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The paper shows the connections between some importance indices for the components in an engineering coherent system and the performance of the system obtained when a redundancy mechanism is applied to a specific component. A copula approach is used to model the dependency among the components. This approach includes the popular case of independent components. Under some assumptions, it is proved that if component i is more important than component j, then the system obtained by applying a redundancy procedure to the ith component is better, under different stochastic criteria, than that obtained with the jth component. These results can be applied to several redundancy mechanisms. A new importance index is defined to study active redundancies. Some illustrative examples are provided.
Our objective was to determine the frequency of zika (ZIKV), chikungunya (CHIKV) and dengue (DENV) virus coinfection and describe the mortality cases that occurred during the epidemiologic surveillance of the ZIKV epidemic in Colombia. We analysed all cases of suspected ZIKV infection that were reported to the National Institute of Health (October 2015–December 2016). DENV, CHIKV and ZIKV RNA were detected in serum or tissue samples using polymerase chain reaction assay. Medical records of the fatal cases were reviewed. We identified that 23 871 samples were processed. The frequency of viral agents was 439 (1.84%) for DENV, 257 (1.07%) for CHIKV and 10118 (42.38%) for ZIKV. Thirty-four (0.14%) cases of coinfection were identified. The CHIKV–ZIKV coinfection was present in 28 cases (82.3%), DENV–CHIKV in three (8.8%) and DENV–ZIKV in three (8.8%). Seven (20.6%) coinfection cases were fatal (two DENV–CHIKV cases and five CHIKV–ZIKV cases). Two cases were foetal deaths and the others were related to neurological syndrome and sepsis. In conclusion, the frequency of arbovirus coinfection during epidemic of ZIKV was low, and CHIKV–ZIKV coinfection was the most common. Mortality was high among coinfection patients. The role of each virus in the mortality cases of coinfection warrants further studies.
The Samaniego signature is a relevant tool for studying the performance of a system whose component lifetimes are exchangeable. It is well known that the stochastic ordering of the signatures of two systems implies the same for the respective system lifetimes. We prove that the reverse claim is not true when the component lifetimes are independent and identically distributed. There exist small proportions of systems with stochastically ordered lifetimes whose signatures are not ordered. We present a simple procedure in order to check whether the system lifetimes are stochastically ordered even if their signatures are not comparable.
The Shannon entropy based on the probability density function is a key information measure with applications in different areas. Some alternative information measures have been proposed in the literature. Two relevant ones are the cumulative residual entropy (based on the survival function) and the cumulative past entropy (based on the distribution function). Recently, some extensions of these measures have been proposed. Here, we obtain some properties for the generalized cumulative past entropy. In particular, we prove that it determines the underlying distribution. We also study this measure in coherent systems and a closely related generalized past cumulative Kerridge inaccuracy measure.
The main purpose of coatings is to increase the lifetime of cutting tools, to perform continuous and economical material removal process, reducing the frequency of sharpening or replacement of the tool, which contributes to increase quality of product. Therefore, hafnium nitride (HfN) single layer coatings were deposited on High-speed steel by Magnetron Sputtering physical vapour deposition (PVD). The machining on AISI 1020 steel samples were carried out in a computer numerical control (CNC) machine, using coated and uncoated tools, the temperature of the different components were measured (steel bar and tool), due to continuous temperature measurement help to predict tool wear and the quality of finished piece  . In order to evaluate wear resistance and performance, not only temperature data were compared, the tool wear morphological analysis for flank wear was carried using Scanning Electron Microscopy (SEM), and work pieces roughness were checked through their surfaces in an Atomic Force Microscopy (AFM). In most of the parameters evaluated differences between the tools were identified, and results reveals that on HfN coating, occurs less wear, due the proportionality between the energy transfer and the tool deterioration, also the coating improves surface finish of the machined part; all of them are reflected in changes on process temperatures. The use of single layer HfN coating on cutting tools could increase their lifetime, improve the quality of the work piece, and even reduce process time and cost.
pCO2/pH perturbation experiments were carried out under two different pCO2 levels to evaluate effects of CO2-driven ocean acidification on semi-continuous cultures of the marine diatom Skeletonema pseudocostatum CSA48. Under higher pCO2/lowered pH conditions, our results showed that CO2-driven acidification had no significant impact on growth rate, chlorophyll-a, cellular abundance, gross photosynthesis, dark respiration, particulate organic carbon and particulate organic nitrogen between CO2-treatments, suggesting that S. pseudocostatum is adapted to tolerate changes of ~0.5 units of pH under high pCO2 conditions. However, dissolved organic carbon (DOC) concentration and DOC/POC ratio were significantly higher at high pCO2, indicating that a greater partitioning of organic carbon into the DOC pool was stimulated by high CO2/low pH conditions. Total fatty acids (FAs) were significantly higher under low pCO2 conditions. The composition of FAs changed from low to high pCO2, with an increase in the concentration of saturated and a reduction of monounsaturated FAs. Polyunsaturated FAs did not show significant differences between pCO2 treatments. Our results lead to the conclusion that the balance between negative or null effect on S. pseudocostatum ecophysiology upon low pH/high pCO2 conditions constitute an important factor to be considered in order to evaluate the global effect of rising atmospheric CO2 on primary productivity in coastal ocean. We found a significant decrease in total FAs, however no indications were found for a detrimental effect of ocean acidification on the nutritional quality in terms of essential fatty acids.
