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101.
102.
The development of a process for production of acetonitrile using a fluid bed, semi-synthetic, silica-alumina catalyst is described. The effects of reaction temperature and pressure, choice of catalyst, linear gas velocity and the mole ratio of reactants on the yield of acetonitrile from a pilot unit are given. Purification of the product is described. Some details concerning problems encountered in scaling up the process for commercial production are discussed. Experience gained from the operation of a commercial unit relating to the design of fluid bed reactors is summarized. 相似文献
103.
Christian Decker 《应用聚合物科学杂志》1983,28(1):97-107
UV-curable epoxy–acrylate coatings were used to protect poly(vinyl chloride) against superficial degradation. With α-hydroxy–acetophenone photoinitiators, the crosslinking polymerization develops in the ms time scale; 50% degree conversion is reached after irradiation times of 2.5 ms in a nitrogen atmosphere and 17 ms in air. The adhesion of the coating on to the PVC substrate can be greatly improved by inducing a photochemical grafting process. The best results are obtained by incorporating the photoinitiator into the top layer of the PVC sheet. Highly crosslinked epoxy–acrylate coatings are very stable toward UV radiations and chemical agents like organic solvents and strong acids. By their light-screening effect they provide an excellent protection against photodegradation for light-sensitive polymeric materials. 相似文献
104.
Amatore C Chovin A Garrigue P Servant L Sojic N Szunerits S Thouin L 《Analytical chemistry》2004,76(24):7202-7210
Dynamic concentration profiles within the diffusion layer of an electrode were imaged in situ using fluorescence detection through a multichannel imaging fiber. In this work, a coherent optical fiber bundle is positioned orthogonal to the surface of an electrode and is used to report spatial and temporal micrometric changes in the fluorescence intensity of an initial fluorescent species. The fluorescence signal is directly related to the local concentration of a redox fluorescent reagent, which is electrochemically modulated by the electrode. Fluorescence images are collected through the optical fiber bundle during the oxidation of tris(2,2'-bipyridine)ruthenium(II) to ruthenium(III) at a diffusion-limited rate and allow the concentration profiles of Ru(II) reagent to be monitored in situ as a function of time. Tris(2,2'-bipyridine)ruthenium(II) is excited at 485 nm and emits fluorescence at 605 nm, whereas the Ru(III) oxidation state is not fluorescent. Our experiments emphasize the influence of two parameters on the micrometer spatial resolution: the numerical aperture of optical fibers within the bundle and the Ru(II) bulk concentration. The extent of the volume probed by each individual fiber of the bundle is discussed qualitatively in terms of a primary inner-filter effect and refractive index gradient. Experimentally measured fluorescence intensity profiles were found to be in very good agreement with concentration profiles predicted upon considering planar diffusion and thus validate the concept of this new application of imaging fibers. The originality of this remote approach is to provide a global view of the entire diffusion layer at a given time through one single image and to allow the time expansion of the diffusion layer to be followed quantitatively in real time. 相似文献
105.
Stress-induced light guides have been fabricated by an embossing process. The results of detailed loss measurements show that these waveguides can exhibit low optical attenuation. 相似文献
106.
Sabine Aboling 《Zeitschrift für Jagdwissenschaft》2003,49(3):161-190
Zusammenfassung Um die Frage nach dem ökologischen Nutzen einjähriger Wildäcker der Feldflur zu klären, wurden auf 68 Standorten im Tief- und Bergland Niedersachsens während der Vegetationsperiode 2002 die Ansaaten und Pflanzenarten erfasst (letztere vegetationskundlich nachBraun-Blanquet). Jeder Wildacker unterliegt einer individuellen Anbaupraxis; jeder zweite (darunter 26 Stillegungsflächen) besitzt eine andere Einsaat. Das Spektrum der wildwachsenden Pflanzenarten vermittelt zwischen Ackerwildkraut-Gesellschaften und Ruderalen Beifußfluren und ist durch hohe Bauwerte Mehrjähriger gekennzeichnet. Die Artenzahl variiert von 12–63; im Mittel rund 40, im Diepholz-Nienburger Raum 24 Arten. 40% der Wildäcker beherbergen mindestens eine von 17 Arten der Roten Liste. Dabei sind individuenreiche Populationen die Ausnahme und nur auf Standorten mit langer Ackernutzung zu finden. Die quantitative Erfassung der von Rehwild und Feldhase verbissenen Pflanzenarten (Individuenzahl) sowie die Feststellung der pflanzenartspezifischen Äsungspräferenz (Anteil Äcker, wo Art beäst im Verhältnis zur Zahl, wo Art auftrat) ergab 23 Kultur- und 67 Wildpflanzenarten. Süßgräser, aromatische und niederliegende Pflanzenarten werden weniger angenommen; hochwüchsige, milchsaftführende und saftige bevorzugt, vor allem die Rauhe Gänsedistel (Sonchus asper L.ssp. asper). Je artenreicher der Wildacker, desto mehr Arten beäst das Wild. Die wildwachsende Flora der Wildäcker erfüllt damit eine obligate Funktion im sommerlichen Nahrungsspektrum. Eine Deckung von Kulturpflanzen über 80% führt dagegen zur Abnahme der Äsung sowie tendenziell auch zum Rückgang von Roten-Liste-Arten. Durch die regelmäßige Bestellung ackerfähiger Grenzertragsstandorte mit Feldfrüchten tragen Wildäcker zum Schutz erhaltenswerter Segetalvegetation bei, deren Restitution in Fällen kleiner Populationsgrößen der beteiligten Arten dringend geboten ist. Zur Ausschöpfung des natürlichen Standortpotentials wird ein Pilotprojekt Ausgleichsmaßnahme Wildäsungsfläche angeregt.Eingesetzt wurde ein Druckkostenzuschuß des Hessischen Ministeriums für Umwelt, Ländlichen Raum und Verbraucherschutz, für dessen Gewährung verbindlich gedankt wird. - Die Schriftleitung 相似文献
107.
