A new cross-scaling method to deal with the porous flow problem

The finite volume method （FVM） and the lattice Boltzmann method （LBM） are coupled with each other to construct a new cross-scaling method to deal with the porous flow problem. To check the effectiveness of our developed cross-scaling LBM-FVM, the above mentioned problem is also solved by the well known LBM-LBM. Based on the data checking of the published data and the results of LBM-FVM and LBM-LBM, good agreement is observed.

Measurement of ^(232)Th(n,2n)^(231)Th reaction cross-sections at neutron energies of 14.1 MeV and 14.8 MeV using neutron activation method

In this study, the activation cross-sections were measured for ^(232)Th(n,2n)^(231)Th reactions at neutron energies of 14.1 and 14.8 MeV, which were produced by a neutron generator through a T(d,n)~4He reaction. Induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. In the cross-section calculations, corrections were made regarding the effects of gamma-ray attenuation, dead-time, fluctuation of the neutron flux, and low energy neutrons. The measured cross-sections were compared with the literature data, evaluation data(ENDF-B/VII.1, JENDL-4.0 and CENDL-3.1), and the results of the model calculation(TALYS1.6).

Efficient Calculation of the Radar Cross Section at the Interior Resonance by the Inverse Power Method

It is well known that the incorrect results will be given using either the electric or magnetic field integral equation to calculate the radar cross section (RCS) of a closed body at the interior resonance. In this paper, an effective iterative technique is used to correct the calculated surface current density from the electric field integral equation. The radar cross section is computed for an infinite conducting circular cylinder at the interior resonance, and the obtained results are in good agreement with the analytical results. The backscattering cross section of an infinite triangular cylinder in the vicinity of a resonant frequency is also calculated. It is shown that the presence method is efficient and accurate.

Three Measurement Methods of Two-photon Absorption Cross-section

Through the experimental design and theoretical analysis, three technologies used for characterizing the two-photon absorption(TPA) properties, such as nonlinear transmission experiment and theory, Z-scan technology and two-photon induced fluorescence method, are introduced. The properties of the three experiments to be utilizable and realizable under desirable limitation are simply analyzed. The advantages of the measurements for TPA characterization are also analyzed.

RADAR CROSS-SECTION COMPUTATIONS OF ARBITRARILY COMPLICATED TARGETS BY APPLYING THE PANEL METHOD

The present paper deals with the method for the radar cross-section (RCS)computations of arbitrarily complicated targets based on the work by D. Klement et al.(1988).This method is convenient in use, fast in operation and precise in calculating RCS of a complicatedtarget. With this method, the RCS of classic scatterers, for example, a cone and a cylinder, arecomputed with the result of good agreement with experimental data. Furthermore, the RCS’of an aircraft model at various attitudes are calculated with the result of good agreement withexperimental data also.

Hyperstatic reaction method for calculations of tunnels with horseshoe-shaped cross-section under the impact of earthquakes

Tunnels are now an integral part of the infrastructure in major cities around the world. For many reasons, these tunnels have horseshoe-shaped cross-sections with round top and flat bottom. This paper presents some improvements to the use of the Hyperstatic Reaction Method-HRM for analysing tunnels with horseshoe-shaped cross-sections when these tunnels operate under the influence of earthquakes, particularly in cases when the tunnel lining is a continuous lining. The analysis used parameters of a tunnel from the Hanoi metro system, as well as parameters of the strongest earthquake that may occur in the central Hanoi area in the improved HRM and 2 D numerical methods using the ABAQUS software. On the basis of the results obtained, the paper gives conclusions about the HRM methodology when it is used to calculate tunnels that have horseshoe cross-sections operating under the influence of earthquakes.

Validation method for simulation models with cross iteration

Cross iteration often exists in the computational process of the simulation models, especially for control models. There is a credibility defect tracing problem in the validation of models with cross iteration. In order to resolve this problem, after the problem formulation, a validation theorem on the cross iteration is proposed, and the proof of the theorem is given under the cross iteration circumstance. Meanwhile, applying the proposed theorem, the credibility calculation algorithm is provided, and the solvent of the defect tracing is explained. Further, based on the validation theorem on the cross iteration, a validation method for simulation models with the cross iteration is proposed, which is illustrated by a flowchart step by step. Finally, a validation example of a sixdegree of freedom (DOF) flight vehicle model is provided, and the validation process is performed by using the validation method. The result analysis shows that the method is effective to obtain the credibility of the model and accomplish the defect tracing of the validation.

