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1.
基于ViewGIS的太阳辐射精度检验与误差分析 总被引：1，自引：1，他引：0
通过本研究为农林业相关部门应用ViewGIS3.0计算当地太阳直接辐射强度及其分布规律提供科学依据。采用实地观测山西省平鲁区黄土丘陵沟壑区、丘陵缓坡风沙区、土石山区、冲积平原区4种不同立地类型的太阳直接辐射值与ViewGIS3.0模拟得出的直接辐射值进行对比分析。研究表明,ViewGIS3.0对太阳直接辐射瞬时值模拟精度在90%以上;晴空条件下日累积辐射量的模拟误差在5%以内,少云条件下其误差在10%以内;云层是使误差增大的主要原因。证明该软件对于计算一天及数天以上的太阳直接辐射量,完全可以达到满意结果,具有重要的实用价值。 相似文献
2.
单层柱面网壳抗连续倒塌性能 总被引：1，自引：0，他引：1
研究了不同荷载布置形式、支承方式条件下,单层柱面网壳的抗连续倒塌性能和倒塌破坏模式,采用基于构件承载能力的敏感性评价指标,分析了初始缺陷、压杆失稳等因素对杆件、节点敏感性指标的影响。结果表明,当采用四边支承时,满跨均布荷载起控制作用,跨中节点为敏感构件,与之相邻斜杆为关键构件;当采用纵向两边支承时,半跨均布荷载起控制作用,杆件和节点的敏感性指标在1/3跨处最大,支座处最小。当考虑初始缺陷时,杆件、节点重要性系数分别增大了41%和53%;当考虑压杆失稳时,杆件和节点重要性系数分别增大了45%和62%。通过对关键构件进行加强,可以优化该类结构的抗连续倒塌性能。 相似文献
3.
为提高丘陵山地谷子机械化播种水平,明确机械精量播种模式下播距和播量对张杂谷10号生长特性及产量的影响,通过自走式多功能小粒种子播种机JAS-502B播种,研究不同播种参数对张杂谷10号生长发育和产量的影响。结果表明,随着播距减小和播量增大,谷子株高、叶绿素b含量、胞间CO2浓度、最大光化学量子产量和结穗数明显升高,茎粗、叶面积、干重、叶绿素a含量、类胡萝卜素含量、净光合速率、蒸腾速率、气孔导度、表观光合电子传递速率、硝酸还原酶活性、可溶性蛋白含量和穗粒重明显降低,叶绿素（a+b）含量、非光化学猝灭系数和光化学猝灭系数无显著差异。在本试验条件下,使用F轮和X轮播种均可提高张杂谷10号产量,使用YJ轮播种谷子产量较低。不同播距条件下谷子产量差异不显著,张杂谷10号是通过分蘖数来调节穗数,实现低密度条件下的增产。 相似文献
4.
《中国农学通报》2019,(12)
为了在进行滨海及盐碱地湿地修复时筛选出耐盐的沉水植物,笔者研究了苦草、轮叶黑藻、金鱼藻、穗花狐尾藻、篦齿眼子菜、小茨藻6种常用沉水植物的耐盐性及4项生理指标。在室内模拟条件下,分别用不同浓度的NaCl溶液对6种沉水植物进行盐分胁迫,每周进行盐害症状的观测,并测定叶片叶绿素a、叶绿素b、脯氨酸、可溶性蛋白及丙二醛的含量。结果表明,在6种沉水植物中,耐盐性为:小茨藻篦齿眼子菜金鱼藻苦草、轮叶黑藻穗花狐尾藻。其中,小茨藻和篦齿眼子菜能在盐度为15‰和8‰的盐胁迫条件下存活。金鱼藻的最高耐受盐度为6‰,苦草和轮叶黑藻的盐度胁迫能力较弱均为4‰,穗花狐尾藻的盐度胁迫能力最弱,仅为2‰。该试验为沿海及盐碱化地区的水生态系统修复提供理论依据,为项目工程实践及沉水植物的抗盐生理学研究奠定基础。 相似文献
5.
