594 research outputs found
Cartel in the Indian cement industry: An attempt to identify it
No full textThis article is devoted to the problem of the detection of overt or tacit collusion equilibrium in the context of the choice of the appropriate econometric method, a choice that is determined by the amount of information that the observer possesses. The author addresses this problem in two steps. First, to provide a theoretical background, he uses a collusion marker based on structural disturbances in a price process'; variance. Then, he applies a Markov switching model with switching in variance regimes. The author considers this method adequate and coherent with the problem structure and the research objective, and useful for assessing the functionality of the collusion marker he uses. He uses the model to examine the Indian cement industry in the period 1994-2009 and finds some objective indications of collusion and competition phases. These phases are confirmed by certain historical facts as well as by numerous research articles
Proper motion, spectra, and timing of PSR J1813-1749 using Chandra and NICER
No full textPSR J1813-1749 is one of the most energetic rotation-powered pulsars known, producing a pulsar wind nebula (PWN) and gamma-ray and TeV emission, but whose spin period is only measurable in X-ray. We present analysis of two Chandra data sets that are separated by more than 10 yr and recent NICER data. The long baseline of the Chandra data allows us to derive a pulsar proper motion μRA=(-0.067 ± 0.010) yr-1 and μDec.=(-0.014 ± 0.007) yr-1 and velocity v ≈ 900-1600 km, s-1 (assuming a distance d = 3-5 kpc), although we cannot exclude a contribution to the change in measured pulsar position due to a change in brightness structure of the PWN very near the pulsar. We model the PWN and pulsar spectra using an absorbed power law and obtain best-fitting absorption NH=(13.1 ± 0.9) × 1022 cm-2, photon index Γ = 1.5 ± 0.1, and 0.3-10 keV luminosity LX ≈ 5.4 × 1034, s-1(d/5 kpc)2 for the PWN and Γ = 1.2 ± 0.1 and LX ≈ 9.3 × 1033, s-1(d/5 kpc)2 for PSR J1813-1749. These values do not change between the 2006 and 2016 observations. We use NICER observations from 2019 to obtain a timing model of PSR J1813-1749, with spin frequency ν = 22.35 Hz and spin frequency time derivative nu=(-6.428 ± 0.003) × 10-11Hz, s-1. We also fit ν measurements from 2009 to 2012 and our 2019 value and find a long-term spin-down rate nu=(-6.3445 ± 0.0004) × 10-11Hz, s-1. We speculate that the difference in spin-down rates is due to glitch activity or emission mode switching
Possibilities of Diagnosing the Processes in the Injection System of a Marine Diesel Engine
No full textIstnieje możliwość zastosowania sygnału emisji akustycznej do diagnozowania układu wtryskowego silnika okrętowego. Wykorzystując dekompozycję sygnału z użyciem metody falkowej można określić istotne parametry procesu wtrysku oraz niektóre z uszkodzeń układu wtryskowego. Dokonano analizy rejestrowanego sygnału emisji akustycznej. Do oceny pracy wybranych elementów zaproponowano utworzenie nowego współczynnika będącego miarą sygnału, która może być zastosowana do szybkiej oceny uszkodzenia.It is possible to apply an Acoustic Emission (AE) signal for diagnosing the fuel injection system of a marine diesel engine. By the signal decomposition using the wavelet method we can determine significant parameters of injection and some failures of the injection system. For the estimation of operation of selected elements the author proposes to create a coefficient being a signal measure suitable for quick diagnosis of a failure
INVESTIGATION OF THE NATURE OF STRATEGIC INTERACTIONS IN THE POLISH WHOLESALE FUEL MARKET: STATISTICAL ANALYSIS OF A MARKET STRUCTURE AND A PRICE MECHANISM
No full textThe study is devoted to preliminary analysis of the Polish petroleum industry and the wholesale level of the fuel market in the context of strategic interactions’ research. In the paper, the structure of the Polish petroleum industry (refining sector) and the wholesale level of the market were analyzed, in order to extract every factors influencing the shape of theoretical strategic interaction model. As a result, the key characteristics of the industry, the wholesale market, the players and price creation mechanism have been isolated. Basing on that findings, the Author has pointed to essential elements of the theoretical model of strategic interactions (game model), which can be constructed as a possible model of players’ behavior
