期刊文献+
共找到124篇文章
< 1 2 7 >
每页显示 20 50 100
The Confirmation of Hypothesis of the Absolute Reference System 被引量:1
1
作者 Konstantinos Patrinos 《Journal of Applied Mathematics and Physics》 2020年第6期999-1015,共17页
The <span style="font-family:Verdana;font-size:12px;">purpose of the research in this article is the examination of the agreement of the hypothesis of the absolute reference system with the results of ... The <span style="font-family:Verdana;font-size:12px;">purpose of the research in this article is the examination of the agreement of the hypothesis of the absolute reference system with the results of experiments that have been implemented in the past in order to confirm the special theory of relativity. To achieve this goal, we have chosen for discuss</span><span style="font-family:Verdana;">ing</span><span style="font-family:Verdana;"> a theoretical topic of electromagnetism, that of electromagnetic mass</span><span style="font-family:Verdana;"> calculation, and some experiments, some of which concern the transverse Doppler effect in a rotated system, two experiments that concern the kinetic energy measurement of accelerated electrons, one of which is the well known Bertozzis experiment, one experiment that concern</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> the propagation of Coulomb fields and one more experiment that</span><span style="font-size:14pt;font-family:;" "=""> </span><span style="font-family:Verdana;">concern</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> the effect of annihilation. The basic principles of the hypothesis of the absolute reference system, and the electromagnetic theory derived from these principles, are used to explain the experimental results. In these examples, the hypothesis of the absolute reference system is confirmed, since the experimental results agree with the predictions of this hypothesis. Also, in the discussion of calculation of electromagnetic mass is addressed the difficulty of solving this problem, when someone tr</span><span style="font-family:Verdana;">ies</span><span style="font-family:Verdana;"> to solve this according to the energy-mass relation of the theory of relativity.</span> 展开更多
关键词 absolute reference System Electromagnetic Mass Transverse Doppler Effect Kinetic Energy of Accelerated Electrons
下载PDF
Absolute Reference Values of the Real Gas
2
作者 Albrecht Elsner 《Engineering(科研)》 2018年第5期270-290,共21页
With his publication in 1873 [1] J. W. Gibbs formulated the thermodynamic theory. It describes almost all macroscopically observed properties of matter and could also describe all phenomena if only the free energy U -... With his publication in 1873 [1] J. W. Gibbs formulated the thermodynamic theory. It describes almost all macroscopically observed properties of matter and could also describe all phenomena if only the free energy U - ST were explicitly known numerically. The thermodynamic uniqueness of the free energy obviously depends on that of the internal energy U and the entropy S, which in both cases Gibbs had been unable to specify. This uncertainty, lasting more than 100 years, was not eliminated either by Nernst’s hypothesis S = 0 at T = 0. This was not achieved till the advent of additional proof of the thermodynamic relation U = 0 at T = Tc. It is noteworthy that from purely thermodynamic consideration of intensive and extensive quantities it is possible to derive both Gibbs’s formulations of entropy and internal energy and their now established absolute reference values. Further proofs of the vanishing value of the internal energy at the critical point emanate from the fact that in the case of the saturated fluid both the internal energy and its phase-specific components can be represented as functions of the evaporation energy. Combining the differential expressions in Gibbs’s equation for the internal energy, d(μ/T)/d(1/T) and d(p/T)/d(1/T), to a new variable d(μ/T)/d(p/T) leads to a volume equation with the lower limit vc as boundary condition. By means of a variable transformation one obtains a functional equation for the sum of two dimensionless variables, each of them being related to an identical form of local interaction forces between fluid particles, but the different particle densities in the vapor and liquid spaces produce different interaction effects. The same functional equation also appears in another context relating to the internal energy. The solution of this equation can be given in analytic form and has been published [2] [3]. Using the solutions emerging in different sets of problems, one can calculate absolutely the internal energy as a function of temperature-dependent, phase-specific volumes and vapor pressure. 展开更多
关键词 ENTROPY reference VALUE S (M V 0) = 0 INTERNAL Energy reference VALUE U (M Tc) = 0 ...