Perceived control has shown predictive value for anxiety severity symptoms as well as cognitive-behavior therapy outcomes. The most commonly used measure of perceived control is the Anxiety Control Questionnaire (ACQ), and more recently the ACQ Revised (ACQ-R). However, both questionnaires have shown structural inconsistencies among several studies. Also, although the ACQ and ACQ-R seem to be multidimensional instruments, a single total score have been commonly used. This study examined the internal structure of the ACQ-R Spanish version using exploratory factor and exploratory bi-factor analysis in a sample of 382 college students and 52 people diagnosed of panic disorder (with or without agoraphobia). Also, in this study we assessed the preliminary diagnostic value of the ACQ-R scores. The results indicated that the ACQ-R Spanish version structure consisted of two factors: one related with perceived control of internal emotional reactions (Emotion Control) and another related with perceived control of external events (Threat and Stress Control). Both specific factors can be adequately summarized by a general factor (General Anxiety Perception of Control; CFI = .973, TLI = .954, RMSEA = .039; p = .002), which accounted for 70% of the common explained variance. The correlations between the ACQ-R scores and with variables like anxiety (r = –.66) or anxiety sensitivity (r = –.50) presented the expected pattern of results. Either the two dimensions structure or the total score have proved to be a good tool to distinguish between participants with panic disorder and non-clinical samples (area under the curve = 0.79).
Our study tested the hypothesis that older adults and men use more adaptive emotion regulatory strategies but fewer negative emotion regulatory strategies than younger adults and women. In addition, we tested the hypothesis that rumination acts as a mediator variable for the effect of age and gender on depression scores. Differences in rumination, problem solving, distraction, autobiographical recall and depression were assessed in a group of young adults (18–29 years) compared to a group of older adults (50–76 years). The older group used more problem solving and distraction strategies when in a depressed state than their younger counterparts (ps < .05). The younger participants reported more rumination (p < .01). Women scored higher in depression scores and lower in distraction than men (ps < .05). There were no significant effects of age, gender, or interaction of age by gender on the recall of specific autobiographical memories (ps > .06). Ordinary least squares regression analyses with bootstrapping showed that rumination mediated the association between age, gender and depression scores. These results suggest that older adults and men select more adaptive strategies to regulate emotions than young adults and women with rumination acting as a significant mediator variable in the association between age, gender, and depression.
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.
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.
An argument can be defined as a set of statements of a given language in which the truth of one of them (the conclusion) is assured by the truth of the others (the premises). Logic has to do with the study of arguments, but it is not a discipline oriented to describe our actual practices of argumentation and reasoning. It does not purport to examine the actual psychological processes or states of mind of people. In particular, it is not an empirical task whose outcome varies with different universes of analysis (i.e., different human groups and times). Instead, logic is concerned with a critical evaluation of argumentation; with patterns of correct reasoning.
However, this is still inaccurate as a proper characterization of logic, because any critical assessment of argumentation depends on the implicit goals ascribed to it, and there is not one but a plurality of goals we may seek to accomplish in our argumentative practices. For example, if we intend to persuade an audience, arguments will be evaluated as good or bad according to their merits to the extent that the audience is actually persuaded by our words. That would be an example of a rhetorical assessment of argumentation.
So far we have been dealing with the problem of the foundations of deontic logic, particularly with the controversial relation between propositions and norms. And although the thesis that norms are proposition-like entities is highly controversial (we have, in fact, rejected that point of view), there is no disputing the propositional character of the discourse about norms. It is unreasonable to deny the possibility of formulating true or false descriptive statements about the norms that belong to a certain normative system.
The difference between genuine norms and statements about norms is quite apparent. However, as previously noticed, the problem is that the very same words (e.g., “Parking is not allowed here”) may be used, depending on the context, either to formulate a norm (when the speaker is a norm-authority) or to express a norm-proposition (about the norms issued by a certain authority). Perhaps this ambiguity helps to explain the unfortunate reason why, although the distinction with different names has been noticed by several authors, it has received little attention in the analysis of the logic of normative discourse.
A considerable number of books and papers have analyzed normative concepts using new techniques developed by logicians; however, few have bridged the gap between the English legal culture and the Continental (i.e. European and Latin American) tradition in legal philosophy. This book addresses this issue by offering an introductory study on the many possibilities that logical analysis offers the study of legal systems. The volume is divided into two sections: the first covers the basic aspects of classical and deontic logic and its connections, advancing an explanation of the most important topics of the discipline by comparing different systems of deontic logic and exploring some of the most important paradoxes in its domain. The second section deals with the role of logic in the analysis of legal systems by discussing in what sense deontic logic and the logic of norm-propositions are useful tools for a proper understanding of the systematic structure of law.
