Due to their high efficiency and low ‎cost, electrostatic electron accelerators with a moderate energy, are used in the industry. In an electrostatic accelerator, the acceleration tube plays the role of dividing ‎the potential of the high-voltage terminal so that it accelerates the beam incrementally in a straight line. In this ‎paper, an acceleration tube for a Dynamitron accelerator with a voltage of 500 kV is designed by CST Studio ‎Suite software. In this design, an electron gun with flat cathode, and a current of 50 mA was used. In order to ‎extract the beam from the electron gun, two filters are used: electrodes and the lens electrode, with voltages of 495 and ‎‎481 kV, respectively; besides for electron acceleration, 13 electrodes with a potential step of 37 kV have been ‎designed. To hold the electrodes and prevent electrical discharges between the electrodes, insulating ‎sheets made of Pyrex are used. At the end of the acceleration tube, a 50mA beam current, a waist radius of less than 0.5 ‎mm, a 73nm radian emittance, and a 0.15μperv beam were obtained. The dimensions of the acceleration tube ‎and the results of investigating the change in the radius of the electrodes, the displacement and deviation of ‎the angles of the first electrode relative to the axis of the acceleration tube are presented in this paper‎.‎

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River morphology is the science of knowing the river system in terms of general shape, dimensions and characteristics of hydraulic geometry, the direction and longitudinal profile of the bed, as well as the mechanism of its changes. Morphological study is needed to understand the current conditions and the potential for future river changes in the future, and perhaps it is only that it is possible to predict the natural behavior of the river in relation to natural changes or actions arising from the implementation of various river engineering projects. Most of the water structures such as dams, bridges and pumping stations are located in the margins of rivers that can be affected by changes in river morphology. Application of remote sensing images and Geographical Information Systems (GIS) can be effective to achieve a more accurate analysis. Today, land use change, vegetation cover and morphological changes of rivers in River Engineering Sciences are of great importance using remote sensing and GIS techniques. Yamani and Sharafi (2012) showed that morphological changes and erosion of the Herrud River from the upstream downstream has decreased. Also, the geological and lithological structures of the bed and river bank are the most important factors in the stability of the bed. Yousefi et al. (2013). In order to investigate the changes of some Meander parameters in the Karun River using Landsat satellite images, morphological parameters of 20 Meanders were determined in an interval of 128 km length of Karun River after the preparation of a land use map for each period. Rashidi et al. (2016) studied geomorphologic changes of the Karoon River bed and its causes from 1334 to 1391. The results indicate significant changes in river morphology including latitudes, meanders, and sedimentary islands due to the decrease in the discharge, the construction of multiple bridges along the path, geological factors and vegetation. The study of past research shows that the study of river morphology in other countries has also been of great importance. Clerici et al. (2015) examined the morphological changes of the Taro River in Italy over the last two centuries and showed that human beings have made the most of the changes for agricultural and industrial purposes, the construction of multiple bridges and casualization. According to the research, the main issue of this research is to investigate the changes in the Gamasiab River, which in recent years has threatened the communication paths, landscapes and, in summary, human structures along the river banks. Therefore, the objective is to study the variation of the morphology of the Gamasiab river from the point of view of the central radius and angle, and the number of archs during the 1990-2013 period, and the extent of the development of the piers.

Earthquake is a natural phenomenon that ignoring it causes irreparable damage, therefore seismic vulnerability assessment of residential districts is one of the necessities of urban management. By creating an appropriate model and employing a variety of spatial and non-spatial data and analyzing geographic information and multicriteria decision-taking systems one can assess and analyze seismic vulnerability of cities against earthquakes. In this study Ashkezar city as one of Yazd province cities is chosen for vulnerability assessment. In this study radius model is used for vulnerability assessment. This model’ s input data is: 1-the size of the district under study 2-district population 3-total number of buildings 4-soil properties 5-vital arteries information 6-earthquake scenario; and its output data is earthquake magnitude, damages on buildings, vital arteries and casualties. The results show that earthquake damages by two possible scenarios in the district under study are very low so that in southwest fault scenario the damage is low and in eastern fault scenario there is no damage.

This paper deals with the threshold radius that warrants the use of single restraining rail for transit and railroads. Different railways use different threshold radius from 91m to 365m to provide restraining rail. These threshold figuresare probably experience driven choices. The need for restraining rail may be related to a so-called derailment alarmcoefficient of 1. 2 sustained over 2m length (According to UIC leaflet 518 a safe maximum value of Y/Q ratio of 0. 8over the length of 2m is recommended) but it needs a wheel/rail interaction software to estimate derailment coefficient. The author is not aware if it has been done for this purpose. A quick and simple assessment method is developed here. A restraining rail reduces the angle of attack (AOA) to reduce the likelihood of wheel climb derailment and to reducewear provided it is installed close enough to the inner (lower) rail to prevent flange contact with the outer (higher)running rail. Angle of attack depends on wheel base, curve radius and free play. The threshold radius is formulatedby considering these three parameters. An assumption made to derive the equation is that twice the AOA on tangenttrack due to free play is a critical AOA on circular curves to warrant a restraining rail. The assumption is validatedby comparing the threshold radius obtained by the formula with real world examples. It is also shown that curvatureresistance of the threshold radius is too high to warrant a restraining rail. If the radius of the curve is less than thresholdradius then the restraining rail needs to be extended into the spiral up to a point where the radius matches with thethreshold radius. A formula substantially based on current practice is given to determine the extension of singlerestraining rail into the spiral subject to a minimum requirement.

