Core Shape Research Articles

Cold Quark–Gluon Plasma EOS Applied to a Magnetically Deformed Quark Star with an Anomalous Magnetic Moment

We consider a QCD cold-plasma-motivated Equation of State (EOS) to examine the impact of an Anomalous Magnetic Moment (AMM) coupling and small shape deformations on the static oblate and prolate core shapes of quark stars. Using the Fogaça QCD-motivated EOS, which shifts from the high-temperature, low-chemical-potential quark–gluon plasma environment to the low-temperature, high-chemical-potential quark stellar core environment, we consider the impact of an AMM coupling with a metric-induced shape deformation parameter in the Tolman–Oppenheimer–Volkov (TOV) equations. The AMM coupling includes a phenomenological scaling that accounts for the weak and strong field characteristics in dense matter. The EOS is developed using a hard gluon and soft gluon decomposition of the gluon field tensor and using a mean-field effective mass for the gluons. The AMM is considered using the Dirac spin tensor coupled to the EM field tensor with quark-flavor-based magnetic moments. The shape parameter is introduced in a metric ansatz that represents oblate and prolate static stellar cores for modified TOV equations. These equations are numerically solved for the final mass and radius states, representing the core collapse of a massive star with a phase transition leading to an unbound quark–gluon plasma. We find that the combined shape parameter and AMM effects can alter the coupled EOS–TOV equations, resulting in an increase in the final mass and a decrease in the final equatorial radius without collapsing the core into a black hole and without violating causality constraints; we find maximum mass values in the range 1.6 Mʘ < M < 2.5 Mʘ. These states are consistent with some astrophysical, high-mass magnetar/pulsar and gravity wave systems and may provide evidence for a core that has undergone a quark–gluon phase transition such as PSR 0943 + 10 and the secondary from the GW 190814 event.

Unmoderated molten salt reactors design optimisation for power stability

The critical region of unmoderated molten salt reactors consists in a cavity filled with a liquid fuel. The lack of internal structure implies a complex flow structure of the circulating fuel salt. A preliminary core shape optimization has been performed during the EVOL European project to limit recirculation and hotspots. This optimization was based on a Reynolds Averaged Navier Stokes (RANS) approach, but the latter only provides time-averaged values for velocity and temperature. However, the power stability is sensitive to thermal fluctuations induced by the flow turbulence itself, even at steady state without pump flow rate or heat extraction variation. This phenomenon is studied using a Detached Eddies Simulation approach to solve the turbulence in the reactor and get a time dependent temperature distribution and then the reactivity fluctuations. A new geometry is proposed to limit the total power fluctuations from 7.5% for the preconceptual EVOL geometry down to 1.2%.

An Improved Strain Sensor Based on Long-Period Fiber Grating With a Local Ellipse-Core Structure

In this paper, we proposed a novel long-period fiber grating strain sensor based on local ellipse-core fiber (LEC-LPFG). The LEC-LPFG was fabricated by laser polishing and local heating methods, which could efficiently transform a single-mode fiber (SMF) into a periodic ellipse-core fiber. The effects associated with the fiber elliptical core shape were shown to significantly influence the strain sensitivity of the LEC-LPFG. Further, it was demonstrated that the LEC-LPFG has a high strain sensitivity of −20.2 pm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> and a temperature sensitivity of 68.6 pm/°C. Our work provides a new technology for straightforward, low-cost, and large-scale productions of premium fiber optical strain sensors which are desirable in many practical applications.

