922017 research outputs found
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Corneal densitometry to assess the corneal cysteine deposits in patients with cystinosis
No full textAims: To assess the suitability of corneal densitometry measurements obtained with Scheimpflug imaging in estimating the corneal changes caused by cystine deposits in the cornea in patients with cystinosis.Methods: Scheimpflug imaging (Pentacam) was performed for 14 cystinosis patients and 16 age matched controls. Pentacam data was used for analysis of the corneal densitometry at different zones in the cornea for cystinosis patients and controls. The densitometry measurements were compared to the corneal crystal scores obtained from the slitlamp images for patients with cystinosis.Results: There was no statistically significant difference in keratometry measurements between the two groups (p>0.05). Corneal thickness was found to be significantly higher in the control group when compared to cystinosisgroup (p=0.0004). The Mean corneal densitometry was significantly higher in cystinosis patients when compared to the control group at most of the corneal layers and zones. The corneal densitometry readings for the right and left eyes showed moderate positive correlation with the corneal crystal score with a ceiling effect being reached at the maximum corneal crystal score of 3.Conclusion: Corneal densitometry obtained through Pentacam can be used as an objective estimate of the level of cystine crystals present in patients with cystinosis. The clinical estimate of corneal crystal score, although effective at low levels of crystal deposition, does not allow for accurate estimates of change when the level of crystal deposition is high leading to limited utility when assessing treatment effects. Hence, densitometry measurements can potentially be used to assess treatment efficacy of cystinosis treatments in clinical settings
Race and Histories of Place: the racialisation of representational space in Govanhill and Butetown
No full textWe argue that the stories told about the histories and nature of places, are vehicles for narrating race. Drawing on interviews with professionals and community workers in Butetown in Cardiff and Govanhill in Glasgow, we explore how they negotiated – and contested - racialized histories of place, constructing different versions or claims to belong. Drawing on Henri Lefebvre’s spatial concepts we explore this conceptualisation through examination of the two areas which have distinct histories, and present experiences, of migration and racialization. In discussion of the accounts from the two distinct areas we show that narratives of the past have a political resonance which shape accounts of current experiences of migration. Accounts of place are often related in relationship to comparisons with and narratives of other places and to global processes of trade and migration. Whilst these racialised narratives are contested, they also shape responses to social problems faced by communities
Modelling and controller design for a five-link inverted pendulum
No full textThe inverted pendulum is a fast-moving, highly nonlinear and unstable system with multiple variables and nonminimum phase that requires effective stabilization controllers. Therefore, studies into inverted pendulum systems theoretically and practically have great significance. The Euler-Lagrange Equation is used to calculate the mathematical model for a five-link inverted pendulum system. Linear Quadratic Gaussian (LQG) and H∞ are implemented using the developed model, with the Kalman Filter serving as the observer. The closed-loop system are simulated by the Matlab-Simscape platform and the controller are evaluated in relation to the system performance
Approximation of Wave Packets on the Real Line
No full textIn this paper we compare three different orthogonal systems in L2(R) which can be used in the construction of a spectral method for solving the semi-classically scaled time dependent Schrödinger equation on the real line, specifically, stretched Fourier functions, Hermite functions and Malmquist–Takenaka functions. All three have banded skew-Hermitian differentiation matrices, which greatly simplifies their implementation in a spectral method, while ensuring that the numerical solution is unitary – this is essential in order to respect the Born interpretation in quantum mechanics and, as a byproduct, ensures numerical stability with respect to the L2(R) norm. We derive asymptotic approximations of the coefficients for a wave packet in each of these bases, which are extremely accurate in the high frequency regime. We show that the Malmquist–Takenaka basis is superior, in a practical sense, to the more commonly used Hermite functions and stretched Fourier expansions for approximating wave packets
Statistical Disclosure Control and Developments in Formal Privacy: In Memoriam to Chris Skinner
No full textI provide an overview of the evolution of Statistical Disclosure Control (SDC) research over the last decades and how it has evolved to handle the data revolution with more formal definitions of privacy. I emphasize the many contributions by Chris Skinner in the research areas of SDC. I review his seminal research, starting in the 1990’s with his work on the release of UK Census sample microdata. This led to a wide-range of research on measuring the risk of re-identification in survey microdata through probabilistic models. I also focus on other aspects of Chris’ research in SDC. Chris was the recipient of the 2019 Waksberg Award and sadly never got a chance to present his Waksberg Lecture at the Statistics Canada International Methodology Symposium. This paper follows the outline that Chris had prepared in preparation for that lecture
Pore-scale Large Eddy Simulation of Turbulent Flow and Heat Transfer over Porous Media
