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Three parabolic trough collectors, with its two axes sun manual tracking system were designed, constructed, and operated in order to generate hot water and moderate temperature steam. An experimental investigation for testing the performance of a PTC is presented. The tests have been carried out in NAJAF climatic conditions (32.02 N, 44.33 E) during selective days of August. The thermal performance of PTC evaluated according to the Standard ASHRAE 93-1986 (RA 91) and the efficiency curve for the PTC was estimated. In the performance analysis of the PTC array, the effects of collector inlet temperature, ambient conditions, two cases for glass receiver and the variation in mass flow rate of the working fluid were investigated. A peak efficiencies close to (50% and 18.8%) were obtained for solar collectors with evacuated and non-evacuated glass receiver respectively at higher flow rate. The collector efficiency equation that is obtained in the present work agrees with other researches.

Abstract: Statement of Problem: The concentration of fluoride in water is usually higher in areas around the coal mines. Zarand region in the south-east of Iran is known for its coal mines. Some studies have shown the high prevalence of fluorosis and some studies reported high levels of fluoride in the region. Objectives: This study aimed to use Geographic Information System (GIS) to assess the relationship between water fluoride content and the prevalence of fluorosis and its spatial distribution in Zarand region. Materials and Methods: This cross-sectional study aimed to recruit 550 people aged 7-40 years in Zarand. Dental examination for fluorosis was conducted based on the Dean’s Index. The level of fluoride in the water was determined in samples of water taken from 35 areas. Information on fluorosis and fluoride content was mapped on GIS. Results: Most participants lived in rural areas (87.25%) and had an educational status of high school level (66%). About 23% of the examined people had normal teeth, 10% had severe and 67% had mild to moderate fluorosis. Distribution of severe fluorosis was higher in areas with higher levels of fluoride in the water according to GIS map. Conclusions: GIS map clearly showed a positive relationship between the prevalence and severity of fluorosis with the level of fluoride in water in Zarand. The GIS analysis may be useful in the analysis of other oral conditions.

Al-Khirat gas power plant in Iraq experiences significant reductions in power output and efficiency during the hot and dry summer season as an effect of a decrease in air mass flow rate resulting from rising ambient temperatures. To address this issue, upstream cooling systems are implemented and their performance is evaluated through energy and exergy analysis. This study tends to do a comparative study of a gas turbine performance with and without upstream cooling systems with power output, thermal efficiency, exergy efficiency, specific fuel feeding, consumed fuel mass flow rate, and exergy destruction rates. The findings show that upstream cooling systems (UPCS) can effectively mitigate the negative effects of high ambient temperatures on gas turbine performance, especially in Iraq's hot, dry summers. Our study found that higher air temperatures led to a significant drop in gas turbine efficiency, with a 35 K increase in inlet air temperature reducing power production by 27.4%. However, implementing UPCS increased thermal efficiency by 11.5% and exergy efficiency by 11.2%. [ABSTRACT FROM AUTHOR]

The growing population and expansion of rural activities, along with changing climatic patterns and the need for water during drought periods, have led to a rise in the water demand worldwide. As a result, the construction of water storage structures such as dams has increased in recent years to meet the water needs. However, dam construction can bring significant alterations to the natural flow regime of rivers, and it is therefore essential to understand the potential effects of human structures on the hydrological regime of rivers to reduce their destructive impacts. This study analyzes the hydrological changes in the Shahrchai River in response to the Shahrchai Dam construction in Urmia, Iran. The study period was from 1950 to 2017 at the Urmia Band station. The Indicators of Hydrological Alteration (IHA) were used to analyze the hydrological changes before and after regulating, accounting for land use changes and climatic factors. The results revealed the adverse effects of the Shahrchai Dam on the hydrological indices. The analysis showed an increase in the average flow rate during the summer season and a decrease in other seasons. However, the combined effects of water transferring for drinking purposes, a decrease in permanent snow cover upstream of the dam, and an increase in water use for irrigation and agricultural purposes resulted in a decrease in the released river flow. Furthermore, the minimum and maximum daily flow rates decreased by approximately 85% and 65%, respectively, after the construction of the Shahrchai Dam. Additionally, the number of days with maximum flow rates increased from 117 days in the pre-dam period to 181 days in the post-dam period. As a concluding remark, the construction of the Shahrchai Dam, land use/cover changes, and a decrease in permanent snow cover had unfavorable effects on the hydrological regime of the river. Therefore, the hydrological indicators should be adjusted to an acceptable level compared to the natural state to preserve the river ecosystem. The findings of this study are expected to guide water resource managers in regulating the sustainable flow regime of permanent rivers.

