Fast Prediction of Contrast Detection Probability

Contrast detection probability (CDP) is proposed as an IEEE P2020 metric to predict camera performance intended for computer vision tasks for autonomous vehicles. Its calculation involves comparing combinations of pixel values between imaged patches. Computation of CDP for all meaningful combinations of m patches involves approximately 3/2(m2-m).n4 operations, where n is the length of one side of the patch in pixels. This work presents a method to estimate Weber contrast based CDP based on individual patch statistics and thus reduces to computation to approximately 4n2m calculations. For 180 patches of 10×10 pixels this is a reduction of approximately 6500 times and for 180 25×25 pixel patches, approximately 41000. The absolute error in the estimated CDP is less than 0.04 or 5% where the noise is well described by Gaussian statistics. Results are compared for simulated patches between the full calculation and the fast estimate. Basing the estimate of CDP on individual patch statistics, rather than by a pixel-to-pixel comparison facilitates the prediction of CDP values from a physical model of exposure and camera conditions. This allows Weber CDP behavior to be investigated for a wide variety of conditions and leads to the discovery that, for the case where contrast is increased by decreasing the tone value of one patch and therefore increasing noise as contrast increases, there exists a maxima which yields identical Weber CDP values for patches of different nominal contrast. This means Weber CDP is predicting the same detection performance for patches of different contrast.

Design of Series-Fed Bandwidth-Enhanced Microstrip Antenna Array for Millimetre-Wave Beamforming Applications

A novel series-fed microstrip patch array antenna for 37/39 GHz beamforming is proposed. To improve the antenna bandwidth, two of the patches are modified with truncated corners in the diagonal direction. This truncation generates two degenerate resonances which result in a flattened frequency response of the input impedance. Then, the recessed microstrip feeds for the other two patches are designed to yield a proper current distribution for radiation while maintaining minimal return loss, wide bandwidth, and low sidelobes. Though the individual patch antenna is elliptically polarized due to the truncated corners, a phased array with linear polarization can still be obtained by alternately deploying left-handed and right-handed elliptically polarized patches. For validation of the proposed design, an array is fabricated with 16 elements on a substrate with 10 mil thickness and εr =2.2. The beamforming capability of the proposed array is also demonstrated. The experiment results agree well with the simulation and show that the antenna gain and the return loss bandwidth can be more than 21 dBi and 8%, respectively.

Expansion of Feral Cereal Rye (Secale cereale L.) on Non-crop Hillsides in Northern Utah

Feral cereal rye is an aggressive, persistent winter annual grass. Although feral rye has been documented as a weed in Utah cropland for many years, it has only recently been described as a weed of natural areas in Utah. After feral rye was observed on hillside locations where it had not previously been present, research was conducted to evaluate expansion rates in isolated patches and on a landscape scale. Individual patch measurements indicated expansion rates of 17%, 42%, 44%, and 112% in 2009. The landscape expansion rates were 1%, 4%, 8%, 21%, and 50% in the same year. The spread of feral rye appears to have occurred primarily on south- to west-facing slopes where the density and diversity of native species is limited. The expansion of feral rye into natural, undisturbed areas indicates that this species should be closely monitored. The relatively short seed longevity and current small infestations make it a good candidate for early detection/rapid response efforts.

Effects of vasopressin and cAMP on single amiloride-blockable Na channels

To determine the mechanism by which vasopressin increases sodium transport in sodium-transporting, tight epithelia, we examined single amiloride-blockable Na channels in membrane patches from cultured distal nephron cells (A6) either before or after treatment with arginine vasopressin. Pretreatment of cells with vasopressin (40 mU/ml) for 40-50 min increases NPo (N, the number of Na channels; Po, the open probability of an individual Na channel). The increase in NPo is due to an increase in the number of conductive Na channels with little or no change in the open probability of individual Na channels. Pretreatment of cells for 1 h with 1 mM N6,2'-O-dibutyryladenosine 3', 5'-cyclic monophosphate (DBcAMP) also increased NPo. The increase in NPo caused by DBcAMP pretreatment is also due to the increase in the number of conductive Na channels with no change in the open probability of individual Na channels. Cells pretreated with cholera toxin (CTX; 250 ng/ml) for 4 h appeared similar to cells that had been treated with vasopressin or DBcAMP; that is, the number of Na channels per patch increased with little or no effect on the open probability of individual Na channels. For patches from many untreated cells, when the frequency of occurrence is plotted against the number of channels in an individual patch, the histogram consists of a single peak with a number of channels per patch of 2.0 +/- 1.5 (+/- SD, 126 patches). After pretreatment of cells with vasopressin, DBcAMP, or CTX, the same histogram contains two peaks after vasopressin of 1.8 +/- 1.2 and 9.2 +/- 1.5 (+/- SD, 38 and 53 patches, respectively). These observations suggest that pretreatment of cells with vasopressin, DBcAMP, or CTX may act by promoting insertion of clusters of new sodium channels.

Effect of a baited trap on the foraging movements of juvenile western rock lobsters, Panulirus cygnus George

The influence of a commercial trap on the foraging movements of juvenile P. cygnus was determined by tracking animals to which electromagnetic tags had been attached. Catch rates were low. Tagged lobsters were caught on eight occasions; on 14 occasions, tagged lobsters visited the trap and stayed for several hours during the night, but left by morning. The greatest distance travelled by a lobster from down stream to the baited trap was 120 m. On 19 occasions lobsters upcurrent from the trap passed as close as 20 m without going to the trap, although other lobsters as far away as 75 m upcurrent visited the trap. Previous tracking records of individuals foraging upcurrent of the trap suggest that these lobsters' visits may have been due to the trap's location within their foraging range rather than to detection of the bait. Present trapping techniques used to estimate the densities of juvenile lobsters on individual patch reefs may be biased because lobsters on neighbouring reefs as far away as 120 m could be attracted to the baited trap. The present results also suggest that some lobsters may leave the traps before sunrise, and that traps set closer than 120 m apart may fish competitively for the same individuals.