A Deficiency Problem of the Least Squares Finite Element Method for Solving Radiative Transfer in Strongly Inhomogeneous Media

The accuracy and stability of the least squares finite element method (LSFEM) and the Galerkin finite element method (GFEM) for solving radiative transfer in homogeneous and inhomogeneous media are studied theoretically via a frequency domain technique. The theoretical result confirms the traditional understanding of the superior stability of the LSFEM as compared to the GFEM. However, it is demonstrated numerically and proved theoretically that the LSFEM will suffer a deficiency problem for solving radiative transfer in media with strong inhomogeneity. This deficiency problem of the LSFEM will cause a severe accuracy degradation, which compromises too much of the performance of the LSFEM and makes it not a good choice to solve radiative transfer in strongly inhomogeneous media. It is also theoretically proved that the LSFEM is equivalent to a second order form of radiative transfer equation discretized by the central difference scheme

FINAL SIMULATION RESULTS FOR DEMONSTRATION CASE 1 AND 2

The goal of this DOE Vision-21 project work scope was to develop an integrated suite of software tools that could be used to simulate and visualize advanced plant concepts. Existing process simulation software did not meet the DOE's objective of ''virtual simulation'' which was needed to evaluate complex cycles. The overall intent of the DOE was to improve predictive tools for cycle analysis, and to improve the component models that are used in turn to simulate equipment in the cycle. Advanced component models are available; however, a generic coupling capability that would link the advanced component models to the cycle simulation software remained to be developed. In the current project, the coupling of the cycle analysis and cycle component simulation software was based on an existing suite of programs. The challenge was to develop a general-purpose software and communications link between the cycle analysis software Aspen Plus{reg_sign} (marketed by Aspen Technology, Inc.), and specialized component modeling packages, as exemplified by industrial proprietary codes (utilized by ALSTOM Power Inc.) and the FLUENT{reg_sign} computational fluid dynamics (CFD) code (provided by Fluent Inc). A software interface and controller, based on an open CAPE-OPEN standard, has been developed and extensively tested. Various test runs and demonstration cases have been utilized to confirm the viability and reliability of the software. ALSTOM Power was tasked with the responsibility to select and run two demonstration cases to test the software--(1) a conventional steam cycle (designated as Demonstration Case 1), and (2) a combined cycle test case (designated as Demonstration Case 2). Demonstration Case 1 is a 30 MWe coal-fired power plant for municipal electricity generation, while Demonstration Case 2 is a 270 MWe, natural gas-fired, combined cycle power plant. Sufficient data was available from the operation of both power plants to complete the cycle configurations. Three runs were completed for each Demonstration Case--(1) an initial baseline run using the existing component libraries in Aspen Plus{reg_sign}, (2) a second run where one of the library components was replaced with an ALSTOM Power proprietary code, and (3) a third run where a cycle component was replaced with a FLUENT{reg_sign} CFD simulation. Each of the three runs was successfully completed over a range of loads. This report documents the case runs and discusses the viability and capabilities of the linkage/interface software

Compression Ratio Influence on Maximum Load of a Natural Gas Fueled HCCI Engine

This paper discusses the compression ratio influence on maximum load of a Natural Gas HCCI engine. A modified Volvo TD100 truck engine is controlled in a closed-loop fashion by enriching the Natural Gas mixture with Hydrogen. The first section of the paper illustrates and discusses the potential of using hydrogen enrichment of natural gas to control combustion timing. Cylinder pressure is used as the feedback and the 50 percent burn angle is the controlled parameter. Full-cycle simulation is compared to some of the experimental data and then used to enhance some of the experimental observations dealing with ignition timing, thermal boundary conditions, emissions and how they affect engine stability and performance. High load issues common to HCCI are discussed in light of the inherent performance and emissions tradeoff and the disappearance of feasible operating space at high engine loads. The problems of tighter limits for combustion timing, unstable operational points and physical constraints at high loads are discussed and illustrated by experimental results. Finally, the influence on operational limits, i.e., emissions peak pressure rise and peak cylinder pressure, from compression ratio at high load are discussed