下载PDF
A New Hybrid Order Approach to Morphological Color Image Processing Based on Reduced Order with Adaptive Absolute Reference
3
作者 S. Ouattara A. Kouassi +3 位作者 J. C. Okaingni A. Koffi G. Loum A. Clement 《Engineering(科研)》 2016年第9期633-645,共14页
Mathematical morphology can process the binary and grayscale image successfully. This theory cannot be extended to the color image directly. In color space, a vector represents a pixel, so in order to compare vectors,... Mathematical morphology can process the binary and grayscale image successfully. This theory cannot be extended to the color image directly. In color space, a vector represents a pixel, so in order to compare vectors, vectoriel orderings must be defined first. This paper addresses the question of the extension of morphological operator to the case of color images. The proposed method used the order by bit mixing to replace the conditional order. Our order is based on a combination of reduced and bit mixing ordering of the underlying data. Additionally it is a total ordering. Since it not only solves the problems of false color generated by the marginal order but also those of multiple extrema generated by reduced order. The performance of the introduced operators is illustrated by means of different applications: color gradients for segmenting, image smoothing (noise suppression) by median filter operator and Laplacian operators. Examples of natural color images and synthetic color images are given. Experimental results show the improvement brought by this new method. 展开更多
关键词 Multicomponent Image Vector Order Adaptive absolute referent Bit Mixing Morphological Operators
下载PDF
A New Vectorial Order Approach Based on the Classification of Tuples Attribute and Relative Absolute Adaptive Referent: Applications to Multicomponent Images
4
作者 Adles Francis Kouassi Sié Ouattara +4 位作者 Jean-Claude Okaingni Adama Koné Wognin Joseph Vangah Georges Loum Alain Clement 《Journal of Software Engineering and Applications》 2017年第6期546-563,共18页
In this paper, we are presenting a new vector order, a solution to the open problem of the generalization of mathematical morphology to multicomponent images and multidimensional data. This approach uses the paradigm ... In this paper, we are presenting a new vector order, a solution to the open problem of the generalization of mathematical morphology to multicomponent images and multidimensional data. This approach uses the paradigm of P–order. Its primary principle consists, first in partitioning the multi-component image in the attribute space by a classification method in different numbers of classes, and then the vector attributes are ordered within each class (intra-order-class). And finally the classes themselves are ordered in turn from their barycenter (inter-class order). Thus, two attribute vectors (or colors) whatever, belonging to the vector image can be compared. Provided