shahram yousefi

Sustainable management of renewable natural resources has special importance and sensitivity in Iran. Identify elements of the forest including forest types, is the most consistent way to manage natural resources and especially forests. River forests are important areas for preserving biodiversity and ensuring the sustainability of the forest ecosystem. On this principle, it is necessary to know and understand the state of the structure of these forests and the types of trees in them and to know the evolutionary process of forest ecosystems before any planning. The aim of this study is forests typing of Maroon riverbank.
Material and

116 plots were chosen with an area of 100 using a systematic random sampling method with dimensions of grid for the study area. In each plot, tree and shrub species, canopy cover in the area of plot were estimated and recorded according to Braun-Blanquet scale corrected. Various parameters such as frequency, abundance and density were calculated. Through the sum of the above three relative parameters, the IVI index was obtained for each species. In order to compare the degree of similarity between types, Sorenson's similarity index was used. Relative abundance values for each species in pure and mixed types were set on a 10-unit scale and divided into four specific groups. After determining the tree types of the area, their map was drawn through IDW interpolation method in GIS10.1 software.

In pure type, Tamarix ramosissima and Populus euphratica, with the highest and lowest frequency (6.7 and 3.3) are indicated as high and low respectively. In general, three types were found
including pure, mixed with two and three species. The most amount of Sorenson similarity index was determined between two types of Tamarix-Populus and Tamarix-Lycium (93%) and also Populus-Tamarix and Populus-Lycium (92%). The lowest similarity index value of 12% to 15% was observed between the Populus-Lysium-Tamarix type with pure Tamarix, Tamarix-Lysium, Tamarix-Populus and Populus-Tamarix types. Minimum and maximum maturity index was obtained for pure types (50%) and mixed types (79%), respectively. Pure types have low maturity and mixed types have high maturity. The maturity index for the entire region was 72%, which indicates high maturity.
Discussion and

The tree cover of the river forests of Maroon Behbahan were classified into pure and mixed types on a general scale. The number of two pure types of Tamarix and Populus and seven mixed types including four cases of two types and three cases of three types were obtained. Three species (Tamarix arceuthoides, Populus euphratica and Lycium Shawii) are generally important in the creation of regional types. Among the pure and mixed types, Tamarix was recognized as the most abundant species. The great similarity between pure Tamarix, Tamarix-Lycium and Tamarix-Populus types is due to the common and dominant presence of Tamarix in these types. A variety of different types in a limited area represents complex river ecosystems.

Optimized structural architect of an Unmanned Lambda Wing Aerial Vehicle (ULWAV) during conceptual design has proven to be a significant challenge due to its unconventional configuration and no historical data for the structural architect. This paper aims to develop a new approach for structural design layout of new generation unconventional aircraft especially for ULWAV. The first step in this approach is to investigate the affecting parameters on structural architecture of these aircrafts then using of modal analysis to identification the behavior of these unconventional geometries for a general methodology development. The result of this modal analysis is apportion aircraft geometry to conventional substructures with already well-established defined architect. ULWAV structure architecture has been done by combining the structural architecture of sub-sections and with respect to requirements for systems installation, stealth design objective and packaging requirements. Here the CATIA software is used to optimize general architect with parametric model. To validate the results, the maximum static stress and maximum displacement of the structure were calculated using MSC / Patran software and compared with the values obtained from the optimization process. Dynamic analysis and buckling stability of structural composite shells are also controlled below. The architect methodology was applied to a case study of an ULWAV. The weight of the optimized structure has also been confirmed by typical case study researches.

In order to measure the strain due to the shear force applied on a wing's spar, it is necessary to install a strain gauge on the neutral axis. In cases such as a circular hole on the neutral axis, it is impossible to install a strain gauge. Therefore, by installing strain gauges outside the cutting area of the hole, it will be useful to measure the shear load. Therefore, the main objective of this study is to investigate the effect of circular slices on the accuracy of strain gauge data acquired for calculating shear load. In this regard, the front spar structure of a lightweight aircraft with two sections are considered as strain gauge bridges. In the laboratory for each measurement section, a bridge is installed on the neutral axis and another two bridges with certain distances from the neutral axis are installed. Concentrated load at specific points has been applied by linear electromotor actuators equipped with S-type load cells. Using the calibration method of ground loads, the load equations are written and finally by using of strain gauge signals which extracted from the test, the concentrated loads are calculated. The forces are calculated in non-creep conditions and in spite of the cuts in the sections, and the differences between them are evaluated. Accordingly, the effect of circular slices on the accuracy of the output of the strain gauge bridges was determined. The results show the correctness of the tests and the accuracy of the load equations.