Geochemistry of sedimentary rocks from Permian–Triassic boundary sections of Tethys Himalaya: implications for paleo-weathering, provenance, and tectonic setting

The geochemical characteristics of two sections—the Permian–Triassic boundary(PTB) Guryul Ravine section, Kashmir Valley, Jammu and Kashmir,India; and the Attargoo section, Spiti Valley, Himachal Pradesh, India—have been studied in the context of provenance, paleo-weathering, and plate tectonic setting.These sections represent the siliciclastic sedimentary sequence from the Tethys Himalaya. The PTB siliciclastic sedimentary sequence in these regions primarily consists of sandstones and shales with variable thickness. Present studied sandstones and shales of both sections had chemical index of alteration values between 65 and 74; such values reveal low-to-moderate degree of chemical weathering. The chemical index of weathering in studied samples ranged from 71 to 94, suggesting a minor K-metasomatism effect on these samples. Plagioclase index of alteration in studied sections ranged from 68 to 92, indicating a moderate degree of weathering of plagioclase feldspars. The provenance discriminant function diagram suggests that the detritus involved in the formation of present studied siliciclastic sedimentary rocks fall in quartzose sedimentary and felsic igneous provenances. These sediments were deposited in a passive continental margin plate tectonic setting according to their location on a Si_2 O versus K_2O/Na_2 O tectonic setting diagram.

Exponential Time Differencing Method for a Reaction-Diffusion System with Free Boundary

For reaction-diffusion equations in irregular domains with moving boundaries,the numerical stability constraints from the reaction and diffusion terms often require very restricted time step sizes,while complex geometries may lead to difficulties in the accuracy when discretizing the high-order derivatives on grid points near the boundary.It is very challenging to design numerical methods that can efficiently and accurately handle both difficulties.Applying an implicit scheme may be able to remove the stability constraints on the time step,however,it usually requires solving a large global system of nonlinear equations for each time step,and the computational cost could be significant.Integration factor(IF)or exponential time differencing(ETD)methods are one of the popular methods for temporal partial differential equations(PDEs)among many other methods.In our paper,we couple ETD methods with an embedded boundary method to solve a system of reaction-diffusion equations with complex geometries.In particular,we rewrite all ETD schemes into a linear combination of specificФ-functions and apply one state-of-the-art algorithm to compute the matrix-vector multiplications,which offers significant computational advantages with adaptive Krylov subspaces.In addition,we extend this method by incorporating the level set method to solve the free boundary problem.The accuracy,stability,and efficiency of the developed method are demonstrated by numerical examples.

基于梯度增量level-set方法的复杂物体入水砰击数值模拟

复杂结构物自由表面砰击问题,如空投鱼雷、水空无人航行器潜水和高速船出入水,一直是海洋工程领域的研究热点。本文采用梯度增量level-set和虚拟网格法数值模拟复杂结构物的入水砰击,采用时间半隐式有限差分法求解不可压缩Navier-Stokes方程,虚拟网格法可重构复杂结构物界面插值模块并施加无滑移边界条件,梯度增量level-set法可捕捉非线性自由表面翻卷、射流等物理现象。基于以上方法模拟二维圆柱的常速入水砰击,并与试验和数值结果对比,验证本文数值方法的正确性。最后,数值模拟二维船型剖面和飞机剖面的入水砰击,分析了冲击压力、运动响应、压力分布和自由表面运动随入水角度的变化规律。同时,通过模拟可观察到复杂结构浸入水中后的流体分离、射流和小角度空气腔等典型砰击物理现象。

Topology Optimization for Steady-State Navier-Stokes Flow Based on Parameterized Level Set Based Method

In this paper,we consider solving the topology optimization for steady-state incompressibleNavier-Stokes problems via a new topology optimization method called parameterized level set method,which can maintain a relatively smooth level set function with a local optimality condition.The objective of topology optimization is to􀀀nd an optimal con􀀀guration of theuid and solid materials that minimizes power dissipation under a prescribeduid volume fraction constraint.An arti􀀀cial friction force is added to the Navier-Stokes equations to apply the no-slip boundary condition.Although a great deal of work has been carried out for topology optimization ofuidow in recent years,there are few researches on the topology optimization ofuidow with physical body forces.To simulate theuidow in reality,the constant body force(e.g.,gravity)is considered in this paper.Several 2D numerical examples are presented to discuss the relationships between the proposed method with Reynolds number and initial design,and demonstrate the feasibility and superiority of the proposed method in dealing with unstructuredmesh problems.Three 3D numerical examples demonstrate the proposedmethod is feasible in three-dimensional.

