237,051 research outputs found
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
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
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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
Traces and shards of self-injury: Strange accounting with “Author X”
No full textIn this strange account autoethnography, three or four authors explore their lived experiences with self-injury. Strange accounting is both a post-modern style of text, and a method for keeping identities concealed when risks and secrets are in play. Author X, a post-modern place-keeper for an anonymous author who may or may not have contributed to this manuscript, introduces a new dimension and layer of concealment. With Author X in-play and under erasure, the reader will never be sure if there were three or four authors on this manuscript. Through strange accounting, a post-structuralist/postmodernist frame will be applied to understanding the self-injury experience. We frame self-injury as a social practice and, for some, an everyday norm, while remaining acutely aware of the stigma surrounding the topic of self-injury. Each of us, coupled with Author X, provide the others cover to trace stories of self-injury through the literature, our flesh, and our lives
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
Y ( 4260 ) → γ + X ( 3872 ) in the diquarkonium picture
Full text linkThe observed Y(4260) o gamma + X(3872) decay is a natural consequence of the diquark-antidiquark description of Y and X resonances. In this note we attempt an estimate of the transition rate, Gamma_m rad, by a
non-relativistic calculation of the electric dipole term of a diquarkonium bound state. We compute Gamma_m rad for generic composition values of the isospin of X and Y. Specializing to I=0 for X(3872), we find Gamma_m rad=
496~keV for Y(4260) with I=0 and Gamma_m rad= 179~keV for I=1. Combining with BESIII data, we derive upper bounds to B(Y o J/Psi+pi+pi) and to Gamma(Y o mu^+ mu^-). We expect to confront these results with forthcoming data from electron-positron and hadron colliders
Ji Han xiang chen zhuan
No full text[V.1-2]. 前漢相臣傳 : 十二卷 -- [v.3-5]. 後漢相臣傳 : 十六卷 -- [v.6]. 季漢相臣傳 : 六卷.[V.1-2]. Qian Han xiang chen zhuan : shi er juan -- [v.3-5]. Hou Han xiang chen zhuan : shi liu juan -- [v.6]. Ji Han xiang chen zhuan : liu juan.魏顯國纂述 ; 魏一鵬編次.綫裝, 1函.框22x14.3公分, 10行20字, 白口, 單黑魚尾, 四周單邊, 版心上鐫題名, 中鐫卷次, 下鐫葉次及小題.刻書年據《四庫全書存目叢書》鈐有"元鑑齋", "潤州笪重光鑒定印", "毛氏收藏子孫永保"印.Library's copy: 本館只存《歷代相臣傳》中《前漢》, 《後漢》, 《季漢》共六冊.Xian zhuang, 1 han.Kuang 22 x 14.3 gong fen, 10 hang 20 zi, bai kou, dan hei yu wei, si zhou dan bian, ban xin shang juan ti ming, zhong juan juan ci, xia juan ye ci ji xiao ti.Ke shu nian ju "Si ku quan shu cun mu cong shu"Wei Xianguo zuan shu ; Wei Yipeng bian ci.Qian you "Yuan jian zhai", "Runzhou Da Chongguang jian ding yin", "Mao shi shou cang zi sun yong bao" yin.Library's copy: ben guan zhi cun "Li dai xiang chen zhuan" zhong "Qian Han", "Hou Han", "Ji Han" gong liu ce
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A new RBF neural network with boundary value constraints
No full textWe present a novel topology of the radial basis function (RBF) neural network, referred to as the boundary value constraints (BVC)-RBF, which is able to automatically satisfy a set of BVC. Unlike most existing neural networks whereby the model is identified via learning from observational data only, the proposed BVC-RBF offers a generic framework by taking into account both the deterministic prior knowledge and the stochastic data in an intelligent manner. Like a conventional RBF, the proposed BVC-RBF has a linear-in-the-parameter structure, such that it is advantageous that many of the existing algorithms for linear-in-the-parameters models are directly applicable. The BVC satisfaction properties of the proposed BVC-RBF are discussed. Finally, numerical examples based on the combined D-optimality-based orthogonal least squares algorithm are utilized to illustrate the performance of the proposed BVC-RBF for completeness
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Enhanced colour encoding of materials discrimination information for multiple view dual-energy x-ray imaging
No full textThis thesis reports an investigation into dual-energy X-ray discrimination techniques. These techniques are designed to provide colour-coded materials discrimination information in a sequence of perspective images exhibiting sequential parallax. The methods developed are combined with a novel 3D imaging technique employing depth from motion or kinetic depth effect (KDE). This technique when applied to X-ray images is termed KDEX imaging and was developed previously by the university team for luggage screening applications at security checkpoints. A primary motivation for this research is that the dual-energy X-ray techniques, which are routinely incorporated into ‘standard’ 2D luggage scanners, provide relatively crude materials discrimination information. In this work it was critical that robust materials discrimination and colour encoding process was implemented as the sequential parallax exhibited by the KDEX imagery may introduce colour changes, due to the different X-ray beam paths associated with each perspective image. Any introduction of ‘colour noise’ into the resultant image sequences could affect the perception of depth and hinder the ongoing assessment of the potential utility of the dual-energy KDEX technique. Two dual-energy discrimination methods have been developed, termed K-II and W-E respectively. Employing the total amount of attenuation measured at each energy level and the weight fraction of layered structures, a combination of the K-II and the W-E techniques enables the computation and extraction of a target objects’ effective atomic number (Zeff) and its surface density (ρS) in the presence of masking layers
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