Silver nanoparticles were obtained by reduction method. Various techniques, such as UV-Vis spectroscopy, transmission electron microscopy （TEM） and light-scattering spectroscopy, were used to characterize nanopartic...Silver nanoparticles were obtained by reduction method. Various techniques, such as UV-Vis spectroscopy, transmission electron microscopy （TEM） and light-scattering spectroscopy, were used to characterize nanoparticles. Sodium borohydride or sodium citrate was adopted as reduction regent, and polyvinyl alcohol or polyethylene glycol was adopted as stabilizing regent. An experimental condition was studied in detail. After the water was eliminated, the silver nanoparticle was fixed in the solid polymer. The silver nanoparticle in polymer could be re-dissolved in water. It was found that light scattering characteristic of silver nanoparticle storied in polymer was not changed. A new method of storing silver nanoparticles in solid polymer was given in this paper.展开更多
Urban aerosols have a large effect on the deterioration of air quality and the degradation of atmospheric visibility.Characterization of the chemical composition of PM 2.5 and in situ measurements of the optical prope...Urban aerosols have a large effect on the deterioration of air quality and the degradation of atmospheric visibility.Characterization of the chemical composition of PM 2.5 and in situ measurements of the optical properties of aerosols were conducted in July 2008 at an urban site in Guangzhou,Southern China.The mean PM 2.5 concentration for the entire period was 53.7±23.2 μg m 3.The mean PM 2.5 concentration (82.7±25.4 μg m 3) on hazy days was roughly two times higher than that on clear days (38.8±8.7 μg m 3).The total water-soluble ion species and the total average carbon accounted for 47.9%±4.3% and 35.2%±4.5%,respectively,of the major components of PM 2.5.The increase of secondary and carbonaceous aerosols,in particular ammonium sulfate,played an important role in the formation of haze pollution.The mean absorption and scattering coefficients and the single scattering albedo over the whole period were 53±20 M m 1,226±111 M m 1,and 0.80±0.04,respectively.PM 2.5 had a high linear correlation with the aerosol extinction coefficient,elemental carbon (EC) was correlated with aerosol absorption,and organic carbon (OC) and SO 4 2 were tightly linked to aerosol scattering.展开更多
We propose a novel channel model for massive multiple-input multiple-out （MIMO） communication systems that incorporate the spherical wave-front assumption and non-stationary properties of clusters on both the array ...We propose a novel channel model for massive multiple-input multiple-out （MIMO） communication systems that incorporate the spherical wave-front assumption and non-stationary properties of clusters on both the array and time axes. Because of the large dimension of the antenna array in massive MIMO systems, the spherical wave-front is assumed to characterize near-field effects resulting in angle of arrival （AoA） shifts and Doppler frequency variations on the antenna array. Additionally, a novel visibility region method is proposed to capture the non-stationary properties of clusters at the receiver side. Combined with the birth-death process, a novel cluster evolution algorithm is proposed. The impacts of cluster evolution and the spherical wave-front assumption on the statistical properties of the channel model are investigated. Meanwhile, corresponding to the theoretical model, a simulation model with a finite number of rays that capture channel characteristics as accurately as possible is proposed. Finally, numerical analysis shows that our proposed non-stationary channel model is effective in capturing the characteristics of a massive MIMO channel.展开更多
We consider the approximate acoustic cloaking in an inhomogeneous isotropic background space.By employing transformation media,together with the use of a sound-soft layer lining right outside the cloaked region,we sho...We consider the approximate acoustic cloaking in an inhomogeneous isotropic background space.By employing transformation media,together with the use of a sound-soft layer lining right outside the cloaked region,we show that one can achieve the near-invisibility by the"blow-up-a-small-region"construction.This is based on novel scattering estimates corresponding to multiple multi-scale obstacles located in an isotropic space.We develop a novel system of integral equations to decouple the nonlinear scattering interaction among the small obstacle components,the regular obstacle components and the inhomogeneous background medium.展开更多
文摘Silver nanoparticles were obtained by reduction method. Various techniques, such as UV-Vis spectroscopy, transmission electron microscopy （TEM） and light-scattering spectroscopy, were used to characterize nanoparticles. Sodium borohydride or sodium citrate was adopted as reduction regent, and polyvinyl alcohol or polyethylene glycol was adopted as stabilizing regent. An experimental condition was studied in detail. After the water was eliminated, the silver nanoparticle was fixed in the solid polymer. The silver nanoparticle in polymer could be re-dissolved in water. It was found that light scattering characteristic of silver nanoparticle storied in polymer was not changed. A new method of storing silver nanoparticles in solid polymer was given in this paper.
