步进电机步距角的正余弦细分原理     

张竹恒  周尊源  孙淑琴 《时间频率学报》1997,(1)

步进电机的步距角由于受到机械结构和经典细分驱动电路的限制，只能适量的减小，但对于许多精密设备的控制及高精度的定位系统，其步距角的分辨率还应提高，正金弦细分驱动电路很好地解决了这一问题。它的主要特点是和计算机或单片机的接口简单、转速连续可调；增减EPROM的地址线可灵活改变细分数；电机运行平稳、振动小、噪声低。  相似文献   

STEP FUNCTION TECHNIQUE FOR ESTIMATING DATA UNCERTAINTY IN EXPERIMENTAL RESULTS     

《地理学报(英文版)》1991,(3)

An additive model is used to express the observed value of a sample characteristic as the sum of the truesample characteristic and a value of the data collection error,commonly known as experimental error.The data uncertainty of the experimental results(or of a survey data set)is defined as the expectedsquared error.The expected squared error may change with the sample characteristic,e.g.the errormoment could be concentration-dependent.The relationship between the error variance and the analyteconcentration may not be very distinct.In such a case the data transformation to stabilize the errormoments may not be appropriate.A step function is proposed as an alternative way to represent thesecond moment of the error.The data uncertainty is defined as the weighted average of the step valuesof the second raw moment of the error,using the appropriate proportions of the routine samples asweights.The data uncertainties associated with the different data collection stages were evaluated by usingregional soil survey data.  相似文献   

MORPHOLOGICAL CHARACTERISTICS OF FREE BENDS     

R.S.CHALOV  +  A.S.ZAVADSKI  + 《国际泥沙研究》1999,(3)

1　ＩＮＴＲＯＤＵＣＴＩＯＮ　Ａｍｏｎｇｔｈｅｄｉｖｅｒｓｉｔｙｏｆｅｘｉｓｔｉｎｇｒｉｖｅｒｃｈａｎｎｅｌｐｒｏｃｅｓｓｅｓ,ｍｅａｎｄｅｒｉｎｇｉｓｔｈｅｍｏｓｔｃｏｍｍｏｎａｎｄｆｒｅｑｕｅｎｔｏｎｅ.Ｉｔｉｓｔｙｐｉｃａｌｌｙｔｈｅｃｏｍｍｏｎ?..  相似文献   

The Co-seismic Response of Underground Fluid in Yunnan to the Nepal MS8.1 Earthquake     

Zhang Li  Su Youjin  Luo Ruijie  Gao Wenfei  Zhang Ping 《中国地震研究》2017,31(2):201-212

In this paper, statistics are taken on the co-seismic response of underground fluid in Yunnan to the Nepal M_S8.1 earthquake, and the co-seismic response characteristics of the water level and water temperature are analyzed and summarized with the digital data. The results show that the Nepal M_S8.1 earthquake had greater impact on the Yunnan region, and the macro and micro dynamics of fluids showed significant co-seismic response. The earthquake recording capacity of water level and temperature measurement is significantly higher than that of water radon and water quality to this large earthquake; the maximum amplitude and duration of co-seismic response of water level and water temperature vary greatly in different wells. The changing forms are dominated by fluctuation and step rise in water level, and a rising or falling restoration in water temperature. From the records of the main shock and the maximum strong aftershock,we can see that the greater magnitude of earthquake, the higher ratio of the occurrence of co-seismic response, and in the same well, the larger the response amplitude, as well as the longer the duration. The amplitude and duration of co-seismic response recorded by different instruments in a same well are different.Water temperature co-seismic response almost occurred in wells with water level response, indicating that the well water level and water temperature are closely related in co-seismic response, and the well water temperature seismic response was caused mainly by well water level seismic response.  相似文献   

新21号泉地震异常特征分析     

李新勇  杨晓芳  崔勇  张涛 《内陆地震》2014,(2):188-194

通过对新疆呼图壁新21泉近23年的观测资料系统梳理分析认为,该泉动水位对其300 km范围内的中强地震有较好的短临异常显示,异常特征为"阶跃"型和"脉冲"型,同时当该泉对其100 km范围内4级地震有较强的同震响应时,可能对后续中强地震的发生有一定的前兆指示意义。  相似文献   

