Techniques to Understand Computer Simulations: Markov Chain Analysis

The aim of this paper is to assist researchers in understanding the dynamics of simulation models that have been implemented and can be run in a computer, i.e. computer models. To do that, we start by explaining (a) that computer models are just input-output functions, (b) that every computer model can be re-implemented in many different formalisms (in particular in most programming languages), leading to alternative representations of the same input-output relation, and (c) that many computer models in the social simulation literature can be usefully represented as time-homogeneous Markov chains. Then we argue that analysing a computer model as a Markov chain can make apparent many features of the model that were not so evident before conducting such analysis. To prove this point, we present the main concepts needed to conduct a formal analysis of any time-homogeneous Markov chain, and we illustrate the usefulness of these concepts by analysing 10 well-known models in the social simulation literature as Markov chains. These models are: • Schelling\'s (1971) model of spatial segregation • Epstein and Axtell\'s (1996) Sugarscape • Miller and Page\'s (2004) standing ovation model • Arthur\'s (1989) model of competing technologies • Axelrod\'s (1986) metanorms models • Takahashi\'s (2000) model of generalized exchange • Axelrod\'s (1997) model of dissemination of culture • Kinnaird\'s (1946) truels • Axelrod and Bennett\'s (1993) model of competing bimodal coalitions • Joyce et al.\'s (2006) model of conditional association In particular, we explain how to characterise the transient and the asymptotic dynamics of these computer models and, where appropriate, how to assess the stochastic stability of their absorbing states. In all cases, the analysis conducted using the theory of Markov chains has yielded useful insights about the dynamics of the computer model under study.Computer Modelling, Simulation, Markov, Stochastic Processes, Analysis, Re-Implementation

Estudo da produ??o de concentrados de min?rio de ferro a partir dos rejeitos da barragem de germano.

Programa de P?s-Gradua??o em Engenharia Mineral. Departamento de Engenharia de Minas, Escola de Minas, Universidade Federal de Ouro Preto.Esse trabalho investigou a possibilidade de se produzir concentrados de min?rio de ferro que atendessem ?s especifica??es atuais da Samarco, utilizando uma amostra dos rejeitos da barragem de Germano. Na caracteriza??o da amostra, determinou-se uma granulometria muito fina, um baixo teor de ferro (26%) e um elevado teor de hematita especular (85%), al?m de uma maior concentra??o dos minerais de ferro nas fra??es abaixo de 44?m. Devido a essas caracter?sticas, foram realizados inicialmente ensaios de pr?-concentra??o por peneiramento, concentra??o magn?tica e concentra??o centr?fuga. Na seq??ncia, foram realizados ensaios de concentra??o considerando cinco fluxogramas, envolvendo como m?todos principais a concentra??o magn?tica e a flota??o. Os concentrados obtidos apresentaram baixos teores de f?sforo, elevados teores de hematita especular e teores de s?lica pr?ximos ?s especifica??es de alto forno. A especifica??o de s?lica de um concentrado para redu??o direta n?o foi prontamente obtida e mostrou-se mais dif?cil, fato atribu?do ? presen?a no concentrado de outras esp?cies portadoras de s?lica, al?m do quartzo. Os fluxogramas envolvendo peneiramento e concentra??o magn?tica foram os que se mostraram mais promissores para o tratamento dos rejeitos. Mesmo sem otimiza??es, foram obtidas recupera??es em peso de 25% e met?lica de 67%, com teores de s?lica no concentrado na faixa de 3%. Por possuir configura??o semelhante ao circuito de concentra??o da Samarco, a op??o incluindo deslamagem e flota??o foi melhor estudada atrav?s de um projeto de experimentos para os ensaios de flota??o e tamb?m considerando a introdu??o de uma etapa de escrubagem anterior ? deslamagem. Os resultados obtidos n?o recomendam a utiliza??o desse tipo de circuito para o tratamento dos rejeitos da barragem de Germano.This research investigated the possibilities of producing iron ore concentrates in accordance with the specifications of the concentrates produced by Samarco, using a sample of Germano?s tailings dam. The sample characterization determined a very fine size distribution, a low iron grade (26%) and a high specular hematite content (85%), beyond a high concentration of iron minerals in fractions below 44?m. Due to these characteristics, pre-concentration tests using screening, magnetic and and centrifugal concentration were carried out first. Following, concentration tests were carried out considering five flowsheets, considering flotation and magnetic concentration as major methods. The concentrates obtained showed a low phosphorous grade, a high specular hematite content and silica grades close to the blast furnace specifications. The silica specification for direct reduction wasn?t readily achieved, and seemed to be more difficult to be, fact attributed to others mineral species containing silica, different from quartz, found in the concentrates. The flowsheets using screening and magnetic concentration were the most promissory to treat the tailings. Even without optimization, weight and iron recoveries of 25 and 67% were obtained, and concentrates with silica grades around 3%. Due to its similarity with Samarco?s concentration flowsheet, the option with desliming and flotation was better studied using a design of experiments for flotation tests and also considering a scrubbing stage before desliming. The results obtained don?t recommend this flowsheet to the treatment of the tailings of Germano?s dam

