Miracle-dz/UniFAR-FTUs huggingface dataset:
Thin actions on CAT(0) spaces

We study groups of isometries of packed, geodesically complete, CAT$(0)$-spaces for which the systole at every point is smaller than a universal constant depending only on the packing, deducing strong rigidity results. We show that if a space as above has some negative curvature behaviour then it cannot support a thin action: this generalizes the classical Margulis Lemma to a broader class of spaces.
Assessing Self-Organization in Agile Software Development Teams

ABSTRACT Self-organization, based on the Socio-Technical Design (STS) work design principles, is considered a hallmark of agile software development (SD) teams and an antecedent of motivation and innovation at work. However, while self-organization is considered a salient success factor in agile SD, past research has shown that there are many hurdles in self-organizing. Yet, the actual level of self-organization practiced in agile teams has not been investigated. In this study we develop a measure to do so using the nine principles of STS work design by Cherns [15]. We found that while the level of self-organization varies across agile projects, on each of the nine dimensions the level of self-organization in agile teams was found to be significantly higher than those using plan-driven methods. Furthermore, self-organization was found to positively affect the motivation and innovativeness of SD teams.
University of Birmingham Numerical simulations of the separated flow around a freight train passing through a tunnel using the sliding mesh technique

The main aim of this investigation is to analyse the flow around a freight train as it passes through a tunnel. The separated flow around the train nose is related to energy losses, lateral vibration, noise, streamline deviation and influences the velocity magnitudes around the train. Such effects are expected to become more important with the prospect of increasing freight train speeds. The numerical simulations performed in this study use a Class 66 locomotive connected to eight container wagons, scaled to 1/25 th , moving at a train speed of 33.5m/s through a tunnel with a blockage ratio of 0.202. The k-omega model combined with a high advection scheme, solves the governing equations on a structured hexahedral mesh using the sliding mesh technique. The pressure histories at the tunnel walls and train surface as well as the velocity field around the train were validated with experimental data obtained using a moving model. The longest separation bubble is found at the middle-height and middle-width of the locomotive due to extended corners at these regions. When the train enters the tunnel, the separation length is reduced by 32% at the roof and 31% at the sides, compared to open air. The maximum separation length is found at the sides of the train where it reattaches at 19% of the locomotive length, influencing the velocity peak at a short distance from the train surface. The larger the
Spatial and Temporal Characteristics of Asymmetries in Tropical Cyclones

Azimuthally asymmetric perturbations are important to hurricanes because they can influence the track, structure, and intensity of a hurricane. In this work, we applied space‐time spectral analysis on both dynamic and thermodynamic fields of these perturbations and found two distinct power peaks in most of the fields. We obtained the structure of each mode by first filtering the fields through a frequency‐wavenumber spectral window selected for each mode and then regressing these fields on an index based on the filtered radar reflectivity. We found that the fast‐propagating wave is dominated by perturbations near the eyewall, and its structure is similar to that of the unstable mixed vortex Rossby inertia gravity wave. The other peak corresponds to a slow‐propagating wave that has comparable perturbations in and beyond the eyewall. The slow wave has a retrograde intrinsic propagating speed and has a vertical structure that resembles that of convectively coupled waves.
Can we model otolith growth and opacity patterns as a response to environmental factors and fish metabolism ? A DEB-based framework

This report presents a conceptual and numerical model of the formation of fish otoliths within a DEB-based (Dynamic Enerby Budget) framework. The proposed model relies on two mains assumptions: 1. The precipitation of the calcium carbonate in the endolymph is controlled by organic precursors; 2. The activity of these organic precursors can be modelled as a DEB product, i.e. as a function of metabolic fluxes, such as somatic growth and maintenance fluxes; 3. The existence of a temperature-driven effect on the dynamics of the precipitation of calcium carbonate for given conditions in the activities of ionic precursors; From these assumptions, a DEB-based otolith model is described relating the dynamics of the otolith growth and opacity to temperature and feeding conditions. An extension to the simulation of otolith images is presented. This model is shown to conform to a number of well-known facts on otolith. Besides, comparisons between model simulations and real otolith patterns are reported for different cases: otolith data from rearing experiments and otolith patterns from two different cod stocks, namely Barents sea cod and North Sea cod. This example illustrates the great potential of the proposed approach.
Low Frequency Radio Pulses Produced by Terrestrial Gamma‐Ray Flashes

