Lennard-Jones Viscosities in Wide Ranges of Temperature and Density: Fast Calculations Using a Steady–State Periodic Perturbation Method

A method for fast calculation of viscosity from molecular dynamics simulation is revisited. The method consists of using a steady-state periodic perturbation. A methodology to choose the amplitude of the external perturbation, which is one of the major practical issues in the original technique of Gosling et al. [Mol. Phys. 26: 1475 (1973)] is proposed. The amplitude of the perturbation required for fast caculations and the viscosity values for wide ranges of temperature and density of the Lennard-Jones (LJ) model fluid are reported. The viscosity results are in agreement with recent LJ viscosity calculations. Additionally, the simulations demonstrate that the proposed approach is suitable to efficiently generate viscosity data of good quality.     

Power limits for secondary devices operating on TV white spaces

The use of TV white spaces as an alternative to overcome spectrum scarcity is a huge opportunity for new telecommunication systems and services. While being attractive for its desirable propagation characteristics, this part of the spectrum imposes a major difficulty from design and regulatory perspectives: how to optimize the use of spectrum and to ensure the protection of primary users, TV systems for example, at the same time. This paper discusses strategies to be adopted by geo-location database operators to calculate adaptive maximum permitted power levels for secondary devices, according to permissible levels of interference into the digital terrestrial television primary system.     

Muscle composition and fatty acid profile in lambs fattened in drylot or pasture

The effects of two fattening systems on muscle composition and fatty acid profile were determined in an experiment using samples of the longissimus dorsi (LD) muscle of 24 ram lambs (slaughter weight 29–31 kg). The fattening systems were: (i) drylot (a mixture of maize, soybean, wheat and minerals) and (ii) grazing (Cynodon dactylon). The lambs fattened in the drylot system presented higher fat levels (p<0.01), but lower concentrations of moisture (p<0.01) and cholesterol (p<0.05). The lipid content presented a negative correlation with moisture and protein. In lambs fattened in the drylot system increasing levels of fatness of LD muscle were associated with a decrease (p<0.05) in myristic and palmitic acids, but myristic, palmitic and linoleic acids increased (p<0.05) as the cholesterol levels of the muscles increased.     

Applying SMT-based verification to hardware/software partitioning in embedded systems

When performing hardware/software co-design for embedded systems, the problem of which functions of the system should be implemented in hardware (HW) or in software (SW) emerges. This problem is known as HW/SW partitioning. Over the last 10 years, a significant research effort has been carried out in this area. In this paper, we present two new approaches to solve the HW/SW partitioning problem by using verification techniques based on satisfiability modulo theories (SMT). We compare the results using the traditional technique of integer linear programming, specifically binary integer programming and a modern method of optimization by genetic algorithm. The experimental results show that SMT-based verification techniques can be effective in particular cases to solve the HW/SW partition problem optimally using a state-of-the-art model checker based on SMT solvers, when compared against traditional techniques.     

A scheduling algorithm for QoS support in IEEE802.11 networks

This article presents a scheduling algorithm for the IEEE 802.11e hybrid coordination function under definition by the IEEE 802.11e task group. HCF can be used to provide IP quality of service guarantees in IEEE802.11e infrastructure WLANs. The enhanced distributed coordination function is mainly used for data transmission without QoS guarantees, but can also be used to decrease the transmission delay of QoS-sensitive traffic. Scheduling of queued packets follows a delay-earliest-due-date algorithm. The proposed algorithm is compatible with the link adaptation mechanisms implemented in commercial WLANs, as it limits the amount of time during which the stations control the wireless medium. The performance of the algorithm is evaluated through computer simulation and compared with the reference scheduler presented by the IEEE 802.11e task group.     

