Reactive dissolution of sedimentary rocks in flue gas desulfurization : modeling and experimental investigation

Svavel f��rekommer i kol och olja och oxideras vid f��rbr��nning till svaveldioxid (SO2). ��rligen utsl��pps stora m��ngder svaveldioxid som ��stadkommer sura regn, minskning av stratosf��riskt ozon och sjukdomar. Av dessa orsaker ��r det n��dv��ndigt att minska utsl��ppen av svaveldioxid. Den teknologi som r��r planering av reaktorer och processer f��r r��kgasavsvavling (FGD) har utvecklats kraftigt och idag anv��nder man olika typer av l��sningar. De vanligaste alternativen f��r FGD ��r v��tskrubber- och semitorra skrubbersystem (Spray Dry Scrubbers, SDS) och injektionsprocesser f��r absorbenter. SDS-processer har studerats bland annat av Ahlbeck [4] och Klingspor [5] och injektionsprocesser av Alvfors [6]. Kalksten, som i huvusak best��r av kalciumkarbonat, anv��nds i r��kgasavsvavling p�� grund av sin f��rm��ga att binda svavel i form av sulfatsalter. Den vanligaste r��kgasavsvavlingsmetoden ��r v��tskrubbning, d��r det sediment��ra stenmaterialets uppl��sningshastighet ��r en av de faktorer som p��verkar resultatet mest. Utv��rdering av kalkstensreaktivitet ��r d��rf��r speciellt viktig vid planering och drift av anl��ggningar f��r r��kgasavsvavling. M��ls��ttningen med detta arbete var att modellera uppl��sningen av olika typers kalksten f��r att f�� en kvantitativ utv��rdering av kvaliteten p�� de analyserade proverna. D��rtill testades ��ven karbonatbiprodukter fr��n st��lindustrin f��r att utv��rdera m��jligheter att anv��nda andra r��material. Det transienta f��rloppet har analyserats, varvid uppl��sningshastigheten modellerades bl.a. i avseende p�� tid och pH. Under arbetets g��ng har antalet empiriska korrelationer minskats till f��rdel f��r fysikaliska modeller av diffusiva och konvektiva masstransportfenomen. En m��ls��ttning var att skapa en effektiv och snabb metod f��r att testa olika absorbenter f��r r��kgasavsvavling under transienta f��rlopp. I arbetet anv��ndes PSD-analys, gjordes pH-m��tningar och andra utv��rderingar av de fysikaliska parametrar som ing��r i ber��kningarna. On-line m��tningar f��r de icke-station��ra variablerna tid och pH ger m��jlighet att eliminera os��kerheter. Vissa modeller kan vara komplicerade. En modell f��r uppl��sningshastigheten med mer detaljerad utv��rdering av parametrar och f��rre approximationer ��r d��rf��r n��dv��ndig d�� man vill utv��rdera reaktionshastigheten f��r fasta partiklar i sur milj��. Arbetet utf��rdes under fyra ��r och fem peer review-artiklar ing��r i avhandlingen.

Molecular modeling of asymmetric induction in heterogeneously catalyzed hydrogenation of the C=O bond

