7,104 research outputs found
L'ordre et le désordre dans les matériaux, Ed. F. Reynaud, N. Clement, J.J. Couderc, 1984
No full textPetiau Jacqueline. L'ordre et le désordre dans les matériaux, Ed. F. Reynaud, N. Clement, J.J. Couderc, 1984. In: Bulletin de Minéralogie, volume 108, 5, 1985. p. 734
L'ordre et le désordre dans les matériaux, Ed. F. Reynaud, N. Clement, J.J. Couderc, 1984
No full textPetiau Jacqueline. L'ordre et le désordre dans les matériaux, Ed. F. Reynaud, N. Clement, J.J. Couderc, 1984. In: Bulletin de Minéralogie, volume 108, 5, 1985. p. 734
Direct visualization of bimodal-propagation-induced spatial self-imaging
No full textWe exploit silica defects photoluminescence for directly visualizing the self-imaging arising from the interference of LP01 and LP11 modes of a bimodal optical fiber. This provides a length-independent method to determine the fiber cut-off
Dielectric relaxation phenomena of UV-cured epoxy systems treated with layer-by-layer nanosilica assemblies
No full textThis work focuses on dielectric relaxation phenomena of hybrid organic-inorganic epoxy systems obtained through the application of a Layer-by-Layer (LbL) silica assembly on a UV-cured epoxy system, based on the copolymerization of a cycloaliphatic diepoxy monomer (namely 3,4-epoxycyclohexylmethyl-3',4'-epoxy-cyclohexane carboxylate-CE) with a flexibilizing comonomer (1,6-hexanediol diglycidyl ether-HDGE). More specifically, UV-cured HDGE/CE films (containing 30 wt.% CE) were LbL treated by 10 and 20 silica bilayers (positively charged/negatively charged) on both sides. The dielectric properties of the LbL treated films were investigated and compared to those of the untreated counterparts, using broadband dielectric spectroscopy over a wide range of frequencies (10 -1 Hz-1 MHz) and over a temperature span ranging from 173 to 373 K. The frequency dependence of the dielectric losses for the analysed films allowed to highlight three relaxation peaks, associated with molecular motions of the polymer chains (γ, β and α), which turned out to evolve as a function of temperature. Furthermore, the thermal properties obtained using thermogravimetric analysis and differential scanning calorimetry have been assessed. The results were correlated with the structural morphology of the copolymer film with the nanosilica bilayers
Observation of supercontinuum spiral emission in optical fibers
No full textIn this work, we reveal that when using femtosecond pump pulses, one has access to a different regime, where the peak power inside the MM fiber may reach and even surpass the critical power Pcr for catastrophic self-focusing (this is about 10 MW in fused- silica). When these peak power levels are reached, the propagating light beam undergoes a so-called filamentation phenomenon, leading to the so-called conical emission (CE)]. In our experiments, we report for the first time the formation of a supercontinuum spiral emission (SSE), where the spectral components of the output beam are spatially separated in the far-field emitted at the fiber output
Infrared light power transmission limitation of optical fibers
No full textLuminescence from silica defects is associated with a multiphoton absorption mechanism, responsible for strong nonlinear losses in graded-index multimode optical fibers. Our experiments reveal the existence of a fundamental limitation to the power transmission capabilities of optical fibers
Cooperative performance measurement proposal (a test with the cooperfic© tool for wine cooperatives in Languedoc-Roussillon)
No full textPurpose: French wine cooperatives show differences of corporate objectives, but also common ones with private wine merchants, as they face a common economic environment. The traditional controlling and financial models do not seem adequate to measure ‘sustainable social economy’ performances advocated by the cooperatives’ philosophy. The main difficulty is that their specific corporate governance introduces competition between short term maximum payments to their grape suppliers-patrons and long term investment potentials. How, therefore, facing this “cooperative dilemma”, should they balance these conflicting objectives, and which performance measurement specificities should wine cooperatives adopt? Design/methodology: In order to try and answer this question, the design of an adapted data base appears to be necessary. It should take into account the apparent antinomy of the