The wave propagation problem is one of the most important topics studied by numerous researchers. Therefore, in this paper, the background of the researches on the propagation of anti-plane SH-waves in a non-homogeneous linear elastic orthotropic medium is presented based on the topographic features as a case study. In this regard, a brief review is illustrated on the theoretical expression of the elasticity of non-homogeneous materials, scalar wave equation, and the technical literature of the obtained Green's functions to solve the mentioned problems. The researchers have proposed various approaches for seismic analysis of topographic features where their studies are categorized according to the development. In general, these methods can be divided into analytical, semi-analytical, and numerical methods. Despite the high accuracy of analytical methods, their lack of flexibility in modeling and analyzing the complex features in accordance with real paradigms in nature, has forced the researchers to use alternative approaches such as numerical methods. In recent decades, increasing the power of computers besides the development of numerical approaches has made researchers eager to use them for analyzing wave propagation problems as well as predicting the real responses of topographic features more than ever. Based on the formulation, the numerical methods can be usually divided in two general categories known as the domain and boundary methods. The common domain methods are including the Finite Element Method (FEM) and Finite Difference Method (FDM), which require discretization of the whole body including internal parts of the model and its boundaries. Although the simplicity of domain methods makes them favorable for seismic analysis of finite media, the models are complicated because of discretizing the whole body and its boundaries at a considerable distance from the desired zone. In boundary methods that are mostly known today as the Boundary Element Method (BEM), due to the concentration of meshes only around the boundary of the desired features, automatic satisfaction of wave radiation conditions at infinity, reducing the volume of input data and analysis time is remarkably achieved as well. On the other hand, because of the large contribution of analytical processes in solving various problems by BEM, the high accuracy of the obtained results is guaranteed. Therefore, the BEM provides a better manner for analyzing the infinite/semi-infinite problems. The BEM formulation can be formed in two categories, full and halfplane. In full-plane BEM, in addition to truncate the model from a full-space, it is required to discretize all the boundaries of the problem including the interfaces, smooth ground surface, and enclosing boundaries. This leads to approximate the satisfaction of stress-free conditions on the ground surface and makes its results less accurate in some cases. In the half-plane BEM approach, the discretization of smooth surface and definition of fictitious elements for enclosing boundaries are ignored, and the stress-free boundary condition of the surface is satisfied in an exact process. Despite difficult implementation and creating large equations in the half-plane BEM compared to the full-plane case, the mentioned advantages help to make the simple models. According to the appropriateness of the BEM in the analysis of wave propagation problems, especially in the presence of topographic features, this method is expanded in two mediums of isotropic and orthotropic. This paper is recommended as a starting point for all researchers who are interested in the field of seismic analysis of homogeneous and non-homogeneous sites.

This paper presents the complete algorithm of site response analysis of nonhomogeneous topographic structures using transient two-dimensional boundary element method (BEM). Seismic behavior of various topographic features including canyon, half plane, sedimentary filled valley and ridge sections, subjected to incident SV and P waves are analysed. The analysis shows the efficiency of the proposed algorithm and its advantage over common transformed domains methods in forming a basis for extension to non-linear behavior.

Introduction: Endodontic files which are used to clean and shape the root canal space differ from each other regarding technical specifications. Recently, K-type files are repeatedly studied on their cutting efficiency. This study aims to evaluate the tip design and cutting efficiency of 5 brands of K-files, available in Iran dental market (naming Dentsply, Thomas, Mani, Perfect and Larmrose). Methods and Materials: In this descriptive study, topographic features of file tips were investigated by the scanning electron microscope (SEM). Those features included tip symmetry, tip design, tip angle, and the distance from the tip to the lowest flute. SEM images (×250 magnification) of files were prepared. Statistical tests (Fisher's exact test, Chi-square, ANOVA, and t test) were used and P<0. 05 was considered as significant. Results: Dentsply files had the most number of morphologically pyramidal sharp tips and the greatest tip angles. However, Larmrose files were the most frequent files having cutting sharp tips. Symmetrical tips existed among 100% of Dentsply and Mani brands. No significant differences were found with respect to distance from the file tip to the lowermost flute between different file brands of this study (P=0. 2, One way ANOVA). Conclusion: Dentsply and Mani files possessed the most symmetrical tips and greatest tip angles. With respect to tip length, all 5 brands were satisfactory. However, neither of 5 brands evaluated topographically were outstanding in every aspect.

