A novel box-counting method for quantitative fractal analysis of threedimensional pore characteristics in sandstone

Fractal theory offers a powerful tool for the precise description and quantification of the complex pore structures in reservoir rocks,crucial for understanding the storage and migration characteristics of media within these rocks.Faced with the challenge of calculating the three-dimensional fractal dimensions of rock porosity,this study proposes an innovative computational process that directly calculates the three-dimensional fractal dimensions from a geometric perspective.By employing a composite denoising approach that integrates Fourier transform(FT)and wavelet transform(WT),coupled with multimodal pore extraction techniques such as threshold segmentation,top-hat transformation,and membrane enhancement,we successfully crafted accurate digital rock models.The improved box-counting method was then applied to analyze the voxel data of these digital rocks,accurately calculating the fractal dimensions of the rock pore distribution.Further numerical simulations of permeability experiments were conducted to explore the physical correlations between the rock pore fractal dimensions,porosity,and absolute permeability.The results reveal that rocks with higher fractal dimensions exhibit more complex pore connectivity pathways and a wider,more uneven pore distribution,suggesting that the ideal rock samples should possess lower fractal dimensions and higher effective porosity rates to achieve optimal fluid transmission properties.The methodology and conclusions of this study provide new tools and insights for the quantitative analysis of complex pores in rocks and contribute to the exploration of the fractal transport properties of media within rocks.

Fabrication and abrasive wear properties of metal matrix composites reinforced with three-dimensional network structure

Reticulated polyurethane was chosen as the preceramic material for preparing the porous preform using the replication process. The immersing and sintering processes were each performed twice for fabricating a high-porosity and super-strong skeleton. The aluminum magnesium matrix composites reinforced with three-dimensional network structure were prepared using the infiltration technique by pressure assisting and vacuum driving. Light interfacial reactions have played a profitable role in most of the ceramic-metal systems. The metal matrix composites interpenetrated with the ceramic phase have a higher wear resistance than the metal matrix phase. The volume fraction of ceramic reinforcement has a significant effect on the abrasive wear, and the wear rate can be decreased with the increase of the volume fraction of reinforcement.

Symplectic analysis for elastic wave propagation in two-dimensional cellular structures

On the basis of the finite element analysis, the elastic wave propagation in cellular structures is investigated using the symplectic algorithm. The variation principle is first applied to obtain the dual variables and the wave propagation problem is then transformed into two-dimensional （2D） symplectic eigenvalue problems, where the extended Wittrick-Williams algorithm is used to ensure that no phase propagation eigenvalues are missed during computation. Three typical cellular structures, square, triangle and hexagon, are introduced to illustrate the unique feature of the symplectic algorithm in higher-frequency calculation, which is due to the conserved properties of the structure-preserving symplectic algorithm. On the basis of the dispersion relations and phase constant surface analysis, the band structure is shown to be insensitive to the material type at lower frequencies, however, much more related at higher frequencies. This paper also demonstrates how the boundary conditions adopted in the finite element modeling process and the structures＇ configurations affect the band structures. The hexagonal cells are demonstrated to be more efficient for sound insulation at higher frequencies, while the triangular cells are preferred at lower frequencies. No complete band gaps are observed for the square cells with fixed-end boundary conditions. The analysis of phase constant surfaces guides the design of 2D cellular structures where waves at certain frequencies do not propagate in specified directions. The findings from the present study will provide invaluable guidelines for the future application of cellular structures in sound insulation.

Design,Synthesis and Crystal Structure of Two One-dimensional Zigzag Chain-like Compounds

Two one-dimensional chain-like cyanide-bridged compounds, [Fe（Phen）2（CN）2Ni（Cyclam）]（ClO4）2·DMF-2H2O 1 （Cyclam = 1,4,8,11-tetraaza-cyclotetradecane, Phen = 1,10-phenanthroline, and DMF = N,N-dimethylformamide） and [Fe（Phen）2（CN）2Zn（Cyclam）]（PF6）2·CH3CN 2, were prepared by the reaction of [Fe（Phen）2（CN）2]·2H2O with M（Cyclam）^2＋ （M = Ni, Zn）. In complexes 1 and 2, the metal atoms are connected alternatively with CN groups. X-ray structure and IR analyses for 1 and 2 were performed. Structure analysis revealed that both complexes are centrosymmetric and the geometry around each metal atom is an octahedron. The two complexes crystallize in triclinic with space group of P^1-. For 1, a = 10.439（4）, b = 14.976（7）, c = 15.914（8）A,α = 83.168（15）, β = 74.338（15）, γ = 78.023（15）°, V = 2338.3（18）A^3, Z = 2, Mr = 1035.37, Dc = 1.471 g/cm^3, F（000） = 1076,μ = 0.895 mm^-1, the final R = 0.0616 and wR = 0.1414 for 5849 observed reflections （1 〉 2σ（I））. For 2, a = 9.656（6）, b = 15.404（9）, c = 15.822（10）A, α = 78.68（2）, β= 78.917（19）, γ = 77.15（2）°, V = 2223（2）A^3, Z = 2, Mr = 1064.87, Dc = 1.587 g/cm^3, F（000） = 1078,μ = 1.032 mm^-1, the final R = 0.0672 and wR = 0.1595 for 6819 observed reflections （I 〉 2σ（I））.

