Ultrasonic study of molecular association of poly(vinyl chloride) solution in tetrahydrofuran

Ultrasonic absorption, velocity, adiabatic compressibility, relaxation time and relaxation amplitude measurements are reported on poly(vinyl chloride) (PVC) solution in tetrahydrofuran (THF) using pulsed ultrasonic apparatus operating at 2 MHz and 313 K. Results show a linear increase of velocity. density, viscosity, absorption coefficient, relaxation time and relaxation amplitude values with the increase of PVC concentration in THF. In contrast the compressibility decreases with increasing PVC concentration. This suggests interaction between PVC and THF molecules.     

Electrolyte/Structure?Dependent Cocktail Mediation Enabling High?Rate/Low?Plateau Metal Sulfide Anodes for Sodium Storage

As promising anodes for sodium-ion batteries, metal sulfides ubiquitously suffer from low-rate and high-plateau issues, greatly hindering their application in f...     

Deposition thickness based high-throughput nano-imprint template

International Technology Roadmap for Semiconductors 2003 projected nano-imprint lithography has the potential of high throughput, sub-20 nm resolution, and low cost [S.Y. Chou, P.R. Krauss, P.J. Renstrom, Appl. Phys. Lett. 67 (1995) 3144; Science 272 (1996) 85, J.A. Rogers, C. Mirkin, Mater. Res. Bull. 26 (2001)]. For nano-imprint lithography, a template with 1X resolution is required. The existing industrial infrastructure for supporting deep ultra violet 4X photo masks by e-beam and/or a laser beam scanning writer does not offer pitch (center-to-center distance of an array of patterned lines) less than ∼60 nm [<http://public.itrs.net/2003ITRS>]. For nano-imprint lithography to be accepted across the industry, a reproducible simple fabrication process to make a high resolution, single emboss template is essential [L. Jay Guo, J. Phys. D: Appl. Phys. 37 (2004) R123-R141]. Here we show, a general fabrication method and fabricated nano-imprint templates with sub-15 nm template line width and 10 nm pitch length through out the entire 200 mm wafer, varying the deposition thickness of multiple alternate films, using atomic layer deposition. Although multilayer nano-imprint templates and their exciting use have been demonstrated, [W.J. Dauksher et al., J. Vac. Sci. Technol. B 22 (2004) 3306, B. Heidari, et al., The 49th international conference on electron, ion and photon beam technology and nanofabrication, Orlando, Florida, 2005, William M. Tong, et al., Proc. SPIE 5751 (2005) 46-55, N.A. Melosh, A. Boukai, F. Diana, B. Gerardot, A. Badolato, P.M. Petroff, J.R. Heath, Science 300 (2003) 112] such a small pitch was not shown and either complex lattice mismatch-based epitaxially grown films or unconventional etch chemistry was used. The bare necessity was a simple and economical fabrication process for a high throughput nano-imprint template. In that context, we have developed a template fabrication process using classical micro-fabrication techniques. Successful use of these techniques made the template fabrication process simple, economical, and expedient. Also a novel technique to provide flexible and accurate alignment for nanowire patterning has been described. In this technique, nanowire patterning is accomplished on the entire wafer with a single impression. Industry level batch-fabrication of our scheme illustrates its reproducibility and manufacturability. We anticipate, this simple, economical and time saving technique will help researchers and developers to perform their experiment on nano-scale feature patterned substrates easily and conveniently.     

