We propose a new two-fold integration transformation in p-q phase space∫∫^∞-∞dpdq/π e^2i(p-x)(q-y)f(p,q)≡G(x,y),which possesses some well-behaved transformation properties. We apply this transformation t...We propose a new two-fold integration transformation in p-q phase space∫∫^∞-∞dpdq/π e^2i(p-x)(q-y)f(p,q)≡G(x,y),which possesses some well-behaved transformation properties. We apply this transformation to the Weyl ordering of operators, especially those Q-P ordered and P-Q ordered operators.展开更多
Hail is one of the important weather disasters that affects the Beijing-Tianjin(BT) region.To better understand and to improve the forecasting of hail events over the BT region,the precursor weather conditions for hai...Hail is one of the important weather disasters that affects the Beijing-Tianjin(BT) region.To better understand and to improve the forecasting of hail events over the BT region,the precursor weather conditions for hail based on 30 previous hail events were derived.It was found that the high-level trough and low-level cold front over the Mongolian region,the accumulated convective available potential energy,the decrease of the height of the 0℃-isotherm in the morning,and the persistence and intensification of these factors from morning to afternoon are valuable clues for forecasting the occurrence of hail events over the BT region.展开更多
Using the coupled Dyson-Schwinger equation for the fermion propagator at finite chemical potential μ, we investigate the fermion chiral condensate when the gauge boson mass is nonzero in QED3. We show that the chiral...Using the coupled Dyson-Schwinger equation for the fermion propagator at finite chemical potential μ, we investigate the fermion chiral condensate when the gauge boson mass is nonzero in QED3. We show that the chiral symmetry restores when the boson mass is large enough, and the critical boson mass depends little on μ.展开更多
Within the framework of finite temperature field theory this paper discusses the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton diagram level with a finite chemical potential The effective...Within the framework of finite temperature field theory this paper discusses the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton diagram level with a finite chemical potential The effective widths (damping rates) are introduced to regulate the pinch singularities and then gives a reliable estimation of the shear viscous coefficient.The finite chemical potential contributes positively compared to the pure temperature case. The result agrees with that from the kinetics theory qualitatively.展开更多
Accessibility to organic carbon(OC) budget is required for sustainable agricultural development and ecosystem preservation and restoration. Using geostatistical models to describe and demonstrate the spatial variabili...Accessibility to organic carbon(OC) budget is required for sustainable agricultural development and ecosystem preservation and restoration. Using geostatistical models to describe and demonstrate the spatial variability of soil organic carbon(SOC) will lead to a greater understanding of this dynamics. The aim of this paper is to present the relationships between the spatial variability of SOC and the topographic features by using geostatistical methods on a loess mountain-slope in Toshan region, Golestan Province, northern Iran. Hence, 234 soil samples were collected in a regular grid that covered different parts of the slope. The results showed that such factors as silt, clay, saturated moisture content, mean weighted diameter(MWD) and bulk density were all correlated to the OC content in different slope positions, and the spatial variability of SOC more to slope positions and elevations. The coefficient of variation(CV) indicated that the variability of SOC was moderate in different slope positions and for the mountain-slope as a whole. However, the higher variability of SOC(CV = 45.6%) was shown in the back-slope positions. Also, the ordinary cokriging method for clay as covariant gave better results in evaluating SOC for the whole slope with the RMSE value 0.2552 in comparison with the kriging and the inverse distance weighted(IDW) methods. The interpolation map of OC for the slope under investigation showed lowering SOC concentrations versus increasing elevation and slope gradient. The spatial correlation ratio was different between various slope positions and related to the topographic texture.展开更多
The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-10^1 (Cr) were studied by gravimetric method and temperature-programmed desorpt...The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-10^1 (Cr) were studied by gravimetric method and temperature-programmed desorption (TPD) experiments. The MIL-101 crystals were synthesized by microwave irradiation method. The ad- sorption isotherms and kinetic curves of n-hexane on the MIL-101 were measured. Desorption activation energies of n-hexane from the MIL-10^1 were estimated by TPD experiments. The resulthowed that equilibrium amount ofn-hexane adsorbed on the MIL-10^1 was up to 5.62 mmol.g- 1 at 298 K and 1.6 x10^4 Pa, much higher than that of some activated carbons, zeolltes and so on. The isotherms of n-hexane on the MIL-101 could be well fitted with Langmuir-Freundlich model. TPD spectra exhibit two types of adsorption sites on the MIL-101 with desorption activation energies of 39.41 and 86.69 kJ. mol-1. It reflects the surface energy heterogeneity on the MIL-10I frameworks for n-hexane adsorption. The diffusion coefficients of n-hexane are in the range of (1.35- 2.35 ) x 10 - 1 o cm2. s - 1 with ad sorotion activation enerv of 16.33 kl. mol - 1.展开更多
