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1.
《中国粉体技术》2022,(1):108-119
综述喷雾干燥的原理;粒子组分重分布、固化及固化后形态的改变等形成过程;喷雾干燥工艺对粒子性质的影响;空气动力学直径、密度、表面疏水处理等提高干粉吸入剂肺部沉积的粒子工程策略。认为喷雾干燥在肺部给药方面的主要优势是通过操纵和控制各种参数实现对颗粒特性的优化;结合粒子工程技术与合适的赋形剂,可以获得理想的喷雾干燥颗粒,使其最大限度地沉积在肺部靶向部位;通过优化颗粒空气动力学直径、降低颗粒密度以及对微粒进行表面疏水处理可以弥补喷雾干燥微粒在粉末流动性、分散性以及药物稳定性等方面的缺点。  相似文献   

2.
Journal of Materials Science: Materials in Electronics - Detection of volatile organic compounds is of utmost importance in numerous applications such as medical diagnosis, air quality monitoring,...  相似文献   

3.
Aspects of particulate dry deposition in the urban environment   总被引:1,自引:0,他引:1  
Micro-scale deposition models, typically used for pipes, were adapted to outdoor situations and combined with computational fluid dynamics (CFD) calculations of flow conditions in order to study the fine structure of the deposition velocity on ground, walls, and roofs in an urban environment. Several deposition modeling techniques taken from the literature were used for the predictions. The urban geometry was represented by two different blocks of houses, which together with two wind directions gave four different cases to study. The calculations show large local variations of the deposition velocity resulting in a pattern similar to the variation of the friction velocity. This demonstrates the strong dependence of the deposition velocity on the friction velocity. Further alteration of the deposition velocity is caused by the variation of the micro-scale roughness and different surface temperatures. The results presented provide some guidance for where to look for hotspots of deposited material and also show that a representation of the deposition velocity in a city by only one or just a few values is a great simplification locally and could lead to serious mistakes.  相似文献   

4.
Clinical investigation shows a dramatic relation between deposition of particles in lung’s pathways and respiratory system diseases. Particle deposition may also play a major role in drug delivery via respiratory system. Previous researches on symmetric and 5-lobe models for rat, dog, hamster and human show that, the deposition fraction of fine particles (between 0.1 and 0.7 μm) is minimum. A multi-path asymmetric 5-lobe model of Horsfield et al. is employed to construct the airway tree. Since the data are based on lung casting, asymmetric properties of the model are more realistic. Deposition of 0.01–10 μm particles is calculated during inhalation using published formulas in every branch. Here, we measured the deposition up to alveolar region. Accumulative deposition versus particle diameter predicts less deposition in comparison with symmetric models in as much as our model is asymmetric. The flow is divided based on distal volume. Particle deposition for 0.01 μm is in good agreement with other models but for 1 μm different trend in lower generations is observed. It is concluded that the asymmetric pattern gives different deposition fraction in all regions, since the distinctive geometric properties of the model is in some extent different from that of symmetric model. But, the accumulative deposition trend is similar in both symmetric and asymmetric models.  相似文献   

5.
Simulation of deposit growth on a two-dimensional substrate was studied based on a new model that tracks individual cubic particles as they form a deposit structure. The present model is an extension of the classical ballistic deposition model. Effects of three different parameters were studied. These include an attraction parameter that is a measure of the particle to particle attractions, an interaction length within which the particles are assumed to influence and be influenced by surrounding particles, and allowed sticking positions (face-face, edge-edge and corner-corner) that favor particular growth directions. Structures with widely varying properties were obtained using this model. The three parameters were found to have considerable effect on the structure including indications of morphological phase transformations. A new property of the system (saturated roughness/deposit growth rate) was identified that can classify the different types of growth into a single type.  相似文献   

6.
A predictive model for particulate filled composite materials   总被引:1,自引:0,他引:1  
Our predictive model for particulate filled composite materials is applied to epoxy resin toughened by rubber spheres. Good agreement is found between predicted values of stiffness and experimental measurements. The variability of yield stress with volume fraction is explained. The observed fracture processes, including rubber cavitation, are explored; the importance of thermal stresses is highlighted. The fracture behaviour of these materials is discussed in the light of these predictions.  相似文献   

