基于形态谱和形状特征的平面四杆机构设计方法

连杆轨迹曲线与连杆机构参量之间存在着复杂的非线性关系,用具有旋转、缩放、平移不变特性的形状谱和几何参数作为联合特征,描述了连杆轨迹曲线的结构形态特征和整体形状特征,并构建曲线形态的识别、比较方法,实现了连杆轨迹曲线描述最小的数据冗余;利用人工神经网络拟合了连杆轨迹曲线与连杆机构之间的非线性关系,获取与预期轨迹最为吻合的连杆曲线参数,实现了机构的快速综合设计.以512幅连杆曲线图像为学习库,64幅图像为工程测试样本的实验数据说明了本文方法的可行性,并分析了误差产生的原因.     

液体射流泵空化噪声与振动试验

针对液体射流泵的空化噪声与振动进行了试验研究;运用B＆K加速度仪和水听器对射流泵各部位在不同工况下的空化噪声与振动进行了测量。结果表明：（1）射流泵空化噪声以单极子声源为主,随着流速和紊流度的增大,偶极子作用逐渐增大;（2）射流泵空化噪声与振动随空化程度加剧而更强烈,最强烈处也从喉管向扩散管转移;（3）射流泵面积比越小,达到临界空化前噪声频谱波动越强,临界空化之后噪声谱级趋于平稳,随频率增加而递减;（4）初生空化出现前后噪声在整个频域范围内都有一个较大的跃升,约5-10 dB,此跃升可作为判断初生空化的参考方法;（5）泵体3个正交方向振动并不相同,径向振动较轴向更为明显。     

车辆半主动悬架新型控制算法的研究

车辆1/4悬架模型不能反映车辆的俯仰情况,且一般控制算法多以簧载质量加速度作为反馈,具有一定的局限性。为更好地改善悬架性能,本文建立了车辆1/2半主动悬架4自由度模型,针对悬架为一非线性、有时滞、不确定系统,提出了一种新型控制算法(在模糊控制的基础上引入PID控制),且在MATLAB中分别进行了时域和频域仿真,并就簧载质量加速度、悬架动挠度、轮胎动载荷与被动悬架、模糊控制半主动悬架进行比较。结果表明,该算法对簧载质量加速度、悬架动挠度、轮胎动载荷的改善非常有效,对车辆悬架的控制和开发具有较大的参考价值。     

利用振动特性诊断流程泵的运行工况

用所建立的用于描述振动强度的范数说明了泵在偏离原设计工况运行时会导致泵轴向力和径向力的增大。将流程泵叶轮叶片和压水室的隔舌看作旋涡发生体，在不同运行工况下在叶片后缘以及隔舌两侧串联发生的卡门涡街的发射频率是不同的。采用加速度传感器采集的振动信号正反应了这种工况变动。通过对振动信号进行基于EMD的能量算子解调以及频谱分析，发现得到的最大幅值处的频率就是叶轮叶片的通过频率。试验表明，得到的次大幅值处的频率就是卡门涡街的发射频率，可根据该频率处幅值的相对大小来判断泵是否在合理的工况内运行。     

气吸式免耕播种机种箱振动特性的研究——基于MatLab

利用振动信号采集系统PULSE软件,将加速度传感器安装于种箱附近,将振动信号通过六通道采集卡采集,通过无线网桥发射-接收信号,将信号传送到计算机;利用Mat Lab分析软件,将采集到的信号进行分析处理,得到每个通道的采集振幅图,选取振幅图中若干个频率-振幅坐标值进行Mat Lab数据拟合。结果表明:气吸式免耕播种机主要为低频振动,随着作业速度不同,频谱图的峰值就不同,速度越大,峰值越高且出现峰值的点越多;通过数据拟合可知,拟合直线越顺滑,表明此处振动对种箱排种效果越好。     

随机取样技术中的数据处理

取样技术是一种广泛应用的信息处理技术。通过对模拟信号的取样量化处理，可以得到便于计算机处理的数字信号。若使被取样信号不失真，取样频率必须高于被取样信号最高频率分量2倍，这对于高频信号不容易做到。为此提出了随机取样技术，即用低频脉冲序列对高频信号随机取样，通过大量样值来统计出原信号的某些特征。     

