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Showing papers by "Edinburgh Napier University published in 2018"


Journal ArticleDOI
TL;DR: The purpose of this study was to finalize the development of the International Trauma Questionnaire (ITQ), a self‐report diagnostic measure of post‐traumatic stress disorder (PTSD) and complex PTSD (CPTSD), as defined in the 11th version of theInternational Classification of Diseases (ICD‐11).
Abstract: Sections ePDFPDF PDF Tools Share Abstract Objective The purpose of this study was to finalize the development of the International Trauma Questionnaire (ITQ), a self‐report diagnostic measure of post‐traumatic stress disorder (PTSD) and complex PTSD (CPTSD), as defined in the 11th version of the International Classification of Diseases (ICD‐11). Method The optimal symptom indicators of PTSD and CPTSD were identified by applying item response theory (IRT) analysis to data from a trauma‐exposed community sample (n = 1051) and a trauma‐exposed clinical sample (n = 247) from the United Kingdom. The validity of the optimized 12‐item ITQ was assessed with confirmatory factor analyses. Diagnostic rates were estimated and compared to previous validation studies. Results The latent structure of the 12‐item, optimized ITQ was consistent with prior findings, and diagnostic rates of PTSD and CPTSD were in line with previous estimates. Conclusion The ITQ is a brief, simply worded measure of the core features of PTSD and CPTSD. It is consistent with the organizing principles of the ICD‐11 to maximize clinical utility and international applicability through a focus on a limited but central set of symptoms. The measure is freely available and can be found in the body of this paper.

465 citations


Journal ArticleDOI
TL;DR: The potential exposure of humans to household dust fibres during a meal to compare with amounts of MPs present in edible mussels was determined and an allometric relationship between the number of MPs and the mussels wet weight was observed.

430 citations


Journal ArticleDOI
TL;DR: Overall, microbiological hazards are significant; therefore, ways to reduce sources of contamination and a deeper understanding of pathogen survival and growth on fresh produce in the field are required to reduce risk to human health and the associated economic consequences.

303 citations


Journal ArticleDOI
TL;DR: In this article, a machine-learning-based statistical model of the distribution of carbon density using spatially comprehensive data at a 30'm resolution was developed for mangrove soil carbon stocks.
Abstract: With the growing recognition that effective action on climate change will require a combination of emissions reductions and carbon sequestration, protecting, enhancing and restoring natural carbon sinks have become political priorities. Mangrove forests are considered some of the most carbon-dense ecosystems in the world with most of the carbon stored in the soil. In order for mangrove forests to be included in climate mitigation efforts, knowledge of the spatial distribution of mangrove soil carbon stocks are critical. Current global estimates do not capture enough of the finer scale variability that would be required to inform local decisions on siting protection and restoration projects. To close this knowledge gap, we have compiled a large georeferenced database of mangrove soil carbon measurements and developed a novel machine-learning based statistical model of the distribution of carbon density using spatially comprehensive data at a 30 m resolution. This model, which included a prior estimate of soil carbon from the global SoilGrids 250 m model, was able to capture 63% of the vertical and horizontal variability in soil organic carbon density (RMSE of 10.9 kg m−3). Of the local variables, total suspended sediment load and Landsat imagery were the most important variable explaining soil carbon density. Projecting this model across the global mangrove forest distribution for the year 2000 yielded an estimate of 6.4 Pg C for the top meter of soil with an 86–729 Mg C ha−1 range across all pixels. By utilizing remotely-sensed mangrove forest cover change data, loss of soil carbon due to mangrove habitat loss between 2000 and 2015 was 30–122 Tg C with >75% of this loss attributable to Indonesia, Malaysia and Myanmar. The resulting map products from this work are intended to serve nations seeking to include mangrove habitats in payment-for- ecosystem services projects and in designing effective mangrove conservation strategies.

