White球状Patchy模型中纵波传播研究

在球坐标系下用直接求解孔隙弹性方程的方法计算了介观尺度下空间周期排列的White球状Patchy模型中纵波传播问题.首先对纵波的衰减和频散进行了计算,并引入了物理学上声子晶体原理来解释高频时纵波在White球状模型中传播的异常现象.在含水饱和度和速度关系的研究中发现,在低频段用等效流体理论和Gassmann理论估计流体Patchy饱和岩石中的纵波速度完全能够满足当前地震勘探的要求.随后的具有相同含气饱和度但有不同周期的Patchy模型研究结果表明,随着空间周期变大,低频的纵波频散变得明显,纵波衰减峰频率向低频移动,但峰值几乎不变.最后,对单元外层含水中心含油的White球状Patchy模型和中心含气White球状Patchy模型进行研究、对比,发现孔隙流体流动对孔隙介质中的纵波频散、衰减影响显著.另外,在具体数值求解过程中用缩减方程组规模的方法解决了线性方程组严重病态得不到正确结果的问题.

周期成层Patchy模型中纵波的频散和衰减研究

本文用孔隙介质力学的方法来研究纵波在介观周期成层Patchy模型的传播问题.相对于White方法,该方法少了不同介质分界面处的流体压力不等的假设,推导过程更为严密;和Dutta的双相方程解耦方法比较,文中方法直接求解双相方程,形式上更为直观.当纵波通过周期成层孔隙模型时,在低频段用孔隙弹性力学得到纵波频散和衰减结果与用White公式得到的结果符合得很好;周期成层的Patchy孔隙模型由于其空间排列的周期性使其成为孔隙弹性声子晶体,在其频散和衰减曲线上的高频段会出现多个禁带和通带,这使得速度不会随频率单调递增,衰减峰也不只一个.对于地震频段,随着渗透率降低模型的衰减峰向低频移动,这和实际观测结果一致,和传统Biot理论预测结果正相反;随着含气量上升纵波衰减峰值先上升后下降,其最大值出现在含气量0.1左右,这和相关实验结果一致.研究结果表明该模型可以定性解释观测到的地震衰减结果.

Patchy粒子聚集的统计力学研究

应用统计力学原理对AaBb型Patchy粒子的聚集过程进行研究,考察了典型平均物理量在聚集过程中的变化情况.首先基于配分函数导出体系的平衡自由能及描述Patchy粒子之间联接作用的质量作用定律,进而获得团簇的数量分布函数.进一步给出Patchy团簇的数均和重均聚合度以及物理凝胶化条件,探讨了凝胶化区域与Patchy粒子数之间的依赖关系.同时给出Patchy团簇生长的微分动力学方程,并进行了相应的Monte Carlo模拟.本文旨在揭示Patchy粒子的内在和外在因素对体系聚集态结构的影响,为实现对Patchy粒子体系的有效调控提供理论依据.

A_a型Patchy胶体粒子的相态结构

根据热力学微扰理论研究了Aa型Patchy胶体的相态结构,考察了Patch之间的缔合强度及Patch数目对体系相态结构的调控机制.利用相平衡原理给出了Patchy胶体的流体、玻璃态固体和面心立方晶体之间转变及溶胶-凝胶转变的相图,讨论了玻璃态和晶态固相的成核机制、临界现象和相变问题.研究结果表明,Patchy胶体粒子之间的缔合作用和Patch数目可以显著地调控体系的三相点、临界温度和临界密度等特征.在高温条件下,Patchy胶体以一次成核方式结晶;而在低温条件下则以两步成核方式逐步成核结晶,中间经过非晶态的玻璃态固相作为过渡.说明Patchy粒子之间的缔合作用对其相态结构具有决定性影响,因而成为调控体系聚集态结构的重要因素.

Propagation and attenuation of P-waves in patchy saturated porous media

We establish a patchy saturation model and derive the seismic wave equations for patchy saturated porous media on the basis of Biot＇s equations and Johnson＇s bulk modulus. We solve the equations, obtain the attenuation coefficients, and analyze the characteristics of wave attenuation in the seismic frequency range. The results suggest that seismic waves show attenuation and dispersion in partially saturated rocks in the low frequency range. With frequency increasing, attenuation increases. The attenuation of P-waves of the second kind is more pronounced in agreement with Biot＇s theory. We also study the effect of porosity, saturation, and inner sphere radius on the attenuation of the P-waves of the first kind and find that attenuation increases with increasing frequency and porosity, and decreases with increasing frequency and degree of saturation. As for the inner sphere radius, wave attenuation is initially increasing with increasing frequency and inner sphere radius less than half the outer radius. Subsequently, wave attenuation decreases with increasing frequency and inner sphere radius is higher than half the outer sphere radius.

