检索结果-南通市图书馆

Robust THP Design with the Presence of Errors in CSIT Acquisition

在线全文

学校读者我要写书评

暂无评论

China Communications 2010年第2期7卷 78-86页

作者： Wang Xuzhen Niu Kai He Zhiqiang yu guangwei Li Hui Inforrnation Theoryand Technology Education and Research Center Beijing University of Posts and Telecommunications Beijing 100876 China The Pilot College Beijing University of Technology Beijing 101101 China

In this paper, a robust THP is proposed for broadcast channel in multi-user multi-input multi-output (MU-MIMO) system, in which the channel uncertainty caused by feedback delay and mobile speed is taken into account. In order to acquire the imperfect channel state information at transmitter (CSIT), a dynamic CSIT model is introduced where the channel temporal and spatial correlations are considered. By utilizing the unchanged channel statistics and accurate outdated feedback channel information jointly, the imperfect CSIT is obtained as the channel estimate and error covariance. Based on the obtained imperfect CSIT, a Minimum Mean-Square Error (MMSE) Tomlinsion-Harashima precoding (THP) is designed and the closed-form solution is derived by the Lagrangian multiplier approach under total power constraint. Simulation results are provided to indicate the preferable performances of the robust THP. Performance analysis with respect to feedback delay and mobile speed is also given.

关键词： MU-MIMO channel estimate imperfect channel state

Crystal Growth and Characterization of Ca3NbGa3Si2O14 Single Crystal

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2006年第z1期24卷 197-199页

作者： Shi Xuzhong yuan Duorong Cheng Xiufeng Guo Shiyi yu guangwei Li Zhanfa State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China

Single crystals of Ca3NbGa3Si2O14 (CNGS) with ordered Ca3Ga2Ge4O14 (CGG) structure were successfully grown from stoichiometric melts by conventional Czochralski technique along the a-axis and two large (001) facets and two small (100) facets appear in every crystal. An arrangement of parallel steps and a clear height change were observed in (001) facet by atomic force microscopy (AFM). High-resolution X-ray diffraction (HRXRD) results indicate that CNGS crystals have good quality and free low-angle boundaries. The crystals also exhibit good optical quality and high optical transmittance in c-direction.

关键词： czochralski method gallium compounds atomic force microscopy

Investigation of the 6H-SiC (0001) surface by AFM

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2008年第5期15卷 654-658页

作者： Shouzhen Jiang guangwei yu Yingmin Wang Xiaobo Hu Xiangang Xu Minhua Jiang State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China College of Physics and Electronics Shandong Normal University Jinan 250014 China

Micropipe and step structures on 6H-SiC （0001） surface were investigated by an atomic force microscopy （AFM）. On the facet,all micropipes examined are the origins of spiral steps,indicating that dislocations intersect the surface at these points. Micropipes are empty-core super-dislocations as originally described by Frank. The micropipe radius increases with the square of the dislocation Burgers vector. From the center to the periphery,step structures change with different surface inclinations. Regular step is observed within the central faceted area. Step bunching and atomically rough surfaces are observed within the peripheral convex area. If the inclination with respect to the （0001） plane is large enough,step bunching of 15R-SiC can be observed.

关键词： atomic force microscopy micropipes step bunching polytypes

Study of ciprofloxacin removal by biochar obtained from used tea leaves

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2018年第11期30卷 20-30页

作者： Jie Li guangwei yu Lanjia Pan Chunxing Li Futian You Shengyu Xie Yin Wang Jianli Ma Xiaofu Shang Key Laboratory of Urban Pollutant Conversion Institute of Urban Environment Chinese Academy of Sciences Xiarnen 361021 China University of Chinese Academy of Sciences Beijing 100049 China Tianjin Huankelijia Environment Remediation Technology Co. Ltd. Tianjin 300191 China

In this study, used tea leaves （UTLs） were pyrolyzed to obtain used tea-leaf biochar （UTC）, and then the UTC was used as an adsorbent to remove ciprofioxacin （CIP） from aqueous solutions. Batch experiments were conducted to investigate the CIP adsorption performance and mechanism. The results showed that the CIP-adsorbing ability first increased and then declined as the UTC pyrolysis temperature increased. The UTC obtained at 450℃ presented excellent CIP-absorbing ability at pH 6 and 40℃. The maximum monolayer adsorption capacity was 238.10 mg/g based on the Langrnuir isotherm model. The pseudo-second-order kinetic equation agreed well with the CIP adsorption process, which was controlled by both external boundary layer diffusion and intra-particle diffusion. The characterization analysis revealed that the - OH groups, G=C bonds of aromatic rings, C- H groups in aromatic tings and phenolic C - O bonds play vital roles in the CIP adsorption process, and that the N - C, N - O, O- C-O and C- OH groups of UTC were consumed in large quantities. π-π interactions, hydrogen bonding and electrostatic attraction are inferred as the main adsorption mechanisms. The present work provides not only a feasible and promising approach for UTLs utilization but also a potential adsorbent material for removing high concentrations of CIP from aqueous solutions.

