Concurrent Features Research Articles

The infant skull: a vault of information.

The art of interpreting skull radiographs is slowly being lost as trainees in radiology see fewer plain radiographs and depend more heavily on computed tomography and magnetic resonance imaging. Nevertheless, skull radiographs still provide significant information that is helpful in finding pathologic conditions and appreciating their extents. Abnormalities in the skull may be reflected as variations in the density, size, and shape of the skull, as well as skull defects. Skeletal dysplasias may manifest as a generalized decrease in calvarial density (hypophosphatasia, osteogenesis imperfecta), a generalized increase in calvarial density (osteopetrosis), or a focal increase in density (frontometaphyseal dysplasia). Diffusely decreased or increased calvarial density is usually associated with a process that affects the entire skeleton. Therefore, correct differentiation among these dysplasias depends on other concurrent features. Decreased size of the cranial vault at birth generally implies an underlying insult to the brain, including fetal alcohol syndrome and the so-called TORCH infections (toxoplasmosis, rubella, cytomegalovirus infection, herpes simplex). Macrocephaly may result from skeletal dysplasia or an increase in the intracranial volume (eg, due to underlying anomalies of the brain such as hydrocephalus).

Parallel elementwise processable functions in concurrent clean

The behaviour of concurrent and parallel programs can be specified in a functional style. Functional programming style has some inherent concurrent features. However, for a higher degree of expressing parallelism there is a need for new language constructs. In this paper, we introduce Concurrent Clean modules for evaluation strategies in order to control the evaluation degree, the dynamic behaviour, and the parallelism. The usage of the strategies will be illustrated by the parallel elementwise processing method. The implementation of the method in the lazy functional programming language Concurrent Clean operates with a two arguments two values elementwise processable function. In order to obtain abstract type specification for the generalised manipulation of the linear data structures like lists, arrays, and strict arrays, a linear data structure class module is defined. The programming style is skeleton based. Skeletons in functional languages are higher-order functions. The skeleton given in this paper represents a generalisation of the map function. It is triply parameterized: by an elementwise processable function, by type specification, and by the strategy parameter that defines the dynamic behaviour of the program.

Knowledge in action: logical foundations for specifying and implementing dynamical systems

Modeling and implementing dynamical systems is a central problem in artificial intelligence, robotics, software agents, simulation, decision and control theory, and many other disciplines. In recent years, a new approach to representing such systems, grounded in mathematical logic, has been developed within the AI knowledge-representation community. This book presents a comprehensive treatment of these ideas, basing its theoretical and implementation foundations on the situation calculus, a dialect of first-order logic. Within this framework, it develops many features of dynamical systems modeling, including time, processes, concurrency, exogenous events, reactivity, sensing and knowledge, probabilistic uncertainty, and decision theory. It also describes and implements a new family of high-level programming languages suitable for writing control programs for dynamical systems. Finally, it includes situation calculus specifications for a wide range of examples drawn from cognitive robotics, planning, simulation, databases, and decision theory, together with all the implementation code for these examples. This code is available on the book's Web site.

A Hierarchical Manufacturing Route Planner Based on Heuristic Algorithm: Design and Evaluation

This paper presents the design and evaluation of a manufacturing route planner for flexible manufacturing systems. The aim of the planner is to find the optimal manufacturing routes for jobs using well-designed cost functions. This route planner, which is based on heuristic [A*] strategy, has been designed to work under dynamic arrival pattern environment. The proposed algorithm consists of two level; the cell level, which controls the jobs flow between cells, and the machine level which controls the jobs flow between the machines inside the cells selected at first level.The solutions of the route planner are contained in a dynamic knowledge base that passes information to the sequencing and monitoring stage. The suggested model has also the capability to detect and response with suitable alternation for the damaged elements in the manufacturing system. To improve the performance of the planner, the design is organized into distributed programming media using the concurrent features of the modula-2 programming language. Finally, two case studies are considered to illustrate the functionality of the proposed algorithm.

