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Monthly Notices of the Royal Astronomical Society, 2011

We present a modification of the standard halo model with the goal of providing an improved description of galaxy clustering. Recent surveys, like the Sloan Digital Sky Survey (SDSS) and the Anglo-Australian Two-degree survey (2dF), have shown that there seems to be a correlation between the clustering of galaxies and their properties such as metallicity and star formation rate, which are believed to be environment-dependent. This environmental dependence is not included in the standard halo model where the host halo mass is the only variable specifying galaxy properties. In our approach, the halo properties i.e., the concentration, and the Halo Occupation Distribution -HODprescription, will not only depend on the halo mass (like in the standard halo model) but also on the halo environment. We examine how different environmental dependence of halo concentration and HOD prescription affect the correlation function. We see that at the level of dark matter, the concentration of haloes affects moderately the dark matter correlation function only at small scales. However the galaxy correlation function is extremely sensitive to the HOD details, even when only the HOD of a small fraction of haloes is modified.

The Astrophysical …, 2009

Monthly Notices of the Royal Astronomical Society, 2010

Comparing clustering of differently biased tracers of the dark matter distribution offers the opportunity to reduce the sample or cosmic variance error in the measurement of certain cosmological parameters. We develop a formalism that includes bias nonlinearities and stochasticity. Our formalism is general enough that can be used to optimise survey design and tracers selection and optimally split (or combine) tracers to minimise the error on the cosmologically interesting quantities. Our approach generalises the one presented by of circumventing sample variance in the measurement of f ≡ d ln D/d ln a. We analyse how the bias, the noise, the non-linearity and stochasticity affect the measurements of Df and explore in which signal-to-noise regime it is significantly advantageous to split a galaxy sample in two differently-biased tracers. We use N-body simulations to find realistic values for the parameters describing the bias properties of dark matter haloes of different masses and their number density. We find that, even if dark matter haloes could be used as tracers and selected in an idealised way, for realistic haloes, the sample variance limit can be reduced only by up to a factor σ 2tr /σ 1tr 0.6. This would still correspond to the gain from a three times larger survey volume if the two tracers were not to be split. Before any practical application one should bear in mind that these findings apply to dark matter haloes as tracers, while realistic surveys would select galaxies: the galaxy-host halo relation is likely to introduce extra stochasticity, which may reduce the gain further.

Ingeniería de Mantenimiento

When William Shakespeare first wrote Othello, through having a black character like Othello, he wanted to address the issue of racism and how people's perception of race can cause misjudgment. He skillfully does this by having a character like Iago to show how racism can make one see a person in a completely inaccurate way. Iago's harsh judgments on Othello,

2011

Thesis by S.U.S. Moda 2011 at Wright State University 104 pages german keywords: Wankelmotor / Kreiskolbenmotor English Keywords: Wankel Engine / Wankel Rotary Engine / Rotary Piston Engine / Rotary Combustion Engine Deals with a Rotary Engine by UEL TABLE OF CONTENTS CHAPTER 1: INTRODUCTION 1.1 Direct Injection Engine 1.2 Why Direct Injection Engine 1.3 Fuel injection in direct injection engine 1.4 Computational Fluid dynamics for DISI engine 1.5 Literature review 1.6 Combustion and equivalence ratio 1.7 Motivation for the Thesis 1.8 Research Objectives 1.9 Thesis Outline CHAPTER 2 MODELING AND MESHING 2.1 Reciprocating engine 2.1.1 Modeling and Meshing 2.1.2 Dynamic mesh motion 2.2 Rotary engine 2.2.1 Modeling and Meshing 2.2.2 Dynamic mesh motion CHAPTER 3 NUMERICAL METHODS 3.1 Turbulence Modeling 3.1.1 The spalart- Allamaras model 3.1.2 Standard K-e model 3.1.3 RNG K-e model 3.1.4 Realizable K-e model 3.2 Combustion models 3.3 Fuel Injection parameters 3.4 Solver settings CHAPTER 4 EXPERIMENTAL VALIDATION AND DIESEL FUEL TEST 4.1 Validation 4.1.1 Geometric validation 4.1.2 Validation of boundary conditions and parameters 4.1.3 Validation of output 4.2 Study of Validation case 4.2.1 Air flow in the chamber 4.2.2. Fuel air interaction and vaporization 4.2.3. Fuel geometry interaction 4.2.4. Excess fuel 4.2.5 Combustion 4.3 Diesel fuel in validation case 4.3.1. Air flow in the chamber and Excess fuel 4.3.2. Fuel air interaction and vaporization 4.3.3. Fuel geometry interaction 4.3.4. Combustion CHAPTER 5 PARAMETRIC STUDY OF DIESEL FUEL 5.1 Parametric study on reciprocating engine with diesel fuel 5.1.1. Injection velocity 5.1.2. Injection time 5.1.3. Particle size 5.1.4. Multiple plume injection 5.1.4.1 Injection modeling 5.1.4.2 Parametric study 5.1.5. Conclusions from parametric study 5.2 Results 5.3 DISI diesel fuel Rotary engine 5.3.1 Modeling and Meshing 5.3.2 Cold flow study 5.3.2.1. Turbulence of air in the chamber 5.3.2.2. Maximum temperature and pressure at TDC 5.3.2.3. Injection location and orientation of injection 5.4 Simulations of Rotary engine with diesel fuel DISI technology 5.4.1 DISIR_M 5.4.1.1. Air fuel interaction and fuel vaporization 5.4.1.2. Combustion 5.4.1.3. Power output 5.4.2 Comparison between DISIR_M, DISIR_MP and DISIR_MPL 5.4.2.1. Fuel distribution 5.4.2.2. Combustion 5.4.2.3. Power output CHAPTER 6 CONCLUSIONS CHAPTER 7 RECOMMENDATIONS AND FUTURE WORK REFERENCES

The potential of biodegradable polymers and more particularly that of polymers obtained from renewable resources such as the polysaccharides (e.g., starch) have long been recognized. However, these biodegradable polymers have been largely used in some applications (e.g., food industry) and have not found extensive applications in the packaging industries to replace conventional plastic materials, although they could be an interesting way to overcome the limitation of the petrochemical resources in the future. The fossil fuel and gas could be partially replaced by greener agricultural sources, which should participate in the reduction of CO2 emissions. Bio-based and biodegradable plastics can form the basis for environmentally preferable, sustainable alternative to current materials based exclusively on petroleum feed stocks. These bio-based materials offer value in the sustainability/life-cycle equation by being a part of the biological carbon cycle, especially as it relates to carbon-based polymeric materials such as plastics, water soluble polymers and other carbon based products like lubricants, biodiesel, and detergents. Identification and quantification of bio based content uses radioactive C-14 signature. Biopolymers are generally capable of being utilized by living matter (biodegraded), and so can be disposed in safe and ecologically sound ways through disposal processes (waste management) like composting, soil application, and biological wastewater treatment. Single use, short-life, disposable products can be engineered to be bio-based and biodegradable.