Equivalent Cores Research Articles

Copper permalloys for fluxgate magnetometer sensors

Abstract. Fluxgate magnetometers are commonly used to provide high-fidelity vector magnetic field measurements. The magnetic noise of the measurement is typically dominated by that intrinsic to a ferromagnetic core used to modulate (gate) the local field as part of the fluxgate sensing mechanism. A polycrystalline molybdenum–nickel–iron alloy (6.0–81.3 Mo permalloy) has been used in fluxgates since the 1970s for its low magnetic noise. Guided by previous investigations of high-permeability copper–nickel–iron alloys, we investigate alternative materials for fluxgate sensing by examining the magnetic properties and fluxgate performance of that permalloy regime in the range 28 %–45 % Cu by weight. Optimizing the alloy constituents within this regime enables us to create fluxgate cores with both lower noise and lower power consumption than equivalent cores based on the traditional molybdenum alloy. Racetrack geometry cores using six layers of ∼30 mm long foil washers consistently yield magnetic noise around 4–5 pT/Hz at 1 Hz and 6–7 pT/Hz at 0.1 Hz, meeting the 2012 1 s INTERMAGNET standard of less than 10 pT/Hz noise at 0.1 Hz.

Core hole electron screening in InSb

The application of a potential model to the analysis of differences between the Auger parameters of InSb and the elemental materials yields a value 1.82±0.07Å for the core hole screening distance in InSb. It also yields a value of 0.22 ± 0.49 e for the charge transfer in InSb. Shifts in the Auger parameters of elements between their metallic states and in a compound semiconductor are interpreted using a novel method based on quantifying atomic core potential, as a quantum mechanical observable, in terms of its dependence on the valence charge and the number of atomic core holes. The core hole screening distance is ∼30% larger than half the interatomic distance between the nearest neighbors and, by the equivalent cores model, is expected to be the screening radius of Sn and Te impurities in InSb.

RTL Design of CISC CPU IP Core

Abstract: Recent developments on programmable logic technology had promoted the microprocessor design task from big companies targeting the mass market to the everyday designer as intellectual property (IP) cores toward the system on-a-chip (SOC) approach. This paper shows the VHDL IP 8-bit CISC microprocessor core development which is intended as an open core for teaching applications in the digital systems laboratory. The core is fully open and therefore, the user can have access to all internal signals as well as the opportunity to make changes to the structure itself which is very useful when lecturing microprocessor design. The main advantages of the present core, compared with commercially available equivalent cores, are that it is not vendor sensitive allowing its implementation in almost any FPGA family and being an open core, it can be fully monitored and modified to fit specific design constrains. Several tests were performed to the microprocessor core, including an embedded microcontroller with RAM, ROM and I/O capabilities. The present development includes a meta-assembler and linker to embed user programs in a ROM, which is automatically generated as a VHDL description

Axial response of flax fibre reinforced polymer-skinned tubes with lightweight foam cores and bioresin blend

The response of non-slender flax fibre reinforced polymer (FFRP)-skinned foam filled tubes under axial compression was investigated using 39 specimens. Different cross-ply fibre arrangements and foam densities (33–65 kg/m3) were tested; the responses were compared to hollow FFRP tubes and Glass-FRP (GFRP) skinned tubes. Although axial behaviour was not significantly affected by changing foam density, hollow tubes were weaker than foam filled sections. This suggests that low density foam is effective at preventing premature failure. FFRP-skinned tubes with a skin thickness of 6.4 mm behaved similarly to GFRP-skinned tubes with a skin thickness of 3.4 mm in terms of strength and stiffness but were considerably better at absorbing energy. Specific strength and stiffness were highest with the lightest foam. The best performing FFRP-skinned tubes had specific strengths about 75% that of GFRP-skinned tubes with similar dimensions and equivalent foam cores.

Deterioration of oil quality during sample storage: Are stored reservoir core samples a viable resource for oil viscosity determination?

