In-situ constructed SnO_(2) gradient buffer layer as a tight and robust interphase toward Li metal anodes in LATP solid state batteries

Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP),of much interest owing to its high ionic conductivity,superior air stability,and low cost,has been regarded as one of the most promising solid-state electrolytes for next-generation solid-state lithium batteries(SSLBs).Unfortunately,the commercialization of SSLBs is still impeded by severe interfacial issues,such as high interfacial impedance and poor chemical stability.Herein,we proposed a simple and convenient in-situ approach to constructing a tight and robust interface between the Li anode and LATP electrolyte via a SnO_(2)gradient buffer layer.It is firmly attached to the surface of LATP pellets due to the volume expansion of SnO_(2)when in-situ reacting with Li metal,and thus effectively alleviates the physical contact loosening during cycling,as confirmed by the mitigated impedance rising.Meanwhile,the as-formed SnO_(2)/Sn/LixSn gradient buffer layer with low electronic conductivity successfully protects the LATP electrolyte surface from erosion by the Li metal anode.Additionally,the LixSn alloy formed at the Li surface can effectively regulate uniform lithium deposition and suppress Li dendrite growth.Therefore,this work paves a new way to simultaneously address the chemical instability and poor physical contact of LATP with Li metal in developing low-cost and highly stable SSLBs.

AN ASYMPTOTIC METHOD FOR ANALYZING THE STRESS IN A FUNCTIONALLY GRADIENT MATERIAL LAYER ON A SURFACE OF A STRUCTURAL COMPONENT

A simple and effective method for analyzing the stress distribution in a Functionally Gradient Material(FGM) layer on the su;face of a structural component is proposed in this paper. Generally, the FGM layer is very thin compared with the characteristic length of the structural component, and the nonhomogeneity exists only in the thin layer. Based on these features, by choosing a small parameter I which characterizes the stiffness of the layer relative to the component, and expanding the stresses and displacements on the two sides of the interface according to the parameter lambda, then asymptotically using the continuity conditions of the stresses and displacements on the interface, a decoupling computing process of the coupling control equations of the layer and the structural component is realized. Finally, two examples are given to illustrate the application of the method proposed.

Effect of slope gradient on the subsurface water flow velocity of sand layer profile

Subsurface water flow velocity influences the hydrodynamic characteristics of soil seepage and the interaction between subsurface water flow and surface runoff during soil erosion and sediment transport.A visualized method and equipment was adopted in this study to observe the subsurface water flow.Quartz sand was used as the test material of subsurface water flow and fluorescent dye was used as the indicator for tracing subsurface water flow.Water was supplied at the same flow discharge to the three parts at the bottom of the test flume,and the subsurface water flow were determined with four slope gradients(4°,8°,10°,and 12°).The results showed that the seepage velocity gradually increased with increasing slope gradient.The pore water velocity at different depths of sand layer profile increased with increasing slope gradient,whereas the thickness of the flow front gradually decreased.For the same slope gradient,the pore water velocity in the lower layer was the largest,whereas the thickness of the flow front was the smallest.Comparative analysis of the relationship between seepage velocity and pore water velocity at different depths of sand layer profile showed that the maximum relative difference between the measured pore water velocity and the computational pore water velocity at different depths of sand profile in the experiment was 4.38%.Thus,the test method for measuring the subsurface water flow velocity of sand layer profile adopted in this study was effective and feasible.The development of this experiment and the exploration of research methods would lay a good test foundation for future studies on the variation law of subsurface water flow velocity and the determination of flow velocity in purple soils,thus contributing to the improvement of the hydrodynamic mechanism of purple soils.

