基于数据拟合分析坡面土壤侵蚀的临界坡度

通过不同雨强、坡度的多段模拟降雨实验,将坡度与坡面侵蚀模数进行二次多项式拟合,求得不同条件下坡面侵蚀的临界坡度。实验结果表明,临界坡度会随着雨强、降雨历时的变化而产生规律性变化。雨强越大,临界坡度越大,对坡面侵蚀临界坡度的影响越强烈;降雨历时增加,坡面侵蚀的临界坡度也随之增大,雨强越大,临界坡度增速越快,且增速拐点出现越早。在坡面侵蚀初期,坡度增加加强了坡面径流对坡面泥沙的搬运作用,减弱了坡面的溅蚀作用,使得在一定坡度范围内坡度大的坡面细沟侵蚀开始时间晚于坡度小的坡面,这是临界坡度产生的原因之一。随着坡面侵蚀过程的发展,坡面侵蚀主要发生于细沟的边缘、侧壁和底部,不同坡度坡面单位时间内的侵蚀模数差值减少且趋于稳定,坡度对于侵蚀模数的影响逐渐减小,临界坡度逐渐消失。该研究可为完善黄土区的土壤侵蚀机理提供理论依据。     

Do we need higher-order comoments to enhance mean-variance portfolios? Evidence from a simplified jump process

We consider a joint distribution that decomposes asset returns into two independent components: an elliptical innovation (Gaussian) and a systematic non-elliptical latent process. The paper provides a tractable approach to estimate the underlying parameters and, hence, the assets’ exposures to the latent non-elliptical factor. Additionally, the framework incorporates higher-order moments, such as skewness and kurtosis, for portfolio selection. Taking into account estimation risk, we investigate the economic contribution of the non-elliptical term. Overall, we find weak empirical evidence to support the inclusion of the non-elliptical term and, hence, the higher-order comoments. Nonetheless, our findings support the mean–variance (MV) decision rule that incorporates the elliptical term alone. Excluding the non-elliptical term results in more robust mean–variance estimates and, thus, enhanced out-of-sample performance. This evidence is significant among stocks that exhibit a strong deviation from the Gaussian property. Moreover, it is most pronounced during market turmoils, when exposures to the latent factor are highest.     

Distant but Close in Sight: Firm-level Evidence on French–German Productivity Gaps in Manufacturing

We study productivity-level distributions of manufacturing firms in France and Germany, and how these distributions evolved across the Great Recession. We show the presence of a systematic productivity advantage of German firms over French ones in the decade 2003–2013, but the gap has narrowed down after the Great Recession. Convergence is explained by the better growth performance of French firms in the post-recession period, especially of those located in the top percentiles of the productivity distribution. We also highlight the role of sectoral growth, firm size, and export intensity in explaining the above convergence. In contrast, the contribution of allocative efficiency was small.     

一种改进的机载卫通天线跟踪算法

在圆锥扫描实现过程分析的基础上，提出了一种改进的机载卫通天线跟踪算法。结合天线方位、俯仰方向图及其三维重构法，对该跟踪算法进行了理论推导。运用Matlab曲线拟合仿真，给出了天线跟踪调整方向和角度的计算公式，最后分析了实际应用中需要注意的一些问题。飞行试验表明，该改进的圆锥扫描跟踪技术提高了天线伺服系统的跟踪精度和跟踪速度，很好地满足了机载卫星通信的需求。     

The Evolution of Income Composition Inequality in Italy, 1989–2016

We study the evolution of inequality in income composition in terms of capital and labor income in Italy between 1989 and 2016. We document a rise in the share of capital income accruing to the bottom of the distribution, while the top of the distribution increases its share of labor income. This implies a falling degree of income composition inequality in the period considered and a weaker relationship between the functional and personal distribution of income in Italy. This result is robust to various specifications of self-employment income; nonetheless, it hinges crucially on the treatment of rental incomes. While the dynamics of imputed rents has brought about a more equitable distribution of capital incomes across the income distribution, that of actual rents has led to higher concentration of capital incomes at the top in the decade preceding the outbreak of the financial crisis. Finally, we conceptualize a rule of thumb for policy makers seeking to reduce income inequality in the long run.     

False dichotomy alert: Improving subjective-probability estimates vs. raising awareness of systemic risk

Taleb et al. (2022) portray the superforecasting research program as a masquerade that purports to build “survival functions for tail assessments via sports-like tournaments.” But that never was the goal. The program was designed to help intelligence analysts make better probability judgments, which required posing rapidly resolvable questions. From a signal detection theory perspective, the superforecasting and Taleb et al. programs are complementary, not contradictory (a point Taleb and Tetlock (2013) recognized). The superforecasting program aims at achieving high hit rates at low cost in false-positives, whereas Taleb et al. prioritize alerting us to systemic risk, even if that entails a high false-positive rate. Proponents of each program should, however, acknowledge weaknesses in their cases. It is unclear: (a) how Taleb et al. (2022) can justify extreme error-avoidance trade-offs, without tacit probability judgments of rare, high-impact events; (b) how much superforecasting interventions can improve probability judgments of such events.