Supercritical Carbon Dioxide Isolation of Cellulose Nanofibre and Enhancement Properties in Biopolymer Composites

The physical properties, such as the fibre dimension and crystallinity, of cellulose nanofibre (CNF) are significant to its functional reinforcement ability in composites. This study used supercritical carbon dioxide as a fibre bundle defibrillation pretreatment for the isolation of CNF from bamboo, in order to enhance its physical properties. The isolated CNF was characterised through zeta potential, TEM, XRD, and FT-IR analysis. Commercial CNF was used as a reference to evaluate the effectiveness of the method. The physical, mechanical, thermal, and wettability properties of the bamboo and commercial CNF-reinforced PLA/chitin were also analysed. The TEM and FT-IR results showed the successful isolation of CNF from bamboo using this method, with good colloidal stability shown by the zeta potential results. The properties of the isolated bamboo CNF were similar to the commercial type. However, the fibre diameter distribution and the crystallinity index significantly differed between the bamboo and the commercial CNF. The bamboo CNF had a smaller fibre size and a higher crystallinity index than the commercial CNF. The results from the CNF-reinforced biocomposite showed that the physical, mechanical, thermal, and wettability properties were significantly different due to the variations in their fibre sizes and crystallinity indices. The properties of bamboo CNF biocomposites were significantly better than those of commercial CNF biocomposites. This indicates that the physical properties (fibre size and crystallinity) of an isolated CNF significantly affect its reinforcement ability in biocomposites. The physical properties of isolated CNFs are partly dependent on their source and production method, among other factors. These composites can be used for various industrial applications, including packaging.     

Respiratory Motion Correction of Compressively Sampled Myocardial Perfusion Data by Using Robust Matrix Decomposition

Motion correction is a challenging problem in free breathing undersampled cardiac perfusion magnetic resonance images. It is due to aliasing artifacts in the reconstructed images and the rapid contrast changes in the perfusion images. In addition to the reconstruction limitations, many registration algorithms underperforms in the presence of the rapid intensity changes. In this paper, we propose a novel motion correction technique that reconstructs the motion-free images from the undersampled cardiac perfusion MR data. The technique utilizes the robust principal component analysis along with the periodic decomposition to separate the respiratory motion component that can be registered, from the unchanged contrast intensity variations. It was tested on synthetic data, simulated data, and the clinically acquired data. The performance of the method was qualitatively assessed and validated by comparing manually acquired time–intensity curves of the myocardial sectors to automatically generated curves before and after registration.     

Low content Ni and Cr co-doped LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> with enhanced capacity retention

Nanoparticles of the pure and Ni–Cr co-doped lithium manganese oxides Li[Ni_xCr_yMn_2-x-y]O₄ (x = y = 0.01–0.05) have been synthesized by sol–gel method using citric acid as a chelating agent. The effect of low-content doping was noted reflecting the faster ionic movement in the cathode material. The phase structure and morphology of the materials are characterized by XRD, FTIR, SEM and TEM. Electrochemical and impedance measurements established that low-content Ni–Cr substitution substantially improves the structural stability and high rate cycling performance of LiMn₂O₄. Among all the investigated compositions, LiNi_0.01Cr_0.01Mn_1.98O₄ demonstrated the best electrochemical performance. At a substantially high current rate of 5 C, 82% of the initial discharge capacity at 0.1 C is retained. Remarkably, after deep cycling at high rates, a discharge capacity of 104 mAhg^?1 is resumed upon reducing the current rate to 0.1 C which is 91% of the specific capacity in the first cycle.     

Approximation of Pseudoresolvents

After a short introduction where a few main notions and results are recalled, we state some results connected with generated and L_∞-type pseudoresolvents. Among others, we give theorems of characterization both for L_∞-type pseudoresolvents and for their generators. The relation between L_∞-type pseudoresolvents and C₀-equicontinuous semigroups is also pointed out. The last part of the present paper is devoted to approximation of pseudoresolvents and their generators. If are generated pseudoresolvents and A_n, A their generators, we investigate conditions under which A is approximated by A_n and R is approximated by R_n, n ≥ 1. In addition, we give conditions under which a sequence of generated pseudoresolvents approximates a pseudoresolvent, and in this case we study the connection between generators. Received: February 14, 2008., Revised: June 2, 2008., Accepted: August 24, 2008.     

An analytic solution of an oscillatory flow through a porous medium with radiation effect

Analytical solutions for two-dimensional oscillatory flow on free convective-radiation of an incompressible viscous fluid, through a highly porous medium bounded by an infinite vertical plate are reported. The Rosseland diffusion approximation is used to describe the radiation heat flux in the energy equation. The resulting non-linear partial differential equations were transformed into a set of ordinary differential equations using two-term series. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and non-harmonic functions. The free-stream velocity of the fluid vibrates about a mean constant value and the surface absorbs the fluid with constant velocity. Expressions for the velocity and the temperature are obtained. To know the physics of the problem analytical results are discussed with the help of graph.     

