Aerospace Defense

Abstract In this work, an attempt was made to prepare thin layers of nanostructured cadmium selenide (CdSe) based on a simple solution method of chemical bath deposition (CBD), which commercially has an accessible precursor. In the chemical solution bath layering method, manufacturing factors play a significant role and determine the characteristics of the final product. In this research, the effect of an important factor, the concentration of primary solutions of selenium and cadmium ions, which is one of the most important factors in the formation of cadmium selenide, and it will be observed that the change in the concentration of these metal and non-metal ions strongly affects the type of electronic structure of the material. In comparison with the sputtering methods, in the chemical solution deposition method, there is a high control in the formation of solid deposits with different combinations of metal and non-metal binary compounds. Changing the selenide ionconcentration changes the size of the energy band gap. It has been observed that the energy gap increases with the increase of selenide non-metal ion concentration.

Abstract This article aims at the improvement of Synthetic Aperture Radar (SAR) resolution by using a Matched Filter (MF) based on the Fractional Fourier Transform (FrFT) that has been called a Matched Slope Filter (MSF). Generally, the received SAR signals are processed by well-known algorithms to extract the final image, such as the Chirp Scaling Algorithm (CSA) and the Range Doppler Algorithm (RDA). Implementing a Matched Filter (MF) that aims at compressing the received signal in the range and azimuth directions is a principal part of these algorithms to deliver target positioning and high resolution. Because the transmitted signal by SARs has often been Linear Frequency Modulated (LFM), the received echo from the targets in the range direction is the LFM. On the other hand, there is always a chirp signal in the azimuth orientation. Thus, this paper proposes the Matched on Slope Filter to improve the compression of the azimuth signals. It's clear the proposed method has been adopted for LFM signal compression in the range direction also. The evaluation results show that our method that uses the FrFT in the time-frequency domain for implementing a Matched Slope Filter enhances the resultant azimuth resolution and reduces the sidelobe level compared to the other frequency-based method.

Abstract In this paper, a rotor position estimation algorithm based on sliding mode observer (SMO) and phase-locked loop (PLL) for permanent magnet synchronous motor (PMSM) control in STM32L431RCT6 microcontroller is presented. The proposed SMO and PLL-based observer has two advantages compared to the conventional SMO observer: reducing the undesirable phenomenon of chattering and improving the accuracy of rotor position estimation. In this research, a hybrid sensorless control system for PMSM drive has been designed, using the I-f startup method and a smooth transition to sensorless closed-loop vector control with SMO and PLL. C programming language is used to implement field vector control, phase-locked loop, sliding mode observer, proportional-integral controllers, space vector pulse width modulation, and coordinate transformations. The proposed method is implemented using STM32 family 32-bit microcontrollers. In the following, the presented laboratory results show the desirable performance of the proposed observer.

Abstract Software testing operations, as one of the fundamental methods for evaluating the quality of software products, are employed throughout various stages of software development and maintenance. With the increasing complexity and ubiquity of software, the need for performance and efficiency testing methods with a suitable balance between reducing time and increasing accuracy is felt.

In this study, automated software testing methods using Biogeography-Based Optimization algorithms, coupled with the bat algorithm, have been investigated, resulting in the production of a high-performance covering array. These innovations, along with the utilization of optimized data structures, have not only aided in managing software complexity but also addressed the success requirements of software projects. This research is recommended for enhancing the quality of software products, focusing on producing covering arrays with high efficiency and improving the performance of software testing.

Abstract In recent decades, the use of drones as part of urban and regional transport infrastructure, as well as military applications, has developed extensively. Contrarily, their high aerodynamic noise is one of the serious challenges to obtaining a certificate of airworthiness for these flying devices. The most important source of noise in multi-rotors, airplanes, and propeller drones with electric motors or even turboprop engines is the noise caused by propellers. In the present study, to learn more about the mechanisms affecting the propeller's noise at low Reynolds numbers and to investigate the sensitivity of the noise to the propeller rotational speed and the polar angle of its propagation, the far-field noise of a drone propeller has been evaluated experimentally. The results show that the propeller's noise includes tonal and broadband noise, so that at low frequencies, the largest propeller tonal noise occurs at the blade pass frequency, and its harmonics are still visible up to high frequencies. On the other hand, the broadband components of noise predominate in the medium and high-frequency ranges. The increase in propeller rotational speed has led to an increase in the amplitude of both the tonal and broadband noise spectrum, so that the values of the overall sound pressure level and the noise spectra of the propeller at the first blade pass frequency have increased with the increment of the propeller speed. Finally, the results showed that broadband noise has a higher sensitivity to the polar angle of sound propagation than tonal noise.

Abstract In this research, 1 and 2-dihydroxy-9 and 10-anthraquinone ( Alizarin Red ) has been introduced for the first time as a sequential chemosensor to detect and measure Cu2+ and arginine in an aqueous medium. The reaction of Alizarin Red (Aliz) and Cu2+in the first step shows a noticeable change from pale orange to pale purple, in addition, in the second step the reaction between (Aliz-Cu) and arginine shows a noticeable color change from pale purple to deep purple.

The results showed that Alizarin Red and Aliz-Cu have strong binding affinity and good detection limit for Cu2+ and arginine, respectively. For Cu2+, the linear range and detection limit are 4.78-43.98, 0.43 μmol L−1, and for arginine, the linear range and detection limit are 7.15-107.78, 0.65 μmol L−1. Finally, by using this method, we successfully measured these two species in real samples (drinking water in military barrack, mineral water and in the blood serum of soldiers).