5,527 research outputs found
Testing for inconsistencies in the estimation of UK capital structure determinants
This article analyses the determinants of the capital structure of 1054 UK companies from 1991 to 1997, and the extent to which the influence of these determinants are affected by time-invariant firm-specific heterogeneity. Comparing the results of pooled OLS and fixed effects panel estimation, significant differences in the results are found. While the OLS results are generally consistent with prior literature, the results of our fixed effects panel estimation contradict many of the traditional theories of the determinants of corporate financial structure. This suggests that results of traditional studies may be biased owing to a failure to control for firm-specific, time-invariant heterogeneity. The results of the fixed effects panel estimation find larger companies to have higher levels of both long-term and short-term debt than do smaller firms, profitability to be negatively correlated with the level of gearing, although profitable firms tend to have more short-term bank borrowing than less profitable firms, and tangibility to positively influence the level of short-term bank borrowing, as well as all long-term debt elements. However, the level of growth opportunities appears to have little influence on the level of gearing, other than short-term bank borrowing, where a significant negative relationship is observed
Design of Spacecraft Formation Orbits Relative to a Stabilized Trajectory
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76533/1/AIAA-8433-932.pd
Assessment of Connections Between Knowledge- Based Economy Characteristics and Selected Macroeconomic Categories in the European Union's Countries by Means of Panel Models
The aim of the article is to analyze the impact of knowledge-based economy variables on the selected macroeconomic categories - the share of total investments in GDP and the employment rate- in European Union's countries in the years 2000-2007, conducted with application of panel models.Celem artykułu jest analiza wpływu zmiennych opisujących gospodarkę opartą na wiedzy na podstawowe kategorie makroekonomiczne - udział całkowitych inwestycji w PKB i stopę zatrudnienia - w krajach Unii Europejskiej (z podziałem na kraje UE-15 i nowe kraje członkowskie UE) w latach 2000-2007, przeprowadzona w oparciu o modele panelowe
Critical behavior of the 3-state Potts model on Sierpinski carpet
We study the critical behavior of the 3-state Potts model, where the spins
are located at the centers of the occupied squares of the deterministic
Sierpinski carpet. A finite-size scaling analysis is performed from Monte Carlo
simulations, for a Hausdorff dimension . The phase
transition is shown to be a second order one. The maxima of the susceptibility
of the order parameter follow a power law in a very reliable way, which enables
us to calculate the ratio of the exponents . We find that the
scaling corrections affect the behavior of most of the thermodynamical
quantities. However, the sequence of intersection points extracted from the
Binder's cumulant provides bounds for the critical temperature. We are able to
give the bounds for the exponent as well as for the ratio of the
exponents , which are compatible with the results calculated from
the hyperscaling relation.Comment: 13 pages, 4 figure
Fisher Renormalization for Logarithmic Corrections
For continuous phase transitions characterized by power-law divergences,
Fisher renormalization prescribes how to obtain the critical exponents for a
system under constraint from their ideal counterparts. In statistical
mechanics, such ideal behaviour at phase transitions is frequently modified by
multiplicative logarithmic corrections. Here, Fisher renormalization for the
exponents of these logarithms is developed in a general manner. As for the
leading exponents, Fisher renormalization at the logarithmic level is seen to
be involutory and the renormalized exponents obey the same scaling relations as
their ideal analogs. The scheme is tested in lattice animals and the Yang-Lee
problem at their upper critical dimensions, where predictions for logarithmic
corrections are made.Comment: 10 pages, no figures. Version 2 has added reference
The Carnegie Supernova Project I: methods to estimate host-galaxy reddening of stripped-envelope supernovae
We aim to improve upon contemporary methods to estimate host-galaxy reddening
of stripped-envelope (SE) supernovae (SNe). To this end the Carnegie Supernova
Project (CSP-I) SE SNe photometry data release, consisting of nearly three
dozen objects, is used to identify a minimally reddened sub-sample for each
traditionally defined spectroscopic sub-types (i.e, SNe~IIb, SNe~Ib, SNe~Ic).
Inspection of the optical and near-infrared (NIR) colors and color evolution of
the minimally reddened sub-samples reveals a high degree of homogeneity,
particularly between 0d to +20d relative to B-band maximum. This motivated the
construction of intrinsic color-curve templates, which when compared to the
colors of reddened SE SNe, yields an entire suite of optical and NIR color
excess measurements. Comparison of optical/optical vs. optical/NIR color excess
measurements indicates the majority of the CSP-I SE SNe suffer relatively low
amounts of reddening and we find evidence for different R_(V)^(host) values
among different SE SN. Fitting the color excess measurements of the seven most
reddened objects with the Fitzpatrick (1999) reddening law model provides
robust estimates of the host visual-extinction A_(V)^(host) and R_(V)^(host).
