The Puzzle of Environmental Politics

In this report we study estimation of time-delays in linear dynamical systems with additive noise. Estimating time-delays is a common engineering problem, e.g. in automatic control, system identification and signal processing. The purpose with this work is to test and evaluate a certain class of methods for time-delay estimation, especially with automatic control applications in mind. Particularly interesting it is to determine the best method. Is one method best in all situations or should different methods be used for different situations? The tested class of methods consists essentially of thresholding the cross correlation between the output and input signals. This is a very common method for time-delay estimation. The methods are tested and evaluated experimentally with the aid of simulations and plots of RMS error, bias and confidence intervals. The results are: The methods often miss to detect because the threshold is too high. The threshold has nevertheless been selected to give the best result. All methods over-estimate the time-delay. Nearly the whole RMS error is due to the bias. None of the tested methods is always best. Which method is best depends on the system and what is done when missing detections. Some form of averaging of the cross correlation, e.g. integration to step response or CUSUM, is advantageous. Fast systems are easiest. White noise input signal is easiest and steps is hardest. The RMS-errors are high in average (approximately greater than 6 sampling intervals). The error is lower for fast system or for high SNR

Hysteresis and unemployment : a preliminary investigation

This paper points out what hysteresis is using a simple model of market entry and exit. A procedure for calculating hysteresis indices for economic time series is outlined. Some preliminary results are presented to assess the explanatory power of hysteresis variables with regard to the equilibrium rate of unemployment in the UK. We find that both natural and "unnatural" variables enter a cointegrating vector for UK unemployment 1959-1996. The natural variable is the replacement ratio. The 'unnatural' variables are the hysteresis index of the exchange rate; and hysteresis indices for the real oil price and the real interest rate

Inefficiency of classically simulating linear optical quantum computing with Fock-state inputs

Aaronson and Arkhipov recently used computational complexity theory to argue that classical computers very likely cannot efficiently simulate linear, multimode, quantum-optical interferometers with arbitrary Fock-state inputs [Aaronson and Arkhipov, Theory Comput. 9, 143 (2013)]. Here we present an elementary argument that utilizes only techniques from quantum optics. We explicitly construct the Hilbert space for such an interferometer and show that its dimension scales exponentially with all the physical resources. We also show in a simple example just how the Schr\"odinger and Heisenberg pictures of quantum theory, while mathematically equivalent, are not in general computationally equivalent. Finally, we conclude our argument by comparing the symmetry requirements of multiparticle bosonic to fermionic interferometers and, using simple physical reasoning, connect the nonsimulatability of the bosonic device to the complexity of computing the permanent of a large matrix.Comment: 7 pages, 1 figure Published in PRA Phys. Rev. A 89, 022328 (2014

Snaking and isolas of localised states in bistable discrete lattices

We consider localised states in a discrete bistable Allen-Cahn equation. This model equation combines bistability and local cell-to-cell coupling in the simplest possible way. The existence of stable localised states is made possible by pinning to the underlying lattice; they do not exist in the equivalent continuum equation. In particular we address the existence of 'isolas': closed curves of solutions in the bifurcation diagram. Isolas appear for some non-periodic boundary conditions in one spatial dimension but seem to appear generically in two dimensions. We point out how features of the bifurcation diagram in 1D help to explain some (unintuitive) features of the bifurcation diagram in 2D.Comment: 14 page

Online measurements of the emissions of intermediate-volatility and semi-volatile organic compounds from aircraft

A detailed understanding of the climate and air quality impacts of aviation requires measurements of the emissions of intermediate-volatility and semi-volatile organic compounds (I/SVOCs) from aircraft. Currently both the amount and chemical composition of aircraft I/SVOC emissions remain poorly characterized. Here we characterize I/SVOC emissions from aircraft, using a novel instrument for the online, quantitative measurement of the mass loading and composition of low-volatility organic vapors. Emissions from the NASA DC8 aircraft were sampled on the ground 143 m downwind of the engines and characterized as a function of engine power from idle (4% maximum rated thrust) through 85% power. Results show that I/SVOC emissions are highest during engine idle operating conditions, with decreasing but non-zero I/SVOC emissions at higher engine powers. Comparison of I/SVOC emissions with total hydrocarbon (THC) measurements, VOC measurements, and an established emissions profile indicates that I/SVOCs comprise 10–20% of the total organic gas-phase emissions at idle, and an increasing fraction of the total gas-phase organic emissions at higher powers. Positive matrix factorization of online mass spectra is used to identify three distinct types of I/SVOC emissions: aliphatic, aromatic and oxygenated. The volatility and chemical composition of the emissions suggest that unburned fuel is the dominant source of I/SVOCs at idle, while pyrolysis products make up an increasing fraction of the I/SVOCs at higher powers. Oxygenated I/SVOC emissions were detected at lower engine powers (≤30%) and may be linked to cracked, partially oxidized or unburned fuel components.United States. Dept. of Energy. Office of Science (Small Business Innovation Research Program Grant DE-SC0001666)United States. Environmental Protection Agency (National Center for Environmental Research Grant RD834560

