نشریه فناوری در مهندسی هوافضا
سال دوم شماره 3 (پیاپی 6، پاییز 1397)

Undoubtedly water bodies are one of the important ecosystems in the world. Therefore, monitoring and protection of their health is one of the main priorities of the top natural resource managers of each country. The protection of the water bodies using conventional and traditional methods is a difficult and costly task. On the other hand, new technologies and sciences such as satellite or aerial remote sensing can be suitable and cost-effective for many environmental applications. Monitoring the quality of water bodies is one of the applications of remote sensing. Consequently, concepts, advantages, methods, and limitations of remote sensing in monitoring water bodies are presented in this study. Based on results, empirical, analytical, and semi-empirical/ semi-analytical approaches can be effectively used to extract water quality parameters from captured images in remote sensing.

This research aimed to study urban growth modeling of Rasht city using remote sensing and neural network techniques. To this purpose, land use changes have been detected by analyses of Landsat and sentinel images. Due to improvement of spectral and spatial resolutions of sentinel images compared with Landsat ones, it seems to observe improvements in the accuracy of image processing and monitoring of temporal changes. Map production from images was carried out by combining several classification methods using a decision tree approach and achieving best results from the Sentinel image with the Kappa coefficient of 0.92. For growth urban modeling, the images captured in years 2000 and 2011 were used in a neural network. In order to validate the model, the 2017 map was predicted using the generated model. The matching of the predicted map with the 2017 reference map based on the overall accuracy and Kappa coefficients was 0.9113 and 0.8422, respectively. Finally, according to efficiency of the model, the proposed method was used to predict the 2025 map.

In this paper, we study and introduce the drag force reduction in flexible structures. Firstly, a review of the inspiration of this phenomenon by nature is presented, and thenthe amount of drag force reduction in the flexible structure is measured experimentally. The obtained results show that this reduction can be up to 50% of the total drag force. In addition, influential factors on this phenomenon have been investigated.

A prodigious revolution will be happened in urban public transportation in future years. This revolution will be along with entrance of air taxis and other flying vehicles. firstly, in this paper an introduction about obligation of using this system is presented. Most frequent designs for this air taxis are small vertical take-off and landing aircrafts with electric or hybrid propulsion systems. These aircrafts are noteworthy for designers due to the need for low space to take-off and landing and also they have low operational emissions and high safety furthermore, designs of well-known companies are investigated. Some obstacles are existed in arrival of these air taxis into marketing plans that will be investigated in 11 items and some solutions will be presented for them. The aim of this study is to introduce modern air taxis and presents some solutions for entering to the market in order to have 3D transportation environment.

In this paper, MEMS-based micro-propulsions designed for small satellites are investigated and compared. Micro-propulsions based on this technology have many advantages over conventional systems, including small size, high integration, mass production, low power consumption and minimum cost. In addition, MEMS thrusters can produce very accurate, small, and repeatable thrusts required for controlling micro/nano satellites. These systems include cold gas, liquid propellant, digital solid propellant, resistojet, and electrospray micro thrusters. Solid and liquid propellant systems have the highest thrust among others. At the same time, electrospray microthrusters have the highest specific impulse, while cold gas and resistojet systems have the least. Finally, the technology readiness levels are different in these systems and there are some design challenges in using MEMS technology that still require further research.

At the beginning of the 12th century, numerous attempts were made to build rockets; however, serious scientific activities began in the late nineteenth and early twentieth centuries. These activities eventually led to the construction of liquid fuel rockets in 1942. After the Second World War, most of these activities continued in the United States and in the (then) Soviet Union, resulting in the construction of a series of large rockets that were later modified, completed and further developed. A highlight of this rocket development was the Saturn rocket, which realized the dream of space travel between 1969 and 1972 and brought man to the moon.