基于Copula 函数的边坡可靠度高效分析方法

将Copula函数与高效蒙特卡洛方法结合,提出了含相关随机变量的边坡可靠度高效分析方法。以两个岩质边坡稳定性问题为例验证了所提方法的有效性。结果表明,该方法相比于直接蒙特卡洛方法在保证边坡失效概率的准确性的同时计算效率更高。Copula函数可以构造出具有不同相关结构的岩土体参数的联合概率分布,与高效蒙特卡洛方法(即蒙特卡洛重要抽样方法和子集模拟)结合能高效地处理含多种相关随机变量的边坡可靠度计算问题,相比于现行的Nataf变换方法结果更能体现岩土边坡真实稳定性。此外,该方法也能高效地计算含有复杂的隐式功能函数的边坡可靠度,研究成果拓展了高效蒙特卡洛方法在边坡可靠度分析中的应用。     

吕梁山地区植被物候变化及对气候的响应

吕梁山地区地形垂直差异明显,植被对气候变化反应敏感,研究吕梁山地区植被物候变化,探索植被物候变化与气候的响应关系,旨在为高海拔山区植被物候研究和生态治理提供借鉴。基于2000—2015年MODIS NDVI时间序列数据,通过动态阈值法提取吕梁山地区的植被物候,对气温、降水进行空间插值,并对植被2个关键物候期与气候因素进行偏相关分析。结果表明：（1）植被生长季开始日期(the start of the growing season,SOS)提前的区域约占85.7%,其中16.2%显著提前;植被生长季结束日期(the end of the growing season,EOS)推迟的区域约占90.6%,其中33.3%显著推迟。（2）区内74.8%、87.7%植被SOS分别与气温、降水呈负相关,气温升高或降水增加,植被SOS提前。植被SOS在高海拔山区受4月气温影响显著,而低海拔地区受4月降水影响显著。（3）区内72.6%、65.1%植被EOS分别与气温、降水呈正相关,气温升高或降水增加,植被EOS推迟。植被EOS在北部和西部地区受11月气温影响显著,而高海拔地区受9月降水影响显著。2000—2015年吕梁山地区植被物候发生显著变化,各地区对气温、降水的响应不同,研究结果可为区域物候、气候变化研究和陆地生态治理提供科学依据。     

Effects of Altitude Change on Nutritional Quality and Elymus nutans Regularity in Qinghai-Tibet Plateau

In order to reveal the effects of different altitudes on the nutritional quality of wild forage in Qinghai-Tibet Plateau,this study used Elymus nutans as the tested plants to evaluate the changes of nutrient contents and the correlation between the nutrient contents and altitudes.Four sampling sites were set up at altitudes of 2 562,2 660,2 775 and 2 905 m with the vertical distance among each sampling point was about 100 m.The results showed that the crude protein,ash and phosphorus contents of Elymus nutans decreased significantly with an increase in altitudes.The crude protein contents decreased by 1.87 % with each 100 m increase in altitudes.The variation rule of crude protein contents with altitudes in the simulated curve was "y=–0.0187x+63.244 (R~2=0.9557)".The crude ash contents decreased by 1.77% with each 100 m increase in altitudes.The variation rule of crude ash contents with altitudes in the simulated curve was "y=–0.0177x+56.144 (R~2=0.978)".Neutral detergent fiber (NDF) and acid detergent fiber (ADF) showed an overall increasing trend with the increase of altitudes,but the most obvious increase was at 2 775 m.The contents of crude fat and Ca did not change regularly with altitudes.     

Characterizing Spatial Variability of Soil Textural Fractions and Fractal Parameters Derived from Particle Size Distributions

Soil particle size distribution (PSD) is a fundamental physical property affecting other soil properties. Characterizing spatial variability of soil texture is very important in environmental research. The objectives of this work were: 1) to partition PSD of 75 soil samples, collected from a flat field in the University of Guilan, Iran, into two scaling domains using a piecewise fractal model to evaluate the relationships between fractal dimensions of scaling domains and soil clay, silt, and sand fractions and 2) to assess the potential of fractal parameters as an index used in a geostatistical approach reflecting the spatial variability of soil texture. Features of PSD of soil samples were studied using fractal geometry, and geostatistical techniques were used to characterize the spatial variability of fractal and soil textural parameters. There were two scaling domains for the PSD of soil samples. The fractal dimensions of these two scaling domains (D₁ and D₂) were then used to characterize different ranges of soil particle sizes and their relationships to the soil textural parameters. There was a positive correlation between D₁ and clay content (R² = 0.924), a negative correlation between D₁ and silt content (R² = 0.801), and a negative correlation between D₂ and sand content (R² = 0.913). The geometric mean diameter of soil particles had a negative correlation with D₁ (R² = 0.569) and D₂ (R² = 0.682). Semivariograms of fractal dimensions and soil textural parameters were calculated and the maps of spatial variation of D₁ and D₂ and soil PSD parameters were provided using ordinary kriging. The results showed that there were also spatial correlations between D₁ and D₂ and particle size fractions. According to the semivariogram models and validation parameters, the fractal parameters had powerful spatial structure and could better describe the spatial variability of soil texture.     

