Force Measurement System for Roller-Ski Skating

For a detailed biomechanical analysis of roller-ski skating a precise measurement of ground reaction forces is needed in addition to the measurement of the kinematic parameters. An innovative portable force measuring system was developed from processed roller-skis and ski poles equipped with strain gauges. The measuring system can measure normal (with respect to the upper surface of the roller-ski) and transverse forces (in the axial direction of the wheel) on each wheel, and axial forces in the ski poles. Force sensors are connected by cables to the data acquisition system carried in a backpack by the runner. In case of terrain usage, also a portable computer and a power supply are carried in the backpack. Calibration procedure for this measurement system is presented and measurement uncertainty of the sensors is calculated. The estimated measurement uncertainty of the entire measuring chain of individual roller-ski sensor, at a confidence level of 95 %, is up to ± 2,34 % of the maximum calibration forces. For the sensors of the poles this value makes up to ± 1,47 % of the maximum calibration force. Sample data from a roller-ski skating trial on a treadmill is presented and interpreted

Kinematics of the Truck Mounted Hydraulic Cranes

Truck mounted hydraulic cranes are widely used in the timber and in the waste disposal industry. They have a specific design, where dead weight, size in the folded position and the position of the gripper in the folded position are of particularly importance. Functionality of the crane is therefore expressed with load handling capabilities and also with the functionality during road transportation of the payload, when the crane is in the folded position on the truck. For handling of heavier loads, nowadays mainly two types of cranes are used - the K cranes and the Z cranes. The main advantage of the K cranes is higher load capacity in comparison with the Z cranes when cranes of approximately the same weight are compared. On the other hand the main advantage of the Z cranes is their capability of folding in position, transvers to truck length. In the paper the kinematics of the mechanisms of the characteristic size K and Z cranes are analysed and mutually compared. The main accent is on the discussion about their load capacity

Modeling energy usage patterns of a PC and ways of improving it's energy efficiency

This paper describes current status of modeling energy usage patterns for PCs, provides insight in their energy consumption, energy costs and CO2 emission. It also provides possible solutions for improving energy efficiency and energy savings. The study involved analysis of two different mode settings (High Performance and Power Saver mode) of same computer and gaming test case study. Usage patterns for both modes were modeled based on Intel®'s EEP methodology. Workload was simulated with StressMyPC freeware software. PC energy consumption while executing workload was measured with Trotec® BX11 measuring device during 15 days testing period, 8 hours a day. Computer and monitor were separately observed

Inorganic pollutants in disused wood and in boards made of disintegrated wood

Zaradi vse večjega povpraševanja po lesu tudi odsluženi les pridobiva na pomenunajpogosteje ga uporabljamo v energetske namene ali za izdelavo ivernih plošč. Pogosto je onesnažen z različnimi kemikalijami (površinski premazi, biocidi, ostanki gradbenega materiala), ki nam povzročajo težave po koncu življenjske dobe. Da bi ugotavljali prisotnost anorganskih onesnaževal v slovenskem odsluženem lesu, smo na deponiji Ljubljanskega podjetja Snaga odvzeli 30 vzorcev in jih kvalitativno in kvantitativno analizirali z rentgenskim fluorescenčnim spektrometrom (XRF). Vrednosti smo primerjali s koncentracijo onesnažil v ploščah iz dezintegriranega lesa, slovenskih lesnopredelovalnih podjetij. V odsluženem lesu, kot tudi v nekaterih uvoženih ploščah, smo najpogosteje ugotovili prisotnost naslednjih kemijskih elementov: Cl, Cr, Fe, Cu, Zn, in Pb. To nakazuje, da se vsaj del onesnaženega lesa uporabi tudi za izdelavo ivernih plošč.Because of higher demands on wood, there is increased need for disused wood as well, predominantly used for energetic purposes or for production of particleboards. Disused wood is frequently polluted with different chemicals (surface coating, biocides, remains of the construction materials, etc.), causing troubles at the end of the service life. To analyze the presence of inorganic pollutants in Slovenian disused wood 30 samples were collected on the waste site of the Snaga Company in Ljubljana. They were qualitatively and quantitatively analyzed using X-ray fluorescent spectrometry (XRF). The results were compared to the concentrations of the pollutants in the boards made of disintegrated wood. Samples of the boards were gathered from Slovenian companies. The presence of Cl, Cr, Fe, Cu, Zn and Pb elements were found in disused wood and in some imported boards as well. This indicates that at least part of the polluted wood is used also for the production of particleboards

Contribution of various loads to the convex shape of rock wool insulation slabs during production

