Techniques of Informatics and Microelectronics for Integrated Systems Architecture

A novel design technique is proposed for storage elements which are insensitive to radiation-induced single-event upsets. This technique is suitable for implementation in high density ASICs and static RAMs using submicron CMOS technology.

Abstract On the basis of simulated data, this study compares the relative performances of the Bayesian clustering computer programs structure , geneland , geneclust and a new program named tess . While these four programs can detect population genetic structure from multilocus genotypes, only the last three ones include simultaneous analysis from geographical data. The programs are compared with respect to their abilities to infer the number of populations, to estimate membership probabilities, and to detect genetic discontinuities and clinal variation. The results suggest that combining analyses using tess and structure offers a convenient way to address inference of spatial population structure.

The increased operating frequencies, geometry shrinking and power supply reduction that accompany the process of very deep submicron scaling, affect the reliable operation of very deep submicron ICs. The effects of various noise sources are becoming of great concern. In particularly, it is predicted that single event upsets induced by alpha particles and cosmic radiation will become a cause of unacceptable error rates in future very deep submicron and nanometer technologies. This problem, concerning in the past more often parts used in space, will affect future ICs at sea level. This challenging problem has to be solved otherwise technological progress will be blocked soon. Thus, fault tolerant design is becoming necessary, even for commodity applications. But economic constraints of commodity applications exclude the use of traditional, high-cost fault tolerant techniques. This work uses time redundancy techniques to derive low cost soft-error tolerant implementations for logic networks.

We propose a new scheme for built-in test (BIT) that uses multiple-polynomial linear feedback shift registers (MP-LFSR's). The same MP-LFSR that generates random patterns to cover easy to test faults is loaded with seeds to generate deterministic vectors for difficult to test faults. The seeds are obtained by solving systems of linear equations involving the seed variables for the positions where the test cubes have specified values. We demonstrate that MP-LFSR's produce sequences with significantly reduced probability of linear dependence compared to single polynomial LFSR's. We present a general method to determine the probability of encoding as a function of the number of specified bits in the test cube, the length of the LFSR and the number of polynomials. Theoretical analysis and experiments show that the probability of encoding a test cube with s specified bits in an s-stage LFSR with 16 polynomials is 1-10/sup -6/. We then present the new BIT scheme that allows for an efficient encoding of the entire test set. Here the seeds are grouped according to the polynomial they use and an implicit polynomial identification reduces the number of extra bits per seed to one bit. The paper also shows methods of processing the entire test set consisting of test cubes with varied number of specified bits. Experimental results show the tradeoffs between test data storage and test application time while maintaining complete fault coverage.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Kauno klinikų filialas Vaikų reabilitacijos ligoninė Lopšelis (K520000)

We introduce a new Bayesian clustering algorithm for studying population structure using individually geo-referenced multilocus data sets. The algorithm is based on the concept of hidden Markov random field, which models the spatial dependencies at the cluster membership level. We argue that (i) a Markov chain Monte Carlo procedure can implement the algorithm efficiently, (ii) it can detect significant geographical discontinuities in allele frequencies and regulate the number of clusters, (iii) it can check whether the clusters obtained without the use of spatial priors are robust to the hypothesis of discontinuous geographical variation in allele frequencies, and (iv) it can reduce the number of loci required to obtain accurate assignments. We illustrate and discuss the implementation issues with the Scandinavian brown bear and the human CEPH diversity panel data set.

Abstract Neural networks are increasingly popular in geophysics. Because they are universal approximators, these tools can approximate any continuous function with an arbitrary precision. Hence, they may yield important contributions to finding solutions to a variety of geophysical applications. However, knowledge of many methods and techniques recently developed to increase the performance and to facilitate the use of neural networks does not seem to be widespread in the geophysical community. Therefore, the power of these tools has not yet been explored to their full extent. In this paper, techniques are described for faster training, better overall performance, i.e., generalization, and the automatic estimation of network size and architecture.

In nanometric technologies, circuits are increasingly sensitive to various kinds of perturbations. Soft errors, a concern for space applications in the past, became a reliability issue at ground level. Alpha particles and atmospheric neutrons induce single-event upsets (SEU), affecting memory cells, latches, and flip-flops, and single-event transients (SET), initiated in the combinational logic and captured by the latches and flip-flops associated to the outputs of this logic. To face this challenge, a designer must dispose a variety of soft error mitigation schemes adapted to various circuit structures, design architectures, and design constraints. In this paper, we describe various SEU and SET mitigation schemes that could help the designer meet her or his goals.

