过碳酰胺分子合成条件优化、晶体结构及其热稳定性

采用四因素、三水平的方法研究了过碳酰胺分子合成中物料比、反应温度、反应时间、稳定剂的种类对合成收率的影响,获得了合成的最佳工艺条件。 在最佳合成条件下,测得过碳酰胺的产率可达到99%,活性氧含量最高可达到17.5%。 通过热分析方法研究了过碳酰胺分子热稳定性。 研究表明,温度超过65 ℃过碳酰胺含量和含氧量均迅速下降。 利用X射线单晶衍射仪测定了其晶体结构,使用Diamond软件解析出过碳酰胺分子的三维空间超分子结构及其氢键的连接方式。     

甲烷氯代反应条件的系统化探究与教学实施策略的优化

甲烷氯代反应是高中化学教学中成功率较低的实验。系统探索了温度、光照条件、反应物比例对该反应过程和结果的影响,研究发现,阳光或高压汞灯照射是反应快速进行的必要条件,温度在25 ℃以上能加快反应进行,甲烷与氯气体积比为1:3能提高氯代反应的程度。在进行甲烷氯代反应的实验教学中,应基于以上该反应条件的探究结果制定符合具体情况要求的优化实施策略。     

系统组分数的确定

分析了组分数表达式中各个量的意义,并举例说明组分数的计算。讨论了化学平衡和反应进行到底2种情形对系统组分数的影响:化学平衡中生成物只有1相的,化学平衡考虑与否不会影响组分数;可进行到底的反应,在特定条件下可按照化学平衡来处理。最后总结了快速确定系统组分数的步骤。     

含摩擦与碰撞平面多刚体系统动力学线性互补算法

基于接触力学理论和线性互补问题的算法, 给出了一种含接触、碰撞以及库伦干摩擦, 同时具有理想定常约束(铰链约束) 和非定常约束(驱动约束) 的平面多刚体系统动力学的建模与数值计算方法. 将系统中的每个物体视为刚体, 但考虑物体接触点的局部变形, 将物体间的法向接触力表示成嵌入量与嵌入速度的非线性函数,其切向摩擦力采用库伦干摩擦模型. 利用摩擦余量和接触点的切向加速度等概念, 给出了摩擦定律的互补关系式; 并利用事件驱动法, 将接触点的黏滞-滑移状态切换的判断及黏滞状态下摩擦力的计算问题转化成线性互补问题的求解. 利用第一类拉格朗日方程和鲍姆加藤约束稳定化方法建立了系统的动力学方程, 由此可降低约束的漂移, 并可求解该系统的运动、法向接触力和切向摩擦力, 还可以求解理想铰链约束力和驱动约束力. 最后以一个类似夯机的平面多刚体系统为例, 分析了其动力学特性, 并说明了相关算法的有效性.      

Sixth harmonic generation of 1064-nm laser in KBBF prism coupling devices under two kinds of gas conditions

The conversion efficiency on the sixth harmonic of 1064 nm in KBe2BO3F2 （KBBF） at different gas pressures in two kinds of gases, helium and nitrogen, is measured and compared. In the both gases, maximum conversion efficiency on the sixth harmonic of 1064 nm in high vacuum is nearly 10% of 355 nm, which is almost four times higher than that in low vacuum. The maximum average output power at 177.3 nm is 670 ttW with the repetition rate of 10 Hz and the duration of 20 ps in high vacuum. It indicates that the sixth harmonic generation in high vacuum is more preferable than that in low vacuum.     

计算机仿真实验在物理实验教学中的应用

1大学物理实验课的特点物理实验的课前预习非常重要．但由于实验条件有限,学生预习时,只能根据教材对实验做出初步的了解,而对实验过程、实验仪器的操作并不能很好地把握．对一些操作难度大的实验,如分光计,密立根油滴等实验,如果只简单地预习一下教材上的知识,很难理解仪器原理,更不可能掌握仪器的操作步骤．由于缺乏高质量的课前预习,使难度较大、操作复杂的实验很难在规定的时间内完成．     

质子交换膜燃料电池动态启动特性的实验研究

实际应用时燃料电池的运行条件会随时间不断地变化,因此是一个非稳态过程.本文研究了在不同的加湿条件以及反应气流量下电池的启动特性.结果表明:随着气体流量的增大,电池启动速度加快;对电池加湿有利于提高电池的启动性能.     

A Few Remarks on Milburn Equation

After presenting the infinite operator-sum form solution to the Milburn equation dp/dt=γ（UρU^f - ρ）=γU[p, Uf], where U=e^-iH/hγ, and verifying that this equation preserves the three necessary conditions of density operators during time evolution, we prove that the yon Neumann entropy increases with time. We also point out that if A and B both obey the Milburn equation, then theproduct AB obeys （d/dt）（AB） = γU[AB, U^f]-（1/γ）（dA/dt）（dB/dt）, which violates the Milburn equation, this reflects that a pure state will evolve to a mixture in general     

Performance of Organic Field Effect Transistors with Self-Improved Cu/Organic Interfaces

We fabricate pentacene-based organic field effect transistors （OFETs） with Cu as source and drain （S-D） electrodes. The fabricated devices stored for ten hours under ambient atmospheric conditions exhibit superior performance compared with the as-prepared devices. The field-effect mobility increases from 0. 012 to 0.03 cm^2 V^-1 s^-1, and the threshold voltage downshifts from -14 to -9 V. The on/off current ratios are close to the order of 10^4. The improved performance of the stored devices is attributed to the formation of thin Cu oxide at the Cu electrodes/organic interfaces. These results suggest a simple and available way to optimize device properties and to reduce fabrication cost for OFETs.     

Dynamic Processes of Cross-Tail Current in the Near-Earth Magnetotail

Current dynamic processes in realistic magnetotail geometry simulations under various driven conditions and Hall effects. are studied by Hall magnetohydrodynamic （MHD） Associated with the external driving force, a thin current sheet with a broad extent is built up in the near-Earth magnetotail. The time evolution for the formation of the current sheet comprises two phases： slow growth and a fast impulsive phase before the near-Earth disruption of the current sheet resulting from the fast magnetic reconnection. The simulation results indicate that as the external driving force increases, the site and the tailward speed of the near-Earth current disruption region are closer to the Earth and faster, respectively. Whether the near-Earth disruption of the current sheet takes place or not is mainly controlled by Hall effects. It is found that there is no sudden disruption of the current sheet in the near-Earth region if the ion inertial length is below di= 0.04.