THE VOLLEYBALL APPROACH: AN EXPLORATION OF RUN-UP LAST STRIDE LENGTH WITH JUMP HEIGHT AND DEVIATION IN LANDING

The main aim of present research was to find out a significant correlation between approach run-up last stride length and the height of jump and landing deviation. Fourteen top elite volleyball players have been served for this study. A Mikro-Mak Motion Analyzer with Win-Analyze program has been used for this study. A Philips video camera with 240 frames per second has also been used to better trace the markers on the shoulder, hip, knee, ankle, and toe. The program enabled us to find out the displacement and velocity of all parts and especially the toes’ in order to measure the different last stride lengths and the deviation from vertical axis. Although we were expecting to get a significant correlation between this parameter and jump height, as in long stride the CG is displaced in longer range with higher horizontal motion than when the player jumps with shorter stride, but the findings did not support this idea. The results are given in Tables 1-4

Improvement in Performance of a Thermochemical Heat Storage System by Implementing an Internal Heat Recovery System

A lab-scale prototype of a thermochemical heat storage system, employing a water-zeolite 13X as the working pair, is designed and optimized for providing hot tap water. During the hydration process, humid air is introduced to the packed bed reactor filled with dehydrated zeolite 13X, and the released heat of adsorption heats up the air passing through the reactor. The hot outflow air is led to an air-to-water heat exchanger integrated in a water tank and heats up the water. The residual heat in the exhaust air is used to preheat the reactor inflow in an air-to-air heat exchanger. The temperatures of all system components are measured, and the thermal powers and heat losses are calculated. Experiments are performed in the system with and without using the heat recovery, and improvement in performance of the heat storage system is investigated

THE RELATIONSHIP BETWEEN THE LACTATE TURNPOINT AND THE TIME AT VO2 max DURING A CONSTANT VELOCITY RUN TO EXHAUSTION

The aim of present work was to examine the relationship between the running velocity at the lactate turn-point (vLTP) and the time at which VO can be sustained (TVO ) during a continuous run to exhaustion at a minimal running velocity that yields VO (vVO ). Pearson’s correlation coefficient was used to determine the association between vLTP and TVO and between other selected physiological variables. Correlations between the relative vLTP and v VO was significant (r=0.63) at the

Design of a thermochemical heat storage system for tap water heating in the built environment

Replacing the use of fossil fuel by solar energy, as one of the most promising sustainable energy sources, is of high interest, because of climate change and depletion of fossil resources. However, to reach high solar fractions and to overcome the mismatch between supply and demand of solar heat, storage of solar energy is necessary. A reliable method for long term heat storage is to use thermochemical materials, TCMs. The heat storage process is based on a reversible adsorption-desorption reaction of water vapor on the TCM, which is exothermic in one direction and endothermic in the reverse direction. In this research, Zeolite 13X is used as TCM. The system is an open sorption heat storage system for providing hot tap water. In the experimental test setup, the humid air is provided in a bubble column by blowing air from bottom of the column. The exothermic hydration process starts with humid air entering into a packed bed reactor filled with zeolite 13X. The reactor is a vertical cylindrical tank which is made of steel; it has a layer of Teflon inside and has a layer of insulation outside. The temperature profile in the reactor is measured as a function of time both along the flow direction and perpendicular to the flow by thermocouples. In addition, input and output temperatures and humidity are measured. In the resulting adsorption reaction between water vapor and TCM, energy is released. This released energy heats up the air flow which passes through the reactor and the hot output air flow is used to heat up the water in a water tank. The water tank is also a vertical cylindrical tank which is made of steel and has a layer of insulation outside. The hot output air from the reactor passes through a coiled tubing inside the water tank to heat up water. The temperature of the water in the tank is measured at two different heights. A problem in open solid sorption systems using air as heat transport medium is the limited temperature step which can be achieved in the sorption bed. In the present study this problem is solved using a heat recovery system enabling higher output air temperatures. The residual heat in the exhaust air is used to preheat the reactor inflow, in an air-to-air heat exchanger. In the endothermic dehydration process, the hydrated zeolite is dried with hot air. In this study, a lab-scale prototype TCM based heat storage system is designed and optimized, which, by making use of a heat recovery loop, is able to provide hot tap water. Results of the experimental investigation on charge-discharge cycles will be presented.<br/

Voltage control in distributed generation systems based on complex network approach

In this paper, a new approach for modeling of voltage control problem in distributed generation systems based on the complex network theory is proposed. Distributed generationsystems (DGS) including renewable energy sources are highly complex nonlinear dynamical systems by nature. There are many theoretical and practical challenges to apply the existing control technologies to them. The novel approach, introduced in this paper, embeds the complex network theory into the voltage control problem of DGS; i.e. the voltage control of DGS is introduced as a synchronization problem in complex networks. Complex network methodology shows a promising simplification inthe analysis as well as timely response in large-scale systems. Thanks to the well-developed graph theory as well as advancements in control of multi-agent systems,the model presented in this paper, candealwith real-time hierarchical multi-objective requirements of control problems in DGS. Finally, the pinning control approach is applied to the model in order to solve the voltage synchronization problem of the microgrid

Comparison of Bone Mineral Density in Lumbar Spine between Athletic and Non-Athletic Premenopausal Women

Abstract: Background & Aims: The purpose of the present research was to compare the bone mineral density (BMD) of lumbar spine between athletic and non-athletic premenopausal women. Methods: Fifteen female athletes (runner) with the mean age of 33.80 ± 4.81 years, mean height of 164.13 ± 5.31 cm, mean weight of 57.33 ± 4.22 kg, and mean body mass index (BMI) of 21.41 ± 2.21 kg/m2 and 15 female non-athletes with yhe mean age of 36.73 ± 5.02 years, mean height of 161.20 ± 4.17 cm, mean weight of 68.00 ± 10.67 kg, and mean BMI of 26.78 ± 4.34 kg/m2 at the premenopausal age (30-45 years) were participated. The BMD of lumbar spines were measured by dual-energy X-ray absorptiometry (DEXA). The collected data were analyzed through t-test statistical methods. Results: Based on T-score and Z-score criteria, all of athletes had normal bone tissue while, 13.3 percent of non-athletes were osteopenic. Moreover, the BMD of lumbar in athletes was significantly more than non-athletes. Furthermore, in the lumbar spine region, significant differences observed between the T-score and Z-score values for both athletes and non athletes. Conclusion: It seems likely that running can increase the BMD of lumbar in premenopausal women; therefore, it can play an important role in preventing osteoporosis as an effective non-medicine method. Keywords: Bone mineral density, T-score, Z-score, Premenopausal, Women, Athlet