Thermally expanded graphite was functionalized with 4-bromophenyl addends using the in situ diazonium formation procedure,and after mild sonication treatment in N,N’-dimethylformamide,thin graphene layers were exfoli...Thermally expanded graphite was functionalized with 4-bromophenyl addends using the in situ diazonium formation procedure,and after mild sonication treatment in N,N’-dimethylformamide,thin graphene layers were exfoliated from the bulk graphite.These chemically-assisted exfoliated graphene(CEG)sheets had higher solubility than pristine graphene without any stabilizer additive.More than 70%of these soluble flakes had less than 5 layers.Energy filtered transmission electron microscopy(EFTEM)elemental mapping provided evidence of the edge-selective diazonium functionalization with graphene.A majority of the Br signals came from the edges of the CEG indicating that the basal planes were not highly functionalized.The CEG was also characterized by X-ray photoelectron spectroscopy,atomic force microscopy,Raman spectroscopy,and transmission electron microscopy.展开更多
In this paper, the problem of parameter estimation of the combined radar signal adopting chaotic pulse position modulation （CPPM） and linear frequency modulation （LFM）, which can be widely used in electronic count...In this paper, the problem of parameter estimation of the combined radar signal adopting chaotic pulse position modulation （CPPM） and linear frequency modulation （LFM）, which can be widely used in electronic countermeasures, is addressed. An approach is proposed to estimate the initial frequency and chirp rate of the combined signal by exploiting the second-order cyclostationarity of the intra-pulse signal. In addition, under the condition of the equal pulse width, the pulse repetition interval （PRI） of the combined signal is predicted using the low-order Volterra adaptive filter. Simulations demonstrate that the proposed cyclic autocorrelation Hough transform （CHT） algorithm is theoretically tolerant to additive white Gaussian noise. When the value of signal noise to ratio （SNR） is less than 4 dB, it can still estimate the intra-pulse parameters well. When SNR = 3 dB, a good prediction of the PRI sequence can be achieved by the Volterra adaptive filter algorithm, even only 100 training samples.展开更多
基金We thank the U.S.Department of Energy's Office of Energy Efficiency and Renewable Energy within the Hydrogen Sorption Center of Excellence,No.DE-FC-36-05GO15073,the Air Force Office of Scientific Research(CONTACT),the Office of Naval Research through a Multidisciplinary University Research Initiative(MURI)with the University of California,Berkeley(00006766)and the Advanced Energy Consortium(member companies include BP America Inc.,Baker Hughes Inc.,Conoco-Phillips,Halliburton Energy Services Inc.,Marathon Oil Corp.,Occidental Oil and Gas,Petrobras,Schlumberger,Shell,and Total)for financial support.Thanks to Dr.Wenhua Guo for assistance with the TEM.
文摘Thermally expanded graphite was functionalized with 4-bromophenyl addends using the in situ diazonium formation procedure,and after mild sonication treatment in N,N’-dimethylformamide,thin graphene layers were exfoliated from the bulk graphite.These chemically-assisted exfoliated graphene(CEG)sheets had higher solubility than pristine graphene without any stabilizer additive.More than 70%of these soluble flakes had less than 5 layers.Energy filtered transmission electron microscopy(EFTEM)elemental mapping provided evidence of the edge-selective diazonium functionalization with graphene.A majority of the Br signals came from the edges of the CEG indicating that the basal planes were not highly functionalized.The CEG was also characterized by X-ray photoelectron spectroscopy,atomic force microscopy,Raman spectroscopy,and transmission electron microscopy.
基金supported by the National Natural Science Foundation of China under Grant 61172116
文摘In this paper, the problem of parameter estimation of the combined radar signal adopting chaotic pulse position modulation （CPPM） and linear frequency modulation （LFM）, which can be widely used in electronic countermeasures, is addressed. An approach is proposed to estimate the initial frequency and chirp rate of the combined signal by exploiting the second-order cyclostationarity of the intra-pulse signal. In addition, under the condition of the equal pulse width, the pulse repetition interval （PRI） of the combined signal is predicted using the low-order Volterra adaptive filter. Simulations demonstrate that the proposed cyclic autocorrelation Hough transform （CHT） algorithm is theoretically tolerant to additive white Gaussian noise. When the value of signal noise to ratio （SNR） is less than 4 dB, it can still estimate the intra-pulse parameters well. When SNR = 3 dB, a good prediction of the PRI sequence can be achieved by the Volterra adaptive filter algorithm, even only 100 training samples.
