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Sulfide elimination by intermittent nitrate dosing in sewer sediments

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Journal of Environmental Sciences 2015年第1期27卷 259-265页

作者： Yanchen Liu Chen Wu Xiaohong zhou David z.zhu Hanchang Shi School of Environment Tsinghua University Department of Civil and Environmental Engineering University of Alberta

The formation of hydrogen sulfide in biofilms and sediments in sewer systems can cause severe pipe corrosions and health hazards, and requires expensive programs for its prevention. The aim of this study is to propose a new control strategy and the optimal condition for sulfide elimination by intermittent nitrate dosing in sewer sediments. The study was carried out based on lab-scale experiments and batch tests using real sewer sediments. The intermittent nitrate dosing mode and the optimal control condition were investigated. The results indicated that the sulfide-intermittent-elimination strategy by nitrate dosing is advantageous for controlling sulfide accumulation in sewer sediment. The oxidation–reduction potential is a sensitive indicator parameter that can reflect the control effect and the minimum N/S（nitrate/sulfide）ratio with slight excess nitrate is necessary for optimal conditions of efficient sulfide control with lower carbon source loss. The optimal control condition is feasible for the sulfide elimination in sewer systems.

关键词： Sewer system Sulfide elimination Sediment Optimal condition Intermittent nitrate dosing

Simulation of open channel flows by an explicit incompressible mesh-free method

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Journal of Hydrodynamics 2023年第2期35卷 287-298页

作者： zhi-jian Huang Ti-bing Xu David z.zhu Song-da zhang School of Civil and Environmental Engineering and Geography Science Ningbo UniversityNingbo315211China Department of Civil and Environmental Engineering University of AlbertaAlbertaCanada Ningbo River Management Center Ningbo315303China

In this study,to simulate open channel flows,an explicit incompressible mesh-free method is employed in which the pressure field is obtained by explicitly solving the pressure Poisson *** capture the velocity information in open channel flows,the source term in the pressure Poisson equation is modified while the spatial discretization of gradient and Laplacian models is based on the moving particle semi-implicit(MPS)*** inflow boundary condition is treated by injecting fluid particles into the domain according to the inlet discharge,and the outflow condition is handled by prescribing the pressure distribution and removing the fluid particles beyond the *** explicit incompressible mesh-free method is then used to simulate open channel flows,including weir flow,hydraulic jump,and flow over an *** the simulations,velocity distribution and flow pattern are *** simulated results are compared to available experimental measurements and other numerical *** is a good agreement between the simulated results and the experimental *** shows that the explicit incompressible mesh-free method can reproduce the flow characteristics in the open channel flows.

关键词： Mesh-free method explicit scheme weir flow hydraulic jump velocity distribution

Two-dimensional pipe leakage through a line crack in water distribution systems

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Journal of zhejiang University-Science A(Applied Physics & Engineering) 2013年第5期14卷 371-376页

作者： Shuai GUO Tu-qiao zHANG Wei-yun SHAO David z.zhu Yuan-yu DUAN College of Civil Engineering and Architecture Zhejiang University Deptment of Civil and Environmental Engineering University of AlbertaEdmontonABT6G 2W2Canada

In water distribution systems,water leakage from cracked water pipes is a major concern for water ***,the relationship between the leakage rate and the water pressure can be modeled by a power function developed from the orifice *** paper presents an approximate solution for the computation of the steady-state leakage rate through a longitudinal line crack of a water distribution pipe considering the surrounding soil *** derived solution agrees well with results of numerical *** with the traditional models,the new solution allows assessment of all the parameters that related with leakage including the pressure head inside the pipe,hydraulic conductivity,crack size and its position,and pipe size and its depth.

关键词： Leakage Pipe crack Soil Water distribution systems Water pipes

Air entrainment in a vertical dropshaft with limited air supply

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Theoretical & Applied Mechanics Letters 2018年第5期8卷 315-319,362页

作者： Qiang Ding Yiyi Ma David z.zhu Department of Civil Engineering Zhejiang University Department of Civil and Environmental Engineering University of Alberta

Dropshafts are vertical structures widely used in urban drainage systems and buildings for water *** this paper,a physical model study was conducted to investigate the air entrainment in the dropshaft under various flow regimes with and without air *** from the experiments,the air entrainment mechanisms varied with the water flow regimes in the *** there was no water plug formed in the dropshaft,air could be supplied directly from *** the water plug was formed,while without venting,the air was replenished only from downstream intermittently and then in the form of large air bubble traveling upwards to the airspace at the top;while with venting,air was mainly replenished from the dropshaft top and no large air bubble was *** experimental results also showed that the amount of entrained air in the dropshaft with venting was greater than that without venting.

关键词： Air entrainment Air supply Bubble Flow regime Dropshaft

High mechanical strengths and ductility of stainless steel 304L fabricated using selective laser melting

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Journal of Materials Science & Technology 2019年第2期35卷 388-394页

作者： Q.B.Nguyen z.zhu F.L.Ng B.W.Chua S.M.L.Nai J.Wei Singapore Institute of Manufacturing Technology Institute of Research and Development Duy Tan University

Achieving not only high mechanical strengths but also high ductility is recently established using an additive manufacturing technique called selective laser melting. In the present study, stainless steel 304 L fully dense samples were successfully printed using the 3 D systems – ProX 300 printing machine. The ductility and tensile yield strength were almost two and three times higher compared to those of ASTM cast's alloy. Honey comb like nano-cellular structure with different orientation was observed in the fine grains(~4μm) due to fast cooling rate. In addition, the formation of martensite phase in random grains is also a contributor to the strengths. Furthermore, negative residual stresses in the build and horizontal directions were detected and assisted further increase in the tensile strength. Fractography revealed the ductile feature of plastic deformation and the crack openings at unmelted particles or pores.

