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81.
Interest in advanced modulation formats for optical communication systems has so far experienced two major waves. The first one was motivated by the potential to enhance receiver sensitivity of thermal noise-limited systems using coherent detection in combination with phase shift keying. It ended with the advent of optical amplification, enabling high sensitivities together with polarization insensitive, simple and stable direct detection. The second wave is still rolling, fueled by the potential of advanced modulation formats to increase robustness of optical transmission systems against signal distortions. Due to performance limitations given by direct detection and nonlinear effects in the transmission fiber, it is not decided yet, whether there will be widespread application in carrier networks. 相似文献
82.
This paper deals with the problem of finding graph layerings restricted to a given maximal width. However, other than previous approaches for width-restricted layering, we take into account the space for dummy nodes, which are introduced by edges crossing a layer. The main result is that the problem of finding a width-restricted layering under consideration of dummy nodes is NP-complete even when all regular nodes have the same constant width and all dummy nodes have the same constant width. 相似文献
83.
The biochemical basis for considering tannins as digestion inhibitors has been reexamined. Both stimulatory and inhibitory effects of tannins on tryptic hydrolysis are reported. We show how stimulation may result from tannin-induced structural changes in the substrate protein, effectively denaturing it. The surfactant and bile constituent cholic acid also produced similar stimulatory effects. These results have considerable implications for normal digestive physiology as well as for the impact of tannins on argicultural and natural herbivore populations. 相似文献
84.
85.
Jennifer G. Winter M. Catherine Eimers Peter J. Dillon Lem D. Scott Wolfgang A. Scheider Campbell C. Willox 《Journal of Great Lakes research》2007,33(2):381-396
Total phosphorus (TP) inputs to Lake Simcoe have led to hypolimnetic dissolved oxygen (DO) depletion and loss of cold water fish habitat. Since 1990, efforts have been made to reduce the total TP input to the lake below a defined target of 75 t/year, which was predicted to lead to reductions in spring TP concentration and improvements in end-of-summer hypolimnetic DO concentrations. The total TP load to the lake during the most recent period of record (1998/99-2003/04) ranged from 53 to 76 t/yr and averaged 67 t/yr, compared to an average of 114 t/yr estimated between 1990/91 and 1997/98 (range 85-157 t/yr). Reductions in TP loads from the catchment via tributary discharge (∼26 t) accounted for the majority of the decrease in total load between the two time periods. Total P concentrations decreased significantly in four out of six long-term monitored tributaries; however, concentrations in all six tributaries remain above the level recommended to avoid nuisance plant growth (30 μg/L). Although TP loads to the lake are currently below the target 75 t/yr, excessive growths of filamentous algae and macrophytes continue to be a problem in the nearshore zone. End-of-summer minimum hypolimnetic DO concentrations (average 4.3 mg/L, 1998/99-2003/04) remain substantially below the level (7 mg/L) that is considered protective of lake trout. Efforts to reduce TP loads to the lake therefore need to continue. 相似文献
86.
Aus Betriebsergebnissen bei der Pfannenentschwefelung ist ein negativer Einfluß oxidierender Gasphasen bekannt. Daher war es das Ziel der eigenen Untersuchungen in einer geeigneten Apparatur die Wirkung oxidierender Bedingungen in der Gasphase sowohl auf den Verlauf des Schwefelabbaues in der Schlacke als auch des Schwefeltransportes aus dem Roheisen in die Schlacke zu untersuchen. Oxidierende Gasphasen erwirken bei der Pfannenentschwefelung an der Phasengrenze Schlacke/Gas eine Oxidation des Schwefels aus der Schlacke, ohne jedoch bei ruhender Schlackenschicht ein Oxidationspotential in der Schlacke aufzubauen, das bis zur Phasengrenze Roheisen/Schlacke durchgreift und dort die Entschwefelung des Roheisens durch die Siliciumgehalte stört. Sowohl die Entschwefelung des Roheisens als auch die Oxidation des Schwefels aus der Schlacke werden durch höhere Temperaturen und durch eine Rührwirkung gefördert. Der Schwefeltransport wird bei den ungerührten wie bei den gerührten Schmelzen durch Diffusionsvorgänge gesteuert und auch hier durch steigende Temperaturen und rührende Kräfte begünstigt. 相似文献
87.
Peter Su Adrian Gerlich Motomichi Yamamoto Thomas H. North 《Journal of Materials Science》2007,42(24):9954-9965
The formation of local melted films during friction stir spot welding of as-cast AZ91D and thixomolded AZ91 material is investigated.
The average temperatures close to the tip of the rotating pin vary from 438 to 454 °C during the dwell period in friction
stir spot welding. These measured temperature values are higher than the melting temperature of α-Mg + Mg17Al12 eutectic (437 °C). It is suggested that the temperature in the stir zone during the dwell period is determined by the relative
proportions of α-Mg and (α-Mg + Mg17Al12) eutectic material, which are incorporated during friction stir spot welding. Based on the stir zone temperature measurements
and a detailed examination of material located at the root of the pin thread it is suggested that material is moved downwards
via the pin thread and into the stir zone during the dwell period in friction stir spot welding. Evidence of local melted
film formation is observed in the stir zone of AZ91 spot welds. It is suggested that melted films are retained since their
dissolution rate is much slower in the high temperature stir zone than it is when melted films is formed in the stir zone
during Al 7075-T6 friction stir spot welding. The spontaneous melting temperature, solute diffusion rate and the thermodynamic
driving force for droplet dissolution are much higher during Al 7075-T6 friction stir spot welding. 相似文献
88.
Global competition, commitment to the Kyoto Protocol and a deregulated, integrated European electricity market will in all probability increase the demand for energy efficiency on the part of companies in Sweden. Investment decisions are an important part of meeting the new demands, because they decide the future efficiency of industrial energy systems. The objective of this study is to investigate, from a managerial perspective, the need to improve decision support in some industries, which can help to facilitate and improve investment decisions concerning energy efficiency. This work has been conducted through in-depth interviews with representatives for a number of energy-intensive companies and non-energy-intensive companies from different sectors. One need that was identified was the improvement of working methods in order to support the decision-making process. Here, external players seem to be playing an increasingly important role. Access to correct information, better follow-up activities, and transparent, understandable calculations are also considered to be important. The study will form the foundation for subsequent work on decision support and energy efficiency in industry. 相似文献
89.
Peter Welander 《软件》2007,(1):54-55
由于威斯康星州政府的环保法规非常严格.因此在该州新建设一座燃煤电厂并非易事。燃煤电厂高耸的烟囱以及由此产生的酸雨.与威斯康星州原有的由森林、湖泊以及狩猎场组成的户外运动场的形象格格不入.所有.一直以来威斯康星州总是作为电力净输入州也就不足为奇了。 相似文献
90.
Peter Eaton Andrea Ragusa Caroline Clavel Cristina T Rojas Paul Graham Raúl V Durán Soledad Penadés 《IEEE transactions on nanobioscience》2007,6(4):309-318
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents. 相似文献