Moore’s Law has reached the point at which we can build single-chips with multiple processors and significant amounts of memory. Multiprocessor systems-on-chips (MPSoCs) have opened up new application areas, such as low-power and real-time embedded systems. This talk will review the architectures of multiprocessor systems-on-chips and the design methodologies used to create them. MPSoCs make use of advanced processors, memory systems, and on-chip networks, often delivered as intellectual property modules. The design methodologies required to design these complex systems build on earlier VLSI techniques but must address many new problems as well.

The demands of scalable, low latency and power efficient system-on-chip interconnect cannot only be satisfied by point-to-point or shared-bus interconnects. In this paper, we propose a new asynchronous network-on-chip (NOC) architecture which provides low latency transfers. This architecture is implemented as a GALS system, where chip units are built as synchronous islands, connected together using a delay insensitive asynchronous network-on-chip topology. The proposed NOC protocol and its asynchronous implementation are presented as well as the multi-level modeling approach using SystemC language and transaction-level-modeling. Preliminary simulation results show that the asynchronous NOC can offer 5 Gbytes/s throughput in a 0.13 /spl mu/m CMOS technology.

Abstract: Fault tolerant circuits are currently required in several major application sectors. Besides and in complement to other possible approaches such as proving or analytical modeling whose applicability and accuracy are significantly restricted in the case of complex fault tolerant systems, fault-injection has been recognized to be particularly attractive and valuable. Fault injection provides a method of assessing the dependability of a system under test. It involves inserting faults into a system and monitoring the system to determine its behavior in response to a fault. Several fault injection techniques have been proposed and practically experimented. They can be grouped into hardware-based fault injection, software-based fault injection, simulation-based fault injection, emulation-based fault injection and hybrid fault injection. This paper presents a survey on fault injection techniques with comparison of the different injection techniques and an overview on the different tools.

This work is a contribution to a drastic change in standard signal processing chains. The main objective is to reduce the power consumption by one or two orders of magnitude. Integrated Smart Devices and Communicating Objects are application domains targeted by this work. In this context, we present a new class of Analog-to-Digital Converters (ADCs), based on an irregular sampling of the analog signal, and an asynchronous design. Because they are not conventional, a complete design methodology is presented. It determines their characteristics given the required effective number of bits and the analog signal properties. it is shown that our approach leads to a significant reduction in terms of hardware complexity and power consumption. A prototype has been designed for speech applications, using the STMicroelectronics 0.18-/spl mu/m CMOS technology. Electrical simulations prove that the factor of merit is increased by more than one order of magnitude compared to synchronous Nyquist ADCs.

