Dynamic thermo-mechanical responses of road-soft ground system under vehicle load and daily temperature variation

A complete road-soft ground model is established in this paper to study the dynamic responses caused by vehicle loads and/or daily temperature variation.A dynamic thermo-elastic model is applied to capturing the behavior of the rigid pavement,the base course,and the subgrade,while the soft ground is characterized using a dynamic thermo-poroelastic model.Solutions to the road-soft ground system are derived in the Laplace-Hankel transform domain.The time domain solutions are obtained using an integration approach.The temperature,thermal stress,pore water pressure,and displacement responses caused by the vehicle load and the daily temperature variation are presented.Results show that obvious temperature change mainly exists within 0.3 m of the road when subjected to the daily temperature variation,whereas the stress responses can still be found in deeper places because of the thermal swelling/shrinkage deformation within the upper road structures.Moreover,it is important to consider the coupling effects of the vehicle load and the daily temperature variation when calculating the dynamic responses inside the road-soft ground system.

Monitoring models for base flow effect and daily variation of dam seepage elements considering time lag effect

Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.

Daily variations of airborne pollen in Beijing Olympic Park during August of three consecutive years and their relationships with meteorological factors

A three-year aeropalynological study was carried out in the month of August for each of the three years 2005, 2006 and 2007 in the Beijing Olympic Park. A total of 19550 pollen grains were counted （15057 grains in 2005, 2717 in 2006 and 1776 in 2007） for the following taxa： Gramineae, Chenopodiaceae, Humulus L., Artemisia L., Ambrosia L. and Pinus L. The analysis indicated that in the three consecutive years of 2005-007, airborne pollen types and daily number of pollen in August in the Beijing Olympic Park were closely related to environmental change and vegetation composition. The daily variations of airborne pollen displayed similar patterns in August in each of the three years, which were affected positively by periods of daily sunshine, negatively by daily relative humidity and daily precipitation. Continuously high daily temperatures and stable daily wind speeds seemed to have little effect on the fluctuation of airborne pollen.

Spatial variations in daily average CO_2 concentrations above wetland surface of Xianghai National Nature Reserve, China

Horizontal and vertical variations of daily average CO 2 concentration above the wetland surface were studied in Xianghai National Nature Reserve of China in August, 2000 The primary purpose was to study spatial distribution characteristics of CO 2 concentration on the four levels of height(0 1 m, 0 6 m, 1 2 m and 2 m) and compare the differences of CO 2 concentration under different land covers. Results showed that daily average CO 2 concentration above wetland surface in Xianghai National Natural Reserve was lower than that above other wetlands in northeast China as well as the worldwide average, suggesting that Xianghai wetland absorbed CO 2 in August and acted as “sink” of CO 2 The horizontal variations on the four levels of height along the latitude were distinct, and had the changing tendency of “decreasing after increasing” with the increase of height. The areas with obvious variations were consistent on different levels of height, and those with the highest variations appeared above surface of shore, sloping field, Typha wetland and Phragmites wetland; the vertical variations were greatly different, with the higher variations in Phragmites wetland and Typha wetland, and the lands near the shore and the sloping field with the lower variations. Spatial variations of daily average CO 2 concentrations above wetland surface were affected by surface qualities and land covers.

Daily variation of radon gas and its short-lived progeny concentration near ground level and estimation of aerosol residence time

