2.5D scattering of incident plane SV waves by a canyon in layered half-space

This paper presents a 2.5D scattering of incident plane SV waves by a canyon in a layered half-space by using the indirect boundary element method （IBEM）. A free field response analysis is performed to provide the displacements and stresses on the boundary of the canyon where fictitious uniform moving loads are applied to calculate the Green＇s fi.mctions for the displacements and stresses. The amplitudes of the loads are determined by the boundary conditions. The free field displacements are added to the fictitious uniform moving loads induced displacements and the total response is obtained. Numerical calculations are performed for a canyon with homogenous and in one layer over bedrock. The effects of the thickness and stiffness of the layer on the amplification are studied and discussed.

Green's function of multi-layered poroelastic half-space for models of ground vibration due to railway traffic

This study proposes a Green＇s function, an essential representation of water-saturated ground under moving excitation, to simulate ground borne vibration from trains. First, general solutions to the governing equations of poroelastic medium are derived by means of integral transform. Secondly, the transmission and reflection matrix approach is used to formulate the relationship between displacement and stress of the stratified ground, which results in the matrix of the Green＇s function. Then the Green＇s function is combined into a train-track-ground model, and is verified by typical examples and a field test. Additional simulations show that the computed ground vibration attenuates faster in the immediate vicinity of the track than in the surrounding area. The wavelength of wheel-rail unevenness has a notable effect on computed displacement and pore pressure. The variation of vibration intensity with the depth of ground is significantly influenced by the layering of the strata soil. When the train speed is equal to the velocity of the Rayleigh wave, the Mach cone appears in the simulated wave field. The proposed Green＇s function is an appropriate representation for a layered ground with shallow ground water table, and will be helpful to understand the dynamic responses of the ground to complicated moving excitation.

Seismogram Synthesis in Multi-layered Half-space Part Ⅰ. Theoretical Formulations

In the past two decades numerous studies were made to develop and improve the theory and practical computation techniques of synthesizing theoretical seismograms for the model of multi-layered half-space. Today, synthesizing theoretical seismograms in multi-layered half-space is an important tool for understanding the structure of the Earth’s interior as well as the seismic source process from well-recorded seismograms data. As part of a review of the state-of-the-art, in this article I shall present a systematic and self-contained theory of elastic waves in multi-layered half-space media based on the developments in the past two decades.

In-plane dynamic Green's functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic half-space

The dynamic stiffness method combined with the Fourier transform is utilized to derive the in-plane Green’s functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic（TI）half-space.The loaded layer is fixed to obtain solutions restricted in it and the corresponding reactions forces,which are then applied to the total system with the opposite sign.By adding solutions restricted in the loaded layer to solutions from the reaction forces,the global solutions in the wavenumber domain are obtained,and the dynamic Green’s functions in the space domain are recovered by the inverse Fourier transform.The presented formulations can be reduced to the isotropic case developed by Wolf（1985）,and are further verified by comparisons with existing solutions in a uniform isotropic as well as a layered TI halfspace subjected to horizontally distributed loads which are special cases of the more general problem addressed.The deduced Green’s functions,in conjunction with boundary element methods,will lead to significant advances in the investigation of a variety of wave scattering,wave radiation and soil-structure interaction problems in a layered TI site.Selected numerical results are given to investigate the influence of material anisotropy,frequency of excitation,inclination angle and layered on the responses of displacement and stress,and some conclusions are drawn.

A new layered space-time detection algorithm for frequency selective fading multiple-input multiple-output channels based on particle filter

In this paper, a new observation equation of non-Gaussian frequency selective fading Bell Labs layered space time （BLAST） architecture system is proposed, which is used for frequency selective fading channels and non-Gaussian noise in an application environment of BLAST system. With othogonal matrix triangularization （QR decomposition） of the channel matrix, the static observation equation of frequency selective fading BLAST system is transformed into a dynamic state space model, and then the particle filter is used for space-time layered detection. Making the full use of the finite alphabet of the digital modulation communication signal, the optimal proposal distribution can be chosen to produce particle and update the weight. Incorporated with current method of reducing error propagation, a new space-time layered detection algorithm is proposed. Simulation result shows the validity of the proposed algorithm.

