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61.
Hysteresis effects are reported for ZrO2 oxygen sensors exposed to non-equilibrium oxygen/hydrocarbon gas mixtures. With oxygen/toluene at 800° C, voltage-composition curves differ following composition changes (a) from excess oxygen to excess toluene and (b) from excess toluene to excess oxygen. A catalysis model is developed to account for this behaviour: the Thiele modulus of the catalyst/electrode is presumed to differ under (a) net oxidizing and (b) net reducing conditions. Large scale voltage fluctuations, sometimes exceeding 400 mV, were observed in experiments with oxygen/isobutane mixtures at 600° C. This behaviour is analysed in terms of a kinetic model involving stochastic variations of relative mass transfer coefficients of oxygen and isobutane. 相似文献
62.
Numerical solutions of differential equations for diffusion-controlled adsorption processes in spherical particles are presented for slow diffusion of gaseous molecules followed by rapid adsorption according to the Langmuir isotherm. As the parameter in the denominator of the Langmuir equation is increased the rate increases and the generalized rate curves shift progressively from that for the linear isotherm, the Langmuir parameter = 0, to the curve of the parabolic law. Adsorption and desorption cycles are considered and parameters are provided for relating any of these processes to the generalized curves. A simple linear equation was shown to approximate the rate curves with moderate accuracy. 相似文献
63.
The decomposition of sec-butyl acetate on de-ashed 20-to 30-mesh coconut-shell charcoal (1500 m2/g) was studied in a fixed bed reactor in the temperature range 300–375°C, and at partial pressures of 1 atm. and 0.29 atm. The ester decomposed principally to n-butene and acetic acid, and only small amounts of other products were found. The ratio of 1-butene to 2-butene was about 1:1, very close to that observed for thermal decomposition of the ester but far removed from the equilibrium butene ratio. The butene selectivity was independent of conversion. The rate of reaction followed the rate equation r = kA PE/1 + APE This expression corresponds to surface reaction on one site being rate controlling. The activation energy of rate constant k was 32.7 kcal/mole, compared to 46.6 kcal/mole for the gas-phase reaction. The temperature dependence of adsorption constant A showed a heat adsorption of 12 kcal/mole. Gas chromatographic measurements confirmed this value and also showed that ester is the principal adsor-bate on the charcoal. 相似文献
64.
Tensile property data for polystyrene samples of varying polydispersity are correlated with various parametric measures of molecular weight. Traditional measures of molecular weight, such as M?n, M?w, and M?z, are shown to be unable to account for the variation of tensile properties with molecular weight. However, a new molecular weight parameter, termed the failure property parameter, is able to provide a single relationship between tensile strength and the parameter for both the broad and narrow distribution polymers. The form of this parameter is consistent with its having origins in the view that it is the entanglement network in an amorphous polymer that provides the observed strength properties. Specifically for polystyrene, the failure property parameter results indicate that material below 60,000 molecular weight does not contribute to polymer strength. Although the results of this investigation are specifically for polystyrene, the arguments used to develop the failure property parameter are not dependent on polymer chemical structure. Consequently, we believe that both the concepts and definition of this new parameter are applicable to all amorphous polymers. 相似文献
65.
Duwayne M. Anderson 《Israel journal of chemistry》1968,6(3):349-355
Certain aspects of the phenomena of undercooling and ice nucleation in soils are discussed with respect to recently established properties of phase boundary water in soils. Nucleation temperature as a function of water content is given for representative clays. In view of the fact that silicate surfaces seem always to be separated from ice by an interfacial layer of unfrozen, liquid like water a new concept of heterogeneous nucleation is outlined. It is proposed that ice nucleation occurs in the undercooled interfacial water layer at some distance removed from the particle surfaces. This concept, in effect, suggests that heterogeneous nucleation (nucleation of ice due to the influence of a substrate) in all its essential aspects may be only a special case of homogeneous nucleation (no substrate present) of water. 相似文献
66.
J. C. Harris R. M. Anderson J. Satanek 《Journal of the American Oil Chemists' Society》1961,38(3):123-127
Previous papers have reported radiotagged fatty soil removal from glass either by solvents or by aqueous solutions of sodium
tripolyphosphate and other builders. This paper provies soil-removal data for aqueous systems of both pure and built surfactant
compositions of the nonionic and alkylbenzene sulfonate types. In general, nonionics are the most effective detergents for
the system fatty soil/glass; the 10-mole ethylene oxide adduct products show peak soil-removal. Nonionic surfactants appear
most effective for soil removal when used in baths closely approaching their cloud-points. Though modification of hydrophobe
by EO addition can affect cloud point, peak soil-removal effectiveness seems to be controlled by hydrophobe selection. Highest
soil removal for the alkylbenzene series occurred with the longer alkyl chain (pentadecyl).
