bluuebunny/crossref_metadata_2025 huggingface dataset:
Collaborative Simulation of Mechanical Structure and Control Systems of Leighton Chajnantor Telescope
Authors: Yao Yi-Wei , Chen Wei-Rui , Wang Zheng
Published: March 2023

Leighton Chajnantor Telescope (LCT) will be moved from the summit of Maunakea, Hawaii to Chajnantor Plateau, Chile and be refurbished there. Strong wind disturbance at the new site will bring great challenges to the servo control of LCT. It is necessary and important to develop a simulation platform that behaves as close as possible to the real telescope for testing the performance of the designed servo controller. In this paper, a collaborative simulation platform of LCT based on Adams and Matlab/Simulink is constructed. On this platform, the mechanical structure model of LCT can be integrated with its control system model such that a collaborative simulation of the mechanical structure and the control system of LCT can be conducted. The mechanical structure model of LCT, which contains both rigid body models (i.e., the mount) and flexible body models (i.e., the primary reflector), is developed by using Adams. The servo system model and the wind disturbance model are constructed by using Matlab/Simulink. By conducting collaborative simulation, the performances of the servo controller based on the rigid body model and the rigid-flexible coupling model of LCT are compared. The comparison shows that the controller designed based on the rigid body model does not perform well when it is employed to control the rigid-flexible coupling model of LCT. However, by readjusting parameters of the servo controller, its performance can be further improved when applied to the rigid-flexible coupling model. Therefore, an LCT model of integrated mechanical structure and control systems is very helpful for analyzing its performance more accurately and designing a better servo controller.
Full-frame Data Reduction Method: A Data Mining Tool to Detect the Potential Variations in Optical Photometry
Authors: Dai Zhi-Bin , Zhou Hao , Cao Jin
Published: March 2023

A Synchronous Photometry Data Extraction (SPDE) program, performing indiscriminate monitoring of all stars appearing in the same field of view of an astronomical image, is developed by integrating several Astropy affiliated packages to make full use of time series observed by traditional small/medium aperture ground-based telescopes. The complete full-frame stellar photometry data reductions implemented for the two time series of cataclysmic variables: RX J2102.0+3359 and Paloma J0524+4244 produce 363 and 641 optimal light curves, respectively. A cross-identification with SIMBAD finds 23 known stars, of which 16 are red giant-/horizontal-branch stars, 2 W UMa-type eclipsing variables, 2 program stars, an X-ray source and 2 Asteroid Terrestrial-impact Last Alert System variables. Based on the data products from the SPDE program, a follow-up light curve analysis program identifies 32 potential variable light curves, of which 18 are from the time series of RX J2102.0+3359, and 14 are from that of Paloma J0524+4244. They are preliminarily separated into periodic, transient, and peculiar types. By querying for the 58 VizieR online data catalogs, their physical parameters and multi-band brightness spanning X-ray to radio are compiled for future analysis.
Period Investigation on Two W UMa Binaries HH UMa and V1175 Her
Authors: Chang Linfeng , Zhu Liying , Meng Fangbin
Published: March 2023

HH UMa and V1175 Her are two W UMa contact binary systems whose periods were reported as undergoing secular increase. In this paper, we improved their period analyses with a more extensive database of eclipse timings, finding that both periods show cyclic variation. The cyclic variation could be attributed to a Light Travel Time Effect induced by a third body. Both circular orbit and eccentric orbit cases were considered. For HH UMa, the cyclic variation with a period of around 20 yr has been detected, which may be caused by a third body with the mass larger than 0.23 M
⊙. However, no parabolic variation was detected in its O−C curve, implying the balance of the mass transfer between the two components and the angular momentum loss from the binary system. As to V1175 Her, a long-term period increase superposed on a periodic oscillation was detected. The period increase with a rate of about dP/dt = 2 × 10−7day yr−1 indicates the mass transfer from the less massive component to its companion. The cyclic variation of about 7.5 yr could be caused by a hierarchical third body with a minimal mass exceeding 0.46M
⊙ orbiting around the central binary. This mass is larger than that of the less massive component of the binary, which means that the secondary component was not replaced by the third body during early stellar interactions, implying that it keeps original dynamical information. By removing angular momentum from the central binary system, the tertiary component has played a significant role in the formation of contact binaries.
Deciphering the relationship between vegetation and Indian summer monsoon rainfall
Authors: Samuel Jerry B , Chakraborty Arindam , Paleri Anagha
Published: March 2023