Integrated magnetics optimization process for an interleaved three‐phase buck converter at 500 kHz

AbstractThe optimization of magnetics in power converters switching at high frequencies is needed to achieve high power density and high efficiency. This work provides the design and optimization process of a coupled inductor used in a three‐phase interleaved buck converter that is part of a two‐stage motor drive circuit. The converter uses wide‐bandgap switch devices to reduce switching losses under high‐frequency operation and a coupled inductor that integrates three independent inductors to reduce the number and size of magnetic components. The relationship between the equivalent inductance of the coupled inductor and the coupling coefficient is analysed for different core shapes under various duty cycles. The optimization procedure for the three‐phase coupled inductor core structure is presented that allows for the coupling coefficient to be reduced by adding magnetic volume to reduce the inductor current ripple, while the core loss is reduced by 10.5%. A prototype of the 500‐W three‐phase interleaved converter that operates at 500 kHz with the proposed integrated magnetics technology was tested in experiment, exhibiting a maximum efficiency of 98.63% at full load power.

Numerical analysis of damage mechanisms for 3D-printed sandwich structures using a meshless method

Finite element analysis is a widely used simulation technique to analyze structural components and the mechanical behavior of materials under different loading conditions. The major steps involved in finite element simulations are the definition of the basic parameters and the discretization in elements of the component, also known as preprocessing, the analysis of the models and the post-processing by the representation and the interpretation of the obtained results. On the particular case of complex geometries obtained by fused deposition modeling, the most time consuming of these three steps is that of preprocessing, because on traditional finite element technology is require that the real geometry of the CAD model is simplified to be meshed and analyzed. Nowadays, different techniques have been proposed and developed with this objective: reduce costs in terms of time and specialized human resources because the workflow is easier and simpler. One of these methods is known as the meshless method, which do not require connection between nodes and are based on the interaction of the points of the geometry with the neighbors, so the processor analyzes the real CAD geometry and no simplifications are needed. The present work uses the meshless method based on the theory of external approximation as an alternative to the classic finite element method. In numerical simulations, the influence of core shape is evaluated on the failure mode of the 3D-printed lightweight structures. Three cell core patterns were numerically evaluated under tensile and three-point bending tests: out-of-plane hexagonal honeycomb, S-shape corrugated, and in-plane hexagonal honeycomb cores. The nucleation and propagation of cracks had more heterogeneous profiles for in-plane hexagonal honeycomb cores, showing greater unpredictability in the susceptible areas to failure. The numerical analysis with the meshless method showed a potential for a fast prediction and a low computational cost analysis.

Power Supply Based on Inductive Harvesting From Structural Currents

Monitoring infrastructure offers functional optimization, lower maintenance cost, security, stability, and data analysis benefits. Sensor nodes require some level of energy autonomy for reliable and cost-effective operation, and energy-harvesting methods have been developed in the last two decades for this purpose. Here, a power supply that collects, stores, and delivers regulated power from the stray magnetic field of current-carrying structures is presented. In cm-scale structures the skin effect concentrates current at edges at frequencies even below 1 kHz. A coil-core inductive transducer is designed. A flux-funneling soft magnetic core shape is used, multiplying power density by the square of funneling ratio. A power management circuit combining reactance cancelation, voltage doubling, rectification, supercapacitor storage, and switched inductor voltage boosting and regulation is introduced. The power supply is characterized in house and on a full-size industrial setup, demonstrating a power reception density of 0.36, 0.54, and 0.73 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> from a 25-A root-mean-square structural current at 360, 500, and 800 Hz, respectively, corresponding to the frequency range of aircraft currents. The regulated output is tested under various loads and cold starting is demonstrated. The introduced method may enable power autonomy to wireless sensors deployed in current-carrying infrastructure.

Natural convection characteristics of honeycomb fin with different hole cells for battery phase-change material cooling systems

As a nature production the lightweight honeycomb is used as a fin to increase the contact area with the PCM and improve its overall thermal conductivity. In this paper the effects of different honeycomb core shapes, sizes, and arrangements on melting under natural convection were investigated to determine the optimal honeycomb cell parameters. In this study, transient simulations based on VOF and enthalpy-porosity methods are developed, and the results show that compared with heat conduction, the melting time under natural convection conditions can be reduced. By analyzing different shapes, it is discovered that the melting effects of triangles, trapezoids, rectangles, and rhombuses are better than that of hexagons, the triangular melting time is reduced by 23.1%. The orthogonal experiments show that the ranking order of the effects on melting time and natural convection is Ra > Shape > LHR. Furthermore, the optimal honeycomb hole core parameters are obtained from the analysis of a single factor. Compared with the hexagonal honeycomb fin, a battery's PCM with an optimal triangular honeycomb fin under natural convection exhibits a 23.3% increase in terms of temperature decrease.

