bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of viscous dissipation on the conjugate heat transfer between the walls of a porous microchannel
Authors: Monsivais I G , Méndez F , Lizardi J J , Ramos E A 
Published: April 2022

Abstract
In this work, the finite element method was used to study numerically the viscous dissipation that occurs when a Newtonian fluid circulates through a porous microchannel that operates as a heat sink, in which a constant heat flux is applied from the outer walls of the porous microchannel into the fluid. Taking into account that this is a conjugate problem, where the temperature fields of both the porous medium and the wall are unknown, there are two well-known asymptotic limits in the literature that allow us to obtain the solution for this problem: the first one is the thermally thick wall limit

γ

/

β

w

2

=
1

, which has been widely studied previously by other authors; the second one is the thermally thin wall limit

γ

/

β

w

2

=
25

, where the longitudinal effects of heat conduction in the microchannel wall are considerably more important than the ones occurring in the transverse direction. Therefore, in this study, we analyze the competition between these effects and viscous dissipation, as well as the influence that both have on the temperature profiles of the fluid and the wall. The results show that for Br ≥ 0.1, a notable temperature increase occurs in the system, which offers interesting results that have not been reported in the literature yet, because from χ = 0.6 (Br = 0.1), there is a higher temperature in the center of the microchannel than in the vicinity of the wall; that is, the fluid temperature is higher at η = 0 with respect to the temperature value at η = 1. This situation becomes more evident as the Brinkman number increases; for example, for Br = 1, the temperature in the center of the microchannel increases up to 23% with respect to the fluid temperature at the wall. Finally, the decrease of the Darcy number does not have a considerable effect on the temperature profiles.
A theoretical investigation of nonlinear optical and electronic molecular parameters of hexabutyloxytryphenylene and halogenated hexabutyloxytryphenylene molecules using density functional theory (DFT) for nonlinear device applications
Authors: Pal Bhavna , Mishra Mirtunjai , Singh Devendra , Kumar Devesh 
Published: April 2022

AbstractIn this work, we discuss the molecular properties of hexabutyloxytryphenylene (HAT4) and halogenated HAT4 using density functional theory (DFT) with B3LYP method and Pople basis set (6-31G, 6-31G*, 6-31G**) for the generation of non-linear optical and electronic parameters. Using DFT method, the dependence of electro-optical parameters of halogenated HAT4 such as dipole moment, mean polarizability, anisotropy in polarizability and hyperpolarizability along with global parameters such as ionization potential, electron affinity, electronegativity, chemical hardness and electrophilicity index on the halogens in the core of the considered molecules has been studied in this work. Further, the frontier molecular orbital analysis for pure HAT4 and halogenated HAT4 molecules has been carried out. The proposed study helps us to analyse the effect of halogenation on the linear, non-linear as well as thermodynamical properties of HAT4 molecules such as HOMO-LUMO gap, thermal energy, entropy and specific heat capacity. The effect of halogenation also leads to understand the modification of nonlinear parameters of HAT4 for the interaction of nonlinear fields.
The cavity method for minority games between arbitrageurs on financial markets
Authors: Ritmeester Tim , Meyer-Ortmanns Hildegard 
Published: April 2022

Abstract
We use the cavity method from statistical physics for analyzing the transient and stationary dynamics of a minority game that is played by agents performing market arbitrage. On the level of linear response the method allows to include the reaction of the market to individual actions of the agents as well as the reaction of the agents to individual information items of the market. This way we derive a self-consistent solution to the minority game. In particular we analyze the impact of general nonlinear price functions on the amount of arbitrage if noise from external fluctuations is present. We identify the conditions under which arbitrage gets reduced due to the presence of noise. When the cavity method is extended to time dependent response of the market price to previous actions of the agents, the individual contributions of noise can be pursued over different time scales in the transient dynamics until a stationary state is reached and when the stationary state is reached. The contributions are from external fluctuations in price and information and from noise due to the choice of strategies. The dynamics explains the time evolution of scores of the agents’ strategies: it changes from initially a random walk to non-Markovian dynamics and bounded excursions on an intermediate time scale to effectively random switching in the choice between strategies on long time scales. In contrast to the Curie–Weiss level of a mean-field approach, the market response included by the cavity method captures the realistic feature that the agents can have a preference for a certain choice of strategies without getting stuck to a single choice. The breakdown of the method in the phase transition region indicates possible market mechanisms leading to critical volatility and a possible regime shift.
Exact results for interacting hard rigid rotors on a d-dimensional lattice
Authors: Saryal Sushant , Dhar Deepak 
Published: April 2022

