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91.
The development direction of railways is toward the improvement of capacity and service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automaton models, in this paper, we develop a model to analyze the mixed running processes of trains with maximal speeds of 500 km/h and 350 km/h respectively in the moving block system. In the proposed model, we establish some sound rules to control the running processes of a train, where the rules include the departure rules in the intermediate stations, the overtaking rules, and the conditions of speed limitation for a train stopping at a station or passing through a station. With the consideration of the mixed ratio and the distance between two adjacent stations, the properties of the train traffic flow (including capacity and average speed) are simulated. The numerical results show that the interactions among different trains will affect the capacity, and a proper increase of the spatial distance between two adjacent stations can enhance the capacity and the average speed under the moving block. 相似文献
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We report new Raman features of epitaxial graphene (EG) on Si-face 4H-SiC prepared by pulsed electron irradiation (PEI). With increasing graphene layers, frequencies of G and 2D peaks show blue-shifts and approach those of bulk highly-oriented pyrolytic graphite. It is indicated that the EG is slightly tension strained and tends to be strain-free. Meanwhile, single Lorentzian line shapes are well fitted to the 2D peaks of EG on SiC(O001) and their full widths at half maximum decrease with the increasing graphene layers, which indicates that the multilayer EG on Si-face can also contain turbostratic stacking by our PEI route instead of only AB Bernal stacking by a traditional thermal annealing method. It is worth noting that the stacking style plays an important role on the charge carrier mobility. Therefore our findings will be a candidate for growing quality graphene with high carrier mobility both on the Si- and C-terminated SiC substrate. Mechanisms behind the features are studied and discussed. 相似文献
94.
电荷转移能级和缺陷形成能的计算对探索半导体材料的n型和p型掺杂效率具有重要的指导意义。基于第一性原理方法,结合二维带电缺陷计算理论,系统计算了二维类石墨烯氮化铝(graphene-like AlN, g-AlN)中四种(C_Al,Si_Al,Ge_Al,Sn_Al)可能的n型掺杂体系的结构、磁学、电学以及缺陷性质。结果表明,四种体系的最稳定价态均为+1价和0价,Sn_Al具有较深的施主能级,不具备为二维g-AlN提供n型载流子的条件,而C_Al,Si_Al,Ge_Al表现为浅能级施主特性,均能在一定条件下成为理想的施主杂质,其中Si_Al具有最浅的施主特性以及最低的缺陷形成能,因而是二维g-AlN中实现n型掺杂的首选掺杂剂。另外,在p型二维g-AlN中,四种掺杂原子都会成为有效的空穴捕获中心,严重降低p型载流子导电率。研究数据将会为实验上实现二维g-AlN n型掺杂提供理论解释和指导。 相似文献
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Spontaneous vesicle formation has been observed in aqueous mixtures of tri-(N-dodecyldimethylhydroxypropylammonium chloride) phosphate (PTA) and bis-(2-ethylhexyl) sulfosuccinate (Aerosol OT), which is supported by negative-staining TEM and dynamic light scattering. The range of vesicle formation in the PTA/AOT mixtures is wide and monodisperse vesicles are obtained. The vesicle diameter increases with the total surfactant concentration. Tubular microstructures, vesicle fusion, and vesicle-tubular microstructure transition have been also observed by negative-staining TEM. The vesicle formation mechanism is discussed from the viewpoint of molecular geometry, conformation, and the interaction between surfactant molecules. 相似文献
99.
水溶液中氨基酸与甲脲的焓相互作用 总被引:6,自引:0,他引:6
用LKB-2277精密微热量计测定了298.15 K时甘氨酸、L-丙氨酸、L-丝氨酸、L-缬 氨酸、L-苏氨酸和L-脯氨酸六种α-氨基酸分别与甲脲分子在水溶液中的混合过程焓变及 这些溶质分子在水溶液中的稀释焓.实验数据根据McMillan-Mayer理论进行回归分析,得到 各级交叉焓相互作用系数.讨论了不同氨基酸与甲脲分子的相互作用机制.结果表明,氨基酸 的两性离子部分、α-碳上的非极性脂肪侧基、极性的羟基侧基和五元吡咯环结构对交叉焓 对作用系数hxy具有不同贡献.与尿素相比,甲脲分子中-CH3基团的引入明显增强了分子的 疏水性. 相似文献
100.
离子液体-水的混和溶剂中,纳米TiO2的制备与表征 总被引:1,自引:2,他引:1
以钛酸正丁酯为前驱物,采用溶胶-凝胶低温水热方法,以离子液体(1-乙基-3-甲基咪唑醋酸盐)和水为混合溶剂,制备了锐钛矿相的纳米二氧化钛。产物经XRD,TEM,N2吸附-脱附等表征,结果表明与纯水相比,混和溶剂中制备的二氧化钛具有较高的纯度,结晶度和热稳定性,且缩短反应时间到24 h,所得颗粒尺寸10 nm与在纯水中反应48 h所得颗粒尺寸7 nm相当,说明离子液体的存在可促进锐钛矿相二氧化钛的结晶和生长。另外,该产物表面积可达238 m2·g-1。本文还进一步研究了该产物对甲基橙水溶液的光降解作用,结果表明,用此方法制备的TiO2对甲基橙降解作用优于商业P25二氧化钛。 相似文献