This paper presents a polynomial dimensional decomposition (PDD) method for global sensitivity analysis of stochastic systems subject to independent random input following arbitrary probability distributions. The method involves Fourier-polynomial expansions of lower-variate component functions of a stochastic response by measure-consistent orthonormal polynomial bases, analytical formulae for calculating the global sensitivity indices in terms of the expansion coefficients, and dimension-reduction integration for estimating the expansion coefficients. Due to identical dimensional structures of PDD and analysis-of-variance decomposition, the proposed method facilitates simple and direct calculation of the global sensitivity indices. Numerical results of the global sensitivity indices computed for smooth systems reveal significantly higher convergence rates of the PDD approximation than those from existing methods, including polynomial chaos expansion, random balance design, state-dependent parameter, improved Sobol’s method, and sampling-based methods. However, for non-smooth functions, the convergence properties of the PDD solution deteriorate to a great extent, warranting further improvements. The computational complexity of the PDD method is polynomial, as opposed to exponential, thereby alleviating the curse of dimensionality to some extent. Mathematical modeling of complex systems often requires sensitivity analysis to determine how an output variable of interest is influenced by individual or subsets of input variables. A traditional local sensitivity analysis entails gradients or derivatives, often invoked in design optimization, describing changes in the model response due to the local variation of input. Depending on the model output, obtaining gradients or derivatives, if they exist, can be simple or difficult. In contrast, a global sensitivity analysis (GSA), increasingly becoming mainstream, characterizes how the global variation of input, due to its uncertainty, impacts the overall uncertain behavior of the model. In other words, GSA constitutes the study of how the output uncertainty from a mathematical model is divvied up, qualitatively or quantitatively, to distinct sources of input variation in the model [1].

Reliability Engineering and System Safety

By doping an organic compound functioning as an electron donor (hereinafter referred to as donor molecules) into an organic compound layer contacting a cathode, donor levels can be formed between respective LUMO (lowest unoccupied molecular orbital) levels between the cathode and the organic compound layer, and therefore electrons can be injected from the cathode, and transmission of the injected electrons can be performed with good efficiency. Further, there are no problems such as excessive energy loss, deterioration of the organic compound layer itself, and the like accompanying electron movement, and therefore an increase in the electron injecting characteristics and a decrease in the driver voltage can both be achieved without depending on the work function of the cathode material.

Light Emitting Device

This paper considers improving the confidentiality of visible light communication (VLC) links within the framework of physical-layer security. We study a VLC scenario with one transmitter, one legitimate receiver, and one eavesdropper. The transmitter has multiple light sources, while the legitimate and unauthorized receivers have a single photodetector, each. We characterize secrecy rates achievable via transmit beamforming over the multiple-input, single-output (MISO) VLC wiretap channel. For VLC systems, intensity modulation (IM) via light-emitting diodes (LEDs) is the most practical transmission scheme. Because of the limited dynamic range of typical LEDs, the modulating signal must satisfy certain amplitude constraints. Hence, we begin with deriving lower and upper bounds on the secrecy capacity of the scalar Gaussian wiretap channel subject to amplitude constraints. Then, we utilize beamforming to obtain a closed-form secrecy rate expression for the MISO wiretap channel. Finally, we propose a robust beamforming scheme to consider the scenario wherein information about the eavesdropper's channel is imperfect due to location uncertainty. A typical application of the proposed scheme is to secure the communication link when the eavesdropper is expected to exist within a specified area. The performance is measured in terms of the worst-case secrecy rate guaranteed under all admissible realizations of the eavesdropper's channel.

Physical-Layer Security for MISO Visible Light Communication Channels

Color-shift keying (CSK) is a visible light communication intensity modulation scheme, outlined in IEEE 802.15.7, that transmits data imperceptibly through the variation of the color emitted by red, green, and blue light emitting diodes. An advantage of CSK is that the power envelope of the transmitted signal is fixed; therefore, CSK reduces the potential for human health complications related to fluctuations in light intensity. In this work, a rigorous design framework for high order CSK constellations is presented. A key benefit of the frame work is that it optimizes constellations while accounting for crosstalk between the color communication channels. In addition, and unlike previous approaches, the method is capable of optimizing 3-D constellations. Furthermore, a prototype CSK communication system is presented to validate the performance of the optimized constellations, which provide gains of 1–3 dB over standard 805.15.7 constellations.

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Design and Implementation of Color-Shift Keying for Visible Light Communications

LED light bulbs include openings in base or cover portions, and optional forced flow elements, for convective cooling. Thermally conductive optically transmissive material may be used for cooling, optionally including fins. A LED light engine may be fabricated from a substrate via planar fabrication techniques and shaped to form a substantially rigid upright support structure. Mechanical, electrical, and thermal connections may be made between a LED light engine and a LED light bulb.

Led light bulbs

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Practical Lighting Design with LEDs

A method for preferential scattering of certain wavelengths of light and/or dispersing light in an LED or LED bulb. The method includes emitting light from at least one LED die, and scattering the light from the at least one LED die by dispersing a plurality of particles having a size a fraction of at least one dominant wavelength of the light from the at least one LED die in the LED outer shell or in an LED bulb or in an at least one shell of an LED bulb. Alternatively, the method includes emitting light from the at least one LED die, and dispersing the light from the at least one LED die by distributing a plurality of particles having a size one to a few times larger than a dominant wavelength of the light from the LED in an outer shell, or body of the LED bulb.

Method of light dispersion and preferential scattering of certain wavelengths of light for light-emitting diodes and bulbs constructed therefrom

An LED bulb (10) having a bulb-shaped shell (30), a thermally conductive plastic material (60) within the bulb-shaped shell, and at least one LED (50) within the bulb-shaped shell. The bulb also includes a base (20), wherein the base is dimensioned to be received within a standard electrical socket.

Plastic LED bulb

An LED bulb having bulb-shaped shell and thermally conductive fluid or gel within the shell. The bulb includes at least one LED within the shell. The bulb includes at least one LED within the shell and a base. The base can be configured to fit within an electrical socket and can include a series of screw threads and a base pin, wherein the screw threads and base pin are dimensioned to be received within a standard electrical socket. Alternatively, the base can be configured to fit within a suitable electric socket.

Carol Lenk

Papers

Practical Lighting Design with LEDs

Method of light dispersion and preferential scattering of certain wavelengths of light for light-emitting diodes and bulbs constructed therefrom

Plastic LED bulb

Heat removal design for led bulbs

Practical Lighting Design With LEDs: Lenk/Practical Lighting Design