Land surface utilization in the Indian subcontinent has undergone dramatic transformations over the years, altering the region’s surface energy flux partitioning. The resulting changes in moisture availability and atmospheric stability can be critical in determining the season’s monsoon rainfall. This study uses fully coupled global climate model simulations with idealized land cover to elucidate the consequences of land surface alterations. We find that an increase in forest cover, in general, increases precipitation in India. However, precipitation is not a linear function of forest-covered-area due to the spatially heterogeneous nature of the impact. A fully forest-covered India receives less precipitation than when the forest covers only the eastern side of India, occupying just about half the area. This signifies the importance of the east-west gradient in vegetation cover observed over India. Using an energy balance model, we diagnose that the diverse nature of this precipitation response results from three different pathways: evaporation from the surface, the net energy input into the atmosphere, and moist stability. Evaporation exhibits a linear relationship with forest-covered-area and reveals minimal spatial heterogeneity. On the contrary, the influence through the other two pathways is found to be region specific. Rainfall modulation via changes in net energy input is dominant in the head Bay of Bengal region, which is susceptible to convective systems. Whereas impact through stability changes is particularly significant south of 20∘ N. In addition, we find that moisture advection modulates the significance of these pathways over northwest India. Thus, the impact of land cover changes act via three effective mechanisms and are region dependent. The findings in this study have broader ramifications since the dominant region-specific mechanisms identified are expected to be valid for other forcings and are not just limited to the scenarios considered here.
A 3D characterization of equiaxed grains induced by mediated nucleation in additively manufactured Inconel 718
Authors: Cazic I , Engstler M , Zollinger J , Ghanbaja J , Kandaoui M El , Appolaire B
Published: March 2023

In additive manufacturing of Ni-based alloy IN718, what causes Icosahedral Short-Range Order (ISRO) or iQC mediated nucleation of equiaxed grains is still not understood. In order to have a better comprehension of the microstructure formation, a more comprehensive characterization both on grain structure and chemical heterogeneities must be achieved. In this work, a scanning electron microscope equipped with a focused ion beam (FIB) allowed to perform a 3D EDS chemical analysis and EBSD orientation mapping of the volume in an equiaxed grain zone. After the 3D reconstruction of the equiaxed grains has been performed, grain-to-grain orientation analysis allowed to analyze multiple twin boundaries orientation relationships in a volume containing hundreds of grains. Chemical mapping using EDS allowed to identify TiC inclusions from which a five-fold symmetry axis seem to emerge, indicating a potential nucleation site. Such areas were analyzed in transmission electron microscopy (TEM) to investigate the different present phases. The nucleation sequence and potential origin of mediated nucleation are further discussed, opening new prospects for grain refinement in additively manufactured nickel-based alloys.
β grain refinement during solidification of Ti-6Al-4V in Wire-Arc Additive Manufacturing (WAAM)
Authors: Kennedy J. R. , Davis A.E , Caballero A.E. , Pickering E.J. , Prangnell P.B.
Published: March 2023

Constructing titanium aerospace parts by near-net-shape processing has the potential to greatly reduce cost and lead time, one method for this is Wire-Arc Additive Manufacturing (WAAM). Conventional WAAM processing with the most common Ti alloy, Ti-6Al-4V, results in solidification by epitaxial growth from previously deposited layers and a structure dominated by columnar β grains which are heavily <001> fibre textured and cm’s in scale. In order to prevent these large grains from forming, while maintaining deposition parameters, the solidification conditions were modified by the additions of particles to the melt; either using inoculant, TiN particles, or the solutal growth restrictor, Y, also added as elemental powder that dissolved in the melt. The powder particles were added by adhering them to the deposited tracks to avoid the costs of manufacturing new wires. With TiN inoculants the morphology of β grains was completely modified to equiaxed grains averaging 300 μm in diameter. Y additions narrowed the columnar grains from 1-2mm to 100-300 μm. Y also induced a change to equiaxed grains, late in solidification, in the region which was remelted by subsequent deposition. However, Yttria particles were found to have formed interdendritically with an interconnected skeletal morphology. High-resolution EBSD analysis showed both TiN and yttria particles exhibit specific orientation relationships with the solidified β grains, which were confirmed experimentally.
Large-scale phase-field simulations for dendrite growth: A review on current status and future perspective
Authors: Takaki T
Published: March 2023

The current status of large-scale phase-field (PF) simulations for dendrite growth is reviewed by focusing on the study conducted by our group. The discussion includes the competitive growth of multiple columnar dendrites, dendrite growth with liquid flow and solid motion, permeability prediction, and cross-scale simulations using the PF method. All PF simulations introduced here were executed using a graphics processing unit (GPU) or a GPU supercomputer to significantly accelerate the PF simulations. Finally, the future perspectives of large-scale dendrite-growth PF simulations are discussed.
Effect of laser scanning velocity on the microstructural changes and mechanical properties of the H13 steel part treated by laser surface remelting
Authors: Xie Jichang , Di Ruifeng , Li Jishuai , Liu Yanan , Raoelison Rija Nirina , Rachik Mohamed
Published: March 2023

This paper investigates the effect of laser scanning velocity on the structural changes and mechanical properties of a H13 steel part treated by laser surface remelting. A high energy density laser with a large laser beam was used to improve the processing efficiency. The room temperature phases are dominated by martensite, retained austenite, and carbides. The laser treatment effects under various exposition conditions are compared in terms of heat affected depth, surface topography, and mechanical properties. The strengthening mechanisms include grain refinement, dislocation and precipitation strengthening, which act simultaneously during the laser remelting process to confer a high hardness at the surface of the H13 steel workpiece. Due to its higher yield strength and lower elongation, failure in the remelting zone occurred at the grain boundaries of the dendrites and in between the heat affected zone (HAZ) and the parent metal (Base Metal). These results can support the mass production of surface hardened H13 steel moulds using a laser treatment (high laser density and large laser heat source) with apprehensible changes of properties.
Grain structure predictions for metallic additive manufacturing processes
Authors: Dreelan D , Ivankovic A , Browne D J
Published: March 2023