Abstract
We study the entropy of a set of identical hard objects, of general shape, with each object pivoted on the vertices of a d-dimensional regular lattice of lattice spacing a, but can have arbitrary orientations. When the pivoting point is situated asymmetrically on the object, we show that there is a range of lattice spacings a, where in any orientation, a particle can overlap with at most one of its neighbors. In this range, the entropy of the system of particles can be expressed exactly in terms of the grand partition function of coverings of the base lattice by dimers at a finite negative activity. The exact entropy in this range is fully determined by the second virial coefficient. Calculation of the partition function is also shown to be reducible to that of the same model with discretized orientations. We determine the exact functional form of the probability distribution function of orientations at a site. This depends on the density of dimers for the given activity in the dimer problem, which we determine by summing the corresponding Mayer series numerically. These results are verified by numerical simulations.
The evolution of creep curves of high impact polystyrene and polyurethane specimens after aging
Authors: Arutyunyan A R 
Published: April 2022

Abstract
Specimens of high impact polystyrene and polyurethane were studied for creep at room temperature and constant tensile force without aging and after aging according to various programs. For polyurethane specimens after aging, an increase in creep time for a given deformation by 3 times compared to specimens without aging is observed. For high impact polystyrene in the creep experiments after aging, a decrease of deformation by 6.5 times and the time to fracture by more than 24 times, compared with specimens without aging is shown. To describe the obtained experimental creep curves for polyurethane and polystyrene specimens without aging and after aging, modified versions of linear elastic–viscous models of Maxwell and Voigt written in the effective time scale are used. A good agreement between the theoretical and experimental creep curves is observed.
Examples of exact solutions to boundary value problems of the theory of elasticity for a truncated wedge
Authors: Kovalenko M D , Menshova I V , Kerzhaev A P , Yu G 
Published: April 2022

Abstract
The paper presents examples of exact solutions to boundary value problems of the theory of elasticity for a truncated wedge. The straight sides of the wedge are free, and normal stresses are given on its circular “end” (the tangential stresses are considered equal to zero). The solutions are sought in the form of expansions in Papkovich–Fadle eigenfunctions. The coefficients of the expansions are determined in a simple explicit form.
Investigation of mechanical properties and fracture surface of cylindrical specimens of Al 6101 alloy under static tension
Authors: Magomedova D K , Churakova A A , Gunderov D V 
Published: April 2022

Abstract
The data on the study of mechanical properties of cylindrical specimens of Al alloy 6101 in different states under static tension at room temperature are presented. The specimens were tested after natural aging, artificial aging, and ECAP. The surface of fractures of these specimens was also investigated using an electron microscope, and a chemical analysis of elements on the surface of fractures was carried out. Basing on the performed study, it can be concluded that alloy 6101 shows the highest strength (ultimate tensile strength 350 MPa) after ECAP treatment in UFG state. It was confirmed due to the chemical analysis that destruction pores in this material originate on particles of secondary phases based on impurity iron.
Stress analysis of composites with interfacial bridged cracks and damaged zones
Authors: Perelmuter M 
Published: April 2022

Abstract
Stress analysis of composite structures with bridged cracks and damaged zones is performed with the direct boundary integral equations method in axisymmetric formulation. It is assumed that: a) the crack faces interact in some zones behind of the cracks edges (bridged zones); b) these zones width can be comparable to the whole crack size; c) adjacent parts of the structure can be connected by mechanical ligaments (including interfaces ahead of cracks fronts) and the relative displacements of these parts can occur under the loading (these zones consider as damaged zones). The boundary element software to solve axisymmetric problems of elasticity with interfacial bridged cracks and damaged zones was developed. The results for different properties of composite materials and bonds are presented. Applications the bridged crack approach to modeling of cracks self-healing is remarked.
The role of intermediate structures in the combustion of high-energy condensed systems
Authors: Babuk V A , Budnyi N L , Nizyaev A A , Naryzhnyi S Yu , Kuklin D I 
Published: April 2022

