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The study was carried out to investigate the effective soil and topographic features on distribution of plant types in Sanib Taftan Watershed in Sistan-and-Balouchestan Province, Iran. Initially, land units map was specified by combining three maps of slope, aspect and altitude. Five types including Artemisia santolina- Hammada salicornica, Artemisia sieberi- Amygdalus lycioides, Artemisia lehmaniana- Amygdalu slycioides, Amygdalus lycioides-Amygdalus scoparia, Pistacia atlantica- Amygdalus scoparia were identified. Sampling of vegetation in the land units was conducted using linear transect method, so that presence and absence of the plant species, canopy cover, stone and pebbles, litter and bare soil percent were catculated in 50 or 100 m transects (2-4 m2 plots) in a randomized systematic method. Soil sampling was done with respect to the width of each land unit (from 0-30 cm depth). Principal component analysis (PCA) was conducted on vegetation and plant type-environmental variables matrix. The most important and effective factors in vegetation distribution of the studied area were slope, altitude, soil texture (silt and sand) and total nitrogen and the factors related to topography (slope and altitude) were more effective than those related to the soil.

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The mean fiber length of three beech trees (Fagus orientalis L.) at the lower and higher points (1% and 75% tree height) of the stem at an intermediate altitude (500-1000m) in the Caspian forests in Sari region were 1.36 and 1.22mm respectively, close to the values in three trees at high altitude (1000-1500m), that were found to be 1.39 and 1.36 mm. The mean fiber lengths of the whole stem, using stem formula, were considered as 1.31 and 1.38mm at intermediate and high altitudes and so were very close each other. Juvenile wood portions in the stem comprised 17 annual rings, which took up 7.3% of the stem by volume at intermediate altitude. At high altitude, these values were obtained as 18 annual growth rings, and 8.75% juvenile wood in the stem. The reason for greater juvenile wood at high altitude was somehow a wider ring width at higher elevation. The mean ring width of lower and upper points of the stem at intermediate altitude were found to be 1.82 and 2.95mm respectively; meanwhile, at high altitude, the findings were 2.97, 3.37mm. Despite the data obtained, t- test comparison was conducted between mean fiber lengths of the two heights of the stems at two altitudes, and no significant differences were found at the 1% level. The exploitation age was strongly dependent on how much juvenile wood there was in the stems, that at high altitude was greater than at intermediate. However, statisti-cal comparison showed no significant differences between that and the 1% level. There-fore, altitude in the range of about 500m showed no important impact on beech fiber length, exploitation age or juvenile wood border in Caspian forests.

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The following paper outlines a study conducted on the abundance, distribution, and diversity of butterflies in Mt. Koritnik. located in the Republic of Kosovo, during 2019–2022. This research resulted in a total of 8166 recorded specimens, which belonged to 6 butterfly families, 50 genera and 131 species. The richest family in terms of abundance was Nymphalidae with 4611 specimens (56.47%), followed by Lycaenidae 1924 specimens (23.56%), Pieridae 856 (10.48%), 561 Hesperiidae (6.87%), Papilionidae 179 specimens (2.19%) and Riodinidae with 24 specimens (0.29%). In terms of species richness, Nymphalidae were the richest with 55 species, Lycaenidae 40, followed by 15 Pieridae, 15 Hesperiidae, 5 Papilionidae and 1 Roidinidae. Among 131 registered species, 11 have Near Threatened status in Europe. Our results indicated that species richness and abundance of butterflies were significantly negatively correlated with altitude (p<0.01), whereas they showed a strong positive correlation (p<0.01) with the temperature. The highest abundance and number of species were presented in the lower altitudinal range and the numbers decreased with altitude increasing. Activities such as intensive agriculture, grazing, fires and illegal timber cutting, which were observed during our survey, may be the main threats for butterflies in Mt. Koritnik in the future, therefore, we suggest the data from this research serve as a basic information for authorities to monitor future changes in butterfly diversity.

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Ants (Hym., Formicidae) have been recognized as vital components of arid ecosystems. Determining the diversity patterns of ants and the ecological factors behind these patterns is expected to improve our understanding of the functioning of arid ecosystems. Here, we explored patterns of ant species diversity and community composition along an elevational gradient (800 to 2800 m) in the arid area of Central Iran. The elevational gradient in ant diversity and the effects of environmental factors on various indices of ant diversity and species composition were investigated using generalized linear mixed models and variance partitioning analysis. We recorded 34 ant species of 12 genera and 8 tribes from 120 surveyed quadrats. Climate variables were the most important predictors of ant community structure. Indices of ant alpha diversity including Hill numbers and taxonomic diversity increased with elevation. Hill numbers were negatively influenced by temperature, while they were positively affected by precipitation. The observed diversity pattern could be explained by the diversity-productivity hypothesis. In our study area, the maximum primary productivity and consequently the maximum species diversity occurred at high elevations, where precipitation is high and temperature is lower than the extremes that could limit plant productivity. Ant assemblages are expected to become increasingly composed of warm-tolerant species in response to warmer and drier conditions driven by climate change. The distribution of species with lower heat tolerance will be limited to high-elevation areas in Central Iran. These areas could act as refuges for ants and should be considered priorities for conservation