Additive manufacturing has transformed the way we think about component fabrication. Generating a geometry in a layer-by-layer fashion presents many advantages over traditional subtractive methods, but also presents many challenges pertaining to the highly localised and energetic nature of the heat source. Since the material passes through multiple heating and cooling cycles throughout the build, some of which completely melt and erase the microstructure, a dynamic simulation is necessary to determine the grain structure that emerges. Grains are generally, but not exclusively, highly textured with columnar grains commonly spanning multiple layers. Fast, efficient and parallelised envelope cellular automata based models are used to simulate the nucleation and growth of the individual crystals that comprise the grain structure, with trade-offs being made between intra-grain detail and computational efficiency so that meso-scale simulations are possible. Simplified, but physically sound thermal models are used to predict the thermal conditions at the melt pool periphery, which are weakly coupled to the grain growth model. Dendrite tip kinetics models are used to determine alloy specific growth laws as a function of local undercooling. The effect of various processing parameters on as-solidified grain size, morphology and texture are investigated for aluminium alloys 3D printed by laser powder bed fusion.
On modelling conjugated heat transfer in the thin slab CC mold and solid shell formation under the applied EMBr
Authors: Vakhrushev A , Karimi-Sibaki E , Wu M , Ludwig A , Nitzl G , Tang Y , Hackl G , Watzinger J , Bohacek J , Kharicha A
Published: March 2023

Continuous casting (CC) became one of the dominant steel production technologies throughout last decades. Better quality, energy savings and high production rates are the main aims of the research especially in the field of the thin slab casting (TSC). The electromagnetic brake (EMBr) is applied to control the highly turbulent flow after the fresh melt is fed through the ports of a submerged entry nozzle (SEN). The numerical modelling is a perfect tool to investigate the multiphase phenomena of the turbulent flow in the CC mold, heat transfer and solidification coupled with the effects of the magnetohydrodynamics (MHD). Traditionally the heat transfer in the CC mold during the numerical simulations is predefined by the heat flux profile which could be taken from the plant measurements, published data, or is described by the semi-empirical formulas. In all these cases the heat extraction in the CC mold cavity is strictly predefined and is not significantly influenced by the transient flow behavior. Moreover, the heat flux, used in a simulation, is frequently measured for the different flow pattern inside the mold. That is especially important when the EMBr effects on the solid shell formation are investigated. Thereby, the presented study considers the coupled heat transfer in the water-cooled copper mold, including the averaged thermal resistance between the slab and mold, implemented using OpenFOAM® open-source CFD software. The melt flow, the temperature field, and the induced electric current density are compared between the traditional approach (the applied heat flux) and the modelled heat transfer in the TSC mold. Different scenarios are studied without and with the applied magnetic field.
Potential eutectic accumulation in single crystal turbine blade due to geometry effect: a numerical study
Authors: Zhang H J , Liu X S , Ma D X , Ludwig A , Kharicha A , Wu M H
Published: March 2023

Inhomogeneous distribution of the eutectic phase in single crystal (SC) turbine blades is detrimental to its mechanical properties. In a recent publication, it was reported that an accumulation of eutectics was observed on the upper surface of solidification units (e.g. shroud of a turbine blade), whereas fewer eutectics were detected at the bottom. This kind of casting defect brings a huge challenge to the production of turbine blades since the accumulated eutectics cannot be dissolved completely by heat treatment. A sample with three pairs of platforms/shrouds was designed to study the geometry effect on eutectic accumulation. In the current study, the simulation was performed by coupling ProCAST with our previously developed multiphase volume-average solidification model. In the first step, the thermal field including radiation in the furnace and heat conductivity in the casing and mould was calculated via ProCAST. Then, the obtained temperature profiles were set as thermal boundary conditions of the casting to predict the eutectic accumulation and formation of freckles. Based on the simulation results, convective plumes arising from the thermosolutal buoyancy transport solute-enriched liquid upward, which causes the solute pile-up and the final eutectic accumulation at the top surface in each platform. Freckles accompanied with eutectic accumulation was also observed at the corner of the sample. The calculated inhomogeneous distribution of the eutectics agrees well with experimental observations. Knowledge about the geometrical effect on eutectic accumulation is extended.
Anisotropic Mechanical Behaviour of Nickel Based Single Crystal Superalloy CMSX-4 for Prediction of Grain Recrystallization during Homogenization Heat Treatment Following Solidification
Authors: Hazemann E , Zhang Y , Inal K , Gandin Ch A , Long M , Niane N T , Pinto Mora A , Maguin V , Leduc M , Jaquet V , Bellet M
Published: March 2023

