Characterization and thermal degradation kinetics of poly(l‐lactide) nanocomposites with carbon nanotubes

The purpose of this research was to study the thermal degradation kinetics of nanocomposites of poly(l ‐lactide) (PLLA) with carbon nanotubes (CNT) in order to provide further insight into their thermal stability. Nanocomposites were prepared by solvent casting with 1, 3, and 5% by weight of pristine CNT (P‐CNT) or functionalized CNT (F‐CNT), and were characterized using infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic‐mechanical‐thermal analysis. The kinetic parameters of thermal decomposition were determined employing Coats‐Redfern method to calculate the reaction order and E₂ function model to calculate the activation energy (Ea). We found no major changes in PLLA glass transition temperatures due to CNT presence, but melt‐crystallization temperature increased slightly in some composites. In general, composites consisting of 3% or 5% of F‐CNT had superior thermal stability than did pure polymer or P‐CNT composites. This improved thermal stability was revealed by slightly higher degradation and onset temperatures, and Ea obtained from kinetic analysis. In addition, 3% or 5% of F‐CNT in PLLA composites slightly enhanced the storage modulus above the glass transition. Therefore, functionalization promoted, in some extent, better morphology and dispersion of CNT into the matrix, which was responsible for improved thermal stability and thermomechanical performance of composites at higher temperatures relative to pure polymer. POLYM. ENG. SCI., 55:710–718, 2015. © 2014 Society of Plastics Engineers     

CAD tools for bridging microsystems and foundries

To move microsystems from research prototypes to an industrial market, CMP, the French multiproject wafer service, has adapted an existing commercial tool to the automated design of micromachined devices     

A microwave scattering model for layered vegetation

A microwave scattering model was developed for layered vegetation based on an iterative solution of the radiative transfer equation up to the second order to account for multiple scattering within the canopy and between the ground and the canopy. The model is designed to operate over a wide frequency range for both deciduous and coniferous forest and to account for the branch size distribution, leaf orientation distribution, and branch orientation distribution for each size. The canopy is modeled as a two-layered medium above a rough interface. The upper layer is the crown, containing leaves, stems, and branches. The lower layer is the trunk region, modeled as randomly positioned cylinders with a preferred orientation distribution above an irregular soil surface. Comparisons of results obtained using this model with measurements from deciduous and coniferous forests show good agreement at several frequencies for both like and cross polarizations     

Thermal, microstructural and textural characterisation of gelatinised corn, cassava and yam starch blends

The functional properties of mixtures of maize, cassava and yam starches and their relationships with microstructural characteristics were investigated. Experiments were performed following the simplex‐centroid design with internal points and restrictions (upper limit) for yam starch proportion. The statistical model used (Scheffé canonical equation) was a powerful tool to predict the pastes behaviour within the limits of the experimental area. Polynomials with second level interactions were applied to obtain the surface response. Viscoelastic attributes of mixtures differed from those of individual starches. As shown by differential scanning calorimetry and microscopical observations, physical properties of the mixtures depended on the type of networks obtained. These networks varied upon yam, corn and cassava starch proportions as each one has a particular characteristic: gelatinisation temperature, granule size, swelling capacity and amylose/amylopectin ratio among others.     

Robust hyperspectral image coding with channel-optimizedtrellis-coded quantization

This paper presents a wavelet-based hyperspectral image coder that is optimized for transmission over the binary symmetric channel (BSC). The proposed coder uses a robust channel-optimized trellis-coded quantization (COTCQ) stage that is designed to optimize the image coding based on the channel characteristics. This optimization is performed only at the level of the source encoder and does not include any channel coding for error protection. The robust nature of the coder increases the security level of the encoded bit stream, and provides a much higher quality decoded image. In the absence of channel noise, the proposed coder is shown to achieve a compression ratio greater than 70:1, with an average peak SNR of the coded hyperspectral sequence exceeding 40 dB. Additionally, the coder is shown to exhibit graceful degradation with increasing channel errors     

