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排序方式: 共有340条查询结果,搜索用时 15 毫秒
1.
Jefferson Fabrício Cardoso Lins Hugo Ricardo Z. Sandim Hans-Jürgen Kestenbach 《Journal of Materials Science》2007,42(16):6572-6577
The present paper reports the experimental results on the microstructural and textural characterization of a hot-rolled IF
steel. The IF steel was hot-rolled in multiple passes in the austenitic field (1,070 °C) followed by air-cooling. SEM, TEM,
and LOM were used to image the microstructure of the material. The global texture was determined by X-ray diffraction (XRD)
technique. The mesotexture of selected regions was investigated by electron backscatter diffraction (EBSD). Results show the
presence of a diffuse (nearly random) and weak texture in the hot-band that consists of recrystallized polygonal grains and
subgrains. The fraction of boundaries with misorientations comprised in the interval 2° ≤ ψ < 15° was found to be lower than
5%. It can be concluded that these low angle boundaries and the presence of subgrains can be associated to the existence of
a few areas softened by recovery during or after hot rolling in austenitic field. 相似文献
2.
In this paper, we present an algorithm for the systematic calculation of Lie point symmetries for fractional order differential equations (FDEs) using the method as described by Buckwar & Luchko (1998) and Gazizov, Kasatkin & Lukashchuk (2007, 2009, 2011). The method has been generalised here to allow for the determination of symmetries for FDEs with n independent variables and for systems of partial FDEs. The algorithm has been implemented in the new MAPLE package FracSym (Jefferson and Carminati 2013) which uses routines from the MAPLE symmetry packages DESOLVII (Vu, Jefferson and Carminati, 2012) and ASP (Jefferson and Carminati, 2013). We introduce FracSym by investigating the symmetries of a number of FDEs; specific forms of any arbitrary functions, which may extend the symmetry algebras, are also determined. For each of the FDEs discussed, selected invariant solutions are then presented. 相似文献
3.
Andrew Grayland Chris Jefferson Ian Miguel Colva M. Roney-Dougal 《Annals of Mathematics and Artificial Intelligence》2009,57(1):75-102
Variable symmetries in a constraint satisfaction problem can be broken by adding lexicographic ordering constraints. Existing general methods of generating such sets of ordering constraints can require a huge number of constraints. This adds an unacceptable overhead to the solving process. Methods exist by which this large set of ordering constraints can be reduced to a much smaller set automatically, but their application is also prohibitively costly. In contrast, this paper takes a bottom-up approach. It examines some commonly-occurring families of groups and derives a minimal set of ordering constraints sufficient to break the symmetry each group describes. These minimal sets are then used as building blocks to generate minimal sets of ordering constraints for groups constructed via direct and imprimitive wreath products. Experimental results confirm the value of minimal sets of ordering constraints, which can now be generated much more cheaply than with previous methods. 相似文献
4.
Y Jefferson 《Canadian Metallurgical Quarterly》1995,66(4):21-7, 29
The dental profession is not static, but dynamic. New research findings, along with medical and technological advances, necessitate constant re-examination of treatment philosophies and techniques. What were acceptable treatment techniques in the past may not necessarily be the most effective and best techniques for our patients today. Currently, many practitioners feel that the only treatment for the correction of a skeletal Class III abnormality is via orthognathic surgery in older patients. In some cases it may be the only treatment option. But in most cases today, there are more conservative, non-surgical treatment alternatives in correcting Class III problems in younger aged children. In treating facial-skeletal problems, it must be emphasized that the human face is a biological masterpiece of form and function. Its importance has been documented in arts and sciences since the beginning of modern civilization. It is important enough so that individuals who are blessed with attractive features are afforded greater opportunities in our society. Attractive faces are associated with intelligence, honesty and good work ethics. With the advent of orthognathic surgery, functional appliance, functional regulator, and myofunctional therapy, the dental profession has the capability of leveling out the playing field for many individuals in our society. It does so by being able to correct problems closely associated with the human psyche--the human face. The ability to change facial features brings tremendous prestige to our profession. Along with this prestige comes greater responsibility. Our ability to change facial features entails greater understanding of facial balance and harmony. Ricketts states that the face must conform to stringent proportions known as the "divine proportion" in order for it to be