区域贸易政策不确定性、策略选择与中国多产品企业出口产品种类——基于中国-东盟《框架协议》的准自然实验

多产品企业产品种类调整有助于实现企业内资源优化配置。文章匹配2001—2013年中国工业企业数据、海关进出口产品数据与WITS关税数据,以中国-东盟《框架协议》签署作为准自然实验,通过双重差分的方法探究区域贸易政策不确定性对中国多产品企业出口产品种类的影响。实证结果表明,《框架协议》签署带来的区域贸易政策不确定性下降促使中国多产品企业显著增加出口产品种类,与Bernard et al.(2011)基于美加自由贸易区的研究结果形成了鲜明对比,主要原因在于东盟市场与北美市场的规模、产品结构等方面存在显著差异。此外,区域贸易政策不确定性下降对采取不同竞争策略的多产品企业出口种类的影响存在显著差异,采取质量竞争策略的多产品企业比采取数量竞争策略的多产品企业在《框架协议》签署的外生冲击下,增加更多的出口产品种类。此外,《框架协议》签署对区域贸易政策不确定性下降幅度更大的多产品企业出口产品种类的促进作用更加明显。进一步,《框架协议》签署带来的区域贸易政策不确定性下降对多产品企业出口产品种类增加的影响主要通过创新效应发生作用,而学习效应没有显著的作用。以上结论在稳健性检验中仍然成立。该研究为中国实施FTA战略、评估RCEP政策,以及理解中国制造业企业的出口多样化和企业内产品组合决策提供了新的视角。

地方政府支持与区域市场需求规模不确定性对高校技术转移效率的影响——来自中国“211工程”大学的证据

利用中国75所"211工程"大学1998—2002年间的面板数据,采用随机前沿方法(SFA)实证分析了地方政府支持和区域市场需求规模不确定性对高校技术转移效率的影响.研究结果表明:当地政府的财政资金支持,作为其对高校技术转移最直接的支持方式,显著促进了高校技术转移效率的提高;而区域市场需求规模的波动,由于导致技术转让风险的增大,会对转移效率产生负面影响.另外,对比分析了各高校人均产出效率和由SFA方法所测效率,并提出了相应的政策建议.

区域贸易政策不确定性与中国出口企业僵尸化——以中国-东盟自由贸易区为例

区域贸易政策不确定性是影响中国出口企业僵尸化的因素。本文选取中国—东盟自由贸易区作为研究的切入点与视角,采用企业层面数据,运用倍差法探究区域贸易政策不确定性的大幅下降给中国出口企业僵尸化造成的影响。结果发现,《中国—东盟全面经济合作框架协议》付诸实施所引致的区域贸易政策不确定性的大幅下降明显抑制了中国出口东盟企业的僵尸化。这种抑制效果的发挥因出口企业的所有制、所在地区以及要素密集程度的差异而展现出明显的异质性。机制检验结果显示,区域贸易政策不确定性的大幅下降主要依托学习效应、竞争效应、进口中间品贸易环境改善等路径来遏制出口企业的僵尸化,其中进口中间品贸易环境改善的作用最为明显。实证结果从区域贸易政策不确定性降低的视角为抑制中国出口企业僵尸化提供了新思路。

区域贸易政策不确定性与出口企业创新研究——以中国-东盟自由贸易区为例

以中国-东盟自由贸易区正式成立为例,结合2001—2013年中国工业企业数据库和中国海关数据库,使用双重差分法(DID)探究区域贸易政策不确定性对出口企业创新的影响。结果显示:中国-东盟自由贸易区正式成立带来的区域贸易政策不确定性降低有利于中国出口企业创新,提高企业的专利申请量和专利质量。并且这一效应在混合贸易企业、资本密集型企业、民营企业以及向东盟出口企业中更为显著。机制分析表明,区域贸易政策不确定性下降会通过扩大出口市场规模、促进企业提高创新投入,从而影响企业创新。因此,高质量实施区域自由贸易区战略能够降低中国出口企业面临的贸易政策不确定性风险,促进企业创新。

