Jorge Amzalak Navarro | Ucla (original) (raw)

Papers by Jorge Amzalak Navarro

TEST, 2022

For a given pair of random lifetimes whose dependence is described by a time-transformed exponent... more For a given pair of random lifetimes whose dependence is described by a time-transformed exponential model, we provide analytical expressions for the distribution of their sum. These expressions are obtained by using a representation of the joint distribution in terms of bivariate distortions, which is an alternative approach to the classical copula representation. Since this approach allows one to obtain conditional distributions and their inverses in simple form, then it is also shown how it can be used to predict the value of the sum from the value of one of the variables (or vice versa) by using quantile regression techniques.

Mathematics, 2020

New weak notions of positive dependence between the components X and Y of a random pair (X,Y) hav... more New weak notions of positive dependence between the components X and Y of a random pair (X,Y) have been considered in recent papers that deal with the effects of dependence on conditional residual lifetimes and conditional inactivity times. The purpose of this paper is to provide a structured framework for the definition and description of these notions, and other new ones, and to describe their mutual relationships. An exhaustive review of some well-know notions of dependence, with a complete description of the equivalent definitions and reciprocal relationships, some of them expressed in terms of the properties of the copula or survival copula of (X,Y), is also provided.

TEST, 2021

Given a finite set of independent random variables, assume one can observe their sum, and denote ... more Given a finite set of independent random variables, assume one can observe their sum, and denote with s its value. Efron in 1965, and Lehmann in 1966, described conditions on the involved variables such that each of them stochastically increases in the value s, i.e., such that the expected value of any non-decreasing function of the variable increases as s increases. In this paper, we investigate conditions such that this stochastic monotonicity property is satisfied when the assumption of independence is removed. Comparisons in the stronger likelihood ratio order are considered as well.

Statistical Methods & Applications, 2022

Introduction to System Reliability Theory, 2021

Dependence Modeling, 2018

We prove that different conditional distributions can be represented as distorted distributions. ... more We prove that different conditional distributions can be represented as distorted distributions. These representations are used to obtain stochastic comparisons and bounds for them based on properties of the underlying copula. These properties can be used to explain the meaning of mathematical properties of copulas connecting them with dependence concepts. Some applications and illustrative examples are provided as well.

TEST, 2017

Comparison results for inactivity times of k-out-of-n and general coherent systems with dependent... more Comparison results for inactivity times of k-out-of-n and general coherent systems with dependent components / Navarro, Jorge; Longobardi, Maria; Pellerey, Franco.-In: TEST.

Journal of Applied Probability, 2017

Recently, Rao et al. (2004) introduced an alternative measure of uncertainty known as the cumulat... more Recently, Rao et al. (2004) introduced an alternative measure of uncertainty known as the cumulative residual entropy (CRE). It is based on the survival (reliability) function F̅ instead of the probability density function f used in classical Shannon entropy. In reliability based system design, the performance characteristics of the coherent systems are of great importance. Accordingly, in this paper, we study the CRE for coherent and mixed systems when the component lifetimes are identically distributed. Bounds for the CRE of the system lifetime are obtained. We use these results to propose a measure to study if a system is close to series and parallel systems of the same size. Our results suggest that the CRE can be viewed as an alternative entropy (dispersion) measure to classical Shannon entropy.

Advances in Applied Probability, 2016

In this paper we investigate different methods that may be used to compare coherent systems havin... more In this paper we investigate different methods that may be used to compare coherent systems having heterogeneous components. We consider both the case of systems with independent components and the case of systems with dependent components. In the first case, the comparisons are based on the new concept of the survival signature due to Coolen and Coolen-Maturi (2012) which extends the well-known concept of system signatures to the case of components with lifetimes that need not be independent and identically distributed. In the second case, the comparisons are based on the concept of distortion functions. A graphical procedure (called an RR-plot) is proposed as an alternative to the analytical methods when there are two types of components.

