bluuebunny/crossref_metadata_2025_split huggingface dataset:
A laser absorption sensor for fuel slip monitoring in high-humidity flue gases from ammonia combustion
Authors: Ma Liuhao , Wang Wei , Zhou Chen , Wang Yu 
Published: May 2023

Abstract
Ammonia has been recently recognized as a promising carbon-free fuel to help decarbone both the power and industrial heating sectors. However, fuel slip during ammonia combustion is of high concern because of the high toxicity of the chemical, motivating the development of sensitive sensors for real-time monitoring of ammonia emission in combustion flue gases. In this work, a near-infrared absorption spectroscopic sensor was developed for trace ammonia (NH3) measurements in high-humidity flue gas environments with water vapor (H2O) mole fractions up to 40%. The focus on high humidity is motivated by the facct that ammonia combustion generally leads to flues gases with notably higher water vapor concentations as compared to conventional hydrocarbons. The sensor used a distributed feedback laser to target the NH3 absorption line near 6612.73 cm−1. Proof-of-concept tests were conducted in a high-temperature multi-pass cell with a controlled temperature of 500 K and pressure of 1 atm. A custom-designed variable humidity generator was used to provide a reference NH3/N2 mixture with a controlled H2O mole fraction (10%–40%) to simulate ammonia combustion flue gases. Direct absorption spectroscopy and wavelength modulation spectroscopy were both used to ensure a relatively large dynamic range. H2O-induced broadening effects on the measured absorption profile were quantified. The developed sensor was firstly validated against NH3/N2 mixtures with different H2O concentrations, with a lower detection limit of 76 ppb achieved. Real-time measurements of NH3 slip in the flue gases from CH4/NH3/air flames and CH4/NH3 co-firing industrial furnace were performed as a demonstration of the sensor for time-resolved ammonia monitoring with sufficient accuracy, sensitivity, and time response.
A method combining half width of point spread function with maximum gradient of image gray for single-camera three-dimensional spray velocity detection
Authors: Wang Hui , Wang Xiangyu , Long Guohui , Wang Ning , Wang Chao , Shao Liwei 
Published: May 2023

Abstract
When a defocus image is obtained by direct imaging, it is hard to determine whether the detected object is in the front or rear of the focal plane. This is called the ambiguity problem and it causes great trouble in the 3D-particle tracking velocimetry (PTV) defocus method, which obtains the defocus location by directly obtaining depth information from the intensity along the radial direction of particles. This study proposes a method to obtain the true position of a particle based on the asymmetry feature of the defocus image with respect to the focal plane. The method distinguishes two ambiguous positions with equal width of point spread function (PSF) width by introducing a parameter derived from the maximum gradient of image gray. The method also derives a mathematical expression for the half width of PSF(χ) considering aberration. The method is validated by a calibration technique, which shows that in 19 out of 20 experimental conditions correct results are obtained. We apply the method to measure the 3D velocity of an airflow jet with 3D-PTV and compare it with computational fluid dynamics results, which show a maximum error of 8.8 %. Furthermore, the method is used to measure a real spray as an example, and obtains a 3D vector map and velocity cumulative distribution of the measured area.
Cathode shorts design and its effects on the device characteristics of small-size light-triggered thyristors
Authors: Yin Jinchao , Bai Yujie , Cao Jian , Liu Guipeng , Zhou Ming , Yang Jianhong 
Published: May 2023

Abstract
Cathode shorts are an essential part in light-triggered thyristors (LTTs) that are utilized to achieve adequate dv/dt capability and switching characteristics. In this paper, we designed cathode shorts structures specifically for small-size LTTs; the patterns and structural parameters were shown. Devices were fabricated and measured, and the influences of the cathode shorts on device performance were examined. The results showed that, based on the optimized design, the cathode shorts allowed excellent dv/dt capability and switching performance while achieving good optoelectronic properties.
Multi-beam piezoelectric systems by means of dynamically equivalent stiffness concept
Authors: Febbo Mariano , Prado Bruno F A , Smarzaro Vinícius C , Bavastri Carlos A 
Published: May 2023

