Pramana最新文献

{"title":"Significance of waste discharge concentration on the fluid flow over a squeezing porous slider: solution by improved residual power series method","authors":"M C Jayaprakash,&nbsp;T Ramachandran,&nbsp;Ambati Vijay Kumar,&nbsp;Vikas Kaushik,&nbsp;Sanjeev Kumar Joshi,&nbsp;A S Siddesh,&nbsp;Nehad Ali Shah,&nbsp;J Rekha","doi":"10.1007/s12043-024-02874-4","DOIUrl":"10.1007/s12043-024-02874-4","url":null,"abstract":"<div><p>The current analysis focusses on the three-dimensional viscous flow caused by an expanding or contracting porous slider under the impact of heat source<span>(/)</span>sink, magnetic field and waste discharge concentration. The amount of fluid injected to levitate the slider is not constant; rather, it varies over time based on the slider's location at any given moment. The fluid flow between the ground and the slider is represented by the unsteady nonlinear equations of motion, which are converted into ordinary differential equations by employing the apt similarity transformations. These simplified equations are solved by applying the hybrid residual power series method (HRPSM). Using graphical representations, the physical behaviour of significant parameters is investigated. Tabular data are used to compare the hybrid residual power series method and the numerical scheme to check the convergence and accuracy of the hybrid residual power series method. A rise in the magnetic parameter results in a very modest rise in the fluid's longitudinal velocity in the regions closest to the upper or lower plates and a clear drop in the liquid's longitudinal velocity in the centre region. An increase in pollutant external-source parameter increases the amount of pollutants introduced into the fluid system.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s12043-024-02874-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Projective exponential anti-synchronisation of space–time discrete Lur’e oscillator networks with uncertain Markov jumps","authors":"Shaobin Rao,&nbsp;Tianwei Zhang","doi":"10.1007/s12043-025-02891-x","DOIUrl":"10.1007/s12043-025-02891-x","url":null,"abstract":"<div><p>This paper investigates global projective anti-synchronisation in the mean-square sense in the asymptotic and exponential schemes of space–time discrete Markovian Lur’e dynamical networks with uncertain transition probabilities and Dirichlet boundary values. The findings of this study are noteworthy with regard to global projective asymptotic and exponential anti-synchronisation in the mean-square sense for the proposed discrete Markovian networks. The networks incorporate the Lyapunov–Krasovskii functional, which includes a double sum representing the delay-dependent components. Furthermore, the findings of this study indicate that the global projective asymptotic and exponential anti-synchronisation of space–time discrete Markovian Lur’e dynamical networks with uncertain transition probabilities can be achieved through the design of small diffusion intensities. It was unexpected to discover that the uncertain transition probabilities have no influence on the conditions that guarantee the global projective asymptotic and exponential anti-synchronisation of the networks. This paper presents a framework for exploring the issues of global projective asymptotic or exponential anti-synchronisation for space–time discrete Markovian networks, with the objective of identifying potential applications in a range of contexts. In conclusion, an illustrative example is provided to demonstrate the efficacy of the aforementioned method.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s12043-025-02891-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermomagnetic peristaltic Casson flow in a microchannel containing a Darcy–Brinkman porous medium under the influence of oscillatory, thermal radiation, slip and heat source effects","authors":"G Shankar,&nbsp;P Deepalakshmi,&nbsp;E P Siva,&nbsp;D Tripathi,&nbsp;O Anwar Bég","doi":"10.1007/s12043-024-02869-1","DOIUrl":"10.1007/s12043-024-02869-1","url":null,"abstract":"<div><p>The objective of this article is to study mathematically the magnetohydrodynamic (MHD) unsteady non-Newtonian oscillatory blood flow and heat transfer in microchannels containing a Darcy–Brinkman porous medium. The Casson fluid model is deployed. Additionally, the effects of heat source, nonlinear thermal radiation and Hall current are included. Convective heating and slip at the internal boundaries of the microchannel are also examined. Utilising a set of non-dimensional variables, the governing partial differential equations and associated boundary conditions are transformed into a non-dimensional form. By solving the transformed model, exact solutions are obtained. Graphical representations depict the influence of different physical characteristics on the velocity and temperature patterns. In addition, this study incorporated a parametric analysis to demonstrate the impacts of key parameters on Nusselt number and wall shear stress. Increased values of thermal radiation and Casson rheological parameters produce intensified velocity fields. Blood flow is also controlled by modulating the intensity of the external magnetic field and the regulation of the blood temperature is achieved by modifying its thermal conductivity. With an increment in thermal Biot number (<i>Bh</i>) (stronger convective heating at the microchannel walls) there is a uniform increase in temperatures. With the elevation in the Hall parameter, more complex streamline patterns are generated and there is an increase in the magnitude of trapped boluses. An increment in Grashof number (<i>Gr</i>), i.e. stronger thermal buoyancy force, accelerates the flow. Elevation in the Nusselt number is produced with a stronger heat source (<i>S</i>). With greater frequency (<i>ω</i>), the blood flow is more strongly modified by periodic fluctuations in the driving pressure and this produces an elevated amplitude of velocity oscillations, thereby increasing the average velocity of the blood. Increasing slip (<span>(gamma ))</span> generates significant flow deceleration in the microchannel. This work, which focusses on the thermal radiation in the blood flow, will significantly influence therapeutic strategies for hyperthermia. Specifically, the analysis provides a good foundation for more sophisticated computational fluid dynamics (CFD) studies and will enhance our understanding and management of blood flow and heat transfer in, for example, arterial hemodynamics.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446581","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}

