A low profile fractal Defected Ground structure (DGS) antenna is presented for super-wideband (SWB) wireless communication applications. The designed antenna covers a very wide frequency range from 1 to 27.4 GHz (impedance bandwidth of 186%) with |S11|<-10 dB. Moreover, In spite of small electrical dimension of the proposed antenna (0.11 λ× 0.11 λ), a large bandwidth dimension ratio of 15372 is resulted. The SWB operation is achieved by using fractal DGS on the Ground Plane to improve the impedance characteristics between adjacent resonant frequencies. The antenna consists of a 34×34×1.6 mm3 FR4 substrate with a dielectric constant of 4.4 and a narrow rectangular radiator. A multi-frequency resonance characteristic is obtained by increasing the fractal slot iterations on the Ground Plane. The simulation results are verified by experimental measurements. Measured data are in good agreement with the simulated results. The frequency- and time-domain characteristics of the antenna including impedance matching, far-field patterns, gain, radiation efficiency, group delay, and fidelity factor are presented and discussed. The results indicate that the antenna has good performance over the entire operating bandwidth which make it very potential candidate for integration in SWB wireless communication systems.

A novel geometry of polarization and frequency reconfigurable antenna is proposed in this paper. Proposed antenna consists of an L shaped patch antenna, where arms are separated using PIN-diode. Two parasitic elements, shorted back element and edge tapered Defected Ground structure with slot are used for achieving wide impedance and axial ratio bandwidth. It acts as circular polarized antenna with 1.183 GHz axial ratio band width and 3.09 GHz impedance bandwidth in ON state of both diodes and act as linear polarized frequency reconfigurable antenna at remaining states of diodes. Proposed antenna can be used in C band wireless applications like RADAR, satellite communication etc.

A new broadband slim microstrip antenna with a narrow Ground Plane for GPS (1575. 42 MHz), Glonass (1600 MHz), GSM (1800 MHz), LTE (1700 MHz), DAB (1452 MHz) and satellite phone (Iridium, 1616-1626. 5 MHz; Inmarsat and Ligado, 1525-1646. 5 MHz and Thuraya, 1525-1661 MHz) applications is proposed. The antenna is comprised of a slim rectangular patch, a shorting pin, and a meander-line structure. Its strip-like shape helps to be easily mounted inside the portable devices. The antenna has a dimension of approximately 0. 43λ ×0. 02λ ×0. 008λ while achieving a gain and an efficiency of 2. 4 dB and 95%, respectively. Using a Defected Ground Plane the antenna impedance bandwidth (|S11|<− 6 dB) of 32. 6% from 1. 44 to 2 GHz is observed. In order to validate simulation results, a prototype of the proposed printed antenna is fabricated and tested. Good agreement between the simulation and measurement results is obtained.

Most members of structures whose useful life has elapsed need to be repaired. These members may be damaged by a variety of factors. Due to the high cost of reconstruction, a large portion of countries’ development budgets are spent annually repairing and rehabilitate these structures. Compressive members such as columns are one of the most important components in a structure that play a major role in bearing and transporting all the vertical and lateral loads of the building. Basically, no column can bear to its fullest capacity and is failed by buckling. As a result, many researchers are interested in retrofitting and increasing column strength using new materials and methods. In this investigation, damaged circular hollow section steel columns with vertical and horizontal notches and different percentages of 25, 50, 75 and 100% were examined, also the effects of Carbon Fiber Reinforced Polymer (CFRP) for strengthening has been studied. 26 specimens of steel Circular Hollow Section (CHS) column with the same height and different damage dimensions under compressive load were analyzed by ABAQUS 2016 software. The main problem with slender columns is the global buckling under compressive loads. In order to improve the accuracy of the analysis, a combined method was used to study the post-buckling of the plastic zone. For this purpose, the specimens were first subjected to elastic buckling analysis and then Riks non-linear analysis with global and local imperfections was conducted. The results showed that the defect reduces the bearing capacity and rigidity of the steel columns and horizontal defect is more effective in reducing ultimate load in compare to vertical damage. Horizontal-defective columns experienced ‎significantly lower load bearing capacity than ‎vertical-defective columns and can reduce final load up to 52% ‏ in 100% damage, which this reduction indicated that by increasing damage along the perimeter of the column section, final load decreased sharply. The results also showed that it is critical when the deficiency zone is entirely destroyed, while the effect of damage less than 25% was maximum 2.66%. Columns failure occurred in the form of global and local buckling; in all cases global buckling emerged in the form of the column bending, but the local buckling was different according to the type of the damage. ‎Failure modes of the control column is global ‎buckling with focus on the middle of the ‎column, for non-strengthened specimens with ‎horizontal and 100% damage, local buckling‎‏ ‏is shrinkage of ‎notch edges and for vertical notch is defect ‎edges opening. In specimens with a lower percentage of damage, local buckling occurred for horizontal defects in the form of the inward buckling on the middle and for the vertical ones was outward buckling. ‎Strengthening of columns retrofitted with CFRP presented that these kind of fibers have a positive effect on significant gaining ultimate load capacity, delaying defect buckling, controlling fractures and reducing stresses at the damaged area. CFRP strengthening of Defected cases using 4 layers, restored the reduction of ultimate load up to 51%, which shows the proper performance of the fibers in retrofitting.

