Kodakkal Kannan Viswanathan

Bio: Kodakkal Kannan Viswanathan is an academic researcher from Universiti Teknologi Malaysia. The author has contributed to research in topics: Boundary value problem & Spline (mathematics). The author has an hindex of 14, co-authored 75 publications receiving 665 citations. Previous affiliations of Kodakkal Kannan Viswanathan include SRM University & AMET University.

Asymmetric free vibrations of laminated annular cross-ply circular plates including the effects of shear deformation and rotary inertia: Spline method

Abstract: Asymmetric free vibrations of annular cross-ply circular plates are studied using spline function approximation. The governing equations are formulated including the effects of shear deformation and rotary inertia. Assumptions are made to study the cross-ply layered plates. A system of coupled differential equations are obtained in terms of displacement functions and rotational functions. These functions are approximated using Bickley- type spline functions of suitable order. Then the system is converted into the eigenvalue problem by applying the point collocation technique and suitable boundary conditions. Parametric studies have been made to investigate the effect of transverse shear deformation and rotary inertia on frequency parameter with respect to the circumferential node number, radii ratio and thickness to radius ratio for both symmetric and anti-symmetric cross-ply plates using various types of material properties.

Free vibration of symmetric angle ply truncated conical shells under different boundary conditions using spline method

Abstract: Free vibration of symmetric angle-ply laminated truncated conical shell is analyzed to determine the effects of frequency parameter and angular frequencies under different boundary condition, ply angles, different material properties and other parameters The governing equations of motion for truncated conical shell are obtained in terms of displacement functions The displacement functions are approximated by cubic and quintic splines resulting into a generalized eigenvalue problem The parametric studies have been made and discussed

Calculation of 8+ isomers of even-even nuclei 76 ni to 94 pd for n=48 neutrons

Abstract: Study of the properties of nuclear isomers is a current research focus. We have studied the systematic 8+ isomeric levels, half-lives, deformation parameters, and reduced transition probabilities between 8+ ? 6+ state of even-even 76Ni to 94Pd nuclei for N = 48 neutrons. The calculated half-lives and quadrupole moments are compared with the experimental values. Moreover, we have studied the systematic B (E2) values, intrinsic quadrupole moments and values of s/s2SPas a function of atomic number (Z) for N = 48 neutrons.

Transition probability from the ground to the first-excited 2^+ state of even-even nuclides

Abstract: Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths. Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000. The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.

Compound Copper Chalcogenide Nanocrystals

Abstract: This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), en...

Trapped charge-driven degradation of perovskite solar cells

Abstract: Perovskite solar cells have shown unprecedent performance increase up to 22% efficiency. However, their photovoltaic performance has shown fast deterioration under light illumination in the presence of humid air even with encapulation. The stability of perovskite materials has been unsolved and its mechanism has been elusive. Here we uncover a mechanism for irreversible degradation of perovskite materials in which trapped charges, regardless of the polarity, play a decisive role. An experimental setup using different polarity ions revealed that the moisture-induced irreversible dissociation of perovskite materials is triggered by charges trapped along grain boundaries. We also identified the synergetic effect of oxygen on the process of moisture-induced degradation. The deprotonation of organic cations by trapped charge-induced local electric field would be attributed to the initiation of irreversible decomposition.

A piperidinium salt stabilizes efficient metal-halide perovskite solar cells.

Abstract: Longevity has been a long-standing concern for hybrid perovskite photovoltaics. We demonstrate high-resilience positive-intrinsic-negative perovskite solar cells by incorporating a piperidinium-based ionic compound into the formamidinium-cesium lead-trihalide perovskite absorber. With the bandgap tuned to be well suited for perovskite-on-silicon tandem cells, this piperidinium additive enhances the open-circuit voltage and cell efficiency. This additive also retards compositional segregation into impurity phases and pinhole formation in the perovskite absorber layer during aggressive aging. Under full-spectrum simulated sunlight in ambient atmosphere, our unencapsulated and encapsulated cells retain 80 and 95% of their peak and post-burn-in efficiencies for 1010 and 1200 hours at 60° and 85°C, respectively. Our analysis reveals detailed degradation routes that contribute to the failure of aged cells.

Quantum dot-sensitized solar cells

Abstract: Quantum dot-sensitized solar cells (QDSCs) have emerged as a promising candidate for next-generation solar cells due to the distinct optoelectronic features of quantum dot (QD) light-harvesting materials, such as high light, thermal, and moisture stability, facilely tunable absorption range, high absorption coefficient, multiple exciton generation possibility, and solution processability as well as their facile fabrication and low-cost availability. In recent years, we have witnessed a dramatic boost in the power conversion efficiency (PCE) of QDSCs from 5% to nearly 13%, which is comparable to other kinds of emerging solar cells. Both the exploration of new QD light-harvesting materials and interface engineering have contributed to this fantastically fast improvement. The outstanding development trend of QDSCs indicates their great potential as a promising candidate for next-generation photovoltaic cells. In this review article, we present a comprehensive overview of the development of QDSCs, including: (1) the fundamental principles, (2) a history of the brief evolution of QDSCs, (3) the key materials in QDSCs, (4) recombination control, and (5) stability issues. Finally, some directions that can further promote the development of QDSCs in the future are proposed to help readers grasp the challenges and opportunities for obtaining high-efficiency QDSCs.