Uncertainty in forest simulators and forest planning systems

The forest simulator is a computerized model for predicting forest growth and future development as well as effects of forest harvests and treatments. The forest planning system is a decision support tool, usually including a forest simulator and an optimisation model, for finding the optimal forest management actions. The information produced by forest simulators and forest planning systems is used for various analytical purposes and in support of decision making. However, the quality and reliability of this information can often be questioned. Natural variation in forest growth and estimation errors in forest inventory, among other things, cause uncertainty in predictions of forest growth and development. This uncertainty stemming from different sources has various undesirable effects. In many cases outcomes of decisions based on uncertain information are something else than desired. The objective of this thesis was to study various sources of uncertainty and their effects in forest simulators and forest planning systems. The study focused on three notable sources of uncertainty: errors in forest growth predictions, errors in forest inventory data, and stochastic fluctuation of timber assortment prices. Effects of uncertainty were studied using two types of forest growth models, individual tree-level models and stand-level models, and with various error simulation methods. New method for simulating more realistic forest inventory errors was introduced and tested. Also, three notable sources of uncertainty were combined and their joint effects on stand-level net present value estimates were simulated. According to the results, the various sources of uncertainty can have distinct effects in different forest growth simulators. The new forest inventory error simulation method proved to produce more realistic errors. The analysis on the joint effects of various sources of uncertainty provided interesting knowledge about uncertainty in forest simulators.

Tutorial on NK model

NK model, proposed by Kauffman (1993), is a strong simulation framework to study competing dynamics. It has been applied in some social science fields, for instance, organization science. However, like many other simulation methods, NK model has not received much attention from Management Information Systems (MIS) discipline. This tutorial, thus, is trying to introduce NK model in a simple way and encourage related studies. To demonstrate how NK model works, this tutorial reproduces several Levinthal’s (1997) experiments. Besides, this tutorial attempts to make clear the relevance between NK model and agent-based modeling (ABM). The relevance can be a theoretical basis to further develop NK model framework for other research scenarios. For example, this tutorial provides an NK model solution to study IT value cocreation process by extending network structure and agent interactions.

Ravinnon kasvinsuojeluainejäämät

Kasvinsuojeluaineita käytetään elintarviketuotannossa kasvitautien ehkäisemiseen sekä kasvintuhoojien vaikutusten ajoittamiseen ja kasvun säätelyyn. Käytettyjen tehoaineiden riskinarviointi yksi kerrallaan on tuottanut tärkeää perustietoa, mutta se ei ole antanut selkeää kokonaiskuvaa kuluttajien altistumisesta. Tämän vuoksi asetelmaa tarkasteltiin kokonaisvaltaisesti, ottaen kaikki elintarvikkeista havaitut tehoainejäämät mukaan arvioon kumulatiivisesti. Aikuisten lisäksi mukana on ensi kertaa myös lapsiryhmiä. Ensimmäistä kertaa Suomessa tarkastellaan sekä pitkäaikaista että akuuttia altistusta. Esitetty kumulatiivinen riskinarviointi perustuu vuosina 2002- 2008 kasvinsuojeluainejäämien valvonnassa yhteensä 10 565 elintarvikenäytteestä saatuihin tutkimustuloksiin. Lisäksi riskinarvioinnissa on käytetty Terveyden ja hyvinvoinnin laitoksen ja DIPP-konsortion tuottamia aikuisten ja lasten ruoankulutustietoja (Finravinto 2007 ja DIPP-ravintotutkimukset). Ravinnon välittämälle tehoainejäämien altistukselle on tunnusomaista matala perustaso, jossa esiintyy lyhytaikaisia altistushuippuja. Kun ravinnon välittämä pitkäaikainen altistus kasvinsuojeluaineille on hyväksyttävällä tasolla, ei lyhytaikaisen altistuksen tilanne kaikilta osin ole yhtä hyvä. Kolmivuotiailla lapsilla todennäköisyys aRfD:n ylittymiselle on organofosfaattien ja karbamaattien osalta ollut suurempi kuin 0,1 % eli enemmän kuin yksi tuhannesta, mikä ei vielä vastaa tavoitteita. Ylitykset aiheutuvat tuontituotteista,koska niiden taustalla olevia karbamaatteja ja organofosfaatteja ei enää käytetä Suomessa. Myönteistä kehitystä on tapahtunut, mutta tilannetta on aiheellista edelleen seurata.

