关联规则挖掘AprioriTid算法优化研究

提出了一种基于事务压缩和项目压缩的AprioriTid优化算法。该算法的特点是：项目集采用关键字识别,同时对事务数据进行事务和项目压缩。从而省去了Apriori算法和AprioriTid算法中的剪枝和模式匹配步骤,减小了扫描事务数据库的大小,提高了发现规则的效率。通过实验表明,优化的算法执行效率明显优于AprioriTid算法。     

Elastoplastic analysis of tubular joints of offshore platforms

The subject of this paper is the analysis and design of complex tubular joints, eventually including internal and external gussets and stiffener rings, corresponding to fixed and mobile offshore structures.Two different joints are analysed. In the first case an X joint is studied for elastic and elastoplastic behaviour, loading up to collapse in order to determine ultimate strength and safety factor. Finite elements which can reproduce the elastic and plastic singularities of the stress and the strain fields in the crack tip, are then used for the analysis of a T joint. Both direction and rate are considered in the crack propagation, and an elastoplastic analysis is carried out, to determine the crack opening displacement (COD).Finally, the consideration of fatigue effects in tubular joints is discussed, and techniques for evaluating fatigue life are outlined.     

Using low energy β-sources for radiography

Radiography is a useful technique in forensic document examination. X-ray equipment required for the production of suitable long wavelength X-rays [Gentz rays] is expensive, fragile and often troublesome to use. The associated techniques can be bothersome and often require expensive accessories. Certain beta-emitting isotopes, e.g. tritium, ⁶³ Ni and ¹⁴C can be fabricated into very practical and useful substitutes. We describe several of these and illustrate some typical results.     

Hard pure carbon coatings from a voltage-assisted arc

A simple apparatus is described that produces hard carbon coatings by accelerating ions produced by a carbon arc operating in vacuum. Coatings up to 1.1 μm thick have been produced on a variety of metals and semiconductors.     

Curvature effects in the buckling of symmetrically-laminated rectangular plates with transverse shear deformation

It is shown that the effect of stress discontinuities from ply-to-ply must be taken into account when curvature terms are included along with shear deformation in the buckling analysis of rectangular, symmetrically-laminated plates. Such ply-stress discontinuities lead to curvature terms in the governing equations which differ considerably from those derived for homogeneous plates. Critical buckling loads are determined for orthotropic laminates subjected to biaxial inplane loading and for cylindrical bending of anisotropic plates subjected to uniaxial compression loading. Simply-supported boundary conditions are considered in conjunction with the rectangular, orthotropic laminate, while simply-supported and clamped boundaries are considered for the case of cylindrical bending of anisotropic plates. Numerical results indicate that the curvature terms have little effect on critical buckling loads for the laminates investigated. The effect of transverse shear deformation is shown to depend on the degree of boundary constraint, laminate stacking geometry, and inplane load ratio.     

Direct measurement of the surface temperature of falling films

In non-isothermal absorption of highly soluble gases and vapours in falling liquid films the heat and mass transfer are coupled by the interfacial temperature (that is, film surface temperature).Without measuring this temperature the mass transfer coefficient cannot be determined independently, that is, without an additional assumption concerning the heat transfer.Measuring methods by contacting the film are not suitable when determining the interfacial temperature, as the film flow is disturbed severely.In this paper a non-contacting method using an infrared pyrometer is described. This technique was installed and calibrated in situ in an absorber column, so that local heat and mass transfer coefficients could be determined.     

The U.S. hot dry rock project

Early attempts to hydraulically fracture and connect two wells drilled at the Hot Dry Rock (HDR) site at Fenton Hill in New Mexico produced a large volume of fractured rock, but no connection. Microearthquakes triggered by fracturing indicated that the stimulated rock zones grew in unexpected directions. Consequently one of the wells was sidetracked at a depth of 2.9 km. It was redrilled into the zones of most intense microseismic activity, and flow connections were achieved. Hydraulic communication was improved by supplemental stimulation using recently developed high temperature and high pressure open hole packers. Preliminary testing indicates a reservoir with heat production capability which greatly surpasses that attained in the earlier Phase I reservoir. Longer term testing in 1987 and 1988 will provide more complete information on reservoir behaviour.