Flow dynamics and structure of solid pellets along the channel of a single screw extruder

Plasticating single screw extrusion involves the progressive compaction and heating of loose solid pellets that eventually melt, form a relatively homogenous stream and are subsequently pumped through a shaping tool. Traditional analyses of the solids conveying stage assume the sliding of an elastic solid plug due to differential wall friction coefficients. However, not only the corresponding predictions may fail considerably, but it is also well known that, at least in the initial screw turns, pellets are far from compact. This work follows previous efforts to model the flow of solids in the hopper and initial screw turns using the Discrete Element Method (DEM). The model considers the development of normal and tangential forces resulting from the inelastic collisions between the pellets and between them and the neighbouring metallic surfaces. As an example of the capability of the model to capture detailed features of granular flow, the effect of pellet size on flow is discussed.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BPD/39381/2007

Modelling pellet flow in single extrusion with DEM

Plasticating single-screw extrusion involves the continuous conversion of loose solid pellets into a pressurized homogeneous melt that is pumped through a shaping tool. Traditional analyses of the solids conveying stage assume the movement of an elastic solid plug at a fixed speed. However, not only the corresponding predictions fail considerably, but it is also well known that, at least in the initial screw turns, the flow of loose individual pellets takes place. This study follows previous efforts to predict the characteristics of such a flow using the discrete element method. The model considers the development of normal and tangential forces resulting from the inelastic collisions between the pellets and between them and the neighbouring metallic surfaces. The algorithm proposed here is shown to be capable of capturing detailed features of the granular flow. The predictions of velocities in the cross- and down-channel directions and of the coordination number are in good agreement with equivalent reported results. The effect of pellet size on the flow features is also discussed

Strange filamentary structures ("fireballs") around a merger galaxy in the Coma cluster of galaxies

We found an unusual complex of narrow blue filaments, bright blue knots, and H-alpha emitting filaments and clouds, which morphologically resembled a complex of ``fireballs,'' extending up to 80 kpc south from an E+A galaxy RB199 in the Coma cluster. The galaxy has a highly disturbed morphology indicative of a galaxy--galaxy merger remnant. The narrow blue filaments extend in straight shapes toward the south from the galaxy, and several bright blue knots are located at the southern ends of the filaments. The Rc band absolute magnitudes, half light radii and estimated masses of the bright knots are -12 - -13 mag, 200 - 300 pc and 10^6-7 Msolar, respectively. Long, narrow H-alpha emitting filaments are connected at the south edge of the knots. The average color of the fireballs is B - Rc = 0.5, which is bluer than RB199 (B - R = 0.99), suggesting that most of the stars in the fireballs were formed within several times 10^8 yr. The narrow blue filaments exhibit almost no H-alpha emission. Strong H-alpha and UV emission appear in the bright knots. These characteristics indicate that star formation recently ceased in the blue filaments and now continues in the bright knots. The gas stripped by some mechanism from the disk of RB199 may be traveling in the intergalactic space, forming stars left along its trajectory. The most plausible fireball formation mechanism is ram pressure stripping by high-speed collision between the galaxy and the hot intra-cluster medium. The fireballs may be a snapshot of diffuse intra-cluster population formation, or halo star population formation in a cluster galaxy.Comment: 13 pages, 14 figures, submitted to Ap

Signal processing and frequency-dependent associative memory based on nanoswitches

A signal processing concept based on nanoscale switches whose conductance can be tuned by an external stimulus between two (ON and OFF) states is proposed and analyzed theoretically. The building block of the system is formed by a metal nanoparticle linked to two electrodes by an organic ligand and a molecular switch. When we apply an alternating potential to the system of the same frequency as the periodic variation between the ON and OFF states induced on the switch, the net charge delivered by the system exhibits a sharp resonance. This resonance can be used to process an external signal by selectively extracting the weight of the different harmonics. In addition, a frequency-dependent associative memory that exploits the resonance property is also demonstrated. The general properties of the signal processing concept that are required for practical implementation are analyzed for different temperatures, times, conductance ratios, applied potentials, and noise [email protected] [email protected]

The influence of CeF₃ on radiation hardness and luminescence properties of Gd₂O₃–B₂O₃ glass scintillator

