Linearization design method in class-F power amplifier using artificial neural network

This paper represents the design of a class-F power amplifier (PA), its artificial neural network (ANN) model and a PA linearization method. The designed PA operates at 1.8 GHz with gain of 12 dB and 1dB output compression point (P1dB) of 36 dBm. The proposed ANN model is used to predict the output power of designed class-F PA as a function of input and DC power. This model utilizes the designed class-F PA as a block, which could be used in a desired linearization circuit. In addition, the power added efficiency (PAE) and the other specifications of a PA, related to power can be predicted using the proposed model. A simple feedforward technique is used to improve the linearity of designed PA. For verification, this linearization method is compared with presented neural network model simulations. The results show the improvement of P1dB from 36 to 41 dBm, which is predicted using the proposed model. Also, the PAE of the final linearized circuit PA is predicted.     

Three-dimensional modeling of system of vibrating spherical balls using discrete element method

The modeling of particulate systems has been an important focus of research worldwide, as these are fairly common in nature, such as rain drops in air, snowfall, and several industrial processes such as chemistry, agriculture, pharmaceutical, powder metallurgy, soil mechanics, casting, cement manufacturing, civil, and etc. In recent years, one of important aspects of the granular material physics in industries is controlling way of the granular flow. One of the best ways of controlling the flow is the use of mechanical vibrations to guide the particles in desirable way. In this paper the effect of horizontal harmonic vibration on the particles flow is theoretically and experimentally investigated. During the base vibration, the spherical particles collide with each other and with the walls as well, causing a global pattern of particle motion which is interpreted as flow. The motion of spherical particles and the interaction forces due to the vibration is obtained numerically via discrete element method (DEM). Finally, the presented numerical model is compared with the experimental one and a good agreement between them is noticed.     

The influence of addition of carbon nanotube and graphene platelets on characteristics of carbon/basalt fiber reinforced intra-ply hybrid composites

In this study, effects of addition of carbon nanotubes (CNTs) and graphene platelets (GPLs) on characteristics of carbon/basalt fiber reinforced intra-ply hybrid composites were investigated. The composites were fabricated using vacuum assisted resin infusion molding (VARIM) method in two types including bare and 0.1, 0.5 wt.% of GPL and CNT nanoparticles filled hybrid composites. Fabricated normal and multiscale composites were cut by water jet and mechanical properties of specimens were examined by tensile, flexural, SBS experiments. Therefore, the modulus of elasticity, flexural modulus, tensile and flexural strength and ILSS of bare and multiscale composites were compared. Thermomechanical properties of fabricated composites were evaluated by dynamic mechanic analyze (DMA), thermogravimetric analyze ( TGA) and thermal conductivity (TC) tests and storage modulus, loss modulus, damping ratio, glass transition temperature, weight loss and derivative weight loss were compared in fabricated normal and multiscale composites. Similarly, modal properties of fabricated composites such as natural frequency and damping factor were obtained by vibrational tests and compared in fabricated composites. According to the results, the addition of carbon-based nanoparticles improved the characteristics of carbon/basalt fiber intra-ply hybrid composites. The response of composites was directly proportional to the addition ratio of the carbon-based nanoparticles.     

Ten-year outcomes for pathologic node-positive patients treated in RTOG 75-06

PURPOSE: This study was conducted to see what fraction of prostate cancer patients with biopsy-proven nodes are free of cancer 10 years after radiation treatment. METHODS AND MATERIALS: RTOG protocol #75-06 included 90 patients with biopsy-proven pelvic nodal involvement treated with radiation. They have been continuously follow-up since treatment. When feasible, current prostate-specific antigen (PSA) levels have been solicited from patients clinically cancer-free (no evidence of disease, NED) at 10 years, to confirm cure. RESULTS: The 10-year survival was 29%, the 10-year clinical NED survival 7%. PSA levels were obtained in 2 of 5 10-year clinical NED patients, they were both less than 0.8 ng/ml. The 2 proven cures were both clinical stage T-3, Gleason Score 6 and 8, and had 2 and 1 positive nodes, respectively. Multivariate analysis showed Gleason sum was significantly associated with clinical survival without disease. CONCLUSION: A small fraction of node-positive patients are cured at 10-year follow-up by radiation therapy (2 of 90 with PSA +3 of 90 by clinical endpoints). Innovative treatment programs should be directed at node-positive patients in an effort to improve the fraction cured.     

