A double perturbation strategy is presented to solve the asymptotic solutions of a Johnson-Segalman （J-S） fluid through a slowly varying pipe. First, a small parameter of the slowly varying angle is taken as the sma...A double perturbation strategy is presented to solve the asymptotic solutions of a Johnson-Segalman （J-S） fluid through a slowly varying pipe. First, a small parameter of the slowly varying angle is taken as the small perturbation parameter, and then the second-order asymptotic solution of the flow of a Newtonian fluid through a slowly varying pipe is obtained in the first perturbation strategy. Second, the viscoelastic parameter is selected as the small perturbation parameter in the second perturbation strategy to solve the asymptotic solution of the flow of a J-S fluid through a slowly varying pipe. Finally, the parameter effects, including the axial distance, the slowly varying angle, and the Reynolds number, on the velocity distributions are analyzed. The results show that the increases in both the axial distance and the slowly varying angle make the axial velocity slow down. However, the radial velocity increases with the slowly varying angle, and decreases with the axial distance. There are two special positions in the distribution curves of the axial velocity and the radial velocity with different Reynolds numbers, and there are different trends on both sides of the special positions. The double perturbation strategy is applicable to such problems with the flow of a non-Newtonian fluid through a slowly varying pipe.展开更多
Stress Joint （SJ） plays a key role in the Top Tensioned Riser （TTR） system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate...Stress Joint （SJ） plays a key role in the Top Tensioned Riser （TTR） system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications.展开更多
We present a detailed study of a superjunction （S J） nanoscale partially narrow mesa （PNM） insulated gate bipolar transistor （IGBT） structure. This structure is created by combining the nanoscale PNM structure a...We present a detailed study of a superjunction （S J） nanoscale partially narrow mesa （PNM） insulated gate bipolar transistor （IGBT） structure. This structure is created by combining the nanoscale PNM structure and the SJ structure together. It demonstrates an ultra-low saturation voltage （Vce（sat）） and low turn-off loss （Eoff） while maintaining other device parameters. Compared with the conventional 1.2 kV trench IGBT, our simulation result shows that the gce（sat） of this structure decreases to 0.94 V, which is close to the theoretical limit of 1.2 kV IGBT, Meanwhile, the fall time decreases from 109.7 ns to 12 ns and the Eoff is down to only 37% of that of the conventional structure. The superior tradeoff characteristic between Vce（sat） and Eoff is presented owing to the nanometer level mesa width and SJ structure. Moreover, the short circuit degeneration phenomenon in the very narrow mesa structure due to the collector-induced barriers lowering （CIBL） effect is not observed in this structure. Thus, enough short circuit ability can be achieved by using wide, floating P-well technique. Based on these structure advantages, the SJ-PNM-IGBT with nanoscale mesa width indicates a potentially superior overall performance towards the IGBT parameter limit.展开更多
In this study, aqueous extraction method is used because of its high extraction ratio, light fastness and also functional properties. In 1st phase, for dyeing S/J cotton knit fabric with green walnut power ferrous sul...In this study, aqueous extraction method is used because of its high extraction ratio, light fastness and also functional properties. In 1st phase, for dyeing S/J cotton knit fabric with green walnut power ferrous sulfate is considered as a mordant. In this study, three different mordanting methods such as pre-, meta-, and post-mordanting are conveyed the dyeing process with the state of metallic mordant and without metallic salt mordants. In 2nd phase, in dyeing for fixation ferrous sulfate was considered as mordants. Furthermore, the analysis and evaluation of each colour dyed material was done through following two terms for instance CIELAB (L*, a*, and b*) and K/S values. According to AATCC test methods, colour fastness to washing, crocking, perspiration of the dyed samples is determined whereas according to the ISO standard, the colour fastness to light was estimated and tested. When dyeing was carried out on S/J cotton knit fabric through considering optimum parameter like at 80°C for 60 min and at pH 4 which showed optimum results. From the results we can see, very good wash fastness was obtained while there is no fading of the colour, whereas the outstanding and moderate level of colour fastness to light and crocking is achieved.展开更多
