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Showing 10 results for Elevation


Volume 4, Issue 2 (6-2016)
Abstract

The aim of the study is the classification of landform based on elevation, slope, relief and curvature inputs (old method) and topographic position index (TPI) (new method) in the south of Bojnoord. The input data for the two methods is a digital elevation model (DEM). The results of topographic position index (TPI) model showed that most area of landform were covered by class 5 (plains small) and the lowest area of landform was covered with open slope (class 6) (< 0.1%). The results of landform classification using elevation, slope, relief and curvature showed that the upper terraces (shoulder) were located in the many parts of the study area (green color). Plateau (back slope) landform was located in center, some parts of the west and south of the study area. In general, with increasing slope and elevation different types of landforms occur. Thus slope, elevation, relief and curvature are effective in preparing the landform classification map. The comparison of the two methods showed that the TPI method was more accurate because the method revealed more details.

Volume 6, Issue 2 (7-2018)
Abstract

Aims: The information on species richness (SR) can be used to help establish conservation strategies or to predict future patterns of biodiversity under global change. The aim of the present study was the prediction of spatial distribution of plant species richness in the Valdarreh Rangelands, Mazandaran, Iran by Macroecological Modelling (MEM) and Stacked Species Distribution Models (S-SDM).
Materials & Methods: This experimental study was carried out in the Valdarreh rangelands. In the present study compared the direct, macroecological approach for modeling species richness with the more recent approach of stacking predictions from individual species distributions. Both approaches performed in reproducing observed patterns of species richness along an elevation gradient were evaluated. MEM was implemented by relating the species counts to environmental predictors with statistical models, assuming a Poisson distribution. S-SDM was implemented by modelling each species distribution individually, assuming a binomial distribution.
Findings: The direct MEM approach yielded nearly unbiased predictions centered around the observed mean values, but with a lower correlation between predictions and observations, than that achieved by The S-SDM approaches. This method also cannot provide any information on species identity and, thus community composition. Predicted SR by S-SDM was correlated by a Spearman p of 0.76 with the observed SR. The MEM-predicted SR achieved a Spearman rank correlation of 0.32 with S-SDM. The species richness along the elevational gradient for MEM and S-SDM were 0.21 and 0.82, respectively.
Conclusion: MEM and S-SDM have complementary strengths and both can be used in combination to obtain better species richness predictions.


Volume 9, Issue 1 (3-2005)
Abstract

Tabriz has special restrictions in its physical development. From the view point of geomorphology view, the city is faced with hazards for developing, such as: earthquakes, mass movements and floods. Geomorphologic hazards of the city have been reviewed in this paper. The aim of this study is classification of stable and unstable regions of Tabriz. For attaining this aim, Geographic Information System (GIS), Digital Elevation Model (DEM) and Normalized Difference Vegetation Index (NDVI) have been used. Landsat satellites images (type TM) have been used for increasing the accuracy of needed data. Mixing all data in GIS environment generated the maps of limitations for city development and of hazardous areas of the city. Maps can be classified in two groups: a) The map of ruggedness of the city and its suburbs, b) The maps of geomorphologic hazardous areas of the city for developing such as: the map of hydrological hazards, land-cover limitations, instabilities of lithological conditions and faults distribution in the city and its suburbs. The maps are applicable in the development planning of the city. The results showed that banks of Mehraneh Roud, and also Baghmisheh and Valiasr areas are considered hazardous area in Tabriz. However, earthquakes hazards are equal in the city and suburbs because of sub-faults distributed in all area of the city.

Volume 10, Issue 4 (12-2022)
Abstract

Aim This study was conducted to investigate the association between plant species diversity indices with topographic variables in the rangelands of Hir county, Ardabil Province, Iran.
Materials & Methods Random-systematic sampling was performed in three elevation profiles at 11 sites. The elevation was divided into five classes, slope into three classes, and aspect into four classes. Indices of plant species richness, Margalef’s, Menhinick’s, Hill evenness, density, and dominance were calculated. Indices in different classes of topographic variables were analyzed using one-way analysis of variance (ANOVA) and Duncan's mean comparison.
Findings Results showed that the highest value of the Shannon-Wiener indices was observed in the elevation class of 1800-2000 meters above sea level (masl). The highest values of plant species evenness, richness, and diversity of Simpson’s and Shannon-Wiener were related to the slope of 0-20%. The values of species richness indices and dominance in the southwest direction, and Menhinick’s richness in the northwest direction, were higher than the other directions. At the level of Plant Functional Types (PFTs), the highest amount of evenness is at the grasses PFT and elevation classes of 1800-2000 and 2400-2600 masl. The maximum amount of Hill evenness at the shrub PFT and slope of 40-60%. The highest amount of Margalef’s richness and Shannon-Wiener plant diversity was in the forbs PFT and in the southwest direction.
Conclusion According to the results, elevation, and slope have the greatest effect and the aspects of the slope have the least effect on the diversity of plant species in the region.

