Low-frequency surface waves in a structured magnetized dusty plasma

It is shown that charged dust particles carrying a considerable proportion of the negative charge of a structured magnetized plasma can lead to low-frequency electromagnetic surface waves which otherwise do not exist. The waves are Alfvén-like and propagate across the stationary external magnetic field with a frequency below the ion cyclotron but much above the dust cyclotron frequency. The dispersion characteristics of the modes are obtained and applications to space plasmas discussed. Copyright 1999 by the American Geophysical Union.

Series in vector spherical harmonics : an efficient tool for solution of nonlinear problems in spherical plasmas

The series expansion of the plasma fields and currents in vector spherical harmonics has been demonstrated to be an efficient technique for solution of nonlinear problems in spherically bounded plasmas. Using this technique, it is possible to describe the nonlinear plasma response to the rotating high-frequency magnetic field applied to the magnetically confined plasma sphere. The effect of the external magnetic field on the current drive and field configuration is studied. The results obtained are important for continuous current drive experiments in compact toruses. © 2000 American Institute of Physics.

Resonant generation of the second harmonic of a surface wave on a plasma-metal boundary

The process of resonant generation of the second harmonic of the surface wave, propagating along the external magnetic field at the plasma-metal boundary is considered. The periodic process of the energy exchange between the first and the second harmonics of the wave is investigated as well. It is shown that the process under study is periodic one. The analytical expressions are obtained and numerical estimations are presented for characteristic time of nonlinear energy exchange. The self-action effect of main frequency wave is account for harmonics interaction. It is shown that the effect leads to nonlinear phenomena attenuation, which expresses in narrowing possible value interval of harmonics amplitudes during energy exchange process and in increasing the nonlinear interaction time.

Self-interaction of high-frequency surface waves in magnetoactive plasma planar waveguide

The nonlinear effect of hf surface waves self-interaction in a magnetoactive planar plasma waveguide is studies. The waveguide structure under consideration can be formed by gaseous or semiconducting homogeneous plasma, which is limited by a perfectly conducting metal surface. The surface (localized near the surface) wave perturbations propagating on the plasma-metal boundary perpendicular to the constant external magnetic field, are investigated. The nonlinear frequency shift connected with interaction of the second harmonic and static surface perturbations with the main frequency wave, is determined using the approximation of weak nonlinearity. It is shown that the process of double-frequency signal generation is the dissipative one as a result of bulk wave excitation on the surface wave second harmonic.

Effect of heating nonlinearity on propagation of high-frequency surface waves at the semiconductor-metal interface

In approximation of weak heating influence of electron heating in the high-frequency surface wave field on propagation of surface wave (heating nonlinearity) is considered. It is shown that high-frequency surface wave propagates in direction perpendicular to the external magnetic field at the semiconductor-metal interface. A nonlinear dispersion equation is obtained and studied that allows to make conclusions about the contribution of heating nonlinearity to nonlinear process of considered interaction.

Parametric excitation of high-frequency surface waves in a plasma-metal waveguide structure

The problem concerning the excitation of high-frequency surface waves (SW) propagating across an external magnetic field at a plasma-metal interface is considered. A homogeneous electric pump field is applied in the direction transverse with respect to the plasma-metal interface. Two high-frequency SW from different frequency ranges of existence and propagating in different directions are shown to be excited in this pump field. The instability threshold pump-field values and increments are obtained for different parameters of the considered waveguide structure. The results associated with saturation of the nonlinear instability due to self-interaction effects of the excited SW are given as well. The results are appropriate for both gaseous and semiconductor plasmas.

Two-channel waveguide modulator based on surface wave propagating in a semiconductor-metal thin-film structure

The results of theoretical investigations of two-channel waveguide modulator based on Surface Wave (SW) propagation are presented. The structure studied consists of two n-type semiconductor waveguide channels separated from each other by a dielectric gap and coated by a metal. The SW propagates at the semiconductor-metal interface across an external magnetic field which is parallel to the interface. An external dc voltage is applied to the metal surface of one channel to provide a small phase shift between two propagating modes. In a coupled mode approximation, two possible regimes of operation of the structure, namely as a directional coupler and as an electro-optical modulator, are considered. Our results suggest new applications in millimeter and submillimeter wave solid-state electronics and integrated optics.

