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A bondingness term is further developed to aid in heat of formation (ΔfHº) calculations for C, N, O and S containing molecules. Bondingness originated from qualitative investigations into the antibonding effect in the occupied MOs of ethane. Previous work used a single parameter for bondingness to calculate ΔfHº in an alkane homologous series using an additivity scheme. This work modifies the bondingness algorithm and uses the term to parameterise a test group of 345 molecules consisting of 17 subgroups that include alkanes, alkenes, alkynes, alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, amines, amides, diazenes, nitriles, nitroalkanes, nitrates, thiols and benzenoids. Comparing experimental with calculated ΔfHº values, a standard deviation for the residuals of 6.3 kJ mol 1 can be achieved using bondingness with a simple steric repulsion term (SSR) in a bond additivity scheme, and a standard deviation of 5.2 kJ mol 1 can be achieved using a Lennard-Jones potential. The method is compared with the group method of Pedley, which for a slightly smaller set of 338 molecules, a subset of the test set of 345 molecules, gives a standard deviation of 7.0 kJ mol 1. Bondingness, along with SSR or a Lennard-Jones potential, is parameterised in the lowest level of ab initio (HF-SCF) or semiempirical quantum chemical calculations. It therefore may be useful in determining the ΔfHº values for the largest molecules that are amenable to quantum chemical calculation. As part of our analysis we calculated the difference between the lowest energy conformer and the average energy of a mixture populated with higher energy conformers. This is the difference between the experimental ΔfHº value and the ΔfHº calculated for a single conformer. Example calculations which we have followed are given by Dale and Eliel et al.. Dale calculates the energy difference for molecules as large as hexane using relative energies based on the number of 1,4 gauche interactions. We have updated these values with constant increments ascertained by Klauda et al. as well as ab initio MP2 cc-pVDZ relative energies and have included calculations for heptane and octane.

Cette thèse s'articule autour du concept "système de vision à base de rétine électronique". Le travail de cette thèse porte plus particulièrement sur la conception et la réalisation d'un capteur d'image CMOS logarithmique avec une fonction de compensation on-chip du BSF (Bruit Spatial Fixe). Les expériences récentes montrent qu'un capteur d'image ayant une réponse logarithmique, similaire à celle de l'œil humain, est très adapté pour des applications de vision. Cette réponse logarithmique donne non seulement un signal image directement proportionnel au contraste optique mais aussi une plage dynamique de fonctionnement très étendu liée à la compression opérée par la fonction logarithmique.<br />L'un des principaux problèmes dans un capteur d'image logarithmique, est le BSF. Ce bruit réduit la qualité de l'image et limite l'utilisation de ce type de capteur dans des applications de vision. Dans cette thèse, nous avons exploré une structure radicalement différente de celle utilisée par beaucoup d'autres chercheurs : utilisation d'une photodiode en mode photovoltaïque plutôt qu'en mode photoconducteur. Cette photodiode combinée avec un transistor d'initialisation permet de générer un signal de référence noir dans n'importe qu'elle condition lumineuse. Cette nouvelle approche ouvre la voie à une compensation on-chip du BSF simple et efficace. Ce photorécepteur a été intensément étudié dans cette thèse. Un circuit prototype a été conçu et fabriqué dans une technologie CMOS standard 0,8um via le service CMP français. Il a été entièrement testé et caractérisé. Le résultat expérimental a non seulement validé les prédictions théoriques mais aussi a démontré une bonne qualité de l'image et aussi une bonne sensibilité en condition de faible illumination. Certains problèmes de conception et phénomènes électriques ont été également étudiés dans cette thèse. Des solutions proposées à ces problèmes peuvent être intéressantes pour les concepteurs et les chercheurs dans ce domaine. A la fin, quelques questions en suspens sur le capteur d'image logarithmique ont été soulignées et des directions de recherche correspondantes ont été précisées.

