Symmetry and phase-selected NMR spectra of liquid crystalline samples

It is demonstrated that the NMR spectra of liquid crystalline samples can be simplified by using multiple quantum filtering. In a system of N spin-12 nuclei, the N or (N-1)-multiple quantum filtered spectra (NQF or (N-1)QF) contain lines which originate only from transitions among the eigenstates belonging to the highest symmetry class of the spin permutation group. In addition the NQF spectra are divided further into two sets of lines which differ in phase by 180 degrees. A method for simulating and analysing multiple quantum filtered spectra is described, with examples from molecules with up to eight interacting spins.     

Analysis of the transverse heat transfer coefficients in a dual channel ITER-type cable-in-conduit conductor

This paper describes a new method to determine the equivalent heat transfer coefficients, i.e., radial and azimuthal, in CICC’s with parallel cooling channels. The method is based on the measurement of the steady state temperature response to a step heating. The experiment is modelled by a set of transport equations for the temperature distribution that contain explicitly the parametric dependence on the transverse heat transfer coefficients. The equations are solved analytically and the values of the equivalent transverse heat transfer coefficients are obtained as the best fit of the experimental temperature distributions. We show the results obtained with the method by application to a short length sample experiment in the SULTAN test facility using an ITER-type CICC with special instrumentation, and with heaters to generate a variety of heat slugs. The values of heat transfer coefficient are consistent with expected values, based in particular on the theory of dispersion in porous media.     

构成廉价电感测量仪的单个IC

本设计实例显示了如何构建一个可靠的低成本的简单电感测量仪.电感测量仪的基础是一个皮尔斯(Pierce)CMOS缓冲振荡器(图1).代替普通的石英晶体,连接待测电感.     

Dynamic scaling in sputter grown tungsten thin films

The evolution of a tungsten thin film grown by magnetron sputtering was studied using a dynamic scaling approach. Film growth was followed in-situ and in real-time by monitoring both the specular and the diffuse X-ray scattered intensities as a function of the time of deposition. The analysis of the scattering data allowed us to determine the two Power Spectral Density (PSD) functions, which describe the thin film topography. The time-dependent PSD-function, which describes the dynamic of the external film surface, is found to obey a universal scaling form, which characterizes the thin film growth. The data collapse of these PSDs into a single master curve was achieved using scaling exponents α = 0.18 ± 0.02 and β = 0.06 ± 0.01. In addition, by analyzing the temporal variation of the roughness conformity, it has been demonstrated that the replication factor decreases exponentially with increasing film thickness and spatial frequency. Hence, for a 25 nm thick film the vertical correlation disappears for spatial frequencies p greater than 3.6 μm^− 1.     

Diffusion boundaries behaviour during a parabolic flight

The behaviour of a diffusion boundary between distilled water and a 1% sodium chloride solution during a parabolic flight has been observed. The presence of a few percent of Earth gravity pulses during the micro gravity conditions is sufficient to largely perturb the diffusion boundary that stabilises again during the subsequent normal gravity conditions present inside the aircraft at the end of each parabola. A numerical simulation of the boundary behaviour agrees with the experimental observation. Student flying team     

Environmental impact of uranium mining and ore processing in the Lagoa Real District, Bahia, Brazil

Uranium mining and processing at Lagoa Real (Bahia, Brazil) started in 2000. Hydrogeochemical monitoring carried out from 1999 to 2001 revealed generally good quality of the water resources outside and inside the mineralized area. No chemical contamination in waters for domestic uses was observed. Hydrochemical characteristics did not vary significantly after 1 year of U exploitation, as compared to premining conditions. Due to the short time of mining, the results cannot exclude future variations in water quality. Leaching experiments helped to describe processes of ore and waste degradation. Sulfate was identified as an indicator for different types of contamination. Potential hazards related to local climate (hot rainy season) were identified. They indicate that tailings derived from the ore processing, destabilized by sulfuric acid attack, may induce acidification and salinization in the surrounding environment. Another potential source of environmental impact could be linked to local radium-rich mineralization, originating radon emission.     

(UWB)<Superscript>2</Superscript>: Uncoordinated,Wireless, Baseborn Medium Access for UWB Communication Networks

