Uniqueness of the Perfect Fusion Grid on ℤ d

Region merging methods consist of improving an initial segmentation by merging some pairs of neighboring regions. In a graph, merging two regions, separated by a set of vertices, is not straightforward. The perfect fusion graphs defined in J. Cousty et al. (J. Math. Imaging Vis. 30:(1):87–104, 2008) verify all the basic properties required by region merging algorithms as used in image segmentation. Unfortunately, the graphs which are the most frequently used in image analysis (namely, those induced by the direct and the indirect adjacency relations) are not perfect fusion graphs. The perfect fusion grid, introduced in the above mentioned reference, is an adjacency relation on ℤ ^d which can be used in image analysis, which indeed induces perfect fusion graphs and which is “between” the graphs induced by the direct and the indirect adjacencies. One of the main results of this paper is that the perfect fusion grid is the only such graph whatever the dimension d.

A Timing Assumption and Two t-Resilient Protocols for Implementing an Eventual Leader Service in Asynchronous Shared Memory Systems

This paper considers the problem of electing an eventual leader in an asynchronous shared memory system. While this problem has received a lot of attention in message-passing systems, very few solutions have been proposed for shared memory systems. As an eventual leader cannot be elected in a pure asynchronous system prone to process crashes, the paper first proposes to enrich the asynchronous system model with an additional assumption. That assumption (denoted AWB) is particularly weak. It is made up of two complementary parts. More precisely, it requires that, after some time, (1) there is a process whose write accesses to some shared variables be timely, and (2) the timers of (t−f) other processes be asymptotically well-behaved (t denotes the maximal number of processes that may crash, and f the actual number of process crashes in a run). The asymptotically well-behaved timer notion is a new notion that generalizes and weakens the traditional notion of timers whose durations are required to monotonically increase when the values they are set to increase (a timer works incorrectly when it expires at arbitrary times, i.e., independently of the value it has been set to). The paper then focuses on the design of t-resilient AWB-based eventual leader protocols. “t-resilient” means that each protocol can cope with up to t process crashes (taking t=n−1 provides wait-free protocols, i.e., protocols that can cope with any number of process failures). Two protocols are presented. The first enjoys the following noteworthy properties: after some time only the elected leader has to write the shared memory, and all but one shared variables have a bounded domain, be the execution finite or infinite. This protocol is consequently optimal with respect to the number of processes that have to write the shared memory. The second protocol guarantees that all the shared variables have a bounded domain. This is obtained at the following additional price: t+1 processes are required to forever write the shared memory. A theorem is proved which states that this price has to be paid by any protocol that elects an eventual leader in a bounded shared memory model. This second protocol is consequently optimal with respect to the number of processes that have to write in such a constrained memory model. In a very interesting way, these protocols show an inherent tradeoff relating the number of processes that have to write the shared memory and the bounded/unbounded attribute of that memory.     

Approximation of functions by perceptrons: a new approach

We provide a constructive proof of the theorem of function approximation by perceptrons (cf Leshno et al. [1], Hornik [2]) when the activation function ψ isC∞ with all its derivatives non 0 at 0. We deal with uniform approximation on compact sets of continuous functions on ℜ ^d ,d≥1. This approach is elementary and provides some approximation results for the derivatives along with some bounds for the hidden layer.     

Estimation of combined ice and wind load on overhead transmission lines

In recent years, the design of high-voltage transmission lines has been increasingly optimized. In areas where ice accretion on conductors is possible, the load resulting from added weight or increased aerodynamic forces becomes an important design parameter. At present, calculations for combined ice-wind loads do not take the effect of accretion shape into account. In this study, ice accretions are formed on a conductor in a wind tunnel for three types of ice: soft rime, hard rime and glaze. Aerodynamic vertical and horizontal forces are then measured for different wind velocities. It is shown that when the wind remains in the direction of ice build-up, the aerodynamic force due to the asymmetric shape is responsible for a significant increase in the total force and that the present combined ice-wind load calculations can dangerously underestimate the risk of an overload.     

