Dispersion polymerization of styrene and methyl methacrylate initiated by poly(oxyethylene) macromonomeric azoinitiators

Macromonomeric poly(oxyethylene) azoinitiators (macroinimers) MIM-400 and MIM-1500 were synthesized and characterized by IR and NMR spectroscopy and DSC techniques. The dispersion polymerizations of styrene and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimers (MIM-400 and MIM-1500) in water/ethanol were investigated at 60°C. The rate of polymerization was found to increase with increasing concentration of MIM and the increase was more pronounced in the styrene system. In the range of medium conversions the rate of polymerization was found to be proportional to the 1.7th and 1.6th power of [MIM-400] and [MIM-1500] for MMA and to the 2.5th power of [MIM-400] for styrene, respectively.     

Flow shop scheduling to minimize the total completion time with a permanently present operator: Models and ant colony optimization metaheuristic

This paper studies the one-operator m-machine flow shop scheduling problem with the objective of minimizing the total completion time. In this problem, the processing of jobs and setup of machines require the continuous presence of a single operator. We compare three different mathematical formulations and propose an ant colony optimization based metaheuristic to solve this flow shop scheduling problem. A series of experiments are carried out to compare the properties of three formulations and to investigate the performance of the proposed ant colony optimization metaheuristic. The computational results show that (1) an assignment-based formulation performs best, and (2) the ant colony optimization based metaheuristic is a computationally efficient algorithm.     

A nonlinear model for optimizing the performance of a multi‐product production line

This paper examines the measures of performance and in particular addresses the throughput of an automated production line processing multiple products. The line is composed of a sequence of workstations connected in series with finite buffers in between. We explore the effects of buffer size on attenuating the impact of line blocking and starvation that can cause a reduction in the output. Such effects are analyzed through a nonlinear mathematical programming model and the implications are examined. The aim of the model is to achieve the best performance subject to available workstation capacity without overexpenditure on buffer size. Single and multi‐objective optimizations are carried out in the paper. A numerical example of a production line with a given configuration of workstations; workstation capacity; and job mix is presented to demonstrate the model and its application. A discussion of the impact of buffer size on maximum throughput is also provided. The paper is concluded with a discussion on the decision‐making implications.     

Distributed phase shifters using (Ba,Sr)TiO3 thin films on sapphire and glass substrates

Abstract

Sol-gel solutions were synthesized by using various alkoxides of polyhydric alcohol, carboxylate and stabilizer. Stability of modified sol-gel solution was good enough to keep its properties after at least three months although that of ordinary sol-gel solution is not good.

SBT films were fabricated on Pt(200nm)/Ti(20nm)SiO₂(500nm)/Si substrate at under 700°C by using modified sol-gel solution. Range of drying temperature was 200 to 400°C and that of RTA was 550 to 700°C. At high drying temperature, decrease of crystallinity for SBT films was observed accompanied by nucleation of Sr carbonate. On the other hand, SBT film dried at under 250°C and crystallized at 700°C shows high crystallinity of layer perovskite.

SBT film derived from conventional sol-gel solution used to show strong crystal orientation of c-axis. In case of modified sol-gel solution, RTA temperature and amount of added stabilizer influenced crystal orientation of film. So it was possible that to control crystal orientation of SBT films by adjust RTA condition and amount of stabilizer. Stability of sol-gel solution and property of SBT films were influenced by component of solvent, electric properties of SBT films especially I-V property were improved.

Using low temperature deposition process at 650°C, SBT films derived from modified sol-gel solution show superior ferroelectric properties to SBT thin films derived from conventional MOD solution.     

Synthesis of comb-type amphiphilic graft copolymers derived from chlorinated poly(ɛ-caprolactone) via click reaction

