Near-field coherent source localization by planar array design

This paper is concerned with near-field source localization for scenarios where coherent narrowband sources exist. In this paper, we propose a new method in which we design a general planar array with a covariance matrix whose rank is not decreased by the coherence between sources. Moreover, conditions for the sensor locations in the designed planar array are derived to reach maximum effective array aperture. The proposed method uses second order statistics and features a separable range-bearing search to reduce the computational complexity. This method localizes near-field sources with a number of one-dimensional searches in two steps. In the first step, ranges of sources is estimated using one 1D search and in the second step, the bearing of each signal source is estimated using the corresponding range estimated in the first step. Simulation results show that the performance of the proposed method is comparable with the Cramer–Rao bound.

     

Characterisation of spray‐dried microparticles containing iron coated by pectin/resistant starch

Iron is one of three major minerals in human body. However, the iron deficiency is a medical problem in developed and underdeveloped countries due to its poor oral absorption or insufficient iron intake. Encapsulation could solve problems associated with oral iron consumption. Various advantages including low cost, biodegradability, biocompatibility and large‐scale production have been included in the current study. In a modified encapsulation method, iron microparticles were prepared using low methoxy pectin and resistant starch during spray drying. Covalent and hydrogen bonds were formed between iron and pectin and between polymers, respectively. Particles sized 3.5 ± 1.14 μm and showed spherical shapes. The yield of particles was 72.07%, and solubility and loading efficiency were 33.64% ± 0.88 and 34.79%, respectively. In conclusion, using iron as a cross‐linker of pectin molecules resulted in microparticles with appropriate properties of lowering organoleptic changes and a better bioavailability especially in dairy‐based products for food fortification.     

Edge‐functionalized graphene nanoplatelets with polystyrene by atom transfer radical polymerization: grafting through carboxyl groups

The surface modifier 3‐((4‐hydroxybutoxy)dimethylsilyl)propyl methacrylate (CD), which contains a double bond and a hydroxyl group, was synthesized through a coupling reaction of 1,4‐butanediol and (3‐methacryloxypropyl)dimethylchlorosilane. Subsequently, graphene oxide (GO) was functionalized with different amounts of CD from its edge carboxyl groups. Then, grafting through atom transfer radical polymerization of styrene in the presence of various amounts of the edge‐functionalized GO was carried out to evaluate the effect of graphene loading along with graft density. A peak at 3.8 ppm in the ¹H NMR spectrum of CD associated with the methylene adjacent to the Si–O group indicated a successful coupling reaction. Attachment of CD on the edges of GO was evaluated using X‐ray photoelectron and Fourier transform infrared spectroscopies. Expansion of GO interlayer spacing by functionalization was evaluated using X‐ray diffraction. The ordered and disordered crystal structure of carbon was studied using Raman spectroscopy. The close I_D/I_G values for GO and various kinds of functionalized graphenes show the preserved graphitic crystallite size. Relaxation behaviour of polystyrene chains in the presence of graphene nanoplatelets and also the effect of graft content on chain confinement were studied using differential scanning calorimetry. High‐graft‐density nanocomposites show higher glass transition temperatures. Morphology of graphene nanoplatelets was studied using scanning electron and transmission electron microscopies. The flat and smooth morphology of graphene nanoplatelets is disturbed and also the transparency of the nanoplatelets decreases during the oxidation and functionalization processes. © 2014 Society of Chemical Industry     

A Set of Three Mutually Orthogonal Latin Squares of Order 15

In this paper we have exhibited a set of three mutually orthogonal latin squares of order 15 associated with a Kirkman-Steiner triple system of the corresponding order.     

Effect of montmorillonite clay and biopolymer concentration on the physical and mechanical properties of alginate nanocomposite films

Alginate-based nanocomposites at different montmorillonite clay (MMT) loadings were produced by solvent casting method. The combined effect of biopolymer and MMT content on the mechanical and physical properties of the obtained nanocomposites was investigated. The MMT weight percent relative to alginate was varied from 1% to 5% and polymer concentration was 1 and 1.5% w/v. Films containing 5% (wt/wt) of MMT show, with respect to neat alginate, reduced water permeability of about 19% and 22% and an increased water solubility of about 36% and 40%, for 1% and 1.5% alginate films, respectively. The tensile strength of neat alginate films increased significantly with increasing alginate concentration (about 36%) but slightly increased with increasing clay content up to 3%. The values of elongation decreased with increasing the both of clay content and polymer concentration. Results on X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed well developed exfoliated nanocomposite films especially at low level of nanoclay addition.     