Mechanical properties of electroformed copper layers with gradient microstructure

The electroformed copper layer with gradient microstructure was prepared using the ultrasonic technique. The microstructure of the electroformed copper layer was observed by using an optical microscope （OM） and a scanning electron microscope （SEM）. The preferred orientations of the layer were characterized by X-ray diffraction （XRD）. The mechanical properties were evaluated with a Vicker＇s hardness tester and a tensile tester. It is found the gradient microstructure consists of two main parts： the outer part （faraway substrate） with columnar crystals and the inner part （nearby substrate） with equiaxed grains. The Cu-（220） preferred orientation increases with the increasing thickness of the copper layer. The test results show that the microhardness of the electroformed copper layer decreases with increasing grain size along the growth direction and presents a gradient distribution. The tensile strength of the outer part of the electroformed copper layer is higher than that of the inner part but at the cost of ductility. Meanwhile, the integral mechanical properties of the electroformed copper with gradient microstrucmre are significantly improved in comparison with the pure copper deposit.

Impact toughness of a gradient hardened layer of Cr5Mo1V steel treated by laser shock peening

Laser shock peening（LSP） is a widely used surface treatment technique that can effectively improve the fatigue life and impact toughness of metal parts.Cr5Mo1 V steel exhibits a gradient hardened layer after a LSP process.A new method is proposed to estimate the impact toughness that considers the changing mechanical properties in the gradient hardened layer.Assuming a linearly gradient distribution of impact toughness,the parameters controlling the impact toughness of the gradient hardened layer were given.The influence of laser power densities and the number of laser shots on the impact toughness were investigated.The impact toughness of the laser peened layer improves compared with an untreated specimen,and the impact toughness increases with the laser power densities and decreases with the number of laser shots.Through the fracture morphology analysis by a scanning electron microscope,we established that the Cr5Mo1 V steel was fractured by the cleavage fracture mechanism combined with a few dimples.The increase in the impact toughness of the material after LSP is observed because of the decreased dimension and increased fraction of the cleavage fracture in the gradient hardened layer.

THE BOUNDARY LAYER SOLUTIONS OF THE INTERFACE PROBLEM CONSIDERING THE STRAIN GRADIENT

Acoording to the classical elastic theory, there is always adiscontinuity of rotation angle on the interface different materials.This illogic result can be overcome by the strain gradient plasticitytheory. In the light of this theory, there is a group of boundarylayer solutions near the in- terface, which have made importantadjustment of the classical results.

Effect of an adverse pressure gradient on the streamwise Reynolds stress profile maxima in a turbulent boundary layer

It is widely accepted that in a turbulent boundary layer （TBL） with adverse pressure gradient （APG） an outer peak usually appears in the profile of streamwise Reynolds stress. However, the effect of APG on this outer peak is not clearly understood. In this paper, the effect of APG is analysed using the numerical and experimental results in the literature. Because the effect of upstream flow is inherent in the TBL, we first analyse this effect in TBLs with zero pressure gradient on flat plates. Under the individual effect of upstream flow, an outer peak already appears in the profile of streamwise Reynolds stress when the TBL continues developing in the streamwise direction. The APG accelerates the appearance of the outer peak, instead of being a trigger.

IN SITU GRADIENT DOUBLE-LAYER COMPOSITES OF Al-Fe ALLOY BY CENTRIFUGAL CASTING

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Gradient nanoporous phenolics as substrates for high-flux nanofiltration membranes by layer-by-layer assembly of polyelectrolytes

Thin film composite(TFC) membranes represent a highly promising platform for efficient nanofiltration(NF)processes. However, the improvement in permeance is impeded by the substrates with low permeances. Herein,highly permeable gradient phenolic membranes with tight selectivity are used as substrates to prepare TFC membranes with high permeances by the layer-by-layer assembly method. The negatively charged phenolic substrates are alternately assembled with polycation polyethylenimine(PEI) and polyanion poly(acrylic acid)(PAA)as a result of electrostatic interactions, forming thin and compact PEI/PAA layers tightly attached to the substrate surface. Benefiting from the high permeances and tight surface pores of the gradient nanoporous structures of the substrates, the produced PEI/PAA membranes exhibit a permeance up to 506 L? m-2?h-1?MPa-1, which is ~2–10 times higher than that of other membranes with similar rejections. The PEI/PAA membranes are capable of retaining N 96.1% of negatively charged dyes following the mechanism of electrostatic repulsion. We demonstrate that the membranes can also separate positively and neutrally charged dyes from water via other mechanisms.This work opens a new avenue for the design and preparation of high-flux NF membranes, which is also applicable to enhance the permeance of other TFC membranes.

