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排序方式: 共有233条查询结果,搜索用时 187 毫秒
21.
Baldacchini G Bonfigli F Faenov A Flora F Montereali RM Pace A Pikuz T Reale L 《Journal of nanoscience and nanotechnology》2003,3(6):483-486
X-ray microradiographs of small biological objects, such as animals and plant materials at micrometric resolution, are currently performed by various methods, all of which are limited by the resolution or the dynamic range of the image detectors. Here a novel X-ray image detector is discussed, in which the previous limitations have been overcome. A film of lithium fluoride salt is used as a detector, in which the stored biological image is read by observing the optically stimulated visible luminescence of the active color centers, efficiently produced by the X-rays. 相似文献
22.
Due to an increase in the commercial use of biodiesel and biodiesel blends, both ASTM D 6751 and EN 14214 include the acid
number (AN) as an important quality parameter. It was found that determination of AN of biodiesel and biodiesel blends using
the ASTM D 974 results in large values of repeatability (up to 73.41%) and larger percentage error (up to 42.88%). Therefore,
ASTM D 974 has been modified using a lower concentration of base (0.02 M KOH instead of 0.1 M KOH) as well as reducing the
amount of toxic titration solvent from 100 mL to only 10 mL. This makes the modified ASTM D 974 as a green analytical method
which uses a reduced amount of toxic solvent. This modified method significantly reduced the maximum percentage error from
42.88 to 5.92%. The application of this modified ASTM D 974 for the determination of AN of biodiesel and biodiesel blends
was studied. The accuracy of this modified ASTM D 974 for biodiesel (B100) was measured to be within 3.51% over the AN range
of 0.313–0.525 mg KOH/g and maximum repeatability was decreased from 8.37 to 2.75% within this AN range which is far below
the ASTM D 974 stated repeatability specifications. For B20, B10, B5, B2, and B1, the most accurate values were measured at
AN values of 0.177, 0.067, 0.072, 0.126, and 0.096 mg KOH/g, respectively. Excellent linearity values of R
2 for calculated and experimentally determined AN were obtained. The difference between the experimental and the calculated
AN for all biodiesel and biodiesel blend samples was within ± 0.018 mg KOH/g. This extensive study has demonstrated that this
modified ASTM D 974 is a reliable method for the determination of AN and could be used for establishing the specifications
of AN for biodiesel and biodiesel blends ranging from B1 to B20 in quality standards. 相似文献
23.
The analysis of FTIR absorption spectra of CO and of12CO-13CO isotopic mixtures is reported for gold catalysts supported on a number of oxides. Relationships between the nanostructure
and the CO adsorbing properties of the different gold catalysts are discussed. In particular, on titania supported gold, where
particles of metallic nature are present, two kinds of surface sites do adsorb CO, the 6-coordinated corners and the 7- coordinated
edges, while the terrace sites, 8 coordinated, are not able to adsorb even at 90 K. Moreover, the adsorbing sites are not
isolated, but mutually interacting. On zirconia supported gold, the adsorbing sites, mutually interacting, are exposed at
the surface of non metallic gold nanoclusters. Almost isolated and negatively charged gold adsorbing nanoclusters have been
highlighted on the sample supported on reduced ceria, and, finally, isolated cationic sites on oxidized gold supported on
a mixed ceria-titania oxide have been detected. 相似文献
24.
Lubo Liu Christine M. Rust Joseph R. V. Flora C. Marjorie Aelion 《Canadian Metallurgical Quarterly》2002,128(12):1128-1138
A one-dimensional mathematical model was developed to simulate pH control using an encapsulated phosphate buffer during denitrification in a sand column. The parameters required for the model were obtained from direct physical measurement, from a tracer study to characterize the dispersion coefficient in the column, and from batch experiments designed to obtain an empirical expression describing the variation of the first-order rate constant for the encapsulated buffer core release with pH. First-order kinetic constants describing the rates of denitrification and ethanol biodegradation were obtained by fitting the model to column runs without the encapsulated buffer. With these parameters, the model was subsequently used to predict the performance of column runs containing the encapsulated buffer. Since denitrification was essentially complete in the sand columns, an increase in the effluent pH was observed. This pH increase was counteracted by the controlled release of the acidic core of the encapsulated buffers added in the columns. The model reasonably predicted the release of the encapsulated buffer core and the performance of the encapsulated buffer for controlling pH in the column. 相似文献
25.