{"title":"Influence of Cu content on the fractal and multifractal properties of Zn–Mg–Cu composites","authors":"Maryam Gholizadeh Arashti","doi":"10.1007/s12043-024-02885-1","DOIUrl":"10.1007/s12043-024-02885-1","url":null,"abstract":"<div><p>In this work, the morphology and fractal properties of Zn–Mg and Zn–Mg–Cu nanocomposites were investigated. Zn–Mg–Cu nanocomposites with 2, 3 and 4% by weight of Cu were prepared by electrochemical method on FTO glass substrate and compared with Zn–Mg nanocomposite. The surface properties of the nanocomposites were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM images confirm that the morphology and grain size depend on the amount of Cu doping. The grain size decreases with increasing Cu concentration. Statistical analysis based on 3D AFM images showed that surface roughness (<i>S</i>_q) and fractal dimension (<i>D</i>_f) decreased with increasing Cu concentration. <i>D</i>_f obtained using the log(count) vs. log(box size) curve showed that <i>D</i>_f is independent of scan size and pixel resolution. The <i>D</i>_f values of ZM3, ZM3C2, ZM3C3 and ZM3C4 were calculated to be 2.48, 2.44, 2.36 and 2.30, respectively. It can be concluded that the lacunarity coefficient <i>β</i> of all the nanocomposites has a high degree of surface microstructure homogeneity with <i>β</i> &lt; 0.07. Multifractal behaviour was observed for all nanocomposites, with the multifractal degree of Zn–Mg–Cu nanocomposites being reduced compared to that of Zn–Mg nanocomposites.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s12043-024-02885-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Negative frequencies in the scattering properties of parity–time symmetry and anti-parity–time symmetry","authors":"Stéphane Boris Tabeu,&nbsp;Fernande Fotsa-Ngaffo,&nbsp;Aurélien Kenfack-Jiotsa","doi":"10.1007/s12043-024-02872-6","DOIUrl":"10.1007/s12043-024-02872-6","url":null,"abstract":"<div><p>We present the scattering properties of parity–time (PT)-symmetric and anti-parity–time (APT)-symmetric systems embedded in a new electronic waveguide. The set-up is built around imaginary resistors and positive or negative other components. These combinations give rise to a real spectrum in breakable and unbreakable PT symmetries. When it exists, the transition marks the passage from real to complex eigenvalues whereas in the APT symmetry, the eigenvalues pass from pure imaginary to complex eigenvalues. The frequencies of cells in PT-symmetric configurations must have the same sign whereas in APT-symmetric configurations, the frequencies must have opposite signs. The electrical line presented can drive negative frequencies and gives the possibility to demonstrate the existence of a mirror behaviour in scattering properties of the PT symmetry. We derive the condition of appearance of the coherent perfect absorber and laser, unidirectional invisibility from one or both sides of the system. In APT symmetry, only the coherent perfect absorber exists in the two configurations of waveguides used. The respect of the law of conservation depends on the nature of the eigenspectrum peculiar to each type of the dimer.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446428","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}

