Split Surface Research Articles

Unique Electronic States in Non-centrosymmetric Cubic Compounds

We succeeded in growing single crystals of \(\hbox {Yb}_{4}\hbox {Sb}_{3}\), Ullmannite(NiSbS)-type compounds, \(\hbox {Pd}_{3}\hbox {Bi}_{2}\hbox {Si}_{2}\), EuPtSi, and EuPtGe with the non-centrosymmetric cubic structures by the Bridgman method. Split Fermi surface properties are clarified for \(\hbox {Yb}_{4}\hbox {Sb}_{3}\) and \(\hbox {Pd}_{3}\hbox {Bi}_{2}\hbox {Si}_{2}\). As for EuPtSi and EuPtGe with the cubic chiral structure, we observed the first-order like antiferromagnetic ordering at the Neel temperatures \(T_N=4.0\,{\rm K}\) and 3.4 K, respectively, which are small in magnitude compared with ordering temperatures of 10–100 K in the usual divalent Eu compounds, reflecting the frustration of spins in the chiral structure.

Influence of Vacuum Mixing on the Carbonation Resistance and Microstructure of Reactive Powder Concrete Containing Secondary Copper Slag as Supplementary Cementitious Material (SCM)

This study aims to examine the effect of vacuum mixing on the carbonation resistance and microstructure of reactive powder concrete (RPC), made with secondary copper slag as partial cement replacement. In order to obtain a homogenous mixture, a high speed mixer with vacuum was applied. Accelerated carbonation tests (10% CO2, 20°C and 60% RH) were performed on RPC, mixed under vacuum conditions, as a comparison to RPC mixed at atmospheric pressure. The evolution of the carbonation depth was determined by spraying phenolphthalein on a freshly split RPC surface at varying ages (1 to 16 weeks). The microstructure of RPC was investigated by a mercury intrusion porosimeter (MIP). The pozzolanic activity of QCS was determined by the Chapelle test, taking into account the carbonation effect on the reference system.The results obtained, showed that no carbonation was detected after 90 days for the RPC containing copper slag both under vacuum condition and atmospheric pressure. The presence of copper slag in the RPC tends to increase the porosity reduction and decrease the strength enhancement when applying vacuum mixing to the mixture. The result of the Chapelle test indicated that the secondary copper slag did not tend to consume much portlandite.

Non-Destructive Imaging of Water Permeation through Cementitious Materials Using MRI

In this study, water permeation through cementitious materials was observed using magnetic resonance imaging (MRI). The influence of cement type on the magnetic resonance signal was studied subsequent to determining the parameters required for imaging. Consequently, adequate imaging of water permeating through hardened cement paste (HCP) made with white Portland cement was achieved, while water permeation through ordinary Portland cement-based HCP yielded poor signal. HCPs maintained at various levels of relative humidity (RH) were observed, and the signal was detected only from those maintained at an RH of higher than 85%. The water permeation depths in HCP were observed by using MRI, and the measured depths were compared to those measured via a spraying water detector on the split surface of the specimens. As a result, good agreement was confirmed between the two methods. Additionally, MRI was applied to concrete specimens; although it was found that water was not detected when a lightweight aggregate was used, water permeation through concrete with limestone aggregate was detectable via MRI. MRI will help in understanding how water permeation causes and accelerates concrete deteriorations such as rebar corrosion and freezing and thawing.

Deforming super Riemann surfaces with gravitinos and super Schottky groups

The (super) Schottky uniformization of compact (super) Riemann surfaces is briefly reviewed. Deformations of super Riemann surface by gravitinos and Beltrami parameters are recast in terms of super Schottky group cohomology. It is checked that the super Schottky group formula for the period matrix of a non-split surface matches its expression in terms of a gravitino and Beltrami parameter on a split surface. The relationship between (super) Schottky groups and the construction of surfaces by gluing pairs of punctures is discussed in an appendix.

Određivanje površinske temperature tla područja Splita metodom daljinske detekcije

Određivanje površinske temperature tla područja Splita metodom daljinske detekcije

Quasiparticle Scattering in the Rashba Semiconductor BiTeBr: The Roles of Spin and Defect Lattice Site.

