Philips

About: Philips is a company organization based out in Vantaa, Finland. It is known for research contribution in the topics: Signal & Layer (electronics). The organization has 68260 authors who have published 99663 publications receiving 1882329 citations. The organization is also known as: Koninklijke Philips Electronics N.V. & Royal Philips Electronics.

Duality and Biorthogonality for Weyl-Heisenberg Frames

Abstract: Let $a>0, b>0, ab<1;$ and let $g\in L^2({\Bbb R}).$ In this paper we investigate the relation between the frame operator $S:f\in L^2({\Bbb R})\rightarrow \sum_{n,m}\,(f,g_{na,mb})\,g_{na,mb}$ and the matrix $H$ whose entries $H_{k,l\,;\,k',l'}$ are given by $(g_{k'/b,l'/a},g_{k/b,l/a})$ for $k,l,k',l'\in{\Bbb Z}.$ Here $f_{x,y}(t)={\rm exp}(2\pi iyt)\,f(t-x),$ $t\in{\Bbb R}$ , for any $f\in L^2({\Bbb R}).$ We show that $S$ is bounded as a mapping of $L^2({\Bbb R})$ into $L^2({\Bbb R})$ if and only if $H$ is bounded as a mapping of $l^2({\Bbb Z}^2)$ into $l^2({\Bbb Z}^2).$ Also we show that $AI\leq S\leq BI$ if and only if $AI\leq\frac{1}{ab}\,H\leq BI,$ where $I$ denotes the identity operator of $L^2({\Bbb R})$ and $l^2({\Bbb Z}^2),$ respectively, and $A\geq 0,$ $B<\infty.$ Next, when $g$ generates a frame, we have that $(g_{k/b,l/a})_{k,l}$ has an upper frame bound, and the minimal dual function $^{\circ}\gamma$ can be computed as $ab\,\sum_{k,l}\,(H^{-1})_{k,l\,;\,o,o}\,g_{k/b,l/a}.$ The results of this paper extend, generalize, and rigourize results of Wexler and Raz and of Qian, D. Chen, K. Chen, and Li on the computation of dual functions for finite, discrete-time Gabor expansions to the infinite, continuous-time case. Furthermore, we present a framework in which one can show that certain smoothness and decay properties of a $g$ generating a frame are inherited by $^{\circ}\gamma.$ In particular, we show that $^{\circ}\gamma\in{\cal S}$ when $g\in{\cal S}$ generates a frame $({\cal S}$ Schwartz space). The proofs of the main results of this paper rely heavily on a technique introduced by Tolimieri and Orr for relating frame bound questions on complementary lattices by means of the Poisson summation formula.

Large amplitude light-induced motion in high elastic modulus polymer actuators

Abstract: Well-defined gradients in molecular alignment have been used as tools to generate large amplitude, light-induced deformations in stiff polymer networks. These systems are reversible, monolithic and based on a simple one-step self-assembly process. To fabricate the actuators, diacrylate dopants containing azobenzene moieties were blended with liquid crystalline diacrylate hosts and photopolymerized in a twisted configuration. The resulting twisted networks were heavily crosslinked with room temperature elastic moduli on the order of 1 GPa. Regardless of the temperature with respect to the glass transitions, subsequent exposure to UV radiation induced anisotropic expansion/contraction, and simple variations in geometry were used to generate uniaxial bending or helical coiling deformation modes. Because mechanical energy is directly related to elastic modulus, these systems are expected to provide significantly greater work output than contemporary polymer actuator materials.

Europium (III) in oxide glasses: Dependence of the emission spectrum upon glass composition

Abstract: Several Eu3+-doped silicate, germanate, borate and phosphate glasses have been investigated in order to study the dependence of the Eu3+ emission spectrum upon the host composition. In these glasses, variations in the Eu3+ emission spectrum are considered to be restricted to differences in the intensities of the 5 D 0 → 7 F 2 and 5 D 0 → 7 F 4 , bands, which depend on the Judd-Ofelt parameters Ω 2 and Ω 4 respectively. In germanate glasses, the network-former ions (exchanging Ge by Si), the modifier ions and the modifier concentration have been varied. Evaluation of the Eu3+ emission in these glasses reveals that the 5 D 0 → 7 F 2 intensity ( Ω 2 ) depends on short-range effects such as the covalency of the Eu3+ ligands and structural changes in the vicinity of the Eu3+ ion. The 5 D 0 → 7 F 4 intensity ( Ω 4 ) seems to depend mainly on long-range effects (related to bulk properties of the glass). Studies of (99 1 2 − x) B 2 O 3 ·x Li 2 O · 1 2 Eu 2 O 3 glasses reveal a rather large difference in Ω 2 when the network former units change from tetrahedral BO4 units to BO3 triangles. For phosphate glasses hardly any trends are observed between the Eu3+ emission bands and the glass composition. This is ascribed to the structural differences between phosphate glasses and other oxide glasses.

Coherent Optical Generation and Inspection of Two-dimensional Periodic Structures

Abstract: Three spatial filtering projects using periodic structures are presented. The aim of the first two methods is to produce from one object (or from a few identical objects, side by side) many identical images, side by side. In the third project irregularities of periodic objects are detected.

Improved motion robustness of remote-PPG by using the blood volume pulse signature

Abstract: Remote photoplethysmography (rPPG) enables contact-free monitoring of the blood volume pulse using a color camera. Essentially, it detects the minute optical absorption changes caused by blood volume variations in the skin. In this paper, we show that the different absorption spectra of arterial blood and bloodless skin cause the variations to occur along a very specific vector in a normalized RGB-space. The exact vector can be determined for a given light spectrum and for given transfer characteristics of the optical filters in the camera. We show that this 'signature' can be used to design an rPPG algorithm with a much better motion robustness than the recent methods based on blind source separation, and even better than the chrominance-based methods we published earlier. Using six videos recorded in a gym, with four subjects exercising on a range of fitness devices, we confirm the superior motion robustness of our newly proposed rPPG methods. A simple peak detector in the frequency domain returns the correct pulse-rate for 68% of total measurements compared to 60% for the best previous method, while the SNR of the pulse-signal improves from − 5 dB to − 4 dB. For a large population of 117 stationary subjects we prove that the accuracy is comparable to the best previous method, although the SNR of the pulse-signal drops from + 8.4 dB to + 7.6 dB. We expect the improved motion robustness to significantly widen the application scope of the rPPG-technique.