3D scattering of obliquely incident plane SV waves by an alluvial valley embedded in a fluid-saturated, poroelastic layered half-space

The indirect boundary element method is used to study the 3D dynamic response of an infinitely long alluvial valley embedded in a saturated layered half-space for obli- quely incident SV waves. A wave-number transform is first applied along the valley＇s axis to reduce a 3D problem to a 2D plane strain problem. The problem is then solved in the section perpendicular to the axis of the valley. Finally, the 3D dynamic responses of the valley are obtained by an inverse wave-number transform. The validity of the method is con- firmed by comparison with relevant results. The differences between the responses around the valley embedded in dry and in saturated poroelastic medium are studied, and the effects of drainage conditions, porosity, soil layer stiffness, and soil layer thickness on the dynamic response are dis- cussed in detail resulting in some conclusions.

Space Charge Layer Eff ect in Sulfide Solid Electrolytes in All-Solid-State Batteries: In-situ Characterization and Resolution

All-solid-state lithium batteries(ASSLBs)have advantages of safety and high energy density,and they are expected to become the next generation of energy storage devices.Sulfide-based solid-state electrolytes(SSEs)with high ionic conduc-tivity and low grain boundary resistance exhibit remarkable practical application.However,the space charge layer(SCL)eff ect and high interfacial resistance caused by a mismatch with the current commercial oxide cathodes restrict the develop-ment of sulfide SSEs and ASSLBs.This review summarizes the research progress on the SCL eff ect of sulfide SSEs and oxide cathodes,including the mechanism and direct evidence from high performance in-situ characterizations,as well as recent progress on the interfacial modification strategies to alleviate the SCL eff ect.This study provides future direction to stabilize the high performance sulfide-based solid electrolyte/oxide cathode interface for state-of-the-art ASSLBs and future all-SSE storage devices.

Dynamic soil-tunnel interaction in layered half-space for incident plane SH waves

The dynamic soil-tunnel interaction is studied by indirect boundary element method （IBEM）, using the model of a rigid tunnel in layered half-space, which is simplified to a single soil layer on elastic bedrock, subjected to incident plane SH waves. The accuracy of the results is verified through comparison with the analytical solution. It is shown that soil-tunnel interaction in layered half-space is larger than that in homogeneous half-space and this interaction mechanism is essentially different from that of soil-foundation-superstructure interaction.

Dynamic soil-tunnel interaction in layered half-space for incident P-and SV-waves

The dynamic soil-tunnel interaction is studied by the model of a rigid tunnel embedded in layered half-space, which is simplified as a single soil layer on elastic bedrock to the excitation of P- and SV-waves. The indirect boundary element method is used, combined with the Green＇ s function of distributed loads acting on inclined lines. It is shown that the dynamic characteristics of soil-tunnel interaction in layered half-space are different much from that in homoge- neous half-space, and that the mechanism of soil-tunnel interaction is also different much from that of soil-founda- tion-superstructure interaction. For oblique incidence, the tunnel response for in-plane incident SV-waves is com- pletely different from that for incident SH-waves, while the tunnel response for vertically incident SV-wave is very similar to that of vertically incident SH-wave.

Time domain method for calculating free field motion of a layered half-space subjected to obliquely incident body waves

In numerical simulation of wave scattering under oblique incident body waves using the finite element method, the free field motion at the incident lateral boundary induced by the background layered half-space complicates the computational area. In order to replace the complex frequency domain method, a time-domain method to calculate the free field motion of a layered half-space subjected to oblique incident body waves is developed in this paper. The new method decouples the equations of motion used in the finite element method and offers an interpolation formula of the free field motion. This formula is based on the fact that the apparent horizontal velocity of the free field motion is constant and can be calculated exactly. Both the theoretical analysis and numerical results demonstrate that the proposed method offers a high degree of accuracy.

3D Diffraction of obliquely incident SH waves by twin infinitely long cylindrical cavities in layered poroelastic half-space

Abstract This paper studies three-dimensional diffraction of obliquely incident plane SH waves by twin infinitely long cylindrical cavities in layered poroelastic half-space using indirect boundary element method. The approach is validated by comparison with the literature, and the effects of cavity interval, incident frequency, and boundary drainage condition on the diffraction are studied through numerical examples. It is shown that, the interaction between two cavities is significant and surface displacement peaks become large when two cavities are close, and the surface displacement may be significantly amplified by twin cavities, and the influence range with large amplification can be as wide as 40 times of the cavity radius. Surface displacements in dry poroelastic case and saturated poroelastic cases with drained and undrained boundaries are evidently different under certain circumstances, and the differences may be much larger than those in the free-field response.

