The paper proposes an evolutionary computational model, multiple structure computational model,from simulaing the behavior of the ecosystem. Some numerical experiments shoal the new model can solve some GA-hard proble...The paper proposes an evolutionary computational model, multiple structure computational model,from simulaing the behavior of the ecosystem. Some numerical experiments shoal the new model can solve some GA-hard problems. Using the concept of adaility in abaptability' in ecology, we give a theoretical analysis to explain why the new model is efficient.展开更多
The stress state in a rock mass is complex. Stress redistribution around underground excavation may lead to various failure modes, including compressive-shear, tensile-shear, and tensile failures. The ability to perfo...The stress state in a rock mass is complex. Stress redistribution around underground excavation may lead to various failure modes, including compressive-shear, tensile-shear, and tensile failures. The ability to perform laboratory tests with these complex stress states is significant for establishing new strength criteria. The present paper introduces a new rock testing system with “tensile-compressive-shear”loading functions. The device includes bi-directional and double-range hydraulic cylinders, auxiliary loading equipment, and roller rows that can perform direct compressive-shear tests, direct tensile tests,and direct tensile-shear tests. The testing system provides maximum vertical and lateral loading forces of2000 k N and allows testing cubical rock specimens with dimensions of 0.5 m × 0.5 m × 0.5 m. The performance of the testing machine was evaluated by testing a rock-like material based on cement mortar under compressive-shear, tensile, and tensile-shear stress states. The failure process and deformation characteristics were monitored during loading using acoustic emission(AE) transient recorder,piezoelectric AE sensors, a high-speed camera, and a thermal infrared camera. The failure mechanism was investigated by analyzing AE counts, AE amplitude, strain, and temperature changes on the rock specimen surface. The test results confirmed that the testing system could successfully simulate the abovementioned stress path. The AE counts and amplitude responses were influenced by different failure modes. The temperature response during the compressive-shear test indicated the development of a high-temperature band on the rock specimen surface. In contrast, a negligible temperature change was observed during the tensile and tensile-shear tests. The newly developed multifunctional rock testing system allows laboratory tests under various failure modes. The monitoring results of multiple variables during rock failure tests provide valuable information on failure characteristics.展开更多
Professor Duzheng YE＇s name has been familiar to me ever since my postdoctoral years at MIT with Professors Jule CHARNEY and Norman PHILLIPS, back in the late 1960 s. I had the enormous pleasure of meeting Professor ...Professor Duzheng YE＇s name has been familiar to me ever since my postdoctoral years at MIT with Professors Jule CHARNEY and Norman PHILLIPS, back in the late 1960 s. I had the enormous pleasure of meeting Professor YE personally in 1992 in Beijing. His concern to promote the very best science and to use it well, and his thinking on multi-level orderly human activities, reminds me not only of the communication skills we need as scientists but also of the multi-level nature of science itself. Here I want to say something（a） about what science is;（b） about why multi-level thinking—and taking more than one viewpoint—is so important for scientific as well as for other forms of understanding; and（c） about what is meant, at a deep level, by ＂scientific understanding＂ and trying to communicate it, not only with lay persons but also across professional disciplines. I hope that Professor YE would approve.展开更多
文摘The paper proposes an evolutionary computational model, multiple structure computational model,from simulaing the behavior of the ecosystem. Some numerical experiments shoal the new model can solve some GA-hard problems. Using the concept of adaility in abaptability' in ecology, we give a theoretical analysis to explain why the new model is efficient.
基金funding support from the National Natural Science Foundation of China (Grant Nos. U1806226 and 51979154)。
文摘The stress state in a rock mass is complex. Stress redistribution around underground excavation may lead to various failure modes, including compressive-shear, tensile-shear, and tensile failures. The ability to perform laboratory tests with these complex stress states is significant for establishing new strength criteria. The present paper introduces a new rock testing system with “tensile-compressive-shear”loading functions. The device includes bi-directional and double-range hydraulic cylinders, auxiliary loading equipment, and roller rows that can perform direct compressive-shear tests, direct tensile tests,and direct tensile-shear tests. The testing system provides maximum vertical and lateral loading forces of2000 k N and allows testing cubical rock specimens with dimensions of 0.5 m × 0.5 m × 0.5 m. The performance of the testing machine was evaluated by testing a rock-like material based on cement mortar under compressive-shear, tensile, and tensile-shear stress states. The failure process and deformation characteristics were monitored during loading using acoustic emission(AE) transient recorder,piezoelectric AE sensors, a high-speed camera, and a thermal infrared camera. The failure mechanism was investigated by analyzing AE counts, AE amplitude, strain, and temperature changes on the rock specimen surface. The test results confirmed that the testing system could successfully simulate the abovementioned stress path. The AE counts and amplitude responses were influenced by different failure modes. The temperature response during the compressive-shear test indicated the development of a high-temperature band on the rock specimen surface. In contrast, a negligible temperature change was observed during the tensile and tensile-shear tests. The newly developed multifunctional rock testing system allows laboratory tests under various failure modes. The monitoring results of multiple variables during rock failure tests provide valuable information on failure characteristics.
文摘Professor Duzheng YE＇s name has been familiar to me ever since my postdoctoral years at MIT with Professors Jule CHARNEY and Norman PHILLIPS, back in the late 1960 s. I had the enormous pleasure of meeting Professor YE personally in 1992 in Beijing. His concern to promote the very best science and to use it well, and his thinking on multi-level orderly human activities, reminds me not only of the communication skills we need as scientists but also of the multi-level nature of science itself. Here I want to say something（a） about what science is;（b） about why multi-level thinking—and taking more than one viewpoint—is so important for scientific as well as for other forms of understanding; and（c） about what is meant, at a deep level, by ＂scientific understanding＂ and trying to communicate it, not only with lay persons but also across professional disciplines. I hope that Professor YE would approve.
