基于24Model-D-ISM的地铁站火灾疏散影响因素研究

为预防地铁站火灾事故,深入了解地铁站火灾人员疏散影响因素间的内在联系与层次结构,基于第6版“2-4”模型(24Model)分析63起地铁站火灾疏散事故,充分考虑各个因素之间的交互作用,提取19个影响地铁站人员疏散的关键因素,建立地铁站火灾人员疏散影响因素指标体系;采用算子客观赋权法(C-OWA)改进决策试验与评价实验法(DEMATEL),确定地铁站火灾人员疏散的重要影响因素;在此基础上,采用解释结构模型(ISM)分析各个因素间的层次结构及相互作用路径,构建地铁站火灾人员疏散影响因素的多级递阶结构模型。研究结果表明:疏散引导、恐慌从众行为、人员拥挤为地铁站火灾人员疏散的关键影响因素;地铁站火灾人员疏散受表层因素、中间层因素、深层因素共同作用的影响,其中,疏散教育与培训、设施维护与检查、疏散预案等因素是根源影响因素,重视根源影响因素的改善有利于从本质上预防和控制事故的发生。

Contribution to the Full 3D Finite Element Modelling of a Hybrid Stepping Motor with and without Current in the Coils

The paper presents our contribution to the full 3D finite element modelling of a hybrid stepping motor using COMSOL Multiphysics software. This type of four-phase motor has a permanent magnet interposed between the two identical and coaxial half stators. The calculation of the field with or without current in the windings (respectively with or without permanent magnet) is done using a mixed formulation with strong coupling. In addition, the local high saturation of the ferromagnetic material and the radial and axial components of the magnetic flux are taken into account. The results obtained make it possible to clearly observe, as a function of the intensity of the bus current or the remanent induction, the saturation zones, the lines, the orientations and the magnetic flux densities. 3D finite element modelling provide more accurate numerical data on the magnetic field through multiphysics analysis. This analysis considers the actual operating conditions and leads to the design of an optimized machine structure, with or without current in the windings and/or permanent magnet.

基于LSTM-Informer模型的液压支架压力时空多步长预测

目前多步液压支架压力预测大多为单步液压支架压力的累计预测,单步累计次数越多,累计误差就越大,影响预测精度。针对该问题,提出了一种基于长短时记忆(LSTM)-Informer模型的液压支架压力时空多步长预测方法。采用卡尔曼滤波消除液压支架压力数据中的振动噪声后,在工作面端部和中部各选取相邻的5台液压支架压力数据建立2个时空数据集(数据集1和数据集2),并对时空数据进行标准化预处理。将时空数据输入LSTM模型提取时空特征,并将提取的时空特征输入Informer模型的编码器,经过位置编码后利用多头概率稀疏自注意力来关注压力序列的变化特征,经过最大池化和一维卷积消除最终输出特征图的冗余组合。利用多头概率稀疏自注意力来关注压力序列的变化特征,将Informer模型的解码器改为全连接层,得到液压支架压力的预测结果。实验结果表明:与基于门控循环单元(GRU)、LSTM和Informer模型的预测方法相比,基于LSTM-Informer模型的预测方法在预测6,12,24步长液压支架压力时的均方根误差(RMSE)和平均绝对误差(MAE)均最小;其中基于数据集1预测的6步长液压支架压力的RMSE分别降低了41.63%,49.74%,11.85%,MAE分别降低了41.75%,50.00%,12.00%;基于数据集2预测的6步长液压支架压力的RMSE分别降低了48.15%,59.86%,19.88%,MAE分别降低了49.87%,54.90%,13.16%。

Effect of Time Step Size and Turbulence Model on the Open Water Hydrodynamic Performance Prediction of Contra-Rotating Propellers

A growing interest has been devoted to the contra-rotating propellers （CRPs） due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibration. Compared with the single-screw system, it is more difficult for the open water performance prediction because forward and aft propellers interact with each other and generate a more complicated flow field around the CRPs system. The current work focuses on the open water performance prediction of contra-rotating propellers by RANS and sliding mesh method considering the effect of computational time step size and turbulence model. The validation study has been performed on two sets of contra-rotating propellers developed by David W Taylor Naval Ship R ＆ D center. Compared with the experimental data, it shows that RANS with sliding mesh method and SST k-ω turbulence model has a good precision in the open water performance prediction of contra-rotating propellers, and small time step size can improve the level of accuracy for CRPs with the same blade number of forward and aft propellers, while a relatively large time step size is a better choice for CRPs with different blade numbers.