Voice over IP (VoIP) is a real time application that allows transmitting voice through the Internet network. Recently there has been amazing progress in this field, mainly due to the development of voice codecs that react appropriately under conditions of packet loss, and the improvement of intelligent jitter buffers that perform better under conditions of variable inter packet delay. In addition, there are other factors that indirectly benefited VoIP. Today, computer networks are faster due to the advances in hardware and breakthrough algorithms. As a result, the quality of VoIP calls has improved considerably. However, the quality of VoIP calls under extreme conditions of packet loss still remains a major problem that needs to be addressed for the next generation of VoIP services. This thesis concentrates in making an analysis of the effects that network impairments, such as: delay, jitter, and packet loss have in the quality of VoIP calls and approaches to solve this problem. Finally, we analyze the impact of introducing forward error correction (FEC) Piggybacking and Reed Solomon codes for VoIP. To measure the mean opinion score of VoIP calls we develop an application based on the E-Model, and utilize perceptual evaluation of speech quality (PESQ).

he influence of two levels of yeast cell wall on phase one laying hen performance was investigated in this study. A total of 75 Lohmann W-36 replacement pullets, 17-weeks-old, were distributed among 75 laying hen cages (1 bird per pen). A total of 3 treatments were sequentially assigned to pens and each treatment had 25 replicates. Feeds were prepared according to the management guide for those birds and a single basal diet was divided into three treatments. First was the control basal diet only with no feed additives. The second was the basal diet supplemented with 250 ppm of yeast cell wall (YCW 250) and the third treatment was the basal diet supplemented with 500 ppm of yeast cell wall (YCW 500). Individual birds per cage served as the experimental unit for this study. Feed and water were offered ad libitum. Data were collected when birds were 21 weeks old and hen day egg production was > 90%. Treatment YCW 250 resulted in significantly higher egg weight than the control and YCW 500 treatment in the first and second production period and was higher than YCW 500 in the third and fourth production period. Feed consumed per dozen eggs was significantly lower in treatment YCW 500 versus treatment YCW 250, but not significantly lower than the control for the first production period and all treatments were not different from each other for the rest of the study. Average feed consumed per bird per day, and monthly cumulative egg production was not different between treatments. Period feed conversion ratios were lower for the second and fourth period (P = 0.15 and 0.18 respectively). There was no treatment effect on interior egg quality except for yolk color for the YCW 500 treatment in the fourth period which had significantly higher Roche color scores than the YCW 250 treatment. Specific gravity, egg shell thickness, egg shell weight, and percent shell weight were significantly higher in hens fed YCW 500 versus YCW 250. Egg shell breaking force was significantly higher in hens fed YCW 250 versus the control group. Overall, feeding a diet supplemented with yeast cell wall improved laying hen performance and 250 ppm YCW had the most significant influences, particularly with respect to increasing egg weight in early production laying hens.

In this study, metal-oxide-semiconductor (MOS) capacitances were prepared with rf magnetron sputtering of Ta2O5 on both n-type GaN and p-type GaN. And metal-insulator-semiconductor (MIS) capacitances were prepared with conjugated rigid-rod polymers PBT on n-type GaN. The processes of fabrication the diodes were shown, and the structures of MOS/MIS diodes were represented. Hysteresis was observed in high-frequency capacitance-voltage (C-V) measurements. And the hysteresis was changed with different scanning delay time on scanning step. They were ascribed to mobile charges and interface charges. The carrier concentration were calculated and compared with the Hall results. The flatband voltage and threshold voltage were calculated and compared with C-V curves which were measured.

Aim of this work was, to investigate the preparation of Si NC memories by sputter deposition. The milestones are as follows: - Review of relevant literature. - Development of processes for an ultrathin tunnel-oxide and high quality sputtered SiO2 for use as control-oxide. - Evaluation of methods for the preparation of an oxygen-deficient silicon oxide inter-layer (the precursor of the Si NC layer). - Characterization of deposited films. - Establishment of techniques capable of probing the phase separation of SiOx and the formation of Si NC. - Establishment of annealing conditions compatible with the requirements of current CMOS technology based on experimental results and simulations of Si NC formation. - Preparation Si NC memory capacitors using the developed processes. - Characterization of these devices by suitable techniques. Demonstration of their memory functionality.

Reproduction de : Thèse de doctorat : Electronique : Reims : 2004. / Titre provenant de l'écran titre. Bibliogr. p. 187-191.

Thèse de doctorat : Dispositifs de l'Electronique Intégrée : Villeurbanne, INSA : 2002. / Titre provenant de l'écran-titre. Bibliogr. p. 221-230.

Reproduction de : Thèse de doctorat : Conception de circuits micro-électroniques et micro-systèmes : Toulouse, INPT : 2006. / Titre provenant de l'écran-titre. Bibliogr. 120 réf.