A family of integrable differential-difference equations is derived from a new matrix spectral problem. The Hamiltonian forms of obtained differential-difference equations are constructed. The Liouville integrability ...A family of integrable differential-difference equations is derived from a new matrix spectral problem. The Hamiltonian forms of obtained differential-difference equations are constructed. The Liouville integrability for the obtained integrable family is proved. Then, Bargmann symmetry constraint of the obtained integrable family is presented by binary nonliearization method of Lax pairs and adjoint Lax pairs. Under this Bargmann symmetry constraints, an integrable symplectic map and a sequences of completely integrable finite-dimensional Hamiltonian systems in Liouville sense are worked out, and every integrable differential-difference equations in the obtained family is factored by the integrable symplectie map and a completely integrable tinite-dimensionai Hamiltonian system.展开更多
An approach which combines direct numerical simulation （DNS） with the Lighthill acoustic analogy theory is used to study the potential noise sources during the transition process of a Mach 2.25 flat plate boundary l...An approach which combines direct numerical simulation （DNS） with the Lighthill acoustic analogy theory is used to study the potential noise sources during the transition process of a Mach 2.25 flat plate boundary layer. The quadrupole sound sources due to the flow fluctuations and the dipole sound sources due to the fluctuating surface stress are obtained. Numerical results suggest that formation of the high shear layers leads to a dramatic amplification of amplitude of the fluctuating quadrupole sound sources. Compared with the quadrupole sound source, the energy of dipole sound source is concentrated in the relatively low frequency range.展开更多
A new method of unscented extended Kalman filter （UEKF） for nonlinear system is presented. This new method is a combination of the unscented transformation and the extended Kalman filter （EKF）. The extended Kalman...A new method of unscented extended Kalman filter （UEKF） for nonlinear system is presented. This new method is a combination of the unscented transformation and the extended Kalman filter （EKF）. The extended Kalman filter is similar to that in a conventional EKF. However, in every running step of the EKF the unscented transformation is running, the deterministic sample is caught by unscented transformation, then posterior mean of non- lineadty is caught by propagating, but the posterior covariance of nonlinearity is caught by linearizing. The accuracy of new method is a little better than that of the unscented Kalman filter （UKF）, however, the computational time of the UEKF is much less than that of the UKF.展开更多
Based on the principle of equivalent phase comparison frequency, we propose a group-period phase comparison method. This method can be used to reveal the inherent relations between periodic signals and the change laws...Based on the principle of equivalent phase comparison frequency, we propose a group-period phase comparison method. This method can be used to reveal the inherent relations between periodic signals and the change laws of the phase difference. If these laws are applied in the processing of the mutual relations between frequency signals, phase comparison can be accomplished without frequency normalization. Experimental results show that the method can enhance the measurement resolution to 10-13/s in the time domain.展开更多
Based on the principle of quantized delay-time, a super-high resolution time interval measurement method is proposed based on time-space relationships. Using the delay-time stability that time and frequency signal tra...Based on the principle of quantized delay-time, a super-high resolution time interval measurement method is proposed based on time-space relationships. Using the delay-time stability that time and frequency signal travel in a specific medium, the measured time interval can be quantized. Combined with the phase coincidence detection technique, the measurement of time can be changed into the measurement of space length. The resolution and the stability of the measurement system are easily improved. Experimental results show that the measurement resolution of the measured time interval depends on the length difference of the double delay-time unit. When the length difference is set up on millimeter level or sub-millimeter level, super-high measurement resolution from hundreds of picosecond to tens of picosecond can be obtained.展开更多
