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As the LED Light spectrum continues to evolve and researchers now better understand how lighting has a profound effect on sleep, alertness, performance and health, WalaLight implements cost-efficient, environmentally-friendly lighting solutions. In addition to cost savings on utilities, WalaLight can dramatically reduce the need for lighting maintenance and replacement"By using WalaLight, physical and mental well-being improves through optimal circadian rhythms," Zuker said. "We can also reset the biological clock for jet lag, as well as circumvent seasonal effect disorder, PTSD, ADHD and many other disorders."

Headquartered in Boca Raton, Florida, WalaLight is designed and manufactured in North America by a special division of uSaveLED, an industry leading supplier of commercial and industrial energy-efficient LED lighting products. WalaLight's Healthy Circadian Lighting provides clients across the nation with cost-efficient, environmentally-friendly, long-life, highly-certified lighting solutions designed to save them money on utility costs, while also dramatically reducing the need for lighting maintenance and replacement.

"We're able to provide the appropriate spectrum of lighting through our smart Kelvin changing technology. This, in turn, vastly improves behavior and performance," WalaLight Chief Technology Officer, Rodney Smith, said. "We focus on keeping people healthy instead of waiting for health problems to occur, by generating the right amount of light therapy."
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  Problem formulation and numerical solution Alerter l'administrateur Recommander à un ami Lien de l'article 


  Inside the waveguide, the electric field, E, and the magnetic field, H, are governed by the 3D Maxwell's equations,

  where μ, ε, and σ are the permeability, permittivity, and conductivity of the medium. Inside the coaxial cable, under the assumption that only the TEM mode is supported, the potential difference, V, and the current, I, satisfy the 1D transport equation23,

  where Zc and c are the characteristic impedance and the phase velocity inside the k-directed coaxial CCTV coaxial cable. The terms V???ZcI and V?+?ZcI represent signals traveling inside the coaxial cable in the negative and positive k-direction, respectively.

  We assume that both the coaxial cable and the waveguide extend to infinity (matched). Moreover, we assume that the only signal source is an incoming energy, Win,wg, associated with the TE10 mode, propagating inside the waveguide towards the negative z axis; see Fig. 1. The incoming energy through the coaxial cable, Win,coax, is assumed to be zero. Under the above assumptions, we can write the following energy balance for the cable–waveguide system,

  where the right side is the total outgoing energy that consists of the energy existing through the coaxial CCTV coaxial cable Wout,coax, the reflected energy in the waveguide Wout,wg, and the ohmic loss inside the domain Ω. Inspecting expression (4), we note that a natural design objective is to maximize the signal coupled to the coaxial cable (cable A or cable B), Wout,coax, which implicitly implies the minimization of the remaining two terms Wout,wg and . Therefore, given the incoming energy, Win,wg, we formulate the conceptual optimisation problem

  subject to the set of governing equations and boundary conditions.

  We numerically solve equations (1), (2), and (3) by the FDTD method30. Let σ be a vector that holds the conductivity components at each Yee edge inside the domain Ω. The goal is to find the σ that maximizes the outgoing energy through the coaxial CCTV coaxial cable, which we accomplish through a gradient-based optimisation method. Let p be a vector of the same dimension as σ storing the design variables that are actually updated by the optimisation algorithm; it holds that 0?≤?pi?≤?1 for each component of p. The design variables should interpolate between the conductivity values representing a good dielectric (pi?=?0) and a good conductor (pi?=?1). However, there is a vast variation in the conductivity value between a good dielectric and a good conductor. For example, the free space has σ?=?0?S/m and the copper has σ?=?5.8?×?107?S/m. The average of these values still represents a good conductor, so the use of a linear interpolation between these values would make the algorithm overly sensitive for small changes of almost vanishing design variables. We therefore use the following exponential interpolation scheme:

  which gives σmin?=?10?3?S/m and σmax?=?105?S/m for pi?=?0 and pi?=?1, respectively. Numerical experiments show a low sensitivity of the objective function to variations in σ outside the range [σmin, σmax], and the conductivity value for pi?=?1/2 now indeed represents a lossy material that is neither a good dielectric nor a good conductor.

  Formally, our optimisation problem reads.

  Aucun commentaire | Ecrire un nouveau commentaire Posté le 26-05-2017 à 10h17

 To relax the strong self-penalisation Alerter l'administrateur Recommander à un ami Lien de l'article 

where is the outgoing energy through the coaxial CCTV coaxial cable computed by the FDTD method, and N is the number of Yee edges inside the design domain Ω. The spectral density of the incoming energy, , will implicitly determine the frequencies for which the structure will be optimised. To address the wideband objective function in optimisation problem (7), we use a time-domain sinc signal to impose the incoming energy, , inside the waveguide. A sinc signal with infinite duration has a flat energy spectral density over a specific bounded frequency interval31. To realise a reasonable simulation time, we truncate the sinc signal after 8 lobes. The truncated sinc signal is modulated to the center of the frequency band of interest and its bandwidth is set to cover this frequency band. The objective function gradient is computed using the solution to an adjoint-field problem, which is also a FDTD discretization of Maxwell’s equations, but is fed with a time reversed version of the observed signal at the coaxial cable32. For any number of design variables, the gradient of the objective function can be computed with only two FDTD simulations, one to the original-field problem and one to the adjoint-field problem.

