基于图形旋转系统的渐进网格研究     

张晔芝谷士文  费耀平 《湖南农业大学学报(自然科学版)》2004,31(4)

拓扑简化可以为渐进网格带来更好的效果，但目前几乎所有的渐进网格方法都不支持拓扑简化，而且edge collapse和vertex split操作有时会产生非流形．针对这些问题，提出了基于图形旋转系统的渐进网格法．以基于图形旋转系统的数据结构和操作实现了渐进网格，用图形旋转系统的操作集合构建了edge collapse和vertex split操作．在此基础上，通过扩展新操作即可进行任意拓扑变化，从而实现拓扑简化，  相似文献   

纤维目数对纤维板力学性能和成本的影响研究     

张成旭  花军  陈光伟 《林产工业》2020,57(3):19-24

采用热磨法研磨纤维,研究不同纤维目数(40~100目,20~120目,10~130目)对纤维板力学性能和成本的影响。在保证制作质量合格的纤维板试件基础上,对其进行力学性能试验,验证确定纤维目数区间的合理性,并利用确定的纤维目数区间进行密度和施胶量的单因素对比分析;分析其对力学性能和成本的影响。研究结果表明:纤维目数在40~100目时,可通过降低试件密度或减小施胶量,在保证制品较好力学性能的前提下降低制备成本,可实现优质优价经济效益最大化;从纤维板制品制备成本分析得出:采用上述三种纤维目数区间,在保证制品质量要求的前提下,可实现纤维目数区间与制品质量等级的合理匹配,达到合理利用原材料降低成本的效果。  相似文献   

轴流式油气混输泵压缩级流场CFD模拟分析   总被引：8，自引：3，他引：8  

马希金  王宏亮  赵学 《农业机械学报》2006,37(2):41-44

利用Fluent计算软件,采用非定常滑动网格技术和非结构网格来模拟油气混输泵单个压缩级三维流场,通过对气液两相介质在流道内的流动情况的分析,为改进压缩级的设计提供了依据。试验证明,该方法在油气混输泵的设计中是有效的。  相似文献   

Loop细分技术在犁体曲面造型中的应用   总被引：1，自引：1，他引：1  

庞明勇  卢章平  陈翠英  李青林 《农业机械学报》2004,35(5):58-61

阐述了细分方法的基本思想以及基于三角网格的Loop细分模式的原理和方法；提出了在相关几何造型、有限元分析和动态仿真软件配合下，基于OpenGL环境或CAD二次开发环境的复杂犁体曲面造型的细分方案；对犁体曲面的控制网格生成、边界限定等关键技术进行了讨论。利用该方法可以有效缩短复杂犁体曲面的造型、计算和分析时间。  相似文献   

Microhabitat use of the diamond darter     

Stuart A. Welsh  Dustin M. Smith  Nate D. Taylor 《Ecology of Freshwater Fish》2013,22(4):587-595

The only known extant population of the diamond darter (Crystallaria cincotta) exists in the lower 37 km of Elk River, WV, USA. Our understanding of diamond darter habitat use was previously limited, because few individuals have been observed during sampling with conventional gears. We quantified microhabitat use of diamond darters based on measurements of water depth, water velocity and per cent substrate composition. Using spotlights at night‐time, we sampled 16 sites within the lower 133 km of Elk River and observed a total of 82 diamond darters at 10 of 11 sampling sites within the lower 37 km. Glides, located immediately upstream of riffles, were the primary habitats sampled for diamond darters, which included relatively shallow depths (<1 m), moderate‐to‐low water velocities (often < 0.5 m·s^?1) and a smooth water surface. Microhabitat use (mean ± SE) of diamond darters was estimated for depth (0.47 ± 0.02 m), average velocity (0.27 ± 0.01 m·s^?1) and bottom velocity (0.15 ± 0.01 m·s^?1). Substrate used (mean ± SE) by diamond darters was predominantly sand intermixed with lesser amounts of gravel and cobble: % sand (52.1 ± 1.6), % small gravel (12.2 ± 0.78), % large gravel (14.2 ± 0.83), % cobble (19.8 ± 0.96) and % boulder (1.6 ± 0.36). Based on our microhabitat use data, conservation and management efforts for this species should consider preserving glide habitats within Elk River. Spotlighting, a successful sampling method for diamond darters, should be considered for study designs of population estimation and long‐term monitoring.  相似文献   