7.
Summary A set of displacement equations of motion suitable for describing the dynamic behavior of composite materials is derived. The composite material may be a fiber-reinforced composite or a particulate composite. The composite is represented by a lattice model in which the continuous mass distribution of the actual body is replaced by a system of springs attached to small rigid masses. Effective values are determined for the masses of the rigid bodies and the stiffnesses of the springs. The kinetic and strain energies stored in an extended composite medium are expressed in terms of the displacements at the positions of the mass points. By employing Taylor series expansions, and by replacing summations by integrations, representative kinetic and strain energy densities are obtained. Thus, transition to a continuum is achieved. Subsequent application of Hamilton's principle gives the displacement equations of motion which are of the same form as those of a first strain-gradient theory of linear elasticity. The proposed set of equations yield dispersion of plane harmonic waves propagating in an infinite composite medium, and dispersion relations are of the same type as those of crystal lattice theories. The dispersion curve for longitudinal waves propagating in the direction normal to the fibers is plotted together with the dispersion curve obtained from experimental investigations, and good agreement is found between the two.Zusammenfassung Ein Satz von Bewegungsleichungen für die Verschiebungen, zum Beschreiben des dynamischen Verhaltens von Verbundwerkstoffen, wird hergeleitet. Der Verbundwerkstoff kann faser-oder teilchenverstärkt sein. Er ist dargestellt als ein Gitter-Modell, in welchem die stetige Massenverteilung des wirklichen Körpers durch ein System von Punkt-Massen, verbunden mit Federn, ersetzt ist. Die effektiven Werte der Masse der Punkt-Massen und der Federkonstanten der Federn werden bestimmt. Die kinetische Energie und die Verzerrungsenergie, die in einem Körper gespeichert sind, werden durch die Verschiebungen der Punktmassen ausgedrückt. Mit Hife der Taylor-Reihen-Entwicklung und durch Ersetzen der Summen durch Integrale werden die Ausdrücke, für die kinetische Energie und die Verzerrungsenergie abgeleitet. Auf diese Weise geht man zum Kontinuum über. Die Anwendung des Hamilton-Prinzips gibt die Bewegunsgleichungen der Verschiebungen, welche von der gleichen Art wie die Gleichungen der ersten Verzerrungsgradient-Theorie der linearen Elastizitätstheorie sind. Der abgeleitete Satz von Gleichungen ergibt die Dispersion von ebenen, harmonischen, sich im unendlichen Verbundwerkstoff fortpflanzenden Wellen. Die Dispersionsgleichungen sind vom gleichen Typ wie diejenigen der Kristall-Gitter-Theorie. Die Dispersionskurve für longitudinale Wellen, die sich senkrecht zur Faser fortpflanzen, ist zusammen mit der Dispersionskurve der experimentellen Untersuchung dargestellt, und man erkennt, daß die beiden Ergebnisse gut übereinstimmen.
Ein mechanisches Modell für faser- und teilchenverstärkte Verbundwerkstoffe.

With 5 Figures

Presented at the 14th International Congress of Theoretical and Applied Mechanics, Delft, The Netherlands, August 30 to September 4, 1976.  相似文献   

8.
The increasing use of particulate composites in various weight sensitive applications such as aerospace and marine industries requires strict quality assurance methods. Non-destructive evaluation techniques such as ultrasound are currently used for characterization of these materials. Attenuation coefficient is one of the important parameters required for characterizing materials using ultrasound. Incorrect attenuation coefficient may lead to misdiagnosis of structures that could cause potential disaster. The present study focuses on developing a model for predicting the pulse-echo ultrasonic attenuation coefficient in particulate composites that takes into account the effect of particle size, porosity, and radius ratio. Attenuation loss from absorption, scattering, and resonance of glass particles is incorporated in the model. Interaction between the particles is neglected and the scattered energy is assumed to be entirely lost. Attenuation coefficient predicted from the model is compared with Yamakawa’s model and experiment.  相似文献   

9.
The zeta potential of particles is a key factor in the electrophoretic deposition process. It plays a role in the stabilization of the suspension by determining the intensity of repulsive interactions as well as in determining the direction and velocity of particle migration.The zeta potential can be controlled by addition of charging agents such as acids, bases, and specifically adsorbed ions or polyelectrolytes, to the suspension. Thus there exist a variety of additives that affect the charge magnitude and its polarity. These additives act by different mechanisms.The main criteria for the selection of a charging agent are the preferred polarity and deposition rate of the particles. While the deposition rate is directly dependent on the zeta potential, which is determined by the charging additive, the influence of such an additive is exerted also by its effect on the ionic conductivity of the suspension. The latter determines the potential drop in the bulk of the suspension, which constitutes the driving force for the transfer of the particles to the electrodes.The present work will describe the methodology developed at Cerel for the selection of a charging agent based on its effect on the zeta potential/pH curve, on the isoelectric point and on the ionic conductivity of the suspension.  相似文献   

