bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical study of implosion instability mitigation in magnetically driven solid liner dynamic screw pinches
Authors: Shipley G. A. , Ruiz D. E. , Jennings C. A. , Yager-Elorriaga D. A. , Schmit P. F.
Published: February 2024

Magnetized liner inertial fusion experiments on the Z accelerator suffer from magneto-Rayleigh–Taylor instabilities (MRTI) that compromise integrity of the imploding cylindrical liner, limiting achievable fusion fuel conditions and ultimately reducing magneto-inertial fusion target performance. Dynamic screw pinches (DSP) provide a method to reduce MRTI in-flight via application of magnetic field line tension to the imploding liner outer surface. In contrast with z-pinches that drive implosions with an azimuthal magnetic field, dynamic screw pinches enforce an additional axial drive magnetic field component, making the overall drive magnetic field helical. As the liner implodes, cumulative MRTI development is reduced by dynamically shifting the orientation of the fastest growing instability modes. Three-dimensional magnetohydrodynamic simulations show that the DSP mechanism effectively stabilizes initially solid cylindrical liner implosions driven by Z-scale current pulses, indicating that MRTI mitigation increases with the ratio of axial to azimuthal drive magnetic field components (i.e., the drive field ratio). We also performed a spectral analysis of the simulated imploding density distributions, extracting wavelength and pitch angle of the simulated MRTI structures to study their dynamics during the implosion. Simulations of liners initially perturbed with drive-field-aligned sinusoidal structures indicate that MRTI mitigation in DSP implosions decreases with perturbation wavelength, once again suggestive of magnetic field line tension effects.
A circular photogalvanic effect in two-dimensional electron gas on the surface of SrTiO3
Authors: Yamamoto Mahiro , Nishijima Taiki , Ohshima Ryo , Ando Yuichiro , Shiraishi Masashi
Published: February 2024

A spin-splitting state due to a Rashba-type spin–orbit interaction is investigated using two-dimensional electron gas (2DEG) at the surface of SrTiO3. The circular photogalvanic effect is utilized to detect the spin-splitting state. Both the polarization and incident light angle dependence of the measured photocurrent generated in the 2DEG unequivocally show the presence of surface spin splitting in the 2DEG, and variation of the carrier densities of the 2DEG provides further supporting evidence. This finding could pave the way for investigating spin textures and spin physics in two-dimensional carrier gas systems.
Enhanced room-temperature magnetic field effect on spin-polarized excitons of cesium lead bromine-magnetite nanocomposites
Authors: Ma Yongfu , Huang Ruiqin , Gong Hongmei , Kang Enze , Chen Jingge , Cao Quanliang , Han Yibo
Published: February 2024

The generation and manipulation of spin-polarized electrons are the basis of spintronic applications. Spin injection from a ferromagnetic surface or heterojunction to a semiconductor adjacent layer is often used to create spin-polarized carriers; however, for halide perovskites, due to the mismatch of lattice parameters with most ferromagnets at room temperature, this spin injection is challenging. In this study, we synthesize all-inorganic perovskite CsPbBr3 surrounded by Fe3O4 magnetic nanoparticles. It is found that this nanocomposite shows both magnetization and magnetic field-induced circularly polarized photoluminescence at room temperature. Specifically, with the attachment of Fe3O4 nanoparticles closely on the surface of CsPbBr3 nanocrystals, both the degree of circular polarization and g-factor enhanced by 3.5 times compared with that of pure CsPbBr3. The phenomenon should be due to the formation of exciton magnetic polaron through the coupling of the magnetic aligned nanoparticles with the excitonic state of the host semiconductor in the external magnetic field. The effective spin injection provides a method of controlling the excitonic spin polarization of all-inorganic halide perovskites for spintronic applications.
Interface-induced transverse resistivity anomaly in AgNbO3/SrRuO3 heterostructures
Authors: Liu Ruxin , Xu Ruijie , Chen Yequan , Zhou Liqi , Zhuang Wenzhuo , Zhang Xu , Zhang Chong , Chen Zhongqiang , Chen Liming , Wang Xuefeng
Published: February 2024

The transverse resistivity anomaly with a hump feature, associated with topological magnetic textures, is of paramount importance for the applications of next-generation chiral spintronic devices. However, the origin of the hump feature still remains debated due to the complicated mechanism, not merely assigned to the intrinsic topological Hall effect (THE). In this work, we observe the apparent transverse resistivity hump characteristic superimposed on the Hall signals in AgNbO3/SrRuO3 (ANO/SRO) heterostructures. The intrinsic THE is ruled out by minor-loop and current density measurements. Combining the microscopic characterization and the two-channel anomalous Hall effect fitting, the hump feature is unambiguously attributed to the synergetic contribution from the SRO layer and the interfacial intermixing thin layer of ANO and SRO.
Explaining the evolution of gossip
Authors: Pan Xinyue , Hsiao Vincent , Nau Dana S. , Gelfand Michele J.
Published: February 2024

