检索结果-南通市图书馆

Lead, Zinc and Iron Pollutants Load Assessment in Selected Rivers in Southern Nigeria: Implications for Domestic Uses

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of water resource and Protection 2024年第1期16卷 58-82页

作者： Ochuko Ushurhe Ozabor Famous Ezekiel Ovuokerie Gunn Sapere-Obi Martha Ladebi Department of Environment Management and Toxicology Faculty of Environmental Sciences Dennis Osadebay University Asaba Nigeria Department of Urban and Regional Planning Niger Delta University Wilberforce Island Nigeria Department of Disaster Management School of Built Environment University of Salford Salford UK

The aim of the study is to comparatively assess the concentrations of lead, zinc and iron in Rivers Ase, Warri and Ethiope, in Nigeria. Monthly water samples were collected from six randomly selected sites along the rivers course. 72 water samples were collected from each river at 0 - 15 cm depths. Samples were analysed based on the standard methods recommended by the WHO for testing lead, zinc and iron. The assessment of the water quality was done using the water Quality Index (WQI) of the Canadian Council of Ministers of the Environment (CCME-WQI). While hypotheses were tested using ANOVA. Findings indicated that CCME-WQI values were 47.3, 66.52 and 78.7. This meant that the water quality of River Ase is impaired and departed from desirable levels, while that of Warri and Ethiope were considered to occasionally be impaired and depart from desirable levels. The ANOVA model showed that there is a significant variation in heavy metal load in the selected rivers at P water was put to domestic uses such as drinking (20.5%) preparing food (17.8%), bathing (19.8%), washing clothes and dishes (21.3%), brushing teeth (13.3%), and catering for domestic animals (7.5%). Poverty (49.5%) was the major reason for the use of river water for domestic purposes. The locals highlighted that they usually suffer from cholera (26.8%), diarrhoea (25.8%), dysentery (24%) and typhoid (23.5%) as a result of using the river water. The study recommended routine monitoring of anthropogenic and geologic activities, testing of the water regularly amongst others.

关键词： Assessment water-Quality-Index Domestic Heavy-Metals

Bursting phenomena as well as the bifurcation mechanism in a coupled BVP oscillator with periodic excitation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第7期25卷 151-157页

作者：张晓芳吴磊毕勤胜 faculty of Civil engineering and Mechanics Jiangsu University

We explore the complicated bursting oscillations as well as the mechanism in a high-dimensional dynamical *** introducing a periodically changed electrical power source in a coupled BVP oscillator, a fifth-order vector field with two scales in frequency domain is established when an order gap exists between the natural frequency and the exciting *** the analysis of the generalized autonomous system, bifurcation sets are derived, which divide the parameter space into several regions associated with different types of dynamical behaviors. Two typical cases are focused on as examples,in which different types of bursting oscillations such as sub Hopf/sub Hopf burster, sub Hopf/fold-cycle burster, and doublefold/fold burster can be observed. By employing the transformed phase portraits, the bifurcation mechanism of the bursting oscillations is presented, which reveals that different bifurcations occurring at the transition between the quiescent states（QSs） and the repetitive spiking states（SPs） may result in different forms of bursting oscillations. Furthermore, because of the inertia of the movement, delay may exist between the locations of the bifurcation points on the trajectory and the bifurcation points obtained theoretically.

关键词： coupled BVP oscillator two timescales bursting oscillations bifurcation mechanism

Synergistic effect of a new wedge-bond-type anchor for CFRP tendons

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2015年第6期22卷 2260-2266页

作者：谢桂华刘荣桂陈蓓李明君石天罡 faculty of Civil engineering and Mechanics Jiangsu University

In order to improve the anchoring force of anchors for carbon fiber reinforced polymer(CFRP) tendons further, a new wedge-bond-type anchor for CFRP tendons was developed. The increment in anchoring force induced by the clamping segment of anchor was studied. Taking the deformation of all parts in clamping segment in the transverse direction into consideration, the calculation formula for the increment of anchoring force was proposed based on the linear elastic hypotheses. The proposed model is verified by experiments and conclusions are drawn that the anchoring force is influenced mainly by the inclination angle of clamping pieces, the length of clamping part and the thickness of bonding medium. Especially, the thickness of bonding medium should be lowered in design to improve the synergistic effect of anchors.