Atmospheric concentrations of radon（^（222）Rn） gas and its short-lived progenies^（218）Po,^（214）Pb, and^（214）Po were continuously monitored every four hours at the ground level in Jeddah city, Kingdom of Saudi Arabia. The measurements were performed three times every week, starting from November 2014 to October 2015. A method of electrostatic precipitation of positively charged^（218）Po and ^（214）Po by a positive voltage was applied for determining^（222）Rn gas concentration. The short-lived^（222）Rn progeny concentration was determined by using a filter holder connected with the alpha-spectrometric technique. The meteorological parameters（relative air humidity, air temperature, and wind speed） were determined during the measurements of^（222）Rn and its progeny concentrations.^（222）Rn gas as well as its short-lived progeny concentration display a daily and seasonal variation with high values in the night and early morning hours as compared to low values at noon and in the afternoon. The observed monthly atmospheric concentrations showed a seasonal trend with the highest values in the autumn/winter season and the lowest values in the spring/summer season. Moreover, and in parallel with alphaspectrometric measurements, a single filter-holder was used to collect air samples. The deposited activities of^（214）Pb and the long-lived^（222）Rn daughter ^（210）Pb on the filter were measured with the gamma spectrometric technique. The measured activity concentrations of^（214）Pb by both techniques were found to be relatively equal largely. The highest mean seasonally activity concentrations of ^（210）Pb were observed in the autumn/winter season while the lowest mean were observed in the spring/summer season. The mean residence time（MRT） of aerosol particles in the atmospheric air could be estimated from the activity ratios of ^（210）Pb/^（214）Pb.

Spatial and Temporal Variations of Daily Ranges of the Geomagnetic Vertical Component in the Chinese Mainland

In this paper, we use the daily ranges of the vertical magnetic intensity of approximately 76 geomagnetic stations from January 1, 2008 to December 31, 2010 to analyze the spatial and temporal characteristics of Z ranges. The results are summarized as follows: (1) Temporally, we use regressive analysis and FFT analysis to analyze the data. The results show that the Z component daily ranges of all stations have an obvious cyclical variation, the computed Fourier spectra of all data sets have clearly resolved the required periodicities in the data, in the form of distinct peaks at days 365, 183, 22, and 73, and the power spectra of day 365 is the highest in all periods. (2) In terms of spatial variation, the daily ranges show nonlinear variation with latitude in China. The results show the existence of a point of inflexion (maximal value point) nearby at about 25°N, the daily ranges of Z rise from 15°~25°N and have a good linear decrease variation along with 25°~50°N. (3) Compared with the spatial and temporal variations of Z daily ranges with the Sq current inversion, we found that the spatial and temporal characteristics of Z ranges are decided mainly by the spatio-temporal evolution of the Sq current system. (4) If the latitudes of the maximum amplitudes of variation of the vertical component in the geomagnetic quiet days are roughly taken as the latitudes corresponding to the foci of Sq overhead current system, we can see that these latitudes of foci become higher in summer, are lowest in winter and highest during Equinoxes, displaying conspicuous monthly and daily variations. For two successive geomagnetic quiet days, the latitudes of foci may vary ten degrees.

Diurnal Variation of Photosynthetic Physiological Characteristics of Kadsura coccinea(Lem.)A.C.Smith

[Objectives]This study was conducted to investigate the diurnal variations of photosynthetic and physiological characteristics in 3-year-old Kadsura coccinea(Lem.)A.C.Smith plants.[Methods]A Li-6400 portable photosynthetic system was used to study the diurnal variations of the photosynthetic physiological characteristics of K.coccinea.[Results]The diurnal variation of the net photosynthetic rate(Pn)of K.coccinea leaves showed a"double peak"curve,and there was a lunch break at noon.The maximum value of Pn[4.51 mmol/(m^(2)·s)]appeared at 10:00,and the daily average Pn was 3.98 mol/(m^(2)·s);and the stepwise regression analysis showed that photosynthetically active radiation(PAR)and stomatal conductance(Gs)were the main factors affecting Pn.The partial correlation analysis and path analysis showed that the order of effects on Pn was Gs>PAR.[Conclusions]This study provides a reference for further research on the development and utilization of K.coccinea.

