选好参照物 解题更容易(初二、初三)

本刊2002年第9期《巧妙解决流水问题》一文中,是将问题纯数学化了,如以物理角度分析,选定恰当的参照物,解答则相当简单.     

大导演出道

1965年,一个19岁的美籍犹太青年考入了美国加州大学长滩分校,攻读电影及电子艺术专业。大三时,这个狂热地做着导演梦的小伙子拍了一部24分钟的短片。讲的是一对在沙漠相遇的年轻恋人的故事。     

一种稳定的蓝色有机电致发光材料

In order to compare two kinds of blue electroluminescent materials,we have investigated two kinds of blue OLEDs with the similar structure ITO/CuPc/NPB/JBEM:perylene/Alq/Mg:Ag[device(J)] and ITO/CuPc/NPB/DPVBi:perylene/Alq/Mg:Ag[device(D)].The difference of luminance and efficiency was not obvious for the two devices,However,there was remarkable difference for their lifetime.The device(J) achieved longer half lifetime of 1035h at initial luminance of 100 cd/m^2,and that of device(D) was only255h,According to their energy level diagrams,the differentce of their stability may originate from different host materials in the two devices.It may be attributed to the better thermal stability of JBEM molecues than that of DPVBi.It is shown that JBEM may be a promising blue organic electroluminescent material with great stability.     

由学生的反唇相讥想到的

课堂上,有一位中队委员思想开了小差,老师为了促使他“醒悟”,要他用“以身作则”这个成语造句。学生低头不语。于是,老师带着讥讽的口吻造了一句：“中队干部上课应该以身作则,自觉遵守纪律！”谁知,话音刚落,该学生却站起来回敬了一句：“老师是光荣的人民教师,教育学生必须以身作则,怎么能挖苦学生呢？”霎时,全班轰动,气得老师脸色发白…… 这位老师为什么会碰壁？原因在于他严重地损伤了学生的自尊心。 自尊心是一种个人要求受到尊重的感情。它促使学生爱护自己在集体中的声誉,它是学生积极向上和克服缺点的内部动力。任何…     

激子限域结构的蓝紫色有机电致发光器件

Three types of blue-violet light-emitting devices based on an exciton-confined structure have been prepared, in which different materials were used as emitting layers and hole-transporting layers. They had structures of ITO/CuPc/NPB/CPB/TPBi/Alq3/LiF/Al(DNC), ITO/CuPc/JO3/CBP/TPBi/Alq3/LiF/Al(DJC ) and ITO/CuPc/JO3/FNPD/TPBi/Alq3/LiF/Al(DJF). Here copper phthalocyanine (CuPc) acted as hole-injecting layer( HIL), N, N-bis-(1-naphthyl)-N, N-diphenyl-1. lbiphenyl-4-4-diamine(NPB) and J03 bole-transporting layers ( HTLs), 4,4‘-dicarbazolyl-1,1‘ -biphenyl (CBP) and FNPD as emitting layers( EMLs), N, arylbenzimidazoles (TPBi) as holeblocking layer ( HBL ), and tris(8-quinolinolato ) aluminium complex ( Alq3 ) as electron- transporting layer ( ETL). TPBi applied here is a good confinement to both charges and excitons, which make the devices emit blue-violet light originating from the emitter, CBP and FNPD. Their characteristics have also been investigated. The result shows that the device DNC based on NPB/CBP has the best performance among the three devices. The excellence of DNC is attributed to the better hole-transporting ability of NPB as compared with J03, and the better emitting ability of CBP as compared with FNPD, although the best matching of energy levels is found in the hole-transporting layer and emitting layer of the device DJP.     

一种新型联苯乙烯衍生物--蓝色有机电致发光材料

A new blue electroluminescent material,distyrylarylene(DSA)derivative,4,4‘-bis[2,2-(1-naphthyl,phenyl)vinyl]-1,1-biphenyl(NPVBi)is designed and synthesized.The DSA derivative shows better thermal stability because of its high glass transition temperature.A blue organic light emitting diode(OLED0with the structure ITO/TPD/NPVBi/Alq/LiF/Al is studied.The electroluminescent(EL0spectrum of the OLED exhibits that light emission originates from NPVBi with a peak at 460nm,its Commission Internationale de l‘Eclairage(CIE)color coordinates are x=0.16,y=0.15,and showing independence of CIE color coordinates on current density.The new DSA derivative is expectable as a new candidate for blue light emitter in OLEDs.