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991.
根据GB/T212-2008《煤的工业分析方法》中的规定,在测定挥发分时,通过实验对比,无烟煤中水分随着煤的变质程度加深而呈规律性变化。从泥炭、褐煤、烟煤到年轻无烟煤水分逐渐减少,从年轻无烟煤到老年无烟煤的水分又逐渐增加。由于煤中水分过高和煤的氧化增重,导致挥发分测定值产生负值,影响挥发分的测定结果。 相似文献
992.
In this study, we used metal organic chemical vapor deposition to form gallium nitride (GaN) epilayers on c- and a-axis sapphire
substrates and then used the nanoscratch technique and atomic force microscopy (AFM) to determine the nanotribological behavior
and deformation characteristics of the GaN epilayers, respectively. The AFM morphological studies revealed that pile-up phenomena
occurred on both sides of the scratches formed on the GaN epilayers. It is suggested that cracking dominates in the case of
GaN epilayers while ploughing during the process of scratching; the appearances of the scratched surfaces were significantly
different for the GaN epilayers on the c- and a-axis sapphire substrates. In addition, compared to the c-axis substrate, we
obtained higher values of the coefficient of friction (μ) and deeper penetration of the scratches on the GaN a-axis sapphire
sample when we set the ramped force at 4,000 μN. This discrepancy suggests that GaN epilayers grown on c-axis sapphire have
higher shear resistances than those formed on a-axis sapphire. The occurrence of pile-up events indicates that the generation
and motion of individual dislocation, which we measured under the sites of critical brittle transitions of the scratch track,
resulted in ductile and/or brittle properties as a result of the deformed and strain-hardened lattice structure. 相似文献
993.
在有机合成实验教学中,通过优选实验项目、设计实验体系及改进实验方法等手段,达到节约环保、减少物料的使用与排放、在实验过程中引导学生树立绿色化学思想观念和增强环境保护意识的目的. 相似文献
994.
995.
996.
Vivian Maria Carminato Blanco Lucas Tadeu Fuess Marcelo Zaiat 《International Journal of Hydrogen Energy》2017,42(17):12181-12196
Biohydrogen (bioH2) production via dark fermentation is an attractive approach to overcome the drawbacks of conventional hydrogen production methods and represents a preliminary alternative for the management of organic wastes. Fundamental studies are still required to enhance the performance of bioH2 production systems, with emphasis on the development of novel reactor configurations. The anaerobic structured-bed reactor (ASTBR) is a recently developed configuration with great potential for bioH2 production, although operating strategies are still required to minimize biomass washout in such systems. In this context, calcium dosing has been investigated as a strategy to enhance both biomass retention and bioH2 production rates in the ASTBR. The present study employed varying COD/calcium ratios (4423, 2079, 1357, 1012, 884, and 632) in continuous experiments under mesophilic conditions (25 °C). Calcium dosing effectively enhanced biomass retention within the ASTBR, directly increasing the availability of metabolic energy for different metabolic pathways rather than cell synthesis. An optimal COD/calcium ratio of 1360 was mathematically estimated for bioH2 production, which is consistent with the results obtained experimentally. The specific organic loading rate (SOLR) was better controlled at this ratio, indicating the establishment of balanced conditions in terms of substrate availability and biomass concentration. Conversely, bioH2 production was severely impaired at COD/calcium values below and above the optimal range, most likely due to enhancement of the homoacetogenic pathway as a result of unbalanced conditions in the SOLR. Furthermore, biomass accumulation did not strongly affect the mean residence time of the ASTBR, facilitating its robust and enhanced solid retention. 相似文献
997.
Heavy gas oil biodesulfurization by Rhodococcus erythropolis ATCC 4277: optimized culture medium composition and evaluation of low‐cost alternative media 下载免费PDF全文
998.
In this study, we investigated the effect of post weld annealing treatments on the mechanical properties of a Ti–6Al–4V alloy following electron beam welding (EBW). The operational parameters used in this EBW process together with suitable annealing treatments appeared to substantially enhance the tensile properties of the Ti–6Al–4V weldment, suggesting that EBW is a promising method for industrial application. Moreover, we report for the first time that γ-TiAl + α2-Ti3Al formed in the fusion zone of the Ti–6Al–4V EBW weldment and exhibited the same lamellar structure, orientation relationship, deformation mechanism, and slip system as common Ti–Al-based alloys do. The presence of these intermetallic compounds affected the mechanical properties of the weldment. We discuss the related phase transformation, microstructural evolution, and characteristics of the precipitates formed. 相似文献
999.
Shu Y. Sun Wen G. Jiang Yu P. Zhao 《International Journal of Food Science & Technology》2012,47(1):100-106
To compare the influence of cultivars on the production of aroma compounds and polyphenols, eight cherry varieties (six sweet and two sour) were fermented into cherry wines, and their compositions were analysed. Results showed that by headspace solid microextraction coupled to gas chromatography–mass spectrometry (HS‐SPME‐GC‐MS), a total of twenty‐first aromatic compounds, mostly consisting of esters, acids, terpenoids and C13‐norisoprenoids, were identified, and eleven polyphenols including five anthocyanins and six phenolic acids were quantified using HPLC. May Duck and Early Richmond wines contained significantly higher levels of phenolic acids (>42 mg L?1) that were associated with high contents of chlorogenic and neochlorogenic acids and also relatively high amounts of octanoic acid and β‐damascenone (odour activity values ≥1000). Hongdeng, Zhifuhong and Bing wines were characterised by higher concentrations of anthocyanins (>41 mg L?1) and also relatively higher levels of isopentyl acetate. Lapins and Governer Wcod wines were distinguished by lower concentrations of polyphenols and relatively higher contents of ethyl 3‐methylbutanoate. 相似文献
1000.
W. Kuznik M.G. BrikI. Cie?lik A. MajchrowskiL. Jaroszewicz N.S. AlZayedA.M. El-Naggar I. SildosS. Lange V. KiiskI.V. Kityk 《Journal of Alloys and Compounds》2012,511(1):221-225
We present a complex fluorescence study of a series of gadolinium oxide polycrystalline powders singly, doubly and triply doped with trivalent rare earth ions (Er3+, Tb3+, and Dy3+), to explore a possibility of their use as materials for white light emitting diodes. The excitation and luminescence spectra along with the decay kinetics were measured in the temperature range from 6 to 300 K. The luminescence efficiency was studied within the visible spectral range, i.e. −400 nm to 750 nm under excitation by 355 nm third harmonic Nd:YAG laser pulses. Singly doped Er3+ sample gave stronger luminescence signals, but others showed significantly larger decay lifetimes. The successive rare earths doping leads to substantial changes of the spectral positions due to the up-conversion processes. In the singly (Er3+) doped sample, following the time resolved spectrum and decay curves, there are two different types of emissions: at 660 nm and at shorter wavelengths (below 640 nm) the red emission's lifetime is ten times longer than at shorter wavelengths. The singly doped sample shows unclear temperature-dependence of luminescence with lifetime at 550 nm (the longest at 100 K, similarly at 6 K and 300 K) and achieved luminous efficacy 73.5 lm/W. 相似文献