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31.
《Carbon》2014
Four commercial activated carbons with different chemical and textural characteristics were modified by gamma irradiation under five different conditions: irradiated in absence of water, in presence of ultrapure water, in ultrapure water at pH = 1.0 and 1000 mg L−1 Cl−, in ultrapure water at pH = 7.5 and 1000 mg L−1 Br−, and in ultrapure water at pH = 12.5 and 1000 mg L−1 NO3−. Changes in surface chemistry were studied by X-ray photoelectron spectroscopy; pH of point of zero charge, total acidic groups and total basic groups, which were determined by assessment with HCl and NaOH; and textural changes were determined by obtaining the corresponding adsorption isotherms of N2 and CO2. Outcomes show that the activated carbon surface chemistry can be modified by gamma irradiation and that the changes depend on the irradiation conditions. Modifications in the sp2 hybridization of the surface carbons suggest that the irradiated carbons undergo graphitization. Measurements of structural parameters indicate that the irradiation treatment does not modify the textural properties of the carbons. Finally, studies of pristine and irradiated activated carbons using diffuse reflectance spectroscopy with the Kubelka–Munk function revealed a reduction in band gap energy in the irradiated carbons associated with an increase in sp2 hybridization of the carbon atoms. 相似文献
32.
V. B. Singh Kalpana Yadav Reecha Kapur V.S.S. Yadavalli 《国际自动化与计算杂志》2007,4(4):359-368
Since the early 1970s tremendous growth has been seen in the research of software reliability growth modeling.In general, software reliability growth models (SRGMs) are applicable to the late stages of testing in software development and they can provide useful information about how to improve the reliability of software products.A number of SRGMs have been proposed in the literature to represent time-dependent fault identification/removal phenomenon;still new models are being proposed that could fit a greater number of reliability growth curves.Often,it is assumed that detected faults axe immediately corrected when mathematical models are developed.This assumption may not be realistic in practice because the time to remove a detected fault depends on the complexity of the fault,the skill and experience of the personnel,the size of the debugging team,the technique,and so on.Thus,the detected fault need not be immediately removed,and it may lag the fault detection process by a delay effect factor.In this paper,we first review how different software reliability growth models have been developed,where fault detection process is dependent not only on the number of residual fault content but also on the testing time,and see how these models can be reinterpreted as the delayed fault detection model by using a delay effect factor.Based on the power function of the testing time concept,we propose four new SRGMs that assume the presence of two types of faults in the software:leading and dependent faults.Leading faults are those that can be removed upon a failure being observed.However,dependent faults are masked by leading faults and can only be removed after the corresponding leading fault has been removed with a debugging time lag.These models have been tested on real software error data to show its goodness of fit,predictive validity and applicability. 相似文献
33.
M. A. Dippenaar M. D. Sole J. L. Van Rooy G. J. du Toit J. L. Reynecke 《Bulletin of Engineering Geology and the Environment》2005,64(4):347-360
Determining the thickness of a LNAPL (light non-aqueous phase liquid) hydrocarbon plume in the fractured rock surrounding
a borehole is a very important aspect in determining the quantity and degree of contamination of the groundwater and soil,
as well as deciding on applicable remediation measures. This review aims to compare some of the field and empirical methods
to eventually propose a method of confirming the plausibility of the determined thickness. General insight is supplied relating
to the occurrence of groundwater in the Earth’s crust, the basic principles of multiphase flow and the properties of the three
fluids of importance, being water, Jet A-1 fuel and air. From the methods applied, the field bail-down method of Hughes et
al. and the mathematical approach according to CONCAWE supplied reasonable results, with the Zillox and Muntzer equation providing
no rational outcome due to changing water levels from regular bailing of the LNAPL. Furthermore, practically none of these
methods have been developed for deep, fractured aquifers. By plotting regular depths to water and fuel on the abscissa axis
with free product thickness on the ordinate, the depth to water and depth to fuel linear plots will intersect where the free
product thickness equals zero. This indicates the static water level (i.e., the ground water level prior to hydrocarbon contamination)
and by subtracting this from the free product depth, a maximum product thickness is obtained.
相似文献
34.