Abstract
Energy harvesting devices allow to obtain forms of energy present in nature and to convert them into electrical energy. One way of generating energy from mechanical vibrations is by using beams of piezoelectric materials. This paper proposes an alternative methodology for characterizing the dynamic behavior of a vibrating composite system composed of a cantilever steel base beam (primary system) and a piezoelectric beam attached to it. The approach involves representing the piezoelectric beam using an equivalent dynamic stiffness at its base. This simplifies the mathematical representation of the compound system and enables the system dynamics to be described solely in terms of the generalized coordinates of the primary system, which is advantageous in optimization environments where a reduced number of equations can facilitate analysis. To determine the equivalent dynamic stiffness, different mathematical models of one and multiple degrees of freedom are presented, including the description of the polyamide base of the piezoelectric sheet. An inverse problem is used to identify system parameters, and the energy generation over a wide range of frequencies is analyzed. Experimental frequency response functions of the voltage–acceleration type are obtained to validate numerical findings, demonstrating that the proposed methodology is a cost-effective alternative for parameter identification or optimal design in energy generation.
Stochastic processes in a confining harmonic potential in the presence of static and dynamic measurement noise
Authors: Meyer Philipp G , Metzler Ralf 
Published: May 2023

Abstract
We consider the overdamped dynamics of different stochastic processes, including Brownian motion and autoregressive processes, continuous time random walks, fractional Brownian motion, and scaled Brownian motion, confined by an harmonic potential. We discuss the effect of both static and dynamic noise representing two kinds of localisation error prevalent in experimental single-particle tracking data. To characterise how such noise affects the dynamics of the pure, noise-free processes we investigate the ensemble-averaged and time-averaged mean squared displacements as well as the associated ergodicity breaking parameter. Process inference in the presence of noise is demonstrated to become more challenging, as typically the noise dominates the short-time behaviour of statistical measures, while the long time behaviour is dominated by the external confinement. In particular, we see that while static noise generally leads to a more subdiffusive apparent behaviour, dynamic noise makes the signal seem more superdiffusive. Our detailed study complements tools for analysing noisy time series and will be useful in data assimilation of stochastic data.
Interaction of electrons and positrons with two-dimensional artificially generated proton lattice and with carbon lattice
Authors: Al-Ajaleen M , Tőkési K 
Published: May 2023

Abstract
A many-body classical trajectory Monte Carlo (CTMC) method is applied in the study of scattering probabilities of electrons and positrons after interacting with a two-dimensional (2D) artificially generated, uniform lattice, composed of fixed protons. We used different lattice parameters between the protons for different simulations, where the projectiles have kinetic energies of 500 and 1000 eV. We found a very strong focusing of electrons and a very strong defocusing of the positrons at lower lattice parameters. Furthermore, we found, these effects get weaker with increasing lattice parameters. Interesting changes took place at lattice parameters 2 and 3 au. which are close to the lattice parameter between carbon atoms in graphene of value 2.68 au. We also performed a simulation of a defective lattice by removing some protons and noticed distinguishable changes in the spectra compared to the spectra of an ideal lattice. This comparison may open a way for the detection of lattice defects in real samples.
A peak in the power spectrum of primordial gravitational waves induced by primordial dark magnetic fields
Authors: Kanno Sugumi , Mukuno Ann , Soda Jiro , Ueda Kazushige 
Published: May 2023

Abstract
Dark gauge fields have been discussed as candidates for dark matter recently. If they existed, primordial dark magnetic fields during inflation would have existed. It is believed that primordial gravitational waves (PGWs) arise out of quantum fluctuations during inflation. We study the graviton-dark photon conversion process in the presence of background primordial dark magnetic fields and find that the process induces the tachyonic instability of the PGWs. As a consequence, a peak appears in the power spectrum of PGWs. It turns out that the peak height depends on the direction of observation. The peak frequency could be in the range from 10-5 to 103 Hertz for GUT scale inflation. Hence, the observation of PGWs could provide a new window for probing primordial dark magnetic fields.
Enhancement of second-order gravitational waves at Q-ball decay
Authors: Kasuya Shinta , Kawasaki Masahiro , Murai Kai 
Published: May 2023

