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Search Results: 1 - 10 of 119461 matches for " 袁金国 "
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基于模型模拟的植被ndvi与观测天顶角和lai的关系
马晶晶,
遥感技术与研究 , 2014,
Abstract: 利用prospect和sail模型模拟了不同叶绿素含量、不同lai和不同观测天顶角下的植被冠层反射率,分析了ndvi随lai、观测天顶角和叶绿素含量的变化规律。结果表明:叶绿素影响冠层反射率主要在可见光波段,冠层反射率随叶绿素含量的增加而下降;冠层反射率随观测天顶角的增加而增加,而lai较高时,其受观测天顶角的影响较小。观测天顶角相同时,随叶绿素含量的增加ndvi呈上升趋势;叶绿素含量一定时,ndvi随lai的增加而增加。lai为1时,在不同叶绿素含量下,随观测天顶角的增加,ndvi呈先下降后上升的趋势,拐点在观测天顶角65°或70°处,而lai为3、5和7时,ndvi呈现下降趋势。叶绿素含量较高时,ndvi受观测天顶角的影响较小。当lai较大和叶绿素含量较低时,ndvi随观测天顶角的增加(>70°)下降较快。
多源遥感数据融合应用研究
,王卫
地球信息科学学报 , 2005,
Abstract: 多源遥感数据融合是遥感技术向纵深发展的必然趋势。本文对多源遥感数据融合算法的应用特点,从基于像元的融合、特征的融合以及决策级融合3个层次上进行了详细的分析,并以河北丰宁县为例,说明遥感数据融合方法在遥感信息提取中的具体应用对所用数据进行预处理,然后对1999年LandsatTM数据进行主成分变换,前3个主成分占总信息量的97.8%,主成分逆变换后的结果影像更清晰,层次更丰富。信息提取时选择TM全色和主成分变换后的多光谱数据融合后的影像,波段4、3、2和波段5、4、3的彩色合成方案,并对植被指数和穗帽变换后的绿度指数进行了分析,遥感影像与DEM以及与GIS空间数据的信息融合也可以提高遥感信息提取的精度。最后分析了多源遥感数据融合尚待解决的问题及努力方向。
基于时间序列的电力负荷数据分析
Analysis of Electric Load Data Based on Time Series
 [PDF]

, 陈礼定,,
Advances in Applied Mathematics (AAM) , 2016, DOI: 10.12677/AAM.2016.52028
Abstract: 时间序列分析方法是电力负荷预测领域的重要工具之一,它主要通过建立相关模型描述历史数据随时间动态变化的规律以预测未来的值。本文采用温特线性与指数平滑法和季节乘积ARIMA模型对电力负荷实测数据进行建模,然后分别使用平均相对误差MAPE衡量预测精度。研究结果表明:两种方法均有较高的拟合与预测精度。
Time series analysis method is one of the important tools in the field of power load forecasting. It mainly describes the law of the historical data dynamic change over time to predict the future value by establishing a relevant model. In this paper, Winter’s exponential smoothing method and seasonal ARIMA model are applied to model estimating on the power load data, and the authors use the Mean Absolute Percentage Error (MAPE) to measure the accuracy. The results prove that both of them have high fitting and forecasting precision.
负压下ch4/空气层流预混火焰的自发辐射
曾科,谭建国,
燃烧科学与技术 , 2014, DOI: 10.11715/rskxjs. R201301023
Abstract: 采用实验与数值模拟相结合的方法,对负压下甲烷空气层流预混火焰自发辐射进行了研究.由数值模拟建立起同时模拟oh(a)、ch(a)和c2(d)共3种激发态粒子自发辐射的一维模型,实验拍摄平面火焰自发辐射图像,提取激发态粒子峰值光强和峰值粒子数密度作为研究层流预混火焰自发辐射的主要参数.结果表明,当量比小于或等于1时,oh(a)最先达到峰值,c2(d)紧接着达到峰值,ch(a)最后达到峰值;当量比大于1时,oh(a)最先达到峰值,ch(a)紧接着达到峰值,c2(d)最后达到峰值;峰值比值oh(a)/ch(a)和c2(d)/ch(a)是当量比的单调函数.
