Architectural optimization for microelectronic packaging

The aim of this paper is to provide a methodical approach for architectural optimization of power microelectronic devices. Because critical parameters of electronic devices are linked with reliability, architectural optimization, selection of the geometrical parameters of device and optimization of these parameters by iteration method associated by numerical analysis of reliability have to be achieved. In this way, this paper discusses about a methodical and numerical approach for the optimization of reliability in electronic devices, in particular the influence of geometrical parameters on the device reliability.     

Influence of the Cooling Temperature on the Mechanical Behavior of an Oxidized Self-Healing Ceramic Matrix Composite

Composites made of ceramic for both fibers and matrix are aimed at being used in aerospace applications, which means being submitted to mechanical stresses at high temperatures in oxidizing and corrosive environments for long durations. The oxidation/corrosion resistance of these materials is linked to their ability to self-heal by creating an oxide phase which can restrict the access of the oxygen into the bulk of the material. During thermomechanical cycles, the distribution of O₂ inside the material as well as the distribution and the state of the liquid oxides will undergo some modifications. A specific test has been conceived and performed in order to evidence the influence of the viscosity of this oxide on the mechanical properties of the material. Results have shown that the stiffening which is observed seems to be proportional to the increase in the viscosity of the sealing oxide, in conjunction with the decrease in the temperature.     

Synthesis of poly(methyl methacrylate)-g-poly(dimethyl siloxane) graft copolymers via a miniemulsion process

Summary In this article, we describe the synthesis of a PMMA-g-PDMS graft copolymer via a miniemulsion process. A highly hydrophobic PDMS macromonomer was copolymerized in the presence of MMA. Latex particles were obtained with a high yield and a complete incorporation of the macromonomer by using AIBN as initiator, SDS as a surfactant and a PMMA-b-PEO block copolymer as a cosurfactant, with a given amount of methanol in order to reduce the interfacial tension. The characterization of the resulting latex by ¹H NMR and QELS evidenced the interest of such a process in order to copolymerize monomers with very different solubilities and to obtain directly a graft copolymer in aqueous dispersion. Received: 12 March 2001/ Revised version: 15 September 2001/ Accepted: 15 September 2001     

A simple analytical model to study and control azimuthal instabilities in annular combustion chambers

This study describes a simple analytical method to compute the azimuthal modes appearing in annular combustion chambers and help analyzing experimental, acoustic and large eddy simulation (LES) data obtained in these combustion chambers. It is based on a one-dimensional zero Mach number formulation where N burners are connected to a single annular chamber. A manipulation of the corresponding acoustic equations in this configuration leads to a simple dispersion relation which can be solved by hand when the interaction indices of the flame transfer function are small and numerically when they are not. This simple tool is applied to multiple cases: (1) a single burner connected to an annular chamber (N = 1), (2) two burners connected to the chamber (N = 2), and (3) four burners (N = 4). In this case, the tool also allows to study passive control methods where two different types of burners are mixed to control the azimuthal mode. Finally, a complete helicopter chamber (N = 15) is studied. For all cases, the analytical results are compared to the predictions of a full three-dimensional Helmholtz solver and a very good agreement is found. These results show that building very simple analytical tools to study azimuthal modes in annular chambers is an interesting path to control them.     

A reference-calibration method for tenderness perception using psychophysical models

A main advantage of the reference-calibration method is the use of the standard references with the scale values to establish the relationship between sensory and instrumental data which is then used to predict sensory attributes of unknown samples. This study was conducted to predict tenderness perception using instrumental methods through a reference-calibrated model. Chicken breast fillets deboned at 9 different times were cooked and instrumentally tested by a compression test. The fillets were also evaluated by 7 trained panelists. Three different psychophysical models were employed to correlate reference scores with the peak forces and to predict tenderness. The results showed that the Stevens and Beidler models fitted well the peak forces to the reference scores. After calibration, the models were used to predict tenderness scores for all the fillets. This study implied that references could be used to calibrate not only panelists but also instruments for predicting tenderness perception.     