Study on tapered crossed subwavelength gratings by Fourier modal method

Fourier modal method incorporating staircase approximation is used to study tapered crossed subwavelength gratings in this paper. Three intuitive formulations of eigenvalue functions originating from the prototype are presented, and their convergences are compared through numerical calculation. One of them is found to be suitable in modeling the diffraction efficiency of the circular tapered crossed subwavelength gratings without high absorption, and staircase approximation is further proven valid for non-highly-absorptive tapered gratings. This approach is used to simulate the ＂moth-eye＂ antireflection surface on silicon, and the numerical result agrees well with the experimental one.

基于多特征SAD-Census变换的立体匹配算法

视差不连续区域和重复纹理区域的误匹配率高一直是影响双目立体匹配测量精度的主要问题,为此,本文提出一种基于多特征融合的立体匹配算法。首先,在代价计算阶段,通过高斯加权法赋予邻域像素点的权值,从而优化绝对差之和(Sum of Absolute Differences,SAD)算法的计算精度。接着,基于Census变换改进二进制链码方式,将邻域内像素的平均灰度值与梯度图像的灰度均值相融合,进而建立左右图像对应点的判断依据并优化其编码长度。然后,构建基于十字交叉法与改进的引导滤波器相融合的聚合方法,从而实现视差值再分配,以降低误匹配率。最后,通过赢家通吃(Winner Take All,WTA)算法获取初始视差,并采用左右一致性检测方法及亚像素法提高匹配精度,从而获取最终的视差结果。实验结果表明,在Middlebury数据集的测试中,所提SAD-Census算法的平均非遮挡区域和全部区域的误匹配率为分别为2.67%和5.69%,测量200~900 mm距离的平均误差小于2%;而实际三维测量的最大误差为1.5%。实验结果检验了所提算法的有效性和可靠性。

A method of analysing experimental data of nuclear reaction cross sections

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Solving multi-object radar cross section based on wide-angle parabolic equation method

Based on a Pade approximation, a wide-angle parabolic equation method is introduced for computing the multiobject radar cross section （RCS） for the first time. The method is a paraxial version of the scalar wave equation, which solves the field by marching them along the paraxial direction. Numerical results show that a single wide-angle parabofic equation run can compute multi-object RCS efficiently for angles up to 45 ° . The method provides anew and efficient numerical method for computation electromagnetics.

基于BA-SVR混合模型的果蔬生鲜物流需求预测模型研究

本文通过构建BA-SVR混合模型对果蔬生鲜物流需求进行预测研究。首先通过互联网大数据搜索技术构建果蔬生鲜需求指数相关网络关键词词库,进而采用皮尔森(Pearson)相关分析和逐步回归选择预测因子。其次,结合果蔬自身特点以及物流市场变动因素,提出了果蔬生鲜物流指数(Fruit&Vegetable Logistic Index, FVLI)概念,分析了FVLI变动的影响变量,使其成为反映物流市场信息变动的重要指标。再次,利用蝙蝠算法(Bat Algorithm, BA)自动更新迭代参数的优势,将其引入到支持向量回归(Support Vector Regression, SVR)模型中,用于优化SVR模型中自由参数值,进而构建BA-SVR混合模型对北京市果蔬生鲜需求变化趋势进行模拟仿真及实证预测。最后根据构建的性能预测指标,通过确立的基准模型与其进行对比,评估BA-SVR混合模型性能的优劣,从而提出一种可以用于果蔬生鲜物流信息短期预测的改进方法。

