期刊文献+
共找到611篇文章
< 1 2 31 >
每页显示 20 50 100
Non-use value assessment for wetland ecosystem service of Hongxing National Nature Reserve in northeast China 被引量:1
1
作者 Xin Jin Jianzhang Ma +1 位作者 Tijiu Cai Xiaoxin Sun 《Journal of Forestry Research》 SCIE CAS CSCD 2016年第6期1435-1442,共8页
By the contingent value method, we studied the non-use value of wetland ecosystem service of Hongxing National Nature Reserve (HNNR) in Heilongjiang Pro- vince, northeast China. The proportion of respondents willing... By the contingent value method, we studied the non-use value of wetland ecosystem service of Hongxing National Nature Reserve (HNNR) in Heilongjiang Pro- vince, northeast China. The proportion of respondents willing to pay (WTP) for protection of HNNR was 63 %. The WTP ratio was affected by geographical area, contact nature, personal preferences, and familiar degree of the respondents. The WTP value was affected by age, education level and career of the respondents. The mainly reasons for people rejecting to pay for protecting HNNR were "I am not familiar to HNNR" and "I had no capacity for additional spending because of low income". Weighted average individual WTP value was CNY 59.26 Yuan ind.^-1 year^-1 for all the respondents with WTP. The total non-use ecosystem service value of HNNR was CNY 1430 million Yuan in 2013. The heritage value was highest followed by existence value and option value. From the high ecosystem service value in HNNR, it is very important to construct nature reserve for protecting natural ecosystems and human sustainable use of natural resources. 展开更多
关键词 Ecosystem service Non-use value Hongxing National Nature Reserve - Xiaoxing'an Mountains
下载PDF
A Compact Difference Scheme for Multi-point Boundary Value Problems of Heat Equations
2
作者 Xuping Wang Zhizhong Sun 《Communications on Applied Mathematics and Computation》 2019年第4期545-563,共19页
In this paper,a compact difference scheme is established for the heat equations with multi-point boundary value conditions.The truncation error of the difference scheme is O(τ2+h^4),where t and h are the temporal ste... In this paper,a compact difference scheme is established for the heat equations with multi-point boundary value conditions.The truncation error of the difference scheme is O(τ2+h^4),where t and h are the temporal step size and the spatial step size.A prior estimate of the difference solution in a weighted norm is obtained.The unique solvability,stability and convergence of the difference scheme are proved by the energy method.The theoretical statements for the solution of the difference scheme are supported by numerical examples. 展开更多
关键词 HEAT EQUATION - Multi-point BOUNDARY value CONDITION Compact DIFFERENCE scheme Energy method
下载PDF
Jacobi-Sobolev Orthogonal Polynomialsand Spectral Methods for Elliptic Boundary Value Problems
3
作者 Xuhong Yu Zhongqing Wang Huiyuan Li 《Communications on Applied Mathematics and Computation》 2019年第2期283-308,共26页
