Showing 14 results for Dem
G.a. G. A. Sharzei, M.a. M. A. Ghetmiri, M. M. Rastifard,
Volume 6, Issue 1 (4-2002)
Abstract
This paper studies the structure of cost and production of rice using cross section data from rice farming in Guilan in 1997. A translog cost function is specified for this purpose and estimated, using Iterative Seemingly Unrelated Regressions for both the short and the long run where all factors are taken to be variables. The results of the study are as follows:
1. Neither in the short-run nor in the long-run is the possibility of technical substitution among the factors of production strong.
2. Own and cross price elasticity of demand for inputs are positive but less than one, hence limited substitutability among inputs is possible as the result of a change in input prices.
3. As the structure of production of rice in Guilan exhibits increasing returns to scale, increased allocation of land to the production of rice could result in a lower price of the product.
4. Inputs are not homogeneous, therefore, not all producers are faced with the same price for the same input. Nevertheless, the cost of production has been lower for those farmers who have paid a higher price for an input. Therefore, the higher price for inputs is more than that compensated by the quality of each input in the production process.
5. Due to the inelasticity of the demand for rice with respect to prices, a large price increase is required to stimulate farmers to allocate more resources to the production of rice.
6. Since the possibility of substitution among inputs is limited, a large increase in relative prices is required in order to change the structure of rice production.
A. A. Talebi, E. Rakhshani, S. E. Sadeghi, Y. Fathipour,
Volume 6, Issue 3 (10-2002)
Abstract
Fertility, developmental time and adult longevity of walnut aphid, Chromaphis juglandicola (Kalt.) and its parasitoid wasp, Trioxys pallidus (Hal.) were studied under controlled conditions with a constant temperature of 26±2oC, relative humidity of 60±5%, and 16:8 (L:D) photoperiod. Populations of walnut aphid and parasitoid wasp were reared on walnut seedling in a growth chamber. The mean developmental period, daily fertility rate, and progeny sex ratio were combined to construct demographic life tables. From these tables, intrinsic natural rate of increase (rm), net reproductive rate (R0) and mean generation time (Tc) were calculated. The net reproductive rate (female offsprings per female per generation) and intrinsic rate of natural increase values were 34.69 and 0.278 in walnut aphid and 53.85 and 0.385 in parasitoid, respectively. The mean generation time was 12.75 days in walnut aphid and 10.35 days in parasitoid. Values of rw (weekly multiplication of the females) indicates that T. pallidus is able to multiply 14.81 times per week, whereas the population of walnut aphid multiplies by only 7.001 times in the same period. The population of parasitoids doubled within 1.8 days while the aphid took 2.49 days. Mean pre-imaginal period was 9.14±0.34 days for male and 9.16±0.12 days for female parasitoids on a mixture of different nymphal stages of host. In walnut aphid it was 9.30±0.10 days. The pre-imaginal periods of parasitoid decreases as the aphid host ages. Longevity of adult male and female was 6.17±0.22 and 6.87±0.23 days, respectively, and 12.24±0.94 days for walnut aphid.
J. Torkmani, Sh. Shajari,
Volume 12, Issue 44 (7-2008)
Abstract
The main objective of this paper is to study the differential impacts of various irrigation water pricing policies. The methodology used is based upon Multi-Attribute Utility Theory (MAUT) mathematical programming models and also simulation. Two kinds of data needed to feed the models were obtained from official records and surveying. The analysis of water pricing policy indicates that the most important relative savings take place in the more conservative farmers due to their risk-aversion behavior. Also it can be seen that in the elastic segments of the demand curves the increase in the price of water encourages great saving in consumption due to changes in mixed crops, crops production by deficit irrigation methods and production of rain-fed crops. Results clearly demonstrate that each homogenous group of farmers displays different behavior patterns related to this natural resource. Therefore, this shows the usefulness of differential analysis in evaluating the impact of water pricing policy.
A Akhavan, M Bahar, Gh Saeedi, M Lak,
Volume 13, Issue 47 (4-2009)
Abstract
To understand the role of relative humidity rate, host genotype, inoculation method and growth stage in epidemiology of bean common blight, two greenhouse experiments were carried out monitoring epiphytic population size of Xanthomonas axonopodis pv. phaseoli (Xap) and disease severity. The result showed significant differences among genotypes, inoculation methods and growth stages for epiphytic population size and sam effects except genotypes for disease severity. The epiphytic population size was significantly higher on spray inoculated Khomein cultivar of bean during flowering (R6). However, the relative humidity rates did not significantly affect population dynamics of epiphytic Xap and the disease severity. Two field experiments were also carried out to determine the effects of irrigation systems (furrow irrigation and overhead sprinkler irrigation), inoculation method, growth stage and their interactions on epiphytic population size of Xap and disease severity. The result showed that the epiphytic population size and disease severity were higher on spray inoculated plants irrigated with overhead sprinkler system during pods filling (R8). In this study, a significant positive correlation was found between epiphytic population size of Xap and bean common bacterial blight severity.