207 citations


Journal ArticleDOI
18 Oct 2018-PLOS ONE
TL;DR: A comprehensive map of reviews relating to Motivational Interviewing is created to signpost stakeholders to the best available evidence and identify a large volume of low quality evidence and many areas of overlapping research.
Abstract: Background The challenge of addressing unhealthy lifestyle choice is of global concern. Motivational Interviewing has been widely implemented to help people change their behaviour, but it is unclear for whom it is most beneficial. This overview aims to appraise and synthesise the review evidence for the effectiveness of Motivational Interviewing on health behaviour of adults in health and social care settings. Methods A systematic review of reviews. Methods were pre-specified and documented in a protocol (PROSPERO–CRD42016049278). We systematically searched 7 electronic databases: CDSR; DARE; PROSPERO; MEDLINE; CINAHL; AMED and PsycINFO from 2000 to May 2018. Two reviewers applied pre-defined selection criteria, extracted data using TIDIER guidelines and assessed methodological quality using the ROBIS tool. We used GRADE criteria to rate the strength of the evidence for reviews including meta-analyses. Findings Searches identified 5222 records. One hundred and four reviews, including 39 meta-analyses met the inclusion criteria. Most meta-analysis evidence was graded as low or very low (128/155). Moderate quality evidence for mainly short term (<6 months) statistically significant small beneficial effects of Motivational Interviewing were found in 11 of 155 (7%) of meta-analysis comparisons. These outcomes include reducing binge drinking, frequency and quantity of alcohol consumption, substance abuse in people with dependency or addiction, and increasing physical activity participation. Conclusions We have created a comprehensive map of reviews relating to Motivational Interviewing to signpost stakeholders to the best available evidence. More high quality research is needed to be confident about the effectiveness of Motivational Interviewing. We identified a large volume of low quality evidence and many areas of overlapping research. To avoid research waste, it is vital for researchers to be aware of existing research, and the implications arising from that research. In the case of Motivational Interviewing issues relating to monitoring and reporting fidelity of interventions need to be addressed.

202 citations


Journal ArticleDOI
TL;DR: Several behaviours and cardiovascular disease risk factors appear modifiable in the shorter term with use of mobile apps, but evidence for effectiveness requires larger, controlled studies of longer duration.
Abstract: BackgroundMobile technologies are innovative, scalable approaches to reducing risk of cardiovascular disease but evidence related to effectiveness and acceptability remains limited. We aimed to explore the effectiveness, acceptability and usefulness of mobile applications (apps) for cardiovascular disease self-management and risk factor control.DesignSystematic review with meta-synthesis of quantitative and qualitative data.MethodsComprehensive search of multiple databases (Medline, Embase, CINAHL, SCOPUS and Cochrane CENTRAL) and grey literature. Studies were included if the intervention was primarily an app aimed at improving at least two lifestyle behaviours in adults with cardiovascular disease. Meta-synthesis of quantitative and qualitative data was performed to review and evaluate findings.ResultsTen studies of varying designs including 607 patients from five countries were included. Interventions targeted hypertension, heart failure, stroke and cardiac rehabilitation populations. Factors that impro...

183 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the thermal performance of conventional dry air cooling and mist cooling and showed that mist cooling can offer lower and more uniform temperature distribution compared to dry air, which is a potential solution for the thermal management system of the battery module.

167 citations


Journal ArticleDOI
TL;DR: There is a significant positive relationship between loneliness and psychosis in people with psychosis, and this robust finding should be considered in clinical practice and treatment provision for those with psychotic disorders.
Abstract: Loneliness may be related to psychotic symptoms but a comprehensive synthesis of the literature in this area is lacking. The primary aim of the current study is to provide a systematic review and meta-analysis of the association between loneliness and psychotic symptoms in people with psychosis. A search of electronic databases was conducted (PsychINFO, MEDLINE, EMBASE, and Web of Science). A random effects meta-analysis was used to compute a pooled estimate of the correlation between loneliness and psychotic symptoms. Study and outcome quality were assessed using adapted versions of the Agency for Healthcare Research and Quality (AHRQ) tool and GRADE approach, respectively. Thirteen studies were included, providing data from 15 647 participants. A moderate association between psychosis and loneliness was observed (k = 13, N = 15 647, r = .32, 95% CI 0.20, 0.44; I2 = 97.56%; moderate quality evidence). Whether loneliness was assessed by a single-item or a more comprehensive measure had no moderating effect on the estimate. Results indicate that there is a significant positive relationship between loneliness and psychosis. Further studies are needed to determine the causal status of this relationship, but this robust finding should be considered in clinical practice and treatment provision for those with psychotic disorders.

