Wind speed change regionalization in China(1961-2012)

This research quantitatively recognized the wind speed change using wind speed trend and trend of wind speed variability from 1961 to 2012 and regionalized the wind speed change on a county-level basis.The mean wind speed observation data and linear fitting method were used.The findings suggested that level-I regionalization includes six zones according to wind speed trend value in different regions,viz.Northeast ChinaeNorth China substantial declining zone,EasteCentral China declining zone,Southeast China slightly declining zone,Southwest China very slightly declining zone,Northwest China declining zone,and QinghaieTibetan Plateau slightly declining zone.Level-II regionalization divides China into twelve regions based on trend of wind speed variability and the level-I regionalization results.

Valid Regions of Formulas of Sound Speed in Bubbly Liquids

There are numerous formulae relating to the predictions of sound wave in the cavitating and bubbly flows. However, tile valid regions of those formulae are rather unclear from the view point of physics. In this work, the validity of the existing formulae is discussed in terms of three regions by employing the analysis of three typical lengths involved （viscous length, thermal diffusion length and bubble radius）. In our discussions, viscosity and thermal diffusion are both considered together with the effects of relative motion between bubbles and liquids. The importance of relative motion and thermal diffusion are quantitatively discussed in a wide range of parameter zones （including bubble radius and acoustic frequency）, The results show that for large bubbles, the effects of relative motion will be prominent in a wide region.

Structural analysis and design of frost resistance function for subgrade of high-speed railway ballasted track in cold regions

According to the technical characteristics of short fixed wheelbase of a high-speed carriage, a subgrade-track integrated space mechanical response analysis model is proposed for trains under the action ofbiaxial load after the comparison of the stress distribution characteristics of the ballast track subgrade bed structures for high-speed railway under the action of uniaxial load and biaxial load. The loading threshold value （high-cycle long-term dynamic strength） under the circum- stance where the cumulative deformation of subgrade structure gradually develops and finally reaches the convergent state, and its relationship with the foundation coefficient K30 were deduced, based on the characteristics of cumulative defor- mation evolution obtained from the unit structure filling model test under the action of cyclic loading. In view of structure stability and frost resistance requirements of the railway subgrade in cold regions, technical conditions to maintain good service performance of subgrade structure of high-speed railway ballasted track are discussed and analyzed. Study results show that the additive effect manifests itself obviously for railway train bogies under the action of biaxial load than uni- axial load, which has a significant dynamic effect on the subgrade bed bottom and a slight effect on the surface layer. Thus, the adoption of a biaxial load model in the design of a high-speed railway subgrade accurately reflects the vehicle load. Pursuant to the structure design principle, the design method of the subgrade structure of high-speed railway ballasted track is proposed to meet the technical requirements such as structural strength, bearing stiffness and high-cyclic and long-term stability. Technical indicators are obtained for the variation of thickness of the surface layer of reinforced sub- grade bed in the double-layer subgrade mode along with the change of K30 at the subgrade bed bottom. The double-layer structure mode of ＂closure on the upper layer and drainage on the lower layer＂ was proposed in order to meet the water- proofing and drainage requirements of the upper layer of the subgrade bed in cold regions. A dense-framework graded gravel filler with weak water permeability at a coefficient of 10 4 cm/s is used on the upper layer and the void-framework graded gravel filler at the water permeability coefficient of 10 2 cm/s is adopted on the lower layer.

Comparisons between Movement Speed of Main Types of Dunes:A Case Study of Desert Areas in Hexi Region of Gansu Province

In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.

An empirical study on impact of high-speed rail on eco-relationship of regional tourist

Study on the eco-relationship of regional tourism is a evaluation about the present situation and potential of regional tourist resources. In order to breaking the situation of the lack of coordination on tourist destination in Guizhou province, understanding it after the opening of the Gui-Guang high-speed rail is beneficial. This paper constructs an evaluation index system about the eco-relationship of the regional tourist from five parts- the resource value, the tourist market, the traffic location, the reception conditions and the resource types. To summarize the changes of the tourist eco-relationship of samples before and after the opening of the high-speed rail,it calculates the weight by the judgment matrix, and then uses the cluster analysis of SPSS and the basis for judging the eco-relationship of regional tourist. To choose the emphasis and to guide the direction on tourism industry in Guizhou Province in the future high-speed rail era, a case study of the regional tourist destination in Guizhou section of the Gui-Guang high-speed rail is carried out.