N S, A Alizadeh, S Mosa Nejad,
Volume 13, Issue 48 (7-2009)
Abstract
A comprehensive study is underway now to determine the predicting factors of rice blast and its loss assessment in Guilan province. In a preliminary study, the effect of climatic factors on spores population and forecasting the disease were considered. So, during cultivation season of 2006 and 2007, some fields were chosen five kilometers away from weather stations in three regions of Guilan, including, Rasht, Lahijan and Anzali, and the daily spore population was measured on slides. Climatic data including precipitation (mm), maximum and minimum daily temperature, maximum and minimum daily humidity and sunny hours were obtained from weather stations. Then the relation between spore population and weather data was analyzed, and the most important climatic factors affecting spore population and predicting of rice blast were determined. It was concluded that climatic factors such as precipitation (mm), maximum daily temperature, minimum daily humidity and sunny hours are the most important factors for predicting rice blast in Guilan province. Spore population was positively correlated with precipitation, increase of daily minimum humidity, decrease of daily maximum temperature and decrease of sunny hours. The blast disease occurred in the fields during next 7 to10 days.
M Zibaei, R Rahmani,
Volume 13, Issue 48 (7-2009)
Abstract
In this study the causality relationship among variables in chicken and beef markets were investigated based on annual data from 1974 to 2004 in the I.S. of Iran. For this purpose, causality algorithms emerging from directed acyclic graphs were used in two cases, one based on co- integration analysis and innovation correlation matrix of Vector Error Correction Model (VECM) and the other using data directly. In the investigation of causality process, PC algorithm based on partial correlations and GES (Greedy Equivalent Search) based on Bayesian network model were used. The results revealed that there is no specific causality relation between chicken and beef consumption and their price indices. Thus it seems other variables and government interventions are effective factors in these markets. Therefore, this model is an instrument for forecasting changes of these variables. In these markets there are causality relations among price indices, quantities of consumption and other variables. Beef price index as endogenous variable, is under the effect of chicken price index, non meat food price index, non food price index, per capita expenditure and quantity of chicken consumption. The quantity of beef consumption is predetermined and isn’t under the effect of other variables. Chicken price index is endogenous and under the effect of beef price index, per capita expenditure and non food price index. Also chicken quantity consumption is endogenous and under the effect of beef quantity consumption and non meat food price index. With respect to the findings, for effectiveness, policy initiatives aimed at improving in meat industry should be different for different meat markets and the method of directed graphs can be used a s a guideline.
J Torkamani, H Dehghanpor,
Volume 13, Issue 48 (7-2009)
Abstract
The objective of this study was to investigate the demand of food and nonfood commodities among urban and rural households. To this aim, an appropriate functional form and approximation index were established. Then, Deaton and Mulbaer Iterative (DMI) approach as a linear approximation of Almost Ideal Demand System was used. The study horizon was also 1362-1383(1983-2004). The findings revealed that for urban households housing, fuel, power and furniture, household operations and entertainment, education and food, beverages, tobacco are considered necessary. While clothing, footwear and medical care and transport, communication and other goods are consumed as superior commodities. For urban households, a weak complementary and substitution relation among selected commodities was recognized. In the case of rural households clothing, footwear and food, beverages, tobacco were revealed to be necessary, while housing, fuel, power and medical care and entertainment, education were found superior. For the rural households only furniture and house operation was found elastic. The compensated and uncompensated self price elasticizes were similar regarding the sign and magnitude coefficients for rural and urban households.
M. H. Zibaei, A. M. Akhoond-Ali,
Volume 20, Issue 78 (1-2017)
Abstract
Water scarcity is a major and structural problem in arid and semi-arid regions across the world that greatly concerns environmental policy-makers. The problem of adjusting the demand exceeding the sustainable supply has been mainly tackled with demand policies, particularly through investment in water saving technology and promotion of irrigation efficiency programs. However, there have been very few evaluations of these programs and many of those that exist raise serious doubt about the programs’ effectiveness in reducing the consumptive use of water, due to the occurrence of the rebound effect. In this study, a sample of 243 farmers in Fars province who have the sprinkler irrigation system installed in their farms was interviewed to collect needed data for investigating the rebound effect using AHP and ordered logit regression model. The results indicated that 74.5 percent of sampled farmers have experienced medium to large rebound effect. It was also found that the amount of dry and fallow land during installation of sprinkler irrigation system have a positive relationship with the probability of occurrence of the rebound effect. Finally, the results of this study can be used to determine the probability of the rebound effect occurrence after installment of the sprinkler system for farms where data is available. For example, in the farms with farm features 24, probability of the rebound effect as a result of water saving measures at the low, medium and high levels are 0.4, 32 and 67.4 percent, respectively. Therefore, we must apply specific water conservation and efficiency practices in such farms based on a combined use of technical, economic, social and political tools to reduce pressure on scarce water supplies.
