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Dynamic keyhole behavior and keyhole instability in high power fiber laser welding of stainless steel
摘要： A three-dimensional numerical model, considering the real-time multiple reflections of a laser beam, adiabatic bubble model and shear stress, was developed to study the dynamic keyhole behavior and keyhole instability in fiber laser welding of stainless steel. The inner dynamic keyhole behavior and weld defect formation were directly observed in a high resolution assisted by transparent glass. The numerical and experimental results showed that the keyhole width reached the quasi-steady state earlier than the keyhole depth did during fiber laser welding of stainless steel. Due to the large recoil pressure at rear keyhole wall caused by the irradiation of laser energy reflected by the bulge at the front keyhole wall, the rear keyhole wall was severely deformed at keyhole bottom and keyhole middle. The rear keyhole wall was collapsed due to the high surface tension pressure and hydrostatic pressure. The whole keyhole collapse was attributable to the capillary instability of the keyhole associated with large depth/width ratio and the strong flow of the bulges at the keyhole wall. When the laser power was increased, the keyhole depth/width ratio was increased, so the keyhole was more capillary instable. The average inclined angle of the front keyhole wall was decreased.
关键词： Bubble formation,Dynamic keyhole behavior,Keyhole instability,Fiber laser welding
更新于2025-11-28 14:24:20
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Super-resolution microscopy reveals significant impact of M2e-specific monoclonal antibodies on influenza A virus filament formation at the host cell surface
摘要： Influenza A virions are highly pleomorphic, exhibiting either spherical or filamentous morphology. The influenza A virus strain A/Udorn/72 (H3N2) produces copious amounts of long filaments on the surface of infected cells where matrix protein 1 (M1) and 2 (M2) play a key role in virus filament formation. Previously, it was shown that an anti-M2 ectodomain (M2e) antibody could inhibit A/Udorn/72 virus filament formation. However, the study of these structures is limited by their small size and complex structure. Here, we show that M2e-specific IgG1 and IgG2a mouse monoclonal antibodies can reduce influenza A/Udorn/72 virus plaque growth and infectivity in vitro. Using Immuno-staining combined with super-resolution microscopy that allows us to study structures beyond the diffraction limit, we report that M2 is localized at the base of viral filaments that emerge from the membrane of infected cells. Filament formation was inhibited by treatment of A/Udorn/72 infected cells with M2e-specific IgG2a and IgG1 monoclonal antibodies and resulted in fragmentation of pre-existing filaments. We conclude that M2e-specific IgGs can reduce filamentous influenza A virus replication in vitro and suggest that in vitro inhibition of A/Udorn/72 virus replication by M2e-specific antibodies correlates with the inhibition of filament formation on the surface of infected cells.
关键词： influenza A virus,viral replication,super-resolution microscopy,filament formation,M2e-specific monoclonal antibodies
更新于2025-11-21 11:08:12
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Non-radiation creation of complex centers in wide-gap oxide crystals
摘要： It is shown that complex aggregate centers of oxygen divacancy type (F2 centers) and interstitial aluminum type near the anion vacancy (Ali+) are formed in anion-deficient crystals of corundum (α-Al2O3-δ) and beryllium oxide (BeO1-δ) under thermo-optical treatment (TOT). These centers are similar to those created in stoichiometric α-Al2O3 and BeO crystals under neutron irradiation. It is important to note that thermal stability of the TOT-created complex centers is higher than that of similar neutron-induced centers. It is also established that the probability of their formation is related to the temperature of the TOT, the wavelength of the stimulating light, and the initial anionic deficiency manifested as F+ and F centers (anion vacancies with one and two electrons, respectively).
