bluuebunny/crossref_metadata_2025 huggingface dataset:
Beam commissioning of the demonstrator setup for the superconducting continuous wave HIM/GSI-Linac
Authors: Miski-Oglu M , Aulenbacher K , Barth W , Basten M , Burandt C , Busch M , Conrad T , Dziuba F , Gettmann V , Heilmann M , Kuerzeder T , List J , Lauber S , Podlech H , Rubin A , Schnase A , Schwarz M , Yaramyshev S
Published: December 2019

During successful beam commissioning of the superconducting 15-gap Crossbar H-mode (CH) cavity at GSI Helmholtzzentrum für Schwerionenforschung heavy ions up to the design beam energy have been accelerated. The design acceleration gain of 3.5 MeV inside a length of less than 70 cm has been reached with full transmission for heavy ion beams of up to 1.5 pμA. The measured beam parameters confirm sufficient beam quality. The machine beam commissioning is a major milestone of the R&D for the superconducting heavy ion continuous wave linear accelerator HELIAC (HElmholtz LInear ACcelerator) of Helmholtz Institute Mainz (HIM) and GSI, developed in collaboration with IAP Goethe-University Frankfurt (GUF). The next step is the procurement and commissioning of the so called “Advanced Demonstrator” – the first of four cryomodules for the entire accelerator HELIAC. Results of further Demonstrator beam tests, as well as the status of the “Advanced demonstrator” project will be reported.
Towards the first beams from the ADIGE injector for the SPES Project
Authors: Galatà A , Roncolato C , Bisoffi G , Francescon P , Bellan L , Bermudez J , Bortolato D , Comunian M , Conte A , De Lazzari M , Gelain F , Marcato D , Miglioranza M , Moisio M F , Munaron E , Pavinato S , Pedretti D , Pisent A , Rossignoli M , Roetta M , Savarese G , Bellato M , Angot J , Bondoux D , Thuillier T , Andreev V.
Published: December 2019

The ADIGE (Acceleratore Di Ioni a Grande carica Esotici) injector of the SPES (Selective Production of Exotic Species) project is now in an advanced phase of installation. Its main components have been designed following particular needs of the project: first, an Electron Cyclotron Resonance (ECR)-based Charge Breeder (SPES-CB), to boost the charge states of the radioactive ions produced at SPES and allow their post-acceleration. Then, a stable 1+ source and a complete electrostatic beam line to characterize the SPES-CB. Finally, a unique Medium Resolution Mass Spectrometer (MRMS, R=1/1000), mounted on a high voltage platform downstream the SPES-CB, to clean the radioactive beam from the contaminants induced by the breeding stage. This contribution describes the status of the injector, in particular the installation of the platform housing the MRMS, the access and safety system adopted and the first beams to be extracted from the stable 1+ source.
The “Physics Beyond Colliders” Projects for the CERN M2 Beam
Authors: Banerjee D. , Bernhard J. , Brugger M. , Charitonidis N. , de Jesus V. , Gatignon L. , Gerbershagen A. , Montbarbon E. , Rae B. , Rosenthal M. , Van Dijk M.W.U. , Veit B.M. , D’Alessandro G.L. , Cholak S.
Published: December 2019

Physics Beyond Colliders is an exploratory study aimed at exploiting the full scientific potential of CERN’s accelerator complex up to 2040 and its scientific infrastructure through projects complementary to the existing and possible future colliders. Within the Conventional Beam Working Group (CBWG), several projects for the M2 beam line in the CERN North Area were proposed, such as a successor for the COMPASS experiment, a muon programme for NA64 dark sector physics, and the MuonE proposal aiming at investigating the hadronic contribution to the vacuum polarisation. We present integration and beam optics studies for 100 – 160 GeV/c muon beams as well as an outlook for improvements on hadron beams, which include RFseparated options and low-energy antiproton beams and radiation studies for high intensity beams. In addition, necessary beam instrumentation upgrades for beam particle identification and momentum measurements are discussed.
Implementation of CERN secondary beam lines T9 and T10 in BDSIM
Authors: D’Alessandro G , Boogert S T , Gibson S , Nevay L J , Shields W , Bernhard J , Gerbershagen A , Rosenthal M
Published: December 2019

CERN has a unique set of secondary beam lines, which deliver particles extracted from the PS and SPS accelerators after their interaction with a target material reaching energies up to 400 GeV. These beam lines provide a crucial contribution for test beam facilities, and host several fixed target experiments. A correct operation of the beam lines requires precise simulations of the beam optics and studies on the beam-matter interaction, radiation protection, beam equipment survival etc. BDSIM combines tracking studies with energy deposition and beam-matter interaction simulations within one software framework. This paper presents studies conducted on secondary beam lines with BDSIM for the beam lines T9 and T10. We report the tracking analysis and the energy deposition along the beam line. Tracking analysis validation is demonstrated via comparison to existing tracking codes.
Transverse profile shaping of a charged-particle beam using multipole magnets - Formation of hollow beams -
Authors: Yuri Yosuke , Fukuda Mitsuhiro , Yuyama Takahiro
Published: December 2019

