747 research outputs found
Technical Note: Approximate Bayesian parameterization of a process-based tropical forest model
No full textInverse parameter estimation of process-based models is a long-standing
problem in many scientific disciplines. A key question for inverse parameter
estimation is how to define the metric that quantifies how well model
predictions fit to the data. This metric can be expressed by general cost or
objective functions, but statistical inversion methods require a particular
metric, the probability of observing the data given the model parameters,
known as the likelihood.
For technical and computational reasons, likelihoods for process-based
stochastic models are usually based on general assumptions about variability
in the observed data, and not on the stochasticity generated by the model.
Only in recent years have new methods become available that allow the
generation of likelihoods directly from stochastic simulations. Previous
applications of these approximate Bayesian methods have concentrated on
relatively simple models. Here, we report on the application of a
simulation-based likelihood approximation for FORMIND, a parameter-rich
individual-based model of tropical forest dynamics.
We show that approximate Bayesian inference, based on a parametric likelihood
approximation placed in a conventional Markov chain Monte Carlo (MCMC)
sampler, performs well in retrieving known parameter values from virtual
inventory data generated by the forest model. We analyze the results of the
parameter estimation, examine its sensitivity to the choice and aggregation
of model outputs and observed data (summary statistics), and demonstrate the
application of this method by fitting the FORMIND model to field data from an
Ecuadorian tropical forest. Finally, we discuss how this approach differs
from approximate Bayesian computation (ABC), another method commonly used to
generate simulation-based likelihood approximations.
Our results demonstrate that simulation-based inference, which offers
considerable conceptual advantages over more traditional methods for inverse
parameter estimation, can be successfully applied to process-based models of
high complexity. The methodology is particularly suitable for heterogeneous
and complex data structures and can easily be adjusted to other model types,
including most stochastic population and individual-based models. Our study
therefore provides a blueprint for a fairly general approach to parameter
estimation of stochastic process-based models
Identiteter och världsbild : "hårdkokt" skriftbruk i Thorsten Jonssons noveller
No full textidentity and worldview – “hard-boiled” writing in Thorsten Jonsson’s short storiesThis article deals with the Swedish author Thorsten Jonsson (1910–50) and his first short story collection Som det brukar vara (1939) [‘As it usually is’]. The nar- rative represents a new modernistic literary trend in Swedish prose in the 1930s. i take my starting point in Burgess & ivanič’s (2010) theories of the act of writing involving many different identities, and particularly what Burgess & ivanič iden- tify as the discursive self. By contemporary readers and critics the discursive self in the short story collection was often connected with an American hard-boiled literary ideal, often linked to ernest Hemingway’s writings. in this article i dis- cuss the common textual features of the two authors’ first collections, but also the differences that emerge when looking through the linguistic surface. The analysis shows that Thorsten Jonsson’s discursive self is based upon a northern Swedish culture, Hemingway’s on an urban American one. </p
Measures of excess liquidity
No full textThe aim of this note is to provide an overview of various measures of excess liquidity, which can be defined as the deviation of the actual stock of money from an estimated equilibrium level. Given their dynamic nature, the excess liquidity measures under review are - in the light of long and variable lags of monetary policy - very useful tools to quantify future price pressures. In addition, excess liquidity measures consider inflation as a purely monetary phenomenon: neither the output gap nor liquidity gap - although both form an integral part of the concepts - an be held responsible for inducing a persistent rise in the price level. Despite strong theoretical support, the usefulness of excess liquidity measures depends on the stability of money demand, a question which has of course to be answered in the realm of empirical research. --P-star,excess liquidity,monetary policy,ECB
A case for money in the ECB monetary policy strategy
No full textOne major outcome of the review of the ECBs two pillar monetary policy strategy, which was published on 8 May 2003, has been the de facto downgrading of the hitherto prominent role assigned to the stock of money. According to the authors judgement, however, there is a strong theoretical and empirical rationale for the ECB monetary policy to pay close attention to the information content of money in the form of M3. However, the authors argue the ECB should make use of the so-called price gap or real money gap concept rather than the reference value as the latter runs the risk of giving misleading policy recommendations and compromising the indicator quality of the stock of money. Making use of M3 seems all the more rational as currently no better inflation indicator appears to exist in providing inflation forecasts in the euro area. --P-star,real money gap,excess liquidity,ECB
Why is unemployment so high in Bulgaria?
