A novel route for the preparation of CoCr<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposite starting from Co(II)–Cr(III) carboxylate complex combinations

This study reports the preparation and characterization of the spinel CoCr₂O₄. In order to obtain 20% CoCr₂O₄/80% SiO₂ and 50% CoCr₂O₄/50% SiO₂ (mol%) nanocomposites, we have used a versatile pathway based on the thermal decomposition of some particular precursors, Co(II) and Co(III) carboxylate-type complex combinations, inside the SiO₂ matrix. The ligands of these coordination compounds result in the redox reaction between Co(II) and Cr(III) nitrates and 1,3-propylene glycol by heating at 150 °C of the gels (tetraethylorthosilicate–metal nitrates–1,3-propylene glycol). The as-obtained precursors, embedded in silica gels, were characterized by FT-IR spectrometry and thermal analysis. Both precursors decompose up to 350 °C, leading to the corresponding metal oxides inside the silica matrix. X-ray diffraction of the powders annealed at different temperatures has evidenced the formation of CoCr₂O₄ starting with 400 °C for 20% CoCr₂O₄/SiO₂ and 300 °C for 50% CoCr₂O₄/SiO₂. This behaviour can be explained by the fact that, by thermal decomposition of the chromium carboxylates, a nonstoichiometric chromium oxide Cr₂O_3+x is formed. At ~ 400 °C, Cr₂O_3+x turns to α-Cr₂O₃, which interacts with CoO leading to cobalt chromite nuclei inside the pores of the silica matrix. CoCr₂O₄ has been obtained as nanocrystallites homogenously dispersed within the silica matrix as resulted from XRD, TEM and EDX mapping, with mean particle size in the range 5–20 nm.     

Expansive sulphate aluminate cements

The possibility to prepare expensive sulphate aluminate masses from certain wastes (phosphogypsum and belitic waste) and usual raw materials (limestone, bauxite) has been investigated. The chemical and minerological composition of these synthetic clinkers as well as the nature of their hydration products has been determined by current methods. The mechanism of cement expansion and the factors affecting the correlation between mechanical strength and expansion have been also studied.     

iVoIP: an intelligent bandwidth management scheme for VoIP in WLANs

Voice over Internet Protocol (VoIP) has been widely used by many mobile consumer devices in IEEE 802.11 wireless local area networks (WLAN) due to its low cost and convenience. However, delays of all VoIP flows dramatically increase when network capacity is approached. Additionally, unfair traffic distribution between downlink and uplink flows in WLANs impacts the perceived VoIP quality. This paper proposes an intelligent bandwidth management scheme for VoIP services (iVoIP) that improves bandwidth utilization and provides fair downlink–uplink channel access. iVoIP is a cross-layer solution which includes two components: (1) iVoIP-Admission Control, which protects the quality of existing flows and increases the utilization of wireless network resources; (2) iVoIP-Fairness scheme, which balances the channel access opportunity between access point (AP) and wireless stations. iVoIP-Admission Control limits the number of VoIP flows based on an estimation of VoIP capacity. iVoIP-Fairness implements a contention window adaptation scheme at AP which uses stereotypes and considers several major quality of service parameters to balance the network access of downlink and uplink flows, respectively. Extensive simulations and real tests have been performed, demonstrating that iVoIP has both very good VoIP capacity estimation and admission control results. Additionally, iVoIP improves the downlink/uplink fairness level in terms of throughput, delay, loss, and VoIP quality.     

Improving learner quality of experience by content adaptation based on network conditions

Apart from user characteristics, properties of the network over which the content is delivered and device on which the content is displayed affect end-user perceived quality. This paper presents a learner quality of experience (QoE) model that apart from the user-related content adaptation, considers delivery performance-based content personalisation in order to improve user experience when interacting with an online learning system.A comparison-based study on the benefit of using the proposed learner QoE model in adaptive and personalized education was conducted involving the original AHA! and QoEAHA – a version of AHA! enhanced with the learner QoE model. Testing results demonstrate significant benefits in terms of learning achievement, learning performance, learner navigation and user QoE in favour of the learner QoE model-enhanced solution.     

Efficient delivery of multimedia streams over broadband networks using QOAS

Quality Oriented Adaptation Scheme (QOAS) is compared against other adaptive schemes such as TCP Friendly Rate Control Protocol (TFRCP), Loss-Delay-based Adaptation Algorithm (LDA+), and a nonadaptive (NoAd) solution when streaming multiple multimedia clips with various characteristics over broadband networks. Streaming efficiency is assessed in terms of loss rate, bandwidth utilization, number of concurrent clients and end-user perceived quality. Simulation results show that using QOAS a significantly higher number of simultaneous clients can be served than when using the other schemes given a target average end-user quality. This is while having higher bandwidth utilization. Testing results also indicate that higher performance is achieved when streaming to the same number of clients using QOAS than when other solutions are used.     

