Asynchronous techniques for system-on-chip design

SoC design will require asynchronous techniques as the large parameter variations across the chip will make it impossible to control delays in clock networks and other global signals efficiently. Initially, SoCs will be globally asynchronous and locally synchronous (GALS). But the complexity of the numerous asynchronous/synchronous interfaces required in a GALS will eventually lead to entirely asynchronous solutions. This paper introduces the main design principles, methods, and building blocks for asynchronous VLSI systems, with an emphasis on communication and synchronization. Asynchronous circuits with the only delay assumption of isochronic forks are called quasi-delay-insensitive (QDI). QDI is used in the paper as the basis for asynchronous logic. The paper discusses asynchronous handshake protocols for communication and the notion of validity/neutrality tests, and completion tree. Basic building blocks for sequencing, storage, function evaluation, and buses are described, and two alternative methods for the implementation of an arbitrary computation are explained. Issues of arbitration, and synchronization play an important role in complex distributed systems and especially in GALS. The two main asynchronous/synchronous interfaces needed in GALS-one based on synchronizer, the other on stoppable clock-are described and analyzed

Basement membrane proteoglycans: modulators Par Excellence of cancer growth and angiogenesis.

Proteoglycans located in basement membranes, the nanostructures underling epithelial and endothelial layers, are unique in several respects. They are usually large, elongated molecules with a collage of domains that share structural and functional homology with numerous extracellular matrix proteins, growth factors and surface receptors. They mainly carry heparan sulfate side chains and these contribute not only to storing and preserving the biological activity of various heparan sulfate-binding cytokines and growth factors, but also in presenting them in a more active configuration to their cognate receptors. Abnormal expression or deregulated function of these proteoglycans affect cancer and angiogenesis, and are critical for the evolution of the tumor microenvironment. This review will focus on the functional roles of the major heparan sulfate proteoglycans from basement membrane zones: perlecan, agrin and collagen XVIII, and on their roles in modulating cancer growth and angiogenesis

Spatiotemporal Modeling of Swedish Scots Pine Stands

The growth-interaction (GI) process is used for the spatiotemporal modeling of measurements of locations and radii at breast height made at three different time points of the individual trees in 10 Scots pine (Pinus sylvestris) plots from the Swedish National Forest Inventory. The GI process places trees at random locations in the study region and assigns sizes to the trees, which interact and grow with time. It has been used to model plots in previous studies and to improve the fit we suggest some modifications: a different location assignment strategy and a different open-growth (growth under negligible competition) function. We believe that the calibration data contain trees that are too small to reflect the open growth properly, which primarily affects the carrying capacity parameter. To better represent the open growth of Scots pines, we evaluate the open growth from a separate set of data (size and age measurements of older and larger single Scots pines). A linear relationship is found between the plot's estimated site indices and the sizes, and this is exploited in the estimation of the carrying capacity. We finally estimate the remaining GI process parameters and test the goodness of fit on simulated predictions from the fitted model

Speed and Energy Performance of an Asynchronous MIPS R3000 Microprocessor

This paper presents the speed and energy figures for an asynchronous implementation of a MIPS R3000 microprocessor. The design is almost entirely QDI and introduces a new fine-grained pipeline. The performance figures show that this design is four times as efficient as equivalent clocked designs and that its cycle time in FO4 units compares to that of high-performance dynamic pipelines

Green's functions for parabolic systems of second order in time-varying domains

We construct Green's functions for divergence form, second order parabolic systems in non-smooth time-varying domains whose boundaries are locally represented as graph of functions that are Lipschitz continuous in the spatial variables and 1/2-H\"older continuous in the time variable, under the assumption that weak solutions of the system satisfy an interior H\"older continuity estimate. We also derive global pointwise estimates for Green's function in such time-varying domains under the assumption that weak solutions of the system vanishing on a portion of the boundary satisfy a certain local boundedness estimate and a local H\"older continuity estimate. In particular, our results apply to complex perturbations of a single real equation.Comment: 25 pages, 0 figur

Actors that Unify Threads and Events

There is an impedance mismatch between message-passing concurrency and virtual machines, such as the JVM. VMs usually map their threads to heavyweight OS processes. Without a lightweight process abstraction, users are often forced to write parts of concurrent applications in an event-driven style which obscures control flow, and increases the burden on the programmer. In this paper we show how thread-based and event-based programming can be unified under a single actor abstraction. Using advanced abstraction mechanisms of the Scala programming language, we implemented our approach on unmodified JVMs. Our programming model integrates well with the threading model of the underlying VM

Estimating Forest Age and Site Productivity using Time Series of 3D Remote Sensing Data

