高速动车组横梁应变场光纤测量与反演研究

针对高速动车组车底底架横梁的应变场反演问题,基于模态叠加法和传感器优化配置理论,提出一种根据部分测点的实测单向应变反演结构空间应变场的方法。以结构的应变模态为输入,以模态坐标独立性为目标,基于信息熵理论建立了传感器优化配置的数学模型,再根据模态坐标和振型采用正则化方法反演结构应变场。仿真计算结果表明,无噪声干扰下,反演的精度较高,最大均方误差为9.87×10~(-12),并且正则化方法可以有效抑制噪声对结果的影响。搭建了基于光纤光栅传感系统的测试试验台,基于实测应变数据和模态结果反演应变场,结果表明,反演后的应变幅值相对误差带为1.21%~10.79%,反演数据和实测数据的均方误差带为0.80~3.69。该方法能够准确识别结构的模态坐标,为获取高速列车关键结构的应变场分布提供参考。

双馈风电机组双模并网控制策略

当前,我国陆上风电场大多采用双馈机组,虽然其变流器容量小、成本低,但是通常只能在±30%的转差率范围内运行,在低转速下无法正常并网。为了提高低转速工况下双馈风电机组的发电量,文章提出一种双模并网控制方案。其建立了双馈电机定子短接的异步数学模型,以确定最终短接电阻的取值范围;提出了双模柔性切换策略,即在转速较低时机组以异步模式运行,转速升高后机组以常规的双馈模式运行,从而实现低转速也能发电运行。仿真结果表明,低转速下,异步模式相较双馈模式,转子电流畸变率最大可降低55%,功率控制精度也更高(功率波动幅值可控制在3 kW以内);且采用柔性切换策略后,暂态冲击电流减小36%以上,仅150 ms就可达到新稳态,验证了风电机组双模并网控制策略的有效性和可行性。

热带大气对流垂直结构与降水模拟偏差的关系:基于GAMIL3模式的分析

针对LASG/IAP发展的大气环流模式GAMIL(Grid-point Atmospheric Model of IAP LASG)的两个版本GAMIL2(G2)和GAMIL3(G3),评估了其对热带降水气候态以及对流垂直结构的模拟能力,在此基础上探究了新版本模式降水模拟改进的原因以及热带对流垂直结构与降水模拟偏差的关系。两个版本的GAMIL模式都较好地捕捉到了热带降水的主要特征,且G3的模拟结果整体优于G2。新版本的主要改进在于显著减小了热带西北太平洋正降水偏差。水汽收支诊断显示,模式降水偏差主要来源于蒸发项和水汽垂直平流动力项,而后者的偏差则来自于对流强度和对流垂直结构的共同作用。对流垂直结构偏差主要存在于赤道印度洋与赤道大西洋区域,表现为大气低层辐合分量偏小,对流卷出层高度偏高;在热带西北太平洋与赤道东太平洋区域,模式较好地还原了典型的“头重型”和“脚重型”对流垂直结构,但依然存在有整体性的对流偏深。湿静力能(MSE)收支显示,热带西北太平洋区域过量的净能量通量是模式垂直运动偏差的主要来源。而对流垂直结构偏深造成的总湿稳定度(Gross Moist Stability,简称GMS)偏大,在一定程度上抵消了模式中的净能量通量偏差,抑制了模拟的对流强度。诊断结果显示,G3中热带西北太平洋区域的降水改善主要源于对流强度正偏差的减小。G3中对流阈值和层云阈值的下调,使得对流发生频率增加,从而抑制了过大的对流强度。热带对流垂直结构与降水偏差有着紧密且多样的联系,在未来模式发展中应当予以重视。

Selectively converting CO_(2) to HCOOH on Cu-alloys integrated in hematite-driven artificial photosynthetic cells