Anuario Filosofico, 1997

El presente artículo tiene como objetivo comparar las teorías de las ideas históricas de Wilhelm ... more El presente artículo tiene como objetivo comparar las teorías de las ideas históricas de Wilhelm von Humboldt (1767-1835) y Leopold von Ranke (1795-1886) con el concepto de idea propuesto por Fichte en sus escritos populares, y especialmente en las lecciones de 1805 Sobre la esencia del erudito y sus apariciones en el ámbito de la libertad. Con ello no pretendo dar una respuesta a la cuestión de si estos textos de Fichte influyeron o no sobre Humboldt y Ranke, sino que mi intención es simplemente analizar qué diferencias y semejanzas hay entre los conceptos de idea de estos tres autores, sin añadir a este análisis afirmaciones sobre la dependencia de unos respecto de otros. En todo caso, no he podido hallar testimonios de una lectura por parte de Humboldt de los mencionados escritos de Fichte, mientras que las notas que Ranke tomó de su lectura de Sobre la esencia del erudito y La introducción a la vida beata están publicadas en Aus WerkundNachlass. Comienzo presentando brevemente el concepto de idea de Fichte, y a continuación me ocuparé con más detenimiento de

Journal of Applied Probability, 2015

We have found a mistake in the proofs of Navarro (2008, Theorem 2.3(b) and 2.3(c)) due to misappl... more We have found a mistake in the proofs of Navarro (2008, Theorem 2.3(b) and 2.3(c)) due to misapplication of properties of hazard rate and likelihood ratio orders. In this paper we show with an example that the stated results do not hold. This example is interesting since it proves some unexpected properties for these orderings under the formation of coherent systems. The result stated in Navarro (2008, Theorem 2.3(a)) for the usual stochastic order is correct.

Journal of the Chemical Society, Dalton Transactions, 1998

European Journal of Operational Research, 2015

Consider a general coherent system with independent or dependent components, and assume that the ... more Consider a general coherent system with independent or dependent components, and assume that the components are randomly chosen from two different stocks, with the components of the first stock having better reliability than the others. Then here we provide sufficient conditions on the component's lifetimes and on the random numbers of components chosen from the two stocks in order to improve the reliability of the whole system according to different stochastic orders. We also discuss several examples in which such conditions are satisfied and an application to the study the optimal random allocation of components in series and parallel systems. As a novelty, our study includes the case of coherent systems with dependent components by using basic mathematical tools (and copula theory).

The North American Journal of Economics and Finance, 1999

This paper constructs a social accounting matrix for Honduras to serve as a database for the comp... more This paper constructs a social accounting matrix for Honduras to serve as a database for the computable general equilibrium (or CGE) model adapted to the characteristics of the Honduran economy. A number of simulations of economic policy modifications were carried out to quantify their possible impact on Honduran economy. This paper first considers the general characteristics of the Honduran economy and the main policy reforms put into effect these last few years. CGE model characteristics for Honduras are briefly presented, and the Honduran SAM for 1991 is described. Several simulations were run to assess the impact of selected policy changes. Results show that, in general, structural modification policies used to redirect the Honduran economy outwards (trade liberalization and devaluation of the lempira) favor agriculture, not only in terms of its domestic production but also concerning income distribution. The results are consistent with the ones proposed in the literature on economic development that maintains that interventionist policies linked to the import substitution model that were in fashion until the eighties were anti-agrarian. On the other hand, a reduction in public expenditure promotes less the Honduran rural sector, though it does not stop doing so. However, results also point to the fact that there are underlying problems in carrying out these liberalization measures. The clearest case is free trade, since compensating the drastic reductions to state income that are brought by the reduction or elimination of tariffs is no easy task.

Revista de biología marina y oceanografía, 2013

From the 32 worldwide post nesting Chelonia mydas sub populations 2 are found in the Mexican Coas... more From the 32 worldwide post nesting Chelonia mydas sub populations 2 are found in the Mexican Coasts, one of them in Michoacan (Pacific Ocean) and the other in the Yucatán Peninsula (Atlantic Ocean). Lack of information about migration patterns, home ranges and anthropogenic interaction are factors that contribute to the int rinsic vulnerability of C. mydas populations anywhere around the world. The objective of this investigation was to identify migration routes and critical marine habitats for post nesting C. mydas individuals in the Yucatán Peninsula. Between June 2011 and January 2012 4 C. mydas post nesting individuals were tracked using satellite telemetry, 2 of them from continental beaches and the other 2 from insular ones. A geographic information system was used to integrate the collected information and used to identify migration routes for C. mydas as well as to estimate their home ranges. Three turtles moved and remained over the marine platform in the Banco de Campeche in Mexican territory, while one of the turtles migrated outside Mexican waters to Dry Tortuga (Florida, USA). The home ranges areas used by nesting females in continental beaches were significantly larger and further from the coast compared to those registered for females tracked from insular beaches. Based on the results we recommend management strategies planning for conservation of C. mydas in the Yucatán Peninsula.

