Camera Observations Research Articles

The Influence of the Gap Phenomenon on the Occurrence of Consecutive Discharges in WEDM Through High-Speed Video Camera Observation

The Wire Electrical Discharge Machining (WEDM) process is an accurate method for manufacturing high-added-value components for industry. Continuous developments in the process have resulted in specialized machines used in sectors such as aerospace and biomedical engineering. However, some fundamental aspects of the discharge process remain unresolved. This work aims to study the influence of discharge location and bubble expansion on the occurrence of subsequent discharges. A high-speed video camera observation system was constructed to capture images of each discharge. From the acquired images, an algorithm was devised to determine the discharge location based on grayscale analysis. Moreover, the voltage and current waveforms of the discharges and the framing signals of the high-speed video camera were then obtained using an oscilloscope. Synchronizing the observation images and signals allowed for calculating the delay time for each single discharge. The results indicate that most of the discharges occurred near the boundary of the bubble and during bubble expansion. This finding has been observed for a variety of machining conditions and can be explained by the effect of the debris particles concentrated at the bubble boundary. This study provides useful information for better understanding the discharge process in WEDM.

Investigation of Photoinduced Deterioration in Shadow Puppet Artifacts Collected from the National Shadow Pupperty Museum in Chengdu, China

Shadow puppet artifacts are a special type of cultural heritage made from animal skin, possessing significant cultural and artistic value. However, there is insufficient attention to the scientific preservation of these artifacts, and systematic research on their protection is lacking. In particular, light as an important factor and related conservation studies are weak. This study investigates the photoinduced deterioration of shadow puppet artifacts from the National Shadow Pupperty Museum in Chengdu collection. Based on the xenon arc lamp are a common method of light aging, the modern rawhide samples were aged by the xenon arc lamp to simulate photoinduced deterioration. After artificial light aging, the samples were stored in a stable environment (with temperature maintained at 22 ± 2°C and relative humidity maintained at 50 ± 5%RH) for 150 days. It attempts to avoid further deterioration of the samples due to drastic cyclic changes in the environment. And continuously observe changes in characteristics during this process to verify the potential reversibility of photoinduced deterioration. Comprehensive assessments were conducted to gauge the extent of deterioration. In order to assess the deterioration, a series of analytical techniques were used. Moisture gain or loss was inferred from mass changes, and colorimetric measurements were measured using the CIELAB formula. Macroscopic and microscopic morphological damage was documented through camera, stereo microscope, and scanning electron microscope observations. Fourier transform infrared spectroscopy (FTIR) assessed amide bond degradation and moisture loss, while thermogravimetry/differential thermogravimetry (TG/DTG) evaluated collagen denaturation and thermal stability. The results indicated that prolonged light exposure caused significant deterioration, including color fading, moisture evaporation, and structural damage such as shrinkage and cracking. The findings indicate that light exposure is a crucial factor in the preservation of shadow puppet artifacts. Therefore, it is essential to implement careful management strategies in museum environments to ensure the protection of these artifacts.

Fractal dimension analysis of lightning discharges of various types based on a comprehensive literature review

In this study, photographic records of natural lightning flashes obtained from high-speed video camera observations are analyzed based on an extensive literature review. The purpose of this work is to estimate the fractal dimension of lightning discharges and to analyze and evaluate the effect of lightning type (downward and upward flashes during their propagation as well as return strokes) and lightning polarity (negative and positive). Three methods of fractal dimension estimation are employed namely the: (i) box-counting, (ii) sandbox, and (iii) correlation method, utilizing algorithms developed in MATLAB software. Appropriate image processing techniques are employed to guarantee precision in fractal dimension estimation. A thorough discussion is conducted by comparing the estimated fractal dimension values with those previously documented in the relevant literature based on field observations. The mean fractal dimension of downward negative leaders for the three methods (1.18, 1.31, 1.38) aligns well with previous studies, while positive downward leaders exhibit lower values (1.08, 1.15, 1.26), denoting a reduced branching behavior; upward leaders demonstrate slightly higher fractal dimensions than downward ones. Additionally, an attempt to correlate the lightning return stroke peak current with the fractal dimension is made. The outcomes of this research may assist in facilitating precise modeling of the lightning attachment phenomenon, thereby contributing to the development of safer lightning protection systems.

