A hybridized approach to optimal tolerance synthesis of clutch assembly

Specifying proper tolerances for manufactured goods results in greater savings and improved performance, which may ultimately determine whether a product succeeds or fails in the marketplace. In the past, tolerance specification has been more an art than a science, and is largely dependent upon experiences. A more scientific and reliable approach is presented in this paper. A hybrid of Nelder-Mead simplex method and particle swarm optimization (NM-PSO) is introduced for the design of tolerance of the machine elements of an overrunning clutch assembly. The objective is to obtain tolerances of the individual components so that the cost of manufacturing and quality loss is minimized. Experimental results demonstrate that hybrid NM-PSO is extremely effective and efficient in locating best-practice optimal solutions compared to geometric programming (GP), genetic algorithm (GA), and particle swarm optimization (PSO) methods.     

Synthesis and characterization of a new hyperbranched organic–inorganic solid polymer electrolyte with cyanuric chloride as a core element

A new hyperbranched organic–inorganic hybrid electrolyte based on the use of 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride, CC) as the coupling core to couple with oligo(oxyalkylene)-amines, followed by condensation with (3-glycidoxypropyl)-trimethoxysilane (GLYMO) and complexed with LiClO₄, has been prepared and characterized. The Vogel–Tamman–Fulcher (VTF) like conductivity behavior is observed in the present organic–inorganic hybrid electrolytes with a maximum ionic conductivity value of 4.4 × 10⁻⁵ S cm⁻¹ at 30 °C. Multinuclear NMR techniques are used to provide a microscopic view for the specific interaction between the polymer chains and Li⁺ cations and their dynamic behaviors. The results of 2D ¹H–¹³C wide-line separation (WISE) and ⁷Li static line NMR width measurements divulge that the mobility of the ⁷Li cations is strongly related to a dynamic environment created by the polymer motion in the amorphous phase. The combined results of conductivity and ⁷Li pulse-gradient spin-echo (PGSE) NMR self-diffusion coefficient measurements reveal that the conductivity enhancement at low salt concentrations is mainly caused by the high mobility of the lithium cations.     

Poly(vinyl alcohol)‐controlled synthesis of monodispersed crosslinked poly(methyl methacrylate) microparticles with significantly improved mechanical properties

A facile synthesis concept focusing on the poly(vinyl alcohol) (PVA) concentration induced interfacial energy effects in seed swelling polymerization was realized for the successful fabrication of a series of monodispersed poly(methyl methacrylate) (PMMA) microparticles with four crosslinking agents, 2,2‐bis[(methacryloyloxy)methyl]butyl methacrylate, 1,2‐ethanediyl bis(2‐methylacrylate), 1,3‐divinylbenzene and 1,2‐ethanediyl diacetate. We revealed a special role of PVA in regulating the diffusion of crosslinking agents as well as the swelling degree of latex seeds and, more noticeably, the consequent improved mechanical properties of the crosslinked PMMA microparticles formed. The highest recovery rate obtained from the PMMA microparticles with 0.6 wt% PVA approached 67%, which is higher than or comparable to reported values. This work not only developed a new facile synthesis approach for producing highly uniform tough crosslinked PMMA microparticles for more potential applications but also provided valuable insights into fundamental aspects of seed swelling polymerization. © 2019 Society of Chemical Industry     

Fabrication and evaluation of the electrochemical performance of the anode-supported solid oxide fuel cell with the composite cathode of La0.8Sr0.2MnO3−δ-Gadolinia-doped ceria oxide/La0.8Sr0.2MnO3−δ

The anode-supported single cell was constructed with porous Ni-Yittria-stabilized zirconia (YSZ) as the anode substrate, an airtight YSZ as the electrolyte, and a screen-printed La_0.8Sr_0.2MnO_3−δ (LSM)-Gadolinia-doped ceria (GDC)/LSM double-layer cathode. The SEM results show that the YSZ thin film is highly integrated, fully dense with a thickness of 13 μm, and exhibits excellent compatibility between cathode and electrolyte layers. The effects of feed rates of the reactants, temperature, and contact pressure between the current collector and the unit cell were systematically investigated. The results are based on the assumption that the anode contribution to the polarization resistance is negligible. Our analysis showed that the electrochemical reaction is limited by mass transfer control when the airflow rate is decreased to 500 ml min⁻¹. The maximum power density is 204.6 mW cm⁻² at 800 °C with H₂ and air at flow rates of 800 and 2000 ml min⁻¹, respectively. According to the AC-impedance data, the resistances of charge transfer at the electrode/electrolyte interface are 3.79 and 1.90 Ω cm². The resistances of oxygen-reduction processes are 3.63 and 1.01 Ω cm² at 700 and 800 °C, respectively. The results from the sensitivity analysis of the variation of contact pressure between current collectors and membrane electrode assembly (MEA) show that the influence is enhanced at the regions of the high current density.     

