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MCHOKeM algorithm with assured bandwidth allocation in DiffServ networks

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Journal of Systems Engineering and Electronics 2010年第4期21卷 531-536页

作者： haifeng du Yang Xiao Kiseon Kim Institute of Information Science Beijing Jiaotong University Beijing 100044 P. R. China Department of Information and Communications Gwangju Institute of Science and Technology Gwangju 500-712 Korea

An active queue management（AQM） algorithm called MCHOKeM is presented,which is borrowed from CHOKeW that draws multi-packets at random from the buffer,the multi-packets are compared with an arriving packet and abandoned if they are from the same *** MCHOKeM uses multiple virtual queues for different priority packets and enhances the drawing function by adjusting the maximum number of draws based on the current status of virtual queue *** number of parameters that MCHOKeM needs to maintain is determined by the number of priority levels being supported by the router,which usually has a small limited *** order to explain the features of MCHOKeM,an analytical model is used.A series of simulation tests to evaluate the performance are given.

关键词： congestion control theory differentiated services(DiffServ) transaction control protocol(TCP) protection fairness analysis.

Asymmetric Catalysis with Chiral Frustrated Lewis Pairs

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Chinese Journal of Chemistry 2020年第6期38卷 625-634页

作者： Wei Meng Xiangqing Feng haifeng du Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Molecular Recognition and FunctionInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The chemistry of frustrated Lewis pairs(FLPs)provides the most important approach for the metal-free hydrogenation and *** progress has been achieved in this area for the past *** promising results have also been *** perspective article mainly focuses on the recent advances for the synthesis of chiral Lewis acidic boranes in category of three protocols,1)hydroboration of chiral internal alkenes with Piers'borane HB(C6F5)2;2)in situ hydroboration of chiral alkenes or alkynes without any purification;3)and substitution reaction of(C6F5)nBCl3-n with chiral organometallic reagents,as well as their applications in the metal-free asymmetric hydrogenations and hydrosilylations.

关键词： chiral hydrogenation Chiral

Chiral Dienes: From Ligands to FLP Catalysts

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Chinese Journal of Chemistry 2022年第9期40卷 1109-1116页

作者： Xiangqing Feng Wei Meng haifeng du Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Molecular Recognition and FunctionInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Olefins are very easily accessible compounds which are both popular substrates in synthetic chemistry and good ligands in the organometallic *** dual character makes olefins a rich source of chiral ligands and catalysts for asymmetric ***,we willbriefly summarize our studies on the development of chiral diene ligands for transition-metal catalyzed asymmetric reactions and chiral FLP catalysts for asymmetric metal-free hydrogenations and *** acyclic chiral diene ligands as well as P/olefin and S/olefin hybrid ligands were developed for Rh or Pd-catalyzed asymmetric *** these ligands in hand,we further put forward a novel strategy for acquiring chiral FLP catalysts via the in situ hydroboration of chiral dienes with Piers'*** catalysts proved to be highly ffective for asymmetric metal-free hydrogenations and hydrosilylations of imines,ilyl enol ethers,ketones,and aromatic N-heterocycles.

关键词： Asymmetric catalysis Chiral dienes Frustrated Lewis pair Conjugated addition Hydrogenation

Progress and challenges in magnetic skyrmionics

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Chinese Physics B 2022年第8期31卷 73-81页

作者： haifeng du Xiangrong Wang Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field LaboratoryHFIPSAnhuiChinese Academy of SciencesHefei 230031China Physics Department The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

Magnetic skyrmions are two-dimensional localized topological spin-structures characterized by the skyrmion number that measures the number of times of spins wrapping the Bloch sphere. Skyrmions behave like particles under an external stimulus and are promising information carriers. Skyrmions can exist as an isolated object as well as skyrmion condensates in crystal structures, helical/conical states, mazes or irregular stripy states with emergent electromagnetic fields. Thus,skyrmions provide a nice platform for studying fundamental physics, other than its applications in spintronics. In this perspective, we briefly review some recent progress in the field and present an outlook of the fundamental challenges in device applications.

关键词： magnetic skyrmions

Asymmetric Hydrogenation of Phenanthridines with Chiral Boranes

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Chinese Journal of Chemistry 2024年第6期42卷 631-635页

作者： Guangyu Cui Xiangqing Feng haifeng du Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Molecular Recognition and FunctionInstitute of ChemistryChinese Academy of SciencesBeijing100190 China University of Chinese Academy of Sciences Beijing100049 China

The asymmetric hydrogenation of N-heteroarenes provides an efficient method for the synthesis of optically active cyclic secondary *** this paper,we described an asymmetric hydrogenation of phenanthridines using a chiral mono-alkene-derived borane.A variety of dihydrophenanthridines were furnished in high yields with up to 93%*** current catalytic system was very sensitive for the steric hindrance of *** substituents at one phenyl group of phenanthridines were required to obtain the high *** large substituents on the carbon of the C=N bonds would diminish the reactivity sharply.

