Micro-scale to nano-scale generators for energy harvesting: Self powered piezoelectric, triboelectric and hybrid devices

Chandrasekaran, Sundaram,Bowen, Chris,Roscow, James,Zhang, Yan,Dang, Dinh Khoi,Kim, Eui Jung,Misra, R.D.K.,Deng, Libo,Chung, Jin Suk,Hur, Seung Hyun Elsevier 2019 Physics reports Vol.792 No.-

<P><B>Abstract</B></P> <P>This comprehensive review focuses on recent advances in energy harvesting of micro-scale and nano-scale generators based on piezoelectric and triboelectric effects. The development of flexible and hybrid devices for a variety of energy harvesting applications are systematically reviewed. A fundamental understanding of the important parameters that determine the performance of piezoelectric, triboelectric and hybrid devices are summarized. Current research directions being explored and the emerging factors to improve harvester functionality and advance progress in achieving high performance and durable energy conversion are provided. Investigations with regard to integrating flexible matrices and optimizing the composition of the piezoelectric and triboelectric materials are examined to enhance device performance and improve cost-effectiveness for the commercial arena. Finally, future research trends, emerging device structures and novel materials in view of imminent developments and harvesting applications are presented.</P>

Structurally tuned lead magnesium titanate perovskite as a photoelectrode material for enhanced photoelectrochemical water splitting

Chandrasekaran, S.,Kim, E.J.,Chung, J.S.,Yoo, I.K.,Senthilkumar, V.,Kim, Y.S.,Bowen, C.R.,Adamaki, V.,Hyun Hur, S. Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.309 No.-

This is the first demonstration of four distinct types of Lead Magnesium Titanate (PMT) perovskites including spheres, flakes, hierarchical flower and thin microbelt shapes that were finely tuned via facile solution method to develop cost effective and high performance photoanode materials for water splitting. The influence of solvent effects during structural tuning, purity, morphology, optical absorption, structural phase transition and stoichiometric formation of the prepared Lead Magnesium Titanate perovskites has been discussed in detail. A remarkable observation is that the thin microbelts structured PMT perovskite (PMTT) exhibited an excellent water splitting performance and it is more sensitive to the illuminated visible light. Owing to the unique structural features, the photoconversion efficiency value of PMTT perovskite is ~3.9, 3.54, 2.85 and 1.52 times higher than those of other prepared PMT perovskites including pristine PbTiO<SUB>3</SUB>. The excellent water splitting performance of PMTT (thin microbelts) may be ascribed to the remarkable structural features that include a large surface area, high optical absorbance, more active sites and high interface area of the microbelts, which provide large contact areas between the electrolyte and highly active materials for electrolyte diffusion and a rapid route for charge transfer with minimal diffusion resistance. In addition, each thin microbelt is directly in contact with the Ni foam substrate, which can also shorten the diffusion path for the electrons. The demonstrated approach paves the way for low-cost and high-throughput production of next generation, high performance and highly active water splitting perovskite photocatalysts.

Modeling and Control of Three-Phase Self-Excited Induction Generator Connected to Grid

Chandrasekaran Natarajan,Karthikeyan A 한국전기전자재료학회 2017 Transactions on Electrical and Electronic Material Vol.18 No.5

This paper presents the dynamic modeling, analysis, and control of an AC/DC/AC-assisted, self-excited induction generator connected to the grid. The dynamic model includes wind turbine models with pitch control, gear boxes, self-excited induction generators, excitation capacitance, inductive load models, controlled six-pulse rectifiers, and novel state-space models of a grid-connected inverter. The system has been simulated to verify its capabilities of buildup voltage, stator flux response, stator phase current, electromagnetic torque, and magnetizing inductance variation during both the dynamic and steady states with a variable-speed prime mover. The complete setup of the above dynamic models was simulated using MATLAB/SIMULINK.

STRUCTURE OF COEXTENSIONS OF REGULAR SEMIGROUPS BY RECTANGULAR BANDS

Chandrasekaran, V.M. 한국전산응용수학회 2003 Journal of applied mathematics & informatics Vol.12 No.1

In this paper, we described the structure of coextensions of regular semigroups by rectangular bands.

Nonlinear response of stiffened triceratops under impact and non-impact waves

Chandrasekaran, Srinivasan,Nassery, Jamshed Techno-Press 2017 Ocean systems engineering Vol.7 No.3

