一种新型光纤光栅锈蚀传感器及其对混凝土结构钢筋锈蚀监测实验研究

设计一种新型光纤光栅锈蚀传感器,主要由锈蚀体、不锈钢体和2段串联的光纤布拉格光栅（FBG）组成。缠绕于锈蚀体表面的FBG监测钢筋的锈胀应变,缠绕于不锈钢体表面的FBG用作温度补偿器,消除温度变化对锈胀应变监测的影响。此外,设计电化学加速腐蚀实验,探究该传感器在不同强度等级混凝土中的工作性能。结果表明,该传感器监测质量腐蚀率的灵敏度为0.02%,监测范围大于1%,可实时监测混凝土中钢筋的锈蚀过程及特征,为预警钢筋锈蚀引起的钢筋混凝土结构耐久性损失提供阈值,在结构健康监测领域具有较大的应用价值。     

An experimental study: Integration device of Fiber Bragg grating and reinforced concrete beam for measuring debris flow impact force

The impact effect of boulder within debris flow is the key factor contributing to peak impact as well as to the failure of debris flow control work. So accurate measuring and calculating the impact force of debris flow can ensure the engineering design strength. However, limited to the existing laboratory conditions and piezoelectric sensor performance, it is impossible, based on the conventional measurements, to devise a computing method for expressing a reliable boulder impact force. This paper has therefore designed a new measurement device according to the method of integrating Fiber Bragg grating (FBG) and reinforced concrete composite beam (RCB) for measuring the impact force of debris flows, i.e. mounting FBG on the axially stressed steel bar in the composite beam at regular intervals to monitor the steel strain. RCB plays the role of contacting debris flow and protecting FBG sensors. Taking this new device as the experimental object, drop testing is designed for simulating and reflecting the boulder impact force. In a series of impacting tests, the relationship between the peak dynamic strain value of the steel bar and the impact force is analyzed, and based on which, an inversion model that uses the steel bar strain as the independent variable is established for calculating the boulder impact force. The experimental results show that this new inversion model can determine the impact force value and its acting position with a system error of 18.1%, which can provide an experimental foundation for measuring the impact force of boulders within the debris flow by the new FBG-based device.     

基于马尔可夫链和最大后验准则的模拟静止气象卫星数据地表组分温度反演

地表组分温度比像元混合温度具有更强的物理意义和实用价值,是定量遥感反演的一个重要研究方向。本文以马尔可夫链和最大后验准则地表温度尺度转换方法,结合静止气象卫星数据高时间分辨率的特点,通过模拟静止气象卫星数据地表组分温度反演进行分析和验证。在研究过程中,地面被简化为由植被和土壤两组分组成,同时假设邻近像元的植被和土壤组分温度相同。鉴此,本文通过模拟构建20×20像元大小的静止气象卫星混合像元图像,并对各像元各时刻温度添加均值为0标准差为2K的随机误差,最终应用所提算法估算各像元各时刻的植被和土壤组分温度大小。精度分析结果表明,该算法能够较为精确地反演植被和土壤组分温度,且误差基本控制在2K以内。此外,本文还进一步讨论了算法的适用性及其对混合像元温度误差、植被覆盖度误差,以及邻近像元植被覆盖度变化范围的敏感度。分析结果再次证明,该方法对混合像元温度误差和植被覆盖度误差都具有较低的敏感性,在最大温度误差条件(均值为1.8K,标准差为5K)和最大植被覆盖度误差(均值为0.18,标准差为0.2)的条件下,各组分温度的估算精度分别能控制在3K和2K以内,满足精度要求。但是,由于组分温度初值的确定方法,对所计算窗口内植被覆盖度变化范围有较强的敏感性,反演结果与植被覆盖度变化范围相关,要求窗口内植被覆盖度变化范围足够大才能满足初值估算的精度要求。     

Response of ecosystem respiration to experimental warming and clipping at daily time scale in an alpine meadow of tibet

The alpine meadow,as one of the typical vegetation types on the Tibetan Plateau,is one of the most sensitive terrestrial ecosystems to climate warming.However,how climate warming affects the carbon cycling of the alpine meadow on the Tibetan Plateau is not very clear.A field experiment under controlled experimental warming and clipping conditions was conducted in an alpine meadow on the Northern Tibetan Plateau since July 2008.Open top chambers(OTCs) were used to simulate climate warming.The main objective of this study was to examine the responses of ecosystem respiration(R eco) and its temperature sensitivity to experimental warming and clipping at daily time scale.Therefore,we measured R eco once or twice a month from July to September in 2010,from June to September in 2011 and from August to September in 2012.Air temperature dominated daily variation of Reco whether or not experimental warming and clipping were present.Air temperature was exponentially correlated with R eco and it could significantly explain 58～96% variation of R eco at daily time scale.Experimental warming and clipping decreased daily mean R eco by 5.8～37.7% and-11.9～23.0%,respectively,although not all these changes were significant.Experimental warming tended to decrease the temperature sensitivity of R eco,whereas clipping tended to increase the temperature sensitivity of R eco at daily time scale.Our findings suggest that R eco was mainly controlled by air temperature and may acclimate to climate warming due to its lower temperature sensitivity under experimental warming at daily time scale.     

