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Joint source-channel coded multidimensional modulation for variable-length codes

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Science China(Information Sciences) 2014年第6期57卷 19-30页

作者： CHENG Chen tu GuoFang ZHANG Can School of Electronic Electrical and Communication EngineeringUniversity of Chinese Academy of Sciences

Resource-constrained networks such as deep space communications and mobile communications have the phenomena such us large-scale path loss,small-scale fading,and multipath effect,which are very hostile for information *** Shannon’s source-channel coding theory with multidimensional modulation,an en/decoding method is proposed in this article called variable-length symbol-level joint sourcechannel and multidimensional *** symbol-level source a priori information,an optimized symbol-level L-dimensional m-ary phase shift keying(LD-mPSK)constellation mapping function has been derived,which can increase free Euclidean distance between modulated symbols and enhance the decoding *** has been shown in the simulation results that the proposed scheme can achieve more than 2 dB signal-to-noise ratio gains compared with the conventional bit-level schemes under the condition of the same error rate.

关键词： joint source-channel en/decoding variable-length codes multidimensional modulation setpartitioning constellation mapping

Assessment of COVID-19 aerosol transmission in a university campus food environment using a numerical method

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Geoscience Frontiers 2022年第6期13卷 265-278页

作者： m.Zhao C.Zhou T.Chan C.tu Y.Liu m.Yu Laboratory of Aerosol Science and Technology China Jiliang UniversityHangzhouChina Department of mechanical Engineering The Hong Kong Polytechnic UniversityKowloonHong KongChina College of modern Science China Jiliang UniversityHangzhouChina

With the prevalence of COVID-19,the phenomenon of viruses spreading through aerosols has become a focus of *** in university dining halls have a high risk of exposure to respiratory droplets from others without the protection of face masks,which greatly increases the risk of COVID-19 ***,the transmission mechanism of respiratory droplets in extremely crowded dining environments should be *** this study,a numerical simulation of coughing at dining tables under two conditions was performed,namely the presence and absence of protective partitions,and the evaporation and condensation of aerosol droplets in the air were *** using the numerical method,we analyzed and verified the isolation effect of dining table partitions in the propagation of aerosol *** effect of changes in room temperature on the diffusion of coughed aerosols when partitions were present was *** demonstrated how respiratory droplets spread through coughing and how these droplets affect ***,we proposed a design for a dining table partition that minimizes the transmission of COVID-19.

关键词： COVID-19 transmission University dining hall Cough Table partition Computational fluid dynamics

Fabrication, characterization and evaluation of mesoporous activated carbons from agricultural waste： Jerusalem artichoke stalk as an example

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Frontiers of Environmental Science & Engineering 2015年第2期9卷 206-215页

作者： Lei YU Chen tu Yongming LUO Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil Science Chinese Academy of Sciences N anjing 210008 China Key Laboratory of Coastal Zone Environmental Processes Institute of Coastal Zone Research Chinese Academy of Sciences Yantai 264003 China Department of Environmental Engineering Nanjing Forestry University Nanjing 210037 China

This work explores the feasibility of Jerusalem artichoke stem （JAS）, an agricultural waste, as an alternative precursor for fabrication of mesoporous activated carbon （mAC） via conventional ZnC12 activation. The as-prepared JAS-mACs were characterized by thermogravimetric, nitrogen gas adsorption isotherm and high resolution scanning electron microscopy analysis. The interacting effects of chemical dosage, activation temperature and time on the mesoporosity, mesopore volume and carbon yield were investigated, and further optimized by response surface methodology （RSm）. The Brunauer-Emmett-Teller surface area, mesoporosity and mesopore volume of the JAS-mAC prepared under optimum condition were identified to be 1631 m^2·g ^-1, 90.16% and 1.11 cm3·g ^-1, respectively. Compared with commercial activated carbons, this carbon exhibited a comparable monolayer adsorption capacity of 374.5 mg .g 1 for methylene Blue dye. The findings suggest that RSm could be an effective approach for optimizing the pore structure of fabricated activated carbons.