Molecular Dynamics Simulations of Homogeneous Nucleation

Nucleation is the first step in a phase transition where small nuclei of the new phase start appearing in the metastable old phase, such as the appearance of small liquid clusters in a supersaturated vapor. Nucleation is important in various industrial and natural processes, including atmospheric new particle formation: between 20 % to 80 % of atmospheric particle concentration is due to nucleation. These atmospheric aerosol particles have a significant effect both on climate and human health. Different simulation methods are often applied when studying things that are difficult or even impossible to measure, or when trying to distinguish between the merits of various theoretical approaches. Such simulation methods include, among others, molecular dynamics and Monte Carlo simulations. In this work molecular dynamics simulations of the homogeneous nucleation of Lennard-Jones argon have been performed. Homogeneous means that the nucleation does not occur on a pre-existing surface. The simulations include runs where the starting configuration is a supersaturated vapor and the nucleation event is observed during the simulation (direct simulations), as well as simulations of a cluster in equilibrium with a surrounding vapor (indirect simulations). The latter type are a necessity when the conditions prevent the occurrence of a nucleation event in a reasonable timeframe in the direct simulations. The effect of various temperature control schemes on the nucleation rate (the rate of appearance of clusters that are equally able to grow to macroscopic sizes and to evaporate) was studied and found to be relatively small. The method to extract the nucleation rate was also found to be of minor importance. The cluster sizes from direct and indirect simulations were used in conjunction with the nucleation theorem to calculate formation free energies for the clusters in the indirect simulations. The results agreed with density functional theory, but were higher than values from Monte Carlo simulations. The formation energies were also used to calculate surface tension for the clusters. The sizes of the clusters in the direct and indirect simulations were compared, showing that the direct simulation clusters have more atoms between the liquid-like core of the cluster and the surrounding vapor. Finally, the performance of various nucleation theories in predicting simulated nucleation rates was investigated, and the results among other things highlighted once again the inadequacy of the classical nucleation theory that is commonly employed in nucleation studies.

Optimum Design for External Seismic Stability of Geosynthetic Reinforced Soil Walls: Reliability Based Approach

In this paper, an analytical study considering the effect of uncertainties in the seismic analysis of geosynthetic-reinforced soil (GRS) walls is presented. Using limit equilibrium method and assuming sliding wedge failure mechanism, analysis is conducted to evaluate the external stability of GRS walls when subjected to earthquake loads. Target reliability based approach is used to estimate the probability of failure in three modes of failure, viz., sliding, bearing, and eccentricity failure. The properties of reinforced backfill, retained backfill, foundation soil, and geosynthetic reinforcement are treated as random variables. In addition, the uncertainties associated with horizontal seismic acceleration and surcharge load acting on the wall are considered. The optimum length of reinforcement needed to maintain the stability against three modes of failure by targeting various component and system reliability indices is obtained. Studies have also been made to study the influence of various parameters on the seismic stability in three failure modes. The results are compared with those given by first-order second moment method and Monte Carlo simulation methods. In the illustrative example, external stability of the two walls, Gould and Valencia walls, subjected to Northridge earthquake is reexamined.

Optimum Design for External Seismic Stability of Geosynthetic Reinforced Soil Walls: Reliability Based Approach

In this paper, an analytical study considering the effect of uncertainties in the seismic analysis of geosynthetic-reinforced soil (GRS) walls is presented. Using limit equilibrium method and assuming sliding wedge failure mechanism, analysis is conducted to evaluate the external stability of GRS walls when subjected to earthquake loads. Target reliability based approach is used to estimate the probability of failure in three modes of failure, viz., sliding, bearing, and eccentricity failure. The properties of reinforced backfill, retained backfill, foundation soil, and geosynthetic reinforcement are treated as random variables. In addition, the uncertainties associated with horizontal seismic acceleration and surcharge load acting on the wall are considered. The optimum length of reinforcement needed to maintain the stability against three modes of failure by targeting various component and system reliability indices is obtained. Studies have also been made to study the influence of various parameters on the seismic stability in three failure modes. The results are compared with those given by first-order second moment method and Monte Carlo simulation methods. In the illustrative example, external stability of the two walls, Gould and Valencia walls, subjected to Northridge earthquake is reexamined.

