38 research outputs found
The Sri Lankan Debt Crisis: Is there a way out?
No full textThis thesis deals with the current debt crisis is Sri Lanka, which was brought about by rapid development following the end of the civil war, and how best to prevent future debt crises by providing recommendations to policy makers. This thesis makes use of two models, the Balance-of-Payments (BOP) Constrained growth model, and the Flying Goose Model (FGM) of development which was observed in East Asian countries during their fast-paced growth period. The BOP model is used to identify industries within Sri Lanka’s economy which have a high income elasticity of demand by the rest of the world. The results of the data analysis find that Sri Lanka has a high income elasticity of demand in the machinery and chemical sectors with in the manufacturing industry. The Sri Lankan economy is also diagnosed in the context of the FGM to understand in what stage of the FGM Sri Lanka is in, by means of carrying out non-parametric analysis on the FDI per capita, the trade dependence ratio, the revealed comparative advantage index and other economic parameters. From the evidence presented by the two models, policy recommendations go in the direction of promoting selective industrial policy, in order to enhance the growth of these targeted industries identified by the BOP model through means of accelerating the Flying Goose Model of development
Inverse membrane problems in elasticity
No full textThe inverse elasticity problem of determining the undeformed, deflated, configuration of a nonlinear elastic membrane, given the deformed configuration enclosing an incompressible fluid under known pressure, is considered. It is shown that, in practical cases, it is enough to determine only the undeformed metric tensor, and it is also shown how the two- and three-dimensional cases are fundamentally different. For the three-dimensional case, we set up and classify the partial differential equations to be solved, prove existence of an undeformed state given an undeformed metric and study the axisymmetric case in detail. © The author 2009. Published by Oxford University Press; all rights reserved
Durability Performance of Concrete Structures Built with Low Carbon Construction Materials
No full textAbstractHere, we demonstrate the feasibility of industrial application of low carbon supplementary cementitious materials (i.e. geopolymer concrete) by investigating the durability performance of eight years aged reinforced geopolymer concrete structure exposed to ambient environment. The corrosion performance of reinforcement bar in concrete and permeability characteristic of cover concrete is investigated by using non-destructive techniques. The results reveal that the reinforcement in geopolymer concrete exhibits higher corrosion risk in atmospheric environment and this attributes to the deterioration of long term durability performance for geopolymer concrete
Advancing Regulatory Science With Computational Modeling for Medical Devices at the FDA's Office of Science and Engineering Laboratories
No full textProtecting and promoting public health is the mission of the U.S. Food and Drug Administration (FDA). FDA's Center for Devices and Radiological Health (CDRH), which regulates medical devices marketed in the U.S., envisions itself as the world's leader in medical device innovation and regulatory science–the development of new methods, standards, and approaches to assess the safety, efficacy, quality, and performance of medical devices. Traditionally, bench testing, animal studies, and clinical trials have been the main sources of evidence for getting medical devices on the market in the U.S. In recent years, however, computational modeling has become an increasingly powerful tool for evaluating medical devices, complementing bench, animal and clinical methods. Moreover, computational modeling methods are increasingly being used within software platforms, serving as clinical decision support tools, and are being embedded in medical devices. Because of its reach and huge potential, computational modeling has been identified as a priority by CDRH, and indeed by FDA's leadership. Therefore, the Office of Science and Engineering Laboratories (OSEL)—the research arm of CDRH—has committed significant resources to transforming computational modeling from a valuable scientific tool to a valuable regulatory tool, and developing mechanisms to rely more on digital evidence in place of other evidence. This article introduces the role of computational modeling for medical devices, describes OSEL's ongoing research, and overviews how evidence from computational modeling (i.e., digital evidence) has been used in regulatory submissions by industry to CDRH in recent years. It concludes by discussing the potential future role for computational modeling and digital evidence in medical devices
Interpretation of the loading/wetting behaviour of compacted soils within the MPK framework: Part II Dynamic compaction
