The M/G/1 queue with permanent customers

The authors examine an M/G/1 FCFS (first come, first served) queue with two types of customers: ordinary customers, who arrive according to a Poisson process, and permanent customers, who immediately return to the end of the queue after having received a service. The influence of the permanent customers on queue length and sojourn times of the Poisson customers is studied using results from queuing theory and from the theory of branching processes. In particular, it is shown that, when the service time distributions of the Poisson customers and all K permanent customers are negative exponential with identical means, the queue length and sojourn time distributions of the Poisson customers are the (K+1)-fold convolution of those for the case without permanent customers     

On the establishment of an access VPN in broadband access networks

Many corporate networks use the Internet as a cost-effective substitute for expensive leased lines and long-distance telephone calls, for allowing their users to have on-demand connectivity into their intranets through ad hoc tunnels, a concept known as access VPN. Establishing an access VPN in a broadband access network is very often a difficult networking challenge that requires several tunnels to be established between the various involved entities. This is especially the case in an open broadband access network where the association between a host and its ISP is not known to the network in advance. This article discusses several schemes for establishing an access VPN in a broadband access network, and explains the need for the various tunnels in each scheme.     

Scanning and Sequential Decision Making for Multidimensional Data–Part I: The Noiseless Case

We investigate the problem of scanning and prediction (ldquoscandiction,rdquo for short) of multidimensional data arrays. This problem arises in several aspects of image and video processing, such as predictive coding, for example, where an image is compressed by coding the error sequence resulting from scandicting it. Thus, it is natural to ask what is the optimal method to scan and predict a given image, what is the resulting minimum prediction loss, and whether there exist specific scandiction schemes which are universal in some sense. Specifically, we investigate the following problems: first, modeling the data array as a random field, we wish to examine whether there exists a scandiction scheme which is independent of the field's distribution, yet asymptotically achieves the same performance as if this distribution were known. This question is answered in the affirmative for the set of all spatially stationary random fields and under mild conditions on the loss function. We then discuss the scenario where a nonoptimal scanning order is used, yet accompanied by an optimal predictor, and derive bounds on the excess loss compared to optimal scanning and prediction. This paper is the first part of a two-part paper on sequential decision making for multidimensional data. It deals with clean, noiseless data arrays. The second part deals with noisy data arrays, namely, with the case where the decision maker observes only a noisy version of the data, yet it is judged with respect to the original, clean data.     

On the Effect of the "Third-Person Effect": Perceived Influence of Media Coverage and Residential Mobility Intentions

This study demonstrates that third-person perceptions regarding the influence of media coverage of peripheral towns indirectly affect the desire to consider moving. It is argued that regardless of whether people's perceptions of where they live are really shaped by media coverage, if people believe others are affected by this coverage more than they are, they are more likely to consider relocation. We investigated whether the perceived stigmatization of peripheral development towns in Israel has an impact on the desire of their residents to stay or leave, over and above the disaffection with actual living conditions in these communities. Using structural equation modeling ( N = 472), we show that third-person estimations indeed influence both perceptions and behavioral intentions.     

The effect of Cu diffusion on the TDDB behavior in a low-k interlevel dielectrics

The effect of Copper on TDDB failure in a structure incorporating a low-k interlevel dielectric was studied theoretically and experimentally. Interdigitated comb capacitor structures were prepared with and without Cu metallization and stressed at 4.0 to 6.6 MV/cm at 150C. The samples without Cu did not fail to over 1800 hours at 4 MV/cm whereas the samples with Cu exhibited a median time to failure (t₅₀) of 45 minutes. At 6.6 MV/cm, the t₅₀ was 1.8 hours for the Cu free samples. This experiment demonstrated the importance of Cu in the TDDB behaviour of low-k dielectrics, but also demonstrated that the presence of Cu was not a necessary condition for failure. The effect of Cu diffusion on TDDB behaviour was studied in the context of the “Impact Damage” model. Both field assisted ionic diffusion and diffusion of neutral Cu was considered. It is seen that the behaviour at low fields near use conditions may have little relationship to the predictions obtained from the results of typical TDDB testing.     

