Quasi-3D Numerical Simulation of Tidal Hydrodynamic Field

Based on the 2D horizontal plane numerical model, a quasi-3D numerical model is established for coastal regions of shallow water. The characteristics of this model are that the velocity profiles;can be obtained at the same time when the equations of the value of difference between the horizontal current velocity and its depth-averaged velocity in the vertical direction are solved and the results obtained are consistent with the results of the 2D, model. The circulating flow in the rectangular area induced by wind is simulated and applied to the tidal flow field of the radial sandbanks in the South Yellow Sea. The computational results from this quasi-3D model are in good agreement with analytical results and observed data. The solution of the finite difference equations has been found to be stable, and the model is simple, effective and practical.

混凝土3D细观模型及准静态力学行为分析

混凝土是应用最广泛的建筑材料,在细观尺度上由砂浆、粗骨料和界面过渡区(Interface Transition Zone,ITZ)组成,建立3D细观模型是揭示荷载作用下混凝土材料内部损伤机理的重要研究方法。基于传统的“生成-投放”法建立空间随机分布的随机凸多面体粗骨料模型,并提出骨料重力沉降和粒径缩放建模方法,实现了粗骨料体积率在50%范围内可调控;采用四面体网格划分多面体粗骨料以表征其真实形状;采用等效于零厚度粘结单元的粘结接触表征ITZ,解决了20μm~50μm厚度ITZ的网格划分问题;采用RHT材料模型表征砂浆和骨料,建立了混凝土3D细观有限元模型。随后开展了准静态单轴压缩、单轴拉伸、劈裂拉伸、双轴加载和三轴压缩条件下混凝土试件力学行为的有限元模拟。通过与试验应力-应变关系和试件破坏模式进行对比,验证了所建立的混凝土3D细观有限元模型的可靠性。进一步分析了砂浆、骨料和ITZ的强度,以及骨料粒径和体积率对混凝土单轴压缩力学性能的影响。结果表明增大砂浆强度可显著提高混凝土强度,而骨料和ITZ强度的影响较小;增大砂浆强度和ITZ强度可使混凝土峰值应变显著增大,而增大骨料强度导致混凝土峰值应变略有减小;降低粗骨料体积率和增大骨料最大粒径均可使混凝土强度略有增大且峰值应变减小。

3D打印连续苎麻纤维增强聚乳酸复合材料的准静态侵彻性能

传统成型工艺制造的合成纤维增强复合材料逐渐无法满足低成本、快速制造、环境友好等要求。因此,选取连续苎麻纤维增强聚乳酸(PLA)基生物质复合材料,采用原位浸渍3D打印工艺成型不同铺层方式的样件。利用准静态侵彻测试评估了铺层方式、支撑跨距与冲头直径比(跨距比)及增强材料对侵彻性能的影响,并通过背光法实时监测侵彻过程中复合材料的损伤行为。结果表明,连续苎麻纤维的加入使样件的侵彻强度提升了51.5%(单向)和52.9%(正交);正交铺层的复合材料样件与单向铺层相比,吸收的能量和最大侵彻力分别提升了24.9%、13.1%;打印样件的侵彻力和能量吸收能力随着跨距比的降低而显著增加,跨距比为10时的正交铺层复合材料与跨距比为5时相比,强度提升了202.4%。最后通过样件的多尺度失效特征分析及侵彻机理研究,揭示了3D打印生物质复合材料的铺层结构-侵彻性能的关系。

On Nonlinear Stability Theorems of 3D Quasi-geostrophic Flow

Nonlinear stability criteria for quasi-geostrophic zonally symmetric flow are improved by establishing an optimal Poincard inequality. The inequality is derived by a variational calculation considering the additional invariant of zonal momentum. When applied to the Eady model in a periodic channel with finite zonal length, the improved nonlinear stability criterion is identical to the linear normal-mode stability criterion provided the channel meridional width is no greater than 0.8605... times its channel length （which is the geophysically relevant case）.

