regression model

Soil-wheel interaction is very attractive topic for agricultural researchers for its effect on the energy consumption and soil properties especially in agriculture. The purpose of this research is measuring soil-wheel contact area under the effect of independent variables of vertical load on the tire, tire inflation pressure and tire forward speed at controlled condition of soil bin also its prediction using adaptive neuro-fuzzy inference system. The tests were accomplished at two forward speeds (0.386 and 0.879 km/h), three inflation pressures (18, 25 and 32 psi), three vertical loads (150, 300 and 450 kg) plus 3 replications and totally 54 passes. All data analysis was done using Genstat software. Results showed that increase of vertical load on the wheel caused to increase of soil-wheel contact area and increment of inflation pressure caused to decrease of it. Low forward speed had not effect on the soil-wheel contact area. Furthermore, correlation coefficient (R2) of ANFIS models (0.9182) was very more than regression one (0.359). Thus, ANFIS models could predict the soil-wheel contact area with high accuracy using measured input variables included vertical load, tire inflation pressure and forward speed at soil bin.

The four-wheel drive and rear-wheel drive tractors are commonly used in agricultural operations. In order to investigate the effect of a type of driving system a series of tests were performed usin the three driving systems of foour wheel drive, rear wheel drive and front wheel drive in different axle loads of 0, 150 and 300 kg, tire inflation pressures of 170, 200 and 230 kPa and travel speeds of 1.26, 3.96 and 6.78 km/h. Bulk density was measured as an indicator of soil compaction at different depths of 10, 20, 30 and 40 cm. Also, under the different conditions, the drive wheel slip was measured. To carry out the tests, the four-wheel tractor of Goldoni 240 was used which has the ability to work with mentioned driving systems. The experiments were carried out under controlled conditions in a soil channel  with the length of 3 m and a width and depth of 1 and 0.6 m, respectively. Test were conducted in completely randomised block design with three repetations and results were analysied using SPSS 22 software. The results showed that by changing the driving system from 4WD to RWD and FWD, there was a significant increase in soil density, with the lowest density associated with 4WD system and the highest density related to FWD. The reason for increasing the density by changing the driving system can be attributed to different slip levels in each of these systems due to the lower slip percentage of the 4WD system than the other two systems.  Increasing axial load increased soil boulk density. Of note that with increasing the axial load, the stress was transferred from the surface soil to the subsoil layers. As the axial load on tire increases, the subsoil density was closer to the surface layer. Increased axial load on tire and decreasing tire pressure reduced wheel slip. Stepwise regression model with determination coefficient of 0.92 and according to calculated standard coefficients showed that axial load, soil depth, type of driving system, tractor speed, and finally tire pressure, have the greatest effect on soil bulk density, respectively.

Tillage as a preliminary step for agricultural production consumes large amounts of energy. Regarding the energy crisis and the greenhouse gas emissions caused by the indiscriminate use of fossil fuels, many efforts have been done to reduce energy consumption as much as possible. The aim of this case study is to evaluate the effect of design and operational parameters of cultivators on the required tensile force and fuel consumption during tillage operation with a farm cultivator which had 8 shanks with specific blade geometry on a clay loam soil with specific moisture content. Experiments were carried out using response surface method and central composite design (CCD) by taking three levels of tractor forward speed (3, 5 and 7 km/h), three widths of the blade (5, 10 and 15 cm) and three tillage depth (6, 12 and 18 cm). Design Expert 8.0.6 software was used for experimental data analysis. The results showed that the blade width, forward speed and tillage depth had a significant effect on fuel consumption and tensile strength at %1 probability level. The relationship between the dependent and independent variables was presented as a second-order regression model and optimal values of independent variables were determined. The maximum desirability was determined at tillage depth of 18 cm, the forward speed of 7 km/h and a blade width of 5 cm.

