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61.
The cohesive model becomes popular in crack analysis for its clear physical background and flexible implementation. The cohesive traction–separation law, however, is a critical point and will generally be empirically assumed. In the present paper the cohesive traction–separation law is investigated based on constrained three-dimensional atomistic simulations. The computations under mode I conditions show that crack growth even in the nano-scale single-crystal aluminum is in the form of void nucleation, growth and coalescence, which is similar to ductile fracture at meso-scale. The concentrations of the atomic tensile stress and the atomic hydrostatic stress at a certain distance from the crack tip characterize void nucleation and final crack growth. The Mises stress does not play a role in the material failure in the nano-scale. This implies that ductile failure under mode I loading condition is dominated by the normal traction, which agrees with the assumption of the cohesive zone model. Variations of the atomic stresses near the crack tip provide the theoretical background for the cohesive zone model and can be used to identify the cohesive traction–separation law. The traction curve is very sensitive to the distance to the crack tip, which is related with the stress triaxiality. The atomistic simulations show tendentious agreement with the known cohesive traction–separation laws, whereas the scattering of the atomic stress versus separation implies effects of the hydrostatic stress in the traction–separation law. The computation provides important information for constructing the cohesive zone model. 相似文献
62.
This research aimed to evaluate a straw bale house located in Bavaria, Germany. An extensive test program was carried out. The experimental work includes compression tests, moisture content, thermal stability of bales and pH. The in situ work includes temperature and relative humidity inside the straw bale wall. The stress-strain behavior of straw bales was investigated including nonlinearity and anisotropy. Thermal stability of bales under constant temperature and relative humidity was studied considering time dependence. The moisture content of straw bale was about 11%, while pH value inside the bale was about 7.29. Moreover, the temperature and the relative humidity between the interior (inside straw bale wall) and the exterior were investigated. 相似文献
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64.
Localized Collection of Airborne Analytes: A Transport Driven Approach to Improve the Response Time of Existing Gas Sensor Designs 下载免费PDF全文
Jun Fang Se‐Chul Park Leslie Schlag Thomas Stauden Jörg Pezoldt Heiko O. Jacobs 《Advanced functional materials》2014,24(24):3706-3714
The detection of single binding has been a recent trend in sensor research introducing various sensor designs where the active sensing elements are nanoscopic in size. Currently, transport and collection of airborne analytes for gas sensors is either diffusion based or non‐localized and it becomes increasingly unlikely for analytes to interact with sensing structures where the active area is shrunk, trading an increased sensitivity with a slow response time. This report introduces a corona discharge based analyte charging method and an electrodynamic nanolens based analyte concentration concept to effectively transport airborne analytes to sensing points to improve the response time of existing gas sensor designs. Localized collection of analytes over a wide range, including microscopic particles, nanoparticles, and small molecules, is demonstrated. In all cases, the collection rate is several orders of magnitudes higher than in the case where the collection is driven by diffusion. The collection scheme is integrated on an existing SERS (surface‐enhanced Raman spectroscopy) based sensor. In terms of response time, the process is able to detect analytes at 9 ppm (parts per million) within 1 s. As a comparison, 1 h is required to reach the same signal level when diffusion‐only‐transport is used. 相似文献
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66.
Heiko von Drachenfels 《Informatik-Spektrum》2005,28(2):136-143
Die objektorientierte Programmierung ist in der Praxis fast schon zum Synonym für Programmierung überhaupt geworden. 相似文献
67.
Kersten S. Rabe Dipl.‐Biochem. Mark Spengler Dr. Michael Erkelenz Dipl.‐Biotechnol. Joachim Müller Dipl.‐Chem. Valerie J. Gandubert Dr. Heiko Hayen Dr. Christof M. Niemeyer Prof. Dr. 《Chembiochem : a European journal of chemical biology》2009,10(4):751-757
The big screen : We have devised a high‐throughput screening method for organic peroxide‐dependent P450 reactivity by taking advantage of a previously undescribed activity of catalase, which was used as reporter enzyme. This two‐step assay, followed by liquid chromatography/mass spectrometry analyses, allowed the facile identification of several new substrates for bacterial P450 enzymes.
68.
An on-site laboratory with direct access to cleaned and conditioned steel mill gases was recently put into operation. The long-term performance and stability of Clariant's MegaMax®800 methanol synthesis catalyst utilizing steel mill gases is currently being investigated. First test results revealed that in order to investigate deactivation mechanisms arising from particular properties of the cleaned steel mill gases, the overlaying effect of thermal deactivation of the catalyst has to be minimized. 相似文献
69.
Erik Zipperling Benedikt Dahlmann Markus Zdrallek Christian Derksen Stefan Eicker Heiko Serafin 《化学,工程师,技术》2021,93(4):624-631
Demands on production, distribution and consumption of electrical energy change fundamentally with the energy revolution. Energy purchasing costs for inflexible consumers are rising and proceeds of inflexible producers are sinking. Companies are able to reduce costs by marketing operational flexibility options. This article sets out the need of flexibility in the energy system and the new marketing options. Flexibility potentials within infrastructure plants of a chemical park are analyzed, evaluated regarding marketing and activated in the presented research project FlexChemistry. 相似文献
70.
There is a widely used linear strategy to determine the parameters specific cake resistance and filter medium resistance in incompressible cake filtration. In this article, it is intended to demonstrate that this strategy has some disadvantages and should be replaced by an alternative nonlinear approach which yields more exact results. Even though the gains in precision are small for most cases, the nonlinear strategy is favored because it involves no extra effort and is grounded in the same physical theory as the original approach. This claim is based on a broad simulation study using noisy data with known parameter values to compare both fitting strategies and judge their accuracies. 相似文献