Source contributions to ambient VOCs and CO at a rural site in eastern China

Ambient data on volatile organic compounds (VOCs) and carbon monoxide (CO) obtained at a rural site in eastern China are analyzed to investigate the nature of emission sources and their relative contributions to ambient concentrations. A principal component analysis (PCA) showed that vehicle emissions and biofuel burning, biomass burning and industrial emissions were the major sources of VOCs and CO at the rural site. The source apportionments were then evaluated using an absolute principal component scores (APCS) technique combined with multiple linear regressions. The results indicated that 71%±5% (average±standard error) of the total VOC emissions were attributed to a combination of vehicle emissions and biofuel burning, and 7%±3% to gasoline evaporation and solvent emissions. Both biomass burning and industrial emissions contributed to 11%±1% and 11%±0.03% of the total VOC emissions, respectively. In addition, vehicle emissions and biomass and biofuel burning accounted for 96%±6% of the total CO emissions at the rural site, of which the biomass burning was responsible for 18%±3%. The results based on PCA/APCS are generally consistent with those from the emission inventory, although a larger relative contribution to CO from biomass burning is indicated from our analysis. © 2004 Elsevier Ltd. All rights reserved

Effective modulus of polycrystalline aggregates in different geometrical configurations

In the present study, a finite element scheme with random distribution strategy is employed to systematically investigate the modulus difference of polycrystalline copper aggregates in different geometrical configurations (three-dimensional bulk and thin film configurations). Firstly, the finite element simulation is performed to estimate the effective elastic constants in three-dimensional bulk configuration. The numerical estimations are in good agreement with the existing analytical solutions and experimental measurements. Secondly, the proven finite element scheme is extended to the prediction of the effective moduli of the free-standing and substrate-attached thin films. For the free-standing thin film, the effective Young's modulus decreases with reducing the film thickness. For the substrate-attached thin film, its effective modulus is affected by the relative stiffness between the substrate and the film. The spread of the effective moduli in different configurations could be as large as 20%. © 2010 Elsevier B.V.postprin

Electric assumptions for piezoelectric laminate analysis

In computational analysis of piezoelectric laminates which may comprise piezoelectric and non-piezoelectric plies, the transverse electric field is often assumed to be piecewise constant along the transverse direction. This conventional assumption may lead to significant errors unless the piezoelectric ply is considerably thinner than the overall thickness of the laminate. To this end, two alternate assumptions termed EL and DC on the spatial distributions of the electric variables are proposed. In EL, the transverse electric field is taken to be piecewise linear along the transverse direction. In the DC assumption, the transverse electric displacement is taken to be piecewise constant along the transverse direction. The rationales leading to the proposed assumptions are discussed. Numerical examples indicate that the proposed assumptions are markedly more accurate than the conventional one. However, EL becomes inaccurate when its piecewise function spans more than one ply. In this light, DC often consumes less electric potential d.o.f.s and is more efficient than EL. © 2003 Elsevier Ltd. All rights reserved.postprin

Characteristics of nonmethane hydrocarbons (NMHCs) in industrial, industrial-urban, and industrial-suburban atmospheres of the Pearl River Delta (PRD) region of south China

In a study conducted in late summer 2000, a wide range of volatile organic compounds (VOCs) were measured throughout five target cities in the Pearl River Delta (PRD) region of south China. Twenty-eight nonmethane hydrocarbons (NMHCs; 13 saturated, 9 unsaturated, and 6 aromatic) are discussed. The effect of rapid industrialization was studied for three categories of landuse in the PRD: Industrial, industrial-urban, and industrial-suburban. The highest VOC mixing ratios were observed in industrial areas. Despite its relatively short atmospheric lifetime (2-3 days), toluene, which is largely emitted from industrial solvent use and vehicular emissions, was the most abundant NMHC quantified. Ethane, ethene, ethyne, propane, n-butane, i-pentane, benzene, and m-xylene were the next most abundant VOCs. Direct emissions from industrial activities were found to greatly impact the air quality in nearby neighborhoods. These emissions lead to large concentration variations for many VOCs in the five PRD study cities. Good correlations between isoprene and several short-lived combustion products were found in industrial areas, suggesting that in addition to biogenic sources, anthropogenic emissions may contribute to urban isoprene levels. This study provides a snapshot of industrial, industrial-urban, and industrial-suburban NMHCs in the five most industrially developed cities of the PRD. Increased impact of industrial activities on PRD air quality due to the rapid spread of industry from urban to suburban and rural areas, and the decrease of farmland, is expected to continue until effective emission standards are implemented. Copyright 2006 by the American Geophysical Union

