Nonlinear dimensionality reduction by locally linear embedding

Many areas of science depend on exploratory data analysis and visualization. The need to analyze large amounts of multivariate data raises the fundamental problem of dimensionality reduction: how to discover compact representations of high-dimensional data. Here, we introduce locally linear embedding (LLE), an unsupervised learning algorithm that computes low-dimensional, neighborhood-preserving embeddings of high-dimensional inputs. Unlike clustering methods for local dimensionality reduction, LLE maps its inputs into a single global coordinate system of lower dimensionality, and its optimizations do not involve local minima. By exploiting the local symmetries of linear reconstructions, LLE is able to learn the global structure of nonlinear manifolds, such as those generated by images of faces or documents of text.     

Spectral light-reflection data dimensionality reduction for timely detection of yellow rust

Precision Agriculture - Yellow rust (YR) wheat disease is one of the major threats to worldwide wheat production, and it often spreads rapidly to new and unexpected geographic locations. To cope...     

基于几何非线性动力组合地基梁模型的漏粪地板自振特性

针对农业工程中猪舍漏粪地板的动力响应问题,采用静力分析方法,对漏粪地板进行自振特性进行研究。在考虑地基的压缩和剪切刚度、梁的弯曲和剪切变形、运动的平动和转动惯性力以及轴力的二阶效应的基础上,建立了几何非线性压剪平转动Timoshenko弹性地基梁动力基本方程,并给出了动力位移和内力方程;提出了组合地基梁的自振特性分析方法,对典型猪舍漏粪地板自振周期及振型进行了计算。结果表明：组合地基梁的周期及振型规律明显异于普通梁;不同结构参数对漏粪地板自振周期的影响程度各不相同：端部缝间板条不改变振动特性;支承长度和地基刚度作用显著;剪切变形、转动惯性力和地基剪切刚度引起的偏差较小,可忽略其影响。本研究建立的几何非线性动力组合地基梁模型能够用于猪舍漏粪地板舒适性验算和动力安全性设计。     

几何非线性非保守系统弹性动力学两类变量的广义拟变分原理的应用

非线性非保守系统弹性动力学的广义变分原理的研究,是一个相当重要的研究领域。它不仅在有限元素法和其它近似计算方法中得到广泛应用,而且可以方便地求得非线性非保守系统弹性动力学问题的精确解。文章应用几何非线性非保守系统弹性动力学中的第一类两类变量广义拟余能原理,研究了一个典型的非保守动力学系统边值问题的动态特性,并给出同时求解一个典型的几何非线性非保守系统的内力和变形两类变量的计算方法。     

A cellular framework for gut-looping morphogenesis in zebrafish

Many vertebrate organs adopt asymmetric positions with respect to the midline, but little is known about the cellular changes and tissue movements that occur downstream of left-right gene expression to produce this asymmetry. Here, we provide evidence that the looping of the zebrafish gut results from the asymmetric migration of the neighboring lateral plate mesoderm (LPM). Mutations that disrupt the epithelial structure of the LPM perturb this asymmetric migration and inhibit gut looping. Asymmetric LPM migration still occurs when the endoderm is ablated from the gut-looping region, suggesting that the LPM can autonomously provide a motive force for gut displacement. Finally, reducing left-sided Nodal activity randomizes the pattern of LPM migration and gut looping. These results reveal a cellular framework for the regulation of organ laterality by asymmetrically expressed genes.     

A geometric and topological system for supporting agricultural subsidies in Slovenia

This paper presents a system for supporting agricultural subsidies in Slovenia. First, an overview is given of specific areas of Slovenia’s land, considered as zones. Then, the system, which explores the computational power of today’s clients is briefly introduced. Some features of the geometric and topological system (GTS), is introduced. This application has been used successfully for 3 years and has turned out to be effective and stable.     

A nonlinear feedback technique for greenhouse environmental control

Climate control for protected crops brings the added dimension of a biological system into a physical system control situation. The plants in a greenhouse impose their own needs, significantly affect their ambient conditions in a nonlinear way, and add long-time constants to the system response. Moreover, the thermally dynamic nature of a greenhouse suggests that disturbance attenuation (load control of external temperature, humidity, and sunlight) is far more important than is the case for controlling other types of buildings. This paper presents a feedback–feedforward approach to system linearization and decoupling for climate control of greenhouses and more specifically for the operation of ventilation/cooling and moisturizing. The proposed method consists of three parts: (a) a model-based feedback–feedforward compensation of external disturbances (loads) on the basis of input–output linearization and decoupling; (b) the transformation of user-defined desired settings for temperature and humidity into feasible controller setpoints, taking into account the constraints imposed by the capacities of the actuators and the psychrometric laws; and (c) additional PI outer loops to compensate for model uncertainties and deviations from expected disturbances (weather). Moreover, some tuning tests lump together several physical system parameters to be easily identified, and the method guarantees accuracy in setpoint tracking while simplifying stability issues. The proposed method is applicable to any air-conditioning system and is expected to gain wide acceptance in modern climate control systems.     