In the case of the SE SNe with relatively low amounts of reddening, a preferred
value of R_(V)^(host) is adopted for each sub-type, resulting in estimates of
A_(V)^(host) through Fitzpatrick (1999) reddening law model fits to the
observed color excess measurements. Our analysis suggests SE SNe reside in
galaxies characterized by a range of dust properties. We also find evidence SNe
Ic are more likely to occur in regions characterized by larger R_(V)^(host)
values compared to SNe IIb/Ib and they also tend to suffer more extinction.
These findings are consistent with work in the literature suggesting SNe Ic
tend to occur in regions of on-going star formation.Comment: Abstract abridged to fit allowed limit. Resubmitted to A&A, 34 pages,
19 figures, 6 tables. Constructive comments welcome
Experimental Studies of Low-field Landau Quantization in Two-dimensional Electron Systems in GaAs/AlGaAs Heterostructures
By applying a magnetic field perpendicular to GaAs/AlGaAs two-dimensional
electron systems, we study the low-field Landau quantization when the thermal
damping is reduced with decreasing the temperature. Magneto-oscillations
following Shubnikov-de Haas (SdH) formula are observed even when their
amplitudes are so large that the deviation to such a formula is expected. Our
experimental results show the importance of the positive magneto-resistance to
the extension of SdH formula under the damping induced by the disorder.Comment: 9 pages, 3 figure
Rheological State Diagrams for Rough Colloids in Shear Flow
To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.National Science Foundation (U.S.) (Award 1232937)National Science Foundation (U.S.) (Award 1602183)United States. Army Research Office (Grant W911NF10-1-0518
Comprehensive Observations of the Bright and Energetic Type Iax SN 2012Z: Interpretation as a Chandrasekhar Mass White Dwarf Explosion
We present UV through NIR broad-band photometry, and optical and NIR
spectroscopy of Type Iax supernova 2012Z. The data set consists of both early
and late-time observations, including the first late phase NIR spectrum
obtained for a spectroscopically classified SN Iax. Simple model calculations
of its bolometric light curve suggest SN 2012Z produced ~0.3 M_sun of (56)Ni,
ejected about a Chandrasekhar mass of material, and had an explosion energy of
~10^51 erg, making it one of the brightest and most energetic SN Iax yet
observed. The late phase NIR spectrum of SN 2012Z is found to broadly resemble
similar epoch spectra of normal SNe Ia; however, like other SNe Iax,
corresponding visual-wavelength spectra differ substantially compared to all
supernova types. Constraints from the distribution of IMEs, e.g. silicon and
magnesium, indicate that the outer ejecta did not experience significant mixing
during or after burning, and the late phase NIR line profiles suggests most of
the (56)Ni is produced during high density burning. The various observational
properties of SN 2012Z are found to be consistent with the theoretical
expectations of a Chandrasekhar mass white dwarf progenitor that experiences a
pulsational delayed detonation, which produced several tenths of a solar mass
of (56)Ni during the deflagration burning phase and little (or no) (56)Ni
during the detonation phase. Within this scenario only a moderate amount of
Rayleigh-Taylor mixing occurs both during the deflagration and fallback phase
of the pulsation, and the layered structure of the IMEs is a product of the
subsequent denotation phase. The fact that the SNe Iax population does not
follow a tight brightness-decline relation similar to SNe Ia can then be
understood in the framework of variable amounts of mixing during pulsational
rebound and variable amounts of (56)Ni production during the early subsonic
phase of expansion.Comment: Submitted to A&A, manuscript includes response to referee's comments.
39 pages, including 16 figures, 9 table
Motivational Social Visualizations for Personalized E-Learning
A large number of educational resources is now available on the Web to support both regular classroom learning and online learning. However, the abundance of available content produces at least two problems: how to help students find the most appropriate resources, and how to engage them into using these resources and benefiting from them. Personalized and social learning have been suggested as potential methods for addressing these problems. Our work presented in this paper attempts to combine the ideas of personalized and social learning. We introduce Progressor + , an innovative Web-based interface that helps students find the most relevant resources in a large collection of self-assessment questions and programming examples. We also present the results of a classroom study of the Progressor + in an undergraduate class. The data revealed the motivational impact of the personalized social guidance provided by the system in the target context. The interface encouraged students to explore more educational resources and motivated them to do some work ahead of the course schedule. The increase in diversity of explored content resulted in improving students’ problem solving success. A deeper analysis of the social guidance mechanism revealed that it is based on the leading behavior of the strong students, who discovered the most relevant resources and created trails for weaker students to follow. The study results also demonstrate that students were more engaged with the system: they spent more time in working with self-assessment questions and annotated examples, attempted more questions, and achieved higher success rates in answering them
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