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Jayakumar T.,Annamalai K. 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.2
The main aim of this research was to investigate the mechanical behavior of aluminum (LM25) alloy hybrid metal matrix composites for high-temperature applications. The L25 alloy is hybrid reinforced with varying silicon carbide (SiC), niobium carbide (NbC), and magnesium oxide (MgO) nanoparticle compositions. Hybrid particle-reinforced composites are manufactured by means of a liquid manufacturing technique. The hot tensile behavior of the LM25 matrix and hybrid composites was examined under the temperature condition 30 °C–400 °C as per ASTM B557 and ASTM E8M standards using a hot tensile test rig. In addition, the surface morphology of the LM25 alloy and SiC-, NbC-, and MgO-reinforced composites was investigated using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). The results of the surface morphology investigation of the composites revealed that the SiC, NbC, and MgO particles were homogenously scattered within the matrix and revealed clearer interface bonding. In tensile test, the LM25 alloy/ 3wt% SiC, NbC, and MgO (LMSMN-3) composite showed a yield and tensile strength around 230.82 MPa and 251.71 MPa, which was 25% larger than the LM25 alloy materials, whereas LM25 alloy/1wt% SiC, NbC, and MgO (LMSMN-1) and LM25 alloy/2wt% SiC, NbC, and MgO (LMSMN-2) composites showed a yield and tensile strength of 176.45 MPa, 203.71 MPa,192 MPa, and 211.32 MPa, respectively, which was 23% and 16.75% higher than the LM25 alloy under room temperature condition. Also, at elevated temperatures such as 200℃ and 400℃, the LMSMN-3 composite exhibited a maximum increase in the tensile properties, i.e., 48.28% at 200℃ and of 61.12% at 400℃.
Jayakumar S.,Ramachandran A.,Bhaskaran G.,Lee Jung Bin 대한공간정보학회 2007 대한공간정보학회지 Vol.15 No.4
대축척(1:50,000)지도의 산림 정보는 산림지역 보호에 중요한 자료로 이용된다. 그러나 대상지역인 인도 Tamil Nadu의 Eastern Ghats(EG) 지역에는 대축척 지도를 사용할 수 없기 때문에 위성 데이터를 이용한 산림의 변화 탐지를 적용하여 분석하였다. 대상지역의 1990년과 2003년의 산림의 변화에 대한 연구 결과 약 10가지의 산림 종류가 관측되었으며 가장 변화가 큰 지역은 상록수와 낙엽수지역에서 관측되었다. Information on forest type and cover density status of the present and past on large scale (1:50,000) is very much needed for conservation of any forest region. Such large-scale maps are not available for the Eastern Ghats (EG) of Tamil Nadu. This study deals with the preparation of forest type and cover density map of EG of Tamil Nadu during 2003 and the changes it has undergone between 1990 and 2003 using appropriate satellite data. About 10 forest types have been identified and mapped. Major changes have been observed in the forest types such as evergreen, and deciduous.
Urban sprawl and its impact on the land cover-a geospatial study
Jayakumar, S.,Enkhbaatar, Lkhagva,Heo, Joon The Korean Society for Geospatial Information Syst 2008 대한공간정보학회지 Vol.16 No.4
The present study was aimed to estimate the urban sprawl in a historical city of India using series of satellite data between 1968 and 2005(37 years) and GIS. The total area of the Tiruchirappalli city was 1991.96 ha during 1968 and it was expanded into 4335.98 ha(117.67%) during 2005. The average growth rate per year was 63.35 ha. This 117.67% growth was at the cost of agriculture land(97.81%) and water body(2.19%). The satellite data used in this study were found to be good source of information for this kind of analysis and further studies are need to estimate the impact of this city expansion on agriculture yield and ground water.
