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Search Results: 1 - 10 of 11875 matches for " Liqian Yin "
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Pollution Characteristics of PM2.5 during a Typical Haze Episode in Xiamen, China  [PDF]
Fuwang Zhang, Jinsheng Chen, Tianxue Qiu, Liqian Yin, Xiaoqiu Chen, Jianshuan Yu
Atmospheric and Climate Sciences (ACS) , 2013, DOI: 10.4236/acs.2013.34044
Abstract:

In this study, mass concentrations and chemical compositions of fine particles, mass concentrations of coarse particles, light extinction, and meteorological parameters in the atmosphere ofXiamenwere presented and analyzed to study the chemical and optical characteristics of a typical haze episode from Dec 25, 2010 to Jan 1, 2011. The major chemical compositions of PM2.5, such as water soluble inorganic ions (WSIIs), carbonaceous fractions (mainly composed of organic carbon (OC) and elemental carbon (EC)), and elements were determined. The results showed that with the typical haze episode process, the concentrations of PM2.5 mass, WSIIs, OC, EC, and TE first increased and then decreased. The average concentrations of PM2.5 mass in the stages of Before Haze, During Haze, and After Haze were (88.80 ± 19.97), (135.41 ± 36.20), and (96.35 ± 36.26) μg/m3, respectively. The corresponding average concentrations of secondary organic carbon (SOC) were 6.72, 8.18, and 10.39 μg/m3, accounting for 46.5%, 27.0%, and 61.0% of OC, respectively. S42- , NO3-, and NH4+ were three major WSIIs species, accounting for 31.4%, 26.0%, and 12.1% of total WSIIs. The major elements in PM2.5 were S, K, Fe, Zn, Pb, Ti, and Mn, covering 97.9% of the total elements, while the percentage of the other ten elements was only 2.1%. The average value of light extinction coefficients (bext) was 371.0 ±147.1 Mm-1 during the typical haze episode. The average percentage contributions to bext were 39.3% for organic mass, 19.9% for elemental carbon, 16.0% for ammonium sulfate, 13.0% for coarse mass, and 11.8% for ammonium nitrate.

Variability of Sand Mobility Surrounding Cylinder Object Freely Resting on the Seabed under the Action of Typhoon  [PDF]
Chongguang Pang, Liqian Liu
International Journal of Geosciences (IJG) , 2014, DOI: 10.4236/ijg.2014.57062
Abstract:

In sandy sediments, scour and fill is the key process contributed to mine burial. The scour processes surrounding the cylinder mines freely resting on the sandy seabed under the 12-hr combined action of tidal currents and wind-generated waves, especially over typhoon events are numerically simulated using the DRAMBUIE model. The East China Sea is a good case study due to the dominant impact of summer typhoon events on sediment transport and scour. The numerical results show that the scour depth generally increases with time under the combined current and wave stresses exerted on the seabed, while the depth of the scour pit depends on infill once the currents subside. There is a positive relationship between the scour depth and the bottom orbital velocity after experiencing 12-hr wave action including storm waves, while the relation is not linear. The experimental results also display an elevated trend for scour depth with the increase of orbital velocity. The numerical results reveal a surprising phenomenon: the mobility of sand altering with the increasing bed shear stress larger than the certain threshold, which is also manifested as the curves of scour depth with the different grain size might cross each other. For laboratory experiments, the variability of sand mobility does not occur, likely because typhoon storm waves cannot be reproduced in the flume. More numerical tests indicate that the intersection will be triggered by the division of critical Shields parameter. The preliminary analysis suggests that the phenomenon never documented is likely generated from the error of empirical formulae.

Quantification, morphology and source of humic acid, kerogen and black carbon in offshore marine sediments from Xiamen Gulf, China
Yanting Chen,Jinping Zhao,Liqian Yin,Jinsheng Chen,Dongxing Yuan,
Yanting Chen
,Jinping Zhao,Liqian Yin,Jinsheng Chen,Dongxing Yuan

环境科学学报(英文版) , 2013,
Abstract: Three types of macromolecular organic matters (MOMs), i.e. humic acid (HA), kerogen+black carbon (KB), and black carbon (BC) were extracted from marine sediments of Xiamen Gulf, southeast of China. The chemical composition, morphological property and source of the three extractions were characterized by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS) and scanning electron microscope (SEM). The results showed that KB was the predominant fraction in MOMs, which accounted for 61.79%-89.15% of the total organic content (TOC), while HA consisted less than 5%. The relative high contents of kerogen and BC, and low contents of HA in the samples indicated that anthropogenic input might be the major source of organic matter in marine sediments near the industrial regions. The characterization of SEM, not only revealed morphological properties of the three fractions, but also allowed a better understanding of the source of MOMs. The δ13C values of the three fractions suggested that materials from terrestrial C3 plants were predominant. Furthermore, the anthropogenic activities, such as the discharge of sewage, coal and biomass combustion from industry nearby and agricultural practices within drainage basin of the Jiulong River, were remarkably contributed to the variations in δ13C values of MOMs in the offshore marine sediments.
Chemical compositions of PM2.5 aerosol during haze periods in the mountainous city of Yong''an, China
Liqian Yin,Zhenchuan Niu,Xiaoqiu Chen,Jinsheng Chen,Lingling Xu,Fuwang Zhang,
Liqian Yin
,Zhenchuan Niu,Xiaoqiu Chen,Jinsheng Chen,Lingling Xu,Fuwang Zhang