Combined proportional navigation law for interception of high-speed targets

A new proportional navigation(PN) guidance law,called combined proportional navigation(CPN),is proposed.The guidance law is designed to intercept high-speed targets,which is a common case for ballistic targets.The range of target-to-interceptor speed ratio during target interception is derived when guidance laws are applied in high-speed targets interception,and the effectiveness of negative navigation ratio in the PN-based guidance law is proven analytically in some lemmas.Based on the lemmas,the lateral acceleration command of CPN is defined,and the solution to the appearance of singularity in time-varying navigation ratio is given.The simulation results show that CPN can determine headon engagement(as PN) or tail-chase engagement(as RPN) through initial path angle compared with PN and retro proportional navigation(RPN),and can adjust the value of navigation ratio for head-on engagement or tail-chase engagement.Therefore,the capture region of CPN is larger than that of other guidance laws using PN-based methods.

Biased retro-proportional navigation law for interception of high-speed targets with angular constraint

A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results(trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation(BPN), proportional navigation and retro-proportional navigation. The results show that,at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.

高铁开通对区域资本流动的影响

文章研究发现,高铁开通促进了中国区域资本流动,提高了外省向本省的资本流入规模。中国东、中部地区高铁开通对区域资本流动具有正向影响,但对西部地区却存在较小的负向影响。文章据此提出,各地应因地制宜地推进高铁建设,以高铁建设连通全国各区域,促进要素合理流动。

高速铁路开通对区域经济发展影响实证分析

为探究高速铁路对不同区域经济影响作用的差异性及原因,以兰新(兰州市-乌鲁木齐市)高铁和哈大(哈尔滨市-大连市)高铁为研究对象,从实证视角出发,采用双重差分模型分析高速铁路开通对沿线区域人均国内生产总值(GDP)的影响。对2010-2020年高铁沿线城市的经济数据进行分析得到:兰新高铁的开通使得沿线区域人均GDP增长18000元,而哈大高铁则抑制沿线区域的经济发展;具体到省份,兰新高铁对甘肃省的经济促进作用达到19000元,而哈大高铁使得黑龙江的人均GDP下降2400元;辽宁省铁岭县、开原市和昌图县的边缘化是哈大高铁开通后辽宁省经济增长不显著的主要原因,而去掉三座城市后的人均GDP增长达到13000元。实证结果表明,高速铁路的开通对沿线区域的经济发展既有正面影响也有负面影响,在区位优势和生产要素流动作用下,增强大城市的虹吸效应,使得不同城市获取的经济效益存在较大差异。

高铁开通与企业异地并购

企业异地并购是资本跨区域流动的重要方式,能够实现资源优化配置。以2008—2022年中国企业的异地并购事件为样本,基于PSM-DID模型,实证检验以高铁建设为代表的交通基础设施对企业异地并购的作用及机制。研究结果显示,高铁开通能够提高所在城市的企业进行跨区域并购的活跃度,增加企业的异地并购次数。该结论经过两阶段最小二乘法、平行趋势检验、安慰剂检验后依然成立。机制分析结果显示,高铁通车后,并购交易方之间的信息不对称降低,造成信息敏感度更高的跨行业/企业并购次数明显增加。异质性分析结果表明,高铁开通的经济效应在经济资源市场化配置比例高的地区以及中西部城市更为明显。本文的研究丰富和拓展了地理经济学和资本跨区域流动的相关研究,有助于理解交通基础设施、政府干预对本地经济发展的影响。

