检索结果-南通市图书馆

Time-domain training sequences design for MIMO OFDM channel estimation

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第4期9卷 464-469页

作者： zhen lu Jian-hua GE Department of Electronic Engineering Shanghai Jiao Tong Universiry Shanghai 200240 China Department of Communications Engineering Xidian University Xi＇an 710071 China

This paper describes a Least Squares (LS) channel estimation scheme for MIMO OFDM systems based on time-domain training sequence. We first compute the minimum mean square error (MSE) of the LS channel estimation, and then derive the optimal criteria of the training sequence with respect to the minimum MSE. It is shown that optimal time-domain training sequence should satisfy two criteria. First, the autocorrelation of the sequence transmitted from the same antenna is an impulse function in a region longer than the channel maximum delay. Second, the cross-correlation between sequences transmitted from different antennas is zero in this region. Simulation results show that the estimator using optimal time-domain training sequences has better performance than that using optimal frequency training sequence at low signal-to-noise ratio (SNR). To reduce the training overhead, a suboptimal training sequence is also proposed. Comparing with optimal training sequence, it has low computation complexity and high transmission efficiency at the expense of little performance degradation.

关键词： MIMO OFDM Channel estimation Time-domain training sequence

Efficient photoelectrodes based on two-dimensional transition metal dichalcogenides heterostructures:from design to construction

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2022年第4期41卷 1142-1159页

作者： Xiang-Chao lu Yi-zhen lu Cong Wang Yang Cao State Key Laboratory of Physical Chemistry of Solid Surfaces Collaborative Innovation Center of Chemistry for Energy Materials(iChEM)College of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China Pen-Tung Sah Institute of Micro-Nano Science and Technology Xiamen UniversityXiamen 361005China

Hydrogen production by photoelectrochemical(PEC) water splitting converts the inexhaustible supply of solar radiation to storable H2 as clean energy and thus has received widespread *** efficiency of PEC water splitting is largely determined by the properties of the ***-dimensional(2 D) layered transition metal dichalcogenides(TMDs) are promising candidates for photoelectrodes due to their atomic layer thickness,tunable bandgap,large specific surface area,and high carrier ***,the construction of 2 D TMDs heterostructures provides freedom in material design,which facilitates the further improvement of PEC water *** review begins by describing the mechanism of PEC water splitting and the advantages of 2 D TMDbased heterostructures for photo ***,the design considerations of the heterostructures for enhanced PEC efficiency are comprehensively reviewed with a focus on material selection,band engineering,surface modification,and long-term ***,current challenges and future perspectives for the development of photoelectrodes based on 2 D TMDs heterostructures are addressed.

关键词： Two-dimensional transition metal van der Waals heterostructure Photoelectrode Photoelectrochemical cell Water splitting

SUPPLY CHAIN OPTIMIZATION IN CONTEXT OF PRODUCTION FLOW NETWORK

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science and Systems Engineering 2016年第3期25卷 351-369页

作者： lu zhen Dan Zhuge Jingqi Lei School of Management Shanghai University Shanghai 200444 China

For large multinational companies, the complex production process of their finished goods usually contains plenty of stages, which constitute a production flow network. Each production stage in the production flow network can be undertaken by one or more suppliers. This study proposes a stochastic programming model for the production flow network oriented supply chain network design problem, which optimizes the decision of allocating stages to suppliers with the objective of minimizing the total expected costs of production and transportation among suppliers under uncertain demands of customers. A local branching based solution method is developed to solve the model. A case study on applying this model to a large automobile company is performed. In addition, some numerical experiments are conducted to validate the effectiveness of the proposed model and the efficiency of the proposed solution method.

关键词： Supply chain network production allocation stochastic programming

Pseudo-Differential Operators on Sobolev and Lipschitz Spaces

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2010年第1期26卷 131-142页

作者： Yan LIN Shan zhen lu Department of Mathematics China University of Mining and Technology Beijing 100083 P. R. China School of Mathematical Sciences Beijing Normal University Beijing 100875 P. R. China

In this paper, by discovering a new fact that the Lebesgue boundedness of a class of pseudo- differential operators implies the Sobolev boundedness of another related class of pseudo-differential operators, the authors establish the boundedness of pseudo-differential operators with symbols in Sρ,δ^m on Sobolev spaces, where ∈ R, ρ≤ 1 and δ≤ 1. As its applications, the boundedness of commutators generated by pseudo-differential operators on Sobolev and Bessel potential spaces is deduced. Moreover, the boundedness of pseudo-differential operators on Lipschitz spaces is also obtained.

关键词： pseudo-differential operator Sobolev space Bessel potential space Lipschitz space

Weighted Estimates for Iterated Commutators of Multilinear Fractional Operators

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2012年第9期28卷 1769-1778页

作者： Zeng Yan SI Shan zhen lu School of Mathematics and Information Science He'nan Polytechnic University School of Mathematical Science Beijing Normal University

The author establishes weighted strong type estimates for iterated commutators of multi- linear fractional operators.

