Photoactive and self-cleaning TiO2-SiO2 thin films on 316L stainless steel

In this study, TiO₂-SiO₂ nanocomposite films with different amounts of SiO₂ were prepared by sol-gel process and were coated onto stainless steel 316L. The effect of addition of various amount of SiO₂ in the precursor solution on the photocatalysis, photo-generated hydrophilicity and self-cleaning property of TiO₂ thin films was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, water contact angle measurements and UV spectroscopy. In the tested ranges of SiO₂ content and sintering temperature, the highest photocatalytic activity and self-cleaning property were observed in the 15 mol% SiO₂ sample sintered at 750 °C. Addition of less than 30 mol% SiO₂ had a suppressive effect on the transformation of anatase to rutile and on the crystal growth of anatase in the sintering heat treatment. Phase separation occurred in the composite films for SiO₂ content of 30 mol% or more.     

PLGA-PEG-PLGA tri-block copolymers as an in-situ gel forming system for calcitonin delivery

Summary One of the main routes of peptide and protein delivery is parenteral. The need for daily or repetitive injection of these parenteral formulations is the main cause of patient non-compliance. The objective of this study was to prepare a controlled delivery system for peptide and proteins to increase patient compliance. Biodegradable triblock copolymers of PLGA and PEG (PLGA-PEG-PLGA) were synthesized and characterized using various content of glycolide. Solutions of PLGA-PEG-PLGA containing calcitonin as a model peptide were prepared and drug release from the sol-gel systems was evaluated in two different incubation conditions. Zero order release kinetics was achieved for up to 100 hours. No significant burst release effect was observed. It seemed that surface gelation was the main cause of drug release control. The release data fitted to Higuchi’s modeling and showed good correlation. It can be concluded that in situ gelling system prepared in this study can be used for a weekly peptide delivery system.     

Hybrid intelligent parameter estimation based on grey case-based reasoning for laminar cooling process

In this paper, a hybrid intelligent parameter estimation algorithm is proposed for predicting the strip temperature during laminar cooling process. The algorithm combines a hybrid genetic algorithm (HGA) with grey case-based reasoning (GCBR) in order to improve the precision of the strip temperature prediction. In this context, the hybrid genetic algorithm is formed by combining the genetic algorithm with an annealing and a local multidimensional search algorithm based on deterministic inverse parabolic interpolation. Firstly, the weight vectors of retrieval features in case-based reasoning are optimised using hybrid genetic algorithm in offline mode, and then they are used in grey case-based reasoning to accurately estimate the model parameters online. The hybrid intelligent parameter estimation algorithm is validated using a set of operational data gathered from a hot-rolled strip laminar cooling process in a steel plant. Experiment results show the effectiveness of the proposed method in improving the precision of the strip temperature prediction. The proposed method can be used in real-time temperature control of hot-rolled strip and has potential for parameter estimation of different types of cooling process.     

A block matrix representation of permutation networks

This work provides a mathematical framework for topologically-independent analysis of permutation networks. First, a structure-dependent representation is provided using matrices whose entries are switching expressions. Then, a transformation is presented which maps these matrices into structure-independent representations which are matrices whose entries are 0/1 matrices. Algebraic tools for manipulating the second type of matrices are also provided. Notions such as permutations realizable by a network, the rearrangeability property, and series and parallel connections of networks are defined and discussed with regard to the proposed representations.     

THERMAL CONDUCTIVITY OF GASEOUS AMMONIA IN THE TEMPERATURE RANGE 358-925 K.

Thermal conductivity of research grade pure ammonia gas has been measured by the column method at pressures of 12.9, 26.5, and 45.0 kN/m² over the temperature range 358 to 925 K. The maximum probable error of measurement is 1.5% at 874 K and it increases in magnitude as the temperature decreases. At 405 K, it is about 4.8%. The experimental data are correlated by the following cubic polynomial in temperature:

k(T)=5.237× 10^-3 + 5.179 × 10^-4 T + 8.404 × 10^-7 T² + 1.557 × 10^-10 T³.

Here k is in mW/cm-K and T is in K.