Abstract
The recent observation of 4He favors a large lepton asymmetry at the big bang
nucleosynthesis. If Q-balls with a lepton charge decay after the electroweak phase transition,
such a large lepton asymmetry can be generated without producing too large baryon asymmetry. In
this scenario, Q-balls dominate the universe before the decay and induces the sharp transition
from the early matter-dominated era to the radiation-dominated era. In this transition, the
gravitational waves (GWs) are enhanced through a second-order effect of the scalar perturbations.
We evaluate the density of the produced GWs and show that pulsar timing array observations can
probe this scenario depending on the amplitude of the scalar perturbations.
Evolution of circuit complexity in a harmonic chain under multiple quenches
Authors: Pal Kuntal , Pal Kunal , Gill Ankit , Sarkar Tapobrata 
Published: May 2023

Abstract
We study Nielsen’s circuit complexity in a periodic harmonic oscillator chain, under single and multiple quenches. This simple system is amenable to analytical computations and yet offers considerable insight into the dynamics of quantum information. For a single quench scenario, we highlight some important differences between our results that explicitly use the wavefunction, as compared to the recently proposed covariance matrix method and point out the consequences. In a multiple quench scenario, the complexity shows remarkably different behaviour compared to the other information theoretic measures, such as the entanglement entropy and the out of time ordered correlator. In particular, the latter is known to show signs of chaos in this integrable system, but our results indicate the contrary. We further show the presence of a ‘residual complexity,’ i.e. after two successive quenches, when the frequency returns to its initial value, the complexity has a non-zero lower limit. Further, applying a large number of successive quenches, the complexity of the time evolved state can be increased to a high value, which is not possible by applying a single quench. Finally, we show that this simplistic model exhibits the interesting phenomenon of ‘complexity crossover’ between two successive quenches performed at different times.
Zero-mode entanglement across a conformal defect
Authors: Capizzi Luca , Eisler Viktor 
Published: May 2023

AbstractWe consider a free-fermion chain with a conformal defect that features an extended zero mode, and study the entanglement properties in its mixed ground state. The zero-mode induced degeneracy modifies the density of states in the single-particle entanglement spectrum, which can be calculated via the full counting statistics. For a homogeneous chain, the resulting change in the Rényi entropy is derived analytically for arbitrary subsystem ratios in the thermodynamic limit. For a conformal defect located in the center, analogous results can be obtained for the half-chain entanglement. In particular, we observe parity effects for half-chains with even/odd sites, which do not decay with size.
Application of the porous media approach to a Standing Wave Thermoacoustic Engine for CFD simulations
Authors: Meglio Armando Di , Massarotti Nicola 
Published: May 2023

Abstract
In this article, an application of the macroscopic porous media approach, suitable for CFD simulations in oscillating flows, is proposed for a simplified Standing Wave Thermo-Acoustic Engine (SWTAE), composed of a hot buffer tube, a stack - where the energy conversion takes place - and the rest of the resonator. While for a Travelling Wave Thermo-Acoustic Engine (TWTAE) a macroscopic model for porous media has been successfully applied to both regenerators (similar to the stack in a SWTA) and heat exchangers, for SWTAE this is not true. The results illustrate that a Local-Thermal Non-Equilibrium model is required to start up the SWTAE, otherwise (with the Local Thermal Equilibrium model) the thermoacoustic instability cannot arise. Furthermore, the comparison between the simulation conducted at the microscopic scale and that one at the macroscopic level, depicts that a purely Darcy-linear model employed for the macroscopic model, characterized for oscillating flows, overpredicts the pressure amplitude at periodic steady-state. For this reason, a Forchheimer-like coefficient needs to be implemented to fit the macroscopic solution with the microscopic one.
Experimental study of a R290 variable geometry ejector
Authors: Besagni Giorgio , Inzoli Fabio , Croci Lorenzo , Brignoli Vittorio , Smolka Jacek , Palacz Michal , Haida Michal , Bodys Jakub , Fingas Rafal , Nowak Andrzej J. , Melka Bartlomiej , Stebel Michal , Piechnik Edyta 
Published: May 2023

