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A general tail item representation enhancement framework for sequential recommendation

Frontiers of Computer science 2024年第6期18卷 137-148页

作者： Mingyue CHENG Qi LIU Wenyu ZHANG Zhiding LIU Hongke ZHAO Enhong CHEN Anhui Province Key Laboratory of Big Data Analysis and Application University of Science and Technology of China&State Key Laboratory of Cognitive IntelligenceHefei 230026China College of Management and Economics Tianjin UniversityTianjin 300072China

Recently advancements in deep learning models have significantly facilitated the development of sequential recommender systems(SRS).However,the current deep model structures are limited in their ability to learn high-quality embeddings with insufficient ***,highly skewed long-tail distribution is very common in recommender ***,in this paper,we focus on enhancing the representation of tail items to improve sequential recommendation *** empirical studies on benchmarks,we surprisingly observe that both the ranking performance and training procedure are greatly hindered by the poorly optimized tail item *** address this issue,we propose a sequential recommendation framework named TailRec that enables contextual information of tail item well-leveraged and greatly improves its corresponding *** the characteristics of the sequential recommendation task,the surrounding interaction records of each tail item are regarded as contextual information without leveraging any additional side *** approach allows for the mining of contextual information from cross-sequence behaviors to boost the performance of sequential *** a light contextual filtering component is plug-and-play for a series of SRS *** verify the effectiveness of the proposed TailRec,we conduct extensive experiments over several popular benchmark *** experimental results demonstrate that TailRec can greatly improve the recommendation results and speed up the training *** codes of our methods have been available.

关键词： sequential recommendation long-tail distribution training accelerating

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Difference analysis in terahertz wave propagation in thermochemical nonequilibrium plasma sheath under different hypersonic vehicle shapes

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Chinese Journal of Aeronautics 2023年第10期36卷 137-151页

作者： Wenchong OUYANG Qi LIU Zhengwei WU School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China Joint Laboratory of Plasma Application Technology Institute of Advanced TechnologyUniversity of Science and Technology of ChinaHefei 230031China CAS Key Laboratory of Geospace Environment University of Science and Technology of ChinaHefei 230026China

Research on terahertz communication under different vehicles has important guiding significance for the design of future hypersonic vehicle and Radio Frequency(RF)*** this paper,a joint simulation model of plasma flow under thermochemical nonequilibrium state and terahertz transmission is developed to investigate the differences in terahertz wave transmission characteristics under different vehicle shapes and the related *** comparing the plasma sheath characteristics and terahertz transmission among HIFIRE-5b(Hypersonic International Flight Research Experimentation-5b),RAM C(Radio Attenuation Measurement C)and ARD(Atmospheric Reentry Demonstrator)vehicles,it is found that the sheath thickness and electron density of ARD vehicles is significantly larger than that of HIFIRE-5b and RAM C vehicles,resulting in greater terahertz wave *** absorption plays a major role in the terahertz attenuation of vehicles,and the contribution of reflection effects is only observed in the ARD vehicle due to its larger plasma sheath thickness and spatial structure *** on the above comparison results,a shape design scheme of reducing the vehicle head and tail for mitigating RF blackout is proposed,and the scheme is proved by further analyzing the effects of different vehicle heads and tails on the terahertz *** the decrease of the head radius and tail width of hypersonic vehicle,the wave attenuation at the same terahertz frequency decreases,and the contribution of reflection effect to wave attenuation gradually ***,the shape design scheme of reducing the vehicle head and tail can effectively alleviate the RF blackout problem,which provides an important reference value for future hypersonic vehicle design.

关键词： Hypersonic vehicles Plasma flow Plasma sheaths Shape optimization Terahertz waves Wave propagation

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Response characteristics of PWR primary circuit under SBLOCAs considering steam bypass discharging

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nuclear science and Techniques 2024年第6期35卷 189-201页

作者： Shuai Yang Xiang-Bin Li Yu-Sheng Liu Jia-Ning Xu De-Chen Zhang School of Nuclear Science and Engineering North China Electric Power UniversityBeijing 102206China Beijing Key Laboratory of Passive Safety Technology for Nuclear Energy Beijing 102206China Nuclear and Radiation Safety Center MEPBeijing 100084China

