inversion

摘要： Atmospheric stellar occultation observation technology is an advanced space-based detection technology that can measure the vertical distribution of trace gas composition,temperature,and aerosol content in a planet’s atmosphere.In this study,an inversion algorithm of the onion-peeling method was constructed to invert the transmittance obtained from the forward mask.The method used a three-dimensional ray-tracing simulation to obtain the transmission path of the light in the Earth’s atmosphere.The relevant parameters were then combined in the high-resolution transmission molecular absorption(HITRAN)database,and line-by-line integration was performed to calculate the atmospheric transmittance.The transmittance value was then used as an input to calculate the vertical distribution of oxygen molecules when using the single-wavelength inversion of the onion-peeling method.Finally,the oxygen molecule content was compared with the value attained by the Mass Spectrometer and Incoherent Scatter Radar Extended(MSISE00)atmospheric model to determine the relative error of our model.The maximum error was found to be 0.3%,which is low enough to verify the reliability of our algorithm.Using Global-scale Observations of the Limb and Disk(GOLD)measured data to invert the oxygen number density,we calculated its relative deviation from the published result to further verify the algorithm.The inversion result was affected by factors such as prior data,the absorption spectral line type,the ellipticity of the Earth,and the accuracy of the orbit.Analysis of these error-influencing factors showed that the seasons and the Earth’s ellipticity affected the accuracy of the model only 0.001%and could therefore be ignored.However,latitude and solar activity had a greater impact on accuracy,on the order of 0.1%.The absorption line type affected the accuracy of the model by as much as 1%.All three of these factors therefore need to be considered during the inversion process.

摘要： A method for reconstructing crustal velocity structure using the optimization of stacking receiver function amplitude in the depth domain,named common conversion amplitude(CCA)inversion,is presented.The conversion amplitude in the depth domain,which represents the impedance change in the medium,is obtained by assigning the receiver function amplitude to the corresponding conversion position where the P-to-S conversion occurred.Utilizing the conversion amplitude variation with depth as an optimization objective,imposing reliable prior constraints on the structural model frame and velocity range,and adopting a stepwise search inversion technique,this method efficiently weakens the tendency of easily falling into the local extremum in conventional receiver function inversion.Synthetic tests show that the CCA inversion can reconstruct complex crustal velocity structures well and is especially suitable for revealing crustal evolution by estimating diverse velocity distributions.Its performance in reconstructing crustal structure is superior to that of the conventional receiver function imaging method.

摘要： In contrast to highly conserved mitogenomic architecture in most metazoan lineages,which indicates that rearrangement events are generally strongly selected against,a limited number of often unrelated lineages exhibit highly elevated architectural evolution rates.The underlying reasons for this discontinuity in the mitogenomic evolution remain unknown.Previously we sequenced the mitochondrial genome of the first Camallanoidea species,Camallanus cotti(Nematoda:Chromadorea:Spirurina:Camallanidae),and found that it exhibited a highly disrupted architecture.We hypothesised that disrupted architecture might be a synapomorphic feature of the sister-clades Camallanoidea and Dracunculoidea.In this study,we sequenced mitogenomes of three freshwater fish-parasitic nematodes:Camallanus lacustris(Camallanidae),and two Philometridae(Dracunculoidea)species,Clavinema parasiluri,and Philometra sp.In partial agreement with the working hypothesis,both Camallanoidea species had exceptionally large mitogenomes of 18–19 Kbp,albeit the underlying reasons differed:in C.lacustris it was the existence of a single enlarged noncoding region of
5.5 Kbp.A segment of this region exhibited an inverted base composition skew,which is indicative of a sequence inversion or recombination event.Camallanidae is the second identified chromadorean(first for Spirurina)family that exhibits within-family protein-coding gene rearrangements,and the absence of trnL1 and trnF may be a synapomorphy for Camallanoidea.The underlying reason for the disrupted architecture of Camallanidae does not appear to be a particular event shared by their common ancestor,but rather an underlying mechanism that makes disruptive events more likely in this lineage.In disagreement with the working hypothesis,Spiruromorpha and Oxyuridomorpha exhibited even more highly rearranged gene orders and greater overall branch lengths than Camallanomorpha.However,withininfraorder architecture was highly conserved and leaf nodes very short.This indicates that common ancestors of Spiruromorpha and Oxyuridomorpha clades underwent a period of rapid mitochondrial evolution(both sequence and architecture),followed by a stabilisation after the taxonomic radiation.In contrast to this,Camallanomorpha,and particularly Camallanidae,appear to have entered a period of elevated evolutionary rates after the initial radiations of these two taxa.As a result of this evolutionary discontinuity,there was a strong correlation between the gene order rearrangement rate(GORR)and the overall branch length(0.81),but there was no correlation between the strength of purifying selection(ω?dN/dS)and the overall branch lengths(0.05)and GORR(0.04).These findings have important repercussions for future phylogenetic and other evolutionary studies of Spirurina.