Solid/Liquid Separation of Pig Manure by Biological Flotation: Pilot-Scale Study

Many problems are associated with pig manure production like high biochemical oxygen demand, chemical oxygen demand, nitrogen, and phosphorus contents. Manure produces may be used in land spreading for agricultural purposes. Over application of liquid manure or runoff caused by precipitation contribute notably to surface or overland flow of phosphorus. In this study, the LISOX process is proposed for use in medium size farms, namely a 2,000-head swine farm. The LISOX process uses biological passive flotation, without any gas addition, to enable the flocs to rise to the surface. Results show that this technology is able to considerably reduce the solids content in the final effluent to 1.1±0.3% and reached solids content of 17.9±2.6% in the combined solid manure obtained at the end of the LISOX process. Total phosphorus (Pt) concentrations have been reduced from 1,234±428?mg/L to 146±46?mg/L in the final effluent, while a value of Pt of 20.6±7.9?g/kg has been obtained in the final solid fraction of the treated manure. The initial ammonium ion/total phosphorus ratio of 2.3±1.0 has been increased to respectively 16.4±4.6 and 17.6±5.4 after the primary and the secondary flotation, which is clearly much higher than the target value (NH4/Pt>7).     

Modelling mechanical properties of spruce and Douglas fir timber by means of X-ray and grain angle measurements for strength grading purpose

This study proposes a model using data from a scanner (X-ray and grain angle measurements) to perform strength grading. The research also includes global measurements of modulus of elasticity (obtained by vibrations and ultrasound methods), static bending stiffness and bending strength of 805 boards of Douglas fir and 437 boards of spruce. This model can be used in an industrial context since it requires low computational time. The results of this study show that the developed model gives better results than the global non-destructive measurements of the elastic modulus commonly used in the industry. It also shows that this improvement is particularly higher in the case of Douglas fir than for spruce. The comparison has been made on both the quality of the mechanical properties assessment and on the improvement of the grading process according to the European standards by using different index.     

A MC-CDMA system analysis in a software radio context

This paper presents a Multi-Carrier Code Division Multiple Access (Mc-Cdma) system analysis in a software radio context. Based on a combination of multi-carrier modulation and code division multiple access,Mc-Cdma benefits from the main advantages from both schemes: high spectral efficiency, high flexibility, multiple access capabilities, etc. It is firstly shown why, nowadays,Mc-Cdma is undoubtedly a high potential candidate for the air interface of the 4G cellular networks. TheMc-Cdma concept and the block-diagrams of the transmitter and the receiver are presented first. Afterwards, the technical issues concerning the processing devices for the implementation ofMc-Cdma systems in a software radio context are analysed. The advantages and disadvantages of Digital Signal Processors (Dsps) and Field Programmable Gate Arrays (Fgpas) components are discussed. The implementation ofMc-Cdma systems and the integration of signal processing algorithms as Fast Hadamard Transform (Fht) and Inverse Fast Fourier Transform (Ifft) are considered and analysed for the first time. Finally, implementation results with a mixed prototyping board are presented. Then, it is shown that a new combination of the flow graphs ofFht andIfft leads to interesting computation savings and that hardware structures asFgpas are more adapted thanDsps to those intensive computation functions. Finally, for the completeMc-Cdma modem implementation, the necessity of a Co-Design methodology is highlighted in order to obtain the best matching between algorithms and architecture.     

An improved observation model for super-resolution under affine motion.

Super-resolution (SR) techniques make use of subpixel shifts between frames in an image sequence to yield higher resolution images. We propose an original observation model devoted to the case of nonisometric inter-frame motion as required, for instance, in the context of airborne imaging sensors. First, we describe how the main observation models used in the SR literature deal with motion, and we explain why they are not suited for nonisometric motion. Then, we propose an extension of the observation model by Elad and Feuer adapted to affine motion. This model is based on a decomposition of affine transforms into successive shear transforms, each one efficiently implemented by row-by-row or column-by-column one-dimensional affine transforms. We demonstrate on synthetic and real sequences that our observation model incorporated in a SR reconstruction technique leads to better results in the case of variable scale motions and it provides equivalent results in the case of isometric motions.