The effect of adjacent channel interference on the capacity of FDMAcellular systems

In FDMA cellular radio systems, the adjacent channel interference (ACI) is suppressed by the IF filter and also by a distance factor. Channels immediately adjacent to each other in frequency are assigned to different cells and, as such, the distance plays a role in reducing their mutual interference. The authors study the feasibility of optimizing the frequency spacing between carriers such that the combined effect of distance and IF filter will be enough to control the interference while allowing the maximum number of channels in a given bandwidth. They also study the decision feedback equalizer (DFE) as a means to reduce any excess ACI that results from reducing the channel spacing. The paper starts with a model that estimates the cumulative probability density of the signal to adjacent channel interference ratio (SIR) as a function of the channel spacing. They then present the results of a computer simulation study to estimate the performance of DFE in mitigating the effect of ACI. The results indicate that, under the conditions of slow flat fading and selection diversity, the DFE is very effective in reducing the effect of excess ACI interference which allows for a considerable reduction in the frequency spacing     

Mineralocorticoid hormone receptor and the epithelial sodium channel in a human leukemic cell line

A Cell extract from the HEL (human erythroblastic leukemia) cell line was positive for both the epithelial sodium channel (ENaC) and the mineralocorticoid receptor (MCR) as glycosylated 82-84 kDa bands, and a single 102 kDa band, respectively, in Western blots using polyclonal antibodies raised against these proteins. The immunofluorescent labeling of the MCR in all cell lines showed a nucleocytoplasmic localization of the receptor whereas the ENaC was exclusively membrane-bound. These results were confirmed by confocal microscopy. The expression of the MCR in HEL cells was evident as a predicted band of 843 bp (234 amino acids) after total RNA from HEL cells had been reverse transcribed and then amplified by PCR; the ENaC was similarly evident as a predicted band of 520 bp. In both cases, near 100% identity was observed between the deduced amino acid sequences of the PCR products and those from known human sources. The multiplication of HEL cells was influenced by antagonists (RU 26752, ZK 91587) targeted for specificity to the MCR and this was reversed by the natural hormone aldosterone. These steroids also provoked chromatin condensation in the HEL population.     

Simultaneous determination of Sunset yellow and Tartrazine in soft drinks using gold nanoparticles carbon paste electrode

The monitoring of synthetic dyes in foods is very important due to their potential harmfulness to human beings. Herein, a carbon-paste electrode (CPE) that is chemically modified with gold nanoparticles (nAu) was fabricated and used for the determination of Sunset yellow (SY) and Tartrazine (Tz). Cyclic and differential pulse voltammetry (CV and DPV) results revealed two well-resolved anodic peaks for SY and Tz with remarkably increase in oxidation signals of these colourants. Based on this, a novel electrochemical method was developed for the simultaneous determination of SY and Tz. High sensitivity and selectivity, sub-micromolar detection limit, high reproducibility and regeneration of the electrode surface by simple polishing make the nAu-CPE electrode very suitable for the determination of SY and Tz in commercially available soft drinks. The detection limits was 3.0 × 10⁻⁸ and 2.0 × 10⁻⁹ mol l⁻¹ for SY and Tz, respectively, which are remarkably lower than those reported previously for SY and Tz using other modified electrodes.     

Nonlinear modeling and analysis of a Doherty power amplifier driven by non-constant envelope signals

A circuit-level CAD method based on circuit envelope (CE) simulation is presented to analyze the nonlinear behavior of Doherty power amplifiers (DPAs) in LDMOS technology, when driven by non-constant envelope signals. In this paper, a general nonlinear model has been extracted for an RF LDMOS power transistor. Then, a complete CE analysis is applied to a designed DPA using the extracted model at 3.5?GHz. To solve the CE equation at specific envelope samples, analytic expressions are developed for the Jacobian matrix and an effective method for quick calculation is suggested. Employing this nonlinear analysis gives insight for optimum design of DPAs and provides an accurate tool to precisely model the nonlinearity of the amplifier in order to predict its distortion effects in modern communication systems.     

Developing a composite based elliptic spring for automotive applications

An automotive suspension system is designed to provide both safety and comfort for the vehicle occupants. In this study, finite element models were developed to optimize the material and geometry of the composite elliptical spring based on the spring rate, log life and shear stress parameters. The influence of the ellipticity ratio on the performance of woven roving–wrapped composite elliptical springs was investigated both experimentally and numerically. The study demonstrated that composite elliptical springs can be used for light and heavy trucks with substantial weight reduction. The results showed that the ellipticity ratio significantly influenced the design parameters. Composite elliptic springs with ellipticity ratios of a/b = 2 had the optimum spring parameters.     