盐胁迫对裸果木幼苗光合特性的影响

本研究以一年生裸果木幼苗为材料，采用盆栽育苗方式，设计7个不同浓度NaCl溶液（CK、0.2%、0.4%、0.6%、0.8%、1.0% 和1.2%）模拟盐分胁迫，测定分析了其叶片气体交换参数、光响应曲线及叶绿素荧光参数的变化规律。结果表明：随着盐浓度的增加，叶片净光合速率（P_n）、气孔导度（G_s）和蒸腾速率（T_r）均呈下降趋势，NaCl浓度≥0.4%时，各处理P_n、G_s和T_r均显著低于CK；气孔限制值（L_s）和瞬时水分利用效率（WUE）随盐浓度增加呈先升后降趋势，胞间CO₂浓度（C_i）呈相反趋势，NaCl浓度为0.4%时，L_s达到最大值，而C_i达到最小值，说明P_n下降以气孔限制因素为主，而当NaCl浓度≥0.6%时，以非气孔限制为主要因素。随着盐胁迫程度的增大，最大净光合速率（P_nmax）、暗呼吸速率（R_d）、光饱和点（L_SP）、表观量子效率（A_QY）逐渐降低，光补偿点（L_CP）逐渐增加，表明盐分抑制了幼苗对光的吸收、利用和转换能力。叶片PSII潜在活性（F_v/F₀）、原初光能转化效率（F_v/F_m）、实际光化学效率（Φ_PSII）、电子传递速率（ETR）和光化学猝灭系数（q_p）随着盐浓度的增加呈下降趋势；非光化学猝灭系数（NPQ）在≤0.4%NaCl处理下较CK显著增加，盐浓度≥0.8%时，NPQ显著下降。基质的NaCl浓度在0.2%和0.4%时，裸果木叶片P_n、F_v/F₀、F_v/F_m下降不显著，WUE有所提高，PSII系统可以通过耗散过剩的光能保护光合机构，表现出一定的耐盐性；但盐浓度超过0.6%时，光合生态幅变窄，光合机构受到明显破坏，显著抑制了光合作用能力。     

高温胁迫下银杏离体枝条叶片的叶绿素荧光特性

银杏是一种重要经济树种，随着全球气温升高，高温适应性问题已经影响了其在低纬度区域的栽培。为了探明高温胁迫对银杏叶片光合过程的影响，本研究中离体银杏枝条被置于不同温度（25 ℃、30 ℃、35 ℃、40 ℃、45 ℃）下处理，随即对其叶绿素荧光参数进行监测。 结果显示：40 ℃以上高温胁迫下，银杏叶片的光系统II（PSⅡ）潜在光化学效率（Fv/Fo）、最大光化学效率（Fv/Fm）显著下降；最大荧光（Fm）、最大相对电子传递速率（rETRmax）、PSⅡ实际光化学效率（Yield）、光化学淬灭系数（qP）均显著下降；而初始荧光（Fo）和非光化学淬灭系数（NPQ）在40℃以上高温胁迫下显著上升。本研究表明，银杏离体枝条叶片光合作用对温度变化较敏感，推测高温可能伤害了光合机构，从而对光能的吸收、转换与光合电子传递都有显著的影响。银杏离体枝条叶片的叶绿素荧光动力学参数对高温的敏感性，可能有助于快速筛选和培育耐高温的银杏品种。     

Gas Exchange of Five Warm‐Season Grain Legumes and their Susceptibility to Heat Stress