Investigation of high internal phase water-in-oil emulsion on coal gasification fine slag flotation decarburization and its oil saving mechanism

Froth flotation stands as the preferred technique for the separation of charcoal and ash from coal gasification fine slag (CGFS). However, the presence of a well-developed pore structure and an abundance of oxygen-containing functional groups on the surface of residual charcoal necessitates the use of substantial dosage of collectors during the flotation of CGFS. To address this, a high internal phase water-in-oil (HIP W/O) emulsion, with an internal phase water volume fraction of 85 %, was formulated for the flotation decarburization of CGFS, with the objective of reducing the collector dosage. The outcomes of flotation tests demonstrated that at dosages of 50 kg/t for kerosene and 15.04 kg/t for the organic liquid of the HIP W/O emulsion, both were capable of yielding tailings with an ash content exceeding 95 %. The results from Cryo-SEM and viscosity tests suggest that the high viscosity characteristics of the HIP W/O emulsion are primarily attributed to the compact arrangement of emulsion droplets and the active influence of emulsifiers at the oil–water interface. High-speed camera observations revealed that the HIP W/O emulsion droplets exhibited a tendency to disperse into bar-shaped flocs with larger particle sizes in water. This particular dispersion morphology is advantageous for enhancing the oil agglomeration flotation mechanism within the flotation decarburization process of CGFS. LF-NMR tests have further substantiated that the emulsion droplets are not readily absorbed by the microporous structure of the residual charcoal within the CGFS. Wettability tests and FTIR analyses have demonstrated that the hydrophobic modification of the residual charcoal surface, achieved through the HIP W/O emulsion, markedly surpasses that of conventional kerosene. The combination of these results indicates that the use of HIP W/O emulsion in the flotation decarbonization process of CGFS offers multiple benefits. It not only significantly reduces the dosage of organic collectors required, but also enhances the economic efficiency and effectiveness of the flotation process, presenting a novel reagent option for the decarbonization of CGFS.

Dynamic behavior regulation of droplet transfer based on arc-bubble control by ultrasound-induced during underwater wet welding

In comparison to welding in air, the periodic formation of unstable arc bubbles is a significant factor contributing to the unstable mass transfer process during underwater wet welding (UWW). Up to now, there is no ideal method to control droplet transfer and improve arc stability. In this study, the ultrasound-induced method (UIM) was used to regulate the droplet transition behavior and improve the process stability. The behavior features and key mechanisms of arc-bubble and droplet transfer induced by ultrasound were revealed with the employment of highspeed camera and X-ray observation, respectively. The incident angle of ultrasound was taken as a variable to reveal its effects and mechanism of action on the behaviors of arc bubble and droplet transfer, weld formation quality, microstructure, and property of weld joint. The results show that ultrasound-induced a new rising mode of arc bubble, which can significantly reduce the repulsive resistance that come from the bubble rising on the droplet transfer process. Compared with underwater wet welding without ultrasound, the average diameter of molten droplets reduces from 3.2 mm to 1.7 mm, and the droplet transfer frequency increases from 7.8 Hz to 13 Hz as the incident angle of ultrasound increases to 60°. In addition, the weld seam without obvious defects could be produced by UWW with UIM, of which the Variation coefficient of weld reinforcement is reduced from 21.3 to 11.6 and 17.4 at an ultrasonic incident angle of 30° and 45°. With increasing of ultrasound incident angle, it showed that the microhardness of the weld joint has a slight increase. In the heat-affected zone, the microhardness for the joint increased from 290 HV to 320 HV while the incident angle increased to 60°. This research shows that an appropriate incident angle of ultrasound can obtain good-quality joints which has a stable metal transfer process in underwater wet welding.

