Distribution-free estimation of sphere size distributions from slabs showing overprojection and truncation,with a review of previous methods

A distribution-free method is presented for unfolding the size distribution of an aggregate of disjoint opaque spherical particles in a translucent medium, from the circular profiles observed in the orthogonal projection of sections of a certain thickness through the medium. This situation pertains especially to light and transmission electron microscopy. The model accounts for overprojection (or ‘Holmes effect’) due to section thickness, and for two forms of truncation (or ‘missing profiles’ mechanisms), simultaneously. The profile data may be grouped into an arbitrary class system, chosen by the user, and the procedure can be programmed in a medium-size desk calculator. In order to incorporate the above features, however, we had to choose a finite-difference unfolding algorithm, the advantages and disadvantages of which are discussed early in the paper in the context of the main alternative unfolding procedures hitherto available. The performance of the method is tested against three sets of real data previously analysed by a maximum likelihood method (Keidinget al., 1972).     

Effect of droplet size on the droplet behavior on the heterogeneous surface

Journal of Mechanical Science and Technology - The characteristics of a three-dimensional hemispherical droplet on a heterogeneous surface were studied using the Lattice Boltzmann method (LBM). The...     

Freeze-fracturing: a review of methods and results

Freeze-fracturing may be accomplished either under vacuum, or at atmospheric pressure. The devices available for freeze-cleaving are discussed in relation to the vacuum and temperature conditions prevailing during cleaving, etching and replication. It is concluded that most specimens can be satisfactorily cleaved (even at 4 K), and processed using simple cleavage devices and systems that provide ample cold-trapping protection for the specimen. Only for special purposes are microtome assemblies or ultra-high vacuum units essential. The fracturing process may produce artefacts by plastic deformation. Such artefacts have been noted in both non-biological and biological polymers cleaved at temperatures as low as 4 K. Contamination of the frozen surface need not be a problem provided that the specimen is transferred under ‘safe’ conditions, and is protected by well-designed cold traps. Freeze-cleavage and freeze-sectioning are compared. It is considered that there will be a temperature range for most heterogeneous specimens within which both cleavage and fracturing may occur, depending upon the nature of the molecules in the cleavage/sectioning plane. Local heating during freeze-sectioning will produce deformation artifacts as in freeze-cleavage, and may also lead to more general surface ‘flow’. The relationships between sectioning and fracturing biological specimens at low temperature require further clarification.     

Investigation of droplet size distribution in two-phase flows using a combined method for recording droplet fluorescence and diffraction scattering of light

A prototype of a combined measurement system (MS) based on the fluorescent and small-angle methods of determining the parameters of a fuel-air spray using a pulsed laser as a light source and a color digital video camera to record spray sections was designed and tested. The tests of the MS showed that it has good performance and is suitable for determining the characteristics of advanced atomizers in a pressure chamber. Spatial concentration distributions of aerosols generated by a centrifugal atomizer were studied. Distributions of time-averaged Sauter diameters of droplets, their concentration, and the circumferential inhomogeneity of droplet concentration in the spray cross section were obtained. A study of fuel atomization from a plate was performed showing the possibility of using this device in power plants to improve the atomization performance compared to the atomization of a free jet in crossflow.     

Principles and limitations of immunohistochemical methods

Immunofluorescence is an ingenious method in histochemical research as it is possible to solve problems which are impossible to approach with other methods. Everyone using this method must be aware that immunohistochemistry is a field still developing and full of weeds and thorns. In particular, one must be aware that the method consumes a great amount of time when all the factors involved are taken into account. An uncritical use of this method will not only give wrong results but also bring it into discredit.     

Combination of thresholding and fitting methods for measuring nanoparticle sizes and size distributions in (S)TEM

The practical need for a simple and reliable tool for routine size analysis of nanoparticles with diameters down to a few nm embedded in a polymer matrix motivated the development of a new approach. The idea underlying the method proposed in this work is to combine intensity thresholding and contrast fitting procedures in the same software for particle recognition and measurements of sizes and size distributions of nanoparticles in transmission and scanning transmission electron microscopy images. Particle recognition in images is performed in an interactive process of manual setting the numerical threshold level after image preprocessing. We show that fitting the calculated gray level distribution to the real images is able to provide a maximum accuracy in measurements of the particle diameters in contrast to thresholding approaches. The fitting procedure is applied in the vicinity of nanoparticle images with the mass‐thickness, diffraction, and chemical contrast. The grayscale function associated to the nanoparticle thickness is described using polynomial with degree ? 2 and undetermined coefficients. The program for particle detection and size measurement— An alyzer of Na noparticles ( AnNa )—has been written and is described here. It was successfully tested on systems containing Ag nanoparticles grown and stabilized in aqueous solutions of different polymers for biomedical use and is available from the authors.     

