High-resolution underwater digital elevation models(DEMs)are important for water and soil conservation,hydrological analysis,and river channel dredging.In this work,the underwater topography of the Panjing River in Sh...High-resolution underwater digital elevation models(DEMs)are important for water and soil conservation,hydrological analysis,and river channel dredging.In this work,the underwater topography of the Panjing River in Shanghai,China,was measured by an unmanned surface vessel.Five different interpolation methods were used to generate the underwater DEM and their precision and applicability for different underwater landforms were analyzed through cross-validation.The results showed that there was a positive correlation between the interpolation error and the terrain surface roughness.The five interpolation methods were all appropriate for the survey area,but their accuracy varied with different surface roughness.Based on the analysis results,an integrated approach was proposed to automatically select the appropriate interpolation method according to the different surface roughness in the surveying area.This approach improved the overall interpolation precision.The suggested technique provides a reference for the selection of interpolationmethods for underwater DEMdata.展开更多
The “shooting and bouncing rays” (SBR) technique is used to analyze the electromagnetic scattering characters of ocean rough surfaces varying with time. Some numerical results are presented and compared with the met...The “shooting and bouncing rays” (SBR) technique is used to analyze the electromagnetic scattering characters of ocean rough surfaces varying with time. Some numerical results are presented and compared with the method of moments, and some factors, such as the incident angle, polarization and frequency are investigated which influence on electromagnetic scattering characters of ocean rough surfaces.展开更多
With the theory of rough surfaces scattering,a numerical formula for calculating the bistatic and backscattering radar cross section from randomly dielectric rough surfaces is derived by using phase-perturbation techn...With the theory of rough surfaces scattering,a numerical formula for calculating the bistatic and backscattering radar cross section from randomly dielectric rough surfaces is derived by using phase-perturbation technique.The backscattering laser radar cross sections per unit of some rough samples are computed at λ=1.06μm.The numerical results are in good agreement with experimental data.展开更多
Background: The accuracy of the final prosthesis is affected by the final impression technique and master cast production. The aim of the present study was to evaluate the effect of the functional impression technique...Background: The accuracy of the final prosthesis is affected by the final impression technique and master cast production. The aim of the present study was to evaluate the effect of the functional impression technique with various impression materials on the surface characteristic of dental stone casts and their clinical effect on the retention of complete dentures. Method: Specimens of three impression materials/stone casts were fabricated. The specimens of the impression materials/stone casts were divided into three equal groups (I, II, and III). The impression materials used were as follows: tissue conditioner group (I), zinc oxide (ZEO) (group II) and poly (vinyl siloxane) (PVS) (group III). Cylindrical split aluminium moulds were designed to receive the impression materials and the stone mixture. The surface roughness of the stone cast specimens of the three groups (I, II, and III) was measured with a surface profilometer and analyzed by a scanning electron microscope. A clinical study included five severely resorbed mandibular edentulous alveolar ridges and edentulous maxillary arches. Each subject received three heat-cured acrylic resin dentures, fabricated using the functional impression technique. The three dentures were identical except for the different impression materials used from Groups I, II and III. The retentive force of each denture for each subject was measured. Result: The results of this study revealed that the mean value of surface roughness of the stone cast surface of group I was higher than group II and group III. A statistically significant difference was observed in surface roughness and the retentive dislodging force between the three studied groups. Although using a tissue conditioner as a functional impression material led to a high level of surface roughness and good retention, it could not produce the same smooth surface quality of PVS or ZEO. These data were supported by SEM analysis. The complete dentures for these patients require important oral and denture hygiene care. Conclusion: Complete dentures made using functional impression technique with PVC as a final impression material are more comfortable, retentive and stable.展开更多
Grinding operation is a finishing process often employed when high precision and narrow geometric tolerances are required.These requirements can be achieved only if cutting conditions are properly selected,especially ...Grinding operation is a finishing process often employed when high precision and narrow geometric tolerances are required.These requirements can be achieved only if cutting conditions are properly selected,especially the cooling-lubrication technique.In general,grinding is performed in presence of cutting fluid,however,due to the environmental impacts and costs of the conventional coolant delivery technique(flow rates from 4 L/min to 300 L/min),alternative cooling-lubrication techniques have been developed on restriction of the coolants use.Among the several techniques,MQL(minimum quantity of lubricant)technique has received special attention from machining users because of its advantages in terms of surface quality of workpiece and drastic reduction in use of coolant.In this context,this paper evaluated the performance of the MQL technique as compared to the flood coolant in peripheral surface grinding of AISI P100(VP100)steel with conventional aluminum oxide grinding wheel in relation to the surface roughness(Ra and Rz).Input parameters tested were equivalent chip thickness(0.09μm,0.18μm and 0.27μm)and flow rate of the cutting fluid(60 mL/h,150 mL/h and 240 mL/h)of the MQL system.Results showed that the grinding with MQL technique provided lower surface roughness values compared to conventional flood cooling,especially when machining under the intermediary cutting conditions.Also,with exception of heq of 0.09 m,the MQL technique resulted in lower values of Rz parameter as compared to the conventional coolant technique,regardless of the flow rate tested.展开更多
基金supported by the NationalNatural Science Foundation of China(Grant No.42102318)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning.