By testing a substantial number of tripler and z-cut KDP and DKDP crystals, we have observed that at 355nm, the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test. It is pro...By testing a substantial number of tripler and z-cut KDP and DKDP crystals, we have observed that at 355nm, the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test. It is proved that laser conditioning is an efficient way to improve the damage resistance. The efficiency of laser conditioning becomes increasingly good with smaller ramping fluence steps. We have also found that the damage resistance of the z-cut crystal is higher than the triplet cut, and the pinpoint number is definitely less in the z-cut crystal. The reason for these observations is discussed.展开更多
An all-optical encryption-decryption method using an exclusive-or gate based on the cross-phase modulation between O-band and C-band light waves is proposed. The feasibility of the encryptionecryption technique is ver...An all-optical encryption-decryption method using an exclusive-or gate based on the cross-phase modulation between O-band and C-band light waves is proposed. The feasibility of the encryptionecryption technique is verified by handling binary signals at 2.5 Gbps, with less than 3dB penalty of extinction ratio and i dB polarization dependent loss.展开更多
We propose a protocol of remote information concentration achieved by a four-particle cluster state. To achieve the task, Bell state measurement and unitary operation are needed. The result shows a peculiar phenomenon...We propose a protocol of remote information concentration achieved by a four-particle cluster state. To achieve the task, Bell state measurement and unitary operation are needed. The result shows a peculiar phenomenon that the remote information concentration is not always successful but with certain probability.展开更多
A circular magnetic multi-pole line-cusp ion source with a nominal 45 keV 25 A hydrogen ion beam is developed for the neutraJ beam injector of the HL-2A tokomak. At present, this bucket ion source can produce a 40 keV...A circular magnetic multi-pole line-cusp ion source with a nominal 45 keV 25 A hydrogen ion beam is developed for the neutraJ beam injector of the HL-2A tokomak. At present, this bucket ion source can produce a 40 keV 20 A hydrogen ion beam for less than lOOms on a test bed, and a 35 ke V 13A ion beam for 300ms on the injector of the HL-2A tokomak. The 1/e half-width of the ion beam power profile is about 6.0 ± 0.2 em at the positionof 3.26m downstream from ion source, and the corresponding divergence degree is nearly 1.1. The optimum perveance matched conditions were obtained experimentally, and were in good agreement with the values from experiential equation of Uhlemann et al. The maximum of optimum perveance reached 2.2 × 10^-6 A/V^1.5 for 38 keV beam energy. An ion beam with above 60% H^＋ species fraction can be achieved, which was measured by Ha light Doppler shift spectroscopy. According to research results, a neutral beam with a total power of more than 0.6 MW was successfully injected into the plasma of the HL-2A Tokomak in 2008.展开更多
Carbon nanotubes （CNTs） are potential strain sensors due to their excellent mechanical and spectral properties. A new theoretical model of a CNT strain sensor is obtained by applying the polarized Raman properties o...Carbon nanotubes （CNTs） are potential strain sensors due to their excellent mechanical and spectral properties. A new theoretical model of a CNT strain sensor is obtained by applying the polarized Raman properties of CNTs, which calculates the synthetic contributions of Raman spectra from the CNTs in random directions. By using this theoretical model, the analytic relationship between planar strain components and the Raman shift increment of uniformly dispersed CNTs is obtained, which is applicable for accurately characterizing the strain in random directions on the surface of a measured microsystem.展开更多
A steady two-dimensional magnetohydrodynamic stagnation point flow towards a stretching sheet with variable surface temperature is investigated. The analytic solution is obtained by homotopy analysis method. The conve...A steady two-dimensional magnetohydrodynamic stagnation point flow towards a stretching sheet with variable surface temperature is investigated. The analytic solution is obtained by homotopy analysis method. The convergence region is computed and the feature of the solution is discussed.展开更多
The imaginary time step （ITS） method is applied to solve the Dirac equation with the nonlocal potential in coordinate space by the ITS evolution for the corresponding Schrfdinger-like equation for the upper componen...The imaginary time step （ITS） method is applied to solve the Dirac equation with the nonlocal potential in coordinate space by the ITS evolution for the corresponding Schrfdinger-like equation for the upper component. It is demonstrated that the ITS evolution can be equivalently performed for the Schrodinger-like equation with or without localization. The latter algorithm is recommended in the application for the reason of simplicity and efficiency. The feasibility and reliability of this algorithm are also illustrated by taking the nucleus ^16O as an example, where the same results as the shooting method for the Dirae equation with localized effective potentials are obtained.展开更多
