Phenolic composition and functional properties of wild mint (Mentha longifolia var. calliantha (Stapf) Briq.)

Mints (Mentha species) are widely used as food, medicine, spice, and flavoring agents. At the present work, phenolics profile of infusion and ethanol extract of Mentha longifolia was determined using an RP–HPLC–DAD system. Total bioactive contents, radical scavenging, reducing power, metal chelating, and enzyme inhibitory activities relevant to Alzheimer’s disease, diabetes mellitus, and skin disorders were evaluated. Sixteen phenolic compounds (ten phenolic acids and six flavonoids) were identified in the extracts in which sinapic acid (7132 µg/g extract) and rosmarinic acid (6260 µg/g extract) were the most abundant compounds. Strong antioxidant effects were observed in 1,1-diphenyl-2-picrylhydrazyl radical, 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), cupric ion reducing activity, ferric reducing antioxidant power, phosphomolybdenum, and metal chelating assays. Results indicated selective acetylcholinesterase inhibitory activity and high α-amylase and α-glucosidase inhibitory potential. Findings showed that M. longifolia has promising health benefits due to its high concentration of useful phenolic compounds and has great potential for possible applications in the preparation of functional ingredients.     

Uncertainty based distributed generation expansion planning in electricity markets

Decision making under uncertainty is a difficult task in most areas. The distributed generation expansion planning is certainly one of the problems where it is difficult to find an optimal solution for, due to the existence of various uncertain parameters that affect the optimal solution. This paper presents a distributed generation planning strategy based on the multi-objective decision making (MODM) approach under uncertainties. The proposed strategy achieves a Pareto set of locations, sizes, and typical types, for new DG installations in a case-study power network (as the result of a multi-objective optimization). The technical constraints of DG units are also considered in the MODM process. The effects of the uncertain parameters on choosing the best plan(s) are considered using robustness, flexibility, and risk exposure attributes. This aim is performed based on a composite index which is weighted sum of the three mentioned attributes. This paper considers four categories of uncertain parameters including the peak loading factor, electricity market price, and investment and operating costs for the DG long-term planning.     

Protection of titanium metal by nanohydroxyapatite coating with zirconia and alumina second phases

In this study hydroxyapatite (HA)/zirconia/alumina composite coatings on titanium metal was carried out using Sol-Gel dip coating and calcination process. Hydroxyapatite-Alumina-Zirconia sol, coated samples in three processes by changing final sol stirring time, aging time, calcination temperature of synthesized powder and prepared coating and rate of coating. Some parts of prepared sol were also synthesized and became powder in all three processes. Scanning electron microscopy was used to estimate the particle size of the surface and for morphological analysis. The functional group and crystallization characteristics of the powders were analyzed using (FTIR) and X-Ray diffraction (XRD). Results show that the morphology of HA-Alumina-Zirconia coatings is more homogenous in the second process with 2 hours final sol stirring time, 20 hours aging time under stirring at 60, 675°C calcination temperature for coating and 850°C for powder and 60mm/min rate of dip coating.     

Effect of Bainite Morphology on Mechanical Properties of the Mixed Bainite-martensite Microstructure in D6AC Steel

The effect of bainite morphology on mechanical properties of the mixed bainite-martensite microstructure in D6AC low alloy ultra-high strength steel has been studied in the present work. For this purpose, samples austenitized at 910 C for 40 min were quenched in three different ways. Some of the samples were directly oil-quenched, some others were quenched in salt bath at 330 C and the remaining samples were quenched in salt bath at 425 C for various holding times. All samples were tempered at 200 C for 2 h. Microstructures were examined by optical microscopy (OM) and scanning electron microscopy (SEM). Fracture surfaces also were studied by SEM. Results showed that the mixed microstructure containing martensite and 28 vol.% of the lower bainite exhibited higher yield and tensile strengths than the fully martensitic microstructure. This could be mainly attributed to the partitioning of the prior austenite grains by the lower bainite and enhancing the strength of lower bainite in the mixed microstructure by plastic constraint. Charpy V-notch (CVN) impact energy and ductility were improved by increasing the volume fraction of the lower bainite. This is not the case about the mixed microstructure containing the upper bainite and martensite. As a result, the tensile and CVN impact properties of mixed upper bainite-martensite microstructure are lower than those of the fully martensitic microstructure. Finally, fractography studies showed cleavage fracture at the surface of CVN impact specimens with martensitic and upper bainitic microstructures confirming the tendency to brittle behavior.     

Influence of Pulse Electrodeposition and Heat Treatment on Microstructure,Tribological, and Corrosion Behavior of Nano-Grain Size Co-W Coatings

In the present study, Co-W nano-structured alloy coatings are produced on low-carbon steel substrate by means of pulse electrodeposition from a citrate-based bath under different average current densities and duty cycles. The results indicate that the coating deposited under 60% of duty cycle and 1 A/dm² of average current density exhibit optimum pulse plating conditions with 44.38 wt.% W, 37 nm grain size, and 758 HV microhardness. The effect of heat treatment temperature on microstructure, composition, corrosion behavior, and morphology of amorphous deposited Co-W alloy with 44 wt.% W was investigated. The microhardness of the coating increased to 1052 HV after heat treatment at 600 °C, which is due to the formation of Co₃W and CoWO₄ phases in the deposit. Furthermore, the coatings heat-treated at 600 °C had lower friction coefficients and better wear resistance under various loads than before heating.     

