Comparison of History Effects in Magnetization in Weakly pinned Crystals of high-TcT_c and low-Tc_c Superconductors

A comparison of the history effects in weakly pinned single crystals of a high $T_c$ YBa$_2$Cu$_3$O$_{7 - \delta}$ (for H $\parallel$ c) and a low $T_c$ Ca$_3$Rh$_4$Sn$_{13}$, which show anomalous variations in critical current density $J_c(H)$ are presented via tracings of the minor magnetization hysteresis loops using a vibrating sample magnetometer. The sample histories focussed are, (i) the field cooled (FC), (ii) the zero field cooled (ZFC) and (iii) an isothermal reversal of field from the normal state. An understanding of the results in terms of the modulation in the plastic deformation of the elastic vortex solid and supercooling across order-disorder transition is sought.Comment: Presented in IWCC-200

Vortex Phase Diagram of weakly pinned YBa2_2Cu3_3O7−δ_{7-\delta} for H ∥\parallel c

Vortex phase diagram in a weakly pinned crystal of YBCO for H $\parallel$ c is reviewed in the light of a recent elucidation of the process of `inverse melting' in a Bismuth cuprate system and the imaging of an interface between the ordered and the disordered regions across the peak effect in 2H-NbSe$_2$. In the given YBCO crystal, a clear distinction can be made between the second magnetization peak (SMP) and the peak effect (PE) between 65 K and 75 K. The field region between the peak fields of the SMP (H$^m_{smp}$) and the onset fields of the PE (H$^{on}_{pe}$)is not only continuously connected to the Bragg glass phase at lower fields but it is also sandwiched between the higher temperature vortex liquid phase and the lower temperature vortex glass phase. Thus, an ordered vortex state between H$^m_{smp}$ and H$^{on}_{pe}$ can get transformed to the (disordered) vortex liquid state on heating as well as to the (disordered) vortex glass state on cooling, a situation analogous to the thermal melting and the inverse melting phenomenon seen in a Bismuth cuprate.Comment: Presented in IWCC-200

Issues and challenges in sedentary behavior measurement

Previous research has shown the negative impact of sedentary behavior on health, including cardiovascular risk factors, chronic disease-related morbidity, and mortality. Accurate measurement of sedentary behavior is thus important to plan effective interventions and to inform public health messages. This article (a) provides an overview of the nature and importance of sedentary behavior, (b) describes measurement methods, including subjective and objective measurement tools, (c) reviews the most important measurement and data processing issues and challenges facing sedentary behavior researchers, and (d) presents key findings from the most recent sedentary behavior measurement-related research. Both subjective and objective measures of sedentary behavior have limitations for obtaining accurate sedentary behavior measurements compliant with the current definitions of sedentary behavior, especially when investigating sedentary behavior as part of the full spectrum of physical behaviors. Regardless of the sedentary behavior measure chosen, researchers must be aware of all possible sources of error inherent to each technique and minimize those errors, thereby increasing validity of the outcome data

Optimization of thermoplastic blend matrix HDPE/PLA with different types and levels of coupling agents

High-density polyethylene (HDPE) and poly(lactic) acid (PLA) blends with different ratios of both polymers, namely, 30:70, 50:50, and 70:30, were produced. Polyethylene-grafted maleic anhydride and a random copolymer of ethylene and glycidyl methacrylate were also considered as compatibilizers to modify HDPE/PLA optimal blends and were added in the amounts of 1, 3, and 5 wt.%. Different properties of the blends were evaluated by performing tensile tests and scanning electron microscopy to analyze blend and interfaces morphology. Moreover, thermomechanical analysis through differential scanning calorimetry, thermo-gravimetric analysis, and infrared spectroscopy were also performed. The blend containing equal amounts of HDPE and PLA seemed to present a good balance between amount of bio-derived charge and acceptable mechanical properties. This suggests that these blends have a good potential for the production of composites with lingo-cellulosic fillers

A mooring arrangement optimisation study

Ports want to ensure safe and reliable loading operations for all ships. Increase in ship sizes, especially container ships, potentially cause unsafe mooring situations. For ships moored at quay walls, there is also a lack of international guidelines for mooring arrangements. This paper presents a case study for a moored containership being passed by a vessel of identical dimensions. The behaviour of the moored ship is simulated using UGent’s time-domain mooring software Vlugmoor. Starting from a well-balanced arrangement used in daily operation, three optimisation steps are presented, aiming at lowering the ship motions, which are critical. The first step explores the impact of changing line positioning to reduce line length disparity and improve efficiency in critical force directions. The second step considers a lower fore mooring deck to reduce line steepness, as well as additional winches below the bridge and funnel. The third step proposes replacing medium stiff lines with a very stiff HMPE line, combined with an elastic tail. The effect of these optimisation steps on the ship motions are presented and compared with predictions based on efficiency parameters, expressing the capacity of the configuration to deal with positive and negative surge forces. It is shown that applying these optimisation steps can significantly improve the safety of a moored container ship during a ship passage

