Correction to: Proposed Model for Radio Wave Attenuation due to Rain (RWAR)

Wireless Personal Communications - A correction to this paper has been published: https://doi.org/10.1007/s11277-021-08370-x     

Behavior of perfluoropolyalkylethers under simulated dynamic bearing conditions

Perfluoropolyalkylether (PFPAE) fluids are of interest to the United States Air Force as potential high temperature liquid lubricants in gas turbine engines. PFPAE fluids have desirable thermal and oxidative stability, and favorable temperature/viscosity characteristics. However, their performance depends on the specific base fluids, additives, bearing material used as well as contact conditions and environments. Screening tests using a modified ball‐on‐rod type rolling contact fatigue (RCF) tester were conducted to study the effects of the above variables and lubricant circulation on fatigue life, wear and performance of PFPAE. Post test lubricant samples were analyzed for changes in physical and chemical properties. Traditional testing for viscosity, acid number and weight changes was performed. Fluid degradation was studied using Fourier transform infrared spectroscopy (FTIR), gas chromatography with atomic emission detector (GC‐AED) and supercritical fluid chromatography (SFC). Elemental analysis of the deposits formed at the tribocontact were determined by Auger electron spectroscopy (AES). This revised version was published online in July 2006 with corrections to the Cover Date.     

Spall Propagation Characteristics of Refurbished VIM–VAR AISI M50 Angular Contact Bearings

During times of restricted supply, bearing refurbishment offers an attractive avenue to maintain operational readiness. However, bearing operation after fatigue spall initiation on refurbished bearings has not been extensively studied. In this study, spall propagation characteristics were compared between new and refurbished vacuum induction-melted, vacuum arc remelted AISI M50 208-size angular contact bearings. A control group of new AISI M50 bearings was evaluated for spall propagation characteristics as a baseline. Another group of AISI M50 bearings were subjected to an accumulated 11.5 billion stress cycles at a maximum Hertzian contact stress of 1.93 GPa and a temperature of 127 °C followed by Level II refurbishment. The refurbished bearings were evaluated for spall propagation characteristics and compared to the baseline bearings. Spalls were initiated via seeded Rockwell C hardness indents and propagated at a maximum Hertzian contact stress of 2.65 and 2.41 GPa, respectively, on both groups of bearings. The propagation rates of the bearings were measured in real time using an oil debris monitor. Pre- and post-tested bearings were examined for changes in microstructure, residual stress and retained austenite as a function of depth in the circumferential direction. No statistically significant difference in spall propagation characteristics was observed between new and refurbished bearings at the operating conditions and accumulated stress cycles studied here.     

Effects of Atmospheric Impairments of Satellite Link Operating in Ka Band

Wireless Personal Communications - Over the past decades, satellites have been used to provide a variety of services like voice, data, negation and video. Frequencies above 10 GHz provide...     

Frequency Stabilization for Multi-area Thermal–Hydro Power System Using Genetic Algorithm-optimized Fuzzy Logic Controller in Deregulated Environment

Abstract—This article develops a model of load frequency control for an interconnected two-area thermal–hydro power system under a deregulated environment. In this article, a fuzzy logic controller is optimized by a genetic algorithm in two steps. The first step of fuzzy logic controller optimization is for variable range optimization, and the second step is for the optimization of scaling and gain parameters. Further, the genetic algorithm-optimized fuzzy logic controller is compared against a conventional proportional-integral-derivative controller and a simple fuzzy logic controller. The proposed genetic algorithm-optimized fuzzy logic controller shows better dynamic response following a step-load change with combination of poolco and bilateral contracts in a deregulated environment. In this article, the effect of the governor dead band is also considered. In addition, performance of genetic algorithm-optimized fuzzy logic controller also has been examined for various step-load changes in different distribution unit demands and compared with the proportional-integral-derivative controller and simple fuzzy logic controller.     

Covalently linked Au nanoparticles to a viral vector: potential for combined photothermal and gene cancer therapy

Hyperthermia can be produced by near-infrared laser irradiation of gold nanoparticles present in tumors and thus induce tumor cell killing via a bystander effect. To be clinically relevant, however, several problems still need to be resolved. In particular, selective delivery and physical targeting of gold nanoparticles to tumor cells are necessary to improve therapeutic selectivity. Considerable progress has been made with respect to retargeting adenoviral vectors for cancer gene therapy. We therefore hypothesized that covalent coupling of gold nanoparticles to retargeted adenoviral vectors would allow selective delivery of the nanoparticles to tumor cells, thus feasibilizing hyperthermia and gene therapy as a combinatorial therapeutic approach. For this, sulfo-N-hydroxysuccinimide labeled gold nanoparticles were reacted to adenoviral vectors encoding a luciferase reporter gene driven by the cytomegalovirus promoter (AdCMVLuc). We herein demonstrate that covalent coupling could be achieved, while retaining virus infectivity and ability to retarget tumor-associated antigens. These results indicate the possibility of using adenoviral vectors as carriers for gold nanoparticles.     

