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Search Results: 1 - 10 of 409381 matches for " K.-J. Chao "
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After trees die: quantities and determinants of necromass across Amazonia
K.-J. Chao,O. L. Phillips,T. R. Baker,J. Peacock
Biogeosciences Discussions , 2009,
Abstract: The Amazon basin, one of the most substantial biomass carbon pools on earth, is characterised by strong macroecological gradients in biomass, mortality rates, and wood density from the west to the east. These gradients could affect necromass stocks, but this has not yet been tested. This study aims to assess the stocks and determinants of necromass patterns across Amazonian forests. Field-based and literature data were used to find relationships between necromass and possible determinants. The final regression result was used to estimate and extrapolate the necromass stocks across terra firma Amazonian forests. In eight northwestern and three northeastern Amazonian permanent plots, volumes of coarse woody debris (≥10 cm diameter) were measured in the field and density of each decay class was estimated. Forest structure and historical mortality data were used to determine controlling factors of necromass. Necromass is greater in forests with low stem mortality rates (northeast) rather than forest with high stem mortality rates (northwest) (58.5±10.6 and 27.3±3.2 Mg ha 1, respectively). After integrating all published necromass values, we find that necromass across terra firma forests in Amazonia is positively related to stand biomass, mortality mass input, and average wood density of live trees (ρBA j). We applied these relationships to estimate necromass for plots where necromass has not been measured. The estimates, together with other actual measurements of necromass, were scaled-up to project a total Amazonian necromass of 9.6±1.0 Pg C. The ratio of necromass (on average weighted by forest region) to coarse aboveground biomass is 0.127. Overall, we find (1) a strong spatial trend in necromass in parallel with other macroecological gradients and (2) that necromass is a substantial component of the carbon pool in the Amazon.
After trees die: quantities and determinants of necromass across Amazonia
K.-J. Chao, O. L. Phillips, T. R. Baker, J. Peacock, G. Lopez-Gonzalez, R. Vásquez Martínez, A. Monteagudo,A. Torres-Lezama
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: The Amazon basin, one of the most substantial biomass carbon pools on earth, is characterised by strong macroecological gradients in biomass, mortality rates, and wood density from west to east. These gradients could affect necromass stocks, but this has not yet been tested. This study aims to assess the stocks and determinants of necromass across Amazonian forests. Field-based and literature data were used to find relationships between necromass and possible determinants. Furthermore, a simple model was applied to estimate and extrapolate necromass stocks across terra firma Amazonian forests. In eight northwestern and three northeastern Amazonian permanent plots, volumes of coarse woody debris (≥10 cm diameter) were measured in the field and the density of each decay class was estimated. Forest structure and historical mortality data were used to determine the factors controlling necromass. Necromass is greater in forests with low stem mortality rates (northeast) rather than in forests with high stem mortality rates (northwest) (58.5±10.6 and 27.3±3.2 Mg ha 1, respectively). Using all published necromass values, we find that necromass across terra firma forests in Amazonia is positively related to both forest dynamics (mortality mass inputs and a surrogate for decomposition rate (average wood density of living trees)) and forest structure (biomass), but is better explained by forest dynamics. We propose an improved method to estimate necromass for plots where necromass has not been measured. The estimates, together with other actual measurements of necromass, were scaled-up to project a total Amazonian necromass of 9.6±1.0 Pg C. The ratio of necromass (on average weighted by forest region) to coarse aboveground biomass is 0.127. Overall, we find (1) a strong spatial trend in necromass in parallel with other macroecological gradients and (2) that necromass is a substantial component of the carbon pool in the Amazon.
The role of climate and emission changes in future air quality over southern Canada and northern Mexico
E. Tagaris,K.-J. Liao,K. Manomaiphiboon,S. He
Atmospheric Chemistry and Physics Discussions , 2008,
Abstract: Potential impacts of global climate and emissions changes on regional air quality over southern (western and eastern) Canada and northern Mexico are examined by comparing future summers' (i.e., 2049–2051) average regional O3 and PM2.5 concentrations with historic concentrations (i.e., 2000–2002 summers). Air quality modeling was conducted using CMAQ and meteorology downscaled from the GISS-GCM using MM5. Emissions for North America are found using US EPA, Mexican and Canadian inventories and projected emissions following CAIR and IPCC A1B emissions scenario. Higher temperatures for all sub-regions and regional changes in mixing height, insolation and precipitation are forecast in the 2049–2051 period. Future emissions are calculated to be lower over both Canadian sub-regions, but higher over northern Mexico. Global climate change, alone, is predicted to affect PM2.5 concentrations more than O3: M8hO3 concentrations are estimated to be slightly different in all examined sub-regions while PM2.5 concentrations are estimated to be higher over both Canadian sub-regions (8% over western and 3% over eastern) but 11% lower over northern Mexico. Climate change combined with the projected emissions lead to greater change in pollutant concentrations: M8hO3 concentrations are simulated to be 6% lower over western Canada and 8% lower over eastern Canada while PM2.5 concentrations are simulated to be 5% lower over western Canada and 11% lower over eastern Canada. Although future emissions over northern Mexico are projected higher, pollutant concentrations are simulated to be lower due to US emissions reductions. Global climate change combined with the projected emissions will decrease M8hO3 4% and PM2.5 17% over northern Mexico.
