A novel design procedure for tractor clutch fingers by using optimization and response surface methods

This paper presents a methodology for re-designing a failed tractor transmission component subjected to cyclic loading. Unlike other vehicles, tractors cope with tough working conditions. Thus, it is necessary to re-design components by using modern optimization techniques. To extend their service life, we present a design methodology for a failed tractor clutch power take-off finger. The finger was completely re-designed using topology and shape optimization approach. Stress-life based fatigue analyses were performed. Shape optimization and response surface methodology were conducted to obtain optimum dimensions of the finger. Two design parameters were selected for the design of experiment method and 15 cases were analyzed. By using design of the experiment method, three responses were obtained: Maximum stresses, mass, and displacement depending on the selected the design parameters. After solving the optimization problem, we achieved a maximum stress and mass reduction of 14% and 6%, respectively. The stiffness was improved up to 31.6% compared to the initial design.     

Polymerization of pyrrole derivatives on polyacrylonitrile matrix,FTIR–ATR and dielectric spectroscopic characterization of composite thin films

Oxidative polymerization of acrylonitrile (AN) initiated by Ce(IV)–oxalic acid redox system in the aqueous medium was performed and polyacrylonitrile (PAN)/polypyrrole (PPy) composite thin films were prepared by polymerization of pyrrole on polyacrylonitrile matrix. Effect of concentration of pyrrole derivatives on the resulting polymeric film properties was investigated. The influence of the pyrrole derivative type and content on the dielectric permittivity, dielectric loss and electrical properties of the composite films were analyzed in the frequency range from 0.05 Hz to 10 MHz. For a selected concentration of 200 μl of composite films at 10⁷ Hz, the conductivity was found to be in the following order: PAN–PPy < PAN–PNMPy < PAN–PNPhPy. Dielectric constant increase of the composite films was more obvious when the quantity of n-phenyl pyrrole was increased. A linear relationship was observed between the absorbances (FTIR–ATR) and conductivities (dielectric spectroscopy).     

Effects of the matrix crystallinity,dispersed phase,and processing type on the morphological,thermal, and mechanical properties of polylactide-based binary blends with poly[(butylene adipate)-co-terephthalate] and poly[(butylene succinate)-co-adipate]

In this study, we prepared immiscible blends of 75 wt % polylactide (PLA) with 25 wt % poly[(butylene adipate)-co-terephthalate] (PBAT) through an injection-molding (IM) process and a twin-screw extruder (TSE) followed by IM. An amorphous polylactide (A-PLA) and a semicrystalline polylactide (SC-PLA) were used as the matrixes to investigate the matrix crystallization effect on the morphology and property development of the blends with only IM. A blend of A-PLA with 25 wt % poly[(butylene succinate)-co-adipate] (PBSA) was also prepared through IM to compare its properties with those of the A-PLA–PBAT blends. The morphological, thermal, solid viscoelastic, tensile, and flexural properties of the blends were compared, and their dependency on the evolution of the blend morphology was analyzed. The tensile results show that when IM was used as the sole processing technique, the ductility and toughness were significantly improved only when SC-PLA was used as the matrix. Preprocessing through TSE also resulted in the enhancement of the blend ductility. In A-PLA–PBSA, the vitrification of PLA hindered the crystallization of PBSA to very low temperatures (<0°C) and resulted in a very nonuniform structure with weak intermolecular bonding between phases. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47636.     

Effect of diluents on the porous structure of crosslinked poly(methyl methacrylate) beads

Summary Copolymer beads based on methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) were prepared by suspension polymerization technique. Two different solvents, namely toluene and cyclohexane, were used as the diluents in the polymerization system. It was found that toluene produces pores of radii 2 to 10 nm corresponding to the interstices between the nuclei. In the case of cyclohexane as the diluent, formation of large pores with a broad size distribution from 10 to 1000 nm were observed. These sizes correspond to the spaces between the microspheres and the aggregates forming the copolymer beads. The results indicate that, as in porous styrene-divinylbenzene copolymers, the solvating power of the diluent present during the network formation is mainly responsible for the structural characteristics of porous MMA/EGDM copolymer beads.     

Effect of liquid characteristics on the wetting,capillary migration,and retention properties of fibrous polymer networks

Fluid penetration through porous networks consists of two different phenomena: (1) pore fluid displacement and (2) fluid flow through the pores. The first phenomenon depends on the pore size, the fluid–fluid interfacial tension, and the contact angle. The second phenomenon is pore‐size‐ and viscosity‐dependent. We adapted an experimental methodology often used for measurements of liquid permeability and hydraulic conductivity of soils and applied it to polymeric medical textiles. The methodology made use of a pressure/flow cell in which a sample was mounted. The flow rates were measured during sequences of increasing and decreasing pressures applied to the displacing nonwetting fluid (aqueous solution). The effects of the liquid parameters on penetration were investigated. Surface tension effects were studied with water and two solutions with surface tensions lower than that of pure water; the liquids with lower surface tensions had lower displacement pressures. To study viscosity effects, we used water and two solutions with viscosities higher than that of pure water. Increasing the viscosity not only caused the flow rate to decrease but also caused deformation, that is, enlargement, of the pores. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 282–292, 2005     

Disruptions to women's social identity: A comparative study of workplace stress experienced by women in three geographic regions.

