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ABSTRACT: Knowledge of N-nitrosamine precursors from dissolved organic matter (DOM) is important for water professionals to better control N-nitrosamine formation. The characterization of DOM from the Luan River in Northern China was conducted using Amberlite XAD resins and ultra-filtration methods. N-nitrosamine formation potentials were investigated for various DOM fractions. The removal of the DOM during water treatment were evaluated using dissolved organic carbon (DOC) and ultraviolet absorbance at 254nm (UV(254)) bulk parameters as well as size exclusion chromatography and fluorescence spectroscopy. The results indicated that the XAD-4 hydrophilic fraction, with normalized yields of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosomorpholine (NMOR), and N-nitrosopiperidine (NPIP) of 27.2, 5.2, 5.9, and 6.1ng/mg-DOC, respectively, tended to form more N-nitrosamines than the hydrophobic and the transphilic fractions. The DOM fraction with a molecular weight (MW) below 1kDa, with normalized yields of NDMA, NPYR, NMOR, and NPIP of 39.6, 8.1, 14.7, and 3.3ng/mg-DOC, respectively, tended to form more N-nitrosamines than those with a higher MW. The limited removal of the hydrophilic fraction and the lower MW DOM faction during conventional water treatment processes suggests that the process may not effectively remove the nitrosamine precursors.
Science of The Total Environment 02/2013; 449C:295-301. · 3.29 Impact Factor
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ABSTRACT: It is very important to identify the dominant precursors for N-nitrosamine formation from bulk organic matter, to enhance the understanding of N-nitrosamine formation pathways in water treatment plants and allow the development of practical treatment technologies. In this study, dissolved organic matter (DOM) from two source waters was fractionated with XAD resins and ultrafiltration membranes. The N-nitrosamine formation potential (FP) (ng of N-nitrosamines formed per mg of dissolved organic carbon (DOC)) from raw water and each fraction were measured and correlated with the fluorescence excitation-emission matrix (EEM), molecular weight (MW) and other assays. The results showed that the hydrophilic fraction had N-nitrosamine FP 1.3 to 3.5 times higher than the hydrophobic fraction from both source waters. The DOM fraction with low MW was the dominant fraction in these two source waters and contributed more precursors for N-nitrosamine formation than the larger MW fraction. The EEM spectra indicated there were notable amounts of soluble microbial products (SMPs) and aromatic proteins in the two studied rivers, which probably originated from wastewater discharge. The SMPs tended to be more closely correlated with N-nitrosodimethylamine formation potential than the other DOM components. Higher N-nitrosamine FP were also related to fractions with lower DOC/DON ratios and lower SUVA254 values.
Journal of Environmental Sciences 01/2013; 25(1):85-95. · 1.66 Impact Factor
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ABSTRACT: Let Circ(r, n) be a circular graph. It is well known that its independence number α(Circ(r, n)) = r. In this paper we prove that
a(Circ(r,n) H) = max{ r|H|,na(H)}\alpha (Circ(r,n) \times H) = \max \{ r|H|,n\alpha (H)\}
for every vertex transitive graph H, and describe the structure of maximum independent sets in Circ(r, n) × H. As consequences, we prove
a(G H) = max{ a(G)|V(H)|,a(H)|V(G)|}\alpha (G \times H) = \max \{ \alpha (G)|V(H)|,\alpha (H)|V(G)|\}
for G being Kneser graphs, and the graphs defined by permutations and partial permutations, respectively. The structure of maximum
independent sets in these direct products is also described.
