Testing Core Membership in Public Goods Economies

This paper develops a recent line of economic theory seeking to understand public goods economies using methods of topological analysis. Our first main result is a very clean characterization of the economy's core (the standard solution concept in public goods). Specifically, we prove that a point is in the core iff it is Pareto efficient, individually rational, and the set of points it dominates is path connected. While this structural theorem has a few interesting implications in economic theory, the main focus of the second part of this paper is on a particular algorithmic application that demonstrates its utility. Since the 1960s, economists have looked for an efficient computational process that decides whether or not a given point is in the core. All known algorithms so far run in exponential time (except in some artificially restricted settings). By heavily exploiting our new structure, we propose a new algorithm for testing core membership whose computational bottleneck is the solution of $O(n)$ convex optimization problems on the utility function governing the economy. It is fairly natural to assume that convex optimization should be feasible, as it is needed even for very basic economic computational tasks such as testing Pareto efficiency. Nevertheless, even without this assumption, our work implies for the first time that core membership can be efficiently tested on (e.g.) utility functions that admit "nice" analytic expressions, or that appropriately defined $\varepsilon$-approximate versions of the problem are tractable (by using modern black-box $\varepsilon$-approximate convex optimization algorithms).Comment: To appear in ICALP 201

Managerial networks and strategic flexibility: A QM perspective

Purpose – The paper aims to study the effect of external managerial social networks on strategic flexibility for a quality management (QM) perspective. External social networks can affect strategic flexibility positively. QM also contributes to developing these networks. However, there is currently a wide variety of alternatives for managing quality in organizations, such as ISO standards or the European Foundation for Quality Management model. Thus, different alternatives will influence the external social networks differently in ways that have repercussions for strategic flexibility. Testing these differences is the main purpose of this paper. Design/methodology/approach – A total of 203 valid responses were classified in three groups: non‐QM, ISO, and total quality management (TQM) firms. Then, a comparative ANOVA analysis was performed to test differences among groups. Finally, different regressions were run to test the effects of external social networks (range, size and strength) on strategic flexibility depending of the observed group. Findings – Paper results show that, depending on which QM initiative is implemented in the organization, the effects of external managerial networks on strategic flexibility vary. Thus, in organizations without QM, the range of external social networks influences strategic flexibility negatively, whereas in organizations with ISO standards, this negative effect disappears. In organizations with TQM, the paper finds the positive effect of both size and strength of relations in the networks. Practical implications – The paper facilitates how to differentiate QM alternatives depending on their observed behavior. Originality/value – A new perspective (QM) is observed to test how managerial networks affect strategic flexibility

External managerial networks, strategic flexibility and organizational learning: A comparative study between Non-QM, ISO and TQM firms

"This is an Accepted Manuscript of an article published by Taylor & Francis in Total Quality Management and Business Excellence on 18 Jun 2012, available online: http://wwww.tandfonline.com/10.1080/14783363.2012.669558".This paper studies the effect of external managerial social networks on strategic flexibility and organizational learning, considering three groups of analysis (Non-QM, ISO and TQM firms). At the present, there is a wide variety of alternatives for managing quality in organizations, such as ISO Standards or the EFQM model. Thus, different alternatives will influence the external social networks differently, affecting strategic flexibility and organizational learning, as literature on external social networks suggests that they can affect strategic flexibility and organizational learning positively. Through a comparative ANOVA analysis and step-wise regressions, we observe that external social networks affect strategic flexibility and organizational learning positively, primarily through greater size of the networks. On the other hand, we find that, depending on the QM initiative implemented in the organization, other effects vary. For example, in organizations without QM, the range of external social networks influences strategic flexibility negatively, whereas in organizations with ISO standards, this negative effect disappears. In organizations with TQM, we find the positive effect of both size and strength. For organizational learning, a negative relationship between this capability and network range was found for Non-QM firms group. These relationships turned positive for TQM firms group

Arsenic and vanadium levels in waters in the Union Department, southeast of Córdoba province, Argentina

En Argentina, existen grandes regiones que por sus características edafoclimáticas, poseen excelentes aptitudes agropecuarias, sin embargo, sufren limitaciones de desarrollo debido a la disponibilidad de agua y la calidad del recurso hídrico disponible. Uno de los elementos químicos presentes en el agua, con mayor impacto sobre la salud humana y animal, es el arsénico. La región afectada, abarca las provincias de Córdoba, La Pampa, Santiago del Estero, San Luis, Santa Fe, Buenos Aires, Chaco, Salta, Tucumán, San Juan y Mendoza. El objetivo de este trabajo es analizar la presencia y distribución del arsénico en agua superficial y subterránea en el sudeste de la provincia de Córdoba, una de las zonas más afectadas de Argentina por la presencia de arsénico en el agua.Argentina has large regions with excellent aptitude for agricultural activities. Nevertheless, some areas show development limitations as to water availability and quality. One of the chemical elements in water with great impact on human and animal health is arsenic. The As-affected region includes the provinces of Córdoba, La Pampa, Santiago del Estero, San Luis, Santa Fe, Buenos Aires, Chaco, Salta, Tucumán, San Juan and Mendoza. The aim of this work was to analyze the presence and distribution of arsenic in superficial and ground waters in south-eastern Córdoba province, one of the areas in Argentina most affected by the presence of arsenic in water. Arsenic levels in groundwater were highly variable. The highest values were reported in the phreatic aquifer where arsenic concentration was between 20 and 4600 μg.L-1. Another element found at significant levels in the phreatic aquifer was vanadium whose concentrations were between 30 and 2710 μg.L-1. The presence of vanadium associated with high levels of arsenic could pose a risk to animal health and production.Fil: Pérez Carrera, Alejo Leopoldo. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fernandez Cirelli, Alicia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Arsenic levels in bovine tissues in the southeast of the province Córdoba, Argentina