Gossip, the exchange of personal information about absent third parties, is ubiquitous in human societies. However, the evolution of gossip remains a puzzle. The current article proposes an evolutionary cycle of gossip and uses an agent-based evolutionary game-theoretic model to assess it. We argue that the evolution of gossip is the joint consequence of its reputation dissemination and selfishness deterrence functions. Specifically, the dissemination of information about individuals’ reputations leads more individuals to condition their behavior on others’ reputations. This induces individuals to behave more cooperatively toward gossipers in order to improve their reputations. As a result, gossiping has an evolutionary advantage that leads to its proliferation. The evolution of gossip further facilitates these two functions of gossip and sustains the evolutionary cycle.
Direct-ink-write cross-linkable bottlebrush block copolymers for on-the-fly control of structural color
Authors: Jeon Sanghyun , Kamble Yash Laxman , Kang Haisu , Shi Jiachun , Wade Matthew A. , Patel Bijal B. , Pan Tianyuan , Rogers Simon A. , Sing Charles E. , Guironnet Damien , Diao Ying
Published: February 2024

Additive manufacturing capable of controlling and dynamically modulating structures down to the nanoscopic scale remains challenging. By marrying additive manufacturing with self-assembly, we develop a UV (ultra-violet)-assisted direct ink write approach for on-the-fly modulation of structural color by programming the assembly kinetics through photo-cross-linking. We design a photo-cross-linkable bottlebrush block copolymer solution as a printing ink that exhibits vibrant structural color (i.e., photonic properties) due to the nanoscopic lamellar structures formed post extrusion. By dynamically modulating UV-light irradiance during printing, we can program the color of the printed material to access a broad spectrum of visible light with a single ink while also creating color gradients not previously possible. We unveil the mechanism of this approach using a combination of coarse-grained simulations, rheological measurements, and structural characterizations. Central to the assembly mechanism is the matching of the cross-linking timescale with the assembly timescale, which leads to kinetic trapping of the assembly process that evolves structural color from blue to red driven by solvent evaporation. This strategy of integrating cross-linking chemistry and out-of-equilibrium processing opens an avenue for spatiotemporal control of self-assembled nanostructures during additive manufacturing.
Sleep shapes the associative structure underlying pattern completion in multielement event memory
Authors: Lutz Nicolas D. , Martínez-Albert Estefanía , Friedrich Hannah , Born Jan , Besedovsky Luciana
Published: February 2024

Sleep supports the consolidation of episodic memory. It is, however, a matter of ongoing debate how this effect is established, because, so far, it has been demonstrated almost exclusively for simple associations, which lack the complex associative structure of real-life events, typically comprising multiple elements with different association strengths. Because of this associative structure interlinking the individual elements, a partial cue (e.g., a single element) can recover an entire multielement event. This process, referred to as pattern completion, is a fundamental property of episodic memory. Yet, it is currently unknown how sleep affects the associative structure within multielement events and subsequent processes of pattern completion. Here, we investigated the effects of post-encoding sleep, compared with a period of nocturnal wakefulness (followed by a recovery night), on multielement associative structures in healthy humans using a verbal associative learning task including strongly, weakly, and not directly encoded associations. We demonstrate that sleep selectively benefits memory for weakly associated elements as well as for associations that were not directly encoded but not for strongly associated elements within a multielement event structure. Crucially, these effects were accompanied by a beneficial effect of sleep on the ability to recall multiple elements of an event based on a single common cue. In addition, retrieval performance was predicted by sleep spindle activity during post-encoding sleep. Together, these results indicate that sleep plays a fundamental role in shaping associative structures, thereby supporting pattern completion in complex multielement events.
Terahertz radiation induced by shift currents in liquids
Authors: Li Zheng-Liang , Bian Xue-Bin
Published: February 2024

Considerable progress has been made in the experimental studies on laser-induced terahertz (THz) radiation in liquids. Liquid THz demonstrates many unique features different from the gas and plasma THz. For example, the liquid THz can be efficiently produced by a monochromatic laser. Its yield is maximized with a longer driving-pulse duration. It is also linearly dependent on the excitation pulse energy. In two-color laser fields, an unexpected unmodulated THz field was measured, and its energy dependence of the driving laser is completely different from that of the modulated THz waves. However, the underlying microscopic mechanism is still unclear due to the difficulties in the description of ultrafast dynamics in complex disordered liquids. Here we propose a shift-current model. The experimental observations could be reproduced by our theory successfully. In addition, our theory could be further utilized to investigate the nuclear quantum effect in the THz radiation in H
2
O and D
2
O. This work provides fundamental insights into the origin of the THz radiation in bulk liquids.
The
zonula adherens matura
redefines the apical junction of intestinal epithelia
Authors: Mangeol Pierre , Massey-Harroche Dominique , Sebbagh Michael , Richard Fabrice , Le Bivic André , Lenne Pierre-François
Published: February 2024