毛竹导热系数的神经网络预测模型 总被引：1，自引：0，他引：1
为了准确测算一定范围内的毛竹导热系数,同时改进现有的竹材导热系数研究方法,笔者采用激光闪光法精确测量毛竹导热系数值,并以此为基础,建立毛竹导热系数随不同温度和密度变化的神经网络预测模型。由于原始BP算法收敛速度慢,笔者使用Trainlm函数训练神经网络模型,确定了最佳隐层神经元个数,并对该模型的输出预测值进行线性分析及误差分析。实验结果如下：毛竹导热系数神经网络模型具有很高的预测精度,能准确预测一定条件范围内毛竹的导热系数,从而节省了以往常规试验所花费的大量时间和资源。本研究初步揭示了毛竹导热系数随温度、密度等因素的变化关系,为进一步研究毛竹热物理特性提供了理论依据。 相似文献
6.
[目的]为了在进行滨海及盐碱地湿地修复时筛选出耐盐的沉水植物,本文研究了六种常用沉水植物,苦草、轮叶黑藻、金鱼藻、穗花狐尾藻、篦齿眼子菜、小茨藻的耐盐性及四项生理指标。[方法]在室内模拟条件下,分别用不同浓度的NaCl溶液对六种沉水植物进行盐分胁迫,每周进行盐害症状的观测,并测定叶片叶绿素a、叶绿素b、脯氨酸、可溶性蛋白及丙二醛的含量。[结果]结果表明,在六种沉水植物中,耐盐性为小茨藻>篦齿眼子菜>金鱼藻>苦草、轮叶黑藻>穗花狐尾藻。其中小茨藻和篦齿眼子菜能在盐度为15‰和8‰的盐胁迫条件下存活。金鱼藻的最高耐受盐度为6‰,苦草和轮叶黑藻的盐度胁迫能力较弱均为4‰,穗花狐尾藻的盐度胁迫能力最弱,仅为2‰。[结论]该实验为沿海及盐碱化地区的水生态系统修复提供理论依据,为项目工程实践及沉水植物的抗盐生理学研究奠定基础。 相似文献
7.
采用熟性不同的３个陆地棉品种,在肥水充足的生长条件下,研究了棉株不同载铃量对基信要生育性状的影响。结果表明,棉株载铃量对株高,果枝总长,果节总数均有极强的影响,其影响强度随载铃量的增加而增加,累积影响量随棉株生长发育时间的延长而增大,但棉株铃量对主茎节要节平均长度影响不显著,由此分析了蕾铃脱落和棉株旺长之间的关系,以及棉株在一定地力条件下适宜的单株载铃量。 相似文献
8.
9.
为了研究不同叶幕结构与光合作用之间的相关性,为农业生产和理论研究提供方向。本文通过对影响叶幕结构的因素：栽植密度与叶幕厚度、叶幕方位角和倾斜度、叶幕高度与行间距离、叶幕开张度、叶面积系数、叶面积密度;果树的光合特性：叶片的需光特性、果树净光合速率( Pn)的季节和日变化规律;影响光合作用的内、外界因子;光能的截留和分配的分析,提出研究中存在的问题,为以后的研究提供方向。 相似文献
10.
《种子》2021,(6)
为了研究干旱胁迫对不同品种胡麻(Linum usitatissimum L.)植株生理特性和种子萌发的影响,以陇亚12号、轮选2号和晋亚11号3个胡麻品种为试验材料,在温室条件下,采用营养液沙培法,在其生长至60 d时,利用PEG-6000进行4种水势梯度(0、-0.4、-0.8 MPa和-1.2 MPa)进行人工胁迫处理,分析了植株的株高、主茎分枝数和叶片生理生化等指标。结果表明,随着水分胁迫程度增加,胡麻的株高、主茎分枝数、叶片相对含水量和气孔导度逐渐下降;整体而言,干旱胁迫会显著影响胡麻的生理特性。随着干旱胁迫的加剧,胡麻的可溶性蛋白含量、丙二醛含量及过氧化氢酶活性不断增加;陇亚12号和轮选2号胡麻叶片的可溶性蛋白含量均显著低于晋亚11号(p0.05);陇亚12号的丙二醛含量均显著低于轮选2号和晋亚11号(p0.05,除重度干旱胁迫外);经抗旱锻炼后,陇亚12号的种子萌发率显著高于轮选2号。研究表明,综合比较分析认为,陇亚12号的抗旱性优于晋亚11号和轮选2号,更适宜在北方较干旱地区推广利用。 相似文献
11.
