30 results on '"Olejarczyk A"'
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2. The Use of the XGBoost and Kriging Methods in the Prediction of the Microstructure of CGI Cast Iron
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Łukasz Sztangret, Izabela Olejarczyk-Wożeńska, Krzysztof Regulski, Grzegorz Gumienny, and Barbara Mrzygłód
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compacted graphite iron ,machine learning ,artificial neural networks ,kriging ,xgboost ,Technology (General) ,T1-995 - Abstract
Compacted Graphite Iron (CGI), is a unique casting material characterized by its graphite form and extensive matrix contact surface. This type of cast iron has a tendency towards direct ferritization and possesses a complex set of intriguing properties. The use of data mining methods in modern foundry material development facilitates the achievement of improved product quality parameters. When designing a new product, it is always necessary to have a comprehensive understanding of the influence of alloying elements on the microstructure and consequently on the properties of the analyzed material. Empirical studies allow for a qualitative assessment of the above-mentioned relationships, but it is the use of intelligent computational techniques that allows for the construction of an approximate model of the microstructure and, consequently, precise predictions. The formulated prognostic model supports technological decisions during the casting design phase and is considered as the first step in the selection of the appropriate material type.
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- 2023
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3. La categoría de riesgo ambiental y las experiencias del habitar en un municipio de la cuenca media del Matanza-Riachuelo
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Romina Olejarczyk
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experiencias del habitar ,riesgo ambiental ,cuenca matanza-riachuelo ,municipio de almirante brown ,autoridad de la cuenca matanza-riachuelo ,Geography. Anthropology. Recreation ,Anthropology ,GN1-890 - Abstract
En este artículo me propongo poner en diálogo al “riesgo ambiental”, como categoría ordenadora de las relocalizaciones en el marco de la política de saneamiento de la cuenca Matanza-Riachuelo, con las experiencias del habitar de los vecinos/as que vivían junto a los arroyos en el partido de Almirante Brown y que han sido recientemente relocalizados. En principio, las experiencias del habitar junto al arroyo coinciden con lo que la Autoridad de la Cuenca Matanza Riachuelo define como “riesgo ambiental”, a la vez que desbordan esta definición. La vida junto al arroyo involucra padecimiento y disfrute, el deseo de relocalizarse para no inundarse más y el reconocimiento de habitar un territorio autoproducido que se deja con tristeza. La información y los relatos que aquí presento surgen de un trabajo de campo que vengo desarrollando en dicho municipio desde el año 2019, que consiste en la observación participante en instancias de intervención territorial y en la realización de entrevistas.
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- 2023
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4. Ile wiemy o mieszkankach wsi? Krytyczny przegląd stanu badań nad kobietami wiejskimi w Polsce
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Katarzyna Olejarczyk
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kobieta wiejska ,feminizm ,teoria interseckjonalna ,intersekcjonalność ,Ethnology. Social and cultural anthropology ,GN301-674 ,Folklore ,GR1-950 - Abstract
Niniejszy artykuł omawia stan polskich badań nad kobietami wiejskimi z okresu od 1990 r. do dziś. Przedstawiono tu nie tylko tematykę publikowanych opracowań, ale także zwrócono uwagę na trendy metodologiczne w naukowych eksploracjach zagadnienia. Głównym celem pracy jest dostrzeżenie niedostatków i luk w literaturze przedmiotu oraz zaprezentowanie możliwych perspektyw i narzędzi badawczych, których wprowadzenie umożliwi dokładniejsze zbadanie zagadnienia codzienności kobiet ze wsi.
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- 2023
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5. Modelling of Plastic Flow Behaviour of Metals in the Hot Deformation Process Using Artificial Intelligence Methods
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B. Mrzygłód, A. Łukaszek-Sołek, I. Olejarczyk-Wożeńska, and K. Pasierbiewicz
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adaptive neuro-fuzzy inference system ,rheological model ,inconel 718 ,hot deformation ,Technology (General) ,T1-995 - Abstract
Hot deformation of metals is a widely used process to produce end products with the desired geometry and required mechanical properties. To properly design the hot forming process, it is necessary to examine how the tested material behaves during hot deformation. Model studies carried out to characterize the behaviour of materials in the hot deformation process can be roughly divided into physical and mathematical simulation techniques. The methodology proposed in this study highlights the possibility of creating rheological models for selected materials using methods of artificial intelligence, such as neuro-fuzzy systems. The main goal of the study is to examine the selected method of artificial intelligence to know how far it is possible to use this method in the development of a predictive model describing the flow of metals in the process of hot deformation. The test material was Inconel 718 alloy, which belongs to the family of austenitic nickel-based superalloys characterized by exceptionally high mechanical properties, physicochemical properties and creep resistance. This alloy is hardly deformable and requires proper understanding of the constitutive behaviour of the material under process conditions to directly enable the optimization of deformability and, indirectly, the development of effective shaping technologies that can guarantee obtaining products with the required microstructure and desired final mechanical properties. To be able to predict the behaviour of the material under non-experimentally tested conditions, a rheological model was developed using the selected method of artificial intelligence, i.e. the Adaptive Neuro-Fuzzy Inference System (ANFIS). The source data used in these studies comes from a material experiment involving compression of the tested alloy on a Gleeble 3800 thermo-mechanical simulator at temperatures of 900, 1000, 1050, 1100, 1150oC with the strain rates of 0.01 - 100 s-1 to a constant true strain value of 0.9. To assess the ability of the developed model to describe the behaviour of the examined alloy during hot deformation, the values of yield stress determined by the developed model (ANFIS) were compared with the results obtained experimentally. The obtained results may also support the numerical modelling of stress-strain curves.
