基于梯度推进决策树的日维度交通指数预测模型

城市交通运行监测和预测是掌握交通运行变化特点,制定缓解交通拥堵策略的重要工作,其结果能为公众提供有效的路况信息,亦为政策措施的制定和效果评估提供重要支撑.有别于传统的短时交通预测,本文提出的预测模型不是针对相邻时段的运行状态预测,而是更长跨度上,针对日级别高峰时段交通运行状态的预测.构建了包含时间周期、特殊天气、节假日、限行、大型活动等因素的多维度影响因素集;以长期历史交通指数构建数据训练集,提出了基于梯度推进决策树的日维度路网状况预测模型.应用最优模型进行验证,结果表明,模型预测精度可达90%以上,与其他4种回归模型的对比分析也显示,本文所提出的模型在各项评分中均表现最优,说明其更适合于大样本、多因素的回归分析.本文所提出的日维度预测模型对提升城市路网运行质量、缓解交通拥堵具有重要的应用价值.

论行政法中行政权力的维度

行政法中行政权力的维度有实然和应然之分。前者指一国行政实在法对行政权力在行政法中价值的确立,后者指一国行政实在法应当具有的对行政权力性质和价值的确立。两者并非同一事物,且不具有性质上的相同性或相通性。此种区别使得人们对一国行政实在法有着诸多评判,并根据这些评判设想行政权力维度的价值走向。我们从行政法中行政权力的客观基础及维度指数、现代行政法中有关行政权力的基本规则、我国行政法中行政权力调控机制的构型等方面对行政法中行政权力维度作了分析,目的在于能够对行政权力在行政法中的应然状况有所认识,厘清一个行政权力在行政法中应然状况的基本格局,进而对我国行政法治在今后的进路有所构想。

中国省域尺度环境可持续性时空变化研究

以6个环境维度可持续发展目标(SDGs)为一级指标、27个中国本土化指标为二级指标,构建环境维度可持续发展指数(ESDI)指标体系,研究2016—2020年中国国家及省域层面环境可持续性的时空变化。结果表明,国家层面上,中国ESDI呈总体上升趋势,区域层面ESDI展示出稳定的增长趋势,且呈现出明显的地域分布特征,由东部向中部、西部逐步递减。各项环境维度SDGs之间存在差异,SDG13(气候行动)在2016—2019年无明显变化趋势,而在2020年显著增长,而SDG7(经济适用的清洁能源)、SDG12(负责任消费和生产)在2016—2019年呈线性增长,但在2020年下降。SDG6(清洁饮水和卫生设施)、SDG11(可持续城市和社区)在2016—2020年度呈现增长趋势,SDG11省际差异最小,SDG6省际差异逐年缩小。区域层面时空变化分析显示东部地区在多数指标上得分较高,而西部和东北地区在多个指标上表现较差。

One-dimensional consolidation of double-layered soil with non-Darcian flow described by exponent and threshold gradient

Based on non-Darcian flow law described by exponent and threshold gradient within a double-layered soil, the classic theory of one-dimensional consolidation of double-layered soil was modified to consider the change of vertical total stress with depth and time together. Because of the complexity of governing equations, the numerical solutions were obtained in detail by finite difference method. Then, the numerical solutions were compared with the analytical solutions in condition that non-Darcian flow law was degenerated to Dary's law, and the comparison results show that numerical solutions are reliable. Finally, consolidation behavior of double-layered soil with different parameters was analyzed, and the results show that the consolidation rate of double-layered soil decreases with increasing the value of exponent and threshold of non-Darcian flow, and the exponent and threshold gradient of the first soil layer greatly influence the consolidation rate of double-layered soil. The larger the ratio of the equivalent water head of external load to the total thickness of double-layered soil, the larger the rate of the consolidation, and the similitude relationship in classical consolidation theory of double-layered soil is not satisfied. The other consolidation behavior of double-layered soil with non-Darcian flow is the same as that with Darcy's law.

Cost-benefit timing for applying slurry seal on actual roadway tests in China

Determining the optimal timing is the core of preventive maintenance. Highway agencies always face with the challenge of determining optimal timing for preventive maintenance, particularly in China where there are no condition indicators designed for determining adequate timing for applying preventive maintenance and little literature relating to the development of pavement performance. This work presented the indicators, including crack ratio （Rc）, rutting depth （DR）, international roughness index （IIR） and sideway force coefficient （CsF） to determine the adequate timing for preventive maintenance in China. The proper ranges of each indicator to apply to preventive maintenance were then recommended. They are 0.28%-1.4% for Rc, 10-15 mm for DR, 1.97-3.5 for lrR, 40--50 for CSF. Based on pavement condition survey data collected on the test roads in Hebei Province, China, on the application of slurry seal at different timings, the pavement performance was established and the adequate timings for applying slurry seal was studied. Based on benefit-cost analysis, it is suggested that the fourth year is the optimal timing for applying slurry seal based on the condition in China. A framework is established to determine the adequate timings of applying other preventive maintenance methods.

Cross-scale characteristics of backfill material using NMR and fractal theory

This paper analyzed the pore structure, quantified the pore fractal dimension, calculated the grading index(GI) of mixed aggregate, and studied the relationship among GI, pore structure, and strength to describe the cross-scale characteristics of backfill, which is made from stone powder and cemented tailing. A series of experiments were conducted on stone powder cement tailings backfill(SPCTB). The GI formulas for mixed aggregates, containing stone powder and tailings, were derived based on the Füller theory. The nuclear magnetic resonance(NMR) fractal dimensions of backfills were derived using fractal geometry principles. Compared to the mesopore and macropore fractal dimensions, the correlation between micropore fractal dimension and macro-properties in terms of NMR porosity, pore structure complexity, uniaxial compression strength(UCS), and GI is the most significant. Macropore fractal dimension is generally correlated with UCS and GI and the other properties such as the shape of mixed aggregates also have an impact on fractal dimension. However, mesopore fractal dimension has no obvious relationship with macro-properties. Finally, the relationship between GI and UCS was studied, which contributed to improving backfill’s strength and optimizing gradation.

Electronic Casimir–Polder Force in a One-dimensional Tight-Binding Nanowire at Finite Temperature

We study the effect of two non-interacting impurity atoms near by a one-dimensional nanowire, which is modeled as a tight-binding hopping model. The virtual single-electron hopping between two impurities will induce an additional energy depending on the distance of two impurities, which gives a electronic Casimir–Polder effect. We find that the Casimir–Polder force between the two impurities decreases with the impurity-impurity distance exponentially.And the effects of nanowire and finite temperature on the Casimir–Polder force are also discussed in detail, respectively.