[(n-C_4H_9)_3SnO_2C(CH_2)_2CO_2Sn(C_4H_9-n)_3]: A Novel Three-dimensional Framework Structure of Organotin Complex

The bis(tributyltin) ester of succinic acid was synthesized by the reaction of disodium salt of succinic acid with tributyltin chloride in a molar ratio of 1:2. The crystal structure was determined by X-ray single-crystal diffraction. It belongs to orthorhombic with space group Pccn, a = 20.949(3), b = 17.470(3), c = 20.345(3) , V = 7446(2) 3, Z = 8, Dc = 1.242 g/cm3, m = 1.365 mm-1, F(000) = 2864, R = 0.0544 and wR = 0.1417. The tin atom is of five-coordination in a trigonal bipyramidal structure by bridging two carboxylate groups in different directions and the resulting structure which contains straight twist large ring channels along the axes of a, b and c is a three-dimensional framework polymer containing two different tin atoms.

A Two-dimensional Supramolecular Complex Constructed by 1,10-Phenanthroline Derivative Ligand:Synthesis,Structure and Luminescence

An unusual two-dimensional supramolecular complex, namely, [Cd2（Cl）4（L）2]（1）, has been synthesized by 2-（1 H-imidazo[4,5-f][1,10]phenanthrolin-2-yl）phenol（L） and CdCl2·2.5H2O under hydrothermal conditions. The compound was characterized by elemental analysis, TG and single-crystal X-ray diffraction. It crystallizes in triclinic, space group P1 with a = 10.151（2）, b = 14.119（3）, c = 14.744（3） ？, α = 115.744（4）, β = 108.063（4）, γ = 93.371（4）o, V = 1762.7（7） A°^3, Z = 2, C（38）H（24）Cd2Cl4N8O2, Mr = 991.25, Dc = 1.868 g/cm^3, F（000） = 976, μ（Mo Ka） = 1.560 mm^-1, R = 0.0639 and w R = 0.1307. In 1, two Cd（II） atoms are bridged by two chroline atoms to give a dimer. Neighboring dimers are linked by N–H···Cl hydrogen bonds to afford supramolecular chains, which are further joined together by π-π interactions to result in a supramolecular layer. In addition, luminescent property and thermal behavior of compound 1 have been studied.

The three-dimensional structure and seasonal variation of the North Pacific meridional overturning circulation

The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation （NPMOC） are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data. The NPMOC displays a multi-cell structure with four cells in the North Pacific altogether. The TC and the STC are a strong clockwise meridional cell in the low latitude ocean and a weaker clockwise meridional cell between 7°N and 18°N, respectively, while the DTC and the subpolar cell are a weaker anticlockwise meridional cell between 3°N and 15°N and a weakest anticlockwise meridional cell between 35°N and 50°N, respectively. The DTC, the TC and the STC are all of very strong seasonal variations. As to the DTC, the southward transport is strongest in fall and weakest in spring. For the TC, the northward transport is strongest in winter and weakest in spring, while the southward transport is strongest in fall and weakest in spring, which is associated with the strong southward fiow of the DTC in fall. As the STC, the northward transport is strongest in winter and weakest in summer, while the southward transport is strongest in summer and weakest in spring. This seasonal difference may be associated with the DTC. The zonal wind stress and the east-west slope of sea level play important roles in the seasonal variations of the TC, the STC and the DTC.

Three-dimensional simulation of a Ka-band relativistic Cherenkov source with metal photonic-band-gap structures

This paper presents a three-dimensional particle-in-cell （PIC） simulation of a Ka-band relativistic Cherenkov source with a slow wave structure （SWS） consisting of metal photonic band gap （PBG） structures. In the simulation, a perfect match layer boundary is employed to absorb passing band modes supported by the PBG lattice with an artificial metal boundary. The simulated axial field distributions in the cross section and surface of the SWS demonstrate that the device operates in the vicinity of the π point of a TM01-1ike mode. The Fourier transformation spectra of the axial fields as functions of time and space show that only a single frequency appears at 36.27 GHz, which is in good agreement with that of the intersection of the dispersion curve with the slow space charge wave generated on the beam. The simulation results demonstrate that the SWS has good mode selectivity.

