896 resultados para integrated simulation model
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At the moment there is a lack of methodological approaches to formalization of management of innovative projects relating to production systems, as well as to adaptation and practical use of the existing approaches. This article is about one potential approach to the management of innovative projects, which makes the building of innovative process models possible based on objective approach. It outlines the frameworks for the building of innovative project models, and describes the method of transition from conceptual modelling to innovative project management. In this case, the model alone and together with parameters used for evaluation of the project may be unique and depends on the special features of the project, preferences of decision-making person, and production and economic system in which it is to be implemented. Unlike existing approaches, this concept does not place any restrictions on types of models and makes it possible to take into account the specificities of economic and production systems. Principles embodied in the model allow its usage as a basis for simulation model to be used in one of specialized simulation systems, as well as for information system providing information support of decision-making process in production and economic systems both newly developed by the company (enterprise) and designed on the basis of available information systems that interact through the exchange of data. In addition, this article shows that the development of conceptual foundations of innovative project management in the economic and production systems is inseparable from the development of the theory of industrial control systems, and their comprehensive study may be reduced to a set of elements represented as certain algorithms, models and evaluations. Thus, the study of innovative process may be conducted in both directions: from general to particular, and vice versa.
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Report for the scientific sojourn at the University of California at Berkeley between September 2007 to February 2008. The globalization combined with the success of containerization has brought about tremendous increases in the transportation of containers across the world. This leads to an increasing size of container ships which causes higher demands on seaport container terminals and their equipment. In this situation, the success of container terminals resides in a fast transhipment process with reduced costs. For these reasons it is necessary to optimize the terminal’s processes. There are three main logistic processes in a seaport container terminal: loading and unloading of containerships, storage, and reception/deliver of containers from/to the hinterland. Moreover there is an additional process that ensures the interconnection between previous logistic activities: the internal transport subsystem. The aim of this paper is to optimize the internal transport cycle in a marine container terminal managed by straddle carriers, one of the most used container transfer technologies. Three sub-systems are analyzed in detail: the landside transportation, the storage of containers in the yard, and the quayside transportation. The conflicts and decisions that arise from these three subsystems are analytically investigated, and optimization algorithms are proposed. Moreover, simulation has been applied to TCB (Barcelona Container Terminal) to test these algorithms and compare different straddle carrier’s operation strategies, such as single cycle versus double cycle, and different sizes of the handling equipment fleet. The simulation model is explained in detail and the main decision-making algorithms from the model are presented and formulated.
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In South America, yellow fever (YF) is an established infectious disease that has been identified outside of its traditional endemic areas, affecting human and nonhuman primate (NHP) populations. In the epidemics that occurred in Argentina between 2007-2009, several outbreaks affecting humans and howler monkeys (Alouatta spp) were reported, highlighting the importance of this disease in the context of conservation medicine and public health policies. Considering the lack of information about YF dynamics in New World NHP, our main goal was to apply modelling tools to better understand YF transmission dynamics among endangered brown howler monkey (Alouatta guariba clamitans) populations in northeastern Argentina. Two complementary modelling tools were used to evaluate brown howler population dynamics in the presence of the disease: Vortex, a stochastic demographic simulation model, and Outbreak, a stochastic disease epidemiology simulation. The baseline model of YF disease epidemiology predicted a very high probability of population decline over the next 100 years. We believe the modelling approach discussed here is a reasonable description of the disease and its effects on the howler monkey population and can be useful to support evidence-based decision-making to guide actions at a regional level.
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A major challenge in studying social behaviour stems from the need to disentangle the behaviour of each individual from the resulting collective. One way to overcome this problem is to construct a model of the behaviour of an individual, and observe whether combining many such individuals leads to the predicted outcome. This can be achieved by using robots. In this review we discuss the strengths and weaknesses of such an approach for studies of social behaviour. We find that robots-whether studied in groups of simulated or physical robots, or used to infiltrate and manipulate groups of living organisms-have important advantages over conventional individual-based models and have contributed greatly to the study of social behaviour. In particular, robots have increased our understanding of self-organization and the evolution of cooperative behaviour and communication. However, the resulting findings have not had the desired impact on the biological community. We suggest reasons for why this may be the case, and how the benefits of using robots can be maximized in future research on social behaviour.
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We use a simulation model to study how the diversification of electricity generation portfoliosinfluences wholesale prices. We find that technological diversification generally leads to lower market prices but that the relationship is mediated by the supply to demand ratio. In each demand case there is a threshold where pivotal dynamics change. Pivotal dynamics pre- and post-threshold are the cause of non-linearities in the influence of diversification on market prices. The findings are robust to our choice of behavioural parameters and match close-form solutions where those are available.
