Contingency Model Predictive Control for Automated Vehicles

We present Contingency Model Predictive Control (CMPC), a novel and implementable control framework which tracks a desired path while simultaneously maintaining a contingency plan -- an alternate trajectory to avert an identified potential emergency. In this way, CMPC anticipates events that might take place, instead of reacting when emergencies occur. We accomplish this by adding an additional prediction horizon in parallel to the classical receding MPC horizon. The contingency horizon is constrained to maintain a feasible avoidance solution; as such, CMPC is selectively robust to this emergency while tracking the desired path as closely as possible. After defining the framework mathematically, we demonstrate its effectiveness experimentally by comparing its performance to a state-of-the-art deterministic MPC. The controllers drive an automated research platform through a left-hand turn which may be covered by ice. Contingency MPC prepares for the potential loss of friction by purposefully and intuitively deviating from the prescribed path to approach the turn more conservatively; this deviation significantly mitigates the consequence of encountering ice.Comment: American Control Conference, July 2019; 6 page

Business cycles: the role of energy prices

Oil price shocks have figured prominently U.S. business cycles since the end of World War II—although the relationship seems to have weakened during the 1990s. In addition the economy appears to respond asymmetrically to oil price shocks, rising oil prices hurt economic activity more than falling oil prices help it. This section of the Encyclopedia of Energy sorts through an extensive economics literature that relates oil price shocks to aggregate economic activity. It examines how oil price shocks create business cycles, why they seem to have a disproportionate effect on economic activity, why the economy responds asymmetrically to oil prices, and why the relationship between oil prices and economic activity may have weakened. It also addresses the issue of developing energy policy to mitigate the economic effects of oil price shocks.Petroleum industry and trade

Trumpet slices of the Schwarzschild-Tangherlini spacetime

We study families of time-independent maximal and 1+log foliations of the Schwarzschild-Tangherlini spacetime, the spherically-symmetric vacuum black hole solution in D spacetime dimensions, for D >= 4. We identify special members of these families for which the spatial slices display a trumpet geometry. Using a generalization of the 1+log slicing condition that is parametrized by a constant n we recover the results of Nakao, Abe, Yoshino and Shibata in the limit of maximal slicing. We also construct a numerical code that evolves the BSSN equations for D=5 in spherical symmetry using moving-puncture coordinates, and demonstrate that these simulations settle down to the trumpet solutions.Comment: 11 pages, 6 figures, submitted to PR

Molecular Orbital Studies of Nitrosyl Metalloporphyrin Complexes

Molecular orbital calculations are applied to the study of the structure and bonding of nitrosyl metalloporphyrin complexes. The Fenske-Hall approximate molecular orbital method and the Amsterdam Density Functional (ADF) method are used. The calculations provide qualitative and quantitative explanations for the observed structural differences between the nitrosyl porphyrin complexes ofiron, manganese, and cobalt. It is proposed that the energy of the highest occupied molecular orbital (HOMO) of these complexes is primarily responsible for the observed structural differences. The interaction between the nitrosyl ligand and metal dz2 orbital results in an antibonding orbital that is occupied in the complexes of Fe and Co, but unoccupied in the Mn complex. Bending of the metal-N-O linkage in complexes of Fe and Co results in stabilization of this orbital and consequently a more stable configuration for the complex. In addition, the binding affinity of these complexes for a sixth ligand is influenced by the energy and occupation of this largely metal-based orbital. The conclusions drawn from these calculations may provide evidence for the mechanism of activation of the enzyme soluble guanylyl cyclase, which is activated upon binding NO at metal porphyrin site