The explosion of phylogenetic studies not only provides a clear snapshot of biodiversity, but also makes it possible to infer how the diversity has arisen (see, for example, Purvis and Hector, 2000; Harvey et al., 1996; Nee et al., 1996; Mace et al., 2003). To this aim, variation in speciation and extinction rates have been investigated through their signatures in the shapes of phylogenetic trees (Mooers and Heard, 1997). This issue is of great importance, as fitting stochastic models to tree data would help to understand underlying macroevolutionary processes. Although the prevailing view is that it does not represent phylogenies so well, the most popular model of phylogenetic trees is a branching process introduced by Yule, in which lineages split at random (Yule, 1924). Here we report the study of one major database of published phylogenies using the Yule model as well as several other models. Our results confirm the previous observation that the Yule model is inadequate to describe phylogenetic tree data. In addition, they support the hypothesis that many trees are consistent with a simple branch split model first considered by Aldous in 1996. The analysis of stochastic models of phylogenetic tree shape, which began with Yule in 1924, was revived in the mid-1970s by the Woods Hole Group (Raup et al., 1973; Gould et al., 1977). Their model-based approach yielded the conclusion that lineages have varied in their potential for diversification. As a result of their work, much effort has recently been placed on understanding stochastic models of tree shape and their relationship to phylogenetic data. Among these models, the Equal Rate Markov (ERM, Yule) model is one of the simplest and most-often postulated as a null hypothesis for phylogenetic tree shape. In the ERM model each branch has an equal probability of splitting. Among others, Moran (1958) and Hey (1992) have also studied processes that share the same probability distribution of topologies as the Yule model. A second model—Proportional to Distinguishable Arrangements (PDA)—has also received a lot of attention. The PDA model has the property that all tree topologies are equally likely. Although less direct than for the ERM model, several interpretations of the PDA model in terms of evolutionary processes have been given in the past. For instance, Aldous (1991) found a correspondence between the PDA model and the genealogy of n species sampled from a critical branching process (i.e., including an extinction rate). McKenzie and Steel (2001) additionally established that explosive radiation processes can lead to the PDA model. More recently, Pinelis (2003) proved that multitype branching processes with species quasi-stabilization can also yield PDA-like trees. One aspect of tree shape is particularly important when testing stochastic macroevolutionary models: tree balance. Tree balance usually refers to the topological structure of the tree, not considering the branch lengths. Early studies (Guyer and Slowinski, 1991; Heard, 1992; Guyer and Slowinski, 1993) agreed that reconstructed phylogenies were more imbalanced than was predicted by the ERM model. However, these studies were based on small samples of trees each of them with rather small size. Thus the need for new large-scale studies of phylogenetic tree imbalance has been emphasized several times (e.g., Aldous, 2001). In this study we report a study of phylogenetic imbalance based on one major database—TreeBASE (http://www.treebase.org)—which serves as a searchable, archival repository of data and scientific references (Sanderson et al., 1994). In August 2005, TreeBASE contained 2063 phylogenetic trees with sizes ranging from 3 to 536, and 667 fully resolved binary trees with sizes ranging from 3 to 297. Many of these trees were rooted using one or two outgroup species. Because the outgroup taxa might contribute to an excess of imbalance (Heard, 1992), data were preprocessed by using an automatic outgroup removal procedure. This was done by identifying all trees in which one of the subtrees descended directly from the root had one or two taxa and removing that subtree. After the analysis, the automatic method was checked to produce results similar to true outgroup removal for 50 fully resolved binary trees (see Supplementary Material, http://systematicbiology.org). Two simulation methods were applied in order to solve polytomies by replacing the unresolved nodes either with ERM-like or with PDA-like subtrees. Both methods replaced the polytomic nodes by binary splits. Because there are two distinct available choices, binary splits were simulated according to either the ERM or PDA split distribution. Preprocessing and data analysis were performed using the “ape” and “apTreeshape” R packages (Paradis et al., 2004; Bortolussi et al., 2006). The likelihood-ratio test based on s rejected the ERM model in 48 % of fully resolved trees and in 48 % of ERM solved trees (one-sided test, P < .05, the values were computed using a direct Monte Carlo method, 1000 replicates). Figure 1 displays the distribution of standardized shape indices together with the N(0,1) distribution predicted asymptotically by the ERM model. A deeper look at the data shows that tree shape undergoes a rapid change from the smaller to the intermediate-sized and larger trees. To investigate this transition, we performed maximum likelihood parameter estimation under the beta-splitting model for three sets of trees: fully resolved, ERM solved, and PDA solved (see Supplementary Material). Figure 2 displays the estimated values for the first two data sets (third data set not shown, consistent with the others). A local regression (Cleveland et al., 1992) was performed on the estimated values. Figure 2 shows a rapid convergence around β ≈ − 0.95, very close to the AB model value