钢筋混凝土圆管涵管周土压力的理论及试验研究

对钢筋混凝土圆管涵在填土荷载和车辆荷载作用下的管周土压力进行了现场试验研究,并对管-土共同作用体系进行了弹性有限元分析.在此基础上采用面积等效法提出了钢筋混凝土圆管涵在填土荷载和车辆活栽作用下的土压力计算公式,并与现场试验值及各规范的计算值进行了比较.结果表明:本文计算公式得到的结果与试验值吻合较好.随管顶填土高度hs的增加,管周的竖向土压力系数Ks可取值1.5(hs<1 m)-1.35(hs>10 m)、侧向土压力系数λ可取值0.L(hs<1 m)-0.25(hs>3 m),其中间值可采用线性内插;车辆荷载产生的土压力可按23°扩散角进行计算.     

Mathematical reasoning: induction, deduction and beyond

Mathematics used to be portrayed as a deductive science. Stemming from Polya (1954), however, is a philosophical movement which broadens the concept of mathematical reasoning to include inductive or quasi-empirical methods. Interest in inductive methods is a welcome turn from foundationalism toward a philosophy grounded in mathematical practice. Regrettably, though, the conception of mathematical reasoning embraced by quasi-empiricists is still too narrow to include the sort of thought-experiment which Mueller describes as traditional mathematical proof (Mueller, 1969, p. 295) and which Lakatos examines in Proofs and refutations (Lakatos, 1976). This paper extends the concept of mathematical reasoning along two further dimensions to accommodate thought-experiment.     

Translating insights from the cancer genome into clinical practice

Cancer cells have diverse biological capabilities that are conferred by numerous genetic aberrations and epigenetic modifications. Today's powerful technologies are enabling these changes to the genome to be catalogued in detail. Tomorrow is likely to bring a complete atlas of the reversible and irreversible alterations that occur in individual cancers. The challenge now is to work out which molecular abnormalities contribute to cancer and which are simply 'noise' at the genomic and epigenomic levels. Distinguishing between these will aid in understanding how the aberrations in a cancer cell collaborate to drive pathophysiology. Past successes in converting information from genomic discoveries into clinical tools provide valuable lessons to guide the translation of emerging insights from the genome into clinical end points that can affect the practice of cancer medicine.     

羽状流作用下的非等温空调射流运动研究

在传统非等温射流理论的基础上,考虑由室内热源形成的羽状气流对非等温空调射流的热浮升作用,建立数学模型,得到了在内热源作用下非等温射流运动轨迹方程表达式。同时对不同热源形式、热源大小以及热源位置对空调射流和室内热舒适性的影响进行了实验研究,并根据实验结果对热源与射流的相互作用进行了讨论。结果表明,室内热源的存在将明显改变空调射流的运动轨迹,影响室内热舒适性。     

基于人工神经网络的2A70铝合金形变显微组织预测

在Gleeble-1500热模拟试验机上对2A70铝合金试样在变形程度为60％、变形温度为360℃～480℃、变形速率为0.01～1S^-1的条件下进行等温恒应变速率压缩试验及固溶处理。分析热变形参数对合金固溶后显微组织的影响,结果表明,2A70铝合金的晶粒尺寸随温度的升高而增大,随变形程度和速率的增大而减小。采用BP神经网络的方法预测2A70铝合金固溶处理后的平均晶粒尺寸,对于样本数据,模型的相对误差不超过&#177;5％;对于非样本数据,模型的相对误差不超过&#177;8％。     

印刷图像中隐藏水印的菲涅耳变换方法

在研究数字全息技术、双随机相位加密技术和数字印刷技术的基础上,提出了一种新的菲涅耳全息术水印隐藏方法．该方法将待隐藏水印信息经过菲涅耳加密面进行随机相位加密,并离轴记录其像全息图像,将离轴记录的菲涅耳变换加密面像全息图像,以适当的强度叠加隐藏在载体数字图像中,通过正确密钥可从含水印图像中恢复水印信息．通过打印或数字印刷技术可以将含水印图像印制在证件等印刷品中;印刷品中的含水印载体数字图像通过扫描输入生成数字图像,就可以从中提取所隐藏信息．理论分析和仿真实验证明,该方法具有安全性、鲁棒性和不可见性．该方法在解密时通过解密模板紧贴解密,且只需进行一次逆菲涅耳变换就可提取隐藏水印信息,若使用光学系统解密,调整简单,有利于提高恢复隐藏信息的质量．     

具有非光滑Lyapunov函数控制系统的反馈控制器设计及仿真

研究了Lyapunov函数为一类非光滑函数——极大值函数时,控制系统反馈控制器设计中的数值计算问题,并给出了对系统进行分段常数反馈控制的具体实现方法和步骤。仿真实验结果表明了该控制方法的可行性和有效性。     

二叉树模型用于可转换公司债券定价

可转换公司债券兼具债券、股票和期权3个方面的部分特征,再加上可转债的赎回条款和回售条款,使其定价更为复杂.利用二叉树模型,给出了附有赎回条款和回售条款的可转债的定价方法,分析了赎回条款和回售条款对可转债的影响.