基于微结构-尺度双分解的页岩随机介质模拟和非均质特征分析

页岩储层矿物颗粒、孔/裂隙、干酪根等微观结构呈现明显的尺度化分布特征,常规的单结构单尺度随机介质模拟方法难以完整描述和重构微观尺度的页岩储层介质,本文提出了一种微结构-尺度双分解的随机介质模拟方法.基于龙马溪组页岩数字岩心,将岩心切片按照占比分解为脆性矿物、孔隙、干酪根及背景介质四种类型,对脆性矿物、孔隙和干酪根三种微结构进行尺度分解,通过优化随机介质模型参数,实现精确模拟不同尺度的微结构组分,再按占比进行微结构-尺度双合成.结果表明,微结构-尺度双分解随机介质模拟大幅度提高强非均质页岩储层介质的建模精度.

地理空间的尺度—结构分析模式探讨

本文以地理学、景观生态学有关尺度的研究为基础,应用层次理论,在大、中、基本三种尺度上,就有关地理空间研究的一个重要方面—地理空间的尺度-结构分析模式进行了探讨。初步建立了一种有关地理空间结构与功能表达的空间等级序列,该等级序列能够反映地球表层在不同尺度上的空间结构组成以及它们之间的相互转换关系,以其为基础开展地理空间研究有利于发现不同地理现象的内在成因及其发生机理(在基本尺度上),有利于发现区域不同地理现象的表现形式及其变化过程的动力学机制(在中尺度上)。与传统地理学对于地理空间研究的宏观有余而微观不足的特点相比,该等级序列能够实现地理学的“宏观机制”研究与“微观机理”研究的结合,是现代地理科学有关“定性与定量综合集成”研究的基础。

Bimodal-grained Ti fabricated by high-energy ball milling and spark plasma sintering

Bimodal-grained Ti containing coarse and fine grains was fabricated by high-energy ball milling and spark plasma sintering (SPS). The microstructure and mechanical properties of the compacts sintered by Ti powders ball-milled for different time were studied. Experimental results indicated that when the ball-milling time increased, the microstructure of sintered Ti was firstly changed from coarse-grained to bimodal-grained structure, subsequently transformed to a homogeneous fine-grained structure. Compared with coarse-grained Ti and fine-grained Ti, bimodal-grained Ti exhibited balanced strength and ductility. The sample sintered from Ti powders ball-milled for 10 h consisting of 65.3% (volume fraction) fine-grained region (average grain size 1 μm) and 34.7% coarse-grained region (grain size > 5 μm) exhibited a compress strength of 1028 MPa as well as a plastic strain to failure of 22%.

Fabrication and catalytic behavior of hierarchically-structured nylon 6 nanofiber membrane decorated with silver nanoparticles

A hierarchically‐structured nylon 6 (PA6) nanofiber membrane decorated with silver nanoparticles (Ag NPs) was fabricated by electrospinning and impregnation methods. The as‐fabricated hierarchically‐structured Ag/PA6 nanofiber membrane (HS‐Ag/PA6 NM) exhibits a morphology in which Ag NPs are deposited on the surfaces of both thick fibers and thin fibers. The content and size of theAg NPs can be controlled by varying the concentration of the silver colloid solution. Compared with the non‐hierarchically‐structured Ag/PA6 nanofiber membrane, HS‐Ag/PA6 NM has a higher specificsurface area and exhibits a higher degradation rate for methylene blue of 81.8%–98.1% within2 h. HS‐Ag/PA6 NM can be easily recycled and exhibits good reusability. It retains a degradation rate for methylene blue of 83.5% after five consecutive cycles. The hierarchically‐structured nanofiber membrane is therefore a potential nanocatalyst.