Wireless LANs: From WarChalking to Open Access Networks

This work discusses the evolution of W-LANs from their current status of wireless termination of LAN services to a possible global infrastructure where the access networks become open to multiple operators and a vehicle of a win-win scenario, where both users and operators benefit from the new network architecture. The idea of Open Access Networks (OANs) can go beyond wireless HotSpots and be generalized to a generic shared access infrastructure that fosters service operators competition and drastically reduces the cost of last mile coverage.The general concept of Open Access Networks is detailed, highlighting its difference with the more traditional model of vertical integration of the access network into the global service. About the OANs development, it is shown how to support the quick and smooth evolution of the infrastructure toward a widespread and reliable communication support.Business models are discussed by mentioning the different actors, the market organization and the different organization forms.The final part of the paper is devoted to technical challenges such as access control, security, privacy, roaming, resource exploitation and service differentiation. As an example of how to tackle these problems, we discuss a pricing technique devoted to resource management and billing support.In addition we present a simulation on how the OAN concept can speed-up the deployment of broadband access in a real case.A preliminary version of this paper with the title “Global Growth of Open Access Networks: from WarChalking and Connection Sharing to Sustainable Business” was presented at WMASH 2003. Roberto Battiti received the Laurea degree from the University of Trento, Italy, in 1985 and the Ph.D. degree from the California Institute of Technology (Caltech), USA, in 1990. He has been a consultant in the area of parallel computing and pattern recognition and since 1991 he has been a faculty member at the University of Trento, where he is now full professor of Computer Networks. His main research interests are heuristic algorithms for optimization problems, in particular reactive search algorithms for maximum clique, maximum satisfiability, graph coloring, networks and massively parallel architectures, code assignment in wireless and cellular networks, protocols for pricing and Quality of Service in wireless networks.Prof. R. Battiti is currently Dean of the international Graduate School in Information and Communication Technologies at Trento, Deputy Dean at the Faculty of Science, member of the advisory committee for the future Telecommunications Plan of the Autonomous Province of Trento. Prof. R. Battiti is associate editor of various scientific journals. He is the author of more than fifty scientific publications, including special issues dedicated to experimental algorithmics and wireless on-demand networks.R. Battiti is a member of IEEE Computer Society and ACM Sigmobile. Renato Lo Cigno is Associate Professor at the Department of Computer Science and Telecommunications (DIT) of the University of Trento, Italy. He received a Dr. Ing. degree in Electronic Engineering from Politecnico di Torino in 1988. From 1989 to 2002 has been with the Telecommunication Research Group of the Electronics Department of Politecnico di Torino.From June 1998 to February 1999, he was at the CS Department at UCLA as Visiting Scholar under grant CNR 203.15.8. He is coauthor of more than 90 journal and conference papers in the area of communication networks and systems. His curent research interests are in performance evaluation of wired and wireless networks, modeling and simulation techniques, flow and congestion control, as well as network management and architecture. Renato Lo Cigno is member of the IEEE Communication Society and ACM Sigcomm. Mikalai Sabel received his master degree in radio physics from Belorussian State University in 2002. He is now pursuing his Ph.D. at the international Graduate School of Information and Communication Technologies at University of Trento, Italy. His research interest include wireless LANs, pricing and incentive engineering, IEEE802.11 MAC protocol. His current research is focused on optimization algorithms that can provide stability and maximum global welfare in a non-cooperative environment where singles tries to maximize their own benefit function. Experimentation of such schemes to pricing techniques and micro-payments in TLC networks provides the application environment of the fundamental research. Fredrik Orava is associate professor at KTH, Stockholm, Sweden. He conducts research into scalable (in terms of cost, capacity, number of users and devices etc.) communication system architectures and technologies. He has a MSc in engineering physics from Uppsala University and a PhD in computer systems also from Uppsala University. He previously held positions as researcher at the Swedish Institute for Computer Science (SICS); senior lecturer and manager of the telecommunications systems laboratory at the department for teleinformatics, KTH; acting professor in telecomunication systems at KTH; director for the Swedish Centre for Internet Technologies; and vice president of Dynarc AB with world wide responsibility for product management. Dynarc AB develops, manufactures and sells IP routers for optical IP networks. Bjorn Pehrson is a professor of telecommunication systems at KTH, the Royal Institute of Technology in Stockholm, since 1992, where he has also served as a department chairman and vice dean. He had his PhD from Uppsala University 1975 where he also served as senior lecturer and established a research group in computer and communication technology. During the period 1985-1992 he participated in the establishment of the Swedish Institute of Computer Science. Björn Pehrson research interests are currently focussed on open network topologies allowing different actors forming new value chains to build networks together based on different, sometimes very local business models. The results are applied in testbeds, especially in rural areas and in developing countries.This revised version was published online in August 2005 with a corrected cover date.     

Nanofabrication of 30 nm devices incorporating low resistance magnetic tunnel junctions

In this paper the electron-beam lithography conditions and the nanofabrication process are described for current-perpendicular-to-plane (CPP) pillar devices with 30 nm critical dimensions. This work combines a RAITH-150 tool with a negative e-beam resist (AR-7520) so that dense nanopillar arrays are patterned fast into large area samples. The resist dilution and coating conditions are optimized, aiming at its thickness reduction down to 80 nm. The exposure parameters are tuned for different geometries and dimensions, so that features down to 30 nm are exposed with good accuracy (+/- 1.9 nm) and reproducibility. The complete integration of these nanoelements into CPP devices involved electron beam lithography, ion milling for pattern transfer and chemical-mechanical polishing (CMP). Results on devices incorporating very low resistance-area (R x A) MTJ films deposited by Ion beam assisted deposition are shown, for MTJ stacks with R x A down to 0.8 omega x microm2. Device characterization includes electrical measurement of the pillar resistance and the transfer curves under dc magnetic fields (TMR up to 40%).     

The normal spectral emittance of erbium,dysprosium and samarium above 1000 K

An apparatus for measuring the normal spectral emittance (λ = 0.645 μ.) of metals with very high vapor pressures has been designed and used for erbium, dysprosium and samarium at temperatures above 1000 K. The samples are maintained in an argon atmosphere at a pressure slightly above atmospheric pressure. The measured normal spectral emittances are: Erbium, (solid), ∈ _nλ = 0.372 ± 0.011; (liquid), ∈ _nλ = 0.372 ± 0.011; Dysprosium, (solid), ∈ _nλ = 0.631 – 1.889 × 10^–4 T (deg K); (liquid), ∈ _nλ = 0.297 ± 0.088; Samarium, (solid), ∈ _nλ = 0.437 ± 0.030; (liquid, estimated), ∈ _nλ = 0.437 ± 0.03. TERRY S. KING, formerly Undergraduate Research Helper. DORAB N. BARIA, formerly NSF Presidential Intern and Post-Doctoral Fellow. Prepared for the Energy Research and Development Administration under Contract No. W-7405-eng-82.