No full textThis paper investigates turbulent fluid flow and heat transfer over a porous medium in a channel using pore-scale large eddy simulation. Special attention is placed on the exchange of heat and flow between the porous and non-porous regions through the interface between the two regions. For this purpose, two different porous systems made of a packed bed of spheres and rectangular rods are analysed and the results are compared against a solid block case of the same size. Flow visualization shows that a significant portion of the fluid entering the porous blocks leaks from the porous region to the non-porous region through the porous-fluid interface. To discuss the effects of this flow leakage on the flow features and heat transfer, discussions are made regarding velocity, pressure, and temperature fields, as well as coherent structures, and turbulence production. The flow pattern inside the porous region indicates that the flow leakage clogs the pore channels inside the porous medium which induces a significant reduction in the streamwise momentum of the pore flow. In addition, coherent structures show that flow leakage leads to the creation of counter-rotating vortex pairs of fluid flow within and above the porous block that results in the formation of organized hairpin structures. Finally, the comparison of turbulence production for the porous and solid cases together with the onset growth of the Kelvin-Helmholtz instability on the porous-fluid interface show a reduction in turbulent kinetic energy above the leading edge of porous blocks. This observation implies that for the porous cases the transition to turbulence is postponed to the downstream of the porous block and it is not achieved as fast as the solid block
An online data driven fault diagnosis and thermal runaway early warning for electric vehicle batteries
No full textBattery fault diagnosis is crucial for stable, reliable, and safe operation of electric vehicles, especially the thermal runaway early warning. Developing methods for early failure detection and reducing safety risks from failing high energy lithium-ion batteries has become a major challenge for industry. In this work, a real-time early fault diagnosis scheme for lithiumion batteries is proposed. By applying both the discrete Fréchet distance (DFD) and local outlier factor (LOF) to the voltage and temperature data of the battery cell/module that measured in real time, the battery cell that will have thermal runaway is detected before thermal runaway happens. Compared with the widely used single parameter based diagnosis approach, the proposed one considerably improve the reliability of the fault diagnosis and reduce the false diagnosis rate. The effectiveness of the proposed method is validated with the operational data from electric vehicles with/without thermal runaway in daily use
Expensive Optimization with Production-Graph Resource Constraints: A First Look at a New Problem Class
No full textWe consider a new class of expensive, resource-constrained optimization problems (here arising from molecular discovery) where costs are associated with the experiments (or evaluations) to be carried out during the optimization process. In the molecular discovery problem, candidate compounds to be optimized must be synthesized in an iterative process that starts from a set of purchasable items and builds up to larger molecules. To produce target molecules, their required resources are either used from alreadysynthesized items in storage or produced themselves on-demand at an additional cost. Any remaining resources from the production process are stored for reuse for the next evaluations.We model these resource dependencies with a directed acyclic production graph describing the development process from granular purchasableitems to evaluable target compounds. Moreover, we develop several resource-efficient algorithms to address this problem. In particular, we develop resource-aware variants of Random Search heuristics and of Bayesian Optimization and analyze their performance in terms of anytime behavior. The experimental results were obtained from a real-world molecular optimization problem. Our results suggest that algorithms that encourage exploitation by reusing existing resources achieve satisfactory results while using fewer resources overall.CCS CONCEPTS• Theory of computation→Random search heuristics; • Mathematics of computing→Probabilistic algorithms.KEYWORDSmolecular discovery, production costs, resource constraints, expensive optimization<br/
Impact of migrant and returning farmer professionalization on food production diversity
No full textSince the 2000s, there has been an increasing number of returning and migrant farmers across China. In 2012, China initiated a program for fostering professional farmers, which has caused greater changes for farmers and led to an agricultural shift towards commercial production. Migration has been recognized as a crucial factor affecting the diversity of agricultural production. However, scant attention has been paid to how different types of farmers influence agricultural diversification. Therefore, this study examines the influence of migrant farmers, returning farmers, and local non-migrant farmers on food production diversity. This study collected farm-level data on food production and farmers’ characteristics and applied a negative binomial regression model to estimate the impacts of different types of farmers on agricultural development. The results show that farms operated by migrant farmers had a significantly lower level of food production diversity while farms operated by returning farmers had no significant difference in food production diversity, using farms operated by local non-migrant farmers as the reference category. The variation in agricultural production diversity lies in differences in food production purposes, agricultural and market skills, and various risk-related capacities among the different types of farmers. Farm-level production specialization does not necessarily reduce food diversity and agrobiodiversity at the rural community and regional level
Effect of aging treatment on phase evolution and mechanical properties of selective laser melted Al-Mg-Er-Zr alloy
No full textEr and Zr modified Al-Mg alloy was manufactured by selective laser melting. The effect of aging treatment on phase evolution and mechanical properties of alloy has been studied. The results show that bimodal grain structures (2.8±1.1 μm) could be obtained, thanks to the Al3Zr primary phases promoting the formation of equiaxed grains (0.8±0.3 μm) at the boundary of molten pool. During the aging of 375 ℃, Al3(Er,Zr) particles with the size of 2-5 nm were produced via synergistic precipitation of Er and Zr, which would greatly improve the strength and reach 510±9 MPa. At the same time, the Mg-rich phase was dissolved, the Mn-rich phase was precipitated, and dislocations could accelerate the diffusion of solute atoms during the evolution of the phases