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Composite recommendations： from items to packages

Frontiers of Computer Science 2012年第3期6卷 264-277页

作者： min xie Laks V. S. LAKSHMANAN Peter T. WOOD Department of Computer Science University of British Columbia Vancouver V6T 1Z4 Canada Department of Computer Science and Information Systems Birkbeck University of London London WCIE 7HX UK

Classical recommender systems provide users with a list of recommendations where each recommendation consists of a single item, e.g., a book or DVD. However, sev- eral applications can benefit from a system capable of recom- mending packages of items, in the form of sets. Sample appli- cations include travel planning with a limited budget （price or time） and twitter users wanting to select worthwhile tweeters to follow, given that they can deal with only a bounded num- ber of tweets. In these contexts, there is a need for a system that can recommend the top-k packages for the user to choose from. Motivated by these applications, we consider composite recommendations, where each recommendation comprises a set of items. Each item has both a value （rating） and a cost associated with it, and the user specifies a maximum total cost （budget） for any recommended set of items. Our composite recommender system has access to one or more component recommender systems focusing on different do- mains, as well as to information sources which can provide the cost associated with each item. Because the problem of deciding whether there is a recommendation （package） whose cost is under a given budget and whose value exceeds some threshold is NP-complete, we devise several approximation algorithms for generating the top-k packages as recommen- dations. We analyze the efficiency as well as approximation quality of these algorithms. Finally, using two real and two synthetic datasets, we subject our algorithms to thorough ex- perimentation and empirical analysis. Our findings attest tothe efficiency and quality of our approximation algorithms for the top-k packages compared to exact algorithms.

关键词： recommendation algorithms optimization,top-k query processing

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Selective laser melting of bulk immiscible alloy with enhanced strength:Heterogeneous microstructure and deformation mechanisms

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Journal of Materials Science & Technology 2022年第9期104卷 81-87页

作者： Shengfeng Zhou min xie Changyi Wu Yanliang Yi Dongchu Chen Lai-Chang Zhang MOE Key Lab of Disaster Forecast and Control in Engineering Jinan UniversityGuangzhou 510632China School of Materials Science and Engineering Tianjin Polytechnic UniversityTianjin 300387China Department of Educational Science Hunan First Normal UniversityChangsha 410205China School of Materials Science and Energy Engineering Foshan UniversityFoshan 528225China School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia

To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting(SLM).The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaledγ-Fe particles dispersed in fineε-Cu matrix with a high fraction(~92%)of high-angle grain ***,abundant nanotwins and stacking faults are generated in the interior of nano-scaledγ-Fe particles embedded withinε-Cu *** heterogeneous interface of soft domains(ε-Cu)and hard domains(γ-Fe)not only induces the geometrically necessary dislocations(GNDs)but also affects the dislocation propagation during plastic ***,the bimodal heterogeneous interface,and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of~590 MPa and a good ductility of~8.9%.

关键词： Immiscible alloy Selective laser melting Heterogeneous microstructure Nanotwins Stacking faults

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Stochastic Volatility Modeling based on Doubly Truncated Cauchy Distribution and Bayesian Estimation for Chinese Stock Market

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Acta Mathematicae Applicatae Sinica 2023年第4期39卷 791-807页

作者： Cai-feng WANG Cong xie Zi-yu MA Hui-min ZHAO School of Mathematics and Physics University of Science and Technology BeijingBeijing 100083China School of Business Sun Yat-sen UniversityGuangzhou 510275China

In order to measure the uncertainty of financial asset returns in the stock market, this paper presents a new model, called SV-dt C model, a stochastic volatility(SV) model assuming that the stock return has a doubly truncated Cauchy distribution, which takes into account the high peak and fat tail of the empirical distribution simultaneously. Under the Bayesian framework, a prior and posterior analysis for the parameters is made and Markov Chain Monte Carlo(MCMC) is used for computing the posterior estimates of the model parameters and forecasting in the empirical application of Shanghai Stock Exchange Composite Index(SSECI) with respect to the proposed SV-dt C model and two classic SV-N(SV model with Normal distribution)and SV-T(SV model with Student-t distribution) models. The empirical analysis shows that the proposed SV-dt C model has better performance by model checking, including independence test(Projection correlation test), Kolmogorov-Smirnov test(K-S test) and Q-Q plot. Additionally, deviance information criterion(DIC) also shows that the proposed model has a significant improvement in model fit over the others.