162 citations


Proceedings ArticleDOI
01 Jul 2018
TL;DR: This paper proposed a stochastic answer network (SAN) that simulates multi-step reasoning in machine reading comprehension and achieved state-of-the-art performance on several reading comprehension tasks.
Abstract: We propose a simple yet robust stochastic answer network (SAN) that simulates multi-step reasoning in machine reading comprehension. Compared to previous work such as ReasoNet which used reinforcement learning to determine the number of steps, the unique feature is the use of a kind of stochastic prediction dropout on the answer module (final layer) of the neural network during the training. We show that this simple trick improves robustness and achieves results competitive to the state-of-the-art on the Stanford Question Answering Dataset (SQuAD), the Adversarial SQuAD, and the Microsoft MAchine Reading COmprehension Dataset (MS MARCO).

150 citations


Journal ArticleDOI
TL;DR: The authors explored three different deep-learning-based architectures for multimodal sentiment classification, each improving upon the previous, and evaluated these architectures with multiple datasets with fixed train/test partition.
Abstract: We compile baselines, along with dataset split, for multimodal sentiment analysis. In this paper, we explore three different deep-learning-based architectures for multimodal sentiment classification, each improving upon the previous. Further, we evaluate these architectures with multiple datasets with fixed train/test partition. We also discuss some major issues, frequently ignored in multimodal sentiment analysis research, e.g., the role of speaker-exclusive models, the importance of different modalities, and generalizability. This framework illustrates the different facets of analysis to be considered while performing multimodal sentiment analysis and, hence, serves as a new benchmark for future research in this emerging field.

146 citations


Journal ArticleDOI
TL;DR: The current study sought to advance the existing literature by providing the first assessment of the factorial and discriminant validity of the ICD‐11 proposals for posttraumatic stress disorder and complex PTSD in a nationwide level.
Abstract: Background: The current study sought to advance the existing literature by providing the first assessment of the factorial and discriminant validity of the ICD-11 proposals for PTSD and CPTSD in a nation-wide level. Methods: A nationally representative sample from Israel (n = 1003) using a disorder-specific measure (ITQ; International Trauma Questionnaire) in order to assess PTSD and Complex PTSD along with the Life Events Checklist and the World Health Organization Well-Being Index. Results: Estimated prevalence rates of PTSD and CPTSD were 9.0% and 2.6% respectively. The structural analyses indicated that PTSD and disturbances in self-organization symptom clusters were multidimensional, but not necessarily hierarchical, in nature and there were distinct classes that were consistent with PTSD and CPTSD. Conclusions: These results partially support the factorial validity and strongly support the discriminant validity of the ICD-11 proposals for PTSD and CPTSD in a nationally representative sample using a disorder-specific measure, findings also supported the international applicability of these diagnoses. Further research is required to determine the prevalence rates of PTSD and CPTSD in national representative samples across different countries and explore the predictive utility of different types of traumatic life events on PTSD and CPTSD.