基金supported by the Special Scientific Research Funds for Environment Protection Commonweal Section(Grant Nos.200809143and201009001)the National Basic Research Program of China(Grant No.2010CB428503)+4 种基金the National Natural Science Foundation of China(Grant No.41075096)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.IAP09320)the Research and Development Special Fund for Public Welfare Industry(Meteorology) of the China Meteorological Administration(Grant No.GYHY201006047)the Ministry of Science and Technology of China(Grant No.2010DFA22770)the Innovation Method Fund of China(Grant No.2008IM020500)
文摘Urban aerosols have a large effect on the deterioration of air quality and the degradation of atmospheric visibility.Characterization of the chemical composition of PM 2.5 and in situ measurements of the optical properties of aerosols were conducted in July 2008 at an urban site in Guangzhou,Southern China.The mean PM 2.5 concentration for the entire period was 53.7±23.2 μg m 3.The mean PM 2.5 concentration (82.7±25.4 μg m 3) on hazy days was roughly two times higher than that on clear days (38.8±8.7 μg m 3).The total water-soluble ion species and the total average carbon accounted for 47.9%±4.3% and 35.2%±4.5%,respectively,of the major components of PM 2.5.The increase of secondary and carbonaceous aerosols,in particular ammonium sulfate,played an important role in the formation of haze pollution.The mean absorption and scattering coefficients and the single scattering albedo over the whole period were 53±20 M m 1,226±111 M m 1,and 0.80±0.04,respectively.PM 2.5 had a high linear correlation with the aerosol extinction coefficient,elemental carbon (EC) was correlated with aerosol absorption,and organic carbon (OC) and SO 4 2 were tightly linked to aerosol scattering.
基金Project supported by the National Natural Science Foundation of China （No. 61421061） and the Huawei Innovation Research Program
文摘We propose a novel channel model for massive multiple-input multiple-out （MIMO） communication systems that incorporate the spherical wave-front assumption and non-stationary properties of clusters on both the array and time axes. Because of the large dimension of the antenna array in massive MIMO systems, the spherical wave-front is assumed to characterize near-field effects resulting in angle of arrival （AoA） shifts and Doppler frequency variations on the antenna array. Additionally, a novel visibility region method is proposed to capture the non-stationary properties of clusters at the receiver side. Combined with the birth-death process, a novel cluster evolution algorithm is proposed. The impacts of cluster evolution and the spherical wave-front assumption on the statistical properties of the channel model are investigated. Meanwhile, corresponding to the theoretical model, a simulation model with a finite number of rays that capture channel characteristics as accurately as possible is proposed. Finally, numerical analysis shows that our proposed non-stationary channel model is effective in capturing the characteristics of a massive MIMO channel.
基金supported by National Natural Science Foundation of China(Grant Nos.1110141411201453+1 种基金91130022 and 91130026)National Science Foundation of USA(Grant No.DMS 1207784)
文摘We consider the approximate acoustic cloaking in an inhomogeneous isotropic background space.By employing transformation media,together with the use of a sound-soft layer lining right outside the cloaked region,we show that one can achieve the near-invisibility by the"blow-up-a-small-region"construction.This is based on novel scattering estimates corresponding to multiple multi-scale obstacles located in an isotropic space.We develop a novel system of integral equations to decouple the nonlinear scattering interaction among the small obstacle components,the regular obstacle components and the inhomogeneous background medium.
