Empirical Model of a Human Body Resistance at a Hand-To-Hand DC Flow

Abstract

In recent times the areas of application of direct current systems are being expanded. This may lead to increased risk of electric shock. The subject of investigations described in this paper is a non-linear model of the resistance of the human body under the conditions of direct current electric shock. The aim of the study was to determine the approximate model of the human body resistance at a hand-to-hand DC flow, which may be useful for assessing the effects of the electric shock. The investigations were carried out on three subjects using the hand to hand current path. Experimental studies were conducted within a voltage range of up to 80 V, while the analytical form of the identified model enables extrapolation of the obtained results to a wider range of touch voltages. The identified models allow to evaluate the shock hazard within a voltage range of up to 1500 V. The adopted shock hazard criterion was the probability of ventricular fibrillation of 5 %. The result of the studies was a direct correlation between maximum allowable duration of shock and the touch voltage determined for the three subjects on the basis of the relationship between shock duration and the touch current specified in the IEC report, and of non-linear models of resistance identified on the basis of experimental studies. It was demonstrated that for touch voltages of up to 650 V the fibrillation phenomenon should not occur when the shock duration is shorter than 10 seconds.

Production value optimization with intermediate jig product recirculation

“…This is roughly equivalent to an increase in the production value with jig concentrate recirculation (Fig. 4) [3]. The advantage of the intermediate product recycling, however, is that the feed amount in this case grows very slightly (recirculate only grains with densities similar to the separation density).…”

“…at subsequent A ci values of 6, 9, 12, 15 and 18%: where: PV -production value, PLN, į jig -jig separation density (decision variables of a production maximization algorithm), g/cm 3 , R ip -partial recirculation coefficient of the of the intermediate product, %, M C -concentrate mass, Mg, P Ci -concentrate unit price, dependent on the coal quality, PLN/Mg [8]. All simulation forecasts were carried out using array models of jig separation curves [5].…”

“…All simulation forecasts were carried out using array models of jig separation curves [5]. There was included a hardly-washable feed with characteristics as in the paper [3]. Figure 3 illustrates obtained dependence of the relative production value in a 2 jig rWC layout.…”

The effect of feed overload at secondary coal separation with product recirculation

“…Feed overload can be avoided when the separation densities in both jigs (or more generally in both separators) do not differ much. For example, if in the first jig separation density is equal to 1.700 g/cm 3 , and in a second jeig is equal to 1.950 g/cm 3 , then the increase in the feed amount, with the full recirculation of intermediate product (R ip =100%) is less than 39% and at equal separation densities (1.950 g/cm 3 ), this increase is 3%.…”

“…A better solution to this problem is to recirculate the intermediate product stream because in this case recirculate mainly erroneous particles (Fig. 2b, results obtained for a constant separation density in the first jig -1.950 g/cm 3 and three separation densities in the second jig: 1.450, 1.700 or 1.950 g/cm 3 ). Also in this case the feed amount may be dangerously increased, but it is possible to tune the control in order to avoid this effect.…”