A new, unique signature of the true cusp

Abstract. The "cusp proper" is generally understood to be the region enclosed by the outermost magnetospheric field lines as they map to low altitudes. It is therefore a weak-field region with continuous contact with magnetosheath plasma. Data from the recent Astrid-2 Swedish microsatellite are presented which show a new, unique signature (dubbed the "true cusp") during cusp crossings that can now be shown to be consistently present and with which one can redefine the physical meaning and topology of the cusp. Similar crossings made by the DE-2, UARS and DMSP-F10 satellites also show this same, unique signature although in most cases the spatial resolution was much less than that of the Astrid-2 MEDUSA spectrometer. The presence of concurrent features of the same scale size as the plasma in the energetic particle, field and wave power data shows that this is a real structural feature and not a coincidental structure among plasma instruments. The persistence of this feature may lend new insight into the dynamics of the cusp and magnetospheric particle entry.Key words. Magnetospheric physics (magnetopause, cusp, arid boundary layers; magnetospheric configuration and dynamics)

Combining tasking and transactions, part II

This position paper is a follow-up paper of [1], presented at the last IRTAW workshop. The paper describes a model for providing transaction support for concurrent programming languages such as Ada 95. In order to achieve smooth integration, the use of the concurrency features provided by the Ada language should not be restricted inside a transaction. A transaction model that meets this requirement is presented. Tasks inside such a transaction may spawn new tasks, but also external tasks are allowed to join an ongoing transaction. A blocking commit protocol ensures that no task leaves the transaction before its outcome has been determined. Exceptions are used to inform all participants in case a transaction aborts. Possible interfaces for the Ada programmer are discussed.

ALSPAC--the Avon Longitudinal Study of Parents and Children. I. Study methodology.

ALSPAC (The Avon Longitudinal Study of Parents and Children, formerly the Avon Longitudinal Study of Pregnancy and Childhood) was specifically designed to determine ways in which the individual's genotype combines with environmental pressures to influence health and development. To date, there are comprehensive data on approximately 10,000 children and their parents, from early pregnancy until the children are aged between 8 and 9. The study aims to continue to collect detailed data on the children as they go through puberty noting, in particular, changes in anthropometry, attitudes and behaviour, fitness and other cardiovascular risk factors, bone mineralisation, allergic symptoms and mental health. The study started early during pregnancy and collected very detailed data from the mother and her partner before the child was born. This not only provided accurate data on concurrent features, especially medication, symptoms, diet and lifestyle, attitudes and behaviour, social and environmental features, but was unbiased by parental knowledge of any problems that the child might develop. From the time of the child's birth many different aspects of the child's environment have been monitored and a wide range of phenotypic data collected. By virtue of being based in one geographic area, linkage to medical and educational records is relatively simple, and hands-on assessments of children and parents using local facilities has the advantage of high quality control. The comprehensiveness of the ALSPAC approach with a total population sample unselected by disease status, and the availability of parental genotypes, provides an adequate sample for statistical analysis and for avoiding spurious results. The study has an open policy in regard to collaboration within strict confidentiality rules.

Object-oriented real-time concurrency

The primary goal of a real-time system is predictability. Achieving this goal requires all levels of the system to work in concert to provide fixed worst-case execution-times. Un-fortunately, many real-time systems are overly restrictive, providing only ad-hoc scheduling facilities and basic concurrent functionality. Ad-hoc scheduling makes developing, verifying, and maintaining a real-time system extremely difficult and time consuming. Basic concurrent functionality forces programmers to develop complex concurrent programs without the aid of high-level concurrency features.Encouraging the use of sophisticated real-time theory and methodology, in conjunction with high-level concurrency features, requires flexibility and extensibility. Giving real-time programmers access to the underlying system data-structures makes it possible to interact with the system to incorporate new ideas and fine-tune specific applications. This paper explores this approach by examining its effect on a selection of crucial real-time issues: real-time monitors, timeouts, dynamic-priority scheduling and basic priority inheritance. The approach is implemented in μC++ .

Annotating Java class files with virtual registers for performance

The Java .class file is a compact encoding of programs for a stack-based virtual machine. It is intended for use in a networked environment, which requires machine independence and minimized consumption of network bandwidth. However, as in all interpreted virtual machines, performance does not match that of code generated for the target machine. We propose verifiable, machine-independent annotations to the Java class file to bring the quality of the code generated by a ‘just-in-time’ compiler closer to that of an optimizing compiler without a significant increase in code generation time. This division of labor has expensive machine-independent analysis performed off-line and inexpensive machine-dependent code-generation performed on the client. We call this phenomenon ‘super-linear analysis and linear exploitation.’ These annotations were designed mindful of the concurrency features of the Java language. In this paper we report results from our machine-independent, prioritized register assignment. We also discuss other possible annotations. Copyright © 2000 John Wiley & Sons, Ltd.

