排列熵优化改进变模态分解算法诊断齿轮箱故障

为了准确提取齿轮箱中复合故障特征,该文选用变模态分解(variational mode decomposition,VMD)对振动信号进行处理,它能够将信号分解为多个固有模态函数(intrinsic mode function,IMF),但需预设分解层数k和惩罚因子;因此,为了能够自适应地确定分解层数k,该文提出了排列熵优化算法(permutation entroy optimization,PEO),该算法可以根据待分解信号的特点自适应的确定分解层数k;同时,为了解决VMD算法对噪声的敏感性,该文根据噪声辅助数据分析的思想,提出了改进VMD算法(modified variable modal decomposition,MVMD),该算法首先添加成对符号相反的高斯白噪声到原始信号,再利用VMD算法对其进行分解,经过多次循环,原始信号中的噪声相互抵消,而后将每次循环得到的每层IMF分别进行集成平均。利用该算法分别对含有多故障特征的齿轮箱仿真信号及实测信号进行处理,均提取出了故障特征。该文所提方法对封闭式功率流试验台进行复合故障提取,160和360 Hz的故障频率分别被提取出。该方法为齿轮箱复合故障诊断提供新思路。     

采用HHT算法与卷积神经网络诊断轴承复合故障

针对农业机械装备中滚动轴承复合故障特征提取与智能诊断问题,该文提出了一种将希尔伯特-黄变换的改进算法(improved hilbert-huang transform,IHHT)与卷积神经网络(convolution neural network,CNN)相结合的诊断方法。首先,通过多种群差分进化改进的集合经验模式分解(multiple population differential evolution-ensemble empirical mode decomposition,MPDE-EEMD)和敏感固有模态函数筛选方法来改进HHT,提取出故障信号时频特征。然后,在AlexNet网络模型基础上遍历所有可能的CNN模型组合,构建出适应于滚动轴承故障诊断的CNN网络模型。再将训练集生成的IHHT时频图输入CNN中进行学习,不断更新网络参数;并将该模型应用于测试集,输出故障识别结果。最后,通过滚动轴承单一故障和复合故障2种试验,将所提出的IHHT+CNN方法分别与传统的BP神经网络、DWT+CNN和STFT+CNN方法进行比较。研究表明,该文的IHHT+CNN方法对单一与复合故障的正确率分别达到100%和99.74%,均高于其他3种方法,实现了不同工况下端到端的轴承复合故障智能诊断,并具有较好的泛化能力和鲁棒性。     

采用HHT算法与卷积神经网络诊断轴承复合故障

针对农业机械装备中滚动轴承复合故障特征提取与智能诊断问题,该文提出了一种将希尔伯特-黄变换的改进算法(improved hilbert-huang transform,IHHT)与卷积神经网络(convolution neural network,CNN)相结合的诊断方法。首先,通过多种群差分进化改进的集合经验模式分解(multiple population differential evolution-ensemble empirical mode decomposition,MPDE-EEMD)和敏感固有模态函数筛选方法来改进HHT,提取出故障信号时频特征。然后,在AlexNet网络模型基础上遍历所有可能的CNN模型组合,构建出适应于滚动轴承故障诊断的CNN网络模型。再将训练集生成的IHHT时频图输入CNN中进行学习,不断更新网络参数;并将该模型应用于测试集,输出故障识别结果。最后,通过滚动轴承单一故障和复合故障2种试验,将所提出的IHHT+CNN方法分别与传统的BP神经网络、DWT+CNN和STFT+CNN方法进行比较。研究表明,该文的IHHT+CNN方法对单一与复合故障的正确率分别达到100%和99.74%,均高于其他3种方法,实现了不同工况下端到端的轴承复合故障智能诊断,并具有较好的泛化能力和鲁棒性。     

基于迁移学习和残差网络的农作物病害分类

作物病害对农业产品的质量和产量有重要影响,单一物种病害的分类模型难以应对复杂的农业生产环境.该研究对深度残差网络SE-ResNeXt-101模型进行改进,并基于迁移学习(Transfer Learning,TL)提出了一种农作物病害分类模型TL-SE-ResNeXt-101,用于不指定农作物种类的病害检测分类.在重构的...     

