花生黄曲霉生长预测模型的研究

通过对分离自花生的黄曲霉LYYSS03-3在不同温度(15-35℃)、不同相对湿度(水活度分别为0.5,0.7,0.9)下的菌落生长特性进行检测,采用Boltzmann和Logistic 模型对黄曲霉的生长曲线进行拟合,结果表明,在适宜温湿度阶段,花生黄曲霉的生长曲线更适合用Boltzmann模型拟合.     

基于高光谱特征参数的冬小麦氮营养指数估算

为了实现快速高精度获取冬小麦氮营养指数的高光谱监测技术，利用美国SVC HR-1024I型野外光谱辐射仪对2017-2019年关中地区的冬小麦进行遥感监测，获取“三边”参数、任意两波段光谱指数和植被指数，通过相关性分析和逐步回归分析方法筛选冬小麦氮营养指数的敏感光谱参数，结合偏最小二乘回归(PLSR)、随机森林算法(RFR)、支持向量机回归(SVR)和梯度增强回归(GBDT)建立冬小麦氮营养指数模型，并对模型估算精度进行验证。结果表明，从拔节期到灌浆期，各时期的氮营养指数与任意两波段光谱指数均呈极显著相关，其中拔节期氮营养指数与任意两波段光谱指数相关性均高于其他时期，且基于一阶导数光谱的归一化光谱指数和比值光谱指数与氮营养指数的相关系数最大，为0.66。拔节期基于梯度增强回归的冬小麦氮营养指数预测模型的决定系数(r²)和均方根误差(RMSE)分别为0.96和0.05,模型验证的r²、RMSE和相对预测偏差(RPD)分别为0.95、0.12和2.12,模型预测精度最高。因此，拔节期基于梯度增强回归的冬小麦氮营养指数估算模型可用于冬小麦氮营养监测...     

基于SWAT模型的大安市降水入渗量变化的模拟研究

针对近年的研究热点,通过SWAT模型对半干旱、盐碱化严重的吉林省大安市进行降水入渗模拟。以2000、2004和2008年遥感影像解译得到的土地利用数据为基础,结合SWAT模型的模拟结果,讨论LUCC与降水入渗量的相关关系。2008年与2000年相比,难利用地的面积有所降低,旱地、草地等发生了大面积的增加,研究区内土地状况有所好转。通过SWAT模型运行得到的结果显示:2008年的平均降水入渗量为56.27 mm,比2000年的值高。利用降水入渗系数法进行计算,也得到了2008年的降水入渗量高于2000年的结果,这与SWAT模型模拟得到的结果有着相同的趋势,且平均降水入渗量的标准偏差为5.27,说明SWAT模型对于研究区有良好的适应性。同时,根据土地利用数据和SWAT模型模拟数据可以得知,LUCC对研究区的降水入渗量存在着一定的相关性。     

Rhynchosporium leaf scald disease incidence: seed source and spatial pattern

A programme of field trials for the study of the winter barley–Rhynchosporium commune pathosystem is reported. The associated seedborne disease rhynchosporium leaf scald is regarded as having an important impact on barley yields. The analysis in this study relates to the impact of the seed source (commercial or farm-saved seed) on disease incidence and to the spatial pattern of rhynchosporium leaf scald disease incidence. Disease incidence data were calculated from field data recorded as disease severity. Mean disease incidence was higher in the crops grown from farm-saved seed than in those grown from commercial seed, although great agronomic significance cannot be attached to this result. The spatial pattern of rhynchosporium leaf scald disease incidence was characterized in terms of the binary power law (BPL) and was indicative of an aggregated pattern. Programme-wide BPL results were described using a novel phytopathological application of a random coefficients model. These results have application in field sampling for rhynchosporium leaf scald disease.     

A conceptual model of farmers' decision-making process for nitrogen fertilization and irrigation of durum wheat

With a 2 millions of tons production, France is the second country in the European Union to produce durum wheat. Durum wheat production requires high grain nitrogen concentration. Irrigation and nitrogen fertilization must be managed simultaneously to maximize grain yield and also avoid low protein concentration and environmental impacts. To help advisors and farmers to better manage together these two agricultural operations and to develop innovative managements, developing a biodecisional model is an interesting possibility. However, knowledge is still missing on how farmers already managed these operations and how these two operations are linked. We developed the conceptual model for the decision part of this computer model. We performed a survey of 28 farmers conducted over the five French production areas investigating a diversity of growing conditions to identify the set of possible constraints and farmers' decision rules. To analyze the survey, we first used a general inductive approach on individual cases and then built a conceptual model of the decision with a bottom-up approach. We identified four decision sequences for fertilization (N splitting, choice of N fertilizer, rate of application, fertilization triggering) and five for irrigation (irrigation period, anticipated number of irrigation cycles, irrigation cycles organization, irrigation triggering and irrigation cycle specificities). For each operation, the first three decision sequences refer to strategic decisions. The other decision sequences refer to tactical decisions. Coupling this model with a crop model could provide guidelines for managing durum wheat in the current climatic and economic changing context.     