Modeling and Validation of a Split Cycle Clean Combustion Diesel Engine Concept

This paper is a part of the research happening at the University of Illinois at Chicago together with Caterpillar Inc. for the development and validation of a split cycle clean combustion engine (SCCCE) operating on diesel fuel. A two-cylinder variant of the SCCCE is modeled using Caterpillar's one-dimensional modeling software DYNASTY, following the geometric and boundary specifications given by the University of Pisa in their paper by Musu et al. (2010, "Clean Diesel Combustion by Means of the HCPC Concept," SAE Paper No. 2010-01-1256). The results are compared to validate our modeling methodology. The split cycle clean combustion (SCCC) concept may significantly reduce gaseous and particulate emissions while maintaining high engine efficiency compared to the current state of the art diesel engine. Some manufacturers have been prototyping gasoline engines based on the SCCC concept, but there are no diesel fuel powered SCCC engine prototypes existing in the market. This study will be a significant contribution in the performance evaluation of SCCC diesel engines at high load and part load conditions. A one-dimensional modeling technique was chosen for this study due to the need of a fast running model that could be improved using design of experiments (DOE) analysis. Computational fluid dynamics (CFD) modeling produces more accurate results but limits one's ability to model a large number of configurations due to its large computational overhead that slows down the overall simulation process, thus making CFD models not feasible for this DOE. In order to accurately model an SCCC engine, we first 2010-01-1256). A satisfactory comparison of results confirmed our modeling approach and enabled us to integrate more complex models that will be discussed in future publications

LSMR: An iterative algorithm for sparse least-squares problems

An iterative method LSMR is presented for solving linear systems $Ax=b$ and least-squares problem \min \norm{Ax-b}_2, with $A$ being sparse or a fast linear operator. LSMR is based on the Golub-Kahan bidiagonalization process. It is analytically equivalent to the MINRES method applied to the normal equation A\T Ax = A\T b, so that the quantities \norm{A\T r_k} are monotonically decreasing (where $r_k = b - Ax_k$ is the residual for the current iterate $x_k$). In practice we observe that \norm{r_k} also decreases monotonically. Compared to LSQR, for which only \norm{r_k} is monotonic, it is safer to terminate LSMR early. Improvements for the new iterative method in the presence of extra available memory are also explored.Comment: 21 page

An adaptive projection method for the modeling of unsteady, low-Mach number combustion

In this paper the authors present an adaptive projection method for modeling unsteady, low-Mach reacting flow in an unconfined region. The equations they solve are based on a model for low-Mach number combustion that consists of the evolution equations for density, species concentrations, enthalpy, and momentum coupled with a constraint on the divergence of the flow. The algorithm is based on a projection methodology in which they first advance the evolution equations and then solve an elliptic equation to enforce the divergence constraint. The adaptive mesh refinement (AMR) scheme uses a time-varying, hierarchical grid structure composed of uniform rectangular grids of varying resolution. The integration scheme on the grid hierarchy is a recursive procedure in which a coarse grid is advanced, fine grids are advanced multiple steps to reach the same time as the coarse grid, and the coarse and the fine grids are synchronized. The method is valid for multiple grids on each level and multiple levels of refinement. The method is currently implemented for laminar, axisymmetric flames with a reduced kinetics mechanism and a Lewis number of unity. Two methane-air flames, one steady and the other flickering, are presented as numerical examples

Software Framework for Advanced Power Plant Simulations

This report summarizes the work accomplished during the Phase II development effort of the Advanced Process Engineering Co-Simulator (APECS). The objective of the project is to develop the tools to efficiently combine high-fidelity computational fluid dynamics (CFD) models with process modeling software. During the course of the project, a robust integration controller was developed that can be used in any CAPE-OPEN compliant process modeling environment. The controller mediates the exchange of information between the process modeling software and the CFD software. Several approaches to reducing the time disparity between CFD simulations and process modeling have been investigated and implemented. These include enabling the CFD models to be run on a remote cluster and enabling multiple CFD models to be run simultaneously. Furthermore, computationally fast reduced-order models (ROMs) have been developed that can be 'trained' using the results from CFD simulations and then used directly within flowsheets. Unit operation models (both CFD and ROMs) can be uploaded to a model database and shared between multiple users

