Red | EPFL Graph Search

Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary color (made from magenta and yellow) in the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy. Red pigment made from ochre was one of the first colors used in prehistoric art. The Ancient Egyptians and Mayans colored their faces red in ceremonies; Roman generals had their bodies colored red to celebrate victories. It was also an important color in China, where it was used to color early pottery and later the gates and walls of palaces. In the Renaissance, the brilliant red costumes for the nobility and wealthy wer

Determining The Potential Of Salinity Gradient Energy Source Using An Exergy Analysis

Arash Emdadi

Mixing of fresh (river) water and salty water (seawater or saline brine) in a control fashion would produces an electrical energy known as salinity gradient energy (SGE). Two main conversion technologies of SGE are membrane-based processes; pressure retarded osmosis (PRO) and reverse electrodialysis (RED). In PRO, semipermeable membranes placed between the two streams of solutions allow the transport of water from low-pressure diluted solution to high-pressure concentrated solution. RED requires two alternating semipermeable membranes that allow the diffusion of the ions but not the flow of H2O. Lifetime and power density of the semipermeable membrane are two main factors affecting on deployment of PRO and RED. Semipermeable membranes with lifetime greater than 10 years and power density higher than 5 W/m(2) would lead to faster development of this conversion technology. An exergy analysis of an SGE system of sea-river can be applied to calculate the maximum potential power for electricity generation. Seawater is taken as reference environment (global dead state) for calculating the exergy of water since the seawater is the final reservoir. Once the fresh water is mixed with water of the sea or lake it becomes unuseful for human, agricultural or industrial uses loses all its exergy. Aqueous sodium chloride solution model is used in this study to calculate the thermodynamic properties of seawater. This model does not consider seawater as an ideal model and provides accurate thermodynamics properties of sodium chloride solution. As a case study, exergy calculation of Iran's Urmia Lake- GadarChay River system. The chemical exergy analysis considers sodium chloride (NaCl) as main salt in the water of Lake Urmia. The sodium chloride concentration is more than 200 g/L in recent years. Based on the exergy results the potential power of this system is 329 MW. This results indicates a high potential for constructing power plant for salinity gradient energy conversion.

Amer Soc Mechanical Engineers2016

Spectral cola or how to turn green laser light red

Csaba Forro, Thibaud Humair, Xavier François Mettan

A green laser pointer shone through a glass of cola will appear red when looking from above the glass. Lowering the laser so that it is deeper in the cola, the colour will vary from orange to deep red. Fluorescence and absorption spectra were recorded consistent with the reddening of the laser. The depth dependence of the colour of the immersed laser is attributed to a more significant absorption of the short wavelengths by the cola, making the laser look redder as it is lowered deeper into the cola. To confirm this hypothesis, we simulated the fluorescence spectrum we would get at various depths by applying the Lambert law on our measured fluorescence spectrum. These spectra were then converted into red, green and blue (RGB) values. These values were compared to those measured on images of the immersed laser beam at corresponding depths.

Iop Publishing Ltd2014

Fair colorful k-center clustering

Xinrui Jia, Ola Nils Anders Svensson

An instance of colorful k-center consists of points in a metric space that are colored red or blue, along with an integer k and a coverage requirement for each color. The goal is to find the smallest radius rho such that there exist balls of radius rho around k of the points that meet the coverage requirements. The motivation behind this problem is twofold. First, from fairness considerations: each color/group should receive a similar service guarantee, and second, from the algorithmic challenges it poses: this problem combines the difficulties of clustering along with the subset-sum problem. In particular, we show that this combination results in strong integrality gap lower bounds for several natural linear programming relaxations. Our main result is an efficient approximation algorithm that overcomes these difficulties to achieve an approximation guarantee of 3, nearly matching the tight approximation guarantee of 2 for the classical k-center problem which this problem generalizes. algorithms either opened more than k centers or only worked in the special case when the input points are in the plane.

SPRINGER HEIDELBERG2021

Determining The Potential Of Salinity Gradient Energy Source Using An Exergy Analysis

Arash Emdadi

Amer Soc Mechanical Engineers2016