A new mid-infrared map of the BN/KL region using the Keck telescope

We present a new mid-infrared (12.5micron) map of the BN/KL high-mass star-forming complex in Orion using the LWS instrument at Keck I. Despite poor weather we achieved nearly diffraction-limited images (FWHM = 0.38'') over a roughly 25'' X 25'' region centered on IRc2 down to a flux limit of ~250 mJy. Many of the known infrared (IR) sources in the region break up into smaller sub-components. We have also detected 6 new mid-IR sources. Nearly all of the sources are resolved in our mosaic. The near-IR source ''n'' is slightly elongated in the mid-IR along a NW--SE axis and perfectly bisects the double-peaked radio source ''L''. Source n has been identified as a candidate for powering the large IR luminosity of the BN/KL region (L = 10^5 L_sun). We postulate that the 12 micron emission arises in a circumstellar disk surrounding source n. The morphology of the mid-IR emission and the Orion ''hot core'' (as seen in NH_3 emission), along with the location of water and OH masers, is very suggestive of a bipolar cavity centered on source n and aligned with the rotation axis of the hypothetical circumstellar disk. IRc2, once thought to be the dominant energy source for the BN/KL region, clearly breaks into 4 sub-sources in our mosaic, as seen previously at 3.8 -- 5.0 micron. The anti-correlation of mid-IR emission and NH_3 emission from the nearby hot core indicates that the IRc2 sources are roughly coincident (or behind) the dense hot core. The nature of IRc2 is not clear: neither self-luminous sources (embedded protostars) nor external heating by source I can be definitively ruled out. We also report the discovery of a new arc-like feature SW of the BN object, and some curious morphology surrounding near-IR source ''t".Comment: To appear in The Astronomical Journal, July 2004 (16 pages, 7 figures

Solar Flare Hard X-ray Spectra Possibly Inconsistent with the Collisional Thick Target Model

Recent progress in solar Hard X-ray (HXR) observations with RHESSI data and methods for spectral inversion allow us to study model-independent mean electron flux spectra in solar flares. We report several hard X-ray events observed by RHESSI in which the photon spectra $I(\epsilon)$ are such that the inferred source mean electron spectra are not consistent with the standard model of collisional transport in solar flares. The observed photon spectra are so flat locally that the recovered mean electron flux spectra show a dip around 17-31 keV. While we note that alternative explanations, unrelated to electron transport, have not been ruled out, we focus on the physical implications of this tentative result for the collisional thick-target model.Comment: 12 pages, 3 figures, submitted to Advances in Space Researc

Problems and Progress in Flare Fast Particle Diagnostics

Recent progress in the diagnosis of flare fast particles is critically discussed with the main emphasis on high resolution Hard X-Ray (HXR) data from RHESSI and coordinated data from other instruments. Spectacular new photon data findings are highlighted as are advances in theoretical aspects of their use as fast particle diagnostics, and some important comparisons made with interplanetary particle data. More specifically the following topics are addressed (a) RHESSI data on HXR (electron) versus gamma-ray line (ion) source locations. (b) RHESSI hard X-ray source spatial structure in relation to theoretical models and loop density structure. (c) Energy budget of flare electrons and the Neupert effect. (d) Spectral deconvolution methods including blind target testing and results for RHESSI HXR spectra, including the reality and implications of dips inferred in electron spectra (e) The relation between flare in-situ and interplanetary particle data.Comment: 15 pages, 13 figures, submitted to Advances in Space Researc

Microelectrochemical Sensors for In Vivo Brain Analysis: An Investigation of Procedures for Modifying Pt Electrodes Using Nafion®

Various Nafion® coating procedures were examined in order to design a simple and reproducible coating method to maximise permselective characteristics, and thus eliminate signals from electroactive interferents, in sensors designed for direct in vivo measurements in the brain. Interferents investigated included ascorbic acid (AA), the principal endogenous electroactive interferent present in the brain, and uric acid. Application of the Nafion® (5% commercial solution) using a thermally annealing procedure involving 5 pre-coats, and 2 subsequent dip-bake layers resulted in elimination of interferent signals. It also produced complete blocking of the signal for the neurotransmitter dopamine. The optimum time and temperature for annealing was found to be 5 min at 210 °C. An examination of shelf life over two weeks indicated negligible AA interference over this period. Preliminary investigations with respect to the potential use of these Nafion®-modified Pt electrodes in the design of implantable, first generation, peroxide detecting biosensors indicated that the modified electrode had no effect on O2 permeability but did produce a significant decrease in H2O2 sensitivity. While this may preclude their use in biosensor development they may be more suitable for detection of gaseous neurochemicals such as nitric oxide

Discrimination of prostate cancer cells and non-malignant cells using secondary ion mass spectrometry

This communication utilises Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) combined with multivariate analysis to obtain spectra from the surfaces of three closely related cell lines allowing their discrimination based upon mass spectral ions