简介：Thequadratictransformationmethodisproposedtoestimatethetrabecularspacing(Tb.Sp),animportantindexforosteoporosisdiagnosis.Theperformanceofthisalgorithmwasinvestigatedbyscattermodel,two-dimensionfinitedifferencetimedomain(2D-FDTD)simulationandinvitroexperimentsofbovinecancellousbonespecimens.Comparingwiththeotherfourmethods—autoregressivecepstrum(AR),adaptivefilter-autoregressivecepstral(AFAR),inversefilter-autoregressivecepstrum(InvAR),andsimplifiedinversefiltertracking(SIFT),quadratictransformationismuchmorestableandaccurate.TheresultsdemonstratedthatquadratictransformationisagreatalgorithmforTb.Spestimation.

简介：Toaimattheproblemthatthehorizontaldirectivityindexofthevectorhydrophoneverticalarrayisnothigherthanthatofavectorhydrophone,thehigh-resolutionazimuthestimationalgorithmbasedonthedatafusionmethodwaspresented.TheproposedalgorithmfirstemploysMUSICalgorithmtoestimatetheazimuthofeachdividedsub-bandsignal,andthentheestimatedazimuthsofmultiplehydrophonesareprocessedbyusingthedatafusiontechnique.Thehigh-resolutionestimatedresultisachievedfinallybyadoptingtheweightedhistogramstatisticsmethod.TheresultsofthesimulationandseatrialsindicatedthattheproposedalgorithmhasbetterazimuthestimationperformancethanMUSICalgorithmofasinglevectorhydrophoneandthedatafusiontechniquebasedontheacousticenergyfluxmethod.Thebetterperformanceisreflectedintheaspectsoftheestimationprecision,theprobabilityofcorrectestimation,thecapabilitytodistinguishmulti-objectsandtheinhibitionofthenoisesub-bands.