997 resultados para Stewart, A. M. (Alexander Morrison), 1814-1875.


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The dusky rockfish (Sebastes ciliatus) of the North Pacific Ocean has been considered a single variable species with light and dark forms distributed in deep and shallow water, respectively. These forms have been subjected to two distinct fisheries separately managed by federal and state agencies: the light deep form is captured in the offshore trawl fishery; the dark shallow form, in the nearshore jig fishery. The forms have been commonly recognized as the light dusky and dark dusky rockfishes. From morphological evidence correlated with color differences in some 400 specimens, we recognize two species corresponding with these color forms. Sebastes ciliatus (Tilesius) is the dark shallow-water species found in depths of 5−160 m in the western Aleutian Islands and eastern Bering Sea to British Columbia. The name Sebastes variabilis (Pallas) is resurrected from the synonymy of S. ciliatus to apply to the deeper water species known from depths of 12−675 m and ranging from Hokkaido, Japan, through the Aleutian Islands and eastern Bering Sea, to Oregon. Sebastes ciliatus is uniformly dark blue to black, gradually lightening on the ventrum, with a jet black peritoneum, a smaller symphyseal knob, and fewer lateral-line pores compared to S. variabilis. Sebastes variabilis is more variable in body color, ranging from light yellow to a more usual tan or greenish brown to a nearly uniform dark dorsum, but it invariably has a distinct red to white ventrum. Synonymies, diagnoses, descriptions, and geographic distributions are provided for each species.

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介绍了一种大量程Stewart结构六维力/力矩传感器系统.建立了传感器力/力矩测量数学模型,构建了基于运动学逆解的优化目标函数.提出了一种新的参数标定法,称作分支轮换标定法.基于所研发的六维力/力矩传感器系统进行了实验研究,实验结果表明分支轮换法可以有效地辨识出传感器的结构参数,提高了测量精度.该方法可用于类似结构的六维力/力矩传感器参数标定.

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针对大射电望远镜精调Stewart平台的五自由度运动特性,采用快速极坐标搜索法确定了五自由度大射电望远镜精调Stewart平台的工作空间.通过实例分析验证了所提出的工作空间分析方法的有效性.为大射电望远镜馈源轨迹跟踪实现和精调Stewart平台的设计奠定了坚实的基础.

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基于Stewart平台的六维力传感器具有结构紧凑、刚度大、量程宽等特点,它在工业机器人、空间站对接等领域具有广泛的应用前景。好的标定方法是正确使用传感器的基础。由于基于Stewart平台的六维力传感器是一个复杂的非线性系统,所以采用常规的线性标定方法必将带来较大的标定误差从而影响其使用性能。标定的实质是,由测量值空间到理论值空间的映射函数的确定过程。由函数逼近理论可知,当只在已知点集上给出函数值时,可用多项式或分段多项式等较简单函数逼近待定函数。基于上述思想,本文将整个测量空间划分为若干连续的子测量空间,再对每个子空间进行线性标定,从而提高了整个测量系统的标定精度。实验分析结果表明了该标定方法有效。

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从并联机构与串联机构的运动学等效 ,并联机构本身特征与并联机构实际工作空间出发 ,考虑各分支末端误差对最终运动平台末端误差的影响 ,提出了并联机构位姿误差放大因子分析法·依据位姿误差放大因子具有对误差定量分析的特点 ,该分析方法既可用于机构参数优化 ,又可用于结构精度设计· 最后 ,给出了一个实例说明本方法的有效性·

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Grovier, Kelly, 'Shades of the Prison-House': 'Walking' Stewart, Michel Foucault and the Making of Wordsworth's 'two consciousnesses'' Studies in Romanticism (2005) 44 (3) pp.341-66 RAE2008

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http://www.archive.org/details/alexandermackay00unknuoft/

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http://books.google.com/books?vid=OCLC11413587 View volume 1