The integration of electrochemical CO_(2)reduction(CO_(2)RR) and photoelectrochemical water oxidation offers a sustainable access to valuable chemicals and fuels. Here, we develop a rapidly annealed hematite photoanode with a photocurrent density of 2.83 mA cm^(-2)at 1.7 VRHEto drive the full-reaction. We also present Cu-alloys electrocatalysis extended from CuInSnS4, which are superior in both activity and selectivity for CO_(2)RR. Specifically, the screened CuInSn achieves a CO_(2)to HCOOH Faradaic efficiency of 93% at a cell voltage of-2.0 V by assembling into artificial photosynthesis cell. The stability test of IT exhibits less than 3% degradation over 24 h. Furthermore, in-situ Raman spectroscopy reveals that both CO_(3)^(-2)and CO_(2)are involved in CO_(2)RR as reactants. The preferential affinity of C for H in the ^(*)HCO_(2)intermediate enables an improved HCOOH-selectivity, highlighting the role of multifunctional Cu in reducing the cell voltage and enhancing the photocurrent density.

Strategic comparison of membrane-assisted and membrane-less water electrolyzers and their potential application in direct seawater splitting(DSS)

Electrocatalytic splitting of water by means of renewable energy as the electricity supply is one of the most promising methods for storing green renewable energy as hydrogen. Although two-thirds of the earth’s surface is covered with water, there is inadequacy of freshwater in most parts of the world. Hence, splitting seawater instead of freshwater could be a truly sustainable alternative. However, direct seawater splitting faces challenges because of the complex composition of seawater. The composition, and hence, the local chemistry of seawater may vary depending on its origin, and in most cases, tracking of the side reactions and standardizing and customizing the catalytic process will be an extra challenge. The corrosion of catalysts and competitive side reactions due to the presence of various inorganic and organic pollutants create challenges for developing stable electro-catalysts. Hence, seawater splitting generally involves a two-step process, i.e., purification of seawater using reverse osmosis and then subsequent fresh water splitting. However, this demands two separate chambers and larger space, and increases complexity of the reactor design. Recently, there have been efforts to directly split seawater without the reverse osmosis step. Herein, we represent the most recent innovative approaches to avoid the two-step process, and compare the potential application of membrane-assisted and membrane-less electrolyzers in direct seawater splitting(DSS). We particularly discuss the device engineering, and propose a novel electrolyzer design strategies for concentration gradient based membrane-less microfluidic electrolyzer.

东亚夏季风变化机理的模拟和未来变化的预估：成绩和问题、机遇和挑战

东亚夏季风对于我国东部气候具有重要影响,呈现出多种时间尺度的变化特征。在理解东亚夏季风过去和当前的变化机理、预测和预估其未来变化等方面,气候系统模式发挥着不可替代的作用。但是当前的气候模式在东亚夏季风的模拟上尚存在诸多不足,这使得其模拟结果存在不确定性,既制约了我们对过去和当前季风变化机理的准确理解,又降低了未来预测预估结果的可信度。关于造成季风模拟偏差的原因,既涉及模式本身的性能问题,又与模拟系统的构建、强迫资料的误差、乃至我们当前对季风变化规律自身的认知水平有关。本文以时间尺度为序,从气候态、日变化、年际变率、年代际变率、长期气候变化和未来预估等季风学界关注的热点问题角度,本着总结成绩、归纳问题、寻找机遇、面对挑战的目的,从七个方面系统总结了当前气候模式的水平,归纳了其主要偏差特征,讨论了影响模式性能的可能因素。内容涉及模式分辨率和地形效应、对流和云辐射效应的作用、与季风相关的热带海气相互作用关键过程、内部变率(太平洋年代际振荡)、自然变率(太阳辐照度变化和火山气溶胶强迫)和人为辐射强迫(人为温室气体和气溶胶排放)对季风变化的不同影响、热力和动力过程及气候敏感度对季风环流(副高)和降水预估不确定性的影响等。最后从优化参数、实现场地观测和过程模拟的协同、发展高分辨和对流解析模式等角度,讨论了提升东亚夏季风模拟能力的技术途径。