关键词： Biochar Used tea leaves Ciprofloxacin adsorption Isotherm Kinetics Mechanism

Approximate Analysis of Power Offset over Spatially Correlated MIMO Channels

在线全文

学校读者我要写书评

暂无评论

Communications and Network 2009年第1期1卷 25-34页

作者： guangwei yu Xuzhen WANG 不详

Power offset is zero-order term in the capacity versus signal-to-noise ratio curve. In this paper, approximate analysis of power offset is presented to describe MIMO system with uniform linear antenna arrays of fixed length. It is assumed that the number of receive antenna is larger than that of transmit antenna. Spatially Correlated MIMO Channel is approximated by tri-diagonal toeplitz matrix. The determinant of tri-diagonal toeplitz matrix, which is fitted by elementary curve, is one of the key factors related to power offset. Based on the curve fitting, the determinant of tri-diagonal toeplitz matrix is mathematically tractable. Consequently, the expression of local extreme points can be derived to optimize power offset. The simulation results show that approximation above is accurate in local extreme points of power offset. The proposed expression of local extreme points is helpful to approach optimal power offset.

关键词： MIMO multiplexing gain power offset high snr region toeplitz matrix

Moderate sewage sludge biochar application on alkaline soil for corn growth:a field study

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Biochar 2021年第2期3卷 135-147页

作者： Shengyu Xie guangwei yu Ruqing Jiang Jianli Ma Xiaofu Shang Gang Wang Yin Wang Yongan Yang Chunxing Li CAS Key Laboratory of Urban Pollutant Conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Graduate School of Environmental Studies Tohoku University6‑6‑07 AobaAramaki‑azaAoba‑kuSendaiMiyagi 980‑8579Japan Tianjin Academy of Environmental Sciences Tianjin 300191China Tianjin High Quality Agricultural Products Development Demonstration Center Tianjin 301508China Department of Environmental Engineering Technical University of Denmark2800 Kongens LyngbyDenmark

In view of the risks induced by the inhibitory effects of applying impracticably large amounts of sewage sludge biochar(SSB)to the alkaline soil,this field study investigated the influence of moderate biochar amendments(0,1500,4500,and 9000 kg/hm2)on corn growth,alkaline soil properties,and the uptake of potentially toxic elements(PTEs).The results showed that applying more SSB would decrease the ammonium nitrogen concentration and increase the available phosphorus and potassium concentrations,which inhibited corn plant growth because of high background nutrient levels of the alkaline *** the alkaline soil was amended with 1500 kg/hm2 SSB,the dry weight of 100 niblets increased from 32.11 g in the control to 35.07 *** was no significant variation in the total concentration of PTEs in the *** concentrations of Mn,Ni,Cu,and Zn in niblets decreased from 5.54,0.83,2.26,and 27.15 mg/kg in the control to 4.47,0.62,1.30,and 23.45 mg/kg,***,the health risk from corn consumption was significantly ***,the combination of SSB and fertilizer improved corn growth and reduced the risk of consumption of ***,considering the increase in corn fruit yield and the decrease in consumption risk,applying 1500 kg/hm2 of biochar to alkaline soils is a realistically achievable rate,which can broaden the utilization of SSB for remediation of different types of soil.

关键词： Sewage sludge biochar Alkaline soil Corn growth Soil property Potentially toxic elements Soil remediation

基于多尺度迁移符号动力学熵和支持向量机的轴承诊断方法研究

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

西北工业大学学报 2023年第2期41卷 344-353页

作者：于广伟闫莉西安工业大学机电工程学院陕西西安710021

针对传统数据驱动故障诊断模型在机械系统诊断中存在的泛化能力下降甚至失效的问题,应用迁移学习的思想,提出了基于多尺度迁移符号动力学熵和支持向量机的故障识别算法。采用多尺度符号动力学熵提取故障特征,在此基础上提出基于迁移学... 详细信息

针对传统数据驱动故障诊断模型在机械系统诊断中存在的泛化能力下降甚至失效的问题,应用迁移学习的思想,提出了基于多尺度迁移符号动力学熵和支持向量机的故障识别算法。采用多尺度符号动力学熵提取故障特征,在此基础上提出基于迁移学习的特征映射技术,使非同分布数据的特征在映射后分布差异减小。对多尺度迁移符号动力学熵方法的参数进行优选,将其输入支持向量机中,进一步提高最终的故障识别率。通过轴承故障实验信号的测试证明,基于多尺度迁移符号动力学熵的滚动轴承诊断方法能够有效提升数据驱动故障诊断模型的泛化能力,实现少量样本下滚动轴承不同故障位置的准确识别。

关键词：多尺度迁移符号动力学熵特征提取迁移学习故障诊断滚动轴承

Sliding Mode Control of Multi-Agent Relay Tracking Systems

在线全文

学校读者我要写书评

暂无评论

Sliding Mode Control of Multi-Agent Relay Tracking Systems

The Effect of Two Factor Combination of Three Kinds of Loading on the Soil Clogging in Vertical Flow Constructed Wetland

第37届中国控制会议

作者： yu Deyin Dong Lijing yu guangwei Wang Yipeng School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing Research Institute of Precise Mechatronics and Controls

In this paper, a class of tracking problem of multi-agent systems with switching topologies and replacement of agents is investigated. In particular, it is assumed the agents are randomly deployed in a two-dimensional space, which is divided into numerous subareas with assistance of Voronoi diagram. Agents are dedicated to tracking any intruded targets in this area. During the tracking process, if any tracking agents occurs malfunction, the Voronoi site agent where the target resides joins the *** means that not only the topology but also the tracking agent switches. In order to achieve a successful tracking of the target,the sliding mode controller is designed for the relay tracking system subject to switching both in topologies and agents. Finally,the proposed tracking strategy is verified by a set of simulations.

关键词： multi-agent systems switching topologies sliding mode control relay tracking

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

环境科学前沿（中英文版） 2013年第4期2卷 55-62页

作者： Qiaoling Xu Lihua Cui Ling Zhang Zixia Li guangwei yu College of Natural ResOurce & Environment South China Agricultural University Guangzhou 510642 China