Cell–cell apical junctions of epithelia consist of multiprotein complexes that organize as belts regulating cell–cell adhesion, permeability, and mechanical tension: the tight junction (
zonula occludens
), the
zonula adherens
(
ZA
), and the
macula adherens
. The prevailing dogma is that at the
ZA
, E-cadherin and catenins are lined with F-actin bundles that support and transmit mechanical tension between cells. Using super-resolution microscopy on human intestinal biopsies and Caco-2 cells, we show that two distinct multiprotein belts are basal of the tight junctions as the intestinal epithelia mature. The most apical is populated with nectins/afadin and lined with F-actin; the second is populated with E-cad/catenins. We name this dual-belt architecture the
zonula adherens matura
. We find that the apical contraction apparatus and the dual-belt organization rely on afadin expression. Our study provides a revised description of epithelial cell–cell junctions and identifies a module regulating the mechanics of epithelia.
A model for stimulation of enzyme activity by a competitive inhibitor based on the interaction of terazosin and phosphoglycerate kinase 1
Authors: Riley Mitchell J. , Mitchell Colleen C. , Ernst Sarah E. , Taylor Eric B. , Welsh Michael J.
Published: February 2024

The drug terazosin (TZ) binds to and can enhance the activity of the glycolytic enzyme phosphoglycerate kinase 1 (PGK1) and can increase ATP levels. That finding prompted studies of TZ in Parkinson’s disease (PD) in which decreased neuronal energy metabolism is a hallmark feature. TZ was neuroprotective in cell-based and animal PD models and in large epidemiological studies of humans. However, how TZ might increase PGK1 activity has remained a perplexing question because structural data revealed that the site of TZ binding to PGK1 overlaps with the site of substrate binding, predicting that TZ would competitively inhibit activity. Functional data also indicate that TZ is a competitive inhibitor. To explore the paradoxical observation of a competitive inhibitor increasing enzyme activity under some conditions, we developed a mass action model of TZ and PGK1 interactions using published data on PGK1 kinetics and the effect of varying TZ concentrations. The model indicated that TZ-binding introduces a bypass pathway that accelerates product release. At low concentrations, TZ binding circumvents slow product release and increases the rate of enzymatic phosphotransfer. However, at high concentrations, TZ inhibits PGK1 activity. The model explains stimulation of enzyme activity by a competitive inhibitor and the biphasic dose–response relationship for TZ and PGK1 activity. By providing a plausible mechanism for interactions between TZ and PGK1, these findings may aid development of TZ or other agents as potential therapeutics for neurodegenerative diseases. The results may also have implications for agents that interact with the active site of other enzymes.
Structural topic modeling-based systematic review for service robots’ fault diagnosis: content, popularity and regional differences
Authors: Wang Zheyu , Dong Chengju , Qian Jie , Duan Chaoqun , Sheng Bo , Wang Yuanhang
Published: February 2024

The market for service robots is expanding as labor costs continue to rise. Faced with intricate working environments, fault detection and diagnosis are crucial to ensure the proper functioning of service robots. The objective of this review is to systematically investigate the realm of service robots’ fault diagnosis through the application of Structural Topic Modeling. A total of 289 papers were included, culminating in ten topics, including advanced algorithm application, data learning-based evaluation, automated equipment maintenance, actuator diagnosis for manipulator, non-parametric method, distributed diagnosis in multi-agent systems, signal-based anomaly analysis, integrating complex control framework, event knowledge assistance, mobile robot particle filtering method. These topics spanned service robot hardware and software failures, diverse service robot systems, and a range of advanced algorithms for fault detection in service robots. Asia-Pacific, Europe, and the Americas, recognized as three pivotal regions propelling the advancement of service robots, were employed as covariates in this review to investigate regional disparities. The review found that current research tends to favor the use of artificial intelligence (AI) algorithms to address service robots’ complex system faults and vast volumes of data. The topics of algorithms, data learning, automated maintenance, and signal analysis are advancing with the support of AI, gaining increasing popularity as a burgeoning trend. Additionally, variations in research focus across different regions were found. The Asia-Pacific region tends to prioritize algorithm-related studies, while Europe and the Americas show a greater emphasis on robot safety issues. The integration of diverse technologies holds the potential to bring forth new opportunities for future service robot fault diagnosis.Simultaneously, regional standards about data, communication, and other aspects can streamline the development of methods for service robots’ fault diagnosis.
Growth paths in polycrystalline thin films
Authors: Zöllner D
Published: February 2024

The polycrystalline grain microstructure of metallic thin films coarsens during grain growth in a unique way when the initial grain structure contains multiple grains in the film thickness. A regime with fast coarsening is followed by a regime of slow coarsening. At the same time, the grain structure itself undergoes clear structural changes from a bulk-like to a bamboo-like structure. The overall coarsening process evolves continuously, whereas the growth paths of individual grains do not follow the ones observed and predicted in either two- or three-dimensional grain growth.
Investigating the effect of coolant on cooling rate of engine oil used in automobile industry using Arduino interfaced temperature sensor
Authors: Pandey Amit Kumar , Sharma Raghav , Nikhil  , Choudhary Divyanshu , Bali Neha Batra , Verma Maya , Menon Rashmi , Tanwar Amit
Published: February 2024

Heat is lost by the system due to temperature difference between the hot object and surroundings. Two models which explain cooling are conduction-convection method and radiation method. During an automobile engine operation, both engine and engine oil get heated up. To overcome the problem of excessive heat generated, coolant is used to cool down the system. In present study, cooling rate of engine oil kept at high temperature was studied in the absence and presence of coolant. In the absence of coolant, engine oil follows the natural law of cooling stated by Newton and follows the exponential decay in temperature. Cooling rate constant was estimated through fitting first order and second order exponential decay with experimental data and found to be