关键词： Multilinear fractional operators commutators weighted norm inequalities

Numerical simulation of turbulent combustion: Scientific challenges

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2014年第8期57卷 1495-1503页

作者： REN ZhuYin lu zhen HOU LingYun lu LiuYan School of Aerospace Tsinghua University Center for Combustion Energy Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Tsinghua University Department of Thermal Engineering Tsinghua University Sibley School of Mechanical & Aerospace Engineering Cornell UniversityIthaca NY 14853 USA GE Global Research Center One research circle Niskayuna NY 12309 USA

Predictive simulation of engine combustion is key to understanding the underlying complicated physicochemical processes,improving engine performance,and reducing pollutant *** issues as turbulence modeling,turbulence-chemistry interaction,and accommodation of detailed chemical kinetics in complex flows remain challenging and essential for highfidelity combustion *** paper reviews the current status of the state-of-the-art large eddy simulation(LES)/probability density function(PDF)/detailed chemistry approach that can address the three challenging modelling *** as a subgrid model for LES is formulated and the hybrid mesh-particle method for LES/PDF simulations is *** the development need in micro-mixing models for the PDF simulations of turbulent premixed combustion is *** the different acceleration methods for detailed chemistry are reviewed and a combined strategy is proposed for further development.

关键词： turbulence-chemistry interaction detailed chemistry probability density function mixing models large eddy simulations

Relationship between histone acetylation/deacetylation and gene transcription

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1998年第13期43卷 1057-1063页

作者： zhen lu Yongchao Wang Beijing Normal Univ Key Lab Cell Proliferat & Regulat Biol Beijing 100875 Peoples R China

In eukaryotes, nucleosome is the basic unit of chromatin. Nucleosome is composed of an octamer of histone proteins (two molecules each of histones H 2A , H 2B , H 3 and H 4) and DNA strand wound around the octamer. Some data show that core histone octamer can affect gene transcription both \%in vitro\% and \%in vivo.\% Recent results indicate that histone acetylation/deacetylation is a key step to regulate activity of genes. This article summarizes some coactivators, such as GCN5p, P300/CBP and TAF Ⅱ 250, which are recently found to have histone acetyltransferase activity. The relationship between these coactivators and gene activation is also described. Besides, this article concerns some corepressors which have histone deacetylase activity, such as Rpd3p, HDAC2. These corepressors combine with other protein complex and then repress transcription. Finally, some problems to be solved and the future direction in this active field are discussed.

关键词： Histone acetylation/deacetylation transcriptional regulation.

Preface:Special Issue on Operations Research Models and Algorithms in Transportation

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2020年第3期8卷 353-355页

作者： lu zhen School of Management Shanghai UniversityShanghai 200444China

Operations research,popularly known as OR,is a scientific research method or mathematical technique for providing decision making aid in the management of large organizations or organized *** the real world,transportation,a large organized system,is the movement of humans,animals,and goods from one location to *** transportation problem is significantly complicated because of its wide *** modes of transportation include air,land(rail and road),water,cable,pipeline,and *** field of transportation can also be divided into infrastructure,vehicles,and ***,transportation is essential for the development of civilizations,and has been an active topic for decades,while operations research is one of its key *** special issue examines the current progress,challenges and approaches in transportation through operations ***,the scope of this issue covers high-quality original research focusing on the use of OR techniques(mathematical programming models,algorithms and simulation-based approaches,etc.)to deal with transportation problems.

关键词： operations transportation programming

Generalized Commutators for Marcinkiewicz Type Integrals with Variable Kernels

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2011年第3期27卷 471-480页

作者： Hui-xia Mo Shan-zhen lu School of Science Beijing University of Post and Telecommunications Beijing 100876 China School of Mathematical Sciences Beijing Normal University Beijing 100875 China

Let A be a function with derivatives of order m and D γ A ∈■β （0 〈 β 〈 1, ｜γ｜ = m）. The authors in the paper prove that if Ω（x, z） ∈ L ∞ （R n ） × L s （S n 1 ）（s ≥ n/（n β）） is homogenous of... 详细信息

Let A be a function with derivatives of order m and D γ A ∈■β （0 〈 β 〈 1, ｜γ｜ = m）. The authors in the paper prove that if Ω（x, z） ∈ L ∞ （R n ） × L s （S n 1 ）（s ≥ n/（n β）） is homogenous of degree zero and satisfies the mean value zero condition about the variable z, then both the generalized commutator for Marcinkiewicz type integral μ A Ω and its variation μ A Ω are bounded from L p （R n ） to L q （R n ）, where 1 〈 p 〈 n/β and 1/q = 1/p β/n. The authors also consider the boundedness of μ A Ω and its variation μ A Ω on Hardy spaces.

关键词： Marcinkiewicz integral variable kernel Lipschitz space Hardy space