简介:ElectrondensityisakeyparametertocharacterizeMartianionosphericstructureanddynamics.BasedontheephemerisandauxiliaryinformationderivedfromtheSpacecraft,Planet,Instruments,C-matrix,andEvents(SPICE)toolkit,wecalculatedthebendingangleofsignalpathfromthefrequencyresidualsmeasuredbytheMarsExpressRadioScienceExperiment(MaRS)oftheMarsExpress(MEX)missionundertheassumptionofasphericallysymmetricionosphere.Westratifiedtheionosphereintolayersandassumedalinearchangeofbendinganglebetweenlayers,toderiveprofilesinradialdistanceofrefractivitywiththeoptimizedparametersofupperintegrallimitof4890kmandbaselinecorrectionboundaryof3690km.Meanwhile,wealsocomparedtheretrievedelectrondensityprofilesbetweenthefrequencyresidualsofthesingle-frequencyanddifferentialDopplerofthedual-frequency.Intotal,~640electrondensityprofilesofMartianionospherebetweenApril2004andApril2015wereretrievedsuccessfully.Thereare24profilesidentifiedmanuallythatexhibitanadditionalsporadiclayeroccurrencebelowthenormaltwo-layers.Wealsofoundthatthepeakaltitudeofthislayerincreaseswiththemainpeakaltitude.
简介:ThevariousuncertaintiesofMarsenvironmenthavegreatimpactontheprocessofvehiclesenteringtheatmosphere.Toimprovetherobustnessofcontrolsystemagainstthemodelerrorsandtoreducethecomputationalburden,anoptimalfeedbackbasedtrackingcontrollawisdeveloped.Thecontrolschemepresentedinthispaperdeterminestheamplitudeandthereversalsofbankanglerespectivelyinthelongitudinalandlateralflightplane.Ateachcontrolcycle,theamplitudeofthebankangleisobtainedbyanoptimalfeedbackcontrollertominimizetrackingerrors.Thecontrolgainsaretunedaccordingtotheclosed-looperrordynamicsbyusingoptimizationmethods.Thebankreversalsareexecutedifthecrossrangeexceedsapredeterminedcorridorwhichisdesignedbysettingaboundaryfunction.Theaccuracyandrobustnessoftheproposedclosed-loopoptimalfeedbackbasedcontrollawintrackingthereferencetrajectoryisverifiedvia500deviationsimulations,inwhichmodelingerrorsandexternaldisturbancesareconsidered.
简介:目的评价分子吸附再循环系统(MARS)治疗肝功能衰竭的治疗效果与安全性.方法兰州大学第一医院感染科2002年1月~2004年10月对12例患者在内科综合治疗的基础上,加用MARS人工肝治疗.在MARS人工肝治疗前后测定肝肾功能、凝血酶原活动度、电解质等指标.结果12例患者治疗后临床症状明显改善,总胆红素明显下降(P<0.05),血清肌酐和尿素氮清除显著(P<0.05),而凝血酶原活动度、电解质等指标无显著变化(P>0.05).12例患者7例存活(存活率58.3%).结论MARS人工肝治疗肝功能衰竭能有效改善临床症状,显著改善部分生化指标,提高近期存活率,是一种安全可行的治疗方法.
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简介:【摘要】目的:探讨在颅内动脉瘤栓塞术后随访中应用MARs技术的效果分析。方法:在2020年4月至2021年4月时段我院收治的颅内动脉瘤栓塞术患者中选取52例,在术后随访中应用MARs技术诊断,全部患者的曝光条件保持一致,甲组对原始图像使用滤波反投影技术FBP重建图像,乙组对原始图像使用idose迭代重建技术重建图像,丙组对原始图像使用迭代重建联合MARs技术重建图像。分析3组技术图像客观质量和主观质量评分。结果:与甲组相比,乙组、丙组图像客观质量评分较低,且丙组低于乙组(P<0.05);甲组主观质量评分明显低于乙组和丙组,且乙组低于丙组(P<0.05)。结论:在颅内动脉瘤栓塞术后随访中应用MARs技术,可将金属伪影对影像图像的影响降低,获得高质量图像,为术后恢复评估提供可靠依据。