Nonlinear interactions of azimuthal surface waves in magnetoactive plasma filled waveguides

This paper deals with the theoretical studies of nonlinear interactions of azimuthal surface waves (ASW) in cylindrical metal waveguides fully filled by a uniform magnetoactive plasma. These surface-type wave perturbations propagate in azimuthal direction across an external magnetic field, which is directed along the waveguide axis. The ASW is a relatively new kind of surface waves and so far the nonlinear effects associated with their propagation are outside the scope of scientific issues. They are characterized by a discrete set of mode numbers values which define the ASW eigenfrequencies. This fact leads to several peculiarities of ASW compared with ordinary surface-type waves.

Microwave gas discharge produced and sustained by a surface wave propagating along a cylindrical metal antenna with a dielectric coating

The structure of a microwave gas discharge produced and sustained by a surface wave (SW) propagating along a cylindrical metal antenna with a dielectric coating is studied. The SW that produces and sustains the microwave gas discharge propagates along an external magnetic field and has an eigenfrequency in the range between the electron cyclotron and electron plasma frequencies. The presence of a dielectric (vacuum) sheath region separating the antenna from the plasma is assumed. The spatial distributions of the produced plasma density, electromagnetic fields, energy flow density, phase velocity and reverse skin depth of the SW are obtained analytically and numerically.

Keyword field-free conjunctive keyword searches on encrypted data and extension for dynamic groups

We consider the following problem: a user stores encrypted documents on an untrusted server, and wishes to retrieve all documents containing some keywords without any loss of data confidentiality. Conjunctive keyword searches on encrypted data have been studied by numerous researchers over the past few years, and all existing schemes use keyword fields as compulsory information. This however is impractical for many applications. In this paper, we propose a scheme of keyword field-free conjunctive keyword searches on encrypted data, which affirmatively answers an open problem asked by Golle et al. at ACNS 2004. Furthermore, the proposed scheme is extended to the dynamic group setting. Security analysis of our constructions is given in the paper.

Experience has no shadow

This research is situated in the field of practice-led research investigating embodied perspectives on the performance of dance making. In the stock of choreographic literature, the celebrated ‘creativity’ label is associated predominantly with the choreographer and is discussed in terms of product rather than process (Lussier-Ley and Durand-Bush 2009; Hennessey 2003). A reliance on the mystery of inspiration or choreographic genius (Penty 1998) for the production of ‘great’ dance works does not acknowledge the complex and timely process common in the creation of dance (Mace and Ward 2002) nor provide a true representation of the creative contributors (Farrer 2014). The failure to attribute creative impulses and skills to dancers is reminiscent of a time when they were thought of only as instruments in the creative process not active participants and collaborators (Jowitt 2001a; H’Doubler 1957). This project asked the question, to what end do dancers contribute to choreography and how is this contribution valued and recognised? Dancers are integral to the creative process. The research found that the scope of a dancers’ creative involvement in the development of a new work is dependent on: the individual choreographers approach to creating movement; the relationship between dancer and choreographer, and dancer and fellow company members; and the dancers collaborative skills and interpretive skills, versatility, and initiative. Recognition and attribution of dancers’ creative input is dependent on a choreographer’s viewpoint, generosity, and prior creative experiences. The work was created as a part of the Ausdance Queensland 2010 Bell Tower III Choreographic Residency program. Applicants were peer reviewed and vetted by a panel of local and national dance producers. The creative work was presented at the Judith Wright Centre for Live Arts. The project was funded by Ausdance Queensland and Arts Queensland. https://es-es.facebook.com/events/106661226023025/?hc_location=stream

Indigenous epistemology : creating an international Indigenous higher education space in the wake of the western “university of excellence”