with this relation of order, vectors attributes of a multivariate image define a complete lattice ingredient necessary for the definition of the various morphological operators. In fact, this method creates a strong close similarity between vectors in order to move towards an order of the same principle as defined in the set of real numbers. The more the number of classes increases, the more the colors of the same class are similar and therefore the absolute adaptive referent tends to be optimal. On the other hand, the more the class number decreases or equals two, the more our approach tends towards the hybrid order developed previously. The proposed order has been implemented on different morphological operators through different multicomponent images. The fundamental robustness of our approach and that relating to noise have been tested. The results on the gradient, Laplacian and Median filter operators show the performance of our new order. 展开更多
关键词 MULTICOMPONENT Image P-Order Optima ADAPTIVE absolute referENT Intraclass and Interclass Order Morphological Operators Noise
下载PDF
Analysis and prediction of reference evapotranspiration with climate change in Xiangjiang River Basin, China 被引量:5
5
作者 Xin-e Tao Hua Chen +2 位作者 Chong-yu Xu Yu-kun Hou Meng-xuan Jie 《Water Science and Engineering》 EI CAS CSCD 2015年第4期273-281,共9页
Reference evapotranspiration (ETo) is often used to estimate actual evapotranspiration in water balance studies. In this study, the present and future spatial distributions and temporal trends of ETo in the Xiangjia... Reference evapotranspiration (ETo) is often used to estimate actual evapotranspiration in water balance studies. In this study, the present and future spatial distributions and temporal trends of ETo in the Xiangjiang River Basin (XJRB) in China were analyzed. ETo during the period from 1961 to 2010 was calculated with historical meteorological data using the FAO Penman-Monteith (FAO P-M) method, while ETo during the period from 2011 to 2100 was downscaled from the Coupled Model Intercomparison Project Phase 5 (CMIP5) outputs under two emission scenarios, representative concentration pathway 4.5 and representative concentration pathway 8.5 (RCP45 and RCP85), using the statistical downscaling model (SDSM). The spatial distribution and temporal trend of ETo were interpreted with the inverse distance weighted (IDW) method and Mann-Kendall test method, respectively. Results show that: (1) the mean annual ETo of the XJRB is 1 006.3 mm during the period from 1961 to 2010, and the lowest and highest values are found in the northeast and northwest parts due to the high latitude and spatial distribution of climatic factors, respectively; (2) the SDSM performs well in simulating the present ETo and can be used to predict the future ETo in the XJRB; and (3) CMIP5 predicts upward trends in annual ETo under the RCP45 and RCP85 scenarios during the period from 2011 to 2100. Compared with the reference period (1961-1990), ETo increases by 9.8%, 12.6%, and 15.6% under the RCP45 scenario and 10.2%, 19.1%, and 27.3% under the RCP85 scenario during the periods from 2011 to 2040, from 2041 to 2070, and from 2071 to 2100, respectively. The predicted increasing ETo under the RCP85 scenario is greater than that under the RCP45 scenario during the period from 2011 to 2100. 展开更多
