New Classes Of Objects Research Articles

An Object-Oriented Modeling and Simulation Environment for Reactive Systems Development

An environment to support the modeling, analysis, simulation, and development of state transition models, SMOOCHES (State Machines for Object-Oriented Concurrent Hierarchical Engineering Specifications), is presented. SMOOCHES allows the hierarchical construction, analysis, and simulation of state transition models in an object-oriented distributed environment. Statecharts (see Harel 1987b), a powerful mechanism for state transition specification, are fundamental to the development of SMOOCHES. To assist in the specification of hierarchical state transition models for distributed and reactive systems, statecharts are extended by introducing the concept of exit-safe states. SMOOCHES allows the specification of objects in the system with hierarchical state transition models and the derivation of new classes of objects through inheritance. A graphical monitoring system has been developed to represent and simulate the object state life cycles and monitor event generations. The example presented illustrates the modeling and simulation of different state life cycles of an assembly robot.

Towards object-oriented modelling of euclidean geometry

This paper presents an object-oriented approach to interactive modelling of geometric objects. The objects are specified by geometric constructions that are built by mimicing the compass-and-ruler manual approach in a direct manipulation graphical interface. The system adopts a programming-by-example paradigm to enrich construction methods incrementally. New constructions can be used to define new classes of objects or new methods for an existing class. Messages exchanged among objects specify geometric relationships among entities. Messages sent at construction time implicitly form a relationship network, which is preserved during subsequent geometric transformations, so that geometric constraints can be satisfied without resorting to numerical methods. The prototype GEObject is implemented under Actor in a Windows 3.0 environment.

Automated classification of stellar spectra - I. Initial results with artificial neural networks

We have initiated a project to classify stellar spectra automatically from high-dispersion objective prism plates. The automated technique presented here is a simple backpropagation neural network, and is based on the visual classification work of Houk. The plate material (Houk's) is currently being digitized, and contains ≈ 105 stars down to V ≈ 11 at ≈ 2-A resolution from ≈ 3850 to 5150 A. For this first paper in the series we report on the results of 575 stars digitized from 6 plates. We find that even with the limited data set now in hand we can determine the temperature classification to better than 1.7 spectral subtypes from B3 to M4. Our current sample size provides insufficient training set material to generate luminosity and metallicity classifications. Our eventual aims in this project are (1) to create a large and homogeneous digital stellar spectral library; (2) to create a well-understood and robust automatic classification algorithm which can determine temperatures, luminosities and metallicities for a wide variety of spectral types; (3) to use these data, supplemented by deeper plate material, for the study of Galactic structure and chemical evolution; and (4) to find unusual or new classes of objects.

Cluster analysis of the hot subdwarfs in the PG survey

The Palomar Green survey (Green et al., 1986) of faint blue, high galactic-latitude objects, turned up several interesting new classes of objects, such as gravitational lenses (Weyman et al., 1980), the ultra hot star H1504+65 (Nousek et al., 1986), and the PG 1159-035 variables (McGraw et al., 1979). The PG survey forms a mainstay in the investigations of late stages of stellar evolution. Work (Flemming et al., 1986) has already cast light on the important question of the space density of DA’s and continuing work is seeking values for similar population parameters for the subdwarfs: Evolutionary links between the subdwarf stage and white dwarfs will thereby be illuminated.

DEOS — A dynamically extendible object-oriented system

DEOS is an object-oriented environment written in standard C and developed to support a commercial portfolio management system. It supports rune time creation of new classes of objects through messages and text file object definitions. Objects may be modified with additional fields at run time. Separately compiled and linked method functions may be bound to objects at run time.

Syntactic experiments with arrays of functions and operators

The syntactic binding hierarchy of Benkard is refined to produce a numeric table. This table has been used by Bunda and Gerth to implement a syntactic model of APL2. The model is extended to include new classes of objects and strands of objects other than data. Directions for syntactic development are suggested, tending toward a language which achieves flexibility by nesting simple levels in a remarkable parallel with nested arrays. Cautious experimentation with models such as this one is urged before firm extensions are made to the language.

An Interpretability Approach to the Theory of Abstract Data Types1

In this paper, similarly to [1,4,17,20,21,29,30], abstract data types are understood as formalized many-sorted theories based on algorithmic languages (e.g. a language of algorithmic logic [2,16] or a language of dynamic logic [11,29]). Operations on data types, leading from (more) primitive types to compound types, are defined in terms of the interpretability theory (cf. Szczerba [25]). The approach proposed here to defining new types accords with the methods of introducing new classes of objects in programming languages like Simula 67, Pascal, Loglan, Ada.

The extreme ultraviolet explorer

The Extreme Ultraviolet Explorer (EUVE) Mission is described. The purpose of this mission is to search the celestial sphere for astronomical sources of extreme ultraviolet (EUV) radiation (100–1000Å). The search will be accomplished with the use of three EUV telescopes, each sensitive to different bands within the EUV band. A fourth telescope will perform a high sensitivity search of a limited sample of the sky in a single EUV band. In six months, the entire sky will be scanned at a sensitivity level comparable to existing surveys in other more traditional astronomical bandpasses. A substantial number of EUV sources such as hot white dwarfs and stellar coronae are certain to be discovered given our current knowledge. More uncertain is what entirely new classes of objects will be discovered as EUV sources. A moderate resolution (∼ 5Å) spectroscopy option is being considered which would cover the band from 80 to 600Å. This instrument would be capable of providing spectra of at least the 100 brightest EUV sources and would be utilized entirely on a Guest Investigator basis.

