A new simpler coarse-grain model (SCG) for analyzing particle behaviors under fluid flow in a dilute system, by using a discrete element method (DEM), was developed to reduce calculation load. In the ...SCG model, coarse-grained (CG) particles were enlarged from original particles in the same way as the existing coarse-grain model; however, the modeling concept differed from the other models. The SCG model focused on the acceleration by the fluid drag force, and the CG particles’ acceleration coincided with that of the original particles. Consequently, the model imposed only the following simple rule: the product of particle density and squared particle diameter is constant. Thus, the model had features that can be easily implemented in the DEM simulation to comprehend the modeled physical phenomenon. The model was validated by comparing the behaviors of the CG particles with the original particles in the uniform and the vortex flow fields. Moreover, the usability of the SCG model on simulating real dilute systems was confirmed by representing the particle behavior in a classifier. Therefore, the particle behavior in dilute particle-concentration systems would be analyzed more simply with the SCG model.
The collapse phenomena like an avalanche of sinter bed during charging of raw materials in the iron ore sintering are often observed. The collapse phenomena strongly influence the size segregation of ...raw materials in sinter bed, permeability and productivity of sinter. The reasons why collapse phenomena of the sinter bed during charging occur in the iron ore sintering have been discussed using the simulation by DEM (Discrete Element Method) in this work. As factors causing the collapse phenomena, there could be the granule shape of raw materials charged and the adhesion between the granules. First of all, a simulation model which is considered the adhesion force between the granules has been developed. The charging behavior of raw materials on the sintering machine was simulated by DEM. Effects of the adhesion force on deposition and collapse phenomena of the sinter bed were investigated. The deposition angle of the sinter bed obviously increases and the collapse phenomena of granules are clearly observed when the adhesion force was introduced into the granules. The ridges on the surface of the sinter bed which are feature of the collapse phenomena are confirmed. Therefore one of the reasons why the collapse phenomena occur during charging of the raw materials into the sintering machine would be adhesion of granules.
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► Hole drift mobilities of Alq
3 thin films with 5-nm-thick NPB injection layers are determined using impedance spectroscopy (IS) measurements. ► IS measurements enable us to measure ...drift mobilities of semiconductor thin films whose thickness is ∼ 100
nm. ► An injection layer is essential for measurements of drift mobilities in semiconductor thin films with wide band gaps. ► Hole drift mobilities of Alq
3 thin films are determined even using 310-nm-thick NPB hole injection layers.
The hole mobility of tris(8-hydroxy-quinolinato) aluminum (Alq
3) thin films and double layer films of a 4,4′-bisN-(1-naphthyl)-N-phenyl-amino-biphenyl (NPB) and Alq
3, have been determined using impedance spectroscopy (IS) measurements. The theoretical basis of mobility measurement with IS rests on a theory for single-injection space-charge limited current. The NPB thin film operates as an injection layer to reduce the hole injection barrier between an injection electrode and the Alq
3 thin film. The hole mobilities of Alq
3 thin films measured with IS are identical to those measured by a time-of-flight (TOF) transient photocurrent technique. The hole drift mobility determined using IS measurements in NPB/Alq
3 double layer hole-only devices where the thickness of NPB is comparable to that of Alq
3 are also identical to the hole drift mobility of Alq
3 layer. The origin of the observation is discussed using a device simulation and the results are useful for the determination of charge carrier mobility in multilayer devices.
Background
We recently demonstrated that cascade stomach detected by barium studies was correlated with upper gastrointestinal symptoms. We developed a new endoscopic classification of cascade ...stomach and examined its relationship with reflux esophagitis.
Methods
Study 1: the classification (grades 0–3) was based on detecting a ridge that runs from the cardia toward the anterior wall crossing the greater curvature. Inter-observer variation was evaluated by kappa statistics when ten experienced endoscopists used this classification three times each. Study 2: in 710 consecutive subjects (500 men and 210 women) undergoing endoscopic screening, the grade of cascade stomach and incidence of reflux esophagitis were compared.
