农产品电商会影响我国家庭农场的收入吗?

农产品电商作为数字经济直接催生的新业态,为农民增收提供了新渠道。本文以家庭农场为研究对象,基于全国农村固定观察点新型农业经营主体发展指数专项调查的微观数据,对农产品电商的增收效应进行了实证检验。研究结果表明,农产品电商对家庭农场农业经营性收入的提高有明显的促进作用,但农产品电商的增收效应具有异质性。条件分位数处理效应的估计结果显示,农产品电商对中低收入水平家庭农场的增收效果要明显好于中高收入水平的家庭农场,更进一步的中介效应检验证实了自有品牌和产品认证在农产品电商增收效应中的部分中介作用。未来应该提升农村电商的配套服务水平,努力为农产品电商营造良好的电商氛围,以期更好地发挥农产品电商的增收效应。     

Weakly resolvable IV.3 search designs for the pn factorial experiment

A series of weakly resolvable search designs for the pⁿ factorial experiment is given for which the mean and all main effects are estimable in the presence of any number of two-factor interactions and for which any combination of three or fewer pairs of factors that interact may be detected. The designs have N = p(p–1)n+p runs except in one case where additional runs are required for detection and one case where $\text{(p?1)}\text{2}$ additional runs are needed to estimate all (p–1)² degrees of freedom for each pair of detected interactions. The detection procedure is simple enough that computations can be carried out with hand calculations.     

论《古田会议决议》的平等思想

《古田会议决议》蕴含着较为丰富的平等思想,主要表现在经济平等思想、政治平等思想和生活平等思想三个方面,而且每一方面都对当前更好地贯彻落实社会主义核心价值观具有重大的借鉴意义。     

Classification of three-level strength-3 arrays

Generalized aberration (GA) is one of the most frequently used criteria to quantify the suitability of an orthogonal array (OA) to be used as an experimental design. The two main motivations for GA are that it quantifies bias in a main-effects only model and that it is a good surrogate for estimation efficiencies of models with all the main effects and some two-factor interaction components. We demonstrate that these motivations are not appropriate for three-level OAs of strength 3 and we propose a direct classification with other criteria instead. To illustrate, we classified complete series of three-level strength-3 OAs with 27, 54 and 81 runs using the GA criterion, the rank of the matrix with two-factor interaction contrasts, the estimation efficiency of two-factor interactions, the projection estimation capacity, and a new model robustness criterion. For all of the series, we provide a list of admissible designs according to these criteria.