非等比长宽航道扫测图的研制     

张永合  郑行昭  熊指南 《地理空间信息》2009,7(3):159-161

详细介绍了一种长宽比例尺不一致的航道扫测图制作的数学模型和制作方法，采用计算机语言编制的软件对这种航道扫测图的制作方法予以实现，并且通过我国北方某港口航道扫测的工程实例进行了验证。  相似文献   

Solar light, seawater temperature, and nutrients, which one is more important in affecting phytoplankton growth？   总被引：2，自引：1，他引：1  

苗振清  杨东方 《中国海洋湖沼学报》2009,27(4):825-831

Based on research results on the impacts of solar light, seawater temperature, and nutrient available to phytoplankton growth and changes in phytoplankton physiology and assemblage, we discussed the order of influence of these factors. By clarifying the mechanisms and processes of the impacts by these factors, we have determined the rising order of the importance as solar light, seawater temperature, and nutrient silicon (Si). Therefore, for human interests in sustaining economic development, the first thing to be considered is the input of nutrient Si into the ocean, followed by seawater temperature change.  相似文献   

Neural network modelling for mean velocity and turbulence intensities of steep channel flows     

Fi‐John Chang  Han‐Chung Yang  Jau‐Yau Lu  Jian‐Hao Hong 《水文研究》2008,22(2):265-274

The main purpose of this study is to evaluate the potential of simulating the profiles of the mean velocity and turbulence intensities for the steep open channel flows over a smooth boundary using artificial neural networks. In a laboratory flume, turbulent flow conditions were measured using a fibre‐optic laser doppler velocimeter (FLDV). One thousand and sixty‐four data sets were collected for different slopes and aspect ratios at different locations. These data sets were randomly split into two subsets, i.e. training and validation sets. The multi‐layer functional link network (MFLN) was used to construct the simulation model based on the training data. The constructed MFLN models can almost perfectly simulate the velocity profile and turbulence intensity. The values of correlation coefficient (γ) are close to one and the values of root mean square error (RMSE) are close to zero in all conditions. The results demonstrate that the MFLN can precisely simulate the velocity profiles, while the log law and Reynolds stress model (RSM) are less effective when used to simulate the velocity profiles close to the side wall. The simulated longitudinal turbulence intensities yielded by the MFLN were also fairly consistent with the measured data, while the simulated vertical turbulence intensities by the RSM were not consistent with the measured data. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Complete Zonal Problem of the Artificial Satellite: Generic Compact Analytic First Order in Closed Form     

Bernard De Saedeleer 《Celestial Mechanics and Dynamical Astronomy》2005,91(3-4):239-268

This paper is a contribution to the Theory of the Artificial Satellite, within the frame of the Lie Transform as canonical perturbation technique (elimination of the short period terms). We consider the perturbation by any zonal harmonic J _n (n ≥ 2) of the primary on the satellite, what we call here the complete zonal problem of the artificial satellite. This is quite useful for primaries with symmetry of revolution. We give an analytical formula to compute directly the first order averaged Hamiltonian. The computation is carried out in closed form for all terms, avoiding therefore tedious expansions in the eccentricity or in any anomaly; this feature makes the averaging process, not only valid for all kind of elliptic trajectories but at the same time it yields the averaged Hamiltonian in a very short and compact way. The formula allows us to now skip the averaging process, which means an asymptotic gain of a factor 3n/2 regarding the computational cost of the n ^th zonal. Our analytical formulae have been widely checked, by comparison on one hand with published works (Brouwer, 1959) (which contained results for particular zonal harmonics, let’s say typically from J ₂ to J ₈), and on the other hand with the results of 3 symbolic manipulation software, among which the MM (standing for ‘Moon’s series Manipulator’), which has already been used and described in (De Saedeleer B., 2004). Additionally, the first order generator associated with this transformation is given into the same closed form, and has also been validated.  相似文献   

Mohr–Coulomb MiniCLoE model Uniqueness and localization studies,links with normality rule     

R. Chambon  V. Roger 《国际地质力学数值与分析法杂志》2003,27(1):49-68

This paper is devoted to a parametric study of a plane Mohr–Coulomb CLoE model. As CLoE models are designed with a consistency condition, it is possible to define a normality condition and to study its consequences. The positiveness of the second order work which implies the uniqueness of the solution of a small strain boundary value problem is studied firstly. Then the localization criterion is also studied. It is proved that normality has consequences similar to those for classical elasto plastic models. However if induced anisotropy is introduced in the hypoplastic CLoE model, some conclusions are no longer true. Finally plane strain experimental data are used to identify the parameters of the model. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Patterns in stream longitudinal profiles and implications for hyporheic exchange flow at the H.J. Andrews Experimental Forest,Oregon, USA     

Justin K. Anderson  Steven M. Wondzell  Michael N. Gooseff  Roy Haggerty 《水文研究》2005,19(15):2931-2949

