Rotating disk atomization of Gd and Gd-Y for hydrogen liquefaction via magnetocaloric cooling

In order to enable liquid hydrogen fuel cell technologies for vehicles the cost of hydrogen liquefaction should be lowered. The current method of hydrogen liquefaction is the Claude cycle that has a figure of merit (FOM) of 0.3-0.35. New magnetocaloric hydrogen liquefaction devices have been proposed with a FOM\u3e0.5, which is a significant improvement. A significant hurdle to realizing these devices is the synthesis of spherical rare earth based alloy powders of 200õm in diameter. In this study a centrifugal atomization method that used a rotating disk with a rotating oil quench bath was developed to make gadolinium and gadolinium-yttrium spheres. The composition of the spherical powders included pure Gd and Gd0.91Y0.09. The effect of atomization parameters, such as superheat, melt properties, disk shape, disk speed, and melt system materials and design, were investigated on the size distribution and morphology of the resulting spheres. The carbon, nitrogen, and oxygen impurity levels also were analyzed and compared with the magnetic performance of the alloys. The magnetic properties of the charge material as well as the resulting powders were measured using a vibrating sample magnetometer. The saturation magnetization and Curie temperature were the target properties for the resulting spheres. These values were compared with measurements taken on the charge material in order to investigate the effect of atomization processing on the alloys

Active gaming in Dutch adolescents: a descriptive study

<p>Abstract</p> <p>Background</p> <p>Adequate levels of physical activity are part of a healthy lifestyle and in this way linked to better health outcomes. For children and adolescents, the physical activity guideline recommends at least 60 minutes of moderate-to-vigorous physical activity every day. However, many adolescents are not physically active enough and they spend a lot of their time on sedentary activities (such as video games). A new generation of video games that require body movements to play them, so-called "active games", could serve to increase physical activity in adolescents. The activity level while playing these games is comparable to light-to-moderate intensity physical activity. The current study aims to increase our understanding of 1) the demographic characteristics of adolescents who play active games regularly (≥ 1 hour per week) and non-regularly (<; 1 hour per week), 2) time spent on active games, 3) the contribution of active games to daily physical activity and 4) the type and amount of activities being replaced by active gaming.</p> <p>Methods</p> <p>A cross-sectional survey was conducted in a Dutch internet panel, questioning adolescents in conjunction with one of their parents. A random sample of 320 households (with stratification on gender of the parent and the adolescent, the age of the adolescent and the region of the household) was selected that owned a console or application for active video games and that had a child aged 12 through 16 years. 201 child–parent couples (63% response) completed an internet survey with questions about demographics, physical activity and sedentary behaviour, and gaming behaviour. The questionnaire also contained questions designed to assess whether and how active gaming replaces other activities. Besides descriptive analyses, independent t-test, Pearson’s chi-square and Mann–Whitney test (when data were not normally distributed) were used for comparisons between regular and non-regular active gamers.</p> <p>Results</p> <p>Eleven percent of the adolescents with an active game in their household never used the game. There were no significant differences in gender, education level (of adolescent and parent), ethnicity and sedentary behaviour between regular (n = 65) and non-regular active gamers (n = 114). Adolescents’ (regular and non-regular active gamers) meantime spent on active gaming was 80 (± 136) minutes a week; this potentially amounts to 11% of total physical activity. When time spent on active gaming was included in the calculation of the percentage of adolescents that met the physical activity guideline, the percentage increased significantly (p <; 0.05) from 67 to 73%. According to the adolescents, active gaming mainly replaces sedentary screen time such as TV viewing, internet and non-active gaming. Parental opinions concurred with this appraisal.</p> <p>Conclusions</p> <p>The results of this study confirm the idea that active gaming may contribute to an active lifestyle in adolescents, primarily because it potentially contributes substantially to time spent on physical activity. Secondly, active gamers indicate that they spent time on active games which they would have spent otherwise on less active activities.</p

Impacts of governance styles on river restoration in NW Europe

Item does not contain fulltext28th Annual Conference of IAIA - The Art and Science of Impact Assessment, 4 mei 200

Tensions bows as a tool to assess the impacts of institutional change: an example from Dutch floodplain management

Contains fulltext : 72499.pdf (publisher's version ) (Open Access)IAIA2008, 4 mei 200