环境科学学报(英文版) , 2012,
Abstract: Haze phenomena were found to have an increasing tendency in recent years in Yong'an, a mountainous industrial city located in the center part of Fujian Province, China. Atmospheric fine particles (PM2.5) in the urban area during haze periods in three seasons (spring, autumn and winter) from 2007 to 2008 were collected, and the mass concentrations and chemical compositions (seventeen elements, water soluble inorganic ions (WSIIs) and carbonaceous species) of PM2.5 were determined. PM2.5 mass concentrations did not show a distinct difference among the three seasons. The carbonaceous species organic carbon (OC) and elemental carbon (EC) constituted up to 19.2%-30.4% of the PM2.5 mass during sampling periods, while WSIIs made up 25.3%-52.5% of the PM2.5 mass. The major ions in PM2.5 were SO42-, NO3- and NH4+, while the major elements were Si, K, Pb, Zn, Ca and Al. The experimental results (from data based on three haze periods with a 10-day sampling length for each period) showed that the crustal element species was the most abundant component of PM2.5 in spring, and the secondary ions species (SO42-, NO3-, NH4+, etc.) was the most abundant component in PM2.5 in autumn and winter. This indicated that dust was the primary pollution source for PM2.5 in spring and combustion and traffic emissions could be the main pollution sources for PM2.5 in autumn and winter. Generally, coal combustion and traffic emissions were considered to be the most prominent pollution sources for this city on haze days.
Determination of sulfite in flue gas desulfurization with seawater by ion chromatography
离子色谱法测定烟气脱硫海水中的亚硫酸根离子