Although extensive studies have been performed on nitrogen isotopes in lake sediments, understanding the complexity of the δ15N variation related to past environmental and climatic conditions still remains unclear. S...Although extensive studies have been performed on nitrogen isotopes in lake sediments, understanding the complexity of the δ15N variation related to past environmental and climatic conditions still remains unclear. Supported by multi-proxy records including litho-units, organic carbon isotopes, ration of total organic carbon and total nitrogen, organic matter content, bulk dry density, the accumulation rate of organic matter, median grain size, magnetic susceptibility, and Rb/Sr and Ca/Mg ratios obtained from a sedimentary sequence in a small lake (i.e., Dahu Swamp) in the eastern Nanling Mountains in South China, we deduce that variation in the δ15N values results primarily from the sources of organic matter, which are significantly influenced by climatic conditions over the past -16 000 years. A low (or high) lake level resulting from dry (or wet) conditions would lead to more (or fewer) vascular plant remains in the sediments and stronger (or weaker) denitrification associated with hypolimnetic anoxia, resulting in lower (or higher) 615N values. In addition, dry (or wet) conditions would favor weakened (or strengthened) biogeochemical activity in the catchment, which could result in less (or more) external input of δ15N-enriched OM, thus leading to decreased (or increased) δ15N values. Our results indicate that the lake sediment δ15N record in the Nanling Mountains has the potential to provide valuable insight into past East Asian monsoon climate- driven environmental changes.展开更多
The degree pattern of a finite group G associated with its prime graph has been introduced by Moghaddamfar in 2005 and it is proved that the following simple groups are uniquely determined by their order and degree pa...The degree pattern of a finite group G associated with its prime graph has been introduced by Moghaddamfar in 2005 and it is proved that the following simple groups are uniquely determined by their order and degree patterns: All sporadic simple groups, the alternating groups Ap (p ≤ 5 is a twin prime) and some simple groups of the Lie type. In this paper, the authors continue this investigation. In particular, the authors show that the symmetric groups Sp+3, where p + 2 is a composite number and p + 4 is a prime and 97 〈 p ∈π(1000!), are 3-fold OD-characterizable. The authors also show that the alternating groups All6 and A134 are OD-characterizable. It is worth mentioning that the latter not only generalizes the results by Hoseini in 2010 but also gives a positive answer to a conjecture by Moghaddamfar in 2009.展开更多
A detailed stable isotopic study based on benthic foraminifera from 1165 samples of ODP Site 1148 (18° 50.17.3’N, 116° 33.93’E, water depth 3308.3 m), northern South China Sea, provides an excellent oxygen...A detailed stable isotopic study based on benthic foraminifera from 1165 samples of ODP Site 1148 (18° 50.17.3’N, 116° 33.93’E, water depth 3308.3 m), northern South China Sea, provides an excellent oxygen isotopic record with an average resolution of 30 ka. It contains the most continuous δ18O data with highest resolution for the whole Neogene sequence in the world. The δ18O curve shows a step-like increasing upwards and records 5 increases, 3 decreases and 2 stable stages during the Neogene, reflecting the general trend of global cooling. Among these events the δ18O decrease at 17.2–14.5 Ma, and two δ18O increases at 14.5-13.6 and 3.0-2.4 Ma are most marked and globally comparable. The intervals at 13.6-10.2 and 6.0-3.0 Ma with the lowest-amplitude and least fluctuation in δ18O represent the most stable bottom water periods for the South China Sea.展开更多
The effects of the number of significant figures (NSF) in the interpolation polynomial coefficients (IPCs) of the weighted sum of gray gases model (WSGM) on results of numerical investigations and WSGM optimizat...The effects of the number of significant figures (NSF) in the interpolation polynomial coefficients (IPCs) of the weighted sum of gray gases model (WSGM) on results of numerical investigations and WSGM optimization were investigated. The investigation was conducted using numerical simulations of the processes inside a pulverized coal-fired furnace. The radiative properties of the gas phase were determined using the simple gray gas model (SG), two-term WSGM (W2), and three-term WSGM (W3). Ten sets of the IPCs with the same NSF were formcd for every weighting coefficient in both W2 and W3. The average and maximal relative difference values of the flame temperatures, wall temperatures, and wall heat fluxes were determined. The investigation showed that the results of numerical investigations were affected by the NSF unless it exceeded certain value. The increase in the NSF did not necessarily lead to WSGM optimization. The combination of the NSF (CNSF) was the necessary requirement for WSGM optimization.展开更多
基金National Natural Science Foundation of China under Grant Nos.10775097 and 10874174
文摘We propose a new two-fold integration transformation in p-q phase space∫∫^∞-∞dpdq/π e^2i(p-x)(q-y)f(p,q)≡G(x,y),which possesses some well-behaved transformation properties. We apply this transformation to the Weyl ordering of operators, especially those Q-P ordered and P-Q ordered operators.
