Search

Background and Aim: Convolutional neural network (CNN) systems that automatically detect abnormalities from small‐bowel capsule endoscopy (SBCE) images are still experimental, and no studies have directly compared the clinical usefulness of different systems. We compared endoscopist readings using an existing and a novel CNN system in a real‐world SBCE setting. Methods: Thirty‐six complete SBCE videos, including 43 abnormal lesions (18 mucosal breaks, 8 angioectasia, and 17 protruding lesions), were retrospectively prepared. Three reading processes were compared: (A) endoscopist readings without CNN screening, (B) endoscopist readings after an existing CNN screening, and (C) endoscopist readings after a novel CNN screening. Results: The mean number of small‐bowel images was 14 747 per patient. Among these images, existing and novel CNN systems automatically captured 24.3% and 9.4% of the images, respectively. In this process, both systems extracted all 43 abnormal lesions. Next, we focused on the clinical usefulness. The detection rates of abnormalities by trainee endoscopists were not significantly different across the three processes: A, 77%; B, 67%; and C, 79%. The mean reading time of the trainees was the shortest during process C (10.1 min per patient), followed by processes B (23.1 min per patient) and A (33.6 min per patient). The mean psychological stress score while reading videos (scale, 1–5) was the lowest in process C (1.8) but was not significantly different between processes B (2.8) and A (3.2). Conclusions: Our novel CNN system significantly reduced endoscopist reading time and psychological stress while maintaining the detectability of abnormalities. CNN performance directly affects clinical utility and should be carefully assessed. [ABSTRACT FROM AUTHOR]

In this study, the interfacial flow dynamics involving a chemical reaction that produces viscoelastic material at the interface between two liquids is experimentally investigated, and the material is evaluated using interfacial large amplitude oscillatory shear (LAOS) measurements. The flow dynamics indicates fingering patterns at low injection flow rates and fracturing patterns at high flow rates in Hele-Shaw cells, where a more viscous xanthan gum solution is displaced by the less viscous Fe(NO3)3 solution with various concentrations of Fe(NO3)3. The threshold flow rate value of such a transition is different for various concentrations of Fe(NO3)3. Although such a transition without chemical reactions has been discussed, the factors responsible for the transition remain unclear. The flow dynamics in Hele-Shaw cells is considered to flow under large deformation, which exceeds the small amplitude oscillatory shear condition but is under the LAOS condition. Therefore, LAOS measurement of the viscoelastic interface is performed for various concentrations of Fe(NO3)3. Using the characteristic properties extracted from the LAOS measurements, the elastic and viscous forces of the viscoelastic interface are evaluated. We show the transition from fingering to fracturing patterns when the elastic force exceeds a certain value. These findings highlight that rheology under large deformation of the viscoelastic interface plays a crucial role in interfacial flow, where viscoelastic materials are produced by chemical reactions at the interface. In addition, this study should be an example of the successful elucidation of physical phenomena by interfacial LAOS, which has been reported in a very limited number of studies. [ABSTRACT FROM AUTHOR]

Viscous fingering or Saffman-Taylor instability shows fingering interfacial patterns when a more mobile fluid displaces a less mobile one in porous media. The effective interfacial tension (EIT) is like capillary force, acting at the miscible interface on time scales shorter than interface relaxation. It has been numerically reported so far that the fingers are wider with EIT compared with those without EIT. A recent experiment observed finger widening with increasing flow rate in a miscible system with EIT, which is not observed in classical immiscible and miscible systems. In this study, we have numerically investigated the effect of Pe (which corresponds to the injection flow rates in the experiment) on miscible viscous fingering with/without EIT. We have shown that the fingers are monotonically thinner with an increase in Pe in the system without EIT, while finger widening with increasing Pe is observed in the system with EIT. Furthermore, we have also examined a one-dimensional underlying concentration profile and EIT profile by using a one-dimensional diffusion-convection model because EIT is proportional to the squared concentration gradient. We have then shown that the concentration gradient is steeper and, thus, the EIT is larger as Pe is larger. Therefore, this is the first numerical study that can theoretically verify finger widening with increasing flow rate, which occurs only in a miscible system with EIT to the extent of our targeting EIT values, and explain the mechanism by one-dimensional analysis. [ABSTRACT FROM AUTHOR]

