100 research outputs found
sj-pdf-1-imr-10.1177_0300060520979230 - Supplemental material for Association of endothelial nitric oxide synthase intron 4a/b gene polymorphisms and hypertension: a systematic review and meta-analysis
No full textSupplemental material, sj-pdf-1-imr-10.1177_0300060520979230 for Association of endothelial nitric oxide synthase intron 4a/b gene polymorphisms and hypertension: a systematic review and meta-analysis by Xiru Xu, Woruo Ye, Hanqing Chen, Ming Liu, Weimin Jiang and Zhuyuan Fang in Journal of International Medical Research</p
CALCULATION OF FAPAR OVER RAGGED TERRAINS: A CASE STUDY AT SAIHANBA
No full textRemote sense values of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) suffer from the effect of ragged terrain. In this study, the effect of ragged terrain was internalized into the FAPAR model based on recollision probability (FAPAR-P), by improving FAPAR-P in two aspects: calculating the shielding factor to correct for the fraction of diffuse sky radiation to the total radiation, and correcting for the interception probability according to the slope and aspect of each pixel. Then, the new model FAPAR-PR (FAPAR-P Model for Ragged Terrain Area) was established. To validate the new model, we chose Saihanba National Forest Park of Hebei Province as the study area, and compared the FAPAR values derived from the models with FAPAR values measured in situ using photon flux sensors and the SunScan canopy analysis system (Delta-T Devices Ltd., UK). The validation result shows that the FAPAR-PR model is applicable to ragged terrain areas and achieves a high level of accuracy.National Basic Research Program of China [2013CB733402]; National Natural Science Foundation of China [41271346, 91425301, 41230747]CPCI-S(ISTP)[email protected]
ALGORITHM OF LEAF AREA INDEX PRODUCT FOR HJ-CCD OVER HEIHE RIVER BASIN
No full textMiddle-resolution Leaf Area Index (LAI) data are of great importance to scientific research relating to atmospheric composition, climate and weather, and the hydrological cycle. This paper introduces a physically based LAI retrieval technique for HJ-CCD at 30-m resolution. The algorithm is based on a canopy BRDF model that characterizes the surface reflectance as a function of a series of parameters. There are three key factors that influence the LAI retrieval processes: 1) the preprocessing to estimate surface reflectance; 2) the quality of the input land cover data; 3) the accuracy of the input parameters. Accounting for these factors, a 30-m LAI product of Heihe River Basin in the whole year of 2012 is created utilizing the data from HJ-CCD. Then field measurements are used to evaluate the quality of the product. Results show that the algorithm has the ability to produce LAI products as expected. Future researches will focus on reducing the uncertainties brought by the input data and parameters and implementing this algorithm at national scale over China.Engineering, Electrical & ElectronicGeosciences, MultidisciplinaryRemote SensingEICPCI-S(ISTP)
A NEW FAPAR RETRIEVAL MODEL FOR CONTINUOUS VEGETATION
No full textThe Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) is the fraction of incoming solar radiation that is absorbed by green vegetation in the spectral range from 400 nm to 700 nm. FAPAR reflects the energy absorption ability of vegetation canopy. It is a critical input in many land surface models, such as crop growth models, net primary productivity models, climate models and ecological models. Existing models for FAPAR retrieval are complex and difficult to retrieve, most of them cannot be used under cloudy weather. In this paper, a new quantitative FAPAR retrieval model considering the diffuse skylight and multiple scattering between canopy and background is introduced to retrieve FAPAR of vegetation canopy. The model was used to continuous vegetation and was validated by Monte Carlo (MC) simulation and field tests. The conclusion shows that the error is less than 0.32%.Engineering, Electrical & ElectronicGeosciences, MultidisciplinaryRemote SensingEICPCI-S(ISTP)
FAPAR AND BRDF SIMULATION FOR ROW CROP USING MONTE CARLO METHOD
No full textRow crop is an important cultivation form in China. It is considered to be a transitional canopy structure between continuous vegetation and discrete vegetation. Lots of physical models of row crop were established to invert vegetation parameters of row crop. Monte Carlo model is a reliable reference for those physical models. In this paper, row crop was modeled as a series of parallel rectangles with infinity length in one direction. The Monte Carlo (MC) simulation model of row crop was established according to the process of photons tracing. Meanwhile, dissipated energy was counted during the simulation process so that FAPAR and BRDF were calculated. The simulation result was analyzed and compared with continuous vegetation. Some influencing parameters of the simulation were analyzed, including LAI (leaf area index), width of rows, width of space between the rows, solar zenith angle and azimuth angle. And the field experiment data was used to compare with MC simulation result. Result shows row crop MC model is reliable.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000349688101069&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, Electrical & ElectronicGeosciences, MultidisciplinaryRemote SensingEICPCI-S(ISTP)