Based on a proposed method, the mathematical expressions between carbon solubility in Fe-C-j (j=Al, Si, P, S) melts and temperature were obtained. The expressions show the relation of the affecting factors of componen...Based on a proposed method, the mathematical expressions between carbon solubility in Fe-C-j (j=Al, Si, P, S) melts and temperature were obtained. The expressions show the relation of the affecting factors of component j and temperature on carbon solubility, and the activity interaction coefficient of j upon carbon depends on atomic number, covalent radius and electro-negativity. The affecting factors of four elements on carbon solubility are all negative. There is a linear relationship between covalent radius and electro-negativity.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11572203 and11332006)
文摘A double perturbation strategy is presented to solve the asymptotic solutions of a Johnson-Segalman （J-S） fluid through a slowly varying pipe. First, a small parameter of the slowly varying angle is taken as the small perturbation parameter, and then the second-order asymptotic solution of the flow of a Newtonian fluid through a slowly varying pipe is obtained in the first perturbation strategy. Second, the viscoelastic parameter is selected as the small perturbation parameter in the second perturbation strategy to solve the asymptotic solution of the flow of a J-S fluid through a slowly varying pipe. Finally, the parameter effects, including the axial distance, the slowly varying angle, and the Reynolds number, on the velocity distributions are analyzed. The results show that the increases in both the axial distance and the slowly varying angle make the axial velocity slow down. However, the radial velocity increases with the slowly varying angle, and decreases with the axial distance. There are two special positions in the distribution curves of the axial velocity and the radial velocity with different Reynolds numbers, and there are different trends on both sides of the special positions. The double perturbation strategy is applicable to such problems with the flow of a non-Newtonian fluid through a slowly varying pipe.
基金supported by the National High Technology Research and Development Program of China (863 Program,Grant No. 2008AA09A105-04)
文摘Stress Joint （SJ） plays a key role in the Top Tensioned Riser （TTR） system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.61404161)
文摘We present a detailed study of a superjunction （S J） nanoscale partially narrow mesa （PNM） insulated gate bipolar transistor （IGBT） structure. This structure is created by combining the nanoscale PNM structure and the SJ structure together. It demonstrates an ultra-low saturation voltage （Vce（sat）） and low turn-off loss （Eoff） while maintaining other device parameters. Compared with the conventional 1.2 kV trench IGBT, our simulation result shows that the gce（sat） of this structure decreases to 0.94 V, which is close to the theoretical limit of 1.2 kV IGBT, Meanwhile, the fall time decreases from 109.7 ns to 12 ns and the Eoff is down to only 37% of that of the conventional structure. The superior tradeoff characteristic between Vce（sat） and Eoff is presented owing to the nanometer level mesa width and SJ structure. Moreover, the short circuit degeneration phenomenon in the very narrow mesa structure due to the collector-induced barriers lowering （CIBL） effect is not observed in this structure. Thus, enough short circuit ability can be achieved by using wide, floating P-well technique. Based on these structure advantages, the SJ-PNM-IGBT with nanoscale mesa width indicates a potentially superior overall performance towards the IGBT parameter limit.
文摘In this study, aqueous extraction method is used because of its high extraction ratio, light fastness and also functional properties. In 1st phase, for dyeing S/J cotton knit fabric with green walnut power ferrous sulfate is considered as a mordant. In this study, three different mordanting methods such as pre-, meta-, and post-mordanting are conveyed the dyeing process with the state of metallic mordant and without metallic salt mordants. In 2nd phase, in dyeing for fixation ferrous sulfate was considered as mordants. Furthermore, the analysis and evaluation of each colour dyed material was done through following two terms for instance CIELAB (L*, a*, and b*) and K/S values. According to AATCC test methods, colour fastness to washing, crocking, perspiration of the dyed samples is determined whereas according to the ISO standard, the colour fastness to light was estimated and tested. When dyeing was carried out on S/J cotton knit fabric through considering optimum parameter like at 80°C for 60 min and at pH 4 which showed optimum results. From the results we can see, very good wash fastness was obtained while there is no fading of the colour, whereas the outstanding and moderate level of colour fastness to light and crocking is achieved.
文摘Based on a proposed method, the mathematical expressions between carbon solubility in Fe-C-j (j=Al, Si, P, S) melts and temperature were obtained. The expressions show the relation of the affecting factors of component j and temperature on carbon solubility, and the activity interaction coefficient of j upon carbon depends on atomic number, covalent radius and electro-negativity. The affecting factors of four elements on carbon solubility are all negative. There is a linear relationship between covalent radius and electro-negativity.