The use of multipole magnets enables us to transform the transverse profile of a charged-particle beam into various ones that can never be formed through linear beam optics. To date, the formation of a large-area beam with a uniform transverse intensity distribution has been realized using octupole magnets for uniform beam irradiation. Here, we report the first demonstration of the hollow-beam formation using multipole magnets in a beam transport line. Results of beam-formation experiments and tracking simulations are shown. The hollow beam has a steep peak at the edge of the beam and thus has a high contrast between the edge peak and the intensity near the beam center.
New spiral beam screen design for the FCC-hh injection kicker magnet
Authors: Chmielinska A , Barnes M J
Published: December 2019

The injection kicker system for the Future Circular Collider (FCC-hh) must satisfy demanding requirements. To achieve low pulse ripple and fast field rise and fall times, the injection system will use ferrite loaded transmission line type magnets. The beam coupling impedance of the kicker magnets is crucial, as this can be a dominant contribution to beam instabilities. In addition, interaction of the high intensity beam with the real part of the longitudinal beam coupling impedance can result in high power deposition in the ferrite yoke. This gives a significant risk that the ferrite yoke will exceed its Curie temperature: hence, a suitable beam screen will be a critical feature. In this paper, we present a novel concept - a spiral beam screen. The fundamental advantage of the new design is a significant reduction of the maximum voltage induced on the screen conductors, thus decreased probability of electrical breakdown. In addition, the longitudinal beam coupling impedance is optimized to minimize power deposition in the magnet.
Modelling creep induced by internal stresses in freestanding submicron Cu film
Authors: Delannay Laurent , Lemoine Guerric , Coulombier Michaëel , Pardoen Thomas
Published: December 2019

In a lab-on-chip experiment, lithography and selective chemical etching are used to pattern microscopic tensile test samples within a thin metallic layer hosting large internal stresses. After partial release of the layer from the substrate on which it was deposited, the free-standing beam-like structures are stretched by the actuator to which they are connected. The lab-on-chip also comprises cantilever beams which shorten freely upon release from the substrate. Experimental observations of both the instantaneous and the delayed deformations in a 170 nm thick copper film were simulated using a theoretical model. The model properly reproduced the experiments only when accounting for both plasticity and significant kinematic hardening occurring already during the deposition of the polycristalline film. Once released from the substrate, cantilever beams contracted well beyond the elastic range because the amplitudes of back-stresses were sufficient to cause reverse plastic yielding. Large tensile stresses inside the actuated beams led to delayed uniform elongations (creep) exceeding 16%. Such values are much larger than the uniform strain of 5-6% that was observed in beams that underwent necking as soon as the film was released from the substrate, i.e. directly after etching of the sacrificial layer.
Monitoring microstructural evolution in-situ during cyclic loading with high-resolution reciprocal space mapping
Authors: Diederichs Annika Martina , Lienert Ulrich , Pantleon Wolfgang
Published: December 2019

High-resolution reciprocal space mapping using high-energy hard x-rays has been developed to investigate the microstructure of grains located in the bulk of a metallic sample in a non-destructive way in-situ during different loading conditions. The technique allows to identify and follow individual grains and subgrains during ongoing deformation such as loading in tension and compression, during repeated cyclic deformation or even individual load cycles while simultaneously monitoring macroscopic stress and strain. Insight in the structural reorganization within single grains is gained by in-situ monitoring of the characteristic intensity distribution of Bragg reflections from individual grains during cyclic deformation of commercially pure polycrystalline aluminium. By reciprocal space mapping with high angular resolution and combined analysis of the radial and azimuthal information, individual subgrains are tracked during single load cycles with different strain amplitudes. Additionally, changes in mean peak position, peak width and asymmetry of integrated radial profiles from individual grains are analyzed as well as their orientation spread. In this manner, the microstructural evolution in grains embedded in the bulk of polycrystalline specimens is traced and linked to the changing mechanical loads during cyclic deformation.
Roles of transformation interfaces in the design of advanced high strength steels
Authors: Furuhara Tadashi , Zhang Yongjie , Miyamoto Goro
Published: December 2019

Alloy partitioning and segregation or precipitation at transformation interfaces have been important in designing the mechanical properties of final products. Some representative examples in high-strength low-alloy steels are briefly discussed, with an emphasis on the transformation interface. For achieving better strengthening-ductility balance in TRIP-aided low alloy steels, it is essential to control carbon enrichment in austenite during ferrite and bainite transformations and the stability of retained austenite. Recent studies on alloy partitioning including carbon enrichment into austenite, provides a deeper insight into transformation mechanisms. We show that energy dissipation during interface migration and strain energy accumulation are important factors to control carbon enrichment into untransformed austenite during the ferrite/bainite transformation. As a counterpart of TRIP steels, interphase precipitation of alloy carbides during ferrite transformation leads to high yield strength and good elongation in low-carbon ferritic steels. A key for further strengthening is clarification of the conditions for refining the carbide dispersion. It is shown that incoherent ferrite/austenite interfaces are superior nucleation sites for carbides.
Morphological characterization of bicontinuous microstructures using two-point statistics
Authors: Sun Y , Elder K L M , Voorhees P W
Published: December 2019

