Requirements Scenarios Formalization Technique: N Versions Towards One Good Version

Using a notion of simulation introduced by de Roever et al. [9], we define a corresponding notion of bisimulation which we will use as a test to detect formality discrepancy between two formal versions of the same informal scenario. We will also use it, combined with the relation part of, as a test to detect discrepancy between two formal scenarios describing two different informal scenarios. We will describe a way of implementing these formality discrepancy tests in the work place. We call it N-version technique for scenario formalization. This technique allows us to (1) detect formality discrepancy between formal scenario versions corresponding to the same scenario, to (2) validate, for the given scenario, the formalization obtained by a specifier against another obtained by another specifier before bothering the stake-holder with problems of the specifier's creation (formalization errors), and to (3) detect formality discrepancy between the formal scenarios of different informal scenarios if their respective spaces share at least one component.     

An epidemic of roller-blade injuries in children

Roller blading is a new and increasingly popular leisure activity in many countries. We reviewed 110 consecutive patients with roller-blade injuries between 1 January and 30 June 1996. The patients ranged from 4 to 14 years in age (mean 6.5 years). Eighty-three (75.4%) sustained injuries to the upper limb and 27 (24.5%) injured the lower limb. Fifty-six patients, were girls and 54 were boys. Of the 110 patients, 79 (72.7%) sustained fractures, 28 (25.4%) soft tissue injuries and 3 (2.7%) dislocations. Eighty-three (75.4%) of the patients wore no protective equipment on the limbs. Four months following injury 103 (93.6%) patients were fully recovered. The mean duration of school absence was 3 days. Subsequently 101 children returned to using roller-blades following injury. Seventy-three (66.3%) of these now use protective equipment. We found that injuries were unrelated to age or duration of roller-blading experience or to the brand-name of roller blades used, and that most of our patients wore no protective equipment at the time of injury.     

Fast Fourier and discrete wavelet transforms applied to sensorless vector control induction motor for rotor bar faults diagnosis

This paper presents new techniques to evaluate faults in case of broken rotor bars of induction motors. Procedures are applied with closed-loop control. Electrical and mechanical variables are treated using fast Fourier transform (FFT), and discrete wavelet transform (DWT) at start-up and steady state. The wavelet transform has proven to be an excellent mathematical tool for the detection of the faults particularly broken rotor bars type. As a performance, DWT can provide a local representation of the non-stationary current signals for the healthy machine and with fault. For sensorless control, a Luenberger observer is applied; the estimation rotor speed is analyzed; the effect of the faults in the speed pulsation is compensated; a quadratic current appears and used for fault detection.     

Convective flow and heat transfer in a tall porous cavity side-cooled with temperature profile

Natural convection in an air-filled (Prandtl number = 0.7) porous cavity with profiled side cooling and constant bottom heating is investigated over the Rayleigh number range of 1×10⁴ to 1×10⁸ at two Darcy numbers: 1×10^-4 and 1×10^-6. The aspect ratio based on cavity height was varied from 0.5 to 0.1 to investigate penetration length according to linear or sinusoidal temperature profile. The general non-Darcy model adopted in this work was validated against experimental and theoretical results in the literature and Nusselt number was predicted within less than 3% in the worst case. The effect of left wall imposed temperature profile was investigated in detail. Different convective regimes were observed depending on the imposed profile. An active region was found to take place with the linear temperature profile and with extent proportional to Rayleigh number as predicted by scale analysis.     

Hybrid micro electrostatic actuator

A hybrid micro-electrostatic actuator is presented. The actuator integrates a vertical comb driving (VCD) unit and a parallel-plate driving (PPD) unit. The hybrid actuator is fabricated using a one structural layer microfabrication process, i.e., MetalMUMPs instead of a two-layer microfabrication process needed for traditional vertical comb-drive actuators by taking advantage of the residual stress gradient in the MetalMUMPs nickel layer, which raises the moving parts of the actuator above the substrate after release. The hybrid actuator significantly simplifies the fabrication process for vertical comb-drive actuators, i.e., turning a process requiring two structural layers into a process requiring only one structural layer and thus avoids any misalignment between the two layers. The hybrid actuator can generate larger force and then a larger displacement than the actuator having only the VCD with the same area since no extra space is needed for the PPD unit which uses the moving electrode existing in the VCD unit and a fixed electrode under the VCD unit. The VCD and PPD units in the hybrid actuator are subject to the same driving voltage and work together to pull the moving parts of the actuator downward. A model is established for the hybrid actuator to analyze its displacement. The analytical results show that displacement of the moving part of the hybrid actuator is about half of the gap between the electrodes of the PPD unit. Prototypes are fabricated and tested. With a driving voltage of 150 V, the hybrid actuator achieved a measured displacement of 6.48 µm.     

On the realizability of reynolds stress turbulence closures

The realizability of Reynolds stress models in homogeneous turbulence is critically assessed from a theoretical standpoint. It is proven that a well known second-order closure model formulated using the strong realizability constraints of Schumann (1977) and Lumley (1978) is, in fact, not a realizable model. The problem arises from the failure to properly satisfy the necessary positive second time derivative constraint when a principal Reynolds stress vanishes-a flaw that becomes apparent when the nonanalytic terms in the model are made single-valued as required on physical grounds. More importantly, arguments are advanced which suggest that it is impossible to identically satisfy the strong from of realizability in any version of the present generation of second-order closures. On the other hand, models properly formulated to satisfy the weak form of realizability—wherein states of one or two component turbulence are made inaccessible in finite time via the imposition of a positive first derivative condition—are found to be realizable. However, unlike the simpler and more commonly used second-order closures, these models can be ill-behaved near the extreme limits of realizable turbulence due to the way that higher-degree nonlinearities are often unnecessarily introduced to satisfy realizability. Illustrative computations of homogeneous shear flow are presented to demonstrate these points which can have important implications for turbulence modeling.     

Reduction electrochimique des cetones insaturees—VII. Influence de l'acidite du milieu sur le comportement cathodique des cetosulfones

The ketosulfones are known to be reduced electrochemically, in weakly acidic medium with scission of the CS bond. Nevertheless, in strongly acidic media, the electroactive entity being the protonated form of the carbonyl group, the reaction may lead to pinacols. In the case of γ-ketosulfones, the electroreduction in very weakly protic media is followed by the loss of proton of the acidic substrate due to the effect of electrogenerated bases. This chemical cleavage of the CS bond yields to α-ethylenic ketones reducible at the electrolysis potentiel. On the other hand, for the long chained ketosulfones the reduction may occur through a partial intramolecular electron transfer.     

Cathodic behaviour of p-toluenesulfonamides in organic solvents

Cathodic reduction of several secondary and tertiary p-toluenesulfonamides and gem-N-disulfonamides were investigated by cyclic voltammetry and controlled potential electrolysis at mercury electrode in aprotic and protic dmf. In the cleavage of tertiary p-toluenesulfonamides two Faradays per mole were consummed, resulting in the formation of amine and the sulfinate ion. In the case of secondary p-toluenesulfonamides, electrochemically inactive sulfonamide anions were formed at the electrode surface by acid–base reaction between acidic substrate and electrogenerated bases. Sulfonamides anions were obtained also in the solution bulk with adding strong base and by cathodic cleavage of gem-N-disulfonamides in aprotic media. General reduction mechanisms are postulated and structure effects on the scope of the reduction are discussed for more complex sulfonamides.