1,517 research outputs found
The size and performance of public sector activities in Europe
The obvious difference in the economic performance of countries has led to the question why some countries are so much wealthier than others, and whether the size, the structure, and the organisation of the public sector contribute to cross-country income and growth gaps. Public sector activities may have an effect on overall productivity and growth either directly by the level and changes of productivity within the public sector, or indirectly by triggering off productivity changes in private production. This paper is concerned with the former aspect. It provides an overview of the size and the structure of the public sector in Europe and compares it with the US and Japan. This is related to the more recent empirical literature on public sector performance. After reviewing some of the measurement issues related to public services, the evidence on the size of government and its performance is analysed. The results on industrial countries are not fully conclusive, but seem to attribute more efficiency to smaller rather than to larger governments. Public sector reforms to consolidate the size of government are therefore likely to enhance the sector's own productivity and thereby positively contribute to overall economic performance.public sector size, performance of public sector
Geometric Integrators for Schrödinger Equations
The celebrated Schrödinger equation is the key to understanding the dynamics of
quantum mechanical particles and comes in a variety of forms. Its numerical solution
poses numerous challenges, some of which are addressed in this work.
Arguably the most important problem in quantum mechanics is the so-called harmonic
oscillator due to its good approximation properties for trapping potentials. In
Chapter 2, an algebraic correspondence-technique is introduced and applied to construct
efficient splitting algorithms, based solely on fast Fourier transforms, which
solve quadratic potentials in any number of dimensions exactly - including the important
case of rotating particles and non-autonomous trappings after averaging by Magnus
expansions. The results are shown to transfer smoothly to the Gross-Pitaevskii
equation in Chapter 3. Additionally, the notion of modified nonlinear potentials is
introduced and it is shown how to efficiently compute them using Fourier transforms.
It is shown how to apply complex coefficient splittings to this nonlinear equation and
numerical results corroborate the findings.
In the semiclassical limit, the evolution operator becomes highly oscillatory and standard
splitting methods suffer from exponentially increasing complexity when raising
the order of the method. Algorithms with only quadratic order-dependence of the
computational cost are found using the Zassenhaus algorithm. In contrast to classical
splittings, special commutators are allowed to appear in the exponents. By construction,
they are rapidly decreasing in size with the semiclassical parameter and can be
exponentiated using only a few Lanczos iterations. For completeness, an alternative
technique based on Hagedorn wavepackets is revisited and interpreted in the light of
Magnus expansions and minor improvements are suggested. In the presence of explicit
time-dependencies in the semiclassical Hamiltonian, the Zassenhaus algorithm
requires a special initiation step. Distinguishing the case of smooth and fast frequencies,
it is shown how to adapt the mechanism to obtain an efficiently computable
decomposition of an effective Hamiltonian that has been obtained after Magnus expansion,
without having to resolve the oscillations by taking a prohibitively small
time-step.
Chapter 5 considers the Schrödinger eigenvalue problem which can be formulated as
an initial value problem after a Wick-rotating the Schrödinger equation to imaginary
time. The elliptic nature of the evolution operator restricts standard splittings to
low order, ¿ < 3, because of the unavoidable appearance of negative fractional timesteps
that correspond to the ill-posed integration backwards in time. The inclusion
of modified potentials lifts the order barrier up to ¿ < 5. Both restrictions can be
circumvented using complex fractional time-steps with positive real part and sixthorder
methods optimized for near-integrable Hamiltonians are presented.
