针对现有森林资源调查中立木胸径测量工作劳动强度大、效率低,先进设备操作复杂、成本高等问题,结合相机标定、三维重建、机器视觉和近景摄影测量等技术,探索基于智能手机与机器视觉技术的立木胸径测量方法。通过智能手机获取待测立木...针对现有森林资源调查中立木胸径测量工作劳动强度大、效率低,先进设备操作复杂、成本高等问题,结合相机标定、三维重建、机器视觉和近景摄影测量等技术,探索基于智能手机与机器视觉技术的立木胸径测量方法。通过智能手机获取待测立木的图像信息,运用Lab颜色空间模型(Lab color model)和3×3算子对图像进行卷积运算,得到立木图像的视觉显著图;结合HSV颜色模型(色调H,饱和度S,明度V)中的H分量增强图像中立木树干部分的颜色对比度,通过图像分割算法识别并获取自然环境下的目标立木轮廓区域;通过一种改进的带有非线性畸变项的相机标定模型标定智能手机的相机内、外参数,并借助相机参数和二维图像信息进行三维世界坐标重建,从而实现树干1.3 m处胸径的测量。经验证,一定距离内胸径测量结果的相对误差小于2.50%。该方法测量精度较高,符合森林资源调查对胸径测量的精度要求,可应用于森林资源调查。展开更多
Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the ...Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the air/fuel ratio around the stoichiometric point and hence requires an accurate model for air charge estimation.However,high degrees of complexity and nonlinearity of the gas flow in the internal combustion engine make air charge estimation a challenging task.This is more obvious in engines with variable valve timing systems in which gas flow is more complex and depends on more functional variables.This results in models that are either quite empirical(such as look-up tables),not having interpretability and extrapolation capability,or physically based models which are not appropriate for onboard applications.Solving these problems,a novel semi-empirical model was proposed in this work which only needed engine speed,load,and valves timings for volumetric efficiency prediction.The accuracy and generalizability of the model is shown by its test on numerical and experimental data from three distinct engines.Normalized test errors are 0.0316,0.0152 and 0.24 for the three engines,respectively.Also the performance and complexity of the model were compared with neural networks as typical black box models.While the complexity of the model is less than half of the complexity of neural networks,and its computational cost is approximately 0.12 of that of neural networks and its prediction capability in the considered case studies is usually more.These results show the superiority of the proposed model over conventional black box models such as neural networks in terms of accuracy,generalizability and computational cost.展开更多
In order to predict the local scour hole and its evaluation around a cylindrical bridge pier, the computational fluid dynamics （CFD） and theories of sediment movement and transport were employed to carry out numeric...In order to predict the local scour hole and its evaluation around a cylindrical bridge pier, the computational fluid dynamics （CFD） and theories of sediment movement and transport were employed to carry out numerical simulations. In the numerical method, the time-averaged Reynolds Navier-Stokes equations and the standard k-e model were first used to simulate the three-dimensional flow field around a bridge pier fixed on river bed. The transient shear stress on river bed was treated as a crucial hydrodynamic mechanism when handling sediment incipience and transport. Then, river-bed volumetric sediment transport was calculated, followed by the modification of the river bed altitude and configuration. Boundary adaptive mesh technique was employed to modify the grid system with changed river-bed boundary. The evolution of local scour around a cylindrical bridge pier was presented. The numerical results represent the flow pattern and mechanism during the pier scouring, with a good prediction of the maximum scour hole depth compared with test results.展开更多
Chromatography-mass spectrometry(GC-MS)was used to analyze the volatile components of cut tobacco samples with the help of heuristic evolving latent projections(HELP).After extracting with simultaneous distillation an...Chromatography-mass spectrometry(GC-MS)was used to analyze the volatile components of cut tobacco samples with the help of heuristic evolving latent projections(HELP).After extracting with simultaneous distillation and extraction method,the volatile components in cut tobacco were detected by GC-MS.Then the obtained original two-dimensional data were resolved into pure mass spectra and chromatograms.The qualitative analysis was performed by similarity searches in the national institute of standards and technology(NIST)mass database with the obtained pure mass spectrum of each component and the quantitative results were obtained by calculating the volume of total two-way response.The accuracy of qualitative and quantitative results were greatly improved by using the two-dimensional comprehensive information of chromatograms and mass spectra.107 of 141 separated constituents in the total ion chromatogram of the volatile components were identified and quantified,accounting for about 88.01% of the total content.The result proves that the developed method is powerful for the analysis of complex cut tobacco samples.展开更多