S. Zahedi, K. Shahedi, M. Habibnejhad Roshan, K. Solaimani, K. Dadkhah,
Volume 21, Issue 4 (2-2018)
Abstract
Soil depth is a major soil characteristic commonly used in distributed hydrological modeling in order to present watershed subsurface attributes. It strongly affects water infiltration and accordingly runoff generation, subsurface moisture storage, vertical and lateral moisture movement, saturation thickness and plant root depth in the soil. The objective of this study is to develop a statistical model that predicts the spatial pattern of soil depth over the watershed from topographic and land cover variables derived from DEM and satellite image, respectively. A 10 m resolution DEM was prepared using 1:25000 topographic maps. Landsat8 imagery, OLI sensor (May 06, 2015) was used to derive different land cover attributes. Soil depth, topographic curvature, land use and vegetation characteristics were surveyed at 426 profiles within the four sub-watersheds. Box Cox transformations were used to normalize the measured soil depth and each explanatory variable. Random Forest prediction model was used to predict soil depth using the explanatory variables. The model was run using 336 data points in the calibration dataset with all 31 explanatory variables (18 variables from DEM and 13 variables from remote sensing image), and soil depth as the response of the model. Prediction errors were computed for validation data set. Testing dataset was done with the model soil depth values at testing locations (93 points). The Nash-Sutcliffe Efficiency coefficient (NSE) for testing data set was 0.689. The results showed that land use, Specific Catchment Area (SCA), NDVI, Aspect, Slope and PCA1 are the most important explanatory variables in predicting soil depth.
M. Mokarram, A. R. Zarei, Mohammad Javad Amiri,
Volume 22, Issue 3 (11-2018)
Abstract
The aim of this study was to evaluate the effect of increasing DEM spatial resolution on the assessment of the morphometric characteristics of waterways, as well as analysis and modeling of it by using RS and GIS techniques. In this study, which was carried out in the south of Darab city DEM 90 m (as one of the most usable data in waterway modeling), increase spatial resolution of DEM attraction algorithm in neighboring pixels with two models including: touching and quadrant neighboring models to estimate the value of sub-pixels. After manufacturing output images for sub pixels in 2, 3 and 4 scales with different neighborhoods, the best scale with the most appropriate type of neighborhood was determined using ground control points (270 points); then, the values of RMSE were calculated for them. The results showed that with using the Attraction model, the accuracy of the output of images was improved and the spatial resolution of them was increased. Among scales with different neighborhoods, 3 scales and quadrant neighboring model exhibited the most accuracy by the lowest value of RMSE for the DEM 90 meter. Evaluation of waterways morphometric features showed that DEM extracted from attraction algorithm had more ability and accuracy in waterways extraction, Extraction of morphometric complications, and information in the study area.
H. Hasheminejada, M. Sayedbarzin, K. Jeirany, A. Taebi,
Volume 23, Issue 1 (6-2019)
Abstract
Detergents are the main organic pollutants in the industrial and domestic wastewater. Electro-chemistry methods are advanced purification methods developed with high efficiency features. The goal of this study was to investigate the possibility of using electrocoagulation and the complementary flocculation process to achieve the highest removal efficiency of the detergent COD. So, with iron electrode, synthetic samples at the concentrations of 500, 750 and 1000 mg/l (with COD of 217, 268 and 370 mg/l, respectively) and with the initial pH levels of 5, 7.3 and 9 were tested. Variable parameters during the electrocoagulation process included the current duration at 3, 5 and 10 minutes, and the current density was at 4, 10, 16 and 22 mA/cm2. The primary results showed that in the optimum conditions, the coagulation process and complementary flocculation could reduce the sample’s COD with an initial concentration of detergent (500 mg/l) from 217 mgO2/l to 81.30 mgO2/l. The electrocoagulation method could reduce the chemical oxygen demand to below the standard limit of environmental discharge (200 mgO2/l) and compensate for the possibility of the irrigation of green spaces due to water shortages.