中国东部气溶胶在天气尺度上的辐射强迫和对地面气温的影响

本文应用WRF-Chem（Weather Research and Forecasting—Chemistry）模式研究中国东部地区气溶胶及其部分组分（硫酸盐、硝酸盐和黑碳气溶胶）在天气尺度下的辐射强迫和对地面气温的影响.5个无明显降水时间段（2006年8月23～25日、2008年11月10～12日、2008年12月16～18日、2009年1月15～17日和2009年4月27～29日）的模拟显示,气溶胶浓度呈现显著的白天低,夜间高的日变化特征,且北方区域（29.8°～42.6°N,110.2°～120.3°E）平均PM2.5近地面浓度（40～80μg m-3）高于南方区域（22.3°～29.9°N,109.7°～120.2°E,30～47 μg m-3）.气溶胶对地面2m温度（地面气温）有明显的降温效果,在早上08：00（北京时,下同）和下午17：00左右最为显著,最高可降低约0.2～1 K,同时气溶胶的参与改善了模式对地面气温的模拟.本文还通过对2006年8月23～25日一次个例的模拟,定量分析了气溶胶及其部分组分（硫酸盐、硝酸盐和黑碳气溶胶）的总天气效应（直接效应＋间接效应）、直接效应和间接效应分别对到达地面的短波辐射和地面气温的影响.北方区域平均气溶胶直接效应所造成的短波辐射强迫要高于南方区域,分别为-11.3 Wm^-2和-5.8Wm^-2,导致地面气温分别降低了0.074 K和0.039 K.南方区域平均气溶胶间接效应所产的短波辐射强迫高于北方区域,分别为-14.4 W m^-2和-12.4W m^-2,引起的地面气温的改变分别为-0.094K和-0.035K.对于气溶胶组分,硫酸盐气溶胶的直接效应和间接效应的作用相当,其总效应在北方和南方区域平均短波辐射强迫分别为-7.0 Wm^-2和-10.5 Wm^-2,对地面气温的影响为-0.062 K和-0.074 K,而硝酸盐气溶胶的作用略小.黑碳气溶胶使得北方和南方区域平均到达地表的太阳短波辐射分别减少了6.5 Wm^-2和5.8 W m^-2,而地表气温则分别增加了0.053 K和0.017 K,相比于间接效应,黑碳气溶胶的直接效应的影响更加显著.

IPCC第五次评估报告全球和区域气候预估图集评述

与以往4次IPCC评估报告①相比,第五次评估报告（AR5）增加了附录一：“全球和区域气候预估图集”[11.该图集是AR5的特色之一,它利用国际耦合模式比较计划第五阶段（CMIP5）[2]全球气候模式的部分数据,给出了一系列全球和区域气候变化的图形.这些图形显示了全球和若干不同次大陆尺度区域在不同季节的表面气温变化和降水相对变化（平均降水变化百分比）.相对于参考时段（1986-2005年）,该图集给出了CMIP5模式预估的近期（2016-2035年）、中期（2046-2065年）和远期（2081-2100年）的20年平均气候变化.该图集针对全球陆地和海洋平均、26个次大陆SREX区域[3]、极地、加勒比海、印度洋的2个区域和太平洋的3个区域,分别给出了历史模拟和预估的温度和降水相对变化的时间序列,时间跨度为1900-2100年.

基于RBF网络的车载超级电容滑模控制系统

针对地铁在频繁的加速和制动过程中导致电能浪费、牵引网电压的剧烈波动和电网运行不稳定等问题,提出一种基于RBF网络的车载超级电容滑模控制系统。超级电容储能装置通过与双向DC/DC变换器连接,给列车提供牵引或者吸收列车产生的再生制动能量。在Boost模式和Buck模式下,分别设计RBF神经滑模控制器。仿真结果表明,与传统的PI控制相比,神经滑模控制下的车载超级电容储能装置提高了再生制动能量吸收效果,抑制了牵引网电压波动。