基于move-step模型的地铁车站站务通信言语特征分析

规范化的通信用语可以减少沟通双方的交流时间,使接收者获取到准确的信息内容。将地铁车站站务通信按内容分为日常运营信息及突发/紧急事件信息两类,并基于move-step模型将这两类信息分为3个沟通阶段及多个沟通步骤。根据地铁车站站务通信的特点,将其言语特征分为呼叫、指示、请求、声明、通知、回复及通话完毕7种类型,并列举了相应的标准化用语范例。

24Model与LCM原因因素定义对比研究

为探究损失致因模型(LCM)原因因素定义与事故致因“2-4”模型(24Model)存在的异同和优缺点,梳理2个模型各层面原因和结果的定义,对比定义内容及其对事故原因分析等安全实务的指导作用,并以一起瓦斯爆炸事故为例加以实证分析,获得二者分析结果之间的差异。研究结果表明:LCM是首个将管理因素纳入事故致因分析的一维事件序列模型,可明确各层面原因因素的定义和因素间的逻辑关系,但部分定义存在交叉重复的问题,并没有揭示安全工作指导思想等深层次事故致因因素;24Model作为系统性事故致因模型,对各类因素的定义均以组织为主体,描述事件、事故、安全的概念内涵,划分个体安全动作、安全能力和组织安全管理体系的类别并给出含义解析,探究组织安全文化层面的问题并以32个元素体现;2个模型的事故原因分析方法均建立在对各层级原因因素定义的基础上,并适用于模型理论体系本身。

Model Test and Numerical Analysis on Long-Term Mechanical Properties of Stepped Reinforced Retaining Wall

Model tests and numerical analyses of stepped reinforced retaining wall were performed to investigate the effects of rheology of backfill and creep of geogrids on the long-term performance of the structure.The geogrid tensions,soil pressures,wall deformations and foundation pressure were measured during model construction and loading.A visco-elasto-plastic model and an empirical nonlinear visco-elastic model were utilized to simulate the stresses and deformations of geogrid-reinforced earth-retaining wall under long-term loads.By comparing test data with numerical results,it is shown that the foundation pressure distribution is nonlinear,and the lateral constraint of geogrids for backfill can cause a redistribution of foundation pressure.The curve of soil pressure is outside convex at each step initially,and it is close to the distribution for the case of vertical wall subsequently.The variation trend of geogrid tensions at different heights is obtained.Moreover,the failure mechanism and development mode of potential slip surface in retaining wall are proposed.

Development and Experimental Evaluation of a Steady-state Model for the Step-feed Biological Nitrogen Removal Process

In this article,a steady-state mathematical model was developed and experimentally evaluated to inves- tigate the effect of influent flow distribution and volume ratios of anoxic and aerobic zones in each stage on the to- tal nitrogen concentration of the effluent in the step-feed biological nitrogen removal process.Unlike the previous modeling methods,this model can be used to calculate the removal rates of ammonia and nitrate in each stage and thereby predict the concentrations of ammonia,nitrate,and total nitrogen in the effluent.To verify the simulation results,pilot-scale experimental studies were carried out in a four-stage step feed process.Good correlations were achieved between the measured data and the simulation results,which proved the validity of the developed model. The sensitivity of the model predictions was analyzed.After verification of the validity,the step feed process was optimally operated for five months using the model and the criteria developed for the design and operation.During the pilot-scale experimental period,the effluent total nitrogen concentrations were all below 5mg·L -1 ,with more than 90%removal efficiency.

Physical modelling and scale effects of air-water flows on stepped spillways

During the last three decades, the introduction of new construction materials (e.g. RCC (Roller Compacted Concrete), strengthened gabions) has increased the interest for stepped channels and spillways. However stepped chute hydraulics is not simple, because of different flow regimes and importantly because of very-strong interactions between entrained air and turbu- lence. In this study, new air-water flow measurements were conducted in two large-size stepped chute facilities with two step heights in each facility to study experimental distortion caused by scale effects and the soundness of result extrapolation to pro- totypes. Experimental data included distributions of air concentration, air-water flow velocity, bubble frequency, bubble chord length and air-water flow turbulence intensity. For a Froude similitude, the results implied that scale effects were observed in both facilities, although the geometric scaling ratio was only Lr=2 in each case. The selection of the criterion for scale effects is a critical issue. For example, major differences (i.e. scale effects) were observed in terms of bubble chord sizes and turbulence levels al- though little scale effects were seen in terms of void fraction and velocity distributions. Overall the findings emphasize that physical modelling of stepped chutes based upon a Froude similitude is more sensitive to scale effects than classical smooth-invert chute studies, and this is consistent with basic dimensional analysis developed herein.