Extruded TOPAS hollow-core anti-resonant fiber optimized for THz guidance at 0.9THz.

A hollow-core anti-resonant fiber for the THz regime is proposed and demonstrated. The proposed fiber is the hexagonal core shape which is directly extruded using a conventional 3D printer. Experimental results show that by using cyclic olefin copolymer (COC), the proposed fiber design provides a low attenuation of ∼3 dB∕m at ∼ 0.86 THz and ∼15 dB∕m at ∼ 0.42 THz.

The basement membrane controls size and integrity of the Drosophila tracheal tubes.

Biological tubes are fundamental units of most metazoan organs. Their defective morphogenesis can cause malformations and pathologies. An integral component of biological tubes is the extracellular matrix, present apically (aECM) and basally (BM). Studies using the Drosophila tracheal system established an essential function for the aECM in tubulogenesis. Here, we demonstrate that the BM also plays a critical role in this process. We find that BM components are deposited in a spatial-temporal manner in the trachea. We show that laminins, core BM components, control size and shape of tracheal tubes and their topology within the embryo. At a cellular level, laminins control cell shape changes and distribution of the cortical cytoskeleton component α-spectrin. Finally, we report that the BM and aECM act independently-yet cooperatively-to control tube elongation and together to guarantee tissue integrity. Our results unravel key roles for the BM in shaping, positioning, and maintaining biological tubes.

Application of Digital Core Technology in Wellbore Stability Research

Using core to conduct laboratory experiments is one of the important methods for wellbore stability research. However, as the objects of petroleum exploration gradually shift to areas with complex geological conditions, core acquisition is restricted by many problems, such as irregular shapes of cores obtained, low core acquisition rate, long construction time, and increasing operational cost. In recent years, exploration work in the southwest Tarim Basin has been further strengthened. Due to the complex strata and the frequent occurrence of complex well conditions during the drilling process, the problem of on-site coring has become more prominent, which seriously limits the analysis of rock properties. Therefore, scientific and effective cuttings analysis technology is urgently needed. This paper used digital core CT scanning technology to reconstruct the rock skeleton and its mineral facies using drill cuttings. The digital core was established, and the Poisson’s ratio and elastic modulus were calculated. The wellbore stability was analyzed, and the well sections, which were prone to wellbore instability, were determined. On this basis, KCl-polysulfonate drilling fluid was introduced. The influence of drilling fluid on rock strength was evaluated by digital core technology, and water immersion experiments were introduced to verify the experimental results. The results obtained by digital core CT scanning technology were compared with those obtained by triaxial compression experiments and well-logging data calculation, and the feasibility of digital core technology in the wellbore stability study and drilling fluid evaluation was verified.

Analysis of Steady Vortex Rings Using Contour Dynamics Method for Fluid Velocity

Most studies on the shape of the steady vortex ring have been based on the Stokes stream function approach. In this study, the velocity approach is introduced as a trial approach. A contour dynamics method for fluid velocity is used to analyze the Norbury–Fraenkel family of vortex rings. Analytic integration is performed over the logarithmic-singular segment. A system of nonlinear equations for the discretized shape of the vortex core is formulated using the material boundary condition of the core. An additional condition for the velocities of the vortical and impulse centers is introduced to complete the system of equations. Numerical solutions are successfully obtained for the system of nonlinear equations using the iterative scheme. Specifically, the evaluation of the kinetic energy in terms of line integrals is examined closely. The results of the proposed method are compared with those of the stream function approaches. The results show good agreement, and thereby, confirm the validity of the proposed method.