Tillage as a preliminary step for agricultural production consumes large amounts of energy. Regarding the energy crisis and the greenhouse gas emissions caused by the indiscriminate use of fossil fuels, many efforts have been done to reduce energy consumption as much as possible. About half of the energy used in the crop production has been dedicated to tillage operations; hence the optimization of tillage tools performance can lead to decrease the energy loss. Tillage operation in most regions of Iran is carried out by moldboard plow. The ability of this plow in turning the soil has made it impressively different from the other plows. The energy used in tillage operations depends on various factors such as soil type and its conditions (soil moisture and texture), plow depth and forward speed. The aim of this study is to investigate the effect of forward speed, plow depth and soil moisture on fuel consumption and required tensile force during tillage operation with a moldboard plow which uses three plows in clay soil. The current study was carried out to optimize the tillage operation with a moldboard plow in the clay soil. Tillage experiments were performed to evaluate the effect of forward speed, plow depth and soil moisture content on the required tensile force and tractor fuel consumption. A moldboard plow with three single-sided plows was used to conduct experiments. Two tractors (MF285 and U650) and a dynamometer were used to measure the required tensile force. To measure the fuel consumption of the tractor during operation, the fuel level was measured in a separate tank system installed on the tractor's fuel system.
Experiments were carried out using response surface method and central composite design (CCD) by taking three levels of forward speed (4, 5 and 6 kmh-1), three plow depth (20, 25 and 30 cm) and three levels of soil moisture content (12, 16 and 20%). Design Expert 8.0.6 software was used to analyze the experimental data. The result of the analysis of variance showed that the effects of plow depth, forward speed and soil moisture, as well as the interaction between forward speed and moisture content on the fuel consumption during tillage operations with moldboard plow are significant. The results also indicated that the increase in forward speed decreased the fuel consumption. Also, fuel consumption decreased with increasing in moisture content at first, but then increased. The reason for this was probably because of the increased strength of soil particles due to the reduced moisture content (the stronger coherence force between the particles), which required more energy to shear the soil.
According to the results of analysis of variance, it can be concluded that all three factors of forward speed, plow depth and soil moisture had a significant effect on the required tensile force of moldboard plow at %1 probability level. With increasing the plow depth and forward speed, required tensile force increased significantly. The dependent variables were modeled as second order regression equations and optimal values of independent variables were determined. Optimum performance with maximum desirability was determined at forward speed of 5.08 kmh-1, plow depth of 20 cm and soil moisture content of 16.41%. With increasing plow depth, tensile force and fuel consumption increased. Also, tensile force increased with increasing forward speed, but this increase was not severely affected by the plow depth and reduced the fuel consumption. The quadratic regression models can well predict the required tensile force and fuel consumption. Using response surface method, optimum performance was determined at forward speed of 5.08 kmh-1, plow depth of 20 cm and soil moisture content of 16.41%.

Iran as one of the largest producers of poultry in Asia and plays major role in feeding the world's population, particularly in the poultry industry. Research about this industry will help to improve the quality and the quantity of products. Increasing of the concentration of toxic gases such as NH3 (ammonia), CO2 (carbon dioxide), SH2 and CH4 in poultry houses comes from bird activity inside the barn is one of the basic problems of the farming. Increasing the amount of these gases more than standard level would cause heavy mortality and reductions in the production. Ammonia is one of the most toxic gases in poultry houses, which must be controlled. Different studies have been carried out on measurement of ammonia emissions from poultry houses to reduce energy consumption and reduce emissions of ammonia. But no specific study has been found on ammonia emissions in Iran and there is no reliable documents of ammonia emissions from poultry in this country.
In this study a poultry house with 18 thousand chickens was used to measure the emission rate of ammonia, the effect of temperature, moisture and age of chickens on emissions of ammonia in Sabzevar city. The barn was equipped with semi-automatic mechanical ventilation. At the first step of this research all sensors was installed for data collection, i.e., air velocity, temperature, humidity and ammonia concentration. Recorded data information were stored in a central computer. Five digital sensors, model AM2303, have been used to measure the temperature and humidity of the ambient air quality. The concentration of ammonia in the air inputs and outputs of the farm was measured using an ammonia sensor model TGS2444 every 10 seconds throughout the study and recorded in the central system. The average speed of the exhaust air was measured using the hot wire anemometer probe for every fan. The outputs of all sensors was converted to digital data and transferred to the central computer using RS485 cable in each module. Converting of the sensors output to digital data reduces changing the data and probable errors. Ammonia emission rates was found by calculating the concentration of ammonia and measuring the rate of input air and fans exhaust air by ammonia gas equilibrium equation. Relation of the ammonia emission rate was achieved using affective factors such as age of the birds and inside air humidity and temperature by regression method.
The average rate of ammonia emission during broiler growing were measured 89 mg per day for each bird. Ammonia emission rates increased until the age of 37 days and then decreased after the age of 37 days. Age of birds has the highest impact coefficient and temperature and relative humidity of the barn have the least impact coefficients on the ammonia emission rate. The ammonia emission rate has also increased by increasing the age of the bird, temperature and relative humidity of the air. Comparing of the ammonia emission rate derived from regression equation with real conditions showed that the regression equation method has a high precision for estimating the ammonia emission rate.
It is showed that the results of this research can predict the ammonia emission rate in the poultry houses and predict the required ventilation rates to minimize the amount of ammonia concentration. The results of this study can be used for automatic control system to minimize energy consumption in the poultry houses. According to the results, the reduction of temperature and humidity in poultry house can be used to reduce the ammonia level.