Do terrestrial gamma‐ray flashes (TGFs) produce their own radio signatures? To explore this question, we analyze TGF data from the Fermi Gamma‐ray Burst Monitor, independent lightning geolocation data from the National Lightning Detection Network, and low‐frequency (LF) magnetic field waveforms, to determine the relationship between TGF generation and LF waveforms. LF waveforms associated with six TGFs are found to contain a clear and isolated slow pulse (~80‐μs duration) within a sequence of multiple fast pulses (<10‐μs risetime). We find that the slow LF pulse is produced simultaneously with the observed gamma rays, with an uncertainty as small as 7 μs. Simultaneity implies a consistent TGF source altitude range of approximately 10–15 km, which is consistent with previous estimates. These findings provide important evidence that the slow LF pulse, when observed, is associated with TGF production and perhaps produced by the electron acceleration itself.
Modular High Bandwidth Switch-Mode Three-Phase AC Voltage Source

In recent years, the development of general purpose, high bandwidth controllable AC voltage sources (CVSes) is pushed by industry to accelerate the design and / or testing processes of power electronics equipment in order to save costs and efforts. As the term “general purpose” suggests, the potential application area of such a CVS is vast and hence demands for a device which is highly flexible regarding the connection of possible loads or generators and features stringent specifications related to quality and dynamic properties of the output voltage. It is precisely the great flexibility and the increased requirements which make the design of the CVS to be different from standard approaches found in diverse scientific publications. To this day, even though CVS products are already available in the market, the design of such a converter system as well as the optimization of its control have not or only partially been covered in literature. In this Ph.D. thesis, a 100 kW four-quadrant, three-phase, switchmode CVS is researched and designed to achieve a high efficiency, a low construction volume, a very high output voltage control bandwidth, and a very low output voltage ripple. The CVS is realized by connecting ten 10 kW modules in parallel, each of the modules being implemented as an AC–DC–AC converter, consisting of a three-phase AC–DC rectifier input stage, a split DC link with an intermediate voltage circuit, and a three-phase four-leg DC–AC inverter output stage. First, key multi-objective concepts to design, optimize, and control the output and input stages of one 10 kW unit are developed and applied to the system at hand. This especially comprises the motivation to operate each output phase individually, and subsequently the design of the output filter provided individually for each phase and of the output voltage control structure, and in a next step the three-phase EMI input filter design. All design routines are thereby based on multi-objective optimizations. The detailed analyses are fully supported by experimental results carried out on a three-phase three-level T-type converter prototype employing the newest generation of SiC MOSFETs. Second, the input and output stages are electrically interconnected and comprehensive solutions to balance the voltages of the split DC link and to eliminate a ground current for simultaneously grounded mains starpoint and load are elaborated. Finally, a Master-Slave control concept is derived to operate multiple parallel connected CVS modules. The concept is investigated by accurate circuit simulations on the basis of xv
5 Implementation and Applications of the Intelligent Essay Assessor