A simple and accurate method for calculating the optimal width of an annular spiral phase plate （SPP） to generate optical vortices with sidelobe suppression is proposed. The sideloSes can he sharply suppressed when ...A simple and accurate method for calculating the optimal width of an annular spiral phase plate （SPP） to generate optical vortices with sidelobe suppression is proposed. The sideloSes can he sharply suppressed when the ratio of inner and outer radii of an annular SPP is equal to that of the principal ring and the first sidelobe diffracted by a circular SPP with the same topological charge n. Moreover, the ratio of the inner and outer radii of the optimal annular SPP depends only on the topological charge n and is not affected by the incident wavelength or the size of the SPP.展开更多
Thick GaN films of high quality are directly grown on wet-etching patterned sapphire in a vertical hydride vapour phase epitaxy reactor. The optical and structural properties of GaN films are studied using scanning el...Thick GaN films of high quality are directly grown on wet-etching patterned sapphire in a vertical hydride vapour phase epitaxy reactor. The optical and structural properties of GaN films are studied using scanning electronic microscopy and cathodoluminescence. Test results show that initial growth of hydride vapour phase epitaxy GaN occurs not only on the mesas but also on the two asymmetric sidewalls of the V-shaped grooves without selectivity. After the two-step coalescence near the interface, the GaN films near the surface keep on growing along the direction perpendicular to the long sidewall. Based on Raman results, GaN of the coalescence region in the grooves has the maximum residual stress and poor crystalline quality over the whole GaN film, and the coalescence process can release the stress. Therefore, stress-free thick GaN films are prepared with smooth and crack-free surfaces by this particular growth mode on wet-etching patterned sapphire substrates.展开更多
Relationships among the signal coherence-time of matched-field processing （MFP）, the acoustic frequency, the source-receiver range, and the sound speed standard deviation （STD） caused by internal waves in shallow ...Relationships among the signal coherence-time of matched-field processing （MFP）, the acoustic frequency, the source-receiver range, and the sound speed standard deviation （STD） caused by internal waves in shallow water, are numerically investigated based on oceanographic data from two shallow water experiments. It is found that the coherence-time can be fitted with an inverse square-root power of range, a near inverse 1 power of frequency, and inverse 1.3 power of sound speed STD.展开更多
The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are inves...The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are investigated by scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction, as well as potentiodynamic polarization testing. X-ray diffraction results show that the carbonitriding coatings are composed of martensite, anstenite（γ-Fe）, Fe2C, Fe3C, Fe5 C2, FeN and ε-Fe2-3N. After the plasma electrolytic carbonitriding treatment the corrosion resistance of cast iron is clearly improved compared to the substrate, and the coatings produced at 350 V for 30s give the best corrosion resistance.展开更多
An epitaxial graphene （EG） layer is successfully grown on a Si-terminated 6H-SiC （（9001） substrate by the method of thermal annealing in an ultrahigh vacuum molecular beam epitaxy chamber. The structure and morph...An epitaxial graphene （EG） layer is successfully grown on a Si-terminated 6H-SiC （（9001） substrate by the method of thermal annealing in an ultrahigh vacuum molecular beam epitaxy chamber. The structure and morphology of the EG sample are characterized by reflection high energy diffraction （RHEED）, Raman spectroscopy and atomic force microscopy （AFM）. Graphene diffraction streaks can are clearly observed in the Raman spectrum. The AFM about 4-10 layers. be seen in RHEED. The G and 2D peaks of graphene results show that the graphene nominal thickness is展开更多