10.
A model for the toughness of epoxy-rubber particulate composites   总被引:3,自引:0,他引:3  
Epoxy resins are toughened significantly by a dispersion of rubber precipitates. Microscopic examinations of propagating cracks in epoxy-rubber composites reveal that the brittle epoxy matrix cracks, leaving ligaments of rubber attached to the two crack surfaces. The rubber particles are stretched as the crack opens and fail by tearing at large, critical extensions. This fracture mechanism is the basis of a new analytical model for toughening. An increase in toughness (G IC) of the composite is identified with the amount of elastic energy stored in the rubber during stretching which is dissipated irreversibly (e.g. as heat) when the particles fail. The model predicts the failure strain of the particles in terms of their size. It also relates the toughness increase to the volume fraction and tearing energy of the rubber particles. Direct measurements of the tearing strains of rubber particles, and toughness data obtained from epoxy-rubber composites, are in good agreement with the model. The particle-stretching model provides a quantitative explanation, in contribution to existing qualitative theories, for the toughening of epoxy-rubber composites.  相似文献   

11.
A new model for estimating macroscopic permittivity was proposed to predict filler particles' dispersion states in a particulate composite material. In the model, the estimation targets are randomly packed composite materials. The composite materials were represented as a cluster of unit cells. A proposed layer structure model connected the unit cells. The macroscopic permittivity was estimated by calculating the synthetic capacity of the cluster. The proposed model was validated by comparisons between estimated and measured macroscopic permittivity of several particulate composite materials. It was also identified that the proposed model could estimate the permittivity more accurately than an existing theoretical equation's one due to considering the effects for the dispersion states of filler particles. Furthermore, it was indicated that the proposed model could also estimate the dispersion states of filler particles by the measured permittivity. The applicability of the method was confirmed by comparisons between estimated and experimental dispersion states of filler particles.  相似文献   

12.
Bourdet GL 《Applied optics》2003,42(27):5457-5462
Continuous coherent light conversion in a train of short pulses with good efficiency is possible with a multipass interferometer in which the frequency is shifted at every pass with an acousto-optic frequency shifter. This technique allows one to generate a spectrum made of equidistant components, interferences of which build intense light pulses. Unfortunately, both the width and efficiency of the pulses are limited by the losses undergone by the waves traveling through the interferometer cavity. Improvement of the pulse duration, the peak intensity, and the contrast can be expected in such an experiment when an amplifier is set up inside the cavity. I report on theoretical computations related to this apparatus and apply this theoretical model to a high-pressure CO2 amplifier.  相似文献   

13.
14.
Based on the Mori–Tanaka method, a micro-mechanics model is developed to study the effective elastic properties of composites reinforced by regularly distributed particles. The spatial distribution of particles is supposed to be cube symmetric in the three-dimensional space, and the corresponding finite element method (FEM) computation has been performed through a unit cell model. Additionally, particle interaction and distribution are simultaneously taken into account by using the strain Green’s function, and the specified strain Green’s function is determined by utilizing the necessary conditions of geometric symmetry. In order to analyze particle size effect on the effective properties of composites, the Double-inclusion configuration and related theory are introduced to describe the role of the interphase between the matrix and particles. Finally, the overall elastic properties of the composite with regularly distributed particles are described by three independent elastic constants expressed in the explicit form, and the accuracy of the developed model is verified by comparing with FEM results.  相似文献   

15.
6061/X (X = AlN, Si3N4, TiN) aluminum-matrix composites have been prepared by a powder metallurgy process: by mixing aluminum alloy 6061 powder with nitride particles and extruding the mixture at high temperatures. After sintering and aging, the Vickers hardness of the composites has been measured. The results indicate that the Vickers hardness of the composites increases significantly with nitride particle content both before and after aging. The aging behavior of the composites can be interpreted in terms of a simple kinetic model, which was used earlier to predict changes in the yield strength of age-hardened unreinforced aluminum alloys. The model is shown to adequately describe the changes in the hardness of the composites. It is concluded that reinforcing nitride particles increase the precipitation rate, without influencing the nature of the precipitation process in the supersaturated solid solution.  相似文献   

