The Effect of Multiple Compatibilizers on the Impact Properties of Polypropylene/Polystyrene (PP/PS) Blend

Effects of compatibilizers on impact properties of polypropylene/ polystyrene (PP/PS) blends were studied and carried out through melt blending using co- rotating twin-screw extruder. A combination of two compatibilizers, maleic anhydride grafted polypropylene (PP-g-MA) and styrene maleic anhydride (SMA) was applied into PP/PS blends. Results from the Izod impact strengths, SEM observations and contact angle measurements in PP(50)/PS(50) blends indicated a better compatibilization effect with the use of dual compatibilizers. This was most probably due to improved adhesion between phases in PP/PS blend systems. The use of dual compatibilizers in the blend compositions produced higher impact properties in the PP/PS blend systems compared to single compatibilizer system.     

Glowworm swarm optimization (GSO) for optimization of machining parameters

This study proposes glowworm swarm optimization (GSO) algorithm to estimate an improved value of machining performance measurement. GSO is a recent nature-inspired optimization algorithm that simulates the behavior of the lighting worms. To the best our knowledge, GSO algorithm has not yet been used for optimization practice particularly in machining process. Three cutting parameters of end milling that influence the machining performance measurement, minimum surface roughness, are cutting speed, feed rate and depth of cut. Taguchi method is performed for experimental design. The analysis of variance is applied to investigate effects of cutting speed, feed rate and depth of cut on surface roughness. GSO has improved machining process by estimating a much lower value of minimum surface roughness compared to the results of experimental and particle swarm optimization.     

An overview of intelligent selection and prediction method in heterogeneous wireless networks

Heterogeneous wireless access technologies will coexist in next generation wireless networks. These technologies form integrated networks, and these networks support multiple services with high quality level. Various access technologies allow users to select the best available access network to meet the requirements of each type of communication service. Being always best connected anytime and anywhere is a major concern in a heterogeneous wireless networks environment. Always best connected enables network selection mechanisms to keep mobile users always connected to the best network. We present an overview of the network selection and prediction problems and challenges. In addition, we discuss a comprehensive classification of related theoretic approaches, and also study the integration between these methods, finding the best solution of network selection and prediction problems. The optimal solution can fulfill the requirements of the next generation wireless networks.     

Comprehensive comparison on optical properties of samarium oxide (micro/nano) particles doped tellurite glass for optoelectronics applications

Rare-earth oxides microparticles doped tellurite-based glass have been studied extensively to improve the capability of optoelectronic devices. We report a detailed comparison between two sets of glass series containing samarium microparticles and nanoparticles denoted as ZBTSm-MPs and ZBTSm-NPs, respectively. The two sets of glass have been successfully fabricated via melt-quenching technique with chemical formula {[(TeO₂)_0.70 (B₂O₃)_0.30]_0.7 (ZnO)_0.3}_1?y (Sm₂O₃ (MPs/NPs))_y with y?=?0.005, 0.01, 0.02, 0.03, 0.04 and 0.05 mol fraction. The TEM analysis confirmed the existence and formation of nanoparticles in ZBTSm-NPs glasses. The density of ZBTSm-NPs glasses was found higher than ZBTSm-MPs glasses due to the distributions of nano-scale particles in tellurite glass network. There was a linear trend of increment in the refractive index in both sets of glass series along with the concentrations of dopants. The refractive index of ZBTSm-NPs glasses was found higher than ZBTSm-MPs glasses due to the shift in compactness of glass structure with nano-scale particles. In comparison, the absorption peaks of ZBTSm-MPs glasses were greater than ZBTSm-NPs glasses which were mainly due to the restriction of electrons mobility in glass network with nano-scale particles. The optical band gap energy in ZBTSm-NPs glasses was found greater than ZBTSm-MPs glasses which correspond to the widening of forbidden gap with nano-scale particles. The polarizability of ZBTSm-NPs and ZBTSm-MPs was found in non-linear trends along with dopant concentrations. Based on these findings, the improvement of optical properties has been made by introducing samarium oxide nanoparticles in tellurite glass which is beneficial for optoelectronic devices.