Bicontinuous structures are found in a wide range of multiphase materials. We employ the prototypical bicontinuous structure that is found following spinodal decomposition to probe the morphology and evolution of bicontinuous two-phase mixtures during coarsening using two-point statistics of the mean, total curvature, and the interfacial velocity. We find that the relative spatial variations of the interfacial velocity are larger than those of the mean curvature. In addition, interfaces with high positive and high negative values of the mean curvature, total curvature and interfacial velocity are spatially localized. Finally, the spatial distribution of interfaces with near zero interfacial velocity largely resembles that of near zero mean curvature, and have correlations only over very short distances.
Multi-dimensional characterization and controlling of microstructure evolution during solidification of metallic alloys
Authors: Wang Tongmin
Published: December 2019

Metallic alloys are important structural and functional materials and have been widely applied in industry. The performance of metallic alloys strongly depends on the microstructures after solidification. Many effective methods are introduced to control the microstructure evolution during solidification, including grain refining, adding rare earth (RE) elements, applying electric current and/or magnetic field, etc. However the inherent mechanisms affecting the microstructure formation are still unclear due to the limitation of real time and multidimensional characterization technique. With the development of the third generation synchrotron radiation light source, a real time imaging technology in 2D (two dimensional) or 3D (three dimensional) view with strong penetrability, high spatial and temporal resolution, nondestructive features has been developed to break those limitations. In this paper, some application cases during solidification performed in our group are reported in different alloys and using different solidification controlling techniques. Different solidification behaviors in those cases are revealed and discussed.
Sub-grain orientation resolution during continuous loading using only far-field HEDM
Authors: Nygren K E , Pagan D C , Miller M P
Published: December 2019

A far-field data reduction algorithm for high-energy X-ray diffraction microscopy (HEDM) has been adapted to extract sub-grain orientation descriptors in a polycrystalline material during continuous in situ loading experiments. Previously, the standard data reduction algorithm would only extract grain-averaged strains, orientation, and the centroid position. A new descriptor, the grain orientation envelope (GOE), is introduced as a measure of the intragranular microstructure extracted from every grain during a continuous loading experiment. Initial results showing the evolution of a GOE from one grain in the titanium alloy, Ti-7Al, during a tension test is presented as a demonstration of the nature of the data.
Advantages of architectured harmonic structure in structural performance
Authors: Orlov Dmytro , Zhou Jinming , Hall Stephen , Ota-Kawabata Mie , Ameyama Kei
Published: December 2019

The concept of heterogenous materials with architectured harmonic structure (HS) has emerged recently with the aim of enhancing the structural performance of metals. This work presents critical microstructure characteristics contributing to the superior structural performance of harmonic-structured materials using as an example of commercially-pure nickel. Optical and scanning electron microscopy, along with nano-indentation and tensile testing, as well as digital image correlation analysis, were used for this purpose. A brief overview of the structural performance of several representative systems with HS is provided and interesting directions for future studies are discussed.
Understanding structural evolution of nanostructures during deformation from 2D (3D) experiments
Authors: Renk O , Kapp M W , Pippan R
Published: December 2019

Understanding how microstructures evolve during deformation and/or annealing treatments is of fundamental interest, as the underlying structure dictates the resulting property spectrum. This issue is even more important for nanomaterials, where interfaces and defect populations have a stronger effect on mechanical properties. In addition, for nanometals the grain architecture can also be an important parameter for improvement of mechanical properties. However, synthesis of bulk high strength materials by severe deformation with tailored and desired properties requires a thorough understanding about the processes governing their microstructural evolution at large and severe strains. Here, we summarize findings from 2D (3D) experiments uncovering these restoration processes. Interestingly, the main mechanisms seem to change with deformation temperature, causing formation of extremely elongated grain structures at intermediate deformation temperature regimes. Apart from discussing the reasons for this finding, we also present recent results focusing on the mechanisms triggering these restoration processes at low temperatures, highlighting the crucial role of plastic strain to facilitate these processes.
Analysis of in-grain orientation distributions in deformed aluminium using X-ray diffraction and finite elements
Authors: Renversade Loïc , Quey Romain
Published: December 2019

The lattice orientation distributions developing inside individual grains of a polycrystalline aluminium sample subjected to plastic deformation are analysed. In the experiment, diffraction contrast tomography (DCT) and far-field 3D X-ray diffraction microscopy (3DXRD) are used to track the development of the orientation distributions of 466 grains of an aluminium polycrystal deformed in tension to successive strains of 1.0, 1.5, 2.0, 2.5 and 4.5%. A new method is presented and employed to determine the in-grain orientation distributions from broadening of the diffraction spots. The polycrystal deformation is then simulated using the crystal-plasticity finite element method, starting from the initial, DCT-determined microstructure. The experimental and numerical in-grain lattice orientation distributions are analysed and compared in terms of trends over all grains and grain by grain.
The Coupling of Grain Growth and Twinning in FCC Metals
Authors: Thomas Spencer L , Han Jian , Srolovitz David J
Published: December 2019