A green eco-environment for sustainable development: framework and action

Following its 40-year reform and ‘Open Door’ policy, China has recently proposed a new approach to green development and rural revitalization—the idea of Agriculture Green Development (AGD), with the key feature of creating a green eco-environment. In this mini-review we introduce the definition, theory, framework and major components of a green eco-environment as a key part of the AGD. We define a green eco-environment as including four key elements or measures: (1) a green eco-environmental indicator system; (2) environmental monitoring and warning networks; (3) emission standards and environmental thresholds for key pollutants; (4) emission controls and pollution remediation technologies. We have used Quzhou County (a typical county in the center of the North China Plain) as an example to show how detailed air, water and soil monitoring networks, as well as improved farmer practices and pollution control measures (especially ammonia emission mitigation and PM_2.5 pollution reduction), can begin to create a green eco-environment in China and that AGD is possible. We conclude by stressing the need to improve the framework and practice for a green eco-environment, especially the importance of linking proposals and practices for a green eco-environment with the United Nations high priority Sustainable Development Goals.     

下垂控制微电网容错运行的弹性控制框架

提出了一种下垂控制微电网客错运行的弹性控制框架,该框架以一种经济有效的方式实现功率控制.针对微电网中考虑非线性滤波电感的功率控制问题,提出了一种无传感器控制策略.首先,提出了一种虚拟通量模型用来估算输出电压信号,以取消实际电压传感器;然后,分析了非线性滤波电感对电压估计精度的影响,提出了一种基于鲁棒观测器的VF方法来消除这种影响.此外,通过在功率控制和电压控制回路中引入电压估计,提出了一种基于鲁棒观测器的无电压传感器下垂控制方法.仿真结果表明,所提出的控制策略能够在不使用电压传感器的情况下实现理想的功率控制性能.该控制器具有较好地抑制非线性电感影响的能力,提高了系统的可靠性,降低了微电网的设计成本.     

基于社会-生态系统理论的土地健康诊治框架

为实现土地资源可持续利用,构建人地关系视角下的土地健康诊治框架。运用CiteSpace文献计量方法,对土地健康研究进行知识图谱分析,同时基于社会-生态系统(Social-ecological systems,SESs)理论,构建土地健康诊治框架。结果表明:1)土地健康科学内涵的发展过程可作为土地生态系统与社会经济知识健康运行的诊治依据;2)土地健康研究呈现多元分散特征,健康机理、评估方法与实践层面适应性管理是研究热点;3)土地健康诊治框架将社会经济系统和土地生态系统有机整合,由外部驱动子系统、内生驱动子系统和土地利用系统表征3部分组成;4)该诊治框架可以根据特定土地问题进行相应调整,适用性强。因此,基于SESs理论构建土地健康诊治框架有助于理解人地系统的作用过程和互馈机制。     

A kinetic framework for a mammalian RNA polymerase in vivo

We have analyzed the kinetics of assembly and elongation of the mammalian RNA polymerase I complex on endogenous ribosomal genes in the nuclei of living cells with the use of in vivo microscopy. We show that components of the RNA polymerase I machinery are brought to ribosomal genes as distinct subunits and that assembly occurs via metastable intermediates. With the use of computational modeling of imaging data, we have determined the in vivo elongation time of the polymerase, and measurements of recruitment and incorporation frequencies show that incorporation of components into the assembling polymerase is inefficient. Our data provide a kinetic and mechanistic framework for the function of a mammalian RNA polymerase in living cells.     

基于几何非线性圆拱动力模型的拱形温室自振周期分析

针对拱形温室结构动力分析中的杆件弯曲振动问题,采用直接刚度法,对拱形温室自振特性进行研究。在分析拱的弯曲变形、剪切变形、轴向压缩变形、二阶效应以及基于分布质量的平动惯性力和转动惯性力的基础上,建立了圆拱的位移控制方程,求解得到了非线性平转动Timoshenko圆拱动力模型。由定解条件,得到了特征方程,通过求解特征方程,给出了拱形温室自振周期的计算方法。利用本研究模型及其退化模型,计算了拱棚和典型拱形温室结构在不同模型下的自振周期,分析了不同模型的计算结果,分析表明,本研究建立的几何非线性可压缩平转动Euler梁模型可用于拱形温室结构自振周期计算。