{"title":"Lie symmetry reductions and exact solutions of Kadomtsev–Petviashvili equation","authors":"Anukriti,&nbsp;Dig Vijay Tanwar","doi":"10.1007/s12043-024-02887-z","DOIUrl":"10.1007/s12043-024-02887-z","url":null,"abstract":"<div><p>This work intents to obtain symmetry reductions and exact solutions of Kadomtsev–Petviashvili (KP) equation, which describes propagation of long waves on the surface of shallow water. The Lie symmetry method under one-parameter transformation is used to ensure invariance and derive infinitesimal generators. These generators provide similarity variables, which is directed to symmetry reductions of the test equation. This process of reductions recasts test equation into ordinary differential equations (ODEs). These ODEs have finally been solved under various constraints and as a result, exact solutions consisting of arbitrary functions and several arbitrary constants are produced. The solutions are novel and have not yet been published. Due to the existence of arbitrary functions <span>(f_1(t))</span>, <span>(f_2(t))</span>, <span>(f_3(t))</span> and constants, these solutions present a more generalised form than the existing results and give a wide range of possibilities for the interpretation of various physical phenomena. The physical importance of these solutions is demonstrated by numerical simulation revealing a rich variety of soliton structures including line soliton, doubly soliton, multisoliton, solitons on parabolic surface, soliton fission and annihilation behaviour.\u0000</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446513","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}

{"title":"Dissipative stagnation point flow of the Casson nanofluid over a stretching sheet under the influence of porous media, binary chemical reaction and variable surface heat flux condition","authors":"Om Prakash","doi":"10.1007/s12043-024-02873-5","DOIUrl":"10.1007/s12043-024-02873-5","url":null,"abstract":"<div><p>A study is carried out on the dissipative stagnation point flow of the two-dimensional magnetohydrodynamic (MHD) Casson nanofluid over a stretched surface under the influence of porous media, thermal radiation, heat source, binary chemical reaction effects, variable thermal conductivity and variable surface heat flux condition. Similarity transformations are employed to transform the governing equations into ordinary differential equations. Using the R-K fourth-order technique with the shooting method, we numerically solve the aforementioned equations. Graphs and tables present the outcomes for temperature, concentration and velocity distributions. There is a strong agreement between our results and the results from a prior study. This study has proven that the fluids move more slowly due to a magnetic field. Moreover, the increase in the nanofluid temperature is correlated with an increase in thermal radiation and heat source. It is also shown that the increase in the chemical reaction slows down the mass profile but a reverse effect is seen for the activation energy parameter. The mass profile declines as the suction, velocity ratio, thermal conductivity, chemical reaction parameters and Schmidt number increase but a reverse effect is seen for the magnetic field, Casson, thermal radiation and the activation energy parameters.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373296","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}

{"title":"Enhanced THz emission from photoconductive antennas by integrating photonic structures on a semi-insulating GaAs substrate","authors":"Goutam Rana,&nbsp;Abhishek Gupta,&nbsp;Arkabrata Bhattacharya,&nbsp;S P Duttagupta,&nbsp;Shriganesh S Prabhu","doi":"10.1007/s12043-024-02886-0","DOIUrl":"10.1007/s12043-024-02886-0","url":null,"abstract":"<div><p>Tera Hertz photoconductive antennas (THz PCAs) have significantly advanced the THz research by offering room-temperature operation, broad bandwidth and relatively low cost as both emitters and detectors. However, the primary limitation has been their low power output due to inefficient conversion. This article demonstrates a substantial improvement in efficiency (<span>(sim 200%)</span>) by incorporating sub-micron photonic structures on the surface. These photonic structures enhance pump beam coupling, leading to increased photocarrier generation. They also facilitate efficient carrier recombination after THz emission, thereby suppressing carrier screening. Experimental and numerical studies confirm the enhanced photocarrier generation and controlled transport through defect-free paths, further reducing screening effects. The integration of photonic structures into large area emitters (LAEs) holds the potential to develop emitters and detectors suitable for real-world THz systems, overcoming the limitations of the current commercial LAEs that rely on plasmonic structures or antireflection coatings. This innovation has the potential to revolutionise THz technology, enabling the development of more powerful and efficient THz sources and detectors. This can lead to advancements in various fields, including wireless communication, imaging and sensing and spectroscopy.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143107966","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}

