ДЛИТЕЛЬНАЯ ПРОЧНОСТЬ ПЛИТЫ ИЗ КОМПОЗИТА ПОЛИЭСТЕР-ДЕРЕВО

Работа посвящена разработке методики моделирования длительного поведения многослойных композитных конструкций под постоянными сложными нагрузками. Конкретно рассматривается вопрос об оценке длительной прочности некоторой модели из композита стеклопластик-дерево по критерию длительной прочности Гольденблата-Копнова. Рассматриваемая модель является ортотропной трехслойной плитой типа «сэндвич», верхний и нижний слои которой выполнены из стеклотекстолита КАСТ-В, а средний слой - дерево (сосна).Исследование показало, что для подобного типа конструкции использование упомянутого критерия прочности возможно

Caractérisation du matériau bois de structures utilisé en construction par la méthode vibratoire : une technique de mesure non destructive

Le présent article décrit une nouvelle méthode non destructive de caractérisation des poutres de structures en bois. Basée sur l’excitation par vibrations, la méthode développée est fondée sur la théorie de Bernoulli et Timoshenko. Elle a été appliquée aux types de bois lamellé-collé, Laminated Veener Lumbers ainsi qu’aux composites en I, pour les règles de conception, de calculs de dimensionnement et de suivi de leur endommagement. Sur la base d’un vaste programme expérimental de caractérisation des poutres de ces différents types de bois, la comparaison des modules élastiques a été effectuée entre les valeurs estimées par la méthode vibratoire et celles fournies par la méthode statique fondée sur la mesure de la flèche relative. Les résultats obtenus mettent en évidence que la mesure du module d’élasticité par la méthode dynamique non destructive proposée peut être retenue pour caractériser les poutres en vue de la détermination des niveaux de charge des essais de comportement différé et de la durée de vie, deux facteurs phénoménologiques très importants qui, à ce jour, ne sont pas assez clarifiés dans les règles régissant les calculs des poutres à base de bois de grandes dimensions.Mots-clés : vibrations, poutres de structures, durée de vie, flexion circulaire.Characterization of structural wooden beams by vibratory method : a nondestructive technique of measurement This paper describes a new non-destructive characterization method for structural wooden beams. Based on vibrations exciting, the developed method is based on Bernoulli and Timoshenko theory. It has been applied to the lamellate-stuck types, Laminated Veener Lumbers and I composites types, for their design rules, calculations and damage monitoring. Based on an extensive experimental program of beams characterization for such different wood types, comparison of elastic modulus was made between estimated values from vibrations method and those provided by the static method funded on relative arrow or flitch measurement. The obtained results show that elasticity modulus measurement with the proposed nondestructive dynamic method can be used for wood beams characterization, in view of determination of loading levels during delayed behavior testing and lifespan studying, two very important phenomenological factors that, to date, are not sufficiently clarified in the governing rules for larger wood beams calculation.Keywords : vibrations, structures’ beams, lifespan, circular bending

Evaluation of the Mixed Effects of Some Indigenous Strains of Arbuscular Mycorrhizal Fungi on the Growth of Maize Seedlings Under Greenhouse Conditions

The objective of the study was to evaluate the joint effects of three groups of native arbuscular mycorrhizal fungi (AMF) (Glomeraceae, Acaulosporaceae and Diversisporaceae) on the growth of Maize Seedlings. The mycorrhizal fungi were isolated by the wet sieving method through decreasing sieve (300 µm, 125 µm, 63 µm and 38 µm) followed by centrifugation on a sucrose gradient. The growth tests were evaluated in greenhouse conditions for 40 days. After opening a planting hole, two maize (2000 SYNEE-W) seeds, one coated with AMF and the other not coated (Control) were introduced into the planting hole for each treatment. Data on different parameters were evaluated. The results of this study revealed that the maximum heights, the largest noose diameters and the largest numbers of leaves were obtained with treatment "Acaulosporaceae + 50% NPK-Urea" having 20.55% and 17.04% respectively and 11.77% for that of the control. The produced biomass and the leaf area of the maize plants were improved by the treatment "Glomeraceae+ 50NPK-Urea" with a respective increase of 54.97% for fresh above biomass (FAB), 42.94% for fresh underground biomass (FUB) and 55.23% for the leaf area compared with the control. Also, very high frequency of mycorrhiza was recorded with treatment "Glomeraceae" while the largest numbers of mycorrhiza spores and intensity were recorded with treatment "Acaulosporaceae". These results augur the possibility of using these mixed AMF bio-products as organic fertilizers to improve maize productivity in Benin

Effet de la fréquence de récolte et des milieux de dilution sur la qualité du sperme de taureau de race Borgou

La présente étude a pour but d’évaluer la production et la qualité de sperme de 17 taureaux Borgou. L’expérimentation a été réalisée sur la base des séances de récolte tous les 4 jours, pendant 36 jours au cours desquels l’efficacité in vitro de six milieux de dilution sur la motilité et la vitalité des spermatozoïdes (spz) a été testée pendant 28 jours. Les résultats ont montré que la fréquence de récolte expérimentée n’affecte pas la qualité des éjaculats qu’on pourrait utiliser pour l’insémination artificielle à l’état frais (+5 °C). L’effet des différents dilueurs sur la motilité et la viabilité des spermatozoïdes, a prouvé que ces spermatozoïdes supportaient moins bien le milieu à base de lait de coco que ceux à base de jaune d’oeuf et de lait de vache. Cependant, tous les milieux de dilution testés peuvent être utilisés pour conserver les semences +5 °C durant 48 heures. La durée de conservation peut être étendue à 72 heures pour le lait de vache et le jaune d’oeuf.Mots clés: Sperme, insémination artificielle, dilueurs, éjaculats, bovin, Beni