Headspace Liquid-Phase Microextraction Followed by Gas Chromatography–Mass Spectrometry for Determination of Furanic Compounds in Baby Foods and Method Optimization Using Response Surface Methodology

In the present study, a sensitive, rapid, and simple method for determination of furanic compounds in baby foods has been developed. Headspace liquid-phase microextraction (HS-LPME) coupled with gas chromatography–mass spectrometry was used to extract and measure furan, 2-methylfuran, and 2,5-dimethylfuran in baby foods. Effective parameters such as salt amount (NaCl), stirring rate, temperature, and time of extraction were optimized using response surface methodology based on a central composite design to obtain the best conditions for extracting furanic compounds. The optimum parameter values were 1 g NaCl, 700 rpm stirring rate, 40 °C extraction temperature, and 15 min extraction time. The calibration curves were linear over the range of 0.2–200 ng?mL^?1 (R ² ?>?0.99) for all compounds, and the repeatability of the method, described as relative standard deviation, ranged between 3.84 and 7.06 % (n?=?6). The recovery of spiked baby food sample after extraction ranged between 89.33 and 103.64 %, and the best enrichment factor was achieved about 972-fold for furan. The limits of detection and quantitation ranged between 0.021 and 0.038 ng?g^?1 and 0.069 and 0.126 ng?g^?1, respectively. The merit figures of the HS-LPME/GC-MS method showed that it can be considered as a new, fast, and effective alternative method for investigating furanic compounds in baby foods.     

Scanning Near-Field Millimeter-Wave Microscope: Application to a Vector-Coding Technique

The purpose of this paper is to propose an evanescent field-scanning millimeter-wave microscope to bridge the frequency gap that currently exists in probe microscopy. The method is supported by the use of a six-port-based reflectometer operating at 35 GHz in association with a microfabricated resonant micro stripline probe. The simplicity of the method makes it suitable for an industrial context and offers integration possibilities to gain in compacity, reliability, and time operation, in particular. This millimeter-wave microscope is well suited for the characterization of conductors and local electromagnetic properties of dielectrics. The resolution of the probe is experimentally verified by scanning gold lines deposited on a silicon substrate. In addition to the demonstration of the system, we propose to discuss various probe parameters that can be considered to design evanescent millimeter-wave probes (EMPs) for different applications. An original use of the system is suggested through a vector-coding technique of digital information that makes use of the real and imaginary parts of the reflection coefficient.     

Post-Northridge connection with modified beam end configuration to enhance strength and ductility

In order to enhance the strength and ductility of post-Northridge connections with beam depths varying from 450 mm to 912 mm, two parallel horizontal long voids were opened on their beams web. Results showed that the proposed beam end configuration (BEC) is effective in moving the plastic hinge away from the column face. Adding web stiffeners and two tubes at the center of voids were effective in preventing excessive beam flange/web buckling. Based on the analytical results a step by step design procedure is proposed to determine the most suitable geometry for the BEC to achieve adequate connection strength and ductility.     

Evaluation of occupational exposure to naturally occurring radioactive materials in the Iranian ceramics industry

Zircon contains small amounts of uranium, thorium and radium in its crystalline structure. The ceramic industry is one of the major consumers of zirconium compounds that are used as an ingredient at ～10-20 % by weight in glaze. In this study, seven different ceramic factories have been investigated regarding the presence of radioactive elements with focus on natural radioactivity. The overall objective of this investigation is to provide information regarding the radiation exposure to workers in the ceramic industry due to naturally occurring radioactive materials. This objective is met by collecting existing radiological data specific to glaze production and generating new data from sampling activities. The sampling effort involves the whole process of glaze production. External exposures are monitored using a portable gamma-ray spectrometer and environmental thermoluminescence dosimeters, by placing them for 6 months in some workplaces. Internal routes of exposure (mainly inhalation) are studied using air sampling, and gross alpha and beta counting. Measurement of radon gas and its progeny is performed by continuous radon gas monitors that use pulse ionisation chambers. Natural radioactivity due to the presence of 23?U, 232Th and ??K in zirconium compounds, glazes and other samples is measured by a gamma-ray spectrometry system with a high-purity germanium detector. The average concentrations of 23?U and 232Th observed in the zirconium compounds are >3300 and >550 Bq kg?1, respectively. The specific activities of other samples are much lower than in zirconium compounds. The annual effective dose from external radiation had a mean value of ～0.13 mSv y?1. Dust sampling revealed the greatest values in the process at the powdering site and hand weighing places. In these plants, the annual average effective dose from inhalation of long-lived airborne radionuclides was 0.226 mSv. 222Rn gas concentrations in the glaze production plant and storage warehouse were found to range from 10 to 213 Bq m?3. In this study, the estimated annual effective doses to exposed workers were <1 mSv y?1.