Drawing on social identity theory (P. J. Burke, 1991) and the current status of women and equal opportunity legislation, the authors tested several factors associated with distress in working women in the People's Republic of China (PRC), Hong Kong, and the United States. Women in Hong Kong experienced significantly greater levels of life stress than PRC and U.S. women. Reports of negative attitudes toward women, gender evaluation, and avoidance coping were greater for Hong Kong and PRC women than for U.S. women. Hong Kong women reported more use of positive/confrontational coping mechanisms. Negative attitudes toward women had an important influence on life stress across regions. Moderator tests resulted in 2 significant findings: The effect of negative attitudes toward women on life stress was stronger for PRC and Hong Kong women, and the relationship between nervous/self-destructive coping and life stress was stronger for U.S. women. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The effect of aging on spectral parameters of event-related potentials

Forty-two healthy subjects ranging in age from 20 to 73 were divided into three groups according to age; a young group (20-33 years), a middle-aged group (34-49 years) and older group (50-73 years). Event-related potentials (ERPs) of three groups were recorded in two different experimental conditions that the infrequent stimulus was counted (Test 1) or uncounted (Test 2). ERPs were elicited using infrequent and frequent stimuli as red and green lights respectively. Spectral analysis of ERPs showed that decibel (dB) values of 1-2 and 3-4 Hz in young and middle-aged groups while dB value of 1-2 Hz in older group were significantly decreased in Test 2 compared with Test 1. When the number of subjects displaying amplitude maximum in each frequency band was considered, significant differences were found in 1-2 and 5-7 Hz frequency bands of young and middle-aged groups, but no significant differences were found for older group.     

Preparation of an ion-exchange chromatographic support by a "grafting from" strategy based on atom transfer radical polymerization

A new "grafting from" strategy based on surface-initiated atom transfer radical polymerization (ATRP) was first used for the preparation of a polymer-based ion-exchange support for HPLC. The most important property of the proposed method is to be applicable for the synthesis of any type of ion exchanger in both the strong and the weak forms. Monodisperse, porous poly(glycidyl methacrylate-co-ethylene dimethacrylate), poly(GMA-co-EDM) particles 5.8 mum in size were synthesized by "modified seeded polymerization". Poly(dihydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(DHPM-co-EDM) particles were then obtained by the acidic hydrolysis of poly(GMA-co-EDM) particles. The ATRP initiator, 3-(2-bromoisobutyramido)propyl(triethoxy)silane was covalently attached onto poly(DHPM-co-EDM) particles via the reaction between triethoxysilane and diol groups. In the next stage, the selected monomer carrying strong cation exchanger groups, 3-sulfopropyl methacrylate (SPM), was polymerized on the initiator-immobilized particles via surface-initiated ATRP. The degree of polymerization of SPM (i.e., length of polyionic ligand) on the particles was precisely controlled by adjusting ATRP conditions. Poly(SPM)-grafted poly(DHPM-co-EDM) particles obtained with different ATRP formulations were tried as chromatographic packing in the separation of proteins by ion-exchange chromatography. The proteins were successfully separated with higher column yields with respect to the previously proposed materials. The plate heights between 100 and 150 mum were achieved with the column packed with the particles carrying the shortest poly(SPM) chains. The plate height showed no significant increase with increasing flow rate in the range of 0.5-16 cm/min.     

Plasma fibroblast growth factor-23 levels are independently associated with carotid artery atherosclerosis in maintenance hemodialysis patients

Fibroblast growth factor-23 (FGF-23) has been suggested to play a role in vascular calcification in chronic kidney disease. Common carotid artery intima-media thickness (CIMT) assessment and common carotid artery (CCA) plaque identification using ultrasound are well-recognized tools for identification and monitoring of atherosclerosis. The aim of this study was to test that elevated FGF-23 levels might be associated with carotid artery atherosclerosis in maintenance hemodialysis (HD) patients. In this cross-sectional study, plasma FGF-23 concentrations were measured using a C-terminal human enzyme-linked immunosorbent assay kit. Carotid artery intima-media thickness was measured and CCA plaques were identified by B-Mode Doppler ultrasound. One hundred twenty-eight maintenance HD patients (65 women and 63 men, mean age: 55.5 ± 13 years, mean HD vintage: 52 ± 10 months, all patients are on HD thrice a week) were involved. The mean CIMT were higher with increasing tertiles of plasma FGF-23 levels (0.66 ± 0.14 vs. 0.75 ± 0.05 vs. 0.86 ± 0.20 mm, P<0.0001). Log plasma FGF-23 were higher in patients with plaques in CCA than patients free of plaques (3.0 ± 0.17 vs. 2.7 ± 0.23, P<0.0001). Significant correlation was recorded between log plasma FGF-23 and CIMT (r=0,497, P=0.0001). In multiple regression analysis, a high log FGF-23 concentration was a significant independent risk factor of an increased CIMT. Further studies are needed to clarify whether an increased plasma FGF-23 level is a marker or a potential mechanism for atherosclerosis in patients with end-stage renal disease.     

Dynamic Decision Elements for 3-Unit Systems

Simple triplication is widely analyzed either as a static redundancy by itself or as an active core for dynamic redundancy. Its practical value was tested when it was used to protect the hardcore test and repair processor (TARP) of JPL STAR computer and the CPU of Guidance Computer for SATURN V. Two current techniques for using triplicated modules are TMR and TMR/Simplex. In this paper a set of dynamic decision techniques is proposed for better use of triplication, assuming Pr {system is in a specified failure mode | system has failed} is known for all failure modes of concern.