Browse

11 - 20 of 486 items :

  • Geosciences x
Clear All

Abstract

The results of studies of the crushing process in a double toggle jaw crusher are presented. This process was carried out on six sets of crushing plates. The first three of them are used in industrial crushers – plates with a flat working surface and a triangular profile (in this work, under consideration were profiles with teeth angle γ = 90°). The fourth and fifth type refer to plates with a variable pitch t and teeth height with a triangular shape of the teeth. In the sixth solution, plates with variable pitch and width of the wedged teeth are proposed.

The results of the basic process parameters are shown, that is, average degree of fineness n, technical performance Wt, crushing energy L and crushing force F, sieve analysis of crushing product. The obtained results are the basis for the assessment of the suitability of various types of plates, especially plates with a new profile, which have an altered shape in comparison with the plates used in crushers so far.

The crushing tests were carried out with the same dimension of outlet slot er = 24 mm, close to the pitch size for plates with triangular profile. Tests were performed on the “Mucharz” sandstone. Samples from a series of blocks of different size and geometric shape were prepared. This work also presents feed mass influence on crushing process efficiency.

The plates with variable pitch and width of teeth are beneficial because of lower crushing force and energy.

Abstract

Water infiltration through coal stocks exposed to weather elements represents a key issue for many old mining sites and coal-fired power plants from the environmental point of view, considering the negative impact on human health of the deriving groundwater, soil and air pollution. Within this context, the paper investigates the hydraulic behaviour of a self-weight compacted unsaturated coal mass and its impact on the numerical prediction of infiltration induced by rainfall events. In particular, the work focuses on the experimental investigation carried out at different representative scales, from the grain scale to physical modelling. The material, when starting from uncompacted conditions, seems to be characterized by metastable structure, which tends to collapse under imbibition. In addition, direct numerical predictions of the seepage regime through a partially saturated coal mass have been performed. As the compaction of the coal stock induced by dozers has not been taken into account, the numerical simulations represent a conservative approach for the assessment of chemical pollution hazard associated to water infiltration into a real stockpile under operational conditions.

Abstract

The problem of numerical simulation of the material interface response under monotonic and cyclic loading is of fundamental scientific and engineering importance. In fact, such interfaces occur in most engineering and geotechnical structures. The present work is devoted to the deformational response analysis of contact interfaces under monotonic and cyclic loads. The class of materials includes rock and structural joints, soil structure interfaces, masonry and cementitious joints, localized shear bands and so on.

The aim of the proposed model is to simulate the cyclic shear test under constant normal load. The associated dilatancy effect is associated with the configurational effects of asperity interaction or dilatancy of wear debris layer. The large primary asperities are assumed as responsible for interfacial dilation and small size asperities as governing frictional sliding and hysteresis response. The elliptic loading yield function is assumed to translate and rotate during progressive or reverse loading events. The model formulation is discussed and confronted with experimental data.

Abstract

This paper focuses on the setup of axial bearing capacity of open ended tubular steel piles that are used for offshore foundation systems such as those of wind turbines. A comparative evaluation of the most commonly used models for setup prediction shows an upper estimate bound and a lower estimate bound, which correspond approximately to a setup rate of 60% increase per log cycle of time and 20% increase per log cycle of time, respectively. This finding is validated with the results of case histories reported in literature, which show that the setup values of most case histories considered lie in the best estimate zone between the upper estimate zone and the lower estimate zone. The analysis results show a minimum setup factor of approximately 1.5 for 100 days following end of driving of open-ended tubular steel pile driven in sand.

Abstract

This paper presents a laboratory study of the combined effect of the water content and fines content on the mechanical behaviour of Chlef sand in a medium dense state (RD = 65%) and dense state (RD = 80%). Several mechanical parameters were evaluated such as shear strength, cohesion and friction angle at different water content w = 0, 1, 2 and 3% and different fines content Fc = 0, 10, 20, 30 and 40%. The test results showed that the shear strength of Chlef sand decrease with the increase fines content Fc = 0 to 40%, our tests result also showed that the water content has a significant influence on the shear strength which decreases with the increase in the water content w = 0 to 3%. The fines content and the water content have a significant influence on the mechanical parameters c and φ. Cohesion increases with the percentage of fines and decreases with the increase of the water content while the friction angle decreases with the increase the fines content and the water content.

Abstract

The allelopathic potential of essential oil extracts from Artemisia herba-alba Asso. was assessed on seed germination of nine weeds and two wheat varieties. The samples were collected from El-Rasfa région (Sétif, Algeria). The essential oil was extracted using hydrodistillation of aerial part and characterized using gaz chromatography coupled with mass spectroscopy. The bioassays with organic solvent (ethanol) were tested using four different concentrations (0.2, 0.4, 0.6 and 0.8 µl/ml of oil/ethanol) on seed and seedling growth of the nine weeds and two wheat varieties. The yield obtained is 1.19%, and 36 compound had been identified. The main components are: camphor (28.58%), cis-thujone (22.03%), eucalyptol (11.65%) and trans-thujone (7.03%). The results of bioassays show that essential oil extracts has a significant effect on seed germination and seedling growth of the major weed tested and two wheat varieties. In conclusion, this study shows that the essential oil tested has an interesting allelopathic potential.