We investigated the impact of mental fatigue on exploration in a complex computer task. The exploration behavior of participants who underwent a fatigue manipulation (N = 36) was compared with that of a control (nonfatigued) group (N = 32). A distinction was also made between participants with high or low levels of general computer experience. Results showed that fatigued participants used significantly less systematic exploration and made more errors than did nonfatigued participants. Fatigued participants with low computer experience also showed significantly more rigid behavior than did the other participants. No differences were found on the number of subtasks solved. Compared with low-experience participants, highly experienced participants showed significantly more systematic exploration, less unsystematic trial and error, solved more subtasks, and made fewer errors (marginally significant p = .056). Findings were interpreted as the result of reduced task engagement under fatigue and reduced involvement of executive control on behavior. Actual or potential applications of this research include guidelines to prevent detrimental effects of mental fatigue on exploration behavior. 相似文献
108.
Marin-Perianu M. Meratnia N. Havinga P. de Souza L.M.S. Muller J. Spiess P. Haller S. Riedel T. Decker C. Stromberg G. 《Wireless Communications, IEEE》2007,14(6):57-66
Massively deployed wireless sensor and actuator networks, co-existing with RFID technology, can bring clear benefits to large-scale enterprise systems, by delegating parts of the business functionality closer to the point of action. However, a major impediment in the integration process is represented by the variety of customized platforms and proprietary technologies. In this article, we present a three-layer, service-oriented architecture that accommodates different sensor platforms and exposes their functionality in a uniform way to the business application. Our work is motivated by real business cases from the oil and gas industry. In our implementation, we use three sensor platforms (particle, muNode, and Sindrion) integrated through the universal plug and play (UPnP) standard and incorporated into an enterprise software system. The practical tests and application trials confirm the feasibility of our solution but also reveal a number of challenges to be taken into account when deploying wireless sensor and actuator networks at industrial sites. 相似文献
109.
Software engineering curriculum guidelines state that students should practice methods, techniques, and tools. A capstone project is one possibility to address this aim. A capstone project helps the students to increase their problem solving competencies, improve their social skills (e.g., communication skills), and gather practical experience. A crux of such projects is that students perform ldquoreflectiverdquo practice in order to learn from their experiences. The authors believe that experience gathering and reuse are effective techniques to stimulate reflective activities. An adapted free- and open-source Wiki-based system called software organization platform (SOP) is used to support students in managing their observations and experiences. The system can be used for experience exchange within the team and for experience reuse in forthcoming projects. The results of a case study show that standard Wiki functions improve communication and information sharing by means of explicit observation and experience documentation. A total of 183 documented observations and experiences at the end of the project provide a measure for the amount of reflection students have had during the capstone project. Still, the advantages of using Wikis will decrease when no technical adaptations of the Wiki to the learning objectives and to the software engineering tasks are made. Limitations of the case study, future evaluation steps, and planned developments of SOP will be provided in this paper. 相似文献
110.
Children in primary and secondary school are asked to go on the Internet for school purposes while research on hypertext has scarcely investigated how children process and learn from hypertext. We therefore examined how hypertext influences children’s knowledge acquisition from expository text. A group of 71 Dutch children (13 years old) from one secondary school for pre-university education participated in the study. In a within-subjects design with four conditions, we compared: regular linear text, regular text with overview, hypertext, and hypertext with overview. Children’s (a) navigation (i.e., reading time and navigation pattern) and (b) learning (i.e., multiple choice knowledge questions and mind maps) was measured. Although reading times did not differ, the children navigated less linearly in both hypertext conditions than in the regular text with overview condition. The four types of text led to the same deep understanding as measured on the text base level. Analyses of the mind maps, however, showed the children to construct richer situation models after reading hypertext or hypertext with an overview relative to regular linear text and regular text with overview. We therefore conclude that hypertext fosters a deeper level of information processing when appropriately designed relative to regular linear text. 相似文献