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In composite solid propellants, low‐molecular‐weight species such as burning rate catalysts, plasticizer, etc. which migrate into liner and thermal insulation layers during curing and storage invariably result in poor mechanical and ballistic properties of the propellants. In the present study, the migration of the burning rate catalyst, acetyl ferrocene, was investigated spectrophotometrically (UV–visible) by evaluating the extent of hindrance to such migration after applying a barrier (liner) of various crosslink densities between the additive (HTPB‐TDI‐plasticizer–acetyl ferrocene) and nonadditive (HTPB‐TDI) gumstocks replicating the propellant and insulating layer, respectively. Enhancing the crosslink densities of liner via a trifunctional aziridine crosslinking agent inhibited migration. The aging of additive gumstock was done at 60°C and its mechanical properties and extent of acetyl ferrocene migration were also evaluated and analyzed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2538–2545, 2006 相似文献
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Seval Ene Nursel Öztürk 《The International Journal of Advanced Manufacturing Technology》2012,60(5-8):787-797
The objective of this study is to design storage assignment and order picking system using a developed mathematical model and stochastic evolutionary optimization approach in the automotive industry. It is performed in two stages. At the first stage, storage location assignment problem is solved with a class-based storage policy with the aim of minimizing warehouse transmissions by using integer programming. At the second stage, batching and routing problems are considered together to minimize travel cost in warehouse operations. A warehouse in the automotive industry is analyzed, and an optimum solution is obtained from an integer programming model. Due to the computational time required for solving the integer programming problem, a faster genetic algorithm is also developed to form optimal batches and optimal routes for the order picker. The main advantage of the algorithm is the quick response to production orders in real-time applications. The solutions showed that the proposed approach based on genetic algorithms can be applied and integrated to any kind of warehouse layout in automotive industry. 相似文献
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Summary N-vinyl 2-pyrrolidone (VP) / Acrylonitrile (AN) copolymeric hydrogels were synthesized by using γ-radiation and amidoximated for the purpose of uranyl ion adsorption. Optimum amidoximation time was determined by following the uranyl ion, UO2 2+, adsorption capacity. The adsorption of amidoximated copolymers was studied from different uranyl ion solutions (1000–1850 ppm). The results of all adsorption studies showed that the interaction between UO2 2+ and amidoxime groups comply with Langmuir type isotherm. The adsorption capacity was found as 0.54 g UO2 2+ /g dry amidoximated copolymeric hydrogels. From the stoichiometric calculations, it was found that the bonding between UO2 2+ and amidoxime groups is 1 to 4. Received: 7 September 1999/Revised version: 21 February 2000/Accepted: 18 March 2000 相似文献
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Nursel Karakaya Osman G. Ersoy Mehmet A. Oral Turgay Gonul Veli Deniz 《Polymer Engineering and Science》2010,50(4):677-688
The effects of different fillers on physical, mechanical, and optical properties of styrenic‐based thermoplastic elastomers were investigated by experimental study. Poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] block copolymer (SEBS)‐based thermoplastic elastomer composites were prepared in a co‐rotating intermeshing twin‐screw extruder, using silica and calcite as filler materials with three different particle sizes. The loading ratios in the composites were varied. Hardness, density, tensile strength, tear strength, compression set, wear resistance, transmittance, and haze measurements were performed. Thermal properties and morphological structure were investigated by differential scanning calorimeter (DSC) and scanning electron microscopy (SEM), respectively. The results show that, an interaction between silica and the polymer matrix exists, whereas calcite does not show any interaction with the polymer. Therefore, it is concluded that, calcium carbonate can be used in the composite as filler for cost efficiency, whereas silica can be used as reinforcing material in SEBS‐based thermoplastic elastomer composites, when optical properties are also concerned. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers 相似文献
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The development of fibers with desired drug release properties has gained a high research interest for water-soluble drugs with controlled drug delivery systems obtained by coaxial electrospinning technique. The objective of this study is to achieve the controlled-release of doxycycline hyclate (DOXH) from the fabricated electrospun fibers. In this case, three different electrospun core/shell fibers have been successfully fabricated using this technique and the model drug, DOXH, has been entrapped in the core layers. The results of the structural properties and in vitro release studies have been compared with electrospun monostructural fibers fabricated by conventional electrospinning technique. Scanning electron microscopy and transmission electron microscopy images have proved that the fabricated electrospun fibers have core/shell structures. Fourier transform infrared spectroscopy has shown convenient interaction and compatibility between polymers and the model drug. X-ray diffraction analysis has revealed that all the encapsulated DOXH are transferred into amorphous physical state and lost its crystalline state in the fibers. Moreover, drug release studies have demonstrated that the electrospun core/shell fibers show a better-controlled release than the monostructural fibers. It can be concluded that the fibers obtained by blending hydrophilic and hydrophobic polymers such as poly(ε-caprolactone) and poly(ethylene oxide) in both shell and core sides are promising candidate for controlled drug release. 相似文献
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Iron mineralizations in the study area are found in amphibolites in the localities of Buyukoren,Uzunkuyu-Atkayasi,and Karabacak and they display a predominantly banded texture.Their paragenesis is dominated by magnetite and hematite.In this study,iron mineralizations in Sarikaya were examined in terms of rare earth element(REE) contents and attempts were made to determine some physicochemical conditions that had an impact upon their formation.For this purpose,42 ore samples and 17 enriched magnetite samples... 相似文献
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Inflammation of the gallbladder is known to occur in patients with primary sclerosing cholangitis (PSC). However, the histological features of this form of cholecystitis have not been adequately defined. The aim of this study was to compare the inflammatory lesions of PSC-associated cholecystitis with those present in other cholecystopathies. The cases consisted of 11 gallbladders from patients with PSC who underwent liver transplantation. As controls, gallbladders from liver transplant patients with primary biliary cirrhosis (n = 4) and other chronic nonbiliary hepatopathies (n = 8), and 13 cholecystectomies from patients with chronic cholecystitis with (n = 10) and without (n = 3) lithiasis, were studied. The following histological features were tabulated on coded slides: presence, depth of involvement, and distribution of the inflammatory infiltrate, predominant cell type, presence of lymphoid aggregates, epithelial damage, metaplastic changes (pyloric or intestinal), fibrosis, smooth muscle hypertrophy, and presence of Rokitansky-Aschoff sinuses. At variance with the wide range of histological abnormalities present in other forms of chronic cholecystitis, most PSC-related cholecystitis showed a diffuse infiltrate (6 of 11) rich in plasma cells (6 of 11) predominantly confined to the lamina propria (9 of 11). The combination of these three features was present exclusively in PSC (5 of 11 PSC cholecystitis compared with 0 of 25 controls; P = .001). In conclusion, this study suggests that a characteristic form of cholecystitis may develop in patients with PSC. 相似文献
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Synthesis and characterization of poly(N‐vinyl imidazole) hydrogels crosslinked by gamma irradiation
Crosslinked poly(N‐vinyl imidazole) (PVIm) hydrogels in the form of rods have been prepared by 60Co γ‐radiation initiated simultaneous polymerization and crosslinking of N‐vinyl imidazole in bulk and water. In binary aqueous systems, the percentage gelation decreased with increasing water content. The PVIm hydrogels synthesized were further protonated in HCl solutions of different concentration. PVIm and protonated PVIm (H‐PVIm) hydrogels have been characterized using spectroscopic and thermal methods, and the swelling behaviour of these two types of hydrogel has been investigated. PVIm hydrogels originally swelled to 600% (by volume) but in their protonated form at pH 7.0 reached 4000% swelling. © 2002 Society of Chemical Industry 相似文献