基于CERES-Maize模型的玉米水分关键期干旱指数天气保险:以陕西长武为例

水分关键期干旱是影响玉米生长和产量的主要限制因子,构建此时期玉米干旱损失模型,研究干旱指数天气保险,对于合理设计天气指数保险和解决目前传统农业保险的困境,转移农业气象灾害风险具有重要意义。针对作物特定阶段单因子气象灾害影响难以剥离的问题,本研究在西北农林科技大学旱作农业长武试验站进行了连续3a的雨养玉米观测试验,利用田间试验数据(玉米生长发育数据、气象数据、土壤数据和田间管理数据)对CERES-Maize模型进行参数校正和验证,模拟玉米水分关键期(6月21日-8月31日)干旱对生长和产量的影响,构建干旱损失模型;依据长武1990-2019年的气象数据,利用EasyFit软件筛选出玉米水分关键期干旱指数最优分布模型,模拟干旱发生概率;结合干旱损失模型,利用纯费率精算方法厘定玉米水分关键期干旱指数保险费率;采用投影寻踪的统计方法,设计干旱指数保险赔付方案。结果表明,CERES-Maize模型校正和验证的平均绝对相对误差ARE和相对均方根误差RRMSE都小于10%,符合作物模型模拟精度的要求;模拟的干旱指数(DI)与玉米减产率(y,%)间呈显著的线性函数关系,即y=-0.55DI+107.17;Log-logistic模型对干旱指数分布的拟合精度最高,Anderson-Darling(AD)检验值仅为0.20,轻旱、中旱、重旱和特旱发生的概率分别为9.75%、5.90%、3.71%和3.50%。基于Log-logistic模型厘定的玉米水分关键期干旱指数保险费率为5.6%。在玉米生长水分关键期,干旱指数保险的起赔点为DI=185,DI≤185时,进行分级赔付。

深海海底反射会聚区声传播特性

在深海声道条件下,海水折射效应会使得声场出现会聚效应;在不完全声道条件下,深海海底对声场具有重要影响.利用在中国南海海域收集到的一次深海声传播实验数据,研究了深海不完全声道环境下的海底反射对声传播的影响.实验观测到不同于深海会聚区的海底反射会聚现象,在直达声区范围内的海底地形隆起可导致海底反射会聚区提前形成,并使得部分影区的声强明显提高.由于不平坦海底和海面的反射破坏了完全声道环境下的会聚区结构,在60 km范围内存在两个海底反射会聚区,会聚区增益可达10 dB以上,同时在11 km附近的影区和51 km附近形成高声强区域.当接收深度与声源深度相同时,第二会聚区的增益高于第一会聚区.在第一会聚区内,随着接收深度的增加,声线到达结构趋于复杂,多途效应更加明显.使用抛物方程数值分析结合射线理论对深海海底反射会聚区现象产生的物理原因进行了分析解释.研究结果对于声纳在深海复杂环境下的性能分析具有重要的指导意义.

源于陕A群、陕B群玉米自交系在不同密度条件下配合力分析

采用NC-II遗传设计,以郑58、昌7-2为测验种,与17份高密度条件下筛选的玉米自交系组配成34份杂交组合,2014—2015年分别于陕西杨凌、长武、榆林进行3种密度(45 000、67 500和90 000株hm–2)配合力分析试验。采用PROC VARCOMP分析不同密度条件下产量及耐密性相关性状的遗传效应,采用频率直方分布图研究不同密度条件下产量及耐密性相关性状一般配合力(GCA)平均数的变化规律,利用AMMI评价玉米自交系与杂交组合的稳定性。结果表明,产量、倒伏率、茎秆强度主要受加性遗传效应控制,空秆率主要受非加性遗传效应控制。加性遗传效应对产量及耐密性相关性状的贡献率随种植密度的增加呈上升趋势。玉米自交系产量、空秆率、倒伏率、茎秆强度的一般配合力频率均属于正态分布,随着种植密度的增加,产量GCA的平均值提高了0.28,空秆率GCA平均值降低了0.21,倒伏率GCA平均值降低了0.03,茎秆强度GCA平均值增加了0.02。玉米杂交组合产量与玉米自交系产量GCA密切相关(r=0.877**,r=0.811**,r=0.672**)。随着种植密度的增加,表现稳定的玉米自交系及杂交组合的数量呈上升趋势。因此,强化逆境选择压力,实施高密度选择策略,是增强玉米自交系耐密性和抗倒性,提升一般配合力,实现产量增益的有效措施。