ABSTRACT Three-dimensional (3D) data about forest captured by airborne laser scanning (ALS) have revolutionized forest management planning. Accurate, updated large-scale maps of forest variables produced with low costs today support greatly improved decisions about silvicultural treatments compared to the past practice based on field surveyed data only. These maps usually lack important information about forest age and site productivity, as this cannot be accurately assessed from the available ALS data. In Sweden, ALS has recently been performed nation-wide, except the mountainous area, to produce a new and accurate digital terrain model (DTM). This DTM enables extremely costefficient extraction of 3D data about the forest from other sources than ALS, such as automatic stereo-matching of aerial images as well as from single-pass spaceborne interferometric synthetic aperture radar (InSAR). In contrast to ALS, these data sources can provide low-cost time-series of 3D data. Aerial images of Sweden are often available in archives back to approximately 1960, and the TanDEM-X SAR system has the potential to provide new data every second week over large areas. These data have a potentially high value for forest management planning, since they may provide missing and highly important information -forest site productivity, Site Index (SI) and forest age. This pilot study explores a least-squares minimization approach to estimate forest age and SI from time series of 3D data produced by 1) image matching of DMC aerial images, and 2) TanDEM-X SAR data

Using story-based methodologies to explore physics identities:How do moments add up to a life in physics?

[This paper is part of the Focused Collection on Qualitative Methods in PER: A Critical Examination.] This article details methodologies employed to enable sharing and coconstructing the stories of three women’s lives in physics. The first case explores the usefulness of timeline interviewing, where participants narrate episodes that are coconstructed with the researcher as meaningful over time. We illustrate this method in the case of a mature student in Sweden from a working-class background who shared moments that added up to a life outside of physics and then a sharp turn into physics later in life. The second case explores life-history interviewing using a narrative-inquiry approach and deep relationship building which enabled the coconstruction of stories of experiences over time. These moments are coconstructed with the researcher and analyzed using an intersectionality lens to yield a story depicting the transnational experiences of a woman of color moving across various European contexts into the North American physics context. The final case is of a first-generation Canadian woman of color who shared her navigations of in and out of school physics via a method known as the “Rivers of Life.” Using this method, the participant narrates their experiences with physics as a river, using metaphorical tools like rafts, rocks, rapids, tributaries to discuss various moments described as twists and turns over time that together amount to a life in physics. We discuss the value of different approaches to coconstructing narratives with participants and, in particular, the need for this kind of research in physics contexts

Ecological resilience, climate change, and the Great Barrier Reef

The vulnerability assessments in this volume frequently refer to the resilience of various ecosystem elements in the face of climate change. This chapter provides an introduction to the concept of ecological resilience, and its application as part of a management response to climate change threats. As defined in the glossary, resilience refers to the capacity of a system to absorb shocks, resist dramatic changes in condition, and maintain or recover key functions and processes, without undergoing "phase shifts" to a qualitatively different state (Figure 4.1)32, 72. For example, people who are physically and mentally fit and strong will have good prospect of recovery from disease, injury or trauma: they are resilient. In Figure 4.1, a ball placed at position 1 is dynamically stable: not only will it remain in position, but if pushed in any direction, it will return to its original position; thus the ball in this state is resilient, in that it can absorb shocks and return to a similar condition or state. In contrast, a ball placed at position 2 may be initially stable (it will remain in position if undisturbed) but not dynamically stable: if disturbed, it will move away. Thus the ball at position 2 is not resilient, and disturbances will result in a shift in state. If the ball at position 1 is disturbed to anywhere within the red circle, the ball will return to position 1; however, if disturbed further, the ball may not return, but may move to a new, alternate stable state (eg position 3). This system is resilient to disturbances that push it within the red boundary. However, if external factors decreased the depth of position 1, or lowered the saddle at point 2, then the system's resilience would be reduced. By analogy to coral reef ecosystems, position 1 might be a coral-dominated reef, and position 3 algal dominated. A disturbance such as killing coral that is overgrown by algae would move the reef toward an algal-dominated state; if the reef is resilient, this change would be temporary and natural processes would allow coral to re-establish and recover. If not, the algal dominance might be sufficient to preclude coral regrowth or recruitment, and the reef would change trajectory, moving toward algal dominance. Ecological resilience refers to the capacity of an ecosystem, habitat, population or taxon to withstand, recover from or adapt to impacts and stressors, such as climate change, and retain the same structure, processes and functions³². For example, coral reefs are naturally very dynamic, undergoing constant change and disturbances, but, under natural conditions, they have considerable capacity to recover or maintain key processes and functions in the face of such disturbances or pressures. Tropical storms may cause dramatic damage to coral populations, and hence to the physical habitat structure, with dead coral being overgrown by various forms of algae. This will result in a temporarily changed state, and changes in ecological functions. On a resilient reef, over a period of five to 20 years, the altered state is unstable: coral fragments will regrow, and new corals will settle, grow and gradually replace the algae, restoring the reef to coral dominance, and restoring ecological structure and processes. In contrast, however, if human impacts have undermined that resilience, algal growth may be exacerbated, coral regrowth and colonisation may be suppressed, and the altered state and processes may become stable, causing a long-term "phase shift", or change, to algal dominance