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A techno-economic analysis of aquaculture business in Ogun State,Nigeria

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Chinese Journal of Oceanology and Limnology 2009年第2期27卷 415-420页

作者： R. O. KAREEM S. B. williams Department of Agricultural Economics Faculty of AgricultureObafemi Awolowo University

Fish supplies 25% of the total protein source in developing countries. A techno-economic analysis was performed for developing a good business proposal for aquaculture loans to enhance aquaculture development in Nigeria. A case study of catfish Clarias gariepinus framing was conducted in Abeokuta North Local Government of Ogun State, Nigeria. The results show that the fixed cost is N18 338 per year, and the variable cost is N459 700 per year, accounting for the largest amount of the total; therefore, a profit of N43 289 per month can be made. Sensitivity analysis was performed to assess any risk(s) that associated with unfavorable changes in government policy with particular reference to monetary policy. Positive net present value shows that the investment in fish farm is economically feasible and the net investment ratio is 3.52. Also, the benefit-cost ratio is 2.17. The internal rate of return (IRR) is 21% showing that the enterprise is able to offset the interest being charged on the loan. It is therefore worthwhile to invest into fish farm business in the study area. The study suggests that to better sustain the local aquaculture business, the government should create a good conducive environment to foster development of the fish farming. Government intervention is urgently needed to solve problems such as in traditional land tenure, grant credit facilities and subsidies, to enhance the aquacultural development in the country.

关键词： aquaculture net present value B-C ratio net-investment-ratio internal rate of return

Robust H_∞ control for aseismic structures with uncertainties in model parameters

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Earthquake Engineering and Engineering Vibration 2007年第4期6卷 409-416页

作者：宋刚林家浩赵岩 W. Paul Howson Fred W williams State Key Laboratory of Structural Analysis for Industrial Equipment Faculty of Vehicle Engineering and Mechanics Dalian University of Technology Cardiff School of Engineering Cardiff University Cardiff CF24 3AA Wales U.K.

This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LM1 toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 E1 Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters.

关键词： structural control robust H∞ control linear matrix inequality dynamic output feedback parameter uncertainty seismic excitation

A qualitative study on the pulsatile flow phenomenon in a dense fly ash pneumatic conveyor

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Particuology 2014年第6期12卷 81-91页

作者： Wei Chen Kenneth C.williams Isabel Jabs Mark G.Jones Centre for Bulk Solids and Particulate Technologies Newcastle Institute for Energy and ResourcesThe University of Newcastle Faculty of Mechanical Engineering Leibniz University of Hanover

Understanding of the dynamic particulate flow structures within a dense gas-fly ash pneumatic conveyor must be improved in order to better aid its design *** complex pulsatile movement of the gas-fly ash mixture dominates the flow performance within the pipeline,and historically,non-invasive measurement devices such as the electrical capacitance tomography（ECT） were often used to sufficiently capture the flow ***,inadequate studies have been conducted on the pulsatile flow phenomenon,which directly relate to the gas-fly ash two-phase flow *** paper aims to investigate the pulsatile flows using an ECT ***,pulsatile flow patterns under various experimental conditions were obtained through *** within a flow were then characterised into pulse growth and decay segments,which represent the superficial fluidisation and deaeration processes during ***,structural and statistical analyses were performed on the pulse growth and decay *** suggested that the increasing air mass flow rate led to the decrease of the superficial fluidisation/deaeration magnitude,however,the increase of the superficial fluidisation/deaeration ***,the air mass flow rate was indicated as the dominant factor in determining the pulsing statistical *** research provides fundamental insights for further modelling the dense fly ash pneumatic flows.

