Review of individualized current flow modeling studies for transcranial electrical stimulation. - In: Journal of neuroscience research, ISSN 1097-4547, Bd. 101 (2023), 4, S. 405-423, insges. 19 S.
There is substantial intersubject variability of behavioral and neurophysiological responses to transcranial electrical stimulation (tES), which represents one of the most important limitations of tES. Many tES protocols utilize a fixed experimental parameter set disregarding individual anatomical and physiological properties. This one-size-fits-all approach might be one reason for the observed interindividual response variability. Simulation of current flow applying head models based on available anatomical data can help to individualize stimulation parameters and contribute to the understanding of the causes of this response variability. Current flow modeling can be used to retrospectively investigate the characteristics of tES effectivity. Previous studies examined, for example, the impact of skull defects and lesions on the modulation of current flow and demonstrated effective stimulation intensities in different age groups. Furthermore, uncertainty analysis of electrical conductivities in current flow modeling indicated the most influential tissue compartments. Current flow modeling, when used in prospective study planning, can potentially guide stimulation configurations resulting in individually effective tES. Specifically, current flow modeling using individual or matched head models can be employed by clinicians and scientists to, for example, plan dosage in tES protocols for individuals or groups of participants. We review studies that show a relationship between the presence of behavioral/neurophysiological responses and features derived from individualized current flow models. We highlight the potential benefits of individualized current flow modeling.
https://doi.org/10.1002/jnr.25154
Application of capacitive sensors and controlled injection pressure to minimize void formation in resin transfer molding. - In: Polymer composites, ISSN 1548-0569, Bd. 44 (2023), 3, S. 1658-1671
Void formation as a result of irregular resin flow at the flow front is discussed and a practical method for reducing void formation during resin transfer molding (RTM) is introduced. In this study, a sensor system is developed for in situ measurement of resin velocity inside a closed cavity. Assisted by the acquired data, a resin injection system is augmented to automatically adjust the injection pressure and achieve a uniform flow front velocity. It is proven, that the developed system is suited to monitor the resin flow front and is able to sufficiently control flow velocity of a linear flow front. Test specimen produced by this method show significantly reduced void contents in comparison to a common resin transfer molding process.
https://doi.org/10.1002/pc.27195
Steep resonance of parametrically excited active MEMS cantilevers for dynamic mode in Atomic Force Microscopy. - In: Proceedings in applied mathematics and mechanics, ISSN 1617-7061, Bd. 22 (2023), 1, e202200230, S. 1-6
Ongoing developments in nanotechnology demand higher spatial resolution and thus, higher amplitude sensitivity in Atomic Force Microscopy (AFM). In this work, active cantilevers with integrated sensor and actuator systems are parametrically excited using a novel, analog feedback circuit. With that it is possible to adapt the strength and sign of a cubic nonlinearity which provides a bound to the amplitudes in resonance operation. The system response shows steeper resonance curves and therefore higher amplitude sensitivities compared to forced excited cantilevers. Theoretical findings are validated experimentally.
https://doi.org/10.1002/pamm.202200230
Hamiltonicity of graphs perturbed by a random regular graph. - In: Random structures & algorithms, ISSN 1098-2418, Bd. 62 (2023), 4, S. 857-886
https://doi.org/10.1002/rsa.21122
Hamiltonicity of graphs perturbed by a random geometric graph. - In: Journal of graph theory, ISSN 1097-0118, Bd. 103 (2023), 1, S. 12-22
We study Hamiltonicity in graphs obtained as the union of a deterministic n-vertex graph H with linear degrees and a d-dimensional random geometric graph G d (n, r) for any d ≥ 1. We obtain an asymptotically optimal bound on the minimum r for which a.a.s. H ∪ G d (n, r) is Hamiltonian. Our proof provides a linear time algorithm to find a Hamilton cycle in such graphs.
https://doi.org/10.1002/jgt.22901
Relatively bounded perturbations of J-non-negative operators. - In: Complex analysis and operator theory, ISSN 1661-8262, Bd. 17 (2023), 1, 14, insges. 30 S.
