Metric anticipation to manage mobility in mobile mesh and ad hoc wireless networks

In mobile ad hoc networks (MANETs), node mobility management is performed by the routing protocol. It may use metrics to reflect link state/quality. But, the delay between measures of the link quality and its integration in the route computation is very detrimental to the mobility management. Consequently, routing protocols may use lossy links for a few seconds leading to a significant performance deterioration. In this paper, we propose a new routing metric technique calculation which aims at anticipating link quality. Basically, the idea is to predict metric values a few seconds in advance, in order to compensate the delay involved by the link quality measurement and their dissemination by the routing protocol. Our technique is based on measurements of signal strength and is integrated in two classical routing metrics: ETX (expected transmission count) and ETT (expected transmission time). Validations are performed through both simulations and a testbed experimentation with OLSR as routing protocol. NS-3 simulations show that our metric may lead to a perfect mobility management with a packet delivery ratio of 100%. Experiments on a testbed prove the feasibility of our approach and show that this technique reduces the packet error rate by a factor of 3 in an indoor environment compared to the classical metrics calculation.     

Using Bandwidth-Space Partitioning to Improve Cell Coverage and Near-Far Unfair Access Problem in a Noise-Limited CDMA Cellular Network

This paper concerns CDMA cellular networks equipped with conventional matched filter receivers. For this type of cellular networks, two problems exist. One is the inverse relationship between the coverage and capacity, and the other one is the near-far unfair access problem. To resolve these two problems, a bandwidth-space partitioning technique is adopted. Several admission control schemes based on the bandwidth-space partitioning technique are proposed, and their performances are evaluated based on the simulation.Shih-Tsung Yang received his B.S. (1989) and M.S. (1991) degrees in electrical engineering from the National Taiwan University, and Ph.D. (1999) degree in electrical and computer engineering from University of Maryland, College Park.From 1999 to 2000, he was with SBC Technology Resourtces, Inc. where he was involved in the network architecture design for the ATM based networks. From November 2000 to May 2003, he was with Transilica/Microtune where he was involved in the design of Baseband and RF for the wireless communications. Since May 2003, Dr. Yang is now with Genesys Logic, Inc. where he is responsible for the baseband design of the WLAN and Ethernet.Dr. Yang’s research interests are in the area of Digital Communications, Communication networks and signal processing. E-mail: thomas.yang@genesyslogic.com.twAnthony Ephremides received his B.S. degree from the National Technical University of Athens (1967), and M.S. (1969) and Ph.D. (1971) degrees from Princeton University, all in Electrical Engineering. He has been at the University of Maryland since 1971, and currently holds a joint appointment as Professor in the Electrical Engineering Department and in the Institute of Systems Research (ISR) of which he is a founding member. He is co-founder of the NASA Center for Commercial Development of Space on Hybrid and Satellite Communications Networks established in 1991 at Maryland as an off-shoot of the ISR. He served as Co-Director of that Center from 1991 to 1994.He was a Visiting Professor in 1978 at the National Technical University in Athenas, Greece, and in 1979 at the EECS Department of the University of California, Berkeley, and at INRIA, France. During 1985-1986 he was on leave at MIT and ETH in Zurich, Switzerland. He was the General Chairman of the 1986 IEEE Conference on Decision and Control in Athens, Greece and of the 1991 IEEE International Symposium on Information Theory in Budapest, Hungary. He also organized two workshops on Information theory in 1984 (Hot Springs, VA) and in 1999 (Metsovo, Greece). He was the Technical Program Co-Chair of the IEEE INFOCOM in New York City in 1999 and of the IEEE International Symposium on Information theory in Sorrento, Italy in 2000. He has also been the Director of the Fairchild Scholars and Doctoral Fellows Program, an academic and research partnership program in Satellite Communications between Fairchild Industries and the University of Maryland. He won the IEEE Donald E. Fink Prize Paper Award (1992) and he was the first recipient of the Sigmobile Award of the ACM (Association of Computer Machinery) for contributions to wireless communications in 1997. He has been the President of the Information Theory Society of the IEEE (1987) and has served on its Board of Governors almost continuously from 1981 until the present. He was elected to the Board of Directors of the IEEE in 1989 and 1990. Dr. Ephremides has authored or co-authored over 100 technical journal papers and 300 technical conference presentations. He has also contributed chapters to several books and edited numerous special issues of scientific journals. He has also won awards from the Maryland Office of Technology Liaison for the commercialization of products and ideas stemming from his research. He has served on the Editorial Boards of the IEEE Transactions on Automatic Control, IEEE Transactions on Information theory, the Journal of Wireless Networks, and the International Journal of Satellite Communications.He has been the Dissertation Supervisor of over twenty Ph.D. students who now hold prominent positions in academia, industry, and research labs. He is the founder and President of Pontos, Inc., a Maryland company that provides technical consulting services, since 1980.Dr. Ephremides’ interests are in the areas of communication theory, communication systems and networks, queueing systems, signal processing, and satellite communications. His research has been continuously supported since 1971 by NSF, NASA, ONR, ARL, NRL, NSA, and Industry. E-mail: tony@eng.umd.edu     

