101 resultados para Pinning force
Resumo:
The present work explores the impact of α precipitates on β recrystallization following hot deformation of Ti-5Al-5Mo-5V-3Cr with grains larger than 1 mm. A single hot rolling pass of 36 pct reduction was conducted on an aged microstructure containing α precipitates at a temperature well below the β transus temperature. After annealing, a uniformly recrystallized structure with a grain size of ~100 µm is formed. The prior β grain boundaries can be readily identified and it is seen that the primary β grains have been replaced by grains displaying a spread of correlated misorientation angles extending up to the highest allowable values. The annealing comprises two stages. The first stage involves normal β subgrain growth limited by the Zener pinning force of the unstable α precipitates. The second stage corresponds to the onset of β recrystallization at the point where the Zener pinning force drops due to dissolution of the α precipitates. This leads to a uniform distribution of site saturated recrystallization nuclei.
Resumo:
We have measured forces between molecularly smooth solid surfaces separated by thin films of molten polydimethylsiloxane. We show that a long-range repulsion reported in earlier work is not an equilibrium force, but can be attributed to viscous drag effects. Consistent with previous results, the viscosity of the film can be modeled by assuming that a layer of polymer molecules is immobilized or ‘‘pinned’’ at each surface for a time longer than the time scale of the measurements. We propose that this pinning is a result of entanglement-like effects in the vicinity of a wall.
Resumo:
The purpose of this article is to consider whether or not the use of excessive force in effecting an arrest makes the arrest ipso facto unlawful at common law. With a dearth of appellate court authority on point in either Australia or the United Kingdom, the question is presently open. It is my argument that as force is not a minimum condition of an arrest, its excessive use will not, therefore, make unlawful an otherwise lawful arrest. This conclusion is a matter of some import. It exposes an arrester to civil and possibly even criminal liability for assault but not to an action for false imprisonment. It may also have practical repercussions for the possible discretionary exclusion of evidence on public policy grounds. In theory, it should not matter whether excessive force made an arrest unlawful or not, for the public policy discretion permits a judge to exclude evidence illegally or improperly obtained. But common sense suggests that a judge may not be so likely to exclude evidence when the relevant conduct amounts only to police impropriety not illegality.
Resumo:
A force model was developed for crankshaft pin grinding to predict the forces generated during grinding. The force model developed builds on the authors’ previously developed model, which predicted the out-of-roundness in crankshaft pin grinding. The model includes key grinding variables, such as the work removal parameter (WRP), system sti€ ness and Young’s modulus to determine the end forces produced. The model also includes the important geometrical relationships that are unique to this type of grinding. The model was veriŽ ed using an experiential set-up involving sophisticated strain gauge force measurements on a commercial Landis CP grinding machine, with close correlation between the results and the model.
Resumo:
Z-pinning is a newly developed technique to enhance the strength of composite laminates in the thickness direction. Recent experimental and theoretical studies have shown that z-pins significantly improve mode I and mode II fracture toughness. In practice, buckling accompanying delamination is a typical failure mode in laminated composite structures. For a complete understanding of the z-pinning technique towards improvements of the overall mechanical properties of laminated composites, a numerical model is developed in this paper to investigate the influence of z-pins on the buckling composite laminates with initial delaminations under edge-wise compression. The numerical results indicate that z-pinning can indeed effectively increase the compressive strength of the composite laminates provided that the initial imperfection is within a certain range. The magnitude of the improvement is consistent with available experimental data.
Resumo:
Accurate prediction of the roll separating force is critical to assuring the quality of the final product in steel manufacturing. This paper presents an ensemble model that addresses these concerns. A stacked generalisation approach to ensemble modeling is used with two sets of the ensemble model members, the first set being learnt from the current input-output data of the hot rolling finishing mill, while another uses the available information on the previous coil in addition to the current information. Both sets of ensemble members include linear regression, multilayer perceptron, and k-nearest neighbor algorithms. A competitive selection model (multilayer perceptron) is then used to select the output from one of the ensemble members to be the final output of the ensemble model. The ensemble model created by such a stacked generalization is able to achieve extremely high accuracy in predicting the roll separation force with the average relative accuracy being within 1% of the actual measured roll force.
Resumo:
Cooperative control of multiple mobile robots is an attractive and challenging problem which has drawn considerable attention in the recent past. This paper introduces a scalable decentralized control algorithm to navigate a group of mobile robots (swarm) into a predefined shape in 2D space. The proposed architecture uses artificial forces to control mobile agents into the shape and spread them inside the shape while avoiding inter-member collisions. The theoretical analysis of the swarm behavior describes the motion of the complete swarm and individual members in relevant situations. We use computer simulated case studies to verify the theoretical assertions and to demonstrate the robustness of the swarm under external disturbances such as death of agents, change of shape etc.
Resumo:
Introduction:
Injuries sustained by Australian Defence Force (ADF) personnel during non-combat military training and sports activity are associated with increasing costs due to work days lost, medical treatment, compensation, and early retirement. In 2001, the ADF commissioned a systematic review of the evidence-base for reducing injuries associated with physical activity, while at the same time improving physical activity participation rates to sustain a trained, fit and deployable workforce.
Method:
Literature from on-line library databases, relevant unclassified military reports, and material from previously published sport-specific injury countermeasure reviews were systematically and critically analysed to address the study aims.
Results:
Modification of intensity, frequency and duration of basic military training activities and improved equipment is likely to reduce injury occurrence. Sports injury countermeasures used for the civilian population have merit for the ADF physical activity program. Injury countermeasures should be designed to minimise any possible deterrent effect on the motivation to participate in regular physical activity. Increasing the participation of ADF personnel in physical activity in the presence of evidence-based injury prevention strategies has the potential to increase health, fitness and deployability with minimal impact on injury frequency.
Conclusion:
Recommendations arising from the review include injury intervention trials in basic military training and sports. These and other interventions should be supported by refinement to ADF injury surveillance systems. Research should focus on interventions with the greatest gain for fitness, deployability, and cost effectiveness.
Resumo:
Throughout the early 1990s the formal curriculum across all Australian States and Territories was re-organised to accommodate a Key Learning Area (KLA) focus. The KLA approach to schooling marked a departure from an historical reliance on individualised school subjects as the organisers of disciplinary knowledge. Indeed a KLA structure has the potential to promote interdisciplinary teaching and learning, a focus on the skills, values, attitudes and knowledge students are to learn and to break away from the sometimes divisive subject subcultures that permiate schools. In short the potential for a KLA 'movement' of positive benefit to teaching and learning exists.
Over the last decade however, the impact of the 'KLA movement' on teacher practice has become more apparent. Far from being a force for pedagogical change, some KLAs are merely re-badged versions of traditionalist conceptions of school subject and knowledge. This paper draws on data from a study of New South Wales (NSW) history and Human Society and Its Environment (HSIE) teachers and provides an evidenced argument about the use and misuse of Key Learning Areas.