非标准审计意见:规则演进、市场状况与存在问题

审计意见作为反映公司财务可信度、揭示财务风险的第三方独立意见,对提升上市公司财务信息质量起着至关重要的作用。本文首先对审计意见的经济含义和经济后果加以阐述;其次,梳理资本市场30年(1990~2020年)以来,非标准审计意见相关审计准则和监管规则的变迁历史;再次,从整体数量、涉及事项、涉及金额和审计意见变更四个方面,深入分析2017~2019年非标准审计意见市场状况;最后,提炼出非标准审计意见现存问题并给出相关建议。

发现新型化学污染物的技术途径

具有持久性有机污染物环境行为特性(持久性、生物累积性、毒性和长距离迁移能力)的新型化学污染物日益受到政府和研究学者的广泛关注.分析方法学的研究是发现新型化学污染物的关键,其主要难点在于无指定的目标化合物为研究对象,有机污染物环境赋存浓度往往处于痕量水平,且基质干扰效应严重.因此需综合运用前沿技术手段,拓展识别分析的新方法体系.本文从样品前处理方法的应用、引导发现策略的设计、多重结构信息的获取和整合三方面介绍了部分关键技术途径和研究进展,并初步探讨了当前的知识空缺和发展趋势.

Aerodynamic characteristics of rigid coaxial rotor by wind tunnel test and numerical calculation

Focusing on aerodynamic characteristics of rigid coaxial rotor of a high-speed helicopter in hover and forward flight, a wind tunnel test is conducted in the 8 m ? 6 m low-speed straightflow wind tunnel of China Aerodynamics Research and Development Center. In the experiment,a 4 m diameter composite model rigid coaxial rotor is designed and manufactured, and firstorder flapping frequency ratio of the blade is 1.796 to ensure sufficient stiffness at the blade root.Rotor aerodynamic performance is measured under hovering and high advance ratio conditions.Also, the numerical method is used to calculate aerodynamic characteristics in typical states of the rigid coaxial rotor for analysis purpose. The rotor lift-drag ratio and lateral lift offset in the experiment are emphatically analyzed for the rigid coaxial rotor. The results indicate that in forward flight condition, the rotor lift-drag ratio first increases and then decreases with the increment of advance ratio and lift offset. When advance ratio remains constant, with the increment of lift offset, the lift-drag ratio of rigid coaxial rotor first increases and then decreases.

数字图像相关技术在泉州宋代海船船体结构监测与保护中的应用

数字图像相关(DIC)测量技术是一种高精度、非接触的对材料或结构表面在受力或外载荷等因素作用下进行全场位移和应变分析的测量方法。本项目利用数字图像相关技术对泉州宋代古船船尾结构的位移变形情况进行了监测,同时建立船尾有限元模型,对船尾变形位移的数值进行了模拟计算与预估,两者均显示船尾存在缓慢下沉位移现象,有必要对船尾实施加固措施。在对船尾结构进行了加固处理后,再次监测结果表明船尾已没有明显下沉位移的趋势,说明加固措施是有效的。