应用周期性成层Patchy模型分析薄层反射特征

针对地下薄储层的物性对地震波的传播和储层厚度的定量预测影响大的问题,基于周期性成层Patchy模型对薄层进行描述,详细推导了地震波在孔隙薄层介质中的传播规律,给出了薄层反射波的振幅和相位的表达式。针对不同物性参数,进一步分析薄层内地震波多次反射叠加后的振幅谱和相位谱特征,发现薄储层的渗透率、孔隙度和饱和度对薄层多次反射波的振幅和相位的峰值频率均有影响,因此,利用薄层厚度对峰值频率的影响规律预测薄层厚度时,必须考虑薄层的物性参数。利用周期性层状Patchy模型建立的薄层介质,克服了均匀各向同性完全弹性薄层介质的局限性。数值分析结果为薄储层的地震资料解释提供了理论依据。

Contribution of patchy reconnection to the ion-to-electron temperature ratio in the Earth’s magnetotail

The ion-to-electron temperature ratio is a good indicator of the processes involved in the plasma sheet.Observations have suggested that patchy reconnection and the resulting earthward bursty bulk flows(BBFs)transport may be involved in causing the lower temperature ratios at smaller radial distances during southward IMF periods.In this paper,we estimate theoretically how a patchy magnetic reconnection electric field can accelerate ions and electrons differently.If both ions and electrons are non-adiabatically accelerated only once within each reconnection,the temperature ratio would be preserved.However,when reconnection occurs closer to the Earth where magnetic field lines are shorter,particles mirrored back from the ionosphere can cross the reconnection region more than once within one reconnection;and electrons,moving faster than ions,can have more crossings than do ions,leading to electrons being accelerated more than ions.Thus as particles are transported from tail to the near-Earth by BBFs through multiple reconnection,electrons should be accelerated by the reconnection electric field more times than are ions,which can explain the lower temperature ratios observed closer to the Earth.

Numerical investigation of solitary wave run-up attenuation by patchy vegetation

Coastal vegetation is capable of decreasing wave run-up.However,because of regrowth,decay or man-made damage,coastal vegetation is always distributed in patches,and its internal distribution is often non-uniform.This study investigates the effects of patchy vegetation on solitary wave run-up by using a numerical simulation.A numerical model based on fully nonlinear Boussinesq equations is established to simulate the wave propagation on a slope with patchy vegetation.By using the model,the process of solitary wave run-up attenuation due to patchy vegetation is numerically analysed.The numerical results reveal that patchy vegetation can considerably attenuate the wave run-up in an effective manner.In addition,high-density patched vegetation can attenuate the solitary wave run-up more effectively than low-density patched vegetation can.For the same density,patchy vegetation with a uniform distribution has a better attenuation effect on wave run-up compared to that of patchy vegetation with a non-uniform distribution.

A patchy-saturated rock physics model for tight sandstone based on microscopic pore structures

The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks.The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation characteristics in reservoir rocks.In the exploration and production of hydrocarbon reservoirs,the real stratum may be partially saturated with a multi-phase fluid mixture in general.Therefore,it is of great significance to investigate the wave velocity dispersion and attenuation features in relation to pore structures and fluids.In this work,the characteristics of fabric microstructures are obtained on the basis of pressure dependency of dry rock moduli using the effective medium theory.A novel anelasticity theoretical model for the wave propagation in a partially-saturated medium is presented by combining the extended Gurevich squirt-flow model and White patchysaturation theory.Numerical simulations are used to analyze wave propagation characteristics that depend on water saturation,external patchy diameter,and viscosity.We consider a tight sandstone from the Qingyang area of the Ordos Basin in west China and perform ultrasonic measurements under partial saturation states and different confining pressures,where the basic properties of the rock are obtained at the full gas saturation.The comparison of experimental data and theoretical modeling results shows a fairly good agreement,indicating that the new theory is effective.

