8,789 research outputs found

    Dynamical behavior of a complex fluid near an out-of-equilibrium transition: approaching simple rheological chaos

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    We report here an extensive study of sustained oscillations of the viscosity of a complex fluid near an out-of-equilibrium transition. Using well defined protocols, we perform rheological measurements of the onion texture near a layering transition in a Couette flow. This complex fluid exhibits sustained oscillations of the viscosity, on a large time scale (500s) at controlled stress. These oscillations are directly correlated to an oscillating microstrutural change of the texture of the fluid. We observe a great diversity of dynamical behavior and we show that there is a coupling with spatial effects in the gradient v direction. This is in agreement with a carefull analysis of the temporal series of the viscosity with the dynamical system theory. This analysis indicates that the observed dynamical responses do not strictly correspond to 3-dimensional chaotic states, probably because some spatio-temporal effects are present and are likely to play an important role.Comment: submitted to Phys. Rev.

    Analysis of rocket engine injection combustion processes

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    Mixing methodology improvement for the JANNAF DER and CICM injection/combustion analysis computer programs was accomplished. ZOM plane prediction model development was improved for installation into the new standardized DER computer program. An intra-element mixing model developing approach was recommended for gas/liquid coaxial injection elements for possible future incorporation into the CICM computer program

    Semi-geostrophic particle motion and exponentially accurate normal forms

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    We give an exponentially-accurate normal form for a Lagrangian particle moving in a rotating shallow-water system in the semi-geostrophic limit, which describes the motion in the region of an exponentially-accurate slow manifold (a region of phase space for which dynamics on the fast scale are exponentially small in the Rossby number). The result extends to numerical solutions of this problem via backward error analysis, and extends to the Hamiltonian Particle-Mesh (HPM) method for the shallow-water equations where the result shows that HPM stays close to balance for exponentially-long times in the semi-geostrophic limit. We show how this result is related to the variational asymptotics approach of [Oliver, 2005]; the difference being that on the Hamiltonian side it is possible to obtain strong bounds on the growth of fast motion away from (but near to) the slow manifold

    The ontology of causal process theories

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    There is a widespread belief that the so-called process theories of causation developed by Wesley Salmon and Phil Dowe have given us an original account of what causation really is. In this paper, I show that this is a misconception. The notion of "causal process" does not offer us a new ontological account of causation. I make this argument by explicating the implicit ontological commitments in Salmon and Dowe's theories. From this, it is clear that Salmon's Mark Transmission Theory collapses to a counterfactual theory of causation, while the Conserved Quantity Theory collapses to David Fair's phsyicalist reduction of causation

    DNA Is Different:Implications of the Public Perception ofDNA Evidence on Police Interrogation Methods

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    These reform proposals have been met with vehement criticism, most of which stem from a concern that any attempt to prohibit or regulate deceptive interrogation methods would decrease the number of confessions and convictions produced by the criminal justice system. With these concerns in mind, this article proposes a different, more moderate reform: a per se ban on the falsification of DNA evidence during police interrogations. This proposal differs from those described above in three important ways. First, the prohibition on fabricating DNA evidence does not require a change in the voluntariness test used to ascertain the admissibility of a confession. Rather, it fits within current confession law jurisprudence, allowing for easy adoption by state and federal courts, and police departments. Second, the proposal is limited to DNA evidence. It does not include other forensic evidence, such as ballistics, fingerprinting, or blood typing. Instead, it focuses on DNA because of the public perception of DNA infallibility. Finally, the proposal establishes a bright-line rule. Scholars have long complained about the ambiguity of a totality of the circumstances test, which fails to give guidance to lower courts or law enforcement officers, who arguably need it most. Instead, the proposal advocates for a complete prohibition on any interrogation technique designed to convince the suspect that the police have obtained his DNA in connection with the crime. Though more moderate than other reform proposals, it shares one significant similarity: it seeks to increase the fundamental fairness of police interrogation, and to prevent false confessions and wrongful convictions. In short, this article proposes a small step in the right direction. Part II of this article traces the development of the due process voluntariness test for admissibility of confessions, summarizing the law on confession admissibility. Part III describes current police interrogation techniques, focusing on the Reid Method and its likelihood of resulting in false confessions. Part IV turns to the influence of television on the public understanding of law, forensic science, and the use of DNA evidence in law enforcement, arguing that the so-called CSI Effect creates a public perception that DNA evidence is incontrovertible. Part IV concludes that the public perception of the strength of DNA evidence tips the balance of the totality of the circumstances test, such that a confession elicited based upon fabrication of DNA evidence in an interrogation cannot be seen as voluntary. Finally, Part V sets forth the proposal that confessions based on deception regarding DNA evidence be excluded, justifying the proposal under existing law and briefly considering likely criticisms
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