The physical and chemical properties of oil residing in reservoir core samples are strongly susceptible to evaporative processes during storage. In a case study from the Peace River oil sands of Alberta, we performed dead oil viscosity measurements on oils recovered by mechanical extraction of fresh core, the equivalent cores stored for 7 months frozen plus 3 months at ambient conditions (time 1) and for 7 months frozen plus 8 months at ambient conditions (time 2). The dead oil viscosity of oil recovered from fresh core material (8100 cP at 20 °C) was more than an order of magnitude lower than that of the oil subsequently recovered from an equivalent core sample stored frozen for 7 months and then at ambient temperature for 8 months (313,500 cP at 20 °C). The evaporation of light hydrocarbons such as toluene and xylenes during storage is a continuous process responsible for progressive increase in dead oil viscosity. Meanwhile, when comparing the oils recovered from fresh core and aged core samples, the composition of the heavy (low volatility) hydrocarbons remains essentially the same. Because biodegradation is the primary control on oil viscosity and variation in hydrocarbon compositions for this oil sample suite, partial least squares models based on viscosity versus geochemical data may still be used to predict viscosity. Although the physical properties of the oil may be compromised during storage, the distributions of the high molecular weight components retain characteristics, similar to a bar code, that are inherited and representative of the original (fresh) core sample. Therefore, with the proviso that the distributions of high molecular weight components are comparable between fresh cores and aged cores, the viscosity of oil residing in stored core samples can be effectively restored by chemometric-based correlation methods.

Equivalent core concept for large-scale structural-level applications

This study examined the applicability of the equivalent core concept, which replaces a discrete core with a homogenized solid core representing its elastic properties, on a large-scale structure. To this end, numerical verifications were performed for corrugated core structures at two levels, the specimen level and structural level. Before the verifications, analytical equations were gathered from previous reports to obtain the homogenized elastic properties of corrugated cores. At the specimen-level verifications, the maximum deflections of the corrugated core panel specimens subject to three-point bending were calculated with sandwich beam theory, finite element models with discretely modeled cores and equivalent cores. For the structural-level verifications, the maximum deflection and natural frequency were computed from a discrete finite element model and an equivalent model of a railway car body structure. The results revealed that the equivalent models gave excellent agreement with the theoretical values if the same underlying boundary conditions were used; however, greater discrepancies were observed with the discrete models. In addition, for the structural-level verifications the equivalent core model reasonably approximated the discrete model with marginal accuracy. Therefore, employing the equivalent core concept can be expected to save computational costs in the initial design stage of large-scale structures.

Ballistic impact analyses of triangular corrugated plates filled with foam core

The usage of sandwich structure is extensively increasing in lightweight protective structures due to its low density and other useful properties. Sandwich panels made of metal sheets with unfilled cellular cores are found to exhibit lower deflections by comparing to an equivalent monolithic plate of same metal and similar mass per unit density. However, the process of localized impact on solid structures involving plastic deformation, high strain rates, temperature effect, material erosion, etc. does not hold effectively as that of monolithic plate. In present work, the applications of the sandwich plate with corrugated core have been extended to develop optimized lightweight armour using foam as medium of its core by explicit finite element analysis (FEA). The mechanisms of hardened steel projectile penetration of aluminum corrugated sandwich panels filled with foams have been numerically investigated by finite element analysis (FEA). A comparative study is done for the triangular corrugated sandwich plate filled with polymeric foam and metallic foam with different densities in order to achieve the optimum penetration resistance to ballistic impact. Corrugated sandwich plates filled with metallic foams are found to be superior when compared to the polymeric one. The optimized results are then compared with that of equivalent solid and unfilled cores structure to observe the effectiveness of foam-filled corrugated sandwich plate which provides an effective resistance to ballistic response. The novel structure can be the alternative to solid aluminum plate in the applications of light weight protection system.

Interpreting core-level spectra of oxidizing phosphorene: Theory and experiment

We combine ab initio density functional theory calculations with the equivalent cores approximation to determine core-level binding-energy shifts at phosphorus sites caused by oxidation of phosphorene. We find that presence of oxygen increases the core-level binding energies of P atoms and expect binding-energy shifts of up to 6 eV in highly defective geometries. We have identified likely binding geometries of oxygen that help to interpret the observed core-level photoemission spectra in samples at different stages of oxidation and allow us to determine the fractions of specific local geometries.