Light scattering in random media with wavelength-scale structures : astronomical and industrial applications

Light scattering, or scattering and absorption of electromagnetic waves, is an important tool in all remote-sensing observations. In astronomy, the light scattered or absorbed by a distant object can be the only source of information. In Solar-system studies, the light-scattering methods are employed when interpreting observations of atmosphereless bodies such as asteroids, atmospheres of planets, and cometary or interplanetary dust. Our Earth is constantly monitored from artificial satellites at different wavelengths. With remote sensing of Earth the light-scattering methods are not the only source of information: there is always the possibility to make in situ measurements. The satellite-based remote sensing is, however, superior in the sense of speed and coverage if only the scattered signal can be reliably interpreted. The optical properties of many industrial products play a key role in their quality. Especially for products such as paint and paper, the ability to obscure the background and to reflect light is of utmost importance. High-grade papers are evaluated based on their brightness, opacity, color, and gloss. In product development, there is a need for computer-based simulation methods that could predict the optical properties and, therefore, could be used in optimizing the quality while reducing the material costs. With paper, for instance, pilot experiments with an actual paper machine can be very time- and resource-consuming. The light-scattering methods presented in this thesis solve rigorously the interaction of light and material with wavelength-scale structures. These methods are computationally demanding, thus the speed and accuracy of the methods play a key role. Different implementations of the discrete-dipole approximation are compared in the thesis and the results provide practical guidelines in choosing a suitable code. In addition, a novel method is presented for the numerical computations of orientation-averaged light-scattering properties of a particle, and the method is compared against existing techniques. Simulation of light scattering for various targets and the possible problems arising from the finite size of the model target are discussed in the thesis. Scattering by single particles and small clusters is considered, as well as scattering in particulate media, and scattering in continuous media with porosity or surface roughness. Various techniques for modeling the scattering media are presented and the results are applied to optimizing the structure of paper. However, the same methods can be applied in light-scattering studies of Solar-system regoliths or cometary dust, or in any remote-sensing problem involving light scattering in random media with wavelength-scale structures.

Comparative Study of Protein Unfolding in Aqueous Urea and Dimethyl Sulfoxide Solutions: Surface Polarity, Solvent Specificity, and Sequence of Secondary Structure Melting

Elucidation of possible pathways between folded (native) and unfolded states of a protein is a challenging task, as the intermediates are often hard to detect. Here, we alter the solvent environment in a controlled manner by choosing two different cosolvents of water, urea, and dimethyl sulfoxide (DMSO) and study unfolding of four different proteins to understand the respective sequence of melting by computer simulation methods. We indeed find interesting differences in the sequence of melting of alpha helices and beta sheets in these two solvents. For example, in 8 M urea solution, beta-sheet parts of a protein are found to unfold preferentially, followed by the unfolding of alpha helices. In contrast, 8 M DMSO solution unfolds alpha helices first, followed by the separation of beta sheets for the majority of proteins. Sequence of unfolding events in four different alpha/beta proteins and also in chicken villin head piece (HP-36) both in urea and DMSO solutions demonstrate that the unfolding pathways are determined jointly by relative exposure of polar and nonpolar residues of a protein and the mode of molecular action of a solvent on that protein.

Experimental investigation of forming limit, void coalescence and crystallographic textures of aluminum alloy 8011 sheet annealed at various temperatures

In this work, a combined forming and fracture limit diagram, fractured void coalescence and texture analysis have been experimentally evaluated for the commercially available aluminum alloy Al 8011 sheet annealed at different temperatures viz. 200 degrees C, 250 degrees C, 300 degrees C and 350 degrees C. The sheets were examined at different annealing temperatures on microstructure, tensile properties, formability and void coalescence. The fractured surfaces of the formed samples were examined using scanning electron microscope (SEM) and these images were correlated with fracture behavior and formability of sheet metals. Formability of Al 8011 was studied and examined at various annealing temperatures using their bulk X-ray crystallographic textures and ODF plots. Forming limit diagrams, void coalescence parameters and crystallographic textures were correlated with normal anisotropy of the sheet metals annealed at different temperatures. (C) 2013 Politechnika Wroclawska. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Calculation of three-phase methane-ethane binary clathrate hydrate phase equilibrium from Monte Carlo molecular simulations