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- 2022
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6. Region-specific complexity of the intracranial EEG in the sleeping human brain
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Elzbieta Olejarczyk, Jean Gotman, and Birgit Frauscher
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Medicine ,Science - Abstract
Abstract As the brain is a complex system with occurrence of self-similarity at different levels, a dedicated analysis of the complexity of brain signals is of interest to elucidate the functional role of various brain regions across the various stages of vigilance. We exploited intracranial electroencephalogram data from 38 cortical regions using the Higuchi fractal dimension (HFD) as measure to assess brain complexity, on a dataset of 1772 electrode locations. HFD values depended on sleep stage and topography. HFD increased with higher levels of vigilance, being highest during wakefulness in the frontal lobe. HFD did not change from wake to stage N2 in temporo-occipital regions. The transverse temporal gyrus was the only area in which the HFD did not differ between any two vigilance stages. Interestingly, HFD of wakefulness and stage R were different mainly in the precentral gyrus, possibly reflecting motor inhibition in stage R. The fusiform and parahippocampal gyri were the only areas showing no difference between wakefulness and N2. Stages R and N2 were similar only for the postcentral gyrus. Topographical analysis of brain complexity revealed that sleep stages are clearly differentiated in fronto-central brain regions, but that temporo-occipital regions sleep differently.
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- 2022
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7. Application of Artificial Neural Networks in the Analysis of Mechanisms Destroying Forging Tools
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M. Hawryluk, B. Mrzygłód, Z. Gronostajski, M. Głowacki, and I. Olejarczyk-Wożeńska
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decision support system ,durability of forging tools ,artificial neural network ,loss of material ,wear ,Mining engineering. Metallurgy ,TN1-997 ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
This article discusses the results of studies using the developed artificial neural networks in the analysis of the occurrence of the four main mechanisms destroying the selected forging tools subjected to five different surface treatment variants (nitrided layer, pad welded layer and three hybrid layers, i.e. AlCrTiSiN, Cr/CrN and Cr/AlCrTiN). Knowledge of the forging tool durability, needed in the process of artificial neural network training, was included in the set of training data (about 800 records) derived from long-term comprehensive research carried out under industrial conditions. Based on this set, neural networks with different architectures were developed and the results concerning the intensity of the occurrence of thermal-mechanical fatigue, abrasive wear, mechanical fatigue and plastic deformation were generated for each type of the applied treatment relative to the number of forgings, pressure, friction path and temperature.
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- 2020
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8. El riesgo ambiental como categoría para relocalizar a la población de los arroyos en el municipio de Almirante Brown
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Romina Olejarczyk
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cuenca matanza-riachuelo ,relocalizaciones ,riesgo ambiental ,política pública ,versiones ,Geography. Anthropology. Recreation ,Geography (General) ,G1-922 - Abstract
En este artículo reflexiono sobre el riesgo ambiental como categoría oficial que fundamenta y orienta los procesos de relocalización de población de la cuenca Matanza-Riachuelo. Esta categoría, con sus singulares definiciones, ha sido utilizada para crear diversos indicadores, los que han permitido recolectar datos territoriales e incluso producir mapas oficiales. Pero el riesgo ambiental también es la categoría que, por excelencia, fundamenta a la intervención estatal en esta política pública. A su vez, también opera como una categoría nativa presente en el discurso de los actores de esta política pública, tanto en la voz de los decisores como en la de los habitantes de los arroyos. Me propongo, entonces, dar cuenta de esa multiplicidad de sentidos producidos en torno a la noción de riesgo ambiental en las trincheras de esta política pública, desde una perspectiva etnográfica.