关键词： stochastic volatility model doubly truncated Cauchy distribution Bayesian estimation Markov Chain Monte Carlo method deviance information criterion

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Homopolypeptide Vesicles Triggered by Side-Chain Hydration

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Chinese Journal of Polymer Science 2022年第12期40卷 1631-1639,I0009页

作者： Xin-Jie Shi Zhen Liu Yang-Chun xie min Xu Xiao-Hua He School of Chemistry and Molecular Engineering East China Normal UniversityShanghai 200241China School of Physics and Electronic Science Shanghai Key Laboratory of Magnetic ResonanceEast China Normal UniversityShanghai 200241China

The formation of homopolypeptide vesicles and the identification of their self-assembly mechanism have been challenging issues in the field of polymer self-assembly. Using complementary circular dichroism(CD), Fourier transform infrared(FTIR) and low-field nuclear magnetic resonance(LF-NMR) spectroscopies, in this study we show that the higher hydrophilic ability of side-chains is a key factor for the formation of homopolypeptide vesicles from homo poly(Nε-carbobenzoxy-L-lysine)(PZlys), in which the vesicular structures are confirmed by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and atomic force microscopy(AFM) measurements. Poly(γ-benzyl-Lglutamate-co-Nε-carbobenzoxy-L-lysine) [P(BLG-co-Zlys)] containing different molar ratios of BLG to Zlys units with the same peptide backbone as PZlys are used as the controls. The copolypeptides can only form micelles under the same conditions, due to the more hydrophobic nature of their side-chains. These results show that the specific side-chain structure of the polypeptides plays a fundamental role in the self-assembly of homopolypeptides. These findings can be useful to understand how the hydrophilicity of the side chains of amino acid residues on the surface of a protein affects its structures.

关键词： Polypeptide Vesicle Self-assembly Hydrophobic Micelle

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Performance evaluation of the use of tire-derived fuel fly ash as mineral filler in hot mix asphalt concrete

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Journal of Traffic and Transportation Engineering(English Edition) 2020年第2期7卷 249-258页

作者： min ju Choi Yong Joo Kim Hyeok jung Kim Jae jun Lee BILTZONE Co. Ltd.Hwaseong 18514South Korea Korea Institute o f Civil Engineering and Building Technology Goyang-Si 10223South Korea Industry-Academic Cooperation Foundation Center Hankyong National UniversityAnseong-si 17579South Korea Department of Civil Engineering Chonbuk National UniversityJeonju 54896South Korea

According to deplete natural resources and need to protect the environment,the demand of a usage of waste material has significantly *** studies are currently being carried out on the development of innovative and environmentally friendly materials for securing the safety of road users and improving the performance and durability of *** example,studies are currently being conducted on the use of waste tires as a substitute for currently used *** the development of the automobile industry,the amount of waste tire has continuously increased in accordance with the increased vehicle ***-derived fuel(TDF)has been used as a fuel source with generated TDF fly *** filler,made of fine mineral particles of a physical size passing the number 200 standard mesh sieve(75 micron),plays an important role in asphalt mixtures *** paper presents an application of TDF fly ash as filler in hot mix asphalt(HMA).In this study,the performance of TDF fly ash was confirmed through a comparison with three other mineral fillers:stone dust,cement,and hydrated *** tests including Marshall stability test,moisture sensitivity test,dynamic immersion test,and a wheel tracking test were performed to investigate the difference in the behaviors of the samples with different parameters considered in this *** results show that the mechanical performance of hot mix asphalt using TDF fly ash satisfied the quality standard specification of the ministry of Land,Infrastructure and Transport(MOLIT),*** can be concluded that the use of TDF fly ash as a mineral filler in HMA not only satisfied the mechanical properties,but also reduced the volume of the pollutants waste in the environment.

