Search results for "business.product_category"
showing 10 items of 376 documents
Crowdfunding in Africa: Opportunities and Challenges
2020
AbstractThe chapter presents the current state of crowdfunding research and practice in Africa while outlining opportunities and challenges associated with them. Conditions of growing popularity of digital and mobile finance, low penetration of traditional financial institutions, and a long cultural heritage of communal mutual support may enhance crowdfunding uptake. On the other hand, conditions of unclear regulation, relatively low levels of internet access, and societies characterized by low social trust may all hinder crowdfunding uptake. Accordingly, African crowdfunding is at its infancy and involves transitory hybrid practices of early adoption, often involving reliance on foreign co…
Cutting Vibrations
2008
Chapter 8 provides comprehensive engineering knowledge regarding cutting vibrations, their typical sources in machining operations, and methods of their elimination to prevent negative influence on the surface finish (chatter marks). The classification of cutting vibrations including free, forced, and self-excited vibrations is discussed, and all possible sources and mechanisms of all types of cutting vibrations are specified and characterized. The regeneration of surface waviness, which is the predominant mechanism of chatter, is outlined for turning and milling operations. The stability of machining operations based on the stability lobe diagrams is highlighted and their practical applica…
Characterisation of nonoriented electric alloys under nonconventional conditions
1996
The variations of magnetic and loss characteristics of nonoriented cobalt-iron and silicon-iron sheets have been investigated using an Epstein frame. Cobalt-iron alloys have been tested under sinusoidal magnetic flux density with respect to frequency and temperature. Both kinds of alloys have also been investigated with respect to frequency, time constant wavefront and temperature under trapezoidal flux density. The qualitative behaviour is identical under both flux density conditions for all these alloys. These investigations have made it possible to model the variations of iron losses with experimental parameters, except the temperature. These quantitative evolutions differ with alloy and…
Yeasts and Sparkling Wine Production
2019
Sparkling wines are produced in many different countries. Among sparkling wines, some are produced from Charmat or bottle fermentation. In this chapter, the practical methods and principles of producing quality sparkling wine is given in details including each step of the production from viticultural parameters, base wine production up to secondary fermentation. After the second fermentation in bottle, the wine is aged on lees. During aging, yeast autolysis occurred. The mechanisms of yeast autolysis and the compounds released are presented. The consequences of yeast autolysis on wine quality are detailed. Finally the riddling and disgorging operation are presented
Potentialities of microfibers for non linear optics
2010
Micro- and nanofibers present attractive optical properties and may be used in a variety of structures and devices. We report in this work the first global study on the non linear properties of these microfibers: an adequate source is built and its characteristics are described, our first results with a silica loop resonator are presented. Third harmonic generation is obtained in these conditions, however, the low intrinsic non linear index prevents the generation of large non linear effects. The use of highly non linear materials, such as soft glasses, is therefore discussed, with their potentialities and the challenges their integration with standard microfibers represent.
Aspects Regarding the Modelling of Geometric and Strength Calculations of Worm Gears Using CAD Applications
2020
The new processes of plastic deformation of the gears eliminate some of the shortcomings of the old methods of their manufacture, while reducing the production costs and the time of production in series. This scientific paper addresses the issue of worm gears. The focus has been on geometric and strength calculations for this type of gear, using different CAD applications. The use of these applications substantially reduces the time before the actual development of the processing activities, as well as the early encounter of possible problems.
Sub-nanosecond nonlinear pulse shaping in microfiber resonators
2009
Thanks to their small size and large index contrast allowing for tight field confinement, optical microfibers are of great interest in nonlinear optics. Their properties have recently been exploited in various devices for supercontinuum generation, pulse compression [1] and third-harmonic generation [2]. Combining field confinement and field enhancement in a loop or knot resonator can result in low-threshold non-linear microfibre devices, in which pulse shaping effects and bistability can be obtained. Such a behaviour has already been observed at a power level of ten milliwatts with millisecond time response, in the case of thermally-induced non-linearity in silica microfibres [3]. In contr…
Slow and fast nonlinearities in microfiber resonators
2008
Nonlinear optical properties of microfiber resonators are investigated. First, a miniature optical resonator standing in air is realized out of a silica microfiber, and measurements of the intensity transfer function show a wide variety of hysteresis cycles obtained at low scanning frequency of the input power. The results are satisfactorily interpreted through the action of thermally-induced nonlinear phase shifts. Secondly, we discuss the conditions under which the fast Kerr nonlinearity can be used efficiently in microfiber resonators under pulsed optical operation.
Bistable Device based on the Kerr Effect in a Microfiber Resonator
2007
We propose a bistable device based on the Kerr effect in a microfiber resonator. Our simulations show that low switching powers (in the order of a few tens of mW) are expected with tellurite microfibers.
Demonstration of a reef knot microfiber resonator.
2009
We propose a new way to realize a microfiber optical resonator by implementing the topology of a reef knot using two microfibers. We describe how this structure, which includes 4 ports and can serve as an add-drop filter, can be fabricated. Resonances in an all-silica reef knot are measured and good fits are obtained from a simple resonator model. We also show the feasibility of assembling a hybrid silica-chalcogenide reef knot structure.