基于FDS的风扇舱双油池火温度变化特征

航空发动机燃油泄漏形成的油池火威胁发动机运行和飞机安全,为描述风扇舱内油池火复杂的物理传播过程,开展双油池火温度变化特征的研究。首先,基于火灾动力学模拟软件(FDS)建立CFM56-7B发动机风扇舱物理计算模型;然后,比较Trent 800发动机风扇舱单油池火温度计算值与试验值,验证网格独立性;最后,借助探测器和切片分析舱内双油池火的发展过程和温度变化特征。结果表明:双油池火温度在舱内环向上经历增加和振荡准稳态2个变化阶段,其变化幅度与探测器和油池的间距相关;油池火向左偏斜现象导致左半边温度较高;火焰在轴向上经历火羽流上浮、火焰开始融合、融合扩大和完全融合等阶段。

基于FDS大型体育场馆火灾与疏散研究

大型体育场馆聚集人数多,人群密度高,一旦突发状况,大量人流的快速有效疏散成为首要安全问题。以某奥体中心项目为案例,分析大型体育场馆的平面布局、空间类型、功能分布特点、火灾防控的难点;利用FDS软件pyrosim,进行火灾动力学模拟,研究火灾发生后场内烟气温度、CO浓度、烟气的空间数值变化;依托Pathfinder对大型体育场馆人群密集空间进行逃生实景演练,给出有针对性的、有效的疏散优化建议与解决方案。

基于FD-QM的“财务会计理论与实务”线上线下课程建设研究

随着信息技术的迅速发展和教育模式的变革,如何有效提升研究生课程的教学质量和学习效果成为一个重要课题。文章以FD-QM标准为指导,以专硕研究生“财务会计理论与实务”课程为对象,遵循“一致性构建”原则,按照课程建设目标,将学习目标、学习活动、学业考核等进行线上和线下的有机融合,得出课程设计方案。方案经过实施发现,依据FD-QM标准进行课程设计,可降低设计者的主观性与盲目性对课程设计的影响,使得课程设计更为科学合理。遵循FD-QM标准中的“一致性构建原则”可以真正做到“以学生为中心”,让各类课程资源得到更有效地利用。以FD-QM标准为指导设计课程,在提高教学质量的同时,还会帮助课程设计者达成课程建设目标。

基于FDS的管廊电缆火灾动态风险评估研究

为解决管廊或管沟内的电缆敷设密度较大,发生火灾极易形成电力系统的连锁事故等问题,采用FDS仿真软件,综合考虑传感器、喷淋系统、通风系统和防火门等安全屏障不同响应情况构建管廊电缆火灾动态风险评估模型,并应用Arrhenius公式将数值仿真结果指标映射为电缆火灾风险值,进而绘制时变的电缆火灾风险曲线,探究火灾情景下管廊电缆风险动态评估及应急决策优化方案。研究结果表明:喷淋系统是管廊电缆火灾风险的最关键影响因素,喷淋系统的安装位置以及动作状态在很大程度上影响管廊电缆火灾风险。研究结果可为地下管廊电缆线路典型事故的预防、处理和恢复提供应用价值。

基于FDS准则的响应曲面设计预测能力比较

预测能力是实际应用工作者评价设计优劣的重要准则之一,一般地,通过方差散布图可以对一个固定球面上的设计预测能力进行比较和选择,但无法获得对整个设计区域上的比较结果。文章介绍了基于正交表的响应曲面设计(OACD)以及基于极小极大准则的改进设计(OACM),并应用全区域预测方差占比准则——FDS准则对这两类中心组合设计进行预测能力的比较。结果表明,在一个较小方差范围内,OACD得到的FDS结果要优于OACM,而对于大部分给定方差值,OACM的FDS结果要优于OACD。

