Optical frequency-selective filters in ion-exchanged waveguides

A narrow-band reflection (stop-band) optical filter has been constructed in a planar optical waveguide made by ion exchange of silver in soda-lime glass. A comparison of the measured and computed performance of this optical filter is given. The filter has a bandwidth of 0.35 nm at a centre wavelength of 611 nm.     

A High-Level EDA Environment for the Automatic Insertion of HD-BIST Structures

This paper presents a High-Level EDA environment based on the Hierarchical Distributed BIST (HD-BIST), a flexible and reusable approach to solve BIST scheduling issues in System-on-Chip applications. HD-BIST allows activating and controlling different BISTed blocks at different levels of hierarchy, with a minimum overhead in terms of area and test time. Besides the hardware layer, the authors present the HD-BIST application layer, where a simple modeling language, and a prototypical EDA tool demonstrate the effectiveness of the automation of the HD-BIST insertion in the test strategy definition of a complex System-on-Chip.     

Signature-check based unification filter

Among the different processes that entail unification-based grammar parsing, the unification of feature structures is by far the most expensive one in terms of execution time. Unification of the feature structures of a given sentence typically takes between 85 and 98 per cent of the total elapsed time during parsing, thus the need to develop faster unification methods. The approach presented in this paper is based on the fact that, in general, between 60 and 85 per cent of unifications attempted in a typical parse result in failure. Our claim is that the efficient treatment of such unification failures reduces unification time significantly. In this paper we present what we call a unification filter or U-filter, that preprocesses the feature structures to be unified. If the U-filter succeeds, unification is then skipped because the attempt to unify the involved structures would result in failure. On the other hand, when the U-filter does not succeed it is not possible to determine at that moment whether or not the structures unify, so unification is performed. The U-filter stops around 87 per cent of unification failures, and speeds up unification time by an average of around 29 per cent over quasi-destructive graph unification, the fastest unification method known so far.     

Discrimination of self from other males by chemosensory cues in the amphisbaenian (Blanus cinereus).

The authors analyzed the ability of male amphisbaenian (Blanus cinereus) to distinguish self-produced chemical cues from those of other conspecific males. In experiments using randomized block designs, males were presented cotton swabs bearing male stimuli, their own stimuli, and deionized water in counterbalanced sequence. Blanus cinereus directed significantly more tongue flicks at swabs treated with chemical stimuli from precloacal pores and dorsal trunk skin from conspecific males than to their own stimuli from the same sites. Response to their own precloacal pore stimuli did not differ significantly from that to deionized water, but males tongue-flicked their own dorsal trunk skin stimuli more than deionized water. More male amphisbaenians bit swabs bearing the male conspecific stimuli than the other 2 stimuli. These results suggest that males detect their own chemical stimuli from dorsal trunk skin and discriminate between their own stimuli and those of other males. Communication by chemosensory cues in amphisbaenians is discussed in relation to fossoriality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The power of preprocessing in zero-knowledge proofs of knowledge

We show that, after a constant-round preprocessing stage, it is possible for a prover to prove knowledge of a witness for any polynomial-time relation without any further interaction. The number of proofs that can be given is not bounded by any fixed polynomial in the size of the preprocessing. Our construction is based on the sole assumption that one-way functions and noninteractive zero-knowledge proof systems of membership exist.The research by Alfredo De Santis was partially supported by the Italian Ministry of the University and Scientific Research and by CNR. Part of Giuseppe Persiano's work was done while at Harvard University, partially supported by NSF Grant No. NSF-CCR-90-07677.     

Taking advantage of symmetries: Gathering of many asynchronous oblivious robots on a ring

One of the recently considered models of robot-based computing makes use of identical, memoryless mobile units placed in nodes of an anonymous graph. The robots operate in Look–Compute–Move cycles; in one cycle, a robot takes a snapshot of the current configuration (Look), takes a decision whether to stay idle or to move to one of the nodes adjacent to its current position (Compute), and in the latter case makes an instantaneous move to this neighbor (Move). Cycles are performed asynchronously for each robot.In such a restricted scenario, we study the influence of symmetries of the robot configuration on the feasibility of certain computational tasks. More precisely, we deal with the problem of gathering all robots at one node of the graph, and propose a solution based on a symmetry-preserving strategy. When the considered graph is an undirected ring and the number of robots is sufficiently large (more than 18), such an approach is proved to solve the problem for all starting situations, as long as gathering is feasible. In this way we also close the open problem of characterizing symmetric situations on the ring which admit a gathering [R. Klasing, E. Markou, A. Pelc: Gathering asynchronous oblivious mobile robots in a ring, Theoret. Comput. Sci. 390 (1) (2008) 27–39].The proposed symmetry-preserving approach, which is complementary to symmetry-breaking techniques found in related work, appears to be new and may have further applications in robot-based computing.     

The ERI-Designer: A Computer Model for the Arrangement of Furniture

This paper reports a computer program to generate novel designs for the arrangement of furniture within a simulated room. It is based on the engagement-reflection computer model of the creative processes. During engagement the system generates material in the form of sequences of actions (e.g. change the colours of the walls, include some furniture in the room, modify their colour, and so on) guided by content and knowledge constraints. During reflection, the system evaluates the composition produced so far and, if it is necessary, modifies it. We discuss the implementation of the system and some of its most salient features, especially the use of a computational model for creativity in the terrain of design. We argue that this kind of model opens new possibilities for the simulation of the design processes as well as the development of tools.     

Hydrogeochemical exploration of geothermal prospects in the Tecuamburro Volcano region, Guatemala

Chemical and isotopic analyses of thermal and nonthermal waters and of gases from springs and fumaroles are used to evaluate the geothermal potential of the Tecuamburro Volcano region, Guatemala. Chemically distinct geothermal surface manifestations generally occur in separate hydrogeologic areas within this 400 km² region: low-pressure fumaroles with temperatures near local boiling occur at 1470 m elevation in a sulfur mine near the summit of Tecuamburro Volcano; non-boiling acid-sulfate hot springs and mud pots are restricted to the Laguna Ixpaco area, about 5 km NNW of the sulfur mine and 350–400 m lower in elevation; steam-heated and thermal-meteoric waters are found on the flanks of Tecuamburro Volcano and several kilometers to the north in the andesitic highland, where the Infernitos fumarole (97°C at 1180 m) is the primary feature; neutral-chloride hot springs discharge along Rio Los Esclavos, principally near Colmenares at 490 m elevation, about 8–10 km SE of Infernitos. Maximum geothermometer temperatures calculated from Colmenares neutral-chloride spring compositions are 180°C, whereas maximum subsurface temperatures based on Laguna Ixpaco gas compositions are 310°C. An exploration core hole drilled to a depth of 808 m about 0.3 km south of Laguna Ixpaco had a bottom-hole temperature of 238°C but did not produce sufficient fluids to confirm or chemically characterize a geothermal reservoir. Hydrogeochemical data combined with regional geologic interpretations indicate that there are probably two hydrothermal-convection systems, which are separated by a major NW-trending structural boundary, the Ixpaco fault. One system with reservoir temperatures near 300°C lies beneath Tecuamburro Volcano and consists of a large vapor zone that feeds steam to the Laguna Ixpaco area, with underlying hot water that flows laterally to feed a small group of warm, chloriderich springs SE of Tecuamburro Volcano. The other system is located beneath the Infernitos area in the andesitic highland and consists of a lower-temperature (150–190°C) reservoir with a large natural discharge that feeds the Colmenares hot springs.