Experimental study and modelling of Cr (VI) removal from wastewater using Lemna minor

The removal of Cr(VI) from wastewater by Lemna minor was studied both at laboratory and pilot scale. Laboratory tests were conducted under different conditions of initial Cr(VI) concentration (0.5 and 2.0 mg/l) and temperature (285 and 291 K). Batch experiments were carried out during 16 days in which the chromium concentrations, both in the biomass and in wastewater were measured. Data were used to characterize the biouptake capacity of the biomass; results showed that it increases with the temperature and when the initial Cr concentration decreases. The biouptake process could be fitted by an equation, with a correlation coefficient of 0.98. The removal process was assessed using the data of the variation of chromium concentration in the wastewater with respect to time; this allowed obtaining constant parameters which were applied in a mathematical model for the assessment of duckweed systems in a pilot scale plant.     

Analyse numérique et expérimentale du comportement des ouvrages fondés sur un sol mou renforcé par des colonnes ballastées flottantes

This paper work is in the frame of the study about the reduction of settlements in the case of floating columns. The prediction of a settlement remains a prickly problem to which geotechnical engineer is confronted. Experience has shown that structural pathologies are caused by the effects of excessive differential settlements before reaching soil bearing capacity. To palliate this problems in the case of soft and compressible soils, we advocate, as an alternative solution, piles or the reinforcement of the soils with stone columns. This strengthening method, introduced in Algeria in 1999, is economical. However, it does not inihilate settlements but it speeds up the time factor. Numerical modelings by finite element method (FEM) have been carried out through interest into all mechanical and geometrical aspects that are inherent in the meshing of floating stone columns. An analytical formulation of a correction coefficent (μβ) and an abacus of the settlement reduction factor (β) has been suggested. On the other way, the monitoring instrumentation of experimental site since 2008 to 2017 at the level of the harbour lowland of Bejaia has been carried out. It concerns important storage structures fonded on a very compressible ground reinforced by floating stone columns. The records of the settlements at the scale of the structures, according to variable loads recorded in real time, have revealed excessive settlements under the effects of variable stresses from 1 to 3 bars. An exhaustive geological, geotechnical and geomechanical analysis has been carried out for the characterization of the grounds, and numerical modelling by finite element method (FEM) has been carried out. The experimental and numerical investigation of the concerned structures at issue allowed us to confront the results with regard to settlement prediction of an environment reinforced with floating stone columns. The result is a perfect matching in relation to the suggested formula.

     

Transition metal nanoparticles doped carbon paper as a cost-effective anode in a microbial fuel cell powered by pure and mixed biocatalyst cultures

The poor wettability and high cost of the carbonaceous electrodes materials prohibited the practical applications of microbial fuel cells (MFCs) on large scale. Here, a novel nanoparticles of metal sheathed with metal oxide is electrodeposited on carbon paper (CP) to introduce as high-performance anodes of microbial fuel cell (MFC). This thin layer of metal/metal oxide significantly enhance the microbial adhesion, the wettability of the anode surface and decrease the electron transfer resistance. The investigation of the modified CP anodes in an air-cathode MFCs fed by various biocatalyst cultures shows a significant improving in the MFC performance. Where, the generated power and current density was 140% and 210% higher as compared to the pristine CP. Mixed culture of exoelectrogenic microorganism in wastewater exhibited good performance and generated higher power and current density compared to yeast as pure culture. The excellent capacitance with a distinctive nanostructure morphology of the modified-CP open an avenues for practical applications of MFCs.     

Determination of best possible correlation for gas compressibility factor to accurately predict the initial gas reserves in gas-hydrocarbon reservoirs

Gas compressibility factor or z-factor plays an important role in many engineering applications related to oil and gas exploration and production, such as gas production, gas metering, pipeline design, estimation of gas initially in place (GIIP), and ultimate recovery (UR) of gas from a reservoir. There are many z-factor correlations which are either derived from Equation of State or empirically based on certain observation through regression analysis. However, the results of the z-factor obtained from different correlations have high level of variance for the same gas sample under the same pressure and temperature. It is quite challenging to determine the most accurate correlation which provides accurate estimate for a range of pressures, temperatures, and gas compositions. This paper presents a novel method to accurately estimate GIIP of an Australian tight gas field through identification of the most appropriate z-factor correlations, which can accurately determine the z-factor and other PVT properties for a wide range of gas compositions, temperatures, and pressures. The sensitivity study results demonstrated that a single correlation cannot work across the range of pressures and temperatures for a certain gas sample necessary to calculate z-factor during simulation process and/or other analysis, such as material balance and volumetric estimate.     