Abstract
Ejectors are classified as fluid-dynamics controlled devices where the “component-scale” performances are imposed by the local-scale fluid dynamic phenomena. For this reason, ejector performances (measured by the pressure-entrainment ratio coordinate of the critical point) are determined by the connection of operation conditions, working fluid and geometrical parameters. Given such a connection, variable geometry ejector represents a promising solution to increase the flexibility of ejector-based systems. The present study aims to extend knowledge on variable geometry systems, evaluating the local and global performances of the R290 ejector equipped with a spindle. The prototype ejector was installed at the R290 vapour compression test rig adapted and modified for the required experimental campaign. The test campaign considered global parameter measurements, such as the pressure and the temperature at inlets and outlet ports together with the mass flow rates at both inlet nozzles, and the local pressure drop measurements inside the ejector. In addition, the experimental data were gathered for different spindle positions starting from fully open position the spindle position limited by the mass flow rate inside the test rig with the step of 1.0 mm.
Accuracy in evaluating heat transfer coefficient by RANS CFD simulations in a rectangular channel with high aspect ratio - Part 2: channel with ribbed walls
Authors: Corti Maria , Gramazio Pasqualino , Fustinoni Damiano , Vitali Luigi , Niro Alfonso 
Published: May 2023

Abstract
In this paper, a Computational Fluid-Dynamics (CFD) analysis on heat transfer characteristic using Reynolds Averaged Navier-Stokes (RANS) equations on a rectangular channel with ribbed surfaces is presented. Several numerical simulations have been carried out on convective heat transfer of an air flow through a rectangular channel of 1:10 aspect ratio, 120 mm wide, 840 mm long, with 90° ribs. Ribs have a square cross section with 4 mm side and three different values of dimensionless pitch, namely, 10, 20 and 40. Results on convective global heat transfer coefficient, i.e., averaged over the whole channel, have been compared to experimental data obtained in a channel with the same geometry and boundary conditions. Agreement between numerical and experimental data is discussed for the three different pitches considered. As expected, comparisons show a decreasing reliability for increasing complexity. The aim of this work is to find a suitable configuration of a CFD model with RANS that will permit authors to apply it to the range of dimensionless pitches.
Local wall heating effects on aeroacoustic field radiated by an isolated square cylinder in a laminar flow
Authors: Falone M. , D’Alessandro V. , Giammichele L. , Ricci R. 
Published: May 2023

Abstract
The aim of this work is to gain an insight on the effect of the wall heating on the aeroacoustic sound radiated by bluff bodies in laminar flows. In particular, the local thermal treatment of the wall boundary was investigated as a possible method for active controlling the emitted noise. This technique was studied performing direct numerical simulations of the aeroacoustic noise produced by an isolated square cylinder operating at a Reynolds and Mach numbers equal to 150 and 0.2, respectively. In the considered case, the Karman vortex street deriving by the flow/cylinder interaction, produces a lift and drag pulsation on the body surface, leading to a dipolar-like noise emission. In this context, different local thermal fluxes were applied to the cylinder wall in order to reduce its aerodynamic forces fluctuation and, consequently, the associated pressure disturbance that produces the radiated sound. The computations are performed using an OpenFOAM solver that adopts an explicit Runge-Kutta scheme for time integration and a second-order, energy conserving scheme for the convective part of the Eulerian flux. Moreover, the spurious numerical waves reflections at the far-field boundary are damped adopting a sponge-layer approach.
Optimised Electro-Osmotic Flow in Rectangular Microchannels with Smoothed Corners
Authors: Lorenzini Marco , Suzzi Nicola 
Published: May 2023