Computing with Contexts

We investigate a representation of contexts, expressions with holes in them, that enables them to be meaningfully transformed, in particular α-converted and β-reduced. In particular we generalize the set of λ-expressions to include holes, and on these generalized entities define β-reduction (i.e., substitution) and filling so that these operations preserve α-congruence and commute. The theory is then applied to allow the encoding of reduction systems and operational semantics of call-by-value calculi enriched with control, imperative and concurrent features.

A comparison of the concurrency features of Ada 95 and Java

subclasses of an abstract class need to provide implementations for any abstract methods that they inherit. A variable declared of a particular class is intrinsically polymorphic: it can designate objects from that class or from any of its direct or indirect subclasses. Objects are generated on the heap from invocations of constructors. Complementing the class concept is the feature known as an interface. An interface may be viewed as a restricted form of class with no “implementation” aspects. Thus the only methods allowed in an interface are abstract methods, and the only variables allowed in an interface are so-called final variables, which are constants. A class is allowed to extend only one class but may implement an arbitrary number of interfaces; in this sense Java provides some support for multiple inheritance. Here is an example of Java’s main OOP concepts, adapted from [4]: public class Point{ protected static int numPts=0; protected int x, y; public Point(int x, int y){ this.x=x; this.y=y; numPts++; } public static int getNumPts(){ return numPts; } public void shift(int ∆x, int ∆y){ x += ∆x; // Note Unicode character

Practical use of Ada 95's concurrency features

Ada 83 has numerous shortcomings for concurrent systems: it requires additional tasks, adding overhead and increasing interrupt latency, and it has difficulty handling asynchronous transfer of control. Ada 95 offers features that address these shortcomings and simplify concurrent implementation: protected units, interrupt handlers, priority entry queuing, dynamic task priorities, and asynchronous select statements. Using their Flexible Manufacturing System, the authors demonstrate how these features improve Ada and promote efficiency.

Cetacean distributions and oceanographic features near the Kerguelen Plateau

Cetacean surveys were conducted in the austral summer during World Ocean Circulation Experiment hydrolegs I8S and I9S in the southeastern Indian Ocean. The highest density of cetaceans occurred along the southern flank of the Kerguelen Plateau and northern edge of the Princess Elizabeth Trough, where the distribution of whales coincides with the mean positions of the Southern Front of the Antarctic Circumpolar Current (ACC) and southern water mass boundary (Southern Boundary) of the ACC. The topographic steerage of these features of the ACC around the southern edge of the Kerguelen Plateau brings shoaled, nutrient‐rich Upper Circumpolar Deep Water (UCDW) to higher latitude than in adjacent basins. The higher concentrations of cetaceans near the Kerguelen Plateau suggests that whales benefit from a cascade of trophic dynamics associated with the poleward extent of UCDW, the marginal ice edge zone, and the proximity of several oceanographic features: the high latitude penetration and close alignment of the Southern Front and Southern Boundary of the ACC; the unique poleward extent of the Southern Boundary as it is topographically steered around the plateau; the entrainment of macronutrients into the surface mixed layer near the Southern Boundary; isopycnal shoaling in cyclonic eddies; the presence of complex bathymetry; and the advection of a tongue of ice northward along the eastern side of the plateau. The association between these concurrent oceanographic features and whales suggests that the southeastern edge of the Kerguelen Plateau is a predictably productive foraging location for cetaceans and their prey.

Restricted tasking models

High-integrity systems rarely make use of high-level language features such as Ada tasking. In this paper, simple language profiles (of Ada 95 concurrency features) are developed that are appropriate for various levels of integrity. A level-0 model (collection of Ada95 features) defines a minimal language profile and delivers deterministic (non-preemptive) behaviour. Scheduling is undertaken as part of the application and can thus be inspected and verified. Five other models are also presented that give different levels of expressive power. The motivation for this paper is to try and define models that would become de facto standards and that would be directly supported by kernel vendors and other tool suppliers.

An algebraic semantic framework for object oriented languages with concurrency (extended abstract)

Abstract This paper presents an algebraic semantics schema for object oriented languages including concurrent features. A class, the basic syntactic unit of an object oriented language, in our approach denotes a set of algebras determined by an algebraic specification. This specification describes a system of (possibly active) objects interacting via method calls. Extending other approaches, structured classes are modelled in a fully compositional way. This means that the semantic counterpart of class combinators such as inheritance and clientship are specification combinators. A model of records with sharing allows us to describe typical object oriented features like object sharing, inheritance polymorphism and dynamic binding. For modelling the dynamic behaviour of objects, we rely on an algebraic description of labelled transition systems.

