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Search Results: 1 - 10 of 55304 matches for " HU Hai-Qing "
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Controllability of ferromagnetism in graphene
Tianxing Ma,Feiming Hu,Zhongbing Huang,Hai-Qing Lin
Physics , 2009, DOI: 10.1063/1.3485059
Abstract: We systematically study magnetic correlations in graphene within Hubbard model on a honeycomb lattice by using quantum Monte Carlo simulations. In the filling region below the Van Hove singularity, the system shows a short-range ferromagnetic correlation, which is slightly strengthened by the on-site Coulomb interaction and markedly by the next-nearest-neighbor hopping integral. The ferromagnetic properties depend on the electron filling strongly, which may be manipulated by the electric gate. Due to its resultant controllability of ferromagnetism, graphene-based samples may facilitate the development of many applications.
Pairing in graphene: A quantum Monte Carlo study
Tianxing Ma,Zhongbing Huang,Feiming Hu,Hai-Qing Lin
Physics , 2011, DOI: 10.1103/PhysRevB.84.121410
Abstract: To address the issue of electron correlation driven superconductivity in graphene, we perform a systematic quantum Monte Carlo study of the pairing correlation in the t-U-V Hubbard model on a honeycomb lattice. For V=0 and close to half filling, we find that pairing with d+id symmetry dominates pairing with extended-s symmetry. However, as the system size or the on-site Coulomb interaction increases, the long-range part of the d+id pairing correlation decreases and tends to vanish in the thermodynamic limit. An inclusion of nearest-neighbor interaction V, either repulsive or attractive, has a small effect on the extended-s pairing correlation, but strongly suppresses the d+id pairing correlation.
Quantum Monte Carlo Study of Pairing Symmetry and Correlation in Iron-based Superconductors
Tianxing Ma,Hai-Qing Lin,Jiangping Hu
Physics , 2012, DOI: 10.1103/PhysRevLett.110.107002
Abstract: We perform a systematic quantum Monte Carlo study of the pairing correlation in the $S_4$ symmetric microscopic model for iron-based superconductors. It is found that the pairing with an extensive s-wave symmetry robustly dominates over other pairings at low temperature in reasonable parameter region. The pairing susceptibility, the effective pairing interaction and the $(\pi,0)$antiferromagnetic correlation strongly increase as the on-site Coulomb interaction increases, indicating the importance of the effect of electron-electron correlation. Our non-biased numerical results provide a unified understanding of superconducting mechanism in iron-pnictides and iron-chalcogenides and demonstrate that the superconductivity is driven by strong electron-electron correlation effects.
Estimation of carbon release from shrubs, herbages and litters in Daxing''''an Mountains by forest fires in 1980-1999
1980—1999年大兴安岭灌木、草本和地被物林火碳释放估算

HU Hai-qing,SUN Long,
胡海清
,孙龙

应用生态学报 , 2007,
Abstract: By using emission factor (EF), this paper estimated the carbon release and the emission of carbon-containing gases from the shrubs, herbages and litters in main forest types in Daxing' an Mountains by forest fires in 1980-1999. The results showed that the EF of shrubs, herbages and litters differed in different forest types, with the maximum and minimum EF of CO2 being 93.08% and 82.56%, respectively in Ledum palustre - Larix gmelinii forest and Pinus sylvestris var. mongolica forest, the maximum EF of CO and C(X)H(Y) being 10.25% and 0.84%, respectively in P. sylvestris var. mongolica forest, and the minimum EF of CO and C(X)H(Y) being 6.55% and 0.30%, respectively in L. palustre - L. gmelinii forest. Combined with the data of biomass and carbon storage of shrubs, herbages and litters in different forests, it was estimated that the total carbon release from shrubs, herbages and litters by forest fires from 1980 to 1999 accounted for 6.56 Tg and 0.33 Tg x a(-1), occupying 11.55%-16.30% of the total annual emissions in China by forest fires, and the emission of CO2, CO and C(x)H(y) was 22.03 Tg, accounting for 85.20%, 14.21% and 0.59% of the total carbon-containing gases emission, respectively.
A prediction model for forest fire-burnt area based on meteorological factors
基于气象因子的森林火灾面积预测模型

QU Zhi-lin,HU Hai-qing,
曲智林
,胡海清

应用生态学报 , 2007,
Abstract: Based on statistic analysis theory, the occurrence patterns of forest fire in Heilongjiang Province were studied, and the prediction model for forest fire-burnt area was established based on meteorological factors. The results showed that most of forest fires in Larix gmelinii forest region occurred from April to June and in October, and those in broadleaved Korean pine forest region mainly occurred from March to June and in October. By adopting the values of average wind speed, relative humidity and mean temperature, it was predicted that in L. gmelinii forest region, the first three months with greater probability of larger fire occurrence were March, May and June in order, while in broadleaved Korean pine forest region, they were May, March and April. The average precision of the model was 63.3%, suggesting that it could be used to predict the burnt area by forest fires.
Characteristics of gas release during combustion of main arbor and shrub species in Xiaoxing''an Mountain
小兴安岭主要乔、灌木燃烧过程的烟气释放特征

