Smart City Street Lighting System Quality and Control Issues To Increase Energy Efficiency and Safety

According to standards, the lighting system is one of the key elements to provide safety on city roads, defined by quality parameters. LED technology and movement detection sensor interaction bring about new regulation techniques, creating an energy-efficient smart LED lighting system concept. This paper reveals extensive comparative data analysis of Dialux simulation results before the project implementation phase and in-situ quality parameter measurements for various street profiles and LED luminary power types. After the project implementation phase, more than 1000 measurement points are reached. Further, energy efficiency increase issues in smart lighting systems are described in terms of LED luminary dimming profile analysis and future dynamic control application modes. The first findings clearly show that in most cases light output in simulation results is lower than in real situations; therefore, LED luminary power can be decreased, allowing for higher energy savings in first luminary maintenance years, keeping the same defined ME class or safety level. Let us suppose that the traffic intensity data are obtained from smart system sensors. In that case, the ME class can be dynamically selected during different night times, thus increasing safety and providing extra energy savings using the same system elements, as well as leading to better ROI values.

Failure Analysis of Some Commercial Spotlights Based on Light Emitting Diodes

The failure mechanism of two commercial light-emitting diode (LED)-based spotlights with GU10 form factor is analyzed. Through component testing and comparison to nominal values as well as to simulations, it is found that the cause of both device failures is related to damaged components within the drive circuits rather than the LEDs themselves. Both LED heads work as normal when connected to an external direct current (DC) source. The results show that the lack of light output of one spotlight is related to the open circuit caused by damaged resistors and inductors in its drive circuit, while the flickering of the other is related to the malfunction of the integrated circuit providing constant current output. Therefore, improving the quality of the LED drive circuits is considered the most effective way for manufacturers to reduce catastrophic failures of LED spotlights.

Semipolar {202̅1} GaN Edge-Emitting Laser Diode on Epitaxial Lateral Overgrown Wing

Edge-emitting laser diodes (LDs) were fabricated on a reduced dislocation density epitaxial lateral overgrown (ELO) wing of a semipolar {202̅1} GaN substrate, termed an ELO wing LD. Two types of facet feasibility studies were conducted: (1) “handmade” facets, wherein lifted-off ELO wing LDs were cleaved manually, and (2) facets formed on wafers through reactive ion etching (RIE). Pulsed operation electrical and optical measurements confirmed the laser action in the RIE facet LDs with a threshold current of ~19 kAcm−2 and maximum light output power of 20 mW from a single uncoated facet. Handmade facet devices showed spontaneous, LED-like emission, confirming device layers remain intact after mechanical liftoff.

High-k Fluoropolymers Dielectrics for Low-Bias Ambipolar Organic Light Emitting Transistors (OLETs)

Organic light emitting transistors (OLETs) combine, in the same device, the function of an electrical switch with the capability of generating light under appropriate bias conditions. In this work, we demonstrate how engineering the dielectric layer based on high-k polyvinylidene fluoride (PVDF)-based polymers can lead to a drastic reduction of device driving voltages and the improvement of its optoelectronic properties. We first investigated the morphology and the dielectric response of these polymer dielectrics in terms of polymer (P(VDF-TrFE) and P(VDF-TrFE-CFE)) and solvent content (cyclopentanone, methylethylketone). Implementing these high-k PVDF-based dielectrics enabled low-bias ambipolar organic light emitting transistors, with reduced threshold voltages (<20 V) and enhanced light output (compared to conventional polymer reference), along with an overall improvement of the device efficiency. Further, we preliminary transferred these fluorinated high-k dielectric films onto a plastic substrate to enable flexible light emitting transistors. These findings hold potential for broader exploitation of the OLET platform, where the device can now be driven by commercially available electronics, thus enabling flexible low-bias organic electronic devices.