The main task performed by lawyers and legal scholars is the identification of the applicable systems of norms used to develop solutions to legal cases. In the previous chapter, we claimed that the set of externally applicable norms has to be distinguished from the set of valid norms. In virtue of the “open nature” of law, applicable norms need not belong to the same system that provides the criteria of applicability. However, what is the relation that confers systematic structure to the set of externally applicable norms? As applicable norms are not necessarily valid norms, the criterion of legality seems to be inappropriate for determining the structure of such systems. On the contrary, the criterion of deducibility plays a crucial role here, because the logical consequences of general applicable norms are essential for the solution of legal problems.
In Normative Systems, Alchourrón and Bulygin developed a methodology for the analysis of legal problems that seems particularly suitable for applicable systems. In their view, legal problems are questions regarding the normative status of a certain action or set of actions. They illustrate their analysis with an example borrowed from Argentinean Law: the recovery of real estate from a third-party holder that obtained it from someone who was not its owner. Such an action may take place under a certain set of situations or states of affairs, which will be called universe of discourse (UD). The elements of a certain UD are the states of affairs that share a certain property, which is the defining property of that UD. The relevant normative question in this example is whether – and if so, in what circumstances – the third-party holder has the obligation to restore it to its owner, and in what circumstances (if any) is she allowed to retain it. The answers to these questions are dependent on the contents of the legal system under consideration: both legal problems and solutions are always relative to a certain legal system (here, Argentinean Law) that provides the starting point for identifying the applicable norms. However, legal scholars do not need to consider the whole set of valid legal norms at a certain time to find the answer to a problem such as this.
Almost since its origins, deontic logic has been threatened by several paradoxes, elaborated by theorists to highlight different shortcomings that seem to derive from its fundamental axioms. The discovery of such paradoxes led some deontic logicians toward an attitude of general skepticism about the discipline, for as Rescher remarked, “it is…only fair to say that there is virtually no issue in the field upon which a settled consensus has been reached.”
However, no area of logic is free from paradoxes. One of the main impulses at the beginnings of alethic modal logic was a certain sort of discomfort with material implication – for example, the rather counterintuitive consequence that stems from tautologies such as (p→q) ∨ (q→p). But these new developments in modal logic did not generate a skeptical attitude toward it; instead, they were regarded as opportunities for clarifying the properties of logic itself. And in fact, the same goes for deontic logic: from a technical point of view, paradoxes provided a decisive impetus toward sharpening the basic concepts of deontic logic. Thus, even if some of these paradoxes expose serious obstacles for deontic systems, their discussion, as much as the answers that have been offered for each of them, made a significant contribution to the progress of this area of logic. As Russell rightly noticed, paradoxes and puzzles play a crucial role in testing a logical theory.
Throughout this book, we have attempted to show some of the possibilities that logical analysis offers for the study of legal systems. To do so, we have presented an introduction to the basic aspects of deontic logic and contrasted the attitudes of optimism and skepticism about the possibility of accepting logical relationships among norms. In the first chapters, we briefly reviewed the connections between propositional logic, predicate calculus, alethic modal logic, and deontic logic, and then offered a schematic outline of the different systems of deontic logic that constitute the conceptual basis that has generated the most important technical developments in deontic logic. Unlike philosophers who regard norms as a special type of propositions, we have emphasized the pragmatic aspects that characterize directive discourse, and defended the idea that the most promising way to justify the existence of a logic of norms is on the basis of an abstract notion of logical consequence, which allows the development of a genuine logic of norms without making the controversial assumption that norms have truth-values.
Raz made a fundamental step forward in the theoretical reconstruction of legal dynamics when he introduced the distinction between momentary and non-momentary legal systems. The former concept refers to all those norms that are valid at a particular time; the latter is a broader concept that refers to something like the legal history of a particular community. The distinction between momentary and non-momentary legal systems is designed to shed light on the interplay between the changing content of law and its continuity over time, because it helps us to understand the reason why a pair of norms which were valid at different times can be regarded as members of the same municipal law even if they never belonged to the same momentary system. Non-momentary legal systems – also called “legal systems” simpliciter by Raz – show how the legal history of a political community is mainly developed by means of the introduction and elimination of valid norms. In non-momentary legal systems, genetic relations play a fundamental role because they define normative hierarchies and conditions for exercising normative powers. For this reason, Raz stresses that in every legal system there are genetic relations between norms.
In the creation of norms, there is a genetic relation between a power-conferring norm and the new norms created by the exercise of such power. The relevance of such relations among norms seems to be obvious: unlike morality, law often changes by specific normative acts performed by legal authorities. In fact, a person (or organ) is a legal authority only to the extent that she is allowed to modify the deontic status of certain actions. Thus, authority and creation of norms are conceptually related, and any explanation of the nature of law would be defective if this characteristic of legal systems were not taken into consideration.