Analyzing the solution of a system of fuzzy linear equations by a fuzzy distance

We introduce a fuzzy norm on a subset of all fuzzy numbers by a distance and we use it to analyze an approximate solution of a system of fuzzy linear equations. By a theorem we give two error bounds for error of an approximate solution of a system of fuzzy linear equations.     

The Passive Film Characteristics of Cold Deformed Pure Copper

In the present study, the effect of cold deformation on the electrochemical and passive behaviors of pure copper in 0.01 M NaOH solution was investigated. The dislocation density in cold deformation was calculated using a recently developed JAVA-based software, materials analysis using diffraction, based on Rietveld’s whole x-ray pattern fitting methodology. At the thickness reduction of 70%, the microhardness measured as 125.30 HV, which is 1.56 times than that in the annealed pure copper (80.25 HV). Potentiodynamic polarization plots and electrochemical impedance spectroscopy measurements showed that increasing the cold deformation offers better conditions for forming the passive films. In the Mott-Schottky analysis, no evidence for n-type behavior was obtained which indicates that the oxygen vacancies and the copper interstitials did not have any significant population density in the passive films. Also, this analysis revealed that with increasing cold deformation, the acceptor density of the passive films decreased.     

Oxidation of polypropylene in a solution of monochlorobenzene

The oxidation of polypropylene (PP) was performed in a solution of monochlorobenzene using tetrabutyl ammonium permanganate either in the presence or absence of purified air and dodecanol‐1. The experiments were conducted under atmospheric pressure at 128–130°C. The oxidized PP was found to contain polar groups such as carboxylates, carboxylic acids, ketones, esters, etc. as determined by Fourier transform infrared, ultraviolet, nuclear magnetic resonance, and electron spectroscopy for chemical analysis. The presence of the MnO₂ formed upon the decomposition of tetrabutyl ammonium permanganate was determined by electron spectroscopy for chemical analysis. The dodecanol‐1 was used as an accelerator for the oxidation reaction of PP in presence of air. Solubility trials of oxidized PP in toluene and methyl ethyl ketone were performed. A reaction mechanism is proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3417–3424, 1999     

Performance analysis of phase-change material storage unit for both heating and cooling of buildings

Utilisation of solar energy and the night ambient (cool) temperatures are the passive ways of heating and cooling of buildings. Intermittent and time-dependent nature of these sources makes thermal energy storage vital for efficient and continuous operation of these heating and cooling techniques. Latent heat thermal energy storage by phase-change materials (PCMs) is preferred over other storage techniques due to its high-energy storage density and isothermal storage process. The current study was aimed to evaluate the performance of the air-based PCM storage unit utilising solar energy and cool ambient night temperatures for comfort heating and cooling of a building in dry-cold and dry-hot climates. The performance of the studied PCM storage unit was maximised when the melting point of the PCM was ～29°C in summer and 21°C during winter season. The appropriate melting point was ～27.5°C for all-the-year-round performance. At lower melting points than 27.5°C, declination in the cooling capacity of the storage unit was more profound as compared to the improvement in the heating capacity. Also, it was concluded that the melting point of the PCM that provided maximum cooling during summer season could be used for winter heating also but not vice versa.     

Preparation and characterization of poly(2‐acrylamido‐2‐methylpropane‐sulfonic acid) grafted chitosan using potassium persulfate as redox initiator

A grafted material based on chitosan and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) has been successfully prepared in homogenous solution using potassium persulfate as a redox initiator. The grafted copolymer was precipitated during the reaction polymerization. The effects of the reaction temperature and chitosan–potassium persulfate contact time as well as concentrations of AMPS, potassium persulfate, and acetic acid on grafting yield were investigated. The percentage of grafting is gradually increased with the increasing of the AMPS concentration. The extent of grafting can be controlled by setting the appropriate reaction conditions. The maximum percentage of grafting was about 180% under the optimum conditions (1% v/v acetic acid, 50°C reaction temperature, 10 min chitosan–potassium persulfate mixing period, 0.37 mmol of potassium persulfate, and 28.96 mmol AMPS). The grafted chitosan was insoluble in the acid of the grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2314–2318, 2000     

