arXiv subjects

Gejza Dohnal

Publications and source records attributed to Gejza Dohnal.

4 recordsLinked to original sources

arXiv2021

A Letter on Convergence of In-Parameter-Linear Nonlinear Neural Architectures with Gradient Learnings

This letter summarizes and proves the concept of bounded-input bounded-state (BIBS) stability for weight convergence of a broad family of in-parameter-linear nonlinear neural architectures as it generally applies to a broad family of incremental gradient learning algorithms. A practical BIBS convergence condition results from the derived proofs for every individual learning point or batches for real-time applications.

cs.LG↗

arXiv2019

Robust Adaptive Control Charts

In statistical process control, procedures are applied that require relatively strict conditions for their use. If such assumptions are violated, these methods become inefficient, leading to increased incidence of false signals. Therefore, a robust version of control charts is sought to be less sensitive with respect to a breach of normality and independence in measurements. Robust control charts, however, usually increase the delay in the detection of assignable causes. This negative effect can, to some extent, be removed with the aid of an adaptive approach.

stat.OT↗

arXiv2018

On a critical artifact in the quantum yield methodology

For the development and optimization of novel light emitting materials, such as fluorescent proteins, dyes and semiconductor quantum dots (QDs), a reliable and robust analysis of the emission efficiency is crucial. The emission efficiency is typically quantified by the photoluminescence quantum yield (QY), defined by the ratio of emitted to absorbed photons. We show that this methodology suffers from a flaw that leads to underestimated QY values, presenting as a 'parasitic absorption'. This effect has not been described and/or corrected for in literature and is present already under common experimental conditions, therefore, it is highly relevant for a number of published studies. To correct for this effect, we propose a modification to the methodology and a correction procedure.

physics.app-ph↗

arXiv2018

Limits of emission quantum yield determination

The development of new fluorescent molecules and dyes requires precise determination of their emission efficiency, which ultimately defines the potential of the developed materials. For this, the photoluminescence quantum yield (QY) is commonly used, given by the ratio of the number of emitted and absorbed photons, where the latter can be determined by subtraction of the transmitted signal by the sample and by a blank reference. In this work, we show that when the measurement uncertainty is larger than 10% of the absorptance of the sample, the QY distribution function becomes skewed, which can result in underestimated QY values by more than 200%. We demonstrate this effect in great detail by simulation of the QY methodology that implements an integrating sphere, which is widely used commercially and for research. Based on our simulations, we show that this effect arises from the non-linear propagation of the measurement uncertainties. The observed effect applies to the measurement of any variable defined as Z=X/Y, with Y=U-V, where X, U and V are random, normally distributed parameters. For this general case, we derive the analytical expression and quantify the range in which the effect can be avoided.

physics.ins-det↗