No full textThe author seeks to determine the main factors behind poor labor market outcomes in Bulgaria. Unemployment in Bulgaria is high and of long duration. The accumulation of the unemployment stock has been caused by relatively high inflows into unemployment coupled with limited outflows. These features of the Bulgarian labor market are typical of other transition economies in Central Europe and exploring their sources is of broad interest. The author focuses on determinants of and constraints to job creation. He uses data on job creation and job destruction from a survey of employment in all registered firms. He finds that the source of large inflows into unemployment is intensive enterprise restructuring associated with a high pace of job reallocation. However, job creation falls short of job destruction. Three main factors account for the limited job creation and hiring, and thus for low outflows from unemployment: a) The unfriendly business environment, reflected by a low rate of new firm formation, and a relatively small, small and medium enterprise sector. b) Labor market rigidities, including excessive hiring and firing costs. c) Skill and spatial mismatches brought about by enterprise restructuring, as well as low skills and marginalization of the long-term unemployed who cannot successfully compete for new jobs. The author recommends a three pronged strategy to improve labor market performance: (1) removing bureaucratic constraints to entry and expansion of firms; (2) enhancing labor market flexibility through lowering hiring and firing costs; and (3) improving the educational system so as to equip workers with broad and portable skills.Environmental Economics&Policies,Labor Policies,Labor Markets,Public Health Promotion,Health Monitoring&Evaluation,Environmental Economics&Policies,Labor Markets,Health Monitoring&Evaluation,Labor Standards,Banks&Banking Reform
Neighborhood diversity of large trees shows independent species patterns in a mixed dipterocarp forest in Sri Lanka
No full textInteractions among neighbors influence plant performance and should create spatial patterns in local community structure. In order to assess the role of large trees in generating spatial patterns in local species richness we used the individual species-area relationship (ISAR) to evaluate the species richness of trees of different size classes (and dead trees) in neighborhoods with varying size around large trees of different focal species. To reveal signals of species interactions we compared the ISAR function of the individuals of focal species with that of randomly selected nearby locations. We expected that large trees should strongly affect the community structure of smaller trees in their neighborhood, but that these effects should fade away with increasing size class. Unexpectedly we found that only few focal species showed signals of species interactions with trees of the different size classes and that this was less likely for less abundant focal species. However, the few and relatively weak depa..
Zeitschrift für die Geschichte des Oberrheins
No full textInhaltsverzeichnis Band 157 (2009) Eberhard Dobler, Spätmerowingischer Adel in Südalamannien. Christoph Rolker, „Eine Behörde - ein Buch“? Studien zu den Konstanzer Gemächtebüchern. Thorsten Huthwelker, Elizabet de Baviere (†1478) – eine Tochter Pfalzgraf Ludwigs III. als Vertraute der heiligen Colette und die geplante Gründung eines Klarissenkonvents in Heidelberg. Volkhard Huth, Der ,Oberrheinische Revolutionär’. Freigelegte Lebensspuren und Wirkungsfelder eines „theokratischen Terroristen”..
Improvements to the Secure Construction and Utilization of Greedy Embeddings in Friend-to-Friend Overlays
No full textRouting based on greedy network embeddings enables efficient and privacy-preserving routing in overlays where connectivity is restricted to mutually trusted nodes. In previous works, we proposed security enhancements to the embedding and routing procedures to protect against denial-of-service attacks by malicious overlay participants. In this work, we propose an improved timeout scheme to reduce the stabilization overhead of secure tree maintenance in response to node failures and malicious behavior. Furthermore, we present an attack-resistant packet replication scheme that leverages alternative paths discovered during routing
Living with Wolves
No full textWith their return to Germany, wolves leave their traces in personal feelings, in the atmospheres of rural landscapes and even in the sentiments and moods that govern political arenas. Thorsten Gieser explores the role of affects, emotions, moods and atmospheres in the emerging coexistence between humans and wolves. Bridging the gap between anthropology and ethology, the author literally walks in the tracks of wolves to follow their affective agency in a more-than-human society. In nuanced analyses, he shows how wolves move, irritate and excite us, offering answers to the primary question: What does it feel like to coexist with these large predators
Living with Wolves: Affects, Feelings and Sentiments in Human-Wolf-Coexistence
No full textWith their return to Germany, wolves leave their traces in personal feelings, in the atmospheres of rural landscapes and even in the sentiments and moods that govern political arenas. Thorsten Gieser explores the role of affects, emotions, moods and atmospheres in the emerging coexistence between humans and wolves. Bridging the gap between anthropology and ethology, the author literally walks in the tracks of wolves to follow their affective agency in a more-than-human society. In nuanced analyses, he shows how wolves move, irritate and excite us, offering answers to the primary question: What does it feel like to coexist with these large predators
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