粗集中粗元的结构及其拓广

1 引言在决策过程中,如何处理不确定性,已吸引了不少学者的注意,对此,人们提出了各种各样关于不确定性信息的表示模型,及不确定性推理方法,如Shortliffe和Buchanan的不确定因子法,Duda的概率逻辑,Dempster和shafer提出的证据理论方法,Zadeh的模糊集理论,Dubois和Prade提出的可能度推理方法等。近年来,波兰人Pawlak建立的粗集理论在学术界影响很大。

Document classification approach by rough-set-based corner classification neural network

A rough set based corner classification neural network, the Rough-CC4, is presented to solve document classification problems such as document representation of different document sizes, document feature selection and document feature encoding. In the Rough-CC4, the documents are described by the equivalent classes of the approximate words. By this method, the dimensions representing the documents can be reduced, which can solve the precision problems caused by the different document sizes and also blur the differences caused by the approximate words. In the Rough-CC4, a binary encoding method is introduced, through which the importance of documents relative to each equivalent class is encoded. By this encoding method, the precision of the Rough-CC4 is improved greatly and the space complexity of the Rough-CC4 is reduced. The Rough-CC4 can be used in automatic classification of documents.

Discrete element modeling of migration and evolution rules of coarse aggregates in the static compaction process

To investigate migration and evolution rules of coarse aggregates in the static compaction process, an algorithm of generating digital coarse aggregates that can reflect real morphology（ such as shape, size and fracture surface） of aggregate particles, is represented by polyhedral particles based on the discrete element method（ DEM）. A digital specimen comprised of aggregates and air voids is developed. In addition,a static compaction model consisting of a digital specimen and three plates is constructed and a series of evaluation indices such as mean contact force σMCF, wall stress in direction of zcoordinate σWSZZ, porosity and coordination numbers are presented to investigate the motion rules of coarse aggregates at different compaction displacements of 7. 5, 15 and 30 mm. The three-dimensional static compaction model is also verified with laboratory measurements. The results indicate that the compaction displacements are positively related to σMCF and σWSZZ, which increase gradually with the increase in iterative steps. When the compaction proceeds, the digital specimen porosity decreases, but the coordination number increases. The variation ranges of these four indices are different at different compaction displacements. This study provides a method to analyze the compaction mechanism of particle materials such as asphalt mixture and graded broken stone.

A new hole-flanging method for thick plate by upsetting process

Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named upsetting-flanging process, was proposed to obtain a more substantial flange from thick plate. The finite element method （FEM） with DEFORM was utilized to simulate the novel upsetting-flanging process and the influence of geometric parameters on the flange height was studied in details. A series of flanging experiments with A1050P-O were carried out to validate the FEM results, and the variations of Vicker hardness in the plate section were discussed. The results showed that the newly upsetting-flanging process revealed higher flange height and better lip accuracy than the conventional hole-flanging process, and the results between FEM simulations and experiments showed good agreement. Besides, the hardness of the plate around the flange part increases due to the work hardening after the upsetting-flanging process, which reveals better superiority in strength for the subsequent machining or assembling processes.

Effects of Roughness Elements Distribution on Overland Flow Resistance

Roughness elements are various in a mountain area; they include gravel and ground surface vegetation that often result in surface friction drag to resist overland flows. The variation and characteristics of flow resistance strongly impact the overland flow process and watershed floods. In view of the universal existence of natural vegetation, such as Chlorophytum malayense(CM) or Ophiopogon bodinieri(OB), and the sand-gravel bed of the river channel, it is important to understand the role of different types of roughness elements in flow resistance. This study was performed to investigate and compare through flume experiments the behaviors of overland flow resistance by the reaction of multi-scale configuration of different roughness elements. The result showed that the resistance coefficient gradually reduced versus the increase of flow rate in unit width and tended to be a constant when q = 3.0 l/s.m, Fr = 1.0, and Re = 4000 for slopes of 6 to 10 degrees. The gap of the vegetated rough bed and the gravel rough bed is limited to the same as the gap of the two types of vegetation, CM and OB. It was noted that the vegetation contributed to the increase in form resistance negatively and may lead to the mean resistance on decrease. To classify the flow pattern, the laminar flows were described by DarcyWeisbach's equation. In the study the f-Re equation of vegetated bed was developed with f ?5000 Re.The friction coefficient for laminar flows can be regarded as the critical value for identifying the transformation point of the flow pattern.

