Hydraulic and turbulence structure of triangular labyrinth weir‐pool fishways

Detailed laboratory experiments were conducted to analyze and evaluate a new weir‐pool fishway design. The new design consisted of a series of one‐cycle, triangular labyrinth weirs that formed a weir‐pool fish passage. Hydraulic characteristics of flow over the proposed fishway were examined for three pool lengths and a wide range of discharges. It was found that the new design had superior discharge capacity over classical weir‐pool fishways in plunging flow regime. Spatial and point analyses of measured velocity data were carried out to understand turbulence structure and distribution of turbulent flow. The power dissipation per unit volume was calculated for different tests, and it varied nonlinearly with discharge. Based on the limiting criteria for energy dissipation rates of different fish species, the maximum operating discharge for different slopes was extracted for the proposed design. The model‐to‐prototype scaling analysis was performed based on the recommended scaling factor of three for prototype. It was found that the approach velocity of prototype increased by 12%, whereas the total discharge increased by more than five times. The contour plots of time‐averaged velocity indicated that the proposed fishways offered diversified flow fields without exceeding the maximum velocity above the standards recommended for weir‐pool fishways. To study the size, direction, and periodicity of turbulent eddies, magnitude of the most energetic eddy and dominant frequencies were extracted using power spectrum analysis. Quadrant analysis consistently showed that Reynolds shear stresses in ejection and sweep events became weaker as the pool length increased. The small region of strong ejection and sweep events evidenced a good resting place for fish migration, whereas the generated turbulence was large enough to attract fish species to use the passage.     

Fluid physics around conductive deformable flaps within an induced-charge electrokinetically driven microsystem

The induced-charge electrokinetic motion of a conductive deformable flap (which is installed on the walls of a microchannel) is numerically studied in this article. The relationship between the flap orientation (i.e., vertical, horizontal and oblique positions) and its motion is studied. Stagnation point concept is used to explain the behavior of the flap at different situations. The stagnation point is defined as a point on the flap surface where the induced zeta potential is zero. Thus, the flow velocity at this point becomes zero, and the pressure gradient will be maximum. The direction of the flap motion is determined by the location of the stagnation point. As an example, here, it is shown that the obtuse conductive flap moves in the opposite direction of the flow field because in this case, the stagnation point is located on the back surface of the flap. Interaction of two vertical conductive flaps (located at different distances from each other) is also investigated in this paper. The results indicate that if both of the conductive flaps are fixed on the same microchannel wall, two vortices with opposite spin directions are generated between them. These vortices create a low-pressure zone through which the two flaps attract one another. However, when each flap is fixed on upper and lower microchannel walls, the two vortices with same spin directions are generated between the flaps. These two vortices merge and form a high-pressure zone through which two flaps repel each other.     

Trace metal determination in total atmospheric deposition in rural and urban areas

The wet, dry and total atmospheric depositions of some metals (Al, Cd, Cr, Cu, Fe, Na, Pb and Zn) were sampled at two sites and atmospheric fallout fluxes were determined for these locations. This work, led by two different research groups, allowed to reach two main goals: to define a simple analytical procedure to secure accurate shipboard sampling and analysis of atmospheric deposition, and to assess anthropogenic impacts of heavy metals to the environment. The first step about the validation step showed that the prevalent deposition type was dry deposition which represents 40, 60 and 80% for Cd, Cu and Pb, respectively. This prevalence of dry deposition in total atmospheric fallout supported the necessity of funnel wall rinsing which contains 30, 50 and 40% of collected Cd, Cu and Pb, respectively. Moreover, the reproducibility of atmospheric deposition collection was determined. The second step was performed by comparing two sampling sites. A rural sampling site, situated in Morvan's regional park (250 km south-east of Paris), was chosen for its isolation from any local and regional contamination sources. Fluxes obtained in this area were compared with those obtained at an urban site (Créteil, suburb of Paris) allowing comparison between urban and rural areas and demonstrating the impact of anthropogenic activities on atmospheric deposition of Cr, Cu and Pb.     

