مجله بین المللی علوم و فناوری کشاورزی
سال:1386 | دوره: | شماره: |تعداد مقالات:9

A non-linear finite element model could be a useful tool in the development of a method of predicting soil pressure-sinkage behaviour, and can be used to investigate and analyze soil compaction. This study was undertaken to emphasize that the finite element method (FEM) is a proper technique to model soil pressure-sinkage behaviour. For this purpose, the finite element method was used to model soil pressure-sinkage behaviour and a two-dimensional finite element program was developed to perform the required numerical calculations. This program was written in FORTRAN. The soil material was considered as an elastoplastic material and the Mohr-Coulomb elastoplastic material model was adopted with the flow rule of associated plasticity. In order to deal with material nonlinearity, incremental method was adopted to gradually load the soil and a total Lagrangian formulation was used to allow for the geometric non-linear behaviour in this study. The FEM model was verified against previously developed models for one circular footing problem and one strip footing problem and the finite element program was used to predict the pressure-sinkage behaviour of the footing surfaces. Statistical analysis of the verification confirmed the validity of the finite element model and demonstrated the potential use of the FEM in predicting soil pressure-sinkage behaviour. However, experimental verification of the model is necessary before the method can be recommended for extensive use.

Knowledge of the aerodynamic properties of agricultural materials is needed in equipment design for operations such as pneumatic conveying in loading/unloading operations of corn silage into/from silos. While considerable information is available on seed grains, little is known about the aerodynamic behavior of corn (Zea mays L.) silage. In this research, the weighed mean terminal velocity of a sample representative of the entire bulk mass was determined using Wolf and Tatepo’s method. The terminal velocity of various particle types (leaf, stalk and corncob pieces) of chopped forage corn plants, which were kept in silo for six months, at different moisture contents (40-50, 50-60 and 60-70% w.b.) was also studied. The terminal velocity was determined by measuring the air velocity required to suspend a particle in a vertical air stream using a wind tunnel. A 3 × 3 factorial treatment arrangement with 30 replications in a completely randomized design was used to study the effect of moisture content and particle type on the terminal velocity. The mass mean terminal velocities of the corn silage at 40-50, 50-60 and 60-70% moisture contents were 7.1, 7.3 and 7.8 m/s, respectively. The results showed that only the effect of particle type on the terminal velocity of corn silage was significant. The mean values of the terminal velocity of corn leaf, stalk and cob pieces were 3.8, 6.8 and 8.8 m/s, respectively. For each particle type at given moisture content, the terminal velocity was best described by means of the equation of velocity squared in terms of weight.

A systematic parasitological examination was carried out on 266 freshwater fish specimens, belonging to 11 species, from Northwest of Iran during the period from Summer 2001 to Summer 2002. Twelve parasite species including Diplostomum spathaceum, Allocreadium isoporum, Ligula intestinalis, Digrama sp., Caryophylleus laticeps, Rhabdocona hellichi, Eustrongylides excisus, Argulus foliaceus, Lamprolegna compacta, Myxobolus musayevi, M. cristatus, and Neoechinorhynchus rutili were isolated and identified. It was concluded that Sander lucioperca, Albornoides bipunctatus, Capoeta capoeta, Carassius carassius and Barbus capito were five new hosts for those parasites in Iranian freshwater fishes. Furthermore, Myxobolus cristatus is recorded for the first time among Iranian freshwater fishes. All the parasites were collected from natural waters, but these rivers form a very important water reservoir in this area and these parasites can injure cultured fishes under certain conditions.

The phenolic compounds of pomegranate (Punica granatum L.) peel extracted by two methods (solvent and ultrasound-assisted) with five solvents (acetone, methanol, ethanol, water and ethyl acetate) were compared with supercritical fluid extraction (SFE). The total phenolic compounds were determined according to the Folin-Ciocalteu reagent using tannic acid as standard. The overall results showed that acetone with sonication produced the maximum amount of phenolic compounds from pomegranate peel extracts (PPE). Furthermore, the effect of the acetone extract of pomegranate peel (0.010-0.050 %) on the stability of soybean oil during heating at 60oC (oven test method) was determined by measuring peroxide and thiobarbitoric acid values. At a 0.050 % level of pomegranate peel extract, its antioxidant activity was greater than 0.02 % of the two synthetic antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The pomegranate peel extract possessed a relatively high antioxidant activity and might be considered as a rich source of natural antioxidant.