基于自适应多分辨率分析的电动拖拉机驱动功率分配策略

燃料电池分布式驱动电动拖拉机（fuel cell distributed drive electric tractor,FCDET）能够有效解决环境污染和能源紧缺问题、推动农业可持续发展。针对FCDET牵引效率低、续航时间短、氢耗量大等问题,该研究提出了基于自适应多分辨率分析（adaptive multi-resolution analysis,AMRA）的犁耕驱动功率分配策略。首先建立燃料电池系统等效电路模型、总效率求解模型、能量耗散模型以及驱动电机响应模型。一次重构策略基于可调Q因子小波变换（tunable Qfactor wavelet transform,TQWT）,获得有效反应功率信号振荡特性的子序列。二次重构策略将低频子序列经过变分模态分解（variational mode decomposition,VMD）为若干个具有特殊稀疏性质的离散子信号。然后采用麻雀搜索算法（sparrow search algorithm,SSA）实时获取VMD的分解层数和二次惩罚因子的最优组合。最后将二次分解后的子序列和子信号按照频率特性进行重构,并将重构功率信号在各个能量源之间重新分配。以E...     

基于特征迁移学习的变工况下轴向柱塞泵故障诊断

不同工况下的轴向柱塞泵故障数据存在分布差异,现有的基于特征迁移学习的变工况故障诊断方法大多只通过单个传感器信号进行分析,具有一定的局限性和片面性。为了利用多传感器信号提高变工况下轴向柱塞泵故障诊断的性能,该研究提出一种耦合分类器子空间嵌入分布自适应（Subspace Embedded Distribution Adaptation with Coupled Classifiers, SEDACC）方法。该方法利用多传感器信号的频谱数据构造主要数据集和辅助数据集,通过子空间对齐（Subspace Alignment, SA）方法将源域和目标域的主要数据投影到公共子空间中,并采用加权条件最大均值差异（Weighted Conditional Maximum Mean Discrepancy, WCMMD）作为度量进行特征分布的适配。同时,基于结构风险最小化（Structural Risk Minimization, SRM）准则在源域标签数据上学习主分类器,根据主分类器对于目标域的预测结果在目标域辅助数据上学习辅助分类器。通过交替和迭代策略不断优化分类器参数,最后对二者进行加权融合得到最终的诊断模型。通过轴向柱塞泵变工况故障诊断试验进行验证,结果表明,当以垂直于端盖的z方向振动信号为主要数据并使用声音信号（或以平行于端盖的x方向的振动信号）作为辅助数据时,SEDACC方法在6种迁移任务中的平均准确率为99.88%（99.46%）,高于其他方法。此外,所提方法在目标工况样本稀少的情况下仍具有较高的诊断精度,当目标域和源域样本数比值为0.2时,6种迁移任务的平均准确率达到92.66%。研究结果可为更完备与准确的机械故障诊断提供参考。     

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。     

基于EMD多尺度特征熵的水轮机尾水管涡带信息提取

水电机组故障诊断的关键是从状态信号中提取故障特征,因此采用经验模态分解和指标能量相结合的方法,进行水轮机尾水管动态特征信息提取。首先,对信号进行经验模态分解,然后,根据得到的本征模式分量函数计算指标能量,最后,建立基于指标能量的多尺度特征熵,并以此熵值作为故障模式识别的特征向量。以原型水轮机尾水管压力脉动信号为例,进行了应用检验。结果表明,该方法准确性高,并具有良好的水轮机特征向量提取能力,适合分析复杂而特殊的水轮机动态特征信息。     

集合经验模式分解在旋转机械故障诊断中的应用

为了抑制经验模式分解中的模式混淆现象,提高分析精度,引入集合经验模式分解（EEMD）算法。在分析信号上叠加适当的随机高斯白噪声序列,改变信号的局部时间跨度,从而改变一次经验模式分解（EMD）中分析的特征尺度,通过足够多次EMD分解,相当于从多个角度提取信号的本质,最后由所有次分解得出的各本征模态函数（IMF）的均值作为输出,不但消除了人为噪声的影响,还清晰还原了信号的内在过程,准确揭示了其真实物理意义。通过仿真试验和实际的动静碰磨故障案例证实了EEMD算法的有效性,并与基本EMD算法和高频谐波法进行了对比,结果表明,EEMD虽然耗时较多但结果更准确,在旋转机械故障诊断领域应用前景广泛。     

基于小波分析的发动机气缸失火故障诊断

发动机加速过程中失火是常见故障，运用了发动机主轴瞬时转速进行失火故障的诊断。采用磁电式传感器测定了发动机在正常与故障的4种工况下从怠速急加速到高速过程中的瞬时转速，并用db3阶小波对各工况下转速信号进行分解与重构，以重构波形分析对比了各工况下的转速波动状态与加速过程的信息，从而判断发动机是否失火以及失火故障类型。结果表明，发动机失火时，瞬时转速的重构信号与正常工况转速重构信号相比，波动幅值、怠速段和高速段的稳定转速、加速时间有显著差异，这种失火故障的诊断方法是可行的和有效的。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.