A New Method for Converting T_(2) Spectrum into Pore Radius

In this paper,a new method for converting the T_(2)(relaxation time) of NMR(nuclear magnetic resonance) into the pore radius is proposed.Combined with NMR and centrifugation experiments,the relationship between pore radius and T_(2) of the sample was established.The results show that the new method is more reasonable than the traditional method.When the sample was denser and the mercury saturation was lower,the pore distribution curve was obtained by traditional method had a worse agreement with mercury injection experiment,while pore distribution curve of the new method had a better agreement with the mercury injection curve,which reflected the greater advantage of the new method as the reservoir becomes denser.The new method can obtain all the pore information in the sample.The results show that the pores in tight sandstone are mainly consisted with mesopore and macropore,and the connectivity of macropore is better than that of mesopore.The new method can effectively characterize the full pore distribution and the seepage characteristics in different pores interval of tight reservoirs,which had a great significance to evaluate the recoverable resources of tight reservoir.

Multistage Stack with Multiple Pore Radii Applying the Temperature Gradient to a Thermoacoustic Engine

Conventional thermoacoustic engines have a stack pore radius that is almost constant in the axial direction. Hence, a thermoacoustic engine is expected to improve the energy conversion efficiency using a multistage stack with multiple pore radii. The stack comprises several bundles of numerous narrow tubes with specified pore radii. The optimum pore radius of the stack is determined by the oscillation frequency and the temperature in the stack. Consequently, the suitable pore radius changes in the axial direction, because the temperature gradient exists along the stack axis. Therefore, a multistage stack with multiple pore radii is introduced, which achieves a desired optimum pore radius everywhere in the stack. The energy conversion efficiency of the multistage stack, which was studied experimentally for a straight-tube type thermoacoustic engine, was compared with that of a conventional single-stage stack. In these experiments, the improvement of the energy conversion efficiency was confirmed. A numerical method with the transmittance matrix to include the effect of a multistage stack was used, and good agreement between experimental and numerical results was obtained. The results make a future possibilities for stack design intended to higher thermoacoustic engine efficiency expect.

多孔玻璃的性质、用途及制备

介绍了多孔玻璃在科学技术及国民生产中的各种用途 .对多孔玻璃的制备工艺原理作了论述 ,并从玻璃组成、热处理时间和温度、酸度处理以及掺杂等角度阐述了制备工艺中影响孔径大小和分布的因素 .比较了康宁工艺和 PPG工艺 .最后 ,列举了多孔玻璃的一些性质 。

The influence of defects on the effective Young's modulus of a defective solid

It is difficult to establish structure-property relationships in a defective solid because of its inhomogeneous-geometry microstructure caused by defects. In the present research, the effects of pores and cracks on the Young’s modulus of a defective solid are studied. Based on the law of the conservation of energy, mathematical formulations are proposed to indicate how the shape, size, and distribution of defects affect the effective Young’s modulus. In this approach, detailed equations are illustrated to represent the shape and size of defects on the effective Young’s modulus. Different from the results obtained from the traditional empirical analyses, mixture law or statistical method, for the first time, our results from the finite element method （FEM） and strict analytical calculation show that the influence of pore radius and crack length on the effective Young’s modulus can be quantified. It is found that the longest crack in a typical microstructure of ceramic coating dominates the contribution of the effective Young’s modulus in the vertical direction of the crack.

Petrophysical and capillary pressure properties of the upper Triassic Xujiahe Formation tight gas sandstones in western Sichuan,China

The tight sandstones of the Upper Triassic Xujiahe Formation（T_3x） constitute important gas reservoirs in western Sichuan.The Xujiahe sandstones are characterized by low to very low porosity （av.5.22%and 3.62%） for the T_3x^4 and T_3x^2 sandstones,respectively）,extremely low permeability（av. 0.060 mD and 0.058 mD for the T_3x^4 and T_3x^2 sandstones,respectively）,strong heterogeneity,micronano pore throat,and poor pore throat sorting.As a result of complex pore structure and the occurrence of fractures,weak correlations exist between petrophysical properties and pore throat size,demonstrating that porosity or pore throat size alone does not serve as a good permeability predictor.Much improved correlations can be obtained between permeability and porosity when pore throat radii are incorporated. Correlations between porosity,permeability,and pore throat radii corresponding to different saturations of mercury were established,showing that the pore throat radius at 20%mercury saturation（R_（20）） is the best permeability predictor.Multivariate regression analysis and artificial neural network（ANN） methods were used to establish permeability prediction models and the unique characteristics of neural networks enable them to be more successful in predicting permeability than the multivariate regression model.In addition, four petrophysical rock types can be identified based on the distributions of R_（20）,each exhibiting distinct petrophysical properties and corresponding to different flow units.

Near-saturated soil hydraulic conductivity and pore characteristics as influenced by conventional and conservation tillage practices in North-West Himalayan region,India

Tillage plays an important role in modifying soil hydraulic properties.The objective of the present study was to evaluate the effect of conservation tillage practices in a maize-wheat cropping system on nearsaturated soil hydraulic properties and pore characteristics in the North-West Himalayan region,India.Three treatments viz.conventional tillage(CT),minimum tillage(MT),and zero tillage(ZT)were evaluated in terms of field saturated hydraulic conductivity(ks),unsaturated hydraulic conductivity k(h),the inverse of capillary length(a),flow-weighted mean pore radius(r0),numbers of pores per square meter(n0)and water-conducting macroporosity(Ɛ).The above hydraulic conductivity and pore characteristics were derived from steady-state water flux(q)measured using hood infiltrometer at 0,1,and3 cm pressure head for each treatment after seven years of establishment of this tillage experiment.Results revealed significantly(p<0.05)higher values of ks,k(h),a,andƐin ZT as compared with CT.MT had intermediate values.Higher a values suggested a greater gravity-dominated flow under ZT and MT as compared with CT.Analysis of r0 values indicated better connectivity of pores in ZT and MT as compared with CT.Macropore flow suggested that on average pore radii,>0.50 mm conducted about 63.60,68.01,and 75.97%of total flow(at 0 cm pressure head)in the corresponding water-conducting macroporosity of 0.00030,0.00044,and 0.00069%of soil volume under CT,MT,and ZT,respectively.Overall,zero-tillage based agriculture system was found to improve near-saturated soil hydraulic properties.

Development of sintered Ni-Cu wicks for loop heat pipes

The present study fabricated a series of capillary wicks for loop heat pipes (LHPs), using two different methods, the cold-pressing sintering and direct loose sintering, and experimentally investigated the effect of different methods, compositions and sintering parameters on their properties in terms of porosity, permeability and pore radius. Porosity and pore radius were measured by the Archimedes method and Scanning Electron Microscope (SEM), respectively. Permeability of the wicks was compared by calculation using empirical equation. Results show that capillary wicks were successfully fabricated by using two different methods; the optimal capillary wick was found to be sintered at 650°C for 30 min, using direct loose sintering technique, with 90% nickel and 10% copper. The wicks could reach the porosity of 70.07% and the permeability of 10?13 m2 order, with mean pore radius of 0.54 μm.