3.35
×

10

−
4

s

−
1

and

2.39
×

10

−
4

s

−
1

(in first

50

min) respectively. Cooling rate in the presence of coolant was studied which shows rapid decrease in temperature for first few minutes which may be attributed to high heat capacity of coolant which surrounds the hot engine oil. After 50 min of cooling, temperature of both fluids found to decrease exponentially. Thus, the use of coolant was found to absorb the heat content from the engine oil rapidly in comparison to natural environment. Cooling rate constant were estimated through fitting experimental data and found to be

2.44
×

10

−
4

s

−
1

and

2.43
×

10

−
4

s

−
1

for engine oil and coolant respectively. The percentage change in temperature of oil in first two minutes in the presence of coolant was about 70% which is much higher in comparison to cooling without the use of coolant which was about 16% only. For data acquisition of temperature of engine oil and coolant, MAX6675 module with K-type thermocouple is used which were interfaced with the Arduino board.
Teaching the asynchronous general physics course in a crisis context: a case study at Igor Sikorsky Kyiv Polytechnic Institute
Authors: Savchenko Dariya , Chyzhska Tetyana , Shtofel Olha
Published: February 2024

The imposition of martial law and power outages in Ukraine made the first semester of the 2022/2023 academic year at Igor Sikorsky Kyiv Polytechnic Institute a challenge for lecturers and students, especially in learning the general physics course. An asynchronous learning mode became the only possible form in such a situation, so the problem of increasing the efficiency of conducting a lecture, problem sessions, and laboratory work in general physics arose. This study aims to describe the implementation of the discipline of general physics (part 1) promoted in an asynchronous mode by lecturers of the Department of General Physics and Modeling of Physical Processes. We verified that in crisis conditions, it is essential to: (i) provide students with all the necessary material on Moodle course and YouTube channel, allowing them to learn the theoretical material, solve the homework problems, and analyse the data from laboratory work, (ii) give feedback and consultations to students via Zoom/Telegram chat upon request, (iii) give the possibility to perform the laboratory work both in the virtual regime and as YouTube demonstration. The results of the survey of 82 students who studied the general physics course taking into account the recommendations mentioned above revealed that the majority of the surveyed students were completely/to a greater extent satisfied with the level of organisation of asynchronous learning, as well as the level of knowledge obtained, which undoubtedly indicates the effectiveness and efficiency of the proposed approach.
Improved resistive switching characteristics of solution processed ZrO2/SnO2 bilayer RRAM via oxygen vacancy differential
Authors: Choi Kihwan , Pak James Jungho
Published: February 2024

In this study, a solution-processed bilayer structure ZrO2/SnO2 resistive switching (RS) random access memory (RRAM) is presented for the first time. The precursors of SnO2 and ZrO2 are Tin(Ⅱ) acetylacetonate (Sn(AcAc)2) and zirconium acetylacetonate (Zr(C5H7O2)4), respectively. The top electrode was deposited with Ti using an E-beam evaporator, and the bottom electrode used an indium–tin–oxide glass wafer. We created three devices: SnO2 single-layer, ZrO2 single-layer, and ZrO2/SnO2 bilayer devices, to compare RS characteristics such as the I–V curve and endurance properties. The SnO2 and ZrO2 single-layer devices showed on/off ratios of approximately 2 and 51, respectively, along with endurance switching cycles exceeding 50 and 100 DC cycles. The bilayer device attained stable RS characteristics over 120 DC endurance switching cycles and increased on/off ratio ∼2.97 × 102. Additionally, the ZrO2/SnO2 bilayer bipolar switching mechanism was explained by considering the Gibbs free energy (ΔG
o) difference in the ZrO2 and SnO2 layers, where the formation and rupture of conductive filaments were caused by oxygen vacancies. The disparity in the concentration of oxygen vacancies, as indicated by the Gibbs free energy difference between ZrO2 (ΔG
o = −1100 kJ mol−1) and SnO2 (ΔG
o = −842.91 kJ mol−1) implied that ZrO2 exhibited a higher abundance of oxygen vacancies compared to SnO2, resulting in improved endurance and on/off ratio. X-ray photoelectron spectroscopy analyzed oxygen vacancies in ZrO2 and SnO2 thin films. The resistance switching characteristics were improved due to the bilayer structure, which combines a higher oxygen vacancy concentration in one layer with a lower oxygen vacancy concentration in the switching layer. This configuration reduces the escape of oxygen vacancies to the electrode during RS.
TMD material investigation for a low hysteresis vdW NCFET logic transistor
Authors: Blessing Meshach Dason I , Kasthuri N , Nirmal D
Published: February 2024

