Table of Content

22 June 2015, Volume 21 Issue 03

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Metallurgical Materials

Recent advances in the research of gaseous carbon exchange between river water and air interface

DING Hu, LIU Cong-Qiang, LANG Yun-Chao, LI Si-Liang, LI Xiao-Dong, WANG Fu-Shun

2015, 21(03):  275-285.  doi:10.3969/j.issn.1007-2861.2015.01.008

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Gaseous carbon exchange between river water and air interface is an important link of regional and global carbon cycle. It is essential to the precious estimation of terrestrial carbon budget and optimization of carbon cycle model. In this paper, the importance and recent progress in the study of riverine CO₂/CH₄ exchange between water-air interface are introduced, and insufficiency in the related study is pointed out. In the future, more researches need to be carried out on CO₂/CH₄ exchange between water-air interface of rivers under various geo-eco system and human impacts. Methods of paired carbon isotopes, stoichiometry, biomarker, etc., should be used to trace the sources of gaseous carbon (and other carbon forms) and their relative contributions, and to discover related carbon turn over processes. It is suggested that researches combining filed in-situ observing, traditional sample analysis, and laboratory experiments be conducted in the study of carbon exchange between multi-interfaces of soil-water, soil-air, sediment-water and water-air. Key factors that affect carbon exchange between water-air interface should be revealed. The study will provide abasis for related model development and watershed management.

Spatial and seasonal variation of dissolved inorganic carbon isotope compositions in the cascade reservoirs of the Jialing River

LI Xiao-Dong, LIU Xiao-Long, YANG Zhou, LI Qin-Kai, HUANG Jun

2015, 21(03):  286-293.  doi:10.3969/j.issn.1007-2861.2015.01.009

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The Jialing River and its cascade reservoirs were investigated. Wedensely collected water samples along the Jialing River in August 2008 (rain season) and February 2009 (dry season). We determine the contents and isotopic compositions of dissolved inorganic carbon (DIC), and discuss the sources and spatio-temporal variations of DIC. The results show that the average DIC and 13CDIC were 2 018 μmol/L and −8.6‰ in a rainy season, and 3 150 μmol/L and −6.0‰ in a dry season, showing obvious seasonal variations. The ¹³C_DIC values in winter were heavier than in summer, similar to undammed rivers but different from lakes and reservoirs. This indicates that the hydro-geochemical characteristics of waters in the cascade reservoirs of Jialing River are similar to natural rivers

Carbon and nitrogen coupled biogeochemical cycle in cascade reservoirs of the Wujiang River

WANG Bao-Li, LIU Cong-Jiang, WANG Fu-Shun, LIU Xiao-Long, PENG Xi, ZHAO Yan-Chuang

2015, 21(03):  294-300.  doi:10.3969/j.issn.1007-2861.2015.01.013

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Concentrations of dissolved CO₂ and NO₃⁻ were investigated in cascade reservoirs and related river reaches along the Wujiang River to understand temporal and spatial variations. The average of dissolved CO₂ were (113.6±105.7) μmol·L⁻¹, ranging from 1.6 to 934.6 μmol·L⁻¹. The average of NO₃⁻ were (163.0±104.9) μmol·L⁻¹, ranging from 0.4 to 632.0 μmol·L⁻¹. Averages and amplitudes of dissolved CO₂ and NO₃⁻  in the reservoirs are less than those in the rivers. Due to different resources and influencing factors, no significant correlation was found between dissolved CO₂ and NO₃⁻ in rivers. After damming, the activity of phytoplankton was enhanced, and became an important factor controlling material cycle in reservoirs. Photosynthesis and respiration couple C and N biogeochemical cycle, and dissolved CO₂ and NO₃⁻  in reservoirs were significantly correlated. The results indicate that C and N biogeochemical cycles in the original rivers are changed by cascade hydropower exploitation.

Impact of cascade reservoir development on N₂O emissions in the Wujiang River

LIU Xiao-Long, WANG Fu-Shun, BAI Li, LI Si-Liang, WANG Bao-Li, LIU Cong-Jiang, WANG Zhong-Liang

