Multibody dynamics simulation of an all-wheel-drive motorcycle for handling and energy efficiency investigations

It is now possible, through electrical, hydraulic or mechanical means, to power the front wheel of a motorcycle. The aim of this is often to improve performance in limit-handling scenarios including off-road low-traction conditions and on-road high-speed cornering. Following on from research into active torque distribution in 4-wheeled vehicles, the possibility exists for efficiency improvements to be realised by reducing the total amount of energy dissipated as slip at the wheel–road contact. This paper presents the results of an investigation into the effect that varying the torque distribution ratio has on the energy consumption of the two-wheeled vehicle. A 13-degree of freedom multibody model was created, which includes the effects of suspension, aerodynamics and gyroscopic bodies. SimMechanics, from the MathWorks_, is used for automatic generation of equations of motion and time-domain simulation, in conjunction with MATLAB and Simulink. A simple driver model is used to control the speed and yaw rate of the motorcycle. The handling characteristics of the motorcycle are quantitatively analysed, and the impact of torque distribution on energy consumption is considered during straight line and cornering situations. The investigation has shown that only a small improvement in efficiency can be made by transferring a portion of the drive torque to the front wheel. Tyre longevity could be improved by reduced slip energy dissipation

Spherically Symmetric Perturbation of Ultrarelativistic Fluid in Homogeneous and Isotropic Universe

A solution of the linearized Einstein's equations for a spherically symmetric perturbation of the ultrarelativistic fluid in the homogeneous and isotropic universe is obtained. Conditions on the boundary of the perturbation are discussed. The examples of particle-like and wave-like solutions are given.Comment: 8 pages, LaTex, no figure

The set of parameterized k-covers problem

AbstractThe problem of the set of k-covers is a distance measure for strings. Another well-studied string comparison measure is that of parameterized matching. We consider the problem of the set of parameterized k-covers (k-SPC) which combines k-cover measure with parameterized matching. We prove that k-SPC is NP-complete. We describe an approach to solve k-SPC. This approach is based on constructing a logical model for k-SPC

Recent advances in single molecule magnetism of dysprosium-metallofullerenes

This article outlines the magnetic properties of single molecule magnets based on Dy-encapsulating endohedral metallofullerenes. The factors that govern these properties, such as the influence of different non-metal species in clusterfullerenes, the cage size, and cage isomerism are discussed, as well as the recent successful isolation of dimetallofullerenes with unprecedented magnetic properties. Finally, recent advances towards the organization of endohedral metallofullerenes in 1D, 2D, and 3D ordered structures with potential for devices are reviewed

A geometric parameter study of piezoelectric coverage on a rectangular cantilever energy harvester

This paper proposes a versatile model for optimizing the performance of a rectangular cantilever beam piezoelectric energy harvester used to convert ambient vibrations into electrical energy. The developed model accounts for geometric changes to the natural frequencies, mode shapes and damping in the structure. This is achieved through the combination of finite element modelling and a distributed parameter electromechanical model, including load resistor and charging capacitor models. The model has the potential for use in investigating the influence of numerous geometric changes on harvester performance, and incorporates a model for accounting for changes in damping as the geometry changes. The model is used to investigate the effects of substrate and piezoelectric layer length, and piezoelectric layer thickness on the performance of a microscale device. Findings from a parameter study indicate the existence of an optimum sample length due to increased mechanical damping for longer beams and improved power output using thicker piezoelectric layers. In practice, harvester design is normally based around a fixed operating frequency for a particular application, and improved performance is often achieved by operating at or near resonance. To achieve unbiased comparisons between different harvester designs, parameter studies are performed by changing multiple parameters simultaneously with the natural frequency held fixed. Performance enhancements were observed using shorter piezoelectric layers as compared to the conventional design, in which the piezoelectric layer and substrate are of equal length

Optimization of piezoelectric cantilever energy harvesters including non-linear effects