Solving Two-Dimensional Moving-Boundary Problems with Meshless and Level Set Method

During the past decade, increasing attention has been given to the development of meshless methods using radial basis functions for the numerical solution of Partial Differential Equations （PDEs）. A level set method is a promising design tool for tracking, modelling and simulating the motion of free boundaries in fluid mechanics, combustion, computer animation and image processing. In the conventional level set methods, the level set equation is solved to evolve the interface using a capturing Eulerian approach. The solving procedure requires an appropriate choice of the upwind schemes, reinitialization, etc. Our goal is to include Multiquadric Radial Basis Functions （MQ RBFs） into the level set method to construct a more efficient approach and stabilize the solution process with the adaptive greedy algorithm. This paper presents an alternative approach to the conventional level set methods for solving moving-boundary problems. The solution was compared to the solution calculated by the exact explicit lime integration scheme. The examples show that MQ RBFs and adaptive greedy algorithm is a very promising calculation scheme.

基于多头注意力机制字词联合的中文命名实体识别

针对现有基于字词联合的中文命名实体识别方法会引入冗余词汇干扰、模型网络结构复杂、难以迁移的问题,提出一种基于多头注意力机制字词联合的中文命名实体识别算法.算法采用多头注意力机制融合词汇边界信息,并通过分类融合BIE词集降低冗余词汇干扰.建立了多头注意力字词联合模型,包含字词匹配、多头注意力、融合等模块.与现有中文命名实体识别方法相比,本算法避免了设计复杂的序列模型,方便与现有基于字的中文命名实体识别模型结合.采用召回率、精确率以及F 1值作为评价指标,通过消融试验验证模型各个部分的效果.结果表明,本算法在MSRA和Weibo数据集上F 1值分别提升0.28、0.69,在Resume数据集上精确率提升0.07.

带式输送机托辊组振动噪声仿真分析及参数优化

带式输送机托辊组产生的振动噪声受多因素联合影响,为解决其振动噪声过大问题,文章提出一种基于有限元-边界元理论对托辊组振动噪声分析与优化的方法。首先,对托辊组进行模态分析与动力学仿真,探明托辊组的振动特性;然后,基于有限元-边界元复合声场仿真方法,作声场的谐响应分析计算托辊组的声场分布,并搭建实际测试平台验证声学仿真模型的可靠性;最后,结合输送能力与轻量化约束条件,得到托辊组结构参数与工作参数的最优解。结果表明,有限元-边界元法可有效模拟托辊组声场分布和变化规律,优化后托辊组噪声声压级较优化前减小约6.1dB,并且托辊组综合性能均有所改善,可对实际工程中的带式输送机优化设计起到有效的指导作用。

非圆形隧洞衬砌支护下应力与位移的新解法

以往在利用平面弹性复变函数方法进行衬砌支护作用下非圆形隧洞的力学分析时,一般将洞室外域保角映射到象平面的单位圆外域,并认为可以利用同一个映射函数将衬砌截面映射到象平面的圆环域内。当衬砌厚度很薄时,这种方法是可行的,而当衬砌相对较厚时,利用同一映射函数所得到的衬砌截面形状发生严重失真。为解决此问题,本文引入两套映射函数,分别将洞室外域映射到象平面的单位圆的圆外域,衬砌截面映射到圆环域。这种方法可以适应于不同的衬砌厚度,利用这种方式获得的衬砌截面,在衬砌较厚时仍能保证衬砌厚度相对均匀。在求解解析函数过程中不再采用传统的幂级数解法,而是使用边界配点法,将两套映射函数结合,获得了该问题的应力解和位移解。本文以马蹄形隧洞为例,求解结果与ANSYS软件所得数值解吻合很好,分析了衬砌厚度对隧洞应力和位移的影响。根据本文解答可以方便、快捷地进行相近条件下隧道的初步设计。