O efeito alelop?tico do ?leo neem (Azadirachta indica A. Juss) sobre a germina??o e crescimento de plantas de alface ( Lactuca sativa L.)

The present study arises from an informal conversation with a farmer in which he reported that when mixing the leaves of neem trees (Azadirachta indica A. Juss) with cattle manure for use in the domestic orchard, the plants that received this mixture were more vigorous and less susceptible to attack by disease. Chemical inputs currently represent a significant financial cost to agriculture as well as triggering numerous contamination problems for ecosystems and humans. As a substitute for conventional agriculture, alternatives such as agroecology and organic food production have been sought. Following this precept, organic agriculture makes use of different extracts and vegetable oils as a way to boost production, either in the control of diseases and insects, or in improving the vigor and development of plants. Among the options are products derived from neem ( Azadirachta indica A. Juss ), which have been used in the ecological pest management. However, there are few studies showing the allelopathic effects of neem on germination and growth of plants such as lettuce. The objective of the present study was to evaluate the allelopathic effect of different doses of Dalneem ne neem oil ( Azadiracthta indica A. Juss ) diluted in distilled water on the germination and growth of lettuce plants ( Lactuca sativa L .) , cultivating Four Seasons of the Bionatur marca brand cultivated in different experimental systems. Three experiments were carried out. The first experiment in the laboratory, the effect of different doses (0 ml / L, 1 ml / L, 10 ml / L, 20 ml / L, 30 ml / L, 40 ml / L) was evaluated by initial screening. Neem oil on germination of lettuce seeds. In this experiment no significant changes of the neem oil were observed on the germination of lettuce seeds. Thus, a larger number of doses of neem oil (0; 0,001; 0,05; 0,1; 0,5; 1; 5; 10; 15; 20) mL of the oil / L of distilled water). In this screening, no significant changes of the neem oil were observed on the germination of lettuce seeds, although an increase in the fresh mass of the lettuce seedlings was observed at the dose of 0.5 mL / L of neem oil. From these experiments the doses (0 ml / L, 1 ml / L, 10 ml / L, 20 ml / L, 30 ml / L, 40 ml / L) used in experiments 2 and 3 were selected, the effect of neem oil on the growth of lettuce plants cultivated in trays and in pots was evaluated. In the experiments in trays and in pots, the oil of neem, in the different concentrations, was applied to the substrate with the aid of a graduated pisseta. The plants remained under treatment for 25 days. In the plants with 35 days, the chlorophyll index was evaluated using the chlorophyll meter. At the end of the experiments, the plants were collected, washed, and the root and shoot length were evaluated with the aid of a digital caliper, the fresh mass with the aid of an analytical balance and the dry mass after complete oven drying at 65?C also recorded in analytical balance. In addition, aerial part samples were macerated with potassium phosphate buffer, centrifuged and the supernatant was used to determine the concentration of soluble proteins. The data were submitted to analysis of variance and the means were compared by the Tukey test with significance of 5% of probability. When cultured in trays, neem oil applied at the dose of 1 ml / L induced an increase in shoot length, but at doses of 30 ml / L inhibited the growth of this organ in lettuce plants. The same inhibitory effect was also observed at the same doses for root growth. When lettuce plants were grown in pots, significant changes were observed only in shoot length. At the dose 1 ml of neem oil the shoot length was 14% higher when compared to the control treatment, although in the larger doses (30 and 40 mm / L of Neem oil) significant reductions were observed in the length of the aerial part of the plants of lettuce. Chlorophyll indices were not affected by the application of neem oil. In addition, an increase in protein levels was observed when lettuce plants were treated with 20 ml / L of neem oil. Therefore, the results of the present study suggest that neem oil does not affect germination, but affects the growth of lettuce plants and can be used in the management of spontaneous plants.O presente estudo surge de uma conversa informal com um agricultor em que relatou que, ao misturar