Analogue-driven bistable ferroelectric liquid crystals

This paper presents a new driving method allowing fast analogue light modulation with bistable ferroelectric liquid crystals (FLC). The method is evaluated using a functional virtual prototyping design flow. First, a surface stabilized binary FLC cell is modeled in VHDL-AMS language on the basis of well-known theories of FLC. Some physical and environmental phenomena are added (e.g. electronic behavior of the cell, temperature, etc.) in order to improve its reliability. Once the model is validated, a virtual prototype of a FLC pixel is performed by associating the model of the FLC cell and the model of an appropriate wave generator. Simulations show that our new driving method works, but with certain limitations. The most critical one seems to be the high temperature dependence of the pixel response.     

Slug flow in curved microreactors: Hydrodynamic study

The need for eco-friendly and energy saving processes which are substantially compact and give higher efficiency has led to the concept of process intensification (PI). Curved microchannel is such innovative device, which has potential for the intensification of processes currently carried out in conventional straight or T-type microchannels. Curved microchannels utilize the benefits of centrifugal force to its advantage. The present study deals with the numerical simulation of the Taylor flow in curved microchannels, particularly on gas and liquid slugs with varying curvature ratios (i.e., coil to tube diameter=5, 10, 20 and 30). The three-dimensional, unsteady slug flow development in the curved microchannel was carried out using control volume finite difference method (CVFDM). The gas and liquid slug lengths at various operating and fluid conditions were obtained. The slug flow development for different inlet conditions and geometries (premixed feed, T-type and Y-type inlets) was also studied in the curved microchannels. It was found that for low curvature ratio (D/d=3), the phenomenon of flow reversal and slug freezing takes place due to centrifugal and buoyancy forces. For the similar process conditions, with an increase in curvature ratio to 5 and 10, the phenomenon of flow reversal and slug freezing observed was very minor. The non-uniformity in the slug formation was observed for low curvature ratio as compared to the higher curvature ratios. Further the influence of surface tension, viscosity and wall adhesion was studied on slug flow development in the curved microchannels. From the results it was observed that the surface tension, viscosity and wall adhesion have significant influence on slug flow development in curved microchannels.     

Optimization of the gain in Yb^3＋-doped cubic laser crystals of 99.99% purity

This was an outlook on the prediction of the infrared laser potentiality from concentration dependences of the ²F_5/2 experimental decay time in Yb³⁺-doped solid-state crystals mainly on cubic crystals with 99.99% purity which could be extended to laser ceramics of the same composition.     

Etude de la forme temporelle de l’équation intégrale du champ électrique. Application aux antennes

The author is studying the electric field integral equation in the time domain for one and two dimensional surfaces respectively. The equations are solved with the moment method. The algorithms are presented. Special attention is given to their differences and limitations. A few results are presented for canonical cases.     

Fabrication and characterization of fluorescent rare-earth-doped glass-particle-based tips for near-field optical imaging applications

Fluorescent rare-earth-doped glass particles glued to the end of an atomic force microscope tip have been used to perform scanning near-field optical measurements on nanostructured samples. The fixation procedure of the fluorescent fragment at the end of the tip is described in detail. The procedure consists of depositing a thin adhesive layer on the tip. Then a tip approach is performed on a fragment that remains stuck near the tip extremity. To displace the particle and position it at the very end of the tip, a nanomanipulation is achieved by use of a second tip mounted on piezoelectric scanners. Afterward, the particle size is reduced by focused ion beam milling. These particles exhibit a strong green luminescence where excited in the near infrared by an upconversion mechanism. Images obtained near a metallic edge show a lateral resolution in the 180-200-nm range. Images we obtained by measuring the light scattered by 250-nm holes show a resolution well below 100 nm. This phenomenon can be explained by a local excitation of the particle and by the nonlinear nature of the excitation.     

Mechanisms of scale formation and carbon dioxide partial pressure influence. Part II. Application in the study of mineral waters of reference

In the first part, we have designed a new model of evolution for the calco-carbonic system which includes the hydrated forms of CaCO3: CaCO3 amorphous, CaCO3 x 6H2O (ikaite) and CaCO3 x H2O (monohydrate) (J. Eur. Hydr. 30 (1999) 47). According to this model, it is the precipitation of one or other of these hydrated forms which could be responsible for the breakdown of the metastable state. After this first step, the precipitates evolve to dehydrated solid forms. Through the elaboration of computer programs in which the CaCO3(0) (aq) ion pair formation was considered, this model was compared to experimental data obtained by the critical pH method applied to synthetic solutions. In the present article, the same method was applied for four French mineral waters, at 25 degrees C under study. Three samples formed a precipitation during the sodium hydroxide addition. For these three cases, this precipitation began for the CaCO3 H2O saturation. The added volume of sodium hydroxide was more than what was required for neutralizing free CO2 initially in solution. These results indicate that during a spontaneous scaling phenomenon, the pH rises at the same time by loss of the initial free CO2 and of the one produced by the hydrogen carbonate ions decomposition. Then we calculated, at various temperatures for the three studied scaling waters: CO2 partial pressures and loss of total carbon corresponding to the solubility products of CaCO3 hydrated forms. The results show that the partial pressure monitoring of the carbon dioxide is important in managing the behavior of scaling waters.     

CHM: an annotation- and component-based hypervideo model for the Web

Hypervideos are hypermedia documents that focus on video content. While they have long been deployed using specialized software or even hardware, the Web now offers a ground for them to fit into standardized languages and implementations. However, hypervideo design also currently uses very specific models limited to a single class of documents, or very generic hypermedia models that may not appropriately express their specific features. In this article we describe such features, and we introduce CHM, an annotation-driven and component-based model to conceptualize hypervideos through a high level operational specification. An extensible set of high level components is defined to emphasize the presentation and interaction features modeling, while lower level components offer more flexibility and customization opportunities. Being annotation-based, the model promotes a clear separation between video content/metadata and their various potential presentations. We also describe WebCHM, an implementation of CHM with standard Web technologies that provides a general framework to experiment with hypervideos on the Web. Two examples are provided as well as a preliminary usage study of the model and its implementation to validate our claims and proposals.     

Pendubot: combining of energy and intuitive approaches to swing up,stabilization in erected pose

The objective of this paper is to define a strategy for the swing up of a double-link pendulum and its stabilization in the unstable equilibrium state with both erected links. The first joint of this double-link pendulum, which is the suspension joint, is actuated and the second joint is passive. This double-link pendulum, usually called pendubot, is an underactuated system. The double-link pendulum is straightened during the energy boosting process. The swing up control switches to the balancing mode at the instant when the system comes to the basin of attraction. The limits on the torque amplitude are taken into account. The gains of the saturated balancing control are chosen to ensure the basin of attraction as large as possible. Simulation results demonstrate that our strategy is efficient.     

Processing, repairing and cyclic oxidation behaviour of sol–gel thermal barrier coatings

Sol–gel Thermal Barriers Coatings (TBCs) are manufactured using the dip-coating technique optimised in terms of process parameters including sol formulation, rate of withdrawing and heat treatment. The specific mechanisms of sol–gel TBCs, deposited on either NiAl or NiPtAl bond-coated superalloy substrates, are described. The possibility to reinforce and stabilise the crack network formed during the heat treatment or the first oxidation cycles using supplementary dip-coatings and appropriate process parameters is investigated. It is shown that implementing this technique that can be further regarded as an attractive way for repairing TBCs, significantly improves the cyclic oxidation behaviour of the multi-materials systems.