关键词：碳纤维复合材料粘结锚固协同效应楔型粘结介质复合材料筋增量计算倾斜角度

Effect of Primary and Eutectic Mg_2Si Crystal Modifications on the Mechanical Properties and Sliding Wear Behaviour of an Al–20Mg_2Si–2Cu–xBi Composite

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2016年第11期32卷 1083-1097页

作者： Saeed Farahany Hamidreza Ghandvar Nur Azmah Nordin Ali Ourdjini Mohd Hasbullah Idris Department of Materials and Mechanical engineering Buein Zahra Technical University Department of Materials Manufacturing and Industrial Engineering Faculty of Mechanical Engineering Universiti Teknologi Malaysia (UTM) Department of Mechanical engineering Faculty of Engineering University of Ottawa

This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg2Si–2Cu in situ composite treated with different Bi contents. The desired modification of primary Mg2 Si particles was achieved with the addition of 0.4 wt% Bi. Increasing Bi beyond 0.4 wt%resulted in a loss of modification, possibly due to the formation of Al8 MgB iS i4 compound before the precipitation of the primary Mg2 Si. Additionally, the structure of the pseudo-eutectic Mg2 Si was transformed from plate to fibrous, which was consistent with decrease of growth temperature extracted from the cooling curve thermal analysis. Addition of Bi had an effect on the morphology of Al5 Fe Si（β）, Al2Cu（θ） and Al5Cu2Mg8Si6（Q） intermetallic compounds. The tensile strength, elongation percentage, impact toughness, and hardness increased by 6%, 13%, 75%, and 23%, respectively, due to modification of both the primary and eutectic Mg2 Si crystals. The tensile and impact fracture surfaces showed fewer decohered particles in the Bi-treated composite. The enhancement in wear resistance of the Bi-treated composite could be attributed to solid lubricant function of insoluble soft Bi phase and modification effects on Mg2 Si particles.

关键词： Al–Mg2Si Composite Modification Bismuth Mechanical properties Wear

Experimental Investigation on the Thermal Properties of Gypsum Plaster-Rice Husk Ash Composite

在线全文

学校读者我要写书评

暂无评论

Open Journal of Composite Materials 2022年第4期12卷 131-138页

作者： Nuhu Caleb Amulah Abubakar Mohammed El-Jummah Abba Alhaji Hammajam Usman Ibrahim Department of Mechanical engineering Faculty of Engineering University of Maiduguri Maiduguri Nigeria Department of Mechanical engineering Faculty of Engineering Nigerian Army University Biu Nigeria Department of Mechanical engineering Faculty of Engineering Ramat Polytechnic Maiduguri Nigeria

This experimental investigation aims at evaluating the thermal properties of rice husk ash (RHA)—filled gypsum plaster composite for potential applications, as insulating materials. The thermal conductivities of composites of gypsum plaster reinforced with RHA at 0%, 10%, 20%, 30%, and 40% volume fractions were determined experimentally using Lee’s disc method. The experimental results show that integrating RHA reduces the thermal conductivity of gypsum plaster and improves its insulation capacity. The results obtained from the experiments were compared with the Rule of Mixture Model, Maxwell Model, and Russell Model. It was observed that the thermal conductivities obtained from experiments and the theoretical models decreased with an increase in the volume fraction of RHA. The errors associated with the models with respect to experimental results are on the average of 28.7% for Mixture Rule, 31.6% for Russel Model, and 18.8% for the Maxwell Model. An agricultural waste like RHA can be beneficially used for the preparation of composites and, due to improved insulation capability, these composites can be used for applications such as insulation boards and sheathing, hardboard, ceilings of roofs, decorations, etc.

关键词： Rice Husk Ash Thermal Conductivity Gypsum Plaster Lee’s Disc Method Agricultural Waste

Computational investigation of powder coating of nanoparticles in supersonic and hypersonic impactors

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2013年第3期11卷 273-281页

作者： Nima Niksefat Mousa Farhadi Kurosh Sedighi Salman Nourouzi faculty of Mechanical engineering Babol University of Technology

In this study, numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics （CFD） software FLUENT. The objective was to investigate the effects of working parameters such as pressure ratio （50 〈 Po]Pb 〈 800）, nozzle diameters （D=0.23, 0.27, 0.45 mm）, nozzle to plate distance （0.5 〈L/D〈 50）, particle diameter （1 nm〈 dp 〈 100 nm ） and angle between two nozzles. A single-phase 3D unsteady-state model was implemented by the software. For this purpose, a user-defined function （UDF） was employed to implement nanoparticles for different assumptions of Cunningham correction factor. An axisymmetric form of the compressible Navier-Stokes and energy equations was used for both fluid flow and temperature; Lagrangian particle trajectory analysis was used for particle motion. Using the variable Cunningham cor- rection factor showed suitable agreement with experimental data in comparison with other methods. Results show that increase of the distance between nozzle and impaction plate causes increase of Mach number, the distance between bow shock and impaction plate, and the collection efficiency. Maximum jet velocity, distance between bow shock and impaction plate and collection efficiency increase by using two nozzles in supersonic and hypersonic imoactors.

