Static Case Research Articles

In-medium gluon radiation spectrum with all-order resummation of multiple scatterings in longitudinally evolving media

Over the past years, there has been a sustained effort to systematically enhance our understanding of medium-induced emissions occurring in the quark-gluon plasma, driven by the ultimate goal of advancing our comprehension of jet quenching phenomena. To ensure meaningful comparisons between these new calculations and experimental data, it becomes crucial to model the interplay between the radiation process and the evolution of the medium parameters, typically described by a hydrodynamical simulation. This step presents particular challenges when dealing with calculations involving the resummation of multiple scatterings, which have been shown to be necessary for achieving an accurate description of the in-medium emission process. In this paper, we extend our numerical calculations of the fully-resummed gluon spectrum to account for longitudinally expanding media. This new implementation allows us to quantitatively assess the accuracy of previously proposed scaling laws that establish a correspondence between an expanding medium and a “static equivalent”. Additionally, we show that such scaling laws yield significantly improved results when the static reference case is replaced by an expanding medium with the temperature following a simple power-law decay. Such correspondence will enable the application of numerical calculations of medium-induced energy loss in realistic evolving media for a broader range of phenomenological studies.

Comparison of measured and calculated high-viscosity crude oil temperature values in a pipeline during continuous pumping and shutdown modes

The paper investigates the stationary and non-stationary cooling processes of high-viscosity crude oil temperature in the Severnye Buzachi – Karazhanbas pipeline during both pump operations and pump shutdowns. To transport high-viscosity crude oil through pipelines, the hot pumping method is employed. During oil transportation and pump shutdowns, the oil temperature decreases due to heat exchange with the environment, leading to an increase in oil viscosity. As viscosity rises, more power is required from the pumps to move the thickened oil, resulting in higher electricity consumption. To avoid increased operational costs after pump shutdowns, it is crucial to accurately calculate the oil cooling temperature in order to determine the safe shutdown duration and a critical temperature threshold. The Shukhov formula is used to calculate oil temperature during transportation, while a modified version is applied during pump shutdowns. To verify the accuracy of the obtained oil temperature results, the calculated values were compared with the measured values from pipeline sensors in both stationary and non-stationary cases. The novelty of the work is in determining the methodology for calculating the safe shutdown time of a pipeline for high-viscosity oil. The proposed formula was validated using experimental data from SCADA system sensors in real-time.

Anti-plane Yoffe-type crack in flexoelectric material

This work investigates the deformation and polarization fields around a finite anti-plane shear (mode III) crack growing dynamically under steady-state conditions. The leading tip of this finite crack breaks the material while the trailing tip heals it. This fast moving finite crack (referred to as a rupture “pulse” in the geophysics literature) propagates with a constant velocity and with the mechanical and the electrical fields that remain invariant with respect to an observer moving with the crack-tips. This problem belongs to the first type of steady state crack growth problems according to the classification of Freund. The “prototype” problem which refers to an isotropic, body subjected to fracture under tensile loading was first proposed and solved by Yoffe, while finite cracks (or shear pulses) were also analyzed by Freund and by Rice. In the above cases the material was assumed to be linear elastic. Our analysis extends these studies to flexoelectric materials, and it is both theoretical and numerical. It discusses the asymptotic structure of the crack-tip displacement and the polarization fields; it calculates the dynamic energy release rate and presents their dependence on crack-tip velocity. Comparisons are made to the available, classical, elasto-dynamic solutions and to the static case. The influence of the electrical properties of the material on strengthening is also analyzed. Dynamic fracture of flexoelectric materials is of relevance to both the study of earthquake source mechanics and to the analysis of the reliability of micro-electronic devices. This is because both rocks and ceramics are flexoelectric. Indeed, during earthquake rupture processes, dynamic, in-plane shear (Mode-II) and out of plane shear (Mode-III), cracks propagate along faults and exhibit both mechanical and electrical polarization signatures. At an entirely different length scale, flexoelectric ceramics are currently used as sensors and transducers and can experience dynamic shear failure along interfaces when subjected to dynamic loading (e.g. impact.). Failure by dynamic fracture can be detrimental to both their mechanical reliability and electrical functionality.

