Surface Field Research Articles

Neutron star accretion events in AGN discs: mutimessenger implications

ABSTRACT This paper investigates the accretion of neutron stars (NSs) in active galactic nucleus (AGN) accretion discs. We classify potential accretion modes of NSs in AGN discs, proposing a hierarchical model of NS accretion: accretion flow from the Bondi sphere to accretion columns. The accretion of NSs in AGN discs differs from that of BHs, especially within the scale of the NS’s magnetosphere due to its hard surface and magnetic field. As the accretion flow approaches the magnetosphere, the magnetic fields guide the accretion flow to form accretion columns, primarily dominated by neutrinos. While neutrinos generated from single NS accretion may not have observable effects, considering the all-sky background, they contribute to the neutrino background in the sub-MeV energy range comparable to that of supernova explosions. NS accretion may also lead to the generation of mass quadrupole moments, consequently generating gravitational waves (GWs). The GWs, which exhibit characteristic effects like periodic modulations and echoes, could be observed by third-generation GW detectors. The emission of neutrinos and GWs carries away energy and angular momentum brought by accretion, reducing the feedback effect on the AGN disc. This results in an exceptionally high NS accretion rate, leading to a collapse time-scale shorter than the migration-merge time-scale, making it less likely that binary NS mergers originate from AGN discs.

Efficiency enhancement above 31 % of Sb2Se3 solar cells with optimizing various BSF layer

Recent advancements in solar technology have increased the acceptance of antimony selenide (Sb2Se3) due to its advantageous properties. This study aims to enhance the performance of the Sb2Se3 structure by using tungsten disulfide (WS2) as the window layer and copper zinc tin selenide (CZTSe) as the back surface field (BSF) layer, utilizing SCAPS-1D (solar cell and capacitance simulator). An initial investigation of seven potential BSF layers identified CZTSe as the best choice for improving power conversion efficiency (PCE). By carefully simulating various parameters, including the thicknesses of the absorber and window layers, donor and acceptor densities, defect density, shunt resistance, and series resistance, significant performance improvements were achieved. Without the BSF layer, the cell showed a PCE of 28.20 % along with specific values for short circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF). The addition of the BSF layer increased the PCE to 31.52 %, along with enhancements in JSC, VOC, and FF. These results highlight the potential of this approach for developing high-performance Sb2Se3 based solar cells, surpassing conventional designs.

The fabrication and research of pH-responsive cement-based materials with switchable wettability

Recently, intelligent responsive materials have received increasing attention due to the controllability of their wettability. However, research has primarily focused on the surface properties of materials such as sponges and copper meshes, with a notable lack of investigation into cement-based materials in this regard. Currently, multi-functionality has become an inevitable trend in the development of cement-based materials. The controllable and adjustable wettability of cement-based materials can further expand their application scope. In this article, saturated fatty acids and dicarboxylic acids were selected to modify cement-based materials, fully utilizing their rich hydroxyl characteristics. Firstly, the feasibility of developing pH-stimuli-responsive surfaces on cement-based substrates with chosen raw materials was rapidly verified using the immersion method. When the mass fraction of dicarboxylic acid in the modifier is between 60 % and 80 %, the modified substrate surface exhibits hydrophobicity towards neutral liquids and hydrophilicity towards alkaline liquids. Based on this, the corresponding sodium salts of organic acid were synthesized and used as additives, which were then mixed with cement to prepare modified cement-based materials with switchable wettability. Through acid solution treatment, the modified hardened cement paste can transform from initially hydrophilic to hydrophobic, and the conversion angle can reach 90°. This study broadens the application field of intelligent response surfaces and enriches the functionality of cement-based materials.

Development of Low-Cost c-Si-Based CPV Cells for a Solar Co-Generation Absorber in a Parabolic Trough Collector

Concentrator photovoltaics (CPVs) have demonstrated high electrical efficiencies and technological potential, especially when deployed in CPV–thermal (CPV-T) hybrid absorbers, in which the cells’ waste heat can be used to power industrial processes. However, the high cost of tracking systems and the predominant use of expensive multi-junction PV cells have caused the market of solar co-generation technologies to stall. This paper describes the development and testing of a low-cost alternative CPV cell based on crystalline silicone (c-Si) for use in a novel injection-molded parabolic hybrid solar collector, generating both, photovoltaic electricity and thermal power. The study covers two different c-Si cell technologies, namely, passive emitter rear contact (PERC) and aluminum back surface field (Al-BSF). Simulation design and manufacturing are described with special attention to fingerprinting in order to achieve high current carrying capacities for concentrated sunlight. It was determined that Al-BSF cells offer higher efficiencies than PERC for the considered use case. Solar simulator tests showed that the highly doped 4 cm2 cells (50 ohm/sq) reach efficiencies of 16.9% under 1 sun and 13.1% under 60 suns at 25 °C with a temperature coefficient of −0.069%(Abs)/K. Finally, options to further improve the cells are discussed and an outlook is given for deployment in a field-testing prototype.

