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Bounded Evaluation:Querying Big Data with Bounded Resources

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International Journal of Automation and computing 2020年第4期17卷 502-526页

作者： Yang Cao wen-fei Fan Teng-fei Yuan University of Edinburgh Edinburg EH89ABUKUniversity of EdinburghEdinburg EH89ABUK Shenzhen Institute of Computing Sciences Shenzhen UniversityShenzhen 518060China Beijing Advanced Innovation Center for Big Data and Brain Computing Beihang UniversityBeijing 100191China

This work aims to reduce queries on big data to computations on small data,and hence make querying big data possible under bounded resources.A query Q is boundedly evaluable when posed on any big dataset D,there exists a fraction DQ of D such that Q(D)=Q(DQ),and the cost of identifying DQ is independent of the size of *** has been shown that with an auxiliary structure known as access schema,many queries in relational algebra(RA)are boundedly evaluable under the set semantics of *** paper extends the theory of bounded evaluation to RAaggr,i.e.,RA extended with aggregation,under the bag semantics.(1)We extend access schema to bag access schema,to help us identify DQ for RAaggr queries Q.(2)While it is undecidable to determine whether an RAaggr query is boundedly evaluable under a bag access schema,we identify special cases that are decidable and practical.(3)In addition,we develop an effective syntax for bounded RAaggr queries,i.e.,a core subclass of boundedly evaluable RAaggr queries without sacrificing their expressive power.(4)Based on the effective syntax,we provide efficient algorithms to check the bounded evaluability of RAaggr queries and to generate query plans for bounded RAaggr queries.(5)As proof of concept,we extend PostgreSQL to support bounded *** experimentally verify that the extended system improves performance by orders of magnitude.

关键词： Bounded evaluation resource-bounded query processing effective syntax access schema boundedness

Speech Magnitude Spectrum Reconstruction from MFCCs Using Deep Neural Network

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Chinese Journal of Electronics 2018年第2期27卷 393-398页

作者： JIANG wenbin LIU Peilin wen fei Department of Electronic Engineering Shanghai Jiao Tong University Air Control and Navigation Institution Air Force Engineering University

This work proposes a Deep neural network(DNN) based method for reconstructing speech magnitude spectrum from Mel-frequency cepstral coefficients(MFCCs). We train a DNN using MFCC vectors as input and the corresponding speech magnitude spectrum as desired output. Exploiting the strong inference power of DNN, the proposed method has the capability to accurately estimate the speech magnitude spectrum even from truncated MFCC vectors. Experiments on TIMIT corpus demonstrate that the proposed method achieves significantly better performance compared with traditional methods.

关键词： Deep neural network(DNN) Mel-frequency cepstral coefficients(MFCCs) Spectrum reconstruction Speech reconstruction

Effect of non-stationary accretion on spectral state transitions:An example of a persistent neutron star LMXB 4U 1636–536

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Research in Astronomy and Astrophysics 2018年第3期18卷 91-98页

作者： Hui Zhang wen-fei Yu Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences

Observations of black hole and neutron star X-ray binaries show that the luminosity of the hard-to-soft state transition is usually higher than that of the soft-to-hard state transition,indicating additional parameters other than mass accretion rate are required to interpret spectral state *** has been found in some individual black hole or neutron star soft X-ray transients that the luminosity corresponding to the hard-to-soft state transition is positively correlated with the peak luminosity of the following soft state. In this work,we report the discovery of the same correlation in the single persistent neutron star low mass X-ray binary（LMXB） 4 U 1636–536 based on data from the All Sky Monitor（ASM） on board RXTE,the Gas Slit Camera（GSC） on board MAXI and the Burst Alert Telescope（BAT） on board Swift. We also found such a positive correlation holds in this persistent neutron star LMXB in a luminosity range spanning about a factor of four. Our results indicate that non-stationary accretion also plays an important role in driving X-ray spectral state transitions in persistent accreting systems with small accretion flares,which is much less dramatic compared with the bright outbursts seen in many Galactic LMXB transients.

