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A Remark on chen’s Theorem (Ⅱ)

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Chinese Annals of Mathematics,Series B 2008年第6期29卷 687-698页

作者： Yingchun cai Department of Mathematics Tongji University Shanghai 200092 China

Let p denote a prime and P2 denote an almost prime with at most two prime factors. The author proves that for sufficiently large x,∑p≤x p＋2=P2 1〉1.13Cx/log^2x,where the constant 1.13 constitutes an improvement of ... 详细信息

关键词： chen's theorem Sieve Mean value theorem

Fabrication of carbon-supported Al2O3 nanoparticles via spontaneous cross-linking to enhance selective hydrogenation of furfural

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Journal of Energy Chemistry 2025年第1期100卷 612-620页

作者： Weiwei Yu Xinbao Zhang Hongyu chen Yanan Wang Shaoguo Li Fucun chen Zhenni Liu Xiujie Li Xiangxue Zhu State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences

Selective hydrogenation of furfural to furfuryl alcohol is a great challenge in the hydrogenation field due to thermodynamic preference for hydrogenation of C=C over C=***,a novel Al2O3/C-u hybrid catalyst,composed of N-modified dendritic carbon networks supporting Al2O3nanoparticles,was successfully prepared via carbonizing the freeze-dried gel from spontaneous cross-linking of alginate,Al3+and *** obtained carbon-supported Al2O3hybrid catalyst has a high ratio （31%） of Al species in pentahedral-coordinated *** introduction of urea enhances the surface N content,the ratio of pyrrolic N,and specific surface area of catalyst,leading to improved adsorption capacity of C=O and the accessibility of active *** the furfural hydrogenation reaction with isopropyl alcohol as hydrogen donor,Al2O3/C-u catalyst achieved a 90%conversion of furfural with 98.0% selectivity to furfuryl alcohol,outperforming that of commercial γ-***,Al2O3/C-u demonstrates excellent catalytic stability in the recycling tests attributed to the synergistic effect of abundant weak Lewis acid sites and the anchoring effect of the carbon network on *** work provides an innovative and facile strategy for fabrication of carbon-supported Al2O3hybrid catalysts with rich AlVspecies,serving as a high selective hydrogenation catalyst through MPV reaction route.

关键词： Selective hydrogenation Furfural Furfuryl alcohol Cross-linking MPV route

New environmental-friendly yellow pigments Y4-xAxMoO9+δ（A =Ta,Tb）

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Journal of Rare Earths 2019年第7期37卷 741-749页

作者： Mengjun cai Shuaifeng chen Xinsheng Ma Jianding chen National Engineering Research Centre of Ultrafine Powder School of Chemical EngineeringEast China University of Science and TechnologyShanghai 200237China School of Materials Science and Engineering East China University of Science and TechnologyShanghai 200237China

A series of inorganic yellow pigments with general formula Y4-xAxMoO9+δ(A = Ta, Tb), where x = 0,0.05,0.1,0.2, 0.4 for Ta and χ = 0, 0.005, 0.***.0.03, 0.05 for Tb,were synthesized by a conventional ceramic method at 1400 ℃ for 6 h in air. The samples were characterized by XRD,EDS,XPS,SEM,TG-DSC,UV-vis-NIR reflectance spectroscopy and CIE L*a*b* color scales. It is found that the substitution of A(A = Ta, Tb) for Y3+ in Y4 MoO9 decreases the NIR reflectance of the pigment samples, but the developed pigments Y4-xAxMoO9+δ(A = Ta, Tb) still exhibit impressive NIR solar reflectance. The brighter yellow color of inorganic pigments Y4-xAxMoO9+δ(A = Ta, Tb) is available when x is about 0.1 for Ta and 0.01 for Tb. The results make them a series of potential candidates as ecological yellow pigments because of their high reflectance, lightness, intense coloration and excellent thermal and chemical stability.

关键词： Yttrium oxide Molybdenum oxide Tantalum oxide Terbium oxide Inorganic yellow pigment Rare earths

Optimizing polyphase sequences for orthogonal netted radar systems

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Journal of Systems Engineering and Electronics 2012年第4期23卷 529-535页

作者： Wenwu chen Zhengyu cai Rushan chen Zhao Zhao School of Electronic Engineering and Optoelectric Technology Nanjing University of Science and TechnologyNanjing 210094P.R.China

Orthogonal netted radar systems （ONRS） can fundamentally improve the radar performance by using a group of specially designed orthogonal polyphase code signals which require a very low aperiodic autocorrelation peak sidelobe level, low aperiodic cross-correlation, and a good resilience to small Doppler shifts. However, the existing numerical solutions degrade severely in the presence of small Doppler shifts. A new set of polyphase sequences is presented with good correlation properties as well as resilience to Doppler shifts. These sequences are built by using numerical optimization based on correlation properties as well as the Doppler effects on matched filter outputs, which maintains the Doppler tolerance. The statistical simulated annealing algorithm and the greedy code search method are used to optimize the sequences. Correlation and Doppler results are compared with the best-known sequences and show to be superior.

关键词： Doppler resilience netted radar orthogonal polyphasecode simulated annealing (SA).

