La_(0.65)Sr_(0.35-x)Na_xMnO_3的磁卡效应

采用溶胶-凝胶技术制备了钙钛矿型稀土锰氧化物La0.65Sr0.35-xNaxMnO3(x=0.05,0.10,0.15),利用X射线衍射(XRD)和振动样品磁强计(VSM)对样品的结构、居里温度和磁卡效应进行了研究。结果表明,随着Na含量的增加,晶胞体积减小,居里温度提高,当x=0.15时,La0.65Sr0.35-xNaxMnO3的最大磁熵变达到了1.66 J/(kg.K)。     

复合氧化物锰酸盐YMnO_3和HoMnO_3的水热合成及其结构表征

通过水热反应得到了YMnO3和HoMnO3两种钙钛矿复合氧化物,借助于ICP元素分析以及XRD和扫描电镜SEM对其结构进行了分析。结果表明,所得产物为RMnO3型的复合氧化物,并且化合物的结晶度好、纯度高,YMnO3为常见的六方结构化合物,而HoMnO3却表现出特殊的立方相结构特征,是一种亚稳态的结构。     

复合氧化物锰酸盐YMnO_3和HoMnO_3的水热合成及其结构表征

通过水热反应得到了YMnO3和HoMnO3两种钙钛矿复合氧化物,借助于ICP元素分析以及XRD和扫描电镜SEM对其结构进行了分析。结果表明,所得产物为RMnO3型的复合氧化物,并且化合物的结晶度好、纯度高,YMnO3为常见的六方结构化合物,而HoMnO3却表现出特殊的立方相结构特征,是一种亚稳态的结构。     

Sr离子含量的减少对于La0.60Sr0.25Na0.15MnO3材料性能的影响

利用溶胶-凝胶法（sol-gel）制备了稀土锰氧化物多晶样品La0.60Sr0.25-xNa0.15MnO3,发现随着Sr离子含量的减少,样品在室温附近庞磁电阻效应有了明显的改善。在1.8 T的磁场下,对于x=0.05的样品,其CMR值在240~320 K的温区范围内均保持在5.3%（±0.2%）,温度稳定性有显著改善。     

La2／3Sr1／3MnO3单晶的本征低温电阻最小行为研究（英文）

摘要：为了阐明在锰氧化物多晶以及外延薄膜中存在的低温电阻极小值现象,对La2／3Sr1／3MnO3单晶样品的性质进行研究.该单晶样品是利用光学浮区生长炉,在氩气气氛中生长出的高品质晶体,系统研究了退火对La2／3Sr1／3MnO3单晶低温输运行为的影响.结果表明,在退火前样品存在的低温电阻极小值无论是c轴还是ab平面在退火后均消失,这一结果首次证明了在锰氧化物体系中存在的低温电阻极小是一种非本征的物理行为,与实验样品的制备工艺和存在于其中的非完整性具有较强的依赖性,并进一步证明自旋无序散射乃是传统体系出现低温电阻极小的主要原因.     

大型工程高边坡群锚效应的数值研究

开发既能较准确地模拟锚索的力学特性,又能用于大型3维计算的锚索单元,对比分析铺设锚索与否对边坡稳定性的影响。根据某水电站坝址地质图建立边坡3维地质模型,并参照锚索的分布在该模型上用缆索元模拟锚索群,每根锚索的锚固段与周围岩体都处理为耦合,按照实际情况给锚索施加预应力,考虑有/无锚索的2个模型,以施工进程的方式进行有限元分析。结果表明:锚固模型的位移值和多点位移计实测值的趋势和峰值都较为吻合;该边坡在锚固后,绝大部分位置的位移值均有减小,特别是1 730坝基平台处的位移值下降到未进行锚固时的1/3。该锚索单元能有效地模拟锚索群,且具备较高的精度;锚固后边坡的整体稳定性有较大提升。     

基于深度卷积神经网络的睡眠分期模型

针对现阶段数据和特征决定睡眠分期模型的分类精度上限的问题,提出深度卷积神经网络模型. 在模型主体构建方面,并行卷积网络可以自动学习原始信号的时域特征和频域特征,特征融合网络通过空洞卷积和残差连接进行多特征融合,分类网络基于融合后的特征进行睡眠分期. 利用生成少数类过采样技术（SMOTE）减少类别不平衡对分类效果的影响,结合两步训练法对模型进行优化. 实验使用Sleep-EDF数据集的原始单导脑电信号（Fpz-Cz通道）对模型进行20折交叉验证,得到总体精度和宏F₁分别为86.73%和81.70%. 提出的深度卷积模型在没有任何先验知识的情况下,对脑电信号进行端到端的学习,分类准确率优于传统的深度学习模型.     

