Low-frequency GMRT observations of the magnetic Bp star HR Lup (HD 133880)

We present radio observations of the magnetic chemically peculiar Bp star HR Lup (HD 133880) at 647 and 277 MHz with the GMRT. At both frequencies the source is not detected but we are able to determine upper limits to the emission. The 647 MHz limits are particularly useful, with a 5\sigma\ value of 0.45 mJy. Also, no large enhancements of the emission were seen. The non-detections, along with previously published higher frequency detections, provide evidence that an optically thick gyrosynchrotron model is the correct mechanism for the radio emission of HR Lup.Comment: 7 pages, accepted for publication in the Bulletin of the Astronomical Society of India, to appear in the June issu

Land Grant Application- Stevens, Samuel (Mercer)

Land grant application submitted to the Maine Land Office on behalf of Samuel Stevens for service in the Revolutionary War, by their widow Amey.https://digitalmaine.com/revolutionary_war_me_land_office/1854/thumbnail.jp

Ottoman Relations with the Danubian Principalities during the Fifteen Years War (1591-1606)

Ottoman Relations with the Danubian Principalities during the Fifteen Years War (1591-1606

Teachers’ Attrition at Pre-tertiary Level in Ghana: A Qualitative Investigation into its Causes and Suggestions

Education has become an important social service, and its benefits are better reaped through quality of teachers who could improve performance of learners.  However, in Ghana, before teachers gain experience they quit their profession, a behavior popularly known as attrition, now a global challenge. Attrition in Ghana dates back to President Nkrumah’s era in the 60s, when His fee-free education attracted more children and consequently more teachers. However, conditions of service were un attractive at that time, so many vacated their posts to neighboring countries, like Nigeria, Liberia, Cote d’ Ivo ire, etc. Till date the attrition rate is In Ghana is high. The study thus seeks to identify the causes of, and solution to the attrition challenge in Ghana.  With a qualitative hermeneutic phenomenology methodology sampling approach, the researcher sampled for the study five teachers who had resigned their posts, and five who were in the Ghana Education Service.  A qualitative study analysis software (NVivo), was used to generate four themes as follows:  Poor conditions of service and salary; poor image of the profession; and a disunited front of the different groups of teachers—UTAG, POTAG, NAGRAT, and GNAT. The reviewed literature supported the first three themes, but the last one—the disunited front of teachers-- was significantly unique, and not found in previous studies.  Recommendations to raise the image of the teaching profession through school curriculum review; better conditions of service for GES; and a united front for all teachers in Ghana have been suggested. Key words: Attrition, greener pastures, qualitative genre, hermeneutic phenomenology DOI: 10.7176/JEP/10-14-18 Publication date:May 31st 201

Memorization for Good: Encryption with Autoregressive Language Models

Over-parameterized neural language models (LMs) can memorize and recite long sequences of training data. While such memorization is normally associated with undesired properties such as overfitting and information leaking, our work casts memorization as an unexplored capability of LMs. We propose the first symmetric encryption algorithm with autoregressive language models (SELM). We show that autoregressive LMs can encode arbitrary data into a compact real-valued vector (i.e., encryption) and then losslessly decode the vector to the original message (i.e., decryption) via random subspace optimization and greedy decoding. While SELM is not amenable to conventional cryptanalysis, we investigate its security through a novel empirical variant of the classic IND-CPA (indistinguishability under chosen-plaintext attack) game and show promising results on security. Our code and datasets are available at https://github.com/OSU-NLP-Group/SELM.Comment: Main text: 9 pages, 4 figures, 1 table. Work-in-progress. Project website at https://samuelstevens.me/research/encryption

An Investigation of Language Model Interpretability via Sentence Editing

Pre-trained language models (PLMs) like BERT are being used for almost all language-related tasks, but interpreting their behavior still remains a significant challenge and many important questions remain largely unanswered. For example, how does domain-specific pre-training change the dynamics within a model? Is task-specific fine-tuning necessary for model interpretability? Which interpretability techniques best correlate with human rationales? In this work, we re-purpose a sentence editing dataset, where high-quality human rationales can be automatically extracted and compared with model rationales, as a new testbed for interpretability. This enables us to conduct a systematic investigation of the aforementioned open questions regarding PLMs' interpretability and generate new insights. The dataset and code will be released to facilitate future research on interpretability.A one-year embargo was granted for this item.Academic Major: Computer Science and Engineerin