Boltzmann limit is inevitable in conventional MOSFETs, which prevent them to be used for low-power applications. Research in device physics can address this problem by selection of proper materials satisfying our requirements. Recently, 2D transition metal di-chalcogenide (TMD) materials are gaining interest because they help alleviate short-channel effects and DIBL problems. The TMD materials are composed by covalently bonded weak van der Waals (vdW) interaction and can be realized as hetero structures with 2D ferro-electric material CuInP2S6 at the gate stack. This paper demonstrates a vdW negative capacitance field effect transistor (NCFET) structure in TCAD and the design was validated for voltage-current Characteristics. Parametric analysis shows MoS2 with phenomenal on/off ratio, narrow hysteresis than the counterparts. Simulation shows that MoS2 vdW NCFET has a high transconductance of 2.36 µS µm−1. A steep slope of 28.54 mV dec−1 is seen in MoS2 vdW NCFET which promises the performance of logic applications at a reduced supply voltage.
Hall conductance of a non-Hermitian Weyl semimetal
Authors: Dey Soumi , Banerjee Ayan , Chowdhury Debashree , Narayan Awadhesh
Published: February 2024

In recent years, non-Hermitian (NH) topological semimetals have garnered significant attention due to their unconventional properties. In this work, we explore one of the transport properties, namely the Hall conductance of a three-dimensional dissipative Weyl semi-metal formed as a result of the stacking of two-dimensional Chern insulators. We find that unlike Hermitian systems where the Hall conductance is quantized, in presence of non-Hermiticity, the quantized Hall conductance starts to deviate from its usual nature. We show that the non-quantized nature of the Hall conductance in such NH topological systems is intimately connected to the presence of exceptional points. We find that in the case of open boundary conditions, the transition from a topologically trivial regime to a non-trivial topological regime takes place at a different value of the momentum than that of the periodic boundary spectra. This discrepancy is solved by considering the non-Bloch case and the generalized Brillouin zone (GBZ). Finally, we present the Hall conductance evaluated over the GBZ and connect it to the separation between the Weyl nodes, within the non-Bloch theory.
Emergence of first-order and second-order phase transitions in a cyclic ecosystem exposed to environmental impact
Authors: Bhattacharyya Sirshendu
Published: February 2024

A cyclically dominating three-species ecosystem, modeled within the framework of rock-paper-scissor game, is studied in presence of natural death and an effect of the environment. The environmental impact is parameterized along with the death rates in the rate equation of the species densities. Monte-Carlo simulations on this system reveal that the population density bears the signature of first-order and second-order phase transitions in different regimes of the parameters representing natural deaths of the species. The connection of this phenomena with the phase transitions is also supported by the behavior of the basin entropy calculated for the system. The density of total population evidently becomes an order parameter with respect to the change in environmental impact on the system.
Study of the photothermal response of a multilayer structure doped with VO2@Au nanoshells
Authors: Pulford Megan , Hatef Ali
Published: February 2024

In this paper, we demonstrate a theoretical study of a multiphysics problem to solve for the photothermal response of a one-dimensional multilayer structure containing a layer doped with VO2@Au nanoshells. The VO2@Au nanoshell consists of a gold (Au) shell and a core of the phase change material vanadium dioxide (VO2) where the VO2 core transitions from a semiconductor state to a conductor state at the critical temperature of 68 °C. This behaviour results in thermal induced optical tunability through this reversible phase change of the VO2, due to the temperature dependent optical and thermal properties. The presence of the VO2 core, functioning as an ultra-fast and reversible optical phase-change material, leads to the emergence of photothermal induced bistability. The layer doped with the VO2@Au nanoshell is approximated as an effective medium using the Maxwell-Garnett Theory to enable an analytical solution. In this study, the optical response of the multilayer structure is obtained using the Transfer Matrix Method, while the thermal response for both stationary and transient states is solved using the Green’s Function Method and Kirchhoff’s Transformation. These equations are interconnected through the heat source term in the heat diffusion equations, representing the local heat generation induced by the continuous-wave laser applied to the structure. Our findings indicate that at the wavelengths of 658 nm and 747 nm, there are two distinct photothermal responses arising from the phase change of the VO2 core. At these wavelengths, the absorption of light increases and decreases, respectively, because of the VO2 phase change. This analytical method not only offers a thorough exploration of the fundamentals of induced photothermal responses in multilayer structures but also holds considerable potential for various applications, including solar cells, photothermal therapy, and nanothermal sensors.
Higher rogue and rogue-soliton interaction solutions of a (2 + 1) dimensional nonlinear model in fluid mechanics
Authors: Cao Na , Yin XiaoJun , Xu LiYang , Bai ShuTing
Published: February 2024

In this study, two new theorems are generalized. We obtained a new paradigm about the second order rogue wave and multiple exponential functions, and a new paradigm about the second order rogue wave and multiple hyperbolic cosine functions. Six sets of interaction solutions of the model are solved by means of symbolic calculation and two new theorems. Meaningful graphs of the propagation processes along time demonstrated the interaction phenomena for these solutions. The energy transfer process can be observed when the second order rogue waves interact with multiple exponential functions or multiple hyperbolic cosine functions. As a conclusion from our paper, the solitons’ energy transfers to the second order rogue wave at beginning, the rogue wave’s energy dissipates and transfers to the solitons along the time moving. It will contribute to the research on the generation of rogue waves.
Solar radio spectrogram segmentation algorithm based on improved fuzzy C-means clustering and adaptive cross filtering
Authors: Liu Yan , Shen Yu Peng , Song Hong Qiang , Yan Fa Bao , Su Yan Rui
Published: February 2024

