Learning 3D Navigation Protocols on Touch Interfaces with Cooperative Multi-Agent Reinforcement Learning

Using touch devices to navigate in virtual 3D environments such as computer assisted design (CAD) models or geographical information systems (GIS) is inherently difficult for humans, as the 3D operations have to be performed by the user on a 2D touch surface. This ill-posed problem is classically solved with a fixed and handcrafted interaction protocol, which must be learned by the user. We propose to automatically learn a new interaction protocol allowing to map a 2D user input to 3D actions in virtual environments using reinforcement learning (RL). A fundamental problem of RL methods is the vast amount of interactions often required, which are difficult to come by when humans are involved. To overcome this limitation, we make use of two collaborative agents. The first agent models the human by learning to perform the 2D finger trajectories. The second agent acts as the interaction protocol, interpreting and translating to 3D operations the 2D finger trajectories from the first agent. We restrict the learned 2D trajectories to be similar to a training set of collected human gestures by first performing state representation learning, prior to reinforcement learning. This state representation learning is addressed by projecting the gestures into a latent space learned by a variational auto encoder (VAE).Comment: 17 pages, 8 figures. Accepted at The European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases 2019 (ECMLPKDD 2019

Rugged, low-conductance, heat-flow probe

Lightweight, compact probe structure has low thermal conductance to enable accurate measurement of slight temperature gradients. Probe combines ruggedness, high precision, accuracy, and stability. Device can withstand vibration, shock, acceleration, temperature extremes, and high vacuums, and should interest industrial engineers and geologists

Anisotropic high‐field diffusion of holes in silicon

Anisotropy of the silicon valence band leads to a strong dependence of charge carrier transport properties, upon the orientation of the electric field. A detailed anisotropic Monte Carlo method has been applied to the calculation of the hole diffusion coefficient in silicon, studying its dependence on field magnitude and orientation. The longitudinal diffusion coefficient is found to have a dependence on the field orientation which is similar in degree to the more familiar dependence of the drift velocity on field orientation. However, it is found that the transverse diffusion coefficient has a substantially stronger dependence on field orientation. At the highest field which has been studied, 50 kV/cm, the transverse diffusion coefficient almost doubles as one shifts from a field oriented in the [100] direction to one in the [101] direction and considers the [101] transverse direction. © 1995 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70410/2/APPLAB-66-20-2727-1.pd

High‐field thermal noise of holes in silicon: The effect of valence band anisotropy

The effects of valence band anisotropy on longitudinal and transverse high‐field differential mobilities, diffusivities, and thermal noise temperatures were theoretically investigated. The effects were examined for holes in silicon and in several hypothetical materials having systematically varied degrees of valence band anisotropy. The results show a pronounced dependence of the transverse high‐field differential mobility and of the longitudinal high‐field noise temperature upon the degree of anisotropy. This suggests that thermal noise measurements may provide an alternative to magnetotransport methods as a valence bandstructure measurement technique. The results also imply that thermal noise in semiconductor devices can be mitigated by choosing a semiconductor with a low degree of valence band anisotropy and, for a given semiconductor, by properly aligning the device layout with respect to the material crystallographic axes. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70685/2/JAPIAU-80-12-6766-1.pd

Clinical comparison of single-piece and three-piece truncated hydrophobic acrylic intraocular lenses