关键词 reference evapotranspiration (ET0 Spatial-temporal variation Climate change Statistical downscaling Xiangjiang River Basin
下载PDF
Trends in major and minor meteorological variables and their influence on reference evapotranspiration for mid Himalayan region at east Sikkim, India 被引量:1
6
作者 Shweta YADAV Proloy DEB +2 位作者 Sonu KUMAR Vanita PANDEY Pankaj Kumar PANDEY 《Journal of Mountain Science》 SCIE CSCD 2016年第2期302-315,共14页
Abstract: Estimation of evapotranspiration (ET) for mountain ecosystem is of absolute importance since it serves as an important component in balancing the hydrologic cycle. The present study evaluates the performa... Abstract: Estimation of evapotranspiration (ET) for mountain ecosystem is of absolute importance since it serves as an important component in balancing the hydrologic cycle. The present study evaluates the performance of original and location specific calibrated Hargreaves equation (HARG) with the estimates of Food and Agricultural Organization (FAO) Penman Monteith (PM) method for higher altitudes in East Sikkim, India. The results show that the uncalibrated HARG model underestimates ET0 by 0.35 mm day^-1 whereas the results are significantly improved by regional calibration of the model. In addition, this paper also presents the variability in the trajectory associated with the climatic variables with the changing climate in the study site. Non- parametric Mann-Kendall (MK) test was used to investigate and understand the mean monthly trend of eight climatic parameters including reference evapotranspiration (ET0) for the period of 1985 - 2009. Trend of ET0 was estimated for the calculations done by FAO PM equation. The outcomes of the trend analysis show significant increasing (p ≤ 0.05) trend represented by higher Z-values, through MK test, for net radiation (Rn), maximum temperature (Tmax) and minimum temperature (Train), especially in the first months of the year. Whereas, significant (0.01 ≥ p ≤0.05) decreasing trend in vapor pressure deficit (VPD) and precipitation (P) is observed throughout the year. Declining trend in sunshine duration, VPD and ET0 is found in spring (March - May) and monsoon (June - November) season. The result displays significant (0.01≤ p ≤0.05) decreasing ET0 trend between (June - December) except in July, exhibiting the positive relation with VPD followed by sunshine duration at the station. Overall, the study emphasizes the importance of trend analysis of ET0 and other climatic variables for efficient planning and managing the agricultural practices, in identifying the changes in the meteorological parameters and to accurately assess the hydrologic water balance of the hilly regions. 展开更多