关键词： Pneumatic conveying Electrical capacitance tomography Fly ash Pulsatile flows Flow pattern analysis

Microbial mediated arsenic biotransformation in wetlands

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Frontiers of Environmental Science & Engineering 2017年第1期11卷 5-15页

作者： Si-Yu Zhang Paul N. williams Jinming Luo Yong-Guan Zhu State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Beijing Normal University Beijing 100875 China Institute for Global Food Security School of Biological Sciences Queen's University Belfast Belfast BT9 7BN UK Key Laboratory of Drinking Water Science and Technology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China Key Laboratory of Urban Environment and Health Institute of Urban Environment Chinese Academy of Sciences Xiamen 361021 China

Arsenic （As） is a pervasive environmental toxin and carcinogenic metalloid. It ranks at the top of the US priority List of Hazardous Substances and causes worldwide human health problems. Wetlands, including natural and artificial ecosystems （i.e. paddy soils） are highly susceptible to As enrichment; acting not only as repositories for water but a host of other elemental/chemical moieties. While macroscale processes （physical and geological） supply As to wetlands, it is the micro-scale biogeochemistry that regulates the fluxes of As and other trace elements from the semi-terrestrial to neighboring plant/ aquatic/atmospheric compartments. Among these fine-scale events, microbial mediated As biotransformations contribute most to the element＇s changing forms, acting as the ＇switch＇ in defining a wetland as either a source or sink of As. Much of our understanding of these important microbial catalyzed reactions follows relatively recent scientific discoveries. Here we document some of these key advances, with focuses on the implications that wetlands and their microbial mediated transformation pathways have on the global As cycle, the chemistries of microbial mediated As oxidation, reduction and methylation, and future research priorities areas.

关键词： Arsenic Wetland Microbes Switch

Decomposition of biomass gasification tar model compounds over waste tire pyrolysis char

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Waste Disposal and Sustainable Energy 2022年第2期4卷 75-89页

作者： Amal S.Al-Rahbi Paul T.williams Present address:Applied Sciences Department Higher College of TechnologyUniversity of Technology and Applied SciencesMuscatSultanate of Oman School of Chemical and Process Engineering University of LeedsLeedsLS29JTUK

Gasification of biomass produces a syngas containing trace amounts of viscous hydrocarbon tar,which causes serious problems in downstream pipelines,valves and processing *** study focuses on the use of tire-derived pyrolysis char for tar conversion using biomass tar model compounds representative of *** catalytic decomposition of tar model compounds,including methylnaphthalene,furfural,phenol,and toluene,over tire char was investigated using a fixed bed reactor at a bed temperature of 700℃and 60 min time on *** influence of temperature,reaction time,porous texture,and acidity of the tire char was investigated with the use of methylnaphthalene as the tar model *** tar model compounds were found to have higher conversion than those containing a single or multi-aromatic *** reactivity of tar compounds followed the order of furfural>phenol>toluene>*** conversion of the model compounds in the presence of the tire char was much higher than tar thermal *** production increased dramatically with the introduction of tire *** H_(2)potential for the studied tar model compounds was found to be in the range of 40%–50%.The activity of tire char for naphthalene removal was compared with two commercial activated carbons possessing a very well-developed porous *** results suggest that the influence of Brunauer-Emmett-Teller surface area of the carbon on tar cracking is negligible compared with the mineral content in the carbon samples.

关键词： Biomass Gasification Syngas Tar Tire Char

Paleoenvironments and geochemistry across a continuous Permian-Triassic boundary section at Bukk Mountains,Hungary

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Geoscience Frontiers 2021年第3期12卷 214-233页

作者： M.E.Brookfield J.C.williams A.G.Stebbins School for the Environment University of MassachusettsBostonMA 02125USA School of Earth Sciencec The Ohio State UniversityColumbusOH 43210USA

The Bálvány North Permian-Triassic boundary sediments were deposited on a carbonate platform in the tropical part of the western Paleo Tethys *** overall elemental geochemistry of the detailed two-metre-thick section across the boundary that we studied shows that the clastic content of the sediments came from dominantly silica-rich continental sources though with some more silica-poor inputs in the uppermost Permian and lowest Triassic limestones as shown by Ni/Al and Nb/Ta *** inputs bracket,but do not coincide with,the main extinctions and associated C,O and S *** aridity at the Permian-Triassic boundary with increased wind abrasion of suitable Ti-bearing heavy minerals accounts for both the high Ti/Al and Ti/Zr *** geochemical redox proxies suggest mainly oxic depositional conditions,with episodes of anoxia,but with little systematic variation across the Permian-Triassic extinction *** lack of consistent element geochemical changes across the Permian-Triassic boundary occur not only in adjacent shallower-water marine sections,and in other marine sections along the SW Tethys margin such as the Salt Range sections in Pakistan,but also in deeper shelf and oceanic sections,and in non-marine African and European continental *** the absence of significant changes in physical environments,chemical changes in the atmosphere and oceans,reflected in various isotopic changes,drove the Permian-Triassic extinctions.