In 1998 Pearson Knowledge Technologies (formerly Knowledge Analysis Technologies) entered the business of automatically scoring text, such as essays. Prior to that, founders Landauer and Foltz had experimented with using automated essay grading in their large psychology lecture courses beginning in 1994. A typical prompt from that era was: “Describe the differences between classical and operant conditioning. ” The innovation that Pearson Knowledge Technologies (PKT) brought to bear on scoring text was incorporating an automated, mathematical way of representing and assessing the content of text that corresponded to judgments that people make about the similarity in meaning between passages of text and individual words. This scoring technology is based on Latent Semantic Analysis (LSA), a machine-learning method that acquires and represents knowledge about the meaning of words and documents by analyzing large bodies of natural text. LSA is all of the following:
Reconstruction of Temperature and Salinity in the Uupper Layer of the Black Sea Using Pseudo-Measurements on the Underlying Horizons

Introduction. Using the original method consisting in the combined analysis of altimetry data and scanty measurements by the Argo buoys, three-dimensional fields of the temperature and salinity pseudomeasurements were previously reconstructed at the 63-500 m layer horizons, at that the areas to the right of the Rim Current and in the anticyclonic eddies up to the 125 m depth remained unfilled. Data and methods. The algorithm for restoring the unfilled areas by replenishing them with the seawater salinity and temperature values within the layer 2.5–125 m (using the altimetry and the Argo data for 2012 as an example) is proposed. The daily-average salinity (temperature) in the 2.5–125 m layer was reconstructed by correcting the model-predicted salinity (temperature) through the weighted data of its deviations from the pseudo-measurements carried out on the underlying baseline. 150 m horizon was assumed to be the main baseline for which pseudo-measurements are available on the entire horizon of the sea. The weighting factors are determined by the salinity (temperature) covariance functions of the baseline with the model salinity (temperature) on the overlying horizons. The iterative procedure was used to reconstruct the salinity and temperature pseudo-measurements. Results. Comparison of the root-mean-square deviations of the reconstructed salinity fields from the measured ones and its variability showed that in the halocline on the 88 m horizon, its variability was 1.9 times higher than the salinity deviations. Variability of the measured temperature on the 88 m horizon was 1.5 times higher than the deviations of the reconstructed temperature fields. The reconstructed fields of the salinity (temperature) pseudo-measurements were assimilated in the model of the Marine Hydrophysical Institute (MHI) by the adaptive statistic method for reanalysis of the Black Sea fields for 2012. The temperature and salinity fields reconstructed in reanalysis were validated. The cold intermediate layer (CIL) is well reproduced; its temperature is slightly understated. The satellite measurements of the sea surface temperature should be necessarily assimilated in the circulation model. The sea level in the deep-water area reconstructed in reanalysis was quite close to the altimetry one. Discussion and conclusion. Three-dimensional fields of temperature and salinity in the main pycnocline are reconstructed with sufficiently high accuracy in the deep-water part of the Black Sea. The seawater temperature in the surface layer 0–40 m cannot be reconstructed with acceptable accuracy. The approaches proposed in the previous studies and in the present paper can be effective for the other marine areas like the marginal seas of the oceanic type and the oceanic eddies, where relatively homogeneous water masses are observed.
Online Pen Testing

We study a"pen testing"problem, in which we are given $n$ pens with unknown amounts of ink $X_1, X_2, \ldots, X_n$, and we want to choose a pen with the maximum amount of remaining ink in it. The challenge is that we cannot access each $X_i$ directly; we only get to write with the $i$-th pen until either a certain amount of ink is used, or the pen runs out of ink. In both cases, this testing reduces the remaining ink in the pen and thus the utility of selecting it. Despite this significant lack of information, we show that it is possible to approximately maximize our utility up to an $O(\log n)$ factor. Formally, we consider two different setups: the"prophet"setting, in which each $X_i$ is independently drawn from some distribution $\mathcal{D}_i$, and the"secretary"setting, in which $(X_i)_{i=1}^n$ is a random permutation of arbitrary $a_1, a_2, \ldots, a_n$. We derive the optimal competitive ratios in both settings up to constant factors. Our algorithms are surprisingly robust: (1) In the prophet setting, we only require one sample from each $\mathcal{D}_i$, rather than a full description of the distribution; (2) In the secretary setting, the algorithm also succeeds under an arbitrary permutation, if an estimate of the maximum $a_i$ is given. Our techniques include a non-trivial online sampling scheme from a sequence with an unknown length, as well as the construction of a hard, non-uniform distribution over permutations. Both might be of independent interest. We also highlight some immediate open problems and discuss several directions for future research.
Are Changes in Atmospheric Circulation Important for Black Carbon Aerosol Impacts on Clouds, Precipitation, and Radiation?

