双平行线阵的快速一维DOA估计

针对传统子空间算法需要进行特征值分解或奇异值分解等复杂计算的问题，提出一种双平行线阵（Double Parallel Linear Array,DPLA）的快速一维波达方向（Direction of Arrival，DOA）估计算法。算法通过处理互协方差矩阵的第一列元素构造出等效的噪声子空间，再通过求根MUSIC（Multiple Signal Classification）算法得到DOA估计，有效避开了特征值分解或奇异值分解，降低了计算复杂度，提高了运算速度。仿真结果表明，该算法在提高了估计精度的同时减少了估计时间。     

相关信噪比对天线组阵相位估计性能的影响

传统天线组阵理论为了简化分析，均假设反正切相位鉴别器是一种最大似然估计器，其估计方差能够达到克拉美-罗下界。然而当相关信噪比在中等值以下时，这一假设条件不再适用。为此，分析了相关信噪比对相位估计性能的影响。针对传统天线组阵合成性能分析方法在描述低相关信噪比条件下相位估计性能方面存在的问题，通过引入修正因子，得到了相位估计方差的理论公式，实现了对低相关信噪比条件下相位估计性能的准确描述。     

Do fiscal rules cause better fiscal balances? A new instrumental variable strategy

This paper estimates the causal effect of fiscal rules on fiscal balances in a panel of 142 countries over the period 1985–2015. Our instrumental variable strategy exploits the geographical diffusion of fiscal rules across countries. The intuition is that reforms in neighboring countries may affect the adoption of domestic reforms through peer pressure and imitational effects. We find that the mere existence of fiscal rules correlates with lower deficits, but the positive link disappears when endogeneity is correctly addressed. However, when considering the strength of rules through a continuous index of fiscal rules’ design, we show that well-designed rules have a statistically significant impact on fiscal balances. We conduct several robustness tests and show that our results are generally robust and not affected by weak instrument problems.     

Structural current accounts in the European Union countries: cross-sectional exploration

This paper investigates structural determinants of the current account balance and assesses whether the current accounts in the European Union countries were consistent with the calculated structural current accounts between 1995 and 2017. We estimate current account regressions using cross-sectional data for 94 countries in 2008–2016 and confirm the main findings with panel data estimates. We document that the current account depends on the real exchange rate in a nonlinear way. The real exchange rate affects the current account at low income levels, but it ceases to be important at high income levels. Based on structural current account estimates for the European Union countries, we document that after the 2008 crisis current accounts adjusted towards structural current accounts in deficit countries, but persisted above structural current accounts in surplus countries.     

重叠滤波多音系统的频偏性能分析及优化

重叠滤波多音(O-FMT)是针对滤波多音(FMT)系统频谱利用率低的缺点而根据超奈奎斯特(FTN)概念引入子载波重叠得到的方案。鉴于O-FMT系统在频偏环境下的性能缺陷，理论分析了频偏对系统信号各部分的影响，比较了O-FMT与正交频分复用（OFDM）系统的抗频偏性能。针对频偏性能优化问题，提出了基于最佳线性无偏估计（BLUE）的改进盲估计算法，设计了基于频域滤波器系数的内嵌结构进行频偏补偿。仿真实验表明，O-FMT相比OFDM具有更好的抗频偏能力，改进的盲估计算法估计值精度更高，抗干扰、抗衰落能力更强，设计的频偏补偿结构可以使系统获得更好的性能。     

A new perspective on the exporter productivity premium: online trade

We use a unique firm-level data set including 9000 companies from 26 European Union countries covering four different sectors to take a close look at the relationship between online exports and productivity. The online exporter productivity premium is estimated using different techniques (ordinary least squares, quantile regressions and robust estimation). Results consistently indicate that the estimated online exporter productivity premium is statistically different from zero, positive and significant from an economic point of view. European online exporters, according to these results, are approximately 2% more productive than non-online exporters. Productivity differences between firms could be related to variables that are not included in the empirical model. More research would be needed to address this issue in the future.     

机电一体化设备的故障维修特点和可靠性分析

随着我国经济的发展和科学技术的进步,各种机电一体化设备产品也逐渐走进了人们的生活,这就需要相关单位加强对机电一体化设备的故障维修,优化设备性能。为此,论文就机电一体化设备的故障维修特点和可靠性做了简单分析。     

Customizing calories: How rejecting (vs. selecting) ingredients leads to lower calorie estimation and unhealthier food choices

Customization of food products has increased substantially in recent years while the desire for healthiness and an emphasis on understanding and providing calorie information continues to dynamically change the landscape of restaurant retail. The authors report four studies demonstrating that different customization routes (i.e., rejecting alternatives from a full product offering versus adding alternatives to a basic product offering) lead to systematic, but predictable, differences in consumers’ estimations of calories. In particular, this research finds that a rejection (vs. selection) customization process leads consumers to persistently estimate lower calories in the final product, which then improves evaluations of the retailer and leads to unhealthier food choices. These findings occur when consumers estimate calories of the exact same final product using the different paths to customization as well as when they create their own customized final product, while accounting for differences in the quantity and type of ingredients selected, suggesting a very general difference in estimations. This research has important implications for consumers who want to manage their weight and for firms that need to manage consumers’ health perceptions.     

Determinants of County-Level Voting Patterns In the 2012 and 2016 Presidential Elections

ABSTRACT

County-level data are used to estimate the incumbent-party share of the two-party vote in the 2012 and the 2016 U.S. Presidential elections. Using a ‘seemingly unrelated estimation’ procedure the regression results for the two elections show that there were some clear differences in the size of marginal effects for several key covariates. For example, income inequality, the size of the black male and black female populations, the size of the Hispanic male population and percent of the population with a college degree all had significantly larger coefficients in 2016 than in 2012, producing a larger marginal effect in favour of the Democratic candidate’s vote share. On the other hand, counties with increased poverty rates and counties located on the periphery of urban centres had a significantly larger marginal effect favouring the Republican’s vote share in 2016 compared to 2012. Finally, the regression results show that the effects of third-party vote shares, though not statistically different across the two elections, had a positive impact on the Democratic vote share in both elections.     

基于灰色关联分析的公路工程造价估算研究

目前分析公路工程造价相似性问题过多依赖于主观经验判断法,缺乏有效合理的定量方法,本文利用灰色关联度分析原理,提出一种分析公路工程造价相似性的定量方法。首先选取相似案例库,采用熵值法求出该案例库的重要属性特征权重值,再计算出相似案例库与待估案例的灰色关联度,最后得出待估案例的公路工程造价估算值,并通过实例证明该估算模型研究的可行性。