A MAC protocol for Ultra Wide Band (UWB) radio networks named (UWB)² is proposed. The algorithm exploits typical features of impulse radio such as large processing gain, and is conceived in conjunction with a synchronization strategy which foresees the presence of a synchronization sequence in each transmitted packet. (UWB)² adopts a pure Aloha approach; Performance analysis of the synchronization tracking mechanism showed in fact that under the preliminary simplistic hypothesis of an AWGN channel, and for a sufficient number of pulses in the synchronization sequence, a fairly high probability of successful synchronization can be achieved, even in the presence of several users and Multi User Interference (MUI). The multiple access scheme is based on the combination of a common control channel provided by a common Time Hopping (TH) code with dedicated data channels associated to transmitter specific TH codes.Results obtained by simulation indicate that (UWB)² can be successfully applied when the number of users spans from a few tens to about one hundred, for data rates ranging from a few thousands to a few hundreds of bits per second. Network throughput was above 99.8% in all considered simulation settings. Such achievement confirms that (UWB)² is a suitable and straightforward solution for large networks of terminals using impulse radio for transmission at low bit rates.On leave from the Institut für Elektro- und Informationstechnik, College of Engineering, University of Duisburg-Essen, Duisburg, Germany.Maria-Gabriella Di Benedetto obtained her Ph.D. in Telecommunications in 1987 from the University of Rome La Sapienza, Italy. In 1991, she joined the Faculty of Engineering of University of Rome La Sapienza, where currently she is a Full Professor of Telecommunications at the Infocom Department. She has held visiting positions at the Massachusetts Institute of Technology, the University of California, Berkeley, and the University of Paris XI, France. In 1994, she received the Mac Kay Professorship award from the University of California, Berkeley. Her research interests include speech analysis and synthesis, and digital communication systems. From 1995 to 2000, she directed four European projects for the design of UMTS. Since 2000 she has been active in fostering the development of Ultra Wide Band (UWB) radio communications in Europe. Within the 5th framework, she directs for the Infocom Dept. two European projects (whyless.com and UCAN) aimed at the design and implementation of UWB ad-hoc networks. Within the 6th EU Framework her “Networking with UWB” research group participates in the PULSERS Integrated Project which will integrate UWB research and development in Europe for the next years, and in the LIAISON Integrated Project as regards the application of UWB to location-based services. She currently also participates in the HYCON network of excellence. Dr. Di Benedetto is co-editor for the IEEE JSAC Special Issue on UWB Radio in Multi-Access Wireless Communications (December 2002)and for the Journal of Communications and Networks Special Issue on Ultra-Wideband Communications (December 2003). Dr. Di Benedetto recently co-authored with Guerino Giancola a book on Ultra Wide Band from radio to the network, titled “Understanding Ultra Wide Band Radio Fundamentals” and published by Prentice Hall in May 2004.Luca De Nardis received his “Laurea” degree in telecommunications engineering from the University of Rome La Sapienza in 2001 with a thesis on wireless network topologies in the framework of the European project whyless.com. He is now pursuing a Ph.D. in Information and Communication Theory in the INFOCOM Department of the University of Rome. Since 2002, he has been participating in the European IST project UCAN, dealing with application of UWB radio to ad-hoc networking. Currently, he is involved in the 6th Framework European projects PULSERS and LIAISON. His research focuses on UWB technology, ad-hoc communication networks organization, Medium Access Control and routing protocols for wireless networks.Matthias Junk was born in Oberhausen, Germany, in 1978. From 1997 to 2004 he studied electrical engineering with main subject communications at the University of Duisburg-Essen, Germany. In 2004 he received his diploma. During his diploma thesis at the University “La Sapienza” in Rome, Italy, he focused on synchronization problems in Ultrawideband Communication Networks.Guerino Giancola received the Laurea degree (magna cum laude) in Telecommunications Engineering from the University of Rome La Sapienza, Italy, 2001, with a thesis on the analysis and the modelling of electromagnetic propagation in outdoor urban scenarios for mobile radio communications systems. Currently, he is working toward the Ph.D. degree in Information and Communication Theory in the INFOCOM Department of the University of Rome La Sapienza. His research interests include Ultra Wide Band radio technology, multi-carrier transmission techniques, and Medium Access Control protocols. From 2001 to 2002, he participated in a national research project financed by the Italian Ministry for University and Scientific-Technological Research (MURST), project PRIN2000: “OFDM Systems for Applications in the Wireless LANs.” Since 2002, he participates in two European Union research projects within the International Society Technologies program (IST): project No. IST-2001-32710: “Ultra-wideband Concepts for Ad-hoc Networks (UCAN)”, and project No. IST-2000-25197: “Whyless.com-The Open Mobile Access Networks.” From 2003, he also participates in the national research project financed by the Italian Ministry for University and Research (MIUR), project FIRB: VICOM-Virtual Immersive COMmunications.     

Standardized evaluation of techniques for measuring the spectralcompression of the myoelectric signal

A digital algorithm was designed to produce band-limited noise with adjustable median frequency and amplitude. This algorithm produces test signals with spectral characteristics typical of those of the surface myoelectric signals encountered in muscle fatigue studies. These synthesized signals provide the basis for standardized evaluation of the performance of various techniques which monitor the spectral compression of the myoelectric signal during muscle fatigue.     

On the centers of a language

The center of a language has been defined in [7, 8, 9] as the set of all words which have infinite right completions in the language. In this paper we extend this notion by taking into account also left and two-sided completions. Thus, for any language X, we consider the left center C_l(X), the right center C_r(X) and two different bilateral centers C₁(X) and C₂(X). Some properties of these centers are derived. In particular the main results of the paper give some general conditions under which C₁(X)=C₂(X)and C_r(C_l(X))=C_l(C_r(X)). These conditions deal with ‘strong’ and ‘weak’ iteration properties and ‘periodicity’ of a language.