基于距离相关系数和KNN回归模型的森林蓄积量估测研究

【目的】探究Landsat8 OLI数据和KNN算法在森林蓄积量估测中的潜力。【方法】以湖南省湘潭县为研究区,采用Landsat8 OLI数据和同时期的二类调查数据,通过距离相关系数筛选特征,分别采用线性回归模型(MLR)、K-近邻模型(KNN)、距离加权KNN模型(DW-KNN)和优化欧式KNN模型(FW-KNN)对森林蓄积量进行估测。使用十折交叉方法进行精度检验,对检验结果进行对比分析。【结果】3种KNN模型的估测结果均高于传统的线性模型,并且在3种KNN模型中,FW-KNN算法效果最好,决定系数达到0.69,为3种模型中最高;3种KNN模型中,本研究优化欧氏距离KNN模型的估测精度最高,其均方根误差为30.3%,相比于传统KNN模型的均方根误差降低了5.1%,相比于DW-KNN模型降低了3.3%。【结论】采用DW-KNN蓄积量估测结果明显优于其他两种模型,说明通过特征与蓄积量的相关性优化样本间的距离是一种可行的KNN优化方法。     

称重式降水传感器与翻斗雨量传感器测雨性能对比分析

为了观测降水数据的准确性,选取了南通市4个台站2018年4月—10月份的DCS1型称重式降水传感器和SL3-1型翻斗雨量传感器观测的降水数据,分析两者观测的日降水量和降水总量等方面的差异。结果显示：在选取的观测样本中,以人工观测的降雨日数为参考,称重传感器的平均一致率为91.2%;以翻斗传感器观测的降雨日为参考,称重传感器的一致率为94.5%。称重传感器观测的累积降水量与翻斗传感器观测的累积降水量相对平均误差为-1.55%,符合中国气象局规定的相对误差不超过±4%的规范要求。在分析日降水量方面,发现称重传感器比翻斗传感器观测量平均偏小0.29 mm;有明显性降水时,两者在日降水量等级判别上基本一致。称重传感器观测的数据小于翻斗传感器观测的数据概率要高,两种传感器观测的差值分布较为一致。称重传感器在捕捉微量降水的能力不比翻斗传感器差,甚至更好。称重传感器观测的日降水量与翻斗传感器观测的日降水量相关系数为0.99826,达到0.01显著相关的水平。     

自适应最大相关峭度反褶积方法诊断齿轮轴承复合故障

为了解决传统最大相关峭度反褶积(maximum correlated kurtosis deconvolution,MCKD)在故障诊断中容易出现因参数选择不当而影响诊断效果的问题,该文提出了一种基于量子遗传算法(quantum genetic algorithm,QGA)的自适应最大相关峭度反褶积方法(maximum correlated kurtosis deconvolution with quantum genetic algorithm,QMCKD)用于齿轮和轴承复合故障诊断。通过量子遗传算法自适应选择最大相关峭度反褶积的2个关键参数滤波器长度(L)和反褶积周期(T)。使用QMCKD处理原始振动信号,提取复合故障信号中的所有单个故障信号,分别对单个故障信号进行频谱分析从而识别故障特征。在对齿面磨损-滚动轴承外圈损伤复合故障诊断中,QMCKD能够识别齿轮故障频率及其2～4倍频,识别轴承故障频率及其2～6倍频,且主要频率成分周围干扰谱线很少,故障类型容易识别。与直接频谱分析和变分模态分解(variational mode decomposition,VMD)相比,该方法在诊断效果上具有优越性。在对齿根裂纹-轴承滚动体损伤复合故障诊断中,QMCKD能够突出齿轮故障频率及其2～5倍频,突出轴承故障频率及其2～8倍频,齿轮和轴承故障特征明显,验证了方法的稳定性。试验结果表明QMCKD能够有效识别复合故障中齿轮和轴承的故障特征,可用于齿轮箱的齿轮、轴承复合故障诊断。     

Correlation Research of the Serological Test (HI) and Challenge Test of Duck Tembusu Virus Inactivated Vaccine

