我国企业跨国并购与行业内逆向技术溢出

文章将BVD（Zephyr）统计的我国企业跨国并购数据与37个工业行业合并，利用我国2001～2012年37个行业数据实证检验了跨国并购是否促进了行业生产率进步。通过上述研究，我们得到以下几个结论：第一，我国企业跨国并购总体促进了行业生产率进步。第二，在不同目标国的跨国并购对行业生产率进步有不同影响。对高收入国家的跨国并购显著促进了行业生产率进步：对中低收入国家的跨国并购没有明显促进行业生产率进步；对香港地区、澳门地区和传统避税港的跨国并购没有显著促进行业生产率进步，但对其他国家和地区的跨国并购明显促进了行业生产率进步。最后，文章以行业人均产值作为生产效率的代理变量进行稳健性检验，上述结论仍然成立。文章为自然科学基金面上项目“中国企业海外并购与产业国际竞争力研究”（项目批准号：71273142）和自然科学基金青年项目“中国企业对外直接投资的贸易效应和就业效应”（项目批准号：71503221）的阶段性成果

中国工业企业对外直接投资与企业生产率进步

针对企业对外直接投资是否提升了企业生产率问题,我们利用数据匹配法为2004~2006年761家对外直接投资的工业企业找到可供比较的对照组,运用倍差法检验了企业对外直接投资的“生产率效应“。通过检验我们有如下发现:(1)企业对外直接投资显著提升了企业生产率,但提升作用随着时间推移逐渐降低;(2)企业的技术研发型外向投资不一定显著提升企业生产率;(3)东道国发展水平的差异对企业生产率的提升有较大影响。最后,我们还计算了以对外直接投资企业为实验组的平均处理效应,结论仍然稳健。自然科学基金重大研究项目“中国企业海外并购与产业国际竞争力研究”(71273142)的阶段性成

外商并购是“创造”还是“破坏”了我国企业的市场价值

本文利用2004-2015年BVD统计的并购数据研究了外商企业并购对我国企业市场价值的影响。在理论假设的基础上,利用事件研究法分析了在公告日各窗口外商并购对我国被并购企业股票异常收益率的影响。通过事件分析,发现总体来看我国被并购企业获得了显著为正的异常收益率,但所有制、并购规模、支付方式、外资来源国和行业等差异会造成不同影响。相对而言,我国国有企业、现金支付方式、欧美发达国家企业、高新技术和制造业等并购为我国企业创造了更高市场价值。然而,金融行业和其他服务业的并购为我国被并购企业创造的市场价值较低。在此基础上,本文构建计量模型进行检验,发现上述结论仍然成立。此外研究还发现,并购双方行业相关性越大,为我国企业创造的市场价值越大;并购规模越大,创造的市场价值也越大;被并购前我国企业的市值越高,并购后创造的市场价值越低;被并购前我国企业的盈利能力越强或经营效率越高,并购后我国企业获得市场价值越大

On mechanical properties of metallic glass and its liquid vitrification characteristics

A systematic survey of the available data such as elastic constants, density, molar mass, and glass transition temperature of 45 metallic glasses is conducted. It is found that a critical strain controlling the onset of plastic deformation is material-independent. However, the correlation between elastic constants of solid glass and vitrification characteristics of its liquid does not follow a simple linear relation, and a characteristic volume, viz. molar volume, maybe relating to the characteristic size of a shear transformation zone (STZ), should be involved

Analytical Evaluation of Tunnel Reinforcement Effect by PCM Shotcrete Method Using FRP Grid