{"title":"Observed trends in FRB population and bi-modality in the luminosity density distribution","authors":"Nidhi Saini,&nbsp;Gupta Patrick Das","doi":"10.1007/s12043-024-02881-5","DOIUrl":"10.1007/s12043-024-02881-5","url":null,"abstract":"<div><p>Fast radio bursts (FRBs) are radio-transients of extragalactic origin lasting from fractions of a millisecond to hundreds of milliseconds. Their actual physical nature is yet to be ascertained and is still a topic of active research. In this paper, we have considered both non-CHIME and CHIME sources, and have subjected the available FRB data to various analyses. Since CHIME first catalogue provides only the lower bounds to the FRB flux density and fluence, we have devised a novel approach that utilises the ratio of the catalogued lower limits of the flux density <span>(S_{nu _O})</span> to the fluence <span>(F_{nu _O})</span> of individual FRB events to construct several parameters <span>(Xi, i=1,2,ldots ,7)</span> but <span>( i ne 5)</span> to investigate the presence of underlying trends in the CHIME FRB population. These parameters are also computed for the non-CHIME FRB events using the ratio of the measured flux density <span>(S_{nu _O})</span> to the fluence <span>(F_{nu _O})</span>. One of these defined parameters (<i>X</i>7) involve the actual brightness temperature as well as energy density instead of the corresponding bounds, despite one’s ignorance of thess actual size of the FRB emission region. Our first robust conclusion is that the individual non-CHIME FRB events fall under two broad categories based on their peak luminosity densities. This has been explicitly demonstrated for peak luminosity densities calculated at two distinct frequencies – 300 and 450 MHz. Our second robust result is that the parameters <i>Xi</i>s involving the ratio of the flux density to the fluence are almost the same for both CHIME and non-CHIME FRB populations, vindicating our use of these parameters that make use of <span>(S_{nu _O}/ F_{nu _O})</span> and other measured quantities. This universality is also seen in the underlying patterns exhibited by the distributions of the computed parameters <i>Xi</i>s for both CHIME and non-CHIME FRB population, suggesting thereby the existence of two categories even for the FRB events detected by CHIME. Assuming that FRBs are caused by magnetar glitches that lead to an abrupt change in the light cylinder radius, we have considered a simple physical model to address the issue of two categories based on the FRB luminosity density.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109960","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}

{"title":"Numerical analysis for GEM signal and time resolution","authors":"S Swain,&nbsp;S K Sahu,&nbsp;P K Sahu","doi":"10.1007/s12043-024-02859-3","DOIUrl":"10.1007/s12043-024-02859-3","url":null,"abstract":"<div><p>We have investigated the gas electron multiplier (GEM) signal and time resolution using a numerical analysis method. The Garfield<span>(++)</span> simulation package with a known field solver, ANSYS, is used here. To examine the impacts of gas mixture and electron transport characteristics inside the detector, two other softwares, Magboltz and Heed, were utilised. By exploring the effects of detector geometry, electric fields, incoming particle energy and gas mixture characteristics, we tried improving GEM detectors for higher temporal resolution. A single GEM detector was investigated with two radiation sources, i.e., a 5.9 keV <span>(hbox {Fe}^{55})</span> X-ray photon and cosmic muons with energies ranging from 1 MeV to 1 TeV. With Ar:<span>(hbox {CO}_2)</span> gas mixture for a particular set-up, a minimum time resolution of up to around 4 ns was recorded. This number can be reduced even more by using various detector geometries and field settings. A significant result in lowering the temporal resolution was achieved by changing the drift field and percentage of the ionisation component in the gas mixture. The admixture of <span>(hbox {O}_2)</span> and <span>(hbox {N}_2)</span> in the gas medium also improved the detector time performance. It was also observed that the initial particle energy has little effect on the timing accuracy of the detector.\u0000</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109961","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}