Solid lipid nanoparticles of ondansetron HCl for intranasal delivery: development, optimization and evaluation

The present investigation deals with the development and statistical optimization of solid lipid nanoparticles (SLNs) of ondansetron HCl (OND) for intranasal (i.n.) delivery. SLNs were prepared using the solvent diffusion technique and a 2(3) factorial design. The concentrations of lipid, surfactant and cosurfactant were independent variables in this design, whereas, particle size and entrapment efficiency (EE) were dependent variables. The particle size of the SLNs was found to be 320-498?nm, and the EE was between 32.89 and 56.56?%. The influence of the lipid, surfactant and cosurfactant on the particle size and EE was studied. A histological study revealed no adverse response of SLNs on sheep nasal mucosa. Transmission electron microscopic analysis showed spherical shape particles. Differential scanning calorimetry and X-ray diffraction studies indicated that the drug was completely encapsulated in a lipid matrix. In vitro drug release studies carried out in phosphate buffer (pH 6.6) indicated that the drug transport was of Fickian type. Gamma scintigraphic imaging in rabbits after i.n. administration showed rapid localization of the drug in the brain. Hence, OND SLNs is a promising nasal delivery system for rapid and direct nose-to-brain delivery.     

Zinc oxythiomolybdate (ZnMoO2S2) powder as a solid lubricant for high-temperature rolling contact applications

Conventional liquid lubricants being used in today's gas turbine engines will not be able to operate effectively in the hostile bearing environments expected in future turbine engines. The expected high operating temperatures (500–800°C) mandate new and innovative lubrication schemes to achieve success. Recent studies have demonstrated that a new class of solid lubricants, the complex chalcogenides or metal ocythiomolybdates, have good potential for high temperature lubrication. This paper describes the friction, wear and rolling contact endurance of three high-temperature bearing materials using a zinc oxythiomolybdate (ZnMoO₂S₂) powder lubricant. Rolling contact tests were conducted using VIM-VAR M50, micromelt T15 tool steels and silicon nitride (Si₃N₄) at temperatures ranging from 23°C to 649°C, using a modified ball-on-rod type rolling-contact fatigue tester. Significant improvements in friction, endurance and wear were observed at all test temperatures, and with all three materials evaluated, when ZnMoO₂S₂ was used as a lubricant. Overall, silicon nitride exhibited the best frictional and antiwear performance. The lubricant powder exhibited the best tribological performance with T15 and M50 specimens between 177°C and 316°C. Energy Dispersive X-Ray Analysis (EDAX) of wear tracks showed the presence of iron (Fe) on the Si₃N₄ specimens as well as the presence of zinc (Zn) on both the T15 and the M50 specimens.     

Recent advancements in condensers to enhance the performance of solar still: A review

Pure drinking water sources are continuously decreasing day by day in the world and in contrast requirement is continuously increasing. Solar still is a device, which converts the saline water into pure form at a lower cost and is useful in the remote areas. But its less productivity and low efficiency is a significant issue to use it as potable water provider. Solar still productivity can be increased by using flat plate collectors, fins, evacuated tubes, different absorbing, and nanomaterials, but the major problem on its productivity is heat loss from glass cover to the ambient. Condenser reduces the temperature of the water vapor and maintain the condensation to enhance the productivity. This review shows different modification in the design of condenser attached with solar still to enhance the yield. At last the future work on the condenser is also discussed here.     

Sol–gel based layer-by-layer deposits of lanthanum cerium molybdate nanocontainers and their anticorrosive attributes

The present study focuses on the synthesis of novel lanthanum cerium molybdate (LCM) nanoparticles by sol–gel synthesis method and their use in the development of nanocontainers in an anticorrosive coating application. The obtained nanoparticles were used as core material with two different polyelectrolytic shells comprising of polypyrrole (PPY) and polyacrylic acid (PAA) or polyethyleneimine (PEI) and polystyrene sulfonate (PSS) involving the entrapment of benzotriazole (BTA) as the corrosion inhibitor using layer-by-layer (LBL) deposition method. At each step of this nanocontainer synthesis, the thickness of the layers, surface charges and the presence of the functional groups were determined by particle size, zeta potential and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. The X-ray diffractograms (XRD) indicated the change in the crystallinity of the nanoparticles and nanocontainers while thermogravimetric analysis (TGA) showed the thermal degradation behavior of the nanocontainers. The morphological studies conducted using scanning electron microscopy (SEM) exhibited the formation of nanocontainers containing nanoparticles in their cores. The release of BTA from the nanocontainers was evaluated at different pH values. The anticorrosive performance of the nanocontainers was examined by incorporation of the nanoparticles and nanocontainers in a commercial epoxy coating system and to be applied on mild steel and magnesium panels by electrochemical corrosion analysis. Tafel plots demonstrated the decrease in the current density with an increase in the loading percentage of nanocontainers in the epoxy system while Bode plots confirmed the significant improvement in the corrosion protection of the mild steel and magnesium by LCM nanoparticles and nanocontainers.