We report for the first time the effect of ageing due to adaptive control of lighting on the lifecycle costs of luminaire installations. Two types of LED street luminaire were aged (1) as the luminaire lit for 9 hours and then switched off for 3 hours and (2) under intensive ageing using adaptive control conditions mimicking presence of vehicles, where the luminaires were switched with 30-second interval between 100% and 20% power within the cycle of (1). The test continued for 32,000 hours. Luminaire lifetime was found to decrease by 10% due to the intensive adaptive control, which exaggerates the ageing as compared to real traffic conditions. We estimate that a realistic rate of dimming cycles would decrease the luminaire lifetime by 0–2%, increasing the lifecycle costs of a lighting installation by 0–0.7%. With a traffic-aware control system, capable of 50% energy saving in lighting, the lifecycle costs are estimated to reduce by 25% as compared to a similar LED luminaire installation without traffic-aware control, outweighing the costs due to the reduced lifetime. The smart controlling of lighting is considered as a useful way to meet future energy saving targets.

The predictable quantum efficient detector (PQED) is a primary standard of optical power, which utilizes two custom-made induced-junction photodiodes that are mounted in a wedged trap configuration for the reduction of reflectance losses. PQED photodiodes of p-type and n-type were characterized for their dark current dependence on reverse bias voltage at room temperature. As simulations predict that the dark current will decrease exponentially with temperature, the temperature dependence of dark current for the n-type photodiodes was also measured. Two n-type induced-junction photodiodes were assembled inside a liquid nitrogen cryostat. The results from the dark current measurements indicate that the cooled n-type photodiodes are suitable for measuring optical fluxes in the few photon regime. A photon flux of approximately 7,000,000 photons per second was measured using the PQED at a cryogenic temperature with a relative standard uncertainty of 0.15%. The results support the utilization of the PQED as a primary standard of optical power in single and few photon applications.

This paper presents a new tristate-based delay cell to realize the recently proposed delay-based injection locking in ring oscillators. The circuit is then applied to implement a cycliccoupled ring oscillator (CCRO). Compared to an inverter-based CCRO with multi-drive injection, the proposed circuit eliminates the static short-circuit current drawn from the supply when drive circuits are in conflicting logic states, thus reducing the power consumption of the CCRO. The functionality and improved energy efficiency of the proposed circuit is demonstrated with circuit simulations of a CCRO implemented in a 28-nm CMOS process. The CCRO employing the proposed technique achieves up to 25% lower power consumption and over 20% lower powerdelay product (PDP) compared to the inverter-based CCRO.Index Terms-cyclic-coupled ring oscillator (CCRO), timedomain, time resolution, sub-gate-delay, time-to-digital converter.