有等待席位限制的平行多跑道航班起降排队模式研究

根据实际平行多跑道机场终端区飞行和控制程序,利用排队理论讨论2种有等待席位限制的航班起降排队模式:①分列独立、②联合协作模型.求出了这2种排队模式下相关指标.通过比较2种模式下航班队列服务质量和系统工作指标,发现②比①支持更多的航班起降架次并有较高的服务质量.从而,为优化航班起降提出一些建议.     

直接甲醇燃料电池的Ir-Fe/C 阴极催化剂性能

合成了直接甲醇燃料电池的Ir-Fe/C阴极催化剂, 用X射线衍射(XRD)谱和X射线能量色散谱(EDS)等方法对该催化剂进行表征, 研究了碳载Ir-Fe(Ir-Fe/C)催化剂对氧还原的电催化活性和抗甲醇能力. 研究发现, 氧在碳载Ir(Ir/C)和Ir-Fe/C催化剂电极上还原的起始氧还原电位分别为0.57和0.65 V. 在0.2 V下的电流密度分别为4.6和5.8 mA/cm², 表明Ir-Fe/C催化剂对氧还原的电催化性能要优于Ir/C催化剂, 而且Ir-Fe/C催化剂也有很好的抗甲醇能力.     

Bidirectional Quantum Secure Direct Communication Network Protocol with Hyperentanglement

We propose a bidirectional quantum secure direct communication (QSDC) network protocol with the hyperentanglment in both the spatial-mode ad the polarization degrees of freedom of photon pairs which can in principle be produced with a beta barium borate crystal. The secret message can be encoded on the photon pairs with unitary operations in these two degrees of freedom independently. Compared with other QSDC network protocols, our QSDC network protocol has a higher capacity as each photon pair can carry 4 bits of information. Also, we discuss the security of our QSDC network protocol and its feasibility with current techniques.     

我国化学教育政策中社会科学问题的百年回眸与展望*——基于高中化学课程标准(教学大纲)的分析

选取不同时期高中化学课程标准/教学大纲,对其中关于“化学与社会问题”的教育目标、教学内容和教学方法的论述进行文本比对、观念分析。发现课程目标从实用主义走向关注学生核心素养,课程内容从关注工农生产、国防建设走向人类社会共同问题,教学思想在注重知识系统传授还是围绕社会问题学习之间不断探索,体现出对教育认识的不断深入和学科教育的价值提升。最后总结已有经验,寻找未来发展方向和需要研究的问题。     

The Generalized Energy‐Based Fragmentation Approach with an Improved Fragmentation Scheme: Benchmark Results and Illustrative Applications

We propose an improved fragmentation scheme for the generalized energy‐based fragmentation (GEBF) approach, which improves the accuracy of the GEBF approach in total energy calculations and intermolecular interactions. The main modification is to introduce some two‐fragment‐centered primitive subsystems, which are neglected in the previous GEBF implementation. Numerical calculations demonstrate that the present GEBF approach can provide more accurate ground‐state energies and intermolecular interactions. The present GEBF approach with the M06‐2X functional and the cc‐pVTZ basis set are employed to investigate the structures and binding energies in two dimeric species, which are related to pseudopolymorphism of a phenyleneethynylene‐based π‐conjugated molecule. A comparison of the binding free energies in a dimeric species and its corresponding model without C? H???F contacts reveal that the substitution of fluorine atoms weakens the binding of monomers in the dimeric species formed by intermolecular O? H???O hydrogen bonds, but strengthens the binding in the dimer formed by the π–π stacking interaction. Therefore, the C? H???F contacts in these two dimeric species are demonstrated to play a less significant role.