关键词： Additive manufacturing Stainless steel Powder Selective laser melting

Observations on sand jets in viscoplastic fluids

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Theoretical & Applied Mechanics Letters 2012年第5期2卷 23-28页

作者： David z.zhu N.Rajaratnam Deptartment of Civil and Environmental Engineering University of Alberta

Sand jet in non-Newtonian viscoplastic fluid is associated with a number of industrial and engineering applications, including sand capping for the reclamation of oilsands railings ponds and sediment deposition into soft mud. In this study, several experiments were carried out by depositing circular sand jets vertically into viscoplastic fluids, known as Laponite gel. The deformation regimes of sand jets in the gel were investigated. The yield-gravity parameter of the deformed sand drop in the gel was computed.

关键词： non-Newtonian fluid viscoplastic fluid granular flow sand jet

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地下水渗入排污管道的定量方法

中国给水排水 2013年第4期29卷 21-25页

作者：郭帅张土乔 David z.zhu 浙江大学建筑工程学院浙江杭州310058 加拿大阿尔伯特大学土木与环境工程系

在排污管道系统中,地下水的渗入是个普遍问题。随着管材的老化,地下水可通过破损的管壁或接口处渗入管中,渗入的地下水会给环境带来危害并造成经济损失,是一个值得关注的重要问题。为了评估地下水渗入量,发达国家的学者发展并提出了三... 详细信息

在排污管道系统中,地下水的渗入是个普遍问题。随着管材的老化,地下水可通过破损的管壁或接口处渗入管中,渗入的地下水会给环境带来危害并造成经济损失,是一个值得关注的重要问题。为了评估地下水渗入量,发达国家的学者发展并提出了三种定量方法:水量平衡法,同位素示踪法以及污染物负荷法,其中水量平衡法是传统的方法,而后两种方法是近几年提出的新方法。详细介绍了三种方法的原理和特点,通过对比发现:传统的水量平衡法精度低,误差大,但可实施性强,费用低;同位素示踪法精度高,误差小,但对区域水文条件有特定要求,且评估费用高。经综合比较分析后认为,污染物负荷法将是一种有希望得到普遍应用的方法。

关键词：地下水渗入量排污管道

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Editorial

Science China(Information Sciences) 2017年第6期60卷 5-5页

作者： zhongliang JING Bin XU Fuchun SUN George z.zhu Shanghai Jiao Tong University Northwestern Polytechnical University Tsinghua University York University

To improve capabilities for space exploration,it is important to develop on-orbit *** challenges,such as capturing a tumbling satellite and operating in a confined space,complicate the servicing of non-cooperative *** consideration of the challenge,to perform complicated tasks in space,novel mechanisms for applications are in great ***,as mechanisms become more complicated,control technology should be investigated *** question of how to ensure

关键词： flexible link Editorial

Optimization of ultrasonic parameters for effective detachment of biofilm cells in an actual drinking water distribution system

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Journal of zhejiang University-Science A(Applied Physics & Engineering) 2020年第3期21卷 167-178页

作者： Hong-xi PENG Yu SHAO Yi-fu zHANG Ruo-wei WANG David z.zhu Huan-yu CHEN Jing-qing LIU College of Civil Engineering and Architecture Zhejiang UniversityHangzhou 310058China College of Civil Engineering Hunan UniversityChangsha 410082China Civil and Environmental Engineering Department University of AlbertaAlberta T6G 2R3Canada Binhai Industrial Technology Research Institute of zhejiang University Tianjin 300301China

It is important to obtain a considerable quantity of DNA from oligotrophic environments such as a drinking water distribution system(DWDS)to study microbial communities by molecular biotechnology,and DNA yield is always one of the biggest problems when performing metagenomic sequencing on drinking water *** obtain as many microbes as possible,ultrasound has been widely used in cell detachment,but studies on the optimal ultrasonic parameters for biofilm in DWDS have rarely been *** effects of three ultrasonic parameters,including power,duration,and the number of ultrasound treatments(USTs)on the selected monoculture bacteria(Pelomonas sp.)biofilm were studied *** the optimal values of each ultrasonic parameter were initially *** on these values,three levels of each ultrasonic parameter were selected,and then an orthogonal experiment was conducted to further study drinking water biofilm,and finally the optimal ultrasonic parameters for the effective separation of biofilm cells in DWDS were *** results showed that the optimal ultrasonic power,duration,and the number of USTs are 13 W,1 min,and 15,respectively.A 20-min interval is needed between two *** present optimal UST,which does not lose DNA quality,can increase the amount of extractable DNA by at least 4.78 times compared to samples without *** study provides a pretreatment methodology for extracting more and reliable DNA from biofilm in DWDS,and can better solve the problem of DNA collection in oligotrophic environments.

关键词： Biofilm Drinking water distribution system(DWDS) DNA yield DNA quality Ultrasound treatment(UST)