一维/二维复合碳载体组成对Pd催化剂甲醇氧化性能的影响

采用固相-液相两步混合法制备了由碳纳米管（CNTs）和石墨烯纳米片（GNPs）组成的CNTs-GNPs复合载体。以乙二醇还原法将Pd纳米粒子沉积于复合碳载体上,制得Pd/CNTs-GNPs催化剂。以透射电子显微镜、X射线衍射及X射线光电子能谱表征催化剂的形貌、组成和结构;以电化学方法考察催化剂的甲醇电氧化性能。结果表明,Pd/CNTs-GNPs（1/4）（GNPs质量分数为1/4）催化剂具有较大的电化学表面积和较高的甲醇电氧化活性,其甲醇氧化峰电流密度可达Pd/CNTs催化剂的1.97倍。催化剂的高活性得益于CNTs-GNPs载体的一维/二维复合结构使Pd纳米粒子具有良好的分散性能。计时电流实验表明,与单一载体负载Pd催化剂相比,复合载体负载Pd催化剂具有较强的抗中毒能力。     

电流与磁场互生关系的假想与应用

在电流与磁场互生及相互作用关系判断上,目前有安培定则、左手定则、右手定则,但对于电流与磁场互生及相互作用的内在机理却没有探讨。本文从微观假想电子磁场及其特性,通过假想解释了电子、电流、磁场及其相互作用的内在机理。通过内在机理解释了电流与磁场的安培定则、左手定则、右手定则等不同的外在表现形式,并通过内在机理的假想推导出电流与磁场存在的某些特性,以供深一步的研究和探索。     

Dressed Dark Solitons of the Defocusing Nonlinear Schrodinger Equation

The nonlinear Schrodinger equation is proved to be consistent-tanh-expansion （CTE） solvable. Some types of dark soliton solutions dressed by cnoidal periodic waves are obtained by means of the CTE method.     

Interactions between Solitons and Cnoidal Periodic Waves of the Gardner Equation

The Gardner equation is one of the most important prototypic models in nonlinear physics. Many scholars pay much attention to the Gardner equation and various nonlinear excitations of the Gardner equation have been found by many methods. However, it is very difficult to find interaction solutions among different types of nonlinear excitations. In this work, with the help of the Riccati equation, the Gardner equation is solved by the consistent Riccati expansion. Furthermore, we obtain the soliton-cnoidal wave interaction solutions of the Gardner equation.     

227-W output all-fiberized Tm-doped fiber laser at 1908 nm

In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficiency of 51.2%. The output power, to the best of our knowledge, is the highest output at 1908 nm. The beam quality M2 factor is about 1.56. Also discussed in this paper is the dependence of the laser performance on fiber length.     

Effect of noncircular orifice plates on the near flow field of turbulent free jets

In this paper, we experimentally investigate the near-field flow characteristics of turbulent free jets respectively issued from circular, triangular, diamond, rectangular, and notched-rectangular orifice plates into air surroundings. All the orifice plates have identical opening areas or equivalent diameters（De） and their aspect ratios（AR） range from 1 to 6.5. Planar particle image velocimetry（PIV） is used to measure the velocity field at the same Reynolds number of Re = 5 × 10^4,where Re = Ue De/ν with Ue being the exit bulk velocity and ν the kinematic viscosity of fluid. The mean and turbulent velocity fields of all the five jets are compared in detail. Results show that the noncircular jets can enhance the entrainment rate, reflected by the higher acceleration rates of mean velocity decay and spread, shorten the length of the unmixed core,expedite the increase of turbulent intensity compared with the circular counterpart shortened unmixed core, and increase turbulent intensity comparing to the circular counterpart. Among the five jets, the rectangular jet（AR = 6.5） produces the greatest decay rate of the near-field mean velocity, postpones the position at which the 鈥榓xis-switching鈥檖henomenon occurs. This supports that axis switching phenomenon strongly depends on jet initial conditions. In addition, the hump in the centerline variation of the turbulence intensity is observed in the rectangular and triangular jets, but not in the circular jet, nor in diamond jet nor in notched-rectangular jet.     

New experimental measurement of natSe(n, γ) cross section between 1 eV to 1 keV at the CSNS Back-n facility

The ⁷⁴Se is one of 35 p-nuclei, and ⁸²Se is a r-process only nucleus, and their (n, γ) cross sections are vital input parameters for nuclear astrophysics reaction network calculations. The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured. Prompt γ-rays originating from neutron-induced capture events were detected by four C₆D₆ liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was used to analyze the data in the 1 eV to 100 keV region. The deduced neutron capture cross section was compared with ENDF/B-VIII.0, JEFF-3.2, and JENDL-4.0, and some differences were found. Resonance parameters were extracted by the R-matrix code SAMMY in the 1 eV-1 keV region. All the cross sections of ^natSe and resonance parameters are given in the datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.     

激光光栅显微图像检测技术及其应用

介绍一种可以用来测量曲面试件表面应分量（εｚ,εθ,εｚθ）的激光光栅显微图像检测技术（ＩＧＭ）,它能实现从小应变到大应变全过程的高精度定量测量。我们将这一技术成功地应用在铁基形状记忆合金（ＦＳＭＡ）管接头的结构设计中,在这项研究中,首先在管接头结构表面制作了变形的载体－位相型干涉光栅,由结构表面产生的衍射光通宵我学系统后形成新的干涉光栅,我们利用数字图像系统接收了逆相变前后各自的干涉图像,采用带     

吃透课本才能抓住根本——从2004年高考数学阅卷谈中学数学教学

2001年,湖北省开始使用高中新教材,内容有了较大的改变,旧教材的内容中,有一些被减少了,有一些则降低了要求.增加的内容包括函数的极限与导数、向量的部分内容、概率统计的初步知识和线性规划等.2004年的高考题目充分体现了这种变化.如何处理好新增内容的教学呢?我们认为,讲透课本上的内容是十分关键的.