A simulation study of a parametric mixture model of three different distributions to analyze heterogeneous survival data

In this paper a simulation study of a parametric mixture model of three different distributions is considered to model heterogeneous survival data.Some properties of the proposed parametric mixture of Exponential, Gamma and Weibull are investigated.The Expectation Maximization Algorithm (EM) is implemented to estimate the maximum likelihood estimators of three different postulated parametric mixture model parameters.The simulations are performed by simulating data sampled from a population of three component parametric mixture of three different distributions, and the simulations are repeated 10, 30, 50, 100 and 500 times to investigate the consistency and stability of the EM scheme.The EM Algorithm scheme developed is able to estimate the parameters of the mixture which are very close to the parameters of the postulated model.The repetitions of the simulation give parameters closer and closer to the postulated models, as the number of repetitions increases, with relatively small standard errors

Three-dimensional Transient Heat Transfer Characterization of Crossflow Minichannel Heat Exchanger Apparatus

Heat exchangers are the key components in automotive, residential and industrial applications. These are employed in vehicle thermal management systems, thermal regulation process as well as heating, ventilation, air conditioning and refrigeration systems. It is important to assess their performance and behavior in transient situation, especially when a sudden change in their operating conditions takes place. This research advances steady state and transient heat transfer in minichannel heat exchanger (MICHX) with the aim of improving heat transfer and exploring transient response. This study uses three-dimensional (3D) computational models to resolve flow and heat transfer in air-to-liquid crossflow MICHX. A finite volume method based ANSYS FLUENT computational fluid dynamics (CFD) code is used to perform the numerical simulations. Models are verified and validated with both the steady state and the transient experimental data and results available in scientific literatures to represent the real world applications. Very good agreements in numerical predictions have been achieved for all models. The current research consists of five stages. In Stage I, the fundamental laminar heat transfer and flow features are focused and modeled in MICHX and conventional flat tube heat exchanger (FTHX) as a benchmark. For a given Reynolds number within the laminar flow regime, MICHX displays significant enhancement of heat transfer coefficient than that of FTHX. In Stage II, computations of 3D flow and heat transfer are carried out in a 5-pass 3-loop air-to-liquid crossflow MICHX, which is equivalent in size of an automotive radiator. The distributions of fluid flow, liquid-side temperature drop, and heat transfer rate are predicted fairly uniform in each loop of the MICHX. The numerical prediction suggests that a single-loop can be applied to represent the multi-loop for further investigations on similar crossflow MICHX. In Stage III, Aluminum oxide (Al_2 O_3) nanoparticles are incorporated with base fluids to improve heat transfer. Significantly improved thermal performance is predicted for inclusion of the Al_2 O_3 nanoparticles. In Stage IV, two distinct heat exchanger modules, sequential and simultaneous, are modeled to improve their thermal performance. For an identical module size, such as similar frontal area and volume, the simultaneous module provides superior thermal performance compared to the conventional sequential module as a benchmark. Finally, in Stage V, transient behaviour of crossflow MICHX for perturbations in hot fluid inlet temperature and mass flow rate are investigated. Faster response time has been observed for higher step variations. After considering the step variations and detailed regression analyses with important variables and parameters, new correlations for transient temperature and Nusselt number have been developed in the current study. The simultaneous module of MICHX can significantly reduce the energy requirements in automotive applications. The correlations for transient heat transfer can be useful tools for the engineers to design control devices in transient situations

Animation for Visualization of Some Algebraic Concepts

Presenting the sciences and teaching the courses in an interactive way is one of the most attractive aspects of the web and educational technology. Many mathematical softwares demonstrate how these technologies make advance topics more accessible and complex mathematical concepts more understandable. The common problems in mathematics teaching process; is the difficulties, undergraduate students encounter in understanding math concepts, theories and problem solving. These problems can be overcome through using creativity in developing math teaching tools and styles. The objective of this project is to use macromedia Flash to make many confusing and complex math concepts simple, visualized and interesting and also to develop a part of a package of animated and visualized mathematical courses. Flash ability and flexibility are the features of this tool which help the designer to develop demonstrating of algebra concepts in a virtual environment. This research will use Macromedia Flash for developing a visualized package of algebra course (Introduction to Algebra (MTK 3001)

