高铁流视角下的环渤海地区城市网络联系

在区域协调发展大背景下,高铁流作为构建区域均衡发展、区域高质量发展和城市群一体化体系的重要载体,其主导的区域联系特征逐渐成为研究的热点和前沿。基于2010年、2015年和2020年3个时间断面的高铁频次数据,从网络密度、网络中心性、网络效率等角度,探究环渤海地区城市网络演变特征。结果表明:(1)环渤海地区城市联系深度和广度迅速提升,2020年联系量较2010年约增长了6倍,网络集聚性呈先集中后扩散态势;城市群尺度网络规模从大到小依次为京津冀、山东半岛和辽中南城市群,网络均衡性和集聚性特征存在时空差异。(2)环渤海地区城市网络通达性提高,节点城市控制和可达能力增强;城市群尺度节点功能在空间上表现为沿“廊道”向两侧递减分布格局,由轴线联系向面状扩散转变。(3)网络效率依托高铁流的扩散效应和联系紧密程度的提升。环渤海地区,网络效率呈波动上升趋势,网络层级性趋于扁平,传输性和网络连通效率尚待提高。城市群层面,辽中南城市群在网络层级性上趋于扁平,网络效率降低但处于较高水平;京津冀城市群在网络层级性上趋于立体,网络效率虽有提升但仍处于较低水平;山东半岛城市群网络层级性增强,网络效率降低但处于最高水平。

小米生态链模式对高铁流量资源经营开发的启示

高铁流量资源已成为铁路企业一项重要资产,流量资源的经营开发,就是要通过商业模式创新、打造新业态新模式将其转化为经济价值。小米生态链模式发展的成功经验可以总结为价值主张精细化、价值创造协同化、价值获取生态化。铁路企业对高铁流量资源的经营开发,可以借鉴小米生态链模式,充分利用客流资源挖掘新需求,在多元化经营领域,通过资产资本化方式,以平台为载体,积极与社会企业合作,成为多元化领域综合商业生态的搭建者。

高铁流视角下中国城市网络的时空演变研究

交通是中国现代化的开路先锋,高铁是交通运输现代化的重要标志,高铁流空间已成为探索城市和区域空间结构的重要视角。基于2009~2020年全国铁路旅客列车时刻表数据,运用GIS空间分析和社会网络分析法,以中国369个行政单元为研究对象,探讨了中国城市网络强度和网络结构的时空演变特征,剖析了区域内与区域间城市网络发展差异。研究发现:(1)中国城市网络关联强度迅速上升,层级结构由量变转变为质变,中西部城市不断加入最高层级城市梯队。(2)区域内城市网络的网络密度、核心—边缘结构具有显著的时空异质性;沿海地区城市网络关联强度较高、层级结构较多,中部地区城市网络关联强度中等、规模较大,西南地区、西北地区高铁运营时期较晚,但城市网络发展较快,而东北地区高铁运营最早,但城市网络发展最慢。(3)具有跨区域联系的城市对逐年增多,区域间城市网络联系强度持续增强,但仍以低层级联系为主导,跨区域联系最多的地区由东部沿海转变为长江中游;(4)中心度指数均呈上升趋势,度数中心度较高的城市多集中于京沪、京哈—京港澳、路桥、沪昆通道的沿线城市,而中间中心度较高的城市多为行政级别较高的区域中心城市。

区域一体化视角下长三角高铁网络结构特征研究

以长三角区域内的40个地级市作为研究单元,从高铁流的视角切入,通过构建40×40的O-D城市间每日高铁运营频次矩阵,利用社会网络的方法,分析长三角区域高铁网络空间结构特征。结果表明,长三角区域高铁网络流量具有区域核心城市和省会城市指向性的特征,整体网络功能较完善,上海和江苏、浙江两省一市形成高铁网络日流量的核心集聚区。上海、杭州、南京在区域高铁网络中承担重要角色,兼具集聚、辐射和桥梁功能,核心节点城市地位突出。无锡、苏州、常州、合肥、镇江,与其他节点通达性较强,也具有一定的中介功能,是区域高铁网络的重要节点。徐州、宁波、嘉兴、温州、芜湖、扬州在区域高铁流网络中具有一定的集聚或辐射作用,是区域高铁网络的次重要节点。总体上,长三角区域高铁网络空间结构呈现出多中心、核心城市地位突出、节点城市等级结构差异明显的特征。

基于日高铁流量视角的中国高速铁路网络空间特征

构建中国180×180的O-D城市日高铁流量矩阵,基于社会网络分析研究其高铁网络结构特征,结果表明:①中国高铁网络松散,东、中部网络密度大于东北与西部,以长三角为核心的东南与其他区域不均衡特征凸显,东、中、西、东北包含不同的高铁区系与核心。②日高铁流量表现为沿京沪高铁"廊道型"向东西两侧递减弱化的"非对称性"格局,形成京沪、京广、杭福深相串联的高铁大三角主骨架;高铁中心要素也呈现沿京沪、京广、沪昆、杭福深等向线路两侧不规则递减格局,"廊道效应"显著。③胡焕庸线东南侧城市对高铁要素掌控能力大于西北侧,省会或区域中心城市多为高铁通达服务"中介",一线城市高铁空间溢出效应有向二、三线城市过渡态势。