Marama bean is a protein-rich, underutilised, drought-tolerant legume in sub-Saharan Africa. Its utilisation may be increased through value addition into protein-rich flours. Defatted flour from unheated and dry-heated (150 °C/20 min) whole marama beans (UMF and HMF) were analysed for physicochemical and protein-based functional properties. Heating significantly increased in vitro protein digestibility of marama bean flour. Of functional importance are the high levels of tyrosine present in marama bean flours. Heating significantly reduced protein solubility and emulsifying capacity of marama bean flours whilst water absorption capacity was improved. Foaming capacity was not affected by heating. UMF could be useful in food systems requiring high emulsifying capacity, but would not be suitable for applications requiring high water absorption and foaming capacity. Due to its high protein contents, marama bean flour could be used to increase the protein quality of cereal-based foods to help alleviate protein-energy nutrition in the region. 相似文献
35.
Ag-doped nanocrystalline structures of TiO2 in the form of colloidal particles are synthesized by using AgNO3 solution with Acetyl acetone and diacetyl monoxime modified titanium isopropoxide precursor. Thin layers of undoped and Ag-doped TiO2 sols are deposited on conducting glass substrate by dip coating technique. The thin films are developed by repeated coating of the sols for 5, 10 and 15 times which results the formation of thin layers with different thickness. These layers are annealed at 450 °C so as to use them as bottom/ seed layers of fabricating photoanodes for dye sensitized solar cells. The optical properties of undoped and Ag-doped TiO2 thin layers are studied in details. Effective mass model is used to find the particle size and peak wavelength relationship for the nanocrystals of TiO2. Quantum efficiency of dye sensitized solar cells assembled using the fabricated photoanodes with Ag-doped TiO2 shows increase in efficiency by about 4% in comparison to the undoped TiO2 layers. The improved performance is attributed to ease of transportation of electron through passivating layer to the external circuit. 相似文献
36.
In this article, new methodologies for determining the tension distribution and optimal configurations of planar tendon-driven parallel manipulators (TDPMs) are presented. TDPMs are characterized by the use of cables in place of the linear actuators used in most parallel manipulators. Three separate, but inter-related topics are examined in this article, and methodologies for addressing them are proposed. The first is the determination of cable forces for overconstrained tendon-driven manipulators, which is necessary in order to address the second topic, namely, the development of a methodology for workspace determination of tendon-driven manipulators. The final topic examined is the dimensional synthesis of tendon-driven manipulators for a large dextrous workspace. The numerical methodologies developed here have potential for easy application to more complex spatial cases. 相似文献
37.
38.
The theory of non-commutative rings is introduced to provide a basis for the study of nonlinear control systems with time delays. The left Ore ring of non-commutative polynomials defined over the field of meromorphic function is suggested as the framework for such a study. This approach is then generalized to a broader class of nonlinear systems with delays that are called generalized Roesser systems. Finally, the theory is applied to analyze nonlinear time-delay systems. A weak observability is defined and characterized, generalizing the well-known linear result. Properties of closed submodules are then developed to obtain a result on the accessibility of such systems. 相似文献
39.
The combination of gas chromatography (GC) and laser-based resonance-enhanced multiphoton ionization-time-of-flight mass spectrometry (REMPI-TOFMS) represents a three-dimensional analytical method, using the gas chromatographic retention time, the wavelength of the ionization laser for REMPI, and the molecular mass as analytical parameters. In this work, a novel analytical scheme for detection of chlorinated aromatic compounds, including isomeric ensembles, by GC/REMPI-TOFMS is presented. The concept uses an in-line hydrodechlorination catalyst for post- or precolumn derivatization of chlorinated aromatic compounds. The chlorinated aromatics are quantitatively reduced, forming their respective aromatic skeletons. These aromatic skeletons are detected selectively by REMPI-TOFMS. The first results for substance class selective detection of chlorinated benzene isomers are given, and potential applications in the field of the analysis of compounds such as polychlorinated dibenzo-p-dioxins and -furans are discussed. 相似文献
40.
Electrodeposition of PbO2 and Bi–PbO2 on Ebonex was carried out under various conditions, and the surfaces and coating/substrate interfaces examined by SEM, XPS and SIMS. Excellent adhesion to Ebonex was obtained with both crystalline and amorphous surfaces. Low plating temperatures resulted in dark grey, bright PbO2 and black, mirror-like Bi–PbO2 surfaces. Extrapolation of electrode lifetime test data indicated corrosion rates of 716 m yr–1 for PbO2 and 158 m yr–1 for Bi–PbO2. 相似文献