Influence of a large dam on the longitudinal patterns of fish assem- blages in Qingyi Stream

Using seasonally collected data(2009-2010) from 15 sampling sites that represent first- to fifth-order streams within the Qingyi watershed,we examined the spatio-temporal patterns of fish assemblages along two longitudinal gradients to explore the effects of a large dam on fish assemblages at the watershed scale.No significant variation was observed in either species richness or assemblage structure across seasons.Species richness significantly varied according to stream order and gradient.Dam construction appeared to decrease species richness upstream substantially,while a significant decrease between gradients only occurred within fourth-order streams.Along the gradient without the large dam,fish assemblage structures presented distinct separation between two neighboring stream orders,with the exception of fourth-order versus fifth-order streams.However,the gradient disrupted by a large dam displayed the opposite pattern in the spatial variation of fish assemblages related with stream orders.Significant between-gradient differences in fish assemblage structures were only observed within fourth-order streams.Species distributions were determined by local habitat environmental factors,including elevation,substrate,water depth,current discharge,wetted width,and conductivity.Our results suggested that dam construction might alter the longitudinal pattern in fish species richness and assemblage structure in Qingyi Stream,despite the localized nature of the ecological effect of dams.

Watershed segmentation based on hierarchical multi-scale modification of morphological gradient

Watershed segmentation is sensitive to noises and irregular details within the image,which frequently leads to a serious over-segmentation Linear filtering before watershed segmentation can reduce over-segmentation to some extent,however,it often causes the position offset of object contours.For the purpose of reducing over-segmentation to preserve the location of object contours,the watershed segmentation based on the hierarchical multi-scale modification of morphological gradient is proposed.Firstly,multi-scale morphological filtering was employed to smooth the original image.Then,the gradient image was divided into multi-levels by the volume of three-dimension topographic relief,where the lower gradient layers were further modifiedby morphological closing with larger-sized structuring-elements,and the higher layers with the smaller one.In this way,most local minimums caused by irregular details and noises can be removed,while region contour positions corresponding to the target area were largely preserved.Finally,morphological watershed algorithm was employed to implement segmentation on the modified gradient image.The experimental results show that the proposed method can greatly reduce the over-segmentation of the watershed and avoid the position offset of the object contours.

Large-Scale Structural and Geodynamic Mapping of Platform Territories on the Example of Moscow

This paper describes principles, methods and results of a large-scale （1： 25,000） structural-geodynamic mapping of Moscow territory. Neotectonic structures of different ranks--elevations and depressions, lineaments and GDAZ （geodynamic active zones） are presented on the map. Geodynamic active zones are linear or isometric crust volumes of different scales that localized spatially, where conditions for tectonic stress concentration and relaxation, and high gradients of movements and rocks deformity are favorable by different reasons. They differ from active faults, which are rare on geodynamic-stable platform territories, by absence of noticeable displacements in rocks and a more geodynamic stability. Nevertheless, GDAZ can be hazard to engineering buildings, since these zones are favorable for developing exogenous （such as erosion, impoundment, karst, sliding, etc.） and endogenous geological processes （such as seismicity, water-fluid permeability and heat flux）. They can also become migration and localization channels of nature-anthropogenic pollution.

Grain refinement and plastic formability of Mg-14Li-1Al alloy

Al-5Ti-1B master alloy was added into Mg-14Li-1Al(LA141)alloy and then LA141 sheets were prepared by extrusion and cold rolling.The effect of the addition level of Al-5Ti-1B master alloy on the grain size of LA141 alloy was investigated as well as the effects of the total reduction of cold rolling and the annealing temperature on microstructure,mechanical properties and plastic formability of the LA141 sheets.The results show that the optimal addition level of Al-5Ti-1B master alloy into LA141 alloy is 1.25%(mass fraction)and LA141 alloy has the finest grains.With the increase of the total reduction of cold rolling,the grains of the as-rolled LA141 sheets were flattened gradually.A proper anneal temperature of 200℃ is obtained for the cold rolled LA141 sheets. Under this condition,microstructure of the LA141 sheets consists of fine and uniform equiaxed grains and has higher Erichsen cupping index(IE).

Investigation of acoustic scale effects and boundary effects for the similitude model of underwater complex shell-structure

In this paper, the acoustic scale effects and boundary effects for the similitude model of underwater complex shell-structure are investigated. The similitude conditions and relations between the similitude model and its prototype were studied in the references. This paper investigates the acoustic scale effects for the similitude model, which are influenced by loss factor, shear and rotatory inertia. At the same time, the boundary effects which are influenced by surface sound reflection are investigated in the experiment of similitude model. The results show that the acoustic scale effects may be controlled with model designing, the boundary effects can be controlled with experimental designing between the similitude model and its prototype.