Hot-forging Die Cavity Surface Layer Temperature Gradient Distribution and Determinant

Based on the car front-wheel-hub forging forming process of numerical simulation, the temperature gradient expression of forging model cavity near the surface layer was got ten, which illustrates that the forging temperature gradient is related to forging die materials thermal conductivity, specific heat and impact speed, and the correlation coefficient is 0.97. Under the different thermal conductivity, heat capacity and forging speed, the temperature gradient was compared with each other. The paper obtained the relevant laws, which illustrates the temperature gradient relates to these three parameters in a sequence of thermal conductivity 〉 impact speed〉 specific heat capacity. To reduce thermal stress in the near-surface layer of hot forging cavity, the material with greater thermal conductivity coefficient and specific heat capacity should be used.

超声滚压对DC53钢表面性能的影响

为了改善DC53冷作模具钢的表面性能,使用扫描电子显微镜、激光光谱共聚焦显微镜、显微硬度计、球-盘摩擦磨损试验机等设备分析了超声表面滚压加工工艺(USRP)的静压力、滚压道次、振幅、进给量对DC53冷作模具钢表面粗糙度、显微硬度、摩擦因数和磨损的影响规律。结果表明:与未处理DC53模具钢相比,USRP处理后DC53冷作模具钢表面产生了塑性变形,表面粗糙度由5.570μm最低可降为1.067μm,且在DC53冷作模具钢表面产生了晶粒细化现象,引入了梯度硬化层,表面硬度由基体的720 HV最大可提升为818.6 HV,硬化层深度最大可达300μm。摩擦因数降低,磨痕宽度减小,耐磨性能提高。通过极差分析法获得了对粗糙度、显微硬度、摩擦因数影响最大的工艺参数依次为进给量、滚压道次、静压力。通过灰色关联度分析法获得了工艺参数对表面性能的影响次序为静压力>进给量>滚压道次>振幅,最佳工艺参数组合为静压力400 N,滚压道次4次,振幅12μm,进给量0.05 mm。

稠油油藏体相流体非线性渗流理论模型

根据稠油油藏体相流体渗流特点,建立基于稠油吸附边界层和屈服特性影响下的稠油体相流体非线性渗流理论模型及启动压力梯度理论公式,并利用岩心渗流与启动压力梯度试验结果对理论模型计算结果进行验证。结果表明:理论计算结果与试验结果拟合较好,启动压力梯度理论公式计算结果平均偏差为7.77%,稠油油藏体相流体非线性渗流理论模型计算结果平均偏差为7.50%,均在可接受偏差范围内,并且该模型针对不同流变类型的流体渗流都具有较好的普适性。

3/4开口试验段汽车风洞的风阻测量误差分析与修正

汽车风洞用3/4开口试验段模拟真实道路气动环境,有限的试验段尺寸、地面边界层及射流剪切层会干扰流场,从而引起风阻测量误差。根据简化势流模型分析,3/4开口试验段存在模型实体阻塞、喷口阻塞、收集口阻塞以及水平压力梯度4项系统误差源,其中模型实体阻塞让风阻测量值偏低,喷口和收集口阻塞让风阻测量值偏高,彼此平衡抵消机制使3/4开口试验段风洞具有能够适应更大尺寸模型的优势。利用Mercker-Wiedemann修正方法,结合同济大学整车气动声学风洞,计算修正了3辆不同尺寸车型的风阻系数。结果显示:设定风阻系数误差不超过1%为标准,3/4开口试验段汽车风洞最大阻塞比为15%;水平压力梯度对风阻系数误差的影响更大,风洞设计和验收标准应保证dC_(p)(x)/dx≤0.001/m。