KeywordsVertex-transitivity–primitivity–independence number
Acta Mathematica Sinica 05/2012; 28(4):697-706. · 0.47 Impact Factor
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ABSTRACT: The size of the struts in nanoporous cellular solids typically has a secondary influence on the stiffness of the solids, but
it leads to significant stiffening when it is on the same order as the higher-order material parameter. We examined this size-dependence
using the higher-order finite-element method (FEM) in this study. Mathematical analysis showed that the displacement field
that satisfies the conventional Lame equation can serve as a displacement field template in higher-order FEM. Benchmarking
studies showed that results from simulations of beam bending and rod torsion using this FEM approach were in good agreement
with results from analytical solutions and experiments. Using this approach, we showed that the stiffness of cellular solids
is strongly affected by the cellular arrangement and the density when the cell size is on the order of the higher-order material
parameter and that the stiffening behavior in nanoporous polyimide can be explained using higher-order theory. The FEM results
also showed that a porous solid with half the weight can be engineered to become as stiff as a fully dense solid if the porous
microarchitecture is tailored to take advantage of higher-order stiffening.
Journal of Materials Science 05/2012; 44(4):985-991. · 2.02 Impact Factor
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ABSTRACT: Hybrid plasma is an important physical phenomenon in fiber laser-MIG hybrid welding. It greatly affects the stability of the
process, the quality of the weld, and the efficiency of energy coupling. In this paper, clear and direct proofs of these characteristics
are presented through high-speed video images. Spectroscopic analysis is used to describe the characterization of hybrid plasma.
The hybrid plasma forms a curved channel between the welding wire and the keyhole during the fiber laser-MIG hybrid welding
process. The curved channel is composed of two parts. The laser-induced plasma/vapor expands due to the combined effect of
the laser and the MIG arc, forming an ionization duct, which is one part of the curved channel. The resistance of the duct
is smaller than that of other locations because of the rise in electrical conductivity. Consequently, the electrical arc is
guided through the duct to the surface of the material, which is the other part of the curved channel. The spectral intensities
of metal elements in laser-MIG hybrid welding are much stronger than those in MIG-only welding, whereas the spectral intensities
of shielding gas element in laser-MIG hybrid welding are much weaker.
KeywordsCurved channel–Fiber plasma–Hybrid plasma–High-speed video image–Laser-MIG hybrid welding
Journal of Mechanical Science and Technology 04/2012; 25(6):1529-1533. · 0.45 Impact Factor
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ABSTRACT: Natural organic matter (NOM) and particles in source water are responsible for the majority of ultrafiltration (UF) membrane
fouling that occurs during drinking water treatment. This study was conducted to (1) understand the UF membrane fouling phenomena
caused by NOM and turbidity-causing particles and (2) investigate the effect of coagulation pretreatment on the alleviation
of membrane fouling. In this study, kaolinite and humic acid (HA) were used to simulate the particles and NOM present in source
water. The results revealed that the particles contributed to reversible fouling due to cake layer formation on the membrane
surface, but that could be effectively reduced by increasing the frequency of physical backwashing. The results of the molecular
weight (MW) distribution measurements, resin fractionation, SEM and FTIR analyses showed that HA primarily contributed to
irreversible fouling. Taken together, the results of this study imply that the particles and NOM compounds present in source
water may have different fouling behavior, and that particles may mitigate the irreversible fouling caused by HA. The addition
of coagulant can lead to a higher rate of removal of large-sized hydrophobic compounds. Coagulation pretreatment can improve
membrane performance and postpone membrane fouling development effectively, as well as retard the implementation of membrane
chemical cleaning.
Keywordsultrafiltration–membrane fouling–NOM–particles–coagulation
Chinese Science Bulletin 04/2012; 56(6):584-590. · 1.32 Impact Factor
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ABSTRACT: Shanghai is physically and socio-economically vulnerable to accelerated sea level rise because of its low elevation, flat
topography, highly developed economy and highly-dense population. In this paper, two scenarios of sea level rise and storm
surge flooding along the Shanghai coast are presented by forecasting 24 (year 2030) and 44 (year 2050) years into the future
and are applied to a digital elevation model to illustrate the extent to which coastal areas are susceptible to levee breach
and overtopping using previously developed inflow calculating and flood routing models. Further, the socio-economic impacts
are examined by combining the inundation areas with land use and land cover change simulated using GeoCA-Urban software package.
This analysis shows that levee breach inundation mainly occurs in the coastal zones and minimally intrudes inland with the
conservative protection of dike systems designed. However, storm surge flooding at the possible maximum tide level could cause
nearly total inundation of the landscape, and put approximately 24 million people in Shanghai under direct risk resulting
from consequences of flooding (e.g. contamination of potable water supplies, failure of septic systems, etc.).
