Preparation and Characterization of a Novel Hyperbranched Poly(aryl ether ketone) Terminated with Cobalt Phthalocyanine to be Used for Oxidative Decomposition of 2,4,6-Trichlorophenol

Lei Lei,Yunhe Zhang,Xiujie Li,Jianxin Mu,Guibin Wang,Zhenhua Jiang,Shuling Zhang 한국고분자학회 2010 Macromolecular Research Vol.18 No.4

A novel hyperbranched poly(aryl ether ketone) terminated with cobalt phthalocyanine (CoPc-T-HPAEK)was prepared using 1,3,5-tris[4-(4-fluorobenzoyl) phenoxy] benzene (B3), as a ‘core’ molecule, 4,4'-(hexafluoroisopropylidene)diphenol (6F-BPA) as an A2 monomer, and cobalt phthalocyanine as an end-capping reagent. CoPc-THPAEK showed good solubility, thermal stability and catalytic activity in the oxidative decomposition of 2,4,6-trichlorophenol (TCP) under H2O2 or KHSO5. Moreover, the oxidative effect of KHSO5 was superior to that of H2O2,and the catalytic activity of CoPc-T-HPAEK was much higher than that of linear poly(aryl ether ketone) terminated with cobalt phthalocyanine (CoPc-T-LPAEK) and linear poly(aryl ether ketone) with a cobalt phthalocyanine pendant unit (CoPc-S-LPAEK).

Modeling and Analyzing Per-flow Throughput in IEEE 802.11 Multi-hop Ad Hoc Networks

( Lei Lei ),( Xinru Zhao ),( Shengsuo Cai ),( Xiaoqin Song ),( Ting Zhang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.10

In this paper, we focus on the per-flow throughput analysis of IEEE 802.11 multi-hop ad hoc networks. The importance of an accurate saturation throughput model lies in establishing the theoretical foundation for effective protocol performance improvements. We argue that the challenge in modeling the per-flow throughput in IEEE 802.11 multi-hop ad hoc networks lies in the analysis of the freezing process and probability of collisions. We first classify collisions occurring in the whole transmission process into instantaneous collisions and persistent collisions. Then we present a four-dimensional Markov chain model based on the notion of the fixed length channel slot to model the Binary Exponential Backoff (BEB) algorithm performed by a tagged node. We further adopt a continuous time Markov model to analyze the freezing process. Through an iterative way, we derive the per-flow throughput of the network. Finally, we validate the accuracy of our model by comparing the analytical results with that obtained by simulations.

Validation of the C-Test amongst Chinese ESL Learners

Lei Lei 아시아영어교육학회 2008 The Journal of Asia TEFL Vol.5 No.2

Evolution of Microstructure and Mechanical Property of Wire Arc Additive Manufactured Al–Cu Metallic Component after Simulated Thermal Service

Leilei Wang,Dan Chen,Zhuanni Gao,Feiyue Lyu,Xiaohong Zhan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.12

Wire arc additive manufacturing (WAAM) has advantages such as high manufacturing flexibility and efficiency, making itfeasible to fabricate large-scale aircraft components. Additive manufactured aircraft component suffers thermal processesduring manufacturing and high-speed flight, affecting their microstructure, mechanical property, and lifetime. As-builtmicrostructure and residual stress of the WAAM component and its evolution during thermal service are essential but nearlyabsent from the literature. This paper studies the evolution characteristic of microstructure, temperature field, stress distribution,and mechanical properties of 2319 aluminum alloy during the WAAM process and simulated high-speed flight. Resultsindicate that equiaxed grains and dendrite size in the top region increase slightly after thermal service, the grain distributionbecomes more uniform, and the boundary between layers is far less evident than the as-built state. After thermal service, theWAAM component inherits the as-built mechanical properties. The lower wire feeding rate and the higher scanning speedcan significantly reduce the maximum stress value of the WAAM component and change the stress distribution during thermalservice. Tensile strength of WAAM sample increases after 1st thermal service and decreases after 10th thermal service. The existence of many dimples in the fracture indicates that the tensile fracture mode of the WAAM sample is microporousaggregation fracture. The number of dimples and particles in the fracture reduces significantly after the 10th thermal service,resulting in a decrease in fracture plasticity and tensile strength of the WAAM component.

A Method of Plagiarism Source Retrieval and Text Alignment Based on Relevance Ranking Model

Leilei Kong,Zicheng Zhao,Zhimao Lu,Haoliang Qi,Feng Zhao 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.12

The problem of text plagiarism has increased because of the digital resources available on the World Wide Web. Source Retrieval and Text Alignment are two core tasks of plagiarism detection. A plagiarism source retrieval and text alignment system based on relevance ranking model is described in this paper. Not only the source retrieval task but also the text alignment task is all regarded as a process of information retrieval, and the relevance ranking is used to search the plagiarism sources and obtain the candidate plagiarism seeds. For source retrieval, BM25 model is used, while for text alignment, Vector Space Model is exploited. Furthermore, a plagiarism detection system named HawkEyes is developed based on the proposed methods and some demonstrations of HawkEyes are given.

