Investigation of direct solar-to-microwave energy conversion techniques

Identification of alternative methods of producing microwave energy from solar radiation for purposes of directing power to the Earth from space is investigated. Specifically, methods of conversion of optical radiation into microwave radiation by the most direct means are investigated. Approaches based on demonstrated device functioning and basic phenomenologies are developed. There is no system concept developed, that is competitive with current baseline concepts. The most direct methods of conversion appear to require an initial step of production of coherent laser radiation. Other methods generally require production of electron streams for use in solid-state or cavity-oscillator systems. Further development is suggested to be worthwhile for suggested devices and on concepts utilizing a free-electron stream for the intraspace station power transport mechanism

Developing Belief in Online Teaching: Efficacy and Digital Transformation

Digital pedagogies, blended, hybrid, and online learning are not new, indeed discussions about their role in higher education are well documented. With some notable exceptions however, many of these discussions, and many more attempts at implementation, have been small in scale, operating at the level of a single course, or even single members of staff. Barriers at national, institutional and personal levels all contributed to slow uptake of digital learning. The summer of 2020 though saw institutions across the UK, and indeed the world, forced into rapid transition to online learning in the face of the COVID-19 pandemic. This paper examines our work supporting a school - which achieved high student satisfaction rates - within a large post-92 university in this transition. With specific attention to academic identity and efficacy, we examine the approaches that were taken in helping academics to climb over the digital hurdle towards good online teaching. We suggest that a three-pronged approach is needed to overcome these barriers and create the belief in digital that is needed for a successful online transition, and for continued growth. These are a collective ‘all in it together’ approach, placing curriculum, rather than technology at the heart of the work, and also ensuring solid institutional support that does not rely on early adopters

Rotor balancing using high breakdown-point and bounded-influence estimators

In industrial field, one of the most important practical problems of rotating machinery concerns rotor balancing. Many different methods are used for rotor balancing. Traditional influence coefficient method is often employed along with weighted least squares in order to reduce vibration amplitude, typically at selected rotating speeds like critical or operating ones. Usually the selection of the weights of the least-squares algorithm is manually made by a skilled operator that can decide in which speed range the vibration reduction is more effective. Several methods have been proposed in order to avoid operator's arbitrariness and an automatic procedure based on robust regression is introduced in this paper. In particular, the analysis is focused on high breakdown-point and bounded-influence estimators. Theoretical aspects and properties of these methods are investigated. The effectiveness and robustness of the proposed balancing procedure are shown by means of an experimental case using a test-rig

Nonlinear Effects Caused by Coupling Misalignment in Rotors Equipped with Journal Bearings

Misalignment is one of the most common sources of trouble of rotating machinery when rigid couplings connect the shafts. Ideal alignment of the shafts is difficult to be obtained and rotors may present angular and/or parallel misalignment (defined also as radial misalignment or offset). During a complete shaft revolution, a periodical change of the bearings load occurs in hyperstatic shaft-lines, if coupling misalignment between the shafts is excessive. If the rotating machine is equipped with fluid-film journal bearings, the change of the loads on the bearing causes also the variation of their instantaneous dynamic characteristics, i.e. damping and stiffness, and the complete system cannot be considered any longer as linear. Despite misalignment is often observed in the practice, there are relatively few studies about this phenomenon in literature and their results are sometimes conflicting. The authors aim at modeling accurately this phenomenon, for the first time in this paper, and giving pertinent diagnostic information. The proposed method is suitable for every type of shaft-line supported by journal bearings. A finite element model is used for the hyperstatic shaft-line, while bearing characteristics are calculated by integrating Reynolds equation as a function of the instantaneous load acting on the bearings, caused also by the coupling misalignment. The results obtained by applying the proposed method are shown by means of the simulation, in the time domain, of the dynamical response of a hyperstatic shaft-line. Nonlinear effects are highlighted and the spectral components of the system response are analyzed, in order to give diagnostic information about the signature of this type of fault

Dynamic characterization of two structures realized with different technology: metalworking vs. metal foam sandwiches

In this paper, a comparison between two different machine tool columns is presented. The two columns are realized with a different technology: classic metalworking versus metal foam sandwiches. The aim of the experimental tests is at evaluating their different mechanical performances and characteristics, with a particular focus on the damping. The comparison is carried in terms of both modal analysis and wide frequency range excitation, as described in the paper. A new method is introduced by the authors to deem which technology is the best, based on overall energy dissipated in a wide range of frequency

Participatory planning for eco-trekking on a potential World Heritage site: The communities of the Kokoda Track

