Effect of Modulus Heterogeneity on the Equilibrium Shape and Stress Field ofαPrecipitate in Ti-6Al-4V

For media with inclusions(e.g.,precipitates,voids,reinforcements,and others),the difference in lattice parameter and the elastic modulus between the matrix and inclusions cause stress concentration at the interfaces.These stress fields depend on the inclusions’size,shape,and distribution and will respond instantly to the evolving microstructure.This study develops a phase-field model concerningmodulus heterogeneity.The effect of modulus heterogeneity on the growth process and equilibrium state of theαplate in Ti-6Al-4V during precipitation is evaluated.Theαprecipitate exhibits strong anisotropy in shape upon cooling due to the interplay of the elastic strain and interfacial energy.The calculated orientation of the habit plane using the homogeneous modulus ofαphase shows the smallest deviation fromthat of the habit plane observed in the experiment,compared to the case where the homogeneous modulus ofβphase is adopted.In addition,the equilibrium volume ofαphase within the systemusing homogeneousβmodulus exhibits the largest dependency on the applied stresses.The stress fields across theα/βinterface are further calculated under the assumption of modulus heterogeneity and compared to those using homogeneous modulus of eitherαorβphase.This study provides an essential theoretical basis for developing mechanics models concerning systems with heterogeneous structures.

Effect of boundary conditions on shakedown analysis of heterogeneous materials

The determination of the ultimate load-bearing capacity of structures made of elastoplastic heterogeneous materials under varying loads is of great importance for engineering analysis and design. Therefore, it is necessary to accurately predict the shakedown domains of these materials. The static shakedown theorem, also known as Melan's theorem, is a fundamental method used to predict the shakedown domains of structures and materials. Within this method, a key aspect lies in the construction and application of an appropriate self-equilibrium stress field(SSF). In the structural shakedown analysis, the SSF is typically constructed by governing equations that satisfy no external force(NEF) boundary conditions. However, we discover that directly applying these governing equations is not suitable for the shakedown analysis of heterogeneous materials. Researchers must consider the requirements imposed by the Hill-Mandel condition for boundary conditions and the physical significance of representative volume elements(RVEs). This paper addresses this issue and demonstrates that the sizes of SSFs vary under different boundary conditions, such as uniform displacement boundary conditions(DBCs), uniform traction boundary conditions(TBCs), and periodic boundary conditions(PBCs). As a result, significant discrepancies arise in the predicted shakedown domain sizes of heterogeneous materials. Built on the demonstrated relationship between SSFs under different boundary conditions, this study explores the conservative relationships among different shakedown domains, and provides proof of the relationship between the elastic limit(EL) factors and the shakedown loading factors under the loading domain of two load vertices. By utilizing numerical examples, we highlight the conservatism present in certain results reported in the existing literature. Among the investigated boundary conditions, the obtained shakedown domain is the most conservative under TBCs.Conversely, utilizing PBCs to construct an SSF for the shakedown analysis leads to less conservative lower bounds, indicating that PBCs should be employed as the preferred boundary conditions for the shakedown analysis of heterogeneous materials.

A modified damage and fracture phase field model considering heterogeneity for rock‐like materials

Damage and fracture are the most extensive failure modes of rock materials,which may easily induce disaster and instability of engineering structures.This study developed a nonlocal damage fracture phase field model for rocks considering the heterogeneity of rocks.The modified phase field model introduced the heterogeneity of fracture parameters and modified the governing equations.Meanwhile,the free energy was constructed by the elastic strain energy sphere‐bias decomposition and the plastic strain energy.As for the numerical implementation,the three layers finite elements method structure was used in the frame of the finite element method.The ability of the modified phase field model has been illustrated by reproducing the experiment results of rock samples with pre‐existing cracks under compression.