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Se presenta un nuevo modelo integrado de evaluación para el stock norte-centro de la anchoveta peruana que permite reconstruir y hacer un seguimiento de la estructura de longitudes del stock desde un modelo basado en edades. El modelo fue calibrado usando estimados acústicos de biomasa y estructuras de tallas provenientes de cruceros científicos y de desembarques de la pesquería. Para la calibración se utilizó un algoritmo evolutivo con diferentes funciones de aptitud para cada variable calibrada (biomasas y capturas). Se presentan los estimados mensuales de biomasa total, biomasa desovante, reclutamiento y mortalidad por pesca obtenidos por el modelo de evaluación integrada para el periodo 1964-2008. Se encontraron tres periodos cualitativamente distintos en la dinámica de anchoveta, entre 1961-1971, 1971-1991 y 1991 al presente, que se distinguen tanto por las biomasas medias anuales como por los niveles de reclutamiento observado.
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Rapport de synthèse : L'article qui fait l'objet de ma thèse évalue une nouvelle approche pédagogique pour l'apprentissage de certains chapitres de physiopathologie. Le dispositif pédagogique se base sur l'alternance d'apprentissage ex-cathedra et de l'utilisation d'un site web comprenant des vignettes cliniques. Lors de la consultation de ces-dernières, l'étudiant est invité à demander des examens de laboratoire dont il pourrait justifier la pertinence selon le cas clinique étudié. La nouveauté du procédé réside dans le fait que, préalablement à son cours ex-cathedra, l'enseignant peut consulter les statistiques de demandes de laboratoire et ainsi orienter son cours selon les éléments mal compris par les étudiants. A la suite du cours ex-cathedra, les étudiants peuvent consulter sur internet la vignette clinique complète avec des explications. A l'issue de tout le cours, une évaluation auprès des étudiants a été conduite. Le procédé a été mis en place durant deux années consécutives et l'article en discute notamment les résultats. Nous avons pu conclure que cette méthode innovatrice d'enseignement amène les étudiants à mieux se préparer pour les cours ex-cathedra tout en permettant à l'enseignant d'identifier plus précisément quelles thématiques étaient difficiles pour les étudiants et donc d'ajuster au mieux son cours. Mon travail de thèse a consisté à créer ce dispositif d'apprentissage, à créer l'application web des vignettes cliniques et à l'implanter durant deux années consécutives. J'ai ensuite analysé les données des évaluations et écrit l'article que j'ai présenté à la revue 'Medical Teacher'. Après quelques corrections et précisions demandées par le comité de lecture, l'article a été accepté et publié. Ce travail a débouché sur une seconde version de l'application web qui est actuellement utilisée lors du module 3.1 de 3è année à l'Ecole de Médecine à Lausanne. Summary : Since the early days of sexual selection, our understanding of the selective forces acting on males and females during reproduction has increased remarkably. However, despite a long tradition of experimental and theoretical work in this field and relentless effort, numerous questions remain unanswered and many results are conflicting. Moreover, the interface between sexual selection and conservation biology has to date received little attention, despite existing evidence for its importance. In the present thesis, I first used an empirical approach to test various sexual selection hypotheses in a population of whitefish of central Switzerland. This precise population is characterized by a high prevalence of gonadal alterations in males. In particular, I challenged the hypothesis that whitefish males displaying peculiar gonadal features are of lower genetic quality than other seemingly normal males. Additionally, I also worked on identifying important determinant of sperm behavior. During a second theoretical part of my work, which is part of a larger project on the evolution of female mate preferences in harvested fish populations, I developed an individual-based simulation model to estimate how different mate discrimination costs affect the demographical behavior of fish populations and the evolutionary trajectories of female mate preferences. This latter work provided me with some insight on a recently published article addressing the importance of sexual selection for harvesting-induced evolution. I built upon this insight in a short perspective paper. In parallel, I let some methodological questions drive my thoughts, and wrote an essay about possible synergies between the biological, the philosophical and the statistical approach to biological questions.
