An experiment on deformation of flame under the effect of focusing shock wave reflection is performed with the help of multiple-spark camera to understand the flame instability of the deformation process. Methane and ...An experiment on deformation of flame under the effect of focusing shock wave reflection is performed with the help of multiple-spark camera to understand the flame instability of the deformation process. Methane and oxygen are mixed stoichiometrically to be used in the experiment. Based on Navier-Strokes equations,two-dimensional axisymmetric elementary reactions are numerically simulated. And the simulation results are solved by optical calculation. Shaded pictures by simulation fit well with experimental photos. Focusing reflecton shock waves can affect the flame,which accelerates the deformation of flame and renders violent burning in high-energy flammable gases behind waves. Therefore anticlockwise whirlpool appears. It clusters around the external surface of flame and has a tendency to develop toward the right. Finally,the whirlpool focuses on the right side of the flame,which involves the fresh unfired gases into the whirlpool circle,and consequently the head of mushroom cloud is formed. Meanwhile,when shock wave passes through the flame,the intensity of the shock waves on the axis is strengthened.展开更多
Phase gradient metasurfaces（PGMS） offer a fascinating ability to control the amplitude and phase of the electromagnetic（EM） waves on a subwavelength scale, resulting in new applications of designing novel microwav...Phase gradient metasurfaces（PGMS） offer a fascinating ability to control the amplitude and phase of the electromagnetic（EM） waves on a subwavelength scale, resulting in new applications of designing novel microwave devices with improved performances. In this paper, a reflective symmetrical element, consisting of orthogonally I-shaped structures, has been demonstrated with an approximately parallel phase response from 15 GHz to 22 GHz, which results in an interesting wideband property. For practical design, a planar antenna is implemented by a well-optimized focusing metasurface and excited by a self-designed Vivaldi antenna at the focus. Numerical and experimental results coincide well. The planar antenna has a series of merits such as a wide 3-d B gain bandwidth of 15–22 GHz, an average gain enhancement of 16 d B, a comparable aperture efficiency of better than 45% at 18 GHz, and also a simple fabrication process. The proposed reflective metasurface opens up a new avenue to design wideband microwave devices.展开更多
A high-contrast grating（HCG） focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given ...A high-contrast grating（HCG） focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given in detail.A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment.The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested.The test results show that the focal length is in the range of 11.81-12 mm,which is close to the designed focal length of 15 mm.The reflectivity is almost above 0.56 within a bandwidth of 50 nm.At a distance of 11.86 mm,the light is focused to a round spot with the highest concentration,which is much smaller than the size of the incident beam.The FWHM of the reflected light beam decreases to 120 nm,and the intensity increases to 1.18.展开更多
Western Canada’s oil sands hold the third-largest hydrocarbon deposits in the world.Bitumen,a very heavy petroleum,is currently recovered by surface mining with warm water or in situ.Recovery processes that use organ...Western Canada’s oil sands hold the third-largest hydrocarbon deposits in the world.Bitumen,a very heavy petroleum,is currently recovered by surface mining with warm water or in situ.Recovery processes that use organic solvents are being developed to reduce water usage and tailings production.While solvent-based methods can effectively extract bitumen,removal of residual fine solids from diluted bitumen product(DBP)to meet the pipeline transport requirement of<0.5 wt%solids and water in DBP remains a major challenge.We propose a novel area of application of polymer flocculants for fine solids removal from DBP.In principle,polymer flocculants can be applied to help remove these residual solids in conjunction with physical separation processes to increase process effectiveness and energy efficiency.Several polymers are selected and screened for flocculation behavior using kaolinite suspended in DBP and toluene,as a model system.Focused beam reflectance measurements and force tensiometer techniques are used to determine flocculation and sedimentation in DBP.The observed flocculation and sedimentation rate enhancements indicate that the polymers tested have only minor effects,providing opportunities for advanced polymer development.These findings exemplify the challenges in identifying polymers that may be effective as flocculants in heavy petroleum media.展开更多
文摘An experiment on deformation of flame under the effect of focusing shock wave reflection is performed with the help of multiple-spark camera to understand the flame instability of the deformation process. Methane and oxygen are mixed stoichiometrically to be used in the experiment. Based on Navier-Strokes equations,two-dimensional axisymmetric elementary reactions are numerically simulated. And the simulation results are solved by optical calculation. Shaded pictures by simulation fit well with experimental photos. Focusing reflecton shock waves can affect the flame,which accelerates the deformation of flame and renders violent burning in high-energy flammable gases behind waves. Therefore anticlockwise whirlpool appears. It clusters around the external surface of flame and has a tendency to develop toward the right. Finally,the whirlpool focuses on the right side of the flame,which involves the fresh unfired gases into the whirlpool circle,and consequently the head of mushroom cloud is formed. Meanwhile,when shock wave passes through the flame,the intensity of the shock waves on the axis is strengthened.
