检索结果-南通市图书馆

Nitrogen Mineralization in Soils Along a Vegetation chronosequence in Hong kong

Pedosphere 2005年第2期15卷 181-188页

作者： L.M.MARAFA k.c.chau centre for Environmental Policy and Resource Management Centre for Environmental Policy and Resource Management Department of Geography and Resource ManagementThe Chinese University of Hong KongShatinNew TerritoriesHong Kong (China)Department of Geography and Resource ManagementThe Chinese University of Hong KongShatinNew TerritoriesHong Kong (China)

This research examined nitrogen mineralization in the top 10 cm of soils along a vegetation gradient in Hong kong at sites where fire has been absent for 0, 1, 3, 6 and 17 years (at the time of the study), and the relationships between N mineralization and successional development of vegetation in the absence of fire. The sites including a newly burnt area (S1), short grassland (S2), tall grassland (S3), mixed tall grassland and shrubland (S4), and woodland (S5) were selected,and the in situ core incubation method was used to estimate nitrogen mineralization. Throughout the 60-day incubation in four periods, more nitrogen was mineralized at the S3 and S4 sites, the predominantly grassland sites, which contained the highest levels of soil organic matter (SOM) and total kjeldahl nitrogen (TkN), than the S1 site, while immobilization occurred at the S2 and S5 sites. Leaching loss decreased with successional development of the vegetation, in the order of S1 ＞ S2 ＞ S3 ＞ S4 ＞ S5. The pattern of nitrogen uptake with ecological succession was less conspicuous, being complicated by the immediate effect of fire and possibly the ability of the woodland species to extract nitrogen from the deeper *** the absence of fire for 3 to 6 years, the build-up of SOM and TkN was accompanied by active mineralization, thus paving the way for the invasion of shrub and tree species. A close relationship existed between nitrogen mineralization and ecological succession with this vegetation gradient. Inherent mechanisms to preserve nitrogen in a fire-prone environment including immobilization and uptake and the practical relevance of nitrogen mineralization to reforestation are discussed.

关键词：氮矿化连续发展植被生长序列火灾影响土壤有机氮

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

面向全息MIMO 6G通信的电磁信道建模理论与方法

引用

电子与信息学报 2024年第5期46卷 1940-1950页

作者：黄崇文季然魏丽宫铁瑞陈晓明沙威杨军张朝阳 Yuen chau 浙江大学信息与电子工程学院杭州310027 新加坡科技与设计大学新加坡487372 西安交通大学信息与通信工程学院西安710049 中兴通讯股份有限公司深圳518000 新加坡南洋理工大学新加坡639798

全息多输入多输出(HMIMO)是6G通信中的新兴技术,相应阵列由固定物理孔径下的密布天线单元组成。全息MIMO是电磁约束下Massive MIMO天线技术的拓展。全息MIMO系统在有效提升无线通信性能方面具有极大的潜力。比如,可用最小的功率损耗实... 详细信息

全息多输入多输出(HMIMO)是6G通信中的新兴技术,相应阵列由固定物理孔径下的密布天线单元组成。全息MIMO是电磁约束下Massive MIMO天线技术的拓展。全息MIMO系统在有效提升无线通信性能方面具有极大的潜力。比如,可用最小的功率损耗实现尽可能大的连续孔径,灵活控制目标方向的电磁波传输等。但是,由于全息MIMO系统包含大量的紧密分布的天线单元,且单元之间的距离小于半波长,因而造成严重的电磁耦合作用。这些耦合使传统的独立同分布的信道假设失效。因此,如何设计一个有效且贴近实际的信道建模成为当前全息MIMO研究中最具挑战性的问题之一。针对该挑战,该文研究了基于电磁场理论的4种信道建模方式,它们都能很好描述全息MIMO系统中的电磁波传输特征。第1种是基于平面格林函数的精确信道建模方式,该方式将自由空间中点对点的格林函数扩展到平面之间积分形式的格林函数,通过积分计算来构造两个全息MIMO平面之间的通信信道,但该方法的复杂度较高。第2, 3种方法则分别采用了平面波展开和球面波展开来近似全息MIMO的通信信道,这两种方案的复杂度更低。其中,基于平面波展开的信道建模形式相对简单,更适用于远场,但是会低估单元强耦合时的最大系统容量;基于球面波展开的信道建模能更好捕捉电磁波信道几何特征,但其复杂度较高。最后介绍基于随机格林函数的信道建模方法,主要描述富散射环境或瑞利信道中电磁波的随机特性。