Black carbon (BC) aerosols strongly absorb solar radiation, but their effective radiative forcing and impacts on regional climate remain highly uncertain owing to strong feedbacks of BC heating on clouds, convection, and precipitation. This study investigates the role of large‐scale circulation changes in governing such feedbacks. In the HadGEM3 climate model BC emissions were increased to 10 times present‐day values while keeping sea surface temperatures fixed, to assess the rapid adjustments to increased BC absorption. The BC perturbation led to an effective radiative forcing of 2.7 W/m2 and a 0.13‐mm/day reduction in global precipitation. There were also large shifts in the spatial distribution of tropical convection, increased low cloud over oceans, and a weakening and poleward shift of midlatitude storm tracks, especially in the Northern Hemisphere. In a parallel experiment, horizontal winds were nudged toward meteorological reanalyses to deliberately suppress circulation responses while allowing changes to the thermodynamic structure of the atmosphere. Surprisingly, BC had approximately the same impact on global‐mean radiation and global precipitation in the nudged experiment, even though regional changes in clouds and convection were not fully captured. The results show that large‐scale dynamical responses to BC are important for regional impacts but have a limited role in determining the effective radiative forcing and global‐mean climate response. The rapid adjustments of clouds, radiation, and global precipitation were primarily a response to increased radiative absorption and atmospheric stability. This implies that short nudged simulations may be sufficient to assess absorbing aerosol impacts on global‐mean radiation and precipitation.
Simulation of streamflow with statistically downscaled daily rainfall using a hybrid of wavelet and GAMLSS models

ABSTRACT A rainfall–streamflow model is proposed, in which a downscaled rainfall series and its wavelet-based decomposed sub-series at optimum lags were used as covariates in GAMLSS (Generalized Additive Model in Location, Scale and Shape). GAMLSS is applied in climate change impact assessment using CMIP5 general climate model to simulate daily streamflow in three sub-catchments of the Onkaparinga catchment, South Australia. The Spearman correlation and Nash-Sutcliffe efficiency between the observed and median simulated streamflow values were high and comparable for both the calibration and validation periods for each sub-catchment. We show that the GAMLSS has the capability to capture non-stationarity in the rainfall–streamflow process. It was also observed that the use of wavelet-based decomposed rainfall sub-series with optimum lags as covariates in the GAMLSS model captures the underlying physics of the rainfall–streamflow process. The development and application of an empirical rainfall–streamflow model that can be used to assess the impact of catchment-scale climate change on streamflow is demonstrated.
Spatial patterns of meadow sensitivities to interannual climate variability in the Sierra Nevada

Conservation of montane meadows is a high priority for land and water managers given their critical role in buffering the effects of climate variability and their vulnerability to increasing temperatures and evaporative demands. Recent advances in cloud computing have provided new opportunities to examine ecological responses to climate variability over the past few decades and at large spatial scales. In this study, we characterized the sensitivities (magnitude and direction of the slope) of meadow vegetation responses to interannual variations in climate. We calculated sensitivity as the regression slope between a 31‐year (1985–2016) time series of Landsat‐derived vegetation indices characterizing late‐season vegetation vigour and water balance variables from the Basin Characterization Model. We identified April 1 snowpack as the climate variable the majority of meadows were most sensitive to. We assessed how vegetation sensitivities to snowpack varied with hydrogeomorphic context (e.g., climate, geology, soils, watershed geometry, and land cover) across the Sierra Nevada mountain range using factor analysis to reduce the dimensionality of the hydrogeomorphic data and multiple linear regression to model sensitivity responses. We found that meadow sensitivities to snowpack varied with long‐term average meadow climate, indicators of watershed subsurface water storage capacity, and indicators of meadow vegetation composition. Alpine and subalpine meadows with high average annual precipitation but limited catchment subsurface storage exhibited the largest sensitivities. Our results provide a novel regional perspective on spatial patterns of meadow sensitivities to climate variability and the landscape‐scale hydrogeomorphic factors that influence late‐season water availability in meadow ecosystems in the Sierra Nevada.
Homogeneous Regionalization via L-Moments for Mumbai City, India