KeywordsSea-level rise–Storm surge–Flood–Land use and land cover change–Shanghai
Environmental earth sciences 04/2012; 63(2):407-414. · 1.06 Impact Factor
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ABSTRACT: SAM is a most important data platform of many economic analysis methods, but great deal time and energy are immersed in SAM
construction and adjustment, the problem that we try to solve in this paper by aggregate-disaggregate rules, automatic calculation
program, and summary information iteration in Excel so that model constructers and analysts can concentrate themselves on
such professional works as model research, shock study, results analysis, and so on.
KeywordsSocial Accounting Matrix (SAM)–Input-Output (IO) Table–Aggregate-disaggregate Rule
07/2011: pages 15-22;
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ABSTRACT: Particles and natural organic matter (NOM) are two major concerns in surface water, which greatly influence the membrane filtration process. The objective of this article is to investigate the effect of particles, NOM and their interaction on the submerged ultrafiltration (UF) membrane flux under conditions of solo UF and coagulation and PAC adsorption as the pretreatment of UF. Particles, NOM and their mixture were spiked in tap water to simulate raw water. Exponential relationship, (J(P)/J(P0) = a x exp{-k[t-(n-1)T]}), was developed to quantify the normalized membrane flux dynamics during the filtration period and fitted the results well. In this equation, coefficient a was determined by the value of J(P)/J(P0) at the beginning of a filtration cycle, reflecting the flux recovery after backwashing, that is, the irreversible fouling. The coefficient k reflected the trend of flux dynamics. Integrated total permeability (SigmaJ(P)) in one filtration period could be used as a quantified indicator for comparison of different hybrid membrane processes or under different scenarios. According to the results, there was an additive effect on membrane flux by NOM and particles during solo UF process. This additive fouling could be alleviated by coagulation pretreatment since particles helped the formation of flocs with coagulant, which further delayed the decrease of membrane flux and benefited flux recovery by backwashing. The addition of PAC also increased membrane flux by adsorbing NOM and improved flux recovery through backwashing.
Journal of Environmental Sciences 01/2011; 23(12):1970-6. · 1.66 Impact Factor
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ABSTRACT: China has suffered frequent source water contamination accidents in the past decade, which has resulted in severe consequences to the water supply of millions of residents. The origins of typical cases of contamination are discussed in this paper as well as the emergency response to these accidents. In general, excessive pursuit of rapid industrialization and the unreasonable location of factories are responsible for the increasing frequency of accidental pollution events. Moreover, insufficient attention to environmental protection and rudimentary emergency response capability has exacerbated the consequences of such accidents. These environmental accidents triggered or accelerated the promulgation of stricter environmental protection policy and the shift from economic development mode to a more sustainable direction, which should be regarded as the turning point of environmental protection in China. To guarantee water security, China is trying to establish a rapid and effective emergency response framework, build up the capability of early accident detection, and develop efficient technologies to remove contaminants from water.
Environmental Science & Technology 01/2011; 45(1):161-7. · 4.80 Impact Factor
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ABSTRACT: To improve the deficiency of the control system of finish cooling temperature (FCT), a new model developed from a combination
of a multilayer perception neural network as the self-learning system and traditional mathematical model were brought forward
to predict the plate FCT. The relationship between the self-learning factor of heat transfer coefficient and its influencing
parameters such as plate thickness, start cooling temperature, was investigated. Simulative calculation indicates that the
deficiency of FCT control system is overcome completely, the accuracy of FCT is obviously improved and the difference between
the calculated and target FCT is controlled between −15 °C and 15 °C.