β = − 1. Histograms of the shape statistics serm after ERM standardization (serm− E[serm])/σ[serm] and density of the standard normal distribution. The means and variances have been estimated using 1000 Monte Carlo replicates. The dark bars in the histograms correspond to the test rejection area (P < .05). (A) Fully resolved trees from TreeBASE. (B) All trees with ERM simulation for solving polytomies. Maximum likelihood estimates of the parameter β in the beta-splitting model. The AB model corresponds to the value β = −1. A local regression curve and the line β = −.95 are also plotted. (A) Fully resolved trees from TreeBASE. (B) All trees with ERM model simulation for solving polytomies. Table 1 reports the median and variance of the maximum likelihood estimator for intervals corresponding to the 20th-percentiles of tree sizes. The means of were located at similar values and the variances decreased quickly as tree size increased. Note that the results for data within the smaller percentiles may not be very meaningful. The automatic outgroup removal procedure may have indeed added considerable balance to the smaller trees. The bias introduced may be particularly large in cases where the outgroups were not studied or were removed before submission of trees to the database. Median and variance estimates of the maximum likelihood estimator β for two datasets: a, Binary trees in TreeBASE. b, ERM-solved trees. The intervals are based on the 20% quantiles of the tree size distribution. Median and variance estimates of the maximum likelihood estimator β for two datasets: a, Binary trees in TreeBASE. b, ERM-solved trees. The intervals are based on the 20% quantiles of the tree size distribution. Figure 3 displays the values of the shape statistic s as a function of tree size, and the predictions of the ERM, AB, and PDA models computed from Monte Carlo replicates. In addition, we used MC replicates to estimate the P-values P(S ≥ s) for every tree under the three models. If the trees were in fact sampled from one of these models, the P-values would have uniform probability distribution for that model. The plots in Figure 4 demonstrates that uniform P-values occurred under the AB model only. Figure 3 and Figure 4 support the view that the AB model fits to the TreeBASE data rather well. Values of the shape statistic s as a function of the number of taxa, and the values predicted by the ERM, AB, and PDA models for trees of size greater than 15. This graphic supports the fit of the AB model to TreeBASE data (fully resolved trees). The figure is plotted in a log-log scale. U-plot: quantiles of the P-values of the shape statistic versus quantiles of the uniform distribution. The null models used to compute the P-values are the ERM, AB, and PDA models. During the last decade, evolutionary biologists have often observed an excess of imbalance from phylogenetic data. In their review, Mooers and Heard (1997) reported several possible explanations for this phenomenon, including errors in molecular data, incompleteness of trees, and bias due to approximate reconstruction methods. Such criticisms still apply to the phylogenies stored in TreeBASE, but the use of numerous peer-reviewed entries must have reduced the biases from such errors and reconstruction methods. Incompleteness may, however, be contributing to the trend toward extra imbalance. The phenomenon may have been amplified in studies where species were removed from the analysis deliberately and selectively (see Mooers, 1995). Our main result says that the data generally agree with a very simple probabilistic model: Aldous' Branching. However, it leaves us with the issue of providing biological motivation for this model. One interpretation can start from the intuition that models with random diversification rates might be more appropriate for describing the Tree of Life than are models with deterministic rates. Some models of random diversification were investigated earlier by Heard (1996), who wrote that estimated trees from the literature correspond to very high, perhaps even implausibly high, levels of rate variation. The results presented in this study may weaken the conclusions of previous works that assumes uniform branch split models for the Tree of Life and may hence limit the impact of theoretical predictions about evolutionary history that were made under such models. Structural parameters of the branching topology of the Tree of Life may indeed differ considerably. These results have been confirmed by a simultaneous study of the same data by D. Ford using others models (Ford, 2005). Our results suggest that alternative models with greater levels of tree imbalance than the ERM model may be more appropriate in further studies of large trees (e.g., AB model, nondeterministic speciation rates). Gould et al. (1977) wrote “How different then is the world from the stochastic system? … The answer would seem to be not very.” The results presented here suggest that the world is not very different from the stochastic system as long as the right stochastic system is considered. The Supplementary Material is available from the Systematic Biology website:http://systematicbiology.org. The authors are grateful to Mike Steel for fruitful discussions at the “Mathematics of Evolution and Phylogeny Conference” held in Paris, July 2005, and for his review and syntheses that greatly contributed to improve the original manuscript. They wish to thank David Aldous and Arne Mooers for comments on an early version of the manuscript. They warmly thank Noah Rosenberg for his suggestions and assistance. The authors thank Stephen Heard, Rod Page, and an anonymous reviewer for their constructive remarks. OF was partly supported by grants from the IMAG Institute project ALPB, and the French ministry of research ACI-IMPBIO.

