pinecone/core-2020-05-10-deduplication huggingface dataset:
Stochastic Coagulation and the Timescale for Runaway Growth

We study the stochastic coagulation equation using simplified models and
efficient Monte Carlo simulations. It is known that (i) runaway growth occurs
if the two-body coalescence kernel rises faster than linearly in the mass of
the heavier particle; and (ii) for such kernels, runaway is instantaneous in
the limit that the number of particles tends to infinity at fixed collision
time per particle. Superlinear kernels arise in astrophysical systems where
gravitational focusing is important, such as the coalescence of planetesimals
to form planets or of stars to form supermassive black holes. We find that the
time required for runaway decreases as a power of the logarithm of the the
initial number of particles. Astrophysical implications are briefly discussed.Comment: 16 pages, 4 figures, 1 appendi
The Size-Frequency Distribution of the Zodiacal Cloud: Evidence from the
  Solar System Dust Bands

Recent observations of the size-frequency distribution of zodiacal cloud
particles obtained from the cratering record on the LDEF satellite (Love and
Brownlee 1993) reveal a significant large particle population (100 micron
diameter or greater) near 1 AU. Our previous modeling of the Solar System dust
bands (Grogan et al 1997), features of the zodiacal cloud associated with the
comminution of Hirayama family asteroids, has been limited by the fact that
only small particles (25 micron diameter or smaller) have been considered. This
was due to the prohibitively large amount of computing power required to
numerically analyze the dynamics of larger particles. The recent availability
of cheap, fast processors has finally made this work possible. Models of the
dust bands are created, built from individual dust particle orbits, taking into
account a size-frequency distribution of the material and the dynamical history
of the constituent particles. These models are able to match both the shapes
and amplitudes of the dust band structures observed by IRAS in multiple
wavebands. The size-frequency index, q, that best matches the observations is
approximately 1.4, consistent with the LDEF results in that large particles are
shown to dominate. However, in order to successfully model the `ten degree'
band, which is usually associated with collisional activity within the Eos
family, we find that the mean proper inclination of the dust particle orbits
has to be approximately 9.35 degrees, significantly different to the mean
proper inclination of the Eos family (10.08 degrees).Comment: 49 pages total, including 27 figure pages. Submitted to Icaru
A High Spectral Resolution Atlas of Comet 122P/de Vico

On 3 and 4 October, 1995, we obtained high spectral resolving power (R=\lambda/\Delta\lambda = 60,000) observations of comet 122P/de Vico using the 2DCoude cross-dispersed echelle spectrograph on the 2.7-m telescope of McDonald Observatory. The spectra cover the wavelength range from 3830A--10192A. The spectra from 3830--5776A are continuous; from 5777--10192A there are increasing interorder gaps. The comet was at a heliocentric distance of 0.66au and a geocentric distance of 1.0au. Comet de Vico has a very high gas-to-dust ratio and the spectra have excellent signal/noise. These two factors combined to yield spectra with a large number of emission lines. We have collected laboratory molecular line lists and have used these line lists in order to identify as many of the detected lines as possible. We have identified 12,219 emission lines and have located another 4,055 lines which we cannot identify. We present representative spectra and identifications along with a description of our plans to make these spectra and identifications available to the community. This atlas should prove a valuable tool for future studies of comets
Evidence for an extended scattered disk

By telescopic tracking, we have established that the orbit of the trans-neptunian object (2000 CR$_{105}$) has a perihelion of $\simeq$44 AU, and is thus outside the domain controlled by strong gravitational close encounters with Neptune. Because this object is on a very large, eccentric orbit (with semimajor axis $a\simeq$216 AU and eccentricity $e\simeq$0.8) this object must have been placed on this orbit by a gravitational perturbation which is {\it not} direct gravitational scattering off of any of the giant planets (on their current orbits). The existence of this object may thus have profound cosmogonic implications for our understanding of the formation of the outer Solar System. We discuss some viable scenarios which could have produced it, including long-term diffusive chaos and scattering off of other massive bodies in the outer Solar System. This discovery implies that there must be a large population of trans-neptunian objects in an `extended scattered disk' with perihelia above the previously-discussed 38 AU boundary
An origin for the linear magnetic anomalies on Mars through accretion of terranes: implications for dynamo timing

The proposed existence of magnetic lineations in the Terra\ud
Cimmeria and Terra Sirenum regions of Mars was initially explained\ud
by Earth-like sea-floor spreading. Here we argue instead\ud
that these lineations could have been formed at a convergent plate\ud
margin through collision and accretion of terranes. A similar process\ud
produced banded magnetic anomalies, similar in geometry and\ud
even in size to those in Earth’s North American Cordillera. Because\ud
only sparse and generally weak anomalies have been detected\ud
in the martian northern lowlands, which could constitute an analog\ud
to the terrestrial oceanic crust, it is possible that the magnetic\ud
field stopped its activity while crustal recycling was still active in\ud
Mars
Iceland's national information infrastructure