高铁流视角下的中国县域网络结构特征与演化研究

高铁通过改变城市间的连接性和联系强度来影响城市网络的结构、功能和关系。随着中国高铁网络的延伸与升级,基于高铁流来认识和解构城市网络成为了重要的途径之一。论文从高铁流出发,借助2008—2018年高铁客运班次数据和社会网络分析方法,对中国县域网络结构特征和演化进程进行分析。结果表明:①高铁网络密度逐年提高。东中部地区的中心度值较高,枢纽地位明显,多条高铁干线的核心交汇点易生成高中介度节点。②多重网络结构层级性辨识出具有演化分异的层级特征和复杂多样的联系格局。第一、第二层级节点效应显著,区位优势明显;第三层级是网络的延伸和细化。③地域邻近程度和空间联系强度决定了凝聚子群的构成,受高铁线路布局的影响,子群呈现"多核化"趋势,具体表现为延伸、合并和新增3种演化类型。

Calculus of the Railway Vertical Stiffness Depending on the Base Plate Stiffness and the Ballast for High Speed Railways

The study aims to determine a mathematical formula that correlates the vertical stiffness of the principal elements of a high speed railway. To do this, beginning on the traditional formulations, a new mathematical model has been proposed, and has been verified and confirmed with the real information of high speed railways. Finally, there has been obtained a simple expression that correlates simply the vertical stiffness of the railway with the vertical stiffness of the elements that compound it, essentially with the base plate and the ballast system set. On the other hand, also the accuracy of the model has been verified to select the stiffness of the base plate and the ballast system depending on one of this stiffness and the total vertical stiffness that it is wanted. With this simplified formula, it is possible to optimize the vertical stiffness of the railway to obtain the best behavior in each zone and to reduce the final cost of the use of the via, taking in consideration the energy needed to move the trains, the maintenance cost, the useful life, etc.. The process to optimize the railway stiffness in each point depends on the vertical stiffness of the ballast and the sub-ballast, and it is possible to use different plate bases with different stiffness to obtain the optimal stiffness that has been previously obtained with a cost and maintenance analysis.

Microstructure and properties of high silicon aluminum alloy with 2% Fe prepared by rheo-casting

The morphology changes of both Fe-containing intermetallic compounds and the primary Si phase of Al-20Si-2Fe- 2Cu-0.4Mg-1.0Ni-0.5Mn （mass fraction, %） alloy produced by semi-solid rheo-diecasting were studied. The semi-solid slurry of high silicon aluminum alloy was prepared by direct ultrasonic vibration （DUV） which was imposed on the alloy near the liquidus temperature for about 2 rain. Then, standard test samples of 6.4 mm in diameter were formed by semi-solid rheo-diecasting. The results show that the DUV treatment suppresses the formation of needle-like ,β-Al5（Fe,Mn）Si phase, and the Fe-containing intermetallic compounds exist in the form of fine Al4（Fe, Mn）Si2 particles. Additionally, the primary Si grows up as fine and round particles with uniform distribution in α（Al） matrix of this alloy under DUV treatment. The tensile strengths of the samples at the room temperature and 573 K are 230 MPa and 145 MPa, respectively. The coefficient of thermal expansion （CTE） between 25 ℃ and 300 ℃ is 16.052 8×10^-6 ℃^-1, and the wear rate is 1.55%. The hardness of this alloy with 2% Fe reaches HB146.3. It is discovered that modified morphology and uniform distribution of the Fe-containing intermetallic compounds and the primary Si phase are the main reasons for reducing the CTE and increasing the wear resistance of this alloy.

Preparation of Fe_3O_4/Mn OOH core–shell nanoparticles by a high-frequency impinging stream reactor

Well-defined Fe3O4/Mn OOH nanoparticles with 61.1 emu·g-1in magnetization intensity and 90.53 m2·g-1in surface area have been synthesized by a new-style of high-frequency impinging stream(HFIS)reactor.In this reactor,two streams first collided together to form nano Fe3O4suspension,which subsequently flew through an S-shaped main channel to generate high-frequency reversing high-gravity fields.At the same time,24 thin liquid sheets impinged into the main channel at the frequencies higher than 100 Hz to create nano Fe3O4/Mn OOH colloids.The obtained powders were characterized by transmission electron microscopy/energy dispersive spectrometer(TEM/EDS),X-ray diffraction(XRD),Brunner–Emmet–Teller(BET)and vibrating sample magnetometer(VSM).Experimental results indicated that low coating ratio prolonged the induction period of heterogeneous nucleation.The high-frequency impingements of 24 thin liquid sheets greatly accelerated the macro-mixing and the initial dispersion.The high-frequency reversing high-gravity fields promoted the mesoand micro-mixing.As a result,nano Fe3O4cores were fleetly and uniformly covered by Mn OOH precursor.As a continuously operated and static high-gravity reactor,the high-frequency impinging stream(HFIS)reactor is being developed to the large-scaled and low-cost production of various nanocomposites.