近水面水下爆炸二维Level-set数值模拟

水下爆炸是一个多介质、动边界、瞬态非线性过程,捕捉介质之间交界面的变化是数值模拟的一个难点。本文采用Level-set方法来描述水下爆炸气体产物和流体交界面以及自由表面变化,应用TVD(Total Variation Diminishing)计算技术求解Level-set流场,首先建立了近水面水下爆炸的二维数值方法,然后,将该方法推广到流场内有刚性结构的情况,考虑了冲击波和刚性结构物的相互作用。为了模拟无限边界流场问题,引进了Thompson建立的无反射边界条件。

基于最大联盟粗糙集的三支聚类

针对邻域粗糙集模型受邻域参数影响大、刻画样本信息时不够精细等问题,提出了一种基于最大联盟理论的粗糙集模型。在标准化邻域信息系统后,引入最大联盟集来描述邻域颗粒信息,使得邻域粗糙集模型对信息的划分更加精细,从而显著降低了边界域的不确定性。将该模型与三支聚类相结合,设计了一种基于最大联盟粗糙集的三支聚类算法。在6个UCI公共数据集上进行对比实验,结果表明,所提算法相较于对比算法具有更好的聚类质量,在处理边界域样本时具有更高的比较正确率。

无人自主系统能力边界参数自适应判别方法

为有效应对仿真测试面临的维度灾难问题,降低传统全参数空间遍历中所需的仿真次数,需要获取针对性的仿真数据以准确反映实验数据建模特征,以较少的仿真次数获得信息量丰富且代表原始数据特征的样本。提出一种面向无人自主系统能力边界参数自适应判别的数字化仿真测试模型,采用多权重结构的佳点集进行初始构建,结合自适应核函数边界点判别算法,通过高斯过程回归对模型进行迭代优化,自适应地判别无人自主系统的能力边界。实验结果表明:该方法能够降低建模所需数据量,提高自适应参数边界判别的效率,为提升智能无人系统试验的效率提供了高效途径。

BMI对乳腺癌放疗计划靶区外放边界的预判研究

目的:探讨体质量指数(body mass index,BMI)对乳腺癌患者治疗中位移误差的影响,为乳腺癌放射治疗中计划靶区外放边界提供数据支持。方法:回顾性分析本中心乳腺癌治疗的患者153例,利用CBCT获取摆位误差,并对数据进行挖掘,计算出两组因BMI的不同而导致的误差和PTV外放的差别。结果:从左乳和右乳的摆位误差分析计算得出:在考虑BMI情况下,左乳在腹背Z方向的摆位误差随BMI的增大而略有增大。右乳在Rx方向的摆位误差随BMI的增大而增大。左乳中,腹背Z方向外扩边界随BMI增大而逐渐增大。右乳中,头脚Y方向外扩边界随BMI增大而增大。结论:医师可根据乳腺癌的左右位置和BMI的大小来判断Mptv的扩大或者缩小,从而为患者提供更个性化精准化治疗。

关于环评报告中大气环境防护距离设置的研究

2018年12月1日,2018年版大气环境导则实施,其对大气环境防护距离的定义与2008年版定义并不一致,时至今日,部分环保管理工作人员对此并未注意到,导致仍存在大量的认知偏差,甚至争议。正是基于此,根据大气环境导则中的相关规定,结合环评实际工作经验,对大气环境防护距离设置进行了研究分析,以供广大环境影响评估工作人员参考。

Existence of solutions for fourth-order boundary value problem with parameter

This paper is a sequel to a previous paper （Yang, Y. and Zhang, J. H. Existence of solutions for some fourth-order boundary value problems with parameters. Nonlinear Anal. 69（2）, 1364-1375 （2008）） in which the nontrivial solutions to the fourthorder boundary value problems were studied. In the current work with the same conditions near infinity but different near zero, the positive, negative, and sign-changing solutions are obtained by the critical point theory, retracting property, and invariant sets.