Astrophysics with continuous gravitational waves
No full textDirect detection of gravitational waves has become a powerful new tool of multi-messenger astrophysics. Apart from short-duration (transient) events, such as the inspirals and mergers of stellar-mass compact objects, we envisage other signal types of much longer duration—continuous gravitational waves. Traditionally associated with neutron star astrophysics, and hence with their largely unknown dense-matter interiors, continuous gravitational waves are now also entering other fields of astrophysics, namely, searches for dark matter, primordial black holes or exotic particles. Their long duration allows for qualitatively new possibilities, such as reproducible studies and tests of gravitational theory. This Review summarizes the results obtained in the recent O3 observing run of the LIGO–Virgo–KAGRA collaboration, the current status of the data analysis and the theoretical ideas related to astrophysical models. We show that O3 observations have started probing astrophysically relevant scenarios, and discuss how the improved sensitivity of the currently ongoing O4 observing run may offer a real possibility for a first detection of continuous gravitational waves
Proper motion, spectra, and timing of PSR J1813-1749 using Chandra and NICER
No full textPSR J1813-1749 is one of the most energetic rotation-powered pulsars known, producing a pulsar wind nebula (PWN) and gamma-ray and TeV emission, but whose spin period is only measurable in X-ray. We present analysis of two Chandra data sets that are separated by more than 10 yr and recent NICER data. The long baseline of the Chandra data allows us to derive a pulsar proper motion μRA=(-0.067 ± 0.010) yr-1 and μDec.=(-0.014 ± 0.007) yr-1 and velocity v ≈ 900-1600 km, s-1 (assuming a distance d = 3-5 kpc), although we cannot exclude a contribution to the change in measured pulsar position due to a change in brightness structure of the PWN very near the pulsar. We model the PWN and pulsar spectra using an absorbed power law and obtain best-fitting absorption NH=(13.1 ± 0.9) × 1022 cm-2, photon index Γ = 1.5 ± 0.1, and 0.3-10 keV luminosity LX ≈ 5.4 × 1034, s-1(d/5 kpc)2 for the PWN and Γ = 1.2 ± 0.1 and LX ≈ 9.3 × 1033, s-1(d/5 kpc)2 for PSR J1813-1749. These values do not change between the 2006 and 2016 observations. We use NICER observations from 2019 to obtain a timing model of PSR J1813-1749, with spin frequency ν = 22.35 Hz and spin frequency time derivative nu=(-6.428 ± 0.003) × 10-11Hz, s-1. We also fit ν measurements from 2009 to 2012 and our 2019 value and find a long-term spin-down rate nu=(-6.3445 ± 0.0004) × 10-11Hz, s-1. We speculate that the difference in spin-down rates is due to glitch activity or emission mode switching.</p
Deformation and crustal rigidity of rotating neutron stars
No full textAims. We calculate parameters A and B of the Baym-Pines model of the
hydro-elastic equilibrium of rotating neutron stars. Parameter A
determines the energy increase of a non-rotating star due to a quadrupolar
deformation of its shape. Parameter B determines residual
quadrupolar deformation due to the crustal shear strain
in a neutron star that spun down to a non-rotating state.
Methods. The calculations of
are based on precise numerical 2D calculations for rotating neutron
stars with the realistic equations of state (EOSs) of dense matter.
An approximate, but quite precise, formula for B is
used, which allows us to separate the contribution of
the crust from the dependence on the
stellar mass M and radius R. The elastic shear strain
distribution within the crust is modeled following
Cutler et al. (2003). Realistic
EOSs of neutron star cores are used, some of them with
high-density softening due to the
appearance of hyperons or a phase transition to an exotic state.
