Brain connectivity measures: computation and comparison

In this article computation and comparison of causality measures which are used in determination of brain connectivity patterns is investigated. Main analyzed examples included published computation and comparisons of Directed Transfer Function ‐ DTF and Partial Directed Coherence ‐ PDC. It proved that serious methodology mistakes were involved in measure computations and comparisons. It is shown that the neighborhood of zero is of accented importance in such evaluations and that the issues of semantic stability have to be treated with more attention. Published results on the relationship of these two important measures are partly unstable with small changes of zero threshold and pictures of involved brain structures deduced from the cited articles have to be corrected. Analysis of the operators involved in evaluation and comparisons is given with suggestions for their improvement and complementary additional actions

Measures and Metrics of Biological Signals

The concept of biological signals is becoming broader. Some of the challenges are: searching for inner and structural characteristics; selecting appropriate modeling to enhance perceived properties in the signals; extracting the representative components, identifying their mathematical correspondents; and performing necessary transformations in order to obtain form for subtle analysis, comparisons, derived recognition, and classification. There is that unique moment when we correspond the adequate mathematical structures to the observed phenomena. It allows application of various mathematical constructs, transformations and reconstructions. Finally, comparisons and classifications of the newly observed phenomena often lead to enrichment of the existing models with some additional structurality. For a specialized context the modeling takes place in a suitable set of mathematical representations of the same kind, a set of models M, where the mentioned transformations take place. They are used for determination of structures M, where mathematical finalization processes are preformed. Normalized representations of the initial content are measured in order to determine the key invariants (characterizing characteristics). Then, comparisons are preformed for specialized or targeted purposes. The process converges to the measures and distance measurements in the space M. Thus, we are dealing with measure and metric spaces, gaining opportunities that have not been initially available. Obviously, the different aspects in the research or diagnostics will demand specific spaces. In our practice we faced a large variety of problems in analysis of biological signals with very rich palette of measures and metrics. Even when a unique phenomena are observed for slightly different aspects of their characteristics, the corresponding measurements differ, or are refinements of the initial structures. Certain criteria need to be fulfilled. Namely, characterization and semantic stability. The small changes in the structures have to induce the small changes in measures and metrics. We offer a collection of the models that we have been involved in, together with the problems we met and their solutions, with representative visualizations

Koncept brodskih elektroenergetskih sustava u brodova s dinamičkim pozicioniranjem

Brodovi s ugrađenim sustavom za dinamičko pozicioniranje zadržavaju poziciju na kojoj se nalaze, pod određenim unaprijed zadanim uvjetima (valovi, vjetar, morska struja). Pritom se u ovisnosti o nivoima složenosti sustava dinamičkog pozicioniranja (DP1, DP2, DP3) postavljaju različiti zahtjevi prema ugrađenim elektroenergetskim sustavima. Osnovni zahtjev koji se postavlja je da u slučaju jedne greške, brod ne smije izgubiti poziciju. To uključuje sustave proizvodnje električne energije, sustav distribucije električne energije, te potrošače za pomoćne strojarske sustave koji izravno ili neizravno sudjeluju u održavanju pozicije broda. Rad se zasniva na projektu „Broda za polaganje kabela“, Gr. 507 sa sustavom dinamičkog pozicioniranja DP2”, koji se gradi u Uljanik Brodogradilištu i trebao bi biti predan naručitelju polovicom 2015 god

Numerical simulation of the plunge stage in friction stir welding alloys EN AW 2024 T 351 and EN AW 7049A T 652

