Search results

Obtaining coal and rock pressure relief depth of the floor was 70m, with the working face advancing, the pressure relief depth and range became larger, to achieve stable at a certain number；affected by the mining of 2-2 coal, coal and rock mass strength of its floor was weak, the largest damage depth was about 18m, this result would provide a basis to the roadway of the 3-1 coal in different coal pitch; affected by the mining, the goaf overburden and floor of 2-2 coal working face appeared "O" shape fracture zone, the floor rock fissure of 2-2 coal got through to the roof of 3-1 coal, cracks formed transfixion, which made the pressure change of 3-1 coal working face, Mine pressure appearance tended to be ease, it would be easily control if the roadway of 3-1 coal was arranged in the area of pressure relief.
Roof rock was mainly fine-grained sandstone and siltstone, floor lithology was mainly sandy mudstone and siltstone.The coal seam thickness of first mining regional between 1.3 ~ 3.5m, an average of 2.0m.
Table 1 Rock mechanics parameters The name of the coal and rock Thickness /m Bulk density/ kg·m-3 Bulk /GPa Shear modulus/GPa Tension /MPa Cohesion /MPa Friction /° Roof overburden 29.5 2500 5.5 3.3 6.2 2.6 32 The main roof sandstone 18.0 2600 4.5 2.8 5.6 2.1 31 2-2up coal 2.5 1350 2.5 1.2 0.8 0.6 28 Direct roof of shale 7.0 2600 3.5 2.8 3.6 2.1 31 2-2middle coal 2.0 1350 2.5 1.2 0.8 0.6 28 Direct sandy mudstone 6.0 2200 2.7 1.6 1.2 1.06 29 2-2low coal 1.5 1350 2.5 1.2 0.8 0.6 28 The old number grain of sand 18.0 2400 3.8 1.8 1.6 1.2 28 3-1up coal 1.5 1350 2.5 1.2 0.8 0.6 28 Roof of 3-1coal 6.0 2400 3.2 2.6 1.4 1.1 27 3-1coal 4.0 1350 2.5 1.2 0.8 0.6 28 Floor of 3-1coal 6.0 2400 3.6 2.6 2.4 1.2 32 2.2 Analysis of simulation results Simulation of floor pressure relief was shown in figure 2.
With the working face advancing, the pressure relief depth and range became larger, to achieve stable at a certain number；the mining of 2-2 coal working face had great influence to the pressure relief of 3-1 coal

They investigated effects of parameters such as grain size of grinding stone (gss), pattern of grinding stone (ps), hardness of grinding stone (hs) etc. to surface roughness and grinding rate.
They determined that surface roughness increases and grinding rate decreases as grinding stone grain size grows bigger, grinding rate decreases and surface roughness increases as feed rate increases.
A dependency of grinding performance on interaction between grinding stone grain sizes and work piece and relations between this interaction with grain dispersion, sharpening and grinding kinematics were explained by Chen and Rowe [10].
There is very limited number of studies in academic literature about CNC grinding.

Such an addition was reported to have silica-scavenging effect and to reduce the ceria sintering temperature, which is important to avoid excessive grain growth [15,16].
SEM showed that grains of both constituents are distributed randomly, with minor agglomeration of the grains of the same phase.
The ion transference numbers (tO), estimated from the oxygen permeability values, increase with temperature from 0.0018 to 0.0055 at 1123-1248 K [12].
Kilner, Grain boundary conduction of Ce0.9Gd0.1O2-δ ceramics derived from oxalate coprecipitation: effects of Fe loading and sintering temperature, Solid State Ionics 176 (2005) 377-384

As the surfactant concentration increased, the number of micelles that formation of pore skeleton also increased.
During the high temperature anneal, crystal growth with rutile structure and the grain growth are occurred, but the presence of the interior pores inhibit the orientation of the particle growth.
From this observation, we can say that grain growth and crystallization was limited by porous structure, i.e., controlled mass transfer even after high temperature annealing at 900oC from the presence of interior pores.
That is to say, disordered micro-porous structure with agglomerated and enlarged pores could be synthesized because mesopores act as template for the inter-pores between enlarged titania grains.
In the case of annealing temperature at 900oC under vacuum atmosphere, crystallization and grain growth was limited by interior pore structure and disordered and enlarged micro-porous structure was synthesized.

