Flow of a micropolar fluid in a micro-channel under the action of an alternating electric field: Estimates of flow in bio-fluidic devices

The paper is devoted to a study of the electro-osmotic flow of a micropolar bio-fluid, when the flow takes place between two plates that are in a state of periodic vibrations. Considering blood as a micropolar fluid, it is found that the amplitude of oscillation of the microparticles of blood increases when the micropolar effect is pronounced more and more and that a rise in DebyeHückel parameter enhances both the velocity and microrotation gradient. The results provide guidelines for the improvement of design of bio-sensing and micro-fluidic devices. The study leads to the conclusion that electrical double layers formed in the vicinity of the wall can significantly alter the flow dynamics of physiological fluids in micro-bio-fluidic devices.     

Application of Froude dynamic similitude in anaerobic baffled reactors to prediction of hydrodynamic characteristics of a prototype reactor using a model reactor

An anaerobic baffled reactor is a system developed in recent decades and has been used as part of the treatment of high-strength wastewater. Since the function of this system is based on its hydrodynamic features, hydrodynamics and the regime of the flow through the reactor are crucial. In this study, a prototype reactor with eight chambers, which had a total volume of 48 L, and a model reactor, whose dimensions were half of those of the prototype reactor, were used. The Froude dynamic similitude in these reactors was investigated. The results show that the curve dimensionless variances were 0.089 and 0.096 for the prototype and model reactors, respectively, the short-circuiting indices were 0.483 and 0.489 for the prototype and model reactors, respectively, the effective volume and short-circuiting index measurement errors were both 1%, the hydraulic efficiency error was 2%, and the Peclet and dispersion number errors were both 7%. Most of the compared indices were close to one another in value. Therefore, the model reactor can be used based on the Froude dynamic similitude to determine hydrodynamic characteristics of a baffled reactor at a full scale.     

Public–private partnerships for water in Asia: a review of two decades of experience

This article reviews the development of public–private partnerships (PPP) in water services in Asia over the last two decades and situates the Asian experience within the wider global context. Through a comparative analysis of PPP data from two different sources, the article highlights the critical issue of how ‘private’ is defined in understanding the extent of PPP in Asia, due to the important role played by enterprises under mixed public and private ownership. The article identifies cyclical patterns of development of PPP in the water sector across countries and the use of hybrid contractual and institutional arrangements for PPPs.     

Effect of compressive stress on the dispersion relation of the flexural–gravity waves in a two-layer fluid with a uniform current

The explicitly analytical solution is derived for the dispersion relation of the flexural–gravity waves in a two-layer fluid with a uniform current. The upper fluid is covered by a thin plate with the presence of the elastic, compressive and inertial forces. The density of each of the two immiscible layers is constant. The fluids of finite depth are assumed to be inviscid and incompressible and the motion be irrotational. A linear system is established within the framework of potential theory. A new representation for the dispersion relation of flexural–gravity waves in a two-layer fluid is derived. The critical value for the compressive force is analytically determined. The dispersion relation for the capillary–gravity with an inertial surface in a two-layer fluid can be obtained in parallel. Some known dispersion relations can be recovered from the present solution.     

Lipid peroxidation in the freshwater shrimp Caridina nilotica as a biomarker of Roundup(?) herbicide pollution of freshwater systems in South Africa

Glyphosate-based herbicides used to control weeds and invading alien plant species in South Africa ultimately end up in freshwater ecosystems, but no South African environmental water quality guideline exists to regulate these bio-active chemicals. Ecotoxicological tests to assess the possibility of using lipid peroxidation (LPx) in Caridina nilotica as a potential biomarker of Roundup(?), a glyphosate-based herbicide, pollution were conducted. In two separate tests, 40 days post hatch shrimps were exposed to different concentrations of 4.3, 6.7, 10.5, 16.4, 25.6 and 40.0 mg/L in a 96 h acute toxicity test; and 2.2, 2.8, 3.4, 4.3 and 5.4 mg/L in a 21 d chronic toxicity test, using static-non renewal and static-renewal methods, respectively. Shrimp whole body LPx was estimated by thiobarbituric acid reactive species (TBARS) assay, performed by a malondialdehyde (MDA) reaction with 2-thiobarbituric acid (TBA) measured spectrophotometrically. Final MDA concentrations were expressed as nmol MDA produced/mg protein. Results showed that LPx was significantly lower in control animals than in animals exposed to different Roundup(?) concentrations, (p < 0.05). The present work provides an ecotoxicological basis for the possible use of LPx in Caridina nilotica as a biomarker for monitoring Roundup(?) pollution in freshwater ecosystems.     