Tema ovog rada je proučavanje faze probijanja korišćenjem numeričkog modela. Analizirana je promena temperature i sile probijanja u toku faze probijanja postupka zavarivanja trenjem mešanjem za legure aluminijuma visoke čvrstoće EN AW 2024 T 351 i EN AW 7049A T 652, pri različitim brzinama rotacije alata. Numerički rezultati pokazuju da maksimalne temperature u postupku zavarivanja trenjem mešanjem mogu biti povećane sa povećanjem brzine rotacije alata i da su temperature manje od temperature topljenja materijala koji se zavaruje. Pri istim brzinama rotacije alata, registrovana je veća temperatura kod legure aluminijuma EN AW 2024 T 351 i veća sila probijanja - otpor materijala kod legure EN AW 7049A T 652. Sa povećanjem brzine rotacije alata, sila probijanja može biti smanjena. Trodimenzionalni model konačnih elemenata faze probijanja je razvijen korišćenjem ABAQUS programskog paketa za proučavanje termomehaničkih procesa faze probijanja. Spregnuti termo-mehanički model konačnih elemenata koristi proizvoljnu Lagranž-Ojlerovu formulaciju, Džonson-Kukov zakon i Kulonov zakon trenja. U ovoj analizi se temperatura, pomjeranje i mehaničke reakcije posmatraju istovremeno. Generisanje toplote u postupku zavarivanja trenjem mešanjem se može podeliti na tri dela:generisanje toplote trenjem od čela alata, generisanje toplote trenjem od trna alata i generisanje toplote od plastičnih deformacija u blizini trna alata.This paper investigates the plunge stage using numerical modeling. Change of temperature and plunge force have been analyzed during the plunge stage of the FSW procedure for high hardness aluminum alloys EN AW 2024 T 351 and EN AW 7049A T 652, at different speed of tool rotation. Numerical results indicate that the maximum temperature in the FSW process can be increased with the increase of the rotational speed and that temperature is lower than the melting point of the welding material. Higher temperature was registered at the aluminum alloy EN AW 2024 T 351 at the same speed of tool rotation, and higher plunge force - resistance of material was registered at the alloy EN AW 7049A T 652. When the rotational speed is increased, the plunge force can be reduced. A three-dimensional finite element model (FEM) of the plunge stage was developed using the commercial code ABAQUS to study the thermo-mechanical processes involved during the plunge stage. A coupled thermo-mechanical 3D FE model using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law and the Coulomb's Law of friction. In this analysis, temperature, displacement and mechanical responses are determined simultaneously. The heat generation in FSW can be divided into three parts: frictional heat generated by the tool shoulder, frictional heat generated by the tool pin, and heat generated by material plastic deformation near the pin region

Numerical simulation of the plunge stage in friction stir welding alloys EN AW 2024 T 351 and EN AW 7049A T 652

Tema ovog rada je proučavanje faze probijanja korišćenjem numeričkog modela. Analizirana je promena temperature i sile probijanja u toku faze probijanja postupka zavarivanja trenjem mešanjem za legure aluminijuma visoke čvrstoće EN AW 2024 T 351 i EN AW 7049A T 652, pri različitim brzinama rotacije alata. Numerički rezultati pokazuju da maksimalne temperature u postupku zavarivanja trenjem mešanjem mogu biti povećane sa povećanjem brzine rotacije alata i da su temperature manje od temperature topljenja materijala koji se zavaruje. Pri istim brzinama rotacije alata, registrovana je veća temperatura kod legure aluminijuma EN AW 2024 T 351 i veća sila probijanja - otpor materijala kod legure EN AW 7049A T 652. Sa povećanjem brzine rotacije alata, sila probijanja može biti smanjena. Trodimenzionalni model konačnih elemenata faze probijanja je razvijen korišćenjem ABAQUS programskog paketa za proučavanje termomehaničkih procesa faze probijanja. Spregnuti termo-mehanički model konačnih elemenata koristi proizvoljnu Lagranž-Ojlerovu formulaciju, Džonson-Kukov zakon i Kulonov zakon trenja. U ovoj analizi se temperatura, pomjeranje i mehaničke reakcije posmatraju istovremeno. Generisanje toplote u postupku zavarivanja trenjem mešanjem se može podeliti na tri dela:generisanje toplote trenjem od čela alata, generisanje toplote trenjem od trna alata i generisanje toplote od plastičnih deformacija u blizini trna alata.This paper investigates the plunge stage using numerical modeling. Change of temperature and plunge force have been analyzed during the plunge stage of the FSW procedure for high hardness aluminum alloys EN AW 2024 T 351 and EN AW 7049A T 652, at different speed of tool rotation. Numerical results indicate that the maximum temperature in the FSW process can be increased with the increase of the rotational speed and that temperature is lower than the melting point of the welding material. Higher temperature was registered at the aluminum alloy EN AW 2024 T 351 at the same speed of tool rotation, and higher plunge force - resistance of material was registered at the alloy EN AW 7049A T 652. When the rotational speed is increased, the plunge force can be reduced. A three-dimensional finite element model (FEM) of the plunge stage was developed using the commercial code ABAQUS to study the thermo-mechanical processes involved during the plunge stage. A coupled thermo-mechanical 3D FE model using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law and the Coulomb's Law of friction. In this analysis, temperature, displacement and mechanical responses are determined simultaneously. The heat generation in FSW can be divided into three parts: frictional heat generated by the tool shoulder, frictional heat generated by the tool pin, and heat generated by material plastic deformation near the pin region