Scaling symmetry reductions of coupled KdV systems

Abstract In this paper we discuss the Painlevé reductions of coupled KdV systems. We start by comparing the procedure with that of stationary reductions. Indeed, we see that exactly the same construction can be used at each step and parallel results obtained. For simplicity, we restrict attention to the t2 flow of the KdV and DWW hierarchies and derive respectively 2 and 3 compatible Poisson brackets, which have identical structure to those of their stationary counterparts. In the KdV case, we derive a discrete version, which is a non-autonomous generalisation of the well known Darboux transformation of the stationary case.

Relaxation of the kinematic dynamo equations

We compute the exact relaxation and Λ \Lambda -convex hull of the kinematic dynamo equations and show that they coincide. We also find the relaxation in the stationary case and present applications to the infinite-time limit in the kinematic dynamo problem.

Effect of crossflow orientations in the impinging jet flow channel on flow and heat transfer enhancement under rotations

An experimental and numerical investigation was conducted to elucidate the flow and heat transfer characteristics of a row of impinging jets within a confined, rotating channel. The study focused on a jet Reynolds number (Rej) of 9,000, examining three distinct crossflow orientations: radially outward (ROCF), radially inward (RICF), and a combined radially outward and inward (ROICF) scheme. Jet-to-impingement surface distances (h/dj) of 2, 4, and 6 (where dj represents the jet orifice diameter) were considered, along with channel rotation speeds corresponding to Rotation numbers (Ro) from 0 to 0.0046. Heat transfer on the leading and trailing sides of the impinging jets was measured using a steady thermochromic liquid crystal (TLC) technique under constant heat flux conditions. Additionally, RANS simulations were employed to investigate the flow fields associated with the impinging jets. The results reveal that in both the ROCF and RICF schemes, heat transfer, characterized by the Nusselt number, decreases from upstream to downstream for each impinging jet. Increasing the rotation number (Ro) leads to enhanced heat transfer, with the trailing side exhibiting marginally higher values than the leading side. In the ROICF scheme, at h/dj = 2, a more uniform Nusselt number distribution is observed across all jet holes compared to the ROCF and RICF schemes, and this uniformity increases with higher Ro. However, for h/dj = 4 or 6, the heat transfer becomes non-uniform and can even deteriorate below the stationary case at high Ro numbers, attributed to the combined effects of Coriolis and centrifugal forces.

Invariant regimes of Spencer scaling law for magnetic compression of rotating FRC plasma

Abstract The scaling laws for the magnetic compression of a toroidally rotating field reversed configuration (FRC) have been investigated in this work. The magnetohydrodynamics (MHD) simulations of the magnetic compression on rotating FRCs employing the NIMROD code (Sovinec et al 2004 J. Comput. Phys. 195 355), are compared with the Spencer’s one-dimensional (1D) theory (Spencer et al 1983 Phys. Fluids 26 1564) for a wide range of initial flow speeds and profiles. The toroidal flow can influence the scalings directly through the alteration of the compressional work as also evidenced in the 1D adiabatic model, and indirectly by reshaping the initial equilibrium. However, in comparison to the static initial FRC equilibrium cases, the pressure and the radius scalings remain invariant for the magnetic compression ratio B w 2 / B w 1 up to 6 in presence of the initial equilibrium flow, suggesting a broader applicable regime of the Spencer scaling law for FRC magnetic compression. The invariant scaling has been proven a natural consequence of the conservation of angular momentum of both fluid and magnetic field during the dynamic compression process.

Numerical study on heat transfer of two-phase fluid in helical coil pipe under ocean condition

The thermal hydraulic characteristics and heat transfer of two-phase fluid in helical coil once-through steam generator under ocean conditions like rolling and heaving motions are studied numerically. A CFD model is established to analyze the effects of motion parameters like amplitude, period and rolling radius and the heat flux distribution are discussed. The analysis shows that the overall heat transfer decreases under ocean conditions, but the overall deterioration is limited, indicting the helical coil pipe has the stability for ocean conditions. The additional forces like Coriolis, centrifugal and inertial forces introduced by rolling motion are analyzed theoretically and the result shows it detorts the original two main vortexes responsible for high heat transfer due to its spiral geometry, making heat transfer fluctuates up and down periodically near the steady state value. As rolling height increases, the heat transfer is nonlinear due to the competition between Coriolis force and centrifugal and inertial forces. As rolling amplitude increases, the heat transfer variation increases and the local heat transfer deterioration is severely aggravated, indicating high rolling amplitude should be avoided as possible. Increasing rolling period makes heat transfer behavior more approximate to static case as gravity and centrifugal force due to spiral geometry is dominate. Under heaving motion, the overall heat transfer decreases, and increasing heaving amplitude and decreasing period make the fluctuation more severe.

