我国进一步推进水价改革的思考

随着工业化和城市化的发展,供水成本的不断上升和水资源的日益稀缺已经成为经济社会发展的一大障碍。水价政策能够在解决这些问题上发挥重要的作用。无论是工业和服务业用水、城市居民用水还是农业用水,其价格都应该体现水资源成本、供水成本和环境成本。水价改革必须在确定保障正常生产生活的基本用水量的基础上,通过水资源成本和环境成本在水价格中的充分体现,兼顾水企业和用水主体的利益,达到节约用水和水资源环境可持续发展的目的。     

统计学专业案例教学法应用的探索

统计学专业实施案例教学法首先要制定教学计划、建立案例素材库,其次要组织教学过程、评估教学效果。同时,要正确处理好案例教学法与传统教学法的关系,重视案例库的建立,加强统计分析软件的运用,鼓励学生参与项目研究,提高教师素质。     

Strategic Purity and Efficiency in the Motor Carrier Industry: A Multiyear Panel Investigation

Two questions facing motor carrier managers are (1) whether carriers should specialize in providing full truckload (TL) or less‐than‐truckload (LTL) services vis‐à‐vis offering mix of both and (2) whether this decision is contingent on carrier size. Yet, the literature provides little guidance because research to date has offered contradictory theoretical predictions and inconsistent empirical findings. Drawing on the theory of strategic purity and information processing theory, we explain why service specialization is likely to increase carriers' technical efficiency and why size will have a more pronounced effect on technical efficiency for carriers specializing in LTL services versus TL services. To test our theory, we assemble a panel data set from archival government sources regarding general freight motor carriers' provision of LTL and TL services. We measure carriers' technical efficiency using data envelopment analysis and test our hypotheses by fitting a series of panel data mixed‐effects models. Our results indicate that carriers are most technically efficient when they specialize in one service type. We also find that size positively affects technical efficiency but only for carriers specializing in LTL services; no returns to scale with regard to technical efficiency exist for carriers specializing in TL services.     

袁店一矿主井箕斗装载硐室优化施工工艺快速施工

介绍装载硐室通过优化施工工艺,精心组织、科学管理,采用正台阶掘进法分上、下台阶施工装载硐室,总结了一套科学、实效的施工工艺,从而保证快速施工。     

Predictive spatial network analysis for high-resolution transport modeling,applied to cyclist flows,mode choice,and targeting investment

Betweenness is a measure long used in spatial network analysis (SpNA) to predict flows of pedestrians and vehicles, and more recently in public health research. We improve on this approach with a methodology for combining multiple betweenness computations using cross-validated ridge regression to create wide-scale, high-resolution transport models. This enables computationally efficient calibration of distance decay, agglomeration effects, and multiple trip purposes. Together with minimization of the Geoffrey E. Havers (GEH) statistic commonly used to evaluate transport models, this bridges a gap between SpNA and mainstream transport modeling practice. The methodology is demonstrated using models of bicycle transport, where the higher resolution of the SpNA models compared to mainstream (four-step) models is of particular use. Additional models are developed incorporating heterogeneous user preferences (cyclist aversion to motor traffic). Based on network shape and flow data alone the best model gives reasonable correlation against cyclist flows on individual links, weighted to optimize GEH (r² = 0.78, GEH = 1.9). As SpNA models use a single step rather than four, and can be based on flow data alone rather than demographics and surveys, the cost of calibration is lower, ensuring suitability for small-scale infrastructure projects as well as large-scale studies.     

How Much Are Car Purchases Driven by Home Equity Withdrawal?

Previous research indicates that changes in housing wealth affect consumer spending on cars. We find that home equity extraction plays only a small role in this relationship. Consumers rarely use funds from equity extraction to purchase a car directly, even during the mid‐2000s’ housing boom; this finding holds across three nationally representative household surveys. We find in credit bureau data that equity extraction does lead to a statistically significant increase in auto loan originations, consistent with equity extraction easing borrowing constraints in the auto loan market. This channel, though, accounts for only a tiny share of overall car purchases.     

西部大开发蓝图的轮廓与起笔

本文对西部大开发的意义、开发模式的选择、开发的方针以及开发的程序和步骤提出了自己的看法和意见.目的在于参与讨论和抛砖引玉.     

浅谈油田污水处理过程中的质量控制

质量管理和生产流程控制是企业生存与发展的重要因素,针对油田污水处理过程,提出从药剂、设备、人员、指标等方面进行质量控制,并针对污水处理生产工艺流程,对影响指标的各个因素进行了分析,从管＂结果＂变为管＂因素＂,对各个控制段和控制点的指标及时进行检验,把不合格品消失在它的形成过程之中,并做到不断的质量改进。     

基于神经网络的无刷直流电机故障诊断和容错控制方法的研究

提出并设计了一种针对无刷直流电机控制器的故障诊断和容错控制方法。该神经网络状态观测器由实际非线性控制系统进行训练,根据实际系统和神经网络观测器输出残差,容错控制系统能够被确定下来。针对系统控制器、电流和速度传感器的故障条件进行了仿真分析,容错控制通过使用补偿控制器实现,保证系统故障条件下的稳定性和性能。结果表明,所提出的方法能有效地定位错误故障和时间,消除干扰并提高系统的鲁棒性。     

感应电动机伺服驱动系统自适应控制系统研究

本文针对性的提出了基于递归型小波神经网络的自适应控制性能的方案,该算法计算量减少,简化了控制结构,它可随着伺服驱动系统的运行情况的改变控制系统的结构参数,提高了伺服驱动系统对参数变化的性能,同时,也较好地改善了伺服驱动控制系统的稳态性能。通过仿真的结果验证了该控制系统方案的有效性和可行性。