Infinite Three-Dimensional Coordination Polymers: Synthesis and Structures of [Cd (4,4'-bpy)_2 (H_2O)_2]_n (pic)_(2n),[Zn (4,4'-bpy)_2 (H_2O)_2]_n(pic)_(2n) (H_2O)_(2n), and [Zn (4,4'-bpy)_2 (H_2O)_2]_n (4,4'-bpy)_n(H_2O)_n (pic)_(2n)

Three Complexes of the formula [Cd (4,4'-bpy)_2 (H_2O)_2]_n. (pic)_(2n) (1) [Zn (4,4'-bpy)_2 (H_2O)]_n (4,4'-bpy)_n(H_2O)_n (pic)-(2n) (2) and [Zn (4,4'-bpy)_2 (H_2O)]_n (4,4'-bpy)_n (pic)-(2n)(H_2O)_n (3) (4.4'-bpy = 4.4'-bipyridine. pic = picric anion ) have been synthesized and characterized by elemental analysis and single-crystal x-ray diffraction. They all have infinite three-dimensional network structure. crystallizing in the monoclinic space group C2/c (1) and Cc (2.3).

Three-dimensional structure of lymphatics in rabbit stomach

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A DESIGN OF THREE-DIMENSIONAL SPATIAL DATA MODEL AND ITS DATA STRUCTURE IN GEOLOGICAL EXPLORATION ENGINEERING

The key to develop 3-D GISs is the study on 3-D data model and data structure. Some of the data models and data structures have been presented by scholars. Because of the complexity of 3-D spatial phenomenon, there are no perfect data structures that can describe all spatial entities. Every data structure has its own advantages and disadvantages. It is difficult to design a single data structure to meet different needs. The important subject in the3-D data models is developing a data model that has integrated vector and raster data structures. A special 3-D spatial data model based on distributing features of spatial entities should be designed. We took the geological exploration engineering as the research background and designed an integrated data model whose data structures integrats vector and raster data byadopting object-oriented technique. Research achievements are presented in this paper.

Synthesis and Crystal Structure of One-dimensional Chain Complexes [K(18-C-6)]_2[M(mnt)_2](M=Zn,Hg)

The reactions of 18 crown 6 with each of K 2(M=Zn, Hg; mnt=1,2 dicyanoethene 1,2 dithiolate, C 2S 2(CN) 2- 2) were studied and novel complexes [K(18 C 6)] 2[Zn(mnt) 2](1) and [K(18 C 6)] 2[Hg(mnt) 2](2) were characterized by elemental analysis, IR spectrum and X ray diffraction analysis. Complex 1 displays a one dimensional chain of [K(18 C 6)] 2[Zn(mnt) 2] bridged by K O interactions between adjacent [K(18 C 6)] + units. Complex 2 is also a one dimensional chain of [K(18 C 6)] 2[Hg(mnt) 2] bridged by K...S weak interactions between adjacent [K(18 C 6)] + and [Hg(mnt) 2] 2- .

The Luminescence of The Phosphor Sr_2ZrO_4 with One-dimensional Chains Structure

A new type of phosphor Sr2ZrO4 with one-dimensional structure was prepared bysolid reaction and its luminescence is seen at room temperature. The excitation and emissionspectra were measured and display broad maximum at 354 nm and 386 nm respectively. Themechanism of this luminescence is ascribed to charge transfer.

Structured mirror array for two-dimensional collimation of a chromium beam in atom lithography

Direct-write atom lithography,one of the potential nanofabrication techniques,is restricted by some difficulties in producing optical masks for the deposition of complex structures.In order to make further progress,a structured mirror array is developed to transversely collimate the chromium atomic beam in two dimensions.The best collimation is obtained when the laser red detunes by natural line-width of transition 7S3 → 7P40 of the chromium atom.The collimation ratio is 0.45 vertically（in x axis）,and it is 0.55 horizontally（in y axis）.The theoretical model is also simulated,and success of our structured mirror array is achieved.

