Search results

Coal seam roof and floor more stable, coal seam roof is quartz, feldspar, fine-grained sandstone, the horizontal and wavy bedding of rock are development, the thickness of coal seam roof about 6~7m.
In the upper part of immediate roof is about 14m medium-grained sandstone[1].
The distribution of ground crack caused by 2304 working face mining of Han jia wan coal mine was: crack approximately parallel to working face, this kind of ground crack mainly distribution at the central of gob, crack was approximately parallel to working face, it appeared ahead of the working face mining, when the working face passed, crack reached the maximum,and then be closed as the time passed by[8]; cracks near open-off cut and the top slopes, the number of crack at top slopes is larger and length and width of crack is larger, and the extension direction of crack is generally perpendicular to tilt direction of slopes, there is only a small fissuring crack at the base position of bottom slopes.

It has many eximious characters such as high purity, small grain size, narrow grain diameter distributing, large specific surface, good reaction activity, high adsorption capacity, excellent heat stability, and so on.
Through large numbers of experiment, two feasible schemes were confirmed finally.

Introduction Semi-solid thixoforming processes rely on a material microstructure made of globular solid grains more or less connected to each other, thus forming a solid skeleton deforming into a liquid phase.
During processing, the material structure changes with the processing history due to the agglomeration of the particles and the breaking of the grains bonds.
Acknowledgment The authors wish to acknowledge the Wallon Region for its financial support to the THIXOWAL project (Marshall Plan/Mecatech program, convention number 6315) in the context of which this work was performed.

Although no universal constitutive equation exists for die compaction, a number of general features are expected (or assumed) when modeling confined granular materials under load in a uniform and axisymmetric die.
In addition, it is known that at low applied stress, granular systems are locally inhomogeneous on a grain by grain scale and geometric complexity is expected to cause considerable deviation from these simple assumptions.

The grinding wheel topography, cutting edge shape parameters, and wheel grains position distribution are random, not to mention that grinding process is non-linear and indeterminate.
But it can't always attain a satisfying machining result because of the comparative limitation of the knowledge rule of the expert system and the limited number of the training sample of the fuzzy neural networks.
Meanwhile the dynamic machining process cannot be completely controlled since the grinding process is influenced by many uncertain factors, such as the random of the wheel topography, cutting edge shape parameter and wheel grain position distribution, and some unknown grinding principles.

Due to the influence of welding heat input, changes take place in the structure of heat affected zone with grains becoming larger; The formation of carbon chromium compounds result in diminished the capacity of samples’ self-passivation.
At the same time, microbial produce a large numbers of metabolic products.
Non-uniform grains in welding heat affected zone and the carbon- chromium compounds cause corrosion resistance more worse.

S. steels, a number of both Japanese and British grade steels also have been friction stir welded.
Results are for longitudinal samples and thus contain only the fine grain, weld metal microstructure.
A lower peak temperature results in a finer ferrite grain size associated with the higher travel speed, higher strength weld.

When using PFC, a large quantity of back-calculation of micro-mechanical parameters such as cement and grain stiffness and strength from laboratory test results are needed.
During initialization, FLAC sends the number of segments and the coordinates of each segment to PFC.
Table 1 The properties of schist used in PFC/FLAC coupling simulation PFC assemble Ubiquitous joint model in FLAC property value property value Grains Intact rock mass Rmin [mm] 7.2 Youngs modulus (GPa) 4.6 Dmax/Dmin 1.66 Poisson's rate 0.32 r [kg/m3] 2700 Cohesion (MPa) 0.58 Ec [GPa] 6.1 Friction angle ( °) 33.28 kn/ks 2.5 Dilation angle ( °) 0 m 0.5 Cement Bedding plane l 1 Cohesion (MPa) 4.3 Ec [GPa] 7.2 Friction angle ( °) 35 Kn/ks 2.5 Dilation angle ( °) 0 sc [MPa] 7±2 tc [MPa] 7±2 Fig. 4 present the simulation results of PFC/FLAC coupled model, in FLAC model, we used the plastic zone to present the EDZ, in PFC model the crack distribution was directly used to present the EDZ.

Introduction Nano calcium carbonate is the chemical synthesised product whose grain diameter is in the context of 1-100nm rang.
Nano calcium carbonate also widely used in rubber, papermaking, coatings, printing ink, etc. [1-6] Surface effect is the properties change due to the ratio of nano surface atomic and total number of atoms sharply increasing along with the diminishing of the nano particle size.
The grain size also fluctuated with the amount additive A increase, when dosage was 0.3 wt.% Ca(OH)2, a maximum of 47nm was achieved, and a minimum size of 36.5nm emerged at dosage of 0.7 wt.% Ca(OH)2.

A number of different metals and metal oxide nanoparticles have so far been encapsulated into the shell of conducting polymers, giving rise to a host of composites [12–18].
From Fig. 4b, it can be seen that the morphology of the composite differs much from that of pure ZrO2 nanoparticles, when ANI is oxidated with amm- onium persulfate in the presence of ZrO2 nanoparticles, the grain size of composite becomes bigger.
As the ZrO2 concentration increases, the compactness of the sample increases causing coupling through the grain boundaries to become stronger which could enhance the conductivity [24]. 3 Conclusions PANI/ZrO2 composite has been prepared by in-situ polymerization of ANI in the presence of ZrO2 nanoparticles.