文摘High-resolution underwater digital elevation models(DEMs)are important for water and soil conservation,hydrological analysis,and river channel dredging.In this work,the underwater topography of the Panjing River in Shanghai,China,was measured by an unmanned surface vessel.Five different interpolation methods were used to generate the underwater DEM and their precision and applicability for different underwater landforms were analyzed through cross-validation.The results showed that there was a positive correlation between the interpolation error and the terrain surface roughness.The five interpolation methods were all appropriate for the survey area,but their accuracy varied with different surface roughness.Based on the analysis results,an integrated approach was proposed to automatically select the appropriate interpolation method according to the different surface roughness in the surveying area.This approach improved the overall interpolation precision.The suggested technique provides a reference for the selection of interpolationmethods for underwater DEMdata.
文摘The “shooting and bouncing rays” (SBR) technique is used to analyze the electromagnetic scattering characters of ocean rough surfaces varying with time. Some numerical results are presented and compared with the method of moments, and some factors, such as the incident angle, polarization and frequency are investigated which influence on electromagnetic scattering characters of ocean rough surfaces.
文摘With the theory of rough surfaces scattering,a numerical formula for calculating the bistatic and backscattering radar cross section from randomly dielectric rough surfaces is derived by using phase-perturbation technique.The backscattering laser radar cross sections per unit of some rough samples are computed at λ=1.06μm.The numerical results are in good agreement with experimental data.
文摘Background: The accuracy of the final prosthesis is affected by the final impression technique and master cast production. The aim of the present study was to evaluate the effect of the functional impression technique with various impression materials on the surface characteristic of dental stone casts and their clinical effect on the retention of complete dentures. Method: Specimens of three impression materials/stone casts were fabricated. The specimens of the impression materials/stone casts were divided into three equal groups (I, II, and III). The impression materials used were as follows: tissue conditioner group (I), zinc oxide (ZEO) (group II) and poly (vinyl siloxane) (PVS) (group III). Cylindrical split aluminium moulds were designed to receive the impression materials and the stone mixture. The surface roughness of the stone cast specimens of the three groups (I, II, and III) was measured with a surface profilometer and analyzed by a scanning electron microscope. A clinical study included five severely resorbed mandibular edentulous alveolar ridges and edentulous maxillary arches. Each subject received three heat-cured acrylic resin dentures, fabricated using the functional impression technique. The three dentures were identical except for the different impression materials used from Groups I, II and III. The retentive force of each denture for each subject was measured. Result: The results of this study revealed that the mean value of surface roughness of the stone cast surface of group I was higher than group II and group III. A statistically significant difference was observed in surface roughness and the retentive dislodging force between the three studied groups. Although using a tissue conditioner as a functional impression material led to a high level of surface roughness and good retention, it could not produce the same smooth surface quality of PVS or ZEO. These data were supported by SEM analysis. The complete dentures for these patients require important oral and denture hygiene care. Conclusion: Complete dentures made using functional impression technique with PVC as a final impression material are more comfortable, retentive and stable.
基金This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil(CAPES)—Finance Code 001The authors are grateful too to the FAPEMIG and the Post Graduate Program of Mechanical Engineering of UFU for financial support.Authors are also grateful to Villares Metals(Brazil)+1 种基金Saint Gobain Abrasives for supporting this work with workpiece material and wheel.One of authors thanks CNPq(PQ 2013 Project No.308067/2013)for the research scholarship and FAPEMIG project process No.PPM-00265-13 for financial supportThe authors are also thankful to ABCM for transferring the copyright of the article.
文摘Grinding operation is a finishing process often employed when high precision and narrow geometric tolerances are required.These requirements can be achieved only if cutting conditions are properly selected,especially the cooling-lubrication technique.In general,grinding is performed in presence of cutting fluid,however,due to the environmental impacts and costs of the conventional coolant delivery technique(flow rates from 4 L/min to 300 L/min),alternative cooling-lubrication techniques have been developed on restriction of the coolants use.Among the several techniques,MQL(minimum quantity of lubricant)technique has received special attention from machining users because of its advantages in terms of surface quality of workpiece and drastic reduction in use of coolant.In this context,this paper evaluated the performance of the MQL technique as compared to the flood coolant in peripheral surface grinding of AISI P100(VP100)steel with conventional aluminum oxide grinding wheel in relation to the surface roughness(Ra and Rz).Input parameters tested were equivalent chip thickness(0.09μm,0.18μm and 0.27μm)and flow rate of the cutting fluid(60 mL/h,150 mL/h and 240 mL/h)of the MQL system.Results showed that the grinding with MQL technique provided lower surface roughness values compared to conventional flood cooling,especially when machining under the intermediary cutting conditions.Also,with exception of heq of 0.09 m,the MQL technique resulted in lower values of Rz parameter as compared to the conventional coolant technique,regardless of the flow rate tested.