Computational modelling of large-scale fire spread through informal settlements

Informal settlements are a global phenomenon and are characterised by low quality construction and dense layouts, generally as a result of a lack of application of formal building regulations. They may be known by another name, such as slums or shantytowns, or exist in more novel contexts, for example refugee camps and homeless tented communities. However, a consistent feature of informal settlements in any context is their exposure to fire risk. Fire risk presents both as risk of fire ignition – how often fires occur – and risk of fire spread. Where there is a high risk of fire spread, a localised fire in an individual home may swiftly develop to the scale of tens or hundreds of homes. In some cases this may result in injury and loss of life, but the predominant issue is the extensive scale of property loss to communities that already exist in impoverished and precarious circumstances. There is vital need to understand and quantify fire spread risk factors to develop mitigation measures that may be used to protect informal settlements from large-scale fires. In recent years, a growing set of experiments have contributed to knowledge around how fires in informal structures, particularly of the type found in Cape Town’s expansive informal settlements, grow and spread. This knowledge is rooted in fundamental concepts used in fire science and engineering such as compartment fire dynamics, heat transfer and material ignition. However, it is practically challenging and cost-prohibited to scale experimentation to settlement-scale fire spread where multiple adjacent structures may be involved in the fire. As such, it is proposed that computational tools are developed to simulate fire spread through settlements, such that mitigation measures can be quantitatively tested and refined at settlement-scale, thus reducing the need for costly experimentation. Large-scale urban fire spread models have existed since the 1950s but have largely focussed on the phenomenon of post-earthquake fire spread. Additionally, it is only in the last 20 years that modellers have moved away from simplistic empirical models towards dynamic ‘physics-based’ models that attempt to explicitly define the fire behaviour. Previous models have achieved this to varying degrees of success, with many failing to conceptualise the underlying fire behaviour in a physically realistic manner even if at settlement-scale they may visually appear to be representative of fire spread. Intrinsic to this failure is a distinct lack of robust model validation. However, one model – of post-earthquake fire spread in Japan – sets itself apart with a clear underpinning of well-reasoned fire behaviour at the key unit of analysis for any urban fire model, the compartment fire. This thesis presents the adoption and integration of this model for application in informal settlements, both contextualising it to a new physical domain and proposing improved methods for modelling key aspects of fire behaviour. The thesis is underpinned by particularly strong focus on local-level validation, showing that the model accurately captures key fire characteristics at the level of individual compartments before even considering outcomes at settlement scale. The first area of focus is on the compartment fire, the fundamental unit of analysis of the model. It is contextualised for informal settlements by adapting fuel loads and boundary conditions to align with values from experiments. Additionally, a new fuel-oxygen mixing model is implemented where previously over-efficient combustion was being assumed within the compartment. In combination with timestep refinement, this also contributed to stabilisation of the compartment fire, where previously the model destabilised due to its inability to resolve gas flows and the neutral plane for ventilation-controlled fires. The result is a stable compartment fire model that can sustain ventilation-controlled conditions and which compares well to key metrics – temperature, heat release rate and oxygen concentration – when compared to experimental results. New phenomena of cardboard lining ‘flashover’ and externally-heated accelerated fire growth are also implemented in the model for the first time. Subsequently, the external thermal environment – external flaming, radiative heat transfer and ignition – is investigated. Prior external flame models are found to be rigid, context-specific and insensitive to wind. Given informal settlement fires are known to be sensitive to wind and highly driven by flame impingement and high local levels of radiation, it is crucial to model external venting flame as accurately as possible. Computational fluid dynamics (CFD) models are utilised to derive new correlations for external venting flame dimensions. Ignition is then modelled as a dependence on both radiation and flame impingement, where previously these have been treated as two independent mechanisms. The model is also adapted to reflect the dynamic and intermittent nature of external flames, such that probability is built into flame dimensions, based on data from experiments and CFD models. The new method is appropriately sensitive to wind speed and direction, to a degree not yet achieved in prior urban fire spread models. Development of both the compartment fire and external flame submodels was conducted at the local scale, modelling only one or two compartments at a time. Finally, the model is examined in a domain of 20 structures (as per a previous experiment) to assess how newly implemented submodels affect fire spread at the multi-structure level. This first verifies the efficacy of the new model in capturing the characteristics of fire spread in informal settlements compared to the original model. It also shows the dynamic response of the model to wind-driven conditions. Additionally, this process helps to uncover where there are still errors or inconsistent conceptualisation of fire spread behaviours, particularly associated with the model’s reading and mapping of the spatial environment. Thus, it provides the basis and scope for continued adaptation of the model to increase its robustness. Overall, interrogation of previous ‘physics-based’ models uncovered a lack of robust validation which inspired the approach taken in this research of developing the model at high resolution. Specific submodels had to be carefully examined and developed to ensure they were first stable and physically reasonable and, secondly, contextually appropriate for informal settlements. Though the research stopped short of application to entire informal settlement domains, the underlying model functionality has been updated with significantly more detailed and robust representation of real fire behaviour than has previously been applied in any large urban fire spread context. Future application to informal settlements or adaptation for other urban environments should be much expedited as a result