Sign-Changing Solutions for Discrete Dirichlet Boundary Value Problem

Using invariant sets of descending flow and variational methods, we establish some sufficient conditions on the existence of sign-changing solutions, positive solutions and negative solutions for second-order nonlinear difference equations with Dirichlet boundary value problem. Some results in the literature are improved.

On the Thinnes of Non-tangential Sets

Let Ω R d and ξ∈Ω. Let E be any non tangential subset of Ω.We prove that if E is internal thin at ξ, then it is minimal thin at any minimal Martin boundary point of Ω.

Non-simultaneous quenching for a slow diffusion system coupled at the boundary

This paper deals with the quenching behavior of positive solutions to the Newton filtration equations coupled with boundary singularities.We determine quenching rates for non-simultaneous quenching at first,and then establish the criteria to identify the simultaneous and non-simultaneous quenching in terms of the parameters involved.

Eco-geographical Regionalization of China:An Approach Using the Rough Set Method

Eco-geographical regionalization involves dividing land into regions by considering both intra-regional consistency and interregional disparity and is based on the pattern of differentiation of eco-geographical elements.Owing to the complexity of the land surface,and the limitation of data and appropriate methods,regions in China have hitherto been mapped manually,meaning that the process of mapping was non-repeatable.To make the regionalization technique repeatable,this study aimed to extract and quantify the expert knowledge of regionalization using an automated method.The rough set method was adopted to extract rules of regionalization based on the existing eco-geographical regionalization map of China,as well as its corresponding meteorological and geological datasets.Then,the rules for regionalization were obtained hierarchically for each natural domain,each temperature zone,and each humidity region.Owing to differences in zonal differentiation,the rule extraction sequence for the eastern monsoon zone and Tibetan Alpine zone was temperature zone first followed by humidity region,with the reverse order being applied for the northwest arid/semi-arid zone.Results show that the extracted indicators were similar to those of the existing(expert-produced)regionalization scheme but more comprehensive.The primary indicator for defining temperature zones was the≥10℃ growing season,and the secondary indicators were the January and July mean temperatures.The primary and secondary indicators for identifying humid regions were aridity index and precipitation,respectively.Eco-geographical regions were mapped over China using these rules and the gridded indicators.Both the temperature zones and humidity regions mapped by the rules show≥85%consistency with the existing regionalization,which is higher than values for mapping by the commonly used simplified method that uses the classification of one indicator.This study demonstrates that the proposed rough set method can establish eco-geographical regionalization that is quantitative and repeatable and able to dynamically updated.

水库和大坝地理信息数据集的对比及其应用研究进展

水资源时空分布不均的现象普遍存在,修建水库是调节水资源最有效的手段之一,在中国,已建成的各类水库达九万多座。科学和智慧地调度以最大化水库群的工程效益和水安全保障能力,亟需全面的、准确的、地理信息化的水库和大坝数据集作为支撑,提供包括水库和大坝的位置以及水库边界、大坝高度、库容、用途等属性信息。近年来,多个水库和大坝数据集相继发表,极大地推动了水库和大坝相关的大尺度研究,但各个数据集在数据量和属性内容上存在明显的差异,亟待开展数据集的对比差异与应用需求分析。介绍了目前公开发表的水库和大坝数据集,总结了水库和大坝信息的多种数据来源和数据集的生产过程,比较了各数据集在大坝的位置和分类、水库的边界上的差异,重点比较了各数据集在中国的统计差异和空间分布特征,并探究了数据集中存在的数据时效性、水库与湖泊的重复定义、水库面积大小差异等问题。梳理了基于此类数据的热点研究问题:水库防洪、发电、灌溉效益评估,水库和大坝的水文效应、碳效应、截留效应研究,以及对河流生境破碎化的评估等。最后展望了水库和大坝数据集的生产和应用发展趋势。研究发现数据集中大型水库数量多、属性全面,小型水库数量少、属性不足,且不同数据集之间存在诸多的差异,未来需要进一步完善水库和大坝的数据记录,协调各数据集的差异以实现对水库和大坝的完全模拟。