Degradation of lining concrete happens naturally in the tunnels that have been commissioned for several decades, which require proper maintenance to ensure their safety and effective functions. The PCM shotcrete method by means of FRP grid, with the characters of high strength, low weight, high workability, strong resistance to corrosion, and negligible influence on the existing structures, has been used in tunnel maintenance to repair the damaged lining of some aged tunnels. Up to now, the construction cases are still few, and the design routine of this method based on quantitative evaluation on the reinforcement effect has not been established. In this study, the shear bond strength and the shear stiffness of typical FRP grids were estimated by conducting direct shear tests on FRP-PCM specimens. Those parameters were input into a numerical model of tunnel to quantitatively estimate the displacement control effect of the FRP-PCM method on tunnel lining. The experiment and numerical simulation results show that the FRP-PCM method has good reinforcement effect on tunnel lining and has high potential to be applied extensively in the maintenance of aged tunnels

Formation Mechanism Of Lamellar Chips During Machining Of Bulk Metallic Glass

The uniqThe unique lamellar chips formed in turning–machining of a Vit 1 bulk metallic glass (BMG) are found to be due to repeated shearband formation in the primary shear zone (PSZ). A coupled thermomechanical orthogonal cutting model, taking into account force, free volume and energy balance in the PSZ, is developed to quantitatively characterize lamellar chip formation. Its onset criterion is revealed through a linear perturbation analysis. Lamellar chip formation is understood as a self-sustained limit-cycle phenomenon: there is autonomous feedback in stress, free volume and temperature in the PSZ. The underlying mechanism is the symmetry breaking of free volume flow and source, rather than thermal instability. These results are fundamentally useful for machining BMGs and even for understanding the physical nature of inhomogeneous flow in BMGs.ue lamellar chips formed in turning–machining of a Vit 1 bulk metallic glass (BMG) are found to be due to repeated shearband

Rational Design of the "Alternate" Steel Sheet Pile Method Based on Numerical Simulation by Finite Difference Method

Subsidence and heaving are produced in the peripheral ground when the banking is constructed on soft ground, and various damages in its environ structure is caused. The steel sheet pile method is often used as a countermeasure in order to reduce such ground deformation. However, in the installation of the long pile, it is very uneconomical, and the long term execution period is also needed for the embankment. This study is to clarify the installation effect of the \u27alternate\u27 steel sheet pile method based on the in-situ observation, model experiment and numerical analysis

稀薄大气密度涨落对高空超高速飞行器气动性能的影响

地球周围的大气环境特性,随高度的上升,显著变化。对于本文关心的高度100km附近高超声速飞行器气动特性而言,稀薄大气密度涨落影响是一个重要的问题。按照大气层划分,高度100 km属于热层。热层的下界高度约86 km,上界高度与太阳活动有关,在太阳宁静期约为200 km,太阳活动期约500 km。热层下接中间层(高度50～86 km),上连电离层(高度80～1000 km),大气研究已知,中间层主要受重力波和湍流影响,电离层主要受太阳活动和地磁效应影响。高度100 km附近空域,处在热层下界,重力波、湍流、太阳活动和地磁效应等均有影响,理论上需要Navier-Stokes方程和Maxwell方程..

Comparison of the simulated and LIDAR measured atmospheric density and temperature in transitional flow regime

The understanding of the atmosphere in the transitional flow regime is quite limited,due to the limited accuracy of measurement data.In the proposed paper,the atmospheric density and temperature at around 100 km altitude are analyzed,by using numerical simulation,empirical model,satellite data an..

Dynamic Fracture Instability Of Tough Bulk Metallic Glass

We report the observations of a clear fractographic evolution from vein pattern, dimple structure, and then to periodic corrugation structure, followed by microbranching pattern, along the crack propagation direction in the dynamic fracture of a tough Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit.1) bulk metallic glass (BMGs) under high-velocity plate impact. A model based on fracture surface energy dissipation and void growth is proposed to characterize this fracture pattern transition. We find that once the dynamic crack propagation velocity reaches a critical fraction of Rayleigh wave speed, the crack instability occurs; hence, crack microbranching goes ahead. Furthermore, the correlation between the critical velocity of amorphous materials and their intrinsic strength such as Young's modulus is uncovered. The results may shed new insight into dynamic fracture instability for BMGs. (C) 2008 American Institute of Physics