Abstract
Electro-osmotic flows are a means of circulating polar fluids through microchannels without resorting to mechanical pumping. The lack of moving parts, of noise and the ease of integration in silicon chips make them an interesting option for microchip cooling and miniaturized total analysis systems. This paper describes an optimization in terms of first- and second-law analysis of the cross-section of a microchannel subject to electro-osmotic flow. Starting from rectangular cross-sections of different aspect ratios, its corners are progressively smoothed and the resulting Poiseuille and Nusselt numbers computed. Performance evaluation criteria are then used to assess the change in, among others, heat transfer rate, temperature difference between wall and bulk fluid, and equivalent pumping power. The entropy number is also computed and the results commented. It is found that the latter criterion highlights a configuration of minimum entropy generation, whereas the trends of the heat transfer and temperature difference are opposite to that of the equivalent pumping power.
Stability analysis of dual viscous flows saturating a vertical porous pipe
Authors: Celli M , Barletta A , Brandão P V , da C Hirata S , Ouarzazi M N 
Published: May 2023

Abstract
The linear stability analysis of a mixed convection viscous flow in a vertical porous pipe is here investigated. The contribution of viscous heating is assumed to be non negligible. A fully developed flow regime is assumed for the basic state. The local balance equations for this state display dual stationary solutions. The dual branches of stationary solutions are determined numerically. Since the pipe is characterised by an isothermal lateral surface, the viscous heating is the sole cause of the buoyancy force. In order to investigate the stability of the basic dual solutions, small amplitude disturbances with the form of normal modes are superposed to the basic state. The solution of the eigenvalue problem obtained allows one to determine the growth rate associated to both the basic solution branches. The sign of the growth rate determines whether the particular basic solution is stable or unstable.
A new derivation of the Minkowski metric
Authors: Chappell James M , Hartnett John G , Iannella Nicolangelo , Iqbal Azhar , Berkahn David L , Abbott Derek 
Published: May 2023

Abstract
The four dimensional spacetime continuum, as first conceived by Minkowski, has become the dominant framework within which to describe physical laws. In this paper, we show how this four-dimensional structure is a natural property of physical three-dimensional space, if modeled with Clifford geometric algebra

C
ℓ
(

R

3

)

. We find that Minkowski spacetime can be embedded within a larger eight dimensional structure. This then allows a generalisation of the invariant interval and the Lorentz transformations. Also, with this geometric oriented approach the fixed speed of light, the laws of special relativity and a generalised form of Maxwell’s equations, arise naturally from the intrinsic properties of the algebra without recourse to physical arguments. We also find new insights into the nature of time, which can be described as two-dimensional. Some philosophical implications of this approach as it relates to the foundations of physical theories are also discussed.
Linking stem rehydration kinetics to hydraulic traits using a novel method and mechanistic model
Authors: O’Keefe Kimberly , Smith Duncan D , McCulloh Katherine A 
Published: May 2023

Abstract

Background
Despite the recognized importance of hydraulic capacitance as a mechanism used by plants to maintain hydraulic functioning during high transpiration, characterizing the dynamics of capacitance remains a challenge.

Methods
We used a novel ‘two-balance method’ to investigate relationships between stem rehydration kinetics and other hydraulic traits in multiple tree species, and we developed a model to explore stem rehydration kinetics further.

Key Results
We found that: (1) rehydration time constants and the amount of water uptake occurring during rehydration differed significantly across species; (2) time constants did not change with declining water potential (Ψ), while water uptake increased at lower Ψ in some species; (3) longer time constants were associated with lower wood density, higher capacitance and less negative stem pressures causing 50 % loss of hydraulic conductivity (P50); (4) greater water uptake occurred in stems with lower wood density and less negative P50 values; and (5) the model could estimate the total hydraulic resistance of the rehydration path, which cannot be measured directly.

Conclusions
Overall, the two-balance method can be used to examine rehydration dynamics quickly and thoroughly in detached woody stems. This method has the potential to improve our understanding of how capacitance functions across tree species, which is an often-overlooked component of whole-plant hydraulics.