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553.2 Ouvrages de la bibliothèque en indexation 553
Affiner la recherche40Ar/39Ar dating of alunite from the pueblo viejo gold-silver district, Dominican Republic / Antonio Arribas in Economic geology, Vol. 106 N° 6 (Septembre/Octobre 2011)
in Economic geology > Vol. 106 N° 6 (Septembre/Octobre 2011) . - pp. 1059-1070
Titre : 40Ar/39Ar dating of alunite from the pueblo viejo gold-silver district, Dominican Republic Type de document : texte imprimé Auteurs : Antonio Arribas, Auteur ; Isabel Arribas, Auteur ; Grenville Draper, Auteur Année de publication : 2011 Article en page(s) : pp. 1059-1070 Note générale : Géologie économique Langues : Anglais (eng) Mots-clés : Alunite Gold-silver district Dominican republic Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : New 40Ar/39Ar ages for alunite from the Moore and Monte Negro deposits in the Pueblo Viejo district, as well as from a newly discovered alunite-bearing zone on Loma la Cuaba west of the known deposits, are reported here. The ages range from about 80 to 40 Ma, with closely adjacent samples exhibiting very different ages. Interpretation of these results in the context of estimated closure temperatures for alunite and the geologic and tectonic evolution of Hispaniola does not lead to a simple conclusion about the age of mineralization. The simplest interpretation, that mineralization was caused by a buried Late Cretaceous (~80 Ma) intrusion, is complicated by lack of intrusions of this age in the area and absence of alteration in overlying limestone. The alternative interpretation, that mineralization was formed during Early Cretaceous (~110 Ma) magmatism and that the 40Ar/39Ar ages were completely reset by Late Cretaceous thrusting, is complicated by a lack of information on the timing and thermal effects of thrusting in central Hispaniola. Alunite studies have yielded similar unclear results in other pre-Cenozoic ore systems, notably those of the Lachlan fold belt in Australia. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/106/6/1059.abstract [article] 40Ar/39Ar dating of alunite from the pueblo viejo gold-silver district, Dominican Republic [texte imprimé] / Antonio Arribas, Auteur ; Isabel Arribas, Auteur ; Grenville Draper, Auteur . - 2011 . - pp. 1059-1070.
Géologie économique
Langues : Anglais (eng)
in Economic geology > Vol. 106 N° 6 (Septembre/Octobre 2011) . - pp. 1059-1070
Mots-clés : Alunite Gold-silver district Dominican republic Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : New 40Ar/39Ar ages for alunite from the Moore and Monte Negro deposits in the Pueblo Viejo district, as well as from a newly discovered alunite-bearing zone on Loma la Cuaba west of the known deposits, are reported here. The ages range from about 80 to 40 Ma, with closely adjacent samples exhibiting very different ages. Interpretation of these results in the context of estimated closure temperatures for alunite and the geologic and tectonic evolution of Hispaniola does not lead to a simple conclusion about the age of mineralization. The simplest interpretation, that mineralization was caused by a buried Late Cretaceous (~80 Ma) intrusion, is complicated by lack of intrusions of this age in the area and absence of alteration in overlying limestone. The alternative interpretation, that mineralization was formed during Early Cretaceous (~110 Ma) magmatism and that the 40Ar/39Ar ages were completely reset by Late Cretaceous thrusting, is complicated by a lack of information on the timing and thermal effects of thrusting in central Hispaniola. Alunite studies have yielded similar unclear results in other pre-Cenozoic ore systems, notably those of the Lachlan fold belt in Australia. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/106/6/1059.abstract
in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 133 N° 6 (Novembre 2011) . - 12 p.
Titre : Active steering assistance for lane keeping and lane departure prevention Type de document : texte imprimé Auteurs : Nicoleta Minoiu Enache, Auteur ; Saïd Mammar, Auteur ; Benoit Lusetti, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Dynamic systems Langues : Anglais (eng) Mots-clés : Collision avoidance Control system synthesis Linear matrix inequalities Optimisation Road accidents Road vehicles Steering systems Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : Single-vehicle road departure accidents represent a substantial amount of today's accidents. This paper presents the design and experimental test of an active steering assistance system that offers two functions: lane departure avoidance by temporary activation and maintaining vehicle heading by permanent activation. Each of the two functions can be used exclusively or in combination. Specific constraints related to each of the two functions are taken into account in the control design of the steering assistance by using LMI (linear matrix inequality) and BMI (bilinear matrix inequality) optimization methods. Consequently, lane overshoot is minimized for assistance activations near the border of the lane even during curve negotiation and robust lane keeping is ensured. Furthermore, the effects on lane keeping performance of simultaneous steering by the driver and the assistance are theoretically quantified. The results are verified using a fully equipped prototype vehicle. The obtained field test is consistent with the expected performance. DEWEY : 553 ISSN : 0022-0434 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA000133000006 [...] [article] Active steering assistance for lane keeping and lane departure prevention [texte imprimé] / Nicoleta Minoiu Enache, Auteur ; Saïd Mammar, Auteur ; Benoit Lusetti, Auteur . - 2012 . - 12 p.
