Reducing Buffer Requirements in Core Routers using Dynamic Buffering

Earlier studies have exploited statistical multiplexing of flows in the core of the Internet to reduce the buffer requirement in routers. Reducing the memory requirement of routers is important as it enables an improvement in performance and at the same time a decrease in the cost. In this paper, we observe that the links in the core of the Internet are typically over-provisioned and this can be exploited to reduce the buffering requirement in routers. The small on-chip memory of a network processor (NP) can be effectively used to buffer packets during most regimes of traffic. We propose a dynamic buffering strategy which buffers packets in the receive and transmit buffers of a NP when the memory requirement is low. When the buffer requirement increases due to bursts in the traffic, memory is allocated to packets in the off-chip DRAM. This scheme effectively mitigates the DRAM access bottleneck, as only a part of the traffic is stored in the DRAM. We build a Petri net model and evaluate the proposed scheme with core Internet like traffic. At 77% link utilization, the dynamic buffering scheme has a drop rate of just 0.65%, whereas the traditional DRAM buffering has 4.64% packet drop rate. Even with a high link utilization of 90%, which rarely happens in the core, our dynamic buffering results in a packet drop rate of only 2.17%, while supporting a throughput of 7.39 Gbps. We study the proposed scheme under different conditions to understand the provisioning of processing threads and to determine the queue length at which packets must be buffered in the DRAM. We show that the proposed dynamic buffering strategy drastically reduces the buffering requirement while still maintaining low packet drop rates.

Multiclass Core Vector Machine

Even though several techniques have been proposed in the literature for achieving multiclass classification using Support Vector Machine(SVM), the scalability aspect of these approaches to handle large data sets still needs much of exploration. Core Vector Machine(CVM) is a technique for scaling up a two class SVM to handle large data sets. In this paper we propose a Multiclass Core Vector Machine(MCVM). Here we formulate the multiclass SVM problem as a Quadratic Programming(QP) problem defining an SVM with vector valued output. This QP problem is then solved using the CVM technique to achieve scalability to handle large data sets. Experiments done with several large synthetic and real world data sets show that the proposed MCVM technique gives good generalization performance as that of SVM at a much lesser computational expense. Further, it is observed that MCVM scales well with the size of the data set.

Rough Core Vector Clustering

Support Vector Clustering has gained reasonable attention from the researchers in exploratory data analysis due to firm theoretical foundation in statistical learning theory. Hard Partitioning of the data set achieved by support vector clustering may not be acceptable in real world scenarios. Rough Support Vector Clustering is an extension of Support Vector Clustering to attain a soft partitioning of the data set. But the Quadratic Programming Problem involved in Rough Support Vector Clustering makes it computationally expensive to handle large datasets. In this paper, we propose Rough Core Vector Clustering algorithm which is a computationally efficient realization of Rough Support Vector Clustering. Here Rough Support Vector Clustering problem is formulated using an approximate Minimum Enclosing Ball problem and is solved using an approximate Minimum Enclosing Ball finding algorithm. Experiments done with several Large Multi class datasets such as Forest cover type, and other Multi class datasets taken from LIBSVM page shows that the proposed strategy is efficient, finds meaningful soft cluster abstractions which provide a superior generalization performance than the SVM classifier.

Behavior of Sandwich Beams With Functionally Graded Rubber Core in Three Point Bending

The three-point bending behavior of sandwich beams made up of jute epoxy skins and piecewise linear functionally graded (FG) rubber core reinforced with fly ash filler is investigated. This work studies the influence of the parameters such as weight fraction of fly ash, core to thickness ratio, and orientation of jute on specific bending modulus and strength. The load displacement response of the sandwich is traced to evaluate the specific modulus and strength. FG core samples are prepared by using conventional casting technique and sandwich by hand layup. Presence of gradation is quantified experimentally. Results of bending test indicate that specific modulus and strength are primarily governed by filler content and core to sandwich thickness ratio. FG sandwiches with different gradation configurations (uniform, linear, and piecewise linear) are modeled using finite element analysis (ANSYS 5.4) to evaluate specific strength which is subsequently compared with the experimental results and the best gradation configuration is presented. POLYM. COMPOS., 32:1541-1551, 2011. (C) 2011 Society of Plastics Engineers

Hexa-arm star shaped hydrazone derivatives from hexakis(4-formylphenoxy)-cyclotriphosphazene core

