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971.
972.
Juan Manuel Reyna-González José Antonio Bautista-Martínez Ignacio González 《Polymer》2006,47(19):6664-6672
Poly(3,6-N-vinylcarbazole) films were prepared by electrochemical oxidation of N-vinylcarbazole on a Pt electrode using acetonitrile as solvent and tetraethylammonium tetrafluoroborate as electrolyte. The electrosynthesis was carried out by electrical potential cycling in the presence of two different bases: tetraethylammonium benzoate (Bz−) and tetraethylammonium phthalate (Ph−). These salts were expected to modify the acidity level of the electrolyte since they can act as scavengers for the protons released during the polymerization, when the reaction takes place in the carbazole unit.Products were characterized by cyclic voltammetry, scanning electron microscopy, FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, absorption spectroscopy and four-probe electrical conductivity measurements. Both bases influenced significantly the chemical structure and morphology of the deposited materials. The presence of Ph− in the electrolyte decreases the cross-linking of the electrodeposited polymer, leading to a poly(3,6-N-vinylcarbazole) bearing a more uniform morphology, higher thermal stability and electrical conductivity compared to those of the polymers obtained in the presence of Bz− and without acidity control. 相似文献
973.
Mónica Gómez Antonio Pérez Víctor Valcárcel Carmen Cerecedo Francisco Guitián 《Journal of the American Ceramic Society》2006,89(4):1266-1272
In this work a novel method for production of silicon carbide (SiC) pieces, which involves the heating of silicon (Si) preforms immersed in graphite powder is presented. Such preforms were obtained via low-pressure injection molding (LPIM), although any other conformation route can be used. The process can be carried out at modest temperatures and gradients in standard furnaces used for processing other ceramics. These features make this process a simpler and cheaper alternative, when compared with other methods of SiC fabrication. The variables affecting the process have been identified, and an optimum-heating ramp has been established. Under these conditions, the obtained SiC products show no remnant-free Si, and their mechanical behavior allows their use in several less-demanding SiC applications, for which expensive high-performance SiC products are unaffordable. In the proposed chain of reactions, CO( g ) is responsible for the carburization of the pieces. All phases present are identified, and their distribution is explained by means of competitive reactions. In our opinion, this novel method can be extended to an industrial scale because it is simple and involves cheap raw materials. 相似文献
974.
Input-output stability of systems with backlash 总被引:1,自引:0,他引:1
The objective of this work is to study the stability of systems with backlash, from an input-output point of view. In the first part, an L∞ analysis is addressed. This analysis provides not only conditions for boundedness of the loop signals, but also results on existence of solutions, based on Schauder fixed point theorem. In the second part, the system is studied using an L2 or conic sector approach. The backlash graph is confined into certain conic sector, which is shown to be optimum or maximal. The conic inequality induces frequencial conditions on the linear part, which are further relaxed introducing dynamic multipliers. In the third part, both L∞ and L2 techniques are combined reaching a final criterion which results in a Popov-like stability condition. 相似文献
975.
Marcello Antinucci Bruno Chevalier Antonio Ferriolo 《Solar Energy Materials & Solar Cells》1995,39(2-4)
The development of full solid-state electrochromic (EC) devices on polymeric substrate is underway within a CEC BRITE-EURAM project (Project “FREDOPS”, BE-4137) carried out by four industries, two universities and two research centers from Belgium, Denmark, France, and Italy. The specific goal of this project is to develop a Fast Response Electrochromic Device On Polymeric Substrate (FREDOPS); in order to satisfy the required range of specifications in terms of fast response, long term performance and high contrast ratio, several systems based on different materials have been tested. The full cells consist of an electrochromic material layer and a counter electrode, inserted between two PET/ITO layers and separated by a polymeric electrolyte. Different types of polymeric electrolytes, counter electrodes and electrochromic layers have been developed, studied and checked. Full devices have been assembled using different combinations. Voltammetric and spectrophotometric measurements have been executed to check the electrochromic behaviour of the developed layers in half and full cells. Comparison of the electrochromic performances of different materials based cells has led to the rejection of several solutions due to poor performance and incompatibilities between layers. Considering that the electrochromic devices are finalised for different uses (window, sunroof,…), some performance specifications for each application are defined. A testing bench for cycling and ageing was developed. The present paper discusses these results in order to indicate the best performance. 相似文献
976.
S Natarajan ND Theise SN Thung L Antonio F Paronetto P Hytiroglou 《Canadian Metallurgical Quarterly》1997,21(3):312-318
The deaths of 10 heroin body packers are reported and contrasted to those of cocaine body packers. Only one was a woman, and all were traveling to or from Colombia. Drug packets deteriorated in the gastrointestinal tract and caused the deaths of eight victims. Accomplices removed drug packets from two of these smugglers after death occurred. One died of peritonitis stemming from a small-bowel obstruction caused by the drug packets, and one died from the recreational use of heroin (nasally ingested). The heroin recovered was < or = 881 g, and the drug purity of the contraband in three cases was between 65% and 73%. Blood concentrations of morphine were < 1.0 mg/L in four victims; no morphine was detected in the smuggler who died of peritonitis. However, two victims had blood morphine concentrations of 4.4 mg/L and 6.7 mg/L, respectively, and three had morphine concentrations of 35.8, 39.4, and 52.6 mg/L, respectively. Fatal heroin body packing differs from cocaine body packing in that individuals may have extremely high drug levels in their blood and their accomplices appear to be more likely to abandon them in a remote location after attempting to remove the drug packets after death has occurred. 相似文献
977.
978.
979.
Some results on synchronization and maximality of very pure codes are given. 相似文献
980.