遗传算法的FPGA硬件实现

针对遗传算法软件实现速度慢、效率低的缺点,提出了便于算法实现的串行和流水线两种硬件实现方案。详细描述了设计方案,选择算子、交叉变异算子结构,种群以及适应度的存储和流水线结构,并在流水线中引入并行机制。利用函数极值和旅行商问题分别对方案的资源耗费、运行速度的有效性进行了验证。实验结果显示,这两种硬件实现方法结构简单,资源耗费少,运算速度和运行效率较软件实现大大提高,运行速度平均提升2~3个数量级,为算法在一些实时性要求较高的场合得到应用提供了良好基础。     

The effects of biofilm on the transport of stabilized zerovalent iron nanoparticles in saturated porous media

The transport of stabilized zerovalent iron nanoparticles (nZVI) has recently been the topic of extensive research due to its proven potential as an in situ remediation tool. However, these studies have ignored the effects of biofilms—complex aggregations of bacterial cells and excreted extracellular polymeric substances present in nearly all aquatic systems—on the transport of these particles. This study examines the effects of Pseudomonas aeruginosa (PAO1) biofilm, at a cell concentration similar to that reported for saturated aquifers, on the transport of commercially available, poly (acrylic acid) stabilized nZVI (pnZVI) in 14 cm long columns packed with saturated glass beads at salt concentrations of 1 and 25 mM NaCl. Compared to retention on uncoated columns, in the presence of biofilm the retention of pnZVI increased at higher ionic strength, while ionic strength played no role in retention of these nanoparticles in the absence of biofilm. The Tufenkji-Elimelech correlation equation predicts lower retention of pnZVI on biofilm coated columns compared to uncoated columns due to a lower Hamaker constant, and DLVO energy considerations predict the most favorable attachment to uncoated porous media at higher ionic strength. A steric (polymer-mediated) model that considers the combined influence of steric effects of polymers and DLVO interactions is shown to adequately describe particle retention in columns.     

Biosorption of nanoparticles to heterotrophic wastewater biomass

Sorption to activated sludge is a major removal mechanism for pollutants, including manufactured nanoparticles (NPs), in conventional activated sludge wastewater treatment plants. The objectives of this work were to (1) image sorption of fluorescent NPs to wastewater biomass; (2) quantify and compare biosorption of different types of NPs exposed to wastewater biomass; (3) quantify the effects of natural organic matter (NOM), extracellular polymeric substances (EPS), surfactants, and salt on NP biosorption; and (4) explore how different surface functionalities for fullerenes affect biosorption. Batch sorption isotherm experiments were conducted with activated sludge as sorbent and a total of eight types of NPs as sorbates. Epifluorescence images clearly show the biosorption of fluorescent silica NPs; the greater the concentration of NPs exposed to biomass, the greater the quantity of NPs that biosorb. Furthermore, biosorption removes different types of NPs from water to different extents. Upon exposure to 400 mg/L total suspended solids (TSS) of wastewater biomass, 97% of silver nanoparticles were removed, probably in part by aggregation and sedimentation, whereas biosorption was predominantly responsible for the removal of 88% of aqueous fullerenes, 39% of functionalized silver NPs, 23% of nanoscale titanium dioxide, and 13% of fullerol NPs. Of the NP types investigated, only aq-nC₆₀ showed a change in the degree of removal when the NP suspension was equilibrated with NOM or when EPS was extracted from the biomass. Further study of carbonaceous NPs showed that different surface functionalities affect biosorption. Thus, the production and transformations in NP surface properties will be key factors in determining their fate in the environment.     

A fate and transport model for Asian carp environmental DNA in the Chicago area waterways system

Detection of environmental DNA (eDNA) is widely employed to infer the presence of endangered or invasive species in the aquatic environment. Detection of eDNA, however, does not guarantee the presence of the species in question. The location, time, and nature of the eDNA source are unknown. An eDNA fate and transport model can help to address these unknowns. Construction of such a model requires resolution of multiple issues including: 1) Quantification of eDNA concentration in the environment; 2) Quantification of the eDNA source; 3) Quantification of decay rate; and, 4) Model application and validation. We address these issues and present the results of a fate and transport model for eDNA originating from an invasive species, silver carp (Hypophthalmicthys molitrix), in the Chicago Area Waterways System, USA. Results indicate the presence of roughly 4600?kg of silver carp, distributed along the major axes of the system, is required to produce the eDNA detected in routine monitoring. Positive detection of eDNA in a sample suggests a source within days and km of the sample time and location.     

Impact of environmental conditions on the suitability of microconstituents as markers for determining nutrient loading from reclaimed water

Nitrogen and phosphorous loading into waterways from designated beneficial uses of reclaimed water is a growing concern in many parts of the United States. Numerous studies have documented that organic microconstituents present in the reclaimed water can be utilized as indicators of its influence on surface water bodies. However, little to no information is available on the environmental attenuation of these microconstituents relative to the nutrients, which is a critical component in determining the effectiveness or limitations of those markers as a tool for elucidating their origins. In this study, the stability of selected markers (sucralose, carbamazepine, gadolinium anomaly, iohexol, and atenolol) was evaluated through bench-scale studies designed to simulate environmental conditions associated with biodegradation, adsorption, and photolysis. The primary pathway for nitrogen reduction was biodegradation (greater than 99%) while the highest phosphorous removal was due to adsorption (30–80%). Soils with low organic content were selected for this study. Sucralose was the most recalcitrant microconstituent in the environment with less than 15% removal by adsorption, biodegradation, or photolysis. Iohexol was too susceptible to photolysis (90% removal), and atenolol was susceptible to biodegradation (60–80% removal). Gd anomaly was fairly stable (less than 30% removal) in the environment. Carbamazepine was another efficacious marker for wastewater, but was susceptible (50% removal) to photolysis. Of the selected microconstituents, only atenolol showed any similarity with the attenuation observed for nitrate and none of the microconstituents showed any similarity with the attenuation observed for phosphorus.     