Application of the Beauty of Meaning in Chinese Sculpture Art

Chinese sculpturing is a significant form of expression in traditional Chinese art. Like other traditional art forms, Chinese sculpture art is also deeply influenced by the philosophical ideas of its predecessors, striving for the beauty of subtle and implicit meaning in artistic expression. This article provides a brief interpretation of the beauty of meaning in Chinese sculpture art, with a focus on analyzing its application in Chinese sculpture art. This article analyzes the role of the beauty of meaning in the development of Chinese sculpture art from the fields of lines, blocks, surfaces, spatial patterns, and freehand brushwork, to provide reference and inspiration for relevant artists and sculpture designers.

Annual degradation rates and soiling losses of photovoltaic systems composed of recent crystalline silicon technologies in temperate climate

AbstractThe purpose of this study is to investigate the annual degradation rates of photovoltaic (PV) systems composed of PV modules based on recent crystalline silicon (c‐Si) PV technologies. We investigated the annual degradation rates of four PV systems composed of different c‐Si PV technologies, comprising p‐type multi‐crystalline silicon with a passivated emitter rear cell, n‐type silicon heterojunction, p‐type single‐crystalline silicon (sc‐Si) with an aluminum back surface field, and n‐type (sc‐Si) solar cell technologies. These systems were located in Gunma Prefecture in Japan and were measured over 6 years. Furthermore, the effects of soiling on the annual degradation rates of these PV systems were examined by partially surface cleaning the PV arrays two times. The results obtained indicate that the apparent annual degradation rates of the PV strings before surface cleaning were 0.8, 1.6, 1.4, and 1.2%/year, respectively, because of optical losses due to dust particles. However, the inherent annual degradation rates of the PV strings after surface cleaning were 0.1, 0.6, 0.0, and 0.3%/year, respectively. These low degradation rates indicate that the PV systems composed of the recent c‐Si PV technologies all offered reasonably stable performance that was reduced by 3.6%, 5.5%, 7.3%, and 4.8%, respectively because of the effects of surface soiling, although the surfaces of the PV arrays had been washed by plentiful rainfall under their humid subtropical climatic operating conditions.

Comparative simulation analysis of μc Si:H and SnS BSF layers in CIGS solar cells

In this paper, we presented Cu(In1-xGax)Se2 (CIGS) based solar cells in which hydrogenated microcrystalline silicon (μc Si:H) and tin sulfide (SnS) are used as back surface field (BSF) layers. In CIGS thin film solar cell technology, thickness serves a crucial factor. Optimizing absorber thickness reduces the usage of scarce and expensive materials such as indium (In) and gallium (Ga) in CIGS cells. Integrating a heavily doped layer between the absorber and the back surface, known as the back surface field (BSF) layer, in solar cell design is a successful strategy for minimizing the thickness of the absorber layer. The suggested configuration utilizes μc-Si:H and SnS as the back surface field (BSF) layer. The buffer layer in this configuration employs less harmful InP instead of the typically utilized CdS layer. All the simulation work is performed using SCAP-1D simulation tool. The utilization of μc Si:H and SnS BSF layers yields optimized efficiencies of 31.51% and 31.01%, respectively. This simulation work demonstrates that use of a proper BSF layer is very effective not only in performance enhancement but also in reducing absorber material thickness.