基金supported by the Scientific Research Foundation for Returned Scholars of the State Personnel Ministry of China,the Research Foundation of Institute of Urban Meteorology, CMA (Grant No. UMRF 200809)the R&D Special Fund for Public Welfare Industry (Meteorology) (Grant No. GYHY200906003)the National Basic Research Program of China (Grant No. 2009CB421406)
文摘Hail is one of the important weather disasters that affects the Beijing-Tianjin(BT) region.To better understand and to improve the forecasting of hail events over the BT region,the precursor weather conditions for hail based on 30 previous hail events were derived.It was found that the high-level trough and low-level cold front over the Mongolian region,the accumulated convective available potential energy,the decrease of the height of the 0℃-isotherm in the morning,and the persistence and intensification of these factors from morning to afternoon are valuable clues for forecasting the occurrence of hail events over the BT region.
基金We would like to thank Prof. Jia-Lun PING for helpful discussions.
文摘Using the coupled Dyson-Schwinger equation for the fermion propagator at finite chemical potential μ, we investigate the fermion chiral condensate when the gauge boson mass is nonzero in QED3. We show that the chiral symmetry restores when the boson mass is large enough, and the critical boson mass depends little on μ.
基金supported by National Natural Science Foundation of China under Grant Nos.10675052,10575043,and 10747135
文摘Within the framework of finite temperature field theory this paper discusses the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton diagram level with a finite chemical potential The effective widths (damping rates) are introduced to regulate the pinch singularities and then gives a reliable estimation of the shear viscous coefficient.The finite chemical potential contributes positively compared to the pure temperature case. The result agrees with that from the kinetics theory qualitatively.
基金Gorgan University of Agricultural Sciences and Natural Resources for the support of this study
文摘Accessibility to organic carbon(OC) budget is required for sustainable agricultural development and ecosystem preservation and restoration. Using geostatistical models to describe and demonstrate the spatial variability of soil organic carbon(SOC) will lead to a greater understanding of this dynamics. The aim of this paper is to present the relationships between the spatial variability of SOC and the topographic features by using geostatistical methods on a loess mountain-slope in Toshan region, Golestan Province, northern Iran. Hence, 234 soil samples were collected in a regular grid that covered different parts of the slope. The results showed that such factors as silt, clay, saturated moisture content, mean weighted diameter(MWD) and bulk density were all correlated to the OC content in different slope positions, and the spatial variability of SOC more to slope positions and elevations. The coefficient of variation(CV) indicated that the variability of SOC was moderate in different slope positions and for the mountain-slope as a whole. However, the higher variability of SOC(CV = 45.6%) was shown in the back-slope positions. Also, the ordinary cokriging method for clay as covariant gave better results in evaluating SOC for the whole slope with the RMSE value 0.2552 in comparison with the kriging and the inverse distance weighted(IDW) methods. The interpolation map of OC for the slope under investigation showed lowering SOC concentrations versus increasing elevation and slope gradient. The spatial correlation ratio was different between various slope positions and related to the topographic texture.
基金Supported by the National Natural Science Foundation of China(21276092)the Research Foundation of State Key Lab of Subtropical Building Science of China(C713001z)+2 种基金the Science and Technology Research Foundation of Guangzhou City,China(200910814001)Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control(2011A060901011)the Fundamental Research Funds for the Central Universities(2013ZZ0060 and 2013ZM0056)
文摘The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-10^1 (Cr) were studied by gravimetric method and temperature-programmed desorption (TPD) experiments. The MIL-101 crystals were synthesized by microwave irradiation method. The ad- sorption isotherms and kinetic curves of n-hexane on the MIL-101 were measured. Desorption activation energies of n-hexane from the MIL-10^1 were estimated by TPD experiments. The resulthowed that equilibrium amount ofn-hexane adsorbed on the MIL-10^1 was up to 5.62 mmol.g- 1 at 298 K and 1.6 x10^4 Pa, much higher than that of some activated carbons, zeolltes and so on. The isotherms of n-hexane on the MIL-101 could be well fitted with Langmuir-Freundlich model. TPD spectra exhibit two types of adsorption sites on the MIL-101 with desorption activation energies of 39.41 and 86.69 kJ. mol-1. It reflects the surface energy heterogeneity on the MIL-10I frameworks for n-hexane adsorption. The diffusion coefficients of n-hexane are in the range of (1.35- 2.35 ) x 10 - 1 o cm2. s - 1 with ad sorotion activation enerv of 16.33 kl. mol - 1.