Abstract The purpose of this study was to evaluate the predictive accuracy of habitat suitability models, identifying the potential distribution range of Dorema ammoniacum, and its habitat requirements in the rangelands of Yazd province, central Iran. Bafgh, Mehriz and Nadoushan, were three habitats that were identified, and sampling was conducted in each habitat using a random-systematic method. A set of 10 plots were established (at equal distances) along 350 m long 18 transects. Soil samples (two depths: 0–30 and 30–60 cm from 36 profiles) were collected and measured in the laboratory. Elevation, slope, and aspect maps were derived, and climate information was collected from nearby meteorological stations. The habitat prediction of the species was modeled using Logistic Regression (LR), Maximum Entropy (MaxEnt), and Artificial Neural Network (ANN). The Kappa coefficient and the area under the curve (AUC) were calculated to assess the accuracy of the forecasted maps. The LR model for habitat prediction of the studied species in Mehriz (K = 0.67) and Nadoushan (K = 0.56) habitats were identified as good. The MaxEnt model predicted the habitat distribution for the selected species in Bafgh and Mehriz habitats as excellent (K = 0.89, AUC = 0.76, K = 0.89, AUC = 0.98), and in the Nadoushan habitat as very good (K = 0.78, AUC = 0.85). However, the ANN model predicted Bafgh and Nadoushan habitats as excellent and Mehriz habitat as very good (K = 0.87, K = 0.90, and K = 0.63, respectively). In general, in order to protect species D. ammoniacum, the development of its habitats in other areas of Yazd province and the habitats under study in conservation programs should be given priority.

Introduction Runoff and the rainfall-runoff relationship are one of the most fundamental research topics in hydrology. Due to the increasing trend of flood occurrence and the resulting damages, it is necessary to determine the flood-producing priority areas and prioritize the sub-watersheds in terms of flood control projects and integrated management of watersheds. The primary contributing areas in runoff generation and the affecting factors should be identified in a flood management project. Understanding the flood occurrence potential of watersheds can be useful in formulating different flood management plans, allocating necessary funds, water resources management, watershed management, and erosion control programs. Watershed Modeling System (WMS) as an integrated flood modeling software can simulate flood hydrographs considering the required parameters. Among the common runoff estimation methods, the SCS curve number method is the most common in estimating flood volume and flood runoff height. Land use changes as an important factor in the alteration of watershed hydrologic response can accelerate soil erosion and biodiversity loss. Land use change affects the curve number and consequently, discharge and flood hydrographs, as assessed in the current study. Materials and Methods The Khiavchai Watershed, with an area of about 134 km2 has been chosen as the study area. The annual rainfall of the study area is 343.8 mm. Toward the hydrologic modeling in the study area, the slope map of the watershed has been derived from the DEM of the study area using the ArcMap software. The maximum daily rainfall of 11 rating gauge stations has been obtained and the raw data has been processed using a common statistical test to check the data quality and homogeneity of SPSS software. The maximum 24-h rainfall data were analyzed using Easy Fit software to select the best statistical distribution. The 3-parameter Pearson distribution (as the best probability distribution function), has been used to calculate the rainfall values in 2 to 100-year return periods. The maximum daily rainfall values were entered into the ArcGIS software and the spatial distribution mapping was done using the IDW method. The average maximum daily precipitation with different return periods was converted to 6-h precipitation. The SCS and WMO rainfall patterns were compared in the study area, and the WMO rainfall patterns were selected as the appropriate input for the model. The maximum annual instantaneous discharge values have been used in estimating the flood discharge in 2, 5, 10, 25, 50, and 100-year return periods using EasyFit software. The input model parameters (slope map, slope direction, curve number, and soil hydrological group) were prepared in ArcGIS and Arc-Hydro software. Results and Discussion The results showed that the maximum flood discharge increases intensely with an increase in the return period. The average CN value of the basin was obtained at 76, the initial loss coefficient was obtained at 0.202, and the STRTL value was obtained at 16.203. According to the increasing curve number values, the infiltration time and the time to reach the peak are reduced. Therefore, by increasing the curve number by 5, 15, and 25%, respectively, the time to reach the peak is 240, 180, and 135 min, and the base time of the hydrograph has decreased by 1035, 885, and 750 min. Meanwhile, the peak value of the simulated flood hydrograph has increased from 1.74 to 6.466, 27.491, and 109.694 m3 s-1. With an increase of 25% curve number, the peak discharge in the return period of 10, 25, 50, and 100 years has increased to 13, 9, 7.5, and 6.3, respectively. The results show that the effect of changes in curve number values on the flood discharge, in the low return period is much more than the high return period. So in the return period of 100 years with 25% changes in curve number, the peak flood discharge value is 6.38 times in the 2-year return period. The results indicate that the least change in the type of land use (in order to reduce permeability) causes a considerable increase in flood discharge in the region. Conclusion The effects of changes in CN values have been assessed in the current research in a modeling framework to estimate the flood hydrograph components. Comparison of the estimated flood hydrograph components against observation values has been evaluated using relative error and root mean square error. The values of these statistical indices were obtained with the least error related to the 3-parameter lognormal distribution of about 10.32% and 8.68 m3 s-1. By comparing the results of the maximum flood analysis and the WMS model, it can be concluded that the simulated data are consistent with the observed flood records in the Pole-Solatani river gauge station located at the outlet of the Khiavchai Watershed.

