Investigation of the effect of carbonaceous supports on the activity and stability of supported palladium catalysts for methanol electro-oxidation reaction

In this study, nitrogen doped graphene (NG) and multi-walled carbon nanotubes (MWCNT) were used as supporting materials for palladium active phase to investigate their performance in direct methanol fuel cells (DMFCs). The facile and low temperature solvothermal method was used for the synthesis of NG. Palladium nanoparticles were deposited on the surface of NG and MWCNT by a modified polyol reduction method. The morphologies and microstructures of the prepared catalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Also, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were carried out to evaluate the electrocatalytic activity and the durability of the obtained catalysts towards methanol oxidation reaction. Pd/NG catalyst had a better activity and durability of methanol electrocatalytic oxidation rather than Pd/MWCNT catalyst, which is related to good dispersion of Pd nanoparticles on the surface of nitrogen doped graphene and the physicochemical characteristics of NG.     

Synthesis of submicron zeolite LTA particles from natural clinoptilolite and industrial grade chemicals using one stage procedure

A powdered natural clinoptilolite-rich tuff (100 mesh) from Semnan region of Iran was successfully converted to higher value-added synthetic zeolite A (submicron particles of ~ 200–300 nm) in a single stage procedure under a hydrothermal condition. Effect of different parameters such as crystallization temperature, sodium hydroxide concentration, solid/liquid ratio (the mass of clinoptilolite; g; to the volume of sodium hydroxide solution; ml) and crystallization duration on the final product were investigated. The formation of zeolite A was ascertained by X-ray powder diffraction, X-ray florescence (chemical analysis), and scanning electron microscopy techniques. The results were revealed that reaction temperature of 353 K, sodium hydroxide concentration of 2 M, crystallization time of 4 h, and solid to liquid ratio of 1/18 were optimized condition for this conversion.     

Investigation on the Effect of Pre-heating with Butane Gas Torch in Formability of High Tension Steel (HTS) by Using Taguchi Experimental Method in Roll Forming Process

This study was carried out to evaluate a new roll forming process involving pre-heating using a gas torch. The temperature distribution for the formed sheet was observed using a 3D-IR graph generated from a thermal imaging camera. The appropriate distance between the formed sheet and the butane gas torch was also determined based on the results of the flame characteristics. The thermal effects of the formed sheet were confirmed by the temperature distribution. Spring-back analysis was applied to the Nominal the Best characteristic of Taguchi’s experimental method. In spring-back analysis, the forming speed is an influential variable. Bow analysis was applied to the Smaller the best characteristic of Taguchi’s experimental method. Lastly, at room temperature, the roll forming process was performed with pre-heating and formability was analyzed with respect to spring-back, bow and variance of bending angle (buckling). Spring-back, bow and buckling with the roll forming process involving pre-heating got improved by 0.97°, 0.17 mm and 0.20, respectively, compared to the same processes at room temperature. Forming speed appeared to have the most influence on the formability and pre-heating was found to improve the formability in the roll forming process.     

Modeling buffer utilization in cell-based networks

Variable bit rate traffic is characteristically bursty and the arrivals are highly correlated. New network technology carries such traffic in cell-based networks where the service is a discrete time, deterministic process with the service rate determined by bandwidth negotiated by the user. Managing such networks is hard, and predicting cell loss at a station with limited buffer capacity K is essential to enable the user to negotiate his quality of service requirements. We present an analysis to determine the queue length distribution and the loss probability in such circumstances. For our analysis, we use an m-phase Markov Modulated Bernoulli Process with binomial distributed batch arrivals and deterministic service and limited capacity K, i.e. a MMBP^[X]_(m)/D/1 − K queuing system. We show that the system can be analyzed using the so-called unfinished work approach. The validity of our evaluation technique is illustrated by comparing our analytical results against those obtained from an event-driven siimulation of the same system.     

