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Search Results: 1 - 10 of 164069 matches for " B. Siva Kumar "
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B. Siva Kumar,M. Kasturaiah,C. Suresh Reddy
International Journal of Chemical Sciences and Research , 2011,
Abstract: New eight-membered phosphorous heterocyclic compounds such as 2,10 – dichloro – 12 – trichloromethyl - 6 – substituted xanthato – 12H – dibenzo[d,g] [1,3,2] dioxaphosphocin 6–sulfides were synthesized by reacting equimolar quantities of alcohols, carbondisulfide and 2,6,10-trichloromethyl-12H–dibenzo[d,g] [1,3,2] dioxaphosphocin 6 – sulfide(1) in the presence of dimethylaminopyridene(DMAP). The structures of the products were confirmed by analytical and IR, 1H, 13C, 31P, Mass spectral data and they were tested for their antimicrobial activity.
B.Siva kumar,K.Tharani,S.venkatasen
International Journal of Soft Computing & Engineering , 2012,
Abstract: In a typical wireless mobile ad hoc network (MANET) using a shared communication medium, every node receives or overhears every data transmission occurring in its vicinity. However, this technique is not applicable when a power saving mechanism (PSM) such as the one specified in IEEE 802.11 is employed, where a packet advertisement period is separated from the actual data transmission period. When a node receives an advertised packet that is not destined to it, it switches to a low-power state during the data transmission period, and thus, conserves power. However, since some MANET routing protocols such as Dynamic Source Routing (DSR) collect route information via overhearing, they would suffer if they are used with the IEEE 802.11PSM. Allowing no overhearing may critically deteriorate the performance of the underlying routing protocol, while unconditional overhearing may offset the advantage of using PSM. This paper proposes a new communication mechanism, called Random Cast or Rcast, via which a sender can specify the desired level of overhearing in addition to the intended receiver by using(Adhoc On-demand Distance Vector) AODV protocol. Therefore, it is possible that only a random set of nodes overhear and collect route information for future use. Rcast improves not only the energy efficiency, but also the energy balance among the nodes, without significantly affecting the routing efficiency
Bringing out Fluids Experiments from Laboratory to In Silico – A Journey of Hundred Years  [PDF]
Manickam Siva Kumar, Pichai Philominathan
American Journal of Computational Mathematics (AJCM) , 2011, DOI: 10.4236/ajcm.2011.14033
Abstract: By making use of the developments in the fields of numerical methods, computational technology and fluid dynamics models, computational fluid dynamics (CFD) progress forward to play an active role today in various industrial, academic and research activities. In many cases, CFD simulations replace expensive and time consuming laboratory experiments successfully by allowing engineers and scientists to capture pressure, velocity and force distributions. Researchers are now able to test various theoretical conditions unavailable in the laboratory and CFD studies help them to get deeper insights on existing theories. The century-old history started just to solve some stress analysis problems numerically and today CFD methodology is being applied not only in fluid dynamics also in chemical engineering, mineral processing, fire engineering, sports, medical imaging and even in acoustics. This paper reviews the growth of CFD as a discipline and discusses its contemporary methodology.
Comparison between Multi-Layer Perceptron and Radial Basis Function Networks for Sediment Load Estimation in a Tropical Watershed  [PDF]
Hadi Memarian, Siva Kumar Balasundram
Journal of Water Resource and Protection (JWARP) , 2012, DOI: 10.4236/jwarp.2012.410102
Abstract: Prediction of highly non-linear behavior of suspended sediment flow in rivers has prime importance in environmental studies and watershed management. In this study, the predictive performance of two Artificial Neural Networks (ANNs), namely Radial Basis Function (RBF) and Multi-Layer Perceptron (MLP) were compared. Time series data of daily suspended sediment discharge and water discharge at the Langat River, Malaysia were used for training and testing the networks. Mean Square Error (MSE), Normalized Mean Square Error (NMSE) and correlation coefficient (r) were used for performance evaluation of the models. Using the testing data set, both models produced a similar level of robustness in sediment load simulation. The MLP network model showed a slightly better output than the RBF network model in predicting suspended sediment discharge, especially in the training process. However, both ANNs showed a weak robustness in estimating large magnitudes of sediment load.
