Fast methods to solve the unloading problem of a cylindrical cavity or tunnel excavated in elasto-perfectly plastic, elasto-brittle or strain-softening materials under a hydrostatic stress feld can be derived based on...Fast methods to solve the unloading problem of a cylindrical cavity or tunnel excavated in elasto-perfectly plastic, elasto-brittle or strain-softening materials under a hydrostatic stress feld can be derived based on the self-similarity of the solution. As a consequence, they only apply when the rock mass is homogeneous and so exclude many cases of practical interest. We describe a robust and fast numerical technique that solves the tunnel unloading problem and estimates the ground reaction curve for a cylindrical cavity excavated in a rock mass with properties depending on the radial coordinate, where the solution is no longer self-similar. The solution is based on a continuation-like approach(associated with the unloading and with the incremental formulation of the elasto-plastic behavior), fnite element spatial discretization and a combination of explicit sub-stepping schemes and implicit techniques to integrate the constitutive law, so as to tackle the diffculties associated with both strong strain-softening and elasto-brittle behaviors. The developed algorithm is used for two practical ground reaction curve computation applications. The frst application refers to a tunnel surrounded by an aureole of material damaged by blasting and the second to a tunnel surrounded by a ring-like zone of reinforced(rock-bolted) material.展开更多
We have grown underdoped (х = 0.11, 0.12) and optimally doped (x = 0.16)La2-хSrхCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have ma...We have grown underdoped (х = 0.11, 0.12) and optimally doped (x = 0.16)La2-хSrхCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have made much effort to optimize the preparation procedures.For example,we haveadopted the sol-gel route to prepare a highly fine and homogeneous La2-хSrхCuO4 precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth,and we have also used quite a slow growth rate. The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves,with the full-width-at-half-maximum being only 113-150 arcseconds, which are the best data reported so far for La2-хSrхCuO4 crystals.The superconducting critical temperatures of the grown crystals are 30, 31 and 38.5 K for х = 0.11, 0.12 and 0.16 samples, respectively,according to magnetic measurements.展开更多
We present a moment-based alternative approach to retrieve multiple scattering contrasts from x-ray analyzer-based imaging. By use of the properties of moments of convolutions, the multiple-image radiography approach ...We present a moment-based alternative approach to retrieve multiple scattering contrasts from x-ray analyzer-based imaging. By use of the properties of moments of convolutions, the multiple-image radiography approach is theoretically validated. Furthermore, higher order moments of the object scattering distribution, inaccessible in multiple-image radiography, are simultaneously provided by this alternative approach. It is experimentally demonstrated that the skew and kurtosis information related to the distribution of sub-pixel features within the object can be obtained from those complementary contrasts. Finally, the sensitivity of the retrieved multiple scattering contrasts is investigated experimentally. The finding that the sensitivity is inversely proportional to the square root of the detected photon number essentially indicates that the retrieval of moments with an order higher than two can be achieved without increasing exposure time or dose. The presented alternative approach provides an access to the exploitation of multiple scattering contrasts, which is expected to be useful in biomedical research, materials science, security screening, etc.展开更多
This paper introduces horizon control, seismic control, logging control and facies control methods through the application of the least squares fitting of logging curves, seismic inversion and facies-controlled techni...This paper introduces horizon control, seismic control, logging control and facies control methods through the application of the least squares fitting of logging curves, seismic inversion and facies-controlled techniques. Based on the microgeology and thin section analyses, the lithology, lithofacies and periods of the Permian igneous rocks are described in detail. The seismic inversion and facies-controlled techniques were used to find the distribution characteristics of the igneous rocks and the 3D velocity volume. The least squares fitting of the logging curves overcome the problem that the work area is short of density logging data. Through analysis of thin sections, the lithofacies can be classified into eruption airfall subfacies, eruption pyroclastic flow subfacies and eruption facies.展开更多
Neovascularization is correlative with many processes of diseases, especially for tumor growth, invasion, and metastasis. What is more, these tumor microvessels are totally different from normal vessels in morphology....Neovascularization is correlative with many processes of diseases, especially for tumor growth, invasion, and metastasis. What is more, these tumor microvessels are totally different from normal vessels in morphology. Therefore, observation of the morphologic distribution of microvessels is one of the key points for many researchers in the field. Using diffraction enhanced imaging (DEI), we observed the mirocvessles with diameter of about 40 μm in mouse liver. Moreover, the refraction image obtained from DEI shows higher image contrast and exhibits potential use for medical applications.展开更多