16.
Lee SK  Kim JH  Jeong MG  Song MJ  Lim DS 《Nanotechnology》2010,21(50):505302
Micron-sized and precise patterns of nanocrystalline CVD diamond were fabricated successfully on substrates using dispersed nanodiamond particles, charge connection by electrostatic self-assembly, and photolithography processes. Nanodiamond particles which had been dispersed using an attritional milling system were attached electrostatically on substrates as nuclei for diamond growth. In this milling process, poly sodium 4-styrene sulfonate (PSS) was added as an anionic dispersion agent to produce the PSS/nanodiamond conjugates. Ultra dispersed nanodiamond particles with a ζ-potential and average particle size of - 60.5 mV and ~ 15 nm, respectively, were obtained after this milling process. These PSS/nanodiamond conjugates were attached electrostatically to a cationic polyethyleneimine (PEI) coated surface on to which a photoresist had been patterned in an aqueous solution of the PSS/nanodiamond conjugated suspension. A selectively seeded area was formed successfully using the above process. A hot filament chemical vapor deposition system was used to synthesize the nanocrystalline CVD diamond on the seeded area. Micron-sized, thin and precise nanocrystalline CVD diamond patterns with a high nucleation density (3.8 ± 0.4 × 10(11) cm(-2)) and smooth surface were consequently fabricated.  相似文献   

17.
We show that the flux-field expansion derived by Boghosian & Coveney for the Rothman-Keller immiscible fluid model can be derived in a simpler and more general way in terms of the completely symmetric tensor kernels introduced by those authors. Using this generalized flux-field expansion we show that the more complex amphiphilic model of Boghosian, Coveney & Emerton can also be derived from an underlying model of particle interactions. The consequences of this derivation are discussed in the context of previous equilibrium Ising-like lattice models and other non-equilibrium mesoscale models.  相似文献   

18.
Problems related to the critical size of aerosol particles, when the vapor condensation coefficient depends on the particle size, the influence of electromagnetic fields, as well as on the presence of adsorbable foreign gases in the system, are studied theoretically. The problem of the critical size of particles in chemical deposition is discussed.  相似文献   

19.
The National Radiological Protection Board's advisory Group on Non-ionising Radiation has recommended further study on the effects of electric charge on the deposition of 0.005-1 microm particles in the lung. Estimates have been made regarding the integrated ion exposure within the corona plume generated by a power line and by ionisers in an intensive care unit. Changes in the charge state of particles with sizes in the range 0.02-13 mum have been calculated for these exposures. The corona plume increases the charge per particle of 0.02 and 0.1 microm particles by the order of 0.1. The ionisers in the intensive care unit produced negative ions-as do power lines under most conditions. Bacteria can carry in the order of 1000 charges (of either sign) and it is shown that the repulsion between such a negatively charged bacterium and negative ions prevents further ion deposition by diffusion charging. Positively charged bacteria can, however, be discharged by the ions which are attracted to them. The data provide no support for the hypothesis that ion exposure, at the levels considered, can increase deposition in the lung.  相似文献   

20.
Inhalation exposure to particles <10 microm in size that are suspended in the troposphere (PM10) is a factor in respiratory and cardiovascular diseases. The extent of the injury, local to systemic inflammation, is dependent on the number, size, and composition of the particles to which an individual is exposed. The physical properties of and compounds on PM10 that are responsible for these adverse effects on human health are the subject of intense investigation. Here, we report a laboratory method that involved the creation of 1-120 particles per trial that were of known size and composition, followed by deposition of them directly onto individual human lung cells within a cell culture, and after an incubation period, a downstream biological response was measured. To illustrate this methodology, particles that each contained 50 pg of lipopolysaccharide were created and deposited onto individual cells over a region <0.36 mm2 within a genetically modified A549 cell culture. The biological readout was the relative expression of intercellular cell adhesion molecule 1 after 24 h of incubation using an immunocytochemistry assay. The apparatus and methodology introduced here enables studies at the interface between the relevant but diverse areas of atmospheric particle chemistry and lung cell biology to identify the chemical and physical factors of PM10 that cause/exacerbate respiratory and cardiovascular diseases by triggering various biological pathways.  相似文献   

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