In this work, we have selected three number of stepped type solar stills of the same overall dimensions 620 mm (W) × 808 mm (L) but with different absorber surface areas due to the variation in the shape of the b...In this work, we have selected three number of stepped type solar stills of the same overall dimensions 620 mm (W) × 808 mm (L) but with different absorber surface areas due to the variation in the shape of the basin surface. The other design parameters like depth of water, thickness of glass cover, insulation thickness, type of condensing cover, absorbing material provided over the basin, and angle of inclination of the still were kept constant to study the effect of shape of the absorber surface over the distillate yield obtained. The shape of the absorber surface provided in the basins of solar stills A, E and F was flat, convex and concave respectively. When the convex and concave type stepped solar stills are used, the average daily water production has been found to be 56.60% and 29.24% higher than that of flat type stepped solar still respectively. Also an economic analysis was made. The payback period of flat type, convex type and concave type stepped solar still is 823 days, 525 days and 637 days respectively. Thus, the convex type solar still gives the returns within the least possible time as compared to other two types of stepped solar stills. The laboratory tests were conducted to test the quality of water after distillation. The tests indicate that the quality of water in terms of pH, electrical conductivity, total hardness, TDS, Alkalinity, Nitrates etc. is well within the desirable limits as prescribed by WHO for Indian specific conditions.展开更多
This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on ...This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the AI：Ti composition with no more than 50 at.% Al. The specific contact resistance （SCR） is obtained to be as low as 2.6 × 10-6Ωcm2 for the bilayered Ti（100 nm）/Al（100 nm） contact treated with 3 rain rapid thermal annealing （RTA） at 1000 ℃. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti3SiC2 dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti3 SiC2 layer with （0001）-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing.展开更多
Under Type-Ⅱ progressively hybrid censoring, this paper discusses statistical inference and optimal design on stepstress partially accelerated life test for hybrid system in presence of masked data. It is assumed tha...Under Type-Ⅱ progressively hybrid censoring, this paper discusses statistical inference and optimal design on stepstress partially accelerated life test for hybrid system in presence of masked data. It is assumed that the lifetime of the component in hybrid systems follows independent and identical modified Weibull distributions. The maximum likelihood estimations(MLEs)of the unknown parameters, acceleration factor and reliability indexes are derived by using the Newton-Raphson algorithm. The asymptotic variance-covariance matrix and the approximate confidence intervals are obtained based on normal approximation to the asymptotic distribution of MLEs of model parameters. Moreover,two bootstrap confidence intervals are constructed by using the parametric bootstrap method. The optimal time of changing stress levels is determined under D-optimality and A-optimality criteria.Finally, the Monte Carlo simulation study is carried out to illustrate the proposed procedures.展开更多
In this paper the propagation of elegant Hermite-cosh-Gaussian, elegant Laguerre Gaussian, and Bessel Gaussian beams through a Kerr left-handed metamaterial （LHM） slab have been studied. A split-step Fourier method ...In this paper the propagation of elegant Hermite-cosh-Gaussian, elegant Laguerre Gaussian, and Bessel Gaussian beams through a Kerr left-handed metamaterial （LHM） slab have been studied. A split-step Fourier method is used to investigate the propagation of laser beams through this media. Numerical simulation shows that Gaussian beams have different focusing behaviors in a Kerr LHM slab with positive or negative nonlinearity. Beam focusing happens in slabs with positive nonlinearity and not in slabs with negative nonlinearity; however, negative nonlinearity is required for a Kerr LHM slab to act like a lens. Additionally, the focusing properties of beams can be controlled by controlling the thickness of the slab or the input power of the incident beam. A multilayer structure is also proposed to have beam focusing by thinner slabs and passing longer distances.展开更多
文摘In this work, we have selected three number of stepped type solar stills of the same overall dimensions 620 mm (W) × 808 mm (L) but with different absorber surface areas due to the variation in the shape of the basin surface. The other design parameters like depth of water, thickness of glass cover, insulation thickness, type of condensing cover, absorbing material provided over the basin, and angle of inclination of the still were kept constant to study the effect of shape of the absorber surface over the distillate yield obtained. The shape of the absorber surface provided in the basins of solar stills A, E and F was flat, convex and concave respectively. When the convex and concave type stepped solar stills are used, the average daily water production has been found to be 56.60% and 29.24% higher than that of flat type stepped solar still respectively. Also an economic analysis was made. The payback period of flat type, convex type and concave type stepped solar still is 823 days, 525 days and 637 days respectively. Thus, the convex type solar still gives the returns within the least possible time as compared to other two types of stepped solar stills. The laboratory tests were conducted to test the quality of water after distillation. The tests indicate that the quality of water in terms of pH, electrical conductivity, total hardness, TDS, Alkalinity, Nitrates etc. is well within the desirable limits as prescribed by WHO for Indian specific conditions.
基金supported by the Key Specific Projects of Ministry of Education of China(Grant No.625010101)the National Natural Science Foundation of China(Grant No.61234006)+2 种基金the Natural Science Foundation of Shaan Xi Province,China(Grant No.2013JQ8012)the Doctoral Fund of Ministry of Education of China(Grant No.20130203120017)the Specific Project of the Core Devices,China(Grant No.2013ZX0100100-004)
文摘This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the AI：Ti composition with no more than 50 at.% Al. The specific contact resistance （SCR） is obtained to be as low as 2.6 × 10-6Ωcm2 for the bilayered Ti（100 nm）/Al（100 nm） contact treated with 3 rain rapid thermal annealing （RTA） at 1000 ℃. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti3SiC2 dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti3 SiC2 layer with （0001）-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing.
基金The authors are grateful for the financial support of this work from National Natural Science Foundation of China(No.20021002,29925310,29833090)Ministry of Science and Technology(2001CB610506).
基金supported by the National Natural Science Foundation of China(71401134 71571144+1 种基金 71171164)the Program of International Cooperation and Exchanges in Science and Technology Funded by Shaanxi Province(2016KW-033)
文摘Under Type-Ⅱ progressively hybrid censoring, this paper discusses statistical inference and optimal design on stepstress partially accelerated life test for hybrid system in presence of masked data. It is assumed that the lifetime of the component in hybrid systems follows independent and identical modified Weibull distributions. The maximum likelihood estimations(MLEs)of the unknown parameters, acceleration factor and reliability indexes are derived by using the Newton-Raphson algorithm. The asymptotic variance-covariance matrix and the approximate confidence intervals are obtained based on normal approximation to the asymptotic distribution of MLEs of model parameters. Moreover,two bootstrap confidence intervals are constructed by using the parametric bootstrap method. The optimal time of changing stress levels is determined under D-optimality and A-optimality criteria.Finally, the Monte Carlo simulation study is carried out to illustrate the proposed procedures.
文摘In this paper the propagation of elegant Hermite-cosh-Gaussian, elegant Laguerre Gaussian, and Bessel Gaussian beams through a Kerr left-handed metamaterial （LHM） slab have been studied. A split-step Fourier method is used to investigate the propagation of laser beams through this media. Numerical simulation shows that Gaussian beams have different focusing behaviors in a Kerr LHM slab with positive or negative nonlinearity. Beam focusing happens in slabs with positive nonlinearity and not in slabs with negative nonlinearity; however, negative nonlinearity is required for a Kerr LHM slab to act like a lens. Additionally, the focusing properties of beams can be controlled by controlling the thickness of the slab or the input power of the incident beam. A multilayer structure is also proposed to have beam focusing by thinner slabs and passing longer distances.
