نشریه مکانیزاسیون کشاورزی
سال سوم شماره 1 (بهار 1394)

Solar energy is the most important source of renewable energies. Using solar energy in greenhouse heating during the cold season could be of great importance. In this study, six most commonly used shapes of greenhouses including: even span, uneven span, vinery, single span, arch and quonset types were selected for comparison from received solar radiation point of view for Tabriz city climate condition. These greenhouses were investigated for both east–west and north–south orientations, built all in the same dimensions. Results showed that the single span greenhouse received the maximum and quonset one received the minimum solar radiation. The single span greenhouse in east–west orientation received more radiation as compared to other greenhouses during the winter months. In summer months north–south orientation of an arch shape greenhouse received the most solar radiation. The single span greenhouse in east–west orientation appeared to be the best year-round greenhouse productions in Tabriz region. This shape received 8% more radiation as compared to an average amount of a normal greenhouse and can be used for crop production in winter. Results also showed that in the single span greenhouse oriented in east–west direction, about 60% of the incoming radiation was intercepted by the southern faced greenhouse roof.

The main objective of this study was to obtain the highest rain-fed wheat yield in front of optimum tillage method. In this regards, different tillage methods were applied in order to increase the income and reduce the production costs. Therefore, an experiment was carried out on the research farm of Gorgan University of Agricultural Sciences and Natural Resources, in 2009-2010. The statistical analyses of the experiment were carried out based on randomised complete block design at four replications. The plots attributed to five tillage methods namely: a) mounted moldboard plough with three bottoms followed by disc harrow; b) rotavator, alone; c) disc harrow, alone; d) chisel plough, alone and e) no-till. Wheat seed was planted in these plots under the afore-mentioned tillage methods. The results showed that no-till method was not suitable for rain-fed wheat yield; because it led to a considerable yield reduction. Grain and straw yields in no-till plots was 1305.6 and 3072.1 kg/ha, respectively. The income obtained from grain and straw in no-till method and as well the total income was 4,700,160, 3,072,100 and 7,772,260 Rials/ha, respectively. With considering of the yield and tillage fees in these methods, the net benefit in moldboard plough followed by disc harrow was greater than other tillage methods. The ploughing cost at this intensive tillage was greater than others due to more fuel consumption. Moreover, the income in the moldboard ploughed plots followed by disc harrow was 12,671,020 Rials/ha and ploughing cost was 600,000 Rials/ha. Therefore, the net benefit was 12,071,020 Rials/ha. Seed and fertilizer consumption and their costs in these various tillage methods were similar. The results also showed that increase of the intensity of tillage operation, and/or soil disturbance between the rows after planting led to reduction in potassium fertilizer requirement.

In the present work, the rheological properties of two varieties of tomatoes were studied under creep recovery test. A factorial experiment in the form of completely randomized design was used to determine the effects of storage time and variety on the viscoelastic properties. The results showed that 4-elements model (Burgers model) can explain the rheological behavior of the products with highest determination coefficients. The variety had a significant effect on the coefficients of elasticity, viscosity and retardation times at 1% level of probability. The values for the mentioned parameters in Shaghayegh cultivar was greater compared to that of Ergon cultivar. Also, the elastic modulus values increased with increasing storage time, where the values for the coefficients of viscosity and retardation times reduced at the same time.

Increasing world population and changes in consumption patterns have increased energy demand. Most of this energy is provided by fossil fuels which not only they cause environmental issues but also are depleting. One of these renewable energy resources is solar energy. Therefore, different technologies are used to take advantage of solar energy. One of the useful technologies is air-type flat plate solar collectors used for heating houses and greenhouses and drying food or industrial materials. In this research in order to evaluate and optimize solar energy usage, three air-type flat plate solar collectors were designed and fabricated. In two of these collectors, two flat and V-shape obstacles were mounted on a MDF plate with an angel of 45 degree and these plates were fixed at 4 cm under absorber plate. In addition, the obstacles had 5 cm width and 3.2 cm height. The third collector had no obstacle. For measuring the temperature in different parts of absorber plates and each collector obstacles plate, eighteen LM35 sensors were used. Inlet air mass flow rate prepared by a fan with a flow rate of 0.032 kg/s. Results showed that collector efficiency for the flat obstacles was more than that of two other collectors. The peak efficiency at solar noon (around 1 pm) in the flat type collector in comparison with the simple and V-shaped collectors were more than 20% and 11.2%, respectively. In addition, the peak efficiency of the V-shaped type collector was more than 7.3%, compared to simple type collector.

