bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase transitions in 2d orders coupled to the Ising model
Authors: Glaser Lisa
Published: March 2021

The 2d orders are a sub class of causal sets, which is especially amenable to computer simulations. Past work has shown that the 2d orders have a first order phase transition between a random and a crystalline phase. When coupling the 2d orders to the Ising model, this phase transition coincides with the transition of the Ising model. The coupled system also shows a new phase, at negative β, where the Ising model induces the geometric transition. In this article we examine the phase transitions of the coupled system, to determine their order, as well as how they scale when the system size is changed. We find that the transition at positive β seems to be of mixed order, while the two transitions at negative β appear continuous/first order for the Ising model/the geometry respectively. The scaling of the observables with the system size on the other hand is fairly simple, and does, where applicable, agree with that found for the pure 2d orders. We find that the location of these transitions has fractional scaling in the system size.
Canonical Noether and the energy–momentum non-uniqueness problem in linearized gravity
Authors: Baker Mark Robert
Published: March 2021

Recent research has highlighted the non-uniqueness problem of energy–momentum tensors in linearized gravity; many different tensors are published in the literature, yet for particular calculations a unique expression is required. It has been shown that (A) none of these spin-2 energy–momentum tensors are gauge invariant and (B) the Noether and Hilbert energy–momentum tensors are not, in general, equivalent; therefore uniqueness criteria is difficult to specify. Conventional wisdom states that the various published energy–momentum tensors for linearized gravity can be derived from the canonical Noether energy–momentum tensor of spin-2 Fierz-Pauli theory by adding ad-hoc ‘improvement’ terms (the divergence of a superpotential and terms proportional to the equations of motion), that these superpotentials are in some way unique or physically significant, and that this implies some meaningful connection to the Noether procedure. To explore this question of uniqueness, we consider the most general possible energy–momentum tensor for linearized gravity with free coefficients using the Fock method. We express this most general energy–momentum tensor as the canonical Noether tensor, supplemented by the divergence of a general superpotential plus all possible terms proportional to the equations of motion. We then derive systems of equations which we solve in order to prove several key results for spin-2 Fierz–Pauli theory, most notably that there are infinitely many conserved energy–momentum tensors derivable from the ‘improvement’ method, and there are infinitely many conserved symmetric energy–momentum tensors that follow from specifying the Belinfante superpotential alone. This disproves several recent claims that the Belinfante tensor is uniquely associated to the Hilbert tensor in spin-2 Fierz–Pauli theory. We give two new energy–momentum tensors of this form. Most importantly, since there are infinitely many energy–momentum tensors of this form, no meaningful or unique connection to Noether’s first theorem can be claimed by application of the canonical Noether ‘improvement’ method.
Electric-dipole forbidden transitions for probing atomic state preparation: the case of the Autler–Townes effect
Authors: Ramírez-Martínez F , Ponciano-Ojeda F , Hernández-Gómez S , Del Ángel A , Mojica-Casique C , Hoyos-Campo L M , Flores-Mijangos J , Sahagún D , Jáuregui R , Jiménez-Mier J
Published: March 2021

This work demonstrates an scheme in which a weak electric quadrupole (E2) transition with a controlled frequency detuning in a ladder configuration is used as an extremely non-perturbing probe for precisely identifying subtle details of the effects driven by AC fields coupling atomic states and the preparation of quantum states. For this purpose, we provide a precise experimental and theoretical study of the Autler Townes (AT) effect derived from a strong electric dipole transition stimulated by a resonant laser beam and probed by the E2 interaction. The experiment was carried out for a 87Rb atomic gas at room temperature in a velocity-selective scheme. The AT effect was monitored via the splitting of the fluorescence spectra associated with the spontaneous decay to the ground state. The theoretical description incorporates the modification of standard few-level schemes introduced by forbidden electric-dipole transitions selection rules. We develop an analytic ladder three-level scheme to approximate the cyclic 5S1/2
F = 2 → 5P3/2
F = 3 → 6P3/2
F = 1, 2, 3 → 5S1/2
F = 2 path. Other levels that could have effects on the fluorescence are included via a fourth level with effective parameters. Doppler effects and finite bandwidths of the laser beams are included in the theoretical model to closely reproduce the experimental results.
Effect of gaps on magnetic noise of cylindrical ferrite shield
Authors: Lu Jixi , Sun Chang , Ma Danyue , Yang Ke , Zhao Junpeng , Han Bangcheng , Quan Wei , Zhang Ning , Ding Ming
Published: March 2021

Cylindrical ferrite shields consisting of multiple annuli can provide low-magnetic-noise environments. However, the gaps between different parts of the shield adversely affect the shielding performance. In this study, we numerically study the influence of the gaps on both the axial and radial magnetic noise of the multi-annular ferrite shield with different gap widths, permeabilities, and aspect ratios using the generalized Nyquist relation and the finite element method. Our study indicates that as the gap width increases, the axial magnetic noise decreases, while the radial magnetic noise increases. For the shield with a gap width of 0.10 mm and an aspect ratio of one in our study, the axial magnetic noise decreases by 5.2%, and the radial magnetic noise increases by 8.3%–33.5%. The difference in the increase is related to the permeability, and gaps have smaller effect on the radial magnetic noise of the shield with lower permeabilities. Therefore, compared with the no-gap shield, the multi-annular ferrite shield can provide an even better low-magnetic-noise environment along the axial direction. Although the gaps can induce an increase of the radial magnetic noise, this detrimental effect can be suppressed significantly by using a ferrite material with lower permeability and reducing the gap width. Our findings can aid in the application and optimization of low-noise ferrite shields.
Mathematical modelling of the conductivity in CZTiS-CZSnS as a function of synthesis temperature
Authors: Mesa M Patarroyo , Báez Y T Castellanos , Cerón-Achicanoy M A , Gómez-Cuaspud J , Chaparro W Aperador , López E Vera
Published: March 2021

