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Acoustic Emission Analysis for Wind Turbine Blade Bearing Fault Detection Under Time-Varying Low-Speed and Heavy Blade Load Conditions
No full textThis article uses acoustic emission (AE) analysis to diagnose an industrial-scale and slow-speed wind turbine blade bearing. The main challenge for AE analysis is that the fault signals are mingled with heavy noise. As a result, the objective of this paper is to filter the raw AE signals and extract weak fault signals. To achieve this goal, a general linear and nonlinear auto-regressive (GLNAR) model is firstly developed to exploitthe nonlinear characteristics of the AE signals. Then, the Sparse Augmented Lagrangian (SAL) algorithm is applied to learn the built GLNAR model and filter the raw AE signals. The characteristics of SAL is that it is a novel sparse representation technique which can convert the original filtering problem into a number of sub-optimization problems, and these sub-problems can be solved separately. Finally, as the blade bearing rotatesat fluctuating speeds, the filtered signals are resampled so that the bearing fault type can be diagnosed in the order domain. The proposed diagnostic framework was validated in several experiments under time-varying low-speed and heavy-blade-load conditions. The results indicate that our proposed methods are effective and accurate
Multi-objective Workforce Allocation in Construction Projects
No full textManaging construction projects is a complex, resource-intense and risky task that involves the organization and management of people skilled in the design and completion of construction projects. Embarking on a construction project means to plan the allocation of resources and labour, while ensuring that the output (e.g. a new building) meets a certain quality, and is delivered in time and within budget without breaching contractual obligations. We formulate a simplified version of this task as a constrained multi-objective optimization problem, and then use a non-dominated sorting genetic algorithm to tackle the problem. In addition to providing a formal definition of the problem, further contributions of this work include the validation of the methodology using real data of construction projects varying in scale and resource-utilisation; the use of real data is scarce in the construction project management area. We also perform a scenario-based analysis to understand how the approach reacts to changing environmental parameters (such as availability of resources). Finally, we discuss practical implications. Our empirical analysis highlights that the proposed approach improves significantly in terms of project budget, quality, and duration targets, when compared with the industry standard.</p
Quenched Local Limit Theorem for Random Walks Among Time-Dependent Ergodic Degenerate Weights
No full textWe establish a quenched local central limit theorem for the dynamic random conductance model on Zd only assuming ergodicity with respect to spacetime shifts and a moment condition. As a key analytic ingredient we show H¨older continuity estimates for solutions to the heat equation for discrete finite difference operators in divergence form with time-dependent degenerate weights. The proof is based on De Giorgi’s iteration technique. In addition, we also derive a quenched local central limit theorem for the static random conductance model on a class of random graphs with degenerate ergodic weights
Characterizing Dislocation Loops in Irradiated Zr alloys by X-ray Line Profile Analysis of Diffraction Patterns with Satellites
No full textIn this work we extend the convolutional multiple whole profile (CMWP) line profile analysis (LPA) procedure to determine the total dislocation density and character of irradiation-induced dislocation loops in commercial polycrystalline Zr specimens. Zr alloys are widely used in the nuclear industry as fuel cladding materials in which irradiation-induced point defects evolve into dislocation loops. LPA has long been established as a powerful tool to determine the density and nature of lattice defects in plastically deformed materials. The CMWP LPA procedure is based on the Krivoglaz-Wilkens theory in which the dislocation structure is characterized by the total dislocation density and the dislocation arrangement parameter, ρ and M. In commercial Zr alloys irradiation-induced dislocation loops broaden peak profiles mainly in the tail regions and occasionally generate small satellites next to the Bragg peaks. In this work we have solved the two challenges in powder diffraction patterns of irradiated