Parameter estimation of the electrothermal model of the ferromagnetic core

The paper presents a new form of the electrothermal model of the ferromagnetic core for SPICE and the way, in which the parameters of the model are determined. The manner of determining magnetic, geometric and thermal parameters of this model is described. The correctness of the proposed model and the manner of determining the values of the parameters are verified by comparing the calculated and measured characteristics of the selected ferromagnetic cores.     

Analysis of Experimental Grain Boundary Distributions Based on Boundary-Space Metrics

Grain boundary distributions in the space of macroscopic boundary parameters are basic statistical characteristics of boundary networks. To avoid artifacts caused by the currently used computation method, it is proposed to utilize the kernel density estimation technique and to determine boundary distributions based on metric functions defined in the boundary space. A distribution is calculated at points of interest by summing areas of boundaries that fall within specified distances from these points. The new method is illustrated on experimental data of a nickel-based superalloy.     

ANN–supported control strategy for a solid oxide fuel cell working on demand for a public utility building

The idea of control strategy of SOFC operating to meet demand of a public utility building was presented. The strategy was formulated with the support of Artificial Neural Network. The network was used to predict the demand for electricity. The calculations were carried out on the example of a building of the Institute of Heat Engineering Warsaw University of Technology. The control strategy is influenced by various factors depending on changes in market conditions and operating characteristics of the cell. We can define different objective functions eg: working for own needs, for maximum profit and maximum service life. The article presents a simulation of SOFC operation for demand profile of the IHE building from the selected time period.     

Modification of Fe and Al elemental powders’ sintering with addition of magnesium and magnesium hydride

An attempt to modify sintering of iron and aluminium elemental powders with use of small additions of Mg and MgH₂ was presented in this paper. The kinetics of such modified sintering was investigated using DSC technique, XRD analysis and SEM observations. Significant changes in the mechanism of exothermal formation reaction of Fe–Al intermetallic phases in compositions doped with magnesium and its hydride was observed. Initiation temperature of Self-propagating High-temperature Synthesis (SHS) reaction was pronouncedly shifted to lower value as compared with undoped composition. Influence of additions on the SHS reaction kinetics parameters was also calculated with use of the JMA model and changes of the Avrami exponent value of specific phase formation was noticed. Positive effect of MgH₂ addition on partial homogeneity of final product was also studied.     

The influence of electron beam irradiation,plastic deformation,and re‐irradiation on crystallinity degree,mechanical and sclerometric properties of GUR 1050 used for arthroplasty

The article describes the influence of an electron beam irradiation (I), plastic deformation (D), and re‐irradiation (R) on the properties of ultrahigh molecular weight polyethylene (GUR 1050). It was found that the modification through irradiation entailed a gradual increase in the degree of crystallinity (after irradiation–I). After plastic deformation and re‐irradiation (IDR) the degree of crystallinity decreases which had a direct influence on the mechanical properties. The polymer irradiation only (technique I) resulted in an increase in the maximum stress as compared with the material in the initial state. The application of deformation and re‐irradiation (technique IDR) allowed increasing the deformation resistance by more than 40%. Moreover, the irradiation with an electron beam resulted in the increase in hardness (H) and Young's modulus (E) proportionally to the applied irradiation dose and in the reduction of total indentation work (W_tot) and its components. After deformation and re‐irradiation the polyethylene hardness went down. The application of technique (I) caused an improvement to the material abrasion resistance (reduction of parameter PD–working scratch depth) with the increasing irradiation dose. The introduction of deformation and re‐irradiation did not have a material impact on parameter (PD) increasing at the same time elastic properties of UHMWPE (increase in parameter NPS–elastic recovery). Modification IDR has changed the wear mechanism (β) toward ploughing and has increased the abrasion‐resistance index (W_β) and also significantly reduced the coefficient of friction (μ) of GUR 1050. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43683.     