Véronique Jollet Flora Chambon Franck Rataboul Amandine Cabiac Catherine Pinel Emmanuelle Guillon Nadine Essayem 《Topics in Catalysis》2010,53(15-18):1254-1257
The dissolution of cellulose under 5 MPa of H2 in the absence of catalyst is temperature and time dependant. The presence of Pt/γ-Al2O3 increases the initial rate of dissolution. The presence of H2/Pt is essential although its exact role has not been well elucidated. 相似文献
26.
Effect of kaolin and copper based products and of starter cultures on green table olive fermentation
Randazzo CL Fava G Tomaselli F Romeo FV Pennino G Vitello E Caggia C 《Food microbiology》2011,28(5):910-919
In the present study table olives treated in field with kaolin and copper based products against “olive-fruit fly” were fermented using two selected strains of lactic acid bacteria (LAB). The fermentation process was monitored up to 260 days from brining through physico-chemical, microbiological and sensorial analyses. Results showed a dominance of LAB and yeasts and low level of Enterobacteriaceae counts throughout the whole process both in un-treated and treated samples. When investigating the effect of the single treatments on microbial dynamics, ANOVA results highlighted that copper based products affected significantly the control sample, while the sample inoculated with LAB starters maintained high level throughout the process, guaranteeing the fermentation process. Different behavior was revealed by yeasts population, which was partially influenced by copper treatment at the beginning of the fermentation.The polyphasic approach used in the present study, which combined sensory evaluation to microbial counts and physico-chemical characteristics, let to the conclusion on the importance of starter cultures in fermentation of table olives especially those treated with “non-conventional” pesticide, which could be used to prevent olive fly damage. 相似文献
27.
Nb2O5/SiO2 and Pd/Nb2O5/SiO2 catalysts were studied for the liquid phase syntheses of mesityl oxide (MO) and methyl isobutyl ketone (MIBK) in a fixed bed flow reactor (FBR). Catalyst activities as high as 1.7 g/h gcat and selectivities ranging from 93.4 to 100% for MO synthesis were observed. The catalyst activity was found to be a strong function of space velocity likely due to product inhibition. A synergistic effect was observed whereby the catalyst activity for all organic products increased by 22% and the MIBK productivity increased by 20% at 160 °C and WHSV = 8.6 h?1 from the introduction of hydrogen to the reactor. However, the MIBK selectivity was constrained to less than 83.5% due to competing reactions. 相似文献
28.
D2S: Document-to-sentence framework for novelty detection 总被引:2,自引:1,他引:1
Novelty detection aims at identifying novel information from an incoming stream of documents. In this paper, we propose a
new framework for document-level novelty detection using document-to-sentence (D2S) annotations and discuss the applicability
of this method. D2S first segments a document into sentences, determines the novelty of each sentence, then computes the document-level
novelty score based on a fixed threshold. Experimental results on APWSJ data show that D2S outperforms standard document-level
novelty detection in terms of redundancy-precision (RP) and redundancy-recall (RR). We applied D2S on the document-level data
from the TREC 2004 and TREC 2003 Novelty Track and find that D2S is useful in detecting novel information in data with a high
percentage of novel documents. However, D2S shows a strong capability to detect redundant information regardless of the percentage
of novel documents. D2S has been successfully integrated in a real-world novelty detection system. 相似文献
29.
The hydrodesulfurization (HDS) of the highly refractory sulfur-containing compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), and the effect of the basic and non-basic nitrogen heterocyclic compounds, such as quinoline and carbazole, on HDS using a dispersed unsupported Mo catalyst and in situ generated hydrogen were studied. Experimental results indicated that the dispersed unsupported Mo catalyst was effective for the HDS of 4,6-DMDBT in a mixture containing DBT. The direct desulfurization pathway (DDS) was the preferred pathway for the HDS of DBT while the hydrogenation pathway (HYD) was the preferred pathway for the HDS of 4,6-DMDBT under our experimental conditions. A strong inhibitive effect of the basic quinoline or the non-basic carbazole on the HDS of each of the sulfur-containing compounds was observed. The DDS and HYD pathways in the HDS of the refractory sulfur-containing compounds were affected to a different extent by the nitrogen-containing compounds, suggesting that different active sites were involved in these two reaction pathways. 相似文献
30.
Obtaining new information in a short time is becoming crucial in today’s economy. A lot of information both offline or online is easily acquired, exacerbating the problem of information overload. Novelty mining detects documents/sentences that contain novel or new information and presents those results directly to users (Tang, Tsai, & Chen, 2010). Many methods and algorithms for novelty mining have previously been studied, but none have compared and discussed the impact of term weighting on the evaluation measures. This paper performed experiments to recommend the best term weighting function for both document and sentence-level novelty mining. 相似文献