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Assessment of Environmental Sources, Levels and Distribution of Polycyclic Aromatic Hydrocarbons within Nzoia Catchment Area in Kenya

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Journal of Environmental Protection 2019年第6期10卷 772-790页

作者： Agripina Shitandayi Francis Orata fred lisouza Department of Pure and Applied Chemistry Masinde Muliro University of Science and Technology Kakamega Kenya Centre of Excellence in Water Resource Management (CEWARM) Masinde Muliro University of Science and Technology Kakamega Kenya

Continuous concerns about Polycyclic Aromatic Hydrocarbons (PAHs) presence in the environment have raised concern because of their toxic effects to various organisms. Sugarcane farming and cane processing industries are major economic activities within River Nzoia catchment area in Kenya. For instance, the sugar industries produce wastes and by products which can cause PAHs emission and environmental contamination in addition to activities related to rapid urbanization that is being observed within the catchment. This study presents a report on sources and distribution of PAHs levels in sugarcane by products waste, sediments, water and soils within the River Nzoia catchment area. Soil and sediment samples were extracted by soxhlet extraction using dichloro-methane and with C-18 catridges. Analyte separation and identification was done by GC-MS. Fourteen PAHs were detected with concentration ranges of;0.6 μg/L - 80 μg/L for water, 0.01 μg/kg - 1200 μg/kg for soils and 0.13 μg/kg - 19.6 μg/kg for sediments. Bagasse waste had PAHs concentrations in the range of 0.4 - 14 μg/kg, and filter cake in the range of 1.7 - 30 μg/kg. Boiler waters reported the presence of 8 PAHs. The ratio of concentrations of PAHs in boiler water, filter cake and bagasse waste to the soils and water samples within the vicinity to the sugar processing companies did not indicate a point source of contamination;rather it pointed to diffuse sources. The same results were observed for water and sediment samples obtained in the vicinity of waste dumpsite. Variation of PAHs concentrations from sugar manufacturing processes corresponded to the kind and conditions of the processes. Lower molecular weight PAHs dominated in water sample. The presense of benz: 1) pyrene, benz 2) flourancene and Indeno(123,cd)pyrene in both water and sludge soils are of concern since this water is abstracted for domestic use, while sludge soil is used as fertilizer in agricultural farms. Although the levels of PAHs obtained

关键词： Polycyclic Aromatic Hydrocarbons Sugarcane by Products Sources and Distribution Waste Disposal

General Compartmental Epidemic Models

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Chinese Annals of Mathematics,Series B 2010年第3期31卷 289-304页

作者： fred BRAUER Department of Mathematics University of British Columbia

The age of infection approach introduced by Kermack and Mckendrick in 1927 gives a unified way of describing and analyzing a variety of epidemic models, including models with multiple stages, treatment, and heterogeneous mixing. The author gives a description of the main results for such models, emphasizing the use of the final size relation to estimate the size of the epidemic.

关键词： Epidemic models Treatment models Basic reproduction number Final size relation

Focal distance tabu search

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Science China(Information Sciences) 2021年第5期64卷 5-16页

作者： fred GLOVER Zhipeng Lü Meta-Analytics Inc. School of Computer Science and Technology Huazhong University of Science and Technology

Focal distance tabu search modifies a standard tabu search algorithm for binary optimization by augmenting a periodic diversification step that drives the search away from a current best(or elite) solution until the objective function deteriorates beyond a specified threshold or until attaining a lower bound on the distance from the originating solution. The new augmented algorithm combines the threshold and lower bound approaches by introducing an initial focal distance for the lower bound which is updated when the diversification step is completed. However, rather than terminating the diversification step at the customary completion point, focal distance tabu search(TS) retains the focal distance bound through additional search phases designed to improve the objective function, drawing on a strategy proposed with strategic *** algorithm realizes this strategy by partitioning the variables into two sets which are managed together with an abbreviated tabu search process. An advanced version of the approach drives the search away from a collection of solutions rather than a single originating solution, introducing the concept of a signature solution to guide the search. The method can be employed to augment a variety of other metaheuristic algorithms such as those using threshold procedures, late acceptance hill climbing, iterated local search, breakout local search, GRASP, and path relinking.

