Potential use of model predictive control for optimizing the column flotation process     

M. Maldonado  A. Desbiens  R. del Villar 《International Journal of Mineral Processing》2009,93(1):26-33

A constrained model predictive control (MPC) strategy is proposed to deal with the problem of optimizing flotation column operation using secondary variables. Froth depth, collection zone gas hold-up and bias rate are selected as secondary variables to be controlled whereas tailing, wash-water and gas flow rate are used as manipulated variables. The control problem was formulated in order to minimize the tracking error of the gas hold-up and bias rate by maintaining gas flow rate, wash-water flow rate and bias rate within their operational limits. In particular, a strategy was conceived to optimize the column flotation process based on establishing an unreachable high set point for the gas hold-up (which is equivalent to maximizing the bubble surface area available for particle collection at a given flotation reagent dosage and thus recovery), while simultaneously satisfying operational constraints (such as ensuring a positive bias rate to prevent gangue entrainment and therefore concentrate grade deterioration). Several other operational constraints on wash-water, gas rate, gas hold-up and bias rate were considered, their use being justified from a processing point of view. Since this study deals with the hydrodynamic characteristics of flotation columns, a pilot flotation column working with a two-phase system is sufficient to demonstrate the advantages of using predictive control for this process optimization.  相似文献   

Tectonic framework of the eastern Alboran and western Algerian Basins,western Mediterranean   总被引：2，自引：2，他引：0  

A. Mauffret  A. Maldonado  A. C. Campillo 《Geo-Marine Letters》1992,12(2-3):104-110

Recent progress in the knowledge of the Alboran region subaerial geology and the results of the Garcia del Cid seismic cruises stimulate a reexamination of the tectonic framework of the southwestern part of the Mediterranean. The subaerial geology is governed by a north-south stress field, whereas the marine structures indicate an east-west stress regime. This apparent contradiction results from a difference in age of the tectonics. The main marine extensional features are related to the opening of basins toward the southwest during Burdigalian-Langhian times, while the subaerial structures were developed during a compressional regime from the Tortonian period up to the present.  相似文献   

An improved response spectrum method for calculating seismic design response. Part 2: Non-classically damped structures     

G. O. Maldonado  M. P. Singh 《地震工程与结构动力学》1991,20(7):637-649

A response spectrum method which combines the analytical advantage of the mode acceleration formulation and the practical advantage of the mode displacement formulation is developed for seismic response calculation of non-classically damped structures. It reduces the error associated with the truncation of the high frequency modes without explicitly using them in the analysis. The method is especially effective for calculating the response of stiff structural systems and also for calculating the response quantities which are strongly affected by high frequency modes. Even with flexible structures, it is shown to provide more accurate response results than the results obtained with the mode displacement approach.  相似文献   

Sponge waste that fuels marine oligotrophic food webs: a re‐assessment of its origin and nature          下载免费PDF全文

Manuel Maldonado 《Marine Ecology》2016,37(3):477-491

It has recently been realized that sponges take up much of the dissolved organic matter (DOM) available in the water of reefs. The energy derived from this DOM is suggested to be invested in renewing the sponge filter cells (choanocytes) every few hours, generating an outflow of detrital particulate organic matter (POM) that is rapidly ingested by other invertebrates. By this DOM‐to‐POM recycling, sponges are proposed to fuel the food web of oligotrophic marine communities, including reefs, caves and deep‐sea environments. In four species studied herein by electron microscopy, the POM found in the outgoing aquiferous canals had a complex composition, with large between‐species differences. It may include choanocytes (0–52%), and also mesohyl cells, such as archeocytes (9–20%) and spherulous, and granular cells with inclusions (27–90%). Exocytosed vesicles also occurred. Surprisingly, to end up into the outgoing canals, the internal mesohyl cells squeezed between the epithelial cells (endopinacocytes) of the canal wall. Mesohyl cells were also able to transfer their inclusions to the endopinacocytes, which in turn extruded their acquired vesicle loads into the canal lumen. The unanticipated abundant participation of mesohyl cells and endopinacocytes in the production of POM appears to be an ordinary process that occurs continuously in the sponges, mostly related to elimination of digestion leftovers and excretion by‐products. Therefore, POM is generated by sponges irrespective of whether the primary food source is particulate (evidence from this study) or DOM (previous literature). Altogether, these results indicate that the cellular mechanisms behind the relevant organic‐matter recycling carried out by sponges are more diverse than initially anticipated. The varying ratios of choanocytes/mesohyl cells in the POM across species suggest that different sponge species may impact differently the energetics of food webs of the respective oligotrophic habitats where they dominate.  相似文献   

