Oscillation damping of chiral string loops

Chiral cosmic string loop tends to the stationary (vorton) configuration due to the energy loss into the gravitational and electromagnetic radiation. We describe the asymptotic behaviour of near stationary chiral loops and their fading to vortons. General limits on the gravitational and electromagnetic energy losses by near stationary chiral loops are found. For these loops we estimate the oscillation damping time. We present solvable examples of gravitational radiation energy loss by some chiral loop configurations. The analytical dependence of string energy with time is found in the case of the chiral ring with small amplitude radial oscillations.Comment: 10 pages, 2 figures. Accepted for publication in Physical Review

A review on the applicability of remanufacturing in extending the life cycle of marine or offshore components and structures

One of the most significant and value-added End of Life (EoL) recovery strategies in the Circular Economy is remanufacturing in which the functionality and performance of products are retained. In the marine industry, the intensity of remanufacturing is low compared to other transportation industries such as aerospace, automotive and rail. This paper discusses current issues on Design for Remanufacturing (DfRem) in the marine industry and provides insights into how remanufacturing plays a significant role in enhancing reliability and safety during the extended life of marine products and structures. Today, with the large number of ships approaching EoL, remanufacturing should be the way forward due to its positive impact on the environment and socio-economy. While marine components such as engines, propeller shafts, compressors and pumps have been successfully remanufactured in many parts of the world, remanufacturing of large structures such as hull and vessels have not been reported thus far. As in all other industries, remanufacturing has to be initiated with a paradigm shift in the business models, designing parts and structures for efficient remanufacturing, and the establishment of relevant policies and standards in order to pave the way towards a more sustainable marine industry in the future

Chiral Superconducting Membranes

We develop the dynamics of the chiral superconducting membranes (with null current) in an alternative geometric approach either making a Lagrangian description and a Hamiltonian point of view. Besides of this, we show the equivalence of the resulting descriptions to the one known Dirac-Nambu-Goto (DNG) case. Integrability for chiral string model is obtained using a proposed light-cone gauge. In a similar way, domain walls are integrated by means of a simple ansatz. We compare the results with recently works appeared in the literature.Comment: Latex file, 17 pages, no figures. Improved version, typos corrected, Comments and references adde

Life Cycle Assessment as a complementary utility to regulatory measures of shipping energy efficiency

The purpose of this paper is to document that LCA, aside from showing indication of compliance to both current IMO regulatory metrics (i.e. EEDI and EEOI) –not only as a practical environmental indicator, but also as a tool able to highlight energy efficiency–, can also be used in parallel to these, serving as a complementary utility able to assist with their practical implementation. An LCA model formulation is summarised and also applied on a case study vessel, utilising it for validation, and additionally for comparing the LCA approach to the IMO regulatory metrics. Results show that aside from the environmental score of CO2 emissions per unit of work –recognised by the current regulatory metrics–, LCA can also offer NOx and SOx scores, along with other hazardous releases. Moreover, LCA –aside from showing compliance to the formulation of both IMO regulatory metrics– is able to present material and energy utilisation throughout different stages within the vessel's lifetime. Lastly, it is documented that LCA can be used in parallel to the regulatory metrics, in order to efficiently emphasise detailed environmental information. Furthermore, the implementation of LCA could be considered as a potential aid for the European Commission's recent MRV legislation

Quantum tunneling of superconducting string currents

We investigate the decay of current on a superconducting cosmic string through quantum tunneling. We construct the instanton describing tunneling in a simple bosonic string model, and estimate the decay rate. The tunneling rate vanishes in the limit of a chiral current. This conclusion, which is supported by a symmetry argument, is expected to apply in general. It has important implications for the stability of chiral vortons.Comment: 16 pages, 2 figure

Analysis of maritime transport accidents using Bayesian networks

A Bayesian network–based risk analysis approach is proposed to analyse the risk factors influencing maritime transport accidents. Comparing with previous studies in the relevant literature, it reveals new features including (1) new primary data directly derived from maritime accident records by two major databanks Marine Accident Investigation Branch and Transportation Safety Board of Canada from 2012 to 2017, (2) rational classification of the factors with respect to each of the major types of maritime accidents for effective prevention, and (3) quantification of the extent to which different combinations of the factors influence each accident type. The network modelling the interdependency among the risk factors is constructed by using a naïve Bayesian network and validated by sensitivity analysis. The results reveal that the common risk factors among different types of accidents are ship operation, voyage segment, ship type, gross tonnage, hull type, and information. Scenario analysis is conducted to predict the occurrence likelihood of different types of accidents under various situations. The findings provide transport authorities and ship owners with useful insights for maritime accident prevention

LFI 30 and 44 GHz receivers Back-End Modules

The 30 and 44 GHz Back End Modules (BEM) for the Planck Low Frequency Instrument are broadband receivers (20% relative bandwidth) working at room temperature. The signals coming from the Front End Module are amplified, band pass filtered and finally converted to DC by a detector diode. Each receiver has two identical branches following the differential scheme of the Planck radiometers. The BEM design is based on MMIC Low Noise Amplifiers using GaAs P-HEMT devices, microstrip filters and Schottky diode detectors. Their manufacturing development has included elegant breadboard prototypes and finally qualification and flight model units. Electrical, mechanical and environmental tests were carried out for the characterization and verification of the manufactured BEMs. A description of the 30 and 44 GHz Back End Modules of Planck-LFI radiometers is given, with details of the tests done to determine their electrical and environmental performances. The electrical performances of the 30 and 44 GHz Back End Modules: frequency response, effective bandwidth, equivalent noise temperature, 1/f noise and linearity are presented

A Fuzzy Rule-Based Bayesian Reasoning Approach for Risk Assessment of Petroleum Transportation Systems

Petroleum Transportation Systems (PTSs) play an important role in the movement of crude oil from its production sites to the end users. Such systems are complex because they often operate in a dynamic environment. Therefore, safe operations of the key components in the systems such as port and transportation are vital for the success of PTSs. Risk assessment is a powerful tool to ensure the safe transportation of crude oil. This paper applies a mathematical model to identify and evaluate the operational hazards associated with PTSs, by combining a Fuzzy Rule-Based (FRB) method and Bayesian Networks (BNs). This hybrid model has been found capable of assisting decision-makers in measuring and improving the PTSs’ safety, and dealing with the inherent uncertainties in risk data

Risk analysis of petroleum transportation using fuzzy rule-based Bayesian reasoning

Petroleum transportation systems (PTSs) play a critical role in the movement of crude oil from its production sites to end users. Such systems are complex because they often operate in a dynamic environment. Safe operations of the key components in PTSs such as port and shipping are vital for the success of the systems. Risk assessment is a powerful tool to ensure the safe transportation of crude oil. This paper applies a mathematical model to identify and evaluate the operational hazards associated with PTSs, by incorporating a fuzzy rule-based (FRB) method with Bayesian networks (BNs). Its novelty lies in the realisation of risk analysis and prioritisation of the hazards in PTSs when historical failure data is not available. This hybrid model is capable of assisting decision-makers in measuring and improving the PTSs' safety, and dealing with the inherent uncertainties in risk data

Charged and superconducting vortices in dense quark matter

Quark matter at astrophysical densities may contain stable vortices due to the spontaneous breaking of hypercharge symmetry by kaon condensation. We argue that these vortices could be both charged and electrically superconducting. Current carrying loops (vortons) could be long lived and play a role in the magnetic and transport properties of this matter. We provide a scenario for vorton formation in protoneutron stars.Comment: Replaced with the published version. A typographical error in Eq. 2 is correcte