A novel lens cap designed for the RGB LEDs installed in an ultra‐thin and directly lit backlight unit of large‐sized LCD TVs

Abstract— The objective of this study is to design a novel cone‐shaped lens cap on LEDs in order to achieve high optical efficiency in an ultra‐thin directly lit RGB LED backlight unit (BLU) for large‐sized LCD TVs. The use of the novel lens cap could play the role of a diffuser, a low light‐efficiency component in a BLU, in order to gain higher efficiency and simultaneously provide satisfactory uniformity in light distribution. The novel cone‐shaped lens is coated with aluminum on the outside surface of the cone for mirroring effects to reflect most of the LED emitted light horizontally and then reflect the light at the BLU boundaries, and then, finally to the output plane. In this way, bright spots on the output plane of the BLU can be avoided, leading to increased uniformity. Simulations were conducted to design and optimize varied aspects of the designed lens and BLU, including the cone angle of the proposed lens and the LED spacing (pitch). To further achieve color balance, a known Genetic Algorithm is used to search for the optimal angular placement of each RGB LED, resulting in better color balance. Finally, a prototype BLU for large‐sized 37‐in. LCD TVs with the proposed lens was built to verify the expected performance.     

Compression along the Easy-Glide Orientation of Ultrafine and Fine-Grained Mg-3Al-1Zn Alloy

The deformation behavior of textured ultrafine-grained (UFG) and fine-grained (FG) Mg-3Al-1Zn alloy compressed along the easy-glide orientation was studied. It was found that severe strain localization within very thin shear bands (SBs) caused the loss of ductility in UFG Mg-3Al-1Zn alloy. Increasing grain size increases the width of SBs, which decreases the degree of strain localization. The reason for the occurrence of severe strain localization in textured UFG Mg-3Al-1Zn alloy is proposed.     

Calculation of effective doses for broad parallel photon beams

Values of effective dose (E) were calculated for the entire range of incident directions of broad parallel photon beams for selected photon energies using the Monte Carlo N-Particle (MCNP) transport code with a hermaphroditic phantom. The calculated results are presented in terms of conversion coefficients transforming air kerma to effective dose. This study also compared the numerical values of E and H(E) over the entire range of incident beam directions. E was always less than H(E) considering all beam directions and photon energies, but the differences were not significant except when a photon beam approaches some specific directions (overhead and underfoot). This result suggests that the current H(E) values can be directly interpreted as E or, at least, as a conservative value of E without knowing the details of irradiation geometries. Finally, based on the distributions of H(E) and E over the beam directions, this study proposes ideal angular response factors for personal dosimeters that can be used to improve the angular response properties of personal dosimeters for off-normal incident photons.     

The 6th International Conference on Properties and Applications ofDielectric Materials (ICPADM'2000); and the history of the ICPADM

In the interest of having written notes on some of the history of the DEIS activities, Prof. Kao, Founder of the International Conference on Properties and Application of Dielectric Materials, was asked to set down in writing some of his memories of how the ICPADIM came about. From the beginnings of the DEIS, the Society had sponsored conferences on electrical insulation in North America. Under the leadership of Eric Forster, who was the Meetings Chair for a number of years, the Society broadened its scope and began to sponsor meetings outside of North America. It is of historical interest to understand how the ICPADM came about. It was the first Pan-Asian conference sponsored by the DEIS and continues to hold the distinction of being our only Pan-Asian conference. Prof. Kao, one of the keynote speakers' at the ICPADM 2000, compares the most recent conference with the first in a "Reporter's Notebook" format. He has also drawn from his memory as to how the original conference came about     

Effect of Sr-doping on the structural and electrical properties of gadolinium manganite oxide

The crystal structure and electrical conductivity of the perovskite oxide system Gd_1-xSr_xMnO_3± (x = 0–0.5) were investigated. The effect of the level of Sr-doping on these properties was examined. An orthorhombic GdFeO₃-type structure (space group Pbnm) was found for all oxides. The room temperature lattice parameters were determined from the XRD data. A large distortion of the unit cell was observed in the case of the undoped compound. The distortion was gradually reduced with increasing Sr content. The unit cell volume decreased on Sr-doping. The electrical conductivity of the oxides was measured from room temperature up to 800°C. The small polaron hopping conductivity model can adequately describe the electrical conductivity behavior. The activation energy decreases as x increases.     

Coating and Characterization of Titania Membrane on Porous Ceramic Supports

In this article, we reported experimental results on the development of microstructure of the membrane layer deposited on a porous support. The changes in porosity and mean pore diameter were followed as a function of layer thickness. It was found that in addition to particle packing and sintering within the membrane layer, the porous structure of support surface also exhibited certain effects on membrane microstructure until a critical thickness was reached. After that, the porous characteristics of a membrane would be totally determined by the packing and sintering characteristics of particles. It was also shown that the surface roughness could be reduced from about 1.5 m of the support, to 0.8 m after coating with 0.5 m titania particle and further reduced to about 0.55 m after another coating with 30 nm titania colloids. With proper dispersing and coating procedures, we could reduce the mean pore diameter from about 1.5 m of the support to 0.12 m, while the gas permeability was only changed from 500 × 10–7 to 250 × 10–7 mol/m2 s Pa.     

Achieving Optimum Performance in a High Pressure Sodium Lighting System

In spite of the many advantages of a high pressure sodium (HPS) lighting system, some problems do exist and compromises must be made. The lighting designer should be thoroughly familiar with the characteristics of all the integral components which make it up, such as lamps, ballasts, starters, luminaires, and poles. The most pertinent characteristics of these components are discussed. By proper selection of various components, they can function well together to achieve an optimum system performance.     

Matching Charge Extraction Contact for Infrared PbS Colloidal Quantum Dot Solar Cells

Infrared solar cells (IRSCs) can supplement silicon or perovskite SCs to broaden the utilization of the solar spectrum. As an ideal infrared photovoltaic material, PbS colloidal quantum dots (CQDs) with tunable bandgaps can make good use of solar energy, especially the infrared region. However, as the QD size increases, the energy level shrinking and surface facet evolution makes us reconsider the matching charge extraction contacts and the QD passivation strategy. Herein, different to the traditional sol-gel ZnO layer, energy-level aligned ZnO thin film from a magnetron sputtering method is adopted for electron extraction. In addition, a modified hybrid ligand recipe is developed for the facet passivation of large size QDs. As a result, the champion IRSC delivers an open circuit voltage of 0.49 V and a power conversion efficiency (PCE) of 10.47% under AM1.5 full-spectrum illumination, and the certified PCE is over 10%. Especially the 1100 nm filtered efficiency achieves 1.23%. The obtained devices also show high storage stability. The present matched electron extraction and QD passivation strategies are expected to highly booster the IR conversion yield and promote the fast development of new conception QD optoelectronics.