Ultra-thin large-aperture vacuum windows for millimeter wavelengths receivers

Targeting faint polarization patterns arising from Primordial Gravitational Waves in the Cosmic Microwave Background requires excellent observational sensitivity. Optical elements in small aperture experiments such as Bicep3 and Keck Array are designed to optimize throughput and minimize losses from transmission, reflection and scattering at millimeter wavelengths. As aperture size increases, cryostat vacuum windows must withstand larger forces from atmospheric pressure and the solution has often led to a thicker window at the expense of larger transmission loss. We have identified a new candidate material for the fabrication of vacuum windows: with a tensile strength two orders of magnitude larger than previously used materials, woven high-modulus polyethylene could allow for dramatically thinner windows, and therefore significantly reduced losses and higher sensitivity. In these proceedings we investigate the suitability of high-modulus polyethylene windows for ground-based CMB experiments, such as current and future receivers in the Bicep/Keck Array program. This includes characterizing their optical transmission as well as their mechanical behavior under atmospheric pressure. We find that such ultra-thin materials are promising candidates to improve the performance of large-aperture instruments at millimeter wavelengths, and outline a plan for further tests ahead of a possible upcoming field deployment of such a science-grade window

Synthetic mooring ropes for marine renewable energy applications

Copyright © 2015 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Renewable Energy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Renewable Energy (2015), DOI: 10.1016/j.renene.2015.03.058Synthetic mooring ropes have a proven track record of use in harsh operating conditions over the past two decades. As one of the main users of ropes for permanent mooring systems, the oil and gas industry has opted for these components because they possess performance characteristics and economies of scale which are in many respects superior to steel components. Given this accrued experience, it is unsurprising that several marine renewable energy (MRE) device developers have utilised synthetic ropes, motivated by the need to specify economical, reliable and durable mooring systems. Whilst these components are potentially an enabling technology for the MRE sector, this is a new field of application which can feature highly dynamic mooring tensions and consequently existing certification practices may not be directly applicable. Based on the expertise of the authors, this paper provides a state-of-the-art overview of synthetic ropes in the context of MRE mooring systems, including key information about aspects of specification (performance attributes, classification and testing) as well as application (installation, degradation, maintenance, inspection and decommissioning). It is the intention of this review to provide valuable insight for device developers who are considering using ropes in the specification of fit for purpose mooring systems.European Regional Development Fund through the Interreg IV-A programm

Abrasion process between a fibre mooring line and a corroded steel element during the transit and commissioning of a Marine Renewable Energy device

Copyright © 2015 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Engineering Failure Analysis. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Engineering Failure Analysis, Vol 60, (2016)] DOI: 10.1016/j.engfailanal.2015.11.037The interaction between fibre rope and steel parts on vessels (fairlead and roller) is technically well understood but not commonly published in codes or practised by mariners. What appears to be a smooth steel surface to the naked eye can still be abrasive medium to synthetic mooring components. There are very few reports of external rope abrasion tests in the literature. The surface finish at the contact between the rope and the steel guide can cause damage and consequently prematurely degrade the exposed yarns of the rope and thus reduce the overall load bearing capacity of the rope. The ISO 18692 standard [1] recommends that prolonged cycling of a rope around rollers should be avoided, however it is specified that occasional bending and running over rollers is allowable. There are two guides to specify surface roughness. MEG 3 [2] states that steel fairleads should be polished to Ra10, but in practice this may be difficult to achieve or obtain with carbon steel. US Navy guide also states that the surface of steel should have better than 125 μi or 3.2Ra [3]. The study presented here discusses the bending of a synthetic rope around a roller during transportation. It relates the motion behaviour of the vessel to rope wear and provides a detailed numerical simulation correlated with post analysis of the rope after the failure. The investigations show that the roughness of the steel roller caused the abrasion of the rope and was exacerbated through the vessel dynamics, leaving a residual strength of 14% MBL, before rupture. The experimental tests have established a linear behaviour between strength loss and surface roughness and it was observed that the abrasion mainly occurs in the early stages of load cycling. The presented work recommends the use of lubricated nylon or polished stainless steel instead of carbon steel rollers to limit abrasive rope wear. The paper also devises a methodology to carefully assess and quantify potential rope abrasion to ensure that the residual rope strength withstands the required load capacity.Marine Renewables Commercialisation Fund (MRCF) administrated by the Carbon Trust under the Array Technology Innovation Programm