An evolutionary economics approach to ecosystem dynamics

Biology and evolution lie at the heart of the ecosystem metaphor that is recurrently applied in the digital era. Although the evolution and analogy with evolutionary biology is acknowledged within the research domains of business ecosystems and digital ecosystems, several key definitions and self-organizing properties of ecosystems have not been fully explored. In addition, the diffusion process of radical innovations altering the structure of an ecosystem remains elusive. This paper addresses this deficiency through a cross-fertilization of multiple research domains, by introducing evolutionary economics concepts based on insights from biology. The research synthesis presented serves for the introduction of a novel perspective on ecosystem analysis. Practitioners will gain insight in how to apply concepts from evolutionary economics when determining their position in an ecosystem. Trade-offs can then be considered and balanced to positively impact firm performance as well as the ecosystem in which the firm operates

The Role of Indigenous Knowledge in the Effective Collective Management of the Communal Rangelands

Numerous scientific studies have highlighted the complexities associated with the collective management of communal rangelands. To date, policy interventions in rangelands have largely ignored people’s traditional ways of managing, with adverse effects on rangeland productivity. Thus, local knowledge has not been considered in spatial planning, despite the fact that local rural communities are often repositories of key indigenous knowledge. Hence this study set out to evaluate the role of indigenous knowledge in the management of the communal rangeland in Cata and Guquka, now and in the future. This was achieved through the use of Participatory GIS (PGIS), specifically participatory mapping to analyse how the communities use and view their rangelands now and how this has changed over time, and whether this can form a potential resource for effective communal rangeland management in the future. Results revealed that Cata and Guquka participants held extensive indigenous and spatial knowledge in relation to their communal areas. However, the existing knowledge is not translated into effective management of the communal rangelands, instead it is trapped in the older generation. These findings were attributed to social challenges including an ageing population, lack of youth involvement, fear of livestock theft, lack of mutual trust amongst community members and lack of resources such as fencing, access to dipping tanks and government services, and financial constraints. Thus, factors inhibiting the use of the existing indigenous knowledge for effective management of the communal rangelands in Cata and Guquka are more social than environmental. This suggests that new policy approaches incorporating local people’s indigenous knowledge in spatial planning which takes into account their unique local situations and the relationships between people and their resources are necessary. When people feel like their voices are heard and opinions valued, the adoption and sustainability of policy-based interventions becomes less challenging. Therefore, indigenous local knowledge, if effectively harnessed, could form a key component in adaptive management of these communal rangelands

Partnership, ownership and control: the impact of corporate governance on employment relations

Prevailing patterns of dispersed share ownership and rules of corporate governance for UK listed companies appear to constrain the ability of managers to make credible, long-term commitments to employees of the kind needed to foster effective labour-management partnerships. We present case study evidence which suggests that such partnerships can nevertheless emerge where product market conditions and the regulatory environment favour a stakeholder orientation. Proactive and mature partnerships may also be sustained where the board takes a strategic approach to mediating between the claims of different stakeholder groups, institutional investors are prepared to take a long-term view of their holdings, and strong and independent trade unions are in a position to facilitate organisational change

Using System Dynamics to Explore the Water Supply and Demand Dilemmas of a Small South African Municipality

This paper explores the challenges faced by small municipalities in providing water services in a developing world context of increasing urban demand. The paper uses a case study of the Sundays River Valley Municipality (SRVM) in South Africa. The municipality faces multiple dilemmas in reconciling its available water supply with growing demand for potable water in the primary urban settlement in the area, in a struggle that is typical of the broad category of South African municipalities to which the SRVM belongs. These dilemmas are explored using a system dynamics model, referred to as the ‘Kirkwood water demand system dynamics model’ (K-DEM). This paper specifically introduces the K-DEM structure,which is aimed at investigating the impacts of households progressively receiving full water and sanitation services; the use of rainwater harvesting as an alternative form of water supply; and the possible effect of a household-level water conservation / water demand management programme. Baseline results are discussed, and areas for future research identified. Paper presented at the 32nd International Conference of the System Dynamics Society, 21-24 July 2014, in Delft, the Netherlands.WordMac OS X 10.8.5 Quartz PDFContex