No abstract

In this work, we report low-loss single-mode integrated optical waveguides in the near ultra-violet and visible spectral regions with aluminum oxide (Al 2 O 3 ) films using an atomic layer deposition (ALD) process. Alumina films were deposited on glass and fused silica substrates by the ALD process at substrate/chamber temperatures of 200 °C and 300 °C. Transmission spectra and waveguide measurements were performed in our alumina films with thicknesses in the range of 210 -380 nm for the optical characterization. Those measurements allowed us to determine the optical constants (n w and k w ), propagation loss, and thickness of the alumina films. The experimental results from the applied techniques show good agreement and demonstrate a lowloss optical waveguide. Our alumina thin-film waveguides is well transparent in the whole visible spectral region and also in an important region of the UV; the measured propagation loss is below 4 dB/cm down to a wavelength as short as 250 nm. The low propagation loss of these alumina guiding films, in particular in the near ultra-violet region which lacks materials with high optical performance, is extremely useful for several integrated optic applications.

Passenger car equivalents (PCEs) have been used extensively in the Highway Capacity Manual to establish the impact of trucks, buses, and recreational vehicles on traffic operations. PCEs are currently being used for studying freeways, multilane highways, and two-lane highways. A heavy-vehicle factor is directly given for the impact of heavy vehicles at signalized intersections (and indirectly along arterials). These PCE values are typically based on a limited number of simulations and on older simulation models. In addition, the impact of variables such as traffic flow, truck percentage, truck type (i.e., length and weight/horsepower ratio), grade, and length of grade on PCEs has not been evaluated in depth for all facility types. The methodology for developing PCEs for different truck types for the full range of traffic conditions on freeways, two-lane highways, and arterials is described. Given the scope of this research and the variability of traffic conditions to be examined, simulation was selected as the most appropriate tool. The resulting PCE values for freeways, two-lane highways, and arterials indicated that some variables, such as percentage of trucks, do not always have the expected effect on PCEs, whereas other variables, such as vehicle type, are crucial in the calculations. Generally, major differences in PCEs occurred for the longer and steeper grades. There was great variability in PCE values as a function of the weight/horsepower ratio as well as of vehicle length.Passenger car equivalents (PCEs) have been used extensively in the Highway Capacity Manual (1,2) to establish the impact of trucks, buses, and recreational vehicles (RVs) on traffic operations. PCEs are currently being used for freeways, multilane highways, and twolane highways. PCE values for freeways and multilane highways are given as a function of grade, length of grade, and percentage of trucks, buses, or RVs. For two-lane highways, PCEs are given as a function of the type of terrain and level of service or average upgrade speed for trucks, buses, and RVs. The impact of heavy vehicles at signalized intersections (and indirectly along arterials) is given as a function of the percentage of heavy vehicles. The impact of grade is considered independently of heavy-vehicle presence for two-lane highways and for signalized intersections.These PCE values are typically based on small databases and a limited number of simulations with older models (3). In addition, the impact of variables such as traffic flow, truck percentage, truck type (i.e., length and weight/horsepower ratio), grade, and length of grade on PCEs has not been evaluated in depth for all facility types. The methodology for developing PCEs for different truck types for the full range of traffic conditions on freeways, two-lane highways, and arterials is described. Given the scope of this research and the variability of traffic conditions to be examined, simulation was selected as the most appropriate tool. It must be noted that the research described here was performed as p...

The stabilization of a relatively simple microwave oscillator tunable across the full X-band based on a laser subjected to optical feedback is achieved. Specifically, a resonance effect based on locking the two inherent dynamic frequencies of the system, as well as optoelectronic feedback are utilized to achieve a sub-ps jitter and typical phase noise in the range of −107 dBc/Hz at 10 kHz offset from an oscillation frequency that can be tuned from 5.5 to 12.1 GHz. Further, the microwave signal is extracted from the laser-diode injection terminals and eliminates the need for multiple lasers, radio-frequency filters, and external RF sources. This architecture therefore realizes a compact and low-cost microwave photonic oscillator.

The lane change models used in today's traffic simulators often do not determine lane change actions in terms of the evaluation of sequential plans, but rather in terms of the utility of the very next lane change action. This has the disadvantage of not being able to account for the influence of delayed rewards, such as the simulated vehicle moving across a slow lane to a better-performing non-adjacent lane. This research presents a lane change model which at every simulation time step, builds a tree of potential maneuver sequences, and selects the lane change action according to planning over a time horizon. The model was calibrated using a vehicle trajectory data set and shown to give improved realism of lane change actions of individual vehicles, compared to a lane change model without sequential planning.