Coherent twin boundaries (CTBs) routinely form during the annealing of polycrystalline metals, in the absence of an applied stress. Molecular dynamics (MD) simulations of normal grain growth in nanocrystalline metals show such annealing twins as well the formation of twin junctions. MD simulations and theoretical analyses demonstrate how these junctions form and that their formation necessarily retards grain boundary (GB) migration. Both CTB and GB migration occurs via disconnection motion. We identify the types of disconnections important for CTB migration and show the disconnection pile-ups at TJs during GB migration are responsible for CTB formation in the vicinity of TJs. Analysis further shows that at least two types twinning partials are to be expected during TJ migration and that these give rise to the multiple twinning near migrating TJs observed in the MD simulations.
Effect of strain gradient on the microstructure and mechanical properties of pearlitic steel
Authors: Ahlström Johan , Zhang Xiaodan
Published: December 2019

Pearlitic steels, with a combination of good strength and wear properties, are commonly used for railway rails. The passage of trains creates large shear strain gradients in the surface layer of rails. Knowledge of the microstructural evolution and material properties as related to the shear strain in this layer is therefore important for prediction both of crack evolution and fatigue life. A bi-axial torsion-compression machine was used to deform fully pearlitic R260 rail steel test bars to create a similar gradient structure. Uniaxial tension and compression tests were performed on these pre-deformed test bars to evaluate the mechanical properties of the material. The local microstructural parameters, such as thickness of the ferrite and cementite lamellae, the dislocation density in the ferrite lamellae, the interlamellar spacing and eth local hardness at different places across the diameter of the bars, as well as microstructural evolution across the radius, were characterized. An attempt to set up a correlation between the local microstructural parameters, hardness and the macro mechanical properties is made and discussed in the present study.
Effect of heterogeneous laser surface treatment on mechanical properties of interstitial free steel
Authors: Cai Pengzhan , Lian Xiaojin , Tang Zhixiang , Zhang Ling , Wang Tingting , Chai Linjiang , Wu Guilin
Published: December 2019

Laser surface treatment was applied to a Ti-added interstitial-free steel by linear-scanning. The distance between each linear scan was 1.5 mm and the width of the laser-modified zone for each scan was 1 mm. These process parameters result in a heterogeneous surface, containing hard laser-modified lamella separated by non-treated material. It is found that after the treatment, higher strength and good ductility can be obtained. Electron channelling contrast imaging was used to investigate the structure of the sample, which was then compared with the untreated one to reveal the origin of the improved mechanical behaviour of the laser surface-treated steel.
In-situ study of microstructural evolution and local strain distribution during tensile loading of near-micrometre grain size aluminium
Authors: Gao W Q , Zhang C L , Zhang S Q , Godfrey A
Published: December 2019

A combined digital image correlation (DIC) and electron backscatter diffraction (EBSD) study of local strain distribution and microstructural evolution during tensile loading has been carried on samples of near-micrometre grain size Al prepared by spark plasma sintering. To achieve the required spatial resolution and allow combined DIC and EBSD measurements a method of surface patterning using colloidal silica was developed. The DIC results reveal a wide variety in heterogeneity of plastic strain, both in terms of the average strain experienced by each grain and regarding the extent and nature of strain localization within individual grains. No obvious correlation is found between the heterogeneity in plastic strain and either Schmid factor, grain size or the pattern of local grain rotations. The experiments also allow investigation of the pattern of crystal rotation during tension in near-micrometer grain size samples and reveal differences in the mean grain rotation and the in-grain orientation spread.
Imaging modalities at the Swedish Materials Science beamline at PETRA III
Authors: Hegedüs Z , Müller T , Hektor J , Larsson E , Bäcker T , Haas S , Conceiçao ALC , Gutschmidt S , Lienert U
Published: December 2019

High-energy synchrotron radiation has been demonstrated to be a powerful tool for materials characterization. The development of novel methodologies is still ongoing, driven by major technological advances regarding the available source brilliance and efficient large area detectors. The Swedish Materials Science beamline at PETRA III is dedicated to materials characterization by high-energy X-rays and scheduled to enter into user operation starting August 2019. The beamline has been designed in particular for the combination of two complementary techniques: wide and small angle scattering and imaging. The beamline design is presented briefly and the different techniques are reviewed with regard to the contrast mechanisms and the ability to obtain spatially resolved information.
Visualization of low-misorientation dislocation structures from orientation data using customized All-Euler maps
Authors: Hong Chuanshi
Published: December 2019

A method for visualization of low-misorientation dislocation structures from orientation data obtained by electron backscatter diffraction (EBSD) in scanning electron microscopy is presented. The method is termed “customized All-Euler maps”. The microstructure of high purity (99.996 wt.%) aluminum lightly rolled to a thickness reduction of 12% is presented as a case study. Dislocation structures with misorientations across dislocation boundaries approaching the orientation precision of standard EBSD (∼0.5°) are revealed using the customized All-Euler maps. Cautions and limitations in using such maps are discussed.
Quantification of recrystallization kinetics in industrially processed 5xxx aluminum alloy sheet
Authors: Lei X C , Sanders R E , Yang X F , Jensen D Juul
Published: December 2019

