Further observations on the use of fungicides to control Peronosclerospora sacchari (T. Miyake) Shirai and K. Hara in sugarcane in Papua New Guinea

Abstract

Many biologists perceive organisms as constantly evolving and therefore consider the host plant ranges of biological control agents as labile. Host plant ranges are thus likely to undergo adaptive change should environmental conditions change, for example following successful biological control. As a consequence, the introduction of biological control agents against weeds is considered by many to be an inherently unsafe practice with non‐target plants at risk of attack. However, despite the introduction of over 600 insect species from one geographic region to another for biological weed control during this century, there are relatively few documented cases of changes in host plant range. Purported instances are discussed in relation to behavioural and genetic concepts. It is concluded that apparent additions to the host range can, in all of the cases examined, be explained in terms of established behavioural concepts of pre‐adaptation, threshold change resulting from host deprivation, and effects of experience (learning). The inappropriateness of the often‐used term host shift’ to describe these cases is demonstrated, and it is concluded that evidence from biological weed control contradicts some aspects of ecological and evolutionary theory.     

生态规划推进基层社会治理范式转换研究

本研究旨在通过分析包容性生态规划中各利益相关者的作用,指出其能够推动社会治理范式的转换。生态规划是中国正在推行的区域国土空间规划的一项重要内容,它是沟通自然与社会生态系统的桥梁,通过生态规划过程推进基层社会治理能力是区域国土空间规划能够取得成效的关键。本研究基于2000年以来的研究和实践,分析生态规划中基层政府及其部门、公众、规划师、其他社会力量等各方在生态规划的编制、实施、监测与评估等交互合作过程中的作用,将生态规划面临的两种社会治理范式进行了比较,指出生态规划包容合作的治理范式有能力助力社会治理范式转换。通过对包容性生态规划过程的描述,指出可以通过其具体过程中协调主体间性的方式助力社会治理转变为各利益相关者共同参与的、多方合作的治理体系和多元协商平台。     

一种新型双离合自动变速器的换挡品质研究

以一种新型的双离合自动变速器为模型,在AMESim平台上,以不同的油压变化率作为仿真的前提条件,搭建滑磨功和冲击度仿真模型,并对这两个指标进行仿真分析,仿真结果得到油压变化率对换挡品质的影响.最后,利用遗传算法对油压变化率进行优化,优化结果改善了变速器的换挡品质.     

基于卡尔曼滤波的橘小实蝇成虫运动轨迹优化跟踪

为了实现橘小实蝇虫口密度的精准监测,该文将机器视觉技术作为田间橘小实蝇成虫入侵自动化监测的感知方法。通过对监测区域内运动目标和背景的颜色分析,提出了基于卡尔曼(Kalman)滤波的运动目标颜色均值漂移跟踪算法,优化了多目标运动轨迹跟踪效果。该算法通过图像处理和匹配技术提取了橘小实蝇成虫在虫口监测区域二维平面X轴和Y轴方向上的位置坐标和速度分量,推算了橘小实蝇成虫运动轨迹递推关系。基于动态系统的状态序列线性最小方差估计理论和成虫运动轨迹关系分析,构建了卡尔曼滤波状态估计模型,并建立其预测和修正方程实现了橘小实蝇成虫运动目标位置估计。通过在虫口监测区域开展单目标和多目标分散及粘连条件下的成虫跟踪试验,试验结果表明颜色均值漂移跟踪算法对橘小实蝇成虫单目标跟踪具有较好的适应性,成虫监测计数准确率达100%,对于多目标分散和粘连情况跟踪处理效果较差,计数准确率分别下降至86%和76%;通过在颜色空间均值漂移跟踪算法的基础上引入Kalman滤波器估算目标运动的近似位置,实现了对橘小实蝇成虫分散和粘连多目标运动的持续跟踪优化,监测计数准确率分别提升至96%和93%。机器视觉技术实时跟踪橘小实蝇成虫在虫口监测区域运动轨迹试验进一步验证了橘小实蝇成虫虫口密度监测的可行性,为田间橘小实蝇成虫发生自动化监测技术研究提供了参考。     

基于改进均值漂移算法的绿色作物图像分割方法

针对绿色农作物图像背景复杂且分割难的问题,提出一种基于改进均值漂移算法的分割方法。采用均值漂移算法对图像进行平滑和分割时,带宽的选择直接影响平滑和分割的结果。传统的均值漂移分割方法需要人为地设定空域带宽和值域带宽这2个参数。该文首先根据绿色作物图像的颜色特点,提取图像的颜色指数;然后采用均值漂移算法,将图像的颜色信息与空间信息结合起来,根据作物图像颜色分布的丰富程度定义自适应空域带宽,采用渐近积分均方差来获得自适应值域带宽,对图像进行平滑滤波;最后采用 Otsu 方法将平滑后的图像分成两部分：绿色部分和背景部分。试验结果表明,该方法能够有效地分割出绿色作物,并在分割性能上明显优于常规的颜色指数方法,作物图像的错分率均小于6.5%。     