Dynamic systems
Langues : Anglais (eng)
in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 133 N° 6 (Novembre 2011) . - 12 p.
Mots-clés : Collision avoidance Control system synthesis Linear matrix inequalities Optimisation Road accidents Road vehicles Steering systems Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : Single-vehicle road departure accidents represent a substantial amount of today's accidents. This paper presents the design and experimental test of an active steering assistance system that offers two functions: lane departure avoidance by temporary activation and maintaining vehicle heading by permanent activation. Each of the two functions can be used exclusively or in combination. Specific constraints related to each of the two functions are taken into account in the control design of the steering assistance by using LMI (linear matrix inequality) and BMI (bilinear matrix inequality) optimization methods. Consequently, lane overshoot is minimized for assistance activations near the border of the lane even during curve negotiation and robust lane keeping is ensured. Furthermore, the effects on lane keeping performance of simultaneous steering by the driver and the assistance are theoretically quantified. The results are verified using a fully equipped prototype vehicle. The obtained field test is consistent with the expected performance. DEWEY : 553 ISSN : 0022-0434 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA000133000006 [...]
in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 134 N° 1 (Janvier 2012) . - 11 p.
Titre : Adaptive and efficient ammonia storage distribution control for a two-catalyst selective catalytic reduction system Type de document : texte imprimé Auteurs : Ming-Feng Hsieh, Auteur ; Wang, Junmin, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Dynamic systems Langues : Anglais (eng) Mots-clés : Adaptive control Air pollution control Ammonia Chemical sensors Control system synthesis Diesel engines Storage Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : This paper presents an adaptive urea-SCR dosing control design for a two-catalyst SCR system. A novel SCR ammonia storage distribution control (ASDC) approach aiming to simultaneously increase the SCR NOx conversion efficiency and reduce the tailpipe ammonia slip was proposed and experimentally validated. Based on the insight into SCR operational principles, a high ammonia storage level at the upstream part of the catalyst can generally yield a higher NOx reduction efficiency while a low ammonia storage level at the downstream part of the catalyst can reduce the undesired tailpipe ammonia slip. To achieve such an ammonia storage distribution control, a two-catalyst (in series) SCR system with NOx and NH3 sensors was devised. Grounded in a newly developed SCR control-oriented model, an adaptive (with respect to the SCR ammonia storage capacity) controller was designed to control the urea injection rate for achieving different ammonia storages in the two catalysts. Experimental data from a US06 test cycle conducted on a medium-duty Diesel engine system showed that, with the similar total engine-out NOx emissions and NH3 (AdBlue) consumptions, the proposed ASDC strategy simultaneously reduced the tailpipe NOx emissions by 57% and the ammonia slip by 74% in comparison to those from a conventional controller. DEWEY : 553 ISSN : 0022-0434 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA000134000001 [...] [article] Adaptive and efficient ammonia storage distribution control for a two-catalyst selective catalytic reduction system [texte imprimé] / Ming-Feng Hsieh, Auteur ; Wang, Junmin, Auteur . - 2012 . - 11 p.
Dynamic systems
Langues : Anglais (eng)
in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 134 N° 1 (Janvier 2012) . - 11 p.
Mots-clés : Adaptive control Air pollution control Ammonia Chemical sensors Control system synthesis Diesel engines Storage Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : This paper presents an adaptive urea-SCR dosing control design for a two-catalyst SCR system. A novel SCR ammonia storage distribution control (ASDC) approach aiming to simultaneously increase the SCR NOx conversion efficiency and reduce the tailpipe ammonia slip was proposed and experimentally validated. Based on the insight into SCR operational principles, a high ammonia storage level at the upstream part of the catalyst can generally yield a higher NOx reduction efficiency while a low ammonia storage level at the downstream part of the catalyst can reduce the undesired tailpipe ammonia slip. To achieve such an ammonia storage distribution control, a two-catalyst (in series) SCR system with NOx and NH3 sensors was devised. Grounded in a newly developed SCR control-oriented model, an adaptive (with respect to the SCR ammonia storage capacity) controller was designed to control the urea injection rate for achieving different ammonia storages in the two catalysts. Experimental data from a US06 test cycle conducted on a medium-duty Diesel engine system showed that, with the similar total engine-out NOx emissions and NH3 (AdBlue) consumptions, the proposed ASDC strategy simultaneously reduced the tailpipe NOx emissions by 57% and the ammonia slip by 74% in comparison to those from a conventional controller. DEWEY : 553 ISSN : 0022-0434 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA000134000001 [...]
in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 133 N° 6 (Novembre 2011) . - 08 p.