基于FDS的甲醇罐区池火灾事故后果模拟研究

大容量的甲醇罐区在化工生产项目中往往以危险化学品重大危险源的形式存在,是防灭火的重点目标。为了有效选取最佳灭火位置、科学应急处置,通过池火灾模型分析与计算,确定在常年风向一定时,无风、平均风速、中等风速和最大风速四种情况下甲醇储罐区池火灾热辐射强度和范围。文章以徐州某化工厂甲醇罐区为例,利用FDS软件构建火灾模型,分析不同热辐射强度对周围设施的破坏情况,完成热辐射演化三维仿真效果,为最佳灭火位置设置提供建议。

基于FDS的飞机客舱内饰材料的参数优化研究

为了优化飞机客舱火灾数值模型并提高其模拟的精确度,采用火灾动力学三维模拟软件FDS(Fire Dynamics Simulator)建立全尺寸A320客舱火灾模型,通过对飞机客舱典型内饰材料热物理性参数的敏感性分析,探究这些参数对飞机客舱火灾动态模拟结果的影响程度。结果表明,飞机内饰材料的密度、比热系数、参考温度等参数都会对火灾的热释放速率(Heat Release Rate,HRR)和燃烧过程产生影响,在不同误差范围内的变化会导致热释放速率的增加或减少,其中参考温度的变化会导致热释放速率的峰值提前90 s到达。

基于正交试验和FDS的狭小面积高空间火灾烟气扩散规律研究

为提高狭小面积高空间场所的排烟效率,采用正交试验和火灾动力学模拟工具(FDS),对49组工况下的狭小面积高空间场所进行火灾模拟,研究其火灾危险性和烟气扩散规律。结果表明:场所面积和火源位置是影响火灾危险性的主要因素;烟气高度评价指标在评估火灾风险性时更敏感,应优先考虑;在相同时间下,场所面积为50 m^(2)的烟气高度明显低于200 m^(2);在进行狭小面积高空间场所的烟气扩散规律研究时,需综合考虑场所的功能和可燃物情况等因素。研究结果可为类似场所排烟系统优化设计提供参考。

Dimension by Dimension Finite Volume HWENO Method for Hyperbolic Conservation Laws

In this paper,we propose a finite volume Hermite weighted essentially non-oscillatory(HWENO)method based on the dimension by dimension framework to solve hyperbolic conservation laws.It can maintain the high accuracy in the smooth region and obtain the high resolution solution when the discontinuity appears,and it is compact which will be good for giving the numerical boundary conditions.Furthermore,it avoids complicated least square procedure when we implement the genuine two dimensional(2D)finite volume HWENO reconstruction,and it can be regarded as a generalization of the one dimensional(1D)HWENO method.Extensive numerical tests are performed to verify the high resolution and high accuracy of the scheme.

Scalable Temporal Dimension Preserved Tensor Completion for Missing Traffic Data Imputation With Orthogonal Initialization

Dear Editor,This letter puts forward a novel scalable temporal dimension preserved tensor completion model based on orthogonal initialization for missing traffic data(MTD)imputation.The MTD imputation acts directly on accessing the traffic state,and affects the traffic management.

An Exploration of the Three Dimensions and Epochal Strengths of Building a Human Community With a Shared Future

The idea of a human community with a shared future was proposed by the Communist Party of China(CPC)Central Committee with Comrade Xi Jinping at its core for the future development of human beings to face up to the most important question in today's world:“What is happening to the world and what should we do?”It profoundly answers the question of the world,history,and the times.The theory of a human community with a shared future is an innovative theory with a multidimensional formation logic that guides humanity toward continually seeking common interests and values.This paper dives into the profound motivations behind building a human community with a shared future from historical,cultural,and practical dimensions and analyzes its epochal value from both domestic and international perspectives.This not only helps exert China's role in the international community,contributing Chinese strength to the construction of a peaceful,stable,and prosperous human society,but also enhances the influence of the idea of a human community with a shared future in the international community,accelerating the building of a human community with a shared future that considers the legitimate concerns of all countries,and aiding in solving the crises facing the world.

