Evolution of Agrometeorology at the Global Level

( M. V. K. Sivakumar ) 한국농림기상학회 2003 학술발표논문집 Vol.2003 No.1

Cobalt substituted layered O3 and P2-type Na-Ti-Ni-Co-O anode materials for emerging sodium-ion batteries

K. Kannan,M. Kouthaman,P. Arjunan,R. Subadevi,M. Sivakumar 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.102 No.-

Sodium ion batteries (SIBs) are considered as a propitious candidate for large scale energy storage devicesdue to the copious of sodium resources in earth crust and low cost. In this work, layered Cobalt (Co) substitutedO3-type NaTi0.6Ni0.3Co0.1O2 (O3-NTNC) and P2-type Na0.5Ti0.6Ni0.3Co0.1O2 (P2-NTNC) anodematerials were prepared by solid-state reaction for SIBs. The prepared O3-NTNC and P2-NTNC can beassigned to rhombohedral and hexagonal structure with the space group of R-3m and P63/mmc respectively,using Rietveld refinement. O3-NTNC and P2-NTNC delivered the reversible capacity of 108 and96 mAh g 1 at 0.1C and revealed coulombic efficiency over 90% even after 50 cycles. In addition, partialCo-substitution enhanced the structural stability of the obtained materials during sodiation and desodiationprocess.

농업기상학의 역사

M.V.K. Sivakumar 한국농림기상학회 2004 한국농림기상학회지 Vol.6 No.2

Agricultural meteorology has advanced during the last 100 years from a descriptive to a quantitativescience using physical and biological principles. The agricultural comunity is becoming more aware thatusing climate and weather information will improve their profitability and this will no doubt increase thedemand for agrometeorological services. Hence it is timely that the needs and perspectives foragrometeorology in the 21st Century are grouped under two major headings: agrometeorological servicesfor agricultural production and agrometeorological support systems for such services. Emphasis must beplaced on the components of such suport systems comprising of data, research, policies and training/education/extension. As Monteith (2000) mentioned, food supplies ultimately depend upon the skill withwhich farmers can exploit the potential of good weather and minimize the impact of bad weather. Recentdissemination of agrometeorological information etc., provide agrometeorologists the tools necesary helpthe farmers improve such skills. The future for operational applications of agricultural meteorologyappears bright and such applications could contribute substantially to promote sustainable agricultureand alleviate poverty.

Evolution of Agrometeorology at the Global Level

Sivakumar, M.V.K. 한국농림기상학회 2004 한국농림기상학회지 Vol.6 No.2

농업기상은 지난 100년동안 서술적인 학문에서 물리학적 및 생물학적 법칙을 활용하는 정량적인 학문적으로 발전되어 왔다. 농업인들은 기후와 기상정보의 이용으로 수익을 개선할 수 있다는 점을 더욱 깊이 인식하게 되었고, 이는 농업기상서비스에 대한 수요를 증대로 이어질 것이라는 점은 의심할 여지가 없다. 그러므로 21세기 농업기상의 필요성과 전망을 크게 두 가지 주제로 구분하는 것은 시의 적절하다 할 수 있다. 즉 농업생산을 위한 농업기상서비스와 이들 서비스를 지원하기 위한 농업기상자원시스템의 중요한 구성요소인 자료, 연구, 정책 및 훈련/교육/지도의 중요성이 더욱 강조될 것이다. 몬티쓰박사가 말한 바와 같이, 식량공급은 궁극적으로 기상자원의 잠재성을 탐구하거나 악기상의 영향을 최소화하는 농민의 기술력에 좌우될 것이다. 장비, 자료관리체계, 기후예측, 작물모의, 농업기상정보 배분등에 있어서의 최근 발전으로 인해 농민이 이러한 핵심기술을 습득, 향상시키는 것을 돕기 위해 필요한 도구들이 농업기상학자들에게 제공되고 있다. 따라서 향후 농업기상기술의 현장활용은 그 전도가 매우 밝다 하겠으며, 이러한 기술의 현장활용을 통해 지속농업의 촉진 및 빈곤타파 등에 농업기상이 근원적인 커다란 기여를 할 수 있을 것이다. Agricultural meteorology has advanced during the last 100 years from a descriptive to a quantitative science using physical and biological principles. The agricultural community is becoming more aware that using climate and weather information will improve their profitability and this will no doubt increase the demand for agrometeorological services. Hence it is timely that the needs and perspectives for agrometeorology in the 21^(st) Century are grouped under two major headings: agrometeorological services for agricultural production and agrometeorological support systems for such services. Emphasis must be placed on the components of such support systems comprising of data, research, policies and training/ education/extension. As Monteith (2000) mentioned, food supplies ultimately depend upon the skill with which farmers can exploit the potential of good weather and minimize the impact of bad weather: Recent developments in instrumentation, data management systems, climate prediction, crop modelling, dissemination of agrometeorological information etc., provide agrometeorologicts the tools necessary help the farmers improve such skills. The future for operational applications of agricultural meteorology appears bright and such applications could contribute substantially to promote sustainable agriculture and alleviate poverty.

