摘要：探索具有深紫外相位匹配能力的新型非线性光学材料是当前研究热点.本文从硼氧阴离子框架出发,发现由π共轭BO_(3)基团组成一维(BO_(2))∞链的电子离域导致了极化特性增强,可实现非线性光学性能的优化.据此,本文预测了以(BO_(2))∞链为阴离子框架的CaBO_(2)F体系.重点研究了三种能量最低的结构CaBO_(2)F-Ⅰ,CaBO_(2)F-Ⅱ和CaBO_(2)F-Ⅲ,设计了热力学上可进行的反应路径.第一原理计算表明,CaBO_(2)F-Ⅰ,CaBO_(2)-F-Ⅱ和CaBO_(2)F-Ⅲ具有较宽的带隙,合适的双折射(0.076–0.108@1064 nm)和较大的倍频系数(2.1–2.7×KdP).其中,计算得到CaBO_(2)F-Ⅰ的最短相位匹配波长在约为195 nm(基于HSE06带隙修正剪刀算符),证明了含有定向电子离域的(BO_(2))∞链是深紫外非线性光学材料的潜在阴离子框架.本文通过将机理研究与验证性的结构预测相结合实现了自上而下设计深紫外非线性光学结构模板,该研究为探索新型非线性光学材料提供了新的策略.

摘要：在建造长大海底隧道时,为了加固隧道结构并节省成本,通常会改变隧道部分区段的截面面积,这将导致隧道内的空气动力学特性发生变化。本文通过对比变截面(VCS)隧道和常规(CCS)隧道,研究了突变截面对长隧道内压力瞬变和列车风的影响。数值模拟采用rNG k-ε湍流模型,通过动模型试验进行了验证。结果表明,越接近突变截面VCS隧道和CCS隧道内的正峰值压力之间的差异越大,在5.43 km处达到最大值7.63%。在两种隧道之间纵向列车风的差异最高达18.7%,但在其他两个方向上几乎相同。此外,突变截面对隧道不同区域的影响不相同。本研究对长大变截面隧道的参数设计和隧道内附属设施的布置具有参考价值。

摘要：To solve the problem of slow leaching speed of copper,surfactant was added into lixivium as leaching agent in the *** on physical chemistry and seepage flow mechanics,the leaching mechanics of surfactant was *** solution surface tension and surfactant adsorbing on the surface of ore have a significant impact on the surface wetting *** leaching rate for response,the study screened out three main factors by Plackett-Burman design method:the sulfuric acid concentration,surfactant concentration and *** these three factors,the surfactant concentration is the most important contributor to leaching *** obtaining the experiment center by the steepest ascent experiment,a continuous variable surface model was built by response surface *** solving quadratic polynomial equation,optimal conditions for leaching were finally obtained as follows:the sulfuric acid concentration was 60 g/L,the surfactant concentration was 0.00914 mol/L,and the temperature was 45 °*** leaching rate was 66.81% in the optimized leaching conditions,which was close to the predicted value,showing that regression result was good.

摘要：This paper proposes a theoretical method using finite element analysis(FEA) to calculate the plastic collapse loads of pressure vessels under internal pressure,and compares the analytical methods according to three criteria stated in the ASME Boiler Pressure Vessel Code. First,a finite element technique using the arc-length algorithm and the restart analysis is developed to conduct the plastic collapse analysis of vessels,which includes the material and geometry non-linear properties of vessels. Second,as the mechanical properties of vessels are assumed to be elastic-perfectly plastic,the limit load analysis is performed by em-ploying the Newton-raphson algorithm,while the limit pressure of vessels is obtained by the twice-elastic-slope method and the tangent intersection method respectively to avoid excessive deformation. Finally,the elastic stress analysis under working pressure is conducted and the stress strength of vessels is checked by sorting the stress results. The results are compared with those obtained by experiments and other existing models. This work provides a reference for the selection of the failure criteria and the calculation of the plastic collapse load.

摘要：万尼尔构型旨在描述万尼尔函数在实空间上的局域位置及其携带的电荷信息,这一物理概念的提出为刻画天然及人工晶体结构中的波函数提供了全新的视角.在二维高阶拓扑绝缘体中,万尼尔构型中的分数化电荷可以作为一种内禀的拓扑不变量来表征湮灭在体连续谱中的角模式.本文报告了一项基于测量谱电荷分布观测声学体系中万尼尔构型的实验研究.作者在构建的声子晶体中测得了表现为分数化谱电荷的拓扑角模式反常,这种模式反常可以作为一种易于观测的实空间拓扑指标对湮灭在体态中的拓扑角模式进行先验判别.在此基础上,通过将不同的万尼尔构型按照多种方式进行组合,将原本湮没在体连续谱中的角模式调制至带隙中.在组合后的声子晶体中,平庸相和非平庸相结构均可以作为包覆层,从而为在带隙中构造和调控拓扑角模式提供了一种新思路.该研究有望应用于设计高品质因子声谐振腔、声通信以及传感增强等领域.