Zr alloys: (a) we have made determination of the M values from the long tail regions of peaks unequivocal and (b) have fitted satellites separately, using physically well-established principles, in order to exclude them from the dislocation determination process. Referring to the theory of heterogeneous dislocation distributions we have justified determination of the total dislocation density from the main peaks free from satellites. We characterize the dislocation loop structure by the total dislocation density of loops and the M parameter correlated to the dipole character of dislocation loops. The extended CMWP procedure is applied to determine the total dislocation density, the dipolecharacter of dislocation loops and the fractions of <a> and <c> type loops in proton or neutron irradiated polycrystalline Zr alloys used in the nuclear energy industry
Modelling Precipitate Amorphization in Zircaloys
No full textThe second phase particles (SPPs) that occur in Zircaloys can undergo amorphization and loss of iron in-reactor, which can have a profound effect on corrosion resistance and irradiation growth. In this paper, a classical model is presented that predicts the interaction between these processes, based on a previously proposed physical mechanism that considers iron release and transport from the SPP as the controlling factor. It is assumed that iron is released into a mobile state by a homogeneous and continuous amorphization and recrystallization process. As iron is released, it diffuses out of the SPP, causing the relative stability of the amorphous phase to increase, until a persistent amorphous layer forms. The model predicts the growth rate of this layer and the rate at which iron is lost from the SPP. It has been used to explore the effect of flux, temperature, and initial SPP iron concentration on the amorphous layer growth and iron loss kinetics. It is predicted that whilst iron loss is correlated with the thickness of the amorphous layer, the relationship is not a simple scaling, and depends on conditions. The model is also able to explain the observed occurrence of an amorphous layer only in an intermediate temperature range as a natural consequence of the competition between the same fundamental mechanisms
Glutarate hydroxylation by the carbon starvation-induced protein D. A computational study into the stereo- and regioselectivity of the re-action.
No full textThe carbon starvation-induced protein D (CsiD) is a recently characterized iron(II)/α-ketoglutarate-dependent oxygenase that activates a glutarate molecule as substrate at the C2 position to exclusively produce (S)-2-hydrox-yglutarate products. This selective hydroxylation reaction by CsiD is an important component of the lysine biodegradation pathway in Escherichia coli; however, little is known on the details and the origin of the selectivity of the reaction. So far, experimental studies failed to trap and characterize any short-lived catalytic cycle intermediates. As no computational studies have been reported on this enzyme either, we decided to investigate the chemical reaction mechanism of glutarate activation by an iron(IV)-oxo model of the CsiD enzyme. In this work, we present a density functional theory study on a large active site cluster model of CsiD and investigate the glutarate hydroxylation pathways by a high-valent iron(IV)-oxo species leading to (S)-2–hydroxyglutarate, (R)-2-hydroxyglutarate and 3-hydroxyglutarate. In agreement with experimental observation, the favorable product channel leads to pro-S C2H hydrogen atom abstraction to form (S)-2-hydroxyglutarate. The reaction is stepwise with a hydrogen atom abstraction by an iron(IV)-oxo species followed by OH rebound from a radical intermediate. The work presented in this paper shows that despite the fact that the CH bond strengths at the C2 and C3 positions of glutarate are similar in the gas-phase, substrate binding and positioning guides the reaction to an enan-tioselective reaction process by destabilizing the hydrogen atom abstraction pathways for the pro-R C2H and C3H posi-tions. Our studies predict the chemical properties of the iron(IV)-oxo species, and its rate-constants with glutarate substrate and its deuterated form. Moreover, the work shows little protein motions during the catalytic process, while substrate entrance into the substrate binding pocket appears to be guided by three active site arginine residues that position the substrate for pro-S C2H hydrogen atom abstraction
Effect of Ag on cathodic activation and corrosion behaviour of Mg-Mn-Ag alloys