Microwave sintering of iron deficient Ni–Cu–Zn ferrites for multilayer chip inductors

M. Penchal Reddy,W. Madhuri,G. Balakrishnaiah,N. Ramamanohar Reddy,K.V. Sivakumar,V.R.K. Murthy,R. Ramakrishna Reddy 한국물리학회 2011 Current Applied Physics Vol.11 No.2

This study was aimed at the low temperature synthesis of iron deficient samples of Ni―Cu―Zn ferrite using the microwave sintering technique. The samples were sintered at 950 ℃ for 30 min. Microstuctural and structural analyses were carried out using a scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The lattice parameter was found to increase with increasing nickel concentration. The porosity calculated using X-ray density and measured density also shows a decreasing behavior with increasing nickel concentration. The variation of saturation magnetization was studied as a function of nickel concentration. All the compositions indicate that they are ferrimagnetic in nature. Initial permeability plotted against temperature at 10 kHz showed a sharp drop at Curie transition temperature and values observed at transition are found to be dependent on the nickel concentration. The dielectric constant, dielectric loss tangent and ac conductivity of all samples were measured at room temperature as a function of frequency. These parameters decrease with increase in frequency for all of the samples. The present ferrites are well suitable for the application in multilayer chip inductor due to its low temperature sinterability, good magnetic properties and low loss at high frequency.

Transport properties of intermetallic compounds YT₄Al₈ (T = Mn and Cu)

Y. K. Kuo,K. M. Sivakumar,C. S. Lue 한국자기학회 2010 한국자기학회 학술연구발표회 논문개요집 Vol.2010 No.12

Tracking/Erosion Resistance Analysis of Nano-Al(OH)₃ Filled Silicone Rubber Insulating Materials for High Voltage DC Applications

P. Kannan,M. Sivakumar,K. Mekala,S. Chandrasekar 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.1

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano Al(OH)₃ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nanofiller concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

Optimization of stir casting process parameter using response surface meth odology

Senthilkumar KM,Sivakumar A,Rohokale Milind Shivaji,S.K. Tamang,Giriraj M 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2

Response surface methodology is used to optimize the stir casting process parameters for the aluminium metal matrixcomposite reinforced with boron carbide with several weight percentages. The stir casting process parameters used in thiswork are the weight percentage of the reinforcing element, stir casting mixing time and particle size of the reinforcing elementused in the fabrication of the metal matrix composite. The levels are chosen and central composite design is implemented tooptimize the tensile strength of the metal matrix composite. The analysis of variance is calculated and the estimated regressioncoefficients for the tensile strength are obtained. Also the residual plots and the contour plots are plotted and discussed here.

Tracking/Erosion Resistance Analysis of Nano-Al(OH)₃ Filled Silicone Rubber Insulating Materials for High Voltage DC Applications

Kannan, P.,Sivakumar, M.,Mekala, K.,Chandrasekar, S. The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.1

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

Sulfur cloaked with different carbonaceous materials for high performance lithium sulfur batteries

P. Rajkumar,K. Diwakar,R. Subadevi,R.M. Gnanamuthu,M. Sivakumar 한국물리학회 2019 Current Applied Physics Vol.19 No.8

Carbon matrices have attracted the attention enthusiastically as the improver materials of sulfur for rechargeable lithium-sulfur battery. In this work, various morphologies (sphere, fiber, tube and layer) based carbon materials have been used for preparing the sulfur-carbon binary composites via melt diffusion method for lithium-sulfur battery application. The prepared binary composites have been characterized for its structural and morphological information using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and, Scanning and Transmission electron microscopy. The electrochemical studies are characterized by cyclic voltammetry, charge-discharge and cycle life after being assembled as lithium-sulfur cell. The S-prGO composite exhibits the initial discharge capacity of 893 mAh g−1 and it sustains over 50 cycles (598 mAh g−1) at 0.1C, with low capacity fading rate when compared to the other composites studied. A remarkable electrochemical performance indicates that the sheet like morphology can accommodate the volume expansion of sulfur and the oxygen groups containing GO minimize the dissolution of lithium polysulfides.