The electrical behavior of photovoltaic materials related with Cu2ZnTiS4and Cu2ZnSnS4materials were analyzed as function of synthesis temperature in accordance with a new mathematical model based on the Kramers–Kronig equations with a high reliability. The samples were obtained through a hydrothermal route and a subsequent thermal treatment of solids at 550 °C for 1 h under nitrogen flow (50 ml min−1). The characterization was done by x-ray diffraction, ultraviolet spectroscopy (UV), Raman spectroscopy, atomic force microscopy (AFM) and solid state impedance spectroscopy (IS) techniques. The structural characterization, confirm the obtention of a tetragonal material with spatial groupI-42m, oriented along (1 1 2) facet, with nanometric crystal sizes (5–6 nm). The AFM and Raman analysis confirm a high level of chemical homogeneity and correlation with the synthesis temperature, associated with the roughness of the samples. The UV spectroscopy confirm a band gap around 1.4–1.5 eV, evidencing the effectiveness of the synthesis process. The IS results at room temperature with a probability of 95%, confirm a high consistency of data with respect to values of real and imaginary impedance, allowing to obtain information of the conductance, reactance and inductance, achieving conductivity values around 10−5and 10−3Ω−1 m−1in comparison with traditional mathematical models used for this purpose.
Simplified chemical processed Cd1−x
Al
x
S thin films for high-performance photodetector applications
Authors: Deva Arun Kumar Karuppiah , Mele Paolo , Anitha M , Varadharajaperumal S , Alagarasan Devarajan , Alhokbany Norah S , Ahamad Tansir , Alshehri Saad M
Published: March 2021

In this present investigation, we report the effect of aluminum (Al) doping on the photoelectric performance of cadmium sulfide (CdS) thin films prepared by cost-effective automatic nebulizer spray method. The doping of Al concentrations varied from 1 at.% to 9 at.% in the steps of 3 at.%. X-ray diffraction (XRD) patterns show hexagonal crystal structure with polycrystalline nature and the enrichment of crystallite sizes as a function of Al doping concentrations. The formed impurity phase i.e. CdO might be helpful in enhancing the photoelectric performance by its additional photo-generated charge carriers. The optical studies confirm the maximum absorption showed in the visible spectral range with the corresponding minimum bandgap of 2.28 eV for 6 at.% of Al. The room temperature photoluminescence studies show an increase of near-band-edge (NBE) emission as a function of Al doping concentration and this NBE is close to the obtained bandgap in terms of wavelength. In addition, the observed red emission at 635 nm is due to the surface-related impurities or native defect states. From the present work, the observed responsivity (R), external quantum efficiency (EQE) and detectivity (D*) of the CdS:Al detectors are 8.64 AW−1, ∼2018% and 9.29 × 1011 jones, respectively for the optimum 6 at.% of CdS:Al film. The performance of CdS:Al films reported in this work are significantly improved when compared with literature reports. The present investigation, therefore offers a potential material, CdS:Al, as a photodetector for various scientific and industrial applications.
Structure-property correlations and scaling in the magnetic and magnetocaloric properties of GdCrO3 particles
Authors: Shi Jianhang , Sauyet Theodore , Dang Yanliu , Suib Steven L , Seehra Mohindar S , Jain Menka
Published: March 2021

The structure, magnetic, and magnetocaloric (MC) properties of orthorhombic nanocrystalline GdCrO3 with six particle sizes: ⟨d⟩ = 87, 103, 145, 224, 318, and 352 nm are reported. The particle size was tailored by annealing under different temperatures and estimated by scanning electron microscopy. With increase in ⟨d⟩, Goldschmidt tolerance factor t, orthorhombic strain s, and out-of-plane Cr–O1–Cr bond angle first decrease, reaching minimum values for ⟨d⟩ = 224 nm, and then increase for sample with ⟨d⟩ = 318 nm and 352 nm, thus showing a V-shaped variation. Temperature dependence of the magnetization (M) reveals an antiferromagnetic transition at

