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

Variance reduction and signal-to-noise ratio: Reducing uncertainty in spectral ratios

This paper uses an unusually large dataset to study scatter in site-effect estimation, focusing on how the events that increase uncertainty can be removed from the dataset. Four hundred seventy-three weak motion earthquake records from the surface and bedrock of a 178-m-deep borehole in Aegion, Gulf of Corinth, Greece, are used to evaluate spectral ratios. A simple statistical tool, variance reduction (VR), is first used to identify two groups of events that lie closest and farthest from the average, which is considered here as the initial best estimate of the site response. The scatter in the original dataset is found to be due to the group of events with smallest VR. These events can be removed from the dataset in order to compute a more reliable site response. However, VR is not normally used to choose records for site-effect studies, and it cannot be applied to the usual small datasets available. The signal-to-noise ratio (SNR) is normally used to this end, for which reason we investigate whether SNR can be used to achieve similar results as VR. Signal-to-noise ratio is estimated using different definitions. Data selection based on SNR is then compared to that using VR in order to define an SNR-based criterion that discriminates against events that, according to VR, increase scatter. We find that defining the SNR of a surface record as the mean value over a frequency range around the resonant peak (here, 0.5–1.5 Hz) and using a cutoff value of 5 may be used in this case to exclude most events for which VR is small. This process is also applied to the downhole station, where we obtain similar results for a cutoff value of 3

PARAMETRIC ANALYSIS OF DEPOSITION PRESSURE CONTROLLED MULTI-AXIS FREEFORM FABRICATION

Additive manufacturing is being explored as one of the most promising in-space manufacturing techniques. The presence of micro-gravity enables the fabrication of support-free sparse structures with ease. Sparse lattice structures (e.g. trusses) are attractive for space applications as they can be tailored for specific load paths. Previous studies have identified a positive correlation between deposition pressure and inter-layer adhesion in 3D printing. However, excessive deposition pressures negatively influence the in-orbit printing accuracy. Therefore, a parametric investigation was conducted to determine the optimal deposition pressure to fabricate mechanically sound trusses in orbit. Support-free arches with varying nodal deposition pressures were 3D printed using a multiaxis robotic manipulator with integrated force sensors. Mechanical testing of these arches concluded that the strength improvement plateaus and registers no significant increase in (joint) strength after a certain deposition pressure, characterized by the properties of the extrude. Integration of a force-feedback facilitates free-form printing of complex, multi-layered, support-free structures in terrestrial environments. In a free-floating space environment, it assists in optimizing the overall printing process.Mechanical Engineerin

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

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.EThOS - Electronic Theses Online ServiceNational Foundation of Scholarships (IKY) GreeceGBUnited Kingdo

Challenges Emerging from Future Cloud Application Scenarios

The cloud computing paradigm encompasses several key differentiating elements and technologies, tackling a number of inefficiencies, limitations and problems that have been identified in the distributed and virtualized computing domain. Nonetheless, and as it is the case for all emerging technologies, their adoption led to the presentation of new challenges and new complexities. In this paper we present key application areas and capabilities of future scenarios, which are not tackled by current advancements and highlight specific requirements and goals for advancements in the cloud computing domain. We discuss these requirements and goals across different focus areas of cloud computing, ranging from cloud service and application integration, development environments and abstractions, to interoperability and relevant to it aspects such as legislation. The future application areas and their requirements are also mapped to the aforementioned areas in order to highlight their dependencies and potential for moving cloud technologies forward and contributing towards their wider adoption

Management of Urinary Retention in Patients with Benign Prostatic Obstruction : A Systematic Review and Meta-analysis

Context: Practice patterns for the management of urinary retention (UR) secondary to benign prostatic obstruction (BPO; UR/BPO) vary widely and remain unstandardized. Objective: To review the evidence for managing patients with UR/BPO with pharmacological and nonpharmacological treatments included in the European Association of Urology guidelines on non-neurogenic male lower urinary tract symptoms. Evidence acquisition: Search was conducted up to April 22, 2018, using CENTRAL, MEDLINE, Embase, ClinicalTrials.gov, and World Health Organization International Clinical Trials Registry Platform. This systematic review included randomized controlled trials (RCTs) and prospective comparative studies. Methods as detailed in the Cochrane handbook were followed. Certainty of evidence (CoE) was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Evidence synthesis: Literature search identified 2074 citations. Twenty-one studies were included (qualitative synthesis). The evidence for managing patients with UR/BPO with pharmacological or nonpharmacological treatments is limited. CoE for most outcomes was low/very low. Only alpha 1-blockers (alfuzosin and tamsulosin) have been evaluated in more than one RCT. Pooled results indicated that a1-blockers provided significantly higher rates of successful trial without catheter compared with placebo [alfuzosin: 322/540 (60%) vs 156/400 (39%) (odds ratio {OR} 2.28, 95% confidence interval {CI} 1.55 to 3.36; participants = 940; studies = 7; I-2 = 41%; low CoE); tamsulosin: 75/158 (47%) vs 40/139 (29%) (OR 2.40, 95% CI 1.29 to 4.45; participants = 297; studies = 3; I-2 = 30%; low CoE)] with rare adverse events. Similar rates were achieved with tamsulosin or alfuzosin [51/87 (59%) vs 45/84 (54%) (OR 1.28, 95% CI 0.68 to 2.41;participants = 171; studies = 2; I-2 = 0%; very low CoE)]. Nonpharmacological treatments have been evaluated in RCTs/prospective comparative studies only sporadically. Conclusions: There is some evidence that usage of alpha 1-blockers (alfuzosin and tamsulosin) may improve resolution of UR/BPO. As most nonpharmacological treatments have not been evaluated in patients with UR/BPO, the evidence is inconclusive about their benefits and harms. Patient summary: There is some evidence that alfuzosin and tamsulosin may increase the rates of successful trial without catheter, but little or no evidence on various nonpharmacological treatment options for managing patients with urinary retention secondary to benign prostatic obstruction. (c) 2019 European Association of Urology. Published by Elsevier B.V. All rights reserved.Peer reviewe