地磁异常识别技术在松原5.7级地震前的应用研究

运用地磁异常识别技术对2018年5月28日松原5.7级地震前的地磁异常展开研究。采用加卸载响应比法、逐日比法、日变化空间相关法、异常叠加法对吉林省三岗台、通化台及东北地区邻近的大连台、营口台、朝阳台、铁岭台等台站,运用松原5.7级地震前18个月内的地磁预处理分钟值数据进行计算分析和异常判定识别。研究结果表明:在加卸载响应比法、逐日比法和日变化空间相关法的基础上,运用异常叠加法提取的地磁异常,其预测的位置与真实值更加接近,预测结果对省内地震具有重要的指示意义。

海南翁田台地电场数据质量及频谱分析

地电场观测系统的观测对象是地电场强度矢量,其目的是通过观测地表的地电场强度,探索地震前地电场的变化,获得地下电性结构及其变化规律,开展孕震过程中大地电场的变化特征研究。本文对翁田台地电场自建台以来的数据进行了详细的梳理,通过计算差值和相关系数来分析数据自运行以来的质量情况,总结数据质量较好的原因,并对下一步如何提高数据质量给出一些建议。翁田台地电场观测数据曲线存在明显1峰1谷的日变形态,对其进行频谱分析,优势周期为24、12、6 h,以24 h为主。运用优势方位角的方法计算发现,2017—2018年优势方位角存在收窄和偏转现象,对该异常进行了分析与探讨。

2012—2019年昌吉冬季降雪日变化特征分析

利用2012-2019年冬季昌吉回族自治州(简称“昌吉州”)11个国家级台站逐时降水资料,运用常规统计方法,对昌吉州冬季降雪日变化特征进行分析。结果表明:昌吉州冬季降雪量空间分布与海拔高度呈正相关,与纬度呈显著的负相关,降雪强度与纬度关系密切。昌吉州逐时累积降雪量呈双峰型分布,主峰出现在17时,次峰出现在08时;西部呈三峰型特征,主次峰值分别出现在17、14、08时;东部呈准单峰单谷型,峰值发生在19时,谷值出现在13时。昌吉州冬季降水以短时降水事件为主,对冬季降水量贡献为64%,12 h以上长持续性降水事件发生概率很小,仅在部分台站偶有发生。西部和东部冬季降水日循环与降水持续性关系较密切,其中持续3~4 h降水事件对西部和东部冬季降水量贡献最大,随着持续时间的延长对降水量的贡献变小。

民用机场温度年循环和日循环变化对民用飞机载量影响研究

为提升航空公司的经济效益和飞机利用率,结合前期研究成果,分析和比较我国48个4E和4F机场1980—2020年近40年的气候和地表面大气温度的年循环和日循环特征,采用插值法和一元线性回归分析方法对温度和计算得到的飞机载量数据进行研究分析,研究可知:1)我国大部分机场的最高气温一般会产生在7月份;2)随着机场的纬度增高,机场年平均气温值会随之减小;3)随着海拔高度的增加,机场年平均气温值会有所减小;4)我国机场一般夏季气温日较差大于冬季,但不如春季大;5)由于陆地上气温日较差大于海洋,机场地理位置距海(或大型水体)越远,日较差就会越大。建议从优化航班的班表时刻、选择优势机型执行特殊航线和加强高温条件的起飞性能减载放行评估三个方面提升民用飞机的有效载量。

大连地区ECMWF细网格模式阵风预报误差检验与分析

阵风的预报误差检验对实际工作中的精细化预报订正具有一定的指导意义,同时对精细化预报中如何消除误差日变化的影响提供了借鉴。选取2017—2019年3~72 h逐日逐3 h欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecast,ECMWF)细网格10 m阵风和10 m平均风预报资料,基于大连地区9个国家气象观测站实况逐3 h极大风资料进行预报误差检验分析。结果表明:按预报风级和实况风级分类的预报误差对比检验均表明ECMWF细网格预报整体偏大,平均误差为0.96 m·s-1,但具体到各风级时两种分类的预报误差统计结论并不一致,按预报风级分类的检验更符合基于模式预报开展的实际预报工作。以预报为基准统计,各风向、各风级、各站的预报误差均差异明显,风级越大预报偏大的程度越高,风向也表现出随风级增大误差增大的趋势。阵风预报的平均误差具有明显日变化,08:00(北京时,下同)前后误差最大,20:00前后误差最小,主要由10 m平均风的平均误差日变化所致。全部预报个例与实况各时效预报相关系数均在0.7以上,具体到各风级、风向时,各风向相关性均较好,而各风级的相关系数则明显降低,8级及以上风力预报的可信度大幅下降。