Generalized Jacobi polynomials with indexes α,β∈ R are introduced and some basic properties are established. As examples of applications,the second- and fourth-order elliptic boundary value problems with Dirichlet ... Generalized Jacobi polynomials with indexes α,β∈ R are introduced and some basic properties are established. As examples of applications,the second- and fourth-order elliptic boundary value problems with Dirichlet or Robin boundary conditions are considered,and the generalized Jacobi spectral schemes are proposed. For the diagonalization of discrete systems,the Jacobi-Sobolev orthogonal basis functions are constructed,which allow the exact solutions and the approximate solutions to be represented in the forms of infinite and truncated Jacobi series. Error estimates are obtained and numerical results are provided to illustrate the effectiveness and the spectral accuracy. 展开更多
关键词 Generalized JACOBI POLYNOMIALS Spectral method - Jacobi-Sobolev ORTHOGONAL BASIS functions ELLIPTIC boundary value problems Error analysis
下载PDF
Reflection of Liberal Values in the Georgian Press in 1918-1921
4
作者 Manana Shamilishvili Mari Tsereteli 《International Relations and Diplomacy》 2016年第5期341-352,共12页
This study deals with the values and orientation of Georgian social and political publications in the times of the Georgian Democratic Republic (1918-1921). It also shows how the press of that time reflected the ide... This study deals with the values and orientation of Georgian social and political publications in the times of the Georgian Democratic Republic (1918-1921). It also shows how the press of that time reflected the idea of "Georgian Europeanism" based on liberal values that took shape as an anti-colonial concept in the journalism of the late 19th century. The opposed dominant ideological projects of that era comprised on the one hand, National Democratic and Socialist Federalist parties that aspired to preserve national identity and carry out changes and on the other hand, ruling Social Democrats (who initially neglected national identity, but later shared the idea). This opposition was clearly reflected in the media discourse of that time, which implied the following rights based on the principles of classical liberalism: freedom of conscience and expression, rule of law, personal independence, and individual rights. Other elements were added to this list later. The issue of religious tolerance also became topical. Journalist texts of the period reflected and rationalised the values recognised in today's democratic and liberal communities. The research was carried out in the archives of the periodicals of the aforementioned period (newspapers Sakhalkho Sakme, Sakartvelo, Ertoba, and Sakartvelos Respublika) by means of systematising and classifying retrieved materials and making a substantive and varietal analysis of individual media texts. 展开更多
关键词 Georgian journalism the Georgian Party Press in 1918-1921 the liberal values the idea of Georgian Europeanism
下载PDF
Risk measurement of international oil and gas projects based on the Value at Risk method 被引量:2
5
作者 Cheng Cheng Zhen Wang +1 位作者 Ming-Ming Liu Xiao-Hang Ren 《Petroleum Science》 SCIE CAS CSCD 2019年第1期199-216,共18页