Simulation optimal design of a compliant mechanism with circular notch flexure hinges based on the equivalent beam methodology

This paper presents an in-depth study of Equivalent beam model (EBM).Firstly three-dimensional (3D) finite element analysis (FEA) model for circular flexure hinge developed by Zettl et al.was verified by the comparison with Smith’s experimental results and the 3D FEA model was feasible within 5.5% error.Then the accuracy of Timoshenko short-beam due to shear force was verified based on finite element method.The results showed that the EBM has good accuracy within 5% error for 1≤r/t≤3.Finally the EBM methodology was applied for the simulation optimal design of a bridge-type compliant mechanism.The results showed that the EBM methodology has very high numerical efficiency and satisfactory accuracy for simulation optimal design of planar compliant mechanism with flexure hinges.     

Adsorption of BSA on Carbon-coated Fe_3O_4 Microspheres Activated with 1-ethyl-3-(3-dimethylaminopropyl)-Carbodiimide Hydrochloride

Carbon-coated Fe_3O_4( Fe_3O_4/C) microspheres activated with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride(EDC) were prepared, characterized and applied to adsorb bovine serum albumin(BSA). The prepared magnetic microspheres had spherical core-shell structure with a uniform and continuous carbon coating coupled with activation by EDC, and possessed superparamagnetic characteristics. The experimental results showed that the adsorption amount of BSA on the EDC-activated Fe_3O_4/C(Fe_3O_4/C-EDC) microspheres was higher than that on the Fe_3O_4/C microspheres. The maximum adsorption of BSA on Fe_3O_4/C-EDC microspheres occurred at pH 4.7, which was the isoelectric point of BSA. At low concentrations(below 1.0 M), salt had no noticeable effect on BSA adsorption. The BSA adsorption of Fe_3O_4/C-EDC microspheres had a better fit to the Langmuir model than the Freundlich isotherm and Temkin isotherm model, and the kinetic data were well described by the pseudo-second-order model. The adsorption equilibrium could be reached within 20 min. High desorption efficiency(97.6%) of BSA from Fe_3O_4/C-EDC microspheres was obtained with 0.5 M Na_2HPO_4(pH 9.4) as the desorbent.     

Hybrid Level of Detail Algorithm for Real-Time Rendering of Large-Scale Terrain

Real-ti me rendering of terrain model is one of themost difficult tasks of computer graphics,especiallywhen the scale of a terrain model is very large.LODis ani mportant techniquetoresolvethis problem.Ac-cording to the evolution,there are two kinds ofLOD:…     

苯异丙基胺类兴奋剂兴奋强度理论研究

通过量子化学密度泛函理论(density functional theory,DET)中B3 LYP方法,在6-31G基组水平上计算18种苯异丙基胺类兴奋剂(phenyl-isopropyl-amine dopes,PPAD)的28个量化参数qc.用这18种兴奋剂的甲基二甲氧基苯丙胺( dimethoxy-methyl-amphetamine,DOM)样作用强度y及其量化参数,建立定量结构-活性关系(quantitative structure-activity relationships,QSAR)模型,经最佳变量子集回归建立最佳四元数学模型,传统判定系数R2为0.852,逐一剔除法交互验证系数R2cv为0.742.结果表明,苯环中C1原子、N原子及苯环上的净电荷(QC1、QN和QB)和次最高占据轨道能ENHOMO是影响兴奋剂DOM样作用强度的重要因素.该模型可用于对兴奋剂DOM样作用强度进行理论分析和预测.     

催化臭氧化水中硝基苯速率常数的影响因素

为考察催化臭氧化降解水中硝基苯的表观速率常数随剂量因素的演进,采用半连续流批次实验检测臭氧投量、硝基苯初始质量浓度和蜂窝陶瓷催化剂用量对单独臭氧氧化和臭氧/蜂窝陶瓷氧化工艺降解水中硝基苯的表观反应速率常数的影响规律.结果表明,在不同的臭氧投量(0.987~2.732 mg/L)、不同的硝基苯初始质量浓度(50~250μg/L)和不同的蜂窝陶瓷催化剂用量(1~5个)下,2种氧化工艺对硝基苯的降解均遵循假一级反应动力学模型,且2种工艺的表观反应速率常数都分别与臭氧投量、硝基苯初始质量浓度和蜂窝陶瓷催化剂的用量成正相关性.     

Application of gas wettability alteration to improve methane drainage performance: A case study

Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines, but negative effects may occur as the fracturing fluids are absorbed into the coal seam. Gas wettability alteration(GWA) technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change. However, there have been few reported field tests in coal mines using GWA technology. This paper describes a pilot-scale field test in Xinjing coal mine, Yangquan, China. The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP) was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process. The study focuses on the comparison of two boreholes(Boreholes #9 and #10) and one other borehole(Borehole #8) with and without using GWA approach. A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration. The field test results showed that the average methane drainage rates of Boreholes #9(39.28 m~3/d) and #10(51.04 m3/d) with GWA treatment exceeded that of Borehole #8(21.09 m~3/d) without GWA treatment,with an increase of 86.3% and 142.1%, respectively. The average methane concentrations of Boreholes #9(4.05%) and #10(6.18%) were 64.6% and 151.2% higher than that of Borehole #8(2.46%), respectively. On the other hand, the dewatering ratio of Boreholes #9(4.36%) and #10(3.11%) was almost 19 times and 13 times greater than that of Borehole #8(0.22%). These field test results were in agreement with the experimental data. The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines. Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.     