Conclusions and pointers to further research are detailed in Chapter 6, with a special
focus on optimal quantum control.Bader, PK. (2014). Geometric Integrators for Schrödinger Equations [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/38716TESISPremios Extraordinarios de tesis doctorale
Didaktisch-methodische Perspektiven auf nationale Stereotype: Facetten einer unterrichtspraktischen Konkretisierung
In this article we address a central theme of how lessons in German and Danish that sensitise students for national clichés (stereotypes) can be designed. By introducing the training aids that support a language teaching about German and Danish clichés, we move concrete materials and results from teaching lessons in German and Danish schools as well as other educational institutions in the centre of our focus. Programmatically, a didactic-methodical model of sensitisation, reflexion and criticism is explained. Theoretical and terminological differentiations on the subject areas stereotype and stereotyping and to dimensions of stereotypes refer to the topical linguistic and social-psychological research discussion. Thoughts on the verisi-militude of national stereotypes from a didactic view decide the contribution
Comparison of random‐effects meta‐analysis models for the relative risk in the case of rare events - a simulation study
Pooling the relative risk (RR) across studies investigating rare events, for example, adverse events, via meta‐analytical methods still presents a challenge to researchers. The main reason for this is the high probability of observing no events in treatment or control group or both, resulting in an undefined log RR (the basis of standard meta‐analysis). Other technical challenges ensue, for example, the violation of normality assumptions, or bias due to exclusion of studies and application of continuity corrections, leading to poor performance of standard approaches. In the present simulation study, we compared three recently proposed alternative models (random‐effects [RE] Poisson regression, RE zero‐inflated Poisson [ZIP] regression, binomial regression) to the standard methods in conjunction with different continuity corrections and to different versions of beta‐binomial regression. Based on our investigation of the models' performance in 162 different simulation settings informed by meta‐analyses from the Cochrane database and distinguished by different underlying true effects, degrees of between‐study heterogeneity, numbers of primary studies, group size ratios, and baseline risks, we recommend the use of the RE Poisson regression model. The beta‐binomial model recommended by Kuss (2015) also performed well. Decent performance was also exhibited by the ZIP models, but they also had considerable convergence issues. We stress that these recommendations are only valid for meta‐analyses with larger numbers of primary studies. All models are applied to data from two Cochrane reviews to illustrate differences between and issues of the models. Limitations as well as practical implications and recommendations are discussed; a flowchart summarizing recommendations is provided
Optimal design of the Wilcoxon-Mann-Whitney-test
In scientific research, many hypotheses relate to the comparison of two
independent groups. Usually, it is of interest to use a design (i.e., the
allocation of sample sizes and for fixed ) that maximizes
the power of the applied statistical test. It is known that the two-sample
t-tests for homogeneous and heterogeneous variances may lose substantial power
when variances are unequal but equally large samples are used. We demonstrate
that this is not the case for the non-parametric Wilcoxon-Mann-Whitney-test,
whose application in biometrical research fields is motivated by two examples
from cancer research. We prove the optimality of the design in case of
symmetric and identically shaped distributions using normal approximations and
show that this design generally offers power only negligibly lower than the
optimal design for a wide range of distributions. Please cite this paper as
published in the Biometrical Journal (https://doi.org/10.1002/bimj.201600022)
ML-Based Teaching Systems: A Conceptual Framework
As the shortage of skilled workers continues to be a pressing issue, exacerbated by demographic change, it is becoming a critical challenge for organizations to preserve the knowledge of retiring experts and to pass it on to novices. While this knowledge transfer has traditionally taken place through personal interaction, it lacks scalability and requires significant resources and time. IT-based teaching systems have addressed this scalability issue, but their development is still tedious and time-consuming. In this work, we investigate the potential of machine learning (ML) models to facilitate knowledge transfer in an organizational context, leading to more cost-effective IT-based teaching systems. Through a systematic literature review, we examine key concepts, themes, and dimensions to better understand and design ML-based teaching systems. To do so, we capture and consolidate the capabilities of ML models in IT-based teaching systems, inductively analyze relevant concepts in this context, and determine their interrelationships. We present our findings in the form of a review of the key concepts, themes, and dimensions to understand and inform on ML-based teaching systems. Building on these results, our work contributes to research on computer-supported cooperative work by conceptualizing how ML-based teaching systems can preserve expert knowledge and facilitate its transfer from SMEs to human novices. In this way, we shed light on this emerging subfield of human-computer interaction and serve to build an interdisciplinary research agenda
