Head-to-tail bonded perylene bisimide(PBI)dyads with different branched alkyl chains substituted at the terminal imide position show various stacking modes,which results in different effects on the excitonic processes...Head-to-tail bonded perylene bisimide(PBI)dyads with different branched alkyl chains substituted at the terminal imide position show various stacking modes,which results in different effects on the excitonic processes and electron transportation.The dyad bearing branched alkyl chains with the branching sites close to the imide positions forms homogeneously amorphous state,while with branching sites being away from the imide positions the PBI core tend to stack with multiple modes.There are fewer energy trapping sites in the homogeneously amorphous state,but in the multiple stacking system the strongπ-πinteractions give more trapping sites.Our study demonstrates that the aggregation state of PBI-based acceptors plays an important role in the performances of organic solar cells(OSCs).Multiple stacking needs to be diminished to avoid the constrained exciton dissociation and retarded charge transport in the active layer.展开更多
In this paper, we investigate the issues of initialization and deployment of wireless sensor networks（WSNs） under IEEE 802.11 b/g interference and fading channels using frequency hopping（FH）. We propose an FH algo...In this paper, we investigate the issues of initialization and deployment of wireless sensor networks（WSNs） under IEEE 802.11 b/g interference and fading channels using frequency hopping（FH）. We propose an FH algorithm for WSNs, which is implemented and tested with a pair of nodes employing IPv6 over low power wireless personal area networks（6 LoWPAN） standard.The merits and demerits of the proposed FH scheme in WSNs are studied under strong IEEE 802.11 b/g interference and frequency selective fading channels. We compare the performance results of the proposed FH scheme with those obtained by single-channel radio in WSNs, and show that FH maintains very reliable data rates in the presence of adverse conditions where the single-channel radio fails. We determine a minimum center frequency offset of channels between IEEE 802.15.4 and IEEE 802.11 b/g-based networks, which guarantees the error free network operation of IEEE802.15.4 using a single channel. We design a second FH procedure comprising only four free channels（15, 20, 25, and 26） of IEEE 802.15.4 standard, and show that in the presence of nearby IEEE 802.11 b/g interference, the IEEE 802.15.4 data rate using this method is always 98% and more.展开更多
The widespread 5G base stations can be potential jammers for the vulnerable BeiDou B1I receivers due to its low power.Therefore,a novel analytical model is derived for the 5G signal to evaluate its impact on acquisiti...The widespread 5G base stations can be potential jammers for the vulnerable BeiDou B1I receivers due to its low power.Therefore,a novel analytical model is derived for the 5G signal to evaluate its impact on acquisition performance under three decision methods.The good agreement between the Monte Carlo method(MCM)through software defined receiver(SDR)and the derived expressions validates the effectiveness of the proposed algorithm.It can be found that the receivers exhibit varied responses for different 5G waveforms and decision strategies.The receiver also shows the least endurances for some kind of 5G waveforms,however,this kind of adverse effect can be cancelled by a reduced interference signal ratio(ISR),an increased integration time or a larger accumulation times.展开更多
The aim of this paper is to investigate the effect of nitrite intercalated Mg-Al layered double hydroxides(Mg-Al LDH-NO_(2))on mortar durability under the coexisting environment of Cl−and SO_(4)^(2-).Cl−and SO_(4)^(2-...The aim of this paper is to investigate the effect of nitrite intercalated Mg-Al layered double hydroxides(Mg-Al LDH-NO_(2))on mortar durability under the coexisting environment of Cl−and SO_(4)^(2-).Cl−and SO_(4)^(2-) binding properties of Mg-Al LDH-NO_(2) in simulated concrete pore solutions,Cl−and SO_(4)^(2-) diffusion properties of mortars with Mg-Al LDHNO 2 were examined.The steel corrosion and resistance of mortar against SO_(4)^(2-) attack were also evaluated.The results indicate that Mg-Al LDH-NO_(2) can effectively adsorb the Cl−and SO_(4)^(2-) in simulated concrete pore solution,and inhibit the diffusion of Cl−and SO_(4)^(2-) into cement mortars.The presence of SO_(4)^(2-) can greatly affect the uptake amount of Cl−,and there is a coupled effect of Cl−and SO_(4)^(2-) on their penetration into mortar specimens.In addition,Mg-Al LDH-NO_(2) can greatly upgrade the resistance of mortars against SO_(4)^(2-) attack and well prevent the steel from corrosion.However,Cl−will aggravate the SO_(4)^(2-) attack and SO_(4)^(2-) can initially decrease and then increase the steel corrosion.展开更多
LRS, XRD, UV-DRS and TPR techiques have been used to characterize supported tungsten oxide catalysts. Experimental results show that WO<sub>3</sub> is highly dispersed on γ-Al<sub>2</sub>O<...LRS, XRD, UV-DRS and TPR techiques have been used to characterize supported tungsten oxide catalysts. Experimental results show that WO<sub>3</sub> is highly dispersed on γ-Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, SnO<sub>2</sub> and ZrO<sub>2</sub> until a complete monolayer coverage is achieved. However, WO<sub>3</sub> is poorly dispersed on SiO<sub>2</sub> Raman spectroscopy is a very powerful technique for distinguishing highly dispersed and crystalline WO<sub>3</sub> on the surface. For the samples with monolayer coverage of WO<sub>3</sub>, the Raman shift of surface W-O species varies with the support. The support stabilizes surface W-O species and substantially suppresses its reduction and changes the reduction process as well. The coordination state of the W-O species on the support surface depends on the loading and the crystalline structure of the support. The Raman shift and T<sub>m</sub> value of the TPR peak of the surface W-O species are correlated with the interaction between WO<sub>3</sub> and the support.展开更多
文摘Head-to-tail bonded perylene bisimide(PBI)dyads with different branched alkyl chains substituted at the terminal imide position show various stacking modes,which results in different effects on the excitonic processes and electron transportation.The dyad bearing branched alkyl chains with the branching sites close to the imide positions forms homogeneously amorphous state,while with branching sites being away from the imide positions the PBI core tend to stack with multiple modes.There are fewer energy trapping sites in the homogeneously amorphous state,but in the multiple stacking system the strongπ-πinteractions give more trapping sites.Our study demonstrates that the aggregation state of PBI-based acceptors plays an important role in the performances of organic solar cells(OSCs).Multiple stacking needs to be diminished to avoid the constrained exciton dissociation and retarded charge transport in the active layer.