汶川地震序列早期特征及成因探讨     

代炜  严武建 《高原地震》2009,21(3):1-10

地震序列的特征和震型判定工作有助于抗震救灾工作的开展,对其发生成因的研究是解决地震预报难题必须面对的科学问题。汶川8．0级地震序列的初步研究表明：①余震沿龙门山断裂带分布于宽100km,长约330km的带状区域内,并侧向于主震震中的北侧;②序列发展初期有2个快速衰减过程;③序列类型为主震一余震型,最大强余震6．4级;④序列的空间演化过程,强余震震源机制结果和地震精确定位结果分析表明,序列具有分段特征;⑤8．0级地震的发震构造是龙门山断裂带,发震构造在剖面上呈现出“犁形”或“铲形”。地球物理勘探和壳、幔结构反演结果表明,自青藏高原穿越龙门山到四川盆地存在地幔阶梯,上地幔阶梯的阻挡作用使得物质东移速率减慢,并蕴积了汶川8．0级地震所需能量。地震的产生正是东西向应力平衡被打破的结果,余震沿龙门山断裂的分布是高原地壳在印度板块的推挤作用下向北北东方向的运动得以继续的表现。整个龙门山断裂带都参与了活动,龙门山断裂带北端作为断裂带的止裂端与南段同期活动。  相似文献   

山东省飞机增雨降水区分级预报方法研究          下载免费PDF全文

龚佃利  王以琳  谢考宪 《应用气象学报》2001,12(Z1):139-145

利用1997～2000年春秋季山东主要降水天气系统中尺度客观分析和降水模拟资料，统计分析了与降水密切相关的15个因子，并对因子的稳定性进行检验。用全部入选因子的前5个主成分作为新的预报因子，建立全省25个区域0～6h和0～12h平均降水量的3类判别方程，判别效果较好。以此方法为基础建立的决策系统为增雨作业指挥提供了实用性技术工具。  相似文献   

豫西嵩县盆地周边地区地震空区地质环境初探     

韩德润  苏怡之 《地震地质》1995,17(4):432-438

通过时豫西嵩县中～新生代断陷盆地构造类型、断裂发育及其活动程度的初步分析，认为该盆地及其邻区具有断裂发育规模小、新构造活动程度低、盆内无次级断裂及其所围限的地堑和地垒断块构造发育等特征，从而形成了被深断裂割开的地震空区  相似文献   

Fracture step structure: geometrical characterization and effects on fluid flow and breakthrough curve     

N.D. Khang  K. Watanabe 《Engineering Geology》2004,75(1):107-127

Groundwater flow and solute transport through fractured rock is highly responsive to the hydraulic anisotropy and heterogeneity that are specific to every major fracture. A major fracture is modeled as the combination of some primal master fractures and several splay fractures that branch out from primal master fractures: step structures (or jog parts). Step structures are commonly observed along a major fracture on various scales. Master fractures were formed and developed by shear movement while some splay fractures were formed by extension normal to their wall. This difference in fracturing process may lead to a permeability difference between master fractures and splay fractures which seems to be one of the major factors controlling flow and solute transport through the fracture networks due to its hydraulic anisotropic and heterogeneous features. This study is composed of two major components: (1) identification and characterization of a step structure from borehole data; (2) evaluation of effect of some idealized step structures on breakthrough curve by numerical simulations. The fracture data of four 1000-m boreholes were used to make clear fracture patterns in the Tono area of Japan. Some major fractures were identified using stereographic projection technique. On the basis of these results, several idealized models of a major fracture having a step was constructed for the numerical study. The obtained results from numerical simulations clearly imply that geometry of step structure plays an important role in flow and transport through the fracture networks.  相似文献   

下垫面粗糙度突变时的内边界层研究     

周定文 《高原气象》1989,8(4):370-377

本文介绍了下垫面粗糙度突变时内边界层的形成过程,阐述了内边界层研究的意义,总结和分析了内边界层在理论研究、实验和观测以及数值模拟方面的主要成果。  相似文献