as folhas das ?rvores de neem( Azadirachta indica A. Juss ) com esterco bovino, para uso no pomar dom?stico, as plantas que receberam esta mistura se mostraram mais vigorosas e menos suscet?veis aos ataques por doen?as. Os insumos qu?micos representam atualmente um significativo custo financeiro para a agricultura al?m de desencadear in?meros problemas de contamina??o para os ecossistemas e aos humanos. Dessa forma, em substitui??o a agricultura convencional tem se buscado alternativas tais como a agroecologia e produ??o org?nica de alimentos. Seguindo este preceito, a agricultura org?nica faz uso de diferentes extratos e ?leos vegetais como forma de potencializar a produ??o, seja no controle de doen?as e insetos, ou na melhoria do vigor e desenvolvimento das plantas. Dentre as op??es est?o os produtos derivados do neem ( Azadirachta indica A. Juss ), os quais vem sendo utilizados no manejo ecol?gico de pragas. No entanto, s?o escassos os estudos mostrando os efeitos alelop?ticos do neem sobre a germina??o e crescimento de plantas tal como a alface. Assim, o objetivo do presente estudo foi avaliar o efeito alelop?tico de diferentes doses de ?leo de neem da marca Dalneem?(Ec) dilu?dos em ?gua destilada sobre a germina??o e crescimento de plantas de alface( Lactuca sativa L.), cultivar Quatro Esta??es da marca Bionatur? cultivada em diferentes sistemas experimentais. Para isso foram realizados tr?s experimentos. O primeiro experimento em laborat?rio, avaliou-se atrav?s de uma triagem inicial o efeito de diferentes doses (0 ml/L, 1 ml/L, 10 ml/L, 20 ml/L, 30 ml/L, 40 ml/L) de ?leo de neem na germina??o de sementes de alface. Em tal experimento n?o foram observadas altera??es significativas do ?leo de neem sobre a germina??o de sementes de alface. Assim, em uma segunda triagem, ainda em laborat?rio, foi utilizada um n?mero mais amplo de doses de ?leo de neem (0; 0,001; 0,05; 0,1; 0,5; 1; 5; 10; 15; 20) mL do ?leo/ por L de ?gua destilada). Neste screening foram observadas altera??es significativas do ?leo de neem sobre a germina??o das sementes de alface, embora um incremento na massa fresca das pl?ntulas de alface tenha sido observado na dose de 0,5 mL/L de ?leo de neem. A partir destes experimentos foram selecionadas as doses (0 ml/L, 1 ml/L, 10 ml/L, 20 ml/L, 30 ml/L, 40 ml/L) de ?leo de neem dissolvidos em ?gua destilada utilizadas nos experimentos em bandeja e nos vasos, o ?leo foi aplicado ao substrato com o aux?lio de uma pisseta graduada, avaliou-se o efeito do ?leo de neem sobre o crescimento de plantas de alface cultivadas. As plantas permaneceram sob tratamento durante 25 dias. Nas plantas com 35 dias foi realizada a avalia??o do ?ndice de clorofila, utilizando o aparelho clorofil?metro. Ao final dos experimentos, as plantas foram coletadas, lavadas, sendo avaliado o comprimento da raiz e parte a?rea com o aux?lio de um paqu?metro digital, a massa fresca com o aux?lio de uma balan?a anal?tica e a massa seca ap?s secagem completa em estufa a 65?C tamb?m registrada em balan?a anal?tica. Al?m disso, amostras de parte a?rea foram maceradas com tamp?o fosfato de pot?ssio, centrifugadas e o sobrenadante foi utilizado para a determina??o da concentra??o de prote?nas sol?veis. Os dados foram submetidos ? an?lise de vari?ncia e as m?dias foram comparadas pelo teste de Tukey com signific?ncia de 5 % de probabilidade. Quando cultivadas em bandejas, o ?leo de neem aplicado na dose de 1 ml/L induziu um incremento no comprimento da parte a?rea, mas nas doses a partir de 30 ml/L inibiu o crescimento deste ?rg?o em plantas de alface. O mesmo efeito inibit?rio foi tamb?m observado nas mesmas doses para o crescimento de ra?zes. Quando as plantas de alface foram cultivadas em vasos, altera??es significativas foram observadas somente quanto ao comprimento da parte a?rea. Na dose 1 ml de ?leo de neem o comprimento da parte a?rea foi 14% maior quando comparado ao tratamento controle, embora nas doses maiores (30 e 40 mm/L de ?leo de Neem) foram observadas redu??es significativas no comprimento da parte a?rea das plantas de alface. Os ?ndices de clorofila n?o sofreram altera??es pela aplica??o do ?leo de neem. Al?m disso, um incremento nos n?veis de prote?nas foi observado quando plantas de alface foram tratadas com 20 ml/L de ?leo de neem. Portanto, os resultados do presente estudo sugerem que o ?leo de neem n?o altera a germina??o, mas afeta o crescimento de plantas de alface, podendo o mesmo ser utilizado no manejo de plantas espont?neas