The Sequence Labeling Approach for Text Alignment of Plagiarism Detection

( Leilei Kong ),( Zhongyuan Han ),( Haoliang Qi ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.9

Plagiarism detection is increasingly exploiting text alignment. Text alignment involves extracting the plagiarism passages in a pair of the suspicious document and its source document. The heuristics have achieved excellent performance in text alignment. However, the further improvements of the heuristic methods mainly depends more on the experiences of experts, which makes the heuristics lack of the abilities for continuous improvements. To address this problem, machine learning maybe a proper way. Considering the position relations and the context of text segments pairs, we formalize the text alignment task as a problem of sequence labeling, improving the current methods at the model level. Especially, this paper proposes to use the probabilistic graphical model to tag the observed sequence of pairs of text segments. Hence we present the sequence labeling approach for text alignment in plagiarism detection based on Conditional Random Fields. The proposed approach is evaluated on the PAN@CLEF 2012 artificial high obfuscation plagiarism corpus and the simulated paraphrase plagiarism corpus, and compared with the methods achieved the best performance in PAN@CLEF 2012, 2013 and 2014. Experimental results demonstrate that the proposed approach significantly outperforms the state of the art methods.

Super-Twisting Sliding Mode Observer Based Speed Sensorless Torque Control for PMSG Used in Wind Turbines

Leilei Guo,Xing Zhang,Shuying Yang,Zhen Xie,Lifeng Qi,Lingxiang Wang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

A speed sensorless torque control method for permanent magnet synchronous generator (PMSG) based on super-twisting sliding mode observer (STSMO) is proposed in this paper. Active back electromotive force (BEMF) can be obtained based on the STSMO. With the observed active BEMF, the rotor position angle and the speed are estimated by a phase-locked loop. Besides, a stator flux and electromagnetic torque (EMT) observation method is proposed based on the observed active BEMF. Compared to the traditional method, the robustness of the proposed one to the parameters of PMSG is improved. Then a speed sensorless EMT closed-loop control system is established. The simulation and experimental results verify the effectiveness of the proposed algorithm.

A method for evaluating the stiffness of a cabin suspension system for fork lift trucks

Leilei Zhao,Changcheng Zhou,Yuewei Yu,Fuxing Yang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.10

The stiffness parameters of cabin suspension have an important effect on the comfort of fork lift trucks. Analysis of the cabin system of fork lift trucks often requires the retrieval of the stiffness parameters of cabin suspension systems. Convenient methods of retrieving stiffness parameters without dismantling the cabin suspension system cannot be obtained unless a special bench test is conducted. This process is inconvenient for researchers and technicians. A cabin model with three degrees of freedom was constructed, including a simulation model, to provide a convenient method for retrieving stiffness parameters. A model for the identification of stiffness parameters was established on the basis of the test data and the simulation model. The stiffness parameters were identified through a case study and the values retrieved coincide with the test results. The results show that the method built is reliable and provides an effective way of retrieving the stiffness parameters of cabin suspension for fork lift trucks.

The First Stage of Developing the Adolescent Friendship Social Capital Scale

Leilei Xu 한국아동학회 2012 Child studies in Asia-Pacific context Vol.2 No.1

The purpose of the study was to generate the candidate items for the Adolescent Friendship Social Capital Scale. Both inductive and deductive approaches were used to generate the scale items. Halpern`s conceptual map of social capital served as the theoretical basis of this scale, and guided the development of items. Semi-structured interviews with adolescents in Sydney, Melbourne and Beijing generated the initial pool of scale items. Twenty-six items were generated for the Adolescent Friendship Social Capital Scale. The items are organised in four theoretical constructs: Bonding Networks, Bridging Norms, Bridging Sanctions, and Linking Networks. Each item is a short statement followed by a five-point Likert scale anchored by 1= "Strongly disagree" and 5= "Strongly agree". The scale has several advantages over previous measures of adolescent friendship networks and friendship social capital. The scale has a strong and clear theoretical structure, the scale items demonstrate initial construct and content validity, and the format of the scale enables the collection of continuous data. However, in order to ensure the validity and reliability of the scale, another two stages of research need to be conducted in the future: scale development and scale evaluation.

Highly dispersed Ni-La catalysts over mesoporous nanosponge MFI zeolite for low-temperature CO2 methanation: Synergistic effect between mesoporous and microporous channels

Leilei Xu,Xueying Wen,Mindong Chen,Chufei Lv,Yan Cui,Xianyun Wu,Cai-e Wu,Zhichao Miao,Xun Hu 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.100 No.-

The mesoporous nanosponge MFI silicate zeolite was facilely fabricated by employing the long chainammonium as the structure-directing agent. The zeolite with both mesoporous and microporouschannels were selected as the support of Ni-La catalysts for methanation of CO2. Various techniques wereused to characterize the catalysts systematically. The effects of the La2O3 promotor and pore morphologyof the support on the catalytic performance were carefully investigated. Our study demonstrated that Lapromoter could be beneficial to the increase of the surface basicity and the enhancement of the metallicNi dispersion. This would intensify the processes of the CO2 chemisorption and H2 dissociation in CO2methanation. Besides, we also found that the catalyst supported on mesoporous nanosponge MFI zeoliteperformed higher activity and better long-term stability than the reference catalysts supported on bulkMFI and MCM-48, suggesting that the synergistic effect between the mesoporous and microporouschannels displayed unique advantages. Kinetic study revealed that both the nanosponge structure andLa2O3 promoter contributed to decreasing the reaction activation energy. Therefore, the present highlydispersed Ni-La catalyst over mesoporous nanosponge MFI zeolite promised a potential catalystcandidate for low-temperature CO2 methanation reaction.