Effect of wall thickness on the end corrections of the extended inlet and outlet of a double-tuned expansion chamber

Simple expansion chambers, the simplest of the muffler configurations, have very limited practical application due to the presence of periodic troughs in the transmission loss spectrum which drastically lower the overall transmission loss of the muffler. Tuned extended inlet and outlet can be designed to nullify three-fourths of these troughs, making use of the plane wave theory. These cancellations would not occur unless one altered the geometric lengths for the extended tube in order to incorporate the effect of evanescent higher-order modes (multidimensional effect) through end corrections or lumped inertance approximation at the area discontinuities or junctions. End corrections of the extended inlet and outlet have been studied by several researchers. However the effect of wall thickness of the inlet/outlet duct on end correction has not been studied explicitly. This has significant effect on the tuning of an extended inlet/outlet expansion chamber. It is investigated here experimentally as well as numerically (through use of 3-D FEM software) for stationary medium. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

Energy efficiencies of end-use devices in an electro-metallurgical industry: A critical study

The inefficient use of energy in a large number of industries is slowly developing into a major energy crisis in the already power-starved Karnataka State, India. This study attempts to bring out the present inefficient pattern of energy use in an electro-metallurgical industry. It also brings out the considerable scope for energy conservation, especially by increasing the efficiency of the end-use devices used. This concept, when extended to other industries, wherein increasing efficiency of the end-use devices would provide the desired end results with small energy input. This, in turn, would result in a slower rate of energy growth as well as saving in energy use.

CA/TG sequence at the 5' end of oligo(A)-tracts strongly modulates DNA curvature

An analysis of the base pair doublet geometries in available crystal structures indicates that the often reported intrinsic curvature of DNA containing oligo-(d(A).d(T)) tracts may also depend on the nature of the flanking sequences. The presence of CA/TG doublet in particular at the 5' end of these tracts is expected to enhance their intrinsic bending property. To test this proposition, three oligonucleotides, d(GAAAAACCCCCC), d(CCCCCCAAAAAG), d(GAAAAATTTTTC), and their complementary sequences were synthesized to study the effect of various flanking sequences, at the 5' and 3' ends of the A-tracts, on the curvature of DNA in solution. An analysis of the polyacrylamide gel electrophoretic mobilities of these sequences under different conditions of salts and temperatures (below their melting points) clearly showed that the oligomer with CA/TG sequence in the center was always more retarded than the oligomer with AC/GT sequence, as well as the oligomer with AT/AT sequence. Hydroxyl radical probing of the sequences with AC/GT and CA/TG doublet junctions gives a similar cutting pattern in the A-tracts, which is quite different from that in the C-tracts, indicating that the oligo(A)-tracts have similar structures in the two oligomers. KMnO4 probing shows that the oligomer with a CA/TG doublet junction forms a kink that is responsible for its inherent curvature and unusual electrophoretic mobility. UV melting shows a reduced thermal stability of the duplex with CA/TG doublet junction, and circular dichroism (CD) studies indicate that a premelting transition occurs in the oligomer with CA/TG doublet step before global melting but not in the oligomer with AC/GT doublet step, which may correspond to thermally induced unbending of the oligomer. These observations indicate that the CA/TG doublet junction at the 5' end of the oligo(A)-tract has a crucial role in modulating the overall curvature in DNA.

CA\TG Sequence at the 5'end of Oligo(A)-tracts Strongly Modulates DNA Curvature

An analysis of the base pair doublet geometries in available crystal structures indicates that the often reported intrinsic curvature of DNA containing oligo-(d(A).d(T)) tracts may also depend on the nature of the flanking sequences. The presence of CA/TG doublet in particular at the 5' end of these tracts is expected to enhance their intrinsic bending property. To test this proposition, three oligonucleotides, d(GAAAAACCCCCC), d(CCCCCCAAAAAG), d(GAAAAATTTTTC), and their complementary sequences were synthesized to study the effect of various flanking sequences, at the 5' and 3' ends of the A-tracts, on the curvature of DNA in solution. An analysis of the polyacrylamide gel electrophoretic mobilities of these sequences under different conditions of salts and temperatures (below their melting points) clearly showed that the oligomer with CA/TG sequence in the center was always more retarded than the oligomer with AC/GT sequence, as well as the oligomer with AT/AT sequence. Hydroxyl radical probing of the sequences with AC/GT and CA/TG doublet junctions gives a similar cutting pattern in the A-tracts, which is quite different from that in the C-tracts, indicating that the oligo(A)-tracts have similar structures in the two oligomers. KMnO4 probing shows that the oligomer with a CA/TG doublet junction forms a kink that is responsible for its inherent curvature and unusual electrophoretic mobility. UV melting shows a reduced thermal stability of the duplex with CA/TG doublet junction, and circular dichroism (CD) studies indicate that a premelting transition occurs in the oligomer with CA/TG doublet step before global melting but not in the oligomer with AC/GT doublet step, which may correspond to thermally induced unbending of the oligomer. These observations indicate that the CA/TG doublet junction at the 5' end of the oligo(A)-tract has a crucial role in modulating the overall curvature in DNA.