What's in a name? Taxonomy and nomenclature of invasive gobies in the Great Lakes and beyond

The species identities, scientific names, and relationships of Eurasian gobies that invaded the Laurentian Great Lakes – and other species that are predicted to invade in the future – are evaluated here using recently resolved DNA characters. The Round Goby and the Freshwater Tubenose Goby entered the Great Lakes ca. 1990 via ballast water originating from Black Sea ports. The Round Goby spread extensively throughout the Great Lakes and adjacent rivers, whereas the Freshwater Tubenose Goby recently began to expand its range. Both species also are widely invasive in Eurasia, dispersing via canals and shipping. Several of their relatives – the Monkey, Racer, and Bighead gobies – also are invasive in Eurasia, and are predicted to invade the Great Lakes. We discuss results from phylogenetic analyses of DNA sequences from 4 mitochondrial and nuclear gene regions, and provide a revision of their scientific nomenclature. The Freshwater Tubenose Goby was redefined as Proterorhinus semilunaris, which is markedly different and distinctive from the Marine Tubenose Goby Proterorhinus marmoratus. The genus Neogobius, as formerly defined, contained multiple evolutionary lineages and incorrect scientific names. We thus restricted Neogobius to just 4 species—including the Round Goby Neogobius melanostomus and the Black Sea Monkey Goby Neogobius fluviatilis. Several previously recognized subgenera, which were incorrectly grouped in Neogobius, were elevated to the level of genera. Notably, the Racer Goby became Babka gymnocephalus and the Bighead Goby now is Ponticola kessleri. These changes made the names consistent with their true relationships and species characters, which are essential for identifying and characterizing these gobies in invasive and native habitats.     

Acetylcholinesterase activity in the freshwater shrimp Caridina nilotica as a biomarker of Roundup(?) herbicide pollution of freshwater systems in South Africa

The use of Caridina nilotica whole-body acetylcholinesterase (AChE) activity as a potential biomarker of Roundup(?) pollution of aquatic ecosystems was investigated. Forty days post hatch (dph) shrimps were exposed to different concentrations of 0.0, 4.3, 6.7, 10.5, 16.4, 25.6 and 40.0 mg/L in a 96 h acute toxicity test; and 0.0, 2.2, 2.8, 3.4, 4.3 and 5.4 mg/L in a 21 d chronic toxicity test. Whole-body AChE activities were determined at the end of the exposure periods by spectrophotometric assay of sample extract; activities were then normalized against protein contents in the samples and expressed in nanomoles of substrate hydrolyzed. Results of both tests showed that AChE activity was concentration-dependent. Mean AChE activities and standard deviations (±SD) for 96 h acute toxicity were 3.6239 (± 0.4185), 3.4157 (± 1.1842), 2.537 (± 1.3989), 2.4253 (± 1.4202), 2.4127 (± 1.9097), 2.0017 (± 1.1080) and 2.316 (± 0.4001) nmol/min/mg protein; while activity levels for 21 d test were 3.6907(± 0.3401), 2.8473 (± 0.713), 2.9134 (± 0.9879), 2.6738 (± 0.7117), 2.3019 (± 0.4464) and 2.1478 (± 0.864) nmol/min/mg protein. Reference basal AChE activity for 40 dph C. nilotica based on the two control groups was estimated as 3.6907 (± 0.3401) nmol/min/mg proteins. The present work provides ecotoxicological basis for the possible use of AChE activity in C. nilotica as a biomarker for monitoring Roundup(?) pollution in freshwater systems.     