基于B-S模型的环保项目投资评价

以ABC公司环保产品开发为例,针对传统项目投资评价在环保项目上的缺点,分析了将实物期权理论运用到环保项目投资评价中的可行性,并运用B-S模型进行定量分析,以期为环保项目投资提供一个新的思路,同时也使环保项目决策变得更加合理。     

一种改进的开关磁阻电机磁链模型

开关磁阻电机(SRM)特殊的结构使建立其磁链模型比较困难。根据SRM运行的周期特点,从数学角度用傅里叶级数模型对其进行解析,通过权系数将傅里叶级数模型与传统指数模型结合,得到一个新的改进模型。用提出的改进模型与指数函数模型、傅里叶级数模型分别对Ansoft Maxwell仿真得到的磁链数据进行拟合。对比解析结果,证明提出的改进模型具有更高的解析精度,适合解析磁链。     

应用光谱反射测定的植物、土壤及混合光谱特性

以野外采集的土壤与活体植物叶片为研究对象,采用美国生产的SVC HR-1024便携式地物光谱仪,测定了纯土壤、纯植物叶片以及不同植物叶片盖度下的土壤光谱反射率,并对混合光谱特性进行了分析研究,建立了植物叶片盖度光谱估算模型。结果表明:(1)随着植物叶片盖度的增加,土壤光谱曲线逐渐呈现"五谷四峰"的特征,但始终不会高于植被光谱曲线;(2)植物叶片盖度与原始高光谱组成的差值、比值和归一化值3种形式的指数存在着良好的相关性,差值指数的显著性最为明显,组合较好的波段为410~710 nm与700~1400 nm,能反映相关系数最大的波段为690 nm和450 nm;(3)通过一元线性回归法、多元线性逐步回归法和偏最小二乘回归法预测植物叶片盖度可知:光谱特征参数与植物叶片盖度之间具有相关性,其中光化学指数与植被衰减指数的相关系数较大,模型拟合度较高,R^2均达到0.8以上;3种光谱特征参数(植被指数、红边参数、光谱吸收特征参数)中,植被指数与植物叶片盖度建立的模型最稳定、精度最高,可以有效地估算植物叶片盖度3种方法中,多元线性逐步回归法最适宜建立植物叶片盖度预测模型。     

Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages,distribution, and habitat associations

We compared the assemblage structure, spatial distributions, and habitat associations of mountain whitefish (Prosopium williamsoni) morphotypes and size classes. We hypothesised that morphotypes would have different spatial distributions and would be associated with different habitat features based on feeding behaviour and diet. Spatially continuous sampling was conducted over a broad extent (29 km) in the Calawah River, WA (USA). Whitefish were enumerated via snorkelling in three size classes: small (10–29 cm), medium (30–49 cm), and large (≥50 cm). We identified morphotypes based on head and snout morphology: a pinocchio form that had an elongated snout and a normal form with a blunted snout. Large size classes of both morphotypes were distributed downstream of small and medium size classes, and normal whitefish were distributed downstream of pinocchio whitefish. Ordination of whitefish assemblages with nonmetric multidimensional scaling revealed that normal whitefish size classes were associated with higher gradient and depth, whereas pinocchio whitefish size classes were positively associated with pool area, distance upstream, and depth. Reach‐scale generalised additive models indicated that normal whitefish relative density was associated with larger substrate size in downstream reaches (R² = 0.64), and pinocchio whitefish were associated with greater stream depth in the reaches farther upstream (R² = 0.87). These results suggest broad‐scale spatial segregation (1–10 km), particularly between larger and more phenotypically extreme individuals. These results provide the first perspective on spatial distributions and habitat relationships of polymorphic mountain whitefish.     

AM80-0.2Sr-1.5Ca镁合金高温压缩过程动态再结晶模拟

在Gleeble-1500热压缩实验机上对AM80-0.2Sr-1.5Ca镁合金进行高温压缩实验，得到了该合金在温度为300~450 ℃、应变速率为0.01~1 s-1条件下的流变应力曲线.结合改进的Laasraoui-Jonas（L-J）位错密度模型和Kock-Mecking（K-M）位错密度模型，获得AM80-0.2Sr-1.5Ca镁合金在改进的L-J位错密度模型中的应变硬化参数和应变软化参数，建立该合金的动态再结晶模型.利用DEFORM-3D软件，实现了对AM80-0.2Sr-1.5Ca镁合金在450 ℃热压缩实验时微观组织演变和位错密度变化过程的有限元模拟，并与实际热压缩实验微观组织进行对比.研究结果表明：在相同的温度和应变量下，应变速率较低时，AM80-0.2Sr-1.5Ca镁合金组织粗大且晶粒分布不均，随着应变速率增大，再结晶组织细小均匀模拟与实验结果一致，说明求解的应变硬化参数和应变软化参数准确，所建立的动态再结晶模型能准确预测该合金高温压缩过程动态再结晶过程.