The operational availability of mining shovels is the focus of this work. The hypothesis is that energy quality is responsible for the frequent shut downs of the shovels. Previous engineering studies have highlighted a large presence of harmonics and reactive power in the mine loop electric system. A common solution proposed was to use a combination of active filters, larger mobile substations, shorter mining cables and equipment location constraints. The aim of this paper is to produce a precise diagnosis of the source and nature of the energy quality issues. Mine loop electric quality monitoring, system modeling, equipment technologies and shovel´s histograms are considered. Results are measured against IEEE standards and shovel´s voltage regulation susceptibility. With the diagnosis the goal was to produce a reliable cost effective solution. Different alternatives are crosschecked with this paper proposal. The solution presented provides energy quality well within shovel´s susceptibility and improves energy efficiency. The lower energy consumption pays the investment required and is currently under construction. I. Mining Cable (7.2[kV]) Power Line (13.8[kV])0093-9994 (c)

Aims. In this work, we present an extended study of the dust environment of a sample of short-period comets and their dynamical history. With this aim, we characterize the dust tails when the comets are active, and we make a statistical study to determine their dynamical evolution. The targets selected were 22P/Kopff, 30P/Reinmuth 1, 78P/Gehrels 2, 115P/Maury, 118P/Shoemaker-Levy 4, 123P/West-Hartley, 157P/Tritton, 185/Petriew, and P/2011 W2 (Rinner). Methods. We use two different observational data sets: a set of images taken at the Observatorio de Sierra Nevada and, the A f ρ curves provided by the amateur astronomical association Cometas-Obs. To model these observations, we use our Monte Carlo dust tail code. From this analysis, we derive the dust parameters, which best describe the dust environment: dust loss rates, ejection velocities, and size distribution of particles. On the other hand, we use a numerical integrator to study the dynamical history of the comets, which allows us to determine with a 90% confidence level the time spent by these objects in the region of Jupiter family comets. Results. From the Monte Carlo dust tail code, we derived three categories according to the amount of dust emitted: weakly active (115P, 157P, and Rinner), moderately active (30P, 123P, and 185P), and highly active (22P, 78P, and 118P). The dynamical studies showed that the comets of this sample are young in the Jupiter family region, where the youngest ones are 22P (∼100 yr), 78P (∼500 yr), and 118P (∼600 yr). The study points to a certain correlation between comet activity and time spent in the Jupiter family region, although this trend is not always fulfilled. The largest particle sizes are not tightly constrained, so that the total dust mass derived should be regarded as a lower limit.

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This paper presents an energy quality evaluation of an open pit mine distribution system. A number of operational disruptions affecting mine shovels have been related to energy quality. Previous investigations have highlighted the large presence of harmonics as the main factor responsible for these problems. The aim of this paper is to produce an energy quality baseline and a precise diagnosis of the source and nature of the energy quality issues based on standards and the susceptibility of different technologies used by the shovels at the site. The random nature of the load composed by multiple shovels and drills requires computer simulation to predict worst-case scenarios. For this purpose a voltage regulation and harmonic distortion study was conducted with the model parameters tuned by measurements taken in mobile substations of the mine energy loop. A major aim of this study is to establish the relationship between energy quality and energy efficiency.

Aims. This paper is a continuation of the first paper in this series, where we presented an extended study of the dust environment of a sample of short-period comets and their dynamical history. On this occasion, we focus on comets 81P/Wild 2 and 103P/Hartley 2, which are of special interest as targets of the spacecraft missions Stardust and EPOXI. Methods. As in the previous study, we used two sets of observational data: a set of images, acquired at Sierra Nevada and Lulin observatories, and the A f ρ data as a function of the heliocentric distance provided by the amateur astronomical association Cometas-Obs. The dust environment of comets (dust loss rate, ejection velocities, and size distribution of the particles) was derived from our Monte Carlo dust tail code. To determine their dynamical history we used the numerical integrator Mercury 6.2 to ascertain the time spent by these objects in the Jupiter family Comet region. Results. From the dust analysis, we conclude that both 81P/Wild 2 and 103P/Hartley 2 are dusty comets, with an annual dust production rate of 2.8 × 10 9 kg yr −1 and (0.4−1.5) × 10 9 kg yr −1 , respectively. From the dynamical analysis, we determined their time spent in the Jupiter family Comet region as ∼40 yr in the case of 81P/Wild 2 and ∼1000 yr for comet 103P/Hartley 2. These results imply that 81P/Wild 2 is the youngest and the most active comet of the eleven short-period comets studied so far, which tends to favor the correlation between the time spent in JFCs region and the comet activity previously discussed.