Synthesis, structures, and magnetic properties of Fe4-Ln2 (Ln = Tb, Ho, and Er) clusters with N, N, N′, N′-tetrakis-(2-hydroxyethyl)ethylenediamine

Three isostructural heterometallic {FeIII4LnIII2} coordination clusters are reported with genernal formula; [FeIII4LnIII2(μ4-O)2(Hedte)2(piv)6(NO3)2]∙2MeCN∙2CH2Cl2 {Ln = Tb(1), Ho(2) and Er(3), where Hedte = N,N,N,N′--tetrakis-(2-hydroxyethyl)ethylenediamine; piv = pivalic acid}. These clusters are obtained by reacting the FeCl2·4H2O, pivalic acid, Ln(NO3)3·6H2O, and H4edte in MeCN/CH2Cl2. X-ray measurements revealed that 1–3 clusters exhibit a “butterfly” core shape. Solid-state dc-magnetic susceptibility measurement indicates the ferromagnetic interactions in 1 while 2 and 3 demonstrates dominated antiferromagnetic interactions.

All-Atom Simulation Method for Zeeman Alignment and Dipolar Assembly of Magnetic Nanoparticles.

Magnetic nanoparticles (MNPs) can organize into novel structures in solutions with excellent order and unique geometries. However, studies of the self-assembly of smaller MNPs are challenging due to a complicated interplay between external magnetic fields and van der Waals, electrostatic, dipolar, steric, and hydrodynamic interactions. Here, we present a novel all-atom molecular dynamics simulation method to enable detailed studies of the dynamics, self-assembly, structure, and properties of MNPs as a function of core sizes and shapes, ligand chemistry, solvent properties, and external field. We demonstrate the use and effectiveness of the model by simulating the self-assembly of oleic acid ligand-functionalized magnetite (Fe3O4) nanoparticles, with spherical and cubic shapes, into rings, lines, chains, and clusters under a uniform external magnetic field. We found that the long-range electrostatic interactions can favor the formation of a chain over a ring, the ligands promote MNP cluster growth, and the solvent can reduce the rotational diffusion of the MNPs. The algorithm has been parallelized to take advantage of multiple processors of a modern computer and can be used as a plugin for the popular simulation software LAMMPS to study the behavior of small MNPs and gain insights into the physics and chemistry of different magnetic assembly processes with atomistic details.

A Brief Review on Structural, Morphological, Magnetic and Dielectric Behavior of Divalent Cation-substituted Nanocrystalline Cobalt Ferrite

Abstract: Spinel ferrites nanoparticles have received much more focus due to their promising applications in various technologies, such as magnetic refrigerators, microwave devices, colour imaging, high-density recording media and magnetic fluids. Nano-crystalline cobalt ferrite has been widely studied for its distinctive properties, like cubic magneto crystalline anisotropy, high coercivity, reasonable saturation magnetization, great chemical constancy, wear resistance and electrical insulation. Thus, cobalt ferrite has its own applications in the arena of high-frequency devices, magneto-optical devices, memory cores, recording media and spintronics and also in the biomedical sector, such as MRI, drug delivery schemes and magnetic hyperthermia. Reduced dimensionality of ferrite nanoparticles is having differences in properties when compared to its bulk counterparts. Size modulation of the physico-chemical properties of cobalt ferrite gives a distinctive response in the nanosized scale, permitting for material engineering in order to meet different necessities while addressing its different applications. The present study gives a brief review of significant effects on structural, dielectric and magnetic properties of cobalt spinel ferrite with different cation substitutions, like Mg2+, Ni2+, Zn2+, Cu2+, In2+ ...etc. This study regarding the size and its dispersity, core shell design, shape, crystallinity and surface decoration with hybrid derivatives opens up a wide variety of prospects for elementary studies as well as for growth and revolution in the field of ferrites. Keywords: Spinel ferrite, Structural properties, Microstructural properties, Magnetic properties, Dielectric properties.