Amdahl's law in the era of process variation

In this paper we propose to extend Amdahl's law for modelling multicores with process variation using simple mathematical techniques. We consider three major families of multicore processors - symmetric, asymmetric, and dynamic. We consider a conservative operating mode for setting the target frequency plain, and a more optimised method opt. Subsequently, we propose three separate corollaries to the standard Amdahl's law to model the performance of different multicore configurations with different modes of operation. We observe that most of the major trends published in prior work or the ones that we observe through Monte Carlo simulations can be explained by a simple hypothetical concept called an equivalent core. The crux of our approach is to look at a set of equivalent cores with no variation that have the same performance as the target system. It is much simpler and much more intuitive to reason in terms of equivalent cores. Along with being an effective analytical tool, it can be used to speed up a lot of heuristics, and can be exposed to higher level software for advanced scheduling decisions. Lastly, we validate our models with experiments on a real system, and the maximum error is limited to 8%.

Neutronic Feasibility Assessment of Liquid Salt–Cooled Pebble Bed Reactors

This study investigates the neutronic characteristics of the Pebble Bed-Advanced High Temperature Reactor (PB-AHTR), which combines TRISO fuel technology and liquid salt [flibe (2LiF-Be2F)] cooling. Compared to equivalent helium-cooled cores, the flibe-cooled cores feature a significantly larger fraction of neutron loss to coolant absorption but also a reduced neutron loss to leakage. The flibe also significantly contributes to neutron slowing-down and allows an increase of the pebbles’ heavy metal-to-carbon volume ratio as compared to helium-cooled cores. In order to guarantee all negative reactivity coefficients, and in particular coolant void and temperature feedbacks, the carbon-to-heavy metal atom ratio must not exceed 300 to 400, depending on the fuel kernel diameter. The maximum burnup attainable from a PB-AHTR that is fueled with 10% enriched uranium and operated in continuous refueling is ˜130 GWd/t HM; this is comparable to the maximum burnup achieved in other high-temperature reactors, either liquid salt or gas cooled. Compared to helium-cooled pebble bed reactors, the PB-AHTR pebbles can be loaded with 2.5 times more fuel, resulting in a smaller number of pebbles to fabricate and a smaller spent-fuel volume to handle per energy generated. Relative to a light water reactor, the PB-AHTR offers improved natural uranium ore utilization and reduced enrichment capacity.

Assembly of [(η5-C5Me5)MoS3Cu3]-Supported One-Dimensional Chains with Single, Double, Triple, and Quadruple Strands

The construction of a new set of [(eta5-C5Me5)MoS3Cu3]-based supramolecular compounds with different one-dimensional (1D) arrays from two preformed clusters [PPh4][(eta5-C5Me5)MoS3(CuX)3] (X = Br (1a), NCS (1b)) with 1,2-bis(4-pyridyl)ethane (bpe) and 1,3-bis(4-pyridyl)propane (bpp) is presented. Reactions of 1a with bpe in different molar ratios afforded ([((eta5-C5Me5)MoS3Cu3) 2(mu-bpe)3.5Br4].MeCN) n (2), ([((eta5-C5Me5)MoS3Cu3)2(mu-bpe)3Br4].Sol)n (3a: Sol = DMSO.3MeCN; 3b: Sol = 2aniline.3MeCN), ([((eta5-C 5Me5)MoS3Cu3)2(mu-bpe)3(bpe)Br4].0.35DMF)n (4), and ([((eta5-C5Me5)MoS3Cu3)2(mu-bpe)2(mu-Br)(mu3-Br)Br2].DMF.MeCN)n (5). On the other hand, treatment of 1a or 1b with bpp produced [(eta5-C5Me5)MoS3Cu3(mu-bpp)(mu-Br)Br]n (6) and ([((eta5-C5Me5)MoS3Cu3)2(mu-bpp)3(mu-NCS)2(NCS)](NCS))n (7). Compounds 2-7 have been characterized by elemental analysis, UV-vis spectroscopy, IR spectroscopy, 1H NMR, and X-ray analysis. In 2, each [(eta5-C5Me5)MoS3Cu3] core serves as an angular two-connecting node to link other equivalent cores by single and double bpe bridges to form a 1D "Great Wall"-like chain. In 3a and 3b, the [(eta5-C5Me5)MoS3Cu3] cores are linked alternatively by single and double bpe bridges to give a 1D zigzag chain. In 4, six cluster cores (two as a two-connecting node and four as a three-connecting node) are connected by four single bpe and two double bpe bridges to form a cyclohexane-shaped repeating unit, which is further fused with other units to generate a 1D double-stranded chain. Compound 5 has a simple 1D zigzag chain consisting of the cluster cores linked by single bpe bridges. In 6, the cluster cores are linked by single bpp bridges to give a 1D helical chain, which further holds two symmetry-related chains through C-H...Br hydrogen-bonding interactions, thereby forming a 1D H-bonded triple-stranded chain. Compound 7 has a rare 1D quadruple chain, in which the [(eta5-C5Me5)MoS3Cu3] cores work as planar four- and five-connecting nodes to interconnect other equivalent cores through single bpp bridges and single and double thiocyanate bridges. In addition, the third-order nonlinear optical properties of 1a, 2, 3a, and 4-7 in aniline were also investigated by using the Z-scan technique with a 4.5 ns pulse laser at 532 nm.