 

Volume 11, Issue 0 (3-2007)
Abstract

Many of well known Iranian hydrocarbon reserves are concentrated in the anticlinal oil traps of the Asmari Formation. Fractures are too important in fluid flow simulation, because of their impacts on anisotropy and heterogeneity of the Asmari carbonate reservoirs. In order to fracture network modeling of the Asmari reservoirs, it’s necessary to have information about many parameters that most of them can not be got from the well data. Therefore, the extracted data from the remote sensing studies of the Asmari outcrops can be as a basis for determining these parameters. The remote sensing imagery is one of the main techniques available to geologists for locating and extracting fracture systems. The Kuh-e Asmari anticline in marginal part of the Zagros Fold-thrust belt has been selected for remote sensing studies of the faulting/ fracturing systems in the Asmari outcrops. In this study, Landsat (ETM+) images, ASTER images (with high spectral resolution), IRS-PAN images (with high spatial resolution), and a detailed Digital Elevation Model (with scale 1:25,000) covering the Kuh-e Asmari anticline were used. The geometrical correction, data processing and image enhancement of the satellite images were carried out in ER Mapper 6.4. Furthermore, to improve the fracture study, some 3D models were made by draping satellite images on the DEM. In this study, many data were extracted about the fracture traces. The results were delivered as figures,maps, 3D models and statistical graphs. The statistical and structural analysess of the Kuh-e Asmari anticline showed faulting/ fracturing systems which have been formed by different mechanisms, and in different times. The results of this study can be used for fracture pattern modeling and prediction hydrocarbon flow in the Asmari reservoirs.

Volume 11, Issue 1 (2-2023)
Abstract

Aim: Recognition of habitat status and ecological responses of species to environmental variables are prerequisites for better management and providing the ecological needs of each species. This study assessed the current status and distribution of Viburnum lantana L. and described its ecological characteristics in the lowest limit of its distribution in the northern hemisphere, Arasbaran forests.
Materials and Methods: The presence sites of Viburnum lantana L. (wayfaring trees) were selected based on the field observations and library sources, then to collect data, the 114 circular samples with a radius of 17.84 m were laid systematically and randomly out. Within each sampling area the characteristics of each woody species including species name, diameter at the breast height (DBH) and the height of all wayfaring trees and other species were measured. The relative importance value (RIV) of species across all sample plots was calculated to describe the dominant species composition.
 
Chellappa Selvakumar, Chandran Ashokkumar, Shunmugavelayutham Sundar, Fabio de Oliveira Roque, Mariappan Gunasekaran,
Volume 11, Issue 2 (6-2025)
Abstract

The Palni Hills, part of the Western Ghats Mountain range in southern India, constitute a biodiversity hotspot, and their high elevation creates unique ecological conditions. Despite global recognition of the region as a biodiversity hotspot, many taxonomic groups remain poorly studied, including mayflies. We conducted a survey of mayflies in the Palni Hills to document the current diversity profile and analyse their altitudinal distribution patterns, ranging from 346 to 1685 m asl. Our sampling from April to October 2023 covered eleven sites, resulting in the collection of 788 individuals, representing 24 species, 16 genera, and six families. Four species are reported for the first time from Palni Hills. Notably, the families Baetidae, Heptageniidae, and Leptophlebiidae were the most species-rich, although individual population densities remained low. We have provided the updated taxonomic hierarchy, current diversity profile, and abundance of mayflies of Palni Hills. We have also highlighted the knowledge gaps in the taxonomy and distribution of Ephemeroptera within this study area

Volume 12, Issue 4 (3-2013)
Abstract

This paper develops new results on the use of model predictive control to regulate the attitude of a ground station antenna. Two degree of freedom AZ-EL pedestal is considered as ground station antenna. Permanent Magnet Synchronous Motors are taken into consideration as the best choice for satisfaction of control objectives as actuators. The design is based on a two cascade controller consist of MPC and a simple feedback linearization, respectively. The proposed approach provides more smooth tracking and lower energy consumption with respect to analogous works. The model predictive controller employs integral action, resulting in zero steady-state error and load torque disturbance rejection. Realistic disturbances caused by wind and load is considered and applied to an industry-sized pedestal. The reference data of azimuth and elevation angles are chosen from a real tracking mission. The comparison of simulation results by typical PI controller, verify the effectiveness of the proposed method.

