Numerical investigation of effective parameters of falling film evaporation in a vertical-tube evaporator

Wastewater treatment is one of the most effective solutions to manage the problem of water scarcity. Falling film evaporators are excellent technology in wastewater treatment plants. These wastewater evaporators provide high heat transfer, short residence time in the heating zone, and high-purity distilled water. In the present study, the mechanism of turbulent falling film evaporation in a vertical tube has been investigated. A model has been developed for symmetrical two-dimensional pure and saline water flow in a vertical tube under constant wall heat flux. The numerical simulation has been carried out by a commercial computational fluid dynamics code. The evaporation of saturated liquid film is simulated utilizing a two-phase volume of fluid method and Tanasawa phase-change model. The main objective of this study is to evaluate the effects of water salinity, liquid Reynolds number, wall heat flux, and liquid film thickness on the two-phase heat transfer coefficient and vapor volume fraction. The numerical heat transfer coefficients are compared with the obtained results by Chen's empirical correlation. With a MAPE ≤ 11%, this study proves that the numerical method is highly effective at predicting the heat transfer coefficient. Moreover, the empirical coefficient of the Tanasawa model and the minimum thickness of the falling film are determined.     

Nanosized polypyrrole affected by surfactant agitation for emulsion polymerization

Nanosized conductive polypyrrole (PPy) powders were prepared using emulsion polymerization with aid of high speed agitation. Different agitation speeds from 650 to 24,000 rpm were used with different anionic, cationic, and non-ionic surfactants. Then, the effects of the agitation speed and surfactant species were examined in terms of their physical and electrical properties of conductivity and powder size. Prepared PPy nanopowders exhibited high conductivity values of 10 S/cm regions, when sodium dodecylbenzenesulfonate (SDBS) and sodium dodecylsulfate (SDS) were used. The powder dispersion of the resultant PPy was also observed to be dependent on the agitation speed and surfactant type. The morphology shown by SEM and TEM revealed that the anionic SDBS surfactant could effectively disperse into nanosized aggregates of the PPy. The results showed that the combination of the anionic surfactants and high agitation in the emulsion polymerization could produce nanosized PPy powders with higher conductivity.     

Effect of indium concentration on morphology and optical properties of In-doped ZnO nanostructures

In-doped ZnO nanostructures with different indium concentrations were grown using a thermal evaporation method. The In-doped ZnO nanostructures with a low concentration of indium exhibited a javelin shape, while the In-doped ZnO nanostructures with a high concentration of indium showed a flake shape. In addition, undoped ZnO nanojavelins were grown under the same conditions, but the sizes of these undoped ZnO nanojavelins were larger than the In-doped ZnO nanojavelins. It was shown that the In³⁺ cations played a crucial role in controlling the size. X-ray diffraction and Raman spectroscopy clearly showed hexagonal structures for all of the products. However, the Raman results demonstrated that the In-doped ZnO nanoflakes had a lower crystalline quality than the In-doped ZnO nanojavelins. Furthermore, photoluminescence (PL) measurements confirmed the Raman results. Moreover, the PL results demonstrated a larger band-gap for the In-doped ZnO nanostructures in comparison to the undoped ZnO.     

Analysis of antibiotic resistance patterns and detection of mecA gene in Staphylococcus aureus isolated from packaged hamburger

Presence of Staphylococcus aureus, antibiotic resistance pattern and PCR detection of mecA gene in isolated strains were investigated in total of 256 packaged hamburgers in Iran-Tehran. For this purpose we used standard disk-diffusion method and sensitive and specific PCR technique, respectively. Results showed that 25% of samples were positive for S. aureus. Resistance to meticillin, erythromycin, penicillin G, cefazolin, ciprofloxasin, vacomycin and amoxiclave was determined 89%, 20.3%, 18.7%, 15.6%, 14%, 26.6% and 12.5%, respectively. According to the obtained results from PCR analysis of methicillin-resistant S. aureus (MRSA), mecA gene was present in 100% of the resistant isolates, 0% of intermediate-resistance isolates and 25% of susceptible isolates. The results obtained from PCR detection of mecA gene showed high correlation with standard disk diffusion test.     