Elliptic flow of thermal photons in heavy-ion collisions at Relativistic Heavy Ion Collider and Large Hadron Collider

We calculate the thermal photon transverse momentum spectra and elliptic flow in $\sqrt{s_{NN}} = 200$ GeV Au+Au collisions at RHIC and in $\sqrt{s_{NN}} = 2.76$ TeV Pb+Pb collisions at the LHC, using an ideal-hydrodynamical framework which is constrained by the measured hadron spectra at RHIC and LHC. The sensitivity of the results to the QCD-matter equation of state and to the photon emission rates is studied, and the photon $v_2$ is discussed in the light of the photonic $p_T$ spectrum measured by the PHENIX Collaboration. In particular, we make a prediction for the thermal photon $p_T$ spectra and elliptic flow for the current LHC Pb+Pb collisions.

Top-spin analysis of new scalar and tensor interactions in e(+)e(-) collisions with beam polarization

We utilize top polarization in the process e(+)e(-) -> t (t) over bar at the International Linear Collider ( ILC) with transverse beam polarization to probe interactions of the scalar and tensor type beyond the standard model and to disentangle their individual contributions. Ninety percent confidence level limits on the interactions with realistic integrated luminosity are presented and are found to improve by an order of magnitude compared to the case when the spin of the top quark is not measured. Sensitivities of the order of a few times 10(-3) TeV-2 for real and imaginary parts of both scalar and tensor couplings at root s = 500 and 800 GeV with an integrated luminosity of 500 fb(-1) and completely polarized beams are shown to be possible. A powerful model-independent framework for inclusive measurements is employed to describe the spin-momentum correlations, and their C, P, and T properties are presented in a technical appendix.

Efficiency of nonhomologous DNA end joining varies among somatic tissues, despite similarity in mechanism

Failure to repair DNA double-strand breaks (DSBs) can lead to cell death or cancer. Although nonhomologous end joining (NHEJ) has been studied extensively in mammals, little is known about it in primary tissues. Using oligomeric DNA mimicking endogenous DSBs, NHEJ in cell-free extracts of rat tissues were studied. Results show that efficiency of NHEJ is highest in lungs compared to other somatic tissues. DSBs with compatible and blunt ends joined without modifications, while noncompatible ends joined with minimal alterations in lungs and testes. Thymus exhibited elevated joining, followed by brain and spleen, which could be correlated with NHEJ gene expression. However, NHEJ efficiency was poor in terminally differentiated organs like heart, kidney and liver. Strikingly, NHEJ junctions from these tissues also showed extensive deletions and insertions. Hence, for the first time, we show that despite mode of joining being generally comparable, efficiency of NHEJ varies among primary tissues of mammals.

CAITG sequence at the 5' end of Oligo(A)-tracts strongly modulates DNA curvature

An analysis of the base pair doublet geometries in available crystal structures indicates that the often reported intrinsic curvature of DNA containing oligo-(d(A).d(T)) tracts may also depend on the nature of the flanking sequences. The presence of CA/TG doublet in particular at the 5' end of these tracts is expected to enhance their intrinsic bending property. To test this proposition, three oligonucleotides, d(GAAAAACCCCCC), d(CCCCCCAAAAAG), d(GAAAAATTTTTC), and their complementary sequences were synthesized to study the effect of various flanking sequences, at the 5' and 3' ends of the A-tracts, on the curvature of DNA in solution. An analysis of the polyacrylamide gel electrophoretic mobilities of these sequences under different conditions of salts and temperatures (below their melting points) clearly showed that the oligomer with CA/TG sequence in the center was always more retarded than the oligomer with AC/GT sequence, as well as the oligomer with AT/AT sequence. Hydroxyl radical probing of the sequences with AC/GT and CA/TG doublet junctions gives a similar cutting pattern in the A-tracts, which is quite different from that in the C-tracts, indicating that the oligo(A)-tracts have similar structures in the two oligomers. KMnO4 probing shows that the oligomer with a CA/TG doublet junction forms a kink that is responsible for its inherent curvature and unusual electrophoretic mobility. UV melting shows a reduced thermal stability of the duplex with CA/TG doublet junction, and circular dichroism (CD) studies indicate that a premelting transition occurs in the oligomer with CA/TG doublet step before global melting but not in the oligomer with AC/GT doublet step, which may correspond to thermally induced unbending of the oligomer. These observations indicate that the CA/TG doublet junction at the 5' end of the oligo(A)-tract has a crucial role in modulating the overall curvature in DNA.

Five-level inverter scheme for an open-end winding induction machine with less number of switches

Higher level of inversion is achieved with a less number of switches in the proposed scheme. The scheme proposes a five-level inverter for an open-end winding induction motor which uses only two DC-link rectifiers of voltage rating of Vdc/4, a neutral-point clamped (NPC) three-level inverter and a two-level inverter. Even though the two-level inverter is connected to the high-voltage side, it is always in square-wave operation. Since the two-level inverter is not switching in a pulse width modulated fashion and the magnitude of switching transient is only half compared to the convention three-level NPC inverter, the switching losses and electromagnetic interference is not so high. The scheme is experimentally verified on a 2.5 kW induction machine.