一种试验与仿真联合的阻尼车轮降噪效果评价方法

提出一种实验室测试和数值仿真结合的阻尼车轮降噪效果评价方法。以低噪声技术中的约束阻尼车轮为例,建立车轮全有限元模型,利用实验室测试获取的车轮振动频响结果和有限元模型仿真结果进行对比验证模型有效性,通过参数识别方法获取车轮模态参数,并将模态阻尼比应用于预测模型分析线路运行条件下的轮轨噪声降噪量,结合实验室测试的车轮降噪量来综合评价阻尼车轮减振降噪性能。研究结果表明:线路运行仿真预测结果与实际线路运行轮轨噪声降噪效果相符,说明所提出的方法合理且能满足现场评价分析应用需求。

夏季硫酸盐和黑碳气溶胶对中国云特性的影响

利用WRF-Chem(Weather Research and Forecasting model coupled with Chemistry)模式研究2006年8月1日—9月1日中国区域硫酸盐和黑碳气溶胶对云特性的影响。模式验证利用了卫星和地面观测的气象要素、化学物质浓度、气溶胶光学特性和云微物理特性。模式性能评估表明该模式能较好地抓住气象要素(温度、降水、相对湿度和风速)的量级和空间分布特征。通过与地面观测和MODIS卫星数据对比发现,尽管模式模拟还存在偏差,但还是能较好模拟出气溶胶物种的地表浓度、气溶胶光学厚度(AOD)、云光学厚度(COD)、云量(CLDF)、云顶云滴有效半径(CER)和云水路径(LWP)。通过两个敏感性试验(分别增加二氧化硫和黑碳排放量至控制试验排放的3倍)与控制试验的对比发现硫酸盐比黑碳更易成为云凝结核,在中国东部云顶云滴数浓度和其它云特性参数对二氧化硫排放增加的响应均从北向南呈递增,这与地面湿度分布有关。云滴有效半径对硫酸盐气溶胶的响应符合气溶胶第一间接效应的定义,即硫酸盐气溶胶增多,云滴数浓度增加,云滴有效半径减少,但是对黑碳气溶胶的响应在各区域不尽相同。还发现黑碳对云量的影响远大于硫酸盐,主要原因是由于黑碳气溶胶直接辐射效应(对太阳光的吸收)导致的云的"燃烧"作用。

高速磁浮单线隧道车体压力载荷特征

高速磁浮列车通过隧道过程中将引起剧烈的压力波动,造成司乘人员耳感舒适性、车体及其零部件、隧道衬砌及辅助设施的气动疲劳寿命问题,有必要对磁浮列车高速通过隧道时压力波效应进行研究。采用一维可压缩非定常不等熵流动模型和广义黎曼变量特征线法对单列车通过隧道时车体压力载荷进行数值模拟研究,初步揭示隧道长度、列车速度、阻塞比对车外压力波的影响规律;得出时速500~600 km/h速度下基于最大正负值和最大压力峰峰值的最不利隧道长度;论证了列车通过隧道产生的压力波幅值与列车速度平方成正比的适用范围,总结了压力最值与速度的拟合关系式。本文研究方法和结果可为车体设计选用气动载荷提供参考依据。

基于人机工程理论的复兴号动车组驾驶室分析方法

为了改善列车驾驶员的工作环境并降低驾驶员的疲劳程度,通过对列车驾驶室的布局设计进行人机工程校核与优化,在提高驾驶员的工作效率的同时,保证列车行驶的安全性与可靠性。以复兴号某车型的驾驶室为研究对象,利用RAMSIS软件开发环境建立了具适用于本研究的三维人体模型;依据《UIC 651标准》等相关标准对列车驾驶室的驾驶员伸及性、前方视野性、空间性、仪表盘视野性以及坐姿舒适性等方面进行了人机工程校核,针对欠缺合理之处进行了优化;在此基础上,利用G1评价方法对已设计的驾驶室布局进行了评价,评价结果表明对列车驾驶室布局设计方法优于传统车型的驾驶室设计,对列车驾驶室的布置具有重要的指导意义。

