To estimate the geometric characteristics, especially wet areas and section areas, of three dimensional numerical conceptual aircraft models, a method based on surface elements is proposed. On the premise that numerou...To estimate the geometric characteristics, especially wet areas and section areas, of three dimensional numerical conceptual aircraft models, a method based on surface elements is proposed. On the premise that numerous surface elements are generated to represent each component surface, a component wet area of the surface is estimated by adding up the areas of such elements that are not covered by any other component surfaces. The elements are also used to get the section polygons of such composite surfaces as the whole aircraft at a given body station, then a section area is approximated with the sum of trapezoidal areas between such sides of polygons that are not covered by any other component and a reference axis. Practical application to a computer aided aircraft conceptual design system shows that the methed is applicable to different kinds of conceptual aircraft models and its precision is satisfying to the conceptual design.展开更多
In this study,SEM,EDS,XRD and other test methods were used to study the effects of different Ga contents(0~2 wt.%)on microstructure,electrical conductivity,spreading area and mechanical properties of Sn-9Zn-3Bi solder...In this study,SEM,EDS,XRD and other test methods were used to study the effects of different Ga contents(0~2 wt.%)on microstructure,electrical conductivity,spreading area and mechanical properties of Sn-9Zn-3Bi solder.The results revealed that the microstructure of Sn-Zn-Bi-Ga solder alloy was mainly composed ofβ-Sn,Zn-rich,Bi-rich phase and Sn-Zn eutectic structure.The Ga can significantly improve the wettability of Sn-Zn-Bi on the pure copper,the maximum wetting area was 105.3 mm^2.With the increase of the Ga content the melting point of the solders decreased from 195℃to 177℃.In addition,the Ga element can increase the oxidation resistance of solder.Its conductivity showed a decreasing trend with the gradual increase of the Ga content.With the increased of the Ga content the IMC(Intermetallic Compound)of Sn-Zn-Bi-xGa/Cu is only Cu5Zn8 and its thickness decreased remarkably.展开更多
Semi-circular open channel plays an important role in various applications and the measurement of its discharge is of interests.In this study,theoretical formulae for free overflow in a semi-circular channel are devel...Semi-circular open channel plays an important role in various applications and the measurement of its discharge is of interests.In this study,theoretical formulae for free overflow in a semi-circular channel are developed and presented for the discharge and wetted area relationship.The traditional discharge formulation and available experimental data are used to verify and validate the proposed relationships.The discharges calculated by using the proposed relationship show very good agreement with the experimental data sets.The results from this study supply the basis for circular weir development.展开更多
文摘To estimate the geometric characteristics, especially wet areas and section areas, of three dimensional numerical conceptual aircraft models, a method based on surface elements is proposed. On the premise that numerous surface elements are generated to represent each component surface, a component wet area of the surface is estimated by adding up the areas of such elements that are not covered by any other component surfaces. The elements are also used to get the section polygons of such composite surfaces as the whole aircraft at a given body station, then a section area is approximated with the sum of trapezoidal areas between such sides of polygons that are not covered by any other component and a reference axis. Practical application to a computer aided aircraft conceptual design system shows that the methed is applicable to different kinds of conceptual aircraft models and its precision is satisfying to the conceptual design.
基金Natural Science Foundation of Shaanxi Provincial Department(No.51974243)Science and Technology Program of Xi'an(Grant No.201805037YD15CG21(16))+1 种基金Natural Science Foundation of Shaanxi Provincial Department(No.2019JZ-31)Natural Science Foundation of Shaanxi Provincial Department(No.2019JQ-284).
文摘In this study,SEM,EDS,XRD and other test methods were used to study the effects of different Ga contents(0~2 wt.%)on microstructure,electrical conductivity,spreading area and mechanical properties of Sn-9Zn-3Bi solder.The results revealed that the microstructure of Sn-Zn-Bi-Ga solder alloy was mainly composed ofβ-Sn,Zn-rich,Bi-rich phase and Sn-Zn eutectic structure.The Ga can significantly improve the wettability of Sn-Zn-Bi on the pure copper,the maximum wetting area was 105.3 mm^2.With the increase of the Ga content the melting point of the solders decreased from 195℃to 177℃.In addition,the Ga element can increase the oxidation resistance of solder.Its conductivity showed a decreasing trend with the gradual increase of the Ga content.With the increased of the Ga content the IMC(Intermetallic Compound)of Sn-Zn-Bi-xGa/Cu is only Cu5Zn8 and its thickness decreased remarkably.
基金supported by Natural Science Foundation of China under project No.40635027with financial support from State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau in China.
文摘Semi-circular open channel plays an important role in various applications and the measurement of its discharge is of interests.In this study,theoretical formulae for free overflow in a semi-circular channel are developed and presented for the discharge and wetted area relationship.The traditional discharge formulation and available experimental data are used to verify and validate the proposed relationships.The discharges calculated by using the proposed relationship show very good agreement with the experimental data sets.The results from this study supply the basis for circular weir development.
