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M-estimator, and D-optimality model construction using orthogonal forward regression
No full textThis correspondence introduces a new orthogonal forward regression (OFR) model identification algorithm using D-optimality for model structure selection and is based on an M-estimators of parameter estimates. M-estimator is a classical robust parameter estimation technique to tackle bad data conditions such as outliers. Computationally, The M-estimator can be derived using an iterative reweighted least squares (IRLS) algorithm. D-optimality is a model structure robustness criterion in experimental design to tackle ill-conditioning in model Structure. The orthogonal forward regression (OFR), often based on the modified Gram-Schmidt procedure, is an efficient method incorporating structure selection and parameter estimation simultaneously. The basic idea of the proposed approach is to incorporate an IRLS inner loop into the modified Gram-Schmidt procedure. In this manner, the OFR algorithm for parsimonious model structure determination is extended to bad data conditions with improved performance via the derivation of parameter M-estimators with inherent robustness to outliers. Numerical examples are included to demonstrate the effectiveness of the proposed algorithm
INNOVATIVE PILLAR[6]ARENE-BASED STATIONARY PHASES FOR HIGH-RESOLUTION GAS CHROMATOGRAPHIC ANALYSES
No full textIn this work, the synthesis, fabrication, and characterization of new stationary phases based on pillar[6]arene derivative modified by long alkyl chains (P6A-C10) for high-resolution gas chromatographic (GC) analyses are reported. Pillar[n]arenes are a new class of macrocyclic hosts that can accommodate specific guests due to their highly symmetrical and rigid pillar architectures with π-electron rich cavities. Quantum chemistry calculations have been performed, showing a difference in non-covalent interactions with the P6A-C10 pillar framework, which leads to specific selectivity for aromatic compounds. The GC columns prepared with these innovative stationary phases exhibited a medium polarity, and good reproducibility for run-to-run, day-to-day, and column-to-column analyses [1], demonstrating great potential as new stationary phases in separation science. Furthermore, peculiar advantages are achieved if compared with the commercial HP-5, HP-35, DB-17, and PEG-20M columns, showing unmatched resolving capabilities toward chloroaniline, bromoaniline, iodoaniline, toluidine, and xylene isomers [2].
References:
1. Sun, T., Chen, R., Huang, Q., Ba, M., Cai, Z., Hu, S., Liu, X., Nardiello, D., & Quinto, M., ACS Appl. Mater. Interfaces 14 (2022) 56132−56142.
2. Sun, T., Chen, R., Huang, Q., Ba, M., Cai, Z., Chen, H., Qi, Y., Chen, H., Liu, X., Nardiello, D., & Quinto, M., Anal. Chim. Acta 1251 (2023) 340979
Influence of ac ageing on space charge dynamics in LDPE
No full textPolymeric materials have been widely used as insulation in power industry due to their excellent electrical properties. However, these properties deteriorate in time irreversibly when the material is subjected to electric stress. Although space charge is believed to play an important role in ac ageing, exact mechanisms are poorly understood due to very limited experimental data. In the present work efforts have been made to investigate the influence of ac ageing on space charge dynamics in low-density polyethylene (LDPE). LDPE films with 200mm were aged at 50 kV/mm at 50 Hz for various times at ambient temperature. Space charge dynamics in the samples prior to and after ageing were monitored using the pulsed electroacoustic (PEA) technique under dc electric stress. The results indicate that there is a significant amount of homocharge accumulation in the unaged sample due to charge injection. These injected charges are the captured by the deep traps originated from the interface between crystalline and amorphous regions in LDPE. Ageing under ac condition does not necessarily lead to an increase in amount of charge in the bulk but leads to an increase in mobility of charge carriers. Chemical analysis by infrared spectroscope (FTIR) reveals there are chemical changes taken place in the bulk of the material after ac ageing. It is believed that the chemical changes introduce shallow traps which promote the movement of charge carriers in the bulk. Consequently, the injected charges spread across the sample
DTU Wind Turbine Blade Damage Inspection Dataset using Thermography