Participatory Rural Appraisal (PRA) is an approach to data collection in participatory research. In this approach, the researcher is required to acknowledge and appreciate that research participants have the necessary knowledge and skills to be partners in the research process. PRA techniques were used to collect data on the Kokoda Track, Papua New Guinea, illuminating the communities' perceptions of eco-trekking and how they could better benefit from it. This case study is an example of the implementation of community-based eco-tourism development and of understanding the multiplicity of forces that support or undermine it. © The Australian National University

On model updating of turbo-generator set

Models can be applied for simulating dynamical behavior of rotating machinery or specific faulty conditions. Efficient model updating techniques could be very useful for increasing model accuracy. Model updating of rotor systems is significantly different with respect to the well-known model updating techniques and related modal analyses performed in the field of vibrating structures. This paper investigates both the difficulties and the conditions of rotor vibrations measurement tests as well as the approximations introduced in the rotor model. Some experimental cases of turbo-generator machines indicate the difficulties and problems in the identification of eigen-frequencies and damping modal parameter. In the second part of the paper uncertainties and non-linearity of the model are investigated. An example of updating of some shaft and bearing parameters by means of an evolutionary algorithm, for fitting the natural frequencies of a shaft line, is presented and discussed. Model updating techniques of bearing coefficients are also discussed and a procedure is proposed to avoid misleading results of widely-used model updating approaches

Squeeze Film Damper Modeling: A Comprehensive Approach

Squeeze film dampers (SFDs) are components used in many industrial applications, ranging from turbochargers to jet engines. SFDs are applied when the vibration levels or some instability threatens the safe operation of the machine. However, modeling these components is difficult and somewhat counterintuitive due to the multiple complex phenomena involved. After a thorough investigation of the state of the art, the most relevant phenomena for the characterization of the SFDs are highlighted. Among them, oil film cavitation, air ingestion, and inertia are investigated and modeled. The paper then introduces a numerical model based on the Reynolds equation, discretized with the finite difference method. Different boundary conditions for oil feeding and discharging are implemented and investigated. The model is validated by means of experimental results available in the literature, whereas different designs and configurations of the feeding and sealing system are considered. Eventually, an example of the application of a SFD to a compressor rotor for the reduction of vibration and correction of the instability is proposed. The paper provides an insight regarding the critical aspects of modeling SFDs, underscoring the limits of the numerical model, and suggesting where to further develop and improve the modeling

'Alive after five' : constructing the neoliberal night in Newcastle upon Tyne.

The development of the ‘night-time economy’ in the UK through the 1990s has been associated with neoliberal urban governance. Academics have, however, begun to question the use and the scope of the concept ‘neoliberalism’. In this paper, I identify two common approaches to studying neoliberalism, one exploring neoliberalism as a series of policy networks, the other exploring neoliberalism as the governance of subjectivities. I argue that to understand the urban night, we need to explore both these senses of ‘neoliberalism’. As a case study, I take the ‘Alive After Five’ project, organised by the Business Improvement District in Newcastle-upon-Tyne, which sought to extend shopping hours in order to encourage more people to use the city at night. Drawing from Actor-Network-Theory, I explore the planning, the translation, and the practice of this new project. In doing so, I explore the on-going nature and influence of neoliberal policy on the urban night in the UK

Dynamic, thermal, and vibrational analysis of ball bearings with over-skidding behavior

The term "over-skidding" indicates that the cage rotational speed ratio exceeds the theoretical value as ball purely rolls on the raceway. Different from the skidding phenomenon that occurs in low-load and high-speed bearing, over-skidding usually occurs in large-size angular contact bearings, and it is still difficult to suppress under high load conditions. The main forms of damage to the raceway by over-skidding are spinning and gyro slip. To further explore the vibration characteristics and thermal effects of this phenomenon, a set of over-skidding tests of an angular contact bearing with a bore diameter of 220 mm were conducted on an industrial-size test bench. Through the experiment, the influence of axial load, rotational speed, and lubrication conditions on the occurrence of over-skidding were determined. Based on a previous dynamics model, the heat generation and thermal network models were integrated in the present study to predict the over-skidding and its thermal behavior. The model was validated in terms of the measured degree of over-skidding and temperature rise. The results showed that the degree of over-skidding reaches up to 12% of the theoretical value, and the friction power loss of the ball-pocket accounts for 30% of the total power loss. The analysis of the vibration signal showed a strong correlation between the bearing vibration characteristics and over-skidding behavior, thereby providing a way to indirectly measure the degree of over-skidding