Abstract
During the combustion of high-energy condensed systems, the formation of an intermediate structure - a skeleton layer, is possible, which has a significant effect on the combustion process. An experimental study was carried out to determine the nature of the effect of the curing of the binder on forming this structure. The article shows the specific role of the used hardener, polyethylene polyamine, presents the solutions for simulating the phenomena in the surface layer in the presence and absence of a skeleton layer, as well as shows the possibility of predicting the characteristics of the combustion process.
The influence of gasifier operating parameters on syngas composition of coal-fired power plant with CO2 capture
Authors: Sedacheva O V , Nesterova G A , Abaimov N A , Ryzhkov A F 
Published: April 2022

Abstract
This work investigated the influence of the operating parameters of the gasifier (pressure, temperature of the syngas at the outlet of the gasifier and the O2/CO2 ratio in the blast) on the composition of the syngas in relation to the Allam cycles and oxy-fuel IGCC. Thermodynamic modeling of the operation of Shell (Allam cycle) and MHI (oxy-fuel IGCC cycle) gasifiers by the entropy maximization method was carried out. For the Shell gasifier, a significant increase in methane concentration with an increase in pressure to 40 MPa has been revealed; it indicates the need to make changes to the syngas gas cleaning system. The optimal temperature at the outlet of the gasifier (1100°C) has been found for the MHI gasifier. At this temperature, there were high values of CO and H2, and, hence, the heating value of syngas. For both gasifiers, the most theoretically reasonable ratio of O2/CO2 in blast was 0.3, at which CO reached almost maximum values and decreased its growth rate.
Pyrolysis of boron-containing compositions upon exposure to radiant energy
Authors: Basalaev S A , Kuznetsov V T , Rashkovskiy S A 
Published: April 2022

Abstract
The article describes a method and a design of the experimental setup for determining the mass rate of pyrolysis of boron-containing compositions upon exposure to radiant energy and presents experimental data on the mass rate of pyrolysis of binary mixtures consisting of aluminum dodecaboride and polybutadiene binder SKDM-80 depending on the mass fraction of aluminum dodecaboride in the content and heat flux density. It is noted that the ratio of the mass rate of pyrolysis to the mass fraction of the binder in the sample for a given heat flux density depends weakly on the AlB12 content in the sample. This fact indicates that the presence of AlB12 in the mixture affects the sample heating intensity and the binder destruction rate and that AlB12 is carried away under the impact of outflowing gaseous products of the binder pyrolysis.
Improvement of Velocity Distribution Function Measurement of Hydrogen Atoms in ion Source Discharges
Authors: Tokai T , Bito K , Shimabukuro Y , Wada M 
Published: April 2022

Abstract
The efficiency of negative hydrogen (H-) ion surface production in an ion source should be highly dependent upon the velocity distribution function of neutral atomic hydrogen (H0) striking the plasm grid (PG). A system composed of forming an atom beam, rotating beam chopper, ionizer and pulse count unit has been constructed to measure H0 velocity distribution functions. The background noise due to stagnation of hydrogen gas in the region between the beam formation skimmer and the ion source PG was improved by inserting a flow reflection structure. The short life time of the secondary electron emission detector (SEM) was prolonged by properly setting the hydrogen ion trajectories from the ionizer to the the first dynode of the SEM. The system is running stably to record the velocity distribution function but statistical noise synchronized to the trigger pulse of the chopper must be removed before the measurment of change in H0 velocity distribution functions dependin upon the type of discharge.
Measurement of ionization, charge exchange and ion confinement times in charge breeder ECR ion sources with short pulse 1+ injection of metal ions
Authors: Luntinen M , Angot J , Tarvainen O , Toivanen V , Thuillier T , Koivisto H 
Published: April 2022