Variability of Northeast China River Break-up Date

This paper investigates the variability of the break-up dates of the rivers in Northeast China from their icebound states for the period of 1957-2005 and explores some potential explanatory mechanisms. Results show that the break-up of the two major rivers （the Heilongjiang River and Songhuajiang River） was about four days earlier, and their freeze-up was about 4-7 days delayed, during 1989 2005 as compared to 1971 1987. This interdecadal variation is evidently associated with the warming trend over the past 50 years. In addition, the break-up and freeze-up dates have large interannual variability, with a standard deviation of about 10-15 days. The break-up date is primarily determined by the January February-March mean surface air temperature over the Siberian-Northeast China region via changes in the melting rate, ice thickness, and snow cover over the ice cover. The interannual variability of the break-up date is also significantly connected with the Northern Annular Mode （NAM）, with a correlation coefficient of 0.35-0.55 based on the data from four stations along the two rivers. This relationship is attributed to the fact that the NAM can modulate the East Asian winter monsoon circulation and Siberian-Northeast China surface air temperature in January February-March.

速度600km/h单列磁浮列车通过隧道时压力载荷特征研究

列车由明线高速行驶突入隧道的瞬间,列车周围的空气流动空间骤然变小,车头前方的空气受到压缩压力急剧升高,形成初始压缩波,并以当地声速向隧道出口端传播。当列车尾部进入隧道时,由于列车尾部占据的空间得以释放,空气压力突然降低,形成膨胀波。压缩波与膨胀波传播到隧道端口被反射为具有相反性质的波,两者相互叠加,导致隧道内产生剧烈的压力波动。文章采用一维可压缩非定常不等熵流动模型和广义黎曼变量特征线方法对速度600 km/h单列磁浮列车通过隧道时压力波问题进行数值模拟研究,通过对隧道内压力变化形成原理的分析,揭示了隧道内气动载荷的变化特性,以及车体表面压力幅值和隧道长度、列车速度、阻塞比之间的变化规律。研究结果可为高速磁浮列车通过隧道时洞内和车体气动载荷设计提供数据参考。

不同填料顺序下路基沉降分析

针对杨林船闸原状淤泥质土,进行一维压缩试验,研究一次加荷和多次加荷试验下的固结特性。结合典型路基断面,运用ABAQUS软件建立时间硬化蠕变模型和D-P弹塑性模型,得到不同填料顺序下杨林船闸附近高速公路路基工后沉降。试验表明,多次加荷试验下,主、次固结的分界点时间变大,即多次加荷试验主固结完成时间大于一次加荷试验主固结完成时间。模拟结果显示,未考虑蠕变情况下路基沉降量小于考虑蠕变情况下路基沉降量。把蠕变考虑进来时一次填料计算的沉降量大于多次填料计算的沉降量,同时也验证了多次加荷可有效降低次固结沉降。

How the “Best” Models Project the Future Precipitation Change in China

Projected changes in summer precipitation characteristics in China during the 21st century are assessed using the monthly precipitation outputs of the ensemble of three ＂best＂ models under the Special Report on Emissions Scenarios （SRES） A1B, A2, and B1 scenarios. The excellent reproducibility of the models both in spatial and temporal patterns for the precipitation in China makes the projected summer precipitation change more believable for the future 100 years. All the three scenarios experiments indicate a consistent enhancement of summer precipitation in China in the 21st century. However, the projected summer precipitation in China demonstrates large variability between sub-regions. The projected increase in precipitation in South China is significant and persistent, as well as in North China. Meanwhile, in the early period of the 21st century, the region of Northeast China is projected to be much drier than the present. But, this situation changes and the precipitation intensifies later, with a precipitation anomaly increase of 12.4%0-20.4% at the end of the 21st century. The region of the Xinjiang Province probably undergoes a drying trend in the future 100 years, and is projected to decrease by 1.7%-3.6% at the end of the 21st century. There is no significant long-term change of the projected summer precipitation in the lower reaches of the Yangtze River valley. A high level of agreement of the ensemble of the regional precipitation change in some parts of China is found across scenarios but smaller changes are projected for the B1 scenario and slightly larger changes for the A2 scenario.