三种地宝兰属植物叶片解剖结构及光合特性的比较研究

为探讨地宝兰属植物的叶片解剖结构及光合特性,该研究对狭域濒危种贵州地宝兰(Geodorum eulophioides)及广布种地宝兰(G.densiflorum)、大花地宝兰(G.attenuatum)的叶片解剖结构、光合日变化、光响应曲线、CO_(2)响应曲线、叶绿素含量等指标进行测定。结果表明:(1)3种地宝兰属植物的叶肉细胞没有海绵组织和栅栏组织分化,气孔仅分布于下表皮;与地宝兰和贵州地宝兰相比,大花地宝兰具有更大的叶片厚度和较小的气孔密度,表现出更适应弱光环境的结构特征。(2)3种地宝兰属植物的净光合速率(Pn)日变化均呈“双峰型”曲线,其光合“午休”主要由非气孔限制引起;Pn和水分利用效率(WUE)日均值大小均表现为大花地宝兰>地宝兰>贵州地宝兰,表明贵州地宝兰积累光合产物的能力更弱,对干旱环境的适应能力可能更差。(3)3种地宝兰属植物均为阴生植物,地宝兰的光补偿点(LCP)最小、光饱和点(LSP)最大,对光强适应范围较宽;大花地宝兰具有较高的最大净光合速率(Pmax)和表观量子效率(AQY),其光合能力较强;贵州地宝兰的Pmax和潜在最大净光合速率(Amax)最小,其光合能力和对CO_(2)的利用能力更弱。(4)地宝兰和大花地宝兰的叶绿素a(Chl a)、叶绿素b(Chl b)和总叶绿素(Chl)含量均显著(P<0.05)高于贵州地宝兰。(5)3种地宝兰属植物的叶片厚度、叶肉厚度、叶绿素含量与Pmax间存在显著(P<0.05)相关性。综上认为,与地宝兰和大花地宝兰相比,贵州地宝兰的光合能力和适应性较差,这可能与其濒危有很大关系;适当遮阴和增加CO_(2)浓度有利于3种地宝兰属植物的光合作用。该研究结果为贵州地宝兰濒危原因的分析及3种地宝兰属植物种质资源保育提供了参考依据。

混合盐碱胁迫对骏枣叶片结构和光合荧光特性的影响

为进一步探究骏枣对混合盐碱胁迫的生理响应机制,在骏枣盛果期分别设计0、60、120、180、240、300 mmol·L^(-1)的NaCl和NaHCO_(3)混合盐溶液来模拟土壤盐碱复合胁迫环境,分析不同胁迫水平下骏枣叶片的显微结构、超微结构及光合、荧光参数的变化。结果表明,在混合盐碱胁迫下,骏枣叶片的厚度、角质层厚度、表皮厚度和栅栏组织厚度均随着胁迫水平的增加呈先上升后下降趋势;海绵组织厚度和细胞结构疏松度呈逐渐下降趋势。在混合盐溶液高于180 mmol·L^(-1)时,叶绿体内的嗜锇颗粒数量明显增多,且体积变大,基质片层结构松散;同时,随着胁迫水平的增加,叶片的净光合速率、气孔导度与蒸腾速率逐渐降低,胞间CO_(2)浓度升高,光合限制以非气孔因素为主。在240、300 mmol·L^(-1)高胁迫水平处理下,叶片初始荧光(F_(0))显著升高,而最大荧光(F_(m))、F_(v)/F_(m)、F_(v)/F_(0)显著降低,单位反应中心吸收的光能(ABS/RC)、用于还原QA的能量(TR_(o)/RC)、热耗散的能量(DI_(o)/RC)均呈先下降后上升趋势,而用于电子传递的能量呈持续下降趋势。综上,较高水平的盐碱胁迫会使骏枣叶片的超微结构发生明显变化,抑制其光合能力,使嗜锇小体增多、变大,并出现淀粉粒。以上结果为深入研究枣的耐盐机制提供了理论基础。