Synthesis of Starch Copolymers by Silicon Tetrachloride Plasma‐Induced Graft Polymerization

Corn starch was surface‐functionalized by 13.56 MHz RF SiCl₄‐plasma, in situ reacted with ethylenediamine for stabilization, and subsequently graft‐polymerized using dichlorodimethylsilane as monomer. SiCl₄‐plasma treatment was studied and discharge parameters were optimized. X‐ray photoelectron spectroscopy (XPS/ESCA), Fourier transformed infrared spectroscopy (FTIR), scanning electron spectroscopy (SEM), gas chromatography/mass spectroscopy (GC‐MS), and differential thermal analysis/thermal gravimetry (DTA/TG) proved the presence of a polydimethylsiloxane (PDMS) graft‐copolymer layer on the modified starch‐granule surfaces. These analyses show that the surface morphology of starch granules, the thermal properties, the swelling characteristic, and the hydrophilicity of starch were all changed due to the existence of a protective hydrophobic PDMS layer. It is suggested that the starch graft‐copolymer might find its applications as reinforcing component in silicone‐rubber materials for starch‐based composites.     

Workspace Analysis of a Six-Degrees of Freedom, Three-Prismatic- Prismatic-Spheric-Revolute Parallel Manipulator

This paper studies the workspace of a six-degrees-of-freedom parallel manipulator of the general three-PPSR (prismatic-prismatic- spheric-revolute) type. It is known that a drawback of parallel manipulators is their limited workspace. To develop parallel mechanisms with a larger workspace is of use to potential applications. The mechanism of a three-PPSR manipulator and its variations are briefly analysed. The workspace is then investigated and the effects of joint limit and limb interference on the workspace shape and size are numerically studied. The constituent regions of the workspace corresponding to different classes of manipulator poses are discussed. It is shown that the workspace of this parallel manipulator is larger than that of a comparable Stewart platform, especially in the vertical direction.     

Synthesis and characterization of novel biodegradable pentablock copolymers from L‐lactide,p‐dioxanone and poly (ethylene glycol)

ABCBA type pentablock copolymers, in which the A, B and C blocks are poly (p‐Dioxanone) (PPDO), poly (L‐Lactide) (PLLA), and polyethylene glycol (PEG), respectively, were synthesized via a two‐step ring‐opening polymerization in bulk using stannous octoate as the catalyst. PLA‐b‐PEG‐b‐PLA Triblock copolymer was synthesized at first and then p‐Dioxanone monomers as the other blocks were added to it. In the first step, poly ethylene glycol and, in the second step, triblock copolymer acts as the macro initiator. The obtained copolymers were identified by ?1&/sup;H&/I;, ?13&/sup;CNMR&/I; and IR&/I; spectroscopy. The intrinsic viscosity of copolymers was measured in chloroform/phenol (3/1 v/w) solution. The thermal properties, such as melting point, melting enthalpy and crystallinity, were studied. From the results of differential scanning calorimetry and thermal gravimetric analysis, it was observed that the PPDO blocks show similar crystallization behavior like homopolymer and also melting temperature of two PPDO end blocks raise with an increase in DON content in copolymer.     

Study of lattice damage produced by neon implantation into AlInN

Neon ions were implanted into MOCVD grown wurtzite AlInN/GaN hetrostructures with dose ranging from 10¹⁴ to 9 × 10¹⁵ ions/cm². Structural characterization was carried out by X-ray diffraction and the dose dependence of strain was monitored before and after annealing. An increase in strain was observed in low dose regime until it saturates at a dose of 5 × 10¹⁵ cm⁻² and decreased with further increase in dose. Strain accumulation is attributed to the clustering of individual defects whereas decrease in level of strain is due to the capturing of defects by fixed sinks.