Journal ArticleDOI
TL;DR: In this paper, a review of the application of metal foam in fuel cells and solar power systems is presented, where metal foam has been applied to the electrodes, gas diffusion layer and flow field of fuel cells to enhance performance.
Abstract: Fuel cells and solar energy are promising candidates for electricity generation. It is forecast that fuel cells and solar power systems will play an important role in reducing the greenhouse gas footprint and replacing fossil fuels. Therefore, the limitations of fuel cells and solar power systems, such as low efficiency, high cost, and low reliability, must be addressed appropriately to enable their full potentials. Metal foam is a new class of material that has gained immense attention due to its excellent properties suitable for a wide range of applications. Its unique characteristics distinguish it from typical solid metals. The properties of metal foam can be modified during the fabrication stage by manipulating its physical structure. The goal of this paper is to review the application of metal foam in fuel cells and solar power systems. Besides, the performance of metal foam in fuel cells and solar systems is also discussed. Metal foam has been applied to the electrodes, gas diffusion layer and flow field of fuel cells to enhance performance, especially in regard to current density and flow distribution. Furthermore, metal foam is a heat exchanger for the solar energy harvesting system to improve its efficiency. Superior performances in experimental testing allows the possibility of commercialization of metal foam products in the renewable energy field.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated embodied carbon assessments, considering the data used and the methodological assumptions made, and showed that there are still considerable variations in how the methodology is applied, leading to substantial limitations in comparing results and drawing conclusions.
Abstract: Life cycle assessment (LCA) is becoming increasingly mainstream as an early-stage design-decision tool for buildings. Still, there are considerable variations in how the method is currently used, leading to limitations in comparing the results and the conclusions that can be drawn. These variations are due to several factors and LCA modellers must make multiple methodological decisions during an assessment. This has resulted, unsurprisingly, in a variety of approaches, and a wide range of outcomes. Academics have produced numerous case studies on particular buildings, aiming towards a detailed understanding of the energy and carbon impacts. However, very few case studies are detailed enough to allow for an in-depth comparison. This article investigates in detail these embodied carbon assessments, considering the data used and the methodological assumptions made. An in-depth analysis shows that there are still considerable variations in how the methodology is applied, leading to substantial limitations in comparing results and drawing conclusions. Results may differ by two orders of magnitude, thus limiting the understanding of how real mitigation might best be achieved. Without immediate action, embodied carbon will become a ‘second wave’ of performance gap in environmental assessments of buildings. Both greater transparency and greater conformity must be embraced by the LCA community and enforced by policymakers and professional bodies.

Journal ArticleDOI
TL;DR: In older, community-dwelling adults, consumer wearables accurately measure step count and activity duration, as confirmed by reference devices and validation methods Further research is required to understand how co-morbidities, gait and activity levels interact with monitoring in free-living environments.

Journal ArticleDOI
TL;DR: In this article, the feasibility of cold ironing in a medium sized port with several small berths, based on the case of Aberdeen, was examined and the substantial external cost benefits would return the system capital and operating costs in only 7.0 years, or 3.5 years if subsidised 50% by the EU.
Abstract: Emissions from shipping contribute significantly to both climate change and local air pollution. Cold ironing (onshore power supply) reduces emissions while ships are berthed in port by providing power from shore-side electricity rather than onboard auxiliary generators. Previous research has focused on installing the technology in large ports but if policy goals (particularly in the EU) are to be achieved then smaller ports must also install the technology. Therefore, this study examines the feasibility of installing cold ironing in a medium sized port with several small berths, based on the case of Aberdeen. Vessel call data were analysed to calculate energy demand and a cold ironing system was designed, including separate OPS units for numerous small berths. The total capital cost was £6.6 m (€7.4 m) and the system could save annual emissions of 108 tonnes of NOx, 2.7 tonnes of PM and 4,767 tonnes of CO2 emissions worth £1.3 m (€1.4 m). Payback scenarios were examined via SCBA, based on the external costs of potential emission savings. In the best case scenario, the substantial external cost benefits would return the system capital and operating costs in only 7.0 years, or 3.5 years if subsidised 50% by the EU. Challenges result from several small berths needing individual OPS units, long cables and cable reel storage, as well as the need for several vessels to install the onboard technology, which must be overcome if ports besides the large cruise and container ports are to install cold ironing.

Journal ArticleDOI
TL;DR: Nursing faculty need to undertake more rigorous research to determine if mobile technology can improve learning outcomes, how best to personalise mobile apps to students needs and ensure both hardware devices and educational software can be integrated in practice to support clinical training.

