Optimisation of composite boat hulls using first principles and design rules

The design process is becoming increasingly complex with designers balancing societal, environmental and political issues. Composite materials are attractive to designers due to excellent strength to weight ratio, low corrosion and ability to be tailored to the application. One problem with composite materials can be the low stiffness that they exhibit and as such for many applications they are stiffened. These stiffened structures create a complex engineering problem by which they must be designed to have the lowest cost and mass and yet withstand loads. This paper therefore examines the way in which rapid assessment of stiffened boat structures can be performed for the concept design stage. Navier grillage method is combined with genetic algorithms to produce panels optimised for mass and cost. These models are constrained using design rules, in this case ISO 12215 and Lloyd's Register Rules for Special Service Craft. The results show a method that produces a reasonable stiffened structure rapidly that could be used in advanced concept design or early detailed design to reduce design time

SO₂ emissions from basaltic eruptions, and the excess sulfur issue

Volcanic SO2 can affect the Earth's environment. Where no direct measurements of SO2 in the atmosphere are available, a petrologic method of assessing sulfur release from the magma must be used. However, in studies of arc-derived eruptions, satellite-based measurements of SO2 emissions using Total Ozone Mapping Spectrometer (TOMS) data are orders of magnitude greater than those calculated petrologically, implying that a separate S-rich gas phase in the magma chamber may be responsible for the excess sulfur. We test whether this applies in other settings. For Icelandic and Hawaiian basalts we find that petrologic SO2 values are comparable to measurements of SO2 by TOMS. Thus, for non-arc basalts, the petrologic method gives reliable estimates of SO2 released. The implied absence of excess sulfur in non-arc basaltic magmas is a reflection of source magma conditions, notably lower fO2 and volatile contents than arc magmas, inhibiting the exsolution of a S-rich gas prior to eruption

A rapid method for reliability analysis of composite tophat stiffened structures using a first principles method and design rules

Composite materials are increasingly being used within engineering, especially in low weight applications. A significant drawback that these materials exhibit is their variability. There is a growing trend towards stochastic analysis of marine structures and this is even more important for scenarios that have a high variability. To implement these new techniques it is important to be able to, rapidly and accurately, determine reliability during the design phase. Therefore, a reliability analysis, utilising a rapid implementation, has been performed on plates that have been designed using two different sets of design rules and a first principles method. The results show that whilst, under the limits investigated, the reliability of the design rules are slightly safer than those found using first principles; the sensitivity analysis shows that each of the design rules generates a different reaction from each variable, encouraging different types of structures through their idiosyncrasies. Furthermore the method shown allows a rapid analysis to be performed on complex composite structures in a relatively short time frame using either first principles methods or design rules

Implementation of a generic concurrent engineering environment framework for boatbuilding

Boatbuilding is a growth market with global competition and tight profit margins. Concurrent engineering is not presently prevalent within the boatbuilding industry and yet this is a technique that has found much success in other industries. A methodology has, therefore, been developed to aid design in the leisure boatbuilding industry. This environment uses collaborative engineering and automated communication to aid the passing of direct communication between all members of the design team. This paper determines the characteristics of importance within boatbuilding and relates these to a framework concurrent engineering environment aimed specifically at this industry. The current work focuses on the structural and production subsystems in an attempt to improve design for production. The use of concurrent engineering tools has been highlighted with an example

Investigation into skin stiffener debonding of top-hat stiffened composite structures

Top-hat stiffened plates provide an efficient structure for engineering applications. During service debonding between the stiffener and the plate is often observed and parametric studies of open section stiffeners have shown that debond size and location have a significant effect on the damage mode of the panel. However, these studies do not consider the interaction of failure modes and do not assess the ultimate failure of the structure. In this paper top-hat stiffened composite structures are assessed considering debond damage between the stiffener and plate. A non-linear finite element model is used to perform a parametric study on the effect of both damage and the panel’s geometry on the failure modes, ultimate strength and its damage tolerance. Results show that top-hat stiffened panels exhibit a trend between ultimate strength and the debond size with crack initiation not necessarily propagating. Geometric imperfections accelerate buckling but can provide an arrest point for crack propagation

Novel margin management to enhance Auchenorrhyncha biodiversity in intensive grasslands