Resins containing α-hydroxyphosphonic acid groups used for adsorption of dyes from wastewater

The synthesis of styrene–divinylbenzene copolymers functionalized with α-hydroxyphosphonic acid groups is presented. The phosphorus content was determined in order to calculate the degree of functionalization with pendant α-hydroxyphosphonic group, with values of 0.66 for St–1%DVB_HOPHOS and 3.14 for St–6.7%DVB_HOPHOS. Their characterization by IR, thermogravimetry is reported. The kinetics of adsorption of three dyes on St–6.7%DVB_HOPHOS polymer was studied.     

Evaluation of a functionalized copolymer as adsorbent on direct dyes removal process: Kinetics and equilibrium studies

Functionalized polymeric microbeads were investigated as adsorbent for the removal of three direct dyes from aqueous solutions. The effects of different experimental parameters, such as initial dye concentration, temperature, and solution pH on the adsorption process were investigated. The adsorption process can be conducted with very good result at normal working conditions: neutral pH and normal temperature. The maximum percentage removal obtained was 99.11% for the symmetrical disazo dye, 90.14% for asymmetrical disazo dye, and 98.53% for trisazo dye. The adsorption kinetics followed the pseudo‐second‐order equation for all three investigated dyes in all working conditions. The experimental data were fitted to Langmuir, Freundlich, Sips, and Redlich–Peterson isotherm models, and the best fit was obtained with Sips model. Thermodynamic parameters (ΔH°, ΔS°, and ΔG°) revealed that dye adsorption is an endothermic and spontaneous process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

SELECTIVE SEPARATION OF URANYL ION FROM TRU'S IN A COMBINED SOLVENT EXTRACTION PROCESS USING TETRAHYDROFURAN-2,3,4,5-TETRACARBOXYLICACID

ABSTRACT

Selective partitioning of uranyl from transuranic elements in a solvent extraction system which employs a neutral organophosphorus extractant and an aqueous complexant has been demonstrated in a previous report. The extractant solution combines octyl(phenyl)-N,N-diisobutylcarbamoylrnethylphosphine oxide (CMPO), diamyt(amyl)phosphonate (or tributylphosphate), and di(t-butylcyclohexano)-18-crown-6 in Isopar L, and is designed for simultaneous removal of strontium, technetium, lanthanides and actinides from radioactive wastes. The aqueous complexant is tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA). In this report, the separation of UO₂ ²⁺ from Np(IV), Eu(III), Am(III), and Pu(IV) using the Combined Process Solvent has been optimized. Potentiometric titration and NMR spectroscopic results describe the distribution of THFTCA into the organic phase as a function of acidity and [THFTCA]. Further potentiometric titration experiments have determined the stoichiometry and stability of uranyl complexes in the aqueous phase. The thermodynamic data indicate that the uranyl complexes are anomalously weak which partially accounts for the selectivity. Ternary complexes involving, UO₂ ²⁺ CMPO, and THFTCA in the extractant phase also appear to play a role.     

Atmospheric induced nanoparticles due to the urban street dust

ABSTRACT

Urban street dust (SD) represents a natural source of mineral floating particles (FP) in the atmosphere. The FP particles have usually a wide range of sizes. These particles were monitored and collected by automatic stations in Cluj-Napoca, Romania. The SD and FP samples were investigated by XRD and SEM-EDX analysis. The obtained results prove that both, SD and FP, have a similar composition, namely quartz, clay particles (e.g., muscovite, and kaolinite), calcite, and trace of lepidocrocite. Nanostructural features and fine micro-scaled particles are observed. Quartz and clay nanoparticles were found in SD samples as well as in FP samples. The AFM investigation reveals a nano-size range for quartz particles between 80–90 nm, and 40–60 nm diameter for clay particles. Similar values were obtained by TEM microscopy. The high resolution microscopy results were confirmed by the values obtained by Scherrer formula applied to the XRD patterns. Composition and dimensional similarities found for the nanoparticles in SD and FP samples prove that mineral nanofractions in atmosphere were induced by the urban environmental interactions with the SD. Results provide valuable information on the size, shape, and composition of nanoparticles induced in atmosphere by winds and by environmental interactions with the SD. This work contributes to the evaluation of the air pollution and simultaneously it offers a basis for an improved life quality for Cluj-Napoca population.     

DE-BAR: Device Energy-Centric Backlight and Adaptive Region of Interest Mechanism for Wireless Mobile Devices

One of the main challenges in the smart-phone world is that they are battery constrained and the development of battery technologies have not kept pace with the required energy demand. In particular, there are still significant technological gaps on developing energy-aware solutions that would prolong the battery life of devices without affecting the quality of the distributed video/multimedia content. In this aspect, this paper proposes DE-BAR—a process based innovation that will provide a seamless battery saving mechanism, based on backlight and adaptive region of interest of the streamed multimedia content. This work intends to look at the nature of the video/multimedia content that is received in the device and adapts the energy consumption dynamically at three levels: Screen Colour, backlight and Intensity; and adaptive Region-of-Interest (RoI) based variation in the multimedia content. Notably, the work provides the mechanism for real-time adaptation. The colour intensity, number of RoI for the video sequence and the frame rate is decided by the spatial and temporal complexity of the video. The energy consumption is measured using an Arduino board while video quality is analyzed using extensive subjective tests. The results indicate that more than 50% energy could be saved in the device while retaining above average perceptual video quality.