Titre : Adaptive position control of an electrohydraulic servo system with load disturbance rejection and friction compensation Type de document : texte imprimé Auteurs : Honorine Angue-Mintsa, Auteur ; Ravinder Venugopal, Auteur ; Jean-Pierre Kenné, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Dynamic systems Langues : Anglais (eng) Mots-clés : Adaptive control Electrohydraulic control equipment Feedback Friction Lyapunov methods Position control Robust control Servomechanisms Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : Electrohydraulic servo systems (EHSS) are used for several engineering applications, and in particular, for efficient handling of heavy loads. These systems are characterized by pronounced nonlinearities and are also subject to parameter variations during operation, friction effects, and variable loads. Several studies have addressed the nonlinear nature of EHSS; however, only a few control schemes explicitly address friction and load disturbance effects along with parameter variations. Fuzzy and/or sliding mode versions of feedback linearizing controllers have been used to compensate for the external loads disturbances in the control of EHSS. However, real-time implementations issues limit the use of these techniques. While adaptive control using a feedback-linearization based controller structure has been shown to be effective in the presence of parameter variations, load and friction effects are typically not considered. In this paper, we present a nonlinear adaptive feedback linearizing position controller for an EHSS, which is robust to parameter uncertainty while achieving load disturbances rejection/attenuation and friction compensation. The adaptation law is derived using a Lyapunov approach. Simulation results using the proposed controller are compared to those using a nonadaptive feedback linearizing controller as well as a proportional-integral-derivative (PID) controller, in the presence of torque load disturbance, friction, and uncertainty in the hydraulic parameters. These results show improved tracking performance with the proposed controller. To address implementation concerns, simulation results with noise effects and valve saturation are also presented. DEWEY : 553 ISSN : 0022-0434 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013300 [...] [article] Adaptive position control of an electrohydraulic servo system with load disturbance rejection and friction compensation [texte imprimé] / Honorine Angue-Mintsa, Auteur ; Ravinder Venugopal, Auteur ; Jean-Pierre Kenné, Auteur . - 2012 . - 08 p.
Dynamic systems
Langues : Anglais (eng)
in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 133 N° 6 (Novembre 2011) . - 08 p.
Mots-clés : Adaptive control Electrohydraulic control equipment Feedback Friction Lyapunov methods Position control Robust control Servomechanisms Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : Electrohydraulic servo systems (EHSS) are used for several engineering applications, and in particular, for efficient handling of heavy loads. These systems are characterized by pronounced nonlinearities and are also subject to parameter variations during operation, friction effects, and variable loads. Several studies have addressed the nonlinear nature of EHSS; however, only a few control schemes explicitly address friction and load disturbance effects along with parameter variations. Fuzzy and/or sliding mode versions of feedback linearizing controllers have been used to compensate for the external loads disturbances in the control of EHSS. However, real-time implementations issues limit the use of these techniques. While adaptive control using a feedback-linearization based controller structure has been shown to be effective in the presence of parameter variations, load and friction effects are typically not considered. In this paper, we present a nonlinear adaptive feedback linearizing position controller for an EHSS, which is robust to parameter uncertainty while achieving load disturbances rejection/attenuation and friction compensation. The adaptation law is derived using a Lyapunov approach. Simulation results using the proposed controller are compared to those using a nonadaptive feedback linearizing controller as well as a proportional-integral-derivative (PID) controller, in the presence of torque load disturbance, friction, and uncertainty in the hydraulic parameters. These results show improved tracking performance with the proposed controller. To address implementation concerns, simulation results with noise effects and valve saturation are also presented. DEWEY : 553 ISSN : 0022-0434 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013300 [...]
