Interpreting the hydrogen adsorption on organic groups functionalized MOF-5s by statistical physics model

The hydrogen adsorption isotherms at equilibrium on four adsorbents (MOF-5 and three modified MOF-5s named, CH₃-MOF-5, Br-MOF-5 and Cl-MOF-5) were studied using a monolayer model with four adsorption sites energies. The analytical expression of this model was developed using the grand canonical ensemble in statistical physics by taking some working hypotheses involving some physicochemical parameters which can describe the adsorption process. These parameters are: four numbers of hydrogen adsorbed molecules per site (n₁, n₂, n₃ and n₄), four receptor site densities (N_M1, N_M2, N_M3 and N_M4), four saturation adsorbed quantities (Q₁, Q₂, Q₃ and Q₄) and four adsorption energies (??₁, ??₂, ??₃ and ??₄). The evolutions of these parameters in relation with temperature were discussed to understand and interpret the adsorption process at different temperatures. Fitting results revealed that the adsorption of hydrogen on MOF-5 is an exothermic physisorption process. The adsorption surface is inhomogeneous with many site energies. The fitting of the adsorption site is achieved by an aggregate of hydrogen molecules. The adopted model expression is used to derive the thermodynamic potential functions which govern the sorption mechanism such as entropy S_a, free enthalpy of Gibbs G and internal energy E_int.     

Physicochemical Properties of Different Types of Starch Phosphate Monoesters

Different types of starch were phosphorylated to different degrees of substitution using monosodium and disodium hydrogen orthophosphate at 160 °C under vacuum. Generally, phosphation enhanced the physicochemical properties of the modified starches compared to their native counterparts. Solubility and swelling power greatly increase when phosphorylation was carried out to a low degree of substitution, while the solubility and swelling power decreased gradually by increasing the degree of substitution. However, the values of the monoesters were still higher than those of the corresponding native polysaccharides. Viscosities of different starch types except corn amylose showed the highest values at the lowest degree of substitution, when the degree of phosphation increased the viscosity values decreased. Native potato starch formed a clear paste (96% transmittance) due to the presence of phosphate groups while the paste clarity of potato starch decreased gradually by increasing the degree of phosphation. Generally, phosphorylation increased the light transmittance of the other starches investigated at the lowest degree of substitution but the clarity decreased by increasing the degree of substitution.     

Application of time series and polynomial learning networks to robot trajectory error control

A compensatory control scheme based on measured errors at the end-effector is proposed using polynomial learning networks and time series modeling. Based on experimental data from an industrial manipulator programmed forms straight-line motion, trajectory deviations are modeled using both techniques. The performance of the models are compared at different locations in the workspace. It is shown that the robot arm signature can be obtained and that models from both techniques can be used to forecast trajectory errors. A method to implement the proposed scheme is also given.     

Pressure control in a PEM fuel cell via second order sliding mode

Pressure difference inside the Polymer Electrolyte Membrane Fuel Cells (PEMFC) arises due to load variations, during which the pressure difference between anode and cathode rises. Practically, this problem can be avoided by equalizing anode and cathode pressures, to protect the fuel cell from permanent damage. This paper focuses on pressure regulation in the anode and cathode sides of the PEMFC. The control objective is achieved using second order sliding mode multi-input multi-output (MIMO) controller based on “Twisting algorithm”. Parametric uncertainty is formally presented and included in a nonlinear dynamic fuel cell model. The resultant nonlinear controller is robust and is proved to guarantee performance around any equilibrium point and under parametric uncertainty. Simulation results show that the proposed controller has a good transient response under load variations.     

Effect of mineralogical composition and kerogen content on oil shale natural floatability

Mineralogical composition is one of the important factors that affect the performance of separation processes. In the current study, two oil shale samples, from El-Nakhil and El-Bieda localities, differ in their mineralogical composition, were subjected to flotation tests. Chemical analysis, differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), and microscopic examination are among the used characterization techniques. In addition, their responses for upgrading by flotation were conducted as a function of pH, solid-liquid ratio, stirring speed and different particle sizes. The characterization results indicated that the kerogen content in El-Nakhil sample was 30% while in El-Beida sample was 10%. On the other hand, the flotation results indicated that El-Bieda responses better than that of El-Nakhil in terms of the difference in kerogen % between the original sample and the concentrated ones. The difference in flotation results of two samples can be explained by the difference in kerogen morphology as well as its interaction with surrounding matrix. In El-Bieda the kerogen has a laminated structure but in El-Nakhil it appears as laminated liptinitic component, in addition to the higher carbonate content in El-Nakhil sample in comparison to higher clay content in El-Bieda sample.     

