The orientation, chirality, and dynamics of solar eruptive filaments are key to our understanding of the magnetic field of coronal mass ejections (CMEs), and therefore to predicting the ...geoeffectiveness of CMEs arriving at Earth. However, confusion and contention remain over the relationship between the filament chirality, magnetic helicity, and the sense of rotation during eruption. To resolve the ambiguity in observations, in this paper we used stereoscopic observations to determine the rotation direction of filament apex and the method proposed by Chen et al. to determine the filament chirality. Our sample of 12 eruptive active-region filaments establishes a strong one-to-one relationship, i.e., during the eruption, sinistral/dextral filaments (located in the southern/northern hemisphere) rotate clockwise/counterclockwise when viewed from above, and corroborates a weak hemispheric preference, i.e., a filament and related sigmoid both exhibit a forward (reverse) S shape in the southern (northern) hemisphere, which suggests that the sigmoidal filament is associated with a low-lying magnetic flux rope with its axis dipped in the middle. As a result of rotation, the projected S shape of a filament is anticipated to be reversed during eruption.
Multiple winding angle filament-wound (FW) structures may lead to more uniform strength for all filament layers, while there is no analysis method for deformation and stresses calculation of FW ...cylinder with variation wound angle. Deformation and stresses of a thick cylinder with multi-angle winding hybrid filament under axial loading and internal and external pressure were investigated. The deformation and stresses of each orthotropic unit of fiber layers, as well as longitudinal stress along the fiber direction, transverse stresses perpendicular to the fiber direction and shear stress in fiber layer were obtained analytically. The degenerated case of the model includes single winding angle FW cylinder, FW vessel with a liner, and sandwich pipe with one or multiple core layers. Numeric results of finite element models are present, which are very close to the theoretical results. The research shows that material utilization and working pressure can be increased by multi-angle FW procedure.
This article aims at solving the problem of broken-filament online detection and tracking during the process of carbon fiber production. Owing to the complex background and unique broken-filament ...shape, it is challenging to achieve the broken-filament online detection with high accuracy via classical machine vision methods, even general convolutional neural network (CNN)-based methods. Moreover, the carbon fiber strands are usually merged during the winding process, which would lead to the broken-filament location and tracking errors due to wrong segmentation and numbering of carbon fiber strands. To address these problems, we propose a vision-based method to achieve broken-filament online detection and tracking. First, an image collection module is designed to capture high resolution carbon fiber strand data. Then, a novel broken-filament detection network (BFDNet) is proposed to detect broken-filaments, including a feature learning part and a new anchor generation scheme, which is implemented based on the RetinaNet framework. Especially, the feature learning part contains several multiscale kernel fusion blocks (MKFBs) that are composed of convolution kernels of different sizes. Finally, a pixel projection method is proposed to segment and number carbon fiber strands for tracking. Our method achieves satisfactory performance for broken-filament online detection in terms of accuracy compared with several state-of-the-art methods designed for feature learning based on the classical object detection framework. Moreover, our method has been applied in practical applications for broken-filament inspection tasks in factories.
Filament eruptions occurring at different places within a relatively short time internal, but with a certain physical causal connection, are usually categorized as sympathetic eruptions. Studies of ...sympathetic eruptions are not uncommon. However, in these studies the causal links between sympathetic eruptions remain rather speculative. In this work, we present detailed observations of a sympathetic filament eruption event in which an identifiable causal link between two eruptive filaments is observed. On 2015 November 15, two filaments (F1 in the north and F2 in the south) were located at the southwestern quadrant of the solar disk. Their main axes were almost parallel to each other. Around 22:20 UT, F1 began to erupt, forming two flare ribbons. The southwestern ribbon apparently moved southwest and invaded the southeast part of F2. This continuous intrusion caused F2's eventual eruption. Accompanying the eruption of F2, flare ribbons and post-flare loops appeared in the northwest region of F2. Meanwhile, neither flare ribbons nor post-flare loops could be observed in the southeastern area of F2. In addition, the nonlinear force-free field extrapolations show that the magnetic fields above F2 in the southeast region are much weaker than those in the northwest region. These results imply that the overlying magnetic fields of F2 were not uniform. So we propose that the southwest ribbon formed from eruptive F1 invaded F2 from its southeast region with relatively weaker overlying magnetic fields relative to its northwest region, disturbing F2 and leading F2 to eventually erupt.
In this review, the potential failures and flaws associated with fused deposition modeling (FDM) or fused filament fabrication (FFF) 3D printing technology are highlighted. The focus of this article ...is on presenting the failures and flaws that are caused by the operational standpoints and which are based on the many years of experience with current and emerging materials and equipment for the 3D printing of polymers and composites using the FDM/FFF method. FDM or FFF 3D printing, which is also known as an additive manufacturing (AM) technique, is a material processing and fabrication method where the raw material, usually in the form of filaments, is added layer-by-layer to create a three-dimensional part from a computer designed model. As expected, there are many advantages in terms of material usage, fabrication time, the complexity of the part, and the ease of use in FDM/FFF, which are extensively discussed in many articles. However, to upgrade the application of this technology from public general usage and prototyping to large-scale production use, as well as to be certain about the integrity of the parts even in a prototype, the quality and structural properties of the products become a big concern. This study provides discussions and insights into the potential factors that can cause the failure of 3D printers when producing a part and presents the type and characteristics of potential flaws that can happen in the produced parts. Common defects posed by FDM printing have been discussed, and common nondestructive detection methods to identify these flaws both in-process and after the process is completed are discussed. The discussions on the failures and flaws in machines provides useful information on troubleshooting the process if they happen, and the review on the failures and flaws in parts helps researchers and operators learn about the causes and effects of the flaws in a practical way.
