Shape dependence of resistance force exerted on an obstacle placed in a gravity‐driven granular silo flow

Resistance force exerted on an obstacle in a gravity‐driven slow granular silo flow is studied by experiments and numerical simulations. In a two‐dimensional granular silo, an obstacle is placed just above the exit. Then, steady discharge flow is made and its flow rate can be controlled by the width of exit and the position of obstacle. During the discharge of particles, flow rate and resistance force exerting on the obstacle are measured. Using the obtained data, a dimensionless number characterizing the force balance in granular flow is defined by the relation between the discharge flow rate and resistance‐force decreasing rate. The dimensionless number is independent of flow rate. Rather, we find the weak shape dependence of the dimensionless number. This tendency is a unique feature for the resistance force in granular silo flow. It characterizes the effective flow width interacting with the obstacle in granular silo flow. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3849–3856, 2018     

Segregation Behavior Found in Poly(2-ethylhexyl acrylate)/Poly-(vinylidenefluoride-co-hexafluoro acetone) Blends

The surface and bottom compositions of poly(2-ethylhexyl acrylate) (P2EHA)/poly-(vinylidene fluoride-co-hexafluoro acetone) [P(VDF-HFA)] blends were investigated by XPS analysis. In these blends, the enriched P(VDF-HFA) layer was observed from the top surface to a few nm depth, while the P2EHA component segregated at the bottom (the surface in contact with release liner). The probe tack values of the bottom side were remarkably larger than those of the surface side for the P2EHA/P(VDF-HFA) blends because the characteristic segregation structure was formed. We expected that the P2EHA/P(VDF-HFA) blends could be utilized as a non-backing pressure sensitive adhesive (PSA) tape. The effects of the film thickness of the blends and the molecular weights of P2EHA on the segregation structure were also examined. We thought that segregation behavior found in P2EHA/P(VDF-HFA) blends was caused by several factors, such as surface tension, miscibility, density, and rate of solvent casting.     

Temperature Effect on Hydrogen Generation by the Reaction of γ-Al2O3-Modified Al Powder with Distilled Water

The effect of temperature on the reaction of γ-Al₂O₃-modified Al powders with distilled water was investigated. It was found that by increasing the temperature up to 40°C, the hydrogen generation speed can be enhanced one to two orders of magnitude relative to that at room temperature (18°C). X-ray analyses and transmission electron microscopy observations revealed that the reaction by-product at 40°C is bayerite (Al(OH)₃), which is chemically neutral. The present results imply that slightly increasing the temperature is an effective way to get the target hydrogen generation speed.     

Influence of coal characteristics on CO2 gasification

The rate of CO₂ gasification of a coke is one of the most important qualities of metallurgical coke. Many workers are trying to estimate the rate of CO₂ gasification of coke by studying properties of coal, such as the reflectance of vitrinite and the amounts of inertinite and ash in coal. The specific-gravity separation method is used to prepare coals which possess almost the same reflectance, but contain different amounts of inertinite and ash. The relation between the rate of gasification and the properties of coal is quantitatively explained.     

Test results of a catalytically assisted combustor for a gas turbine

A catalytically assisted ceramic combustor for a gas turbine was designed and tested to achieve low NO_x emissions. This combustor is composed of a burner and a ceramic liner. The burner consists of an annular preburner, six catalytic combustor segments and six premixing nozzles, which are arranged in parallel and alternately. In this combustor system, catalytic combustion temperature is controlled under 1000 °C, premixed gas is injected from the premixing nozzles to the catalytic combustion gas and lean premixed combustion over 1300 °C is carried out in the ceramic liner. This system was designed to avoid catalyst deactivation at high temperature and thermal shock fracture of the ceramic honeycomb monolith of the catalyst. A 1 MW class combustor was tested using LNG fuel. Firstly, NO_x emissions from the preburner were investigated under various pressure conditions. Secondly, two sets of honeycomb cell density catalysts and one set of thermally pretreated catalysts ware applied to the combustor, and combustion tests were carried out under various pressure conditions. As a result, it was found that the main source of NO_x was the preburner, and total NO_x emissions from the combustor were approximately 4 ppm (at 16% O₂) at an adiabatic combustion temperature of 1350 °C and combustor inlet pressure of 1.33 MPa.     

Dynamic mechanical properties of crosslinked polyisoprene under deformation

Summary Molecular motions of elastomers under deformations were observed through dynamic mechanical measurements. Composite master curves of dynamic moduli E and E and loss tangent tan over a wide range of frequency and in a state of elongation were obtained by the time-temperature superposition procedure. It is found that both moduli increase with strain, . The slope of the dispersion curve of E become more gradual with the increase in , while that of E is almost unchanged. The increment of E is generally larger than that of E, which does not agree with the N. W. Tschoegl prediction, E ^* ()=f() E _o ^* (), where E ^* () and E _o ^* () are complex moduli at the strain of and O, respectively, and f() is the function of only . The difference in the strain dependence of E from E was found to correspond to the strain dependence of the equilibrium modulus.     

Interfacial reaction and its influence on phase morphology and impact properties of modified‐polyacetal/thermoplastic polyurethane blends

The cationic polymerization of 1,3,5‐trioxane, 1,3‐dioxolane and a small amount of 2‐hydroxyacetic acid (HAA) was carried out, and the resulting modified‐polyacetal (POM) was blended with thermoplastic polyurethane (TPU) in melt. The results of ¹H NMR analysis indicated that HAA was almost incorporated in the modified‐POM, and that the resulting carboxyl end‐group and hydroxyl end‐group in the modified‐POM reacted with TPU during the melt blending. There were many boundary layers between the cavities and matrix in the modified‐POM/TPU (82/18 by weight) blend that was etched with tetrahydrofuran (THF), and the diameter of the cavities became ～0.3–1 μm long when the blending time reached 10 min. The results of scanning electron microscopic (SEM) observation and dynamic mechanical analysis (DMA) indicated that the modified‐POM/TPU blend had a good compatibility because of the interfacial reaction between the modified‐POM and TPU phase in the blend. The modified‐POM/TPU blend exhibited higher Charpy impact strength when compared with a normal‐POM/TPU blend; the toughness of the modified‐POM/TPU blend attributed to the good compatibility between the two phases. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4375–4382, 2006     

Determination and correlation of LLE and SLE data for the system aniline+cyclohexane

A newly developed laser light scattering technique was used for the determination of mutual solubilities in the aniline+cydohexane system at moderate pressures. The liquid-liquid equilibria (LLE) were measured from the region of solid-liquid equilibria (SLE) to the upper critical solution temperature. Freezing points in this system were determined by a cooling curve method. The solubility data were correlated with the NRTL equation.     

纳米级超精密定位工作台的研究

研制了一套基于激光莫尔信号的超精密定位工作台,定位台以微型计算机为核心,采用激光莫尔传感器检测位置偏差,通过光、机、电的有机结合,可实现纳米级超精密自动定位.定位装置采用串联型粗、微双驱动的精密定位系统,粗动台由步进电动机通过精密丝杠机构直接驱动,可实现大行程微米级定位,微动台由压电陶瓷驱动器驱动,可实现纳米级定位.针...     

基于RBF神经网络精密定位预测控制研究

为了实现高速高精度定位，在RBF神经网络单步预测模型的基础上，建立多步预测控制系统，为当前高速定位控制提供操作指导。在定位过程中通过预测位置与实际位置比较，灵活调整定位速度。实验表明神经网络预测控制是实现高速高精度定位的有效手段。