To evaluate the technical factors affecting drift and droplet size of turbo liner sprayer and its regression analysis while spraying, a research was conducted in canola fields at the Ramin Agriculture and Natural Resources University of Khuzestan in1394 year. Three-factor factorial experiment with three replications in a completely randomized design was performed. The first factor was the pressure of the sprayer with three levels (10, 25 and 35 bar), the second factor was fan speed with two levels (1998 and 2430 rpm) and the third factor was forward speed at two levels (9 and 13.5 km/ hr). With increasing spraying pressure, fan speed as well as forward speed, the drift was increased and the droplet size and sediment were decreased at the level of significant 1% value. According to the results of linear regression analysis for drift, sediment and droplet size, the pressure has the greatest effect on drift, DV50 and sediment.

In this study, a single layer sliced potato was dried using an infrared lamp heating under vacuum over three levels of radiant power including 100, 150 and 200 W, three slices thickness 1, 2 and 3 mm and the absolute pressure of 20, 80, 140 and 760 mmHg. Samples were dried in triplicate to achieve 6% moisture content (wet based) which is suitable for long-term storage. Drying rate was monitored during experiments. The shrinkage of sliced potato was measured using image processing. The results showed that increasing infrared radiation and reducing absolute pressure at the same slice thickness, could cause drying time to be reduced but shrinkage increased. Thickness of the slices and infrared radiation power had a significant impact (P

Agricultural mechanization is a method for transiting from traditional agriculture towards industrial and sustainable one. Due to the limitation of natural resources and increasing population we need to have economical production of agricultural crops. For reaching this destination; agricultural mechanization has a remarkable role. So it is necessary to have an extensive view for mechanization، because with the help of mechanization the agricultural inputs such as seeds، fertilizer and even water and soil can effectively be managed for an economical and sustainable production. This study has been carried out in many provinces of Iran. The data of agricultural tractors and cereal combine harvesters were firstly gathered by means of questionnaire. The tractors were categorized in four power levels of less than 45، 45 to 80، 80 to 110، and more than 110 hp. In addition، it was also carried out for cereal combine harvesters; it was in three power levels، i. e. between 100 to 110، 110 to 155 and 155 to 210 horse-power in 3 ages، i. e. less than 13، between 13 to 20، and more than 20 years. Information regarding to cultivation areas، production volume، and yield of main crops gathered from statistics of Ministry of Jihad-e-Agriculture. Then agriculture mechanization level index (hp ha-1) in each province was calculated. Four main crops including irrigated and rain-fed wheat and irrigated and rain-fed barley، which met the required criteria to be used in the model، were statistically analyzed. Correlation analysis was carried out in order to get an effective model between yield of the four main crops in Iran and agriculture mechanization level index. Pearson correlation index showed that there is a direct and significant correlation between these variables. Subsequently، outliers were identified in order to get a model with necessary efficiency to predict the yield through mechanization level index، by scatter diagram and estimating regression lines in 1% probability level. The effective model was estimated with acceptable coefficient of determination 0. 851، after removing outliers.

Effective operation of a system is related to acceptable programming of repair and service activities. Efficient managerial programming is associated with accurate estimation of maintenance system parameters. In this study، four tractors failure rate was investigated by completing 300 questionnaires from tractor operators in Khuzestan Province. The operators were interviewed in four regions of the province. Under study variables included driver experience، level of education، driving license، skill training course، work location (region and city)، type of service and maintenance، storage conditions، distance to first workshop، distance from shelter to farm، machine age، annual use hours and number of failure. Regression analysis by estimating an exponential function showed that the variables such as age of tractor، annual hours used and type of service and maintenance affected the failure rate of each four type tractors. For one percent increase in age of tractor and annual use hours، failure rate increased about 0. 6% and 0. 24%، respectively. Also، failure rate in MF285، MF399 and U650 tractors was about 0. 383، 0. 453 and 0. 143 percent more than JD3140 tractor، respectively. The preventive maintenance causes 0. 252 percent decrease in failure rate.

Due to the importance of weed control and the limitations of mechanical methods in some places، in this research the water jet cutting for weed control was investigated. The cutting tests were performed on camel thorn weed in Shahid Bahonar university of Kerman. The water jet pressure of 90 bars was achieved with the aid of a suitable pump. The cutting time was studied in a completely randomized factorial design experiment (CRD) with five replications. Factors of experiments are: stem diameter in 2 levels (smaller and larger than 5 mm)، distance of spraying jet from weeds in 3 levels (10، 20 and 30 cm) and two types of plant holders: blade and plate. The results showed that stem diameter and jet distance from the weed stem had significant effects on cutting time (at the 1%). The mean comparison of parameters showed that with increase of stem diameter the cutting time increased and any increase in jet distance from the weeds decreased the cutting time linearly with R2=0. 96 and R2=0. 99 for small and large diameter weeds، respectively. The minimum cutting time was measured at 30 cm of the jet from small diameter of stems. A multivariate linear regression model was also proposed for cutting weed parameters. It can be concluded that due to the flexibility of water jet cutting for restricted places، hydrodynamic control of weeds is proposed as a complementary method and sometimes a competing substitute method.