Mechanical analysis of double-layered circular graphene sheets as building material embedded in an elastic medium

Possessing the unique and highly valuable properties, graphene sheets(GSs) have attracted increasing attention including that from the building engineer due to the fact that Graphene can be utilized to reinforce concrete and other building materials. In this work, the nonlocal elastic theory and classical plate theory(CLPT) are used to derive the governing equations. The element-free framework for analyzing the buckling behaviors of double layer circular graphene sheets(DLCGSs) relying on an elastic medium is proposed. Pasternak-type model is adopted to describe the elastic medium. Accordingly, the influences of boundary conditions, size of GSs and nonlocal parameters on the buckling behavior of DLCGSs are investigated. The results show that the OP buckling modes are only sensible to the van der Waals forces.

Numerical investigation of velocity distribution of turbulent flow through vertically double-layered vegetation

The velocity structures of flow through vertically double-layered vegetation(VDLV)as well as single-layered rigid vegetation(SLV)were investigated computationally with a three-dimensional(3D)Reynolds stress turbulence model,using the computational fluid dynamics(CFD)code FLUENT.The detailed velocity distribution was explored with a varying initial Froude number(Fr),with consideration of the steady subcritical flow conditions of an inland tsunami.In VDLV flows,the numerical model successfully captured the inflection point in the profiles of mean streamwise velocities in the mixing-layer region around the top of short submerged vegetation.An upward and downward movement of flow occurred at the positions located just behind the tall and short vegetation,respectively.Overall,higher streamwise velocities were observed in the upper vegetation layer due to high porosity,with Pr=98%(sparse vegetation,where Pr is the porosity),as compared to those in the lower vegetation layer,which had comparatively low porosity,with Pr=91%(dense vegetation).A rising trend of velocities was found as the flow passed through the vegetation region,followed by a clear sawtooth distribution,as compared to the regions just upstream and downstream of vegetation where the flow was almost uniform.In VDLV flows,a rising trend in the flow resistance was observed with the increase in the initial Froude number,i.e.,Fr?0.67,0.70,and 0.73.However,the flow resistance in the case of SLV was relatively very low.The numerical results also show the flow structures within the vicinity of short and tall vegetation,which are difficult to attain through experimental measurements.

Simulation study of a magnetocardiogram based on a virtual heart model:effect of a cardiac equivalent source and a volume conductor

In this paper, we present a magnetocardiogram （MCG） simulation study using the boundary element method （BEM） and based on the virtual heart model and the realistic human volume conductor model. The different contributions of cardiac equivalent source models and volume conductor models to the MCG are deeply and comprehensively investigated. The single dipole source model, the multiple dipoles source model and the equivalent double layer （EDL） source model are analysed and compared with the cardiac equivalent source models. Meanwhile, the effect of the volume conductor model on the MCG combined with these cardiac equivalent sources is investigated. The simulation results demonstrate that the cardiac electrophysiological information will be partly missed when only the single dipole source is taken, while the EDL source is a good option for MCG simulation and the effect of the volume conductor is smallest for the EDL source. Therefore, the EDL source is suitable for the study of MCG forward and inverse problems, and more attention should be paid to it in future MCG studies.

A Kinematic Thermal Model for Descending Slabs with Velocity Boundary Layers:A Case Study for the Tonga Subducting Slab

For the purpose of investigating the influence of metastable olivine（MO） phase transformations on both deep seismicity and stagnation of slabs,we constructed a 2-dimensional finite element thermal model for a 120 Ma-old 50°dipping oceanic lithosphere descending at 10 cm/yr with velocity boundary layers,which would mitigate the interference of constant velocity field for the slab. The resulting temperatures show that most of intermediate and deep earthquakes occurring within the Tonga slab are occurring inside the 800℃and 1200℃isotherm,respectively.The elevation of olivine transformation near～410 km and respective persistence of metastable olivine and spinel within the transition zone and beneath 660 km would thus result in bimodal positive,zonal,negative density anomalies,respectively.These results together with the resulting pressure anomalies may reflect the stress pattern of the Tonga slab：（i） slab pull force exerts above a depth of～230 km;（ii） MO existence changes the buoyancy force within the transition zone and facilitates slab stagnation at a depth of 660 km;（iii） as the subducting materials accumulated over 660 km,deepest earthquakes occur due to MO transformation;（iv） a flattened‘slab’ may penetrate into the lower mantle due to the density increment of Sp transformation.

