P. C. Ray

Bio: P. C. Ray is an academic researcher from Government College of Engineering and Leather Technology. The author has contributed to research in topics: Nonlinear system & Ferroelectricity. The author has an hindex of 14, co-authored 37 publications receiving 522 citations. Previous affiliations of P. C. Ray include West Bengal University of Technology & Indian Statistical Institute.

The effect of thermocapillarity on the flow of a thin liquid film on a rotating disc

Abstract: Gradual formation of a thin liquid film on a hot/cold rotating disc under the action of thermocapillary force is studied analytically. It is found that the thermocapillary force acting on the free surface enhances the thinning rate for cooling the disc.

Periodicities of solar electron flare occurrence: analysis of cycles 21–23

Abstract: The data of energetic solar electron fluences measured in two ranges of energy values (E > 0.6 and 2 MeV) by the IMP-8 spacecraft of NASA, in the solar cycles 21, 22 and a major part of the current cycle 23, have been analysed for the first time by three different methods to detect periodicities accurately. Power spectral analysis of electron flux data shows a periodicity of ∼152 d for cycle 21, ∼330 and ∼604 d for cycle 22 and ∼152 and ∼176 d for the current cycle 23. The respective periodicities are found to be independent of the electron energy as are the other kinds of solar activity reported by earlier researchers, thus indicating the intimate relationship of electron emission with solar activity.

Film cooling on a rotating disk

Abstract: The unsteady flow of a liquid film on a cold rotating disk is analysed by means of matched asymptotic expansion under the assumptions of radially uniform film thickness that varies with time. The velocity, the temperature and the rate of heat transfer are determined. It is shown how the uniform film thins with time for fixed values of the cooling or heat dissipating parameter β, and the Prandtl number σ. When either β increases or σ decreases, the film thickness increases, which implies that a relative resistance to film thinning is developed inside the film- A zone S, bounded by a curve in the r-z plane, may be delineated such that the temperature is minimum on this curve. Thus, heat flows from the disk to the fluid, inside the zone S, and in the opposite direction outside S.

An approach to the Klein-Gordon equation for a dynamic study in ferroelectric materials.

Abstract: Ferroelectric materials such as lithium niobate and lithium tantalate show a non-linear hysteresis behaviour, which may be explained by dynamical system analysis. The behaviour of these ferroelectrics is usually explained by domains and domain wall movements. So, the spatial variation of the domain wall was studied previously in order to see its effect on the domain wall width in the context of the Landau-Ginzburg functional. In the present work, both temporal and spatial variations of polarization are considered, and by using the Euler-Lagrange dynamical equation of motion, a Klein-Gordon equation is derived by taking the ferroelectrics as a Hamiltonian system. An interaction has been considered between the nearest neighbour domains, which are stacked sideways in a parallel array with uniform polarization. This interaction term is associated with the spatial term and when this interaction is assumed to be zero, the spatial term vanishes, giving rise to a Duffing oscillator differential equation, which can be also studied by a dynamic system analysis.

Dynamics and stability of thin liquid films

Abstract: The dynamics and stability of thin liquid films have fascinated scientists over many decades: the observations of regular wave patterns in film flows down a windowpane or along guttering, the patterning of dewetting droplets, and the fingering of viscous flows down a slope are all examples that are familiar in daily life. Thin film flows occur over a wide range of length scales and are central to numerous areas of engineering, geophysics, and biophysics; these include nanofluidics and microfluidics, coating flows, intensive processing, lava flows, dynamics of continental ice sheets, tear-film rupture, and surfactant replacement therapy. These flows have attracted considerable attention in the literature, which have resulted in many significant developments in experimental, analytical, and numerical research in this area. These include advances in understanding dewetting, thermocapillary- and surfactant-driven films, falling films and films flowing over structured, compliant, and rapidly rotating substrates, and evaporating films as well as those manipulated via use of electric fields to produce nanoscale patterns. These developments are reviewed in this paper and open problems and exciting research avenues in this thriving area of fluid mechanics are also highlighted.

Defect–Domain Wall Interactions in Trigonal Ferroelectrics

Abstract: Domains and domain walls are a fundamental property of interest in ferroelectrics, magnetism, ferroelastics, superconductors, and multiferroic materials. Unlike magnetic Bloch walls, ideal ferroelectric domain walls are well accepted to be only one to two lattice units wide, over which polarization and strain change across the wall. However, walls in real ferroelectrics appear to show unexpected property variations in the vicinity of domain walls that can extend over micrometer length scales. This chapter specifically reviews the local electrical, elastic, optical, and structural properties of antiparallel domain walls in the trigonal ferroelectrics lithium niobate and lithium tantalate. It is shown that extrinsic point defects and their clustering play a key role in the observed local wall structure and influence macroscale properties by orders of magnitude. The review also raises broader and yet unexplored fundamental questions regarding intrinsic widths, defect–domain wall interactions, and static versus dynamic wall structure.

The Radiation Assessment Detector (RAD) Investigation

Abstract: The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) is an energetic particle detector designed to measure a broad spectrum of energetic particle radiation. It will make the first-ever direct radiation measurements on the surface of Mars, detecting galactic cosmic rays, solar energetic particles, secondary neutrons, and other secondary particles created both in the atmosphere and in the Martian regolith. The radiation environment on Mars, both past and present, may have implications for habitability and the ability to sustain life. Radiation exposure is also a major concern for future human missions. The RAD instrument combines charged- and neutral-particle detection capability over a wide dynamic range in a compact, low-mass, low-power instrument. These capabilities are required in order to measure all the important components of the radiation environment. RAD consists of the RAD Sensor Head (RSH) and the RAD Electronics Box (REB) integrated together in a small, compact volume. The RSH contains a solid-state detector telescope with three silicon PIN diodes for charged particle detection, a thallium doped Cesium Iodide scintillator, plastic scintillators for neutron detection and anti-coincidence shielding, and the front-end electronics. The REB contains three circuit boards, one with a novel mixed-signal ASIC for processing analog signals and an associated control FPGA, another with a second FPGA to communicate with the rover and perform onboard analysis of science data, and a third board with power supplies and power cycling or “sleep”-control electronics. The latter enables autonomous operation, independent of commands from the rover. RAD is a highly capable and highly configurable instrument that paves the way for future compact energetic particle detectors in space.

Analytic solutions for a liquid film on an unsteady stretching surface

Abstract: The momentum and heat transfer in a laminar liquid film on a horizontal stretching sheet is analyzed by the Homotopy analysis method (HAM). Analytic series solutions are given and compared with numerical results given by other authors. The good agreement between them shows the effectiveness of HAM to the problem of liquid film on an unsteady stretching surface.