Intermediate water links to Deep Western Boundary Current variability in the subtropical NW Atlantic during marine isotope stages 5 and 4

Records from Ocean Drilling Program Sites 1057 and 1059 (2584 m and 2985 m water depth, respectively) have been used to reconstruct the behavior of the Deep Western Boundary Current (DWBC) on the Blake Outer Ridge (BOR) from 130 to 60 kyr B.P. (marine isotope stage (MIS) 5 and the 5/4 transition). Site 1057 lies within Labrador Sea Water (LSW) but close to the present‐day boundary with Lower North Atlantic Deep Water (LNADW), while Site 1059 lies within LNADW. High‐resolution sortable silt mean () grain size and benthic δ13C records were obtained, and changes in the DWBC intensity and spatial variability were inferred. Comparisons are made with similar proxy records generated for the Holocene from equivalent depth cores on the BOR. During MIS 5e, evidence at Site 1057 suggests slower relative flow speeds consistent with a weakening and a possible shoaling of the LSW‐sourced shallower limb of the DWBC that occupies these depths today. In contrast, the paleocurrent record from the deeper site suggests that the fast flowing deep core of the DWBC was located close to its modern depth below 3500 m. During this interval the benthic δ13C suggests little chemical stratification of the water column and the presence of a near‐uniform LNADW‐dominated water mass. After ∼111 kyr B.P. the record at Site 1057 increases to reach values similar to Site 1059 for the rest of MIS 5. The strengthening of flow speeds at the shallow site may correspond to the initiation of Glacial North Atlantic Intermediate Water formation also suggested by a divergence in the benthic δ13C records with Site 1057 values increasing to ∼1.2‰. Coupled suborbital oscillations in DWBC flow variability and paleohydrography persisted throughout MIS 5. Comparison of these data with planktonic δ18O records from the sites and alkenone‐derived sea surface temperature (SST) estimates from the nearby Bermuda Rise suggest a hitherto unrecognized degree of linkage between oscillations in subtropical North Atlantic SST and DWBC flow.

Construction of [(η5-C5Me5)MoS3Cu3]-Based Supramolecular Assemblies from the [(η5-C5Me5)MoS3(CuNCS)3]- Cluster Anion and Multitopic Ligands with Different Symmetries