Quantification of impact of climate uncertainty on regional air quality
K.-J. Liao,E. Tagaris,K. Manomaiphiboon,C. Wang
Atmospheric Chemistry and Physics Discussions , 2008,
Abstract: Impacts of uncertain climate forecasts on future regional air quality are investigated using downscaled MM5 meteorological fields from the NASA GISS and MIT IGSM global climate models and the CMAQ model in 2050 in the continental US. Three future climate scenarios: high-extreme, low-extreme and base, are developed for regional air quality simulations. GISS, with the IPCC A1B scenario, is used for the base case. IGSM results, in the form of probabilistic distributions, are used to perturb the base case climate to provide 0.5th and 99.5th percentile climate scenarios. Impacts of the extreme climate scenarios on concentrations of summertime fourth-highest daily maximum 8-h average ozone are predicted to be up to 10 ppbv (about one-eighth of the current NAAQS of ozone) in some urban areas, though average differences in ozone concentrations are about 1–2 ppbv on a regional basis. Differences between the extreme and base scenarios in annualized PM2.5 levels are very location dependent and predicted to range between 1.0 and +1.5 μg m 3. Future annualized PM2.5 is less sensitive to the extreme climate scenarios than summertime peak ozone since precipitation scavenging is only slightly affected by the extreme climate scenarios examined. Relative abundances of biogenic VOC and anthropogenic NOx lead to the areas that are most responsive to climate change. Such areas may find that climate change can significantly offset air quality improvements from emissions reductions, particularly during the most severe episodes.
On Some Problems of James Miller
Bhowmik,B; Ponnusamy,S; Wirths,K.-J;
Cubo (Temuco) , 2010, DOI: 10.4067/S0719-06462010000100003
Abstract: we consider the class of meromorphic univalent functions having a simple pole at and that map the unit disc onto the exterior of a domain which is starlike with respect to a point . we denote this class of functions by . in this paper, we find the exact region of variability for the second taylor coefficient for functions in . in view of this result we rectify some results of james miller.
On Some Problems of James Miller
B Bhowmik,S Ponnusamy,K.-J Wirths
Cubo : A Mathematical Journal , 2010,
Abstract: We consider the class of meromorphic univalent functions having a simple pole at and that map the unit disc onto the exterior of a domain which is starlike with respect to a point . We denote this class of functions by . In this paper, we find the exact region of variability for the second Taylor coefficient for functions in . In view of this result we rectify some results of James Miller. Consideramos la clase de funciones univalentes meromoforficos teniendo un polo simple en y la aplicación del disco unitario sobre el exterior de un dominio el cual es estrellado con respecto al punto . Denotamos esta clase de funciones por . En este artículo encontramos la región exacta de variabilidad del segundo coeficiente de Taylor para funciones in . En vista de estos resultados nosotros rectificamos algunos resultados de James Miller.
混合元——在结构分析中用处如何?
K.-J.BatHe胡雨村
力学进展 , 1991, DOI: 10.6052/1000-0992-1991-2-J1991-030
Abstract: 采用有限元方法分析复杂工程问题取得的巨大成功,我们是非常熟悉的。目前,已有大量的市售计算机程序可以分析结构问题、固体问题、传热问题以及流体流动问题。这些程序在计算机辅助工程中有广泛的应用。而最大的应用领域还是结构分析。这里我们注意到,这些市售计算机程序几乎全部采用以位移法的有限元分析(当然,有时也用“减缩积分”)为基础的组件。
Characteristics of cloud-to-ground lightning activity over Seoul, South Korea in relation to an urban effect
S. K. Kar, Y.-A. Liou,K.-J. Ha
Annales Geophysicae (ANGEO) , 2007,
Abstract: Cloud-to-ground (CG) lightning flash data collected by the lightning detection network installed at the Korean Meteorological Administration (KMA) have been used to study the urban effect on lightning activity over and around Seoul, the largest metropolitan city of South Korea, for the period of 1989–1999. Negative and positive flash density and the percentage of positive flashes have been calculated. Calculation reveals that an enhancement of approximately 60% and 42% are observed, respectively, for negative and positive flash density over and downwind of the city. The percentage decrease of positive flashes occurs over and downwind of Seoul and the amount of decrease is nearly 20% compared to upwind values. The results are in good agreement with those obtained by Steiger et al. (2002) and Westcott (1995). CG lightning activities have also been considered in relation to annual averages of PM10 (particulate matter with an aerodynamic diameter smaller than 10 μm) and sulphur dioxide (SO2) concentrations. Interesting results are found, indicating that the higher concentration of SO2 contributes to the enhancement of CG lightning flashes. On the other hand, the contribution from PM10 concentration has not appeared in this study to be as significant as SO2 in the enhancement of CG lightning flashes. Correlation coefficients of 0.33 and 0.64 are found between the change in CG lightning flashes and the PM10 and SO2, respectively, for upwind to downwind areas, suggesting a significant influence of the increased concentration of SO2 on the enhancement of CG flashes.
