In the present work, forced oscillations of a single, spherical, encapsulated gas bubble, immersed in an unbounded thixotropic liquid, is investigated numerically. Relying on the Moore's model to represent the thixotropicity of the liquid, and the Kelvin-Voigt model to represent the viscoelasticity of the enclosing shell, the modified integrodifferential Rayleigh-Plesset equation is solved numerically using the Gauss-Laguerre Quadrature (GLQ) method. It is shown that the thixotropic behavior of the surrounding liquid plays a key role in the emergence of harmonics. It is also shown that the viscoelastic properties of the shell material and also its wall thickness can dramatically affect the rise of harmonics for encapsulated contrast bubbles used in medical sonography.

Erosion, erosion–corrosion, and synergistic behaviors of AISI 420 stainless steel were studied in 3.5 wt.% NaCl solution containing silica sand with the size of 250–500 μm as erodent particle. The erosion and erosion–corrosion tests were carried out according to ASTM G11909 standard and the synergism was calculated. The tests were performed using a slurry jet apparatus at a jet velocity of 6.5 m/s, sand concentration of 90 g/l, and various impinging angles of 20 deg–90 deg. Scanning electron microscope (SEM) was used to study the eroded surfaces and erosion mechanisms. The SEM images showed that under low impacting angles, cutting deformation was the main erosion mechanism while impact and work hardening could be responsible for material removal at high impacting angles. The results showed that the maximum erosion–corrosion and synergism rates occurred at an impingement angle of about 50 deg while the maximum pure erosion rate was obtained at impingement angle of about 35 deg. Energy dispersive spectrometry (EDS) analysis showed that an oxide layer was formed on the surfaces of the samples during erosion–corrosion tests. This oxide layer could make the surface more brittle and could lead to an increment of about 15 deg in the angle of the maximum removal rate. The formation and the subsequent removal of the nonprotective oxide layer as well as possible initiation and propagation of pits during erosion–corrosion tests could lead to higher erosion–corrosion rate compared to pure erosion resulting in a positive synergism under the conditions tested.

Over the past decades, research on language teachers' engagement in action research (AR) and more recently on their emotion labor has exponentially grown. However, little research is available on how AR and emotion labor intersect to shape language teacher professional development. This study addressed this gap by reporting on how four Iranian English language teachers used emotion labor as professional development work during participation in an AR project. Data were collected from reflective journals and classroom observations as well as the associated postclass discussions during the enactment of AR, and from interviews at two junctures in time, once during the course and once longitudinally after six and 12 months. Data analyses revealed that the teachers used AR as a mechanism for minimizing the gap between their internal feelings and external expectations, and gradually developed the identity of a teacher–researcher by using the affordances emotion labor provided. Moreover, the teachers retrospectively developed emotional learning, which facilitated their response to institutional expectations in the short term and to the professional discourses of teaching in the long term. We conclude the paper with implications for teacher education to better understand how emotions feature in AR and how emotion labor could be employed for AR‐induced professional development.

No abstract

In the present work, the effect of a fluid's thixotropic behavior is investigated numerically on the frequency response of an encapsulated gas microbubble. Relying on Moore's model to represent the thixotropicity of the surrounding liquid and the Kelvin-Voigt model to represent the viscoelasticity of the enclosing shell, the modified integro-differential Rayleigh-Plesset equation is solved numerically using Gauss-Laguerre Quadrature (GLQ) method. It is shown that by an increase in the breakdown-to-buildup ratio new harmonics are generated. Also, the resonance frequency of the bubble is predicted to shift to lower values by an increase in this ratio with the effect being more evident for the harmonics. An increase in the viscosity ratio in the Moore's model is predicted to lower the resonance frequency of the bubble with the effect being most significant for the main frequency.