Thickness-averaged model for numerical simulation of electroosmotic flow in three-dimensional microfluidic chips

The microfiuidic system is a multi-physics interaction field that has at- tracted great attention. The electric double layers and electroosmosis are important flow-electricity interaction phenomena. This paper presents a thickness-averaged model to solve three-dimensional complex electroosmotic flows in a wide-shallow microchan- nel/chamber combined （MCC） chip based on the Navier-Stokes equations for the flow field and the Poisson equation to the electric field. Behaviors of the electroosmotic flow, the electric field, and the pressure are analyzed. The quantitative effects of the wall charge density （or the zeta potential） and the applied electric field on the electroosmotic flow rate are investigated. The two-dimensional thickness-averaged flow model greatly simplifies the three-dimensional computation of the complex electroosmotic flows, and correctly reflects the electrookinetic effects of the wall charge on the flow. The numerical results indicate that the electroosmotic flow rate of the thickness-averaged model agrees well with that of the three-dimensional slip-boundary flow model. The flow streamlines and pressure distribution of these two models are in qualitative agreement.

Co-flocculation mechanism and physical model

Analysed and summarized the dynamics and chemical factors in the co (co-agulation)-flocculation process. A completely new definition for co-flocculation was given. If a colloid particle didn抰 contact with drug to emerge (physical) chemical effect, the possi-bility for the colloid particle to coagulate (flocculate) was rather small, only at the floccula-tion stage; it may be caught by net or settled by differential sedimentation. Base on sev-eral assumed important premises, the several steps and physical model of co-flocculation process were given, and the mixing, coagulation and flocculation were proposed accord-ing to their essentiality.

基于注意力循环神经网络的联合深度推荐模型

为了向用户推荐符合兴趣偏好的项目,设计一种基于注意力循环神经网络的联合深度推荐模型。将双层注意力机制设置于网络中,该模型由五个部分构成,在输入层中生成联合深度推荐模型的输入矩阵,通过序列编码层对项目评论文本语义展开正向和反向编码,获得隐藏状态输出,并将其输入双层注意力机制中,提取项目特征,利用全连接层提取用户偏好特征。在预测层中建立项目与用户的交互模型,获得项目评分,为用户推荐高评分的项目。为了提高模型精度,加权融合MSE损失函数、CE损失函数和RK损失函数建立组合损失函数,对深度联合训练模型展开训练,提高模型的推荐性能。仿真结果表明,所提方法具有良好的推荐效果,能够适应不断变化的市场需求和用户行为。

A Numerical Research on a Compressibility-correlated Langtry＇s Transition Model for Double Wedge Boundary Layer Flows

A new compressibility correlation is introduced in the Langtry＇s local variable-based transition model to investigate the phe- nomenon on double wedge shock/boundary layer interactions. The cmnputational analysis compared with experimental data has been made to assess the influence of the wall temperature and the leading edge nose radius on a hypersonic double wedge boundary layer. It has been found that the laminar boundary layer separation occurs on the first ramp. Furthermore, the wall temperature and the leading edge nose radius have remarkable influence on the separation characteristics in the kink. Comparison of the calculated pressure coefficient distribution and the boundary layer profile with the experimental data shows that better results can be achieved when using the modified transition model.

Double-layer ramp-metering model for incident congestion on expressway

In order to ensure stable traffic capacity and avoid incident congestion, a double-layer ramp metering model is proposed in this paper, based on coordination control theory, to predict and control the traffic flow at each on-ramp, when there is incident congestion on the expressway. The function of the lower model is to recognize where the incident congestion exists, based on an adaptive neural net- work with inputs of traffic flow, velocity and density. The outputs of the lower model are the number of section where the congestion occurs, the number of ramp which should be controlled, and real-time traffic flow information. These outputs should be transmitted to the upper model. The function of the upper model is to design the ramp-metering strategy based on nonlinear theory. The outputs of the up- per model are a ramp-metering rate and traffic-flow state after ramp controlling on the expressway. The results of the simulation show that the double-layer ramp metering model could shorten the delay by about 25%, and the variance of the model results is 0. 002, which could certify the control strategy is equitable.

Interfacial electrokinetic characteristics before and after bioleaching microorganism adhesion to pyrite

Zeta potentials of pyrite and Acidithiobacillus ferrooxidans cultured by sulfur in different levels of ionic strength and pH values were measured by Coulter Delsa 440SX zeta potential determinator. Meanwhile, the effects of bacterial adhesion and bacterial concentration on zeta potential of pyrite after adsorption were investigated. The results show that with the increase of ionic strength, zeta potentials of pyrite decrease in the range of pH 2.5?10.5 and the isoelectric point(IEP) of mineral shifts to the left. It is also found that the specific adsorption on pyrite of chloride ion can affect zeta potentials of pyrite sharply. As bacterial adsorption occurs, IEP of pyrite shifts towards that of Acidithiobacillus ferrooxidans; as bacterial concentration is increscent, this tendency is even larger and more obvious. Finally, a reasonable explanation for above-mentioned experimental phenomena was given by electrical double layer model and surface ionization model.