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STUDY OBJECTIVES: Besides their well-established role in circadian rhythms, our findings that the forebrain expression of the clock-genes Per2 and Dbp increases and decreases, respectively, in relation to time spent awake suggest they also play a role in the homeostatic aspect of sleep regulation. Here, we determined whether time of day modulates the effects of elevated sleep pressure on clock-gene expression. Time of day effects were assessed also for recognized electrophysiological (EEG delta power) and molecular (Homer1a) markers of sleep homeostasis. DESIGN: EEG and qPCR data were obtained for baseline and recovery from 6-h sleep deprivation starting at ZT0, -6, -12, or -18. SETTING: Mouse sleep laboratory. PARTICIPANTS: Male mice. INTERVENTIONS: Sleep deprivation. RESULTS: The sleep-deprivation induced changes in Per2 and Dbp expression importantly varied with time of day, such that Per2 could even decrease during sleep deprivations occurring at the decreasing phase in baseline. Dbp showed similar, albeit opposite dynamics. These unexpected results could be reliably predicted assuming that these transcripts behave according to a driven damped harmonic oscillator. As expected, the sleep-wake distribution accounted for a large degree of the changes in EEG delta power and Homer1a. Nevertheless, the sleep deprivation-induced increase in delta power varied also with time of day with higher than expected levels when recovery sleep started at dark onset. CONCLUSIONS: Per2 and delta power are widely used as exclusive state variables of the circadian and homeostatic process, respectively. Our findings demonstrate a considerable cross-talk between these two processes. As Per2 in the brain responds to both sleep loss and time of day, this molecule is well positioned to keep track of and to anticipate homeostatic sleep need. CITATION: Curie T; Mongrain V; Dorsaz S; Mang GM; Emmenegger Y; Franken P. Homeostatic and circadian contribution to EEG and molecular state variables of sleep regulation. SLEEP 2013;36(3):311-323.
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Empirical studies indicate that the transition to parenthood is influenced by an individual's peer group. To study the mechanisms creating interdepen- dencies across individuals' transition to parenthood and its timing we apply an agent-based simulation model. We build a one-sex model and provide agents with three different characteristics regarding age, intended education and parity. Agents endogenously form their network based on social closeness. Network members then may influence the agents' transition to higher parity levels. Our numerical simulations indicate that accounting for social inter- actions can explain the shift of first-birth probabilities in Austria over the period 1984 to 2004. Moreover, we apply our model to forecast age-specific fertility rates up to 2016.
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BACKGROUND: Physician training in smoking cessation counseling has been shown to be effective as a means to increase quit success. We assessed the cost-effectiveness ratio of a smoking cessation counseling training programme. Its effectiveness was previously demonstrated in a cluster randomized, control trial performed in two Swiss university outpatients clinics, in which residents were randomized to receive training in smoking interventions or a control educational intervention. DESIGN AND METHODS: We used a Markov simulation model for effectiveness analysis. This model incorporates the intervention efficacy, the natural quit rate, and the lifetime probability of relapse after 1-year abstinence. We used previously published results in addition to hospital service and outpatient clinic cost data. The time horizon was 1 year, and we opted for a third-party payer perspective. RESULTS: The incremental cost of the intervention amounted to US$2.58 per consultation by a smoker, translating into a cost per life-year saved of US$25.4 for men and 35.2 for women. One-way sensitivity analyses yielded a range of US$4.0-107.1 in men and US$9.7-148.6 in women. Variations in the quit rate of the control intervention, the length of training effectiveness, and the discount rate yielded moderately large effects on the outcome. Variations in the natural cessation rate, the lifetime probability of relapse, the cost of physician training, the counseling time, the cost per hour of physician time, and the cost of the booklets had little effect on the cost-effectiveness ratio. CONCLUSIONS: Training residents in smoking cessation counseling is a very cost-effective intervention and may be more efficient than currently accepted tobacco control interventions.
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Ramp metering has been successfully implemented in many states to improve traffic operations on freeways. Studies have documented the positive mobility and safety benefits of ramp metering. However, there have been no studies on the use of ramp metering for work zones. This report documents the results from the first deployment of temporary ramp meters in work zones in the United States. Temporary ramp meters were deployed at seven urban short-term work zones in Missouri. Safety measures such as driver compliance, merging behavior, and speed differentials were extracted from video-based field data. Mobility analysis was conducted using a calibrated simulation model and the total delays were obtained for under capacity, at capacity, and over capacity conditions. This evaluation suggests that temporary ramp meters should only be deployed at work zone locations where there is potential for congestion and turned on only during above-capacity conditions. The compliance analysis showed that non-compliance could be a major safety issue in the deployment of temporary ramp meters for under-capacity conditions. The use of a three-section instead of a traditional two-section signal head used for permanent ramp metering produced significantly higher compliance rates. Ramp metering decreased ramp platoons by increasing the percentage of single-vehicle merges to over 70% from under 50%. The accepted-merge-headway results were not statistically significant even though a slight shift towards longer headways was found with the use of ramp meters. Mobility analysis revealed that ramp metering produced delay savings for both mainline and ramp vehicles for work zones operating above capacity. On average a 24% decrease in total delay (mainline plus ramp) at low truck percentage and a 19% decrease in delay at high truck percentage conditions resulted from ramp metering.