关键词： accretion accretion disks - X-rays binaries - stars neutron

Measuring fine molecular structures with luminescence signal from an alternating current scanning tunneling microscope

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Communications in Theoretical Physics 2022年第12期74卷 52-61页

作者： fei wen Guohui Dong Hui Dong Graduate School of China Academy of Engineering Physics Beijing 100084China School of Physics and Electronic Engineering Sichuan Normal UniversityChengdu 610068China

In scanning tunneling microscopy-induced luminescence(STML),the photon count is measured to reflect single-molecule properties,e.g.,the first molecular excited *** energy of the first excited state is typically shown by a rise of the photon count as a function of the bias voltage between the tip and the *** remains a challenge to determine the precise rise position of the current due to possible experimental *** this work,we propose an alternating current version of STML to resolve the fine structures in the photon count *** measured photon count and the current at the long-time limit show a sinusoidal *** zero-frequency component of the current shows knee points at the precise voltage as the fraction of the detuning between the molecular gap and the DC component of the bias *** propose to measure the energy level with discontinuity of the first derivative of such a zero-frequency *** current method will extend the application of STML in terms of measuring molecular properties.

关键词： alternating current scanning tunneling microscope inelastic electron scattering single-molecule electroluminescence molecular energy levels

Power spectral properties of the soft spectral states in four black hole transients

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Research in Astronomy and Astrophysics 2021年第7期21卷 143-154页

作者： Dong-Ming Mao wen-fei Yu Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China University of Chinese Academy of Sciences Beijing 100049China

The X-ray variability in the soft X-ray spectral state of black hole binaries is primarily characterized by a power-law noise(PLN), which is thought to originate from the propagation of the modulation in the mass accretion rate of a standard accretion disk flow. Such a PLN has also been revealed in the disk spectral component in the hard and the intermediate states in several black hole binaries. Here we present an investigation of the Rossi X-ray Timing Explorer(RXTE) observations of four black hole transients in which soft spectral states were observed twenty times or more. We show that in the soft spectral state, the PLN index varied in a large range between –1.64 and –0.62, and the fractional rms variability calculated in the 0.01 – 20 Hz frequency range reached as large as 7.67% and as low as 0.83%. Remarkably,we have found evidence of an inclination dependence of the maximal fractional rms variability, the averaged fractional rms variability and the fractional rms variability of the median in the sample based on current knowledge of inclination of black hole binaries. An inclination dependence has only been predicted in early magnetohydrodynamic simulations of isothermal disks limited to a high-frequency regime. In theory,the noise index is related to the physics of inward propagation of disk fluctuations, while the fractional rms amplitude reflects the intrinsic properties of the magnetohydrodynamic nature of the accretion *** results therefore suggest that X-ray variability in the soft state can be used to put constraints on the properties of the accretion flow as well as the inclination of the accretion disk.

关键词： X-rays:general X-rays:binaries X-rays:individual:4U 1630-47 H 1743-322 XTE J1817-330 XTE J1859+226

Effect of tempering on bonding characteristics of cross wedge rolling 42CrMo/Q235 laminated shafts

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Journal of Iron and Steel Research International 2020年第10期27卷 1170-1178页

作者： Shuai Zhu wen-fei Peng Xue-dao Shu Zhejiang Provincial Key Laboratory of Part Rolling Technology Ningbo UniversityNingbo 315211ZhejiangChina

To further improve the comprehensive properties of 42CrMo/Q235 laminated shafts produced by cross wedge *** treatment of the shafts was *** and bending tests were carried out to compare the changes in mechanicalproperties before and after heat *** results showed that the interfacial bonding strength increased most aftertempering at 350℃for 45 *** microstructure of the interface was observed using a digital *** resultsshowed that the dispersed oxides on the interface were basically eliminated by using the scheme of tempering at 350 cand holding for 45 *** reasons for the change in mechanical properties were explained from the point of theinterfacial *** electron microscopy was used to analyze the micro-morphology of the tensile *** was observed that after tempering at 350℃and holding for 45 min,the dimple holes became larger and deeper,and thestructure of fracture became more uniform and *** the point of the tensile fracture *** reasons for thechange in mcchanical propcrties wcrc explained as well.

