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排序方式: 共有499条查询结果,搜索用时 18 毫秒
21.
Gaëtan Compère Jean‐François Remacle Johan Jansson Johan Hoffman 《International journal for numerical methods in engineering》2010,82(7):843-867
In this paper, we identify and propose solutions for several issues encountered when designing a mesh adaptation package, such as mesh‐to‐mesh projections and mesh database design, and we describe an algorithm to integrate a mesh adaptation procedure in a physics solver. The open‐source MAdLib package is presented as an example of such a mesh adaptation library. A new technique combining global node repositioning and mesh optimization in order to perform arbitrarily large deformations is also proposed. We then present several test cases to evaluate the performances of the proposed techniques and to show their applicability to fluid–structure interaction problems with arbitrarily large deformations. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
22.
In this work, a sensitivity analysis has been performed on a finite element model of glass-lubricated extrusion of stainless steel tubes. Fifteen model parameters, including ram speed, billet and tool temperatures, friction coefficients and heat transfer coefficients, were considered. The aim of the study was to determine the parameters that are most important for the response of the extrusion force. The relationship between the model parameters and the responses was analyzed by a calculation of two different regression models: one linear polynomial model and one model that includes interaction terms. Additional simulations were then carried out to validate the regression models. The results show that the initial billet temperature is the factor that has the strongest impact on the extrusion force within the parameter ranges studied in this work. The goodness of prediction and goodness of fit are very good for both regression models. 相似文献
23.
Ove Wolfgang Arne Haugstad Birger Mo Anders Gjelsvik Ivar Wangensteen Gerard Doorman 《Energy》2009,34(10):1642
The Norwegian Energy Act that came into force in 1991 deregulated the electricity market and removed the former obligation power companies had to supply electricity to the geographical area they were responsible for. Hence producers can supply electricity on the basis of profitability. In 2007 the Energy Act was evaluated by the Government. As a part of this, a study concerning hydro reservoir handling before and after deregulation was carried out by SINTEF. Public statistics show that average hydro reservoir levels measured in per cent of reservoir capacity have been reduced after 1990. We have used the power-market model EMPS1 (EFI's Multi-area Power-market Simulator) to analyze if this reduction can be explained by natural variation in climatic variables or by structural changes that have occurred after 1990. Simulation results show that the reduced reservoir levels cannot be explained by natural variation in climatic variables. Structural changes such as increased transmission capacities can, however, explain some of the reduction. Our study does not indicate that the present reservoir handling gives reservoir levels that are too low. In this paper we also describe the stochastic dynamic optimization problem for long-term hydropower scheduling, and we explain how this problem actually is solved by the EMPS model. 相似文献
24.
A new citation search strategy is proposed for Information Retrieval (IR) based on the principle of polyrepresentation (Ingwersen, 1992, 1996). The strategy exploits logical overlaps between a range of cognitively different interpretations of the same
documents in a structured manner, i.e. so-called cognitive overlaps of representations. The strategy is essentially a "cycling
strategy" starting with documents retrieved by a subject search, wherefrom new documents are identified automatically by following
the network of citations in scientific papers backwards and forwards in time. In contrast to earlier citation search strategies
the proposed strategy does not require known relevant documents (seed documents) as a starting point, but may be based on
a subject search. A pilot study is reported where the ability of the strategy to retrieve additional relevant documents is
analysed. Results show that a very large amount of documents can be retrieved by the strategy, and that these may be segmented
in a number of distinct "overlap levels". It is demonstrated that the combined core of the higher-level overlaps contains
higher relevance density than found in the original retrieval results. Based on these results it is suggested that the documents
be displayed in order of their presence in higher-level overlaps, so as to maximise the chances that as many relevant documents
as possible will be presented first to a user.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
25.
Given a set $\T$ of rooted, unordered trees,
where each $T_i \in \T$ is distinctly leaf-labeled by a set $\Lambda(T_i)$
and where the sets $\Lambda(T_i)$ may overlap,
the maximum agreement supertree problem~(MASP) is to construct a distinctly
leaf-labeled tree $Q$
with leaf set $\Lambda(Q) \subseteq $\cup$_{T_i \in \T} \Lambda(T_i)$
such that $|\Lambda(Q)|$ is maximized and for each $T_i \in \T$,
the topological restriction of $T_i$ to $\Lambda(Q)$ is isomorphic to
the topological restriction of $Q$ to $\Lambda(T_i)$.