Study on the influence of the cotton storage process on the quality indicators of fiber and yarn

This article defines fiber quality indicators that differ in laboratory conditions from the upper, middle and lower layers of Bukhara-6 breeding varieties of cotton, in the modern system HVI 1000 SA. Based on the results of the study, histograms of changes in the quality of cotton fiber in the layers of the harem are presented. As an alternative, the quality indicators of yarn obtained in the laboratory spinning device “Sherli” of small size from fiber were determined. As can be seen from the analysis of the test results, it was found that the comparative elongation strength of cotton obtained from the lower layer of the stack, the upper average length, elongation at break, the light output coefficient, decreased compared to other layers of the stack, on the contrary, the index of hip fibers, increased, decreased compared to other layers of the stack. In addition, according to the results of the tests obtained, the fiber viscosity index was obtained – the correlation between the properties of fibers and the properties of yarn, the thread viscosity index was estimated by the CSP (COUNT STRENGTH PRODUKT) coefficient, which was determined by the formula for carded yarn obtained in the laboratory spinning device “Sherli” from fiber stored in the refrigerator. The obtained results showed that the relationship between fiber properties and yarn properties due to the fact that the maturity index of a thread is at the top of the stack compared to the middle and lower part of the stack.

Simulation of a Ridge-Type Semiconductor Laser with Transversal Diffraction Gratings

This paper reports on improvement of stability of the fundamental horizontal transverse mode in a ridge-type semiconductor laser by incorporating transversal diffraction gratings. Kinks do not appear in current versus light-output curves by appropriately designing the number of the grating periods when the mesa width is 5 μm in which kinks exist in current versus light-output curves for conventional ridge-type semiconductor lasers.

The effect green YF3:ER3+,YB3+ phosphor on luminous flux and color quality of multi-chip white light-emitting diodes

The purpose of this paper is to demonstrate the advantages of the green phosphor YF₃:Er³⁺,Yb³⁺combined with multi-chip package to the enhancement of lighting efficiency of modern WLEDs. In an effort to improve the quality of WLEDs and create a new generation of lighting device, green phosphor YF₃:Er³⁺,Yb³⁺is added into the phosphor compounding of the WLED package to improve the color quality and lighting capacity. Through experiments, WLEDs with YF₃:Er³⁺,Yb³⁺green phosphor has shown improved results in lighting performance specifically in color homogeneity and light output of WLEDs in the ACCT range from 5600-7000 K. However, the color quality scale (CQS) declines gradually. Therefore, if the appropriate concentration and size of YF₃:Er³⁺,Yb³⁺ are determined, the performance of MCW-LEDs will be enhanced and become more stable.

Mass-ratio and Magnetic Flux Dependence of Modulated Accretion from Circumbinary Disks

Accreting supermassive binary black holes (SMBBHs) are potential multimessenger sources because they emit both gravitational-wave and electromagnetic (EM) radiation. Past work has shown that their EM output may be periodically modulated by an asymmetric density distribution in the circumbinary disk, often called an “overdensity” or “lump;” this modulation could possibly be used to identify a source as a binary. We explore the sensitivity of the overdensity to SMBBH mass ratio and magnetic flux through the accretion disk. We find that the relative amplitude of the overdensity and its associated EM periodic signal both degrade with diminishing mass ratio, vanishing altogether somewhere between 1:2 and 1:5. Greater magnetization also weakens the lump and any modulation of the light output. We develop a model to describe how lump formation results from internal stress degrading faster in the lump region than it can be rejuvenated through accretion inflow, and predicts a threshold value in specific internal stress below which lump formation should occur and which all our lump-forming simulations satisfy. Thus, detection of such a modulation would provide a constraint on both mass ratio and magnetic flux piercing the accretion flow.

On-chip light detection using integrated microdisk laser and photodetector bonded onto Si board

Characteristics of a compact III–V optocoupler heterogeneously integrated on a silicon substrate and formed by a 31 µm in diameter microdisk (MD) laser with a closely-spaced 50 µm × 200 µm waveguide photodetector are presented. Both optoelectronic devices were fabricated from the epitaxial heterostroctructures with InGaAs/GaAs quantum well-dot layers. The measured dark current density of the photodetector was as low as 2.1 µA cm−2. The maximum link efficiency determined as the ratio of the photodiode photocurrent increment to the increment of the microlaser bias current was 1%–1.4%. The developed heterogeneous integration of III–V devices to silicon boards by Au-Au thermocompression bonding is useful for avoiding the difficulties associated with III–V epitaxial growth on Si and facilitates integration of several devices with different active layers and waveguides. The application of MD lasers with their lateral light output is promising for simplifying requirements for optical loss at III–V/Si interface.