Innovative Magnetic Circuits for Boost Converters’ and EMI Filters’ Integrated Inductor

In this paper, the innovative magnetic circuits to integrate both inductors used in an EMI filter (a common-mode (CM) choke and a differential-mode (DM) choke) and a boost converter (power inductor) are presented. Three integrated magnetic core geometries, i.e. UIU, EIU, and EI shapes of the magnetic cores are proposed. To evaluate the effectiveness of proposed integrated magnetic core geometries, the electrical operating conditions and EMI reduction performances of the conventional boost converter with EMI filter using discrete magnetic cores are compared with that of the innovative boost converter with EMI filter using the proposed integrated magnetic cores. From the experimental results, it can be concluded that with the proposed EIU shape of the magnetic cores, one “I” magnetic core can be eliminated where the electrical performances are not degraded. Moreover, in term of EMI reduction performances, innovative boost converter with EMI filter using the EIU shape of the magnetic core provides a good EMI attenuation which is comparable to the case of the conventional boost converter with EMI filter using discrete magnetic cores.

Evaluation of Floor Acceleration for the Seismic Design of Non-Structural Elements according to the Core Shape

최근 비구조요소의 피해사례가 증가하면서 비구조요소 내진설계에 관한 많은 연구가 진행되고 있다. 하지만 대부분의 연구는 평면적 요소보다는 수직적 요소나 시스템적 요소를 변수로 층가속도를 평가하고 있다. 때문에 본 논문에서는 횡력저항에 많은 부분을 차지하는 코어를 평면적 변수로 사용하여 비구조요소 내진설계를 위한 층가속도에 대해 평가하였다. 정사각형의 2축대칭의 평면에서 코어의 형태(위치 및 비중)변화에 따라 서로 다른 5개의 평면과 각 평면마다 5층, 10층, 15층, 20층의 층수를 가진 총 20개의 모델로 선형시간이력해석을 수행하였다. 분석 결과 코어 위치에 따라 편심을 받는 평면에서는 층가속도가 최대 1.7배의 비틀림 증폭이 발생하였고 구조물의 중층부에서 비틀림의 영향이 가장 큰 것을 확인할 수 있었다. 편심이 없이 코어의 비중만 변화한 평면에서는 주기 0.4694초를 기준으로 이하일 때는 주기가 증가할수록 층가속도가 저층부에서는 감소하고 고층부에는 증가하며, 반대로 주기 0.4694초 이상일 때는 주기가 증가할수록 층가속도가 저층부에서는 증가하고 고층부에는 감소한다는 것을 확인할 수 있었다. 또한, 구조물의 층수는 최대층가속도에 영향을 주지 못하는 것을 확인하였다.

Behavior of hollow concrete-filled rectangular GFRP tube beams under bending

Concrete-filled fiber reinforced polymer (FRP) tube (CFFT) members have become increasing popular, while the study on CFFT beams especially hollow CFFT beams is rather limited. This paper presents an experimental study on the flexural behaviour of hollow concrete-filled rectangular glass fiber reinforced polymer (GFRP) tubes beams. A total of six beams was fabricated and tested by using four-point bending. The parameters investigated in this study included the size of the hollow cores (0%, 5.7%, 12%, 27%) and the shape of the hollow cores (circle and rectangle). The experimental results show that the hollow CFFT beams exhibit an almost linear load–displacement behaviour and a brittle failure mode. The flexural stiffness of the hollow CFFT beams is slightly affected by the size and shape of the hollow cores. In addition, the proposed theoretical model verifies that the hollow core in the tension region also has a small effect on flexural strength of the hollow CFFT beams, and the flexural behavior is highly depended on the material properties of the GFRP tubes. In comparison with the conventional steel reinforced concrete beams, the hollow CFFTs beams have a lighter dead weight and a higher load-carry capacity.