3D magnetotelluric inversions with unstructured finite-element and limited-memory quasi-Newton methods

Traditional 3D Magnetotelluric(MT) forward modeling and inversions are mostly based on structured meshes that have limited accuracy when modeling undulating surfaces and arbitrary structures. By contrast, unstructured-grid-based methods can model complex underground structures with high accuracy and overcome the defects of traditional methods, such as the high computational cost for improving model accuracy and the difficulty of inverting with topography. In this paper, we used the limited-memory quasi-Newton(L-BFGS) method with an unstructured finite-element grid to perform 3D MT inversions. This method avoids explicitly calculating Hessian matrices, which greatly reduces the memory requirements. After the first iteration, the approximate inverse Hessian matrix well approximates the true one, and the Newton step(set to 1) can meet the sufficient descent condition. Only one calculation of the objective function and its gradient are needed for each iteration, which greatly improves its computational efficiency. This approach is well-suited for large-scale 3D MT inversions. We have tested our algorithm on data with and without topography, and the results matched the real models well. We can recommend performing inversions based on an unstructured finite-element method and the L-BFGS method for situations with topography and complex underground structures.

基于数字图像像素单元建立准三维FLAC^(3D)模型

在实际应用中,即使是建立较为简单的不规则准三维模型,FLAC3D也存在一定难度,因此,提出了一种快速建立FLAC3D准三维模型的方法,即基于数字图像像素单元的位置属性建立FLAC3D准三维模型,并根据像素单元的颜色属性对所建立模型进行分组,以便实现对模型单元赋予不同属性材料或者建立不同功能模块(如开挖、回填)。借助上述思想,采用Visual Basic语言编写了IMAGE-FLAC3D接口程序,实现了FLAC3D软件建模的直观、快速和自动化。通过建立土石混合体有限差分模型和库岸滑坡有限差分模型,检验了该方法及程序的有效性和可行性。在此基础上,借助强度折减法对所建立库岸滑坡模型进行稳定性分析,分析结果与极限平衡法所得结果相近,说明了所建模型的可计算性。该方法可作为数字图像服务于岩土工程的典型范例。

基于VIC⁃3D技术的自复位梁柱节点抗震性能试验

为降低强震对传统钢筋混凝土框架结构梁柱节点的破坏水平,提升梁柱节点在震后的可修复性,设计了一种内置超弹性形状记忆合金(shape memory alloy,简称SMA)筋的新型自复位梁柱节点。基于对不同配筋构造形式和SMA筋不同配筋率等因素的考虑,设计制作了4个1/5缩尺比例梁柱节点并进行了拟静力试验。通过非接触全场应变测量系统(video image correlate⁃3d,简称VIC⁃3D)对低周往复加载作用下各节点塑性铰区的整体位移和应变进行了实时测摄,获得了相应的竖向位移和主应变全过程云图。对起裂阶段、裂缝发展阶段和自复位阶段3个阶段进行研究,对比分析了各节点的破坏过程以及耗能能力、位移延性、刚度退化和自复位等性能。试验结果表明:内置超弹性SMA筋可有效提升节点的滞回耗能和自复位性能,延缓塑性核心区混凝土的开裂,改善开裂后的损坏程度,提升节点的经济可修复性;一定范围内,增大SMA筋配筋率可有效延缓节点的刚度退化速度,但对节点的极限承载力和自复位性能的提升影响不大。

复杂3D寄生电容器的虚拟多介质切割

虚拟多介质是一种基于直接边界元的寄生电容快速提取方法 .介绍复杂互连寄生电容器的结构及对其实现虚拟多介质切割的方法 .实际算例表明 ,该算法可靠 。

基于3D打印半导体热电材料的PEMFC温控系统

提出了一种基于3D打印半导体热电材料的温控系统,系统主要由散热模块、水循环模块以及控温模块三个模块组成。本项目创新性地设计了类圆弧状制冷片,利用3D打印技术,实现了碲化铋基半导体热电材料的复杂成型,进而制得了类棱台状的热电臂。热电臂的新型变截面结构可以强化半导体的瞬态超冷性能,能够提半导体高热电材料的利用率,且端面面积保持与传统半导体制冷器相同,大大提高了其制冷效率。

准噶尔盆地石南地区白垩系储层地球物理方法识别

准噶尔盆地石南地区白垩系清水河组底砾岩中相继获得工业油流,但该套储层却具有多层系立体式含油及纵、横向变化大的特点,急需解决储层识别与精细刻画的难题。本文在精确地震地质层位标定的基础上,采用地震层位拉平残余厚度“三步法”恢复白垩系清水河组一段古地貌,结合自然伽马拟声波储层预测,基本查明了沉积的主控因素及砂体空间展布特征。研究成果为石南地区白垩系储层预测提供了有效的方法组合,为白垩系清水河组砂砾岩油气藏的油气勘探提供了充分的科学依据,可有效降低勘探风险。

