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1.
根据广州1市2007-2011年的逐日太阳辐射和日照时间观测数据,对广州市的月太阳总辐射、散射辐射、水平面直射辐射以及每月日最大总辐射辐照度历年平均值进行了计算。分析了广州市太阳辐射量的变化特征,根据Angstrom—Prescott模型,推导出了太阳总辐射月均值及日值的估算经验公式,对所得到的经验公式运用平均百分误差、平均偏差、均方根误差进行了误差分析,结果表明能满足工程应用的要求。 相似文献
2.
Environmental impact prediction using remote sensing images 总被引：1，自引：0，他引：1
Pezhman ROUDGARMI Masoud MONAVARI Jahangir FEGHHI Jafar NOURI Nematollah KHORASANI 《浙江大学学报(A卷英文版)》2008,9(3):381-390
Environmental impact prediction is an important step in many environmental studies. A wide variety of methods have been developed in this concern. During this study, remote sensing images were used for environmental impact prediction in Robatkarim area, Iran, during the years of 2005-2007. It was assumed that environmental impact could be predicted using time series satellite imageries. Natural vegetation cover was chosen as a main environmental element and a case study. Environmental impacts of the regional development on natural vegetation of the area were investigated considering the changes occurred on the extent of natural vegetation cover and the amount of biomass. Vegetation data, land use and land cover classes （as activity factors） within several years were prepared using satellite images. The amount ofbiomass was measured by Soil-adjusted Vegetation Index （SAVI） and Normalized Difference Vegetation Index （NDVI） based on satellite images. The resulted biomass estimates were tested by the paired samples t-test method. No significant difference was observed between the average biomass of estimated and control samples at the 5% significance level. Finally, regression models were used for the environmental impacts prediction. All obtained regression models for prediction of impacts on natural vegetation cover show values over 0.9 for both correlation coefficient and R-squared. According to the resulted methodology, the prediction models of projects and plans impacts can also be developed for other environmental elements which may be derived using time series remote sensing images. 相似文献
3.
Wolfgang Huber Veit Phillip Josef Höllthaler Caroline Schultheiss Bernd Saugel Roland M. Schmid 《Journal of Zhejiang University. Science. B》2016,17(7):561-567
Objective
Comparison of global end-diastolic volume index (GEDVI) obtained by femoral and jugular transpulmonary thermodilution (TPTD) indicator injections using the EV1000/VolumnView® device (Edwards Lifesciences, Irvine, USA).Methods
In an 87-year-old woman with hypovolemic shock and equipped with both jugular and femoral vein access and monitored with the EV1000/VolumeView® device, we recorded 10 datasets, each comprising duplicate TPTD via femoral access and duplicate TPTD (20 ml cold saline) via jugular access.Results
Mean femoral GEDVI ((674.6±52.3) ml/m2) was significantly higher than jugular GEDVI ((552.3±69.7) ml/m2), with P=0.003. Bland-Altman analysis demonstrated a bias of (+122±61) ml/m2, limits of agreement of ?16 and +260 ml/m2, and a percentage error of 22%. Use of the correction-formula recently suggested for the PiCCO® device significantly reduced bias and percentage error. Similarly, mean values of parameters derived from GEDVI such as pulmonary vascular permeability index (PVPI; 1.244±0.101 vs. 1.522±0.139; P<0.001) and global ejection fraction (GEF; (24.7±1.6)% vs. (28.1±1.8)%; P<0.001) were significantly different in the case of femoral compared to jugular indicator injection. Furthermore, the mean cardiac index derived from femoral indicator injection ((4.50±0.36) L/(min·m2)) was significantly higher (P=0.02) than that derived from jugular indicator injection ((4.12±0.44) L/(min·m2)), resulting in a bias of (+0.38±0.37) L/(min·m2) and a percentage error of 19.4%.Conclusions
Femoral access for indicator injection results in markedly altered values provided by the EV1000/VolumeView®, particularly for GEDVI, PVPI, and GEF.4.
