Assessment of the mean and variance of the random regular transmittance through a dispersion of large cylinders using numerical simulations

In two previous papers [J. Opt. Soc. Am. A15, 1698 (1998)JOAOD60740-323210.1364/JOSAA.15.001698; J. Opt. Soc. Am. A16, 2737 (1999)JOAOD60740-323210.1364/JOSAA.16.002737] the theory of fluctuations in the regular transmittance T through a flowing dispersion of large slender cylindrical particles was presented. The theory covers, among other things, expressions for the expected value muT and the variance sigma(T)(2) of T in the two extreme cases when the cylinders are much shorter or much longer than the diameter of the optical beam used. Intermediate lengths were not treated. Numerical simulation is used to demonstrate the random behavior of T for intermediate cylinder lengths. The simulation results are consistent with the theory and provide a reliable estimate of the measurements produced by this analysis process. The result of the simulation is summarized as a fitted Bézier function model. The advantage of the simulation lies primarily in estimating measurement errors caused by the presence of intermediate length particles in measurement applications.     

Dissolution and precipitation behavior of ternary solid dispersions of ezetimibe in biorelevant media

Abstract

The effects of different formulations and processes on inducing and maintaining the supersaturation of ternary solid dispersions of ezetimibe (EZ) in two biorelevant media fasted-state simulated intestinal fluid (FaSSIF) and fasted-state simulated gastric fluid (FaSSGF) at different temperatures (25?°C and 37?°C) were investigated in this work.

Ternary solid dispersions of EZ were prepared by adding polymer PVP-K30 and surfactant poloxamer 188 using melt-quenching and spray-drying methods. The resulting solid dispersions were characterized using scanning electron microscopy, differential scanning calorimetry (DSC), modulated DSC, powder X-ray diffraction and Fourier transformation infrared spectroscopy. The dissolution of all the ternary solid dispersions was tested in vitro under non-sink conditions.

All the prepared solid dispersions were amorphous in nature. In FaSSIF at 25?°C, the melt-quenched (MQ) solid dispersions of EZ were more soluble than the spray-dried (SD) solid dispersions and supersaturation was maintained. However, at 37?°C, rapid and variable precipitation behavior was observed for all the MQ and SD formulations. In FaSSGF, the melting method resulted in better solubility than the spray-drying method at both temperatures.

Ternary solid dispersions show potential for improving solubility and supersaturation. However, powder dissolution experiments of these solid dispersions of EZ at 25?°C may not predict the supersaturation behavior at physiologically relevant temperatures.     

Demonstration-based learning and control for automatic grasping

We present a method for automatic grasp generation based on object shape primitives in a Programming by Demonstration framework. The system first recognizes the grasp performed by a demonstrator as well as the object it is applied on and then generates a suitable grasping strategy on the robot. We start by presenting how to model and learn grasps and map them to robot hands. We continue by performing dynamic simulation of the grasp execution with a focus on grasping objects whose pose is not perfectly known.     

The kinetics of ettringite formation and dilatation in a blended cement with β-hemihydrate and anhydrite as calcium sulfate

The phase formation, heat of hydration and dilatation in a blended cement consisting of 50 wt.% calcium aluminate cement, 25 wt.% Portland cement and 25 wt.% calcium sulfate were studied (w/c=1). The calcium sulfate was β-hemihydrate, anhydrite and mixes of the two. Kinetic expressions describing the ettringite formation in the pastes with the pure calcium sulfates were found. Hydration reactions were suggested and the phase development was compared to the hydration heat by mass and heat balances. When the calcium sulfate was 75 and 50 wt.% β-hemihydrate, the systems behaved as a linear combination of the 100 and 0 wt.% blends. At 25 wt.%, the hydration kinetics differed from the other blends. With only β-hemihydrate, the last 50% of ettringite formation was accompanied by expansion, mainly caused by interaction of crystals growing radially on cement grains. In the paste with only anhydrite, ettringite crystals grew in solution and produced no expansion.     

