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Search Results: 1 - 10 of 803 matches for " Mircea Marinescu "
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Second Law Analysis of the Turbulent Flat Plate Boundary Layer
Dorin Stanciu,Mircea Marinescu,Dragos Isvoranu
International Journal of Thermodynamics , 2000, DOI: 10.5541/ijot.38
Abstract: Until now the second law analysis of turbulent flow relied only on the irreversibilities performed by the mean velocity and mean temperature gradients. Using the Reynolds decomposition of the volumetric entropy generation rate expression we found that the dissipation rates of both, turbulent kinetic energy and fluctuating temperature variance, also represent the irreversibilities of the flow. Applying the above results, the second law analysis of the turbulent boundary layer shows that the maximum values of the "mean motion irreversibilities" (generated by the mean velocity and mean temperature gradient) are located at the wall, while the maximum values of the "turbulent irreversibilities" (performed by the dissipation rate of turbulent kinetic energy and fluctuating temperature variance) are located in the buffer sublayer. As a consequence, for a given location on the plate, the integral values of the "mean motion irreversibilities" are approximately constant and the "turbulent irreversibilities" grow up with the boundary layer thickness. This paper was presented at the ECOS’00 Conference in Enschede, July 5-7, 2000
The Influence of Swirl Angle on the Irreversibilities in Turbulent Diffusion Flames
Dorin Stanciu,Mircea Marinescu,Alexandru Dobrovicescu
International Journal of Thermodynamics , 2007, DOI: 10.5541/ijot.198
Abstract: The objective of this paper is to investigate the volumetric irreversibilities of turbulent swirling diffusion flames. The theoretical background of analysis relies on the local transport exergy equation, which allows the formulation of the well-known Gouy-Stodola theorem at the continuum level. It is already known that, in the case of turbulent flame, the chemical, thermal and mass diffusion irreversibilities represent in order of enumeration the predominant sources of exergy destruction. But these irreversibilities have a more complicated structure than in the laminar flames because the turbulent fluctuations generate new and important irreversibility sources, strongly influencing all the mechanisms mentioned above. Using numerical techniques for flow and multi-species balance equations, this paper tries to emphasize the role of both, swirling number and turbulent intensity field, not only in the burning process intensification but also in the irreversibility creation.
Second Law Analysis of Diffusion Flames
Dorin Stanciu,Dragos Isvoranu,Mircea Marinescu,Yalcin Gogus
International Journal of Thermodynamics , 2001, DOI: 10.5541/ijot.57
Abstract: The objective of this paper is to investigate the sources of volumetric irreversibilities in both laminar and turbulent diffusion flames. The theoretical background of analysis relies on the local exergy transport equation, which allows the microscopic formulation of the well-known Gouy-Stodola theorem. For laminar reacting flows, the volumetric entropy generation rate expression includes the viscous, thermal, diffusion and chemical components. Their expressions show that the corresponding irreversibilities are uncoupled if the combustion process occurs at constant pressure. The numerical simulation of a methane-air combustion process shows that the thermal, chemical and diffusive irreversibilities represent, in order of enumeration, the predominant irreversibilities in the laminar diffusion reacting flows. In the case of turbulent diffusion flames, the viscous, thermal, diffusion and chemical mean components have to be expressed in accordance with the combustion model. Two combustion models are used: the multi-species approach based on the eddy-break formulation of mean reaction rate, and the assumed probability density function for a conserved scalar that relies on the flame sheet model. For a diffusion methane-air jet flame, the distribution of mean irreversibility components is presented. Taking into account the technical importance of diffusion flames, the analysis could serve to improve the combustion geometry and the flow condition.
A Parametric Approach to the Bi-criteria Minimum Cost Dynamic Flow Problem  [PDF]
Mircea Parpalea
Open Journal of Discrete Mathematics (OJDM) , 2011, DOI: 10.4236/ojdm.2011.13015
Abstract: This paper presents an algorithm for solving Bi-criteria Minimum Cost Dynamic Flow (BiCMCDF) problem with continuous flow variables. The approach is to transform a bi-criteria problem into a parametric one by building a single parametric linear cost out of the two initial cost functions. The algorithm consecutively finds efficient extreme points in the decision space by solving a series of minimum parametric cost flow problems with different objective functions. On each of the iterations, the flow is augmented along a cheapest path from the source node to the sink node in the time-space network avoiding the explicit time expansion of the network.
