航空喷气燃料RP-3运动粘度特性研究

采用振动弦法,在相同温度不同压力和相同压力不同温度条件下开展航空喷气燃料RP-3的运动粘度特性试验,研究航空喷气燃料运动粘度随温度和压力的变化规律。结果表明:随着温度的增大,喷气燃料RP-3的运动粘度逐渐变小,低温条件下更为明显。随着压力的增大,喷气燃料运动粘度缓慢增加,压力对喷气燃料运动粘度的影响较小。     

Group vaporization of liquid fuel sprays

In the simplest models of spray combustion it is assumed that the droplets burn individually according to the “d²-law.” Both theory and experiment show that this model only will be valid if the spray is extremely dilute, otherwise the droplets burn collectively in what is known as the group combustion mode. Most of work on spherical droplet cloud is limited to monodisperse sprays; however it is important to determine how the particle size distribution will affect group combustion, particularly the sheath combustion mode. In order to gain preliminary indication of the effect of the droplet size distribution of the vaporization process, the behavior of spays with a bimodal droplet size distribution is examined. The present study shows that for a cloud which is initially in saturated equilibrium the droplet size distribution changes the profiles of temperature and fuel vapor mass fraction within the vaporization wave at the edge of the cloud; however, the size distribution does not affect the overall evaporation characteristics such as the vaporization rate and the cloud lifetime in the sheath combustion limit considered here. It is shown that as before the cloud radius decreases according to a “d²-law” with a modified vaporization constant.     

Multimodal microscopy by digital image processing

A matching algorithm is proposed for aligning microscope images obtained using different modalities, making use of cross-correlations of outputs from Prewitt's edge filter. Brightfield, phase contrast and differential interference contrast microscope images of algal and bacterial cells from an experimental, high-rate algal pond are used for illustration. The information content of multimodal images is explored using principal components analysis and colour displays, and an image which represents optical thickness is constructed digitally.     

A study of the relation between nozzle geometry,internal flow and sprays characteristics in diesel fuel injection systems

This study examines the influence of geometry on the internal flow and macroscopic behavior of the spray in Diesel nozzles. For this investigation, two bi-orifice nozzles were employed : one cylindrical and one conical. The first step is to use a non-destructive characterization method which is based on the production of silicone moulds so that the precise internal geometry of the two nozzles can be measured. At this stage the nozzles have been characterized dimensionally and therefore the internal flow can be studied using CFD calculations. The results gained from this experiment make it possible also to ascertain the critical cavitation conditions. Once the critical cavitation conditions have been identified, the macroscopic parameters of the spray can be studied in both cavitating and non-cavitating conditions using a test rig pressurized with nitrogen and with the help of a image acquisition system and image processing software. Consequently, research can be carried out to determine the influence that cavitation has on macroscopic spray behavior. From the point of view of the spray macroscopic behavior, the main conclusion of the paper is that cavitation leads to an increment of the spray cone angle. On the other hand, from the point of view of the internal flow, the hole outlet velocity increases when cavitation appears. This phenomenon can be explained by the reduction in the cross section of the liquid phase in the outlet section of the hole.     

Speckle pattern correlation by digital image processing

Digital Speckle Pattern Interferometry (DSPI) has been implemented using a commercial image processing system. The pipeline image processor produces real-time correlation fringes and allows rapid automatic evaluation of correlograms. On-line operation gives quantitative results after 2–3 min.     

航空图像压缩中双正交小波提升设计

利用小波消失矩与其对应的滤波器在z=1处零点阶数的关系,提出了一种设计最佳提升系数的迭代算法.该算法克服了用提升格式方法时求解高阶导数计算复杂的缺陷,通过求解一组简单的线性方程组来设计基于任意双正交小波的提升系数,从而实现了根据具体要求动态地、迭代地设计小波的目的.该算法可以用于设计对称和非对称的小波,并在航空图像压缩中取得压缩倍数为49.913 2,峰值信噪比(PSNR)达46.279 61的良好效果.     

Atomization characteristics of emulsified fuel oil by instant emulsification

The breakup and spray formation of swirl liquid jets with respect to the instant emulsification of heavy fuel oil and water were experimentally investigated. The effects of the degree of emulsion and flashing on the macro- and microscopic spray parameters were measured optically in terms of the rotor speed, mixture ratio, and nozzle exit temperature. Enhanced emulsification and flashing improved the spray characteristics. The effect of flashing on the Sauter mean diameter of the spray decreased as the degree of emulsion increased. However, when flashing occurred, the effect of instant emulsification was small because of the blades in the emulsion chamber and filter prior to the nozzle inlet, which served as a static mixer.     

