Polyamine Functionalized Magnetite Nanoparticles as Novel Adsorbents for Cu(II) Removal from Aqueous Solutions

Three novel magnetic adsorbents were synthesized through the immobilization of di-, tri-, and tetraamine onto the surface of silica coated magnetite nanoparticles. The adsorbents were characterized by XRD patterns, FTIR spectroscopy, elemental and thermogravimetric analysis, magnetic measurements, SEM/TEM, EDX spectroscopy, and N₂ adsorption/desorption isotherms. Their capacity to remove copper ions from aqueous solutions was investigated and discussed comparatively. The equilibrium data were analyzed using Langmuir and Freundlich isotherms. The kinetics was evaluated using the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The best interpretation for the equilibrium data was given by the Langmuir isotherm for the tri- and tetraamine functionalized adsorbents, while for the diamine functionalized adsorbent the Freundlich model seemed to be better. The kinetic data were well fitted to the pseudo-second-order model. The overall rate of adsorption was significantly influenced by external mass transfer and intraparticle diffusion. It was observed that the adsorption capacity at room temperature decreased as the length of polyamine chain immobilized on the adsorbent surface increased, the maximum adsorption capacities being 52.3 mg g^?1 for 1,3-diaminopropan functionalized adsorbent, 44.2 mg g^?1 for diethylenetriamine functionalized adsorbent, and 39.2 mg g^?1 for triethylenetetramine functionalized adsorbent. The sorption process proved to be highly dependent of pH. The results of the present work recommend these materials as potential candidates for copper removal from aqueous solutions.     

Evaluation of Transport Capacity through Liquid Membranes of Some Crown Ether‐Siloxane Copolymers

The complexation ability of some linear crown ether‐siloxane copolymers of ester or amide type with cations as K⁺ and NH₄⁺ was investigated spectrophotometrically in order to select the polysiloxane receptors that achieve good ion transport ability by bulk liquid membrane systems. The transport properties of the potassium picrate through a liquid membrane using siloxane‐crown ether polyamide as carrier were discussed.     

The effect of HRG gas addition on diesel engine combustion characteristics and exhaust emissions

Extensive studies have been dedicated in the last decade to the possibility to use hydrogen in the dual-fuel mode to improve combustion characteristics and emissions of a diesel engine. The results of these studies, using pure hydrogen or hydrogen containing gas produced through water electrolysis, are notably different.The present investigation was conducted on a tractor diesel engine running with small amounts of the gas—provided by a water electrolyzer—aspirated in the air stream inducted in the cylinder. The engine was operated at light and medium loads and various speeds.It was found that the addition of HRG gas has a slight negative impact, up to 2%, on the engine brake thermal efficiency. Smoke is significantly reduced, up to 30%, with HRG enrichment, while NO_x concentrations vary in both senses, up to 14%, depending on the engine operation mode. A relative small amount of HRG gas can be used with favorable effects on emissions and with a small penalty in thermal efficiency.     

Molecularly imprinted “bulk” copolymers as selective sorbents for gallic acid

We report the synthesis of molecularly imprinted sorbents, selective for gallic acid. The particles were prepared by using acrylic acid, acrylonitrile, and hydroxyethyl methacrylate as functional monomers, whereas ethyleneglycol dimethacrylate and 1,4‐buthanediol dimethacrylate were used as crosslinkers. Preparation and manipulation protocols were adjusted considering template's nature. To highlight the influence of monomer/crosslinker nature upon imprinted particles, the adsorption capacity, the imprinting factor, and the distribution and selectivity coefficients were calculated. An imprinting factor of 3.53 and a selectivity coefficient of 6.86 were found for hydroxyethyl methacrylate/ethylene glycol methacrylate system. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci. 2013     

Quantised sine signals estimation algorithm for portable digital signal processor based instrumentation

The principles for the development of portable instrumentation equipment (multimeters, frequency meters, etc.) using quantised sine signals, with a common unknown fixed frequency, and an estimation algorithm implemented on digital signal processors (DSPs) are described. An unknown internal sine signal is generated. For measurements, analog to digital converters (ADCs) acquire multiple samples of sine signals, which are quantised and transmitted to the DSP. A precise quantised sine signal, with a common unknown fixed frequency, signal estimation algorithm, for DSP-based instrumentation, is presented. An iterative process is performed to obtain amplitudes, phases, dc components, common frequency and to control the ADC number of bits. Final solutions depend on the initial values, obtained using different classical estimation algorithms. The accuracy of the initial values of iterations and the number of used points have a large influence on the speed of convergence. The algorithm stops when quantisation conditions are satisfied.     

Quantisation-based video watermarking in the wavelet domain with spatial and temporal redundancy

In this article we introduce a new public digital watermarking technique for video copyright protection working in the discrete wavelet transform domain. The scheme uses binary images as watermarks. These are embedded in the detail wavelet coefficients of the middle wavelet sub-bands. The method is a combination of spread spectrum and quantisation-based watermarking. Every bit of the watermark is spread over a number of wavelet coefficients with the use of a secret key. The resilience of the watermarking algorithm was tested against a series of eight different attacks using different videos. To improve the resilience of the algorithm we use error correction codes and embed the watermark with spatial and temporal redundancy. The proposed method achieves a very good perceptual quality with mean peak signal-to-noise ratio values of the watermarked videos of more than 40 dB and high resistance to a large spectrum of attacks.     

Application of Optimal Homotopy Asymptotic Method for solving nonlinear equations arising in heat transfer

We consider one of the newest analytical methods, the Optimal Homotopy Asymptotic Method (OHAM), to solve nonlinear equations arising in heat transfer. Two specific applications are considered: cooling of a lumped system with variable specific heat and the temperature distribution equation in a thick rectangular fin radiation to free space. Results obtained by OHAM, which does not need small parameters are compared with numerical results and a very good agreement was found. This method provides us with a convenient way to control the convergence of approximation series and adjust convergence regions when necessary. The results reveal that the proposed method is explicit, effective and easy to use.     

State complexity of unique rational operations

For each basic language operation we define its “unique” counterpart as being the operation that results in a language whose words can be obtained uniquely through the given operation. These unique operations can arguably be viewed as combined basic operations, placing this work in the popular area of state complexity of combined operations on regular languages. We study the state complexity of unique rational operations and we provide upper bounds and empirical results meant to cast light into this matter. Equally important, we hope to have provided a generic methodology for estimating their state complexity.     

Adaptive relevance feedback for large-scale image retrieval

Content-based image retrieval aims at substituting traditional indexing based on manual annotation by using automatically-extracted visual indexing features. Novel techniques are needed however to efficiently deal with the semantic gap (i.e. the partial match between the low-level features and the visual content). Here, we investigate a query-free retrieval approach first proposed by Ferecatu and Geman. This approach relies solely on an iterative relevance feedback mechanism that drives a heuristic sampling of the collection, and aims to take explicitly into account the semantic gap. Our contributions are related to three complementary aspects. First, we formalize a large-scale approach based on a hierarchical tree-like organization of the images computed off-line. Second, we propose a versatile modulation of the exploration/exploitation trade-off based on the consistency of the system internal states between successive iterations. Third, we elaborate a long-term optimization of the similarity metric based on the user searching session logs accumulated off-line. We implemented a web-application that integrates all our contributions, and distribute it under the AGPL Version 3 free software license. We organized user-based evaluation campaigns using ImageNet dataset, and show empirically that our contributions significantly improve the retrieval performance of the original framework, that they are complementary to each other, and that their overall integration is consistently beneficial.