Journal ArticleDOI
29 May 2018
TL;DR: This paper outlines recent work within the areas of pharmaceutical traceability, data sharing, clinical trials, and device tracking within the blockchain infrastructure.
Abstract: There are several areas of healthcare and well-being that could be enhanced using blockchain technologies. These include device tracking, clinical trials, pharmaceutical tracing, and health insurance. Within device tracking, hospitals can trace their asset within a blockchain infrastructure, including through the complete lifecycle of a device. The information gathered can then be used to improve patient safety and provide after-market analysis to improve efficiency savings. This paper outlines recent work within the areas of pharmaceutical traceability, data sharing, clinical trials, and device tracking. Keywords: Asset Tracking, Blockchain, Drug tracking, Ethereum, Healthcare, Internet of Things, IoT

Journal ArticleDOI
TL;DR: The role of dry biofilms in spreading HCAIs may be underestimated and the risk may be further exacerbated by inefficient cleaning and disinfection practices for hospital surfaces.


Journal ArticleDOI
TL;DR: The nature of human-computer interaction in the world that the digital transformation is creating will require (mutual) trust between humans and intelligent, or seemingly intelligent, machines, but what does it mean to trust an intelligent machine?
Abstract: Intelligent machines have reached capabilities that go beyond a level that a human being can fully comprehend without sufficiently detailed understanding of the underlying mechanisms. The choice of moves in the game Go (generated by Deep Mind?s Alpha Go Zero [1]) are an impressive example of an artificial intelligence system calculating results that even a human expert for the game can hardly retrace [2]. But this is, quite literally, a toy example. In reality, intelligent algorithms are encroaching more and more into our everyday lives, be it through algorithms that recommend products for us to buy, or whole systems such as driverless vehicles. We are delegating ever more aspects of our daily routines to machines, and this trend looks set to continue in the future. Indeed, continued economic growth is set to depend on it. The nature of human-computer interaction in the world that the digital transformation is creating will require (mutual) trust between humans and intelligent, or seemingly intelligent, machines. But what does it mean to trust an intelligent machine? How can trust be established between human societies and intelligent machines?

Journal ArticleDOI
TL;DR: It is shown that in such cases the truncation error of process-based LCA outweighs the aggregation error of hybrid LCA, and it is demonstrated that even simple process systems can have higher dominant eigenvalues, provided they are based on realistic data.

Journal ArticleDOI
TL;DR: Comparisons of prevalence rates of PTSD/CPTSD based on each diagnostic system and the diagnostic associations for ICD-11 CPTSD and DSM-5 PTSD have implications for differential diagnosis and for the development of targeted treatments for CPTSS.
Abstract: The American Psychiatric Association and the World Health Organization provide distinct trauma-based diagnoses in the fifth edition of the Diagnostic and Statistical Manual (DSM-5), and the forthcoming 11th version of the International Classification of Diseases (ICD-11), respectively. The DSM-5 conceptualizes posttraumatic stress disorder (PTSD) as a single, broad diagnosis, whereas the ICD-11 proposes two "sibling" disorders: PTSD and complex PTSD (CPTSD). The objectives of the current study were to: (a) compare prevalence rates of PTSD/CPTSD based on each diagnostic system; (b) identify clinical and behavioral variables that distinguish ICD-11 CPTSD and PTSD diagnoses; and (c) examine the diagnostic associations for ICD-11 CPTSD and DSM-5 PTSD. Participants in a predominately female clinical sample (N = 106) completed self-report scales to measure ICD-11 PTSD and CPTSD, DSM-5 PTSD, and depression, anxiety, borderline personality disorder, dissociation, destructive behaviors, and suicidal ideation and self-harm. Significantly more people were diagnosed with PTSD according to the DSM-5 criteria (90.4%) compared to those diagnosed with PTSD and CPTSD according to the ICD-11 guidelines (79.8%). An ICD-11 CPTSD diagnosis was distinguished from an ICD-11 PTSD diagnosis by higher levels of dissociation (d = 1.01), depression (d = 0.63), and borderline personality disorder (d = 0.55). Diagnostic associations with depression, anxiety, and suicidal ideation and self-harm were higher for ICD-11 CPTSD compared to DSM-5 PTSD (by 10.7%, 4.0%, and 7.0%, respectively). These results have implications for differential diagnosis and for the development of targeted treatments for CPTSD.