Modifiering av metallytor med starkt adsorberade kirala organiska molekyler ��r eventuellt den mest relevanta teknik man vet i dag f��r att skapa kirala ytor. Den kan utnyttjas i katalytisk produktion av enantiomeriskt rena kirala f��reningar som beh��vs t.ex. som l��kemedel och aromkemikalier. Trots m��nga f��rdelar av asymmetrisk heterogen katalys j��mf��rt med andra s��tt f��r att f�� kirala f��reningar, har den ��nd�� inte blivit ett allm��nt verktyg f��r storskaliga till��mpningar. Detta beror t.ex. p�� brist p�� djupare kunskaper i katalytiska reaktionsmekanismer och ursprunget f��r asymmetrisk induktion. I denna studie anv��ndes molekylmodelleringstekniker f��r att studera asymmetriska, heterogena katalytiska system, speciellt hydrering av prokirala karbonylf��reningar till motsvarande kirala alkoholer p�� cinchona-alkaloidmodifierade Pt-katalysatorer. 1-Fenyl-1,2-propandion (PPD) och n��gra andra f��reningar, som inneh��ller en prokiral C=O-grupp, anv��ndes som reaktanter. Konformationer av reaktanter och cinchona-alkaloider (som kallas modifierare) samt v��tebundna 1:1-komplex mellan dem studerades i gas- och l��sningsfas med metoder som baserar sig p�� v��gfunktionsteori och t��thetsfunktionalteori (DFT). F��r ber��kningen av protonaffiniteter anv��ndes ocks�� h��gst noggranna kombinationsmetoder s��som G2(MP2). Den relativa populationen av modifierarnas konformationer varierade som funktion av modifieraren, dess protonering och l��sningsmedlet. Flera reaktant���modifierareinteraktionsgeometrier beaktades. Slutsatserna p�� riktning av stereoselektivitet baserade sig p�� den relativa termodynamiska stabiliteten av de diastereomeriska reaktant���modifierare-komplexen samt energierna hos ��- och ��*-orbitalerna i den reaktiva karbonylgruppen. Adsorption och reaktioner p�� Pt(111)-ytan betraktades med DFT. Regioselektivitet i hydreringen av PPD och 2,3-hexandion kunde f��rklaras med molekyl���yta-interaktioner. Storleken och formen av klustret anv��nt f��r att beskriva Pt-ytan inverkade inte bara p�� adsorptionsenergierna utan ocks�� p�� de relativa stabiliteterna av olika adsorptionsstrukturer av en molekyl. Populationerna av modifierarnas konformationer i gas- och l��sningsfas korrelerade inte med populationerna p�� Pt-ytan eller med enantioselektiviteten i hydreringen av PPD p�� Pt���cinchona-katalysatorer. Vissa modifierares konformationer och reaktant���modifierare-interaktionsgeometrier var stabila bara p�� metallytan. Teoretiskt ber��knade potentialenergiprofiler f��r hydrering av kirala ��-hydroxiketoner p�� Pt implicerade preferens f��r parvis additionsmekanism f��r v��te och selektiviteter i harmoni med experimenten. De uppn��dda resultaten ��kar uppfattningen om kirala heterogena katalytiska system och kunde d��rf��r utnyttjas i utvecklingen av nya, mera aktiva och selektiva kirala katalysatorer.

Applications of graph transformation in tools for domain-specific modeling languages

The use of domain-specific languages (DSLs) has been proposed as an approach to cost-e ectively develop families of software systems in a restricted application domain. Domain-specific languages in combination with the accumulated knowledge and experience of previous implementations, can in turn be used to generate new applications with unique sets of requirements. For this reason, DSLs are considered to be an important approach for software reuse. However, the toolset supporting a particular domain-specific language is also domain-specific and is per definition not reusable. Therefore, creating and maintaining a DSL requires additional resources that could be even larger than the savings associated with using them. As a solution, di erent tool frameworks have been proposed to simplify and reduce the cost of developments of DSLs. Developers of tool support for DSLs need to instantiate, customize or configure the framework for a particular DSL. There are di erent approaches for this. An approach is to use an application programming interface (API) and to extend the basic framework using an imperative programming language. An example of a tools which is based on this approach is Eclipse GEF. Another approach is to configure the framework using declarative languages that are independent of the underlying framework implementation. We believe this second approach can bring important benefits as this brings focus to specifying what should the tool be like instead of writing a program specifying how the tool achieves this functionality. In this thesis we explore this second approach. We use graph transformation as the basic approach to customize a domain-specific modeling (DSM) tool framework. The contributions of this thesis includes a comparison of di erent approaches for defining, representing and interchanging software modeling languages and models and a tool architecture for an open domain-specific modeling framework that e ciently integrates several model transformation components and visual editors. We also present several specific algorithms and tool components for DSM framework. These include an approach for graph query based on region operators and the star operator and an approach for reconciling models and diagrams after executing model transformation programs. We exemplify our approach with two case studies MICAS and EFCO. In these studies we show how our experimental modeling tool framework has been used to define tool environments for domain-specific languages.

Knowledge modeling for innovative companies: case of business incubator

The paper presents a study which is aimed at building a knowledge model for a case company ��� business incubator ���Ingria��� (St. Petersburg, Russia). The business incubator is one of its kind organization in St. Petersburg, and one of the few in Russia, providing services for innovative entrepreneurial companies at an international level. Business incubation impact is deeply researched from the point of view of knowledge engineering. The paper also provides a broad analysis of various knowledge engineering tools used for visualization of knowledge, as well as knowledge modeling techniques.

