Frequency stabilization of an ultraviolet semiconductor disk laser

We report a tunable, narrow-linewidth UV laser based on intracavity second-harmonic generation in a red semiconductor disk laser. Single-frequency operation is demonstrated with a total UV output power of 26 mW. By servo-locking the fundamental frequency to a reference Fabry–Pérot cavity, the linewidth of the UV beam has been reduced to 16 kHz on short timescales and 50 kHz on a 1 s timescale, relative to the reference

What Happened on Deliberation Day?

What are the effects of deliberation about political issues? This essay reports the results of a kind of Deliberation Day, involving sixty-three citizens in Colorado. Groups from Boulder, a predominantly liberal city, met and discussed global warming, affirmative action, and civil unions for same-sex couples; groups from Colorado Springs, a predominately conservative city, met to discuss the same issues. The major effect of deliberation was to make group members more extreme than they were when they started to talk. Liberals became more liberal on all three issues; conservatives became more conservative. As a result, the division between the citizens of Boulder and the citizens of Colorado Springs were significantly increased as a result of intragroup deliberation. Deliberation also increased consensus, and dampened diversity, within the groups. Hence Deliberation Day produced group polarization, in the distinctive form of ideological amplification. Implications are explored for the uses and structure of deliberation in general.

Characterization of single-crystal synthetic diamond for multi-watt continuous-wave Raman lasers

A continuous-wave diamond Raman laser is demonstrated with an output power of 5.1 W at 1217 nm. This Raman laser is intracavity pumped by a side-pumped Nd:YLF rod laser: a 43-fold brightness enhancement between the Nd:YLF and diamond Raman lasers is observed, with the M2 beam propagation factor of the diamond Raman laser measured to be <; 1.2. Although higher output powers are demonstrated in a similar configuration using KGd(WO4)2 (KGW) as the Raman laser material (6.1 W), the brightness enhancement is much lower (2.5 fold) due to the poorer beam quality of the KGW Raman laser (M2 <; 6). The Raman gain coefficient of single-crystal synthetic diamond at a pump wavelength of 1064-nm is also measured: a maximum value of 21±2 cm/GW is returned compared to 5.7±0.5 cm/GW for KGW at the same wavelength

Tunable narrow linewidth AlGaInP semiconductor disk laser for Sr atom cooling applications

We report a frequency stabilised semiconductor disk lasers based on AlGaInP and operating at 689 nm, a wavelength of interest for atomic clocks based on strontium atoms. With a gain structure designed for emission at around 690 nm, more than 100 mW of output power was generated in single frequency operation. We show that the source can be tuned over 8 nm with picometer precision. By servo-locking the frequency to the side of fringe of a reference cavity, we demonstrate rms frequency noise of 5.2 kHz

MIRIAM: A Multimodal Chat-Based Interface for Autonomous Systems

We present MIRIAM (Multimodal Intelligent inteRactIon for Autonomous systeMs), a multimodal interface to support situation awareness of autonomous vehicles through chat-based interaction. The user is able to chat about the vehicle's plan, objectives, previous activities and mission progress. The system is mixed initiative in that it pro-actively sends messages about key events, such as fault warnings. We will demonstrate MIRIAM using SeeByte's SeeTrack command and control interface and Neptune autonomy simulator.Comment: 2 pages, ICMI'17, 19th ACM International Conference on Multimodal Interaction, November 13-17 2017, Glasgow, U

Modelling solids friction factor for dense-phase pneumatic conveying of powders

This paper presents results from an investigation into power-function modelling of solids friction factor for the dilute-phase and fluidised dense-phase (FDP) conveying of powders. Three different diameters/lengths of pipeline were used to generate a wide range of steady-state data and also explore important scale-up issues. The effect of pressure tapping locations on the data and derived models was also investigated. Different sets of power-function model solutions were used for comparison purposes and also to check scale-up stability and accuracy. Comparisons with predictions from recent models developed by other researchers are included. It is concluded that certain forms of the power function model are more stable (in terms of scale-up) than others. The paper also demonstrates how existing models can go unreliable or unstable under certain scale-up conditions and discusses possible causes of such problems

Theoretical Modelling of Rotary Valve Air Leakage for Pneumatic Conveying Systems

Rotary valve air leakage is an important parameter for the design and operation of many dilute- and dense-phase pneumatic conveying systems. Previous methods to estimate air leakage have been largely empirical and have been found inaccurate and/or limited in their use. This paper describes a new theoretical model that has been developed to estimate rotary valve (radial clearance) air leakage. Model predictions are compared with experimental data obtained on a rotating and stationary valve subjected to a wide range of operating pressures typical of dilute- and dense-phase systems. Knowing accurately the air leakage present for any given situation, the required total supplied air mass flow rate can be determined properly for the pneumatic conveying system, so that optimal transport velocities can be established

Evaluation of Belt Conveyor Trajectories

Since the early 1900s, numerical methods have been used to predict the trajectory of material discharged from a belt conveyor. These methods range from the very basic to complex iterative approaches. Some methods predict similar paths and others vary noticeably, however it is clear that they cannot all be correct. The discrete element method (DEM) is also becoming more widely accepted as a design tool, however, hesitation still exists in some quarters stemming from the lack of experimental validation available. A conveyor transfer research facility has been commissioned at the University of Wollongong to experimentally investigate particle flow mechanisms through a variety of conveyor transfers. As part of this research, preliminary investigations into conveyor trajectories have been undertaken at varying belt speeds and material flow rates using granular polyethylene pellets. This paper presents the trajectory results of an experimental test program and compares these findings with numerous numerical trajectory methods as well as DEM simulations in an attempt to validate the predictive approaches available to generate conveyor trajectories. Early findings suggest the method of Booth provided the most accurate prediction, while the DEM also compares favourably to the experimental results

The influence of perceived causation on judgments of time: an integrative review and implications for decision-making

Recent research has shown that the perception of causality affects the judgment of elapsed time: an interval between an action and a subsequent event seems to be shorter when people believe that action has caused the event. This article reviews past work on the phenomenon and integrates the findings from the different settings in which it has been observed. The effect is found for actions people have personally taken, as well as for those they have simply read or heard about. It occurs for very short intervals (e.g., milliseconds) as well as longer periods (e.g., months or years). Beliefs and expectations about different types of causal forces and their trajectories over time can affect the degree of time compression in some settings. But the tendency toward compression of time is the default and dominant response: It persists when people think of generic causal relations and is enhanced when people opt for the quickest interpretation of causal relations. This robust influence of causality on time judgment appears to be linked to the basic tendency to rely on temporal proximity in processing causal relations and to people's early experience with the physical-mechanical world. Past work has focused primarily on the implications of time compression for the sense of agency, but this phenomenon has implications also for decisions that depend on time judgment. The compression of subjective time elapsed between actions and outcomes makes people more optimistically plan the timing of a focal action in the future, experience its effect earlier in the future, and be less likely to switch to an alternative course of action. The tendency toward compression can thus endow an action with a sort of privileged status or advantage