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71.
Optimization of bolt thread stress concentrations 总被引:2,自引:0,他引:2
Designs of threaded fasteners are controlled by different standards, and the number of different thread definitions is large. The most commonly used thread is probably the metric ISO thread, and this design is therefore used in the present paper. Thread root design controls the stress concentration factor of threads and therefore indirectly the bolt fatigue life. The root shape is circular, and from shape optimization for minimum stress concentration it is well known that the circular shape is seldom optimal. An axisymmetric Finite Element formulation is used to analyze the bolted connection, and a study is performed to establish the need for contact modeling with regard to finding the correct stress concentration factor. Optimization is performed with a simple parameterization with two design variables. Stress reduction of up to 9% is found in the optimization process, and some similarities are found in the optimized designs leading to the proposal of a new standard. The reductions in the stress are achieved by rather simple changes made to the cutting tool. 相似文献
72.
73.
We investigate connections between arithmetic properties of rings and topological properties of their prime spectrum. Any property that the prime spectrum of a ring may or may not have, defines the class of rings whose prime spectrum has the given property. We ask whether a class of rings defined in this way is axiomatizable in the model theoretic sense. Answers are provided for a variety of different properties of prime spectra, e.g., normality or complete normality, Hausdorffness of the space of maximal points, compactness of the space of minimal points. 相似文献
74.
Niels Vigand Pedersen 《Aequationes Mathematicae》1994,48(2-3):228-253
Summary For a simply connected solvable Lie group we specify the structure of the product, the inverse and the exponential map expressed in suitable coordinates (canonical coordinates of the second kind), and point out that in these coordinates the product and inverse are expressed entirely in terms of polynomials, exponential functions and trigonometric functions. We devise algorithms for computing the product, the inverse and the exponential map. 相似文献
75.
76.
Consider a Hilbert space
equipped with a time-structure, i.e., a resolution E of the identity on
defined on subsets of some linearly ordered set Λ. For which x and y in
is it possible to find a causal (time respecting) compact operator T, so that Tx = y? When T is required to be a Hilbert-Schmidt operator and (Λ, E) is sufficiently regular, this question is answered in terms of the “time-densities” of x and y. The condition is that the integral ∝gLμx({s t})−1 dμy(t) should be finite, where μx and μy are the measures on Λ given by μx(Ω) = ¦|E(Ω)x¦|2 and μy(Ω) = ¦|E(Ω)y¦|2. Further a solution is given for the related problem of minimizing the sum of ¦|Tx − y¦|2 and the squared Hilbert-Schmidt norm ¦|R¦|22 of T. 相似文献
77.
The effective heat conduction of short fibre reinforced materials considering the fibre distribution
This contribution focuses on the effective heat conductivity of short fibre reinforced materials. For this purpose, a representative volume element (RVE), which is able to represent all possible fibre orientation distributions, is introduced and modelled in ABAQUS. Subsequently, the effective heat conductivity of the RVE is derived, employing a numerical homogenisation scheme, and a phenomenological material model is fitted to those results. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
78.
The spatially controlled positioning of functional materials by self-assembly is one of the fundamental visions of nanotechnology. Major steps towards this goal have been achieved using DNA as a programmable building block. This tutorial review will focus on one of the most promising methods: DNA origami. The basic design principles, organization of a variety of functional materials and recent implementation of DNA robotics are discussed together with future challenges and opportunities. 相似文献
79.
Munch HK Heide ST Christensen NJ Hoeg-Jensen T Thulstrup PW Jensen KJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(26):7198-7204
Self-assembly of proteins mediated by metal ions is crucial in biological systems and a better understanding and novel strategies for its control are important. An abiotic metal ion ligand in a protein offers the prospect of control of the oligomeric state, if a selectivity over binding to the native side chains can be achieved. Insulin binds Zn(II) to form a hexamer, which is important for its storage in vivo and in drug formulations. We have re-engineered an insulin variant to control its self-assembly by covalent attachment of 2,2'-bipyridine. The use of Fe(II) provided chemoselective binding over the native site, forming a homotrimer in a reversible manner, which was easily followed by the characteristic color of the Fe(II) complex. This provided the first well-defined insulin trimer and the first insulin variant for which self-assembly can be followed visually. 相似文献
80.
This review provides an overview of direct and indirect technologies to screen protein–ligand interactions with mass spectrometry.
These technologies have as a key feature the selection or affinity purification of ligands in mixtures prior to detection.
Specific fields of interest for these technologies are metabolic profiling of bioactive metabolites, natural extract screening,
and the screening of libraries for bioactives, such as parallel synthesis libraries and small combichem libraries. The review
addresses the principles of each of the methods discussed, with a focus on developments in recent years, and the applicability
of the methods to lead generation and development in drug discovery. 相似文献