THE UNIFIED MODEL OF BRDF FOR THE VEGETATION CANOPY
No full textThe canopy bidirectional reflectance function (BRDF) characterizes the radiometric interface among vegetation, solar and the sensor, a stable, accurate and operational canopy BRDF model is the basis of retrieving canopy structure and biophysical parameters such as leaf area index and albedo by remote sensing method. The canopy reflectance can be divided into single scattering reflectance and multiple scattering reflectance. After the bidirectional gap fraction was derived by Poisson distribution, a new single scattering reflectance model was developed with Geometrical Optic model at leaf scale. The continuous canopy and discrete vegetation were unified by clumping index. So the area ratio of four components (sunlit crown, sunlit background, shadow crown and sunlit background) is parameterized. In order to simplify the expression of multiple scattering, a recollision probability based scattering model was used instead of the Radiative Transfer model. The validation using ground measurements has proved the reliability of the model.CPCI-S(ISTP)[email protected]
THE SPATIAL SCALING EFFECT OF CANOPY FAPAR RETRIEVED BY REMOTE SENSING
No full textClimate and land-atmosphere models rely on accurate land-surface parameters, such as the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR). It is known that FAPAR values retrieved from remote sensing images suffer from scaling effects. Scaling transformation aims to derive accurate FAPAR values at a specific scale from values at other scales. In this paper, scaling effect mechanism and the scale transformation algorithm are derived using Taylor series expansion method based on FAPAR-P model, after the model was simplified. The scaling algorithm was validated in Heihe River Basin. The multiscale FAPAR are inversed from of 5 m, 50 m and 100 m hyperspectral reflectance data. The scale transformation formula was used and the results agreed well with the actual values.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000349688101067&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, Electrical & ElectronicGeosciences, MultidisciplinaryRemote SensingEICPCI-S(ISTP)
ESTIMATING CROP NET PRIMARY PRODUCTION USING HIGH SPATIAL RESOLUTION REMOTE SENSING DATA
No full textNet Primary Productivity (NPP) is crucial in modelling global carbon cycle. There are a lot of studies focused on NPP evaluation using remote sensing method, resulting in different evaluation models. Most of the models are based on large spatial scale such as national or global, leading to retrieval errors in heterogeneous pixels and difficulties in field validation. This paper develops a new, remote sensing NPP evaluation method to estimate NPP on high spatial resolution. The model uses a newly improved Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) Model which is based on the recollision probability (FAPAR-P Model) to calculate the Absorbed Photosynthetic Active Radiation (APAR), which improves the accuracy of APAR estimation. The study area was the midstream of Heihe River Basin, located mostly in Zhangye, Gansu province, China.National Natural Science Foundation of China [41271346, 41571329, 41230747, 91425301, 41501359]; Major State Basic Research Development Program of China [2013CB733402]CPCI-S(ISTP)[email protected]
Demographic Change and the Labour Supply Constraint
No full textChina’s economic growth has, hitherto, depended on its relative abundance of production labour and its increasingly secure investment environment. Within the next decade, however, China's labour force will begin to contract. This will set its economy apart from other developing Asian countries where relative labour abundance will increase, as will relative capital returns. Unless there is a substantial change in population policy, the retention of China’s large share of global FDI will require further improvements in its investment environment, in its factor productivity and/or in its labour force participation rates. The links between demographic change, labour participation rates and growth performance are explored here using a new global demographic model that is integrated with an adaptation of the GTAP-Dynamic global economic model in which regional households are disaggregated by age and gender. China’s share of global investment, and hence its growth rate in per capita terms, is found to depend sensitively on its labour force growth and this, in turn, depends on both fertility and labour force participation. Rates of aged participation are low in China but likely to increase and this could offset the growth-retarding effects of fertility decline and ageing.
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