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关键词： 柴油机   废气再循环   排放控制策略  

摘要： 针对废气再循环(exhaust gas recirculation,EGR)控制方法瞬时响应性差、跟随性差的问题,提出利用文丘里流量公式计算EGR阀的需求开度,根据经过EGR阀的废气需求流量与实际废气流量的偏差进行闭环修正,得到EGR阀的控制开度。通过MATLAB/Simulink软件平台对EGR控制策略进行离线仿真,将该控制策略集成在发动机控制系统中并在硬件试验台架上进行验证。结果表明,基于废气流量闭环的文丘里EGR方案能够更好地提高空气系统控制准确度及瞬时响应性。

关键词： kinetic theory   hydrodynamic limit   diffusion equations  

摘要： We consider a kinetic model whose evolution is described by a Boltzmann-like equation for the one-particle phase space distribution f(x, v, t). There are hard-sphere collisions between the particles as well as collisions with randomly fixed scatterers. As a result, this evolution does not conserve momentum but only mass and energy. We prove that the diffusively rescaled f(epsilon)(x, v, t) = f(epsilon(-1)x, v, epsilon(-2)t) tends, as epsilon -> 0, to a Maxwellian M-rho,M-0,M-T = rho/(2 pi T)(3/2) exp[-vertical bar v vertical bar(2)/2T], where rho and T are solutions of coupled diffusion equations and estimate the error in L-x,v(2).

关键词： Particle shape   Sphericity   Sugar cane bagasse   Aspect ratio   Image analyses  

摘要： Sugarcane bagasse is used as energy source in the sugar cane industry. An appropriate characterization of their physical and morphological properties is vitally important for their use in the gasification and combustion processes. This work makes a study of the size and shape distribution of the bagasse generated in a sugarcane mill based upon two important factors that influence their physical properties, such as aspect ratio (AR) and sphericity. The distribution of the grain sizes has been determined for the analyzed samples;the shapes of the particles has been determined by a manual method and through an image-analysis method, using the Image) software. It has been observed that sugarcane bagasse has a larger length than the other analyzed biomasses, with an almost similar width. The aspect ratio was between 2.14 and 5.5 for all the studied size ranges (9.5-0.15 mm). For particles with diameters smaller than 0.3 mm, the aspect ratio has a similar behavior to the other biomasses, with a reported value of 2.5. The determined sphericity was between 0.27 and 0.558, with a mean value of 0.397. (C) 2019 Published by Elsevier Ltd.

关键词： Axial fans   fans   fans   blowers  

摘要： Due to the low production cost, circular arc blades are often applied to axial fans as outlet guide vane. At present, there is less available information focusing on the flow loss and flow structure of circular arc blades in the open literature. In particular, the influence of leading edge and trailing geometries on the aerodynamic performance of circular arc blades remains unknown. In this study, the circular arc blades edge with different leading edge and trailing edge are investigated and compared with numerical and experimental methods to detect the aerodynamic performance of the circular arc blades and the influence of their leading edge and trailing edge on the flow loss and flow structure. The flow loss and turning angle of both investigated blades are shown to dependent on the incidence angle. The flow structures of both blades are built on the basis of numerical and experimental oil-flow pictures. Additionally, the separation bubbles at the leading edge of the blade and the distribution of the flow loss on the measuring plane are shown and discussed.

关键词： Convection   Micropolar nanofluid   Magnetic field-dependent (MFD) viscosity   Coupling parameter  

摘要： In this work, the characteristics of the thermogravitational energy transport of a micro-polar nanoliquid in a chamber have been numerically analyzed considering the influence of micro-rotations on the thermal characteristics of the flow. The dynamic viscosity is assumed as a function of the magnetic field vector. The results indicate that the reduction or increase in the energy transport rate by augmenting the Hartmann number depends on the vortex viscosity parameter. Also, increasing the coupling parameter reduces the heat transport rate. At low values of the vortex viscosity or coupling parameters, the increased Rayleigh number will augment the energy transport intensity. When the vortex viscosity (or coupling) parameter has high value, there is an ascending-descending tendency of the Nusselt number with augmenting Rayleigh number. Considering the coupling parameter, the heat transport rate is reduced or increased by increasing the magnetic field-dependent. It can be seen that, for low vortex viscosity, the dispersion of nanoparticles will increase the Nusselt number. When the vortex viscosity rises, there is a completely opposite behavior with the previously described state. Also, the variation of the heat transport rate by inclining of magnetic field entirely depends on the value of the coupling. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Kernel   Manifolds   Hyperspectral imaging   Task analysis   Support vector machines   Geodesic flow kernel (GFK)   hyperspectral images (HSIs)   multiple kernel learning (MKL)   spatial-spectral classification   unsupervised classification  

