Effect of wall surface wettability on collective behavior of hydrogen microbubbles rising along a wall

This paper presents an experimental study of the influence of wall surface wettability on the behavior of hydrogen microbubbles rising along a nearly vertical wall. Multiple optical diagnostics, including particle tracking velocimetry, have been employed for the study. The microbubble behavior observed along three different kinds of wall surfaces (hydrophobic, hydrophilic, and super-hydrophilic) was characterized by the microbubble-wall attachment, bubble size distribution, bubble coalescence, and microbubble layer formation. Microbubbles rising along the wall with poor wettability soon attach to the wall and grow to millimeters in size as a result of bubble coalescence. Such millimeter-sized bubbles detach from the wall because of their increased buoyancy, and eventually enhance transverse diffusion of microbubbles, which is known as the sweep-out effect. In contrast, in the case of very good wettability, almost no microbubbles attach to the wall and smoothly form a thin microbubble layer in the wall proximity. The observed phenomena contradict our intuitive expectation of the effect of surface wettability on gas bubbles, and hence may be regarded as a feature of microbubbles that distinguishes them from large bubbles

Effect of heated wall inclination on natural convection heat transfer in water with near-wall injection of millimeter-sized bubbles

Natural convection heat transfer from a heated wall in water with near-wall injection of millimeter-sized bubbles is studied experimentally. Velocity and temperature measurements are conducted in the nearwall region. In the range of the heated wall angles from 0 to 40 degrees from the vertical, the heat transfer coefficient increases by up to an order of magnitude with bubble injection. The ratio of the heat transfer coefficient with bubble injection to that without injection increases with the wall inclination angle. Based upon measured liquid temperature distributions and liquid flow velocity profiles, enhancement of heat transfer by bubble injection is explained by two mechanisms. First, wall-parallel transport of cold liquid into the thermal boundary layer is enhanced by the bubble-driven flow. Second, wall-normal mixing of warm liquid and cold liquid occurs, as a result of wall-normal velocity fluctuations of the liquid phase activated by a combination of bubble rising motion, vortex shedding from the bubbles, and unsteady vortices formed within the boundary layer. The unsteady vortices travel along the wall together with the bubbles, primarily contributing to the enhancement of heat transfer at higher wall inclination angles

Model for the glass transition in amorphous solids based on fragmentation

A model for the glass transition in a heating process has been proposed. In the model, noncrystalline solids are assumed to be assemblies of pseudomolecules or structural units. When the noncrystalline solid is heated, a bond breaking process becomes dominant compared with a rebinding process of broken bonds. At high temperature, successive bond breaking causes the fragmentation of the solid and the fragment size becomes smaller as the temperature further increases. Consequently, the solid begins to show some viscous behavior when the fragment size reaches a critical value. To construct mathematical expressions for the fragmentation model, we employed a simple rate equation for the bond breaking process first and then obtained the temperature dependence of dangling bond density in a noncrystalline solid. Second, the expressions for the fragment density and size as a function of temperature were obtained based on the following assumptions: (1) bond breaking takes place mainly at the boundaries between pseudomolecules, (2) once buds of microcracks are generated, successive bond breaking occurs mostly at the tip of the microcracks, and (3) the fragments are Voronoy polyhedra. Finally, the diffusion coefficient in the system was obtained by assuming the vacancy mechanism in solids and then the temperature dependence of viscosity was derived through Stokes-Einstein relation. To examine the present model, applications of the model to the phase changes of α-Si in heating processes are carried out and the results were discussed

RCABench: Open Benchmarking Platform for Root Cause Analysis

Fuzzing has contributed to automatically identifying bugs and vulnerabilities in the software testing field. Although it can efficiently generate crashing inputs, these inputs are usually analyzed manually. Several root cause analysis (RCA) techniques have been proposed to automatically analyze the root causes of crashes to mitigate this cost. However, outstanding challenges for realizing more elaborate RCA techniques remain unknown owing to the lack of extensive evaluation methods over existing techniques. With this problem in mind, we developed an end-to-end benchmarking platform, RCABench, that can evaluate RCA techniques for various targeted programs in a detailed and comprehensive manner. Our experiments with RCABench indicated that the evaluations in previous studies were not enough to fully support their claims. Moreover, this platform can be leveraged to evaluate emerging RCA techniques by comparing them with existing techniques.Comment: Accepted by NDSS 2023 Workshop on Binary Analysis Research (BAR); Best Paper Awar

Prediction and validation of a mechanism to control the threshold for inhibitory synaptic plasticity

Synaptic plasticity, neuronal activity-dependent sustained alteration of the efficacy of synaptic transmission, underlies learning and memory. Activation of positive-feedback signaling pathways by an increase in intracellular Ca2+ concentration ([Ca2+]i) has been implicated in synaptic plasticity. However, the mechanism that determines the [Ca2+]i threshold for inducing synaptic plasticity is elusive. Here, we developed a kinetic simulation model of inhibitory synaptic plasticity in the cerebellum, and systematically analyzed the behavior of intricate molecular networks composed of protein kinases, phosphatases, etc. The simulation showed that Ca2+/calmodulin-dependent protein kinase II (CaMKII), which is essential for the induction of synaptic plasticity, was persistently activated or suppressed in response to different combinations of stimuli. The sustained CaMKII activation depended on synergistic actions of two positive-feedback reactions, CaMKII autophosphorylation and CaMKII-mediated inhibition of a CaM-dependent phosphodiesterase, PDE1. The simulation predicted that PDE1-mediated feedforward inhibition of CaMKII predominantly controls the Ca2+ threshold, which was confirmed by electrophysiological experiments in primary cerebellar cultures. Thus, combined application of simulation and experiments revealed that the Ca2+ threshold for the cerebellar inhibitory synaptic plasticity is primarily determined by PDE1

形成的授業評価を通した授業改善の試み

The purpose of this study is to examine improvement of exercise skill and the formative class evaluation of students through apparatus gymnastics classes. The classes consisted in small steps and analogical exercise are recognized as effective teaching by professionals on P. E. The student-subjects were in the fourth grade at elementary schools and the observation covered mat exercise classes. The teachers were young and had two years educational experience, and they felt some difficulty to organize effective P. E. classes. The result of the analysis is that mat exercise subjects created with small steps were effective for students to acquire better exercise skills. But the formative class evaluation outcomes were not positive. Taking these different outcomes into considerations for more detail analysis, it is important to focus on not only teaching skills but also on teaching strategies through all classes