Search results for " Distortion"
showing 10 items of 154 documents
Mappings of finite distortion: Sharp Orlicz-conditions
2003
We establish continuity, openness and discreteness, and the condition $(N)$ for mappings of finite distortion under minimal integrability assumptions on the distortion.
Mappings of Finite Distortion : Compactness of the Branch Set
2017
We show that an entire branched cover of finite distortion cannot have a compact branch set if its distortion satisfies a certain asymptotic growth condition. We furthermore show that this bound is strict by constructing an entire, continuous, open and discrete mapping of finite distortion which is piecewise smooth, has a branch set homeomorphic to an (n - 2)-dimensional torus and distortion arbitrarily close to the asymptotic bound. Peer reviewed
Minimization of detent force in a 1 kW linear permanent magnet generator for the conversion of sea waves energy: Numerical and experimental validation
2015
Linear permanent magnet generators are widely considered for the direct conversion of energy contained in sea waves [1-3]. Both planar and tubular structures have been proposed [4-6] and all these structures present several advantages: relative high efficiency, simplicity of the structures, high sturdiness. However, as all other linear machines they present some drawbacks: oscillations in the movement, distortion in the generated electromotive force (emf), etc. In this paper we focus our attention on the parasitic oscillations of the translator which are caused by the presence of a high detent force. Detent force is generated by the fact that magnetic energy presents a minimum when the leng…
Instruments, rules, and household debt: the effects of fiscal policy
2015
In this paper, we look at the interplay between the level of household leverage in the economy and fiscal policy, the latter characterised by different combinations of instruments and rules. When the fiscal rule is defined on lump-sum transfers, government spending or consumption taxes, the impact multipliers of transitory fiscal shocks become substantially amplified in an environment of easy access to credit by impatient consumers, regardless of the primary instruments used. However, when the government reacts to debt deviations by raising distortionary taxes on income, labour or capital, the effects of household debt on the size of the impact output multipliers vanish or even reverse, no …
Graphical THD minimization procedure for single phase five-level converters
2017
This paper proposes two graphycal procedure to mitigate h harmonics and to minimize the total harmonic distortion (THD), respectively. The paper considers a five-level inverter and fundamental frequency modulation: it computes the two switching angles able to reduce low order harmonics and able to minimize the THD. Simulation results are obtained and, in order to validate the proposed procedure, an experimental prototype is built and experimental results are carried out. The comparison between simulation and experimental results confirms the accuracy of the proposed graphycal procedure. It is shown that the switching angles to mitigate the third-fifth and the third-fifth-seventh harmonics e…
Harmonic sources detection in power systems via nonactive power measurements according to IEEE Std. 1459–2010: Theoretical approach and ex…
2010
In this paper an enhanced decision-making strategy is presented for the detection of harmonic sources in power systems able to detect also which is the prevailing nature of the disturbance (nonlinearity or unbalance). It makes use of some simple indices, which are evaluated by means of the measurements of some nonactive power quantities, proposed by the authors and derived from the approach of the IEEE Std. 1459–2010. The decision-making rules for the proposed strategy are presented and discussed by means of simulation and experimental tests. The results obtained are presented, showing the effectiveness of the proposed strategy for the detection of the dominant harmonic source upstream or d…
The role of perceptual contrast non-linearities in image transform quantization
2000
Abstract The conventional quantizer design based on average error minimization over a training set does not guarantee a good subjective behavior on individual images even if perceptual metrics are used. In this work a novel criterion for transform coder design is analyzed in depth. Its aim is to bound the perceptual distortion in each individual quantization according to a non-linear model of early human vision. A common comparison framework is presented to describe the qualitative behavior of the optimal quantizers under the proposed criterion and the conventional rate-distortion based criterion. Several underlying metrics, with and without perceptual non-linearities, are used with both cr…
A feedback view of behavioural distortions from perceived public service gaps at ‘street‐level’ policy implementation: The case of unintended outcome…
2020
This paper discusses the limitations and risks associated with the use of output-oriented measures to assess public school performance. In particular, it questions the capability of the performance measures set by external institutions, with respect to schools, to support sustainable educational outcomes. To this end, the ‘street-level bureaucracy’ theory is used in the paper as a basis to analyse the behavioural distortions generated by perceived public service gaps at school level policy implementation. Such unintended behavioural effects are often a major cause of disappointing outcomes when test-based accountability systems are adopted. In the second part of the paper, an insight model …
Mappings of exponentially integrable distortion: Decay of the Jacobian
2018
We establish an integrability result on the reciprocal of the Jacobian determinant for a mapping of exponentially integrable distortion and thus answer a question raised by S. Hencl and P. Koskela.
Jahn–Teller effects in Au25(SR)18
2016
The relationship between oxidation state, structure, and magnetism in many molecules is well described by first-order Jahn–Teller distortions. This relationship is not yet well defined for ligated nanoclusters and nanoparticles, especially the nano-technologically relevant gold-thiolate protected metal clusters. Here we interrogate the relationships between structure, magnetism, and oxidation state for the three stable oxidation states, 1, 0 and +1 of the thiolate protected nanocluster Au25(SR)18. We present the single crystal X-ray structures of the previously undetermined charge state Au25(SR)18+1, as well as a higher quality single crystal structure of the neutral compound Au25(SR)180 . …