Quasilinear theory of collisionless Fermi acceleration in a multicusp magnetic confinement geometry

Particle motion in a cylindrical multiple-cusp magnetic field configuration is shown to be highly (though not completely) chaotic, as expected by analogy with the Sinai billiard. This provides a collisionless, linear mechanism for phase randomization during monochromatic wave heating. A general quasilinear theory of collisionless energy diffusion is developed for particles with a Hamiltonian of the form $H_0+H_1$, motion in the \emph{unperturbed} Hamiltonian $H_0$ being assumed chaotic, while the perturbation $H_1$ can be coherent (i.e. not stochastic). For the multicusp geometry, two heating mechanisms are identified --- cyclotron resonance heating of particles temporarily mirror-trapped in the cusps, and nonresonant heating of nonadiabatically reflected particles (the majority). An analytically solvable model leads to an expression for a transit-time correction factor, exponentially decreasing with increasing frequency. The theory is illustrated using the geometry of a typical laboratory experiment.Comment: 13 pages (.tex file, using REVTeX), 11 figures (.eps files). Sep. 30: Word "collisionless" added to title, abstract and text slightly revised in response to referee's comments (to be published in Phys. Rev. E

Le rôle du récepteur scavenger B type I, SR-BI, dans l'absorption et le métabolisme du cholestérol au niveau intestinal

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Automatic Datapath Abstraction Of Pipelined Circuits

Pipelined circuits operate as an assembly line that starts processing new instructions while older ones continue execution. Control properties specify the correct behaviour of the pipeline with respect to how it handles the concurrency between instructions. Control properties stand out as one of the most challenging aspects of pipelined circuit verification. Their verification depends on the datapath and memories, which in practice account for the largest part of the state space of the circuit. To alleviate the state explosion problem, abstraction of memories and datapath becomes mandatory. This thesis provides a methodology for an efficient abstraction of the datapath under all possible control-visible behaviours. For verification of control properties, the abstracted datapath is then substituted in place of the original one and the control circuitry is left unchanged. With respect to control properties, the abstraction is shown conservative by both language containment and simulation. For verification of control properties, the pipeline datapath is represented by a network of registers, unrestricted combinational datapath blocks and muxes. The values flowing through the datapath are called parcels. The control is the state machine that steers the parcels through the network. As parcels travel through the pipeline, they undergo transformations through the datapath blocks. The control- visible results of these transformations fan-out into control variables which in turn influence the next stage the parcels are transferred to by the control. The semantics of the datapath is formalized as a labelled transition system called a parcel automaton. Parcel automata capture the set of all control visible paths through the pipeline and are derived without the need of reachability analysis of the original pipeline. Datapath abstraction is defined using familiar concepts such as language containment or simulation. We have proved results that show that datapath abstraction leads to pipeline abstraction. Our approach has been incorporated into a practical algorithm that yields directly the abstract parcel automaton, bypassing the construction of the concrete parcel automaton. The algorithm uses a SAT solver to generate incrementally all possible control visible behaviours of the pipeline datapath. Our largest case study is a 32-bit two-wide superscalar OpenRISC microprocessor written in VHDL, where it reduced the size of the implementation from 35k gates to 2k gates in less than 10 minutes while using less than 52MB of memory

Actuated MOEMS Micro-Mirror based on PMN-PT Piezoelectric Material.

International audienceThis paper investigates the use of a PMN-PT [001] piezoelectric actuator to be integrated in smart Micro-Opto-Electrical-Mechanicals Systems (MOEMS). Unlike most piezoelectric materials, PMN-PT [001] can generate large-stroke out-of-plane displacement. This is due to its very high longitudinal piezoelectric coefficient of tu to 4500 pm/V. After an introduction on MOEMS actuation and a short description of the Reconfigurable Free Space Micro-Optical Bench (RFS-MoB) in which the studied actuator may be included is presented, a bulk actuator is proposed. FEM simulations are then presented highlighting some tradeoffs : increased displacement with the reduction in size while decreasing the optical aberration. It was observed that for actuators with a smaller surface than 800 x 800 µm2 and 200 µm thick, displacement larger than 325 nm is largely achievable and that the size of the usable area of the actuator varies in size with the applied voltage

Cavitation Erosion Tests Performed by Indirect Vibratory Method on Stainless Steel Welded Samples with Hardened Surface

