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Combining Topic Modeling with Grounded Theory: Case Studies of Project Collaboration
No full textThis paper proposes an Artificial Intelligence (AI) Grounded Theory for management studies. We argue that this novel and rigorous approach that embeds topic modelling will lead to the latent knowledge to be found. We illustrate this abductive method using 51 case studies of collaborative innovation published by Project Management Institute (PMI). Initial results are presented and discussed that include 40 topics, 6 categories, 4 of which are core categories, and two new theories of project collaboration
Quantifying the Impacts of Modelling Assumptions on Accuracy and Computational Efficiency for Integrated Water-Energy System Simulations Under Uncertain Climate
No full textJointly managing water and energy systems, rather than treating each system independently, is recognised as an approach that can lead to a more cost-effective and reliable supply, which is particularly critical in water-rich and developing countries. This has motivated the development of various integrated water-energy simulators, each one catering for specific modelling needs through the use of specific sets of modelling assumptions, e.g., representing water and energy with balance equations, or dedicated river flow and power network equations. In this context, it becomes critical to assess the effectiveness of different modelling assumptions to improve the design of water-energy simulators. In particular, it is important to develop a methodology that can identify, based on a systematic assessment process, the portfolios of modelling assumptions that better capture the uncertain future conditions in the water and energy sectors, e.g., climate-driven stresses and shocks such as water scarcity, temperature rise, etc. To address this challenge, this paper proposes a Mixed Integer Linear Programming (MILP) integrated water-energy system simulation methodology designed to adapt and quantify different modelling assumptions under various weather-related conditions (e.g., water scarcity and high temperatures). The models were developed to capture the characteristics of non-pressurised water systems (e.g., channels and rivers) and electricity systems. The methodology is used to investigate typical modelling assumptions (e.g., temporal resolutions and water and power system models) and novel approaches to model the impacts of high temperatures on generation capacity to capture the effects of extreme weather on power generation. The methodology is demonstrated on the Ghanaian integrated water-energy system. The results highlight the benefits in terms of computational costs and modelling accuracy, of the customisable simulation, and provide guidance to select adequate modelling assumptions
Simultaneous Distillation-Extraction for Manufacturing Ultra-High-Purity Electronic-Grade Octamethylcyclotetrasiloxane (D4)
No full textUltra-high-purity (UHP) electronic-grade octamethylcyclotetrasiloxane (D4) is the key precursor of low-dielectric constant (low-k) SiCOH films to manufacture integrated circuits (IC), meeting the stringent requirements of the rapidly developing semiconductor industry. Commonly, metallic impurities in D4 were removed by multiple unit operations of adsorption, filtration, and distillation, which could reduce the concentration of a single metallic impurity below 1 ppb. However, D4 with higher purity is required by semiconductor production due to an increase in transistor density. Herein, a novel method based on the integrated simultaneous distillation-extraction (SDE) was developed for manufacturing UHP electronic-grade D4. The lab and pilot scale experiments showed that the purity of water and D4 has a positive correlation. Based on the experimental data, a double-column process, consisting of azeotropic/extractive distillation column and precision distillation column with UNIQUAC method, was established to access the feasibility of scaling up the SDE process. According to the simulation results, D4 with the purity >99.999 wt.% and total metallic impurities (TMI) content below 1 ppb could be obtained using ultra-pure water. Keywords: Octamethylcyclotetrasiloxane (D4), Process integration, Simultaneous distillation-extraction, Electronic-Grade<br/
CAST: Learning both Geometric and Texture Style Transfers for Effective Caricature Generation
No full textGiven a photo of a subject, ability to generate a caricature image that captures distinct characteristics of the subject but with certain exaggeration of their prominent features is of fundamental importance to image processing and facial recognition. There are two main challenges in this task: shape exaggeration and style transfer. The former morphs and exaggerates key facial features of the subject, while the latter generates caricature images in a certain artistic style. In this paper, we propose a CAricature Style Transfer (CAST) framework for caricature generation. There are two modules in the proposed framework. The first is a geometric warping module. Different from the existing style transfer methods, we incorporate the Whitening and Coloring Transformation (WCT) in the geometric style transfer. The WCT is learned on photo and caricature landmarks or the caricature landmark space of a specific artist and is capable of transforming input photo landmarks to caricature landmarks. The second module is a texture style rendering module. We propose a new style transfer method by considering a semantic region-aligned style transfer via affinity constraint. Given a reference caricature image as the style reference, this module is capable of transferring styles between the same or similar semantic regions in caricatures and photos. Furthermore, it can transfer visual attributes of the reference caricatures (such as mouth shape and expressions) to the output caricatures. Experiments have shown desirable effects of the proposed method in transferring both the geometric and artistic texture styles of caricatures. Both qualitative and quantitative results show that the CAST framework is more effective compared than the state-of-the-art caricature generation methods
21 new long-term variables in the GX 339−4 field: two years of MeerKAT monitoring
No full textWe present 21 new long-term variable radio sources found commensally in two years of weekly MeerKAT monitoring of the low-mass X-ray binary GX 339−4. The new sources vary on time scales of weeks to months and have a variety of light curveshapes and spectral index properties. Three of the new variable sources are coincident with multi-wavelength counterparts; and one of these is coincident with an optical source in deep MeerLICHT images. For most sources, we cannot eliminate refractive scintillation of active galactic nuclei as the cause of the variability. These new variable sources represent 2.2 ± 0.5 per cent of the unresolved sources in the field, which is consistent with the 1-2 per cent variability found in past radio variability surveys. However, we expect to find short-term variable sources in the field as well as these 21 new long-term variable sources. We present the radio light curves and spectral index variability of the new variable sources, as well as the absolute astrometry and matches to coincident sources at other wavelengths
