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排序方式: 共有1521条查询结果,搜索用时 15 毫秒
1.
基于湖北省382份茶叶种植户调研数据,采用随机前沿生产函数模型“一步估计”法分析贫困山区农户茶叶生产技术效率和影响因素。研究结果表明:样本户茶叶种植存在较大改进空间;样本户资本和劳动力投入剩余;茶园的海拔、树龄、茶农是否加入合作社、种植面积、户主是否受过种茶培训等因素对农户茶叶生产技术效率有重要影响。因此,提出紧抓乡村振兴战略机遇,推动贫困山区茶产业高质量发展;建立茶产业“三项补贴”,改善茶园基础设施条件;优化茶叶种植布局,提高合作社服务水平;成立茶产业发展基金,加快培育职业茶农,以提高贫困山区农户茶叶生产技术效率。  相似文献   
2.
We use a modified version of the stochastic frontier model to estimate oligopoly markups above the perfectly competitive frontier, separating out deterministic markups from purely stochastic markups. Using data from 42 US food processing industries between 1990 and 2010, empirical results indicate a widespread incidence of oligopoly power, with Lerner indexes averaging approximately 21%. Further, the estimated markups increase with industrial concentration but decrease with price elasticities and imports. Finally, the estimated Lerner indexes are in the range of previous food industry estimates using New Empirical Industrial Organization (NEIO) models.  相似文献   
3.
By integrating Battese and Coelli’s (1995) model and the spatial autoregressive model (SAR), a spatial autoregressive stochastic frontier model for panel data is developed. The main feature of this frontier model is a spatial lag term of explained variables and the joint structure of a production possibility frontier with a model of technical inefficiency. The model addresses both spatial dependence and heteroskedastic technical inefficiency. This study applies maximum likelihood methods considering the endogenous spatial lag term. The proposed model nests several existing models. Further, an empirical analysis using data on the Japanese manufacturing industry is conducted and the existing models are tested against the proposed model, which is found to be statistically supported. The findings suggest that estimates in the existing spatial and non-spatial models may exhibit bias because of lack of determinants of technical inefficiency, as well as a spatial lag. This bias also affects the technical efficiency score and its ranking.  相似文献   
4.
在广义空间调制(GSM)系统中,最大似然(ML)检测可以取得最优的检测性能,然而其计算复杂度随激活天线数的增加急剧增长。针对这一问题,提出了一种基于稀疏重构理论的低复杂度检测算法——正则化正交匹配追踪(ROMP)算法。该算法首先根据信道矩阵和当前残差的内积选取多个候选激活天线索引,接着对候选天线索引按正则化标准进行可靠性验证,剔除错误索引,缩小信号的搜索空间,最后通过求解最小二乘问题估计信号。仿真结果表明,与经典的正交匹配追踪(OMP)算法相比,所提算法以少许复杂度的增加为代价极大提升了检测性能,能够在检测性能与复杂度之间取得更好的折中。  相似文献   
5.
The paper presents a new methodology, based on tensor decomposition, to map dynamic trade networks and to assess its strength in forecasting economic fluctuations at different periods of time in Asia. Using the monthly merchandise import and export data across 33 Asian economies, together with the US, EU and UK, we detect the community structure of the evolving network and we identify clusters and central nodes inside each of them. Our findings show that data are well represented by two communities, in which People's Republic of China and Japan play the major role. We then analyze the synchronisation between GDP growth and trade. Furthermore we apply our model to the prediction of economic fluctuations. Our findings show that the model leads to an increase in predictive accuracy, as higher order interactions between countries are taken into account.  相似文献   
6.
文章通过将中间产品生产厂商的异质性结构引入罗默三部门内生增长模型中,构建了一个基于垂直创新的技术进步模型。运用该模型对后发经济体技术赶超中不同阶段间过渡时存在的技术进步模式转型陷阱的问题进行理论性分析。通过研究发现,技术赶超过程中要依次经历专注模仿、模仿并且创新、专注创新三个阶段。后发经济体技术进步会从一个阶段进入下一个阶段,然而各个阶段间技术进步模式转型不是自然发生的,而是存在着转型陷阱。第一次转型会经历创新停滞陷阱,第二次转型可能会出现模仿陷阱,而陷入模仿陷阱的经济体在技术水平达到一定程度时会出现技术进步减缓甚至是倒退。后发经济体一旦陷入模仿陷阱将很难接近世界技术前沿,技术赶超也就无法实现。  相似文献   
7.
