ABSTRACT
A new method using three dimensions of cloud continuity, including range dimension, Doppler dimension, and time dimension, is proposed to discriminate cloud from noise and detect more weak cloud signals in vertically pointing millimeter-wave cloud radar observations by fully utilizing the spatiotemporal continuum of clouds. A modified noise level estimation method based on the Hildebrand and Sekhon algorithm is used for more accurate noise level estimation, which is critical for weak signals. The detection method consists of three steps. The first two steps are performed at the Doppler power spectrum stage, while the third step is performed at the base data stage. In the first step, a new adaptive spatial filter combined with the Kuwaraha filter and the Gaussian filter, using the ratio of mean to standard deviation as the adaptive parameter, is applied to initially mask the potential cloud signals to improve the detection performance at the boundary of cloud and noise. Simulations of boundary cases were performed to compare our adaptive filter and normal Gaussian filters. Box filters are used in steps two and three to remove the remaining noise. We applied our method to cloud radar observations with TJ-II cloud radar at the Nanjing University of Information Science & Technology. The results showed that our method can detect more weak cloud signals than the usual methods, which are performed only at the Doppler power spectrum stage or the base data stage.
ABSTRACT
It is important to monitor the take-off and landing of civil aircraft using passive detection methods. Due to the strict aircraft safety requirements and the electromagnetic environment around an airport, using too many active detection methods should be avoided. Using an aircraft's microwave radiation signal detection is very advantageous because it does not actively emit signals and has a strong cloud penetration, suitable for all-weather observation. This paper introduces a synthetic aperture microwave radiation system for monitoring the take-off and landing of civil aircraft, which is characterized by real-time two-dimensional imaging, and the image refresh rate can reach 10 ms, which meets the high refresh rate requirements for aircraft imaging. Applicable system parameters and antenna array distribution scheme and imaging algorithm are given. Then the paper focuses on the error analysis and correction method of the system. The correction method is simple and fast, which avoids the disadvantage that the error needs to be corrected regularly in the laboratory environment, and is suitable for airport application. Finally, the simulation and experimental results show that this technology can be used for real-time monitoring of civil aircraft during take-off and landing, and it is a practical means to assisting landing.
ABSTRACT
The monolithic integration of light-emission with a standard logic transistor is a much-desired multifunctionality. Here, a high-efficiency light-emitting transistor (LET) employing an inorganic quantum dots (QDs) emitter and a laser-annealed vertical metal-oxide heterostructure is reported. The experimental results show that the peak efficiency and luminance of this QDs LET (QLET) are 11% and 8000 cdm-2 , respectively at a monochromatic emitting light wavelength of 585 nm. As far as it is known, these are among the highest values ever achieved for LETs. More importantly, the QLET exhibits an ultrahigh electron mobility of up to 25 cm2 V-1 S-1 , a lower efficiency roll-off (7% at high 3000 cdm-2 ), and excellent stability with long-duration gate stress switching cycles. Additionally, this approach is compatible with those used in conventional large-area silicon electronic manufacturing and can enable a scalable and cost-effective procedure for future integrated versatile displays and lighting applications.