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We aim in this study to increase our knowledge of the Odonata in the Aures, an unexplored region of northeastern Algeria, using single-species occupancy model (spOccupancy R package) coupled with spatial interpolation technique (kriging ArcGis) to assess the relationships between elevation and odonatan species distribution. From time windows of about 90 days (June to August 2021), a total of 22 odonatan species belonging to 2 suborders (Anisoptera and Zygoptera) have been recorded in 15 sampling wet biotopes; among them the endangered Calopteryx exul. Our modelling shows that 62% of the odonatological community has a uniform probability of being present in the studied area. The probability of detecting a species is similar during each survey for 90% of the odonatological community except for the endangered Calopteryx exul (p ˂ 0.05) and Crocothemis erythraea (p ˂ 0.05). We also found that Ischnura graellsii and I. saharensis are the most common species; they are predicted to occur in more than 60% of sites, followed by Anax imperator, Orthetrum chrysostigma, and Platycnemis subdilatata, where they occur in about 50% of the wet biotopes sampled. Finally, our modelling revealed no evidence for a significant altitudinal variation (500 to 1900 meters above sea level) impact on both occupancy and detectability of the majority of the odonatan species, except for Crocothemis erythraea and Sympetrum fonscolombii. The kriging interpolation indicates that they are concentrated within the altitude range of 400 m to 1000 m.

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In this paper, the design algorithm of a second throat exhaust diffuser applicable in altitude tests of large expansion ratio nozzles is presented. In this algorithm, the geometric parameters of the exhaust diffuser are classified into primary and secondary parts. The primary geometric parameters are calculated from normal shock theory incorporating with a correction coefficient. However, the secondary parameters are selected from the previously reported experimental results. Numerical simulation tool is utilized to satisfy the design candidates and to finalize the correction factor. Axis-symmetric compressible Navier–Stokes equations incorporated with two equation Kω-SST turbulence model are solved to extract the supersonic exhaust diffuser flow features. As a first stage of numerical analysis, we use an unsteady pressure-based solver to accelerate the solution procedure. At the second stage, we use steady density-based solver to enhance the accuracy of our solutions. The current numerical method is properly validated by experimental reported results in the literature. Finally, we focused on simulation results of a designed diffuser and described the flow futures at different boundary conditions. The simulation results are confirmed that the designed diffuser is suitable for proposed altitude test.

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During transient phase of motor burning in an altitude test simulator, the low momentum exhaust combustion gases could not establish supersonic flow in the exhaust diffuser. This leads to a reverse flow of the exhaust gases into the vacuum chamber through the annular gap between nozzle and diffuser walls. This spoils the vacuum in the chamber and it is potentially dangerous for measurement instruments inside the vacuum chamber. In this research; at the first, the physics of the flow at initial transient phase of motor burning is investigated numerically and the backflow phenomenon is illustrated. Then, the influences of backflow arrester (BFA) in variations of vacuum chamber pressure and temperature are studied at the transient starting phase. It has been found that applying BFA to decrease the backflow to the vacuum chamber has no significant effect on starting time of the diffuser but it has strong effect on peak pressure and temperature reduction of the vacuum chamber. It is although found that attaining to the steady condition in vacuum chamber is delayed with this instrument. However, using one-way backflow arrester of reasonable size, both the starting time of diffuser and the peak temperature of the vacuum chamber experience a strong reduction. Although, the vacuum chamber steady condition is accelerated with this alternative. Therefore, this device is more suitable than conventional BFA for transient starting phase of the altitude test simulators.

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In this paper, a C-programming code is produced to introduce the best propulsion system including an internal combustion engine combined with turbochargers. Because the power of internal combustion engine will reduce as the altitude increasing, it is required to use one or more turbochargers in order to compensate the loss of power which is caused by reduced ambient air pressure. For this purpose, a code is written that will be able to introduce the best turbochargers combination including intercoolers, according to the target power and the desired altitude of the UAV flight. In other words, input required parameters of the code is the target power of the engine and desired altitude of flight and output of the code is number and characteristics of the turbochargers with their exact manufacturing company names and also the number of intercoolers required for best performance of propulsion system. It should be noted that, if the turbochargers that is chosen by the program are not available, user can select of the similar turbochargers with similar characteristics without any significant difference in performance of the propulsion system.

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In this research, the performance study of an altitude test simulator at transient phase of motor burnout is conducted by numerical approach. Using a time dependent pressure profile of a motor in burnout phase, the unsteady exhaust flow is simulated in the main sections of the altitude test simulator, i.e. high expansion ratio nozzle, second throat exhaust diffuser, and vacuum chamber. Present investigation shows that in spite of the high pressure starting condition of the altitude simulator, the supersonic flow in the diffuser tends to breakdown at relatively low combustion pressure in the motor terminating phase. At the breakdown condition, the nozzle exhaust hot gases directed into the vacuum chamber through the annular gap between nozzle and diffuser walls. Present simulation shows that the overall temperature of fluid in vacuum chamber is reached up to 2000 K after the motor burnout. Really, It is potentially dangerous for measurement instruments inside the vacuum chamber. Furthermore; in this research, the influences of backflow arrester (BFA) in variations of vacuum chamber temperature are studied at this transient terminating phase. It has been shown that, the BFA can decrease the exhaust streaming into the chamber in initial breakdown periods. Results show that utilizing a suitable BFA size, the safe temperature condition could be established in vacuum chamber during and after the transient terminating phase of motor.

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