HU Hai-qing,LI Ao-bin,
胡海清
,李敖彬

应用生态学报 , 2008,
Abstract: The amounts of CO2, CO, CxHy, SO2 and NO released from the combustion of 10 arbor and 9 shrub species in Liangshui Forest Farm of Xiaoxing'an Mountain were determined, with the release amounts and emission factors of these gases calculated. The results showed that the released CO2, the total amount of carbon-containing gases, and the mean value of the total amount of the 5 gases during combustion were larger for arbors than for shrubs, being 1277.04 and 1149.06 mg x g(-1), 1476.27 and 1147.18 mg x g(-1), and 1486.21 and 1459.67 mg x g(-1), respectively, while an opposite pattern of the mean release of CO, NO and SO2 was observed, being 231.58 and 282.93 mg x g(-1), 3.61 and 5.03 mg x g(-1), and 6.32 and 7.46 mg x g(-1) for the arbor and shrub species, respectively. The emission factors of CO2 and CO were also larger for arbors than for shrubs, being 2.8853 and 2.7718, and 0.4558 and 0.2425, respectively.
Estimation of total carbon-containing gas emission from main tree species in forest fires in Daxing''an Mountains
大兴安岭森林火灾中主要乔木树种含碳气体释放总量的估算

HU Hai-qing,GUO Fu-tao,
胡海清
,郭福涛

应用生态学报 , 2008,
Abstract: 应用排放因子法估算了1980-2005年间大兴安岭林区森林火灾中5种主要乔木树种含碳气体总的释放量.结果表明:不同乔木树种燃烧释放含碳气体的排放因子不同,其中樟子松的CO2平均排放因子最大, 山杨的CO2平均排放因子最小;落叶松和山杨的CO和CxHy平均排放因子最大,山杨和落叶松的CO和CxHy平均排放因子最小.结合5种主要乔木树种各器官的含碳率和总生物量,得出25年间5种乔木共释放CO2 16.58 Tg、CO 1.61 Tg、CxHy 0.54 Tg.其中落叶松的CO2、CO和CxHy释放量分别为5.00、0.63和0.05 Tg; 樟子松为0.225、0.023和0.003 Tg; 白桦为11.22、0.83和0.41 Tg;山杨为0.022、0.004和0.00034 Tg;蒙古栎为3.12、0.13和0.062 Tg.
Magnetic Impurities in Graphene
F. M. Hu,Tianxing Ma,Hai-Qing Lin,J. E. Gubernatis
Physics , 2011, DOI: 10.1103/PhysRevB.84.075414
Abstract: We used a quantum Monte Carlo method to study the magnetic impurity adatoms on graphene. We found that by tuning the chemical potential we could switch the values of the impurity's local magnet moment between relatively large and small values. Our computations of the impurity's spectral density found its behavior to differ significantly from that of an impurity in a normal metal and our computations of the charge-charge and spin-spin correlations between the impurity and the conduction band electrons found them to be strongly suppressed. In general our results are consistent with those from poor man's scaling and numerical renormalization group methods.
Spatial point process for spatial distribution pattern of lightning-caused forest fires in DaXing'an Mountains
应用空间点模式方法研究大兴安岭雷击火空间分布格局

GUO Fu-Tao,HU Hai-Qing,MA Zhi-Hai,
郭福涛
,胡海清,马志海

生态学报 , 2009,
Abstract: The study of spatial pattern of forest fire locations is important to predict the fire occurrence as well as to understand the role of fire in landscape processes. A spatial statistical analysis of lightning-caused fires in Daxing′anling between 1988 and 2005, was carried out to investigate the spatial pattern of fires. Fire locations were found to be spatially clustered. The results also showed that there are some "hot-point" areas in Daxing′anling and geographical coordinates of those areas are 123°06′E,52°20′N;123°41′E,51°34′N;124°08′E,50°48′N, respectively.
Estimation of carbon emissions due to forest fire in Daxing'an Mountains from 1965 to 2010
1965–2010年大兴安岭森林火灾碳排放的估算研究

HU Hai-Qing,WEI Shu-Jing,SUN Long,
胡海清
,魏书精,孙龙

植物生态学报 , 2012,
Abstract: Aims Forest fire is a major disturbance factor for forest ecosystems and an important pathway of decreasing vegetation- and soil-carbon storage. Scientifically and effectively measuring carbonaceous gases emission from forest fire is important in understanding the significance of forest fire in carbon balance and climate change. However, carbon emissions from forest fire remain unclear. Our objective was to estimate carbon emissions from forest fires from 1965 to 2010 in Daxing’an Mountains of Heilongjiang Province, China. Methods We used a geographic information system (GIS) based modeling approach to generate emission estimates using a two-step procedure. First, we calculated total carbon released from forest fires in Daxing’an Mountains for selected years between 1965 and 2010 by merging and analyzing several measurement parameters. Second, we calculated amounts of four carbonaceous gases released during the burns, carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and nonmethane hydrocarbon (NMHC), using several different experimentally derived emission factors. The origin of each of the inputs used in our models is based on a combination of analysis of forest fire statistics, forest resources inventory, field research and laboratory experiments. Important findings Direct total carbon emissions from forest fires in Daxing’an Mountains during 1965–2010 are about 2.93 × 107 t, and mean annual carbon emissions are about 6.38 × 105 t per year, accounting for 5.64% of the direct total carbon emissions from forest fires in China. Carbon atmospheric emissions of CO2, CO, CH4 and NMHC from forest fires were 1.02 × 108 t, 9.41 × 106 t, 5.41 × 105 t and 2.11 × 105 t, respectively, and mean annual emissions of CO2, CO, CH4, and NMHC from forest fires were 2.22 × 106 t, 2.05 × 105 t, 1.18 × 104 t and 4.59 × 103 t, respectively, accounting for 5.46%, 7.56%, 10.54% and 4.06% of the amounts of four carbonaceous gases released from forest fires in China, respectively. Our results indicate that combustion efficiency of coniferous broad-leaved mixed forests is lower than other forest types, and burned area of coniferous broad-leaved mixed forests accounts for 21.23% of total burned area, but carbon emissions accounts for 7.81% of total carbon emissions.
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