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Search Results: 1 - 10 of 217481 matches for " N. Kumar "
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A Novel Biodegradable Poly (Hydroxybutanedioic Acid-co-2-hydroxypropane-1,2,3-tricarboxylic Acid) Copolymer for Water Treatment Applications  [PDF]
N. Mithil Kumar, K. Kanny
Open Journal of Organic Polymer Materials (OJOPM) , 2013, DOI: 10.4236/ojopm.2013.32009
Abstract: Minimizing the formation of inorganic scale deposits in industrial water continues to be a challenge for water treatment systems. In order to meet this challenge a novel biodegradable poly (DL-malic acid-co-citric acid) copolymer, effective in providing calcium carbonate scale inhibition was developed. Synthesis and characterization of the biodegradable, water-soluble and polyester copolymer was performed. Synthesis was done by direct bulk melt condensation in the absence of a catalyst above 150°C. Characterization of the copolymer was carried out using infrared absorption spectra (FTIR), differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) equipment. In the present work the precipitation of calcium carbonate from relative supersaturated solutions at different weight ratios of comonomer inhibition rates have been studied. The results indicate that the copolymer is an effective calcium carbonate descaling inhibitor that suppresses the growth process against calcium mineral scale deposits.
Effect of FCAW Process Parameters on Weld Bead Geometry in Stainless Steel Cladding  [PDF]
V. Vasantha Kumar, N. Murugan
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2011, DOI: 10.4236/jmmce.2011.109064
Abstract: Recently automated and / or robotic welding systems have received a great deal of attention because they are highly suitable not only to enhance production rate and quality, but also to decrease cost and time to manufacture for a given product. To get the desired quality welds it is essential to have complete control over the relevant process parameters in order to obtain the required bead geometry. Mathematical models need to be developed to have such control and to make effective use of automated and / or robotic arc welding process.
Void Aware Position Based Opportunistic Routing for QoS in Mobile Ad Hoc Networks  [PDF]
V. Raji, N. Mohan Kumar
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.78132
Abstract: The unique anywhere, anytime wireless communication support offers, tremendous potential for the next generation of applications in a Mobile Ad-hoc Network (MANET). The Quality of Service (QoS) has been the ever demanding task of wireless communication to satisfy the application requirements. Geographical routing employs a greedy forwarding technique to deliver the packets to the destination and to owe the communication void, it fails to render the expected level of QoS. Opportunistic routing technique effectively utilizes the advantages of broadcasting nature of thewireless medium and selects a set of forwarding candidates instead of relying on a greedy node.To improve the efficiency of QoS routing in sparse and highly dynamic network topology, this paper proposes the Void-Aware Position based Opportunistic Routing (VAPOR). The VAPOR maintains 2-hop neighbor information to take a routing decision, but it is limited to 1-hop informationwhen the node density is high. It efficiently balances the storage overhead and communicationdelay due to void and it increases the network throughput even under a sparse network. To provide a certain assurance level for packet reachability, VAPOR decides the potential forwardersbased on the forwarding probability that measures link stability, capacity, and connectivity factor. It adaptively favors a path that avoids frequent link failure and unreliable link usage. By limitingthe propagation area of duplicate packets, VAPOR reduces wastage of network resources, and ittakes the advantage of concurrent batch forwarding to avoid further duplication and unnecessary delay.
Damping Factor Estimation of a Flexible-Matrix-Composite Body Pump  [PDF]
N. P. Kumar, H. Ghoneim
Journal of Materials Science and Chemical Engineering (MSCE) , 2016, DOI: 10.4236/msce.2016.47009
Abstract:

Two very important factors which determine the effectiveness of a pump are its volumetric and power efficiencies. Yin and Ghoneim constructed a prototype of a Flexible-Matrix-Composite (FMC) body pump with a very high volumetric efficiency or pumping potential (the relative volume reduction due to a relative input stroke). The high volumetric efficiency is attributed to the geometry of the pump’s structure (hyperboloid) as well as the high negative effective Poisson’s ratio of the 3-layer [θ/β/θ] flexible-matrix-composite (carbon/polyurethane) laminate adopted for the body of the pump. However, the power efficiency of the pump was not evaluated. It is the objective of the current paper to obtain an estimate of the power efficiency of the pump. The viscoelastic properties of the 3-layer FMC (carbon/polyurethane) laminate are evaluated experimentally using the Dynamic Mechanical Analyzer (DMA) as well as analytically by applying the correspondence principle together with the micro-mechanics approach. In order to obtain an estimate of the power efficiency of the FMC body pump, the axial and shear loss factors of a laminated infinitely long cylindrical tube as functions of β and θ fiber orientation angles are determined employing the Adam and Bacon approach. The analysis engenders high loss factors (greater than 0.4), which suggests that the power efficiency of the proposed pump using the 3-layer carbon/polyurethane laminate may be low.

Empirical Investigation of Herding under Different Economic Setups  [PDF]
Ashish Kumar, K. N. Badhani
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.815205
Abstract: Present study is an attempt to analyse the presence of herding in different economic conditions. A mix of developed and developing countries is selected from different corners of the word. Our sample comprises 35 world markets, out of which 18 are emerging markets while 17 are developed markets. Daily data of all constituents stocks of the representative indices of these markets are extracted over most recent period ranging from Jan. 2000 to Apr. 2018. Applying different methodologies static and time varying, we find that only 11 markets out of 35 exhibit significant herding behaviour. These markets majorly belong to Asia, Africa and Middle East. We also try to relate herding with region, culture and state of economy and do not find any significant relation of these variables with herding.