The assembly of a new family of [(eta5-C5Me5)MoS3Cu3]-supported supramolecular compounds from a preformed cluster [PPh4][(eta5-C5Me5)MoS3(CuNCS)3].DMF (1.DMF) with four multitopic ligands with different symmetries is described. Reactions of 1 with 1,2-bis(4-pyridyl)ethane (bpe) (Cs symmetry) or 1,4-pyrazine (1,4-pyz) (D2h symmetry) in aniline gave rise to two polymeric clusters {[{(eta5-C5Me5)MoS3Cu3}2(NCS)3(mu-NCS)(bpe)3].3aniline}n (2) and [(eta5-C5Me5)MoS3Cu3(1,4-pyz)(mu-NCS)2]n (3). On the other hand, solid-state reactions of 1 with 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) (D3h symmetry) or 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin (H2tpyp) (D4h symmetry if 21H and 23H of the H2tpyp are omitted) at 100 degrees C for 12 h followed by extraction with aniline yielded another two polymeric clusters {[(eta5-C5Me5)MoS3Cu3(tpt)(aniline)(NCS)2].0.75aniline. 0.5H2O}n (4) and {[(eta5-C5Me5)MoS3Cu3(NCS)(mu-NCS)(H2tpyp)0.4(Cu-tpyp)0.1].2aniline.2.5benzene}n (5). These compounds were characterized by elemental analysis, IR spectra, UV-vis spectra, 1H NMR, and X-ray analysis. Compound 2 consists of a 2D (6,3) network in which [(eta5-C5Me5)MoS3Cu3] cores serve both a T-shaped three-connecting node and an angular two-connecting node to interconnect other equivalent units through single bpe bridges, double bpe bridges, and mu-NCS bridges. Compound 3 has a 3D diamondlike framework in which each [(eta5-C5Me5)MoS3Cu3] core, acting as a tetrahedral connecting node, links four other neighboring units by 1,4-pyz bridges and mu-NCS bridges. Compound 4 contains a honeycomb 2D (6,3)core(6,3)tpt network in which each cluster core, serving a trigonal-planar three-connecting node, links three pairs of equivalent cluster cores via three tpt lignads. Compound 5 has a rare scalelike 2D (4,62)core(42,62)ligand network in which each cluster core acts as a T-shaped three-connecting node to link with other equivalent ones through mu-NCS bridges and H2tpyp (or Cu-tpyp) ligands. The results showed that the formation of the four different multidimensional topological structures was evidently affected by the symmetry of the ligands used. In addition, the third-order nonlinear optical properties of 1-5 in aniline were also investigated by using Z-scan techniques at 532 nm.

On the validity of the equivalent cores approximation for computing X-ray photoemission and photoabsorption spectral bands

We evaluate the performance of the equivalent cores (Z+1) approximation for computing core photoemission and photoabsorption spectral bands versus full self-consistent field optimizations. Franck–Condon factors are obtained using the linear coupling model with the multi-dimensional vibronic coupling constants computed from analytical calculations of the ground state frequencies and normal coordinates, and excited state energy gradients evaluated at the ground state equilibrium geometry. We use carbon monoxide, formaldehyde, chloromethanes and some mono-substituted benzenes for the purpose. Considering other inherent approximations in the calculations, we find that the equivalent core model works well for band shapes and comparatively better for excitations of strong modes and ionization of deeper core levels. The approximation also works somewhat better for photoemission than for discrete photoexcitation.

A general algorithm for obtaining simple structure of core arrays in N-way PCA with application to fluorometric data

Simplifying the structure of core arrays from N-way PCA or Tucker3 models is desirable to allow for easy interpretation of the factor estimates. In the present paper, first a general algorithm for maximizing a differentiable goal function depending on a set of orthogonal matrices is formulated and then specified to the problem of estimating orthonormal transformation matrices for rotating core arrays to simpler structure. The generality of the chosen approach allows to cope with all possible transformation criteria by just changing one command in the implementation. In particular, the classical body- and slice-wise diagonalization of core arrays as well as the recently proposed maximization of the variance of squared entries are covered. The stability of the algorithm is addressed by a simulation study using 120 three-way core arrays of dimension (4,4,4). Each core array instantiates a class of 50 equivalent cores by random orthonormal transformations. Theoretically, each core within a given class has the same optimum with respect to the chosen criterion, and the ability of the algorithm to provide that result has been investigated. The algorithm proves to work with a high degree of stability and consistency in optimizing the three discussed goal functions. In addition, theoretical convergence results of the algorithm are provided. In particular, monotonic convergence of functional values and convergence of iterates towards a stationary solution are proven. To illustrate the effect of maximizing the variance-of-squares and the functionality of the algorithm, the proposed method is applied to a three-way data array from fluorometric analysis of fractions obtained from low-pressure chromatographic separation of a preliminary sugar product, thick juice. A significant gain in simplicity is achieved, and in particular optimizing variance-of-squares provides a simple core structure for the data under investigation. The proposed algorithms for maximizing variance-of-squares, body diagonality and slice-wise diagonality have been implemented in MATLAB and are available by contact to the authors.

