Vibratory comminution of A12O3 powders

Translated from Poroshkovaya Metallurgiya, No. 8(332), pp. 6–9, August, 1990.     

Thermodynamic efficiency of heat exchangers

Expressions are obtained to determine the exergetic efficiency of heat exchangers _a as a function of such dimensionless parameters as the energetic efficiency of the heat exchangers, the relationship between the thermal equivalents of the thermal carriers, the dimensionless initial temperature of the hot heat carrier ¯T₁=T₁/T_m and the temperature of the environment ¯T₀= T₀/T_m. In the domain of high environment temperature the quantity _a rises with the increase in the value of the parameter ¯T₁ while in the domain of low environment temperature the dependence _a=f(¯T₁) is extremal in nature and reached maximal values for ¯T₁=1.75–2.25.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 6, pp. 935–942, December, 1990.     

Computed tomographic imaging of the coronary arterial tree-use of local tomography

It has been demonstrated previously (see E.L. Ritman and A.A. Bove, in State of the Art in Quantitative Coronary Arteriography, p.67-78, 1986) that coronary artery anatomy can be visualized using high-speed, volume-scanning X-ray CT (computed tomography). In the current study it is demonstrated that local image reconstruction (i.e. the reconstruction kernel is ~2(+) mm long), as distinct from more conventional global image reconstruction (i.e. 200(+) mm kernel length), has the advantage of reducing the need for operator interactive image processing. In addition, the local reconstruction algorithm eliminates the need for recording the X-ray projection data over the full transaxial extent of the thorax because it requires only the X-ray attenuation data over the region of the heart. This latter aspect reduces the dynamic range requirements for the sensors and could reduce total X-ray exposure.     

Information analysis of single photon emission computed tomography with count losses

An analysis is presented of the information transfer from emitter-space to detector-space in single photon emission computed tomography (SPECT) systems. The analysis takes into account the fact that count loss side information is generally not available at the detector. Side information corresponds to the number gamma-rays lost deleted due to lack of interaction with the detector data. It is shown that the information transfer depends on the structure of the likelihood function of the emitter locations associated with the detector data. This likelihood function is the average of a set of ideal-detection likelihood functions, each matched to a particular set of possible deleted gamma-ray paths. A lower bound is derived for the information gain due to incorporating the count loss side information at the detector. This is shown to be significant when the mean emission rate is small or when the gamma-ray deletion probability is strongly dependent on emitter location. Numerical evaluations of the mutual information, with and without side information, associated with information-optimal apertures and uniform parallel-hole collimators are presented.     

A methodology for modeling the distributions of medical images and their stochastic properties

The probabilistic distribution properties of a set of medical images are studied. It is shown that the generalized Gaussian function provides a good approximation to the distribution of AP chest radiographs. Based on this result and a goodness-of-fit test, a generalized Gaussian autoregressive model (GGAR) is proposed. Its properties and limitations are also discussed. It is expected that the GGAR model will be useful in describing the stochastic characteristics of some classes of medical images and in image data compression and other applications.     

Composition of acid tars from production of oils

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 2, pp. 32–35, February, 1990.