Enhancing the Simplified Surface Energy Balance (SSEB) approach for estimating landscape ET: Validation with the METRIC model

Evapotranspiration (ET) can be derived from satellite data using surface energy balance principles. METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) is one of the most widely used models available in the literature to estimate ET from satellite imagery. The Simplified Surface Energy Balance (SSEB) model is much easier and less expensive to implement. The main purpose of this research was to present an enhanced version of the Simplified Surface Energy Balance (SSEB) model and to evaluate its performance using the established METRIC model. In this study, SSEB and METRIC ET fractions were compared using 7 Landsat images acquired for south central Idaho during the 2003 growing season. The enhanced SSEB model compared well with the METRIC model output exhibiting an r² improvement from 0.83 to 0.90 in less complex topography (elevation less than 2000 m) and with an improvement of r² from 0.27 to 0.38 in more complex (mountain) areas with elevation greater than 2000 m. Independent evaluation showed that both models exhibited higher variation in complex topographic regions, although more with SSEB than with METRIC. The higher ET fraction variation in the complex mountainous regions highlighted the difficulty of capturing the radiation and heat transfer physics on steep slopes having variable aspect with the simple index model, and the need to conduct more research. However, the temporal consistency of the results suggests that the SSEB model can be used on a wide range of elevation (more successfully up 2000 m) to detect anomalies in space and time for water resources management and monitoring such as for drought early warning systems in data scarce regions. SSEB has a potential for operational agro-hydrologic applications to estimate ET with inputs of surface temperature, NDVI, DEM and reference ET.     

圆柱螺纹牙型非接触检测失真校正

在对圆柱螺纹进行非接触检测时,螺纹牙型会产生失真现象,为此提出图像校正的方法。从螺纹牙型失真的几何原理出发,建立相应的螺纹数学模型,对采集的螺纹图像进行校正,获得真实的螺纹牙型,并通过软件仿真和试验验证了该模型的正确性。同时表明图像校正的方法提高了圆柱螺纹非接触检测的精度、效率。     

Modeling height-diameter relationship for artificial monoculture Metasequoia glyptostroboides in sub-tropic coastal megacity Shanghai,China

Tree height is a key variable in forest monitoring studies and for forest management. However, tree height measurement is time consuming, and the recommended procedure is to use estimates from tree height (H) - diameter at breast height (DBH) models. Increasingly, H-DBH models are being developed for urban forests, providing tools to forest management and ecosystem services estimation. Here, we compared model forms and approaches for predicting H as a function of DBH and additional stand level covariates variables. Four model forms were evaluated: (i) basic models (which only used DBH as predictor variable); (ii) generalized models (which used DBH and other predictor variables based on the best basic model); (iii) a mixed-effects model based on the best basic model; and (iv) a mixed-effects model based on the generalized model. Several sampling designs aimed at minimizing height measurement were tested in terms of accuracy and applicability. Taking predicted accuracy and investigation cost into account, we recommend generalized non-linear mixed-effects model (NLME) when there were two or less tree height measurements taken in a given stand. The basic NLME model could be calibrated when there were 3 or more tree height measurements, depending on the required level of accuracy and investigation cost. Additionally, we first reported that soil pH as a covariate variable in H-DBH model and our generalized NLME model implied that the difference in the H-DBH relationship caused by pH varies among different stands. This finding may be attributable to differing biological properties of the similar alkaline tolerance species.     

近红外反射光谱测定玉米完整籽粒蛋白质和淀粉含量的研究

 以128份常用普通玉米自交系及杂交种的混合籽粒样品为材料,采用偏最小二乘(PLS)回归法,对近红外反射光谱(NIRS)测定玉米完整籽粒蛋白质、淀粉含量的可行性和方法进行了研究。结果表明,采用一阶导数+多元散射校正预处理、谱区为10000～4000cm-1和一阶导数+直线扣减预处理、谱区为9000～4000cm-1,分别建立的蛋白质、淀粉含量的校正模型,其校正和预测效果最佳。其校正决定系数(R2cal)均大于0.97,交叉验证和外部验证决定系数(R2cv、R2val)为0.92～0.95,各项误差(RMSEE     

近红外光谱法非破坏性测定绿豆籽粒粗蛋白质含量的研究

为了找到一种快速、简单的测定绿豆品质的方法,利用瑞典波通(Perten)公司生产的DA7200二极管阵列近红外光谱仪,以来自我国绿豆主产区的77份绿豆资源为试验材料,对样品进行光谱扫描,并测定了直链淀粉含量的参比数据。结果表明:定标集和检验集样品的蛋白质含量预测值与化学测定值之间均呈极显著的正相关,相关系数分别为0.977 2和0.963 1;所建定标模型具有较高的预测精度。本研究利用近红外光谱仪对完整绿豆粗蛋白质的分析,可直接用于育种材料选择以及突变体筛选和种质资源的评价等研究。     

Establishing Soil Silicon Test Procedure and Critical Silicon Level for Rice in Louisiana Soils