in Economic geology > Vol. 105 N° 4 (Juin/Juillet 2010) . - pp. 777-793
Titre : Age and origin of orogenic gold mineralization in the otago schist belt, south island, New Zealand : constraints from lead isotope and 40Ar/39Ar dating studies Type de document : texte imprimé Auteurs : James K. Mortensen, Auteur ; David Craw, Auteur ; Douglas J. MacKenzie, Auteur Année de publication : 2011 Article en page(s) : pp. 777-793 Note générale : Economic geology Langues : Anglais (eng) Mots-clés : Orogenic gold Lead isotope Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The Otago Schist belt of southern New Zealand hosts numerous orogenic gold deposits that formed in a range of structural and lithological settings during and after Mesozoic metamorphism. Previous 40Ar/39Ar dating studies in the Otago Schist belt indicate formation ages of ~106 to 101 Ma for late, postmetamorphic, gold-bearing quartz veins and shear zones. Samples of hydrothermal muscovite from several mineralized quartz vein systems were dated using the 40Ar/39Ar method. Muscovite from a gold-bearing quartz stockwork vein at the Macraes mine, which is a relatively old mineralized system that formed during the latter stages of metamorphism, yields a well-defined plateau age of 135.1 ± 0.7 Ma. Fine-grained muscovite from a quartz shear vein at Macraes gives a rising age spectrum with a maximum age of 135.7 Ma. Five 40Ar/39Ar dates from the scheelite-bearing vein swarm in the Glenorchy district are interpreted to indicate that mineralization occurred between 142 and 134 Ma, and that relatively slow cooling and/or minor thermal overprints have disturbed the age spectra of some of the samples. Lead isotope compositions for a total of 42 sulfide samples from 17 separate mineralized zones in the Otago Schist belt are relatively radiogenic, consistent with an entirely upper crustal source for the Pb (and presumably Au). The Pb data define a less radiogenic and a more radiogenic cluster, with no overlap. Lead isotope compositions from the sulfides from the Macraes group of deposits form part of a less radiogenic cluster, together with Pb isotope compositions for sulfides from scheelite-rich veins in the Glenorchy camp. Lead isotope compositions for sulfides from younger, postmetamorphic quartz veins and shear zones fall exclusively in the more radiogenic cluster. The new 40Ar/39Ar dating results and Pb isotope studies, in conjunction with previously published work, demonstrate that most orogenic gold mineralization within the Otago Schist belt formed during two discrete mineralizing events—one at 142 to 135 Ma and a later one at approximately 106 to 101 Ma. We interpret the two pulses of gold mineralization to reflect sequential extraction of ore-forming components from the deeper part of the Otago Schist belt during short-lived thermal events. The younger event was probably associated with subduction of an actively spreading ridge, and similar ridge subduction may have been involved in the older event. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/4/777.abstract [article] Age and origin of orogenic gold mineralization in the otago schist belt, south island, New Zealand : constraints from lead isotope and 40Ar/39Ar dating studies [texte imprimé] / James K. Mortensen, Auteur ; David Craw, Auteur ; Douglas J. MacKenzie, Auteur . - 2011 . - pp. 777-793.
Economic geology
Langues : Anglais (eng)
in Economic geology > Vol. 105 N° 4 (Juin/Juillet 2010) . - pp. 777-793
Mots-clés : Orogenic gold Lead isotope Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The Otago Schist belt of southern New Zealand hosts numerous orogenic gold deposits that formed in a range of structural and lithological settings during and after Mesozoic metamorphism. Previous 40Ar/39Ar dating studies in the Otago Schist belt indicate formation ages of ~106 to 101 Ma for late, postmetamorphic, gold-bearing quartz veins and shear zones. Samples of hydrothermal muscovite from several mineralized quartz vein systems were dated using the 40Ar/39Ar method. Muscovite from a gold-bearing quartz stockwork vein at the Macraes mine, which is a relatively old mineralized system that formed during the latter stages of metamorphism, yields a well-defined plateau age of 135.1 ± 0.7 Ma. Fine-grained muscovite from a quartz shear vein at Macraes gives a rising age spectrum with a maximum age of 135.7 Ma. Five 40Ar/39Ar dates from the scheelite-bearing vein swarm in the Glenorchy district are interpreted to indicate that mineralization occurred between 142 and 134 Ma, and that relatively slow cooling and/or minor thermal overprints have disturbed the age spectra of some of the samples. Lead isotope compositions for a total of 42 sulfide samples from 17 separate mineralized zones in the Otago Schist belt are relatively radiogenic, consistent with an entirely upper crustal source for the Pb (and presumably Au). The Pb data define a less radiogenic and a more radiogenic cluster, with no overlap. Lead isotope compositions from the sulfides from the Macraes group of deposits form part of a less radiogenic cluster, together with Pb isotope compositions for sulfides from scheelite-rich veins in the Glenorchy camp. Lead isotope compositions for sulfides from younger, postmetamorphic quartz veins and shear zones fall exclusively in the more radiogenic cluster. The new 40Ar/39Ar dating results and Pb isotope studies, in conjunction with previously published work, demonstrate that most orogenic gold mineralization within the Otago Schist belt formed during two discrete mineralizing events—one at 142 to 135 Ma and a later one at approximately 106 to 101 Ma. We interpret the two pulses of gold mineralization to reflect sequential extraction of ore-forming components from the deeper part of the Otago Schist belt during short-lived thermal events. The younger event was probably associated with subduction of an actively spreading ridge, and similar ridge subduction may have been involved in the older event. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/4/777.abstract
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