This study systematically investigated the Lean Blowoff(LBO)limits of Two-Dimensional(2D)bluff-body stabilized premixed flames by varying the air mass flow rate,inflowtemperature,bluff-body width,and fuel type.The dat...This study systematically investigated the Lean Blowoff(LBO)limits of Two-Dimensional(2D)bluff-body stabilized premixed flames by varying the air mass flow rate,inflowtemperature,bluff-body width,and fuel type.The data of LBO limits were analyzed and fittedaccording to the Damk?hler(Da)and Reynolds(Re)numbers,and the fitting accuracy of LBO datawas highly improved by a modified characteristic length simultaneously considering the length andwidth of the bluff body,which is usually neglected in the previous studies.Moreover,to our knowl-edge,this is the first time that simultaneous transverse and spanwise OH*-Chemiluminescence(CL)imaging has been performed to examine the three-dimensional behavior of the LBO process.The flame stability is heavily affected by the mass and energy transport between reactants andproducts in both directions,potentially leading to the flame pinch-off.The intensity and positionof the upstream flame after pinch-off are decisive to the occurrence of the following LBO.Whenthe upstream flame after pinch-off is weak and close to the bluff body,it cannot re-ignite thedownstream unburnt gas.Subsequently,a permanent downstream extinction occurs,and theLBO takes place.The results help understand the LBO mechanism of 2D bluff-body stabilizedflames.展开更多
The objective of this study is to demonstrate that tensile stress resulting due to applied force on cornea can be accurately measured by using a time-domain common-path optical coherence tomography （OCT） system with...The objective of this study is to demonstrate that tensile stress resulting due to applied force on cornea can be accurately measured by using a time-domain common-path optical coherence tomography （OCT） system with an external contact reference. The unique design of the common-path OCT is utilized to set up an imaging system in which a chicken eye is placed adjacent to a glass plate serving as the external reference plane for the imaging system. As the force is applied to the chicken eye, it presses against the reference glass plate. The modified OCT image obtained is used to calculate the size of contact area, which is then used to derive the tensile stress on the cornea. The drop in signal levels upon contact of reference glass plate with the tissue are extremely sharp because of the sharp decline in reference power levels itself, thus providing us with an accurate measurement of contact area. The experimental results were in good agreement with the numerical predictions. The results of this study might be useful in providing new insights and ideas to improve the precision and safety of currently used ophthalmic surgical techniques. This research outlines a method which could be used to provide high resolution OCT images and a precise feedback of the forces applied to the cornea simultaneously.展开更多
Controlled aliasing in parallel imaging results in higher acceleration （CAIPIRINHA） for simultaneous multislice imaging has been proposed recently, which combines multiband excitation and phase cycling techniques to...Controlled aliasing in parallel imaging results in higher acceleration （CAIPIRINHA） for simultaneous multislice imaging has been proposed recently, which combines multiband excitation and phase cycling techniques to reduce scan time and improve subsequent imaging reconstruction. In this work, the total variation （TV） regularization method is used to further improve CAIPIRINHA. The TV regularization uses an edge-preserving prior, which establishes a relationship between neighboring pixels for image reconstruction. It reduces artifacts and suppresses noise amplification simultaneously. The results are presented with a standard eight-channel head coil with an acceleration factor of 4, where the TV-regularized CAIPIRINHA generates an improved reconstruction as compared with a typical nonregularized CAIPIRINHA.展开更多
Multicolor imaging has been widely applied across various biological and medical applications,especially essential for probing diverse biological structures.However,existing multicolor imaging methods often sacrifice ...Multicolor imaging has been widely applied across various biological and medical applications,especially essential for probing diverse biological structures.However,existing multicolor imaging methods often sacrifice either simultaneity or speed,posing a challenge for simultaneous imaging of over three fluorophores.Here,we proposed off-axis spectral encoding multicolor microscopy(OSEM)with a single camera that simultaneously captures encoded multicolor signals and reconstructs monochromatic images by decoding.Based on the natural intensity modulation difference of a single illumination spot across off-axis detection positions,we adjusted the multicolor excitation beams with distinct off-axis offsets from the same detection position to achieve spectral encoding.The method achieved multicolor simultaneous imaging in a single camera without extra sacrifice of frame rate.We evaluated OSEM's imaging performance by imaging multicolor synthetic samples and fluorescent microbeads.We also demonstrated that OSEM reduced imaging time by 5.8 times and achieved 99%accuracy in classifying and counting multicolor fluorescent bacteria,outperforming sequential imaging.We obtained four-color fluorescent optical-sectioning images of a mouse brain slice at a speed of 2.85 mm^(2)∕s,demonstrating its effectiveness for high-throughput multicolor imaging of large tissue samples.These results indicate that OSEM offers a reliable and efficient tool for multicolor fluorescent imaging of large biological tissues.展开更多