A steerable complex wavelet construction and its application to image denoising.

This work addresses the design of a novel complex steerable wavelet construction, the generation of transform-space feature measurements associated with corner and edge presence and orientation properties, and the application of these measurements directly to image denoising. The decomposition uses pairs of bandpass filters that display symmetry and antisymmetry about a steerable axis of orientation. While the angular characterization of the bandpass filters is similar to those previously described, the radial characteristic is new, as is the manner of constructing the interpolation functions for steering. The complex filters have been engineered into a multirate system, providing a synthesis and analysis subband filtering system with good reconstruction properties. Although the performance of our proposed denoising strategy is currently below that of recently reported state-of-the-art techniques in denoising, it does compare favorably with wavelet coring approaches employing global thresholds and with an "Oracle" shrinkage technique, and presents a very promising avenue for exploring structure-based denoising in the wavelet domain.     

A nonparametric statistical method for image segmentation using information theory and curve evolution.

In this paper, we present a new information-theoretic approach to image segmentation. We cast the segmentation problem as the maximization of the mutual information between the region labels and the image pixel intensities, subject to a constraint on the total length of the region boundaries. We assume that the probability densities associated with the image pixel intensities within each region are completely unknown a priori, and we formulate the problem based on nonparametric density estimates. Due to the nonparametric structure, our method does not require the image regions to have a particular type of probability distribution and does not require the extraction and use of a particular statistic. We solve the information-theoretic optimization problem by deriving the associated gradient flows and applying curve evolution techniques. We use level-set methods to implement the resulting evolution. The experimental results based on both synthetic and real images demonstrate that the proposed technique can solve a variety of challenging image segmentation problems. Futhermore, our method, which does not require any training, performs as good as methods based on training.     

A Catalytic and Positively Thermosensitive Molecularly Imprinted Polymer

A catalytic and positively thermosensitive molecularly imprinted polymer is reported. This unique imprinted polymer was composed of 4‐nitrophenyl phosphate‐imprinted networks that exhibited a thermosensitive interpolymer interaction between poly(2‐trifluoromethylacrylic acid) (PTFMA) and poly(1‐vinylimidazole) (PVI), which contains catalytically active sites. At a relatively low temperature (such as 20 °C), this imprinted polymer did not demonstrate significant catalytic activity for the hydrolysis of 4‐nitrophenyl acetate due to the interpolymer complexation between PVI and PTFMA, which blocked access to the active sites of PVI and caused shrinking of the polymer. Conversely, at higher temperatures (such as 40 °C), this polymer showed significant catalytic activity resulting from the dissociation of the interpolymer complexes between PVI and PTFMA, which facilitated access to the active sites of PVI and inflated the polymer. Unlike previously reported poly(N‐isopropylacrylamide)‐based molecularly imprinted polymers, which demonstrated decreased molecular recognition and catalytic activity with increased temperatures, i.e., negatively thermosensitive molecular recognition and catalysis abilities, this imprinted polymer exploits the unique interpolymer interaction between PVI and PTFMA, enabling the reversed thermal responsiveness.     