Sphere size distributions from finite thickness sections: a forward approach employing a genetic algorithm

We formulate, implement and test a robust method of determining sphere size distributions from finite thickness planar sections. The method uses a forward approach in which populations of proposed distributions are tested against the input data and refined using a genetic algorithm. This method is then applied to a real-world data set concerning endo- and exocytotic vesicles in the apical region of tip growing pollen tubes of Arabidopsis thaliana .     

采样样本的容量对雾滴尺寸测量精度影响的试验研究

用雾滴采集装置在自行建立的高压喷雾系统上对雾滴进行了样本采集,用机器视觉方法对雾滴尺寸进行了统计与测量,将机器视觉方法测量结果与PDPA测量结果相比较,深入分析了雾滴采样样本对雾滴尺寸测量精度的影响.试验结果表明:雾滴采样样本容量越大,雾滴尺寸测量精度也越高,当雾滴样本容量大于4 000个时,雾滴特征直径D0.632的测量精度可达5%以内;不同粒径的雾滴个体对雾滴尺寸测量精度的影响不同,大粒径雾滴对尺寸测量精度的影响远大于小粒径雾滴,雾滴尺寸测量时尤其应注意准确统计大粒径雾滴.     

Selecting the size of helium nanodroplets using time-resolved probing of a pulsed helium droplet beam

We show that helium nanodroplets generated using a pulsed valve undergo velocity dispersion according to their size. This makes it possible to use temporal selection to probe nanodroplets of a particular size within the pulsed gas profile rather than changing the expansion conditions as is done when using continuous helium nanodroplet sources. The variation in mean droplet size achievable within a single gas pulse can extend over more than an order of magnitude.     

State-of-the-art methods and results in tool condition monitoring: a review

This paper presents a review of the state-of-the-art in sensors and signal processing methodologies used for tool condition monitoring (TCM) systems in industrial machining applications. The paper focuses on the technologies used in monitoring conventional cutting operations, including drilling, turning, end milling and face milling, and presents important findings related to each of these fields. Unlike existing reviews, which categorize results according to the methodology used, this paper presents results organized according to the type of machining operation carried out. By extensively reviewing and categorizing over one hundred important papers and articles, this paper is able to identify and comment on trends in TCM research, and to identify potential weaknesses in certain areas. The paper concludes with a list of recommendations for future research based on the trends and successful results observed, thus facilitating the cross-fertilization of ideas and techniques within the field of TCM research. An erratum to this article can be found at     

Improvements on a laser scattering technique for droplet size measurements applied to a gas-liquid separation equipment

The knowledge of droplet size distributions in a gas-liquid separation equipment is of high relevance due to the importance of removal efficiency in these systems. Different techniques could be used to measure droplet size, being one of them the diffraction of a laser beam. The laser is located behind glasses, being the formation of droplets on the glasses one of the main problems encountered when using this technique.Due to this major problem, different innovative solutions have been proposed and implemented to the gas-liquid separation column in order to obtain satisfactory results. A shutter mechanism, a purge gas and combination of these two solutions were tested. It was shown that the modified technique is suitable for liquid droplet measurements under ambient conditions.It has been also shown that the combination of these two solutions reduced considerably the amount of droplets that interacts with the glasses, allowing getting better data.     

Temperature and acid droplet size effects in acid neutralization of marine cylinder lubricants

Temperature and acid droplet size effects on the rate of acid neutralization by Marine Cylinder Lubricants were investigated by using a heating-capillary video microscopy. The neutralization experiments were performed inside a ∼200-μm capillary micro-reactor and the progress of reaction was recorded in real time. Increasing temperature dramatically impacted on the neutralization rate. While the effect of acid droplet size was negligible initially, it might affect the rate as well when a droplet got smaller than a certain level.     

Determination of vesicle size distributions by freeze-fracture electron microscopy

The most common electron microscopic technique for obtaining information on size distributions of uncollapsed membrane vesicles is based on the method of van Venetie (1980). This technique involves the sizing of only those vesicles that were freeze fractured at their equatorial planes. As a result, only a small number of images can be used to generate size distributions. Further, the technique is susceptible to systematic error. An alternate approach is to consider the complete distribution of image sizes and use this distribution to determine the average size and distribution of the vesicles. It is shown that the mean vesicle size is 4/π times the mean image size. As well, a parameter, m, which can be determined from the image distribution, can be used to characterize the vesicle distribution. The advantage of this new approach is that images of all vesicles are used, leading to a statistically better determination of vesicle sizes.     

