Criteria and formulas for the calculation of the fluidization rate

An equation of motion is derived for individual particles in a fluidized bed of a monodisperse material in connection with the onset of fluidization. Dimensionless complexes have been derived on the basis of this equation and these are used to process the experimental data. A theoretical formula is derived.     

Relationships between the characteristics of petroleum feedstocks and the graphitizability of the petroleum cokes

To clarify relationships between characteristics of raw materials and physical properties of derived petroleum cokes, studies are made of the carbonization of petroleum fractions and the graphitization of cokes made by pyrolysis in an autoclave under constant pressures. The coke derived from the saturate fraction which has a low aromaticity had a needle coke structure. The fluidity of carbonization processes is important in controlling the microscopic texture of coke. A relationship was obtained between the chemical structural parameters of the fractions and X-ray peak intensity of the graphitized cokes derived therefrom. It was shown that coke quality had a bearing on the number of condensed aromatic rings and the substituted side chain groups of the raw materials.     

Phenomenological derivation of the Onsager reciprocal relations

The Onsager reciprocal relation for a linear dissipative system with two fluxes is derived within the framework of a phenomenological approach using the property of nonnegative definiteness of the dissipative function. It is established that the Onsager relations are valid when the generalized fluxes are zero for nonzero generalized thermodynamic forces. In the general case, the Onsager reciprocal relations can be phenomenologically derived based on the theory of matrices and determinants or on the Prigogine principle of the entropy production minimum.     

Bounds on the area under the receiver operating characteristic curve for the ideal observer

A new upper bound is derived on the area under the receiver operating characteristic curve for the ideal observer in a signal-detection task. This upper bound is determined by the values of the likelihood-generating function and its second derivative at the origin. This bound is compared with other bounds on ideal-observer performance that have been derived recently, and it is also shown how this bound leads to some asymptotic results for approximations to ideal-observer performance.     

Experimental investigation of the effect of the signal-to-noise ratio on the characteristics of forced capillary disintegration of a jet

Dependences of the signal-to-noise ratio in a jet in the case of forced capillary disintegration of the jet (FCDJ) on the excitation signal, the mean jet velocity, the velocity distribution in the jet, and the jet diameter are derived. It is shown that, for equal excitation amplitudes, the signal-to-noise ratio in the case of FCDJ depends on the jet diameter and the velocity profile. A relationship between the relative scatter of diameters of the droplets formed as a result of FCDJ and the signal-to-noise ratio is derived.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 4, pp. 544–550, April, 1991.     

Correlations between the components of stationary radiation in scattering media

Stationary radiation in a radiating, absorbing, and scattering medium is described by linear transport equations, which enables one to represent the radiation intensity as the sum of intensities, each of which is defined by its primary source of radiation and by the transmission of this radiation through the medium. In a scattering medium, the transmission depends on the characteristics of interaction between radiation and matter in the entire volume of the object. Fairly simple general correlations are derived between the intensity components that are independent of the concrete characteristics of the object. Previously, such correlations have only been derived for the case of heat radiation on the basis of the results of analysis of radiation equilibrium in a closed isothermal cavity. In the latter case, the correlations are derived from the condition of stationarity based on the analysis of the equation for the probability of complete disappearance of emerging radiation. The radiation may be arbitrary (it must not necessarily be heat radiation). The object may be of any shape and inhomogeneous. The surrounding walls may be both transparent and nontransparent. External lighting is possible. The correlations include quantities which are subjected to investigations in spectroscopic experiments. The use of the derived correlations in experiments with dust-laden plasma is described.     

Analytical solution for the bond strength of externally bonded reinforcement

Interfacial behavior is critical to composite structures and materials reinforced by externally bonded reinforcement. Numerous empirical and semi-empirical models have been developed for evaluating interfacial bond strength. Analytical solutions have been derived for interfaces with infinite bond lengths, but no closed-form solutions have been derived for the bond strength of an interface with an arbitrary bond length. An analytical solution is derived in this work for the strength of a general externally bonded interface. With the analytical method, the interesting snapback phenomenon in simple pull-off tests is theoretically studied, and an invariant is identified as the condition for it to occur. Furthermore, a methodology is provided to evaluate the interfacial material properties based on a given empirical bond model.     