Reservoir heterogeneity analysis using multi-directional textural attributes from deep learning-based enhanced acoustic impedance inversion:A study from Poseidon,NW shelf Australia

Reservoir heterogeneities play a crucial role in governing reservoir performance and management.Traditionally,detailed and inter-well heterogeneity analyses are commonly performed by mapping seismic facies change in the seismic data,which is a time-intensive task.Many researchers have utilized a robust Grey-level co-occurrence matrix(GLCM)-based texture attributes to map reservoir heterogeneity.However,these attributes take seismic data as input and might not be sensitive to lateral lithology variation.To incorporate the lithology information,we have developed an innovative impedance-based texture approach using GLCM workflow by integrating 3D acoustic impedance volume(a rock propertybased attribute)obtained from a deep convolution network-based impedance inversion.Our proposed workflow is anticipated to be more sensitive toward mapping lateral changes than the conventional amplitude-based texture approach,wherein seismic data is used as input.To evaluate the improvement,we applied the proposed workflow to the full-stack 3D seismic data from the Poseidon field,NW-shelf,Australia.This study demonstrates that a better demarcation of reservoir gas sands with improved lateral continuity is achievable with the presented approach compared to the conventional approach.In addition,we assess the implication of multi-stage faulting on facies distribution for effective reservoir characterization.This study also suggests a well-bounded potential reservoir facies distribution along the parallel fault lines.Thus,the proposed approach provides an efficient strategy by integrating the impedance information with texture attributes to improve the inference on reservoir heterogeneity,which can serve as a promising tool for identifying potential reservoir zones for both production benefits and fluid storage.

Influence of Magnetic Field on the Rectification Process of Binary Heterogeneous Azeotrope

To improve separate effect of binary heterogeneous azeotrope in the magnetic field with different magnetic induction intensity, the influence of magnetic field on the rectification process of binary heterogeneous azeotrope was investigated with 1-butanol-water system. The results show that the composition of liquid-liquid phase equilibrium of 1-butanol-water system has definitely changed, the composition of 1-butanol in light phase （1-butanol layer） increases by 1.1700-1.6300 and the composition of water in heavy phase （water layer） increases by 1.2100-1.5800 under the influence of magnetic field. By separation of magnetization, the composition of 1-butanol increases by 0.800-1.200 and the recovery ratio of 1-butanol increases by 1.600-2.500. Magnetic field has positive effect, however, the magnetized effect is not in proportion to magnetic induction intensity and has an optimum condition, in the range of 0.25 T-0.3 T.

Discovering exact,gauge-invariant,local energy–momentum conservation laws for the electromagnetic gyrokinetic system by high-order field theory on heterogeneous manifolds

Gyrokinetic theory is arguably the most important tool for numerical studies of transport physics in magnetized plasmas.However,exact local energy–momentum conservation laws for the electromagnetic gyrokinetic system have not been found despite continuous effort.Without such local conservation laws,energy and momentum can be instantaneously transported across spacetime,which is unphysical and casts doubt on the validity of numerical simulations based on the gyrokinetic theory.The standard Noether procedure for deriving conservation laws from corresponding symmetries does not apply to gyrokinetic systems because the gyrocenters and electromagnetic field reside on different manifolds.To overcome this difficulty,we develop a high-order field theory on heterogeneous manifolds for classical particle-field systems and apply it to derive exact,local conservation laws,in particular the energy–momentum conservation laws,for the electromagnetic gyrokinetic system.A weak Euler–Lagrange(EL)equation is established to replace the standard EL equation for the particles.It is discovered that an induced weak EL current enters the local conservation laws,and it is the new physics captured by the high-order field theory on heterogeneous manifolds.A recently developed gauge-symmetrization method for high-order electromagnetic field theories using the electromagnetic displacement-potential tensor is applied to render the derived energy–momentum conservation laws electromagnetic gauge-invariant.

Spatial-temporal Distribution Characteristics of Global Seismic Clusters and Associated Spatial Factors

Earthquakes exhibit clear clustering on the earth. It is important to explore the spatial-temporal characteristics of seismicity clusters and their spatial heterogeneity. We analyze effects of plate space, tectonic style, and their interaction on characteristic of cluster.Based on data of earthquakes not less than moment magnitude(M_w) 5.6 from 1960 to 2014, this study used the spatial-temporal scan method to identify earthquake clusters. The results indicate that seismic spatial-temporal clusters can be classified into two types based on duration: persistent clusters and burst clusters. Finally, we analysed the spatial heterogeneity of the two types. The main conclusions are as follows: 1) Ninety percent of the persistent clusters last for 22-38 yr and show a high clustering likelihood;ninety percent of the burst clusters last for 1-1.78 yr and show a high relative risk. 2) The persistent clusters are mainly distributed in interplate zones, especially along the western margin of the Pacific Ocean. The burst clusters are distributed in both intraplate and interplate zones, slightly concentrated in the India-Eurasia interaction zone. 3) For the persistent type, plate interaction plays an important role in the distribution of the clusters’ likelihood and relative risk. In addition, the tectonic style further enhances the spatial heterogeneity. 4) For the burst type,neither plate activity nor tectonic style has an obvious effect on the distribution of the clusters’ likelihood and relative risk. Nevertheless,interaction between these two spatial factors enhances the spatial heterogeneity, especially in terms of relative risk.

