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排序方式: 共有185条查询结果,搜索用时 31 毫秒
61.
轮式移动机器人大转向航向跟踪控制 总被引:4,自引:2,他引:2
为了防止轮式移动机器人在大弯道路跟踪时出现过度转向而引起较大跟踪误差或偏离预定路径,提出了种能适应大转向的航向跟踪控制方法,利用机器人前轮偏角的绝对方向作为控制器反馈航向,仿真实验结果表明,该方法与以机器人车体航向作为反馈量的常规方法相比,在大转向航向跟踪时能有效志改善系统的动态特性,减少超调和振荡,提高基于航向控制的轮式移动机器人大弯道路径跟踪性能。 相似文献
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涉农企业的发展对加速我国农业结构调整,提高农民整体收入具有重要的意义。从企业生态角度分析了目前影响涉农企业发展的社会、经济和自然等因素,并针对影响企业发展的障碍提出了相应的对策。 相似文献
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太原市冲积平原区包气带防止潜水污染的分析 总被引:2,自引:0,他引:2
根据戈里德别尔格提出的确定敏感性指数的思路,应用模糊评判法对太原市冲积平原区包气带防止潜水污染的敏感性进行了定性分析,并在此基础上提出了相应的防治措施。 相似文献
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应用变分累积展开方法研究SU(3)格点规范理论相结构,对有限温各向同性和异性SU(3)格点规范模型的Polyakov线,计算到第三级.结果表明:当维数D3时有层相存在,且在高温下夸克是解禁的. 相似文献
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Coarse (PM2.5-10) and fine (PM2.5) atmospheric particulate samples were collected in summer and winter during 2005-2007 in the juncture belt between urban and rural areas of Beijing. Elements, ions, organic/elemental carbon (OC/EC) and polynuclear aromatic hydrocarbons (PAHs) were determined to obtain some latest information about the particulate pollution in the juncture belt of Beijing. Particulate matter levels at this site were high as compared with the levels at other sampling sites in Beijing. Pollution elements, secondary ions and PAHs were enriched in fine particles rather than in coarse particles. An obvious seasonal variation of the chemical composition of PM was observed. Source apportionment results showed that secondary components were the largest mass contributor of PM2.5, accounting for 28%; whereas soil-related sources were the largest contributor of PM2.5-10, explaining about 49% of the total mass. The abnormal levels of soil heavy metals at the electronic waste disassembly site in the upwind villages suggested the potential impact of such activities to the environment. 相似文献
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Owing to the rapidly increasing output of nano-scale titanium dioxide (TiO2) particles, their potential risk for central nerve system (CNS) has elicited much concern recently. Microglia is the resident macrophage in CNS and essential for the homeostasis of the CNS microenvironment. They are supposed to response to nanoparticles depositing in the brain tissues. Therefore, we investigated the cytotoxic effects of TiO2 NPs on microglia N9 cells in vitro. Results of propidium iodide/fluorescein diacetate (PI/FDA) double staining and MTT test clearly showed that TiO2 NPs more efficiently affected the viability of microglia N9 cells. Further Hoechst 33258 staining and flow cytometric analysis proved that nano-scale but not normal scale TiO2 induced apoptosis in vitro, These data suggest that TiO2 NPs can elicit apoptosis of N9 cells in vitro and thus present a potential risk for CNS. 相似文献
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CHEN Ao LIU BingBing HOU YuanYuan WEN GeHui LIU DeDi LU ShuangChen LI ZePeng LI XiangLin ZOU YongGang ZOU Bo LI DongMei CUI Tian &|ZOU GuangTian 《科学通报(英文版)》2009,54(14):2539-2542
We studied the coating of C60 nanorods with nickel by electroless plating method and investigated their magnetic properties. The morphology and structure of the nickel layer coated on C60 nanorods were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Raman spectroscopy. The coated nickel is in the form of nano-sized crystals and becomes a continuous layer as reaction time increases. The hysteresis loop shows a super paramagnetic characteristic similar to that of nanometer-sized nickel particle. These results suggest that the average size of nickel particles on C60 rods is below 10 nm. Our study has shown that electroless plating is an efficient and simple method for coating C60 nanorods with nickel. 相似文献
70.
基于当代红旗营子群是否应该解体这一观点,研究了崇礼红旗营子群中黑云斜长片麻岩的地质地球化学特征。研究表明原岩为泥质沉积岩,其特点为SiO2〉56%,Al2O3〉MgO,Na2O〉K2O,Na2O/(Na2O+K2O)〉0.5,且其他氧化物与SiO2含量呈现出有规律的变化,随着岩石中SiO:含量的增加,TiO2,AL2O3,FeO,Fe2O3,MgO,CaO,Na2O和K2O呈明显下降趋势。稀土元素总量较低;轻重稀土分离程度较高,LREE/HREE的值为5.16~7.98,La。/Yb。的值为4.28~8.62,轻稀土富集,重稀土平坦分布,稀土配分曲线表现出中等程度的负Eu异常,δEu的值为0.73~0.83。稀土元素Ce基本无异常或略显负异常,表明其形成环境可能为一浅海相或边缘海或被陆地封闭海。 相似文献