In the present work, a methodology to identify parameters of an elastic viscoplastic behaviour law is presented. Orthotropic elasticity and Hill48 plastic anisotropy for as-cast CMSX-4 are considered. In order to obtain the corresponding parameters by inverse analysis, an experimental database is built by tensile/relaxation tests at constant temperatures between 800°C and 1200°C on specimens oriented along <001>, <110> and <111> directions at different strain rates. Tests are performed with a resistive heating machine, using infrared thermography and digital image correlation. The obtained mechanical behaviour is very dependent on specimen orientation at all tested temperatures. Recrystallization behaviour is also very relevant to the specimens’ orientation.
Observation of peritectic couple growth for a hyper-peritectic alloy under microgravity conditions
Authors: Ludwig A , Mogeritsch J P
Published: March 2023

Under specific conditions, peritectic alloys can form microstructures that behave similar to regular eutectic alloys, with two solid phases growing in a coupled manner directly from the melt. This so-called peritectic couple growth (PCG) is significantly affected by convection. Thus, Bridgman-type experiments were performed onboard the International Space Station using the transparent peritectic alloy, tris(hydroxymethyl)aminomethane–neopentyl glycol (TRIS–NPG). Under these purely diffusive conditions, the formation of PCG, its development over time, and its dependence on the applied process conditions were studied. In this paper, we provide novel insights into the appearance of PCG and the challenges associated with corresponding experiments.
In situ solidification of eutectic Al-33wt%Cu droplets
Authors: Valloton J , Mahdi N , Rabago L , Chung J , Henein H
Published: March 2023

Al-33wt%Cu eutectic droplets were rapidly solidified using Impulse Atomization, a drop tube technique. The samples were then processed in situ in an SEM using an HTN-0101 MEMS heating chip manufactured by Norcada. The temperature of the chip, as well as the heating and cooling rates, can be easily set using the chip’s control software, allowing for heating and cooling rates as fast as 1000°C/second. The droplets were heated above the eutectic melting temperature. Thanks to the oxide skin, the droplets retained their spherical shape, which allowed in situ solidification experiments. The live feed of the surface of the droplet obtained with the SEM was recorded during the experiments alongside the temperature-time profile. Various cooling rates were imposed and the liquid samples were shown to undercool prior to solidification. The resulting eutectic morphologies and spacings were then analyzed as a function of the cooling rates and undercoolings.
Microstructure evolution during directional solidification of off-eutectic Al-Cu-Mg alloys
Authors: Ezemenaka Dominic , Small Samuel , Genau Amber
Published: March 2023

Building on previous studies of invariant ternary eutectic Al-Al2Cu-Al2CuMg, this work aims to deepen our understanding of the microstructural possibilities in the Al-rich region of the Al-Cu-Mg phase diagram by considering the solidification behaviour of several off-eutectic compositions. Four Al-Cu-Mg alloys were directionally solidified at a constant growth rate (1.25 μm/s) and thermal gradient (9-14 K/mm) using a Bridgman-type furnace and analysed using a combination of scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and differential scanning calorimetry. Qualitative and quantitative analyses showed a preference for faceted Al2Cu dendrites surrounded by a ternary eutectic matrix in the two Mg-poor samples, even though one composition was not in the primary Al2Cu phase region. The two Al-poor samples consisted of large regions of three different intermetallic phases and little eutectic, making these samples very brittle.
Preliminary system for data assimilation to infer material parameters from directional solidification experiments: twin experimental study using phase-field method
Authors: Imai Y , Sakane S , Ohno M , Yasuda H , Takaki T
Published: March 2023

The integration of phase-field (PF) simulations and in situ observations is a promising approach for understanding dendrite growth. In this study, a preliminary data assimilation system is developed to integrate PF simulations and in situ real-time X-ray radiography during the directional solidification of a binary alloy. In this system, only the region around the tip of a primary arm is used for data assimilation. The validity of the developed system is confirmed through twin experiments for columnar dendrite growth with different inclined angles of preferred growth direction.
Simulation of dendritic grain structures with a Cellular Automaton – Parabolic Thick Needle model
Authors: Wu Y , Senninger O , Gandin Ch-A
Published: March 2023

A multiscale numerical model, coupling the Cellular Automaton (CA) method to the Parabolic Thick Needle (PTN) method, is developed to compute dendritic microstructures. It is applied to directional solidification of bi-crystals under a frozen temperature approximation with fixed temperature gradient and fixed cooling rate. A dendritic branch is modeled as a cylinder headed by a parabolic tip. Its kinetics is computed using the PTN method from the composition field in the liquid in the vicinity of the parabola. This dendritic branch takes part in the definition of a grain envelope by its integration in a CA growth algorithm. The so-called Cellular Automaton – Parabolic Thick Needle (CAPTN) model can simulate the growth of dendritic grains while accounting for non-steady diffusion fields. The PTN method is implemented using Finite Element (FE) method on a heterogeneous mesh. An adaptive FE mesh strategy is developed to optimize computational time. The grain boundary orientation angle of a diverging bi-crystal configuration is investigated at steady state and compared to the Phase-Field (PF) method and the classical CA method. It is shown that contrary to the CA method, the CAPTN model is in good agreement with data deduced from PF simulations, demonstrating the interest of this coupling in the modeling of dendritic growth.
Time evolution of interface shape distribution of equiaxed dendrite: A phase-field study
Authors: Ohno Munekazu , Kudo Mikihiro , Kim Geunwoo , Yamada Ryo , Shibuta Yasushi , Takaki Tomohiro
Published: March 2023