Real-time mapping of photo-sono therapy induced cavitation using Doppler optical coherence tomography.

Photo-sono therapy (PST) is an innovative anti-vascular approach based on cavitation-induced spallation. Currently, passive cavitation detection (PCD) is the prevalent technique for cavitation monitoring during treatment. However, the limitations of PCD are the lack of spatial information of bubbles and the difficulty of integration with the PST system. To address this, we proposed a new, to the best of our knowledge, cavitation mapping method that integrates Doppler optical coherence tomography (OCT) with PST to visualize bubble dynamics in real time. The feasibility of the proposed system has been confirmed through experiments on vascular-mimicking phantoms and in vivo rabbit ear vessels, and the results are compared to high-speed camera observations and PCD data. The findings demonstrate that Doppler OCT effectively maps cavitation in real time and holds promise for guiding PST treatments and other cavitation-related clinical applications.

Insights into ground strike point properties in Europe through the EUCLID lightning location system

Abstract. Evaluating the risk of lightning strikes to a particular structure typically involves adhering to the guidance outlined in IEC 62305-2. Among the multitude of factors influencing the overall risk, flash density emerges as a crucial parameter. According to its definition, each flash is assigned only one contact point to ground. Nevertheless, it is well known that, on average, flashes exhibit multiple ground termination points as shown by high-speed camera observations. In this research, lightning data collected by the European Cooperation for Lightning Detection (EUCLID) network are utilized in combination with a ground strike point (GSP) algorithm that aggregates individual strokes within a flash into ground strike points. This approach enables the examination of spatio-temporal patterns of GSPs across Europe throughout a decade, spanning from 2013 to 2022. Average GSP densities exhibit variations across the European continent, mirroring the observed patterns in flash densities. The highest densities are concentrated along the Adriatic Sea and the western Balkan region, reaching peak values of up to 8.5 GSPs km−2 yr−1. The spatial distribution of the mean number of ground strike points per flash reveals a noticeable increase in the Mediterranean, Adriatic, and Baltic Sea regions compared to inland areas. Moreover, it has been determined that the average number of GSPs per flash reaches its peak between September and November. Additionally, a daily pattern is discernible, with the lowest number of GSPs per flash occurring between 12:00 and 18:00 UTC (universal time coordinated). It is found that 95 % of the separation distances between distinct GSPs are less than 6.7 km. Lastly, it is worth noting that the presence of the Alps has an impact on GSP behaviour, resulting in lower GSP counts in comparison to the surrounding areas, along with the shortest average distances between different GSPs.

Expediting the Convergence of Global Localization of UAVs through Forward-Facing Camera Observation

Expediting the Convergence of Global Localization of UAVs through Forward-Facing Camera Observation

Invasion in cold: weather effects on winter activity of an alien mesopredator at its northern range

Whether an invasive species thrives in cold ecosystems depends on its response to winter weather. A potential threat to these ecosystems in Europe is the invasive raccoon dog (Nyctereutes procyonoides). The survival of this mesopredator is supported in cold weather, because it can periodically use winter sleep, but its winter activity levels compared to native mesopredators remain unclear. We investigated the winter behaviour of raccoon dogs in Finland, near the edge of their invasion front, and compared their activity to native red foxes and badgers. Using wildlife cameras, we found that raccoon dogs do reduce activity during the coldest months, but camera observations did not strongly correlate with temperature perhaps due to feeding at camera sites. That is, artificial food sources may have increased raccoon dogs’ winter activity. Nevertheless, they responded more clearly to temperature drops than red foxes, but were more active than badgers that were mostly dormant and thus absent from our data. GPS-tracked raccoon dogs remained at some level active through winter, even near subarctic regions, but the cold and snowy weather clearly decreased activity and individuals stayed close to their nests during the coldest periods. Overall, these findings suggest that raccoon dogs can maintain some winter activity even in extremely cold environments, and they readily exploit human-provided resources. This potential ability to thrive in cold regions highlights the invasive potential of raccoon dogs. As winters become milder due to climate change, their numbers could increase significantly within cold-adapted ecosystems, impacting native species and posing conservation challenges.