Behavioral Feature and Correlative Detection of Multiple Types of Node in the Internet of Vehicles

Undoubtedly,uncooperative or malicious nodes threaten the safety of Internet of Vehicles(IoV)by destroying routing or data.To this end,some researchers have designed some node detection mechanisms and trust calculating algorithms based on some different feature parameters of IoV such as communication,data,energy,etc.,to detect and evaluate vehicle nodes.However,it is difficult to effectively assess the trust level of a vehicle node only by message forwarding,data consistency,and energy sufficiency.In order to resolve these problems,a novel mechanism and a new trust calculating model is proposed in this paper.First,the four tuple method is adopted,to qualitatively describing various types of nodes of IoV;Second,analyzing the behavioral features and correlation of various nodes based on route forwarding rate,data forwarding rate and physical location;third,designing double layer detection feature parameters with the ability to detect uncooperative nodes and malicious nodes;fourth,establishing a node correlative detection model with a double layer structure by combining the network layer and the perception layer.Accordingly,we conducted simulation experiments to verify the accuracy and time of this detection method under different speed-rate topological conditions of IoV.The results show that comparing with methods which only considers energy or communication parameters,the method proposed in this paper has obvious advantages in the detection of uncooperative and malicious nodes of IoV;especially,with the double detection feature parameters and node correlative detection model combined,detection accuracy is effectively improved,and the calculation time of node detection is largely reduced.

不同老化方式下新旧沥青的扩散融合

分别制备了热氧老化沥青和热氧-紫外老化沥青,构建了新、旧沥青双层扩散模型,并且通过相对浓度与扩散系数的模拟计算、拉拔试验与荧光显微镜试验研究了新、旧沥青扩散融合程度与温度、沥青四组分的关系.结果表明:热氧-紫外老化沥青更不易与基质沥青扩散融合,与基质沥青的黏附性较差;在10~40℃内,新、旧沥青能够快速扩散融合,超过40℃后,升高温度对扩散融合的促进作用逐渐减小,且对热氧-紫外老化沥青与基质沥青的扩散融合促进作用的减小速率更大;沥青四组分扩散系数的大小顺序依次为:饱和分>芳香分≥胶质>沥青质,经紫外老化后,四组分的扩散系数均有所下降,沥青质的降幅最大.

可重构低熵智能车间布局建模与优化

针对智能车间布局,采用单元布局的方式分别对单元间布局和单元内布局进行建模,设计涵盖物料搬运成本、时间损失成本、单元重构成本、设备成本、车间面积利用率和布局柔性等面向低熵化车间布局的多目标函数,给出包括边界约束、间距约束和固定位置约束等符合车间实际情况的定量约束条件。针对车间布局模型多变量、多约束和非线性的特点,设计一种基于精英策略和自适应交叉、变异算子的双层遗传元胞算法进行求解。通过典型企业作业车间布局改造实例分析,验证模型和算法的可行性和有效性。

双层虚拟垂线时差法流量计算模型实证研究

为提高天然河道河流流量在线监测精度,基于超声波时差法多层测流技术,提出并构建了双层虚拟垂线时差法流量计算模型,对江苏省秦淮新河水利枢纽泄洪期进行了计算,并与同期开展的走航ADCP流量比测结果进行对比分析。结果表明,该双层虚拟垂线时差法流量计算方法在一定程度上克服了由于天然河道水情条件复杂而导致率定期长的难题,河道流量测验精度高,计算的泄洪期河道流量与走航ADCP测量数据基本一致,相关系数为0.999,相对误差均在15%以内,在一定程度上能够满足洪水期河道流量测验精度要求。

双层永磁体结构高速永磁电机转子涡流损耗解析模型

对于采用低电导率护套高电导率永磁体的表贴式高速永磁电机,在永磁体和保护套之间增加一层低电导率的永磁体,可有效降低永磁体上的涡流损耗。目前,对于双层永磁体转子结构的电机在使用有限元软件进行转子涡流损耗计算时,因为需要寻求两种永磁体不同厚度配比下的最优方案,所以要进行大量参数化,导致计算时间长、效率低。针对这一问题,该文基于精确子域法,建立了一个考虑定子开槽以及涡流反作用影响的双层永磁体结构转子涡流损耗解析模型,可同时对电枢磁场和负载磁场下双层永磁体结构转子涡流损耗进行求解,并且该模型可扩展至多层永磁体复合结构的转子涡流损耗计算。在此基础上分析了双层永磁体结构下外层永磁体不同厚度和不同材料对转子涡流损耗和内层永磁体消耗量的影响。最后通过有限元仿真和C型铁心实验验证了该解析模型的有效性。