基金supported by the Important National Science and Technology Specific Project of China(2018ZX03001020-0052016ZX03001022-006)+2 种基金the National Natural Science Foundation of China(61771308)the Shanghai Science and Technology Committee(16DZ1100402)the Special Project of Military and Civilian Integration of Shanghai Economic and Information Committee with the name"Ultra High Sensitivity UAV Communication System Based on Radar Related Technology"
文摘In this paper, we investigate the issues of initialization and deployment of wireless sensor networks（WSNs） under IEEE 802.11 b/g interference and fading channels using frequency hopping（FH）. We propose an FH algorithm for WSNs, which is implemented and tested with a pair of nodes employing IPv6 over low power wireless personal area networks（6 LoWPAN） standard.The merits and demerits of the proposed FH scheme in WSNs are studied under strong IEEE 802.11 b/g interference and frequency selective fading channels. We compare the performance results of the proposed FH scheme with those obtained by single-channel radio in WSNs, and show that FH maintains very reliable data rates in the presence of adverse conditions where the single-channel radio fails. We determine a minimum center frequency offset of channels between IEEE 802.15.4 and IEEE 802.11 b/g-based networks, which guarantees the error free network operation of IEEE802.15.4 using a single channel. We design a second FH procedure comprising only four free channels（15, 20, 25, and 26） of IEEE 802.15.4 standard, and show that in the presence of nearby IEEE 802.11 b/g interference, the IEEE 802.15.4 data rate using this method is always 98% and more.
文摘The widespread 5G base stations can be potential jammers for the vulnerable BeiDou B1I receivers due to its low power.Therefore,a novel analytical model is derived for the 5G signal to evaluate its impact on acquisition performance under three decision methods.The good agreement between the Monte Carlo method(MCM)through software defined receiver(SDR)and the derived expressions validates the effectiveness of the proposed algorithm.It can be found that the receivers exhibit varied responses for different 5G waveforms and decision strategies.The receiver also shows the least endurances for some kind of 5G waveforms,however,this kind of adverse effect can be cancelled by a reduced interference signal ratio(ISR),an increased integration time or a larger accumulation times.
基金Project(51478164)supported by the National Natural Science Foundation of ChinaProject(BK20181306)supported by Natural Science Foundation of Jiangsu Province,China。
文摘The aim of this paper is to investigate the effect of nitrite intercalated Mg-Al layered double hydroxides(Mg-Al LDH-NO_(2))on mortar durability under the coexisting environment of Cl−and SO_(4)^(2-).Cl−and SO_(4)^(2-) binding properties of Mg-Al LDH-NO_(2) in simulated concrete pore solutions,Cl−and SO_(4)^(2-) diffusion properties of mortars with Mg-Al LDHNO 2 were examined.The steel corrosion and resistance of mortar against SO_(4)^(2-) attack were also evaluated.The results indicate that Mg-Al LDH-NO_(2) can effectively adsorb the Cl−and SO_(4)^(2-) in simulated concrete pore solution,and inhibit the diffusion of Cl−and SO_(4)^(2-) into cement mortars.The presence of SO_(4)^(2-) can greatly affect the uptake amount of Cl−,and there is a coupled effect of Cl−and SO_(4)^(2-) on their penetration into mortar specimens.In addition,Mg-Al LDH-NO_(2) can greatly upgrade the resistance of mortars against SO_(4)^(2-) attack and well prevent the steel from corrosion.However,Cl−will aggravate the SO_(4)^(2-) attack and SO_(4)^(2-) can initially decrease and then increase the steel corrosion.
基金Project supported by National sience Foundation of China
文摘LRS, XRD, UV-DRS and TPR techiques have been used to characterize supported tungsten oxide catalysts. Experimental results show that WO<sub>3</sub> is highly dispersed on γ-Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, SnO<sub>2</sub> and ZrO<sub>2</sub> until a complete monolayer coverage is achieved. However, WO<sub>3</sub> is poorly dispersed on SiO<sub>2</sub> Raman spectroscopy is a very powerful technique for distinguishing highly dispersed and crystalline WO<sub>3</sub> on the surface. For the samples with monolayer coverage of WO<sub>3</sub>, the Raman shift of surface W-O species varies with the support. The support stabilizes surface W-O species and substantially suppresses its reduction and changes the reduction process as well. The coordination state of the W-O species on the support surface depends on the loading and the crystalline structure of the support. The Raman shift and T<sub>m</sub> value of the TPR peak of the surface W-O species are correlated with the interaction between WO<sub>3</sub> and the support.