We improve known perturbation results for self-adjoint operators in Hilbert spaces and prove spectral enclosures for diagonally dominant J-self-adjoint operator matrices. These are used in the proof of the central result, a perturbation theorem for J-non-negative operators. The results are applied to singular indefinite Sturm-Liouville operators with Lp-potentials. Known bounds on the non-real eigenvalues of such operators are improved.
https://doi.org/10.1007/s11785-022-01263-2
On the complexity of finding well-balanced orientations with upper bounds on the out-degrees. - In: Journal of combinatorial optimization, ISSN 1573-2886, Bd. 45 (2023), 1, 30, S. 1-14
https://doi.org/10.1007/s10878-022-00962-y
Communication science in Türkiye: how communication research and education developed over the years. - In: Publizistik, ISSN 1862-2569, Bd. 68 (2023), 1, S. 89-108
In Türkiye, communication science falls under the category of social sciences and is regarded as an interdisciplinary scientific field focused on empirical research. The field is influenced by communication science developments of the West in terms of developing theories and methodology, and it faces challenges when it comes to the systematisation of theories and research methods created by different research traditions; their critical evaluation, development, and the failure to put theories to practical use. In order to ascertain the present condition of the field, this article explores the institutionalisation of communication science at universities and its potential tendencies as an academic field of study, its research trends, and the characteristics of communication science studies.
https://doi.org/10.1007/s11616-022-00766-4
Sensitivity analysis of combinatorial optimization problems using evolutionary bilevel optimization and data mining. - In: Annals of mathematics and artificial intelligence, ISSN 1573-7470, Bd. 91 (2023), 2/3, S. 309-328
Sensitivity analysis in general deals with the question of how changes in input data of a model affect its output data. In the context of optimization problems, such an analysis could, for instance, address how changes in capacity constraints affect the optimal solution value. Although well established in the domain of linear programming, sensitivity analysis approaches for combinatorial optimization problems are model-specific, limited in scope and not applicable to practical optimization problems. To overcome these limitations, Schulte et al. developed the concept of bilevel innovization. By using evolutionary bilevel optimization in combination with data mining and visualization techniques, bilevel innovization provides decision-makers with deeper insights into the behavior of the optimization model and supports decision-making related to model building and configuration. Originally introduced in the field of evolutionary computation, most recently bilevel innovization has been proposed as an approach to sensitivity analysis for combinatorial problems in general. Based on previous work on bilevel innovization, our paper illustrates this concept as a tool for sensitivity analysis by providing a comprehensive analysis of the generalized assignment problem. Furthermore, it is investigated how different algorithms for solving the combinatorial problem affect the insights gained by the sensitivity analysis, thus evaluating the robustness and reliability of the sensitivity analysis results.
https://doi.org/10.1007/s10472-022-09827-w
A note on the invertibility of the Gabor frame operator on certain modulation spaces. - In: The journal of Fourier analysis and applications, ISSN 1531-5851, Bd. 29 (2023), 1, 3, S. 1-20
We consider Gabor frames generated by a general lattice and a window function that belongs to one of the following spaces: the Sobolev space $$V_1 = H^1(\mathbb {R}^d)$$, the weighted $$L^2$$-space $$V_2 = L_{1 + |x|}^2(\mathbb {R}^d)$$, and the space $$V_3 = \mathbb {H}^1(\mathbb {R}^d) = V_1 \cap V_2$$consisting of all functions with finite uncertainty product; all these spaces can be described as modulation spaces with respect to suitable weighted $$L^2$$spaces. In all cases, we prove that the space of Bessel vectors in $$V_j$$is mapped bijectively onto itself by the Gabor frame operator. As a consequence, if the window function belongs to one of the three spaces, then the canonical dual window also belongs to the same space. In fact, the result not only applies to frames, but also to frame sequences.
https://doi.org/10.1007/s00041-022-09980-0