ECMWF模式对我国西南环横断山区冬季近地面2m温度的预报评估

从冬季平均温度、温度日变化及日较差等方面入手,基于2021年CLDAS逐小时产品评估了ECMWF全球高分辨率确定性数值预报产品对我国西南环横断山区复杂地形区近地面2 m温度的预报能力,并通过区分高地形区(川西高原)和低地形区(四川盆地南部),对比了不同地形区近地面2 m温度预报的偏差特征。结果表明:(1)ECMWF模式可合理预报我国西南环横断山区冬季平均2 m温度的空间分布特征,但偏差分布与地形高度有关,随着地形高度的增加,预报偏差呈增大趋势。(2)ECMWF模式很好再现了西南环横断山区冬季温度的日变化特征,峰值时刻出现在14:00(北京时);各时刻温度的预报偏差在不同地形高度存在差异,川西高原和横断山区的最大负偏差出现在下午,四川盆地南部的最大负偏差出现在早晨。同时,高地形区各时刻的预报偏差均高于低地形区。(3)ECMWF模式对日内各时刻不同地形处2 m温度的空间分布均有合理预报,但偏差存在日变化特征。特别是在横断山区高地形区,其在各时刻有不同的冷暖偏差特征。(4)在环横断山区温度日较差预报偏差较大的区域(大致为昆明准静止锋线发生频次较高的区域),模式对于温度日较差较大的日数,其2 m温度的预报偏差要大于日较差较小的日数,且在该区域内,温度日较差的预报偏差相对不稳定。

施氮对河西走廊灌区青贮玉米抽雄期光合日变化、农艺性状及干物质量的影响

【目的】探究施氮对河西走廊灌溉区青贮玉米光合日变化和农艺性状及干物质量的影响,寻求河西走廊灌溉区最佳施氮量。【方法】以青贮玉米金铃67号为研究对象,于2022年在河西走廊灌溉区开展大田试验,设置5种施氮水平N0(0 kg/hm^(2))、N1(218 kg/hm^(2))、N2(249 kg/hm^(2))、N3(280kg/hm^(2))、N4(311 kg/hm^(2)),分析不同施氮水平对青贮玉米抽雄期叶片相对叶绿素含量(SPAD)、光合特性、农艺性状及干物质量的差异。【结果】N3处理下青贮玉米的SPAD相较于N0提高17.56%;N3处理下净光合速率、水分利用率分别提高17.42%、36.56%,N4处理蒸腾速率和气孔导度分别比N0高50.00%、49.14%,胞间二氧化碳N2处理比N0高42.96%,农艺性状及干物质量均以N3处理最高,相比N0株高、基径、叶面积指数、干物质量分别提高10.60%、18.18%、41.05%、34.59%。【结论】河西灌区施氮量280 kg/hm^(2)能够提高抽雄期玉米光合特性、农艺性状及干物质量。

亚热带山地景区不同类型景观小气候特征——以贵阳市花溪公园为例

以山地景区——贵阳市花溪公园为研究对象,选取了5种典型近自然类型景观,以其附近的人工硬化地表为对照,对小气候相关指标进行日变化情况的监测。结果表明,不同植被类型景观均对区域内小气候有降温增湿作用,灌丛对风速影响最为明显;植被类型与水体均会对小气候效应具有改善作用;光照强度、紫外线强度、土壤温度可在一定程度上反映小气候的变化。山地景区建设时需注重不同植被类型的景观搭配及对植被类型-水体的复合效应的综合考虑,以期营造更为舒适的景观小气候环境。

