Magnetorheological elastomer （MRE） is a new kind of smart materials, the rheological properties can be controlled rapidly by the external magnetic field. It is mainly composed of rubber and micron-sized ferromagneti...Magnetorheological elastomer （MRE） is a new kind of smart materials, the rheological properties can be controlled rapidly by the external magnetic field. It is mainly composed of rubber and micron-sized ferromagnetic particles, which forms a chain-like structure. Therefore its mechanical, electric, and magnetic properties can be changed by the applied magnetic field, which is called as the magneto-induced effect. But this effect is not remarkable enough currently for the engineering application. So it is important for material preparation to optimize parameters to enhance the magneto-induced effect. In this work, based on chain-like model, some factors influencing the magneto-induced effect of MRE were analyzed theoretically by using dipole method with the normal distribution of chain＇s angle introduced. The factors included the oblique angle of particles chains, magnetic field intensity, and shear strain, etc. Some experiments were also carried out.展开更多
The map folding method for the conversion between Boolean expression and COC expansions is analyzed. Based on it, the tabular techniques are proposed for the conversion between Boolean expression and COC expansion and...The map folding method for the conversion between Boolean expression and COC expansions is analyzed. Based on it, the tabular techniques are proposed for the conversion between Boolean expression and COC expansion and for the derivation of GOC expansions with fixed polarities. The Fast Tabular Technique (FTT) for the conversion from the Boolean expression to the GOC expansion with the required polarity is also proposed. The simulative result shows this FTT is faster than others in references because of its inherent parallelism.展开更多
Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The ho...Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The hole-transport layer is a N,N’-bis(3-methyphenyl)-N,N’-diphenylbenzidine film. The doped emitting layer consists of 8-(quinolinolate)-aluminum as the host and rubrene as the emission dopant. The doped device demonstrated a brightness in excess of 40 000 cd/m 2 and the maximum external quantum efficiency of 3.4%, which is about six times and four times respectively greater than those of the undoped device. For no packaged deviced, a luminance half-life on the order of about 230 h has been achieved under a constant current density of 15 mA/cm 2, starting at 500 cd/m 2 at the room temperature.展开更多
The consensus problem of a linear discrete-time multi- agent system with directed communication topologies was investigated. A protocol was designed to solve consensus with an improved convergence speed achieved by de...The consensus problem of a linear discrete-time multi- agent system with directed communication topologies was investigated. A protocol was designed to solve consensus with an improved convergence speed achieved by designing protocol gains. The clo6ed-loop multi.agent system converged to an expected type of consensus function, which was divided into four types： zero, non- zero constant vector, bounded trajectories, and ramp trajectories. An algorithm was further provided to construct the protocol gains, which were determined in terms of a classical pole placement algorithm and a modified algebraic Riccati equation. Finally, an example to illustrate the effectiveness of theoretical results was presented.展开更多
A new silole monomer with two 4-（N,N-dimethylamino）phenyl substitutions on silicon atom as designed and synthesized. Three copolymers PF-N-HPS1, PF-N-HPS10 and PF-N-HPS20 were then obtained by copolymerizations of 2...A new silole monomer with two 4-（N,N-dimethylamino）phenyl substitutions on silicon atom as designed and synthesized. Three copolymers PF-N-HPS1, PF-N-HPS10 and PF-N-HPS20 were then obtained by copolymerizations of 2,7-fluorene deriva- tives with the silole monomer at feed ratios of 1%, 10%, and 20%. Their UV-vis absorption, electrochemical, photolumines- cent, and electroluminescent （EL） properties were investigated. PF-N-HPS possessed HOMO levels of -5.25-5.58 eV, and showed green emissions. Using PF-N-HPS as the emissive layer, three different polymer light-emitting diodes were fabricated as device A with ITO/PEDOT/PF-N-HPS/A1, device B with ITO/PEDOT/PF-N-HPS/Ba/A1, and device C with ITO/PEDOT/ PF-N-HPS/TPBI/Ba/A1. For the device A, PF-N-HPS only showed very low EL efficiency of 0.06-0.33 cd/A, indicating that the A1 cathode could not inject electron efficiently to the emissive polymers containing the 4-（N,N-dimethylamino）phenyl groups. For the device B, low work function Ba supplied better electron injections, and the EL efficiency could be improved to 0.85-1.44 cd/A. TPBI with a deep HOMO level of -6.2 eV could enhance electron transport and hole blocking. Thus modi- fied recombinations and largely elevated EL efficiency of 4.56-7.96 cd/A were achieved for the device C. The separation of the emissive layer and metal cathode with the TPBI layer may also suppress exciton quenching at the cathode interface.展开更多