Throughput Analysis and Admission Control for IEEE 802.11a

We propose a new Markov model for the distributed coordination function (DCF) of IEEE 802.11. The model incorporates carrier sense, non-saturated traffic and SNR, for both basic and RTS/CTS access mechanisms. Analysis of the model shows that the throughput first increases, and then decreases with the number of active stations, suggesting the need for an admission control mechanism.We introduce such a mechanism, which tries to maximize the throughput while maintaining a fair allocation. The maximum achievable throughput is tracked by the mechanism as the number of active stations increases. An extensive performance analysis shows that the mechanism provides significant improvements.Mustafa Ergen received the B.S. degree in electrical engineering from Middle East Technical University (METU) and was the METU Valedictorian in 2000. He received the M.S. and Ph.D. degrees in electrical engineering in 2002 and 2004, the MOT certificate of HAAS Business School in 2003, and the M.A. degree in International and Area Studies in 2004 from the University of California, Berkeley.Dr. Ergen has been conducting research in wireless communication networks with an emphasis on sensor networks, wireless LAN and OFDM systems and is the author of many works in the field, including the book (with A.R.S. Bahai and B.R. Saltzberg) Multi-Carrier Digital Communications: Theory and Applications of OFDM (New York: Springer, 2004).He is National Semiconductor Post Doctoral Fellow and was awarded eight times Bulent Kerim Altay Award by department of electrical engineering in METU and received Best Student Paper Award in IEEE ISCC 2003 and has an invited paper in IEEE GLOBECOM CAMAD 200.Pravin Varaiya is Nortel Networks Distinguished Professor in the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley. From 1975 to 1992, he was also Professor of Economics at Berkeley. His research is concerned with communication networks, transportation, and hybrid systems. He has taught at MIT and the Federal University of Rio de Janeiro, Varaiya has held a Guggenheim Fellowship and a Miller Research Professorship. He received an Honorary Doctorate from L’Institut National Polytechnique de Toulouse, and the Field Medal of the IEEE Control Systems Society. He is a Fellow of IEEE and a member of the National Academy of Engineering. He is on the editorial board of several journals, including “Discrete Event Dynamical Systems” and “Transportation Research-C.” He has co-authored three books and more than 250 technical papers. The second edition of “High-Performance Communication Networks” (with Jean Walrand) was published by Morgan-Kaufmann in 2000. “Structure and interpretation of signals and systems” (with Edward Lee) was published in 2002 by Addison-Wesley.     

Renewable and Storage Energy Integration for Smart Grid Housing

This paper presents the design,implementation and testing of an embedded system that integrates solar and storage energy resources to smart homes within the smart microgrid.The proposed system provides the required home energy by installing renewable energy and storage devices.It also manages and schedules the power flow during peak and off-peak periods.In addition,a two-way communication protocol is developed to enable the home owners and the utility service provider to improve the energy flow and the consumption efficiency.The system can be an integral part for homes in a smart grid or smart microgrid power networks.A prototype for the proposed system was designed,implemented and tested by using a controlled load bank to simulate a scaled random real house consumption behavior.Three different scenarios were tested and the results and findings are reported.Moreover,data flow security among the home,home owners and utility server is developed to minimize cyber-attacks.     

Collision avoidance slot allocation scheme for multi-cluster wireless sensor networks

This paper introduces a collision avoidance slot allocation scheme for Time Division Multiple Access (TDMA) based Medium Access Control (MAC) in multi-cluster wireless sensor networks. TDMA MAC protocols have built-in active-sleep duty cycle that can be leveraged for limiting idle listening. Also, they can overcome the overhearing problem, thus have better energy efficiency. Enabling concurrent intra-cluster communications using a single radio channel is a key issue in TDMA MAC protocols. Using orthogonal frequency channels or different Code Division Multiple Access codes for different adjacent clusters can solve the problem at the expense of cost. In this paper, we propose a new distributed slot allocation protocol called  Coordinated   Time   Slot   Allocation (CTSA) that can reduce collisions significantly using a single radio channel. We use simulations to study the effects of different system parameters on the performance of our proposed protocol. Simulation results show that applying CTSA over clustering protocols can significantly reduce collisions. It also shows fast convergence for our proposed CTSA protocol. In this paper we apply our CTSA scheme to the Low Energy Adaptive Clustering Hierarchy protocol which forms the basis for many cluster based routing protocols. CTSA is also compared with the SRSA algorithm proposed by Wu and Biswas (Wirel Netw 13(5):691–703, 2007) by means of simulation.     

Spectral efficiency (SE) enhancement of NOMA system through iterative power assignment

Wireless Networks - This paper studies enhancing non-orthogonal multiple access (NOMA) spectral efficiency (SE) through optimizing the assigned power to each NOMA user depending on their channel...