  Optimisation problem (7) is strongly self-penalised towards the lossless design cases. More precisely, solving problem (7) by gradient-based optimisation methods leads, after only a few iterations, to designs consisting mainly of a good conductor (σmax) or a good dielectric (σmin). The reason for the strong self-penalisation can be explained by energy balance (4) as follows. To maximize CCTV coaxial cable the outgoing energy, Wout,coax, for a given incoming energy, Win,wg, the energy losses, , inside the design domain should by minimized. The intermediate conductivities contribute to higher energy losses than the extreme conductivities, as pointed out in the introduction. Thus, any gradient-based optimisation method will attempt to minimize the energy losses, , by moving the edge conductivities towards the lossless cases (σmin and σmax). Unfortunately, the resulting optimised designs often consist of scattered metallic parts and exhibit bad performance24.

  To relax the strong self-penalisation, we use a filtering approach that imposes some intermediate conductivities inside the design domain during the initial phase of the optimisation. To do so, we replace pi by qi in expression (6), where the vector q?=?Kp, in which the filter matrix K is a discrete approximation of an integral operator with support over a disc with radius R. The filter replaces each component in the vector p by a CCTV coaxial cable weighted average of the neighbouring components, where the weights vary linearly from a maximum value at the center of the disc to zero at the perimeter. To avoid lossy final designs, we solve optimisation problem (7) through a series of subproblems, where after the solution of subproblem n, the filter radius is reduced by setting Rn+1?=?0.8?Rn. We start with a filter radius R1?=?40Δ, where Δ denotes the FDTD spatial discretization step. Each subproblem is iteratively solved until a stopping criterion for optimisation, based on the first-order necessary condition, is satisfied. To update the design variables, we use the globally convergent method of moving asymptotes (GCMMA)33.

 

  We investigate the design of transitions between a 50?Ohm coaxial CCTV coaxial cable (probe diameter 1.26?mm, outer shield diameter 4.44?mm) and and two standard waveguides; the WR90 (a?=?22.86?mm and b?=?10.16?mm) and the WR430 waveguides (a?=?109.22?mm and b?=?54.61?mm). The first cutoff frequency of the WR90 waveguide is f10?=?6.56?GHz and the second is f20?=?13.12?GHz, while the WR430 waveguide has f10?=?1.37?GHz and f20?=?2.75?GHz. The frequency band of interest in both cases is the band between the first and the second cutoff frequencies, where only the TE10 mode can propagate (below, we refer to this bandwidth as the bandwidth objective). These frequency bands correspond to a relative bandwidth of 66.7% for the WR90 waveguide and 67.0% for the WR430 waveguide. In our numerical experiments, we use uniform FDTD grids. For the WR90 waveguide we use a spatial step size Δ?=?0.127?mm, and for the WR430 waveguide Δ?=?0.607?mm. In both cases, a 16 cell perfectly matched layer (PML) is used to terminate the waveguide and 15 cells of free space separate the end of the design domain and the beginning of the PML. We use an in-house FDTD code implemented to run on graphics processing units (GPU) using the parallel computing platform CUDA (https://developer.nvidia.com/what-cuda). One solution to Maxwell’s equations takes around 5?minutes and around 4?GB of memory is required for computing the objective function gradient. The waveguide walls and the coaxial probe are assigned a conductivity value of σ?=?5.8?×?107?S/m.

 

  Aucun commentaire | Ecrire un nouveau commentaire Posté le 26-05-2017 à 10h19

 To relax the strong self-penalisation Alerter l'administrateur Recommander à un ami Lien de l'article 

where is the outgoing energy through the coaxial CCTV coaxial cable computed by the FDTD method, and N is the number of Yee edges inside the design domain Ω. The spectral density of the incoming energy, , will implicitly determine the frequencies for which the structure will be optimised. To address the wideband objective function in optimisation problem (7), we use a time-domain sinc signal to impose the incoming energy, , inside the waveguide. A sinc signal with infinite duration has a flat energy spectral density over a specific bounded frequency interval31. To realise a reasonable simulation time, we truncate the sinc signal after 8 lobes. The truncated sinc signal is modulated to the center of the frequency band of interest and its bandwidth is set to cover this frequency band. The objective function gradient is computed using the solution to an adjoint-field problem, which is also a FDTD discretization of Maxwell’s equations, but is fed with a time reversed version of the observed signal at the coaxial cable32. For any number of design variables, the gradient of the objective function can be computed with only two FDTD simulations, one to the original-field problem and one to the adjoint-field problem.

