简介：Atwo-dimensional(2D)opticaltrue-timedelay(TTD)beam-formingsystemusingacompactfibergratingprism(FGP)foraplanarphasedarrayantenna(PAA)isproposed.Theopticalbeam-formingsystemmainlyconsistsofaTTDunitbasedonthesamecompactFGP,onetunablelaserforelevationbeamsteering,andacontrolledwavelengthconverterforazimuthbeamsteering.AplanarPAAusingsuch2DopticalTTDunithasadvantagessuchascompactness,lowbandwidthrequirementfortunablelasersources,andpotentialforlarge-scalesystemimplementations.Theproof-of-conceptexperimentresultsdemonstratethefeasibilityoftheproposedscheme.

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简介：AgraphGiscalledchromatic-choosableifitschoicenumberisequaltoitschromaticnumber,namelych(G)=χ(G).Ohba’sconjecturestatesthateverygraphGwith2χ(G)+1orfewerverticesischromaticchoosable.ItisclearthatOhba’sconjectureistrueifandonlyifitistrueforcompletemultipartitegraphs.Recently,Kostochka,StiebitzandWoodallshowedthatOhba’sconjectureholdsforcompletemultipartitegraphswithpartitesizeatmostfive.Butthecompletemultipartitegraphswithnorestrictionontheirpartitesize,forwhichOhba’sconjecturehasbeenverifiedarenothingmorethanthegraphsKt+3,2*(k-t-1),1*tbyEnotomoetal.,andKt+2,3,2*(k-t-2),1*tfort≤4byShenetal..Inthispaper,usingtheconceptoff-choosable(orL0-size-choosable)ofgraphs,weshowthatOhba’sconjectureisalsotrueforthegraphsKt+2,3,2*(k-t-2),1*twhent≥5.Thus,Ohba’sconjectureistrueforgraphsKt+2,3,2*(k-t-2),1*tforallintegerst≥1.

简介：ThemoleculartransformationsofcarboxylicacidsinheavyacidicSLcrudebeforeandaftertrueboilingpointdistillationwereexaminedbyultra-highresolutionnegative-ionelectrosprayionization(ESI)Fouriertransformioncyclotronresonancemassspectrometry(FT-ICRMS).Theacidclass(heteroatomnumber),type(znumbers)andcarbonnumberdistributionswerepositivelycharacterized.Itwasfoundoutthatthetotalacidnumber(TAN)ofSLcrudedecreasedaftertrueboilingpointdistillation,andtheabundanceofO2classinmassspectrawasalsofoundtobereducedfrom67.6%to34.5%inSLTBPmixedcrudeasmeasuredbyMSspectra,indicatingtoapotentialcarboxylicaciddecomposition.However,itwasinterestingthatthecarboxylicacidstypedistributioninbothoilswasalmostthesamealthoughtheirrelativeabundanceinSLTBPmixedcrudeturnedtobemuchlower,suggestingthatvariouspetroleumcarboxylicacidtypeshavethesimilarthermaldecompositionreactionbehavior.Furthermore,foreachO2typeofacidsinSLTBPmixedcrude,theabundanceofcarboxylicacidswithcarbonnumberhigherthan35wasreducedgreatly,especiallyforthosewithcarbonnumberhigherthan60,themasspeaksofwhichwerenearlytotallyremoved,indicatingthatthelargecarboxylicacidmoleculesinheavyfractionsdecomposedmoresignificantlybecauseoflongerheatingtimeduringthetrueboilingpointdistillationprocess.Asaresult,thereductionofTANmaybecausedbythethermaldecompositionofcarboxylicacidsespeciallythosewithhighcarbonnumber,suggestingthatquickdistillationormuchlowerpressureisrequiredtoavoidthethermaldecomposition.

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简介：摘 要：《普通高中英语课程标准（2017 年版）》提出了指向学科核心素养的英语学习活动观，即通过学习理解、应用实践、迁移创新三个层次的学习活动促进学生学科核心素养的提升。本课以普通高中教科书英语（上教版） 课文Finding One’s True Vocation 为例，对于文学阅读课堂如何实践英语学习活动观进行了探究。学生在主题情境的引领下思索故事中的关键问题、挖掘情节转折点、反思原因，最后合作编排并表演课本剧。

简介：摘 要：《普通高中英语课程标准（2017 年版）》提出了指向学科核心素养的英语学习活动观，即通过学习理解、应用实践、迁移创新三个层次的学习活动促进学生学科核心素养的提升。本课以普通高中教科书英语（上教版） 课文Finding One’s True Vocation 为例，对于文学阅读课堂如何实践英语学习活动观进行了探究。学生在主题情境的引领下思索故事中的关键问题、挖掘情节转折点、反思原因，最后合作编排并表演课本剧。

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