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石嘴山市浅层地下水的环境背景值 被引量:9
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作者 方媛 吴昊 +1 位作者 霍晨琛 钱会 《环境化学》 CAS CSCD 北大核心 2016年第7期1361-1371,共11页
根据水文地质条件将研究区划分为单一潜水区和多层结构区两个地下水环境背景值单元,以石嘴山市大武口区和惠农区1997年和2008年的浅层地下水水质分析数据为依据,主要采用迭代标准差法和计算分布函数法对两个背景值单元内的15项指标进行... 根据水文地质条件将研究区划分为单一潜水区和多层结构区两个地下水环境背景值单元,以石嘴山市大武口区和惠农区1997年和2008年的浅层地下水水质分析数据为依据,主要采用迭代标准差法和计算分布函数法对两个背景值单元内的15项指标进行了背景值范围的计算.在此基础上比较分析了研究区背景值的时空分异特征,结果表明,气象、水文、人类活动等变化较大的因素会使地下水的化学组分随时间呈现出一定的变化,即地下水环境背景值的时间差异性;而地形地貌、含水层岩性、地下水径流条件的差异是影响不同地下水环境背景值单元内相同指标背景值差异的主要因素,即背景值具有空间差异性.对地下水环境背景值进行水质评价,结果表明,2008年较1997年,地下水质量变差. 展开更多
关键词 环境背景值 浅层地下水 石嘴山 迭代系数法 计算分布函数
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On the Probability Density Function of the Real and Imaginary Parts in WFRFT Signals 被引量:7
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作者 Xiaolu Wang Lin Mei +1 位作者 Zhenduo Wang Naitong Zhang 《China Communications》 SCIE CSCD 2016年第9期44-52,共9页
Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. ... Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. The wide interest is primarily due to its appealing characteristics, such as the robust performances in different types of selective fading channels and a great deal of potential for secure communications. According to the literatures, the HC signal and SC or MC signal probability distributions are different. In particular, some benefits of this HC scheme are brought by the quasi-Gaussian distribution of WFRFT signals. However, until now researchers have only presented statistic properties through computer simulations, and the accurate expressions of signals are not derived yet. In this paper, we derive the accu- rate and rigorously established closed-form expressions of Probability Density Function (PDF) of WFRFT signal real and imaginary parts with a large number of QPSK subcarriers, and this PDF can describe the behavior of data modulated by WFRFT, avoiding the complex computation for extensive computer simulations. Furthermore, the components of PDF expression are described and analyzed, and it is revealed that the tendency of signal quasi-Gaussian changes with the increasing of the parameter a (a in (0,1]). To validate the analytical results, extensive simulations have been conducted, showing a very good match between the analytical results and the real situations. The contribution of this paper may be useful to deduce the closed form expressions of Bit Error Ratio (BER), the Complementary Cumulative Distribution Function (CCDF) of Peak to Average Power Ratio (PAPR), and other analytical studies which adopt the PDF. 展开更多
关键词 weighted-type fractional Fourier transform probability density function single carrier MULTI-CARRIER hybrid carrier
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Design and Implementation of Distributed Numerical Control in Flexible Manufacturing System
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作者 周炳海 余传猛 +1 位作者 奚立峰 曹永上 《Journal of Donghua University(English Edition)》 EI CAS 2004年第1期1-6,共6页
To monitor, control and manage the work process of computer numerical control machine tools in a flexible manufacturing system (FMS) effectively, the distributed numerical coutrol (distributed-NC) software should be i... To monitor, control and manage the work process of computer numerical control machine tools in a flexible manufacturing system (FMS) effectively, the distributed numerical coutrol (distributed-NC) software should be innovated with the characteristics of modularization and reconfiguration. In this paper, firstly, distributed-NC functions in the FMS environment are described. Then, we present a design and development method of the real time distributed-NC that is on the basis of the re-coufigurable software and hardware platform and with an object-oriented model concept. Finally, to verify the proposed method, the distributed-NC software has been implemented in VC++ 6.0 and has been tested in connection with the different physical flexible manufacturing shops. 展开更多
关键词 flexible manufacturing system distributed numerical control communication protocol computer numerical control.
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关中盆地潜水环境背景值研究 被引量:6
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作者 霍晨琛 钱会 吴昊 《河南水利与南水北调》 CAS 2016年第4期99-106,134,共9页
依据关中盆地内487组水质检测数据,在深入分析关中盆地地下水流场、补给径流排泄条件和地下水环境状况的基础上,对研究区进行了较为详细的地下水环境单元划分,运用迭代标准差法和计算分布函数法,求取了关中盆地潜水主要常量组分K^++Na... 依据关中盆地内487组水质检测数据,在深入分析关中盆地地下水流场、补给径流排泄条件和地下水环境状况的基础上,对研究区进行了较为详细的地下水环境单元划分,运用迭代标准差法和计算分布函数法,求取了关中盆地潜水主要常量组分K^++Na^+、Ca^2+、Mg^2+、Cl^-、SO4^2-、HCO3^-、TDS的环境背景值,分析了各组分背景值的空间分布规律及形成因素。结果表明:地下水补、径、排条件和水文地球化学作用对区内主要常量组分背景值的空间分布起主要控制作用,其中区内阴离子以HCO3^-为主,阳离子渭河北岸以K^++Na^+为主,渭河南岸以Ca^2+为主;在渭河以北地区水文地球化学作用主要以矿化和蒸发浓缩作用为主,渭河以南地区以溶滤作用为主。其结果为关中盆地地下水污染评价、水资源开发与保护等提供了科学依据。 展开更多
关键词 环境背景值 地下水 迭代标准差 计算分布函数 关中盆地
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The distribution of normalized zero-sets of random meromorphic functions
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作者 YAO WeiHong 《Science China Mathematics》 SCIE 2011年第6期1119-1128,共10页
This paper is concerned with the distribution of normalized zero-sets of random meromorphic functions.The normalization of the zero-set plays the same role as the counting function for a meromorphic function in Nevanl... This paper is concerned with the distribution of normalized zero-sets of random meromorphic functions.The normalization of the zero-set plays the same role as the counting function for a meromorphic function in Nevanlinna theory.The results generalize the theory of Shiffman and Zelditch on the distribution of the zeroes of random holomorphic sections of powers of positive Hermitian holomorphic line bundles.As in a very special case,our paper resembles a form of First Main Theorem in classical Nevanlinna Theory. 展开更多
关键词 random meromorphic functions Poincar'e-Lelong formula DISTRIBUTION currents dirac delta function normalized counting divisors
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