区域贸易政策不确定性对中国出口企业产品质量的影响——以中国—东盟自由贸易区为例

本文基于异质性企业贸易模型,论证了区域自由贸易协定框架下贸易政策不确定性对出口企业产品质量的作用机理。在此基础上,本文以CAFTA为例,基于2001—2007年中国工业数据库、中国海关数据库,采用倍差法(DID)对理论分析结果进行了经验检验,得到以下结论:区域贸易政策不确定性的降低显著提升了中国出口企业的产品质量;国有企业、私营企业、外资企业的产品质量均获得了显著改善,外资企业改善程度最大;东部及中西部地区出口企业的产品质量均获得了明显提高,东部地区企业提升效果最为显著;劳动密集型企业和资本密集型企业的产品质量提升效果显著,但技术密集型企业不显著;进入及退出企业的产品质量均获得了有效提升,进入企业更为突出。本文的研究结果为在FTA框架下提升中国出口产品质量提供了新的视角。

区域贸易政策不确定性与企业成本加成——来自中国多产品企业的微观证据

提升外贸企业出口定价能力是中国外贸高质量发展的重要内容。本文以中国—东盟自由贸易区建立为例,探究实施自由贸易区战略,签订自由贸易协定带来的区域贸易政策不确定性(RTPU)下降对中国多产品企业出口产品成本加成率的影响及作用机制。研究发现:RTPU下降会显著提升中国企业出口产品的成本加成率;在多产品企业内部,RTPU下降对企业核心出口产品的成本加成率的提升效应更大。作用机制体现在,RTPU下降存在不完全的成本传递效应以及产品整体质量提升效应,进而提升产品的成本加成率;RTPU下降后,企业通过缩减产品组合,生产高质量核心产品的方式优化内部资源配置,着力提升其核心产品成本加成率。此外,本文还发现RTPU下降仅对采取成本竞争策略的企业、通过一般贸易出口的产品的成本加成率具有提升效应。本文的结论为中国深化区域合作,提升外贸企业出口定价能力提供了新的依据。

区域贸易政策不确定性与出口企业对外直接投资的行为选择——以中国-东盟自由贸易区为例

文章通过以中国-东盟自由贸易区为对象,并利用2001~2013年间的微观企业层面数据,实证检验了区域贸易政策不确定性的降低对中国出口企业对外直接投资行为选择的影响。结论表明,中国-东盟自由贸易区的确定建立所带来的区域贸易政策不确定性降低,促进了中国出口东盟的企业对该区直接投资的行为选择。研究进一步发现,不同所有制类型、地区、要素密集度的出口东盟的企业在这一过程中的行为选择呈现出显著的异质性。最后,通过机制检验发现,区域贸易政策不确定性降低主要通过学习型效应、竞争效应及改善出口中间品贸易环境等途径来促进中国出口东盟的企业对该区的直接投资行为选择,其中学习型效应所起的作用最大,占总效用的比重达57%。

基于电压耐受曲线区域划分的可调速驱动器电压暂降耐受能力分析

为准确评估可调速驱动器受电压暂降影响的变化情况,弥补现有可调速驱动器电压暂降耐受能力研究的不足,对可调速驱动器的电压暂降耐受能力进行测试。在现有研究的基础上,制定了相应的测试计划,搭建了实测平台对三台不同型号的设备进行测试。将测试获得数据进行极值化处理,得到可调速驱动器电压耐受曲线不确定性区域。为更精确地分析可调速驱动器受暂降影响动作机理,提出一种基于电压耐受曲线区域划分的可调速驱动器电压暂降耐受能力分析方法。着重分析电压暂降发生在故障区域时,不同影响因素下可调速驱动器直流侧电压、输出端电流、电机转矩、转速的波形变化情况。揭示了输入暂降信号与设备工作特性之间的响应规律。

Generalized Uncertainty Principle and Black Hole Entropy of Higher-Dimensional de Sitter Spacetime

Recently, there has been much attention devoted to resolving the quantum corrections to the Bekenstein-- Hawking black hole entropy. In particular, many researchers have expressed a vested interest in the coetticient of the logarithmic term of the black hole entropy correction term. In this paper, we calculate the correction value of the black hole entropy by utilizing the generalized uncertainty prlnciple and obtain the correction term caused by the generalized uncertainty principle. Because in our calculation we think that the Bekenstein-Hawking area theorem is still valid after considering the generalized uncertainty principle, we derive that the coefficient of the logarithmic term of the black hole entropy correction term is positive. This result is different from the known result at present. Our method is valid not only for four-dimensional spacetimes but also for higher-dimensional spacetimes. In the whole process, the physics idea is clear and calculation is simple. It offers a new way for studying the entropy correction of the complicated spacetime.

