The investigation of limiting factors of earnings management for companies’ listed Tehran stock exchange

The current study was to examine the limiting factors of earnings management for companies’ listed Tehran stock exchange. The study was a kind of applied, descriptive- correlative research. All listed companies in Tehran stock exchange were selected as  statistical population during 2009 to 2013. So, data was gathered by library method  and collected by systematic eliminated sampling method. The results show that there is  a significant inverse relationship between board size and earnings management in companies’ listed Tehran stock exchange. The result doesn’t show any significant relationship between dividend and earnings management in companies’ listed Tehran stock exchange.Keywords: real earnings management; accrual earnings management; discretionary accruals; non-discretionary accruals; intensive factor

Structure-property relations of metallic materials with multiscale microstructures

Nanostructured metals have higher strength than those of the coarse grained metals but suffer from the extremely limited ductility. Development of the multiscale microstructures can improve the ductility of these high strength materials due to the introduction of a specific range of grain sizes in micro level. The present work relates the multiscale microstructures in metals to their overall structure properties using a fractal theory and the modified mean-field method, where three microstructural parameters are introduced and thus mechanical properties such as strength and ductility are presented as a function of these microstructural parameters. Meanwhile, with the applications of the finite element method, the multiscale unit cell approach is also critically developed and applied with a focus on predicting the related stress-strain relations of the metals with multiscale microstructures. For verification of these proposed theoretical and numerical algorithms, the mechanical properties of the pure copper with three-grain microstructures are investigated and the results from FEA and theoretical solutions have a reasonable agreement

Minimising the impact of scale-dependent galaxy bias on the joint cosmological analysis of large scale structures

We present a mitigation strategy to reduce the impact of non-linear galaxy bias on the joint ‘3 × 2pt’ cosmological analysis of weak lensing and galaxy surveys. The Ψ-statistics that we adopt are based on Complete Orthogonal Sets of E/B Integrals (COSEBIs). As such they are designed to minimize the contributions to the observable from the smallest physical scales where models are highly uncertain. We demonstrate that Ψ-statistics carry the same constraining power as the standard two-point galaxy clustering and galaxy-galaxy lensing statistics, but are significantly less sensitive to scale-dependent galaxy bias. Using two galaxy bias models, motivated by halo-model fits to data and simulations, we quantify the error in a standard 3 × 2pt analysis where constant galaxy bias is assumed. Even when adopting conservative angular scale cuts, that degrade the overall cosmological parameter constraints, we find of order 1σ biases for Stage III surveys on the cosmological parameter S8 = σ8(Ωm/0.3)α. This arises from a leakage of the smallest physical scales to all angular scales in the standard two-point correlation functions. In contrast, when analysing Ψ-statistics under the same approximation of constant galaxy bias, we show that the bias on the recovered value for S8 can be decreased by a factor of ∼2, with less conservative scale cuts. Given the challenges in determining accurate galaxy bias models in the highly non-linear regime, we argue that 3 × 2pt analyses should move towards new statistics that are less sensitive to the smallest physical scales

Density-functional theory of strongly correlated Fermi gases in elongated harmonic traps

Two-component Fermi gases with tunable repulsive or attractive interactions inside quasi-one-dimensional (Q1D) harmonic wells may soon become the cleanest laboratory realizations of strongly correlated Luttiger and Luther-Emery liquids under confinement. We present a microscopic Kohn-Sham density-functional theory of these systems, with specific attention to a gas on the approach to a confinement-induced Feshbach resonance. The theory employs the one-dimensional Gaudin-Yang model as the reference system and transfers the appropriate Q1D ground-state correlations to the confined inhomogeneous gas {\it via} a suitable local-density approximation to the exchange and correlation energy functional. Quantitative understanding of the role of the interactions in the bulk shell structure of the axial density profile is thereby achieved. While repulsive intercomponent interactions depress the amplitude of the shell structure of the noninteracting gas, attractive interactions stabilize atomic-density waves through spin pairing. These should be clearly observable in atomic clouds containing of the order of up to a hundred atoms.Comment: 13 pages, 9 figures, submitte

