Thermal properties of extruded injection‐molded poly(lactic acid) and milkweed composites: Degradation kinetics and enthalpic relaxation

To determine the degree of compatibility between poly(lactic acid) (PLA) and different biomaterials, PLA was compounded with milkweed fiber, a new crop oil seed. After oil extraction, milkweed remaining cake retained approximately 10% residual oil, 47% protein, and 10% moisture. The fiber (300 μm) was added at 85 : 15 and 70 : 30 PLA : Fiber and blended by extrusion (EX) followed by injection molding (IM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used for testing the composites. After melting in the DSC sealed pans, composites were cooled by immersion in liquid nitrogen and aged (stored) at room temperature for 0, 7, 15, and 30 days. After storage, samples were heated from room temperature to 180°C at 10°C/min. The pure PLA showed a glass transition (T_g) at 60.3°C and the corresponding ΔCp was 0.464 J/g/°C followed by crystallization and melting transitions. The enthalpic relaxation (ER) of neat PLA and composites steadily increased as a function of storage time. Although the presence of fiber had little effect on ER, IM reduced it. The percentage crystallinity of neat unprocessed PLA dropped by 95 and 80% for the EX and IM, respectively. The degradation activation energy (E_a) of neat PLA exhibited a significant drop in nitrogen environment, whereas increased in air, indicating PLA resistant to heat degradation in the presence of oxygen. Overall, IM appeared to decrease E_a of the composites, whereas milkweed significantly reduced E_a values in nitrogen environment. Enzymatic degradation of the composites revealed higher degradation rate for the EX samples versus IM, whereas 30% milkweed exhibited higher weight loss compared to the 15%. The degradation mechanism was observed by looking at the percent conversion as a function of E_a from the TGA data, where multisteps degradation occurred mostly in air. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Phospholipids and poly(glutamic acid)/hydrolysed gluten: Interaction and kinetics

The effect of poly(glutamic acid) (PGA) and hydrolysed wheat gluten (HG) on the thermal and kinetics properties of lysophosphatidylcholine (LPC) was determined using DSC. A model system containing PGA or HG was added to 40% LPC aqueous suspension. The results from the study showed reduced ΔH values as a function of PGA molecular weight, which signified some kind of penetration of PGA or HG into the LPC bi-layer but not enough to minimise the order of LPC vesicle structure. The ability of LPC molecules to rearrange itself into a bi-layer again was evident in the emergence of crystallisation profiles in the course of the cooling cycle. The calculated activation energy (E_a) of pure LPC vesicle disruption (heating) and formation (cooling) was 696.6 and 520.4 kJ/mol, respectively. Overall, the trend of lower E_a as a function of PGA molecular weight was apparent during both heating and cooling cycles. Although, both PGA and HG reduced the E_a, HG was less effective in reducing E_a. The purported molecular interaction between phospholipids and gluten has been confirmed using FT-IR spectroscopy. The FT-IR results indicated that interactions occurred in LPC/HG blends and in model mixtures consisting of LPC/PGA with different molecular weight.     

Oats protein isolate: Thermal,rheological, surface and functional properties

Oat protein isolate (OPI) was extracted in 0.015 N NaOH and acetylated or succinylated. The thermal analysis of the isolate showed a glass transition (T_g) at 43.4 °C and ΔC_p of 0.102 J/g/°C. The positive net charge of OPI and the positive or neutral charge of the modified OPI were apparent from the free capillary zone electrophoresis (FZCE) profiles. Acetylation significantly lowered foaming and emulsifying properties of OPI, while succinylation showed the highest foaming capacity, foam stability, and emulsion stability. Acetylated OPI showed the highest surface hydrophobicity compared to the other samples, while OPI was the most soluble of all. The water holding capacity of all samples analyzed was the same except for acetylated-crosslinked (ACXL). The surface tension test confirmed that unmodified and modified OPI possessed surface activity and the equilibrium surface tensions decreased sharply with increasing protein concentration and leveled off to a constant value. The elastic modulus, G′, for the acetylated OPI suspension exhibited the highest value, while the G′ of the crosslinked (XLOPI) had the lowest. The plateau of G′, was 2961 Pa, 920 Pa, 223 Pa, 41 Pa, and 1.8 Pa for the ACOPI, ACXL, SOPI, and XL, respectively.     

