Improving Retrieval Performance by Region Constraints and Relevance Feedback

In this paper, region features and relevance feedback are used to improve the performance of CBIR. Unlike existing region-based approaches where either individual regions are used or only simple spatial layout is modeled, the proposed approach simultaneously models both region properties and their spatial relationships in a probabilistic framework. Furthermore, the retrieval performance is improved by an adaptive filter based relevance feedback. To illustrate the performance of the proposed approach, extensive experiments have been carried out on a large heterogeneous image collection with 17,000 images, which render promising results on a wide variety of queries.     

BREAM: A probabilistic Bystander and Resident Exposure Assessment Model of spray drift from an agricultural boom sprayer

Complex simulation models are available to predict the level of exposure to bystanders and residents after a crop spraying event. In this paper we consider a particle-tracking spray drift model whose input parameters define particular scenarios of interest. Model outputs based on fixed values for these inputs ignore natural random variation and therefore give no indication of realistic variation in exposures, nor do they quantify the probability of rare extreme exposures. We describe a probabilistic modelling framework that allows the effect of variability in the input parameters to be quantified. An efficient statistical method for approximating the spray drift model is used, by creating a statistical emulator. An additional statistical model is then used to link airborne spray outputs to bystander exposures based on measured data. Uncertainty and variability are quantified in this model component. Validation of our approach is considered in two stages: first the accuracy of the emulator is assessed, as a surrogate for the true spray model. Secondly, the overall probabilistic outputs are compared with corresponding field measurements. Results are presented for a selection of typical exposure risk scenarios for bystanders and residents, illustrating the potential to generate a richer source of information for decision-makers. Sensitivity analysis results suggest strategies to reduce risk, such as minimising boom height.     

农业灌溉系统的随机一区间规划模型

研究了不确定性环境下农业灌溉系统的水资源分配问题。视水资源可利用量为随机变量,其他参数均为区间数,建立了其随机-区间规划模型。用满意度方法首先把含随机变量的不等式转化为其等价类,再用区间线性规划方法将其转化为求目标函数最好最优值与最差最优值的两个子模型。两个子模型解的组合即为原模型目标函数的最优取值区间。最后用实例说明该模型的实用性与有效性。与已有方法相比,此方法更简单明了,计算结果的区间长度更小。     

土壤环境质量评价的径向基函数神经网络的模型设计与应用

针对土壤环境质量评价缺乏精确客观的评价数值作为目标集的难点,研究了构建起对应升序排列的训练、检验样本集。在此基础上,定义以检验集输出评价结果的排序误排率作为判定各参数组合下RBF网络性能优劣的指标,以此性能指标为依据,在MATLAB6.5环境下,用编程语句实现了应用于该质评工作的径向基函数网络的大量参数组合的全面快速寻优,克服了目前用试凑法进行参数组合优选的随机性,确保所选参数组合为使整体性能最优的组合。利用确立的网络对象,以某地土壤重金属监测值为实例,对监测点进行质评,评价结果表明:该设计好的网络的评价结果科学、稳定、表达精度高。     

运用SAS广义线性混合模型分析裂区试验数据

裂区设计能够灵活地增加试验处理和进行误差分级控制,在农业试验中应用广泛.但数据的统计分析较复杂,目前有效的相关统计软件十分缺乏.为了建立操作简单、实用性强、计算结果无误的统计分析手段,采用SAS广义线性混合模型(GLIMMIX)程序模块进行裂区设计数据的统计和分析,并通过实例分析说明GLIMMIX相较于传统一般线性模型...     

自适应遗传算法及其在渗流参数反演中的应用

利用水头实测资料,以渗透系数为待反演的参数,在采用基本遗传算法进行参数反演研究的基础上,针对简单遗传算法难以确定交叉率和变异率的最佳值及计算量较大、易早熟等缺点,提出以自适应遗传算法来解决工程中的这类反演问题;为力求使改进的遗传算法计算量更小,收敛性更强,同时结合简单的二稳定渗流有限元算例,在相同的情况下分别用简单遗传算法和自适应遗传算法进行了反演计算。结果表明,自适应遗传算法在保持简单遗传算法优点的同时,有效地提高了算法的收敛性,并在一定程度上克服了简单遗传算法的早熟问题。因此,自适应遗传算法为渗流领域求解反演问题提供了新的途径。     

两种自然保护区设计方法——数学建模和计算机模拟

传统的自然保护区设计方法是打分法和Gap分析法,这两种方法简单易行但可靠性不高;地理信息系统(GIS)在保护区设计领域的应用也为人熟悉。关注近年来快速发展而国内使用不多的两种方法——数学建模和计算机模拟。数学建模主要用来从一组备选地块中选择一部分组成自然保护区,包括线性和非线性模型,用启发式算法或最优化算法求解。启发式算法具有速度快、灵活等优点,但解通常不是最优的,不能保证稀缺资源的最优化利用。最优化算法运算效率低,变量较多比如数百时就可能遇到计算困难,但解是最优的。预计两种算法都将继续发展。计算机模拟主要用于保护区评价、功能区划分、预测特定环境比如空间特征和气候变化对物种的影响等,多用启发式算法,与其它软件结合把结果以图画显示出来。两种方法特别是计算机模拟均要求保护区设计者有较强的专业知识。讨论了两种方法面临的问题和新的研究方向,至少包括:1)基础数据依然需要完善;2)一些新的因素比如动态性和不确定性如何在模型中考虑并与其它因素结合;3)气候变化预景下模拟参数如何评估和调整;4)如何协调保护与发展的关系;5)方法的实际应用需要研究者与决策者之间建立交流机制;6)多领域专家和相关利益方应有机会参与保护区设计。     