Solar radio spectrograms contain essential information, such as the duration type; therefore, recognizing and detecting solar radio spectrograms are significant for the further study of solar radio. With the upgrading of solar radio observation, considering the equipment that has already generated amounts of data, researchers have begun to use machine learning methods to recognize and detect solar radio spectrograms to resolve the weaknesses of manual identification, such as time consumption. However, the spectrograms are characterized by noise or insignificant outburst features, which affect the recognition and detection of solar radio spectrograms. In contrast, extracting the burst region separately and the more distinctive spectrogram features will help identify and detect it. Therefore, to remove the burst domain of the radio spectrogram better, this paper combines the idea of image segmentation and proposes a solar radio spectrogram segmentation algorithm based on improved fuzzy C-means (FCM) clustering and adaptive cross filtering for the extraction of the burst domain of solar radio spectrograms. This algorithm has multiple processing steps. The first step is solar radio spectrogram segmentation with the improved FCM based on the kernel-induced distance by incorporating spatial constraints combined with random walk and adaptive affiliation linking (RWAKFCM_S). The second step is adaptive cross filtering, eliminating the noise clustered in bursts. The results show the following. (1) The RWAKFCM_S proposed in this paper has better anti-noise and segmentation performance than other methods in the synthetic, natural, and solar radio spectrogram segmentation experiments; it can also overcome the problems of noise sensitivity when segmenting spectrograms by traditional FCM. (2) The RWAKFCM_S can satisfy the high accuracy and rate of solar radio spectrogram segmentation demands. (3) The adaptive cross filtering proposed in this paper can eliminate noise clustered in the eruption domain. (4) The proposed method enables burst region extraction.
Study of exponential wormhole metric in f(R) gravity
Authors: Nath Partha Pratim , Sarma Debojit
Published: February 2024

In this work, we have studied ‘the exponential form’ of space-time metric in some of the viable f(R) gravity models, viz. exponential gravity model, Starobinsky gravity model, Tsujikawa model, and Gogoi-Goswami f(R) gravity model. Here, we have calculated the parameters including energy density, tangential pressure, and radial pressure for these corresponding models of f(R) gravity. Subsequently, we have investigated the energy conditions, viz. null energy condition (NEC), weak energy condition (WEC), strong energy condition (SEC), and dominant energy condition (DEC) for the considered models. We have also explained the suitable stability conditions for these models through related plots. We observed that the exponential wormhole metric obeys all the necessary energy conditions in f(R) gravity without violating any flare-out or stability conditions. Out of four considered viable f(R) gravity models, the exponential, the Tsujikawa, and the Gogoi-Goswami f(R) gravity models are found to be more suitable for the exponential wormhole to exist, although all these models have some constraints on the ranges of the parameters used.
Time Variability of FUV Emission from Cool Stars on Multi-year Timescales
Authors: Kamgar Leo , France Kevin , Youngblood Allison
Published: February 2024

The physical and chemical properties of planetary atmospheres are affected by temporal evolution of ultraviolet (UV) radiation inputs from their host stars at all time scales. While studies of X-ray/UV flare properties and long-term stellar evolution of exoplanet host stars have provided new constraints regarding stellar inputs to exoplanetary systems, the UV temporal variability of cool stars on the timescale of stellar cycles remains largely unexplored. To address this gap in our understanding of the UV temporal variability of cool stars, we analyze far-ultraviolet (FUV) emission lines of ions that trace the chromosphere and transition region of nearby stars (C ii, Si iii, Si iv, and N v; formation temperatures ∼ 20–150 kK) using data from the Hubble Space Telescope (HST) and International Ultraviolet Explorer (IUE) archives spanning temporal baselines of months to years. We select 33 unique stars of spectral types F-M with observing campaigns spanning over a year, and create ionic light curves to evaluate the characteristic variability of cool stars on such timescales. Screening for large flare events, we observe that the relative variability of FUV light curves decreases with increasing stellar effective temperature, from 30% to 70% variability for M-type stars to <30% variability for F and G-type stars. We also observe a weak trend in the temporal variability with the Ca ii

R

HK

′

stellar activity indicator, suggesting that stars with lower Ca ii activity exhibit a smaller range of FUV flux variability. Screening for data sets with optimal temporal spread, and a sufficient number of individual observations, we select 5 data sets for further periodicity analysis (HST α Centauri A, HST α Centauri B, IUE α Centauri B, IUE ϵ Eri, IUE ξ Boo). Various periodic structures within the FUV flux were detected, with most significant being a 79 days frequency present within the IUE observations of ξ Boo, with a significance of 6σ, and a periodic signal in the FUV observations of α Centauri B, for both HST and IUE measurements, at ≈210 days frequency with significance of 3σ and 3.7σ, respectively. Our results suggest that extreme ultraviolet flux from cool stars varies by less than a factor of two on decade timescales, significantly smaller than variations on flare or stellar evolutionary timescales.
Optical Transient Source AT2021lfa: A Possible “Dirty Fireball”
Authors: Ye Xue-Mei , Wei Da-Ming , Zhu Yi-Ming , Jin Zhi-Ping
Published: February 2024