“十字”缝合法在腹腔镜APR会阴部切口重建中的应用

目的:探讨“十字”缝合法在腹腔镜腹会阴联合切除术(abdominoperineal resection,APR)会阴部切口重建中的应用。方法:选取2017年1月—2022年12月钦州市第一人民医院胃肠外科收治的60例低位直肠癌患者。随机将其分为试验组和对照组,各30例。两组均给予腹腔镜APR,试验组腹腔镜APR会阴部切口重建应用“十字”缝合法,对照组腹腔镜APR会阴部切口重建应用常规间断缝合法。比较两组围手术期指标,术后7 d切口愈合情况,并发症。结果:试验组手术时间、住院时间均短于对照组,术中出血量及引流量均少于对照组,正常饮食时间、腹腔引流管拔管时间均早于对照组,差异有统计学意义(P<0.05)。试验组切口愈合情况优于对照组,差异有统计学意义(P<0.05)。试验组并发症发生率低于对照组,差异有统计学意义(P<0.05)。结论:“十字”缝合法用于腹腔镜APR会阴部切口重建,能够降低切口张力,促进伤口愈合,住院时间短。

基于组合赋权-DEA的跨境铁路外部环境风险评价

研究目的:跨境铁路大多穿越不同国家,铁路沿线的自然、社会环境条件复杂多变,给跨境铁路外部环境安全带来巨大威胁。为保障跨境铁路平稳运行,采用组合赋权-DEA方法在全面识别跨境铁路沿线风险的基础上进行风险评价,旨在为跨境铁路风险管理工作提供借鉴。研究结论:(1)全面识别跨境铁路沿线外部环境风险,从自然环境与社会环境方面共选取30个风险指标构建跨境铁路外部环境风险评价指标体系,结合AHP-熵权法对各风险指标组合赋权;(2)应用基于DEA的风险评价方法,以各风险指标发生的概率和后果为变量,对跨境铁路外部环境风险进行评价和排序;(3)研究结果显示,跨境铁路侵限风险应予以重点关注,安保区内违法生产经营次之;(4)本文研究可为跨境铁路沿线外部环境安全管理工作提供新的思路,保障跨境铁路运输更加平稳高效运行。

MRI特征辅助分类乳腺癌分子亚型的临床研究

目的 应用磁共振(MRI)图像中提取的特征和机器学习方法来帮助区分乳腺癌分子亚型,以期为临床诊治提供参考。方法 回顾性分析我院于2021年10月-2023年10月间确诊的178例乳腺癌患者的临床资料,每个患者肿瘤的形状、MRI特征和基于直方图的特征是使用内部软件从增强前和三次增强后的MRI图像上提取的。同时收集临床和病理资料。基于机器学习模型识别重要的成像特征并建立预测IDC亚型的模型。采用留一法交叉验证(LOOCV)避免模型过度拟合,采用Kruskal-Wallis检验确定统计学意义。结果 LOOCV过程生成一个具有不同特征的模型,在排名前20位的特征中,有11项在IDC亚型之间存在显著差异(P<0.05)。综合前九种病理和影像特征,预测模型对IDC亚型的识别准确率为83,4%。病理和影像联合模型对各亚型的准确率分别为89.2%(ERPR1)、63.6%(ERPR-/HER21)和8 2.5%(TN)。当仅结合前9个成像特征时,预测模型在LOOCV上识别IDC亚型的总体准确率为71.2%。病理和影像联合模型对各亚型的准确率分别为69.9%(ERPR1)、62.9%(ERPR-/HER21)和81.0%(TN)。结论 我们开发了一个基于机器学习的预测模型,该模型使用从M RI提取的特征来区分具有显著预测能力的IDC亚型。

复杂受荷下盾构隧道原型结构试验平台的研发与实证

盾构隧道结构在全寿命周期中往往将面临诸多复杂荷载状态,如注浆、偏载、偏转等非对称偏不利工况。为验证结构在这些复杂荷载状态下的适用性,探究结构力学性能,开展足尺原型结构试验研究往往是最为直接而有效的手段。既有原型试验主要关注隧道结构在简单对称荷载条件下的力学性能,鲜有关注复杂非对称荷载状态。为拓展原型试验的适用范围,提出了适用于不同断面盾构隧道结构的原型试验平台和用于模拟复杂荷载状态的试验荷载设计方法。该方法适用于任意加载点布置和液压站分组的试验系统,可对注浆、偏载、偏转等复杂荷载状态下结构响应进行精确模拟。通过类矩形盾构隧道、双圆隧道和圆形隧道的偏载原型结构试验研究,验证了试验平台和试验荷载设计方法的适用性。进一步针对试验关键参数的分析表明,控制目标权重系数的调整能有效满足不同的试验模拟要求;基于试验荷载设计方法优化的迭代算法能有效考虑计算模型或边界支承条件的非线性;环箍钢绞线和千斤顶的组合加载模式能将拟合误差水平降低至千斤顶加载模式的1/5,但需要删去部分加载点使试验荷载合理且适用;对于越复杂的结构和荷载,精确模拟结构状态需要的试验系统独立荷载组数越高,对试验平台的要求也越高。