A Zipper‐Like On/Off‐Switchable Molecularly Imprinted Polymer

A zipper‐like on/off‐switchable molecularly imprinted polymer is reported. This unique imprinted polymer was composed of template‐imprinted polymeric networks that incorporate zipper‐like interactions between poly(acrylamide) (PAAm) and poly(2‐acrylamide‐2‐methyl propanesulfonic acid) (PAMPS). This polymer showed marginal recognition ability towards the imprint species under low temperature conditions, due to the interpolymer interaction between PAAm and PAMPS, which inhibited access to the imprinted networks. In contrast, at relatively high temperatures (such as 40 °C), the polymer demonstrated significant molecular recognition ability towards the imprint species resulting from the dissociation of the interpolymer complexes of PAAm and PAMPS, which enabled access to the imprint networks. Unlike previously reported PNIPAm‐based imprinted polymers, which demonstrate alterable molecular recognition simply because of the thermosensitive hydrophilicity/hydrophobicity of PNIPAm, this polymer employed a zipper‐like supramolecular architecture between PAAm and PAMPS, thereby enabling switchable molecular recognition.     

Asphaltene Deposition During Steam-Assisted Gravity Drainage: Effect of Non-Condensable Gases

Asphaltene deposition was investigated during laboratory-scale steam-assisted gravity drainage (SAGD) experiments to probe in situ upgrading of a heavy oil. Tests were conducted with and without the addition of non-condensable gases (carbon dioxide or n-butane) to the steam. The apparatus was a three-dimensional scaled physical model packed with crushed limestone saturated with 12.4° API heavy-crude oil. Temperature, pressure, and production data, as well as the asphaltene content of the produced oil, were monitored continuously during the experiments. For small well separations, as the fraction of non-condensable gas in the steam increased, the steam condensation temperature and the steam-oil ratio decreased. As a result of lower temperature, the heavy oil was less mobile in the steam chamber relative to pure steam injection. Thus, the heating period was prolonged and the recovery, as well as the rate of oil recovery, decreased. Asphaltene content of the oil produced as a result of pure steam injection decreased initially showing deposition of asphaltene within the porous matrix of the model. As the steam injection continued, the asphaltene content of the produced oil increased but remained below the initial value. Thus, the produced oil indicated some in situ upgrading. As the carbon dioxide concentration in the steam increased, greater asphaltene deposition occurred; however, no significant change in asphaltene content was found when n-butane was added to the steam. Post-experimental analyses of the porous media for asphaltene content confirmed retention for the pure steam and steam with added CO₂ experiments. Numerical simulation of the asphaltene deposition process using a pure solid deposition model corroborated experimental findings and showed that deposition occurred mainly at the steam-chamber boundary.     

用时域反射仪对先进BGA封装中供封装故障隔离

集成电路封装技术变得越来越复杂，其制造的故障分析（FA）十分复杂。介绍了用时域反射仪对先进封装中的故障隔离技术，这种尝试是通过比较法进行研究的。通过在球栅阵列倒装一芯片（fcBGA）和低外形细节距球栅阵列堆叠芯片（stacked—die LFBGA）封装中采用时域反射仪并在分析中卓越的实施证明了这种方法是可行的，其中包括信号质量改善以及范围选择。并使用软件模拟来观测在各种故障模式下的时域反射仪信号，以便以不同的故障模式研究时域反射仪性能。得到的观测结果有助于在封装中用时域反射仪进行故障分析隔离．     

在双镶嵌铜互联中O.13微米器件生成用的基于PVD和ALD阻挡层的先进技术

1. Introduction The requirement of minimal bottom coverageand thick sidewall coverage for PVD-based films forlow via resistance and improved stress migration isnot easy to achieve with traditional depositionmethods. Modern I-PVD techniques give high bot-tom coverage, due to the ionized component of thedeposition flux. Sidewall coverage tends to be low,which is mainly due to off-normal deposition fluxand a less than unity sticking coefficient.     

Materials and Wireless Microfluidic Systems for Electronics Capable of Chemical Dissolution on Demand

Electronics that are capable of destroying themselves, on demand and in a harmless way, might provide the ultimate form of data security. This paper presents materials and device architectures for triggered destruction of conventional microelectronic systems by means of microfluidic chemical etching of the constituent materials, including silicon, silicon dioxide, and metals (e.g., aluminum). Demonstrations in an array of home‐built metal‐oxide‐semiconductor field‐effect transistors that exploit ultrathin sheets of monocrystalline silicon and in radio‐frequency identification devices illustrate the utility of the approaches.