Integrability and Exact Solutions of the(2+1)-dimensional KdV Equation with Bell Polynomials Approach

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Acta Mathematicae Applicatae Sinica 2022年第4期38卷 861-881页

作者： Jun-cai PU Yong chen School of Mathematical Sciences Shanghai Key Laboratory of Pure Mathematics and Mathematical PracticeEast China Normal UniversityShanghai 200062China College of Mathematics and Systems Science Shandong University of Science and TechnologyQingdao 266590China

In this paper,the bilinear formalism,bilinear B?cklund transformations and Lax pair of the(2+1)-dimensional KdV equation are constructed by the Bell polynomials *** N-soliton solution is derived directly from the bilinear ***,based on the two-soliton solution,the lump solution is given out analytically by taking special parameters and using Taylor expansion *** the help of the multidimensional Riemann theta function,multiperiodic(quasiperiodic)wave solutions for the(2+1)-dimensional KdV equation are obtained by employing the Hirota bilinear ***,the asymptotic properties of the one-and two-periodic wave solution,which reveal the relations with the single and two-soliton solution,are presented in detail.

关键词： the bilinear formalism bilinear B?cklund transformations Lax pair lump solution periodic wave solution the asymptotic properties

Personalized query suggestion diversification in information retrieval

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Frontiers of Computer Science 2020年第3期14卷 129-141页

作者： Wanyu chen Fei cai Honghui chen Maarten DE RIJKE Science and Technology on Information Systems Engineering Laboratory National University of Defense TechnologyChangsha 410073China Informatics Institute University of AmsterdamAmsterdam1098XHThe Netherlands

Query suggestions help users refine their queries after they input an initial *** work on query suggestion has mainly concentrated on approaches that are similarity-based or context-based,developing models that either focus on adapting to a specific user(personalization)or on diversifying query aspects in order to maximize the probability of the user being satisfied(diversification).We consider the task of generating query suggestions that are both personalized and *** propose a personalized query suggestion diversification(PQSD)model,where a user's long-term search behavior is injected into a basic greedy query suggestion diversification model that considers a user's search context in their current *** aspects are identified through clicked documents based on the open directory project(ODP)with a latent dirichlet allocation(LDA)topic *** quantify the improvement of our proposed PQSD model against a state-of-the-art baseline using the public america online(AOL)query log and show that it beats the baseline in terms of metrics used in query suggestion ranking and *** experimental results show that PQSD achieves its best performance when only queries with clicked documents are taken as search context rather than all queries,especially when more query suggestions are returned in the list.

关键词： query suggestion personalization query suggestion diversification

A new method to predict fatigue crack growth rate of materials based on average cyclic plasticity strain damage accumulation

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Chinese Journal of Aeronautics 2013年第1期26卷 130-135页

作者： chen Long cai Lixun Yao Di School of Mechanics and Engineering Southwest Jiaotong University

By introducing a fatigue blunting factor, the cyclic elasto-plastic Hutchinson-Rice-Rosengren （HRR） field near the crack tip under the cyclic loading is modified. And, an average damage per loading-cycle in the cyclic plastic deformation region is defined due to Manson-Coffin law. Then, according to the linear damage accumulation theory-Miner law, a new model for predicting the fatigue crack growth （FCG） of the opening mode crack based on the low cycle fatigue （LCF） damage is set up. The step length of crack propagation is assumed to be the size of cyclic plastic zone. It is clear that every parameter of the new model has clearly physical meaning which does not need any human debugging. Based on the LCF test data, the FCG predictions given by the new model are consistent with the FCG test results of Cr2Ni2MoV and X12CrMoWVNbN 10-1-1. What＇s more, referring to the relative researches, the good predictability of the new model is also proved on six kinds of materials.

关键词： Cyclic elasto-plastic HRR field Cyclic plasticity strain damage Fatigue crack growth Low cycle fatigue Miner linear damage accumulation

Joint optimization of maintenance inspection and spare provisioning for aircraft deteriorating parts

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Journal of Systems Engineering and Electronics 2017年第6期28卷 1133-1140页

作者： Jing cai Xin Li Xi chen College of Civil Aviation Nanjing University of Aeronautics and Astronautics Shanghai Aircraft Customer Service Co. Ltd.

With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the ***, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost ***, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.

关键词： joint optimization maintenance spare provision aircraft part Wiener process

Prediction of fatigue crack growth rate for smallsized CIET specimens based on low cycle fatigue properties

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Chinese Journal of Aeronautics 2018年第4期31卷 740-748页

作者： chen BAO Lixun cai Kaikai SHI Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong University

Based on experiments of low cycle fatigue for 5083-H112 aluminum alloy, two energybased predictive models have been introduced to predict the fatigue crack growth behaviors of traditional Compact Tension（CT） and small-sized C-shaped Inside Edge-notched Tension（CIET）specimens with different thicknesses and load ratios. Different values of the effective stress ratio U are employed in the theoretical fatigue crack growth models to correct the effect of crack *** indicate that the two predictive models show different capacities of predicting the fatigue crack growth behaviors of CIET and CT specimens with different thicknesses and load *** accuracy of predicted results of the two models is strongly affected by the method for determination of the effective stress ratio U. Finally, the energy-based Shi＆cai model with crack closure correction by means of Newman＇s method is highly recommended in prediction of fatigue crack growth of CIET specimens via low cycle fatigue properties.

关键词： CIET specimen Crack closure correction Energy-based fatigue crack growth predictive model Low cycle fatigue 5083-H112 aluminum alloy