This paper develops a generalized 3-dimensional 14-DOF dynamic model for hypoid gear which considers the time-varying friction coefficient and lubrication situation. We propose a mixed elastohydrodynamic lubrication(EHL) friction model of hypoid gear tooth contact to reflect the realistic lubricant situation in gear transmission system consisted of full film contact and asperity contact. Under the mixed lubrication condition, the effects of time-varying friction coefficient on gear dynamic is analyzed. The load sharing coefficient is used to calculate the instantaneous friction coefficient at each contact point along the contact path. Friction coefficient model based on mixed elastohydrodynamic lubrication(Mixed EHL) is incorporated into the dynamic model to predict the dynamic mesh force and transmission error with constant and time-varying friction coefficient. The simulation results under a wide range of speed and load show that the time-varying friction coefficient has a marginal effect on the dynamic response. 相似文献
12.
Analysis on tooth root stress and influencing factors of crossed beveloid gears with small shaft angle 总被引：1，自引：0，他引：1
In order to accurately calculate the tooth root stress of spatial crossed beveloid gears with small shaft angle, an exact geometry-based numerical computation method is proposed based on the spatial gearing theory and the finite element theory. Using the proposed method, the mathematical tooth surface model and the mesh model of a crossed beveloid gear pair with small shaft angle is created and the tooth root stress distribution is analyzed. Then the influences of the key design parameter which is the clearance coefficient, torque load, offset error, shaft angle error, pinion axial position error and gear axial position error on the tooth root stress are investigated. The results show that the increasing of the clearance coefficient can decrease the maximum tooth root stress. The root stresses distribute smoothly along the tooth width direction at a light torque load level. For heavy torque load level, the root stresses are parabolic in shape. Also, the existence of offset error and shaft angle error can increase the maximum value of the root stress obviously and the positive and negative value of the errors can change the position of the maximum root stress along opposite direction. For the pinion and gear axial position errors, they have less effect on root stress distribution. 相似文献
13.
The contact analysis on the double enveloping hourglass worm gearing is very important to control its efficient contact zone and contact quality. Nevertheless, current meshing analysis under the rigid condition cannot really reflect its tooth-surface contact. In this paper, the contact Finite Element Method is used to analyze the tooth contact of double enveloping hourglass worm gearing under the manufacturing error and the elastic deformation caused by the load. The load sharing among the contact tooth pairs and variations of contact zone are investigated. As compared with the result of rigid analysis, the contact zone is obviously shifted. This analysis method can provide a base for the conjugating control of the double enveloping hourglass worm gearing. 相似文献
14.
The manufacturing quality and technology of gearbox, which is a core component, is the key guarantee for the superior performance of wind turbine. Wind turbine gearbox manufacturing is a comprehensiveness technique involved multiple disciplines. To realize the digital lean manufacturing, the in-depth research on the fundamental process theory and the process control method should be carried out by taking full advantage of the existing techniques. Also, some new technologies, new processes and new materials should be investigated and applied. By considering the structural features and the actual operational condition for wind turbine gearbox and combining production practices, the requirements and characteristics of the process techniques are summarized. The research state, existing problems, applications and development tendency of high-performance wind turbine gear manufacturing, housing manufacturing and planet carrier manufacturing are analyzed. Then some methods are proposed to improve the manufacturing efficiency and control the heat treatment deformation. Finally, the test techniques for wind turbine are introduced. It has project practical significance for the manufacturing of wind turbine gearboxes. 相似文献
15.