关键词： Permian-Triassic boundary Paleoenvironments geochemistry Hungary Bukk

Signalization options to improve capacity and delay at roundabouts through microsimulation approach:A case study on arterial roadways in Ghana

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Journal of Traffic and Transportation Engineering(English Edition) 2021年第1期8卷 70-82页

作者： Kwame Kwakwa Osei Charles Anum Adams williams Ackaah Yolanda Oliver-Commey Regional Transport Research and Education Centre Kumasi(TRECK)Department of Civil EngineeringKwame Nkrumah University of Science and TechnologyKumasiGhana Building and Road Research Institute of the Council for Scientific and Industrial Research(CSIR-BRRI) KumasiGhana Pennoni Associates Inc. PhiladelphiaPA 19103USA

Roundabouts are very useful when flows are balanced but can have operational challenges when flows *** roundabouts on arterial roadways in Ghana experience recurring congestion during peak *** four roundabouts between Ejisu Municipality and Asokwa Municipality on the N6 highway are typical of the situation found on arterials *** experience recurring long queues and delays during the peak hours and over-representation of truck rollover *** Ghana,historically,most roundabouts with capacity problems have been developed into interchanges at very high cost without consideration of other effective at-grade *** roundabouts are signalized,various configurations can be explored to enhance capacity while preserving the safety *** simulation techniques,various configurations and design options were tested for their effectiveness at two of the roundabouts,located at KNUST police station and Ejisu,with similar demand and high left turning *** objectives of this study were to a)evaluate the performance of the selected roundabouts on the corridor;b)explore alternative intersection configurations to improve capacity and *** video data collection techniques,2-h time stamped footages of AM and PM peak traffic flows were captured for two *** design parameters of the existing roundabouts,queue lengths,travel times,and approach flows were also *** models of the selected roundabouts were developed and calibrated for the baseline *** unconventional roundabout configuration,with a phase for major road through traffic were simulated and assessed for capacity,delay and queue *** results showed that signalized roundabout intersections effectively increased capacity by as much as 50%in some cases,reduced delay and queue length significantly,and maintained the benefits of roundabouts including *** performance could be further enhanced by introducing separate

关键词： Transportation Signal strategy Roundabout Road safety VISSIM microsimulation Congestion

Photonic elementary cellular automata for simulation of complex phenomena

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Light(Science & Applications) 2023年第7期12卷 1309-1317页

作者： Gordon H.Y.Li Christian R.Leefmans James williams Alireza Marandi Department of Applied Physics California Institute of TechnologyPasadenaCA91125USA Department of Electrical Engineering California Institute of TechnologyPasadenaCA91125USA

Cellular automata are a class of computational models based on simple rules and algorithms that can simulate a wide range of complex ***,when using conventional computers,these'simple'rules are only encapsulated at the level of *** can be taken one step further by simplifying the underlying physical ***,we propose and implement a simple photonic hardware platform for simulating complex phenomena based on cellular *** this special-purpose computer,we experimentally demonstrate complex phenomena,including fractals,chaos,and solitons,which are typically associated with much more complex physical *** flexibility and programmability of our photonic computer present new opportunities to simulate and harness complexity for effcient,robust,and decentralized information processing using light.

关键词： hardware computer automata

Is Magnetic Flux a Valuable Tool for the Analysis of Electrophotographic-Printed Documents?

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Journal of Forensic Science and Medicine 2018年第4期4卷 197-202页

作者： williams David Mazzella Bing Li Ecole des Sciences Criminelles Faculty of LawCriminal Justice and Public AdministrationUniversity de LausanneLausanneSwitzerland Key Laboratory of Evidence Law and Forensic Science Ministry of EducationInstitute of Evidence Law and Forensic ScienceChina University of Political Science and LawBeijingChina

The goal of this preliminary study was to evaluate the potential application of magnetic flux for document *** this investigation,we examined the homogeneity of magnetic flux over the entire page of sample documents a... 详细信息

关键词： Black toner electrophotographic printing system magnetic flux magnetism