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减税激励、企业规模与资本劳动比 被引量:1
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作者 李艳 王康宁 +1 位作者 陈斌开 白重恩 《经济学报》 2023年第1期162-192,共31页
资本深化(资本劳动比的提高)是中国企业转型升级和生产效率提升的重要渠道,但是文献关于中小企业资本深化的研究还不够。本文使用《中国税务局调查数据》,运用双重差分方法(DD),考察固定资产加速折旧政策对不同规模企业资本劳动比的差... 资本深化(资本劳动比的提高)是中国企业转型升级和生产效率提升的重要渠道,但是文献关于中小企业资本深化的研究还不够。本文使用《中国税务局调查数据》,运用双重差分方法(DD),考察固定资产加速折旧政策对不同规模企业资本劳动比的差异性影响,并探究其背后的作用机制以及对生产效率的提升作用。研究发现:首先,政策显著提升了企业资本劳动比,试点企业的资本劳动比非试点企业平均提高了6.7%,中型企业受到政策影响最大,小型企业次之,大型企业基本不受影响。其次,机制研究表明加速折旧政策显著改善了大中小企业现金流,促进中型企业增加投资,促进小型企业使用资本替代低技能劳动,省级宏观数据也发现存在低学历劳动力被替代的现象。最后,政策显著提升了中小企业的生产效率。研究税收激励对不同规模企业资本和劳动的替代关系是优化企业内部要素配置效率的关键,同时对于综合评估减税降费政策效果、针对性破除制约高质量发展的机制障碍和深化供给侧改革,也具有重要现实意义。 展开更多
关键词 税收激励 融资约束 资本劳动比 生产效率
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Effects of Dietary Starch Source on Nutrient and Energy Absorption via the Portal Vein of Growing Pigs
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作者 Qiuzhong Dai kangning wang +3 位作者 Yulong Yin Tiejun Li Ruilin Huang Yan Hu 《Journal of Animal Science and Biotechnology》 SCIE CAS 2010年第3期175-181,共7页
Four crossbred (Duroc x Landrace x Yorkshire) boars, weighing an average of 22.40 ± 1.08 kg and fitted with permanent catheters in their portal and mesenteric veins as well as their carotid artery,were utilized... Four crossbred (Duroc x Landrace x Yorkshire) boars, weighing an average of 22.40 ± 1.08 kg and fitted with permanent catheters in their portal and mesenteric veins as well as their carotid artery,were utilized in a 4 × 4 latin square design experiment in order to investigate the effects of different starch sources (maize ,brown rice, sticky rice, and resistant starch) on the absorption of energy sources through the portal vein. Portal blood flow averaged 30.68, 28.40, 29.99, and 30. 12 mL/min per kg BW for pigs fed the maize, brown rice, sticky rice, and resistant starch diets, respectively, and did not dif- fer (P 〉 0.05) between treatments. The absorptions of glucose, plasma ammonia, and total amino acids were significantly lower (P 〈 0.05 ) in pigs fed the resistant starch diet than pigs fed the other starch sources. In contrast, significantly ( P 〈 0.05 ) higher amounts of propionate and total volatile fatty acids were absorbed from the portal vein of pigs fed resistant starch than pigs fed diets based on maize, brown rice, or sticky rice. In addition, significantly (P 〈 0.05) more lactic acid was absorbed from the portal vein by pigs fed the sticky rice diet than pigs fed the other three diets. The energy absorbed from the portal vein in the form of glucose and amino-N as well as the total energy absorbed was significantly (P 〈 0.05) lower in pigs fed the resistant starch diet than pigs fed the other three starch sources. In contrast, the amount of energy absorbed in the form of volatile fatty acids was significantly (P 〈 0.05 ) higher in pigs fed resistance starch than pigs fed the other three starch sources. The total energy absorbed through the portal vein as a percentage of the gross energy and digestible energy consumed in pigs fed maize were 50.8% and 54.6%, respectively, which were significantly (P 〈 0.05 ) higher than the values in pigs fed resistant starch (41.5% and 46.6% respectively). The results indicate that energy is absorbed in different forms and with different utilization efficiencies in the digestive tract of pigs as a result of feeding different starch sources. Starch sources supplying most of their energy in the form of glucose had higher energy utilization efficiencies, while starch sources supplying most of their energy in the form of volatile fatty acids or lactic acid had lower energy utilization efficiencies. 展开更多
关键词 ENERGY growing pigs NUTRIENTS portal vein absorption starch source
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非随机分布式大数据的稳健回归及其在非凸惩罚学习中的应用
