Investigation of rheology and morphology to follow physical fibrillar network evolution through fiber spinning of PP/PA6 blend fiber

This work is aimed at investigating the influence of fibrillar morphology of deformed Polyamide 6 (PA6) droplets dispersed in Polypropylene (PP) matrix on the melt viscoelastic behavior of their blends. The blends of PP with various amounts of PA6 (1%, 6%, 10%, and 20%) were prepared by melt mixing in a co‐rotating twin screw extruder and fibrillated by fiber spinning process. Scanning Electron Microscopy revealed that the PA6 spherical droplets form fibrillar inclusions after fiber spinning. The steady and transient shear rheological responses of samples were evaluated in both linear and nonlinear ranges of deformation. Non‐terminal behavior of storage modulus at low frequency appeared as a typical characteristic of fibrillar morphology whose width and value depend on fibril growth. Storage modulus and complex viscosity of the blends containing PA6 fibrillated structure were remarkably enhanced compared to as‐extruded samples. The fibrillar‐induced elasticity of the fibers is a distinguishable behavior which was revealed by conducting transient stress and creep‐recovery measurements and upon appearing mature fibrils, elasticity of the polymer blend fibers increased significantly. POLYM. ENG. SCI., 58:1251–1260, 2018. © 2017 Society of Plastics Engineers     

Solving unit commitment problem using a novel version of harmony search algorithm

In this context, a novel structure was proposed for improving harmony search (HS) algorithm to solve the unit comment (UC) problem. The HS algorithm obtained optimal solution for defined objective function by improvising, updating and checking operators. In the proposed improved self-adaptive HS (SGHS) algorithm, two important control parameters were adjusted to reach better solution from the simple HS algorithm. The objective function of this study consisted of operation, start-up and shut-down costs. To confirm the effectiveness, the SGHS algorithm was tested on systems with 10, 20, 40 and 60 generating units, and the obtained results were compared with those of the simple HS algorithm and other related works.     

Linear and nonlinear melt viscoelastic properties of fibrillated blend fiber based on polypropylene/polytrimethylene terephthalate

Polymer Bulletin - This work was aimed at understanding the influence of fibrillar morphology on melt viscoelastic properties of polymer blends containing various blend ratios...     

Synthesis and characterization of Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 nanocomposite for Heck reaction

Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 nanocomposite was prepared and characterized by XRD, FT-IR, UV–vis, BET and TEM techniques. The catalytic performance of this novel heterogeneous catalyst was determined for Heck reaction. Its stability was excellent and it could be reused eight times without much loss of activity in Heck reaction.     

Low-temperature Magnesiothermic Synthesis of Mesoporous Silicon Carbide from an MCM-48/Polyacrylamide Nanocomposite Precursor

Mesoporous silicon carbide with high specific surface area was successfully synthesized from an MCM-48/ polyacrylamide nanocomposite precursor in the temperature range of 550—600℃（below the melting point of Mg） by means of a magnesiothermic reduction process.The MCM-48/polyacrylamide precursor nanocomposite was prepared by in-situ polymerization of acrylamide monomer in the presence of mesoporous MCM-48 synthesized by sol-gel method.The physicochemical properties and microstructures of the nanocomposite precursor and the low-temperature SiC product were characterized by X-ray diffraction（XRD）, differential scanning calorimetry-thermo gravimetric analysis（DSC-TGA）,transmission electron microscopy （TEM） and N₂ adsorption—desorption.TEM micrographs and Brunauer—Emmett—Teller（BET） gas adsorption studies showed that the SiC powder was nanocrystalline and had a specific surface area of 330 m²/g and a mesoporosity in the range of 2—10 nm.The presence of an exothermic peak in the DSC trace corresponds to the self-combustion process of the SiC magnesiothermic synthesis.The results also show that the carbon in excess to that required to produce SiC plays a role in the reduction of the SiO₂.The mechanism of magnesiothermic synthesis of mesoporous SiC is discussed.     

Construction Surety Bonding

The qualification process in the construction bond business is very complicated, labor-intensive, and time-consuming. The construction bond underwriting processes contain subjective judgments that require human involvement to reach decisions. Thus, underwriting evaluations are bound to be very difficult, ambiguous, and have potentially great losses. This paper identifies and classifies quantitative and qualitative risk factors impacting construction bond underwriting, to improve the quality of the evaluation analysis and to reduce the highly unstructured environment and the subjectivity of the bond evaluation in underwriting. The methodology provides a systematic information analysis for the heuristic knowledge of the construction surety bonds underwriting process, provides better control over the risk assessment process by providing independent judgments for the major decision factors and an overall judgment for the final contractor's risk assessment decision, and reduces the time and effort required of the current evaluation process to reach a certain decision and to simplify the complicated nature of this process.