No full textThe effect of Ag on cathodic activation and corrosion behaviour of Mg-Mn-Ag alloys are investigated in the present work. During corrosion, Mg-Ag intermetallic phase undergoes dealloying to form porous Ag-rich remnant whereas Ag in the alloy matrix is dissolved to form Ag+ ions that subsequently redeposit on the alloy surface via displacement reaction with Mg to form Ag nanoparticles, which lead to significant cathodic activation. The cathodic activation is a self-catalysed process since enhanced cathodic activity promotes anodic dissolution which, consequently, results in further enhancement of cathodic activity. Thus, the corrosion rate of Mg-2Mn-4Ag alloy increases significantly with immersion time
IPIP27A cooperates with OCRL to support endocytic traffic in the zebrafish pronephric tubule
No full textEndocytosis is a fundamentally important process through which material is internalized into cells from the extracellular environment. In the renal proximal tubule, endocytosis of the abundant scavenger receptor megalin and its co-receptor cubilin play a vital role in retrieving low molecular weight proteins from the renal filtrate. Although we know much about megalin and its ligands, the machinery and mechanisms by which the receptor is trafficked through the endosomal system remain poorly defined. In this study, we show that Ipip27A, an interacting partner of the Lowe syndrome protein OCRL, is required for endocytic traffic of megalin within the proximal renal tubule of zebrafish larvae. Knockout of Ipip27A phenocopies the endocytic phenotype seen upon loss of OCRL, with a deficit in uptake of both fluid-phase and protein cargo, which is accompanied by a reduction in megalin abundance and altered endosome morphology. Rescue and co-depletion experiments indicate that Ipip27A functions together with OCRL to support proximal tubule endocytosis. The results therefore identify Ipip27A as a new player in endocytic traffic in the proximal tubule in vivo and support the view that defective endocytosis underlies the renal tubulopathy in Lowe syndrome and Dent-2 disease
Corbino FETs in magnetic field: highly tunable photodetectors
No full textWe study gated field effect transistors (FETs) with an eccentric Corbino-disk geometry, such that the drain spans its circumference while the off-center inner ring acts as a source. An AC THz potential difference is applied between source and gate while a static source-drain voltage, rectified by the nonlinearities of FET electrons, is measured. When a magnetic field is applied perpendicular to the device, a strong resonance appears at the cyclotron frequency. The strength of the resonance can be tuned by changing the eccentricity of the disk. We show that there is an optimum value of the eccentricity that maximizes the responsivity of the FET
No Association Between Breast Pain and Breast Cancer. A Prospective Cohort Study of 10,830 Symptomatic Women Presenting to a Breast Cancer Diagnostic Clinic
No full textBackground Women with breast pain constitute upto 20% of breast clinic attendees.Aim To investigate breast cancer incidence in women presenting with breast pain and establish health economics of referring women with breast pain to secondary care.Design & Setting Prospective cohort study of all consecutive women referred to a breast diagnostic clinic over 12 months.Methods Women were categorised by presentation into 4 distinct clinical groups and cancer incidence investigated.Results Of 10 830 women, 1972 (18%) were referred with breast pain, 6708 (62%) with lumps, 480 (4%) with nipple symptoms,1670 (15%) with ‘other’ symptoms. Mammography, performed in 1112 women with breast pain, identified cancer in 8 (0.7%). In 1972 women with breast pain, breast cancer incidence was 0.4% compared with ~5% in each of the three other clinical groups. Using ‘breast lump’ as reference, odds ratio (OR) of women referred with breast pain having breast cancer was 0.05 (95% confidence interval 0.02–0.09; P<0.001). Compared to reassurance in primary-care, referral was more costly (net cost £262) without additional health benefits (net Quality Adjusted Life Year (QALY) loss -0.012). Greatest impact on the incremental cost effectiveness ratio (ICER) was when QALY loss due to referral associated anxiety was excluded. Primary-care reassurance no longer dominated, but the ICER remained greater (£45,528/QALY) than typical UK National Health Service cost-effectiveness thresholds.Conclusions This study shows that referring women with breast pain to a breast diagnostic clinic is an inefficient use of limited resources. Alternative management pathways could improve capacity and reduce financial burden