Dynamic response analysis of offshore triceratops with stiffened buoyant legs under impact and non-impact waves is presented. Triceratops is relatively new-generation complaint platform being explored in the recent past for its suitability in ultra-deep waters. Buoyant legs support the deck through ball joints, which partially isolate the deck by not transferring rotation from legs to the deck. Buoyant legs are interconnected using equally spaced stiffeners, inducing more integral action in dispersing the encountered wave loads. Two typical nonlinear waves under very high sea state are used to simulate impact and non-impact waves. Parameters of JONSWAP spectrum are chosen to produce waves with high vertical and horizontal asymmetries. Impact waves are simulated by steep, front asymmetric waves while non-impact waves are simulated using Stokes nonlinear irregular waves. Based on the numerical analyses presented, it is seen that the platform experiences both steady state (springing) and transient response (ringing) of high amplitudes. Response of the deck shows significant reduction in rotational degrees-of-freedom due to isolation offered by ball joints. Weak-asymmetric waves, resulting in non-impact waves cause steady state response. Beat phenomenon is noticed in almost all degrees-of-freedom but values in sway, roll and yaw are considerably low as angle of incidence is zero degrees. Impact waves cause response in higher frequencies; bursting nature of pitch response is a clear manifestation of the effect of impact waves on buoyant legs. Non-impact waves cause response similar to that of a beating phenomenon in all active degrees-of-freedom, which otherwise would not be present under normal loading. Power spectral density plots show energy content of response for a wide bandwidth of frequencies, indicating an alarming behaviour apart from being highly nonlinear. Heave, being one of the stiff degrees-of-freedom is triggered under non-impact waves, which resulted in tether tension variation under non-impact waves as well. Reduced deck response aids functional requirements of triceratops even under impact and non-impact waves. Stiffened group of buoyant legs enable a monolithic behaviour, enhancing stiffness in vertical plane.

Structure of the Double Four-spiral Semigroup

CHANDRASEKARAN, V.M.,LOGANATHAN, M. Department of Mathematics 2003 Kyungpook mathematical journal Vol.43 No.4

In this paper, we first give an alternative description of the fundamental orthodox semigroup $\bar{A}$(1, 2). We then use this to represent the double four-spiral semigroup $DSp_4$ as a regular Rees matrix semigroup over $\bar{A}$(1, 2).

Influence of severe drought on mineral nutrient status in eastern white pine (Pinus strobus L)

Chandrasekaran Umashankar,변시연,김근효,허우진,한아름,이영상,김현석 한국산림과학회 2023 Forest Science And Technology Vol.19 No.3

The photochemical process of photosynthesis is significantly influenced by the availability of nutrients. The purpose of this research is to ascertain how photosynthetic pigment function is affected by nutrient elemental changes caused by severe drought stress. Using elemental analysis, we looked at the changes in mineral nutrient composition in eastern white pine (Pinus strobus L) seedlings 32 days after drought treatment. According to our findings, severe drought resulted in a significant and non-significant decrease in the contents of Chl “b and a”, respectively. The elemental composition of iron (Fe), zinc (Zn), magnesium (Mg), potas- sium (K), phosphorus (P) and nitrogen (N) was measured. After severe drought treatment, leaf nutrient status showed a significant decline in total N (control-1.57 ± 0.1; drought- 0.65 ± 0.07), P (control-959.4 ± 17; drought-645 ± 46), Mg (control-1030.4 ± 33; drought- 750.7 ± 76), and K (control-3062.5 ± 32; drought-1853.3 ± 198), with a non-significant decrease in leaf Fe (control-120.3 ± 20; drought-98.9 ± 28) and increase in leaf Zn (control-33.49 ± 2; drought-39.05 ± 4). A positive correlation was found between the content of Fe, P, Mg, K, and N in leaf Chl “b”, but only a positive correlation was found between the content of Zn in leaf Chl “a” during severe drought. During severe drought, nutrient reallocation has a sig- nificant impact on leaf chlorophyll levels, as evidenced by this correlation.

Response of triceratops to impact forces: numerical investigations

Chandrasekaran, Srinivasan,Nagavinothini, R. Techno-Press 2019 Ocean systems engineering Vol.9 No.4

Triceratops is one of the new generations of offshore compliant platforms suitable for ultra-deepwater applications. Apart from environmental loads, the offshore structures are also susceptible to accidental loads. Due to the increase in the risk of collision between ships and offshore platforms, the accurate prediction of structural response under impact loads becomes necessary. This paper presents the numerical investigations of the impact response of the buoyant leg of triceratops usually designed as an orthogonally stiffened cylindrical shell with stringers and ring frames. The impact analysis of buoyant leg with a rectangularly shaped indenter is carried out using ANSYS explicit analysis solver under different impact load cases. The results show that the shell deformation increases with the increase in impact load, and the ring stiffeners hinder the shell damage from spreading in the longitudinal direction. The response of triceratops is then obtained through hydrodynamic response analysis carried out using ANSYS AQWA. From the results, it is observed that the impact load on single buoyant leg causes periodic vibration in the deck in the surge and pitch degrees of freedom. Since the impact response of the structure is highly affected by the geometric and material properties, numerical studies are also carried out by varying the strain rate, and the location of the indenter and the results are discussed.

Genome editing: a robust technology for human stem cells

Chandrasekaran, A. P.,Song, M.,Ramakrishna, S. Birkh?user 2017 Cellular and molecular life sciences Vol.74 No.18

SPLIT MAP AND IDEMPOTENT SEPARATING CONGRUENCE

CHANDRASEKARAN, V. M.,LOGANATHAN, M. 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.18 No.1

Let T be a regular semigroup and let S be a regular subsemigroup of T. In this paper we study the relationship between the idempotent separating congruence on S and the idempotent separating congruence on T, when T and S are connected by a splitmap ${\theta} : T {\to} S$.