A series of novel hexasubstituted cyclophosphazene hydrazones [N(3)P(3)(-OC(6)H(4)-p-CH=N-NH-C(O)-C(6)H(4)-p-X)(6)] (X = H, Br, Cl, F, OH, OCH(3), CH(3), NO(2), NH(2)) were prepared by a sixfold condensation reaction of [N(3)P(3)(-OC(6)H(4)-p-CHO)(6)] with para-substituted benzoic hydrazides [NH(2)-NH-C(O)-C(6)H(4)-p-X] with excellent yields (91-98%). The structures of the compounds were confirmed by elemental analysis, FT-IR, (1)H, (13)C, (31)P, 2D-HSQC NMR and mass spectrometry (MALDI-TOF). All the synthesized cyclophosphazene hydrazones exhibit high thermal stability. The crystal structure of a homogeneously substituted hexakis(4-formylphenoxy)-cyclotriphosphazene was determined by X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group P2(1)/n with a = 16.558(3) angstrom, b = 10.250(2) angstrom, c = 23.429(5) angstrom, alpha = gamma = 90.00 degrees, beta = 90.461(4)degrees, V = 3976.5(14) angstrom(3) and Z = 4. The R value is 0.0823 for 4290 observed reflections. The conformations of the 4-formylphenoxy-groups are different at the three phosphorus atoms. (C) 2011 Elsevier B.V. All rights reserved.

Control of Molecular Weight and Polydispersity of Hyperbranched Polymers Using a Reactive B(3) Core: A Single-Step Route to Orthogonally Functionalizable Hyperbranched Polymers

Molecular weight and polydispersity are two structural features of hyperbranched polymers that are difficult to control because of the statistical nature of the step-growth polycondensation of AB(2) type monomers; the statistical growth also causes the polydispersity index to increase with percent conversion (or molecular weight). We demonstrate that using controlled amounts of a specifically designed B(3) core, containing B-type functionality that are more reactive than those present in the AB(2) monomer, both the molecular weight and the polydispersity can be readily controlled; the PDI was shown to improve with increasing mole-fraction of the B(3) core while the polymer molecular weight showed an expected decrease. Incorporation of a ``clickable'' propargyl group in the B(3) core unit permitted the generation of a core-functionalizable hyperbranched polymer. Importantly, this clickable core, in combination with a recently developed AB(2) monomer, wherein the B-type groups are allyl ethers and A is an hydroxyl group, led to the generation of a hyperbranched polymer carrying orthogonally functionalizable core and peripheral groups, via a single-step melt polycondensation. Selective functionalization of the core and periphery using two different types of chromophores was achieved, and the occurrence of fluorescence resonance energy transfer (FRET) between the donor and acceptor chromophores was demonstrated.

Instabilities of soft elastic microtubes filled with viscous fluids: Pearls, wrinkles, and sausage strings

A linear stability analysis is presented to study the self-organized instabilities of a highly compliant elastic cylindrical shell filled with a viscous liquid and submerged in another viscous medium. The prototype closely mimics many components of micro-or nanofluidic devices and biological processes such as the budding of a string of pearls inside cells and sausage-string formation of blood vessels. The cylindrical shell is considered to be a soft linear elastic solid with small storage modulus. When the destabilizing capillary force derived from the cross-sectional curvature overcomes the stabilizing elastic and in-plane capillary forces, the microtube can spontaneously self-organize into one of several possible configurations; namely, pearling, in which the viscous fluid in the core of the elastic shell breaks up into droplets; sausage strings, in which the outer interface of the mircrotube deforms more than the inner interface; and wrinkles, in which both interfaces of the thin-walled mircrotube deform in phase with small amplitudes. This study identifies the conditions for the existence of these modes and demonstrates that the ratios of the interfacial tensions at the interfaces, the viscosities, and the thickness of the microtube play crucial roles in the mode selection and the relative amplitudes of deformations at the two interfaces. The analysis also shows asymptotically that an elastic fiber submerged in a viscous liquid is unstable for Y = gamma/(G(e)R) > 6 and an elastic microchannel filled with a viscous liquid should rupture to form spherical cavities (pearling) for Y > 2, where gamma, G(e), and R are the surface tension, elastic shear modulus, and radius, respectively, of the fiber or microchannel.