Journal ArticleDOI
TL;DR: The need for post-match fatigue monitoring is debated, the real-world relevance of the current research literature is critique, the practical burden relating to measurement tools and protocols, and the collection, interpretation and application of data in the field are discussed.
Abstract: Participation in soccer match-play leads to acute and transient subjective, biochemical, metabolic and physical disturbances in players over subsequent hours and days. Inadequate time for rest and regeneration between matches can expose players to the risk of training and competing whilst not entirely recovered. In professional soccer, contemporary competitive schedules can require teams to compete in excess of 60 matches over the course of the season with periods of fixture congestion occurring, prompting much attention from researchers and practitioners to the monitoring of fatigue and readiness to play. A comprehensive body of research has investigated post-match acute and residual fatigue responses. Yet the relevance of the research for professional soccer contexts is debatable, notably in relation to the study populations and designs employed. Monitoring can indeed be invasive, expensive, time inefficient, and difficult to perform routinely and simultaneously in a large squad of regularly competing players. Uncertainty also exists regarding the meaningfulness and interpretation of changes in fatigue response values and their functional relevance, and practical applicability in the field. The real-world need and cost-benefit of monitoring must be carefully weighed up. In relation to professional soccer contexts, this opinion paper intends to (1) debate the need for post-match fatigue monitoring; (2) critique the real-world relevance of the current research literature; (3) discuss the practical burden relating to measurement tools and protocols, and the collection, interpretation and application of data in the field; and (4) propose future research perspectives.

Journal ArticleDOI
TL;DR: It is feasible to promote sunscreen use and SSE in the context of an adolescent school-based psychoeducation intention and significant associations were found between sunscreen use, planning and 2 illness perceptions (identity and consequence) and between SSE, planning, and 3 illness perceptions.
Abstract: Skin cancer rates are increasing. Interventions to increase adolescent sunscreen use and skin self-examination (SSE) are required. Quasi-experimental design; 1 control and 4 intervention group schools in Scotland, UK. Participants were 15–16 year old students on the school register. The intervention was a theoretically-informed (Common-Sense Model and Health Action Process Approach) 50-min presentation, delivered by a skin cancer specialist nurse and young adult skin cancer survivor, to students in a classroom, supplemented by a home-based assignment. Outcome variables were sunscreen use intention, SSE intention/behaviour, planning, illness perceptions and skin cancer communication behaviour, measured 2 weeks pre- and 4 weeks post- intervention using self-completed pen and paper survey. School attendance records were used to record intervention up-take; students self-reported completion of the home-based assignment. Pearson’s chi-square test, analysis of variance, and non-parametric Wilcoxon Signed Ranks Test were used to measure outcomes and associations between variables. Focus groups elicited students’ (n = 29) views on the intervention. Qualitative data were analysed thematically. Five of 37 invited schools participated. 639 (81%) students in intervention schools received the intervention; 33.8% completed the home-based assignment. 627 (69.6%) of students on the school register in intervention and control schools completed a questionnaire at baseline; data for 455 (72.6%) students were available at baseline and follow-up. Focus groups identified four themes – personal experiences of skin cancer, distaste for sunscreen, relevance of SSE in adolescence, and skin cancer conversations. Statistically significant (p < 0.05) changes were observed for sunscreen use, SSE, planning, and talk about skin cancer in intervention schools but not the control. Significant associations were found between sunscreen use, planning and 2 illness perceptions (identity and consequence) and between SSE, planning and 3 illness perceptions (timeline, causes, control). It is feasible to promote sunscreen use and SSE in the context of an adolescent school-based psychoeducation intention. Further research is required to improve study uptake, intervention adherence and effectiveness. ISRCTN11141528

Journal ArticleDOI
TL;DR: In this article, a novel segmented micro-channel is introduced to improve the thermal performance of the straight-channel heat sink, and the bottom of the heat sink is subjected to a constant heat flux condition and water is used as a coolant.

