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[en] Visible light communication (VLC) uses an intensity-modulation and direct-detection scheme to transmit data. The light source utilized in VLC structures is constantly switched on and off rapidly, resulting in flickering. Furthermore, most of illumination systems exclude dimming support to permit customers to dim the light source to the desired stage. Therefore, the modulation scheme for information transmission in VLC should consist of flicker mitigation and dimming manage abilities. Double inverse pulse position modulation (DIPPM), sub-carrier pulse position modulation (SC-L-PPM), and M-ary variable pulse position modulation (M-VPPM) are recommended for minimizing the flicker issues and supporting an excessive degree of dimming for VLC systems. In this paper, a comparison is introduced between DIPPM, SC-L-PPM, and M-VPPM according to error performance and bit rate. In addition, a simulation is carried out to measure the optical power distribution for a LED lamp in an indoor room topology for each modulation technique. The obtained results indicated that SC-L-PPM is the best choice regarding the bit error rate (BER) and optical power distribution compared to the other two schemes. A 10−6 BER is achieved with a very low power requirement at L = 8, while a remarkable power distribution of 1.5–6.5 dBm is observed from 3 × 5 × 5 m3 room corners to the center, respectively. According to the bit rate, it is noticed that, M-VPPM is the most efficient one compared to the two other schemes. It achieves 2.3 × 107 bps at a signal to noise ratio (SNR) of 22 dB and M = 8.
[en] Dye penetrant testing and magnetic particle testing are among conventional NDT methods. For increased sensitivity, fluorescence dyes and particles can be used with ultraviolet (black) lights. UV flaw detection lights have different spectra. With the help of photo-filters, the output lights are transferred to UV-A and visible zones. UV-A light can be harmful to human eyes in some conditions. In this research, UV intensity and spectrum were obtained by a Radio-spectrometer for two different UV flaw detector lighting systems. According to the standards such as ASTM E709, UV intensity must be at least 10 W/m2 at a distance of 30 cm. Based on our measurements; these features not achieved in some lamps. On the other hand, intensity and effective intensity of UV lights must be below the some limits for prevention of unprotected eye damage. NDT centers are usually using some type of UV measuring devices. A method for the estimation of effective intensity of UV light has been proposed in this research.
[en] Full text: Two new salicylidene derivatives (Salicylidene-4,6-dimethylaminopyridine, KM1, and Salicylidene-5-bromo-4,6-dimethylaminopyridine, KM2) reactive to Excited State Intramolecular Proton Transfer (ESIPT) were synthesized as a strategy to produce white light emitters. These molecules were characterized by 1H and 13C NMR, IR, MS, and single crystal X-ray diffraction. Their photophysical properties were explored in terms of steady-state and time-resolved electronic spectroscopies in different organic solvents, which induces or disrupt intramolecular hydrogen bond formation, hence, the phototautomeric balance. The experiments, it was possible to observe how the insertion of a bromine atom affected the structure of the salicylidene causing a red-shift in the absorption band. The emission spectra in solution of both compounds have a predominance of enol emission at λem = 420 nm. Time-Correlated Single Photon Counting (TCSPC) technique allowed the obtention of KM1 and KM2 fluorescence lifetimes as 0.3 ns to their enolic forms, and 1.2 ns for their phototautomeric forms in THF solutions). In the solid state, the emission spectra favored the tautomers emissions as a consequence of crystal packing. Due to the emission spectra in solution and solid-state, we combined the molecules with the semiconductor polymer poly (9-vinylcarbazole) (PVK) for the characterization of the electroluminescence spectra in host-guest systems as active layers of all-solution processed OLEDs. Because of the complex deactivation processes evolved, white light was produced. Different molar ratios between polymer host and each salicylidene guests were used to avoid the aggregation and balance both species electron emission. The best device of KM2 with 0.3% mol mol-1, produced a chromaticity of (0.32, 0.27) according to the Commission Internationale de L’Eclairage (CIE) 1931 scale, is slightly violet. The same device using KM1 with the same molar ratio reached (0.33, 0.34), what is considered a pure white. (author)
