890 resultados para economic production model


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In this paper we describe the main causes of the recent financial crisis as a result of many theoretical, methodological, and practical shortcomings mostly according to heterodox, but also including some important orthodox economists. At theoretical level, there are problems concerning teaching and using economic models with overly unrealistic assumptions. In the methodological front, we find the unsuspected shadow of Milton Friedman’s ‘unrealisticism of assumptions’ thesis lurking behind the construction of this kind of models and the widespread neglect of methodological issues. Of course, the most evident shortcomings are at the practical level: (i) huge interests of the participants in the financial markets (banks, central bankers, regulators, rating agencies mortgage brokers, politicians, governments, executives, economists, etc. mainly in the US, Canada and Europe, but also in Japan and the rest of the world), (ii) in an almost completely free financial and economic market, that is, one (almost) without any regulation or supervision, (iii) decision-taking upon some not well regarded qualities, like irresponsibility, ignorance, and inertia; and (iv) difficulties to understand the current crisis as well as some biases directing economic rescues by governments. Following many others, we propose that we take this episode as an opportunity to reflect on, and hopefully redirect, economic theory and practice.

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Studies with organic systems have shown the feasibility and ecological and social sustainability of these agroecosystems, unlike the systems agrochemicals (conventional) production. Some studies have concluded that for the model agrochemical exists less interaction between the flow of internal energy, basically the crop receives all inputs to production with no increase in "energy quality" within the system, while in the organic model of production has increased interaction between different resources in the system. The current economic and ecological crisis, exposed no sustainability of the production pattern of industrialized agriculture developed in a way, showing the dependence of developed countries on imports of agricultural commodities produced in the third world, among there coffee. Given these facts, developed a survey to identify problems in the Alta Paulista region, west of São Paulo State, in relation to coffee production systems. Actually, the fundamental problem, according to the research, farmers in this region, is to choose a viable production system correctly (environmental, social and economic); agrochemical or organic. The objectives of this study were to analyze the yield of production systems and agro-chemical and organic coffee in the period from 2003 to 2007, in 30 producing properties, located in this region, in order to point the production system to produce the highest yield. According to the methodology of CONAB, data collected were recorded on spreadsheets to be used as variables in statistical analysis models and mathematics. We performed a descriptive analysis of productivity data and were used for statistical analysis tests for parametric and nonparametric analysis of variance. The mathematical analyses of the curves were prepared with Origin for Windows 6.0 software, which uses numerical methods to fit the data supplied to a function of variable parameters. Unlike conventional systems of production, the organic system showed greater viability of the production model. Furthermore, with the quantitative modeling proposal, it is possible to perform the evaluation of these types of investments, providing more security to the farmer at the time of decision.

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L’elaborato finale presentato per la tesi di Dottorato analizza e riconduce a unitarietà, per quanto possibile, alcune delle attività di ricerca da me svolte durante questi tre anni, il cui filo conduttore è l'impatto ambientale delle attività umane e la promozione dello sviluppo sostenibile. Il mio filone di ricerca è stato improntato, dal punto di vista di politica economica, sull'analisi storica dello sviluppo del settore agricolo dall'Unità d'Italia ai giorni nostri e dei cambiamenti avvenuti in contemporanea nel contesto socio-economico e territoriale nazionale, facendo particolare riferimento alle tematiche legate ai consumi e alla dipendenza energetica ed all'impatto ambientale. Parte della mia ricerca è stata, infatti, incentrata sull'analisi dello sviluppo della Green Economy, in particolare per quanto riguarda il settore agroalimentare e la produzione di fonti di energia rinnovabile. Enfasi viene posta sia sulle politiche implementate a livello comunitario e nazionale, sia sul cambiamento dei consumi, in particolare per quanto riguarda gli acquisti di prodotti biologici. La Green Economy è vista come fattore di sviluppo e opportunità per uscire dall'attuale contesto di crisi economico-finanziaria. Crisi, che è strutturale e di carattere duraturo, affiancata da una crescente problematica ambientale dovuta all'attuale modello produttivo, fortemente dipendente dai combustibili fossili. Difatti la necessità di cambiare paradigma produttivo promuovendo la sostenibilità è visto anche in ottica di mitigazione del cambiamento climatico e dei suoi impatti socio-economici particolare dal punto di vista dei disastri ambientali. Questo punto è analizzato anche in termini di sicurezza internazionale e di emergenza umanitaria, con riferimento al possibile utilizzo da parte delle organizzazioni di intervento nei contesti di emergenza di tecnologie alimentate da energia rinnovabile. Dando così una risposta Green ad una problematica esacerbata dall'impatto dello sviluppo delle attività umane.