No full textDynamic compaction is commonly used to construct structural fills for various geo-infrastructures. Current practice is to specify a minimum dry density and moisture content criterion to be used in the field on the basis of Proctor compaction carried out in the laboratory. Nonetheless, we still do not have practical methods for predicting the compacted clay behaviour under expected mechanical and environmental loadings. Current theories are difficult to apply in practice due to difficulty in determining the necessary parameters. In this paper, the recently developed MPK framework is extended to cover dynamically compacted soils, with significant supporting experimental evidence. Two types of soils are used; lightly reactive kaolin and reactive Merri Creek clay. Since the compaction stress was unknown for dynamic compaction, recompression of soil specimens from compacted soil was used to establish the Loading Wetting State Boundary Surface (LWSBS). Independent tests showed that the framework can predict well the behaviour of compacted soils under loading/unloading and yielding, collapse during wetting, change of loading yield stress after wetting, and swelling pressure development during constrained wetting. The value of the approach is that the testing methods are straight-forward, do not require specialised equipment and the testing times are much shorter. In addition, the uncertainty that laboratory dynamic compaction may not relate directly to field roller compaction can be addressed with the developed framework. Soil specimens obtained from field soil pads compacted by actual rollers can be used to establish the LWSBS. This information will allow the prediction of the likely behaviour of field compacted fills under expected environmental and mechanical loadings under one-dimensional conditions. Extension to triaxial conditions would require further experimental work and theoretical modelling.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
An equation to predict maximum pipe stress incorporating internal and external loadings on buried pipes
No full textPipelines used for water and other services are very important lifelines in modern society. As many of these pipelines have been laid sometime in the last century or earlier, in most cases their condition has deteriorated primarily by electro-chemical and (or) micro-biological corrosion. This paper describes the application of 3-D finite element method to analyse a buried pipe subject to external and internal loads. Firstly, the finite element model is validated against the data from field tests. Subsequently, the results of these 3-D finite element analyses are used to develop a closed-form expression to predict maximum stresses in pipes of different sizes buried in different soil types. Having obtained a good agreement between the proposed model outcomes and 3-D FE results, the proposed model has been validated against the field test data under different internal and external loadings. The verified outcomes of the model revealed that it can be used to predict maximum stresses without conducting full scale finite element analyses, which often requires specific computational resources and computational skills. Further, the proposed model can be used in probabilistic analyses where a large number of calculations need to be carried out to account for uncertainty of the input variables.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Charging Infrastructure and Grid Integration for Electromobility
No full textElectric vehicle (EV) charging infrastructure will play a critical role in decarbonization during the next decades, energizing a large share of the transportation sector. This will further increase the enabling role of power electronics converters as an energy transition technology in the widespread adoption of clean energy sources and their efficient use. However, this deep transformation comes with challenges, some of which are already unfolding, such as the slow deployment of charging infrastructure and competing charging standards, and others that will have a long-term impact if not addressed timely, such as the reliability of power converters and power system stability due to loss of system inertia, just to name a few. Nevertheless, the inherent transition toward power systems with higher penetration of power electronics and batteries, together with a layer of communications and information technologies, will also bring opportunities for more flexible and intelligent grid integration and services, which could increase the share of renewable energy in the power grid. This work provides an overview of the existing charging infrastructure ecosystem, covering the different charging technologies for different EV classes, their structure, and configurations, including how they can impact the grid in the future.</p
Using Curiosity for an Even Representation of Tasks in Continual Offline Reinforcement Learning