The aim of this study was to simulate the runoff in the upstream of Chehlgezi hydrometery station in the Gheshlagh Dam watershed, Kurdistan province using SWAT hydrological model. In addition, the results have been evaluated using selected efficiency criteria in the calibration and validation stages, then the performance of the SWAT model is evaluated in simulating the monthly runoff in upland of Gheshlagh Dam. The input model parameters were optimized using the SWAT-CUP optimizer. The calibration and validation of the model was done using SUFI-2 algorithm during 1989-2016 and 2016-2018 periods, respectively. The sensitivity analysis shows that the SCS runoff curve number, Manning’s "n" value for overland flow, minimum and maximum yearly rate of snowmelt, minimum water depth in the shallow aquifer for "revap" were sensitive parameters in flow simulation. The Nash-Sutcliffe and R2 values were 0.62 and 0.65 in the calibration stage, and 0.61 and 0.68 in validation stage, respectively. The results proved the efficiency of the SWAT in monthly flow simulating. According to the results, 55% of the total rainfall entering the watershed has been converted to evapotranspiration, 30% infiltrated into soil and stored as soil moisture, and 15% converted into surface flow component. The results provide useful information on watershed water balance. Flow simulation in different climatic conditions and land-use scenarios in the future can help to sound water resources management.

Introduction and ObjectiveAwareness of the pattern of spatial and temporal variations of the rainfall erosivity is essential for improving soil erosion estimates, especially considering snow cover in different months. In the Caspian Sea Basin, due to the low distance between mountain regions and rainy plain, estimation of rainfall erosivity factor without considering snow cover correction coefficients is associated with a significant uncertainty. Accordingly, the current study aims to analyze the spatiotemporal variations of the rainfall erosivity factor with considering snow cover correction coefficient in the Iranian part of the Caspian Sea Basin.Materials and Methods To prepare monthly, seasonal and annual rainfall erosivity factor, monthly rainfall data of 56 synoptic stations of the Caspian Sea Basin were obtained from the national meteorological organization and statistical yearbooks with a common statistical period of 20-25 years (1996-2020). As a result, the rain erosive layer in different time bases using Co-Kriging geostatistical method with auxiliary variable of height above sea level with less root mean square error (RMSE) was used as the most common evaluation index and selection of the optimal method. Then the monthly snow cover layer was prepared from MOD10CM product and the rainfall erosivity for each month was modified.Results and Discussion Based on the results, the average annual rainfall erosivity factor of the Iranian part of the Caspian Sea Basin was 254.61 (MJ mm ha-1 hr-1), while by considering the snow cover correction coefficient, the rainfall erosivity value was redused to 210.53 (MJ mm ha-1 hr-1). Also, Bandar Anzali and Manjil synoptic stations have the highest and lowest values of the average annual rainfall erosivity factor equal to 749.30 and 162.87 (MJ mm ha-1 hr-1), respectively. In addition, after considering the snow cover correction coefficient, the highest monthly rainfall erosivity values of 27.27, 25.81 and, 25.56 MJ mm ha-1 hr-1 were observed in April, October and, November, respectively. On the other hand, 12.81% of the studied area is in the medium to very high levels of rainfall erosivity in the northern part of the Caspian Sea Basin, which can be used to prioritize different areas in order to carry out conservation measures to reduce the effect of the rainfall erosivity factor on the amount of soil erosion and sediment yield were used.Conclusion and Suggestions Based on the results of the current research, it can be stated that the fluctuation of rainfall erosivity in different months and seasons is also affected by the rainfall time distribution throughout the year. Therefore, the maximum amounts