Joint consideration of energy‐efficiency and coverage‐preservation in microsensor networks

This paper presents an energy‐efficient and coverage‐preserving communication protocol which distributes a uniform energy load to the sensors in a wireless microsensor network. This protocol, called Distance‐based Segmentation (DBS), is a cluster‐based protocol that divides the entire network into equal‐area segments and applies different clustering policies to each segment to (1) reduce total energy dissipation and (2) balance the energy load among the sensors. Therefore, it prolongs the lifetime of the network and improves the sensing coverage. Moreover, the proposed routing protocol does not need any centralized support from a certain node which is at odds with aiming to establish a scalable communication protocol. Results from extensive simulations on two different network configurations show that by lowering the number of wasteful transmissions in the network, the DBS can achieve as much as a 20% reduction in total dissipated energy as compared with current cluster‐based protocols. In addition, this protocol is able to distribute energy load more evenly among the sensors in the network. Hence, it yields up to a 66% increase in the useful network lifetime. According to the simulation results, the sensing coverage degradation of the DBS is considerably slower than that of the other cluster‐based protocols. Copyright © 2009 John Wiley & Sons, Ltd.     

Bearings Fault Diagnosis Using Vibrational Signal Analysis by EMD Method

ABSTRACT

Studying vibrational signals is one reliable method for monitoring the situation of rotary machinery. There are various methods for converting vibrational signals into usable information for fault diagnosis, one of which is the empirical mode decomposition method (EMD). This article is about diagnosing bearing faults using the EMD method, employing nondestructive test. Vibration signals are acquired by a bearing test machine. The discrete wavelet bases are used to translate vibration signals of a roller bearing into time-scale representation. Then, an envelope signal can be obtained by envelope spectrum analysis of wavelet coefficients of high scales. Local Hilbert marginal spectrum can be obtained by applying thr EMD method to the envelope signal from which the faults in a roller bearing can be diagnosed and fault patterns can be identified. The results have shown bearing faults frequencies are easily observable. There is a variant of the EMD method called the ensemble EMD (EEMD), which overcomes the mode mixing problem which may occur when the signal to be decomposed is intermittent. The EEMD method is also applied to the acquired signals, and the two methods were compared. While the outcomes of both methods do not differ much, one important merit of the EMD is that it has much less computational processing time than EEMD.     

The effect of mordant salts on antibacterial activity of wool fabric dyed with pomegranate and walnut shell extracts

Natural dyes have attracted increasing worldwide attention because of the carcinogenicity and environmental effects of synthetic dyes. In this study, wool fabric was treated with tannin‐rich extracts of Punica granatum peel and walnut shell in combination with some mordants. The effect of various mordants on the colorimetric and antibacterial properties of wool fabrics was investigated. The results showed that pretreatment with metallic mordants substantially improved the dyeing and fastness properties of wool fabrics. The extracts of Punica granatum peel and walnut shell showed a significant antibacterial activity at 5% concentration. In addition, antibacterial activity was dramatically enhanced using metallic salts. The antibacterial activity of samples dyed with natural dyes and without any mordant was not good, while the mordanted samples with copper, aluminum and tin salts obtained considerable antimicrobial properties following lightening and washing fastness. The extracts of Punica granatum peel and walnut shell can be considered as viable alternatives instead of artificial antibacterial agents for hospital textiles as well as an effective anti‐odour agent for sports and household textiles.     

Facile synthesis and X-ray peak broadening studies of Zn1−xMgxO nanoparticles

Magnesium-doped ZnO nanoparticles (NPs) (Zn_1?xMg_xO-NPs, x = 0.0, 0.01, 0.03, and 0.05) were synthesized by a simple sol–gel method. The compounds were synthesized at calcination temperatures of 650 °C for 2 h. The synthesized Zn_1?xMg_xO-NPs were characterized by X-ray diffraction analysis (XRD) and high-magnification transmission electron microscopy (TEM). The XRD results revealed that the sample product was crystalline with a hexagonal wurtzite phase. The TEM showed Zn_1?xMg_xO-NPs with nearly spherical and hexagonal shapes. The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the Zn_1?xMg_xO-NPs. Physical parameters such as strain, stress, and energy–density values were calculated more precisely for all reflection peaks of XRD corresponding to the wurtzite hexagonal phase of ZnO in the 20°–100° range from the SSP results. The effect of doping on the optical band-gap was also investigated. The results showed that Mg²⁺ is a good dopant to control some of the ZnO properties, with minimum defects to its structure.     