Errors and Artefacts in Agent-Based Modelling

The objectives of this paper are to define and classify different types of errors and artefacts that can appear in the process of developing an agent-based model, and to propose activities aimed at avoiding them during the model construction and testing phases. To do this in a structured way, we review the main concepts of the process of developing such a model – establishing a general framework that summarises the process of designing, implementing, and using agent-based models. Within this framework we identify the various stages where different types of errors and artefacts may appear. Finally we propose activities that could be used to detect (and hence eliminate) each type of error or artefact.Verification, Replication, Artefact, Error, Agent-Based Modelling, Modelling Roles

Shared value creation and crowdfunding in Brazil.

Approaching the theory of creating shared value (Kramer & Porter, 2011) with the basic social elements of crowdfunding in Brazil. The idea was to explore the complementarity of the concepts governing the CF in line with the theory of Porter and Kramer. Through literature review and empirical discussion is intended to answer two central questions regarding the theme developed in this essay: i) which elements of the theory of creating shared value are found in crowdfunding? ii) how occurs the creation of shared value in business developed in crowdfunding platforms? Methodology. Theoretical Essay. Findings. It is possible to make a theoretical approach of the themes studied in this trial, as we take the social and financial perspective of crowdfunding and their relationships with the creation of value for the company and investor

Sem?foro com Sistema de Temporiza??o por Figuras Geom?tricas

Com o intuito de apresentar um novo padr?o de sistema de temporiza??o, foi desenvolvido um sem?foro que exibe a contagem de tempo por meio do movimento de rota??o realizado por figuras geom?tricas. Para isso, o dispositivo ? composto por um ?nico foco luminoso de se??o quadrada, constitu?do por LEDs do tipo RGB, o qual exibe as cores associando cada uma delas a uma figura geom?trica distinta. No que tange a alimenta??o el?trica, o sem?foro desenvolvido far? uso da energia el?trica produzida por um painel fotovoltaico, que transforma a energia solar em el?trica