Use of a pulsed column contactor as a continuous oxalate precipitation reactor

The current objective of coprecipitating uranium, and minor actinides in order to fabricate a new nuclear fuel by direct (co)precipitation for further transmutation, requires to develop specific technology in order to meet the following requirements: nuclear maintenance, criticity, and potentially high flowrates due to global coprecipitation. A new type of device designed and patented by the CEA was then tested in 2007 under inactive conditions and with uranium. The patent is for organic confinement in a pulsed column (PC). Actually, pulsed columns have been working for a long time in a nuclear environment, as they allow high capacity, sub-critical design (annular geometry) and easy high activity maintenance. The precipitation reaction between the oxalate complexing agent and a surrogate nitrate - cerium(III) or neodymium(III) alone, or coprecipitated uranium(IV) and cerium(III) - occurs within an emulsion created in the device by these two phases flowing with a counter-current chemically inert organic phase (for example tetrapropylene hydrogen—TPH) produced by the stirring action of the column pulsator. The precipitate is confined and thus does not form deposits on the vessel walls (which are also water-repellent); it flows downward by gravity and exits the column continuously into a settling tank.The results obtained for precipitation of cerium or neodymium alone in a short column of small diameter have demonstrated that high throughputs are feasible without system malfunctions. The measured particle size of the precipitates ranges from 20 to 40 μm on average, and the measured device outflow indicates that the precipitation reaction is complete. These results suggest that this laboratory design can be extrapolated to an industrial column. Moreover, a recent test campaign demonstrated that a uranium-cerium coprecipitate easily forms when the two nitrates are mixed in a pulsed column of the same size operating under very similar process conditions. Qualitatively, the coprecipitate meets the process requirements to filter, calcine and fabricate the new nuclear fuel in the downstream steps.     

Quantitative x-ray microanalysis of spherical inclusions embedded in a matrix using a SEM and Monte Carlo simulations

The current schemes of quantification of x-ray microanalysis in the SEM [ZAF and σ(ρZ) methods] are valid for specimens of homogeneous composition. The determination of the chemical composition of small inclusions using these techniques is impossible because the volume of x-ray emission is not of homogeneous composition. A scheme of quantification to determine the composition of small inclusions embedded in a matrix has been developed using Monte Carlo simulations. This scheme is similar to that developed by Kyser and Murata (1974) for the quantification of thin foils deposited on a substrate using x-ray microanalysis in the SEM.     

Effect of gate length in InAs/AlSb HEMTs biased for low power or high gain

The effect of gate-length variation on DC and RF performance of InAs/AlSb HEMTs, biased for low DC power consumption or high gain, is reported. Simultaneously fabricated devices, with gate lengths between 225 nm and 335 nm, have been compared. DC measurements revealed higher output conductance g_ds and slightly increased impact ionization with reduced gate length. When reducing the gate length from 335 nm to 225 nm, the DC power consumption was reduced by approximately 80% at an f_T of 120 GHz. Furthermore, a 225 nm gate-length HEMT biased for high gain exhibited an extrinsic f_T of 165 GHz and an extrinsic f_max of 115 GHz, at a DC power consumption of 100 mW/mm. When biased for low DC power consumption of 20 mW/mm the same HEMT exhibited an extrinsic f_T and f_max of 120 GHz and 110 GHz, respectively.     

Study of the Action of Static and Dynamic Fusimotor Fibers With a Mechanical Model of the Mammalian Muscle Spindle

A model of the mammalian muscle spindle having three distinct parts is proposed. The three parts, which consist of a mechanical filter, a transducer, and an encoder, are closely related with their physiological counterparts. A study of the generator potentials for the primary and secondary endings of the spindle was performed by means of an analog computer simulation of the model. The afferent responses of the spindle under a phasic stretch with and without fusimotor fibers simulation are also studied. Finally, frequencygrams (see text) are obtained under the condition of ?1 (dynamic) stimulation acting on both nuclear bag and nuclear chain fibers. The model yields results that are directly comparable with physiological data obtained under similar conditions.