Artificial Maturation of the Highly Active Heterodimeric [FeFe] Hydrogenase from Desulfovibrio desulfuricans ATCC 7757

Hydrogenases catalyze the reduction of protons and oxidation of molecular hydrogen with high turnover frequencies and low overpotentials under ambient conditions. The heterodimeric [FeFe] hydrogenase from Desulfovibrio desulfuricans has an exceptionally high activity, and can be purified aerobically in an oxygen-stable inactive state. Recently, it was demonstrated that monomeric [FeFe] hydrogenases produced recombinantly in Escherichia coli can be artificially maturated by simply incubating the inactive “apo” enzymes with the synthetic [2Fe] cofactor mimic [Fe₂(adt)(CO)₄(CN)₂]²⁻. Here, we use the same technique to produce the heterodimeric “apo” hydrogenase from D. desulfuricans in E. coli with a high yield and purity, and maturate the “apo” enzyme with [Fe₂(adt)(CO)₄(CN)₂]²⁻ to generate fully active “holo” enzyme. Interestingly, the rate of the artificial maturation process with D. desulfuricans is significantly slower than that for all other hydrogenases tested so far. The artificially maturated enzyme is spectroscopically and electrochemically identical to the native enzyme and shows high rates of hydrogen production (3700 s⁻¹) and hydrogen oxidation (63,000 s⁻¹). We expect that our highly efficient production method will facilitate future studies of this enzyme and other related [FeFe] hydrogenases from Desulfovibrio species.     

Modeling of the degradation kinetics of biodegradable scaffolds: The effects of the environmental conditions

The rate of hydrolytic degradation of tissue‐engineered scaffolds made from bioresorbable polyesters is dependent on several factors. Some are related to the properties of the degrading polymeric material, but others are related to the geometry of the porous structure and the operating environment. It is well known that the rate of hydrolytic degradation of a given object, porous or nonporous, is lower when it is exposed to dynamic conditions, a flowing medium, than when it operates in static conditions. The most likely reason is the more efficient removal of the acidic degradation products from the vicinity of the polymeric material when it is operating in a flowing medium. In this article, we present a new phenomenological reaction–diffusion model of aliphatic polymer degradation. The model can be used to predict the significance of various factors in in vitro degradation tests, with particular reference to the flow of the degradation medium, and the frequency of medium replacement in the case of static conditions. The developed model was used to simulate the degradation of poly(dl ‐lactide‐co‐glycolide) scaffolds with different porosities subjected to static and dynamic testing conditions. The results confirm that the porosity of the scaffold had a significant influence on the degradation rate. It was shown that the combination of dynamic conditions and high porosity effectively reduced the mass loss and molecular weight loss of the degrading polymer. However, the effect of changes in the velocity of the flowing medium had a negligible effect on the rate of degradation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40280.     

Clickable poly(ionic liquid)s for modification of glass and silicon surfaces

Covalent attachment of poly(ionic liquid)s (PILs) by click chemistry on glass or silicon (Si) surfaces was performed. Poly[1-(4-vinylbenzyl)-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] (polyVBBI⁺Tf₂N⁻), and copolymers of polyVBBI⁺Tf₂N⁻ with fluorescein O-methacrylate were synthesized by conducting an atom transfer radical polymerization (ATRP) from initiators containing azide or thioacetate groups. The azide- and thiol-terminated PILs were then successfully grafted onto alkyne and alkene modified glass/Si wafers by thermal azide–alkyne cycloaddition and photoinitiated thiol-ene click reactions, respectively. The modified surfaces were characterized by contact angle measurements and ellipsometry. The fluorescent PIL functionalized surfaces showed strong fluorescence under UV irradiation. This procedure of tethering PILs to substrates also provides an easy way to change the surface hydrophilicity by replacing the anions in the grafted PILs. The present approach could be readily applied for surface modifications with other types of PILs or their copolymers to achieve different functionalities on various surfaces.