Two bipolar materials,2,5-bis(2-(9H-carbazole-9-yl)phenyl)-1,3,4-oxadiazole(o-CzOXD)and 2,5-bis(2-(3',6'-di-tert-butyl-9H-carbazole-9-yl)phenyl)-1,3,4-oxadiazole(tBu-o-CzOXD),were synthesized according to repo...Two bipolar materials,2,5-bis(2-(9H-carbazole-9-yl)phenyl)-1,3,4-oxadiazole(o-CzOXD)and 2,5-bis(2-(3',6'-di-tert-butyl-9H-carbazole-9-yl)phenyl)-1,3,4-oxadiazole(tBu-o-CzOXD),were synthesized according to reported methods.In parallel study,it was demonstrated that introduction of inert tert-butyl group improved material thermal stability,even though this modification only had a slight influence to the photophysical and electrochemical properties of these materials.A comparative study focusing on effects of heat treatment was carried out on the quartz glass substrates with vacuum deposited films containing one of the bipolar host doped with 6 wt%fac-tris(2-phenylpyridinato-N,C2’)iridium(Ir(ppy)3).Results show that when the two samples were heated,the absorption,emission,and photo images of the host:dopant system changed,with the o-CzOXD suffering more severe degradation under high temperature,which is consistent with their thermal stability.In addition,it was proved that the high temperature-annealed host:dopant system can enhance the emission of the dopant.This finding was used as a guideline to improve our device performance.We fabricated two types of phosphorescent organic light-emitting devices(PhOLEDs),one was based on o-CzOXD,the other was based on tBu-o-CzOXD.They had analogous structure.We investigated the effect of heat on device performance by selectively annealing.Although these two freshly prepared devices exhibited similar performance,when annealed at 90°C for 10 min,the OLEDs based on tBu-o-CzOXD showed significant performance enhancement,which can be attributed to the observation that annealing Ir(ppy)3 doped host can change film morphology and enhance the dopant emission.The maximum efficiencies of the freshly prepared tBu-o-CzOXD device were 25.8 cd A-1,23.1lm W-1,and 9.3%;whereas those for annealed device were 47.0 cd A-1,42.2 lm W-1,and 13.4%.展开更多
Transparent organic light-emitting devices(TOLEDs) based on a stacked alloy cathode of LiF/Al:Ag are investigated. The devices have a structure of indium-tin-oxide(ITO)/4,4′,4′′-Tris[2-naphthyl(phenyl)amino]triphen...Transparent organic light-emitting devices(TOLEDs) based on a stacked alloy cathode of LiF/Al:Ag are investigated. The devices have a structure of indium-tin-oxide(ITO)/4,4′,4′′-Tris[2-naphthyl(phenyl)amino]triphenylamine(2T-NATA)(25 nm)/N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine(NPB)(40 nm)/tris-(8-hydroxyquinoline) aluminum(Al_(q_3))(50 nm)/LiF(1 nm)/Al:Ag(1:3)(x), where the thicknesses of cathode metal layers(Al:Ag) are adjusted, respectively, from 70 nm to 100 nm. In the experiment, it is found that the Li F(1 nm)/Al:Ag(1:3)(75 nm) has good electron injection efficiency. Compared with an Al-only cathode, the turn-on voltage is lowered. At the voltage of 10 V, the luminances for bottom emission from ITO anode side and top emission from metal cathode side are 2 459 cd/m^2 and 1 729 cd/m^2, respectively. Thanks to electron injection enhancement by using Al:Ag cathode, we can obtain a better energy level matching between the cathode and the organic layer, thus the devices have lower turn-on voltage and higher luminance. The total transmittance of the devices can achieve about 40% at the wavelength of 550 nm.展开更多
A transparent 3-mercaptopropyl trimethoxysilane(MPTMS)/Ag/MoO3 composite anode is introduced to fabricate green organic light-emitting diodes(OLEDs). Effects of the composite anode on brightness and operating voltage ...A transparent 3-mercaptopropyl trimethoxysilane(MPTMS)/Ag/MoO3 composite anode is introduced to fabricate green organic light-emitting diodes(OLEDs). Effects of the composite anode on brightness and operating voltage of OLEDs are researched. By optimizing the thickness of each layer of the MPTMS/Ag/MoO3 structure, the transmittance of MPTMS/Ag(8 nm)/Mo O3(30 nm) reaches over 75% at about 520 nm. The sheet resistance is 3.78 ?/□, corresponding to this MPTMS/Ag(8 nm)/MoO3(30 nm) structure. For the OLEDs with the optimized anode, the maximum electroluminescence(EL) current efficiency reaches 4.5 cd/A, and the maximum brightness is 37 036 cd/m2. Moreover, the OLEDs with the optimized anode exhibit a very low operating voltage(2.6 V) for obtaining brightness of 100 cd/m2. We consider that the improved device performance is mainly attributed to the enhanced hole injection resulting from the reduced hole injection barrier height. Our results indicate that employing the MPTMS/Ag/MoO3 as a composite anode can be a simple and promising technique in the fabrication of low-operating voltage and high-brightness OLEDs.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.50830202 and No.60804018） and the Plan of the Excellent Talent for the New Century （NCET-07-0910）. The authors also appreciate the help in the experimental instruments of Professor Xing-long Gong of University of Science and Technology of China deeply.
