Single-trial dynamical estimation of event-related potentials: a Kalman filter-based approach

A method for single-trial dynamical estimation of event-related potentials (ERPs) is presented. The method is based on recursive Bayesian mean square estimation and the estimators are obtained with a Kalman filtering procedure. We especially focus on the case that previous trials contain prior information of relevance to the trial being analyzed. The potentials are estimated sequentially using the previous estimates as prior information. The performance of the method is evaluated with simulations and with real P300 responses measured using auditory stimuli. Our approach is shown to have excellent capability of estimating dynamic changes form stimulus to stimulus present in the parameters of the ERPs, even in poor signal-to-noise ratio (SNR) conditions.     

Empirical methods for determination of ionization gauge relative sensitivities for different gases

The relative sensitivities of a Bayard-Alpert ionization gauge for various organic molecules have been measured. There is a good correlation with total ionization cross section at 75 eV. For monofunctional compounds a correlation with number of electrons is seen with different functional groups on different lines. The best general correlation is with the polarizability, α, with R_x=0.36α +0.30, where R_x is the chemical sensitivity relative to N₂=1.00. Alkanes and the noble gases have slightly larger R_x values than predicted by this equation.     

Minimum-Energy Broadcasting in Multi-hop Wireless Networks Using a Single Broadcast Tree

In this paper we address the minimum-energy broadcast problem in multi-hop wireless networks, so that all broadcast requests initiated by different source nodes take place on the same broadcast tree. Our approach differs from the most commonly used one where the determination of the broadcast tree depends on the source node, thus resulting in different tree construction processes for different source nodes. Using a single broadcast tree simplifies considerably the tree maintenance problem and allows scaling to larger networks. We first show that, using the same broadcast tree, the total power consumed for broadcasting from a given source node is at most twice the total power consumed for broadcasting from any other source node. We next develop a polynomial-time approximation algorithm for the construction of a single broadcast tree. The performance analysis of the algorithm indicates that the total power consumed for broadcasting from any source node is within 2H(n−1) from the optimal, where n is the number of nodes in the network and H(n) is the harmonic function. This approximation ratio is close to the best achievable bound in polynomial time. We also provide a useful relation between the minimum-energy broadcast problem and the minimum spanning tree, which shows that a minimum spanning tree may be a good candidate in sparsely connected networks. The performance of our algorithm is also evaluated numerically with simulations. A preliminary version of this work appeared in the Proceedings of WiOpt’04: Modeling and Optimization in Mobile, Ad hoc and Wireless Networks, University of Cambridge, UK, March 2004. Ioannis Papdimitriou was fully supported for this work by the Public Benefit Foundation “ALEXANDER S. ONASSIS”, Athens, Greece. Ioannis Papadimitriou was born in Veria, Greece, in 1976. He received his five year Diploma from the Department of Electronic and Computer Engineering, Technical University of Crete (Chania), Greece, in 1999 (graduating 2nd in class). He is currently a postgraduate student - Ph.D. candidate at the Telecommunications division, Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece. His doctoral thesis deals with the design of wireless ad hoc networks. His research interests include broadcast and multicast communication, energy conservation, routing and topology control protocols, MAC layer and QoS issues. During his studies he has been honored with awards and scholarships by the Technical University of Crete, the Hellenic Telecommunications Organization S.A.(OTE S.A.) and Ericsson Hellas S.A. Mr. Papadimitriou has been a member of the Technical Chamber of Greece (TEE) since March 2000, and he has been supported by the Public Benefit Foundation ALEXANDER S. ONASSIS, Athens, Greece, with a scholarship for his doctoral studies from October 2001 to March 2005. Leonidas Georgiadis received the Diploma degree in electrical engineering from Aristotle University, Thessaloniki, Greece, in 1979, and his M.S. and Ph.D. degrees both in electrical engineering from the University of Connecticut, in 1981 and 1986, respectively. From 1981 to 1983 he was with the Greek army. From 1986 to 1987 he was Research Assistant Professor at the University of Virginia, Charlottesville. In 1987 he joined IBM T.J. Watson Research Center, Yorktown Heights, as a Research Staff Member. Since October 1995, he has been with the Telecommunications Department of Aristotle University, Thessaloniki, Greece. His interests are in the area of wireless networks, high speed networks, distributed systems, routing,scheduling, congestion control, modeling and performance analysis. Prof. Georgiadis is a senior member of IEEE Communications Society. In 1992 he received the IBM Outstanding Innovation Award for his work on goal-oriented workload management for multi-class systems.x     

Effect of meat appearance on consumer preferences for pork chops in Greece and Cyprus

The effect of meat appearance on consumers’ preferences for pork chops was assessed using images manipulated for appearance characteristics. Data were collected from 412 consumers in Greece and Cyprus. Consumers were asked for their preference for pork chops from a book of computer-modified images and then completed a questionnaire of socio-demographic information, including eating and purchasing behaviour. Consumers under the age of 35 years showed preferences for dark red, lean pork, while consumers aged 35 years and older preferred either dark or light red pork. Gender appeared to be an important selection factor as men showed an increased preference for dark red pork while women preferred the light red. Consumers who stated that they like pork for its taste (91%) preferred either dark or light red pork chops while those who like pork for reasons other than taste preferred dark red, lean pork. Urban consumers preferred light red, fatty pork chops while the rural consumers preferred the dark red pork chops.     