Mapping the structure of science through usage

Summary Science has traditionally been mapped on the basis of authorship and citation data. Due to publication and citation delays such data represents the structure of science as it existed in the past. We propose to map science by proxy of journal relationships derived from usage data to determine research trends as they presently occur. This mapping is performed by applying a principal components analysis superimposed with a k-means cluster analysis on networks of journal relationships derived from a large set of article usage data collected for the Los Alamos National Laboratory research community. Results indicate that meaningful maps of the interests of a local scientific community can be derived from usage data. Subject groupings in the mappings corresponds to Thomson ISI subject categories. A comparison to maps resulting from the analysis of 2003 Thomson ISI Journal Citation Report data reveals interesting differences between the features of local usage and global citation data.     

A three-dimensional micromechanics model for the damage of brittle materials based on the growth and unilateral effect of elliptic microcracks

Based on the analysis of a representative elliptic microcrack embedded in a RVE, the additional compliance tensor induced by an embedded opening/closed microcrack is derived, and that corresponding to the kinked growth of a closed elliptic microcrack is also derived by making use of its approximately equivalent simplification. The effect of the microcracks is analyzed with the Taylor’s scheme by introducing an appropriate probability density function. A three-dimensional micromechanics damage model is obtained for brittle materials, assuming numerous randomly distributed elliptic microcracks and taking into account their deformation, frictional sliding, growth and kinked growth.     

Finite temporal measurements of the statistical characteristics of the atmospheric coherence length

Based on the theory of stationary random processes, the probability density function of the atmospheric coherence length measured in a finite time period is derived analytically and verified experimentally. An iteration method is proposed to obtain Fried's coherence length within a finite time measurement.     

Estimating the effects of structural vibration on adaptive optics system performance

This paper presents analytical tools developed for estimating the effects of structural vibration on closed-loop adaptive optics system image quality. The general equation for the normalized intensity distribution of an image subject to structural vibration is derived. The resulting two-dimensional theoretical point spread function is computed numerically and compared with empirical data obtained on sky at the Multiple Mirror Telescope Observatory. A simplified analytical expression for the normalized intensity distribution is derived for long exposures and used to quantify the effects on Strehl and spot full width at half-maximum as a function of vibration amplitude, telescope diameter, and observation wavelength.     

Analysis of the horizontal effective thermal conductivity of a fluidized alumina bed under steady-state conditions

A critical relation is derived for calculating the thermal conductivity of a fluidized alumina bed. Based on the solution to the equation, formulas are then derived for evaluting the nonuniformity factor of the temperature field in a fluidization chamber which is heated around its walls.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 2, pp. 301–308, August, 1971.     

A modified model for the estimation of fatigue life derived from random vibration theory

When a component is subjected to variable-amplitude loading, if the fundamental stress–life cycle relationship and an accumulation rule are given, then the fatigue damage or fatigue life of the component can be calculated and/or estimated. In the present paper, random vibration theory is incorporated into the analysis of the above problem. Several formulas are thus derived. Experimental work is then carried out to verify the derived formulas. Comparison is made among the results calculated based on different formulas, different accumulation rules and different random loading. It is concluded that the derived formulas do provide us with quick prediction of the fatigue damage or fatigue life when a component is subjected to variable-amplitude loading that has a certain random nature.     

On the mechanics of the bow and arrow

Summary Some aspects of the dynamics of the bow and arrow have been considered. The governing equations are derived by means of Hamilton's principle. The resulting non-linear initial-boundary-value problem is solved numerically by use of a finite-difference method. The influence of the characteristic quantities on the performance of a bow is discussed.     

