The equipment used in various fields contains an increasing number of parts with curved surfaces of increasing size.Five-axis computer numerical control(CNC)milling is the main parts machining method,while dynamics an...The equipment used in various fields contains an increasing number of parts with curved surfaces of increasing size.Five-axis computer numerical control(CNC)milling is the main parts machining method,while dynamics analysis has always been a research hotspot.The cutting conditions determined by the cutter axis,tool path,and workpiece geometry are complex and changeable,which has made dynamics research a major challenge.For this reason,this paper introduces the innovative idea of applying dimension reduction and mapping to the five-axis machining of curved surfaces,and proposes an efficient dynamics analysis model.To simplify the research object,the cutter position points along the tool path were discretized into inclined plane five-axis machining.The cutter dip angle and feed deflection angle were used to define the spatial position relationship in five-axis machining.These were then taken as the new base variables to construct an abstract two-dimensional space and establish the mapping relationship between the cutter position point and space point sets to further simplify the dimensions of the research object.Based on the in-cut cutting edge solved by the space limitation method,the dynamics of the inclined plane five-axis machining unit were studied,and the results were uniformly stored in the abstract space to produce a database.Finally,the prediction of the milling force and vibration state along the tool path became a data extraction process that significantly improved efficiency.Two experiments were also conducted which proved the accuracy and efficiency of the proposed dynamics analysis model.This study has great potential for the online synchronization of intelligent machining of large surfaces.展开更多
A new synchronization scheme for chaotic（hyperchaotic） maps with different dimensions is presented.Specifically,given a drive system map with dimension n and a response system with dimension m,the proposed approach ...A new synchronization scheme for chaotic（hyperchaotic） maps with different dimensions is presented.Specifically,given a drive system map with dimension n and a response system with dimension m,the proposed approach enables each drive system state to be synchronized with a linear response combination of the response system states.The method,based on the Lyapunov stability theory and the pole placement technique,presents some useful features：（i） it enables synchronization to be achieved for both cases of n 〈 m and n 〉 m;（ii） it is rigorous,being based on theorems;（iii） it can be readily applied to any chaotic（hyperchaotic） maps defined to date.Finally,the capability of the approach is illustrated by synchronization examples between the two-dimensional H′enon map（as the drive system） and the three-dimensional hyperchaotic Wang map（as the response system）,and the three-dimensional H′enon-like map（as the drive system） and the two-dimensional Lorenz discrete-time system（as the response system）.展开更多
Interstellar dust plays a crucial role in astrophysics,affecting the observed properties of stars and galaxies by absorbing and scattering light.The extinction curve,which describes how this effect varies with wavelen...Interstellar dust plays a crucial role in astrophysics,affecting the observed properties of stars and galaxies by absorbing and scattering light.The extinction curve,which describes how this effect varies with wavelength,is characterized by the parameter RðVÞ,defined as the ratio of total to selective extinction.展开更多
Background Linear ablation of left atrium （LA） guided by three dimensional （3-D） electroanatomical mapping （Carto） has been used in many centres worldwide for the treatment of atrial fibrillation （AF） instead ...Background Linear ablation of left atrium （LA） guided by three dimensional （3-D） electroanatomical mapping （Carto） has been used in many centres worldwide for the treatment of atrial fibrillation （AF） instead of pure anatomical approaches. There were little data about linear ablation of LA guided by Carto and double Lasso catheters in China. We report the results of linear ablation of LA guided by both Carto and double Lasso catheters. Methods After the anatomical model of LA and all pulmonary veins （PVs） had been established, circumferential ablations of the left pulmonary vein antrum and the right pulmonary vein antrum were performed with 2 circumferential mapping catheters （Lasso） placed within the ipsilateral superior and inferior PVs. The endpoint of ablation was abolishment or dissociation of the pulmonary vein potentials （PVPs）. Oral amiodarone or propafenone was taken for at least 3 months by patients with persistent AF, permanent AF or those whose PVPs had not been isolated completely. The recurrence of atrial tachyarrhythmias was observed 3 months after the procedure. Results There were 106 patients （mean age, 51.4±9.9 years）. Seventy-eight patients had paroxysmal AF, 12 persistent AF and 16 permanent AF. Onset of atrial fibrillation occurred in 52 patients during ablation procedure. Thirty-two patients restored to sinus rhythm eventually after the procedure. Abolishment or dissociation of PVPs was accomplished during the procedure in 94 patients （88.7%）. The duration of procedure and exposure to X-ray were （213±45） minutes and （32.5± 12.8） minutes, respectively. Among the 87 patients followed up for over 3 months, 62 were free of atrial tachyarrhythmias （including 8 patients who were still taking oral amiodarone）. The success rate was 71.3% in the first procedure. Two patients had pericardial effusion treated by pericardial puncture and effusion drainage. No pulmonary vein stenosis, atrioesophageal fistula, stroke or procedural death occurred. Conclusions Combination of double Lasso catheters with 3-D electroanatomical mapping to guide the linear ablation of left atrium procedure can confirm the isolation of PVPs.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.52005078,U1908231,52075076).
