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A mathematical model of a cascade separator with two or several initial material inputs into the apparatus is developed. We can significantly affect the compositions of final products by feeding material to various stages of the cascade. It is very important for processes whose objective is to obtain powders with specified compositions. By way of example, we can mention copper powders for aircraft and motor-cars industries. The requirements for such powders include limitations on the contents of three different fractions within the total range of powder sizes. Since the sizes of these fractions are much below 100 microns, it is practically impossible to separate them using sieves for further preparation of required compositions on an industrial scale. However, this problem is solved by separation methods by dividing the initial material between two inputs into the apparatus. It is practically impossible to solve this problem empirically. We have managed to do it using the mathematical model described in the present paper. [ABSTRACT FROM AUTHOR]

We report on the power and microwave noise performance of AlGaN/GaN high electron-mobility transistors (HEMTs) at frequencies f > 18 GHz (K- and K a-bands). At 20 GHz, a record continuous-wave output power of 1.6 W has been achieved on an eight-finger 500-/[micro]m total gate-periphery device. At 29 GHz, a 120-/[micro]m gate-periphery device showed a pulsed output density of 1.6 W/mm with an associated gain of 6.7 dB and power-added efficiency of 26 %. Minimum noise figure of 1.5 dB has been achieved on a 0.2/[micro]m x 200/[micro]m device at 26 GHz. The data demonstrate the viability of AlGaN/GaN HEMTs for high-frequency power and low-noise amplifier applications. Index Terms--GaN, high electron-mobility transistor (HEMT), K-band, microwave noise, microwave power.

The problem of symmetrical cascade with the initial material feed to an even stage has been solved previously. Since even and odd stages in a duplex cascade differ, material feeding to an odd stage essentially affects the character of material distribution in the cascade stages. The main point is that it considerably affects the composition of separation products, i.e. represents another means of controlling the final product composition. [ABSTRACT FROM AUTHOR]

Entropy is a key parameter in the analysis of properties of mass systems. This notion was first formulated in thermodynamics and then expanded to many branches of knowledge. A successful attempt to formulate the notion of entropy for two-phase flows was made. As a result of the analysis of entropy correlation with other parameters characterizing a critical two-phase flow, a statistical identity has been determined for this process. The statistical identity establishes the balance of potential and kinetic energy between the parameters characterizing two-phase flows. [ABSTRACT FROM AUTHOR]

In this paper, we present detailed on-wafer S-parameter and noise parameter measurements and modeling of InP/InAlAs/InGaAs high electron mobility transistors (0.1-[micro]m gate length) at cryogenic temperatures. Various physical effects influencing small-signal parameters, especially the radio-frequency (RF) transconductance and RF output resistance and their temperature dependence, are discussed in detail. Accurate on-wafer noise parameter measurements are carried out from 300 to 18 K, and the variation of the equivalent noise temperatures of drain and source ([T.sub.d] and [T.sub.g]) are modeled against temperature. Based on these models, a cryogenic low-noise amplifier in the Ka-band is developed with a record-low noise temperature of 10 K. Index Terms--Cryogenic, high electron mobility transistor (HEMT), impact ionization, low-noise amplifier (LNA), noise, small-signal model.

Theoretical notions of mass transfer processes in cascade separation of bulk materials have not been adequately developed as yet [1]. In this paper we have derived linear difference equation of the second order for a cascade with initial feeding top any stage proceeding from mass exchange regularities. The solution of these equations has allowed us to determine quantitative dependences of the material distribution over the cascade stages, which serve the basis of the method of predictive estimate of the process results. We have also examined the model of the material distribution coefficient formation at individual cascade stages. We have checked the adequacy of this model to experimental data. It is noteworthy that the obtained theoretical results are phenomenological, i.e. they can be applied to the processes of separation of different physical nature, e.g. of isotopes, liquid media, gases, etc. [ABSTRACT FROM AUTHOR]