Jurors\u27 Perceptions of False Confessions

This study examined the effect of mock jurors’ perceptions of a defendant’s false confession vs. no confession (false confession presence), coercive interrogation techniques vs. panic-escape (false confession reason), and expert witness testimony vs. defendant explanation vs. expert witness testimony plus defendant explanation for his false confession (source). The four hypotheses and one research question pertained to main effects and interaction effects of false confession presence, false confession reason, and source (separately) and expert witness conditions combined on five outcome variables. Outcome variables were defendant’s guilt, trustworthiness, suggestibility, susceptibility to external influences, and juror’s likelihood of changing their verdict. Using Amazon Mechanical Turk (MTurk), mock jurors (N = 415) were randomly assigned to one of twelve conditions, in which they read a murder trial scenario and answered questions regarding the outcome variables. Main effects of false confession were found within the defendant’s perceived guilt, trustworthiness, and suggestibility. Main effects of source were also found, such that the defendant’s perceived guilt, suggestibility, and susceptibility to external influences were significant, as was to jurors’ likelihood of changing their verdict (guilty/not guilty) but follow-up analyses yielded an inconsistent pattern. Expert witness testimony reduced perceptions of guilt and suggestibility, and decreased jurors’ openness to changing their verdict. Numerous False Confession x Reason interactions emerged pertaining to the defendant’s perceived guilt, trustworthiness, and suggestibility, as well as the jurors’ likelihood of changing their verdict (guilty/not guilty). A series of planned contrasts comparing the false confession/coercive interrogation/expert witness vs. the false confession/panic-escape/expert witness conditions; the false confession/coercive interrogation/defendant vs. false confession/panic-escape/defendant condition; and the false confession/coercive interrogation/expert witness + defendant vs. false confession/panic-escape/expert witness + defendant showed no significant differences in jurors’ perceptions of the defendant’s guilt. Keywords: jurors’ perceptions, false confession

Reducing instrumentation errors caused by circumferential flow field variations in multi-stage axial compressors

Abstract The effects of blade row interactions on stator-mounted instrumentation in axial compressors are investigated using unsteady numerical calculations. The test compressor is an 8-stage machine representative of an aero-engine core compressor. For the unsteady calculations, a 180deg sector (half-annulus) model of the compressor is used. It is shown that the time-mean flow field in the stator leading edge planes is circumferentially non-uniform. The circumferential variations in stagnation pressure and stagnation temperature respectively reach 4.2% and 1.1% of the local mean. Using spatial wave number analysis, the incoming wakes from the upstream stator rows are identified as the dominant source of the circumferential variations in the front and middle of the compressor, while towards the rear of the compressor, the upstream influence of the eight struts in the exit duct becomes dominant. Based on three circumferential probes, the sampling errors for stagnation pressure and stagnation temperature are calculated as a function of the probe locations. Optimization of the probe locations shows that the sampling error can be reduced by up to 77% by circumferentially redistributing the individual probes. The reductions in the sampling errors translate to reductions in the uncertainties of the overall compressor efficiency and inlet flow capacity by up to 50%. Recognizing that data from large-scale unsteady calculations is rarely available in the instrumentation phase for a new test rig or engine, a method for approximating the circumferential variations with single harmonics is presented. The construction of the harmonics is based solely on the knowledge of the number of stators in each row and a small number of equi-spaced probes. It is shown how excursions in the sampling error are reduced by increasing the number of circumferential probes.Industry funde

A direct image of the obscuring disk surrounding an active galactic nucleus

Active galactic nuclei (AGN) are generally accepted to be powered by the release of gravitational energy in a compact accretion disk surrounding a massive black hole. Such disks are also necessary to collimate powerful radio jets seen in some AGN. The unifying classification schemes for AGN further propose that differences in their appearance can be attributed to the opacity of the accreting material, which may obstruct our view of the central region of some systems. The popular model for the obscuring medium is a parsec-scale disk of dense molecular gas, although evidence for such disks has been mostly indirect, as their angular size is much smaller than the resolution of conventional telescopes. Here we report the first direct images of a pc-scale disk of ionised gas within the nucleus of NGC 1068, the archetype of obscured AGN. The disk is viewed nearly edge-on, and individual clouds within the ionised disk are opaque to high-energy radiation, consistent with the unifying classification scheme. In projection, the disk and AGN axes align, from which we infer that the ionised gas disk traces the outer regions of the long-sought inner accretion disk.Comment: 14 pages, LaTeX, PSfig, to appear in Nature. also available at http://hethp.mpe-garching.mpg.de/Preprint

