The tunable band structure and the ability to convert ultraviolet light (UV) photons into measurable electrical signals without an external power supply make the nano-scale spinel structure of nickel cobaltite (NiCo2O4; SNC) an attractive ternary metal oxide semiconductor for use as a UV light photodetector (UPD). In this paper, the SNC was prepared using a simple, one-step hydrothermal method and characterized by various analytical techniques. I-V characteristics were comprehensively studied over a range of -5 to + 5 V to evaluate the dependence of the net current in an SNC-based UPD (UNC) on the variations in temperature, bias voltage, and power density (PD) of 365 nm-UV light. It was found that the device exhibits diode-like characteristics with acceptable photoresponse behaviors. This device not only demonstrated a modified Richardson constant of 22.85 A.cm− 2.K− 2 but also exhibited a high contrast ratio and significant short-circuit current at 0 V, indicating its self-powered nature. The UNC exposed photoresponsivity of 0.88 A/W, detectivity of 10.75 × 1010 Jones, external quantum efficiency of 299.4
The cognitive radio network (CRN) consists of multiple secondary users (SUs) and primary users (PUs). In fact, the spectrum of each PU is shared by the several SUs without or with determined interference with PUs (i.e., licensed users), which enhances spectral efficiency. Spectrum sensing is one of the solutions to improve the secondary network (SN) performance and primary network (PN) in the opportunistic spectrum access of the CRN. In this case, by assistance of intelligent reflecting surface (IRS), the received signal strength and therefore, the communication of SNs and PNs are enhanced according to the spectrum sensing results. On the other words, IRS utilization leads to the coverage, data rates and power efficiency improvement in cognitive radio networks. In this work, we consider multi IRS-assisted CRN with multiple SNs, PNs and IRSs. The main goal of this study is maximizing the SNs’ sum rates by obtaining the user-IRS association and optimizing secondary transmitters (STs) beamforming, sensing duration of each PU and three stages IRS phase shifts matrices for each SN and each IRS, respectively while average achievable rate requirement of PUs, the STs’ maximum transmit power and the detection performance constraints are maintained. For solving the non-convex optimization problem, an iterative algorithm is utilized based on the Gradient Descent framework. Simulation results verify that the user-IRS assignment leads to more spectral efficiencies of both primary and secondary transmissions in the proposed IRS-assisted CRN compared to the benchmark algorithms.
Recent studies have focused on distinguishing permanent faults from transients and detecting secondary arc extinction. A simple method for detecting secondary arc extinction is to compare the measured voltages on the sides of the faulty phase with the threshold voltage. Along the faulty phase, a voltage drop (magnetic voltage) is created when the power flow (due to load) passes through the sound line conductors due to inductive coupling between the phases. As a result of this voltage drop, voltage deviations occur on both sides of the faulty phase, resulting in incorrect detection of the secondary arc extinction. To overcome this problem, a novel method has been developed, which relies on mutual communication signals between the substations on both sides of the line, allowing for the correct detection of the secondary arc extinction especially in high loading conditions of the line. Also, a novel formulation has been derived for the calculation of opened phase voltage in an untransposed line to threshold voltage adopting. To verify the validity and accuracy of the proposed method, some cases are implemented in EMTP by creating faults in different locations of a transmission line.
Iran’s location in a seismic zone and the existence of numerous structures built based on outdated seismic design codes necessitate a closer examination of the building design process. Among the issues arising during earthquakes, especially in large cities, is the occurrence of structural pounding. Most studies conducted on structural pounding have been two-dimensional, with rigid supports and for homogeneous structures. However, two-dimensional modeling eliminates torsion and neglects soil-structure interaction effects, which alters the structural behavior compared to reality. Moreover, there is a significant difference between the behavior of structures made of different materials, such as steel and reinforced concrete. Therefore, it is necessary to investigate the pounding phenomenon for heterogeneous structures, considering torsion and soil-structure interaction, and to determine a safe separation distance. In this research, by three-dimensional modeling of steel and concrete structures subjected to seven scaled selected earthquake records, adjacent to each other, at heights of 5, 11, and 17 stories, situated on a flexible soil foundation at various distances, the structural pounding phenomenon and the determination of a safe separation distance were studied. The results indicate that torsion leads to an 11
Dealing with phenomena such as gas hydrate formation, which threatens sustainable production by blocking transmission lines, is a priority during field operations. The presence of laboratory data on gas hydrate thermodynamic equilibria, as well as models that can estimate it with acceptable approximation within the range of the field temperature and pressure profile, seems essential for safe and sustainable production by mitigating the risks associated with hydrate formation. The aim of the present work is to examine the pressure-temperature region of the hydrate zone, at which stable hydrate forms thermodynamically, for the South Pars gas field with natural gas composition including hydrogen sulfide (H2S) in the presence of monoethylene glycol (MEG) and methanol (MeOH), commercially used with the intention of performing thermodynamic inhibition. First, static experimental high-pressure tests were performed at levels of 10 wt%, 20 wt%, and 30 wt%. The presence of two thermodynamic inhibitors shifted the hydrate equilibrium curve (i.e., the border of the hydrate zone) to lower temperatures. The average suppression temperature in the presence of MEG with the concentration of 10 wt%, 20 wt%, and 30 wt% is 1.1 degrees C, 4.9 degrees C, and 9.5 degrees C, respectively. In return for the presence of MeOH, it was observed as 4.0 degrees C, 8.7 degrees C, and 15.2 degrees C, representing a more potent inhibitory effect of MeOH compared with MEG. Then, a thermodynamic model was provided exclusively to anticipate the South Pars gasfield hydrate equilibrium conditions based on the fugacity difference of water in the hydrate and aqueous phases. The model incorporated the van der Waals-Platteeuw (vdW-P) model, Peng-Robinson (PR) equation of state (EOS), and nonrandom two-liquid (NRTL) activity coefficient model related to the hydrate phase, vapor phase, and alcohol/glycol solutions, respectively. The optimized parameters of the model were determined using a genetic algorithm (GA) technique. The prediction of the model showed acceptable accuracy, with average absolute pressure deviations below 7% compared with the experimental results.
