W-shaped enhanced-bandwidth patch antenna for wireless communication

In this paper a novel form of the familiar E-shaped patch antenna is presented. In the presented approach, by using the genetic algorithm (GA) based on fuzzy decision-making, some modifications have been implemented to the incorporated slots which lead to even more enhancement in the antenna bandwidth. The MOM (Method of Moment) is employed for analysis at the frequency band of 1.8GHz–2.6GHz by the optimization parameters of supply locations and slot dimensions. In the implemented fuzzy system, inputs are parameters like population, and outputs are parameters like recombination to produce the next generation. Fuzzy inference system (FIS) is used for the control of GA parameters. The design is also optimized by successive iterations of a computer-aided analysis package and experimental modifications. Prototype antenna, resonating at wireless communication frequencies of 1.88 and 2.37 GHz, has been constructed and experimental results are in relatively good agreement with the analysis. Dimensions of the modified slots for bandwidth enhancement, while maintaining good radiation characteristics, have been determined and the obtained antenna bandwidth of 36.7% is larger than that of a corresponding unslotted rectangular microstrip antenna or a conventional E-Shaped patch antenna. Details of the antenna design approach and experimental results are presented and discussed.     

Effect of fabrication process parameters on the apex‐radius of STM tungsten nanotip

Scanning tunneling microscope (STM) has found a wide application in nanoscience and nanotechnology. This microscope uses an ultra‐sharp metallic tip for image acquisition. Resolution of STM images depends largely on the radius of the tip apex; the smaller the radius the higher the resolution. In the present research, an experimental set‐up was designed and implemented for fabrication of STM tungsten nanotip using electrochemical‐etching method with the aim of optimization of nanotip fabrication process parameters by using Taguchi method. These parameters are electrolyte concentration, immersion length of the tungsten wire, inner diameter of the cathode tube, and the process voltage. It was found that the optimum level of the process parameters for gaining minimum radius of the nanotip apex is electrolyte concentration of 2 M/lit, wire immersion length of 4 mm, cathode tube inner diameter of 55 mm, and voltage of 3.5 V within the range of experiments. By setting the process parameters on the optimum level, the radius of the nanotip apex was decreased by five times in comparison to the mean value of the experimental results. The radius of the nanotip apex was improved down to about 10 nm under the optimum conditions. SCANNING 31: 65–74, 2009. © 2009 Wiley Periodicals, Inc.     

Solid modeling of space stations in a concurrent processing environment

This article presents solid modeling of space station structures in a multiprocessing environment such as the Cray YMP 8/864. A space station is modeled as a collection of space trusses. Elements of trusses are created concurrently using constructive solid geometry. Concurrent solid modeling of large structures can be integrated with parallel algorithms for optimization of such structures in order to fully automate their computer-aided design in a multiprocessing environment.     

Extraction optimization of a hydrocolloid extract from cress seed (Lepidium sativum) using response surface methodology

Extraction conditions for maximum values of yield, viscosity and minimum protein content of hydrocolloid extract from Lepidium sativum seed were investigated using response surface methodology. A Central Composite Face Design (CCFD) with four independent variables: temperature (25–85 °C); pH (3–10); extraction time (10–25 min) and water to seed ratio (10:1–80:1) was used to study the response variables (yield, viscosity and protein content). Data analysis showed that all the variables significantly (p < 0.05) affected the extraction yield and viscosity, whereas the effect of water to seed ratio on protein content was not significant (p > 0.05). Applying a desirability function method the optimum parameters were: extraction temperature 35 °C, pH 10, water to seed ratio of 30:1 and an extraction time of 15 min. At this optimum point, apparent viscosity, yield and protein content were 0.2 Pa s, 6.46% and 0.57%, respectively. The experimental values were very close to the predicted values and were not statistically different (p > 0.05).     

Physicochemical aspects of hydrocolloid extract from the seeds of Lepidium sativum

Acid equivalent weight, intrinsic viscosity and FT‐IR measurements have demonstrated a polyelectrolyte nature to Lepidium sativum seed extract. The polyelectrolyte nature relates to the carboxyl groups carried by galacturonic acid and glucuronic acid unit. The seed extract exhibited pronounced shear thinning in steady shear rheology and a weak gel type behaviour in dynamic rheology when the concentration is high i.e. > 1%. Such behaviour suggests the ability of L. sativum seed extract to structure a liquid, thus showing the possibility of applying it as a novel thickener and stabiliser in aqueous systems. The characteristic could be due to a strong tendency of molecular association of L. sativum seed extract as found for high M/G ratio galactomannans, and possibly also the enhanced macromolecular entanglement due to relatively rigid chain conformation. Temperature dependence study showed that the rheological properties of L. sativum structured solution is stable against temperature variation.     

Effect of chemical speciation on toxicity of mercury to Escherichia coli biofilms and planktonic cells

While it is known that microbial uptake of mercury (Hg) by planktonic cultures is influenced by the extracellular speciation of mercury in aquatic systems, Hg uptake in biofilm cultures is understudied. We compared the importance of Hg(II) speciation in toxicity to both planktonic and biofilm cultures of the Gram-negative bacterium Escherichia coli 055. Variable chloride chemistry experiments were carried out to modify mercury speciation. Biofilms were observed to be more resistant to Hg than planktonic cells. In both planktonic and biofilm cultures, the toxicity of Hg increased and then decreased along the chloride gradient. The percent reduction in cell viability was linearly related to the concentration of HgCl2(0) when Hg-chloro complexes dominated the speciation, consistent with a passive diffusion model. However, toxicity to both planktonic cells and biofilms at low salinities could not be explained by passive diffusion alone, which suggests that microbial uptake of Hg in both planktonic cells and biofilms may occur by both passive diffusion of neutral species and facilitated uptake. The relationship between toxicity and chloride concentration was similar in the presence and absence of a biofilm, indicating that the presence of the biofilm does not drastically change the relative availability of the dominant mercury species.     

Encapsulation of palladium nanoparticles by multiwall carbon nanotubes‐graft‐poly(citric acid) hybrid materials

Citric acid was polymerized onto the surface of functionalized multiwall carbon nanotubes (MWCNT‐COOH) and MWCNT‐graft‐poly(citric acid) (MWCNT‐g‐PCA) hybrid materials were obtained. Due to the grafted poly(citric acid) branches, MWCNT‐g‐PCA hybrid materials not only were soluble in water but also were able to trap water soluble metal ions. Reduction of trapped metal ions in the polymeric shell of MWCNT‐g‐PCA hybrid materials by reducing agents such as sodium borohydride led to encapsulated metal nanoparticles on the surface of MWCNT. Herein palladium nanoparticles were encapsulated and transported by MWCNT‐g‐PCA hybrid materials (MWCNT‐g‐PCA‐EPN) and their application as nanocatalyst toward Heck reaction in different conditions was investigated. The catalytic activity of palladium ions supported by MWCNT‐g‐PCA hybrid materials (MWCNT‐g‐PCA‐PdCl₂) toward Heck reactions is much more than for MWCNT‐g‐PCA‐EPN. Structure, characteristics and catalytic activity of synthesized systems was investigated using spectroscopy and microscopy methods. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010