Charge transport in disordered materials : simulations, theory, and numerical modeling of hopping transport and electron-hole recombination

Min avhandling behandlar hur oordnade material leder elektrisk str��m. Bland materialen som studeras finns ledande polymerer, d.v.s. plaster som leder str��m, och mer allm��nt organiska halvledare. Av de h��r materialen har man kunnat bygga elektroniska komponenter, och man hoppas p�� att kunna trycka hela kretsar av organiska material. F��r de h��r till��mpningarna ��r det viktigt att f��rst�� hur materialen sj��lva leder elektrisk str��m. Termen oordnade material syftar p�� material som saknar kristallstruktur. Oordningen g��r att elektronernas tillst��nd blir lokaliserade i rummet, s�� att en elektron i ett visst tillst��nd ��r begr��nsad t.ex. till en molekyl eller ett segment av en polymer. Det h��r kan j��mf��ras med kristallina material, d��r ett elektrontillst��nd ��r utspritt ��ver hela kristallen (men i st��llet har en v��ldefinierad r��relsem��ngd). Elektronerna (eller h��len) i det oordnade materialet kan r��ra sig genom att tunnelera mellan de lokaliserade tillst��nden. Utg��ende fr��n egenskaperna f��r den h��r tunneleringsprocessen, kan man best��mma transportegenskaperna f��r hela materialet. Det h��r ��r utg��ngspunkten f��r den s�� kallade hopptransportmodellen, som jag har anv��nt mig av. Hopptransportmodellen inneh��ller flera drastiska f��renklingar. Till exempel betraktas elektrontillst��nden som punktformiga, s�� att tunneleringssannolikheten mellan tv�� tillst��nd endast beror p�� avst��ndet mellan dem, och inte p�� deras relativa orientation. En annan f��renkling ��r att behandla det kvantmekaniska tunneleringsproblemet som en klassisk process, en slumpvandring. Trots de h��r grova approximationerna visar hopptransportmodellen ��nd�� m��nga av de fenomen som upptr��der i de verkliga materialen som man vill modellera. Man kan kanske s��ga att hopptransportmodellen ��r den enklaste modell f��r oordnade material som fortfarande ��r intressant att studera. Man har inte hittat exakta analytiska l��sningar f��r hopptransportmodellen, d��rf��r anv��nder man approximationer och numeriska metoder, ofta i form av datorber��kningar. Vi har anv��nt b��de analytiska metoder och numeriska ber��kningar f��r att studera olika aspekter av hopptransportmodellen. En viktig del av artiklarna som min avhandling baserar sig p�� ��r att j��mf��ra analytiska och numeriska resultat. Min andel av arbetet har fr��mst varit att utveckla de numeriska metoderna och applicera dem p�� hopptransportmodellen. D��rf��r fokuserar jag p�� den h��r delen av arbetet i avhandlingens introduktionsdel. Ett s��tt att studera hopptransportmodellen numeriskt ��r att direkt utf��ra en slumpvandringsprocess med ett datorprogram. Genom att f��ra statisik ��ver slumpvandringen kan man ber��kna olika transportegenskaper i modellen. Det h��r ��r en s�� kallad Monte Carlo-metod, eftersom sj��lva ber��kningen ��r en slumpm��ssig process. I st��llet f��r att f��lja r��relsebanan f��r enskilda elektroner, kan man ber��kna sannolikheten vid j��mvikt f��r att hitta en elektron i olika tillst��nd. Man st��ller upp ett system av ekvationer, som relaterar sannolikheterna f��r att hitta elektronen i olika tillst��nd i systemet med fl��det, str��mmen, mellan de olika tillst��nden. Genom att l��sa ekvationssystemet f��s sannolikhetsf��rdelningen f��r elektronerna. Fr��n sannolikhetsf��rdelningen kan sedan str��mmen och materialets transportegenskaper ber��knas. En aspekt av hopptransportmodellen som vi studerat ��r elektronernas diffusion, d.v.s. deras slumpm��ssiga r��relse. Om man betraktar en samling elektroner, s�� sprider den med tiden ut sig ��ver ett st��rre omr��de. Det ��r k��nt att diffusionshastigheten beror av elf��ltet, s�� att elektronerna sprider sig fortare om de p��verkas av ett elektriskt f��lt. Vi har unders��kt den h��r processen, och visat att beteendet ��r v��ldigt olika i endimensionella system, j��mf��rt med tv��- och tredimensionella. I tv�� och tre dimensioner beror diffusionskoefficienten kvadratiskt av elf��ltet, medan beroendet i en dimension ��r linj��rt. En annan aspekt vi studerat ��r negativ differentiell konduktivitet, d.v.s. att str��mmen i ett material minskar d�� man ��kar sp��nningen ��ver det. Eftersom det h��r fenomenet har uppm��tts i organiska minnesceller, ville vi unders��ka om fenomenet ocks�� kan uppst�� i hopptransportmodellen. Det visade sig att det i modellen finns tv�� olika mekanismer som kan ge upphov till negativ differentiell konduktivitet. Dels kan elektronerna fastna i f��llor, ��terv��ndsgr��nder i systemet, som ��r s��dana att det ��r sv��rare att ta sig ur dem d�� elf��ltet ��r stort. D�� kan elektronernas medelhastighet och d��rmed str��mmen i materialet minska med ��kande elf��lt. Elektrisk v��xelverkan mellan elektronerna kan ocks�� leda till samma beteende, genom en s�� kallad coulombblockad. En coulombblockad kan uppst�� om antalet ledningselektroner i materialet ��kar med ��kande sp��nning. Elektronerna repellerar varandra och ett st��rre antal elektroner kan leda till att transporten blir l��ngsammare, d.v.s. att str��mmen minskar.