基金Project supported by the National Natural Science Foundation of China(Grant No.61372034)
文摘Phase gradient metasurfaces（PGMS） offer a fascinating ability to control the amplitude and phase of the electromagnetic（EM） waves on a subwavelength scale, resulting in new applications of designing novel microwave devices with improved performances. In this paper, a reflective symmetrical element, consisting of orthogonally I-shaped structures, has been demonstrated with an approximately parallel phase response from 15 GHz to 22 GHz, which results in an interesting wideband property. For practical design, a planar antenna is implemented by a well-optimized focusing metasurface and excited by a self-designed Vivaldi antenna at the focus. Numerical and experimental results coincide well. The planar antenna has a series of merits such as a wide 3-d B gain bandwidth of 15–22 GHz, an average gain enhancement of 16 d B, a comparable aperture efficiency of better than 45% at 18 GHz, and also a simple fabrication process. The proposed reflective metasurface opens up a new avenue to design wideband microwave devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61274044,61574019 and 61020106007)the National Basic Research Program of China(Grant No.2010CB327600)+4 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130005130001)the Natural Science Foundation of Beijing,China(Grant No.4132069)the Key International Science and Technology Cooperation Project of China(Grant No.2011RR000100)the 111 Project of China(Grant No.B07005)the Program for Changjiang Scholars and Innovative Research Team in Universities of China(Grant No.IRT0609)
文摘A high-contrast grating（HCG） focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given in detail.A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment.The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested.The test results show that the focal length is in the range of 11.81-12 mm,which is close to the designed focal length of 15 mm.The reflectivity is almost above 0.56 within a bandwidth of 50 nm.At a distance of 11.86 mm,the light is focused to a round spot with the highest concentration,which is much smaller than the size of the incident beam.The FWHM of the reflected light beam decreases to 120 nm,and the intensity increases to 1.18.
文摘Western Canada’s oil sands hold the third-largest hydrocarbon deposits in the world.Bitumen,a very heavy petroleum,is currently recovered by surface mining with warm water or in situ.Recovery processes that use organic solvents are being developed to reduce water usage and tailings production.While solvent-based methods can effectively extract bitumen,removal of residual fine solids from diluted bitumen product(DBP)to meet the pipeline transport requirement of<0.5 wt%solids and water in DBP remains a major challenge.We propose a novel area of application of polymer flocculants for fine solids removal from DBP.In principle,polymer flocculants can be applied to help remove these residual solids in conjunction with physical separation processes to increase process effectiveness and energy efficiency.Several polymers are selected and screened for flocculation behavior using kaolinite suspended in DBP and toluene,as a model system.Focused beam reflectance measurements and force tensiometer techniques are used to determine flocculation and sedimentation in DBP.The observed flocculation and sedimentation rate enhancements indicate that the polymers tested have only minor effects,providing opportunities for advanced polymer development.These findings exemplify the challenges in identifying polymers that may be effective as flocculants in heavy petroleum media.
