简介:摘要飞机的起落架系统为飞机在地面停放和操作时提供支撑作用。起落架系统包括两个主起落架和一个前起落架。本文主要介绍了B737的起落架系统、系统部件,一些实例故障分析和维护方法,对B737的起落架系统有更深的了解。
简介:High-frequencystocktrendpredictionusingmachinelearnershasraisedsubstantialinterestinliterature.Nevertheless,thereisnogoldstandardtoselecttheinputsforthelearners.Thispaperinvestigatestheapproachofadaptiveinputselection(AIS)forthetrendpredictionofhigh-frequencystockindexpriceandcomparesitwiththecommonlyuseddeterministicinputsetting(DIS)approach.TheDISapproachisimplementedthroughcomputationoftechnicalindicatorvaluesondeterministicperiodparameters.TheAISapproachselectsthemostsuitableindicatorsandtheirparametersforthetime-varyingdatasetusingfeatureselectionmethods.Twostate-of-the-artmachinelearners,supportvectormachine(SVM)andartificialneuralnetwork(ANN),areadoptedaslearningmodels.AccuracyandF-measureofSVMandANNmodelswithboththeapproachesarecomputedbasedonthehigh-frequencydataofCSI300index.TheresultssuggestthattheAISapproachusingt-statistics,informationgainandROCmethodscanachievebetterpredictionperformancethantheDISapproach.Also,theinvestmentperformanceevaluationshowsthattheAISapproachwiththesamethreefeatureselectionmethodsprovidessignificantlyhigherreturnsthantheDISapproach.
简介:可编程控制器(简称PLC)是专为在工业环境中应用而设计的一种工业控制用计算机,具有抗干扰能力强,可靠性高,体积小等优点,是实现机电一体化的理想装置。本文分析了数控中的PLC,进而论述了PLC实现数控系统的定位控制。
简介:摘要介绍PLC系统故障的查找方法,从气味、声音、温度的异常,简易查找PLC控制系统的故障;如异常不明显,则按系统故障查找流程判断故障在系统内/外部,再按一定顺序细化查找故障