On peridynamic acoustics

We consider a nonlocal (peridynamic) version of the classical forced wave equation. This scalar three-dimensional equation contains a weight function (the “micromodulus”) and a length parameter (the “horizon”) that have to be selected. We investigate various properties (the locality limit as the horizon shrinks, plane waves and group velocity), paying attention to how these properties depend on the choice of the micromodulus. We solve the forced peridynamic equation in the static case (avoiding divergent integrals) and in the time-harmonic case (with a radiation condition, when needed).

Exergy and Entropy Analysis of Heat Exchanger Under Mechanical Vibration and Magnetic Field

Abstract The present study primarily investigates the exergy and entropy generation in a heat exchanger influenced by the combined effects of mechanical vibrations and magnetic fields. A rectangular channel with dimensions 40 mm in length and 4 mm in width was examined using magnets of varying strengths and subjected to vibrations and magnetic fields. The Reynolds number (Re) investigated in this study ranges from 150 to 300. Both, magnetic field and vibrations, generated intricate patterns and contours, highlighting their interaction with flow dynamics. As vibrational intensity increased, the Nusselt number amplified correspondingly. While the introduction of magnetic field also enhanced the Nusselt number (Nu), the impact of vibrations was more pronounced. A maximum Nu enhancement of 225.9% was achieved at a Re 300, under the influence of vibrations at 5 mm and 25 Hz, and a magnetic field strength of 2000 G. The study further revealed that exergy efficiency decreases progressively with increasing Re but improves with higher vibrational intensity, reaching a peak of 52.81% at 5 mm and 25 Hz. Additionally, it was observed that irreversibility (φ) decreases with increasing vibrational and magnetic strengths. The ratio of entropy generation under the vibrational and magnetic influence to that of static case peaked at a value of 2.4 under vibrational intensity of 5 mm and 25 Hz, and magnetic field strength of 2000 G.

Using the nonlinearity of a PEM water electrolyzer cell for its dynamic model characterization

The voltage response of a water electrolyzer at low frequencies is characterized by a combination of a static polarization curve and dynamic, capacitive effects. In this paper, a model combining these two phenomena is created, which incorporates the Butler–Volmer equation in parallel with a capacitance in order to produce differential equations for the activation overpotentials separately on both electrodes. A parameter fitting methodology is then developed for obtaining the seven model parameters from a set of low-frequency, high-amplitude dynamic waveform measurements. The method is further implemented in an electrolyzer modeling toolbox for MATLAB. The model built in this study is proven to predict well both static and dynamic voltage responses down to the 1Hz frequency. At higher frequencies and at small amplitudes the model reduces to the Randles equivalent circuit, and in a static case to the polarization curve of the cell. The proposed methodology can be used for probing individual electrode properties with full-cell measurements and providing a reliable tool for simulating water electrolyzer voltage responses with arbitrary waveforms and amplitudes.

Real-time delivered dose assessment in carbon ion therapy of moving targets

Abstract Purpose:
Real-time adaptive particle therapy is being investigated as a means to maximize the treatment delivery accuracy. To react to dosimetric errors, a system for fast and reliable verification of the agreement between planned and delivered doses is essential. This study presents a clinically feasible, real-time 4D-dose reconstruction system, synchronized with the treatment delivery and motion of the patient, which can provide the necessary feedback on the quality of the delivery.
Methods:
A GPU-based analytical dose engine capable of millisecond dose calculation for carbon ion therapy has been developed and interfaced with the next generation of the Dose Delivery System (DDS) in use at Centro Nazionale di Adroterapia Oncologica (CNAO). The system receives the spot parameters and the motion information of the patient during the treatment and performs the reconstruction of the planned and delivered 4Ddoses. After each iso-energy layer, the results are displayed on a graphical user interface by the end of the spill pause of the synchrotron, permitting verification against the reference dose.
The framework has been verified experimentally at CNAO for a lung cancer case based on a virtual phantom 4DCT. The patient’s motion was mimicked by a moving Ionization Chambers (ICs) 2D-array.
Results:
For the investigated static and 4D-optimized treatment delivery cases, real time dose reconstruction was-achieved with an average pencil beam dose calculation speed up to more than one order of magnitude smaller than the spot delivery. The reconstructed doses have been benchmarked against offline log-file based dose reconstruction with the TRiP98 treatment planning system, as well as QA measurements with the ICs 2D-array, where an average gamma-index passing rate (3%/3mm) of 99.8% and 98.3%, respectively, were achieved.
Conclusion:
This work provides the first real-time 4D-dose reconstruction engine for carbon ion therapy. The framework integration with the CNAO DDS paves the way for a swift transition to the clinics.