Spin-transfer torque magnetic tunnel junction (MTJ) is a promising candidate for nonvolatile memories thanks to its high speed, low power, infinite endurance, and easy integration with CMOS circuits. However, a relatively high current flowing through an MTJ is always required by most of the switching mechanisms, which results in a high electric field in the MTJ and a significant self-heating effect. This may lead to the dielectric breakdown of the ultrathin (~1 nm) oxide barrier in the MTJ and cause functional errors of hybrid CMOS/MTJ circuits. This paper analyzes the physical mechanisms of time-dependent dielectric breakdown (TDDB) in an oxide barrier and proposes an SPICE-compact model of the MTJ. The simulation results show great consistency with the experimental measurements. This model can be used to execute a more realistic design according to the constraints obtained from simulation. The users can estimate the lifetime, the operation voltage margin, and the failure probability caused by TDDB in the MTJ-based circuits.

We have developed a scanning thermal imaging method that uses a fluorescent particle as a temperature sensor. The particle, which contains rare-earth ions, is glued at the end of an atomic force microscope tip and allows the determination of the temperature of its surrounding medium. The measurement is performed by comparing the relative integrated intensity of two fluorescence lines that have a well-defined temperature dependence. As an example of application, we show the temperature map on an operating complementary metal-oxide-semiconductor integrated circuit.

BACKGROUND: Despite the mounting clinical burden of heart failure, the biomolecules that control myocardial tissue remodeling are poorly understood. TIMP-3 is an endogenous inhibitor of matrix metalloproteinases (MMPs) that has been found to be deficient in failing human myocardium. We hypothesized that TIMP-3 expression prevents maladaptive tissue remodeling in the heart, and accordingly, its deficiency in mice would alone be sufficient to trigger progressive cardiac remodeling and dysfunction similar to human heart failure. METHODS AND RESULTS: Mice with a targeted timp-3 deficiency were evaluated with aging and compared with age-matched wild-type littermates. Loss of timp-3 function triggered spontaneous LV dilatation, cardiomyocyte hypertrophy, and contractile dysfunction at 21 months of age consistent with human dilated cardiomyopathy. Its absence also resulted in interstitial matrix disruption with elevated MMP-9 activity, and activation of the proinflammatory tumor necrosis factor-alpha cytokine system, molecular hallmarks of human myocardial remodeling. CONCLUSIONS: TIMP-3 deficiency disrupts matrix homeostasis and the balance of inflammatory mediators, eliciting the transition to cardiac dilation and dysfunction. Therapeutic restoration of myocardial TIMP-3 may provide a novel approach to limit cardiac remodeling and the progression to failure in patients with dilated cardiomyopathy.

IC technologies are approaching the ultimate limits of silicon in terms of channel width, power supply and speed. By approaching these limits, circuits are becoming increasingly sensitive to noise, which will result on unacceptable rates of soft-errors. Furthermore, defect behavior is becoming increasingly complex resulting on increasing number of timing faults that can escape detection by fabrication testing. Thus, fault tolerant techniques will become necessary even for commodity applications. This work considers the implementation and improvements of a new soft error and timing error detecting technique based on time redundancy. Arithmetic circuits were used as test vehicle to validate the approach. Simulations and performance evaluations of the proposed detection technique were made using time and logic simulators. The obtained results show that detection of such temporal faults can be achieved by means of meaningful hardware and performance cost.

This paper examines aspects of design technology required to explore advanced logic-circuit design using carbon nanotube field-effect transistor (CNTFET) devices. An overview of current types of CNTFETs is given and highlights the salient characteristics of each. Compact modeling issues are addressed and new models are proposed implementing: 1) a physics-based calculation of energy conduction sub-band minima to allow a realistic analysis of the impact of CNT helicity and radius on the dc characteristics; 2) descriptions of ambipolar behavior in Schottky-barrier CNTFETs and ambivalence in double-gate CNTFETs (DG-CNTFETs). Using the available models, the influence of the parameters on the device characteristics were simulated and analyzed. The exploitation of properties specific to CNTFETs to build functions inaccessible to MOSFETs is also described, particularly with respect to the use of DG-CNTFETs in fine-grain reconfigurable logic.

A micro power generator harvesting vibration energy by resonant inertial oscillation of a piezoelectric laminated cantilever with proof mass was designed, fabricated, and characterized. The active part with 2 µm thick PZT on 5 µm silicon was equipped with interdigitated electrodes to achieve higher voltages. A coupling constant k2=5% was derived from the difference in resonance frequencies at low and high impedance. At optimal load impedance, a voltage of 1.6 V and an output power of 1.4 µW was measured with a 0.8x1.2 mm cantilever having an active area of 0.8x0.4 mm, excited with 2g at 870 Hz.

We present a design flow for the generation of application-specific multiprocessor architectures. In the flow, architectural parameters are first extracted from a high-level system specification. Parameters are used to instantiate architectural components, such as processors, memory modules and communication networks. The flow includes the automatic generation of communication coprocessor that adapts the processor to the communication network in an application-specific way. Experiments with two system examples show the effectiveness of the presented design flow.