Shedding of Cavitation Clouds in an Orifice Nozzle

Focused on the unsteady property of a cavitating water jet issuing from an orifice nozzle in a submerged condition, this paper presents a fundamental investigation of the periodicity of cloud shedding and the mechanism of cavitation cloud formation and release by combining the use of high-speed camera observation and flow simulation methods. The pattern of cavitation cloud shedding is evaluated by analyzing sequence images from a high-speed camera, and the mechanism of cloud formation and release is further examined by comparing the results of flow visualization and numerical simulation. It is revealed that one pair of ring-like clouds consisting of a leading cloud and a subsequent cloud is successively shed downstream, and this process is periodically repeated. The leading cloud is principally split by a shear vortex flow along the nozzle exit wall, and the subsequent cloud is detached by a re-entrant jet generated while a fully extended cavity breaks off. The subsequent cavitation cloud catches the leading one, and they coalesce over the range of x/d≈1.8~2.5. Cavitation clouds shed downstream from the nozzle at two dominant frequencies. The Strouhal number of the leading cavitation cloud shedding varies from 0.21 to 0.29, corresponding to the injection pressure. The mass flow rate coefficient fluctuates within the range of 0.59~0.66 at the same frequency as the leading cloud shedding under the effect of cavitation.

Experimental investigation of borehole breakout formation in Gosford sandstone

This study investigates the in-situ borehole breakout formation using true-triaxial laboratory experiments on cubic Gosford sandstone. Four series of tests have been conducted under varying stress conditions following two approaches: PD method (loading onto specimens with pre-drilled boreholes) and PS method (loading onto intact specimens and then conducting drilling). Borehole camera observations show that a large amount of rock debris remains within the breakout zone under the PD conditions, while clear V-shaped notches are observed in the PS tests. The breakout geometries are extracted based on point cloud data obtained from 3D scanning. Both breakout width and normalised depth under both testing approaches exhibit positive correlations with the maximum horizontal stress while decreasing with minimum horizontal stress. The PS tests tend to yield wider and deeper breakouts compared to the PD tests. The difference in breakout width is generally consistent across various stress conditions at approximately 10° – 15°, whereas the variation in the normalised breakout depth increases with the severity of the borehole failure. The discrepancies are believed to be attributed to the excavation unloading induced strength-weakening and removal of rock debris by circulating fluid and drilling vibration. The outcomes of this study demonstrate that the stress path has critical impacts on the rock failure behaviours around openings, and the PS tests are suggested for investigating the borehole breakout phenomenon.

Continual learning approaches to hand–eye calibration in robots

This study addresses the problem of hand–eye calibration in robotic systems by developing Continual Learning (CL)-based approaches. Traditionally, robots require explicit models to transfer knowledge from camera observations to their hands or base. However, this poses limitations, as the hand–eye calibration parameters are typically valid only for the current camera configuration. We, therefore, propose a flexible and autonomous hand–eye calibration system that can adapt to changes in camera pose over time. Three CL-based approaches are introduced: the naive CL approach, the reservoir rehearsal approach, and the hybrid approach combining reservoir sampling with new data evaluation. The naive CL approach suffers from catastrophic forgetting, while the reservoir rehearsal approach mitigates this issue by sampling uniformly from past data. The hybrid approach further enhances performance by incorporating reservoir sampling and assessing new data for novelty. Experiments conducted in simulated and real-world environments demonstrate that the CL-based approaches, except for the naive approach, achieve competitive performance compared to traditional batch learning-based methods. This suggests that treating hand–eye calibration as a time sequence problem enables the extension of the learned space without complete retraining. The adaptability of the CL-based approaches facilitates accommodating changes in camera pose, leading to an improved hand–eye calibration system.

