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Scintillations of pulsar radio signals caused by the interstellar medium can in principle be used for interstellar interferometry. Changes of the dynamic spectra as a function of pulsar longitude were in the past interpreted as having spatially resolved the pulsar magnetosphere. Guided by this prospect we used VLBI observations of PSR B1237+25 with the Arecibo and Green Bank radio telescopes at 324 MHz and analyzed such scintillations at separate longitudes of the pulse profile. We found that the fringe phase characteristics of the visibility function changed quasi-sinusoidally as a function of longitude. Also, the dynamic spectra from each of the telescopes shifted in frequency as a function of longitude. Similar effects were found for PSR B1133+16. However, we show that these effects are not signatures of having resolved the pulsar magnetosphere. Instead the changes can be related to the effect of low-level digitizing of the pulsar signal. After correcting for these effects the frequency shifts largely disappeared. Residual effects may be partly due to feed polarization impurities. In view of our analysis we think that observations with the intend of spatially resolving the pulsar magnetosphere need to be critically evaluated in terms of these constraints on interstellar interferometry., Comment: 17 pages, 11 figures, submitted to the Astrophysical Journal

The work describes a system for converting VLBI observation data using the algorithms of coherent dedispersion and compensation of two-bit signal sampling. Coherent dedispersion is important for processing pulsar observations to obtain the best temporal resolution, while correction for signal sampling makes it possible to get rid of a number of parasitic effects that interfere with the analysis of the diffraction pattern of pulsars. A pipeline has been established that uses the developed converter and the ASC Software Correlator, which will allow reprocessing all archived data of Radioastron pulsar observations and to conduct a search for giant pulses, which requires the best temporal resolution., Comment: 16 pages, 4 figures

The aim of our work was to study the spatial structure of inhomogeneities of interstellar plasma in the directions of five pulsars: B0823+26, B0834+06, B1237+25, B1929+10, and B2016+28. Observations of these pulsars were made with RadioAstron space-ground radio interferometer at 324 MHz. We measured the angular size of the scattering disks to be in range between 0.63 and 3.2 mas. We determined the position of scattering screens on the line of sight. Independent estimates of the distances to the screens were made from the curvature of parabolic arcs revealed in the secondary spectra of four pulsars. The model of uniform distribution of inhomogeneities on the line of sight is not suitable. According to the results, we came to the conclusion that scattering is mainly produced by compact plasma layers and the uniform model of inhomogeneties distribution on the line of sight in not applicable., 15 pages, 12 figures

An established methodology for estimating precipitation amounts from satellite-based soil moisture retrievals is applied to L-band products from the Soil Moisture Active Passive (SMAP) and Soil Moisture and Ocean Salinity (SMOS) satellite missions and to a C-band product from the Advanced Scatterometer (ASCAT) mission. The precipitation estimates so obtained are evaluated against in situ (gauge-based) precipitation observations from across the globe. The precipitation estimation skill achieved using the L-band SMAP and SMOS datasets is higher than that obtained with the C-band product, as might be expected given that L-band is sensitive to a thicker layer of soil and thereby provides more information on the response of soil moisture to precipitation. The square of the correlation coefficient between the SMAP-based precipitation estimates and the observations (for aggregations to ~100 km and 5 days) is on average about 0.6 in areas of high rain gauge density. Satellite missions specifically designed to monitor soil moisture thus do provide significant information on precipitation variability, information that could contribute to efforts in global precipitation estimation. ispartof: Water Resources Research vol:52 issue:9 pages:7213-7225 ispartof: location:United States status: published

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In this paper, we analyze axiomatic issues of unconventional computations from a methodological and philosophical point of view. We explain how the new models of algorithms changed the algorithmic universe, making it open and allowing increased flexibility and creativity. However, the greater power of new types of algorithms also brought the greater complexity of the algorithmic universe, demanding new tools for its study. That is why we analyze new powerful tools brought forth by the axiomatic theory of algorithms, automata and computation.

This document is the result of the Rural Territorial Dynamics Program, implemented by Rimisp in several Latin American countries in collaboration with numerous partners. The program has been supported by the International Development Research Center (IDRC, Canada). We authorize the non-for-profit partial or full reproduction and dissemination of this document, subject to the source being properly acknowledged.

This paper attempts to understand the coexistence of the material and nonmaterial aspects of our lives. By synthesizing ideas about structures, physical entities, mental phenomena, and symbolic relations, we argue that the nonmaterial can emerge from the material, and then the nonmaterial may mediate the production of material entities. Finally, this cycle is applied to notions of creativity and invention.

In this work, topological spaces are enriched by additional structures in order to give a more realistic representation of real life phenomena and computational processes and at the same time, to provide for utilization of the powerful technique developed in topology. The suggested approach is based on the concept of a discontinuity structure or scale Q in a topological space X. This structure serves as a scale for the initial topology on X. Problems of science and engineering need such a scale because all measurements and the majority of computations are performed in a definite scale and problems of scalability are important both for physical theories and computational algorithms. Taking a mapping of a topological space X with the discontinuity structure Q into a topological space Y with a discontinuity structure R, we define (Q,R)-continuity, weak (Q,R)-continuity, and R-continuity of this mapping. Fuzzy continuous functions, which are studied in neoclassical analysis, are examples of R-continuous mappings. Different properties of scales, Q-open, Q-closed sets, and (Q,R)-continuous mappings are obtained.

When planning new facilities, one is interested to know whether and by how much the new technique is superior to already existing ones. We describe a general approach permitting to evaluate the relative merits of various techniques used in astrophysical observations, following the theory of model parameter estimation. It is applied to compare two-aperture optical long baseline interferometry to classical spectroscopy, both used to define the model parameters of the P Cyg wind. The wind modeling was done using an efficient approximation for computation of the line source function; it allowed to analyse about 10e5 points in the parametric space of P Cyg envelope models. It is shown that interferometry offers no real advantage if the object can be described by stationary spherically symmetric models with a priori fixed thermal structure. However, if the object must be described by a model with a large number of free parameters, e.g. when the thermal structure of the envelope is not fixed a priori, then the interferometric measurements can reduce the error in model parameters determination by an order of magnitude. In the case of P Cyg, the reduction of errors provided by interferometry is highest for the baseline lengths in the range 45--90 m. This illustrates the capacity of the proposed method to be used for optimization of interferometric configurations. The simplifications adopted for this first trial application are critically analyzed, and future improvements are indicated., LaTeX2.09e + aa.cls + graphics.sty, 14 pages, 7 figures. Accepted for publication in Astron. Astrophys. Suppl

On the basis of a structural-naming reconstruction of scientific knowledge we give a description of the main subsystems of mathematical theories. The role of the theory of named sets for the exact analysis of their components is given. For the case of set theory we consider also some dynamic aspects.

The overall performance of a supply-chain (SC) is influenced significantly by the decisions taken in its production-distribution (P-D) plan. A P-D plan integrates decisions in production, transport and warehousing as well as inventory management. One key issue in the performance evaluation of a Supply Network (SN) is the modeling and optimization of P-D planning problem considering its actual complexity. Based on the integration of Aggregate Production Planning and Distribution Planning, this paper firstly develops a mixed integer formulation for a two-echelon supply network considering the real-world variables and constraints. A multi-objective genetic algorithm (MOGA) is then designed for the optimization of the developed mathematical model. Finally, a real-world case study incorporating multiple products, multiple plants, multiple warehouses, multiple end-users, and multiple time periods will be considered for investigating the performance evaluation of the MOGA method against the traditional approaches of SC planning.