A new approach for GNSS spoofing detection using power and signal quality monitoring

Abstract Global Navigation Satellite System (GNSS) signals are highly susceptible to spoofing attacks. Signal Quality Monitoring (SQM) methods are simple and easy to detect spoofing. However, traditional SQM methods are only effective for matched-power cases and exhibit high detection probability only for a short time. This study introduces a new approach, exploiting anomalies in receiver correlation outputs during spoofing. It efficiently detects signal amplitude fluctuations and correlation peak distortions. The Texas Spoofing Test Battery (TEXBAT) dataset is used to evaluate the detection performance of the proposed approach. The results show that the proposed approach has excellent detection performance in various spoofing cases, including matched-power, overpowered, static, and dynamic cases. This approach surpasses traditional SQM metrics in detection probability and sensitivity to spoofing stages. Importantly, the proposed approach detects spoofing early.

The Impact of Dynamic Effects on the Results of Non-Destructive Falling Weight Deflectometer Testing.

The article investigates the impact of applying a dynamic computational model that considers inertia forces on pavement deflections under rapidly changing loads over time. This study is particularly relevant to the modelling of falling weight deflectometer (FWD) testing. Initially, the article examines the deflection values obtained from computational models under loads with varying frequencies. In this context, considering inertia forces was significant for load durations shorter than 0.04 s. In such cases, the results of static and dynamic analyses differed considerably. One application of FWD measurement results is determining the stiffness moduli of pavement layers using backcalculation. The study explored the impact of incorporating inertia forces into the pavement model on the estimated values of stiffness moduli obtained via backcalculation. The results revealed differences of several percent between the stiffness moduli calculated using dynamic and static numerical models. Subsequently, the key pavement deformations and fatigue life were determined using the obtained moduli. Again, significantly different results were observed between dynamic and static cases. Based on these findings, it can be concluded that dynamic effects should not be ignored when using FWD testing for backcalculation. Additionally, the article addresses the sensitivity of backcalculation results, which is crucial for the accurate interpretation of the obtained data.

Laboratory Evaluation of Geosynthetic Interface Friction under Low Stress.

In landfill cover, geosynthetic packages are often used to fulfil different and simultaneous functions: drainage, waterproofing, separation, reinforcement, and soil protection. In this regard, various types of geosynthetics are combined in succession to allow for water and biogas drainage and to waterproof, reinforce, and provide protection from erosion over the useful lifetime, ranging over many decades if we consider the long phases of disposal, closure, and quiescence of the landfill itself. The creation of the composite cover barrier requires the evaluation of various interfaces' frictional strength under low contact stresses, both in static and seismic cases. The main purpose of this study is to summarize the results of past laboratory tests carried out on different geosynthetic-geosynthetic and geosynthetic-soil-geosynthetic interfaces using experimental instrumentation developed at the geotechnical laboratory of the University of Padua, which allows for the characterization of the interface geosynthetic friction at low contact stresses. The main aspects highlighted are the kinematic mode of failure, the wearing of the contact surfaces, the presence or absence of interstitial fluid, and, finally, the density level of the granular soil in contact with the geosynthetics.

The Outcome of Walking Cold Patients with Potential Mild Hypothermia to Safety-A Mountain Rescue Case Series.

Some experts recommend that ambulant hypothermic patients should be rewarmed, fed, and not permitted to exercise for 30 min because of concerns that afterdrop can cause cardiac instability. We investigated the outcome of ambulant hypothermic patients in a case series from mountain rescue teams in Great Britain. A questionnaire was used to collect information on a series of adult patients with a clinical diagnosis of mild hypothermia. All patients were alert on the AVPU scale and evacuated by walking from the mountain. The outcome measures were survival or a change in management because of medical deterioration during evacuation. A series of 108 eligible cases were reported over a 5-year period. When rescuers arrived on the scene, 98 (91%) patients were stationary, and 10 (9%) were still mobile. Thirty-eight (39%) of the stationary cases were walked immediately off the mountain without any on-scene delay. In the remaining 60 (61%) stationary cases, the decision was taken to delay evacuation to provide food, drinks, and additional clothing. In 3 cases, the use of heat packs indicated an intention to actively rewarm. In cases where the on-scene time was reported, 27 (79%) were known to be mobile again within 20 min. All patients survived, and no adverse medical events occurred in all 108 cases. In this study, no adverse events occurred because of immediate mobilization, suggesting that in these cases, there appears to be minimal risk of early activity.

