共查询到20条相似文献,搜索用时 187 毫秒
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建立了基于支持向量机技术的石油期货价格预测方法.该方法使用价格序列一阶差分及其滞后值建模,采用径向基(RBF)核函数和序贯最小优化(SMO)算法,通过综合验证方式确定包括嵌入维数在内的各参数.实证研究表明,支持向量机方法比RBF神经网络和ARIMA模型预测精度更高,具有很好的应用前景. 相似文献
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为提高抽水蓄能电站系统运行的稳定性和可靠性,提出了一种通过主站发电机瓦温信息构建发电机故障诊断模型的方法。以温度值作为特征量构建了支持向量机故障诊断模型,结合麻雀算法全局寻优和局部寻优自由切换的优势,将故障识别正确率作为迭代更新的目标函数,对支持向量机的惩罚因子以及核函数半径的参数组合进行优化。根据麻雀种群位置优化特点,给出了基于麻雀搜索算法进行SVM参数优化的详细步骤流程,并对采集的水泵发电机实测温度数据进行验证和分析。实测数据表明,所提方法可对下导瓦间隙偏小、冷却器容量不足、透平油老化、杂质混入等故障模式进行识别。与若干现行同类方法进行对比分析可知,基于温度分析的发电机故障诊断方法可为抽水储能发电机运行状态监测及主站电机的安全可靠运行提供有益参考。 相似文献
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随着近些年上海市信息化的迅猛发展,信息产业对社会经济各领域产生了广泛而深远的影响,进而直接和间接地影响了各行各业对于电力的需求。通过对上海市1995~2004年信息产业增加值与总用电量的对数线性回归分析和进一步的相关性检验,得到了可用于电力需求预测的线性对数模型。最后,运用此模型对上海市“十一五”期间的用电需求作出了预测。 相似文献
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本文对山东省经济社会发展和电力需求进行了分析,研究了影响电力需求的主要因素,在此基础上,对山东省经济社会未来发展及未来电力需求进行了定量预测。 相似文献
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《Food Policy》2017
Many countries are faced with the problem of monitoring poverty indicators when different food data collection methodologies have been used in national household surveys over the years. This paper provides a comprehensive analysis of this problem in the case of Niger. The paper assesses the impact of three methods of food data collection on the welfare distribution, and poverty and inequality measures in Niger. The study leverages a food consumption experiment to evaluate the three methods of food data collection implemented in the country’s most recent national household surveys. The first method was 7-day recall, the second was usual month, and the third was 7-day diary. The study finds that there was a large difference in measures of consumption and poverty between the first two methods (which yielded similar results) and the 7-day diary method. Annual per capita consumption from the 7-day recall method was, on average, 28 percent higher than that from the 7-day diary method. This gap exists not only at the mean of the distribution, but at every level. The observed differences in measured annual per capita consumption leads to differences in poverty and inequality measures even when alternate poverty lines are used. 相似文献
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概要分析了煤化工的总体发展趋势,系统分析了煤化工两个重点发展领域即煤制化工材料和新型煤基化学燃料。以产业链分析的方法系统梳理了煤制化工材料产业的3个分支即煤制塑料、煤制化纤、煤制橡胶,比较分析了各类煤基液体化学燃料和煤基气体化学燃料的发展潜力,提出了煤基化学燃料的发展重点和需要解决的主要问题。分析计算了2012年煤化工的煤炭消费量和消费结构,不仅计算了煤化工的煤炭消费总量,更根据不同煤化工产品及其不同生产工艺,计算了分煤种的煤炭消费量。根据2020年煤化工产品发展预测及其生产工艺变化预测,计算了2020年煤化工的煤炭消费总量和分煤种的煤炭消费量。 相似文献
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National consumption indicators are frequently compiled using food supply estimates in the absence of reliable household or individual intake data. The authors examine the relationship between these three levels of information and in particular, the potential ‘losses’ of energy in the food system, comparing data from different countries and over time. They demonstrate the unreliability of supply estimates as proxy indicators of consumption and question their current usage in statements about global hunger and the links between health and food intake. 相似文献
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我国“三驾马车”与电力需求关系研究 总被引:1,自引:0,他引:1