Investigation of the Effect of Mesh Size on the Effectiveness of Hotplate Aqua Regia Extractions     

《Communications in Soil Science and Plant Analysis》2012,43(2):159-166

Aqua regia extractions with subsequent inductively coupled plasma determinations are a very common method of elemental analysis of soils and sediments. Before extraction, the material must be dried and sieved. Small variations in this early step can have a significant impact on the later outcomes, especially for unassisted (for example, without ultrasonic or microwave) extraction procedures. Therefore the impact of mesh size on the sieving process was investigated. A mesh size of 2.0 mm or greater yielded unacceptably high variations between the subsamples and a very poor recovery rate when compared to a 0.063-mm sieve. A mesh size of 0.3 mm resulted in the best outcomes, losing nearly no material in the fine sediment samples and about a tenth in the coarse samples. The precision was high for the 0.3-mm samples as well, only negligibly surpassed by the 0.1-mm samples for some materials.  相似文献   

帆式张网网囊网目选择性能研究   总被引：3，自引：0，他引：3  

程家骅  陈雪忠  黄洪亮  胡永生  魏建国 《中国水产科学》2000,7(4):64-68

分别对规格为４０、５０、６０、７０和８０ｍｍ网目的帆式张网网囊进行各４０网次的选择性试验,分析不同网囊规格的网目选择性能,探讨东海区帆式张网网囊的最小网目尺寸。结果表明,选择规格５５ｍｍ的网囊网目尺寸较为适宜。  相似文献   

Analysis of mesh breaking loads in cotton gill nets: Possible solution to ghost fishing     

Yoshiki Matsushita  Shusuke Machida  Haruyuki Kanehiro  Fumio Nakamura  Naoto Honda 《Fisheries Science》2008,74(2):230-235

ABSTRACT:   A small number of fishers in Chiba Prefecture of eastern Japan use cotton gill nets to catch Japanese spiny lobster Panulirus japonicus. To examine the advantages of cotton gill nets, we analyzed changes in mesh breaking load of a new cotton gill net used in a fishing operation. A new cotton gill net was also soaked in a seawater tank to simulate ghost fishing conditions. The average mesh breaking load of new cotton mesh was 50.3 N. This value decreased to 19.0 N after 38 days (∼912 h), and after 82 days (∼1968 h) the mesh could be easily torn (breaking load 0.07 N). Under fishing conditions, the cumulative soak time was only 744.4 h over 19 months. The average breaking load at the end of this period was 43.1 N, a strength 86% that of the presoaked mesh. The mesh breaking load of a cotton gill net continuously soaked for 744.4 h was 26.1 N, as estimated from tank experiment data. Thus, a cotton gill net maintains reasonable strength under typical use conditions, but will degrade if lost at sea.  相似文献   

滑移齿轮换挡防脱挡设计     

周钰  王敏峰  谢太林 《拖拉机与农用运输车》2009,36(1)

介绍了一种拖拉机滑移齿轮换挡防脱挡结构,在不增加成本的情况下,有效地解决了滑移齿轮换挡脱挡的难题。  相似文献   

可调百叶窗式风机工况调节装置的研究设计   总被引：1，自引：1，他引：0       下载免费PDF全文

张丽君  吕新民  党革荣  郭贵生 《西北农业学报》2007,16(3):285-288

在风机性能测试中，风机工况调节一直是制约着风机性能参数自动和重复获取的主要原因之一。应用可调百叶窗网栅开度来代替原有形式的工况调节装置，克服了筛网叠加和贴纸条法的难以重复及锥形节流器的气流不均匀等问题，同时结合先进的测控技术、传感器等技术，从而便于实现风机工况调节的自动控制。  相似文献