T

N

Cr

∼
168

K for ⟨d⟩ ⩾ 224 nm and

T

N

Cr

∼
167

K for ⟨d⟩ < 224 nm and an essentially d-independent spin-reorientation at T
SR = 9 K. M measured at 5 K and 7 T first increases with increase in ⟨d⟩, reaching maximum value for sample with ⟨d⟩ = 224 nm, and then decreases for samples with ⟨d⟩ = 318 nm and 352 nm, showing an inverted-V variation with ⟨d⟩. Similar ⟨d⟩-dependence is observed for the magnetic entropy change (MEC) and relative cooling power (RCP) showing a close relationship between the structural and magnetic properties of GdCrO3 nanoparticles investigated here. The 224 nm sample with the minimum values of t, s, and Cr–O1–Cr bond angle exhibits the maximum value of MEC (−ΔS) = 37.8 J kg−1 K−1 at 5 K under a field variation (ΔH) of 7 T and its large estimated RCP of 623.6 J Kg−1 is comparable with those of typical MC materials. Both (−ΔS) and RCP are shown to scale with the saturation magnetization M
S, suggesting that M
S is the crucial factor controlling their magnitudes. Assuming (−ΔS) ∼ (ΔH)
n
, the temperature dependence of n for the six samples are determined, n varying between 1.3 at 5 K to n = 2.2 at 130 K in line with its expected magnitudes based on mean-field theory. These results on structure-property correlations and scaling in GdCrO3 suggest that its MC properties are tunable for potential low-temperature magnetic refrigeration applications.
Growth of h-BN/graphene heterostructure using proximity catalysis
Authors: Yang Hui , Wang Bojun , Niu Xiaobin , Guo Guo-Ping
Published: March 2021

In this study, a proximity catalysis route was developed for the fast growth of graphene/h-BN vertical heterostructures on Cu foils, which shows much improved synthesis efficiency (500 times faster than other routes) and good crystalline quality graphene (large single crystalline length up to 10 μm). The key advantage of our synthesis route is the introduction of fresh Cu foil (or Cu foam) into the high-temperature zone using a turntable. At high temperatures, Cu vapor acts as a gaseous catalyst, which can reduce the energy barrier of graphene growth and promote the decomposition of carbon sources. Therefore, after the first layer of hexagonal boron nitride is grown on the Cu substrate, another layer of graphene can be grown by introducing a fresh catalyst. Our calculations have revealed the catalytic effect and graphene growth contribution of Cu vapor evaporated by the suspended catalyst. We also investigated the growth sequence of graphene from 1 to 24 carbon atoms on h-BN/Cu and determined the morphology evolution of these carbon clusters. In this regard, multilayer stacked heterogeneous structures can be synthesized, thus increasing their potential applications in high performance electronic devices and energy harvesting/transition directions.
Transfer learning from ECG to PPG for improved sleep staging from wrist-worn wearables
Authors: Li Qiao , Li Qichen , Cakmak Ayse S , Da Poian Giulia , Bliwise Donald L , Vaccarino Viola , Shah Amit J , Clifford Gari D
Published: March 2021

Objective. To develop a sleep staging method from wrist-worn accelerometry and the photoplethysmogram (PPG) by leveraging transfer learning from a large electrocardiogram (ECG) database. Approach. In previous work, we developed a deep convolutional neural network for sleep staging from ECG using the cross-spectrogram of ECG-derived respiration and instantaneous beat intervals, heart rate variability metrics, spectral characteristics, and signal quality measures derived from 5793 subjects in Sleep Heart Health Study (SHHS). We updated the weights of this model by transfer learning using PPG data derived from the Empatica E4 wristwatch worn by 105 subjects in the ‘Emory Twin Study Follow-up’ (ETSF) database, for whom overnight polysomnographic (PSG) scoring was available. The relative performance of PPG, and actigraphy (Act), plus combinations of these two signals, with and without transfer learning was assessed. Main results. The performance of our model with transfer learning showed higher accuracy (1–9 percentage points) and Cohen’s Kappa (0.01–0.13) than those without transfer learning for every classification category. Statistically significant, though relatively small, incremental differences in accuracy occurred for every classification category as tested with the McNemar test. The out-of-sample classification performance using features from PPG and actigraphy for four-class classification was Accuracy (Acc) = 68.62% and Kappa = 0.44. For two-class classification, the performance was Acc = 81.49% and Kappa = 0.58. Significance. We proposed a combined PPG and actigraphy-based sleep stage classification approach using transfer learning from a large ECG sleep database. Results demonstrate that the transfer learning approach improves estimates of sleep state. The use of automated beat detectors and quality metrics means human over-reading is not required, and the approach can be scaled for large cross-sectional or longitudinal studies using wrist-worn devices for sleep staging.
Plasma plume expansion with pulsed electron neutralization
Authors: Habl L , Lafleur T , Rafalskyi D , Chabert P
Published: March 2021

Electrons neutralizing the ion beam from a gridded ion source are typically provided by an external cathode. This cathode emits a continuous current that ensures quasi-neutrality of the plume, and current balance of the ion source. A new type of neutralization scheme has recently been identified in the context of radio-frequency (RF) biased ion sources, where instead of a continuous electron current, the plume is neutralized by electron pulses emitted from the same plasma source as the ion beam itself. In contrast to conventional gridded ion sources, experiments have shown that pulsed neutralization produces hot electrons with a strongly anisotropic energy distribution in the plume. By making use of a two-dimensional particle-in-cell (PIC) simulation, we analyze the pulsed neutralization and plasma expansion to understand the fundamental plume physics in these systems, and perform a direct comparison with the expansion observed in typical DC systems. Electron trapping in the near-field plume region is found to be critical for ensuring quasi-neutrality, and the plume potential is observed to be higher than the downstream acceleration grid potential to prevent excessive electron backstreaming into the plasma source. This potential difference results in the formation of high-energy electron beams that generate collective plume oscillations with frequencies above the applied RF frequency. A detailed parametric study is performed to investigate the influence of the pulse frequency, emission current, and capacitance between the source and outer surrounding boundaries. In particular, the pulse frequency and emission current have a significant effect on the resulting plume potential, and the effectiveness of the resulting ion beam neutralization.
Storing short single-photon-level optical pulses in Bose–Einstein condensates for high-performance quantum memory
Authors: Saglamyurek Erhan , Hrushevskyi Taras , Rastogi Anindya , Cooke Logan W , Smith Benjamin D , LeBlanc Lindsay J
Published: March 2021