Agricultural intensification, including changes in cutting, grazing and fertilizer regimes, has led to declines in UK and NW European grassland biodiversity. We aimed to develop field margin management practices that would support invertebrate diversity and abundance on intensively managed grassland farms, focusing on planthoppers and leafhoppers (Auchenorrhyncha). Replicated across four farms in south-west England, we manipulated conventional management practices (inorganic fertilizer, cutting frequency and height, and aftermath grazing) to create seven treatments along a gradient of decreasing management intensity and increasing sward architectural complexity. Auchenorrhyncha were sampled annually between 2003 and 2005. Auchenorrhyncha abundance and species richness was highest in the most extensively managed treatments. Abundance was lowest with frequent cutting, while species richness was lowest where cattle grazing occurred. Unexpectedly, application of inorganic fertilizer had no effect on Auchenorrhyncha abundance or species richness. Management options that enhance invertebrate diversity, while allowing the remainder of the field to be managed conventionally, represent a potentially important conservation tool for many lowland improved grasslands. Extensification of conventional management in field margin areas of such grasslands are likely to benefit this numerically dominant component of grassland invertebrate fauna. These management practices have the potential to be incorporated into existing UK and European agri-environment schemes

Hydrophosphination of Activated Alkenes by a Cobalt(I) Pincer Complex

Herein we report the synthesis of three heteroleptic first-row transition metal(II) complexes containing carbazolido NNN pincer ligands and conversion to the corresponding metal(I)-carbonyl complexes via a reductive carbonylation route. These complexes are precatalysts for the hydrophosphination of activated alkenes, affording a cobalt-catalysed hydrophosphination process that solely and selectively yields the ß addition (anti-Markovnikov) product. The scope of this transformation has been investigated using a variety of activated alkenes. Isolation and characterisation of substrate-coordinated intermediates reveal available coordination sites, which provide insight into the proposed catalytic cycle

Ocean-rafted pumice constrains postglacial relative sea-level and supports Holocene ice cap survival

Distally deposited tephra from explosive volcanic eruptions can be a powerful tool for precise dating and correlation of sedimentary archives and landforms. However, the morphostratigraphic and chronological potential of ocean-rafted pumice has been under-utilized considering its long observational history and widespread distribution on modern and palaeo-shorelines around the world. Here we analyze the geochemical composition and elevation data of 60 samples of ocean-rafted pumice collected since 1958 from raised beaches on Svalbard. Comparison of pumice data with postglacial relative sea-level history suggests eight distinct pumice rafting events throughout the North Atlantic during the Middle and Late Holocene. Analyzed ocean-rafted pumice exhibit consistent silicic composition characteristic of deposits from Iceland’s volcanic system, Katla. Eruption-triggered jökulhlaups are key drivers of the transport of pumice from the Katla caldera to beyond the coast of Iceland and into the surface currents of the North Atlantic Ocean. Thus, the correlation of distinct, high-concentration pumice horizons from Katla deposited along raised Middle Holocene beach ridges in Svalbard further advocates for the persistence of the Mýrdalsjökull ice cap through the Holocene thermal maximum

Persistence of a Continuous Stochastic Process with Discrete-Time Sampling: Non-Markov Processes

We consider the problem of `discrete-time persistence', which deals with the zero-crossings of a continuous stochastic process, X(T), measured at discrete times, T = n(\Delta T). For a Gaussian Stationary Process the persistence (no crossing) probability decays as exp(-\theta_D T) = [\rho(a)]^n for large n, where a = \exp[-(\Delta T)/2], and the discrete persistence exponent, \theta_D, is given by \theta_D = \ln(\rho)/2\ln(a). Using the `Independent Interval Approximation', we show how \theta_D varies with (\Delta T) for small (\Delta T) and conclude that experimental measurements of persistence for smooth processes, such as diffusion, are less sensitive to the effects of discrete sampling than measurements of a randomly accelerated particle or random walker. We extend the matrix method developed by us previously [Phys. Rev. E 64, 015151(R) (2001)] to determine \rho(a) for a two-dimensional random walk and the one-dimensional random acceleration problem. We also consider `alternating persistence', which corresponds to a < 0, and calculate \rho(a) for this case.Comment: 14 pages plus 8 figure