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81.
结合连铸坯凝固规律及轻压下技术改善铸坯中心偏析的冶金原理,建立宽板坯轻压下率理论模型。根据某厂连铸宽板坯实际生产条件,以传热模型计算的铸坯凝固温度数据作为轻压下率模型计算条件,分析拉速、浇注温度、坯壳凝固收缩特性对铸坯轻压下率的影响规律。结果表明,在相同的拉速和浇注温度条件下,铸坯轻压下率沿拉坯方向的分布总体呈减小趋势;拉速较高时的起始轻压下率小于拉速较低时对应的起始轻压下率;拉速与平均轻压下率呈线性递减关系:拉速每升高0.1m/min,平均轻压下率减小0.015mm/m;浇注温度越低,轻压下区起始轻压下率的值越高;浇注温度对平均轻压下率的影响较小,浇注温度每升高10℃,平均轻压下率仅减小0.002 5mm/m;铸坯外部凝固坯壳的收缩对整个轻压下区平均轻压下率的贡献量为20.4%~22.3%。 相似文献
82.
阮博 《西安联合大学学报》2010,13(1)
我党历来重视军事斗争准备,建国以来,我党在军事斗争的实践中形成了具有鲜明时代特色的毛泽东军事斗争准备、邓小平军事斗争准备思想、江泽民军事斗争准备思想以及胡锦涛军事斗争准备思想,这些思想一脉相承又与时俱进,是我们把握战争规律、搞好国防建设、巩固执政地位的重要思想指南。 相似文献
83.
A tidal bore is a unique Earth surface process, characterized by its highly destructive energy, predictable periodicities and magni-tudes, and the production of characteristic sedimentary features. Tidal bores and associated rapid flood flows are highly turbulent flows of the upper-flow regime with a velocity over several meters per second. Reynolds (Re) and Froude (Fr) numbers, respectively, are larger than 104 and 1.0, making them significantly different from regular tidal flows but analogous to turbidity currents. Until now, understanding of tidal-bore depositional processes and products has been limited because of the difficulty and hazards involved with gauging tidal bores directly. The Qiantang bore is known as the largest breaking bore in the world. Field surveys were carried out in May 2010, along the north bank of the Qiantang Estuary to observe the occurrence of peak bores, including regular observations of current, water level and turbidity at the main channel. Several short cores were sampled on the intertidal flats to study the characteristic sedimentary features of tidal bores. Hydrodynamic and sedimentological studies show that the processes of sediment resuspension, transport and deposition are controlled primarily by the tidal bores, and the subsequent abruptly accelerated and decelerated flood flows, which only account for one tenth of each semidiurnal tidal cycle in the estuary. Tidal-bore deposits are generally poorly sorted because of rapid sedimentation after highly mixed suspension by intense turbulence. This behavior is characteristic of the absence of tractive-current depositional components in a C-M diagram. It also goes along with well-developed massive bedding, graded bedding, basal erosion structures, convolute bedding and dewatering structures. Together, these sedimentary features can constitute fingerprinting of turbidites, widely distributed in the deep-water environment. However, a tidal bore is triggered by intensely deformed tidal waves propagating into a shallow-water environment, which returns to regular tidal flows rapidly after the passage of the bore head. The tidal-bore deposits are usually bounded by the intertidal-flat deposits with typical tidal beddings at the top and on both flanks. The difference between tidal-bore deposits (TBD) and tidal sandy/muddy deposits (TSD/TMD) is evident not only in sedimentary structures, but also in the grain-size composition. They can be clearly distinguished in grain-size bivariate plots, typically the plot of mean grain size vs. standard deviation (or sorting). Some trend variations generally exist in mean grain size with TBD>TSD>TMD, sorting with TMD>TBD>TSD (larger value indicating poorer sorting), and both skewness and kurtosis with TSD>TBD>TMD. These findings will undoubtedly shed new light on our understanding of tidal-bore sedimentology, ancient tidal-bore sedimentary facies and environments, and related oil-and-gas field prospecting. 相似文献
84.
We studied the evolution of cooperation in the prisoner’s dilemma game on a square lattice where the size of the interaction neighborhood is considered. Firstly, the effects of noise and the cost-to-benefit ratio on the maintenance of cooperation were investigated. The results indicate that the cooperation frequency depends on the noise and cost-to-benefit ratio: cooperation reaches a climax as noise increases, but it monotonously decreases and even vanishes with the ratio increasing. Furthermore, we investigated how the size of the interaction neighborhood affects the emergence of cooperation in detail. Our study demonstrates that cooperation is remarkably enhanced by an increase in the size of the interaction neighborhood. However, cooperation died out when the size of the interaction neighborhood became too large since the system was similar to the mean-field system. On this basis, a cluster-forming mechanism acting among cooperators was also explored, and it showed that the moderate range of the neighborhood size is beneficial for forming larger cooperative clusters. Finally, large-scale Monte Carlo simulations were carried out to visualize and interpret these phenomena explicitly. 相似文献
85.
86.
铝酸钙水泥是目前铁沟浇注料最为常用的结合剂,但水泥中CaO的存在容易造成材料抗高炉熔渣侵蚀性能的恶化,因此超低水泥和无水泥浇注料被广泛研究.以板状刚玉、碳化硅、氧化铝微粉等为主要原料,研究了结合剂ρ-Al2O3和铝酸钙水泥配比加入量对Al2O3-SiC-C浇注料各种性能的影响.实验结果表明ρ-Al2O3可以替代传统的铝酸钙水泥结合剂,实现高炉铁沟浇注料无水泥化,比传统的浇注料具有更佳的性能. 相似文献
87.
分析了图书馆的社会责任,阐述了低碳经济背景下图书馆面临的机遇和挑战,提出了低碳经济背景下图书馆承担社会责任的举措。 相似文献
88.
89.
To further increase the throughput of wireless multi-hop networks,a distributed scheduling method is proposed,which takes physical interference model into account.It is assumed that nodes in the network can perform physical carrier sensing,and the carrier sensing range can be set to different values.In the traditional carrier sensing mechanism,the carrier sensing range is computed under the protocol interference model,which is not accurate.Here the optimal carrier sensing range with physical interference model is achieved.Each sending node implements the distributed approach in three phases at each time slot,and all the concurrent transmissions are interference free.Good performance can be achieved under this scheduling approach.The approximation ratio of the distributed method to the optimal one is also proved. 相似文献
90.
在对应急管理系统的需求分析、体系结构、系统功能等进行详细研究的基础上,遵循面向对象的软件工程思想,按照统一软件开发过程,结合基于Web的软件开发技术,建立了基于Java和AJAX构架、具有Ⅳ层分布式体系结构的系统。统计青藏铁路线上的每个职工的各项体检数据,建立专家分析库,并利用专家库中的规则对其进行分析,评估职工的健康程度,从而判断出该名职工是否可以在高原上工作,同时预测出哪个工作群体属于高危群体。除完成上述功能外,该系统还运用设施区位理论,对沿线的医疗设施进行合理布局,实现当有病患出现时的最优调度,从而达到对青藏铁路沿线职工的健康进行监测、生命安全进行保障的目的。 相似文献