Hybrid finite-discrete element modelling of asperity degradation and gouge grinding during direct shearing of rough rock joints

A hybrid finite-discrete element method was implemented to study the fracture process of rough rock joints under direct shearing. The hybrid method reproduced the joint shear resistance evolution process from asperity sliding to degradation and from gouge formation to grinding. It is found that, in the direct shear test of rough rock joints under constant normal displacement loading conditions, higher shearing rate promotes the asperity degradation but constraints the volume dilation, which then results in higher peak shear resistance, more gouge formation and grinding, and smoother new joint surfaces. Moreover, it is found that the joint roughness affects the joint shear resistance evolution through influencing the joint fracture micro mechanism. The asperity degradation and gouge grinding are the main failure micro-mechanism in shearing rougher rock joints with deeper asperities while the asperity sliding is the main failure micro-mechanism in shearing smoother rock joints with shallower asperities. It is concluded that the hybrid finite-discrete element method is a valuable numerical tool better than traditional finite element method and discrete element method for modelling the joint sliding, asperity degradation, gouge formation, and gouge grinding occurred in the direct shear tests of rough rock joints.

Geo-rough Space

Rough set is a new approach to uncertainties in spatial analysis.In this paper,rough set symbols are simplified and standardized in terms of rough interpretation and specialized indication.Rough spatial entities and their topological relationships are also proposed in rough space,thus a universal intersected equation is developed,and rough membership function is further extended with the gray scale in our case study.We complete three works.First,a set of simplified rough symbols is advanced on the basis of existing rough symbols.Second,rough spatial entity is put forward to study the real world as it is,without forcing uncertainties into crisp set.Third,rough spatial topological relationships are studied by using rough matrix and their figures.The relationships are divided into three types,crisp entity and crisp entity (CC),rough entity and crisp entity (RC),and rough entity and rough entity (RR).A universal intersected equation is further proposed.Finally,the maximum and minimum maps of river thematic classification are generated via rough membership function and rough relationships in our case study.

How to Apply TPM in Equipment Management for Chinese Enterprises

The paper studies an effective way for Chinese enterprises to implement Total Productive Maintenance （TPM） to cut cost and increase efficiency under the impact of financial crisis. It first reviews the definition and objectives of TPM, clarifies how TPM supports lean objectives, and suggests seven steps and essential elements for Chinese enterprises to implement TPM systematically and successfully. The paper also puts the steps and essential elements into practice in a Chinese enterprise, which are proven effective and we hope the proposals are helpful for Chinese enterprises to change their extensive operation in equipment management.

Study the Effect of Boron and Titanium to Resist Corrosion in the Salt Solution for the Alloy （Al-Cu-Mg）

The alloy （AI-Cu-Mg） alloy important one dating back to the series （2xxx） where copper foundries basic element which represents the number （2）, the study relied on foundries add elements boron （B） and titanium （Ti） and then use a heat treatment （homogenizing process） to improve the corrosion resistance in saline （NaC1 3.5%） of the base alloy （A1-Cu-Mg）, was prepared four types of alloys （A, B, C, D） depending on the chemical composition. The results showed that the corrosion resistance in saline solution was the best resistance in the alloy （D） （A1-2% Cu-2% Mg-0.1% B-1.0% Ti） compared with the rest of bullion when an examination of corrosion of the alloy prepared after homogenizing. But by examining the surface roughness of the alloy ingot turned out that （D） is softer than the rest of the surface alloys and this is due to the addition of boron and titanium together increases surface smoothness in alloys because it works to reduce the grain size.

A New 3D Meso-mechanical Modeling Method of Coral Aggregate Concrete Considering Interface Characteristics

On the basis of the three-dimensional(3D)random aggregate&mortar two-phase mesoscale finite element model,C++programming was used to identify the node position information of the interface between the aggregate and mortar elements.The nodes were discretized at this position and the zero-thickness cohesive elements were inserted.After that,the crack energy release rate fracture criterion based on the fracture mechanics theory was assigned to the failure criterion of the interface transition zone(ITZ)elements.Finally,the three-phase mesomechanical model based on the combined finite discrete element method(FDEM)was constructed.Based on this model,the meso-crack extension and macro-mechanical behaviour of coral aggregate concrete(CAC)under uniaxial compression were successfully simulated.The results demonstrated that the meso-mechanical model based on FDEM has excellent applicability to simulate the compressive properties of CAC.

Polishing Techniques of Stainless Steel Molding Die for the Slumping Method of Glass Optical Components

In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies used to form thin glass components is investigated. The surface roughness of the polished stainless steel molding die surface is below Rz = 200 nm （P-V） at 15 h polishing with 0.5 % alumina polishing liquid. In the case of polishing process with only the weight of molding die and a polishing pressure of 0.5 kPa, polishing times are approximately 60 h and 20 h, respectively. Final surface roughness polished stainless steel molding die surface with pressure of 0.5 kPa is Rz = 7 nm （P-V）, rms -- 1.6 nm and Ra = 1.4 nm. In a thin glass component manufacturing method, ＂slumping method＂, surface roughness before glass forming is rms = 0.7 nm and Ra = 0.6 nm, and after is rms = 0.7 nm and Ra = 0.6 nm. Therefore, there were no observable changes their surface roughness.