Characterization of boride coatings on a ductile cast iron

In this work, the EN-GJS-400-15 cast iron was pack-borided in a powder mixture composed of 5% B₄C, 5% NaBF₄ and 90% SiC at the three temperatures: 900, 950 and 1000°C for 2, 4 and 6 h, respectively. The pack-borided EN-GJS-400-15 cast iron was characterized by the following experimental techniques: optical microscopy, XRD analysis and Microhardness Vickers tester. The growth kinetics of boride layers was also investigated. As a consequence, the boron activation energy was found to be 212.28 kJ mol^–1 for the EN-GJS-400-15 cast iron. Based on a regression model, a useful equation was derived to estimate the boride layer thickness as a function of the boriding parameters (time and temperature). A good agreement was then obtained between the predicted values of boride layers thicknesses and those measured experimentally. In addition, an iso-thickness diagram was proposed to be used as a simple tool to select the boride layers thicknesses according to the potential applications of EN-GJS-400-15 cast iron in industry.     

Radio resource management for LTE-A relay-enhanced cells with spatial reuse and max–min fairness

One of the major issues in LTE-Advanced (LTE-A) systems is the poor capacity at the cell edge. This is mainly due to the interference experienced by the users as a result of the aggressive frequency reuse usually implemented. Relaying offers an attractive solution for this problem by offering better links than those with the eNodeB (eNB) for the terminals suffering from high path loss or high interference. However, adding relays complicates the resource allocation problem at the eNB and therefore the need for more efficient schemes arises. This is also aggravated by the reuse of resource blocks (RBs) by the relays to fully exploit the scarce spectrum, which, in turn, leads to intra-cell interference. In this paper, we study the joint power and resource allocation problem in LTE-A relay-enhanced cells that exploit spatial reuse. To guarantee fairness among users, a max–min fair optimization objective is used. This complex problem is solved using coordinate ascent and the difference of two convex functions (DC) programming techniques and the proposed scheme indeed converges to a local-optimum quickly. This is shown to be a satisfactory solution according to the simulation results that indicate an almost sevenfold increase in the 10th percentile capacity when compared to previously proposed solutions.     

A new video magnification technique using complex wavelets with Radon transform application

Magnifying micro-movements of natural videos that are undetectable by human eye has recently received considerable interests, due to its impact in numerous applications. In this paper, we use dual tree complex wavelet transform (DT-CWT), to analyze video frames in order to detect and magnify micro-movements to make them visible. We use DT-CWT, due to its excellent edge-preserving and nearly-shift invariant features. In order to detect any minor change in object’s spatial position, the paper proposes to modify the phases of the CWT coefficients decomposition of successive video frames. Furthermore, the paper applies Radon transform to track frame micro-movements without any temporal band-pass filtering. The paper starts by presenting a simple technique to design orthogonal filters that construct this CWT system. Next, it is shown that modifying the phase differences between the CWT coefficients of arbitrary frame and a reference one results in image spatial magnification. This in turn, makes these micro-movements seen and observable. Several simulation results are given, to show that the proposed technique competes very well to the existing micro-magnification approaches. In fact, as it manages to yield superior video quality in far less computation time.     

Optimize adaptive media playout using dynamic fuzzy logic control for video streaming

Multimedia Tools and Applications - Adaptive Media Playout (AMP) controls adapt playout rate to prevent buffer outage and to reduce delay in playout. Most AMP techniques use buffer fullness or its...     

Aluminizing nickel foam by a slurry coating process

A simple, one-step slurry coating technique was used to aluminize open cell nickel metal foam at low temperature and short hold-down time. Three slurries of different composition, heat-treated at 650 °C for 2 h, were used to investigate the possibility of developing an aluminide coating on a commercially produced Ni foam. In all cases a dense, well-adhered to the Ni substrate aluminide coating of several μm thickness was produced. The thickness and aluminide phase and composition (NiAl and/or Ni₃Al) of the coating strongly depend on Al content and the mix of activators in the slurry.     

Macroporous calcium phosphate ceramic implants for sustained drug delivery

Limited blood circulation to the skeletal tissue is a major cause of reduced therapeutic effects seen with drugs administered by conventional systemic ways. To resolve this issue and obtain a sufficiently high local concentration to induce therapeutic effects, several implanted drug delivery systems have been developed for hard tissues using biomaterials.We have designed a drug delivery device based on hydroxylapatite (HA) and tested it in vitro using metronidazol and chloramphenicol as model compounds. Porous HA ceramics were prepared with two different shapes (cylindrical and spherical). Known amounts of drugs were introduced inside a drilled hole and sealed with wax. The ceramics were then suspended in stirred distilled water in closed polypropylene vials. Drug release was observed during several weeks.A mathematical model used to describe drug release from HA was elaborated based on the expressions of Fick's laws. The experimental kinetic results could be related to ceramic constitution and to drug localization.