Evolution, safety, and highly pathogenic influenza viruses

Experience with influenza has shown that predictions of virus phenotype or fitness from nucleotide sequence are imperfect and that predicting the timing and course of evolution is extremely difficult. Such uncertainty means that the risk of experiments with mammalian-transmissible, possibly highly virulent influenza viruses remains high even if some aspects of their laboratory biology are reassuring; it also implies limitations on the ability of laboratory observations to guide interpretation of surveillance of strains in the field. Thus, we propose that future experiments with virulent pathogens whose accidental or deliberate release could lead to extensive spread in human populations should be limited by explicit risk-benefit considerations.     

方差分析的回归分析法

方差分析模型作为线性模型,其设计矩阵是不满秩的,只要设置适当的边界条件,就可以用回归分析的算法进行方差分析。本文对单向与两向分类非平衡方差分析问题具体地给出了边界条件,使之有效地用回归分析程序进行分析。     

机械设计计算若干问题的讨论

本文讨论了机械设计计算的若干问题,提出改进试凑法的一般途径,特别讨论了图线查找、表格查找和计算公式求解等3种直接求解法,同时导出几个设计计算公式。算例表明,直接求解法是一种简捷、实用的方法.     

Multiobjective optimization subject to uncertainty: Application to irrigation strategy management

In agricultural systems, multiple objectives and uncertainty are often part of the game when optimization is at stake. Multiobjective dominance rules cannot be simply applied due to this uncertain behavior. We propose some extensions of the well-known Pareto rules to enable the discrimination of multicriteria dominating groups of outcomes. These groups are either the various uncertain outcomes of a decision, or more generally a set of outcomes associated to different decisions and/or different random occurrences. Based on the Pareto dominance rules, we propose definitive, acceptable and undecidable dominance comparisons with regard to two candidate groups. The comparisons of all candidate groups allow to rank them from a multicriteria evaluation perspective. This ranking process is used as the evaluation step of a hierarchical decomposition procedure where the best ranked region is selected as the one to be investigated further. We apply these multicriteria extensions to look for optimal irrigation strategies. The yield, the total amount of water and the number of irrigation rounds are simulated to get economical, environmental and social perspectives simultaneously. Although the computation requires a high amount of simulation runs, the algorithm succeeds in reproducing the front of the non-dominated evaluations. The major interest resides in the width of the front achieved. This new information gives direct indication to the decision maker about the reliability of the outcomes with regard to the weather uncertainty, as well as the sensitivity of the outcomes with regards to the strategies application.     

车用三效催化转化器劣化性能数值模拟

本文提出了证券投资组合的一个新模型.该模型综合考虑了证券的收益率、证券分红和证券价格的关系,并将证券分红和证券价格作为系统的随机参数处理,建立了证券投资组合的随机规划模型.利用机会约束规划方法,我们研究了将所建立的随机规划模型转化为普通光滑优化问题求解的方法,得到了该类问题求解的有效途径.     

The Regional Multi-Agent Simulator (RegMAS): An open-source spatially explicit model to assess the impact of agricultural policies

Regional Multi-Agent Simulator (RegMAS) is an open-source spatially explicit multi-agent model framework specifically designed for long-term simulations of the effects of policies on agricultural systems. Using iterated conventional optimisation problems as agents’ behavioural rules, it allows for a bidirectional integration between geophysical and social models where spatially distributed characteristics are taken into account in the programming problem of the optimising agents. With RegMAS it is possible to simulate the local specific response to a given policy (or scenario), where policies, together with macro- and regional characteristics, are read into the program in specially formatted spreadsheets and standard GIS files.The paper presents the model logic and structure and describes its functioning by applying it to a case-study, where RegMAS results are compared with conventional agent-based modelling to demonstrate the advantages of spatial explicitness. The simulation refers to the impact of the recent “Health Check” of the CAP on farm structures, income and land use in a hilly area of a central Italian region (Marche).     