关键词： Asphalt mixture TDF fly ash Marshal stability Moisture sensitive TSR

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TRAFFIC EMISSION TRANSPORTATION IN STREET CANYONS

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Journal of Hydrodynamics 2009年第1期21卷 108-117页

作者： xie Xiao-min WANG Jia-song HUANG Zhen Key Laboratory for Power Machinery and Engineering of State Education ministry Shanghai Jiao Tong University Shanghai 200240 China

Spatial distributions of traffic-related pollutants in street canyons were investigated by field measurements and Computational Fluid Dynamics （CFD）. Two typical street canyons were selected for field monitoring, and a three-dimensional numerical model was built based on Reynolds-averaged Navier-Stokes equations equipped with the standard κ-ε turbulence models for CFD simulations. The study shows that the pollutant concentrations of vehicle emission correlate well with the traffic volume variation, wind direction and wind speed. The wind direction and speed at the roof level determine overwhellmingly the flow field and the distributions of pollutant concentrations in the street canyon. When the wind speed is equal to zero, the pollutant concentrations on the breath height of the both sides of the street canyon are almost the same. When the wind direction is perpendicular to the street, one main vortex is formed with a shape depending on the building structure on both sides of the street, the pollutant is accumulated on the leeward side, and the pollutant concentrations at the breath height on the leeward side are 2 to 3 times as those at the breath height on the windward side. If the wind direction makes some angles with the street canyon, the pollutant concentration will be higher on the leeward side because one main vortex will also be formed in the vertical section of the canyon by the perpendicular component of the wind. But pollutant concentrations decrease in the canyon because pollutants are dispersed along the axis of the street. Pollutants at different heights of the vertical section decrease with height, i.e. there are concentration gradients in the vertical section, and the pollutant concentrations on the leeward side of the upstream building are much higher than those on the windward side of the downstream building.

关键词： traffic emission street canyon field measurement CFD modeling

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Research on space-time coupling action laws of anchor-cable strengthening supporting for rock roadway in deep coal mine

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Journal of Coal Science & Engineering(China) 2012年第2期18卷 113-117页

作者： CHANG ju-cai xie Guang-xiang Key Laboratory of Safe and High Efftciency mining Ministry of EducationAnhui University of Science and TechnologyHuainan 232001China

In order to obtain space-time coupling relationship of anchor-cable to improve supporting effect for deep coal mine rock roadway, FLAC3D was used to investigate into mechanical characteristics of the roadway whose crosssection shape was vertical wall and semi-circular arch when the roadway was supported by bolts and metal mesh. The results show that the extent of stress concentrations, the range failure zone, and the deformation at the roof center and two spandrels of roadway are greater than those at other positions, except at the floor. The reasonable positions of anchor-cable supporting are the roof center and two spandrels of roadway. The anchor-cable should be installed at good time with bolts supporting after roadway driving be- cause it can improve the stress states of deep surrounding rock around the roadway and control the roadway deformation effec- tively. The engineering practice has proven that the sustained deformation of deep surrounding rocks is effectively controlled when the anchor-cable supporting is adopted at reasonable positions of the roadway at good time.

关键词： space-time coupling relationship anchor-cable supporting deep coal mine rock roadway

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A practical synthesis of a new series of isoflavanones

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Chinese Chemical Letters 2012年第8期23卷 907-910页

作者： ju Na Liu Shu Rong Ban Hong Yu xie Qing Shan Li School of Pharmaceutical Science Shanxi Medical UniversityTaiyuan 030001China

A practical six-step synthesis of 12 methylated and hydroxylated isoflavanones was accomplished starting from readily available m-xylene. A significant improvement of this procedure included application of the simple and commercially available reagents, avoidance of expensive reagents and catalysts, simple operations and excellent yields.

