基于高光谱成像的苹果轻微损伤检测有效波长选取

为了确定可用于苹果早期轻微损伤检测的有效波长,以具有代表性的阿克苏苹果为研究对象,采用高光谱成像技术和分段主成分分析方法对损伤发生仅为半小时之内的苹果进行损伤检测研究,对比分析不同光谱区域主成分分析对识别结果的影响,优选出识别光谱区域(780～1000nm)。基于此光谱区域结合主成分图像权重系数获取2个有效波长(820和970nm),并利用这2个波长和全局阈值理论开发了多光谱轻微损伤提取算法。利用独立测试集中25个正常苹果和25个损伤苹果对算法的性能进行评估,结果表明,正常果的识别率为100%,损伤果的识别率为96%,整体检测精度为98%。该研究所获得的有效波长可为开发基于多光谱成像技术的苹果损伤检测系统提供参考。     

单盘多行独立气道式蔬菜精量排种器设计与试验

针对现有多行气吸式排种器因共用气室造成风压要求高、损失大的问题,设计一种单盘多行独立气道式蔬菜精量排种器,降低排种过程所需的风压值,减少风压损失.对排种盘、气道盘、搅种装置、清种器等关键部件进行结构设计,利用JPS 12型排种器性能试验台进行排种性能试验并对试验结果进行分析.通过单因素试验,得到在负压值1～2 kPa、...     

Using fuzzy clustering algorithms to describe the distribution of trace elements in arable calcareous soils in northwest Iran

Accumulation of trace elements in arable soils is an important global hazard worldwide. In this research, the available content of Zn, Fe, B, Co, Cu, Mn, Mo and other soil parameters (pH, organic carbon content, carbonates and electrical conductivity) were analysed in northwest Iran. Concentration levels of trace elements were relatively low in areas with high pH values and low organic matter content, and only the Mo value exceeded the reference threshold. Based on the correlation among the elements, two datasets were produced. The first consists of Fe and Mn data, while the second contains Zn, B, Co, Cu and Mo data. Two fuzzy clustering approaches, Fuzzy C-means (FCM) and Gustafson–Kessel (GK), were applied for clustering both datasets. Multiple accumulation of trace elements was investigated from the clustering results and then visualized in spatial regionalization maps. The fuzzy clustering evaluating indices showed that the GK method was more appropriate than FCM for clustering datasets. The results revealed that the first and second datasets were divided into seven and six clusters, respectively. Fuzzy clustering analyses combined with geostatistical methods were used to map the spatial variability of each cluster. This method enabled the monitoring of multiple metal accumulation in large agricultural soils.     

Differential impacts of climate variability on yields of rainfed barley and legumes in semi-arid Mediterranean conditions

Climate change has emerged as a major concern for crop production. This study used a field experiment to examine the differential yield responses of barley, lentil, common vetch, and bitter vetch to weather in the Mediterranean region. Crops were grown in a 10-year rotation trial in Lebanon. Precipitation and temperature were used as explanatory variables in simple linear correlation and standardized multiple-regression analyses. Grain yields were not correlated with annual precipitation. Barley grain yield was correlated positively with precipitation from March to May (r = 0.70) and the rainfall distribution index (r = 0.71), but negatively with mean May temperature (r = –0.62) and absolute minimum temperature in January (r = –0.91). Unlike barley, legume grain yield was not correlated with any rainfall parameters. Common vetch grain yield was negatively correlated with mean May temperature (r = –0.68). Grain yield of the two vetches were also correlated negatively with the absolute minimum temperature in January, but grain yield of lentil was not correlated with any weather variable. Standardized multiple-regression analyses showed that mean May temperature had the strongest influence on grain yield of barley, lentil, and common vetch, indicating that, under climate change, higher temperature may have a more deleterious effect on grain yield than lower rainfall. The negative correlation between common vetch and barley grain yields and temperature in May suggests that early sowing to induce earlier flowering and maturity to escape the hot summer may be an option to increase common vetch and barley grain yields.     

春秋分日保温被顶卷对南北向大棚内光照影响的模拟

选取跨度为12m、高4.2m的塑料大棚,研究模拟计算春秋分时一日内不同时间段保温被遮光阴影带在棚内东西向的移动位置和距离,模拟保温被顶卷对大棚内东西向不同位置光合有效辐射日总量（DLI）分布的影响,并对棚内遮光情况进行实测计算,分析棚内东西向DLI分布规律。模拟计算结果表明,大棚内东西向中点位置的DLI最小,为10.91mol·m−2·d−1。自中点处向东西各1m范围内为棚内DLI低值区域,由10.91mol·m−2·d−1变为12.20mol·m−2·d−1,上升了11.8%。向东西两侧距离中点越远DLI值越大,最大值为13.70mol·m−2·d−1,位于棚两侧边缘,距中点6m处。实测结果表明,大棚内DLI值也表现为东西向中点位置最小,为7.31mol·m−2·d−1,自中点处向东西各1m范围内为棚内DLI低值区域,由7.31mol·m−2·d−1变为7.56mol·m−2·d−1,上升了3.4%。向东西两侧距离中点越远DLI值越大,最大值为12.70mol·m−2·d−1,位于大棚两侧边缘,距中点6m处。DLI的实测值与模拟计算值变化规律基本一致,均表现为在大棚内中点位置最小,沿大棚中点向东西两侧各逐渐增加,且在光环境较差的季节,中间区域的DLI值过低会限制喜光作物的正常生长。     