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Globalization has increased the pressure on organizations and companies to operate in the most efficient and economic way. This tendency promotes that companies concentrate more and more on their core businesses, outsource less profitable departments and services to reduce costs. By contrast to earlier times, companies are highly specialized and have a low real net output ratio. For being able to provide the consumers with the right products, those companies have to collaborate with other suppliers and form large supply chains. An effect of large supply chains is the deficiency of high stocks and stockholding costs. This fact has lead to the rapid spread of Just-in-Time logistic concepts aimed minimizing stock by simultaneous high availability of products. Those concurring goals, minimizing stock by simultaneous high product availability, claim for high availability of the production systems in the way that an incoming order can immediately processed. Besides of design aspects and the quality of the production system, maintenance has a strong impact on production system availability. In the last decades, there has been many attempts to create maintenance models for availability optimization. Most of them concentrated on the availability aspect only without incorporating further aspects as logistics and profitability of the overall system. However, production system operator’s main intention is to optimize the profitability of the production system and not the availability of the production system. Thus, classic models, limited to represent and optimize maintenance strategies under the light of availability, fail. A novel approach, incorporating all financial impacting processes of and around a production system, is needed. The proposed model is subdivided into three parts, maintenance module, production module and connection module. This subdivision provides easy maintainability and simple extendability. Within those modules, all aspect of production process are modeled. Main part of the work lies in the extended maintenance and failure module that offers a representation of different maintenance strategies but also incorporates the effect of over-maintaining and failed maintenance (maintenance induced failures). Order release and seizing of the production system are modeled in the production part. Due to computational power limitation, it was not possible to run the simulation and the optimization with the fully developed production model. Thus, the production model was reduced to a black-box without higher degree of details.