Measurement of electron probe beam diameter by digital image processing

The present report illustrates a computerized method for precise measurement of the diameter of an electron beam. The value of this measurement extends beyond simply providing an accurate estimate of resolution. Other salient areas which will benefit include quantitative X-ray microanalysis, energy loss spectroscopy, diffraction studies, and electron beam lithography. The biological sciences as well as the material sciences will gain enormously from improved accuracy in measurement (control) of beam diameter. It is anticipated that most or all of the mathematical manipulations outlined in this paper will be incorporated into digital electronic packages which will perform the functions automatically for setting the electron beam diameter to the scientist's choice. The purpose of the present report is to indicate some of the principles involved so that as electron microscopy becomes more computerized and automated, the user will have some understanding of what the electronics are doing rather than simply depressing a button or two and ignoring the power of what resides within the walls of the instrument. The performance of a scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM) is roughly determined by the incident electron probe beam size (diameter) involving a sufficient electron current. In the present paper, the diameter of an ultrafine electron beam is measured indirectly from the information given by the blurring of an edge in a STEM or a SEM image of a crystalline specimen with fine, sharp edges. The obtained data were processed by digital image processing methods which give an accurate value of the beam diameter. For confirming the validity of this method, a suitable simulation based on the convolution theorem was performed. By using this measurement, we could measure the diameter of an ultrafine electron beam down to 2 nm, which could not be measured easily by previous techniques.     

利用图像处理技术评价硅片表面清洗率

介绍了一种基于Matlab图像处理工具箱技术的评价硅片表面污染颗粒激光清洗率的新方法。借助Matlab图像处理工具箱,对清洗前后硅片表面光学显微镜照片进行处理,编写硅片表面激光干法清洗率的评价程序,统计清洗前后硅片表面评价区域的污染颗粒个数,对清洗效果进行定量评价。研究结果证明,利用此方法统计的颗粒数准确度达97.6%,得到的激光清洗率准确度达99.2%。结果表明,借助图像处理技术评定清洗效果是一种高效、快速、准确的新方法。     

Digital image processing of crystalline specimens examined by electron microscopy

Crystalline specimens imaged in the electron microscope are analysed using digital processing. Some principles of structural analysis using the method of Fourier decomposition are discussed. Complementary techniques, such as enhancement by gradient and Laplacian operators, have been found useful in analysing electron micrographs. The application of these techniques to some problems in Materials Science and Biology are reviewed. By selecting and phase-correcting spots in the computed diffraction pattern, it was possible to localize atoms, molecules, and their defective arrangement in evaporated gold, sputter-deposited tungsten films, and single crystals of cadmium selenide. Digital processing based on the theory of helical diffraction was used to explore the three-dimensional arrangement of molecules in cellular components of alveolar soft part sarcoma, Hirano bodies, and neurofibrillar tangles in the human brain.     

Numerical simulations and surrogate-based optimization of cavitation performance for an aviation fuel pump

We used computational modeling to investigate the cavitation performance of an aviation fuel pump, and optimize structural parameters using the surrogate-based method. In the numerical simulation, a rotation-curvature correction was adapted to the k-ε turbulence model, and a four-component surrogate fuel was selected to reproduce the physical properties of the China RP-3 kerosene. Then the performance of the aviation fuel pump was predicted. In the optimization, based on the series of the numerical results, Surrogate-based analysis and optimization (SBAO) was used to optimize the structural parameters of the fuel pump (the variation of the outlet blade angle for the inducer △β _b1 and the variation of the inlet blade angle for the impeller △β _b2). The results show that the prediction of cavitation performance agrees well with the experimental data. The results show that cavitation areas are mainly distributed in the inlet of the inducer. The volume of cavities grows with the decreasing NPSHa. The head of the fuel pump has a sudden head-drop when NPSHa ≤ 5.64 m. Furthermore, the surrogate-based approach is available in structural optimization of the fuel pump. The cavitation performance of the optimized pump improved about 22 % with a little drop of head coefficient when △β _b1 = 4.33° and △β _b2 = 3.24°. The numerical approach employed in this paper can accurately predict the cavitating flow of the high rotating speed fuel pump and the surrogate-based method is available in the structural optimization for a better cavitation performance.