The annealing kinetics of two aluminum alloys AA5xxx is investigated. The volume fraction of recrystallized material, Vv, is determined for a series of partly recrystallized samples both by hardness measurements and by electron back scattering diffraction (EBSD). Because of extended recovery overlapping with recrystallization, in particular in AA5182, it is not straightforward to estimate Vv from the hardness measurements. Two methods are suggested: one relying solely on the hardness data, and one in which EBSD data are used to estimate the hardness at the onset of recrystallization. Effects of the choice of method and of parameters on the resulting annealing kinetics are analysed, and the potential and limitations of the two methods are discussed.
Microstructural evolution of Ta-4%W during cold rolling
Authors: Ma Guoqiang , Godfrey Andrew , Chen Qiang , Wu Guilin , Hughes Darcy A. , Hansen Niels
Published: December 2019

Tantalum alloys are regarded as materials with great potential for challenging environments due to their exceptional mechanical properties, especially at high temperatures. To analyse deformation mechanisms and the relationship between microstructure and strength, characterization of the deformation microstructure of Ta-4%W during cold rolling from 10% to 50% has been carried out by transmission electron microscopy combined with electron backscatter diffraction investigations. The microstructural evolution of Ta-4%W was found to follow the same general framework as FCC metals (Al, Cu, Ni) and IF steel, with added complexity due to the additional constraints on dislocation motion.
Heterogeneous microstructure of low-carbon lath martensite with continuous yielding behavior in Fe-C-Mn alloys
Authors: Sugiyama M , Sawa G , Hata K , Maruyama N
Published: December 2019

High strength steels have been rapidly developed for several kinds of application fields such as light weight automobile bodies, multistory buildings, and oil well tubulars. With an increase of strength, the use of the low-carbon lath martensite phase puts this component as the main microstructure, or a part of the dual phase one. However, the martensite is a non-equilibrium phase, and the microstructure is also a heterogeneous composite-like one including of fine carbides and retained austenite. In order to understand the hierarchical structure, multi-scale microscopic techniques have been utilized. Internal twins in a lath and some large lath domains with fine carbides are revealed by scanning electron microscope (SEM) and transmission electron microscope (TEM) observations, although a conventional low-carbon martensite is known to include mainly dislocations in the lath structure. The heterogeneous microstructure is discussed based on a model of the local difference of transformation temperature of each lath block segment during cooling. On the plasticity of low-carbon lath martensite, the continuous yielding behavior is one characteristic property, and the elastic limit is obtained by the cyclic tensile test. The heterogeneous deformation behavior is detected as a periodic strain partitioning among lath blocks in a grain by digital imaging correlation analysis using in situ SEM tensile testing.
Extraction of grain boundary curvature from voxel-based representations of polycrystalline microstructures
Authors: Wang Mingyan , Wu Shuang , Krill Carl E.
Published: December 2019

Extracting the curvature of grain boundaries from 3D voxel-based representations of microstructure is challenging. Previous investigations have concluded that the accuracy of curvature estimation depends strongly on the degree of smoothing after a microstructure has been meshed. We find that best results are obtained when the degree of smoothing is determined on a boundary-by-boundary basis. Evaluating a voxelized representation of a Reuleaux tetrahedron of known boundary curvature, we establish that, for a given boundary, the optimal smoothing power minimizes the coefficient of variation (CV) of local curvature. We apply the minimum-CV criterion to the extraction of grain boundary curvatures from a measurement of polycrystalline Al-5 wt% Cu performed by 3D x-ray diffraction (3DXRD) microscopy. The results show that grain boundaries in this sample are surprisingly flat. Moreover, boundaries of larger area manifest lower curvature, while higher curvature values are observed solely for boundaries of smaller area.
Simultaneous enhancement of strength and ductility in a finegrained Fe-30Mn-0.11C steel at 77 K
Authors: Wang Y H , Kang J M , Chen X M , Yu T , Hansen N , Huang X
Published: December 2019

High Mn austenitic steels are a class of materials for cryogenic applications. Previous studies on Fe-34.5Mn-0.04C austenitic steels have shown that refining grain size can suppress the formation of deformation-induced ε and α’ martensite and improve the tensile strength and ductility at temperatures down to 123 K. Here we report a new observation of simultaneous increase of strength and ductility at liquid nitrogen temperature (77 K) in a fine grained Fe-30Mn-0.11C (wt. %) steel where the addition of 0.11%C stabilizes the austenite. This improvement is attributed to complete suppression of martensitic transformation and enhanced occurrence of deformation twinning.
Recent progress in dilatometry for quantitative analysis of precipitation kinetics
Authors: Würschum Roland , Enzinger Robert , Hengge Elisabeth , Sprengel Wolfgang
Published: December 2019

