Thermal property,morphology, and hydrolysis ability of poly(lactic acid)/chitosan nanocomposites using polyethylene oxide

Poly(lactic acid) (PLA) and chitosan (CS) are two natural resource polymers, which have been applied widely into different fields. Polymer composites based on PLA and CS have some advantages such as good adhesion, biodegradability, biocompatibility, and high stability. They can be prepared by different methods including the solution, emulsion, and electrospinning methods. In this work, the PLA/chitosan nanocomposites were prepared by solution method using poly(ethylene oxide) (PEO) as a compatibilizer in order to improve interaction and dispersion between PLA and CS phases. The characterization and morphology of the above nanocomposites were determined by Fourier Transform Infrared Spectroscopy (FTIR), thermograviety analysis, differential scanning calorimetry, and scanning electron microscopy. Hydrolysis ability of PLA/CS nanocomposites with and without PEO was also investigated in acid and phosphate buffer solutions. The obtained results showed the compatibility between PLA and CS phases in the PLA/CS nanocomposites using PEO was improved clearly and weight loss of PLA/CS/PEO nanocomposites in the above environments lower than that of PLA/CS nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41690.     

An Edge-Based Smoothed Discrete Shear Gap Method Using the C0-Type Higher-Order Shear Deformation Theory for Analysis of Laminated Composite Plates

The edge-based smoothing discrete shear gap method (ES-DSG3) using three-node triangular elements is combined with a C⁰-type higher-order shear deformation theory (HSDT) to give a new linear triangular plate element for static, free vibration, and buckling analyses of laminated composite plates. In the ES-DSG3, only the linear approximation is necessary, and the discrete shear gap method (DSG) for triangular plate elements is used to avoid the shear locking and spurious zero energy modes. In addition, the stiffness matrices are calculated relying on smoothing domains associated with the edges of the triangular elements through an edge-based strain smoothing technique. Using the C⁰-type HSDT, the shear correction factors in the original ES-DSG3 can be removed and replaced by two additional degrees of freedom at each node. The numerical examples demonstrated that the ES-DSG3 show remarkably excellent performance compared to several other published elements in the literature.     

A hybrid machine learning model to estimate self-compacting concrete compressive strength

This study examined the feasibility of using the grey wolf optimizer (GWO) and artificial neural network (ANN) to predict the compressive strength (CS) of self-compacting concrete (SCC). The ANN-GWO model was created using 115 samples from different sources, taking into account nine key SCC factors. The validation of the proposed model was evaluated via six indices, including correlation coefficient (R), mean squared error, mean absolute error (MAE), IA, Slope, and mean absolute percentage error. In addition, the importance of the parameters affecting the CS of SCC was investigated utilizing partial dependence plots. The results proved that the proposed ANN-GWO algorithm is a reliable predictor for SCC’s CS. Following that, an examination of the parameters impacting the CS of SCC was provided.     

Comparative study of photoinitiator curing efficiency using regression data analysis

Regression data analysis was used to compare two alphahydroxy ketone, 1-hydroxycyclohexyl phenyl ketone (HCPK) and2-hydroxy-2-methyl-1phenyl-propan-1-one (HMPP) and two phosphine oxide, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide (TPO) and bis (2,6-dimethoxybenzoyl) 2,4,4-trimethyl pentyl phosphine oxide (DMBAPO) photoinitiators in a thin coating application. Phosphine oxide is inherently more efficient, especially in white pigmented systems than alpha hydroxy ketone because of its stronger and broader absorption at longer wavelength. Due to molecular weight dilution effect, it is usually required to have a higher TPO concentration in a formulation than HCPK or HMPP to overcome oxygen inhibition. On the molecular level, however, DMBAPO is the most reactive photoinitiator among all of them. Data analysis also suggests that the number of initiating free radicals generated by DMBAPO is twice of that generated by HCPK or HMPP or TPO. This study also confirms that in thin coating applications the use of either nitrogen blanket orphotoinitiator blend is a good method for increasing productivity and reducing formulation cost. Additives Div., 540 White Plains Rd., Tarrytown, NY 10591-1900     

Ether lipid biosynthesis: isolation and molecular characterization of human dihydroxyacetonephosphate acyltransferase

In this paper we describe isolation and molecular characterization of human dihydroxyacetonephosphate acyltransferase (DAP-AT). The enzyme was extracted from rabbit Harderian gland peroxisomes and isolated as a trimeric complex by sucrose density gradient centrifugation. From peptide sequences matching EST-clones were obtained which allowed cloning and sequencing of the cDNA from a human cDNA library. The nucleotide-derived amino acid sequence revealed a protein consisting of 680 amino acid residues of molecular mass 77187 containing a C-terminal type 1 peroxisomal targeting signal. Monospecific antibodies raised against this polypeptide efficiently immunoprecipitated DAP-AT activity from solubilized peroxisomal preparations, thus demonstrating that the cloned cDNA codes for DAP-AT.     