In agricultural mechanization projects, operations and practices should be accomplished in a certain sequence as well as in a short time period. Otherwise, the expenses due to the timeliness of the practices will be created. To prevent these expenses, scientific planning of the projects is an appropriate solution. In different industries, project management principles are employed for satisfactory planning. The basic insight in whole approaches is the use of networks. In this research, PERT and CPM networks due to high capabilities have been used as robust tools for planning and timing the carrot production mechanization. In this regard, required data and information were gathered. The project activities were determined and WBS was drawn. Finally, PERT and CPM networks related to the project were illustrated and analyzed. Results showed this project has 25 critical paths and the earliest time to complete the project is 187.5 days and the variance and standard deviation values were 26 and 5.09, respectively. The model of the present network is capable to answer statistical questions and provide a bright insight for the project manager to make timely decisions. Consequently, the mechanized carrot production project goes ahead as programmed with high productivity.

Downy Mildew of cucurbits is one of the most important diseases of cucumber in humid areas and greenhouses. It can lead to significant damages to the quality and quantity of the product, if not diagnosed on time. In this study, the possibility of using image processing for determining the downy mildew of greenhouse cucumber was investigated. The captured images from cucumber leaves at several stages of disease severity were processed in Image Processing toolbox of MATLAB programming software. Color images were transferred to several color spaces and then color components were examined by discriminant analysis. Cr color component was determined to be suitable to detect disease spots in leaf and was used to develop the recognition algorithm. The accuracy of algorithm in terms of identify the infected areas of leaves was 97.4±1.4 percent. Discriminant analysis was also used to classify the severity of the disease. Results revealed that image processing is a suitable method for accurate diagnosis of downy mildew in greenhouse cucumber leaves. Discriminant analysis is also a useful tool to classify disease severity in images resulted from image processing.

Tractor operators get exposed in a wide range of vibrations, so that they lead to discomfort and long term or permanent disorders. One solution for this problem is decreasing transmitted vibration to the driver by selecting a suitable seat cushion. Therefore, an ergonomic seat cushion was designed for Iranian operators especially and compared with the available seat. Both of seat cushions were analyzed in the frequency range of 3 to 66 Hz in four excited vibrations of 5.0, 1, 5.1 and 2 m/s2 for three groups of drivers with masses of 55, 70 and 85 kg by using finite element method. The results of this study showed that the ergonomic seatpan cushion can provide more comfort and convenience for the driver in excited vibrations range and this seat cushion can be a suitable alternative to the available seat-pan cushion. However, the investigation of the output vibration magnitude on the seat backrest regions showed that the available seat backrest provides more comfort and convenience for the driver in comparison with the ergonomic seat cushion. Therefore, the combination of the ergonomic seat-pan cushion and the available seat backrest can improve the efficiency of the available seat cushion of the tractor to reduce transmitted vibrations to the driver.

The ecological domain includes some aspects of agriculture that has not a good development until now. Commercial greenhouse is one of the most effective cultivation methods need to more attentions. Researches are on intelligent greenhouses with some important aspects such as receiving the maximum solar radiation and having the minimum heat loss. In recent study, the application of Artificial Neural Network models to predict inside air humidity and soil temperature beside on some inside and outside parameters were investigated. For this purpose, data was recorded from a semi-solar greenhouse located at agricultural faculty of Tabriz University using several temperature and humidity sensors, solar meter and hot wire. This greenhouse has the best structure between all typical kinds of greenhouse and furthermore has the best situation about heat lost and gain the most solar radiation between all types of greenhouses in this region. Single layer multilayer perceptron (MLP) models with LM learning rule and different neurons in hidden layer were used. The results showed that 4-9-1 and 5-6-1 topology with R2 =0.9945 and 0.9971have the highest precision to predict the soil temperature and inside air humidity in semi-solar greenhouse. For theses topologies, MAPE and RMSE were 1.1060, 1.1956% and 1.0353, 0.2502°C, respectively. Comparison between the results of ANN and multiple linear regression (MLR) models showed that ANN is more powerful than mathematical models in this subject. Also results showed that Artificial Neural Network can be used to control automatically the greenhouse environmental parameters with minimum cost in the future.