IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-27 DOI: 10.1007/s12043-024-02858-4

Mohanasubha Ramasamy, Suresh Kumarasamy, Dianavinnarasi Joseph, Jeeva Arulanantham Muthu, Karthikeyan Rajagopal

{"title":"Dynamics and routes to strange non-chaotic behaviour in MEMS resonators: analysis and characterisation","authors":"Mohanasubha Ramasamy, Suresh Kumarasamy, Dianavinnarasi Joseph, Jeeva Arulanantham Muthu, Karthikeyan Rajagopal","doi":"10.1007/s12043-024-02858-4","DOIUrl":"10.1007/s12043-024-02858-4","url":null,"abstract":"<div><p>The present study deals with the dynamics of microelectromechanical system (MEMS) resonators, especially the exploration of strange non-chaotic attractor (SNA) in MEMS resonators. SNAs often arise in systems driven by quasiperiodic forces, where the system is subjected to multiple frequencies that are incommensurate. When we apply the quasiperiodic forces, we identify the presence of SNA regions in the MEMS oscillators through bifurcation and Lyapunov analysis. Subsequently, we analyse the route of SNA in the considered system. In our analysis, the first identified route to SNA is the fractilisation route which is validated through various analyses, such as Poincaré map, distribution of finite-time Lyapunov exponents, Lyapunov variance, singular continuous spectrum and recurrence analysis. Moreover, two additional routes to SNA, namely Haegy–Heamel route and intermittency route, are identified and thoroughly investigated, and the presence of SNA is confirmed using singular continuous spectrum analysis. This work helps to understand SNA that can be important in fields like signal processing, where distinguishing between chaotic and non-chaotic signals is crucial. In particular, the emergence and characterisation of SNAs in MEMS resonators open avenues for further research and applications in nonlinear dynamics and chaotic systems.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142889728","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

Response surface methodology for the optimisation of heat transfer rate for concatenated non-Newtonian fluid flow over a curved stretching sheet 响应面法优化非牛顿流体在弯曲拉伸板上的串联传热率

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-20 DOI: 10.1007/s12043-024-02838-8

Pradeep Kumar, F Almeida, B Nagaraja, A R Ajaykumar

{"title":"Response surface methodology for the optimisation of heat transfer rate for concatenated non-Newtonian fluid flow over a curved stretching sheet","authors":"Pradeep Kumar, F Almeida, B Nagaraja, A R Ajaykumar","doi":"10.1007/s12043-024-02838-8","DOIUrl":"10.1007/s12043-024-02838-8","url":null,"abstract":"<div><p>The current article unveils the repercussions obtained from analysing the Casson–Williamson nanofluid flow across a curved stretched surface using the Darcy–Forchheimer model. The modelling is contemplated with homogeneous–heterogeneous chemical reactions. The impact of nonlinear thermal radiation, exponential heat source and magnetic field is considered. Further, response surface methodology is a statistical technique used to understand the association of parametric factors under consideration on the response which is the Nusselt number in the present context. The prime aim of this modelling is to give optimal conditions for producing the highest heat transfer rate to build an efficient model with the aid of sensitivity analysis. In addition, entropy propagated in the media is provided to enhance the importance of this investigation. Runge–Kutta–Fehlberg 4–5th order technique has been used to obtain the numerical output. The analysis reveals that the first-order slip component has a negative effect on velocity distribution, whereas the second-order slip factor has the opposite effect. The Nusselt number decreases as the unsteadiness parameter reaches its maximum value and when the sheet is susceptible to intense radiation. Graphical representations of streamlines and isotherms are provided to illustrate the flow and heat distribution. The sensitivity analysis emphasises that the Brownian motion parameter has positive sensitivity, whereas thermophoresis and an exponential heat source have negative sensitivity on the Nusselt number.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142859550","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

Entropy optimisation of a viscous bioconvective nanofluid flow with Coriolis and Lorentz forces using bivariate spectral quasi-linearisation technique 基于二元谱准线性化技术的粘性生物对流纳米流体科氏力和洛伦兹力的熵优化

IF 1.9 4区物理与天体物理

Pramana Pub Date : 2024-12-20 DOI: 10.1007/s12043-024-02855-7

Shweta Mishra, Hiranmoy Mondal, Prabir Kumar Kundu

引用次数: 0

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 等离子体介质中激波的碰撞：行波解

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 两个带电耦合振荡器在普通热浴中的量子朗之万动力学和长时间行为

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 重离子碰撞中对称能对电磁场的影响

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 粗糙元素对微通道混合的影响

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 电解过程中金属氢化物表面量子隧穿的研究

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

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