关键词： Formation of complex defects,Wide-gap anion-deficient oxide crystals,Thermoluminescence,Optical absorption,Thermostability of complex defects,Thermo-optical treatment
更新于2025-11-19 16:56:35
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An Insight into the Mechanisms of the Scale Inhibition. A Case Study of a Novel Task-specific Fluorescent-tagged Scale Inhibitor Location on Gypsum Crystals
摘要： Scaling in reverse osmosis facilities, boilers, heat exchangers, evaporation plants, and oilfield applications is a serious problem worldwide. In order to provide a new insight into the mechanism of the scale formation and inhibition, a novel fluorescent-tagged 1-hydroxy-7-(6-methoxy-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)heptane-1,1-diyl-di(phosphonic acid), (HEDP-F) was synthesized and applied for the fluorescent microscope visualization of gypsum crystals formation in supersaturated aqueous solutions. The visualization of HEDP-F location at gypsum crystals, has demonstrated that the bisphosphonate molecules do not act as they are expected to do according to the current scale inhibition theory. At ambient temperature the gypsum macrocrystals are found to form, and then to grow without visible sorption of bisphosphonate on the crystal edges or any other gypsum crystal growth centers. A tentative nonconventional mechanism of scale inhibition in the bulk supersaturated aqueous solutions of gypsum is proposed.
关键词： crystal formation,scale formation,visualization,gypsum,mechanisms of scale inhibition,fluorescent-tagged bisphosphonate
更新于2025-11-19 16:46:39
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Rapid gas-liquid detonation synthesis of core-shell structural graphite coated TiO2 nanoparticles
摘要： Here we demonstrate a simple, rapid for the controlled synthesis of core-shell structural graphite coated TiO2 nanoparticle (TiO2@G), which are directly prepared by detonation chemical decomposition of the gas-liquid mixture of CH4, O2, C6H6 and TiCl4 in milliseconds. Various techniques, including XPS, TEM, XRD and Raman were employed to investigate the products. It is found that the sphere, good disperse mixed crystal TiO2 nanoparticles with crystal size of 10–30 nm were coated with thick graphite layers. Based on Zeldovich Neuman-Doring (ZND) model, the detonation synthesis mechanism of core-shell structure TiO2@G is discussed. This rapid synthesis method can be extended to the preparation of other core-shell materials.
关键词： Gas-liquid detonation,Graphite coated TiO2,Core-shell structure,Composite materials,Formation mechanism
更新于2025-11-14 17:04:02
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A CubeSat Train for Radar Sounding and Imaging of Antarctic Ice Sheet
摘要： In spite of more than 50 years of airborne radar soundings of Antarctic ice by the international community, there are still large gaps in ice thickness data. We propose a CubeSat satellite mission for complete sounding and imaging of Antarctica with 50 CubeSats integrated with a VHF radar system to sound the ice and image the ice-bed. One of the major challenges in orbital sounding of ice is off-vertical surface clutter that masks weak ice-bed echoes. We must obtain fine resolution both in the along track and cross track directions to reduce surface clutter. We can obtain fine resolution in the along track direction by synthesizing a large aperture by taking advantage of the forward motion of a satellite. However, we need a large antenna-array to obtain fine resolution in the cross track direction. We propose a train of 50 CubeSats with optimized offset position to obtain a 500-m long aperture and also coherently combine data from multiple passes of the train to obtain a very large aperture of 1-2 km in the cross track direction. Our initial analysis shows that we can obtain measurements with horizontal resolution of about 200 m and vertical resolution of about 20 m. The CubeSat will carry a transmitter and receiver with peak transmit power of about 50 W. We will synchronize all transmitters and receivers with a Ka-band system that serves as a communication link between the earth and Cubesats to downlink data and as command and control for the CubeSats.
关键词： cryosphere,imaging,CubeSat,Satellite formation,Antarctica,sounding
更新于2025-09-23 15:23:52
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A CATALOG OF LOW-MASS STAR-FORMING CORES OBSERVED WITH SHARC-II AT 350 <i>μ</i> m
摘要： We present a catalog of low-mass dense cores observed with the SHARC-II instrument at 350 μm. Our observations have an effective angular resolution of 10″, approximately 2.5 times higher than observations at the same wavelength obtained with the Herschel Space Observatory, albeit with lower sensitivity, especially to extended emission. The catalog includes 81 maps covering a total of 164 detected sources. For each detected source, we tabulate basic source properties including position, peak intensity, flux density in fixed apertures, and radius. We examine the uncertainties in the pointing model applied to all SHARC-II data and conservatively find that the model corrections are good to within ～3″, approximately 1/3 of the SHARC-II beam. We examine the differences between two array scan modes and find that the instrument calibration, beam size, and beam shape are similar between the two modes. We also show that the same flux densities are measured when sources are observed in the two different modes, indicating that there are no systematic effects introduced into our catalog by utilizing two different scan patterns during the course of taking observations. We find a detection rate of 95% for protostellar cores but only 45% for starless cores, and demonstrate the existence of a SHARC-II detection bias against all but the most massive and compact starless cores. Finally, we discuss the improvements in protostellar classification enabled by these 350 μm observations.