The effect of CeF3 concentration and γ-irradiation on the physical, optical and luminescence properties of Gd2O3–B2O3–CeF3 glasses were studied in this work. Before irradiation, the addition of CeF3 in glass degraded the network connectivity observed from FTIR and possibly created the non-bridging oxygen (NBO) in glass structure. This NBO caused the reduction of Ce3+/Ce4+ ratio in XANES, the red-shift in transmission spectra and the raise of refractive index with addition of CeF3 content. Such red-shift also was influenced by 4f–5d transition of Ce3+ dopant. This ion generated the strongest photoluminescence (PL) and radioluminescence (RL) in 0.3 mol% CeF3-doped glass with nanoseconds decay time. The irradiation with γ-rays damaged the glass structure, broke the chemical bonds, and created color center in the glass network. The non-bridging oxygen hole center (NBOHC), that absorbed photons in the visible light region, caused the darkening, color change and increment of refractive index. These irradiation effects on glass were mitigated by the addition of CeF3 that the electron donation of Ce3+ decreased the number of NBOHC. The Ce3+/Ce4+ ratio in most glasses after irradiation then reduced compared to them before irradiation, resulting to the decrease in PL and RL intensity. Our results confirm that CeF3 can enhance the radiation hardness of glass and the 0.3 mol% CeF3-doped glass is a promising glass scintillator.Kaewnuam E., Wantana N., Ruangtaweep Y., et al. The influence of CeF₃ on radiation hardness and luminescence properties of Gd₂O₃–B₂O₃ glass scintillator. Scientific Reports 12, 11059 (2022); https://doi.org/10.1038/s41598-022-14833-3

Derivatives of meromorphic functions of finite order

A result is proved concerning meromorphic functions of finite order in the plane such that all but finitely many zeros of the second derivative are zeros of the first derivative

Growth, strain, and spin-orbit torques in epitaxial Ni-Mn-Sb films sputtered on GaAs

We report current-induced spin torques in epitaxial NiMnSb films on a commercially available epiready GaAs substrate. The NiMnSb was grown by cosputtering from three targets using optimized parameters. The films were processed into microscale bars to perform current-induced spin-torque measurements. Magnetic dynamics were excited by microwave currents, and electric voltages along the bars were measured to analyze the symmetry of the current-induced torques. We found that the extracted symmetry of the spin torques matches those expected from spin-orbit interaction in a tetragonally distorted half-Heusler crystal. Both fieldlike and dampinglike torques are observed in all the samples characterized, and the efficiency of the current-induced torques is comparable to that of ferromagnetic metal/heavy-metal bilayers

NIHILISME PADA MAHASISWA MUSLIM AKTIVIS KAMPUS (Studi Terhadap Mahasiswa Muslim Aktivis Kampus di Kota Malang)

Nihilisme yang diramalkan oleh Nietzsche kini telah menjangkiti masyarakat. Dan Nihilisme terdapat dalam tubuh mahasiswa muslim aktivis kampus yang memiliki kegiatan-kegiatan positif serta memahami bagaimana seharusnya ideologi Islam. Penelitian ini mencoba mencari bagaimana latar belakang mahasiswa muslim aktivis kampus yang mengalami nihilisme, bagaimana proses terjadinya nihilisme serta bagaimana bentuk-bentuk nihilisme pada mahasiswa muslim aktivis kampus. Penelitian ini menggunakan pendekatan kualitatif dengan metode deskriptif serta penentuan subyek purposive berikut metode pengumpulan datanya dengan menggunakan wawancara mendalam, observasi dan dokumentasi. Penelitian ini menggunakan konsep nihilisme yang digagas oleh Nietzsche di mana nihilisme merupakan situasi runtuhnya nilai-nilai absolut dalam diri individu. Sehingga dengan teori ini dapat dikontekstualisasikan pada tubuh mahasiswa muslim aktivis kampus di kota Malang. Nihilisme benar-benar terjadi pada mahasiswa muslim aktivis kampus namun sampai pada nihilisme pasif karena banyak sekali pemikiran mereka yang mempertanyakan kebenaran agama serta perilaku yang jauh dari syariat agama namun pada hakikatnya masih membutuhkan nilai tertinggi yang menaunginya

Development and operational experience of magnetic horn system for T2K experiment

A magnetic horn system to be operated at a pulsed current of 320 kA and to survive high-power proton beam operation at 750 kW was developed for the T2K experiment. The first set of T2K magnetic horns was operated for over 12 million pulses during the four years of operation from 2010 to 2013, under a maximum beam power of 230 kW, and $6.63\times10^{20}$ protons were exposed to the production target. No significant damage was observed throughout this period. This successful operation of the T2K magnetic horns led to the discovery of the $\nu_{\mu}\rightarrow\nu_e$ oscillation phenomenon in 2013 by the T2K experiment. In this paper, details of the design, construction, and operation experience of the T2K magnetic horns are described.Comment: 22 pages, 40 figures, also submitted to Nuclear Instrument and Methods in Physics Research,

The Hyper Suprime-Cam SSP Survey: Overview and Survey Design

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea in Hawaii. A team of scientists from Japan, Taiwan and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg$^2$ in five broad bands ($grizy$), with a $5\,\sigma$ point-source depth of $r \approx 26$. The Deep layer covers a total of 26~deg$^2$ in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg$^2$). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.Comment: 14 pages, 7 figures, 5 tables. Corrected for a typo in the coordinates of HSC-Wide spring equatorial field in Table