Evolution of the spectral index after inflation

In this article we investigate the time evolution of the adiabatic(curvature) and isocurvature (entropy) spectral indices after end of inflation for all cosmological scales and two different initial conditions. For this purpose,we first extract an explicit equation for the time evolution of the comoving curvature perturbation (which may be known as the generalized Mukhanov-Sasaki equation). It shall be manifested that the evolution of adibatic spectral index severely depends on the intial conditions and just for the super-Hubble scales and adiabatic initial conditions is constat as be expected.Moreover,it shall be clear that the adiabatic spectral index after recombination approach to a constant value for the isocurvature perturbations.Finally,we re-investgate the Sachs-Wolfe effect and show that the fudge factor 1/3 in the adiabatic ordinary Sachs-Wolfe formula must be replaced by 0.4.Comment: 18 pages,4figure

On the perturbation theory in spatially closed background

In this article,we investigate some features of the perturbation theory in spatially closed universe. We will show that the perturbative field equations in a spatially closed universe always have two independent adiabatic solutions provided that the wavelengths of perturbation modes are very longer than the Hubble horizon. It will be revealed that these adiabatic solutions do not depend on the curvature directly. We also propound a new interpretation for the curvature perturbation in terms of the unperturbed geometry.Comment: 25 pages,no figures,accepted for publiction in EPJ

Parameter identification of a mechanical ductile damage using Artificial Neural Networks in sheet metal forming.

In this paper, we report on the developed and used of finite element methods, have been developed and used for sheet forming simulations since the 1970s, and have immensely contributed to ensure the success of concurrent design in the manufacturing process of sheets metal. During the forming operation, the Gurson–Tvergaard–Needleman (GTN) model was often employed to evaluate the ductile damage and fracture phenomena. GTN represents one of the most widely used ductile damage model. In this investigation, many experimental tests and finite element model computation are performed to predict the damage evolution in notched tensile specimen of sheet metal using the GTN model. The parameters in the GTN model are calibrated using an Artificial Neural Networks system and the results of the tensile test. In the experimental part, we used an optical measurement instruments in two phases: firstly during the tensile test, a digital image correlation method is applied to determinate the full-field displacements in the specimen surface. Secondly a profile projector is employed to evaluate the localization of deformation (formation of shear band) just before the specimen’s fracture. In the validation parts of this investigation, the experimental results of hydroforming part and Erichsen test are compared with their numerical finite element model taking into account the GTN model. A good correlation was observed between the two approaches

Effect of Ductile Damage Evolution in Sheet Metal Forming: Experimental and Numerical Investigations

The numerical simulation based on the Finite Element Method (FEM) is widely used in academic institutes and in the industry. It is a useful tool to predict many phenomena present in the classical manufacturing forming processes such as necking, fracture, springback, buckling and wrinkling. But, the results of such numerical model depend strongly on the parameters of the constitutive behavior model. In the first part of this work, we focus on the traditional identification of the constitutive law using oriented tensile tests (0°, 45°, and 90° with respect to the rolling direction). A Digital Image Correlation (DIC) method is used in order to measure the displacements on the surface of the specimen and to analyze the necking evolution and the instability along the shear band. Therefore, bulge tests involving a number of die shapes (circular and elliptic) were developed. In a second step, a mixed numerical–experimental method is used for the identification of the plastic behavior of the stainless steel metal sheet. The initial parameters of the inverse identification were extracted from a uniaxial tensile test. The optimization procedure uses a combination of a Monte-Carlo and a Levenberg-Marquardt algorithm. In the second part of this work, according to some results obtained by SEM (Scaning Electron Microscopy) of the crack zones on the tensile specimens, a Gurson Tvergaard Needleman (GTN) ductile model of damage has been selected for the numerical simulations. This model was introduced in order to give informations concerning crack initiations during hydroforming. At the end of the paper, experimental and numerical comparisons of sheet metal forming applications are presented and validate the proposed approach