An Integration of Predictive Coding and Phenomenological Approaches
Current theories in the framework of hierarchical predictive coding propose
that positive symptoms of schizophrenia, such as delusions and hallucinations,
arise from an alteration in Bayesian inference, the term inference referring
to a process by which learned predictions are used to infer probable causes of
sensory data. However, for one particularly striking and frequent symptom of
schizophrenia, thought insertion, no plausible account has been proposed in
terms of the predictive-coding framework. Here we propose that thought
insertion is due to an altered experience of thoughts as coming from
“nowhere”, as is already indicated by the early 20th century phenomenological
accounts by the early Heidelberg School of psychiatry. These accounts
identified thought insertion as one of the self-disturbances (from German:
“Ichstörungen”) of schizophrenia and used mescaline as a model-psychosis in
healthy individuals to explore the possible mechanisms. The early Heidelberg
School (Gruhle, Mayer-Gross, Beringer) first named and defined the self-
disturbances, and proposed that thought insertion involves a disruption of the
inner connectedness of thoughts and experiences, and a “becoming sensory” of
those thoughts experienced as inserted. This account offers a novel way to
integrate the phenomenology of thought insertion with the predictive coding
framework. We argue that the altered experience of thoughts may be caused by a
reduced precision of context-dependent predictions, relative to sensory
precision. According to the principles of Bayesian inference, this reduced
precision leads to increased prediction-error signals evoked by the neural
activity that encodes thoughts. Thus, in analogy with the prediction-error
related aberrant salience of external events that has been proposed
previously, “internal” events such as thoughts (including volitions, emotions
and memories) can also be associated with increased prediction-error signaling
and are thus imbued with aberrant salience. We suggest that the individual’s
attempt to explain the aberrant salience of thoughts results in their
interpretation as being inserted by an alien agent, similarly to the emergence
of delusions in response to the aberrant salience of sensory stimuli
Interdisciplinary research on the example of Seoul (Republic of Korea)
The dissertation project is presented to describe, evaluate and investigate the megacity Seoul by several interdisciplinary and city-morphologic aspects, picking the city’s green belt out as a central element of the urban development. The closed and unique green belt is hypothesised to structure the metropolitan area of Seoul and to have especially sustainable effects on the urban development. A literature research outlines four parameters: city structure, mobility, environmental quality and urban quality. The city structures of Seoul and the planning history are described in a first step, followed by the recording of the environmental quality within the megacity region, as well as, the mobility by means of different parameters. The interpretation of these three working steps will lead, in conjunction with the results of qualitative and quantitative public-opinion polls on quality of life, to new findings about the importance of the green belt. The results to be anticipated will be summarised as suggestions on green-belt policy to transfer them to the urban development of other fast growing regions
Low daily dose of 3 mg monacolin K from RYR reduces the concentration of LDL-C in a randomized, placebo-controlled intervention
AbstractHypercholesterolemia and elevated homocysteine concentrations are associated with cardiovascular risk. Previous studies have demonstrated a cholesterol-lowering effect of red yeast rice (RYR) supplements which contained 5 to 10 mg of monacolin K. We hypothesized that the intake of a low monacolin K dose may likewise reduce low-density lipoprotein–cholesterol (LDL-C) and other plasma lipids. In secondary analyses, we tested the homocysteine lowering effect of folic acid, which was also included in the study preparation. Therefore, we conducted a randomized, double-blind, and placebo-controlled intervention study. One hundred forty-two nonstatin-treated participants with hypercholesterolemia (LDL-C ≥ 4.14 ≤ 5.69 mmol/L) were randomized to the supplement group with RYR or the placebo group. Participants of the supplement group consumed 3 mg monacolin K and 200 μg folic acid per day. A significant (P < .001) reduction of LDL-C (−14.8%), total cholesterol (−11.2%), and homocysteine (−12.5%) was determined in the supplement group after 12 weeks. A total of 51% of the participants treated with RYR achieved the limit of LDL-C <4.14 mmol/L advised and 26% reached the threshold level of homocysteine <10 μmol/L. No significant changes were exhibited within the placebo group. Other parameters remained unchanged and no intolerances or serious adverse events were observed. In conclusion, we demonstrated that a low dose of daily 3 mg monacolin K from RYR reduces the concentration of LDL-C; a risk factor for cardiovascular diseases
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