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The emissions, filtration and oxidation characteristics of a diesel oxidation catalyst (DOC) and a catalyzed particulate filter (CPF) in a Johnson Matthey catalyzed continuously regenerating trap (CCRT ®) were studied by using computational models. Experimental data needed to calibrate the models were obtained by characterization experiments with raw exhaust sampling from a Cummins ISM 2002 engine with variable geometry turbocharging (VGT) and programmed exhaust gas recirculation (EGR). The experiments were performed at 20, 40, 60 and 75% of full load (1120 Nm) at rated speed (2100 rpm), with and without the DOC upstream of the CPF. This was done to study the effect of temperature and CPF-inlet NO2 concentrations on particulate matter oxidation in the CCRT ®. A previously developed computational model was used to determine the kinetic parameters describing the oxidation characteristics of HCs, CO and NO in the DOC and the pressure drop across it. The model was calibrated at five temperatures in the range of 280 – 465° C, and exhaust volumetric flow rates of 0.447 – 0.843 act-m3/sec. The downstream HCs, CO and NO concentrations were predicted by the DOC model to within ±3 ppm. The HCs and CO oxidation kinetics in the temperature range of 280 - 465°C and an exhaust volumetric flow rate of 0.447 - 0.843 act-m3/sec can be represented by one ’apparent’ activation energy and pre-exponential factor. The NO oxidation kinetics in the same temperature and exhaust flow rate range can be represented by ’apparent’ activation energies and pre-exponential factors in two regimes. The DOC pressure drop was always predicted within 0.5 kPa by the model. The MTU 1-D 2-layer CPF model was enhanced in several ways to better model the performance of the CCRT ®. A model to simulate the oxidation of particulate inside the filter wall was developed. A particulate cake layer filtration model which describes particle filtration in terms of more fundamental parameters was developed and coupled to the wall oxidation model. To better model the particulate oxidation kinetics, a model to take into account the NO2 produced in the washcoat of the CPF was developed. The overall 1-D 2-layer model can be used to predict the pressure drop of the exhaust gas across the filter, the evolution of particulate mass inside the filter, the particulate mass oxidized, the filtration efficiency and the particle number distribution downstream of the CPF. The model was used to better understand the internal performance of the CCRT®, by determining the components of the total pressure drop across the filter, by classifying the total particulate matter in layer I, layer II, the filter wall, and by the means of oxidation i.e. by O2, NO2 entering the filter and by NO2 being produced in the filter. The CPF model was calibrated at four temperatures in the range of 280 – 465 °C, and exhaust volumetric flow rates of 0.447 – 0.843 act-m3/sec, in CPF-only and CCRT ® (DOC+CPF) configurations. The clean filter wall permeability was determined to be 2.00E-13 m2, which is in agreement with values in the literature for cordierite filters. The particulate packing density in the filter wall had values between 2.92 kg/m3 - 3.95 kg/m3 for all the loads. The mean pore size of the catalyst loaded filter wall was found to be 11.0 µm. The particulate cake packing densities and permeabilities, ranged from 131 kg/m3 - 134 kg/m3, and 0.42E-14 m2 and 2.00E-14 m2 respectively, and are in agreement with the Peclet number correlations in the literature. Particulate cake layer porosities determined from the particulate cake layer filtration model ranged between 0.841 and 0.814 and decreased with load, which is about 0.1 lower than experimental and more complex discrete particle simulations in the literature. The thickness of layer I was kept constant at 20 µm. The model kinetics in the CPF-only and CCRT ® configurations, showed that no ’catalyst effect’ with O2 was present. The kinetic parameters for the NO2-assisted oxidation of particulate in the CPF were determined from the simulation of transient temperature programmed oxidation data in the literature. It was determined that the thermal and NO2 kinetic parameters do not change with temperature, exhaust flow rate or NO2 concentrations. However, different kinetic parameters are used for particulate oxidation in the wall and on the wall. Model results showed that oxidation of particulate in the pores of the filter wall can cause disproportionate decreases in the filter pressure drop with respect to particulate mass. The wall oxidation model along with the particulate cake filtration model were developed to model the sudden and rapid decreases in pressure drop across the CPF. The particulate cake and wall filtration models result in higher particulate filtration efficiencies than with just the wall filtration model, with overall filtration efficiencies of 98-99% being predicted by the model. The pre-exponential factors for oxidation by NO2 did not change with temperature or NO2 concentrations because of the NO2 wall production model. In both CPF-only and CCRT ® configurations, the model showed NO2 and layer I to be the dominant means and dominant physical location of particulate oxidation respectively. However, at temperatures of 280 °C, NO2 is not a significant oxidizer of particulate matter, which is in agreement with studies in the literature. The model showed that 8.6 and 81.6% of the CPF-inlet particulate matter was oxidized after 5 hours at 20 and 75% load in CCRT® configuration. In CPF-only configuration at the same loads, the model showed that after 5 hours, 4.4 and 64.8% of the inlet particulate matter was oxidized. The increase in NO2 concentrations across the DOC contributes significantly to the oxidation of particulate in the CPF and is supplemented by the oxidation of NO to NO2 by the catalyst in the CPF, which increases the particulate oxidation rates. From the model, it was determined that the catalyst in the CPF modeslty increases the particulate oxidation rates in the range of 4.5 – 8.3% in the CCRT® configuration. Hence, the catalyst loading in the CPF of the CCRT® could possibly be reduced without significantly decreasing particulate oxidation rates leading to catalyst cost savings and better engine performance due to lower exhaust backpressures.

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Climate plays an important role in controlling rates of weathering and weathered regolith production. Regolith production functions, however, seldom take climate parameters into account. Based on a climate-dependent weathered regolith production model, at low denudation rates, relative regolith thicknesses are less sensitive to changes in precipitation rates, while at high denudation rates, small changes in climatic parameters can result in complete stripping of hillslopes. This pattern is compounded by the long residence times and system response times associated with low denudation rates, and vice versa. As others have shown, the transition between regolith-mantled and bedrock slopes is dependent on the ratio of denudation to production. Here, we further suggest that this is itself a function of precipitation rate and temperature. We suggest that climatic parameters can be easily incorporated into existing soil production models and that such additions improve the predictive power of soil production models. (C) 2013 Elsevier B.V. All rights reserved.

