Model-based stagnation pressure control in a supersonic wind tunnel

Upravljanje parametrima strujanja u aerotunelima je oblast intenzivnog istraživanja poslednjih godina, sa ciljem poboljšanja kvaliteta i efikasnosti rada aerotunelskih instalacija. Ovaj rad predstavlja pokušaj da se doprinese boljem razumevanju upravljanja zaustavnim pritiskom u supersoničnim instalacijama prekidnog dejstva. Razmotrena je strategija upravljanja zaustavnim pritiskom u aerotunelu T-38 Vojnotehničkog instituta u Beogradu. Poboljšani matematički model supersoničnih aerotunelskih instalacija je predložen i primenjen na aerotunel T-38. Tačnost sa kojom matematički model predviđa odziv instalacije u uslovima supersoničnog strujanja demonstrirana je poređenjem podataka iz simulacija i eksperimenata. Matematički model je upotrebljen za uvođenje izmenjenog algoritma upravljanja u polazni upravljački sistem aerotunela T-38. Aerotunelski eksperimenti su potvrdili predviđanja modela u pogledu smanjenja vremena uspostavljanja strujanja i povećanja raspoloživog vremena za merenje, čime je postignuto značajno poboljšanje efikasnosti rada aerotunela.The flow parameters control in wind tunnels is an area of intense research in recent years, with the aim of improving quality and efficiency of the wind tunnel operation. In this paper, an attempt is made to contribute to a better understanding of the stagnation pressure control in supersonic blowdown-type facilities. The stagnation pressure control strategy in the VTI Belgrade T-38 wind tunnel is discussed. An improved mathematical model for a supersonic wind tunnel is suggested and applied to the T-38 facility. Comparisons of simulation and experimental data are made to demonstrate accurate prediction of the facility response in supersonic flow conditions by the mathematical model. The model is used to incorporate a modified feedforward control in the original T-38 wind tunnel control system. The actual wind tunnel tests confirm model-predicted decrease of flow stabilization time and increase of available measurement time, bringing significant improvement in the wind tunnel operation efficiency

Model-based stagnation pressure control in a supersonic wind tunnel

Upravljanje parametrima strujanja u aerotunelima je oblast intenzivnog istraživanja poslednjih godina, sa ciljem poboljšanja kvaliteta i efikasnosti rada aerotunelskih instalacija. Ovaj rad predstavlja pokušaj da se doprinese boljem razumevanju upravljanja zaustavnim pritiskom u supersoničnim instalacijama prekidnog dejstva. Razmotrena je strategija upravljanja zaustavnim pritiskom u aerotunelu T-38 Vojnotehničkog instituta u Beogradu. Poboljšani matematički model supersoničnih aerotunelskih instalacija je predložen i primenjen na aerotunel T-38. Tačnost sa kojom matematički model predviđa odziv instalacije u uslovima supersoničnog strujanja demonstrirana je poređenjem podataka iz simulacija i eksperimenata. Matematički model je upotrebljen za uvođenje izmenjenog algoritma upravljanja u polazni upravljački sistem aerotunela T-38. Aerotunelski eksperimenti su potvrdili predviđanja modela u pogledu smanjenja vremena uspostavljanja strujanja i povećanja raspoloživog vremena za merenje, čime je postignuto značajno poboljšanje efikasnosti rada aerotunela.The flow parameters control in wind tunnels is an area of intense research in recent years, with the aim of improving quality and efficiency of the wind tunnel operation. In this paper, an attempt is made to contribute to a better understanding of the stagnation pressure control in supersonic blowdown-type facilities. The stagnation pressure control strategy in the VTI Belgrade T-38 wind tunnel is discussed. An improved mathematical model for a supersonic wind tunnel is suggested and applied to the T-38 facility. Comparisons of simulation and experimental data are made to demonstrate accurate prediction of the facility response in supersonic flow conditions by the mathematical model. The model is used to incorporate a modified feedforward control in the original T-38 wind tunnel control system. The actual wind tunnel tests confirm model-predicted decrease of flow stabilization time and increase of available measurement time, bringing significant improvement in the wind tunnel operation efficiency

Alterations of medial prefrontal cortex bioelectrical activity in experimental model of isoprenaline-induced myocardial infarction

Background Clinical and animal studies have found that anxiety and depression are significantly more common after acute myocardial infarction (AMI). The medial prefrontal cortex (PFC) has a dual role: in higher brain functions and in cardiovascular control, making it a logical candidate for explaining the perceived bidirectional heart-brain connection. We used parallel Electrocardiography (ECG) and Electrocorticography (ECoG) registration to investigate AMI-induced changes in medial PFC bioelectrical activity in a rat model of AMI. Materials and methods Adult male Wistar albino rats were used in the study. Gold-plated recording electrodes were implanted over the frontal cortex for ECoG recording. ECG was recorded via two holter electrodes attached on the skin of the back fixed in place by a jacket. Induction of AMI was performed by isoprenaline (150 mg/kg, i.p.). ECoG and ECG signals were registered at baseline, during 3 hours after isoprenaline administration and at 24 hours after isoprenaline administration. Results Significant increases of theta, alpha, and beta electroencephalographic (EEG) band power were observed in different time intervals after isoprenaline administration. Significant increase of theta band peak frequency was also observed during the first hour after isoprenaline administration. No statistically significant differences in band-power activity were found between the pre-isoprenaline measurements and 24 hours after administration. Conclusion Our results demonstrate significant increases in EEG band power of alpha beta and theta bands during isoprenaline-induced AMI model. These are the first findings to connect heart damage during isoprenaline- induced AMI to disturbances in the cortical bioelectrical activity. © 2020 Vorkapić et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The study was supported by Ministry of Science Education and Technological Development of Serbia, Grant No. 175032 and 175016. The TECNALIA provided support in the form of salary for author MI, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of this author are articulated in the ‘author contributions’ section. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Design criterion to select adequate control algorithm for electro-hydraulic actuator applied to rocket engine flexible nozzle thrust vector control under specific load

