Graphs with maximum degree 6 are acyclically 11-colorable

An acyclic k-coloring of a graph G is a proper vertex coloring of G, which uses at most k colors, such that the graph induced by the union of every two color classes is a forest. In this note, we prove that every graph with maximum degree six is acyclically 11-colorable, thus improving the main result of Yadav et al. (2009) [11].     

邯郸市地热能开发利用中排放水问题探讨

地热能的开发应用在邯郸市正处在发展期。对近几年邯郸市开发的地热井调查,发现地热水矿化度极高且含有大量氯化物、硫酸盐等物质,地热废水绝大部分没有经过任何处理直接外排,对周围生态环境和工农业生产造成了很大危害。针对排放水水质、水量的不同特点,介绍了相应的处理方法。值得注意的是这种高矿化度、高水温的地热排放水在国家排放标准中没有给予指标限制,这些排放水的危害在某些方面存在潜伏期,危害一旦显现,治理难度极大,必须引起相关部门的高度重视。     

一种释放负离子面膜的研制

论述了一种负离子面膜的研制过程。在面膜的制作过程中通过适当的途径加进负离子添加剂,从而使负离子在皮肤表面发挥还原性作用,使已经氧化的皮肤还原,恢复健康状态。通过多次实验,所得产品负离子释放量超过了700个/cm3,具有释放负离子稳定持久、发射远红外线、杀菌、消毒、保健等功效,达到了健康要求。     

非均相金属钯配体催化剂的研究进展

Suzuki-Miyaura反应是一类具有工业化应用前景的C-C键合成反应。反应多数是在均相金属钯配体催化剂催化下完成。均相催化具有催化效率高、产品选择性好等优点,但催化剂回收困难,增加了反应成本,限制了其应用。非均相金属钯配体催化剂是将均相金属钯配体催化剂固载到载体上,使其在不影响反应活性和选择性的同时,实现循环使用,已成为Suzuki-Miyau-ra反应的研究热点。对几年来以有序介孔材料MCM-41和SBA-15、无机载体SiO2和Al2O3、聚苯乙烯和聚乙二醇等合成材料以及天然高分子材料为载体,制备非均相金属钯配体催化剂的方法及其催化性能进行了综述。     

2-[4-(9H-9-咔唑)-苯基]蒽醌的合成与表征

以苯酐和咔唑为原料,通过Friedel-Crafts酰基化、浓硫酸催化、Ullman、Suzuki偶联等反应,合成了标题化合物,并对该化合物进行紫外可见吸收和荧光分析。     

Stability boundary analysis of the dynamic voltage restorer in weak systems with dynamic loads

In this contribution, a stability analysis for a dynamic voltage restorer (DVR) connected to a weak ac system containing a dynamic load is presented using continuation techniques and bifurcation theory. The system dynamics are explored through the continuation of periodic solutions of the associated dynamic equations. The switching process in the DVR converter is taken into account to trace the stability regions through a suitable mathematical representation of the DVR converter. The stability regions in the Thevenin equivalent plane are computed. In addition, the stability regions in the control gains space, as well as the contour lines for different Floquet multipliers, are computed. Besides, the DVR converter model employed in this contribution avoids the necessity of developing very complicated iterative map approaches as in the conventional bifurcation analysis of converters. The continuation method and the DVR model can take into account dynamics and nonlinear loads and any network topology since the analysis is carried out directly from the state space equations. The bifurcation approach is shown to be both computationally efficient and robust, since it eliminates the need for numerically critical and long‐lasting transient simulations. Copyright © 2011 John Wiley & Sons, Ltd.     

区域能源互联网的发展现状与政策建议

多能耦合型区域能源互联网有利于提高能源利用效率,促进就近消纳可再生能源和降低污染物排放。区域能源互联网的发展需要更有效的政策措施体系。对中国多能耦合型区域能源互联网发展现状进行系统分析,从投资主体、技术应用、重点市场、相关政策等4个方面总结目前发展阶段的特点,并识别出目前存在的技术问题、政策问题和运营问题等关键问题。分析国外为解决这三类问题所积累的政策措施经验,包括规划、跨部门协作、法规、补贴政策、示范项目政策等。针对中国区域能源互联网发展存在的问题,参考国际上成功的政策经验,为中国区域能源互联网发展提出4点政策建议。     

Room temperature ferromagnetic ordering of NiO films through exchange coupling

NiO films were deposited by sputtering with a relatively high oxygen partial pressure, followed by subsequent annealing in air. The as-deposited film is amorphous. The amorphous film gradually turns to crystalline structure with the increase in annealing temperature. The film annealed at 673 K shows strong ferromagnetism at room temperature, whereas, there is no room-temperature ferromagnetic ordering for the as-deposited amorphous NiO film or the film after annealed at 873 K. The ferromagnetism is due to the finite size effect and the high Curie temperature above room temperature is associated with the interaction between ferromagnetic NiO crystalline nanoclusters and antiferromagnetic amorphous matrix.     

Dihydroazulene Photoswitch Operating in Sequential Tunneling Regime: Synthesis and Single‐Molecule Junction Studies

Molecular switches play a central role for the development of molecular electronics. In this work it is demonstrated that the reproducibility and robustness of a single‐molecule dihydroazulene (DHA)/vinylheptafulvene (VHF) switch can be remarkably enhanced if the switching kernel is weakly coupled to electrodes so that the electron transport goes by sequential tunneling. To assure weak coupling, the DHA switching kernel is modified by incorporating p‐MeSC₆H₄ end‐groups. Molecules are prepared by Suzuki cross‐couplings on suitable halogenated derivatives of DHA. The synthesis presents an expansion of our previously reported bromination–elimination–cross‐coupling protocol for functionalization of the DHA core. For all new derivatives the kinetics of DHA/VHF transition has been thoroughly studied in solution. The kinetics reveals the effect of sulfur end‐groups on the thermal ring‐closure of VHF. One derivative, incorporating a p‐MeSC₆H₄ anchoring group in one end, has been placed in a silver nanogap. Conductance measurements justify that transport through both DHA (high resistivity) and VHF (low resistivity) forms goes by sequential tunneling. The switching is fairly reversible and reenterable; after more than 20 “ON‐OFF” switchings, both DHA and VHF forms are still recognizable, albeit noticeably different from the original states.