The paper presents the results of cavitation erosion tests performed on two types of samples. The materials of the samples are frequently used for manufacturing and repairs of the hydro turbines components submitted to cavitation. The first sample was made by welding of an austenitic stainless steel on austenito-feritic base material. The second sample was made similarly with the first but with a martensitic base material. After the welding processes, on both samples was applied a hardening treatment by surface peening. The cavitation erosion tests were performed on vibratory equipment using the indirect method with stationary specimen. The results show a good cavitation erosion resistance on both samples

Breaking with the coupled engine

Studies on driving led to the conclusion that many drivers stop the engine or switch off the ignition while driving in order to save fuel and this entails dangerous consequences. In fact the experimental determinations performed prove that the best braking is by having the ignition on; it reduces the braking distance, it avoids locking up the tires by keeping at the same time the vehicle stability

The Environmental Remediation of Clark Island − A Former AlliedSignal Inc. Site

Clark Island is a 63 ha island located in Lake St-Francis, part of the St-Lawrence River, Québec, Canada. Since the early 40s the island has been used for the production of mineral acids by its fanner owner, Allied Chemicals Limited. Acidic wastes were placed over large portions of the island. The presence of these waste materials together with contaminated soils was identified as a potential threat to the nearby river water quality as well as to the underlying bedrock groundwater quality. A major remedial investigation and feasibility study was initiated in 1987. The approved scope of the remediation project included the construction of one 60,000 m3 single lined cell for the placement of contaminated soils, and one 130,000 m3 double lined cell for the placement of acidic wastes. The remediation project was implemented during the 1991-1993 period. In order to assess the efficiency of the remediation, a detailed environmental monitoring program was implemented during the works and in the following years. The general conclusion of this major project is that confining acidic wastes in lined cells provide a safe and economical way to avoid detrimental consequences to the environment

Duo-bimorph actuator made of PMN-PT [011] : 3D modeling, development and characterization.

International audienceThis paper reports the development of a duo-bimorph cantilevered actuator made of PMN-PT material and intended for large-stroke micro-scale manipulation. The principle of operation is piezoelectric, but with a series of material-induced particularities: PMN-PT is reputed for its very high piezoelectric and electromechanical coupling characteristics, but exhibits a lower coercive field which prevents driving in a fully bipolar manner. Instead of the uniaxial [001] plate, by using the anisotropic [011] cut, a positive transverse d31 piezoelectric coefficient may be exploited. This allows the extension of the structure with the applied voltage, which is particularly beneficial for micro-gripping. After an introductory part in piezo-materials and duo-bimorph structures, a comprehensive static three-dimensional displacement modeling is provided by means of constitutive matrix equations. The actuator micro-manufacturing is presented, followed by the experimental characterization. Compared to the classical PZT structures, the actuation is increased by a factor of two, up to 600 μm in the transversal plane and up to 20 μm longitudinally. Some perspectives related to 3 DoF (Degrees of Freedom) micro-manipulation tasks are finally approached

Contributions regarding the study of the braking system of cars

Braking process of a vehicle is complex, giving possibility to the driver to reduce car’s speed or to stop it at big speed in a short distance. Using the diagrams registered for the different working conditions, defined accordingly with the experimental plan, there have been analyzed the values of deceleration, variation of speed and the covered space for each specified moment of braking. As result of the experimental researches, we have reached the conclusion that a good behavior at cars braking is registered when the diagrams of deceleration variation in relation with braking time have a symmetric shape

RETAINED SURGICAL SPONGE IN A DOG: CLINICAL ASPECTS AND SURGICAL APPROACH

Although retained surgical sponges are rarely reported, their clinical aspect can sometimes vary and therefore, the diagnosis can be challenging. An eight-year-old mixed breed dog was brought in for a skin lesion on the lateral abdominal wall that appeared nine weeks previously, which could not be treated even though both local and general therapy had been carried out. During antibiotic administration, the dog’s condition improved, but once the treatment was completed, the wound and secretions started to reappear. Diagnosis of a retained surgical gauze was based on history, clinical signs, radiological examination and confirmed by surgical exploration. This article aims to describe the clinical and surgical findings of this pathology, which appeared four years after the surgical procedure, in order to disseminate knowledge about the complications that may occur if negligence, disorganisation or lack of emergency protocols exists