It is shown that many real complex networks share distinctive features, such as the small-world effect and the heterogeneous property of connectivity of vertices, which are different from random networks and regular l...It is shown that many real complex networks share distinctive features, such as the small-world effect and the heterogeneous property of connectivity of vertices, which are different from random networks and regular lattices. Although these features capture the important characteristics of complex networks, their applicability depends on the style of networks. To unravel the universal characteristics many complex networks have in common, we study the fractal dimensions of complex networks using the method introduced by Shanker. We find that the average ＇density＇ （p（r ） ） of complex networks follows a better power-law function as a function of distance r with the exponent dl, which is defined as the fractal dimension, in some real complex networks. Furthermore, we study the relation between df and the shortcuts Nadd in small-world networks and the size N in regular lattices. Our present work provides a new perspective to understand the dependence of the fractal dimension df on the complex network structure.展开更多
Composite materials with interpenetrating network structures usually exhibit unexpected merit due to the cooperative interaction. Locally resonant phononic crystals （LRPC） exhibit excellent sound attenuation perform...Composite materials with interpenetrating network structures usually exhibit unexpected merit due to the cooperative interaction. Locally resonant phononic crystals （LRPC） exhibit excellent sound attenuation performance based on a periodical arrangement of sound wave scatters. Inspired by the interpenetrating network structure and the LRPC concept, we develop a locally network anechoic coating （LNAC） that can achieve a wide band of underwater strong acoustic absorption. The experimental results show that the LNAC possesses an excellent underwater acoustic absorbing capacity in a wide frequency range. Moreover, in order to investigate the impact of the interpenetrating network structure, we fabricate a faultage structure sample and the network is disconnected by hard polyurethane （PU）. The experimental comparison between the LNAC and the fanltage structure sample shows that the interpenetrating network structure of the LNAC plays an important role in achieving a wide band strong acoustic absorption.展开更多
A super thin elastic rod is modeled with a background of DNA super coiling structure, and its dynamics is discussed based on the Jourdain variation. The cross section of the rod is taken as the object of this study an...A super thin elastic rod is modeled with a background of DNA super coiling structure, and its dynamics is discussed based on the Jourdain variation. The cross section of the rod is taken as the object of this study and two velocity spaces about are coordinate and the time are obtained respectively. Virtual displacements of the section on the two velocity spaces are defined and can be expressed in terms of Jourdain variation. JourdMn principles of a super thin elastic rod dynamics on arc coordinate and the time velocity space are established, respectively, which show that there are two ways to realize the constraint conditions. If the constitutive relation of the rod is linear, the Jourdain principle takes the Euler-Lagrange form with generalized coordinates. The Kirchhoff equation, Lagrange equation and Appell equation can be derived from the present Jourdain principle. While the rod subjected to a surface constraint, Lagrange equation with undetermined multipliers may be derived.展开更多
基金Supported by the Science and Technology Plan Projects of the Educational Department of Shandong Province of China under GrantNo. J08LI08
文摘A family of integrable differential-difference equations is derived from a new matrix spectral problem. The Hamiltonian forms of obtained differential-difference equations are constructed. The Liouville integrability for the obtained integrable family is proved. Then, Bargmann symmetry constraint of the obtained integrable family is presented by binary nonliearization method of Lax pairs and adjoint Lax pairs. Under this Bargmann symmetry constraints, an integrable symplectic map and a sequences of completely integrable finite-dimensional Hamiltonian systems in Liouville sense are worked out, and every integrable differential-difference equations in the obtained family is factored by the integrable symplectie map and a completely integrable tinite-dimensionai Hamiltonian system.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10872205 and 10632050, and the National Basic Research Program of China under Grant No 2009CB724100.
文摘An approach which combines direct numerical simulation （DNS） with the Lighthill acoustic analogy theory is used to study the potential noise sources during the transition process of a Mach 2.25 flat plate boundary layer. The quadrupole sound sources due to the flow fluctuations and the dipole sound sources due to the fluctuating surface stress are obtained. Numerical results suggest that formation of the high shear layers leads to a dramatic amplification of amplitude of the fluctuating quadrupole sound sources. Compared with the quadrupole sound source, the energy of dipole sound source is concentrated in the relatively low frequency range.