On the Physical Basis of Self-Organization  [PDF]
Mircea Sanduloviciu
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.43051
Abstract:

Experiments performed with the aim to explain pattern formation in plasma devices offer, as I will show in this survey, a new insight into the mechanism by which locally matter transits spontaneously from a disordered state into an ordered one. The essential news revealed by these experiments is the identification of a population of electrons that, driven at a critical distance from thermal equilibrium, is able to act as the organizer of the emergence and the survival of a complexity starting from chaos, i.e., from electric sparks the appearance of which is controlled by deterministic chaos. Supplied at a constant rate with thermal energy extracted by electrons from plasma, the complexity survives in a dynamical state performing operations in agreement with a code directly related to electrons thermal energy distribution function. Acting as a constituent of the matter, the population of electrons intrinsically controls the emergence and the survival of the complexity. Performing operations directly related to electron’s thermal energy distribution function, the complexity evolves stepwise in more advanced self-organized dynamical states, when this function is changed by an additional injection of energy. A set of nonlinear phenomena, not explainable by classical processes is involved in the mechanism by which the complexity emerges, survives and evolves. Thus, phenomena like Bose-Einstein condensation, macroscopic quantum coherence, direct and alternate Josephson effects, electron tunneling, negative differential impedance and others, potentially explain the emergence, functionality and vitality, i.e., the dynamical state of the complexity.

Transaction Costs and Economic Performance: An Institutional Approach
Cosmin MARINESCU
Economia : Seria Management , 2012,
Abstract: The institutional arrangements, such as the property private order, market, law and other social institutions, governance, cannot function without certain costs. Such costs are not generally or necessarily measurable, but their identification helps understanding how the economic activity is organised and, therefore, appropriately explaining its performances. The study illustrates the fundamental theoretical research on the issue of transaction costs, as reflected in the institutional analysis entitled “Transaction Costs Economics”. The inherent connection between the transaction costs and the entrepreneurial activity indicates the need to restate and extend the neoclassical approach. The argument calls up the institutional context of the property rights, which are in fact decisive for the manifestation of entrepreneurship. The restatement of the approach relates to knowing the fact that the property rights and the transaction costs influence the entrepreneurial activity and, therefore, the overall economic performances.
The Limit between the Rational and Irrational Behaviour in the Economic Science
Cristian MARINESCU
Theoretical and Applied Economics , 2012,
Abstract: Although three years have passed since the onset of the deepest recession from 1929, the most world economies are still fragile, the slipping into another recession being imminent for many of them. “It is a sin to waste a crisis” without learning something of the causes that generated it, said Nouriel Roubini, but this time the problems facing the economic science are related even to the own concepts of the promoted model, while to change something in the economy it is need a reconceptualization of the economic science.The context of the current economic model has failed to anticipate the economic crisis and fails to propose sustainable measure of the economic recovery and this because it starts from the wrong premises, such as assuming that the behavior of the subjects within the market is always rational.In this work we will demonstrate that the irrational behavior of the participants to the economic life has led to imbalances of these markets and we will try to distinguish between the rational and the irrational economic behaviors, to identify the operating area of economic science at this time.
Development Economics and Economic Development: Why do Institution Matter?
Cosmin Marinescu
Theoretical and Applied Economics , 2007,
Abstract: Economic development is a complex phenomenon, at least when speaking about understanding its real sources, despite the simplifying tendencies of economic growth neoclassical theories. These orthodox theories limit themselves to identifying the necessary conditions - such as capital accumulation and technological progress - for production increasing. But, in order to explain "why" people are saving, investing, learning and looking for knowledge, we must take into consideration the institutions that define any economic system. Within society, people are perceptive to a system of general rules that provides incentives and constraints for human behavior. Institutions' and human action's mutuality, and also its economic and political implications, explain the essential importance of institutions in economic science and the institutional approach viability.
Competitive Advantaje Anatomy: from Methodological Holism to State Capture
Cosmin Marinescu
Theoretical and Applied Economics , 2006,
Abstract: According to the orthodox theory of international trade, the argument of selective industrial policy means the state capability of identifying competitive advantages and to exploit them. In this approach, I want to emphasize the necessity of a critical reconsideration of the “competitive advantage” and “national competitiveness”, and also of the implications deriving from these concepts over public policy. First of all, I analyzed the scientifically basis of competitiveness: on the free market, the competitive advantage is given by the entrepreneurial ability, which so becomes the real source of the economic success. Being given any other conditions, meaning here a market affected by state’s interventionism, reaching “competitive advantages” derives from rent-seeking activities which attend to capture public policy.
Economic Science and Postmodernism: Ethics Return
Cosmin MARINESCU
Theoretical and Applied Economics , 2011,
Abstract: The ideas have a fundamental importance for world’s destiny. Within the human civilization world of thinking, the scientific ideas represent the essence of logical structure of human mind and the truths about the human action and society that can be discovered by man. In this approach, I will argue why the scholar honest-mindedness must be his principle in life. In world’s vision about post-modernity, the only faith today is that everything is relative or otherwise stated that there is no ultimate criterion for making absolute hierarchies in order to distinguish truth from false. Thus has gradually appeared the less desired idea that ethical standards represent simple social conventions, fact that would impede the possibility of ethically validating a multitude of “alternative institutional arrangements”, including the ones contradictory with human nature and individual freedom. This study represents a plea for the virtues of logic and faith in truth and justice. Moreover, the original signification of the word “science” – scientia – is correct knowledge. Bearing this clarification in mind, the researchers would maybe become more responsible in calling any approach as being a “scientific” one and implicitly they would become more exigent with their own creations.
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