Bi-xin Chen Si Wang Wei-dong Yang Ren-chang Yan Xuan Chen Qing-yu Zhang 《浙江大学学报(A卷英文版)》2017,18(2):151-162
Air pollution has become the predominant environmental problem caused by rapid industrialization and urbanization in China. In this study, measurements of the concentrations of PM2.5, PM10, SO2, NO2, CO, and O3 at six monitoring stations in Baotou, China were used to investigate the characteristics of heavy haze pollution in Dec. 12–25, 2013. Source locations of PM2.5 in Baotou were identified using satellite remote sensing data, an air mass trajectory model, and a conditional probability function (CPF). The results showed that the average concentrations of PM2.5 and PM10 were (113.8±84.0) μg/m3 and (211.1±149.2) μg/m3, respectively. The similar trends in temporal variation of the air pollutants PM2.5, PM10, SO2, NO2, and CO suggested they may share common sources. The results of satellite observations and backward trajectories supported the hypothesis that the pollutants causing the haze event originated mainly from local anthropogenic sources. According to the CPF analysis, low-speed winds from the south and southwest, upwind industrial emissions, and the northern mountains were mainly responsible for the formation of haze in Baotou. The study provides some insights to help governments optimize industrial layouts for improving air quality in the future. 相似文献
5.
世界各国新一代静止轨道气象卫星陆续发射升空,成像仪是主要载荷之一。通过对美国、日本、欧洲和中国等新一代静止气象卫星成像仪特性的研究分析,客观认识我国静止气象卫星水平的差距和不足,为我国风云四号02星成像仪特性优化提供参考。在波段设置方面,欧美日均为16个通道,我国的FY-4A为14个光谱通道;在时空分辨率方面,各国水平相当,略有差异,可见光波段分辨率为0.5~1km,红外波段2~4km,全圆盘观测10~15min;在观测模式方面,FY-4A的多通道扫描成像辐射计和MTG的灵活组合成像仪先进行一次全圆盘观测,再进行多次区域观测,不同扫描资料时间间隔不均等。GOES-R的先进基线成像仪和Himawari-8的先进葵花成像仪观测时间采用碎片化设计,即各种扫描模式交叉进行,不同扫描资料时间间隔均等,非常有利于预报员对天气进行系统分析。 相似文献
6.
随着多种遥感卫星的发射成功,有了许多可利用的多传感器、多时相、多分辨率和多光谱遥感影像。针对日益庞大的卫星遥感影像数据,根据具体研究工作的需要,结合贵州高原山区特殊的自然地理条件,从各卫星影像数据的参数、质量、价格、应用等方面结合具体案例加以分析和探讨,对在贵州这一特殊的地形区遥感影像的选择具有一定的参考作用和指导意义。 相似文献
7.
Multi-year monitoring of paddy rice planting area in Northeast China using MODIS time series data 总被引：1，自引：0，他引：1
Jing-jing SHI Jing-feng HUANG Feng ZHANG 《Journal of Zhejiang University. Science. B》2013,14(10):934-946
The objective of this study was to investigate the tempo-spatial distribution of paddy rice in Northeast China using moderate resolution imaging spectroradiometer(MODIS) data.We developed an algorithm for detection and estimation of the transplanting and flooding periods of paddy rice with a combination of enhanced vegetation index(EVI) and land surface water index with a central wavelength at 2130 nm(LSWI2130).In two intensive sites in Northeast China,fine resolution satellite imagery was used to validate the performance of the algorithm at pixel and 3×3 pixel window levels,respectively.The commission and omission errors in both of the intensive sites were approximately less than 20%.Based on the algorithm,annual distribution of paddy rice in Northeast China from 2001 to 2009 was mapped and analyzed.The results demonstrated that the MODIS-derived area was highly correlated with published agricultural statistical data with a coefficient of determination(R2) value of 0.847.It also revealed a sharp decline in 2003,especially in the Sanjiang Plain located in the northeast of Heilongjiang Province,due to the oversupply and price decline of rice in 2002.These results suggest that the approaches are available for accurate and reliable monitoring of rice cultivated areas and variation on a large scale. 相似文献
8.
介绍了一种GPS软件接收机的设计方法.该设计采用软件无线电设计理念,主要包括前端模块、捕获模块、跟踪模块、同步模块、导航解算模块以及其他辅助模块.捕获模块采用基于圆周相关的捕获算法,通过FFT(快速傅立叶变换)分别作用于输入信号和本地码信号将运算变换到频域内处理.该算法可得到C/A码起始相位和分辨率为1 kHz的载波频率信号,但此载波频率精细度差,不能直接用于跟踪环路.为提高载波频率分辨率,采用基于相位关系计算的精频估计算法.实验表明应用精频捕获算法得到的载波精频估计误差在几赫兹以内,可直接用于后续跟踪环路. 相似文献
9.
