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Evaluating the consistency of ensemble forecasts
Get PDFEnsemble forecasts play an essential role in providing early warnings to mitigate the impact of
hazardous weather events. However, there are still many areas where ensemble information is
not fully exploited. One key issue limiting the uptake of ensemble forecasts is the jumpiness that
can sometimes occur between successive forecasts. Ensemble forecasts show the range of
future weather scenarios that can occur, allowing users to make appropriate risk-based
decisions. Occasionally a new forecast seems to contradict the previous forecast by introducing
a new weather scenario that was not represented in the previous ensemble. Such
inconsistencies can cause users to lose confidence in the forecasting system.
This thesis aims to improve the diagnosis and understanding of these ensemble forecast
inconsistencies. First, a methodology is developed to quantify the consistency between a
sequence of ensemble forecasts valid for a given time, taking account of the full ensemble
distribution. This enables a quantitative evaluation of the consistency or jumpiness between
successive forecasts, providing insights into the relationship between jumpiness, skill and
spread.
The thesis also provides practical guidance to address user concerns about ensemble jumpiness.
It provides specific guidance that will enable users to make better use of the available
operational ensemble tropical cyclone track and genesis forecasts. The thesis shows that
evaluation of forecast consistency is complementary to the current focus on skill and ensemble
spread, and that an integrated approach using both skill and consistency measures can be
beneficial in evaluation of ensemble forecast performance.
Implementation of this approach at NWP centres will ensure that users have the necessary
information and guidance to mitigate the impact of run-to-run jumpiness and will provide
feedback to model developers on model weaknesses, complementing existing evaluation tools.
The research in this thesis will help improve the utilisation of ensemble forecasts to provide
early warnings of significant weather hazards, contributing to the UN Early Warnings for All
initiative
Environmental life cycle assessments of decentralized municipal solid waste management: a novel waste-to-compost approach
Get PDFGlobal waste generation is expanding rapidly in parallel with population expansion and urbanization, posing municipal solid waste management difficulties. This study examined the environmental impacts of domestic organic waste generated in the Dhaka North City Corporation in Bangladesh, a country with a fast-growing population and economy. No previous environmental life cycle assessment has been conducted in a decentralized waste-to-compost facility in Dhaka, nor has the environmental impact of manual informal labor be considered.
Four major waste management scenarios were compared: conventional windrow composting (S1), proposed automated composting using an EP-1000 machine (S2), and existing practices of sanitary (S3) and unsanitary (S4) landfilling. The four scenarios' environmental impacts were assessed using OpenLCA software. Environmental Life cycle assessment (ELCA) of the four scenarios was conducted using OpenLCA software for their environmental impact.
Results revealed that decentralized waste-to-compost process scenarios (S1 and S2) were lower than those of the conventional landfill scenarios (S3 and S4). The overall quantity of total yearly GWP100 from decentralized compost facility of S1 (1.14 million Mg CO2-eq Mg–1) and S2 (411 kg CO2-eq Mg–1) were multifold lower than emissions from conventional landfilling of S3 (~ 2.12 million Mg of CO2-eq Mg–1) and S4 (~ 3.87 million Mg of CO2-eq Mg–1) scenarios reflecting the environment-friendly outcome of the former than the latter scenarios. Similar trends of lesser quantities of FAETP, HTP, and TEP were noticed depicting the S1 and proposed S2 scenarios as better options than conventional landfill of S3 and S4 scenarios. In conclusion, the development of decentralized waste-to-compost facilities in Dhaka or other similar units across the globe can prove a better and more sustainable waste management strategy with a greater potential to mitigate adverse impacts of climate change and environmental pollution
Heat exchanger design and performance evaluation for a high-temperature heat pump system under different two-phase correlations: 4E analysis