Viscoelastic representation of surface waves in patchy saturated poroelastic media

Wave-induced flow is observed as the domi- nated factor for P wave propagation at seismic frequencies. This mechanism has a mesoscopic scale nature. The inhomogeneous unsaturated patches are regarded larger than the pore size, but smaller than the wavelength. Surface wave, e.g., Rayleigh wave, which propagates along the free surface, generated by the interfering of body waves is also affected by the mesoscopic loss mechanisms. Recent studies have reported that the effect of the wave-induced flow in wave propagation shows a relaxation behavior. Viscoelastic equivalent relaxation function associated with the wave mode can describe the kinetic nature of the attenuation. In this paper, the equivalent viscoelastic relaxation functions are extended to take into account the free surface for the Rayleigh surface wave propagation inpatchy saturated poroelastic media. Numerical results for the frequency-dependent velocity and attenuation and the time-dependent dynamical responses for the equivalent Rayleigh surface wave propagation along an interface between vacuum and patchy saturated porous media are reported in the low-frequency range （0.1-1,000 Hz）. The results show that the dispersion and attenuation and kinetic characteristics of the mesoscopic loss effect for the surface wave can be effectively represented in the equivalent vis- coelastic media. The simulation of surface wave propaga- tion within mesoscopic patches requires solving Blot＇s differential equations in very small grid spaces, involving the conversion of the fast P wave energy diffusion into the Blot slow wave. This procedure requires a very large amount of computer consumption. An efficient equivalent approach for this patchy saturated poroelastic media shows a more convenient way to solve the single phase visco- elastic differential equations.

Crystallization, Vitrification, and Gelation of Patchy Colloidal Particles

We present the phase diagrams for neutral patchy colloidal particles whose surface is decorated by different number of identical patches,where each patch serves as an associating site.The hard-core Lennard-Jones(LJ)potential and associating interaction are incorporated into the free energies of patchy particles in phases of the uid(F),random close packing(RCP),and face-centered-cubic(FCC)crystal.A rich phase structure of patchy particles with F-F,F-RCP,and F-FCC transitions can be observed.Meanwhile,the sol-gel transition(SGT)characterizing the connectivity of patchy particles is also investigated.It is shown that,depending on the number of patches and associating energy,the F-F transition might be metastable or stable with respect to the F-RCP and F-FCC transitions.Meanwhile,the critical temperatures,critical densities,triple points,and SGT can be significantly regulated by these factors.

Importance of bird traits for seed dispersal patterns of co-fruiting trees in a patchy forest

Habitat fragmentation is globally one of the most important drivers of change in biodiversity.Seed dispersal by birds is crucial for tree regeneration in remnant patchy forests,yet how bird traits affect seed dispersal pattern is still poorly understood.We studied the extent to which bird traits affect seed-removal networks and whether these traits affect seed deposition and seedling recruitment for 3 co-fruiting tree species(Taxus chinensis,Cin­namomum bodinieri and Machilus thunbergii)in a patchy forest.A total of 17,18 and 10 bird species were re­corded foraging for seeds of T.chinensis,M.thunbergii and C.bodinieri,respectively.Frequency of bird visi­tation increased with tail length,wing length and body length.Furthermore,bird body length,bill length,body weight and wing length were important in the strength of the seed removal network.During foraging,6 bird species exhibited different patterns of microhabitat utilization and their perching frequency increased with bird weight and tarsus length.As a consequence,frequency of habitat use,bird length and tarsus length were im­portant in determining the number of deposited seeds.For seedling recruitment,seedling number increased with bird tarsus length and weight,but decreased with wing length.Overall,our results showed that various bird traits not only affected seed removal,but also influenced the subsequent processes of seed deposition and seed­ling distribution in a patchy forest.These results thus highlight the importance of large-bodied birds for plant recruitment and point out the need to prioritize the protection and conservation of these birds in remnant patchy forests.

Facile synthesis of asymmetric patchy Janus Ag/Cu particles and study of their antifungal activity

Asymmetric patchy Ag/Cu Janus nanoparticles(NPs)were synthesized via a“seed-mediated”approach.This is the first report of synthesis of nanometer sized metal-based Janus NPs without using complicated methods.Selective adsorption of the surfactant onto the seed NPs leads to the formation of Janus type structure.Subsequently the reduction potential of Ag+/Ag0 and Cu2+/Cu0 systems directs the formation of the“patch”.The patchy Janus NPs show significant antifungal activity towards a potent rice pathogen thus offering the prospect of future application in crop protection.

