Seabed Physical Parameter Research Based on Active-Source OBS Data in the Chukchi Sea Shelf of the Arctic

The acquisition of seabed physical parameters is one of the focuses of marine acoustic researches.However,the activesource ocean bottom seismometer(OBS)detection method in the marine geophysical research is rarely used to acquire seabed physical parameters,and less work is performed in the Arctic.In this study,two active-source OBS data collected from the 9th and 11th Chinese National Arctic Research Expedition(CHINARE)are selected to obtain the physical parameters of seabed sediments.Two kinds of energy spark are used as the active sources,while the cost function inversion method is used based on the arrival time difference between the reflected and direct waves.The thickness and sound velocity of the sediment layers are obtained by inversion,and the empirical formula is used to calculate the physical parameters of the seabed sediment,which are compared with the measured results.The cost function inversion method based on the time difference of arrival of the reflected and direct waves is tested to be effective and feasible in the inversion of seabed parameters from active-source OBS data.The method is further applied to obtain the physical parameters of Chukchi seabed sediments,which provides the idea and reference for the application of marine geophysical activesource OBS detection technology in the inversion of polar seabed physical parameters.

Efficient silicon integrated four-mode edge coupler for few-mode fiber coupling

Here,we designed a broadband,low loss,compact,and fabrication-tolerant silicon-based four-mode edge coupler,composed of a 1×3 adiabatic mode-evolution counter-taper splitter and a triple-tip inverse taper.Based on mode conversion and power splitting,the proposed structure can simultaneously realize efficient mode coupling from TE_(0),TM_(0),TE_(1),and TM_(1) modes of multimode silicon waveguides to linearly polarized(LP),LP^(01,x),LP_(01,y),LP_(11a,x),and LP_(11a,y),modes in the few-mode fiber.To the best of our knowledge,we proposed the first scheme of four LP modes coupling,which is fully compatible with standard fabrication process.The 3D finite-difference time-domain simulation results show that the on-chip conversion losses of the four modes remain lower than 0.62 dB over the 200 nm wavelength range,and total coupling losses are 4.1 dB,5.1 dB,2.1 dB,and 2.9 dB for TE_(0)-to-LP_(01,x),TM_(0)-to-LP_(01,y),TE_(1)-to-LP_(11a,x),and TM_(1)-to-LP_(11a,y),respectively.Good fabrication tolerance and relaxed critical dimensions make the four-mode edge coupler compatible with standard fabrication process of commercial silicon photonic foundries.

Empirical likelihood inference and goodness-of-fit test for logistic regression model under two-phase case-control sampling

Due tocost effectiveness and hIgh efidengy.two-phase Qse control sampling has been wldely used In epldemlology studles.We dewelop a seml-parametric empinial lkellood approach to two-phase ase-control data under the logst regresslon model.we show that the maxmum empintal lklhoo estimaton has an aymptotically nomal dstibutlon,n,and the empincal lke-lthood ratlo fllws an aymptotcallycentral chi-square dstibution We find that the maxdmum empintial lkellhood estimator Is equal to Breslow and Holubkow(1997175 madimum lkelhood estimator.Evenso,the lmting dstribution of the lkelhood ratio,helhlodratlo based interval,and test are all new.Futhemmiore,we construct new Kolmogorov-smimnov type godnes-F-fit tests to test the vlldation of the undertying lglstic rgressonmodelLour simulation results and a real pplcaion show that the lola based Interval and test hawe certain mentsowver the wald-type counterparts and that the proposed godness-f-f test Is vald.