Journal ArticleDOI
TL;DR: It is suggested that in order to verify this, it is necessary for smart cities to first baseline the social-demographic structure of retrofit proposals, to assess whether the regional innovation creates the wealth needed to under-grid the sustainability of city-districts.

Journal ArticleDOI
TL;DR: Panton–Valentine leukocidin (PVL), a pore-forming cytotoxic secreted toxin, has been associated with severe Staphylococcus aureus pneumonia and prototypical skin lesions and suffers from a selective reporting bias towards community-associated methicillin-resistant S. a Aureus.

Journal ArticleDOI
24 Jan 2018
TL;DR: Acute:chronic markers showed association however with poor prediction ability, and the AUC ≤0.60 for all markers and Youden Index (close to 0) showed poor prediction.
Abstract: Purpose: To examine association and prediction of load-based markers (rate of perceived exertion) with non-contact injuries.Materials and methods: Thirty-four elite Italian football players (age 26...

Journal ArticleDOI
TL;DR: This study considers the cloud market where various resources in the form of Virtual Machine (VM) instances can be provisioned and then leased to clients with QoS guarantees, and proposes a novel Service Level Agreement (SLA) framework for cloud computing, in which a price control parameter is used to meet QoS demands for all classes in the market.
Abstract: In the current cloud business environment, the cloud provider (CP) can provide a means for offering the required quality of service (QoS) for multiple classes of clients. We consider the cloud market where various resources such as CPUs, memory, and storage in the form of Virtual Machine (VM) instances can be provisioned and then leased to clients with QoS guarantees. Unlike existing works, we propose a novel Service Level Agreement (SLA) framework for cloud computing, in which a price control parameter is used to meet QoS demands for all classes in the market. The framework uses reinforcement learning (RL) to derive a VM hiring policy that can adapt to changes in the system to guarantee the QoS for all client classes. These changes include: service cost, system capacity, and the demand for service. In exhibiting solutions, when the CP leases more VMs to a class of clients, the QoS is degraded for other classes due to an inadequate number of VMs. However, our approach integrates computing resources adaptation with service admission control based on the RL model. To the best of our knowledge, this study is the first attempt that facilitates this integration to enhance the CP's profit and avoid SLA violation. Numerical analysis stresses the ability of our approach to avoid SLA violation while maximizing the CP's profit under varying cloud environment conditions.

Journal ArticleDOI
TL;DR: In this paper, a series of triaxial test DEM simulations examine the influence of particle-size distribution and particle shape on the critical state behavior of granular materials using discrete element method simulations on both spherical and non-spherical particle assemblies.
Abstract: This paper presents an investigation into the effects of particle-size distribution on the critical state behavior of granular materials using discrete element method (DEM) simulations on both spherical and non-spherical particle assemblies. A series of triaxial test DEM simulations examine the influence of particle-size distribution (PSD) and particle shape, which were independently assessed in the analyses presented. Samples were composed of particles with varying shapes characterized by overall regularity (OR) and different PSDs. The samples were subjected to the axial compression through different loading schemes: constant volume, constant mean effective stress, and constant lateral stress. All samples were sheared to large strains to ensure that a critical state was reached. Both the macroscopic and microscopic behaviors in these tests are discussed here within the framework of the anisotropic critical state theory. It is shown that both OR and PSD may affect the response of the granular assemblies in terms of the stress–strain relations, dilatancy, and critical state behaviors. For a given PSD, both the shear strength and fabric norm decrease with an increase in OR. The critical state angle of shearing resistance is highly dependent on particle shape. In terms of PSD, uniformly distributed assemblies mobilize higher shear strength and experience more dilative responses than specimens with a greater variation of particle sizes. The position of the critical state line in the e–p′ space is also affected by PSD. However, the effects of PSD on critical strength and evolution of fabric are negligible. These findings highlight the importance of particle shape and PSD that should be included in the development of constitutive models for granular materials.