MST radar and polarization lidar observations of tropical cirrus
Y. Bhavani Kumar,V. S. Siva Kumar,A. R. Jain,P. B. Rao
Annales Geophysicae (ANGEO) , 2003,
Abstract: Significant gaps in our understanding of global cirrus effects on the climate system involve the role of frequently occurring tropical cirrus. Much of the cirrus in the atmosphere is largely due to frequent cumulus and convective activity in the tropics. In the Indian sub-tropical region, the deep convective activity is very prominent from April to December, which is a favorable period for the formation of deep cumulus clouds. The fibrous anvils of these clouds, laden with ice crystals, are one of the source mechanisms for much of the cirrus in the atmosphere. In the present study, several passages of tropical cirrus were investigated by simultaneously operating MST radar and a co-located polarization lidar at the National MST Radar Facility (NMRF), Gadanki (13.45° N, 79.18° E), India to understand its structure, the background wind field and the microphysics at the cloud boundaries. The lidar system used is capable of measuring the degree of depolarization in the laser backscatter. It has identified several different cirrus structures with a peak linear depolarization ratio (LDR) in the range of 0.1 to 0.32. Simultaneous observations of tropical cirrus by the VHF Doppler radar indicated a clear enhancement of reflectivity detected in the vicinity of the cloud boundaries, as revealed by the lidar and are strongly dependent on observed cloud LDR. An inter-comparison of radar reflectivity observed for vertical and oblique beams reveals that the radar-enhanced reflectivity at the cloud boundaries is also accompanied by significant aspect sensitivity. These observations indicate the presence of anisotropic turbulence at the cloud boundaries. Radar velocity measurements show that boundaries of cirrus are associated with enhanced horizontal winds, significant vertical shear in the horizontal winds and reduced vertical velocity. Therefore, these measurements indicate that a circulation at the cloud boundaries suggest an entrainment taking place close to these levels. The analysis of simultaneous lidar and MST Radar observations can thus yield valuable information on the structure and dynamics of the cirrus, specifically near the boundaries of such clouds. Key words. Atmospheric composition and structure (cloud physics and chemistry; instruments and technique) - Meteorology and atmospheric dynamics (tropical meteorology)
Lidar measurements of mesospheric temperature inversion at a low latitude
V. Siva Kumar,Y. Bhavani Kumar,K. Raghunath,P. B. Rao
Annales Geophysicae (ANGEO) , 2003,
Abstract: The Rayleigh lidar data collected on 119 nights from March 1998 to February 2000 were used to study the statistical characteristics of the low latitude mesospheric temperature inversion observed over Gadanki (13.5° N, 79.2° E), India. The occurrence frequency of the inversion showed semiannual variation with maxima in the equinoxes and minima in the summer and winter, which was quite different from that reported for the mid-latitudes. The peak of the inversion layer was found to be confined to the height range of 73 to 79 km with the maximum occurrence centered around 76 km, with a weak seasonal dependence that fits well to an annual cycle with a maximum in June and a minimum in December. The magnitude of the temperature deviation associated with the inversion was found to be as high as 32 K, with the most probable value occurring at about 20 K. Its seasonal dependence seems to follow an annual cycle with a maximum in April and a minimum in October. The observed characteristics of the inversion layer are compared with that of the mid-latitudes and discussed in light of the current understanding of the source mechanisms. Key words. Atmospheric composition and structure (pressure, density and temperature). Meterology and atmospheric dynamics (climatology)
Odontogenic Fibromyxoma of Maxilla: A Rare Case Report
G. Siva Prasad Reddy,B. Surya Kumar,Radhika Muppa,Shravan Kumar Regonda
Case Reports in Dentistry , 2013, DOI: 10.1155/2013/345479
Synthesis, Spectral characterization and antimicrobial activity of 2-(substituted)-2,2-[1,3- dihydro-(3,4-1,2,5-oxadiazolediyl) diaza][5 , 5 -dimethyl-1 , 3 -propanediyl) dioxy] phosphoranes
Y. Hari Babu,A. Uma Ravi Sankar,B. Siva Kumar,C. Suresh Reddy
Organic Communications , 2010,
Abstract: The cyclic oxadiazolediyl dioxachlorophosphine precursor on subsequent reaction with various alcohols underwent halide displacement to give 2-substituted diaza phospholes. These phospholes on oxidative addition with di hydroxy alcohols form corresponding phosphoranes The antimicrobial activities of these compounds were evaluated and they exhibited significant antimicrobial activity.
One-Pot Synthesis and Antimicrobial Activity of Novel α-Aminophosphonates Using TMG
B. Siva Kumar,Y. Haranadha Reddy,C. Radha Rani,G. Chnadra Sekhar Reddy
Journal of Chemistry , 2011, DOI: 10.1155/2011/906320
Effect of Series Resistance and Interface State Density on Electrical Characteristics of Au/SiO2/n-GaN Schottky Diodes
M. Siva Pratap Reddy,B. Prasanna Lakshmi,A. Ashok Kumar,V. Rajagopal Reddy
Journal of Nano- and Electronic Physics , 2011,
Abstract: We have investigated the current-voltage (I V) characteristics of (Au/SiO2/n-GaN) metal-insulator-semiconductor (MIS) Schottky diodes and compared with (Au/n-GaN) metal-semiconductor (MS) Schottky diode. The effect of SiO2 on the surface preparation of n-GaN (MIS) Schottky diode is analyzed. The extracted Schottky barrier height and ideality factor of the MS Schottky diode is found to be 0.79 eV and 1.45 respectively. It is observed that the Schottky barrier height increases to 0.86 eV and ideality factor decreases to 1.3 for MIS diode. The interface state density as determined by Terman’s method is found to be 3.79 × 1012 and 3.41 × 1010 cm-2 eV-1 for the MS and MIS Schottky diodes, respectively. In addition, the values of series resistance (Rs) are determined using Cheung’s method. The I V characteristics confirmed that the distribution of Nss, Rs and interfacial layer are important parameters that influence the electrical characteristics of MIS Schottky diodes.
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