An Improved Extreme Learning Machine Prediction Model for Ionospheric Total Electron Content

Earth’s ionosphere is an important medium for navigation,communication,and radio wave transmission.Total Electron Content(TEC)is a descriptive quantify for ionospheric research.However,the traditional empirical model could not fully consider the changes of TEC time series,the prediction accuracy level of TEC data performed not high.In this study,an improved Extreme Learning Machine(ELM)model is proposed for ionospheric TEC prediction.Improvements involved the use of Empirical Mode Decomposition(EMD)and a Fuzzy C-Means(FCM)clustering algorithm to pre-process data used as input to the ELM model.The proposed model fully uses the TEC data characteristics and expected to perform better prediction accuracy.TEC measurements provided by the Centre for Orbit Determination in Europe(CODE)were used to evaluate the performance of the improved ELM model in terms of prediction accuracy,applicable latitude,and the number of required training samples.Experimental results produced a Mean Relative Error(MRE)and a Root Mean Square Error(RMSE)of 8.5%and 1.39 TECU,respectively,outperforming the ELM algorithm(RMSE=2.33 TECU and MRE=17.1%).The improved ELM model exhibited particularly high prediction accuracy in mid-latitude regions,with a mean relative error of 7.6%.This value improved further as the number of available training data increased and when 20-doys data were trained,achieving a mean relative error of 4.9%.These results suggest the proposed model offers higher prediction accuracy than conventional algorithms.

Influence of Range Gate Width on Detection Probability and Ranging Accuracy of Single Photon Laser Altimetry Satellite

The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed,according to the LiDAR equation,single photon detection equation and the Monte Carlo method to simulate the experiment.The simulated results show that the probability of detection is not affected by the range gate,while the probability of false alarm is relative to the gate width.When the gate width is 100 ns,the ranging accuracy can accord with the requirements of satellite laser altimeter.But when the range gate width exceeds 400 ns,ranging accuracy will decline sharply.The noise ratio will be more as long as the range gate to get larger,so the refined filtering algorithm during the data processing is important to extract the useful photons effectively.In order to ensure repeated observation of the same point for 25 times,we deduce the quantitative relation between the footprint size,footprint,and frequency repetition according to the parameters of ICESat-2.The related conclusions can provide some references for the design and the development of the domestic single photon laser altimetry satellite.

Expert consensus on the use of human serum albumin in adult cardiac surgery

Introduction Albumin,which is a 65-kDa liver-synthesized protein,accounts for nearly 50%of total plasma protein and contributes to approximately 80%of intravascular oncotic pressure.Albumin helps maintain microvascular integrity,functions as an antioxidant,and transports hormones,fatty acid,bile salts,bilirubin,electrolytes(e.g.,calcium,magnesium,copper,zinc,et al.),and drugs.[1–3]Human serum albumin(HSA)is a sterile,liquid albumin product derived from large pools of human plasma by fractionation and pasteurization.The medical use of HAS could date back to approximately the time of World War II.

Synthesis and dissociation of soliton molecules in parallel optical-soliton reactors

Mode-locked lasers have been widely used to explore interactions between optical solitons,including bound-soliton states that may be regarded as“photonic molecules”.Conventional mode-locked lasers normally,however,host at most only a few solitons,which means that stochastic behaviours involving large numbers of solitons cannot easily be studied under controlled experimental conditions.Here we report the use of an optoacoustically mode-locked fibre laser to create hundreds of temporal traps or“reactors”in parallel,within each of which multiple solitons can be isolated and controlled both globally and individually using all-optical methods.We achieve on-demand synthesis and dissociation of soliton molecules within these reactors,in this way unfolding a novel panorama of diverse dynamics in which the statistics of multi-soliton interactions can be studied.The results are of crucial importance in understanding dynamical soliton interactions and may motivate potential applications for all-optical control of ultrafast light fields in optical resonators.

Broadband mid-infrared supercontinuum generation in dispersion-engineered As_(2)S_(3)-silica nanospike waveguides pumped by 2.8 μm femtosecond laser

Broadband mid-infrared(IR)supercontinuum laser sources are essential for spectroscopy in the molecular fingerprint region.Here,we report generation of octave-spanning and coherent mid-IR supercontinua in As_(2)S_(3)-silica nanospike hybrid waveguides pumped by a custom-built 2.8μm femtosecond fiber laser.The waveguides are formed by pressure-assisted melt-filling of molten As_(2)S_(3) into silica capillaries,allowing the dispersion and nonlinearity to be precisely tailored.Continuous coherent spectra spanning from 1.1μm to 4.8μm(30 dB level)are observed when the waveguide is designed so that 2.8μm lies in the anomalous dispersion regime.Moreover,linearly tapered millimeter-scale As_(2)S_(3)-silica waveguides are fabricated and investigated for the first time,to the best of our knowledge,showing much broader supercontinua than uniform waveguides,with improved spectral coherence.The waveguides are demonstrated to be long-term stable and water-resistant due to the shielding of the As_(2)S_(3) by the fused silica sheath.They offer an alternative route to generating broadband mid-IR supercontinua,with applications in frequency metrology and molecular spectroscopy,especially in humid and aqueous environments.