文摘A new method of unscented extended Kalman filter （UEKF） for nonlinear system is presented. This new method is a combination of the unscented transformation and the extended Kalman filter （EKF）. The extended Kalman filter is similar to that in a conventional EKF. However, in every running step of the EKF the unscented transformation is running, the deterministic sample is caught by unscented transformation, then posterior mean of non- lineadty is caught by propagating, but the posterior covariance of nonlinearity is caught by linearizing. The accuracy of new method is a little better than that of the unscented Kalman filter （UKF）, however, the computational time of the UEKF is much less than that of the UKF.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60772135 and 10703004, and the CAST Innovation Foundation of China under Grant No 20080403.
文摘Based on the principle of equivalent phase comparison frequency, we propose a group-period phase comparison method. This method can be used to reveal the inherent relations between periodic signals and the change laws of the phase difference. If these laws are applied in the processing of the mutual relations between frequency signals, phase comparison can be accomplished without frequency normalization. Experimental results show that the method can enhance the measurement resolution to 10-13/s in the time domain.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60772135 and 10703004, and the CAST Innovation Foundation of China under Grant No 20080403.
文摘Based on the principle of quantized delay-time, a super-high resolution time interval measurement method is proposed based on time-space relationships. Using the delay-time stability that time and frequency signal travel in a specific medium, the measured time interval can be quantized. Combined with the phase coincidence detection technique, the measurement of time can be changed into the measurement of space length. The resolution and the stability of the measurement system are easily improved. Experimental results show that the measurement resolution of the measured time interval depends on the length difference of the double delay-time unit. When the length difference is set up on millimeter level or sub-millimeter level, super-high measurement resolution from hundreds of picosecond to tens of picosecond can be obtained.
基金Supported by the National Natural Science Foundation of China under Grant No 10676019.
文摘By testing a substantial number of tripler and z-cut KDP and DKDP crystals, we have observed that at 355nm, the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test. It is proved that laser conditioning is an efficient way to improve the damage resistance. The efficiency of laser conditioning becomes increasingly good with smaller ramping fluence steps. We have also found that the damage resistance of the z-cut crystal is higher than the triplet cut, and the pinpoint number is definitely less in the z-cut crystal. The reason for these observations is discussed.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60072004 and 60877057, and the National High-Tech Research and Development Program of China under Grant No 2007AA01Z270.
文摘An all-optical encryption-decryption method using an exclusive-or gate based on the cross-phase modulation between O-band and C-band light waves is proposed. The feasibility of the encryptionecryption technique is verified by handling binary signals at 2.5 Gbps, with less than 3dB penalty of extinction ratio and i dB polarization dependent loss.
基金Supported by the Natural Science Foundation of Hunan Province under Grant No 06JJ50118.
文摘We propose a protocol of remote information concentration achieved by a four-particle cluster state. To achieve the task, Bell state measurement and unitary operation are needed. The result shows a peculiar phenomenon that the remote information concentration is not always successful but with certain probability.
文摘A circular magnetic multi-pole line-cusp ion source with a nominal 45 keV 25 A hydrogen ion beam is developed for the neutraJ beam injector of the HL-2A tokomak. At present, this bucket ion source can produce a 40 keV 20 A hydrogen ion beam for less than lOOms on a test bed, and a 35 ke V 13A ion beam for 300ms on the injector of the HL-2A tokomak. The 1/e half-width of the ion beam power profile is about 6.0 ± 0.2 em at the positionof 3.26m downstream from ion source, and the corresponding divergence degree is nearly 1.1. The optimum perveance matched conditions were obtained experimentally, and were in good agreement with the values from experiential equation of Uhlemann et al. The maximum of optimum perveance reached 2.2 × 10^-6 A/V^1.5 for 38 keV beam energy. An ion beam with above 60% H^＋ species fraction can be achieved, which was measured by Ha light Doppler shift spectroscopy. According to research results, a neutral beam with a total power of more than 0.6 MW was successfully injected into the plasma of the HL-2A Tokomak in 2008.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10732080 and 10502014.