Regional Climate Change and Uncertainty Analysis based on Four Regional Climate Model Simulations over China

Four sets of climate change simulations at grid spacing of 50 km were conducted over East Asia with two regional climate models driven at the lateral bounda- ries by two global models for the period 1981-2050. The locus of the study was on the ensemble projection of cli- mate change in the mid-21st century （2031-50） over China. Validation of each simulation and the ensemble average showed good performances of the models overall, as well as advantages of the ensemble in reproducing present day （1981 2000） December-February （DJF）, June-August （JJA）, and annual （ANN） mean temperature and precipitation. Significant wanning was projected for the mid-21st century, with larger values of temperature increase found in the northern part of China and in the cold seasons. The ensemble average changes of precipitation in DJF, JJA, and ANN were determined, and the uncertainties of the projected changes analyzed based on the consistencies of the simulations. It was concluded that the largest uncertainties in precipitation projection are in eastern China during the summer season （monsoon pre-cipitation）.

Uncertainty in crossing time of 2 °C warming threshold over China

The 2 ℃ warming target has been used widely in global and regional climate change research. Previous studies have shown large uncertainties in the time when surface air temperature （SAT） change over China will reach 2℃ rela- tive to the pre-industrial era. To understand the uncertainties, we analyzed the projected SAT in the twenty-first century using 40 state-of-the-art climate models under two Repre- sentative Concentration Pathways （RCP4.5 and RCPS.5） from the Coupled Model Intercomparison Project Phase 5. The 2℃ threshold-crossing time （TCT） of SAT averaged across China was around 2033 and 2029 for RCP4.5 and RCP8.5, respectively. Considering a 4-1o- range of inter- model SAT change, the upper and lower bounds of the 2 ℃ TCT could differ by about 25 years or even more. Uncer- tainty in the projected SAT and the warming rate around the TCT are the two main factors responsible for the TCT uncertainty. The former is determined by the climate sensi- tivity represented by the global mean surface temperature response. About 45 % of the intermodel variance of the projected 2 ~C TCT for averaged SAT over China can be explained by climate sensitivity across the models, which is contributed mainly by central and southern China. In a cli- mate more sensitive to CO2 forcing, stronger greenhouse effect, less stratus cloud over the East Asian monsoon region, and less snow cover on the Tibetan Plateau result in increased downward longwave radiation, increased shortwave radia- tion, and decreased shortwave radiation reflected by the surface, respectively, all of which may advance the TCT.

Qualitative and quantitative uncertainties in regional rainfall frequency analysis

Uncertainty exists widely in hydrological analysis, and this makes the process of uncertainty assessment very im- portant for making robust decisions. In this study, uncertainty sources in regional rainfall frequency analysis are identified for the first time. The numeral unite spread assessment pedigree （NUSAP） method is introduced and is first employed to quantify qual- itative uncertainty in regional rainfall frequency analysis. A pedigree matrix is particularly designed for regional rainfall frequency analysis, by which the qualitative uncertainty can be quantified. Finally, the qualitative and quantitative uncertainties are com- bined in an uncertainty diagnostic diagram, which makes the uncertainty evaluation results more intuitive. From the integrated diagnostic diagram, it can be determined that the uncertainty caused by the precipitation data is the smallest, and the uncertainty from different grouping methods is the largest. For the downstream sub-region, a generalized extreme value （GEV） distribution is better than a generalized logistic （GLO） distribution; for the south sub-region, a Pearson type III （PE3） distribution is the better choice; and for the north sub-region, GEV is more appropriate.