A compact free space quantum key distribution system capable of daylight operation

A free space quantum key distribution system has been demonstrated. Consideration has been given to factors such as field of view and spectral width, to cut down the deleterious effect from background light levels. Suitable optical sources such as lasers and RCLEDs have been investigated as well as optimal wavelength choices, always with a view to building a compact and robust system. The implementation of background reduction measures resulted in a system capable of operating in daylight conditions. An autonomous system was left running and generating shared key material continuously for over 7 days.     

中国不同光气候分区地面日光光谱的观测与分析

我国地域辽阔,各地光气候有很大区别,为了扩大和提高太阳能与天然光的利用范围及利用效率,采用一种便携式的光谱扫描仪,对我国不同光气候分区的7个代表性城市(昆明、西宁、北京、深圳、南京、南昌和重庆)一天中不同太阳高度角对应时刻的地面直射日光光谱在380～780 nm可见光谱段进行了跟踪观测,分析了不同光气候分区城市一天中不同太阳高度角对应时刻的日光光谱变化规律,比较了不同光气候分区城市的日光光谱曲线,总结了日光光谱辐射强度的影响因素。分析表明：不同光气候分区城市一天中不同太阳高度角对应时刻的日光光谱辐射强度不同,但日光光谱功率的分布和走向基本一致,总体呈先上升后下降的趋势,最大峰值出现在475 nm附近,380～475 nm之间光谱功率分布曲线出现陡升,475～700 nm之间曲线有下降趋势但基本平稳,＞700 nm曲线出现了反复的较大起伏;不同光气候分区城市的日光光谱功率分布曲线的分布和走向也基本一致,没有明显的与不同光气候分区直接相关的日光光谱功率分布差异性规律;日光光谱辐射强度与太阳高度角和日面状况密切相关。     

Daylight perceptive lighting and data fusion with artificial neutral network

The basic concept of daylight perceptive is that the artificial light automatically dims to the appropriate level to keep constant indoor illumination when sufficient daylight is not available. Energy efficient character of daylight perceptive lighting was analyzed and a method to evaluate energy saving was present; according to the presentation, the more energy is saved if the longer T_last—duration of indoor illumination being is less than threshold. A daylight perceptive controller was developed and the output power of LED light source under different PWM was measured, according to the measurement, work current and output power of LED is proportional to duty cycle. With two sensors, a data fusion method was put forward to exclude interference and improve lighting comfort. With more than two sensors, data fusion based on neutral network was discussed.     

Influence of summer daylight saving time on scattered erythemal solar ultraviolet exposures

The research question of whether there are any influences in the scattered or diffuse erythemal UV exposures to a horizontal plane over a five month period due to the change from standard time to daylight saving time, has been investigated by using physical measurements and applying them to both standard time and daylight saving time. The diffuse erythemal UV was considered for fixed lunch break times and fixed morning and afternoon break times. The cases considered were for groups of the population who are predominantly indoors and who spend their break times outdoors in shade. The biggest influence on the diffuse UV exposures of changing to daylight saving time is the timing of the outdoor meal and break times. The change causes a reduction in diffuse erythemal exposure for early or morning breaks and an increase in the diffuse erythemal exposure for late or afternoon breaks. Similarly, for the lunch break times, the changes in exposure are influenced by the timing of the break with respect to solar noon. Indoor workers who take their breaks outside in a shaded area may have a change in their exposure to diffuse UV due to a shift to daylight saving time, however the magnitude of this change and whether it is a positive or negative change in exposure will depend on the timing of the break. The increase in diffuse UV exposure due to the afternoon break may be negated by the decrease in exposure due to the morning break. In this case, the effect on diffuse UV exposures due to changing to daylight saving time will be minimal.