关键词： mesoporous activated carbon response sur-face methodology adsorption isotherm agricultural wastes

The 2-pebbling Property for Dense Graphs

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Acta mathematica Sinica,English Series 2013年第3期29卷 557-570页

作者： Ze tu GAO Jian Hua YIN Department of mathematics College of Information Science and Technology

Given a distribution of pebbles on the vertices of a connected graph G, a pebbling move on G consists of taking two pebbles off one vertex and placing one on an adjacent vertex. The pebbling number f（G） is the smallest number m such that for every distribution of m pebbles and every vertex v, a pebble can be moved to v. A graph G is said to have the 2-pebbling property if for any distribution with more than 2f（G） - q pebbles, where q is the number of vertices with at least one pebble, it is possible, using pebbling moves, to get two pebbles to any vertex. Snevily conjectured that G（s, t） has the 2- pebbling property, where G（s, t） is a bipartite graph with partite sets of size s and t （s 〉 t）. Similarly, the ~,pebbling number fl（G） is the smallest number m such that for every distribution of m pebbles and every vertex v, ~ pebbles can be moved to v. Herscovici et al. conjectured that fl（G） ≤ 1.5n ＋ 8l -- 6 for the graph G with diameter 3, where n = IV（G）I. In this paper, we prove that if s ≥ 15 and G（s,t）

关键词： Pebbling number 2-pebbling property bipartite graph

Theoretical Analysis on Inter-Core Crosstalk Suppression model for multi-Core Fiber

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China Communications 2016年第8期13卷 192-197页

作者： Jiajing tu Xueqin Xie Keping Long School of Computer and Communication Engineering University of Science and Technology Beijing (USTB)

Decreasing mode coupling coefficient(κ) is an effective approach to suppress the inter-core crosstalk. Therefore, we deploy a low index rod and rectangle trench in the middle of two neighboring cores to reduce κ so that the overlap of electric field distribution can be suppressed. We also propose approximate analytical solution(AAS) for κ of two crosstalk suppression models, which are two cores with one low index rod deployed in the middle and two cores with one low index rectangle trench deployed in the middle. We then do some modification for the results obtained by AAS and the modified results are proved to agree well with that obtained by finite element method(FEm). Therefore, we can use the modified AAS to get inter-core crosstalk for abovementioned two models quickly.

关键词： multi-core fiber crosstalk mode coupling coefficient

Facile Fabrication of Hierarchically Porous Carbonaceous monoliths with Ordered mesostructure via an Organic Organic Self-Assembly

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Nano Research 2009年第3期2卷 242-253页

作者： Chunfeng Xue Bo tu Dongyuan Zhao Department of Chemistry Shanghai Key Lab of Molecular Catalysis and Innovative MaterialsKey Laboratory of Molecular Engineering of PolymersLaboratory of Advanced MaterialsFudan UniversityShanghai 200433China

A simple strategy for the synthesis of macro-mesoporous carbonaceous monolith materials has been demonstrated through an organic organic self-assembly at the interface of an organic scaffold such as polyurethane(PU)*** porous carbonaceous monoliths with cubic(Im m)or hexagonal(p6mm)mesostructure were prepared through evaporation induced self-assembly of the mesostructure on the three-dimensional(3-D)interconnecting struts of the PU foam *** preparation was carried out by using phenol/formaldehyde resol as a carbon precursor,triblock copolymer F127 as a template for the mesostructure and PU foam as a sacrificial monolithic *** hierarchical pore system was macroscopically fabricated with cable-like mesostructured carbonaceous *** carbonaceous monoliths exhibit macropores of diameter 100450μm,adjustable uniform mesopores(3.87.5 nm),high surface areas(200870 m2/g),and large pore volumes(0.170.58)cm3/*** with the corresponding evaporation induced self-assembly(EISA)process on a planar substrate,this facile process is a time-saving,labor-saving,space-saving,and highly effi cient pathway for mass production of ordered mesoporous materials.