基于GA-ANN模型的A2/O工艺运行参数优化

影响A~2/O工艺运行的参数有许多,这些因素相互联系、相互作用,影响工艺效率.为了弥补控制单一变量法或者设计正交试验法的不足,综合考察多种运行参数对工艺运行效果的影响,建立了基于遗传算法进行全局寻优的神经网络模型(GA-ANN模型),并应用于某城市污水处理厂A~2/O工艺的运行优化.获得该厂调试运行期间154组有效监测数据后,随机选取2/3的数据用于GA-ANN模型的求解,1/3的数据用于模型的检验,对工艺运行参数进行优化,得到最佳运行参数组合.结果显示,建立基于遗传算法的神经网络模型用于A~2/O工艺运行参数的优化是可行的,可以为污水处理厂运行参数的设置提供理论参考,对调试工作、提高工艺运行效率具有一定的实际指导意义.     

Simulation and Analysis of Ring Compression Using RP/RVP Meshless Method

1 Introduction Modeling and simulation by numerical computationtechnology,suchasthefinite element and boundary ele-ment methods ,play more and more i mportant roles in the field of product design and manufacture . These nu-merical assistances convert traditional processing to the digital manufacture way. However ,these mesh-basedcomputation approaches always meet puzzles of severe mesh distortion anditerative remeshinginlarge deforma-tion problems . Meshless methods[1]discard the dependence on…     

Analysis and Optimization of Inside-Cushion Structure in High-Speed Hydraulic Cylinders

An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders. First, the three stages of cushion processes are discussed according to the varying flow area as the piston moves. Then, to establish a precise mathematical model, the states of the flow field are estimated in terms of the Reynolds number. Accordingly, the simulation model parameterized against measured data is developed and verified by experiment. Last, the average velocity, peak cushion pressure, and terminal velocity are defined to evaluate cushion performance. According to these optimized objectives, the non-linear programming by quadratic Lagrange (NLPQL) algorithm is applied to optimize the structure parameters. The optimization results indicate that the peak cushion pressure is reduced by 28% and terminal velocity is reduced by 21% without reduction of average velocity.     

渗流计算的一种实用方法

对于有自由面的求取的渗流问题,介绍了一种可以不进行迭代求解渗流问题的自由面的新方法,并且采用常用的商用软件解决饱和非饱和渗流问题.将新的边界处理方法应用到多种材料的土石坝及坝基的渗流分析中,可以用一般的商用有限元软件进行饱和非饱和、稳定非稳定的渗流问题的计算,并结合某堤防工程进行稳定渗流分析,得到了较好的结果.     

主动控制电致伸缩液压悬置隔振特性仿真

采用电致伸缩材料作为主动控制作动器的智能悬置,利用Matlab软件,并考虑了惯性通道、解耦通道以及电致伸缩作动器的非线性,建立了该悬置的仿真模型。选择滤波后的 x LMS算法作为控制算法,通过仿真计算研究了该悬置的隔振性能。采用查表的办法由控制位移求解控制电压,能有效地避免作动器非线性对系统性能的不良影响。研究结果表明:对系统施加控制后,传递到车身上的振动大大减弱,在6 s内振动力降到未施加主动控制时的3%,20s后降到未施加主动控制时的1%。说明采用主动控制能有效地改善悬置的隔振性能。     

Three-dimensionally Ordered Macroporous Phosphotungstic Acid/SiO_2 for Efficient Catalytic Oxidative Desulfurization

Three-dimensionally ordered(3DOM) macroporous phosphotungstic acid/SiO_2(HPW/SiO_2) materials were prepared by using colloidal crystal as templates and applied for oxidative desulfurization(ODS) of the model fuel oil. The obtained HPW/SiO_2 materials were characterized through scanning electron microscopy, powder X-ray diffraction, N_2 sorption, and Fourier transform infrared spectroscopy. The results indicated that 3 DOM HPW/SiO_2 possessed hierarchical pore architectures which contained ordered macropores and disordered mesopores, with the Keggin type HPW embedded in the framework of pore structure. The removal rate of dibenzothiophene(DBT) could reach 100% under the optimum conditions, moreover. The performance was only slightly decreased for the regenerated catalyst after 7 cycles.     

Macro-mechanical properties of columnar jointed basaltic rock masses

From the geological structure of the columnar jointed rock mass, a visual model was established in software AUTOCAD by programming based on the algorithm of the Voronoi diagram. Furthermore, a program to convert the AUTOCAD model into 3DEC (3-dimensional distinct element code) model was developed, and a numerical model was established in 3DEC. Moreover, the results of triaxial compression tests of columnar jointed rock masses were simulated numerically. The REV (representative element volume) scale was studied, and the result shows that the REV size is 3 m × 3 m. The proposed approach, the established model and the numerical simulation were applied to study the macro-mechanical properties and the equivalent strength parameters of the columnar jointed rock mass. The numerical simulation results are in good accordance with the in-situ test results.