Get PDFSupplying district heat and assisting the integration of renewable electricity, high-temperature heat pump technology is foreseen to play an essential role in renewable energy-powered thermal energy storage systems. However, existing studies on high-temperature heat pump performance prediction are usually based on utilizing specific heat transfer correlations of heat exchangers. It is difficult to guide the selection and combination of the two-phase correlations in the heat exchanger design and system performance assessment of the high-temperature heat pump. In the present study, we aim to focus on the impact of different two-phase correlations, and a comparative study is conducted among 8 correlations (4 flow condensation ones and 4 flow boiling ones) adopted for component design and system performance prediction. The results show that for designed condensers or evaporators, the dimensions, costs, and carbon emissions are significantly affected by different two-phase correlations. Among 16 pairs of two-phase correlations, little fluctuation of the system performance is observed at the design heat source temperature 80 °C. While at off-design heat source temperatures of 85, 90 or 95 °C, the energetic and exergetic performance parameters are significantly affected with high relative differences (9.88% of heating capacity, 3.27% of coefficient of performance, and 6.76% of exergy efficiency). Also, the system's economic and environmental performance indexes are influenced to some extent, with visible relative uncertainties (1.91% of the heating cost, 4.44% of the payback time, and 6.38% of the carbon emission). This research will help to promote the selection and utilization of two-phase correlations for the plate heat exchanger design and system assessment in larger renewable energy-powered high-temperature heat pump applications
Real-time workflow scheduling in hybrid clouds with privacy and security constraints: a deep reinforcement learning approach
No full textHybrid clouds offer more capacity and flexibility than public or private clouds alone, making them popular in business settings. However, they also complicate the scheduling of workflow applications due to their complex computing resources. Furthermore, significant concerns about exposing sensitive data on public clouds and securing data transmission add additional challenges to the scheduling process. Although various workflow scheduling strategies
for hybrid clouds that address privacy and security concerns have been proposed, they have inherent limitations. Many of these methods, including heuristic and metaheuristic approaches, are tailored for batch processing and are not suitable for real-time scenarios where workflows can arrive unpredictably. Additionally, they often prioritize security over reducing execution time and costs, compromising overall efficiency. To tackle these challenges, we introduce a scheduling system in Hybrid clOuds that considers Privacy
and Security constraints, called HOPS. HOPS utilizes Deep Reinforcement Learning to dynamically assign workflows to virtual machines in real-time, and aims to minimize both makespan and operational costs while adhering to privacy and security standards. We provide a comprehensive overview of the design of HOPS, and our experimental results clearly show its advantages over existing methods in terms of makespan, cost efficiency, and the success rate, with privacy and security compliance
Foreign subsidiary performance in multinational enterprises: the role of business development capabilities and resource deployment
Get PDFThe research on subsidiary capability building highlights the importance of creating new capabilities in host countries while the resource management view emphasises effective resource structuring, bundling, and deployment actions to achieve competitive advantages and value creation. Building upon these theoretical advances, we develop a conceptual framework that examines the direct and combined impacts of subsidiary-level business development capabilities encompassing both product and market development, and resource deployment on the performance of foreign subsidiaries of multinational enterprises. We empirically test this framework using survey data from manufacturing and service subsidiaries, archival data from parent firms, and host country data from public sources. The empirical results support our hypotheses. We discuss the implications of our findings for both theory and practice
A Review of the arctic-West African monsoon nexus: How arctic sea ice decline influences monsoon system
Get PDFThe West African Monsoon (WAM) is a crucial component of the regional climate system, affecting agriculture, water resources and livelihoods across West Africa. Recent studies have suggested that changes in Arctic sea ice extent, driven primarily by anthropogenic climate change, could exert significant influences on the behaviour of the WAM. This review paper summarises the current state of knowledge on how Arctic sea ice melt has affected the WAM system over the last decades. Utilizing observations data and modelling studies aim at enhancing our understanding of the influence of Artic sea ice loss on WAM. This paper also explores the mechanisms driving the connections between Arctic sea ice melting and the WAM, discusses the potential implications for regional climate variability, and identifies key challenges and opportunities for future research in this important area of study
Nutrient use and methane emissions in growing beef fed different protein sources and a pasture-based diet
