Timelike and Spacelike Matter Inheritance Vectors in Specific Forms of Energy-Momentum Tensor

This paper is devoted to the investigation of the consequences of timelike and spacelike matter inheritance vectors in specific forms of energy-momentum tensor, i.e., for string cosmology (string cloud and string fluid) and perfect fluid. Necessary and sufficient conditions are developed for a spacetime with string cosmology and perfect fluid to admit a timelike matter inheritance vector, parallel to $u^a$ and spacelike matter inheritance vector, parallel to $x^a$. We compare the outcome with the conditions of conformal Killing vectors. This comparison provides us the conditions for the existence of matter inheritance vector when it is also a conformal Killing vector. Finally, we discuss these results for the existence of matter inheritance vector in the special cases of the above mentioned spacetimes.Comment: 27 pages, accepted for publication in Int. J. of Mod. Phys.

Comparison of CFD and DSMC Using Calibrated Transport Parameters

Hypersonic re-entry flows span a wide range of length scales where regions of both rarefied and continuum flow exist. Traditional computational fluid dynamics (CFD) techniques do not provide an accurate solution for the rarefied regions of such mixed flow fields. Although direct simulation Monte Carlo (DSMC) can be used to accurately capture both the continuum and rarefied features of mixed flow fields, they are computationally expensive when employed to simulate the low Knudsen number continuum regimes. Thus, a hybrid framework for seamlessly combining the two methodologies, CFD and DSMC, continues to be a topic of significant research effort. Ensuring consistency in the reaction kinetics and transport models employed within CFD and DSMC is a crucial requirement for obtaining a reliable solution from a hybrid framework for combined continuum/rarefied high speed flows. This paper represents one of the first studies to utilize the calibrated transport parameters developed to ensure consistency between CFD and DSMC solvers. The new variable soft sphere (VSS) parameters are compared to both previous standard variable hard sphere (VHS) parameters and also to solutions from the CFD transport properties that the new parameters were developed to reproduce

Hubungan Antara Keadilan Organisasi dan Keterikatan Karyawan dengan Kepuasan Kerja pada Karyawan PT Mekar Armada Jaya Magelang

HUBUNGAN ANTARA KEADILAN ORGNISASI DAN KETERIKATAN KARYAWAN DENGAN KEPUASAN KERJA PADA KARYAWAN PT MEKAR ARMADA JAYA MAGELANG Maria Stephani Dwitya Program Studi Psikologi Fakultas Kedokteran Universitas Sebelas Maret ABSTRAK Masyarakat usia dewasa di dunia menghabiskan sebagian besar waktu terjaganya di tempat kerja, oleh karenanya studi mengenai kepuasan kerja memiliki peran penting baik dalam peningkatan kualitas hidup individu maupun efektivitas organisasi. Kepuasan kerja merupakan sikap dan perasaan positif individu terhadap pekerjaannya sebagai hasil penilaian terhadap pekerjaan tersebut. Penilaian karyawan terhadap pekerjaannya tersebut dapat dipengaruhi berbagai faktor baik internal maupun eksternal, diantaranya keadilan organisasi dan keterikatan karyawan. Keadilan organisasi merupakan keseluruhan persepsi karyawan apakah mereka diperlakukan secara adil atau tidak dalam sebuah organisasi. Keterikatan karyawan merupakan kondisi hubungan positif karyawan dengan pekerjaannya meliputi dimensi fisik, kognitif, dan emosional dalam memenuhi peran dan tugas kerjanya. Penelitian ini bertujuan untuk mengetahui hubungan antara keadilan organisasi dan keterikatan karyawan dengan kepuasan kerja, hubungan antara keadilan organisasi dengan kepuasan kerja, dan hubungan antara keterikatan karyawan dengan kepuasan kerja pada karyawan PT Mekar Armada Jaya Magelang. Populasi dalam penelitian ini adalah karyawan tetap PT Mekar Armada Jaya Magelang sejumlah 754 karyawan. Sampling yang digunakan adalah Cluster Random Sampling dan diperoleh lima unit kerja sebagai sampel dengan total sampel 160 karyawan. Instrumen yang digunakan adalah skala kepuasan kerja, skala keadilan organisasi, dan skala keterikatan karyawan. Hasil penelitian menunjukkan terdapat hubungan yang positif dan signifikan antara keadilan organisasi dan keterikatan karyawan dengan kepuasan kerja karyawan PT Mekar Armada Jaya Magelang , ditunjukkan dengan Fhitung = 45,176 (>Ftabel 3,00), p=0,000 (p<0,05), dan koefisien korelasi R=0,604. Secara parsial, terdapat hubungan yang positif dan signifikan antara keadilan organisasi dengan kepuasan kerja dengan nilai korelasi 0,389 dan p=0,000 (p<0,05). Terdapat hubungan yang positif dan signifikan antara keterikatan karyawan dengan kepuasan kerja dengan nilai korelasi 0,167 dan p=0,001 (p<0,05). Nilai R2 yang diperoleh sebesar 0,365 berarti sumbangan pengaruh variabel keadilan organisasi dan keterikatan karyawan pada kepuasan kerja adalah sebesar 36,5%. Besarnya sumbangan efektif keadilan organisasi terhadap kepuasan kerja sebesar 23,98% dan sumbangan efektif keterikatan karyawan terhadap kepuasan kerja sebesar 12,52%. Kata kunci: keadilan organisasi, keterikatan karyawan, kepuasan kerja