DETERMINATION OF OPTIMUM RATE CONSTANTS FOR AUTOCATALYTIC REACTION OF TAR SAND RECOVERV PROCESS

ABSTRACT

In this paper a parameter optimization technique is introduced involving a minimization algorithm. The technique is applicable to a wide range of problems involving data analysis. In particular, it is applied to the first-order initial-value problem describing the autocatalytic reaction of tar sand recovery process, as a result of which, the optimal reaction rate constants for a given set of experimental data are obtained. The analytical solution to the governing differential equation corresponding to these optimal parameter values is then shown to fit the experimental data. Numerical results are presented in graphical form for three different sets of data, and discussion and conclusions are provided subsequently.     

Effects of alkali and ultraviolet treatment on colour strength and mechanical properties of jute yarn

In this study, jute yarns were treated with an aqueous alkali solution and ultraviolet light to improve dyeability. Ultraviolet light treatments were carried out at an air pressure of 1 atm, under water and vacuum, and all the samples were dyed with reactive dyes. Virgin samples and treated jute yarns were analysed by Fourier Transform–infrared spectroscopy. K/S values were determined by a reflective spectrophotometer and used to establish the fixation values and colour strength of the dyed samples. The tensile mechanical properties of the samples were also measured by a tensile testing apparatus and were compared with the virgin samples. Alkali treatment resulted in a reduction in carbonyl group concentration. However, atmospheric ultraviolet light treatment increased carbonyl group concentration. Dyeability and dye fixation values for atmospheric and underwater ultraviolet light‐treated samples increased. Furthermore, the loss of tensile strength for alkali‐treated samples was much greater than others (up to 50%) in comparison with ultraviolet light‐treated samples.     

The Effect of Holding Liquid Aluminum Alloys on Oxide Film Content

Melts of commercially pure liquid aluminum, and an Al-7Si-0.3Mg alloy, were cast into molds designed to produce entrainment of oxide film defects. The melts were held for periods of up to 20 minutes to investigate whether changes in the oxide film defects in the melt could occur, once sufficient time had elapsed for consumption of their internal atmosphere. The alloys were characterized by the determination of their Weibull modulus, examination of fracture surfaces under scanning electron microscopy (SEM), and determination of their porosity characteristics. The Weibull moduli of the ultimate tensile strength (UTS) values of the Al-7Si-0.3Mg alloy were reduced initially by holding in the liquid state for 10 minutes, but then the values increased after holding for 20 minutes. This high Weibull modulus was found despite oxide films being observed on the fracture surfaces. In the case of the commercial purity Al, the UTS Weibull moduli increased only slightly with holding for 20 minutes. The results suggested that holding of Al alloys in the liquid state influenced the scatter of mechanical properties by influencing the porosity content of the castings, which was related to their oxide film content. Some evidence for healing of a double oxide film defect with time was also found in the commercial purity Al alloy.     

Nonintrusive Monitoring and Control of Metallurgical Processes by Acoustic Measurements

The feasibility of developing a new online monitoring technique based on the characteristic acoustic response of gas bubbles in a liquid has been investigated. The method is intended to monitor the chemistry of the liquid through its relation to the bubble sound frequency. A low-temperature model consisting of water and alcohol mixtures was established, and the frequency of bubbles rising under varying concentrations of methanol was measured. It was shown that the frequency of the sound created by bubble pulsation varies with the percentage of alcohol in water. The frequency drops sharply with the increase in methanol content up to 20 wt pct, after which the decreases is gradual. Surface tension seems to be a critical liquid property affecting the sound frequency through its two-fold effects on the bubble size and the pulsation domain. The dependence between the frequency and the liquid composition suggests the feasibility of developing an acoustic-based technique for process control purposes.     

Report of the Third Workshop on the Usage of NetFlow/IPFIX in Network Management

The Network Management Research Group (NMRG) organized in 2010 the Third Workshop on the Usage of NetFlow/IPFIX in Network Management, as part of the 78th IETF Meeting in Maastricht. Yearly organized since 2007, the workshop is an opportunity for people from both academia and industry to discuss the latest developments of the protocol, possibilities for new applications, and practical experiences. This report summarizes the presentations and the main conclusions of the workshop.