关键词 reference evapotranspiration (ET0 Climatic variables Trend analysis Mann-Kendall's test Monthly variation East Sikkim hilly region
下载PDF
基于0-1膨胀二项分布的客观贝叶斯分析
7
作者 吴懿祺 肖翔 古晞 《计算机应用与软件》 北大核心 2024年第4期46-52,59,共8页
在医疗卫生、金融证券等应用领域,经常会同时出现零观测值、一观测值较多的情况。为更好地拟合这类数据,提出一种0-1膨胀二项分布模型并进行客观贝叶斯分析。采用数据扩充策略,基于完全似然函数,得到Jeffreys先验和reference先验。采用W... 在医疗卫生、金融证券等应用领域,经常会同时出现零观测值、一观测值较多的情况。为更好地拟合这类数据,提出一种0-1膨胀二项分布模型并进行客观贝叶斯分析。采用数据扩充策略,基于完全似然函数,得到Jeffreys先验和reference先验。采用WinBUGS软件和R软件进行数值模拟,设定不同的样本量和参数真值,对不同的无信息先验进行评估。对2020年1月28日与2月22日COVID-19死亡人数进行分析,结果表明,在小样本情形下基于客观贝叶斯先验π_(R3)下的拟合效果比π_(R1)和π_(R2)要好。 展开更多
关键词 0-1膨胀二项分布 客观贝叶斯 Jeffreys先验 reference先验 数据扩充
下载PDF
Identification of Dominant Climate Variables on Spatiotemporal Variation in Reference Evapotranspiration on the Loess Plateau,China
8
作者 LI Xiaofei LIANG Wei +6 位作者 JIAO Lei YAN Jianwu ZHANG Weibin WANG Fengjiao GOU Fen WANG Chengxi SHAO Quanqin 《Chinese Geographical Science》 SCIE CSCD 2022年第4期620-642,共23页
Reference evapotranspiration(ET_(0))is a vital component in hydrometeorological research and is widely applied to various aspects,such as water resource management,hydrological modeling,irrigation deployment,and under... Reference evapotranspiration(ET_(0))is a vital component in hydrometeorological research and is widely applied to various aspects,such as water resource management,hydrological modeling,irrigation deployment,and understanding and predicting the influence of hydrologic cycle variations on future climate and land use changes.Quantifying the influence of various meteorological variables on ET_(0) is not only helpful for predicting actual evapotranspiration but also has important implications for understanding the impact of global climate change on regional water resources.Based on daily data from 69 meteorological stations,the present study analyzed the spatiotemporal pattern of ET_(0) and major contributing meteorological variables to ET_(0) from 1960 to 2017 by the segmented re-gression model,Mann-Kendall test,wavelet analysis,generalized linear model,and detrending method.The results showed that the annual ET_(0) declined slightly because of the combined effects of the reduction in solar radiation and wind speed and the increase in vapor pressure deficit(VPD)and average air temperature in the Loess Plateau(LP)during the past 58 yr.Four change points were detected in 1972,1990,1999,and 2010,and the annual ET_(0) showed a zigzag change trend of‘increasing-decreasing-increasing-decreasing-increasing’.Wind speed and VPD played a leading role in the ET_(0) changes from 1960 to 1990 and from 1991 to 2017,respectively.This study confirms that the dominant meteorological factors affecting ET_(0) had undergone significant changes due to global climate change and vegetation greening in the past 58 years,and VPD had become the major factor controlling the ET_(0) changes on the LP.The data presented herein will contribute to increasing the accuracy of predictions on future changes in ET_(0). 展开更多
