城市规模、高铁开通与经济协同发展——以京津冀城市群为例

为了研究高铁开通对区域经济发展的影响,特别是中心城市在城市群中对其他城市发展的影响,以京津冀城市群为考察对象,选取区域内13个地级及以上城市为研究样本,以1995～2017年城市间的面板数据为实证样本,通过构建城市规模、高铁开通两个计量模型,并对模型可能的内生性问题进一步考察、模型的稳健性进行检验,就区域内中心城市是引领带动还是产生“虹吸效应”,高铁开通对城市协同发展有什么影响等问题展开研究。研究表明,城市规模对城市间的经济协同发展有影响,人口规模、经济规模以及土地规模的不同集聚导致这一影响效应不同,城市间的地理距离对这一影响效应存在明显的调节作用; 同时,高铁开通这一外生事件对城市间的经济协同发展也有影响,且高铁开通在城市规模对经济协同发展影响的路径中也存在显著的调节效应。     

CsCl-C2H5OH—H2O三元体系在35℃下平衡溶解度研究

采用自制的相平衡研究装置,测定了CsCl-C2H5OH-H2O三元体系在35℃下的平衡溶解度密度及折光率数据。在该实验中乙醇的质量分数在0—1．0范围内。同时也测定了不饱和三元体系在不同醇水比例下的密度和折光率值,并对其进行了拟合。实验结果表明,随乙醇质量分数的增加CsCl在水中的溶解度逐渐降低。并且在乙醇质量百分含量为10．73％-49.59％范围内体系出现了分层现象。用四元参数方程对溶解度进行了拟合。     

高职学生英语学习策略与英语学习成绩关系的研究

采用问卷对某职业学院高职学生的英语学习策略的情况进行了调查。调查目的是了解高职学生的学习策略状况,策略对成绩的相关性和预测力,及高分组与低分组在策略上的差异。研究结果表明高职学生一般地使用学习策略,只有管理策略和形式操练策略对成绩在统计意义上既有相关影响又有预测力,并且高分组和低分组在功能操练策略和母语策略上的差异不显著,而在管理策略和形式操练策略上有显著差异。     

论叙事文学中的时间意识类型

时间意识并不是随着文学的诞生而进入文学创作的,但是没有时间意识文学便无法生存。从人类的生存经验来看,时间分为过去、现在和将来三个维度。而叙事文学作为一种叙事艺术,必然与这三种时间维度有密切的关系。     

飞秒激光作用下环己酮离子解离的进一步研究

本文首先介绍了环己酮离子在飞秒激光作用下,在激发态解离的主要碎片为:C4H5O+、C3H3O+、C3H6+、C3H3+和C2H2O+。而后基于物质不灭定律和电荷守恒定律,给出在前面每一碎片的形成过程中,也应形成另外一些碎片产物。最后利用基于密度泛函理论的B3LYP方法,求出了这些碎片产物的结构。     

Triadic configurations in limited choice sociometric networks: Empirical and theoretical results

Previous research demonstrated that information contained in triad censuses from heterogeneous collections of social networks occupies a high dimensional space. Regions of this space, and locations of triad censuses within it, are largely defined by lower order network properties: network density and dyad distributions [Faust, K., 2006. Comparing social networks: size, density, and local structure. Metodološki Zvezki (Advances in Methodology and Statistics) 3 (2), 185–216; Faust, K., 2007. Very local structure in social networks. Sociological Methodology 37, 209–256]. The current paper extends comparative work on triad censuses by addressing three related issues. First, it determines and interprets the space occupied by triad censuses for 128 friendship networks gathered using a limited choice sociometric protocol. Second, it constructs a theoretical space for triad censuses expected given lower order graph properties and examines the dimensionality and shape of this space. Third, it brings together these lines of investigation to determine where the empirical triad censuses reside within the theoretical space. Results show that the empirical triad censuses are almost perfectly represented in one dimension (explaining 99% of the data) and that network density explains over 96% of the variance in locations on this dimension. In contrast, the theoretical space for triad censuses is at least four-dimensional, with distinctive regions defined by network density and dyad distributions. Within this theoretical space, the empirical triad censuses occupy a restricted region that closely tracks triad censuses expected given network density. Results differ markedly from prior findings that the space occupied by triad censuses from heterogeneous social networks is of high dimensionality. Results also reinforce observations about constraints that network size and density place on graph level indices.     

Conditional and predictive probability integral transforms

The conditional probability integral transform, used in goodness-of-fit tests, is compared with its Bayesian counterpart, the predictive probability integral transform, and it is shown that under suitable conditions, in the presence of an adequate group structure, they yield the same transformed random variable, usually uniform on the unit interval.     

IMPATT器件的大信号分析

在适当简化的物理模型上,借助计算机对IMPATT器件进行了大信号分析。计算给出了线性缓变DDR IMPATT器件的导纳、功率、效率等参数以及它们与频率、偏流、射频电压、串联电阻的依赖关系。     

Towards a unified definition of maximum likelihood

A unified definition of maximum likelihood (ml) is given. It is based on a pairwise comparison of probability measures near the observed data point. This definition does not suffer from the usual inadequacies of earlier definitions, i.e., it does not depend on the choice of a density version in the dominated case. The definition covers the undominated case as well, i.e., it provides a consistent approach to nonparametric ml problems, which heretofore have been solved on a more less ad hoc basis. It is shown that the new ml definition is a true extension of the classical ml approach, as it is practiced in the dominated case. Hence the classical methodology can simply be subsumed. Parametric and nonparametric examples are discussed.     

Predictor distribution and forecast accuracy of threshold models

In the present paper the predictor distribution of a SETAR (Self Exciting Threshold Autoregressive) model (Tong and Lim, 1980) has been investigated when the lead time is greater than the threshold delay.After a brief presentation of the model under study, some relevant aspects of the density forecasts are shown highlighting how they can be used to generate more accurate predictions and to estimate an approximation of the probability density function of the SETAR predictors. The performances of competing predictors have been evaluated through a simulation study and an application to financial market data of the daily Nikkey 300 stock market returns.