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941.
942.
A combination of concept (the product portfolio and the product life cycle) and empirical research (the PIMS study) can aid in clarifying the key issues involved in the selection of a firm's core strategies. Strategy control is multistage: periodic re-evaluation of strategy alternatives by use of the marketing audit; an analytical framework for control of chosen strategies by breaking down components and reporting their performance variances; and 'marketing segment' analysis for control of the detailed marketing plan.? 相似文献
943.
The problem of determining minimum total distance to be travelled by a salesman, who is to visit given cities each only once (i.e. the travelling salesman problem) is one of the most studied problems in computational mathematics. Finding an exact solution is not only intractably difficult, but also exceedingly costly. However, we implemented efficient optimal algorithms for both symmetric and asymmetric distance problems. The programs implemented can solve problems up to 180 cities in reasonable computer time. 相似文献
944.
Knowledge elicitation is accepted as being one of the most problematic areas in the creation of a knowledge-based system.A large amount of research has already concentrated on finding more efficient and effective techniques for eliciting knowledge from an individual expert. However, little attention has been given to the involvement of more than one source of expertise in knowledge-based system development.This paper is based on the authors' practical experience gained when developing a knowledge-based system for the conceptual design of bridges. It shows that the use of more than one expert throughout the knowledge elicitation process can improve both the efficiency of the approach and the quality of the knowledge acquired. 相似文献
945.
946.
Polystyrene packaging material taint was sensorily evaluated in cocoa powder for drinks and chocolate flakes using short-cut signal detection measures on differences between control and test samples and on recognition of styrene. No differences were observed in cocoa powder for drinks and plain chocolate flakes treated with 0.5 dm2 polystyrene of 1 mm thickness. However, differences were detected in milk chocolate flakes and plain chocolate flakes, which were in contact with a larger area or thicker polystyrene packaging material. The latter results were confirmed by the styrene recognition test, so polystyrene is a potential source of off-flavour for chocolate products. The amount of residual styrene in the polystyrene used was about 320 ppm, while the amounts of styrene ranged from 7 to 132 ppb in cocoa drinks and from 414 to 1447 ppb in chocolate flakes. 相似文献
947.
Summary The uniqueness of some helical flows of a second grade fluid, between two infinite circular cylinders, is proved. Initially, the fluid is at rest and flow is produced by the motion of the cylinders. Finally, the special case of a flow in a circular cylinder is considered. 相似文献
948.
Y. K. Cheung W. G. Jin O. C. Zienkiewicz 《International journal for numerical methods in engineering》1991,32(1):63-78
The application of the Trefftz method for calculating wave forces on offshore structures is presented. Indirect and direct formulations using complete and non-singular systems of Trefftz functions for the Helmholtz equation are posed in this paper. An effective technique using different interpolation functions for the velocity potential and wave force are suggested to improve the computational accuracy of the wave force. The numerical examples show that the present method is highly efficient and accurate. 相似文献
949.
The effect of temperature on crazing mechanisms in polystyrene 总被引:1,自引:0,他引:1
A. M. Donald 《Journal of Materials Science》1985,20(7):2630-2638
At room temperature scission is the dominant mechanism for the modification of the entanglement network required for craze formation in polystyrene, but as the temperature is increased towardsT
g, there is the possibility that disentanglement processes may contribute. These will be most important for short chains. If disentanglement can occur, a molecular weight dependence of the crazing stress as a function of temperature will result. This prediction is tested by straining thin films of a range of monodisperse samples of polystyrene at temperatures between 40 and 90° C. The nature of the ensuing deformation has been characterized by transmission electron microscopy. It is observed that whereas only crazing occurs over the entire temperature range for the lowest molecular weight sample, shear processes become important for higher molecular weight materials. For the longest chains, crazing is almost entirely suppressed at 80° C, with the preferential formation of shear deformation zones occurring. These observations are consistent with the idea that disentanglement is playing a significant role in craze formation at sufficiently high temperatures. 相似文献
950.
Axial-field electrical machines offer an alternative to the conventional machines. In the axial-field machine, the airgap flux is axial in direction and the active current carrying conductors are radially positioned. This paper presents the design characteristics, special features, manufacturing aspects and potential applications for axial-field electrical machines. The experimental results from several prototypes, including d.c. machines, synchronous machines and single-phase machines are given. The special features of the axial-field machine, such as its planar and adjustable airgap, flat shape, ease of diversification, etc., enable axial-field machines to have distinct advantages over conventional machines in certain applications, especially in special-purpose applications. 相似文献