A New Quassinoid from Brucea javanica

Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3)....     

改进遗传算法及其在钻井液设计中的运用

在深井、超深井以及地层复杂等条件下，为了避免或减少钻井事故的发生，达到优质快速钻井的目的，选择合适的钻井液体系至关重要。基于案例推理（CBR，Case-Based Reasoning）的钻井液设计中，钻井液体系由岩性、井型和井深等属性推理得出，但属性权重的分配会对推理结果产生显著的影响；遗传算法在优化属性权重时，存在收敛速度慢、收敛精度低的缺点。针对上述问题，提出一种解决CBR中属性权重分配问题的改进遗传算法。首先，对遗传算子进行改进：选择算子方面，利用指数尺度变换法优化个体选择；交叉算子方面，对算术交叉中的比例因子进行自适应调整；变异算子方面，改进个体变异方向，保持种群多样性。其次，从个体适应度和交叉个体的差异程度两方面实现交叉概率自适应调整。最后，通过对UCI数据集的对比实验，证明了改进后的遗传算法能改善全局收敛性能，提高CBR的准确率。将该算法运用到基于CBR的钻井液设计中，实验结果表明，所提方法能够优化属性权重的分配，进而提高钻井液设计的质量。     

Time-dependent Ginzburg–Landau equations for multi-gap superconductors

We numerically solve the time-dependent Ginzburg–Landau equations for two-gap superconductors using the finite-element technique. The real-time simulation shows that at low magnetic field, the vortices in small-size samples tend to form clusters or other disorder structures. When the sample size is large, stripes appear in the pattern. These results are in good agreement with the previous experimental observations of the intriguing anomalous vortex pattern, providing a reliable theoretical basis for the future applications of multi-gap superconductors.     

Pentapnictogen heterocyclic monoanions: Structure,stability, and aromaticity

Inorganic planar ring-shape molecules with 4n + 2 π electrons are always the focus of experimental synthesis and theoretical research due to their potential aromaticity and stability. In this work, the whole series of five-membered heterocycle monoanions X _nY_5-n⁻ (X, Y = group 15 elements; n = 1-4) were thoroughly investigated by means of density functional theory calculations. They all have large formation energies and HOMO-LUMO gap energies, suggesting the potential thermodynamic and kinetic stability. Their aromaticities are comparable to that of typical aromatic hydrocarbons. Their thermal stabilities were firmly established by the ab initio molecular dynamics simulations. As most of them are predicted for the first time, their various spectra were simulated for experimental characterization. Furthermore, we demonstrate that these five-membered cyclic anions can be employed as η⁵-ligand to construct novel all-inorganic metallocenes, which may serve as the building blocks of low-dimensional nanomaterials.     

开放性辅导答疑机制的研究与实现

在简要分析了已有远程辅导答疑模式的基础上，提出了一种新型的开放性辅导答疑机制，对此答疑机制进行了分析，并进一步讨论了基于此机制的远程辅导答疑系统的设计与实现．     

二氧化硅胶态晶体的合成

以正硅酸乙酯为原料，采用控制凝聚法制备出173nm和297nm两种不同粒径的单分散二氧化硅微球乳液，并在一定湿度和温度下，利用乳液的单分散性，在表面张力的驱使下完成微球的自组装，从而得到三维有序的二氧化硅胶态晶体。扫描电镜显示：晶体呈面心立方结构，晶体表面至现出鲜艳的颜色，其波长与微球的直径相对应。     

高频强泵浦场激发的等离子体参量不稳定性的特性

本文论证了当泵浦波的强度足够强时,在相当普遍的条件下,对均匀等离子体,唯一可以发生的参量不稳定性是类似于弱场的振荡二束不稳定性(OTSI)。对均匀及弱不均匀等离子体,高频强泵浦场激发的参量不稳定性都是绝对不稳定性。同样的性质在磁化等离子体中也可以得到。 关键词：     

NA列加权乘积和的完全收敛性

本文讨论了NA和几类加权部分和及加权乘积和的完全收敛性，其中部分结果要优于iid列的已知结论。     

基元阀在汽轮机进汽阀研究中的应用

阀碟型线对汽轮机进汽阀的性能影响很大，本文设计了三种形式的基元阀，通过数值模拟手段研究了阀碟型线对流场的影响；得出了不同阀碟形式的性能．     

新颖外燃式湿空气燃气轮机循环及性能研究

本文首先提出一种新型的高效燃煤燃气轮机循环一外燃式湿空气透平循环动力系统。由于外燃的特点，作功工质为洁净湿空气，从而可以实现水的回收，是对常规ＨＡＴ循环的突破；另外洁净湿空气排放不受通常烟气露点限制，从而可回收利用湿空气降温时的低温凝结潜热，提高了加湿能力，从而提高系统性能。揭示了新型循环的基本规律；推导出具有湿化特点的约束方程和系统性能简明表达式，指明影响系统性能的关键因素。在透平初温为８５０℃的工况下，系统热效率高达４８．１１％。基于能量品位梯级利用原理和系统集成方法论，通过探索充分而合理利用中低温余热的有效途径，开拓洁净煤燃气轮机总能系统的新方向。