This work refers to the synthesis of a series of novel chlorinated poly(?-caprolactone) (PCL) for further functionalization of PCL. For this aim, chlorine gas was passed through into the chloroform solution to obtain chlorinated polycaprolactone. The chlorine contents in chlorinated PCL were between 0.9 and 1.6 mol%. The molecular weights of the polymers (M _n) changed from 4853 to 9497 g/mol. As the amount of passing chlorine gas increases, the molecular weight of the chlorinated PCL was found to decrease. Pendant chloride groups of PCL were reacted with sodium azide to prepare PCL with pendant azide groups (PCL-N₃). Poly-(ethylene glycol) methyl ether (mPEG) was reacted with propargyl chloride to achieve alkynyl mPEG (mPEG-alkyn). Click reaction was then carried out by the reaction between PCL-N₃ and mPEG-alkyn to obtain PCL-g-PEG comb-type amphiphilic graft copolymer. Interestingly, SEM images of the PCL-g-PEG comb-type amphiphilic graft copolymers showed the highly microporous structure. The resulting products were characterized by ¹H NMR, FT-IR, gel-permeation chromatography, SEM, surface tension, contact angle and water uptake measurements, differential scanning calorimeter and thermogravimetric analyses techniques.     

A rare cause of abdominal pain: Catheter in the middle hepatic vein

Hemodialysis catheters are vital for chronic renal failure patients. Permanent tunneled dialysis catheters may be inserted through the jugular, subclavian, and femoral veins. In this paper, we aimed to present the computed tomography findings of a chronic renal failure patient who had referred our clinic with abdominal pain and dyspnea symptoms. This patient had a formerly inserted hemodialysis catheter for chronic renal failure and her catheter was found to be extending towards the middle hepatic vein with the tip leaning onto the parenchyma. Hemodialysis catheters can provide instant vascular access and can also be used for the consecutive procedures. Permanent hemodialysis catheters are ideal for long‐term use when placing an arteriovenous fistula is contraindicated or is no longer possible under conditions like advanced heart failure, peripheral artery disease or short life expectancy. The internal jugular, subclavian, the femoral veins, and the inferior vena cava can be used for catheter insertion. The tip of the catheters inserted in the neck or the thorax must extend to the vena cava superior. Catheter malposition may both lead to fatal outcomes and ineffective dialysis. It is important to obtain chest X‐rays after the procedure, particularly to detect catheter malposition.     

Optimization of elastic spring supports for cantilever beams

Structural and Multidisciplinary Optimization - In this study,a new approach of optimization algorithm is developed. The optimum distribution of elastic springs on which a cantilever Timoshenko...     

Hydroxylation of pendant vinyl groups of poly(3‐hydroxy undec‐10‐enoate) in high yield

Poly(3‐hydroxy undec‐10‐enoate) (PHU) was synthesized by feeding Pseudomonas oleovarans with 10‐undecenoic acid and nearly 100% hydroxylation of double bonds of PHU was achieved by hydroboration–oxidation reaction using 9‐borobicyclononane. The disappearance of vinyl signals of PHU in proton and ¹³C NMR spectra was observed. Acetylation of hydroxylated PHU was conducted for molecular weight measurements. Molecular weight and polydispersity of hydroxylated PHU were found to be 10,000 and 1.23, respectively, while that of the originals was 32,000 and 2.42. Decomposition temperatures of original and hydroxylated PHU were 280 and 200°C, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2132–2139, 2005     

Synthesis of PMMA‐PTHF‐PMMA and PMMA‐PTHF‐PST linear and star block copolymers

Combination of cationic, redox free radical, and thermal free radical polymerizations was performed to obtain linear and star polytetramethylene oxide (poly‐THF)‐polymethyl methacrylate (PMMA)/polystyrene (PSt) multiblock copolymers. Cationic polymerization of THF was initiated by the mixture of AgSbF₆ and bis(4,4′ bromo‐methyl benzoyl) peroxide (BBP) or bis (3,5,3′,5′ dibromomethyl benzoyl) peroxide (BDBP) at 20°C to obtain linear and star poly‐THF initiators with M_w varying from 7,500 to 59,000 Da. Poly‐THF samples with hydroxyl ends were used in the methyl methacrylate (MMA) polymerization in the presence of Ce(IV) salt at 40°C to obtain poly(THF‐b‐MMA) block copolymers containing the peroxide group in the middle. Poly(MMA‐b‐THF) linear and star block copolymers having the peroxide group in the chain were used in the polymerization of methyl methacrylate (MMA) and styrene (St) at 80°C to obtain PMMA‐b‐PTHF‐b‐PMMA and PMMA‐b‐PTHF‐b‐PSt linear and star multiblock copolymers. Polymers obtained were characterizated by GPC, FT‐IR, DSC, TGA, ¹H‐NMR, and ¹³C‐NMR techniques and the fractional precipitation method. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 219–226, 2004