The Ebro Deep-Sea Fan system     

C. Hans Nelson  Andres Maldonado  Francis Coumes  Henri Got  Andre Manaco 《Geo-Marine Letters》1983,3(2-4):125-131

The Ebro Fan System consists of en echelon channel-levee complexes, 50×20 km in area and 200-m thick. A few strong reflectors in a generally transparent seismic facies identify the sand-rich channel floors and levee crests. Numerous continuous acoustic reflectors characterize overbank turbidites and hemipelagites that blanket abandoned channel-levee complexes. The interlobe areas between channel complexes fill with homogeneous mud and sand from mass flow and overbank deposition; these exhibit a transparent seismic character. The steep continental rise and sediment “drainage” of Valencia Trough at the end of the channel-levee complexes prevent the development of distributary channels and midfan lobe deposits.  相似文献   

Plio-Quaternary margin growth patterns in a complex tectonic setting: Northeastern Alboran Sea     

B. Alonso  A. Maldonado 《Geo-Marine Letters》1992,12(2-3):137-143

Four main seismic sequences of Plio-Quaternary age identified in the northeastern Alboran Sea record the main phases of margin and basin development. The geometry and thickness of these sequences reveal that the Motril and Almeria basins contain the main sediment depocenters. Sea level fluctuations and sediment input were probably the most significant factors controlling growth patterns, but the presence of structural barriers and the active tectonism influenced sediment traps and downslope gravity processes.  相似文献   

Large Amplitude Magnetic Anomalies in the Northern Sector of the Powell Basin,NE Antarctic Peninsula     

Suri/ntildeach  E.  Galindo-Zaldivar  J.  Maldonado  A.  Livermore  R. 《Marine Geophysical Researches》1997,19(1):65-80

Magnetic profiles obtained during the Hesant 92/93 cruise with the R/V Hesperides show large amplitude anomalies (up to 1000 nT) along a 100 km wide band in the northern margin of the Powell Basin. The anomalies, which are also locally identified in the eastern and western margins, are attributed to the continuation of the two branches of the Antarctic Peninsula Pacific Margin Anomaly (PMA). Interactive modelling of two-dimensional bodies in four profiles oriented NNW-SSE allows us to determine the main features of the magnetic source bodies within the continental crust. These are elongated in a N60/degE trend, and their base is located at a depth exceeding 15 km. Equivalent magnetic susceptibilities mostly between 0.07 and 0.1 (SI) are obtained. These values are consistent with the hypothesis that remanent magnetisation of the magnetic source bodies is sub-parallel to the present geomagnetic field (norÍmally magnetised). The general trends of the bathymetry a nd the geometry of the acoustic basement on multichannel seismic profiles are consistent with the upper surface of magnetic bodies. In order to match the observed anomalies it is also necessary to consider a second tabular shaped body with induced magnetisation in almost all the profiles, which could represent layers 2 and 3 of the oceanic crust of the Powell Basin. Three different geometries of connection between the anomalies in the Powell Basin margins and the PMA branches are discussed. The most plausible one is the occurrence of two branches, although they are closer together than in the Bransfield Strait. The northern branch would continue along the fragments of continental crust of the South Scotia Ridge located at the northern boundary of the Powell Basin, whereas the southern branch would be located only in the eastern and western passive margins of the Powell Basin. The apparent splitting of the southern branch of the anomalous body indicates that it was emplaced before Oligo cene times, when the opening of this basin occurred, and that it was subsequently fragmented during the Cenozoic. A possible time of formation of the PMA body would be during the long Cretaceous normal polarity interval, which also coincides with a peak in magmatic activity along the Antarctic Peninsula.  相似文献   

Initial phase of the West Scotia mid-oceanic ridge opening     

Al. A. Schreider  A. A. Schreider  J. Galindo-Zaldivar  A. Maldonado  Y. Martos-Martin 《Oceanology》2012,52(4):540-544

