فصلنامه تحقیقات مهندسی کشاورزی
سال سیزدهم شماره 3 (پاییز 1391)

Grade control structures are hydraulic structures used to stabilize a river bed. Scour downstream of this structure is the main cause of its failure. Studies have developed numerous empirical relations for scour depth prediction that designers must choose between to decide the most effective equation for a specific application. This study tested the condition of submerged jets over beds of sediments (median size = 1.5, 2.4, 3.15 mm) downstream of a weir for discharges of 10, 15, 20 l/sec and tail water depths of 16, 21, 26 cm. The analysis applied multi-dimensionless group regression using Minitab software to predict maximum scour depth. All previous relations were compared to the data and it was found that the relations developed by Veronese A, Mason and Arumugam, Agostino and Ferro, and Chee and Padiyar predict the scour depth better than do other relations. In addition, a new relation was developed that produced better results at RMSE = 0.015 and coefficient correlation = 94%.

Iran has limited water resources that require preservation and reducing water loss from reservoirs, especially in arid and semi arid regions. There are a number of methods available for to control water loss from reservoirs and canals. Concrete linings in water reservoirs and ponds are durable, but their efficiency is limited. Geomembrane sheets are another method of controlling leakage from water reservoirs. In this research, high density polyethylene was used to lining a concrete water reservoir to test its suitability for water proofing and chemical resistance. The benefits and drawbacks of this new lining material were investigated in the design, execution and operation stages. Subsequently, the effectiveness of this liner to control water loss was tested under different. The results showed that a geomembrane liner over a concrete lining requires special consideration during design, installation and maintenance and accessories such as pipes and sumps to reduce excessive stress on the liner. The analysis of water leakage from the liner showed that proper design and installation of the liner and accessories reduce water loss about 38% and limit leakage to 16.9 mm/day/m2.

This research evaluated the effects of onion curing methods on the qualitative traits of Iranian onion cultivars (Azarshahr Red, Neishabour Red, Kashan White, Qom White). Testing was carried out in the autumn and winter of 2007. The experimental design was factorial with two factors and three replicates. The factors were traditional and sunlight curing methods at 42°C for 12 hr for 48°C for 4 hr and four onion cultivars. Bulb qualitative traits of firmness, sprouting percentage, total soluble solids content, vitamin C content and pyruvic acid content (pungency index) were recorded after four months storage. Results showed that onions stored using the different curing methods showed significant differences in firmness, weight loss, sprouting, vitamin C and pungency rate. Kashan White, Neishabour Red and Qom Whitedemonstrated higher firmness. Bulbs cured at 42°C in sunlight had a higher rate of sprouting compared to those stored at 48°C. Pyruvic acid content in the sunlight method was higher than for the other method; the percentage of vitamin C was higher for onions cured at 42°C. Qom White onions cured solely in sunlight produced fewer losses and suitable quality traits, thus, this treatment is recommended.

Dehulling is an important step in walnut processing that has considerable effect on the quality, chemical and microbial properties of walnuts. Improving dehulling can increase the quality of the final product. This research studied the effect of genotype and hulling method on walnut properties. Oneexperiment was performed as a factorial in a randomized complete block design with three replications in the food industrial laboratory of the Agricultural Research Center in Kerman. Chemical (fat oxidation, percent of moisture), aflatoxin and sensorial (color, taste, general acceptance) properties of seven genotypes (20, 21, 77, 88, 95, 211, 264) and their kernels were evaluated using two walnut hulling methods (industrial and traditional). The data were analyzed in and compared using a Duncan t test at p = 5%. The results showed minimum fat oxidation in walnut samples for genotypes 95 and 264 and in kernel samples for genotype 264. Moisture content in all samples was in the required range and the hulling methods for genotype 21 had minimum fat oxidation. The study showed that genotypes 77, 88 and 264 had the toughest skin and no aflatoxin was observed in these genotypes. Walnut samples 21 and 88 and kernel genotypes 24, 21 and 88 had the best taste and color. Hulling method had no significant effect on the sensorial properties of the walnut and kernel samples. Interaction between treatments showed that the industrial hulling method with genotype 21 was better for both walnuts and kernels. The sensorial and chemical properties of genotype 21 are more suitable for cultivation and, because there was no aflatoxin detected in industrial hulling, this method is most effective for processing walnuts.