The Majestic, Unfathomable Universe

tronomy is the oldest of the physical sciences, perhaps the human race's oldest science. When our early ancestors first began to make systematic observations of celestial phenomena is unknown, but arguments are made that the menhirs, patterns of stones erected in Western Europe thousands of years ago, of which Stonehenge is the most famous example, were astronomical computers or astronomical filing systems. All recorded civilizations have studied the heavens and computed the recurrences of such things as eclipses and planetary positions. Although the main reason for compiling the information was fortune-telling, ancient astronomers developed a sophisticated understanding of celestial appearances (if not celestial mechanics), which they bequeathed to their successors. Modern astronomy began with the application of scientific mnodes of thought and telescopic means of observation in the hands of such people as Copernicus, Galileo, Brahe, Kepler (though Kepler too was called upon to tell fortunes) and Newton. We are now in a period that could be called postmodern astronomy, witnessing the progress of a revolution begun theoretically by Einstein and Friedmann and observationally by Hubble. It asks again and in different terms the age-old question that may have animated the minds of the prehistoric people who first piled up the menhirs and certainly occurred to the ancient astronomers of the historic period: What sort of universe do we live in; what is its shape and size and form, and what are its laws? Concurrently another astronomical revolution has been taking place, one that extends and complicates the other. It is the extension of observations to regions of the electromagnetic spectrum invisible to human eyes, the radio, the X-ray, the infrared, the ultraviolet. The extension has led to the discovery of new classes of objects that extend and complicate the basic cosmological and astrophysical problems. Quasars are a case in point. Without radio astronomy their peculiarity might well never have been discovered. The peculiarity is that although quasars look as compact as stars, they radiate energy in amounts proper to whole galaxies and even more. Cosmologists want to know where the quasars are and what they have to say about the size and shape of the universe. Astrophysicists (often the same people) want to know what they are, what produces their tremendous energy. Many answers have been suggested to the questions. Not one of them is uncontroverted. If quasars are as far away as the redshifts in their light would lead people to believe, then they are some of the most distant objects ever seen. With them we are looking billions of years into the past, seeing glimpses of what the universe looked like then. If space is indeed curved in the right way, as we continue to look farther and farther out, we may eventually see the back of ouLr own heads ~~~~~~~~ _*

Radio structure of extragalactic X-ray sources

The radio properties ofUhuru X-ray sources with fairly certain extragalactic identifications are described briefly. Radio to X-ray flux ratios are low for rich clusters of galaxies and high for double radio sources. There is some evidence from the Abell 426 (Perseus) and Abell 1367 clusters that a radio galaxy in a rich cluster may be the centre of extended X-ray emission. Nuclei of galaxies have an enormous range in X-ray luminosity; the known range is from ∼1030 W for our galaxy to ∼3×1038 W for 3C 273. Unidentified X-ray sources at high galactic latitudes may include new classes of objects with very low radio to X-ray flux ratios or hard X-ray emission.

Surprises at Serpukhov

Physicists construct ever more energetic particle accelerators in order to probe ever finer details of natural structures. As the energy of the probing particles has gone up, the center of attention has progressed from atoms to nuclei to the structure of such particles as protons and neutrons themselves. With each major increase in energy have come surprises, new classes of objects, new kinds of physical properties, that have forced radical changes in theory. But now, at the level of probing the structure of the so-called elementary particles themselves, some physicists have thought there ought to be a limit. Other physicists are not so sure. The latest step in the parade of energy increases is the 76-billion-electron-volt (GeV) synchrotron at Serpukhov in the Soviet Union. It is more than twice as energetic as anything that operated before it, and when it began experiments about two years ago, the question in physicists' minds was whether experimentation in this range would bring surprises or whether it would merely confirm and extend information already gathered at lower energies. The first Serpukhov experiments have already shown enough surprises to have theorists shaking their heads. Further results are now eagerly awaited. Among the first experiments were so-called total cross-section experiments intended to find out in a general way where things are at this energy range. The cross section reveals the probability that anything at all will happen when an accelerated particle is shot at a target. It depends on a wave that is associated with each particle, the socalled de Broglie wave named for Prince Louis de Broglie, who first suggested its existence in the early 1920's. The de Broglie wave is a way of measuring the probability of a particle's being somewhere in a given volume at a given time; its wavelength determines the area over which a particle's influence is felt, and the probability of some interaction with a target depends on this. At low energies the de Broglie wavelength is larger than the physical size of the particle, but as the energy goes up the wavelength decreases. Eventually a point should come where the wavelength becomes less than the physical size of the particle. At this point the total cross section becomes dependent on the size of the particle and should remain constant if the energy is further increased. But the Serpukhov results are showing that the total cross sections do not approach constant values as fast as current theory indicates they should. A related surprise is that the total cross sections for a particle and that for its antiparticle do not come together at high energies as theory says they should. At low energies the total cross sections for particle and antiparticle differ, since there are natural rules that prohibit antimatter from doing some of the things matter can do. At high energy these rules should lose their effect, and theory says the two cross sections should come to the same value, but experimentally they are not exhibiting the expected behavior. These things seem to be saying that there is something in the nature of the particles that exhibits itself at Serpukhov energies that was not taken into account in present theory, but theorists have so far not come up with an explanation. Other experiments have looked for more surprises. Serpukhov has looked for quarks, the theoretically predicted building blocks out of which the particles are supposed to be made, but has not found them. For several months the accelerator has been shut down for a rearrangement of the experimental hall and beams. When it reopens one of the first experiments will be less direct check of the quark theory than a search for quarks themselves: an investigation of negative mesons. This experiment will be done in collaboration with the CERN laboratory in Geneva as was some of the cross-section work. The quark theory says that all particles are built of either two or three subparticles called quarks, and on this basis makes predictions about their masses and other properties. Previous experiments at CERN have found a series of negatively charged mesons that fit the predictions of the quark theory especially well. The forthcoming