Superior creep resistance of this steel is attributed to stability of tempered martensite lath structure (TMLS) consisting of prior austenite grains (PAG), packets, blocks, lath and containing a high density of dislocations and a dispersion of secondary phase particles.
The dislocation densities were estimated by counting the individual dislocations in the grain/subgrain interiors per unit area on at least six arbitrarily selected typical TEM images for each data point [3,4].
The density of particles located at (sub)grain/lath boundaries was determined as the number of particles per unit boundary length.
Results and Discussion 1 Tempered martensite lath structure The TMLS of the 9Cr-3Co-3W-VNbB steel is characterized by an average size of prior austenite grains (PAGs) of 20 μm.

The cohesion of the grains with the cement paste was high at those temperatures, which caused grain cracks in numerous sites.
The fracture surfaces tended to be more tortuous, and fewer cracks across the grains were observed, the grains were pulled out of the cement paste.
A complete load-displacement curve can represent a number of findings: the initial stiffness, the ultimate load capacity, the displacements at cracking and failure, hardening and softening properties, etc.

Since the 1950s, a large number of controllable reservoirs have been built in the Taihang Mountain area.
The first layer has a thickness of 0.1 m and the grain size of the inverted filter (d）is 0.25-1.00 mm; the second layer has a thickness of 0.1 m and the grain size of the inverted filter (d）is 1.00-5.00 mm; and the third layer has a thickness of 0.1 m and the grain size of the inverted filter (d）is 5.00-20.00 mm.
The smaller sized sand grains cannot pass through the larger sized layer to ensure there is no deformation in the filter layer.

It is possible to observe that the quality of the welding string with the addition of feldspar is highly superior to the other one, because of the improved arc stability and reduced number of superficial porosities.
Ferrite-carbide aggregates, primary grain boundary ferrite and ferrite with aligned and non-aligned second-phase were also detected in the weld zone.
A relevant amount of primary grain boundary ferrite was also observed.
Microstructure refining with the use of epoxy resins is evident and the smaller grains tend to be less ductile than the coarse grains on commercial electrode weld zone.

Tuinstra-Koening[15] have brought to a discussion that the relationship between the grain size and the ID/IG is inversely proportional by comparing R and the results from X-ray diffraction.
The wave number,the half band width and the values of R after fitting were shown in table 1.
This made the value of R smaller and the size of crystalline grain bigger than their reality.
From 973K, the value of R reduced and the size of crystalline grains augmented with the rise of baking temperature indicating that high-temperature is propitious to the increase of degree of order, the decrease of carbon laying at the edge and the accretion of amorphous graphite. 4.Summary (1)There are two scattering peaks in the elementary Ranman Spectra of BCP prepared with bamboo charcoal powder and clay and carbonized at high-temperature.One peak appearing between 1346cm-1 and 1371cm-1is the D band charactering disordered carbon structure and belonging to A1g velum.
The samller the half-width of D and G peaks is,the bigger the degree oforder of BCP and the size of crystalline grains are.

Because of that, Allen et al. [1] used electron beam surface remelting to characterize the phase content formed in a number of model 1200 series Al alloys with solidification velocities in the range 2-50 mm.s-1, likewise that used during industrial operations.
It is generally found that as the grain size decreases, the strength of a metal increases.
The wellknown Hall-Petch equation shows that the yield strength is proportional to the reciprocal of the square root of the grain diameter [9].
For cast metals, however, it is not always true that the strength improves with decreasing grain size.
There appears to be no significant effect of grain size reduction on mechanical properties of as-cast unmodified hypoeutectic Al-Si alloys [10].