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911.
912.
913.
电子设备、仪器的广泛使用产生的电磁辐射已成为当今的重要污染之一。电磁辐射分为天然和人为两种,严重危害和影响着人类的生活和生产。人们要重视电磁辐射,从行政、科学技术、个人生活方面加强对电磁辐射的防范。 相似文献
914.
M. Gharebaghi R.M.A. Irons L. Ma M. Pourkashanian A. Pranzitelli 《International Journal of Greenhouse Gas Control》2011
Oxy-fuel combustion is considered as one of the most promising technologies for carbon capture and storage (CCS). In this study, a commercial computational fluid dynamics (CFD) code has been employed for the simulation of an air-fired coal combustion and an oxy-fired coal combustion with recycled flue gas in a 1 MWth combustion test facility. Reynolds–averaged Navier–Stokes (RANS) solutions have been obtained for both cases. Results indicate that the CFD code with existing physical sub-models can provide a reasonable prediction for the air-fired combustion. However, the prediction for the oxy-fired case has not been as satisfactory as expected. In order to assess the impact of the turbulence treatment in CFD on the predictions, large eddy simulation (LES) has been performed for oxy-fired case and compared with the results from the RANS simulation and the available experimental data. Although the results suggest that LES can provide a more realistic prediction of the shape and the physical properties of the flame, there has not been significant improvement in the prediction of the temperature. In addition, the complexity of the problem requires more detailed experimental data for the validation of the LES. In order to improve the validity of numerical simulations for design purposes, further modelling improvements for oxy-coal combustion that are necessary for more accurate predictions are addressed. Based on this study, it is envisaged that the complexity in the oxy-coal combustion process requires more detailed analyses of the available physical sub-models. 相似文献
915.
916.
Spatially distributed modeling of the long-term carbon balance of a boreal landscape 总被引:1,自引:0,他引:1
Ajit Govind Jing Ming ChenPierre Bernier Hank MargolisLuc Guindon Andre Beaudoin 《Ecological modelling》2011,222(15):2780-2795
Spatially and temporally distributed information on the sizes of biomass carbon (C) pools (BCPs) and soil C pools (SCPs) is vital for improving our understanding of biosphere-atmosphere C fluxes. Because the sizes of C pools result from the integrated effects of primary production, age-effects, changes in climate, atmospheric CO2 concentration, N deposition, and disturbances, a modeling scheme that interactively considers these processes is important. We used the InTEC model, driven by various spatio-temporal datasets to simulate the long-term C-balance in a boreal landscape in eastern Canada. Our results suggested that in this boreal landscape, mature coniferous stands had stabilized their productivity and fluctuated as a weak C-sink or C-source depending on the interannual variations in hydrometeorological factors. Disturbed deciduous stands were larger C-sinks (NEP2004 = 150 gC m−2 yr−1) than undisturbed coniferous stands (e.g. NEP2004 = 8 gC m−2 yr−1). Wetlands had lower NPP but showed temporally consistent C accumulation patterns. The simulated spatio-temporal patterns of BCPs and SCPs were unique and reflected the integrated effects of climate, plant growth and atmospheric chemistry besides the inherent properties of the C pool themselves. The simulated BCPs and SCPs generally compared well with the biometric estimates (BCPs: r = 0.86, SCPs: r = 0.84). The largest BCP biases were found in recently disturbed stands and the largest SCP biases were seen in locations where moss necro-masses were abundant. Reconstructing C pools and C fluxes in the ecosystem in such a spatio-temporal manner could help reduce the uncertainties in our understanding of terrestrial C-cycle. 相似文献
917.
苗期棉花对向日葵列当种子萌发诱导作用初探 总被引:1,自引:0,他引:1
以5个推广棉花(Gossypium hirsutum L.)品种(中棉所63、中棉所57、中棉所47、中棉所44和中棉所41)为研究对象,利用盆栽试验分别采集棉花苗期3个时期(二叶一心、四叶一心和六叶一心期)的根际土和植株样品,并用其甲醇浸提测试对向日葵列当(Orobanche cumana Wallr.)种子的发芽率。结果表明,根际土、植株样(根、茎和叶)甲醇浸提液诱导种子发芽率高低顺序为根际土〉根〉茎〉叶,表明棉花的根际土和根的甲醇提取液对向日葵列当种子的萌发诱导作用较强。3个时期中,二叶一心期诱导向日葵列当的发芽在品种之间不存在显著性差异,表现为较稳定的诱导种子萌发作用。综合得出,棉花二叶一心期的根际土和根的甲醇提取液对向日葵列当种子萌发的诱导作用较强,二叶一心期为棉花作为"诱捕作物"生物防除寄生杂草提供科学依据。 相似文献
918.
类二噁英多氯联苯生殖毒性的研究进展 总被引:1,自引:0,他引:1
类二噁英多氯联苯(DlPCBs)作为典型的环境内分泌干扰物,会干扰接触个体或其后代的内分泌功能,破坏机体的神经系统、免疫系统,尤其对生殖系统的影响最为明显,比如对生殖器官的形态与功能、生殖内分泌、原始生殖细胞及其受精和早期胚胎发育等产生严重影响,最终导致各种生殖系统疾病的发生。DlPCBs的蓄积性及半挥发性使其在环境中分布广泛,半衰期长的特点使其将对动物及人类的生存和健康造成难以想象的影响。本文综述了DlPCBs的分类与构成、一般性质、生殖毒性以及其可能的致病机理,并对DlPCBs生殖毒性机理研究的重点方向进行了展望。 相似文献
919.
Jinyu Sun Xuhui Wang Anping Chen Yuecun Ma Mengdi Cui Shilong Piao 《Environmental monitoring and assessment》2011,179(1-4):1-14
How urban vegetation was influenced by three decades of intensive urbanization in China is of great interest but rarely studied. In this paper, we used satellite derived Normalized Difference Vegetation Index (NDVI) and socioeconomic data to evaluate effects of urbanization on vegetation cover in China??s 117 metropolises over the last three decades. Our results suggest that current urbanization has caused deterioration of urban vegetation across most cities in China, particularly in East China. At the national scale, average urban area NDVI (NDVIu) significantly decreased during the last three decades (P?<?0.01), and two distinct periods with different trends can be identified, 1982?C1990 and 1990?C2006. NDVIu did not show statistically significant trend before 1990 but decrease remarkably after 1990 (P?<?0.01). Different regions also showed difference in the timing of NDVIu turning point. The year when NDVIu started to decline significantly for Central China and East China was 1987 and 1990, respectively, while NDVIu in West China remained relatively constant until 1998. NDVIu changes in the Yangtze River Delta and the Pearl River Delta, two regions which has been undergoing the most rapid urbanization in China, also show different characteristics. The Pearl River Delta experienced a rapid decline in NDVIu from the early 1980s to the mid-1990s; while in the Yangtze River Delta, NDVIu did not decline significantly until the early 1990s. Such different patterns of NDVIu changes are closely linked with policy-oriented difference in urbanization dynamics of these regions, which highlights the importance of implementing a sustainable urban development policy. 相似文献
920.
从内河船舶污染防治法规体系、防治船舶污染管理手段以及防治船舶污染意识3个方面,详细分析目前内河防治船舶污染水域监管工作现状和存在问题,并为内河防治船舶污染水域监督工作提出对策与建议. 相似文献