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- 2023
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9. Fault Diagnosing of Cycloidal Gear Reducer Using Statistical Features of Vibration Signal and Multifractal Spectra
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Iwona Komorska, Krzysztof Olejarczyk, Andrzej Puchalski, Marcin Wikło, and Zbigniew Wołczyński
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cycloidal gearbox ,diagnostics ,multifractal analysis ,Chemical technology ,TP1-1185 - Abstract
The article presents a method for diagnosing cycloidal gear damage on a laboratory stand. The damage was simulated by removing the sliding sleeves from two adjacent external pins of the cycloidal gearbox. Damage to the sliding sleeves may occur under operating conditions and can lead to the destruction of the gear unit. Hence, early detection is essential. Signals from torque sensors, rotational speed sensors and vibration acceleration sensors of input and output shafts for various rotational speeds and transmission loads were recorded. The frequency analysis of these signals was carried out. Due to the fluctuation of the rotational speed, the frequency spectrum gives an approximate picture and is not useful in detecting this type of damage. The statistical characteristics of the signal were determined. However, only statistical moments of higher orders, such as kurtosis, are sensitive to the tested damage. Therefore, the use of multifractal analysis of the vibration signal using the wavelet leader method (WLMF) was considered. Then log-cumulants of the multifractal spectrum were selected as the new signal features.
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- 2023
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10. Commentary: Is So-Called 'Split Alpha' in EEG Spectral Analysis a Result of Methodological and Interpretation Errors?
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Elzbieta Olejarczyk and Aleksander Sobieszek
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split alpha peak ,EEG ,spectral analysis ,Fourier transform ,instantaneous frequency ,Empirical Wavelet Transform ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Published
- 2021
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11. Functional Source Separation-Identified Epileptic Network: Analysis Pipeline
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Elzbieta Olejarczyk, Filippo Zappasodi, Lorenzo Ricci, Annalisa Pascarella, Giovanni Pellegrino, Luca Paulon, Giovanni Assenza, and Franca Tecchio
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focal epilepsy ,EEG ,transcranial Direct Current Stimulation (tDCS) ,Functional Source Separation (FSS) ,Higuchi Fractal Dimension (HFD) ,Directed Transfer Function (DTF) ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
This proof-of-concept (PoC) study presents a pipeline made by two blocks: 1. the identification of the network that generates interictal epileptic activity; and 2. the study of the time course of the electrical activity that it generates, called neurodynamics, and the study of its functional connectivity to the other parts of the brain. Network identification is achieved with the Functional Source Separation (FSS) algorithm applied to electroencephalographic (EEG) recordings, the neurodynamics quantified through signal complexity with the Higuchi Fractal Dimension (HFD), and functional connectivity with the Directed Transfer Function (DTF). This PoC is enhanced by the data collected before and after neuromodulation via transcranial Direct Current Stimulation (tDCS, both Real and Sham) in a single drug-resistant epileptic person. We observed that the signal complexity of the epileptogenic network, reduced in the pre-Real, pre-Sham, and post-Sham, reached the level of the rest of the brain post-Real tDCS. DTF changes post-Real tDCS were maintained after one month. The proposed approach can represent a valuable tool to enhance understanding of the relationship between brain neurodynamics characteristics, the effects of non-invasive brain stimulation, and epileptic symptoms.
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- 2022
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12. Conflictos (y ausencia de conflictos) en las relocalizaciones del Matanza-Riachuelo. Reflexiones preliminares en un municipio de la cuenca media
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Romina Olejarczyk
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cuenca matanza-riachuelo ,relocalizaciones ,cuenca media ,conflictos ,política pública ,Geography (General) ,G1-922 - Abstract
En este artículo reflexiono sobre los conflictos que se suscitan en las relocalizaciones de la cuenca Matanza-Riachuelo. La categoría de conflicto –que ha sido ampliamente desarrollada en el campo de las ciencias sociales– opera, a su vez, como un término nativo utilizado, principalmente, por los decisores y ejecutores de esta política pública. Por un lado, esta categoría nativa hace referencia al “gran conflicto” inaugural de la causa: la problemática ambiental en Villa Inflamable. Por otro lado, es utilizada para realizar una distinción entre “territorios conflictivos” o “territorios ausentes de conflictos” con los que, en consecuencia, es posible articular (o no) las acciones de esta política. Presentaré los avances de un incipiente trabajo de campo de corte cualitativo en el municipio de Almirante Brown para dar cuenta de la multiplicidad de conflictos que transcurren en las trincheras de esta política pública.