An understanding of the morphology of growing dendrites in alloys is needed for an analysis of microsegregation, as well as an estimation of the permeability for macroscopic fluid dynamics. Quantitative phase-field simulations were used to study the growth process of three-dimensional (3D) equiaxed dendrites in an Al-1.0 mass%Cu alloy during continuous cooling. The dendrites were analysed using an interface shape distribution (ISD) map, which provides the probability of the local interface having a morphology with a given curvedness (C) and shape factor (S). Morphological changes in the microstructure can be measured sensitively from the change in the average value of the curvedness 〈C〉 relative to the solid volume fraction. The ISD map continued to change over time during continuous cooling, implying that it was not time-invariant. Furthermore, when microstructural changes occurred, similarities between the ISD maps were observed, independent of the cooling rates and system sizes.
Phase-field lattice Boltzmann model of growth and buoyancy driven motion of dendritic particles: the effect of Coriolis force
Authors: Rátkai L , Gránásy L , Pusztai T
Published: March 2023

A phase-field lattice Boltzmann (PFLB) model we developed recently (Rátkai L, Pusztai T and Gránásy L 2019 npj Comput. Mater.
5 113) was adapted to investigate the effect of Coriolis force on the solidification morphology forming in a centrifuge. The moving particles are handled using an overlapping multi-grid scheme, assigning a separate moving grid to each individual particle, with attached local fields. Relying on this approach, solidification problems, in which solute diffusion, melt flow, solid motion, the effect of gravity and collision of the particles occur simultaneously can be modelled. Using relevant properties of an Al-Ti alloy, the interaction of columnar and equiaxed solidification was studied. It was found that the Coriolis force influences the path of the falling dendritic particles, which in turn governs the position, at which the transition between columnar and equiaxed morphologies takes place.
Characterisation of mesosegregations in large steel ingots
Authors: Gutman L , Kennedy J R , Roch F , Clément A Marceaux dit , Salsi L , Cauzid J , Rouat B , Combeau H , Založnik M , Zollinger J
Published: March 2023

The chemical composition mapping of low-alloyed steel ingots used for the nuclear industry is crucial in the manufacturing of forgings and their final quality mastering. Mechanical properties of forged and hot-rolled steels may be affected by chemically segregated bands. These bands arise from segregations that appear at the scale of a few grains in the as-cast structure: the so-called mesosegregations. While segregation at the scale of dendrite arms (microsegregation) and the scale of the casting (macrosegregation) is well understood and can be readily characterized, only little is known about the formation of mesosegregation. The first step towards understanding the cause behind mesosegregation formation can be brought through comprehensive chemical characterisation at the scale of several grains (mesoscopic scale), which requires using different characterisation techniques compared to micro- or macrosegregation characterisation. We developed a sampling and characterisation methodology that allows segregations to be mapped at the mesoscopic scale using micro X-ray fluorescence (μXRF). Characterisation technique, sampling methodology, and sample size must be adapted to consider the different solidification structures; both at smaller (dendrite arms, grains) and larger (macrostructure) scales. Segregations were characterised on a 113 x 98 mm2 steel plate extracted from a low-alloyed steel large ingot.
Computational fluid dynamics calculations of binary representation of Ni-base superalloy solidification in frustum geometries
Authors: Allen J D T , Green N , Warnken N
Published: March 2023

CFD calculations were carried out on a number of frustum geometries from the experimental literature on freckling of superalloys. The effects of two imposed thermal fields were investigated, flat and inclined. Experiments document that when thermal fields are inclined the cold side is more prone to formation of freckles; our results conclude that rising liquid plumes in advance of the solidification front, which can correlate to freckles, are more abundant and intense on the cold side. Also, modelled plume activity is greater in inward sloping frustum geometries as opposed to outward sloping ones, which also agrees with established literature. Complex flow patterns were observed in inclined geometries and there is a clear interplay and competition between both the thermal and solutal aspects of flow, with flow being significantly changed, sometimes reversed in direction in some capacity. Our results also offer insight into the incubation length for plume and resultant freckle formation after the transition between frustums, with some critical distance of advance of the solidification front necessary to initiate and establish other plumes that feed into the main one circulating liquid flow which is locally intense enough to potentially create a freckle.
Growth of Si particles and Al dendrites during solidification of a hypereutectic Al-Si-Cu alloy
Authors: Zimmermann G , Sturz L , Schaberger-Zimmermann E , Pickmann Ch
Published: March 2023