A high-stability non-contact dilatometer based on two-beam Michelson interferomtry was developed recently, enabling isothermal measurements of relative length changes in the sub-10−5 regime with minimized drift over times as long as 106 s. This advanced technique opens up novel potentials for quantitative studies of precipitation phenomena, which are associated with tiny relative length changes that have not been accessible before. Using a dilute Al-Mg- Si alloy as a case study, the amount of the metastable coherent β″- and of the semi-coherent β’-phase, as well as the amount of the stable β-phase could be determined quantitatively from isothermal length change measurements. This is accomplished by the distinct length change features that arise from the volume excess due to the precipitates, on the one hand, and the contraction of the matrix upon precipitation of solute atoms, on the other hand. Moreover, reaction-rate analyses of isothermal length change variations yield the kinetic parameters for the formation and transformation of the precipitates.
Deformation microstructures and strength of face-centered cubic high/medium entropy alloys
Authors: Yoshida Shuhei , Ikeuchi Takuto , Bai Yu , Shibata Akinobu , Hansen Niels , Huang Xiaoxu , Tsuji Nobuhiro
Published: December 2019

In this study we report the deformation microstructures and strength of medium entropy alloys (MEAs) and high entropy alloys (HEAs), which are defined as alloys composed of four or less, and five or more principal elements, respectively, with (near-) equi-atomic concentrations. The friction stress (fundamental resistance to dislocation motion in the crystal lattice) and Hall-Petch relationship of various MEAs (CoCrFeNi, CoCrNi, etc.), taken as subsystems of the equi-atomic CoCrFeMnNi HEA, were precisely measured at room temperature. Experimental values of the friction stresses were found to fit with a theoretical model proposed by Toda-Caraballo et al. very well, which indicates that the strength of the alloys is closely related to a heterogeneously distorted crystal lattice. At the same time, values of the average lattice distortion in the alloys were found to be comparable to those in some dilute alloys, contradicting the belief that “severe” lattice distortion is a reason for the higher strength than in dilute systems. Finally, a strengthening mechanism due to element-element interactions was proposed as an additional mechanism in FCC HEAs and MEAs.
Influence of rapid annealing on the evolution of fractal abnormal grains in nanocrystalline Pd–10 at% Au
Authors: Zeller R A , Fey H J , Braun C , Birringer R , Krill III C E
Published: December 2019

During abnormal grain growth, certain grains grow to much larger sizes than their neighbors. Usually, such abnormal grains expand in all directions at roughly the same speed, but in nanocrystalline Pd-10 at% Au, they appear to send forth dendritic offshoots into the surrounding matrix, resulting in highly irregular, fractal-like grain shapes. Exploiting the fast heating capabilities of a salt-bath oven, we have investigated the influence of heating rate on the evolution of fractal grain morphologies in nanocrystalline Pd-10 at% Au. In this material, the nanocrystalline matrix is stable at 170°C, but fractal grains appear within minutes at 200°C and 270°C, followed by fast growth until impingement. Surprisingly, the higher dwell temperature leads to a smaller average grain size in the fully impinged state. For the latter, no additional grain growth is observed at longer dwell times, but the fractal dimension of grain boundaries decreases with time at 270°C. These findings are consistent with abnormal grain formation being governed by a temperature-dependent nucleation process, upon which is superimposed the usual capillary driving force for grain growth; however, the mechanism by which boundaries migrate through the nanocrystalline matrix while retaining fractality remains unclear.
Thermal stability of laser shock peening processed Ni-based superalloy DZ17G
Authors: Zhou Guangni , Shen Hao , Zhu Wenxin , Tamura Nobumichi , Chen Kai , Zhang Yubin
Published: December 2019

Ni-based superalloys are widely used in challenging environments due to their exceptional mechanical properties. To enhance their resistance to damage, surface modification by laser shock pinning (LSP) is an approach to improve performance of superalloys. Considering that superalloys are typically used at high temperatures, the thermal stability of the LSP-processed material should be studied. In this article, the hardness and microstructure of a LSP-processed Ni superalloy, DZ17G, are characterized after annealing at various temperatures (up to 1000 °C) for different time periods. The results show that the majority of the strength increase achieved at the sample surface from LSP processing is lost after annealing at 800 °C for 10 h. Detailed microstructural characterization by synchrotron μXRD and metallography shows that the hardness decrease is due primarily to the annihilation of dislocations, and no recrystallization occurs in the temperature range studied.
Grey box identification and adaptive control in a water level system
Authors: Rodriguez R , Paredes V , Noa G , Trucios L
Published: December 2019

We study the application of Adaptive Control to estimate external disturbances in a Water Level System model, taking advantage of a constructed nonlinear grey box identification that allows to exploit its dynamics. The external disturbances will be specially related to valve manipulations considering limited sensing information using only water height sensors. Our methodology is twofold: (1) Using a grey box model to identify the plant under an operating point and, (2) using adaptive control to react against changes in the system or perturbations on the valve and still lead to a convergent and asymptotically stable controller.
Simple discrete time traction control for a two-wheeled mobile robot
Authors: Dahlan M , Sutapun A , Sangveraphunsiri V
Published: December 2019