Macroscopic and microscopic trans-scale characteristics of pore structure of mine grouting materials

The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnectivity was investigated using binary images captured from thin sections and a random walk pore spectral dimension (RWPSD) algorithm. The experimental results show that the microstructure of the grouting materials used consisted of interlayer pores, gel pores, capillary pores, circular air holes, and small fractures, and tailings can fill some gaps in the hydration product structure and dense hydration products. There is a positive correlation between pore interconnectivity and curing time. In addition, there is a relationship between pore interconnectivity and porosity. With increasing porosity and pore interconnectivity, a non-uniform pore structure occurs in mine grouting materials with an accelerator and results in reduced setting time and later strength.

Structures of semantic networks: how do we learn semantic knowledge

Global semantic structures of two large semantic networks, HowNet and WordNet, are analyzed. It is found that they are both complex networks with features of small-world and scale-free, but with special properties. Exponents of power law degree distribution of these two networks are between 1.0 and 2. 0, different from most scale-free networks which have exponents near 3.0. Coefficients of degree correlation are lower than 0, similar to biological networks. The BA （Barabasi-Albert） model and other similar models cannot explain their dynamics. Relations between clustering coefficient and node degree obey scaling law, which suggests that there exist self-similar hierarchical structures in networks. The results suggest that structures of semantic networks are influenced by the ways we learn semantic knowledge such as aggregation and metaphor.

Microstructure Analysis of TC4/Al 6063/Al 7075 Explosive Welded Composite Plate via Multi-scale Simulation and Experiment

Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding.The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction(EBSD).A methodology combining finite element method-smoothed particle hydrodynamics(FEM-SPH)and molecular dynamics(MD)was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale.The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration,without discernible defects or cracks.The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces.Furthermore,the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer.The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results.MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase,and the simulated thickness of interfacial diffusion aligns well with experimental outcomes.The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates.Furthermore,this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.

Passive Control of Turbulent Jet Flow with Wedged Nozzle

Turbulent flow field of the free jet with circular nozzle and wedged nozzles is measured using hot wire anemometry with resolution higher than the smallest turbulence time scale. Wavelet analysis is employed to perform multi-scale decomposition of instantaneous turbulence fluctuating velocity signals, and the energy distribution of the turbulent multi-scale eddy structures over scales is studied using wavelet coefficients. Investigation of the multi-scale eddy structures of circular jet and various wedged jets reveals the transport of the energy of these wedged jets in the space from the axis to the side of the jet, as compared with the circular jet. Furthermore, not only the eddy structures at the wedge tines in the near field are crashed, but also the interactions such as eddy structure union and entrainment take place at different longitudinal and normal locations along with the development of the jets because of the existence of wedges.

Numerical simulation of the structure and variation of upwelling off the east coast of Hainan Island using QuikSCAT winds

The spatial structure and variation of the upwelling in the waters east and northeast of Hainan Island, China during 2000-2007 were investigated using a nested high-resolution Princeton Ocean Model (POM) forced by QuikSCAT winds. The model produced good simulations of the summer upwelling and the seasonal and annual variability. Strong upwelling occurs from mid-July to mid-August with a peak east of Hainan Island associated with the southwesterly monsoon in the South China Sea. Sensitivity experiments indicated that when the local wind stress controls the variability of the upwelling, the large-scale circulation significantly enhances the upwelling northeast of Hainan Island by inducing a local upwelling and transporting cold water northeast-ward along the island's east coast. The joint effects of the local wind stress and large-scale circulation result in stronger upwelling northeast of Hainan Island. This implies that the annual variation of the upwelling northeast of Hainan Island is controlled not only by the local alongshore wind stress but also by the large-scale circulation. This result will help us investigate the decadal variation of the upwelling in this region in the future.

Allowed Parameter Regions for a Tree—Level Inflation Model

The early universe inflation is well known as a promising theory to explain the origin of large-scale structure of universe and to solve the early universe pressing problems. For a reasonable inflation model, the potential during inflation must be very flat, at least, in the direction of the inflaton. To construct the inflaton potential all the known related astrophysics observations should be included. For a general tree-level hybrid inflation potential, which is notdiscussed fully so far, the parameters in it are shown how to be constrained via the astrophysics data observed and to be obtained to the expected accuracy, and to be consistent with cosmology requirements.