Hypereutectic Al-Si alloys containing up to 16-20 wt% Si and often several wt% Cu are widely applied in automobile and aerospace industry, because of their high wear resistance and high-temperature resistance. The mechanical and physical properties of these alloys are strongly influenced by the size and morphology of the primary silicon particles. Here, rod-like bulk samples of hypereutectic Al-18wt%Si-10wt%Cu alloys were solidified in a Bridgman-Stockbarger furnace with different solidification parameters. Microstructure analysis of longitudinal and radial cross-sections demonstrated nearly equiaxed growth of Silicon particles in the 3D samples. At low cooling rate a few but larger Si particles exist compared to many and smaller Si particles for solidification with higher cooling rate. Also the structure of the Al dendrites is much finer at higher cooling rates. Additionally, sheet-like samples were solidified under isothermal cooling conditions. A real-time observation method using X-ray radiography allowed for the in-situ observation. During cooling down below the liquidus temperature, facetted Si particles are the first to nucleate. Reaching the nucleation temperature of Al, growth of non-facetted Al dendrites was observed simultaneously in the whole melt, generally not starting from the surface of existing Si particles. Some Al dendrites growing in the plane of the sheet-like samples develop rather rapidly in one direction, whereas other Al dendrites grow more equiaxed, which is attributed to different grain orientations of the Al-rich dendrites in quasi-2D solidification.
Solidification of Al-Mn-based alloys under various processing parameters
Authors: Markoli B , Leskovar B , Zaky A , Naglič I
Published: March 2023

A number of Al-Mn-based alloys were investigated with a view to their commercialization. Various casting techniques were used to affect the constitution of the alloys studied from crystalline to quasi-crystalline as well as other metastable states. Variations in cooling rates and chemical composition, along with other processing parameters, have been shown to allow us to control the final constitution and properties of what we believe could be the next generation of commercial Al-based alloys.

Our research has shown that the solidification process of Al-Mn based alloys with additions of other metallic elements can lead to the formation of very complex final states, opening up possibilities for designing and controlling the properties of alloys.

The solidification process in the alloys studied proved to be very complex, but can be explained by basic knowledge of the crystallisation of metallic melts. We have discovered that by changing the processing parameters and the chemical composition of the alloys in a controlled way, it is possible to tailor the final properties of the alloys, making them attractive for commercial purposes.
Microphysiological systems to study colorectal cancer: state-of-the-art
Authors: Ramos Pedro , Carvalho Mariana R , Chen Wei , Yan Le-Ping , Zhang Chang-Hua , He Yu-long , Reis Rui L , Oliveira Joaquim M
Published: March 2023

Basic pre-clinical research based on 2D cultures have been very valuable in colorectal cancer (CRC) research but still have failed to improve patient prognostic outcomes. This is because they simply do not replicate what happens in vivo, i.e. 2D cultured cells system cannot replicate the diffusion constraints usually found in the body. Importantly, they also do not mimic the dimensionality of the human body and of a CRC tumour (3D). Moreover, 2D cultures lack the cellular heterogeneity and the tumour microenvironment (TME) such as stromal components, blood vessels, fibroblasts, and cells of the immune system. Cells behave differently whether in 2D and 3D, in particular their different genetic and protein expression panels are very different and therefore we cannot fully rely on drug tests done in 2D. A growing field of research based on microphysiological systems involving organoids/spheroids or patient-derived tumour cells has become a solid base for a better understanding of the TME and as a result is a step towards personalized medicine. Furthermore, microfluidic approaches have also started to open possibilities of research, with tumour-on-chips and body-on-chips being used in order to decipher complex inter-organ signalling and the prevalence of metastasis, as well as CRC early-diagnosis through liquid biopsies. Herein, we focus on the state-of-the-art of CRC research with emphasis on 3D microfluidic in vitro cultures—organoids, spheroids—drug resistance, circulating tumour cells and microbiome-on-a-chip technology.
Experimental and finite element simulation study of the mechanical behaviors of aluminum foam-filled single/double tubes
Authors: Yanjun Zhao , Yunfei Cao , Liuyang Li , Jingrui Zhang , Xiukang Chen
Published: March 2023

Aluminum foam-filled tubes are complicated structures created by filling one or more thin-walled metal tubes with varying shapes in cross-sections with aluminum foam. We optimized the structure of aluminum foam-filled tubes using software simulation, compression, and three-point bending experiments. Filling aluminum foam not only improves the axial compressive performance and bending strength of the thin-walled metal tube but also eliminates the disadvantage of the low strength of the aluminum foam. The aluminum foam-filled single tube exhibited significant improvements in load-bearing and energy absorption, with a one-time increase in load-bearing and five times increase in energy absorption compared with an empty tube. The aluminum foam-filled single tube with a smaller diameter-to-thickness ratio has a higher load-bearing capacity. In contrast, the length-to-diameter ratio has a lower impact on load-bearing capacity. Once the filling length reaches the effective filling length, the structure can still support higher loads and effectively reduce its overall weight. The compression and bending properties in the double-tube structure filled with foam aluminum improved significantly compared with the empty tube and single-tube structure filled with aluminum foam. The total compressive energy absorption capacity in the double-tube structure filled with aluminum foam is 2.01 times that of the empty tube and 1.81 times that in the single-tube-filled structure. When the wall thickness of the filled stainless steel tube is 1.0 mm, the total bending energy absorption and the specific absorption energy of the aluminum foam-filled double tube structure are 1.5 and 2.1 times that of the corresponding aluminum foam-filled single tube, respectively.
Disentangling the effect of the hole-transporting layer, the bottom, and the top device on the fill factor in monolithic CIGSe-perovskite tandem solar cells by using spectroscopic and imaging tools
Authors: Kafedjiska I , Farias Basulto G , Ruske F , Maticiuc N , Bertram T , Kaufmann C A , Schlatmann R , Lauermann I
Published: March 2023