Traction controls usually need dynamic parameters as an approximated reference in the model, such as inertia and friction or heavily computational estimator, such as slip ratio estimator and friction estimator. This paper is shown that the dynamic parameters in the traction controller can be negligible in some cases, internal sensor state variables and gain parameters are enough to retain some traction controllability. The controller is derived from the model following control method (MFC) on a discrete domain. Experiments are performed, in order to evaluate the efficiency of the simplified controller using a two-wheeled mobile robot, by comparing slippage between the position and velocity control scheme with and without the traction control scheme. The experimental results show that the proposed traction control scheme is able to suppress the slip and very simple to implement.
Implementation of an automatic control system on a roaster of peruvian andes grains
Authors: Garcia Luis , Lupaca Mario , Cardenas Diego , Munoz Karol
Published: December 2019

This paper presents the results of the automation of a roaster of grains grown in the Peruvian Andes. The research work consisted in developing an automatic control system for the temperature and speed of rotation of the drum of a gas roaster machine with mechanical-electrical control. The new system is based on a PLC with a proportional control algorithm for temperature and an open loop for drum rotation, which allows the grain temperature to develop, in time, the predefined curves for its 3 types: corn, broad beans and soybeans. The cultivation of these in the various microclimates along the Andes Mountains gives them unique characteristics that condition the proper roasting to the operator’s experience. To that end, a matrix was developed with parameters whose values were determined by tests conducted by expert operators in manual roasting. The experimental results showed that the roasted beans reached the desired quality characteristics such as humidity, color, aroma and flavor, as well as a decrease in the duration of the process and in fuel consumption, as well as the reduction of waste for over-roasting.
Motion control of self-driving vehicles on rough roads
Authors: Shapovalov I , Gafurov S , Klimchik A
Published: December 2019

Control of self-driving vehicles is one of the-up-to-date tasks. Vehicles are non-linear dynamic systems with a large number of parameters. When it is supposed to move on a rough road with a lot of abrupt turns, significant unpredictable and unmeasurable disturbances emerge and the control quality degrades significantly. We implemented model predictive path integral (MPPI) control to deal with significant unmeasured disturbances. To approve efficiency of the proposed controller, we conducted simulation of complex car motion on a plane under the control of PID, and MPPI controllers. Performance of controllers is comparatively equal in stable modes, when reference position and velocity do not change. MPPI controllers outperform PID ones in unstable modes due to their ability to predict a vehicle behavior. Also, MPPI is the best choice for the rejection of significant external disturbances.
Invariance, controlled invariance and conditioned invariance in structured systems and applications to disturbance decoupling
Authors: Conte G , Perdon A M , Zattoni E , Moog C H
Published: December 2019

In this paper, dynamical systems whose structure is defined by means of a simple, directed graph are considered. These objects can be used to model structured systems or, more generally, networks of systems and systems of systems, where the relations between state, input and output variables or, respectively, between agents are known only for being zero or nonzero. Using an approach that is conceptually similar to the geometric approach developed for linear time-invariant systems, suitable notions of invariance, controlled invariance and conditioned invariance are introduced and related to the action of feedbacks. The results are used to provide general solvability conditions for disturbance decoupling problems expressed in graph-theoretic terms.
Acoustic performance of locally resonant layer backing with panel-water-panel termination
Authors: Han-Feng Ye , Shi-Peng Wang , Yue Wu , Meng Tao
Published: December 2019

The acoustic performance of locally resonant layer backing with the “panel-water-panel” termination has been studied. Using the finite element software COMSOL, the acoustic model of locally resonant layer has been given firstly. Then, the effect of several parameters including incident angles, cell numbers and cavity defects, on the sound absorption performance of locally resonant layer have been numerically analyzed.
Adaptive stabilization of two complex-conjugate dominant poles and quality indices of oscillating transient process in systems with interval parametric uncertainty
Authors: Khozhaev I V
Published: December 2019

The paper is dedicated to a development of a controller synthesis method for control systems with an interval parametric uncertainty. The method combines two approaches to controller synthesis: adaptive one and interval one; also it is based on a pole domination principle. Therefore, the method allows providing desired control quality by placing two complex-conjugate dominant poles as necessary and reducing an influence of all other poles on a transient process in conditions of an interval parametric uncertainty. Application example of the synthesis method is provided; results of simulation modelling of a system, synthesized with the help of the method, are also provided.
ClinVAP: a reporting strategy from variants to therapeutic options
Authors: Sürün Bilge , Schärfe Charlotta P I , Divine Mathew R , Heinrich Julian , Toussaint Nora C , Zimmermann Lukas , Beha Janina , Kohlbacher Oliver
Published: December 2019

Motivation

Next-generation sequencing has become routine in oncology and opens up new avenues of therapies, particularly in personalized oncology setting. An increasing number of cases also implies a need for a more robust, automated and reproducible processing of long lists of variants for cancer diagnosis and therapy. While solutions for the large-scale analysis of somatic variants have been implemented, existing solutions often have issues with reproducibility, scalability and interoperability.