Diaphragms, beyond supporting gravity loads and transferring them to vertical structural elements, play a crucial role in collecting lateral forces and distributing them among lateral resistant systems. In some cases, due to architectural considerations in the design of braced steel building frames, structural designers are compelled to shift the braces in the structure's plan, classifying them under structures with out-of-Plane offset irregularity. In such structures, the horizontal diaphragm between the shifted braces must effectively transfer the shear forces induced by earthquakes. Therefore, investigating the behavior of these diaphragms is imperative for the analysis and design of these structures. The objective of this research is to investigate the seismic behavior, drift demands, over-strength factor, and the degree of vulnerability of discontinuous concentrically braced frames (CBFs) when subjected to earthquakes. To achieve this goal, two three-dimensional CBFs of 3 and 6 stories, both with and without out-of-Plane offset irregularity, incorporating inelastic diaphragm behavior, were taken into account through pushover and nonlinear time-history dynamic analyses using ABAQUS. The examination of the results indicated that the concrete diaphragm existing in the discontinuity region, with a thickness of five centimeters, has been damaged at a 45-degree angle. It lacks the ability to transfer the shear force resulting from the lateral load of the braces. This is in contrast to thicknesses of 10 and 20 centimeters, where the diaphragm in the mentioned area remains undamaged. Given the information provided, it seems that, with the minimum thickness specified in Iranian National Building Code (part 9), was vulnerable to the transferred shear forces. Additionally, it was found that the inter-story drift demands of the frames exceed the estimations proposed by the building code.

In this paper, a continuum model is proposed so that a Stone-Wales (SW) Defected carbon nanotube (CNT) is replaced by an initial circumferential crack in a continuum cylindrical shell. For this purpose, the critical energy release rate and then the fracture toughness of a Defected CNT are calculated using the results of an existing atomistic-based continuum finite element simulation. Finally, the equivalent crack length is obtained from the fracture toughness. The proposed model can be applicable tovarious kinds of continuum-based simulations of nano-structures like nano-composites and nano probes where the fracture resistance studies become important. It is concluded for a case study that the armchair (12, 12) CNT containing a SW defect could be replaced with a continuum cylindrical shell with a circumferential crack length of 0.83 nm. Furthermore, the damage variable is discussed to achieve a method for estimating the effective Young's modulus of Defected nanotubes with numerous defects subjected to the progressive damage. This estimation method is evaluated by the atomistic based FE simulation of a double Defected CNT.

Many steel structures are damaged due to environmental factors such as accidental loads, exhaustion, rust, and phenomena such as cavitation and time passes. Dams’ bottom outlets are one of the important components of these structures that are subject to numerous hydraulic problems such as cavitation vibration, which causes damage and needs repair. One of the novelties for refining is the use of Carbon Fiber Reinforced Polymer (CFRP). In this paper, the effect of CFRP on gate strengthening under cavitation vibration load and the effect of damage on maximum vibration by using ABAQUS were studied. In order to observe the effects of failure on the maximum vibration of the outlet, two damages were applied to the front or back of the gate. Finally, the damaged gates were reinforced with two layers of CFRP. The outcomes showed that damage resulted in maximum vibration increase and polymer fibers has a significant effect on reducing vibrations and stresses caused by cavitation pressure.