Results
In study 1, the kappa values at the third assessment were 0.85, 0.58, 0.50, and 0.78 for each grade, respectively, while overall agreement was 0.68. In study 2, the incidence of reflux esophagitis in men was 20 % in grade 0, 17 % in grade 1, 25 % in grade 2, and 30 % in grade 3, showing significant differences. Among women, the incidence of reflux esophagitis in each grade was 9, 3, 6, and 35 %, respectively, also showing significant differences. Multivariate analysis showed that independent risk factors for reflux esophagitis were cascade stomach (odds ratio = 2.20), body mass index, and hiatus hernia in men, as well as cascade stomach (odds ratio = 9.01) and smoking tobacco in women.
Conclusions
This endoscopic classification of cascade stomach showed acceptable inter-observer variation. Cascade stomach is a risk factor for reflux esophagitis.
Rupture of an air bubble on the solid surfaces ISHIHARA, Shingo; TAGAWA, Yoshiyuki; KAMEDA, Masaharu
Journal of Fluid Science and Technology,
01/2018, Letnik:
13, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We investigate behavior of bouncing and rupturing air bubbles on solid surfaces experimentally. We focus our attention to how the hydrophilicity of the solid surface alters the rupture process. We ...observe motion of the single bubble of a fixed diameter on several flat glass plates using high-speed cameras. In this experiment, we use two kinds of plate whose contact angles are different from each other. The bubble rises and bounces on the glass surface several times without touching the plate. It is found that, on the weakly hydrophilic glass plate whose contact angle is 65 degree, the liquid film between the bubble and the solid surface ruptures within about a hundred milliseconds after bouncing. The rupture starts at a single site. In contrast, on a highly hydrophilic glass whose contact angle is 7.6 degree, rupture time becomes much longer, i.e. more than 30 minutes. The rupture starts at several sites simultaneously. Note that in the both cases bounce times, bounce intervals, and bounce distance, are quite similar. Quite large difference in onset of rupture indicates that the existence of surface nanobubbles on the weakly hydrophilic glass enhances the rupture of liquid film. In the case of highly hydrophilic glass, the penetration of air into the liquid film after the rupture exhibits the pattern similar to viscous fingering.
A method has been proposed for the determination of energetic distributions of localized states in organic semiconductors by the analysis of the impedance spectra (T. Okachi, T. Nagase, T. Kobayashi, ...and H. Naito, Appl. Phys. Lett. 94 (2009) 043301). High energetic resolution of the method is demonstrated experimentally in organic semiconductor diodes using a polyfluorene derivative, poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine), by detecting a structured localized-state distribution. The method is a powerful tool for the determination of energetic distributions of localized states with high energetic resolution in organic thin film devices such as organic light-emitting diodes and organic solar cells.
•High energetic resolution measurement of localized state has been demonstrated.•Poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB) was examined.•TFB has a structured localized-state distribution.
In the bottom region of blast furnaces during the ironmaking process, the liquid iron and molten slag drip into the coke bed by the action of gravity. In this study, a practical multi-interfacial ...smoothed particle hydrodynamics (SPH) simulation is carried out to track the complex liquid transient dripping behavior involving two immiscible phases in the coke bed. Numerical simulations were performed for different conditions corresponding to different values of wettability force between molten slag and cokes. The predicted dripping velocity changes and interfacial shape were investigated. The relaxation of the surface force of liquid iron plays a significant role in the dripping rate; i.e., the molten slag on the cokes acts as a lubricant against liquid iron flow. If the attractive force between the coke and slag is smaller than the gravitational force, the slag then drops together with the liquid iron. When the attractive force between the coke and slag becomes dominant, the iron-slag interface will be preferentially detached. These results indicate that transient interface morphology is formed by the balance between the momentum of the melt and the force acting on each interface.
The effect of contact resistance on the determination of charge carrier mobility in single-injection space-charge-limited (SCL) diodes is numerically examined. Contact resistance is inevitably ...involved in the equivalent circuit of the SCL diodes. It is found that the mobility is accurately determined when it is less than or equal to 1.0 × 10−5 cm2 V−1 s−1 even in the presence of contact resistance at a semiconducting layer thickness of 100 nm, which is comparable to the active layer thickness of organic electronic devices, such as organic light-emitting diodes and organic photovoltaic devices. In contrast, when the input mobility is greater than 1.0 × 10−4 cm2 V−1 s−1 for the numerical calculation, the calculated mobility decreases with increasing contact resistance. Such information is an important guideline for the accurate measurements of mobility in single-injection SCL diodes.
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