YIN Liqian,YUAN Dongxing,GUO Juan,LIU Xiyao,
尹丽倩
,袁东星,郭娟,刘锡尧

色谱 , 2009,
Abstract: The technology for flue gas desulfurization (FGD) with seawater is widely adopted by coal-fired power plants in coastal areas. SO2 in the flue gas is absorbed by alkaline seawater and transfered in aqueous phase as sulfite (SO2~3), and most SO2~3 is transformed to sulfate (SO2~4) after an aeration process. The remaining SO2~3 in the seawater discharged to sea area may be harmful to marine organism because of its biological toxicity, thus it is necessary to determine the concentration of SO2~3 in the seawater for desulfurization. In this study, the method of determination of SO2~3 in the seawater by ion chromatography was investigated. The separation was achieved on an IonPac AS14A column with 14 mmol/L NaOH-12 mmol/L Na2CO3 solution as the mobile phase at a flow rate of 1.2 mL/min, and the detection was performed by a pulsed amperometric detector. Formaldehyde was added as a protective agent when sampling because the SO2~3 is easy to be oxidized. To avoid the formation of Mg(OH)2 in the mobile phase with high pH value which might block the column, the Mg2+ in seawater was precipitated by NaOH solution (pH 12.0) before sample determination. The method showed good linearity within the range of 0~100 mg/L with an average recovery of 116.8%. The method detection limit (MDL) reached as low as 0.05 mg/L. The relative standard deviations (RSD) for seawater matrix samples spiked at levels of 7.5, 25.0 and 75.0 mg/L were 2.1%, 3.1% and 4.0% (n=9), respectively. The method has been applied for the determination of SO2~3 in flue gas desulfurization seawater with the advantages of being fast, sensitive and selective.
Recent advances on trusted computing in China
Wei Dong,LiQian Chen
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5550-z
Abstract: This article highlights some recent research advances on trusted computing in China, focusing mainly on the methodologies and technologies related to trusted computing module, trusted computing platform, trusted network connection, trusted storage, and trustworthy software.
Eco-Environmental Quality Assessment of Xining City Based on GIS and AHP
Zhang Liqian,Cai Jianming
Modern Applied Science , 2012, DOI: 10.5539/mas.v6n4p84
Abstract: This paper studies the Analytic Hierarchy Process (AHP), and puts forward the ecological environment AHP index of Xining City accordingly. By using GIS technology, Five-Laps-linkage Thought and Traffic Lights Principle, the writer makes a qualitative and quantitative analysis of Eco-environmental Quality, and gives an accurate and objective assessment to the Eco-environmental Quality of Xining City. These assessments would help a lot for government to determine the ecological environment protection policies. Studies show that, social circle, hydrosphere, atmosphere, lithosphere and biosphere make a decline in turn influence to Xining Eco-environmental Quality assessment, and hence the mean, social circle is the strongest influence to Xining Eco-environmental Quality. For a long time, the ecological environment in this area is in a precarious position; as a result, we should prevent to make aggressive decision during the urbanization, value the quality instead of quantity. Focus on the development of eco-industries; and gradually improve the Eco-environmental Quality in some area where is not so good; using the coordinative development principle between resources, environment and economy to guide regional urbanization.
An Online Manifold Learning Approach for Model Reduction of Dynamical Systems
Liqian Peng,Kamran Mohseni
Mathematics , 2012,
Abstract: This article discusses a newly developed online manifold learning method, subspace iteration using reduced models (SIRM), for the dimensionality reduction of dynamical systems. This method may be viewed as subspace iteration combined with a model reduction procedure. Specifically, starting with a test solution, the method solves a reduced model to obtain a more precise solution, and it repeats this process until sufficient accuracy is achieved. The reduced model is obtained by projecting the full model onto a subspace that is spanned by the dominant modes of an extended data ensemble. The learning procedure is computed in the online stage, as opposed to being computed offline, which is used in many projection-based model reduction techniques that require prior calculations or experiments. After providing an error bound of the classical POD-Galerkin method in terms of the projection error and the initial condition error, we prove that the sequence of approximate solutions converge to the actual solution of the original system as long as the vector field of the full model is locally Lipschitz on an open set that contains the solution trajectory. Good accuracy of the proposed method has been demonstrated in two numerical examples, from a linear advection-diffusion equation to a nonlinear Burgers equation. In order to save computational cost, the SIRM method is extended to a local model reduction approach by partitioning the entire time domain into several subintervals and obtaining a series of local reduced models of much lower dimensionality. The accuracy and efficiency of the local SIRM are shown through the numerical simulation of the Navier--Stokes equation in a lid-driven cavity flow problem.
Symplectic Model Reduction of Hamiltonian Systems
Liqian Peng,Kamran Mohseni
Mathematics , 2014,
Abstract: In this paper, a symplectic model reduction technique, proper symplectic decomposition (PSD) with symplectic Galerkin projection, is proposed to save the computational cost for the simplification of large-scale Hamiltonian systems while preserving the symplectic structure. As an analogy to the classical proper orthogonal decomposition (POD)-Galerkin approach, PSD is designed to build a symplectic subspace to fit empirical data, while the symplectic Galerkin projection constructs a reduced Hamiltonian system on the symplectic subspace. For practical use, we introduce three algorithms for PSD, which are based upon: the cotangent lift, complex singular value decomposition, and nonlinear programming. The proposed technique has been proven to preserve system energy and stability. Moreover, PSD can be combined with the discrete empirical interpolation method to reduce the computational cost for nonlinear Hamiltonian systems. Owing to these properties, the proposed technique is better suited than the classical POD-Galerkin approach for model reduction of Hamiltonian systems, especially when long-time integration is required. The stability, accuracy, and efficiency of the proposed technique are illustrated through numerical simulations of linear and nonlinear wave equations.
Existence of a nontrivial solution for a strongly indefinite periodic Schrodinger-Poisson system
Shaowei Chen,Liqian Xiao
Mathematics , 2014,
Abstract: We consider the Schr\"odinger-Poisson system \begin{eqnarray}\left\{\begin{array} [c]{ll} -\Delta u+V(x) u+|u|^{p-2}u=\lambda \phi u, & \mbox{in}\mathbb{R}^{3},\\ -\Delta\phi= u^{2}, & \mbox{in}\mathbb{R}^{3}. \end{array} \right.\nonumber \end{eqnarray} where $\lambda>0$ is a parameter, $3< p<6$, $V\in C(\mathbb{R}^{3}) $ is $1$-periodic in $x_j$ for $j = 1,2,3$ and 0 is in a spectral gap of the operator $-\Delta+V$. This system is strongly indefinite, i.e., the operator $-\Delta+V$ has infinite-dimensional negative and positive spaces and it has a competitive interplay of the nonlinearities $|u|^{p-2}u$ and $\lambda \phi u$. Moreover, the functional corresponding to this system does not satisfy the Palai-Smale condition. Using a new infinite-dimensional linking theorem, we prove that, for sufficiently small $\lambda>0,$ this system has a nontrivial solution.
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