Large-scale quantum networks require quantum memories featuring long-lived storage of non-classical light together with efficient, high-speed and reliable operation. The concurrent realization of these features is challenging due to inherent limitations of matter platforms and light–matter interaction protocols. Here, we propose an approach to overcome this obstacle, based on the implementation of the Autler–Townes-splitting (ATS) quantum-memory protocol on Bose–Einstein condensate (BEC) platform. We demonstrate a proof-of-principle of this approach by storing short pulses of single-photon-level light as a collective spin-excitation in a rubidium-BEC. For 20 ns long-pulses, we achieve an ultra-low-noise memory with an efficiency of 30% and lifetime of 15 μs. The non-adiabatic character of the ATS protocol (leading to high-speed and low-noise operation) in combination with the intrinsically large atomic densities and ultra-low temperatures of the BEC platform (offering highly efficient and long-lived storage) opens up a new avenue toward high-performance quantum memories.
First-principles study of mechanical and thermodynamic properties of W-V alloys
Authors: Cui Zilin , Zhang Xin , Xu Yuhong , Lei Guangjiu , Tang Changjian , Chen Xi , Li Heng , Liu Yangyang , Zhu Yiqin , Li Ming , Geng Shaofei , Liu Qijun , Ni Yuxiang , Liu Haifeng , Wang Xianqu , Huang Jie , Liu Hai , Cheng Jun
Published: March 2021

The lattice structure, mechanical properties, electronic structure and thermodynamic properties of W1−xVx alloys (x = 0, 0.0625, 0.125, 0.25, 0.3125, 0.5 and 1) were calculated and simulated by first-principles method based on DFT. The mechanical properties including Poisson’s ratio, elastic moduli and B/G ratio were analysed via V concentration. The simulated results showed the ductility of alloys getting improved while the strength decreased with the addition of vanadium. And we calculated the anisotropy of Young’s modules and ideal tensile strength. The projected density of states is calculated to analyse the electronic structure. Furthermore, thermodynamic properties like Debye temperature and low temperature heat capacity were also calculated in this work. All the results can provide reference for selecting plasma facing materials in fusion reactor design.
Double photoionization of atomic oxygen: Feshbach resonances in the two-electron continuum
Authors: Gorczyca T W , P Ballance C , Manson S T , Kilcoyne D , Stolte W C
Published: March 2021

We describe a joint experimental and theoretical investigation on oxygen double photoionization—the emission of two electrons from atomic oxygen following single photon absorption. High-resolution experimental measurements were performed at the Advanced Light Source, revealing sharp resonance structure superimposed on the more familiar Wannier-like, nearly-linear background. These resonance features are attributed to ionization-plus-excitation Feshbach resonances embedded in the double ionization continuum, doubly-excited states that lie above the double-ionization threshold. Such features are absent in the double photoionization cross section of He, or other quasi-two-electron systems, for which the doubly-ionized atomic core remains inert. For a corresponding theoretical analysis, the R-matrix with pseudostates (RMPS) method was invoked by calculating final-state, two-electron resonances-plus-continua wavefunctions and corresponding single-photon absorption cross sections. Overall agreement is found in the direct, background double photoionization cross section. However, the RMPS method, using a small basis due to practical computational limitations, was unable to reproduce quantitatively the smooth background or the sharper resonance features observed in the measurements, showing instead large-scale oscillations about the experimental background, and characteristic pseudoresonance jitter, associated with an insufficient convergence of the pseudostate representation to the true two-electron infinite series of Feshbach resonances embedded in the two-electron continuum. The prominent resonance structure observed highlights the need to consider multiple excitation processes in atoms more complex than He or quasi-two-electron systems.
Orbital and Stellar Parameters for 2M06464003+0109157: A Double-lined Eclipsing Binary of Spotted, Sub-solar Twins
Authors: Miller Annaliese , Kounkel Marina , Boggio Chase , Covey Kevin , Price-Whelan Adrian M.
Published: March 2021

We calculated physical and orbital properties for 2M06464003+0109157, a 1.06 day eclipsing double lined spectroscopic binary. We modeled the system’s ASAS-SN and TESS light curves, measuring the system’s inclination and radii of each component. Extracting radial velocities for each component from 6 SDSS/APOGEE spectra, we measured the system’s mass ratio and performed a full orbital fit. Our analysis indicates that 2M06464003+0109157 has components with nearly equal masses (m
1/m
2 = 0.99 ± 0.01; M
1,2 = 0.57 ± 0.015 M
☉) and comparable radii (R
1 = 0.66 ± 0.05 R
☉, R
2 = 0.57 ± 0.06 R
☉). The solution required two star spots to incorporate the out of eclipse variation that is seen in the light curve. We report our full characterization of this system, and prospects for similar analyses using survey data to measure precise physical and orbital properties for EBs.
Synthesis and characterizations of boron and nitrogen co-doped high pressure and high temperature large single-crystal diamonds with increased mobility*
Authors: Miao Xin-Yuan , Ma Hong-An , Zhang Zhuang-Fei , Chen Liang-Chao , Zhou Li-Juan , Li Min-Si , Jia Xiao-Peng
Published: March 2021