Solute dispersion along unsteady groundwater flow in a semi-infinite aquifer
N. Kumar,M. Kumar
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 1998,
Abstract: Analytical and numerical solutions are obtained for dispersion of pollutants along unsteady groundwater flow in a longitudinal direction through semi-infinite aquifers the permeability of which is either uniform or varies with position. Sources of pollution are both a concentrated point input at the origin and a spatially distributed background source. One expression chosen to represent the seasonal pattern of the time dependent velocity is sinusoidal behaviour over a year. The solutions obtained predict the time and distance from the location at which an input concentration is introduced at which the pollution concentration becomes harmless. Also, the time period for rehabilitating a polluted aquifer for human use can also be assessed.
Cut-off free finite zero-point vacuum energy and the cosmological missing mass problem
N. Kumar
Physics , 1999,
Abstract: As the mass-energy is universally self-gravitating, the gravitational binding energy must be subtracted self-consistently from its bare mass value so as to give the physical gravitational mass. Such a self-consistent gravitational self-energy correction can be made non-perturbatively by the use of a gravitational `charging' technique, where we calculate the incremental change $dm$ of the physical mass of the cosmological object, of size $r_o$ due to the accretion of a bare mass $dM$, corresponding to the gravitational coupling-in of the successive zero-point vacuum modes, i.e., of the Casimir energy, whose bare value $\Sigma_{\bf k} \hbar ck$ is infinite. Integrating the `charging' equation, $dm = dM - (3\alpha/5)Gm\Delta M/r_o c^2$, we get a gravitational mass for the cosmological object that remains finite even in the limit of the infinite zero-point vacuum energy, i.e., without any ultraviolet cut-off imposed. Here $\alpha$ is a geometrical factor of order unity. Also, setting $r_o = c/H$, the Hubble length, we get the corresponding cosmological density parameter $\Omega \simeq 1$, without any adjustable parameter. The cosmological significance of this finite and unique contribution of the otherwise infinite zero-point vacuum energy to the density parameter can hardly be overstated.
Deflection of Ultra Slow Light by Earth Gravity on Laboratory Length Scale
N. Kumar
Physics , 2007, DOI: 10.1209/0295-5075/82/60002
Abstract: The high speed of light in vacuo together with the weakness of Earth gravity rules out any experimental detection of gravitational deflection of light on the laboratory length scale. Recent advances in coherent optics that produce ultra slow light in highly dispersive media with the group velocities down to ~102 ms-1, or even less, however, open up this possibility. In this work, we present a theoretical study for a possible laboratory observation of the deflection of such an ultra slow light in the highly dispersive medium under Earth gravity. Our general relativistic calculation is based on the Gordon optical metric modified so as to include dispersion. The calculated linear vertical deflection turns out to be ~0.1 mm for a horizontal traversal of 0.1 m, and a group speed vg ~ 102 ms-1. Experimental realizability and some conceptual points involved will be briefly discussed.
Deflection of ultra slow light under gravity
N. Kumar
Physics , 2007,
Abstract: Recent experiments on ultra slow light in strongly dispersive media by several research groups reporting slowing down of the optical pulses down to speeds of a few metres per second encourage us to examine the intriguing possibility of detecting a deflection or fall of the ultra slow light under Earth's gravity, i.e., on the laboratory length scale. In the absence of a usable general relativistic theory of light waves propagating in such a strongly dispersive optical medium in the presence of a gravitational field, we present a geometrical optics based derivation that combines {\it the effective gravitational refractive index} additively with the usual optical dispersion. It gives a deflection, or the vertical fall $\Delta$ for a horizontal traversal $L$ as \[ \Delta = \frac{L^2}{2}\big(\frac{R_{\oplus G}}{R_\oplus^2}\big) n_g \big(\frac{1}{1+n_g\frac{R_{\oplus G}}{R_\oplus}}\big), \] where $R_{\oplus G}/R_\oplus$ is the ratio of the gravitational Earth radius($R_{\oplus G}$) to its geometrical radius $R_\oplus$, and $n_g$ is the group refractive index of the strongly dispersive optical medium. The expression is essentailly that for the Newtonian fall of an object projected horizontally with the group speed $v_g=c/n_g$, and is tunable refractively through the index $n_g$. For $L \sim 1 m$ and $n_g = c/v_g \sim 10^8$ (corresponding to the ultra-slow pulse speed $\sim few \times 1 ms^{-1}$), we obtain a fall $\Delta \sim 1 \mu m$, that should be measurable $-$ in particular through its sensitive dependence on the frequency that tunes $n_g$.
Supersolid and the non-uniform condensate
N. Kumar
Physics , 2005,
Abstract: We construct a model of non-uniform condensate having a spatially modulated complex order parameter that makes it kinematically an x-ray solid, i.e., a real mass density wave, but one admitting an associated superfluid flow. Intrinsic to this state is a non-classical translational inertia which we derive for the case of a potential flow. Connection to the non-classical rotational inertia observed in recent experiments on solid helium-4 is discussed. Our semi-phenomenological treatment suggests a flow-induced supersolid-to-superdfluid transition.
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