The applicability and effectiveness of cluster analysis

An insight into the characteristics which determine the performance of a clustering algorithm is presented. In order for the techniques which are examined to accurately cluster data, two conditions must be simultaneously satisfied. First the data must have a particular structure, and second the parameters chosen for the clustering algorithm must be correct. By examining the structure of the data from the Cl flight line, it is clear that no single set of parameters can be used to accurately cluster all the different crops. The effectiveness of either a noniterative or iterative clustering algorithm to accurately cluster data representative of the Cl flight line is questionable. Thus extensive a prior knowledge is required in order to use cluster analysis in its present form for applications like assisting in the definition of field boundaries and evaluating the homogeneity of a field. New or modified techniques are necessary for clustering to be a reliable tool

Definition of smolder experiments for Spacelab

The feasibility of conducting experiments in space on smoldering combustion was studied to conceptually design specific smoldering experiments to be conducted in the Shuttle/Spacelab System. Design information for identified experiment critical components is provided. The analytical and experimental basis for conducting research on smoldering phenomena in space was established. Physical descriptions of the various competing processes pertaining to smoldering combustion were identified. The need for space research was defined based on limitations of existing knowledge and limitations of ground-based reduced-gravity experimental facilities

Internal Friction and Vulnerability of Mixed Alkali Glasses

Based on a hopping model we show how the mixed alkali effect in glasses can be understood if only a small fraction c_V ofthe available sites for the mobile ions is vacant. In particular, we reproduce the peculiar behavior of the internal friction and the steep fall (''vulnerability'') of the mobility of the majority ion upon small replacements by the minority ion. The single and mixed alkali internal friction peaks are caused by ion-vacancy and ion-ion exchange processes. If c_V is small, they can become comparable in height even at small mixing ratios. The large vulnerability is explained by a trapping of vacancies induced by the minority ions. Reasonable choices of model parameters yield typical behaviors found in experiments.Comment: 4 pages, 4 figure

\u3ci\u3eEragrostis Curvula\u3c/i\u3e Effects on Above and Below-Ground Plant Species Richness and Diversity

Monitoring and managing the soil seed bank is fundamental to land management as it constitutes the future generations of invasive plant communities. Invasive plants have traits that result in high recruitment through increased seed generation, short seed dormancy and phenotypic plasticity. Furthermore, invasive plants with growth forms that inhibit the growth and recruitment of other species can lead to monocultures and associated reduction in above-ground biodiversity, potentially negatively impacting the soil seed bank diversity and ecosystem functions and services. Eragrostis curvula is one such species that has many of these invasive traits, including high propagule generation, and can exclude plant species from establishing in the above-ground population, thus negatively impacting above-ground biodiversity, as measured by species richness and Shannon diversity index. However, our findings suggest it has not significantly impacted the soil seed bank species diversity or richness across eight sites within the Snowy Monaro region when competition is removed as a limiting factor. Our findings provide valuable information on a path to invasive plant species management. If E. curvula above-ground biomass is controlled, other species dormant in the soil seed bank may recruit in the ecosystem, provided they remain viable in the soil seed bank. However, to date, our research has not investigated the species composition of these sites in detail. With such a high density of potentially germinating seeds in a soil seed bank and the adverse effects the species can have on the above-ground species diversity and richness, E. curvula needs integrated management to mitigate its spread and ecosystem and economic impact

A Description of Summer Physical Oceanographic Conditions in Rupert Bay (James Bay, Canada)

Measurements of current velocity, temperature, salinity, and water level were made over a period of two months in Rupert Bay, James Bay (Canada). From an analysis of the current meter time series, the circulation and distribution of physical properties were found to be dominated by the tides, with the semi-diurnal component being the predominant component. An analysis of variance revealed that 77% of the salinity variations were related to the tides. Vertically homogeneous conditions prevailed in many areas because of a large tidal amplitude/depth ratio of 0.625, causing intense mixing in two-thirds of the estuary. Non-tidal velocity components were found to be 0(1) less than tidal currents, with the long-term mean circulation directed out of the bay. Non-tidal water level variations were well correlated with the wind. The maximum cross-correlation coefficient was calculated to be 0.77 for a 7 hour lag. The centrifugal force, Coriolis force, and baroclinic pressure gradient were dominant forces driving the secondary flows of the bay. Tidal fronts were found to be either aligned parallel to the main axes of principal channels or around small downstream islands with the arrangement influenced by bottom topography.Key words: estuary, circulation, tides, salinity, mixing, secondary flow, frontRÉSUMÉ. Des données de vitesse de courant, de température, de salinité et de niveau d’eau furent échantillonnées pendant une période de deux mois dans la Baie de Rupert, Baie James (Canada). Suite à l’analyse des séries chronologiques alors obtenues, il apperait que la circulation et la répartition des propriétés physiques étaient déterminées par les marées et que la constituante semi-diurne y dominait toute autre constituante de la marée. Une analyse de variance a révélé que 77% des variations de la salinité étaient attribuables aux marées semi-diurne. L’homogénéité de la colonne d’eau observée en plusieurs endroits semblait liée au fort rapport amplitude/profondeur (0,625) qui favoriserait un intense phénomène de mélange pour les deux tiers de l’estuaire. Les composantes de la vitesse étaient O(1) moins que les courants de marée. La circulation à long terme étaient dans la direction avale. Les variations de niveau d’eau non expliquées par la marée étaient apparemment induites par le vent; le coefficient de correlation croisée maximum calculé ont été de 0.77 pour un déphasage de 7 heures. Les fronts de marées observés soit étaient parallèles à les axes principaux des chenaux principaux ou suivaient le contour des petites îles sises en aval à l’entrée de la baie. L’arrangement de ces fronts semblait être influencé par la topographie du fond marin.Mot clés: estuaire, circulation, marées, salinité, mélange, courant secondaire, fron