[en] Artificial light is a tangible manifestation of economic and social development, as well as a response to certain needs, especially comfort and civil and road safety. However, this use has been so associated with technological progress that its invasion of daily life has been almost imperceptible. With the recent increase in night lighting (11 million light points in 2016 according to the French Agency for the Environment and Energy Management) and the production of new lamp technologies (in particular light-emitting diodes or LEDs), societal concerns have emerged and are growing. These concerns include light pollution and the impact of blue light on human health and the environment. The scientific community has also taken up the subject, publishing in recent years a large and ever-increasing number of articles on the effects of artificial light at night on fauna and flora as well as on human health. In this review, we propose a synthesis of knowledge on human health effects of light based on scientific reports and an update of recent scientific production. We also briefly describe the potential beneficial effects of light, especially blue light, on well-being as well as the different types of lamps and their health effects. (authors)
[en] Accounting for 10% of the electricity consumption in the US, artificial lighting represents one of the easiest ways to cut household energy bills and greenhouse gas (GHG) emissions by upgrading to energy-efficient technologies such as compact fluorescent lamps (CFL) and light emitting diodes (LED). However, given the high initial cost and rapidly improving trajectory of solid-state lighting today, estimating the right time to switch over to LEDs from a cost, primary energy, and GHG emissions perspective is not a straightforward problem. This is an optimal replacement problem that depends on many determinants, including how often the lamp is used, the state of the initial lamp, and the trajectories of lighting technology and of electricity generation. In this paper, multiple replacement scenarios of a 60 watt-equivalent A19 lamp are analyzed and for each scenario, a few replacement policies are recommended. For example, at an average use of 3 hr day−1 (US average), it may be optimal both economically and energetically to delay the adoption of LEDs until 2020 with the use of CFLs, whereas purchasing LEDs today may be optimal in terms of GHG emissions. In contrast, incandescent and halogen lamps should be replaced immediately. Based on expected LED improvement, upgrading LED lamps before the end of their rated lifetime may provide cost and environmental savings over time by taking advantage of the higher energy efficiency of newer models. (letter)
[en] Artificial light is a tangible manifestation of economic and social development, as well as a response to certain needs, especially comfort and civil and road safety. However, this use has been so associated with technological progress that its invasion of daily life has been almost imperceptible. With the recent increase in night lighting (11 million light points in 2016 according to the French Agency for the Environment and Energy Management) and the production of new lamp technologies (in particular light-emitting diodes or LEDs), societal concerns have emerged and are growing. These concerns include light pollution and the impact of blue light on human health and the environment. The scientific community has also taken up the subject, publishing in recent years a large and ever-increasing number of articles on the effects of artificial light at night on fauna and flora as well as on human health. In this review, we propose a synthesis of knowledge on human health effects of light based on scientific reports and an update of recent scientific production. This review updates knowledge of the chrono-biological effects of light at night, particularly blue light. We also briefly describe the potential beneficial effects of light on well-being. (authors)
[en] The UN electricity for all initiative promotes branded solar products based on the argument that otherwise households won't have access to such technologies. We argue that non-branded products have already reached households; hence access is not an issue, at least for richer households. Yet, a justification of branded products can be made based on their durability and thus reduced electronic waste. Subsidies can be paid to reach also the poor. (authors)
[fr]L'initiative des Nations Unies 'L'electricite pour tous' vise a promouvoir les installations solaires de marque en se fondant sur l'argument selon lequel sans cela, les menages n'auront pas acces a de telles technologies. Nous estimons que les produits sans marque sont deja utilises dans les menages. Par consequent, l'acces n'est pas un probleme, au moins pour les menages les plus riches. Cependant, une justification des produits de marque peut etre donnee sur la base de leur durabilite et donc de la faible quantite de dechets electroniques. Des subventions peuvent etre versees pour permettre egalement l'acces aux menages les plus pauvres. (auteurs)