文摘Carbon nanotubes （CNTs） are potential strain sensors due to their excellent mechanical and spectral properties. A new theoretical model of a CNT strain sensor is obtained by applying the polarized Raman properties of CNTs, which calculates the synthetic contributions of Raman spectra from the CNTs in random directions. By using this theoretical model, the analytic relationship between planar strain components and the Raman shift increment of uniformly dispersed CNTs is obtained, which is applicable for accurately characterizing the strain in random directions on the surface of a measured microsystem.
文摘A steady two-dimensional magnetohydrodynamic stagnation point flow towards a stretching sheet with variable surface temperature is investigated. The analytic solution is obtained by homotopy analysis method. The convergence region is computed and the feature of the solution is discussed.
基金Supported by the National Basic Research Program of China under Grant No 2007CB815000, and the National Natural Science Foundation of China under Grant No 10775004.
文摘The imaginary time step （ITS） method is applied to solve the Dirac equation with the nonlocal potential in coordinate space by the ITS evolution for the corresponding Schrfdinger-like equation for the upper component. It is demonstrated that the ITS evolution can be equivalently performed for the Schrodinger-like equation with or without localization. The latter algorithm is recommended in the application for the reason of simplicity and efficiency. The feasibility and reliability of this algorithm are also illustrated by taking the nucleus ^16O as an example, where the same results as the shooting method for the Dirae equation with localized effective potentials are obtained.
文摘A simple and accurate method for calculating the optimal width of an annular spiral phase plate （SPP） to generate optical vortices with sidelobe suppression is proposed. The sideloSes can he sharply suppressed when the ratio of inner and outer radii of an annular SPP is equal to that of the principal ring and the first sidelobe diffracted by a circular SPP with the same topological charge n. Moreover, the ratio of the inner and outer radii of the optimal annular SPP depends only on the topological charge n and is not affected by the incident wavelength or the size of the SPP.
基金Supported by the National High-Technology Research and Development Program of China under Grant Nos 2006AA03A143, the National Natural Science Foundation of China under Grant No 60806001, and the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No ISCAS2008T03.
文摘Thick GaN films of high quality are directly grown on wet-etching patterned sapphire in a vertical hydride vapour phase epitaxy reactor. The optical and structural properties of GaN films are studied using scanning electronic microscopy and cathodoluminescence. Test results show that initial growth of hydride vapour phase epitaxy GaN occurs not only on the mesas but also on the two asymmetric sidewalls of the V-shaped grooves without selectivity. After the two-step coalescence near the interface, the GaN films near the surface keep on growing along the direction perpendicular to the long sidewall. Based on Raman results, GaN of the coalescence region in the grooves has the maximum residual stress and poor crystalline quality over the whole GaN film, and the coalescence process can release the stress. Therefore, stress-free thick GaN films are prepared with smooth and crack-free surfaces by this particular growth mode on wet-etching patterned sapphire substrates.
基金Supported by Knowledge Innovation Program of the Chinese Academy of Sciences under Grant No KZCX1-YW-12-2, and the National Natural Science Foundation of China under Grant No 10734100.
文摘Relationships among the signal coherence-time of matched-field processing （MFP）, the acoustic frequency, the source-receiver range, and the sound speed standard deviation （STD） caused by internal waves in shallow water, are numerically investigated based on oceanographic data from two shallow water experiments. It is found that the coherence-time can be fitted with an inverse square-root power of range, a near inverse 1 power of frequency, and inverse 1.3 power of sound speed STD.
基金Supported by the National Natural Science Foundation of China under Grant No 10675165, and the Project of International Cooperation and Exchanges NSFC-KOSEF （No 10811140326）.
