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S. Paulsamy,길봉섭,K.K. Vijayakumar,P. Senthilkumar 한국생태학회 2009 Journal of Ecology and Environment Vol.32 No.4
The rare endemic plant, Smilax wightii, is generally distributed in shola forests at high altitudes in Nilgiri Biosphere Reserve, the Western Ghats, southern India. To determine the ecological status of the species, we surveyed 11 major shola forests in that region. S. wightii has a limited distribution in all sholas (frequency value of <13%). The density of the species is generally around 15/100 m² in the sholas except in Thiashola where it occurred at a density of 40 individuals/100 m². The density of S. wightii was generally greater in the margins of the shoals, while the interior forests contained fewer individuals per unit area. The basal cover occupied by this species ranged between 2246 and 3144 mm²/100 m². The importance value index for S. wightii was >2 in all shoals, which indicates that the species occupies an important position in the lower stratum of shola forests of Nilgiri Biosphere Reserve.
Paulsamy, S.,Vijayakumar, K.K.,Kil, Bong-Seop,Senthilkumar, P. The Ecological Society of Korea 2009 Journal of Ecology and Environment Vol.32 No.4
The rare endemic plant, Smilax wightii, is generally distributed in shola forests at high altitudes in Nilgiri Biosphere Reserve, the Western Ghats, southern India. To determine the ecological status of the species, we surveyed 11 major shola forests in that region. S. wightii has a limited distribution in all sholas (frequency value of < 13%). The density of the species is generally around $15/100\;m^2$ in the sholas except in Thiashola where it occurred at a density of 40 individuals/$100\;m^2$. The density of S. wightii was generally greater in the margins of the shoals, while the interior forests contained fewer individuals per unit area. The basal cover occupied by this species ranged between 2246 and $3144\;mm^2/100\;m^2$. The importance value index for S. wightii was >2 in all shoals, which indicates that the species occupies an important position in the lower stratum of shola forests of Nilgiri Biosphere Reserve.
In vitro Antioxidant Activity of Ethanolic Extract of Chlorophytum borivilianum
R. Govindarajan1,,N. Sreevidya1,,M. Vijayakumar1,,M. Thakur2,,V.K. Dixit2,,S. Mehrotra*1,,P. Pushpangadan1 한국생약학회 2005 Natural Product Sciences Vol.11 No.3
Chlorophytum borivilianum Baker (Antharicaceae) comonly referred as ‘Safed Musli’ has beenwidely used in the Indian traditional systems of medicine to treat various diseases like rheumatism apart fromaphordisiac properties. C. borivilianum was screened for the first time to determine its antioxidant activity,isolation of the sapogenins and standardization of the isolated sapogenin fraction using HPTLC. Potent antioxidantactivity of ethanolic extract was found by their ability to scavenge DPPH (84.51%), hydroxyl radical (48.95 %),feryl bi-pyridyl complex (84.53%) along with the inhibition of lipid peroxidation (67.17%) at 100g/mlconcentration. The ethanolic extract also exhibited significant inhibition of superoxide anion radical generated byplant in the traditional system especially its use as a Rasayana drug.
MIMO Cognitive Radio Spectrum Sharing Using Spatial Coding and User Scheduling for Fading Channels
Vijayakumar Ponnusamy,Dr. S. Malarvizhi 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.3
Spectrum scarcity is one of the issue in wireless communication. Dynamic spectrum sharing is the solution for this problem in which the underutilized spectrums are utilized efficiently. Multiple Input Multiple Output (MIMO) based cognitive radio using spatial coding is used to dynamically share the spectrum which allows simultaneous usage of spectrum by more than one user. The drawback of spatial coding is the achievable capacity get reduced with the increased number of cognitive users which limits the number of users to share the spectrum. In order to maximize the number of secondary users sharing the spectrum of the primary user, this paper presents a cluster based multiple primary and secondary user’s MIMO spatial coding which provides higher capacity. The entire network is divided into number of cluster based on the location such that each cluster will be interference free from other. Each cluster is designed with one primary user and many secondary users and a User Scheduling algorithm called Cluster Based Max Signal Power User Scheduling (CBMSPUS) is proposed to select two best secondary users in each cluster. Since the performance of spatial coder depends on the channel matrix, this paper analyze the spatial pre-coder under Rayleigh, Rican and Nakagami fading channels with multiple users and evaluate the capacity of users under CBMSPUS scheduling algorithm. The results show that the Nakagami fading channel achieves high capacity than others. Primary user calculated capacity is 10.8bits/HZ /channel at low SNR region and 14.2 bits/HZ/channel at high SNR region. The secondary user archives maximum capacity of 9.8bits/HZ /channel at low SNR and 13 bits/HZ/channel at high SNR. The Proposed Scheduling method offers maximum of 15dB gain comparing FIFO scheduling algorithm.
Nagamuthu, S.,Vijayakumar, S.,Lee, S.H.,Ryu, K.S. New York] ; North-Holland 2016 APPLIED SURFACE SCIENCE - Vol.390 No.-
MnCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets and FeMn<SUB>2</SUB>O<SUB>4</SUB> nanospheres were synthesized using a hydrothermal method. Choline chloride was used as the capping agent during the preparation of the nanoparticles. XRD patterns confirmed the spinel structure of MnCo<SUB>2</SUB>O<SUB>4</SUB> and FeMn<SUB>2</SUB>O<SUB>4</SUB>. XPS measurements were used to determine the oxidation state of the prepared spinel metal oxides. HRTEM images revealed the formation of hexagonal nanosheets of MnCo<SUB>2</SUB>O<SUB>4</SUB> and nanospheres of FeMn<SUB>2</SUB>O<SUB>4</SUB>. Electrochemical measurements were made for both positive and negative electrodes using three electrode systems. MnCo<SUB>2</SUB>O<SUB>4</SUB> Exhibits 282Cg<SUP>-1</SUP> and FeMn<SUB>2</SUB>O<SUB>4</SUB> yields 110Cg<SUP>-1</SUP> at a specific current of 1Ag<SUP>-1</SUP>. Hybrid supercapacitor device was fabricated using MnCo<SUB>2</SUB>O<SUB>4</SUB> as the positive and FeMn<SUB>2</SUB>O<SUB>4</SUB> as the negative electrode material. The hybrid supercapacitor device was delivered a maximum power of 37.57kWkg<SUP>-1</SUP>.
