sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which ob...sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: ① The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; ② The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; ③ Before the main rupture of the rock sample the obvious ″tendency anomaly′ and ′short-term anomaly″ were observed, and some of them could be likely considered as the ″impending earthquake ″anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically.展开更多
Laser surface transformation hardening becomes one of the most modern processes used to improve fatigue and wear properties of steel surfaces. In this process, the material properties and the heating parameters are th...Laser surface transformation hardening becomes one of the most modern processes used to improve fatigue and wear properties of steel surfaces. In this process, the material properties and the heating parameters are the factors that present the most significant effects on the hardened surface attributes. The control of these factors using predictive modeling approaches to achieve desired surface properties leads to conclusive results. However, when the dimensions of the surface to be treated are larger than the cross-section of the laser beam, various laser-scanning patterns are involved. This paper presents an experimental investigation of laser surface hardening of AISI 4340 steel using different laser scanning patterns. This investigation is based on a structured experimental design using the Taguchi method and improved statistical analysis tools. Experiments are carried out using a 3 kW Nd: YAG laser source in order to evaluate the effects of the heating parameters and patterns design parameters on the physical and geometrical characteristics of the hardened surface. Laser power, scanning speed and scanning patterns (linear, sinusoidal, triangular and trochoid) are the factors used to evaluate the hardened depth and the hardened width variations and to identify the possible relationship between these factors and the hardened zone attributes. Various statistical tools such as ANOVA, correlations analysis and response surfaces are applied in order to examine the effects of the experimental factors on the hardened surface characteristics. The results reveal that the scanning patterns do not modify the nature of the laser parameters’ effects on the hardened depth and the hardened width. But they can accentuate or reduce these effects depending on the type of the considered pattern. The results show also that the sinusoidal and the triangular patterns are relevant when a maximum hardened width with an acceptable hardened depth is desired.展开更多
Brief introduction of experiments,laboratories and stations in geomorphology.The achievements in experimental fluvial geomorphology gained in the last 30 years in China include channel pattern modelling,studies on inf...Brief introduction of experiments,laboratories and stations in geomorphology.The achievements in experimental fluvial geomorphology gained in the last 30 years in China include channel pattern modelling,studies on influence of boundary conditions,applications of fluvial geomorphology,its experimental theories and techniques,etc.Problems in fluvial geomorphic experiments are indicated,tendencies in the development of this branch of geomorphology are predicted,and suggestions are made.展开更多
In coping with the global financial crisis, all levels of the Chinese government and foreign trade firms have not only created new practices but have also changed their goal from transforming the growth pattern of for...In coping with the global financial crisis, all levels of the Chinese government and foreign trade firms have not only created new practices but have also changed their goal from transforming the growth pattern of foreign trade to transforming the development pattern of joreign trade. China＇s experience shows that economic instruments such as Net Barter Terms of Trade （NBTT） and the smile curve theory have limitations when it comes to interpreting foreign trade. If used improperly, scientific theories often lead to.fallacies. Transjbrming the development pattern of China＇s .foreign trade requires the following changes： national income distribution, foreign trade competition, market exploration, and resource utilization. We advise that competent authorities create a reasonable and operational system of assessment indicators.展开更多
文摘sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: ① The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; ② The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; ③ Before the main rupture of the rock sample the obvious ″tendency anomaly′ and ′short-term anomaly″ were observed, and some of them could be likely considered as the ″impending earthquake ″anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically.
文摘Laser surface transformation hardening becomes one of the most modern processes used to improve fatigue and wear properties of steel surfaces. In this process, the material properties and the heating parameters are the factors that present the most significant effects on the hardened surface attributes. The control of these factors using predictive modeling approaches to achieve desired surface properties leads to conclusive results. However, when the dimensions of the surface to be treated are larger than the cross-section of the laser beam, various laser-scanning patterns are involved. This paper presents an experimental investigation of laser surface hardening of AISI 4340 steel using different laser scanning patterns. This investigation is based on a structured experimental design using the Taguchi method and improved statistical analysis tools. Experiments are carried out using a 3 kW Nd: YAG laser source in order to evaluate the effects of the heating parameters and patterns design parameters on the physical and geometrical characteristics of the hardened surface. Laser power, scanning speed and scanning patterns (linear, sinusoidal, triangular and trochoid) are the factors used to evaluate the hardened depth and the hardened width variations and to identify the possible relationship between these factors and the hardened zone attributes. Various statistical tools such as ANOVA, correlations analysis and response surfaces are applied in order to examine the effects of the experimental factors on the hardened surface characteristics. The results reveal that the scanning patterns do not modify the nature of the laser parameters’ effects on the hardened depth and the hardened width. But they can accentuate or reduce these effects depending on the type of the considered pattern. The results show also that the sinusoidal and the triangular patterns are relevant when a maximum hardened width with an acceptable hardened depth is desired.
文摘Brief introduction of experiments,laboratories and stations in geomorphology.The achievements in experimental fluvial geomorphology gained in the last 30 years in China include channel pattern modelling,studies on influence of boundary conditions,applications of fluvial geomorphology,its experimental theories and techniques,etc.Problems in fluvial geomorphic experiments are indicated,tendencies in the development of this branch of geomorphology are predicted,and suggestions are made.
文摘In coping with the global financial crisis, all levels of the Chinese government and foreign trade firms have not only created new practices but have also changed their goal from transforming the growth pattern of foreign trade to transforming the development pattern of joreign trade. China＇s experience shows that economic instruments such as Net Barter Terms of Trade （NBTT） and the smile curve theory have limitations when it comes to interpreting foreign trade. If used improperly, scientific theories often lead to.fallacies. Transjbrming the development pattern of China＇s .foreign trade requires the following changes： national income distribution, foreign trade competition, market exploration, and resource utilization. We advise that competent authorities create a reasonable and operational system of assessment indicators.