Rad razmatra problematiku kako na najbolji način izabrati algoritam upravljanja za elektro- hidraulični aktuator sa definisanim opterećenjem. Polazi se od pretpostavke idealnog algoritma upravljanja koji se prilagođava stvarnoj konfiguraciji elektrohidrauličnog aktuatora i definisanom opterećenju. Razmatra se netipično fleksibilno opterećenje, viskozoelastično, sa znatnim histerezisom koji dodatno zavisi od vremena odnosno temperature. Predlažu se dva načina modelovanja opterećenja i prikazuje se koliko opcije modelovanja opterećenja utiču na stvarni odziv aktuatorskog sistema. U razmatranom slučaju glavni poremećaj je spoljna sila prouzrokovana realnim oscilacijama sile potiska.The paper presents the challenge of finding the best criterion in selecting adequate control algorithm for electro-hydraulic actuator with a defined load. The ideal control algorithm that adapts to the actual configuration of electro-hydraulic actuator and defined load is used as an initial assumption. Atypical flexible load that is viscose-elastic, with a significant level of hysteresis that also depends on time and temperature is considered as well. Two types of load modeling approaches are proposed, accompanied by presentation on how load modeling options affect the actual response of an actuator system. The main disturbance, in this case, is considered to be external force generated by thrust force real oscillations

Measurement of the direct damping derivative in roll of the two calibration missile models

U ovom radu opisano je merenje prigušnog derivativa stabilnosti u valjanju u aerotunelu T- 38. Prikazani su rezultati dobijeni na dva kalibraciona modela: Basic Finner Model i Modified Basic Finner Model. Uređaj za merenje derivativa stabilnosti je uređaj sa prinudnim oscilacijama modela i to sa primarnim oscilatornim kretanjem u ravni valjanja. Pobudni moment u valjanju meren je petokomponentnom aerovagom sa mernim trakama. Ova aerovaga je projektovana i izrađena za dinamička aerotunelska merenja. Amplitude i fazni stavovi pobudnog momenta određeni su u frekventnom domenu primenom kros-korelacione metode. Rezultati dobijeni u aerotunelu T-38 upoređeni su sa objavljenim eksperimentalnim rezultatima dobijenim u Arnold Engineering Development Center-von Karman 4ft aerotunelu.Measurement of the direct damping derivative in roll in the T-38 wind tunnel is described in this paper. The T-38 wind tunnel data for the Basic Finner Model and Modified Basic Finner model are shown. The forced oscillation technique was used for these measurements. The roll apparatus for the stability derivatives measurement is a full-model forced oscillation apparatus with primary angular oscillation around a longitudinal axis of the model. The excitation moment in roll was measured with the five- component strain gauge balance. This balance was designed and built for the wind tunnel dynamic measurements. The amplitudes and phase shifts of the excitation moment were calculated in frequency domain by applying cross-correlation technique. The T-38 wind tunnel results are compared with published experimental results of the Arnold Engineering Development Center-von Karman 4ft wind tunnel

A POSSIBLE WAY OF PERFORMING THE STADIUM RACE AT THE FESTIVITY GAMES IN OLYMPIA

The subject of this paper is a complex one, given that it deals with track and field, history, history of art and archeology. Intensive studies in this field began with the renewed Olympic Games in Athens in 1896. The beginning of the new millennium and modern technology have brought the first attempts at animation regarding the possible ways of performing the events at the ancient Olympic Games, among which was the stadium race. The problems that arose with the progress of a one-stade track and field race through a period of 12 centuries at the Festivity Games in Olympia can be solved integrally through aspects of axiological, epistemological and ontological questions, as well as through the experimental method of a possible way of performing the one-stade track and field race, which was represented at the Festivity Games in Olympia. Different analyses, descriptions, hypotheses and views by many authors dealing with the subject of ancient track and field events and way they were performed were the reason for this study in light of a possible way of performing the stadium race. The aim of this study was to define the most authentic way of performing the stadium race at the ancient Olympic Games. Historical and experimental methods were used in this study. Research results indicate that there were differences in this event was performed during the 12 centuries of life of the Festivity Games in Olympia. The research has been justified by an effort to clarify existing scientific hypotheses concerning a possible manner of performing the one-stade race at the ancient Olympic Games.

Precision: A motor capability that defines a successful basketball player

Precision, as a basic motor ability, represents, along with coordination, the least explored area of motorics. Insufficient research of this phenomenon is also true of basketball. Within it, we monitor displays of precision in the most specific of all conditions - during a basketball game. This paper represents a review of research concerning precision, with a brief critical overview of the mentioned phenomenon. Apart from the conclusions, which speak about precision as the basic motor capability (and have been presented as products of speculation and earlier findings), a review of empirical research related to situational precision has also been presented. These studies have been aimed at finding a connection between shot patterns and distance to target; goal visualisation; influence of skeleton dimension on precision. One of the goals of this paper is to point out the significance of precision of players at guard position, which could be a significant selection factor

Wind tunnel measurement quality in testing of a standard model

Tests of standard models serve to confirm the overall accuracy and measurement quality in a wind tunnel facility and to confirm confidence in results obtained. The wide-accepted criteria for evaluation of the wind tunnel measurement quality are based on methodology of a few supposedly identical tests of the standard model. Wind tunnel data uncertainty is being considered in the form of test data repeatability. Based on this methodology the overall reliability of the Serbian trisonic wind tunnel is certified and verified. Test data are also correlated with those from other wind tunnel facilities