Methane and ethane are the simplest hydrocarbon molecules that can form clathrate hydrates. Previous studies have reported methods for calculating the three-phase equilibrium using Monte Carlo simulation methods in systems with a single component in the gas phase. Here we extend those methods to a binary gas mixture of methane and ethane. Methane-ethane system is an interesting one in that the pure components form sII clathrate hydrate whereas a binary mixture of the two can form the sII clathrate. The phase equilibria computed from Monte Carlo simulations show a good agreement with experimental data and are also able to predict the sI-sII structural transition in the clathrate hydrate. This is attributed to the quality of the TIP4P/Ice and TRaPPE models used in the simulations. (C) 2014 Elsevier B.V. All rights reserved.

Interphase anisotropy effects on lamellar eutectics: A numerical study

In directional solidification of binary eutectics, it is often observed that two-phase lamellar growth patterns grow tilted with respect to the direction z of the imposed temperature gradient. This crystallographic effect depends on the orientation of the two crystal phases alpha and beta with respect to z. Recently, an approximate theory was formulated that predicts the lamellar tilt angle as a function of the anisotropy of the free energy of the solid(alpha)-solid(beta) interphase boundary. We use two different numerical methods-phase field (PF) and dynamic boundary integral (BI)-to simulate the growth of steady periodic patterns in two dimensions as a function of the angle theta(R) between z and a reference crystallographic axis for a fixed relative orientation of alpha and beta crystals, that is, for a given anisotropy function (Wulff plot) of the interphase boundary. For Wulff plots without unstable interphase-boundary orientations, the two simulation methods are in excellent agreement with each other and confirm the general validity of the previously proposed theory. In addition, a crystallographic ``locking'' of the lamellae onto a facet plane is well reproduced in the simulations. When unstable orientations are present in the Wulff plot, it is expected that two distinct values of the tilt angle can appear for the same crystal orientation over a finite theta(R) range. This bistable behavior, which has been observed experimentally, is well reproduced by BI simulations but not by the PF model. Possible reasons for this discrepancy are discussed.

Análise de unidades de pré-purificação de ar por adsorção

Os principais constituintes do ar, nitrogênio, oxigênio e argônio, estão cada vez mais presentes nas indústrias, onde são empregados nos processos químicos, para o transporte de alimentos e processamento de resíduos. As duas principais tecnologias para a separação dos componentes do ar são a adsorção e a destilação criogênica. Entretanto, para ambos os processos é necessário que os contaminantes do ar, como o gás carbônico, o vapor dágua e hidrocarbonetos, sejam removidos para evitar problemas operacionais e de segurança. Desta forma, o presente trabalho trata do estudo do processo de pré-purificação de ar utilizando adsorção. Neste sistema a corrente de ar flui alternadamente entre dois leitos adsorvedores para produzir ar purificado continuamente. Mais especificamente, o foco da dissertação corresponde à investigação do comportamento de unidades de pré-purificação tipo PSA (pressure swing adsorption), onde a etapa de dessorção é realizada pela redução da pressão. A análise da unidade de pré-purificação parte da modelagem dos leitos de adsorção através de um sistema de equações diferenciais parciais de balanço de massa na corrente gasosa e no leito. Neste modelo, a relação de equilíbrio relativa à adsorção é descrita pela isoterma de Dubinin-Astakhov estendida para misturas multicomponentes. Para a simulação do modelo, as derivadas espaciais são discretizadas via diferenças finitas e o sistema de equações diferenciais ordinárias resultante é resolvido por um solver apropriado (método das linhas). Para a simulação da unidade em operação, este modelo é acoplado a um algoritmo de convergência relativo às quatro etapas do ciclo de operação: adsorção, despressurização, purga e dessorção. O algoritmo em questão deve garantir que as condições finais da última etapa são equivalentes às condições iniciais da primeira etapa (estado estacionário cíclico). Desta forma, a simulação foi implementada na forma de um código computacional baseado no ambiente de programação Scilab (Scilab 5.3.0, 2010), que é um programa de distribuição gratuita. Os algoritmos de simulação de cada etapa individual e do ciclo completo são finalmente utilizados para analisar o comportamento da unidade de pré-purificação, verificando como o seu desempenho é afetado por alterações nas variáveis de projeto ou operacionais. Por exemplo, foi investigado o sistema de carregamento do leito que mostrou que a configuração ideal do leito é de 50% de alumina seguido de 50% de zeólita. Variáveis do processo foram também analisadas, a pressão de adsorção, a vazão de alimentação e o tempo do ciclo de adsorção, mostrando que o aumento da vazão de alimentação leva a perda da especificação que pode ser retomada reduzindo-se o tempo do ciclo de adsorção. Mostrou-se também que uma pressão de adsorção maior leva a uma maior remoção de contaminantes.