Geometry optimization of core electron excited molecules

We demonstrate the feasibility of calculations of geometries and potential energy surfaces of core ionized and core excited states of molecular species including full optimization of all electronic and nuclear degrees of freedom. We show by examples that geometry optimization leads to symmetry broken nuclear conformations for ionization/excitation of symmetry delocalized core orbitals. Comparisons between results with the equivalent cores approximation and with full optimization pinpoint the role of the valence-core penetration to obtain the correct optimum geometry, especially along weaker bending and torsion modes.

Core Electron Energies, Infrared Intensities, and Atomic Charges

Carbon 1s electron binding energies determined by X-ray photoelectron spectroscopy and mean dipole moment derivatives obtained from experimental infrared intensities are shown to be related through the simple potential model proposed by Siegbahn and collaborators. The sp3 carbon atoms in 13 halomethanes, 2 ethanes, 3 methylacetylenes, cyclopropane, and ethylene oxide have 1s energies, which, after correction for electrostatic potentials from neighboring atoms, are linearly related to the carbon mean dipole moment derivatives, presenting a slope of 15.50 ± 0.29 eV/e. The sp2 carbons of ethylene, three haloethylenes, and three carbonyl compounds also exhibit a linear relationship having a significantly different slope of 17.37 ± 0.87 eV/e. The sp carbon atoms in acetylenes, cyanides, CO, CS2, CO2, and OCS show a third linear relationship, with a slope of 18.90 ± 0.75 eV/e. These slopes are proportional to the inverse atomic radii of sp3, sp2, and sp carbon atoms and according to the simple potential equation can be interpreted as estimates of Coulomb repulsion integrals involving these hybridized orbitals and the 1s core electron orbitals. Two basic assumptions of the potential model are investigated. The effect of relaxation energies on the 1s electron ionization processes is estimated as the difference between ΔSCF ionization energies and Koopmans' frozen orbital estimates obtained from 6-31G(d,p) wave functions. These results are compared with values obtained previously from the equivalent cores estimating procedure. Also the conceptual validity of identifying the carbon mean dipole moment derivatives as atomic charges is discussed within the framework of the charge−charge flux-overlap model.

Studies of C 1s → π* triplet states of carbon monoxide, benzene, ethylene, and acetylene

The (C 1s−1,π*) triplet states of carbon monoxide, benzene, ethylene, and acetylene have been studied using electron energy loss spectroscopy with low-energy (near-threshold) excitation. The singlet–triplet splitting for the (C 1s−1,π*) states of the hydrocarbon species were measured for the first time. Intermediate neglect of differential overlap (spectroscopic) (INDO/S) calculations within the equivalent cores approximation were used to calculate (1s−1, π*) singlet–triplet splittings. The calculated values are in reasonable agreement with the experimental values for the hydrocarbon species but are significantly underestimated for CO. A strong correlation between singlet–triplet splittings and oscillator strengths for the 1s → π* transitions was noted and rationalized in terms of the dependence of both factors on the spatial overlap of 1s and π* wave functions.

Full geometry optimizations of core ionized species and their equivalent core ions: an ab initio study of energies, geometries, charges and vibrational frequencies

Full geometry optimizations have been performed on the C1s and O1s core ionized states of ethanal and on the corresponding equivalent core ions using ab initio 6–31G ∗ Hartree-Fock SCF calculations. The good agreement between the calculated properties of the core hole and equivalent core ions provides further justification for the use of the equivalent cores approximation for calculating properties of core ionized species. Exceptions to the excellent geometry predictions observed in ethanal occurred in two cases where stereochemically significant lone pairs were present.

The equivalent cores approximation: An ab initio study of nuclear relaxation energies and charge distributions

Ab initio 6-31G * Hartree-Fock SCF calculations have been performed on the C 1s ionized states of aniline and the corresponding equivalent core ions (the aminopyridinium ions) at the aniline optimized geometry. Together with results from the geometry-optimized amino-pyridinium ions, the effect of nuclear relaxation of the equivalent core ions on calculated binding energy shifts and the use of equivalent core ions for predicting electronic properties of core hole states are investigated.