Richard Grace

Driver drowsiness/fatigue is an important cause of combination-unit truck crashes. Drowsy driver detection methods can form the basis of a system to potentially reduce accidents related to drowsy driving. We report on efforts performed at the Carnegie Mellon Driving Research Center to develop such in vehicle driver monitoring systems. Commercial motor vehicle truck drivers were studied in actual fleet operations. The drivers operated vehicles that were equipped to measure vehicle performance and driver psychophysiological data. Based on this work, two drowsiness detection methods are being considered. The first is a video-based system that measures PERCLOS, a scientifically supported measure of drowsiness associated with slow eye closure. The second detection method is based on a model to estimate PERCLOS based on vehicle performance data. A non-parametric (neural network) model was used to estimate PERCLOS using measures associated with lane keeping, steering wheel movements and lateral acceleration of the vehicle.

Hypernuclear lifetime and partial decay-rate measurements made at the Brookhaven National Laboratory Alternating Gradient Synchrotron are reported for $_{\mathrm{\ensuremath{\Lambda}}}^{5}\mathrm{He}$ and $_{\mathrm{\ensuremath{\Lambda}}}^{12}\mathrm{C}$. The mesonic and nonmesonic decays are compared to existing weak-interaction calculations. In particular, the nonmesonic reaction \ensuremath{\Lambda}N\ensuremath{\rightarrow}NN is discussed as an example of a nonleptonic weak process for which calculations have been reported using various effective weak Hamiltonians.

The observation of $\ensuremath{\Lambda}$-hypernuclear levels in $_{\ensuremath{\Lambda}}^{12}\mathrm{C}$ by associated production through the (${\ensuremath{\pi}}^{+}, {K}^{+}$) reaction is reported. The $_{\ensuremath{\Lambda}}^{12}\mathrm{C}$ excitation-energy spectra were recorded at laboratory scattering angles of 5.6\ifmmode^\circ\else\textdegree\fi{}, 10.3\ifmmode^\circ\else\textdegree\fi{}, and 15.2\ifmmode^\circ\else\textdegree\fi{}. They show two major peaks---one attributed to the ground state, and one about 11 MeV higher. These results are compared to the strangeness-exchanging (${K}^{\ensuremath{-}}, {\ensuremath{\pi}}^{\ensuremath{-}}$) reaction. The measured cross sections are compared to relativistic distorted-wave Born-approximation calculations.

The spectra of levels in the hypernuclei $_{\ensuremath{\Lambda}}^{13}\mathrm{C}$, $_{\ensuremath{\Lambda}}^{14}\mathrm{N}$, and $_{\ensuremath{\Lambda}}^{18}\mathrm{O}$, excited by 800-MeV/c kaons in the (${K}^{\ensuremath{-}}$,${\ensuremath{\pi}}^{\ensuremath{-}}$) reaction, have been observed at the Brookhaven alternating-gradient synchrotron. Data were recorded for scattering angles from 0\ifmmode^\circ\else\textdegree\fi{} to 25\ifmmode^\circ\else\textdegree\fi{}, corresponding to momentum transfers from 50 to 330 MeV/c. The levels are interpreted in terms of a $\ensuremath{\Lambda}$ hyperon coupled to a strangeness-zero nuclear core. The results provide insights into the properties of the $\ensuremath{\Lambda}$-nucleon and $\ensuremath{\Lambda}$-nucleus interactions.

$\ensuremath{\gamma}$-ray transitions of energy 2.034 \ifmmode\pm\else\textpm\fi{} 0.023 MeV in the hypernucleus $_{\ensuremath{\Lambda}}^{7}\mathrm{Li}$ and 3.079 \ifmmode\pm\else\textpm\fi{} 0.040 MeV in the hypernucleus $_{\ensuremath{\Lambda}}^{9}\mathrm{Be}$ are observed. In both cases, the energy of the $\ensuremath{\gamma}$ ray in the hypernucleus $_{\ensuremath{\Lambda}}^{A}Z$ is very close to the energy of the first excited state of the nuclear core. The $\ensuremath{\gamma}$ rays are interpreted as arising from core transitions in the presence of the $\ensuremath{\Lambda}$ particle. The size of the shift places limits on the strength of the $\ensuremath{\Lambda}N$ spin-dependent interaction.