We synthesized and investigated the boron-doped and boron/nitrogen co-doped large single-crystal diamonds grown under high pressure and high temperature (HPHT) conditions (5.9 GPa and 1290 °C). The optical and electrical properties and surface characterization of the synthetic diamonds were observed and studied. Incorporation of nitrogen significantly changed the growth trace on surface of boron-containing diamonds. X-ray photoelectron spectroscopy (XPS) measurements showed good evident that nitrogen atoms successfully incorporate into the boron-rich diamond lattice and bond with carbon atoms. Raman spectra showed differences on the as-grown surfaces and interior between boron-doped and boron/nitrogen co-doped diamonds. Fourier transform infrared spectroscopy (FTIR) measurements indicated that the nitrogen incorporation significantly decreases the boron acceptor concentration in diamonds. Hall measurements at room temperature showed that the carriers concentration of the co-doped diamonds decreases, and the mobility increases obviously . The highest hole mobility of sample BNDD-1 reached 980 cm2⋅V−1⋅s−1, possible reasons were discussed in the paper.
Beryllium-driven structural evolution at the divertor surface
Authors: Cusentino M.A. , Wood M.A. , Thompson A.P.
Published: March 2021

Erosion of the beryllium first wall material in tokamak reactors has been shown to result in transport and deposition on the tungsten divertor. Experimental studies of beryllium implantation in tungsten indicate that mixed W–Be intermetallic deposits can form, which have lower melting temperatures than tungsten and can trap tritium at higher rates. To better understand the formation and growth rate of these intermetallics, cumulative molecular dynamics (MD) simulations of both high and low energy beryllium deposition in tungsten were performed. In both cases, a W–Be mixed material layer (MML) emerged at the surface within several nanoseconds, either through energetic implantation or a thermally-activated exchange mechanism, respectively. While some ordering of the material into intermetallics occurred, fully ordered structures did not emerge from the deposition simulations. Targeted MD simulations of the MML to further study the rate of Be diffusion and intermetallic growth rates indicate that for both cases, the gradual re-structuring of the material into an ordered intermetallic layer is beyond accessible MD time scales(⩽1 μs). However, the rapid formation of the MML within nanoseconds indicates that beryllium deposition can influence other plasma species interactions at the surface and begin to alter the tungsten material properties. Therefore, beryllium deposition on the divertor surface, even in small amounts, is likely to cause significant changes in plasma-surface interactions and will need to be considered in future studies.
Beam modulation and bump-on-tail effects on Alfvén eigenmode stability in DIII-D
Authors: Van Zeeland M.A. , Bardoczi L. , Gonzalez-Martin J. , Heidbrink W.W. , Podesta M. , Austin M. , Collins C.S. , Du X.D. , Duarte V.N. , Garcia-Munoz M. , Munaretto S. , Thome K.E. , Todo Y. , Wang X.
Published: March 2021

Beam modulation effects on Alfvén eigenmode stability have been investigated in a recent DIII-D experiment and show that variations in neutral beam modulation period can have an impact on the beam driven Alfvén eigenmode spectrum and resultant fast ion transport despite similar time-averaged input power. The experiment was carried out during the current ramp phase of L-mode discharges heated with sub-Alfvénic 50–80 kV deuterium neutral beams that drive a variety of Alfvén eigenmodes unstable. The modulation period of two interleaved beams with different tangency radii was varied from shot to shot in order to modify the relative time dependent mix of the beam pitch angle distribution as well as the persistence of a bump-on-tail feature near the injection energy (a feature confirmed by imaging neutral particle analyzer measurements). As the beam modulation period is varied from 7 ms to 30 ms on/off (typical full energy slowing down time of τ
slow ≈ 50 ms at mid-radius), toroidicity-induced Alfvén eigenmodes (TAEs) located in the outer periphery of the plasma become intermittent and coincident with the more tangential beam. Core mode activity changes from reversed shear Alfvén eigenmodes (RSAEs) to a mix of RSAE and beta-induced Alfvén eigenmodes. Discharges with 30 ms on/off period do not have a persistent bump-on-tail feature, have the lowest average mode amplitude and least fast ion transport. Detailed analysis of an individual TAE using TRANSP kick modeling (Monte Carlo evolution of the distribution function with probabilistic ‘kicks’ by the AEs) and the resistive MHD code with kinetic fast ions, MEGA, find no strong role of energy gradient drive due to bump-on-tail features. Instead, the observed TAE modulation with interleaved beams is likely a pitch angle dependent result combined with slowing down of the tangential beam between pulses. For the conditions investigated, bump-on-tail contributions to TAE drive were found to be 5% or less of the total drive at any given time.
Identification heavy metal pollution in biological samples around cement plant in Aceh, Indonesia using Laser Induced Breakdown Spectroscopy ( LIBS)
Authors: Yuza N , Ajrina H , Lahna K , Ramli M , Suliyanti M M , Idris N
Published: March 2021