Results. The values and were calculated for
(where Mmax is the maximum allowable mass) for seven
EOSs of neutron star core,
combined with several crust models. A standard formula based on the
incompressible fluid model is shown to severely underestimate the value of A. For the values of are nearly EOS-independent
and are given (within a few percent) by a
universal formula . We derive the
scaling of B with respect to R and M,
also valid for a thick crust. We show that B for
accreted crust strongly depends on pycnonuclear fusions
at
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Tetrathiafulvalene Schiff-base ligands and anion receptors
No full texttextOver the last decade, the classic organic donor tetrathiafulvalene (TTF) has emerged as an important functionality in supramolecular systems and complex ligand chemistry. Due to synthetic advances, TTF is no longer a moiety strictly limited to the area of charge transfer salts in material science. In fact, many complex systems incorporating the electron rich donor system are known. More can be imagined. This doctoral dissertation describes the author's journey in designing, synthesizing, and studying various compounds in which the TTF moiety serves a practical purpose, oftentimes giving known molecules new functions. The reported findings have led to a greater understanding of anion binding effects on TTF-containing anion receptors, the use of transition metals to pre-organize [pi]-faces for through-space donor-acceptor interactions, and the introduction of actinide species to tetrathiafulvalene ligands. The first Chapter provides a brief introduction and a short history of TTF chemistry. It also provides an overview describing the fundamental properties of TTF compounds, including TTF dimeric behavior and redox properties. Chapter 2, as the major focus of this dissertation, details the use of a flexible TTF-modified macrocyclic ligand, which upon metallation can effectively preorganize two TTF units to interact when oxidized. Specifically, a new way to stabilize the through-space mixed-valence TTF dimer, in which a transition metal can affect the degree of interaction between the two TTF units, is described. The mixed-valence TTF species in question could see use as components in molecular machines and could play an important role as molecular organic conductors, and discussions along these lines are included in this chapter. These mixed valence complexes were investigated by spectroscopic (¹H-NMR, UV-Vis NIR titrations, and EPR analysis) and X-ray single crystallographic analyses involving both the neutral and oxidized products. Chapter 3 introduces the synthesis, characterization, and electrochemistry of the first TTF-ligand to form a complex with an actinide cation. Chapter 4 details the synthesis, binding studies and X-ray single crystallographic analyses of a TTF-based electrochemical sensor for dihydrogen phosphate anion detection. Experimental procedures and characterization data are reported in Chapter 5.Chemistr
Estimating the equation of state from measurements of neutron star radii with 5% accuracy
No full textInternational audienceContext. Observations of heavy (⋍2 M⊙) neutron stars, such as PSR J1614−2230 and PSR J0348+0432, in addition to the recent measurement of tidal deformability from the binary neutron-star merger GW170817, place interesting constraints on theories of dense matter. Currently operating and future observatories, such as the Neutron star Interior Composition Explorer (NICER) and the Advanced Telescope for High ENergy Astrophysics (ATHENA), are expected to collect information on the global parameters of neutron stars, namely masses and radii, with an accuracy of a few percent. Such accuracy will allow for precise comparisons of measurements to models of compact objects and significantly improve our understanding of the physics of dense matter.Aims. The dense-matter equation of state is still largely unknown. We investigate how the accuracy of measurements expected from the NICER and ATHENA missions will improve our understanding of the dense-matter interior of neutron stars.Methods. We compared global parameters of stellar configurations obtained using three different equations of state: a reference (SLy4 EOS) and two piecewise polytropes manufactured to produce mass-radius relations indistinguishable from an observational point of view, i.e. within the predicted error of radius measurement. We assumed observational errors on the radius determination corresponding to the accuracies expected for the NICER and ATHENA missions. The effect of rotation was examined using high-precision numerical relativity computations. Because masses and rotational frequencies might be determined very precisely in the most optimistic scenario, only the influence of observational errors on radius measurements was investigated.Results. We show that ±5% errors in radius measurement lead to ~10% and ~40% accuracy in central parameter estimations for low-mass and high-mass neutron stars, respectively. Global parameters, such as oblateness and surface area, can be established with 8–10% accuracy, even if only compactness (instead of mass and radius) is measured. We also report on the range of tidal deformabilities corresponding to the estimated masses of GW170817 for the assumed uncertainty in radius.Key words: equation of state / dense matter / stars: neutro
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