多谐波源接入的城市配电网SAPF优化配置方法

针对分布式光伏和电动汽车充电设施等新谐波源渗透率高及分散接入造成的城市配电网谐波污染分散化与全网化问题,构建一种兼顾配电网谐波治理成本与治理成效的并联型有源电力滤波器选址定容双层优化模型。首先,外、内层模型分别以配电网谐波治理成本最小和电压畸变率最低为目标函数;然后,采用粒子群优化算法和遗传算法分别求解,实现配电网谐波治理效益最高的目标;最后,选取IEEE 33节点系统进行仿真,验证了所建模型对配电网谐波治理装置优化配置的有效性。

物联网双层耦合动力学信息传播模型研究

信息传播模型的研究是物联网领域的重要组成部分,它有助于提高物联网系统的性能和效率,促进物联网技术的进一步发展,针对物联网通信中影响信息传播的因素复杂且不稳定的问题,该文提出一种双层耦合信息传播模型SIVR-UAD,通过分析物联网中不同状态的设备和用户对信息传播的影响,建立了6种耦合状态,并利用马尔科夫方法分析耦合节点的状态变化过程,找到信息传播平衡点,最后通过理论分析证明了模型的平衡点的唯一性以及稳定性。仿真结果表明,在3组不同的初始耦合节点数下,SIVR-UAD模型中的6种耦合节点数量变化始终趋向同一稳定水平,证明了该模型的平衡点和稳定性。

考虑能耗指标的双层自动化立体仓储系统布局研究

为解决仓储系统运行过程中能源消耗过大的问题,针对双层自动化立体仓库进行了能耗分析,建立了双层仓储系统存储、检索任务时间模型以及考虑物品自重的穿梭车(提升机、电梯)运动能耗模型,并利用仿真实验研究了仓库中自动小车及提升机的速度、加速度,货架布局对于仓库运行能耗、吞吐量的关系和影响。实验结果显示增加穿梭车速度、加速度都会提升系统吞吐量,速度对吞吐量的提升更大;增加电梯加速度、速度会适当降低能耗。达到吞吐量500条件下,新的系统布局可以降低20%左右的能耗并提升2.7%的吞吐量,帮助物流企业建立更加合理的仓库布局设计,从而减少存储和检索过程中的能源消耗。

天然气水合物固态流化开采井筒多相流动模型

为了研究水合物浆体输送过程中水合物分解规律与井筒多相流动特征,基于气-液-固三相的质量、动量和能量守恒方程,考虑水合物分解引起的相间传热和传质,结合双层连续管开采水合物的工艺特点,建立了水合物相变条件下全瞬态非等温气-液-固多相流动模型。基于MWD实测温度数据对模型的准确性进行了验证。利用模型分析了水合物浆体输送过程中,井筒温度、井筒压力、水合物分解速率与各相体积分数随开采时间变化的规律。模拟结果表明:在开采前2 h内,水合物分解速率较为缓慢,管内各相体积分数变化较小;随着开采时间的延长,管内各相体积分数发生显著变化;在开采约5 h后达到稳定状态,此时井口气相体积分数约为40%;此外,在井下举升泵位置处,固-液相体积分数均发生显著突变。研究结果对深入了解水合物开发过程中的多相流动规律具有一定的参考价值,有助于水合物开采技术的进一步发展。

高速公路立体复合扩容设计的仿真模型研究

针对传统交通仿真技术在高速公路立体复合扩容场景存在评估精度不足、应用效果甚微的问题,提出了一种面向高速公路立体复合扩容设计的仿真模型构建方法。选取深圳市机荷高速改扩建工程为研究对象,梳理路网设施、交通需求数据、驾驶行为模型参数等3大仿真模型建模要素,提出仿真建模的技术流程;对包含互通立交、收费站、上下匝道等重点基础设施的全路网进行仿真建模,基于交通量预测模型获取项目范围的出行OD矩阵,完成交通需求建模;引入驾驶模拟仿真技术,构建高速公路立体复合扩容的驾驶模拟场景,设计并开展驾驶模拟实验,采用K均值聚类算法将驾驶行为划分为激进、保守、正常3个类别,并分别分析驾驶行为特征,据此对仿真驾驶行为模型参数进行标定,提升仿真模型精度。仿真结果表明:该模型构建方法,可以有效标定期望速度、车头时距、临界间隙等参数,从而提升仿真模型分析精度。