关键词： tabu search diversification strategic oscillation adaptive partitioning metaheuristics

CREATING BALANCED AND CONNECTED CLUSTERS TO IMPROVE SERVICE DELIVERY ROUTES IN LOGISTICS PLANNING

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Journal of Systems Science and Systems Engineering 2010年第4期19卷 453-480页

作者： Buyang CAO fred GLOVER Esri Inc. 380 New York Street CA 92373 USA OptTek Systems Inc. 2241 17th Street Boulder CO 80302 USA

A challenging problem in real world logistics applications consists in planning service territories for customer deliveries, in contexts where customers must be clustered into groups that satisfy various conditions such as balance and connectivity. In this paper we propose new algorithms for producing such clusters based upon special procedures for exploiting Thiessen polygons. Our methods are able to handle multiple criteria for balancing the clusters, such as the number of customers in each cluster, the service revenue in each cluster, or the delivery/pickup quantity in each cluster. Computational results demonstrate the efficacy of our new procedures, which are able to assist users to plan service personal service territories and vehicle routes more efficiently.

关键词： Clustering K-means logistics routing Thiessen polygon

Benefits of High-voltage SiC-based Power Electronics in Medium-voltage Power-distribution Grids

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Chinese Journal of Electrical Engineering 2021年第1期7卷 1-26页

作者： fred Wang Shiqi Ji Department of Electrical Engineering and Computer Science The University of TennesseeTN 37996USA Oak Ridge National Lab Oak RidgeTN 37830USA Department of Electrical Engineering Tsinghua UniversityBeijing 100084China

Medium-voltage(MV)power electronics equipment has been increasingly applied m distnbution grids,and high-voltage(HV)silicon carbide(SiC)power semiconductors have attracted considerable attention in recent *** paper first overviews the development and status of HV SiC power ***,MV power-converter applications in distribution grids are summarized and the benefits of HV SiC in these applications are ***,including conventional and asynchronous microgrids,that can fully demonstrate the benefits of HV SiC power semiconductors are selected to investigate the benefits of HV SiC in detail,including converter-level benefits and system-level ***,an asynchronous microgrid power-conditioning system(PCS)prototype using a 10 kV SiC MOSFET is presented.

关键词： Silicon carbide power semiconductor distribution grid asynchronous microgrid power-conditioning system

Universal optimality of digital nets and lattice designs

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Science China Mathematics 2009年第11期52卷 2309-2320页

作者： HICKERNELL fred J Department of Applied Mathematics Illinois Institute of Technology

This article considers universal optimality of digital nets and lattice designs in a regression model. Based on the equivalence theorem for matrix means and majorization theory,the necessary and sufficient conditions for lattice designs being φp-and universally optimal in trigonometric function and Chebyshev polynomial regression models are obtained. It is shown that digital nets are universally optimal for both complete and incomplete Walsh function regression models under some specified conditions,and are also universally optimal for complete Haar wavelet regression models but may not for incomplete Haar wavelet regression models.

关键词： Chebyshev polynomial Haar wavelet Trigonometric function Walsh function 62K15 62K10

A methodology for simulating 2D shock-induced dynamic stall at flight test-based fluctuating freestream

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Chinese Journal of Aeronautics 2019年第10期32卷 2223-2238页

作者： Khider AL-JABURI Daniel FESZTY fred NITZSCHE Department of Mechanical and Aerospace Engineering Carleton University