【Objective】The objective of this paper was to evaluate the correlation of the serological test (HI) and challenge test of duck Tembusu virus inactivated vaccine.【Method】Three batches of vaccines ( laboratory trial products) were used to immunize the 51-day-old young ducks and 260-day-old laying ducks by intramuscular injection in 0.15, 0.3, 0.5 and 1.0 mL, respectively. Secondary immunization was proceeded in the same doses and route at 14 day after primary immunization. Ducks were regrouped according to the HI titer and challenged with 0.5 mL (100 DID₅₀) DTMUV at day 28 after secondary immunization. Serum samples were collected at 2 days later for virus isolation and laying ducks were dissected at 8 days later to observe the ovarian lesions. All the results were counted to evaluate the immune potency of vaccines. The correlation of HI titer and immune protection rate was analyzed.【Result】The protection rate of immunized young ducks with HI titer of 1:5 or lower, 1:10, 1:20, 1:40, 1:80, 1:160, 1:320, 1:640 was 50% (20/40), 43.8% (7/16), 74.3% (26/35), 86.7% (26/30), 96.6% (57/59), 92.7% (51/55), 95% (38/40) and 100% (11/11), respectively. The protection rate was 48.2% with HI titer lower than 1:20, while the rate was 74.3% with HI titer of 1:20 and 93.8% with HI titer of 1:40 or greater. In laying ducks, the protection rate of flocks with HI titer of 1:5 or lower, 1:20, 1:40 and 1:80 was 66.7% (12/18), 83.3% (10/12), 95.2% (20/21) and 100% (15/15), respectively. The protected proportion of ducks with HI titer of 1:10, 1:160, 1:320 and 1:640 was 2/3, 7/7, 1/1 and 2/2, respectively. The protection rate was 66.7% with HI titer of 1:10 or below, while the rate was 83.3% with HI titer of 1:20 and 97.8% with HI titer of 1:40 or greater. There were significant positive correlations between the HI titer and the immune protection rate both in young ducks and laying ducks. The Spearman’s correlation coefficient was 0.905 (P<0.01) and 0.932 (P<0.01), respectively. 【Conclusion】There were positive correlations between the HI titer and the immune protection rate of duck Tembusu virus inactivated vaccine (strain HB). The HI detection could be used to evaluate the efficacy of duck Tembusu virus inactivated vaccine (strain HB) instead of challenge test. The HI titer of 1:20 could be defined as the criteria of protection for the duck Tembusu virus inactivated vaccine after immunization.     

不同地区楼葱栽培种的性状与品质分析

为了研究不同地区楼葱的特性,试验对我国不同地区12个楼葱栽培种的数量性状和品质性状进行了测定分析。14个数量性状的相关分析结果显示,主成分分析数量指标后,单株质量、株高、假茎质量、花葶高、叶形指数和假茎指数影响分类;相关性分析说明主要数量指标间具有极显著相关性(P<0.01)。聚类分析后,遗传距离为3.1时可将楼葱种质根据所得主要数量性状分为4个类群。测定不同地区楼葱6个品质指标后,相关性分析结果表明,紧实度与蛋白质含量、干物质率、香辛油含量、总糖含量、游离氨基酸总量存在着极显著正相关或相关性,主成分分析表明主成分反映了89.99%的原有信息量,楼葱的干物质率与紧实度为主要成分;应用灰色关联度分析了品质与数量性状的关系,假茎直径、出叶孔间距、单株质量这3个数量性状对楼葱品质的影响居前3位。研究表明楼葱种质材料具有极其丰富的遗传多样性,宁夏同心2个地区黄水桥HSQ、石羊圈SYJ的楼葱种质距其他种质资源间亲缘关系最远且干物质率含量及紧实度最高。     

刈割次数对苜蓿相关表型性状与饲草产量的影响

试验选取4份苜蓿材料,设4次刈割处理,观察测试表型性状及干物质的变化动态,并用DPS7.05数据处理系统对各性状指标与饲草产量的关系进行计算分析,以探讨刈割次数对苜蓿表型性状及饲草产量的影响,为高效优质生产提供依据。结果表明,刈割频度显著影响苜蓿越冬率(P<0.05),苜蓿株高、茎粗、茎叶比、分枝数等指标均随刈割次数增加呈明显降低趋势,其中WL525苜蓿首次刈割与其他3次刈割时的株高、茎粗均呈现显著性差异(P<0.05),茎叶比差异性不显著(P>0.05);而苜蓿饲草产量则随刈割次数增多而增加,与刈割1次的情况相比,WL525苜蓿刈割4次后产量增量最多,达1885kg/hm₂;4次刈割后试验材料饲草总产量从高到底的次序依次为WL525>WL903>赛迪>惊喜。全部材料中与饲草产量关联度最大的指标为株高和茎粗,其中株高与惊喜苜蓿饲草产量的关联系数最大,达0.3751;茎粗与WL525苜蓿、WL903苜蓿饲草产量的关联系数最大,分别为0.2854、0.1944。