Invariance of motor patterns in side-volleyed kick in football

Predmet ove studije je stepen uspešnosti izvođenja bočnog volej udarca u fudbalu u osdnosu na kinematiku lopte i mehaničke uslove izvođenja pokreta. Studija je izrađena sa ciljem da se kod vrhunskih fudbalera odredi, iz aspekta razmene brzine i preciznosti, šema optimizovanja kretanja po kriterijumu efikasnosti i ekonomičnosti bočnog volej udarca. Istraživanje je sprovedeno na uzorku od 30 ispitanika – profesionalnih fudbalera koji su članovi nacionalne selekcije Srbije, i koji nastupaju u inostranim klubovima (FC Chelsea, FC Benfica, FC Genk, FC München 1860, FC Leiria, FC Košice, FC Luch – Energia, FC London City) i Super lige Srbije (FK Crvena zvezda, FK Partizan, FK OFK Beograd). Ispitanici su imali zadatak da izvedu bočni volej udarac gađajući gol loptom koja im je dolazila u tri visine i tri brzine. Uzorak varijabli se sastojao iz dve kriterijumske (brzina i visina lopte) i 25 prediktorskih varijabli. Merenje kinematskih varijabli je izvršeno u hali Fakulteta sporta i fizičkog vaspitanja pomoću 3D infra-crvenog sistema QUALISYS. Dobijeni podaci su obrađeni deskriptivnom i komparativnom statistikom. Utvrđena su dva načina izvođenja bočnog volej udarca u odnosu na brzinu i visinu lopte. Za visoke i brze lopte pokret se izvodi „zamrznutom“ pozicijom segmenata kinetičkog lanca, tj. koristi se relativno simultana kinematička šema. Za niske i spore lopte koristi se otvorena kinematička šema („bič“). Utvrđeno je postojanje promena u kinematičkoj adaptaciji lokomotornog aparata na različite mehaničke uslove izvođenja pokreta bočnog volej udarca. Povećanjem brzine dolazeće lopte povećava se brzina realizacije pokreta i skraćuje egzekutivna faza po trajanju. Dobijeni rezultati ukazuju da se po principu Bernštajnovih sinergija slaganje brzina pojedinačnih segmenata odvija na različit način u odnosu na zadatu brzinu lopte. Potvrđena je generalna teorija upravljanja brzim pokretima u delu koji ukazuje da se fudbaler iz aspekta vizuelne percepcije najmanje adaptira na prebrze i prespore lopte. Postoji direktan uticaj brzine i visine lopte na održanje dinamičke stabilnosti sistema. Postoji sličan način upravljanja pokretom za niske i srednje lopte kada je u pitanju kontrola trajanja...The subject of this study is the degree of success of performing a side kick volley in football compared to the kinematics of the ball and the mechanical conditions of the movement performance. The study has been aimed in order to determine (define), from the aspect of the speed exchange rate and accuracy, the pattern of the optimizing the movement on the criterion of the side kick volley efficiency in the professional football players. The research has been conducted on 30 (thirty) subjects – the professional football players who are the members of the Serbian national team and who play in the foreign clubs (FC Chelsea, FC Benefica,FC Genk, FC München 1860 ,FC Leiria,FC Kosice, FC Luch – Energia, FC London City) and the members of the Serbian Super League ( FC Crvena Zvezda, FC Partizan, FC OFK Beograd). The respondents were asked to perform the side kick volley goal by hitting the ball coming in three (3) heights and three (3) speeds. The sample of the variables consisted of two (2) criteria (the speed and the height of the ball) and 25 predictor variables. The measurement of the kinematic variables has been carried out in the hall of the Faculty of Sport and Physical Education with the 3D infra – red system QUALISYS. The gathered data have been analysed by the descriptive and comparative statistics. Two ways of performing the side kick volley in terms of the speed and the height of the ball have been given. For the high and fast balls the movement is being performed in the frozen position of the kinetic chain segments, i. e. the relatively simultaneous kinematic scheme is being used. For the low and slow balls the open kinematic scheme (“whip”) is being used. The existance of the changes in kinematic adaptation of the locomotor system to different mechanic conditions when performing the side volley shot has been indetified. With (by) the increase of the coming ball speed, the speed of the realization of the movement is being increased and the lasting of the executive phase is being reduces. The results indicate that, by the principle of Bernstein’s synergies, the matching of the speeds of the individual segments has been performed in a a way different from the given speed of the ball. The general theory of the fast movement control, in the section indicating that the football player, from the aspect of visual perception adapts the least to the balls coming too fast or too slow, has been confirmed. There is a direct effect of the speed and height of the ball on the maintenance of the dynamic stability of the system. There is a similar way of managing the movement for the low and medium balls considering the control of the lasting period..