There is a need to identify measurable characteristics of stream channel morphology that vary predictably throughout stream networks and that influence patterns of hyporheic exchange flow in mountain streams. In this paper we characterize stream longitudinal profiles according to channel unit spacing and the concavity of the water surface profile. We demonstrate that: (1) the spacing between zones of upwelling and downwelling in the beds of mountain streams is closely related to channel unit spacing; (2) the magnitude of the vertical hydraulic gradients (VHGs) driving hyporheic exchange flow increase with increasing water surface concavity, measured at specific points along the longitudinal profile; (3) channel unit spacing and water surface concavity are useful metrics for predicting how patterns in hyporheic exchange vary amongst headwater and mid‐order streams. We use regression models to describe changes in channel unit spacing and concavity in longitudinal profiles for 12 randomly selected stream reaches spanning 62 km² in the H.J. Andrews Experimental Forest in Oregon. Channel unit spacing increased significantly, whereas average water surface concavity (AWSC) decreased significantly with increasing basin area. Piezometer transects installed longitudinally in a subset of stream reaches were used to measure VHG in the hyporheic zone, and to determine the location of upwelling and downwelling zones. Predictions for median pool length and median distance between steps in piezometer reaches bracketed the median distance separating zones of upwelling in the stream bed. VHG in individual piezometers increased with increasing water surface concavity at individual points in the longitudinal profile along piezometer transects. Absolute values of VHG, averaged throughout piezometer transects, increased with increasing AWSC, indicating increased potential for hyporheic exchange flow. These findings suggest that average hyporheic flow path lengths increase—and the potential for hyporheic exchange flow in stream reaches decreases—along the continuum from headwater to mid‐order mountain streams. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

教改是提高大学生就业率的关键环节   总被引：1，自引：0，他引：1  

时新荣 《成都信息工程学院学报》2006,21(5):744-750

从当前我国人力资源市场上大学生就业难的现象切入，通过分析大学生就业市场供求双方的经济关系，说明求职大学生在素质上与用人单位的需求之间存在较尖锐的矛盾，是大学生就业难的重要原因。解决大学生就业难的关键环节之一是通过教改提高大学生的综合素质。  相似文献   

一种低复杂度近最佳的MIMO信号检测算法     

刘金铸  薛婷 《南京气象学院学报》2013,5(2):167-170

在多输入多输出(MIMO)系统的信号检测算法中,最大似然(ML)算法具有最佳检测性能,但因其复杂度随天线数及调制阶数的增加呈指数增加而不实用.排序干扰逐次消去的最小均方误差(MMSE-OSIC)算法具有很低的复杂度,但因迭代检测过程中的差错传播使得检测性能与最佳检测相比有很大差距.针对以上算法的缺点,提出了一种低复杂度近最佳的MIMO信号检测算法,该算法对MMSE-OSIC算法的检测顺序进行调整,首先通过比较信道逆矩阵行向量的范数确定最弱信号层,对该发射信号的所有可能值进行遍历搜索,在保证最弱信号层尽可能正确检测的前提下,对剩余信号层采用MMSE-OSIC算法检测.理论分析及仿真结果表明,该算法有效抑制了迭代检测过程中的差错传播,几乎达到了最佳检测性能,同时具有较低的复杂度,在检测性能与复杂度之间给出了很好的折衷.  相似文献   

基于自适应分组的预警信息发布系统     

徐冬卫  沈晓东  陈苏婷 《南京气象学院学报》2013,5(1):73-76

介绍了DAB(数字音频广播)主业务信息通道的传输结构及其作用,提出了一种应用于DAB发射机在主业务信息通道传输文字模块的设计方案.该设计针对现有DAB发送文字信息所需的多样性、实时性和经济性的要求,基于MOT(多媒体对象传输)协议传输规范,利用自适应分组模式传输机制提高了DAB发射系统发送文本信息(气象预警信息、交通信息等)的灵活性和子信道容量的利用率.该方案已通过自适应分组编码软件实现.  相似文献   

济南双偏振多普勒天气雷达在线自动标定数据质量分析评估          下载免费PDF全文

杨传凤  刁秀广  张骞  魏海文 《山东气象》2020,40(4):114-123

阐述了CINRAD/SA-D双偏振多普勒天气雷达（简称“双偏振雷达”）标定技术,统计分析了济南双偏振雷达试运行以来在线自动标定数据和该时间段内的维护维修情况,从雷达几十个标定状态性能参数中,遴选对雷达探测数据质量影响最大的发射峰值功率Pt、相位噪声σφ、噪声系数NF、反射率标定系数SYSCAL、差分反射率因子ZDR、差分传播相移ΦDP等性能参数,分析评估在线自动标定数据质量。结果表明：1）峰值功率维持在679.68 kW,H（水平）和V（垂直）双通道的峰值功率长期运行吻合一致性较好。2）H和V双通道噪声系数均值分别维持在1.66 dB和1.73 dB,双通道数据总体分布稳定,且具有较好的一致性;标定数据的异常来源于外界干扰,占0.39%,受外界干扰H通道多于V通道,干扰造成接收机灵敏度降低了1.5 dB,导致雷达产品异常。3）反射率标定ΔSYSCAL最小值为-0.46 dB,最大值为0.25 dB,满足±2 dB的技术指标要求。4）I/Q相角法标定相位噪声均值为0.051 3°,实物对消能力60 dB与估测地物杂波抑制能力61.36 dB结果基本吻合,证实了雷达系统具有较好的地物杂波抑制能力。5）采用机内CW、TS双信号源标定法,接收双通道幅度和相位的标准差：ZDR-CW和ΦDP-CW分别为0.025 dB和0.735,ZDR-TS和ΦDP-TS分别为0.044 dB和1.116°,满足接收双通道一致性的技术指标,但CW信号标定结果明显小于TS信号标定结果,表明双路方位旋转关节对接收链路信号幅度和相位的一致性有影响,导致ZDR-TS和ΦDP-TS标定结果比ZDR-CW和ΦDP-CW出现更大的偏差,因此随着双偏振雷达的长期运行,对方位旋转关节带来的幅度和相位固有偏差进行测试和订正非常重要。  相似文献