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The effect of heterogeneous environments upon the dynamics of invasion and the eradication or control of invasive species is poorly understood, although it is a major challenge for biodiversity conservation. Here, we first investigate how the probability and time for invasion are affected by spatial heterogeneity. Then, we study the effect of control program strategies (e.g. species specificity, spatial scale of action, detection and eradication efficiency) on the success and time of eradication. We find that heterogeneity increases both the invasion probability and the time to invasion. Heterogeneity also reduces the probability of eradication but does not change the time taken for successful eradication. We confirm that early detection of invasive species reduces the time until eradication, but we also demonstrate that this is true only if the local control action is sufficiently efficient. The criterion of removal efficiency is even more important for an eradication program than simply ensuring control effort when the invasive species is not abundant.
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The current study proposes a new procedure for separately estimating slope change and level change between two adjacent phases in single-case designs. The procedure eliminates baseline trend from the whole data series prior to assessing treatment effectiveness. The steps necessary to obtain the estimates are presented in detail, explained, and illustrated. A simulation study is carried out to explore the bias and precision of the estimators and compare them to an analytical procedure matching the data simulation model. The experimental conditions include two data generation models, several degrees of serial dependence, trend, level and/or slope change. The results suggest that the level and slope change estimates provided by the procedure are unbiased for all levels of serial dependence tested and trend is effectively controlled for. The efficiency of the slope change estimator is acceptable, whereas the variance of the level change estimator may be problematic for highly negatively autocorrelated data series.
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Despite the considerable evidence showing that dispersal between habitat patches is often asymmetric, most of the metapopulation models assume symmetric dispersal. In this paper, we develop a Monte Carlo simulation model to quantify the effect of asymmetric dispersal on metapopulation persistence. Our results suggest that metapopulation extinctions are more likely when dispersal is asymmetric. Metapopulation viability in systems with symmetric dispersal mirrors results from a mean field approximation, where the system persists if the expected per patch colonization probability exceeds the expected per patch local extinction rate. For asymmetric cases, the mean field approximation underestimates the number of patches necessary for maintaining population persistence. If we use a model assuming symmetric dispersal when dispersal is actually asymmetric, the estimation of metapopulation persistence is wrong in more than 50% of the cases. Metapopulation viability depends on patch connectivity in symmetric systems, whereas in the asymmetric case the number of patches is more important. These results have important implications for managing spatially structured populations, when asymmetric dispersal may occur. Future metapopulation models should account for asymmetric dispersal, while empirical work is needed to quantify the patterns and the consequences of asymmetric dispersal in natural metapopulations.
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As a result of forensic investigations of problems across Iowa, a research study was developed aimed at providing solutions to identified problems through better management and optimization of the available pavement geotechnical materials and through ground improvement, soil reinforcement, and other soil treatment techniques. The overall goal was worked out through simple laboratory experiments, such as particle size analysis, plasticity tests, compaction tests, permeability tests, and strength tests. A review of the problems suggested three areas of study: pavement cracking due to improper management of pavement geotechnical materials, permeability of mixed-subgrade soils, and settlement of soil above the pipe due to improper compaction of the backfill. This resulted in the following three areas of study: (1) The optimization and management of earthwork materials through general soil mixing of various select and unsuitable soils and a specific example of optimization of materials in earthwork construction by soil mixing; (2) An investigation of the saturated permeability of compacted glacial till in relation to validation and prediction with the Enhanced Integrated Climatic Model (EICM); and (3) A field investigation and numerical modeling of culvert settlement. For each area of study, a literature review was conducted, research data were collected and analyzed, and important findings and conclusions were drawn. It was found that optimum mixtures of select and unsuitable soils can be defined that allow the use of unsuitable materials in embankment and subgrade locations. An improved model of saturated hydraulic conductivity was proposed for use with glacial soils from Iowa. The use of proper trench backfill compaction or the use of flowable mortar will reduce the potential for developing a bump above culverts.