RF CMOS body-effect circuits

After a theoretical and analytical study of the body effect in MOS transistors, this paper offers two useful models of this parasitic phenomenon. Thanks to these models, a design methodology, which takes advantage of the bulk terminal, allows to turn this well-known body-effect drawback into an analog advantage, giving thus an efficient alternative to overcome the design constraints of the CMOS VLSI wireless mass market. To illustrate the approach, four RF building blocks are presented. First, a 0.9 V 10 dB gain LNA, covering a frequency range 1.8-2.4 GHz, thanks to a body-effect common mode feedback, is detailed. Secondly, a body-effect linearity controlled pre-power amplifier is presented exhibiting a 5 dB m input compression point (ICP1) variation under 1.8 V power supply for half the current consumption. Lastly, two mixers based on body-effect mixing are presented, which achieve a 10 dB conversion gain under 1.4 V for a −52 dB LO-to-RF isolation. Well suited for low-power/low-voltage applications, these circuits implemented in a 0.18 μm CMOS VLSI technology are dedicated to multi-standard architectures and system-on-chip implementations.     

Kinetic study of hydrogen sulfide absorption in aqueous chlorine solution

Hydrogen sulfide (H₂S) is currently removed from gaseous effluents by chemical scrubbing using water. Chlorine is a top-grade oxidant, reacting with H₂S with a fast kinetic rate and enhancing its mass transfer rate. To design, optimize and scale-up scrubbers, knowledge of the reaction kinetics and mechanism is requested. This study investigates the H₂S oxidation rate by reactive absorption in a mechanically agitated gas–liquid reactor. Mass transfer (gas and liquid sides mass transfer coefficients) and hydrodynamic (interfacial area) performances of the gas–liquid reactor were measured using appropriated physical or chemical absorption methods. The accuracy of these parameters was checked by modeling the H₂S absorption in water without oxidant. A sensitivity analysis confirmed the robustness of the model. Finally, reactive absorption of H₂S in chlorine solution for acidic or circumneutral pH allowed to investigate the kinetics of reaction. The overall oxidation mechanism could be described assuming that H₂S is oxidized irreversibly by both hypochlorite anion ClO⁻ (k = 6.75 × 10⁶ L mol⁻¹ s⁻¹) and hypochlorous acid ClOH (k = 1.62 × 10⁵ L mol⁻¹ s⁻¹).     

Effect of Anisotropic Microstructure on the Viscous Properties of an LTCC Material

The sintering behavior of a glass–ceramic (commercial material Ceramtape GC) was characterized using the discontinuous sinter-forging technique. The uniaxial viscosity E ^p and the viscous Poisson's ratio n^p of the composite body were determined as a function of density. Particular attention was paid to microstructural changes in order to quantify the anisotropy induced by load application. Pores and alumina particles were found to be both oriented perpendicular to the applied load direction. Finally, the experimental results were used to predict the value of the hydrostatic sintering stress.     

Strain heterogeneities and local anisotropy in crimped glass wool

A Digital Image Correlation method is used to study a compression test carried out on crimped glass wool samples to determine the displacement field, which reveals strain heterogeneities and further localization. The structure of the wool is locally strongly anisotropic, even though the preferential orientation varies significantly in space. This structure is analyzed using an ad hoc orientation detection tool. It is shown that the strain amplitude can be correlated with texture gradients for this type of material.     

Autonomous car decision making and trajectory tracking based on genetic algorithms and fractional potential fields

Intelligent Service Robotics - This article deals with the issue of trajectory optimization of autonomous terrestrial vehicles on a specific range handled by the human driver. The main...     

Scanning tunnelling microscopy study of activated carbon fibres

Scanning tunnelling microscopy (STM) has been used to study isotropic pitch-based carbon fibres before and after steam activation. The results show that the present carbon fibre precursor exhibits a particulate surface which is very favourable for the formation of activated carbon fibre. After activation, the carbon fibre surface becomes much more porous and rougher, and the mesopores are evidently present on the surface. Because the scale is down to atomic resolution, the STM observations offer direct evidence for the existence of micropores on the surface of the activated carbon fibres. In addition, the surface textures of both fibres are presented and discussed.     

Energy site distribution of carbon black surfaces by inverse gas chromatography at finite concentration conditions

Inverse gas chromatography (IGC) at finite concentration has been used to characterize the surface energy of a series of carbon blacks. It is known that there are many structural defects on carbon black surface and the surface energy is heterogeneously distributed. Using different molecular probes, IGC at finite concentration allows the determination of the surface energy sites distribution.     

Coplanar perturbation of a crack lying on the mid-plane of a plate

Several groups have studied experimentally the deformation of the front of mode I cracks propagating quasistatically along the interface between bonded plates. The theoretical interpretation of such experiments has always been based up to now on a formula of Rice (ASME J Appl Mech 52:571–579, 1985); this formula provides the first-order variation of the local mode I stress intensity factor resulting from some small, but otherwise arbitrary coplanar perturbation of the front of a semi-infinite crack in an infinite body. To be applicable to bonded plates, this formula requires that the characteristic distance of variation of this perturbation in the direction of the crack front be small compared to all other characteristic dimensions of the problem, and first of all the thickness of the plates. This condition is unfortunately frequently violated in practice. The purpose of this paper is therefore to provide a more exact formula for the variation of the local stress intensity factor, for the specific cracked geometry and boundary conditions used in experiments; this should allow for more accurate theoretical interpretations. This is done in two steps. The first one consists in adapting Rice’s (ASME J Appl Mech 52:571–579, 1985) treatment, applicable to the extreme case of plates of infinite thickness, to the other extreme one of plates of infinitesimal thickness, using the standard Love-Kirchhoff plate theory. An interesting outcome of the analysis is that the distance from the crack front to the boundary of the plate acts as a “cutoff length”, in the sense that when the distance between two points on the crack front gets larger than it, the influence of the crack advance at the first point upon the stress intensity factor at the second diminishes quickly; the plate thickness, however, plays no similar role. The second step consists in supplementing the theoretical expressions applicable to extreme values of the plate thickness with finite element computations providing results for intermediate values. These computations lead to the definition of a simple, approximate but accurate “interpolation formula” for the variation of the local stress intensity factor, applicable to plates of arbitrary thickness.     

Cytomegalovirus encephalitis in an immunocompetent adult

Cytomegalovirus encephalitis in immunologically normal patients is rarely reported in the literature. Only seven cases have been previously reported. CMV infection was diagnosed in a 24-year-old, immunologically normal female presenting a severe clinical picture due to encephalitis. Diagnosis was based on detection of CMV DNA in the CSF with the polymerase chain reaction. Administration of ganciclovir was followed by an immediate improvement.