The experimental values are compared with three kinetic theory expressions for thermal conductivity of polyatomic gases in conjunction with the Stockmayer (12-6-3) potential. It is concluded that none of the theories can accurately predict the thermal conductivity of ammonia and probably of polar gases in general. The diffusion coefficient characterizing the transport of vibrational energy is computed as a function of temperature and on the basis of experimental data and the theory due to Ahtye. It has been long known that the transfer of energy by polyatomic and polar molecules is quite complex because of the presence of internal degrees of freedom and the possibility of resonant energy transfer in the latter (Hirschfelder, Curtiss and Bird, 1964).     

Chlorinated pesticide residues in meat and fat from animals raised in iran

Meat and fat samples (310) from carcasses of cattle, sheep, goats and camels from different regions of Iran were analyzed to determine concentrations of chlorinated pesticide residues. DDT, DDE, TDE, lindane, dieldrin and endrin were detected in the adipose tissues and meat of all species. Incidence as well as concentration of most pesticide residues were lowest in the camel and highest in the sheep. External fat samples were satisfactory for pesticide monitoring. The concentration of DDT did not exceed the World Health Organization (WHO) maximum limit for meat and fat.     

A fully Lagrangian mixed discrete least squares meshfree method for simulating the free surface flow problems

This paper presents a fully Lagrangian mixed discrete least squares meshfree (MDLSM) method for simulating the free surface problems. In the proposed method, the mass and momentum conservation equations are first discretized in time using the projection method. The resulting pressure Poisson equation is then re-written in the form of three first-order equations in terms of the pressure field and its first-order derivatives. The mixed discrete least squares meshless method is then used to solve this system of equations and simultaneously calculate the pressure field and its gradients. The advantage of the proposed Lagrangian MDLSM is twofold. First, the pressure gradients are directly computed and, therefore, they enjoy higher accuracy than those calculated in the conventional DLSM via a post-processing method. The more accurate pressure gradient will in turn lead to more accurate velocity field when used in the momentum equations. Second, the proposed Lagrangian MDLSM method can be more efficient than the corresponding original Lagrangian DLSM method, for the specific number of nodes, since the costly calculation of the shape function second derivatives required for solving the pressure Poison equation are avoided in each time step of the simulation. Several free surface problems are solved and the results are presented and compared to those of DLSM method. The results indicate the superior efficiency and accuracy of the proposed Lagrangian MDLSM method compared to those of the existing Lagrangian DLSM method in the literature.

     

Formation of 3D networks in polylactic acid by adjusting the cross-linking agent content with respect to processing variables: a simple approach

High-performance biodegradable polymers have attracted considerable attention over the years because of their eco-friendly nature. The effects of processing variables on the efficiency of crosslinking, and the rheological and thermal properties of cross-linked polylactic acid (XPLA) have not been comprehensively addressed yet. In this work, XPLA was prepared through solution casting followed by curing in an oven. Enhancements in properties could be quantified in terms of structural changes in 3D structure of XPLA by varying the amount of dicumyl peroxide (DCP) as a cross--linking agent and curing temperature and time. The XPLAs were characterized by differential scanning calorimetry, thermo-gravimetric analysis, swelling, and rheological techniques. The swelling data revealed an increase in gel fraction by 1.32% per 1 °C temperature rise in the range of 125–195 °C. The results were also indicative of an increase in gel faction by 0.32% per minute in the time range of 5–100 min. Maximum variation in gel fraction occurred at 195 °C with high peroxide content. At this temperature, the variation rate of gel content was about 14.99%. With gel formation evolution, especially at 85% completion stage, the melting point was vanished. Rheological measurements showed that the Newtonian plateau disappeared for the cross-linked samples, simultaneously with the onset of shear thinning and zero-shear viscosity, through which the molecular weight obtained by the Mark–Houwink equation shifted to lower frequencies. A mathematical model based on the Charlesby–Pinner equation was developed for predicting the gel content of the XPLA as a function of curing time and peroxide concentration. The Flory–Huggins parameter also changed during the cross-linking process as a function of cross-linking density. This study is focused on adjusting cross-linking density and processing factors, like temperature and time, to achieve an XPLA with desirable properties.