皖江城市带承接长三角产业转移的行业选择分析

皖江城市带承接产业转移示范区作为国家级示范区,对其研究可以为其他地区的产业承接提供借鉴。基于产业梯度理论,首先根据产业梯度系数确立各市的优势产业,然后根据相对产业梯度系数,针对各市的重点建设产业给出建议。研究表明,皖江示范区承接长三角的产业转移主要集中在化工、金属冶炼、电气机械、装备制造业、纺织等行业。由于产业承接的重复性要注意协调竞争,同时还要注意承接资源依赖型和高污染型行业时做好环境保护工作。     

Factors related to tree growth across urban-rural gradients in the Midwest,USA

Several environmental factors influence tree growth at any site. The objective of this study was to examine the relationship between biotic and abiotic factors and tree growth rate (mean ring width averaged over the last 10 years) in settings ranging from urban to rural. Six clusters, each with five communities and two rural parks, were sampled in Illinois, Iowa, Minnesota, Missouri, and Wisconsin, for a total sample of 320 trees. Within each community, trees in parks, and along residential and commercial streets were sampled. Five species were sampled: silver maple (Acer saccharinum L.), honeylocust, (Gleditisia triacanthos L.), hackberry (Celtis occidentalis L.), black maple (Acer nigrum Michx F.), and basswood (Tilia americana L.). Factors were investigated for three scenarios: (i) all trees sampled in all clusters, (ii) a single species, all clusters, and (iii) all species, a single cluster.Baseline variables (cluster, place population, site, species, and age) accounted for 49–71% of observed variation in growth rate. Combined biotic factors accounted for 5 to 6% of observed variation. For all species in a single cluster, combined abiotic factors accounted for 11% of observed variation. Biotic factors related to growth rate detected using multivariate analyses included number of other trees within 9 m, presence of disease and insects, and human-induced mechanical injury. Abiotic factors that were related to tree growth included presence of pavement and core bulk density. For trees in rural parks, number of other trees within 20 m, and for trees in both rural and community parks, number of other trees within 9 m of sample trees were associated with decreased growth rate.     

百年来对《资本论》的一个误读--商品价值是以简单劳动为尺度来计量的吗?

当今世界,各种劳动的知识化水平千差万别,同一时间内创造的价值量相去甚远.根据马克思关于商品价值实体的概念和商品价值相对性原理,衡量各种劳动创造价值的能力的尺度应该是社会平均劳动而非简单劳动.诚然,马克思在<资本论>中说过,各种劳动的计量单位是简单劳动,但马克思所说的简单劳动实际上就是指社会平均劳动.后人没有注意到这一点,因此,传统的商品价值量公式就成了没有前提条件的永远适用的教条而未能与时俱进.     

低渗透未饱和油藏产能计算及其影响因素研究

研究了低渗透未饱和油藏的产能公式,通过达西公式,推导并得到了考虑启动压力梯度和介质变形的未饱和油藏的IPR曲线方程。结合矿场数据对IPR曲线方程进行了验证,并研究了启动压力梯度、介质变形、含水率对产量的影响。研究结果表明：在相同条件下,启动压力梯度越大、变形系数越大,产油量越低;井底流压小于饱和压力时,IPR曲线存在最大产量点(拐点);相同条件下启动压力梯度越小、变形系数越大,最大产量点对应的井底流压越高。含水率变化对最大产量点位置影响不大。研究成果对合理开发低渗透未饱和油藏具有理论指导意义。     

无约束最优化问题的扰动梯度算法

给出了一种扰动梯度算法.证明了在一定条件下,算法产生的序列全局收敛到最优化问题的稳定点,这个算法特别适用求解大规模优化问题.     

Social dimensions of gradients in urban ecosystems

Urban ecosystems are complex mosaics in which the biophysical characteristics are transformed over time by a concentrated, diverse set of human activities. Understanding their complexity requires the continuing development of interdisciplinary approaches. The use of gradient approaches has pointed towards the need to examine in greater detail the roles of human influences. In this paper, I propose the addition of three social dimensions to characteristics defining urban gradients: landuse, land management effort, and historical context. These dimensions correspond with major types of social activities that modify the physical environment. They are intended to augment research by explicitly elaborating on the social factors contributing to the variation along the complex, indirect gradients that typify urban areas.The diversity of urban landuses has numerous influences, obvious and subtle, on the complex urban land gradients. Incorporating new information on historical and spatial characteristics of management practices supports more direct fine-scale analyses of the impact of human activities on the environment. This path of inquiry also requires engaging in more detailed research on historical dimensions of urban development in conjunction with biophysical analyses. Examples from Columbia, South Carolina, illustrate the ways that social and historical processes contribute to urban ecology.     

城镇化和我国农村剩余劳动力梯度转移模式

文章从我国城镇化和劳动力转移的现实出发,总结了目前我国农村劳动力转移存在的主要问题,并对传统的人口迁移模型给予述评,在此基础上提出了农村劳动力的梯度转移模式,最后给出一些政策建议。      

Hypothesis testing for the dispersion parameter of the hyper-Poisson regression model

The Poisson distribution is widely used to deal with count data, however, it is unable to capture the dispersion problems. The hyper-Poisson distribution is a particular case of the extended Conway–Maxwell distribution which takes into account the dispersion phenomena of the count data. The main motivation to consider this model is the possibility to link the mean to the regressor variables in very natural way to solve testing problems. So, this paper will be focalized in the gradient statistics to detect dispersions and to compare with the classical likelihood ratio statistic. Two illustrative applications are considered.     

Comparison of various machine learning algorithms for estimating generalized propensity score

In this paper, we conducted a simulation study to evaluate the performance of four algorithms: multinomial logistic regression (MLR), bagging (BAG), random forest (RF), and gradient boosting (GB), for estimating generalized propensity score (GPS). Similar to the propensity score (PS), the ultimate goal of using GPS is to estimate unbiased average treatment effects (ATEs) in observational studies. We used the GPS estimates computed from these four algorithms with the generalized doubly robust (GDR) estimator to estimate ATEs in observational studies. We evaluated these ATE estimates in terms of bias and mean squared error (MSE). Simulation results show that overall, the GB algorithm produced the best ATE estimates based on these evaluation criteria. Thus, we recommend using the GB algorithm for estimating GPS in practice.