing turbomachinery analysis code, have been extended to include the ability to solve the external and internal flow fields of a boundary-layer ingesting inlet. Flow solutions are presented and compared with experimental data for several high-Reynolds-number flows to validate the solver modifications. The upstream flowfield was coupled to a hypothetical compressor fan to present a fully developed distortion to the fan. Although the total pressure distortion upstream of the fan was symmetrical for this geometry, the pressure rise generated by the fan blades was not, because of the velocity nonuniformity of the distortion. Total pressure profiles at various axial locations are computed to identify the overall distortion pattern, how the distortion evolves through the blade passages and mixes out downstream of the blades, and where any critical performance concerns might be. Stall cells are identified that are stationary in the absolute frame and are fixed to the inlet distortion. Flow paths around the blades are examined to study the stall mechanism. Rather than a typical airfoil stall, it is observed that the nonuniform pressure loading in the radial direction promotes a three-dimensional dynamic stall. The stall occurs at a point of rapid incidence angle oscillation observed when a blade passes through a distortion and re-attaches when the blade sees more uniform flow outside the distortion.

A combination of high electrical conductivity and mechanical strength in AA1070 commercially pure aluminum wires fabricated by KoBo extrusion

Abstract In this work, the effect of KoBo extrusion process parameters on the extrusion force, microstructure, mechanical properties and electrical resistivity of wires fabricated from AA1070 commercially pure aluminum, is analyzed. It is found that applied parameters of the KoBo extrusion process have a strong impact on changes in the extrusion force. The smallest variation of the extrusion force was recorded for the KoBo extrusion conducted with a small oscillation angle and a high extrusion rate. The relatively small alteration of the extrusion force results in a more homogeneous microstructure and mechanical properties of the wires. As compared to the material in the annealed state, the KoBo extruded wires exhibit almost two-fold higher ultimate tensile strength and only a slightly lowered electrical conductivity. The best combination of electrical conductivity and mechanical strength was 60.3 % International Annealed Copper Standard and ultimate tensile strength of 152 MPa, respectively. These results are highly competitive to those reported for AA1070 aluminum subjected to other continuous plastic deformation methods (e. g. the cryorolling combined with a heat treatment). A high electrical conductivity and enhanced mechanical properties (in respect to the as annealed material), clearly indicate that the KoBo extruded AA1070 wires are potentially useful for moderately loaded electrical engineering applications.

Light neutrino mass spectrum with one or two right-handed singlet fermions added

We analyse two cases of the minimal extension of the Standard Model when one or two right-handed fields are added to the three left-handed fields. A second Higgs doublet (two Higgs doublet model – 2HDM) is included in our model. We calculate one-loop radiative corrections to the mass parameters which produce mass terms for the neutral leptons. In both cases we numerically analyse light neutrino masses as functions of the heavy neutrino masses. Parameters of the model are varied to find light neutrino masses that are compatible with experimental data of solar Δm⊙2 and atmospheric Δmatm2 neutrino mass differences for normal hierarchy. We choose values for the parameters of the tree-level by numerical scans, where we look for the best agreement between computed and experimental neutrino oscillation angles.

Oscillation Energy Analysis of Inter-Area Low-Frequency Oscillations in Power Systems

Low-frequency inter-area oscillation is a potentially dangerous phenomenon in power systems involving exchange of power among generators in different areas. In this paper, we study the characteristics of inter-area oscillation by analyzing the distribution of the oscillation energy. First, we introduce equations for the kinetic energy of generators and the potential energy of network branches, derived from the linearization of system dynamic equations. Then, we study the mode composition and the distribution of the generators' kinetic energy during low-frequency oscillations. A modal kinetic energy participation factor is proposed for evaluating the participation of each generator in the oscillation. The relationships among electromagnetic power oscillation distribution, rotor speed deviation, and generator kinetic energy are analyzed and compared to their modal parameter left eigenvectors, right eigenvectors, and linear participation factors, respectively. The bus voltage angle deviation, active power oscillation, and branch potential energy are calculated using the right eigenvector from modal analysis. The distribution characteristics of voltage angle oscillation and branch potential energy in inter-area oscillation is developed. The simulation results for a four-generator two-area system and the New England 10-machine 39-bus system illustrate the feasibility and validity of the proposed theory and method for analysis of inter-area oscillations.

Study on Periodic MHD Flow with Temperature Dependent Viscosity and Thermal Conductivity past an Isothermal Oscillating Cylinder

Temperature dependent viscosity and thermal conducting heat and mass transfer flow with chemical reaction and periodic magnetic field past an isothermal oscillating cylinder have been considered. The partial dimensionless equations governing the flow have been solved numerically by applying explicit finite difference method with the help Compaq visual 6.6a. The obtained outcome of this inquisition has been discussed for different values of well-known flow parameters with different time steps and oscillation angle. The effect of chemical reaction and periodic MHD parameters on the velocity field, temperature field and concentration field, skin-friction, Nusselt number and Sherwood number have been studied and results are presented by graphically. The novelty of the present problem is to study the streamlines by taking into account periodic magnetic field.

The effect of age on Cheddar cheese melting, rheology and structure, and on the stability of feed for cheese powder manufacture

Age-related changes to the rheology and structure of Cheddar for cheese powder manufacture, and how this influences the stability of cheese feed during pre-spray-drying storage, were investigated. Cheddar cheese (3, 5, 7, 9, 12 and 15 months old) was analysed for meltability by the Schreiber Test and small angle oscillation measurements. Results showed increasing stiffness and reduced activation energy for initiation of milk fat melting with age. Cheese feeds for manufacture of cheese powder were made, with or without emulsifying salts (ES), and analysed for emulsion stability. In the absence of ES, feeds made from 3 month old Cheddar were significantly more stable than those made from 5 month old cheese. A similar significant increase in emulsion stability was observed for cheeses of 7 months of age compared with 12 months, indicating the necessity to use Cheddar cheese aged 3 months or less to produce stable cheese feeds without ES.

Experimental simulation of friction and wear of carbon yarns during the weaving process

Nowadays many mechanical composite parts are reinforced by carbon weaving material. During the weaving process some damage to the carbon yarns appears that decreases the final mechanical properties of the part. This study focused on the friction interactions that occurred between warp yarns. A specific kinematic experiment has been done in order to simulate the weaving movement of these yarns, which induces friction. By varying experimental parameters, initial normal load, oscillation frequency and oscillation angle, it is possible to understand their influence on friction phenomena and fibre damage. The energies induced during friction have also been studied. The results obtained show that the coefficient of friction decreases with the increase of normal load, but is not influenced by the oscillation frequency. Yarn wear, i.e. filament breaks, appears beyond a certain normal load. The friction energy increases with normal load and oscillating angle but does not depend on oscillation frequency.