Underwater Inhomogeneous Light Field Based on Improved Convolutional Neural Net Fish Image Recognition

In this paper, artificial intelligence image recognition technology is used to improve the recognition rate of individual domestic fish and reduce the recognition time, aiming at the problem that it is difficult to easily observe the species and growth of domestic fish in the underwater non-uniform light field environment. First, starting from the image data collected by polarizing imaging technology, this paper uses subpixel convolution reconstruction to enhance the image, uses image translation and fill technology to build the family fish database, builds the Adam-Dropout-CNN (A-D-CNN) network model, and its convolution kernel size is 3 × 3. The maximum pooling was used for downsampling, and the discarding operation was added after the full connection layer to avoid the phenomenon of network overfitting. The adaptive motion estimation algorithm was used to solve the gradient sparse problem. The experiment shows that the recognition rate of A-D-CNN is 96.97% when the model is trained under the domestic fish image database, which solves the problem of low recognition rate and slow recognition speed of domestic fish in non-uniform light field.

地幔不均一性与地幔循环的多维表征和原因思考

地幔早先经核-幔-壳分异形成,后受不同尺度对流和循环的影响,因而具有不均一性特征。近三十年来,地幔化学通过研究大洋玄武岩发现了多样地幔端元和非放射性同位素证据并证明了地幔不均一性,逐渐建全了地幔地球化学体系。然而,地幔不均一性如何对应于时空尺度的地幔循环,以及地球演化如何影响地幔不均一性等,仍不清楚。此外,地球物理研究显示,岩石圈厚度差异、中下地幔的波速异常体以及俯冲板片形态的观测为纵横向对流系统提供了空间不均一性证据支持。联合地球化学和地球物理手段对研究地幔不均一性至关重要,用好透视地幔成分与结构的“双目镜”已成为共识。本文从地幔不均一性结合地球化学场、地球物理的不同表现形式,以及现今及历史时期的洋陆格局的对比,多维度联系地幔循环和演化,思考了超大陆旋回与地幔不均一化的内在逻辑。强调了从全球演化角度看地幔不均一性的重要性和提出多手段联合建立地幔循环驱动模型的展望。

非均相体系在微通道中的封堵性能研究

基于大庆油田天然岩心孔隙尺度分布特征建立了微通道模型,考虑非均相体系中的分散相和连续相的变形及流动特征,以相场法建立流动模型并用有限元方法求解,模拟了分散相颗粒在微通道内的生成,并实现了颗粒分选,研究了微观孔喉结构中匹配系数和孔喉比对颗粒封堵性能的影响。结果表明,颗粒在微观孔喉结构中发生弹性封堵时,孔喉入口处压力随颗粒运移通过而呈现周期性变化;颗粒与孔喉最佳匹配系数为[1.0,1.4),此区间内颗粒能够在孔喉入口处暂时封堵,变形运移通过孔喉后恢复原形;当孔隙直径相同时,匹配系数和孔喉比越大,颗粒通过压力越大;颗粒粒径越大,颗粒通过压力临界值越小。

合作研发与技术交易谁更有利于技术融合:以人工智能多层专利网络为例

技术融合能够显著提高企业创新能力,是产业融合的基础。合作研发和技术交易是常见的技术创新模式。为探究不同创新模式下的技术融合影响因素,以人工智能产业为例构建组织-技术多层网络模型,从技术异质性和创新能力异质性两个维度探究不同创新模式下组织合作伙伴异质性对技术融合的影响。研究表明,在合作研发模式下,技术异质性、创新能力异质性有利于技术融合;在技术交易模式下,创新能力异质性有利于技术融合,技术异质性不利于技术融合。