     

A study on structural stability of bismuth titanate with lanthanum doping for improved ferroelectric properties

Bismuth titanate \((\hbox {Bi}_{4}\hbox {Ti}_{3}\hbox {O}_{12})\) with different lanthanum (La) concentrations (0.25, 0.50, 0.75 and 1.0 mol%) was successfully prepared via soft combustion route. It was found that the change of diffraction peaks shown by X-ray diffraction is attributed to the doping effect in \(\hbox {Bi}_{4}\hbox {Ti}_{3}\hbox {O}_{12}\). This was also supported by the presence of additional peak that corresponds to La in the range of 800–860 eV, proved by X-ray photoelectron spectroscopy. In addition, the enlarged region of Bi 4f, Bi 4d, Ti 2p, La 3d and O 1s of doping sample was clearly seen after deconvolution. Based on binding energy position, it can be unambiguously stated that the Ti ions in the tetravalent state are surrounded by the perovskite layer of \(\hbox {Bi}_{4}\hbox {Ti}_{3}\hbox {O}_{12}\), which may also imply the formation of oxygen vacancies in the vicinity of the \(\hbox {Bi}_{2}\hbox {O}_{2}\) layer. In comparison with \(\hbox {Bi}_{4}\hbox {Ti}_{3}\hbox {O}_{12}\), the green emission intensity was abruptly decreased with La doping. This indicates that La doping suppresses the formation of oxygen vacancies by stabilizing the adjacent oxide ions. Thus, the improved polarization shown by ferroelectric hysteresis loop is associated with the reduction in oxygen and bismuth vacancies due to La doping.     

The use of a partially simulated exothermic reactor to test nonlinear algorithms

Two nonlinear control algorithms for controlling nonlinear systems include the receding horizon method and the nonlinear neural network inverse model methods. These methods have been found to be useful in dealing with difficult-to-control nonlinear systems, especially in simulated systems. However although much simulation work has been performed with these methods, simulation only is inadequate to guarantee that these algorithms could be successfully implemented in real plants. For this reason, a relatively low cost and simple online experimental configuration of a partially simulated continuous reactor has been devised which allows for the realistic testing of a wide range of nonlinear estimation and control techniques i.e. receding horizon control and neural network inverse model control methods. The results show that these methods are viable and attractive nonlinear methods for real-time application in chemical reactor systems.     

Design,Synthesis and Cytotoxic Evaluation of o-Carboxamido Stilbene Analogues

Resveratrol, a natural stilbene found in grapes and wines exhibits a wide range of pharmacological properties. Resveratrol is also known as a good chemopreventive agent for inhibiting carcinogenesis processes that target kinases, cyclooxygenases, ribonucleotide reductase and DNA polymerases. A total of 19 analogues with an amide moiety were synthesized and the cytotoxic effects of the analogues on a series of human cancer cell lines are reported. Three compounds 6d, 6i and 6n showed potent cytotoxicity against prostate cancer DU-145 (IC₅₀ = 16.68 μM), colon cancer HT-29 (IC₅₀ = 7.51 μM) and breast cancer MCF-7 (IC₅₀ = 21.24 μM), respectively, which are comparable with vinblastine. The resveratrol analogues were synthesized using the Heck method.     

Dynamics and stability of ethylene polymerization in multizone circulating reactors

Multizone circulating bed reactors (MZCR) have the exclusive characteristics of producing polymers of different molecular weights in a single particle. Traditional fluidized bed reactors, on the other hand, can produce only one kind of molecular weight with relatively narrow distribution. A dynamic model for the MZCR is used to illustrate the basic dynamic behavior of the new reactor design used for polyethylene production. The model is used to study the copolymerization of ethylene with butene. Several parameter sensitivity analyses are performed to show the computer-simulated time responses for reactor temperature, number-average molecular weight, weight-average molecular weight, catalyst feed rate and the monomer/comonomer concentration along the reactor length. At certain operating conditions dynamic instability is observed and the results for the effect of cooling water temperature, catalyst feed rate, monomer and comonomer initial feed concentration on the reactor temperature and polymer molecular weight reveal that the system is very sensitive to disturbances in the heat exchanger coolant temperature. Also, at some operating conditions, the reactor temperature oscillates above the polymer melting temperature. Temperature runaway above polymer softening point is a serious problem which may cause polymer melting and hence reactor shutdown. The oscillatory behavior of the reactor temperature necessitates a suitable temperature control scheme to be installed.