关键词： Deoxybenzoins Isoflavanones Synthesis

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e^(+)e^(-)→Λ_(c)+Λ_(c)^(- ) Cross Sections and the Λ_(c)^(+) Electromagnetic Form Factors within the Extended Vector Meson Dominance Model

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Chinese Physics Letters 2024年第2期41卷 36-41页

作者：陈诚闫冰谢聚军 Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Sciences and Technology University of Chinese Academy of SciencesBeijing 101408China College of Mathematics and Physics Chengdu University of TechnologyChengdu 610059China Southern Center for Nuclear-Science Theory(SCNT) Institute of Modern PhysicsChinese Academy of SciencesHuizhou 516000China

Within the extended vector meson dominance model,we investigate the𝑒e^(+)e^(-)→Λ_(c)+Λ_(c)^(- ) reaction and the electromagnetic form factors of the charmed baryon𝛬 Λ_(c)^(+)𝑐.The model parameters are determined by fitting them to the cross sections of the process𝑒e^(+)e^(-)→Λ_(c)+Λ_(c)^(- ) and the magnetic form factor|G_(M)|of Λ_(c)^(+) .By considering four charmonium-like states,called𝜓(4500),𝜓(4660),𝜓(4790),and𝜓(4900),we can well describe the current data on the𝑒e^(+)e^(-)→Λ_(c)+Λ_(c)^(- ) reaction from the reaction threshold up to 4.96 *** addition to the total cross sections and|𝐺M|,the ratio|G_(E)/G_(M)|and the effective form factor|Geff|for Λ_(c)^(+) 𝑐are also calculated,and found that these calculations are consistent with the experimental *** the fitted model parameters,we have also estimated the charge radius of the charmed Λ_(c)^(+) baryon.

关键词： fitted radius meson

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Hyper-crosslinked Conjugated Microporous Polymers with Increased Micropores Promotes Confining Polymerization for Electromagnetic Absorption Application

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Chinese Journal of Polymer Science 2023年第8期41卷 1305-1316,I0011页

作者： Hao Chen Fang-Yuan Chu Hai-Yan Zhuang Lu Wang Zhi-min Ye Wei Dong Zhi-Peng xie A-ming xie School of Mechanical Engineering Nanjing University of Science&TechnologyNanjing 210094China State Key Laboratory for Marine Corrosion and Protection Luoyang Ship Material Research Institute(LSMRI)Xiamen 361100China School of Chemistry and Chemical Engineering Nanjing University of Science&TechnologyNanjing 210094China

Conjugated microporous polymers have excellent skeleton structures but poor electrical conductivity limits their applications in microwave *** solve this problem,a strategy of molecular expansion and confining polymerization is proposed in this work to synthesize conductive hyper-crosslinked conjugated microporous *** topology of the conjugated microporous polymer is changed into a three-dimensional skeleton structure with high specific surface area by using molecular expansion technique,and the controlled growth of polypyrrole in the channel constructs a unique network *** balance of excellent composite backbone structure,proper conductivity,attenuation capability and impedance matching enable the material to exhibit electromagnetic wave absorption *** a result,with low filler loading of 10 wt%,a strongest reflection loss of-52.68 d B and a maximum effective bandwidth of 5.76 ***,CST simulations of the radar scattering cross section have been carried out to verify the excellent material *** study provides new concepts for new conductive polymers and broadens the application of hyper-crosslinked conjugated microporous polymer in the field of electromagnetic wave absorption.

关键词： Hyper-crosslinked conjugated microporous polymer Electromagnetic wave absorbing Molecular expansion Polypyrrole

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