水下高速公路盾构隧道联络通道冻结施工模拟分析

公路盾构隧道联络通道建设面临较大的不确定性和风险,通常采用人工地层冻结法进行施工。以孟加拉吉大港卡纳普里河底盾构隧道联络通道为研究对象,分析联络通道施工过程中冻土帷幕和结构衬砌受力情况,研究采用双圈管冻结施工过程中冻土帷幕发展规律。针对施工期和运营期衬砌受力的最不利工况进行验算,分析积极冻结和维护冻结阶段温度场的变化,并研究部分不确定参数的敏感性。分析结果表明,该联络通道设计施工方案合理可行。

基于数据驱动的动车组镍镉电池记忆效应消除策略研究

在碱性镍镉蓄电池长期未彻底充放电的情况下,蓄电池会产生次级放电平台,称为“记忆效应”。该效应会导致电池可释放容量降低,需要定期消除。在动车组蓄电池检修中,传统的“记忆效应”消除方法耗时过长,会对检修工作带来很大压力。为了降低储能检修成本,对动车组镍镉电池“记忆效应”消除策略优化方案开展研究。以实际动车组三级修镍镉蓄电池电池为研究对象,通过分析电池的充放电循环中的参数特征,结合大量的电池充放电实验,提取出与电池容量密切相关的特征数据。首先,通过特征筛选和降维组合,搭建线性模型和非线性模型的交叉加权耦合方法,创建近似模型以反映电池的真实可释放容量,消除镍镉电池不一致性对优化方案实验设计带来的系统误差。其次,在此基础上,通过调整影响电池状态的高影响因子变量,构建正交实验方案。研究动车组镍镉蓄电池“记忆效应”快速、安全的消除策略。最后,通过重复验证实验和安全性检测实验对该策略进行实证,研究结果表明,提出的镍镉蓄电池“记忆效应”消除策略能够有效恢复镍镉电池真实容量,并且能够极大地缩减时间成本(约44.15%),并且有利于缓解蓄电池因过充导致电池劣化现象。该消除方案对于提升动车组镍镉电池的维护效率及确保其安全性具有重要意义。

基于区间毕达哥拉斯犹豫模糊熵和交叉熵的ELECTRE II决策方法

针对属性权重完全未知或部分已知,属性值为区间毕达哥拉斯犹豫模糊数的多属性决策问题,提出了基于区间毕达哥拉斯犹豫模糊熵和交叉熵的ELECTRE II法。首先给出区间毕达哥拉斯犹豫模糊数的区间形式的得分函数和精度函数,定义新的距离测度。然后基于区间毕达哥拉斯犹豫模糊数的模糊因子、直觉因子和幅度因子,给出熵和交叉熵公式,并证明其性质,提出了基于熵和交叉熵确定属性权重的方法。最后提出了区间毕达哥拉斯犹豫模糊环境下的改进的ELECTRE II法,利用综合优势值对方案进行排序,并通过算例和比较分析验证了该方法的可行性和有效性。

农科特色有机化学课程的教学探索与实践

立足高等农林教育,从教学案例、教学方法、教师团队建设等方面对有机化学课程教学进行了探索和实践。教学实践表明,激发了学生的学习兴趣,拓展了学生的视野,助力学生领略了有机化学研究前沿(尤其是与农科交叉融合应用前沿)魅力,培养了学生的文化素养、职业素养和科学素养,塑造了学生“知农爱农”的情怀,厚植了学生的家国情怀;实现了知识传授、能力培养与价值引领的同向同行和交相辉映,有效解决了公共基础课与专业教育需求不能完全匹配的问题,充分发挥了课程在农科人才培养中的作用。