Atmospheric refraction of radio waves on occultation satellite-to-satellite paths

The atmospheric refraction on occultation paths between GPS satellites and Formosat-3 low-earth-orbit satellites is analyzed. The dependences of the bending angle on the minimum height of the ray path for the European part of Russia are presented. An analytical approximation of the mean vertical profile of the refractive angle for a four-year period is given, and data on slow seasonal and diurnal variations and rapid bending-angle fluctuations observed in the troposphere are presented. It is pointed out that the height profile of the angle of refraction is a good candidate for an indicator of long-term climatic changes in the state of the atmosphere.     

Cyclic strength of corrosion-resistant high-nitrogen austenitic 05Kh22AG15N8MF steel during repeated tension

The static and fatigue cyclic strength of high-strength corrosion-resistant nitrogen-bearing austenitic 05Kh22AG15N8MF steel are studied in various structural states after hot rolling at 1100°C (water quenching from 1150°C, subsequent annealing at 800°C for 1 and 10 h, and cooling in air). The maximum life and a higher fatigue limit (400 MPa) are shown to be characteristic of hot-rolled samples with a finegrained austenitic structure and numerous twins. The mechanisms of fatigue crack propagation are studied.     

Optimal state estimation in MAP event flows with unextendable dead time

We consider the optimal estimation problem for the states of a MAP event flow with two states; it is one of the mathematical models for an incoming stream of claims (events) in digital integral servicing networks. The observation conditions for this flow are such that each event generates a period of dead time during which other events from the flow are inaccessible for observation and do not extend the dead time period (unextendable dead time). We find an explicit form for posterior probabilities of the flow states. The decision about the flow state is made with the maximal a posteriori criterion. We show numerical results obtained with our explicit formulas and imitational modeling.     

Processing of investigation results of solid fuel burning in liquid medium

The method of computer-based examination of the burning process with the help of up-to-date hardware and software tools is presented. The character of solid fuel burning in liquid medium under different pressures is identified.     

Quasistatic bifurcation states of super-deep vertical drill strings

The problem of buckling of a long spinning rod containing an internal flow of a homogeneous liquid and undergoing compression and tension is considered in the paper. The authors derive the resulting equations to model stability of deep drilling strings according to the integrated calculation scheme, involving the string body and its lower section. The problem-solving procedure is proposed. Typical examples are discussed. The critical values of parameters for the elastic equilibrium of the system are found. The stability loss forms are determined.     

Fluorinated xanthates as collecting agents in copper-nickel ore flotation

Research data on intensification of copper-nickel ore flotation by applying the fluorinated xanthates are reported. Introduction of fluorinated agents at 3–50% rate of the total collector consumption improves the recovery of valuable components. It is established experimentally that the copper and nickel recovery into the flotation concentrate grows by over 10%.     

Gelatinization properties of wheat flour as determined by empirical and fundamental rheometric method

Certain empirical rheological methods are in extensive use in wheat and/or flour research to assess starch gelatinization and pasting behavior primarily due to easy performance and good correlation with final product quality. However, their applications are often associated with specific drawbacks that could be limiting factors for certain applications, such as poor definition of the measured parameters, time-consuming nature, difficulties in interpretation of results, large sample sizes, etc. The listed shortcomings can be overcome by application of fundamental rheological methods that are based on well-defined rheological parameters such as stress, strain, viscosity and modulus. The objective of this study was to optimize the fundamental rheological method for determination of the gelatinization properties of wheat flour that correspondents to the standard widely accepted empirical rheological method—Amylograph method and to compare them in order to determine whether they can be interchangeable depending on different analytical needs. The obtained results have shown that the application of fundamental rheometric procedure for determination of pasting properties of wheat flour provides reliable determination of the gelatinization properties of wheat flour. Moreover, substantial advantages of fundamental rheometric method over the empirical one were identified including smaller sample size, ability to set the desirable heating and shear rate, shorter test duration and better precision.     

Classification of Intact Cereal Flours by Front-Face Synchronous Fluorescence Spectroscopy

Synchronous fluorescence spectroscopy, a technique that measures both the absorption and the emission properties of a sample in a single measurement, was used for the analysis and classification of intact cereal flours (wheat, corn, rye, buckwheat, rice, and barley). Total synchronous fluorescence spectra recorded in constant wavelength mode show clear differences in the emission spectra of different flours due to variances in intrinsic fluorophore concentrations and their microenvironments. Principal component analysis, cluster analysis, and partial least squares discriminant analysis are used to assess the ability of synchronous fluorescence measurements to differentiate and classify intact samples of different flour types. The flour specimens were obtained directly from a market in Belgrade and had different expiration dates to provide a more representative set of samples. The results of the current analysis suggest that chemometric methods applied on synchronous fluorescence data can discriminate and classify flour types and that the best results are achieved using a combination of synchronous fluorescence measurements at synchronous intervals of 7 and 20 nm. The quality of results, the high speed of measurements, and the avoidance of extensive sample preparation make synchronous fluorescence spectroscopy a promising technique for cereal research.