THE EFFECTS OF A SPECIFIC TRAINING PROGRAM ON THE KINEMATIC PARAMETERS OF THE JUMP SHOT AMONG ELITE FEMALE HANDBALL PLAYERS

The aim of this research was to determine the effects of an eight-week specific training program on the kinematic parameters of the jump shot at 9m from the goal, among elite female handball players. The sample of participants consisted of 30 female handball players (height: 1.73±0.08 m; mass: 69±8.9 kg; body mass index-BMI 22.9±2 kg/m2; training experience: 12.3±6.2 yrs), competing in the first national handball league of the Republic of Serbia. The research was longitudinal in nature, with an initial and final measuring. The experimental treatment included a 30 min replication of the regular training session, with specifically designed exercises (work with medicine balls, stabilizer training, and strength training in a gym). 12 kinematic variables of the jump shop were analyzed using the Kinovea software program, ver. 0.8.2. The analysis of covariance and the effect size (ES) determined a positive effect of the specific program on the kinematic parameters of the jump shot, especially on the variables of height and maximal ball flight velocity

Contact stresses in gear teeth due to tip relief profile modification

In this paper the linear tip relief profile modification has been observed. This kind of modification has been considered to be potentially dangerous considering micro-pitting initiation as a consequence of contact pressure increase. The amount of tip relief profile modification depends on the elastic gear tooth deflection that needs to be compensated. The standard gear model without linear tip relief profile modification, as well as the modified one, has been discretized by finite elements and analyzed using the finite element method to compare Hertz contact stresses on tooth flank, as influenced by the mentioned profile modification

Influence of design parameters on the behaviour of cross-spring pivots

Compliant mechanisms gain at least part of their mobility from the deflection of the flexible member. They are characterised by high precision, possibility of monolithic manufacturing, as well as the absence of backlash and wear. Numerical methods are used in this work to characterise the behaviour of compliant rotational mechanisms, known as cross-spring pivots, aimed at ultrahigh-precision positioning applications. The results obtained by using nonlinear finite element calculations are compared with experimental data reported in literature. The finite element model developed in this way makes it possible to conider the influence of lateral loads and of non-symmetrical pivot configurations where the angle or point of intersection of the leaf springs can be varied. This allows assessing the influence of the cited design parameters on the minimisation of the parasitic shifts of the geometric centre of the pivot, as well as on the minimisation of the variability of the rotational stiffness of the pivot while ensuring its stability. The obtained results allow determining design solutions applicable in ultrahigh-precision positioning applications, e.g. in the production or in handling and assembly of MEMS devices

Influence of Tip Relief Profile Modification on Involute Spur Gear Stress

This paper deals with the effects of linear tip profile modification on the stress of tooth root and tooth flank of involute spur gears. An increase in the tooth flank stress due to the tip profile modification is potentially hazardous because there is an increased risk of micro pitting initiation. The required magnitude of tip relief profile modification depends on the magnitude of tooth elastic deformation that needs to be compensated for. In order to study the effects of linear tip profile modification on gear stress, two matching finite element models of involute spur gear pairs have been created, and tip relief profile modification has been applied to one pair. Tooth root and tooth flank stresses in both gear pairs have been compared in order to establish the effect of tip relief profile modification on gear stress

Influence of design parameters on the behaviour of cross-spring pivots

Compliant mechanisms gain at least part of their mobility from the deflection of the flexible member. They are characterised by high precision, possibility of monolithic manufacturing, as well as the absence of backlash and wear. Numerical methods are used in this work to characterise the behaviour of compliant rotational mechanisms, known as cross-spring pivots, aimed at ultrahigh-precision positioning applications. The results obtained by using nonlinear finite element calculations are compared with experimental data reported in literature. The finite element model developed in this way makes it possible to conider the influence of lateral loads and of non-symmetrical pivot configurations where the angle or point of intersection of the leaf springs can be varied. This allows assessing the influence of the cited design parameters on the minimisation of the parasitic shifts of the geometric centre of the pivot, as well as on the minimisation of the variability of the rotational stiffness of the pivot while ensuring its stability. The obtained results allow determining design solutions applicable in ultrahigh-precision positioning applications, e.g. in the production or in handling and assembly of MEMS devices

Issues in the mechanical engineering design of high-precision kinematic couplings