低渗强非均质性碳酸盐岩气藏优化配产新方法

针对低渗强非均质性碳酸盐岩气藏开发早期经典气井优化配产方法的不适应问题,文中建立了基于节点分析法的径向复合地层系统流动方程,以及地层压力描述方程、流动压力描述方程与井筒流动方程联合求解的动态资料耦合优化配产方法。在产量优化过程中,首先用图解法确定气井的产量区间,再采用耦合优化配产方法确定气井不同生产制度下油压、稳产期等动态变化规律,以此为依据对气井配产进行优化。该方法已在四川盆地某特大型气藏进行了应用,应用结果符合气藏地质和生产动态认识,验证了其实用性与可靠性。

知识共创视角下协同要素异质性、知识场活性对社区创新绩效的影响

以资源基础理论和团队异质性理论为依托,从知识共创视角提炼出社区知识协同中多维要素异质性的计量方法和共创情境的表征变量,利用Python程序爬取魅族社区数据,考察不同要素对创新绩效的差异化影响,以及知识场活性在其中发挥的中介传递作用。研究结果显示:知识共创过程中用户异质性、内容异质性和表达形式异质性对社区知识场活性具有正向影响,情感异质性对知识场活性具有倒U型影响;知识场活性对创新绩效具有正向影响,且在用户异质性、内容异质性、表达形式异质性与创新绩效关系中发挥部分中介作用。

鄂尔多斯盆地苏里格气田西南部致密储层非均质性特征及对成藏的制约

致密砂岩气藏是我国非常规油气资源的重要组成,其储层非均质性严重影响了致密气成藏和甜点区优选,进而制约了气田高效开发。为进一步揭示储层非均质性成因及对致密气成藏的影响,选取鄂尔多斯盆地苏里格气田西南部山1段和盒8段致密储层为例,通过岩芯观察、扫描电镜、薄片鉴定、生产和测井分析等技术手段,研究储层非均质特征,探讨沉积作用和微观孔隙演化对非均质性和成藏的影响。结果表明,储层非均质性多表现为层内粒度的垂向韵律性、夹层的不均匀分布、渗透率的平面分布差异等;储层非均质性受沉积作用和成岩作用共同影响,沉积作用控制了水动力条件、砂体展布、厚度和砂体构型,储层微观非均质性受岩矿组构和孔隙演化影响;不同厚度和构型的复合砂体,多样的矿物组分、孔隙结构,致密气的选择性充注,共同造成了苏里格地区致密储层的非均质性及含气性差异。复合砂体的高孔渗部位是致密气开采的甜点区,但是在优选有利区时不应只关注这些厚层的高孔渗砂体,也应关注规模小、非均质性稍强的透镜状砂体,需要充分考虑到储层非均质性对致密气成藏的影响。

声悬浮高温小球轴向稳定性研究

针对驻波声悬浮高温小球的轴向稳定性,建立了声−热−流−重力场耦合的物理模型,采用有限元方法计算了高温小球周围空间的不均匀温度场和声场,分析了驻波声场中直径2 mm的氮化硅小球在300~2000 K温度区间的轴向悬浮稳定性,并通过常温下声悬浮实验验证了仿真模型的准确性。结果表明在初始悬浮间距满足谐振并保持不变的条件下,随着悬浮小球的温度升高,小球的平衡位置降低,并且存在能保持稳定悬浮状态的温度最大值。在小球升温的过程中,通过反馈调节发射端−反射端间距和发射端激励电压,可以在一定程度上保持高温小球的轴向悬浮稳定性。

磁场中加速器小野X线射束在非均匀模体中的剂量沉积特性研究

目的利用蒙特卡洛模拟方法研究磁场中加速器输出的小野X线射束在非均匀模体中的剂量沉积特性。方法使用通用蒙卡程序EGSnrc并结合Varian官方提供的相空间文件搭建TrueBeam 6 MV机头模型,在源皮距为100 cm处分别模拟10 cm×10 cm的常规野和2 cm×2 cm的小野。先模拟常规野在均匀水模体中的能量沉积以验证模型的正确性,再模拟小野分别在非均匀的水-肺-水模体和水-骨-水模体中的能量沉积,在空间中添加与射束方向正交的1.5 T静态磁场后再进行模拟,最后分析剂量沉积特性。结果常规野的结果显示,无磁场时,Dmax深度为1.5 cm;磁场存在时,建成区缩短且Dmax深度前移至1.1 cm。小野的结果显示,磁场的存在导致原本的剂量沉积特性反转:水-肺-水模体中,两个交界面处分别有36.92%和-36.44%的剂量改变;水-骨-水模体中,两个交界面处分别有-11.17%和10.89%的剂量改变。结论磁场的存在会使加速器输出的小野射束在模体中的剂量沉积情况发生较大程度改变,特别是在非均匀介质的交界处。