DESIGN OF FIRST ORDER DIFFERENTIATOR WITH PARALLEL ALL-PASS STRUCTURE

In this paper a new method for design of the first order differentiator is presented. The proposed differentiator consists of two parallel branches, i.e. direct path and IIR all-pass filter. The described design method allows one to obtain solution with minimum mean relative error at the desired region by controlling the ratio of phase response extremes. A small relative magnitude error, as well as a low phase error, at low frequencies is condition for good time domain behaviour. The obtained differentiator can be realized by means of only two multipliers, hence being a good choice for real time applications. The proposed solution provides a lower magnitude error than several known differentiators with similar phase error

The concentrations of Fe, Cu and Zn in selected wines from South-East Serbia

Fruits and vegetables constitute the cheapest source of essential trace elements for the majority of people living in developing countries. The Cu, Fe and Zn contents in twenty selected wine samples produced in the South-East region of Serbia were determined by flame atomic absorption spectrometry. The Cu concentrations varied from 0.07 to 0.57 ppm in wines, and the Fe concentrations fluctuated from 2.93 to 36.2 ppm, while the Zn levels were in the range from 0.21 to 0.67 ppm. The established contents of Cu and Zn showed that wines from this part of the world could serve as good dietary sources of the essential trace metals, and the determined values were within the allowed me¬tals levels in wines for human consumption

The Concept of Creating and Designing of Overview Digital Hydrological Atlas Maps within the GIS Project

The paper presents the possibility of drafting and modelling of a part of geographic content of four overview atlas maps of Digital Hydrological Atlas of Serbia (DHAS), scale 1: 5000 000 by using available open access cartographic sources and data, and applying cartographic methods and established steps of GIS digitization. The mapping territory and the approximate DHAS structure have been defined in the paper, as well as the mathematical elements of the overview atlas maps. A way of obtaining new modified overview atlas maps through the GIS integration of various cartographic data representing a part of the territory of the continent of Europe has been presented. The advantages of contemporary cartographic and GIS systems for modelling digital atlases and thematic hydrological atlas maps have been explained

Numerical modelling of concrete-filled steel tubular short columns under axial compression

The paper presents three-dimensional numerical models of short concrete-filled steel tubular circular columns that can successfully describe the column behaviour under axial compression. Several of the most commonly used material models for the steel part and a concrete portion of the column are evaluated in the models. In addition, the paper presents a new proposal for the extension of the Eurocode 2 stress-strain relation to make it suitable for describing the complex behaviour of concrete inside the steel tube. This model overcomes the current limitations of the Eurocode 2 design guide, referring to the limitation for the concrete curve in compression to 3.5‰ strain. The ultimate axial column strength obtained by the proposed model is compared to the ultimate column capacity calculated by a simplified method provided in Eurocode 4. All presented numerical models are validated on a set of experiments from the literature and demonstrate good agreement. The comments about the accuracy of each model are provided, along with the identified limitations

Promene ekscitabilnosti motorne kore udružene sa zamorom mišića kod obolelih od Parkinsonove bolesti