Optical Tellegen metamaterial with spontaneous magnetization

The nonreciprocal magnetoelectric effect, also known as the Tellegen effect, promises a number of groundbreaking phenomena connected to fundamental (e.g., electrodynamics of axion and relativistic matter) and applied physics (e.g., magnetless isolators). We propose a three-dimensional metamaterial with an isotropic and resonant Tellegen response in the visible frequency range. The metamaterial is formed by randomly oriented bi-material nanocylinders in a host medium. Each nanocylinder consists of a ferromagnet in a single-domain magnetic state and a high-permittivity dielectric operating near the magnetic Mie-type resonance. The proposed metamaterial requires no external magnetic bias and operates on the spontaneous magnetization of the nanocylinders. By leveraging the emerging magnetic Weyl semimetals, we further show how a giant bulk effective magnetoelectric effect can be achieved in a proposed metamaterial, exceeding that of natural materials by almost four orders of magnitude.Comment: 11 pages, 4 figure

Microwave driven synthesis of narrow bandgap alpha-tin nanoparticles on silicon

This work proposes a microwave-based synthetic route for the preparation of tin nanospheres with a diamond-like a-phase structure on silicon. The main characteristics of the synthesized material are an extraordinarily narrow (around 50 meV) direct bandgap and an improved thermal stability (up to 200° C). Structural and compositional characterizations showed a core–shell structure comprised of an outer amorphous oxide shell and inner core containing a-phase tin domains. Microwaves turned out to be instrumental in achieving the specific nanostructures reported, due to their peculiar heating characteristics. Low pressure, low temperature and compatibility with integrated circuits manufacturing represent the most innovative features of the present synthetic process

Classification of Spanish ports using cluster analysis

El sistema portuario español es sumamente complejo y admite el estudio desde numerosos puntos de vista En este artículo se estudian los puertos según su actividad y sus características externas para la clasificación en agrupaciones. Para ello se han utilizado indicadores que reflejan la actividad portuaria y se han aplicado sobre las 28 Autoridades Portuarias españolas. Con estos indicadores se ha aplicado una metodología específica para a través del análisis de conglomerados (cluster) para averiguar cuáles son los agrupamientos que se producen. El análisis cluster se complementa con otros análisis estadísticos: análisis multivariante y componentes principales, para conocer qué indicadores son los más relevantes en las agrupaciones y cómo se comportan. Los resultados finales obtenidos muestran que este tipo de estudios estadísticos son apropiados para realizarse en el entorno portuario y que los agrupamientos reflejan correctamente la realidad portuaria.The Spanish port system is extremely complex and admits the study from many points of view. In this article the ports are studied from the point of view of classification in clusters according to their external characteristics. For this purpose, indicators have been used that reflect the port activity and have been applied on the 28 Spanish Port Authorities. With these indicators, a specific methodology has been applied through the analysis of clusters (cluster) to find out which clusters are produced. The cluster analysis is complemented by other analyzes (main components, multivariate analysis and individual indicators) to know which indicators are the most relevant in clusters and how they behave. The final results obtained show that this type of statistical studies are appropriate to be carried out in the port environment and that the groupings correctly reflect the port reality

Pair distribution function in a two-dimensional electron gas

We calculate the pair distribution function, $g(r)$, in a two-dimensional electron gas and derive a simple analytical expression for its value at the origin as a function of $r_s$. Our approach is based on solving the Schr\"{o}dinger equation for the two-electron wave function in an appropriate effective potential, leading to results that are in good agreement with Quantum Monte Carlo data and with the most recent numerical calculations of $g(0)$. [C. Bulutay and B. Tanatar, Phys. Rev. B {\bf 65}, 195116 (2002)] We also show that the spin-up spin-down correlation function at the origin, $g_{\uparrow \downarrow}(0)$, is mainly independent of the degree of spin polarization of the electronic system.Comment: 5 figures, pair distribution dependence with distance is calculate

A preliminary study into the criterion validity of the modified Modified Ashworth scale using the new measure of the alpha motoneuron excitability in spastic hemiplegia

The Modified Ashworth Scale (MAS) is the most widely used clinical test for the measurement of muscle spasticity. This scale that suffers from limitations and lack of reliability and validity has recently been remodified. The aim of the present study is to investigate the criterion validity of the new Modified MAS(MMAS) in the upper limb in post-stroke hemiplegia, using the Hslope/Mslope (Hslp/Mslp) as a novel index of alpha motor neuron excitability. Prior to the validity study, the reliability of the MMAS was evaluated in 30 hemiplegic patients. The raters agreed on 23 patients (0.76). The MMAS had good inter-rater reliability (κ= 0.63, SE = 0.11, p 0.05): There was also no relationship between the clinical scale of MMAS and either the traditional Hmax/ Mmax ratio (r = -0.06) or the new index Hslp/Mslp (r = 0.24) of spinal excitability. This preliminary study recruited a small number of patients, and failed to confirm a linear correlation between these variables. A study with a larg number of patients is suggested to clarify the outcome