Use data from permanent sampling points in growth and yield modeling

This study was carried to evaluate the efficiency of the Bitterlich method in growth and yield modeling of the even-aged Eucalyptus stands. 25 plots were setup in Eucalyptus grandis cropped under a high bole system in the Central Western Region of Minas Gerais, Brazil. The sampling points were setup in the center of each plot. The data of four annual mesurements were colleted and used to adjust the three model types using the age, the site index and the basal area as independent variables. The growths models were fitted for volume and mass of trees. The efficiency of the Bitterlich method was confirmed for generating the data for growth and yield modeling.

Hipsometric relationship modeling using data sampled in tree scaling and inventory plots

This work evaluated eight hypsometric models to represent tree height-diameter relationship, using data obtained from the scaling of 118 trees and 25 inventory plots. Residue graphic analysis and percent deviation mean criteria, qui-square test precision, residual standard error between real and estimated heights and the graybill f test were adopted. The identity of the hypsometric models was also verified by applying the F(Ho) test on the plot data grouped to the scaling data. It was concluded that better accuracy can be obtained by using the model prodan, with h and d1,3 data measured in 10 trees by plots grouped into these scaling data measurements of even-aged forest stands.

Modeling and Analysis of Noise and Interconnects for On-Chip Communication Link Design

This thesis considers modeling and analysis of noise and interconnects in onchip communication. Besides transistor count and speed, the capabilities of a modern design are often limited by on-chip communication links. These links typically consist of multiple interconnects that run parallel to each other for long distances between functional or memory blocks. Due to the scaling of technology, the interconnects have considerable electrical parasitics that affect their performance, power dissipation and signal integrity. Furthermore, because of electromagnetic coupling, the interconnects in the link need to be considered as an interacting group instead of as isolated signal paths. There is a need for accurate and computationally effective models in the early stages of the chip design process to assess or optimize issues affecting these interconnects. For this purpose, a set of analytical models is developed for on-chip data links in this thesis. First, a model is proposed for modeling crosstalk and intersymbol interference. The model takes into account the effects of inductance, initial states and bit sequences. Intersymbol interference is shown to affect crosstalk voltage and propagation delay depending on bus throughput and the amount of inductance. Next, a model is proposed for the switching current of a coupled bus. The model is combined with an existing model to evaluate power supply noise. The model is then applied to reduce both functional crosstalk and power supply noise caused by a bus as a trade-off with time. The proposed reduction method is shown to be effective in reducing long-range crosstalk noise. The effects of process variation on encoded signaling are then modeled. In encoded signaling, the input signals to a bus are encoded using additional signaling circuitry. The proposed model includes variation in both the signaling circuitry and in the wires to calculate the total delay variation of a bus. The model is applied to study level-encoded dual-rail and 1-of-4 signaling. In addition to regular voltage-mode and encoded voltage-mode signaling, current-mode signaling is a promising technique for global communication. A model for energy dissipation in RLC current-mode signaling is proposed in the thesis. The energy is derived separately for the driver, wire and receiver termination.