Astra: Evaluating Translations from Alloy to SMT-LIB

We present a variety of translation options for converting Alloy to SMT-LIB via Alloy's Kodkod interface. Our translations, which are implemented in a library that we call Astra, are based on converting the set and relational operations of Alloy into their equivalent in typed first-order logic (TFOL). We investigate and compare the performance of an SMT solver for many translation options. We have three translation axes, and in total, twelve different combinations. We compare using only one universal type to recovering Alloy type information from the Kodkod representation and using multiple types in TFOL. We compare a direct translation of the relations to predicates in TFOL to one where we recover functions from their relational form in Kodkod and represent these as functions in TFOL. We compare representations in TFOL with unbounded scopes to ones with bounded scopes, either pre or post quantifier expansion. We propose characteristics for classifying problems, which we hypothesize affect the performance. We provide a set of test cases with different characteristics, and by testing our translation on our tests, we create a statistical model to correlate characteristics to the performance of different translation options. We propose hypotheses regarding SMT solvers and modelling guidelines, and test them based on our empirical results. Our results across all these dimensions provide directions for portfolio solvers, modelling improvements, and optimizing SMT solvers. At the end, we present a set of questions that suggest future work. These questions are based on results we could not justify or find a reason for. The subjects of these questions are SMT solvers and modelling optimizations

Analysis of the thinning phenomenon variations in sheet metal forming process

In many manufacturing areas such as the automotive industry (outer panels, inner panels, stiffeners etc...), the packaging industry (petfood containers, beverage cans etc...) and the household appliances industry (housings etc...), the control of the thinning variations in sheet metal forming process is a major point to study in order to ameliorate the final quality of the produced parts. In this framework, several bulge tests have been developed in order to study the thinning phenomenon during sheet metal forming processes. In this presentation, measurement of the thickness of the deformed specimens has been done using the ImageAnalyser software (based on an image analysis technique) developed by the CMAO research group in the LGP. The AISI 304L stainless steel has been selected as the tested material. Both a cylindrical and an elliptical die allowing the analysis of the thickness variation versus the load ratio and the anisotropy of sheet have been used in this work. In a second part of this communication, we present a numerical model based on the Hill 1948 anisotropic material model. The numerical results are discussed and compared with the experiments

Curvature and topology dependency of the cosmological spectra

In this article we investigate dependency of the adiabatic and entropy spectral indices of the cosmological perturbations on the geometry and topology of the background universe. Our discussion includes the post-inflationary universe i.e. radiation-dust mixture era. For this purpose, we first extract an explicit equation describing evolution of the comoving curvature perturbation in the FLRW universe with arbitrary spatial sectional curvature. We may percept when $K\neq 0$, curvature scale would be as significant as the perturbations scales to recognize the behavior of the spectral indices. We also focus on the entropy perturbation in order to extract behavior of the isocurvature spectral index in terms of the curvature index and time. Our analysis shows that spectra of curvature and entropy perturbations in sub-horizon scales could be function of topology. Moreover, an accurate analysis makes clear that time-average of isocurvature index in case $K=0$ is about zero,so that imprint of entropy perturbation in time duration may be negligible. We also consider evolution of the cosmological indices for super-curvature modes in the case $K=-1$. In the most results dependency to curvature, initial conditions and scale modes are thoroughly vivid.Comment: 9 pages,12 figure

The effect of endurance training and taxol consumption on cyclooxygenase-2 and prostaglandin E2 levels in the liver tissue of mice with cervical cancer

Background: Herbs have a strong anti-cancer effect. Also, exercise is one of several lifestyle factors known to lower the risk of developing cancer. The aim of this study was to investigate the effect of endurance training and taxol on cyclooxygenase-2 and prostaglandin E2 in the liver tissue of mice with cervical cancer. Materials and Methods: In this experimental study, 35 female C57 mice were randomly divided into 5 groups (n=7 in each group): control (healthy), control (cancer), complement (cancer), training-supplementary (cancer) and training (cancer). The implantation of cancerous tumors was performed under the skin of the upper pelvis. The training group completed the endurance training protocol, which included 3 sessions per week, 50 minutes per session, at a speed of 14-18 m/s for six weeks. A dose of 60 mg/kg/day of pure taxol was injected intra peritoneally. The dependent variables of this study were measured 24 hours after the last training session by ELISA. Results: The results showed that the use of taxol and endurance training reduced the levels of cyclooxygenase-2 and prostaglandin E2 in the liver tissues of C57 mice with cervical cancer. Conclusion: Induction of the cancerous tissue in mice with cervical cancer increases the levels of cyclooxygenase-2 and prostaglandin E2 and endurance training along with taxol may reduce these levels