摘要： The reservoir thickness of sub-member of Lower Permain in the south of the eastern margin of Ordos Basin is thin and large variable i laterally. And the seismic response characteristics of sandstone reservoir are doubly interfered by the strong reflection sidelobes of overlying 5# coal seam and underlying 8# coal seam. In view of this situation, in order to better eliminate the influence of upper and lower coal seams and improve the accuracy of reservoir prediction, the strategy of de-strong seismic reflection and de-logging (curve) interference is adopted to carry out the matching of logging and seismic, and on this basis, uses the seismic waveform indication inversion to predict the thin sandstone. The steps are as follows: firstly, by using wavelet decomposition and reconstruction technology, select the seismic wavelet component that can better characterize the reservoir or oil & gas to reasonablely reconstruct seismic data, weaken the influence of the strong reflection from overlying 5# coal seam and underlying 8# coal seam, and highlight the response of weak seismic reflection of tight sandstone in Shan 23 sub-member;Then, the acoustic value of coal seam is corrected to that of mudstone on the logging curve to maintain the consistency of logseismic data. This method realizes the effective identification of sandstone reservoir in Shan 23 sub-member, and greatly improves the target-penetrated rate and sandstone-penetrated rate of horizontal wells.

摘要： Numerical back analysis is a valuable tool available to rock mechanics researchers and practitioners.Recent studies related to back analysis methods focused primarily on applications of increasingly sophisticated optimization algorithms(primarily machine learning algorithms)to rock mechanics problems.These methods have typically been applied to relatively simple problems;however,more complex back analyses continue to be conducted primarily through ad hoc manual trial-and-error processes.This paper provides a review of the basic concepts and recent developments in the field of numerical back analysis for rock mechanics,as well as some discussion of the relationship between back analysis and more broadly established frameworks for numerical modelling.The challenges of flexible constraints,non-uniqueness,material model limitations,and disparate data sources are considered,and representative case studies are presented to illustrate their impacts on back analyses.The role of back analysis(or“model calibration”)in bonded particle modelling(BPM),bonded block modelling(BBM),and synthetic rock mass(SRM)modelling is also considered,and suggestions are made for further studies on this topic.

摘要： In this study,a groundwater exploration survey was conducted using the DC Resistivity(DCR)method in a hydrogeological setting containing a perched aquifer.DCR data were gathered and an electrical tomography section was recovered using conventional four-electrode instruments with a Schlumberger array and a two-dimensional(2D)inversion scheme.The proposed scheme was tested over a synthetic threedimensional(3D)subsurface model before deploying it in a field situation.The proposed method indicated that gathering data with simple four-electrode instruments at stations along a line and 2D inversion of datasets at multiple stations can recover depth intervals of the studied aquifer in the hydrogeological setting even if it has a 3D structure.In this study,2D inversion of parallel profiles formed a pseudo-3D volume of the subsurface resistivity structures and mapped out multiple resistive(>25 ohm·m)bodies at shallow(between 50-100 m)and deep sections(>150 m).In general,the proposed method is convenient to encounter geological units that have limited vertical and spatial extensions in any direction and presents resistivity contrast from groundwater-bearing geologic materials.

摘要： Traditional acquisition method of sound speed profiles using hydro-acoustic instruments is accurate but time-consuming and costly.To overcome this problem,some inversion methods have been developed over the last few decades.In this study,a comprehensive comparison of two inversion methods–the acoustic inversion method(AIM)and the satellite observation reconstruction method(SOR)–is presented.For AIM,the sound speed profile is first parameterized by the empirical orthogonal function(EOF)and the optimal parameters are searched by simulated annealing algorithm with respect to the cross-correlation function of the receiving signal and the simulation signal.For SOR,remotely sensed data are used to construct sound speed profiles.An experiment was conducted in the northeast of the South China Sea to verify the two methods.Both methods can obtain sound speed profiles quickly and cheaply.Compared with the sound speed profiles obtained by a conductivity-temperature-depth(CTD)instrument,the root-meansquare-error(RMSE)of AIM is 0.55 m s−1 and that of SOR is 1.71 m s−1.It is clear that AIM provides better inversion performance than SOR.Another primary benefit of AIM is that this method has no limitation to the inversion depth.The simulation results of sound propagation in regard to the inversed sound speed profiles show that the transmission losses of AIM and CTD are consistent and that of SOR is adversely affected by the inversion error of the sound speed and the inversion depth.But SOR has particular advantages in the inversion coverage.Together,all of these advantages make the AIM particularly valuable in practice.

摘要： In view of the satellite cloud-derived wind inversion has the characteristics of large scale,intensive computing and time-consuming serial inversion algorithm is very difficult to break through the bottleneck of efficiency.We proposed a parallel acceleration scheme of cloud-derived wind inversion algorithm based on MPI cluster parallel technique in this paper.The divide-and-conquer idea,assigning winds vector inversion tasks to each computing unit,is identified according to a certain strategy.Each computing unit executes the assigned tasks in parallel,namely divide-and-rule the inversion task,so as to reduce the efficiency bottleneck of long inversion time caused by serial time accumulation.In the scheme of parallel acceleration based on MPI cluster,an algorithm based on performance prediction is proposed to effectively implement load balance of MPI clusters.Through the comparative analysis of experiment data using the parallel scheme of this parallel technology framework,it shows that this parallel technology has a certain acceleration effect on the cloud-derived wind inversion algorithm.The speedup of the MPI-based parallel algorithm reaches 14.96,which achieved the expected estimate.At the same time,this paper also proposes an efficiency optimization algorithm for cloud-derived wind inversion.In the case that the inversion of wind vector accuracy loss is minimal,the optimized algorithm execution time can be up to 13 times faster.

摘要： The semi-autobiographical novel Waterland by twentieth-century British writer Graham Swift has been recognized as a popular work by British literary critics.Under the guidance of Mikhail Bakhtin’s theory of the literary chronotope,this paper analyses both the various types of chronotope in the novel as well as the author’s historical view between different times and spaces through the dialogue.