Large-scale field shear tests on ten specimens of the red-sandstone embankment at a highway in Hunan,China,were performed to examine mechanical characteristics and parameters of red-sandstone.The curves of thrust-disp...Large-scale field shear tests on ten specimens of the red-sandstone embankment at a highway in Hunan,China,were performed to examine mechanical characteristics and parameters of red-sandstone.The curves of thrust-displacement,failure mode,and shear strength parameters for red-sandstone with different water contents,different compactions,and different grain size distributions were obtained from the tests.A practical procedure of in-situ test for red-sandstone embankment was proposed to normalize the test equipment and test steps.Based on three-dimensional thrust-sliding limit equilibrium method,the formulas for calculating strength parameters of red-sandstone considering three-dimensional sliding surface were inferred.The results show that red-sandstone has typical complete curves of stress-strain,strain softening,which are caused by the special structure of red-sandstone;water content and compaction are important factors for strength and failure mode of red-sandstone;The average value of cohesion and internal friction angle of the specimens calculated by three-dimensional technique are 21.56 kPa and 29.29°,respectively,and those by traditional two-dimensional method are 25.52 kPa and 33.76°,respectively.展开更多
Proton exchange membrane fuel cell (PEMFC) stack temperature and cathode stoichiometric oxygen are very important control parameters. The performance and lifespan of PEMFC stack are greatly dependent on the parameters...Proton exchange membrane fuel cell (PEMFC) stack temperature and cathode stoichiometric oxygen are very important control parameters. The performance and lifespan of PEMFC stack are greatly dependent on the parameters. So, in order to improve the performance index, tight control of two parameters within a given range and reducing their fluctuation are indispensable. However, control-oriented models and control strategies are very weak junctures in the PEMFC development. A predictive control algorithm was presented based on their model established by input-output data and operating experiences. It adjusts the operating temperature to 80 ℃. At the same time, the optimized region of stoichiometric oxygen is kept between 1.8?2.2. Furthermore, the control algorithm adjusts the variants quickly to the destination value and makes the fluctuation of the variants the least. According to the test results, compared with traditional fuzzy and PID controllers, the designed controller shows much better performance.展开更多
文摘针对现有森林资源调查中立木胸径测量工作劳动强度大、效率低,先进设备操作复杂、成本高等问题,结合相机标定、三维重建、机器视觉和近景摄影测量等技术,探索基于智能手机与机器视觉技术的立木胸径测量方法。通过智能手机获取待测立木的图像信息,运用Lab颜色空间模型(Lab color model)和3×3算子对图像进行卷积运算,得到立木图像的视觉显著图;结合HSV颜色模型(色调H,饱和度S,明度V)中的H分量增强图像中立木树干部分的颜色对比度,通过图像分割算法识别并获取自然环境下的目标立木轮廓区域;通过一种改进的带有非线性畸变项的相机标定模型标定智能手机的相机内、外参数,并借助相机参数和二维图像信息进行三维世界坐标重建,从而实现树干1.3 m处胸径的测量。经验证,一定距离内胸径测量结果的相对误差小于2.50%。该方法测量精度较高,符合森林资源调查对胸径测量的精度要求,可应用于森林资源调查。
文摘Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the air/fuel ratio around the stoichiometric point and hence requires an accurate model for air charge estimation.However,high degrees of complexity and nonlinearity of the gas flow in the internal combustion engine make air charge estimation a challenging task.This is more obvious in engines with variable valve timing systems in which gas flow is more complex and depends on more functional variables.This results in models that are either quite empirical(such as look-up tables),not having interpretability and extrapolation capability,or physically based models which are not appropriate for onboard applications.Solving these problems,a novel semi-empirical model was proposed in this work which only needed engine speed,load,and valves timings for volumetric efficiency prediction.The accuracy and generalizability of the model is shown by its test on numerical and experimental data from three distinct engines.Normalized test errors are 0.0316,0.0152 and 0.24 for the three engines,respectively.Also the performance and complexity of the model were compared with neural networks as typical black box models.While the complexity of the model is less than half of the complexity of neural networks,and its computational cost is approximately 0.12 of that of neural networks and its prediction capability in the considered case studies is usually more.These results show the superiority of the proposed model over conventional black box models such as neural networks in terms of accuracy,generalizability and computational cost.