The rotating solutions beyond the spontaneous scalarization in Einstein-Maxwell-scalar theory

The Einstein-Maxwell-scalar (EMS) theory with a quartic coupling function features three branches of fundamental black hole (BH) solutions, labeled as cold, hot, and bald black holes. The static bald black holes (the Reissner-Nordström BH) exhibit an intriguing nonlinear instability beyond the spontaneous scalarization. We study the rotating scalarized black hole solutions in the EMS model with a quartic coupling function through the spectral method numerically. The domain of existence for the scalarized BHs is presented in the spin-charge region. We found that the rotating solutions for both the two scalarized branches possess similar thermodynamic behavior compared to the static case while varying the electric charge. The BH spin enlarges the thermodynamic differences between the cold and hot branches. The profile of the metric function and the scalar field for the scalarized BHs is depicted, which demonstrates that the scalar field concentrates more on the equatorial plane in contrast to the axisymmetric region as the spin increases.

Analytical Analysis of Buckling Of Layered Composite Columns

Abstract: Lightweight composite construction is of great interest in the design and manufacture of spacecraft and marine vehicles because of high specific stiffness and strength. In addition, sandwich construction offers enhanced corrosion resistance, noise suppression and reduction in life-cycle costs. There are several issues and questions related to the use of composite construction that require attention and answers. One of the important issues is the prediction of buckling loads, under either static or sudden load application. For the static case, closed form solutions are derived for a symmetric composite column under axial compression and for various boundary conditions. In this study, improved analytical models are developed to characterize interface behavior of layered composite column-type structures. The mechanics models of the bonded interface with and without adhesive layer are established, from which the interface fracture, delamination buckling, free vibration and stress analysis across the adhesive layer of corresponding interface are studied.

On an Oberbeck-Boussinesq model relating to the motion of a viscous fluid subject to heating

Abstract This article surveys some results in the study of Iannelli [Su un modello di Oberbeck-Boussinesq relativo al moto di un fluido viscoso soggetto a riscaldamento, Fisica Matematica, Istituto Lombardo (rend. Sc.) A 121 (1987), 145–191], in which the motion of a viscous, compressible fluid in a two-dimensional domain, subject to heating at the walls, is studied. A global existence and uniqueness theorem for the time-dependent problem is given, and also, under more stringent assumptions, an existence and uniqueness theorem in the stationary case is given. A theorem on the asymptotic behavior for t → ∞ t\to \infty of the time-dependent solutions is proved.

Transverse Oscillations and Kelvin–Helmholtz Instability in Curved Arcade Loops with Siphon Flows

The effect of plasma flow in curved arcade loops on transverse waves and oscillations is examined analytically. The model under study is a semicircular magnetic slab with finite transverse extensions and a mass flow inside, in the zero-β plasma approximation. It is found that in the quasi-perpendicular propagation limit, the model supports two fast surface modes: one with higher (FSW+) and another with lower (FSW−) frequency. For a weak flow, the frequency of the FSW+ (FSW−) increases (decreases) as the flow speed grows in both propagating and quasi-standing wave regimes. We show that the FSW+ and FSW− are subjected to the Kelvin–Helmholtz (KH) instability, and the threshold flow is greater (less than) the internal Alfvén speed for the FSW+ (FSW−). The presence of plasma flow results in modifying the period ratio P 1/2P 2 of the fundamental harmonic to the first overtone with P 1/2P 2 less (more) than 1 for the FSW+ (FSW−), and this effect degenerates in the straight waveguide limit. The sub-Alfvénic flow can prohibit resonant absorption of kink modes when the frequencies of the FSW+ and FSW− become out of the Alfvén continuum. It is also shown that in the static case and for a weak flow case, the FSW+ (FSW−) is interpreted as a vertically (horizontally) polarized kink mode, while for moderate flow, both modes have oblique polarization. We apply the developed theory to interpret the observational cases of kink oscillations in coronal loops with signatures of a siphon flow and the onset of KH instability induced by the blowout jet along a loop-shaped magnetic structure.