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Search Results: 1 - 10 of 1700 matches for " Valenzuela "
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Effect of Pretreatment of Sulfide Refractory Concentrate with Sodium Hypochlorite, Followed by Extraction of Gold by Pressure Cyanidation, on Gold Removal  [PDF]
Alejandro Valenzuela, Jesús L. Valenzuela, José R. Parga
Advances in Chemical Engineering and Science (ACES) , 2013, DOI: 10.4236/aces.2013.33021
Abstract:

The majority of the refractory gold and silver occurs in occlusion in sulphides, then precious metal dissolution is possible by first oxidizing auriferous sulfide concentrate using sodium hypochlorite-sodium-hydroxide solution followed of pressure cyanidation of the oxidized concentrate, for the extraction of precious metals. This process was conducted and evaluated under cyanide and oxygen pressure. This versatile approach offers many advantages, including low temperatures, low pressure and less costly materials of construction than conventional pressure oxidation. In this study, the effect of oxygen pressure, concentration of sodium hypochlorite, temperature, and initial pH, in precious metals recovery and As removal were evaluated using a 24 factorial design. Characterization of the ores showed that pyrite and arsenopyrite were the main minerals present on the concentrate. The best results for gold extraction were obtained with oxygen pressure of 80 psi, 10% (w/w) sodium hypochlorite, temperature of 80, at pH = 13, and a constant stirring speed of 600 rpm. These conditions allowed an approximated 60% of gold and 90% of silver extractions in 1 hr.

Transformaciones y conflictos en el agro chaque?o durante los ′90. Articulaciones territoriales de una nueva racionalidad productiva
Valenzuela,Cristina;
Mundo agrario , 2005,
Abstract: the transformations happened in the agricultural sector del chaco in ′90, constitute a concrete example of processes of unequal geographic development. as of 1999 this province, stopped being the main argentine cotton producer to get up itself to seedtime of soybean genetically modified, turned the main national culture. the replacement of a productive logic that sustained provincial the economic and social organization for more than four decades by other than privileged the efficiency and the smaller comparative costs, provoked conflicts and reactions differentials in the sector according to the selective vulnerability of the involved actors. the objective of this paper is to deepen available in that process, establishing the main characteristics of the occurred transformations and determine the proportions its effects as much, as the answers of the different agents from the sector (a majority of small traditional producers supported by nongovernmental organizations, a minority of medium and great producers industralists and the provincial government).
La arquitectura-arquitectura: Una colección de cosas raras y valiosas
Valenzuela,Luis;
ARQ (Santiago) , 2002, DOI: 10.4067/S0717-69962002005000008
Abstract: the distinction between an architecture thought for the client and another for the school and the academia becomes stronger, everyday. this duality which registers apparent contradictions is embodied in each young architect?s experience of incursion into the real labour market. the predominance of stereotypes and styles recorded as the client?s desires and aspirations turns the architect into a performer, one that learns to please and also to endure sacrifices
Plantas transformables: La vivienda colectiva como objeto de intervención
Valenzuela,Carolina;
ARQ (Santiago) , 2004, DOI: 10.4067/S0717-69962004005800022
Abstract: the ground plan may be understood as the genetic material of space, and though it is not able to specify which acts will occur in it, it is very precise in indicating which ones cannot. in collective housing, the problem that cannot be solved by a standard floor plan is obvious. new questions about typologies, construction and building strategies are raised by the search for floor plans that are capable of change, driven by the rise of unpredictable new family arrangements and the waning of traditionally dominant social patterns.
Dispositivos de la globalización: la construcción de grandes proyectos urbanos en Ciudad de México
Valenzuela,Alfonso;
EURE (Santiago) , 2013, DOI: 10.4067/S0250-71612013000100004
Abstract: the territorial impact of globalization materializes with the construction of large urban projects, which serve as contact points within cities related to the circuits of capital. by means of a gramscian approach we use santa fe - a megaproject in the western part of mexico city - as a case study of a corporative development project inscribed in global hegemonic flows. building upon the concept of global devices to designate such projects, they become the urban space link to global capital. however, such devices operate at a different speed than the rest of the city, as instrument of a vertical economic power in the midst of a distant, impoverished and unrelated to globalflows horizontality.
Periferia e infraestructura en el paradero 14
Valenzuela,Luis;
ARQ (Santiago) , 2005, DOI: 10.4067/S0717-69962005006000011
Abstract: infrastructure as the matrix for urban development is a concept that offers a different point of entry to the planning issue. implementing some types of infrastructure can offer more information for future development, and have more impact on it, than some regulations or subsidies, as the changes at the edges of our cities show. the idea of infrastructure can be explicitly related to surplus value, real estate development, value added and urban expansion.
Características psicometricas de una escala para caracterizar el Sentido del Aprendizaje Escolar
VALENZUELA,JORGE;
Universitas Psychologica , 2009,
Abstract: in the context of school motivation, we know that taking the student's task motivation in consideration is not enough. it is also necessary to consider the meaning the student assigns to the specific task of learning at school, and to rethink didactic designs accordingly. to do so, we have developed a tool (sas-student) that allows us to charactere the meaning of school learning. the instrument was validated with a sample of 405 chilean students (male and female) of 6th elementary (11 years) and 5th high (16 years), from different socioeconomic strata. the psychometric features of this tool show the same factorial structure in both levels, appropriate reliability coefficients and a high level of discrimination. these results support the construct validity and reliability of a test that is not only useful for research, but that also gives teachers potentially relevant information for their pedagogic planning.
Plantas transformables: La vivienda colectiva como objeto de intervención
Carolina Valenzuela
ARQ , 2004,
Abstract: La planta puede entenderse como el material genético del espacio: y aunque no es capaz de se alar qué actos ocurrirán en él, es precisa indicando lo que nunca podrá pasar. En la vivienda colectiva, el problema que una planta tipo no puede solucionar aparece nítido. Nuevas preguntas a las tipologías, la construcción y las estrategias inmobiliarias surgen de la búsqueda de plantas capaces de cambiar, empujada por la aparición de esquemas familiares impredecibles y la atenuación de patrones sociales dominantes. The ground plan may be understood as the genetic material of space, and though it is not able to specify which acts will occur in it, it is very precise in indicating which ones cannot. In collective housing, the problem that cannot be solved by a standard floor plan is obvious. New questions about typologies, construction and building strategies are raised by the search for floor plans that are capable of change, driven by the rise of unpredictable new family arrangements and the waning of traditionally dominant social patterns.
Periferia e infraestructura en el paradero 14
Luis Valenzuela
ARQ , 2005,
Abstract: La noción de infraestructura como matriz de desarrollo urbano abre otra entrada al problema de la planificación. La implementación de ciertas infraestructuras puede entregar más información a los desarrollos futuros (y de paso ser más determinante) que algunas ordenanzas o subsidios; los cambios en las periferias de nuestras ciudades dan cuenta de este fenómeno. La idea de infraestructura aparecería ligada de manera explícita a la de plusvalía, desarrollo inmobiliario, valor agregado y expansión urbana. Infrastructure as the matrix for urban development is a concept that offers a different point of entry to the planning issue. Implementing some types of infrastructure can offer more information for future development, and have more impact on it, than some regulations or subsidies, as the changes at the edges of our cities show. The idea of infrastructure can be explicitly related to surplus value, real estate development, value added and urban expansion.
América Latina: el presidencialismo en crisis
Arturo Valenzuela
Pensamiento Constitucional , 1996,
Abstract: El ensayo no presenta resumen.
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