A new PM2.5 inlet, based on the particle cup impactor configuration, was designed for sampling fine particles smaller than 2.5 μm in aerodynamic diameter and for operating at a flow rate of 5 l/min, as the devices, which are used to analyze the chemical composition of the particles, have good efficiency only at low‐volume flow rates. The performance of the inlet was evaluated in a test chamber, and the optimum dimensions of the particle cup impactor were determined by varying the nozzle‐to‐cup distance. Additional experiments covering flow rates between 3 and 10 l/min with particle sizes between 0.8 and 5.0 μm were carried out in the test chamber. The performance indicated that a nozzle‐to‐cup distance of 1.1 mm would yield a sharp size cutoff. The results from the tests showed that the inlet had a cutoff size of 2.55 μm in aerodynamic diameter at a flow rate of 5 l/min.
Floating-base InGaP/GaAs heterojunction phototransistors (HPTs) with low doped extrinsic base region are demonstrated. Electrical and optical characteristics of the fabricated HPTs with and without SiN x passivation are investigated. Moreover, the optical gain of these HPTs is compared in terms of variation of the emitter size. The SiN x passivated HPTs with 50×50 Pm 2 of emitter size showed the superior high optical gain. The devices exhibited very high optical gain of 159 at optical power of 100 nW under 635 nm illumination.
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