A study was conducted for identification of heavy metal pollution from biological sample as a potential proxy of environmental pollution due to industrial waste. The identification was conducted using the emerging analytical tool, namely laser induced breakdown spectroscopy (LIBS). The sample was collected from seawater near a cement plant in Aceh. Samples is a conch shell. The sample was dried in the open air and then prepared in the form of a pellet. The analysis was made by generating a plasma on the pellet sample using an Nd-YAG laser with a wavelength of 1,064 nm which is focused with a lens that has a focal length (f = 15 cm) by varying laser energy under low pressure of 3 Torr of air surrounding gas. Emission from the generated plasma was transmitted to the Maya2000 spectrometer optical detector using an optical fiber and then the emission spectrum of each element is displayed on the monitor. The results showed that the snail shell contained the salts and heavy metal elements K, Pb, Gd, Se, Mg, Rb, Fe, and Xe. Thus, it can be concluded that the heavy metal elements Pb and Fe can be detected LIBS technique from the biological sample.
Dynamic networking and channel access strategies of hybrid communication network for intelligent ship
Authors: Huang Xiaoyun , Liu Wen
Published: March 2021

Based on the architecture of the hybrid maritime communication system, the shipboard hybrid communication network structure is presented for multi-network and multi-mode transmission networking equipment of intelligent ship. The paper briefly introduces the proposed dynamic networking and channel access strategies for the communication system of ship-to-ship and ship-to-shore, as well as the communication data types and priorities, quantitative description for each data and performance of each link. Those strategies make the shipboard communication link will be established automatically and flexibly with many modern communication technologies which will be selected depending on the current conditions of the radio channel and the requirements and preferences of the user. Simulation experiments show that those strategies could achieve the flexible and efficient data transmission with high throughput and low delay, using the advantage of each communication technology.
CFD numerical simulations of inertia stopping of a very large gas carrier using overset grid technology and body-force propeller
Authors: Hao Hao , Weimin Chen , Zixin Wu
Published: March 2021

With the development of International shipping, waterways all over the world are becoming increasingly crowded. Research on inertia stopping ability of large ships is essential to voyage safety. At present, the inertial stopping of ship is mainly measured by ship model test, and there is little work to study the performance using CFD technology. STARCCM+based on the ship 6-DOF motion and overset grid technology and body-force method are used to numerically simulate the inertia stopping maneuver of a very large gas carrier. By controlling the rotation speed of the propeller, the ship is in a stable state of motion. Then set the speed to zero.The motion state and detailed flow field information of the ship model during motion can be got by solving viscous flow field. To verify the accuracy of numerical prediction results, ship model test is launched. Both the trajectory of the ship and the value of the characteristic parameter match very well.
Numerical study on the scale effect of high-skew propeller E1619
Authors: Liu L W , Chen M X , Wu Y H , Zhang Z G , Wang X Z
Published: March 2021

In this study, a large skewed propeller INSEAN E1619 model with 7 blades working in open water conditions has been numerically simulated by an inhouse URANS (Unsteady Reynolds-averaged Navier-Stokes) code coupled with dynamic overset grid approach. Grid and time-step sensitivity analysis of the propeller model has been conducted and the numerical results have been compared with available experimental data performed by INSEAN aimed to validate the numerical method. Propeller open water characteristics have been compared for models with different scales at given advance coefficient to evaluate scale effect of this high-skew propeller. Non-dimensional pressures on different scaled models have been compared between models with different scales. Results show that propeller’s thrust and torque increase with the increase of propeller scale, which is mainly due to the increase of pressure component. It could be found that the pressure on suction side near the trailing edge decreases with the increase of propeller’s scale.
Millimeterwave reflectivity tests on MetOp-SG MWI On Board Calibration Target
Authors: Simonetto A. , Cuttaia F. , Biggi M. , Lapini R. , Lupi T. , Mandolesi N. , Matticari G. , Morgante G. , Salaris P. , Salghetti Drioli L. , Terenzi L.
Published: March 2021

The On-Board Calibration Target (OBCT) for the Micro-Wave
Imager instrument on the MetOp-SG-B satellite is a microwave
blackbody, operating between 14 and 220 GHz (extended frequency
range), providing the MWI receivers with a warm calibration
reference. It is designed for an emissivity better than 0,9999 over
the MWI 26 channels (including dual polarization channels). The OBCT
radiometric performance has been extensively verified in ISTP
(formerly IFP) microwave laboratory, by measuring reflectivity over
the extended bandwidth. Measurement techniques and results are
described in this paper, showing that the OBCT models tested so far
are fully compliant with the MWI requirements.
Effect of aerosol-induced snow darkening on the direct radiative effect of aerosols over the Himalayan region
Authors: Usha K H , Nair Vijayakumar S , Babu S Suresh
Published: March 2021