Electrochemical determination of ascorbic acid at the surface of a graphite electrode modified with multi-walled carbon nanotubes/tetradecyltrimethylammonium bromide

A multi-walled carbon nanotubes (MWCNTs)–tetradecyltrimethylammonium bromide (TTAB) film-coated graphite electrode (GE) was fabricated, and the electrochemical oxidation of ascorbic acid (AA) was studied in Britton–Robinson (B–R) buffer (pH 7.0) using cyclic, square wave, and differential pulse voltammetry (CV, SWV, and DPV). An electroanalytical study of AA and acetaminophen (ACOP) and of several mixtures of these compounds in different ratios was made. A sensitive linear voltammetric response for AA was obtained for the concentration range of 5 × 10⁻⁷ to 1.7 × 10⁻⁴ mol L⁻¹, with a correlation coefficient of 0.992, and the detection limit for AA was found to be 1.1 × 10⁻⁷ mol L⁻¹ using DPV. The relative standard deviation (RSD) was 2.7%, suggesting that the film electrode has excellent day-to-day reproducibility. The proposed voltammetric approach was also applied to the determination of the AA concentration in commercial tablets.     

Probabilistic Multiobjective Operation Management of MicroGrids With Hydrogen Storage and Polymer Exchange Fuel Cell Power Plants

This paper models and solves the operation management problem of MicroGrids (MGs) including cost and emissions minimization under uncertain environment. The proposed model emphasizes on fuel cells (FCs) as a prime mover of combined heat and power (CHP) systems. An electro‐chemical model of the proton exchange membrane fuel cell (PEMFC) is used and linked to the daily operating cost and emissions of the MGs. A reformer is considered to produce hydrogen for PEMFCs. Moreover, in high thermal load intervals, in order to make the MG more efficient, a part of produced hydrogen is stored in a hydrogen tank. The stored hydrogen can be reused by PEMFCs to generate electricity or be sold to other hydrogen consumers. A probabilistic optimization algorithm is devised which consists of 2m + 1 point estimate method to handle the uncertainty in input random variables (IRVs) and a multi‐objective Self‐adaptive Bee Swarm Optimization (SBSO) algorithm to minimize the cost and emissions simultaneously. Several techniques are proposed in the SBSO algorithm to make it a powerful black‐box optimization tool. The efficiency of the proposed approach is verified on a typical grid‐connected MG with several distributed energy sources.     

Application of Numerical Method to Investigation of Fatigue Crack Behavior Through Friction Stir Welding

Fatigue crack propagation through a friction stir welded (FSW) joint of 2024-T351 Al alloy is investigated numerically. The governing relationships for predicting the crack behavior including incremental crack length, crack growth rate, and crack growth direction are presented. Stress intensity is calculated based on displacement correlation technique, and fatigue crack growth through the FSW joint is investigated under linear elastic fracture mechanics (LEFM) using the Paris model. The concepts of crack closure, residual stress, and stress relaxation are incorporated into the Paris model to support the final results. Maximum circumferential tensile stress method is applied to predict the crack growth direction. Finally, the numerical approaches are employed to the high number of elements in the framework of Fracture Analysis Code (FRANC2D/L) to simulate the fatigue crack propagation through the FSW joint including various zones with different material properties. Fatigue lifetime of the welded joint is predicted by implementing the same procedure for various loading values. The obtained numerical results are validated with the experimental work (Ali et al., Int J Fatigue 30:2030–2043, 2008).

Mechanical Behavior of CrMo4 Steel With Dual-Phase Microstructure

Multi-phase microstructures having good ductility may replace the conventional microstructures in different technological applications such as pressure vessels.Mechanical properties including the fracture behavior and the service life of pressure vessels are strongly affected by the microstructure.The objective of this study was to investigate the correlation between different dual-phase microstructures and mechanical properties of 42CrMo4 (AISI 4140) steel.To produce the martensite-bainite (M-B),the martensite-ferrite (M-F),and the ferrite-bainite (F-B) microstructures,the step quenching heat treatment was used.Mechanical properties of heat treated samples including the strength,ductility,and impact energy were measured.Tensile experiments revealed a discontinuous yielding in the F-B specimen with ferritic matrix.Fracto\graphic results showed high concentration bright facets (BFs) on broken specimen surfaces indicating the brittle cleavage fracture was the predominant mechanism in the dual-phase microstructures.     

Developing a hybrid, carbon/glass fiber-reinforced, epoxy composite automotive drive shaft

In this study, a finite element analysis was used to design composite drive shafts incorporating carbon and glass fibers within an epoxy matrix. A configuration of one layer of carbon–epoxy and three layers of glass–epoxy with 0°, 45° and 90° was used. The developed layers of structure consists of four layers stacked as [+45_glass°/-45_glass°/0_carbon°/90_glass°]. The results show that, in changing carbon fibers winding angle from 0° to 90°, the loss in the natural frequency of the shaft is 44.5%, while, shifting from the best to the worst stacking sequence, the drive shaft causes a loss of 46.07% in its buckling strength, which represents the major concern over shear strength in drive shaft design.