Persistence and degradation of metalaxyl,lindane, fenvalerate and deltamethrin during the wine making process

The persistence and degradation of four acaricides (metalaxyl, lindane, fenvalerate and deltamethrin), used to control pests in vineyards, in experimental must and wine samples, have been studied. Commercial formulations of the pesticides were added to non-settled must and their fate during a common vinification method for white and red wines was investigated. Analytes in the extracts were determined by GC/EIMS after a solid-phase extraction on polymeric cartridges to isolate them from the must and wine samples. It was verified that white wines generally contained higher amounts of residues. Moreover, some degradation products, not reported until now, have been observed in the samples in addition to some compounds – byproducts from the manufacturing and excipients – initially present in the commercial formulations.     

Distribution and fate of nonylphenol in an aquatic microcosm

An aquatic microcosm consisting of four compartments, namely surface microlayer (SM), water sediment and biota (zebra fish), was developed to investigate the distribution and fate of nonylphenol (NP) in an aquatic environment. Level III and level IV fugacity-based multimedia models were used to calculate the distribution and fate of NP. Data obtained from model calculations were in good agreement with those of the experiments. Results of the model calculations showed that 86.50% of all NP input was removed by advective outflow, while 61.99% of the remainder was distributed to the sediment phase, 34.89% to the water phase, 2.50×10⁻²% to SM and 3.13% to the biotic phase. This finding demonstrates that sediment plays a key role in the fate of NP and acts as a sink in the aquatic environment. Bioconcentration factor (BCF) of NP in the zebra fish was high and varied in different parts of the fish. The highest BCF was 1440 in the viscera. After the uptake experiment, depuration of NP in clean water indicated that, the concentration of residue NP in the zebra fish was still high. This implies that NP in fish can pose a potential threat to human health due to its bioaccumulation in the food chain.     

A study on pesticide runoff from paddy fields to a river in rural region--1: field survey of pesticide runoff in the Kozakura River, Japan

Runoff characteristics of nine kinds of herbicides from paddy fields were surveyed in the Kozakura River, that is one of the tributaries flowing into the Lake of Kasumigaura, over a period of 23 April to 30 June (before and after rice transplantation) of year. The flow rates of river water and the concentrations of herbicides in the river water were measured every day in May and every 2 days in April and June at six survey sites along the river. The runoff characteristics of herbicides were elucidated by taking account of the rainfall data, the detailed application data (application date and quantities of herbicides applied to each paddy field in a region), and their physico-chemical properties. The runoff rates (the runoff/application amounts ratio) were calculated for each herbicide, resulting in the range of 8.2-22.4%. The runoff rates were correlated fairly well with octanol-water partition coefficient, logP(ow), rather than with water solubility of herbicides.     

A life cycle methodology for mapping the flows of pollutants in the urban environment

This paper presents an integrated life cycle methodology for mapping the flows of pollutants in the urban environment, following the pollutants from their sources through the environment to receptors. The sources of pollution that can be considered by this methodology include products, processes and human activities. Life cycle assessment (LCA), substance flow analysis (SFA), fate and transport modelling (F&TM) and geographical information systems (GIS) have been used as tools for these purposes. A mathematical framework has been developed to enable linking and integration of LCA and SFA. The main feature of the framework is a distinction between the foreground and background systems, where the foreground system includes pollution sources of primary interest in the urban environment and the background comprises all other supporting activities occurring elsewhere in the life cycle. Applying the foreground–background approach, SFA is used to track specific pollutants in the urban environment (foreground) from different sources. LCA is applied to quantify emissions of a number of different pollutants and their impacts in both the urban (foreground) and in the wider environment (background). Therefore, two “pollution vectors" are generated: one each by LCA and SFA. The former comprises all environmental burdens or impacts generated by a source of interest on a life cycle basis and the latter is defined by the flows of a particular burden (substance or pollutant) generated by different sources in the foreground. The vectors are related to the “unit of analysis" which represents a modified functional unit used in LCA and defines the level of activity of the pollution source of interest. A further methodological development has also included integration of LCA and SFA with F&TM and GIS. A four-step methodology is proposed to enable spatial mapping of pollution from sources through the environment to receptors. The approach involves the use of GIS to map sources of pollution, application of the LCA–SFA approach to define sources of interest and quantify environmental burdens and impacts on a life-cycle basis. This is followed by F&TM to track pollution through the environment and by the quantification of site-specific impacts on human health and the environment. The application of the integrated methodology and the mathematical framework is illustrated by a hypothetical example involving four pollution sources in a city: incineration of MSW, manufacture of PVC, car travel and truck freight.     

Mediation in dyadic data at the level of the dyads: A structural equation modeling approach.

An extended version of the Common Fate Model (CFM) is presented to estimate and test mediation in dyadic data. The model can be used for distinguishable dyad members (e.g., heterosexual couples) or indistinguishable dyad members (e.g., homosexual couples) if (a) the variables measure characteristics of the dyadic relationship or shared external influences that affect both partners; if (b) the causal associations between the variables should be analyzed at the dyadic level; and if (c) the measured variables are reliable indicators of the latent variables. To assess mediation using Structural Equation Modeling, a general three-step procedure is suggested. The first is a selection of a good fitting model, the second a test of the direct effects, and the third a test of the mediating effect by means of bootstrapping. The application of the model along with the procedure for assessing mediation is illustrated using data from 184 couples on marital problems, communication, and marital quality. Differences with the Actor-Partner Interdependence Model and the analysis of longitudinal mediation by using the CFM are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)