Abstract
We present the formation and eruption of a sigmoidal filament driven by rotating network magnetic fields (RNFs) near the center of the solar disk, which was observed by the 1 m aperture New ...Vacuum Solar Telescope at the Fuxian Solar Observatory on 2018 July 12. Counterclockwise RNFs twist two small-scale filaments at their northeastern foot-point region, giving a rotation of nearly 200° within about 140 minutes. The motion of the RNF has a tendency to accelerate at first and then decelerate obviously, as the average rotation speed increased from 10 to 150° hr
−1
, and then slowed down to 50° hr
−1
. Coalescence then occurs between filaments F1 and F2. Meanwhile the fine structures in the southwestern region of the filament was involved in another interaction of coalescence. The subsequent EUV brightening due to plasma heating is observed in the two interaction regions. These interacting structures, including F1, F2 and the fine structures in the southwestern region, eventually evolve into a larger-scale sigmoidal filament twisted in the same direction as the RNFs gave. The twist of the sigmoidal filament has exceeded 4
π
and the filament finally erupted. The motion of the sigmoidal filament remains uniform until a nearby jet collides, causing the filament to erupt faster. These results provide evidence that RNF plays an important role in the formation and eruption of the sigmoidal filament. The phenomena also suggests that the kink instability is the trigger mechanism for the filament eruption.
ABSTRACT We investigate whether flux cancellation is responsible for the formation of a very massive filament resulting in the spectacular eruption on 2011 June 7. We analyze and quantify the amount ...of flux cancellation that occurs in NOAA AR 11226 and its two neighboring active regions (ARs 11227 & 11233) using line-of-sight magnetograms from the Heliospheric Magnetic Imager. During a 3.6 day period building up to the eruption of the filament, 1.7 × 1021 Mx, 21% of AR 11226's maximum magnetic flux, was canceled along the polarity inversion line (PIL) where the filament formed. If the flux cancellation continued at the same rate up until the eruption then up to 2.8 × 1021 Mx (34% of the AR flux) may have been built into the magnetic configuration that contains the filament plasma. The large flux cancellation rate is due to an unusual motion of the positive-polarity sunspot, which splits, with the largest section moving rapidly toward the PIL. This motion compresses the negative polarity and leads to the formation of an orphan penumbra where one end of the filament is rooted. Dense plasma threads above the orphan penumbra build into the filament, extending its length, and presumably injecting material into it. We conclude that the exceptionally strong flux cancellation in AR 11226 played a significant role in the formation of its unusually massive filament. In addition, the presence and coherent evolution of bald patches in the vector magnetic field along the PIL suggest that the magnetic field configuration supporting the filament material is that of a flux rope.
Intermediate filaments (IFs) are encoded by the largest gene family among the three major cytoskeletal protein groups. Unique IF compliments are expressed in selective cell types, and this expression ...is reflected in their involvement, upon mutation, as a cause of or predisposition to more than 80 human tissue-specific diseases. This Review Series covers diseases and functional and structural aspects pertaining to IFs and highlights the molecular and functional consequences of IF-associated diseases (IF-pathies). Exciting challenges and opportunities face the IF field, including developing both a better understanding of the pathogenesis of IF-pathies and targeted therapeutic approaches.
Abstract
Solar filament eruptions can generate coronal mass ejections (CMEs), which are huge threats to space weather. Thus, we need to understand their underlying mechanisms. Although many authors ...have studied the mechanisms for several decades, we still do not fully understand in what conditions a filament can erupt to become a CME or not. Previous studies have discussed extensively why a highly twisted and already erupted filament will be interrupted and considered that a strong overlying constraint field seems to be the key factor. However, few of them study filaments in the weak field, namely, quiescent filaments, as it is too hard to reconstruct the magnetic configuration there. Here we show a case study, in which we can fully reconstruct the configuration of an intermediate filament with the MHD-relaxation extrapolation model and discuss its initial eruption and eventual failure. By analyzing the magnetic configuration, we suggest that the reconnection between the erupting magnetic flux rope (MFR) and the overlying field are the key factors that constrained the eruption of the filament. There is observational evidence that MFRs will reconnect with peripheral field lines. Usually, the reconnection between an MFR and peripheral fields will weaken the overlying constraint and promote further eruption, but in some cases in which the magnetic configuration of an MFR is far different from peripheral fields, the reconnection will play a negative role in MFR eruption.
PDF
