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21.
Topology optimization of fluids in Stokes flow 总被引:1,自引:0,他引:1
We consider topology optimization of fluids in Stokes flow. The design objective is to minimize a power function, which for the absence of body fluid forces is the dissipated power in the fluid, subject to a fluid volume constraint. A generalized Stokes problem is derived that is used as a base for introducing the design parameterization. Mathematical proofs of existence of optimal solutions and convergence of discretized solutions are given and it is concluded that no regularization of the optimization problem is needed. The discretized state problem is a mixed finite element problem that is solved by a preconditioned conjugate gradient method and the design optimization problem is solved using sequential separable and convex programming. Several numerical examples are presented that illustrate this new methodology and the results are compared to results obtained in the context of shape optimization of fluids. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
22.
Wagner AM Fegley MW Warner JB Grindley CL Marotta NP Petersson EJ 《Journal of the American Chemical Society》2011,133(38):15139-15147
Methods for synthetically manipulating protein structure enable greater flexibility in the study of protein function. Previous characterization of the Escherichia coli aminoacyl tRNA transferase (AaT) has shown that it can modify the N-terminus of a protein with an amino acid from a tRNA or a synthetic oligonucleotide donor. Here, we demonstrate that AaT can efficiently use a minimal adenosine substrate, which can be synthesized in one to two steps from readily available starting materials. We have characterized the enzymatic activity of AaT with aminoacyl adenosyl donors and found that reaction products do not inhibit AaT. The use of adenosyl donors removes the substrate limitations imposed by the use of synthetases for tRNA charging and avoids the complex synthesis of an oligonucleotide donor. Thus, our AaT donors increase the potential substrate scope and reaction scale for N-terminal protein modification under conditions that maintain folding. 相似文献
23.
Hans Petersson 《Mathematische Annalen》1955,129(1):370-390
Ohne Zusammenfassung 相似文献
24.
Hans Petersson 《Archiv der Mathematik》1970,21(1):574-577
Ohne Zusammenfassung 相似文献
25.
The general mobility matrix formulation of the problem of multi-point, coupled structures is discussed and some of the disadvantages are emphasized. Two principally different ways of rearranging the general mobility matrix into corresponding effective mobilities, useful for expressing the vibratory power input to the receiving structure, are investigated theoretically. The two concepts of effective mobility, namely effective point mobility in which the points are considered individually with the interaction between the points taken into account and effective overall mobility in which a space averaged point mobility is deduced, have also been verified experimentally. In addition, some useful approximations of these quantities are derived. 相似文献
26.
The nuclear spin lattice relaxation timeT 1 of the23Na,85Rb,87Rb,133Cs,14N nuclei is measured in NaCN, RbCN and CsCN as a function of temperature below and above the ferroelastic phase transition temperatureT c. BelowT c the behaviour ofT 1 of the alkali nuclei renders possible to determine the flip frequency of the CN molecules and its temperature dependence. AboveT c from the14NT 1 the correlation time τc of the rotational motions of the CN molecules and its temperature dependence is determined. An empirical rule is verified demonstrating that atT c the correlation times take nearly the same values for all cyanides. For the high and low temperature phases one obtains atT c about τc=5·10?13s and τc=5·10?11s, respectively. The results are discussed with respect to the mechanism of the phase transition. 相似文献
27.
We study the strong coupling limit of U(N) or SU(N) gauge theories with fermions on a lattice. The integration over the gauge and fermion degrees of freedom is performed by analytic methods, leading to a partition function in terms of localized meson and baryon fields. A method for deriving a systematic expansion in the inverse of the space-time dimension of the corresponding Green functions is developed. It is applied to the study of spontaneous breakdown of chiral symmetry, which occurs for any U(N) or SU(N) theory with fermions in the fundamental representation. Meson and baryon spectra are then computed, and found to be in close agreement with those obtained by numerical methods at finite coupling. The pion decay constant is estimated. 相似文献
28.
Hans Petersson 《Mathematische Annalen》1954,127(1):33-81
Ohne Zusammenfassung 相似文献
29.
Hans Petersson 《Commentarii Mathematici Helvetici》1956,31(1):111-144
Ohne Zusammenfassung 相似文献
30.