Follow-up regimes for sick-listed employees: a comparison of nine north-western European countries
No full textThe Covid-19 pandemic has revealed the importance of social protection systems, including income security, when health problems arise. The aims of this study are to compare the follow-up regimes for sick-listed employees across nine European countries, and to conduct a qualitative assessment of the differences with respect to burden and responsibility sharing between the social protection system, employers and employees. The tendency highlighted is that countries with shorter employer periods of sick-pay typically have stricter follow-up responsibility for employers because, in practice, they become gatekeepers of the public sickness benefit scheme. In Germany and the UK, employers have few requirements for follow-up compared with the Nordic countries because they bear most of the costs of sickness absence themselves. The same applies in Iceland, where employers carry most of the costs and have no obligation to follow up sick-listed employees. The situation in the Netherlands is paradoxical: employers have strict obligations in the follow-up regime even though they cover all the costs of the sick-leave themselves. During the pandemic, the majority of countries have adjusted their sick-pay system and increased coverage to reduce the risk of spreading Covid-19 because employees are going to work sick or when they should self-quarantine, except for the Netherlands and Belgium, which considered that the current schemes were already sufficient to reduce that risk
Evaluating the Use of Phosphate to Mitigate Caustic-PbSCC of Alloy 690TT
No full textPhosphate additions to Pb-caustic water chemistry were investigated as possible avenue to mitigate against caustic Lead-Assisted Stress Corrosion Cracking (PbSCC) of Alloy 690TT at around 310°C. Dosing with 1,700 ppm of phosphate promoted a small beneficial effect in PbSCC resistance. However, with 3,000 ppm of phosphate, mitigation was only achieved for as received surfaces, whilst polished surfaces displayed localized attack. Advanced materials characterization revealed that a similar crack tip composition was generated in different solutions. It is suggested that phosphate decreased the PbSCC kinetics by partly sequestering Pb from the bulk environment, although not below the threshold value required to prevent cracking
Soil abiotic properties shape plant functional diversity across temperate grassland plant communities
No full textThere is increasing awareness that plant community functional properties can be an important driver of ecosystem functioning. However, major knowledge gaps exist about how environmental factors, especially climate and soil abiotic properties, shape plant functional diversity at a regional scale. Furthermore, at those scales the relationships between plant functional and taxonomic diversity have rarely been considered. Here, we used a large database of plant species and functional trait data from 180 temperate grasslands across England, covering a broad range of grassland types, climatic conditions and management intensities, the last having a strong influence on multiple soil variables. Our specific aims were to: 1) identify the dominant environmental factors explaining variation in different facets of plant community functional properties, including community weighted means (CWMs) of functional traits and various multi-trait functional diversity indices; and 2) test whether the relationship between plant functional and taxonomic diversity is mediated by environmental factors at a regional scale. We found that soil abiotic properties (pH, and nutrient stocks), but not climate, were the main environmental factors explaining grassland plant functional diversity at a regional scale, with a significant contribution of soil nutrient stoichiometry (N/P ratio). Two indices of plant community functional properties, namely CWMs of specific leaf area and relative growth rate, were explained by interactions between soil pH and N and mean annual precipitation, soil pH soil N and soil N/P ratio. These indices were also negatively related with taxonomic diversity under certain soil abiotic conditions, specifically high soil clay content, pH and N/P. Together, our results indicate that soil abiotic properties rather than climate factors shape plant functional diversity across temperate grassland plant communities at a regional scale. They also suggest that interactions between environmental factors play a significant role in shaping patterns of plant community functional properties. Our findings are of importance for the design and interpretation of future studies using trait and diversity measures as proxies of ecosystem services at regional scales
An asymptotic approach to proving sufficiency of Stein characterisations
No full textIn extending Stein's method to new target distributions, the first step is to find a Stein operator that suitably characterises the target distribution. In this paper, we introduce a widely applicable technique for proving sufficiency of these Stein characterisations, which can be applied when the Stein operators are linear differential operators with polynomial coefficients. The approach involves performing an asymptotic analysis to prove that only one characteristic function satisfies a certain differential equation associated to the Stein characterisation. We use this approach to prove that all Stein operators with linear coefficients characterise their target distribution, and verify on a case-by-case basis that all polynomial Stein operators in the literature with coefficients of degree at most two are characterising. For X denoting a standard Gaussian random variable and Hp the p-th Hermite polynomial, we also prove, amongst other examples, that the Stein operators for Hp(X), p = 3; 4; : : : ; 8, with coefficients of minimal possible degree characterise their target distribution, and that the Stein operators for the products of p = 3; 4; : : : ; 8 independent standard Gaussian random variables are characterising (in both settings the Stein operators for the cases p = 1; 2 are already known to be characterising). We leverage our Stein characterisations of H3(X) and H4(X) to derive characterisations of these target distributions in terms of iterated Gamma operators from Malliavin calculus, that are natural in the context of the Malliavin-Stein method