Kopsia Singapurensis提取物对酸性介质中低碳钢的缓蚀效应(英文)

The influence of the alkaloid extract of Kopsia singapurensis on the corrosion behavior of mild steel (MS) in 1 mol·L-1 HCl and 1 mol·L-1 H2SO4 was studied using electrochemical techniques, viz., potentiodynamic polarization and AC impedance. The experimental results clearly show that the plant extract effectively inhibits corrosion in both acid media and the inhibition efficiency obtained from the electrochemical techniques is in good agreement. Furthermore, the polarization technique indicates that the extract acts as an anodic type inhibitor in HCl and as a mixed type in H2SO4. Scanning electron microscopy (SEM) was carried out to examine the surface morphological changes of metal specimens in both the inhibited and uninhibited solutions. SEM images show the formation of an adsorbed layer over the metal surface by the inhibitor molecule. The presence of alkaloidal constituents in the plant extract was confirmed by Fourier transform infrared (FTIR) spectroscopy and chemical analysis.     

Influence of a Fe/activated carbon catalyst and reaction parameters on methane decomposition during the synthesis of carbon nanotubes

In our experimental work on carbon nanotubes synthesis, the influence of pre-treatment and reaction temperature conditions over Fe catalyst loaded on low-cost activated carbon (AC) in the catalytic chemical vapor deposition of methane was studied. Catalyst with the metal concentration of 5 mass % calcined at 350°C and reduced at 450°C was effective in CH₄ decomposition giving 98 % conversions. TEM images showed that thin multi-walled carbon nanotubes (MWNTs) with the average internal diameter of ∼ 8 nm and the wall thickness of ∼ 2.5 nm were obtained over unreduced Fe/AC catalyst at the reaction temperature of 850°C. On the other hand, broader filamentous nanostructures with the diameter of ∼ 22 nm and the wall thickness of ∼ 3.72 nm were observed over reduced catalyst.     

Ionic Conductivity in Solutions of Poly(ethylene oxide) and Lithium Perchlorate

Summary: Solution casting technique served to prepare solid solutions of lithium perchlorate and poly(ethylene oxide) (PEO) having different molecular masses. Salt concentrations of solutions were varied between around 2 and 13 wt%. Crystallinity and melting point depression served to determine composition and content of amorphous phase as well as thermodynamic behavior of the solutions. Conductivity as a function of salt concentration in the amorphous phase follows a power law at constant temperature (30 °C). It results that both exponent and mobility of charge carriers increase with ascending molecular mass of PEO. The mobility follows an increase with molecular mass proportional to M^2.8 indicating dependence of mobility on interstitial volume between chain molecules. Deviation of solution from perfect behavior can be evaluated by melting point depression. Accordingly, increase in conductivity is preferably related to approach to perfect solution behavior. Determination of dielectric function allows some conclusion about ion pair formation in the systems under discussion. It turns out that probability of ion pair formation decreases with increasing molecular mass of PEO in agreement with thermodynamic behavior of the solutions.     

HMOAM: hybrid multi-objective genetic optimization for facial analysis by appearance model

Successful hybridization of single-objective evolutionary algorithm with gradient based methods has shown promising results. However, studies of hybridized Multi-Objective Evolutionary Algorithm are limited, especially in the domain of image analysis. This paper presents a novel methodology of hybridization of multi-objective genetic algorithm for the real world optimization problem of facial analysis of multiple camera images by 2.5D Appearance Model. Facial large lateral movements make acquisition and analysis of facial images by single camera inefficient. Moreover, non-convex multi-dimensional search space formed by the face search by appearance model requires an efficient optimization methodology. Currently, with wide availability of inexpensive cameras, a multi-view system is as practical as a single-view system. To manage these multiple informations, multi-objective genetic algorithm is employed to optimize the face search. To efficiently tackle the problem of non-convexity of the search space, hybridization of NSGA-II (Non-dominated Sorting Genetic Algorithm) with Gradient Descent is proposed in this paper. For this hybridization, we propose a gradient operator in NSGA-II, which computes gradients of the solutions in conjunction with the existing operator of mutation. Thus, it does not increase the computational cost of the system. Another proposition includes a unique method of calculating the relevant information of each camera in a multiple camera system which makes the hybridization procedure efficient and robust. Our proposed algorithm is applied on different facial poses of CMU-PIE database, webcam face images and synthetic face images, and the results are compared with a single view system and a non-hybrid multiple camera system. Simulation results validate the efficiency, accuracy and robustness achieved.