可交联的PMMA型和PS型高热稳定性二阶非线性光学材料的合成与表征

采用封管反应的方法,以较高产率(80%以上)合成了一系列含环氧基团的可交联PMMA型和PS型极化聚合物材料,该材料具有很好的成膜性.用DSC和T_gA等方法研究了聚合物固化前后的热性能,结果表明,由于聚合物在极化后期经热固化使引入的环氧基团开环交联,聚合物的玻璃化转变温度(T_g)较固化前明显提高30～50K.同时,固化后的聚合物具有较高的热分解温度(T_d>543K).对聚合物的二阶非线性光学性质的测试结果表明,在室温下放置100h后,聚合物的电光系数r₃₃值均保持在初始值的75%以上.这是由于环氧基团的开环使固化后的聚合物本身产生一定程度的交联,导致取向后的发色团被聚合物的交联网禁锢而不易弛豫,从而使这类PMMA型和PS型二阶非线性聚合物材料的热稳定性能得以提高.     

Keggin三取代型杂多阴离子183W NMR化学位移的特征模式＊

The reaction of SiW₉O^10-₃₄ and GeW₉O^10-₃₄ with metal cations leads to Keggin trisubstituted polyoxoanions.A review of all known trisubstituted Keggin anions demonstrates characteristic patterns of ¹⁸³W NMR chemical shifts.     

电场对Au—Ag薄膜结构影响的AFM和VAXPS研究

利用原子力显微镜（ＡＦＭ）和变角Ｘ射线光电子谱（ＶＡＸＰＳ）技术研究了Ａｕ－Ａｇ／ＳｉＯ２体系在直流电场作用下，Ａｕ，Ａｇ电迁移的特点及所引起的薄膜结构的变化，观察到较低温度下Ａｕ，Ａｇ聚集状态的显著变化，发现电迁移过程中Ａｕ－Ａｇ薄膜与ＳｉＯ２基底之间存在界面化学反应，膜层中Ａｕ，Ａｇ，Ｓｉ等元素的化学状态发生了相应的变化，这些结构表明ＳｉＯ２表面上Ａｕ－Ａｇ复合薄膜电迁移不只是一个水平方向的扩     

Impulsive synchronization and control of directed transport in chaotic ratchets

The impulsive synchronization problem of two identical chaotic ratchets is investigated in this paper. We demonstrate that the impulsive method to control directed transport is applicable when there are multiple co-existing attractors in phase space transporting particles in different directions. Numerical simulations are carried out to illustrate the effectiveness of the proposed method.     

Alleviating hysteresis and improving device stability of perovskite solar cells via alternate voltage sweeps

The anomalous hysteresis in a perovskite solar cell induced by an asymmetric field is confirmed by a capacitance–voltage measurement. By applying several cycles of alternating reverse and forward scans, this hysteresis phenomenon is obviously alleviated, resulting in a hysteresis-less state in the perovskite solar cell. Meanwhile, the open-circuit voltage and power conversion efficiency of the perovskite solar cell are enhanced by 55.74% and 61.30%, respectively, while the current density and fill factor keep almost invariable. The operation of alleviating hysteresis is essential for further research and is likely to bring in performance gains.     

带回热器的跨临界CO2空气源热泵系统性能实验研究

本文对带回热的跨临界CO_2空气源热泵循环在不同压缩机频率下运行时的特性进行了热力性能分析。结果表明:在25 Hz和30 Hz压缩机频率下,系统COP_h随排气压力的升高都存在峰值。在35 Hz压缩机频率下,由于受限于系统高温保护,系统COP_h随排气压力的升高逐渐增大,从趋势来看也存在峰值。压缩机频率升高,出水温度、气冷器出口温度和排气温度都升高,CO_2质量流量增加,系统COP_h减小。与25 Hz和35 Hz压缩机频率下的系统性能相比,30 Hz压缩机频率下的系统运行性能更优,系统最大COP_h为3.88,对应的最优排气压力为9.2 MPa,对应的最高出水温度为91.1℃。     

Signatures of strong interlayer coupling in γ-InSe revealed by local differential conductivity

Interlayer coupling in layered semiconductors can significantly affect their optoelectronic properties. However, understanding the mechanisms behind the interlayer coupling at the atomic level is not straightforward. Here, we study modulations of the electronic structure induced by the interlayer coupling in the γ-phase of indium selenide (γ-InSe) using scanning probe techniques. We observe a strong dependence of the energy gap on the sample thickness and a small effective mass along the stacking direction, which are attributed to strong interlayer coupling. In addition, the moiré patterns observed in γ-InSe display a small band-gap variation and nearly constant local differential conductivity along the patterns. This suggests that modulation of the electronic structure induced by the moiré potential is smeared out, indicating the presence of a significant interlayer coupling. Our theoretical calculations confirm that the interlayer coupling in γ-InSe is not only of the van der Waals origin, but also exhibits some degree of hybridization between the layers. Strong interlayer coupling might play an important role in the performance of γ-InSe-based devices.     

Linear and nonlinear generalized consensuses of multi-agent systems

Consensus in directed networks of multiple agents, as an important topic, has become an active research subject. Over the past several years, some types of consensus problems have been studied. In this paper, we propose a novel type of consensus, the generalized consensus （GC）, which includes the traditional consensus, the anti-consensus, and the cluster consensus as its special cases. Based on the Lyapunov＇s direct method and the graph theory, a simple control algorithm is designed to achieve the generalized consensus in a network of agents. Numerical simulations of linear and nonlinear GC are used to verify the effectiveness of the theoretical analysis.     

Al掺杂对MgB2电子结构和超导电性的影响

建立了不同Al掺杂浓度的Mg1-xAlxB2模型并进行几何优化,讨论了掺杂对系统几何构型、能带结构、电子态密度、键布居和超导转变温度的影响.结果表明,随着Al掺杂浓度的增加,B-Mg离子键增强,B-B共价键减弱,B-Al间的弱共价键增强,能带展宽,费米面附近的态密度降低,超导电性减弱.     

新高考制度下开设大学物理预修课程的思考

在新一轮高考改革制度下, 高考物理出现学考和选考两种模式, 即高中毕业学生存在了物理知识的差 异性, 这为大学物理的教学带来新的挑战. 一方面通过问卷调查分析了本校高考学考和选考物理的比例及其成因; 另一方面, 针对新高考带来的物理知识的差异性, 提出了在本校开设大学物理预修课程的必要性和可行性, 并详细 分析该课程的教学目标、 课时设置、 教学模式等