文章借鉴Khandelwal et al.(2013)扩展的产品质量异质性模型,构建了一个两国之间产品贸易的一般均衡模型,并推导企业出口模式选择影响产品质量升级的理论框架,再利用2000-2013年中国工业企业和海关数据构建双重差分模型对理论假说进行...文章借鉴Khandelwal et al.(2013)扩展的产品质量异质性模型,构建了一个两国之间产品贸易的一般均衡模型,并推导企业出口模式选择影响产品质量升级的理论框架,再利用2000-2013年中国工业企业和海关数据构建双重差分模型对理论假说进行系统检验。结果发现:(1)直接出口企业对产品质量的提升效应明显高于间接出口企业,"反事实"检验和安慰剂检验的结果依然稳健。(2)通过异质性分析发现,东部地区企业出口的产品质量提升效应显著高于中西部地区企业,而且中西部地区的间接出口抑制出口产品质量提升;民营、外资企业直接出口和间接出口对产品质量提升效应均高于国有企业。(3)进一步研究企业出口模式的动态转换效应发现,企业由间接出口转向直接出口显著提升了出口产品质量,并且生产率较高的企业通过提升出口固定成本效率而加速出口产品质量升级。展开更多
We analyze mathematical models governing planar flow of chemical reaction from unburnt gases to burnt gases in certain physical regimes in which diffusive effects such as viscosity and heat conduction are significant....We analyze mathematical models governing planar flow of chemical reaction from unburnt gases to burnt gases in certain physical regimes in which diffusive effects such as viscosity and heat conduction are significant. These models can be then formulated as the Navier-Stokes equations for exothermically reacting compressible fluids. We first establish the existence and dynamic behavior, including stability, regularity, and large-time behavior, of global discontinuous solutions of large oscillation to the Navier-Stokes equations with constant adiabatic exponent γ and specific heat Cv. Our approach for the existence and regularity is to combine the difference approximation techniques with the energy methods, total variation estimates, and weak convergence arguments to deal with large jump discontinuities; and for large-time behavior is an a posteriori argument directly from the weak form of the equations. The approach and ideas we develop here can be applied to solving a more complicated model where γand cv vary as the phase changes; and we then describe this model in detail and contrast the results on the asymptotic behavior of the solutions of these two different models. We also discuss other physical models describing dynamic combustion.展开更多
文摘文章借鉴Khandelwal et al.(2013)扩展的产品质量异质性模型,构建了一个两国之间产品贸易的一般均衡模型,并推导企业出口模式选择影响产品质量升级的理论框架,再利用2000-2013年中国工业企业和海关数据构建双重差分模型对理论假说进行系统检验。结果发现:(1)直接出口企业对产品质量的提升效应明显高于间接出口企业,"反事实"检验和安慰剂检验的结果依然稳健。(2)通过异质性分析发现,东部地区企业出口的产品质量提升效应显著高于中西部地区企业,而且中西部地区的间接出口抑制出口产品质量提升;民营、外资企业直接出口和间接出口对产品质量提升效应均高于国有企业。(3)进一步研究企业出口模式的动态转换效应发现,企业由间接出口转向直接出口显著提升了出口产品质量,并且生产率较高的企业通过提升出口固定成本效率而加速出口产品质量升级。
基金Supported in part by the National Science Foundation under Grants DMS-9971793, INT-9987378,and INT-9726215.Supported in part by the National Science Foundation under Grant DMS-9703703.Supported in part by the National Science Foundation under Grants
文摘We analyze mathematical models governing planar flow of chemical reaction from unburnt gases to burnt gases in certain physical regimes in which diffusive effects such as viscosity and heat conduction are significant. These models can be then formulated as the Navier-Stokes equations for exothermically reacting compressible fluids. We first establish the existence and dynamic behavior, including stability, regularity, and large-time behavior, of global discontinuous solutions of large oscillation to the Navier-Stokes equations with constant adiabatic exponent γ and specific heat Cv. Our approach for the existence and regularity is to combine the difference approximation techniques with the energy methods, total variation estimates, and weak convergence arguments to deal with large jump discontinuities; and for large-time behavior is an a posteriori argument directly from the weak form of the equations. The approach and ideas we develop here can be applied to solving a more complicated model where γand cv vary as the phase changes; and we then describe this model in detail and contrast the results on the asymptotic behavior of the solutions of these two different models. We also discuss other physical models describing dynamic combustion.
