共查询到20条相似文献，搜索用时 31 毫秒
1.
针对不同设备设计不同喷液量,飞行参数验证防治效果,从而验证无人机在稻田全程应用的可能性,旨在探索2种小型多旋翼植保无人机低空喷洒在整个水稻生长时期病虫草害防治过程中的防效。结果表明:当喷洒水田封闭式除草剂的喷洒量为10650、15000 mL/hm2,其对杂草的株防效与鲜重防效与人工电动喷雾相近。在病虫害的防治试验中,使用推荐用量且喷洒量为10650、15000 mL/hm2时,以及使用70%推荐用量（减量30%）且喷洒量为15000 mL/hm2时,防治效果均与人工电动喷雾器无显著差异。通过验证,选择合适的药剂,配合科学的喷洒参数,可在保证药效的前提下减少农药使用量。多旋翼植保无人机在水稻田有进行大面积全程飞防植保应用有广阔的前景。 相似文献
2.
Study on constant current control of inductive power transfer with parameter identification 总被引：1，自引：0，他引：1
Aiminy at magnetic exciting current (resonant current) control, a constant current control method based on dynamic parameter identification is put forward. With energy conversion analysis, the energy storage, supply and dissipation functions of the system resonant network are constructed. The reflecting impedance identification functions are obtained by constructing the energy equilibrium relations in a period and among several periods. Furthermore, a constant current control strategy by regulating the system input voltage with Buck converter is presented. Combining the relations among system input voltage, the envelope of resonant current and the input of Buck converter, the constant current control law is proposed. The control law is verified with experiments. For the proposed method, in parameter identification, only the data of zero crossing point of resonant voltage and current are required, which reduces the complexity and costs of sampling system. Also, the constant current control law does not need complex computation and is easy to implement. 相似文献
3.
作物气孔导度模型研究进展及应用现状 总被引：1，自引：0，他引：1
旨在为作物耗水和碳水交换相关研究的模型选择提供理论指导,本研究归纳了气孔导度对单一和综合环境因子的响应情况;对现有气孔导度模型进行了分类和比较,包括基于Jarvis模型建立和改进的经验模型、基于BWB模型建立和改进的半经验模型、基于ABA调控建立和改进的模型、基于保卫细胞膨压控制理论建立和改进的模型;并概述了气孔导度模型在作物水分利用研究领域的应用,以叶片气孔导度和冠层导度的定量关系为切入点建立多尺度联合的机理模型将是未来作物耗水尺度拓展研究的热点。 相似文献
4.
基于VRML的虚拟园林设计要素构建 总被引：2，自引：1，他引：1
虚拟现实技术应用于园林设计,可利用动态和交互方式对未来的园林进行身临其境的全方位审视,可达到传统的园林效果图所无法达到的效果,然而目前虚拟技术在园林中的应用比较少。笔者基于VRML技术对园林设计要素的（植物、建筑、地形和水体）构建进行探索,实现了园林设计四大要素的三维模型构建和互联网上的漫游与交互功能。研究表明基于VRML构建园林设计要素的方法是行之有效的,而且效果比较好。 相似文献
5.
The mountain hazards like snow avalanches, landslides, rock falls, debris flows and so on all have strong power of destruction which seriously threaten human’s lives and belongings. Therefore, it is necessary to study more the development of these disasters in order to prevent them. Setting up obstacles is the primary measure to control the movement and deposition process of mountain hazards. For the study of the influence of this measure on the development of disasters, the numerical simulation calculation aiming at the flow and deposition process of the granulars flowing past different built obstacles was made by the theory of SH granular flow and the method of finite volume discretization based on Roe's Scheme. Futhermore, the influence of different settings of obstacles on the granular flow is discussed. The numerical results show that the settings of obstacles have a great effect on the process of granular flow. That is, the effective precaution against the disasters is no other than setting up the obstacles correctly. As the numerical simulation calculation can optimize the setting of obstacle, it provides a reasonable and economic reference scheme of disaster prevention and planning of mountain area. 相似文献
6.
As for the actuation redundancy, strong nonlinearity and uncertainty, a kind of single-point preview control approach for the unmanned high-speed four-wheel-independent-drive & steering (4WID-4WIS) vehicle path tracking is proposed based on the control allocation and the Active Disturbance Rejection Control(ADRC) methods. The vehicle single-point preview system dynamic model for path tracking is built. The control system architecture with the control allocation unit as the core is constructed. The decouple single-point preview ADRC controller for path tracking is designed. Then the quasi-inertial parts used to generate control objectives are proposed and its rationality is discussed. The control allocation solution method for the 4WID-4WIS vehicle path tracking is subsequently presented. The simulations are conducted to illustrate the validity of the single-point preview control method proposed. The results show that the unmanned high-speed 4WID-4WIS vehicle can track the circular arc double-lane change path rapidly and accurately. 相似文献
7.