Get PDFThis study investigated the effects of different protein sources on feed intake, nutrient, and energy utilization, growth performance, and enteric methane (CH4) emissions in growing beef cattle, also evaluated against a pasture-based diet. Thirty-two Holstein × Angus growing beef were allocated to four dietary treatments: a total mixed ration (TMR) including solvent-extracted soybean meal as the main protein source (SB; n = 8), TMR with local brewers' spent grains (BSG; n = 8), TMR with local field beans (BNS; n = 8), and a diet consisting solely of fresh-cut Italian ryegrass (GRA; n = 8). Every four weeks, animals were moved to digestibility stalls within respiration chambers to measure nutrient intakes, energy and nitrogen (N) utilization, and enteric CH4 emissions. Feed intake (Calan gates), nutrient intakes, and CH4 emissions (GreenFeed) were also measured when animals were group-housed. In respiratory chambers, enteric CH4 yield per kg of dry matter intake (DMI), per kg of organic matter intake (OMI), and per kg body weight were lower for GRA. Feces and urine energy outputs were higher (P < 0.001) for GRA steers than concentrate-fed steers. Urinary nitrogen output (UNO, P = 0.011), manure (feces+urine) nitrogen output (MNO, P = 0.039), UNO/nitrogen intake (P < 0.001), and MNO/nitrogen intake (P = 0.005) were higher for GRA. During group-housing periods, CH4 emissions, measured by GreenFeed, were similar to those measured in chambers. Similar CH4 yield between treatments, expressed per kg digestible DMI and digestible OMI, may indicate that the lower diet digestibility was likely the reason for the reduced enteric CH4 emissions in pasture-based diets. The higher energy output and nitrogen losses, and the reduced nitrogen utilization for steers fed the fresh-cut ryegrass diet indicate less efficient energy and nitrogen utilization, which can be considered environmentally undesirable. The lower growth rates in the pasture-based system should also be accounted for when this is adopted for reducing production costs
Times needed to evolve mating cues under allopatry and parapatry
Get PDFThe time needed for the evolution of mating cues that distinguish species, such as species-specific songs or plumage coloration in birds, has received little attention. Aiming to gain some understanding of the timing of the evolutionary process we here present models of how mating cues evolve in populations split into subpopulations between which there may (parapatry) or may not (allopatry) be migration. Mating cues can be either neutral or directly selected. In models in which evolution commences with a substitution at a neutral mating-cue locus, under allopatry there is no selection on the mating cue, but under parapatry selection may be induced on the mating cue by the selective conditions in the subpopulations and the migration rates between them. We use simulation to calculate how selection pressures on mating cues then depend on selective conditions in subpopulations and migration rates between them. In the second part of the paper we demonstrate quantitatively how the resulting selection pressures on new mating cues together with mutation rate affect speciation time. Our results suggest that species-specific songs or plumage colorations that are selectively neutral evolve faster under parapatry than under allopatry, and this may explain the short speciation times that are sometimes reported. Although our modelling assumptions are restrictive so that caution is needed in comparing the results to empirical data, we hope that our main results, showing quantitatively how parapatry can reduce speciation times, will encourage further work relaxing model assumptions or studying different models of mate choice
Development and validation of a short form psychometric tool assessing the caregiving Challenge of Living with Cystic Fibrosis (CLCF-SF) in a child
Get PDFObjective
Caring for a child with cystic fibrosis (CF) is a rigorous daily commitment for caregivers and treatment burden is a major concern. We aimed to develop and validate a short form version of a 46-item tool assessing the Challenge of Living with Cystic Fibrosis (CLCF) for clinical or research use.
Design
A novel genetic algorithm based on ‘evolving’ a subset of items from a pre-specified set of criteria, was applied to optimise the tool, using data from 135 families.
Main outcome measures
Internal reliability and validity were assessed; the latter compared scores to validated tests of parental well-being, markers of treatment burden, and disease severity.
Results
The 15-item CLCF-SF demonstrated very good internal consistency [Cronbach’s alpha 0.82 (95%CI 0.78–0.87)]. Scores for convergent validity correlated with the Beck Depression Inventory (Rho = 0.48), State Trait Anxiety Inventory (STAI-State, Rho = 0.41; STAI-Trait, Rho = 0.43), Cystic Fibrosis Questionnaire-Revised, lung function (Rho = −0.37), caregiver treatment management (r = 0.48) and child treatment management (r = 0.45), and discriminated between unwell and well children with CF (Mean Difference 5.5, 95%CI 2.5–8.5, p < 0.001), and recent or no hospital admission (MD 3.6, 95%CI 0.25–6.95, p = 0.039).
Conclusion
The CLCF-SF provides a robust 15-item tool for assessing the challenge of living with a child with CF