Radial Sizes and Expansion Behavior of ICMEs in Solar Cycles 23 and 24

We attempt to understand the influence of the heliospheric state on the expansion behavior of coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) in solar cycles 23 and 24. Our study focuses on the distributions of the radial sizes and duration of ICMEs, their sheaths, and magnetic clouds (MCs). We find that the average radial size of ICMEs (MCs) at 1 AU in cycle 24 is decreased by ∼33% (∼24%) of its value in cycle 23. This is unexpected as the reduced total pressure in cycle 24 should have allowed the ICMEs in cycle 24 to expand considerably to larger sizes at 1 AU. To understand this, we study the evolution of radial expansion speeds of CME-MC pairs between the Sun and Earth based on their remote and in situ observations. We find that radial expansion speeds of MCs at 1 AU in solar cycles 23 and 24 are only 9 and 6%, respectively, of their radial propagation speeds. Also, the fraction of radial propagation speeds as expansion speeds of CMEs close to the Sun are not considerably different between solar cycles 23 and 24. We also find a constant (0.63 ± 0.1) dimensionless expansion parameter of MCs at 1 AU for both solar cycles 23 and 24. We suggest that the reduced heliospheric pressure in cycle 24 is compensated by the reduced magnetic content inside CMEs/MCs, which did not allow the CMEs/MCs to expand enough in the later phase of their propagation. Furthermore, the average radial sizes of sheaths are the same in both cycles, which is unexpected, given the weaker CMEs/ICMEs in cycle 24. We discuss the possible causes and consequences of our findings relevant for future studies.

Validation of Evaluation Method of Feedback Reactivity for Plant Dynamics Analysis Code During Unprotected Loss of Heat Sink Event in Sodium-Cooled Fast Reactors

Negative reactivity caused by radial expansion of the core is known as one of the inherent safety features in a sodium-cooled fast reactor (SFR). In this paper, the numerical results of the benchmark analyses for the unprotected loss of heat sink (ULOHS) tests in the pool-type experimental SFR in the United States, EBR-II (BOP-302R and BOP-301) are discussed in order to validate the evaluation method of the reactivity feedback equipped in the in-house plant dynamics analysis code named Super-COPD. During the transient of the ULOHS tests as one of the representative issues, the reactor power decreased to the decay heat level due to the negative reactivity caused by the radial expansion of the core. By comparing the numerical results and the experimental data, the profiles of the increase of the core inlet temperature and the decrease of the reactor power calculated by Super-COPD were comparable with those of the experimental data. Applicability of the evaluation method for the reactivity feedback was indicated during the ULOHS event. The refinement of the plenum model of the cold pool by taking account of the thermal stratification was indicated for the future work in order to improve the profile of the core inlet temperature.

Influence of the pressure-dependent resonance frequency on the bifurcation structure and backscattered pressure of ultrasound contrast agents: A numerical investigation

The bifurcation structure of the oscillations of ultrasound contrast agents (UCAs) was studied as a function of the driving pressure for excitation frequencies that were determined using the UCAs pressure-dependent resonances (fs)(fs). It was shown that when excited by the (fs)(fs), the UCA can undergo a saddle-node bifurcation (SNB) to higher amplitude oscillations. The driving pressure at which the SNB occurs is controllable and depends on the (fs)(fs) magnitude. Utilizing the appropriate (fs)(fs), the scattering cross section of the UCAs can significantly be enhanced (e.g., ∼∼ninefold) while at the same time avoiding potential UCA destruction (by limiting the radial expansion ratio <<2). This offers significant advantages for optimizing UCA-mediated imaging and therapeutic ultrasound applications.

Influence of the pressure-dependent resonance frequency on the bifurcation structure and backscattered pressure of ultrasound contrast agents: A numerical investigation

The bifurcation structure of the oscillations of ultrasound contrast agents (UCAs) was studied as a function of the driving pressure for excitation frequencies that were determined using the UCAs pressure-dependent resonances (fs)(fs). It was shown that when excited by the (fs)(fs), the UCA can undergo a saddle-node bifurcation (SNB) to higher amplitude oscillations. The driving pressure at which the SNB occurs is controllable and depends on the (fs)(fs) magnitude. Utilizing the appropriate (fs)(fs), the scattering cross section of the UCAs can significantly be enhanced (e.g., ∼∼ninefold) while at the same time avoiding potential UCA destruction (by limiting the radial expansion ratio <<2). This offers significant advantages for optimizing UCA-mediated imaging and therapeutic ultrasound applications.

An Origami-Based Soft Robotic Actuator for Upper Gastrointestinal Endoscopic Applications

Soft pneumatic actuators have been explored for endoscopic applications, but challenges in fabricating complex geometry with desirable dimensions and compliance remain. The addition of an endoscopic camera or tool channel is generally not possible without significant change in the diameter of the actuator. Radial expansion and ballooning of actuator walls during bending is undesirable for endoscopic applications. The inclusion of strain limiting methods like, wound fibre, mesh, or multi-material molding have been explored, but the integration of these design approaches with endoscopic requirements drastically increases fabrication complexity, precluding reliable translation into functional endoscopes. For the first time in soft robotics, we present a multi-channel, single material elastomeric actuator with a fully corrugated design (inspired by origami); offering specific functionality for endoscopic applications. The features introduced in this design include i) fabrication of multi-channel monolithic structure of 8.5 mm diameter, ii) incorporation of the benefits of corrugated design in a single material (i.e., limited radial expansion and improved bending efficiency), iii) design scalability (length and diameter), and iv) incorporation of a central hollow channel for the inclusion of an endoscopic camera. Two variants of the actuator are fabricated which have different corrugated or origami length, i.e., 30 mm and 40 mm respectively). Each of the three actuator channels is evaluated under varying volumetric (0.5 mls-1 and 1.5 mls-1 feed rate) and pressurized control to achieve a similar bending profile with the maximum bending angle of 150°. With the intended use for single use upper gastrointestinal endoscopic application, it is desirable to have linear relationships between actuation and angular position in soft pneumatic actuators with high bending response at low pressures; this is where the origami actuator offers contribution. The soft pneumatic actuator has been demonstrated to achieve a maximum bending angle of 200° when integrated with manually driven endoscope. The simple 3-step fabrication technique produces a complex origami pattern in a soft robotic structure, which promotes low pressure bending through the opening of the corrugation while retaining a small diameter and a central lumen, required for successful endoscope integration.

Improving the Technology for Producing Pressure Couplings of Bushing-Housing Parts by Using a Power Drive Made of an Alloy with the Shape Memory Effect

The article describes the technology of using a power drive made of an alloy with the shape memory effect to improve the quality of the pressure couplings of bushing-housing. A comprehensive assessment of the existing approaches to the production of a pressure coupling is performed. The risk analysis of the technological process of pressing by the FMEA method is carried out. The flow diagram of the proposed process and the results of an experimental study of the dependence of contact pressures on the radial expansion of a ring load-bearing element made of an alloy with the shape memory effect are presented.