MIMO系统中的数据检测

BLAST提议在MIMO信道中获取更高的频谱利用率,大部分BLAST算法的研究结果认为,在接收端存在时空的白躁声和干扰。现研究在空间和时间都存在干扰的情况下一个MIMO系统的信道估计和数据检测。得到最大似然信道估计和空间干扰相关矩阵。通过利用已知的时间干扰相关特性,按照最小均方误差准则扩展一个时槽（无效的检测）到对多时槽版本。在独立的瑞利衰落信道下估计MIMO系统中未编码的QPSK的误码率。     

中国农业绿色水资源利用效率及时空分异研究

为全面客观了解我国农业绿色水资源利用效率的时空分异特征,推动水生态文明建设和农业绿色用水,运用包含非期望产出的SE-SBM模型,以农业面源污染作为非期望产出,测算了2002—2020年中国31个省级行政区的农业绿色水资源利用效率,并采用ML指数、泰尔指数、“效率-生产率”方阵分析了水资源效率的时空分异特征。结果表明:26个省级行政区的农业绿色水资源利用效率呈平稳波动状态,且大小顺序为东部地区、东北地区、中部地区、西部地区,跨期动态发展各具优劣势;ML指数先减小后增大,73.68%的研究期内EC与TC呈“此消彼长”状态;水资源效率总体差距的62.11%来自主要由西部地区构成的区域内差距,但区域间差距也不可忽视。     

Bounds on the estimation error in the chain ladder method

Buchwalder et al. (2006) have illustrated that there are different approaches for the derivation of an estimate for the parameter estimation error in the distribution-free chain ladder reserving method. In this paper, we demonstrate that these approaches provide estimates that are close to each other for typical parameters. This is carried out by proving upper and lower bounds.     

A note on “Modelling exchange rate returns: which flexible distribution to use?”

Corlu and Corlu [Quant. Finance, 2014, doi: 10.1080/14697688.2014.942231] provided a novel modelling of exchange rate data for nine currencies using five flexible distributions. They stated that the generalized lambda, skew t and normal inverse Gaussian distributions ‘do a good job’. Here, we reanalyse the data and show that a distribution simpler than all of these fits at least as well as these distributions. We also find that the normal inverse Gaussian distribution provides good fits for only one of the data-sets.     

广义Breitung非参数单位根检验研究——基于平稳假设下序列长期方差一致估计的分析

Breitung检验中生成序列的误差项的自相关会影响有限样本性质。本文用平稳假设下序列长期方差的一致估计量作为统计量的分母对其进行了修正。给出了修正后的统计量及其渐近理论,并对修正前后的有限样本性质进行了仿真。结果显示,修正后统计量概率密度的左偏有所减少;当误差项有自相关时,修正后检验的水平扭曲有所改进;当样本较小时,随误差项自回归(移动平均)系数或序列自回归系数的增加,修正后检验的势逐渐大于Breitung检验的势。     

Another Approach to Data Envelopment Analysis in Noisy Environments: DEA+

In this paper a DEA+ labeled approach for efficiency measurement in the stochastic case is presented along with a consistency proof and some preliminary evidence illustrating the small sample performance. DEA+ can basically handle multi-output technologies like standard DEA but allows to filter noise, that might have disturbed production and unlike a related approach does not require panel data. Consistency of DEA+ relies on the assumption of i.i.d. distributed and bounded noise and requires radial efficiency measurement. First Monte Carlo experiments show that a DEA+ based average inefficiency estimator performs well for samples of size n=100 in one-output, two-input settings compared to the corresponding Stochastic Frontier Estimator. Sensitivity of DEA+ performance with respect to parametrization of noise is weak, but higher noise contribution requires much larger sample size for satisfactory results.     

Economic viability of foreign investment in railways: a case study of the China-Pakistan Economic Corridor (CPEC)

Abstract

Pakistan Railways has faced a severe financial crisis in recent years. Pakistan has recently become a partner with China in a mega-investment project under an agreement called the China-Pakistan Economic Corridor (CPEC). Among other things, CPEC also includes a range of investments in Pakistan Railways. This particular study focuses on the analysis of US$8.2 billion investment in the upgrade and expansion of the Karachi-Peshawar railways link, which is also known as the ML-1 (Main Line 1). The study found ML-1 as economically viable with a payback period of 10?years. Furthermore, ML-1 project investment is expected to result in uplifting Pakistan Railways, mainly through an increase in freight and passenger transportation. Some risk factors may hinder the expected economic return from the CPEC investment in Pakistan Railways. These factors include consistency in the government policies, the status of the Pakistani economy in upcoming years, and law and order situations in the country. The study has a utility for the governments of both countries and larger business communities have stakes in the trade between the two countries. It is equally beneficial for the international community, businesses (both in China and Pakistan) and locals of the region associated with the CPEC infrastructure.     

参数不稳定下利差在宏观经济与货币政策中的应用

本文在参数不稳定的情况下考察利差对通货膨胀、经济增长的信息作用,并分析包含利差的混合货币政策规则。基于贝叶斯区制转移模型（MSBVAR）的分析发现：期限利差和信用利差对通货膨胀、经济增长有影响,宏观经济波动使得利差的信息作用存在参数不稳定性,在经济下行时对经济增长有负向信号作用。信用利差对通胀的预测作用比期限利差对通胀的预测作用更强。期限利差和信用利差都在货币政策规则中有参数不稳定性的信息作用。     

利用国内资源成本法考量贸易利益的探讨——以中澳羊毛贸易为例

贸易利益的考量一直是学界关心的问题。本文从国内资源成本法的思想出发,利用DRC近似量化中澳羊毛贸易利益的大小,考察贸易利益的大小变动与产品比较优势变动情况的相关性,并对利用贸易条件方法对贸易利益的考量问题做出探讨,认为从贸易条件角度对贸易利益的衡量应结合国内资源成本的考量。     

THE NORMALIZED CES PRODUCTION FUNCTION: THEORY AND EMPIRICS

Abstract The elasticity of substitution between capital and labor and, in turn, the direction of technical change are critical parameters in many fields of economics. Until recently, though, the application of production functions with specifically non‐unitary substitution elasticities (i.e., non‐Cobb–Douglas) was hampered by empirical and theoretical uncertainties. As recently revealed, ‘normalization’ of production‐technology systems holds out the promise of resolving many of those uncertainties. We survey and assess the intrinsic links between production (as conceptualized in a production function), factor substitution (as made most explicit in Constant Elasticity of Substitution functions) and normalization (defined by the fixing of baseline values for relevant variables). First, we recall how the normalized Constant Elasticity of Substitution function came into existence and what normalization implies for its formal properties. Then we deal with the key role of normalization in recent advances in the theory of business cycles and of economic growth. Next, we discuss the benefits normalization brings for empirical estimation and empirical growth research. Finally, we identify promising areas of future research.