Volume 16, Issue 2 (6-2016)
Abstract

Digital Elevation Models (DEMs) are one of the most important inputs in most rainfall -Runoff models and also in deriving watersheds geomorphological characteristics. One of the most important issues that should be taken into account when using DEMs in rainfall runoff modeling is the effects of DEM source on the results of the models. At present time, radar based DEMs are attracting a considerable attention in many earth related fields. Currently, there are several sources such as: Shuttle Radar Topography Mission (SRTM) data and the advanced space thermal emission radiometer (ASTER) that due to ease of access and free of charge, have an important role in hydrological modeling and the extraction of geomorphological parameters of catchments. This paper addressed the effects of different DEM sources: ASTER, SRTM, and 1:50000 topographic based DEM on the topographic index and performance of a semi- distributed model, called TOPMODEL. The obtained results indicated that by increasing DEM cell size, disregarding its source, the topographic index inceased. Also, it was illustrated that for all cell sizes other that 30 m there was no difference between the results of ASTER and SRTM DEM. Such a coincidence was observed for TOPO DEM for cell sizes larger than 100 m, as well. Results showed that the effect of data resolution on the average daily discharge, average saturation deficit of basin and the average distance to water table level is not meaningful. In daily discharge simulation, the performance of TOPMODEL when using the TOPO DEM ,based on the NASH- SUTCLIFFE efficiency index, was the highest and for the SRTM DEM was the lowest. In flood simulation, upto 200 m resolution, TOPMODEL efficiency was constant disregarding the DEM source, while its efficiency reduced for cell sizes greater than 200 m in all conditions. It was illustrated that by increasing the cell size, surface runoff contribution to total runoff, in contrast to subsurface flow, increased. Furthermore, For all of the sources, increasing the DEM cell size, incresesd the surface runoff contribution and decreased subsurface flow. The percent of surface flow simulated by the model when implementing the DEM of SRTM is the highest. According to achieved results, the percentage of simulated surface runoff from SRTM DEM was higher than the other two sources. It was observed that the number of cells of low slope in SRTM DEM is greater than the other sources, which was concluded as the main reason for this issue. Reducing the slope of a cell could reduce its potential to carry subsurface flow, which in turn could increase the cell potential to be saturated. It was concluded that DEM different sources effects on average saturation deficit and water table is negligible, and these ouputs of TOPMODEL is mainly affected by DEMs cell size. Finally, this important conclusion was drawn from the present research that the information content of ASTER DEM is nearly similar to TOPO DEM and higher than SRTM DEM; therefore, between satellite based DEMs, it is more convenient to use ASTER DEM for rainfall runoff modeling.

Volume 22, Issue 2 (6-2022)
Abstract

Having a long history of seismicity and experienced destructive and deadliest earthquakes make Iran one of the vulnerable countries against earthquakes. Based on the seismic hazard zoning map presented in the Iranian seismic code (2800 provisions), more than 90% of Iranian cities are located in areas with high or very high seismic hazard zones. On the other hand expansion of urbanization in recent decades almost comprises reinforced concrete (RC) buildings. Many of these RC structures constructed in accordance with codes that did not mandate adequate detailing and reinforcement for seismic protection, may have already suffered damage since their erection, due to insufficient maintenance, earthquake activity, or other natural hazards. Therefore providing appropriate solutions for the rehabilitation of such structures has always been considered essential. Metallic energy dissipators have been grown experimentally and theoretically almost for steel structures. U-shaped metallic-yielding damper as one of the most well-known metallic energy dissipators has also developed as a lateral-load resisting system for strengthening existing steel frames. Experimental and theoretical results showed that U-shaped metallic dampers can operate with large displacements in the inelastic range and dissipate energy through the plastic deformation of the steel. The purpose of this study is to take potential advantages of this system to strengthen deficient RC structures. To the best of the authors’ knowledge, this issue has rarely been considered, most of which are limited to small experimental studies. Therefore, it can be useful to study this issue numerically at the real size structural level. In this regard, three RC intermediate moment frames in 4, 6, and 8 stories and irregular in elevation are considered. Irregularity is considered by a setback in elevation of the frames as a special type of irregularity with considerable effect on seismic performance. Frames were first designed deficiently by SAP2000 software according to the provisions of the Iranian national building code and Iranian seismic code for the intermediate reinforced concrete moment-resisting frames. Then the frames strengthen by adding U-shaped metallic-yielding dampers together with inverted V-braces. The nonlinear dynamic time-history analysis is performed on all frames subjected to three far source input motions utilizing PERFORM 3D software. Nonlinear specifications of beams and columns are considered by assigning plastic hinges to them in addition to defining nonlinearity for the dampers. The results of roof displacement, base shear, inter-story drifts, and performance of frames at the life safety structural performance level are monitored for both cases with and without dampers. The use of U-shaped metallic dampers has always reduced significantly the maximum lateral displacement of the buildings. On average, under the three records of Imperial Valley, Manjil, and Tabas, the reduction is obtained as 32, 33, and 22 for 4, 6, and 8 story frames, respectively. Such a significant reduction is also visible in the inter-story drifts.  . No major effect on the maximum base shear force is observed and even in some cases, it is increased up to 10%. Failure of frames reduced by transferring nonlinearity of elements to the dampers and seismic performance assessment indicates that dampers strengthen frames to almost satisfy the requirements of the life safety level.

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