In this paper, in the light of the percolating flow mechanics problems in the field of environmental science research , the transport mechanism and law of the volatile organic pollutants in the soils and the transport model and law of the underground water multi-component reacting solute are discussed, and the gas transport and the second pollution problems in the solid waste landfill are analyzed~ Based on the research given above, the transport process and two aspects of the control mechanisms uncertainty for the volatile organic matter and the necessity to establish the coupling model of multi-component water chemistry model and waterdynamic transport model are pointed out. The result is of great theoretical importance and practical significance to the further understanding of the overlapping research problems in environmental science and percolating flow mechanics. 相似文献
8.
Based on characteristics of transportation infrastructure projects under a PPP model, an early warning risk index system for the private sector was put forward. The system is comprised of 15 indexes from five aspects, including risks associated with politics and law, economics, credit, construction and operation. An early warning risk model was constructed by applying fuzzy set theory and matter element theory. The fuzzy set method helps calculate the weight and evaluation values for qualitative indexes, thereby avoiding the limitations of individual decisions. The matter element method can evaluate comprehensive risks by using the comprehensive relations, is easy to use, and directly gives results. Further empirical research was conducted that verifies this method is scientific and applicable. 相似文献
9.
Chinese urban migrants' sense of place: Emotional attachment,identity formation,and place dependence in the city and community of Guangzhou 总被引：2，自引：0，他引：2
In this paper, we study urban migrants' sense of place in Guangzhou, China, focusing on the structural relations between place attachment, identification and dependence as the three key place dimensions. Through both quantitative structural equation modelling and qualitative analysis of in‐depth interviews data, our research suggests that migrants' sense of place demonstrates complex relationships between the three registers of emotional attachment, identity formation and functional dependence. The construction of sense of place is also related to the personal experiences of living as urban ‘outsiders’. Our research also reveals a striking difference between the city and community levels in terms of the ways in which migrants' sense of place is constructed. Urban migrants tend to exploit the functional utilities of microscopic urban spaces to meet their demands for recreation, education and socialisation. On the other hand, their sense of place to the city is largely compromised by their attachment to the hometown and conditioned by their personal identification to the city. 相似文献
10.
What drives university students to practice social distancing? Evidence from South Korea and Vietnam
Hyeon Jo 《Asia Pacific viewpoint》2023,64(1):47-59
As COVID-19 has caused unprecedented social change, governments are implementing several social measures to control transmission. Among them, social distancing is being enforced in almost all countries and is effective in preventing infection. Based on the importance of social distancing, this study identifies factors influencing the intention towards social distancing. The research model was developed by introducing risk perception in the theory of planned behaviour. To examine the proposed model, a survey was conducted with 339 university students from two countries, South Korea and Vietnam. The data were analysed using the partial least squares method. The results show that social distancing attitude and perceived behavioural control significantly influence social distancing intention. The findings indicate that both affective risk perception and cognitive risk perception serve as imperative factors in the formation of social distancing attitudes, subjective norms and perceived behavioural control. However, subjective norms and nationality do not affect social distancing intention. Based on the results, suggestions are made for policymakers to establish effective social measures. 相似文献
11.
YANG Pei-feng 《保鲜与加工》2004,(3):138-142
In the period of the city space expanding with the high speed, the theories system used to explain the city space is not perfect in our country. It is lack to expand this mechanism, among them research ecosystem' s main factors to particularly should be enhanced, especially the ecological factor. With rational analysis, the paper puts forward the viewpoint that the urban space is in ecological changing period, and considers that the power affecting the urban space expand involves motivity and resistance. Building the corresponding ecological model helps to cognize the city development roundly with ecological model constructed. A few possible ways is put forward which can be used in planning innovation, and have vivid leading function to the frondose city planning method. 相似文献
12.
Double pendulum has four equilibrium points (down down, down up, up down, and up up). Twelve transfer actions and eight spin actions can be formed with these equilibrium points. One of the transfer action, up down to up up (UD2UU) with human simulated intelligent control (HSIC) theory based on sensor motor intelligent schema is studied. Control system designed by HSIC has following advantages: hierarchic control architecture with multi controller and multi control mode; hybrid control law combining close loop and open loop control as well as positive feedback and negative feedback control; associating schema based on characteristic model which takes charge of switch between each control mode. The design process of HSIC controller for UD2UU is discussed. The real time control results demonstrate the validation of the proposed theory and method. 相似文献
13.
14.
Zhao Mingjie Xu Rong 《保鲜与加工》1999,(2):42-48
A method was proposed for calculating the crack tensor by the elastic wave velocities in the orthotropic rock masses,based on the theoretical relations of crack tensor and compliance tensor and elastic wave velocities,The numerical results show that there is a good correlation with the measured data. 相似文献
15.
