检索结果-南通市图书馆

Observations of the first light and the epoch of reionization

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第8期12卷 865-890页

作者： Xiaohui Fan Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China Steward Observatory, The University of Arizona, tucson, 85721, USA Kavli Institute for Astronomy and Astrophysics Peking University Beijing 100871 China Steward Observatory The University of Arizona Tucson 85721 USA

Studying the first generation of stars, galaxies and supermassive black holes as well as the epoch of reionization is one of the fundamental questions of modern as- trophysics. The last few years have witnessed the first confirmation of the discoveries of galaxies, quasars and Gamma-Ray Bursts at z 〉 7, with possible detections at z - 10. There is also mounting evidence that cosmic reionization is a prolonged pro- cess that peaks around z - 10 and ends at z- 6 - 7. Observations of the highest redshift intergalactic medium and the most metal-poor stars in the Galaxy begin to constrain the earliest chemical enrichment processes in the Universe. These observa- tions provide a glimpse of cosmic history over the first billion years after the Big Bang. In this review, we will present recent results on the observations of the high-redshift Universe over the past decade, highlight key challenges and uncertainties in these observations, and preview what is possible with the next generation facilities in studying the first light and mapping the history of reionization.

关键词： galaxies: evolution -- galaxies: formation -- galaxies: high-redshift-- intergalactic medium -- quasars: general -- cosmology: large-scale structure ofuniverse

Application of a multilayer feedforward network to voiced-unvoiced-silence classifications of speech

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Acoustics 1992年第2期11卷 167-178页

作者： QI Yingyong(Department of Speech and Hearing Sciences, University of Arizona , tucson . Arizona 85721)

A procedure has been developed for making voiced, unvoiced, and silence classifications of speech by using a multilayer feedforward net -work. Speech signals were analyzed sequentially and a feature vector was obtained for each segment . The feature vector served as input to a 3-layer feedforward network in which voiced, unvoiced, and silence classification was made. The network had a 6-12-3 node architecture and was trained using the generalized delta rule for back propagation of error . The performance of the network was evaluated using speech samples from 3 male and 3 female speakers . A speaker-dependent classification rate of 94.7% and speaker-independent classification rate of 94.3% were obtained. It is concluded that the voiced, unvoiced , and silence classification of speech can be effectively accomplished using a multilayer feedforward network.

关键词： work IEEE net Application of a multilayer feedforward network to voiced-unvoiced-silence classifications of speech

CHANNEL EROSION DAMAGES AND PROTECTION MEASURES IN SOUTHEAST ARIZONA

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 1999年第2期14卷 19-24页

作者： Fazle KARIM (Pima County Dept. of Transportation and Flood Control, Flood Control Engr. Division, 201 N. Stone Avenue, tucson. Arizona 85701. USA)

Channel morphology of the ephemeral streams in Southeast Arizona is influenced by both lateral and vertical channel changes occurring during major floods. The recent floods in the area have caused a variety of erosion hazards including bank erosion, channel migration, bed degradation. and excessive scour at bridge abutments and piers. The floods of 1983 and 1993 were comparable in terms of peak discharge and duration, but the estimated total damage during the 1993 flood was much lower (about 14%), because of extensive soil cement bank protection constructed along the major rivers after the 1983 flood. The performance of the soil cement bank and bed stabilization during the 1993 flood (protected banks were generally unaffected by flood flows) thus demonstrates the effectiveness of soil cement as the materials for erosion protection measures in ephemeral streams. Advantages of soil cement protection are its ease of construction. low cost, use of in-place soil and environmental attractiveness because of its natural appearance. A new approach for protection against bank erosion and channel migration, using flexible spurs consisting of a series of pile-supported permeable panels of synthetic nets, is described.

关键词： Channel erosion Soil cement protection Bed stabilization

TRANSITION METAL CLUSTERS AS NOVEL PLATFORMS FOR COORDINATION AND ORGANOMETALLIC CHEMISTRY

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

TRANSITION METAL CLUSTERS AS NOVEL PLATFORMS FOR COORDINATIO...

中国化学会第五届全国结构化学学术会议

作者： Zhiping Zheng Department of Chemistry,University of Arizona,tucson,Arizona 85721,USA,

＜正＞Transition metal clusters are a unique class of chemical *** only do they have well-defined molecular structures,they also exhibit interesting and potentially useful properties that are inherent to metal-metal b...