Bubble formation and motion in non-crimp fabrics with perturbed bundle geometry

The motion of the liquid front during impregnation of non-crimp fabrics has been considered by using Sethian’s level set method. Particular attention is put on the creation of bubbles at the liquid front and a virtual 3D model mimicking biaxial fabrics has been built for this purpose. The saturated fluid flow is governed by the Navier–Stokes Equations and Darcy law, while capillary pressure has been accounted for at the liquid flow front and continuity maintained. The influence of perturbation in the bundle geometry has been investigated. Local correlations of the dimensions of neighbouring gaps formed between the bundles are of paramount importance. Focus is on inter-bundle bubbles. An existing model for bubble dynamics is used based on a probabilistic approach for bubbles moving, splitting, merging, and dissolving. The same approach was used for intra-bundle bubbles, the difference being that their motion appears to be much slower. The obtained void fractions of inter-bundle bubbles at different vacuum levels applied at the liquid flow front are compared to those from real mouldings with a high degree of conformity.     

High shear wet granulation modelling—a mechanistic approach using population balances

A population balance approach based on splitting the coalescence kernel into two factors, the first describing the collision frequency of particles and the second describing the collision efficiency, is applied to modelling wet granulation in a high shear mixer. Four different expressions for the collision frequency are compared and discussed. The kernels are the size independent kernel, the shear kernel proposed by Smoluchowski [M. Smoluchowski, “Versuch einer matematischen Theorie der Koagulationskinetic kolloider Lösungen”, Z. Physik. Chem. 92, (1917) 129–168.] and the two kernels proposed by Hounslow [M.J. Hounslow, “The population balance as a tool for understanding particle rate processes”, Kona (1998) 179–193.], i.e. the EKE kernel and the less used kernel based on equipartition of fluctuating translational momentum (ETM kernel). Microcrystalline cellulose (mcc) is granulated under different process conditions and it is found that the ETM kernel best describes the granulation at higher impeller speeds, whereas the EKE kernel gives better agreement at lower impeller speeds. The collision efficiency is assumed to be a function of the liquid saturation. By using this assumption, it was possible to detect similar trends for the remaining part of the collision efficiency regardless of process conditions.     

Initiation of Galling in Metal Forming: Differences Between Aluminium and Austenitic Stainless Steel Studied In Situ in the SEM

High friction and transfer of work material to tool surfaces constitute important industrial problems in forming of many metals and alloys. However, it is very hard to gain a deeper understanding of these phenomena by studying real forming operations. In this paper, we have tried to gain fundamental understanding by avoiding as much as possible of the complexity of real forming. This has been realised by studying the friction and material transfer between well-defined tool material surfaces; uncoated and DLC-coated tool steel, and a needle shaped austenitic stainless steel tip, in situ in the SEM. The tool materials were tested in two conditions; well polished and well polished with local intentional scratches. It was found that work material was immediately transferred to the tool steel surface. When passing an intentional scratch, the local transfer was on a much larger scale, and the friction was higher, but the effect was mostly local. For the polished DLC-coated surface, almost no work material was transferred and the friction was low. An intentional scratch in the polished DLC surface barely influenced the galling behaviour. The present results are discussed in the light of previously published results from an analogous study with aluminium as work material.     

Overview and some issues related to co‐firing biomass and coal

Low heating values, variable chemical compositions, peculiar physical properties, high investment cost and insecurity of biomass feedstocks supply limit the applications of biomass for energy and other processes. Co‐firing biomass and coal has potential for the development of biomass‐to‐energy capacity with significant economic, environmental, and social benefits. However, co‐firing is not straightforward, and some questions need to be addressed due to the differences in chemical compositions and physical properties of biomass and coal. This paper highlights key issues related to co‐firing, including reactor types, feeding, hydrodynamics, ash sintering, fouling, and corrosion, based on previous studies, as well as calculations and analysis. Direct co‐firing is the most common option for biomass and coal co‐firing currently, mostly due to relatively low investment needed to turn existing coal power plants into co‐firing plants. For direct co‐firing, the physical characteristics and chemical compositions of the fuel entering the combustors or gasifiers are critical to an optimum operation. Any biomass mixed with coal needs to have acceptable physical properties. More research is needed on co‐firing biomass and coal, including work on: preparation, handling, storage, and feeding of biomass feedstocks (e.g. drying, torrefaction, pelletization); co‐firing mechanisms; hydrodynamic analysis of co‐firing combustors and gasifiers; boiler/gasifier capacity, slagging, fouling, corrosion, efficiency, reliability, fuel flexibility; lower emissions and gas cleaning; catalyst poisoning; investment and operating costs.