esthetically pleasing. Also, our ability to move facial-skeletal structures entails greater understanding of the biomechanics of the human face. Without this knowledge practitioners can cause iatrogenic problems, such as temporomandibular disorders. Conversely, correcting facial-skeletal abnormalities have been found to alleviate many medical problems, such as chronic headaches, neck-back-shoulder pain, respiratory disorders, auditory disorders, etc. As more and more information is gathered, it is becoming clear that the physical, emotional and psychological health of a human being is intimately related to craniomandibular anatomy. In fact, the jaw and dental structures (with the exception of the tooth enamel) is formed from the neural crest cells along with the endocrine system, while the central nervous system is formed from the neural tube. The entire nervous system, the endocrine system and the dental system are formed from common tissue origin. This can explain why many facial-skeletal corrections are often accompanied by alleviation of many medical and physiological problems. These are exciting times for our profession. However, if we wish to address the needs of our patients well into the next century, we must continue to seek greater and greater knowledge in the area of the craniomandibular anatomy relative to the rest of the human body. It has much to do with facial esthetics, physiologic and psychologic harmony, and TMJ health. This knowledge will enable our profession to have the power to change human lives in a very positive way. As doctors, there can be no greater personal and professional satisfaction than to realize that, through our professional intervention, we are able to offer our patients the possibility of achieving greater happiness and quality of life. 相似文献
5.
Computational Economics - It is possible to model trust as an investment game, where a player in order to receive a reward or a better outcome, accepts a certain risk of defection by another... 相似文献
6.
7.
Voting systems have become controversial in the years following the multiple election disasters that occurred in the United States during and after 2000. Of particular note were the electronic voting (e-voting) systems that were widely deployed to replace the pre-scored punch-card systems, systems that had have been frequently judged to be central to the problem in the 2000 Florida general election. The (premature) deployment of e-voting machines stimulated a new field of security and privacy research around the subject of elections, a subject that has turned out to be more complex and deeper than anyone would have predicted a decade ago. Here we present a sample of some of the finest recent work on election technology from authors on three continents. 相似文献
8.
9.
Christopher Jefferson Angela Miguel Ian Miguel S. Armagan Tarim 《Computers & Operations Research》2006
Peg Solitaire is a well known puzzle, which can prove difficult despite its simple rules. Pegs are arranged on a board such that at least one ‘hole’ remains. By making draughts/checkers-like moves, pegs are gradually removed until no further moves are possible or some goal configuration is achieved. This paper considers the English variant, consisting of a board in a cross shape with 33 holes. Modelling Peg Solitaire via constraint or integer programming techniques presents a considerable challenge and is examined in detail. The merits of the resulting models are discussed and they are compared empirically. The sequential nature of the puzzle naturally conforms to a planning problem, hence we also present an experimental comparison with several leading AI planning systems. Other variants of the puzzle, such as ‘Fool's Solitaire’ and ‘Long-hop’ Solitaire are also considered. 相似文献
10.
Frederick Wieland Lawrence Hawley Abe Feinberg Mike Di Loreto Leo Blume Joseph Ruffles Peter Reiher Brian Beckman Philip Hontalas Steven Bellenot David Jefferson 《Concurrency and Computation》1989,1(1):35-50
This paper analyzes the performance of a discrete-event combat simulation executed on a parallel processor under control of the Time Warp Operating System. Time Warp is in a class of distributed simulation methods called Optimistic methods which have proven to be useful over a wide range of simulations. The combat simulation used for this performance study, called STB88, is a division-corps model incorporating a number of different types of computations. The speed-up for three versions of this model on the Caltech/JPL Mark III Hypercube and the BBN Butterfly parallel processors was measured relative to an efficient sequential execution of the same model on the same hardware. The results indicate that STB88 version 1 achieves a speed-up of 28.6 on 60 Mark III processors, while STB88 version 2 achieves a speed-up of 36.8 on 100 Butterfly processors. Version 3 of STB88 achieved a speed-up of 38.5 on 128 Mark III processors. The versions differed only in their interface to Time Warp. On the Butterfly, the sequential execution completed in 2 hours, while the 100 processor execution completed in 3.2 minutes. 相似文献