基于微博数据的中国人群气温感知时空分异特征及影响因素分析

极端气温事件发生频率的增加对人群的健康带来了很大的影响,深入理解人群对气温变化的感知特征有助于提高应对极端气温事件的预警、适应和管理水平。针对传统调查数据在样本量和覆盖度等方面的不足,本文使用基于微博的社交媒体数据来研究人群对气温感知的定量特征。研究通过建立气温关注度、敏感性和耐受性等指标,调查了中国2017年31个城市的人群对气温感知的空间格局变化与局部变异性,分析了不同季节和不同群体对气温感知的差异性与影响因素。分析结果表明：人群对气温的感知表现出显著的纬度梯度规律性,纬度每下降1°,人群平均的热耐受性增强0.42oC,冷耐受性降低0.31oC,冷敏感性增强0.51;人群对气温的感知在不同季节、不同群体之间也表现出显著的差异性,反季的异常气温更易引起人群对于气温变化的关注,青少年与女性群体对冷更为敏感;气温感知特征的区域差异性与气候分区紧密相关,温带地区的人群比热带显示出更强的热耐受性,而热带地区的人群具有更显著的气温敏感性。本文研究结果可以为理解大尺度上人群对气温变化感知的基本特征和分异规律提供新的规律发现与证据支持。     

真空紫外四色超高温测量的参数优化

利用黑体辐射定律和四色光学测温原理,在3000K～33000K的温度范围和20nm～56nm的真空紫外波段计算了非理想辐射体在四个波长处辐射强度的比率.并从测温灵敏度、测温范围和测温精度等方面对各测温参数的优化进行了讨论.     

Effectiveness of Fiber Bragg Grating monitoring in the centrifugal model test of soil slope under rainfall conditions

Centrifugal model tests are playing an increasingly important role in investigating slope characteristics under rainfall conditions. However, conventional electronic transducers usually fail during centrifugal model tests because of the impacts of limited test space, high centrifugal force, and presence of water, with the result that limited valid data is obtained. In this study, Fiber Bragg Grating (FBG) sensing technology is employed in the design and development of displacement gauge, an anchor force gauge and an anti-slide pile moment gauge for use on centrifugal model slopes with and without a retaining structure. The two model slopes were installed and monitored at a centrifugal acceleration of 100 g. The test results show that the sensors developed succeed in capturing the deformation and retaining structure mechanical response of the model slopes during and after rainfall. The deformation curve for the slope without retaining structure shows a steep response that turns gradual for the slope with retaining structure. Importantly, for the slope with the retaining structure, results suggest that more attention be paid to increase of anchor force and anti-slide pile moment during rainfall. This study verifies the effectiveness of FBG sensing technology in centrifuge research and presents a new and innovative method for slope model testing under rainfall conditions.     

Simulation of phytoplankton biomass in Quanzhou Bay using a back propagation network model and sensitivity analysis for environmental variables

Prediction and sensitivity models,to elucidate the response of phytoplankton biomass to environmental factors in Quanzhou Bay,Fujian,China,were developed using a back propagation(BP) network.The environmental indicators of coastal phytoplankton biomass were determined and monitoring data for the bay from 2008 was used to train,test and build a three-layer BP artificial neural network with multi-input and single-output.Ten water quality parameters were used to forecast phytoplankton biomass(measured as chlorophyll-a concentration).Correlation coefficient between biomass values predicted by the model and those observed was 0.964,whilst the average relative error of the network was-3.46% and average absolute error was 10.53%.The model thus has high level of accuracy and is suitable for analysis of the influence of aquatic environmental factors on phytoplankton biomass.A global sensitivity analysis was performed to determine the influence of different environmental indicators on phytoplankton biomass.Indicators were classified according to the sensitivity of response and its risk degree.The results indicate that the parameters most relevant to phytoplankton biomass are estuary-related and include pH,sea surface temperature,sea surface salinity,chemical oxygen demand and ammonium.     

‘Initial’ Soil Moisture Effects on the Climate in China——A Regional Climate Model Study

In this study,the effects of ‘initial’ soil moisture(SM) in arid and semi-arid Northwestern China on subsequent climate were investigated with a regional climate model. Besides the control simulations(denoted as CTL),a series of sensitivity experiments were conducted,including the DRY and WET experiments,in which the simulated ‘initial’ SM over the region 30 –50°N,75 –105°E was only 5% and 50%,and up to 150% and 200% of the simulated value in the CTL,respectively. The results show that SM change can modify ...     

热解——动力学法测定岩石和化探样品中痕量碘

以五氧化二钒和三氧化二铋为熔剂,研究了分离富集痕量碘的最佳条性,以及影响催化反应速度的因素。用改变温度和时间的方法提高测定方法的灵敏度和扩大碘的测定范围。本方法具有灵敏度高、选择性好、操作简便、快速和经济的特点,最低检出限为0.033ppm碘,标准偏差为4.45％。