Investigation of the corrosion behavior of 304L and 316L stainless steels at high-temperature borated and lithiated water

The effects of temperature and dissolved oxygen on the electrochemical behavior and the oxide film formation of grades 304L and 316L stainless steels at high-temperature borated and lithiated water were investigated by means of potentiodynamic polarization, scanning electron microscopy and X-ray photoelectron spectroscopy. The results revealed that increasing the solution temperature degrades the passivity of the oxide films formed on both grades of steel and shifts their corrosion potential toward more negative potentials. The oxide films formed on the steel samples immersed into the solution containing 20 ppb dissolved oxygen (DO) showed a duplex structure, in which the inner layer was mostly a composition of Cr oxides and the outer layer mainly was a Fe oxide and Ni–Fe spinel. Only a single layer of Cr-rich oxide was observed in the oxide films formed in the solutions with the DO concentrations higher than 20 ppb. Higher amount of Cr in the oxide films formed on the type 316L compared to 304L improves the passivity of the oxide film of this grade of steel and results in a wider passive region in its potentiodynamic polarization curves.     

Analysis of entropy generation in a hydrogen-enriched turbulent non-premixed flame

The analysis of local entropy generation and exergy loss was performed in a turbulent non-premixed H₂-enriched CH₄–air bluff-body flame. Detailed chemical kinetic, transport properties, and turbulence-chemistry interaction were taken into account in using laminar flamelet model for the simulation of combustion process via an in-house, finite volume code. The analysis was based on local entropy generation calculation. Results showed that thermal conduction made the most contribution to entropy generation followed by chemical reaction and mass diffusion, while the contribution of viscous dissipation was negligible. Entropy generation resulting from thermal conduction occurs in a large volume of the domain, while entropy generation resulting from chemical reaction and mass diffusion occurs only near the bluff surface. The effect of H₂ addition to fuel and air preheating on the entropy generation rate was investigated. It was observed that entropy generation and exergy loss were decreased by H₂ addition, mainly due to a decrease in the chemical reaction component of entropy generation, while entropy generation resulting from thermal conduction slightly increased and entropy generation resulting from mass diffusion remained almost constant. Entropy generation resulting from heat conduction by preheating combustion air decreased, while entropy generation resulting from chemical reaction and mass diffusion remained almost constant. The decrease of thermal conduction contribution in entropy generation is so significant that, by preheating air up to 750 K in the case of pure CH₄, chemical reaction becomes the main source of irreversibility. These investigations show that H₂ addition and preheating the combustion air both lead to the improvement of the second law efficiency, although the second law efficiency is more sensitive to flame structure and air temperature.     

Investigation of Geyser Boiling Phenomenon in a Two-Phase Closed Thermosyphon

In this paper, geyser boiling phenomenon (GBP) in a two-phase closed thermosyphon has been investigated experimentally. Here, the effects of the inclination angle, filling ratio, input heat rate, mass flowrate of coolant, and inside diameter of the tube on the GBP have been discussed. Three copper thermosyphons with inside diameters of 14 mm, 20 mm, and 24 mm and a length of 1000 mm were employed. Distilled water was used as the working fluid. A series of experiments was carried out to investigate the effect of the inclination angle range of 5° to 90°, the input heat rate range of 50 to 312.4 W, the coolant mass flow rate range of 0.00389 to 0.0164 kg/s, and the filling ratio range of 15 to 45%. The GBP has been investigated by analyzing the time variations of the evaporator and adiabatic wall temperature and outlet water temperature from condenser jacket. The results show that the period of GBP was longer for higher inclination angles and filling ratios. Furthermore, it was discovered that the GBP did not take place for inclination angles of less than 15°.     

Periodic graphene nanobuds: A novel Li-storage material

The characteristics of lithium adsorption on graphene and periodic graphene nanobuds (PGNBs) have been studied by means of density functional theory calculations. All calculations have been performed within the Perdew–Burke–Erzenhof functional as implemented in the SIESTA package, with a double-ζ plus polarization basis set. Several starting configurations were considered for interacting systems. The results show that the Li atom is strongly adsorbed on a pure graphene with a binding energy of about −0.85 eV. However, the binding energy enhances to −2.58 eV when Li binds to a PGNB at the hollow site above the center of the nonagon ring. It was found that the increase in binding is due to significant charge transfer from the Li to the PGNB. The stability of the Li/PGNB system was evaluated within ab initio molecular dynamics simulation which has been carried out at room temperature. The very favorable binding energy obtained as well as high specific surface of PGNB (due to attached fullerenes) suggest a considerable possibility to experimentally apprehend these novel systems as a superior media for Li ions storage.