Islamic equity portfolios work with a smaller investment universe given the filtering of non-Shari’ah compliant stocks. It has been theoretically argued that this culminates in suboptimal portfolio diversification, which in turn adversely affects risk-adjusted returns. We offer empirical evidence that such a conceived portfolio diversification “penalty” is far from a foregone conclusion, at least empirically. Our results tend to indicate that Islamic portfolios are not invariably handicapped in terms of portfolio diversification. We also explored dimensions that may account for differences in the relative investment performance between Islamic and conventional portfolios, such as portfolio constraints, short selling and market conditions. We believe this paper is among the first to apply substantial empirical analysis specifically with respect to the portfolio diversification perspective on Islamic equity investments.  相似文献   
8.
This research explores the physical infrastructure and flight consolidation efficiency drivers of Eurasian airports regarding their infrastructure and movement productivity levels. A novel Fuzzy Double-Frontier Network DEA (FDFNDEA) model is proposed to investigate the relationship between desirable (freight and passenger turnovers) and undesirable (pollutant emission levels due to aircraft movements) outputs against the respective infrastructure usage, fuel consumed, and movements performed at each of the 23 Eurasian airports from 2000 to 2018. This balance between desirable and undesirable outputs emerges spatially and temporally due to the evolution of the airport system's productive resources at each one of the Eurasian countries over the period observed. Shannon's entropy is used as the cornerstone to quantify the input and output vagueness of this evolution in Triangular Fuzzy Numbers (TFN), thus allowing the accurate building of alternative optimistic and pessimistic double-frontier efficiency. Differently from previous research, Shannon's entropy is the key for measuring input and output vagueness levels in light of the maximal entropy principle. This principle states that the distribution that best represents the current state of knowledge is the one with largest entropy. Maximal entropy yields bias-free decision-making in the sense that the input/output distributional profiles for Eurasian airports contain the maximal possible heterogeneity, working as a robust or best/worst-case scenario against eventual unconsidered assumptions. Hence, optimistic and pessimistic Malmquist Productivity Indexes (MPI) for overall and each stage productivity results are subsequently regressed against contextual variables related to airport characteristics and regional socio-demographic and economic indicators of each Eurasian country using bootstrapped Cauchy regressions. The findings revealed the spatial heterogeneity of productivity factors and airport performance across Eurasia. Results also demonstrated the negative impact of income inequality and the positive impact of private participation on technological progression in the Eurasian airport industry.  相似文献   
9.
This article evaluates the impact of credit constraints on the performance of Chinese agricultural wholesalers. We estimate a stochastic frontier function using transaction and credit data of agricultural wholesalers from across China to estimate the efficiency and productivity impacts of credit constraints on sales of affected agricultural wholesalers. Empirical results show that micro- and smaller wholesalers are disproportionally impacted by credit constraints and that eliminating these constraints would increase the sales of affected agricultural wholesalers by approximately 15%. Thus, policies aimed at providing credit access for these wholesalers would significantly boost the performance of smaller agricultural wholesalers while improving the overall performance of the Chinese food supply chain without requiring additional non-credit inputs.  相似文献   
10.
利用海杂波有效探测海上小目标是目前雷达探测领域的热点问题,具有重要的应用价值。鉴于海杂波是一种非线性非平稳性的雷达回波信号,充分发挥整体平均经验模式分解的优势,将海杂波分解为若干个不同尺度的独立分量。通过研究发现有目标时,分解出的前5个分量与未分解前信号的相关系数明显减小,因此提出了一种新的海杂波背景下的目标检测方法。通过实测和模拟的海杂波数据进行训练和测试,研究结果表明,该方法能有效地实现海杂波下目标的探测,性能优于经典时域下、分数阶傅里叶变换域下以及平均经验模式分解后的广义Hurst指数的目标检测方法。  相似文献   
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