Phase separation is ubiquitous in nature and technology. So far, the focus has primarily been on phase separation occurring in the bulk phase. Recently, phase separation taking place in interfacial areas has attracted more attention – in particular, a combination of interfacial phase separation and hydrodynamics. Studies on this combination have been conducted intensively in this past decade; however, the detailed dynamics remain unclear. Here, we perform fluid displacement experiments, where a less viscous solution displaces a more viscous one in a radially confined geometry and phase separation occurs at the interfacial region. We demonstrate that a finger-like pattern, due to the viscosity contrast during the displacement, can be suppressed by the phase separation. We also claim that the direction of a body force, the so-called Korteweg force, which appears during the phase separation and induces convection, determines whether the fingering pattern is suppressed or changed to a droplet pattern. The change of the fingering pattern to the droplet pattern is enhanced by the Korteweg force directed from the less viscous solution to the more viscous one, whereas the fingering is suppressed by the force directed in the opposite direction. These findings will contribute directly to the higher efficiency of processes such as enhanced oil recovery and CO2 sequestration, where interfacial phase separation is considered to occur during the flow. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this research is to present a new theoretical framework concerning subjective career development in Japan. The framework consists of three concepts, namely, career "drift," "mist," and "hope". Design/methodology/approach: This paper introduces these concepts, including how they were discovered, and the potential strength they possess in expressing the subjective side of a career. The main method used to develop these concepts was the "grounded theory approach" advocated by Glaser and Strauss. Findings: Although findings from this framework alone are limited, it is possible to point out several advantages of this framework compared with traditional stage models of career development. The framework expresses the complex state of mind in which an individual may be placed in the process of career management, especially on how people design or gain direction in an uncertain situation. Research limitations/implications: This framework stands purely in an arena of theoretical arguments. Future research, including both quantitative and qualitative, must be conducted to test the generalizability of this framework. Each concept can be operationalized and scales should be developed. Originality/value: This paper introduces original concepts and a framework derived from qualitative studies in Japan. By looking into different cultural settings, it may trigger a discussion on what is universal and what is local in career theories. Also, the new framework may be used to make sense of careers, which could not be done based on traditional values. (Contains 2 figures.)

A chemical reaction in the flow field affects the physical property of fluids, resulting in changing flow dynamics. The effect of the reaction on the flow dynamics is normally evaluated by comparison between the physical properties of the fluid between pre- and post-reaction. However, our group found a polymeric reacting flow in which a comparison between pre- and post-reaction fluid properties is insufficient to evaluate the influences of the reaction on the flow dynamics (T. Ueki et al., J. Phys. Chem. B, 2019, 123, 4587–4593). In the study, we examined the stirred flow by an impeller in a beaker with a chemical reaction between partially hydrolyzed polyacrylamide (HPAM) solution and Fe(NO3)3 solution. We found that a so-called Weissenberg effect, where the stirred solution climbs up the stirring shaft because of an increase in the viscoelasticity of the mixed solution, transiently appeared in only the halfway of the reaction, although the reaction slightly decreased the solution's viscosity at the final stage under a certain pH and we proposed the mechanism for the temporal increase in the viscoelasticity. In the present study, we conducted similar experiments as our previous study using HPAM solution at various pH and two concentrations of Al(NO3)3 solutions. The unpredictable flow dynamics by comparison between pre- and post-reaction fluid properties, i.e., the appearance and disappearance of the Weissenberg effect, has been observed under a certain pH and Al(NO3)3 concentration. We investigated the mechanism by means of the simultaneous measurement of pH and the stirring torque and the identification of the dominant species of aluminum aqua complexes by the Henderson–Hasselbalch equation. As a result, we proposed two mechanisms of dissapearance of the Weissenberg effect: one is the same for the Fe(NO3)3 case but the other is unique and novel for the Al(NO3)3 case. This study can contribute to the comprehensive understanding of the conditions for the occurrence of the unpredictable dynamics of polymeric reacting flow by comparison between the pre- and post-reaction fluid properties. [ABSTRACT FROM AUTHOR]

We develop coupled evolution equations for viscous fingering (VF) and phase separation in partially miscible systems by combining a simple double-well thermodynamic free energy and Korteweg force with a classical miscible VF model for a binary system. The VF pattern transition into a droplet formation pattern by the spinodal decomposition effect is demonstrated, and the simultaneous increases in the depth of the energy minimum, in the difference in the equilibrium concentrations, and in the Korteweg force, enhance the droplet growth. The pattern's interfacial length increases with the spinodal decomposition effects. These results match the corresponding experimental results. [ABSTRACT FROM AUTHOR]

A method is presented to simulate the fluid dynamics of low- to moderate-Reynolds-number flows around solid objects with complex shapes on a fixed Cartesian grid. On grid points occupied by a solid object, the method forces the fluid motion to be equal to the motion of the solid object, whereas the boundary conditions on the solid-fluid interface are enforced through a specific treatment of grid points close to the interface. The method is fairly easily implemented in both two and three dimensions, and a grid-refinement study shows that the method is globally close to second-order accurate. Steady and unsteady flow results over a cylinder and a sphere fixed in the grid show very good agreement with previous experimental and computational investigations. Computations of a cylinder moving in the grid with a surrounding fluid initially at rest produce results that compare very well with the fixed-cylinder results, thus demonstrating the validity of the method for moving geometry simulations. The method's applicability to investigations of the unsteady aerodynamics of microscale flapping flight is demonstrated through simulations of the fluid dynamics of a flapping cantilever beam and a free-falling two-dimensional 'leaf.'