International oil and gas projects feature high capital-intensity, high risks and contract diversity. Therefore, in order to help decision makers make more reasonable decisions under uncertainty, it is necessary to me... International oil and gas projects feature high capital-intensity, high risks and contract diversity. Therefore, in order to help decision makers make more reasonable decisions under uncertainty, it is necessary to measure the risks of international oil and gas projects. For this purpose, this paper constructs a probabilistic model that is based on the traditional economic evaluation model, and introduces value at risk(VaR) which is a valuable risk measure tool in finance, and applies Va R to measure the risks of royalty contracts, production share contracts and service contracts of an international oil and gas project. Besides, this paper compares the influences of different risk factors on the net present value(NPV) of the project by using the simulation results. The results indicate:(1) risks have great impacts on the project's NPV, therefore, if risks are overlooked, the decision may be wrong.(2) A simulation method is applied to simulate the stochastic distribution of risk factors in the probabilistic model. Therefore, the probability is related to the project's NPV, overcoming the inherent limitation of the traditional economic evaluation method.(3) VaR is a straightforward risk measure tool, and can be applied to evaluate the risks of international oil and gas projects. It is helpful for decision making. 展开更多
关键词 RISK measurement value at RISK INTERNATIONAL oil and gas PROJECTS FISCAL TERMS - Probabilistic model
下载PDF
A REGULAR VALUE OF COMPACT DEFORMATION
6
作者 J.M.Soriano 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2006年第9期1265-1274,共10页
Sufficient conditions were given to assert that between any two Banach spaces over K, Fredholm mappings share at least one .value in a specific open ball. The proof of the result is constructive and based upon continu... Sufficient conditions were given to assert that between any two Banach spaces over K, Fredholm mappings share at least one .value in a specific open ball. The proof of the result is constructive and based upon continuation methods. 展开更多
关键词 regular value continuation methods continuous dependence theorem C^1- homotopy proper mapping compact mapping Fredholm mapping topological complement Sard-Smale theorem
下载PDF
Value Finance Theory
7
作者 Zhaocheng Wang 《Journal of Economic Science Research》 2022年第4期1-7,共7页
With the development of digital economy, metaverse and blockchain, the inherent economic form changes. In the era of digital economy, changes in value have new characteristics. This paper uses the method of political ... With the development of digital economy, metaverse and blockchain, the inherent economic form changes. In the era of digital economy, changes in value have new characteristics. This paper uses the method of political economy to analyze and demonstrate the composition of value. Then it analyzes the economic reasons for the economic depression, insufficient consumption power and unsalable commodities in the digital economy period. And the article gives a specific solution. It has specific application value for all countries to deal with and pass through the economic depression. It has a theoretical guiding role in the stable development of macro economy in the digital economy period. 展开更多
关键词 Commodity value WELFARE minimum disposable expenses Digital economy INFLATION value Unsalable