Small-break superposed station blackout(SBO)accidents are the basic design accidents of nuclear power *** the condition of a small break in the cold leg,SBO further increases the severity of the accident,and the steam bypass discharg-ing system(GCT)in the second circuit can play an important role in guaranteeing core *** explore the influence of the GCT on the thermal-hydraulic characteristics of the primary circuit,RELAP5 software was used to establish a numerical model based on a typical pressurized water reactor nuclear power *** different small breaks in the cold-leg super-posed SBO were selected,and the impact of the GCT operation on the transient response characteristics of the primary and secondary circuit systems was *** results show that the GCT plays an indispensable role in core heat removal during an accident;otherwise,core safety cannot be *** GCT was used in conjunction with the primary safety injection system during the placement *** the break diameter was greater than a certain critical value,the core cooling rate could not be guaranteed to be less than 100 K/h;however,the core remained in a safe state.

关键词： Steam bypass discharging Pressurized water reactor SBLOCA Numerical simulation

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Enhancement of electron–positron pairs in combined potential wells with linear chirp frequency

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Chinese Physics B 2023年第1期32卷 153-160页

作者：王莉李烈娟麦丽开·麦提斯迪克安荣李静静谢柏松张丰收 Institute of Radiation Technology Beijing Academy of Science and TechnologyBeijing 100875China Key Laboratory of Beam Technology of Ministry of Education College of Nuclear Science and TechnologyBeijing Normal UniversityBeijing 100875China

Effect of linear chirp frequency on the process of electron–positron pairs production from vacuum is investigated by the computational quantum field *** appropriate chirp parameters,the number of electrons created under combined potential wells can be increased by two or three *** the low frequency region,frequency modulation excites interference effect and multiphoton processes,which promotes the generation of electron–positron *** the high frequency region,high frequency suppression inhibits the generation of electron–positron *** addition,for a single potential well,the number of created electron–positron pairs can be enhanced by several orders of magnitude in the low frequency region.

关键词： electron–positron pairs linear chirp frequency the computational quantum field theory

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Bρ-defined isochronous mass spectrometry at the storage ring CSRe

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核技术（英文版） 2024年第12期35卷 47-65页

作者： Xu Zhou Meng Wang Yu-Hu Zhang Xiao-Hong Zhou Xin-Liang Yan Yuan-Ming Xing CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern PhysicsChinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

A novel technique of isochronous mass spectrometry(IMS),termed Bρ-defined IMS,was developed at the experimental cooler-storage ring CSRe in Lanzhou for the first *** time-of-flight detectors were installed in a straight section of the CSRe,thereby enabling simultaneous measurements of the velocity and revolution time of each stored short-lived *** technique boosts the broadband precision,efficiency,sensitivity,and accuracy of mass measurements of short-lived exotic *** Bρ-defined IMS,the masses of 22A1,62Ge,64As,66Se,and 70Kr were measured for the first time,and the masses of 65As,67Se,and other 21 nuclides were redetermined with improved *** data have been used in studies of relevant issues regarding nuclear structures and nuclear ***,we review the development of experimental techniques and main physical results and outline plans for future experiments.

关键词： nuclear mass Storage ring Bρ-defined isochronous nuclear structure nuclear astrophysics

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Simulation and experimental comparison of the performance of four-corner-readout plastic scintillator muon-detector system

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nuclear science and Techniques 2024年第11期35卷 1-12页

作者： Lie He Si-Yuan Luo Xiang-Man Liu Yu-Cheng Zou Hai-Feng Zhang Wan-Cheng Xiao Yu-He Huang Xiao-Dong Wang School of Nuclear Science and Technology University of South ChinaHengyang 421001China Key Laboratory of Advanced Nuclear Energy Design and Safety(MOE) University of South ChinaHengyang 421001China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000China School of Physical Sciences University of Science and Technology of ChinaHefei 230026China