Rock wool insulation slabs are produced in special curing ovens, where molten rock wool fibres coated with binder are compressed between two slat conveyors and blown with hot air for vitrification. Often, the cross-section of the final slabs is slightly convex, which is undesirable. The degree of convexity depends on the deformation of the steel crossbars of the slat conveyors, which are subjected to combined pressure and nonlinear temperature loadings. Due to this complex loading state, it is difficult to determine the contribution of individual load to the total deformation. The main aim of the study was to determine these contributions. Temperature and stress measurements of the crossbars were performed during rock wool production. Upon collecting these measurements, a finite element (FE) model of a crossbar was established for the identification of the pressure loading acting on the crossbars, and finally for determination of their deformations. As a main result of the study, an inverse problem-based methodology for the identification of the deflection of a structure due to unknown temperature and pressure loadings was established and applied on the specific case. The deviations between the deformations of the FE crossbars and the final shape of the rock wool slabs were below 10%, which validates the novel methodology

Gap dynamics and structure of two old-growth beech forest remnants in Slovenia.

CONTEXT: Due to a long history of intensive forest exploitation, few European beech (Fagus sylvatica L.) old-growth forests have been preserved in Europe. MATERIAL AND METHODS: We studied two beech forest reserves in southern Slovenia. We examined the structural characteristics of the two forest reserves based on data from sample plots and complete inventory obtained from four previous forest management plans. To gain a better understanding of disturbance dynamics, we used aerial imagery to study the characteristics of canopy gaps over an 11-year period in the Kopa forest reserve and a 20-year period in the Gorjanci forest reserve. RESULTS: The results suggest that these forests are structurally heterogeneous over small spatial scales. Gap size analysis showed that gaps smaller than 500 m(2) are the dominant driving force of stand development. The percentage of forest area in canopy gaps ranged from 3.2 to 4.5% in the Kopa forest reserve and from 9.1 to 10.6% in the Gorjanci forest reserve. These forests exhibit relatively high annual rates of coverage by newly established (0.15 and 0.25%) and closed (0.08 and 0.16%) canopy gaps. New gap formation is dependant on senescent trees located throughout the reserve. CONCLUSION: We conclude that these stands are not even-sized, but rather unevenly structured. This is due to the fact that the disturbance regime is characterized by low intensity, small-scale disturbances

Mass point versus whole-body modelling of skiers for performance evaluation in alpine skiing

The altitude differential of the specific mechanical energy, diff (e$_{mech}$), is used to evaluate skiing performance. It is defined as the negative differential between the skier\u27s total specific mechanical energy (e$_{mech}$) and the altitude of the skier\u27s center of mass (COM). Till now, e$_{mech}$ was obtained upon a mass-point (MP) model of the skier\u27s COM, which neither considered the segmental energies of their relative movements to the COM, nor their rotational kinetic energies. The aims of the study were therefore: (a) to examine the deviations in diff (e$_{mech}$) between the MP and a more complex linked segment (LS) skier model consisting of 15 rigid bodies, which encountered the aforementioned defectiveness, (b) to compare the energy fluctuations of the two skier models, and (c) to investigate the influence of the gate setup on (a) and (b) in giant slalom. Three-dimensional whole-body kinematics of nine skiers was measured using a global navigation satellite system and an inertial motion capture system while skiing on a predefined course divided into a turny and open gate setup. Mechanical energies including their altitude differentials were calculated for the LS and MP models. There were no significant differences in e$_{mech}$ and diff (e$_{mech}$) ski turn averages, as in individual data points, between both skier models for both analyzed gate setups. The energies additionally considered by the LS model presented a negligible part regardless of the gate setup. In conclusion, the MP skier model is sufficiently accurate for the evaluation of the skiing performance with diff (e$_{mech}$)

Energetska učinkovitost avtomatiziranih regalnih skladiščnih sistemov pri uporabi tehnologije regeneracije energije: primer avtomatskega skladiščenja v jeklarski industriji

Z namenom doseganja visoke zalogovne velikosti in zahtevane pretočne zmogljivosti se tudi v jeklarski industriji vse pogosteje uporabljajo avtomatizirani regalni skladiščni sistemi za uskladiščenje težkih polizdelkov oz. jeklenih palic in profilov, nameščenih v namenskih kasetah. Izrazito visoka teža jeklenih palic in profilov ter zahtevane pretočne zmogljivosti z dodatnimi zahtevami tehnično robustnega in visoko učinkovitega skladišča, prinaša s sabo tudi visoko potrošnjo električne energije za delovanja skladišča. V članku je na primeru avtomatiziranega regalnega skladišča za jeklene palice in profile predstavljena možnost zmanjšanja porabe električne energije z uporabo koncepta regeneracije pri zaviranju regalnega dvigala in spuščanju dvižne mize regalnega dvigala

Gap characteristics and gap dynamics processes in the Gorjanci forest reserve.

<p>The numbers in parentheses are relative values calculated per forest reserve area.</p