基于动态负荷的柔性直流配电网功率控制仿真

柔性直流配电网连接有多种不同类型的负荷和电源,其中储能系统的充电行为容易在短时间内集中发生,从而导致电网负荷的快速增加,难以控制其功率波动。为此,提出考虑动态负荷的柔性直流配电网功率波动控制。计算风电场和储能系统整体出力,根据风电出力波动改进储能系统充放电策略,获取充放电量,基于双层模糊控制器,管理改进的储能系统充放电策略,同时计算储能系统的输出功率,通过获得的储能系统输出功率计算负荷率变化量,实现柔性直流配电网的功率波动控制,通过考虑电网负荷的波动,从而减少功率波动对电网稳定性的影响。实验结果表明,所提方法的柔性直流配电网功率波动控制效果更好、且更适合实际应用。

Natural and human-induced changes in summer climate over the East Asian monsoon region in the last half century: A review

In the last half century,a significant warming trend occurred in summer over eastern China in the East Asian monsoon region.However,there were no consistent trends with respect to the intensity of the East Asian summer monsoon(EASM) or the amount of summer rainfall averaged over eastern China.Both of the EASM and summer rainfall exhibited clear decadal variations.Obvious decadal shifts of EASM occurred around the mid- and late 1970 s,the late 1980 s and the early 1990 s,and the late 1990 s and early 2000 s,respectively.Summer rainfall over eastern China exhibited a change in spatial distribution in the decadal timescale,in response to the decadal shifts of EASM.From the mid- and late 1970 s to the late 1980 s and the early 1990 s,there was a meridional tri-polar rainfall distribution anomaly with more rainfall over the Yangtze River valley and less rainfall in North and South China; but in the period from the early 1990 s to the late 1990 s and the early 2000 s the tri-polar distribution changed to a dipolar one,with more rainfall appearing over southern China south to the Yangtze River valley and less rainfall in North China.However,from the early 2000 s to the late 2000 s,the Yangtze River valley received less rainfall.The decadal changes in EASM and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover,Arctic sea ice,sea surface temperatures in tropical Pacific and Indian Ocean,oceaneatmospheric coupled systems of the Pacific Decadal Oscillation(PDO) and AsianePacific Oscillation(APO),and uneven thermal forcing over the Asian continent.Up to now,the roles of anthropogenic factors,such as greenhouse gases,aerosols,and land usage/cover changes,on existing decadal variations of EASM and summer rainfall in this region remain uncertain.

ECHAM5-Simulated Impacts of Two Types of El Nio on the Winter Precipitation Anomalies in South China

The authors used an atmospheric general circulation model （AGCM） of European Centre Hamburg Model （ECHAM5.4） and investigated the possible impacts of eastern Pacific （EP） and central Pacific （CP） El Ni（n）o on the winter precipitation anomalies in South China.A composite analysis suggested much more rainfall during the mature phase of EP El Ni（n）o than in the case of CP El Ni（n）o,and their corresponding observed wet centers to be located in the southeast coast and the region to the south of the Yangtze River,respectively.Results obtained on the basis of model-sensitive run imply that the modelsimulated rainfall anomalies agree well with the observation,and the magnitude of simulated rainfall anomalies were found to be reduced when the amplitude of sea surface temperature anomaly （SSTA） forcing of EP and CP El Ni（n）o was cut down.These results imply that the rainfall anomaly in South China is very sensitive not only to the type of El Ni（n）o but also to its intensity.

Applications of Waveguide Invariant Theory to the Analysis of Interference Phenomena in Deep Water

The waveguide invariant,denoted asβ,can be used to describe the slope of the intensity of a broadband acoustic signal.In deep water,the interference patterns of the areas with dominant waterborne modes and only with bottom bounce modes are greatly different.This phenomenon is illustrated by simulation and explained by the distribution ofβ.The theory shows that in the convergence zone,βapproaches infinity,which leads to the larger slope of sound intensity;on the contrary,in the shadow zone,βis close to 1,leading to smaller slopes.

The effect of amylose on kernel phenotypic characteristics,starch-related gene expression and amylose inheritance in naturally mutated high-amylose maize

High-amylose maize starch has great pote ntial for widespread in dustrial use due to its ability to form strong gels and film and in the food processi ng field,thus servi ng as a resista nt starch source.However,there is still a substa ntial shortage of high-amylose maize due to the limitation of natural germplasm resources,although the well-known amylose extender(ae)gene mutants have bee n found to produce high-amylose maize lines since 1948.In this con text,high-amylose maize lines(13 inbreds and 18 hybrids)originating from a natural amylose mutant in our testing field were utilized to study the correlation between amylose content(AC)and phenotypic traits(kernel morphology and endosperm glossiness),grain filling characteristics,gene expression,and amylose inheritanee.Our results showed that AC was negatively correlated with total starch con tent but was not correlated with grain phe no types,such as kernel full ness,kernel morphology and endosperm glossiness.Maize lines with higher amylose had a greater grain filling rate than that of the controI(B73)during the first 20 days after pollination(DAP).Both starch debranching enzyme(DBE)groups and starch branching enzyme lib(SBEIIb)groups showed a greater abundance in the control(B73)than in the high-amylose maize lines.Male parents directly predicted AC of Fv which was moderately positively correlated with the F2 generation.