Climate Responses to Direct Radiative Forcing of Anthropogenic Aerosols,Tropospheric Ozone,and Long-Lived Greenhouse Gases in Eastern China over 1951–2000

A unified chemistry-aerosol-climate model is applied in this work to compare climate responses to changing concentrations of long-lived greenhouse gases （GHGs, CO2, CH4, N2O）, tropospheric O3, and aerosols during the years 1951-2000. Concentrations of sulfate, nitrate, primary organic carbon （POA）, secondary organic carbon （SOA）, black carbon （BC） aerosols, and tropospheric 03 for the years 1950 and 2000 are obtained a priori by coupled chemistry-aerosol-GCM simulations, and then monthly concentrations are interpolated linearly between 1951 and 2000. The annual concentrations of GHGs are taken from the IPCC Third Assessment Report. BC aerosol is internally mixed with other aerosols. Model results indicate that the sinmlated climate change over 1951-2000 is sensitive to anthropogenic changes in atmospheric components. The predicted year 2000 global mean surface air temperature can differ by 0.8℃ with different forcings. Relative to the climate simulation without changes in GHGs, O3, and aerosols, anthropogenic forcings of SO4^2-, BC, BC＋SO4^2-, BC＋SO4^2- ＋POA, BC＋SO4^2- ＋POA＋SOA＋NO3^-, O3, and GHGs are predicted to change the surface air temperature averaged over 1971-2000 in eastern China, respectively, by -0.40℃, ＋0.62℃, ＋0.18℃, ＋0.15℃, -0.78℃, ＋0.43℃, and ＋0.85℃, and to change the precipitation, respectively, by -0.21, ＋0.07, -0.03, ＋0.02, -0.24, -0.08, and ＋0.10 mm d^-1. The authors conclude that all major aerosols are as important as GHGs in influencing climate change in eastern China, and tropospheric O3 also needs to be included in studies of regional climate change in China.

网络信息安全专业人员培训认证探讨与实践

网络空间的竞争,归根结底是人才竞争.近年来我国发布了一系列网络信息安全政策法规,网络安全专业人才教育和培养工作快速发展,在学历教育、行业管理、人员培训认证等方面都取得了显著成绩.相对美国在国家战略、政策法规、标准规范及实施层面的完善体系,我国的网络安全人员教育培训体系还有待完善.网络安全人才培养取得突破性进展的同时,挑战和机遇并存.

Contribution of the Sea Surface Temperature over the Mediterranean-Black Sea to the Decadal Shift of the Summer North Atlantic Oscillation

Recent observational study has shown that the southern center of the summer North Atlantic Oscillation （SNAO） was located farther eastward after the late 1970s compared to before. In this study, the cause for this phenomenon is explored. The result shows that the eastward shift of the SNAO southern center after the late 1970s is related to the variability of the Mediterranean-Black Sea （MBS） SST. A warm MBS SST can heat and moisten its overlying atmosphere, consequently producing a negative sea level pressure （SLP） departure over the MBS region. Because the MBS SST is negatively correlated with the SNAO, the negative SLP departure can enhance the eastern part of the negative-phase of the SNAO southern center, consequently producing an eastward SNAO southern center shift. Similarly, a cold MBS SST produces an eastward positive-phase SNAO southern center shift. The reason for why the MBS SST has an impact on the SNAO after the late 1970s but why it is not the case beforehand is also discussed. It is found that this instable relationship is likely to be attributed to the change of the variability of the MBS SST on the decadal time-scale. In 1951 1975, the variability of the MBS SST is quite weak, but in 1978 2002, it becomes more active. The active SST can enhance the interaction between the sea and its overlying atmosphere, thus strengthening the connection between the MBS SST and the SNAO after the late 1970s. The above observational analysis results are further confirmed by sensitivity experiments.