No full textPublisher Copyright: © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.In this work, we investigate the means of using curiosity on replay buffers to improve offline multi-task continual reinforcement learning when tasks, which are defined by the non-stationarity in the environment, are non labeled and not evenly exposed to the learner in time. In particular, we investigate the use of curiosity both as a tool for task boundary detection and as a priority metric when it comes to retaining old transition tuples, which we respectively use to propose two different buffers. Firstly, we propose a Hybrid Reservoir Buffer with Task Separation (HRBTS), where curiosity is used to detect task boundaries that are not known due to the task-agnostic nature of the problem. Secondly, by using curiosity as a priority metric when it comes to retaining old transition tuples, a Hybrid Curious Buffer (HCB) is proposed. We ultimately show that these buffers, in conjunction with regular reinforcement learning algorithms, can be used to alleviate the catastrophic forgetting issue suffered by the state of the art on replay buffers when the agent’s exposure to tasks is not equal along time. We evaluate catastrophic forgetting and the efficiency of our proposed buffers against the latest works such as the Hybrid Reservoir Buffer (HRB) and the Multi-Time Scale Replay Buffer (MTR) in three different continual reinforcement learning settings. These settings are defined based on how many times the agent encounters the same task, how long they last, and how different new tasks are when compared to the old ones (i.e., how large the task drift is). The three settings are namely, 1. prolonged task encounter with substantial task drift, and no task re-visitation, 2. frequent, short-lived task encounter with substantial task drift and task re-visitation, and 3. every timestep task encounter with small task drift and task re-visitation. Experiments were done on classical control tasks and Metaworld environment. Experiments show that our proposed replay buffers display better immunity to catastrophic forgetting compared to existing works in all but the every time step task encounter with small task drift and task re-visitation. In this scenario curiosity will always be higher, thus not being an useful measure in both proposed buffers, making them not universally better than other approaches across all types of CL settings, and thereby opening up an avenue for further research.Natalia Díaz-Rodríguez is supported by grant IJC2019-039152-I funded by MCIN/AEI /10.13039/501100011033, by “ESF Investing in your future,” Google Research Scholar Program, and by the European Union through the Marie Curie Postdoctoral Fellowship (Project: 101059332 - RRR-XAI - HORIZON-MSCA-2021-PF-01). J. Del Ser is supported by the Basque Government through the ELKARTEK program and the consolidated research group MATHMODE (IT1456-22).Peer reviewe
Scientific Abstract to Full Paper: Publication Rate over a 3-Year Period in a Malaysian Clinical Research Conference
No full textBackground: The publication rates of abstracts after they were presented at the National Conference for Clinical Research (NCCR), a scientific conference held in Malaysia, was determined to gauge the scientific value of the conference, whilst providing comparative information with other scientific conferences. Methods: All the abstracts that were presented at the NCCR from 2014 to 2016 were analysed. Keywords from the abstract title, along with the first, second, and last author’s name, were searched via PubMed, Google Scholar, and Scopus to determine publication status. Results: A total of 320 abstracts were analysed. Of those, 57 abstracts (17.8%) were published. Almost 70% of published abstracts appeared in open access journals that charge article processing fees. Early publications (≤18 months from the conference date) had higher median journal impact factors compared to later publications. Approximately 42% of the published abstracts had collaborations with the Institute for Clinical Research (ICR) or Clinical Research Centres (CRCs). An increasing number of authors in an abstract and having the first author from a research centre, reduced and increased the odds of publication, respectively. Conclusions: The NCCR publication rate is lower compared to the reported average in other scientific conferences abroad. More encouragement and support to publish should be provided to the presenting authors. Clinicians should also be encouraged to collaborate with research centres such as those from the ICR or CRCs to boost publication likelihoods
L.) in Dominica revealed by single nucleotide polymorphism markers
No full textCacao (Theobroma cacao L.), an introduced tree crop in Dominica, is important for foreign exchange earnings from fine or flavour cocoa. The genetic structure of farmed cacao in Dominica was examined to identify varieties for conservation, breeding, and propagation to improve their cocoa industry. Cacao trees (156) from 73 sites over seven geographical regions were genotyped at 192 single nucleotide polymorphism (SNP) markers. Identity, regional differentiation, phylogenetic, multi-variate, ancestry, and core collection analyses were performed. Farmed cacao germplasm had moderate gene diversity (He = 0.320 ± 0.005) from generally unique trees, but cocoa growing regions were genetically similar. Synonymous matching (16.3%) showed that some clonal material was supplied to farmers. Cacao trees were mainly mixed from Amelonado, Criollo, Iquitos, Contamana, and Marañon ancestries, with predominantly Amelonado–Criollo hybrids. Criollo ancestry, linked to fine or flavour cocoa, was found at more than 30% in 28 unique trees. Forty-five trees, containing the SNP diversity of cacao in Dominica, are recommended as a core germplasm collection. This study identifies promising trees for improving cocoa quality; provides genetic evidence that community, regional, or country-wide pooling would not compromise the exclusive fine or flavour cocoa industry; and discusses other implications towards improving the Dominican cocoa industry.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