Tea, obesity, and diabetes

Tea has been found to possess widespread biological functions based on a variety of laboratory data. The effects of tea on obesity and diabetes have received increasing attention. This paper reviews the evidence for the connections among tea catechins, and obesity and diabetes. Tea catechins, especially (-)-epigallocatechin gallate (EGCG), appear to have antiobesity and antidiabetic effects. While few epidemiological and clinical studies show the health benefits of EGCG on obesity and diabetes, the mechanisms of its actions are emerging based on the various laboratory data. These mechanisms may be related to certain pathways, such as through the modulations of energy balance, endocrine systems, food intake, lipid and carbohydrate metabolism, the redox status, and activities of different types of cells (i. e., fat, liver, muscle, and beta-pancreatic cells). Because the EGCG receptor, the so-called 67-kDa laminin receptor (LR), has been discovered with colocalization of other types of LR and cytoskeleton in both cancer cells and normal cells, this may explain that EGCG possesses numerous actions. The mechanistic results of this review may possibly be utilized in the treatment of obesity, diabetes, and other related diseases using tea- and EGCG-based folk medicines.     

Mutually independent Hamiltonian cycles in alternating group graphs

The alternating group graph has been used as the underlying topology for many practical multicomputers, and has been extensively studied in the past. In this article, we will show that any alternating group graph AG _n , where n??3 is an integer, contains 2n?4 mutually independent Hamiltonian cycles. More specifically, let N=|V(AG _n )|, v _i ??V(AG _n ) for 1??i??N, and ??v ₁,v ₂,??,v _N ,v ₁?? be a Hamiltonian cycle of AG _n . We show that AG _n contains 2n?4 Hamiltonian cycles, denoted by $C_{l}=\langle v_{1},v_{2}^{l},\ldots,v_{N}^{l},v_{1}\rangle$ for 1??l??2n?4, such that $v_{i}^{l} \ne v_{i}^{l'}$ for all 2??i??N whenever l??l??. The result is optimal since each vertex of AG _n has exactly 2n?4 neighbors.     

Polyacrylonitrile microscaffolds assembled from mesh structures of aligned electrospun nanofibers as high-efficiency particulate air filters

Electrospun polyacrylonitrile (PAN) fibers of very small diameters have potential for integration into filters capable of increasing the particle filtration efficiency. To fulfill the requirements for high-efficiency particulate air (HEPA) filters with a reasonable pressure drop, we generated aligned electrospun PAN fibers through pre-alignment at various rotation rates and subsequent solvent vapor annealing (SVA) under a loading. We evaluated the properties of microscaffold filters assembled from aligned electrospun PAN fibers in the form of linear, square, and triangular multiple meshes. The microscaffolds featuring multiple square meshes exhibited dramatically increased filtration efficiency without a significant pressure drop. A nine-layer cross-ply structure provided a filtration efficiency of 99.98% for 0.25-μm particles at a face velocity of 10 cm s^?1; its filtration quality factor was the highest among all of the tested microscaffolds. Thus, HEPA filters featuring a low packing density can be achieved using PAN fibers.

© 2016 American Association for Aerosol Research     

Improved adhesion of PMSQ hard coatings on polymer substrates

Various surface treatment methods were investigated to improve the adhesion of abrasion-resistant polymethylsilsesquioxane (PMSQ) coatings on the optical resins. The adhesion of PMSQ films was improved on polymethylmethacrylate (PMMA), polycarbonate (PC), and PC/acrylonitrile butadiene styrene (ABS) by pretreating their surface with O₂ plasma or chromic acid followed by surface grafting with trimethyl ethoxysilane (TMES). After the O₂ plasma and the subsequent TMES treatments, the adhesion of PMSQ coating on PMMA substrate was significantly enhanced by the reduction of the percentage of peeling area from ~100% to <1% in cross cut tests. After the chromic acid and the subsequent TMES treatments of PC and PC/ABS substrates, the adhesion of PMSQ coatings was also significantly enhanced by reducing the percentages of peeling areas from nearly 100% to 50% and <1%, respectively, for PC and PC/ABS. The PMSQ coating might increase the hardness of the polymer by two to three levels.     

Low gate interface traps AlGaN/GaN HEMTs using a lattice matched ZrZnO transparent gate design

AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) using a radio-frequency magnetron sputtered ZrZnO transparent oxide layer as a gate insulator are investigated and compared with traditional GaN HEMTs. A negligible hysteresis voltage shift in the C–V curves is seen, from 0.09 V to 0.36 V, as the thickness of ZrZnO films increases. The composition of ZrZnO at different annealing temperatures is observed using X-ray photoelectron spectroscopy (XPS). The ZrZnO thin film achieves good thermal stability after 600 °C, 700 °C and 800 °C post-deposition annealing (PDA) because of its high binding energy. Based on the interface trap density analysis, D_it has a value of 2.663 × 10¹² cm⁻²/eV for 10-nm-thick ZrZnO-gate HEMTs and demonstrates better interlayer characteristics, which results in a better slopes for the I_ds degradation (5.75 × 10⁻¹ mA/mm K⁻¹) for operation from 77 K to 300 K. The 10-nm-thick ZrZnO-gate device also exhibits a flat and a stable 1/f noise, as V_GS–V_th, and at various operating temperatures. Therefore, ZrZnO has good potential for use as the transparent film for a gate insulator that improves the GaN-based FET threshold voltage and improves the number of surface defects at various operating temperatures.