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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] 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] 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 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.
[en] The latest research focused on the analysis of algal growth and the dynamics of their growth use the laser diffraction technique, enabling determination of the volume fraction of suspended particles with specific diameters in aqueous solution as well as their fractal dimensions. This study focuses on the possibility of using a laser granulometer to assess the growth dynamics of algae growing in treated wastewater in a hydroponic system, supported by artificial lighting with the use of light-emitting diodes (LEDs). On the basis of the measurements, the fractal dimension (Df) of algae was determined. An attempt was made to apply the modified Avrami equation describing the crystallization process for the analysis of algae growth dynamics in wastewater. Presented results show that the fractal dimension of suspended matter, largely created by algae, in the case of additional lighting of the hydroponic system at night, takes lower values (Df ~ 1.0) than in sewage without additional light source (Df ~ 2.0). In each measurement series, the fractal dimension of particles in the tank with lighting in the end of the experiment was about 33–43% lower than in the tank without LEDs. The analysis of changes in particle diameters calculated on the basis of Avrami equation largely corresponds with the stages of algae growth. During the measurement series with lower air temperatures, the growth of algae in the tank with additional light was faster than in the tank without LEDs. The obtained information can be the basis for determining the effective method of removing algae from wastewater treated in the hydroponic system, before they are discharged to the receiver in order to prevent the outflow of increased concentrations of total suspended solids.
[en] This paper reported on the development history of radiation-resistant LED lighting fixtures as well as the state of demonstration experiments at J-PARC. The demonstration experiments based on gamma irradiation verified that the manufactured radiation-resistant LED lighting fixtures can maintain 70% or above of the initial illuminance even under a high radiation dose such as 2 MGy of gamma ray absorption dose. Lighting fixtures (light sources) were installed at the bottom of the cable rack installed on the side of the accelerator in the main tunnel that holds the J-PARC Main Ring accelerator main body, and long-term demonstration experiments have been conducted since September 2016. The gamma ray absorption dose of the fixture parts was 600 Gy to 800 Gy, and the neutron flux density was 1.9e+13 [cm-2]. In the demonstration experiments so far, it has been confirmed by data that radiation resistance is exhibited even under complex radiation environment, where gamma rays and neutrons having wide energy spectra move in. (A.O.)
[en] The main control-room is the most important monitoring and control center of nuclear power plant, and is also the most complex place in the man-machine interface of the plant. It has been thought the most frequently place where the accidents due to human factors happened. In order to avoid the possibility of error operation of operators caused by the improper lighting design, the human factors consideration for the lighting design is described in this paper according to the characteristics of digital control-room of nuclear power plant nowadays. (author)
[en] Whereas some horticultural production is based on the use of artificial lighting in greenhouses, with a continuous use of this lighting in winter, blue, red and white LEDs are now commonly used instead of sodium lamps. This publication reports the study of the exposure of employees to such a lighting in a specific case as some wavelengths may have harmful effects on eyes and skin. Lamp configuration and models are indicated, and the determination of exposure levels is reported. Risk groups according to a standard are also indicated, as well as exposure thresholds. Risks are assessed according to a European directive. The efficiency of protection goggles is analysed