Gram-scale fabrication of patchy nanoparticles with tunable spatial topology and chemical functionality

Patchy particles,defined as particles with one or more well-defined patches,have attracted much attention due to their anisotropic and.directional interactions.The anisotropic nature of the patchy particle surface enables a certain degree of control over the assembly,process.Enormous efforts have been carried out to design and explore the properties of patchy particles and their collective behaviour.However,the techniques to fabricate patchy particles are still limited in terms of tunability and scalability.In this work,an effective method of fabricating patchy particles with tunable spatial topology and chemical composition of patches is presented.The number,distribution and size of the patches can be tailored by adjusting the packing of the colloidal particles and the processing condition.The active secondary reaction on the polydopamine(PDA)-coated surface and silica surface could functionalize the obtained patchy particles with desired properties to meet different requirements.As a proof of principle,the PDA-coated patches were modified with thiol-based dye via the Michael reaction and the silica surfaces were functionalized with amine-terminated alkoxysilanes via the silane coupling reaction have been demonstrated.Furthermore,the unique properties of PDA,such as reductive ability,powerful'adhesive capability and carbonizable feature,have also been proven to fabricate metallic nanoparticle-decorated patchy particles and anisotropic carbon nanocapsules.The well-defined patchy particles are templated from colloidal crystal and their gram-scale fabrication is easily achieved.These results indicate that our strategy will help access the transformative potential of patchy particles in the rational design and large-scale production of functional materials.

碳酸盐岩储层流体替换中混相流体体积模量的计算

流体替换是研究流体对储层岩石物理参数影响的重要手段。在流体替换过程中,通常使用Woods方程计算混相流体的体积模量,但对于碳酸盐岩储层,由于其基质孔隙度低,岩石内存在不均匀充填的情况,Woods方程不再适用,为此,对斑块充填(Patchy)条件下混相流体体积模量的计算方法进行了更为深入的研究。通过对Patchy模型极端情形的研究,得到了饱和斑块充填情况下混相流体的计算模型。混相流体均匀充填和饱和斑块充填模型分别对应于混相流体充填的两种极端情况,所计算的结果分别是实际混相流体体积模量的上限和下限。考虑实际储层中混相流体的复杂充填状态,将利用Woods方程和Patchy模型计算的流体体积模量取算术平均(VRH模型),所得结果作为近似的混相流体体积模量。南方某探区碳酸盐岩储层实际流体替换结果表明,利用Woods方程和Patchy模型计算的结果有明显差异,利用VRH模型计算的结果是较为可信的。

流体替换方法研究及应用分析

流体替换即为从一种孔隙流体状态下的岩石物理参数计算出另一种流体状态下的岩石物理参数.流体替换对于地震属性分析具有重要作用,其为解释人员进行AVO(振幅随偏移距变化)及四维地震研究提供了正演模拟及定量分析的工具.通常流体替换都是采用基于wood方程的Gassmann流体替换方法.本文借鉴Patchy saturation模型,及Brie经验模型分别提出了针对流体不均匀分布的Patchy saturation模型流体替换方法,及基于经验关系的Brie经验模型流体替换方法.并基于岩石物理实验比较分析了以上三种流体替换方法.通过目标区岩石物理分析,可以从中优选出更合适的流体替换方法,从而为流体的地震响应分析提供正确的指导.

Intraclonal Resource Sharing and Functional Specialization of Ramets in Response to Resource Heterogeneity in Three Stoloniferous Herbs

Environments with reciprocal patchiness of resources, in which the availability of two resources such as light and soil nutrients are patchily distributed in horizontal space and negatively correlated in each patch, are common in many ecosystems. The strategies by which clonal plants adapt to this type of heterogeneous environment were examined in three stoloniferous herbs,Potentilla reptans L. var. sericophylla Franch., P. anserina L. and Halerpestes ruthenica (Jacq.) Qvcz., commonly inhabiting forest understories, grasslands and low saline meadows, respectively. As pairs of connected ramets were subjected to reciprocal patchiness of light and nutrients, stolon connection between the two ramets significantly enhanced biomass of both ramet growing in low light intensity but high soil nutrient condition (LH ramet) and ramet growing in high light intensity but low soil nutrient condition (HL ramet) as well as whole ramet pairs (consisting of LH ramets and HL ramets). Additionally, stolon connection greatly increased root/shoot ratio of LH ramet while significantly decreased that of HL ramet. The results indicate that a reciprocal transportation of resources between interconnected ramets and a functional specialization of ramets in uptake of abundant resources occurred. By resource sharing and functional specialization, clonal plants can efficiently acquire locally abundant resources and buffer the stress caused by reciprocal patchiness of resources.