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El presente trabajo intenta realizar una síntesis de cómo se fue articulando la sociedad a partir del modelo capitalista de producción en el período histórico que transcurre desde el impulso desarrollado en la Segunda Revolución Industrial, a finales del siglo XIX , hasta la primera década del siglo XXI. Este período determinará una forma de integración social que va estar vinculada al trabajo asalariado y ligada a un Estado más presente, articulador y distribuidor de la riqueza social. Algunos de los elementos constitutivos que sostuvieron este modelo fueron el New Deal y la política económica keynesiana, que van a perdurar hasta bien entrada la década de 1970. En esta etapa, la relación capital-trabajo va a entrar en crisis; el modelo keynesiano de pleno empleo no le es útil al capitalismo; y, por lo tanto, el Estado va a permitir la incorporación de un nuevo discurso, enarbolado por los denominados economistas liberales ortodoxos y, ya en la última década del siglo XX , por el economista norteamericano John Williamson, relacionado con un movimiento intelectual denominado "Consenso de Washington"; esto dando lugar una nueva forma de estructuración social en la que van a coexistir ganadores y perdedores del sistema. Se intenta explicar, además, el impacto que provocó en la Argentina adherir al modelo neoliberal a través de una economía abierta (1989-2002). Por último, describimos la situación de la Provincia de San Luis; los dispositivos y mecanismos que utilizó para contrarrestar los dos dígitos de desocupación producidos después del año 2002; para ello, nos referimos al Plan de Inclusión Social, expuesto a través de datos estadísticos tomados del INDEC y de la Dirección Provincial de Estadísticas y Censos de la Provincia de San Luis

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El estado de situación del agro pampeano desde la implantación del modelo económico neoliberal en la década del '70 hasta nuestros días, plantea el desafío de repensar las categorías de análisis que nos permitan abordar el estudio de la vulnerabilidad socio-territorial de los actores sociales implicados en el agro. Los supuestos neoliberales que han conducido el modelo de producción agropecuario de acumulación y rápida rotación de capital, especulación financiera, externalización de costos sociales y ambientales, entre otros generan situaciones de profundas desigualdades socio-territoriales, que incrementan los grados de vulnerabilidad. Resulta ineludible entonces teorizar sobre indicadores que, bajo otros supuestos, nos permitan valorar los niveles de vulnerabilidad para proponer alternativas que respondan al principio de justicia socio-territorial. Para la consecución de dicho objetivo, se parte de un análisis del estado de situación del agro en el sur cordobés; se analizan luego los supuestos neoliberales que han orientado la producción agropecuaria, para pensar caminos alternativos al modelo de capitalismo agrario, a fin de realizar nuestro aporte a la discusión sobre la construcción de indicadores de vulnerabilidad socio-territorial.

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El presente trabajo intenta realizar una síntesis de cómo se fue articulando la sociedad a partir del modelo capitalista de producción en el período histórico que transcurre desde el impulso desarrollado en la Segunda Revolución Industrial, a finales del siglo XIX , hasta la primera década del siglo XXI. Este período determinará una forma de integración social que va estar vinculada al trabajo asalariado y ligada a un Estado más presente, articulador y distribuidor de la riqueza social. Algunos de los elementos constitutivos que sostuvieron este modelo fueron el New Deal y la política económica keynesiana, que van a perdurar hasta bien entrada la década de 1970. En esta etapa, la relación capital-trabajo va a entrar en crisis; el modelo keynesiano de pleno empleo no le es útil al capitalismo; y, por lo tanto, el Estado va a permitir la incorporación de un nuevo discurso, enarbolado por los denominados economistas liberales ortodoxos y, ya en la última década del siglo XX , por el economista norteamericano John Williamson, relacionado con un movimiento intelectual denominado "Consenso de Washington"; esto dando lugar una nueva forma de estructuración social en la que van a coexistir ganadores y perdedores del sistema. Se intenta explicar, además, el impacto que provocó en la Argentina adherir al modelo neoliberal a través de una economía abierta (1989-2002). Por último, describimos la situación de la Provincia de San Luis; los dispositivos y mecanismos que utilizó para contrarrestar los dos dígitos de desocupación producidos después del año 2002; para ello, nos referimos al Plan de Inclusión Social, expuesto a través de datos estadísticos tomados del INDEC y de la Dirección Provincial de Estadísticas y Censos de la Provincia de San Luis

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El estado de situación del agro pampeano desde la implantación del modelo económico neoliberal en la década del '70 hasta nuestros días, plantea el desafío de repensar las categorías de análisis que nos permitan abordar el estudio de la vulnerabilidad socio-territorial de los actores sociales implicados en el agro. Los supuestos neoliberales que han conducido el modelo de producción agropecuario de acumulación y rápida rotación de capital, especulación financiera, externalización de costos sociales y ambientales, entre otros generan situaciones de profundas desigualdades socio-territoriales, que incrementan los grados de vulnerabilidad. Resulta ineludible entonces teorizar sobre indicadores que, bajo otros supuestos, nos permitan valorar los niveles de vulnerabilidad para proponer alternativas que respondan al principio de justicia socio-territorial. Para la consecución de dicho objetivo, se parte de un análisis del estado de situación del agro en el sur cordobés; se analizan luego los supuestos neoliberales que han orientado la producción agropecuaria, para pensar caminos alternativos al modelo de capitalismo agrario, a fin de realizar nuestro aporte a la discusión sobre la construcción de indicadores de vulnerabilidad socio-territorial.