An adaptive control for video transmission over bluetooth

This paper is concerned with transmission of a moving picture expert group (MPEG) video stream over a Bluetooth channel, using an adaptive neuro-fuzzy technique. MPEG variable bit rate (VBR) video sources over a network generally experience long delay and unacceptable data loss, due to high variations in bit rate. Furthermore, transmission rate could be unpredictable in a Bluetooth network due to interferences by other wireless devices or general Bluetooth channel noises. Subsequently, it is almost impossible to transmit VBR data sources over Bluetooth without excessive delay or data loss. In this work, an adaptive scheme is introduced so that the controller may adjust itself to the current state of the system under control. This paper utilizes a traffic-shaping buffer to prevent excessive back-to-back transmissions of MPEG VBR data sources. A novel adaptive neuro-fuzzy scheme regulates the output rate of the buffer to ensure that the video stream from the host conforms to the traffic conditions of the Bluetooth channel during the transmission period. The computer simulation results show that the use of the neuro-fuzzy controller reduces excessive delay and data loss at the host-controller-interface, as compared with a conventional VBR video transmission and a rule-based fuzzy controller (RBF1) in Bluetooth.     

Relative primary adhesion of Pseudomonas aeruginosa, Serratia marcescens and Staphylococcus aureus to HEMA-type contact lenses and an extended wear silicone hydrogel contact lens of high oxygen permeability.

PURPOSE: To compare multiple strains of Pseudomonas aeruginosa and representative isolates of Staphylococcus aureus and Serratia marcescens for their relative primary adhesion to a high Dk silicone hydrogel lens (36% H2O) with that of a HEMA-type lens (58% H2O). METHODS: A radiolabeled cell procedure with a 2-h cell exposure was employed for enumerating bacteria on unworn and worn silicone hydrogel (balafilcon A) and HEMA-type (etafilcon A) hydrogel lenses. RESULTS: The degree of primary adhesion of P. aeruginosa to 7-day worn balafilcon A lens was similar to the degree of adhesion to unworn balafilcon A lenses. The degree of primary adhesion by clinical strains to unworn balafilcon A lenses and etafilcon lenses was strain variable, but did not differ markedly for the two lenses with a given strain of P. aeruginosa. Relative to most of the pseudomonad strains, adhesion to the hydrogel lenses by S. aureus and S. marcescens was non-significant. CONCLUSION: Adhesion of strains of P. aeruginosa to a hydrogel contact lens does not appear to differ appreciably between the HEMA-type etafilcon A and the high Dk silicone hydrogel balafilcon A lens.     

Robust and secure fractional wavelet image watermarking

This paper presents an efficient fractional wavelet transform (FWT) image watermarking technique based on combining the discrete wavelet transform (DWT) and the fractional Fourier transform (FRFT). In the proposed technique, the host image is wavelet transformed with two resolution levels, and then, the middle frequency sub-bands are FRFT transformed. The watermark is hidden by altering the selected FRFT coefficients of the middle frequency sub-bands of the 2-level DWT-transformed host image. Two pseudo-random noise (PN) sequences are used to modulate the selected FRFT coefficients with the watermark pixels, and inverse transforms are finally applied to get the watermarked image. In watermark extraction, we just need the same two PN sequences used in the embedding process and the watermark size. The correlation factor is used to determine whether the extracted pixel is one or zero. The proposed fractional wavelet transform (FWT) image watermarking method is tested with different image processing attacks and under composite attacks to verify its robustness. Experimental results demonstrated improved robustness and security.     

An Applicable Strategy for Improvement Recovery in Simultaneous Analysis of 20 Pesticides Residue in Tea

It is important to have a reliable method to analyze pesticides in tea, a beverage commonly consumed in Iran. A validated method was developed for the determination of 20 pesticides in tea based on QuEChERS sample preparation and capillary gas chromatography‐quadrupole mass spectrometry in selective ion monitoring mode (GC‐MS/SIM) using triphenyl methane (TPM) solution as an internal standard. We used fortified, extracted, and cleaned‐up tea samples instead of calibration standards for quantitation, which substantially reduced adverse matrix‐related effects and negative recovery affected by graphite carbon black (GCB) on pesticide analysis. The recovery of pesticides at 3 concentration (40, 60, and 240 ng/g) ranged from 79.5% to 111.4% (n = 3). The method had acceptable repeatability with RSDr < 20%. The limits of quantification (LOQ) for all pesticides were ≤20 ng/g. The analytical results of the proposed method were in good agreement with proficiency test results (FAPAS, 19116). The recoveries and repeatabilities were in accordance with the criteria set by SANCO Guideline. The validated method was suitable for the analysis of pesticides in tea.