Revisiting Cosmic No-Hair Theorem for Inflationary Settings

In this work we revisit Wald's cosmic no-hair theorem in the context of accelerating Bianchi cosmologies for a generic cosmic fluid with non-vanishing anisotropic stress tensor and when the fluid energy momentum tensor is of the form of a cosmological constant term plus a piece which does not respect strong or dominant energy conditions. Such a fluid is the one appearing in inflationary models. We show that for such a system anisotropy may grow, in contrast to the cosmic no-hair conjecture. In particular, for a generic inflationary model we show that there is an upper bound on the growth of anisotropy. For slow-roll inflationary models our analysis can be refined further and the upper bound is found to be of the order of slow-roll parameters. We examine our general discussions and our extension of Wald's theorem for three classes of slow-roll inflationary models, generic multi-scalar field driven models, anisotropic models involving U(1) gauge fields and the gauge-flation scenario.Comment: 21 pp, 4 .eps figure

Isotropy, shear, symmetry and exact solutions for relativistic fluid spheres

The symmetry method is used to derive solutions of Einstein's equations for fluid spheres using an isotropic metric and a velocity four vector that is non-comoving. Initially the Lie, classical approach is used to review and provide a connecting framework for many comoving and so shear free solutions. This provides the basis for the derivation of the classical point symmetries for the more general and mathematicaly less tractable description of Einstein's equations in the non-comoving frame. Although the range of symmetries is restrictive, existing and new symmetry solutions with non-zero shear are derived. The range is then extended using the non-classical direct symmetry approach of Clarkson and Kruskal and so additional new solutions with non-zero shear are also presented. The kinematics and pressure, energy density, mass function of these solutions are determined.Comment: To appear in Classical and Quantum Gravit

Natural extension of the Generalised Uncertainty Principle

We discuss a gedanken experiment for the simultaneous measurement of the position and momentum of a particle in de Sitter spacetime. We propose an extension of the so-called generalized uncertainty principle (GUP) which implies the existence of a minimum observable momentum. The new GUP is directly connected to the nonzero cosmological constant, which becomes a necessary ingredient for a more complete picture of the quantum spacetime.Comment: 4 pages, 1 figure, v2 with added references, revised and extended as published in CQ

Locus of control and low-wage mobility

We investigate whether non-cognitive skills - in particular Locus of Control - are important determinants of the labour market processes at the low-wage margin. Based on data from the German Socio-Economic Panel, we estimate dynamic multinomial logit models with random effects and investigate whether Locus of Control influences the probability of being higher-paid or low-paid as well as the probability of escaping low wages by moving up to higher-paid employment. Our results reveal a significant amount of state dependence in low pay even after controlling for Locus of Control and other non-cognitive skills. Furthermore, compared to individuals with an external Locus of Control, individuals with a more internal Locus of Control have a significantly higher probability of being higher-paid instead of low-paid. Conditional on being low-paid, individuals with an internal Locus of Control additionally have a significantly higher probability of moving to higher-paid employment in the following year than individuals with an external Locus of Control

New first integral for twisting type-N vacuum gravitational fields with two non-commuting Killing vectors

A new first integral for the equations corresponding to twisting type-N vacuum gravitational fields with two non-commuting Killing vectors is introduced. A new reduction of the problem to a complex second-order ordinary differential equation is given. Alternatively, the mentioned first integral can be used in order to provide a first integral of the second-order complex equation introduced in a previous treatment of the problem.Comment: 7 pages, LaTeX, uses ioplppt.sty and iopl12.sty; to be published in Class. Quantum Gra

Detailed modeling and analysis of spacecraft plume/ionosphere interactions in low Earth orbit

Detailed direct simulation Monte Carlo/particle‐in‐cell simulations involving the interaction of spacecraft thruster plumes with the rarefied ambient ionosphere are presented for steady thruster firings in low Earth orbit (LEO). A nominal mass flow rate is used to prescribe the rocket exit conditions of a neutral propellant species for use in the simulations. The charge exchange interactions of the steady plume with the rarefied ionosphere are modeled using a direct simulation Monte Carlo/particle‐in‐cell methodology, allowing for a detailed assessment of nonequilibrium collisional and plasma‐related phenomena relevant for these conditions. Results are presented for both ram‐ and wake‐flow configurations, in which the thrusters are firing into (ram) or in the direction of (wake) the free stream ionosphere flow in LEO. The influence of the Earth's magnetic field on the development of the ion plume is also examined for three different field strengths: two limiting cases in which B →0 and B → ∞ , and the LEO case in which B =0.5 Gs. The magnetic field is found to have a substantial impact on the resulting neutral and ion plumes, and the gyroscopic motion of the magnetized ions results in a broadening of the ion energy distribution functions. The magnetic field model also incorporates a cross‐field diffusion mechanism which is shown to increase the current density sampled far from the thruster. Key Points Particle‐based model for plume/ionosphere interactions Charge‐exchange reactions modeled using detailed DCS/TCS data B ‐field has a strong influence on the development of plumesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106930/1/jgra50833.pd

Inhomogenized sudden future singularities

We find that sudden future singularities may also appear in spatially inhomogeneous Stephani models of the universe. They are temporal pressure singularities and may appear independently of the spatial finite density singularities already known to exist in these models. It is shown that the main advantage of the homogeneous sudden future singularities which is the fulfillment of the strong and weak energy conditions may not be the case for inhomogeneous models.Comment: REVTEX 4, 5 pages, no figures, a discussion of the most general case include