Using seasonality and particle tracking to trace Intermediate Water in the Strait of Georgia

The Strait of Georgia is a complex system of basins and waterways within the Salish Sea that receives the majority of Greater Vancouver’s wastewater via riverine input and effluent outfalls. It can be nominally divided into three constituent water masses: (1) a riverine surface layer; (2) a deep oceanic layer; and (3) an intermediate layer, composed of a mixture of the surface and deep waters. The intermediate water (IW) layer is the largest layer volumetrically and a primary component of the region’s subsurface estuarine circulation, yet a comprehensive understanding of the system has proved challenging. Here, we use two methods to assess the circulation pathways. The first method uses a synthesis of hydrographic observations to determine seasonal cycles in IW mass characteristics and exploits the spatial variation in seasonal cycle phase and amplitude to age the water mass, infer circulation and mixing, and understand the transport and eventual fate of IW in the Strait of Georgia. The second method uses particle tracking techniques implemented using SalishSeaCast model velocity outputs to similar effect. The IW circulation is found to be more complex than previously anticipated, with a direct alteration of circulation via inputs to the north of the region, a distinct cyclonic flow in the primary basin, and a strong inflowing boundary current on the eastern shores. Furthermore, we find evidence that wastewater tracer concentrations downstream of major effluent outfalls are consistent with our inferences of IW pathways

Modelling the relative risk of large fires across the informal settlements of Cape Town

Home to an estimated 1 billion people globally, informal settlements are urban environments that are subject to a high risk of extensive fire spread. Their dense layouts and light, combustible building materials often facilitate the spread of fire through tens or hundreds of homes at once, rendering the inhabitants homeless. Tackling this issue requires a sound understanding of the many spatial factors which can contribute to fire spread. The aim of this study was to quantify the relative risk of large fires across informal settlements in Cape Town, South Africa – a city which has a notable history of devastating informal settlement fires. This was conducted primarily by developing a risk-scoring model based on fundamental fire dynamics and a survey of expert opinion on informal settlements. The study included a review of past disaster risk studies to aid the establishment of solid principles for the risk modelling method. A ‘pairwise weighted’ risk model was developed, using GIS software to quantify the spatial environment. It showed a good degree of success in identifying settlements that have a history of severe fires, such as Masiphumelele, Imizamo Yethu and Kosovo, as being of very high fire risk. A particular advantage of the model is its ability to recognise three different categories of fire risk, imposed by infrastructural factors both within and external to a settlement, and environmental factors. However, the fire history data used as a metric to verify the accuracy of the model was unfortunately not of sufficient quality to facilitate a rigorous numerical validation of the model. Fire risk mapping for informal settlements is a relatively new field of research, therefore many potential developments to the model were also proposed. The relationship between climate and informal settlement fire spread is currently poorly understood so it must be studied and adapted accordingly within the risk model. This could further contribute to modelling of seasonally variable fire risk. Furthermore, future methods for modelling risk directly from estimates of settlement density should be developed, to allow for automatic satellite image processing. This would be of great benefit as it would speed up the GIS-based data collation process which proved time consuming for this study