关键词 reference evapotranspiration(ET0) change points generalized linear model dominant factors vapor pressure deficit(VPD) Loess Plateau(LP)
下载PDF
基于绝对贪心和预期效率的0-1背包问题优化 被引量:11
9
作者 史岚 张义宏 吕建辉 《计算机应用研究》 CSCD 北大核心 2014年第3期684-687,共4页
在传统求解背包问题的理论基础之上,对难解背包问题进行优化,设计了一种基于绝对贪心策略和预期效率的新算法。针对该算法进行了三组仿真实验,结果表明,算法能够较好地解决一类0-1背包问题,优于贪心算法、回溯法、动态规划算法、分支限... 在传统求解背包问题的理论基础之上,对难解背包问题进行优化,设计了一种基于绝对贪心策略和预期效率的新算法。针对该算法进行了三组仿真实验,结果表明,算法能够较好地解决一类0-1背包问题,优于贪心算法、回溯法、动态规划算法、分支限界算法,该算法的收敛速度是萤火虫群算法的10倍。经过分析数据的离散程度,确定了该算法的适应范围。 展开更多
关键词 0-1背包问题 绝对贪心 预期效率 收敛速度 离散程度
下载PDF
解决证据推理中一类“0绝对化”问题的方法 被引量:7
10
作者 徐从富 耿卫东 潘云鹤 《计算机科学》 CSCD 北大核心 2000年第5期53-56,共4页
1 引言 Dempster-Shafer证据理论应用于不确定性推理领域即为证据推理。证据推理已经成为不确定性推理理论中的一种重要方法,实质上它是一种常识推理。证据推理同其它的不确定性推理方法相比,有其独特的优点,它特别适合表达模糊的、不... 1 引言 Dempster-Shafer证据理论应用于不确定性推理领域即为证据推理。证据推理已经成为不确定性推理理论中的一种重要方法,实质上它是一种常识推理。证据推理同其它的不确定性推理方法相比,有其独特的优点,它特别适合表达模糊的、不确定的和“不知道的”信息,这类信息保存在基本可信度分配BPA(mass函数)中,且在推理过程中保留了这些信息。在证据推理中,最关键的是mass函数的分配与合成。mass函数是一种假设的度量函数,它是人们主观给出的,或者凭经验和感觉给出。文指出领域专家很难恰当地将不确定性和主观信度表示成mass分配。比如在医疗诊断中。 展开更多
关键词 证据推理 0绝对化”问题 不确定性推理
下载PDF
绝对重力控制下的山西地震带2009—2012重力场动态变化 被引量:4
11
作者 冯建林 孙少安 +3 位作者 秦建增 檀玉娟 黄帮武 李德庆 《大地测量与地球动力学》 CSCD 北大核心 2013年第A01期49-52,共4页
通过对山西地震带区域重力测网2009—2012年的绝对与相对重力资料的联合平差,获得了以太原绝对重力点为基准的区域重力场动态变化图像,并分析了太原绝对重力点起算值的选取问题。
关键词 绝对重力 山西地震带 相对重力 平差 基准
下载PDF
基于Web2.0的数字参考咨询服务创新 被引量:17
12
作者 杨思洛 毕艳娜 《图书馆学研究》 2007年第2期75-78,共4页
简述Web2.0与图书馆2.0的发展历史与现状,总结国内外图书馆数字参考咨询服务理论与实践的研究情况。认为基于Web2.0的数字参考咨询服务创新可包括三个层面,并对第二层面,即怎样创新的问题从创新原则、创新方法、创新方式和创新内容等方... 简述Web2.0与图书馆2.0的发展历史与现状,总结国内外图书馆数字参考咨询服务理论与实践的研究情况。认为基于Web2.0的数字参考咨询服务创新可包括三个层面,并对第二层面,即怎样创新的问题从创新原则、创新方法、创新方式和创新内容等方面进行探讨。 展开更多
关键词 数字参考咨询 WEB2.0 图书馆
下载PDF
2011年日本9.0级地震前后GPS基线时间序列分析 被引量:15
13
作者 张风霜 占伟 孙东颖 《地震研究》 CSCD 北大核心 2012年第2期190-200,共11页
利用1999年初至2011年9月中国地壳运动观测网络基准站及中国大陆周边包含日本境内的IGS基准站的资料,分析了2011年3月11日日本9.0级地震前日本境内及周边IGS基准站基线时间序列的变化情况。讨论了该地震对中国大陆GPS基准站的同震影响,... 利用1999年初至2011年9月中国地壳运动观测网络基准站及中国大陆周边包含日本境内的IGS基准站的资料,分析了2011年3月11日日本9.0级地震前日本境内及周边IGS基准站基线时间序列的变化情况。讨论了该地震对中国大陆GPS基准站的同震影响,并对地震后中国大陆GPS基线时序结果的变化情况进行了总结分析。通过分析认为,日本大震后我国东部地区部分GPS基线开始转折拉伸,因而一定程度上缓解了这些基线的趋势性缩短,但是东部地区仍然有部分GPS基线的变化趋势基本不受日本地震的影响,近几年以来的趋势性异常至今仍然存在。 展开更多
关键词 GPS基准站 基线时间序列 构造形变场 日本9.0级地震
下载PDF
多相异步电动机在广义d-q-0参照系中的仿真分析 被引量:3
14
作者 王铁军 孟凡友 吴旭升 《海军工程大学学报》 CAS 北大核心 2008年第5期51-55,共5页
选择合适参照系变换是多相电机分析中的重要内容,文中介绍了广义d-q-0变换的原理和这种变换矩阵的推导过程,阐述了这种变换的物理意义。以双Y移30°异步电动机为对象,在广义d-q-0参照系中建立数学模型并进行仿真,结果验证了这种变... 选择合适参照系变换是多相电机分析中的重要内容,文中介绍了广义d-q-0变换的原理和这种变换矩阵的推导过程,阐述了这种变换的物理意义。以双Y移30°异步电动机为对象,在广义d-q-0参照系中建立数学模型并进行仿真,结果验证了这种变换在动态问题和谐波问题分析中的有效性。 展开更多
关键词 多相异步电动机 d-q-0参照系 谐波
下载PDF
应用酸性铬蓝K的A_N=0双波长补偿系数光度法测定铜(Ⅱ) 被引量:2
15
作者 黄泽南 周琦 +1 位作者 邓昌爱 李红波 《分析科学学报》 CAS CSCD 北大核心 2009年第5期583-586,共4页