High-resolution spectroscopy of the intermediate polar EX Hydrae

EX Hya is one of the best studied, but still enigmatic intermediate polars. We present phase-resolved blue VLT/UVES high-resolution (λ/Δλ ≃ 16.000) spectra of EX Hya taken in January 2004. Our analysis involves a unique decomposition of the Balmer line profiles into the spin-modulated line wings that represent streaming motions in the magnetosphere and the orbital-phase modulated line core that represents the accretion disk. Spectral analysis and tomography show that the division line between the two is solidly located at ∣υrad ∣ ≃ 1200 km s−1, defining the inner edge of the accretion disk at rin ≃ 7 × 109 cm or ∼10R1 (WD radii). This large central hole allows an unimpeded view of the tall accretion curtain at the lower pole with a shock height up to hsh ∼ 1R1 that is required by X-ray and optical observations. Our results contradict models that advocate a small magnetosphere and a small inner disk hole. Equating rin with the magnetospheric radius in the orbital plane allows us to derive a magnetic moment of the WD of μ1 ≃ 1.3 × 1032 G cm3 and a surface field strength B1 ∼ 0.35 MG. Given a polar field strength Bp ≲ 1.0 MG, optical circular polarization is not expected. With an accretion rate Ṁ = 3.9 × 10−11 M⊙ yr−1, the accretion torque is Gacc ≃ 2.2 × 1033 g cm2 s−2. The magnetostatic torque is of similar magnitude, suggesting that EX Hya is not far from being synchronized. We measured the orbital radial-velocity amplitude of the WD, K1 = 58.7 ± 3.9 km s−1, and found a spin-dependent velocity modulation as well. The former is in perfect agreement with the mean velocity amplitude obtained by other researchers, confirming the published component masses M1 ≃ 0.79 M⊙ and M2 ≃ 0.11 M⊙.

Enhanced Surface Fields Driven by Fano Resonances in Silver Nanocube Dimers for Efficient Hot Electron Generation

Enhanced Surface Fields Driven by Fano Resonances in Silver Nanocube Dimers for Efficient Hot Electron Generation

Ozone, nitrogen dioxide, and PM2.5 estimation from observation-model machine learning fusion over S. Korea: Influence of observation density, chemical transport model resolution, and geostationary remotely sensed AOD

High-resolution multi-component estimates of ground-level air pollutants are necessary for assessing their impacts to human health, agriculture, and ecosystems. We demonstrate a high-resolution fusion and downscaling approach over South Korea for May 2016 and May 2021. Daily 1 km fine particulate matter (PM2.5), ozone (O3), and nitrogen dioxide (NO2) concentrations are calculated at ground level using a random forest machine learning (ML) algorithm, with predictors including reanalysis meteorology, satellite aerosol optical depth (AOD), and gridded surface fields from chemical transport models (CTM). The ML model is tested for May 2016, coinciding with the Korea-United States Air Quality Study (KORUS-AQ) intensive field campaign, and for May 2021, to allow incorporation of observations from the Geostationary Environment Monitoring Spectrometer (GEMS). In the tests for May 2016, the correlation coefficients (R) and root mean squared errors (RMSE) relative to withheld observations of daily-averaged pollutants in 10-fold cross-validation are promising: 0.93 (5.5 μg/m3), 0.90 (5.5 ppbv), and 0.95 (4.7 ppbv) for PM2.5, O3, and NO2, respectively. Relative performance is assessed for alternate choices of predictors: (a) 80-km global reanalysis Copernicus Atmosphere Monitoring Service (CAMS) vs. 4-km regional Weather Research and Forecasting model coupled with Chemistry (WRF-Chem); (b) AOD polar-orbiting Moderate Resolution Image Spectroradiometer (MODIS) Multi-Angle Implementation of Atmospheric Correction (MAIAC) vs. geostationary GEMS; and (c) variations in surface observation density. This study is among the very first to incorporate both CTM and GEMS AOD for building surface high resolution multiple air pollution predictions over South Korea.

Wetting and emergence of long-range couplings in arrays of fluid cells.

Critical wetting is of crucial importance for the phase behavior of a simple fluid or Ising magnet confined between walls that exert opposing surface fields so that one wall favors liquid (spin up), while the other favors gas (spin down). We show that arrays of boxes filled with fluid and linked by channels with appropriately chosen opposing walls can exhibit long-range cooperative effects on a length scale far exceeding the bulk correlation length. We give the theoretical foundations of these long-range couplings by using a lattice gas (Ising model) description of a system.

Performance optimization of earth abundant CZTS Kesterite solar cell with efficient interface engineering and back surface field

Performance optimization of earth abundant CZTS Kesterite solar cell with efficient interface engineering and back surface field

A theoretical analysis to reveal the prospects of MoS2 as a back surface field layer in TiS3-based near infrared photodetector

In this article, a photodetector based on TiS3 absorber material, featuring a narrow direct bandgap of 1 eV, has been simulated. Throughout this research, the J-V (current–voltage) curves and spectral responses have been explored by systematically varying the thickness, doping concentration, and defect density of specific layers. The JSC (short circuit current) and VOC (open circuit voltage) of the heterostructure photodetector are found to be 45.77 mA cm−2 and 0.693 V respectively. Also, the responsivity (R) and detectivity (D*) are 0.81 A W−1 and 2.19 × 1014 Jones at a light wavelength of 1100 nm. The spectral response exhibits significantly elevated values within the wavelength range of 800 nm to 1200 nm, indicating the device’s ability to detect light in the near-infrared (NIR) region effectively. The novel research offers valuable insights, emphasizing the material’s suitability for photodetector (PD) applications and signaling a promising direction for further research interest in photodetector development.

