A l'aide de la connexion déterminée par un repère quasi orthonormé, on étudie les surfaces isotropes de défaut 1 (notées V²(1)) incluses dans une variété lorentzienne. Différentes définitions afférentes à ces surfaces sont données, par exemple les courbures de Lipschitz-Killing, les formes de torsions, les surfaces V²(1) doubles isotropes. Les surfaces V²(1) dont la forme de torsion est nulle sont des réglées à génératrice isotrope et à lignes de courbures confondues et la qualité pour un pareil type de surface V²(1) d'être double isotrope (de défaut 1) entraîne la propriété d'être une développable cylindrique.
Concerns over the past few decades have focused, more than ever, on finding and implementing efficient, handy, and renewable sources to reduce pollution. Biomass, in general, and biomass from annual vine cuttings, are renewable sources that can be used by a large amount of the population. Biomass densification in the form of briquettes is an efficient method of obtaining a biofuel with the same characteristics as wood. The production of densified material as a briquette consists of sampling, drying naturally, chopping, grinding and briquetting the vine cuttings. The obtained results showed that the size of the briquettes met the requirements imposed by the standard, with a length between 185 mm and 400 mm and a diameter of 58 ± 0.75 mm, the humidity of the briquettes varying between 5.42%, at Sauvignon Blanc and 7.98% for Pinot Noir, while the durability of the briquettes registered minimum values of 98.17% for Muscat Ottonel and a maximum of 99.14% for Feteasca Neagra, and a unit density with values between 1227 kg/m3 for Feteasca Alba and 1389 kg/m3 for Pinot Noir. The conclusions of these experiments are promising, showing that the densification of biomass from vines cuttings qualifies within the standard requirements for obtaining a valuable biofuel.
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