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61.
摆线轮检测的公法线法 总被引:1,自引:1,他引:1
本文给出了摆线轮最小跨齿数的计算公式及其解的区间;确定了最小跨齿数为最佳测量跨齿数,以及包含三种修形方式的统一的公法线理论测长计算公式,该计算方法已由作者编制了计算程序,当输入摆线轮已知参数时,可准确计算出理论测量位置及理论测长. 相似文献
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63.
关国俊 《城市轨道交通研究》2015,18(1):86-88
对城市轨道交通无线集群系统中车载电台在列车折返过程中出现"未就绪"异常现象的原因进行了详细分析;并结合分析结果对引起此类故障的"同频同色码"现象进行了网络优化,从而避免色码干扰对无线网络的正常运行造成影响。分析表明,不合理的色码规划会给网络带来不良的影响,故在无线网络的建设和维护中,需要对色码进行合理的规划;色码的复用方式应避免与频率的复用方式相同,且同一个小区的邻区组中应避免出现同频同色码小区。 相似文献
64.
A series of Pd/Co3O4 catalysts were prepared by Self-Propagating High-Temperature Synthesis (SHS) method in this study, and electric field was applied for catalytic combustion of lean methane over Pd/Co3O4 catalysts at low temperature. When electric field was applied, the catalytic combustion performance of Pd/Co3O4 catalysts was greatly improved, and the application of electric field could reduce the load of active element Pd to some extent while maintaining the same efficiency. Based on experimental tests and the analysis results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (H2-TPR) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS), the mechanism of catalytic oxidation of CH4 over Pd/Co3O4 catalysts in electric field was proposed. The catalytic combustion of CH4 occurs only when the temperature is higher than 250 °C normally, but when electric field was applied, the whole process of CH4 oxidation was promoted significantly and the reaction temperature was reduced. Electric field could promote the reduction of the support Co3O4 to release the lattice oxygen, resulting in the increase of PdOx and the surface chemisorbed oxygen, which could provide more active sites for the low-temperature oxidation of CH4. Furthermore, electric field could accelerate the dehydroxylation of CoOOH to further enhance the activity of the catalysts. 相似文献
65.
目的通过观察平阳霉素治疗前后鼻息肉病息肉组织的病理变化情况,探讨平阳霉素治疗鼻息肉病的机制。方法应用末端脱氧核苷酸转移酶介导的脱氧三磷酸尿苷缺口末端标记法(TUNEL法)检测凋亡细胞,与相邻连续的HE染色片对位对照观察嗜酸性粒细胞的凋亡情况。结果平阳霉素治疗前鼻息肉组织嗜酸性粒细胞表达显著高于正常下鼻甲(P<0.01);治疗后鼻息肉组织中的嗜酸性粒细胞表达明显低于治疗前(P<0.01);治疗后鼻息肉组织中嗜酸性粒细胞的凋亡指数高于治疗前(P<0.01)。结论嗜酸性粒细胞是鼻息肉病息肉组织中主要的浸润炎细胞;平阳霉素可通过促进嗜酸性粒细胞凋亡达到治疗鼻息肉病的目的。 相似文献
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Variable message signs that provide various types of route guidance information have been widely deployed in large cities. To release proper information only using easily collected data, a simple traffic-condition-based (TCB) route guidance strategy was recently proposed. The strategy works based on the estimation of free-flow and congested traffic conditions and is capable of approximating user optimal equilibrium stably. Due to little consideration of the complexity of urban road networks, the TCB strategy is still away from field applications in urban areas. To further push the strategy toward field tests, this article improves the TCB strategy in the following aspects: supplementing the strategy with a self-regulation ability by considering existing traffic conditions; decomposing link capacity to solve the problem of overlapping routes by comparing link capacity on alternative routes; coping with stochastic traffic; and the impact of signalized intersections by utilizing aggregated data. A scenario for an urban road network in Beijing, China, is simulated to test the improved strategy, and the simulation results clearly indicate the effectiveness of the proposed improvements. The improvements extend the TCB strategy on moderately complicated urban road networks, and still have the advantages of simple diversion rules, easily obtained input data, and stable and effective diversion processes. 相似文献
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Developing a more efficient mass transit system, in highly populated cities, improves the mobility, decreases the dependency
of private cars, alleviates traffic congestion, and provides a more environmentally friendly means of travel. Recently, the
city of Beijing decided to have a target of becoming as a ‘public-transport city’ with a fascinating mass transit system within
a larger plan, of building humanistic, scientific and technological, and green public-transport systems. This work discusses
the governance evolution of the mass transit system of Beijing between 1949–2008, comprised of two groups of transit systems,
the road surface public-transport system (bus, tram, trolley, etc.), and the subway public-transport system. In addition,
a time-series analysis is introduced in an attempt to examine the effect of governance evolution on the two transit systems,
and of the impacts of the governance structural changes on the mass transit system. The time-series model is introduced using
the annual statistics data of the period 1949–2008. The outcome of the analysis is viewed with precaution because of the incompleteness
of the many endogenous and exogenous factors to affect the public-transport demand. Generally speaking it is concluded that
the governance evolution provides beneficial effect of the Beijing mass transit activity; however, for satisfying the significant
increase of the Beijing city’s travel demand and maintaining sustainable development, the governance-involvement pattern needs
to be reformed. 相似文献