The Behaviour of Vertical Bell Laboratories Layered Space-Time Algorithm Combined with Multiuser Detection Schemes in Wireless Communication System

This paper provides the performance analysis of multiuser Vertical Bell Laboratories Layered Space-Time (V-BLAST) system receiver structures for Multiple-input Multiple-Output (MIMO) channel at a base station with assumption of perfect channel estimation and perfect timing delay estimation. In MIMO channels the receivers such as decorrelator, Minimum Mean Square Error (MMSE) and Multistage Parallel Interference Cancellation (MPIC) receiver outperform the conventional receiver. Withal, since the multiple antenna interference led to a strong impact on the performance degradation of a multistage interference cancellation receiver, the performance of MPIC receiver was highly degraded based on system loading.

煤沥青交联改性处理对碳结构的影响

沥青基炭制品的碳结构高度依赖前驱体沥青的性质。采用化学交联的方法对沥青进行改性处理时,尽管化学交联的反应机理为亲电取代反应,但交联剂、催化剂的种类不同,沥青改性程度存在差异,进而影响炭制品结构。以中低温煤沥青为原料,探索3种交联剂(对苯二甲醇(PXG)、苯甲醛(BA)、对苯二甲酰氯(TPC))、5种催化剂(对甲苯磺酸、浓硫酸、浓硝酸、浓盐酸、硼酸)对沥青交联改性后炭制品结构的影响。通过TG-DTG、FT-IR研究交联改性后沥青热稳定性及沥青官能团的变化;借助XRD、Raman表征改性后沥青炭制品的微观结构差异。结果表明:交联剂和催化剂的存在促进了沥青分子的交联,有效阻止了热转化过程中轻组分挥发,提高了沥青的结焦值、软化点、热稳定等指标。以PXG为交联剂,沥青支链上亚甲基CH_(2)的H不易被取代;而以硼酸为催化剂时,支链末端甲基上的H易被取代;以BA为交联剂,取代氢的位置明显发生在芳香环上;以TPC为交联剂、浓硫酸为催化剂时,交联产品的C=0官能团含量增加,说明在这种组合下,TPC参加反应较多。无论与哪种交联剂相结合,浓盐酸为催化剂时,交联反应更易促进苯环上和支链上的C—H键发生取代反应。经过交联改性后的沥青,炭化过程中分子间较强的π-π相互作用减弱,有效阻止碳有序结构的形成,碳无序结构含量I_(D)/I_(G)增大。同时碳微晶层间距d_(002)明显增加,有序堆积平均堆积高度L_(c)减小,芳香层数降低,说明化学交联不仅影响有序碳结构排列,还可抑制碳微晶结构发育。其中硼酸作为催化剂时,催化效果更理想。获得的炭制品d_(002)在同组产品中最大。PXG、硼酸组合与沥青发生交联时,所得碳材料的d_(002)达0.377 nm。本研究为进一步定向调控和构筑沥青基碳材料奠定基础。

河西走廊历史街区层积解析与整体保护策略研究——以张掖市文庙巷街区为例

历史街区的风貌特征与文化资源正在城市更新中不断消逝,张掖市文庙巷历史街区也面临着同样的问题,历史性城镇景观(HUL)理论的出现为解决这一问题提供了新思路。文章从历史性城镇景观理论出发,提取“动态层积”概念,基于城市整体格局及历史文化价值内涵,从“时间—空间”角度入手,运用空间句法对该街区的层积演变进行解读。挖掘其传统教育文化内涵,探索其价值关联,从而更好地进行整体性保护,以期使城市更新和街区保护达成一种“双赢”的结果。

Performance of Cross-Layer Design with Power Allocation in Space-Time Coded MIMO Systems

A cross-layer design(CLD)scheme with combination of power allocation,adaptive modulation(AM)and automatic repeat request(ARQ)is presented for space-time coded MIMO system under imperfect feedback,and the corresponding system performance is investigated in a Rayleigh fading channel.Based on imperfect feedback information,a suboptimal power allocation(PA)scheme is derived to maximize the average spectral efficiency(SE)of the system.The scheme is based on a so-called compressed SNR criterion,and has a closed-form expression for positive power allocation,thus being computationally efficient.Moreover,it can improve SE of the presented CLD.Besides,due to better approximation,it obtains the performance close to the existing optimal approach which requires numerical search.Simulation results show that the proposed CLD with PA can achieve higher SE than the conventional CLD with equal power allocation scheme,and has almost the same performance as CLD with optimal PA.However,it has lower calculation complexity.

