Fuzzy FMEA application to improve purchasing process in a public hospital

Failure mode and effects analysis (FMEA) is one of the well-known techniques of quality management that is used for continuous improvements in product or process designs. While applying this technique, determining the risk priority numbers, which indicate the levels of risks associated with potential problems, is of prime importance for the success of application. These numbers are generally attained from past experience and engineering judgments, and this way of risk assessment sometimes leads to inaccuracies and inconsistencies during priority numbering. Fuzzy logic approach is preferable in order to remove these deficiencies in assigning the risk priority numbers. In this study, a fuzzy-based FMEA is to be applied first time to improve the purchasing process of a public hospital. Results indicate that the application of fuzzy FMEA method can solve the problems that have arisen from conventional FMEA, and can efficiently discover the potential failure modes and effects. It can also provide the stability of process assurance.     

Fair referee assignments for professional football leagues

Assignment of referees to football games is an important problem faced in professional football leagues. Despite its importance, the problem has received limited academic attention. This paper presents a model and analysis of the problem for fair referee assignments, and develops a constructive heuristic and a local search procedure for its solution. Results from an extensive computational study show that the methods are effective in solving the problem in a second of computation time and yielding an excellent solution quality.     

The Effect of Hydrothermal Aging on the Low-Velocity Impact Behavior of Multi-Walled Carbon Nanotubes Reinforced Carbon Fiber/Epoxy Composite Pipes

Chemical transmission lines, petroleum and natural gas lines, pressure vessels, and pipes used in thermal facilities are expected to maintain their mechanical properties for many years without being damaged and not to be corroded in working conditions. The composite materials are the right candidate for these harsh conditions due to their superior properties. Reinforcement of nanoadditives to composite materials improves both the mechanical properties and the resistance to environmental conditions, thereby increasing the lifetime. In this study, multi-walled carbon nanotube (MWCNT) reinforced [±?55°] carbon fiber/epoxy composite pipes produced with filament wound method were used. It was hydrothermally aged in 80 °C distilled water for 1, 2, 3 weeks in order to examine the effect of environmental conditions. In order to investigate its resistance against loads that may occur in working conditions, ring tensile tests (ASTM D 2290–16 procedure A), and low-velocity impact tests at 5, 10, 15 J, energy levels were carried out. The effect of hydrothermal aging on neat and MWCNT added epoxy composite had been examined by considering the aging period. Consequently, the impact resistance of neat and MWCNT added samples decreased with the aging process. Besides, tangential tensile strength loss was 17% in MWCNT reinforced sample and 13% in the neat sample.

     

Synthesis,structural characterization,and antiproliferative/cytotoxic effects of a novel modified poly(maleic anhydride-co-vinyl acetate)/doxorubicin conjugate

Polymer Bulletin - Drug carrier, poly(maleic anhydride-co-vinyl acetate) (MAVA or poly[MA-co-VA]) copolymer, was traditionally synthesized by free radical chain polymerization reaction, in methyl...     

Phase Transfer Catalysis with Quaternary Ammonium Type Gemini Surfactants: <Emphasis Type="Italic">O</Emphasis>-Alkylation of Isovanillin

In this paper, O-alkylation of isovanillin with unusual phase transfer catalysts alkandiyl-α,ω-bis(dimethylalkylammonium bromide) dimeric surfactants (also known as gemini surfactants) is described. Some dimeric surfactants with simple hydrophobic alkyl chains and others with hydrophobic alkyl chains containing ester functionalities with different lengths were synthesized and characterized in our laboratory. The alkylation of isovanillin with alkyl halide was successively carried out in the presence of potassium carbonate and a phase transfer catalyst in tetrahydrofuran. The same reactions were also performed with both the traditional phase transfer catalyst tetrabutylammonium bromide and without any catalyst. The results were compared with those of dimeric surfactants. Consequently, it was expressed that alkandiyl-α,ω-bis(dimethylalkylammonium bromide) dimeric surfactants successively exhibit the character of phase transfer catalysts through environmentally friendly procedures under mild conditions. The most significant feature of this work is that dimeric surfactants have been determined to act as phase transfer agents.     

On decentralized stabilization and structure of linear large scale systems

Connective stabilizability of large-scale systems, which are composed of interconnected subsystems, is considered using decentralized feedback. Both analytical and graph-theoretic conditions are derived directly in terms of the interconnection structure, which ensure that stability of the overall closed-loop system is invariant under the structural perturbations caused by disconnections and reconnections of links among the subsystems. The conditions characterize a large class of decentrally stabilizable systems, which includes all classes of connectively stabilizable interconnected systems considered so far.     

Synthesis and characterization of two-armed poly(ɛ-caprolactone) polymers initiated by the Schiff's base complexes of copper(II) and nickel(II)

Two-armed poly(?-caprolactone) (TAPCL) polymers were successfully synthesized via the ring opening polymerization (ROP) of ?-caprolactone (?-CL) using the Schiff's base complexes [Cu(SAEE)₂] (1) and [Ni(SAEE)₂] (2), which have two hydroxyl functional groups, as the two-site initiators and tin(II) 2-ethylhexanoate (Sn(Oct)₂) as the catalyst in bulk at 115 °C. The Schiff's base complexes (1 and 2) were synthesized by utilizing the concentrated template synthesis method starting from salicyl aldehyde, 2-(2-aminoethoxy) ethanol and related metal acetate salts. The synthesized TAPCL polymers were characterized by GPC, FTIR, UV–vis, and electron paramagnetic resonance (EPR). The molecular weights of TAPCL polymers linearly increased with increasing molar ratio of the monomer to the initiator. The results obtained from FTIR, UV–vis, and EPR studies indicated that TAPCL polymers had the Schiff's base complexes at the junction point of PCL arms. The crystallization behavior of TAPCL was studied by using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Thermal behavior of TAPCL was also investigated by thermogravimetrical analysis (TGA).     

Plasma polymerization‐modified bacterial polyhydroxybutyrate nanofibrillar scaffolds

The design and the development of novel scaffold materials for tissue engineering have attracted much interest in recent years. Especially, the prepared nanofibrillar scaffold materials from biocompatible and biodegradable polymers by electrospinning are promising materials to be used in biomedical applications. In this study, we propose to produce low‐cost and cell‐friendly bacterial electrospun PHB polymeric scaffolds by using Alcaligenes eutrophus DSM 545 strain to PHB production. The produced PHB was characterized by Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Nanofibrous scaffolds were fabricated via electrospinning method that has a fiber diameter approximately 700–800 nm. To investigate cell attachment, cell growth, and antioxidant enzyme activity on positively and negatively charged PHB scaffold, PHB surface was modified by plasma polymerization technique using polyethylene glycol (PEG) and ethylenediamine (EDA). According to the results of superoxide dismutase (SOD) activity study, PEG‐modified nanofibrillar scaffolds indicated more cellular resistance against oxidative stress compared to the EDA modification. As can be seen in cell proliferation results, EDA modification enhanced the cell proliferation more than PEG modification, while PEG modification is better as compared with nonmodified scaffolds. In general, through plasma polymerization technique, surface modified nanofibrillar structures are effective substrates for cell attachment and outgrowth. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013