On the asymptotic character of the stresses near notches in plane problems

Analytical expressions are derived by the conformal mapping techniques of Muskhelishvili for the asymptotic character of the stress fields at the root of notches, re-entrant corners, etc. in plane bodies. It is shown that the stress field can be expressed as the product of a rapidly varying term, which depends only on the known geometry, and a slowly varying term which is associated with the nominal stresses. Using the derived expressions, together with a few stress, strain, or photoe/astic measurements at arbitrary points within the notch region, the entire stress field around the notch can be predicted. This includes the location and magnitude of maximum stress. The suggested technique is applied to a notch with parabolic shape and is shown to yield highly accurate results.     

On the Modeling of Flow in Packed Bed Systems

Modeling of flow and its impact on transport phenomena in packed bed systems is discussed. A detailed flow model based on an improved Brinkman equation has been derived and its solution is presented. This model incorporates a representative voidage function that enabled the generation of velocity profiles that closely followed the voidage profile and highlighted the importance of the wall zone. Two approximate flow models from the literature have been used to obtain velocity profiles for the purpose of comparison with the model derived herein. Significant differences were observed in the location and magnitude of velocity maxima predicted by the various models employed in this work. The impact of such findings on transport phenomena is discussed. A method to obtain a wall zone velocity is suggested to facilitate estimation of transport parameters near the wall.     

Retrieval of total ozone abundances from the ultraviolet region of spectra recorded with an ultraviolet-visible spectrometer

A method is described for deriving total ozone abundances from zenith-sky intensities measured by an UV-visible spectrometer, known as the System of Analysis of Observations at Zenith (SAOZ). Total ozone abundances are determined by comparison of intensity ratios measured at two wavelengths in the UV region with ratios computed with a radiative transfer model. The wavelength pair 320-307 nm was used in this study. Spectra recorded by the SAOZ spectrometer in Oslo (60 degrees N) from the beginning of May 1995 to the end of August 1995 were analyzed, and the results were compared with total ozone measured with a Brewer instrument. The relative difference in derived ozone abundances for the whole period, including days with thin and medium-thick cloud covers, is -0.18 +/- 1.46%. We study the effects of clouds and varying ground albedo on the derived total ozone. Clouds result in an overestimation of the derived total ozone. The error increases with the optical depth tau of the cloud from approximately 2% for an optically thin cloud (tau = 0.5) to approximately 10% for a thick cloud (tau = 50). The ratio between measured intensities at 550 and 350 nm, the so-called color index, can be used as a measure of the cloud optical depth for thin and medium-thick clouds. The effects of thin and medium-thick clouds on the derived ozone abundances can be compensated for by use of an empirical relationship found between the measured color index and the error in the inferred ozone abundances caused by cloud scattering. We also study the influence of changes in the ground albedo and in the ozone profiles on derived total ozone values.     

A new formulation and computation of the triphasic model for mechano-electrochemical mixtures

From the generalized first law of thermodynamics for an irreversible thermodynamical system, a new set of governing equations for the mixture theory is derived based on the triphasic model for mechano-electrochemical mixtures. It is shown that, in the case of electroneutral solution, a new biphasic mixture theory including the electrochemical effects can be derived from the new governing equations. The chemical-expansion stress representing both the influences of deformation on the fixed charge density and the electric potential of fixed charge field is given. For comparison and verification purposes, the numerical solution for a confined compression problem of a charged hydrated soft tissue is computed using the multiquadric method. Received: 1 November 1998     

Influence of the proximity effect on the energy resolution of STJs

The generating function describing statistical processes of X-ray registration in a superconducting tunnel junction (STJ) with proximized electrodes, and the influence of the proximity effect on the mean value of the signal and the energy resolution of the STJ is derived.     

Determination of the near-tip stress fields for the scattering of P-waves by a crack

Summary A conservation law implied by the field equations of linear elastodynamics is derived, and a procedure based on this conservation law is given for the direct determination of the near-tip stress fields arising from the scattering of normally incident P-waves by a crack in a homogeneous, isotropic elastic medium.