Wireless sensing and identification based on radar cross section variability measurement of passive electromagnetic sensors

In this paper, we present the wireless measurement of various physical quantities from the analysis of the radar cross section variability of passive electromagnetic sensors. The technique uses a millimeter frequency-modulated continuous-wave radar for both remote sensing and wireless identification of sensors. Long reading ranges (up to some decameters) are reached at the expense of poor measurement resolution (typically 10 %). A review of recent experimental results is reported for illustration purposes.     

On Construction of Virtual Backbone in Wireless Ad Hoc Networks with Unidirectional Links

Since there is no fixed infrastructure in wireless ad hoc networks , virtual backbone has been proposed as the routing infrastructure to alleviate the broadcasting storm problem. The virtual backbone construction has been studied extensively in {em undirected} graphs, especially in unit disk graphs, in which each node has the same transmission range. In practice, however, transmission ranges of all nodes are not necessarily equal. In this paper, we model such a network as a disk graph, where unidirectional links are considered. To study the virtual backbone construction in disk graphs, we consider two problems: Strongly Connected Dominating Set (SCDS) and Strongly Connected Dominating and Absorbing Set (SCDAS). We propose a constant approximation algorithm and discuss its improvements for the SCDS problem . We also propose a heuristic for the SCDAS problem. Through extensive simulations, we verify our theoretical analysis and also demonstrate that the SCDS can be extended to form an SCDAS with marginal extra overhead.     

A comprehensive study on frictional dependence and predictive accuracy of viscoelastic model for optical glass using compression creep test

Compression creep tests (CCTs) have been widely used in phenomenological characterization of viscoelastic materials such as glasses. However, disturbed by specimen-tool interface friction, the real stress-strain data regarding the pure viscoelastic deformation are frequently misestimated in conventional CCTs, causing decreased accuracies of the derived viscoelastic parameters. This study proposes a comprehensive CCT-based approach to develop a viscoelastic model with weakened frictional disturbance and enhanced predictive accuracy. An integrated calculation procedure is first built to mathematically characterize the frictional and viscoelastic behaviors of glass during compression. Uniaxial CCTs of a typical borosilicate glass (L-BAL42) are then performed at varied frictional conditions. The quantified coefficients of interface friction indicate that a minor frictional disturbance is achieved when Nickel foils are used as interfacial layers, whereby a more realistic viscoelastic constitutive relation of the glass is derived. The obtained frictional and viscoelastic constants are further incorporated into computational modeling of the CCT and precision molding processes. The demonstrated consistencies between the simulated and measured results (creep displacement and molding force) suggest that, by technically slashing the interface friction and theoretically correcting the friction-involved stress in CCTs, the frictional disturbance to experimental stress-strain data can be effectively weakened, and a viscoelastic model of enhanced predictive accuracy can be thus developed.     

A cell‐based smoothed discrete shear gap method using triangular elements for static and free vibration analyses of Reissner–Mindlin plates

The cell‐based strain smoothing technique is combined with discrete shear gap method using three‐node triangular elements to give a so‐called cell‐based smoothed discrete shear gap method (CS‐DSG3) for static and free vibration analyses of Reissner–Mindlin plates. In the process of formulating the system stiffness matrix of the CS‐DSG3, each triangular element will be divided into three subtriangles, and in each subtriangle, the stabilized discrete shear gap method is used to compute the strains and to avoid the transverse shear locking. Then the strain smoothing technique on whole the triangular element is used to smooth the strains on these three subtriangles. The numerical examples demonstrated that the CS‐DSG3 is free of shear locking, passes the patch test, and shows four superior properties such as: (1) being a strong competitor to many existing three‐node triangular plate elements in the static analysis; (2) can give high accurate solutions for problems with skew geometries in the static analysis; (3) can give high accurate solutions in free vibration analysis; and (4) can provide accurately the values of high frequencies of plates by using only coarse meshes. Copyright © 2012 John Wiley & Sons, Ltd.