关键词： Asymmetric catalysis Hydrogenation Nitrogen heterocycles Phenanthridines Frustrated Lewis pairs Chiral boranes

Asymmetric Partial Hydrosilylation of 2,2-Difluoro-1,3-diketones with Chiral Frustrated Lewis Pairs

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Chinese Journal of Chemistry 2024年第8期42卷 853-857页

作者： Ting Liu Xiangqing Feng haifeng du Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Molecular Recognition and FunctionInstitute of ChemistryChinese Academy of SciencesBeijing100190 China University of Chinese Academy of Sciences Beijing100049 China

Comprehensive Summary,The asymmetric partial reduction of 1,3-diketones stands as a straightforward pathway to access optically active β-hydroxyketones. In this paper, an asymmetric Piers-type hydrosilylation of 2,2-difluoro-1,3-diketones was successfully realized by using a frustrated Lewis pair of chiral borane and tricyclohexylphosphine as a catalyst, delivering a variety of α,α-difluoro-β-hydroxyketones in high yields with up to 99% ee. Significantly, no over-reduced diol products were observed even with an excess amount of silanes. The product can be conveniently converted to α,α-difluoro-β-hydroxyester or 1,3-anti-diol via an oxidation with m-CPBA or a reduction with DIBAL-H without obvious loss of ee.

关键词： Asymmetric catalysis Hydrosilylation Ketones Frustrated Lewis pairs Chiral boranes

B(C_(6)F_(5))_(3)-Catalyzed Hydroboration of Alkenes with N-Heterocyclic Carbene Boranes via B-H Bond Activation

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Chinese Journal of Chemistry 2021年第4期39卷 918-926页

作者： Qiaotian Wang Wei Meng Xiangqing Feng haifeng du Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Molecular Recognition and FunctionInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing100049 China

Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C_(6)F_(5))_(3) in an frustrated Lewis pairs manner.A broad range of alkenes including stilbenes,β-methylstyrenes,styrenes,and alkyl-alkenes were suitable substrates for the B(C_(6)F_(5))_(3)-catalyzed hydroboration to furnish the desired products in good to high ***,excellent regioselectivities were obtained in some *** studies indicate that the B-H bond cleavage is likely involved in the rate-determining *** addition,an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also *** current work provides a promising method for the activation of stable borane adducts,which might lead to some interesting transformations in the future.

关键词： Frustrated Lewis pairs Hydroboration B-H bond activation Boranes Alkenes

Optimal approximation of linear systems by artificial immune response

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Science in China(Series F) 2006年第1期49卷 63-79页

作者： GONG Maoguo du haifeng JIAO Licheng Institute of Intelligent Information Processing and Key Laboratory of Radar Signal Processing Xidian University Xi'an 710071 China School of Mechanical Engineering Xi'an Jiaotong University Xi'an 710049 China

This paper puts forward a novel artificial immune response algorithm for optimal approximation of linear systems. A quaternion model of artificial immune response is proposed for engineering computing. The model abstracts four elements, namely, antigen, antibody, reaction rules among antibodies, and driving algorithm describing how the rules are applied to antibodies, to simulate the process of immune response. Some reaction rules including clonal selection rules, immunological memory rules and immune regulation rules are introduced. Using the theorem of Markov chain, it is proofed that the new model is convergent. The experimental study on the optimal approximation of a stable linear system and an unstable one show that the approximate models searched by the new model have better performance indices than those obtained by some existing algorithms including the differential evolution algorithm and the multi-agent genetic algorithm.

关键词： approximation of linear systems artificial immune systems immune response clonal selection,immunological memory

High Sensitive Refractive Index Sensor Based on Cladding Etched Photonic Crystal Fiber Mach-Zehnder Interferometer

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Photonic Sensors 2019年第2期9卷 126-134页

作者： haifeng du Xiaoyan SUN Youwang HU Xinran DONG Jianhang ZHOU State Key Laboratory of High Performance Complex Manufacturing College of Mechanical and Electrical EngineeringCentral South University Changsha 410083 China

A high sensitive refractive index sensor based on the cladding etched photonic crystal fiber (PCF) Mach-Zehnder interferometer (MZI) is proposed, which is spliced a section of photonic crystal fiber between two single modes fibers (SMFs).The interference fringe of the MZI shifts with the variation of the ambient refractive index (RI). It is found that the RI sensitivity slightly decrease with an increase in the interference length. The sensitivities of MZI with 35inm PCF, 40mm PCF, and 45mm PCF are 106.19nm/RIU, 93.33nm/RIU, and 73.64nm/RIU, respectively, in the range of 13.33 to 1.381. After etched, the RI sensitivity of the MZI could be improved obviously. The RI sensitivities of the MZI with 35 mm PCF are up to 211.53nm/RIU and 359.37nm/RIU when the cladding diameter decreases to 112(im and 91 pm, respectively. Moreover, the sensor is insensitive to temperature, and the measured sensitivity is only 9.21 pm/℃ with the range from 20℃ to 500℃. In addition, the sensor has advantage of simple fabrication, low cost, and high RI sensitivity.

关键词： Refractive index sensor Mach-Zehnder interferometer photonic crystal fiber hydrofluoric acid