Human avoidance, selection for darkness and prey activity explain wolf diel activity in a highly cultivated landscape

Wildlife that share habitats with humans with limited options for spatial avoidance must either tolerate frequent human encounters or concentrate their activity into those periods with the least risk of encountering people. Based on 5259 camera trap images of adult wolves from eight territories, we analyzed the extent to which diel activity patterns in a highly cultivated landscape with extensive public access (Denmark) could be explained from diel variation in darkness, human activity, and prey (deer) activity. A resource selection function that contrasted every camera observation (use) with 24 alternative hourly observations from the same day (availability), revealed that diel activity correlated with all three factors simultaneously with human activity having the strongest effect (negative), followed by darkness (positive) and deer activity (positive). A model incorporating these three effects had lower parsimony and classified use and availability observations just as well as a ‘circadian' model that smoothed the use‐availability ratio as function of time of the day. Most of the selection for darkness was explained by variation in human activity, supporting the notion that nocturnality (proportion of observations registered at night vs. day at the equinox) is a proxy for temporal human avoidance. Contrary to our expectations, wolves were no more nocturnal in territories with unrestricted public access than in territories where public access was restricted to roads, possibly because wolves in all territories had few possibilities to walk more than few hundred meters without crossing roads. Overall, Danish wolf packs were 6.5 (95% CI: 4.6–9.6) times more active at night than at daylight, which make them amongst the most nocturnally active wolves reported so far. These results confirm the prediction that wolves in habitats with limited options for spatial human avoidance, invest more in temporal avoidance.

Benthic Biodiversity by Baited Camera Observations on the Cosmonaut Sea Shelf of East Antarctica

A free-fall baited camera lander was launched for the first time on the Cosmonaut Sea shelf of East Antarctica at a depth of 694 m during the 38th Chinese National Antarctic Research Expedition (CHINARE) in 2022. We identified 31 unique taxa (23 were invertebrates and eight were fish) belonging to eight phyla from 2403 pictures and 40 videos. The Antarctic jonasfish (Notolepis coatsi) was the most frequently observed fish taxa. Ten species of vulnerable marine ecosystem (VME) taxa were observed, accounting for 32% of all species. The maximum number (MaxN) of Natatolana meridionalis individuals per image frame was ten, and they were attracted to the bait. The macrobenthic community type were sessile suspension feeders with associated fauna (SSFA), which was shaped by the muddy substrata with scattered rocks. Rocks served as the best habitats for sessile fauna. The study reveals the megafauna community and their habitat by image survey in the Cosmonaut Sea for the first time. It helped us obtain Antarctic biodiversity baselines and monitoring data for future ecosystem health assessment and better protection.

The Retrieval of Ground NDVI (Normalized Difference Vegetation Index) Data Consistent with Remote-Sensing Observations

The Normalized Difference Vegetation Index (NDVI) is widely used for monitoring vegetation status, as accurate and reliable NDVI time series are crucial for understanding the relationship between environmental conditions, vegetation health, and productivity. Ground digital cameras have been recognized as important potential data sources for validating remote-sensing NDVI products. However, differences in the spectral characteristics and imaging methods between sensors onboard satellites and ground digital cameras hinder direct consistency analyses, thereby limiting the quantitative application of camera-based observations. To address this limitation and meet the needs of vegetation monitoring research and remote-sensing NDVI validation, this study implements a novel NDVI camera. The proposed camera incorporates narrowband dual-pass filters designed to precisely separate red and near-infrared (NIR) spectral bands, which are aligned with the configuration of sensors onboard satellites. Through software-controlled imaging parameters, the camera captures the real radiance of vegetation reflection, ensuring the acquisition of accurate NDVI values while preserving the evolving trends of the vegetation status. The performance of this NDVI camera was evaluated using a hyperspectral spectrometer in the Hulunbuir Grassland over a period of 93 days. The results demonstrate distinct seasonal characteristics in the camera-derived NDVI time series using the Green Chromatic Coordinate (GCC) index. Moreover, in comparison to the GCC index, the camera’s NDVI values exhibit greater consistency with those obtained from the hyperspectral spectrometer, with a mean deviation of 0.04, and a relative root mean square error of 9.68%. This indicates that the narrowband NDVI, compared to traditional color indices like the GCC index, has a stronger ability to accurately capture vegetation changes. Cross-validation using the NDVI results from the camera and the PlanetScope satellite further confirms the potential of the camera-derived NDVI data for consistency analyses with remote sensing-based NDVI products, thus highlighting the potential of camera observations for quantitative applications The research findings emphasize that the novel NDVI camera, based on a narrowband spectral design, not only enables the acquisition of real vegetation index (VI) values but also facilitates the direct validation of vegetation remote-sensing NDVI products.

