The paper had pointed out hollow ancient town was the result of urbanization and desire; and analyzed that hollowness made ancient towns degenerate in nature, economy and social function, seriously blocking the sustai...The paper had pointed out hollow ancient town was the result of urbanization and desire; and analyzed that hollowness made ancient towns degenerate in nature, economy and social function, seriously blocking the sustainable development of economic society of ancient towns. Based on the connotation and idea of cultural reproduction, in terms of application of basic theories of cultural ecology and restoration ecology, it had established tourism development of solid ancient towns, which had been analyzed specifically from the perspectives of representation of ancient towns'scene, cultural realization and cultural promotion. By taking Zouwa Ancient Town in the west of the main urban area of Chongqing City for example, it had discussed tourism development practice of ancient towns, emphasized making Zouma scene reappear from the aspects of pattern protection, restoration and treatment of ecological environment, ancient towns' protection and cultural facilities' construction, experiencing and publicizing Zouma culture. It also highlighted taking historical and cultural heritages as the theme of tourist products, and proposed development mode of solid ancient towns, realizing reproduction of cultural heritage.展开更多
We present the numerical simulation results of a model granular assembly formed by spherical particles with tIertzian interaction subjected to a simple shear in the athermal quasi-static limit. The stress-strain curve...We present the numerical simulation results of a model granular assembly formed by spherical particles with tIertzian interaction subjected to a simple shear in the athermal quasi-static limit. The stress-strain curve is shown to separate into smooth, elastic branches followed by a subsequent plastic event. Mode analysis shows that the lowest-frequency vibrational mode is more localized, and eigenvalues and participation ratios of low- frequency modes exhibit similar power-law behavior as the system approaches plastic instability, indicating that the nature of plastic events in the granular system is also a saddle node bifurcation. The analysis of projection and spatial structure shows that over 75% contributions to the non-affine displacement field at a plastic instability come from the lowest-frequency mode, and the lowest-frequency mode is strongly spatially correlated with local plastic rearrangements, inferring that the lowest-frequency mode could be used as a predictor for future plastic rearrangements in the disordered system jammed marginally.展开更多
Introducing the nonlinear Rayleigh damping into the governing equation of the Mode Ⅲ dynamic rupture for standard viscoelastic solid, this equation is a partial differential and integral equation. First, eliminating ...Introducing the nonlinear Rayleigh damping into the governing equation of the Mode Ⅲ dynamic rupture for standard viscoelastic solid, this equation is a partial differential and integral equation. First, eliminating the integral term, a PDE of third_order is obtained. Then, applying the small parameter expansion method, linearized asymptotic governing equation for each order of the small parameter is obtained. Dividing the third_order PDE into an elastic part with known solution, the rest part pertains to viscous effect which is neither a Mathieu equation nor a Hill one. The WKBJ method is still adopted to solve it analytically.展开更多
This paper demonstrates the passively mode-locked Nd：GdVO4 laser operating on the ^4F3/2-^4I9/2 transition at 912 nm by using a semiconductor saturable-absorber mirror for passive mode locking, stable continuous wave...This paper demonstrates the passively mode-locked Nd：GdVO4 laser operating on the ^4F3/2-^4I9/2 transition at 912 nm by using a semiconductor saturable-absorber mirror for passive mode locking, stable continuous wave modelocked 912nm laser was achieved with a repetition rate of 176 MHz. At the incident pump power of 17.7W, 22.6mW average output power of stable mode-locked laser was obtained with a slope efficiency of 0.3%.展开更多
An experimental investigation is carried out to machine SiC ceramic material through the method of high speed plane lapping with solid(fixed) abrasives after the critical condition of brittle-ductile transition is the...An experimental investigation is carried out to machine SiC ceramic material through the method of high speed plane lapping with solid(fixed) abrasives after the critical condition of brittle-ductile transition is theoretically analyzed. The results show that the material removal mechanism and the surface roughness are chiefly related to the granularity of abrasives for brittle materials such as SiC ceramic. It is easily realized to machine SiC ceramic in the ductile mode using W3.5 grit and a high efficiency, low cost and smooth surface with a surface roughness of R_a 2.4?nm can be achieved.展开更多
We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond（fs） laser with a self-frequency doubling Yb：YCa_4O（BO_3）_3 crystal.Sub-40 fs laser pulses were directly generated from the oscillato...We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond（fs） laser with a self-frequency doubling Yb：YCa_4O（BO_3）_3 crystal.Sub-40 fs laser pulses were directly generated from the oscillator without extracavity compression.The central wavelength was tunable from 1039 nm to 1049 nm with a typical bandwidth of 35 nm and an average output power of 53 mW.For the first time,a self-frequency doubled second harmonic green laser with tunable range from 519 nm to 525 nm was observed.展开更多
A compact high power diode-pumped passively mode-locked Nd:YVO_4 laser with high repetition rate is realized.Using an Nd:YVO_4 crystal and a semiconductor saturable absorber mirror(SESAM) in the oscillator, the picose...A compact high power diode-pumped passively mode-locked Nd:YVO_4 laser with high repetition rate is realized.Using an Nd:YVO_4 crystal and a semiconductor saturable absorber mirror(SESAM) in the oscillator, the picosecond pulse output with an average power of 1.38 W, a repetition rate of 3.24 GHz, and a pulse duration of 11.4 ps is achieved. After one stage of amplification, the final output power reaches 11.34 W, corresponding to a total optical-to-optical efficiency of about 32%. The root mean square(RMS) value of power fluctuation is demonstrated to be less than 0.6% in 24 hours,showing a superior stability with the compact configuration.展开更多