基于投入产出理论,从整个社会需求与生产的联系入手,研究“三驾马车”与电力需求之间的关系,为剖析电力与经济的关系提供方法。首先构建了“三驾马车”拉动电力需求的数学模型,然后利用我国已公布的5张竞争型投入产出表编制了5张非竞争型投入产出表,在此基础上测算了我国“三驾马车”对电力需求的拉动作用及其变化情况。研究表明:在我国,“三驾马车”中的消费对电力需求的拉动作用最大,其次是投资,出口的拉动作用最小,2000年以来,消费的拉动作用在逐年下降,投资和出口的拉动作用在逐年上升。 相似文献
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《Food Policy》2020
Since 2005, the European Food Safety Authority (EFSA) has worked in close cooperation with organisations operating in the field towards harmonising dietary survey methodology and building a common European Union (EU) food consumption database. Harmonised food consumption data are the basis for improving accuracy of EU-wide exposure assessments and also supports nutrition surveillance, diet and health related studies. Improved risk assessments assure more targeted risk management and permit more accurate risk communication resulting in increased consumer confidence. The most important step in this direction was the development of the EFSA Comprehensive European Food Consumption Database, which compiles existing national dietary information from the Member States (MS). MS used different methods to collect food consumption data, which makes it difficult to carry out EU-wide analyses or country-to-country comparisons. Furthermore, as the consumption patterns are continuously changing, regular update of the available information is necessary. Therefore, in 2011 EFSA launched the “What’s on the Menu in Europe? - EU Menu” project, with the aim of providing financial and technical support to carry out national dietary surveys in the EU. It focuses on collecting data from six population groups (from three months to 74 years of age) using harmonised methods described in the EFSA Guidance on the EU Menu methodology that has been endorsed by the EU institutions through the EFSA Network on Food Consumption Data. EFSA is currently supporting 36 surveys on children and/or adults from 18 Member States and four pre-accession countries. All projects are expected to be finalised by 2023. 相似文献
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随着经济全球化的深入,产品国际分工形式的转变导致传统贸易总值统计方法无法反应各国在国际贸易中的真实获利。以价值增值的贸易统计方法为研究新型贸易体系提供了新视角。本文首先介绍了3类全球价值链中价值增值的测算方法,分别是基于WIOD数据库的里昂惕夫经典方法、基于I-O投入产出表的总出口分解法、基于微观数据的企业出口分解法。在此基础上总结了基于价值增值的GVC收入、GVC就业、显示性比较优势(RCA)、资源消耗与排放等的应用研究。最后对测算方法的关键方程、使用数据、应用研究和代表论文进行了比较和总结,并提出了未来研究方向。 相似文献
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编制投入产出表涉及大量的数据与计算,滞后问题严重。根据电力与经济呈正相关的原理,将已有的投入产出表及已知相关数据作为经济体的初始状态,以用电量及公布的宏观经济数据作为经济体运行的目标状态,采用ARE(智能体响应均衡)模型,模拟宏观经济的运行。并以用电量为约束的迭代算法让经济体达到目标状态,推出新的投入产出表。在ARE模拟中,各行业的模拟用电量与实际用电量之间的误差越小,得到的投入产出表精度越高。以此方法更新的投入产出表滞后期减少1~2年,可为其他经济模型研究及政策制定提供基础。 相似文献
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《Food Policy》2020
Commercialisation by smallholder farmers has played a major role in agricultural development in many Asian countries, and while there are assumptions that this has led to welfare improvement, in fact there is relatively little evidence on this question. In this paper we use high quality panel data to examine the welfare impact of agricultural commercialisation in a leading Asian producer, Vietnam. We use the five-wave Vietnam Access to Resources Household Survey (VARHS) panel data set from 2008 to 16, three measures of household welfare and create commercialisation indexes in relation to all crops and to rice specifically. We find a significant positive relationship of commercialisation with household asset accumulation, but a negative association with consumption expenditure. 相似文献