The estimation of shear strength of rock mass discontinuity is always a focal, but difficult, problem in the field of geotechnical engineering. Considering the disadvantages and limitation of exist- ing estimation met...The estimation of shear strength of rock mass discontinuity is always a focal, but difficult, problem in the field of geotechnical engineering. Considering the disadvantages and limitation of exist- ing estimation methods, a new approach based on the shadow area percentage （SAP） that can be used to quantify surface roughness is proposed in this article. Firstly, by the help of laser scanning technique, the three-dimensional model of the surface of rock discontinuity was established. Secondly, a light source was simulated, and there would be some shadows produced on the model surface. Thirdly, to obtain the value of SAP of each specimen, the shadow detection technique was introduced for use. Fourthly, compared with the result from direct shear testing and based on statistics, an empirical for- mula was found among SAP, normal stress, and shear strength. Data of Yujian （~ River were used as an example, and the following conclusions have been made. （1） In the case of equal normal stress, the peak shear stress is positively proportional to the SAP. （2） The formula for estimating was derived, and the predictions of peak-shear strength made with this equation well agreed with the experimental re- suits obtained in laboratory tests.展开更多
High speed pseudorandom modulation and photon counting techniques are applied to a three-dimensional imaging lidar system.The specific structure and working principle of the lidar system is described.The actual detect...High speed pseudorandom modulation and photon counting techniques are applied to a three-dimensional imaging lidar system.The specific structure and working principle of the lidar system is described.The actual detector efficiency of a single-photon detector in an imaging system is discussed,and the result shows that a variety of reasons lead to the decrease in detection efficiency.A series of ranging and imaging experiments are conducted,and a series of high-resolution three-dimensional images and a distance value of 1200 m of noncooperative targets are acquired.展开更多
Two-color multiphoton microscopy through wavelength mixing of synchronized lasers has been shown to increase the spectral window of excitable fluorophores without the need for wavelength tuning.However,most currently ...Two-color multiphoton microscopy through wavelength mixing of synchronized lasers has been shown to increase the spectral window of excitable fluorophores without the need for wavelength tuning.However,most currently available dual output laser sources rely on the costly and complicated optical parametric generation approach.In this report,we detail a relatively simple and low cost diamond Raman laser pumped by a ytterbium fiber amplifier emitting at 1055 nm,which generates a first Stokes emission centered at 1240 nm with a pulse width of 100 fs.The two excitation wavelengths of 1055 and 1240 nm,along with the effective two-color excitation wavelength of 1140 nm,provide an almost complete coverage of fluorophores excitable within the range of 1000–1300 nm.When compared with 1055 nm excitation,two-color excitation at 1140 nm offers a 90%increase in signal for many far-red emitting fluorescent proteins(for example,tdKatushka2).We demonstrate multicolor imaging of tdKatushka2 and Hoechst 33342 via simultaneous two-color two-photon,and two-color three-photon microscopy in engineered 3D multicellular spheroids.We further discuss potential benefits and applications for two-color three-photon excitation.In addition,we show that this laser system is capable of in vivo imaging in mouse cortex to nearly 1 mm in depth with two-color excitation.展开更多
基金supported by the China Geological Survey (No.1212011014030)the Major State Basic Research Development Program of China (973 Program) (No.2011CB710600)
文摘The estimation of shear strength of rock mass discontinuity is always a focal, but difficult, problem in the field of geotechnical engineering. Considering the disadvantages and limitation of exist- ing estimation methods, a new approach based on the shadow area percentage （SAP） that can be used to quantify surface roughness is proposed in this article. Firstly, by the help of laser scanning technique, the three-dimensional model of the surface of rock discontinuity was established. Secondly, a light source was simulated, and there would be some shadows produced on the model surface. Thirdly, to obtain the value of SAP of each specimen, the shadow detection technique was introduced for use. Fourthly, compared with the result from direct shear testing and based on statistics, an empirical for- mula was found among SAP, normal stress, and shear strength. Data of Yujian （~ River were used as an example, and the following conclusions have been made. （1） In the case of equal normal stress, the peak shear stress is positively proportional to the SAP. （2） The formula for estimating was derived, and the predictions of peak-shear strength made with this equation well agreed with the experimental re- suits obtained in laboratory tests.
基金supported by the Innovation Fund(No.CXJJ16M102)the National 973 Program of China (No.613192)
文摘High speed pseudorandom modulation and photon counting techniques are applied to a three-dimensional imaging lidar system.The specific structure and working principle of the lidar system is described.The actual detector efficiency of a single-photon detector in an imaging system is discussed,and the result shows that a variety of reasons lead to the decrease in detection efficiency.A series of ranging and imaging experiments are conducted,and a series of high-resolution three-dimensional images and a distance value of 1200 m of noncooperative targets are acquired.
基金supported by the National Institutes of Health(NS082518,CA193038,NS078791 and EB011556)the American Heart Association(14EIA18970041)Cancer Prevention Research Institute of Texas(RR160005)。
文摘Two-color multiphoton microscopy through wavelength mixing of synchronized lasers has been shown to increase the spectral window of excitable fluorophores without the need for wavelength tuning.However,most currently available dual output laser sources rely on the costly and complicated optical parametric generation approach.In this report,we detail a relatively simple and low cost diamond Raman laser pumped by a ytterbium fiber amplifier emitting at 1055 nm,which generates a first Stokes emission centered at 1240 nm with a pulse width of 100 fs.The two excitation wavelengths of 1055 and 1240 nm,along with the effective two-color excitation wavelength of 1140 nm,provide an almost complete coverage of fluorophores excitable within the range of 1000–1300 nm.When compared with 1055 nm excitation,two-color excitation at 1140 nm offers a 90%increase in signal for many far-red emitting fluorescent proteins(for example,tdKatushka2).We demonstrate multicolor imaging of tdKatushka2 and Hoechst 33342 via simultaneous two-color two-photon,and two-color three-photon microscopy in engineered 3D multicellular spheroids.We further discuss potential benefits and applications for two-color three-photon excitation.In addition,we show that this laser system is capable of in vivo imaging in mouse cortex to nearly 1 mm in depth with two-color excitation.