Influence des rations alimentaires a base d’asticots sur la reproduction des poulets locaux au Benin

La productivité des poules nourries avec des rations alimentaires à base de la farine d’asticots a été évaluée sur une durée de 10 semaines. Au total, 36 poulets locaux âgés de 26 semaines répartis suivant l’homogénéité de leurs poids corporel en six lots, à raison de cinq poules pour un coq par lotont été élevés dans une basse-cour. Un dispositif complètement randomisé avec deux traitements R8 et R12 composées respectivement de 8 % MS et 12 % MS de la farine d’asticots et trois répétitions par traitement a été utilisé. La croissance de deux lots de 15 poussins chacun, nourris avec la ration R8 a été mesurée pendant quatre semaines. Le nombre moyen d’oeufs pondu était 13,46 ± 2,06 (R8) et 11,08 ± 0,70 (R12) oeufs par poule, avec des taux d’éclosion estimés à 82,19 ± 3,38 % (R8) et 75,37 ± 4,26 % (R12) (p > 0,05). Les poussins issus des poules nourries avec R12 ont présenté le meilleur gain de poids (p < 0,05). Les deux rations impactent positivement la productivité des poules et la performance pondérale des poussins, montrant que les asticots peuvent valablement substituer la farine de poisson dans l’alimentation de la volaille au Bénin. Mots clés : Bénin, poulets locaux, farine d’asticots, poussins sevrés.   English Title:Influence of maggot-based diets on the reproduction of local chickens in Benin The productivity of hens fed diets based on maggots meal was evaluated over a period of 10 weeks. A total of 36 26-week-old local chickens, distributed according to the homogeneity of their body weight in six batches, at the rate of five hens for one rooster per batch, were reared in a farmyard. A completely randomized device with two treatments R8 and R12 composed respectively of 8% DM and 12% DM of maggot meal and three repetitions per treatment was used. The growth of two batches of 15 chicks each, fed with the R8 ration was measured for four weeks. The average number of eggs laid was 1346 ± 206 (R8) and 1108 ± 070 (R12) eggs per hen, with hatching rates estimated at 8219 ± 338% ( R8) and 7537 ± 426% (R12) (p> 005). Chicks from hens fed R12 showed the best weight gain (p <005). The two rations positively impact the productivity of the hens and the weight performance of the chicks, showing that maggots can validly replace fishmeal in the feeding of poultry in Benin. Keywords: Benin, local chickens, maggot meal, weaned chick

Mycorrhizal Symbiosis for Sustainable Optimization of Tropical Agriculture: A Review of Research

Excessive application of chemical fertilizers and other agrochemicals can cause significant imbalances in soils and agricultural ecosystems. To minimize these impacts, biofertilizers and organic fertilizers are needed to maintain a sustainable production system. The use of subterranean microorganisms in agriculture to stimulate plant growth and improve yields has recently received increasing interest. In this context, mycorrhizae represent a viable solution to mitigate these adverse effects. Mycorrhizal fungi are able to form a symbiotic relationship with the roots of plants in the environment. Mycorrhizal fungus helps the plant to absorb nutrients and water. In addition, mycorrhizal fungi play a crucial role in storing carbon (C) in the soil. Most previous studies have just considered the effects of AMF species on a specific crop in one particular area but have not assessed the balance of AMF in production systems in tropical agriculture. This consideration should allow for the optimization of cropping practices through a review of the work on the use of AMF in tropical agriculture production systems. In this paper, we will discuss, through different examples of experiments carried out in the tropics, the performance of different strategies for managing the potential of AMF to maintain a sustainable production system

Measurement and comparison of individual external doses of high-school students living in Japan, France, Poland and Belarus -- the "D-shuttle" project --

Twelve high schools in Japan (of which six are in Fukushima Prefecture), four in France, eight in Poland and two in Belarus cooperated in the measurement and comparison of individual external doses in 2014. In total 216 high-school students and teachers participated in the study. Each participant wore an electronic personal dosimeter "D-shuttle" for two weeks, and kept a journal of his/her whereabouts and activities. The distributions of annual external doses estimated for each region overlap with each other, demonstrating that the personal external individual doses in locations where residence is currently allowed in Fukushima Prefecture and in Belarus are well within the range of estimated annual doses due to the background radiation level of other regions/countries

Effet De La Technologie, Du Cultivar Et De La Durée De Conservation Sur La Stabilité Et La Qualité Du Lait De Soja (Glycine maxima)

Three technologies named D (wet dehulled soybeans seeds), B (boiled soybean seeds before dehulling) and T (roasted soybean seeds before dehulling) for stabilized soymilk production were tested with TGX (large grain size) and Jupiter (small grain size) cultivars. Production yields, sensory, physicochemical and microbiological characteristics of produced milks were determined over a period of 3 months. . The bottled milk was sterilized at a temperature of 115°C under a pressure of 0.7 bar for one hour. The milks were stored at temperature storage place 27°C (for 3 months). The milk yield for technology D is 90.87 % for the jupiter and 92.01 % for the TGX. These yields are higher than the other technologies. Whatever the technology, the TGX cultivar gives a better yield 92.01 %. Sensory analysis revealed that the milk produced with technology D and jupiter cultivar is more appreciated by the 77 % panelist. This milk has a pH of 7.14 at the day of production and decreases to 6.83 after 3 months of storage. Protein, fat and Dry Soluble Matter (DSM) content decreased after storage by 4.30 to 4.13 %, 1.7 to 1.2 % and from 11.68 to 10.28 °Brix respectively. The viscosity was 1.24 cp at the beginning and 1.38 cp after storage. After 3 months of storage, the milk is stable and its microbiological quality complies with accepted standards in relation to spores, coliforms, yeasts and molds