Control of Molecular Weight and Polydispersity of Hyperbranched Polymers Using a Reactive B(3) Core: A Single-Step Route to Orthogonally Functionalizable Hyperbranched Polymers

Molecular weight and polydispersity are two structural features of hyperbranched polymers that are difficult to control because of the statistical nature of the step-growth polycondensation of AB(2) type monomers; the statistical growth also causes the polydispersity index to increase with percent conversion (or molecular weight). We demonstrate that using controlled amounts of a specifically designed B(3) core, containing B-type functionality that are more reactive than those present in the AB(2) monomer, both the molecular weight and the polydispersity can be readily controlled; the PDI was shown to improve with increasing mole-fraction of the B(3) core while the polymer molecular weight showed an expected decrease. Incorporation of a ``clickable'' propargyl group in the B(3) core unit permitted the generation of a core-functionalizable hyperbranched polymer. Importantly, this clickable core, in combination with a recently developed AB(2) monomer, wherein the B-type groups are allyl ethers and A is an hydroxyl group, led to the generation of a hyperbranched polymer carrying orthogonally functionalizable core and peripheral groups, via a single-step melt polycondensation. Selective functionalization of the core and periphery using two different types of chromophores was achieved, and the occurrence of fluorescence resonance energy transfer (FRET) between the donor and acceptor chromophores was demonstrated.

Dry tribology and nanomechanics of gaseous flame soot in comparison with carbon black and diesel soot

Ethylene gas is burnt and the carbon soot particles are thermophoretically collected using a home-built equipment where the fuel air injection and intervention into the 7.5-cm long flame are controlled using three small pneumatic cylinders and computer-driven controllers. The physical and mechanical properties and tribological performance of the collected soot are compared with those of carbon black and diesel soot. The crystalline structures of the nanometric particles generated in the flame, as revealed by high-resolution transmission electron studies, are shown to vary from the flame root to the exhaust. As the particle journeys upwards the flame, through a purely amorphous coagulated phase at the burner nozzle, it leads to a well-defined crystalline phase shell in the mid-flame zone and to a disordered phase consisting of randomly distributed short-range crystalline order at the exhaust. In the mid-flame region, a large shell of radial-columnar order surrounds a dense amorphous core. The hardness and wear resistance as well as friction coefficient of the soot extracted from this zone are low. The mechanical properties characteristics of this zone may be attributed to microcrystalline slip. Moving towards the exhaust, the slip is inhibited and there is an increase in hardness and friction compared to those in the mid-flame zone. This study of the comparison of flame soot to carbon black and diesel soot is further extended to suggest a rationale based on additional physico-chemical study using micro-Raman spectroscopy.

A Revisit to Capture the Entire Behavior of Ultrasonic Wave Dispersion Characteristics of Single Walled Carbon Nanotubes Based on Nonlocal Elasticity Theory and Flugge Shell Model

In this paper, an ultrasonic wave propagation analysis in single-walled carbon nanotube (SWCNT) is re-studied using nonlocal elasticity theory, to capture the whole behaviour. The SWCNT is modeled using Flugge's shell theory, with the wall having axial, circumferential and radial degrees of freedom and also including small scale effects. Nonlocal governing equations for this system are derived and wave propagation analysis is also carried out. The revisited nonlocal elasticity calculation shows that the wavenumber tends to infinite at certain frequencies and the corresponding wave velocity tends to zero at those frequencies indicating localization and stationary behavior. This frequency is termed as escape frequency. This behavior is observed only for axial and radial waves in SWCNT. It has been shown that the circumferential waves will propagate dispersively at higher frequencies in nonlocality. The magnitudes of wave velocities of circumferential waves are smaller in nonlocal elasticity as compared to local elasticity. We also show that the explicit expressions of cut-off frequency depend on the nonlocal scaling parameter and the axial wavenumber. The effect of axial wavenumber on the ultrasonic wave behavior in SWCNTs is also discussed. The present results are compared with the corresponding results (for first mode) obtained from ab initio and 3-D elastodynamic continuum models. The acoustic phonon dispersion relation predicted by the present model is in good agreement with that obtained from literature. The results are new and can provide useful guidance for the study and design of the next generation of nanodevices that make use of the wave propagation properties of single-walled carbon nanotubes.