cooperatives’ short term and long term objectives, in the context of an economically sustainable development. An original economic and financial measurement model is proposed, and we test it with COOPERFIC?, a decision-aid tool for wine cooperatives, based upon a specially constructed data base in Languedoc-Roussillon. Findings: The exploratory results obtained from the test of an original performance measurement model on an ad hoc sample of wine cooperatives lead to new insights into cooperative performance and to some useful guidelines in terms of cooperative governance. Results show how the conflict between their short term and long term performances could be balanced, in order for this specific type of firm to reach its economic and social objectives Practical implications: A conjoint short and long term economic indicators approach illustrates the necessary balance in the cooperative governance, and constitutes a performance measurement model answering some of these wine cooperatives’ Board and management questions ...French Abstract : Propos: Les caves coopératives françaises font apparaître des points de divergence, mais aussi de convergence avec les négociants en vin, en matière d’objectifs d’entreprise, dans la mesure où elles font face au même environnement économique. Toutefois, les modèles traditionnels financiers et de contrôle de gestion ne semblent pas adaptés à la mesure des performances d’une économie sociale durable, dont les valeurs sont portées par la philosophie coopérative. La principale difficulté réside dans le fait que leur mode de gouvernance spécifique entraîne un conflit permanent entre la rémunération maximale à court terme des vignerons coopérateurs et les capacités d’investissement à long terme. Aussi, face à ce « dilemme coopératif », comment les entreprises coopératives viticoles doivent-elles concilier ces objectifs conflictuels et quels types de mesures de performance spécifiques devraient-elles adopter ? Design/méthodologie: Afin d’arriver à répondre à cette double question, la conception d’une base de données spécifique apparaît nécessaire. Elle se doit de prendre en compte l’apparente antinomie des objectifs à court terme et à long terme des coopératives, dans le cadre d’un développement économique durable. Un modèle de mesure de performance économique et financière est ici proposé et testé à l’aide de l’outil d’aide à la décision COOPERFIC?, spécifique aux caves coopératives du Languedoc-Roussillon. Résultats: Les résultats exploratoires provenant du test d’un modèle original de mesure de la performance sur un échantillon ad hoc de caves coopératives conduit à de nouvelles perspectives en matière de performance coopérative, ainsi qu’à des conseils utiles ayant trait à la gouvernance. Ces résultats montrent la façon dont le conflit entre performances à court terme et à long terme pourrait être maîtrisé en vue d’atteindre les objectifs économiques et sociaux de ce type particulier d’entreprise. Implications managériales: Une approche conjointe des indicateurs économiques à court et long terme illustre le nécessaire équilibre à trouver en matière de gouvernance coopérative et constitue un modèle de mesure de la performance répondant à un certain nombre de questions relatives au conseil d’administration et au management général des coopératives.WINE COOPERATIVES; GOVERNANCE; PERFORMANCE MEASUREMENT; INDICATORS; LANGUEDOC ROUSSILLON; FRANCE
Multiphoton-Absorption-Excited Up-Conversion Luminescence in Optical Fibers
No full textWe experimentally demonstrate a previously unforeseen nonlinear effect in optical fibers: up-conversion luminescence generation excited by multiphoton absorption of femtosecond infrared pulses. We directly estimate the average number of photons involved in the up-conversion process, by varying the wavelength of the pump source. We highlight the role of nonbridging oxygen hole centers and oxygen-deficient center defects and directly compare the intensity of side-scattered luminescence with numerical simulations of pulse propagation
Multiphoton absorption excited upconversion luminescence in multimode optical fiber
No full textShedding light on nonlinear loss occurring close to multimode optical fiber damage threshold, we demonstrate that multiple photons are absorbed by material defects and upconverted to shorter wavelength luminescence. An array of blue emitting points results from the spatial self-imaging in graded-index fibers
- …