关键词：

SOME RECENT PROGRESS IN STUDIES ON ACTIVE CONTROL OF WALL-JET FLOWS

在线全文

cnki会议

学校读者我要写书评

暂无评论

Transactions of Nanjing University of Aeronautics and Astronautics 1994年第2期11卷 119-131页

作者： Zhou Mingde.(Aerospace and Mechanical Engineering,The University of Arizona tucson,Arizona 85721,USA)

Active control of wall his is important in both application and basic researches. In order to establish a solid background for the expected application,it is necessary to perform detailed studies on the base nows,on their stability characteristics and on the identification technique of coherent structures. This paper is a summarizing article rather than a detailed technical report, Its main purpose is just to introduce the recent progress in the related area.

关键词： turbulent flow control wall jets coherent structure flow stability

TTM Interferometric Profiling

在线全文

学校读者我要写书评

暂无评论

TTM Interferometric Profiling

中国光学学会2006年学术大会

作者： Sen Han Veeco Metrology 2650 East Elvira Road, tucson AZ 85706

＜正＞Interferometric profiling has been employed successfully in data storage, semiconductors, materials science, optics, and biosciences for decades. The advanced optical profilers are typical white-light interferometers applied to testing rough surfaces using vertical scanning or smooth surfaces using phase shifting. Due to their high speed, accuracy, and flexibility, optical profilers have been widely used to measure surface features of unpackaged microelectromechanical systems （MEMS） devices.

关键词：

DNA G-quadruplexes as potential anticancer drug targets

在线全文

cnki会议

学校读者我要写书评

暂无评论

DNA G-quadruplexes as potential anticancer drug targets

第一届全国生物物理化学会议暨生物物理化学发展战略研讨会

作者： Danzhou Yang~(1,2,3,4,*) 1 College of Pharmacy,University of Arizona,1703 E.Mabel St,tucson,AZ 85721 2 Arizona Cancer Center,1515 N.Campbell Avenue,tucson,AZ 85724 3 BIO5 Institute,University of Arizona,1140 E.South Campus Dr,tucson,AZ 85721 4 Dept of Chemistry,University of Arizona,tucson,AZ 85721

G-quadruplex DNA secondary structures(Fig 1),formed in specific G-rich sequences,have recently emerged as a new class of molecular targets for cancer *** DNA G-quadruplex secondary structures have been demonstrated as potential regulatory elements in regions of biological significance,such as in human telomeres and in the promoters

关键词：

Bio-Medical Applications and Image Analysis of Microscope Profiler

在线全文

cnki会议

学校读者我要写书评

暂无评论

Bio-Medical Applications and Image Analysis of Microscope Pr...

第十二届中国体视学与图像分析学术会议

作者： SEN Han (Veeco Instruments,Inc.,2650 E.Elvira Road,tucson,AZ 85756,USA)

Interferometric profilers have been widely employed in semiconductor,data storage, MEMS and research fields for more than two decades. These systems are known to produce rapid,accurate, and repeatable characterization of surface roughness, form,film thickness,and more recently dynamic be- havior of MEMS and other moving ***, however,optical profiling has been playing a more and more important role in biosensor,living biological sys- tem and biomedical applications. The measurement of living cells presents technical challenges for standard interferometric *** system must be able to measure objects in fluid,where the index of the cell and fluid is sometimes very simi- ***,the timescales of change for different experi- ments involving living cells can vary greatly,requiring a variety of measurement methodologies to maximize data,including strobed interferometry and video-rate deformation *** addition,the responses of individual cells can differ significantly from one another in a given experiment,making measurement of large numbers of cells in parallel very important to achieve proper statistical sampling of the *** pres- ents challenges both in how to best trade field-of-view for lateral resolution and for how each surface image is analyzed,as the software intelligently track and log in- formation from each of many different ceils simultane- ously. Measurement of inorganic parts,such as cantile- ver arrays,removes some of the challenges associated with ***,the need for varying temporal range,parallelism of measurement across parts,and intelligent analyses that allow the researcher to easily connect theory with the implemented part are still pres- *** paper describes how multiple interferometric techniques,implemented on a single system,can be combined to provide viable measurements of both bio- sensors and cells,enabling collection of data in envi- ronments and with timescales not previously achieva- b

关键词： interferometer optical profiler biosensor cellular measurement

A multi-target approach for isolated word recognition using artificial neural network

在线全文

cnki会议

学校读者我要写书评

暂无评论

Chinese Journal of Acoustics 1994年第2期13卷 160-168页

作者： QI Yingyong and BI Ning(Dept. of Speech and Hearing Sciences. University of Arizona. tucson, AZ 85721 )

We present a multi-target approach in network training for isolated word recognition. In this approach, each word was designated to produce output at more than one-target in the output laycr of the network during *** specification of the target vector was mode based on the statistical or cluster structure of training patterns. Experiments consisted of classification of simulated data and isolated spoken words indicated that the multi-target approach improved the overall performance of the network.

关键词： Neural network Speech recognition