We present monolithic copper–indium–gallium–diselenide (Cu(In,Ga)Se2, CIGSe)-perovskite tandem solar cells with air- or N2-transferred NiO
x
:Cu with or without self-assembled monolayer (SAM) as a hole-transporting layer (HTL). A champion efficiency of 23.2%, open-circuit voltage (V

o
c

) of 1.69 V, and a fill factor (FF) of 78.3% are achieved for the tandem with N2-transferred NiO
x
:Cu + SAM. The samples with air-transferred NiO
x
:Cu + SAM have V

o
c

and FF losses, while those without SAM are heavily shunted. We find via x-ray and UV photoelectron spectroscopy that the air exposure leads to non-negligible loss in the Ni2+ species and changes in the NiO
x
:Cu’s work function and valence band maxima, both of which can negatively impact the V

o
c

and the FF of the tandems. Furthermore, by performing dark lock-in thermography, photoluminescence (PL), and scanning electron microscopy studies, we are able to detect various morphological defects in the tandems with poor performance, such as ohmic shunts originating from defects in the bottom CIGSe cell, or from cracking/delaminating of the perovskite top cell. Finally, by correlating the detected shunts in the tandems with PL-probed bottom device, we can conclude that not all defects in the bottom device induce ohmic shunts in the tandems since the NiO
x
:Cu + SAM HTL bi-layer can decouple the growth of the top device from the rough, defect-rich and defect-tolerant bottom device and enable high-performing devices.
Skin effect suppression for millimeter-wave frequencies through manipulation of permeability
Authors: Yamada Hidenori
Published: March 2023

A new device strategy for suppressing unwanted skin effect in coplanar transmission lines at frequencies beyond 20 GHz is presented. Utilization of the anti-resonance point as a source of imaginary permeability to suppress the skin effect is proposed. This idea is backed up by Kramers-Kronig and published experiments. The principle is independent of Landau–Lifshitz-Gilbert magnetic precession damping. The present work contributes both a greater understanding of skin effect manipulation and a method for obtaining zero skin effect using known laminate materials.
Unipotent Generators for Arithmetic Groups
Authors: Venkataramana T.
Published: March 2023

We sketch a simplification of proofs of old results on the arithmeticity of the group generated by opposing integral unipotent radicals contained in higher rank arithmetic groups.
Exploring Lie theory with GAP
Authors: de Graaf Willem
Published: March 2023

We illustrate the Lie theoretic capabilities of the computational algebra system GAP4 by reporting on results on nilpotent orbits of simple Lie algebras that have been obtained using computations in that system. Concerning reachable elements in simple Lie algebras we show by computational means that the simple Lie algebras of exceptional type have the Panyushev property. We computationally prove two propositions on the dimension of the abelianization of the centralizer of a nilpotent element in simple Lie algebras of exceptional type. Finally we obtain the closure ordering of the orbits in the null cone of the spinor representation of the group

S
p
i
n

13

(

C

)

\mathrm {Spin}_{13}(\mathbb {C})

. All input and output of the relevant GAP sessions is given.
Computability Models: Algebraic, Topological and Geometric Algorithms
Authors: Gilman Jane
Published: March 2023

The discreteness problem for finitely generated subgroups of

P
S
L
(
2
,

R

)

PSL(2,\mathbb {R})

and

P
S
L
(
2
,

C

)

PSL(2,\mathbb {C})

is a long-standing open problem. In this paper we consider whether or not this problem is decidable by an algorithm. Our main result is that the answer depends upon what model of computation is chosen. Since our discussion involves the disparate topics of computability theory and group theory, we include substantial background material.
Picard modular groups generated by complex reflections
Authors: Mark Alice , Paupert Julien , Polletta David
Published: March 2023

In this short note we use the presentations found by the various authors to show that the Picard modular groupsPU⁡(2,1,Od)\operatorname {PU}(2,1,\mathcal {O}_d)withd=1,3,7d=1,3,7(respectively the quaternion hyperbolic latticePSp⁡(2,1,H)\operatorname {PSp}(2,1,\mathcal {H})with entries in the Hurwitz integer ringH\mathcal {H}) are generated by complex (resp. quaternionic) reflections, and that the Picard modular groupsPU⁡(2,1,Od)\operatorname {PU}(2,1,\mathcal {O}_d)withd=2,11d=2,11have an index 4 subgroup generated by complex reflections.
Geometric algorithms for discreteness and faithfulness
Authors: Kapovich Michael
Published: March 2023

In this paper I describe two geometric algorithms for certifying discreteness and freeness of finitely generated subgroups of

O
(
n
,
1
)

O(n,1)

,

S
L
(
n
,

R

)

SL(n,\mathbb {R})

and, more generally, algorithms for discreteness and faithfulness of certain linear representations of finitely-presented groups.
The nuclear isoforms of the Fragile X mental retardation RNA-binding protein associate with genomic DNA bridges
Authors: Ledoux N. , Gauthier-Naud W. , Lavoie O. , Watters V. , Hussein S. , Adjibade P. , Mazroui R.
Published: March 2023