A shunt active filter for compensating harmonics and unbalance in three-phase four-wire systems

ABSTRACT

This paper introduces a split-capacitor shunt Active Power Filter (SC-APF) based on Synchronous Reference Frame (SRF) theory. This topology is used in compensating the currents of 3-Ph unbalanced non-linear loads. The voltage control loop used in SRF which is only suitable in controlling Four-Leg APF (FL-APF) is modified to control Spilt-Capacitor APF (SC-APF). The proposed scheme provides compensating the 3-Ph unbalanced non-linear loads with lower number of switches, passive elements, and sensors. The performance of the SC-APF with the modified calculation algorithm is verified through simulation and experimental studies.     

A new images segmentation method based on modified particle swarm optimization algorithm

The partitioning of an image into several constituent components is called image segmentation. Many approaches have been developed; one of them is the particle swarm optimization (PSO) algorithm, which is widely used. PSO algorithm is one of the most recent stochastic optimization strategies. In this article, a new efficient technique for the magnetic resonance imaging (MRI) brain images segmentation thematic based on PSO is proposed. The proposed algorithm presents an improved variant of PSO, which is particularly designed for optimal segmentation and it is called modified particle swarm optimization. The fitness function is used to evaluate all the particle swarm in order to arrange them in a descending order. The algorithm is evaluated by performance measures such as run time execution and the quality of the image after segmentation. The performance of the segmentation process is demonstrated by using a defined set of benchmark images and compared against conventional PSO, genetic algorithm, and PSO with Mahalanobis distance based segmentation methods. Then we applied our method on MRI brain image to determinate normal and pathological tissues. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 265–271, 2013     

In/Ga inter-diffusion in InAs quantum dot in InGaAs/GaAs asymmetric quantum well

The Photoluminescence spectra (PL), their temperature and power dependence were investigated for the ground state in InAs quantum dots (QDs) embedded in InGaAs asymmetric quantum well (Asym. QW). In-atom segregation is well known phenomena in such structures, which result in altering the inter-atomic distances; as a consequence the thermo-dynamical parameters change as well, namely Debye temperature. The bigger value of Debye temperature for the studied sample with respect to the corresponding bulk value is attributed to In/Ga inter-diffusion during growth. The inter-diffusion process causes non-radiative defects in the sample. As a consequence, rapid decrease in the QDs integrated emission intensity as the temperature increases was occurred.     

Dry cleaning aluminum cell gases from Söderberg cells

This article describes dry cleaning gases from vertical Söderberg cells via a two-step process involving the combustion of tars and CO followed by the chemisorption of HF on smelter-grade alumina. Both steps take place in fluidized-bed reactors. Studied parameters include distributor design, fluidizing velocity, bed temperature, and bed height.     

Bio‐nanocomposite films based on cellulose nanocrystals filled polyvinyl alcohol/chitosan polymer blend

Bio‐nanocomposite films based on polyvinyl alcohol/chitosan (PVA/CS) polymeric blend and cellulose nanocrystals (CNC) were prepared by casting a homogenous and stable aqueous mixture of the three components. CNC used as nanoreinforcing agents were extracted at the nanometric scale from sugarcane bagasse via sulfuric acid hydrolysis; then they were characterized and successfully dispersed into a PVA/CS (50/50, w/w) blend to produce PVA/CS–CNC bio‐nanocomposite films at different CNC contents (0.5, 2.5, 5 wt %). Viscosity measurement of the film‐forming solutions and structural and morphological characterizations of the solid films showed that the CNC are well dispersed into PVA/CS blend forming strong interfacial interactions that provide an enhanced load transfer between polymer chains and CNC, thus improving their properties. The obtained bio‐nanocomposite films are mechanically strong and exhibit improved thermal properties. The addition of 5 wt % CNC within a PVA/CS blend increased the Young's modulus by 105%, the tensile strength by 77%, and the toughness by 68%. Herein, the utilization of Moroccan sugarcane bagasse as raw material to produce high quality CNC has been explored. Additionally, the ability of the as‐isolated CNC to reinforce polymer blends was studied, resulting in the production of the aforementioned bio‐nanocomposite films with improved properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42004.