7,989 research outputs found

    A highly scalable Met Office NERC Cloud model

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    Large Eddy Simulation is a critical modelling tool for scien- tists investigating atmospheric flows, turbulence and cloud microphysics. Within the UK, the principal LES model used by the atmospheric research community is the Met Office Large Eddy Model (LEM). The LEM was originally devel- oped in the late 1980s using computational techniques and assumptions of the time, which means that the it does not scale beyond 512 cores. In this paper we present the Met Office NERC Cloud model, MONC, which is a re-write of the existing LEM. We discuss the software engineering and architectural decisions made in order to develop a flexible, extensible model which the community can easily customise for their own needs. The scalability of MONC is evaluated, along with numerous additional customisations made to fur- ther improve performance at large core counts. The result of this work is a model which delivers to the community signifi- cant new scientific modelling capability that takes advantage of the current and future generation HPC machine

    Maintaining credibility when communicating uncertainty: The role of communication format

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    Research into risk communication has commonly highlighted the disparity between the meaning intended by the communicator and what is understood by the recipient. Such miscommunications will have implications for perceived trust and expertise of the communicator, but it is not known whether this differs according to the communication format. We examined the effect of using verbal, numerical and mixed communication formats on perceptions of credibility and correctness, as well as whether they influenced a decision to evacuate, both before and after an ‘erroneous’ prediction (i.e. an ‘unlikely’ event occurs, or a ‘likely’ event does not occur). We observed no effect of communication format on any of the measures pre-outcome, but found the numerical format was perceived as less incorrect, as well as more credible than the other formats after an ‘erroneous’ prediction, but only when low probability expressions were used. Our findings suggest numbers should be used in consequential risk communications

    Communicating Uncertainty: The Role of Communication Format in Maximising Understanding and Maintaining Credibility

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    This thesis investigates the effect of communication format on the understanding of uncertainty communications and considers the implications of these findings for a communicator’s perceived credibility. The research compares five formats: verbal probability expressions (VPEs; e.g., ‘unlikely’); numerical expressions – point (e.g., ‘20% likelihood’) and range estimates (e.g., ‘10–30% likelihood’); and mixed expressions in two orders (verbal-numerical, e.g., ‘unlikely [20% likelihood]’ and numerical-verbal format, e.g., ‘20% likelihood [unlikely]’). Using the ‘which-outcome’ methodology, we observe that when participants are asked to estimate the probability of the outcome of a natural hazard that is described as ‘unlikely’, the majority indicate outcomes with a value exceeding the maximum value shown, equivalent to a 0% probability. Extending this work to numerical and mixed formats, we find that 0% interpretations are also given to communications using a verbal-numerical format (Chapter 2). If ‘unlikely’ is interpreted as referring to events which will never occur, there could be implications for a communicator’s perceived credibility should an ‘unlikely’ event actually occur. In the low probability domain, we find a communicator who uses a verbal format in their prediction is perceived as less credible and less correct than one who uses a numerical format. However, in the high probability domain (where a ‘likely’ event does not occur) such an effect of format is not consistently observed (Chapter 3). We suggest ‘directionality–outcome congruence’ can explain these findings. For example, the negatively directional term ‘unlikely’ led to harsher ratings because the outcome was counter to the original focus of the prediction (i.e., on its non-occurrence). Comparing communications featuring positively and negatively directional VPEs, we find that communicators are perceived as less credible and less correct given directionality–outcome incongruence (Chapter 4). Our findings demonstrate the influence of pragmatics on (a) the understanding of uncertainty communications and (b) perceived communicator credibility

    Stochastic rounding and reduced-precision fixed-point arithmetic for solving neural ordinary differential equations

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    Although double-precision floating-point arithmetic currently dominates high-performance computing, there is increasing interest in smaller and simpler arithmetic types. The main reasons are potential improvements in energy efficiency and memory footprint and bandwidth. However, simply switching to lower-precision types typically results in increased numerical errors. We investigate approaches to improving the accuracy of reduced-precision fixed-point arithmetic types, using examples in an important domain for numerical computation in neuroscience: the solution of Ordinary Differential Equations (ODEs). The Izhikevich neuron model is used to demonstrate that rounding has an important role in producing accurate spike timings from explicit ODE solution algorithms. In particular, fixed-point arithmetic with stochastic rounding consistently results in smaller errors compared to single precision floating-point and fixed-point arithmetic with round-to-nearest across a range of neuron behaviours and ODE solvers. A computationally much cheaper alternative is also investigated, inspired by the concept of dither that is a widely understood mechanism for providing resolution below the least significant bit (LSB) in digital signal processing. These results will have implications for the solution of ODEs in other subject areas, and should also be directly relevant to the huge range of practical problems that are represented by Partial Differential Equations (PDEs).Comment: Submitted to Philosophical Transactions of the Royal Society

    On the role of pre and post-processing in environmental data mining

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    The quality of discovered knowledge is highly depending on data quality. Unfortunately real data use to contain noise, uncertainty, errors, redundancies or even irrelevant information. The more complex is the reality to be analyzed, the higher the risk of getting low quality data. Knowledge Discovery from Databases (KDD) offers a global framework to prepare data in the right form to perform correct analyses. On the other hand, the quality of decisions taken upon KDD results, depend not only on the quality of the results themselves, but on the capacity of the system to communicate those results in an understandable form. Environmental systems are particularly complex and environmental users particularly require clarity in their results. In this paper some details about how this can be achieved are provided. The role of the pre and post processing in the whole process of Knowledge Discovery in environmental systems is discussed

    The doctoral research abstracts. Vol:7 2015 / Institute of Graduate Studies, UiTM

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    Foreword: The Seventh Issue of The Doctoral Research Abstracts captures the novelty of 65 doctorates receiving their scrolls in UiTM’s 82nd Convocation in the field of Science and Technology, Business and Administration, and Social Science and Humanities. To the recipients I would like to say that you have most certainly done UiTM proud by journeying through the scholastic path with its endless challenges and impediments, and persevering right till the very end. This convocation should not be regarded as the end of your highest scholarly achievement and contribution to the body of knowledge but rather as the beginning of embarking into high impact innovative research for the community and country from knowledge gained during this academic journey. As alumni of UiTM, we will always hold you dear to our hearts. A new ‘handshake’ is about to take place between you and UiTM as joint collaborators in future research undertakings. I envisioned a strong research pact between you as our alumni and UiTM in breaking the frontier of knowledge through research. I wish you all the best in your endeavour and may I offer my congratulations to all the graduands. ‘UiTM sentiasa dihati ku’ / Tan Sri Dato’ Sri Prof Ir Dr Sahol Hamid Abu Bakar , FASc, PEng Vice Chancellor Universiti Teknologi MAR
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