基金Supported by Research Project of Humanities and Social Science of Ministry of Education(No.01JD790003)~~
文摘The paper had pointed out hollow ancient town was the result of urbanization and desire; and analyzed that hollowness made ancient towns degenerate in nature, economy and social function, seriously blocking the sustainable development of economic society of ancient towns. Based on the connotation and idea of cultural reproduction, in terms of application of basic theories of cultural ecology and restoration ecology, it had established tourism development of solid ancient towns, which had been analyzed specifically from the perspectives of representation of ancient towns'scene, cultural realization and cultural promotion. By taking Zouwa Ancient Town in the west of the main urban area of Chongqing City for example, it had discussed tourism development practice of ancient towns, emphasized making Zouma scene reappear from the aspects of pattern protection, restoration and treatment of ecological environment, ancient towns' protection and cultural facilities' construction, experiencing and publicizing Zouma culture. It also highlighted taking historical and cultural heritages as the theme of tourist products, and proposed development mode of solid ancient towns, realizing reproduction of cultural heritage.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11272048 and 51239006the European Commission Marie Curie Actions under Grant No IRSES-294976
文摘We present the numerical simulation results of a model granular assembly formed by spherical particles with tIertzian interaction subjected to a simple shear in the athermal quasi-static limit. The stress-strain curve is shown to separate into smooth, elastic branches followed by a subsequent plastic event. Mode analysis shows that the lowest-frequency vibrational mode is more localized, and eigenvalues and participation ratios of low- frequency modes exhibit similar power-law behavior as the system approaches plastic instability, indicating that the nature of plastic events in the granular system is also a saddle node bifurcation. The analysis of projection and spatial structure shows that over 75% contributions to the non-affine displacement field at a plastic instability come from the lowest-frequency mode, and the lowest-frequency mode is strongly spatially correlated with local plastic rearrangements, inferring that the lowest-frequency mode could be used as a predictor for future plastic rearrangements in the disordered system jammed marginally.
文摘Introducing the nonlinear Rayleigh damping into the governing equation of the Mode Ⅲ dynamic rupture for standard viscoelastic solid, this equation is a partial differential and integral equation. First, eliminating the integral term, a PDE of third_order is obtained. Then, applying the small parameter expansion method, linearized asymptotic governing equation for each order of the small parameter is obtained. Dividing the third_order PDE into an elastic part with known solution, the rest part pertains to viscous effect which is neither a Mathieu equation nor a Hill one. The WKBJ method is still adopted to solve it analytically.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60225005, 60308001, 60321003 and 60490280）.
文摘This paper demonstrates the passively mode-locked Nd：GdVO4 laser operating on the ^4F3/2-^4I9/2 transition at 912 nm by using a semiconductor saturable-absorber mirror for passive mode locking, stable continuous wave modelocked 912nm laser was achieved with a repetition rate of 176 MHz. At the incident pump power of 17.7W, 22.6mW average output power of stable mode-locked laser was obtained with a slope efficiency of 0.3%.
文摘An experimental investigation is carried out to machine SiC ceramic material through the method of high speed plane lapping with solid(fixed) abrasives after the critical condition of brittle-ductile transition is theoretically analyzed. The results show that the material removal mechanism and the surface roughness are chiefly related to the granularity of abrasives for brittle materials such as SiC ceramic. It is easily realized to machine SiC ceramic in the ductile mode using W3.5 grit and a high efficiency, low cost and smooth surface with a surface roughness of R_a 2.4?nm can be achieved.
基金Project supported by the National Major Scientific Instruments Development Project of China(Grant No.2012YQ120047)the National Natural Science Foundation of China(Grant No.61205130)the Doctor Fund from Southwest University,China(Grant No.SWU110645)
文摘We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond（fs） laser with a self-frequency doubling Yb：YCa_4O（BO_3）_3 crystal.Sub-40 fs laser pulses were directly generated from the oscillator without extracavity compression.The central wavelength was tunable from 1039 nm to 1049 nm with a typical bandwidth of 35 nm and an average output power of 53 mW.For the first time,a self-frequency doubled second harmonic green laser with tunable range from 519 nm to 525 nm was observed.
基金Project supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB16030200)the National Natural Science Foundation of China(Grant Nos.11774410 and 61575217)+1 种基金the National Key Scientific Instruments Development Program of China(Grant No.2012YQ120047)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.KJZD-EW-L11-03)
文摘A compact high power diode-pumped passively mode-locked Nd:YVO_4 laser with high repetition rate is realized.Using an Nd:YVO_4 crystal and a semiconductor saturable absorber mirror(SESAM) in the oscillator, the picosecond pulse output with an average power of 1.38 W, a repetition rate of 3.24 GHz, and a pulse duration of 11.4 ps is achieved. After one stage of amplification, the final output power reaches 11.34 W, corresponding to a total optical-to-optical efficiency of about 32%. The root mean square(RMS) value of power fluctuation is demonstrated to be less than 0.6% in 24 hours,showing a superior stability with the compact configuration.