Modeling of electrolyte sorption ��� from phase equilibria to dynamic separation systems

In this thesis, general approach is devised to model electrolyte sorption from aqueous solutions on solid materials. Electrolyte sorption is often considered as unwanted phenomenon in ion exchange and its potential as an independent separation method has not been fully explored. The solid sorbents studied here are porous and non-porous organic or inorganic materials with or without specific functional groups attached on the solid matrix. Accordingly, the sorption mechanisms include physical adsorption, chemisorption on the functional groups and partition restricted by electrostatic or steric factors. The model is tested in four Cases Studies dealing with chelating adsorption of transition metal mixtures, physical adsorption of metal and metalloid complexes from chloride solutions, size exclusion of electrolytes in nano-porous materials and electrolyte exclusion of electrolyte/non-electrolyte mixtures. The model parameters are estimated using experimental data from equilibrium and batch kinetic measurements, and they are used to simulate actual single-column fixed-bed separations. Phase equilibrium between the solution and solid phases is described using thermodynamic Gibbs-Donnan model and various adsorption models depending on the properties of the sorbent. The 3-dimensional thermodynamic approach is used for volume sorption in gel-type ion exchangers and in nano-porous adsorbents, and satisfactory correlation is obtained provided that both mixing and exclusion effects are adequately taken into account. 2-Dimensional surface adsorption models are successfully applied to physical adsorption of complex species and to chelating adsorption of transition metal salts. In the latter case, comparison is also made with complex formation models. Results of the mass transport studies show that uptake rates even in a competitive high-affinity system can be described by constant diffusion coefficients, when the adsorbent structure and the phase equilibrium conditions are adequately included in the model. Furthermore, a simplified solution based on the linear driving force approximation and the shrinking-core model is developed for very non-linear adsorption systems. In each Case Study, the actual separation is carried out batch-wise in fixed-beds and the experimental data are simulated/correlated using the parameters derived from equilibrium and kinetic data. Good agreement between the calculated and experimental break-through curves is usually obtained indicating that the proposed approach is useful in systems, which at first sight are very different. For example, the important improvement in copper separation from concentrated zinc sulfate solution at elevated temperatures can be correctly predicted by the model. In some cases, however, re-adjustment of model parameters is needed due to e.g. high solution viscosity.

Application of Computational Fluid Dynamics in Modeling Blood Flow in Human Thoracic Aorta