Growth and characterization of inTISb for IR-detectors

Epitaxial In_1-xTl_xSb films with compositions up to x = 0.1 have been demonstrated using the metalorganic chemical vapor deposition technique on InSb and GaAs substrates. A specially designed high-temperature source delivery system was used for the low vapor pressure cyclopentadienylthallium source. Tl-compositions in the deposited films were measured by Rutherford backscattering spectroscopy which confirmed the incorporation of up to 10% Tl. Room temperature infrared transmission spectra of InTISb exhibited considerable absorption beyond 7 μm. Photoconductive detectors were fabricated in InTISb films grown on semi-insulating GaAs. Spectral response measurements showed substantial photoresponse at 8.5 to 14 μm. In spite of the large lattice-mismatch (≈14%) between InTISb and GaAs, photoconductive detectors exhibited black-body detectivities (D^* _bb) of 5.0 × 10⁸ cm-Hz^1/2W⁻¹ at 40K.     

Room-temperature CW operation of GaAs-AlGaAs diode lasers on silicon-on-insulator wafers

GaAs-AlGaAs diode lasers have been fabricated on silicon-on-insulator wafers for the first time. Gain-guided graded-index separate-confinement heterostructure single-quantum-well (GRINSCH-SQW) lasers operated CW at room temperature with threshold current as low as 43 mA, differential quantum efficiency as high as 54%, and output power of more than 60 mW/facet. One device operated CW for 75 min at an output power of 1 mW/facet.<>     

Analysis of predistortion, equalization, and ISI cancellationtechniques in digital radio systems with nonlinear transmit amplifiers

An analysis made of the performance of predistortion, equalization, and intersymbol interference (ISI) cancellation techniques in compensating for the transmit amplifier nonlinearity in digital microwave radio systems. The study is carried out using the 64 QAM and 256 QAM signal formats and two values of the roll-off factor in the Nyquist pulse shaping. The simulated compensation techniques include three types of predistortion, two ISI cancellers, and several nonlinear equalizers with or without decision feedback. A basic result is that decision-feedback equalizers do not offer any significant advantage over nonrecursive equalizers. It is also shown that ISI cancelers with a memoryless equalizer as first-stage decision device do not perform any better than nonlinear equalizers of similar complexity. Another contribution an improved fifth-order analog signal predistortion technique is analyzed. The gain that can be achieved using a modified 256 QAM signal constellation that is more robust to nonlinear distortion is quantified     

STUDY OF EXTRACTION METHODS FOR HIGH-ASH COAL USING LOW-BOILING EXTRACTING AGENTS. I. SOLID PHASE EXTRACTION

The quality, as well as the quantity, of coal-derived liquids are investigated using low-boiling extracting agents in solid phase extraction (SPE). A broad range of solvents with different boiling point and polarity are studied in order to generate the desired coal-derived material. The column is packed with the coal under investigation and a sequence of solvents used to desorb the organic material trapped in the carbonaceous matrix. It is shown that the nature of the solvent, the solvent-to-coal ratio and the coal mesh size must be carefully controlled. The method is shown to be reliable for generating coal-derived products since it is performed under mild experimental conditions and generates amounts of material comparable to Soxhlet extraction procedures in much less time. In addition, it is cheap, easy to perform, fast and reproducible.     

Autosomal dominant polycystic kidney disease: urologic complications and results of kidney transplantation: 217 patients

The authors report a retrospective series of 217 cases of autosomal dominant renal polycystic disease collected over a period of 30 years in the urology and nephrology departments of Nantes university hospital. They study the incidence of urological complications, observed in 87 patients (40%), consisting of calculi (15%), infection (22%, with 4 deaths), intracystic haemorrhages (3.5%) and urinary tract compression (2%). The diagnostic and therapeutic methods are presented and discussed. The results of renal transplantation are also analysed: 39 patients were transplanted, 72% retained a functioning kidney with a mean follow-up of 44.9 months (range: 12-108 months) and three patients died as a result of infectious complications. The 1-year and 3-year actuarial transplant survival rate of 92% was similar to that of renal transplantations performed for another form of renal disease. Preparation for renal transplantation remains an essential problem: the two major indications for pre-transplantation nephrectomy were the size of the kidneys and the presence of infection.