Thermal Performance of Building Roof with Infrared Reflective Coatings

This paper investigated the applicability and effects of infrared reflective coating on energy con-sumption of factory building in hot summer and warm winter zone. It first resorted to theoretical calculation, which demonstrated the beneficial effects of infrared reflective coating on reducing building energy consumption. Then it analyzed a field measurement done on two identical rooms respectively with ordinary coated roof and in-frared reflective coated roof from November 2006 to October 2007, on a 24h basis. The measured data include exterior and interior roof surface temperature, indoor air temperature, and indoor globe temperature. The relat-ed weather data is from a weather station near the measured area. The continuous measurement has been accom-plished in southern China, and the measured data indicate that roof surface temperature and heat gain are signifi-cantly decreased in summer while slight negative effects in winter are induced by adopting infrared reflective coating. Thus it is simple and applicable to reduce building energy consumption in this area by applying infrared reflective coating. Regress equation between reduced roof thermal property, such as surface temperature and heat gain, and reduction in absorbed solar radiation shows their highly linear relationship. Based on the mea-sured data, it is estimated that the reduced power consumption is 3.45 kWh/m2·month in June.     

Superconducting nanowire single-photon detection system and demonstration in quantum key distribution

We developed a superconducting nanowire single-photon detection(SNSPD) system based on Gifford-McMahon cryocooler for quantum communication applications.Environmental factors which may influence the system performance are intensively studied.Those factors include temperature fluctuations,the ambient magnetic field and the background radiation.By optimizing the bias circuit,the stability of SNSPD system to electrical noise and disturbance was effectively enhanced,thus making it more suitable for field application.A 4-channel SNSPD system with quantum efficiency higher than 4% at the dark count rate of 10 Hz for λ=1550 nm is integrated and applied into a quantum key distribution(QKD) experiment.QKD was successfully carried out over 100 km optical fiber with the final secure key rate of 1.6 kbps and the quantum bit error rate of less than 2%.