Holding Dissapearance in RTD-based Quantizers

Multiple-valued Logic (MVL) circuits are one of the most attractive applications of the Monostable-to-Multistable transition Logic (MML), and they are on the basis of advanced circuits for communications. The operation of such quantizer has two steps : sampling and holding. Once the quantizer samples the signal, it must maintain the sampled value even if the input changes. However, holding property is not inherent to MML circuit topologies. This paper analyses the case of an MML ternary inverter used as a quantizer, and determines the relations that circuit representative parameters must verify to avoid this malfunction.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Using Multi-Threshold Threshold Gates in RTD-based Logic Design. A Case Study

The basic building blocks for Resonant Tunnelling Diode (RTD) logic circuits are Threshold Gates (TGs) instead of the conventional Boolean gates (AND, OR, NAND, NOR) due to the fact that, when designing with RTDs, threshold gates can be implemented as efficiently as conventional ones, but realize more complex functions. Recently, RTD structures implementing Multi-Threshold Threshold Gates (MTTGs) have been proposed which further increase the functionality of the original TGs while maintaining their operating principle and allowing also the implementation of nanopipelining at the gate level. This paper describes the design of n-bit adders using these MTTGs. A comparison with a design based on TGs is carried out showing advantages in terms of latency, device counts and power consumption.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

The Butcher--Oemler effect at z~0.35: a change in perspective

The present paper focuses on the much debated Butcher-Oemler effect: the increase with redshift of the fraction of blue galaxies in clusters. Considering a representative cluster sample made of seven group/clusters at z~0.35, we have measured the blue fraction from the cluster core to the cluster outskirts and the field mainly using wide field CTIO images. This sample represents a random selection of a volume complete x-ray selected cluster sample, selected so that there is no physical connection with the studied quantity (blue fraction), to minimize observational biases. In order to statistically assess the significance of the Butcher-Oemler effect, we introduce the tools of Bayesian inference. Furthermore, we modified the blue fraction definition in order to take into account the reduced age of the universe at higher redshifts, because we should no longer attempt to reject an unphysical universe in which the age of the Universe does depend on redshift, whereas the age of its content does not. We measured the blue fraction from the cluster center to the field and we find that the cluster affects the properties of the galaxies up to two virial radii at z~0.35. Data suggest that during the last 3 Gyrs no evolution of the blue fraction, from the cluster core to the field value, is seen beyond the one needed to account for the varying age with redshift of the Universe and of its content. The agreement of the radial profiles of the blue fraction at z=0 and z~0.35 implies that the pattern infall did not change over the last 3 Gyr, or, at least, its variation has no observational effect on the studied quantity.Comment: MNRAS, in pres

Redshifts in the Southern Abell Redshift Survey Clusters. I. The Data

The Southern Abell Redshift Survey contains 39 clusters of galaxies with redshifts in the range 0.0 < z < 0.31 and a median redshift depth of z = 0.0845. SARS covers the region 0 21h (while avoiding the LMC and SMC) with b > 40. Cluster locations were chosen from the Abell and Abell-Corwin-Olowin catalogs while galaxy positions were selected from the Automatic Plate Measuring Facility galaxy catalog with extinction-corrected magnitudes in the range 15 <= b_j < 19. SARS utilized the Las Campanas 2.5 m duPont telescope, observing either 65 or 128 objects concurrently over a 1.5 sq deg field. New redshifts for 3440 galaxies are reported in the fields of these 39 clusters of galaxies.Comment: 20 pages, 5 figures, accepted for publication in the Astronomical Journal, Table 2 can be downloaded in its entirety from http://trotsky.arc.nasa.gov/~mway/SARS1/sars1-table2.cs

New Structure In The Shapley Supercluster

We present new radial velocities for 189 galaxies in a 91 sq. deg region of the Shapley supercluster measured with the FLAIR-II spectrograph on the UK Schmidt Telescope. The data reveal two sheets of galaxies linking the major concentrations of the supercluster. The supercluster is not flattened in Declination as was suggested previously and it may be at least 30 percent larger than previously thought with a correspondingly larger contribution to the motion of the Local Group.Comment: LaTex: 2 pages, 1 figure, includes conf_iap.sty style file. To appear in proceedings of The 14th IAP Colloquium: Wide Field Surveys in Cosmology, held in Paris, 1998 May 26--30, eds. S.Colombi, Y.Mellie

Measuring Thickness and Pretilt in Reflective Vertically Aligned Nematic Liquid Crystal Displays

Pretilt angle is a parameter of the utmost importance in the ultimate performance of vertically-aligned negative nematic LC displays. When these devices work in reflective mode, as is the LCOS microdisplays, accurate measurement of pretilt angles becomes a difficult problem, since usual experimental setups based on retardation of the polarization components of the impinging light are proportional to the product effective birefringence (neff - no) times thickness, and any attempt to separate these variables is cancelled out by symmetry. This work shows a relatively simple method capable of separating both variables. An experimental setup specifically aimed at vertically aligned reflective cells has been prepared. At the same time, a simulation model has been developed taking into account the properties of actual reflective displays. Comparison between experimental and theoretical results shows some discrepancies that can be explained assuming that the LC profile contains a residual twist. Including that twist in the model, an excellent agreement between theory and experiment has been achieved. Matching of simulations and measurements yields to the separate determination of pretilt angle and thickness and gives good estimates for the residual twist angle

Evaluation of RTD-CMOS logic gates

Trabajo presentado al 13th DSD celebrado en Lille del 1 al 3 de septiembre de 2010.The incorporation of Resonant Tunnel Diodes (RTDs) into III/V transistor technologies has shown an improved circuit performance: higher circuit speed, reduced component count, and/or lowered power consumption. Currently, the incorporation of these devices into CMOS technologies (RTD-CMOS) is an area of active research. Although some works have focused the evaluation of the advantages of this incorporation, additional work in this direction is required. This paper compares RTD-CMOS and pure CMOS realizations of a set of logic gates which can be operated in a gate-level nanopipelined fashion, thus allows estimating logic networks operating frequency. Lower power-delay products are obtained for RTD/CMOS implementations.This work has been funded by the Spanish Government under project NDR, TEC2007-67245/MIC, and the Junta de Andalucía through the Proyecto de Excelencia TIC-2961.Peer Reviewe

RTD based logic circuits using generalized threshold gates

Trabajo presentado al DCIS celebrado en Grenoble (Francia) del 12 al 14 de noviembre de 2008.Many logic circuit applications of Resonant Tunneling Diodes are based on the MOnostable-BIstable Logic Element (MOBILE). Threshold logic is a computational model widely used in the design of MOBILE circuits, i.e. these circuits are built from threshold gates (TGs). The MOBILE realization of generalized threshold gates is being investigated. Multi-Threshold Threshold Gates (MTTGs) have been proposed which further increase the functionality of the original TGs. Recently, we have proposed a novel MOBILE circuit topology obtained by fundamental properties of threshold functions. This paper describes the design of n-bit adders using these novel MOBILE circuit topologies. A comparison with designs based on TGs and MTTGs is carried out showing advantages in terms of speed and power delay product and device counts.This effort was partially supported by the Spanish Government under project TEC2007-67245 and Andalusian Goverment through project EXC/2007/TIC-2961.Peer Reviewe