A new design of magnetorheological fluid based braking system using genetic algorithm optimization

This paper proposes a new design for an automotive magnetorheological (MR) braking system using multiple rotary disks. We develop an analytical model to calculate the torque and validate our results using finite element analysis considering a non-linear relationship between magnetic field and magnetic flux. Using genetic algorithm, we optimize the system’s dimensions to generate maximum torque. The optimized geometry shows an improvement in output torque compared to existing systems. Moreover, our design directs higher flux onto the MR fluid and subsequently generates greater shear frictions. This design can be used in applications such as rehabilitation devices.     

Synthesis and characterization of monomeric and polymeric pyridinylimine‐based Ni(II) complexes and their catalytic activities in ethylene oligomerization

A new polymeric ligand was synthesized through the reaction of 4‐(pyridinylimine)phenol and formaldehyde in a basic medium, and its corresponding polymer–nickel complexes were formed in a 1:1 molar ratio. The synthesized compounds were characterized using elemental and spectral analyses. The monomeric and polymeric Ni(II) complexes (C₁ and C₂, respectively) were evaluated as catalyst precursors for ethylene oligomerization, using methylaluminoxane as an activator at two different ethylene pressures. C₂ was found to be a more effective pre‐catalyst than C₁, with the co‐catalyst having a similar effect in both cases. C₂ exhibited an activity of 1.282 × 10⁶ g (mol Ni)^?1 h^?1 bar^?1, with an Al:Ni ratio of 2000:1 at room temperature and 1 atm ethylene pressure. Meanwhile C₁ exhibited an activity of 1.126 × 10⁶ g (mol Ni)^?1 h^?1 bar^?1 under similar experimental conditions. At 5 atm ethylene pressure, C₁ favoured the formation of high‐density polyethylene, whereas C₂ favoured the formation of branched low‐density polyethylene. Copyright © 2012 Society of Chemical Industry     

Improvement of the production of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate‐co‐4‐hydroxybutyrate) terpolyester by manipulating the culture condition

BACKGROUND: The aim of this work is to enhance the production of terpolyester poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate‐co‐4‐hydroxybutyrate) (P(3HB‐co‐3HV‐co‐4HB)) produced by a locally isolated bacterium, Cupriavidus sp. USMAA2‐4. The monomer composition was varied by supplementing different carbon precursors and by manipulating the culture condition through one‐stage cultivation. The effect of C/N ratio and different concentrations of carbon source and precursors were investigated in order to produce higher content of this terpolyester. Although research on this biodegradable polyester is abundant, studies on terpolyester P(3HB‐co‐3HV‐co‐4HB) are still limited. RESULTS: Supplementation of oleic acid in accumulation medium increased the bacterial growth and polyhydroxyalkanoate (PHA) accumulation. It was also shown that medium consisting of assorted carbon precursors at C/N 20 gave relatively high dry cell weight and P(3HB‐co‐3HV‐co‐4HB) content. Various compositions of terpolyester were obtained when the concentration of oleic acid and 4HB precursors were manipulated. The combination of oleic acid with γ‐butyrolactone and 1‐pentanol was found to be the best combination to produce high PHA content (81 wt%). The composition of monomer in P(3HB‐co‐3HV‐co‐4HB) was produced in the range 8–13 mol% for 3HV and 9–24 mol% for 4HB, respectively. CONCLUSIONS: The production of P(3HB‐co‐3HV‐co‐4HB) in shake‐flasks successfully produced 81 wt% of PHA content. This manipulated culture condition can be used at larger scale to provide modeling for the production of terpolyester in a bioreactor. Copyright © 2012 Society of Chemical Industry     

Enhanced photocatalytic hydrogen production of noble-metal free Ni-doped Zn(O,S) in ethanol solution

High efficient hydrogen evolved Ni-doped Zn(O,S) photocatalyst with different Ni amounts had been successfully synthesized with a simple method at low temperature. Our Ni-doped Zn(O,S) catalyst reached the highest hydrogen generation rate of 14,800 μmol g^?1 h^?1 or 0.92 mmol g^?1 h^?1 W^?1 corresponding to apparent quantum yield 31.5%, which was 2.3 times higher compared to the TiO₂/Pt used as a control in this work. It was found that a small amount of Ni doped into Zn(O,S) nanoparticles could increase the optical absorbance, lower the charge transfer resistance, accordingly decrease the electron-hole recombination rate, and significantly enhance the photocatalytic hydrogen evolution reaction (HER). The as-prepared catalyst has the characteristics of low cost, low power consumption for activating the catalytic HER, abundant and environmental friendly constituents, and low surface oxygen bonding for forming oxygen vacancies. The photocatalytic performance of Ni-doped Zn(O,S) was demonstrated with a proposed kinetic mechanism in this paper.     

