Utilization of bog iron ores as sorbents of heavy metals

Sorption properties of bog iron ores with respect to Pb, Cu, Zn, Cr are evaluated at various pH. Maximum sorption determined in the experiments equals to 97.0, 25.2, 25.5, 55.0mg/g for lead(II), copper(II), zinc(II), and chromium(III), respectively. Chromium(VI) is bound in the amount of up to 10.0mg/g. The values of desorption indicate that most of the metals remain stably bound to the surface of bog iron ores, indicating that the chemisorption process prevails. The metals are sorbed as cations at the pH values from 4 to 9. Within this pH range up to 100% of the initial metal amount is immobilized. 90-100% of Cr(VI) is sorbed at pH between 3 and 5. Such properties, combined with favorable conditions of shallow mining and resultant low costs, may be regarded as an incentive for local utilization of bog iron ores in the environmental protection practice.     

Comparative study of erbium disilicide thin films grown in situ under ultrahigh vacuum or ex situ with a capping layer

Erbium disilicide (ErSi_2-x) thin films grown by two different techniques are compared using a variety of characterization techniques, both electrical and physical. The first technique involves Er deposition and annealing under ultrahigh vacuum and the second one focuses on Ti/Er/Si(100) stacks evaporated under high vacuum and heated ex situ by rapid thermal annealing. Crystalline phase identification by X-ray diffraction reveals the formation of ErSi_2-x for all the studied samples. Cross-sectional transmission electron microscopy shows that the Ti cap transforms into Ti-Si compounds. The efficient stripping of the capping layer is also demonstrated. Atomic force microscopy evidences the formation of inverted pyramidal defects in both cases, with some improvement for the Ti-capped samples. X-ray photoelectron spectroscopy depth profiles show that the ErSi_2-x films and the ErSi_2-x/Si interfaces are oxygen-free. The extracted Schottky barrier height of ErSi_2-x/n-Si contacts lies around 0.3 eV notwithstanding the annealing temperature or the growth technique. It thus demonstrates a route to form ErSi_2-x thin films that advantageously compares with reference ultrahigh vacuum samples with less stringent fabrication conditions.     

Methodologies of Compressing a Stable Performance Convolutional Neural Networks in Image Classification

Neural Processing Letters - Deep learning has made a real revolution in the embedded computing environment. Convolutional neural network (CNN) revealed itself as a reliable fit to many emerging...     

A numerical analysis of heat and mass transfer processes in a macro-patterned methane/steam reforming reactor

The presented paper focuses on a numerical analysis of a heat and mass transfer process in a novel type of methane/steam reforming reactor. The novelty of the macro-patterned reactor design lies in dividing a reformer into segments of various lengths and reactivity. Precisely, splitting the catalyst and filling the created empty volume with porous, non-reactive, thermal conducting material such as metallic foam. This approach allows for moderating a sharp temperature drop at the inlet of the reactor typical for the endothermic methane/steam reforming process. To analyze the considered system, the mathematical and numerical models of transport phenomena and the reaction kinetics were developed and implemented into an in-house solver. The kinetics of methane/steam reforming was taken from the literature. The outlet composition obtained from the kinetic model was compared with the experimental measurements and good agreement was found. The conducted numerical analysis includes cases that differ from a number and lengths of catalytic and non-catalytic segments. The obtained results indicate that the macro-patterned design is a promising strategy that allows for a significant improvement of temperature distribution in a reforming reactor. It was shown that the proposed approach could help to cut the cost of the catalyst material by allowing for the conversion of methane with a smaller amount of the catalyst close to the reference case.     

Evolution of viscoelastic behaviour of a curing LY5052 epoxy resin in the rubbery state

In this work, we investigate the relationship between the rubbery modulus and the degree of cure for partially to fully cured LY5052 epoxy resin. In particular, this paper experimentally tests an existing model formulated for shear modulus by redefining for in the tensile storage modulus. Experiments to characterize viscoelastic behaviour were performed in a dynamic mechanical and thermal analysis (DMTA) instrument in the frequency domain. Master curves are then created from DMTA using general time–temperature–cure superposition. The master curves are then normalized using the model so that the master curve does not depend on the properties in the rubbery region. This results in a unique master curve that describes the viscoelastic behaviour of the LY5052 epoxy resin for the given conditions. Once the relationship between the rubbery modulus and the degree of cure has been established, the amount of experimental characterization can be reduced. This could lead to the development of simplified experimental methodologies and simplified models to characterize the viscoelasticity of low molecular weight resins like the LY5052 epoxy resin system.     

A 1.235 lower bound on the number of points needed to draw all n-vertex planar graphs

We study a problem of lower bounds on straight line drawings of planar graphs. We show that at least 1.235·n points in the plane are required to draw each n-vertex planar graph with edges drawn as straight line segments (for sufficiently large n). This improves the previous best bound of 1.206·n (for sufficiently large n) due to Chrobak and Karloff [Sigact News 20 (4) (1989) 83-86]. Our contribution is twofold: we improve the lower bound itself and we give a significantly simpler and more straightforward proof.     

Examples of peptide-peptoid hybrid serine protease inhibitors based on the trypsin inhibitor SFTI-1 with complete protease resistance at the P1-P1' reactive site

Research in the field of protease inhibitors is focused on obtaining potent, specific and protease-resistant inhibitors. To our knowledge, there are no reports in the literature that consider the application of N-substituted glycine residues (peptoid monomers) for the design of peptidomimetic protease inhibitors. We hereby present the chemical synthesis and kinetic properties of two new analogues of the trypsin inhibitor SFTI-1 modified at the P1 position. Substitution of Lys5 in SFTI-1 by N-(4-aminobutyl)-glycine and N-benzylglycine, which mimic Lys and Phe, respectively, made these analogues completely protease-resistant at their P1-P1' reactive sites. The analogues synthesised appeared to be potent inhibitors of bovine beta-trypsin and alpha-chymotrypsin. These noncovalent, competitive and selective peptide-peptoid hybrid (peptomeric) inhibitors might open the way to targeting unwanted proteolysis.     

On symbolic dynamics of a chaotic second-order digital filter

This paper presents a contribution to the symbolic analysis of fractal patterns exhibited by a second-order digital filter with modular adder overflow characteristic. We use symbolic dynamics for the analysis of phenomena encountered in the system. We present several new results concerning the existence of admissible sequences for periodic orbits in the filter. an efficient computational algorithm based on rigorous mathematical results presented in the paper enabled us to calculate sequences with long periods, thus allowing deeper understanding of the underlying mechanisms of complex behaviour encountered in the filter.     

Splitter imperfections in annular split-flow thin separation channels: effect on nonspecific crossover

The separation performance of split-flow thin (SPLITT) separation channels generally falls short of ideal behavior. There are many possible contributing factors to the loss of separation resolution, and these are discussed in the text. The possibility that small imperfections in the splitters play a significant role is examined in this study. Computational fluid dynamics is used to determine the flow pattern within an annular SPLITT channel having small imperfections in the inlet splitter. These results are used to calculate the nonspecific crossover of particles from the inner annular inlet to the outer annular outlet under various flow rate regimes. Nonspecific crossover, obtained through convective transport alone, and not the result of field-induced transport, is often used as a check of channel behavior. The results of a typical experimental determination of nonspecific crossover are included for comparison. It is concluded that geometrical imperfections can indeed play a significant role in the loss of resolution observed for these systems.