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldThis article discusses Iceland's national information infrastructure in the year 2000. It focuses on the current information policy and legislation of the country. It looks at this policy as it is presented in government publications from the last 5 years and evaluates its effects, with particular regard to the education, culture and health sectors. It describes the foundation of a nationwide health database in Iceland, which was established by an Act of Parliament taking force on 1 January 1999. The idea for this database came from deCODE, a company that proposes to make use of the homogeneity and the vast genealogical information of the Icelandic nation to develop better drugs for common diseases. The company is a genomics research company, and is currently working with Hoffmann La-Roche. It has gained a 12-year monopoly on building such a database, the formation of which brings up many ethical questions, and also new possibilities for health management
Expert error in trouble-shooting: an exploratory study in electronics

International audienceIt is known that novices show poor problem-solving performances and that they engage in a relatively inefficient inferential reasoning mode. Experts show high performances in routine situations in which they only activate knowledge. The main purpose of this work was to test the hypothesis that, under some conditions, novices may develop a more efficient diagnostic reasoning than experts, i.e. they may discover the cause of a faulty system conducting fewer tests while avoiding fixation errors. This hypothesis mainly relies on the possibility that experts may be victims of their own knowledge format (French and Sternberg, manuscript). It is tested in a faulty electronic circuit trouble-shooting task. Data suggest that novices perform better than experts. Results are discussed with reference to the concepts of schema and expert error
Qualitative modelling of unknown interface behaviour

M. H. Lee, and S. M. Garrett, Qualitative modelling of unknown interface behaviour, International Journal of Human Computer Studies, Vol. 53, No. 4, pp. 493-515, 2000When faced with an interface to an unknown system or device humans adopt exploratory interactive behaviour in order to gain information and insight. This paper describes a computer program which probes, observes and models the input?output space of unknown systems. We use a schema concept as the memory structure for recording events and adopt a constructive approach that avoids preprocessing the raw data. We believe qualitative assessments are important in early analysis and employ techniques from qualitative reasoning research in order to capture correlation behaviour. The aim is to gain insight into the nature of an unknown system for guidance in future model selection. A series of experiments and their results are discussed, together with the assumptions and limitations of the method. We suggest further developments for future experiments that appear promising.Peer reviewe
Expertise and the interpretation of computerized physiological data: implications for the design of computerized monitoring in neonatal intensive care

This paper presents the outcomes from a cognitive engineering project addressing the design problems of computerized monitoring in neonatal intensive care. Cognitive engineering is viewed, in this project, as a symbiosis between cognitive science and design practice. A range of methodologies has been used: interviews with neonatal staff, ward observations and experimental techniques. The results of these investigations are reported, focusing specifically on the differences between junior and senior physicians in their interpretation of monitored physiological data. It was found that the senior doctors made better use of the different knowledge sources available than the junior doctors. The senior doctors were able to identify more relevant physiological patterns and generated more and better inferences than did their junior colleagues. Expertise differences are discussed in the context of previous psychological research in medical expertise. Finally, the paper discusses the potential utility of these outcomes to inform the design of computerized decision support in neonatal intensive care
A domain equation for bisimulation

AbstractSome basic topics in the theory of concurrency are studied from the point of view of denotational semantics, and particularly the “domain theory in logical form” developed by the author. A domain of synchronization trees is defined by means of a recursive domain equation involving the Plotkin powerdomain. The logical counterpart of this domain is described, and shown to be related to it by Stone duality. The relationship of this domain logic to the standard Hennessy-Milner logic for transition systems is studied; the domain logic can be seen as a rational reconstruction of Hennessy-Milner logic from the standpoint of a very general and systematic theory. Finally, a denotational semantics for SCCS based on the domain of synchronization trees is given, and proved fully abstract with respect to bisimulation
Computability on dI-Domains

AbstractIn this paper we investigate a subset of the class of Scott-computable stable functions called Berry-computable. Furthermore we introduce a corresponding notion of an effectively given dI-domain. We obtain the result that the category with these domains as objects and Berry-computable functions as morphisms has all the important attributes of recursive domains and Scott-computable continuous functions, e.g., Cartesian closedness. Moreover, we investigate the relationship between stable functions and sequential algorithms. We show that any Berry-computable function can be computed in a sequential way by a relative algorithm. Additionally, if the codomain of the considered stable function is an atomic dI-domain, we obtain the result that the reverse holds as well
Unreliable Channels Are Easier to Verify Than Perfect Channels