优化精液处理中的密度梯度离心法以提高受精结局的探讨

【目的】本研究旨在改进生殖男科领域现有的精液处理方法,特别是针对双层密度梯度法中的300×g 20 min处理条件,以提高受精结局。【方法】收集2020年7月和9月以及2022年3月和5月在中山大学附属第六医院生殖医学中心进行辅助生殖助孕的1623例患者的精液标本进行实验。预实验中,比较四种不同的双层密度梯度方法(200×g 10 min、200×g 20 min、300×g 10 min和300×g 20 min)处理后标本的精子DNA碎片率和回收率。然后,筛选出一种最优的方法作为新方法,并与目前在用的旧方法(300×g 20 min双层梯度法)进行对比,检验受精率是否有统计学差异。在新方法的基础上,进一步优化为单层密度梯度法,并与双层密度梯度法进行对比,检验是否存在统计学差异。实验过程中严格控制温度、离心速度和离心时间,同时记录每组样本的数量和处理条件。【结果】在保证足够的精子回收率的基础上,发现四种双层密度梯度法中300×g 10 min的精子DNA碎片率低于300×g 20 min。因此,选择300×g 10 min作为新方法进行试验。结果表明,新方法300×g 10 min的总受精率、二核体(2pn)受精率均高于300×g 20 min,且差异有统计学意义(P<0.05);300×g 10 min的卵裂率也略高于300×g 20 min,但差异没有统计学意义(P>0.05)。单层密度梯度法的总受精率、2pn受精率均高于双层密度梯度法,但差异没有统计学意义(P>0.05);单层密度梯度法的卵裂率高于双层密度梯度法,囊胚形成率低于双层密度梯度法,且差异均有统计学意义(P<0.05)。【结论】相对于现有的300×g 20 min双层梯度法,300×g 10 min双层梯度法成功提高了总受精率、2pn受精率、卵裂率,缩短了精液优化处理的时间;而单层密度梯度法虽提高了卵裂率、节约了试剂成本和操作时间,但其囊胚形成率却出现了下降的情况。这些发现为生殖男科领域的精液处理方法提供了有益的指导和启示。

深度神经网络动态分层梯度稀疏化及梯度合并优化方法

针对数据并行方法加速大规模深度神经网络时易出现的通信开销大、训练耗时长、资源利用率不高的问题,提出了一种深度神经网络动态分层梯度稀疏化及梯度合并优化方法。首先,将梯度稀疏化压缩与流水线并行技术相结合,提出动态分层梯度稀疏优化方法,为每层神经网络匹配一个合适的阈值,通过在后续迭代时动态调整该阈值,实现对每层网络传输梯度的自适应压缩。然后,提出了层梯度合并方法,利用动态规划算法对层梯度合并时的通信开销、稀疏化及层梯度计算时间进行权衡优化,求解出最佳的层梯度合并组合,并将多层小尺度梯度张量合并为一层通信,以降低分层梯度决策时引入的过高通信延迟开销。最后,将求解出的最佳层梯度合并组合应用于具体的训练迭代过程。实验结果表明:与已有方法相比,所提方法可在保证模型训练精度的同时大大降低通信开销,提升模型的训练速度;与未压缩方法相比,训练速度最大可提升1.99倍。

滇南不同类型森林优势种幼树枝生态化学计量特征

【目的】探究不同森林类型植物碳(C)、氮(N)、磷(P)生态化学计量特征,对于深入了解物种养分元素的分布格局、受限制状况及吸收利用资源效率具有重要作用。【方法】以滇南地区热带季节雨林、热带山地雨林和中山湿性常绿阔叶林3种森林主要优势种为研究对象,分析不同类型森林上、下层优势种幼树枝C、N、P化学计量特征。【结果】滇南森林优势种幼树枝C含量为441.67~494.33 mg/g,N含量为6.26~12.47 mg/g,P含量为0.34~1.06 mg/g;滇南3种森林优势种幼树枝C、N、P含量平均值总体上随海拔梯度的增加而增加;C∶N的平均值在热带季节雨林最高、热带山地雨林最低;C∶P和N∶P平均值在热带山地雨林最高、中山湿性常绿阔叶最低;3种森林的N∶P平均值均介于10~20之间;上层优势种幼树枝C、N含量平均值低于下层优势种,P含量平均值上层高于下层,上层N∶P低于10,下层优势种接近于20;热带季节雨林中,C∶N与N∶P间呈显著负相关关系(P<0.05);热带山地雨林中,C∶N与C∶P之间呈显著正相关关系(P<0.05);中山湿性常绿阔叶林中,C∶N与C∶P、N∶P之间均呈显著负相关关系(P<0.05);3种森林上、下层优势种幼树枝C、N、P含量之间均无显著相关性。【结论】滇南3种森林优势种幼树枝C、N、P元素含量相对较高,C∶N和C∶P相对较低的分配格局特征。一方面反映出滇南森林植被C元素分解释放相对较快,植被生长受N、P元素共同限制的特征;另一方面,滇南森林上层树种对养分元素的吸收利用效率略高于下层树种。滇南森林物种所处的群落层次对其枝化学计量特征的影响程度大于海拔因素。