Journal ArticlePURPOSE: To determine the clinical differences between three-piece (3P) and single-piece (SP) truncated hydrophobic acrylic intraocular lenses (IOL). DESIGN: Retrospective cohort clinical study. METHODS: The setting was an academic clinical practice. The patient population consisted of subjects without confounding comorbidity that could effect central vision with at least 1-year follow-up after uncomplicated surgical placement of 3P or SP IOLs in the capsular bag and at least 20/25 best-corrected postoperative vision documented. Observation procedures were as follows: logarithm of the minimal angle of resolution (LogMAR) visual acuity (uncorrected and best corrected), digital retroillumination photographs to ascertain posterior capsular opacification (PCO), anterior capsular opacification (ACO), IOL centration, and refractive stability by comparing this refraction with the early postoperative refraction. Patients completed a dysphotopsia questionnaire. Main outcome measures were as follows: LogMAR visual acuity (uncorrected and best corrected), PCO, ACO, IOL centration, refractive stability, and dysphotopsia outcomes comparing 3P and SP. RESULTS: Seventy-five patients were enrolled (36 3P and 39 SP). Corrected and uncorrected visual acuity, refractive stability, and IOL centration were similar. Single piece truncated hydrophobic acrylic intraocular lenses had more PCO (P =.013), less ACO (P =.001), less central flash looking at a peripheral light (P =.044), and less unwanted images to the side of a light source (P =.025) . CONCLUSIONS: Although similar in centration and refractive stability, SP has more PCO, less ACO, and less dysphotopsia than 3P

Monte Carlo studies of ohmic hole mobility in silicon and germanium: Examination of the optical phonon deformation potential

Monte Carlo methods which have been widely used for studying high field electron and hole transport, so far have not been applied to the complex problem of Ohmic hole transport. We present a versatile generalization of the Monte Carlo approach for Ohmic hole mobility studies and apply it to pure silicon and germanium. In particular, we examine the role of the optical phonon deformation potential d0 in controlling the temperature dependence of the mobility.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70383/2/JAPIAU-76-7-4192-1.pd

Anisotropic high‐field transverse differential mobility of holes in silicon

Anisotropy of the silicon valence band does not lead to any significant anisotropy in the longitudinal hole transport properties, but we find that the transverse mobility is quite anisotropic. The transverse mobility represents the response of charge carriers to a small transverse electric field in the presence of a strong longitudinal field. A detailed, anisotropic Monte Carlo method has been applied to the calculation of the hole transverse differential mobility in silicon. The transverse differential mobility is studied both with regard to variations in the orientation, with respect to the crystalline axes, of the high longitudinal electric field, and with regard to variations in the transverse direction of the mobility, taken in the plane perpendicular to the high electric field. The anisotropy of the valence band causes the transverse differential mobility to strongly vary with respect to the electric field orientation. Symmetry considerations show that the transverse differential mobility is isotropic in the {100} and {111} planes and has twofold rotational symmetry in the {101} planes. Our calculations bear this out. Furthermore, we show that the transverse mobility can be much different from the chordal mobility, in distinction to the case for isotropic band structures. © 1995 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69866/2/APPLAB-67-20-2966-1.pd

Dependence of pseudomorphic semiconductor band gap on substrate orientation

For a given misfit we examine the band‐gap variation of a pseudomorphic overlayer on a thick substrate as a function of substrate orientation. The strain tensor is found to be a strong function of the substrate orientation. For both direct and indirect band‐gap overlayers, this results in a significant variation in the band gap as the substrate orientation is changed. However, for indirect band‐gap layers, such as SiGe alloys grown on Si substrates, the change in band gap is accompanied by a lifting of conduction‐band‐edge degeneracies. The magnitude of this splitting may be as large or larger than the change in the band gap. Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69642/2/JAPIAU-69-4-2694-1.pd

Charged carrier transport in Si1−xGex pseudomorphic alloys matched to Si—strain‐related transport improvements

Charge carrier transport studies are reported for Si1−xGex pseudomorphic alloy layers matched to the (001) Si substrate lattice constant. The effect of biaxial compressive strain on transport is studied by first examining the band structure changes via deformation potential theory and then studying the transport via a generalized Monte Carlo approach. Marked improvements in in‐plane hole transport are obtained while significant improvements also occur in the out‐of‐plane electron transport. These changes are ideally suited for use in n(Si)‐p(Si1−xGex)‐n(Si) heterojunction bipolar transistors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71296/2/APPLAB-55-19-2008-1.pd