Regional heterogeneity in direct and snow albedo forcing of aerosols over the Himalayan cryosphere was investigated using a regional climate model coupled with the community land model having snow, ice and aerosol radiation module. Deposition of absorbing aerosols like dust (natural) and black carbon (BC) (anthropogenic) decreases the snow albedo (snow darkening) over the Himalayas. Western Himalayas experiences a large reduction in the snow albedo (0.037) despite having lower BC mass concentration compared to central (0.014) and eastern (0.005) Himalayas. The contribution of BC and dust to the snow albedo reduction is comparable over the western and eastern Himalayas. The inclusion of aerosol-induced snow darkening in to the model reduces its bias with respect to the satellite derived surface albedo by 59%, 53% and 35% over western, central and eastern Himalayas respectively during the spring season. Since surface albedo decides the sign and magnitude of aerosol direct radiative forcing, aerosol induced snow darkening significantly affects the direct radiative effects of aerosols. Hence, the aerosol-induced decrease in snow albedo causes an early reversal in the sign of aerosol direct radiative forcing at the top of the atmosphere from warming to cooling over the western and central Himalayas, which can have implications in the radiation balance and water security over the region.
An exact solution to asymptotic Bethe equation
Authors: Miao Yuan
Published: March 2021

We present an exact solution to the asymptotic Bethe equation of weakly anisotropic Heisenberg spin chain, which is a set of non-linear algebraic equations. The solution describes the low-energy excitations above ferromagnetic ground state with fixed magnetisation, and it has a close relation to generalised Jacobi polynomial. It is equivalent to a generalised Stieltjes problem and in the continuous limit, it becomes a Riemann–Hilbert problem closely related to the finite-gap solutions of classical Landau–Lifshitz field theory.
The Bloch vectors formalism for a finite-dimensional quantum system
Authors: Loubenets Elena R , Kulakov Maxim S
Published: March 2021

In the present article, we consistently develop the main issues of the Bloch vectors formalism for an arbitrary finite-dimensional quantum system. In the frame of this formalism, qudit states and their evolution in time, qudit observables and their expectations, entanglement and nonlocality, etc are expressed in terms of the Bloch vectors—the vectors in the Euclidean space

R

d

2

−
1

, arising under decompositions of observables and states in different operator bases. Within this formalism, we specify for all d ⩾ 2 the set of Bloch vectors of traceless qudit observables and describe its properties; also, find for the sets of the Bloch vectors of qudit states, pure and mixed, the new compact expressions in terms of the operator norms that explicitly reveal the general properties of these sets and have the unified form for all d ⩾ 2. For the sets of the Bloch vectors of qudit states under the generalized Gell‐Mann representation, these general properties cannot be analytically extracted from the known equivalent specifications of these sets via the system of algebraic equations. We derive the general equations describing the time evolution of the Bloch vector of a qudit state if a qudit system is isolated and if it is open and find for both cases the main properties of the Bloch vector evolution in time. For a pure bipartite state of a dimension d
1 × d
2, we quantify its entanglement via the characteristics of the Bloch vectors for its reduced states. The introduced general formalism is important both for the theoretical analysis of quantum system properties and for quantum applications, in particular, for optimal quantum control, since, for systems where states are described by vectors in the Euclidean space, the methods of optimal control, analytical and numerical, are well developed.
Design and Fabrication of an Ablative Pyrolyzer for Production of Bio- lubricants and chemicals in Oil Well Drilling Application
Authors: Adegoke S.O. , Adeleke A.A. , Ikubanni P.P. , Falode A.O , Alawode A.J. , Agboola O.O. , Adediran A.A.
Published: March 2021

In this study, an ablative pyrolyser having 27.1 cm inner diameter, 41.2 cm outer diameter, the full chamber height of 74.7 cm and chamber volume of 40 litres was designed and fabricated. 150KW heater was wounded around the reactor chamber made of stainless steel to provide a higher temperature of up to 1400 °C. The -40 to 105°C capacity heat resistance wires were used to conduct the heater into the electrical panel which has several components such as the contactor, temperature controller, thermocouple wire and so on to give a particular desired working temperature. This pyrolyser applies technology of thermal energy in the heated walls of the pyrolyser being transferred to the biomass by conduction in the absence of oxygen for onward disintegration into gas, bio-oil, and biochar. After fabrication, 12 kg each of Tectona grandis and Rhopalosiphum maidis was fed into the reactor and pyrolyzed at 500 °C, the bio-oil product for both samples were mixed together and distilled at 120 °C and the bio-oil distillate was characterized for density, kinematic viscosity, pH, acid value and free fatty acid content. The bio-oil distillate shows a density of 0.960 g/cc, pH of 7.2, kinematic viscosity of 84 cst and acid value of 42.20 compared to the bio oil crude which showed higher values. This pyrolyser has been found on average to melt 12 kg each of Tectona grandis and Rhopalosiphum maidis to 5353 and 3493 g crude bio-oil respectively for a period of at least 3 h. The mass of bio-char for tectona grandis and Rhopalosiphum maidis were 3325 and 2614 g respectively while the reactor requires 8 h to cool before discharging the bio-char from the reactor. This research work can provide a basic designing formula for effective and workable ablative pyrolyzer fabrication for Nigerian wastes having high energy content.
Socio-Cultural Resilience to Domestic Space Change, the Benin Traditional City Experience, Nigeria
Authors: Ekhaese E N , Evbuoma I K , George T O
Published: March 2021

