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排序方式: 共有181条查询结果,搜索用时 62 毫秒
1.
The non-linear thermo-metallurgical problem, relevant for the cooling of a molten metal including the macro-segregation that
occurs during the cooling process, is studied here. Due to the strong non-linearities involved in phase transformations, it
is necessary to use a fine resolution in space-time in a finite element approximation in order to meet accuracy requirements.
We derive space-time FE-methods based on the discontinuous and continuous Galerkin method in time for the energy equation.
This formulation integrates the stored energy exactly for a given heat flux. When macro-segregation is incorporated into the
model, the problem can be formulated in such a way that the phase-transition drives a flow of species. In addition, diffusion
is possible throughout the domain. The model can be further rewritten using a potential approach. By this approach for modelling
macro-segregation, we are able to obtain discretizations that guarantee that the balance equations are satisfied, and it is
possible to solve the phase-transition problem either as a field problem or as a local problem (defined by a local evolution
rule). 相似文献
2.
Köhler K Lellouch AC Vollmer S Stoevesandt O Hoff A Peters L Rogl H Malissen B Brock R 《Chembiochem : a European journal of chemical biology》2005,6(1):152-161
Cellular signal transduction proceeds through a complex network of molecular interactions and enzymatic activities. The timing of these molecular events is critical for the propagation of a signal and the generation of a specific cellular response. To define the timing of signalling events, we introduce the combination of high-resolution confocal microscopy with the application of small-molecule inhibitors at various stages of signal transduction in T cells. Inhibitors of Src-family tyrosine kinases and actin dynamics were employed to dissect the role of the lymphocyte-specific tyrosine kinase Lck in the formation and maintenance of T cell receptor/CD3-dependent contacts. Anti-CD3epsilon-coated coverslips served as a highly defined stimulus. The kinetics of the recruitment of the yellow fluorescent protein-tagged signalling protein ZAP-70 were detected by high-resolution confocal microscopy. The analysis revealed that at 5 min after receptor engagement, Lck activity was required for maintenance of contacts. In contrast, after 20 min of receptor engagement, the contacts were Lck-independent. The relevance of the timing of inhibitor application provides a pharmacological concept for the maturation of T cell-substrate contacts. 相似文献
3.
Andreas Holmström Fredrik Larsson Kenneth Runesson Stefan Edlund 《Structural and Multidisciplinary Optimization》2008,35(1):69-77
At the development of commercial vehicles, it is necessary to develop cost-optimized components with respect to their entire
lifetime. This requires a product development process that utilizes the possibility to simulate the product performance using
modeling of different degrees of sophistication at any predefined level-of-detail (LOD). For example, the mechanical properties
of a cast component depend strongly on the casting process, the simulation of which requires complex modeling at a high LOD.
In this article, we propose an optimization strategy that is based on the LOD concept to develop cost-effective components.
A sizing optimization of a cast model component is carried out with respect to both the mechanical and thermal response to
exemplify the process. In particular, a (novel) global measure of the temperature in energy norm is introduced as an indicator
of the “production fitness” to ensure high quality of the material properties. This measure is the thermal counterpart of
the well-accepted mechanical strain energy. 相似文献
4.
Nataliya Strokina Jiri Matas Tuomas Eerola Lasse Lensu Heikki Kälviäinen 《Machine Vision and Applications》2016,27(3):387-396
The paper proposes a method for the detection of bubble-like transparent objects in a liquid. The detection problem is non-trivial since bubble appearance varies considerably due to different lighting conditions causing contrast reversal and multiple interreflections. We formulate the problem as the detection of concentric circular arrangements (CCA). The CCAs are recovered in a hypothesize-optimize-verify framework. The hypothesis generation is based on sampling from the partially linked components of the non-maximum suppressed responses of oriented ridge filters, and is followed by the CCA parameter estimation. Parameter optimization is carried out by minimizing a novel cost-function. The performance was tested on gas dispersion images of pulp suspension and oil dispersion images. The mean error of gas/oil volume estimation was used as a performance criterion due to the fact that the main goal of the applications driving the research was the bubble volume estimation. The method achieved 28 and 13 % of gas and oil volume estimation errors correspondingly outperforming the OpenCV Circular Hough Transform in both cases and the WaldBoost detector in gas volume estimation. 相似文献
5.
Ren M.M. Slot John D. Srensen Lasse Svenningsen Wolfgang Moser Morten L. Thgersen 《风能》2019,22(12):1699-1715
The effective turbulence approximation is widely used in the wind energy industry for site‐specific fatigue assessment of wind turbines with reference to loads. It significantly reduces the amount of aero‐elastic simulations required to document structural integrity by integrating out the directional variation of turbulence. Deriving the effective turbulence involves assumptions related to load effect histories, structural dynamics, and material fatigue strength. These assumptions may lead to low accuracy of fatigue load assessments by the effective turbulence compared with full directional simulations. This paper quantifies the implications of the effective turbulence for a multimegawatt wind turbine during normal operation. Analyses based on wind measurements from almost one hundred international sites document that the effective turbulence provides accurate results compared with full sector‐wise simulations, but only when linear SN ‐curves are assumed. For a more advanced steel tower design approach using a bilinear SN ‐curve, a reduction of the cross‐sectional design parameters by almost 10% is achieved. Additional 10% reduction can be obtained if fatigue damage is estimated utilizing the wind direction information. By applying a probabilistic approach, it is shown that this reduction in the design parameter of the steel tower does not compromise the structural integrity when the current IEC 61400‐1 standard is followed. The results presented may improve decision making in site‐specific fatigue assessments of wind turbines and prevent overconservative design, which results from the use of the effective turbulence, and thereby reduce the cost of wind energy. 相似文献
6.
