•A water droplet's impact and its subsequent spreading, recoiling and freezing on a smooth substrate at a supercooled temperature is studied numerically.•Simulated results confirm that a water ...droplet after its impact on a smooth surface at a supercooled temperature can form either a central-pointy icing pattern or a central-cave icingpattern.•A map showing effects of contact angle and Stefan number on the formation of central-pointy icing or central-cave icing patterns on a smooth surface is presented.
A water droplet's impact and its subsequent spreading, recoiling and freezing on a smooth substrate at a supercooled temperature is studied numerically using a 3D pseudo-potential lattice Boltzmann method, in combination with a solid-liquid phase-change model with volume expansion of water at 0°C taken into consideration. Simulated results show that a water droplet after its impact on a smooth surface at a supercooled temperature can form either a central-pointy icing pattern with a single ice peak, or a central-concave icingpattern in a donut shape, depending on the contact angle and the supercooled degree of the wall. Itisshown that the recoiling motion of the droplet after its impact on the supercooled substrate plays the dominant role in the formation of the central-pointy icing or central-concave icing pattern. The central-pointyicingpattern is formed on a substrate having a large contact angle where the recoiling motion of the droplet is strong while the central-concave icing pattern is formed on a substrate having a high degree of supercooled temperature (i.e., a large Stefan number) where the recoiling motion is terminated prematurely because of early nucleation of freezing on the supercooled substrate. The volume expansion during liquid to ice phase-change process at 0°C does affect the movement of the liquid phase although its effect on the formation of icing patterns is small. Effects of movement of freezing fronts on the shape of the icing patterns are illustrated. At fixed values of We= 320 and Re = 164.9, a map showing effects of contact angle and Stefan number (bottom wall temperature) on the formation of central-pointy icing or central-concave icingpatterns after a water droplet's impact (with D0= 100 and Pr = 13.5) on smooth supercooled surfaces is presented.
•A water droplet's impact and its subsequent spreading, recoiling and freezing on a rough substrate at a supercooled temperature are studied numerically.•The freezing patterns in three modes on rough ...surfaces including Hemi-wicking Cassie-Baxter mode, Wenzel mode and Cassie-Baxter mode are investigated.•Maps, showing effects of contact angle and Stefan number on formation of central-pointy icing or central-cave icing patterns of a water droplet after its impact on rough surfaces at supercooled temperatures are presented. Vapor exists in the grooves of the micro-pillars decreases heat conduction between the droplet and the wall, thus, affecting freezing times.
In this paper (Part II of a paper series), a 3D pseudo-potential lattice Boltzmann method in combination with a solid-liquid phase change model with volume expansion taken into consideration (the same model used in Part I) is applied to study a water droplet's impact and its subsequent freezing patterns on rough supercooled substrates, consisting of an array of micro-pillars in a saturated vapor environment. Freezing patterns of the droplet in three different modes on rough surfaces depending on the contact angle are investigated. In the Hemi-wicking Cassie-Baxter mode where the water droplet fills into grooves between micro-pillars completely, heat conduction rate increases because of the increasing contact area of the water droplet and the micro-pillars, and the contact angle becomes smaller which results in the central-concave icing pattern. When the droplets are in the Wenzel mode and the Cassie-Baxter mode on the rough surface, saturated vapor exists between the droplet and the micro-pillars, which brings additional thermal resistance between the supercooled substrate to droplets. This results in lower heat conduction rate which delays ice nucleation time and allows the droplet to complete its recoiling motion that leads to the formation of the central pointy icing pattern. Because static contact angles of rough substrates in these two modes are higher than those of the corresponding smooth substrates, droplets’ recoiling motions on rough substrates are stronger which lead to the formation of central-pointy icing patterns. Regime maps, showing effects of contact angle and Stefan number on formation of central-pointy icing or central-concave icing patterns of a water droplet (with D0 = 100 and Pr = 13.5) after its impact on rough substrates at supercooled temperatures at We= 320 and Re = 164.9 are presented.
We describe the latest version of Microsoft's conversational speech recognition system for the Switchboard and CallHome domains. The system adds a CNN-BLSTM acoustic model to the set of model ...architectures we combined previously, and includes character-based and dialog session aware LSTM language models in rescoring. For system combination we adopt a two-stage approach, whereby acoustic model posteriors are first combined at the senone/frame level, followed by a word-level voting via confusion networks. We also added another language model rescoring step following the confusion network combination. The resulting system yields a 5.1% word error rate on the NIST 2000 Switchboard test set, and 9.8% on the CallHome subset.
Aim
To assess the effect of antibiotics administered in feed on the resistance phenotypes and genotypes of Escherichia coli in the chicken intestine.
Method and Results
Chickens were administered ...amoxicillin, chlortetracycline and florfenicol in feed and 203 intestinal E. coli were examined for their susceptibility to 11 antimicrobial agents and for the presence of antibiotic resistance genes (ARG) using PCR. DNA was extracted from chicken stool samples in 15, 20, 30 and 40 day old chickens. We found that while antibiotic resistance rates increased with time, the relative gene abundance of tet(W), tet(A), cmlA, cfr and sul1 decreased. In contrast, the relative abundance of gene blaTEM and mcr‐1 increased over the experimental period. Pearson correlation analysis indicated that sul1 was correlated with tet(W) (R = 0·630, P < 0·01) and cmlA was correlated with cfr (R = 0·587, P < 0·01). Interestingly, mcr‐1 correlated with tet(W) (R = −0·546, P < 0·05).
Conclusions
Administration of different antibiotic reduced the relative abundance of ARG in chickens but did not halt the expansion of antibiotic resistance.
Significance and Impact of the Study
Changing the pattern of antibiotic types used to prevent antibiotic resistance in chickens is not a viable method to prevent the spread of ARG.
In this second international permeability benchmark, the in-plane permeability values of a carbon fabric were studied by twelve research groups worldwide. One participant also investigated the ...deformation of the tested carbon fabric. The aim of this work was to obtain comparable results in order to make a step toward standardization of permeability measurements. Unidirectional injections were thus conducted to determine the unsaturated in-plane permeability tensor of the fabric. Procedures used by participants were specified in the guidelines defined for this benchmark. Participants were asked to use the same values for parameters such as fiber volume fraction, injection pressure and fluid viscosity to minimize sources of scatter. The comparison of the results from each participant was encouraging. The scatter between data obtained while respecting the guidelines was below 25%. However, a higher dispersion was observed when some parameters differed from the recommendations of this exercise.
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