[en] In 2013 Azuri Technologies, a provider of solar home systems, entered the Rwanda market with USAID support. During project implementation various distribution challenges were encountered and useful lessons learned. Impact studies were conducted which showed households using the Azuri systems benefiting from significantly more hours of light and from the ability to charge phones at home. These households were among the wealthier segments of the rural population indicating affordability challenges for some households. (authors)
[fr]En 2013, Azuri Technologies, fournisseur d'installations solaires domestiques, est entre sur le marche rwandais avec l'aide de l'USAID. Durant la mise en oeuvre du projet, divers problemes de distribution se sont poses qui ont permis de tirer des enseignements pour l'avenir. Des etudes d'impact ont ete realisees; elles ont montre que les menages utilisant les systemes Azuri beneficiaient d'un nombre d'heures d'eclairage significativement plus eleve et de la possibilite de recharger leur telephone a domicile. Ces menages figuraient parmi les segments les plus aises de la population rurale, revelant des problemes d'accessibilite financiere pour certains foyers. (auteurs)
[en] The recent introduction of the Multi-Pulse Shake-The-Box (MP-STB) method opened the possibility of extending 3D Lagrangian particle tracking (LPT) to the investigation of high-speed flows, where long time-resolved sequences of recordings are currently not available due to the limited acquisition frequency of high-speed systems. The MP-STB technique makes use of an iterative approach to overcome the limitations posed by the short observation time offered by a multi-pulse recording sequence. Multi-pulse sequences are typically obtained by synchronizing multiple illumination systems to generate bursts of laser pulses where the time separation can be freely adjusted down to less than a microsecond. Several strategies can be adopted for the recording of multi-pulse sequences; a dual camera system can be adopted to separate the single pulses onto the camera frames (either by means of polarization or timing), while the use of multi-exposed frames allows for the employment of a single imaging system, largely reducing the complexity and cost of the experimental setup. The main strategies to generate multi-pulse recording sequences are presented here; the application and performances of the MP-STB method are discussed based on the analysis of experimental data from the investigation of three turbulent boundary layer flows at velocities ranging from 10 to approximately 30 m/s. Results show the capability of the MP-STB technique in reconstructing accurate track fields which can be exploited both to describe instantaneous flow structures and to produce highly spatially resolved statistics by means of ensemble average in small bins. The iterative reconstruction and tracking strategy for MP-STB can be successfully adapted to the case of multi-exposed frames. Results suggest that, despite the increase in particle image density resulting from the double-exposed particle images, the adoption of multi-exposed recordings has the potential to become the technique of choice for the recording of multi-pulse sequences suitable for Lagrangian particle tracking in high-speed flows. Graphical abstract: .
[en] Illumination plays a key role in getting high resolution imaging. Photonic nanojet is a new lighting system. Since the transverse beam width of the nanojet can reach λ/3, photonic nanojet is usually considered to be the key point for the explanation of the high-resolution microsphere assisted microscopy. However, the polarization of photonic nanojet are usually out of attention. In this work, we investigate the photonic nanojets formed by illuminating a dielectric microcylinder by two plane waves with different linear polarizations. The influences of wavelength and refractive index contrast between the microcylinder and its surrounding, and the cases illuminated by the Gaussian beam are also studied. Numerical results demonstrate that the TM polarization can generate a wider nanojet waist than the TE polarization, and this is produced by the longitudinal component of the TM-polarization illumination. When the Gaussian beam width becomes larger than diameter of the cylinder, the nanojet waists become smaller than that obtained by the cylinder under a plane wave. At last, the reason why the TE polarization has a thinner nanojet waist is given, it is related to the longitudinal component making light transmission far away from optical axis.