Admixture of surfactant and sodium tripolyphosphate provided synergistic compositions with certain 10-EO surfactants. Building
of anionics markedly improved soil removal over the pure material but seldom exceeded the removal by STP alone.
Presented at 34th fall meeting, American Oil Chemists' Society, New York, October 17–19, 1960. 相似文献
67.
Statistical detection of mass malware has been shown to be highly successful. However, this type of malware is less interesting to cyber security officers of larger organizations, who are more concerned with detecting malware indicative of a targeted attack. Here we investigate the potential of statistically based approaches to detect such malware using a malware family associated with a large number of targeted network intrusions. Our approach is complementary to the bulk of statistical based malware classifiers, which are typically based on measures of overall similarity between executable files. One problem with this approach is that a malicious executable that shares some, but limited, functionality with known malware is likely to be misclassified as benign. Here a new approach to malware classification is introduced that classifies programs based on their similarity with known malware subroutines. It is illustrated that malware and benign programs can share a substantial amount of code, implying that classification should be based on malicious subroutines that occur infrequently, or not at all in benign programs. Various approaches to accomplishing this task are investigated, and a particularly simple approach appears the most effective. This approach simply computes the fraction of subroutines of a program that are similar to malware subroutines whose likes have not been found in a larger benign set. If this fraction exceeds around 1.5 %, the corresponding program can be classified as malicious at a 1 in 1000 false alarm rate. It is further shown that combining a local and overall similarity based approach can lead to considerably better prediction due to the relatively low correlation of their predictions. 相似文献
68.
A new algorithm is presented for the modeling and simulation of multi-flexible-body systems. This algorithm is built upon a divide-and-conquer-based multibody dynamics framework, and it is capable of handling arbitrary large rotations and deformations in articulated flexible bodies. As such, this work extends the current capabilities of the flexible divide-and-conquer algorithm (Mukherjee and Anderson in Comput. Nonlinear Dyn. 2(1):10–21, 2007), which is limited to the use of assumed modes in a floating frame of reference configuration. The present algorithm utilizes the existing finite element modeling techniques to construct the equations of motion at the element level, as well as at the body level. It is demonstrated that these equations can be assembled and solved using a divide-and-conquer type methodology. In this respect, the new algorithm is applied using the absolute nodal coordinate formulation (ANCF) (Shabana, 1996). The ANCF is selected because of its straightforward implementation and effectiveness in modeling large deformations. It is demonstrated that the present algorithm provides an efficient and robust method for modeling multi-flexible-body systems that employ highly deformable bodies. The new algorithm is tested using three example systems employing deformable bodies in two and three spatial dimensions. The current examples are limited to the ANCF line or cable elements, but the approach may be extended to higher order elements. In its basic form, the divide-and-conquer algorithm is time and processor optimal, yielding logarithmic complexity O(log(N b )) when implemented using O(N b ) processors, where N b is the number of bodies in the system. 相似文献
69.
E-ARK (European Archiving of Records and Knowledge Preservation) is currently introducing standardization, new tools, and infrastructure into pan-European digital archival systems. The results of this pilot project can be applied to higher education where research data centers are required to preserve data for re-use in accordance with new open policies.We elucidate how the E-ARK best practice survey has informed the development of new information packages for ingest, preservation, and re-use, and show how these can be applied to the Arts, Humanities, and Social Sciences with practical exemplars such as census data. 相似文献
70.
Bethany Anderson Fynnette Eaton Scott W. Schwartz 《New Review of Information Networking》2015,20(1-2):3-15
The digital revolution has changed the daily work of archivists. As a result, archivists have refined their analog practices and initiated new ones to accommodate the unique information creation and access needs of users. While limitless storage and technological obsolescence may be surmountable challenges, appraisal continues to be a necessary component of this preservation enterprise. Macro-appraisal—a top-down functional assessment of an organization’s high-level decision making that defines the enduring value of specific bodies of documentary evidence of these creative or administrative processes—is used to facilitate the management of diverse bodies of born-digital records in archives and special collections. 相似文献