关键词： Heat treatment Cross wedge rolling Interface Microstructure Fracture morphology

In vitro Transient Expression System of Latex C-serum was used for Analysis of Hevein Promoter in Response to Abscisic Acid in Hevea brasiliensis

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Journal of Integrative Plant Biology 2008年第3期50卷 338-344页

作者： Xiao-wen fei Xiao-Dong Deng Institute of Tropical Bioscience and Biotechnology Chinese Agricultural Academy for Tropical Crops Haikou 571101 China Department of Biochemistry Hainan Medical College Haikou 571101 China

Hevein has been found to be an essential element in coagulation of rubber particles in latex of rubber trees. In a previous study, we cloned a 1 241-bp fragment of a 5＇ upstream region of the hevein gene by genome walking. This fragment was analyzed by a 5＇ end nested deletion method in the present study, fused with a uidA （gus） gene to produce a series of tested constructs, which were transferred into C-serum of latex and the Gus activities were detected. Results showed that the fragment from -749 to -292 was sufficient for expression of gus gene in latex, and the fragment from -292 to -168 was crucial in response to abscisic acid inducement. In a transient transgenic test of rubber leaf with particle bombardment, construct Hev749 conferred gus-specific expression in veins, in which the latex tubes mainly distributed. This implies that the fragment from -749 to -292 was laticiferous-specific.

关键词： abscisic acid gus (beta-glucuronidase) gene hevein promoter rubber tree (Hevea brasiliensis)

Exploiting Pre-Trained Network Embeddings for Recommendations in Social Networks

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Journal of Computer Science & Technology 2018年第4期33卷 682-696页

作者： Lei Guo Yu-fei wen Xin-Hua Wang Postdoctoral Research Station of Management Science and Engineering Shandong Normal University Jinan 250014 China School of Management Science and Engineering Shandong Normal University Jinan 250014 China School of Information Science and Engineering Shandong Normal University Jinan 250014 China

Recommender systems as one of the most efficient information filtering techniques have been widely studied in recent years. However, traditional recommender systems only utilize user-item rating matrix for recommendations, and the social connections and item sequential patterns are ignored. But in our real life, we always turn to our friends for recommendations, and often select the items that have similar sequential patterns. In order to overcome these challenges, many studies have taken social connections and sequential information into account to enhance recommender systems. Although these existing studies have achieved good results, most of them regard social influence and sequential information as regularization terms, and the deep structure hidden in social networks and rating patterns has not been fully explored. On the other hand, neural network based embedding methods have shown their power in many recommendation tasks with their ability to extract high-level representations from raw data. Motivated by the above observations, we take the advantage of network embedding techniques and propose an embedding-based recommendation method, which is composed of the embedding model and the collaborative filtering model. Specifically, to exploit the deep structure hidden in social networks and rating patterns, a neural network based embedding model is first pre-trained, where the external user and item representations are extracted. Then, we incorporate these extracted factors into a collaborative filtering model by fusing them with latent factors linearly, where our method not only can leverage the external information to enhance recommendation, but also can exploit the advantage of collaborative filtering techniques. Experimental results on two real-world datasets demonstrate the effectiveness of our proposed method and the importance of these external extracted factors.

关键词： social recommendation network embedding matrix factorization item sequential pattern

Modulation of Amyloid-β Conformation by Charge State of N-Terminal Disordered Region

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Chinese Physics Letters 2012年第8期29卷 288-291页

作者： XI wen-Hui LI wen-fei WANG Wei National Laboratory of Solid State Microstructure and Department of PhysicsNanjing UniversityNanjing 210093

Based on molecular dynamics simulations,we show that variations of the charge states of the histidines,which are the main effects of pH-value change and metal binding,can lead to a drastic change of the intra-peptide interactions of the segment 17–42 and the conformational distribution of the monomeric amyloid-β(Aβ).Since we already knew that the conformational distribution of monomeric Aβcan largely affect Aβfibrillar aggregation,our results suggest that the pH value change and metal binding can affect the Aβaggregation by much more complex mechanism than just affecting the inter-peptide *** fully understand the mechanism of metal binding and pH-value induced Aβaggregation,we also need to consider their effects on the conformational distribution of monomeric Aβ.

关键词： aggregation conformational value