Experimental Study on Energy Evolution and Acoustic Emission Characteristics of Fractured Sandstone under Cyclic Loading and Unloading

To investigate the dynamic response of fractured rock under cyclic loading and unloading, a WHY-300/10 microcomputer-controlled electro-hydraulic servo universal testing machine was used to conduct uniaxial cyclic loading and unloading tests. Simultaneously, acoustic emission (AE) and a CCD high-speed camera were employed to monitor the fracturing characteristics of sandstone. The mechanical properties, energy evolution, AE characteristics, and deformation of 45° sandstone were analyzed. The results indicate that as the load cycle level increases, both the elastic modulus and deformation modulus exhibit a “parabolic” increase, with a rapid rise initially and a slower rate of increase later. The damping ratio generally shows a decreasing trend but tends to rise near the peak load. The total energy, elastic energy, dissipated energy, damping energy, and damage energy all follow exponential function increases with the load level. The b-value fluctuates significantly during the stable crack propagation phase, unstable crack propagation phase, and peak phase. When the FR (Felicity ratio > 1), the rock is relatively stable; when the FR (Felicity ratio < 1), the rock gradually extends towards an unstable state. The Felicity ratio can be used as a predictive tool for the precursors of rock failure. Shear fractures dominate during the compaction and peak phases, while tensile fractures dominate during the crack propagation phase, ultimately leading to a failure characterized by tensile fracture. High-speed camera observations revealed that deformation first occurs at the tips of the prefabricated cracks and gradually spreads and deflects toward the ends of the sandstone. This study provides theoretical support for exploring the mechanical behavior and mechanisms of fractured rock under cyclic loading and unloading, and it has significant practical implications.

Orbital and Physical Characterization of Asteroid Dimorphos Following the DART Impact

The Double Asteroid Redirection Test (DART) mission impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos, on 2022 September 26 UTC. We estimate the changes in the orbital and physical properties of the system due to the impact using ground-based photometric and radar observations, as well as DART camera observations. Under the assumption that Didymos is an oblate spheroid, we estimate that its equatorial and polar radii are 394 ± 11 m and 290 ± 16 m, respectively. We estimate that the DART impact instantaneously changed the along-track velocity of Dimorphos by −2.63 ± 0.06 mm s−1. Initially, after the impact, Dimorphos’s orbital period had changed by −32.7 minutes ± 16 s to 11.377 ± 0.004 hr. We find that over the subsequent several weeks the orbital period changed by an additional 34 ± 15 s, eventually stabilizing at 11.3674 ± 0.0004 hr. The total change in the orbital period was −33.25 minutes ±1.5 s. The postimpact orbit exhibits an apsidal precession rate of 6.7 ± 0.°2 day−1. Under our model, this rate is driven by the oblateness parameter of Didymos, J 2, as well as the spherical harmonics coefficients, C 20 and C 22, of Dimorphos’s gravity. Under the assumption that Dimorphos is a triaxial ellipsoid with a uniform density, its C 20 and C 22 estimates imply axial ratios, a/b and a/c, of about 1.3 and 1.6, respectively. Preimpact images from DART indicate Dimorphos’s shape was close to that of an oblate spheroid, and thus our results indicate that the DART impact significantly altered the shape of Dimorphos.