Let $n = \left| $\cup$_{T_i \in \T} \Lambda(T_i)\right|$,
$k = |\T|$, and $D = \max_{T_i \in \T}\{\deg(T_i)\}$.
We first show that MASP with $k = 2$ can be solved
in $O(\sqrt{D} n \log (2n/D))$ time, which is $O(n \log n)$ when
$D = O(1)$ and $O(n^{1.5})$ when $D$ is unrestricted.
We then present an algorithm for MASP with $D = 2$ whose running time is polynomial if $k = O(1)$.
On the other hand, we prove that MASP is NP-hard for any fixed
$k \geq 3$ when $D$ is unrestricted,
and also NP-hard for any fixed $D \geq 2$ when $k$ is unrestricted even if
each input tree is required to contain at most three leaves.
Finally, we describe a polynomial-time $(n/\!\log n)$-approximation algorithm
for MASP. 相似文献
26.
Combination of biomolecular interaction analysis and mass spectrometric amino acid sequencing 总被引:6,自引:0,他引:6
Natsume T Nakayama H Jansson O Isobe T Takio K Mikoshiba K 《Analytical chemistry》2000,72(17):4193-4198
We describe an approach for the combination of biomolecular interaction analysis (BIA) and electrospray tandem mass spectrometry (ESI/MS/MS) to obtain sequence information on the affinity-bound proteins on the sensor chip of BIA. The procedure is illustrated with stable and unstable interactions of recombinant proteins, i.e., histidine-tagged protein-Ni2+/NTA and 1,4,5-inositol trisphosphate receptor-ligand interactions. The E. coli lysates expressing the recombinant proteins were passed through the sensor chips, and biomolecular interactions were monitored in real time. The molecules detected on the sensor chip were digested by delivering proteolytic enzyme to the sensing flow cells. The resulting on-chip digested peptide mixture at the mid- to low-femtomole level was recovered on a microcapillary reversed-phase precolumn by an on-line system and analyzed using HPLC-MS/MS. In both cases, unambiguous sequence information on the recombinant proteins isolated on the sensor chip was obtained from only a single run of analysis. The combined BIA-MS/MS may prove to be a general and versatile system to discover novel biomolecular interactions and to analyze protein complexes. 相似文献
27.
28.
Jan-Fredrik Jansson 《应用聚合物科学杂志》1973,17(10):2977-2986
In an earlier paper, a “new” viscoelastic function, log J2 = g{log J1}, was defined. For polymers, the linear viscoelastic behavior of which is characterized by “simple segment movements” in their main transition regions, the following general properties are found: (1) The local maxima of the function for different polymers fall along a straight line width the slope approximately equal to 1.1. (2) A characteristical general shape is noticed for the function after shifting along the straight line and reducing the J1 compliance as regards the “frozen in” compliance J10. (3) J1 reflects the storage and J2, the loss mechanisms of the system. The relation J2/J1 is an expression for the average retardation time. 相似文献
29.
Environmental engineering education at universities is a rapidly changing field globally. Traditionally it has resided in the civil engineering program addressing water and wastewater quality, treatment, design and regulatory issues. In recent years environmental engineering has become a much broader field encompassing water, wastewater, soil pollution, air pollution, risk assessment, ecosystems, human health, toxicology, sustainable development, regulatory aspects and much more. The need to introduce environmental engineering/green engineering/pollution prevention/design for the environment concepts to undergraduate engineering students has become recognized to be increasingly important. This need is being driven in part through the US Engineering Accreditation Commission Accreditation Board for Engineering and Technology criteria 2000. Thus there has been a major shift in environmental engineering education and it no longer resides only within the civil engineering discipline. This paper focuses on the development of innovative curricula for a brand new engineering program at Rowan University that integrates environmental education for all engineers. A common course known as "engineering clinic" was developed for all engineering students throughout their eight semesters of engineering education. One of the clinic goals is to integrate engineering design and the environment. The program, in its seventh year, indicates successful implementation of environmental education in all four engineering disciplines in their course work and clinics. 相似文献
30.