Development and application of high-precision multifunction astronomical plate digitizers in China

Before charge-coupled device detectors became widely employed in observational astronomy,for more than a hundred years,the main detection method was photography on astronomical glass plates.Recently,in order to preserve these historical data and maintain their usability,the International Astronomical Union has appealed to all countries for global digitization of astronomical plates by developing or adopting advanced digitization technology.Specialized digitizers with high precision and high measuring speed represent key equipment for this task.The Shanghai Astronomical Observatory and the Nishimura Co.,Ltd in Japan cooperated between 2013 and 2016 to develop the first Chinese high-precision astronomical plate digitizer,which was then used for complete digitization of all nighttime-observation astronomical plates in China.Then,in 2019–2021,the Shanghai Astronomical Observatory independently developed new models of plate digitizers that enabled countries such as Uzbekistan and Italy to digitize their astronomical plates.Additionally,a new high-precision and multifunction digitizer was also used to digitize valuable microscope slides from the Shanghai Natural History Museum,providing a successful example of cross-domain application of high-precision digitization technology.

Two-Layer Information Granulation:Mapping-Equivalence Neighborhood Rough Set and Its Attribute Reduction

Attribute reduction,as one of the essential applications of the rough set,has attracted extensive attention from scholars.Information granulation is a key step of attribute reduction,and its efficiency has a significant impact on the overall efficiency of attribute reduction.The information granulation of the existing neighborhood rough set models is usually a single layer,and the construction of each information granule needs to search all the samples in the universe,which is inefficient.To fill such gap,a new neighborhood rough set model is proposed,which aims to improve the efficiency of attribute reduction by means of two-layer information granulation.The first layer of information granulation constructs a mapping-equivalence relation that divides the universe into multiple mutually independent mapping-equivalence classes.The second layer of information granulation views each mapping-equivalence class as a sub-universe and then performs neighborhood informa-tion granulation.A model named mapping-equivalence neighborhood rough set model is derived from the strategy of two-layer information granulation.Experimental results show that compared with other neighborhood rough set models,this model can effectively improve the efficiency of attribute reduction and reduce the uncertainty of the system.The strategy provides a new thinking for the exploration of neighborhood rough set models and the study of attribute reduction acceleration problems.

3D multiphysic simulations of energy field and material process in radial ultrasonic rolling electrochemical micromachining

The radial ultrasonic rolling electrochemical micromachining(RUR-EMM)combined rolling electrochemical micromachining(R-EMM)and ultrasonic vibration was studied in this paper.The fundamental understanding of the machining process especially the interaction between multiphysics in the interelectrode gap(IEG)was investigated and discussed by the finite element method.The multiphysics coupling model including flow field model,Joule heating model,material dissolution model and vibration model was built.3D multiphysics simulation based on micro dimples process in RUR-EMM and R-EMM was proposed.Simulation results showed that the electrolyte flowed into and out IEG periodically,gas bubbles were easy to squeeze out and the gas void fraction deceased about 16%to 54%,the maximum current density increased by 1.36 times in RUR-EMM than in R-EMM in one vibration period of time.And application of the ultrasonic vibration increased the electrolyte temperature about 1.3–4.4%in IEG.Verification experiments of the micro dimple process denoted better corrosion consistency of array dimples in RUR-EMM,there was no island at the micro dimple bottom which always formed in R-EMM,and an aggregated deviation of less than 8.7%for the micro dimple depth and 4%for the material removal amount between theory and experiment was obtained.