On the analysis of the contact angle for impacting droplets using a polynomial fitting approach

ractical considerations on the measurement of the dynamic contact angle and the spreading diameter of impacting droplets are discussed in this paper. The contact angle of a liquid is commonly obtained either by a polynomial or a linear fitting to the droplet profile around the triple phase point. Previous works have focused on quasi-static or sessile droplets, or in cases where inertia does not play a major role on the contact angle dynamics. Here, we study the effect of droplet shape, the order of the fitting polynomial, and the fitting domain, on the measurement of the contact angle on various stages following droplet impact where the contact line is moving. Our results, presented in terms of the optical resolution and the droplet size, show that a quadratic fitting provides the most consistent results for a range of various droplet shapes. As expected, our results show that contact angle values are less sensitive to the fitting conditions for the cases where the droplet can be approximated to a spherical cap. Our experimental conditions include impact events with liquid droplets of different sizes and viscosities on various substrates. In addition, validating past works, our results show that the maximum spreading diameter can be parameterised by the Weber number and the rapidly advancing contact angle

Conspiracy theory as spatial practice: the case of the Sivas arson attack, Turkey

This article discusses the relationship between conspiratorial thinking and physical space by focusing on the ways conspiracy theories regarding political violence shape and are shaped by the environments in which it is commemorated. Conspiratorial thinking features space as a significant element, but is taken to do so mainly figuratively. In blaming external powers and foreign actors for social ills, conspiracy theorists employ the spatial metaphor of inside versus outside. In perceiving discourses of transparency as the concealment rather than revelation of mechanisms of governance, conspiracy theorists engage the trope of a façade separating the space of power’s formulations from that of its operations. Studying the case of an arson attack dating from 1990s Turkey and its recent commemorations, this article argues that space mediates conspiracy theory not just figuratively but also physically and as such serves to catalyze two of its deadliest characteristics: anonymity and non-linear causality. Attending to this mediation requires a shift of focus from what conspiracy theory is to what it does as a spatial practice

Controlling and characterising the deposits from polymer droplets containing microparticles and salt

It is very well known that as suspension droplets evaporate, a pinned contact line leads to strong outwards capillary flow resulting in a robust coffee ring-stain at the periphery of the droplet. Conversely tall pillars are deposited in the centre of the droplet when aqueous droplets of poly(ethylene oxide) evaporate following a boot-strapping process in which the contact line undergoes fast receding, driven by polymer precipitation. Here we map out the phase behaviour of a combined particle-polymer system, illustrating a range of final deposit shapes, from ring-stain to flat deposit to pillar. Deposit topologies are measured using profile images and stylus profilometery, and characterised using the skewness of the profile as a simple analytic method for quantifying the shapes: pillars produce positive skew, flat deposits have zero skew and ring-stains have a negative value. We also demonstrate that pillar formation can be disrupted using potassium sulphate salt solutions, which change the water from a good solvent to a thetapoint solvent, consequently reducing the size of the polymer coils. This inhibits polymer crystallisation, interfering with the bootstrap process and ultimately preventing pillars from forming. Again, the deposit shapes are quantified using the skew parameter

Investigation of production conditions and powder properties of AUC

WOS: A1996VH02200023Ammonium uranyl carbonate (AUC) powders are prepared by adding 25% ammonium carbonate solution into the uranyl nitrate (UNH) solutions purified with TBP extraction from dissolution of the Canada originated U3O8 commercial concentrate. AUC powders are identified by chemical analysis, TGA/DTG analysis, LR analysis and by single crystal X-ray diffraction. The effects of the precipitation conditions on the powder properties are determined. The particle size of AUC increases with the C/U ratio and temperature while it decreases with the increasing uranium concentration. The mixing rate and the addition rate of ammonium carbonate does not have a considerable effect on the particle size, The reactor and the mixing type have great effects on the flowability of the AUC powders. The most flowable powders are obtained in a conical and air agitated reactor, The flowability of these powders is 2.5 g/s with a specific surface area of 5.59 m(2)/g and particle size of 4 mu m. UO2 converted via AUC is also very flowable (3 g/s) with a specific surface area of 5.1 m(2)/g

Preparation of homogeneous (Th0.8U0.2)O-2 pellets via coprecipitation of (Th,U)(C2O4)(2)center dot nH(2)O powders

WOS: A1997XY86900005Thorium and uranium dioxides form a complete series of solid solutions. The formation from the individual oxides can be performed only by extensive co-milling and reaction at high temperatures. in this study, we prepared 80% ThO2-20% UO2 via coprecipitation of the mixed oxalates from nitrate solutions using an excess of oxalic acid. The parameters which may effect the powder properties were investigated, such as oxalic acid and thorium concentrations, temperature and type of agitation. The specific surface of the oxalates and their derived oxides were measured. Among the precipitation parameters, temperature of 10 degrees C and mechanical stirring resulted in the highest surface area. The coprecipitated Th,U(IV) oxalate powders were decomposed at 350 degrees C, calcinated at 900 degrees C each for 24 h in air and were reduced during 2 h at 650 degrees C in H-2 atmosphere. X-ray diffraction resulted in a single-phase mixed oxide solid solution. The green densities of pellets made from these mixed oxides varied between 36 and 38% TD. Pellets were sintered in flowing CO2 at 1100 degrees C for 30 min and achieved 81% TD. (C) 1997 Elsevier Science B.V