Method For Determination Of Distribution Research Articles

Comparative analysis of experimental and calculation methods for determination of the traction current harmonics distribution in rails

The purpose of this work is to perform the comparative analysis of experimental and calculation methods for determination of the distribution of traction current harmonics in rails. To investigate the distribution of traction current in the rails, the special marks (flags) were set up at a certain distance (100, 300 and 500 m) from the point of measurement along the track. The moments of passing the train past the flags were recorded in a computer due to a sound signal from the train, as well as visual observation. The train was moving in the measuring section in a quasi-stationary mode with an average speed of about 48 km/h. Traction current was measured in circuit of the inter-throttle jumper with using an inductive contactless sensor and registered using computer.The distribution of the return traction current harmonics in rails for AC feeding systems were modeled by using the multi-conductor transmission line (MTL) model.Some discrepancies in the results of experimental and calculation methods were observed. One of main reason of measurement errors were an inaccuracy in determining distances from the train to the measurement point. Calculation errors were related mainly with using inaccurate electrical parameters of track in model, in particular, the track ballast resistance and the ground resistances.However, in general, the considered model can be used for investigation of the traction current harmonic propagation in rails from train, and their influence on the track circuits receivers for different cases including the variation of the track circuits electrical parameters, as well as the number of rolling stock units in the feeder zone. Such analysis of harmonic in rails is important for revealing the causes of failures in railway signalling system operation under simultaneous affecting on it several factors adverse to safe operation.

Inverse projection method for determination of distribution of real CME latitudes applied to the 1997–1998 SOHO LASCO observations

Coronograph observations of coronal mass ejections (CMEs) do not provide the real latitude of their origin. The registered apparent latitude is the projection of the CME trajectory on the plane of the sky, and it may considerably differ from their original location. We show in this paper, how the projection effects can be eliminated from CME latitude distribution. The proposed method is based on the assumption that events move radially, their longitudinal distribution is uniform, and they are all detected. This tool has been applied to SOHO LASCO data, for which detection efficiency was near 100%. The obtained distributions of real latitudes have cut off at ∼20° in 1997 (minimum solar activity) and ∼50° in 1998 (rise phase). The events observed at higher latitudes proved to be only apparent projections of events really originated at lower latitudes.

The problem of protein folding and dynamics: time-resolved dynamic nonradiative excitation energy transfer measurements

The proteins are molecular machines that are self-assembled infinitely diverse, give rise to complex structures of any size, and have well-controlled vectorial modes of conformational changes, driven by thermal motions. Numerous experiments show that the pathway of folding of globular proteins, from the un-ordered state to the native conformations, and their modes of intramolecular motions, are determined by the sequence of the amino acyl residues (the monomers) in the polypeptide chain (the genetic information) of each protein. Attempts to decipher the mechanism by which the multiple transitions, on a wide range of time and distance scales are directed, depend on development of new methods for determination of distributions of intermolecular distances in flexible molecules and their time dependence. Methods based on time resolved measurements of intramolecular dynamic nonradiative excitation energy transfer, combined with protein engineering and site directed labeling were developed. Global analysis of data sets obtained by these measurements yield distributions of probabilities of segments end-to-end distances (EEDP) (in the range of 8 to 80 W chain). Methods for AMP determination of rates of conformational fluctuations and of the folding transitions, down to picosecond time scale, by means of this approach were also developed. Application of this experimental approach in the study of the denatured state of single-domain globular proteins, show that even in the denatured states, these proteins have compact structures. The bovine pancreatic trypsin inhibitor (BPTI) showed in the denatured state at least two conformational subpopulations, one was native-like and the other was characterized by EEDP distributions corresponding to an unfolded polypeptide chain.

Method for the experimental determination od distribution of concentrations at phase interface during mass transfre in liquid—liqiud system with intensive agitation

The question of the existence of equilibrium at interfaces is ors of the central questions both for the construction of various models of mass transfer and for the following practical calculations: (a) of phase resistances from the additivity formulas (which are valid only in the case of the presenee of equilibrium), (b) to reveal the so-called “surface resistance” to mass transfer (which is determined from the deviation from the additivity equation), and (c) of the appearance of interface turbulence. Therefore, this question Is very important, but it has not been resolved. since there are no direct experimental methods for determination of distribution of the concentrations at the phase interface during mass transfer. We formulated a new equation for this distribution. We then compared this equation with other experimental findings and determined the limit of its application. It is shown that this equation may be used for calculating the ratio of the concentrations at the phase interface when there are considerable (big or small) deviations from equilibrium in liquid—liquid systems.

Recent ultracentrifugal investigations on cellulose and cellulose derivatives

AbstractA review is given of physicochemical studies on cellulose and cellulose derivatives made during the years of World War II at the Institute of Physical Chemistry, Uppsala, Sweden. Emphasis has been laid on the principles of the subject and the review deals essentially with some investigations on nitrocellulose by the present author. An outline of the problems of the cellulose chemistry of today serves as an introduction. The principles of molecular weight determinations from Svedberg's equation are briefly mentioned, and the difficulties in the extrapolation of sedimentation constants to zero concentration are discussed. The problem of what sort of average molecular weight is obtained from Svedberg's equation is treated subsequently and methods for determination of distributions from combinations of osmotic and sedimentation experiments described. A table comparing five different sorts of average molecular weights for a numbe of nitrocelluloses is discussed.