Ensuring business and service requirements in enterprise mashups

Information Systems and e-Business Management - During the past few years, mashups have gained wide attention as they utilize Web 2.0 technologies in order to combine data, as well as the...     

Optimal buffer sharing

We address the problem of designing optimal buffer management policies in shared memory switches when packets already accepted in the switch can be dropped (pushed-out). Our goal is to maximize the overall throughput, or equivalently to minimize the overall loss probability in the system. For a system with two output ports, we prove that the optimal policy is of push-out with threshold type (POT). The same result holds if the optimality criterion is the weighted sum of the port loss probabilities. For this system, we also give an approximate method for the calculation of the optimal threshold, which we conjecture to be asymptotically correct. For the N-ported system, the optimal policy is not known in general, but we show that for a symmetric system (equal traffic on all ports) it consists of always accepting arrivals when the buffer is not full, and dropping one from the longest queue to accommodate the new arrival when the buffer is full. Numerical results are provided which reveal an interesting and somewhat unexpected phenomenon. While the overall improvement in loss probability of the optimal POT policy over the optimal coordinate-convex policy is not very significant, the loss probability of an individual output port remains approximately constant as the load on the other port varies and the optimal POT policy is applied, a property not shared by the optimal coordinate-convex policy     

Indentation of an orthotropic layer by a semi-infinite punch

In this paper, a plane elasticity problem treated involving punch indentation of an orthotropic strip resting on a rigid frictionless foundation. A semi-infinite punch and an infinitely long layer were considered, so that the problem was amenable to the Wiener-Hopf technique. Applying Fourier transforms to the governing differential equations and the imposed boundary conditions, we succeeded in formulating a Wiener-Hopf relationship which then yielded the asymptotic estimation of the stress and displacement field in the immediate vicinity of the edge of stamp.     

Bottleneck multicast trees in linear time

On a directed graph with arc costs and a given source node, s, we consider the problem of computing multicast (Steiner) trees spanning any given node subset, V, so that the maximum of the tree arc costs is minimized. We show that this problem can be solved by simply solving the bottleneck path problem, i.e., the problem of determining for each node, t/spl ne/s, a path from s to t so that the maximum of path arc costs is minimized. For the latter problem we provide an implementation of Dijkstra's algorithm that runs in linear time under mild assumptions on arc costs.     

A comprehensive analytical performance model for disk devices underrandom workloads

Our goal is to contribute a common theoretical framework for studying the performance of disk-storage devices. Understanding the performance behavior of these devices will allow prediction of the I/O cost in modern applications. Current disk technologies differ in terms of the fundamental modeling characteristics, which include the magnetic/optical nature, angular and linear velocities, storage capacities, and transfer rates. Angular and linear velocities, storage capacities, and transfer rates are made constant or variable in different existing disk products. Related work in this area has studied Constant Angular Velocity (CAV) magnetic disks and Constant Linear Velocity (CLV) optical disks. We present a comprehensive analytical model, validated through simulations, for the random retrieval performance of disk devices which takes into account all the above-mentioned fundamental characteristics and includes, as special cases, all the known disk-storage devices. Such an analytical model can be used, for example, in the query optimizer of large traditional databases as well as in an admission controller of multimedia storage servers. Besides the known models for magnetic CAV and optical CLV disks, our unifying model is also reducible to a model for a more recent disk technology, called zoned disks, the retrieval performance of which has not been modeled in detail before. The model can also be used to study the performance retrieval of possible future technologies which combine a number of the above characteristics and in environments containing different types of disks (e.g., magnetic-disk-based secondary storage and optical-disk-based tertiary storage). Using our model, we contribute an analysis of the performance behavior of zoned disks and we compare it against that for the traditional CAV disks, as well as against that of some possible/future technologies. This allows us to gain insights into the fundamental performance trade-offs     

A Collision Resolution Protocol for Random Access Channels with Energy Detectors

In this paper, we consider the random accessing of a single slotted channel by a large number of packet-transmitting, bursty users. We assume that feedback broadcasting is available where some different information, in addition to the information assumed by the Capetanakis, Gallager, Massey, etc., models, is included in the feedback. In particular, we assume that the existence of energy detectors permits the broadcasting of the number of collided packets within each collision slot, whenever this number is below a certain limit. We first consider this limit to be infinity, and then a finite small number. For the model considered, we propose and analyze a collision resolution protocol (CRAI), whose implementation is simple. For Poisson input traffic and infinite number of energy detectors, we found that the CRAI is stable for input rates below 0.53237. For finite number of energy detectors, we propose a modified version of the CRAI (MCRAI). We found that the MCRAI reaches the throughput 0.53237, through the utilization of only about eight energy detectors. These protocols, like the ones introduced by Capetanakis, Gallager, Massey, etc., have good delay properties.