中国海洋经济前景预测

中国海洋经济正处于快速发展阶段,加强海洋经济的预测研究将有利于认识海洋经济发展规律、确定全国海洋经济发展目标和实现海洋开发战略目标。文章主要运用趋势外推法和灰色系统理论构建海洋经济预测模型,利用历史统计数据,预测中国海洋经济的发展趋势。     

用直接估计法预测落叶松枯枝含水率的稳定性和外推误差分析

采用Catchpole等提出的直接估计法分析实验室中3组不同直径(0.5,1.0,1.5cm)的兴安落叶松枯枝的失水过程,通过交叉验证研究所得模型的稳定性,并对模型的外推误差进行分析。结果表明:枯枝的时滞和平衡含水率参数变化很小,结果具有良好的稳定性。同一直径的不同枝条在时滞、平衡含水率参数等方面存在差异。模型外推没有改变残差的正态分布,但外推后的残差增大。非外推残差集中出现在数值较小的区间上,而外推残差在这些区间上出现的概率下降,在非外推残差没有出现的数值较大的区间上出现的概率增加。研究给出枯枝在不同含水率预测值时不同残差出现的条件概率和均值。随含水率预测值的增加,残差有增加的趋势,不仅是平均值,大的残差出现的概率也在增加。据此可对外推模型所预测的含水率进行评判,确定其误差均值和不同残差出现的可能性,以减少据此进行的火险预报和火行为预报中的不确定性。用至少4个枯枝的混合数据在一定程度上可降低外推误差,减少这种不确定性。由于所有材料和实验条件最大程度上减少了材料和环境的差异,上述结果也可被看作用模型外推预测野外可燃物含水率时可能出现的误差的下限。     

空间自相关性对冬小麦种植面积空间抽样效率的影响

空间抽样是实现区域农作物面积高效估算的重要手段,农作物分布受自然条件等因素影响普遍存在空间自相关性,但以往针对空间相关性对农作物面积抽样效率的影响研究明显不足.该研究选取安徽省凤台县为研究区,通过2017年4月4景GF-1全色多光谱影像(Panchromatic and Multispectral,PMS)与Googl...     

细分外推与模糊预测在近海水质非线性时序处理中的比较分析

近海水质非线性时间序列通常由于采集范围大、时间间隔长带有一定震荡性和模糊性,这使得对其进行分析与预测有一定的难度。本研究中以某近海水质指标磷酸盐(PO3-4-P)、硝酸盐(NO-3-N)、亚硝酸盐(NO-2-N)、铵盐(TNH+4-N)和硅酸盐(Si O2-3-Si)所形成的5种时间序列为例,采用逼近细分模式导出的细分外推法和多参考加权数据的模糊预测法对近海水质时序预测进行了比较分析,并通过图形与误差计算比较了两种方法的异同。结果表明:采用细分外推法预测序列在整体形状上能更好地逼近初始时序,而模糊预测法在整体逼近精度上占有优势。本研究中提出的预测比较方法可为同类问题的预测与模型选取提供参考依据。     

Soil organic carbon stocks in Flemish grasslands: how accurate are they?

Articles 3·3 and 3·4 of the Kyoto protocol provide Annex I countries the possibility to reduce greenhouse gas emissions through the sequestration of carbon (C) in their terrestrial ecosystems. For such accounting, the 1990 flux is needed and, therefore, a correct knowledge of the baseline (1990) C stocks is necessary. In addition, a correct methodology should be used to investigate the capacity of ecosystems to sequester C through changes in land use or management by the end of the first commitment period (2008–2012). At national and regional scales, formulation of baseline C stocks in terrestrial ecosystems is difficult and uncertain. Differences in method of analysis, sampling depth of soil, lack of sufficient C data and the necessity to extrapolate C data to total soil organic C stocks, provide problems when comparing databases with each other. In this study, three extrapolation models were compared with the classical layer‐based method to determine the model with the best fit. The model with the best predictions, in relation to the classical layer‐based model, uses recent soil C profiles for estimating the parameter k, which represents the decrease in the proportion of soil organic C with depth, and for extrapolating the C data available for 1990 and 2000 to a depth of 1 m. The other two models gave large underestimates.     

生态足迹时间序列趋势外推分析的一种新方法及其应用

应用数学生态学的有关理论与方法,结合生态足迹的概念,提出了一种生态足迹时间序列的新的趋势外推分析方法;并以甘肃省河西绿洲农业区为研究对象,对其生态足迹进行了趋势外推分析的实例计算。结果表明,本研究中的趋势外推分析方法在生态足迹时间序列分析中的应用能够取得较好的结果;但模型本身的不足使其在实际数据存在短期剧烈波动时,拟合的结果与实际值之间存在较大的差距。本研究提出的包含随机影响的趋势外推分析方法进一步补充和完善了原有生态足迹分析方法的不足,在理论和实践中都有较高的指导和应用价值。     

R-factor Pseudo-circular Extension Method

The extension methods of finite length signals for sub band coding associated with wavelet transformation are investigated.Considering the weakness of the existing extension methods,an extension method is presented which is named r factor pseudo circular extension method.It turns out theoretically that the input signal can be reconstructed exactly from the truncated section of the analyzed signals by our method and the method is better than other existing extension methods,as shown in many examples.A new valid way is provided for wavelet transform application in data compression.     

空间抽样方法估算冬小麦播种面积

为改进现行农作物播种面积空间抽样技术体系,该文以山东省为研究区,以冬小麦播种面积为研究对象,通过"3S"技术(遥感、地理信息及全球定位技术)与传统抽样方法的联合应用,选取4种抽样技术(简单随机抽样、按冬小麦种植区划分层抽样、按耕地类型分层抽样和按分县冬小麦面积大小分层抽样),设计8种样本容量水平(变化范围74～333)进行了冬小麦播种面积空间抽样方法试验研究,结果表明:4种抽样方法中,在外推总体相对误差相近条件下,以分县冬小麦播种面积大小为分层标志的分层抽样方法效率最高;基于8种样本容量下的样本观测值进行研究区冬小麦播种面积总体外推与误差估计时,随着样本容量增加,外推总体总值估计值与真值的相对误差随之减小,但总体总值估计量的变异系数(CV)值仍较大。     

The Application of Extrapolation of FEM to the Eigen Value Problems of Waveguide

On the basis of the method of linear finite element and taking the advantage of the theory of finite element extrapolation,the paper discusses the method for calculating the eigenvalue of waveguide.The results show the method is simple and has higher accuracy.     

Assisting nonsoil specialists to identify soil types for land management: an approach using a soil identification key and toposequence models

Conventional soil survey information is often unclear except to specialists. An approach using soil toposequences and a soil identification key was used to aid the translation of soil survey information into a form suitable for a nonspecialist audience with a case study from Brunei. Soil Taxonomy was used to characterize the major soil types; however, to assist end users, a complementary special‐purpose soil classification system was developed in the form of a soil identification key using plain language terms in English that were also translated into Malay. Easily recognized soil features such as depth, colour and texture were used to categorize soils to match Soil Taxonomy classes. To complement the soil identification key, conceptual soil toposequence models presented the soil distribution patterns in a visual format that local land users understood. Legacy soil survey information along with a widespread distribution of 172 soil sites from 35 traverses in 16 study areas provided a dataset to develop and test soil toposequence models and the soil identification key which both proved reliable and robust. The approach demonstrated in Brunei could be applied to other countries and landscapes.