Evaluation of the micro-carburetor

A prototype sonic, variable-venturi automotive carburetor was evaluated for its effects on vehicle performance, fuel economy, and exhaust emissions. A 350 CID Chevrolet Impala vehicle was tested on a chassis dynamometer over the 1975 Federal Test Procedure, urban driving cycle. The Micro-carburetor was tested and compared with stock and modified-stock engine configurations. Subsequently, the test vehicle's performance characteristics were examined with the stock carburetor and again with the Micro-carburetor in a series of on-road driveability tests. The test engine was then removed from the vehicle and installed on an engine dynamometer. Engine tests were conducted to compare the fuel economy, thermal efficiency, and cylinder-to-cylinder mixture distribution of the Micro-carburetor to that of the stock configuration. Test results show increases in thermal efficiency and improvements in fuel economy at all test conditions. Improve fuel/air mixture preparation is implied from the information presented. Further improvements in fuel economy and exhaust emissions are possible through a detailed recalibration of the Micro-carburetor

Paraunitary oversampled filter bank design for channel coding

Oversampled filter banks (OSFBs) have been considered for channel coding, since their redundancy can be utilised to permit the detection and correction of channel errors. In this paper, we propose an OSFB-based channel coder for a correlated additive Gaussian noise channel, of which the noise covariance matrix is assumed to be known. Based on a suitable factorisation of this matrix, we develop a design for the decoder's synthesis filter bank in order to minimise the noise power in the decoded signal, subject to admitting perfect reconstruction through paraunitarity of the filter bank. We demonstrate that this approach can lead to a significant reduction of the noise interference by exploiting both the correlation of the channel and the redundancy of the filter banks. Simulation results providing some insight into these mechanisms are provided

Characterization of solar cells for space applications. Volume 5: Electrical characteristics of OCLI 225-micron MLAR wraparound cells as a function of intensity, temperature, and irradiation

Computed statistical averages and standard deviations with respect to the measured cells for each intensity temperature measurement condition are presented. Display averages and standard deviations of the cell characteristics in a two dimensional array format are shown: one dimension representing incoming light intensity, and another, the cell temperature. Programs for calculating the temperature coefficients of the pertinent cell electrical parameters are presented, and postirradiation data are summarized

Ratchet effect in dc SQUIDs

We analyzed voltage rectification for dc SQUIDs biased with ac current with zero mean value. We demonstrate that the reflection symmetry in the 2-dimensional SQUID potential is broken by an applied flux and with appropriate asymmetries in the dc SQUID. Depending on the type of asymmetry, we obtain a rocking or a simultaneously rocking and flashing ratchet, the latter showing multiple sign reversals in the mean voltage with increasing amplitude of the ac current. Our experimental results are in agreement with numerical solutions of the Langevin equations for the asymmetric dc SQUID.Comment: 10 pages including 5 Postscript figure

Raman scattering investigation across the magnetic and MI transition in rare earth nickelate RNiO3 (R = Sm, Nd) thin films

We report a temperature-dependent Raman scattering investigation of thin film rare earth nickelates SmNiO3, NdNiO3 and Sm0.60Nd0.40NiO3, which present a metal-to-insulator (MI) transition at TMI and an antiferromagnetic-paramagnetic Neel transition at TN. Our results provide evidence that all investigated samples present a structural phase transition at TMI but the Raman signature across TMI is significantly different for NdNiO3 (TMI = TN) compared to SmNiO3 and Sm0.60Nd0.40NiO3 (TMI =/ TN). It is namely observed that the paramagnetic-insulator phase (TN < T < TMI) in SmNiO3 and Sm0.60Nd0.40NiO3 is characterized by a pronounced softening of one particular phonon band around 420 cm-1. This signature is unusual and points to an important and continuous change in the distortion of NiO6 octahedra (thus the Ni-O bonding) which stabilizes upon cooling at the magnetic transition. The observed behaviour might well be a general feature for all rare earth nickelates with TMI =/ TN and illustrates intriguing coupling mechanism in the TMI > T > TN regime.Comment: Revised & published versio

Multi-Instantons and Multi-Cuts

We discuss various aspects of multi-instanton configurations in generic multi-cut matrix models. Explicit formulae are presented in the two-cut case and, in particular, we obtain general formulae for multi-instanton amplitudes in the one-cut matrix model case as a degeneration of the two-cut case. These formulae show that the instanton gas is ultra-dilute, due to the repulsion among the matrix model eigenvalues. We exemplify and test our general results in the cubic matrix model, where multi-instanton amplitudes can be also computed with orthogonal polynomials. As an application, we derive general expressions for multi-instanton contributions in two-dimensional quantum gravity, verifying them by computing the instanton corrections to the string equation. The resulting amplitudes can be interpreted as regularized partition functions for multiple ZZ-branes, which take into full account their back-reaction on the target geometry. Finally, we also derive structural properties of the trans-series solution to the Painleve I equation.Comment: 34 pages, 3 figures, JHEP3.cls; v2: added references, minor changes; v3: added 1 reference, more minor changes, final version for JMP; v4: more typos correcte

Imaging Pauli repulsion in scanning tunneling microscopy

A scanning tunneling microscope (STM) has been equipped with a nanoscale force sensor and signal transducer composed of a single D2 molecule that is confined in the STM junction. The uncalibrated sensor is used to obtain ultra-high geometric image resolution of a complex organic molecule adsorbed on a noble metal surface. By means of conductance-distance spectroscopy and corresponding density functional calculations the mechanism of the sensor/transducer is identified. It probes the short-range Pauli repulsion and converts this signal into variations of the junction conductance.Comment: 4 pages, 4 figures, accepted to Phys. Rev. Let

Entanglement at the boundary of spin chains near a quantum critical point and in systems with boundary critical points

We analyze the entanglement properties of spins (qubits) attached to the boundary of spin chains near quantum critical points, or to dissipative environments, near a boundary critical point, such as Kondo-like systems or the dissipative two level system. In the first case, we show that the properties of the entanglement are significantly different from those for bulk spins. The influence of the proximity to a transition is less marked at the boundary. In the second case, our results indicate that the entanglement changes abruptly at the point where coherent quantum oscillations cease to exist. The phase transition modifies significantly less the entanglement.Comment: 5 pages, 4 figure