关键词： stars: formation,ISM: clouds,submillimeter: ISM,stars: low-mass
更新于2025-09-23 15:23:52
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Fabrication and photocatalytic performance evaluation of hydrodynamic erosion–resistant nano-TiO2–silicone resin composite films
摘要： Herein, we present the preparation of nano-TiO2–silicone resin composite films by double liquid phase spray deposition. The films exhibit better adhesion stability and photocatalytic activity under a hydrodynamic erosion condition than conventional nano-TiO2 composite films. The TiO2 layer morphology and effective TiO2 coverage ratio (CR) were affected by the initial curing time (ICT) of the silicone resin, e.g., the increase in an ICT from 10 to 40 min resulted in a CR change from 79.1 to 98.7%. The surface morphology evolution of composite films was studied under a hydrodynamic erosion period of 4 weeks. Obtained results allowed the 4-week evolution to be divided into four stages (pitting, crack pregnant, banded stripping, and surface stripping periods), additionally revealed that the CR of all samples was remained above 65%. The photocatalytic activity of composite films before and after 4-week hydrodynamic erosion was evaluated by rhodamine B degradation experiments. The 4-week erosion only led to the decrease of the photodegradation efficiencies by less than 40% in all cases. Thus, the fabricated TiO2–silicone composite films demonstrated excellent durability and photocatalytic activity under the conditions of long-term hydrodynamic erosion, allowing one to conclude that this work paves the way to the fabrication of next-generation photocatalytic materials for industrial applications.
关键词： Photocatalysis,Film formation mechanism,Silicone resin,Photodegradation,Hydrodynamic erosion resistance,Nano-TiO2
更新于2025-09-23 15:23:52
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A Study on the Solvent Vapor Induced Film Formation of PS/AgNPs Composites
摘要： In this study, pyrene (P) tagged polystyrene (PS) latex dispersions and silver nanoparticles (AgNPs) were mixed at various weight fractions in the range between 0 and 50 wt%. The prepared mixtures were dropped on the glass substrates by considering drop casting method and were dried at the room temperature. The resultant powder films were then exposed to solvent vapor to monitor how film formation and morphological behaviors of PS/AgNPs composites are altered. Film formation behavior of composites was assessed via fast transient fluorescence (FTRF) which measures the ?uorescence lifetimes of P from its decay traces during vapor exposure process. It was observed that pyrene lifetimes decreased as vapor exposure time, t increased. A Stern–Volmer kinetic analysis was used for low quenching ef?ciencies to interpret the decrease in pyrene lifetimes. UV-Vis (UVV) technique was employed to monitor optical transparency of the films. In the range of 0-20 wt% of AgNPs content, smooth and transparent films were obtained. However, above this range, the films were seen that they have low transparency and poor film formation since the increment in AgNPs content was lead to aggregations. The Prager–Tirrel model was employed to the FTRF data to obtain back-and-forth frequencies, ν, of the reptating PS chains during vapor induced ?lm formation process. SEM images of the samples were taken after film formation process is completed and were found to be consistent with optical and fluorescence quenching data.
关键词： Polystyrene latex,film formation,reptation frequency,fluorescence lifetime,nanocomposites,crossing-density,Silver nanoparticles,vapor-induced
更新于2025-09-23 15:23:52
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<i>Spitzer Planck Herschel</i> Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < <i>z</i> < 3 selected by high star-formation rate
摘要： There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.
关键词： galaxies: star formation,submillimeter: galaxies,infrared: galaxies,galaxies: evolution,galaxies: clusters: general,galaxies: high-redshift
更新于2025-09-23 15:23:52