Background and Objective In recent decades, land use change due to environmental and human factors has caused serious effects on the environment and the economy in Golestan province. On the other hand, wide rangelands and natural areas have been cultivated without observing ecological and scientific principles or have been exploited for special purposes and changing to other uses, while many of these lands are do not have the potential to become new land uses and they have a high potential for erosion, as a result of which we will see soil erosion, especially in sloping lands and the creation of destroyer floods. Therefore, it is necessary and essential to be aware of the type and manner of use and its possible changes over time, which will be important for planning and policymaking in the country. The aim of this study was to detection the land use changes in Golestan province during the years 1986 to 2019 and to predict the land use status of the region for 2050 using the Land change Modeling (LCM) approach. Materials and Methods In order to monitor the trend of land use changes in the study area, Landsat 5 and 8 satellites (TM and OLI sensors for 1986, 2001, and 2019) were used. Interpretation and processing of satellite data were performed in ENVI software. The necessary pre-processing was performed on the images. First, the images were mosaic together and then cut according to the province boundary. In order to identify and separate the phenomena from each other, a false color image was created. Then, the supervised classification method with the maximum likelihood method was used. At this stage, five classes, including rangeland, agriculture, forestry, residential, and water areas were defined. Land use maps for 1986, 2001, and 2019 were prepared. Integration of land cover maps related to 1986, 2001, and 2019 was used as input of LCM model and digital elevation model (DEM) maps and road and stream layers to analyze area changes and prediction of land use changes of 2050. After the necessary analyzes in order to detect land use changes between the intended time periods, change maps and land use transfers were prepared. Finally, the amount of decrease and increase in each land use, the amount of net changes, the net change from other land uses to the desired class, areas without change and transfer from each land use to another land in different land cover classes in the form of maps and charts were prepared and analyzed. Results and Discussion The aim of this study was prediction and modeling of land use changes in a period of 33-years in Golestan province. According to the results during this period, the area of the rangelands has decreased a lot, equivalent to 181181. 25 hectares. Much of the decline in rangelands is due to its conversion into agricultural, which can be attributed to population growth and the need to expand crop land. The area of forest lands during the mentioned years has decreased from 393018. 75 to 349143. 75 hectares in 2019, which has shown a decrease of 43875 hectares (2. 2%). In general, the destruction of rangeland and forest areas is especially visible in developing countries due to population growth, technological growth and non-compliance with ecological principles and law enforcement. Also, the results of classified maps during the mentioned years show that the highest amount of changes in the region is related to agricultural lands, has increased to 173700 hectares equal to 8. 5 % during the same period. The rate of land use changes related to the residential land class has also increased with the increasing trend from 18731. 25 hectares in 1986 to 37518. 75 hectares in 2019, which has increased by 18787. 50 hectares (0. 9%) during this period. Rapid growth of population has led to the development of residential and urban areas and the increase in this type of land use with a relatively steep slope, especially in recent years, which can be part of the government's plans for housing construction in the surrounding areas cities. This increase in the class of agricultural lands is more noticeable, especially in the central and eastern regions of the province, and can be a warning alarm for the future. It means that in an imperceptible trend, rangeland and forest lands become rainfed agricultural lands and after a while unprincipled exploitation, eventually become barren and unusable land. On the other hand, this could indicate an increase in population and demand for housing, and consequently securance of the needs of the residents of the region is a threat to rangeland lands which is necessary instead of increasing the agricultural and residential lands and turning rangeland lands into such land uses, the policy of increasing productivity in the agricultural sector should be pursued. About of water areas, it can be said that during this period, it has increased by 1. 6% or 3268. 75 hectares. This increase in water areas can be partly attributed to heavy rainfall and water intake and even floods in different parts of the province in 2019. Predicting the rate of land use change in 2050 indicates that in the coming years, the area of rangelands and forests will be reduced by 131906. 25 and 291600 hectares, respectively, and in contrast to the area of agricultural land and residential areas will increase to 164137. 50 and 25313. 25 hectares, respectively. Therefore, the adoption of necessary measures and policies to further reduce forest and rangeland will be inevitable. Conclusion Understanding of the conditions of different land uses during the coming periods will facilitate planning for the future by creating information in terms of their spatial distribution pattern, but maintaining and creating sustainable conditions for the future both statistically and it is ecologically one of its limitations. These constraints play an important role in the safe use of different land uses in the planning process. Therefore, creating sustainable conditions in the region and modeling it in order to use the natural resources of a region regularly and sustainably is one of the preconditions for achieving upstream visions and documents, including the sustainable development plan.

Background: Focal fibrocartilaginous dysplasia (FFCD) is a benign lesion and has been reported as a cause of tibia vara in proximal tibia and distal of the femur. It is rare in upper extremity and few cases have been reported in the ulna and radius. Objectives: The aim of the study was to review and report the clinical course, radiographic presentation and treatment results of three cases of FFCD in the distal radius. Patients and Methods: We reviewed the medical records, imaging files, intraoperative anatomical findings and treatment complications of three cases of FFCD in distal radius. All patients underwent tethering fibrotic band resection with lengthening of extensor tendons in one case and distal radius corrective osteotomy in another one. Results: All three patients were male with a mean age of 21. 3 (11-36) months. The mean follow-up period was 28 months. Clinical and radiographic examinations in patients who underwent tethering band resection without osteotomy showed considerable remodeling. Nonunion, multiple surgeries and deformity were the complications in patient who received osteotomy as a part of treatment. Conclusions: The natural history of distal radius FFCD is not clear. Until receiving enough evidences regarding the natural history of this rare lesion, we can recommend the least invasive treatment for the lesion, which is the resection of the fibrous band.