Study on Evaluation Method of Aluminum alloy Pulse MIG Welding Stability Based on Arc Voltage Probability Density

Bring forward a new analytical method in order to evaluate the stability of the process of aluminum alloy pulsed MIG welding. The ratio of the first and the second peak in arc voltage signal probability density was selected to evaluate aluminum alloy pulse MIG welding stability. By calculating the arc voltage signal probability density from 80 sets of welding experiments, the ratio of the two peaks in arc voltage probability in every set was captured. And the evaluation system of aluminum alloy pulse MIG welding stability was established. The smaller the ratio of peaks in arc voltage signal probability density is, the better the stability of the welding will be;the bigger the ratio of peaks in arc voltage signal probability density is, the poorer the stability of the welding will be.

Magnetic Activity and Parameters of 43 Flare Stars in the GWAC Archive

In the archive of the Ground Wide Angle Camera(GWAC),we found 43 white light flares from 43 stars,among which,three are sympathetic or homologous flares,and one of them also has a quasi-periodic pulsation with a period of 13.0±1.5 minutes.Among these 43 flare stars,there are 19 new active stars and 41 stars that have available TESS and/or K2 light curves,from which we found 931 stellar flares.We also obtained rotational or orbital periods of 34 GWAC flare stars,of which 33 are less than 5.4 days,and ephemerides of three eclipsing binaries from these light curves.Combining with low resolution spectra from LAMOST and the Xinglong 2.16 m telescope,we found that L_(Hα)/L_(bol) are in the saturation region in the rotation-activity diagram.From the LAMOST medium-resolution spectrum,we found that Star#3(HAT 178-02667)has double Hαemissions which imply it is a binary,and two components are both active stars.Thirteen stars have flare frequency distributions(FFDs)from TESS and/or K2 light curves.These FFDs show that the flares detected by GWAC can occur at a frequency of 0.5to 9.5 yr^(-1).The impact of flares on habitable planets was also studied based on these FFDs,and flares from some GWAC flare stars may produce enough energetic flares to destroy ozone layers,but none can trigger prebiotic chemistry on their habitable planets.

Related Axis: The Extension to XPath Towards Effective XML Search

We investigate the limitations of existing XML search methods and propose a new semantics, related relation- ship, to effectively capture meaningful relationships of data elements from XML data in the absence of structural constraints. Then we make an extension to XPath by introducing a new axis, related axis, to specify the related relationship between query nodes so as to enhance the flexibility of XPath. We propose to reduce the cost of computing the related relationship by a new schema summary that summarizes the related relationship from the original schema without any loss. Based on this schema summary, we introduce two indices to improve the performance of query processing. Our algorithm shows that the evaluation of most queries can be equivalently transformed into just a few selection and value join operations, thus avoids the costly structural join operations. The experimental results show that our method is effective and efficient in terms of comparing the effectiveness of the related relationship with existing keyword search semantics and comparing the efficiency of our evaluation methods with existing query engines.

Preface

Cloud computing and big data have become increasingly popular and are changing our way of thinking about the world by providing new insights and creating new forms of value. The research of cloud data management is to address the challenges in managing large collections of data in the cloud computing environment, and identifying information of value to business, science, government, and society. The huge volumes of data in cloud computing environments pose major infrastructure challenges, including data storage at Petabyte scale, massively parallel query execution, facilities for analytical processing, online query processing, resource optimization, data privacy and security.