强风作用下带横隔面输电塔动力响应及破坏机理研究

增设横隔面是对输电塔结构进行抗风加固的一种简单有效方式,但增设横隔面后输电塔的动力稳定性变化和破坏机理差异尚未明晰。以某220 kV同塔双回线路ZY2输电塔为研究对象,通过建立输电塔线耦联体系有限元模型,对比了增设横隔面前后的单塔及塔线体系的模态差异,验证了在靠近塔腿节间的交叉斜材处增设横隔面对于输电塔局部振型的抑制作用。采用随机风场模拟,计算不同风速下不同塔段处斜材增设横隔面前后轴力响应变化,结合动力不稳定区域理论计算斜材动力稳定性参数,将其与动力不稳定区域绘制在同一参数平面内并根据某一风速下斜材是否进入动力不稳定区域,来判断不同塔段处斜材增设横隔面前后的失稳风速。结果表明,合理增设横隔面最高可将杆塔破坏风速提高3 m/s。

城际铁路与高速地铁互联互通技术研究——以广州地铁22号线与广佛环城际铁路为例

目前,不同轨道交通制式间主要通过车站换乘的方式实现互联互通,随着珠三角地区城际及地铁线网的完善、经济的发展,旅客出行需求日益增长,对时效性和便捷性要求不断提升,为提高运输质量,有必要进一步研究实现不同轨道交通系统间跨线运营的互联互通。以广州地铁22号线(采用市域D型车)与广佛环城际铁路为例,从客流特征、运输需求、列车运输组织及工程技术方案等方面分析两者实现互联互通的可行性。研究结果表明:广佛环线与广州地铁22号线实现跨线运营在时效性上具有吸引力,具备客流支撑条件;城际线与采用D型车的高速地铁线在主要标准方面采取相关技术措施后可基本实现兼容统一,满足互联互通条件,但需要对信号、无线通信、票务等系统进行相关工程改造和兼容性设计。

高铁建设、知识溢出与区域创新差距

本文构建了包含旅行时间成本和商品贸易成本的新经济地理学模型,阐释了高铁促进知识溢出进而影响区域创新差距的作用机理,并进行实证检验。在商品贸易成本既定的情况下,压缩旅行时间可能会加剧创新要素的空间集聚,但高铁的知识溢出效应可能会缩小区域创新差距。实证结果表明,高铁显著提升区域创新绩效,但同时也拉大了高铁城市之间的组内创新差距,使之成为区域创新总体差距的主要来源。分区域看,高铁在中西部拉大了高铁城市组内的创新差距,而在东部却缩小了组内创新差距对整体差距的贡献;高铁主要加大了中小城市对区域创新差距的贡献程度。此外,降低商品贸易成本会强化高铁对区域创新的影响,不同类型交通基础设施对区域创新呈现出协同作用。研究结论对于高铁网络下提高创新资源配置效率、促进区域协调发展以及在全国统一大市场背景下协同推进区域之间商品和创新要素一体化具有启示意义。

运动边界对高寒动车组转向架区域风雪运动的影响

采用基于Realizable k−ε湍流模型的非定常雷诺时均方法(URANS)和离散相模型(DPM)探究运动边界对高速列车底部风雪运动规律及转向架区域积雪分布的影响。研究结果表明:地面的运动有效缓解了转向架底部气流的流向动能衰弱效应,显著增加了转向架2区域的流向速度分布,并影响了雪粒垂向速度分布,致使转向架1区域的表面积雪质量降低33.6%,转向架2区域的表面积雪质量增加20.1%;列车轮对的旋转未影响转向架底面积雪分布,但轮对旋转使后端板周围雪粒垂向速度大幅增加,进而增加了转向架上表面的积雪分布;相较于旋转轮对,在轮对静止条件下,牵引电机、齿轮箱、构架和后端板表面积雪质量分别降低1.5%、2.9%、3.4%和6.4%,转向架2区域的表面积雪总质量整体降低3.2%,因此,在高速列车转向架区域积雪的数值仿真和风洞试验研究中,要尽可能地实现转向架、地面和轮对之间的相对运动。