This study identified homogeneous rainfall regions using a combination of cluster analysis and the L-moments approach. The L-moments of heavy rainfall events of various durations (0.25, 1, 6, 12, 24, 48, 72, 96, and 120 h) were analysed using seasonal (June-September) rainfall measurements at 47 meteorological stations over the period 20062016. In the primary phase of this study, the homogeneity of Mumbai as a single region was examined by statistical testing (based on L-moment ratios and variations of the L-moments). The K-means clustering approach was applied to the site characteristics to identify candidate regions. Based on the most appropriate distribution, these regions were subsequently tested using at-site statistics to form the final homogeneous regions. For durations above 1h, the regionalisation procedure delineated six clusters of similarly behaved rain gauges, where each cluster represented one separate class of variables for the rain gauges. However, for durations below 1h, the regionalisation procedure was not efficient in the sense of identifying homogeneous regions for rainfall. Furthermore, the final clusters confirmed that the spatial variation of rainfall was related to the complex topography, which comprised flatlands (below or at mean sea level), urban areas with high rise buildings, and mountainous and hilly areas.
A Iron Availability in Calcareous and Non Calcareous Soils as Influenced by Various Sources and Levels of Iron

Iron availability in alkaline and calcareous soils is very much limited due to high pH and presence of the excess amount of carbonate and bicarbonate ions. Iron is though adequately present in soils, it is not always sufficiently available to plants due to their faster conversion into unavailable ferric (Fe3+) forms. The present study was taken up to understand the availability of Fe in soils and its relationship with various soil properties. A laboratory experiment was conducted with two calcareous soils and a noncalcareous soil and incubated for 45 days with various levels (0, 5 and10 kg Fe ha-1) and sources of Fe (FeSO4 and Fe EDTA) on calcareous and noncalcareous soils. The results revealed that increasing levels of Fe either as FeSO4 or Fe EDTA increased the availability in soils and higher availability was noted with the application of 10 kg Fe EDTA in all the three soils. A linear increase in the Fe availability was observed with the addition of Fe EDTA at 10 kg ha-1 up to 45 days while with the addition of 50 kg FeSO4 ha -1 higher availability was noticed up to 30 days after incubation. Inclusion of amendments viz., 12.5 t FYM and 0.25 % Acetic acid though further improved the availability in all soils, the effect was much better with FYM than the acetic acid in calcareous soils than in noncalcareous soil. A strong negative correlation was observed between soil pH and calcareousness with DTPA Fe availability.
Immigrant Communities and Knowledge Spillovers: Danish-Americans and the Development of the Dairy Industry in the United States

Despite the growing literature on the impact of immigration, little is known about the role existing migrant settlements can play for knowledge transmission and the location of industry. We present a case that can illustrate this important mechanism and hypothesize that nineteenth-century Danish American communities helped spread knowledge on modern dairying to rural America. From around 1880 Denmark developed rapidly, and by 1890 it was a world-leading dairy producer. Using a difference-in-differences strategy and data taken from the US census and Danish emigration archives, we find that counties with more Danes in 1880 subsequently both specialized in dairying and used more modern practices. (JEL J15, J61, L66, N31, N51, O33, Q12)