Abstract
The Consecutive Transients (CT) method is used for estimating the characteristic times of ionization, charge exchange and confinement within the plasma of a Charge Breeder Electron Cyclotron Resonance Ion Source (CB-ECRIS). The method reveals differences in the characteristic times between different source configurations, with K9+ charge breeding efficiencies of 8.9 % and 20.4 %, and allows qualitative explanation of the improved breeding efficiency. The increase in K9+ efficiency is accompanied by a decrease in ionization time for low charge states, a decrease of charge exchange time for high charge states, and an overall decrease of the ion confinement time, which increases non-linearly with the charge state. The charge exchange time exhibits a minimum near charge state K8+, indicating low neutral density near the plasma core. The CT-method yields a distribution of possible ne and (Ee) corresponding to the spatial distribution of different charge state ions. The results hint at a non-uniform plasma electron density and energy distribution as well as a nested-layer distribution for the ion populations — hot and dense plasma with high charge state ions near the plasma core.
CERN hadron sources: status and innovation overview
Authors: Wenander F 
Published: April 2022

Abstract
The CERN accelerator complex is served by several different types of hadron sources, producing both high- and low-intensity negative H- beams, highly charged positive stable ions, but also transforming low-charge radioactive ions to higher charges before post-acceleration. Apart from the operational sources, research and development is carried out at dedicated test stands for H- production and pre-acceleration, ECRIS oven experiments and general EBIS development. In this paper, we will report on the performance and the latest development related to the sources. Efforts to enhance the theoretical understanding of the source physics will be briefly reviewed.
Status and prospects of the 60 GHz SEISM ion source
Authors: Andre Thomas , Angot Julien , Baylac Maud , Dumont Pierre Olivier , Lamy Thierry , Sole Patrick , Thuillier Thomas , Debray Francois , Izotov Ivan , Skalyga Vadim 
Published: April 2022

Abstract
SEISM is a unique ECR ion source operating at a frequency of 60 GHz. The prototype is based on a simple magnetic geometry, the cusp, allowing the use of polyhelix coils (developed with LNCMI, Grenoble) to generate the closed ECR surface at 2.14T. The plasma is sustained by a high intensity HF pulse (up to 300kW). Previous experiments at LNCMI have successfully demonstrated the establishment of the nominal magnetic field and the extraction of ion beams with a current density up to 1 A cm-2. The presence of afterglow peaks was also observed, proving the existence of ion confinement in a CUSP ECR source. An experimental campaign is carried out in 2021 using a new transport line designed to improve the transmission of the beam to the new detectors. Short and long-term research plans are presented to transform this high current density into a high intensity ion beam that can be used for accelerators of the future.
Caesium Balance of the ISIS H Penning Ion Source
Authors: Tarvainen O , Faircloth D , Lawrie S , Sarmento T , Abel R , Macgregor J , Cahill C , Stanley T , Whitehead M , Wood T 
Published: April 2022

Abstract
We have developed a model predicting the equilibrium caesium coverage work function of the cathode (in eV) and the expected H- beam current (in arb. units) of the ISIS Penning ion source. The model is based on semi-empirical expressions for the cathode work function, negative ion surface ionization yield, and caesium adsorption and desorption rates. We compare the model predictions to experimental data with 760 μs discharge and 250 μs beam pulses. It is concluded that the ISIS Penning ion source operates near the optimum cathode work function in a wide range of caesium pressures and cathode temperatures. The model implies that long pulse operation of the source requires elevated Cs oven temperature and improved cathode cooling.
Plasma commissioning in a high power external RF-coil volume-type H- ion source
Authors: Lawrie S , Abel R , Faircloth D , Sarmento T , Speed J , Tarvainen O 
Published: April 2022

