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
In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different para...In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.展开更多
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
Aiming at the requirement of autonomous navigation capability of the underwater unmanned vehicle(UUV),a novel bionic method for underwater navigation based on polarization pattern within Snell’s window is proposed.In...Aiming at the requirement of autonomous navigation capability of the underwater unmanned vehicle(UUV),a novel bionic method for underwater navigation based on polarization pattern within Snell’s window is proposed.Inspired by creatures,polarization navigation is a satellite-free navigation scheme and has great potential to be used in the water.However,because of the complex underwater environment,whether UUV polarization navigation can be realized is doubtful.To illustrate the feasibility of underwater polarization navigation,we firstly establish the model of under-water polarization patterns to prove the stability and predictability of the underwater polarization pattern within Snell’s window.Then,we carry out static and dynamic experiments of underwater heading determination based on developed polarization information detection equipment.Finally,we obtain underwater polarization patterns and conduct the tracking experiment at different water depths.The experimental results of the underwater polarization patterns are consistent with the simulation,which proves the correctness of the proposed model.At the water depth of 5 m,the average angle and position error of the tracking experiment are 14.3508°and 4.0812 m,respectively.It is illustrated that underwater polarization navigation is realizable and the precision can meet the real-time navigation requirements of UUV.This study promotes the improvement of underwater navigation ability and the development of marine equipment.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
According to the theory of Matsuoka neural oscillators and with the con- sideration of the fact that the human upper arm mainly consists of six muscles, a new kind of central pattern generator （CPG） neural network c...According to the theory of Matsuoka neural oscillators and with the con- sideration of the fact that the human upper arm mainly consists of six muscles, a new kind of central pattern generator （CPG） neural network consisting of six neurons is pro- posed to regulate the contraction of the upper arm muscles. To verify effectiveness of the proposed CPG network, an arm motion control model based on the CPG is established. By adjusting the CPG parameters, we obtain the neural responses of the network, the angles of joint and hand of the model with MATLAB. The simulation results agree with the results of crank rotation experiments designed by Ohta et al., showing that the arm motion control model based on a CPG network is reasonable and effective.展开更多
The rapid changes in flow pattern due to varying channel widths will make significantly impact on the hydraulic structures and evolutions of open channel. To better understand the impact of varying width, a flume expe...The rapid changes in flow pattern due to varying channel widths will make significantly impact on the hydraulic structures and evolutions of open channel. To better understand the impact of varying width, a flume experiment with adjustable width and a depth-averaged two-dimension numerical model were used to analyze the variations of flow parameters. Our experimental results showed that flow velocity gradually increased with decreasing water depth in converging region, and decreased with increasing water depth in diverging zones. It was also found that the turbulence intensity laws in three directions were not agreed with the theoretical relationships proposed by Nezu and Nakagawa in 1993 in straight open channel flows. The flow in the channel with varying width may change from the supercritical flow to the subcritical flow as a function of Froude number. Our numerical simulations with different flow rates showed that most of the hydraulic jumps in diverging region were submerged jump and the degree of submergence increased with increasing flow rate in gradual channel transition. When the flow rate increased, the range of supercritical flow rapidly decreased and the flow changed from the supercritieal condition to the subcritical condition in diverging sections.展开更多
objective： to analyze the application value of the PBL in the surgical experimental teaching mode. Methods： choose between September 2013 and September 2013 128 clinical professional students, average by using the l...objective： to analyze the application value of the PBL in the surgical experimental teaching mode. Methods： choose between September 2013 and September 2013 128 clinical professional students, average by using the lottery will be divided into control group and the team, every 64 students for 1 set, in surgical experimental teaching as a research courses, the teaching methods for the traditional teaching method in the control group, while the team gives PBL teaching mode, the teaching effect of the final will be two groups of students are analyzed and compared. Results： through different teaching methods for teaching, compared with control group, the group at the student＇s test scores, and the ability to significantly higher, the difference of both P 〈 0.05, there is statistically significant. Conclusion： using PBL teaching mode in the surgical experimental teaching effect is remarkable, can promote the students＇ comprehensive ability and is worth popularizing application.展开更多
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.