O. Mohamadi, M. Heidarpour, S. Jamali,
Volume 23, Issue 3 (12-2019)
Abstract
Shortage of water resources and renewable per capita in last 30 years is put Iran on crisis threshold. Wastewater reuse is one of the battle solutions for water shortage and prevents wastewater depletion and environmental pollution. Thus, a pilot scale experiment was carried out to evaluate an integrated anaerobic/aerobic treatment for removal of BOD5 and COD, also to reduction of hydraulic retention time by considering optimum removal efficiency. The pilot was an anaerobic/aerobic bioreactor type under continuous-feeding regime based on a central composite design. The pilot was studied in different retention time and aeration was carried out between 5-15 hours. According to different retention times for COD removal efficiency, 24 hours was selected as optimum hydraulic retention time, that it is comparable to those obtained for 48 hours and over in plant roughly and could remove COD and BOD in acceptable ranges, results showed that average removal efficiency for BOD5 were 63.86 and 83.99 percent in aerobic and anaerobic phases, respectively. The average removal efficiency for COD was 76.5 and 74.35 percent for anaerobic and aerobic sections, respectively. The average removal efficiency for BOD5 and COD in this integrated aerobic-anaerobic pilot 95.24 and 94.8 percent, respectively.
A. Kheyrandish, S. F. Mousavi, H. R. Ghafouri, S. Farzin,
Volume 23, Issue 4 (12-2019)
Abstract
In this research, conjunctive and integrated operation of surface and ground water resources of Behbahan plain (Maroon dam's reservoir and existing wells, respectively) was investigated. Simulation of allocation of water demands in this basin was performed by four scenarios, using WEAP software: 1) current conditions (M1), 2) reference scenario for the next 16 years (M2), 3) land development scenario (M3), and 4) optimal scenario (M4). The optimal scenario was performed with multi-purpose linear programming. Based on the results, drinking water demands was satisfied completely in all scenarios. Under the scenario of current conditions, all agricultural demands, except the traditional rights, supplied more than 50% in the low-flow months. In the reference scenario, water supply for agricultural demands in some months was less than 100% and even in June and July, the water supply for North and South Irrigation networks of Behbehan plain was less than 10%. In the land development scenario, agricultural demands of all irrigation networks, except Ramhormoz network, satisfied more than 90% in all months. The optimal scenario performed better than other scenarios for minimum Maroon River flow and volume of storage in the reservoir. Comparison of the four scenarios in satisfying the environmental needs also revealed that the optimal scenario performed better than the other three scenarios in the spring months. However, it provided less than 100% of water needs in the whole year. Comparison of the four scenarios also showed that the first two scenarios had the highest reliability percent in the Jayzan-Fajr, South Behbahan and North Behbahan Irrigation Networks and traditional water rights. Frequency of storage-time-probability from the storage volume in the optimal scenario also showed that maximum storage lifetime of the lasting storage volume was 558 million m3 (which was equal to half of the volume of Maroon dam’s reservoir) with the highest probability (60%).
K. Shirani,
Volume 25, Issue 2 (9-2021)
Abstract
Delineation of gully erosion susceptible areas by using statistical models, as well as optimum usage of existing data and information with the least time and cost and more precision, is important. The main objective of this study is to determine the areas accuracy to gully erosion and susceptibility mapping by using data mining of the bivariate Dempster-Shafer, linear multivariate statistical methods and their integration in Semirom watershed, southern Isfahan province. First, the geographical location of a total of 156 randomly gullies were mapped using preliminary reports, satellite imagery interpretation and field survey. In the next step, 14 conditioning parameters of the gullies in the study area were selected including the topographic, geomorphometric, environmental, and hydrologic parameters using the regional environmental characteristics and the multicollinearity test for modeling. Then, the Dempster-Shafer statistical, linear regression, and ensembled methods were developed using 70% of the identified gullies and 14 effective parameters as dependent and independent variables, respectively. The remaining 30% of the gully distribution dataset were used for validation. The results of the multivariate regression model showed that land use, slope and distance to drainage network parameters have the most significant relation to gully occurrence. The gully erosion susceptibility maps were prepared by individual and ensemble methods and they were divided to 5 classes of very low to very high rate. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was used to validate gully erosion susceptibly maps. The verification results showed that the AUC of ensemble method (0.948) is higher than Dempster-Shafer (0.924) and Multivariate regression (0.864) methods. Also, the the seed core area index (SCAI) value of the ensembled model from very low to very high susceptible classes have a decreasing trend that indicating a proper separation of susceptible classes by this model.