Forest classification on the basis of satellite images is a promising technique both for primary map production and for map updating and forest monitoring. For accurate forest classification into three classes, using mapping by canopy cover density “high spatial resolution satellite images have to be used in order to obtain the required spatial detail” [Schneider, 1999]. At the same time, the spectral information necessary for identifying certain class types can most economically be derived from multi-spectral images of medium spatial resolution. Fusion techniques have to be used to combine information from both sources. In this paper, a method was developed for object-level fusion of IRS-1C/1D pan images (5.8 m pixel size) and LANDSAT TM multispectral images (30 m pixel size) and subsequent classification to produce a canopy cover classification of the northern forests of Iran. The study area is located in Sari and its forest regions in 60,000Hec. (Figure 1) The individual processing steps included segmentation of a multi-band image consisting of both the high-spatial-resolution pan image band and medium-spatial-resolution multispectral bands, with proper weighting of the individual bands in the segmentation procedure in order to obtain both fine detail from the pan image and coarser boundary delineations which show up only in multispectral images. For classification, fuzzy logic membership functions were used. Verification of the classification was carried out and checked with error matrix and kappa calculation on a selected transect from a newly classified map. The results showed that employing object-based fusion procedure using medium- and high-resolution data was an appropriate method that improved classification. Comparing the hard work of creating a new topographic map, a pixel-based fusion procedure was demonstrated to be an acceptable method to create a satellite image map (Satmap) for visual monitoring activities and programs. The overall accuracy of the map produced was calculated as a topo-map of the region.

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a significant insect pest of wheat worldwide. The objective of this study was to assess the genetic variation within and between F2-derived families for reaction to RWA using F3 and F4 families originating from individual F2 plants of a cross between the susceptible line (synthetic hexaploid-11) and the resistance cultivar (‘Halt’). The RWA damage of individual plants within each family was measured using different procedures. Their reaction types were combined into a single data for each individual family (derived from an individual F2 plants) and subjected to statistical analysis. Results indicated that the genetic variation between F2-derived families is greater than within F2-derived families for RWA resistance. Broad-sense heritability of RWA resistance, calculated by partitioning phenotypic variation into genetic and environmental components, was 73.2%. A narrow-sense heritability estimate of 30% was obtained for the RWA resistance in the ‘Halt’ × synthetic hexaploid-11 cross using parent-offspring (F3: F4) regression procedure.

The chitinase producing ability of Pseudomonas fluorescens strains viz., PF1, PB2 and FP7 was evaluated in a culture medium with and without a chitin source. The addition of 1% (v/v) chitin in culture medium significantly increased the bacterial population and chitinase activity. Among three strains tested, FP7 responded well to the addition of chitin by producing 31.2% increased chitinase in culture. Western blot analysis with chitinase antibody detected six and five chitinase isoforms in culture inoculated with FP7 and PF1, respectively.

Various basidiomycetes and deuteromycetes, grown in liquid and solid culture media, were compared for their laccase-producing ability and for the inducing effect of soil and agricultural residues on laccase production. Laccase activity in extracts of all solid media was higher than that of the liquid media. In liquid cultures, fungal laccase activity in extracts of pea (Pisum sativum) straw-treated media compared with the other agricultural residue-treated media was significantly low. The laccase-producing ability of Polyporus sp. compared with the other fungi was significantly high whereas that of Trichoderma reesei was markedly low. Laccase activity of Phanerochaete chrysosporium under liquid conditions was strikingly low, however, under solid conditions it increased more than that of the other fungi. With the addition of soil to wheat and rice straw-treated solid media, fungal laccase activity increased significantly.

During 1999-2002, in the course of a faunistic survey of oribatid mites of Iran, twelve species of higher or brachypyline oribatid mites (Brachypylina) belonging to eleven genera and seven families from various localities of Iran were collected: Aleurodamaeus* setosus (Aleurodamaeidae*); Licnobelba* alestensis (Licnobelbidae*); Licnodamaeus fissuratus, L. pulcherrimus (Licnodamaeidae); Damaeus* sp., Subbelba* sp., Belba* cf. minuta (Damaeidae); Damaeolus* cf. ornatissimus, Fosseremus quadripertitus (Damaeolidae); Berlesezetes aegypticus (Microzetidae); Galumna tarsipennata, Pilogalumna boevi (Galumnidae). All the species, six genera and two families, that are the first recorded from Iran are marked by an asterisk.