Scramble Phase Research Articles

Quantitative phase and polarization imaging through an optical fiber applied to detection of early esophageal tumorigenesis.

.Phase and polarization of coherent light are highly perturbed by interaction with microstructural changes in premalignant tissue, holding promise for label-free detection of early tumors in endoscopically accessible tissues such as the gastrointestinal tract. Flexible optical multicore fiber (MCF) bundles used in conventional diagnostic endoscopy and endomicroscopy scramble phase and polarization, restricting clinicians instead to low-contrast amplitude-only imaging. We apply a transmission matrix characterization approach to produce full-field en-face images of amplitude, quantitative phase, and resolved polarimetric properties through an MCF. We first demonstrate imaging and quantification of biologically relevant amounts of optical scattering and birefringence in tissue-mimicking phantoms. We present an entropy metric that enables imaging of phase heterogeneity, indicative of disordered tissue microstructure associated with early tumors. Finally, we demonstrate that the spatial distribution of phase and polarization information enables label-free visualization of early tumors in esophageal mouse tissues, which are not identifiable using conventional amplitude-only information.

Full-field quantitative phase and polarisation-resolved imaging through an optical fibre bundle.

Flexible optical fibres, used in conventional medical endoscopy and industrial inspection, scramble phase and polarisation information, restricting users to amplitude-only imaging. Here, we exploit the near-diagonality of the multi-core fibre (MCF) transmission matrix in a parallelised fibre characterisation architecture, enabling accurate imaging of quantitative phase (error rad) and polarisation-resolved (errors %) properties. We first demonstrate accurate recovery of optical amplitude and phase in two polarisations through the MCF by measuring and inverting the transmission matrix, and then present a robust Bayesian inference approach to resolving 5 polarimetric properties of samples. Our method produces high-resolution (m amplitude, phase; m polarimetric) full-field images at working distances up to 1mm over a field-of-view up to 750×750μm2 using an MCF with potential for flexible operation. We demonstrate the potential of using quantitative phase for computational image focusing and polarisation-resolved properties in imaging birefringence.

Secure Communication Using Scramble Phase Assisting WFRFT

Secure Communication Using Scramble Phase Assisting WFRFT

Validation of an Agent-Based Microscopic Pedestrian Simulation Model at a Scramble Phase Signalized Intersection

Recently, an agent-based pedestrian simulation model was developed at the University of British Columbia to model detailed pedestrian interactions. The model was originally calibrated and validated with video data, collected at a signalized intersection in Vancouver. However, it is important to investigate the applicability of the model in different walking environments. The main objective of this study was to assess the model performance in handling pedestrian interactions at a scramble phase signalized intersection in Oakland, California. The intersection had four conventional crosswalks in addition to two diagonal crosswalks, used during the scramble pedestrian phase. Model parameters were calibrated with a genetic algorithm, which aimed to minimize the location and speed error between simulated and actual trajectories, extracted from the video sequence through computer vision. Validation results showed that the model was capable of reproducing pedestrian trajectories with high accuracy in regard to average location and speed error. The average location error for 271 pedestrians considered in the validation was 0.49 m, while the average speed error was 0.04 m/s. Detailed analysis of crossing speed for both conventional and diagonal crossings was presented, and the ability of the model to produce the same speed distributions observed in actual data was confirmed. Furthermore, the ability of the model to reproduce five interactions that were frequently observed in the data was assessed. Results showed that the model was capable of reproducing the actual behavior taken by pedestrians during these interactions with high accuracy, from 80% to 100%.

The use of gait parameters to evaluate pedestrian behavior at scramble phase signalized intersections

SummaryPedestrian scramble phasing is usually implemented to reduce pedestrian‐vehicle conflicts and therefore increase the safety of the intersection. However, to adequately determine the benefits of scramble phasing, it is necessary to understand how pedestrians react to such an unconventional design. This study investigates changes in pedestrian crossing behavior following the implementation of a scramble phase by examining the spatiotemporal gait parameters (step length and step frequency). This detailed microscopic‐level analysis provides insight into changes in pedestrian walking mechanisms as well as the effect of various pedestrian and intersection characteristics. The study uses video data collected at a scramble phase signalized intersection in Oakland, California. Gait parameters were found to be influenced by pedestrian gender, age, group size, crosswalk length, and pedestrian signal indications. Both average step length and walking speed were significantly higher for diagonally crossing pedestrians compared with pedestrians crossing on the conventional crosswalks. Pedestrians were found to have the tendency to increase their step length more than their step frequency to increase walking speed. It was also found that, compared with men, women generally increase their walking speed by increasing their step frequency more than step length. However, when in non‐compliance with signal indications, women increase their walking speed by increasing their step length more than step frequency. It was also found that older pedestrians do not significantly change their walking behavior when in non‐compliance with signal indications. Copyright © 2014 John Wiley & Sons, Ltd.