Some non-classical properties of a class of new nonlinear coherent states

Some of the properties of a nonlinear coherent state associated with the centre of mass motion of trapped atoms are considered. Especially the autocorrelation function, motional quanta number distribution, the phase properties, the Husimi–Kano Q function and the Wigner–Moyal W function of this nonlinear coherent state are discussed. Jumps in the motional quanta distribution function are reported depending on the dependence on the Lamb–Dicke parameters.     

Radiation synthesis and characterization of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) based hydrogels containing silver nanoparticles

A series of PVA/PVP based hydrogels at different compositions were prepared by gamma irradiation. The gel fraction degree of swelling were investigated. Highly stable and uniformly distributed silver nanoparticles have been obtained onto hydrogel networks. The morphology and structure of (PVA/PVP) hydrogel and dispersion of the silver nanoparticles in the polymeric matrix were examined by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR), respectively. The formation of silver nanoparticles has been confirmed by ultraviolet visible (UV–vis) spectroscopy. A strong characteristic absorption peak was found to be around 420 nm for the silver nanoparticles in the hydrogel nanocomposite. The X-ray diffraction pattern confirmed the formation of silver nanoparticles with average particle size of 12 nm. The diameter distribution of silver nanoparticles was determined by dynamic light scattering DLS. Transmission electron microscope (TEM) showed almost spherical and uniform distribution of silver nanoparticles through the hydrogel network and the mean size of silver nanoparticles ranging is 23 nm. The good swelling properties and antibacterial of PVA/PVP-Ag hydrogel suggest that it can be a good candidate as wound dressing.     

Assessment of a regulatory sanitization process in Egyptian dairy plants in regard to the adherence of some food-borne pathogens and their biofilms

Food-borne pathogens may develop certain strategies that enable them to defy harsh conditions such as chemical sanitization. Biofilm formation represents a prominent one among those adopted strategies, by which food-borne pathogens protect themselves against external threats. Thus, bacterial biofilm is considered as a major hazard for safe food production. This study was designed to investigate the adherence and the biofilm formation ability of some food-borne pathogens on stainless steel and polypropylene surfaces using chip assay, and to validate regular sanitizing process (sodium hypochlorite 250mg/L) for effective elimination of those pathogens. Sixteen pathogenic bacterial strains, previously isolated from raw milk and dairy products at Zagazig city, Egypt (9 Staphylococcus aureus, 4 Cronobacter sakazakii and 3 Salmonella enterica serovar Typhimurium), were chosen for this study. Strains showed different patterns of adherence and biofilm formation on tested surfaces with minor significance between surfaces. The ability of sodium hypochlorite to completely eradicate either adhered or biofilm-embedded pathogens varied significantly depending on the strain and type of surface used. Whilst, sodium hypochlorite reduced tested pathogens counts per cm(2) of produced biofilms, but it was not able to entirely eliminate neither them nor adherent Cronobacter sakazakii to stainless steel surface. This study revealed that biofilm is considered as a sustainable source of contamination of dairy products with these pathogens, and also emphasized the need of paying more attention to the cleaning and sanitizing processes of food contact surfaces.     

Analysis,modeling, identification and control of pancake DC torque motors: Application to automobile air path actuators

This article is focused on the working, modeling and control of pancake DC torque motors, used in automobile engine air path actuators. These motors, with a limited working angle, provide high torque which makes them suitable for use in actuators without any additional gear reduction. The torque is a nonlinear function of the motor angle. This article provides a modeling scheme, suitable for control purposes, which takes into consideration nonlinearities arising from friction and operating temperature. Comparison between simulation and experiments shows the effectiveness of the proposed model. Second order sliding mode control has been applied to the actuators for robust control under the influence of nonlinearities and uncertainties. The effectiveness of the control algorithm has been proven experimentally.