Observations of quasiparticle interference have been used in recent years to examine exotic carrier behavior at the surfaces of emergent materials, connecting carrier dispersion and scattering dynamics to real-space features with atomic resolution. We observe quasiparticle interference in the strongly Rashba split 2DEG-like surface band found at the tellurium termination of BiTeBr and examine two mechanisms governing quasiparticle scattering: We confirm the suppression of spin-flip scattering by comparing measured quasiparticle interference with a spin-dependent elastic scattering model applied to the calculated spectral function. We also use atomically resolved STM maps to identify point defect lattice sites and spectro-microscopy imaging to discern their varying scattering strengths, which we understand in terms of the calculated orbital characteristics of the surface band. Defects on the Bi sublattice cause the strongest scattering of the predominantly Bi 6p derived surface band, with other defects causing nearly no scattering near the conduction band minimum.

Irrigated and rain-fed maize response to different nitrogen fertilizer application methods

ABSTRACTWith the demand for maize increasing, production has spread into more water limited regions. Couple this with increasing resource costs and environmental concerns and the need for efficient nutrient and water management practices has increased. The objective of this trial was to evaluate the effects of different nitrogen (N) fertilizer application methods and timings on maize grain yield, N use efficiency (NUE), and water use efficiency (WUE) under irrigated and rain-fed conditions. Four site-years of data were collected. Fertilizer treatments consisted of all N applied preplant, split surface applied, and split foliarly applied. Irrigation applied prior to and during reproductive growth increased grain yield, NUE, and WUE compared to rain-fed treatments for all site-years. Split surface applied N fertilizer applications typically increased NUE, but not always grain yield compared to preplant applications. The use of split foliar N fertilizer applications was only beneficial in the site-years when leaf burn was not as severe.

Combining Coordination of Motion Actuators with Driver Steering Interaction

Objective: A new method is suggested for coordination of vehicle motion actuators; where driver feedback and capabilities become natural elements in the prioritization.Methods: The method is using a weighted least squares control allocation formulation, where driver characteristics can be added as virtual force constraints. The approach is in particular suitable for heavy commercial vehicles that in general are over actuated. The method is applied, in a specific use case, by running a simulation of a truck applying automatic braking on a split friction surface. Here the required driver steering angle, to maintain the intended direction, is limited by a constant threshold. This constant is automatically accounted for when balancing actuator usage in the method.Results: Simulation results show that the actual required driver steering angle can be expected to match the set constant well. Furthermore, the stopping distance is very much affected by this set capability of the driver to handle the lateral disturbance, as expected.Conclusion: In general the capability of the driver to handle disturbances should be estimated in real-time, considering driver mental state. By using the method it will then be possible to estimate e.g. stopping distance implied from this. The setup has the potential of even shortening the stopping distance, when the driver is estimated as active, this compared to currently available systems. The approach is feasible for real-time applications and requires only measurable vehicle quantities for parameterization. Examples of other suitable applications in scope of the method would be electronic stability control, lateral stability control at launch and optimal cornering arbitration.

Spin resolved bandstructure imaging with a high resolution momentum microscope

We present a spin resolving “momentum microscope” for the high resolution imaging of the momentum distribution of photoelectrons. Measurements of the band structure of a Au(111) single crystal surface demonstrate an energy resolution of ΔE=12meV and a momentum resolution of Δk∥=0.0049A˚−1, measured at the line-width of the spin–orbit split Shockley surface state. The relative accuracy of the k∥ measurement in the order of 10−4A˚−1 reveals a deviation from the ideal two-dimensional free electron gas model of the Shockley surface state, manifested in a threefold radial symmetry. Spin resolution in the full momentum image is obtained by an imaging spin-filter based on low-energy electron diffraction at a Au passivated Ir(100) single crystal. Using working points at 10.5eV and 11.5eV scattering energy with a completely reversed asymmetry of ±60% we demonstrate the efficient mapping of the spin texture of the Au(111) surface state.