AT2021lfa, also known as ZTF21aayokph, was detected by the Zwicky Transient Facility on 2021 May 4, at 05:34:48 UTC. Follow-up observations were conducted using a range of ground-based optical telescopes, as well as Swift/XRT and VLA instruments. AT2021lfa is classified as an “orphan afterglow” candidate due to its rapid flux decline and its reddened color (g − r = 0.17 ± 0.14 mag). For an optical transient source without prompt gamma-ray detection, one key point is to determine its burst time. Here we measure the burst time through fitting the initial bump feature of AT2021lfa and obtain its burst time as 2021 May 3, at 22:09:50 UTC. Using afterglowpy, we model the multi-band afterglow of AT2021lfa and find that the standard model cannot reproduce the late radio observations well. Considering that the microphysical parameters ϵ

e
, ϵ

B
(the energy fraction given to electrons and magnetic field), and ξ

N
(the fraction of accelerated electrons) may vary with time, we then model the afterglow of AT2021lfa taking into account the temporal evolution of the physical parameters ϵ

e
, ϵ

B
, and ξ

N
and find in this case the multi-wavelength observations can be reproduced well. The initial Lorentz factor of AT2021lfa can be estimated from the peak time of the early afterglow, which yields a value of about 18, suggesting that AT2021lfa should be classified as a “dirty fireball.” From the upper limit for the prompt emission energy of AT2021lfa, we obtain that the radiation efficiency is less than 0.02%, which is much smaller than that of ordinary gamma-ray bursts (GRBs). It is also interesting that the fitted values of jet angle and viewing angle are very large, θ

c
∼ 0.66 rad, θ

v
∼ 0.53 rad, which may lead to the low Lorentz factor and radiation efficiency. When compared with GRB afterglow samples, it is evident that the onset bump timescale of AT2021lfa satisfies the empirical relationships observed in GRB samples. Additionally, the luminosity of AT2021lfa falls within the range of observations for GRB samples; however, approximately 1 day after the burst, its luminosity exceeds that of the majority of GRB samples.
Wearable System for Intelligent Monitoring of Assistance and Rescue Dogs
Authors: Chi-Pérez W D , Ríos-Martínez J A , Madera-Ramírez F A , Estrada-López J J
Published: February 2024

Dogs are remarkable animals that can form strong social bonds with humans and excel in various sensory abilities. These qualities make them suitable for training in different domains such as assistance, search, and rescue. However, current training methods are complex, costly, and lengthy because they depend on the trainer’s subjective interpretation of the dog’s behaviour. A more objective and efficient way to train dogs would be to monitor their vital signs and use artificial intelligence to infer their adaptation and progress. In this paper, we propose a wearable system that measures the dog’s vital signs and motion and wirelessly transmits the data to a computer. We test and analyse the performance of our system prototype and discuss its implications for dog training.
Experimental and theoretical heat transmission through a skin phantom using a Ruby IR therapeutic lamp.
Authors: Monsibais Silva E. , Zapata Torres M. , Valaguez Velazquez E.
Published: February 2024

A skin phantom model was developed and characterized to study the interaction of infrared radiation during photothermal therapy. The phantom consists of a platinum silicone matrix with polyethylene oxide containing encapsulated sodium alginate to mimic the concentration of water in human skin. The specific heat and thermal conductivity of each component were experimentally measured. A theoretical model was built with heat transfer equations to simulate the temperature distribution. The experimental results and numerical simulations show that the interaction phenomenon with infrared radiation is superficial, concentrating mostly in the epidermis and part of the dermis. This successfully replicates the actual thermal behaviour of the skin during photothermal therapy. The developed phantom adequately represents the thermal properties and response to infrared radiation of the skin, allowing its use as a surrogate model in thermal imaging and diagnostic applications.
Evaluation of 8-bit eDRAM by varying the aspect ratio of the in-cell transistors
Authors: Rodríguez-Ibarra I. , Argüelles-Lucho P. , Osorio-de-la-Rosa E. , Algredo-Badillo I. , López-Huerta Francisco
Published: February 2024

Embedded dynamic random-access memories (eDRAM) are widely used in the design of embedded systems for the safeguard of information during their operation. However, since these memories are installed in the same chip as the host system, it is crucial to consider their dimensioning. For this reason, in our work, the aspect ratio width and length (W/L) of complementary metal oxide semiconductor (CMOS) transistors inside 3-transistor logic cells (3T) is diversified to evaluate the effect on electrical behavior with area optimization through the figure of merit (FoM): power consumption-delay product of 8-bit memories with an operating frequency of 8.3 MHz, varying the aspect ratio of transistors inside the cell have been obtained 8.6f as lowest and 152.3f as highest FoM values. Those storage devices have been developed on 0.00085 mm2 using a 180-nm CMOS technology.
Evaluation of Assembler and C Programming Languages on PIC16F877 Microcontroller
Authors: Woo‑Garcia Rosa M. , Argüelles-Lucho Primavera , Montes de Oca‑Mora Natanael J. , Salas-Rodriguez Silvestre , Sanchez-Vidal Adrián , Ceron-Alvarez Carlos A. , Osorio-de la Rosa Edith
Published: February 2024

