Search results for "Dam"
showing 10 items of 3828 documents
The probable function of abdominal contractions and liquid drops during the emergence of Zygoptera and Anisoptera (Odonata)
2016
The transition between larval and adult stage in amphibious insects is called emergence. During emergence abdominal contractions and excretion of liquid drops can be observed in several insect orders. Since the function of these processes is not yet known in odonates, this study examines the probable function of abdominal contractions and excretion of liquid drops in Zygoptera and Anisoptera. By subdividing the emergence into 12 successive stages and counting abdominal contractions as well as the excreted liquid drops during these stages we set up a systematic data collection. In all investigated individuals, both processes began in the middle of the entire emergence. We found that abdomina…
Fen and spring vegetation in western Pamir-Alai Mountains in Tajikistan (Middle Asia)
2016
The paper presents the results of phytosociological research on spring and fen vegetation of the western Pamir-Alai Mountains in Tajikistan. In total, 211 relevés were sampled during field studies conducted in 2008–2013 and 2015 with application of the Braun-Blanquet method. Plant communities of spring heads and peat-accumulated fens inhabiting the high montane and alpine zones in the Zeravshan, Hissar, Hazratishoh, Darvaz, Turkestan and Peter the 1st Mountains are described. A hierarchical syntaxonomic synopsis of spring and fen plant communities in the western Pamir-Alai Mountains is provided. As a result of field investigations and numerical analyses, three fen associations: Caricetum ps…
The influence of thermal extremes on coral reef fish behaviour in the Arabian/Persian Gulf
2019
Despite increasing environmental variability within marine ecosystems, little is known about how coral reef fish species will cope with future climate scenarios. The Arabian/Persian Gulf is an extreme environment, providing an opportunity to study fish behaviour on reefs with seasonal temperature ranges which include both values above the mortality threshold of Indo-Pacific reef fish, and values below the optimum temperature for growth. Summer temperatures in the Gulf are comparable to those predicted for the tropical ocean by 2090–2099. Using field observations in winter, spring and summer, and laboratory experiments, we examined the foraging activity, distance from refugia and resting tim…
Effect of Multiple Parasitic Infections on the Tolerance to Pollutant Contamination
2012
8 pages; International audience; The horizontally-transmitted acanthocephalan parasite Polymorphus minutus and the vertically-transmitted microsporidian parasite Dictyocoela roeselum have both been shown to influence on the antitoxic responses of mono-infected Gammarus roeseli exposed to cadmium. The present study investigates the effect of this co-infection on the antitoxic defence responses of naturally infected females exposed to cadmium stress. Our results revealed that, depending on the cadmium dose, bi-infection induced only slight, significant increased cell damage in G. roeseli as compared to non-infection. In addition, the antitoxic defence pattern of cadmium-exposed bi-infected ho…
Selective photocatalytic oxidation of aromatic alcohols in water by using P-doped g-C3N4
2018
A set of bare and P-doped graphitic carbon nitride (g-C3N4) photocatalysts has been prepared by thermal condensation of melamine, urea or thiourea. For the sake of comparison, a g-C3N4 sample obtained in the presence of cyanuric acid and thermally exfoliated C3N4 powders were also studied. The materials were physicochemically characterized and their photocatalytic activity was studied for the selective oxidation of benzyl alcohol (BA), 4-methoxy benzyl alcohol (4-MBA) and piperonyl alcohol (PA) in water suspension both under UV and visible light irradiation. The influence of the type and position of the substituents on conversion and selectivity to aldehyde was remarkable. The presence of P…
Rocking of rigid block on nonlinear flexible foundation
2017
Abstract The two prime models used currently to describe rocking of rigid bodies, the Housner’s model and the Winkler foundation model, can capture some of the salient features of the physics of this important problem. These two models involve either null or linear interaction between the block and the foundation. Hopefully, some additional aspects of the problem can be captured by an enhanced nonlinear model for the base-foundation interaction. In this regard, what it is adopted in this paper is the Hunt and Crossley’s nonlinear impact force model in which the impact/contact force is represented by springs in parallel with nonlinear dampers. In this regard, a proper mathematical formulatio…
Heavy metal uptake by plants from wastewater of different pulp concentrations and contaminated soils
2021
There is a lack of information on the extent of mineral extraction by plants from wastewater in arid and semi-arid environments in developing countries. This research assesses the performance of Alhagi and Mallow plant species for the absorption of heavy metals around the tailings dam of a copper mine in Iran. The industrial wastewater, known as the pulp, from the copper mine site has different concentrations of heavy metals. In a laboratory setting the plants were cultivated and irrigated with different pulp concentrations (0, 20, 40, 60, 80, and 100%) in water. Heavy metals (chromium, manganese, cadmium, and lead) accumulation in the aerial parts and roots of the plants, and the in-situ s…
A Mathematical Model for Vehicle-Occupant Frontal Crash Using Genetic Algorithm
2016
In this paper, a mathematical model for vehicle-occupant frontal crash is developed. The developed model is represented as a double-spring-mass-damper system, whereby the front mass and the rear mass represent the vehicle chassis and the occupant, respectively. The springs and dampers in the model are nonlinear piecewise functions of displacements and velocities respectively. More specifically, a genetic algorithm (GA) approach is proposed for estimating the parameters of vehicle front structure and restraint system. Finally, it is shown that the obtained model can accurately reproduce the real crash test data taken from the National Highway Traffic Safety Administration (NHTSA). The maximu…
A Comparison Study of a Novel Self-Contained Electro-Hydraulic Cylinder versus a Conventional Valve-Controlled Actuator—Part 1: Motion Control
2019
This research paper presents the first part of a comparative analysis of a novel self-contained electro-hydraulic cylinder with passive load-holding capability against a state of the art, valve-controlled actuation system that is typically used in load-carrying applications. The study is carried out on a single-boom crane with focus on the control design and motion performance analysis. First, a model-based design approach is carried out to derive the control parameters for both actuation systems using experimentally validated models. The linear analysis shows that the new drive system has higher gain margin, allowing a considerably more aggressive closed-loop position controller. Several b…
Optimization of Vehicle-to-Vehicle Frontal Crash Model Based on Measured Data Using Genetic Algorithm
2017
In this paper, a mathematical model for vehicle-to-vehicle frontal crash is developed. The experimental data are taken from the National Highway Traffic Safety Administration. To model the crash scenario, the two vehicles are represented by two masses moving in opposite directions. The front structures of the vehicles are modeled by Kelvin elements, consisting of springs and dampers in parallel, and estimated as piecewise linear functions of displacements and velocities, respectively. To estimate and optimize the model parameters, a genetic algorithm approach is proposed. Finally, it is observed that the developed model can accurately reproduce the real kinematic results from the crash test…