Background/Aim. Transcranial magnetic stimulation (TMS) is a standard technique for noninvasive assessment of changes in central nervous system excitability. The aim of this study was to examine changes in responses to TMS in patients suffering from Parkinson's disease (PD) during sustained submaximal isometric voluntary contraction [60% of maximal voluntary contraction (MVC)] of the adductor pollicis muscle, as well as during a subsequent recovery period. Methods. Cortical excitability was tested by single TMS pulses of twice of the motor threshold intensity applied over the vertex. Testing was carried out during the sustained contraction phase every 10 s before and every 5 s after the endurance point, as well as at rest and during brief 60% MVC contractions before (control), immediately after the sustained contraction, and at 5 min intervals during the recovery period. Results. Although the PD patients could sustain the contraction at the required level for as long period of time as the healthy subjects (though contraction level subsided more rapidly after the endurance point), effects of muscle fatigue on the responses to TMS were different. In contrast to the findings observed in the healthy people where motor evoked potentials (MEP) and EMG silent period (SP) in fatigued muscle gradually diminished during contraction up to the endurance point, and increased thereafter, in the majority of patients no changes occurred in MEP size (peak and area) of the adductor pollicis muscle, either before or after the endurance point. On the other hand, changes in the SP of this muscle differed among the subjects, showing a gradual increase, a decrease or no changes in duration. The trends of changes in both MEP size and SP duration in the musculus brachioradialis varied among the tested PD patients, without any consistent pattern, which was in contrast with the findings in the healthy people where both measures showed a gradual increase from the beginning of the sustained contraction. A complete dissociation between changes in MEP and SP during fatigue was also of note, which differed sharply from the findings in the healthy people in who fatigue induced changes in these measures followed identical patterns. Conclusion. These results in the PD patients suggest the presence of impairment and/or compensatory changes in mechanisms responsible for adaptation of voluntary drive as well as for matching between cortical excitation and inhibition which become manifest in demanding motor tasks such as those imposed by muscle fatigue.Uvod/Cilj. Transkranijalna magnetna stimulacija (TMS) je standardna tehnika za neinvazivnu procenu promena ekscitabilnosti centralnog nervnog sistema. Cilj rada je bio da se prikažu promene odgovora na TMS kod obolelih od Parkinsonove bolesti (PB) za vreme trajanja submaksimalne voljne izometrijske kontrakcije [60% maksimalne voljne kontrakcije (MVK)] mišića adductor pollicis, kao i tokom perioda oporavka. Metode. Kortikalna ekscitabilnost testirana je TMS pulsevima dvostruko većeg intenziteta od motornog praga. Testiranje je vršeno za vreme održavanja kontrakcije na svakih 10 s do tačke izdržljivosti i na svakih 5 s posle toga, a, takođe, u miru kao i za vreme kratkotrajnih 60% MVK u periodu pre (kontrola), neposredno posle održavanja kontrakcije, i u intervalima od pet minuta za vreme perioda oporavka. Rezultati. Iako su bolesnici sa PB mogli da održavaju zahtevani nivo kontrakcije jednako dugo kao i zdravi ispitanici (mada je nivo opadao brže nakon tačke izdržljivosti), efekti mišićnog zamora na odgovor izazvan TMS-om bili su različiti. Za razliku od zdravih ispitanika kod kojih se motorni evocirani potencijali (MEP) i trajanje perioda EMG tišine (PT) u zamaranom mišiću postepeno smanjuju tokom kontrakcije do tačke izdržljivosti, a zatim rastu, kod većine bolesnika nije došlo do promena veličine (maksimalna amplituda i površina) MEP mišića adductor pollicis, bilo pre ili posle tačke izdržljivosti. S druge strane, promene PT ovog mišića su se razlikovale među ispitanicima, pokazujući bilo postepeno povećanje, smanjenje ili odsustvo promena. Promene kako amplitude MEP tako i trajanje PT u EMG mišića brahioradialisa varirale su među bolesnicima sa PB, bez nekog dominantnog obrasca, po čemu su se, takođe, razlikovale od promena nađenih kod zdravih ispitanika, kod kojih su se oba parametra postepeno povećavala od početka održavanja tonične kontrakcije. Upadljiva je, takođe, i potpuna disocijacija između promena MEP i PT tokom zamora, što je u oštroj suprotnosti sa nalazom kod zdravih ispitanika gde su promene ovih parametara pratile identičan obrazac. Zaključak. Rezultati kod bolesnika sa PB ukazuju na postojanje oštećenja i/ili kompenzatornih promena mehanizmima odgovornih za adaptaciju voljne pobude i usklađivanja kortikalne eksitacije i inhibicije, koji se manifestuju tokom mišićnog zamora i u drugim zahtevnim motornim zadacima

Supplementary data for article: Čukanović, J.; Tešević, V.; Jadranin, M.; Ljubojević, M.; Mladenović, E.; Kostić, S. Horse Chestnut (Aesculus Hippocastanum L.) Seed Fatty Acids, Flavonoids and Heavy Metals Plasticity to Different Urban Environments. Biochemical Systematics and Ecology 2020, 89. https://doi.org/10.1016/j.bse.2019.103980

Supplementary material for: [https://doi.org/10.1016/j.bse.2019.103980]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/3806

Resistance of Composite Column to Compression and Bending

Design of the composite steel-concrete columns subjected to compression and bending, according to Eurocode 4, is shown in the paper. The effects of imperfections in the axial compression are taken into account indirectly by using the relevant European buckling curves. When a composite column is subjected to combined axial compression and bending, the analysis includes an increase in bending moment due to second order effects. The verification of the column resistance to compression and bending is based on the use of interaction curve. For the cross sections of fully encased columns with the I steel sections, very practical sets of continuous interaction curves are given. The curves are constructed for different composite column dimensions, steel sections and concrete classes

Accuracy Evaluation of Creep and Shrinkage Calculation Methods According to EC4

In the paper, the creep and shrinkage calculation methods for composite steel-concrete beams are presented. The approximate methods AAEM, EM and methods according to Eurocode 4, as well as, the exact method based on the integral relation between stress and strain for concrete are used. For doubly-clamped composite beam, stresses at characteristic points of the cross-section for permanent loading and shrinkage effects are determined. Using the creep limit functions for concrete, the upper and lower limits for stresses are determined. According to these limits, the accuracy of the methods for creep and shrinkage calculation given in EC4 is evaluated

Supplementary data for article: Čukanović, J.; Tešević, V.; Jadranin, M.; Ljubojević, M.; Mladenović, E.; Kostić, S. Horse Chestnut (Aesculus Hippocastanum L.) Seed Fatty Acids, Flavonoids and Heavy Metals Plasticity to Different Urban Environments. Biochemical Systematics and Ecology 2020, 89. https://doi.org/10.1016/j.bse.2019.103980

Supplementary material for: [https://doi.org/10.1016/j.bse.2019.103980]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/3806