Homotopy-based analytical approximation to nonlinear short-crested waves in a fluid of finite depth

A nonlinear short-crested wave system, consisting of two progressive waves propagating at an oblique angle to each other in a fluid of finite depth, is investigated by means of an analytical approach named the homotopy analysis method(HAM). Highly convergent series solutions are explicitly derived for the velocity potential and the surface wave elevation. We find that, at every value of water depth, there is little difference between the kinetic energy and the potential energy for nonlinear waves. The nonlinear short-crested waves with a larger angle of incidence always contain the more potential wave energy. With the aid of the HAM, we obtain the dispersion relation for nonlinear short-crested waves. Furthermore, it is shown that the wave elevation tends to be smoothened at the crest and be sharpened at the trough as the water depth increases, and the wave pressure crests and troughs become steeper with increasing incident wave steepness.     

Stability of fluid flow in a Brinkman porous medium–A numerical study

The stability of fluid flow in a horizontal layer of Brinkman porous medium with fluid viscosity different from effective viscosity is investigated. A modified Orr-Sommerfeld equation is derived and solved numerically using the Chebyshev collocation method. The critical Reynolds number cRe, the critical wave number αc and the critical wave speed cc are computed for various values of porous parameter and ratio of viscosities. Based on these parameters, the stability characteristics of the system are discussed in detail. Streamlines are presented for selected values of parameters at their critical state.     

Capillary effect on the sloshing of a fluid in a rectangular tank submitted to sinusoidal vertical dynamical excitation

Surface tension effects on fluid sloshing in a tank subjected to external excitation has been less studied. This work aims at understanding this phenomenon in order to derive practical solutions to problems faced in several engineering. A tank containing a fluid with a free surface is submitted to gravity and capillary forces and subject to external dynamic excitation. Introduction of vertical sinusoidal dynamical excitation leads to a problem of paramtric oscillations governed by the Mathieu equation. Analysis of the Mathieu equation shows the existence of stable and unstable regions in the stability diagram. Some results induced by harmonic excitations on the fluid sloshing are presented. When the external dynamical excitation amplitude ~ is small, periodic solutions appear in stable regions and when e increases, the fluid behavior is not perfectly periodic and the amplitudes are not regular. Nonlinear effects make the behavior of the fluid complicated and render it almost unpredictable. In stable regions, the solution remains bounded at any time. When changing the perturbation parameter 6, the phase difference increases and also with the increase of the surface tension.     

Behaviour and Performance of a Water Resource System in Québec (Canada) Under Adapted Operating Policies in a Climate Change Context

The behaviour of the water resource system of the Peribonka River (Quebec, Canada) exploited for hydropower is evaluated under various hydrological regimes, using different climate change scenarios. The hydrological regime of the recent past and the regimes of 30 climate projections are considered. The potential hydrological regimes are simulated for climate projections from five general circulation models (GCM) for two greenhouse gas emission scenarios and three temporal horizons (2020, 2050 and 2080). For each hydrological regime, weekly reservoir operating rules are calculated with a dynamic and stochastic optimization model. Simulations of the water resource system with adapted operating rules in these climate change contexts are compared with the management of the water resource system at the control period (1961–1990). For the majority of climate projections, the analysis of simulations in the context of climate change shows an increase in hydropower and in annual unproductive spills. These increases reach 22% and 300%, respectively, compared to the control period. Also, the reliability of a reservoir is compromised for half of the climate projections, with annual probabilities reaching above the maximum operating levels, up to 0.3%, whereas these probabilities were null for the control period. Despite the rise in production, the annual efficiency of the power plants would fluctuate between −5 to +8%, depending on the power plant, the climate projection and the horizon.     

Study on carbon emission accounting in construction and operation of a sponge city in BeijingEI北大核心CSCD

为量化海绵城市建设和运行过程中的碳排放,分析碳排放的关键影响因素,以北京某100 km^(2)片区为研究区,对其海绵城市建设和运行过程中的碳排放进行了估算,分析了海绵城市达标面积比例、径流总量控制率、压力流管网比例等控制指标与碳排放量的相关关系。研究结果表明:海绵城市建设阶段的碳排放主要集中在材料生产阶段,多数设施的材料隐含碳占建设阶段总碳排放量的80%以上,施工相关的碳排放相对较少;在相同雨水控制水平下,灰色雨水基础设施的碳排放高于绿色雨水基础设施;研究区在30 a全生命周期内建设阶段和运行阶段碳排放量(以CO_(2)计)分别为17.36万t和-16.71万t;海绵城市达标面积比例、年径流总量控制率、排水方式是影响海绵城市建设和运行过程中碳排放的关键因素,海绵城市达标面积比例和年径流总量控制率每提高1%,全生命周期碳排放量约分别减少0.19万t和0.25万t,压力流管网比例每减少1%,全生命周期碳排放量平均减少约249 t。     