2015, 21(03):  301-310.  doi:10.3969/j.issn.1007-2861.2015.01.012

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Dams affect hydrologic cycle and water environment through intercepting river water. Therefore, “impounded rivers” or river reservoirs often affect river basin environments. That has become a worldwide problem, especially the effect on N₂O emissions. This study investigates cascade reservoirs in the Wujiang River, and analyzes therelated parameters and N₂O concentrations. It has been shown that the cascade development doeshave impacts on water parameters, nitrogen loadings and N₂O emission. Saturation of N₂O averaged 347% in the entiresurface water represents a N2O source with respect to atmosphere,
under influences of age of reservoirs, nutrient status and organic matters. N₂O is emitted more in spring and summer than in winter and autumn. The key factors of influence are T, pH and DO. Organic matters and nutrient status are important in old reservoirs such as the Wujiangdu reservoir. Nitrification is a dominate process for N₂O emission in surface water. But for water in discharge, denitrification is a dominate process. The annual average N₂O fluxes were 0.33 μmol·m⁻²·h⁻¹ for river water, 0.64 μmol·m⁻²·h⁻¹ for discharge water, and 0.43 μmol·m⁻²·h⁻¹ for surface water in dams. Compared to other surface water
in the world, emission of N₂O acts as moderate emission fluxes in the Wujiang River. High concentration in discharge water should be emphasized since it contributes huge amount of N₂O emission during hydroelectric production.

Partial pressure and diffusion flux of dissolved carbon dioxide in the main stream of the Three Gorge Reservoir and the Caotang River in summer

WU Xue-Qian, CAO Man, FU Jia-Nan, WEI Hao-Bin, JIA Xiao-Bin, DENG Bing, WANG Fu-Shun

2015, 21(03):  311-318.  doi:10.3969/j.issn.1007-2861.2015.01.010

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From May 2013 to July 2013, monthly cruise investigation was conducted to study the partial pressure of dissolved carbon dioxide (pCO₂) in the main stream of the Three Gorge Reservoir and its tributary, the Caotang River. The results show that pCO₂ in the surface water of the Caotang River varied from 15.8 to 226.4 Pa, and 198.8 to 261.1 Pa for the main stream of the Three Gorge Reservoir. Along the water column of the Caotang River, the lowest value of pCO₂ in surface water was 15.8 Pa, and increased rapidly with the depth, and kept stable below 5 m with a maximum value of 294.2 Pa. According to calculations, emission fluxes of CO₂ in the Caotang River in the period of investigation were about 16.46, 4.91 and 30.85 mmol m⁻²·d⁻¹, respectively. In the main stream of the
Three Gorge Reservoir, this flux was 48.54 mmol·m⁻2·d^−1. The results show that the main stream of the Three Gorge Reservoir is a source for atmospheric CO₂, and the tributary Caotang River emits less CO₂ than the main stream, even a sink for atmospheric CO₂ on June.

A Liouville type theorem of semi-linear equations on the Heisenberg group

ZHANG Shu-Tao, ZHAO Qiong, HAN Ya-Zhou

2015, 21(03):  319-330.  doi:10.3969/j.issn.1007-2861.2013.07.052

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Referring to the method of vector fields, this paper studies a class of semilinear  quations on the Heisenberg group and gives a Liouville type theorem, namely, the nonexistence of nontrivial positive solutions. A class of real functional constituted by leftinvariant  vector fields on the Heisenberg group is introduced. Some identities are obtained   by identical deformation. It is proved that any nonnegative solution is trivial according to   the properties of test function and some techniques such as polar coordinates formula on  the Heisenberg group and Young inequality.

A second order accurate mixed legendre-spherical harmonic pseudo-spectral method for the   
Fisher equation

DENG Hong-Mei, HUANG Wei

2015, 21(03):  331-335.  doi:10.3969/j.issn.1007-2861.2014.01.038

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The paper proposes a second mixed Legendre-spherical harmonic pseudospectral  scheme for the Fisher equation in a domain between two concentric balls. Legendre interpolation is used in the radial direction, and spherical harmonic interpolation in other  directions. The second order central difference quotient is used for time derivatives. Numerical  results show high accuracy of the proposed algorithm.

Global stability of an age-structured SIRS epidemic model

ZHANG Zhong-Hua, SUO Yao-Hong

2015, 21(03):  336-343.  doi:10.3969/j.issn.1007-2861.2014.05.010

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An age-structured SIRS epidemic model with screening strategy and infectionage is  formulated. The basic reproductive number is defined. Global stability of equilibria   of the model are disucssed by constructing suitable Lyapunov functions.

Eigenstrain boundary integral equation with local Eshelby matrix for ellipsoidal particles

MA Hang-1, FANG Jing-Be-2

2015, 21(03):  344-355.  doi:10.3969/j.issn.1007-2861.2014.01.039

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Aiming at large scale numerical simulation of particle reinforced materials, a concept of local Eshelby matrix is introduced into a computational model of the eigenstrain boundary integral equation to solve the problem of interactions among particles. The local  Eshelby matrix can be considered as an extension of Eshelby tensor and an equivalent inclusion in a numerical form. Taking the sub-domain boundary element method as the   control, three-dimensional stress analyses are carried out for some ellipsoidal particles in infinite media with the proposed computational model. Numerical examples verify  correctness,  feasibility and high efficiency of the present model with the corresponding solution procedure, showing potential of solving large scale numerical simulations for particle reinforced  materials.