Interest in the participation of Indigenous peoples in higher education has, in recent times, gained momentum with an increasing number of advocates challenging the global history of culturally inept policies and practices imposed within the western higher education system. To address the challenges being presented by Indigenous communities and other groups (often relegated under the banner of disadvantaged or equity) Western Universities are promoting a shift toward inclusive policies and practices. Frustrated with the offerings of the Western Higher Education system, a global movement of Indigenous academics, Elders and knowledge holders are developing strategies to meet the educational needs of their own communities, in order to find a way forward. The mobilization of Elders and Indigenous academics has resulted in the development of a global higher education network which is proving to be a significant force in changing the position of Indigenous participation in higher education. The World Indigenous Network Higher Education Consortium (WINHEC) has presented a significant challenge to those barriers within the western higher education system that has historically demonstrated an inability to develop culturally inclusive practices within their institutions. This paper examines the development of a world Indigenous higher education movement and its contribution to the history of the “university” within the context of western higher education institutions. Outlined in this examination will be a synopsis of the development of the “University of Excellence” and the creation of an international Indigenous space within higher education.

Development of gas sensing technology for ground and airborne applications powered by solar energy : methodology and experimental results

Monitoring gases for environmental, industrial and agricultural fields is a demanding task that requires long periods of observation, large quantity of sensors, data management, high temporal and spatial resolution, long term stability, recalibration procedures, computational resources, and energy availability. Wireless Sensor Networks (WSNs) and Unmanned Aerial Vehicles (UAVs) are currently representing the best alternative to monitor large, remote, and difficult access areas, as these technologies have the possibility of carrying specialised gas sensing systems, and offer the possibility of geo-located and time stamp samples. However, these technologies are not fully functional for scientific and commercial applications as their development and availability is limited by a number of factors: the cost of sensors required to cover large areas, their stability over long periods, their power consumption, and the weight of the system to be used on small UAVs. Energy availability is a serious challenge when WSN are deployed in remote areas with difficult access to the grid, while small UAVs are limited by the energy in their reservoir tank or batteries. Another important challenge is the management of data produced by the sensor nodes, requiring large amount of resources to be stored, analysed and displayed after long periods of operation. In response to these challenges, this research proposes the following solutions aiming to improve the availability and development of these technologies for gas sensing monitoring: first, the integration of WSNs and UAVs for environmental gas sensing in order to monitor large volumes at ground and aerial levels with a minimum of sensor nodes for an effective 3D monitoring; second, the use of solar energy as a main power source to allow continuous monitoring; and lastly, the creation of a data management platform to store, analyse and share the information with operators and external users. The principal outcomes of this research are the creation of a gas sensing system suitable for monitoring any kind of gas, which has been installed and tested on CH4 and CO2 in a sensor network (WSN) and on a UAV. The use of the same gas sensing system in a WSN and a UAV reduces significantly the complexity and cost of the application as it allows: a) the standardisation of the signal acquisition and data processing, thereby reducing the required computational resources; b) the standardisation of calibration and operational procedures, reducing systematic errors and complexity; c) the reduction of the weight and energy consumption, leading to an improved power management and weight balance in the case of UAVs; d) the simplification of the sensor node architecture, which is easily replicated in all the nodes. I evaluated two different sensor modules by laboratory, bench, and field tests: a non-dispersive infrared module (NDIR) and a metal-oxide resistive nano-sensor module (MOX nano-sensor). The tests revealed advantages and disadvantages of the two modules when used for static nodes at the ground level and mobile nodes on-board a UAV. Commercial NDIR modules for CO2 have been successfully tested and evaluated in the WSN and on board of the UAV. Their advantage is the precision and stability, but their application is limited to a few gases. The advantages of the MOX nano-sensors are the small size, low weight, low power consumption and their sensitivity to a broad range of gases. However, selectivity is still a concern that needs to be addressed with further studies. An electronic board to interface sensors in a large range of resistivity was successfully designed, created and adapted to operate on ground nodes and on-board UAV. The WSN and UAV created were powered with solar energy in order to facilitate outdoor deployment, data collection and continuous monitoring over large and remote volumes. The gas sensing, solar power, transmission and data management systems of the WSN and UAV were fully evaluated by laboratory, bench and field testing. The methodology created to design, developed, integrate and test these systems was extensively described and experimentally validated. The sampling and transmission capabilities of the WSN and UAV were successfully tested in an emulated mission involving the detection and measurement of CO2 concentrations in a field coming from a contaminant source; the data collected during the mission was transmitted in real time to a central node for data analysis and 3D mapping of the target gas. The major outcome of this research is the accomplishment of the first flight mission, never reported before in the literature, of a solar powered UAV equipped with a CO2 sensing system in conjunction with a network of ground sensor nodes for an effective 3D monitoring of the target gas. A data management platform was created using an external internet server, which manages, stores, and shares the data collected in two web pages, showing statistics and static graph images for internal and external users as requested. The system was bench tested with real data produced by the sensor nodes and the architecture of the platform was widely described and illustrated in order to provide guidance and support on how to replicate the system. In conclusion, the overall results of the project provide guidance on how to create a gas sensing system integrating WSNs and UAVs, how to power the system with solar energy and manage the data produced by the sensor nodes. This system can be used in a wide range of outdoor applications, especially in agriculture, bushfires, mining studies, zoology, and botanical studies opening the way to an ubiquitous low cost environmental monitoring, which may help to decrease our carbon footprint and to improve the health of the planet.