Electromechanical coupling experimental analysis of permanent magnet AC servo precision drive system
To research the dynamic characteristics of the permanent magnet AC servo precision drive system coupled with multi-factors, the experiment system is constructed with PMAC as the core and IPC as the support platform. Through software prototype system, response signals such as the current, speed and torque are acquired when the system is in the no-load and in the loading operating state, then the theoretical analysis results are compared with the experimental results. So the experiment validates that the electromechanical coupling analysis of the system is correct. This research helps to analyze the influence mechanism and law that the design parameters and electromechanical coupling parameters exerted on the system performance. At the same time, the research is beneficial for dynamic design of the permanent magnet AC servo precision drive system. 相似文献
16.
Continuously variable transmission (CVT) is the ideal transmission for automobile, it is also one of the most important research items of researchers and automobile companies all over the world. The dynamic simulation model is established and integrated control strategy of standing start is proposed for dual mode CVT vehicle, aiming at automatic vehicle with torque converter as a starter and metal pushing belt as a higher transmission equipment (Dual mode CVT vehicle), on the base of engine and torque converter performance experiment. Simulation result shows that vehicle performance can be improved by using the control strategy proposed. The research results provide the theory method of analyzing and designing for CVT vehicle. 相似文献
17.
采用在线监测系统监测进行随钻参数的采样与分析,建立了派生参数与直测参数的理论表达式,提出了多因素组合的地层比功模型,实现了地层地质条件与随钻参数的有机结合。以重庆市某高压变电站施工场地为依托,建立了不同地层如素填土层、粉质粘土层、砂岩层及泥岩层的地层比功演化曲线,对比地勘信息可知,不同地层的比功值存在显著差异。可见,合理的地层比功阈值是辨识地层类型的重要参量。运用统计学原理对勘测孔附近不同地层的比功值阈值进行保值优化,通过地勘获得的地层信息来验证阈值区间的可靠性。进一步采用如上地层比功阈值对该区域的其他桩位所在地层进行分析验证,说明了地层比功阈值优化的统计方法可行,其阈值区间合理,可用于其他赋存环境的地层比功阈值确定及地层识别。 相似文献
18.
保护地番茄叶霉病的发生与防治研究综述 总被引：1，自引：0，他引：1
番茄叶霉病是一种世界性病害,其发生由番茄叶霉菌（Cladosporium fulvum (Cook) Ciferri）侵染引起。自从20世纪80年代以来,随着保护地蔬菜面积的扩大,该病的危害也越来越严重,成为了番茄生产上的重要叶部病害,严重影响番茄产量和品质。国内外科研工作者对叶霉病菌的生物学特性、病害流行规律以及综合防治方面进行了广泛的研究,并制定出一系列防治措施来有效减轻病害造成的损失。在此,仅对上述研究进展及其现存的问题进行简单的综述,同时,对利用生物农药及其植物抗病基因工程在今后保护地番茄叶霉病防治中的前景做了简单的展望。 相似文献
19.
亚洲型舞毒蛾中国地理种群飞行能力初探 总被引：1，自引：1，他引：0
为了探究亚洲型舞毒蛾的飞行能力,以采自河北和内蒙两地的亚洲型舞毒蛾为试验对象,应用昆虫飞行信息系统,分析亚洲型舞毒蛾的最大飞行速度、累计飞行距离和累计飞行时间。结果表明：亚洲型舞毒蛾雌雄个体间飞行能力有显著差异,雄虫比雌虫具有更强的飞行能力,雄虫平均累计飞行距离为6.76 km,雌虫平均累计飞行距离为1.85 km;1日龄成虫已具备较强的飞行能力,在飞行时间、飞行距离上,雌虫随着日龄的增长呈现出明显的线性下降趋势;交配对雄虫的飞行能力无显著影响,雌虫产卵后飞行能力明显下降。 相似文献
20.
客土基盘造林法对滨海盐渍土水盐动态的影响 总被引：1，自引：0，他引：1
为了使得客土基盘造林技术在滨海泥质盐碱地造林绿化应用中有充分的理论依据,以河北唐山市南堡开发区盐渍化土壤为研究对象,通过野外试验,研究了客土基盘造林法对滨海盐渍土水盐运移规律的影响,并比较了不同客土配比方式的排盐、降盐效果。结果表明,对照组（未经改造的原状土）土壤含水量变化规律与降水量变化规律相同或稍有滞后,处理组（以不同客土配比方式制作的客土基盘A1、A2、A3、A4）同样受降水规律的影响,但各土层含水量变化幅度差异较大,且峰值的出现时间不同,不同客土配比方式对0~20 cm、40~60 cm土层含水量影响具有显著性差异,对20~40 cm、60~80 cm影响无显著性差异。对照组含盐量变化与含水量变化存在显著负相关关系,观测结束时,返盐程度剧烈;而处理组则无显著相关关系,总体含盐量保持持续降低。4种不同客土配比方式对各土层含盐量变化影响具有显著性差异,平均含盐量均有大幅下降,总体降盐效果：A1>A3>A2>A4,植物根区含盐量下降效果：A1>A2>A4>A3。综合分析,以A1处理方式,即原状土与基质土以1:2配比制作的客土基盘排盐降盐效果最好。 相似文献