Reconciling 14C and minirhizotron‐based estimates of fine‐root turnover with survival functions

The turnover of fine‐roots is a crucial component for the input of C to the soil. The amount of root litter input is depending on estimates of turnover times from different techniques. Turnover times from fine‐root cameras (minirhizotrons) often yield 75% higher root litter input estimates than turnover times estimated with the bomb‐radiocarbon signature of fine roots. We introduce a generic framework for the analysis of fine‐root ¹⁴C with different survival functions. So far, mostly an exponential function has been used to estimate the turnover time and mean age of fine roots. In the context of the introduced survival function framework we clarify the terms turnover time, mean residence time, mean longevity, and mean age, which are commonly used in studies of root turnover. Using a unique time series of fine‐root ¹⁴C (Fröberg 2012), we test if survival functions other than the exponential function are better in accordance with turnover‐time estimates commonly found with other methods. A survival function that corresponds to a two‐pool model was best in agreement with minirhizotron‐based estimates (mean residence time of 1.9 y). We argue that using fine‐root ¹⁴C and minirhizotron time‐to‐death data together would give the best constraints on fine‐root turnover. At the same time this could allow quantifying systematic biases inherent to both techniques.     

天然香豆素衍生物~（13）C－NMR化学位移研究（Ⅱ）──化学位移加合与降阶模型的研究

运用数学模型对香豆素衍生物１３Ｃ－ＮＭＲ化学位移数据进行了较系统的研究．结果表明，香豆素类化合物的化学位移相对于未取代母体的增量具有良好的加合和降阶性规律．从理论上建立了１３Ｃ－ＮＭＲ化学位移的加合和降阶模型，提出了经验公式．     

西部农村剩余劳动力转移的途径探讨

为了加快西部农村剩余劳动力转移的步伐，促进西部经济发展，本文通过对目前己存在的农村剩余劳动力转移途径的研究，结合西部农村剩余劳动力的现状，提出了一些解决西部农村剩余劳动力转移的有效途径。     

LOCAL PERCEPTIONS OF WOODY VEGETATION DYNAMICS IN THE CONTEXT OF A ‘GREENING SAHEL’: A CASE STUDY FROM BURKINA FASO

After decades of drought in the Sahel, several studies have reported a ‘(re)greening’ of the area. However, most of these studies were based on large scale climatological or remotely sensed observations, with little or no ground truthing. The aim of this study was to assess the local perceptions of the distribution of socio‐economically important tree species in the Sub‐Sahel of Burkina Faso. Semi‐structured interviews were performed with 87 groups of informants from 20 villages belonging to three ethnic groups (Mossi, Fulani and Samo). Univariate and multivariate statistics were used to compare perceptions between the targeted ethnic groups. According to the locals, more than 80 per cent of the 90 listed species were declining, with over 40 per cent identified as threatened, including numerous plants of great economic value. Increasing species were mostly drought‐tolerant plants such as Balanites aegyptiaca. A few species were listed as locally extinct. Gender and age did not significantly affect local knowledge, whereas ethnicity did. The major causes of species decline were identified to be drought, deforestation and bushfires. In all ethnic groups, informants observed a southward shift in species distribution. Local perceptions suggest a general decline in woody vegetation. Thus, the alleged (re)greening in the Sahel might not have reversed the degradation of woody species in the area. Data derived from local ecological knowledge were consistent with that of many ecological studies, suggesting the reliability of people's knowledge for obtaining ecological data. Information from this study can be used as baseline for conservation of species identified as threatened. Copyright © 2011 John Wiley & Sons, Ltd.     

Dynamic simulation of and experimentation with tracked vehicle hydrostatic steering characteristics of zero differential systems of a power shift steering transmission

This research investigated problems influencing tracked vehicles steering dynamic characteristics, such as rolling resistance during straight driving, steering centrifugal resistance, acceleration resistance during straight driving, scratching soil resistance of steering. Based on research about the relationship between the hydraulic steering regulation speed system and its maximum stable work pressure when vehicles have central steering on good roads (such as cement and rural roads), a zero differential hydraulic steering system of power shift steering transmission can ensure that vehicles maintain straight ahead stability through reasonably matching a steering drive system. The test indicates that vehicles have good dynamic characteristics when the work pressure accounted for 60% to 80% of the security work pressure.