of rainfall erosivity in most of the studied areas correspond to the main times of agricultural activities, i.e. planting and harvesting, which are critical times for soil erosion. Investigating the spatial pattern of rainfall erosivity in the Iranian part of the Caspian Sea Basin shows many relative changes between different regions from the plains to the highlands. Although this pattern is somewhat consistent with the pattern of climate changes from drier and less rainy areas to wetter and morerainy areas, the type of precipitation and especially snow in high areas has reduced the rainfall erosivity in these areas. Therefore, the temporal evaluation of rainfall erosivity resulting from the current research, in which the snow cover correction coefficient is applied, with the timing of the presence and density of vegetation on the soil surface, provides more reliable results for land management managers and planners, especially in the agricultural sector, to choose the right type of crops for each will place the area.

Land use/land cover (LULC) change, strongly affects surface water characteristics, especially in urban watersheds. The aim of this study was to determine LULC in the Samian Watershed and assessing its relationship with water quality parameters. In this study, LULC maps was obtained by ENVI software in four periods (1992 to 2016). Then, 9 water quality parameters at five river gauge stations were selected for further analysis. The Mann-Kendall test was performed to examine the trends in water quality parameters and Pearson test was used to assess the correlation between quality parameters and land uses. According to the results, rangeland decreased by 9.75%, irrigated agriculture increased by 8.45%, residential increased by 1.42% and rainfed agriculture increased by 3.29% compared to the first period. Average of TDS and EC in the study periods in Samian and Gilandeh stations, has been increased. The correlation analysis using Pearson test between quality data and LULC also shows that the EC, Ca, Cl, SO4, Mg and Na pameters of had a significant relationship with increasing residential, irrigated and rainfed land uses.

Aim: Erosion is a critical geomorphological process with significant environmental implications, including land degradation, fertility loss, and negative effects on aquatic ecosystems. It is recognized as an environmental hazard due to the substantial damages it can cause.Materials & Methods: This research uses geomorphometric indicators and a fuzzy approach to zoning the soil erosion potential in the Khiavchai area of Meshginshahr. Various variables were used, including slope, aspect, surface curvature, range length, Melton's roughness coefficient, stream power index, drainage density, topographic wetness index, distance from the river, vegetation, precipitation, and geological formations. The information layers were combined based on their impact on erosion using different fuzzifier functions. The fuzzy gamma operator in a GIS platform was utilized to combine and overlay the indicators. Finding: The results revealed that approximately 8.4% of the study area exhibited high erosion potential. In comparison, around 18.7% had a high erosion potential, primarily located in the middle parts of the watershed. The high erodibility in these areas can be attributed to erodible geological formations, steep slopes, and high drainage density. Other contributing factors include predominantly southern and western slope aspects, longer slopes, and poor vegetation. Conclusion: The indicators used in assessing erosion-prone areas provide insights into the geomorphological and hydrological conditions of the study watershed. The prepared erosion map can serve as a foundation for prioritizing soil conservation management measures and reducing the impact of erosion. Innovation: This research employs a combination of geomorphometric indicators and a fuzzy approach to assess soil erosion potential accurately. The practical application lies in utilizing the study's findings to prioritize areas for effectively implementing erosion mitigation and soil conservation measures in land management.