在pH=12.7的NaOH介质中,铜(Ⅱ)与酸性铬蓝K(ACBK)形成深红色配合物,应用该配合物生色对试剂ACBK褪色产生100%相消干扰的波长533 nm作为负峰波长,建立了ACBK测定铜(Ⅱ)的AN=0双波长补偿系数光度法。该法能消除显色剂ACBK褪色对生成... 在pH=12.7的NaOH介质中,铜(Ⅱ)与酸性铬蓝K(ACBK)形成深红色配合物,应用该配合物生色对试剂ACBK褪色产生100%相消干扰的波长533 nm作为负峰波长,建立了ACBK测定铜(Ⅱ)的AN=0双波长补偿系数光度法。该法能消除显色剂ACBK褪色对生成物Cu(ACBK)生色的相消干扰,测得生色法真实吸光度,消除生成物生色对有色剂ACBK褪色的相消干扰;测得褪色法近似真实吸光度,其灵敏度是上述两法之和。于波长λp573 nm,λN533 nm测得信号吸光度补偿系数fs为4.135,信号摩尔吸光系数为4.56×10^4L.mol^-1.cm^-1,是经典光度法的3.73倍。方法线性范围为0.02-1.60 mg.L^-1,配合物的摩尔比为Cu∶ACBK=1∶1。测定了某些水样中的铜(Ⅱ),并对方法进行了检验,回收率为96%-104%。 展开更多
关键词 AN=0双波长补偿系数光度法 100%相消干扰 补偿系数 酸性铬蓝K 铜(Ⅱ)
下载PDF
Web 3.0对虚拟参考咨询的影响 被引量:6
16
作者 胡震 高风霞 《河南职工医学院学报》 2008年第6期612-613,共2页
网络通讯技术的发展日新月异,继Web 1.0、Web 2.0后,Web 3.0这一互联网发展的新趋势将对图书馆的虚拟参考咨询在工具技术、服务模式、人员素质等方面发生作用,促使其最大限度地满足用户全方位、多样化和个性化的需求。
关键词 WEB 3.0 图书馆 参考咨询
下载PDF
评析“Second Life”中的数字参考咨询2.0 被引量:1
17
作者 张剑华 张禹 《中山大学研究生学刊(社会科学版)》 2009年第1期98-103,共6页
"Second Life"是一个新兴的网络在线三维虚拟世界,国外已有很多图书馆在这里提供参考咨询服务,本文通过自身的实践体验对"Second Life"中的参考咨询服务优缺点进行分析。
关键词 SECOND LIFE 参考咨询2.0
下载PDF
基于机器学习算法的ET_(0)预测研究 被引量:5
18
作者 韦琦 卫琦 +4 位作者 徐解刚 柏玥辰 李昕彤 贺敏 徐俊增 《节水灌溉》 北大核心 2022年第11期9-17,共9页
为了解不同机器学习算法在预测不同气候区参考作物腾发量(ET_(0))方面的表现,以中国干旱区和湿润区共计20个气象站点1960-2019年的逐日气象数据为依据,以PM和HS公式计算的ET_(0)为参考,评价了多元逐步回归(SL)、支持向量机(SVM)和高斯... 为了解不同机器学习算法在预测不同气候区参考作物腾发量(ET_(0))方面的表现,以中国干旱区和湿润区共计20个气象站点1960-2019年的逐日气象数据为依据,以PM和HS公式计算的ET_(0)为参考,评价了多元逐步回归(SL)、支持向量机(SVM)和高斯过程回归(GPR) 3种机器学习算法的ET_(0)预测精度及其适用性。结果表明:(1)当分别以PM和HS公式计算的ET_(0)数值为标准时,3种机器学习算法模拟ET_(0)精度大小关系均表现为:GPR>SVM>SL,且GPR算法的模拟精度最高,其相关系数(R~2)均高达0.950以上。(2)当采用同一种机器学习算法时,其在以PM公式计算的ET_(0)为参考值情况下的R~2范围为0.965~0.995、RMSE的范围为0.212~0.260 mm/d、MAE的范围为0.151~0.201 mm/d;以HS公式计算结果为参考值时,其R~2范围为0.935~0.984、RMSE范围为0.832~0.964 mm/d、MAE范围为0.596~0.745mm/d。(3)在不同气候分区,以同一参考公式计算结果为标准值时采用机器学习算法模拟干旱区的ET_(0)精度均优于湿润区,其R~2提高了0.01。(4)对比不同机器学习算法的稳健性,SL和SVM算法在分别以PM和HS公式计算结果为参考值时的稳健性最高,其训练到模拟阶段的R~2变化幅度仅为0.16%和0.11%,而GPR算法稳健性均最低。(5)对比不同机器学习算法训练时间成本,SVM和GPR算法的计算成本显著高于SL算法。综合分析3种算法的ET_(0)预测精度、稳健性和计算成本,SVM算法可推荐为中国干旱区和湿润区较为精准预测参考作物腾发量的方法。且机器学习模拟精度与气象因子的定量关系表明,日照时数(N)变化是影响各算法预测精度的主要因子。 展开更多
关键词 参考作物腾发量 ET_(0)预测精度 算法稳健性 训练时间成本 不同气候区 机器学习算法
下载PDF
0-1膨胀几何分布的客观贝叶斯分析 被引量:2
19
作者 肖翔 古晞 《上海工程技术大学学报》 CAS 2021年第3期266-271,共6页
在医疗卫生、金融证券等应用领域,经常会同时出现零观测值、一观测值较多的情况.为更好地拟合这类数据,提出0–1膨胀几何分布模型并进行客观贝叶斯分析.通过参数变换,得到Jeffreys先验和reference先验.设计后验分布的抽样算法,设置不同... 在医疗卫生、金融证券等应用领域,经常会同时出现零观测值、一观测值较多的情况.为更好地拟合这类数据,提出0–1膨胀几何分布模型并进行客观贝叶斯分析.通过参数变换,得到Jeffreys先验和reference先验.设计后验分布的抽样算法,设置不同的样本量和参数真值,采用数值模拟方法对不同客观先验下的估计效果进行评估. 展开更多
关键词 0-1膨胀几何分布 Jeffreys先验 reference先验 客观贝叶斯分析
下载PDF
四川省0~17岁健康人群全血钙元素的参考区间研究 被引量:1
20
作者 韩莹 王玉 《广东微量元素科学》 CAS 2014年第2期27-30,共4页
目的建立四川省0—17岁人群全血钙元素的正常值参考区间。方法采用原子吸收光谱法对采集到的四川省24347例0—17岁健康人末梢血中的钙元素含量进行测定,用正态分布法和百分位数法确定其参考范围。结果全血钙正态分布法参考范围:0-岁... 目的建立四川省0—17岁人群全血钙元素的正常值参考区间。方法采用原子吸收光谱法对采集到的四川省24347例0—17岁健康人末梢血中的钙元素含量进行测定,用正态分布法和百分位数法确定其参考范围。结果全血钙正态分布法参考范围:0-岁最高,1.56—2.38mmol/L;13-17岁最低,1.34~2.00mmol/L。结论初步建立四川省0—17岁健康人群全血钙的参考范围。 展开更多
关键词 0~17岁 末梢血 参考区间
下载PDF
上一页 1 2 7 下一页 到第
使用帮助 返回顶部