Contamination of freshly slaughtered pig carcasses with enteropathogenic Yersinia spp.: Distribution, quantification and identification of risk factors

A cross-sectional survey was undertaken to determine the overall prevalence of enteropathogenic Yersinia spp. in the tonsils, feces and on carcasses of pigs at slaughter. Moreover, factors associated with Yersinia contamination of freshly eviscerated pig carcasses were studied. Yersinia enterocolitica serotype O:3 was isolated from the tonsils and feces of 55.3% and 25.6% of pigs, and Y. pseudotuberculosis from 1.4% and 0.6%, respectively. The pathogens were also recovered from 39.7% of carcass surfaces post-evisceration. The highest prevalence was found at the mandibular region (28.9%), followed by the sternal region (16.4%), pelvic duct (7.8%), and split surface near the sacral vertebrae (6.9%). Regarding the quantification of the pathogen, the median concentration of pathogenic Y. enterocolitica was 4.14log10CFU/g in tonsils with countable numbers (n=143) and 2.80log10CFU/g for fecal samples with countable numbers (n=26). The quantitative load on the carcass surface was generally low as the majority of the carcass samples (97.0%) had Yersinia concentrations below the detection limit of enumeration (<1.30log10CFU/100cm2). The initial presence of Y. enterocolitica in the tonsils and/or feces was significantly associated with carcass contamination at all sampled areas. Other risk factors for carcass contamination are the splitting of the head together with the carcass, and incision of the tonsils during removal of the pluck. Small adaptations in slaughter practices and the training of slaughterhouse personnel to respect basic hygienic instructions may diminish carcass contamination with enteropathogenic Yersinia.

Numerical and experimental investigation of the cold expansion process with split sleeve in titanium alloy TC4

A series of uniaxial fatigue tests were carried out using specimens containing non-cold expanded and cold expanded holes to assess the effect of split sleeve cold expansion on fatigue behavior of titanium alloy TC4. The fracture surfaces of specimens were observed by scanning electron microscope (SEM). 3D finite element models were also used to analyze the residual stress fields around cold expanded holes. Based on the qualitative finite element analysis (FEA), the multi-axial fatigue lives of the non-cold and cold expanded holes have been predicted by Smith–Watson–Topper (SWT) method and Wang–Brown (WB) method respectively. The effects of the friction between the split sleeve and the hole’s surface were also considered. The results reveal that crack of cold expanded specimen always initiates near entrance face and the crack propagation speed along transverse direction is faster than along axial direction. The lowest compressive stress occurs at the entrance face where crack is preferentially initiated. The mandrel entrance face is the most sensitive region to friction between the split sleeve outer surface and the hole. After cold expansion, fatigue life of TC4 open hole was increased to 1.7–2.2 times. Compared with the result of SWT theory, the result of WB theory is more conservative and reliable.

Asteroseismic measurement of surface-to-core rotation in a main-sequence star

We have discovered rotationally split core g-mode triplets and surface p-mode triplets and quintuplets in a terminal age main-sequence A star, KIC 11145123, that shows both δ Sct p-mode pulsations and γ Dor g-mode pulsations. This gives the first robust determination of the rotation of the deep core and surface of a main-sequence star, essentially model-independently. We find its rotation to be nearly uniform with a period near 100 d, but we show with high confidence that the surface rotates slightly faster than the core. A strong angular momentum transfer mechanism must be operating to produce the nearly rigid rotation, and a mechanism other than viscosity must be operating to produce a more rapidly rotating surface than core. Our asteroseismic result, along with previous asteroseismic constraints on internal rotation in some B stars, and measurements of internal rotation in some subgiant, giant and white dwarf stars, has made angular momentum transport in stars throughout their lifetimes an observational science.