基金supported by the National Natural Science Foundation of China (Grant number 51776015)
文摘In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.
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.
基金supported by the National Natural Science Foundation of China(Grant No.52175265).
文摘Aiming at the requirement of autonomous navigation capability of the underwater unmanned vehicle(UUV),a novel bionic method for underwater navigation based on polarization pattern within Snell’s window is proposed.Inspired by creatures,polarization navigation is a satellite-free navigation scheme and has great potential to be used in the water.However,because of the complex underwater environment,whether UUV polarization navigation can be realized is doubtful.To illustrate the feasibility of underwater polarization navigation,we firstly establish the model of under-water polarization patterns to prove the stability and predictability of the underwater polarization pattern within Snell’s window.Then,we carry out static and dynamic experiments of underwater heading determination based on developed polarization information detection equipment.Finally,we obtain underwater polarization patterns and conduct the tracking experiment at different water depths.The experimental results of the underwater polarization patterns are consistent with the simulation,which proves the correctness of the proposed model.At the water depth of 5 m,the average angle and position error of the tracking experiment are 14.3508°and 4.0812 m,respectively.It is illustrated that underwater polarization navigation is realizable and the precision can meet the real-time navigation requirements of UUV.This study promotes the improvement of underwater navigation ability and the development of marine equipment.
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.
基金supported by the National Natural Science Foundation of China(Nos.11232005 and11472104)
文摘According to the theory of Matsuoka neural oscillators and with the con- sideration of the fact that the human upper arm mainly consists of six muscles, a new kind of central pattern generator （CPG） neural network consisting of six neurons is pro- posed to regulate the contraction of the upper arm muscles. To verify effectiveness of the proposed CPG network, an arm motion control model based on the CPG is established. By adjusting the CPG parameters, we obtain the neural responses of the network, the angles of joint and hand of the model with MATLAB. The simulation results agree with the results of crank rotation experiments designed by Ohta et al., showing that the arm motion control model based on a CPG network is reasonable and effective.
基金supported by the projects of Sichuan Province Science and technology support program (Grant No.2014SZ0163)National Natural Science Foundation of China (Grant No.41171016 and 51579163)the Open Foundation of State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University (SKHL1309)
文摘The rapid changes in flow pattern due to varying channel widths will make significantly impact on the hydraulic structures and evolutions of open channel. To better understand the impact of varying width, a flume experiment with adjustable width and a depth-averaged two-dimension numerical model were used to analyze the variations of flow parameters. Our experimental results showed that flow velocity gradually increased with decreasing water depth in converging region, and decreased with increasing water depth in diverging zones. It was also found that the turbulence intensity laws in three directions were not agreed with the theoretical relationships proposed by Nezu and Nakagawa in 1993 in straight open channel flows. The flow in the channel with varying width may change from the supercritical flow to the subcritical flow as a function of Froude number. Our numerical simulations with different flow rates showed that most of the hydraulic jumps in diverging region were submerged jump and the degree of submergence increased with increasing flow rate in gradual channel transition. When the flow rate increased, the range of supercritical flow rapidly decreased and the flow changed from the supercritieal condition to the subcritical condition in diverging sections.
文摘objective： to analyze the application value of the PBL in the surgical experimental teaching mode. Methods： choose between September 2013 and September 2013 128 clinical professional students, average by using the lottery will be divided into control group and the team, every 64 students for 1 set, in surgical experimental teaching as a research courses, the teaching methods for the traditional teaching method in the control group, while the team gives PBL teaching mode, the teaching effect of the final will be two groups of students are analyzed and compared. Results： through different teaching methods for teaching, compared with control group, the group at the student＇s test scores, and the ability to significantly higher, the difference of both P 〈 0.05, there is statistically significant. Conclusion： using PBL teaching mode in the surgical experimental teaching effect is remarkable, can promote the students＇ comprehensive ability and is worth popularizing application.