Results

Clinical Variant Annotation Pipeline (ClinVAP) is an automated pipeline which annotates, filters and prioritizes somatic single nucleotide variants provided in variant call format. It augments the variant information with documented or predicted clinical effect. These annotated variants are prioritized based on driver gene status and druggability. ClinVAP is available as a fully containerized, self-contained pipeline maximizing reproducibility and scalability allowing the analysis of larger scale data. The resulting JSON-based report is suited for automated downstream processing, but ClinVAP can also automatically render the information into a user-defined template to yield a human-readable report.

Availability and implementation

ClinVAP is available at https://github.com/PersonalizedOncology/ClinVAP.

Supplementary information

Supplementary data are available at Bioinformatics online.
Measuring effects of medication adherence on time-varying health outcomes using Bayesian dynamic linear models
Authors: Campos Luis F , Glickman Mark E , Hunter Kristen B
Published: December 2019

One of the most significant barriers to medication treatment is patients’ non-adherence to a prescribed medication regimen. The extent of the impact of poor adherence on resulting health measures is often unknown, and typical analyses ignore the time-varying nature of adherence. This article develops a modeling framework for longitudinally recorded health measures modeled as a function of time-varying medication adherence. Our framework, which relies on normal Bayesian dynamic linear models (DLMs), accounts for time-varying covariates such as adherence and non-dynamic covariates such as baseline health characteristics. Standard inferential procedures for DLMs are inefficient when faced with infrequent and irregularly recorded response data. We develop an approach that relies on factoring the posterior density into a product of two terms: a marginal posterior density for the non-dynamic parameters, and a multivariate normal posterior density of the dynamic parameters conditional on the non-dynamic ones. This factorization leads to a two-stage process for inference in which the non-dynamic parameters can be inferred separately from the time-varying parameters. We demonstrate the application of this model to the time-varying effect of antihypertensive medication on blood pressure levels for a cohort of patients diagnosed with hypertension. Our model results are compared to ones in which adherence is incorporated through non-dynamic summaries.
White matter hyperintensities are common in midlife and already associated with cognitive decline
Authors: d’Arbeloff Tracy , Elliott Maxwell L , Knodt Annchen R , Melzer Tracy R , Keenan Ross , Ireland David , Ramrakha Sandhya , Poulton Richie , Anderson Tim , Caspi Avshalom , Moffitt Terrie E , Hariri Ahmad R
Published: December 2019

White matter hyperintensities proliferate as the brain ages and are associated with increased risk for cognitive decline as well as Alzheimer’s disease and related dementias. As such, white matter hyperintensities have been targeted as a surrogate biomarker in intervention trials with older adults. However, it is unclear at what stage of aging white matter hyperintensities begin to relate to cognition and if they may be a viable target for early prevention. In the Dunedin Study, a population-representative cohort followed since birth, we measured white matter hyperintensities in 843 45-year-old participants using T2-weighted magnetic resonance imaging and we assessed cognitive decline from childhood to midlife. We found that white matter hyperintensities were common at age 45 and that white matter hyperintensity volume was modestly associated with both lower childhood (ß = −0.08, P = 0.013) and adult IQ (ß=−0.15, P < 0.001). Moreover, white matter hyperintensity volume was associated with greater cognitive decline from childhood to midlife (ß=−0.09, P < 0.001). Our results demonstrate that a link between white matter hyperintensities and early signs of cognitive decline is detectable decades before clinical symptoms of dementia emerge. Thus, white matter hyperintensities may be a useful surrogate biomarker for identifying individuals in midlife at risk for future accelerated cognitive decline and selecting participants for dementia prevention trials.
Experimental Evidence Supporting an Obligate Adult Diapause for Spruce Beetle (Coleoptera: Curculionidae) from British Columbia
Authors: Bleiker K P , Willsey T
Published: December 2019

Insects respond to environmental conditions with a variety of developmental responses which include changing developmental rates, or suppressing development altogether in quiescence or diapause. Such responses have important implications for survival and voltinism. The spruce beetle, Dendroctonus rufipennis Kirby (Coleoptera: Curculionidae), has long been assumed to have an obligatory adult diapause based on field observations that adults always overwinter prior to dispersing and reproducing; however, it has never been experimentally demonstrated and recent evidence suggests that adults in some populations may exhibit facultative tendencies. We examined the emergence of adults at a constant 22°C after exposure to 2°C for 0 (no cold), 25, 50, and 75 d. Our observations of a delayed and extremely protracted emergence period in the absence of a substantive cold period, which could last several months, in combination with rapid, synchronous mass emergence after a substantive cold period, are most consistent with an obligate diapause. Approximately 50% of individuals could complete diapause in 55 d at 2°C, and 75 d of cold was adequate for almost all individuals to complete diapause. Beetles that emerged slowly over time may still have been in diapause; however, additional research would be required to test this hypothesis. Conditions throughout the beetle’s range in Canada should facilitate successful completion of diapause. An obligate adult diapause for spruce beetle populations in western Canada would limit the shortest possible life cycle to 1 yr, but would also serve to maintain an adaptive 1-yr life cycle, especially under a changing climate.