AbstractWe consider the problem of verifying correctness of finite state machines that communicate with each other over unbounded FIFO channels that are unreliable. Various problems of interest in verification of FIFO channels that can lose messages have been considered by Finkel and by Abdulla and Jonsson. We consider, in this paper, other possible unreliable behaviors of communication channels, viz., (a) duplication and (b) insertion errors. Furthermore, we also consider various combinations of duplication, insertion, and lossiness errors. Finite state machines that communicate over unbounded FIFO buffers are a model of computation that forms the backbone of the ISO standard protocol specification languages Estelle and SDL. While the assumption of a perfect communication medium is reasonable at the higher levels of the OSI protocol stack, the lower levels have to deal with an unreliable communication medium; hence our motivation for the present work. The verification problems that are of interest arereachability,unboundedness,deadlock, andmodel-checking against CTL*. All of these problems are undecidable for machines communicating over reliable unbounded FIFO channels. So it is perhaps surprising that some of these problems become decidable when unreliable channels are modeled. The contributions of this paper are (a) an investigation of solutions to these problems for machines with insertion errors, duplication errors, or a combination of duplication, insertion, and lossiness errors, and (b) a comparison of the relative expressive power of the various errors
A Typed Pattern Calculus

AbstractThe theory of programming with pattern-matching function definitions has been studied mainly in the framework of first-order rewrite systems. We present a typed functional calculus that emphasizes the strong connection between the structures of whole pattern definitions and their types. In this calculus, type-checking guarantees the absence of runtime errors caused by non-exhaustive pattern-matching definitions. Its operational semantics is deterministic in a natural way, without the imposition of ad hoc solutions such as clause order or “best fit”. In the spirit of the Curry–Howard isomorphism, we design the calculus as a computational interpretation of the Gentzen sequent proofs for the intuitionistic propositional logic. We prove the basic properties connecting typing and evaluation: subject reduction and strong normalization. We believe that this calculus offers a rational reconstruction of the pattern-matching features found in successful functional languages
Time/Contention Trade-Offs for Multiprocessor Synchronization

AbstractWe establish trade-offs between time complexity and write- and access-contention for solutions to the mutual exclusion problem. Thewrite-contention(access-contention) of a concurrent program is the number of processes that may be simultaneously enabled to write (access by reading and/or writing) the same shared variable. Our notion of time complexity distinguishes between local and remote accesses of shared memory. We show that, for anyN-process mutual exclusion algorithm, if write-contention isw, and if at mostvremote variables can be accessed by a single atomic operation, then there exists an execution involving only one process in which that process executesΩ(logvwN) remote operations for entry into its critical section. We further show that, among these operations,[formula]distinct remote variables are accessed. For algorithms with access-contentionc, we show that the latter bound can be improved toΩ(logvcN). The last two of these bounds imply that a trade-off between contention and time complexity exists even if coherent caching techniques are employed. In most shared-memory multiprocessors, an atomic operation may access only a constant number of remote variables. In fact, most commonly-available synchronization primitives (e.g., read, write, test-and-set, load-and-store, compare-and-swap, and fetch-and-add) access only one remote variable. In this case, the first and the last of our bounds are asymptotically tight. Our results have a number of important implications regarding specific concurrent programming problems. For example, the time bounds that we establish apply not only to the mutual exclusion problem, but also to a class of decision problems that includes the leader-election problem. Also, because the execution that establishes these bounds involves only one process, it follows that “fast mutual exclusion” requires arbitrarily high write-contention. Although such conclusions are interesting in their own right, we believe that the most important contribution of our work is to identify a time complexity measure for asynchronous concurrent programs that strikes a balance between being conceptually simple and having a tangible connection to real performance
Proving Congruence of Bisimulation in Functional Programming Languages

AbstractWe give a method for proving congruence of bisimulation-like equivalences in functional programming languages. The method applies to languages that can be presented as a set of expressions together with an evaluation relation. We use this method to show that some generalizations of Abramsky's applicative bisimulation are congruences whenever evaluation can be specified by a certain natural form of structured operational semantics. One of the generalizations handles nondeterminism and diverging computations
Beyond Recursive Real Functions

AbstractAll recursive real functions are continuous; in fact all theB-recursive real functions are continuous for any oracleB, simply because Turing machines computing them are finite objects. But simple discontinuous functions such as step functions have to be in some sense “easy” if they have recursive values and break points, although they are not computable by the usual definition. It seems unfair to label them noncomputable in the entire region just because of a few break points. In this paper, we investigate the properties of broader classes ofalmost everywhere recursive,weakly almost everywhere recursive, andrecursively approximablereal-valued functions, which capture these “easy” step functions and many other nonrecursive functions. Recursive versions of the classical Lusin and Egoroff Theorems are proved. We also characterize the property of the limit of a recursive sequence of functions and show that different notions of convergence (uniform, pointwise, or in measure) will result in different characterizations of the limiting function
A Temporal Logic for Proving Properties of Topologically General Executions

