Flexural response analysis of passive and active near-surface-mounted joints: experimental and finite element analysis

The near surface mounted system is considered an innovative strengthening technique used to increase the flexural and shear capacity of RC structures. Although, many researches have been carried out to study the flexural response of NSM joints, further research is still required to cover all the controlling parameters. In this research, the effects of the FRP cross sectional area, end anchoring, and partial bonding of the NSM bars were experimentally investigated. A numerical investigation utilizes the non-linear finite element (FE) modeling was also performed using ANSYS^®. Progressive continuum damage mechanics along with the fracture concepts were employed to simulate the damage initiation and propagation at the epoxy-concrete interface. The developed FE models were calibrated and verified using the obtained experimental results. Based on the good agreement obtained between experimental and FE results, the numerical analysis was extended to conduct an extensive parametric investigation. The numerically investigated parameters included the NSM bar length, tensile steel corrosion, concrete compressive strength, Activating/prestressing the NSM reinforcement, and axial stiffness of the prestressed NSM joints.     

Enhancement-mode high electron mobility transistors (E-HEMTs)lattice-matched to InP

The fabrication and characterization of high-speed enhancement-mode InAlAs/InGaAs/InP high electron mobility transistors (E-HEMTs) have been performed. The E-HEMT devices were made using a buried-Pt gate technology. Following a Pt/Ti/Pt/Au gate metal deposition, the devices were annealed in a nitrogen ambient, causing the bottom Pt layer to sink toward the channel. This penetration results in a positive shift in threshold voltage. The dc and RF performance of the devices has been investigated before and after the gate annealing process. In addition, the effect of the Pt penetration was investigated by fabricating two sets of devices, one with 25 nm of Pt as the bottom layer and the other with a 5.0 nm bottom Pt layer. E-HEMTs were fabricated with gate lengths ranging from 0.3 to 1.0 μm. A maximum extrinsic transconductance (g_mext) of 701 mS/mm and a threshold voltage (V_T) of 167 mV was measured for 0.3 μm gate length E-HEMTs. In addition, these same devices demonstrated excellent subthreshold characteristics as well as large off-state breakdown voltages of 12.5 V. A unity current-gain cutoff frequency (f _t) of 116 GHz was measured as well as a maximum frequency of oscillation (f_max) of 229 GHz for 0.3 μm gate-length E-HEMTs     

Fano Resonance by Means of the One-Dimensional Superconductor Photonic Crystals

In the present work, we introduce a study about the reflectance properties of a one-dimensional superconductor photonic crystal in a different manner. Our structure is designed from alternately layers of high-temperature superconducting material (BSCCO) and a conventional superconducting material (Nb) terminated by the dielectric cap layer. The investigated numerical results are essentially based on the basics of the transfer matrix method and the two-fluid model. The numerical results showed the appearance of two sharp peaks, which are referred to Fano and electromagnetic-induced reflectance resonances. Also, we demonstrate the effects of many parameters on the reflectance properties of Fano resonance and the electromagnetic-induced reflectance. The effects of the constituent layer thicknesses, the number of periods, the operating temperature, the angle of incidence, and the refractive index of the dielectric cap layer are all considered. Finally, the effects of hydrostatic pressure on the Fano and EIR resonances are studied and calculated. This structure can play an important role in optical switching devices.     

Evolution of Phononic Band Gaps in One-Dimensional Phononic Crystals that Incorporate High-<Emphasis Type="Italic">T</Emphasis><Subscript>c</Subscript> Superconductor and Magnetostrictive Materials

In this work, we calculate the reflectance of one-dimensional phononic crystals (1D PnCs) using the transfer matrix method. We present numerical results for two different PnC structures, the first one, PnCs1, contains high- T _c superconducting compound (Bi-2223) and the second, PnCs2, contains a giant magnetostrictive material (Terfenol-D). Magnetostriction is a property of ferromagnetic materials that causes them to change their shape/dimensions when subjected to external magnetic field. PnC studies that dealt with such materials are few. In this study, we focus on discussing the effects of the temperature and the magnetic field on the phononic gaps of these PnCs. For PnCs1, numerical results show that local resonant modes of elastic waves with brilliant sharpness can be realized. In addition, increasing the temperature leads to a decrease in the gap width which can be controlled by the magnetic field due to the effect of the magnetic field on the velocity of waves in the high- T _c superconducting compound, the magnetic field effectively can widen the gap. For PnCs2, numerical results show that the gap width increases by increasing the magnetic field because the magnetostrictive material directly expanded in the presence of the magnetic field.     

Synthesis and effect of vanadium pentoxide nanoparticles on dielectric relaxation and ac conductivity of polyvinyl alcohol

The dielectric parameters of polyvinyl alcohol containing 0–0.8 wt. % vanadium pentoxide are studied in the temperature range 20–150 °C at different frequencies: the dielectric constant, dielectric losses, and tangent of the angle of dielectric losses. Cole–Cole plots are used to determine the static dielectric constant and the dielectric constant at infinitely high frequency. The relaxation time is determined at different frequencies as a function of the tangent of the angle of dielectric losses versus the temperature. It is found that the relaxation properties follow the Arrhenius equation, the activation energy decreases with the vanadium pentoxide content in polyvinyl alcohol. An investigation of the dielectric relaxation as a function of temperature at constant frequency revealed two types of relaxation processes: dipole-segmented motion (α-relaxation) and side-chain dipole group motion (β-relaxation). The ac conductivity in the system polyvinyl alcohol––vanadium pentoxide is explained on the basis of the correlated barrier hopping model.     

A self learned invasive weed-mixed biogeography based optimization algorithm for RFID network planning

The optimal placement of the RFID readers inaugurates an ongoing research field, namely the RFID network planning (RNP). The main issue in the RNP is to know how many readers have to be used and what is their best distribution that guarantees fulfillment of multiple objectives. The common RNP objectives are the optimal coverage, readers’ interference avoidance, redundant reader elimination, load balance among deployed readers and minimum power losses, which are considered as conflicting objectives that leads the RNP to be an NP-hard problem need to be solved. The contributions in this paper are: firstly, utilizing both the Biogeography based optimization (BBO) and the Hybrid Invasive Weed-Biogeography based optimization (HIW-BBO) as new algorithms have not used before for solving the RNP. Secondly, we proposed a Self Learning (SL) strategy with a mixed BBO Migration (MBBOM) operation to modify the HIW-BBO algorithm in an algorithm called Self Learned Invasive Weed-Mixed Biogeography based optimization (SLIWMBBO). Thirdly, the performance of the proposed SLIWMBBO algorithm is compared to both the HIW-BBO and the Self Adaptive Cuckoo Search (SACS) optimization algorithms according to a set of 13 benchmark functions. The results of this comparison encourage the application of the SLIWMBBO as an optimization algorithm for solving the complex problems. Lastly, the BBO, HIW-BBO and SLIWMBBO optimization algorithms are used for solving three complex RNP instances and compared to the SACS algorithm. Simulation results of the SLIWMBBO are outstanding and demonstrate its superiority over the compared algorithms.