41 research outputs found
CHES: a space-borne astrometric mission for the detection of habitable planets of the nearby solar-type stars
The Closeby Habitable Exoplanet Survey (CHES) mission is proposed to discover
habitable-zone Earth-like planets of the nearby solar-type stars ( away from our solar system) via micro-arcsecond relative
astrometry. The major scientific objectives of CHES are: to search for Earth
Twins or terrestrial planets in habitable zones orbiting 100 FGK nearby stars;
further to conduct a comprehensive survey and extensively characterize the
nearby planetary systems. The primary payload is a high-quality,
low-distortion, high-stability telescope. The optical subsystem is a coaxial
three-mirror anastigmat (TMA) with a -aperture, field of view and
working waveband. The camera focal plane is composed of 81 MOSAIC scientific
CMOS detectors each with pixels. The
heterodyne laser interferometric calibration technology is employed to ensure
micro-arcsecond level (1 as) relative astrometry precision to meet the
requirements for detection of Earth-like planets. CHES satellite operates at
the Sun-Earth L2 point and observes the entire target stars for 5 years. CHES
will offer the first direct measurements of true masses and inclinations of
Earth Twins and super-Earths orbiting our neighbor stars based on
micro-arcsecond astrometry from space. This will definitely enhance our
understanding of the formation of diverse nearby planetary systems and the
emergence of other worlds for solar-type stars, and finally to reflect the
evolution of our own solar system.Comment: 39 pages, 37 figures, Invited Review, accepted to Research in
Astronomy and Astrophysic
Modulated Initial Resonant Current Control Strategy for Extra-<italic>LC</italic> Auxiliary-Resonant-Snubber-Based Converter to Improve Output Quality in High-Precision Applications
Improving Rice Modeling Success Rate with Ternary Non-structural Fertilizer Response Model
Fertilizer response modelling is an important technical approach to realize metrological fertilization on rice. With the goal of solving the problems of a low success rate of a ternary quadratic polynomial model (TPFM) and to expand the model's applicability, this paper established a ternary non-structural fertilizer response model (TNFM) based on the experimental results from N, P and K fertilized rice fields. Our research results showed that the TNFM significantly improved the modelling success rate by addressing problems arising from setting the bias and multicollinearity in a TPFM. The results from 88 rice field trials in China indicated that the proportion of typical TNFMs that satisfy the general fertilizer response law of plant nutrition was 40.9%, while the analogous proportion of TPFMs was only 26.1%. The recommended fertilization showed a significant positive linear correlation between the two models, and the parameters N-0, P-0 and K-0 that estimated the value of soil supplying nutrient equivalents can be used as better indicators of yield potential in plots where no N or P or K fertilizer was applied. The theoretical analysis showed that the new model has a higher fitting accuracy and a wider application range
Nighttime Cloud Cover Estimation Method at the Saishiteng 3850 m Site
Cloud cover is critical for astronomical sites because it can be used to assess the observability of the local sky and further the fractional photometric time. For cloud monitoring in site-testing campaigns with all-sky cameras, previous studies have mainly focused on moonless images, while the automatic processing methods for moonlight images are explored quite few. This paper proposes an automatic estimation method for cloud cover, which takes all cases of nighttime gray-scale all-sky images into account. For moonless images, the efficient Otsu algorithm is directly used to detect clouds. For moonlight images, they are transformed into cloud feature image using a colorization procedure, and then the Otsu algorithm is used to distinguish cloud pixels from sky pixels on the cloud feature image. The reliability of this method was evaluated on manually labeled images. The results show that the cloud cover error of this method is less than 9% in all scenarios. The fractional photometric time derived from this method is basically consistent with the published result of the Lenghu site
Nighttime Cloud Cover Estimation Method at the Saishiteng 3850 m Site
Cloud cover is critical for astronomical sites because it can be used to assess the observability of the local sky and further the fractional photometric time. For cloud monitoring in site-testing campaigns with all-sky cameras, previous studies have mainly focused on moonless images, while the automatic processing methods for moonlight images are explored quite few. This paper proposes an automatic estimation method for cloud cover, which takes all cases of nighttime gray-scale all-sky images into account. For moonless images, the efficient Otsu algorithm is directly used to detect clouds. For moonlight images, they are transformed into cloud feature image using a colorization procedure, and then the Otsu algorithm is used to distinguish cloud pixels from sky pixels on the cloud feature image. The reliability of this method was evaluated on manually labeled images. The results show that the cloud cover error of this method is less than 9% in all scenarios. The fractional photometric time derived from this method is basically consistent with the published result of the Lenghu site
Ultrahigh Throughput and Efficient Separation of Oil/Water Mixtures Using Superhydrophilic Multi-Scale CuBTC-Coated Meshes
Smart Hierarchical Zeolitic Imidazolate Framework-Coated Stainless Steel Meshes with Switchable Wettability for Oil/Water Separation
Analysis of the influence of the grounding method on the measurement of direct current total electric field on a civil housing platform
Abstract Buildings near direct current transmission lines are sensitive to the electromagnetic environment, and the measurement of the electric field above them is important in engineering design and environmental assessment in China. The models of buildings and probes in the ion flow field were established to explore the accurate measurement method of the electric field above the building. Based on the upstream finite element method and the predictor–corrector method, the influence of whether the probe was grounded or not above the building was studied. On this basis, simulation experiments and real‐type experiments were carried out. The results show that when the electrical conductivity of the building was greater than 10−10 S/m, being grounded or not would not change the results. When the building conductivity was between 10−11 and 10−12 S/m, the electric field measurement results would be increased by 30% to 120% after grounding. In the real‐type experiments on the platform with a plywood roof, the relative error in the electric field when grounded or not was only 2.6%. This proved the reliability of the calculated results. In this paper, the measuring method of the DC space charge‐modified electric field above buildings was analyzed first, and the conclusion that ground wire can be cancelled above buildings with general materials was presented. The research results can provide a technical basis for the accurate measurement of the electric field above the buildings near DC transmission lines