Objective of this study was to compare the heat stress performance of four pulses from dry and hot areas (mungbeans, limabeans, and teparybeans and cowpeas) with that of soybeans. Two experiments were conducted in growth chambers, and data were pooled because results of both experiments were similar. Plants were raised up to flowering at 24/17 °C (day/night) and were then either exposed to these temperatures until maturity or stressed with 33/24 °C for 2 weeks starting at day 1 or 15 after onset of flowering (early vs. late stress). Before, during and after these stress intervals, gas exchange of representative upper leaves was examined; additionally, immediate effects of increasing leaf temperatures from 24 to 32 or 40 °C on chlorophyll fluorescence were assessed. Without heat stress rates of photosynthesis (P_n), and of transpiration (TR), stomatal and mesophyll conductance (g_s, g_m) and intrinsic transpiration efficiency (iTE) differed significantly among the five crops at each date. However, because of crop‐specific time‐courses ranking among unstressed crops was instable with time, so values were integrated or averaged over time. This procedure revealed high P_n potentials in mung‐ and teparybeans and high iTE values in limabeans compared to the other crops. Heat stress lowered P_n and g_s considerably, but increased TR in all five crops. Relative lowering of P_n during heat stress displayed a crop‐specific pattern with limabeans being least susceptible to both early and late heat stress, while cowpeas were highly susceptible to early stress. Effects on P_n were mainly attributable to lowering of g_s and only in part to g_m. The latter was supported by very small changes (<10 %) of various chlorophyll fluorescence signals shortly after raising leaf temperature to 32 °C in all species. However, in limabeans, a decreased electron transport rate (e‐rate, ?18 %) and an increased non‐photochemical quenching (Q_N, +16 %) pointed to an adaptive mechanism to avoid oxidative strains under heat. Leaf temperatures of 40 °C immediately provoked stronger changes in all fluorescence signals than 32 °C; substantial damages at 40 °C were indicated by effective quantum yield, photochemical quenching and ratio of fluorescence decrease in mungbeans and low ones in cowpeas and soybeans. Nevertheless, some adaptive responses of e‐rates and Q_N were observed in all crops and were most expressed in limabeans.     

Accessions of Australian Nicotiana species suitable as indicator hosts in the diagnosis of plant virus diseases

When screening the genusNicotiana for sensitive and differential hosts for a group of mechanically transmissible plant viruses with narrow host ranges, development of systemic symptoms was alsmost exclusively observed in species of three closely related sections of the subgenusPetunioides. These species wereN. miersii (sectionAcuminatae),N. bigelovii andN. clevelandii (Bigelovianae) andN. benthamiana, N. cavicola, N. ingulba, N. occidentalis, N. rosulata andN. rotundifolia (Suaveolentes). Except forN. benthamiana andN. clevelandii, which are already known for their large virus ranges, they are new experimental hosts that appeared very useful for detection of viruses and for differentiation of viruses that closely resemble each other in host range. Accessions of the same species often varied largely in local and systemic viral response. EspeciallyN. benthamiana-9,N. miersii-33 andN. occidentalis-37B (code numbers given by Tobacco Research Laboratory, Oxford, N.C., USA) are recommended for routine inoculation tests. The sensitiveSuaveolentes species mentioned are native to the arid parts of Australia. Collections of these species deserve attention in studies on virus diseases of unknown etiology where experimental hosts are lacking.Samenvatting In het genusNicotiana werden vatbare, gevoelige en differentiële toetsplanten opgespoord door toetsing van vooral de collectie van het Tobacco Research Laboratory (Oxford, N.C., VS) met een aantal virussen waarvoor weinig of geen bruikbare toetsplanten bekend waren. Systemische reacties werden bijna uitsluitend in soorten van drie nauw verwante secties van het subgenusPetunioides waargenomen. Deze soorten warenN. miersii (sectieAcuminatae),N. bigelovii enN. clevelandii (Bigelovianae) enN. benthamiana, N. cavicola, N. ingulba, N. occidentalis, N. rosulata enN. rotundifolia (Suaveolentes). Behalve voor virusvermeerdering bleken deze soorten ook zeer geschikt te zijn voor differentiatie van virussen of virusstammen met een bijna gelijke waardplantenreeks.Collectienummers van één en dezelfde soort konden sterk in lokale en systemische reactie verschillen. VooralN. benthamiana-9,N. miersii-33 enN. occidentalis-37B kunnen voor routine-inoculaties worden aanbevolen. Met uitzondering vanN. benthamiana enN. clevelandii zijn de genoemde soorten of genotypen nieuwe experimentele waardplanten voor de virologie. De soorten die van de sectieSuaveolentes worden genoemd, zijn inheems in de woestijnachtige gebieden van Australië. Verzamelingen daarvan verdienen nadere aandacht bij de diagnostiek van virusziekten waarvoor nog geen experimentele waarplanten voorhanden zijn.