113,892 research outputs found
On the existence spectrum for sharply transitive G-designs, G a [k]-matching
No full textIn this paper we consider decompositions of the complete graph Kv into matchings of uniform cardinality k. They can only exist when k is an admissible value, that is a divisor of v(v−1)/2 with 1≤k≤v/2. The decompositions are required to admit an automorphism group Γ acting sharply transitively on the set of vertices. Here Γ is assumed to be either non-cyclic abelian or dihedral and we obtain necessary conditions for the existence of the decomposition when k is an admissible value with 1<k<v/2. Differently from the case where Γ is a cyclic group, these conditions do exclude existence in specific cases. On the other hand we produce several constructions for a wide range of admissible values, in particular for every admissible value of k when v is odd and Γ is an arbitrary group of odd order possessing a subgroup of order gcd(k,v)
Expert Systems and Fuzzy Logic in WWTP Operation Support: Examples and Applications in AMGA’s Plants
No full textSymmetric bowtie decompositions of the complete graph
No full textGiven a bowtie decomposition of the complete graph Kvadmitting an automorphism group G acting transitively on thevertices of the graph, we give necessary conditions involvingthe rank of the group and the cycle types of the permutationsin G. These conditions yield non--existence results forinstance when G is the dihedral group of order 2v, with, or a group acting transitively on thevertices of K9 and K_{21}. Furthermore, we havenon--existence for K_{13} when the group G is differentfrom the cyclic group of order 13 or for K_{25} when thegroup G is not an abelian group of order 25. Bowtiedecompositions admitting an automorphism group whose action onvertices is sharply transitive, primitive or 1--rotational,respectively, are also studied. It is shown that if the actionof G on the vertices of K_v is sharply transitive, then theexistence of a G--invariant bowtie decomposition is excludedwhen and is equivalent to the existence ofa G--invariant Steiner triple system of order v. We arealways able to exclude existence if the action of G on thevertices of K_v is assumed to be 1--rotational. If,instead, G is assumed to act primitively then existence canbe excluded when v is a prime power satisfying someadditional arithmetic constraint
Assessment of the risk related to environmental damage following major accidents in onshore pipelines
No full textMajor accidents may cause both direct damages to the exposed population and damage to the environment, indirectly affecting the population by the contamination of land, surface water and groundwater. A wide attention was paid to date to the assessment of the direct risk for the population deriving from major accidents (fires, explosions, toxic releases). Less work was devoted to the quantitative assessment of the risk due to the environmental consequences of major accidents. In the present study, an innovative GIS-based approach was developed for the quantitative assessment of the risk caused by damage to the environment deriving from major accidents involving pipelines. The method allows the calculation of local and overall environmental risk indexes, expressed both in physical and monetary terms. These are structured so that in perspective they can be combined with the risk obtained for the exposed population, providing a comprehensive risk figure of the potential consequences of major accidents involving oil pipelines. A specific software tool was developed to support the application of the methodology. A real-life case-study is presented and discussed in order to assess the potentiality of the approach. The results confirm that, in the frame of safety guidelines and good practices for pipelines, the proposed methodology represents a useful tool to fulfil requirements concerning the comprehensive risk assessment of pipeline operation, providing useful information on safety-critical segments and on the expected severity and economic impact of spill scenarios. © 2018 Elsevier Lt
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Some progress on the existence of 1-rotational Steiner Triple Systems
No full textA Steiner Triple System of order v (briefly STS(v)) is 1-rotational under G if it admits G as an automorphism group acting sharply transitively on all but one point.The spectrum of values of v for which there exists a1-rotational STS(v) under a cyclic, an abelian, or a generalized quaternion group, has beenestablished in 1981 (phelps and Rosa), in 2001 (Buratti) and in 2008 (Mishima), respectively.Nevertheless, the spectrum of values of v for which there exists a1-rotational STS(v) under an arbitrary group has not been completely determined yet.This paper is a considerable step forward to the solution of this problem.In fact, we leave as uncertain cases only those for which we have v = (p^3-p)n + 1 = 1 (mod 96)with p a prime, n =1,2,3 mod 4, and the odd part of (p^3-p)n that is square-free and without prime factors congruent to 1 mod 6
Risk-based Vulnerability Analysis of Chemical Facilities Affected by Flooding
No full textFlooding may affect chemical facilities leading to major accidents (fires, explosions, contamination), following damages to structures and equipment. This type of accident is indicated as a “natural-technological” (Natech) event and occurred in the past, often leading to severe accidental scenarios. Recent studies allowed developing a specific methodology aimed at including Natech scenarios triggered by flooding into Quantitative Risk Assessment (QRA) analyses for chemical facilities. The methodology relies on the use of specific fragility models for the evaluation of failure probability of process units affected by flooding. Despite these models consider different types of equipment geometries and flooding conditions, they do not account for the presence of safety barriers (e.g., fire-protection systems, bunds, blanketing system). In the present work, the previously developed QRA methodology is improved in order to provide a risk-based vulnerability analysis of Natech scenarios induced by severe flooding taking into account the presence of safety barriers. The methodology is improved by including the availability assessment of safety barriers based on the possibility the systems have been impacted by the flood. A tailored Failure Mode and Effect and Criticality Analysis (FMECA) is presented for assessing the damages to safety barriers resulting from flooding events. As an example, the analysis of an important safety barrier through the FMECA approach is presented. The study shows an example of both risk informed decision-making concerning protection systems and development of new criteria for the assessment of safety barrier failure in case of natural hazards
Electric performance of the ALICE Silicon Drift Detector irradiated with 1 GeV electrons
No full textThe final version of the ALICE Silicon Drift Detector was irradiated with 1 GeV electrons at the LINAC of the Synchrotron 'Elettra' in Trieste. The electron fluence was equivalent to the total particle fluence expected during 10 years of ALICE operation as far as the bulk damage is concerned. The anode current, the voltage distribution on the integrated divider, and the operation of the MOS injectors were tested. The detector was found to be sufficiently radiation hard for the ALICE experiment
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Multi-target Inherent Safety Indices for the Early Design of Offshore Oil&Gas Facilities
No full textImproved tools are needed to manage major accident hazard of progressively more complex offshore oil&gas systems in environmentally sensitive areas. Inherent safety principles provide a strategic opportunity to reduce major accident hazards since the early design phase, but a suitable metric to orient safer design choices is needed to apply such principles intro practice. This study aims at providing a systematic approach to the assessment of the hazard profile of alternative process designs in offshore oil & gas production facilities. A novel methodology providing a ranking of inherently safer solutions in conceptual design is described. The methodology is able to highlight the different contributors to the safety profile of the offshore oil & gas production system, linking them to the specific features of the design. The proposed approach, based on multi-criteria Key Performance Indicators (KPIs), addresses different targets (people, assets, environment) and provides a quantitative assessment of the safety score, accounting for both the possible accident consequences and their credibility. An application to a case study concerning an offshore facility for gas production is discussed to demonstrate the potential of the methodology
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