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- 2021
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13. Statistical Analysis of Graph-Theoretic Indices to Study EEG-TMS Connectivity in Patients With Depression
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Elzbieta Olejarczyk, Adam Jozwik, Vladas Valiulis, Kastytis Dapsys, Giedrius Gerulskis, and Arunas Germanavicius
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transcranial magnetic stimulation ,graph-based EEG connectivity ,depression ,directed transfer function ,k-NN rule based statistical analysis ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
AimThe objective of this work was to demonstrate the usefulness of a novel statistical method to study the impact of transcranial magnetic stimulation (TMS) on brain connectivity in patients with depression using different stimulation protocols, i.e., 1 Hz repetitive TMS over the right dorsolateral prefrontal cortex (DLPFC) (protocol G1), 10 Hz repetitive TMS over the left DLPFC (G2), and intermittent theta burst stimulation (iTBS) consisting of three 50 Hz burst bundle repeated at 5 Hz frequency (G3).MethodsElectroencephalography (EEG) connectivity analysis was performed using Directed Transfer Function (DTF) and a set of 21 indices based on graph theory. The statistical analysis of graph-theoretic indices consisted of a combination of the k-NN rule, the leave-one-out method, and a statistical test using a 2 × 2 contingency table.ResultsOur new statistical approach allowed for selection of the best set of graph-based indices derived from DTF, and for differentiation between conditions (i.e., before and after TMS) and between TMS protocols. The effects of TMS was found to differ based on frequency band.ConclusionA set of four brain asymmetry measures were particularly useful to study protocol- and frequency-dependent effects of TMS on brain connectivity.SignificanceThe new approach would allow for better evaluation of the therapeutic effects of TMS and choice of the most appropriate stimulation protocol.
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- 2021
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14. Characteristics of ADI Ductile Cast Iron with Single Addition of 1.56% Ni
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Mrzygłód B., Kowalski A., Olejarczyk-Wożenska I., Giętka T., and Głowacki M.
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ductile iron ,heat treatment ,the structure of ADI ,ADI properties ,Mining engineering. Metallurgy ,TN1-997 ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
The results of examinations of microstructure and an analysis of its impact on selected mechanical properties of austempered ductile iron (ADI) were presented in the paper. The ADI was produced from the ductile iron containing 1.56% Ni only alloying addition. The effect of the austempering time and temperature on the microstructure and mechanical properties of the examined cast iron was considered. Constant conditions of austenitizing were assumed and six variants of the austempering treatment were adopted. The studyof mechanical properties included a static tensile test, Charpy impact strength test and Brinellhardness measurement.
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- 2017
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15. Mathematical Model of Bainitic Transformation in Austempered Ductile Iron
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Olejarczyk-Wożeńska I., Adrian H., Mrzygłód B., and Głowacki M.
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Modelling of phase transformations ,Austenite - ferrite transformation ,ADI ,TTT diagrams ,Technology (General) ,T1-995 - Abstract
A mathematical model of austenite - bainite transformation in austempered ductile cast iron has been presented. The model is based on a model developed by Bhadeshia [1, 2] for modelling the bainitic transformation in high-silicon steels with inhibited carbide precipitation. A computer program has been developed that calculates the incubation time, the transformation time at a preset temperature, the TTT diagram and carbon content in unreacted austenite as a function of temperature. Additionally, the program has been provided with a module calculating the free energy of austenite and ferrite as well as the maximum driving force of transformation. Model validation was based on the experimental research and literature data. Experimental studies included the determination of austenite grain size, plotting the TTT diagram and analysis of the effect of heat treatment parameters on the microstructure of ductile iron. The obtained results show a relatively good compatibility between the theoretical calculations and experimental studies. Using the developed program it was possible to examine the effect of austenite grain size on the rate of transformation.
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- 2017
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16. Capabilities and Limitations of Using Desktop 3-D Printers in the Laser Sintering Process
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Michał Olejarczyk, Piotr Gruber, and Grzegorz Ziółkowski
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laser sintering (LS) ,desktop 3D printers ,Computed Tomography (CT) ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Almost one-third of the revenues of the Additive Manufacturing (AM) machines market is generated by desktop systems. A new category of such devices are Laser Sintering (LS) machines, in which we can find a few representatives of this group. A growing interest in the use of desktop AM solutions in research and industry is visible, and therefore an evaluation of its capabilities and limitations is desirable. The presented paper focuses on comparing desktop (Sintratec S1; Sinterit Lisa) and industrial (Formiga P110) LS systems. The properties of raw materials were characterized by Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC), as well as by determining the Particle Size Distribution (PSD) and static and dynamic flowability of powder. Laser Sintering commercial sets were characterized by their mechanical properties (tensile strength), surface quality (roughness), as well as by their accuracy and porosity (computed tomography). The conducted test showed significant differences, especially in the case of material properties and manufacturing repeatability. The found differences between desktop and industrial LS systems suggest that the use of a low-budget LS system, especially for the research and production of end-use parts, has to take into account its limitations.
