The class of Hybrid Linear and Circular Antenna Arrays is presented. The properties of linear and circular antenna arrays are combined to obtain hybrid array types: concentric circular, cylindrical, and coaxial cylindrical antenna arrays. These three types are defined, the expressions of their array factors are derived, their directivities and half power beam widths (HPBW) are simulated. The obtained plots are approximated by curve fitting. Different combinations of excitation currents (e.g. uniform, Chebyshev, Bessel, …) can exist on the elements of the same antenna array.

In this paper, an iterative algorithm for direction of arrival (DoA) estimation of coherent sources with a uniform circular array (UCA) is proposed. There is an additional error in the DoA estimationof signals after mapping UCA to virtual uniform linear array (VULA), due to approximation of beamspace transformation. This error depends on the direction of emitters. In the proposed algorithm, the dominant term of error is reduced using two beamformers. Then, the DoA of coherent sources are estimated by construction of Toeplitz covariance matrix and using the MUSIC algorithm. The processes of DoA estimation and reduction of the approximation error are doneiteratively. Also, an analytical expression is derived for the approximation of bias for DoA estimation of coherent sources. Simulation results show that the proposed algorithm has a better performance in comparison to the conventional methods.

This paper has investigated the flow interference between three circular cylinders of equal diameter in an equilateral-triangular arrangement and also between four circular cylinders in a square arrangement when subjected to a cross-flow. Wind tunnel experiments were conducted to measure force coefficients for six spacing ratios (l/d) varying from 1.5 to 4 at subcritical Reynolds number of 6.08×104. The pressure distributions on the surface of the cylinders were measured, using pressure transducers. It was found that for three cylinders at l/d>2, the upstream cylinder experiences lower mean drag coefficient than that of the downstream ones. Also, the minimum drag coefficient values of the downstream cylinders occur at l/d=1.5 and l/d=2. Moreover, It was revealed that for four cylinders at l/d=1.5, due to severe flow interference between cylinders, there is a difference between lift coefficients for the upstream cylinders. Also, for l/d£2, the mean drag coefficients for downstream cylinders are negative. In addition, it was concluded that the variations in l/d strongly affect the aerodynamic coefficients. Also, by decreasing l/d, the effects of the flow interference between the cylinders increase.

Supplying the energy demanded by spacecraft and satellites is an ever-increasing need. As a result, it is an active field in developing space technologies. In addition to the commonly used rigid substrate solar arrays, flexible substrate and concentrator solar arrays are other available categories. This paper reviewed the developments and commercial technologies in each category. The flexible solar arrays, implemented in several spacecraft during the last two decades, have recently attracted attention in satellites. It seems that these arrays will replace rigid arrays in the near term due to their higher specific power and smaller stow volume than rigid arrays.

Clustered regularly interspaced short palindromic repeats (CRISPR) which is literally defined as a clustered regularly interspaced short palindromic repeats is an adaptive immune system in bacteria, which enables them to detect and destroy the DNA of the virus. In fact, CRISPR is a defense mechanism in prokaryotic cells, which induces resistance to foreign genetic content, such as that found in the plasmid or phages. The proteins involved in this mechanism are called CRISPR associated proteins (CAS) which have the ability to search, cut and eventually transform phage DNA in a specific way. The CAS is a protein with an enzymatic function which can be called nuclease, given the fact that it plays a special role in the DNA sequence and CRISPR arrays. The CRISPR technology allows changes in DNA, which enables to modify and make any changes to any gene in any living creature, much more accurately and better than all previous methods. In this review, we introduce the mechanisms and benefits of CRISPR in genome editing, briefly reviewing CRISPR programs in gene therapy exploration and CRISPR’ s ability to produce different types of mutations through different repair mechanisms.