Dmitry Kondrik Dmitry Pozdnyakov Lasse Pettersson 《International journal of remote sensing》2017,38(22):6179-6205
Making use of the OC CCI (Ocean Colour Climate Change Initiative) satellite data, and based on the developed both Emiliania huxleyi bloom contouring methodologies and binary masks, areas of coccolithophore growth were distinguished without supervision from locations of mass developments of other algae. On these grounds, and employing special processing algorithms, multi-year time series of variations in occurrence, surficial extent, and content of particulate inorganic carbon (PIC) within E. huxleyi blooming areas in the North, Norwegian, Greenland, Barents, and Bering Seas were obtained for the time period 1998–2013. Analysis of algorithmic processing of the OC CCI data permitted to reveal the spatio-temporal sequence of E. huxleyi blooming events in the above seas of the North Atlantic and Arctic Oceans. During the intra-annual cycle, E. huxleyi blooms advance from temperate to higher latitudes along the pathways of the Gulf Stream propagation to the north. Annually, the blooms arise in the vicinity of the Great Britain southern extremity, and further on move northward along the western coast of this Island Country, round it to eventually appear first in the North and Norwegian Seas (in early June), then in the Greenland Sea (in late June), and finally in the Barents Sea (in late July–early September). The regularities in dates of bloom outbreak and their duration are revealed. The bloom areas in the North Atlantic–Arctic water are the lowest in the Greenland Sea (10,000–30,000 km2) and by an order of magnitude higher in the Barents Sea. The same pattern holds for the total PIC content within E. huxleyi blooms: 400 t–14 kt in the Greenland Sea and about 0.35 Mt in the Barents Sea. In the Bering Sea, the temporal and spatial dynamics of E. huxleyi development proved to be highly irregular: before and after the 1997–2001 period of high intensity of this phenomenon, the blooms are sporadic, their extent and PIC production are either very low or insignificant. Regarding the range of E. huxleyi bloom areas in the Bering Sea during 1997–2001, it is rather similar to that of the Barents Sea. However, the PIC content in the Bering Sea, as compared to that in the Barents Sea, is higher by a factor of about two with maximum values reaching 0.4 Mt and, on one occasion (in 2001), even about 0.7 Mt. 相似文献
7.
Lasse AndresenAuthor Vitae 《Network Security》2014,2014(9):18-20
8.
Shuo Huang Ádám Vida Anita Heczel Erik Holmström Levente Vitos 《JOM Journal of the Minerals, Metals and Materials Society》2017,69(11):2107-2112
The effects of V, Cr, and Mn on the magnetic, elastic, and thermal properties of FeCoNiCu high-entropy alloy are studied by using the exact muffin-tin orbitals method in combination with the coherent potential approximation. The calculated lattice parameters and Curie temperatures in the face-centered-cubic structure are in line with the available experimental and theoretical data. A significant change in the magnetic behavior is revealed when adding equimolar V, Cr, and Mn to the host composition. The three independent single-crystal elastic constants are computed using a finite strain technique, and the polycrystalline elasticity parameters including shear modulus, Young’s modulus, Pugh ratio, Poisson’s ratio, and elastic anisotropy are derived and discussed. The effects of temperature on the structural parameters are determined by making use of the Debye–Grüneisen model. It is found that FeCoNiCuCr possesses a slightly larger thermal expansion coefficient than do the other alloys considered here. 相似文献
9.
Using biofuels in power and CHP boilers can pose a challenge for materials performance. Formation of deposits containing e.g. potassium, sulphur, calcium, sodium, and chlorine can result in severe corrosion of conventional steels and alloys at relatively modest temperatures. Given suitable component design and fabrication facilities, coatings may be considered to protect the fireside surfaces. This paper aims to present a systematic approach to the design and selection criteria for protective coatings of boilers. The approach includes modelling of the process and surface conditions, optimisation of the coating process and structure, and performance validation in the laboratory and plant scales. The applied examples have included iron and nickel based HVOF and arc sprayed coatings subjected to verification field testing in boiler testing under aggressive biofuel conditions. The coatings have shown good corrosion resistance in both laboratory tests and long‐term harsh field tests. The paper discusses the used approach for finding a suitable and cost effective coating for biofuel boiler applications. The paper gives test results from microstructural, corrosion resistance and field testing experience for the selected coatings. 相似文献
10.
Jesper Ahrenfeldt Tobias P. Thomsen Ulrik Henriksen Lasse R. Clausen 《Applied Thermal Engineering》2013,50(2):1407-1417
Biomass is a renewable resource from which a broad variety of commodities can be produced. However, the resource is scarce and must be used with care to avoid depleting future stock possibilities. Flexibility and efficiency in production are key characteristics for biomass conversion technologies in future energy systems. Thermal gasification of biomass is proved throughout this article to be both highly flexible and efficient if used optimally. Cogeneration processes with production of heat-and-power, heat-power-and-fuel or heat-power-and-fertilizer are described and compared. The following gasification platforms are included in the assessment: The Harboøre up draft gasifier with gas engine, the Güssing FICFB gasifier with gas engine or PDU, the LT-CFB gasifier with steam cycle and nutrient recycling and finally the TwoStage down draft gasifier with gas engine, micro gas turbine (MGT), SOFC, SOFC/MGT or catalytic fuel synthesis. 相似文献