S. Sahana,G. R. Vijayakumar,R. Sivakumar,D. Sriram,D. V. Saiprasad 대한화학회 2022 대한화학회지 Vol.66 No.3
A simple, efficient, and cost-effective method has been employed for the synthesis of 2,4,5-trisubstituted imidazole derivatives (3a-j) containing quinoline substituent at 2nd position. Title compounds were obtained by multicomponent reaction (MCR), involving aryl substituted 1,2-diketone, quinoline carbaldehyde and ammonium acetate in the presence of acetic acid solvent under mild reaction conditions. The newly synthesized quinoline containing imidazole derivatives were confirmed through FT-IR, 1H-NMR, 13C-NMR and mass spectral analysis. In-vitro microplate alamar blue assay (MABA) to determine the MIC (minimum inhibitory concentration) values against Mycobacterium tuberculosis H37Rv was performed for the synthesized compounds. The synthesized compounds exhibited activity against Mycobacterium tuberculosis and among which compounds, 3d, 3f and 3i showed good activity. The highest activity was showed with compound 3i. The anti-mycobacterial activity results are well correlated with the computational molecular docking analysis, which was performed for the synthesized compounds prior to the evaluation of the activity.
Computation and Communication Efficient Key Distribution Protocol for Secure Multicast Communication
( P. Vijayakumar ),( S. Bose ),( A. Kannan ),( L. Jegatha Deborah ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.4
Secure multimedia multicast applications involve group communications where group membership requires secured dynamic key generation and updating operations. Such operations usually consume high computation time and therefore designing a key distribution protocol with reduced computation time is necessary for multicast applications. In this paper, we propose a new key distribution protocol that focuses on two aspects. The first one aims at the reduction of computation complexity by performing lesser numbers of multiplication operations using a ternary-tree approach during key updating. Moreover, it aims to optimize the number of multiplication operations by using the existing Karatsuba divide and conquer approach for fast multiplication. The second aspect aims at reducing the amount of information communicated to the group members during the update operations in the key content. The proposed algorithm has been evaluated based on computation and communication complexity and a comparative performance analysis of various key distribution protocols is provided. Moreover, it has been observed that the proposed algorithm reduces the computation and communication time significantly.
EXISTENCE OF SOLUTIONS FOR DOUBLE PERTURBED IMPULSIVE NEUTRAL FUNCTIONAL EVOLUTION EQUATIONS
V. VIJAYAKUMAR,S. SIVASANKARAN,M. MALLIKA ARJUNAN 한국산업응용수학회 2011 Journal of the Korean Society for Industrial and A Vol.15 No.4
In this paper, we study the existence of mild solutions for double perturbed impulsive neutral functional evolution equations with infinite delay in Banach spaces. The existence of mild solutions to such equations is obtained by using the theory of the Hausdorff measure of noncompactness and Darbo fixed point theorem, without the compactness assumption on associated evolution system. An example is provided to illustrate the theory.
Velu, Vijayakumar,Mylvaganam, Geetha Hanna,Gangadhara, Sailaja,Hong, Jung Joo,Iyer, Smita S.,Gumber, Sanjeev,Ibegbu, Chris C.,Villinger, Francois,Amara, Rama Rao The American Association of Immunologists, Inc. 2016 JOURNAL OF IMMUNOLOGY Vol.197 No.5
<P>Chronic HIV infection is associated with accumulation of germinal center (GC) T follicular helper (Tfh) cells in the lymphoid tissue. The GC Tfh cells can be heterogeneous based on the expression of chemokine receptors associated with T helper lineages, such as CXCR3 (Th1), CCR4 (Th2), and CCR6 (Th17). However, the heterogeneous nature of GC Tfh cells in the lymphoid tissue and its association with viral persistence and Ab production during chronic SIV/HIV infection are not known. To address this, we characterized the expression of CXCR3, CCR4, and CCR6 on GC Tfh cells in lymph nodes following SIVmac251 infection in rhesus macaques. In SIV-naive rhesus macaques, only a small fraction of GC Tfh cells expressed CXCR3, CCR4, and CCR6. However, during chronic SIV infection, the majority of GC Tfh cells expressed CXCR3, whereas the proportion of CCR4(+) cells did not change, and CCR6(+) cells decreased. CXCR3(+), but not CXCR3(-), GC Tfh cells produced IFN-gamma (Th1 cytokine) and IL-21 (Tfh cytokine), whereas both subsets expressed CD40L following stimulation. Immunohistochemistry analysis demonstrated an accumulation of CD4(+) IFN-gamma(+) T cells within the hyperplastic follicles during chronic SIV infection. CXCR3(+) GC Tfh cells also expressed higher levels of ICOS, CCR5, and alpha 4 beta 7 and contained more copies of SIV DNA compared with CXCR3(-) GC Tfh cells. However, CXCR3(+) and CXCR3(-) GC Tfh cells delivered help to B cells in vitro for production of IgG. These data demonstrate that chronic SIV infection promotes expansion of Th1-biased GC Tfh cells, which are phenotypically and functionally distinct from conventional GC Tfh cells and contribute to hypergammaglobulinemia and viral reservoirs.</P>