INSTRUMENTOS DE ACOMPANHAMENTO E PADRONIZA??O DA EXECU??O E AVALIA??O DE TREINAMENTOS

O presente trabalho foi desenvolvido para conclus?o do curso de Bacharelado em Administra??o do Instituto Federal de Educa??o, Ci?ncia e Tecnologia da Para?ba (IFPB) e teve o objetivo de analisar a avalia??o e execu??o do processo de treinamento em uma ind?stria, no que se refere ao acompanhamento e padroniza??o, e a rela??o destes com a satisfa??o dos funcion?rios e a tomada de decis?o dos gestores. Descreveu-se o processo de treinamento da empresa analisando e identificando-se os problemas por meio da an?lise de conte?do e posteriormente elaborou-se instrumentos de padroniza??o e acompanhamento da execu??o e avalia??o. Quanto aos objetivos, a pesquisa classifica-se como descritiva e quanto ? sua natureza ? aplicada. Considerando os procedimentos t?cnicos utilizados, o trabalho se caracteriza como pesquisa documental e bibliogr?fica. A an?lise evidenciou a aus?ncia de instrumentos que possibilitassem o cumprimento de tarefas estabelecidas no processo de treinamento da empresa e que permitisse uma vis?o macro do processo. Os resultados mostram que instrumentos de padroniza??o e acompanhamento da execu??o e avalia??o dos treinamentos geram: maior controle do processo e conseguinte qualidade dos treinamentos; vis?o macro do processo, subsidiando decis?es assertivas que geram a execu??o efetiva do programa de treinamento; fatores que geram maior satisfa??o e participa??o dos funcion?rios

Modelagem estoc?stica aplicada na estimativa do raio de prote??o de cavidades naturais subterr?neas.

Programa de P?s-Gradua??o em Engenharia Mineral. Departamento de Engenharia de Minas. Escola de Minas, Universidade Federal de Ouro Preto.A atual legisla??o ambiental brasileira determina que na aus?ncia de estudos t?cnicos espec?ficos fica estabelecido um raio m?nimo de 250 m de prote??o, delimitado a partir da proje??o horizontal das cavidades naturais subterr?neas. Esta imposi??o ? contestada por diversos segmentos produtivos brasileiros, em especial a ind?stria da minera??o, j? que a ado??o do raio de prote??o exigido por lei pode restringir de forma significante as reservas minerais lavr?veis, em alguns casos inviabilizando todo um empreendimento. ? consenso entre os estudiosos do tema que a estimativa de um raio m?nimo de prote??o de 250 m ? arbitr?ria, por n?o considerar as especificidades de cada cavidade natural subterr?nea, bem como das opera??es desenvolvidas no seu entorno. Neste sentido, este trabalho apresenta uma proposta de metodologia de estimativa do raio m?nimo de prote??o, considerando as especificidades geomec?nicas das cavidades naturais subterr?neas, com vistas a reduzir o potencial de impacto na integridade f?sica das cavidades frente ?s opera??es de avan?os de lavra, em especial ?s vibra??es ocasionadas por desmontes de rochas com explosivos. Este estudo apresenta um modelo estoc?stico de estimativa de valores de velocidade de pico de part?cula associado a par?metros definidos no desmonte de rochas com explosivos, e um modelo estoc?stico de estimativa de velocidade cr?tica de vibra??es que considera as especificidades geomec?nicas e f?sicas da cavidade analisada. Uma an?lise integrada a partir de t?cnicas de simula??o, dos modelos propostos, permite a estimativa do raio m?nimo de prote??o ?s cavidades naturais subterr?neas, pautado em crit?rios estoc?sticos.The current Brazilian environmental legislation determines that in the absence of specific technical studies a minimum radius of 250 m of protection is established, delimited from the horizontal projection of the natural underground cavities. This imposition is contested by several Brazilian productive segments, especially the mining industry, since the adoption of the radius of protection required by law may significantly restrict the mineral reserves, in some cases rendering an entire enterprise unfeasible. It is a consensus among scholars that the estimate of a minimum radius of protection of 250 m is arbitrary because it does not consider the specificities of each natural underground cavity as well as the operations carried out in its surroundings. In this sense, this work presents a proposal for a methodology for estimating the minimum radius of protection, considering the geomechanical specificities of the natural underground cavities, in order to guarantee the physical integrity of the cavities in front of the mining operations, especially to the vibrations caused by Clearing of rocks with explosives. This study presents a stochastic prediction model of peak particle velocity values associated to parameters defined in the dismantling of rocks with explosives and a stochastic model of critical velocity estimation of vibrations that considers the geomechanical and physical specificities of the analyzed cavity. An integrated analysis based on simulation techniques, of the proposed models, allows the estimation of the minimum radius of protection to the natural underground cavities, based on stochastic criteria