Satellite remote sensing techniques can be used for conducting environmental change detection studies following a natural disaster. Modern computer technology and free access to global satellite imagery allows educators to introduce undergraduate students to the fields of remote sensing and encourage their scientific participation through a research assignment that also serves as an educational exercise. The undergraduate physical science laboratory manuals used in higher education that contain printed remote sensing material often fail to effectively achieve these goals. This class exercise utilizes digital satellite imagery for studying the floods that resulted in the Paraná River region in South America during El Niño 1997–98. In addition, it examines vegetation cover and spectral profiles from the study area in order to further understand and assess the changes that were caused by this recurrent climatic anomaly. 相似文献
10.
Jie Cui Zhi Li Ling-bo Qian Qin Gao Jue Wang Meng Xue Xiao-e Lou Iain C. Bruce Qiang Xia Hui-ping Wang 《Journal of Zhejiang University. Science. B》2013,14(6):487-495
Objective
To investigate the beneficial effect of bicyclol on rat hearts subjected to ischemia-reperfusion (IR) injuries and its possible mechanism.Methods
Male Sprague-Dawley rats were intragastrically administered with bicyclol (25, 50 or 100 mg/(kg·d)) for 3 d. Myocardial IR was produced by occlusion of the coronary artery for 1 h and reperfusion for 3 h. Left ventricular hemodynamics was continuously monitored. At the end of reperfusion, myocardial infarct was measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining, and serum lactate dehydrogenase (LDH) level and myocardial superoxide dismutase (SOD) activity were determined by spectrophotometry. Isolated ventricular myocytes from adult rats were exposed to 60 min anoxia and 30 min reoxygenation to simulate IR injuries. After reperfusion, cell viability was determined with trypan blue; reactive oxygen species (ROS) and mitochondrial membrane potential of the cardiomyocytes were measured with the fluorescent probe. The mitochondrial permeability transition pore (mPTP) opening induced by Ca2+ (200 μmol/L) was measured with the absorbance at 520 nm in the isolated myocardial mitochondria.Results
Low dose of bicyclol (25 mg/(kg·d)) had no significant improving effect on all cardiac parameters, whereas pretreatment with high bicyclol markedly reduced the myocardial infarct and improved the left ventricular contractility in the myocardium exposed to IR (P<0.05). Medium dose of bicyclol (50 mg/(kg·d)) markedly improved the myocardial contractility, left ventricular myocyte viability, and SOD activity, as well decreased infarct size, serum LDH level, ROS production, and mitochondrial membrane potential in rat myocardium exposed to IR. The reduction of ventricular myocyte viability in IR group was inhibited by pretreatment with 50 and 100 mg/(kg·d) bicyclol (P<0.05 vs. IR), but not by 25 mg/(kg·d) bicyclol. The opening of mPTP evoked by Ca2+ was significantly inhibited by medium bicyclol.Conclusions
Bicyclol exerts cardioprotection against IR injury, at least, via reducing oxidative stress and its subsequent mPTP opening. 相似文献11.
12.
一种GPS网络RTK整周模糊度解算方法(英文) 总被引：1，自引：0，他引：1
提出了一种适用于GPS多参考站网络的RTK模糊度固定方法. 首先, 以参与模糊度解算的参考站三角形重心为参考点, 将与其形成高度角最大的卫星选作参考卫星, 进而提供了载波观测值权阵构造的参数以及模糊度网解正确性的检验条件. 然后, 通过双频线性观测数据组合计算双差宽巷模糊度, 并利用无电离层观测数据组合计算L1模糊度浮点解, 引入卡尔曼滤波进行精化, 并实时估计对流层延迟参数. 最后, 通过Z变换对模糊度协因素阵进行去相关, 从而减小模糊度整数解的搜索空间, 提高LABMDA算法固定模糊度的效率. 实验结果表明, 该方法能在40个历元内可靠实现多个参考站间整周模糊度解算. 相似文献
13.
马尾松毛虫发生面积的预测研究 总被引：2，自引：0，他引：2
本文应用多元回归、灰色系统理论和马尔科夫链等数学方法对广东省封开县马尾松毛虫发生面积进行预测．气象因子有：本年中的全年日照时数、7月和10月的日照时数；上一年中的10．11月平均相对湿度和4．7月的日照时数．总种植面积也与发生面积有关， 相似文献
14.