Calibration of crop responses to applied silicon (Si) serves as a basis for developing Si fertilizer recommendation guidelines. A greenhouse experiment was set up in a randomized complete block design with five replications, two sources of Si (wollastonite and slag) and four Si rates (0, 170, 340 and 680 kg ha^?1) to calibrate plant-available Si for growing rice in Louisiana soils. Silicon concentrations were determined in soils using seven different extraction procedures. Based on a quadratic model (p < 0.05), the estimated soil Si critical level using 0.01 M calcium chloride (CaCl₂) for Sharkey clay soil was 110 mg kg^?1 while for Crowley silt loam and Commerce silt loam, levels were 37 and 43 mg kg^?1, respectively. These results suggest that suitability of an extractant that gives the best estimate of plant-available Si could considerably depend on soil type and it is unlikely that there is a universal extractant for all soils.     

Stable carbon isotopes accurately predict diet selection by sheep fed mixtures of C3 annual pastures and saltbush or C4 perennial grasses

The stable carbon isotope technique has been widely used to infer the dietary ecology of a range of animal species; however calibration of the technique with animals fed known diets is essential for accurate back-calculation of dietary preferences. The aim of this study was to identify suitable samples and back-calculation methods to predict short-term (2 to 3 week) dietary selection by sheep among plants with C₃ and C₄ photosynthetic pathways. Variation in integration time of dietary carbon into plasma and faeces; diet-tissue discrimination of carbon isotopes (fractionation) and the importance of accounting for the digestible or indigestible components of the diet was investigated. The results indicate that faecal and rumen samples provided the most accurate prediction of short term dietary changes in sheep selecting between C₃ and C₄ plants. The most accurate back-calculation method for these samples used δ¹³C of the C₃ and C₄ plants and accounted for both diet-tissue discrimination and differences in the indigestibility between the C₃ and C₄ forage. For faecal samples, the organic matter content of the diet originating from C₄ plants could be predicted with a mean error as low as 2.7%. Wool and plasma samples were not conducive to predicting proportion of C4 forage in the diet within 18 days after a change in diet; however plasma could be used to discriminate between animals fed 100% C₃ and C₄ diets after 3 days. The δ¹³C technique provides a valuable tool for researchers when designing pastures for dual environmental and production purposes. An understanding of what sheep select allows for development of appropriate grazing management strategies to optimise productivity and/or persistence of target species.     

轿车底盘评价调校初探

底盘调校是许多开发自主品牌车辆的企业面临的一个技术难题。实践证明,依据合适的评价调校标准,结合整车开发流程,针对整车的制动离合性、操纵稳定性、平顺性以及底盘噪声进行评价调校,可提高整车的行驶安全性和顾客满意度。     

On the use of plate-type normal pressure cells in silos: Part 1: Calibration and evaluation

Pressure cells are measuring devices commonly used in silo research to study loads exerted by a granular material stored against a silo wall. The design of normal pressure cells for use in an experimental silo research project is critical, mainly because measuring errors complicate the interpretation of results. Once the cells have been delivered from the manufacturer to the researcher, they should be calibrated and validated with reference to the measurement of pressure from a granular material against a silo wall. Two related papers deal with a specific plate-type normal pressure cell for use in an installation of three full-scale steel silos with different hopper eccentricities (concentric, half-eccentric and full-eccentric) as part of a silo research project. It was found to be necessary to validate the performance of the cells when measuring pressures in the silos in order to arrive at a solid basis for the interpretation of the pressure measurements in the silo installation aforementioned. This paper presents calibration results from three investigated methods as well as results from a finite element analysis of the plate deflection of the pressure cell which were performed to evaluate the non-linear behaviour of the signal from the cell. Results suggested that the air-pressure calibration method turned out to be the most suitable in this particular case, that a lack of stiffness of the plate cell was revealed and that its boundary constraint conditions were not stable. Amendments were proposed in order to improve the accuracy of measurements. Furthermore, the knowledge acquired from the study of these plate-type cells constitutes the basis of recommendations for another design of pressure cells for which the calibration as well as the interpretations of test results would become simpler.     

A generalized nonlinear mixed-effects height–diameter model for Eucalyptus globulus L. in northwestern Spain

A generalized height–diameter model was developed for Eucalyptus globulus Labill. stands in Galicia (northwestern Spain). The study involved a variety of pure stands ranging from even-aged to uneven-aged. Data were obtained from permanent circular sample plots in which trees were sampled within different radii according to their diameter at breast height. A combination of weighted regression, to take into account the unequal selection probabilities of such an inventory design, and mixed model techniques, to accommodate local random fluctuations in the height–diameter relationship, were applied to estimate fixed and random parameters for several models reported in the relevant literature. The models that provided the best results included dominant height and dominant diameter as fixed effects. These models explained more than 83% of the observed variability, with mean errors of less than 2.5 m. Random parameters for particular plots were estimated with different tree selection options. Height–diameter relationships tailored to individual plots can be obtained by calibration of the height measurements of the three smallest trees in a plot. An independent dataset was used to test the performance of the model with data not used in the fitting process, and to demonstrate the advantages of calibrating the mixed-effects model.