关键词：全息MIMO通信电磁波理论信道建模

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Liouvillian Solutions of Algebraic Ordinary Differential Equations of Order One of Genus Zero

引用

Journal of Systems Science & complexity 2023年第2期36卷 884-893页

作者： NGUYEN Tri Dat NGO Lam Xuan chau Faculty of Basic Science Ho Chi Minh City University of TransportHo Chi Minh CityVietnam Department of Mathematics and Statistics Quy Nhon UniversityQuy Nhon CityVietnam

This paper considers the class of autonomous algebraic ordinary differential equations(AODEs)of order one,and studies their Liouvillian general *** particular,let F(y,w)=0 be a rational algebraic curve over *** authors give necessary and sufficient conditions for the autonomous first-order AODE F(y,y′)=0 to have a Liouvillian solution over ***,the authors show that a Liouvillian solutionαof this equation is either an algebraic function over c(x)or an algebraic function over c(exp(ax)).As a byproduct,these results lead to an algorithm for determining a Liouvillian general solution of an autonomous AODE of order one of genus *** parametrizations of rational algebraic curves play an important role on this method.

关键词： Algebraic ordinary differential equation autonomous differential equation Liouvillian solution rational algebraic curve rational parametrizations

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Palladium-catalyzed Desulfinative cross-coupling of Polyhalogenated Aryl Triflates with Aryl Sulfinate Salts:Inversion of Traditional chemoselectivity

引用

chinese Journal of chemistry 2023年第8期41卷 909-914页

作者： Miao Wang On Ying Yuen chau Ming So State key Laboratory of chemical Biology and Drug Discovery and Department of Applied Biology and chemical Technology The Hong Kong Polytechnic UniversityKowloonHong KongChina Henan key Laboratory of Function-Oriented Porous Materials College of Chemistry and Chemical EngineeringLuoyang Normal UniversityLuoyangHenan471934 China The Hong kong Polytechnic University Shenzhen Research Institute ShenzhenGuangdong518057 China

comprehensive Summary This paper presents the first general examples of palladium-catalyzed desulfinative cross-coupling reaction of polyhalogenated aryl triflates with aryl sulfinate salts showing an inversion of the conventional reactivity order of c-Br>c-cl>*** catalyst system,comprising of Pd(OAc)_(2)and tBuPhSelectPhos,exhibited excellent catalytic reactivity and chemoselectivity toward this *** reaction had a wide range of substrate scopes and provided a simple and efficient method for the construction of functionalized biaryl ***,the c-H···Pd interaction from the methine hydrogen of the c2-cyclohexyl group of the indolyl phosphine ligand with the Pd center may contribute a key factor in reactivity and *** with density functional theory(DFT)calculations,the results revealed that the oxidative addition step in this reaction was a controlling-chemoselectivity step.

关键词： Palladium Phosphane ligands Ichemoselectivity Desulfurization Polyhalogenated aryl triflates

来源：

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

Reconfiguring wireless environments via intelligent surfaces for 6G: reflection, modulation, and security

引用

Science china(Information Sciences) 2023年第3期66卷 60-79页

作者： Jindan XU chau YUEN chongwen HUANG Naveed UL HASSAN George c.ALEXANDROPOULOS Marco DI RENZO Mérouane DEBBAH Engineering Product Development Pillar Singapore University of Technology and Design college of Information Science and Electronic Engineering Zhejiang University Department of Electrical Engineering Lahore University of Management Sciences Department of Informatics and Telecommunications National and Kapodistrian University of Athens Technology Innovation Institute Université Paris-Saclay CNRS Centrale Supélec Laboratoire des Signaux et Systèmes