文摘Magnetorheological elastomer （MRE） is a new kind of smart materials, the rheological properties can be controlled rapidly by the external magnetic field. It is mainly composed of rubber and micron-sized ferromagnetic particles, which forms a chain-like structure. Therefore its mechanical, electric, and magnetic properties can be changed by the applied magnetic field, which is called as the magneto-induced effect. But this effect is not remarkable enough currently for the engineering application. So it is important for material preparation to optimize parameters to enhance the magneto-induced effect. In this work, based on chain-like model, some factors influencing the magneto-induced effect of MRE were analyzed theoretically by using dipole method with the normal distribution of chain＇s angle introduced. The factors included the oblique angle of particles chains, magnetic field intensity, and shear strain, etc. Some experiments were also carried out.
基金Supported by the National Natural Science Foundation of China (No.60273093)the Natural Science Foundation of Zheiinag Province (No.Y104135)
文摘The map folding method for the conversion between Boolean expression and COC expansions is analyzed. Based on it, the tabular techniques are proposed for the conversion between Boolean expression and COC expansion and for the derivation of GOC expansions with fixed polarities. The Fast Tabular Technique (FTT) for the conversion from the Boolean expression to the GOC expansion with the required polarity is also proposed. The simulative result shows this FTT is faster than others in references because of its inherent parallelism.
基金The National Natural Science Foundation of China , National "863" P
文摘Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The hole-transport layer is a N,N’-bis(3-methyphenyl)-N,N’-diphenylbenzidine film. The doped emitting layer consists of 8-(quinolinolate)-aluminum as the host and rubrene as the emission dopant. The doped device demonstrated a brightness in excess of 40 000 cd/m 2 and the maximum external quantum efficiency of 3.4%, which is about six times and four times respectively greater than those of the undoped device. For no packaged deviced, a luminance half-life on the order of about 230 h has been achieved under a constant current density of 15 mA/cm 2, starting at 500 cd/m 2 at the room temperature.
基金Natural Science Foundation of Shandong Province,China(No.ZR2010FZ001)
文摘The consensus problem of a linear discrete-time multi- agent system with directed communication topologies was investigated. A protocol was designed to solve consensus with an improved convergence speed achieved by designing protocol gains. The clo6ed-loop multi.agent system converged to an expected type of consensus function, which was divided into four types： zero, non- zero constant vector, bounded trajectories, and ramp trajectories. An algorithm was further provided to construct the protocol gains, which were determined in terms of a classical pole placement algorithm and a modified algebraic Riccati equation. Finally, an example to illustrate the effectiveness of theoretical results was presented.
基金supported by the National Natural Science Foundation of China (21225418,51003080)the National Basic Research Program of China (2013CB834705)+2 种基金the Youth Science Plan for Light of the Morning Sun of Wuhan City (201271031385)State Key Laboratory of Luminescent Materials and Devices (2012-09)Natural Science Foundation of Hubei Province (2012FFB04705)
文摘A new silole monomer with two 4-（N,N-dimethylamino）phenyl substitutions on silicon atom as designed and synthesized. Three copolymers PF-N-HPS1, PF-N-HPS10 and PF-N-HPS20 were then obtained by copolymerizations of 2,7-fluorene deriva- tives with the silole monomer at feed ratios of 1%, 10%, and 20%. Their UV-vis absorption, electrochemical, photolumines- cent, and electroluminescent （EL） properties were investigated. PF-N-HPS possessed HOMO levels of -5.25-5.58 eV, and showed green emissions. Using PF-N-HPS as the emissive layer, three different polymer light-emitting diodes were fabricated as device A with ITO/PEDOT/PF-N-HPS/A1, device B with ITO/PEDOT/PF-N-HPS/Ba/A1, and device C with ITO/PEDOT/ PF-N-HPS/TPBI/Ba/A1. For the device A, PF-N-HPS only showed very low EL efficiency of 0.06-0.33 cd/A, indicating that the A1 cathode could not inject electron efficiently to the emissive polymers containing the 4-（N,N-dimethylamino）phenyl groups. For the device B, low work function Ba supplied better electron injections, and the EL efficiency could be improved to 0.85-1.44 cd/A. TPBI with a deep HOMO level of -6.2 eV could enhance electron transport and hole blocking. Thus modi- fied recombinations and largely elevated EL efficiency of 4.56-7.96 cd/A were achieved for the device C. The separation of the emissive layer and metal cathode with the TPBI layer may also suppress exciton quenching at the cathode interface.