Mesoscale structure of the central South China Sea detected by SCSMEX Buoy and Argo float

We addressed the mesoscale structure variation of the central South China Sea （SCS） with the measurements by a long-lived Argo float and a high-resolution ATLAS buoy during 1998-2002. T-S diagram indicates cooling and freshening events in 2000 and 2001 with lower salinity （0.5-0.8） and lower temperature （1-1.7℃）. Significant decrease in the net heat flux and increase in the precipitation suggest that the cooling and freshening is due to extra forcing by the atmosphere. Additional to large year-to-year changes, intraseasonal variability is moderate in the research area. The axis of the maximum intraseasonal temperature and salinity signals are mainly located on the thermocline, Typically, amplitude and period of intraseasonal temperature is about 2℃ and 40-60 days, and that of salinity is 0.34）.5 and 35-60 days. Rapidly-changing winds, heat flux, and precipitation are critical in controlling the intraseasonal fluctuations of the mixed layer of the area. Studies on heat and freshwater balance in the mixed-layer further suggest that horizontal advection plays an important role in intraseasonal fluctuation in the upper ocean. In addition, the energetic mesoscale propagation radiated from the east boundary is linked to the intraseasonal variability in winter.

Healing Temperature of Hybrid Structures Based on Genetic Algorithm

The healing temperature of suspen-dome with stacked arches(SDSA)and arch-supported single-layer lattice shell structures was investigated based on the genetic algorithm. The temperature field of arch under solar radiation was derived by FLUENT to investigate the influence of solar radiation on the determination of the healing temperature. Moreover, a multi-scale model was established to apply the complex temperature field under solar radiation. The change in the mechanical response of these two kinds of structures with the healing temperature was discussed. It can be concluded that solar radiation has great influence on the healing temperature, and the genetic algorithm can be effectively used in the optimization of the healing temperature for hybrid structures.

Inflation Scheme Derived from Universal Wave Function Interpretation of String Theory

Inflation is the most commonly accepted theory in cosmology to explain why the universe appears flat, homogeneous, and isotropic, as well as the origin of the large-scale structure of the cosmos and why no magnetic monopoles have been detected. However, so far, the origin of the inflation epoch and what is the hypothetical field, the inflation, giving rise to inflation, remains unknown. String theory is one of the promising candidates for the grand unification theory. Grand unification theory is to use one mathematic formula to describe everything. In this work, we study the inflation scheme in a new development in string theory, UWFIST （universal wave function interpretation of string theory）. We show that from UWFIST we can derive from the fundamental theory that the long-range vibration is the possible candidate of inflation. We estimate the vacuum energy created by the long-range vibration and show that it can indeed drive the inflation.

Effect of ultrasonic power and casting speed on solidification structure of 7050 aluminum alloy ingot in ultrasonic field

With the experiment and finite element simulation, the influences of power ultrasonic on the solidification structure of 7050 aluminum alloy ingot in semi-continuous casting were researched, and the effects of casting speed on solidification structure in ultrasonic field were also analyzed. The experiment and simulation results show that the solidification structure of the ingot is homogeneously distributed, and its grain size is obviously refined at ultrasonic power of 240 W. The average grain sizes, which can be seen from the Leica microscope, are less than 100 μm. When the casting speed is 45-50 mm/min, the best grain refinement is obtained.

Corrosion properties of plastically deformed AZ80 magnesium alloy

AZ80 magnesium alloys were deformed at 200,250,300,350 and 400℃ with different deformation degree of 50%,75%, 83%,87%and 90%,respectively.The corrosion properties of different deformed AZ80 samples were studied by galvanic test in 3.5%NaCl solution.The results show that plastic deformation could improve the corrosion resistance of AZ80 alloy;and the corrosion rate of AZ80 deformed at 250℃ with the deformation degree of 83%was the lowest,which was 33%of the as-cast AZ80 alloy.Further studies of the microstructure show that the refined grain size and continuously distribution ofβphase around the grain boundary did have a positive effect on the improvement of corrosion resistance of AZ80 alloys.For AZ80 alloys,the smaller the grain size is,the more homogeneous the structure is,and the better the corrosion resistance is.