下载PDF
Study on Antibacterial Activity of 2-Methyl-3-(methylthio)Pyrazine Against Three Strains of Spoilage Bacteria
8
作者 Kun LI Guanghe ZHU +1 位作者 Danning FU Lele LI 《Agricultural Biotechnology》 2024年第1期74-77,共4页
Previous studies have shown that glycine and proline are pharmacophores that display antibacterial activity.In the present study,glycine and proline were derivated to diketopiperazine compounds by chemical synthesis m... Previous studies have shown that glycine and proline are pharmacophores that display antibacterial activity.In the present study,glycine and proline were derivated to diketopiperazine compounds by chemical synthesis method,and their antibacterial activities were evaluated by three strains of spoilage bacteria,Escherichia coli,Pseudomonas aeruginosa and Shewanella putrefaciens,and the relationship of their antibacterial activities and structures was also investigated.Uv-vis spectrophotometry was used to determine the growth curves of three kinds of active indicator bacteria.Minimum inhibitory concentration(MIC)was determined by micro broth dilution method.The results showed that 2-methyl-3-(methylthio)pyrazine had significant antibacterial activity against three strains of the bacteria,and its MIC was 1.25%.It indicates 2-methyl-3-(methylthio)pyrazine has the potential to be developed as a kind of preservative in future. 展开更多
关键词 2-Methyl-3-(methylthio)pyrazine Growth curve minimum inhibitory concentration
下载PDF
Variations of Frost-free Period and Its Impact on Grain Yields in Henan Province during 1961-2013 被引量:4
9
作者 闫军辉 傅辉 +1 位作者 周红升 徐新创 《Agricultural Science & Technology》 CAS 2015年第8期1588-1591,1692,共5页
The aim of this study was to investigate the responses of frost dates to global warming and its influences on grain yields. In this study, based on the frost date series defined by daily minimum ground temperature, th... The aim of this study was to investigate the responses of frost dates to global warming and its influences on grain yields. In this study, based on the frost date series defined by daily minimum ground temperature, the spatial and temporal characteristics of first frost date (FFD), last frost date (LFD) and frost-free period (FFP) were analyzed. The impact of extending FFP on major crop yields was also studied. The results were as follows: FFD showed a significantly delaying trend of 2.2 d/10 y, and LFD presented an advancing trend of 2.4 d/10 y. FFP extended at a rate of 4.5 d/10 y due to the later FFD and earlier LFD. The most obvious trend of FFD was in westem Henan, while the most significant trend of LFD and FFP oc- curred in south central parts of the study area. However, in eestem region, the trends of FFD, LFD and FFP were not so obvious. Major crop yield showed a sig- nificant correlation with frost-free period for Henan during 1961-2013. The yields of grain, rice, wheat, and maize increased by 79.5, 90.0, 79.5 and 70.5 kg/hm2 with FFP extending by one day. 展开更多
关键词 Daily minimum ground temperature Frost-free period Grain yield Henan province 1961-2013
下载PDF
基于最小生成树的R^*-树结点分裂算法 被引量:2
10
作者 孙殿柱 孙永伟 +1 位作者 康新才 史阳 《西安交通大学学报》 EI CAS CSCD 北大核心 2011年第5期127-130,共4页