Design and development of a self-supported polymer electrolyte fuel cell system with anodic dead-end operation

Design and operational details for a self-supported polymer electrolyte fuel cell (PEFC) system with anodic dead-end fuel supply and internally humidified cathodic oxidant flow are described. During the PEFC operation, nitrogen and water back diffuse across the Nafion membrane from the cathode to the anode and accumulate in the anode flow channels affecting stack performance. The accumulated inert species are flushed from the stack by purging the fuel cell stack with a timer-activated purge valve to address the aforesaid problem. To minimize the system complexity, stack is designed in such a way that all the inert species accumulate in only one cell called the purge cell. A pulsed purge sequence comprises opening the valve for purge duration followed by purge-valve closing for the hold period and repeating the sequence in cycles. Since self-humidification is inadequate to keep the membrane wet, the anodic dead-end-operated PEFC stack with composite membrane comprising perflourosulphonic acid (Nafion) and silica is employed for keeping the membrane humidified even while operating the stack with dry hydrogen and internally humidified air.

The effect of traffic shaping in efficiently providing end-to-end performance guarantees

This paper reports new results concerning the capabilities of a family of service disciplines aimed at providing per-connection end-to-end delay (and throughput) guarantees in high-speed networks. This family consists of the class of rate-controlled service disciplines, in which traffic from a connection is reshaped to conform to specific traffic characteristics, at every hop on its path. When used together with a scheduling policy at each node, this reshaping enables the network to provide end-to-end delay guarantees to individual connections. The main advantages of this family of service disciplines are their implementation simplicity and flexibility. On the other hand, because the delay guarantees provided are based on summing worst case delays at each node, it has also been argued that the resulting bounds are very conservative which may more than offset the benefits. In particular, other service disciplines such as those based on Fair Queueing or Generalized Processor Sharing (GPS), have been shown to provide much tighter delay bounds. As a result, these disciplines, although more complex from an implementation point-of-view, have been considered for the purpose of providing end-to-end guarantees in high-speed networks. In this paper, we show that through ''proper'' selection of the reshaping to which we subject the traffic of a connection, the penalty incurred by computing end-to-end delay bounds based on worst cases at each node can be alleviated. Specifically, we show how rate-controlled service disciplines can be designed to outperform the Rate Proportional Processor Sharing (RPPS) service discipline. Based on these findings, we believe that rate-controlled service disciplines provide a very powerful and practical solution to the problem of providing end-to-end guarantees in high-speed networks.

Throughput performance of distributed applications in switched networks in presence of end-system bottlenecks

The steady state throughput performance of distributed applications deployed in switched networks in presence of end-system bottlenecks is studied in this paper. The effect of various limitations at an end-system is modelled as an equivalent transmission capacity limitation. A class of distributed applications is characterised by a static traffic distribution matrix that determines the communication between various components of the application. It is found that uniqueness of steady state throughputs depends only on the traffic distribution matrix and that some applications (e.g., broadcast applications) can yield non-unique values for the steady state component throughputs. For a given switch capacity, with traffic distribution that yield fair unique throughputs, the trade-off between the end-system capacity and the number of application components is brought out. With a proposed distributed rate control, it has been illustrated that it is possible to have unique solution for certain traffic distributions which is otherwise impossible. Also, by proper selection of rate control parameters, various throughput performance objectives can be realised.

Common mode DC bus filter for Active Front-End converter

Active Front-End (AFE) converter operation produces electrically noisy DC bus on common mode basis. This results in higher ground current as compared to three phase diode bridge rectifier. Filter topologies for DC bus have to deal problems with switching frequency and harmonic currents. The proposed filter approach reduces common mode voltage and circulates third harmonic current within the system, resulting in minimal ground current injection. The filtering technique, its constrains and design to attenuate common mode voltage and eliminate lower order harmonics injection to ground is discussed. The experimental results for operation of the converter with both SPWM and CSVPWM are presented.

Persistent passive hopping and juggling is possible even with plastic collisions

We describe simple one-dimensional models of passive (no energy input, no control), generally dissipative, vertical hopping and one-ball juggling. The central observation is that internal passive system motions can conspire to eliminate collisions in these systems. For hopping, two point masses are connected by a spring and the lower mass has inelastic collisions with the ground. For juggling, a lower point-mass hand is connected by a spring to the ground and an upper point-mass ball is caught with an inelastic collision and then re-thrown into gravitational free flight. The two systems have identical dynamics. Despite inelastic collisions between non-zero masses, these systems have special symmetric energy-conserving periodic motions where the collision is at zero relative velocity. Additionally, these special periodic motions have a non-zero sized, one-sided region of attraction on the higher-energy side. For either very large or very small mass ratios, the one-sided region of attraction is large. These results persist for mildly non-linear springs and non-constant gravity. Although non-collisional damping destroys the periodic motions, small energy injection makes the periodic motions stable, with a two-sided region of attraction. The existence of such special energy conserving solutions for hopping and juggling points to possibly useful strategies for both animals and robots. The lossless motions are demonstrated with a table-top experiment.