The aim of this study was to simulate blood flow in thoracic human aorta and understand the role of flow dynamics in the initialization and localization of atherosclerotic plaque in human thoracic aorta. The blood flow dynamics in idealized and realistic models of human thoracic aorta were numerically simulated in three idealized and two realistic thoracic aorta models. The idealized models of thoracic aorta were reconstructed with measurements available from literature, and the realistic models of thoracic aorta were constructed by image processing Computed Tomographic (CT) images. The CT images were made available by South Karelia Central Hospital in Lappeenranta. The reconstruction of thoracic aorta consisted of operations, such as contrast adjustment, image segmentations, and 3D surface rendering. Additional design operations were performed to make the aorta model compatible for the numerical method based computer code. The image processing and design operations were performed with specialized medical image processing software. Pulsatile pressure and velocity boundary conditions were deployed as inlet boundary conditions. The blood flow was assumed homogeneous and incompressible. The blood was assumed to be a Newtonian fluid. The simulations with idealized models of thoracic aorta were carried out with Finite Element Method based computer code, while the simulations with realistic models of thoracic aorta were carried out with Finite Volume Method based computer code. Simulations were carried out for four cardiac cycles. The distribution of flow, pressure and Wall Shear Stress (WSS) observed during the fourth cardiac cycle were extensively analyzed. The aim of carrying out the simulations with idealized model was to get an estimate of flow dynamics in a realistic aorta model. The motive behind the choice of three aorta models with distinct features was to understand the dependence of flow dynamics on aorta anatomy. Highly disturbed and nonuniform distribution of velocity and WSS was observed in aortic arch, near brachiocephalic, left common artery, and left subclavian artery. On the other hand, the WSS profiles at the roots of branches show significant differences with geometry variation of aorta and branches. The comparison of instantaneous WSS profiles revealed that the model with straight branching arteries had relatively lower WSS compared to that in the aorta model with curved branches. In addition to this, significant differences were observed in the spatial and temporal profiles of WSS, flow, and pressure. The study with idealized model was extended to study blood flow in thoracic aorta under the effects of hypertension and hypotension. One of the idealized aorta models was modified along with the boundary conditions to mimic the thoracic aorta under the effects of hypertension and hypotension. The results of simulations with realistic models extracted from CT scans demonstrated more realistic flow dynamics than that in the idealized models. During systole, the velocity in ascending aorta was skewed towards the outer wall of aortic arch. The flow develops secondary flow patterns as it moves downstream towards aortic arch. Unlike idealized models, the distribution of flow was nonplanar and heavily guided by the artery anatomy. Flow cavitation was observed in the aorta model which was imaged giving longer branches. This could not be properly observed in the model with imaging containing a shorter length for aortic branches. The flow circulation was also observed in the inner wall of the aortic arch. However, during the diastole, the flow profiles were almost flat and regular due the acceleration of flow at the inlet. The flow profiles were weakly turbulent during the flow reversal. The complex flow patterns caused a non-uniform distribution of WSS. High WSS was distributed at the junction of branches and aortic arch. Low WSS was distributed at the proximal part of the junction, while intermedium WSS was distributed in the distal part of the junction. The pulsatile nature of the inflow caused oscillating WSS at the branch entry region and inner curvature of aortic arch. Based on the WSS distribution in the realistic model, one of the aorta models was altered to induce artificial atherosclerotic plaque at the branch entry region and inner curvature of aortic arch. Atherosclerotic plaque causing 50% blockage of lumen was introduced in brachiocephalic artery, common carotid artery, left subclavian artery, and aortic arch. The aim of this part of the study was first to study the effect of stenosis on flow and WSS distribution, understand the effect of shape of atherosclerotic plaque on flow and WSS distribution, and finally to investigate the effect of lumen blockage severity on flow and WSS distributions. The results revealed that the distribution of WSS is significantly affected by plaque with mere 50% stenosis. The asymmetric shape of stenosis causes higher WSS in branching arteries than in the cases with symmetric plaque. The flow dynamics within thoracic aorta models has been extensively studied and reported here. The effects of pressure and arterial anatomy on the flow dynamic were investigated. The distribution of complex flow and WSS is correlated with the localization of atherosclerosis. With the available results we can conclude that the thoracic aorta, with complex anatomy is the most vulnerable artery for the localization and development of atherosclerosis. The flow dynamics and arterial anatomy play a role in the localization of atherosclerosis. The patient specific image based models can be used to diagnose the locations in the aorta vulnerable to the development of arterial diseases such as atherosclerosis.

MODELING A COMPUTER APPLICATION FOR MANAGEMENT OF MAINTENANCE ACTIVITIES OF UNPAVED ROADS

ABSTRACTThis study presents a contribution to the modeling of a computer application employing a method of serviceability performance for unpaved roads, aiming the management of maintenance/restoration activities of the primary surface layer. The proposed methodology consisted of field inspections during dry (April to September) and rainy (October to March) periods, during which objective evaluations were performed to survey of defects and their densities and degrees of severity. To aid the functional classification of analyzed road sections and the determination of the defect with major influence on the serviceability of these roads, the method of serviceability performance proposed by Silva (2009)was implemented in the Visual Basic for Applications (VBA) language in Microsoft Excel software. With the use of the computer application proposed it was possible to identify among the defects analyzed in field, through the index of serviceability of the sampling unit per defect type (ISUdef), which one had the greatest influence on determining the relative serviceability index per road section (IST). The results allow us to conclude that the computer application Road achieved satisfactory results, since the objective evaluation criteria applied to road sections denotes consistency regarding their serviceability.

