具有脉冲的分数阶Bagley-Torvik 模型边值问题

将具有脉冲的分数阶Bagley-Torvik微分方程边值问题巧妙地转化为积分方程,定义加权Banach空间及全连续算子,运用不动点定理获得该边值问题解的存在性定理.举例说明了定理的应用.最后提出有趣的研究问题.     

分数填补下两非参数总体一般差异的经验似然置信区间

在一定的条件下证明了缺失数据情形基于分数填补方法得到的两非参数总体一般差异指标的经验似然比统计量的渐近分布为加权χ21,由此可构造差异指标的经验似然置信区间.     

基于分数导数研究高强度聚焦超声的非线性声场

在高强度聚焦超声(high intensity focused ultrasound, HIFU) 的研究中, 生物组织的衰减和色散性质会对声能量的空间分布产生影响. 本文提出应用分数导数修正非线性Khokhlov-Zabolotskaya-Kuznetsov (KZK)方程, 研究生物组织中非线性HIFU声场. 对三种生物仿体的衰减和声速色散的理论实验研究表明分数导数应用的可行性, 在此基础上通过数值仿真分析研究了衰减及声速随频率的变化对HIFU焦域分布的影响. 研究结果表明, 在计算强非线性聚焦超声时, 由于高次谐波的强色散作用, 引入分数导数来解决生物组织特殊的衰减以及色散问题可进一步提高HIFU治疗的安全性. 关键词： 分数导数 声衰减 色散 高强度聚焦超声     

b值范围对6种体部扩散模型在前列腺应用的影响评估

论文研究了不同b值采集范围对6种体部扩散模型定量参数计算的影响．研究涉及扩散模型包含单指数模型(Mono)、扩散峰度成像(DKI)、体素内非相干运动模型(IVIM)、扩散拉伸指数模型(SEM)、分数微积分模型(FROC)和随机游走模型(CTRW),b值范围0～2 500 s/mm²．通过扩散模型参数之间的相关性、t检验以及前列腺病灶良恶性鉴别能力三个维度,评估了不同b值采集范围对参数计算的影响．结果显示与参考采样方案相比,随着最大b值降低,所得同一扩散参数感兴趣区域(ROI)均值的差异逐渐增大,但相关性降低不明显,且前列腺病灶良恶性的鉴别能力也保持相似水平．基于实验结果,建议在临床实践中采用b值范围为0～1 500 s/mm²的采集方案．这一方案在具备较高采集效率的同时,一半以上参数与参考采样方案结果的相关性不低于0.98,且良恶性鉴别能力指标曲线下面积(AUC)值的差别小于0.01．此外,不同扩散模型对于b值方案的敏感性存在差异,其中SEM和CTRW模型的参数受b值范围的影响相对较小．     

非线性分数阶Klein-Gordon方程的新的显式解

本文应用一种新的$(G''/G)$-展开法构建了非线性分数阶Klein-Gordon方程的更多、更一般的精确解.利用分数阶复变换,非线性分数阶Klein-Gordon方程被转化为非线性常微分方程.应用扩展的$(G''/G)$-展开法构建非线性分数阶Klein-Gordon方程精确解.得到了一系列新的显式解,包括双曲函数解,三角函数解和负幂次解,利用该方法获得了比以往更丰富的解.     

Super-plasticity of Zr<Subscript>64.80</Subscript>Cu<Subscript>14.85</Subscript>Ni<Subscript>10.35</Subscript>Al<Subscript>10</Subscript> bulk metallic glass at room temperature

Generally, bulk metallic glasses （BMGs） exhibit a very limited plastic deformation under a compression load at room temperature, often less than 2% before fracturing. In this letter, through an appropriate choice of BMGs＇ composition, an amorphous rod of Zr64.80Cu14.85Ni10.35Al10 with a diameter of 2 mm was prepared by using copper mold suction casting. X-ray diffraction and differential scanning calorimetry were utilized to determine its structure and thermal stability, and the uniaxial compression test was adopted to study its plastic deformation behavior at room temperature simultaneously. The results showed that the glass transition temperature and onset temperature of the exothermic reaction of the amorphous rod were 646 and 750 K, respectively, and its micro-hardness was 594.7 Hv. During compression, when the engineering strain and engineering stress arrived at 9.05% and 1732 MPa, respectively, i.e., the true strain and true stress reached 9.42% and 1560 MPa, respectively, the amorphous rod started to yield. After yielding, with the increase of load, the strain increased and the glass rod ulti- mately were compressed into flake-like form. Although the maximum engineering strain was larger than 70%, i.e., the maximum true strain exceeded by 120%, the amorphous specimen was not fractured, indicating that it has super-plasticity at room temperature. Through the appropriate choice of composition and optimization of the technological process, flexible BMG with super-plasticity at room temperature could be produced.     

复杂动态背景中的人脸检测

针对复杂动态背景中的人脸检测问题，提出了一种基于差影运算和肤色识别的检测算法。该算法首先通过改进的差影运算初步确定人脸区域，然后建立一个人脸肤色模型进一步进行肤色匹配．从而实现由粗到细的人脸检测。实验证明，该算法可以适应不同的光照环境，不受人脸大小和朝向的限制。其运算速度和精度均达到实用要求。     

Shale gas exploitation with supercritical CO2 technology

This paper analyzes the physicochemical properties of supercritical CO2, the characteristic of shale gas and shale gas reservoirs. The technologies of drilling, production, fracturing using the supercritical CO2 in shale gas exploration are proposed, to increase the penetration rate, decrease the damage to formation while fracturing, and enhance the recovery of shale gas. It is believed that the huge economic benefits of shale gas exploration with the supercritical CO2 fluid will be obtained, and it also can initiate a new technology field of CO2 in the petroleum engineering.     

船舱CO2泄漏模拟分析

基于计算流体力学对船舱CO2泄漏扩散进行模拟,探究了泄漏速度、阻碍物高度和倾斜角对泄漏扩散的影响.结果表明:CO2泄漏速度越大,向船舱底部沉积愈明显,气体扩散的范围越大,人逃生时间越短;增加阻碍物的高度可显著增加对船舱CO2泄漏的阻碍作用;向左倾斜45°的阻碍物阻碍效果最佳,向右倾斜45°的阻碍物,下风向高浓度CO2区域最大,人员逃生越困难.模拟结果可为船舱CO2泄露事故预防提供参考.     

醇+N-甲基哌嗪二元体系的体积性质

采用振荡管式数字密度计分别测定甲醇、乙醇、正丙醇、异丙醇、丁正醇和异丁醇与N-甲基哌嗪组成的二元体系在298.15K下的密度，计算了超额摩尔体积、超额偏摩尔体积、表观摩尔体积、偏摩尔体积等体积性质，从分子相互作用角度讨论了这些二元体系的体积性质的变化规律，为N-甲基哌嗪的开发和研究提供基础数据和信息。