基金Project(50978095) supported by the National Natural Science Foundation of ChinaProject(IRT0917) supported by the Program for Changjiang Scholars and Innovative Research Team in Chinese UniversityProject supported by China Scholarship Council
文摘In order to predict the local scour hole and its evaluation around a cylindrical bridge pier, the computational fluid dynamics （CFD） and theories of sediment movement and transport were employed to carry out numerical simulations. In the numerical method, the time-averaged Reynolds Navier-Stokes equations and the standard k-e model were first used to simulate the three-dimensional flow field around a bridge pier fixed on river bed. The transient shear stress on river bed was treated as a crucial hydrodynamic mechanism when handling sediment incipience and transport. Then, river-bed volumetric sediment transport was calculated, followed by the modification of the river bed altitude and configuration. Boundary adaptive mesh technique was employed to modify the grid system with changed river-bed boundary. The evolution of local scour around a cylindrical bridge pier was presented. The numerical results represent the flow pattern and mechanism during the pier scouring, with a good prediction of the maximum scour hole depth compared with test results.
基金Project supported by the Postdoctoral Foundation of Changde Cigarette FactoryProject(20060400887) supported by China Postdoctoral Science Foundation
文摘Chromatography-mass spectrometry(GC-MS)was used to analyze the volatile components of cut tobacco samples with the help of heuristic evolving latent projections(HELP).After extracting with simultaneous distillation and extraction method,the volatile components in cut tobacco were detected by GC-MS.Then the obtained original two-dimensional data were resolved into pure mass spectra and chromatograms.The qualitative analysis was performed by similarity searches in the national institute of standards and technology(NIST)mass database with the obtained pure mass spectrum of each component and the quantitative results were obtained by calculating the volume of total two-way response.The accuracy of qualitative and quantitative results were greatly improved by using the two-dimensional comprehensive information of chromatograms and mass spectra.107 of 141 separated constituents in the total ion chromatogram of the volatile components were identified and quantified,accounting for about 88.01% of the total content.The result proves that the developed method is powerful for the analysis of complex cut tobacco samples.
基金Project(200612) supported by Hunan Province Transportation Department of China
文摘Large-scale field shear tests on ten specimens of the red-sandstone embankment at a highway in Hunan,China,were performed to examine mechanical characteristics and parameters of red-sandstone.The curves of thrust-displacement,failure mode,and shear strength parameters for red-sandstone with different water contents,different compactions,and different grain size distributions were obtained from the tests.A practical procedure of in-situ test for red-sandstone embankment was proposed to normalize the test equipment and test steps.Based on three-dimensional thrust-sliding limit equilibrium method,the formulas for calculating strength parameters of red-sandstone considering three-dimensional sliding surface were inferred.The results show that red-sandstone has typical complete curves of stress-strain,strain softening,which are caused by the special structure of red-sandstone;water content and compaction are important factors for strength and failure mode of red-sandstone;The average value of cohesion and internal friction angle of the specimens calculated by three-dimensional technique are 21.56 kPa and 29.29°,respectively,and those by traditional two-dimensional method are 25.52 kPa and 33.76°,respectively.
基金Project (2003AA517020) supported by the National High-Tech Research and Development Program of China
文摘Proton exchange membrane fuel cell (PEMFC) stack temperature and cathode stoichiometric oxygen are very important control parameters. The performance and lifespan of PEMFC stack are greatly dependent on the parameters. So, in order to improve the performance index, tight control of two parameters within a given range and reducing their fluctuation are indispensable. However, control-oriented models and control strategies are very weak junctures in the PEMFC development. A predictive control algorithm was presented based on their model established by input-output data and operating experiences. It adjusts the operating temperature to 80 ℃. At the same time, the optimized region of stoichiometric oxygen is kept between 1.8?2.2. Furthermore, the control algorithm adjusts the variants quickly to the destination value and makes the fluctuation of the variants the least. According to the test results, compared with traditional fuzzy and PID controllers, the designed controller shows much better performance.
