Prognostics of the remaining useful life (RUL) has emerged as a critical technique for ensuring the safety, availability, and efficiency of a complex system. To gain a better prognostic result, degradation information is quite useful because it can reflect the health status of a system. However, due to the lack of accurate information about the plants’ degradation, the prognostic model is usually not well established. To solve this problem, this paper proposes a two-stage strategy that is in the context of data-driven modeling to predict the future health status of a bearing, where the degradation information was estimated by calculating the deviation of multiple statistics of vibration signals of a bearing from a known healthy state. Then, a prediction stage based on an enhanced Kalman filter and an expectation–maximization algorithm were used to estimate the RUL of the bearing adaptively. To verify the effectiveness of the proposed approach, a real-bearing degradation problem was implemented.

A Two-Stage Data-Driven-Based Prognostic Approach for Bearing Degradation Problem

Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards general illumination. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the developments of LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 lumens/W, this is approximately 6 times the efficiency of a conventional incandescent tungsten bulb. Thermal management for the solid-state lighting applications is a key design parameter for both package and system level. Package and system level thermal management is discussed in separate sections. Effect of chip packages on junction to board thermal resistance was compared for both SiC and Sapphire chips. The higher thermal conductivity of the SiC chip provided about 2 times better thermal performance than the latter, while the under-filled Sapphire chip package can only catch the SiC chip performance. Later, system level thermal management was studied based on established numerical models for a conceptual solid-state lighting system. A conceptual LED illumination system was chosen and CFD models were created to determine the availability and limitations of passive air-cooling.

Thermal management of LEDs: Package to system

Glass Ceramic Phosphors: Towards Long-Lifetime High-Power White Light-Emitting-Diode Applications–A Review

A display panel and a display device are provided. The display panel comprises a central region and peripheral regions. The peripheral regions are provided at two opposite ends of the display panel and have a first curvature; the central region is provided between the two opposite ends of the display panel and has a second curvature; and the second curvature of the central region is smaller than the first curvature of the peripheral regions.

Display panel and display device

Reclaiming rare earth elements from end-of-life products: A review of the perspectives for urban mining using hydrometallurgical unit operations

Light emitting diodes reliability review

A backlight assembly includes a light guide plate (LGP) having a stepped portion formed at a corner of the LGP, an optical sheet disposed over the LGP and a receiving container receiving the LGP and the optical sheet. The receiving container includes a bottom plate, first through fourth sidewalls and a first LGP fixing portion. The second sidewall is adjacent to the first sidewall. The third sidewall faces the first sidewall. The fourth sidewall faces the second sidewall. The first through fourth sidewalls are extended upwardly from edge portions of the bottom plate. The first LGP fixing portion is formed at the first sidewall such that the LGP fixing portion corresponds to the stepped portion of the LGP. Therefore, a display device is easily assembled. Furthermore, a defilement that may occur during an assembling process may be reduced to enhance productivity.

Backlight assembly and display device having the same

A light source apparatus includes a light source module, a local dimming control part and a light source driving part. The light source module includes a plurality of light-emitting blocks. Each of the light-emitting blocks includes a first color light source, a second color light source and a third color light source, respectively. The local dimming control part drives the light-emitting blocks by blocks. The local dimming control part sets a reference duty signal for first, second and third color driving signals in accordance with a driving mode of the light source module. The light source driving part generates the first color driving signal, the second color driving signal and the third color driving signal by using the reference duty ratio set in accordance with the driving mode and a driving current having a same peak current level in accordance with the driving mode.

Method of driving a light source, light source apparatus for performing the method and display apparatus having the light source apparatus

Today's decreasing product development cycle time requires rapid and cost-effective reliability analysis and testing. Qualification is the process of demonstrating that a product is capable of meeting or exceeding specified requirements. Light-emitting diode (LED) qualification tests are often as long as 6000 h, but this length of time does not guarantee the typically required lifetime of 10 years or more. This paper presents a prognostics-based technique that reduces the LED qualification time. An anomaly detection technique called the similarity-based metric test is developed to identify anomalies without utilizing historical libraries of healthy and unhealthy data. The similarity-based metric test extracts features from the spectral power distributions (SPDs) using peak analysis, reduces the dimensionality of the features using principal component analysis, and partitions the data set of principal components into groups using a k-nearest neighbor (KNN)-kernel density-based clustering technique. A detection algorithm then evaluates the distances from the centroid of each cluster to each test point and detects anomalies when the distance is greater than the threshold. From this, the dominant degradation processes associated with the LED die and phosphors in the LED package can be identified. In our case study, anomalies were detected at less than 1200 h using the similarity-based metric test. Thus, our method could decrease the amount of LED qualification testing time by providing users with an earlier time to begin remaining useful life prediction without waiting 6000 h as required by industrial standards.

Anomaly Detection of Light-Emitting Diodes Using the Similarity-Based Metric Test

Rare-earth elements (REEs) are used in lighting and optical applications to enable color and light adjustment, miniaturization, and energy efficiency. Common applications of REEs include phosphors for light-emitting diodes, lasers, and electronic video displays. This article reviews how REEs are widely used in these applications. However, supply constraints, including rising prices, environmental concerns over mining and refining processes, and China’s control over the supply of the vast majority of REEs, are of concern for manufacturers. In view of these supply constraints, this article discusses ways for manufacturers of lighting and optical devices to identify potential substitutes and recycling methods for REEs.

Moon-Hwan Chang

Papers

Light emitting diodes reliability review

Backlight assembly and display device having the same

Method of driving a light source, light source apparatus for performing the method and display apparatus having the light source apparatus

Anomaly Detection of Light-Emitting Diodes Using the Similarity-Based Metric Test

Rare-Earth Elements in Lighting and Optical Applications and Their Recycling