涡轮级轮缘封严内非定常流场的准三维LDV测量

研究涡轮级封严内流动和主流的相互作用、相互影响,进一步认识盘腔内燃气入侵等非定常现象,急需流场实验数据验证。针对轮缘封严内空间狭窄、光路安排困难等问题,本文发展了一种用于测量涡轮级轮缘封严内非定常流场的准三维LDV技术,即测量分两步,首先在机匣上安置二维测速系统用符合方式测出径向、切向速度及湍流度,再在轮毂内安置一维探头重复测量,从两次测量数据中计算出轴向速度;该技术借助锁相采样等技术能测出不同动静叶相对位置情况下封严及盘腔内的周期性非定常流场细节,本文给出了部分典型的动态流场测量结果。

Study on three dimensional electromagnetic model for permanent magnet linear synchronous motor

In this paper, with the non-salient pole permanent magnet linear synchronous motor (PMLSM)being cited, by using Fourier transform method and "slot-by-slot", "pole -by-pole" current approach, a 3D electromagnetic field model of PMLSM is established. Special attention is paid to its structure and the influence of longitudinal and transverse end effect. The distribution of electromagnetic field of PMLSM can be obtained directly and promptly by using FFT algorithm. It can also be used for the analysis of other LSM.

Discussion on applying an analytical method to optimize the anti-freeze design parameters for underground water pipelines in seasonally frozen areas

Adopting the quasi-three-dimensional （Quasi-3D） numerical method to optimize the anti-freeze design parameters of an underground pipeline usually involves heavy numerical calculations. Here, the fitting formulae between the safe con-veyance distance （SCD） of a water pipeline and six influencing factors are established based on the lowest water temper-ature （LWT） along the pipeline axis direction. With reference to the current widely used anti-freeze design approaches for underground pipelines in seasonally frozen areas, this paper first analyzes the feasibility of applying the maximum frozen penetration （MFP） instead of the mean annual ground surface temperature （MAGST） and soil water content （SWC） to calculate the SCD. The results show that the SCD depends on the buried depth if the MFP is fixed and the variation of the MAGST and SWC combination does not significantly change the SCD. A comprehensive formula for the SCD is estab-lished based on the relationships between the SCD and several primary influencing factors and the interaction among them. This formula involves five easy-to-access parameters： the MFP, buried depth, pipeline diameter, flow velocity, and inlet water temperature. A comparison between the analytical method and the numerical results based on the Quasi-3D method indicates that the two methods are in good agreement overall. The analytic method can be used to optimize the anti-freeze design parameters of underground water pipelines in seasonally frozen areas under the condition of a 1.5 safety coefficient.

双CCD的准透视系统构成原理及关键技术

提出基于双CCD的准透视系统概念,介绍准透视系统的构成原理,分析准透视系统工作过程中的两项关键技术,指出准透视系统的应用领域及发展。

时移电阻率法三维反演研究

时移电阻率法是监测浅地表物性参数动态变化的有效方法之一.在实际应用中,由于观测噪声随时间变化,基于不同时刻观测数据单独反演所得的电性结构变化可能存在虚假信息.这些时变噪声引起的虚假信息增加了时移电阻率法解释的难度.本文通过在传统的正则化反演目标函数中增加时移约束来调控相邻时刻同一位置的电性差异,以抑制时变噪声产生的虚假变化.在此基础上,采用有限内存拟牛顿法实现了时移电阻率法三维反演.合成数据反演结果表明,相对于不同时刻监测数据单独反演的结果,时移反演可更好的抑制噪声影响,获取更准确的电性结构及其动态变化.野外实验数据反演结果表明,时移反演能更真实刻画实验区域的电性结构变化.上述结果表明,时移反演可以更好的压制由背景噪声引起的假异常,提高反演结果的准确性和解释的可靠性.本研究为时移电阻率法监测浅地表电性结构动态变化提供了一种有效途径.

