摘要：
灾害频发不断困扰乡村,如何精准识别乡村领域的综合灾害风险成为当下防灾减灾的重要内容。为此,以湖南省花垣县232个村为例,基于区域灾害系统理论中风险形成的三要素,定义综合灾害风险指数,并构建体现孕灾环境动态性的评价体系。通过层次分析法(analytic hierarchy process,AHP)-优劣解距离法(technique for order preference by similarity to ideal solution,TOPSIS)、熵权- TOPSIS、AHP和熵权法4种模型比较,开展乡村综合灾害风险研究。结论如下: ①多模型评价结果具有正相关性,数值比为1∶ 0.877∶ 0.740∶ 0.539,且熵权- TOPSIS模型更适合案例区综合灾害风险评价;②案例区综合风险指数的莫兰指数(Moran's I)为0.74,具有较强的空间自相关性,且呈现"西高东低、局部显著"的空间分布特征。文章深化了乡村领域的综合灾害风险评价研究,可为科学指导乡村防灾减灾工作开展、保障乡村振兴战略安全实施提供实践经验和理论依据。
通讯机构：
[Zhaolei Zhang] P;Ph.D. Student, School of Traffic and Transportation Engineering, Changsha Univ. of Science and Technology, Changsha, Hunan 410114, China
摘要：
This paper considers the stability of mixed traffic flow and the necessity of speed control to achieve safety and efficiency goals. Therefore, a speed-coordinated control model is proposed for mixed traffic flow based on stability analysis at an expressway merging area. Firstly, stability intervals are obtained by using an intracluster stability analysis in an intercluster. Secondly, a speed-coordinated control model is set up considering the stability characteristics in a merging area. Finally, an objective function is developed, which considers time-to-collision (TTC), dynamic space occupancy (DSO), and vehicle specific power (VSP). A numerical simulation is built up to analyze the traffic conditions and stability by using the proposed model against a null scenario without using the proposed model. The analysis results indicate that the stability of the intracluster has two regions, and the stability of the intercluster is mainly affected by the speed fluctuation and the distance between the merging cluster and the vehicles on the main road. Secondly, the proposed model tends to gradually achieve a steady state when the position reaches 180 m. Meanwhile, the efficiency of the model is found to be the best when the minimum safe-distance interval is set at (18, 27). In addition, the volatility of TTC drops by 5% and the DSO has reached 11.99% in the acceleration lane optimization together with 18.37% in the main lane optimization. The frequency is found to be the highest when the VSP reaches (10, 20), and the optimized efficiency reaches 45%–50%. The model proposed in this paper will effectively analyze the stability characteristics of mixed traffic flow and provides a research foundation for the stability of mixed traffic flow. Moreover, this model builds up a multi-objective-oriented speed-coordinated control scheme for high-efficiency operations in the merging area and provides technical support for traffic management in the future.
摘要：
The use of phononic crystals and elastic metamaterials has been a significant concern as an efficient approach to attenuate the surface waves of ambient vibration and seismic vibration. In previous research, elastic metamaterials with periodic array of pillars or other forms of standing structures (such as H-fractal steel or built-up structural steel) erected on soil substrate can achieve a low frequency surface wave band gap (BG). However, such metamaterials with standing structures occupy land and affect the esthetics of cities, and buried metamaterials such as cross-like-cavity or hollow-cylinder structures with large size in soils necessitate continual maintenance for the stability of cavity soil structure. Thus, this study proposes two types of periodic hollow steel trenches exhibiting both a Bragg BG and a local resonance BG, the steel plates are used to support the soil on both sides of the trench to meet the stability requirements of cavity soil structure and avoid toppling or landslide of soils. The dispersion relations of periodic hollow steel trenches are calculated by using finite element method and the mechanism of generation for two kinds of BGs are interpreted by the eigenmodes. Furthermore, the effectiveness of periodic hollow steel trenches on isolating surface waves within the BGs is demonstrated in both frequency domain and time domain analysis. Several significant geometrical and material parameters on BGs that can affect the BG are studied as well. This study provides a new approach using the coupling effects of Bragg BG and local resonance BG to simultaneously attenuate the surface waves induced by the ambient and seismic vibration in a more practical way.