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作者 孙晓霏 王康宁 林路 《中国科学:数学》 CSCD 北大核心 2023年第4期615-628,共14页
大数据的分布式统计学习引起了人们的广泛关注.已有方法存在两个显著问题.首先,它们都要求大数据以随机的方式存储在不同机器上,而这一点在实际中很难满足.其次,它们大都基于最小二乘,对重尾误差和异常值很敏感.为了解决这些问题,本文... 大数据的分布式统计学习引起了人们的广泛关注.已有方法存在两个显著问题.首先,它们都要求大数据以随机的方式存储在不同机器上,而这一点在实际中很难满足.其次,它们大都基于最小二乘,对重尾误差和异常值很敏感.为了解决这些问题,本文提出一个稳健的分布式众数回归,并且将其应用到非凸惩罚变量选择中.新方法克服了已有方法所需要的非随机分布假定,而且理论结果也证实了这个论断.随机模拟和实际数据分析也展示了新方法的良好表现. 展开更多
关键词 大规模数据 众数回归 稳健性 变量选择
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Pitch-derived 3D amorphous carbon encapsulated sulfur-rich cathode for aqueous Zn-S batteries
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作者 kangning wang Jianwei wang +3 位作者 Ziqi Zhang Wenlin Zhang Feng Fu Yaping Du 《Science China Chemistry》 SCIE EI CAS CSCD 2023年第9期2711-2718,共8页
Rechargeable aqueous zinc batteries have attracted much attention due to their high security, plentiful zinc resources, and environmental friendliness. However, it can only offer limited specific capacity and energy d... Rechargeable aqueous zinc batteries have attracted much attention due to their high security, plentiful zinc resources, and environmental friendliness. However, it can only offer limited specific capacity and energy density based on ion insertion chemistry cathode. Herein, we design a low-cost and high-energy density aqueous Zn-S battery where the conversion cathode was fabricated by pitch-derived three-dimensional(3D) amorphous carbon encapsulated industrial-grade sulfur powder. The cost of the chemical substances for this aqueous Zn-S battery might be reduced to $9.38 per kW h based on the affordable cost of the raw ingredients. It is found that the PAC/S-60.33% cathode reveals excellent electrochemical performance, including a high reversible capacity(633.5 mAh g^(-1)at 0.5 A g^(-1)), high energy density(297.5 Wh kg^(-1)), an excellent rate capability(204.5 mAh g^(-1) at 5.5 A g^(-1)), as well as good cycling stability(180 mAh g^(-1)after 400 cycles at 5.0 A g^(-1)). Besides, the reaction mechanism of the cathode was investigated using ex-situ X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), and transmission electron microscope(TEM). It was demonstrated that the cathode undergoes a conversion reaction between S and Zn S. Furthermore, the discoveries also offer prospective possibilities to fabricate more secure and inexpensive battery systems. 展开更多
关键词 pitch 3D amorphous carbon sulfur-rich aqueous Zn-S batteries
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基于copula函数的纵向数据复合分位数回归及变量选择 被引量:3
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作者 王康宁 李劭珉 林路 《中国科学:数学》 CSCD 北大核心 2020年第8期1097-1116,共20页
复合分位数回归(composite quantile regression)具有稳健性好和估计效率高的优势,所以其经常被用来替代均值回归.众所周知,纵向数据具有组内相关的特点,如果估计过程中能正确地利用组内相关性,则可以显著地提高估计效率.因此,探讨纵向... 复合分位数回归(composite quantile regression)具有稳健性好和估计效率高的优势,所以其经常被用来替代均值回归.众所周知,纵向数据具有组内相关的特点,如果估计过程中能正确地利用组内相关性,则可以显著地提高估计效率.因此,探讨纵向数据复合分位数回归中如何使用相关性是一个有意义的问题.本文首先利用copula函数方法构建纵向数据复合分位数回归的组内协方差矩阵,进而基于构建的协方差矩阵,提出一个无偏且有效的基于copula函数的复合分位数回归估计方程;进一步,为了进行变量选择,利用基于copula函数的估计方程,提出一个光滑门限(smooth-threshold)的复合分位数回归估计方程方法.本文提出的方法具有很高的灵活性,而且提高了估计的效率.理论结果以及数值模拟和实际数据分析都验证了本文的方法. 展开更多
关键词 复合分位数回归 纵向数据 COPULA函数 有效性 变量选择
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基于众数回归的纵向数据部分线性模型的稳健经验似然及变量选择 被引量:1
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作者 孙晓霏 王康宁 +1 位作者 李劭珉 林路 《中国科学:数学》 CSCD 北大核心 2022年第4期447-466,共20页
众数回归具有稳健性和估计效率高的优势,在某些情形下可以替代均值回归.针对带有高维协变量的纵向数据部分线性模型,本文基于众数回归提出了稳健的经验似然及惩罚的高维众数回归经验似然变量选择方法.新方法能够利用纵向数据的组内相关... 众数回归具有稳健性和估计效率高的优势,在某些情形下可以替代均值回归.针对带有高维协变量的纵向数据部分线性模型,本文基于众数回归提出了稳健的经验似然及惩罚的高维众数回归经验似然变量选择方法.新方法能够利用纵向数据的组内相关性,而且继承了众数回归在稳健性和估计效率方面的优势.基于一些较弱的条件,本文在协变量维数趋于无穷大的高维框架下建立了方法的大样本性质.随机模拟和实际数据分析也验证了方法在有限样本时的表现. 展开更多
关键词 众数回归 高维纵向数据 经验似然 变量选择
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