Wave load resistance of high strength concrete slender column subjected to eccentric compression
Jayakumar, M.,Rangan, B.V. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.3
A computer based iterative numerical procedure has been developed to analyse reinforced high strength concrete columns subjected to horizontal wave loads and eccentric vertical load by taking the material, geometrical and wave load non-linearity into account. The behaviour of the column has been assumed, to be represented by Moment-Thrust-Curvature relationship of the column cross-section. The formulated computer program predicts horizontal load versus deflection behaviour of a column up to failure. The developed numerical model has been applied to analyse several column specimens of various slenderness, structural properties and axial load ratios, tested by other researchers. The predicted values are having a better agreement with experimental results. A simplified user friendly hydrodynamic load model has been developed based on Morison equation supplemented with a wave slap term to predict the high frequency non-linear impulsive hydrodynamic loads arising from steep waves, known as ringing loads. A computer program has been formulated based on the model to obtain the wave loads and non-dimensional wave load coefficients for all discretised nodes, along the length of column from instantaneous free water surface to bottom of the column at mud level. The columns of same size and material properties but having different slenderness ratio are analysed by the developed numerical procedure for the simulated wave loads under various vertical thrust. This paper discusses the results obtained in detail and effect of slenderness in resisting wave loads under various vertical thrust.
Object-oriented Classification and QuickBird Multi-spectral Imagery in Forest Density Mapping
Jayakumar, S.,Ramachandran, A.,Lee, Jung-Bin,Heo, Joon The Korean Society of Remote Sensing 2007 大韓遠隔探査學會誌 Vol.23 No.3
Forest cover density studies using high resolution satellite data and object oriented classification are limited in India. This article focuses on the potential use of QuickBird satellite data and object oriented classification in forest density mapping. In this study, the high-resolution satellite data was classified based on NDVI/pixel based and object oriented classification methods and results were compared. The QuickBird satellite data was found to be suitable in forest density mapping. Object oriented classification was superior than the NDVI/pixel based classification. The Object oriented classification method classified all the density classes of forest (dense, open, degraded and bare soil) with higher producer and user accuracies and with more kappa statistics value compared to pixel based method. The overall classification accuracy and Kappa statistics values of the object oriented classification were 83.33% and 0.77 respectively, which were higher than the pixel based classification (68%, 0.56 respectively). According to the Z statistics, the results of these two classifications were significantly different at 95% confidence level.
Site Suitability Assessment for Joint Forest Management(JFM) - a Geospatial Approach
Jayakumar, S.,Ramachandran, A.,Bhaskaran, G.,Heo, Joon,Kim, Woo-Sun The Korean Society of Remote Sensing 2007 大韓遠隔探査學會誌 Vol.23 No.5
Joint Forest Management(JFM) is a concept of developing partnerships between fringe forest user groups and the Forest Department(FD) on the basis of mutual trust and jointly defined roles and responsibilities with regard to forest protection and development. In India, JFM was started during 1992 and it was implemented in many states. However success rate of JFM activity was not promising. Though there are many factors attributed to the failures, one of the main factors is the JFM site. This paper deals with the significant ground works to be done before planning for JFM using recent technologies such as remote sensing(RS) and Geographic Information System(GIS). Also it deals with the advantages of weighted overlay analysis in selecting suitable sites for JFM taking into consideration the various criteria. As a result of weighted overlay analysis, there were four types of suitability classes viz., less, moderate, highly and un-suitable. The moderately suitable class occupied maximum area(13209.64 ha) than less and highly suitable classes. If JFM is implemented on the suitability area, then the failure could be avoided in the future.
Jayakumar Pathma,Niraikulam Ayyadurai,Natarajan Sakthivel 한국미생물학회 2010 The journal of microbiology Vol.48 No.6
Antagonistic fluorescent pseudomonads isolated from rice rhizospheric soil were characterized using biochemical, taxonomical and molecular tools. Production of cyclopropane fatty acid (CFA) was correlated with their antagonistic potential. Strains were grouped into 18 different genotypes on the basis of amplified ribosomal DNA restriction analysis (ARDRA) and repetitive (rep)-PCR based genotypic fingerprinting analyses. High phylogenetic resolution among antagonistic fluorescent pseudomonad strains was obtained based on the DNA gyrase B subunit (gyrB) and RNA polymerase sigma factor 70 (rpoD) gene sequence analyses. Combined gyrB and rpoD sequence analysis resulted in the accurate estimation of molecular phylogeny and provided a significant correlation between the genetic distances among strains. Present study demonstrated the genetic and functional relationship of fluorescent pseudomonads. The knowledge on genetic and functional potential of fluorescent pseudomonads associated with rice rhizosphere is useful to understand their ecological role and for their utilization in sustainable agriculture.