No full textThis dataset includes blade damage inspection results using passive thermography when the blades are under cyclic loads or in operational wind turbines. The dataset is used in the development of AQUADA and AQUADA PLUS. The related papers are:[1]Chen, X., Shihavuddin, ASM., Madsen, S. H., Thomsen, K., Rasmussen, S., & Branner, K. (2021). AQUADA: Automated quantification of damages in composite wind turbine blades for LCOE reduction. Wind Energy, 24(6), 535-548. https://doi.org/10.1002/we.2587[2]Chen, X., Semenov, S., McGugan, M., Madsen, S. H., Yeniceli, S. C., Berring, P., & Branner, K. (2021). Fatigue testing of a 14.3 m composite blade embedded with artificial defects – damage growth and structural health monitoring. Composites Part A: Applied Science and Manufacturing, 140, [106189]. https://doi.org/10.1016/j.compositesa.2020.106189[3]Chen, X., Janeliukstis, R., & Sarhadi, A. (2022). Thermographic data analytics-based damage characterization in a large-scale composite structure under cyclic loading. Composite Structures, [115525]. https://doi.org/10.1016/j.compstruct.2022.115525 [4] Chen, X., Sheiati S., Shihavuddin, ASM., AQUADA PLUS: Automated Damage Inspection of Cyclic-loaded Large-scale Composite Structures using Thermal Imagery and Computer Vision. Composite Structures https://doi.org/10.1016/j.compstruct.2023.11708
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Sound radiation from a generic bypass duct with bifurcations
No full textThe influence of bifurcations in an aero-engine bypass duct on noise radiation was investigated through high-order accurate three-dimensional numerical simulations. The physical process was described by a set of acoustic perturbation equations (APE), with a background mean flow. Four bifurcation arrangements, with an airfoil cross-section, were regularly placed in circumferential direction. Results of the simulations were compared with those of a clean duct case. A circumferential mode of m=12 with radial mode of n=1 and multi-n modes at a source frequency of 1547 Hz were set as acoustic inputs. Acoustic modes
interfered with the bifurcations resulting in a doubled circumferential mode pattern in the near field acoustic pressure distribution and slightly stronger sound
pressure level behind the bifurcations. Far field noise computations indicated 3.2 dB and 2.0 dB sound pressure level increases for radial mode of n=1 and multi-n
modes respectively. The bifurcations did not alter the radiation angle. A comparison was also made between APE and linearlised Euler equations (LEE). Results showed that the APE simulation produced almost identical far field sound
prediction to the LEE, with a small difference (< 0.8dB) at the main radiation peak angle
Chen, M.-J., Han, Y.-R., Hu, J.-X., Liu, Y.-J. & Huang, B. (2023) Tolypocladium rhizomatum sp. nov.: an endophytic species isolated from the rhizome of Polygonatum cyrtonema. Phytotaxa 606 (3): 201-210.
No full textChen, M.-J., Han, Y.-R., Hu, J.-X., Liu, Y.-J., Huang, B. (2023): Chen, M.-J., Han, Y.-R., Hu, J.-X., Liu, Y.-J. & Huang, B. (2023) Tolypocladium rhizomatum sp. nov.: an endophytic species isolated from the rhizome of Polygonatum cyrtonema. Phytotaxa 606 (3): 201-210. Phytotaxa 607 (1): 114-114, DOI: 10.11646/phytotaxa.607.1.10, URL: http://dx.doi.org/10.11646/phytotaxa.607.1.1
Continuum free-energy formulation for a class of lattice Boltzmann multiphase models
No full textWe characterize theoretically the free energy of the so called 'Shan-Chen' model for non ideal fluid flows
Space Charge Behaviour in LDPE after AC Ageing
No full textSpace charge accumulation after ac ageing and its effect on dc poling has been studied in low-density polyethylene (LDPE). LDPE film samples with thickness of around 180mm were aged at an electric stress of 50kV/mm under 50 Hz ac voltage for various times at ambient temperature. Space charge dynamics in the samples after ageing were monitored using the pulsed electroacoustic (PEA) technique. Except the presence of considerable amount of space charge accumulation in the aged sample, the ageing has also brought a significant influence into the space dynamic under dc poling voltage. The ageing extent was previously investigated by chemical analysis (i.e. Fourier Transform Infrared FTIR and Raman spectrum) revealed little change taken place in the bulk of the material after ac ageing in the time frame studied. This indicates that the space charge measurement may be an effective method for diagnosing the early stage of material deterioration. It also provides additional information about charge mobility and trap depth that can be extracted from space charge profile
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