The main objective of this study was to classify landforms by Topographic Position Index and assessment of the relation between landforms and lithological features. In order to classify landform, the 10 m Digital Elevation Model (DEM) and Geology map (1: 100000) was used. In this paper Topographic Position Index and the deviation from mean elevation (DEV) were used for classification of landforms. The result showed that, the valley was the largest category, with 33. 37 %. The lower slopes was the lowest category, with 5. 63 %. Each of the other four categories (flat area, middle slope, upper slope and ridge) represented between 5. 8 % and 30. 79%. According the results, the most variable classes were the valley, increasing from 20. 62% (50 m) to 55. 7% (750 m), and the middle slope area, decreasing from 6. 4% (50 m) to 1. 01% (750 m). The results of ANOVA showed a significant relationship at 99% probability level for landform classification map and geology formation map. More than 60% of limestone (OMl, El, TRjm, K2, TRkh, Jgr-vc, OMas, K1) were in middle slopes, upper slopes and ridge.

Identifying flood-prone areas is one of the essential strategies in planning to mitigate the damaging effects of floods. In this study, topographic and morphological indices were used to investigate flooding. Due to the effect of hydrogeomorphic features on flooding, these features were extracted by ARCGIS software and watershed modeling system with the help of digital elevation model and topography layers. Due to lack of accurate field data and incidence of soil moisture, vegetation layer and precipitation statistics from remote sensing facilities, soil moisture and precipitation were extracted. In order to control and compare the information extracted from precipitation satellite images dated December 03, 2016, it was selected as a flood sample. Due to the importance of topographic moisture index to describe soil moisture conditions and estimation of physical and hydrological characteristics, this index was used and the output map was classified according to the area. To illustrate flood-prone areas, a hybrid model was used in which the soil surface moisture layers (optical trapezoidal model was extracted from Landsat 8 images), vegetation, precipitation and topographic moisture index were applied. After mapping the maps and weighting, the layers were merged into GIS environment and the flood potential map of the basin was extracted and the basin was flooded with five flood susceptibility ranges, moderate floods, partly floods and floods, respectively. The flood was classified. According to the extraction map and analysis, out of 3279 km2, about 81. 6 km2 (2. 5%) were susceptible to flood and 1. 9% of the area with moderate risk of flood was identified. Most flood prone areas are located in the central plain and the north of the basin in the flat marginal lands of the Simineh River.

Introduction and Objective: In a proper planning of the forest sector, the preparation of quantitative and qualitative maps is a management requirement and is unavoidable for sustainable development. For this effective planning, the latest information on the types of characteristics that are important in decisions regarding the optimal use and protection of forests are needed. This study conducted in order to the modelling spatial estimation of some quantitative characteristics forest using topographic features and its spatial mapping in District-3 of Sangdeh Forests. Material and Methods: Characteristics of number, basal area and volume per hectare were calculated by surveying 150 sample plots (1000 m2). Primary topographic features of altitude, slope, aspect, profile curvature, flat curvature and tangential curvature and secondary topographic features including wetness index and solar radiation were extracted from digital elevation model with 10m resolution. Then, the relationships between forest quantitative characteristics and topographic features were analyzed and modeled using non-parametric method random forest, support vector machine and also parametric multiple linear regressions. Models were evaluated using 30% of the samples. Results: Bias and root mean square error percentages were calculated to select the appropriate model and the results showed that the support vector machine method had the best results for estimating all three measured characteristics. In estimating number per hectare, the polynomial-3 function with mean square error values and skewness is RMSE = 9. 59 and Bias = 1. 62, ground cover with radial base function (RBF) and values of 53. 5, respectively. 30% RMSE and 1. 32-=% Bias and volume per hectare with polynomial function of third degree and values of RMSE = 37. 62 and Bias =-0. 51 were selected as the most appropriate model. The results also showed that the topographic variables of aspect, altitude, solar radiation and tangential curvature had the most influence on the modeling process. Conclusion: The selected model in this study was able to provide some of the necessary information for forest management, but the model alone cannot explain all the reasons affecting the characteristics, so it is recommended to combine other factors such as climatic conditions, latitude, geology, and remote sensing techniques, which play a major role in explanation and interpretation, to improve the accuracy of the forecast.