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- 2020
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17. EEG Phase Synchronization in Persons With Depression Subjected to Transcranial Magnetic Stimulation
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Urszula Zuchowicz, Agata Wozniak-Kwasniewska, David Szekely, Elzbieta Olejarczyk, and Olivier David
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EEG ,repetitive transcranial magnetic stimulation ,brain connectivity ,indices based on graph theory ,Phase Locking Value ,major depression disorder ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Aim: The main objective of this work was to study the impact of repetitive Transcranial Magnetic Stimulation (rTMS) treatment on brain activity in 8 patients with major depressive disorder (MDD) and 10 patients with bipolar disorder (BP). Changes due to rTMS stimulation of the left dorsolateral prefrontal cortex (DLPFC) were investigated considering separately responders and non-responders to therapy in each of both groups. The aim of the research is to determine whether non-responders differ from responders suffered from both diseases, as well as if any change occurred due to rTMS across consecutive rTMS sessions.Methods: The graph-theory-based connectivity analysis of non-linearity measure of phase interdependencies—Phase Locking Value (PLV)—was examined from EEG data. The approximately 15-min EEG recordings from each of participants were recorded before and after 1st, 10th, and 20th session, respectively. PLV calculated from data was analyzed using principal graph theory indices (strength and degree) within five physiological frequency bands and in individual channels separately. The impact of rTMS on the EEG connectivity in every group of patients evaluated by PLV was assessed.Results: Each of four groups reacted differently to rTMS treatment. The strength and degree of PLV increased in gamma band in both groups of responders. Moreover, an increase of indices in beta band for BP-responders was observed. While, in MDD-non-responders the indices decreased in gamma band and increased in beta band. Moreover, the index strength was lower in alpha band for BP- non-responders. The rTMS stimulation caused topographically specific changes, i.e., the increase of the activity in the left DLPFC as well as in other brain regions such as right parieto-occipital areas.Conclusions: The analysis of PLV allowed for evaluation of the rTMS impact on the EEG activity in each group of patients. The changes of PLV under stimulation might be a good indicator of response to depression treatment permitting to improve the effectiveness of therapy.
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- 2019
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18. Complexity Analysis of EEG Data in Persons With Depression Subjected to Transcranial Magnetic Stimulation
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Karolina Lebiecka, Urszula Zuchowicz, Agata Wozniak-Kwasniewska, David Szekely, Elzbieta Olejarczyk, and Olivier David
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EEG ,repetitive transcranial magnetic stimulation ,complexity ,Higuchi fractal dimension ,major depression disorder ,bipolar disorder ,Physiology ,QP1-981 - Abstract
Aim: The aim of this work was to study the neurophysiological effect of repetitive transcranial magnetic stimulation (rTMS) applied to the left dorsolateral prefrontal cortex (DLPFC) in 8 patients with major depression disorder (MDD) and 10 patients with bipolar disorder (BP), considering separately responders and non-responders to rTMS therapy in each of both groups.Methods: The Higuchi’s Fractal Dimension (FD) was analyzed from 64-channels EEG signals in five physiological frequency bands and every channel separately. Changes of FD were analyzed before and after 1st, 10th, and 20th session of rTMS.Results: Some differences in response to the rTMS therapy was found across individual groups. In MDD responders, FD decreased in all bands after longer stimulation (20th session). Whereas, in BP non-responders, FD decreased after 1st session in all bands as well as after 10th session in lower frequencies (delta and theta). In MDD non-responders and BP responders FD increased at the beginning of the therapy (1st and 10th session, respectively), but the final FD value did not changed in comparison to the initial FD value, except the FD decrease for theta band in BP responders. Comparison between groups showed a higher FD in MDD responders than in MDD non-responders in every band before as well as after stimulation. In contrast to MDD patients, FD was lower in BP responders than in BP non-responders in higher frequency bands (alpha, beta, and gamma) in both conditions as well as in lower frequency bands (delta and theta) after stimulation. Comparing both groups of responders, FD was lower in MDD than in BP in every band, except alpha. In case of non-responders, FD was higher in BP than in MDD in all bands in both conditions.Conclusion: The results showed that FD may be useful marker for evaluation of the rTMS effectiveness and the therapy progress as well as for group differentiation between MDD and BP or between responders and non-responders. The changes of FD under the influence of rTMS allow to unambiguously conclude whether the effect of stimulation is positive or negative as well as allow to evaluate an optimal time of rTMS.