Hydrocarbons and heavy metals in the different sewer deposits in the 'Le Marais' catchment (Paris, France): stocks, distributions and origins

The knowledge of the pollution stored in combined sewers is of prime importance in terms of management of wet weather flow pollution since sewer deposits play a significant role as source of pollution in combined sewer overflows. This work, which focused on the hydrocarbon (aliphatic and aromatic hydrocarbons) and metallic (Fe, Zn, Pb, Cu and Cd) pollution fixed to the different kinds of sewer deposits (gross bed sediment [GBS], organic layer [OL] and biofilm), was performed in order to provide a complete overview of the contaminant storage in the 'Le Marais' combined sewer (Central Paris, France). Firstly, our results have shown that, for all kinds of pollutants, a major part was stored in the GBS (87 to 98%), a lesser part in the OL (2 to 13%) and an insignificant part in the biofilm (<1%). These results demonstrated that the potential contribution of biofilm to wet weather pollution was negligible compared to the OL one. Secondly, the investigation of hydrocarbon fingerprints in each deposit has provided relevant information about contamination origins: (1) aliphatic hydrocarbon distributions were indicative of petroleum input in the GBS and reflected a mixture of biogenic and petroleum inputs in the OL and biofilm, (2) aromatic hydrocarbon distributions suggested an important pyrolytic contamination in all the deposits. Finally, the study of pollutant fingerprints in the different deposits and in the suspended solids going through the collector has shown that: (1) the suspended solids were the major component of OL and biofilm while urban runoff seemed to be the main transport mechanism introducing pollutants in the GBS and (2) the residence times in sewer of OL and biofilm were quite short compared to those for GBS.     

Vibration of rotating functionally graded Timoshenko nano-beams with nonlinear thermal distribution

The vibration analysis of rotating, functionally graded Timoshenko nano-beams under an in-plane nonlinear thermal loading is studied for the first time. The formulation is based on Eringen's nonlocal elasticity theory. Hamilton's principle is used for the derivation of the equations. The governing equations are solved by the differential quadrature method. The nano-beam is under axial load due to the rotation and thermal effects, and the boundary conditions are considered as cantilever and propped cantilever. The thermal distribution is considered to be nonlinear and material properties are temperature-dependent and are changing continuously through the thickness according to the power-law form.     

Cyclic Behaviour of Fully-Rigid and Semi-Rigid Steel Beam-to-Column Connections

A test program was considered to clarify the cyclic characteristics of eight full-scale unstiffened extended end-plates with variable parameters and one SidePlate moment connection. All specimens were subjected to 2010 AISC seismic provision loading protocol where flexural strengths were identified at each interstorey drift angle. The results showed that all unstiffened extended end-plate failed to develop full inelastic capacity of connected beams and plastic hinges mainly appeared in the connection’s components. On the other hand, the SidePlate moment connection had the capacity to develop adequate interstorey drift angles up to 0.06 rad, indicating that this type of connection possesses sufficient stiffness and strength to be classified as a rigid and full-strength connection. The results also showed that SidePlate possesses considerably more energy dissipation capacity and an equivalent hysteretic damping ratio compared to unstiffened extended end-plate specimens, especially at higher interstorey drift angles.     

A template-free method to synthesize porous G-C3N4 with efficient visible light photodegradation of organic pollutants in water

Porous graphitic carbon nitride with a high surface area was successfully synthesized without using any template or other substances like metals, just by placing melamine powder into a muffle furnace which was heated to 550?°C in advance. To evaluate the structure, morphology, and optical properties, the high performance g-C₃N₄ (HPCN) was analyzed by XRD, SEM-EDX, TEM, N₂ physisorption, FT-IR analysis, UV–Vis DRS, PL, and Zeta potential. HPCN was able to completely degrade rhodamine B under visible light with the rate constant of 0.086?min^?1, which is 3.5 times higher than the traditional g-C₃N₄. The possible mechanism of RhB photodegradation was discussed in detail, which illustrated the reaction is performed in acidic media much better than neutral and basic solutions, and O₂^? and h⁺ are the key reactive species during the reaction. Moreover, the stability of the photocatalyst was investigated and turned out its photocatalytic activity has not considerably changed after 6 cycles, so it was a highly stable photocatalyst.     

Peer sampling gossip-based distributed clustering algorithm for unstructured P2P networks

Clustering, as an unsupervised learning method and an important process in data mining, is an aspect of large and distributed data analysis. In many applications, such as peer-to-peer systems, huge volumes of data are distributed between multiple sources. Analysis of these volumes of data and identifying appropriate clusters is challenging due to transmission, processing and storage costs. In this paper, a gossip-based distributed clustering algorithm for P2P networks called Efficient GBDC-P2P is proposed, based on an improved gossip communicative approach by combining the peer sampeling and CYCLON protocol and the idea of partitioning-based data clustering. This algorithm is appropriate for data clustering in unstructured P2P networks, and it is adapted to the dynamic conditions of these networks. In the Efficient GBDC-P2P algorithm, distributed peers perform clustering operation in a distributed way only through local communications with their neighbors. Our approach does not rely on the central server to carry out data clustering task and without the need to synchronize operations. Evaluation results verify the efficiency of our proposed algorithm for data clustering in unstructured P2P networks. Furthermore, comparative analyses with other well-established distributed clustering approaches demonstrate the superior accuracy of the proposed method.