نشریه فناوری در مهندسی هوافضا
سال هفتم شماره 2 (پیاپی 25، تابستان 1402)

Inspiring from bird’s wings and flights has long been a fascinating subject. In recent years, due to advent of materials and implementation of bird’s flights, use of morphing wings have created considerable changes in scientific issues related to air vehicles. In this article, for the first time, aerodynamic and aeroacoustic studies of a type of (twist) morphing wing are performed. The main pupose of this article is to numerically investigate aerodynamics and aeroacoustics of a twisted morphing wing for a geometry similar to Shahed- 129 UAV. In the manufaturing part of this article, a new method is introduced, which uses actuators to change the wing’s shape. In this article, k- ω- SST modeling for turbulent flow and Fluent software were used. Our results show that with increase of twist angle and attack angle of up to 15 degrees, both lift and drag increase. In addition, at the same angle of attack, for high twist angles, increasing twist angle increases the growth of vortices, causesing a small increase in lift coefficient.

Determining the controller success percent is one of the important issues in spacecraft active fault-tolerant control. The importance of this subject is mainly related to the random and unpredictable nature of faults. On the other hand, since there exists a wide range of faults, various simulations and evaluating controller success percent will require a large amount of time. To resolve this problem, the present paper uses neural network to determine the controller success percent in various fault conditions. First, the neural network is trained and its performance in predicting controller efficiency is verified. Then, considering the high speed of the trained network, a thorough investigation is performed based on a wide range of faults. The obtained results are physically sensible and show that as the fault increases, the probability of controller success will decrease.

In this paper, the efficiency and reliability of the two- stage AC/DC power electronic converter has been optimized for use in aircraft systems. The optimization is done using multi- objective genetic algorithm (NSGA- II), in order to minimize the objective function. The objective function variables are efficiency and reliability. Markov model is used to evaluate reliability, in which short circuit and open circuit faults are considered for circuit elements. Also, the failure rate of circuit elements using the equations of the military standard (MIL- HDBK- 217), has been calculated. For optimization, The value of inductances and capacitors, the switching frequency of each stage, the transformer turn ratio and the DC link voltage are determined as the input of the objective function, and then sensitivity analysis is performed to eliminate any parameters that are not sensitive to the objective function.Then NSGA- II algorithm parameters including iteration count, population, mutation and crossover probabilities are defined to calculate circuit parameters and reliability evaluation is done in form of mean time to failure (MTTF) considering efficiency parameter. The results indicate that the converter has improved reliability while maintaining high efficiency.

The atmosphere of the Red Planet or Mars contains 95% of carbon dioxide, 3% of nitrogen, 1.6% of argon and only a small amount of oxygen, and in terms of concentration is about one percent of the planet's atmosphere, which makes it virtually impossible for humans to live and survive on Mars. Therefore, it is necessary to find a solution that can provide the necessary oxygen for the survival of living organisms, especially humans, in the Martian atmosphere. Photosynthesis is the most important biochemical reaction on which almost all life depends. This complex process occurs in higher plants, algae and some bacteria such as cyanobacteria. Due to the very low percentage of oxygen in the Martian atmosphere, it seems that the use of photosynthetic species that are anaerobic and tolerant of adverse ecological conditions such as cyanobacteria can provide the oxygen needed by the Red Planet.

The atmosphere of the Red Planet or Mars contains 95% of carbon dioxide, 3% of nitrogen, 1.6% of argon and only a small amount of oxygen, and in terms of concentration is about one percent of the planet's atmosphere, which makes it virtually impossible for humans to live and survive on Mars. Therefore, it is necessary to find a solution that can provide the necessary oxygen for the survival of living organisms, especially humans, in the Martian atmosphere. Photosynthesis is the most important biochemical reaction on which almost all life depends. This complex process occurs in higher plants, algae and some bacteria such as cyanobacteria. Due to the very low percentage of oxygen in the Martian atmosphere, it seems that the use of photosynthetic species that are anaerobic and tolerant of adverse ecological conditions such as cyanobacteria can provide the oxygen needed by the Red Planet.

Increasing the range of conventional bullets has become very important today. Previous technologies increased the range of bullets by a certain amount. These former technologies in artillery shells include the technology of creating a bullet at the base of the bullet and the use of rocket bullet technology. Today, large research companies are using new technology to increase cannonballs. According to these companies, new technologies can increase the range of 155 mm bullets to 155 km. The new technology is the use of solid fuel ramjet technology, which is now very popular. Ramjet motors have no moving parts and at first glance look like a hollow tube, which is mostly used at supersonic speeds. In such engines, in order for the engine to start, the air speed must first reach the required value. In such a case, the ramjet engine will start automatically. In this research, the technology of ram jet bullets and the progress made in it have been investigated. According to the investigations, one of the most important future technologies in artillery shells is the use of ramjet technology.