Proceedings of Latin American & Caribbean Petroleum Engineering Conference, 2007

This work shows the main considerations adopted and proved successful for oilfield reactivation a... more This work shows the main considerations adopted and proved successful for oilfield reactivation and production increase through the handling of very high gross production flow rate with high water/oil ratio. The execution strategy is focused on maximizing the production anticipation in the short-term by taking maximum advantage of the existing facilities and, in the mid- term, by developing facilities with new systems sized with flexibility and supplying them timely. All of these allowing to take advantage of the most suitable technologies existing in the market for handling, separation, treatment and disposition of high produced water flow rates, during the lifetime contract for each oilfield. Examples of this approach are the study cases presented related to water injection for secondary recovery and disposal purposes. The knowledge obtained during the development and operation of a given mature field, has been adapted for its application in another field, and so on, considering particular features and different contractual terms, allowing PESA to success in very mature oilfields with apparently very restricted development opportunities. Introduction The development and operation of mature oilfields in many cases demand handling high volumes of gross production, obsolete and under rated facilities that require huge investments, and tight returns making mandatory the optimization of operating expenses. In order to plan and develop the surface facilities required to reach the objectives for reactivation and production increase in specific mature oilfields, main adopted considerations have been focused on three basic aspects:Increasing both oil production, and recovery factor, as well as advancing oil production when possible (Fig. 1).Optimization of capital expenses (Capex) in new equipment and facilities, considering the convenience of keeping existing equipment and the duration of operative contracts.Reduction of the operating expenses (Opex) during the cycle of life of each projected facility. The advantage of the obtained knowledge during the development and operation of mature fields, and the adaptation for extending its application to a different field, considering its particularities, including different contractual terms, allowed us to develop a high capacity in making fine adjustments to find opportunities in oilfields with high level of maturity. Facilities Design. Criteria The key factors applied in designing facilities in mature oilfields under revitalization are:Handling very high flow rates of gross production, with high water / oil ratios (WOR of 50 to 90, or higher).Applying a multidisciplinary approach (Reservoirs, Wells Construction, Production Engineering, and Surface Facilities) from the feasibility phase of each development. In this way, it's possible to reach production objectives while optimizing Capex, making the most of the existing and proposed surface facilities.Permanently valuating the impact of the facilities design on the operating expenses for each oilfield. All of these factors are considered within the terms and duration of the specific operative contract for each oilfield, which is a real constraint in the planning of each development and a very important element for the project development analysis. A significant common factor in these projects has been the decision to centralize the oil treatment in one facility, having satellites facilities for oil partial dehydration, from where the separated produced water is sent to water treatment plants. These plants are located in order to handle and pump the treated produced water into injection wells for secondary recovery or disposal purpose. (Fig. 2).

Thermochimica Acta, 1985

ABSTRACT

Journal of the American Chemical Society, 2004

Experimental Section Materials. 2-Hydroxypyrimidine•HCl was purchased from Aldrich. [Cu(2-pymo) 2... more Experimental Section Materials. 2-Hydroxypyrimidine•HCl was purchased from Aldrich. [Cu(2-pymo) 2 ]•nH 2 O (1 R) was prepared as previously reported. 1 Note: Apart from the evacuated 1 C , all species host, in their MOF channels, a number of water molecules.

Journal of Multivariate Analysis, 2010

In this paper, we introduce the concepts of average and projected systems associated to a coheren... more In this paper, we introduce the concepts of average and projected systems associated to a coherent (parent) system. We analyze several aspects of these notions and show that they can be useful tools in studying the performance of coherent systems with nonexchangeable components. We show that the average and projected systems are especially useful in studying the tail behavior of reliability, hazard rate and mean residual life functions of the parent system and also in obtaining the tail best systems (under different criteria) by permuting the components at the system structure. Moreover, they can be useful in assessing how the asymmetry of the joint distribution of the component lifetimes (with respect to permutations of the components in the system structure) affects the system performance.