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- 2018
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19. Reflexiones sobre el proceso de mudanza en las políticas de vivienda
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Romina Olejarczyk
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programas federales ,construcción de barrios ,vecinos ,versiones ,Cities. Urban geography ,GF125 ,Urbanization. City and country ,HT361-384 - Abstract
Analiza la experiencia de mudanza de un grupo de familias en el municipio de Avellaneda, provincia de Buenos Aires, Argentina. La propuesta para este análisis es la de reconstruir y poner en relación las distintas versiones que producen y reproducen los sujetos implicados en la implementación de una política pública, en este caso los Programas Federales de Construcción de Viviendas. Este enfoque relacional nos permitirá indagar en la producción de sentidos en relación con el proceso de mudanza, en tanto un espacio y momento claves en la implementación de las políticas de construcción de viviendas.
- Published
- 2015
20. Effect Of Heat Treatment Parameters On The Formation Of ADI Microstructure With Additions Of Ni, Cu, Mo
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Mrzygłód B., Kowalski A., Olejarczyk-Wożenska I., Adrian H., Głowacki M., and Opaliński A.
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ductile iron ,heat treatment ,the microstructure of ADI ,ADI mechanical properties ,Mining engineering. Metallurgy ,TN1-997 ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Metallographic examinations and mechanical tests were carried out on the ductile iron with additions of Ni, Cu and Mo in as-cast state and after austempering. TTT and CCT diagrams were plotted. The heat treatment was performed in six different variants. Studies included qualitative assessment of the microstructure and testing of mechanical properties such as R0,2, Rm, A, Z, HRC, KC. An analysis of the obtained results was also presented.
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- 2015
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21. Influence of process parameters on the properties of austempered ductile iron (ADI) examined with the use of data mining methods
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D. Wilk-Kołodziejczyk, B. Mrzygłód, K. Regulski, I. Olejarczyk-Wożeńska, and K. Jaśkowiec
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ADI ,mechanical properties ,temperature ,data mining ,cluster analysis ,Mining engineering. Metallurgy ,TN1-997 - Abstract
The article presents opportunities offered by the data mining analysis as applied to studies of the effect of process parameters on the mechanical properties of ADI. The applied methods of regression trees and cluster analysis allow for the detection of relationships between parameters and also allow determination of strength and form of the impact of different factors. The results of this study allow the creation of knowledge bases for systems supporting the decision-making process in technology.
- Published
- 2016
22. The EEG Split Alpha Peak: Phenomenological Origins and Methodological Aspects of Detection and Evaluation
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Elzbieta Olejarczyk, Piotr Bogucki, and Aleksander Sobieszek
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split EEG alpha peaks ,functional brain connectivity ,directed transfer function ,spectral analysis ,average reference ,reference electrode standardization technique (REST) ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Electroencephalographic (EEG) patterns were analyzed in a group of ambulatory patients who ranged in age and sex using spectral analysis as well as Directed Transfer Function, a method used to evaluate functional brain connectivity. We tested the impact of window size and choice of reference electrode on the identification of two or more peaks with close frequencies in the spectral power distribution, so called “split alpha.” Together with the connectivity analysis, examination of spatiotemporal maps showing the distribution of amplitudes of EEG patterns allowed for better explanation of the mechanisms underlying the generation of split alpha peaks. It was demonstrated that the split alpha spectrum can be generated by two or more independent and interconnected alpha wave generators located in different regions of the cerebral cortex, but not necessarily in the occipital cortex. We also demonstrated the importance of appropriate reference electrode choice during signal recording. In addition, results obtained using the original data were compared with results obtained using re-referenced data, using average reference electrode and reference electrode standardization techniques.
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- 2017
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23. Mathematical Model of the Processoof Pearlite Austenitization
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Olejarczyk-Wożeńska I., Adrian H., and Mrzygłód B.
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Modelling ,phase transformations ,TTT diagrams ,Mining engineering. Metallurgy ,TN1-997 ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
The paper presents a mathematical model of the pearlite - austenite transformation. The description of this process uses the diffusion mechanism which takes place between the plates of ferrite and cementite (pearlite) as well as austenite. The process of austenite growth was described by means of a system of differential equations solved with the use of the finite difference method. The developed model was implemented in the environment of Delphi 4. The proprietary program allows for the calculation of the rate and time of the transformation at an assumed temperature as well as to determine the TTT diagram for the assigned temperature range.