A theory of weak bisimulation for core CML

Concurrent ML (CML) is an extension of Standard ML of New Jersey with concurrent features similar to those of process algebra. In this papes we build upon John Reppy's reduction semantics for CML by constructing a compositional operational semantics for a fragment of CML, based on higher-order process algebra. We use this to build a semantic theory for CML, based on weak bisimulation equivalence. We give some small examples of proofs about CML expressions, and show that our semantics corresponds to Reppy's up to weak first-order bisimulation.

Intermediate transition in the Venus ionosheath

We present the results of an analysis of Pioneer Venus Orbiter (PVO) plasma and electric and magnetic field data with evidence of a plasma transition along the flanks of the Venus ionosheath for 8 PVO passes near the terminator. This transition occurs between the bow shock and the ionopause and represents a stationary change in the properties of the shocked solar wind that streams around the Venus ionosphere. We find that the intermediate transition is characterized by three concurrent features: (1) A noticeable electric field burst measured with the 30 kHz channel of the electric field detector of the PVO; (2) a severe drop of the magnetic field intensity accompanied by a strong rotation of the magnetic field orientation to a direction closer to the Sun‐Venus axis in the inner ionosheath; and (3) substantially enhanced plasma fluxes detected at the time when these changes in the electric and magnetic fields are measured. The peak particle flux and the peak magnetic field intensity measured at this transition in the data of the 17 PVO orbits are also presented. It is found that large values of the enhanced particle fluxes occur mostly when the peak magnetic field intensity is large.

Comparative embryology of teleostean fishes. I. Development and staging of the american shad, Alosa sapidissima (Wilson, 1811).

A new approach to devising embryological staging systems allows improved phylogenetic comparisons of developmental patterns. As in traditional approaches, morphological features provide the defining criteria for stages, but unlike traditional normal tables, each stage is defined by no more than one or two morphological criteria that are fundamental developmental features of all teleosts. Additional developmental features that occur concurrently with the defining criteria of a stage are treated as variables potentially uncoupled from the defining criteria for that stage. This system is well suited to detect phylogenetic heterochrony and promises to increase our understanding of conserved vs. labile features in teleostean embryology. In this study, I explain the defining criteria for American shad and then make comparisons with other clupeoids. The development of American shad includes 35 stages extending from fertilization to metamorphosis. Comparisons with other clupeoids indicate that the developmental pattern of shad is representative of the early ontogeny of many clupeoids during the embryonic and yolk sac periods and may be conservative for the group. However, several concurrent features, particularly hatching, formation of neuromasts, and opercular development, vary in developmental timing among clupeoids. Comparisons indicate that shad embryos delay the development of these concurrent features relative to other clupeoids. Modifications of the developmental pattern for different species of clupeoids are heterochronic but their phylogenetic and adaptive significance is unknown. © 1995 Wiley-Liss, Inc.

EXPERIENCE USING FORMAL METHODS IN HIGH ENERGY PHYSICS

We report our experience using the formal method VDM++ in high energy physics real-time applications. VDM++ is an extension of the established formal method VDM to include object-oriented, concurrency and real-time features. VDM++ is supported by the VENUS tool-set, comprising an OMT graphical editor, VDM++ syntax and type checker, and a C++ code generator. Formal specification meta-languages allow formal data modeling, algorithm and system behavior specification at a highly abstract level. Once an abstract design has converged it is refined towards a particular implementation, with formal validation of each step if desired. We have applied VDM++ to the design of a fast track pattern recognition algorithm; the design of a global second- level trigger system for LHC experiments; the specification of simulated physics data; and the design of a data router hardware unit for a LHC second-level trigger. We are encouraged by the application of mathematics in an engineering discipline and conclude that formal methods have the potential to make a valuable contribution to the systems development process in high energy physics.

TREATMENT OF CORTICOSTEROID-RESISTANT GIANT CELL ARTERITIS

The literature about the treatment of giant cell arteritis (GCA) is diverse and often includes patients with polymyalgia rheumatica (PMR) who do not have concurrent features of GCA. Consequent heterogeneity has contributed to controversy in the analysis of clinical data. Nevertheless, we have critically reviewed this literature to derive a rational approach to initial and maintenance corticosteroid (CS) therapy and thus define "CS-resistant GCA." In this article, the authors review what has been written about the treatment of presumed CS-resistant disease. Although firm recommendations are lacking, the authors provide algorithms for the treatment of GCA patients who fail to respond to initial CS therapy or who require potentially toxic maintenance-dose CS therapy. A study design that may help to resolve the dilemmas that were found during our analysis is also outlined.