Online Monitoring of Welding Status Based on a DBN Model During Laser Welding

In this research,an auxiliary illumination visual sensor system,an ultraviolet/visible(UVV)band visual sensor system(with a wavelength less than 780 nm),a spectrometer,and a photodiode are employed to capture insights into the high-power disc laser welding process.The features of the visible optical light signal and the reflected laser light signal are extracted by decomposing the original signal captured by the photodiode via the wavelet packet decomposition(WPD)method.The captured signals of the spectrometer mainly have a wavelength of 400-900 nm,and are divided into 25 sub-bands to extract the spectrum features by statistical methods.The features of the plume and spatters are acquired by images captured by the UVV visual sensor system,and the features of the keyhole are extracted from images captured by the auxiliary illumination visual sensor system.Based on these real-time quantized features of the welding process,a deep belief network(DBN)is established to monitor the welding status.A genetic algorithm is applied to optimize the parameters of the proposed DBN model.The established DBN model shows higher accuracy and robustness in monitoring welding status in comparison with a traditional back-propagation neural network(BPNN)model.The effectiveness and generalization ability of the proposed DBN are validated by three additional experiments with different welding parameters.

Soliton resolution and asymptotic stability of N-solutions for the defocusing Kundu–Eckhaus equation with nonzero boundary conditions

In this paper,we address interesting soliton resolution,asymptotic stability of N-soliton solutions and the Painleve asymptotics for the Kundu-Eckhaus(KE)equation with nonzero boundary conditions iq_(t)+q_(xx)-2(l|q|^(2)-1)q+4β^(2)(lql^(4)-1)q+4iβ(lql^(2))_(x)q=0,q(x,0)=q_(0)(x)-±1,x→±∞.The key to proving these results is to establish the formulation of a Riemann-Hilbert(RH)problem associated with the above Cauchy problem and find its connection with the RH problem of the defocusing NLS equation.With the■-steepest descent method and the results of the defocusing NLS equation,we find complete leading order approximation formulas for the defocusing KE equation on the whole(x,t)half-plane including soliton resolution and asymptotic stability of N-soliton solutions in a solitonic region,Zakharov-Shabat asymptotics in a solitonless region and the Painlevéasymptotics in two transition regions.

Detecting the single chiral molecule during the reaction

Detecting an individual molecule during the chemistry dynamics is essential for capturing accurate information about the chemical process in the time domain,which could be achieved by precisely forming single-molecule junctions between two electrodes and reading out the variation in electrical signals[1–3],but has yet to penetrate the stereochemistry study.There is a crucial pursuit of chirality chemistry to develop effective asymmetric synthesis methodologies and reveal the physicochemical mechanisms[4,5].And the key obstacle lies in achieving in situ detection of chiral intermediates in reactions[6].Chirality is a fundamental molecular property arising from the structure asymmetry,with two mirror-image forms known as enantiomers.Due to similar signals of enantiomeric isomers,it is a great challenge to distinguish chiral species and the process of their configurational transformation in single-molecule techniques.It then comes up with a question—how to detect chirality changes in stereochemistry.

Heavy flavour physics and CP violation at LHCb:Aten-year review

Heavy flavour physics provides excellent opportunities to indirectly search for new physics at very high energy scales and to study hadron properties for deep understanding of the strong interaction.The LHCb experiment has been playing a leading role in the study of heavy flavour physics since the start of the LHC operations about ten years ago,and made a range of high-precision measurements and unexpected discoveries,which may have far-reaching implications on the field of particle physics.This review highlights a selection of the most influential physics results on CP violation,rare decays,and heavy flavour production and spectroscopy obtained by LHCb using the data collected during the first two operation periods of the LHC.The upgrade plan of LHCb and the physics prospects are also briefly discussed.