Stabilized nanosilver loaded nylon knitted fabric using BTCA without yellowing

In this study, silver nanoparticles stabilized on the nylon knitted fabric by padding process using 1,2,3,4-butanetetracarboxylic acid (BTCA) and sodium hypophosphite (SHP) without considerable yellowing. This cross-linking combination also dimensionally stabilized the nylon knitted fabric. The SEM images showed the distribution and size of nanosilver within 34 nm. Also, the presence of nanosilver on the fabrics confirmed by EDX and XRD spectrums. The antimicrobial test performed on the treated fabrics against Staphylococcus aureus as a Gram positive and Escherichia coli as a Gram negative bacterium using pour plate test method. A bacterium growth decrease above 96% achieved with 200 ppm nanosilver/BTCA/SHP with standing up to 20 successive rinses. The L*a*b* values had little changes upon increasing the concentration of silver nanoparticles. However the color changes were negligible and the fabric was still white. Moreover, diffuse reflectance spectroscopy, dimensional stability, and water droplet adsorption time as well as statistical analysis of the results investigated and reported.     

Synthesizing and stabilizing silver nanoparticles on polyamide fabric using silver-ammonia/PVP/UVC

A colloidal dispersion of silver nanoparticles were prepared with Tollens’ reagent [Ag(NH₃)₂]⁺ and polyvinyl pyrrolidone (PVP) as a reducing/stabilizing agent trough UVC irradiation and then applied on the nylon fabric by using a simple pad method. The ultraviolet irradiation was assisted to reduce Ag⁺ to Ag⁰. The presence of nanosilver in the solution and on the fabric was confirmed by UV–vis, EDX, SEM and XRD. In addition, the role of PVP as a stabilizing agent on the nylon surface was investigated. Further, an antibacterial test was carried out on the fabrics in the presence of two bacteria namely Staphylococcus aureus and Escherichia coli. The treated fabric with 200 ppm of the above mentioned solution was reduced the bacteria up to 99.2% after 20 washes. Some other properties of the fabric such as color variations, dimensional stability, water droplet adsorption and reflectance spectrum were also carried out and the results thoroughly discussed.     

Effect of laser CO2 irradiation on various properties of polyester fabric: Focus on dyeing

In this research, the effect of CO₂ laser on various properties of polyester fabric specially dyeing was studied. Three disperse dyes of red, yellow, and blue were used and irradiation was performed before and after dyeing. To evaluate the color changes due to laser treatment, CIELAB ΔE color difference values were calculated. The morphology of the irradiated surfaces was examined by scanning electron microscopy. Other properties including color fastness, bending rigidity, wettability, and crystal size were also examined. The results revealed that laser treatment had an increasing effect on the color difference value. Among the three laser parameters examined in this work, laser power had the strongest effect. While no significant color fastness improvement with low laser intensity was observed, high‐intensity laser irradiation increased the light and rubbing fastness. Properties such as wettability and bending rigidity were negatively affected by an increase in laser intensity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Single-step route to diamond-nanotube composite

Candle wax was used as a precursor for the production of a diamond-nanotube composite in a single step. The composite films were fabricated by sulfur-assisted hot-filament chemical vapor deposition technique. The morphology of the composite films was analyzed by scanning electron microscopy and transmission electron microscopy. Raman spectra of the films show characteristic diamond band at 1,332 cm⁻¹, D-band around 1,342 cm⁻¹, and graphitic G-band around 1,582 cm⁻¹. The electron energy-loss spectroscopy recorded at the carbon K-edge region shows signature features of diamond and carbon nanotube in the fabricated material. The ability to synthesize diamond-nanotube composites at relatively low temperatures by a single-step process opens up new possibilities for the fabrication of nanoelectronic devices.     

Catalysis using gold nanoparticles decorated on nanocrystalline cellulose

A novel nanocomposite was prepared by deposition of carbonate-stabilized Au nanoparticles (AuNPs) onto the surface of poly(diallyldimethyl ammonium chloride) (PDDA)-coated carboxylated nanocrystalline cellulose (NCC). The hybrid material possessed AuNPs (1.45% by weight) with an average diameter of 2.95 ± 0.06 nm. The catalytic activity of AuNP/PDDA/NCC for reducing 4-nitrophenol to 4-aminophenol was compared to other Au-supported composites. An activation energy of 69.2 kJ mol(-1) was obtained for the reaction. Indeed, the reaction rate constant k of (5.1 ± 0.2) × 10(-3) s(-1) was comparable to the benchmark literature value obtained using AuNPs (<5 nm in diameter) decorated on a network of crystalline cellulose fibers. Our strategy promotes the use of natural resources to prepare reusable hybrid inorganic-organic materials for important reactions with facilitated product isolation/purification.