Toksikokinetika prometrina u mozgu miševa

Prometryne is a methylthio-s-triazine herbicide. Signifi cant trace amounts are found in the environment, mainly in water, soil, and food plants. The aim of this study was to establish brain and blood prometryne levels after single oral dose (1 g kg-1) in adult male and female mice. Prometryne was measured using the GC/MS assay at 1, 2, 4, 8, and 24 h after prometryne administration. Peak brain and blood prometryne values were observed 1 h after administration and they decreased in a time-dependent manner. Male mice had consistently higher brain and blood prometryne levels than female mice. The observed prometryne kinetics was similar to that reported for the structurally related herbicide atrazine.Prometrin je metiltio-s-triazinski herbicid. Značajne količine prometrina zaostaju u tragovima u okolišu, poglavito u vodi, tlu i biljkama koje rabimo za prehranu. Cilj je rada izmjeriti količinu prometrina koja se apsorbira u mozgu i krvi nakon primijenjene akutne oralne doze (1 g kg-1 tjelesne mase) u odraslih miševa obaju spolova. Razine prometrina u mozgu i krvi izmjerene su GC/MS-om tijekom 1., 2., 4., 8. i 24. sata nakon izlaganja. Utvrđeno je da je udio prometrina koji se zadržava u živčanom tkivu relativno nizak ali detektabilan u odnosu na koncentraciju u krvi i koncentraciju primijenjene doze. Najviše koncentracije u krvi i maseni udjeli u mozgu zabilježeni su tijekom 1. sata nakon izlaganja, a s vremenom izmjerene vrijednosti značajno opadaju. Uočena je značajna razlika između mužjaka i ženki pri čemu mužjaci imaju značajno više razine prometrina u mozgu i krvi nego ženke. Opisana toksikokinetika prometrina pokazuje sličnosti s otprije opisanom i poznatom toksikokinetikom strukturalno sličnog herbicida atrazina

Hvordan bruke musikkterapi i kommunikasjon med personer med demens på sykehjem

Bakgrunn: Jeg har selv erfaring og positive opplevelser fra min praksis innen temaet musikkterapi brukt overfor personer med demens. Dette erfaringsgrunnlaget var utgangspunktet for å utvide og utforske mer om dette temaet gjennom artikler og forsøk utført av kompetente personer på dette området. Hensikt: Hensikten med oppgaven er å belyse problemstillingen, hvordan bruke musikkterapi i kommunikasjon med personer med demens på sykehjem. Jeg vil undersøke hvordan sykepleier kan bruke musikk i kommunikasjon med personer med demens for å skape en god relasjon. Hvordan musikk i form av musikkterapi og individualisert musikk kan brukes for å skape en bedre hverdag for personer med utfordrende atferd med demens. Metode: Jeg har benyttet meg av litteraturstudie som metode. Funn: I de fem forskningsartiklene som jeg brukte som grunnlag for min oppgave var det et entydig resultat, det skal egentlig lite til ved hjelp av musikk og musikkterapi å skape bedre relasjoner mellom sykepleier og personer med demens. I tillegg viste musikken uansett i hvilken form den ble gitt å ha en dempende effekt på angst, uro, forvirring og aggresjon, såkalt utfordrende atferd. Konklusjon: Bakgrunnsmusikk og individualisert musikk er en enkel, effektiv og billig metode som er lett å sette ut i livet for sykepleierne og som har vist seg å ha en positiv effekt hva angår relasjon og samhandling mellom pasient og sykepleier, samt dempning av angst, uro og utfordrende atferd. En kartlegging av musikkpreferanser hva angår pasienten synes å være nødvendig for å få et best mulig resultat

Effect of Nano silica and Salts on Xanthan gum polymer-Bentonite solution

Master's thesis in Petroleum engineeringThe application of nanotechnology shows positive results in the oil and gas industry, with respect to cement, drilling fluid and enhanced oil recovery. In this thesis, an optimized nano-fluid in Xanthan gum (XC) polymer treated bentonite mud system was investigated. The composition of the bestformulated nano-system is: 500g H2O+ 25g Bentonite+ 0.5g XC+ 2.5g KCl+ 0.1g Nano silica. The best-formulated mud system was further analysed for its viscoelastic behaviour. Simulation of its hydraulic and hole cleaning performance were also conducted. The overall result shows that the addition of 0.02 wt.% nano-silica: • Reduces filtrate by 16.67 %. • Improves cutting transport efficiency. • Increases the yield stress and apparent viscosity. Details of the main findings can be found in the conclusion part