Musical spectra, l'espace sensible, and contemporary opera

Something extraordinary occurs in the third scene of Pygmalion, Jean-Philippe Rameau’s acte de ballet of 1748. The title character, a sculptor, is creating a marble statue of a woman. She is so beautiful that he falls in love with his own creation. The intervention of L’Amour, the goddess of love, brings the statue to life; the statue, in turn, declares her love for her creator. Jubilations ensue. At the crucial moment of the statue’s metamorphosis, Pygmalion sings of his joyous bewilderment, accompanied by the most astonishing orchestral sounds. D’où naissent ces accords ? Quels sons harmonieux ! Une vive clarté se répand dans ces lieux ! [From whence spring these chords? What are these harmonious sounds?/p> A vivid brightness fills this place!] The fact that Pygmalion can actually hear the music rising up from the pit is in itself remarkable (Example 1). [Insert Ex. 1 around here] With the obvious exception of divertissements, when an orchestra plays music that is audible to those on stage, since they must dance to it, or instances of musical onomatopoeia such as thunder claps and bird song, operatic characters generally remain oblivious to the musical weft that enfolds them. That this illusion, this conventional pact between stage and audience, is broken here signals an exceptional moment

The Mr. Big Sting in Canada

For approximately the last fifteen years, the Royal Canadian Mounted Police have been mounting highly sophisticated undercover sting operations in Canada known colloquially as Mr. Big stings. These undercover operations involve multiple officers posing as members of a ruthless, powerful and wealthy criminal organization in order to trick suspects into making confessions to serious crimes, nearly always homicides. The undercover officers essentially orchestrate a chance meeting with the suspect, known operationally as the “target”, and exert their considerable influence and resources to convince him that he is being inducted into a criminal gang. The target is typically a person suspected of having committed a murder in the past, but who has never been charged due to lack of evidence. Over a period of months or weeks the undercover officers attempt to build a relationship with the target based on fear, greed, companionship, or a combination of those or other emotions. The target is given tasks to perform which appear criminal in nature, but which are actually staged crimes in which every participant is an undercover officer. The target is eventually told he must meet with the boss of the gang, the “Mr. Big” after whom the sting is named, in order for a final decision to be made on whether or not the target can join the gang. The target is told that he must confess to the previous murder of which he is suspected in order to join the gang. Sometimes the target confesses readily, other times he protests his innocence, but Mr. Big will not accept exculpatory statements. Often further inducements are offered by Mr. Big, most notably a promise to derail the investigation by using his influence over corrupt justice system participants. If the suspect admits culpability he will be charged with the crime and nearly always convicted at trial. Canadian courts have exercised virtually no control over police tactics in these cases. Defence counsel have argued against the use of the evidence on the basis of a breach of the Charter of Rights and Freedoms with regard to the right to silence and also with regard to abuse of process. These arguments have been unsuccessful. Defence counsel have also argued unsuccessfully that the statements should be inadmissible under Canadian hearsay law. It has also been argued, equally unsuccessfully, that the undercover operators should be treated as persons-in-authority, and hence that the statements elicited from the targets should have to be proven voluntary beyond a reasonable doubt. Canadian judges have also been unwilling to allow the defence to lead expert evidence in these cases to tell the trier of fact about the possibility of false confessions. The ultimate result is that there is no control over police tactics in these stings. There has been one proven wrongful conviction as a result of these stings, that of Kyle Wayne Unger. Other wrongful convictions may come to light. Short of its outright abolition, probably the best way to control the sting and prevent wrongful convictions is to subject the statements to a formal voluntariness inquiry