Papers by Keyword: LED

Abstract: GaN-based nanopillar crystals are directly grown on multicrystalline Si and amorphous-carbon-coated graphite substrates whose surfaces are not mirror-polished. Light-emitting diodes (LEDs) of a double-hetero structure are prepared from the nanopillar crystals, and their optical–emission properties are investigated. Despite the substrate type and surface conditions, moderate light emissions are obtained from nanopillar LEDs though the light emissions are not always homogeneous, especially in the LEDs prepared on the graphite-based substrate. Nevertheless, these results will lead to realizations of novel large-area light-emitting devices.

Abstract: The existing heat pipe applied to a LED headlamp has a large size although it has only small area of contact. Therefore, it is difficult to achieve a harmonious radiation of heat along with the difficulty in attaching the LED due to its large volume. This study proposed a plate heat pipe to solve the aforementioned problems. Through the study, the effects of the thickness and acetone filling rate on the heat radiation effects of a plate heat pipe at room temperature and vehicle driving environment were confirmed along with comparison with the heat radiation effects of the existing copper heat pipe. The heat radiation effects were checked by attaching a thermocouple to the evaporator, adiabatic section and condenser of the LED. As the results of the experiment, it was found that a temperature below 120oC, which is the allowable temperature to guarantee the performance of the LED, is maintained. In addition, as the results of comparison of radiation of heat, it was confirmed that the plate heat pipe with a thickness of 2 mm and 20% filled with acetone has a better performance than the existing copper heat pipe.

Abstract: The influence of light irradiation with different intensity parameters and different spectral composition on morphogenic structures, namely green zones of cultivar Dolinny cell cultures was investigated. Light irradiation was generated by 10 types of LEDs with different spectra: cold white (Cold W), white (W), warm white (Warm W), Full spectrum, Red, Deep Red, Yellow, Green, Blue and Royal Blue. It was shown that LEDs with Cold W, W and Royal Blue more actively influenced on green zones generation, while Red, Red Deep, Yellow и Green displayed no results. Standard fluorescent lighting illumination (WFL) was used as a control. The number of induced green zones was lower under control luminescent light (WFL) in comparison with the green zones, which were induced by the illumination of the most active spectra of LEDs, but lifetime of these control structures was longer. After 19 weeks of cultivation, degradation of the green zones of the calli was not observed under control and LEDs Cold W, Warm W, and Blue in the position with maximal intensity of light. The Royal Blue illumination displayed the same results not only in the position with maximum intensity but also at the other intensities approaching the control values (49,3 230 μmol/s*m2).

Abstract: Based on the material properties of AlGaInP LED, this paper proposes an approach for predicting the junction temperature. The junction temperature of AlGaInP LED predicted from this study agrees with the available experimental data. The junction temperature increases with increasing the injection current and substrate thickness of LED.

Abstract: The paper represents the results of the effective lighting introduction based on LED technology on the basis of a green house. It is shown that in order to reduce electricity costs, as well as increase yields, it is necessary to replace traditional sodium lamps with LED lighting lamps. Based on the results obtained, mathematical calculations confirm the above statement.

Abstract: High performance concrete reinforced by technical textiles has found a wide range of applications in recent years. One of the most widespread is the use of this composite for the very thin facade panels of various shapes and technical solutions. This paper presents an unique way how to lighten the facade panels made of high performance concrete (HPC) reinforced by technical textiles, which are additionally equipped with LEDs, so that a sufficient distance can be watch programmed based image displays.

Abstract: Indoor Lighting design of different types of buildings is a very challenging and technology oriented work. Building lighting designing has specific rules and regulations and can be varied depending upon the designers choice. As per National Building Code of India, buildings can be classified according to the use or the character of occupancy in one of the nine groups. These are Group A_(Residential), Group B_(Educational), Group C_(Institutional),Group D_(Assembly ),Group E_(Business), Group F_(Mercantile), Group G_(Industrial) ,Group H_(Storage) and Group J_(Hazardous) types of buildings. With the reduction of energy consumption, there should not be any sacrifice in quality and quantity of light required as per the lighting codes. The shortage of Electrical energy is increasing gradually. As it is the energy source of lighting, the lighting designers should be more concerned about energy efficient lighting system design. LED consumes less power than the conventional luminaires & maintains almost the same lighting level. So, lighting designers are using LED luminaires into their designs now a days. Also, renewable energy sources driven lighting systems should be used. It will be environmental friendly also. A proper lighting design requires consideration of the amount of functional light level provided, the energy consumed and the aesthetic effect supplied by the lighting system. The electrical lighting systems should also consider the impacts of, and ideally be integrated with, daylighting systems. Building lighting design focuses on three fundamental aspects of the illumination of buildings or spaces. The first is the aesthetic appeal of a building. Secondly, the ergonomic aspect: the measure of how much of a function the lighting can achieve. Thirdly is the energy efficiency issue to ensure that light is not wasted by over-illumination, light pollution, by illuminating vacant spaces unnecessarily or by providing more light than needed for the aesthetics or the task.

Abstract: New applications of nanoscale powders of Si, SiO₂ and BaTiO_3, etc. have been developed for vacuum sealing, reflectors in LED devices and thermally cooling membranes from metal surface. The optical transparency and good vacuum sealing were formed in baking temperatures as low as 150°C, 1hr by using nanoscale powders of these materials. We show the several applications of capacitors with the material thicknesses between 1 and 10 μm, and show the thermally cooling enhancements in several metals of Al, Fe and stainless steel up to 2.5deg/s in the metal temperature range higher than 50°C.

Abstract: Two kinds of commercial LED phosphors (green phosphor LuAG:Ce³⁺ and red phosphor CaAlSiN₃:Eu²⁺) with polymethyl methacrylate (PMMA) powders were mixed to prepare film phosphors with tunable emission peak in photoluminescence spectrum by flat vulcanizing machine under the temperature of 170 ^oC and pressure of 2 MPa. The physical phase, surface morphology, transmittance, luminescence spectra of samples were characterized by means of X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM), Ultraviolet-Visible (UV-Vis) spectrophotometry and Fluorescence spectrometer. The results show that the film phosphors phase was consistent with raw phosphors, phosphor particles were uniformly distributed, and fluorescence spectra with different proportions of phosphors in different position can be adjusted. Tested by HSP 3000 spectrum analyzer, the white LEDs fabricated by blue chip and composite film phosphor containing 5 wt% green phosphor and 1.5 wt.% red phosphor, which refers to the remote excitation technique, possessed color coordinate of (0.3715, 0.3280) and color rendering index (CRI) of 87 when it was driven at power of 36 V/140 mA, reaching the international advanced level.

Abstract: The article reports the results of the experiment studied the effect of radiation spectral content (considering its equal intensity in terms of photosynthetically active radiation) on the growth and development of Boets greenhouse tomato breed. We have shown that the effective development of model subjects requires the adaptation of radiation spectral content depending on the growth period and type of a plant, unlike the illumination level. The obtained results demonstrate the necessity of creating an adaptive irradiation unit.