El arsénico es un contaminante natural de aguas subterráneas en una amplia zona de Argentina, en particular el sudeste de la provincia de Córdoba es una de las regiones más afectadas. La información a nivel mundial acerca de la transferencia de arsénico a la cadena agroalimentaria particularmente a productos cárnicos es escasa. En este trabajo, se determinaron las concentraciones de arsénico en riñón, hígado, músculo esquelético y glándula mamaria en bovinos de la zona de estudio. Los órganos donde se registraron las mayores concentraciones de arsénico fueron hígado y riñón. Los niveles hallados en hígado estuvieron entre 27,0 y 46,5 ng/g y en riñón, entre 24,0 y 73,2 ng/g. En las muestras de músculo y glándula mamaria, las concentraciones estuvieron en todos los casos por debajo del límite de detección de la técnica utilizada. Las concentraciones de arsénico en los diferentes tejidos analizados se encontraron dentro de los límites recomendados a nivel nacional.Arsenic is a groundwater contaminant widely distributed in Argentina. One of the most affected area is the southeast of Cordoba province. The information about the transfer of arsenic to the food chain and meat products is scarce. In this study, the concentrations of arsenic in kidney, liver, muscle and udder in cattle in the study area were analyzed. The highest concentrations of arsenic were found in liver and kidney. The levels found in liver ranged from 27.0 to 46.5 ng/g while in kidney, ranged between 24.0 to 73.2 ng /g. In muscle and udder samples arsenic were below the detection limit of the technique in all cases. The levels of arsenic in the analyzed tissues were within the national recommended limits.Fil: Pérez Carrera, Alejo Leopoldo. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pérez Gardiner, M. L.. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; ArgentinaFil: Fernandez Cirelli, Alicia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

DC-Voltage-Ratio Control Strategy for Multilevel Cascaded Converters Fed With a Single DC Source

Recently, a multilevel cascaded converter fed with a single DC source has been presented. An analysis of the steady-state working limits of this type of converter is presented in this paper. Limits of the maximum output voltage and the minimum and maximum loading conditions for stable operation of the converter are addressed. In this paper, a way to achieve any DC voltage ratio (inside the stable operation area of the converter) between the H-bridges of the single-DC-source cascaded H-bridge converter is presented. The proposed DC-voltage-ratio control is based on a time-domain modulation strategy that avoids the use of inappropriate states to achieve the DC-voltage-ratio control. The proposed technique is a feedforward-modulation technique which takes into account the actual DC voltage of each H-bridge of the converter, leading to output waveforms with low distortion. In this way, the dc voltage of the floating H-bridge can be controlled while the output voltage has low distortion independently of the desired DC voltage ratio. Experimental results from a two-cell cascaded converter are presented in order to validate the proposed DC-voltage-ratio control strategy and the introduced concepts.Ministerio de Ciencia y Tecnología TEC2006-03863Junta de Andalucía EXC/2005/TIC-117

Financing low income housing projects through debt conversion in investment

Thesis (Civ. E.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1991.Includes bibliographical references (leaves 74-76).by Leopoldo Pérez-Lavaud.Civ.E

Arsénico. Del agua a los alimentos

Defined as the king of poisons or "poison of kings", arsenic (As) is one of the most widely distributed elements in the environment. Its origin is associated with different geological environments or human activities. In Argentina, different studies have reported elevated levels of As in groundwater and surface water in different regions. These water sources are important for human and animal consumption. At present As has been recognized as one of the most toxic elements, specially through chronic exposure from drinking water or food. The presence of As in food can be a major source of exposure for humans, even greater than drinking water. The concentration of As in food is variable, in different foodstuffs As content range between 0.1and 0.9 μg/g. Total As consumption depends on its concentration in food and the percentage it represents in the diet. In this article we summarize the main results of studies conducted to assess the impact of arsenic in water on food qualit.Fil: Pérez Carrera, Alejo Leopoldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones En Produccion Animal; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; ArgentinaFil: Volpedo, Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones En Produccion Animal; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; ArgentinaFil: Fernandez Cirelli, Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones En Produccion Animal; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentin

Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio

Modulation techniques for multilevel converters can create distorted output voltages and currents if the DC link voltages are unbalanced. This situation can be avoided if the instantaneous DC voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output voltage of the power converter always generates the reference determined by the controller even in worst case voltage unbalance conditions. In addition the possibility of optimizing the DC voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5kVA prototype are presented in order to validate the proposed modulation technique

Smooth Three-Dimensional Route Planning for Fixed-Wing Unmanned Aerial Vehicles With Double Continuous Curvature

This paper presents a smooth flight path planner for maneuvering in a 3D Euclidean space, which is based on two new space curves. The first one is called 'Elementary Clothoid-based 3D Curve (ECb3D)', which is built by concatenating two symmetric Clothoid-based 3D Curves (Cb3D). The combination of these curves allows to reach an arbitrary orientation in 3D Euclidean space. This new curve allows to generate continuous curvature and torsion profiles that start and finish with a null value, which means that they can be concatenated with other curves, such as straight segments, without generating discontinuities on those variables. The second curve is called 'Double Continuous Curvature 3D Curve (DCC3D)' which is built as a concatenation of three straight line segments and two ECb3D curves, allowing to reach an arbitrary configuration in position and orientation in the 3D Euclidean space without discontinuities in curvature and torsion. This trajectory is applied for autonomous path planning and navigation of unmanned aerial vehicles (UAVs) such as fixed-wing aircrafts. Finally, the results are validated on the FlightGear 2018 flight simulator with the UAV kadett 2400 platform