基于最小数据集的黄淮海旱作区耕层土壤质量评价及障碍分析

为探究黄淮海旱作区耕层土壤质量特征,基于土壤物理、化学及剖面特征,建立黄淮海旱作区耕层土壤质量评价指标体系,运用主成分分析法构建耕层质量评价指标的最小数据集(minimum data set,MDS),结合障碍因子诊断模型揭示黄淮海旱作区耕层土壤质量特征及其障碍因素。结果表明:1)研究区耕层土壤质量评价最小数据集由土壤有机质、土壤阳离子交换量、土壤pH、耕作层厚度、耕作层穿透阻力和耕作层压实度构成,基于最小数据集和全指标数据集的耕层土壤质量指数间显著正相关(R2=0.61,P<0.05),Nash有效系数和相对偏差系数分别为0.601和0.181,表明最小数据集的指标能够代替全部数据集指标对黄淮海旱作区耕层质量进行评价;2)研究区耕层土壤质量总体处于中等水平,质量指数为0.25~0.61;适宜耕层各项指标如下:耕作层厚度不小于17.20 cm,耕作层穿透阻力不大于896.10 kPa,耕作层土壤压实度不大于78.01%,pH值为8.01~9.37,有机质不小于17.87 g/kg,阳离子交换量不小于21.13 cmol/kg;3)黄淮海旱作区存在明显的障碍类型,耕层障碍可分为薄化紧实与养分贫瘠障碍耕层、养分贫瘠耕层、土壤紧实型耕层3类。其中有机质含量低、阳离子交换量低、耕作层压实度过高是黄淮海旱作区耕层质量主要障碍。研究为黄淮海旱作区耕层土壤质量提升和改善提供理论支撑。

Trajectory tracking control of characteristic model for nonplanar hex-rotor UAV

The nonplanar hex-rotor unmanned aerial vehicle(UAV)has much higher driving property,greater payload capacity and damage tolerance than quad-rotor UAV.It is difficult to design a highperformance controller of easy engineering implementation for strongly coupled nonlinear hex-rotorUAV system.In response to this practical problem,an adaptive trajectory tracking control based oncharacteristic model for nonplanar hex-rotor is studied.Firstly,the dynamic model for the hex-rotorUAV is devised.Secondly,according to dynamic characteristics,environmental characteristics andcontrol performance requirements,the characteristic model of the hex-rotor UAV is constructed.Then,based on the characteristic model,a golden section adaptive controller is designed to realizetrajectory tracking.Furthermore,the stability analysis of the closed loop hex-rotor system is given.Finally,the validity of the proposed trajectory tracking control method adopted in the nonplanar hex-rotor UAV is demonstrated via numerical simulations and hex-rotor prototype experiments.

分段的波浪整体物理模型试验方法研究

针对既有水池受比尺限制,无法对较大港区进行波浪整体物理模型试验的问题,本文介绍了一种分段的波浪整体物理模型试验的方法,将模拟区域划分为内外两个模型,在内外模型搭接区域进行波浪谱分析,确定内模型的边界条件,从而实现对整个港区的模拟,此方法可为类似工程提供参考。

某海水浴场海岸侵蚀及整治方案研究

某海水浴场受周边工程影响近年发生海岸侵蚀,沙滩流失。本文首先分析了其侵蚀原因,有针对性地提出多个整治方案,采用波浪数学模型进行比选分析,提出推荐方案,并对推荐方案进行泥沙物理模型试验。最后对各方案的整治效果进行比较,可为类似工程提供参考。

乘潮水位在某陆岛交通码头的应用

本文结合某旅游项目,对乘潮历时和累积频率进行了计算,明确了乘潮水位计算三要素的关系,计算结果可为设计工作提供技术支持,同时期望同行能更深入地理解乘潮水位的概念。

星载合成孔径雷达电子侦察技术研究

文中首先阐述了对星载合成孔径雷达进行电子侦察的必要性,建立了星载合成孔径雷达的电子侦察信号模型;其次,梳理了现有的工作参数估计方法,并就线性调频信号参数估计方法,选取短时傅里叶变换、Wigner-Ville分布、小波变换和分数阶傅里叶变换方法,在估计精度和交叉项抑制能力等方面进行了仿真分析对比,并对其优缺点进行了整理;然后,在工作模式判别方面介绍了基于侦收功率的判别方法和智能化判别方法;最后,合理分析了合成孔径雷达电子侦察技术的未来发展方向。

Backstepping sliding mode control with self recurrent wavelet neural network observer for a novel coaxial twelve-rotor UAV

The robust attitude control for a novel coaxial twelve-rotor UAV which has much greater payload capacity,higher drive capability and damage tolerance than a quad-rotor UAV is studied. Firstly,a dynamical and kinematical model for the coaxial twelve-rotor UAV is designed. Considering model uncertainties and external disturbances,a robust backstepping sliding mode control( BSMC) with self recurrent wavelet neural network( SRWNN) method is proposed as the attitude controller for the coaxial twelve-rotor. A combinative algorithm of backstepping control and sliding mode control has simplified design procedures with much stronger robustness benefiting from advantages of both controllers. SRWNN as the uncertainty observer is able to estimate the lumped uncertainties effectively.Then the uniformly ultimate stability of the twelve-rotor system is proved by Lyapunov stability theorem. Finally,the validity of the proposed robust control method adopted in the twelve-rotor UAV under model uncertainties and external disturbances are demonstrated via numerical simulations and twelve-rotor prototype experiments.