时空视域下高速铁路网络与区域空间格局耦合研究——以山东省为例

高速交通已成为推动区域空间格局持续协调发展的重要支撑保障。基于山东省2010年、2015年与2020年高速铁路网络数据以及城市层面数据,分析了山东省高速铁路网络与区域空间格局的耦合关系。研究表明:高速铁路网络对山东省区域交通整体可达性提升有明显的促进作用,经济发展会助力交通可达性的提升;省内区域经济联系总量基本呈现增长态势;山东省交通可达性与经济联系总量的耦合度基本保持均衡发展状态,但省内各城市的耦合协调水平之间存在较大的差距,并且大部分城市交通可达性水平强于经济发展水平,代表着高速铁路网络的带动作用并未得到充分发挥,对经济的整体带动作用不强。

严寒地区高铁站房电气设计要点

严寒地区高铁站房电气设计的目的是能在极端低温环境下,实现高铁站房电气设备的稳定、高效、安全地运行,同时满足乘客的舒适性和安全性需求。文中就严寒地区高铁站房电气设计过程中的要点难点进行分析,提出了严寒地区中型高铁站房的供电方案,给出了防雷接地措施的加强做法,分析了站房体感温度较低的原因并给出提升温度的有效解决方案。文中设计方案以鸡西西站高铁站房为设计实例,站房已建成使用,且处于有效运行中。文中拓展了严寒地区建筑的电气设计思路,为严寒地区高铁站房的电气设计提供了案例参考。

高铁网络建设对物流产业集聚的影响

我国目前已进入高铁时代,空间距离逐渐被时间距离所代替成为影响物流业的关键因素。中部地区各城市的模型兴建和网络化布局,削弱了生产要素流动的空间壁垒,使得其能够在更广的范围进行资源要素优化配置,本文利用2008-2019年中部地区80个城市的高铁开通数据,构建PSM-DID模型分析我国中部地区高铁网络对物流业集聚的影响,研究表明:(1)高铁开通对物流业集聚的影响具有滞后性,初期对物流业集聚的影响并不显著。(2)随着中部地区高铁网络建设的逐步完善,高铁对物流业集聚呈现出明显的促进作用。

敦白高速铁路路基冻胀规律及冻害成因

随着有砟轨道高速铁路的相继开通运营,出现了一定程度的冻害问题,给高速铁路的养护维修工作带来了更大的挑战。本文结合敦白(敦化—白河)高速铁路所处区域气候环境、设计标准,针对其开通以来发生的路基冻胀问题,通过对动态、静态检测数据统计分析,总结路基冻胀规律,初步研究冻胀成因,提出防治对策。结果表明:敦白高速铁路全线路基冬季存在不同程度的冻胀问题,冻融循环期长达5个月,初步分析路基发生冻害的主要原因为线路所处地理位置气温低、入冬前降雨多导致基床含水率高、基床表层级配碎石水泥掺量低,导致表层冻害数量较多。建议采取强化疏排水、不良填料改性、填料强化置换等措施在夏季、秋季进行综合整治,以减少或消灭冬季冻害,降低冬季现场作业频次。

高速列车周围风雪运动特性及转向架区域积雪成因分析

采用基于Realizable k-ε模型的非定常雷诺时均方法(URANS)和离散相模型(DPM)研究高速列车底部转向架及其腔体区域的严重积雪问题。基于高速列车底部风雪两相流时空运动演化特性进行深入分析,并对转向架区域积雪成因进行归纳总结。研究结果表明:大量雪粒跟随转向架区域剪切层下方的高速气流流出转向架区域,部分雪粒在转向架中间区域和后端板附近跟随上扬气流向上扬起并撞击黏附在转向架和后端板迎风面,并在转向架底面形成大量积雪;仅有少量雪粒在后侧电机和后端板附近向上爬升至转向架上方,在后端板顶部相遇汇聚后在低速气流驱动下游离折返至前端板附近并重新汇入车底流场,悬浮雪粒在重力作用下沉积在转向架顶面,并在转向架上表面形成少量积雪。