Structural,dielectric and magnetic manifestation in BaM/PEEK nanocomposite for X band shielding blocks

The microwave absorber nanocomposites consisting of substituted M-type hexaferrite Ba_0.8Gd_0.2Fe_11.5Co_0.5O₁₉ and polyetheretherketone (PEEK) have been investigated for X-band applications. Composites with hexaferrite to PEEK ratios 5:0, 4:1, 3:2, 2:3, 1:4, 0:5 have been synthesized by a micro-emulsion method. XRD results confirm the hexagonal structure of the hexaferrite with average crystallite size up to 37.2 nm. Magnetic properties reveal that saturation magnetization M_s increases whereas coercivity H_c decreases by increasing the ferrite content in the composites. Complex permittivity and permeability have been tailored with ferrite content in the X-band. The dielectric constant reduces from 5.3 to 3.25 while permeability increases up to 1.37 with increasing ferrite concentrations. The microwave results show the minimum reflection loss of ?10.79 dB for composite with 80% ferrite.     

Roadside dust contamination with toxic metals along industrial area in Islamabad,Pakistan

An investigation has been carried out to understand the contamination characteristics of roadside dust in the industrial area of Islamabad, Pakistan. The amounts of Si, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Pb, Zn, Ga, As, Se and Cd were determined from 95 roadside dust samples collected along the Islamabad industrial area using Proton Induced X-ray Emission （PIXE）. The results indicated that concentrations of all elements, except Cd, in the roadside dust were significant. The results of the enrichment factor show that the elementary composition of the roadside dust could be categorized as soil elements from the crust of the earth and elements from anthropogenic pollution. The high enrichment factors imply that elements such Cr, Cu, Pb, Zn, As, Se, Cd, Ni, Co and S came from anthropogenic activities. The source of metal contamination was identified using multivariate statistical analysis. It has been concluded that Ca, Sc, Ti, V, Mn and Fe mainly originate from crustal sources; Cr, Cu, Ni, Pb, Zn and Ga are associated with point-sources from industrial pollution/traffic; and S, Cl, K, As and Se are mainly related to oil/coal combustion.     

Adaptive schemes for distributed web caching

In distributed web caching architectures, institutional proxies take advantage of their neighbors’ contents in order to reduce the number of requests forwarded to the server. Intuitively, the maximum benefit from this cooperation is expected when the proxies that exhibit similar requests are grouped together. The current practice is to follow a static and manual configuration of neighbors. Such an approach has a number of drawbacks: (i) static allocation may not determine the best neighbors, especially if global knowledge of the participating proxies is not available, (ii) a manual allocation places significant administrative burden, (iii) static schemes are insensitive to changes in access patterns, and (iv) they cannot deal with the introduction of new, potentially useful, proxies. In this paper, we propose a set of algorithms that allow proxies to independently explore the network for better neighbors and continuously update their configuration in an adaptive fashion. The simulation experiments illustrate that dynamic neighbor reconfiguration leads to significantly higher hit ratios compared to the static approach. Although some researchers in the past have recognized the need for adaptive caching, to the best of our knowledge this is the first study to propose concrete algorithms and evaluate their efficacy.     

CHROMATOGRAPHIC SEPARATION AND CHARACTERIZATION OF MONO-, DI- AND TRIAROMATIC HYDROCARBONS IN GAS OIL

ABSTRACT

A simple procedure is described for separation of aromatic hydrocarbons into mono-, di- and trinuclear types in Iraqi gas oil. This is accomplished by elution through an alumina adsorption column under standardized conditions. Characterization is performed by UV-absorption and ratio matching method. The method can be used also for investigating aromatic hydrocarbon structures of other petroleum fractions.     

A systematic review of comparative evidence of aspect-oriented programming

ContextAspect-oriented programming (AOP) promises to improve many facets of software quality by providing better modularization and separation of concerns, which may have system wide affect. There have been numerous claims in favor and against AOP compared with traditional programming languages such as Objective Oriented and Structured Programming Languages. However, there has been no attempt to systematically review and report the available evidence in the literature to support the claims made in favor or against AOP compared with non-AOP approaches.ObjectiveThis research aimed to systematically identify, analyze, and report the evidence published in the literature to support the claims made in favor or against AOP compared with non-AOP approaches.MethodWe performed a systematic literature review of empirical studies of AOP based development, published in major software engineering journals and conference proceedings.ResultsOur search strategy identified 3307 papers, of which 22 were identified as reporting empirical studies comparing AOP with non-AOP approaches. Based on the analysis of the data extracted from those 22 papers, our findings show that for performance, code size, modularity, and evolution related characteristics, a majority of the studies reported positive effects, a few studies reported insignificant effects, and no study reported negative effects; however, for cognition and language mechanism, negative effects were reported.ConclusionAOP is likely to have positive effect on performance, code size, modularity, and evolution. However its effect on cognition and language mechanism is less likely to be positive. Care should be taken using AOP outside the context in which it has been validated.     

On the Performance of Phase‐I Bivariate Dispersion Charts to Non‐Normality

A phase‐I study is generally used when population parameters are unknown. The performance of any phase‐II chart depends on the preciseness of the control limits obtained from the phase‐I analysis. The performance of phase‐I bivariate dispersion charts has mainly been investigated for bivariate normal distribution. However, this assumption is seldom fulfilled in reality. The current work develops and studies the performance of phase‐I |S| and |G| charts for monitoring the process dispersion of bivariate non‐normal distributions. The necessary control charting constants are determined for the bivariate non‐normal distributions at nominal false alarm probability (FAP₀). The performance of these charts is evaluated and compared in a situation when samples are generated by bivariate logistic, bivariate Laplace, bivariate exponential, or bivariate t₅ distribution. The analysis shows that the proper consideration to underlying bivariate distribution in the construction of phase‐I bivariate dispersion charts is very important to give a real picture of in or out of control process status. Copyright © 2016 John Wiley & Sons, Ltd.     

EDM of Ti-6Al-4V: Electrode and polarity selection for minimum tool wear rate and overcut

Titanium and its alloys especially Ti-6Al-4V are being widely used numerous application areas. In addition to have iconic properties, Ti-6Al-4V is considered as challenging material in machining perspective that is why it has captured global research focus. In this research, electric discharge machining of Ti-6Al-4V has been carried out by employing four different types of electrode materials (graphite, aluminum, copper, and brass) assigned with two alternate polarities (positive and negative). Selection of the most appropriate tool material and electrode polarity is the important aspect needed to be explored for this alloy. In addition to polarity, discharge current, and pulse time ratio have been considered as process variables owing to have their direct influence in electric discharge machining. Taguchi L9 array has been employed for each of the four electrodes with positive polarity and similarly L9 with negative polarity. Thus, a total number of 72 experiments have been conducted. Tool wear rate and overcut (OC) around the machined surfaces are the response characteristics to be investigated in order to achieve minimum amounts of both of these two responses. Selection of the most suitable tool with common tool polarity has been carried out meeting the decision criteria of minimum tool wear and minimum OC.     

Porous Cobalt Phosphide Polyhedrons with Iron Doping as an Efficient Bifunctional Electrocatalyst

Iron (Fe)‐doped porous cobalt phosphide polyhedrons are designed and synthesized as an efficient bifunctional electrocatalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The synthesis strategy involves one‐step route for doping foreign metallic element and forming porous cobalt phosphide polyhedrons. With varying doping levels of Fe, the optimized Fe‐doped porous cobalt phosphide polyhedron exhibits significantly enhanced HER and OER performances, including low onset overpotentials, large current densities, as well as small Tafel slopes and good electrochemical stability during HER and OER.