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| 1 | Temperature field reconstruction of 3D luminous flames based on light field tomography theory显示文摘Standard plenoptic camera can be used to capture multi-dimensional radiation information of high temperature luminous flame to reconstruct the temperature distribution. In this study, a novel method for reconstructing three-dimensional temperature field is proposed. This method is based on the optical tomography combined with standard plenoptic camera. The flame projection information from different planes is contained in one radiation image. In this model, we introduced the effective concept of the nearest neighbor method in the frequency domain to strip the interference of redundant information in the projection and to realize three-dimensional deconvolution. The flame emission intensity received by the pixels on the charge-coupled device sensor can be obtained according to the optical tomographic model. The temperature distributions of the axisymmetric and nonaxisymmetric flames can be reconstructed by solving the mathematical model with the nearest neighbor method. The numerical results show that three-dimensional temperature fields of high temperature luminous flames can be retrieved, proving the validity of the proposed method. | NIU ZhiTian QI Hong SHI JingWen ZHANG JuQi REN YaTao | 2021 | Science China(Technological Sciences)2021，64，2： | 6 |
| 2 | Three-dimensional temperature reconstruction of diffusion flame from the light-field convolution imaging by the focused plenoptic camera显示文摘The plenoptic imaging technique provides a promising approach to the non-invasive three-dimensional measurement, especially for the high-temperature combustion diagnosis. We establish a light-field convolution imaging model for diffusion flame in this work, considering the radiation transfer process inside the diffusion flame and the light transfer process inside the focused plenoptic camera together. The radiation transfer process is described by the radiation transfer equation and solved by the generalized source multi-flux method. Wave optics theory is adopted to describe the light transfer process, combining Fresnel diffraction and the phase conversion of the lens. The flame light-field image is obtained by the light-field convolution imaging model and adopted as the measurement signal to reconstruct three-dimensional temperature field. The inverse problem of temperature reconstruction is solved by the least square QR decomposition method. The simulative temperature reconstruction work is conducted, including the inverse analysis, the uncertainty analysis, and the measurement noise influence. All the results show that the proposed measurement method is available to reconstruct three-dimensional temperature with satisfactory accuracy and acceptable uncertainty. Both symmetric and asymmetric distributed temperature fields are investigated, and the reconstructed results prove the validity and universality of the measurement method. | SHI JingWen QI Hong YU ZhiQiang AN XiangYang REN YaTao TAN HePing | 2022 | Science China(Technological Sciences)2022，65，2： | 4 |
| 3 | ExExperimental and numerical studies on the prediction of bendability limit of QSTE340 welded tube in NC bending process显示文摘For a low carbon steel tube with small wall factor D/t and bending radius R,the over-thinning induced localized necking is one dominant failure in tube numerical control(NC) bending process,which strongly restricts the bendability limit of the tube.In addition,the deterioration of bendability of a tube is increased by the existence of the weak weld region.Therefore,an important issue is how to determinate and predict the welded tube bendability limit.In the present study,a finite element(FE) model with weld and subdivided heat affected zones under ABAQUS platform is employed to explore the deformation behaviors of welded tube NC bending.A localized necking criterion based on the critical thickness thinning is used to predict the critical principal strains,critical bending radius and burst location during the forming process.It is found that the failures always occur at the rigid supporting point of mandrel flexible balls near the tangent point at the outside of the bend,where the wall thickness of the tube is the lowest.The bending limit curves(BLCs) of the QSTE340 welded tube are obtained by shifting the standard shaped forming limit curve to the critical principal strains along the major strain axis.Comparison between the numerical and experimental results has shown that the BLC and critical bending radius predictions agree well with the experimental results.In addition,the effect of weld positions on BLC is discussed,the weld region shows an almost negligible effect on the forming limit at a non-critical location that is far away from the outside of the bend.However,when the weld is at the large tensile deformation region on the outside of the bend,a decrease of the forming limit strains is seen. | YANG He REN Ning ZHAN Mei ZHANG ZhiYong QIN YaTao JIANG HaoMin DIAO KeShan CHEN XinPing | 2012 | Science China(Technological Sciences)2012，55，8： | 2 |
| 4 | Prediction of the coupled heat radiation and conduction parameters and boundary condition using the unscented Kalman filter显示文摘The boundary emissivity, thermal conductivity, and boundary time-varying heat flux in the participating media are retrieved in this work. In the forward model, the coupled radiation-conduction heat transfer in the participating medium is resolved by the finite volume method combined with discrete ordinates method. The inverse model utilizes the temperature signals at the appropriate position of the medium as the known information and uses the unscented Kalman filter(UKF) as an optimization tool to reconstruct the boundary emissivity, thermal conductivity, and boundary time-varying heat flux. It is found that when the emissivity, thermal conductivity, and boundary time-varying heat flux are reconstructed simultaneously, only the temperature information of two locations is required. The influence of the measurement noise, sampling interval, absorption coefficient,process noise covariance, measurement noise covariance on the accuracy and stability of the retrieval results is investigated in detail. All the reconstruction results indicate that the UKF technique is effective and robust for estimating the photothermal parameters and boundary condition of the radiation-conduction heat transfer problems. | WEN Shuang QI Hong WANG YiFei REN YaTao WEI LinYang RUAN LiMing | 2020 | Science China(Technological Sciences)2020，63，3： | 2 |
| 5 | On the maximum area pentagon in a planar point set显示文摘 | Du Yatao Ding Ren | 2006 | Applied Mathematics Letters2006，19，： | 1 |
| 6 | On maximum area polygons in a planar point set显示文摘 | Du Yatao Ding Ren | 2008 | Elemente der Mathe- matik2008，63，： | 1 |
| 7 | New Proofs About the Number of Empty Convex 4-gons and 5-gons in a Planar Point Set显示文摘 | DU Yatao DING Ren | | 0，，： | 1 |
| 8 | Efficient and robust CNN-LSTM prediction of flame temperature aided light field online tomography显示文摘Light field tomography,an optical combustion diagnostic technology,has recently attracted extensive attention due to its easy implementation and non-intrusion.However,the conventional iterative methods are high data throughput,low efficiency and time-consuming,and the existing machine learning models use the radiation spectrum information of the flame to realize the parameter field measurement at the current time.It is still an offline measurement and cannot realize the online prediction of the instantaneous structure of the actual turbulent combustion field.In this work,a novel online prediction model of flame temperature instantaneous structure based on deep convolutional neural network and long short-term memory(CNN-LSTM)is proposed.The method uses the characteristics of local perception,shared weight,and pooling of CNN to extract the threedimensional(3D)features of flame temperature and outgoing radiation images.Moreover,the LSTM is used to comprehensively utilize the ten historical time series information of high dynamic combustion flame to accurately predict 3D temperature at three future moments.A chaotic time-series dataset based on the flame radiation forward model is built to train and validate the performance of the proposed CNN-LSTM model.It is proven that the CNN-LSTM prediction model can successfully learn the evolution pattern of combustion flame and make accurate predictions. | NIU ZhiTian QI Hong SUN AnTai REN YaTao HE MingJian GAO BaoHai | 2024 | Science China(Technological Sciences)2024，67，1： | 0 |
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