Analysis of the second order accurate uniform equilibrium flux method and its graphics processing unit acceleration

The extension of the Uniform Equilibrium Flux Method (UEFM) to second order accuracy in space is presented. This extension is made possible through the recasting of the original UEFM flux expressions from a volumetric flux to a surface flux, allowing for reconstruction through a Taylor series expansion of the resulting split surface fluxes at the cell interfaces. By doing so, we avoid the difficulties associated with integration of the gradient terms over velocity and physical space as required by the original UEFM fluxes. Analysis of the dissipative qualities of the renewed direction split UEFM flux expressions demonstrate that the numerical dissipation is a function of Mach number, with increasing amounts of dissipation present with increasing Mach numbers. Following this analysis, the higher order UEFM fluxes are applied to large scale parallel computation using Graphics Processing Units, or GPUs, through the use of CUDA. The vector split nature of the UEFM fluxes are well suited to GPU computation due to the high degree of locality. This parallelization is performed using a cell-based parallel paradigm through the creation of several key CUDA kernels for the calculation of split fluxes, gradient of split fluxes and state related computations. The algorithm is executed entirely on the GPU device, with the host remaining idle during the computation stage. The GPU accelerated UEFM algorithm is then applied to the solution of several two dimensional benchmark problems. Speedup of approximately 200 and 171 times for first order accuracy and second order accuracy respectively is demonstrated when using an Nvidia Tesla C2075 computing GPU compared to that of a single core of an Intel Xeon E5-2760 CPU.

The Rashba-split surface state of Sb2Te3(0 0 0 1) and its interaction with bulk states

The electronic structure of the Sb2Te3(0001) surface exhibits a spin–orbit split surface state in a local energy gap of the projected bulk valence band continuum. We investigate this surface state by high-resolution angle-resolved photoemission spectroscopy (ARPES), spin-resolved ARPES and relativistic one-step photoemission calculations. At low wave vectors the dispersion and spin splitting are well-captured by the predictions of the Rashba model for a two-dimensional electron system. With increasing wave vectors, however, the surface state dispersion becomes more complex and the spin splitting size exhibits an unusual non-monotonic evolution. These deviations from the Rashba model arise from the influence of bulk continuum states near the edge of the projected gap. The spin polarization of the surface state remains intact despite the coupling to bulk states.

Asteroseismic measurement of surface-to-core rotation in a main-sequence A star, KIC 11145123

We have discovered rotationally split core g-mode triplets and surface p-mode triplets and quintuplets in a terminal age main sequence A star, KIC 11145123, that shows both $\delta$ Sct p-mode pulsations and $\gamma$ Dor g-mode pulsations. This gives the first robust determination of the rotation of the deep core and surface of a main sequence star, essentially model-independently. We find its rotation to be nearly uniform with a period near 100 d, but we show with high confidence that the surface rotates slightly faster than the core. A strong angular momentum transfer mechanism must be operating to produce the nearly rigid rotation, and a mechanism other than viscosity must be operating to produce a more rapidly rotating surface than core. Our asteroseismic result, along with previous asteroseismic constraints on internal rotation in some B stars, and measurements of internal rotation in some subgiant, giant and white dwarf stars, has made angular momentum transport in stars throughout their lifetimes an observational science.

Electronic structure and anion ordering in(TMTSF)2ClO4and(TMTSF)2NO3: A first-principles study

A first-principles density functional theory study of the Bechgaard salts ${(\mathrm{TMTSF})}_{2}$${\text{ClO}}_{4}$ and ${(\mathrm{TMTSF})}_{2}$${\text{NO}}_{3}$, with special emphasis on the anion ordering transition, is reported. It is found that the main effect of the anion ordering on the band structure occurs through the deformations induced in the TMTSF layers and not through the Coulomb potential of the anions, as it has been almost invariably assumed. It is shown that the anion ordering in ${(\mathrm{TMTSF})}_{2}$${\text{ClO}}_{4}$ leads to a modulation of the dimerization in successive chains and to a noteworthy polarization of the two partially filled bands around the Fermi level into either the TMTSF A or TMTSF B donors. The calculated anion ordering half gap ${\ensuremath{\Delta}}_{AO}$ is found to be small but definitely non-nil, $\ensuremath{\sim}$14 meV. The suppression of the SDW instability in the relaxed samples is attributed to the deterioration of the Fermi surface nesting in the anion ordered phase. The possible nodal structure of the superconducting gap is discussed in relation with the newly calculated split Fermi surface. Anion ordering in ${(\mathrm{TMTSF})}_{2}$${\text{NO}}_{3}$ leads to a smaller half gap, 8.9 meV. The anion ordering in this salt leads to a larger charge transfer between the two donors but to a smaller polarization of the two partially filled electron and hole bands. The weak influence of anion ordering into the low-temperature physics of this salt is related to the different periodicity of the anion ordering which leaves the nested parts of the Fermi surface almost unaltered.