The Shengli I Point Bar on the Yellow River Delta: Three-Dimensional Structures and Their Evolution

Point bars are well developed on the Yellow River delta, an~ which theShengli I point bar is the most typical. The point bar, being about 4 km in length and several tensto more than 100 meters in width, is located on the south side of the Shengli Bridge in KenliCounty, Dongying, Shandong. It is a typical fine-grained point bar with silt, which is predominant,some clay and minor plant debris and clay boulders. The Shengli I Point bar has complicated 3-Dstructures. Firstly, in a plane view, it comprises mainly eight sedimentary units, bar edge, baredge, bar platform, bar plain, bar channel, bar gully, bar pond and bar bay, developing side by sideand superimposed one by one m a complex way. Secondly, its vertical structures are very complex dueto the partial superimposition of the 8 sedimentary units. Besides hydatogenesis, very intensivewind erosion, eolian, ice and meltwater actions are also visible on the Shengli I point bar. Thecomplex form is made even more complicated because of the above co-actions.

LOW-DIMENSIONAL STRUCTURES:SP ARSE CODING FOR NEURONAL ACTIVITY

Neuronal ensemble activity codes working memory.In this work,we developed a neuronal ensemble sparse coding method,which can effectively reduce the dimension of the neuronal activity and express neural coding.Multichannel spike trains were recorded in rat prefrontal cortex during a work memory task in Y-maze.As discretesignals,spikes were transferred into cont inuous signals by estinating entropy.Then the normalized continuous signals were decomposed via non-negative sparse met hod.The non-negative components were extracted to reconstruct a low-dimensional ensemble,while none of the feature components were missed.The results showed that,for well-trained rats,neuronal ensemble activities in the prefrontal cortex changed dynamically during the.working memory task.And the neuronal ensemble is more explicit via using non-negative sparse coding.Our results indicate that the neuronal ensemblesparse coding method can effectively reduce the dimnension of neuronal activity and it is a useful tool to express neural coding.

Three-dimensional visualization of soil pore structure using computed tomography

The geometric and spatial characteristics of pore structures determine the permeability and water retention of soils, which have important effects on soil functional diversity and ecological restoration. Until recently, there have not been tools and methods to visually and quantitatively describe the characteristics of soil pores. To solve this problem, this research reconstructs the geometry and spatial distribution of soil pores by the marching cubes method, texture mapping method and the ray casting method widely used in literature. The objectives were to explore an optimal method for three-dimensional visualization of soil pore structure by comparing the robustness of the three methods on soil CT images with single pore structure and porosity ranging from low (2–5%) to high (12–18%), and to evaluate the reconstruction performance of the three methods with different geometric features. The results demonstrate that there are aliases (jagged edges) and deficiency at the boundaries of the model reconstructed by the marching cubes method and pore volumes are smaller than the ground truth, whereas the results of the texture mapping method lack the details of pore structures. For all the soil images, the ray casting method is preferable since it better preserves the pore characteristics of the ground truth. Furthermore, the ray casting method produced the best soil pore model with higher rendering speed and lower memory consumption. Therefore, the ray casting method provides a more advanced method for visualization of pore structures and provides an optional technique for the study of the transport of moisture and the exchange of air in soil.

Synthesis and One-dimensional Structure of Cobalt(Ⅱ) Complex [(NaOC_2H_5)CoL_2]_n

The treatment of bis(2-hydroxybenzyl)-amine(HL) with NaOH and Co(Ⅱ)(NO) 2 gives isostructural one-dimensional coordination polymers [(NaOC2H5)CoL2]n(1). The cobalt ions have an octahedral geometry and are coordinated by two crystallographically independent ligands which are further linked by μ -O\-\{phenol\} bridged Co and Na atoms to give a one-dimentional structure.

One-dimensional nano-structure of Cu-Zn-Al alloy

Cu-Zn-Al alloy of one dimensional nano-structure was prepared and thestructure of obtained nano-material was characterized by transmission electron microscope (TEM). Itwas shown that there are non-linear oscillations on the surface of Cu-Zn-Al alloy and theconsanguineous connection exists between non-linear oscillation and the growth process of onedimensional nano-structure. The diameter of one dimensional nano-structure is about 40 nm, and theratio of length to diameter is over 40. Finally, the growth mechanism of one dimensionalnano-structure was also studied.

Three-dimensional P velocity structure in Beijing area

A detail three-dimensional P wave velocity structure of Beijing, Tianjin and Tangshan area (BTT area) was deter-mined by inverting local earthquake data. In total 16 048 P wave first arrival times from 16048 shallow and mid-depth crustal earthquakes, which occurred in and around the BTT area from 1992 to 1999 were used. The first arrival times are recorded by Northern China United Telemetry Seismic Network and Yanqing-Huailai Digital Seismic Network. Hypocentral parameters of 1 132 earthquakes with magnitude ML=1.7~6.2 and the three-dimensional P wave velocity structure were obtained simultaneously. The inversion result reveals the com-plicated lateral heterogeneity of P wave velocity structure around BTT area. The tomographic images obtained are also found to explain other seismological observations well.