针对R*-树应用到逆向工程领域时遇到的适用性差等问题,提出了一种新的R*-树结点分裂算法.该算法将R*-树索引结点表示为轴向包围盒,依据轴向包围盒外接球间的重叠度计算结点相似度,并将其作为权值构建结点无向连通图,用来求解结点无向连... 针对R*-树应用到逆向工程领域时遇到的适用性差等问题,提出了一种新的R*-树结点分裂算法.该算法将R*-树索引结点表示为轴向包围盒,依据轴向包围盒外接球间的重叠度计算结点相似度,并将其作为权值构建结点无向连通图,用来求解结点无向连通图的最小生成树.沿最大权值边将最小生成树分裂为2棵子树,并基于结点外接球体积对R*-树结构进行优化,从而实现了R*-树结点分裂.实例表明,R*-树结点分裂算法可处理各种复杂数据的结点分裂问题,能够有效地提高R*-树的构建效率及空间数据的查询效率. 展开更多
关键词 逆向工程 R*- 轴向包围盒 结点相似度 最小生成树
下载PDF
风险资产组合均值-CVaR模型的算法分析 被引量:6
11
作者 李婷 张卫国 《安徽大学学报(自然科学版)》 CAS 北大核心 2006年第6期4-7,共4页
CVaR是指损失超过VaR的条件均值,反映了损失超过VaR时可能遭受的平均损失水平,它克服了VaR的非一致性、非凸性等不足.本文基于CVaR风险计量技术,分析了风险证券的投资收益率在服从正态分布下的风险资产组合均值-CVaR模型,给出了该风险... CVaR是指损失超过VaR的条件均值,反映了损失超过VaR时可能遭受的平均损失水平,它克服了VaR的非一致性、非凸性等不足.本文基于CVaR风险计量技术,分析了风险证券的投资收益率在服从正态分布下的风险资产组合均值-CVaR模型,给出了该风险资产组合有解的条件,以及在该条件满足下,最小均值-CVaR组合的投资比例解析形式和最小值. 展开更多
关键词 风险投资 CVAR 最小解
下载PDF
基于自适应噪声抵消的MIMO-OFDM信道估计 被引量:1
12
作者 王继曾 罗娜 杨宏梅 《计算机工程与设计》 CSCD 北大核心 2009年第17期3971-3973,共3页
对多输入多输出正交频分复用系统的信道估计进行了研究,利用自适应噪声抵消的思想,提出了一种基于自适应噪声抵消和奇异值分解的信道估计方法。该方法首先利用自适应噪声抵消对最小二乘(LS)估计进行去噪处理,然后将其结果用于奇异值分解... 对多输入多输出正交频分复用系统的信道估计进行了研究,利用自适应噪声抵消的思想,提出了一种基于自适应噪声抵消和奇异值分解的信道估计方法。该方法首先利用自适应噪声抵消对最小二乘(LS)估计进行去噪处理,然后将其结果用于奇异值分解(SVD)的MMSE低阶近似方法中。仿真结果表明,利用此方法有效地抑制了噪声的影响,其系统性能优于利用最小二乘方法所获得的系统性能。 展开更多
关键词 正交频分复用 多输入多输出 自适应噪声抵消 奇异值分解 最小均方误差方法
下载PDF
基于HS-BP算法的股票预测 被引量:3
13
作者 王铭泽 《辽宁大学学报(自然科学版)》 CAS 2012年第1期76-79,共4页
为了有效预测股票问题,针对股票走势具有随机波动性和非线性的特点以及BP神经网络收敛速度慢、容易陷入局部极小值的缺点,提出利用和声搜索算法优化BP网络权重的方法改进神经网络,并通过对股票预测指标的分析,建立了股票预测模型,将和... 为了有效预测股票问题,针对股票走势具有随机波动性和非线性的特点以及BP神经网络收敛速度慢、容易陷入局部极小值的缺点,提出利用和声搜索算法优化BP网络权重的方法改进神经网络,并通过对股票预测指标的分析,建立了股票预测模型,将和声搜索算法优化BP网络应用于所建立的模型中求解.实验结果表明,将HS算法和BP神经网络有机结合,加快了网络收敛速度、避免了局部极小值,有效地刻画了股票的随机波动特性,提高了股票预测的准确性. 展开更多
关键词 BP网络 和声搜索算法 股票 预测 权值优化 非线性 波动性 局部极小
下载PDF
基于B-S模型金融衍生品可转债定价的研究 被引量:1
14
作者 张祎 朱家明 《绍兴文理学院学报》 2017年第7期68-73,共6页
作为一种新型的融资渠道,可转债近几年在资本市场上有了飞速发展,针对可转债的价值组成,将其分成纯债券、转换和期权价值三部分,并分别介绍了三种价值的度量方法,利用最小价值原理和B-S定价公式对选取的9只上市可转债理论价值进行估计,... 作为一种新型的融资渠道,可转债近几年在资本市场上有了飞速发展,针对可转债的价值组成,将其分成纯债券、转换和期权价值三部分,并分别介绍了三种价值的度量方法,利用最小价值原理和B-S定价公式对选取的9只上市可转债理论价值进行估计,发现计算出的结果普遍比市价低,最后基于这个发现讨论产生这种偏差的原因. 展开更多
关键词 B-S期权定价模型 可转换债券 最小价值原理 T检验
下载PDF
FSO-OFDM系统的SVD-MMSE信道估计算法 被引量:1
15
作者 赵黎 李豪杰 《西安工业大学学报》 CAS 2011年第5期474-477,共4页
针对基于MMSE的FSO-OFDM系统信道估计算法计算量复杂、对信道矩阵具有奇异性要求等弊端,设计了基于SVD-MMSE算法的FSO-OFDM系统信道估计流程,并通过Monte Carlo方法对SVD-MMSE算法进行了仿真验证,将MMSE算法与SVD-MMSE算法进行了对比分... 针对基于MMSE的FSO-OFDM系统信道估计算法计算量复杂、对信道矩阵具有奇异性要求等弊端,设计了基于SVD-MMSE算法的FSO-OFDM系统信道估计流程,并通过Monte Carlo方法对SVD-MMSE算法进行了仿真验证,将MMSE算法与SVD-MMSE算法进行了对比分析,结果表明SVD-MMSE算法相对于MMSE算法既能降低系统计算复杂度又能保证系统可靠性,即在系统复杂度与性能之间可以得到很好的折衷. 展开更多
关键词 光通信 正交频分复用 信道估计 最小均方误差 奇异值分解
下载PDF
一种基于最小值和Min-Max方法修正的科研项目综合相似度计算方法
16
作者 杜军 谭鹏 +2 位作者 陈曦 李俊 马继涛 《云南民族大学学报(自然科学版)》 CAS 2023年第6期759-763,共5页
对于科研项目查重,常规方法为对科研项目的项目名称、申请书等项目组成部分分别进行相似度计算,加权处理得到综合相似度后再判断项目的相似度,不易区分客观上有一定相似度而实际上不相似的科研项目.提出一种基于最小值和Min-Max方法修... 对于科研项目查重,常规方法为对科研项目的项目名称、申请书等项目组成部分分别进行相似度计算,加权处理得到综合相似度后再判断项目的相似度,不易区分客观上有一定相似度而实际上不相似的科研项目.提出一种基于最小值和Min-Max方法修正的科研项目综合相似度计算方法,先设定项目组成部分相似度最小值,低于最小值的项目组成部分不参与项目综合相似度计算,再基于Min-Max方法对项目组成部分相似度进行修正,经过修正的相似度加权处理后得到项目综合相似度.实验结果表明,基于最小值和Min-Max方法修正的计算方法能较大程度提高似相似实际不相似科研项目综合相似度的精确度. 展开更多
关键词 相似度 科技计划项目 科研项目 MIN-MAX 最小值
下载PDF
M-矩阵Hadamard积最小特征值下界的估计
17
作者 刘新 杨晓英 《四川文理学院学报》 2013年第2期24-27,共4页
通过研究M-矩阵及其逆矩阵的Hadamard积A。A-1的一些性质,给出了A。A-1的最小特征值下界的一些新的估计式,新下界估计式只依赖于矩阵的元素,易于计算.例证表明,所得估计式在一定条件下比现有估计式更为精确.