The reconfigurable intelligent surface(RIS) has been recognized as an essential enabling technology for sixth-generation(6G) mobile communication networks. An RIS comprises a large number of small and low-cost reflecting elements whose parameters can be dynamically adjusted with a programmable *** of these elements can effectively reflect a phase-shifted version of the incident electromagnetic wave. By configuring the wave phases in real time, the propagation environment of the information-bearing signals can be dynamically manipulated to enhance communication reliability, boost transmission rate, expand cellular coverage, and strengthen communication security. In this study, we provide an overview on RIS-assisted wireless communications. Specifically, we elaborate on the state-of-the-art enabling techniques for the RIS technology as well as their corresponding substantial benefits from the perspectives of RIS reflection and RIS modulation. With these benefits, we envision the integration of RISs into emerging applications for6G. In addition, communication security is of unprecedented importance in future 6G networks with ubiquitous wireless services in multifarious verticals and areas. We highlight potential contributions of RISs to physical-layer security, in terms of secrecy rate and secrecy outage probability, exemplified by a typical case study from both theoretical and numerical aspects. Finally, we discuss challenges and opportunities on the deployment of RISs in practice to motivate future research.

关键词： reconfigurable intelligent surface physical-layer security RIS-assisted wireless communications phase modulation 6G

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Reconfigurable intelligent surfaces for wireless communications:Overview of hardware designs,channel models,and estimation techniques

引用

Intelligent and converged Networks 2022年第1期3卷 1-32页

作者： Mengnan Jian George c.Alexandropoulos Ertugrul Basar chongwen Huang Ruiqi Liu Yuanwei Liu chau Yuen the Wireless Research Institute ZTE CorporationBeijing 100029China the State key Laboratory of Mobile Network and Mobile Multimedia Technology Shenzhen 518055China Department of Informatics and Telecommunications National and Kapodistrian University of AthensAthens 15784Greece communications Research and Innovation Laboratory(coreLab) Department of Electrical and Electronics EngineeringKoçUniversityIstanbul 34450Turkey college of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China School of Electronic Engineering and computer Science Queen Mary University of LondonLondonE14NSUK. the Engineering Product Development(EPD)Pillar Singapore University of Technology and DesignSingapore 487372Singapore

The demanding objectives for the future sixth generation(6G)of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures for wireless connectivity,as well as revolutionary communication and computing *** the pioneering candidate technologies for 6G belong the reconfigurable intelligent surfaces(RISs),which are artificial planar structures with integrated electronic circuits that can be programmed to manipulate the incoming electromagnetic field in a wide variety of *** RISs in wireless networks have been recently advocated as a revolutionary means to transform any wireless signal propagation environment to a dynamically programmable one,intended for various networking objectives,such as coverage extension and capacity boosting,spatiotemporal focusing with benefits in energy efficiency and secrecy,and low electromagnetic field *** by the recent increasing interests in the field of RISs and the consequent pioneering concept of the RIS-enabled smart wireless environments,in this paper,we overview and taxonomize the latest advances in RIS hardware architectures as well as the most recent developments in the modeling of RIS unit elements and RIS-empowered wireless signal *** also present a thorough overview of the channel estimation approaches for RIS-empowered communications systems,which constitute a prerequisite step for the optimized incorporation of RISs in future wireless ***,we discuss the relevance of the RIS technology in the latest wireless communication standards,and highlight the current and future standardization activities for the RIS technology and the consequent RIS-empowered wireless networking approaches.

关键词： reconfigurable intelligent surfaces beyond 5G 6G channel modeling hardware architecture channel estimation smart wireless environment standardization

来源：

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

comparison of Flux-Switching Machines With and Without Permanent Magnets

引用

chinese Journal of Electrical Engineering 2015年第1期1卷 78-84页

作者： christopher H.T.Lee k.T.chau c.c.chan Department of Electrical and Electronic Engineering The University of Hong KongHong KongChina

In this paper,three advanced flux-switching(FS)machines,namely the radial-field flux-switching permanent-magnet(RF-FSPM)machine,the radial-field flux-switching Dc-field(RF-FSDc)machine,and the axial-field FSDc(AF-FSDc)machine are quantitatively *** the installation of the high-energy-density PM materials,the RF-FSPM machine can definitely provide the superior torque performances as compared to its magnetless ***,the PM machines suffer from two major fundamental problems,namely the high material costs,and the uncontrollable flux *** utilizing the concept of axial-field structure,the AF-FSDc machine can offer comparable torque performance as the RF-FSPM ***,with the consideration of the cost-effectiveness and the control flexibility,the magnetless AF-FSDc machine has exhibited promising potential in various applications.