Spherulitic formation and characterization of partially fluorinated copolymers and their nanohybrids with functional fillers

Poly[vinylidenefluoride‐co‐(tetrafluoroethylene)] (P(VDF‐TeFE)) exhibited clear spherulitic texture with negative birefringence. The number and growth rates of the spherulites decreased at high crystallization temperature than at low crystallization temperature. Nonetheless, overall larger spherulites were found at high crystallization temperature and the brightness of the spherulites increased very fast at low crystallization temperature, thereafter it seemed as diminution of birefringence. AFM was used to investigate the impact of organo modified nanodiamond(ND) on spherulitic textures, lamellar thickness, and thickness distribution of P(VDF‐TeFE) copolymer. Poly[ethylene‐co‐(tetrafluoroethylene)] (ETFE) also confirmed spherulites structure and the boundaries could be clearly observed. By incorporation of the organo modified nanodiamond (ND) and organo‐modified montmorillonite (MMT) in fluropolymer matrix, it was found that spherulitic texture was seriously disordered and their nanohybrids was found only to have poorly developed spherulite structure. Both of the nanohybrids samples show better crystallization temperature as compared to their neat copolymer samples. Furthermore, the incorporation of nanoparticles decreased the size of the spherulites. POLYM. ENG. SCI., 57:161–171, 2017. © 2016 Society of Plastics Engineers     

Constrained model predictive control of proton exchange membrane fuel cell

A constrained model predictive control (MPC) is designed to regulate the air flow rate of proton exchange membrane fuel cell (PEMFC). Oxygen excess ratio, compressor flow rate and supply manifold pressure are constrained to avoid oxygen starvation, surge and choke phenomena. This is achieved by manipulating compressor voltage and stack current. The choice of the manipulated input to satisfy a constraint is investigated. Surge and choke avoidance is successful, when compressor voltage is manipulated. When stack current is utilized to satisfy surge and choke constraints, a large unrealistic current is needed. Oxygen starvation is successfully avoided utilizing stack current, while compressor voltage manipulation fails to prevent oxygen starvation. Thus, a current governor is implemented to handle oxygen starvation, while the compressor voltage is constrained to avoid surge and choke. Quadratic programming optimization, Laguerre and exponential weight function are employed to reduce the computational burden of the controller. The simulation results prove that the proposed controller managed to satisfy all constraints without any conflict.     

Synthesis and characterization of first‐ and second‐generation polyamide pyridylimine nickel dihalide metallodendrimers and their uses as catalysts for ethylene polymerization

First‐ and second‐generation pyridylimine‐terminated dendrimeric ligands were prepared by the reaction of the corresponding amine‐terminated aromatic polyamide dendrimers with 2‐acetylpyridine. The pyridylimine terminal groups were used as bidentate N,N ligands of nickel halide to prepare the corresponding first‐generation and second‐generation nickel dihalide metallodendrimers C1 and C2 , respectively. The synthesized dendrimers and metallodendrimers were characterized by elemental and spectral analyses. C1 and C2 were evaluated as catalyst precursors for ethylene oligomerization after being activated with methylaluminoxane (MAO) and diethylaluminum chloride (Et₂AlCl) under 1 atm and 5 atm pressure of ethylene. In both cases, the use of 1 atm or 5 atm pressure of ethylene and a 1500:1 Al:Ni molar ratio for C1 and C2 resulted in high catalytic activities toward ethylene polymerization. Upon activation with MAO and Et₂AlCl, C1 exhibited promising activities toward ethylene polymerization and produced linear chain structures that were associated with high density polyethylene. In contrast, C2 produced a polymer with the branching nature of low density polyethylene under similar conditions. © 2014 Society of Chemical Industry