摘要：多分类学习中经常需要考虑在泛化性能和计算开销间进行权衡。本文提出一个生成式概率多分类器,综合考虑了泛化性和学习/预测速率。我们首先证明了我们的分类器具有最大间隔性质,这意味着对于未来数据的预测精度几乎和训练阶段一样高。此外,我们消除了目标函数中的大量的局部变元,极大地简化了优化问题。通过凸分析和概率语义分析,我们设计了高效的在线算法,与经典情形的最大不同在于这个算法使用聚集而非平均化处理梯度。实验证明了我们的算法具有很好的泛化性能和收敛速度。

摘要：目的:为简化三维腹腔镜结构,同时保证其成像和3d视频质量,研发一种新型高清三维腹腔镜系统。创新:采用双光学通道,使用中继透镜延长图像光学传输距离,在中继透镜末端用两个相机接收内窥图像,简化腹腔镜结构,并保证了成像质量。方法:首先,根据图像传感器参数和视场需求大小确定内窥镜光学系统的有效焦距,在此基础上设计包括中继透镜在内的双通道光学镜头(图1)。其次,设计CCU用于采集和处理双通道高清视频图像,并通过HdMI输出将它们同时显示在3d显示器上,由此构建了高清三维腹腔镜系统(图4)。最后,针对双目内窥镜系统采用传统针孔模型计算距离存在较大误差的问题,通过理论分析提出一种新的距离计算方法,并在0-150 mm范围内的距离测量实验中验证该算法的有效性(图3)。结论:新型三维腹腔镜在保证成像质量的基础上简化了系统结构;采用提出的双目系统距离计算方法可以有效提高双目内窥系统的测距精度。

摘要：声束的连续动态扫描在超声成像、水下目标定位和声呐通信等诸多领域发挥关键作用.传统方法通常依赖于发射装置的机械扫描或有源相控阵的波束整形来实时调控声束的空间指向性,存在成本高、尺寸大、主动控制系统复杂而精准操控困难等问题.本文提出并构建了一种基于无源声学超表面的紧凑型静态声呐器件,无需主动控制和机械移动,仅在单一声源的作用下即可实现声束的动态扫描操控.这种新型声呐器件由具有深度亚波长厚度的二值化振幅编码单元组合而成,能够将单一声源发射的梳状频率谱转化为具有相同频率和空间间隔的声焦点阵列,从而引入频率梯度这一新的声波操控自由度,并通过时空声干涉效应产生可连续旋转的动态扫描声束.实验结果验证了所设计超构声呐的高速、宽角度声束扫描性能.此外,通过与传统的相位梯度调控技术结合,该机制还可以对扫描声束的空间形态进行任意的调节.这种基于静态无源超构声呐的声束动态扫描机制为声波的时空调控开辟了新的研究范式,并有望在水下对抗、超声诊疗等重要领域产生实际应用价值.

摘要：With the continuous improvement of the train speed, the dynamic environment of trains turns out to be aerodynamic domination. Solving the aerodynamic problems has become one of the key factors of the high-speed train head design. Given that the aerodynamic drag is a significant factor that restrains train speed and energy conservation, reducing the aerodynamic drag is thus an important consideration of the high-speed train head design. However, the reduction of the aerodynamic drag may increase other aerodynamic forces (moments), possibly deteriorating the operational safety of the train. The multi-objective optimization design method of the high-speed train head was proposed in this paper, and the aerodynamic drag and load reduction factor were set to be optimization objectives. The automatic multi-objective optimization design of the high-speed train head can be achieved by integrating a series of procedures into the multi-objective optimization algorithm, such as the establishment of 3d parametric model, the aerodynamic mesh generation, the calculation of the flow field around the train, and the vehicle system dynamics. The correlation between the optimization objectives and optimization variables was analyzed to obtain the most important optimization variables, and a further analysis of the nonlinear relationship between the key optimization variables and the optimization objectives was obtained. After optimization, the aerodynamic drag of optimized train was reduced by up to 4.15%, and the load reduction factor was reduced by up to 1.72%.

摘要：中国西部山区地形条件和地质构造复杂,为满足高速公路设计要求,路线在山岭重丘区不可避免地要采用深埋特长隧道设计通过。若公路隧道必需通过断层构造,如结构、基础形式选择不当,容易在施工时出现塌方、结构失稳等现象,所以在勘察过程中,应查明断层的基本性质及特征,提供较为准确的资料,避免出现后续问题。本研究区域发生地震的频率和震级都很高,且从现有资料表明小江断裂在第四纪全新世时期仍有活动,属地震高危地段。因此,地质调查,地质钻探、地球物理勘探等一整套综合技术用于识别断层及其特征,以直观地显示一定深度范围内的地下信息。在这项研究中,地球物理勘探大地电磁法被用来分析公路隧道的电性特征及电性结构,重点讨论了小江断裂的电性特征及电性结构,经地质调查及钻探验证了其反演解释等研究成果的正确性,并进一步提出采用波阻抗张量极化图长轴倾角统计结果修正断层倾角的处理解释方法,故可有效获取隧址区大量地质信息以进行预测评价小江断裂,为公路隧道设计及运营提供强有力的技术支撑,也为以后的物探处理解释提供有意义的经验和参考。