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81.
82.
83.
The conversion of readily available 2-halobenzaldehydes into indolo[2,1-a]isoquinolines in two operations represents a very direct entry to this class of molecules. 相似文献
84.
J E Beasley J Sonander P Havelock 《The Journal of the Operational Research Society》2001,52(5):483-493
With increasing levels of air traffic, making effective use of limited airport capacity is obviously important. This paper reports on an investigation undertaken by National Air Traffic Services in the UK into improving runway utilisation at London Heathrow. This investigation centred on developing an algorithm for improving the scheduling of aircraft waiting to land. The heuristic algorithm developed (a population heuristic) is discussed and results presented using actual operational data relating to aircraft landings at London Heathrow. This data indicates that our algorithm could have improved on air traffic control decisions in such cases by between 2–5?% in terms of reducing the timespan required to land all of the aircraft considered. 相似文献
85.
D. Beasley I. Gomez-Morilla N. Spyrou 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):101-105
3D quantitative elemental maps of a section of a strand of hair were produced using a combination of PIXE-Tomography and simultaneous
On/Off Axis STIM-Tomography at the University of Surrey Ion Beam Centre. The distributions of S, K, Cl, Ca, Fe and Zn were
determined using the PIXE-T reconstruction package DISRA. The results were compared with conventional bulk PIXE analysis of
tomographic data as determined using Dan32. The overall concentrations determined by PIXE were compared with elemental concentrations
held in the University of Surrey Hair Database. All the entries currently in the database were produced using INAA. The merits
and possible contributions of tomographic PIXE analysis to analysis of hair are discussed. The conclusions drawn from the
PIXE-Tomography analysis can be used to argue for more stringent procedures for hair analysis at the University of Surrey. 相似文献
86.
Let T be a linear operator on the space of all m×n matrices over any field. we prove that if T maps rank-2 matrices to rank-2 matrices then there exist nonsingular matrices U and V such that either T(X)=UXV for all matrices X, or m=n and T(X)=UXtV for all matrices X where Xt denotes the transpose of X. 相似文献
87.
In this paper we present a genetic algorithm-based heuristic for solving the set partitioning problem (SPP). The SPP is an important combinatorial optimisation problem used by many airlines as a mathematical model for flight crew scheduling.A key feature of the SPP is that it is a highly constrained problem, all constraints being equalities. New genetic algorithm (GA) components: separate fitness and unfitness scores, adaptive mutation, matching selection and ranking replacement, are introduced to enable a GA to effectively handle such constraints. These components are generalisable to any GA for constrained problems.We present a steady-state GA in conjunction with a specialised heuristic improvement operator for solving the SPP. The performance of our algorithm is evaluated on a large set of real-world problems. Computational results show that the genetic algorithm-based heuristic is capable of producing high-quality solutions. 相似文献
88.
We characterize linear preservers for sets of matrix ordered tuples which satisfy extremal properties with respect to factor
rank.
__________
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 13, Algebra,
2004. 相似文献
89.
Zero-term rank of a matrix is the minimum number of lines (rows or columns) needed to cover all the zero entries of the given matrix. We characterize the linear operators that preserve zero-term rank of the m× nreal matrices. We also obtain combinatorial equivalent condition for the zero-term rank of a real matrix. 相似文献
90.
J E Beasley M Krishnamoorthy Y M Sharaiha D Abramson 《The Journal of the Operational Research Society》2004,55(1):54-64
In this paper we define a generic decision problem — the displacement problem. The displacement problem arises when we have to make a sequence of decisions and each new decision that must be made has an explicit link back to the previous decision that was made. This link is quantified by means of the displacement function. One situation where the displacement problem arises is that of dynamically scheduling aircraft landings at an airport. Here decisions about the landing times for aircraft (and the runways they land on) must be taken in a dynamic fashion as time passes and the operational environment changes. We illustrate the application of the displacement problem to the dynamic aircraft landing problem. Computational results are presented for a number of publicly available test problems involving up to 500 aircraft and five runways. 相似文献