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Propeller blade width measurement has been extensively studied in the past using direct and indirect methods, and it plays a great role in determining the quality of the finished products. It has surveyed that previous techniques are usually time-consuming and erroneous due to a large number of points to be processed in blade width measurement. This paper proposes a new method of measuring blade width using two images acquired from different viewpoints of the same blade. And a new feature points matching approach for propeller blade image is proposed in stereo vision measurement. Based on these, pixel coordinates of contour points of the blade in two images are extracted and converted to real world coordinates by image algorithm and binocular stereo machine vision theory. Then, from the real world coordinates, the blade width at any position can be determined by simple geometrical method. 相似文献
845.
针对我国港口安全风险的现状,从系统工程角度,采用层次分析法的基本原理,建立了港口安全风险分析模型,并运用模糊数学构建了隶属函数,求得港口安全风险的模糊评判矩阵,通过模糊评判获得了港口安全风险综合分数.结果表明,该评判方法能够科学合理地综合评价港口安全风险状况,为有关港口部门改善港口安全状况提供决策依据. 相似文献
846.
Mengshi Lu Simin Huang Zuo-Jun Max Shen 《Transportation Research Part B: Methodological》2011,45(8):1251-1265
Product substitution can mitigate supply chain disruptions. However, it may not be very effective without multiple sourcing. In this paper, we consider a supply chain with two downward substitutable products. The products can be ordered from an unreliable supplier or a reliable but more expensive supplier. It is found that in an optimal sourcing policy the higher-grade product should be preferred over the lower-grade product. A sufficient condition is given for an optimal policy where only the higher-grade product is dual-sourced. The effect of substitution is contrasted with the non-substitution case. Numerical study shows the impact of demand variability and correlation on the effect of product substitution and the corresponding optimal sourcing policy. 相似文献
847.
A bayesian dynamic linear model approach for real-time short-term freeway travel time prediction 总被引:1,自引:0,他引:1
Xiang Fei Chung-Cheng Lu Ke Liu 《Transportation Research Part C: Emerging Technologies》2011,19(6):1306-1318
This paper presents a Bayesian inference-based dynamic linear model (DLM) to predict online short-term travel time on a freeway stretch. The proposed method considers the predicted freeway travel time as the sum of the median of historical travel times, time-varying random variations in travel time, and a model evolution error, where the median is employed to recognize the primary travel time pattern while the variation captures unexpected supply (i.e. capacity) reduction and demand fluctuations. Bayesian forecasting is a learning process that revises sequentially the state of a priori knowledge of travel time based on newly available information. The prediction result is a posterior travel time distribution that can be employed to generate a single-value (typically but not necessarily the mean) travel time as well as a confidence interval representing the uncertainty of travel time prediction. To better track travel time fluctuations during non-recurrent congestion due to unforeseen events (e.g., incidents, accidents, or bad weather), the DLM is integrated into an adaptive control framework that can automatically learn and adjust the system evolution noise level. The experiment results based on the real loop detector data of an I-66 segment in Northern Virginia suggest that the proposed method is able to provide accurate and reliable travel time prediction under both recurrent and non-recurrent traffic conditions. 相似文献
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849.
隧道衬砌施工缝蝶形可排水止水带研制 总被引:1,自引:0,他引:1
文章分析了隧道衬砌施工缝渗漏水产生的原因,在可排水中埋式、背贴式止水带技术的基础上开发了蝶形可排水止水带.该止水带属新型中埋式止水带,其断面呈蝶形.安装时将蝴蝶的头部朝向施工缝的迎水侧;从侧面(先浇衬砌段一侧)将止水带压向衬砌段的端头模板,使后浇衬砌段一侧的止水翼变形紧贴端头模板,并用带垫片的钢钉从肋部间隔适当距离逐点固定止水带;先浇衬砌段浇筑并养护一段时间后拆模,先前被压平的后浇衬砌段的止水翼在橡胶等材料弹性的作用下恢复变形;浇筑后浇段衬砌混凝土,即可完成一道施工缝的防水施工.蝶形可排水止水带的优点是:安装方便,容易保证止水带施工质量;属中埋式,可保证在隧道两侧和顶部其周围均能密实;具有可排水功能,在无压力或小压力条件下工作,减少了渗漏机会. 相似文献
850.
随着人们对环境保护的日益重视,越来越多的法规对船舶设计提出更高的环保要求.通过2 500 TEU集装箱船的总体设计,对装载和破舱稳性等总体性能等进行了设计计算,使该船布置合理紧凑,各项指标达到国际先进水平.但燃油舱划分和分布要满足有关新规划,还需作适当调整. 相似文献