A chemically inert Rashba split interface electronic structure of C60, FeOEP and PTCDA on BiAg2/Ag(111) substrates

The fields of organic electronics and spintronics have the potential to revolutionize the electronics industry. Finding the right materials that can retain their electrical and spin properties when combined is a technological and fundamental challenge. We carry out the study of three archetypal organic molecules in intimate contact with the BiAg2 surface alloy. We show that the BiAg2 alloy is an especially suited substrate due to its inertness as support for molecular films, exhibiting an almost complete absence of substrate–molecular interactions. This is inferred from the persistence of a completely unaltered giant spin-orbit split surface state of the BiAg2 substrate, and from the absence of significant metallic screening of charged molecular levels in the organic layer. Spin-orbit split states in BiAg2 turn out to be far more robust to organic overlayers than previously thought.

Change of Hardness of Copper Sheet by Spliting Process

Jointed products such as bus bars of automobiles have been manufactured up to date copper and aluminum by welding or screw fastening. This process causes high cost and low productivity because many process steps and skilled working are needed. As a new technology to solve these problems, splitting process (Warisaki®) technology has been developed. By combining Warisaki® process and crumping technologies, those products can be manufactured with low cost and high productivity in a line. This Warisaki® technology can be extended into the fields such as aircrafts and environmental energy devices, etc., not limited to automobiles. The purpose of this study is to obtain fundamental knowledge on local mechanical property change by Warisaki® process and by some additional deformation processes. Copper specimens (C1100 P-1/4H) with 3mm thickness were split into a pair of branches with 1.5mm thickness and the splitting blade was run with some split steps of 1, 4 and 6mm, and the tip angles were enlarged to 90 and 180 degrees by the secondary bending process. Vickers and dynamic hardnesses of split specimens were measured and the microstructures were observed. As the results, the hardness became about 1.3 times of that in the as-received material by work hardening in the split branches and near the split tip. Marked plastic flow was observed adjacent to the split surface. It was concluded that no crack initiates at the split tip even after increase of the split step and enlargement of the tip.

Elimination of Stick-Slip Motion in Sliding of Split or Rough Surface

Here, we present a mass-less quasi-static model of stick-slip phenomenon built exclusively on the difference between higher static and lower kinetic friction force. The model allows explaining the disappearance of stick-slip motion when elastic surface slid in contact with rigid counter-face bears large amount of small outgrowths. Adjusting the model parameters, it is also possible simulating systems with different transient responses. The results obtained may also be helpful in understanding the variety of sliding behavior of different materials.

Peculiarities of Surface Fracture of B&lt;sub&gt;4&lt;/sub&gt;C Ceramics under Loads

The paper presents experimental results showing the nature of the destruction in the surface layer of В4С ceramics during hardness and fracture toughness tests performed by Vickers diamond pyramid indentation with different applied loads (4.91 - 294.3 N). Ceramics made from boron carbide powder with 10 wt.% additive of submicron fraction of the same powder sintered in spark discharge plasma by Spark Plasma Sintering (SPS-method) under different sintering conditions was studied. Changes of micro hardness and hardness of the samples were measured by micro hardness tester PМТ-3М with the loadsРup to 4.9 N; by micro hardness tester Micromet withP=9.811.77 N; and by hardness tester ТP-7R-1 with the loads of 49 - 294.3 N. Indentation, exposure, and unloading were carried out according to standard method during 30-40 seconds. The microstructure and topography of the surface of ceramic samples splits after indentation were studied by scanning electron microscopy (SEM, microscope JEOL SEM-7500FA). The profiles of the split surface depth were determined by Linnik interferometer МII-4.