A Novel Nonlinear Optimization Method of Inversion for Sea-Bottom Properties

A nonlinear optimization method is proposed to inverse the sea-bottom properties.The method is called seed division algorithm(SDA)and can be used to solve global optimization problem.A numerical test is carried out to inverse the sea-bottom properties.The test is based on SDA and beam displacement ray mode theory.

Three-Dimensional Sound Propagation and Scattering in Two-Dimensional Waveguides

A coupled-mode method for three-dimensional acoustic propagation and scattering in two-dimensional waveguides is presented.This method synthesizes the three-dimensional field solution by using Fourier transform techniques based on a sequence of two-dimensional problems,each of which is solved by a numerical model recently developed by Luo et al.[Chin.Phys.Lett.29(2012)014302].Numerical results indicate that the present model is remarkably accurate,and thus can serve as benchmark against other numerical models.In addition,this model can be applied to realistic problems,and can also be used to analyze horizontal refraction in some range-dependent waveguides in reality,such as the continental shelf environment,ridge-like bathymetry,and underwater trenches.

Numerical Solution of Range-Dependent Acoustic Propagation

The direct global matrix approach can be applied to modeling of range-dependent sound propagation in order to achieve numerically stable and accurate solutions.By solving the global system directly,this method features high efficiency as well as accuracy by avoiding error accumulation.It is an important issue to solve linear systems numerically in the direct global matrix approach,especially for the large-scale problems.An efficient and memory-saving algorithm is developed for solving the global system,in which the global coefficient matrix is treated as a block pentadiagonal matrix.As a result,this numerical model has the ability to solve large-scale problems on regular computers.Numerical examples are also presented to demonstrate the accuracy and efficiency of this method.

Matched Field Source Localization via Environmental Focalization

In a realistic application of matched field processing for source localization,the ability to localize an acoustic source is strongly affected by the uncertainty of the environment.However,accurate environment measurement is a difficult task in large regions of the ocean.We employ a Bayesian approach,referred to here as focalization,to overcome the mismatch by including the environment in the parameter search space.Focalization maximizes the posterior probability density over the unknown source and environmental parameters.The broadband signals recorded by a vertical line array in a Yellow Sea experiment are presented to demonstrate the feasibility of focalization.

Bubble Pulse Cancelation in the Time-Frequency Domain Using Warping Operators

The received shock waves produced by explosive charges are often polluted by bubble pulses in underwater acoustic experiments.A method based on warping operators is proposed to cancel the bubble pulses in the time-frequency domain.This is applied to the explosive data collected during the Yellow Sea experiment in November 2000.The original received signal is first transformed into a warped signal by warping operators.Then,the warped signal is analyzed in the time-frequency domain.Due to the different features between the shock waves and the bubble pulses in the time-frequency domain for the warped signal,the bubble pulses can be easily filtered out.Furthermore,the shock waves in the original time domain can be retrieved by the inverse warping transformation.The autocorrelation functions and the time-frequency representation show that the bubble pulses can be canceled effectively.

Sound Propagation in a Wedge with a Rigid Bottom

Sound propagation in a wedge with perfectly reflecting boundaries is one of the few range-dependent problems with an analytical solution.Since sound propagation towards the wedge apex will be completely backscattered due to the perfectly reflecting boundaries,this test problem is an ideal benchmark for a full two-way solution to the wave equation.An analytical solution for sound propagation in a wedge with a pressure-release sea surface and a pressure-release bottom was presented by Buckingham et al.[J.Acoust.Soc.Am.87(1990)1511].The ideal wedge problem with a rigid bottom is also of great importance in underwater acoustics.We present an analytical solution to the problem with a wedge bounded above by a pressure-release sea surface and below by a rigid bottom,which may be used to provide informative means of investigating the sound field in depth-varying channels,and to establish the accuracy of numerical propagation models for which it is difficult to treat problems with a pressure-release bottom.A comparison of the analytical solution and the numerical solution recently proposed by Luo et al.[Chin.Phys.Lett.29(2012)014302]is also presented,indicating that this numerical propagation model provides high accuracy.

