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41.
Fouad Al Katrib Gerard Chambat Jean-Paul Joseleau 《Journal of the science of food and agriculture》1988,43(4):309-317
Enzymic saccharification of wheat straw in the absence of any pretreatment was only about 20 %. Acid hydrolysis did not improve the overall cellulose enzymic breakdown, nor did pretreatment by flash autohydrolysis under pressure or sodium chlorite delignification. When wheat straw was treated with N-methyl-morpholine-N-oxide (MMNO) at J20°C for 20–30 min, this treatment and subsequent enzymic hydrolysis produced carbohydrate conversion of 73%. Similar results could be obtained by treating straw with 0·1 M sodium hydroxide. When MMNO treatment was combined with any other pretreatment, the saccharification yield was greatly enhanced. Nearly quantitative conversion was obtained by swelling straw in 0·1 M sodium hydroxide followed by MMNO treatment. The results show that lignin content of plant material does not represent the limiting factor to enzymic saccharification. 相似文献
42.
The martensitic transformation behavior, second phases and hardness of Ti51Ni49−xSix shape memory alloys (SMAs) with x = 0, 1 and 2 at.% are investigated. The transformation temperature of one stage martensitic reaction B2 ↔ B19′ is associated with the forward (Ms) and reverse (As) martensitic transformations, respectively. All experimental DSC results such as martensitic transformation peaks (M*) and reverse martensitic transformation peaks (A*) are increased and became sharper with increasing Si-content. The microstructure investigation of the studied SMAs (Ti51Ni49−xSix) showed that there are two types of precipitated second phase particles. The first one is Ti2Ni which mainly located at grain boundaries and intermetallic compound of Ti2(Ni + Si) phase distributed inside the matrix. The volume fraction of these two phases is increased with Si content. Additionally, a small amount of Si remained in solid solution of the matrix of Ti51Ni49−xSix SMAs. Moreover, hardness of Ti51Ni49−xSix SMAs is increased as the Si-content increases. 相似文献
43.
Donggeon Han Yasser Khan Jonathan Ting Simon M. King Nir Yaacobi‐Gross Martin J. Humphries Christopher J. Newsome Ana C. Arias 《Advanced materials (Deerfield Beach, Fla.)》2017,29(22)
A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light‐emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface‐energy‐patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near‐infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs. 相似文献
44.
Yasser Kiani 《热应力杂志》2013,36(12):1495-1518
Based on the uncoupled thermoelasticity assumptions, axisymmetric thermally induced vibrations of a circular plate made of functionally graded materials (FGMs) are analyzed. Each thermomechanical property of the circular plate is assumed to be functions of temperature and thickness coordinate. Solution of the transient one-dimensional heat conduction equation with the arbitrary type of time-dependent boundary conditions is carried out employing the central finite difference method combined with the Crank–Nicolson time marching scheme. Afterwards, with the establishment of the associated Hamilton's principle and the accountancy of the von Kármán type of geometrical non-linearity, the motion equations are obtained with the aid of the conventional multi-term Ritz method. The solution of highly coupled non-linear motion equations is obtained utilizing a hybrid iterative Newton–Raphson–Newmark scheme. After validating the developed computer code, some parametric studies are accomplished to show the influences of various involved parameters. It is shown that temperature dependency, geometrical non-linearity, plate thickness, power law index, and the type of thermal in-plane and out-of-plane mechanical boundary conditions, all affect the temporal evolution of plate characteristics. 相似文献
45.
Synthesis and characterization of new polyurethanes: influence of monomer composition 总被引:1,自引:0,他引:1
Different polyurethanes (PU) were synthesized from polycaprolactone diol, 1.6-hexamethylene diisocyanate and bis(2-hydroxyethyl)terephthalate,
using a two- and one-step methods providing regular and random distributions of starting monomers in the polyurethane chains.
Even with an identical molar monomer composition, the properties of obtained PU are different depending on the method of synthesis.
The chemical structure of PU was characterized by 1H and 13C NMR spectroscopy, as well as by FTIR and UV–Visible spectroscopy. The thermo-mechanical and hydrophilic properties of synthesized
PU were also studied demonstrating the influence of aromatic ring in the macromolecular chain. 相似文献
46.