Error indices (bias, standard error of estimation, and root mean squared error) obtained on different measurement scales under different test-termination rules in computerized adaptive testing (CAT) were examined. Four ability estimation methods (maximum likelihood estimation, weighted likelihood estimation, expected a posterior, and maximum a posterior), three measurement scales (θ, number-correct score, and ACT score), and three test-termination rules (fixed length, fixed standard error, and target information) were studied for a real and a generated item pool. The findings indicated that the amount and direction of bias, standard error of estimation, and root mean squared error obtained under different ability estimation methods were influenced both by scale transformations and by test-termination rules in a CAT environment. The implications of these effects for testing programs are discussed. 相似文献
15.
从高精度卫星影像中道路的半自动提取 总被引：3，自引：0，他引：3
提出一种顾及精度、操作性的从高精度卫星影像中半自动提取道路的方法 .在整个提取过程中选用适当算法 ,尽量减少了提取数据的误差 ,为利用高精度卫星影像对对象的全自动提取开创了一种新的方法 相似文献
16.
时非齐次等式约束线性回归模型回归系数提出广义条件岭估计.证明了在一定的条件下,在均方误差矩阵、均方误差及广义均方误差意义下,广义条件岭估计都优于约束最小二乘估计和狭义条件岭估计. 相似文献
17.
Makarand Phatak 《Resonance》1998,3(9):14-25
With the help of a couple of satellites going around the earth we can find our position on the earth with very high accuracy by measuring ranges from these satellites. The satellite based navigation system is called the GPS (global positioning system). In the first part1 we described the basic principle of the operation of GPS. This part is about the mechanism and uses of GPS. 相似文献
18.
Objective
The aim of the study was to examine caregiver management strategies for child sexual abuse (CSA) when presented with hypothetical scenarios that vary in physical invasiveness.Methods
One hundred fifty three caregivers were given 3 scenarios of CSA with 7 management strategies presented in the 21-item Taking Action Strategies (TAS) scale. Caregivers were asked to rate strategies according to their willingness to carry out each action with rating of 5 = greater likelihood of carrying out the action specified while a rating of 1 = a lower likelihood of carrying out that action. CSA scenarios included exposure to pornography/masturbation, fondling, and penetration while management strategies including fighting the accused, blaming the child, and outreaching to the authorities. Repeated measures ANOVA was used to compare mean TAS scores for the management strategies across CSA scenarios.Results
The difference between TAS scores across the abuse scenarios was statistically significant (p < .001). Mean TAS scores reflected greater preference for taking action if the abusive act was perceived as more physically intrusive (exposure to pornography/masturbation-TAS 3.5, fondling-TAS 3.7, penetration-TAS 3.8). Caregivers reported being less willing to handle a disclosure of CSA without outreach (TAS 2.5 and 2.0 for fighting and blaming the child, respectively) and more willing to manage a disclosure with outreach to authorities (TAS 3.8, 4.5, and 4.7 for outreaching to Child Protective Services [CPS], to the child's healthcare provider and police, respectively). A predictor of caregiver outreach to authorities identified was the caregiver having past interactions with CPS.Conclusion
Perception of the physical invasiveness of CSA and demographic factors can impact caregiver management strategies after a disclosure.Practice implications
Results suggest that several factors influence caregiver management of sexual abuse. These factors warrant further study, as they are potential contributors to declining trends in CSA cases observed. Other implications include the need for educational efforts targeting caregivers. These interventions should focus on dispelling myths about the perceived physical invasiveness of CSA. These perceptions should not mitigate a caregiver's decision to involve the authorities in their management after a disclosure. Lastly, despite criticisms of the child protective systems, caregivers with past encounters with CPS view these related agencies as valuable resources. 相似文献19.
研究了信道估计的均方误差,利用无限长、非因果的维纳滤波器推导出了它的下界.通过对不同衰落信道多普勒谱的积分,求出了相应的信道估计均方误差下界的闭合表达式,并在此基础上得到了分集系统在独立同分布的衰落信道中采用最大比合并时的误码率下界.数值分析结果表明,非理想信道估计下最大比合并的误码率性能是以理想信道估计的结果为下界,并随着最大多普勒频移的增加或信道估计信噪比的减小而逐渐劣化. 相似文献
20.
约束线性回归模型回归系数的广义条件岭估计 总被引：1，自引：0，他引：1
对齐次等式约束线性回归模型回归系数的岭估计进行推广,得出广义条件岭估计．证明了在一定的条件下,在均方误差矩阵、均方误差及广义均方误差意义下广义条件岭估计都优于约束最小二乘估计,并且证明了广义条件岭估计是回归系数的可容许估计． 相似文献