Cosmic-ray muons are highly penetrating background-radiation particles found in natural *** this study,we develop and test a plastic scintillator muon detector based on machine-learning *** detector underwent muon position-resolution tests at the Institute of Modern Physics in Lanzhou using a multiwire drift chamber(MWDC)experimental *** the simulation,the same structural and performance parameters were maintained to ensure the reliability of the simulation *** Gaussian process regression(GPR)algorithm was used as the position-reconstruction algorithm owing to its optimal *** results of the Time Difference of Arrival algorithm were incorporated as one of the features of the GPR model to reconstruct the muon hit *** accuracy of the position reconstruction was evaluated by comparing the experimental results with Geant4 simulation *** the simulation,large-area plastic scintillator detectors achieved a position resolution better than 20 *** the experimental-platform tests,the position resolutions of the test detectors were 27.9 *** also analyzed factors affecting the position resolution,including the critical angle of the total internal reflection of the photomultiplier tubes and distribution of muons in the *** were performed to image both large objects and objects with different atomic *** results showed that the system could image high-and low-Z materials in the constructed model and distinguish objects with significant density *** study demonstrates the feasibility of the proposed system,thereby providing a new detector system for muon-imaging applications.

关键词： Monte Carlo simulation Muon tomography TDOA Machine learning Image reconstruction

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Measurement of the neutron total cross section of^(9)Be at the Back-n white neutron source of CSNS

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Chinese Physics C 2024年第8期48卷 140-152页

作者： Jiangbo Bai Jingyu Tang Liqun Shi Yonghao Chen Han Yi Jie Bao Yu Bao Ping Cao Haolei Chen Zhen Chen Zengqi Cui Ruirui Fan Changqing Feng Keqing Gao Xiaolong Gao MinHao Gu Changcai Han Guozhu He Yongcheng He Yang Hong Yiwei Hu Hanxiong Huang Xiru Huang Haoyu Jiang Wei Jiang Zhijie Jiang Hantao Jing Ling Kang Bo Li Chao Li Jiawen Li Qiang Li Xiao Li Yang Li Jie Liu Shubin Liu Ze Long Guangyuan Luan Changjun Ning Mengchen Niu Binbin Qi Jie Ren Xichao Ruan Zhaohui Song Kang Sun Zhijia Sun Zhixin Tan Xinyi Tang Binbin Tian Lijiao Wang Pengcheng Wang Zhaohui Wang Xiaoguang Wu Xuan Wu Likun Xie Xiaoyun Yang Li Yu Tao Yu Yongji Yu Guohui Zhang Linhao Zhang Qiwei Zhang Xianpeng Zhang Yuliang Zhang Zhiyong Zhang Luping Zhou Zhihao Zhou Kejun Zhu Institute of Modern Physics Fudan UniversityShanghai 200433China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China Sate Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China Institute of High Energy Physics Chinese Academy of Sciences(CAS)Beijing 100049China Spallation Neutron Source Science Center Dongguan 523803China Key Laboratory of Nuclear Data China Institute of Atomic EnergyBeijing 102413China Department of Modern Physics University of Science and Technology of ChinaHefei 230026China State Key Laboratory of Nuclear Physics and Technology School of PhysicsPeking UniversityBeijing 100871China State Key Laboratory of Particle Detection and Electronics Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China Northwest Institute of Nuclear Technology Xi’an 710024China University of Chinese Academy of Sciences Beijing 100049China

The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power *** neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer(NTOX)based on the multi-cell fast fission chamber at the China Spallation Neutron Source(CSNS)-Back-n white neutron source(Back-n).The fission count-neutron energy distributions of ^(235)U and ^(238)U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 *** Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 *** neutron total cross section of^(9)Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy *** the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV,the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5%and 15%,*** the resonance energy region,the measured resonance energies in our experiment were 0.63,0.82,and 2.8 MeV,*** results showed that the total cross section uncertainties of three Be samples were within 2.2%in the energy region below 1 *** total cross section uncertainty of 30 mm Be from ^(235)U was the smallest and less than 5%in the energy region of 0.3 eV−120 *** results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.

关键词： ^(9)Be neutron total cross section CSNS Back-n time-of-flight method transmission method multi-cell fast fission chamber

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Enhancing fairness of trading environment:discovering overlapping spammer groups with dynamic co‑review graph optimization

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Cybersecurity 2025年第2期8卷 242-269页

作者： Chaoqun Wang Ning Li Shujuan Ji Xianwen Fang Zhen Wang Shandong Provincial Key Laboratory of Wisdom Mine Information Technology Shandong University of Science&TechnologyQingdao 266590ShandongChina Anhui Province Engineering Laboratory for Big Data Analysis and Early Warning Technology of Coal Mine Safety Anhui University of Science and TechnologyHuainanChina