不同变异类型魔芋光合特性的比较研究

比较不同变异类型魔芋的光合特性,为魔芋的遗传改良提供参考。以魔芋叶柄不同颜色变异类型(叶柄颜色分别为黑色、白色、红色和青色,以下以黑杆魔芋、白杆魔芋、红杆魔芋和青杆魔芋代称)为材料,并以白魔芋和‘鄂魔芋1号’为对照,运用Li-6400便携式光合测定仪比较其光合特性差异。结果表明,不同变异类型魔芋的光合能力存在一定差异。魔芋的净光合速率(Pn)日变化曲线呈单峰型和双峰型,黑杆魔芋和白魔芋存在“光合午休”现象,其中黑杆魔芋的Pn日均值最大,红杆魔芋的Pn日均值最小。魔芋的Pn-PAR和Pn-CO_(2)响应曲线变化趋势整体较一致但变化程度有所不同,根据响应曲线求得6份魔芋材料的光饱和点为955~1191μmol/(m^(2)·s),光补偿点为1.51~47.05μmol/(m^(2)·s),表观量子效率为0.0235~0.0415;CO_(2)饱和点为1528~1948μmol/mol,CO_(2)补偿点为35.20~96.67μmol/mol,羧化效率为0.0203~0.0340。‘鄂魔芋1号’、黑杆魔芋和青杆魔芋光合表现更佳。

赤水桫椤自然保护区小灵猫及其潜在啮齿类猎物活动节律的季节适应格局

动物的日活动节律具有内源性且受外界生态因素(光周期、气候和食物等)影响,是动物生态适应性特征之一。阐明活动节律与气候和捕食者−猎物的关系,对于理解动物的生存策略、指导保护等至关重要。目前通过红外相机技术探究野生动物日活动节律日益受到学者们的关注。灵猫科动物是热带和亚热带生境中的重要次级消费者之一,但其野外相关研究甚少。本研究基于2016年12月至2022年7月在贵州赤水桫椤国家级自然保护区及其周边区域设置的60个红外相机位点监测影像资料,筛选小灵猫(Viverricula indica)及其相应监测位点的潜在啮齿类猎物数据。通过核密度函数比较分析了保护区内、外的小灵猫及其潜在啮齿类猎物在雨季、旱季的日活动节律特征。结果显示,小灵猫有明显的晨昏两个活动高峰,时间分别是03:00—06:00和19:00—24:00。季节比对发现,小灵猫雨季凌晨活动高峰(03:00—05:00)早于旱季(04:00—06:00),活动强度较旱季高且集中;黄昏后的活动较旱季有所延长。进一步分析其活动与潜在的啮齿类猎物的重叠度,结果发现小灵猫与赤腹松鼠(Callosciurus erythraeus)的重叠度整体较低(雨季,Δ=0.18;旱季,Δ=0.16);与夜行性鼠类的活动节律重叠度高达90%以上,其中旱季的重叠系数(Δ=0.93)高于雨季(Δ=0.90)。此外,在保护区内的小灵猫凌晨活动高峰结束较保护区外延迟约1 h;黄昏后高峰阶段的活动强度(核密度)峰值明显高于保护区外。少许日间活动也主要出现在保护区内。上述结果表明,小灵猫的昼夜节律既有保守性,也具有一定的季节可塑性。这些特征型表现与季节性猎物分布和环境变化关联,并受人类活动的影响。本研究结果对充分认识小灵猫生活史特征以及实现物种有效保护提供数据支持。

基于日尺度旱涝急转指数的重庆市旱涝急转事件演变特征分析

为准确地反映旱涝急转事件的“突发性”与“交替性”特征,对重庆市34个气象站采用日尺度旱涝急转指数DWAAI提取1960—2018年旱涝急转事件,根据重庆市的实际情况划分不同强度旱涝急转事件对应的DWAAI数值范围,探究不同强度旱涝急转事件发生频次的时空演变特征。结果表明:重庆市旱涝急转事件以旱急转涝为主,旱急转涝事件占旱涝急转事件累计次数的85%,主要发生在4—9月,多年平均次数为22.64站次,其中,中度、重度事件占所有旱急转涝事件的11.7%、2.9%;旱急转涝事件频发于重庆市西部、中部及东北部区域,发生频次的变化趋势不显著;涝急转旱事件主要发生在7—9月,多年平均次数为5.60站次,轻度、中度事件占所有涝急转旱事件的92.9%、7.1%;涝急转旱事件在重庆市东南部、中部以及东北部区域的西部地区(如开县)频发,频发地区的发生频次总体呈增加的趋势。研究成果可为保障重庆市及相关地区水安全、加强防旱抗涝减灾工作提供理论基础。