This study reports unexpected localization of nuclear FMRP isoforms in DNA bridges, preventing their accumulation and associated DNA damage.
Histologic and Clinical Outcomes of Patients Developing Post–Liver Transplant Plasma Cell–Rich Rejection
Authors: Ozturk Nazli Begum , Schiano Thomas D , Fiel Maria Isabel
Published: March 2023

Objectives

Plasma cell–rich rejection (PCCR), also known as “plasma cell hepatitis” or “de novo autoimmune hepatitis,” is a cause of allograft dysfunction occurring post–liver transplantation (LT). Patients often develop allograft failure and may require repeat LT. PCRR may fall within the spectrum of different histologies associated with antibody-mediated rejection (AMR), which is associated with donor-specific antibodies (DSAs) and positive complement component C4 (C4d) immunostaining. We sought to analyze the histologic and clinical outcomes of patients having biopsy-proven PCRR as well as to examine its C4d staining and DSA profiles.

Methods

We identified patients having PCRR between 2000 and 2020 using the electronic pathology database at our institution. We included patients who underwent at least one follow-up liver biopsy after establishing the PCRR diagnosis to assess future histologic progression and outcomes. Mean fluorescence intensity for at least one single DSA of 2,000 or higher was considered positive. Histologic diagnosis of PCRR was independently made by an experienced liver pathologist.

Results

A total of 35 patients were included in the study. Hepatitis C virus was the most common etiology for LT (59.5%). Mean ± SD age at LT was 49.0 ± 12.7 years. Forty percent of patients developed PCRR within 2 years of LT. Most patients (68.5%) had negative outcomes, with progression from PCRR to cirrhosis or chronic ductopenic rejection (CDR). Patients who had hepatitis C virus were more likely to develop cirrhosis rather than CDR following the PCRR diagnosis (P = .01). Twenty-three (65.7%) patients had at least one prior episode of T-cell–mediated rejection before being diagnosed with PCRR. DSAs were positive in 16 of 19 patients assessed, and C4d immunostaining was positive in 9 of 10 patients.

Conclusions

Development of PCRR negatively affects liver allograft outcomes and patient survival after LT. The presence of DSA and C4d in PCRR patients supports it to be within the histologic spectrum of AMR.
WITCH-NG: efficient and accurate alignment of datasets with sequence length heterogeneity
Authors: Liu Baqiao , Warnow Tandy
Published: March 2023

Multiple sequence alignment is a basic part of many bioinformatics pipelines, including in phylogeny estimation, prediction of structure for both RNAs and proteins, and metagenomic sequence analysis. Yet many sequence datasets exhibit substantial sequence length heterogeneity, both because of large insertions and deletions in the evolutionary history of the sequences and the inclusion of unassembled reads or incompletely assembled sequences in the input. A few methods have been developed that can be highly accurate in aligning datasets with sequence length heterogeneity, with UPP one of the first methods to achieve good accuracy, and WITCH a recent improvement on UPP for accuracy. In this article, we show how we can speed up WITCH. Our improvement includes replacing a critical step in WITCH (currently performed using a heuristic search) by a polynomial time exact algorithm using Smith–Waterman. Our new method, WITCH-NG (i.e. ‘next generation WITCH’) achieves the same accuracy but is substantially faster. WITCH-NG is available at https://github.com/RuneBlaze/WITCH-NG.

Availability and implementation

The datasets used in this study are from prior publications and are freely available in public repositories, as indicated in the Supplementary Materials.

Supplementary information

Supplementary data are available at Bioinformatics Advances online.
CFAGO: cross-fusion of network and attributes based on attention mechanism for protein function prediction
Authors: Wu Zhourun , Guo Mingyue , Jin Xiaopeng , Chen Junjie , Liu Bin
Published: March 2023

Motivation

Protein function annotation is fundamental to understanding biological mechanisms. The abundant genome-scale protein–protein interaction (PPI) networks, together with other protein biological attributes, provide rich information for annotating protein functions. As PPI networks and biological attributes describe protein functions from different perspectives, it is highly challenging to cross-fuse them for protein function prediction. Recently, several methods combine the PPI networks and protein attributes via the graph neural networks (GNNs). However, GNNs may inherit or even magnify the bias caused by noisy edges in PPI networks. Besides, GNNs with stacking of many layers may cause the over-smoothing problem of node representations.

Results

We develop a novel protein function prediction method, CFAGO, to integrate single-species PPI networks and protein biological attributes via a multi-head attention mechanism. CFAGO is first pre-trained with an encoder–decoder architecture to capture the universal protein representation of the two sources. It is then fine-tuned to learn more effective protein representations for protein function prediction. Benchmark experiments on human and mouse datasets show CFAGO outperforms state-of-the-art single-species network-based methods by at least 7.59%, 6.90%, 11.68% in terms of m-AUPR, M-AUPR, and Fmax, respectively, demonstrating cross-fusion by multi-head attention mechanism can greatly improve the protein function prediction. We further evaluate the quality of captured protein representations in terms of Davies Bouldin Score, whose results show that cross-fused protein representations by multi-head attention mechanism are at least 2.7% better than that of original and concatenated representations. We believe CFAGO is an effective tool for protein function prediction.

Availability and implementation

The source code of CFAGO and experiments data are available at: http://bliulab.net/CFAGO/.