Abstract

The experiment was conducted at the level of a pilot farm located in eastern Algeria under a humid bioclimatic stage, during two successive crop years. The study focused on a F1 generation of barley (Hordeum vulgare L.) consisting of twelve hybrids from a complete diallel cross between the two locals varieties (Saida and Tichedrett) and two other introduced varieties (Nadawa and Fouara). The aim was to determine the value of parental genotypes as genitors and to analyze their descendants, while evaluating the phenotypic variability of ten quantitative variables. Analysis of the variance revealed a significant difference for the whole of parameters studied in the parents as in their descendants. Additive and non-additive effects are involved in the genetic control of the analyzed variables. The Hayman model (1954) seems acceptable for five variables on ten variables studied for which additive effects are more important than dominance effects. The analysis of the heterosis effect was significant for the characters tested. For the productivity of the plant, eight hybrids on twelve have expressed a positive heterosis compared to the mid- parent, six combinations on twelve have registered a positive heterosis compared to the over-batter parent and compared to the best variety with an overall heterosis of 17.53%.

Abstract

This study was conducted to evaluate anti-acetylcholinesterase and insecticidal and antifungal activities of the endophytic fungus Trichoderma sp, isolated from Ricinus communis L. leaves, against Locusta migratoria L. and Botrytis cinerea Pers.: Fr.. To evaluate the insecticidal and antifungal activities, different concentrations of the fungal extract were applied against L. migratoria (0.2, 0.3, 0.4 g/l) and against B. cinerea (1, 2, 3 g/l). It was found that the mortality of the targeted insects was positively proportional to fungal extract concentration and time after exposure (24, 48, 72 hours). The concentration 0.4 g/l appeared to be the most effective after 72 hours with mortality rate of 56.52%. Regarding antifungal activity, the concentration 3 g/l was the most effective against B. cinerea after 7 days, with an inhibition rate of 92.06% (excellent antifungal activity). Moreover, it was found that at 4 ug/ml the fungal extract had a maximum inhibitory capacity of Ache of 80% for acetylcholenesterase. Preliminary phytochemical analyses revealed the presence of alkaloids, flavonoids, phenols and saponins. In addition the colony of this endophytic fungus produced chitinases and proteases, which explained its important antifungal and insecticidal activities.

Abstract

Certain phenolics have been recognized to possessing antibacterial and antifungal activities and high levels of flavonoids and tannins have been reported in several varieties of Sorghum bicolor (L.) Moench. Antimicrobial activity and phenolics contents were investigated in five Algerian sorghum seeds. AS20 sorghum extract showed the highest levels of: total phenolics (3214.46±263.64 mg/100 g), flavonoids (32.03±1.64 mg/100 g) and tannins (615.35±6.10 mg/g) contents; however, comparable flavonoids content was recorded in I27 extract. FZ40 and AS12 flavonoids contents were comparable. Screening for antimicrobial activity, carried out by the disc’s diffusion method revealed an antimicrobial potential of sorghum crude extracts against Gram-positive and Gram-negative bacteria and candida albicans yeast. Minimal inhibition concentration determined by microdilution method varied between 0.2 and 2 mg/ml. the lowest value was recorded with F11 and FZ40 extract against Streptococcus pneumoniae and F11 against Escherichia coli. Bacillus subtilis, Staphylococcus aureus ATTCC6538 and MRSA strains showed sensitivity to all extracts. The results show these sorghums as a potential source of natural anti-streptococcal, anti-staphylococcal and anti-candida substances.

Abstract

The chloroform and ethyl acetate extracts obtained from the aerial parts of Anthriscus vulgaris Bernh. were analyzed by gas chromatography-mass spectrometry (GC-MS). 36 components have been identified in each extract. The major constituents were 1-monooleoylglycerol (20.72%), caffeic acid (15.20%), cinnamic acid (11.31%) and benzene acetic acid (10.95%). The phytochemical study led to the isolation and structural elucidation of three compounds, scopoletin, umckalin and 1-(3’,4’-dihydroxycinnamoyl) cyclopentane-2,3-diol. Moreover the ethyl acetate extract was screened for its possible in vitro antioxidant activity by 2,2-diphenyl-1-picrylhydrazy l(DPPH) and lipid peroxidation inhibition assays in which it displayed a noticeable activity. This study provides the first biological and chemical investigation on Anthriscus vulgaris Bernh. in Algeria.