     

Ribosome substructure investigated by scanning force microscopy and image processing

Scanning force microscopy was used to study the ultrastructure of eukaryotic ribosomes from Chironomus pallidivittatus in the polysomal complex. Positively stained polysomes were imaged, and the resulting three-dimensional ribosomal structures were further processed by statistical analyses of virtual cross-sections parallel to the substrate plane. Structural investigations were based on parameters which are minimally influenced by the tip geometry, like section plane centre or axis ratio. In the lower part of the structure a shift of the section centres was observed, suggesting an attached structure. The geometry of the sections revealed an elliptical shape in the upper part (axis ratio 1.52 ± 0.22), with a less elongated shape in the lower region (axis ratio 1.41 ± 0.18). A model for the surface topography of a positively stained ribosome exhibiting a small subunit attached along the long side of an elliptical large structure is proposed.     

基于形态学图像检测的机械手移栽穴苗识别技术

针对机械移栽穴苗过程中如何有效识别出根系受损的幼苗,进而及时进行分类、补救这一实际问题,提出一种基于机器视觉的移栽穴苗识别方法。该方法根据机械手移栽穴苗特点,对比检测图像土壤基质面积与基准面积;进而通过测定土壤基质完整率,判断样本合格与否。文中从理论和实际的角度说明了形态学图像处理方法处理穴苗移栽图像特点,设计了机械手移栽穴苗识别在线测试系统。最后,对基于形态学图像检测方法的机械手移栽穴苗识别技术和普通图像检测方法进行对比实验。结果表明,本文提出的形态学检测方法对一个72孔穴盘合格检出率提高了6.6%,不合格检出率提高了54.5%。同时,一个穴苗的平均处理时间约为1.82 s。结果表明提出的方法可靠,耗时较短,能够匹配机械手移栽流水线作业时间上的要求,并满足实时处理要求。     

提高DSP图像处理系统实时性的一种有效方法

为解决DSP实时图像处理系统中数据传输的瓶颈问题, 提出了多个数据拼接传输的新方法.以TMS320C6201 DSP为例, 利用DMA支持多种结构数据传输功能.通过对DMA的控制寄存器进行设置, 来实现图像数据的合理拼接, 从而能够有效地提高DSP的数据传输效率.实验结果证明了数据拼接传输可行且有效,对提高DSP图像处理系统的实时性能具有现实意义.     

A study on the behavior and heat transfer characteristics of impinging sprays

The spray/wall interaction is considered as an important phenomenon influencing air-fuel mixing in the internal combustion engines. In order to adequately represent the spray/wall interaction process, impingement regimes and post-impingement behavior have been modeled using experimental data and conservation constraints. The modeled regimes were stick, rebound, spread and splash. The tangential velocities of splashing droplets were obtained using a theoretical relationship. The continuous phase was modeled using the Eulerian conservation equations, and the dispersed phase was calculated using a discrete droplet model. The numerical simulations were compared to experimental results for spray impingement normal to the wall. The predictions for the secondary droplet velocities and droplet sizes were in good agreement with the experimental data.     

Evaluation of form error at semi-spherical tools by use of image processing

In this study, a method is proposed for dimensional measurements of semi-spherical parts for the standard tool electrodes used in Electrical Discharge Machining (EDM). The tool electrode to be measured is magnified by a profile projector. Pictures of some equatorial plane projections of the electrodes are captured by a digital camera before and after machining. The pictures were calibrated with the geometric camera calibration. Then, the profiles are extracted from their background using the adaptive threshold, which is an image processing method. 2D coordinates are first obtained and then converted to 3D coordinates. Using the obtained data, sphericity and radius are calculated by means of the minimum zone method. It is seen that the proposed method can be used for determining the EDM tool electrodes’ form error.     

Recommended slicing positions for adaptive direct slicing by image processing technique

Build time and accuracy are two contradicting issues that have been a major concern in rapid prototyping, and have led to the development of many slicing approaches including those applying adaptive slicing, direct slicing, and adaptive direct slicing concepts. Presented in this paper is an approach for adaptive direct slicing that applies image processing technique to determine appropriate thickness for each sliced layer and to recommend slicing positions on a 3D CAD model. Two orthogonal views of a model are captured and converted to be edge images before being analyzed, and based on the surface complexity on the two edge images, slicing positions are recommended. These positions are passed to the CAD software for slicing activities. This adaptive direct slicing approach has been implemented on LabVIEW platform and compared with uniform direct slicing approach and uniform cusp height approach. The results show that this slicing approach improved slicing performance by reducing the number of layer which has a direct impact on build time while maintaining surface quality at the same level as the thin uniform direct slicing. Since its inputs are the images of a CAD model instead of the model itself, this adaptive direct slicing supports any CAD software.