关键词： Self-assembly synthesis mesoporous materials carbonaceous monolith templating macroporous materials

Photochemical cycloaddition and temperature-dependent breathing in pillared-layer metal–organic frameworks

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Science Bulletin 2019年第24期64卷 1881-1889页

作者： Qingqing Pang Binbin tu Lingyi Yang Qiaowei Li Department of Chemistry Collaborative Innovation Center of Chemistry for Energy Materials (iChEM) and Shanghai Key Laboratory of Molecular Catalysis and InnovativeMaterials Fudan University

Single crystallinity of metal–organic frameworks(mOFs) enables the studies of their flexible behaviors with atomic precision. Here, we investigated the structural transformations triggered by photochemical cycloaddition and with temperature-dependent breathing in a series of pillared-layer mOF structures using a variety of pyrazolecarboxylate linkers for the layers and bipyridyl linkers as the pillars. The ethylenic double bonds from the pillars in close proximity undergo quantitative and seteroselective photochemical [2 + 2] cycloaddition upon UV irradiation, transforming the mOFs into structures with cyclobutane-based pillars. Furthermore, reversible breathing of the new pillared-layer mOF was evidenced by the 10.8% unit cell parameter change along c axis upon temperature change between 298 and 173 K. As revealed by single crystal X-ray diffraction, this transformation originates from the relative flattening of the wavy layers upon cooling. These two different types of characteristic structural transformations responding to inherent reactions and external stimuli happen at single crystalline state, providing a well-defined robust system with controlled flexibility.

关键词： Pillared-layer mOF Photochemical cycloaddition Structural transformation Breathing mOF Reticular chemistry

magnetic properties of SmCo-based permanent magnetic films during 25 to 300 ℃

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Journal of Rare Earths 2013年第10期31卷 988-991页

作者： Long PENG Xiaoqiang tu Lezhong LI Rui WANG College of Optoelectronics Technology Chengdu University of Information Technology Chengdu 610225 China

magnetic properties of the SmCo-based permanent magnetic films prepared on hot substrate with mo and Cr underlayer without subsequent annealing process were investigated by vibrating sample magnetometer （VSm）, X-ray diffraction （XRD）, and en- ergy dispersive X-ray spectroscopy （EDS）. The results showed that the film thickness of the SmCo-based films presented complex effect on the intrinsic coercivity Hci. Optimal Hc~ for the films with mo underlayer, Cr underlayer, and without underlayer was ob- served with different film thicknesses. Furthermore, the monotonous temperature dependence of Hci was found to be strongly corre- lated with the magnetic parameters for the 3.0 μm thick SmCo7 films with mo underlayer. From 25 to 300 ℃, the Hci decreased from 281.6 to 211.2 kA/m with a temperature coefficient of-0.091%/℃, exhibiting good temperature stability.

关键词： rare earth permanent magnets SmCo films magnetic anisotropy constant coercivity

EFFECTS OF ImPURITIES AND RARE EARTH ADDITION ON THE TOUGHENING LEVELS OF Al-Li BASED ALLOYS 2090 AND 1420

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Acta metallurgica Sinica(English Letters) 1998年第3期11卷 163-168页

作者： L.meng T.P.tu Y.Z.Yang m.S.Liu Zhejiang Univ Hangzhou China

The effects of the impurities Fe, Si, Na, K and a rare earth addition, Ce, on the intrinsic and extrinsic toughening levels have been investigated for the Al-Li based alloys 2090 and 1420. 29K reduction in the toughening level for the alloy 2090 with impurities 0.42% Fe+Si or 0.0132% Na+K i4 identified to be caused by the *** improvement on the fracture toughness can be made by adding 0.05%-0.25% Ce to the alloy 2090. The reason behind this is that Ce microalloying can not only enhance both the intrinsic toughening level and the extrinsic toughening level but also suppress the embrittling behavior of the impurities. However, 0.06%-0.15% Ce microalloying fails to bring about any beneficial effect to the toughening level for the alloy 1420.

关键词： Al-Li based alloy impurity Ce addition toughening