Synthesis and characterization of antibacterial polyurethane coatings from quaternary ammonium salts functionalized soybean oil based polyols

In this study, a simple and versatile synthetic approach was developed to prepare bactericidal polyurethane coatings. For this purpose, introduction of both quaternary ammonium salts (QASs), with well-known antibacterial activity, and reactive hydroxyl groups on to the backbone of soybean oil was considered. Epoxidized soybean oil was reacted with diethylamine and the intermediate tertiary amine containing polyol was reacted with two different alkylating agents, methyl iodide and benzyl chloride, to produce MQAP and BQAP, respectively. These functional polyols were reacted with different diisocyanate monomers to prepare polyurethane coatings. Depending on the structure of monomers used for the preparation of polyurethane coatings, initial modulus, tensile strength and elongation at break of samples were in the ranges of 122–339 MPa, 4.6–12.4 MPa and 8.4–46%, respectively. Polyurethane coatings based on isophorone diisocyanate showed proper mechanical properties and adhesion strength (0.41 MPa) for coating application. Study of fibroblast cells interaction with prepared polyurethanes showed promising cells viability in the range of 78-108%. Meanwhile, MQAP based samples with higher concentration of QASs showed better adhesion strength, surface hydrophilicity and antibacterial activity (about 95% bacterial reduction). Therefore, these materials can find applications as bactericidal coating for biomedical devices and implants.     

A spread-sheet model for efficient production and scheduling of a manufacturing line/cell

In this paper we develop an efficient spread-sheet production planning/scheduling model for a resource-constraint production line or a manufacturing cell that produces several products but one at a time with significant changeover time and changeover cost. There are also management and physical constraints related to the operating hours, production capacity and amount of inventory allowed. The production line/cell supplies several products to customers who pull the products according to their own operating policy (working hours) that may be different from manufacture's operating hours. We also show several real-world applications and highlight the benefits and merits of the model.     

A comparative study for synthesis methods of nano-structured (9Ni–2Mg–Y) alloy catalysts and effect of the produced alloy on hydrogen desorption properties of MgH2

9Ni–2Mg–Y alloy powders were prepared by arc melting, induction melting, mechanical alloying, solid state reaction and subsequent ball milling processes. The results showed that melting processes are not suitable for preparation of 9Ni–2Mg–Y alloy due to high losses of Mg and Y. Therefore, 9Ni–2Mg–Y alloy powder was prepared by three methods including: 1) mechanical alloying, 2) mechanical alloying + solid state reaction + ball milling, and 3) mixing + solid state reaction + ball milling. The prepared 9Ni–2Mg–Y alloy powders were compared for their catalytic effects on hydrogen desorption of MgH₂. It is found that 9Ni–2Mg–Y alloy powder prepared by mechanical alloying + solid state reaction + ball milling method has a smaller particle size (1–5 μm) and higher surface area (1.7 m² g⁻¹) than that of other methods. H₂ desorption tests revealed that addition of 9Ni–2Mg–Y alloy prepared by mechanical alloying + solid state reaction + ball milling to MgH₂ decreases the hydrogen desorption temperature of MgH₂ from 425 to 210 °C and improves the hydrogen desorption capacity from 0 to 3.5 wt.% at 350 °C during 8 min.     

Evaluation of a four-point sine wave frequency estimator for portable DSP based instrumentation

A recent frequency estimation method was proposed in a Measurement paper for use in portable DSP based instrumentation. This method is especially important due to its low computational effort making it suitable for fast and low cost instrumentation. It has been found that many parameters can affect the frequency estimation using the proposed method. In this paper, the performance of the method in the presence of additive noise is evaluated, and the influence of signal frequency, initial phase, additive noise and number of analog-to-digital converter bits on the estimator is studied. Some caveats of the practical use of the method are addressed. Detailed numerical simulations based on a Monte Carlo procedure are presented in order to highlight the range of applicability of the method and determine the estimation bias.     

Preparation and Characterization of Novel Polyimide/SiO2 Nano-hybrid Films by In Situ Polymerization

A silicon-based aromatic polyimide (PI) containing pendent aryl rings was synthesized by solution polycondensation of a silicon-containing diamine with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride. Its nano-hybrids with different colloidal SiO₂ concentrations were synthesized by in situ polymerization. The reactions were carried out in presence of 3-aminopropyltriethoxysilane as a coupling agent. The inclusion of the coupling agent in the polymer chain and its co-condensation with SiO₂ nanoparticles afforded a silica network that was interconnected chemically with the PI matrix. The chemical structure of the hybrid materials was analyzed by Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The morphology of the hybrid films and the surface roughness were characterized by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The results indicated that nanometer-scale inorganic particles were homogeneously dispersed throughout the PI matrix with 50–70 nm size range. The best results and favorable miscibility between polymer and silica phases in the nano-hybrids were obtained when up to 40 wt% nanoparticles were introduced into the backbone of PI matrix.