Dynamic mooring simulation with Code_Aster with application to a floating wind turbine

This is the final version of the article. Available from Elsevier via the DOI in this record.The design of reliable station-keeping systems for permanent floating structures such as offshore renewable energy devices is vital to their lifelong integrity. In highly dynamic and/or deep-water applications, including hydrodynamics and structural dynamics in the mooring analysis is paramount for the accurate prediction of the loading on the lines and hence their dimensioning. This article presents a new workflow based on EDF R&D's open-source, finite-element analysis tool Code_Aster, enabling the dynamic analysis of catenary mooring systems, with application to a floating wind turbine concept. The University of Maine DeepCwind-OC4 basin test campaign is used for validation, showing that Code_Aster can satisfactorily predict the fairlead tensions in both regular and irregular waves. In the latter case, all of the three main spectral components of tension observed in the experiments are found numerically. Also, the dynamic line tension is systematically compared with that provided by the classic quasi-static approach, thereby confirming its limitations. Robust dynamic simulation of catenary moorings is shown to be possible using this generalist finite-element software, provided that the inputs be organised consistently with the physics of offshore hydromechanics.IDCORE is funded by the ETI and the RCUK Energy programme, grant number EP/J500847/1. The authors are grateful for the funding provided by these institutions, and to EDF R&D for hosting and supervising the industrial doctorate which expressed the present work

Preparation of delafossite CuFeO2 thin films by rf-sputtering on conventional glass substrate

CuFeO2 CuFeO2 is a delafossite-type compound and is a well known p-type semiconductor. The growth of delafossite CuFeO2 thin films on conventional glass substrate by radio-frequency sputtering is reported. The deposition, performed at room temperature leads to an amorphous phase with extremely low roughness and high density. The films consisted of a well crystallized delafossite CuFeO2 after heat treatment at 450 °C in inert atmosphere. The electrical conductivity of the film was 1 mS/cm. The direct optical band gap was estimated to be 2 eV

Mindfulness Training and Employee Well-being

Purpose - The aim of this paper was to assess the effects of Mindfulness Training (MT) on employee well-being. Mindfulness is the awareness of one’s thoughts, emotions, sensations, actions, and surroundings in the present moment. Methodology – We used pre-post training measures and a four week follow-up on a sample of 23 employees from a UK-based organization. The MT group (n=12) received a weekly two-hour training over eight weeks whilst the control group (n=11) received no training. Qualitative interviews (n=36) were conducted with the MT group at 3 time points to further assess the subjective experiences of training participants. Findings – Compared to the control group, the MT group significantly increased their mindfulness skills including observing and acting with awareness. Scores on well-being i.e. satisfaction with life, hope, and anxiety also improved and were generally maintained at follow-up. Some improvements were seen in the control group too but there was a larger difference in change scores in the MT group on most variables. Qualitative data show additional benefits of MT such as improved concentration at work and better interpersonal relationships. More practice at home led to greater benefits suggesting a dose-response relationship between the amount of practice and substantial benefits. Research limitations/implications – Inviting participants to have a greater amount of practice between sessions may further increase the benefits of mindfulness. Future research should consider a longer follow-up period to further explore the sustainability of the training benefits. Originality/value – Employing a mixed method approach, this study showed that MT is a viable psychological intervention for enhancing employee well-bein

Potential hazard consequences to personnel exposed to the ignition of small volumes of weakly confined stoichiometric hydrogen/air mixture

Many studies have been devoted to understanding the consequence of ignition events that could occur as a result of using hydrogen as an alternative to fossil fuels or when hydrogen is present in large scale industrial or nuclear waste sites. Little attention has however, been given to the effect of explosion in small scale operations: this could involve service work with manual handling and manipulation of gas containing packages or vessels. The purpose of this study is to begin to address this knowledge gap and report the results of an experimental program carried out to simulate the effect of localised and weakly confined small volume hydrogen explosions on personal safety. Three aspects of personal injury consequences are considered; injury from shock loading to the head/brain, skin burns and acoustic/hearing damage. It is concluded from ignition and acoustic noise exposure experiments, carried with stoichiometric hydrogen /air mixtures, that injuries arising from shock loading or burns to the skin are less likely than hearing damage. It is suggested that further work should focus on the noise exposure and hearing damage effects of small scale explosions

Second Aerospace Environmental Technology Conference

The mandated elimination of CFC's, Halons, TCA, and other ozone depleting chemicals and specific hazardous materials has required changes and new developments in aerospace materials and processes. The aerospace industry has been involved for several years in providing product substitutions, redesigning entire production processes, and developing new materials that minimize or eliminate damage to the environment. These activities emphasize replacement cleaning solvents and their application verifications, compliant coatings including corrosion protection systems, and removal techniques, chemical propulsion effects on the environment, and the initiation of modifications to relevant processing and manufacturing specifications and standards