Experiments of unidirectional and bidirectional pedestrian flows through a bottleneck in a channel

YANG Xue, CHEN Li, TIAN Huan-Huan, DONG Li-Yun

2015, 21(03):  356-363.  doi:10.3969/j.issn.1007-2861.2014.04.008

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The self-organization phenomena of pedestrian flow through a bottleneck in a channel are investigated by experiments. Different width of bottlenecks and initial distributions are taken into account. Experiments of unidirectional and bidirectional pedestrian flows through bottlenecks are carried out. Typical characteristics of pedestrian flows are observed, such as fan-shaped aggregation in front of the bottleneck, and sidling through the narrow bottleneck and oscillatory flows. These are formed because of the pedestrian behaviors i.e., following other people walking in the same direction and avoiding conflicts with those in an opposite direction. Similarities and differences between unidirectional and bidirectional pedestrian flows are discussed in the following aspects: coordination of pedestrians, flow and specific flow. It is found that the flow increases with the width of bottleneck in both cases. The specific flow in the bidirectional case deceases monotonously with the width of bottleneck. However, the specific flow in the unidirectional case decreases first, and then increases. When the width of the bottleneck is less than the shoulder-width, the unidirectional pedestrian flow is more efficient. However, the efficiency of walking in the case of bidirectional flows is higher than unidirectional flows when the bottleneck width is slightly larger than the shoulder-width.

Numerical study of flow separation control by setting small plate in front of leading edge of an airfoil

DONG Xiao-Hua-1, SUN Xiao-Jing-2

2015, 21(03):  364-369.  doi:10.3969/j.issn.1007-2861.2014.01.015

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A flow control method using a small plate in front of the leading edge of a   NACA0012 airfoil to achieve good aerodynamic performance is proposed. Effectiveness of  the proposed method is numerically studied by using a self-developed CFD program called  UCFD. At a certain angle of attack, including of parameters including length, initial installation  angle and installation position of the plate on the control of flow separation over  the airfoil are investigated. The optimal length, initial installation angle and installation  position of the small plate are obtained with an orthogonal optimization method that aims  at maximizing the lift-to-drag ratio. Numerical results suggest that this passive flow control   method can efficiently suppress flow separation.

Synthesis and surface properties of novel gemini surfactants

DONG Bin, ZHOU Chen-Qiu, LIU Ya-Fei, ZHANG Zhang

2015, 21(03):  370-375.  doi:10.3969/j.issn.1007-2861.2014.03.010

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A series of cationic gemini surfactants with different spacer chain lengths and hydrophobic groups were synthesized. Fourier transform infrared spectrometry(FT-IR) and mass spectrometry(MS) indicated that the structures of the products were fully identical with the design molecular. Further, measurements of the surface property were conducted, showing that all of them had lower surface tension, and their critical micelle concentration(CMC) obviously declined with the increasing length of the flexible hydrophilic spacer groups and hydrophobic groups. In addition, the emulsifying capacity was better than the traditional single-chain surfactants.

Synthesis and properties of phosphorus-nitrogen  containing phenolic resins

HU Lin-1, YU Ruo-Bing-1, DUAN Jia-Zhen-1, JIAO Zheng-2

2015, 21(03):  376-383.  doi:10.3969/j.issn.1007-2861.2014.01.029

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The phosphorus-nitrogen containing phenolic resins (NP-PF) were synthesized   from formaldehyde, melamine, phenol and phosphorus-containing monomer. The effect of  NP-PF in NP-PF/F51 was investigated. The results show that (1) the curing rate of NPPF/ F51 accelerates with the increase of NP-PF contents; (2) the epoxy resin thermosets  had good thermal stability; and (3) UL94V-0 rating is achieved with a lower Al(OH)3 content  for the NP-PF/F51 system.

Effect of temperature on physic-chemical properties of deep eutectic solvent based on choline chloride and  polyols

HE Zhi-Jiang, YAN Gao, WANG Qi-Hu, YU Xin-Lou, WU Kai, XU Yi

2015, 21(03):  384-392.  doi:10.3969/j.issn.1007-2861.2014.03.005

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Four kinds of deep eutectic solvents (DESs) based on choline chloride and polyols  were prepared. Density, viscosity and conductivity of the four DESs were measured as  functions of temperature in the range of 303～343 K. The results show that the densities of the four DESs sare linearly dependent on temperature. Viscosities decrease with  increasing temperature, and conductivities increase rapidly with increasing temperature,both obeying the Arrhenius exponential law. The activation energy of viscosity and conductivity  were calculated with the Arrhenius formula. The electrochemical windows of the  four DESs were also tested by using cyclic voltammetry at 333 K.