Automated Analysis of Pedestrian Crossing Speed Behavior at Scramble-phase Signalized Intersections Using Computer Vision Techniques

ABSTRACT This study investigates changes in pedestrian speed behavior following the implementation of a scramble phase. The aim is to demonstrate the feasibility of automatic collection of pedestrian data; and to study pedestrian speed variations with respect to design changes to intersection crossings. The results show that the average crossing speed is higher after the implementation of the scramble phase. Within the scramble, the average crossing speed is higher for diagonal crossing than side crosswalk crossing. The average crossing speed is lower for pedestrians crossing during the Walk interval. Pedestrians have higher speed through the first half of the crosswalk.

Use of Genetic Algorithm for Phase Optimization at Intersections with Minimization of Vehicle and Pedestrian Delays

The two objectives of this research were to develop a methodology to optimize signal timing at intersections by minimization of delay for both vehicles and pedestrians and to establish guidance for the selection of the pedestrian crossing phase (two-way or scramble) and the length of the “Walk” phase when the scramble crossing pattern was used. An optimization procedure for signal plans was developed for an isolated intersection. The procedure can provide up to four vehicular phases with either the two-way or scramble pedestrian crossing phase. Genetic algorithms were used to find suitable signal plans because of the existence of a large solution set. Furthermore, the proposed genetic algorithm procedure can generate contour diagrams as selection guides to determine appropriate pedestrian crossing phases at an intersection with different combinations of vehicle volumes and pedestrian volumes. The impacts of relative time values, initial vehicle queues, and geometric designs on the pedestrian phase selection were also determined. According to the contour diagrams, to determine appropriate pedestrian crossing phases, not only do pedestrian volumes and right-turning vehicle volumes need to be taken into account but also through (and left-turning) vehicle volumes should be considered. The scramble crossing reduced delay when the conflicting pedestrian and right-turning vehicle volumes in approaches were high and the through (and left-turning) vehicle volumes in the same approaches were relatively lower. Otherwise, the scramble phase increased delay.

Automated Analysis of Pedestrian–Vehicle Conflicts

This paper presents a novel application of automated video analysis for a before-and-after (BA) safety evaluation of a scramble phase treatment. Data availability has been a common challenge to pedestrian studies, especially for proactive safety analysis. The traditional reliance on collision data has many shortcomings because of the quality and quantity of collision records. Qualitative and quantitative issues with road collision data are more pronounced in pedestrian safety studies. In addition, little information on the mechanism of action implicated can be drawn from collision reports. Traffic conflict techniques have been advocated as supplements or alternatives to collision-based safety analysis. Automated conflict analysis has been advocated as a new safety analysis paradigm that empowers the drawbacks of survey-based and observer-based traffic conflict analysis. One of the areas of focus of pedestrian safety that could greatly benefit from vision-based road user tracking is BA evaluation of safety treatments. This paper demonstrates the feasibility of conducting a BA analysis with video data collected from a commercial-grade camera in Chinatown, Oakland, California. Video sequences for a period of 2 h before and 2 h after scramble were automatically analyzed. The BA results of the automated analysis exhibit a declining pattern of conflict frequency, a reduction in the spatial density of conflicts, and a shift in the spatial distribution of conflicts farther from crosswalks.

Pattern of Self‐Thinning in Jack Pine: Testing the Random Mortality Hypothesis

Spatial statistics were used to examine the pattern of self—thinning in a 0.25—ha even—aged (65 yr old), pure stand of jack pine in the boreal forest near Elk Lake, Ontario, Canada. The positions of 459 living and 916 dead trees were recorded and refined nearest neighbor analysis [G(W)] and second—order spatial statistics [L(t)] were used to examine distributional deviations from both the Poisson expectation and the hypothesis of random mortality. The results indicate that the initial (live + dead, n = 1375) distribution was locally random. By contrast, the distribution of live trees was locally highly regular, while the dead trees were significantly more clumped than random mortality would dictate. It is suggested that the development of a strong regular pattern in the survivors is attributable to differential mortality involving two distinct competitive phases: an early scramble phase involving two—sided competition for soil resources, and a lager contest phase involving one—sided competition for light. Analysis of L(t) for the live trees indicated a mean "area of influence" for each individual of an °3.5 m radius, suggesting that trees may compete directly only with their immediate neighbor.