A comprehensive methodology for simulating 2 D dynamic stall at fluctuating freestream is proposed in this paper.2 D CFD simulation of a SC1095 airfoil exposed to a fluctuating freestream of Mach number 0.537±0.205 and Reynolds number 6.1×10~6(based on the mean Mach number)and undergoing a 10°±10°pitch oscillation with a frequency of 4.25 Hz was *** conditions were selected to be representative of the flow experienced by a helicopter rotor airfoil section in a real-life fast forward *** constant freestream dynamic stall as well as fluctuating freestream dynamic stall simulations were conducted and *** methodology was carefully validated with experimental data for both transonic flow and dynamic stall under fluctuating ***,the results suggest that the fluctuating freestream alters the dynamic stall mechanism documented for constant freestream in a major way,emphasizing that inclusion of this effect in the prediction of dynamic stall related rotor loads is imperative for rotor performance analysis and blades design.

关键词： Mach fluctuation Pitching airfoil Shock-induced dynamic stall Transonic flow Unsteady freestream velocity

The Challenges of Multidisciplinary Education in Computer Science

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Journal of Computer Science & Technology 2011年第4期26卷 636-642页

作者： fred S.Roberts DIMACS Center Rutgers UniversityJerseyNew BrunswickNJU.S.A.

Some of the most important problems facing the United States and China, indeed facing our entire planet, require approaches that are fundamentally multidisciplinary in nature. Many of those require skills in computer science （CS）, basic understanding of another discipline, and the ability to apply the skills in one discipline to the problems of another. Modern training in computer science needs to prepare students to work in other disciplines or to work on multidisciplinary problems. What do we do to prepare them for a multidisciplinary world when there are already too many things we want to teach them about computer science？ This paper describes successful examples of multidisciplinary education at the interface between CS and the biological sciences, as well as other examples involving CS and security, CS and sustainability, and CS and the social and economic sciences. It then discusses general principles for multidisciplinary education of computer scientists.

关键词： multidisciplinary biology sustainability security social sciences economics education

Adsorption mechanisms of PFOA onto activated carbon anchored with quaternary ammonium/epoxide-forming compounds: A combination of experiment and model studies

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Journal of Environmental Sciences 2020年第12期32卷 94-102页

作者： Chen Yuan Yang Huang fred SCannon Zhiwei Zhao Shenzhen Academy of Environmental Science Shenzhen 518001China College of Urban Construction and Environmental Engineering Chongqing UniversityChongqing 400045China Department of Civil and Environmental Engineering Pennsylvania State UniversityUniversity ParkPA 16802USA College of Resources and Environment Chengdu University of Information TechnologyChengdu 610225China

When wood-based activated carbon was tailored with quaternary ammonium/epoxide(QAE) forming compounds(QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid(PFOA) from groundwater. With favorable tailoring, QAE-AC removed PFOA from groundwater for 118,000 bed volumes before halfbreakthrough in rapid small scale column tests, while the influent PFOA concentration was 200 ng/L. The tailoring involved pre-dosing QAE at an array of proportions onto this carbon, and then monitoring bed life for PFOA removal. When pre-dosing with 1 mL QAE, this PFOA bed life reached an interim peak, whereas bed life was less following 3 mL QAE pre-dosing, then PFOA bed life exhibited a steady rise for yet subsequently higher QAE pre-dosing levels. Large-scale atomistic modelling was used herein to provide new insight into the mechanism of PFOA removal by QAE-AC. Based on experimental results and modelling, the authors perceived that the QAE's epoxide functionalities cross-linked with phenolics that were present along the activated carbon's graphene edge sites, in a manner that created mesopores within macroporous regions or created micropores within mesopores regions. Also, the QAE could react with hydroxyls outside of these pore, including the hydroxyls of both graphene edge sites and other QAE molecules. This latter reaction formed new pore-like structures that were external to the activated carbon grains. Adsorption of PFOA could occur via either charge balance between negatively charged PFOA with positively charged QAE, or by van der Waals forces between PFOA's fluoro-carbon tail and the graphene or QAE carbon surfaces.

关键词： Perfluorooctanoic acid Nitrate Carbon Atomistic model Adsorption mechanism