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排序方式: 共有809条查询结果,搜索用时 15 毫秒
81.
Karsten J. Quint Stefan Hartmann Steffen Rothe Nicolas Saba Kurt Steinhoff 《Computational Mechanics》2011,48(1):81-96
An accurate prediction of the temperature distribution in space and time plays an important role in many industrial applications,
in particular when phase transformations are involved. In this article the thermo-physical properties of steel 51CrV4 (SAE
6150) are determined and used in numerical simulations. For the simulation of the temperature field a semi-discrete approach
is used, consisting of a finite element approximation in space and a high order Runge– Kutta integration in time. Several
adaptive high-order time integration method (stiffly accurate diagonally implicit Runge–Kutta methods) are applied and their
computational efficiency is investigated. The theoretical rates of convergence are achieved for all problems, including the
non-linear case. Whereas the second order accurate method of Ellsiepen with time adaptive step-size control proves to be most
efficient. Further, the influence of the material model on the simulation results is studied and the numerical results are
verified by experiments. The best correlation of the simulation and experimental data is achieved using temperature-dependent
parameters. 相似文献
82.
Volatilization of organotin species from municipal waste deposits: novel species identification and modeling of atmospheric stability 总被引:1,自引:0,他引:1
Krupp EM Merle JK Haas K Foote G Maubec N Feldmann J 《Environmental science & technology》2011,45(3):943-950
Organotin compounds are used as pesticides and fungicides as well as additives in plastics. This study identifies the de novo generation of novel volatile organotins in municipal waste deposits and their release via landfill gas. Besides tetramethyltin (Me(4)Sn), a strong neurotoxin, and 5 previously reported organotins, 13 novel ethylated, propylated, and butylated tetraalkyltin compounds were identified. A concentration of 2-4 μg of Sn m(-3) landfill gas was estimated for two landfill sites in Scotland. The atmospheric stability of Me(4)Sn and methylated tin hydrides was determined empirically in a static atmosphere in the dark and under UV light to simulate night- and daytime conditions. Theoretical calculations were carried out to help predict the experimentally obtained stabilities and to estimate the relative stabilities of other alkylated species. Assuming first-order kinetics, the atmospheric half-life for Me(3)SnH was found to be 33 ± 16 and 1311 ± 111 h during day- and nighttime conditions, respectively. Polyalkylation and larger alkyl substitutes tend to reduce the atmospheric stability. These results show that substantial concentrations of neurotoxic organotin compounds can be released from landfill sites and are sufficiently stable in the atmosphere to travel over large distances in night- and daytime conditions to populated areas. 相似文献
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Dr. Erika Leitel Dr. Wolfgang Hüubner Anita Rommel Dr. sc. Karsten Peter Thiessen 《工业材料与腐蚀》1985,36(2):79-87
Electrode kinetics of high purity iron in phosphate electrolytes under solid particle impact (Simulation of erosion corrosion) Erosion-corrosion of high purity iron was simulated by means of a vibration cell in a neutral phosphate electrolyte. The investigations were carried out to explain the initiation processes of this type of corrosion. The results confirm the general conception of the central role of reaction layer destruction in erosion-corrosion processes. Under these conditions a qualitative change in reaction layer formation occur. By solid impact the layers are destroyed locally and so conditions of pit nucleation exist. The destruction of the layers depends on the action of shear forces resulting from tensile or compressive strains. 相似文献
87.
Auf Einladung des Innenausschusses des Deutschen Bundestages fand am 5. M?rz 2007 eine ?ffentliche Anh?rung zum Thema der
Modernisierung des Datenschutzes statt. Gegenstand waren Entschlie?ungsantr?ge der Fraktionen der FDP sowie von Bündnis90/Die
Grünen zum Datenschutzaudit1 sowie zum Scoring und zu Auskunftspflichten bei Datenschutzpannen.2 Eingeladen war auch der Landesbeauftragte für den Datenschutz Mecklenburg Vorpommern, dessen schriftliche Analyse wir mit
den Schwerpunkten der Herausforderungen durch die Technik und des Datenschutzaudits abdrucken. 相似文献
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This paper describes how the World Wide Web (WWW)-delivered visual explanations of programming constructs have been developed and used to supplement the conventional instructional methods and materials traditionally employed in introductory programming courses. The explanations are constructed using inexpensive commercial software that supports the use of animation, graphics, color, and narrative to help students visualize a wide range of concepts and relationships. Initial student feedback suggests WWW-delivered visual explanations appear to be an effective means of addressing the individual learning needs of novice programmers. 相似文献
90.