Preservation and variation of ion-to-electron temperature ratio in the plasma sheet in geo-magnetotail

The ion-to-electron temperature ratio is a good indicator of the processes involved in solar wind plasma entering and being transported inside Earth’s plasma sheet.In this study,we have demonstrated that patchy magnetic reconnection has the potential to preserve the ion-to-electron temperature ratio under certain conditions.If the charged particles are non-adiabatically accelerated no more than once in a single reconnection,the temperature ratio would be preserved;on the other hand,this ratio would not be preserved if they are accelerated multiple times.Consequently,under a northward interplanetary magnetic field(IMF)condition,the reconnection in the nonlinear phase of the Kelvin-Helmholtz instability is the dominant process for solar-originated plasma entering the Earth’s magnetosphere,and the ion-to-electron temperature ratio is preserved inside the plasma sheet.When the direction of the IMF is southward,the reflection of electrons from the magnetic mirror point,and subsequent multiple non-adiabatic accelerations at the reconnection site,are the primary reasons for the observed low ion-to-electron temperature ratio close to the Earth at midnight.While reconnections that occur in the night-side far tail might preserve the ratio,turbulence on the boundaries of the bursty bulk flows(BBFs)could change the ratio in the far tail through the violation of the frozen-in condition of the ions.The plateau in the contour of the calculated ion-to-electron temperature ratio in the down tail distance between 40 and 60 Earth radii may explain the strong correlation between the ion and electron temperatures in the outer central plasma sheet,which has not been clearly understood till date.

Petrogenesis of basaltic shergottite NWA 8656

Most basaltic shergottites are too Mg-rich to represent parent melt compositions because they contain some cumulus pyroxenes. However, basaltic shergottite Northwest Africa(NWA) 8656 with subophitic texture can be used as the parent melt composition in petrogenetic studies because it contains no or rare cumulus pyroxenes. Its pyroxene cores(Mg# 66-68, the most magnesian) are in equilibrium with the bulk rock composition based on major(Fe-Mg) and trace elements(REE—rare earth elements).The patchy zoning of pyroxenes has been interpreted as reflecting a two-stage crystallization history: 1) crystallization of Mg-rich pyroxene cores at depth(50 km, the base of Martian crust), 2) crystallization of Fe-rich pyroxene rims at the shallow depth near the Martian surface with a fast cooling history. The crystallization of Fe-rich pyroxenes and the existence of different symplectites indicate that NWA 8656 underwent eruption. The oxygen fugacity of NWA 8656(QFM –0.9±0.5) suggests an oxidized condition at the late-stage crystallization process, and the CI-normalized REE patterns of different minerals show enrichment in LREE, compared to that of depleted shergottites. Both of these observations suggest a relatively ITE(incompatible trace elements)-enriched signature of NWA 8656, similar to those of other enriched shergottites. The REE compositions of augite core and rim and plagioclase can be successfully reproduced by progressive crystallization without exogenous components, which indicates a closed magmatic system for NWA 8656. Consequently, we conclude that the ITE-enriched signature of NWA 8656 is inherited from an enriched mantle source rather than caused by crustal assimilation. Moreover, partial melting of depleted Martian mantle could not directly yield magmas that have geochemical characteristics similar to enriched shergottite parent magmas, so the enriched and depleted shergottites are derived from distinct mantle sources, and the mantle source of enriched shergottites would be expected to contain ilmenite.

Biostratigraphy and Sequence Stratigraphy of the Tarbur Formation(Maastrichtian)from Iranian Zagros Foreland Basin,Southwest of Iran

Shallow carbonate deposits(Tarbur Formation)were formed in the Zagros foreland basin with dynamic tectonics during the Maastrichtian age.From the viewpoint of reconstruction of depositional conditions in these deposits,studies of biostratigraphy,microfacies,microtaphofacies,and sequence stratigraphy were performed in a single area at Tang-e Shabi Khoon,northwest of Zagros.Based on the identification of two assemblage zones consisting of benthic foraminifera in these strata,the formation was deposited during the middle to late Maastrichtian.The number of cycles in test size and type of coiling in Loftusia decreased from the study area toward the northwest of the Neotethys basin.The input of clastic sediments affected the distribution of Loftusia and rudists in the study area.Nine microfacies,six microtaphofacies,and one terrigenous facies(shale)were identified based on the sedimentary features.These deposits of the middle-late Maastrichtian were deposited on a homoclinal carbonate ramp.The platform can be divided into restricted and semi-restricted lagoon,shoal,and open marine environments.In the study area,the deposits of the Tarbur Formation were deposited during four third-order depositional sequences.Local fault activities affected the formation of depositional sequences in the study area.