Green manuring alters reactive N losses and N pools in arable soils: A meta-regression study

Green manuring is a conservation agricultural practice that improves soil quality and crop yield. However, increasing the active nitrogen (N) and carbon (C) pools during green manure (GM) amendment may accelerate soil N transformation and stimulate N loss. Previous studies have reported the effects of cover crop incorporation on N2O emission; however, the driving mechanisms and other N losses remain unclear. Therefore, we conducted a comprehensive meta-analysis of 109 published articles (517 paired observations) to clarify the effects of GM amendment on soil reactive N (Nr) losses (N2O emissions, NH3 volatilization, and N leaching and runoff), N pools, and N cycling functional gene abundance. The results showed that green manuring increased soil microbial biomass N (MBN) and NO3−-N concentrations and stimulated N2O emission but significantly lowered N leaching and yield-scaled NH3 volatilization. Practices of green manuring made a dominant contribution to the variation in N2O emissions and NH3 volatilization after GM application. Furthermore, applying legume-based GM, using N derived from GM (GMN) as an additional input, and short-term GM amendment each stimulated N2O emissions. In contrast, adopting non-legume GM, using GMN to partially substitute mineral N, and applying GM to the soil surface or paddy field mitigated NH3 loss during GM amendment. Additionally, the variation in NH3 volatilization was positively related to soil pH and N application rate (NAR) but had a negative relationship with mean annual precipitation (MAP). This study highlighted the marked effects of green manuring on soil N retention and loss. Agricultural operations that adopt GM amendment should select suitable GM species and optimize mineral N inputs to minimize N loss.

Assessing lunar paleointensity variability during the 3.9 - 3.5 Ga high field epoch

Numerous paleomagnetic studies suggest that a lunar dynamo, with surface field intensities potentially as high as 40-100 µT, existed between ∼3.9 Ga and ∼3.5 Ga. This period is referred to as the High Field Epoch (HFE). However, the debate over the origin of magnetization recorded in lunar rocks still persists. In addition, whether the Moon could have sustained a continuously strong dynamo during the HFE remains unclear. To unravel the origin of magnetization preserved in lunar rocks and to better characterize the evolution of the ancient lunar dynamo, we conducted a comprehensive set of experiments including rock magnetic tests, electron microscopy, and paleomagnetic investigations on four HFE-aged Apollo 11 mare basalt samples: 10003, 10044, 10069, and 10071. Rock magnetic experiments and electron microscopy indicate that the remanence carriers are kamacite grains of varying sizes and domain states. Sample 10003 recorded a paleointensity of 54.10 ± 4.66 µT. Sample 10044, which was shocked (peak pressure >5 GPa), did not preserve a stable high coercivity remanent magnetization. Samples 10069 and 10071 recorded paleointensities of 61.46 ± 26.09 µT and 10.69 ± 2.87 µT, respectively. A series of hydrostatic pressure experiments, isothermal remanent magnetization (IRM) acquisition experiments, and viscous remanent magnetization (VRM) tests preclude the possibility of our samples containing shock remanent magnetization from transient impact-generated fields, IRM acquisition from exposure to spacecraft fields, and VRM acquisition from exposure to the Earth magnetic field. Overall, our study suggests that the source of these magnetizations was likely the lunar dynamo and may indicate nearly order-of-magnitude magnetic field fluctuations during the HFE.

In situ build surface topography determination in electron beam powder bed fusion

Electron optical imaging is the most promising process monitoring method in electron beam powder bed fusion. State of the art in modern machines is the installation of a single detector in the top center of the build chamber. Exemplary applications are the reconstruction of digital twins of manufactured parts to compare their dimensional accuracy or analysing the top surface of each layer to identify surface features like pores or material transport. Multi-detector systems are currently under research and have shown great potential in reconstructing the surface topography in situ. A recently developed ray tracing model, describing the image formation process, allows to formulate design guide lines for multi-detector systems and provides a method for the computation of the normal vector field of the build surface. This work utilizes the recent progress and presents a newly developed four-detector system and an updated computation chain, which enable build surface topography reconstruction in situ in every layer of a build process. The computation chain contains a normal integration algorithm, which employs Tikhonov regularization to cope with measurement irregularities. The integration method is validated with ex situ measured as-built surfaces. Additionally, first applications are demonstrated and connections to process parameter changes illustrated.