Generalized Coupled-Mode Formulation for Sound Propagation in Range-Dependent Waveguides

An accurate and numerically stable method based on the coupled-mode theory is presented.By applying the direct global matrix approach to obtain the modal expansion coefficients,this method is numerically stable.In addition,appropriately normalized range solutions are introduced,which resolves the overflow problem entirely.Furthermore,we put forward source conditions appropriate for the line-source problem in plane geometry.As a result,this method is capable of dealing with the scenario where a line source is located inside the region of a deformation.Closed-form expressions for coupling matrices are provided for ideal waveguides.Numerical results indicate that the present method is accurate and numerically stable.Consequently,this model can serve as a benchmark in range-dependent propagation modeling.

配电网设备运行维护及可靠性管理研究

伴随着我国社会经济的飞速发展,能源需求总量连年攀升,电力供应已成为影响国家战略安全的重要因素。在此背景下,为保证社会生产生活稳定,我国电力企业正逐步加大配电网体系建设与设备升级工作,配电网运行可靠性得到很大改善,但面对日益增长的供电需求,对配电网供电可靠性形成巨大冲击。文章针对加强配电网设备运行、检修及可靠性管理工作进行分析与探讨,希望借此可对供电可靠率保障工作提供一定借鉴价值。

供配电运行和检修的安全管理分析

根据实际使用场景的危险性,国家有关部门将电气作业列为特种作业的组成内容。电气作业由于涉及到对高压电力资源的一线操作,其自身就带有较强的危险性,除此之外,这项工作内容又直接关系着民生工程,影响着广大人民群众的用电需求和用电稳定性,因此对供配电运行和检修环节加强安全管理有着重要的工作意义。以供配电运行和检修安全管理为主要研究内容,重点探讨加强安全管理的具体措施,分析开展这项工作的实际意义,简要总结当前工作现状和存在的主要问题,最后提出多条有针对性地解决措施。

陕西春玉米子粒含水率与机械粒收质量的关系分析

选择陕西灌溉春玉米区主栽品种12个,2016~2017年在陕西榆林玉米试验站用约翰迪尔收割机子粒机收,调查分析玉米粒收质量指标与子粒水分的关系。结果表明,机收质量指标品种间差异较大,变异系数在23.52%~109.8%;收获时子粒水分平均26.01%,杂质率1.02%,破碎率7.44%,田间产量损失率3.21%。机械粒收玉米破碎率、田间产量损失率与子粒水分均呈显著正相关。当子粒含水率低于25.4%时,破碎率和损失率分别低于8%和3%,符合国标要求,满足机械粒收质量要求。子粒破碎率高是影响陕西灌溉春玉米区机械粒收的关键质量问题,子粒含水率是影响机械粒收质量的主控因素。通过选择子粒脱水快和含水率低品种、合理安排收获时间能够保证陕西春玉米区机械粒收质量。

密植条件下不同玉米品种产量及子粒营养品质相关性状研究

试验以陕单609、榆玉3号、先玉335、郑单958、秋润100、陕单636为供试品种,在67 500株/hm2和82 500株/hm2两种种植密度下,研究增密对不同玉米品种子粒产量和营养品质的影响。结果表明,随着密度的增加,子粒产量、收获穗数、群体干重和LAI显著增加,穗粒数、百粒重和子粒蛋白质含量呈下降趋势,淀粉含量和粗脂肪含量不同品种间呈现不规律变化。密植条件下,品种间子粒产量差异更为明显,陕单609、先玉335和榆玉3号的产量显著高于其他品种,分别较郑单958增产1.98%、11.26%和2.37%。陕单636增密后影响产量的主要因素是粒重,先玉335和郑单958增密后影响产量的主要因素是穗粒数,陕单609、榆玉3号和秋润100增密后影响产量的因素是穗粒数和粒重。因此,选择优良品种,适当增加玉米种植密度,加强田间管理,保证穗粒数和粒重稳定,是实现玉米密植高产优质的重要途径。

玉米冠层结构和群体光合特性对增密的响应

2018~2019年以陕科9号和大丰30为材料,设置4个密度4.5万、6.0万、7.5万和9.0万株/hm^2进行田间试验,分析玉米冠层结构、光合性能以及产量构成指标,研究种植密度对玉米群体特征及产量的影响,确定陕北灌区玉米适宜种植密度。结果表明,两个品种子粒产量随密度增大呈先增加后降低的趋势,均在密度7.5万株/hm^2时产量最高,两年平均产量分别为14.1 t/hm^2和13.2 t/hm^2。随种植密度增大单位面积穗数显著增加,穗粒数和百粒重减少。随着密度的增加,两个品种能够调节穗上中部叶倾角、株型变紧凑,穗位层接收到更多的光能,增加了群体光合速率,积累更多光合同化物,高密度条件下陕科9号协调形态结构和生理功能方面优于大丰30。适当增加密度配合耐密品种是陕北灌区春玉米增产的重要途径,密度7.5万株/hm^2是该区玉米适宜种植密度。