Demand side management of a run-of-mine ore milling circuit

Increasing electricity costs coupled with lower prices for some metals such as platinum group metals require a reevaluation of the operation of grinding processes. Demand side management (DSM) has received increasing attention in the field of industrial control as an opportunity to reduce operating costs. DSM through grinding mill power load shifting is presented in this paper using model predictive control and a real-time optimizer. Simulation results indicate that mill power load shifting can potentially achieve cost reductions of $9.90 per kg of unrefined product when applied to a run-of-mine (ROM) ore milling circuit processing platinum bearing ore. DSM is however still not economically feasible when there is a demand to continuously run the milling circuit at maximum throughputhttp://www.elsevier.com/locate/conengprachb201

Coupled-mode theory for Bose-Einstein condensates

We apply the concepts of nonlinear guided-wave optics to a Bose-Einstein condensate (BEC) trapped in an external potential. As an example, we consider a parabolic double-well potential and derive coupled-mode equations for the complex amplitudes of the BEC macroscopic collective modes. Our equations describe different regimes of the condensate dynamics, including the nonlinear Josephson effect for any separation between the wells. We demonstrate macroscopic self-trapping for both repulsive and attractive interactions, and confirm our results by numerical simulations.Comment: 4 pages, 5 figures; typos removed, figures amended; submitted to PR

A Super-Earth and Sub-Neptune Transiting the Late-type M Dwarf LP 791-18

Planets occur most frequently around cool dwarfs, but only a handful of specific examples are known to orbit the latest-type M stars. Using TESS photometry, we report the discovery of two planets transiting the low-mass star called LP 791-18 (identified by TESS as TOI 736). This star has spectral type M6V, effective temperature 2960 K, and radius 0.17 R o, making it the third-coolest star known to host planets. The two planets straddle the radius gap seen for smaller exoplanets; they include a 1.1R ⊕ planet on a 0.95 day orbit and a 2.3R ⊕ planet on a 5 day orbit. Because the host star is small the decrease in light during these planets' transits is fairly large (0.4% and 1.7%). This has allowed us to detect both planets' transits from ground-based photometry, refining their radii and orbital ephemerides. In the future, radial velocity observations and transmission spectroscopy can both probe these planets' bulk interior and atmospheric compositions, and additional photometric monitoring would be sensitive to even smaller transiting planets

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Demand side management of a run-of-mine ore milling circuit

In South Africa, where 75% of the worlds platinum is produced, electricity tariffs have increased significantly over recent years. This introduces challenges to the energy intensive mineral processing industry. Within the mineral processing chain, run-of-mine ore milling circuits are the most energy-intensive unit processes. Opportunities to reduce the operating costs associated with power consumption through process control are explored in this work. In order to reduce operating costs, demand side management was implemented on a milling circuit using load shifting. Time-of-use tariffs were exploited by shifting power consumption of the milling circuit from more expensive to cheaper tariff periods in order to reduce overall costs associated with electricity consumption. Reduced throughput during high tariff periods was recovered during low tariff periods in order to maintain milling circuit throughput over a week long horizon. In order to implement and evaluate demand side management through process control, a load shifting controller was developed for the non-linear Hulbert model. Implementation of the load shifting controller was achieved through a multi-layered control approach. A regulatory linear MPC controller was developed to address technical control requirements such as milling circuit stability. A supervisory real-time optimizer was developed to meet economic control requirements such as reducing electricity costs while maintaining throughput. Scenarios, designed to evaluate the sensitivities of the load shifting controller, showed interesting results. Mill power set-point optimization was found to be proportionally related to the mineral price. Set-points were not sensitive to absolute electricity costs but rather to the relationships between peak, standard, and off-peak electricity costs. The load shifting controller was most effective at controlling the milling circuit where weekly throughput was between approximately 90% and 100% of the maximum throughput capacity. From an economic point of view, it is shown that for milling circuits that are not throughput constrained, load shifting can reduce operating costs associated with electricity consumption. Simulations performed indicate that realizable cost savings are between R16.51 and R20.78 per gram of unrefined platinum processed by the milling circuit. This amounts to a potential annual cost saving of up to R1.89 m for a milling circuit that processes 90 t/h at a head grade of 3 g/t.Dissertation (MEng)--University of Pretoria, 2015.Electrical, Electronic and Computer EngineeringUnrestricte

A comparison of the ligating properties of the mixed P/O- and P/S-donor ligands Ph2P(CH2)(2)O(CH2)(2)O(CH2)(2)PPh2 and Ph2P(CH2)(2)S(CH2)(2)S(CH2)(2)PPh2 with Group 6 and 7 carbonyls

[M(CO)(4)(nbd)] (M = Cr or Mo) react with L-1 (Ph2P(CH2)(2)O(CH2)(2)O(CH2)(2)PPh2) to give the trans-[Cr(CO)(4)(L-1)] and cis-[Mo(CO)(4)(L-1)] respectively, both of which show coordination of L-1 through the P atoms only, giving 11-membered ring metallocyclic complexes. The crystal structure of [MO(CO)(4)(L-1)] confirms the cis-geometry of the product. The cis-[W(CO)(4)(L-1)] is obtained similarly from [W(CO)(4)(TMPA)]. Prolonged reaction of [MnCl(CO)(5)] with L-1 affords mer-trans-[MnCl(CO)(3)(L-1)], with L-1 functioning as a trans chelate via the phosphine functions. The kinetic product fac-[MnCl(CO)(3)(L-1)] is obtained when short reaction times are used. In contrast, [ReBr(CO)(5)] reacts with L-1 to give [ReBr(CO)(3)(L-1)] as a mixture of geometric isomers. Both 1:1 and 2:1 M:L-2 (L-2 = Ph2P(CH2)(2)S(CH2)(2)S(CH2)(2)PPh2) may be obtained for M = Mn(I) or Mn(0). The [MnCl(CO)(3)(L-2)] exists in solution as the fac isomer with L-2 functioning as a bidentate P,S-donor ligand giving a five-membered chelate ring and with the remaining thioether and phosphine functions uncoordinated. Addition of a further equivalent of [MnCl(CO)(5)] affords the binuclear fac-[{MnCl(CO)(3)}(mu(2)-L-2)], with symmetrical P,S-chelation to each metal centre. Similar behaviour is seen for Mo, thus cis-[{Mo(CO)(4)}(2)(mu(2)-L-2)] involves P,S-chelation to each Mo(0) ion. The related 1:1 species cis-[Mo(CO)(4)(L-2)] exists as a mixture of two compounds each with bidentate L-2 coordination, the P-2-chelate (11-membered ring metallocycle) and P,S-coordinated (five-membered chelate ring) species. The new compounds are characterised by microanalyses, IR, H-1-, C-13{H-1}-, P-31{H-1}-,Mn-55-NMR spectroscopy and mass spectrometry as appropriate. The different ligating properties of the related compounds L-1 and L-2 are discussed