ISP-Net: Fusing features to predict ischemic stroke infarct core on CT perfusion maps

Background: Acute ischemic stroke is one of the leading death causes. Delineating stoke infarct core in medical images plays a critical role in optimal stroke treatment selection. However, accurate estimation of infarct core still remains challenging because of 1) the large shape and location variation of infarct cores; 2) the complex relationships between perfusion parameters and final tissue outcome. Methods: We develop an encoder-decoder based semantic model, i.e., Ischemic Stroke Prediction Network (ISP-Net), to predict infarct core after thrombolysis treatment on CT perfusion (CTP) maps. Features of native CTP, CBF (Cerebral Blood Flow), CBV (Cerebral Blood Volume), MTT (Mean Transit Time), Tmax are generated and fused with five-path convolutions for comprehensive analysis. A multi-scale atrous convolution (MSAC) block is firstly put forward as the enriched high-level feature extractor in ISP-Net to improve prediction accuracy. A retrospective dataset which is collected from multiple stroke centers is used to evaluate the performance of ISP-Net. The gold standard infarct cores are delineated on the follow-up scans, i.e., non-contrast CT (NCCT) or MRI diffusion-weighted image (DWI). Results: In clinical dataset cross-validation, we achieve mean Dice Similarity Coefficient (DSC) of 0.801, precision of 81.3%, sensitivity of 79.5%, specificity of 99.5%, Area Under Curve (AUC) of 0.721. Our approach yields better outcomes than several advanced deep learning methods, i.e., Deeplab V3, U-Net++, CE-Net, X-Net and Non-local U-Net, demonstrating the promising performance in infarct core prediction. No significant difference of the prediction error is shown for the patients with follow-up NCCT and follow-up DWI (P >0.05). Conclusion: This study provides an approach for fast and accurate stroke infarct core estimation. We anticipate the prediction results of ISP-Net could offer assistance to the physicians in the thrombolysis or thrombectomy therapy selection.

Superatomic Orbital Splitting in Coinage Metal Nanoclusters.

The superatomic orbital splitting (SOS) method is developed to understand the electronic structures of coinage metal nanoclusters, in which delocalized electron counts are not magic numbers. Because the symmetry of a metal core can significantly affect the electronic structure of a nanocluster, this method takes the shape of the core into account in determining the order of group orbital levels. By taking nanoclusters as superatoms, a highly positively charged core is established by removing the ligands and staples. The superatomic orbitals split into group orbitals at different energy levels because of the nonspherical shape of the cluster core. Therefore, the electron configuration of the nonmagic-number nanocluster can be qualitatively analyzed without quantum chemical calculations, which is very important for understanding the stability of the cluster.

Experimental and Numerical Study on a Two-stage Coring Method for Stress Measurement: Application to Deep and High-Temperature Geothermal Wells

We discuss the possibility of recording the state of in-situ stress in the shape of a rock core that is sampled using a modified core drilling method. This concept is based on a phenomenon that a cylindrical rock-core expands radially into a slightly elliptical shape along its transverse cross-section when the rock sample is relieved of its in-situ anisotropic stress by drilling. The magnitudes and orientation of in-situ stresses can, in principle, be estimated from the circumferential variation of core expansion. However, it is not possible to evaluate the expansion from a core collected in a conventional way, with a single drilling bit, since it will be in its expanded state when extracted and lacks information about its required pre-expansion dimensions. To overcome this problem, we propose an innovative way of core drilling referred to as Dual-bit Coring. This approach results in a single core that has two signature transverse cross-sections: the first has an elliptical shape resulting from core expansion and the second records the initial circular shape prior expansion. Then, the amount of expansion can be estimated based on the differences between the shapes of those cross-sections. We propose practical drilling tool for carrying out Dual-bits Coring. The tool works mechanically and does not require any electric devices sensitive to high temperatures so that it is expected to function even in deep and high temperature rocks at geothermal fields, such as those encountered in supercritical geothermal systems.