A Systematic Study on the Physicochemical Interactions Between Polymeric Micelles and Mucin: Toward the Development of Optimal Drug Delivery Nanocarriers

AbstractThe optimal performance of drug delivery formulations, including polymeric nanoparticles, relies on particle distribution throughout the body and the interactions with biological barriers, particularly mucosal layers, which often limit their potential. A systematic and comprehensive study is presented through a multidisciplinary approach combining conventional and novel techniques for in vitro studies to understand the key molecular interactions between polymeric micelles and mucin. The results shows that polymeric micelles are integrates within the mucin layer, mirroring its viscoelastic properties, evidenced as a dissipation difference of 0.1 ± 0.44, measured by quartz crystal microbalance with dissipation. Surface‐enhanced Raman scattering reveals predominant hydrogen bonding within the mucin's hydrophilic core, while the isothermal titration calorimetry method confirms multiple non‐specific binding sites on the protein backbone. By performing the periodic acid‐Schiff stain assay, a binding amount of 0.20 mg of mucin per milligram of nanoparticles is quantified. Furthermore, motility studies show the surface binding of mucin on the polymeric nanoparticles influencing their Brownian motion. This study sheds light toward the improvement for a better drug delivery formulation and fabrication of optimal nanoparticle colloidal systems, which can advance translational drug delivery technologies into clinical application while enriching the field of surface and colloidal chemistry.

Photovoltaic efficacy of CNGS as BSF and second absorber for CIGS thin film solar cells- numerical approach by SCAPS-1D framework

Solar cells based on CIGS have outperformed many thin film solar cells using other absorbers. A prospective CIGS active layer-based SC with an ITO/CdS/CIGS/CNGS hetero-structure, with a CdS buffer layer, ITO window layer, and CNGS in dual role: as extra absorber layer, and Back Surface Field (BSF) was suggested in this article. Through the utilization of the unidimensionnal simulation program (SCAPS-1D), the impacts of the absorbers densities of doping and thicknesses, interfacial defects, parasitic resistances, and working temperature on the device have been thoroughly examined. By exploring simulation results, excellent PV metrics, including 1.21 V, 32.25 mA/cm2, 75.08 %, and 29.39 % for Voc,Jsc,FF,andPCE are provided. The suggested hetero-structure based on CIGS, when simulated, offers a useful technique to create new solar cells with more performance than previously published devices.

A comprehensive simulation study of multi-junction solar cell

This study conducts comprehensive simulation analysis of typical triple-junction solar cells using Silvaco ATLAS. Initially, modeling and simulation of the typical triple-junction solar cells under the AM1.5 solar spectrum at 300 K are performed to characterize various performance parameters of the cells under one sun illumination. Subsequently, the impact of the thickness of the top and middle cell layers on the efficiency of the cells is analyzed. Additionally, the influence of doping concentration errors in individual sub-cells on the overall power deviation of the cells is investigated. Moreover, Al0.9Ga0.1As is employed to replace AlInP as the top FSF (Front Surface Field). Furthermore, the study analyzes the variation of internal radiation efficiency of the top and middle sub-cells of the solar cells with concentration factor and bias voltage. Finally, an assessment is made on the effects of different positions and densities of interface defects, as well as the introduction of class-acceptor Gaussian distribution state levels induced by defects, on the performance of the solar cells. The results indicate that this study provides valuable insights for optimizing multi-junction solar cells and analyzing internal physical phenomena.

Design of the RF waveguide network for the klystron-based CLIC main linac RF module

The klystron-based Compact Linear Collider (CLIC) was initially proposed with a low center-of-mass energy of 380 GeV, primarily due to potential cost-effectiveness. To enhance overall cost-efficiency, reliability, and stability, a novel RF module for klystron-based CLIC main linac has been designed and studied. This RF module utilizes two X-band klystrons to feed eight traveling wave accelerating structures, resulting in a beam energy increase of 138 MeV. A key innovation of the new RF module is the integration of double-height waveguides, which contributes to a 30% reduction in surface fields and a 40% decrease in RF loss. To meet the double-height requirement, a majority of the RF components responsible for transmitting the high RF power underwent a redesign. Two solutions, based on the choke mode flange and the L-shape waveguide, were proposed to facilitate the adjustment of the accelerating structures for beam-based alignment. Additionally, bent damping waveguides and HOM loads and a high order Magic-T, were designed for the accelerating structure named CLIC-K. The paper will comprehensively present and describe both the RF design and the integration of the klystron-based CLIC module.