Concurrent Formation of Metallic Glass During Laser Forward Transfer 3D Printing

In recent years, bulk metallic glasses (BMGs) have drawn much research attention and are shown to be of industrial interest due to their superior mechanical properties and resistance to corrosion. In spite of the interest in harnessing MG for microelectromechanical systems devices, there are limitations in manufacturing such micrometer‐scale structures. A novel approach for the fabrication of 3D MG structures using laser‐induced forward transfer (LIFT) is demonstrated. Inherent tremendous cooling rates associated with the metal LIFT process (≈10¹⁰ k s^?1) make the formation of a variety of BMGs accessible, including also various binary compositions. In this work, it is demonstrated that LIFT printing of ZrPd‐based metallic glass microstructures can also be performed under ambient conditions. X‐ray diffraction analysis of the printed structures reveals > 95% of amorphous metal phase. Taking advantage of the properties of BMG, high quality printing of high aspect ratio BMG pillars, and microbridges are demonstrated. It is also shown how a composite, amorphous‐crystalline metal structure with a required configuration can be fabricated using multimaterial LIFT printing. The inherent high resolution of the method combined with the noncontact and multimaterial printing capacity makes LIFT a valuable additive manufacturing technique to produce metallic glass‐based devices.     

Epitaxy of FeAl films on GaAs(100) by molecular beam epitaxy

Intermetallics that coexist with III-V’s in the bulk are expected to form thermodynamically stable overlayers when deposited as a thin film. To the extent that adsorption kinetics do not play a role, these films should be abrupt and able to withstand high temperature processing. Some of these films have been found to be epitaxial after heating in vacuum. FeAl has been found to form pseudomorphic films on InP(l00) substrates and to grow in a layer-by-layer mode even when code-posited. To explore the role of stoichiometry and crystal strain, we have used reflection high energy electron diffraction (RHEED) to compare the growth of Fe _x -Al_1−x on GaAs(l00) to its growth on InP substrates. In both cases RHEED intensity oscillations are observed at 200° C, indicating two-dimensional island formation and layer-by-layer growth. For both, the growth is pseudomorphic on an AlAs buffer layer, with any lattice constant change less than 0.3%. When the intermetallics were codeposited, the growth proceeded via double layer formation forx < 0.7 and via single layers for largex. The films were stable to 550° C. Subsequent growth of AlAs was three dimensional.     

Doping Molecular Monolayers: Effects on Electrical Transport Through Alkyl Chains on Silicon

n‐Si/C_nH_{2n + 1}/Hg junctions (n = 12, 14, 16 and 18) can be prepared with sufficient quality to assure that the transport characteristics are not anymore dominated by defects in the molecular monolayers. With such organic monolayers we can, using electron, UV and X‐ray irradiation, alter the charge transport through the molecular junctions on n‐ as well as on p‐type Si. Remarkably, the quality of the self‐assembled molecular monolayers following irradiation remains sufficiently high to provide the same very good protection of Si from oxidation in ambient atmosphere as provided by the pristine films. Combining spectroscopic (UV photoemission spectroscopy (UPS), X‐ray photoelectron spectroscopy (XPS), Auger, near edge‐X‐ray absorption fine structure (NEXAFS)) and electrical transport measurements, we show that irradiation induces defects in the alkyl films, most likely C?C bonds and C? C crosslinks, and that the density of defects can be controlled by irradiation dose. These altered intra‐ and intermolecular bonds introduce new electronic states in the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of the alkyl chains and, in the process, dope the organic film. We demonstrate an enhancement of 1–2 orders of magnitude in current. This change is clearly distinguishable from the previous observed difference between transport through high quality and defective monolayers. A detailed analysis of the electrical transport at different temperatures shows that the dopants modify the transport mechanism from tunnelling to hopping. This study suggests a way to extend significantly the use of monolayers in molecular electronics.     

Characterization of Secure Multiparty Computation Without Broadcast

A major challenge in the study of cryptography is characterizing the necessary and sufficient assumptions required to carry out a given cryptographic task. The focus of this work is the necessity of a broadcast channel for securely computing symmetric functionalities (where all the parties receive the same output) when one third of the parties, or more, might be corrupted. Assuming all parties are connected via a point-to-point network, but no broadcast channel (nor a secure setup phase) is available, we prove the following characterization:

• A symmetric n-party functionality can be securely computed facing \(n/3\le t<n/2\) corruptions (i.e., honest majority), if and only if it is \((n-2t)\) -dominated; a functionality is k-dominated, if any k-size subset of its input variables can be set to determine its output to some predetermined value.
• Assuming the existence of one-way functions, a symmetric n-party functionality can be securely computed facing \(t\ge n/2\) corruptions (i.e., no honest majority), if and only if it is 1-dominated and can be securely computed with broadcast.

It follows that, in case a third of the parties might be corrupted, broadcast is necessary for securely computing non-dominated functionalities (in which “small” subsets of the inputs cannot determine the output), including, as interesting special cases, the Boolean XOR and coin-flipping functionalities.