Cellulosic blends with poly(acrylonitrile): characterization of hydrogen bonds using regioselectively methylated cellulose derivatives

Hydrogen bonds in cellulosic blends with poly(acrylonitrile) (PAN) were characterized in terms of hydroxyl regiochemistry in the cellulosics using Fourier transform infra-red (FTi.r.) spectroscopy. Regioselectively substituted O-methylcelluloses (MC), 2,3-di-O-methylcellulose (23MC) and 6-O-methylcellulose (6MC), were used as cellulosic model components. Wide-angle X-ray diffraction studies of the cast films of blends having more than 50 wt% cellulosic content showed them to be highly amorphous, indicating the presence of a certain interaction between the cellulosics and PAN. FTi.r. analysis revealed that the hydrogen bonds in cast films washed with solvents were only engaged between the primary hydroxyl groups (OH) at the C-6 position of cellulose and the nitrile group (CN) of the PAN molecule, while there was no evidence for polymer–polymer interactions in the secondary hydroxyl groups at the C-2 and C-3 positions in cellulosics or in the ether oxygens such as ring oxygen (O-5) and glucosidic linkage oxygen. In contrast, the remaining DMAc after film cast seems to have an additional interaction to connect the two polymer components, which makes the blends more miscible. Quantitative analysis was also carried out to ascertain the amounts of OH at the C-6 position engaged in the intermolecular hydrogen bonds.     

Stabilization of the Mass Absorption Cross Section of Black Carbon for Filter-Based Absorption Photometry by the use of a Heated Inlet

In principle, mass concentrations of black carbon (BC) (M _BC) can be estimated by the measurement of the light absorption coefficient of BC. Filter-based methods, which quantify the absorption coefficient (b _abs) from the change in transmission through a filter loaded with particles, have been widely used to measure M _BC. However, reliable determination of M _BC has been very difficult because of the large variability in the mass absorption cross section (C _abs), which is the conversion factor from b _abs to M _BC. Coating of BC by volatile compounds and the co-existence of light-scattering particles contribute to the variability of C _abs. In order to overcome this difficulty, volatile aerosol components were removed before collection of BC particles on filters by heating a section of the inlet to 400°C. We made simultaneous measurements of b _abs by two types of photometers (Particle Soot Absorption Photometer (PSAP) and Continuous Soot Monitoring System (COSMOS)) together with M _BC by an EC-OC analyzer to determine C _abs at 6 locations in Asia. C _abs was stable at 10.5 ± 0.7 m² g ^?1 at a wavelength of 565 nm for BC strongly impacted by emissions from vehicles and biomass burning. The stable C _abs value provides a firm basis for its use in estimating M _BC by COSMOS and PSAP with an accuracy of about 10%. For the quantitative interpretation of the ratio of the C _abs to the model-calculated C _abs?, we measured C _abs for mono-disperse nigrosin particles in the laboratory. The C _abs/C _abs? ratio was 1.4–1.9 at the 100–200 nm diameters, explaining the ratio of 1.8 for ambient BC.     

Properties ofSrMO 3-δ(M=Fe,Co) as oxygen electrodes in alkaline solution

Strontium ferrates and cobaltates with compositions SrFeO_3- (0.060.40) and SrCoO_3- (0.040.30) were synthesized. The dependence of the oxygen electrode properties on the value was examined in 1 mol dm^–3 KOH solution. In the SrFeO_3- series, the samples with 0.24<<0.29, showed the highest activity in both oxygen evolution and reduction reactions. In contrast, no strong dependence on the value was observed in SrCoO_3-, which also showed a high catalytic activity for oxygen evolution.     

Degradation analysis of a Ni-based layered positive-electrode active material cycled at elevated temperatures studied by scanning transmission electron microscopy and electron energy-loss spectroscopy

We investigate the local structural changes in a positive electrode of a lithium ion secondary battery (LiNi_0.8Co_0.15Al_0.05O₂ (NCA) as the active material) associated with charge-discharge cycling at elevated temperatures by scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). STEM-EELS spectral imaging reveals the evolution of a NiO-like phase localized near the surface and grain boundary regions after many cycles. The amounts of capacity fading and resistance increase are discussed based on the results of the semiquantitative estimation of NiO-like and other product phases. We also identify the chemical state of lithium in the NiO-like phase substituting for Ni.     

Contents of various sources of glucose and fructose in rice straw, a potential feedstock for ethanol production in Japan

The major carbohydrates of rice straw samples were determined in order to evaluate the potential of using rice straw as a feedstock for ethanol production in Japan. Straw samples were harvested by cutting the plants at ground level when the grain was mature and immediately heating or chilling the samples. In all cases, significant amounts (62-303 g kg⁻¹) of soft carbohydrates defined as consisting of glucose, fructose, sucrose, starch and ??-1,3-1,4-glucan were detected, in addition to structural carbohydrates (cellulose and xylan). These results indicate that rice straw is a rich source of fermentable sugars from both soft carbohydrates and lignocellulosic portions of the cell wall.     

Enlarging switching frequency in direct torque-controlled inverterby means of dithering

This paper presents a novel, simple method to enlarge switching frequency in the direct torque-controlled inverter for an induction motor drive, which makes an acoustically silent motor operation possible. It is actually impossible to raise the inverter switching frequency in the conventional system, although the hysteresis bandwidths for the stator flux and torque control are sufficiently diminished, because of the delay in estimating the flux and the torque. In order to overcome the problem, the proposed method introduces a dithering technique into the conventional system by superposing triangular waves with high frequency and minute amplitude on the flux error and the torque error, respectively. According to the simulation and experimental results, the stator flux ripple and the torque ripple were suppressed to approximately 30% compared with those of the conventional system. Also, the acoustic noise level of the motor was reduced to less than 56 dB over the whole speed range from 100 to 1500 r/min     

Hugoniot measurement by hyper-velocity impact at velocities up to 9 km/s using a two-stage light-gas gun under optimized shot conditions

The optimization for acceleration of a projectile was performed by varying piston mass in consideration with the correlation with projectile mass and the engineering limits of the two-stage light-gas gun, and the projectile velocity has been achieved 9.2 km/s using the optimum acceleration conditions. Moreover, the Hugoniot measurements of oxygen-free copper were performed using the line reflection method at pressures up to 380 GPa by symmetric impact. The tilt and curvature of shock front were investigated according to the impact velocity, and it is proved to be important that the continuous spatial profile of shock front would be recorded.     

Multiscale modelling of the composite reinforced foam core of a 3D sandwich structure

A key objective dealing with 3D sandwich structures is to maximize the through-thickness stiffness, the strength of the core and the core to faces adhesion. The Napco^® technology was especially designed for improving such material properties and is under investigation in this paper. In particular, the potential of the process is characterized using a micromechanical modelling combined to a parametric probabilistic model. An experimental analysis is further detailed and validates the theoretical estimates of the core-related elastic properties. It is readily shown that the technology is able to produce parts with significantly improved mechanical properties. Finally, thanks to the probabilistic aspect of the modelling, the study allows to establish a link between the randomness of the process and the uncertainties of the final mechanical properties. Thus, the present approach can be used to optimize the technology as well as to properly design structures.