Flexible microwave system to measure the electron number density and quantify the communications impact of electric thruster plasma plumes

An advanced microwave interferometric system operating in the Ku (12–18 GHz) band has been implemented for use in very large vacuum chambers to determine the effects of electromagnetic wave propagation through a plasma plume created by a space electric propulsion thruster. This diagnostic tool is used to nonintrusively obtain the local electron number density as well as provide information necessary for understanding impact to communications and other spacecraft electromagnetic systems. The use of a nonintrusive electromagnetic measurement provides highly accurate line integrated density and avoids problems caused by intrusive measurement techniques. If the plasma is symmetrical, local plasma density can also be determined accurately using well known inversion techniques. A network analyzer acts as a transmitter and receiver while a two axis positioning system maps the amplitude and phase variation of a transmitted signal over one plane of the plasma plume. The utilization of a 6 m×9 m vacuum chamber effectively minimizes plasma boundary effects, but the longer cable path lengths have required a frequency conversion circuit to reduce power loss and phase uncertainty at high frequencies. Two studies are presented: the first is a measurement of the local electron density in the plume of a 1 kW arcjet and the second is a measurement of attenuation in the plume of a stationary plasma thruster. Both the arcjet and SPT emit a steady state conical unmagnetized plasma that is radially symmetric. The arcjet peak density is 1015–1016 m−3 along centerline and the SPT peak density is 1016–1017 m−3 along centerline. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71094/2/RSINAK-68-2-1189-1.pd

A Hall probe diagnostic for low density plasma accelerators

A Hall probe diagnostic was developed for use with plasma thrusters. The Hall generators were mounted at the end of a stainless steel tube heat exchanger. Ceramic cement and a Pyrex tube were used as radiation and particle flux shields, respectively. A thermocouple was used to monitor the temperature of the Hall generator. The low voltage output from the probe was amplified within one meter of the transducer to minimize the effect of noise pick up. A National Institute of Standards and Technology traceable Gaussmeter provided an absolute reference for calibration, and relative calibrations were performed both in a strong electric field and in situ during thruster operation to approximate the conditions in the discharge. The overall accuracy of the diagnostic was ±6 G.±6G. The probes were tested with a Hall-effect thruster, and provided sufficiently accurate data to estimate the magnitude of the closed-drift electron current. © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69868/2/RSINAK-69-6-2546-1.pd

Analysis of chamber simulations of long probes in high-speed, dense plasmas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76739/1/AIAA-2001-1142-128.pd

Current collection to long, thin probes in a dense high-speed flowing plasma

We describe chamber tests of simulated electrodynamic tethers (EDTs) of different geometries operating in a dense, high-speed plasma. The geometries tested were cylindrical, flat-ribbon, and sparse-ribbon or mesh. Several important conclusions that can be drawn from the tests are as follows: the currents collected by cylinder are close to what would be predicted via orbital-motion-limited (OML) current collection theory. The tape tether had comparable current levels to a theoretical equal area OML cylinder collector. However, I–V behavior clearly is different at nearest distances ( ∼ 15λD∼15λD tape width) as compared to furthest test distances ( ∼ 6λD∼6λD tape width). The tape tether did better than a theoretical equal mass solid cylinder. A “knee” in the I–V curves can be seen in the tape/mesh data at a potential that is just above the estimated energy of the incoming beam of ions, at least for the closest distances where Debye length is smallest. Below this knee the current increases rapidly as voltage is increased. Above the knee the current increases at a rate one might expect from OML current-collection models depending on the relative width. This likely is an example of high-speed plasma flow effect. Perpendicular tape orientation performed slightly better than parallel. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87360/2/494_1.pd

Maximizing Payload Mass Fractions of Spacecraft for Interplanetary Electric Propulsion Missions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76389/1/AIAA-17433-786.pd