Pramana最新文献 - Book学术

Synergistic sunspot forecasting: a fusion of time series analysis and machine learning 太阳黑子的协同预测：时间序列分析与机器学习的融合

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-16 DOI: 10.1007/s12043-024-02861-9

Menghui Chen, Suresh Kumarasamy, Sabarathinam Srinivasan, Viktor Popov

{"title":"Synergistic sunspot forecasting: a fusion of time series analysis and machine learning","authors":"Menghui Chen, Suresh Kumarasamy, Sabarathinam Srinivasan, Viktor Popov","doi":"10.1007/s12043-024-02861-9","DOIUrl":"10.1007/s12043-024-02861-9","url":null,"abstract":"<div><p>In this article, we conduct nonlinear time series analysis and utilise machine learning (ML) techniques for predicting and forecasting daily sunspot data sets. Additionally, we review available time series and ML techniques to provide a comprehensive overview. For time series analysis, the variations in the persistence of sunspot data sets were confirmed through Hurst exponent with various time lengths. Moreover, the fast Fourier transform was performed. For the ML approach, prediction and forecasting of sunspot data sets are performed with various simple ML algorithms. Recurrent neural networks (RNN), long–short time memories (LSTM) and gated recurrent unit (GRU) algorithms were used for the prediction. A discussion of the significant outcomes of the sunspot predictions made using the aforementioned algorithms is presented. With the use of these sunspot data sets, several statistical metrics, including <i>R</i>-squared, mean average error (MAE), etc., are examined. Further, the sunspot data forecast was done for more than eight solar cycles with the help of different forecasting algorithms (e.g., neural basis expansion analysis for time series (N-BEATS), neural hierarchical interpolation for the time series (NHITS), etc.). A summary of the sunspot predictions using several ML techniques in an effort to determine the most effective methodology is discussed.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142826307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Nonlinear terms from GLR-MQ evolution 来自 GLR-MQ 演化的非线性项

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-16 DOI: 10.1007/s12043-024-02866-4

G R Boroun

引用次数: 0

Collision of shock waves in plasma medium: a travelling-wave solution

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-13 DOI: 10.1007/s12043-024-02849-5

Sherin Agnus, Rajeswari Seshadri

引用次数: 0

Quantum Langevin dynamics and long-time behaviour of two charged coupled oscillators in a common heat bath

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-13 DOI: 10.1007/s12043-024-02857-5

Koushik Mandal, Suraka Bhattacharjee

引用次数: 0

Influence of symmetry energy on electromagnetic field during heavy-ion collisions

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-13 DOI: 10.1007/s12043-024-02860-w

Dhanpat Sharma, Suneel Kumar

{"title":"Influence of symmetry energy on electromagnetic field during heavy-ion collisions","authors":"Dhanpat Sharma, Suneel Kumar","doi":"10.1007/s12043-024-02860-w","DOIUrl":"10.1007/s12043-024-02860-w","url":null,"abstract":"<div><p>Heavy-ion collision simulations in intermediate energy regime using isospin quantum molecular dynamics model have been proposed as a novel means to glean information about the high density behaviour of nuclear matter. Herein, the influence of modelling the pressure gradient by changing stiffness parameter and isospin asymmetry on the dynamics of charged particles have been investigated. In this research, three different values of stiffness parameter, <span>(gamma =)</span> 0.66 (soft), 1 (stiff) and 2 (super-stiff), to tune the anisotropic transverse pressure gradients have been considered to explore the influence of density-dependent symmetry energy </p><div><div><span>$$begin{aligned} & E_{textrm{sym}}({rho })=E_{textrm{sym}}({rho _{0}}) bigg (frac{rho }{rho _{0}}bigg )^{gamma } end{aligned}$$</span></div></div><p>on the electromagnetic field and energy density evolution. Stiffer symmetry energy (<span>( gamma =)</span> 2) leads to larger pressure gradient than softer symmetry energy (<span>( gamma =)</span> 0.66) that drives stronger expansion resulting in higher intensity of <span>((eB_{y}(0, 0, 0))_{textrm{max}})</span> and <span>(langle | vec {E}cdot vec {B}|rangle _{textrm{max}})</span>. The correlation of eccentricity, nuclear stopping, centrality with the electromagnetic field and energy density have been established for different stiffness parameters. To deepen this study, the influence of isospin asymmetry (<i>N</i>/<i>Z</i>) on the time evolution of electromagnetic field has also been explored.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142810966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effects of rough elements on mixing in microchannels

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-13 DOI: 10.1007/s12043-024-02870-8

Shuai Yuan

{"title":"Effects of rough elements on mixing in microchannels","authors":"Shuai Yuan","doi":"10.1007/s12043-024-02870-8","DOIUrl":"10.1007/s12043-024-02870-8","url":null,"abstract":"<div><p>For incompressible fluids, no discernible differences exist between microscale and macroscale flows. However, surface roughness has emerged as a significant factor influencing mass transport phenomena at the microscale due to the substantial increase in the surface-to-volume ratio. In this work, we establish a model of a cross-shaped micromixer with structural roughness elements using the finite-element software Comsol. A comprehensive study is conducted to assess the effects of roughness parameters on mixing performance. Our findings indicate that the roughness height can improve mixing quality compared to smooth channels, which is attributed to the extrusion of roughness on the working medium at a low Reynolds number (<i>Re</i>) of 1 and the increase of lateral velocity at high <i>Re</i> = 50. When the roughness height is increased from 2 to 20 <i>μ</i>m, the maximum mixing quality is increased by about 7.4 and 32.8% at <i>Re</i> = 1 and 50, respectively. Furthermore, narrowing the roughness pitch enhances the perturbation frequency of microfluidics, thus facilitating the mixing process. When the pitch is reduced from 200 to 20 <i>μ</i>m, the maximum mixing quality at <i>Re</i> = 1 and 50 increases by about 1.9 and 13.8%, respectively. This paper provides new insights into the influence of microrough structures on mixing.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142810989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Investigation of quantum tunnelling on the metallic hydride surfaces in the electrolysis process

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-13 DOI: 10.1007/s12043-024-02847-7

Mehdi Moosavi, Hossein Zaki Dizaji, Amin Seyyedi

引用次数: 0

Lax pairs, infinite conservation laws of stochastic potential Korteweg–de Vries equation and their solutions by using Darboux transformation

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-13 DOI: 10.1007/s12043-024-02856-6

Nanda Kanan Pal, Prasanta Chatterjee, Abdul-Majid Wazwaz, Santanu Raut

引用次数: 0

Solitary pattern solution of fractional Triki–Biswas and generalised KdV–Zakharov–Kuznetsov equations