AZ31B镁合金FDS连接工艺与性能分析

镁合金材料是密排六方结构,常温下可开动的滑移系较少,加工性能较低,容易产生脆性断裂。以AZ31B镁合金挤压板材为例,采用FDS连接工艺进行连接实验,通过优化关键工艺参数如转速、压力、扭矩等,改善连接成形性。参数优化后,连接成形性得到了显著改善,包络面无裂纹,连接剪切强度达到4.9 kN以上。研究了镁合金AZ31B材料FDS连接剪切拉伸过程,分析了两次峰值力的形成原因。

Fractal analysis of major faults and fractal dimension of lineaments in the Indo-Gangetic Plain on a regional scale

The Indo-Gangetic Plain(IGP)is one of the most seismically vulnerable areas due to its proximity to the Himalayas.Geographic information system(GIS)-based seismic characterization of the IGP was performed based on the degree of deformation and fractal dimension.The zone between the Main Boundary Thrust(MBT)and the Main Central Thrust(MCT)in the Himalayan Mountain Range(HMR)experienced large variations in earthquake magnitude,which were identified by Number-Size(NS)fractal modeling.The central IGP zone experienced only moderate to low mainshock levels.Fractal analysis of earthquake epicenters reveals a large scattering of earthquake epicenters in the HMR and central IGP zones.Similarly,the fault fractal analysis identifies the HMR,central IGP,and south-western IGP zones as having more faults.Overall,the seismicity of the study region is strong in the central IGP,south-western IGP,and HMR zones,moderate in the western and southern IGP,and low in the northern,eastern,and south-eastern IGP zones.

A Dynamical System-Based Framework for Dimension Reduction

We propose a novel framework for learning a low-dimensional representation of data based on nonlinear dynamical systems,which we call the dynamical dimension reduction(DDR).In the DDR model,each point is evolved via a nonlinear flow towards a lower-dimensional subspace;the projection onto the subspace gives the low-dimensional embedding.Training the model involves identifying the nonlinear flow and the subspace.Following the equation discovery method,we represent the vector field that defines the flow using a linear combination of dictionary elements,where each element is a pre-specified linear/nonlinear candidate function.A regularization term for the average total kinetic energy is also introduced and motivated by the optimal transport theory.We prove that the resulting optimization problem is well-posed and establish several properties of the DDR method.We also show how the DDR method can be trained using a gradient-based optimization method,where the gradients are computed using the adjoint method from the optimal control theory.The DDR method is implemented and compared on synthetic and example data sets to other dimension reduction methods,including the PCA,t-SNE,and Umap.

A novel box-counting method for quantitative fractal analysis of threedimensional pore characteristics in sandstone

Fractal theory offers a powerful tool for the precise description and quantification of the complex pore structures in reservoir rocks,crucial for understanding the storage and migration characteristics of media within these rocks.Faced with the challenge of calculating the three-dimensional fractal dimensions of rock porosity,this study proposes an innovative computational process that directly calculates the three-dimensional fractal dimensions from a geometric perspective.By employing a composite denoising approach that integrates Fourier transform(FT)and wavelet transform(WT),coupled with multimodal pore extraction techniques such as threshold segmentation,top-hat transformation,and membrane enhancement,we successfully crafted accurate digital rock models.The improved box-counting method was then applied to analyze the voxel data of these digital rocks,accurately calculating the fractal dimensions of the rock pore distribution.Further numerical simulations of permeability experiments were conducted to explore the physical correlations between the rock pore fractal dimensions,porosity,and absolute permeability.The results reveal that rocks with higher fractal dimensions exhibit more complex pore connectivity pathways and a wider,more uneven pore distribution,suggesting that the ideal rock samples should possess lower fractal dimensions and higher effective porosity rates to achieve optimal fluid transmission properties.The methodology and conclusions of this study provide new tools and insights for the quantitative analysis of complex pores in rocks and contribute to the exploration of the fractal transport properties of media within rocks.

