No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

We demonstrated the electro-optical characteristics of gallium nitride (GaN)-based ultraviolet (UV) light emitting diodes (LEDs) with sputtered aluminum nitride (AlN) nucleation layer. The introduction of the ex situ sputtered AlN nucleation layer improved the crystal quality of the GaN and the n-AlGaN layer of the GaN-based UV LEDs. Hence, the 20-mA output power of UV LEDs with ex situ AlN nucleation layers is higher than that of UV LEDs with GaN nucleation layers. In addition, the enhanced power output of UV LEDs with ex situ AlN nucleation could reach around 52% in magnitude at peak emission wavelengths of 370 nm compared with power outputs of UV LEDs with GaN nucleation layers. Furthermore, UV LEDs with ex situ AlN nucleation show improved reliability. The UV LEDs with ex situ AlN nucleation layer revealed a power output drop of around 9% within 168 hours, which is less than the around 14% power drop of UV LEDs with GaN nucleation layer. Index Terms-GaN-based ultraviolet light-emitting diodes (UV-LEDs), sputtered AlN, nucleation layer.

In this study, a full survey of pollutant sources and water quality was conducted, followed by the application of a water quality model (Water Quality Analysis Simulation Program, WASP) to establish strategies of water quality control in Carp Lake, Taiwan. Results of the field investigation show that both point and non-point source (NPS) pollutants were responsible for the poor water quality. The contributions of biochemical oxygen demand (BOD) from point source and NPS pollution were 45.9 and 55.1%, respectively. About 80% of total phosphorus (TP) were contributed by NPS. Additionally, point source and NPS pollution discharged 55.5 and 44.5% of NH 3 -N load, respectively. The Carlson's Trophic State Index ranged from 61.9 to 69.2 showing serious eutrophic problems in Carp Lake. The calculated BOD, NH 3 -N, and TP carrying capacity were approximately 2.8, 0.42, and 0.15 kg per day, respectively. However, the current pollutant loadings are approximately 3.0-5.5 times the calculated carrying capacity. With the help of the calibrated WASP model, remedial strategies for the lake water from short-term to long-term were developed. The completion of the small local sewer system to remove 80% of the point source pollution can serve as a short-term goal while 40-60% of NPS removal by natural treatment systems may serve as a mid-term goal. Furthermore, 80% of both source point and NPS pollution removal can be considered as a long-term strategy. Results of heavy metal analysis show that the enriched sediment would be safe for agricultural applications.