This study utilized molecular methods to identify 22 isolates from traditional dairy products of Azerbaijan. PCR was carried out using the universal primers of 16S rDNA and a fragment of ~1500bp was amplified. Amplified ribosomal DNA restriction analysis was performed using BsuRI, MspI, HindIII, TaqI and Bsp143I. ARDRA results were compared to the restriction profile in enzymatic restriction and bioinformatics analyses (GeneDoc). The isolates were identified as Lactobacillus brevis, plantarum, casei, agilis and saki. To better characterize the isolates, fragments of eight isolates were amplified, cloned and sequenced. The results identified five isolates as L. plantarum, two isolates as L. brevis and one isolate as Lactobacillus sp.

An electronically automated system for grading fruits was designed and its performance was evaluated. The machine comprised of two electronic and mechanical sections; the fruit passed through them and was graded by weight using a 30 N load cell and a supported control. Then The effect of four independent variables on machine performance was investigated. The independent variables in the first test were fruit type (two types), input slope (30°, 40°, 50°), and sensing time (1, 1.5, 2, 2.5, 3 sec). In the second test, the independent factors were fruit shape (apple, kiwi,-fruit) and output slope (10°, 30°, 50°). Three main factors were statistically significant for machine performance (fruits/sec). It was found that the mostimportant factor was the timing of the load cell. Optimum correction of the timers by calculating the timing of fruit passing the sections and gates increased the performance of the machine. Results showed that maximum capacity was achieved for kiwi fruit with an input slope of 50° and 1 sec of time for the load cell, totaling 872.4 fruits/hr.

Active carbon is char derived from pyrolysis of organic materials. It has a high porosity level and is used to filter fluids. Many types of agricultural materials are used to produce active carbon. The trunk of the date palm, with its low density and high porosity, has great potential for producing active carbon. In this research, the bark was pyrolyzed at 450°C for 60 min to produce active carbon. The results indicated that 100 g of wood produced 30 g of active carbon. The density of the active carbon was 0.12 g/cm2 and its iodine number was 585 mg/g. The pyrolysis of the wood was studied using an analytical model and the coefficient of diffusion for volatile compounds leaving the wood was estimated to be 4.2 ×10-8 m2/s. The progress of the pyrolysis was modeled using the finite element method and showed the model was well fitted to the experimental data (R2 = 0.98). The finite element model was superior to the analytical model because it presented more details of the weight changes in the wood during pyrolysis.

An experimental system based on acoustic technology was set up to nondestructively determine the ripeness of two export melon varieties (Zard-Eyvanekey, Sousky-Sabz). The system comprised a mechanical impulse device, sound sensor (sound level meter), recording signal equipment and the melon patch. Fruit was excited by the pendulum and the response signal was detected by non-contact sensing and processed. TSS, moisture content, acoustic and sensory levels were measured at five stages of ripening. Results indicated that, as ripening progressed, sound pressure, mass and TSS increased while resonance frequency and elastic modulus decreased for both varieties. The resonance frequency for Zard-Eyvanekey decreased from 132.25 to 111.33 Hz and for Sousky-Sabz from 128.91 to 111.33 Hz. Sound pressure increased from 49.21 to 57.74 dB for Zard-Eyvanekey and from 49.66 to 58.22 dB for Sousky-Sabz. A sensory evaluation test determined that the period of optimum ripeness of Zard Eyvanekey was at 113.34 Hz and 56.93 dB and for Sousky-Sabz was at 114.26 Hz and 56.25 dB. Changes in resonance frequency and sound pressure were slight and similar for both varieties. These results can be useful for the design of nondestructive sound systems to detect melon ripeness.