一种单输入双输出高增益DC-DC变换器

随着分布式发电在中低压场合的应用越来越广泛,对高增益直流变换器的需求日益增加。提出一种新型单输入双输出高增益DC-DC变换器。该变换器在传统Boost电路基础上引入电容和二极管组成极性反向极,功率端口通过差分连接方式互联,提高了变换器电压增益,降低了开关管电压应力;同时端口功率控制彼此独立,进一步提高了电能路由的灵活性。详细分析了该变换器的电路结构和工作原理,推导出稳态特性下的电压增益、主要开关器件电气应力以及电流纹波等表达式。在此基础上,提出了基于矢量时间作用的模型预测控制策略,建立了该变换器预测模型、推导出开关管矢量时间以及设计了目标函数寻优过程。最后,通过仿真和实验验证了所提变换器及其控制策略不仅可行、有效,而且具有高运行效率与低电压应力。

基于“服务重要性-生态敏感性-生物多样性”的内蒙古生态网络识别及优化

识别生态空间质量,构建区域保护网络对于优化生境布局、提高生态环境承载力以及维持生态系统稳定性具有重要意义。以内蒙古为例,研究构建“服务重要性-生态敏感性-生物多样性”的保护网络识别框架,基于生态系统服务重要性与生态敏感性评价识别生态源地。在此基础上,耦合现有自然保护地体系,利用最小累积阻力模型识别重要生态廊道,构建内蒙古保护网络。通过分析生态廊道与基础设施的空间叠置关系,提取待优化的生态踏脚石与生态障碍点。结果表明:(1)内蒙古Ⅰ级生态源地面积3.80×10^(4) km^(2),占研究区总面积的3.21%,与生态保护红线重合度较高。(2)在自然保护地和Ⅰ级生态源地的基础上,识别潜在生态廊道共84条,总长度约为15910 km,结合生态源地、潜在廊道和鸟类迁徙廊道构建内蒙古保护网络。(3)识别5条鸟类迁徙廊道、10处踏脚石优质生境建设点和81处生态障碍修复点。研究结果为内蒙古生态保护修复工程中物种迁移和能量流动网络的管理建设提供数据支持和位置参考。

Concurent Engineering-oriented Integrated Product Model Based on STEP

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Fixed-Bed Column Adsorption Modeling of MnO4- Ions from Acidic Aqueous Solutions on Activated Carbons Prepared with the Biomass

Activated carbons calcined at 400˚C and 600˚C (AC-400 and AC-600), prepared using palm nuts, collected in the town of Franceville in Gabon, were used to study the dynamic adsorption of MnO4- ions in acidic media on fixed bed column and on the kinetic modeling of experimental data of breakthrough curves of MnO4- ions obtained. Results on the adsorption of MnO4- ions in fixed-bed dynamics obtained on AC-400 and AC-600 adsorbents beds indicated that the AC-400 bed appears to be the most efficient in removing MnO4- ions in acidic media. Indeed, the adsorbed amounts, the adsorbed capacities at saturation and the elimination percentage of MnO4- ions obtained with AC-400 (31.24 mg;52.06 mg·g-1 and 41.65% respectively) were higher compared to those obtained with AC-600 (9.87 mg;16.45 mg·g-1 and 17.79% respectively). The breakthrough curves kinetic modeling revealed that the Thomas model and the pseudo-first-order kinetic model were the most suitable models to describe the adsorption of MnO4- ions on adsorbents studied in our experimental conditions. The results of the intraparticle diffusion model showed that intraparticle diffusion was involved in the adsorption mechanism of MnO4- ions on investigated adsorbents and was not the limiting step and the only process controlling MnO4- ions adsorption. In contrast to AC-400, the intraparticle diffusion on AC-600 bed plays an important role in the adsorption mechanism of MnO4- ions.