AbstractWe present a generalization of the temporal propositional logic of linear time which is useful for stating and proving properties of the generic execution sequence of a parallel program or a non-deterministic program. The formal system we present is exactly that same as the third of three logics presented by Lehmann and Shelah (Information and Control53, 165–198 (1982)), but we give it a different semantics. The models are tree models of arbitrary size similar to those used in branching time temporal logic. The formulation we use allows us to state properties of the “co-meagre” family of paths, where the term “co-meagre” refers to a set whose complement is of the first category in Baire's classification looking at the set of paths in the model as a metric space. Our system is decidable, sound, and, complete for models of arbitrary size, but it has the finite model property; namely, every sentence having a model has a finite model
Maximal Common Subsequences and Minimal Common Supersequences

AbstractThe problems of finding a longest common subsequence and a shortest common supersequence of a set of strings are well known. They can be solved in polynomial time for two strings (in fact the problems are dual in this case), or for any fixed number of strings, by dynamic programming. But both problems are NP-hard in general for an arbitrary numberkof strings. Here we study the related problems of finding a shortest maximal common subsequence and a longest minimal common supersequence. We describe dynamic programming algorithms for the case of two strings (for which case the problems are no longer dual), which can be extended to any fixed number of strings. We also show that both problems are NP-hard in general forkstrings, although the latter problem, unlike shortest common supersequence, is solvable in polynomial time for strings of length 2. Finally, we prove a strong negative approximability result for the shortest maximal common subsequence problem
On Schematological Equivalence of Dataflow Networks

AbstractWe consider the problem of determining when two dataflow networks with uninterpreted nodes always have the same input-output behavior. We define a set of behavior-preserving transformations on networks and show that this set is “schematologically complete”; i.e., networks have the same input-output behavior under all interpretations if and only if they can be transformed into isomorphic networks. As a by product, we obtain a polynomial algorithm for deciding schematological equivalence of dataflow networks
On the Regularity of Petri Net Languages

AbstractPetri nets are known to be useful for modeling concurrent systems. Once modeled by a Petri net, the behavior of a concurrent system can be characterized by the set of all executable transition sequences, which in turn can be viewed as a language over an alphabet of symbols corresponding to the transitions of the underlying Petri net. In this paper, we study the language issue of Petri nets from a computational complexity viewpoint. We analyze the complexity of theregularity problem(i.e., the problem of determining whether a given Petri net defines an irregular language or not) for a variety of classes of Petri nets, includingconflict-free,trap-circuit,normal,sinkless,extended trap-circuit,BPP, andgeneralPetri nets. (Extended trap-circuit Petri nets are trap-circuit Petri nets augmented with a specific type ofcircuits.) As it turns out, the complexities for these Petri net classes range from NL (nondeterministic logspace), PTIME (polynomial time), and NP (nondeterministic polynomial time), to EXPSPACE (exponential space). In the process of deriving the complexity results, we develop adecomposition approachwhich, we feel, is interesting in its own right, and might have other applications to the analysis of Petri nets as well. As a by-product, an NP upper bound of the reachability problem for the class of extended trap-circuit Petri nets (which properly contains that of trap-circuit (and hence, conflict-free) and BPP-nets, and is incomparable with that of normal and sinkless Petri nets) is derived
Power Domains and Iterated Function Systems

AbstractWe introduce the notion of weakly hyperbolic iterated function system (IFS) on a compact metric space, which generalises that of hyperbolic IFS. Based on a domain-theoretic model, which uses the Plotkin power domain and the probabilistic power domain respectively, we prove the existence and uniqueness of the attractor of a weakly hyperbolic IFS and the invariant measure of a weakly hyperbolic IFS with probabilities, extending the classic results of Hutchinson for hyperbolic IFSs in this more general setting. We also present finite algorithms to obtain discrete and digitised approximations to the attractor and the invariant measure, extending the corresponding algorithms for hyperbolic IFSs. We then prove the existence and uniqueness of the invariant distribution of a weakly hyperbolic recurrent IFS and obtain an algorithm to generate the invariant distribution on the digitised screen. The generalised Riemann integral is used to provide a formula for the expected value of almost everywhere continuous functions with respect to this distribution. For hyperbolic recurrent IFSs and Lipschitz maps, one can estimate the integral up to any threshold of accuracy