Mean Dimension for Non-autonomous Iterated Function Systems

In this paper we introduce the notions of mean dimension and metric mean dimension for non-autonomous iterated function systems(NAIFSs for short)on countably infinite alphabets which can be regarded as generalizations of the mean dimension and the Lindenstrauss metric mean dimension for non-autonomous iterated function systems.We also show the relationship between the mean topological dimension and the metric mean dimension.

The Global Attractor and Its Dimension Estimation of Generalized Kolmogorov-Petrovlkii-Piskunov Equation

In this paper, the initial boundary value problem of a class of nonlinear generalized Kolmogorov-Petrovlkii-Piskunov equations is studied. The existence and uniqueness of the solution and the bounded absorption set are proved by the prior estimation and the Galerkin finite element method, thus the existence of the global attractor is proved and the upper bound estimate of the global attractor is obtained.

Lax-Oleinik-Type Formulas and Efficient Algorithms for Certain High-Dimensional Optimal Control Problems

Two of the main challenges in optimal control are solving problems with state-dependent running costs and developing efficient numerical solvers that are computationally tractable in high dimensions.In this paper,we provide analytical solutions to certain optimal control problems whose running cost depends on the state variable and with constraints on the control.We also provide Lax-Oleinik-type representation formulas for the corresponding Hamilton-Jacobi partial differential equations with state-dependent Hamiltonians.Additionally,we present an efficient,grid-free numerical solver based on our representation formulas,which is shown to scale linearly with the state dimension,and thus,to overcome the curse of dimensionality.Using existing optimization methods and the min-plus technique,we extend our numerical solvers to address more general classes of convex and nonconvex initial costs.We demonstrate the capabilities of our numerical solvers using implementations on a central processing unit(CPU)and a field-programmable gate array(FPGA).In several cases,our FPGA implementation obtains over a 10 times speedup compared to the CPU,which demonstrates the promising performance boosts FPGAs can achieve.Our numerical results show that our solvers have the potential to serve as a building block for solving broader classes of high-dimensional optimal control problems in real-time.

基于熵值法和FD法的比选模型在钢筋材料比选中的应用

钢筋因为其受力性能好、适用性强,其在工程中应用范围不断扩大,是目前我国工程领域的主要建材之一。不同工程项目,因其外部环境和使用要求不同,在建造过程中,对钢筋的要求往往不同,如何选取适宜的钢筋是项目建造实施中需要解决的问题,本文基于此问题,选取钢筋比选指标,构建比选模型,结合FD(0-4)法和熵值法确定钢筋比选指标的权重。FD(0-4)法是根据项目的实际情况,将专家的主观经验引入比选模型中,客观化专家对钢筋性能指标的主观意愿的一种方法,该方法确立比选指标的基本权重。熵值法根据比选指标的客观数据变化程度,调整比选指标的基本权重。二种方法结合,量化了专家对项目的理解,考虑了专家意见及经验,又结合了比选指标的客观数据变化情况对比选指标赋权重。该方法为项目建造实施中选取适宜的钢筋提供了思路。

基于FDS的双洞单向隧道火灾温度变化及烟气扩散分析

为应对隧道火情的发生,避免不必要的人员伤亡和财产损失,分析隧道内温度变化和烟气蔓延特性,选择合适纵向风速和烟气蔓延控制方案具有重要的研究价值。为此,采用PyroSim软件,建立公路隧道模型进行FDS数值模拟。模拟最大热释放功率为20 MW的火灾,在三种不同的纵向通风强度下,观测烟气的逆流长度,确定3.5 m/s为此次模拟的临界风速;在三种不同的纵向风下,依据发生火灾时隧道内温度场变化和烟气的扩散蔓延特点,以及人员的疏散和火灾救援影响;模拟隧道烟气控制方案时,为不让烟气通过横通道蔓延至辅隧道中影响人员疏散,确定合适的主辅隧道的纵向通风强度起着十分重要的作用。