A three V-groove (Maxwell-type) kinematic mount design configuration constrains all degrees of freedom of the apparatus mounted onto it, thus allowing its high-precision positioning and re-positioning. The analysis of this mechanical assembly comprises force and moment balances, as well as expressions for stress-strain and error motion calculations. For determined loading conditions and the geometry of the mount, the resulting loads across each groove-ball interface imply, however, the necessity to consider the complex nonlinear Hertz theory of point contacts between elastically deforming solids. The available analytical approaches to the calculation of the conditions at the ball-V groove contacts are hence recalled in this work with the aim of establishing the respective limits of applicability. The obtained results are validated experimentally. A structured calculation procedure is then used to assess the stability of a kinematic mount employed to support a large mechanical component at a particle accelerator facility, depending on the value and orientation of the external loads acting on the studied assembly. Stability conditions for different design configurations are consecutively established

Hrvatski pravopis u razdoblju 1945-1990 : četiri pravopisna priručnika

U ovom smo se radu bavili usporednom analizom četiriju hrvatskih pravopisnih priručnika iz razdoblja 1945–1990. Prvi je Pravopis hrvatskoga ili srpskoga jezika Dragutina Boranića iz 1947. godine. Drugi je Pravopis hrvatskosrpskoga književnog jezika s pravopisnim rječnikom iz 1960. godine, tzv. novosadski pravopis. Analizirali smo značajke toga pravopisa usporedivši ga s Boranićevim Pravopisom i Belićevim Pravopisom srpskohrvatskog književnog jezika iz 1952. Prikazano je što je u pravopisnim pravilima naslijeđeno od hrvatske, a što od srpske tradicije. U pravopisnoj terminologiji izvršeno je izjednačavanje termina. U pravopisnom rječniku zastupljena su oba izgovora – ijekavski i ekavski. Treći je pravopis Babić–Finka–Mogušev Hrvatski pravopis iz 1971. koji napušta zajedničke pravopisne termine, u pravopisnim pravilima i u rječniku preporučuje pojedine oblike i time preuzima kompetencije leksičkog savjetnika. Četvrti pravopis, Anić–Silićev Pravopisni priručnik hrvatskoga ili srpskoga jezika drugačije pristupa obradi pravopisnih pravila te donosi i nove pravopisne termine. Usporedba četiriju pravopisa prikazuje kako je tekla hrvatska pravopisna norma od 1945. do 1990. godine.The aim of this thesis was to describe and compare four Croatian orthography manuals, written in different time periods (1945-1990). These are: „Pravopis hrvatskoga ili srpskoga jezika“ written by Dragutin Boranić in 1947, „Pravopis hrvatskosrpskoga književnog jezika s pravopisnim rječnikom“, written in 1960 which takes the standard variant of the language into consideration, „Hrvatski pravopis“ written by Babić, Finka and Moguš in 1971 and „Pravopisni priručnik hrvatskoga ili srpskoga jezika“ written by Anić and Silić. All orthography manuals are innately different: the second orthography manual features jekavian and ekavian pronunciation.The third orthography manual concentrates on Croatian standard norm, and is therefore composed as a lexical manual. The fourth orthography manual brings a different perspective and offers new orthographic rules. The comparsion of the enumerated orthography manuals offers an extensive insight into the process of the standardization of the Croatian language in the period between 1945-1990

CALIBRATION OF MATERIAL MODELS FOR THE HUMAN CERVICAL SPINE LIGAMENT BEHAVIOUR USING A GENETIC ALGORITHM

Research of biomaterials in loading conditions has become a significant field in the material science nowadays. In order to provide better understanding of the loading effects on material structures, complex material models are usually chosen, depending on their applicability to the material under consideration. In order to provide as accurate as possible the material behavior modeling of the human cervical spine ligaments, the procedure for calibration of two material models has been evaluated. The calibration of material models was based on the genetic algorithm procedure in order to make possible optimization of material parameters identification for the chosen models. The influence of genetic algorithm operators upon the results in evaluated procedure has been tested and discussed here and the simulated behavior of the material has been compared to the experimentally recorded stress stretch relationship of the material under consideration. Since various influential factors contribute to the genetic algorithm performance in calibration of complex material models and identification of material parameters, additional possible improvements have been suggested for further research