Within the thriving e-commerce landscape,some unscrupulous merchants hire spammer groups to post misleading reviews or ratings,aiming to manipulate public perception and disrupt fair market *** phenomenon has prompted a heightened research focus on spammer groups *** the e-commerce domain,current spammer group detection algorithms can be classified into three categories,i.e.,Frequent Item Mining-based,graph-based,and burst-based ***,existing graph-based algorithms have limitations in that they did not adequately consider the redundant relationships within co-review graphs and neglected to detect overlapping members within spammer *** address these issues,we introduce an overlapping spammer group detection algorithm based on deep reinforcement learning named ***,the algorithm filters out highly suspicious products and gets the set of reviewers who have reviewed these ***,taking these reviewers as nodes and their co-reviewing relationships as edges,we construct a homogeneous co-reviewing ***,to efficiently identify and handle the redundant relationships that are accidentally formed between ordinary users and spammer group members,we propose the Auto-Sim algorithm,which is a specifically tailored algorithm for dynamic optimization of the co-reviewing graph,allowing for adjustments to the reviewers’relationship network within the ***,candidate spammer groups are discovered by using the Ego-Splitting overlapping clustering algorithm,allowing overlapping members to exist in these ***,these groups are refined and ranked to derive the final list of spammer *** results based on real-life datasets show that our proposed DRL-OSG algorithm performs better than the baseline algorithms in Precision.

关键词： Spammer groups Homogeneous network Redundant relationships Overlapping members Deep reinforcement learning Ego-splitting algorithm

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Spectroscopic factors of resonance states with the Gamow shell model

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science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 38-45页

作者： Mengran Xie Jianguo Li Nicolas Michel Honghui Li Wei Zuo CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern PhysicsChinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

We provide an investigation of the spectroscopic factor of resonance states in A=5-8 nuclei,utilizing the Gamow shell model(GSM).Within the GSM,the configuration mixing is taken into account exactly with the shell model framework,and the continuum coupling is addressed via the complex-energy Berggren ensemble,which treats bound,resonance,and non-resonant continuum single-particle states on an equal *** a result,both the configuration mixing and continuum coupling are meticulously considered in the *** first calculate the low-lying states of helium isotopes and isotones with the GSM,and the results are compared with that of ab initio no-core shell model(NCSM)*** results indicate that GSM can reproduce the low-lying resonance states more accurately than the *** this,we delve into the spectroscopic factors of the resonance states as computed through both GSM and NCSM,concurrently conducting systematic calculations of overlap functions pertinent to these resonance ***,the calculated overlap function and spectroscopic factor of6He(01+)■νp3/2→^(7)He(3/2_(1)-)with GSM are compared with the results from ab initio NCSM,variational Monte Carlo,and Green’s function Monte Carlo calculations,as well as available experimental *** results assert that wave function asymptotes can only be reproduced in GSM,where resonance and continuum coupling are precisely addressed.

关键词： spectroscopic factor overlap function resonance states continuum coupling isospin symmetry breaking

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Improved isochronous mass spectrometry with tune measurement

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nuclear science and Techniques 2024年第11期35卷 174-181页

作者： Han-Yu Deng Yuan-Ming Xing Xu Zhou Yu-Hu Zhang Xin-Liang Yan Jin-Yang Shi Ting Liao Meng Wang CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern PhysicsChinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

In conventional isochronous mass spectrometry(IMS)performed on a storage ring,the precision of mass measurements for short-lived nuclei depends on the accurate determination of the revolution times(T)of stored ***,the resolution of T inevitably deteriorates due to the magnetic rigidity spread of the ions,limiting the mass-resolving *** this study,we used the betatron tunes Q(the number of betatron oscillations per revolution)of the ions and established a correlation between T and *** this correlation,T was transformed to correspond to a fixed Q with higher *** these transformed T values,the masses of ^(63)Ge,^(65)As,^(67)Se,and ^(71)Kr agreed well with the mass values measured using the newly developed IMS(Bρ-IMS).We also studied the systematics of Coulomb displacement energies(CDEs)and found that anomalous staggering in CDEs was eliminated using new mass *** method of T transformation is highly effective for conventional IMS equipped with a single time-of-flight detector.

关键词： Isochronous Mass Spectrometry Storage ring Tune Natural chromaticity nuclear mass measurement

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