Sultan Daud Khan

Generation of Multiple Fano Resonances in Plasmonic Split Nanoring Dimer

We present a computational study of the plasmonic response of a split nanoring dimer resonator which supports multiple plasmonic Fano-like resonances that arises by the coupling and interference of the dimer plasmon modes. For the generation of Fano resonances with large modulation depths, numerous configurations of the dimer resonator are analyzed which are observed to be highly dependent on the polarization of incident light. Moreover, the influence of dimension of the split nanoring structure on the spectral positions and intensities of the higher order Fano resonances are also investigated, and it is found that the asymmetric Fano line shapes can be flexibly tuned in the spectrum by varying various geometrical parameters. Such Fano resonators are also discovered to offer high values of figure of merit and contrast ratio due to which they are suitable for high-performance biological sensors.

Excitation of Multiple Fano-Like Resonances Induced by Higher Order Plasmon modes in Three-Layered Bimetallic Nanoshell Dimer

The presence of plasmonic Fano-like resonances in the optical response of isolated and dimer metal-dielectric-metal nanostructures are investigated theoretically. The nanostructures are engineered in such a way to support multiple Fano-like resonances that are induced by the interference of bright and dark plasmon modes. It is found that the dimer resonators exhibit different types of Fano resonances for both the transverse and longitudinal polarizations unlike conventional nanodimers. Several configurations of the dimer Fano resonator are analyzed with special emphasis on the Fano spectral line shape. Breaking the symmetry of the dimer nanostructure in various directions control the asymmetric line shape and provides different kinds of unique Fano resonances. In certain cases, the Fano resonators exhibit multiple Fano resonances that are particularly significant for plasmon line shaping and can serve as platforms for multi-wavelength sensing applications.

Twin Dipole Fano Resonances in Symmetric Three-Layered Plasmonic Nanocylinder

A unique metal-dielectric structure composed of symmetric multilayered nanocylinder is demonstrated to support unconventional superradiant and subradiant plasmon modes. Here, the twin distinctive dipole-dipole Fano resonances are observed in the structure within the visible spectrum by carefully selecting the geometrical parameters. The spectral features of these Fano resonances are controlled by changing the incident field polarization and parameters of the nanoparticle. Eventually, an RLC circuit model is proposed to reproduce the optical response of the nanostructure.

Analyzing crowd behavior in naturalistic conditions

Pedestrians, in videos taken from fixed cameras, tend to appear and disappear at precise locations such as doors, gateways or edges of the scene: we refer to locations where pedestrians appear as sources (potential origins) and the locations where they disappear as sinks (potential destinations). The detection of these points and the characterization of the flows connecting them represent a typical preliminary step in most pedestrian studies and it can be supported by computer vision approaches. In this paper we propose an algorithm in which a scene is overlaid by a grid of particles initializing a dynamical system defined by optical flow, a high level global motion information. Time integration of the dynamical system produces short particle trajectories (tracklets), representing dense but short motion patterns in segments of the scene; tracklets are then extended into longer tracks that are grouped using an unsupervised clustering algorithm, where the similarity is measured by the Longest Common Subsequence. The analysis of these clusters supports the identification of sources and sinks related to a single video segment. Local segment information is finally combined to achieve a global set of traces identifying sources and sinks, and characterizing the flow of pedestrians connecting them. The paper presents the defined technique and it discusses its application in a real-world scenario.

Detection of Social Groups in Pedestrian Crowds Using Computer Vision

We present a novel approach for automatic detection of social groups of pedestrians in crowds. Instead of computing pairwise similarity between pedestrian trajectories, followed by clustering of similar pedestrian trajectories into groups, we cluster pedestrians into a groups by considering only start source and stop sink locations of their trajectories. The paper presents the proposed approach and its evaluation using different datasets: experimental results demonstrate its effectiveness achieving significant accuracy both under dichotomous and trichotomous coding schemes. Experimental results also show that our approach is less computationally expensive than the current state-of-the-art methods.

Facing Needs and Requirements of Crowd Modelling: Towards a Dedicated Computer Vision Toolset

The modelling and simulation of pedestrians and crowd dynamics require empirical evidences and quantitative data describing the relevant phenomena that models must be able to reproduce. Computer vision can provide several tools both to semi-automatically acquire the demand of a given situation and actually configure a simulation model, as well as to gather information for the sake of model calibration and validation. This paper proposes methods supporting the segmentation and pedestrian counting of crowd flows, the identification and characterisation of main flows in an analysed scene and the detection of social groups in an observed population. The methods are briefly introduced and the achieved results are presented and discussed with reference to the current state of the art.

Estimating Speeds of Pedestrians in Real-World Using Computer Vision

This paper proposes a novel approach to a computer vision based automatic system for the estimation of pedestrian velocity in real world traffic systems in which a fixed camera is available. The paper will introduce the adopted framework, which includes a preprocessing phase, an identification and tracking phase, and a speed estimation final phase. Speed estimation, implying a conversion from image to real world coordinates, can be carried out with two different techniques that will be discussed in details and evaluated with reference to achieved results.