2002―2011年河北省植被LAI时空变化特征
张宇佳,,,
南京林业大学学报(自然科学版) , 2015, DOI: 10.3969/j.issn.1000-2006.2015.01.016
Abstract: 利用2002―2011年EOS/MODIS数据的植被指数产品MOD15A2和植被类型产品MCD12Q1及气象观测资料,对比分析了7种典型植被的叶面积指数(LAI)的变化趋势,探讨了河北省植被生长季(5―10月)LAI的时空变化特征及其与气温和降水等影响因子的关系。结果表明:河北省植被生长季年均LAI变化在1.0~1.3之间,2008年最高(1.286),2002年最低(1.066); 多年平均 LAI的空间分布表现为位于东北部的承德地区最高(可达5.0以上),位于西北部的张家口地区最低(小于0.5); 7种典型植被生长季年均LAI差异很大,LAI从高到低依次为阔叶林(2.765)、混交林(2.535)、灌丛(1.867)、稀树草原(1.476)、针叶林(1.331)、农田(1.116)和草原(0.967)。显著影响LAI变化的因子有降水、气温、地形、植被类型及其物候期等,且各因子对植被LAI的影响程度不同。
The vegetation index product MOD15A2 and vegetation type product MCD12Q1 of EOS/MODIS data and meteorological data were used in this study. LAI of seven typical vegetation types were compared,and spatial temporal change of LAI in growing seasons in Hebei province from 2002 to 2011 was explored by using linear regression analysis and correlation analysis methods. The relationship between LAI, air temperature and precipitation were also analyzed. The results showed that the annual average LAI values in growing seasons(from May to October)were 1.0-1.3, the highest was 1.286 in 2008, and the lowest was 1.066 in 2002. As for spatial distribution, LAI in Chengde region in the northeast was the highest, which reached more than 5.0, and LAI in Zhangjiakou region in the northwest was the lowest, which reached less than 0.5. The annual average LAI of seven typical vegetation types in growing seasons were very different, and LAI from high to low could be broadleaf forest(2.765), mixed forest(2.535), shrub(1.867), savanna(1.476), coniferous forest(1.331), farmland(1.116)and grassland(0.967). The significant factors influencing LAI were precipitation, air temperature, topography, vegetation types and phenology, and the impact of each factor on vegetation LAI was different
秦皇岛柳江华夏植物群及古环境研究
阎同生,钱金平,,王健
植物学报 , 2000,
Abstract: ?河北秦皇岛柳江晚古生代地层发育,华夏植物群特征明显,向北300公里即达华夏植物群与安加拉植物群混生带,本文详细研究了河北秦皇岛柳江晚古生代植物化石,发现植物化石44属86种,其中蕨类占首位,石松居第二位,并有苏铁、银杏、科达等植物,植物群具有华夏植物群的特点,可划分出6个植物组合,反映植物群演化具有阶段性。植物群演化阶段与古地理环境变化阶段基本同期。据本溪组与太原组中数层海相灰岩的存在,证明该区曾有浅海分布,山西组中、上部转变为三角洲、河口沙坝及堤外泥坪沉积,上、下石盒子组及石千峰组则变为干旱气候环境下陆相湖泊及河流沉积,植物群演化过程阶段性研究表明植物群演化与古地理演化密切相关。
裂纹梁的弹塑性动态断裂
,杰红,相恒波
兵工学报 , 2000,
Abstract: ?本文利用弹塑性线弹簧模型建立了一种裂纹梁的弹塑性动态断裂分析的新方法,它可以对线弹性变形阶段、弹塑性变形阶段、裂纹稳定扩展阶段和裂纹不稳定扩展阶段的裂纹梁动态断裂问题建立易于求解的常微分方程组,并对受均布动载作用的裂纹简支梁给出了数值结果。
天然气重整器内部传递过程的数值模拟
,岳丹婷,
天然气工业 , 2008,
Abstract: ?天然气通过重整反应可以生成氢气,成为燃料电池氢原料的重要来源。目前紧凑型天然气重整器的开发设计,主要集中在材料方面的研究,而内部机理方面的研究较少。对天然气重整器内部流动与传热现象进行了模拟与分析。分析中考虑了化学反应的影响,采用了耦合的边界条件以及可变的热物性参数,建立了描述流通管道和多孔催化剂层内部流动与传热现象的三维数学模型。采用simple算法对模型进行求解,得到了化学反应速率、混合气浓度以及温度等的空间分布。结果表明,化学反应限制在厚度约为1mm的催化剂薄层内进行,沿主流动方向,ch4浓度由19.5%降到7%左右,h2浓度由4.1%上升到13%左右,混合气温度上升约10℃。研究结果对天然气重整器的开发、结构设计具有参考意义。
基于向量拟合法的配电变压器振动特性分析
Power Transformer Vibration Characterization Analysis いby Vectoring Fitting Method

胡敏,彭伟,之俭,
- , 2018, DOI: 10.16450/j.cnki.issn.1004-6801.2018.03.030
Abstract: 尝试使用向量拟合法对变压器表面振动数据进行拟合分析。首先,通过与频域复指数最小二乘法的对比,验证向量拟合法的适用性;其次,用向量拟合法分析变压器表面振动数据,发现变压器由100Hz工作频率及其倍频引起的强迫振动响应占据主导地位,变压器底部靠近铁芯处振动量级更大。将底部振动数据单独进行向量拟合法分析得到局部模态,为振动测点位置优化和故障识别提供参考依据。
Vibration characterization of power transformer is an import key to reliability and trouble shooting, The vector fitting (VF)method is used to analysis vibration test data of power transformer surface. The VF is compared with PolyLSCF method and the experimental data of power transformer is analyzed. It can be found that the 100 Hz operation frequency causes harmonic response, and the vibration level of the transformer bottom is much higher and local mode is checked after sole analysis. The analysis result will provide advice on optimization of measurement point locations and failure recognition.
Photoinduced Resistance Change in an Oxygen-Deficient La 0.9 Sr 0.1 MnO 3-δ Thin Film
严资杰,,,罗炳成,克新,陈长乐
中国物理快报 , 2007,
Abstract: Photoinduced resistance change ( △ R/R) in an oxygen-deficient La0.9Sr0.1MnO3-δ thin film is studied. At room temperature, the resistance change of about 30% and response time of about 75 ns are observed under the illumination with a 532nm laser pulse of 7ns and light power of 750mW. It is also found that △ R/R changes with the light power. The phenomena are explained in terms of the photoinduced hole carriers and localized insulator-to-metal transition, which may have potential applications in optoelectronic devices.
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