基于麻雀优化算法和CNN-BiLISTM的矿压预测模型

为了精准预测工作面顶板来压步距,提出了一种智能预测模型,将融合正余弦和柯西变异的麻雀优化算法(SCSSA)与卷积双向长短期记忆神经网络(CNN-BiLSTM)相结合,从而实现工作面顶板来压步距的精确预测。实验结果表明,SCSSA-CNN-BiLSTM来压步距预测模型预测值与实测值基本吻合,RMSE为1.051,MSE为1.1045,MAE为0.8162,MAPE为0.0566,相关系数R为0.9943,决定系数R2为0.9497,可以完成对于来压步距的预测。以样本1举例,实际值为20.20,而CNN-BiLSTM模型预测值为15.22,SCSSA-CNN-BILSTM模型预测值为18.49;以样本10举列,实际值为9.55,而CNN-BiLSTM模型预测值为13.78,SCSSA-CNN-BILSTM模型预测值为10.60,与未经过优化的CNN-BiLSTM算法相比,预测精度提升了约18%,参数优化效果显著提升。

24 Model在道路运输事故成因中的应用

为预防道路运输事故,基于事故致因“2-4”(24 Model)模型,对2015—2021年发生的215起道路运输事故的行为原因进行研究。从个人层面和组织层面分析导致事故发生的直接原因、间接原因、根本原因及其根源原因。结果表明:发生频次最多的不安全动作是驾驶员超速行驶(占10.67%);22.33%的道路运输事故存在管理者违章安排无资质员工上岗作业;管理者和领导者对57.67%的道路运输事故的发生有重要影响;由人为因素产生的不安全物态占比达71.53%;驾驶员、车辆安全生产管理制度欠缺或执行不到位在根本原因中尤为突出(占20.92%)。基于此,提出道路运输事故预防对策并构建出道路运输系统各因素关系图。

Explicit solutions to some nonlinear physical models by a two-step ansatz

Explicit solutions are derived for some nonlinear physical model equations by using a delicate way of two-step ansatz method.

An Adaptive Time-Step Backward Differentiation Algorithm to Solve Stiff Ordinary Differential Equations: Application to Solve Activated Sludge Models

A backward differentiation formula (BDF) has been shown to be an effective way to solve a system of ordinary differential equations (ODEs) that have some degree of stiffness. However, sometimes, due to high-frequency variations in the external time series of boundary conditions, a small time-step is required to solve the ODE system throughout the entire simulation period, which can lead to a high computational cost, slower response, and need for more memory resources. One possible strategy to overcome this problem is to dynamically adjust the time-step with respect to the system’s stiffness. Therefore, small time-steps can be applied when needed, and larger time-steps can be used when allowable. This paper presents a new algorithm for adjusting the dynamic time-step based on a BDF discretization method. The parameters used to dynamically adjust the size of the time-step can be optimally specified to result in a minimum computation time and reasonable accuracy for a particular case of ODEs. The proposed algorithm was applied to solve the system of ODEs obtained from an activated sludge model (ASM) for biological wastewater treatment processes. The algorithm was tested for various solver parameters, and the optimum set of three adjustable parameters that represented minimum computation time was identified. In addition, the accuracy of the algorithm was evaluated for various sets of solver parameters.

V Model of E-Learning Using Gagne Nine Steps of Education

This paper presents a V-model of e-learning using the well-known Gagne nine steps for quality education. Our suggested model is based on our experience at the computer engineering departments at AL-Hussein Bin Talal University, the University of Jordan and Albalqa Applied University. We applied the recommendations of the nine steps methodology to the e-learning environment. The V model suggested in this paper came up as a result of such application. Although this V model can be subject to some tuning and development in the future it proved to be highly efficient and easy to implement for the teacher and the student.

基于Arrhenius-Weibull模型的ECU步进应力加速试验设计

文章基于Arrhenius-Weibull模型对ECU的加速寿命试验方法展开研究,基于加速模型试验原理选择步进应力施加方式。为满足产品的可靠度指标,通过分析Weibull分布情况计算最小试验样件数量。通过最大似然估计的方法确定产品的Arrhenius-Weibull模型参数,以便完成各个应力阶段的等效转换。通过对步进加速试验设计过程示例,提供一种满足产品寿命参数指标的判断依据,为后续从业者进行相关的加速试验设计提供依据。