Direct numerical simulation of hypersonic transition induced by an isolated cylindrical roughness element

Hypersonic boundary layer transition induced by an isolated cylindrical roughness element is investigated using direct numerical simulation method based on a finite volume formulation.To simulate the transition procedure by resolving the generation and evolvement of small-scale coherent structures,and capture the shock wave at the same time,high-order minimum dispersion and controllable dissipation scheme is validated and then applied.The results are compared with the available measurements in the quiet wind tunnel,such as the dominated frequency and root mean square of pressure.The computational dominated frequency of 19.23 k Hz is very close to the experimental one,21 k Hz.Also,the disturbances of the roughness are mostly generated by the"jet"just before the roughness,and then they travel and develop downstream with the shear layer and vortex shedding.The transition is mainly dominated by the instabilities of both the horseshoe vortex and the shear layer.

Implementation of a Roughness Element to Trip Transition in Large-eddy Simulation

In aerodynamics, the laminar or turbulent regime of a boundary layer has a strong influence on friction or heat transfer. In practical applications, it is sometimes necessary to trip the transition to turbulent, and a common way is by use of a roughness element （e.g. a step） on the wall. The present paper is concerned with the numerical im- plementation of such a trip in large-eddy simulations. The study is carried out on a flat-plate boundary layer con- figuration, with Reynolds number Rex=l.3x 106. First, this work brings the opportunity to introduce a practical methodology to assess convergence in large-eddy simulations. Second, concerning the trip implementation, a volume source term is proposed and is shown to yield a smoother and faster transition than a grid step. Moreover, it is easier to implement and more adaptable. Finally, two subgrid-scale models are tested： the WALE model of Nic0ud and Ducros （Flow Turbul. Combust., vol. 62, 1999） and the shear-improved Smagorinsky model of Ldv^que et al. （J. Fluid Mech., vol. 570, 2007）. Both models allow transition, but the former appears to yield a faster transition and a better prediction of friction in the turbulent regime.

Review on cellular automata simulations of microstructure evolution during metal forming process: Grain coarsening, recrystallization and phase transformation

Cellular automata (CA) algorithm has become an effective tool to simulate microstructure evolution. This paper presents a review on CA modeling of microstructural evolution, such as grain coarsening, recrystallization and phase transformation during metal forming process which significantly affects mechanical properties of final products. CA modeling of grain boundary motion is illustrated and several aspects of recrystallization are described, e.g. nucleation and growth, the development of static and dynamic recrystallization. For phase transformation, attention is paid to such key factors as solute element diffusion and change of systemic chemical free energy. In view of the reviewed works, several open questions in the field of further development of CA simulation are put forward and recommendations to them are given.

优化打浆降能耗 提高生活纸品质

上海东冠纸业与南通华严磨片研究中心协作优化打浆方式和磨浆机磨片。它们采用Broom fin扫帚鳍系列L3型多元合金磨片,改混合打浆为分别打浆,提高了生活纸成纸柔软性和拉力等品质。经生产实践,取得了明显的节能成效。

Tailoring wind properties by various passive roughness elements in a bound- ary-layer wind tunnel

Boundary-layer wind tunnel provides a unique platform to reproduce urban, suburban and rural atmospheric boundary layer （ABL） by using roughness devices such as vortex generators, floor roughness, barrier wails, and slots in the extended test-section floor in the contraction cone. Each passive device impacts wind properties in a certain way. In this study, influence of various passive devices on wind properties has been investigated. Experi- ments using eighteen different configurations of the passive devices have been carried out to simulate urban, sub-urban, and rural climate conditions in a boundary-layer wind tunnel. The effect of each configuration on the wind characteristics is presented. It was found that higher barrier height and more number of roughness elements on the floor, generated higher turbulence and therefore higher model scale factors were obtained. However, in- creased slot width in the extended test-section floor in the contraction cone of the wind tunnel seemed to have a little effect on wind characteristics.

Effect of surface roughness element on near wall turbulence with zero-pressure gradient

In the present paper,we present an investigation on the effect of roughness elements onto near-wall kinematics of a zeropressure-gradient turbulent boundary layer.An array of spanwisely-aligned cylindrical roughness elements was attached to the wall surface to regulate the near-wall low-speed streaky structures.With both qualitative visualization and quantitative measurement,we found that the regularization only occurs in the region below the height of the roughness elements.Statistical analysis on the probability distribution of the streak spanwise spacing showed that the mean spanwise streak spacing is dominated by the roughness elements;however,the latter's effect is in competition with the intrinsic streak generation mechanisms of smooth wall turbulence.Below the top of the roughness elements,local streamwise turbulent fluctuation intensity can be reduced by about 10%.We used POD analysis to depict such regularization effect in terms of near-wall structure modulation.We further found that if the spanwise spacing of roughness elements increased to be larger than the mean streak spacing in the smooth wall turbulence,there is no streak-regularization effect in the buffer region,so that the near-wall streamwise turbulent fluctuation intensity doesn't reduce.