Reservoir Simulation to Diagnose the Causes of Reduced Well Production Efficiency in Coal Bed Methane

This paper gives a detailed description of Coalbed Methane reservoirs and also few case studies have been presented. This report is divided into five different parts, starting with the introduction of the Coalbed Methane reservoir and highlighting the physical aspects of the reservoir.  After reviewing five SPE journal papers, a detailed summary of these papers has been presented in this report.A generalized material balanced equation that accounts for and incorporates the Langmuir isotherm, initial free gas, water expansion and formation compaction. This particular form of material balancing can be used to estimate the original gas in place and unlike other methods does not require an iterative process to solve the equations. Also this report documents the practical application of the proposed material balanced equation. This paper also shares case histories and best practices developed from designing and placing the cement successfully in Coalbed methane wells in India. These case histories include cement design considerations and special cement placement techniques.  Reservoir models that incorporate the unique flow and storage characteristics of CBM reservoirs have been developed to study the production and decline characteristics of the reservoir.Further production facilities described include artificial lift, wellhead separation, gathering systems, compression, gas treating and water disposal. Finally we conclude the report by use of reservoir simulation to diagnose the causes of reduced well production efficiency. Keywords: MBE, CBM, Porosity, Coal, Design system

Strategies for Reducing Energy Consumption in a Student Cafeteria in a Hot-Humid Climate: A Case Study

Increasing attention is being given to energy consumption and potential for energy savings in public buildings in order to improve energy performance. Due to their size and functional requirements, public buildings especially cafeteria facilities tend to consume a significant amount of energy. Furthermore, due to their operational characteristics and construction pattern, unnecessary energy is likely to be used for maintaining acceptable indoor environmental quality. In this study, a student cafeteria at King Fahd University of Petroleum and Minerals, Saudi Arabia, was selected for the assessment of its energy performance and potential energy conservation opportunities. Energy simulation software Visual DOE 4.1 was used to develop an energy performance model for assessing various energy conservation measures pertinent to the building envelope and HVAC system design. Data required for setting up the model were gathered through simple energy audits. The architectural and mechanical drawings and the history of electrical consumption were collected. Various energy conservation strategies were then implemented including standards, single and combined energy conservation measures. These measures resulted in a combined design saving of 27.4%, the HVAC system saving 10.6%, implementation of standards saving about 16.7%, lighting 6.6%, equipment 2.6%, insulation 2.5% and glazing 1.4%. Based on these results, it is apparent that there is a significant potential for improving energy performance and justification to employ the suggested measures for achieving substantial energy savings and minimize energy consumption

OPTIMIZATION OF n-HEXANE REFORMING AND KINETICS OF CATALYST REGENERATION

Catalytic naphtha reforming is practiced extensively in the petroleum-refining industry to convert low research octane number (straight chain paraffin) naphtha feed into high RON component (aromatics and branch isomers) with minimum average molecular weight changes needed for the modern auto-industry. A valuable byproduct, hydrogen, from the process is added bonus needed for hydro processing operations in the refinery. Depending on the operating conditions, hydrogen may be consumed in unwanted hydrocracking reactions which directly contribute to deactivate the catalyst. The present study looks into the optimization of process variable (pressure, temperature and contact time) to maximize isomerization and aromatization (increasing RON value) reaction while minimizing the hydrocracking (catalyst deactivation and reducing RON) reactions in n-hexane reforming using commercially available Pt/Al2O3 catalyst. From the results it is found that high temperature (723 K) with low hydrogen partial pressure (300 KPa) and low contact time (1.78 to 2.4 minutes) favor the production of isomers and aromatics over coke precursors and cracked product species. Addition of CCl4 to the n-hexane reforming process which increases the catalyst acidity, promotes the formation of cracked products. Selective poisoning using dimethyl-disulfide on the other hand is found to decrease monofunctional metal-catalyzed reactions and increased the activity for the isomerization reactions.. To understand and enhance n-hexane reforming the kinetics and catalyst regeneration are also investigated using TGA and TPO analysis. From TPO analysis it was found that applying slow heating rate was the most efficient and convenient way to control the regeneration process. The TGA results indicate that there exist three types of coke categorize as soft, hard and laid coke which can be distinguished by a temperature profile. It was found that the hard coke followed by soft coke makes up the major constituent of the coked catalyst which can be removed successfully by proper regeneration process