紫鹊界梯田失稳机制

为厘清降雨入渗作用对花岗岩区梯田边坡稳定性的影响,本文以湖南省紫鹊界梯田为例,在分析紫鹊界梯田地质条件的基础上,基于有限元数值模拟软件Geostudio多模块的耦合,分析了不同边坡坡度和不同土层厚度在暴雨条件下的渗流场和稳定性。研究结果表明:在降雨强度为90 mm/d、降雨历时为5 d的工况下,坡度为35°和40°的边坡处于失稳状态,稳定性系数与边坡坡度负相关;全风化土层越厚的边坡稳定性系数越低;在降雨历时5 d后,不同土层工况下的稳定性系数相差不大,但无降雨时,全风化土层越薄的边坡明显更加稳定。

草状氧化铝微结构渐变折射率的计算及实验研究

针对草状氧化铝的微纳结构对折射率的影响,采用台体计算法与柱体计算法计算氧化铝的体积,使用Clausius-Mossotti方程式与MATLAB软件拟合计算微纳结构的折射率变化,使用TFC软件进行拟合,最终计算出草状氧化铝的渐变折射率,研究其微结构的形貌特征及渐变折射率的分布,计算其可见光减反射性能。采用电子束沉积氧化铝薄膜,通过对沉积温度、水煮工艺等参数的优化,获得了不同结构的草状氧化铝纳米薄膜,制备了可见光波段420~680 nm的减反射薄膜。

M2高速钢表面激光熔覆WC-12Co梯度涂层的制备工艺与实验研究

文章采用COMSOL数值模拟软件,对M2高速钢表面熔覆WC-12Co涂层和添加Ni60过渡层熔覆WC-12Co梯度涂层进行数值模拟与分析。探究温度梯度随时间的变化规律,并结合梯度实验及涂层的宏观形貌与微观组织分析,总结梯度熔覆的热量耦合控制方法。模拟及实验结果表明:添加Ni60过渡层制备WC-12Co梯度涂层的温度梯度远远小于直接熔覆制备WC-12Co涂层的温度梯度;添加Ni60过渡层制备WC-12Co涂层可以利用直接熔覆制备WC-12Co涂层的激光功率,也可以扩大熔覆制备WC-12Co涂层的功率区间,有利于提高熔覆制备效率;添加Ni60过渡层能够改善涂层内部缺陷,细化组织晶粒;Ni60过渡层中的Ni元素扩散导致WC-12Co涂层的硬度降低,但仍高于基体的硬度性能。

多层复合蜂窝芯结构优化设计及其宽带吸波性能研究

多层蜂窝结构因其优异的吸波性能和高强度结构近来受到广泛关注。本文针对传统多层蜂窝界面处电磁不连续以及浸渍工艺自身精度低等问题,通过3D打印技术制备了一种具有宽频电磁波吸收能力的轻质三层梯度蜂窝结构。中层渐变壁厚蜂窝极大地减少了层与层之间的界面反射,该结构在2.92 GHz~18 GHz内实现反射损耗低于-10 dB,-10 dB相对吸波带宽为144%,且密度仅为0.292 g/cm^(3)。仿真和实验证明了均匀壁厚蜂窝结构与渐变壁厚蜂窝结构的复合设计可以实现界面的电磁连续性,有效改善了阻抗匹配,并提升了电磁波损耗能力,实现了宽频吸收效果。