Reduction of the emissions of greenhouses gases, increasing the share of renewable energy sources (RES) in the energy balance, increasing electricity production from renewable energy sources and decreasing energy dependency represent the main goals of all current strategies in Europe. Biomass co-firing in large coal-based thermal power plants provides a considerable opportunity to increase the share of RES in the primary energy balance and the share of electricity from RES in gross electricity consumption in a country. Biomass-coal co-firing means reducing CO2 and SO2, emissions and it may also reduce NOx emissions, and also represents a near-term, low-risk, low-cost and sustainable energy development. Biomass-coal co-firing is the most effective measure to reduce CO2 emissions, because it substitutes coal, which has the most intensive CO2 emissions per kWh electricity production, by biomass, with a zero net emission of CO2. Biomass co-firing experience worldwide are reviewed in this paper. Biomass co-firing has been successfully demonstrated in over 150 installations worldwide for most combinations of fuels and boiler types in the range of 50–700 MWe, although a number of very small plants have also been involved. More than a hundred of these have been in Europe. A key indicator for the assessment of biomass co-firing is intrduced and used to evaluate all available biomass co-firing technologies. 相似文献
47.
Iron oxide n-Fe2O3 nanowire photoelectrodes were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe2O3 nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density, Jp. The optimized electric oven-made n-Fe2O3 nanowire photoelectrodes showed photocurrent densities of 1.46 mA cm−2 at measured potential of 0.1 V/SCE at illumination intensity of 100 mW cm−2 from a Solar simulator with a global AM 1.5 filter. For the optimized carbon modified (CM)-n-TiO2 synthesized by thermal flame oxidation the photocurrent density for water splitting was found to increase by two fold to 3.0 mA cm−2 measured at the same measured potential and the illumination intensity. The carbon modified (CM)-n-Fe2O3 electrode showed a shift of the open circuit potential by −100 mV/SCE compared to undoped n-Fe2O3 nanowires. A maximum photoconversion efficiency of 2.3% at applied potential of 0.5 V/Eaoc was found for CM-n-Fe2O3 compared to 1.69% for n-Fe2O3 nanowires at higher applied potential of 0.7 V/Eaoc. These CM-n- Fe2O3 and n- Fe2O3 nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). 相似文献
48.
Direct transient stability assessment with excitation control 总被引:1,自引:0,他引:1
Fouad A.-A.A. Vittal V. Ni Y.-X. Pota H.R. Nodehi K. Zein-Eldin H.M. Vasahedi E. Kim J. 《Power Systems, IEEE Transactions on》1989,4(1):75-82
The authors extended the applicability of the transient energy function method by incorporating the exciter effects in the energy of a multimachine power system during the first swing transient. The generator was represented by the two-axis model and the exciter was represented by one gain, one time constant, and one limiter. In this study they compute the parameters of the extended transient energy function, which assumes a constant average internal EMF. The critical value of this transient energy is determined. A procedure for its use in transient stability assessment has been developed and successfully applied to fault disturbances in two test networks 相似文献
49.
The sensitivity of the organic-type G.M. tube is increased by introducing a third electrode (grid) between the cylindrical steel cathode and a concentric tungsten wire anode and applying positive potential to that grid. The optimum position of the grid inside the cathode corresponding to the minimum capacitance of the counter is determined by using the simulation technique. Plateau curves of this tube are obtained for different grid positions. It is justified that the best performance of the tube is determined with the optimum grid position. Plateau curves of the three-electrode G. M. tube are also reported, with optimum grid position, for different values of grid potential. It is found that the sensitivity of the counter can be controlled by variation of the grid potential. 相似文献
50.
Study of features based on nonlinear dynamical modeling in ECG arrhythmia detection and classification 总被引:3,自引:0,他引:3
Owis MI Abou-Zied AH Youssef AB Kadah YM 《IEEE transactions on bio-medical engineering》2002,49(7):733-736
We present a study of the nonlinear dynamics of electrocardiogram (ECG) signals for arrhythmia characterization. The correlation dimension and largest Lyapunov exponent are used to model the chaotic nature of five different classes of ECG signals. The model parameters are evaluated for a large number of real ECG signals within each class and the results are reported. The presented algorithms allow automatic calculation of the features. The statistical analysis of the calculated features indicates that they differ significantly between normal heart rhythm and the different arrhythmia types and, hence, can be rather useful in ECG arrhythmia detection. On the other hand, the results indicate that the discrimination between different arrhythmia types is difficult using such features. The results of this work are supported by statistical analysis that provides a clear outline for the potential uses and limitations of these features. 相似文献