MODELING AND SIMULATION OF RELIEF INFLUENCE ON EUCALYPTUS FORESTS: INTERACTION BETWEEN SOLAR IRRADIANCE AND PRODUCTIVITY

ABSTRACT This study aimed to verify the differences in radiation intensity as a function of distinct relief exposure surfaces and to quantify these effects on the leaf area index (LAI) and other variables expressing eucalyptus forest productivity for simulations in a process-based growth model. The study was carried out at two contrasting edaphoclimatic locations in the Rio Doce basin in Minas Gerais, Brazil. Two stands with 32-year-old plantations were used, allocating fixed plots in locations with northern and southern exposure surfaces. The meteorological data were obtained from two automated weather stations located near the study sites. Solar radiation was corrected for terrain inclination and exposure surfaces, as it is measured based on the plane, perpendicularly to the vertical location. The LAI values collected in the field were used. For the comparative simulations in productivity variation, the mechanistic 3PG model was used, considering the relief exposure surfaces. It was verified that during most of the year, the southern surfaces showed lower availability of incident solar radiation, resulting in up to 66% losses, compared to the same surface considered plane, probably related to its geographical location and higher declivity. Higher values were obtained for the plantings located on the northern surface for the variables LAI, volume and mean annual wood increase, with this tendency being repeated in the 3PG model simulations.

Modeling study of limestone reactions in fluidized bed conditions

Traditionally limestone has been used for the flue gas desulfurization in fluidized bed combustion. Recently, several studies have been carried out to examine the use of limestone in applications which enable the removal of carbon dioxide from the combustion gases, such as calcium looping technology and oxy-fuel combustion. In these processes interlinked limestone reactions occur but the reaction mechanisms and kinetics are not yet fully understood. To examine these phenomena, analytical and numerical models have been created. In this work, the limestone reactions were studied with aid of one-dimensional numerical particle model. The model describes a single limestone particle in the process as a function of time, the progress of the reactions and the mass and energy transfer in the particle. The model-based results were compared with experimental laboratory scale BFB results. It was observed that by increasing the temperature from 850 ��C to 950 ��C the calcination was enhanced but the sulfate conversion was no more improved. A higher sulfur dioxide concentration accelerated the sulfation reaction and based on the modeling, the sulfation is first order with respect to SO2. The reaction order of O2 seems to become zero at high oxygen concentrations.

Computational modeling for irrigated agriculture planning. Part I: general description and linear programming

Linear programming models are effective tools to support initial or periodic planning of agricultural enterprises, requiring, however, technical coefficients that can be determined using computer simulation models. This paper, presented in two parts, deals with the development, application and tests of a methodology and of a computational modeling tool to support planning of irrigated agriculture activities. Part I aimed at the development and application, including sensitivity analysis, of a multiyear linear programming model to optimize the financial return and water use, at farm level for Ja��ba irrigation scheme, Minas Gerais State, Brazil, using data on crop irrigation requirement and yield, obtained from previous simulation with MCID model. The linear programming model outputted a crop pattern to which a maximum total net present value of R$ 372,723.00 for the four years period, was obtained. Constraints on monthly water availability, labor, land and production were critical in the optimal solution. In relation to the water use optimization, it was verified that an expressive reductions on the irrigation requirements may be achieved by small reductions on the maximum total net present value.

Computational modeling for irrigated agriculture planning. Part II: risk analysis

Techniques of evaluation of risks coming from inherent uncertainties to the agricultural activity should accompany planning studies. The risk analysis should be carried out by risk simulation using techniques as the Monte Carlo method. This study was carried out to develop a computer program so-called P-RISCO for the application of risky simulations on linear programming models, to apply to a case study, as well to test the results comparatively to the @RISK program. In the risk analysis it was observed that the average of the output variable total net present value, U, was considerably lower than the maximum U value obtained from the linear programming model. It was also verified that the enterprise will be front to expressive risk of shortage of water in the month of April, what doesn't happen for the cropping pattern obtained by the minimization of the irrigation requirement in the months of April in the four years. The scenario analysis indicated that the sale price of the passion fruit crop exercises expressive influence on the financial performance of the enterprise. In the comparative analysis it was verified the equivalence of P-RISCO and @RISK programs in the execution of the risk simulation for the considered scenario.