نشریه فناوری در مهندسی هوافضا
سال پنجم شماره 3 (پیاپی 18، پاییز 1400)

A new approach is presented for the management of controlling the changes in design process of a triaxis gyroscopic stabilizer for a camera mounted on a flying robot. It includes decision-making and the way of identifying the best Investigation of the control process. As a prototype, the Phantom Flying Robot is considered with 32 components which half of them are related to the geometry of its drone and the others to the triaxis gimbal. Structural links between elements the assumed to be symmetric and are arrayed in a design structure matrix. A constant value for change effect for all links is assumed as well as three values: 0.3, 0.5, and 0.8 for low, medium, and high change properties respectively. Additionally, various components of the system are classified as acceptors or reflectors of changes with aid of some indicators. A normal change diffusion index between -1 and +1 shows the relative strength of each component in absorber-to-enhancer spectrum. The method is implemented in the prototype.

One of the leading challenges in the fabrication of natural fiber composites is the adhesion of the fibers to the matrix. Since improving the adhesion between the fibers and the matrix changes the mechanical properties of natural composites, fiber surface modification has been considered. In this study, the effect of adhesion and surface treatment of date fibers on improving mechanical properties (tension, bending, impact) was investigated. Surface treatment was performed on date palm fibers using two chemicals, sodium chloride, and sodium hydroxide. These fibers were modified in four groups with sodium hydroxide, sodium chloride, sodium chloride, then sodium hydroxide, and finally sodium hydroxide, then sodium chloride. By making different samples and performing standard mechanical tests (tensile, impact bending) and electron microscope (SEM) tests, thermal analysis (TGA), fiber tension, fiber extrusion from the matrix (Pull out) the effects of different groups on improving the adhesion and mechanical properties of composites was examined and verified. The results showed that the surface treatment fiber with sodium chloride showed more resistance against stretching, extrusion of the fiber from the matrix, and degradation due to temperature increase compared to the fiber without surface treatment and with surface treatment. Also, mechanical tests on composites showed an increase and improvement in tensile strength of samples reinforced with sodium hydroxide-modified fibers, and the highest flexural strength with sodium-chloride-modified fibers and a decrease in impact strength with surface treatment fibers in all four groups. ‌‌

The sudden spread of Covid-19 in the world has attracted everyone's attention. In addition, due to the unknown and lack of definitive treatment methods, the World Health Organization and other medical institutions recommend non-pharmacological solutions to control the virus. In this regard, one of the proposed methods is to use masks during this global epidemic as a tool to control the spread of respiratory droplets. Therefore, in this paper, we first examine respiratory events such as breathing, talking, sneezing, and coughing from an engineering perspective and their role in the spread of the virus. In addition, with the help of numerical fluid mechanics, the formation of respiratory droplets and their function in the transmission of infectious respiratory diseases have been studied. Then, the necessity of using a mask and its role in reducing the transmission of the virus is discussed.

Various atmospheric phenomena are the main factor or at least a contributing factor in many aviation accidents. Various weather phenomena such as air temperature, visibility, present weather, clouds, pressure, wind affect aviation safety. Among these elements, the wind condition has the greatest impact on flight safety and mainly, in the landing and take-off stage. Accordingly, in this paper, the effects of wind elements on landing and take-off safety are studied. Examining the impact of different wind conditions on aircraft flight shows that the Crosswind is considered to be the most influential wind situation. Also, sudden and momentary changes in the wind can be dangerous for aircraft during landing and takeoff. ‌‌

The Glide Path altitude adjustment system is one of the tools of the landing navigation system (ILS) that helps the airplane to find its angle related to the runway by sending radio signals. It is done by sending two signals with a predetermined radiation pattern. The ratio of these two signals is used to find the elevation angle. The behavior of the electromagnetic wave sent from the system and its reflection from the ground causes the transmitted pattern to be distorted. This effect, known as the ground effect, is very important in transmitting antenna signals' accurate weight and phase shift. In this paper, the pattern of the transmitted pattern of the G/P system is modeled by considering the ground reflection, and several real systems are simulated. ‌‌

The second law of thermodynamics and exergy is an important issue in the analysis of propulsion systems that have been highly regarded by researchers in recent years. Studies show that the analysis of the first law in air propulsion systems alone has low scientific value, and for a complete study of a system, the second law and exergy should also be considered. Thermodynamic analysis of supersonic air engines, especially Ramjet and Scramjet engines, with the aim of studying their performance, has attracted the attention of many researchers in the last decade. In this method, using thermodynamic laws and exergy analyzes, Ramjet and Scramjet motors are systematically analyzed, and their optimal state is extracted. The main purpose of this study is to review and present the latest research findings in this field, focusing on Ramjet and Scramjet engines.