Detrended analysis of Reynolds stress in a decaying turbulent flow in a wind tunnel with active grids简

Multi-scale properties of Reynolds stress in decaying turbulence in a wind tunnel with high Reynolds number are investigated. Two filtering techniques i.e., the zeroth-order and first-order detrending methods are applied to the two velocity components, where the local mean value (resp. local linear trend) is removed in the former (latter) technique. Some basic statistics for thirty measurements show that the variation is very large at first two locations and relatively small at last two locations. Moderately good power law is found for the mean value of local Reynolds stress at last three measurement locations with scaling exponents approximately being 1.0 and a dual power law exists for the mean value of standard deviation of local Reynolds stress at all four measurement locations with scaling exponents being 0.53 and 0.58 for zerothand first-order filtering respectively. Present results about local Reynolds stress are useful to build and evaluate the model of sub-grid Reynolds stress in large eddy simulations.     

High-speed water impacts of flat plates in different ditching configuration through a Riemann--ALE SPH model

The violent water entry of flat plates is investigated using a Riemann-arbitrary Eulerian-Lagrangian(ALE) smoothed particle hydrodynamics(SPH) model. The test conditions are of interest for problems related to aircraft and helicopter emergency landing in water. Three main parameters are considered: the horizontal velocity, the approach angle(i.e., vertical to horizontal velocity ratio) and the pitch angle, a. Regarding the latter, small angles are considered in this study. As described in the theoretical work by Zhao and Faltinsen(1993), for small a a very thin, high-speed jet of water is formed, and the time-spatial gradients of the pressure field are extremely high. These test conditions are very challenging for numerical solvers. In the present study an enhanced SPH model is firstly tested on a purely vertical impact with deadrise angle α=4°. An in-depth validation against analytical solutions and experimental results is carried out, highlighting the several critical aspects of the numerical modelling of this kind of flow, especially when pressure peaks are to be captured. A discussion on the main difficulties when comparing to model scale experiments is also provided. Then, the more realistic case of a plate with both horizontal and vertical velocity components is discussed and compared to ditching experiments recently carried out at CNR-INSEAN. In the latter case both 2-D and 3-D simulations are considered and the importance of 3-D effects on the pressure peak is discussed for α=4° and α=10°.     

Unpacking water conflicts: a reinterpretation of coordination problems in China’s water-governance system

In China, water conflicts have been traditionally framed as the external costs of economic development and tackled with technocratic measures. This study examines water conflicts through the lens of water diversion, water allocation and water functional zoning. It reframes water conflicts as a result of coordination problems nested in complex inter-jurisdictional interactions. With a game-theoretic illustration, it identifies that individual and group heterogeneities are two challenges to effective coordination. It argues that China’s state-centric water institutions are tailored to optimize overall social utilities, yet they constrain coordination due to insufficient costs and benefits redistribution mechanisms at the local level.     

Stability Analysis of Stakeholders’ Cooperation in Inter-Basin Water Transfer Projects: a Case Study

Water Resources Management - This study investigates the conflict resolution among different stakeholders in a water transfer project. The portion of the Beheshtabad Water Transfer Project in Iran...     

Farmers’ perceptions of irrigation and constraints on rice production in Benin: a stakeholder-consultation approach

ABSTRACT

This article examines rice farmers’ perceptions of irrigation and constraints on rice production in the municipality of Malanville, Benin. Farmers’ positive perceptions of irrigation include the use of irrigation for insurance against drought, crop yield improvement, higher income, food security and poverty reduction. Analysis of constraints reveals that farmers face major constraints such as lack of agricultural credit, poor access to production inputs, inadequate knowledge of water resources management, poor access to agricultural information and markets, and flooding of fields. Specific constraints in the irrigation scheme of Malanville include the high cost of irrigation and unavailability of water.