关键词 M-矩阵 HADAMARD积 最小特征值 下界
下载PDF
严格对角占优M-矩阵‖A^(-1)‖_∞上界的新估计
18
作者 周平 《文山学院学报》 2014年第3期45-48,共4页
根据M-矩阵的特点和性质,对严格对角占优M-矩阵A^(-1)_∞的上界做了进一步研究,并给出相应的估计式,同时得到A的最小特征值下界的估计式;算例表明,这些新估计式改进了现有的结果。
关键词 对角占优 M-矩阵 无穷大范数 最小特征值
下载PDF
基于SVM-MCD的大坝变形监测数据异常值判定 被引量:7
19
作者 杨承志 魏博文 徐镇凯 《人民长江》 北大核心 2022年第3期207-213,219,共8页
变形是最能直观反映混凝土坝运行性能的宏观效应量。考虑到监测数据异常值对监控模型精度与大坝安全性态诊断的不利影响,提出了一种基于支持向量机的混凝土坝变形监测数据异常值判定方法。在分析混凝土坝原型变形监测数据显性异常点的... 变形是最能直观反映混凝土坝运行性能的宏观效应量。考虑到监测数据异常值对监控模型精度与大坝安全性态诊断的不利影响,提出了一种基于支持向量机的混凝土坝变形监测数据异常值判定方法。在分析混凝土坝原型变形监测数据显性异常点的基础上,通过构建基于支持向量机理论(SVM)的高精度计算体系,充分利用结果效应量与驱动环境量之间的映射交互关系,结合最小协方差矩阵(MCD)稳健估计理论对残差序列进行异常值判定,而后将其异常确定值进行有机性替代处理,解决了内蕴复杂环境干预的监测信息挖掘难点。工程实例分析表明:所建判定系统的精准性及泛化能力均得以提升,相比于传统方法具有较好的实用性和鲁棒性,能有效地避免变形监测数据预处理中的误判漏判等困扰。此外,所提出的判定方法经一定的优化和拓展,亦可推广应用于其他水工建筑物的数据异常值判定分析。 展开更多
关键词 安全监测 异常值判定 支持向量机 最小协方差矩阵 混凝土坝
下载PDF
交通方式选择与旅客时间价值研究——以北京-太原客运通道为例 被引量:13
20
作者 侯云仙 杨善奇 《北京交通大学学报(社会科学版)》 CSSCI 北大核心 2016年第2期80-88,共9页
从旅客出行交通方式选择入手,在综合考虑旅客收入、出行费用、出行时间、安全舒适度、服务水平等因素基础上,提出一个简化且合理的时间价值计算模型。以北京-太原客运通道为例,通过对不同收入旅客出行交通方式选择进行调查,计算出不同... 从旅客出行交通方式选择入手,在综合考虑旅客收入、出行费用、出行时间、安全舒适度、服务水平等因素基础上,提出一个简化且合理的时间价值计算模型。以北京-太原客运通道为例,通过对不同收入旅客出行交通方式选择进行调查,计算出不同收入阶层旅客的时间价值。结果发现,不同收入的旅客时间价值是不同的,但不同收入旅客的每小时时间价值约等于该群体每小时人均可支配收入的50%左右。这一结论对各种交通运输工具的定价及交通资源的配置具有一定的借鉴意义。 展开更多
关键词 旅客时间价值 交通方式选择 效用最大化 费用最小法
下载PDF
上一页 1 2 31 下一页 到第
使用帮助 返回顶部