保温被投影对塑料大棚室内光环境及番茄生长性能的影响

保温塑料大棚屋顶保温被夜间有助于减少室内热量流失,但其白天会在室内形成一条阴影带,为了探明室内阴影带的变化以及其对番茄生长发育的影响规律,以陕西杨凌地区18 m跨度非对称保温塑料大棚为试验对象,计算分析了室内栽培区阴影带在一年中的变化规律,同时测试了北屋面水平投影区域和南屋面水平投影区域的太阳辐射,研究不同栽培区域番茄株高、茎粗、叶片光合参数以及番茄单株产量的差异。结果表明:1)与南屋面水平投影区域相比,北屋面水平投影区域晴天、阴天分别有38.9%、27.9%的太阳辐射被遮挡;2)全年北屋面水平投影区域有阴影的天数为231 d,最大遮荫面积可达146.8 m~2,占总栽培区域面积的13.2%;3)南屋面水平投影区域番茄叶片净光合速率、气孔导度、蒸腾速率以及水分利用率显著(P0.01)高于北屋面水平投影区域,平均单株产量要比北屋面水平投影区域高29.5%。总的来说,保温被投影降低了室内北侧栽培区域的太阳辐射,同时也降低了番茄的光合特性及产量,这为优化保温塑料大棚结构参数设计提供了更为深入的理论基础。     

Spatial estimation of surface soil texture using remote sensing data

Understanding the spatial distribution and variability of soil texture is essential for land use planning and other activities related to agricultural management and environmental protection. This study was conducted to evaluate Landsat Enhanced Thematic Mapper (ETM) remote sensing data as auxiliary variables for spatial estimation of surface soil texture using a limited number of soil samples taken from a site located in the city of PingduShandong ProvinceChina. Three methods of evaluating variability in surface soil texture were evaluated: (1) multiple stepwise regression (MSR) based on the relationship between surface soil sandsilt and clay contents and remote sensing data; (2) kriging of surface soil sandsilt and clay contents; (3) cokriging with remote sensing data. Correlation analysis showed that surface soil sandsilt and clay contents were significantly correlated with Landsat ETM digital number (DN) of six bands (Bands 1–5 and Band 7)and the DN of Band 7 explained most of the variability in soil sandsilt and clay contents. The DN of Band 7 was selected as auxiliary data for the estimation of surface soil texture. The cross-validation results indicated that both MSR and kriged estimates had low reliability due to the variations in landscape and the low-density sampling in the study area. Cokriging with remote sensing data significantly improves estimates of surface soil texture compared with MSR and kriging.     

Statistical analysis of nitrogen use efficiency in Northeast China using multiple linear regression and Random Forest

Understanding the spatial-temporal dynamics of crop nitrogen (N) use efficiency (NUE) and the relationship with explanatory environmental variables can support land-use management and policymaking. Nevertheless, the application of statistical models for evaluating the explanatory variables of space-time variation in crop NUE is still under-researched. In this study, stepwise multiple linear regression (SMLR) and Random Forest (RF) were used to evaluate the spatial and temporal variation of NUE indicators (i.e., partial factor productivity of N (PFP_N); partial nutrient balance of N (PNB_N)) at county scale in Northeast China (Heilongjiang, Liaoning and Jilin provinces) from 1990 to 2015. Explanatory variables included agricultural management practices, topography, climate, economy, soil and crop types. Results revealed that the PFP_N was higher in the northern parts and lower in the center of the Northeast China and PNB_N increased from southern to northern parts during the 1990–2015 period. The NUE indicators decreased with time in most counties during the study period. The model efficiency coefficients of the SMLR and RF models were 0.44 and 0.84 for PFP_N, and 0.67 and 0.89 for PNB_N, respectively. The RF model had higher relative importance of soil and climatic covariates and lower relative importance of crop covariates compared to the SMLR model. The planting area index of vegetables and beans, soil clay content, saturated water content, enhanced vegetation index in November & December, soil bulk density, and annual minimum temperature were the main explanatory variables for both NUE indicators. This is the first study to show the quantitative relative importance of explanatory variables for NUE at a county level in Northeast China using RF and SMLR. This novel study gives reference measurements to improve crop NUE which is one of the most effective means of managing N for sustainable development, ensuring food security, alleviating environmental degradation and increasing farmer's profitability.     

基于超声波频谱分析技术的木材孔洞缺陷无损检测

在探讨现有木材无损检测分析方法不足的基础上,根据超声波在木材中的传播规律,提出了用超声波能量衰减和频率成分的改变表征木材缺陷信息的方法,在此基础上用频谱分析处理了超声波信号。通过对木材空洞缺陷进行了多种频谱分析方法对比研究,选用Welch功率谱分析法对红松标准试件进行超声检测。实验结果表明,频谱分析能判断孔洞缺陷的大小和孔洞个数的变化规律,可见缺陷信号频谱丰富。频谱分析能够区分木材孔洞缺陷的大小和个数,而对缺陷的位置区分不明显。     

偏最小二乘回归模型在非点源负荷预测中的应用

将偏最小二乘回归模型应用于流域非点源污染年负荷量预测,并与基于最小二乘的多元线性回归模型预测结果进行了对比。实例计算分析结果表明,偏最小二乘回归分析实现了多元回归、主成分分析和典型相关分析的综合,能较好地处理变量之间的多重相关性问题,建模所需样本少,且计算结果合理,具有较好的推广应用价值。