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- 2014
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24. La jerarquización de la demanda: un análisis comparativo de procesos de adjudicación de viviendas
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Romina Sonia Olejarczyk and Natalia Gabriela Jauri
- Subjects
adjudicación ,adquisición ,adjudicatarios ,requisitos y criterios ,Fine Arts ,Architecture ,NA1-9428 - Abstract
En este trabajo analizaremos comparativamente los procesos de adjudicación y adquisición de viviendas del Subprograma de urbanización de villas y asentamientos en el Municipio de Avellaneda, y del Programa de radicación, integración y transformación de villas en una villa de la Ciudad de Buenos Aires. Nos interesa observar los criterios que se construyen y las disputas que se generan en torno a la definición de los listados de adjudicatarios. En este sentido nos preguntamos: ¿Cómo se construyen los requisitos para la adjudicación de viviendas? ¿Quiénes participan en su definición? ¿Qué aspectos contemplan y cuáles obliteran? ¿A quiénes incluyen y a quiénes excluyen? ¿Qué disputas se generan en torno a éstos? ¿Cómo son apropiados y re-significados por los sujetos? Nos orientan los siguientes supuestos: estos procesos son una parte clave de la implementación de las políticas y se definen en un escenario de disputas entre actores desigualmente involucrados. El singular recorrido que asuman en cada caso tiene que ver con su inscripción –o no– en un proyecto de urbanización de un sector de la ciudad; con si existen o no criterios y espacios relativamente institucionalizados para su definición. Es necesario indagar además sobre la dimensión espacio-temporal que modelará estos procesos.
- Published
- 2013
- Full Text
- View/download PDF
25. Talleres en el 'mientras tanto': la espera en una política habitacional
- Author
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Romina Sonia Olejarczyk
- Subjects
Programas Federales ,Versiones ,Talleres pre-mudanza ,Urban groups. The city. Urban sociology ,HT101-395 ,City planning ,HT165.5-169.9 - Abstract
En el presente artículo me propongo analizar lo que he denominado como “espacios colectivos de espera” en la implementación de una política pública conocida como Programas Federales de Construcción de Viviendas. Estos espacios colectivos de espera son, ni más ni menos, talleres entre los futuros habitantes de los barrios construidos, profesionales del gobierno local y en algunos casos, también funcionarios. Este recorrido me permitirá dar cuenta de cómo en la interacción cotidiana entre actores, a raíz de la implementación de una política pública como la aquí mencionada, se producen y reproducen versiones que dan cuenta de los diferentes modos de significarla. Por lo tanto, al realizar el análisis de las versiones para el caso de los talleres previos a la mudanza que se llevaron a cabo en un municipio del Área Metropolitana de Buenos Aires, podré identificar y analizar las versiones producidas y reproducidas para esta experiencia en particular. Este artículo forma parte de mi investigación más global que prioriza el análisis de las políticas públicas desde una perspectiva relacional. Para ello, he llevado a cabo un trabajo de campo de corte etnográfico del año 2008 al 2012. Los datos que aquí se mencionan surgen de esta experiencia de investigación.
- Published
- 2017
- Full Text
- View/download PDF
26. Graph-based analysis of brain connectivity in schizophrenia.
- Author
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Elzbieta Olejarczyk and Wojciech Jernajczyk
- Subjects
Medicine ,Science - Abstract
The present study evaluated brain connectivity using electroencephalography (EEG) data from 14 patients with schizophrenia and 14 healthy controls. Phase-Locking Value (PLV), Phase-Lag Index (PLI) and Directed Transfer Function (DTF) were calculated for the original EEG data and following current source density (CSD) transformation, re-referencing using the average reference electrode (AVERAGE) and reference electrode standardization techniques (REST). The statistical analysis of adjacency matrices was carried out using indices based on graph theory. Both CSD and REST reduced the influence of volume conducted currents. The largest group differences in connectivity were observed for the alpha band. Schizophrenic patients showed reduced connectivity strength, as well as a lower clustering coefficient and shorter characteristic path length for both measures of phase synchronization following CSD transformation or REST re-referencing. Reduced synchronization was accompanied by increased directional flow from the occipital region for the alpha band. Following the REST re-referencing, the sources of alpha activity were located at parietal rather than occipital derivations. The results of PLV and DTF demonstrated group differences in fronto-posterior asymmetry following CSD transformation, while for PLI the differences were significant only using REST. The only analysis that identified group differences in inter-hemispheric asymmetry was DTF calculated for REST. Our results suggest that a comparison of different connectivity measures using graph-based indices for each frequency band, separately, may be a useful tool in the study of disconnectivity disorders such as schizophrenia.