The programming of microcontrollers is essential for their correct operation, high computational efficiency, low-power solutions, and it is also key to get the most out of their capabilities with the hardware features that each of the microcontroller families has. There are different programming languages that can be used in microcontrollers, in this work we will focus on C and Assembler. C is one of the most widely used due to its efficiency and its ability to control the hardware directly. Assembly is a low-level language that allows more control over the instructions executed in the microcontroller, two songs have been implemented in assembler and C languages and the resources used for their execution on a Microchip PIC16F877 have been analyzed. The research results allow the developer to obtain results for a selection of the optimal hardware platform as well as the programming language according to the required memory utilization. Coding performed in MPLAB software with the asm and XC8 compilers, indicate that the C-code programs cover a larger amount of memory close to 4 times greater or higher.
Impact of Rhodamine B solution on charge carrier generation and photocatalytic performance in CdS/TiO2 heterostructures synthesized by CBD.
Authors: Cruz González N. , Noguez del Águila O. , Roque J. , Silva-Galindo G. , Torres Frausto C. , Zapata-Torres M.
Published: February 2024

This article presents the study of Rhodamine B solution effects on the generation of charge carriers and the photocatalytic performance of CdS/TiO2 heterostructure films. CdS/TiO2 heterostructure films were synthesized using the chemical bath deposition technique (CBD). The structure and morphology of the heterostructures were studied by X-ray diffraction (XRD), and Scanning Electron Microscope (SEM), respectively. The optical properties of the CdS/TiO2 heterostructures were characterized using a UV–vis spectrophotometer. The results showed that the CdS/TiO2 optical band gap energy (Eg) was 2.75 eV, between the TiO2 band gap energy (3.38 eV) and the CdS band gap energy (2.57 eV). The electrochemical characterization indicated that the photocurrent of the CdS/TiO2 heterostructure decreased from 29 mA to 12.4 mA when the UV-vis light source was turned off. The density of charge carriers generated on the surface of the CdS/TiO2 was simulated employing the WXAMPS software. The results suggest that the thickness of the TiO2 layer should be optimized to allow the activation of CdS. Finally, this study concludes that the presence of rhodamine B in the solution attenuates light transmission and affects the generated electron-hole pairs, resulting in poor photocatalytic behavior.
Control strategy and research on energy storage unit participation in power system frequency regulation based on VSG technology
Authors: Lv Zhengqiang , Xu Jia , Pang Yuanqi , Tan Litao , Zheng Han
Published: February 2024

When large-scale photovoltaic power plants are integrated into the grid, it will cause the grid-connected capacity to gradually expand, causing greater harm to the safe and stable operation of the power system, which will affect the FM characteristics of the power system. This requires the PV power plant to actively participate in power system frequency control. Through the PV virtual synchronous generator frequency control technology, coupled with the virtual synchronous PV power plant modeling, the PV new energy units can have the same frequency control characteristics as synchronous generator sets. In the virtual synchronous technology, due to the existence of damping windings, electromagnetic damping will be generated, and it is also due to virtual damping that the virtual synchronous technology has the ability to damp power oscillations. It is also because of the excellent virtual inertia and damping characteristics of the virtual synchronous generator in the grid that this FM technology helps to regulate the frequency fluctuations of the new energy grid, meet the requirements of the power system to maintain stable operation, and then realize the large-scale PV grid connection.
Optimization model of new energy consumption based on load demand-side response
Authors: Guan Yan , Cai Yinong , Gao Xiying , Lu Xinyi
Published: February 2024

As a technically and economically feasible and potentially resource-rich regulation tool, demand-side response can effectively strengthen the guarantee of new energy consumption, and is expected to play an enhanced key role in the construction of new power systems. This paper analyzes the factors affecting the linkage between demand-side and new energy generation side, the promotion of new energy consumption by demand-side response, and proposes a method to respond to the change of new energy output from the customer side, using interruptible load, transferable load, shiftable load, and curtailable load strategies to respond to the peak regulation problem brought by new energy access to the grid. The optimal demand-side response strategy is obtained by constructing a new energy consumption optimization model and solving it with the direct non-inferiority solution method, taking into account the economic and new energy consumption objectives. Finally, the effectiveness of the method is verified by simulating the IEEE 37-node system with multiple new energy configurations.
Passivity and higher-order sliding mode control for doubly-fed induction generation wind power system
Authors: Li Xiaolei , Shao Mingyan , Xu Jiadong , Zhu Yu , Zhang Hongzhe , Li Chen , Dong Xu , Li Siyuan
Published: February 2024

To simplify the model of DGIG and improve the robustness, the variable speed and constant frequency (VSCF) DFIG wind power generation systems from the perspective of energy and robustness were studied. It was based on passivity and sliding mode control (SMC) theory. Firstly, the model of DFIG based on Euler-Lagrange (EL) equations was established, so the original DFIG wind turbine system is divided into electrical and mechanical subsystems. For two subsystems, the electrical subsystem was designed. In contrast, the mechanical subsystem is an energy-consuming system and is stable through selecting suitable design parameters. Hence, the system control algorithm is simplified. A high-order terminal SMC was designed to get a faster speed and better robustness for the speed loop. Simulation results show that the proposed controller is simple and effective. It can guarantee the wind power system outputs constant frequency. The motor speed can also track the reference speed quickly, so the performance of the wind turbine system is improved.