Forensics of Features in the Spectra of Biological Signals

Semantics of spectroscopy of biological signals and criteria of semantic stability are the initial issues in this article. Motivated with some semantic confusion related to our cooperation and elsewhere, we are investigating the circumstances in which spectroscopic features have direct meaning and when that is questioned. Two problems arise immediately: what are additional ways in signal analysis through spectroscopy and generalizations and how can we learn more on the processes investigated. Our aim is to enrich the available methods and tools providing researchers with additional ways in detailed analysis of biological signal spectra and help to overcome some of difficulties. We show some of our work in signal spectroscopy, aiming to signal forensics and to uncover more details in the investigated signals, discuss invariants of involved operators, addressing the WYSIWYG - “what you see is what you get” method property. Ziggurat like structures of spectral features, parallel multiple resolution spectroscopy, application of image processing tools on spectral features and second order spectroscopy take place in the investigation of fine spectrogram feature details. Automatized feature detection and comparisons techniques, are used. These set of procedures represent our improvements and contribution to this important method for analysis of biological signals, illustrated on the examples from our practice, processed with our implementations

HAMILTON ANXIETY SCALE (HAMA) IN INFERTILE WOMEN WITH ENDOMETRIOSIS AND ITS CORRELATION WITH MAGNESIUM LEVELS IN PERITONEAL FLUID

Background: Endometriosis is a complex disease that can result in substantial morbidity, including chronic pain, dysmenorrhea and dyspareunia. There are contradictory reports regarding the connection between acute and chronic stress and magnesium levels in body fluids. Subjects and methods: A prospective study included 87 patients undergoing laparoscopy. The study group included 40 women with endometriosis and the control group consisted of 47 women with other causes of infertility. The levels of fright were determined using HAMA scale. The measurements of Mg levels were performed using biochemical analyzer “Monarch Plus”. Results: One day before the operation, HAMA score was 9.54 ±7.34 in the women with endometriosis, and 6.69 ± 5.51 in the women without endometriosis. The morning before the operation, HAMA score was 8.64 ± 8.10 in the women with endometriosis, and 4.29±2.29 in the women without endometriosis. The second postoperative day, HAMA score was 8.96±7.60 in the women with endometriosis and 6.92±5.16 in the women without endometriosis. Higher HAMA score in the women with endometriosis, in comparison with the control group, in all three time periods has been found, but the differences were not statistically significant (p>0.05). A negative correlation between the concentration of Mg in peritoneal fluid and HAMA score was found in the control group (p<0.01). Conclusions. In infertile women without endometriosis a correlation between Mg concentration in peritoneal fluid and HAMA score was found. No such correlation was found in the women with endometriosis, possibly due to a systemic disorder in endometriosis that might affect Mg transport through the cell membrane

HAMILTON ANXIETY SCALE (HAMA) IN INFERTILE WOMEN WITH ENDOMETRIOSIS AND ITS CORRELATION WITH MAGNESIUM LEVELS IN PERITONEAL FLUID

Background: Endometriosis is a complex disease that can result in substantial morbidity, including chronic pain, dysmenorrhea and dyspareunia. There are contradictory reports regarding the connection between acute and chronic stress and magnesium levels in body fluids. Subjects and methods: A prospective study included 87 patients undergoing laparoscopy. The study group included 40 women with endometriosis and the control group consisted of 47 women with other causes of infertility. The levels of fright were determined using HAMA scale. The measurements of Mg levels were performed using biochemical analyzer “Monarch Plus”. Results: One day before the operation, HAMA score was 9.54 ±7.34 in the women with endometriosis, and 6.69 ± 5.51 in the women without endometriosis. The morning before the operation, HAMA score was 8.64 ± 8.10 in the women with endometriosis, and 4.29±2.29 in the women without endometriosis. The second postoperative day, HAMA score was 8.96±7.60 in the women with endometriosis and 6.92±5.16 in the women without endometriosis. Higher HAMA score in the women with endometriosis, in comparison with the control group, in all three time periods has been found, but the differences were not statistically significant (p>0.05). A negative correlation between the concentration of Mg in peritoneal fluid and HAMA score was found in the control group (p<0.01). Conclusions. In infertile women without endometriosis a correlation between Mg concentration in peritoneal fluid and HAMA score was found. No such correlation was found in the women with endometriosis, possibly due to a systemic disorder in endometriosis that might affect Mg transport through the cell membrane