LayeredModel:一个面向室内空间的移动对象数据模型

基于室内空间的移动对象管理或称室内移动对象管理,是一个崭新而又富有挑战的研究领域.如何建立语义完备并且支持多种应用的室内移动对象模型是一个重要的基础性问题.提出了一个分层的室内移动对象数据模型:LayeredModel.该模型提出了室内空间距离的概念,并使用不同的层次关系表达室内元素、传感器以及移动对象之间的关系.从而能支持多种基于室内空间的应用,例如移动对象的跟踪、监控、导航以及室内最近邻查询等.LayeredModel模型也为后续的室内移动对象的索引、查询的研究奠定了基础.

Ti_(3)C_(2)系MXene原位制备方法的研究及其二维膜的结构调控

作为具有代表性的二维纳米材料之一,MXene通过层层堆叠可以构建具有分子筛分通道的新型二维分离膜。利用氟化锂/盐酸原位生成氢氟酸的方法,系统地研究了刻蚀液浓度对碳化钛(Ti_(3)C_(2))系MXene纳米片结构的影响,并利用热处理探究了MXene二维膜的结构演变。结果表明,当刻蚀剂中F^(-)的摩尔质量是Al^(3+)的7倍及以上时,能获得较好的单层MXene,且纳米片层之间的层间距随着刻蚀剂中F^(-)浓度的提高而增大;利用热自交联反应,可以在增强纳米片层与片层之间作用力的同时,改变纳米片的层间距。

常州市滆湖组土体工程地质层划分及其应用

滆湖组土体是吴标云、李从先(1987)对长江三角洲第四纪地质研究时所命名,命名地点在常州武进寨桥D114孔,因位于滆湖东侧而称之,长江三角洲地区广泛分布,时代为晚更新世(冯金顺,2001)。常州市除低山丘陵和长江漫滩外,广袤的平原区滆湖组土体皆有分布,是常州市工业与民用建筑的主要基础持力层,也是与浅层地下空间开发关系最为紧密的地层。因此,对滆湖组土体进行工程地质层划分.

全固态锂电池正极/电解质界面电阻:从空间电荷层模型到表征及模拟

采用无机固体电解质的全固态锂电池以其高安全性和长寿命等优点,已经成为动力电池领域的重要发展方向之一。随着高室温离子电导率(大于10^(-3)S·cm^(-1))的固体电解质的涌现,锂离子在其中的迁移动力学问题不再是全固态锂电池发展的主要瓶颈。相比之下,正极和固体电解质界面处因空间电荷层等复杂效应导致的高界面电阻成为当前急需解决的难题。本文从(电)化学势及电势的基本概念出发,对描述正极和固体电解质之间化学势差异所导致的空间电荷层的理论模型进行严格推导,以揭示其影响界面电阻的物理本质。接着,本文从实验表征和理论模拟角度出发,综述了当前在观测空间电荷层状态、计算正极/固体电解质界面及其体相锂离子浓度,以及预测界面电阻等方面存在的问题。在此基础上,本文提出了融合空间电荷层模型、数值模拟以及基于实际正极和固体电解质接触处费米能级状态和位置的方法,从而定量评估界面电阻。最后,本文展望了通过优化正极/固体电解质界面来提升全固态锂电池电化学性能的未来发展趋势。通过深入理解界面电阻的物理机制,未来可以采用新的材料设计、界面工程等策略来改善全固态锂电池的性能。这些研究将有助于推动全固态锂电池技术的发展,实现更高效、更安全的能源存储解决方案。

H型栽培架层间距对番茄生长、产量及品质的影响

为探究H型双层立体栽培架合适层间距,为我国中原地区日光温室番茄立体栽培架型的科学设计提供依据,分别设置80、110和140 cm三个层间距建造H型双层栽培架,在春季日光温室内,以粉都53番茄(Solanum lycopersicum L.)为试材,采用营养液膜栽培方式进行试验,监测了三个层间距条件下,上下层的光照变化及对番茄光合性能的影响,测定了番茄生长、产量及品质等相关指标,研究了H型栽培架层间距对番茄生长、产量及品质的影响。结果表明,增加层间距能明显增强下层光照强度、促进番茄生长,提升番茄品质。不同层间距上层番茄之间各指标差异不显著,差异主要集中于下层番茄,其中层间距为140 cm下层番茄的第3、第4穗果平均单果质量、优果率和小区产量均显著高于80 cm和110 cm层间距处理,且总产量分别比后两者显著提高了46.4%和9.5%,可溶性糖含量分别增加了9.6%和7.6%,差异显著。相关性分析得出,层间距为140 cm处理下层番茄的生长情况、产量和品质优于层间距为80 cm和110 cm的原因主要是光照条件更好。综上,说明H型双层立体栽培架种植番茄上下层间距为140 cm时效果最优,可在实际生产中应用。