Automatic segmentation of relevant textures in agricultural images

One important issue emerging strongly in agriculture is related with the automatization of tasks, where the optical sensors play an important role. They provide images that must be conveniently processed. The most relevant image processing procedures require the identification of green plants, in our experiments they come from barley and corn crops including weeds, so that some types of action can be carried out, including site-specific treatments with chemical products or mechanical manipulations. Also the identification of textures belonging to the soil could be useful to know some variables, such as humidity, smoothness or any others. Finally, from the point of view of the autonomous robot navigation, where the robot is equipped with the imaging system, some times it is convenient to know not only the soil information and the plants growing in the soil but also additional information supplied by global references based on specific areas. This implies that the images to be processed contain textures of three main types to be identified: green plants, soil and sky if any. This paper proposes a new automatic approach for segmenting these main textures and also to refine the identification of sub-textures inside the main ones. Concerning the green identification, we propose a new approach that exploits the performance of existing strategies by combining them. The combination takes into account the relevance of the information provided by each strategy based on the intensity variability. This makes an important contribution. The combination of thresholding approaches, for segmenting the soil and the sky, makes the second contribution; finally the adjusting of the supervised fuzzy clustering approach for identifying sub-textures automatically, makes the third finding. The performance of the method allows to verify its viability for automatic tasks in agriculture based on image processing.     

基于代理模型的气动设计稳健优化方法

为了减少不确定分析的计算量,提出了一种基于代理模型的不确定性气动设计优化方法,其中代理模型主要用于简化不确定分析计算过程.运用拉丁方试验设计和Krig-ing建立了代理模型,用随机参数来表示尺寸误差和飞行条件的变化.基于代理模型,以蒙特卡洛模拟法作为不确定分析方法,求解气动性能的均值和方差.在此基础上定义了气动稳健优化问题的表达式,用遗传算法进行求解,并以某翼型的优化问题对该方法进行验证.结果表明,通过该方法得到的最优解对不确定性的敏感度大大减小,同时在不确定的情况下仍然能满足设计约束条件.     

Visual FoxPro程序设计主观题自动阅卷系统设计思路

针对Visual FoxPro程序设计考题的类型,提出了基于程序运行跟踪、程序重点分析、运行结果判断等关键步骤的自动阅卷系统设计思路。     

计算机辅助农业机械运动状态分析的多媒体系统

为了研究农业机械设计的最佳参数或参数范围,应用计算机的机构运动状态模拟分析方法和多媒体技术,开发了计算机辅助农业机械动态分析的多媒体系统,该系统将机构运动分析参数化,能更大地提高机构运动分析的效率和精确度,还将运动分析方法的全过程生动地展示出来.既可用于农业机械等机械设计中也可作为机构运动状态分析的辅助教学软件.     

岔口小流域非点源污染模型AnnAGNPS不确定性分析

为了降低模型模拟计算的不确定性,提高模型在北方典型黄土丘陵沟壑区的适用性,以岔口小流域为研究区,选取可能对非点源污染模型——AnnAGNPS产生影响的10个参数,采用修正的摩尔斯(Morris)分类筛选法,分析参数对模型模拟结果影响的敏感性程度。在此基础上,尝试综合利用一阶误差分析法(FOEA)和自助法(Bootstrap)不确定性分析方法识别重要的不确定性参数,评估参数对模型输出变量的不确定性的贡献。综合两者分析结果表明:对径流模拟计算不确定性影响较大的是径流曲线数、田间持水量;对泥沙、氮磷负荷模拟计算不确定性影响较大的是径流曲线数、地形因子、土壤侵蚀因子、耕作管理因子、水土保持因子、化肥施用量。径流曲线数对模型输出结果的不确定性影响最为显著,表明径流产生过程是泥沙和各种营养盐等侵蚀、搬运的驱动力。泥沙和氮磷的不确定性参数较为一致地表明泥沙是氮磷输出的载体,即在短时暴雨事件下氮磷输出形态通常以泥沙结合态为主,泥沙的不确定性直接影响和决定氮磷等营养物输出的准确性。模型输出结果中泥沙不确定性最大,径流不确定性最小。研究表明,流域水文和土壤侵蚀过程的模拟是校准模型、降低不确定性的关键。在控制和治理流域水土流失及非点源污染时应着重考虑径流曲线数、施肥措施、农田管理方式和水土保持情况。     

Local autonomy and sustainable development: Testing import substitution in more localized food systems

Community initiatives to create more localized food systems ofteninclude the strategy of import substitution, i.e., increasing local foodproduction for local consumption. The purpose of this policy iseffectively to supplant some level of imported food into the region. Weargue that such action can carry social and environmental risks as wellas benefits and we have developed research parameters to measure theimpact of such strategies. Harriet Friedmann's seminal work (1991) onthe employment of import substitution by transnational corporationsprovides a framework to identify possible advantages and disadvantagesof the same approach locally. We propose local autonomy and sustainabledevelopment as positive indicators of a more localized food system.Three units of analysis are proposed to measure changes in localautonomy and sustainable development as a result of import substitutionschemes: fair labor trade, equity and democracy, and environmentalstewardship. We propose that this flexible framework of analysisincreases our ability to describe the shifting and integrated balancebetween more local and more global food systems.     

新疆灌区规划设计中渠系水利用系数的分析

渠系水利用系数在灌区灌溉排水工程规划设计中是个非常重要的设计参数,其数值的大小直接影响到灌区设计方案的调整。常用的估算方法有实测法、经验公式法、实际供水-用水资料分析法和综合分析法,其中综合分析方法应是最可行的。笔者针对新疆地区情况,在经验公式法中导入了管理因子作为校正系数,使渠系水利用系数更趋于接近当地实际情况。