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El presente trabajo intenta realizar una síntesis de cómo se fue articulando la sociedad a partir del modelo capitalista de producción en el período histórico que transcurre desde el impulso desarrollado en la Segunda Revolución Industrial, a finales del siglo XIX , hasta la primera década del siglo XXI. Este período determinará una forma de integración social que va estar vinculada al trabajo asalariado y ligada a un Estado más presente, articulador y distribuidor de la riqueza social. Algunos de los elementos constitutivos que sostuvieron este modelo fueron el New Deal y la política económica keynesiana, que van a perdurar hasta bien entrada la década de 1970. En esta etapa, la relación capital-trabajo va a entrar en crisis; el modelo keynesiano de pleno empleo no le es útil al capitalismo; y, por lo tanto, el Estado va a permitir la incorporación de un nuevo discurso, enarbolado por los denominados economistas liberales ortodoxos y, ya en la última década del siglo XX , por el economista norteamericano John Williamson, relacionado con un movimiento intelectual denominado "Consenso de Washington"; esto dando lugar una nueva forma de estructuración social en la que van a coexistir ganadores y perdedores del sistema. Se intenta explicar, además, el impacto que provocó en la Argentina adherir al modelo neoliberal a través de una economía abierta (1989-2002). Por último, describimos la situación de la Provincia de San Luis; los dispositivos y mecanismos que utilizó para contrarrestar los dos dígitos de desocupación producidos después del año 2002; para ello, nos referimos al Plan de Inclusión Social, expuesto a través de datos estadísticos tomados del INDEC y de la Dirección Provincial de Estadísticas y Censos de la Provincia de San Luis

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El estado de situación del agro pampeano desde la implantación del modelo económico neoliberal en la década del '70 hasta nuestros días, plantea el desafío de repensar las categorías de análisis que nos permitan abordar el estudio de la vulnerabilidad socio-territorial de los actores sociales implicados en el agro. Los supuestos neoliberales que han conducido el modelo de producción agropecuario de acumulación y rápida rotación de capital, especulación financiera, externalización de costos sociales y ambientales, entre otros generan situaciones de profundas desigualdades socio-territoriales, que incrementan los grados de vulnerabilidad. Resulta ineludible entonces teorizar sobre indicadores que, bajo otros supuestos, nos permitan valorar los niveles de vulnerabilidad para proponer alternativas que respondan al principio de justicia socio-territorial. Para la consecución de dicho objetivo, se parte de un análisis del estado de situación del agro en el sur cordobés; se analizan luego los supuestos neoliberales que han orientado la producción agropecuaria, para pensar caminos alternativos al modelo de capitalismo agrario, a fin de realizar nuestro aporte a la discusión sobre la construcción de indicadores de vulnerabilidad socio-territorial.

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We analyze the effect of environmental uncertainties on optimal fishery management in a bio-economic fishery model. Unlike most of the literature on resource economics, but in line with ecological models, we allow the different biological processes of survival and recruitment to be affected differently by environmental uncertainties. We show that the overall effect of uncertainty on the optimal size of a fish stock is ambiguous, depending on the prudence of the value function. For the case of a risk-neutral fishery manager, the overall effect depends on the relative magnitude of two opposing effects, the 'convex-cost effect' and the 'gambling effect'. We apply the analysis to the Baltic cod and the North Sea herring fisheries, concluding that for risk neutral agents the net effect of environmental uncertainties on the optimal size of these fish stocks is negative, albeit small in absolute value. Under risk aversion, the effect on optimal stock size is positive for sufficiently high coefficients of constant relative risk aversion.

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A typical implicit assumption on monopolistic competition models for trade and economic geography is that firms can produce and sell only at one place. This paper fallows endogenous determination of the number of plants in a new economic geography model and examine the stable outcomes of organization choice between single-plant and multi-plant in two regions. We explicitly consider the firms' trade-off between larger economies of scale under single plant configuration and the saving in interregional transport costs under multi-plant configuration. We show that organization change arises under decreasing transportation costs and observe several organization configurations under a generalized cost function.