关键词： Flux-switching magnetless radial-field axial-field cost-effectiveness

来源：

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

clinical efficacy of rosuvastatin in lipid management in chinese patients in Hong kong

引用

chinese Medical Journal 2009年第23期122卷 2814-2819页

作者： Vivian W.Y. Lee T.S. chau Vice EH. Leung kenneth k.c. Lee Brian Tomlinson School of Pharmacy Faculty of Medicine The Chinese University of Hong Kong Hong Kong China Department of Medicine and Therapeutics The Chinese University of Hong Kong Hong Kong China

Background Rosuvastatin has been claimed to be more potent than other statins in its ability to lower the low-density lipoprotein （LDL） cholesterol levels. This study aimed to investigate the clinical efficacy of rosuvastatin in LDL cholesterol lowering therapy for new or switched hyperlipidaemic chinese patients. Methods This study was a retrospective one in patients who took rosuvastatin in the outpatient clinics of Prince of Wales Hospital during the period of July 1,2004 to June 30, 2005. The prescribing pattern, the utilization pattern and the side effect profile were recorded. Attainment of lipid goals for each patient was assessed according to the National cholesterol Education Program Adult Treatment Panel （NcEP ATP） III guidelines. Results A total of 261 chinese patients （mean age （64.8±12） years; 55.6% male） were recruited into the study. The mean LDL-cholesterol level was （3.50±1.29） mmol/L prior to Rosuvastatin and （2.30±1.73） mmol/L after Rosuvastatin treatment （P 〈0.0001）. Rosuvastatin raised the LDL-cholesterol goal achievement rate from 28.0% to 74.3% in all patients combined （P 〈0.0001） and from 11.0% to 79.0% for statin naive patients （P 〈0.0001）. Approximately 4% of patients developed side effects including myalgia, elevated liver enzymes, and dizziness. conclusion Rosuvastatin was effective in improving LDL-cholesterol goal attainment and lowering LDL-cholesterol and triglyceride （TG） levels in either newly started or switched patients.

关键词： cholesterol rosuvastatin clinical efficacy

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

New technique:Detection and location of partial discharge in cast-resin dry-type transformers using a waveguide and a new acoustic emission sensor pair design

引用

Journal of Zhejiang University-Science c(computers and Electronics) 2011年第4期12卷 345-350页

作者： ching-chau SU Jiann-fuh cHEN Department of Electrical Engineering National Cheng Kung University

The acoustic emission (AE) method could be used to detect and locate partial discharges (PD) in cast-resin dry-type ***,due to the high sound attenuation in the filled epoxy,the signal is prone to interference from external noises and thus,in practice,there is little possibility of detecting *** this study,two techniques were developed to alleviate the shortcomings of the AE ***,a waveguide is installed on the high-voltage (HV) windings,so that the acoustic signals of PD will propagate to the AE sensors that are installed on both terminals of the *** location of the winding that has PD can then be detected from the difference in arrival time of the acoustic *** results indicate that the waveguide technique is able to enhance the safety of a measurement system and offers the advantages of easy installation and higher ***,a specially designed AE sensor pair is used to distinguish whether acoustic signals are generated by PD inside the HV winding or by the corona outside the *** these two techniques of waveguide and AE sensor pair not only greatly improves sensitivity but also increases the reliability of the measurement *** test results show that the new techniques can be used to locate precisely the PD in HV windings.

关键词： Partial discharge Acoustic emission cast-resin dry-type transformer Waveguide Acoustic emission sensors

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The roles of atypical protein kinase cs(aPkcs) in the nervous system: targets for neuroregeneration?

引用

Neural Regeneration Research 2020年第8期15卷 1475-1476页

作者： Dennis Dik-Long chau kwok-Fai Lau School of Life Sciences The Chinese University of Hong Kong

The protein kinase c(Pkc)family:Pkc family is a subgroup of the AGc serine-threonine kinases that consists of 10 distinct members in mammals(Spitaler and cantrell,2004).They all contain a c-terminal catalytic domain that is connected to the N-terminal regulatory *** are subdivided into three classes according to their structures and *** classical/conventional Pkc isoforms possess tandem c1 domains that bind to their well-known activators diacylglycerol and phorbol esters and also contain a c2 domain that mediates the binding of ca^2+-sensitive anionic phospholipids.

关键词： domains. subgroup system

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：