In recent years, many reports of damages caused by earthquakes have been observed in different parts of the world, especially after observing the severity of damage in the Mexico City earthquake in 1985, special attention was paid to the discussion of site effect, and many researchers have investigated this issue in Mexico City and also investigated the site effect on the seismic response in other regions. The effects of topography have been stated as an important factor in the amplification of earthquake waves. Due to the great importance of the effect of these features, including valleys and hills, on the seismic response, many researchers investigated this field, while most research on the effect of topography on seismic behavior has been focused on symmetric topographic features.In this research, the seismic behavior of topographic features, including symmetrical and asymmetrical semi-sine valleys and hills with different shape ratios, has been studied. The reason for choosing semi-sine features is that they are the most common form of topographic features in nature, and this is very important in applying the results of the studies. The most important reason for the current study is that in nature, topographic features are rarely seen symmetrically, and studying asymmetric features in seismic studies is necessary.The results in this research have been obtained by using numerical modeling, in order to carry out numerical modeling, the Boundary Element Method (BEM) has been used, which has shown very high accuracy in modeling the distribution of seismic waves among the existing numerical methods.The main goal of this research is to investigate the seismic behavior of symmetric and asymmetric homogeneous two-dimensional semi-sine topographic features. According to the literature review, different studies have investigated the seismic response in different parts of the topographic features, and have pointed out the importance of the topographic shape in the seismic response. In this regard, two symmetric and asymmetric semi-sine topographic features have been studied and their effects on seismic waves with frequency domains of 3 and 5 Hz have been investigated. The symmetrical features consist of eight valleys and semi-sine hills with a half-width of 500 meters and different heights of 125, 250, 375, and 500 meters, which have shape ratios of 0.25, 0.5, 0.75, and 1 respectively. The seismic response has been examined at three points at the top, middle, and bottom of the features. The second part of the study is investigating the seismic behavior of homogeneous and asymmetric topographic features. For this purpose, 10 asymmetric valleys and hills with the same height of 500 meters and different half-widths of 125, 250, 500, 1000, and 2000 meters, have symmetry ratios of 0.25, 0.5, 1, 2, and 4, respectively.In this research, the amplification obtained for features with different shape ratios has been compared with the values suggested by the building codes and the results prove that the effect of features dimensions and asymmetry on the seismic response of topographic features is significantly more than the suggested coefficients in these codes.In the following, the most important results of this study are briefly discussed:In symmetrical hills, the effect of the shape ratio on the spectral amplification increases from the foot to the top of the hills. In addition, the period of the maximum spectral amplification increases with the increase of the aspect ratio.In symmetrical valleys, increasing the shape ratio causes a decrease in the minimum spectral amplification inside the valleys. By moving away from the valleys, a fluctuation of amplification and de-amplification is seen in the seismic wave, which increases the number of these fluctuations with the increase of the shape ratio.The study of the seismic behavior of asymmetric hills shows that as the symmetry ratio increases, the effect of topography on the seismic behavior decreases, especially at the top of the hill, this is clearly visible. In addition, the highest spectral amplification in each symmetry ratio is in the asymmetric part of the hill (the slope with different symmetry ratios).Asymmetric valleys show the effect of asymmetry in the form of intensification in the fluctuation of amplification and de-amplification at the edge that has a greater slope. In addition, in the valley, decreasing in de-amplification is seen with the increase in the symmetry ratio (the symmetry ratio and de-amplification show an opposite relationship).In asymmetric valleys, a side of the valley that has a constant symmetry ratio shows the same behavior in all valleys (valleys with different symmetry ratios), while in asymmetric hills, it can be seen that the asymmetry affects the seismic behavior of the side of the hill that has a constant symmetry ratio.