Coupled Wavenumbers in an Infinite Flexible Fluid-Filled Circular Cylindrical Shell: Comparison between Different Shell Theories

Analytical expressions are found for the wavenumbers in an infinite flexible in vacuo I fluid-filled circular cylindrical shell based on different shell-theories using asymptotic methods. Donnell-Mushtari theory (the simplest shell theory) and four higher order theories, namely Love-Timoshenko, Goldenveizer-Novozhilov, Flugge and Kennard-simplified are considered. Initially, in vacuo and fluid-coupled wavenumber expressions are presented using the Donnell-Mushtari theory. Subsequently, the wavenumbers using the higher order theories are presented as perturbations on the Donnell-Mushtari wavenumbers. Similarly, expressions for the resonance frequencies in a finite shell are also presented, using each shell theory. The basic differences between the theories being what they are, the analytical expressions obtained from the five theories allow one to see how these differences propagate into the asymptotic expansions. Also, they help to quantify the difference between the theories for a wide range of parameter values such as the frequency range, circumferential order, thickness ratio of the shell, etc.

A core study on NOX removal in diesel exhaust by pulsed/ac/dc electric discharge plasma

In this paper a study on effect of different energization on removal of NOX in diesel engine exhaust has been presented. Here we made a detailed qualitative study of effect of pulsed/ac/dc voltage energizations on the NOX treatment of using conventional wire-cylinder reactor configuration. It was observed that amongst different energizations, pulse energization exhibits maximum NOX removal efficiency when compared to ac and dc energizations. For a given specific energy density, wire-cylinder reactor filled with BaTiO3 pellet gives higher NOX removal efficiency when compared to reactor without pellets under both pulse and ac energization. The dc energization does not have much impact on the removal processes. The paper further discusses the individual energization cases in detail.

Ultrasonic Wave Dispersion Characteristics of Fluid-Filled Single-Walled Carbon Nanotubes Based on Nonclassical Shell Model

In this paper, ultrasonic wave propagation analysis in fluid filled single-walled carbon nanotube (SWCNT) is studied using nonlocal elasticity theory. The SWCNT is modeled using Flugge's shell theory, with the wall having axial, circumferential and radial degrees of freedom and also including small scale effects. The fluid inside the SWCNT is assumed as water. Nonlocal governing equations for this system are derived and wave propagation analysis is also carried out. The presence of fluid in SWCNT alters the ultrasonic wave dispersion behavior. The wavenumber and wave velocity are smaller in presence of fluid as compared to the empty SWCNT. The nonlocal elasticity calculation shows that the wavenumber tends to reach the continuum limit at certain frequencies and the corresponding wave velocity tends to zero at those frequencies indicating localization and stationary behavior. It has been shown that the circumferential. waves will propagate non-dispersively at higher frequencies in nonlocality. The magnitudes of wave velocities of circumferential waves are smaller in nonlocal elasticity as compared to local elasticity. We also show that the cut-off frequency depend on the nonlocal scaling parameter and also on the density of the fluid inside the SWCNT, and the axial wavenumber, as the fluid becomes denser the cut-off frequency decreases. The effect of axial wavenumber on the ultrasonic wave behavior in SWCNTS filled with water is also discussed.

Defect-Free Hyperbranched Polydithioacetal via Melt Polymerization

Degree of branching (DB) describes the level of structural perfection of a hyperbranched polymer when compared to its defect-free analogue, namely the dendrimer. The strategy most commonly used to achieve high DB values, specifically while using AB(2) type self-condensations, is to design an AB2 monomer wherein the reaction of the first B-group leads to an enhancement of the reactivity of the second one. In the present study, we show that an AB2 monomer carrying a dimethylacetal unit and a thiol group undergoes a rapid self-condensation in the melt under acid-catalysis to yield a hyperbranched polydithioacetal with no linear defects. NMR studies using model systems reveal that the intermediate monothioacetal is relatively unstable under the polymerization conditions and transforms rapidly to the dithioacetal; because this second step occurs irreversibly during polymer formation, it leads to a defect-free hyperbranched polydithioacetal. TGA studies of the polymerization process provided some valuable insights into the kinetics of polymerization. An additional virtue of this approach is that the numerous terminal dimethylacetal groups are very labile and can be quantitatively transformed by treatment with a variety of functional thiols; the terminal dimethylacetals were, thus, reacted with various thiols, such as dodecanethiol, benzyl mercaptan, ethylmercaptopropionate, and so on, to demonstrate the versatility of these systems as sulfur-rich hyperscaffolds to anchor different kinds of functionality on their periphery.