关键词： Impactor Supersonic and hypersonic flow Nanoparticles Aerosol Aerodynamics

Performance enhancement of filled-type solar collector with U-tube

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2015年第3期22卷 1124-1131页

作者：梁若冰张吉礼赵亮马良栋 faculty of Infrastructure engineering Dalian University of Technology

In order to increase the efficiency of solar collector, a methodology is proposed based on the analysis of its influencing factors, such as thermal conductivity of filled layer, structure forms of filled layer and heat loss coefficient. The results of analysis show that the heat transfer between pipes in evacuated tube is one of the most important factors, which can lead to the decrease of the outlet temperature of working fluid. In order to eliminate the negative influence of the heat transfer between pipes, the hollow filled-type evacuated tube with U-tube(HUFET) was developed, and the heat transfer characteristics of HUFET were analyzed by theoretical and experimental studies. The results show that the thermal resistances decrease with the increase of the thermal conductivity of filled layer. When the thermal conductivity is over 10 W/(m·K), the change of thermal resistances is very ***, the larger the thermal conductivity of filled layer, the less the rate of the energy transfer between the two pipes to the total energy transfer, which is between the absorber tube and the working fluid. There is a little difference between the efficiencies of HUFET and UFET, with the efficiency of HUFET 2.4% higher than that of UFET. Meanwhile, the validation of the model developed was confirmed by the experiment.

关键词：太阳能收集器 U形管填充型性能改善热传导性工作流体填充层影响因素

Histogram of the node strength and histogram of the edge weight: two new features for RGB-D person re-identification

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2018年第9期61卷 112-125页

作者： Zeynab IMANI Hadi SOLTANIZADEH Electrical and Computer engineering faculty Semnan Univercity

Person re-identification is a classical task for any multi-camera surveillance system. Most of the existing researches on re-identification are based on features extracted from RGB images. However,there are many deficiencies in RGB image processing, some of which are requiring a lot of illumination and high computation. In this paper, novel features are proposed for RGB-D person re-identification. First, the complex network approach in texture recognition is modified and its threshold function is changed for using in depth images extracted by RGB-D sensors. Then, two novel measurements named the histogram of the edge weight(HEW) and the histogram of the node strength(HNS) are introduced on complex *** features fit both single-shot and multi-shot person re-identification. In the single-shot case, the HNS is extracted from only one frame while for the multi-shot case it is extracted from both one frame and multi-frames. These proposed measurements are called histogram of the spatial node strength(HSNS)and histogram of the temporal node strength(HTNS) respectively. Subsequently, these measurements are combined with skeleton features using score-level fusion. The method is evaluated using two benchmark databases and the results show that ours outperforms some state-of-the-art methods.

关键词： complex network edge weight graph node strength person re-identification skeleton features

Dipper Throated Optimization Algorithm for Unconstrained Function and Feature Selection

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2022年第7期72卷 1465-1481页

作者： Ali E.Takieldeen El-Sayed M.El-kenawy Mohammed Hadwan Rokaia M.Zaki faculty of Artificial Intelligence Delta University for Science and TechnologyMansoura35712Egypt Department of Communications and Electronics Delta Higher Institute of Engineering and TechnologyMansoura35111Egypt Department of Information Technology College of ComputerQassim UniversityBuraydah51452Saudi Arabia Department of Computer Science College of Applied SciencesTaiz UniversityTaizYemen Intelligent Analytics Group(IAG) College of ComputerQassim UniversityBuraydahSaudi Arabia Higher Institute of engineering and Technology KafrelsheikhEgypt Department of Electrical engineering Shoubra Faculty of EngineeringBenha UniversityEgypt

Dipper throated optimization(DTO)algorithm is a novel with a very efficient metaheuristic inspired by the dipper throated *** has its unique hunting technique by performing rapid bowing *** show the efficiency of the proposed algorithm,DTO is tested and compared to the algorithms of Particle Swarm Optimization(PSO),Whale Optimization Algorithm(WOA),Grey Wolf Optimizer(GWO),and Genetic Algorithm(GA)based on the seven unimodal benchmark ***,ANOVA and Wilcoxon rank-sum tests are performed to confirm the effectiveness of the DTO compared to other optimization ***,to demonstrate the proposed algorithm’s suitability for solving complex realworld issues,DTO is used to solve the feature selection *** strategy of using DTOs as feature selection is evaluated using commonly used data sets from the University of California at Irvine(UCI)*** findings indicate that the DTO outperforms all other algorithms in addressing feature selection issues,demonstrating the proposed algorithm’s capabilities to solve complex real-world situations.

关键词： Metaheuristic optimization swarmoptimization feature selection function optimization