基于物品嵌入向量的会话型推荐算法

传统基于会话的推荐算法主要利用点击物品的时序信息进行建模,忽略了挖掘物品的特征信息,且未利用物品之间的相似性。为提升推荐效果,提出一种新的基于会话的推荐算法SR-I2V。通过Skip-gram模型和层次softmax优化方法学习物品的嵌入向量,由意图递进公式对已发生的物品点击提取出意图特征向量,并根据特征向量相似度计算出每个候选项的推荐分数。实验结果表明,与I2I、PoP和S-POP等传统基于会话的推荐算法相比,该算法在Yoochoose和Diginetica两个数据集上的推荐召回率分别提高了至少4.67个百分点和3.97个百分点,平均倒数排名指标也有相应提高。     

混凝土面板砂砾石坝漫顶溃坝模型研究

基于沟后面板砂砾石坝溃坝案例调研资料及溃坝离心模型试验的反馈分析,提出了一个可描述混凝土面板砂砾石坝漫顶溃决过程的数学模型。该模型的特点是选择可反映高速水流作用下推移质与悬移质运动的坝料输移公式描述宽级配砂砾料的运动特征,以及建立可模拟面板坝每块钢筋混凝土面板在各种变化荷载作用下破坏过程的表达式。选择沟后面板砂砾石坝溃坝案例对建立的模型进行验证,计算结果与实测结果的对比表明:溃口峰值流量、堆石体溃口的顶宽与底宽、折断的面板的数量和各面板的破坏长度、溃坝历时等输出参数的相对误差均控制在±15%以内;由于溃坝过程中面板不断折断,溃口流量过程呈锯齿状抬升。另外,参数敏感性分析的结果表明坝料的冲蚀率和级配特征对溃坝流量过程具有重要的影响。     

双平台反舰导弹对抗典型航母编队突防模型研究

分析了典型航母编队对反舰导弹的防空配置和火力分配原则,研究了编队抗击对反舰导弹突防概率的影响;在此基础上,深入研究了当航母防空火力平均分配和非平均分配时双平台反舰导弹的饱和攻击数目。这种模型能更真实地评估对抗情况下双平台反舰导弹的突防能力,从而可为双平台反舰导弹对抗航母编队的兵力部署提供参考。     

Using PTV through an embankment breach channel

Particle tracking velocimetry was used to determine for the first time the surface velocities upstream, downstream, and through experimental embankment dam breach channels at all stages of breach development. A series of experimental tests was performed, which used varying initial breach geometry. The measurements were made using Styrofoam surface tracking particles and three different video camera angles to obtain 3-dimensional velocity measurements, which were calculated using ArcGIS. Space-time contour maps of velocity were then interpolated for each of the breach scenarios. A maximum surface flow velocity of 2.1 m/s, corresponding to 21 m/s at prototype scale, was measured at the downstream end of the breach channel near the time to peak for the breach outflow. The surface velocities were also converted to average velocities and used in conjunction with breach flow measurements to determine the depth of flow through the breach channel and to make estimates of the sub-aqueous breach geometry. Estimates of flow depth through the breach were used to compare measured outflow results with those determined analytically using the broad-crested weir equation.     

Vanadium Core–Shell Nanorods Inspect Metabolic Changes of Diabetic Retinopathy

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and ranks as the fifth leading cause of visual impairment, but an understanding of DR development has been hampered by the lack of an efficient metabolomic tool. Herein, vanadium core–shell nanorods are developed for metabolic fingerprinting to probe molecular variation in DR. First, a series of vanadium core–shells are constructed with different elemental composition and structural parameters, using silica nanorods to support vanadium oxide. The plasma metabolic fingerprints (MFs) are extracted by the optimized vanadium core–shell nanorod‐assisted laser desorption/ionization mass spectrometry, by analyzing 500 nL of native plasma in seconds. As a result, DR patients are differentiated from non DR controls with a sensitivity of 94% and specificity of 90% using a classification model built on the plasma MFs. Furthermore, DR progression is monitored by a panel of plasma metabolic signatures with gradual changes. This work provides an advanced molecular tool for the metabolomic characterization of DR and may guide the clinical decision making in DR for personalized medicine in the future.     

土坝溃决模型及其发展

大坝溃决的速度和程度很大程度上决定了溃坝洪水波的大小及其传播速度，继而对下游受灾程度和范围产生巨大影响。溃坝模型对溃坝过程进行模拟，预测溃口发展及溃坝洪水过程线，对于大坝失事后果的评估，防洪减灾以及保护人民生命财产安全等具有重要意义。对世界上四十年来出现的各类土坝溃决模型进行了分类和总结，分析了其各自特点；还对一种新出现的土坝溃坝机理学说进行了介绍和分析；并为今后的溃坝模型发展提出了建议。     

关于自然数K次幂和的讨论

本讨论了自然数K次幂求和公式中系数的递归性质，并在此基础上给出了一个借助杨辉三角写出自然数K次幂求和公式的简便方法。     

基于改进熵权-突变级数法的岩爆等级评判

为能够准确预测岩爆等级,从岩性、应力、围岩三方面选取岩爆发生的五个因素作为预测评价指标,通过改进后的熵权公式来计算评价指标的重要程度;结合突变级数法中多维的印第安人茅舍模型对无量纲处理后的岩爆样本数据进行归一化计算得到突变级数值,并划分岩爆等级区间。最后将此方法应用在江边水电站隧道岩爆预测中。结果表明:利用该方法评判岩爆等级,模型维数较多,评判结果客观、准确,和实际工程情况一致,与其他方面相比具有一定优势。     

重物落水后运动过程的数学模型

为更好描述重物落水后的运动过程,设计了模拟封堵溃口小型试验,首先对重物落水后运动过程的影响因素进行分析,对采集的试验数据进行了分类处理,并对典型的试验数据进行比较分析,突出主要影响因素.其次对水中的重物进行了受力分析,以大实心方体为例,初步建立重物在水中运动过程的二阶微分方程模型（模型1）,结合步长搜索法和最小二乘法确...     

爆炸空气冲击波技术在反恐破门中的应用

针对传统的反恐破门手段不能有效、快速、安全地破除防盗门的缺点,提出利用爆炸空气冲击波技术进行破门。炸药爆炸产生的定向空气冲击波作用在目标门上,瞬间形成很大的冲量和超压,迫使门发生严重变形,从门框中脱离出来,以瞬间破除防盗门。分析了战斗部装药设计、定距杆设计和起爆方式等关键技术,并对空气冲击波造成的伤害进行了分析评估。结果表明,该方法能较好地解决目前反恐行动中遇到的快速破除防盗门难题。