Stereology of cubic particles: various estimators for the size distribution

This paper deals with stereological problems for spatial systems of homothetic particles. In contrast to the traditional technique of estimating the size distribution of the particles from the sizes of section profiles we introduce a new method exploiting size and shape of the observed profiles. The shapes of the section profiles contain additional information about the sizes of the particles. This leads to improved stereological estimation of size distribution. As an example the case is studied when the particles form cubes with random edge length. The method is applied to a two-phase WC–Co cermet structure with cubic particles.     

An investigation on effect of geometrical parameters on spray cone angle and droplet size distribution of a two-fluid atomizer

A visual study is conducted to determine the effect of geometrical parameters of a two-fluid atomizer on its spray cone angle. The liquid (water) jets exit from six peripheral inclined orifices and are introduced to a high speed gas (air) stream in the gravitational direction. Using a high speed imaging system, the spray cone angle has been determined in constant operational conditions, i.e., Reynolds and Weber numbers for different nozzle geometries. Also, the droplet sizes (Sauter mean diameter) and their distributions have been determined using Malvern Master Sizer x. The investigated geometrical parameters are the liquid jet diameter, liquid port angle and the length of the gas-liquid mixing chamber. The results show that among these parameters, the liquid jet diameter has a significant effect on spray cone angle. In addition, an empirical correlation has been obtained to predict the spray cone angle of the present two-fluid atomizer in terms of nozzle geometries.     

Revealing local variations in nanoparticle size distributions in supported catalysts: a generic TEM specimen preparation method

The specimen preparation method is crucial for how much information can be gained from transmission electron microscopy (TEM) studies of supported nanoparticle catalysts. The aim of this work is to develop a method that allows for observation of size and location of nanoparticles deposited on a porous oxide support material. A bimetallic Pt‐Pd/Al₂O₃ catalyst in powder form was embedded in acrylic resin and lift‐out specimens were extracted using combined focused ion beam/scanning electron microscopy (FIB/SEM). These specimens allow for a cross‐section view across individual oxide support particles, including the unaltered near surface region of these particles. A site‐dependent size distribution of Pt‐Pd nanoparticles was revealed along the radial direction of the support particles by scanning transmission electron microscopy (STEM) imaging. The developed specimen preparation method enables obtaining information about the spatial distribution of nanoparticles in complex support structures which commonly is a challenge in heterogeneous catalysis.     

Wetting characteristics of a water droplet on solid surfaces with various pillar surface fractions under different conditions

A numerical study was carried out using a molecular dynamics program to examine the wetting characteristics of nano-sized water droplets on surfaces with various pillar surface fractions under different conditions. Square-shaped pillars had surface fractions that increased from 11.1 % to 69.4 %. The pillars had 4 different heights and 3 different surface energies. When the pillar surface fraction changed, the contact angle of a water droplet also changed due to the attraction between the droplet and the pillar surface or the inner attraction of the water molecules. The pillar height also has different effects on the water droplet depending on the magnitude of surface energy.     

On the precision of systematic sampling: a review of Matheron's transitive methods

G. Matheron's theory of regionalized variables provides a suitable basis for obtaining variance approximations for estimators of integrals from systematically sampled observations, with applications in geostatistics, image analysis, stereology and numerical quadrature techniques in general. The approximations are often fairly accurate for practical purposes. The methods are, however, not sufficiently widespread outside the field of geostatistics. The purpose of this paper is to present in an informal way the transitive part of the methods (relevant to the design-based approach) and a number of stereological applications.     

RP及RT技术的原理、方法和应用

从快速制造小批量产品样件和快速制造模具(以及模型和加工工具)方面,阐述了RP及RT技术在材料成形领域中的应用,内容涉及RP及RT技术的原理、方法和五种实用系统的工作过程和适用范围,以及快速原型制造技术在模具制造中的应用。     

Estimation and control of droplet size and frequency in projected spray mode of a gas metal arc welding (GMAW) process

New estimators are designed based on the modified force balance model to estimate the detaching droplet size, detached droplet size, and mean value of droplet detachment frequency in a gas metal arc welding process. The proper droplet size for the process to be in the projected spray transfer mode is determined based on the modified force balance model and the designed estimators. Finally, the droplet size and the melting rate are controlled using two proportional-integral (PI) controllers to achieve high weld quality by retaining the transfer mode and generating appropriate signals as inputs of the weld geometry control loop.