- Published
- 2017
- Full Text
- View/download PDF
27. Age-Related Changes in Electroencephalographic Signal Complexity.
- Author
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Filippo Zappasodi, Laura Marzetti, Elzbieta Olejarczyk, Franca Tecchio, and Vittorio Pizzella
- Subjects
Medicine ,Science - Abstract
The study of active and healthy aging is a primary focus for social and neuroscientific communities. Here, we move a step forward in assessing electrophysiological neuronal activity changes in the brain with healthy aging. To this end, electroencephalographic (EEG) resting state activity was acquired in 40 healthy subjects (age 16-85). We evaluated Fractal Dimension (FD) according to the Higuchi algorithm, a measure which quantifies the presence of statistical similarity at different scales in temporal fluctuations of EEG signals. Our results showed that FD increases from age twenty to age fifty and then decreases. The curve that best fits the changes in FD values across age over the whole sample is a parabola, with the vertex located around age fifty. Moreover, FD changes are site specific, with interhemispheric FD asymmetry being pronounced in elderly individuals in the frontal and central regions. The present results indicate that fractal dimension well describes the modulations of brain activity with age. Since fractal dimension has been proposed to be related to the complexity of the signal dynamics, our data demonstrate that the complexity of neuronal electric activity changes across the life span of an individual, with a steady increase during young adulthood and a decrease in the elderly population.
- Published
- 2015
- Full Text
- View/download PDF
28. Fractal dimension of EEG activity senses neuronal impairment in acute stroke.
- Author
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Filippo Zappasodi, Elzbieta Olejarczyk, Laura Marzetti, Giovanni Assenza, Vittorio Pizzella, and Franca Tecchio
- Subjects
Medicine ,Science - Abstract
The brain is a self-organizing system which displays self-similarities at different spatial and temporal scales. Thus, the complexity of its dynamics, associated to efficient processing and functional advantages, is expected to be captured by a measure of its scale-free (fractal) properties. Under the hypothesis that the fractal dimension (FD) of the electroencephalographic signal (EEG) is optimally sensitive to the neuronal dysfunction secondary to a brain lesion, we tested the FD's ability in assessing two key processes in acute stroke: the clinical impairment and the recovery prognosis. Resting EEG was collected in 36 patients 4-10 days after a unilateral ischemic stroke in the middle cerebral artery territory and 19 healthy controls. National Health Institute Stroke Scale (NIHss) was collected at T0 and 6 months later. Highuchi FD, its inter-hemispheric asymmetry (FDasy) and spectral band powers were calculated for EEG signals. FD was smaller in patients than in controls (1.447±0.092 vs 1.525±0.105) and its reduction was paired to a worse acute clinical status. FD decrease was associated to alpha increase and beta decrease of oscillatory activity power. Larger FDasy in acute phase was paired to a worse clinical recovery at six months. FD in our patients captured the loss of complexity reflecting the global system dysfunction resulting from the structural damage. This decrease seems to reveal the intimate nature of structure-function unity, where the regional neural multi-scale self-similar activity is impaired by the anatomical lesion. This picture is coherent with neuronal activity complexity decrease paired to a reduced repertoire of functional abilities. FDasy result highlights the functional relevance of the balance between homologous brain structures' activities in stroke recovery.
- Published
- 2014
- Full Text
- View/download PDF
29. Predicting cognitive state from eye movements.
- Author
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John M Henderson, Svetlana V Shinkareva, Jing Wang, Steven G Luke, and Jenn Olejarczyk
- Subjects
Medicine ,Science - Abstract
In human vision, acuity and color sensitivity are greatest at the center of fixation and fall off rapidly as visual eccentricity increases. Humans exploit the high resolution of central vision by actively moving their eyes three to four times each second. Here we demonstrate that it is possible to classify the task that a person is engaged in from their eye movements using multivariate pattern classification. The results have important theoretical implications for computational and neural models of eye movement control. They also have important practical implications for using passively recorded eye movements to infer the cognitive state of a viewer, information that can be used as input for intelligent human-computer interfaces and related applications.
- Published
- 2013
- Full Text
- View/download PDF
30. Inter-versiones de las políticas sociales. Relatos sobre drogas y viviendas
- Author
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Ana Laura Candil and Romina Sonia Olejarczyk
- Subjects
drogas ,inter-versiones ,política social ,tecnologías de poder ,territorio ,vivienda ,Social Sciences ,Social history and conditions. Social problems. Social reform ,HN1-995 - Abstract
Los actores sociales que son “sujetos objetivizados/homogeneizados” en la política social escrita no siempre lo son en su implementación, dado que la relación Estado-sociedad se dinamiza en las interacciones de los sujetos y los profesionales. El presente artículo hace un recorrido que explora la política social y el trabajo social en el campo de la vivienda y las drogas ilegales. Así mismo, hace referencia a la interpretación de las intervenciones sociales como inter-versiones
- Published
- 2011
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