基金supported by the National Natural Science Foundation of China(61077021,61076016)the National Basic Research Program of China(2009CB930600)the Funding from Nanjing University of Posts and Telecommunications(NY212076,NY212050)
文摘Two bipolar materials,2,5-bis(2-(9H-carbazole-9-yl)phenyl)-1,3,4-oxadiazole(o-CzOXD)and 2,5-bis(2-(3',6'-di-tert-butyl-9H-carbazole-9-yl)phenyl)-1,3,4-oxadiazole(tBu-o-CzOXD),were synthesized according to reported methods.In parallel study,it was demonstrated that introduction of inert tert-butyl group improved material thermal stability,even though this modification only had a slight influence to the photophysical and electrochemical properties of these materials.A comparative study focusing on effects of heat treatment was carried out on the quartz glass substrates with vacuum deposited films containing one of the bipolar host doped with 6 wt%fac-tris(2-phenylpyridinato-N,C2’)iridium(Ir(ppy)3).Results show that when the two samples were heated,the absorption,emission,and photo images of the host:dopant system changed,with the o-CzOXD suffering more severe degradation under high temperature,which is consistent with their thermal stability.In addition,it was proved that the high temperature-annealed host:dopant system can enhance the emission of the dopant.This finding was used as a guideline to improve our device performance.We fabricated two types of phosphorescent organic light-emitting devices(PhOLEDs),one was based on o-CzOXD,the other was based on tBu-o-CzOXD.They had analogous structure.We investigated the effect of heat on device performance by selectively annealing.Although these two freshly prepared devices exhibited similar performance,when annealed at 90°C for 10 min,the OLEDs based on tBu-o-CzOXD showed significant performance enhancement,which can be attributed to the observation that annealing Ir(ppy)3 doped host can change film morphology and enhance the dopant emission.The maximum efficiencies of the freshly prepared tBu-o-CzOXD device were 25.8 cd A-1,23.1lm W-1,and 9.3%;whereas those for annealed device were 47.0 cd A-1,42.2 lm W-1,and 13.4%.
基金supported by the National Natural Science Foundation of China(Nos.61076066 and 61605105)Shaanxi Science&Technology Development Program(No.2011KTCQ01-09)
文摘Transparent organic light-emitting devices(TOLEDs) based on a stacked alloy cathode of LiF/Al:Ag are investigated. The devices have a structure of indium-tin-oxide(ITO)/4,4′,4′′-Tris[2-naphthyl(phenyl)amino]triphenylamine(2T-NATA)(25 nm)/N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine(NPB)(40 nm)/tris-(8-hydroxyquinoline) aluminum(Al_(q_3))(50 nm)/LiF(1 nm)/Al:Ag(1:3)(x), where the thicknesses of cathode metal layers(Al:Ag) are adjusted, respectively, from 70 nm to 100 nm. In the experiment, it is found that the Li F(1 nm)/Al:Ag(1:3)(75 nm) has good electron injection efficiency. Compared with an Al-only cathode, the turn-on voltage is lowered. At the voltage of 10 V, the luminances for bottom emission from ITO anode side and top emission from metal cathode side are 2 459 cd/m^2 and 1 729 cd/m^2, respectively. Thanks to electron injection enhancement by using Al:Ag cathode, we can obtain a better energy level matching between the cathode and the organic layer, thus the devices have lower turn-on voltage and higher luminance. The total transmittance of the devices can achieve about 40% at the wavelength of 550 nm.
基金supported by the National Natural Science Foundation of China(No.21174036)the National High Technology Research and Development Program of China(863 Program)(No.2012AA011901)the National Basic Research Program of China(973 Program)(No.2012CB723406)
文摘A transparent 3-mercaptopropyl trimethoxysilane(MPTMS)/Ag/MoO3 composite anode is introduced to fabricate green organic light-emitting diodes(OLEDs). Effects of the composite anode on brightness and operating voltage of OLEDs are researched. By optimizing the thickness of each layer of the MPTMS/Ag/MoO3 structure, the transmittance of MPTMS/Ag(8 nm)/Mo O3(30 nm) reaches over 75% at about 520 nm. The sheet resistance is 3.78 ?/□, corresponding to this MPTMS/Ag(8 nm)/MoO3(30 nm) structure. For the OLEDs with the optimized anode, the maximum electroluminescence(EL) current efficiency reaches 4.5 cd/A, and the maximum brightness is 37 036 cd/m2. Moreover, the OLEDs with the optimized anode exhibit a very low operating voltage(2.6 V) for obtaining brightness of 100 cd/m2. We consider that the improved device performance is mainly attributed to the enhanced hole injection resulting from the reduced hole injection barrier height. Our results indicate that employing the MPTMS/Ag/MoO3 as a composite anode can be a simple and promising technique in the fabrication of low-operating voltage and high-brightness OLEDs.