Otimização multimodal através de novas técnicas baseadas em clusterização nebulosa

Neste trabalho, é proposta uma nova família de métodos a ser aplicada à otimização de problemas multimodais. Nestas técnicas, primeiramente são geradas soluções iniciais com o intuito de explorar o espaço de busca. Em seguida, com a finalidade de encontrar mais de um ótimo, estas soluções são agrupadas em subespaços utilizando um algoritmo de clusterização nebulosa. Finalmente, são feitas buscas locais através de métodos determinísticos de otimização dentro de cada subespaço gerado na fase anterior com a finalidade de encontrar-se o ótimo local. A família de métodos é formada por seis variantes, combinando três esquemas de inicialização das soluções na primeira fase e dois algoritmos de busca local na terceira. A fim de que esta nova família de métodos possa ser avaliada, seus constituintes são comparados com outras metodologias utilizando problemas da literatura e os resultados alcançados são promissores.

Sistemas complexos, séries temporais e previsibilidade

Para qualquer sistema observado, físico ou qualquer outro, geralmente se deseja fazer predições para sua evolução futura. Algumas vezes, muito pouco é conhecido sobre o sistema. Se uma série temporal é a única fonte de informação no sistema, predições de valores futuros da série requer uma modelagem da lei da dinâmica do sistema, talvez não linear. Um interesse em particular são as capacidades de previsão do modelo global para análises de séries temporais. Isso pode ser um procedimento muito complexo e computacionalmente muito alto. Nesta dissertação, nos concetraremos em um determinado caso: Em algumas situações, a única informação que se tem sobre o sistema é uma série sequencial de dados (ou série temporal). Supondo que, por detrás de tais dados, exista uma dinâmica de baixa dimensionalidade, existem técnicas para a reconstrução desta dinâmica.O que se busca é desenvolver novas técnicas para poder melhorar o poder de previsão das técnicas já existentes, através da programação computacional em Maple e C/C++.

Evaluación del impacto radiológico ambiental de una industria NORM

[ES]El proceso de soldadura más común es la soldadura por arco metálico con electrodos revestidos. A veces ese revestimiento contiene materiales radiactivos de origen natural (NORMs). En España los electrodos más utilizados son los recubiertos de rutilo mezclado con otros materiales. El rutilo contiene algunos radionúclidos naturales detectables, por lo que puede ser considerado como un NORM. Este trabajo principalmente se centra en la aplicación de la metodología expuesta en la Guía de Seguridad 11.3 del Consejo de Seguridad Nuclear (Metodología para la evaluación del impacto radiológico en las industrias NORM), como una herramienta para obtener las dosis en una fábrica que produce este tipo de electrodo y evaluar el impacto radiológico en una instalación específica. Para ello, se aplicaron en dicha instalación los pasos requeridos por la metodología para su cumplimiento. Se analizaron los beneficios inherentes al estudio y se identificaron las zonas de radiación más altas así como la posición de los trabajadores. Habiendo hecho uso de evaluaciones de dosis llevadas a cabo con anterioridad por otros procedimientos, métodos de simulación, se establecieron las pautas de protección radiológica a seguir para el cumplimiento de dicha guía, mediante la colocación de dosímetros personales y monitores de radiación.