文摘The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are investigated by scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction, as well as potentiodynamic polarization testing. X-ray diffraction results show that the carbonitriding coatings are composed of martensite, anstenite（γ-Fe）, Fe2C, Fe3C, Fe5 C2, FeN and ε-Fe2-3N. After the plasma electrolytic carbonitriding treatment the corrosion resistance of cast iron is clearly improved compared to the substrate, and the coatings produced at 350 V for 30s give the best corrosion resistance.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50872128 and 50802053.
文摘An epitaxial graphene （EG） layer is successfully grown on a Si-terminated 6H-SiC （（9001） substrate by the method of thermal annealing in an ultrahigh vacuum molecular beam epitaxy chamber. The structure and morphology of the EG sample are characterized by reflection high energy diffraction （RHEED）, Raman spectroscopy and atomic force microscopy （AFM）. Graphene diffraction streaks can are clearly observed in the Raman spectrum. The AFM about 4-10 layers. be seen in RHEED. The G and 2D peaks of graphene results show that the graphene nominal thickness is
基金Supported by the National Natural Science Foundation of China under Grant No 10635020,the Program of Introducing Talents of Discipline to Universities under Grant No B08033, the National Key Basic Research Program of China under Grant No 2008CB317106, and the Key Project of the Ministry of Education of China （306022 and IRT0624）.
文摘It is shown that many real complex networks share distinctive features, such as the small-world effect and the heterogeneous property of connectivity of vertices, which are different from random networks and regular lattices. Although these features capture the important characteristics of complex networks, their applicability depends on the style of networks. To unravel the universal characteristics many complex networks have in common, we study the fractal dimensions of complex networks using the method introduced by Shanker. We find that the average ＇density＇ （p（r ） ） of complex networks follows a better power-law function as a function of distance r with the exponent dl, which is defined as the fractal dimension, in some real complex networks. Furthermore, we study the relation between df and the shortcuts Nadd in small-world networks and the size N in regular lattices. Our present work provides a new perspective to understand the dependence of the fractal dimension df on the complex network structure.
基金Supported by the National Natural Science Foundation of China under Grant No 1083201, and the Knowledge Innovation Program of the Chinese Academy of Sciences under Grant No KJCX2-YW-L08.
文摘Composite materials with interpenetrating network structures usually exhibit unexpected merit due to the cooperative interaction. Locally resonant phononic crystals （LRPC） exhibit excellent sound attenuation performance based on a periodical arrangement of sound wave scatters. Inspired by the interpenetrating network structure and the LRPC concept, we develop a locally network anechoic coating （LNAC） that can achieve a wide band of underwater strong acoustic absorption. The experimental results show that the LNAC possesses an excellent underwater acoustic absorbing capacity in a wide frequency range. Moreover, in order to investigate the impact of the interpenetrating network structure, we fabricate a faultage structure sample and the network is disconnected by hard polyurethane （PU）. The experimental comparison between the LNAC and the fanltage structure sample shows that the interpenetrating network structure of the LNAC plays an important role in achieving a wide band strong acoustic absorption.
基金Supported by the National Natural Science Foundation of China under Grant No 10472067.
文摘A super thin elastic rod is modeled with a background of DNA super coiling structure, and its dynamics is discussed based on the Jourdain variation. The cross section of the rod is taken as the object of this study and two velocity spaces about are coordinate and the time are obtained respectively. Virtual displacements of the section on the two velocity spaces are defined and can be expressed in terms of Jourdain variation. JourdMn principles of a super thin elastic rod dynamics on arc coordinate and the time velocity space are established, respectively, which show that there are two ways to realize the constraint conditions. If the constitutive relation of the rod is linear, the Jourdain principle takes the Euler-Lagrange form with generalized coordinates. The Kirchhoff equation, Lagrange equation and Appell equation can be derived from the present Jourdain principle. While the rod subjected to a surface constraint, Lagrange equation with undetermined multipliers may be derived.
