Dilute axion stars converting to photons in the Milky Way's magnetic field

In this paper we examine the possibility of dilute axion stars converting to photons in the weak, large-scale magnetic field of the Milky Way and show that they can resonate with the surrounding plasma and produce a sizable signal. We consider two possibilities for the plasma: free electrons and HII regions. In the former case, we argue that the frequency of the photons will be too small to be observed even by space-based radio telescopes. In the latter case, their frequency is larger, safely above the solar wind cut-off. We provide an estimate of the flux as a function of the decay constant and show that for $f_{a} < 5 \times 10^{11} \text{GeV}$, the signal will be above the radio emission of the solar system's planets and it could potentially be detected by the NCLE instrument which is on board the Chang'e-4 spacecraft. Finally, we calculate the time scale of decay of the axion star and demonstrate that back-reaction can be neglected for all physically interesting values of the decay constant, while the minimum time scale of decay is in the order of a few hours

Analysis and processing of mechanically stimulated electrical signals for the identification of deformation in brittle materials

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The fracture of brittle materials is of utmost importance for civil engineering and seismology applications. A different approach towards the aim of early identification of fracture and the prediction of failure before it occurs is attempted in this work. Laboratory experiments were conducted in a variety of rock and cement based material specimens of various shapes and sizes. The applied loading schemes were cyclic or increasing and the specimens were tested to compression and bending type loading of various levels. The techniques of Pressure Stimulated Current and Bending Stimulated Current were used for the detection of electric signal emissions during the various deformation stages of the specimens. The detected signals were analysed macroscopically and microscopically so as to find suitable criteria for fracture prediction and correlation between the electrical and mechanical parameters. The macroscopic proportionality of the mechanically stimulated electric signal and the strain was experimentally verified, the macroscopic trends of the PSC and BSC electric signals were modelled and the effects of material memory to the electric signals were examined. The current of a time-varying RLC electric circuit was tested against experimental data with satisfactory results and it was proposed as an electrical equivalent model. Wavelet based analysis of the signal revealed the correlation between the frequency components of the electric signal and the deformation stages of the material samples. Especially the increase of the high frequency component of the electric signal seems to be a good precursor of macrocracking initiation point. The additional electric stimulus of a dc voltage application seems to boost the frequency content of the signal and reveals better the stages of cracking process. The microscopic analysis method is scale-free and thus it can confront with the problems of size effects and material properties effects. The AC conductivity time series of fractured and pristine specimens were also analysed by means of wavelet transform and the spectral analysis was used to differentiate between the specimens. A non-destructive technique may be based on these results. Analysis has shown that the electric signal perturbation is an indicator of the forthcoming fracture, as well as of the fracture that has already occurred in specimens.The National Foundation of Scholarships (IKY) Greec

Remote-scope Promotion: Clarified, Rectified, and Verified

Modern accelerator programming frameworks, such as OpenCL, organise threads into work-groups. Remote-scope promotion (RSP) is a language extension recently proposed by AMD researchers that is designed to enable applications, for the first time, both to optimise for the common case of intra-work-group communication (using memory scopes to provide consistency only within a work-group) and to allow occasional inter-work-group communication (as required, for instance, to support the popular load-balancing idiom of work stealing). We present the first formal, axiomatic memory model of OpenCL extended with RSP. We have extended the Herd memory model simulator with support for OpenCL kernels that exploit RSP, and used it to discover bugs in several litmus tests and a work-stealing queue, that have been used previously in the study of RSP. We have also formalised the proposed GPU implementation of RSP. The formalisation process allowed us to identify bugs in the description of RSP that could result in well-synchronised programs experiencing memory inconsistencies. We present and prove sound a new implementation of RSP that incorporates bug fixes and requires less non-standard hardware than the original implementation. This work, a collaboration between academia and industry, clearly demonstrates how, when designing hardware support for a new concurrent language feature, the early application of formal tools and techniques can help to prevent errors, such as those we have found, from making it into silicon

Social Housing as a State-Funded Mega Project: A Case Study From Saudi Arabia

There are many kinds of war. They span from typical military conflicts to socially and politically charged environments, from fiscal colonization to ghostly wars about information and the internet. But what about the fear of a possible war? Could housing initiatives be connected to that? What kind of design methods and standards as well as processes would that specific case entail? What other factors would add pressure to studying and implementing housing projects in this context? What could be the possible measure of such projects’ eventual assessment? This paper is based on the assumption that fear of a spreading of the Arab Spring in the Saudi Kingdom triggered a massive state-funded housing project. The ambitious case of Saudi Arabia’s Ministry of Housing (MoH) will be discussed and gradually unfolded within its social, cultural, economic, and technical-design conditions. The project’s development is discussed both before its launch-conceptualization and throughout its implementation. The original insight given stems from the authors’ participation as lead urban planners in one of the major companies awarded the project

On the Feasibility of Real-Time 3D Hand Tracking using Edge GPGPU Acceleration

This paper presents the case study of a non-intrusive porting of a monolithic C++ library for real-time 3D hand tracking, to the domain of edge-based computation. Towards a proof of concept, the case study considers a pair of workstations, a computationally powerful and a computationally weak one. By wrapping the C++ library in Java container and by capitalizing on a Java-based offloading infrastructure that supports both CPU and GPGPU computations, we are able to establish automatically the required server-client workflow that best addresses the resource allocation problem in the effort to execute from the weak workstation. As a result, the weak workstation can perform well at the task, despite lacking the sufficient hardware to do the required computations locally. This is achieved by offloading computations which rely on GPGPU, to the powerful workstation, across the network that connects them. We show the edge-based computation challenges associated with the information flow of the ported algorithm, demonstrate how we cope with them, and identify what needs to be improved for achieving even better performance.Comment: 6 pages, 5 figure

A survey of empirical findings on unconventional central bank policies

© 2020, Emerald Publishing Limited. Purpose: This paper presents an integrated overview of the empirical literature on the impact of all forms of unconventional monetary policy on macroeconomic variables and on markets. Design/methodology/approach: This survey covers the findings concerning portfolio rebalancing, signaling, liquidity, bank lending and confidence channels. Findings: The positive effect of QE announcements on stock and bond prices seems to be unified across studies. A contagion effect from US QE to other emerging markets is identified, while currency devaluation is present in most cases for the country that its central bank adopted such policies. Moreover, impacts of non-conventional practices on GDP, inflation and unemployment are examined. The studies presenting weak instead of strong positive effects on inflation are more, and these studies, also, present weak positive effects on GDP growth. Originality/value: Based on the large body of research on non-conventional action taking, this is the first survey including effects of each country that adopted quantitative easing (QE) measures and that provides results from every methodology employed in order to estimate unconventional practices\u27 impacts

Building sustainability into services marketing: expanding decision-making from a mix to a matrix

In line with the AMA\u27s revised (2007) definition of marketing, which aligns with the societal marketing orientation by requiring that Marketing create value not just for individual consumers and organisations but also for society at large, this paper proposes a Sustainability Services Marketing (SSM) framework. At present, services marketing managers have little guidance on how to pursue sustainability and achieve sustainable development goals. The SSM addresses this gap in a systematic, holistic and transparent way by ensuring sustainability cascades through the strategic marketing planning process. The traditional services marketing mix is expanded to include partnership, and the eight elements are cross-referenced against the three pillars of the triple bottom line - Planet, People and Profit - to produce the Sustainability Services Marketing Matrix (SSMM). The model is described and illustrated with brief case examples, and implications for theory and practice, and potential directions for further research are discussed