The role of climate and emission changes in future air quality over southern Canada and northern Mexico
E. Tagaris, K.-J. Liao, K. Manomaiphiboon, S. He, J.-H. Woo, P. Amar,A. G. Russell
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: Potential impacts of global climate and emissions changes on regional air quality over southern (western and eastern) Canada and northern Mexico are examined by comparing future summers' (i.e., 2049–2051) average regional O3 and PM2.5 concentrations with historic concentrations (i.e., 2000–2002 summers). Air quality modeling was conducted using CMAQ and meteorology downscaled from the GISS-GCM using MM5. Emissions for North America are found using US EPA, Mexican and Canadian inventories and projected emissions following CAIR and IPCC A1B emissions scenario. Higher temperatures for all sub-regions and regional changes in mixing height, insolation and precipitation are forecast in the 2049-2051 period. Future emissions are calculated to be lower over both Canadian sub-regions, but higher over northern Mexico. Global climate change, alone, is predicted to affect PM2.5 concentrations more than O3 for the projections used in this study: average daily maximum eight (8) hour O3 (M8hO3) concentrations are estimated to be slightly different in all examined sub-regions while average PM2.5 concentrations are estimated to be higher over both Canadian sub-regions (8% over western and 3% over eastern) but 11% lower over northern Mexico. More days are forecast where M8hO3 concentrations are over 75 ppb in all examined sub-regions but the number of days where PM2.5 concentration will be over 15 μg/m3 is projected higher only over western Canada. Climate change combined with the projected emissions lead to greater change in pollutant concentrations: average M8hO3 concentrations are simulated to be 6% lower over western Canada and 8% lower over eastern Canada while average PM2.5 concentrations are simulated to be 5% lower over western Canada and 11% lower over eastern Canada. Although future emissions over northern Mexico are projected higher, pollutant concentrations are simulated to be lower due to US emissions reductions. Global climate change combined with the projected emissions will decrease average M8hO3 4% and PM2.5 17% over northern Mexico. Significant reductions in the number of days where M8hO3 concentrations are over 75 ppb and PM2.5 concentration over 15 μg/m3 are also projected with a significant reduction in peak values.
Evaluation of In-Season Nitrogen Management for Summer Maize in North Central China
S.-C. Zhao,P. He,Z.-M. Sha,S.-L. Xing,K.-J. Li
ISRN Agronomy , 2012, DOI: 10.5402/2012/294514
Abstract: We conducted field experiments in which nitrogen (N) was applied to summer maize at different rates and different basal/topdressing ratios. The experiments were carried out in 2009 in Hengshui and Xinji, Hebei province, China. The results showed that basal application of N was necessary for maize growth in early summer and for high grain yields. For the Hengshui and Xinji sites, 30 and 57?kg N?ha?1, respectively, would meet the N demands of maize before 7-leaf stage. The total rates of 120 and 180?kg N?ha?1, respectively, would maximize grain yields, and in-season N management based on crop N demands and soil N supply could reduce N inputs by more than 50% in Hengshui and 25% in Xinji, respectively, in one maize growth season, compared with farmers' practice, but the sustainability of the optimum N rates for maximum grain yield of next seasons crop needs to be further studied. Optimum N management should take into account the existing nutrient conditions at each site, soil fertility and texture, and crop demands. 1. Introduction The North China Plain (NCP) is one of the most important areas for cereal production in China. To meet the high demands for food, excessive amounts of nitrogen (N) fertilizer have been applied in this intensive agricultural region during the last two decades [1–3]. Summer maize (Zea mays. L.) is one of the staple grain crops in the NCP, and its planting area and total grain production accounted for 32 and 31% of the China maize crop in 2002 [4]. In the Shandong province, one of the provinces in the NCP, the amount of mineral N fertilizer applied to summer maize ranges from 50 to 600?kg N?ha?1, and the average application rate is 240?kg N?ha?1 [5]. These rates of application exceed the requirements of the crop to achieve maximum grain yield [6]. Overapplication of N fertilizer results in accumulation of N as nitrate-N in the soil, leading to groundwater pollution. Residual soil nitrate-N after winter wheat and summer maize harvest was reported to be 316 and 271?kg N?ha?1 in the top 100-cm soil profile when N was applied at rates of 300 and 240?kg N?ha?1, which are the rates used in normal farmers’ practice in this region [7, 8]. In 2001, the groundwater nitrate-N concentration exceeded 45?mg N O 3 ? ?L?1 in 49% of samples from this area [9]. High accumulation of soil nitrate-N and excessive rates of N application result in low nitrogen use efficiency (NUE), and the NUE of summer maize crops in this area has decreased from 30–35% in the 1980s to less than 20% in the 2000’s [10, 11]. At present, normal farmers’ N practice is to
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