文摘The equipment used in various fields contains an increasing number of parts with curved surfaces of increasing size.Five-axis computer numerical control(CNC)milling is the main parts machining method,while dynamics analysis has always been a research hotspot.The cutting conditions determined by the cutter axis,tool path,and workpiece geometry are complex and changeable,which has made dynamics research a major challenge.For this reason,this paper introduces the innovative idea of applying dimension reduction and mapping to the five-axis machining of curved surfaces,and proposes an efficient dynamics analysis model.To simplify the research object,the cutter position points along the tool path were discretized into inclined plane five-axis machining.The cutter dip angle and feed deflection angle were used to define the spatial position relationship in five-axis machining.These were then taken as the new base variables to construct an abstract two-dimensional space and establish the mapping relationship between the cutter position point and space point sets to further simplify the dimensions of the research object.Based on the in-cut cutting edge solved by the space limitation method,the dynamics of the inclined plane five-axis machining unit were studied,and the results were uniformly stored in the abstract space to produce a database.Finally,the prediction of the milling force and vibration state along the tool path became a data extraction process that significantly improved efficiency.Two experiments were also conducted which proved the accuracy and efficiency of the proposed dynamics analysis model.This study has great potential for the online synchronization of intelligent machining of large surfaces.
文摘A new synchronization scheme for chaotic（hyperchaotic） maps with different dimensions is presented.Specifically,given a drive system map with dimension n and a response system with dimension m,the proposed approach enables each drive system state to be synchronized with a linear response combination of the response system states.The method,based on the Lyapunov stability theory and the pole placement technique,presents some useful features：（i） it enables synchronization to be achieved for both cases of n 〈 m and n 〉 m;（ii） it is rigorous,being based on theorems;（iii） it can be readily applied to any chaotic（hyperchaotic） maps defined to date.Finally,the capability of the approach is illustrated by synchronization examples between the two-dimensional H′enon map（as the drive system） and the three-dimensional hyperchaotic Wang map（as the response system）,and the three-dimensional H′enon-like map（as the drive system） and the two-dimensional Lorenz discrete-time system（as the response system）.
文摘Interstellar dust plays a crucial role in astrophysics,affecting the observed properties of stars and galaxies by absorbing and scattering light.The extinction curve,which describes how this effect varies with wavelength,is characterized by the parameter RðVÞ,defined as the ratio of total to selective extinction.
文摘Background Linear ablation of left atrium （LA） guided by three dimensional （3-D） electroanatomical mapping （Carto） has been used in many centres worldwide for the treatment of atrial fibrillation （AF） instead of pure anatomical approaches. There were little data about linear ablation of LA guided by Carto and double Lasso catheters in China. We report the results of linear ablation of LA guided by both Carto and double Lasso catheters. Methods After the anatomical model of LA and all pulmonary veins （PVs） had been established, circumferential ablations of the left pulmonary vein antrum and the right pulmonary vein antrum were performed with 2 circumferential mapping catheters （Lasso） placed within the ipsilateral superior and inferior PVs. The endpoint of ablation was abolishment or dissociation of the pulmonary vein potentials （PVPs）. Oral amiodarone or propafenone was taken for at least 3 months by patients with persistent AF, permanent AF or those whose PVPs had not been isolated completely. The recurrence of atrial tachyarrhythmias was observed 3 months after the procedure. Results There were 106 patients （mean age, 51.4±9.9 years）. Seventy-eight patients had paroxysmal AF, 12 persistent AF and 16 permanent AF. Onset of atrial fibrillation occurred in 52 patients during ablation procedure. Thirty-two patients restored to sinus rhythm eventually after the procedure. Abolishment or dissociation of PVPs was accomplished during the procedure in 94 patients （88.7%）. The duration of procedure and exposure to X-ray were （213±45） minutes and （32.5± 12.8） minutes, respectively. Among the 87 patients followed up for over 3 months, 62 were free of atrial tachyarrhythmias （including 8 patients who were still taking oral amiodarone）. The success rate was 71.3% in the first procedure. Two patients had pericardial effusion treated by pericardial puncture and effusion drainage. No pulmonary vein stenosis, atrioesophageal fistula, stroke or procedural death occurred. Conclusions Combination of double Lasso catheters with 3-D electroanatomical mapping to guide the linear ablation of left atrium procedure can confirm the isolation of PVPs.