The geometrical model of profile error is put forward to describe the tooth surface precision of hypoid gears. The influence of each machine tool setting error on profile error is investigated respectively, and the research of the associativity and compensativity among the machine tool errors are made. The setting errors of machine tool, the optimal modifying parameters and their value are got from the measurement coordinates of hypoid gear real tooth surface, and the adjusted manufacturing shows the geometrical precision of the tooth surface is improved effectively. 相似文献
16.
针对行星齿轮减速器工作过程中传递功率的频繁变化容易导致其运动状态发生突变的问题,探讨行星齿轮传动系统随传递功率的分岔特性。基于2K-H型行星齿轮传动系统纯扭转非线性动力学模型,采用CPNF(continuous Poincaré-Newton-Floquet)方法研究了传递功率对行星齿轮传动系统周期运动稳定性的局部精细分岔规律,运用直接数值积分的方法绘制了系统随功率的全局分岔图,并对两种仿真结果进行了对比。结果发现,在某些参数组合下,行星齿轮传动系统会共存几个稳定或不稳定的周期轨道;当功率在196~220 kW范围内,随着功率值的逐渐增大,行星齿轮传动系统的各种形态的周期轨道均是通过倍周期倒分岔的途径在相应功率分岔点处发生稳定性突变的;在轻载工况下(传递小功率),行星齿轮非线性系统容易呈现混沌运动状态。 相似文献
17.
To address the problems of low carrying capacity and short life of bearings in current ring reducers, a new type of ring reducer is proposed which consists of a two stepped transmission. One is a planetary transmission, and the other is an N type planetary transmission with a low tooth number difference. Based on the analysis of structural features, the transmission principle, and a transmission load situation, a contact finite element model of the new type of ring reducer is set up, and the stress value and the actual pairs of meshing teeth are derived by calculation. Based on gear modification research theory, the second stage transmission gear pairs of the new reducer are modified on its teeth profiles. Results demonstrate that the load capacity of transmission gear pairs have been enhanced greatly. 相似文献
18.
The determination of load share between teeth is a complex problem in gear strength calculation. On the basis of contact finite element method this paper considers the production-assembly error as initial gap to get the finite element model which meets load share between teeth in gear meshing. Through calculating and comparing the result with that from ISO formula to get the load share between teeth which meets the requirements in actual usage. 相似文献
19.
Dynamic characteristics of multi-stage planetary gear trains in shield machine cutter drive 
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下载免费PDF全文 A purely torsional dynamic model of multi-stage planetary gear trains is developed to investigate the dynamic characteristics of the transmission system in shield machine cutter drive. In the model,phase difference between mesh stiffness and error among each stage caused by different initial mesh positions is considered,and other factors such as component bearing stiffness,time-varying mesh stiffness and error are considered as well. Inherent characteristic analysis shows there are more unique and diverse vibration modes in multi-stage planetary gear trains than in single-stage planetary gear trains. Through dynamic response analysis,time-domain and frequency-domain response of dynamic meshing force of each stage is obtained. As the frequency of exciting force of medium-speed and high-speed stage is in proximity to the natural frequency of the system,harmonic resonance tends to occur,which needs to be paid great attention to. Dynamic factors of each stage are also computed and prepare the ground for the dynamic optimizing design of planetary gear trains. 相似文献
20.
Load dynamic matching of supply and demand side based on the utilization of urban sewage heat energy
Flowing dynamic characteristics and its temperature dynamic characteristics of a three-level sewage pipe network in Chongqing were analyzed. A mall's building whole year load was simulated. In the adverse condition of wastewater flow, the market construction peak discharge heat was compared with the sewage heat load, the balance between the most adverse flow and the building demand was found. Explored supply and demand matching method between urban sewage and city building load in flow adverse condition to take full advantage of the urban sewage cold and hot resources. the composite system was adeptcd to make up the most unfavorable flow time of sewage average heat load and the construction load difference; it also puts forward principle of load sharing and control strategy aimed at compound system. 相似文献