Research over time has revealed that activity spaces in domestic home have undergone evolution, adaptation and resilience over the years across Benin residential zones, Nigeria. Space segments/activities sections like cooking/eating, household goods storage, visitors and conveniences sections have somehow remain unchanged in terms of function, meaning, and arrangement. The study identified socio-cultural factors as responsible for resilience of domestic space to change in Benin domestic architecture across Benin City. The paper engaged both qualitative and quantitative research method. Triangulation was adopted for collection through focused group discussion using Semi-structured interview guide, questionnaire, observation guide and photographs. Factor analysis was use to analysis of data in order to reduce the identified socio-cultural factors to sizeable portion. The finding showed that, whilst some activity space, it size and location have evolved in Benin contemporary architecture, the style has remained intact. For instance some activity spaces in some residential zone of the city have been adapted to suit the new realities. Further observation itemised the socio-cultural factors that are responsible for resilient to change in Benin domestic architecture. Result of research underscores the role of culture in process of architectural development amidst rapid urbanization. Research upon completion is expected to be a good case study for measuring resilience to evolution of spaces in typical house setting in any African traditional city.
The role of solvent additive in metal nano-composite doped thin film organic solar cell
Authors: Kesinro R. O. , Boyo A. O , Akinyemi M. L. , Hamed M.S.G. , Kaviyarasu K. , Mola G. T. , Emetere M. E. , Aizebeokhai A. P.
Published: March 2021

In this study, organic solar cells (OSCs) were designed using the solution processing method based on spin coating. The influence of solvent additive (1-chloronapthalene (CN)) and cadmium doped barium nitrate nanoparticle incorporated into the photoactive medium based on poly(3-hexylthiophene-2,5-diyl (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was investigated. The power conversion efficiency of the pristine device was compared to the power conversion efficiency of the devices fabricated with 30v% of 1- chloronapthalene and different weight concentrations of nanoparticles. An optimum efficiency of 3.55 % was attained at 0.3 wt.% with solvent additive compared to 3.25 % obtained for the pristine device. This increase is attributed to a rise in charge transport of 5.32 × 10−2cm2V−1s−1. Further investigation on the morphological properties of the nanoparticles reveals the crystalline nature of the nanoparticle.
Role of Biomaterials in Automation.
Authors: Fayomi O. S. I. , Adedeji A.A. , Agboola O. , Ajala M.O , Bolu C.A , Banjo S.O. , Udoye N. E.
Published: March 2021

Technology in its real sense is in an advanced state to an extent that automation is the present-day mode of operating machinery and equipment. This technique of operating or controlling a process using a highly automatic means via electronic devices thereby reducing the human interface to a minimum, if not rather than eliminating it completely. Transformation of the global workforce has already begun through automation with innovations of robotics, artificial intelligence remote connectivity, additive manufacturing and medical innovations employing the automated means of delivering or administering drugs and performing surgery on patients. In the present day, various forms of automation are increasingly taking over the place of human thereby, putting a threat to supplant it. The role of biomaterials in automation is the main objective in this discuss.

The study revealed that metals play a major role in biomaterials due to its excellent thermal conductivity and mechanical properties.
The nexus of climate change, urban infrastructure and sustainable development in developing countries
Authors: Oloke O.C. , Fayomi O.S.I. , Oluwatayo A. , Adagunodo T.A. , Akinwumi I.I. , Amusan L.M.
Published: March 2021

This study weighed in on the topical issue of climate change impacts and sustainable urban development in developing countries. Climate change is a global challenge that is much discussed at national and international fora. The study reflects on the lot and plight of cities and peri-urban communities in developing countries in the face of lopsided attention on climate change. Extant studies, articles, local and international reports on climate change, urbanization and infrastructure, extant literatures were reviewed to establish the perspective and position of the study. The study examined the global threats of climate change and the local impact of disasters to urban dwellers in developing countries like Nigeria. It further shed light on urbanization process and the state of infrastructure in developing countries. Vulnerability of cities in the areas of infrastructure was brought to the fore with a view to improving the capacity and preparedness against climate change impact. Concepts of climate change, urbanization challenge, urban infrastructure, sustainable development were reviewed to contextualize the study. The study concluded by advocating for positive urbanization to mitigate the effect of climate change and foster sustainable development agenda in developing countries.
Tropospheric attenuation on Satellite-aircraft propagation: A concise review
Authors: Arijaje T. E , Omotosho T. V , Aizebeokhai A. P , Akinwumi S. O
Published: March 2021

The attenuation time together with the Complementary Cumulative Distribution Function of attenuation values play a vital role in the design of communication systems. Passengers on-board during flight can be connected to the internet either via satellite or earth-station depending on the nature of the flight. For long distance flight, this internet connectivity is provided through satellite when the aircraft is flying at the upper troposphere. However, the satellite-aircraft link is subject to attenuation due to the troposphere. A model to characterize the channel has been proposed. In particular, a methodology for the synthesis of attenuation on aircraft-satellite is given by ITU-R P2041 recommendation. However, it has been shown that the impact of tropospheric parameters such as rainfall, cloud, gases etc. On the satellite-aircraft link at different frequencies are insignificant (i.e decreases with height) on the upper troposphere since the aircraft is flying (about 12 km) above the rain height (5 km). The findings will be useful for researchers, scientists and the aviation industries in planning, design and establishing link budget for aircraft-satellite path.