There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Data Mining - Concepts and Techniques.

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Modal solutions of planar photonic crystal waveguides with rectangular air-holes are presented by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, power confinements, modal hybridness, beat lengths and group velocity dispersions are shown for the fundamental and higher order modes of the quasi-TE and TM polarizations.

Finite element modal solutions of planar photonic crystal fibers with rectangular air-holes

Using numerically simulated results, it is shown that an efficient laser-to-fiber coupling is possible by incorporating a uniform spot-size converter (SSC) with two nonidentical but phase matched optical waveguides. Using a "diluted" waveguide with a low index contrast, the power coupling loss can be significantly reduced from 10.4 dB to only 1.15 dB and at the same time 1.0 dB alignment tolerances can also be improved to achieve /spl plusmn/1.8 /spl mu/m. Besides the improved coupling, the beam divergence of the far-field is also reduced considerably to 9/spl deg/, accompanied by a significant lowering of the reflected power from the fiber interface.

Spot-size conversion using uniform waveguide sections for efficient laser-fiber coupling

In this paper, the optical properties of silica nanowires in a Mach-Zehnder-based optical sensor for detecting biomaterial specimens have been studied using the full vectorial H-field formulation of the finite element method. The variation of the propagation constant, the power fraction in the composite nanowires with the variation of the nanowire size and the specimen refractive index, temperature, and wavelength are also presented.

/pdf/characterization-of-silica-nanowires-for-optical-sensing-2xdszv42ik.pdf

Characterization of Silica Nanowires for Optical Sensing

Remote monitoring is fundamental in eHealth and introducing mobile devices in the remote monitoring process can provide additional benefits to both patients and medical personnel. For mobile remote monitoring systems to be successful, however, the authentication process must be in place to prevent the misuse of the system. In this paper we analyse the use of timestamps in the authentication process, showing many advantages timestamps have over other authentication methods. The paper presents the design principles for timestamp based authentication protocols in remote monitoring systems and proposes a specific protocol to implement such a system.

/pdf/timestamp-authentication-protocol-for-remote-monitoring-in-504hlvcs6d.pdf

Timestamp authentication protocol for remote monitoring in eHealth

Face and touch modalities have independently been shown to yield promising results for continuous user authentication. In this study, we present a novel framework that combines these modalities. We show a stacked classifier approach can be used to improve the continuous authentication on mobile devices and address some prevalent issues with the current state-of-the-art. We use a state-of-the-art public dataset containing face and touch-gesture modalities for 50 users. Features are extracted from each modality for each user. We train a set of classifiers for user modalities to provide probability scores on a sample. The scores capture the nuances of each sample and are concatenated into a vector. This vector is used in a meta-level classifier. The scores we obtain from the meta-level classifiers show our approach performs better than previous continuous authentication approaches. We achieve an equal error rate of 3.77% for a single sample. We also show the added robustness a multi-modal approach provides if one modality is compromised.

Muttukrishnan Rajarajan

Papers

Finite element modal solutions of planar photonic crystal fibers with rectangular air-holes

Spot-size conversion using uniform waveguide sections for efficient laser-fiber coupling

Characterization of Silica Nanowires for Optical Sensing

Timestamp authentication protocol for remote monitoring in eHealth

A continuous user authentication scheme for mobile devices