The first map illustrating the position of anomaly C12 extending in the NE-SW direction (25°) in the eastern peripheral part of the West Scotia Ridge is presented. Calculations of the paleomagnetic anomalies show that the spreading initiated in the period corresponding to Chron C12r (31.116?C33.266 Ma ago). Chron C11r (30.217?C30.627 Ma ago) was marked by a 200 km northwestward jump of the spreading axis. The calculation of the Euler poles and the rotation angles made it possible to reconstruct the zone of the initial breakup between South America and the Antarctic Peninsula along the western periphery of the continental Terror Rise.  相似文献   

Large‐scale sediment bodies and superimposed bedforms on the continental shelf close to the Strait of Gibraltar: interplay of complex oceanographic conditions and physiographic constraints     

F. J. Lobo  A. Maldonado  R. Noormets 《地球表面变化过程与地形》2010,35(6):663-679

A previously unknown field of large‐scale sedimentary bodies has been mapped and studied on the continental shelf off the Cape Trafalgar near the Strait of Gibraltar with particular emphasis on the relationship between large‐scale sediment bodies and the superimposed bedforms. This study is based on a grid of 975 km of high‐resolution seismic profiles collected at water depths ranging between 15 and 60 m. High variability of large‐scale sedimentary bodies is attributed to the complex interaction of hydrodynamic agents. The most prominent sedimentary features are sand banks and ridges that indicate long‐term southwest and southward‐directed sediment transport patterns, possibly due to the interplay of two dominant current systems flowing southward and westward. These sediment bodies evolve laterally to distinct external geometries, such as sand shoals in shallow water and sand sheets in the vicinity of larger sand banks that indicate moderate current velocities. In addition, pre‐existing physiography is considered to play a role in the generation of certain sediment bodies, developed over inclined surfaces or confined laterally by elevations. Relationships between superimposed bedforms (mostly very large dunes) and underlying sediment bodies vary across the study area. Most superimposed bedforms occur over the complex mosaic of sediment banks and sheets, suggesting the interaction of several high‐energy currents with different directions, such as tidal and/or wind‐driven currents. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

The transition region and coronal explorer   总被引：5，自引：0，他引：5  

Handy  B.N.  Acton  L.W.  Kankelborg  C.C.  Wolfson  C.J.  Akin  D.J.  Bruner  M.E.  Caravalho  R.  Catura  R.C.  Chevalier  R.  Duncan  D.W.  Edwards  C.G.  Feinstein  C.N.  Freeland  S.L.  Friedlaender  F.M.  Hoffmann  C.H.  Hurlburt  N.E.  Jurcevich  B.K.  Katz  N.L.  Kelly  G.A.  Lemen  J.R.  Levay  M.  Lindgren  R.W.  Mathur  D.P.  Meyer  S.B.  Morrison  S.J.  Morrison  M.D.  Nightingale  R.W.  Pope  T.P.  Rehse  R.A.  Schrijver  C.J.  Shine  R.A.  Shing  L.  Strong  K.T.  Tarbell  T.D.  Title  A.M.  Torgerson  D.D.  Golub  L.  Bookbinder  J.A.  Caldwell  D.  Cheimets  P.N.  Davis  W.N.  Deluca  E.E.  McMullen  R.A.  Warren  H.P.  Amato  D.  Fisher  R.  Maldonado  H.  Parkinson  C. 《Solar physics》1999,187(2):229-260

The Transition Region and Coronal Explorer (TRACE) satellite, launched 2 April 1998, is a NASA Small Explorer (SMEX) that images the solar photosphere, transition region and corona with unprecedented spatial resolution and temporal continuity. To provide continuous coverage of solar phenomena, TRACE is located in a sun-synchronous polar orbit. The ∼700 Mbytes of data which are collected daily are made available for unrestricted use within a few days of observation. The instrument features a 30-cm Cassegrain telescope with a field of view of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec pixels). TRACE contains multilayer optics and a lumogen-coated CCD detector to record three EUV wavelengths and several UV wavelengths. It observes plasmas at selected temperatures from 6000 K to 10 MK with a typical temporal resolution of less than 1 min.  相似文献