Influence of Halide Choice on Formation of Low-Dimensional Perovskite Interlayer in Efficient Perovskite Solar Cells

Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on the formation mechanism,crystallography,and photoelectric properties of the lowdimensional phase still requires further detailed study.In this work,we present key insights into the significance of halide choice when designing passivation strategies comprising large organic spacer salts,clarifying the effect of anions on the formation of quasi-2D/3D heterojunctions.To demonstrate the importance of halide influences,we employ novel neo-pentylammonium halide salts with different halide anions(neoPAX,X=I,Br,or Cl).We find that regardless of halide selection,iodide-based(neoPA)_(2)(FA)_((n-1))PbnI_((3n+1))phases are formed above the perovskite substrate,while the added halide anions diffuse and passivate the perovskite bulk.In addition,we also find the halide choice has an influence on the degree of dimensionality(n).Comparing the three halides,we find that chloride-based salts exhibit superior crystallographic,enhanced carrier transport,and extraction compared to the iodide and bromide analogs.As a result,we report high power conversion efficiency in quasi-2D/3D PSCs,which are optimal when using chloride salts,reaching up to 23.35%,and improving long-term stability.

城市高精度3维控制网的建立与实施

随着似大地水准面精化技术的成熟及应用,建立适合我国的城市现代高精度3维控制网已变得简单容易。本文介绍了基于GPS、水准、现代地球重力场理论和方法,建立集平面、高程、重力场信息于一体的综合性城市现代高精度3维控制网的方法与实施过程,从而为动态的、实时的高精度3维测量提供测绘保障。

Numerical investigation and modeling of sweep effects on inlet flow field of axial compressor cascades

Swept blades are widely utilized in transonic compressors/fans and provide high load,high through-flow,high efficiency,and adequate stall margin.However,there is limited quantitative research on the mechanism of the effect of swept blades on the flow field,resulting in a lack of direct quantitative guidance for the design and analysis of swept blades in fans/compressors.To better understand this mechanism,this study employs a reduced-dimensional force equilibrium method to analyze more than 1500 swept cascades data.Results verify that circumferential fluctuation terms are responsible for inducing radial migration in the inlet airflow field of the swept blade,resulting in variations in the incidence angle and consequently leading to changes in the characteristics of the swept blade.Thus,a combination of simple functions and machine learning is utilized to model the circumferential fluctuation terms and quantify the sweep mechanism.The prediction accuracy of the model is high,with coefficient of determination greater than 0.95 on the test set.When the model is applied in a meridional flow analysis program,the calculation accuracy of the program for the incidence angle is improved by 0.4°and 0.6°at the design and off-design conditions respectively,compensating for the program’s original deficiencies.Meanwhile,the model can also provide quantitative guidance for the design of swept blades,thereby reducing the number of design iterations and improving design efficiency.

A quasi-3-dimensional simulation method for a high-voltage level-shifting circuit structure

A new quasi-three-dimensional （quasi-3D） numeric simulation method for a high-voltage level-shifting circuit structure is proposed. The performances of the 3D structure are analyzed by combining some 2D device structures; the 2D devices are in two planes perpendicular to each other and to the surface of the semiconductor. In comparison with Davinci, the full 3D device simulation tool, the quasi-3D simulation method can give results for the potential and current distribution of the 3D high-voltage level-shifting circuit structure with appropriate accuracy and the total CPU time for simulation is significantly reduced. The quasi-3D simulation technique can be used in many cases with advantages such as saving computing time, making no demands on the high-end computer terminals, and being easy to operate.

准静态拉伸下PBX力学性能的三维细观模拟

为了研究PBX在准静态拉伸下的力学响应行为,探索细观结构对力学性能的影响规律及机制,采用有限元计算方法,结合双线性内聚力模型,基于自编程序构建的PBX三维细观模型,研究了在单轴拉伸条件下颗粒体积分数、颗粒尺寸以及界面性能3个细观参数对PBX力学性能的影响。结果表明,三维模拟获得的宏观力学性能与实验数据能够较好吻合。此外,还发现颗粒体积分数增加会导致杨氏模量显著增加,同时也会导致抗拉强度升高,颗粒体积分数从61.2%增加至95.6%使得抗拉强度升高了38.9%,增加颗粒尺寸则会导致抗拉强度降低,颗粒尺寸从120μm增加到160μm,使其抗拉强度降低了13%;界面性能对抗拉强度的影响最为显著,当界面强度从0.5MPa升至5MPa时,抗拉强度从2.58MPa升至6.82MPa,说明相比于颗粒体积分数及尺寸,改善界面性能是提升PBX抗拉强度更为有效的方法。