航道驳岸软基处理深搅桩施工质量抽检评定方法的实践

结合在航道驳岸软基处理中深搅桩施工质量抽检评定方法的实践,介绍以标准贯入击数、桩身水泥土无侧限抗压强度及芯样状态描述为评分参数的质量检测评分方法。实践表明,这种以定性描述和定量计算相结合的质量评定方法是行之有效的。     

Improving noise assessment at intersections by modeling traffic dynamics

Three families of road noise prediction models can be distinguished. Static noise models only consider free-flow constant-speed traffic with uniformly distributed vehicles. Analytic noise models assume that all vehicles are isolated from one another but account for their mean kinematic profile over the network. Micro-simulation noise models relax the hypothesis of no interaction between vehicles and fully capture traffic flow dynamic effects such as queue evolution. This study compares the noise levels obtained by these three methodologies at signalized intersections and roundabouts. It reveals that micro-simulation noise models outperform the other approaches. Particularly, they are able to capture the effects of stochastic transient queues in under-saturated conditions as well as stop-and-go behaviors in oversaturated regime. Accounting for traffic dynamics is also shown to improve predictions of noise variations due to different junction layouts. In this paper, a roundabout is found to induce a 2.5 dB(A) noise reduction compared to a signalized intersection in under-saturated conditions while the acoustic contributions of both kinds of junctions balance in oversaturated regime.     

Solutions to the optimal network design problem with shipments related to transportation cost

Two versions of an optimal network design problem with shipments proportional to transportation costs are formulated. Extensions of an algorithm developed in prior research for solving these problems are proposed and tested. The performance of the algorithms is found to improve substantially as the dependence of shipments on costs is increased. Moreover, the optimal solutions obtained are unexpectedly robust with respect to a wide range of transportation cost assumptions. These findings could have important computational and policy implications if applicable to larger networks.     

Linking mercury exposure to habitat and feeding behaviour in Beaufort Sea beluga whales

Mercury (Hg) levels in the Beaufort Sea beluga population have been increasing since the 1990's. Ultimately, it is the Hg content of prey that determines beluga Hg levels. However, the Beaufort Sea beluga diet is not understood, and little is known about the diet Hg sources in their summer habitat. During the summer, they segregate into social groups based on habitat use leading to the hypothesis that they may feed in different food webs explaining Hg dietary sources. Methyl mercury (MeHg) and total mercury (THg) levels were measured in the estuarine-shelf, Amundsen Gulf and epibenthic food webs in the western Canadian Arctic collected during the Canadian Arctic Shelf Exchange Study (CASES) to assess their dietary Hg contribution. To our knowledge, this is the first study to report MeHg levels in estuarine fish and epibenthic invertebrates from the Arctic Ocean. Although the Mackenzie River is a large source of Hg, the estuarine-shelf prey items had the lowest MeHg levels, ranging from 0.1 to 0.27 μg/g dry weight (dw) in arctic cisco (Coregonus autumnalis) and saffron cod (Eleginus gracilis) respectively. Highest MeHg levels occurred in fourhorn sculpin (Myoxocephalus quadricornis) (0.5 μg/g dw) from the epibenthic food web. Beluga hypothesized to feed in the epibenthic and Amundsen Gulf food webs had the highest Hg levels matching with high Hg levels in associated food webs, and estuarine-shelf belugas had the lowest Hg levels (2.6 μg/g dw), corresponding with the low food web Hg levels, supporting the variation in dietary Hg uptake. The trophic level transfer of Hg was similar among the food webs, highlighting the importance of Hg sources at the bottom of the food web as well as food web length. We propose that future biomagnification studies incorporate predator behaviour with food web structure to assist in the evaluation of dietary Hg sources.     

浅谈如何根据驾校学员心理特征因材施教

多年从事汽车驾驶教员工作 ,针对数学中出现的各种问题 ,经过多年的潜心研究 ,终于得出了一些独特见解 ,即必须根据学员的心理特征因材施教、因人施教 ,才能提高教学质量 ,完成好汽车驾驶教员工作。     

Local shopping as a strategy for reducing automobile travel

Transportation - Suburban development in the US is widely criticized for its contribution to automobile dependence and its consequences. Not surprisingly, then, a return to more urban-style...     

Assessing the impacts of driving environment on driving behavior patterns

Transportation - Considering the role of behavioral and environmental factors on road accidents and traffic intensities, the characterization of vehicle use and driver behavior opens new...     

The Concept and Practice of Treatment for Damage in Railway Tunnel Linings Caused by High-pressure Karst Water北大核心CSCD

In recent years, railway tunnels in karst areas have frequently suffered flooding after high-intensity rainfall, which seriously affects the safety of tunnel operation and the order of transportation, and even interrupts the traffic. Based on the water hazard case in the Yuanbaoshan Tunnel on the Zhijin-Bijie Railway Line, this paper explores the causes of lining damage in terms of geology, rainfall, and the design and construction of water hazard sections, and puts forward the treatment technology for tunnel water hazards with the core concept of making full use of existing structures and employing open drainage methods in key sections. Besides, this paper simulates and analyzes the formation of hazards and the treatment effect through numerical simulation. The results show that the subjective causes for the damage in tunnel linings include an insufficient understanding of the water-bearing formations at the geological investigation stage, the underestimation of water hazard risks posed by high-intensity rainfall during construction, and the unimproved waterproof and drainage system in the design alteration, while the objective reasons include the development of karst near the tunnel section that passes through the stratum, the strong connectivity of water conduits, and the high-intensity rainfall in a certain period of time on the tunnel site. As for the simulation results, they show that the increase of external water pressure caused by the sudden rise in groundwater level after rainstorm significantly increases the internal force of linings, and eventually leads to a much lower safety factor of sidewall linings and large scale damage, which is in consistency with the characteristics of the actual on-site damage. After on-site emergency treatment, the tunnel structure has become stable and even encountering unprecedentedly heavy rainfall twice, the tunnel has still remained in a good condition. Since then, no water hazards and other disasters have occurred, which proves that the treatment plan is valid. © 2022, Editorial Office of Modern Tunnelling Technology. All right reserved.     

走滑断层错动量大小对铁路隧道结构安全性影响的数值分析北大核心CSCD

走滑断层错动容易使穿越活动断裂带的隧道结构遭受严重的破坏。以某铁路隧道穿越某断裂带为工程背景,采用有限差分数值模拟手段,通过分析不同走滑断层错动量下隧道结构的位移、应力和应变,对隧道结构的安全性进行评判。研究表明:走滑断层错动时,除纵向位移外,随着错动量的增加,隧道结构位移越大,且走滑断层错动对在断层区和上盘区域的隧道结构影响最大;在走滑断层错动量>0.6 m后,隧道结构应力受错动量的影响较小,且隧道结构开始破坏,随着错动量增加,破坏范围增大。     

Simulation des temps de parcours du transport ferroviaire régional du bassin de vie stéphanois dans le cadre du projet Bahn.Ville

The French-German research project Bahn.Ville, dealing with Rail oriented development and intermodality in German and French urban regions, has consisted in identifying the principles and factors of success of an urban development oriented towards rail, and in testing them in the agglomeration of Saint-Étienne. One of the research-actions focussed on identifying and anticipating the potential impacts in terms of urban development of a new transport system, of the tram-train type, on an existing railway line. The effect of the insertion of new stops on the global journey time is one of the criterion of the evaluation of new stops. A simulation method of the journey times is presented in this paper. The interest and the limits of this approach, regarding the rolling stock choice and the insertion of new stops, are emphasized.