基金the Spanish Ministry of Science and Technology for fnancial support awarded under Contract Reference Numbers BIA2009-09673 and MTM2010-21235-C02-02
文摘Fast methods to solve the unloading problem of a cylindrical cavity or tunnel excavated in elasto-perfectly plastic, elasto-brittle or strain-softening materials under a hydrostatic stress feld can be derived based on the self-similarity of the solution. As a consequence, they only apply when the rock mass is homogeneous and so exclude many cases of practical interest. We describe a robust and fast numerical technique that solves the tunnel unloading problem and estimates the ground reaction curve for a cylindrical cavity excavated in a rock mass with properties depending on the radial coordinate, where the solution is no longer self-similar. The solution is based on a continuation-like approach(associated with the unloading and with the incremental formulation of the elasto-plastic behavior), fnite element spatial discretization and a combination of explicit sub-stepping schemes and implicit techniques to integrate the constitutive law, so as to tackle the diffculties associated with both strong strain-softening and elasto-brittle behaviors. The developed algorithm is used for two practical ground reaction curve computation applications. The frst application refers to a tunnel surrounded by an aureole of material damaged by blasting and the second to a tunnel surrounded by a ring-like zone of reinforced(rock-bolted) material.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB0L0302)the National Natural Science Foundation of China (Grant No 10574149)
文摘We have grown underdoped (х = 0.11, 0.12) and optimally doped (x = 0.16)La2-хSrхCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have made much effort to optimize the preparation procedures.For example,we haveadopted the sol-gel route to prepare a highly fine and homogeneous La2-хSrхCuO4 precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth,and we have also used quite a slow growth rate. The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves,with the full-width-at-half-maximum being only 113-150 arcseconds, which are the best data reported so far for La2-хSrхCuO4 crystals.The superconducting critical temperatures of the grown crystals are 30, 31 and 38.5 K for х = 0.11, 0.12 and 0.16 samples, respectively,according to magnetic measurements.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11475170,U1532113,and 11905041)the Fundamental Research Funds for the Central Universities,China(Grant No.PA2020GDKC0024)。
文摘We present a moment-based alternative approach to retrieve multiple scattering contrasts from x-ray analyzer-based imaging. By use of the properties of moments of convolutions, the multiple-image radiography approach is theoretically validated. Furthermore, higher order moments of the object scattering distribution, inaccessible in multiple-image radiography, are simultaneously provided by this alternative approach. It is experimentally demonstrated that the skew and kurtosis information related to the distribution of sub-pixel features within the object can be obtained from those complementary contrasts. Finally, the sensitivity of the retrieved multiple scattering contrasts is investigated experimentally. The finding that the sensitivity is inversely proportional to the square root of the detected photon number essentially indicates that the retrieval of moments with an order higher than two can be achieved without increasing exposure time or dose. The presented alternative approach provides an access to the exploitation of multiple scattering contrasts, which is expected to be useful in biomedical research, materials science, security screening, etc.
基金A Project Funded by National Science and Technology Major Project (2011ZX05001-002-003)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)Key Laboratory for Coalbed Methane Resources and Reservoir formation Process, CUMT, Ministry of Education, China
文摘This paper introduces horizon control, seismic control, logging control and facies control methods through the application of the least squares fitting of logging curves, seismic inversion and facies-controlled techniques. Based on the microgeology and thin section analyses, the lithology, lithofacies and periods of the Permian igneous rocks are described in detail. The seismic inversion and facies-controlled techniques were used to find the distribution characteristics of the igneous rocks and the 3D velocity volume. The least squares fitting of the logging curves overcome the problem that the work area is short of density logging data. Through analysis of thin sections, the lithofacies can be classified into eruption airfall subfacies, eruption pyroclastic flow subfacies and eruption facies.
基金Supported by National Natural Science Foundation of China (30471652)
文摘Neovascularization is correlative with many processes of diseases, especially for tumor growth, invasion, and metastasis. What is more, these tumor microvessels are totally different from normal vessels in morphology. Therefore, observation of the morphologic distribution of microvessels is one of the key points for many researchers in the field. Using diffraction enhanced imaging (DEI), we observed the mirocvessles with diameter of about 40 μm in mouse liver. Moreover, the refraction image obtained from DEI shows higher image contrast and exhibits potential use for medical applications.