摘要： With the increasing acquisition ability of hyperspectral remote sensing images, unsupervised cross-temporal classification (UCTC) of hyperspectral images (HSIs) has attracted more and more attention. In this paper, we focus on cross-temporal HSI classification, i.e., using one labeled HSI to classify the other unlabeled HSI. A multiple geodesic flow kernel learning (MGFKL) framework is proposed to exploit both spatial and spectral features for UCTC with bitemporal HSIs and called S2-MGFKL. The proposed S2-MGFKL method first extracts extended multi-attribute profiles (EMAPs) from the original bitemporal HSIs. The spatial features of the bitemporal HSIs obtained by the same attribute filter are paired up, so are the original spectral features. Second, each pair of features from both source and target domains are used to construct multiple geodesic flows. According to the original definition of GFK, we can obtain the construction of Gaussian base GFKs. The base kernels consist of two parts, the spectral part is obtained base on the same geodesic flow (which is constructed on the bitemporal spectral features) by tuning the kernel scale, while the spatial part is obtained under the same kernel scale but different geodesic flows constructed on different spatial feature pairs. After that, the mean rule is adopted to acquire the combined kernel, which is fed into the supervised vector machine (SVM) to implement the cross-temporal classification task. Experiments are conducted on two real HSI data sets, and the results compared with several well-known methods demonstrate the effectiveness of the proposed method.

摘要： We give a classification of compact solitons for the pluriclosed flow on complex surfaces. First, by exploiting results from the Kodaira classification of surfaces, we show that the complex surface underlying a soliton must be Kahler except for the possibility of steady solitons on minimal Hopf surfaces. Then, we construct steady solitons on all class 1 Hopf surfaces by exploiting a symmetry ansatz.

关键词： Urbanization   Multiple stressors   Stream flow   Contamination   Biological quality   Traits  

摘要： Urban streams provide important ecosystem services to cities' population, from the maintenance of urban biodiversity, temperature, humidity and air quality to improving aesthetics and provision of natural areas for recreation. However, these streams are under multiple-stressors, including artificialization of the channel and flow, poor water quality and cut of riparian vegetation which puts in risk their ecological integrity and consequently their services. In this study, we aimed to understand variations in macroinvertebrate communities and in biological condition as a response to flow and water quality, by following a Mediterranean urban stream over 8 months (December-July). With a monthly periodicity, we sampled invertebrate communities and characterized in situ water physicochemical parameters. The urban stream studied showed a high variation of environmental factors over time. Invertebrate communities were generally poor, with some Ephemeroptera (Baetis sp.) but was dominated by Chironomidae and Oligochaeta that changed over time alongside with environmental conditions. Biological quality based on the Portuguese Invertebrates Index (IPtIS) varied between poor and bad. Multivariate community patterns (at genus level) showed variations in communities over time, as well as in their biological trait patterns (invertebrates' maximal size, reproduction mode, resistance form, feeding habits and locomotion mode). Periods displaying worse biological quality, less diverse communities and lower functional richness corresponded to peaks of discharge, higher conductivity and hardness while the best quality communities were found under lower nitrate concentrations. Our study points out that the detection of impacts or recovery in urban streams through invertebrate communities might require at least the use of genus level as family level does not detect smoother changes. Communities reflect the complex interplay of environmental variables affecting structural and functional n

关键词： Fluidization   MRI   Jets  

摘要： Rapid magnetic resonance imaging (MRI) was used to characterize properties of a single central gas jet injected into a 3D gas fluidized bed under incipient fluidization conditions. Snapshots of both particle concentration and particle velocity are provided. The average jet height, oscillations in jet height and the size of bubbles breaking off from the jet increased with increasing jet velocity. The frequency of bubble breakoff from the jet decreased with increasing jet velocity. The jet height measurements are compared with various correlations in the literature, and the quantitative data provided here can be compared directly with that from numerical simulations and theoretical predictions for validation purposes. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

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