Plasma pretreatment to enhance the sedimentation of ultrafine kaolinite particles: Experiments and mechanisms

Coal-slime water treatment not only has a direct impact on the reuse of water as well as the recovery of coal-slime, but also has an essential significance for the sustainable development of a green ecology and carbon neutrality. In this study, the sedimentation behavior of ultrafine kaolinite particles (the main component of high-ash fine slime) using plasma pretreatment was investigated via sedimentation tests, turbidity detections and high-speed camera observations. The results showed that with plasma pretreatment, the arrival time of the maximum (final) thickness of the thickening layer considerably shortens, the final thickness of the thickening layer slightly decreases, and the turbidity of the supernatant significantly reduces. The mechanism of the plasma pretreatment method for the enhanced sedimentation of ultrafine kaolinite particles was elaborated via laser particle size analysis, microscopic observations, zeta potential determinations, and particle interaction energy calculations. The results showed that with plasma pretreatment, the zeta potential of kaolinite particles lowers, and the decrease in repulsive electrostatic force strengthens the coagulation of kaolinite particles, therefore making kaolinite flocs more compact and enhancing the sedimentation process of ultrafine kaolinite particles. And the enhanced sedimentation mechanism of ultrafine kaolinite particles via plasma pretreatment was drawn.

JWST-TST High Contrast: Asymmetries, Dust Populations, and Hints of a Collision in the β Pictoris Disk with NIRCam and MIRI

We present the first JWST Mid-Infrared Instrument (MIRI) and Near Infrared Camera (NIRCam) observations of the prominent debris disk around β Pictoris. Coronagraphic observations in eight filters spanning from 1.8 to 23 μm provide an unprecedentedly clear view of the disk at these wavelengths. The objectives of the observing program were to investigate the dust composition and distribution and to investigate the presence of planets in the system. In this paper, we focus on the disk components, providing surface brightness measurements for all images and a detailed investigation of the asymmetries observed. A companion paper by Kammerer et al. will focus on the planets in this system using the same data. We report for the first time the presence of an extended secondary disk in thermal emission, with a curved extension bent away from the plane of the disk. This feature, which we refer to as the “cat’s tail,” seems to be connected with the previously reported CO clump, mid-infrared asymmetry detected on the southwest side of the disk, and the warp observed in scattered light. We present a model of this secondary disk sporadically producing dust that broadly reproduces the morphology, flux, and color of the cat’s tail, as well as other features observed in the disk, and which suggests the secondary disk is composed largely of porous, organic refractory dust grains.

Microstructure and properties of Al–Cu–Mg alloy welded by 14 μm single-mode laser small oscillation welding

In this paper, the 14 μm single-mode laser oscillation welding technique was adopted to achieve high-quality welding of 2A12 aluminum alloy. Specifically, its influence on the microstructure and mechanical properties of the joint and the formation mechanism were investigated. The results showed that the ultra-small spot laser (28 μm) was able to achieve sequential oscillation of the molten pool with small amplitude (0.1 mm). The increased frequency caused the average grain size to decrease and the grain boundary length increased in the fusion zone. Meanwhile, the average grain orientation difference increased, and the growth orientation was more dispersed and homogeneous. While reducing weld morphology defects and refining grain microstructure, there was little influence on the penetration and width morphology of the weld. Finally, successfully prepared welds with tensile strength up to 410.4 MPa and elongation simultaneously increased to 4.065 % at 200 Hz. Furthermore, the influence of keyhole oscillation on the molten pool flow at small amplitude was explained by high-speed camera observation, which explored the mechanism of grain growth in the oscillating joints and provided new ideas for the welding of 2xx aluminum alloys.