Abstract
A high power, high duty cycle, negative hydrogen ion source is in development at ISIS. It will operate in pure volume-production mode and is driven by a 52-turn RF-coil mounted external to the plasma chamber. A solid-state amplifier with a maximum output of 100 kW in 50 Hz, 1 ms pulses delivers RF power to the coil via an impedance-matching network. The amplifier has a relatively wide bandwidth, able to deliver full power from 1.8-4.0 MHz. This flexibility allowed straightforward commissioning of the matching network into an inductively-coupled plasma. Striking of the pulsed plasma is facilitated by a compact microwave ignition gun, requiring only 10 W of power at 2.45 GHz to deliver 1 mA seed pulses of electrons. Experiments have shown that it is vital to encapsulate the RF-coil properly to mitigate high voltage sparking. In addition, the location of the coil relative to the ion source’s permanent magnets has a critical effect on the ease of plasma ignition. The result of commissioning work is that a full duty-factor (50 Hz, 800 ^s) plasma has been achieved at nominal operating power (30 kW) and detailed optical studies have begun.
Numerical analysis of isotope effect in NIFS negative ion source
Authors: Kato Ryo , Hoshino Kazuo , Nakano Haruhisa , Shibata Takanori , Miyamoto Kenji , Iwanaka Kengo , Hayashi Katsuya , Hatayama Akiyoshi 
Published: April 2022

Abstract
Result of hydrogen (H) and deuterium (D) experiments done by NIFS research and development negative ion source (RNIS) demonstrated that the co-extracted electron current with the negative ions and the electron density in the driver region in the D experiment have been around three times higher than that in the H experiment. To investigate mechanism of this difference, electron transport simulation using 3D kinetic particle tracking model KEIO-MARC code has been modified and applied to analysis of the isotope effect in the NIFS negative ion source. Simulation result suggests that impacts of isotope effects of sheath potential drop, coulomb collisions, and some reactions of ground state molecules and ions on the electron density is not large to explain the experimental result of the increase in the electron density in the plasma.
H- beam emittance analysis in a multicusp ion source
Authors: George A , Kalvas T , Melanson S , Dehnel M , Broderick N G R 
Published: April 2022

Abstract
Emittance of the ion beam extracted from an ion source is dependent on the initial focusing action at the plasma sheath. The properties of the plasma sheath is further dependent on the local electric fields and charge densities around the sheath. Experiments are conducted for creating different sets of conditions around the plasma sheath in an H- multicusp filament ion source and the resulting emittance of the extracted H- ion beam is measured. Variation of beam emittance under different plasma densities, electrode voltages and gas flows are analysed.
Simulation of Beam Formation in the CERN Negative Ion Source for the Linac4 Accelerator
Authors: Vnuchenko A. , Lettry J. , Mochalskyy S. , Wünderlich D. , Fantz U. , Revel A. , Minea T. 
Published: April 2022

Abstract
Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of the beam formation is essential for optimizing the current and emittance of the H- ion source. We exploited the 3D PIC-Monte Carlo ONIX (Orsay Negative Ion eXtraction) code for studying H- beam formation processes in caesiated negative ion sources. The various geometries of the IS03 prototypes have been implemented into ONIX. The code, designed for neutral injector multi-aperture sources for fusion has been adapted to match the single-aperture extraction region of the Linac4 H- source. A plasma electrode designed to ensure radial metallic boundary conditions was produced and tested. The simulation results of the beam formation region at low plasma density to validate the functionality of the modified ONIX version are presented.
Comparison of ion source plasma responses to extraction grid bias between hydrogen and deuterium operations in NIFS-RNIS
Authors: Nakano H , Masaki S , Rattanawongnara E , Tsumori K , Ikeda K , Hamajima T , Nagaoka K , Osakabe M 
Published: April 2022

Abstract
An isotope effect of negative ion motion in plasma near a plasma grid (PG), which is a plasma-beam boundary grid, has been investigated in a negative hydrogen-ion source with the surface production process of the negative ion on the PG surface. Negative deuterium-ion (D-) density was higher than negative hydrogen-ion (H-) density in the condition without extraction-grid bias (V
egb) and approached the H- density in the condition with V
egb. Thus, the D- density responded stronger than the H- density to the V
egb. The density of the negative hydrogen-ion isotopes and the density response to the V
egb have been organized into respective identical trends by momenta of isotopes emitting from the PG. The Larmor motion can be a dominant mechanism of the negative ion transport from the PG to the plasma.