Fighting with the Sparsity of Synonymy Dictionaries

Graph-based synset induction methods, such as MaxMax and Watset, induce synsets by performing a global clustering of a synonymy graph. However, such methods are sensitive to the structure of the input synonymy graph: sparseness of the input dictionary can substantially reduce the quality of the extracted synsets. In this paper, we propose two different approaches designed to alleviate the incompleteness of the input dictionaries. The first one performs a pre-processing of the graph by adding missing edges, while the second one performs a post-processing by merging similar synset clusters. We evaluate these approaches on two datasets for the Russian language and discuss their impact on the performance of synset induction methods. Finally, we perform an extensive error analysis of each approach and discuss prominent alternative methods for coping with the problem of the sparsity of the synonymy dictionaries.Comment: In Proceedings of the 6th Conference on Analysis of Images, Social Networks, and Texts (AIST'2017): Springer Lecture Notes in Computer Science (LNCS

Assessing photochemical ozone formation in the Pearl River Delta with a photochemical trajectory model

A photochemical trajectory model (PTM), coupled with the Master Chemical Mechanism (MCM) describing the degradation of 139 volatile organic compounds (VOCs) in the troposphere, was developed and used for the first time to simulate the formation of photochemical pollutants at Wangqingsha (WQS), Guangzhou during photochemical pollution episodes between 12 and 17 November, 2007. The simulated diurnal variations and mixing ratios of ozone were in good agreement with observed data (R2=0.80, P<0.05), indicating that the photochemical trajectory model - an integration of boundary layer trajectories, precursor emissions and chemical processing - provides a reasonable description of ozone formation in the Pearl River Delta (PRD) region. Calculated photochemical ozone creation potential (POCP) indices for the region indicated that alkanes and oxygenated organic compounds had relatively low reactivity, while alkenes and aromatics presented high reactivity, as seen in other airsheds in Europe. Analysis of the emission inventory found that the sum of 60 of the 139 VOC species accounted for 92% of the total POCP-weighted emission. The 60 VOC species include C2-C6 alkenes, C6-C8 aromatics, biogenic VOCs, and so on. The results indicated that regional scale ozone formation in the PRD region can be mainly attributed to a relatively small number of VOC species, namely isoprene, ethene, m-xylene, and toluene, etc. A further investigation of the relative contribution of the main emission source categories to ozone formation suggested that mobile sources were the largest contributor to regional O3 formation (40%), followed by biogenic sources (29%), VOC product-related sources (23%), industry (6%), biomass burning (1%), and power plants (1%). The findings obtained in this study would advance our knowledge of air quality in the PRD region, and provide useful information to local government on effective control of photochemical smog in the region. © 2010 Elsevier Ltd

Identification of potential drug resistant mutations in HIV-1 infected patients with long-term undetectable viral load after receiving HAART

This journal suppl. entitled: HIV DART 2010 ... Final Program and Abstract BookSession - Drug Resistance and ModelingConference Theme: Frontiers in drug development for in antiretroviral therapiesBACKGROUND: This study aimed to identify potential drug resistant mutations in proviral DNA in HIV patients with long-term undetectable viral load after receiving HAART. METHOD: Peripheral blood mononuclear cells (PBMC) were collected from 45 patients twice per year from 2005 to 2009. These patients have been receiving effective highly active antiretroviral therapy …published_or_final_versio