Journal of Central South University of Technology 01/2008; 15(1):136-140. · 0.36 Impact Factor
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ABSTRACT: Narrow fractions of Athabasca oil sands-derived synthetic crude oil (SCO) from Canada were obtained by distillation at 20
°C to 500 °C and characterized. The yield and properties, such as density, refractive index, viscosity, freezing point, sulfur
and nitrogen content and UOP K-index, were correlated as a function of boiling temperature (T
b). The properties of naphtha fractions, jet fuel and diesel fractions could be predicted accurately with the correlations,
which are useful for process design considerations, such as optimizing operating conditions of refinery processing units.
The other key properties and characteristics of naphtha fractions, jet fuel, diesel and vacuum gas oil were also determined.
Petroleum Science 01/2007; 4(3):84-90. · 0.47 Impact Factor
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ABSTRACT: Strain recovery after the cessation of shear was studied in model immiscible blends composed of polyisobutylene drops (10–30%
by weight) in a polydimethylsiloxane matrix. Blends of viscosity ratio (viscosity of the drops relative to the matrix viscosity)
ranging from 0.3 to 1.7 were studied. Most of the strain recovery was attributable to interfacial tension, and could be well-described
by just two parameters: the ultimate recovery and a single retardation time. Both these parameters were found to increase
with the capillary number of the drops prior to cessation of shear. For blends that had reached steady shear conditions, the
ultimate recovery decreased with increasing viscosity ratio, whereas the retardation time increased with increasing viscosity
ratio. The retardation time was well-predicted, but the ultimate recovery was over-predicted by a linear viscoelastic model
developed previously by Vinckier etal. (Rheol Acta 38:65–72, 1999).
Rheologica Acta 12/2005; 45(3):297-304. · 2.03 Impact Factor
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ABSTRACT: The solvent extraction of copper and zinc from the bioleaching solutions of low-grade sulfide ores with LIX984 and D2EHPA
was investigated. The influences of extractant content, aqueous pH value, phase ratio and equilibration time on metals extraction
were studied. The results show that LIX984 has a higher selectivity for copper than for iron, zinc and other metals, and has
the copper extraction rate above 97%, while the zinc and iron extraction rate is less than 1.6% respectively. Zinc extraction
is carried out following the copper extraction from the raffinate. The zinc extraction with di(2-ethylhexyl) phosphoric acid
(D2EHPA) is low due to its poor cation exchange. A sodium salt of D2EHPA is used and the zinc extraction rate is enhanced
to above 98%. Though iron (III) is strongly extracted before the extraction of zinc by D2EHPA, it is difficult to strip iron
from the organic phase by sulfuric acid. The zinc stripping rate is above 99% with 100 g/L sulfuric acid, while that of iron
is 0.16%. Hence, the separation of zinc from iron can be achieved by the selective stripping.
Journal of Central South University of Technology 01/2005; 12(1):45-49. · 0.36 Impact Factor
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ABSTRACT: The effects of silver sulfide (Ag2S) on the bioleaching of chalcopyrite and pyrite were investigated in this paper. It has been shown that Ag2S enhanced the yields of bioleaching of chalcopyrite but inhibited the bio-oxidation of pyrite. The addition of Ag2S selectively increased the copper dissolution from the chalcopyrite-containing ores in shake flasks with a recovery of 85.3%
compared with 24.3% without Ag2S, while slightly decreased the iron yields from 51% to 41.8%. The copper extraction of the chalcoopyrite-containing waste
rock in column leaching charged with 18 kg mass increased up to 21.7% in the presence of Ag2S, while only 3.4% in the absence of the catalyst. The mechanism of Ag2S catalysis could be explained well by the “Mixed potential model”.
Journal of Central South University of Technology 01/2002; 9(1):11-15. · 0.36 Impact Factor
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ABSTRACT: New Einstein metrics are constructed on the associated , , and -bundles of principal circle bundles with base a product of Kähler-Einstein manifolds with positive first Chern class and
with Euler class a rational linear combination of the first Chern classes. These Einstein metrics represent different generalizations
of the well-known Einstein metrics found by Bérard Bergery, D. Page, C. Pope, N. Koiso, and Y. Sakane. Corresponding new Einstein-Weyl
structures are also constructed.
Mathematische Annalen 02/1998; 310(3):497-526. · 1.30 Impact Factor