This study aims to investigate the impact of forest exploitation methods on monthly discharge and hydrological indices of river flow using graphical methods in a forested watershed in North Iran. To achieve this, 10 hydrological index changes related to river flow regime influenced by the Shelterwood/clear cutting, Femel cutting, and the Near Nature approach forest cutting methods were assessed. According to the results, it can be stated that the Shelterwood/clear cutting method influenced monthly flow indices by increasing the coefficient of variations and intensifying runoff production, while the Femel cutting and the Near Nature approach methods contributed to regulating the flow regime and sustaining river flow. The influence of various tree-cutting techniques on river flow values and fluctuations is more evident during the wettest months compared to low-water months. The period of Shelterwood/clear cutting disrupted the natural correlation between precipitation and runoff production. Furthermore, the shift from Shelterwood/clear cutting to Femel cutting and the Near Nature approach progressively diminished the slope of the curve, indicating a reduction in monthly runoff at both measurement stations. In conclusion, opting for an appropriate method, such as the Near Nature approach, is preferable from both ecological and hydrological perspectives when managing forest areas in the study region and similar conditions involving comparable topography, climate, soil, and forest stands. The index-based coupled with graphical methodology employed appropriately demonstrates the influence of logging techniques on monthly flow patterns, which provides valuable insights into evaluating the repercussions of alternative management interventions on river flow dynamics.

In this paper, we introduce a semi-analytic procedure for deriving the response spectrum of the synthetic acceleration records generated using the Double-Frequency Model (DFM). DFM is a filtered white noise method for fully non-stationarity synthetic acceleration records. The proposed semi-analytic procedure is based on the theory of the first passage problem, which precludes time and computationally extensive methods such as Monte Carlo simulations. Assuming a slowly-varying envelope and evolutionary transfer functions, the procedure of estimating the elastic response of a structure is implemented in both time and frequency domains. Comparing the results of our model with previous models and approximations, we concluded that for a set of 10000 realizations of the DFM model, the semi-analytic model produces an error of less than 10% for 92% of the realizations. The accuracy of estimations is higher in the short-period compared to the long-period ranges of the response spectrum. Comparing the accuracy of approximations used to arrive at peak factors, results show that Michaelov approximation executed in the frequency domain yields the best results compared to Poisson or Vanmarcke procedures. [ABSTRACT FROM AUTHOR]

A model is developed for determining the interwire/interlayer shear stiffness in axially preloaded multilayered structural strands bent to a constant radius of curvature. The wire bending stresses were found to have two components which are the axial stress in the wire due to shear interactions between the wires in the bent cable and the component due to wires bending about their own axes. The model was applied to the analysis of helical strands. It was found that the axial component of wire stress is larger than the component due to the bending of wires about their own axes.

Background and Objectives: Happiness is one of the basic human needs and a component of mental health which is the cause of increase of social capital. The aim of this study was to investigate the status of happiness in students of Kerman Dental School. Materials and Methods: In this descriptive study, the statistical population included students of Kerman Dental School in the academic year 2017-2018. Oxford Happiness Questionnaire was used to collect data and 241 students who were selected randomly with the proportionate stratification method participated in the study. Data analysis was performed using Mann-Whitney U and Kruskal-Wallis H tests. Results: 151 (62.7%) of the students were girls and 90 (37.3%) were boys. The mean score of student's happiness was 40.04±0.78. Students' happiness status in different demographic variables such as gender (p=0.779), academic year (p=0.092), marital status (p=0.865) and residence (p=0.425) did not show any significant difference. Conclusion: The happiness status of Kerman Dental students was at an acceptable level, but necessary measures must be taken to upgrade it to the excellent level. [ABSTRACT FROM AUTHOR]