  Optimisation problem (7) is strongly self-penalised towards the lossless design cases. More precisely, solving problem (7) by gradient-based optimisation methods leads, after only a few iterations, to designs consisting mainly of a good conductor (σmax) or a good dielectric (σmin). The reason for the strong self-penalisation can be explained by energy balance (4) as follows. To maximize CCTV coaxial cable the outgoing energy, Wout,coax, for a given incoming energy, Win,wg, the energy losses, , inside the design domain should by minimized. The intermediate conductivities contribute to higher energy losses than the extreme conductivities, as pointed out in the introduction. Thus, any gradient-based optimisation method will attempt to minimize the energy losses, , by moving the edge conductivities towards the lossless cases (σmin and σmax). Unfortunately, the resulting optimised designs often consist of scattered metallic parts and exhibit bad performance24.

  To relax the strong self-penalisation, we use a filtering approach that imposes some intermediate conductivities inside the design domain during the initial phase of the optimisation. To do so, we replace pi by qi in expression (6), where the vector q?=?Kp, in which the filter matrix K is a discrete approximation of an integral operator with support over a disc with radius R. The filter replaces each component in the vector p by a CCTV coaxial cable weighted average of the neighbouring components, where the weights vary linearly from a maximum value at the center of the disc to zero at the perimeter. To avoid lossy final designs, we solve optimisation problem (7) through a series of subproblems, where after the solution of subproblem n, the filter radius is reduced by setting Rn+1?=?0.8?Rn. We start with a filter radius R1?=?40Δ, where Δ denotes the FDTD spatial discretization step. Each subproblem is iteratively solved until a stopping criterion for optimisation, based on the first-order necessary condition, is satisfied. To update the design variables, we use the globally convergent method of moving asymptotes (GCMMA)33.

 

  We investigate the design of transitions between a 50?Ohm coaxial CCTV coaxial cable (probe diameter 1.26?mm, outer shield diameter 4.44?mm) and and two standard waveguides; the WR90 (a?=?22.86?mm and b?=?10.16?mm) and the WR430 waveguides (a?=?109.22?mm and b?=?54.61?mm). The first cutoff frequency of the WR90 waveguide is f10?=?6.56?GHz and the second is f20?=?13.12?GHz, while the WR430 waveguide has f10?=?1.37?GHz and f20?=?2.75?GHz. The frequency band of interest in both cases is the band between the first and the second cutoff frequencies, where only the TE10 mode can propagate (below, we refer to this bandwidth as the bandwidth objective). These frequency bands correspond to a relative bandwidth of 66.7% for the WR90 waveguide and 67.0% for the WR430 waveguide. In our numerical experiments, we use uniform FDTD grids. For the WR90 waveguide we use a spatial step size Δ?=?0.127?mm, and for the WR430 waveguide Δ?=?0.607?mm. In both cases, a 16 cell perfectly matched layer (PML) is used to terminate the waveguide and 15 cells of free space separate the end of the design domain and the beginning of the PML. We use an in-house FDTD code implemented to run on graphics processing units (GPU) using the parallel computing platform CUDA (https://developer.nvidia.com/what-cuda). One solution to Maxwell’s equations takes around 5?minutes and around 4?GB of memory is required for computing the objective function gradient. The waveguide walls and the coaxial probe are assigned a conductivity value of σ?=?5.8?×?107?S/m.

 

  Aucun commentaire | Ecrire un nouveau commentaire Posté le 26-05-2017 à 10h20

 http://blog.51.ca/u-709670/2017/05/27/american-shuji-nakamura-shown-here-in-an-undated-photo/ Alerter l'administrateur Recommander à un ami Lien de l'article 

http://blog.51.ca/u-709670/2017/05/27/american-shuji-nakamura-shown-here-in-an-undated-photo/

  Aucun commentaire | Ecrire un nouveau commentaire Posté le 27-05-2017 à 07h25

 Physics For Development Of Blue LED Alerter l'administrateur Recommander à un ami Lien de l'article 

Things You Might Not Know About Charles Darwin
This Sunday, Feb. 12, is , an international day of celebration LED Canopy Light commemorating the birth of Charles Darwin and his contributions to science.   It's also an excuse for science- and evolution-themed  around the globe, and for all of us to take a moment to appreciate the value of science and the wonders of the natural world.   As you prepare to celebrate, here are a few things you might want to know about Darwin — some insights new and old to impress your friends and family.   1. Darwin developed the Theory of Evolution by Natural Selection. Studies consistently find that many Americans — including college students and even pre-service teachers —  critical features of how the process works. You can read through common misconceptions , or review the key ingredients for natural selection — heritable variation that leads to differential reproduction — in this easy  created for 13.7.   2. Darwin wasn't only a meticulous observer of the natural world, he was also a careful reader and a diligent record-keeper when it came to his own habits. Beginning in 1838, Darwin kept a notebook in which he recorded the books he was reading. From 1837 to 1860, he reported reading 687 distinct works of English non-fiction. These years span an important period in the development LED Canopy Light of his thinking, from his return to England from the Galapagos Islands to the publication of .  

  Aucun commentaire | Ecrire un nouveau commentaire Posté le 27-05-2017 à 07h26


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