Trajectory tracking control based on linear active disturbance rejection controller for 6-DOF robot manipulator

The trajectory tracking control for a 6-DOF robot manipulator with multiple inputs and outputs,non-linearity and strong coupling is studied.Firstly,a dynamical model for the 6-DOF robot manipulator is designed.From the view point of practical engineering,considering the model uncertainties and external disturbances,the robot manipulator is divided into 6 independent joint subsystems,and a linear active disturbance rejection controller(LADRC)is developed to track trajectory for each subsystem respectively.LADRC has few parameters that are easy to be adjusted in engineering.Linear expansion state observer(LESO)as the uncertainty observer is able to estimate the general uncertainties effectively.Eventually,the validity and robustness of the proposed method adopted in 6-DOF robot manipulator are demonstrated via numerical simulations and 6-DOF robot manipulator experiments,which is of practical value in engineering application.

杭锦旗黄河南岸灌区土壤质量指数计算方法比较研究

为研究土壤质量评价过程中不同质量指数计算方法的差异与最优组合,采集并测定了内蒙古杭锦旗黄河南岸灌区79个土壤样本的11项理化指标,并基于主成分分析法构建最小数据集,对比分析了主成分分析法和层次分析法2种权重确定方法与隶属度函数、线性评分函数和非线性评分函数3种指标评分方法组合下计算的土壤质量指数,最后通过与全体数据集的自相关精度检验获取最优方法组合。结果表明:1)层次分析法确定的物理指标权重高于主成分分析法,速效养分指标权重低于主成分分析法,隶属度函数、线性评分函数、非线性评分函数对指标分值计算结果的分布趋势基本保持一致,但隶属度函数对物理指标进行评分时具有更高的区分度;2)采用层次分析法确定指标权重,隶属度函数确定指标分值计算的最小数据集土壤质量指数的自相关检验精度最高(R^(2)=0.85),纳什效率系数为0.81,相对偏差系数为0.04;3)最优方法组合下全体数据集和最小数据集的土壤质量指数变化分别是0.25~0.71和0.16~0.78,平均值为0.43和0.45,表明研究区域土壤处于中等质量水平。综上,本研究确定了准确评价杭锦旗黄河南岸灌区土壤质量的最优方法组合,可为今后土壤质量评价研究中指标权重和分值计算方法的选择提供参考。

血管内超声在准分子激光消蚀联合药物涂层球囊治疗下肢动脉硬化闭塞症中的应用价值

目的探讨血管内超声在准分子激光消蚀联合药物涂层球囊治疗下肢动脉硬化闭塞症治疗中的效果。方法本研究为前瞻性病例系列研究,纳入2021年9月至2022年3月在复旦大学附属中山医院接受血管内超声辅助的准分子激光消蚀联合药物涂层球囊治疗的下肢动脉硬化闭塞患者的资料。记录患者病变特点、手术疗效和相关并发症。治疗前后资料的比较采用配对样本t检验。结果共10例患者纳入研究,男性8例,女性2例,年龄(72.0±5.9)岁(范围:61~81岁)。共11处病变,股浅动脉8处,腘动脉3处,病变长度(7.0±2.4)cm(范围:3.2~9.8 cm)。慢性闭塞病变4处,重度狭窄7处。患者均顺利完成手术,技术成功率为10/11,1处病变发生限流性夹层,行补救性支架植入。4处病变钙化分级为3~4级,9处病变钙化弧度≥180°。5处病变在血管内超声测量后选择更大直径的药物涂层球囊。随访(6.0±1.9)个月(范围:3~9个月),患者术后即刻踝肱指数(0.97±0.13比0.48±0.18,t=-7.60,P<0.01)与术后3个月踝肱指数(0.95±0.12比0.48±0.18,t=-7.17,P<0.01)均较术前明显增加。术后3个月的一期通畅率为11/11,无靶病变再干预,溃疡愈合率为3/4。结论血管内超声辅助下准分子激光消蚀联合药物涂层球囊治疗下肢动脉硬化闭塞症的早期结果良好,手术安全。

血管内超声在下肢动脉疾病中的应用进展

准确地评估下肢动脉病变特点对于指导腔内治疗有重要作用,血管内超声作为一种下肢动脉疾病评估技术备受关注。血管内超声可准确评估血管尺寸、病变的形态和性质、动脉夹层累及范围,从而指导腔内治疗方式的选择,以及预测病变再狭窄的发生概率。与作为金标准的数字减影血管造影相比,血管内超声在评估病变几何特征和性质方面具有优势。血管内超声的使用已被证明可提高诊断下肢动脉疾病的准确率,从而改善治疗结局。

Heat exchange at air-sea interface in the South China Sea during monsoon periods in 1986

In order to explore the interaction be- tween the sea and monsoon in the South China Sea, the heat exchanges at air-sea interface during mon- soon periods in 1986 were calculated using observa- tional data. It shows that when the summer monsoon bursts and prevails over the South China Sea, the air-sea interface heat exchange is strong and the latent heat rises rapidly in the intertropical conver- gence zone and the tropic cyclone system near 20.49°N, 114.14°E. On May 24, 1986, the sensible heat became positive in the typhoon system. The heating exchange indicates that heat is transported from ocean to atmosphere, with major contribution of latent heat. When the summer monsoon prevails over the South China Sea and the weather is fine, even SST (sea surface temperature) is high, but sensible heat appears to be negative. The heat exchange indicates that heat is transported from atmosphere to ocean, with major contribution of short-wave radiation absorbed by sea surface and sensible heat. When summer monsoon is over and the northeast monsoon prevails over the South China Sea, the heat ex- change at air-sea interface is very strong. The heat- ing exchange shows that the ocean heats the at- mosphere, with major contribution of latent heat when cold air arrives at the sea surface and the sensible heat rises to positive rapidly. Therefore it can be concluded that the heat exchange at air-sea interface is different from the SST in South China Sea. Whenthe summer monsoon prevails over the South China Sea, the main trend is the ocean responding to the atmosphere.