基金the financial support of the National Natural Science Foundation of China(Nos.U2141221 and 52076136)the National Science and Technology Major Project,China(Nos.J2019-Ⅲ-0004-0047 and Y2022-Ⅲ-0001-0010)+1 种基金the Center for Basic Science of Aero Engines and Gas Turbines Project,China(No.P2022-B-Ⅱ019-001)the Natural Science Foundation of Shanghai,China(Nos.22ZR1467900 and 23ZR1481400)。
文摘This study systematically investigated the Lean Blowoff(LBO)limits of Two-Dimensional(2D)bluff-body stabilized premixed flames by varying the air mass flow rate,inflowtemperature,bluff-body width,and fuel type.The data of LBO limits were analyzed and fittedaccording to the Damk?hler(Da)and Reynolds(Re)numbers,and the fitting accuracy of LBO datawas highly improved by a modified characteristic length simultaneously considering the length andwidth of the bluff body,which is usually neglected in the previous studies.Moreover,to our knowl-edge,this is the first time that simultaneous transverse and spanwise OH*-Chemiluminescence(CL)imaging has been performed to examine the three-dimensional behavior of the LBO process.The flame stability is heavily affected by the mass and energy transport between reactants andproducts in both directions,potentially leading to the flame pinch-off.The intensity and positionof the upstream flame after pinch-off are decisive to the occurrence of the following LBO.Whenthe upstream flame after pinch-off is weak and close to the bluff body,it cannot re-ignite thedownstream unburnt gas.Subsequently,a permanent downstream extinction occurs,and theLBO takes place.The results help understand the LBO mechanism of 2D bluff-body stabilizedflames.
文摘The objective of this study is to demonstrate that tensile stress resulting due to applied force on cornea can be accurately measured by using a time-domain common-path optical coherence tomography （OCT） system with an external contact reference. The unique design of the common-path OCT is utilized to set up an imaging system in which a chicken eye is placed adjacent to a glass plate serving as the external reference plane for the imaging system. As the force is applied to the chicken eye, it presses against the reference glass plate. The modified OCT image obtained is used to calculate the size of contact area, which is then used to derive the tensile stress on the cornea. The drop in signal levels upon contact of reference glass plate with the tissue are extremely sharp because of the sharp decline in reference power levels itself, thus providing us with an accurate measurement of contact area. The experimental results were in good agreement with the numerical predictions. The results of this study might be useful in providing new insights and ideas to improve the precision and safety of currently used ophthalmic surgical techniques. This research outlines a method which could be used to provide high resolution OCT images and a precise feedback of the forces applied to the cornea simultaneously.
基金Project supported by the National Natural Science Foundation of China(Grant No.61671026)the Natural Science Foundation of Beijing,China(Grant No.7162112)
文摘Controlled aliasing in parallel imaging results in higher acceleration （CAIPIRINHA） for simultaneous multislice imaging has been proposed recently, which combines multiband excitation and phase cycling techniques to reduce scan time and improve subsequent imaging reconstruction. In this work, the total variation （TV） regularization method is used to further improve CAIPIRINHA. The TV regularization uses an edge-preserving prior, which establishes a relationship between neighboring pixels for image reconstruction. It reduces artifacts and suppresses noise amplification simultaneously. The results are presented with a standard eight-channel head coil with an acceleration factor of 4, where the TV-regularized CAIPIRINHA generates an improved reconstruction as compared with a typical nonregularized CAIPIRINHA.
基金National Natural Science Foundation of China(62325502,81827901)。
文摘Multicolor imaging has been widely applied across various biological and medical applications,especially essential for probing diverse biological structures.However,existing multicolor imaging methods often sacrifice either simultaneity or speed,posing a challenge for simultaneous imaging of over three fluorophores.Here,we proposed off-axis spectral encoding multicolor microscopy(OSEM)with a single camera that simultaneously captures encoded multicolor signals and reconstructs monochromatic images by decoding.Based on the natural intensity modulation difference of a single illumination spot across off-axis detection positions,we adjusted the multicolor excitation beams with distinct off-axis offsets from the same detection position to achieve spectral encoding.The method achieved multicolor simultaneous imaging in a single camera without extra sacrifice of frame rate.We evaluated OSEM's imaging performance by imaging multicolor synthetic samples and fluorescent microbeads.We also demonstrated that OSEM reduced imaging time by 5.8 times and achieved 99%accuracy in classifying and counting multicolor fluorescent bacteria,outperforming sequential imaging.We obtained four-color fluorescent optical-sectioning images of a mouse brain slice at a speed of 2.85 mm^(2)∕s,demonstrating its effectiveness for high-throughput multicolor imaging of large tissue samples.These results indicate that OSEM offers a reliable and efficient tool for multicolor fluorescent imaging of large biological tissues.