基于异构平台的卷积神经网络加速系统设计

在计算和存储资源受限的嵌入式设备上部署卷积神经网络,存在执行速度慢、计算效率低、功耗高的问题。提出了一种基于异构平台的新型卷积神经网络加速架构,设计并实现了基于MobileNet的轻量化卷积神经网络加速系统。首先,为降低硬件资源消耗以及数据传输成本,采用动态定点数量化和批标准化融合的设计方法,对网络模型进行了优化,并降低了加速系统的硬件设计复杂度;其次,通过实现卷积分块、并行卷积计算、数据流优化,有效提高了卷积运算效率和系统吞吐率。在PYNQ-Z2平台上的实验结果表明,此加速系统实现的MobileNet网络推理加速方案对单幅图像的识别时间为0.18 s,系统功耗为2.62 W,相较于ARM单核处理器加速效果提升了128倍。

基于FPGA误差可控的浮点运算加速器研究

浮点运算是高性能计算(HPC)领域的基础运算。在大数据与云计算的背景下,高性能计算平台需要处理的数据量与日俱增,而且浮点数的舍入误差在大规模、长时程的运算中会产生累积,因此,在提升浮点运算性能的同时保证计算结果的可靠性非常重要。利用现场可编程门阵列(FPGA)可编程、低功耗、灵活性强的特点,针对含复杂单项运算的浮点多项式设计一种浮点运算加速器。基于无误差变换的思想,通过计算得出舍入误差值,将其补偿到浮点数值上,从而实现误差可控。采用异步并行的方式实现运算加速,并通过构建CPU-FPGA平台最大化地利用计算资源,保证计算任务执行的高效性。数据测试结果表明:在不限制对称性下的数值相对论模拟运算中,该加速器在200 MHz的主频下可达到91.85 MFLOPs的峰值性能;与Intel i76700K CPU运行最大线程数的性能相比,该加速器实现了50.54的加速比,并在该条件下获得了平均53.6%的精确结果百分比以及更低的相对误差,表明其具备较高的可靠性。

长岭断陷龙凤山气田营城组储层非均质性研究

龙凤山气田是目前中石化在东北地区勘探开发的首个深盆致密砂岩近饱和高含油凝析气储集系统,主力含气层位营城组储层在空间上表现出了较强的非均质性特征,气层在纵向上、平面上分布规律复杂将制约后续的地质研究工作(于翠玲,2007)。通过对岩心描述和测井资料进行分析,对比地质储量和实际测试生产情况,从层内、层间和平面3个方面分析储层的宏观非均质性。

基于流域尺度的耕地时空格局演变与分异性研究

流域尺度下的耕地分布跨度大,为探究流域耕地时空格局演变规律,基于1990、2000、2010、2020年4期土地利用遥感监测数据,以黄河、淮河、海河和长江4大流域为研究区,利用土地利用转移矩阵、重心模型、核密度方法分析流域耕地与其他土地利用类型转移情况、耕地重心迁移和耕地聚集特征,并对4大流域水田旱地分异现象进行分析。结果表明:1990—2020年间4大流域耕地面积均减小,其中海河流域耕地减小率最大,为9.16%;除海河流域耕地重心向西南方向迁移外,其他流域耕地重心均向东北方向迁移,整体耕地重心向北方向迁移,1990—2020年迁移距离分别为1.8、5.9和5.1 km;4大流域水田、旱地除部分水旱田调整外,主要是在林地、城乡用地和草地3种土地利用之间进行,转移主要发生在2010—2020年期间。1990—2020年黄河流域水田面积减少了9.35%,旱地面积减少了4.91%;淮河流域水田面积增加了3.51%,旱地则减少了7.10%;海河流域水田和旱地分别减少了70.46%和6.71%;长江流域水田和旱地分别减少了8.15%和1.72%。黄河、淮河、海河和长江4大流域为国家水网的主网,与本研究范围一致,研究成果可为进一步研究耕地资源与水网建设匹配性提供必要的前提。