基金Supported by the National Natural Science Foundation of China(Nos.41071137,40671189)the Research Program of Higher Education Institution in Guangdong Province for High-level Talents,and the Natural Science Foundation of Guangdong Province(Nos.S2011010003413,8151063101000044)
文摘Although extensive studies have been performed on nitrogen isotopes in lake sediments, understanding the complexity of the δ15N variation related to past environmental and climatic conditions still remains unclear. Supported by multi-proxy records including litho-units, organic carbon isotopes, ration of total organic carbon and total nitrogen, organic matter content, bulk dry density, the accumulation rate of organic matter, median grain size, magnetic susceptibility, and Rb/Sr and Ca/Mg ratios obtained from a sedimentary sequence in a small lake (i.e., Dahu Swamp) in the eastern Nanling Mountains in South China, we deduce that variation in the δ15N values results primarily from the sources of organic matter, which are significantly influenced by climatic conditions over the past -16 000 years. A low (or high) lake level resulting from dry (or wet) conditions would lead to more (or fewer) vascular plant remains in the sediments and stronger (or weaker) denitrification associated with hypolimnetic anoxia, resulting in lower (or higher) 615N values. In addition, dry (or wet) conditions would favor weakened (or strengthened) biogeochemical activity in the catchment, which could result in less (or more) external input of δ15N-enriched OM, thus leading to decreased (or increased) δ15N values. Our results indicate that the lake sediment δ15N record in the Nanling Mountains has the potential to provide valuable insight into past East Asian monsoon climate- driven environmental changes.
基金the National Natural Science Foundation of China(Nos.11271301,11171364)the National Science Foundation for Distinguished Young Scholars of China(No.11001226)+2 种基金the Fundamental Research Funds for the Central Universities(Nos.XDJK2012D004,XDJK2009C074)the Natural Science Foundation Project of CQ CSTC(Nos.2011jjA00020,2010BB9206)the GraduateInnovation Funds of Science of Southwest University(No.ky2009013)
文摘The degree pattern of a finite group G associated with its prime graph has been introduced by Moghaddamfar in 2005 and it is proved that the following simple groups are uniquely determined by their order and degree patterns: All sporadic simple groups, the alternating groups Ap (p ≤ 5 is a twin prime) and some simple groups of the Lie type. In this paper, the authors continue this investigation. In particular, the authors show that the symmetric groups Sp+3, where p + 2 is a composite number and p + 4 is a prime and 97 〈 p ∈π(1000!), are 3-fold OD-characterizable. The authors also show that the alternating groups All6 and A134 are OD-characterizable. It is worth mentioning that the latter not only generalizes the results by Hoseini in 2010 but also gives a positive answer to a conjecture by Moghaddamfar in 2009.
基金the National Natural Science Foundation of China (Grant No. 49999560) and the State Key Basic Research and Development Plan (Grant No. 2000078502).
文摘A detailed stable isotopic study based on benthic foraminifera from 1165 samples of ODP Site 1148 (18° 50.17.3’N, 116° 33.93’E, water depth 3308.3 m), northern South China Sea, provides an excellent oxygen isotopic record with an average resolution of 30 ka. It contains the most continuous δ18O data with highest resolution for the whole Neogene sequence in the world. The δ18O curve shows a step-like increasing upwards and records 5 increases, 3 decreases and 2 stable stages during the Neogene, reflecting the general trend of global cooling. Among these events the δ18O decrease at 17.2–14.5 Ma, and two δ18O increases at 14.5-13.6 and 3.0-2.4 Ma are most marked and globally comparable. The intervals at 13.6-10.2 and 6.0-3.0 Ma with the lowest-amplitude and least fluctuation in δ18O represent the most stable bottom water periods for the South China Sea.
基金supported by the Ministry of Education,Science and Technological Development of the Republic of Serbia(project No.TR-33018)
文摘The effects of the number of significant figures (NSF) in the interpolation polynomial coefficients (IPCs) of the weighted sum of gray gases model (WSGM) on results of numerical investigations and WSGM optimization were investigated. The investigation was conducted using numerical simulations of the processes inside a pulverized coal-fired furnace. The radiative properties of the gas phase were determined using the simple gray gas model (SG), two-term WSGM (W2), and three-term WSGM (W3). Ten sets of the IPCs with the same NSF were formcd for every weighting coefficient in both W2 and W3. The average and maximal relative difference values of the flame temperatures, wall temperatures, and wall heat fluxes were determined. The investigation showed that the results of numerical investigations were affected by the NSF unless it exceeded certain value. The increase in the NSF did not necessarily lead to WSGM optimization. The combination of the NSF (CNSF) was the necessary requirement for WSGM optimization.