This paper proposes a versatile non-linear model for predicting piezoelectric energy harvester performance. The presented model includes (i) material non-linearity, for both substrate and piezoelectric layers, and (ii) geometric non-linearity incorporated by assuming inextensibility and accurately representing beam curvature. The addition of a sub-model, which utilizes the transfer matrix method to predict eigenfrequencies and eigenvectors for segmented beams, allows for accurate optimization of piezoelectric layer coverage. A validation of the overall theoretical model is performed through experimental testing on both uniform and non-uniform samples manufactured in-house. For the harvester composition used in this work, the magnitude of material non-linearity exhibited by the piezoelectric layer is 35 times greater than that of the substrate layer. It is also observed that material non-linearity, responsible for reductions in resonant frequency with increases in base acceleration, is dominant over geometric non-linearity for standard piezoelectric harvesting devices. Finally, over the tested range, energy loss due to damping is found to increase in a quasi-linear fashion with base acceleration. During an optimization study on piezoelectric layer coverage, results from the developed model were compared with those from a linear model. Unbiased comparisons between harvesters were realized by using devices with identical natural frequencies—created by adjusting the device substrate thickness. Results from three studies, each with a different assumption on mechanical damping variations, are presented. Findings showed that, depending on damping variation, a non-linear model is essential for such optimization studies with each model predicting vastly differing optimum configurations

Variation propagation control in mechanical assembly of cylindrical components

AbstractVariation propagation control is one of the procedures used to improve product quality in the manufacturing assembly process. The quality of a product assembly depends on the product type and the optimization criteria employed in the assembly. This paper presents two assembly procedures of component stacks by controlling variation propagation. The procedures considered are: (i) straight-build assembly by minimizing the distances from the centres of components to table axis; (ii) parallelism-build assembly by minimizing the angular errors between actual and nominal planes. Simulation results are presented for the assembly of four cylindrical components. The results indicate that the variation can be reduced significantly by using these procedures, compared to that without minimization. The results also indicate that the variation not only greatly relies on the assembly procedures, but also on the number of available orientations at the assembly stage. The radial variation increases with the stage for the straight-build assembly, while the angular error decreases with the stage for the parallelism-build assembly. The assembly quality for the two assembly procedures can be improved by increasing the number of orientations. The variation decreases exponentially and monotonically with the number of orientations. The information obtained is useful for manufacturing processes and the assembly modeling

Limits and Possible Consequences of the Development of Agricultural Production: Modeling Agricultural Situations in the Stavropol Territory, USSR

The Food and Agriculture Program at IIASA focuses its research activities on understanding the nature and dimension of the world's food situation and problems, on exploring possible alternative policies which could improve the present situation in the short and long term, and on investigating the consequences of such policies at various levels - global, national and regional -- and in various time horizons. One part of the research activities focussed on investigations of alternative paths of technology transformation in agriculture with respect to resource limitations and environmental consequences in the long term. The general approach and methodology developed for this investigation is being applied in several case studies on the regional level. The reason for the studies is not only to validate the general methodology but also to develop an applicable tool for detailed investigations for a particular region which could then be applied on a number of similar regions. Furthermore, some specific aspects are being addressed in all these case studies which has been initiated within the IIASA's Food and Agriculture Program. This will allow the behavior of various systems to be compared, according to the selected aspects, and analyzed (in different social, economic and natural resource conditions) according to the selected aspects. One of these case studies is of Stavropol, USSR, and covers the whole of this region. This paper describes the first phase of the study, the problems in this region, the aims for solving them, and the first draft of the methodology which is based on the general framework developed at IIASA

Effect of Corbon Content on the Structure and Mechanical Properties of TI-10V-2Fe-3Al Alloy

The effect of carbon content on microstructure and mechanical properties of the transition (α+β)-titanium alloy Ti–10V–2Fe–3Al in a heat-strengthened state was studied. It was established that with the increase of carbon content in the alloy up to the limit of its solubility in a solid solution, the strength of the alloy increases, the plastic characteristics decrease. When the solubility limit of carbon in a solid solution in an alloy is exceeded, the appearance of titanium-based carbide particles was observed, while the strength of the alloy somewhat decreases, due to the decrease of the effect of solid-solution hardening from the elements present in the alloy, which are partially transferred from the solid solution to the titanium-based carbide particles.     Keywords: titanium alloys, titanium carbides, mechanical properties, hardening heat treatment