Research in Early Childhood Education for Sustainability : International Perspectives and Provocations

Sustainability is a global issue that urgently needs addressing, the most serious consequences of which concern children and future generations. This insightful research text tackles one of the most significant contemporary issues of our times – the nexus between society and environment – and how early childhood education can contribute to sustainable living. By offering international and multidisciplinary research perspectives on Early Childhood Education for Sustainability, each chapter explores and investigates the complex topic of sustainability and its relationship to early childhood education. A particular emphasis that runs through this text is young children as empowered citizens, capable of both contributing to and creating change for sustainability. The chapter authors work from, or are aligned with, a transformative education paradigm that suggests the socio-constructivist frameworks currently underpinning Early Childhood Education require reframing in light of the social transformations necessary to address humanity’s unsustainable, unjust and unhealthy living patterns. This research text is designed to be provocative and challenging; in so doing it seeks to encourage exploration of current understandings about Early Childhood Education for Sustainability, offers new dimensions for more deeply informed practice, and proposes avenues for further research in this field.

Investigating early childhood education for sustainability : insights from history and literature

Seemingly straightforward tasks often have a way of becoming complex. This was the case for our guest editorial team charged with creating Early Childhood Australia’s Best of Sustainability publication drawn from the the Australasian Journal of Early Childhood and Every Child. The complexities we encountered ranged from the varied terminologies and understandings of constructs such as education for sustainable development, environmental education and education for sustainability, through to the fundamental lack of published research on which to draw as the basis for a special issue. It is timely to explore these complexities as we face the global challenges of The Critical Decade (DCCEE, 2011) including rising sea levels, extreme weather events and food security. At a local level, the early childhood field in Australia is seeking to interpret sustainability with systemic support from the National Quality Standards(NQS) (ACECQA, 2011), while elsewhere environmental/sustainability education is encouraged through national curricula documents (for example, Singapore Ministry of Education, 2008; Swedish National Agency for Education,2010; Ministry of Education of Korea, 2011). Both The Critical Decade and the NQS provide imperatives to drive early childhood education’s engagement with sustainability. In other words, sustainability in early childhood education is no longer optional, but essential (Elliott, 2010). While some twenty years of advocacy has led to this somewhat subdued celebratory position, in this publication we do recognise the historical contexts that have led to early childhood education for sustainability (ECEfS), as we (Elliott & Davis) phrase it, becoming almost ‘mainstream not marginal’ (Davis, 1999)— a stitching together of the isolated ‘patches of green’, first identified a decade ago by Elliott (NSW EPA, 2003). Here we weave together, through these articles, a story of the evolving history of ECEfS from our particular perspective. In so doing, we also acknowledge that there are other perspectives or ‘paths’ for this field as identified by Edwards and Cutter-McKenzie in their concluding paper to this compilation.