3,534 research outputs found
EffectiveSan: Type and Memory Error Detection using Dynamically Typed C/C++
Low-level programming languages with weak/static type systems, such as C and
C++, are vulnerable to errors relating to the misuse of memory at runtime, such
as (sub-)object bounds overflows, (re)use-after-free, and type confusion. Such
errors account for many security and other undefined behavior bugs for programs
written in these languages. In this paper, we introduce the notion of
dynamically typed C/C++, which aims to detect such errors by dynamically
checking the "effective type" of each object before use at runtime. We also
present an implementation of dynamically typed C/C++ in the form of the
Effective Type Sanitizer (EffectiveSan). EffectiveSan enforces type and memory
safety using a combination of low-fat pointers, type meta data and type/bounds
check instrumentation. We evaluate EffectiveSan against the SPEC2006 benchmark
suite and the Firefox web browser, and detect several new type and memory
errors. We also show that EffectiveSan achieves high compatibility and
reasonable overheads for the given error coverage. Finally, we highlight that
EffectiveSan is one of only a few tools that can detect sub-object bounds
errors, and uses a novel approach (dynamic type checking) to do so.Comment: To appear in the Proceedings of 39th ACM SIGPLAN Conference on
Programming Language Design and Implementation (PLDI2018
Construction of a topological charge on fuzzy S^2 x S^2 via Ginsparg-Wilson relation
We construct a topological charge of gauge field configurations on a fuzzy
S^2xS^2 by using a Dirac operator satisfying the Ginsparg-Wilson relation. The
topological charge defined on the fuzzy S^2xS^2 can be interpreted as a
noncommutative (or matrix) generalization of the 2nd Chern character on
S^2xS^2. We further calculate the number of chiral zero modes of the Dirac
operator in topologically nontrivial gauge configurations. Generalizations of
our formulation to fuzzy (S^2)^k are also discussed.Comment: 30 pages, typo corrected, version published in Phys.Rev.
Collective Variables of Fermions and Bosonization
We first present a general method for extracting collective variables out of
non-relativistic fermions by extending the gauge theory of collective
coordinates to fermionic systems. We then apply the method to a system of
non-interacting flavored fermions confined in a one-dimensional
flavor-independent potential. In the limit of a large number of particles we
obtain a Lagrangian with the Wess-Zumino-Witten term, which is the well-known
Lagrangian describing the non-Abelian bosonization of chiral fermions on a
circle. The result is universal and does not depend on the details of the
confining potential.Comment: 12 pages, plain tex, added new preprint numbe
Chern-Simons matrix model: coherent states and relation to Laughlin wavefunctions
Using a coherent state representation we derive many-body probability
distributions and wavefunctions for the Chern-Simons matrix model proposed by
Polychronakos and compare them to the Laughlin ones. We analyze two different
coherent state representations, corresponding to different choices for electron
coordinate bases. In both cases we find that the resulting probability
distributions do not quite agree with the Laughlin ones. There is agreement on
the long distance behavior, but the short distance behavior is different.Comment: 15 pages, LaTeX; one reference added, abstract and section 5
expanded, typos correcte
Standardisation of magnetic nanoparticles in liquid suspension
Suspensions of magnetic nanoparticles offer diverse opportunities for technology innovation, spanning a large number of industry sectors from imaging and actuation based applications in biomedicine and biotechnology, through large-scale environmental remediation uses such as water purification, to engineering-based applications such as position-controlled lubricants and soaps. Continuous advances in their manufacture have produced an ever-growing range of products, each with their own unique properties. At the same time, the characterisation of magnetic nanoparticles is often complex, and expert knowledge is needed to correctly interpret the measurement data. In many cases, the stringent requirements of the end-user technologies dictate that magnetic nanoparticle products should be clearly defined, well characterised, consistent and safe; or to put it another way—standardised. The aims of this document are to outline the concepts and terminology necessary for discussion of magnetic nanoparticles, to examine the current state-of-the-art in characterisation methods necessary for the most prominent applications of magnetic nanoparticle suspensions, to suggest a possible structure for the future development of standardisation within the field, and to identify areas and topics which deserve to be the focus of future work items. We discuss potential roadmaps for the future standardisation of this developing industry, and the likely challenges to be encountered along the way
Understanding the fidelity effect when evaluating games with children
There have been a number of studies that have compared evaluation results from prototypes of different fidelities but very few of these are with children. This paper reports a comparative study of three prototypes ranging from low fidelity to high fidelity within the context of mobile games, using a between subject design with 37 participants aged 7 to 9. The children played a matching game on either an iPad, a paper prototype using screen shots of the actual game or a sketched version. Observational data was captured to establish the usability problems, and two tools from the Fun Toolkit were used to measure user experience. The results showed that there was little difference for user experience between the three prototypes and very few usability problems were unique to a specific prototype. The contribution of this paper is that children using low-fidelity prototypes can effectively evaluate games of this genre and style
Failure assessment of lightly reinforced floor slabs. I: Experimental investigation
This paper is concerned with the ultimate behavior of lightly reinforced concrete floor slabs under extreme loading conditions. Particular emphasis is given to examining the failure conditions of idealized composite slabs which become lightly reinforced in a fire situation as a result of the early loss of the steel deck. An experimental study is described which focuses on the response of two-way spanning floor slabs with various materials and geometric configurations. The tests enable direct assessment of the influence of a number of key parameters such as the reinforcement type, properties, and ratio on the ultimate response. The results also permit the development of simplified expressions that capture the influence of salient factors such as bond characteristics and reinforcement properties for predicting the ductility of lightly reinforced floor slabs. The companion paper complements the experimental observations with detailed numerical assessments of the ultimate response and proposes analytical models that predict failure of slab members by either reinforcement fracture or compressive crushing of concrete. © 2011 American Society of Civil Engineers
Laughlin Wave Function and One-Dimensional Free Fermions
Making use of the well-known phase space reduction in the lowest Landau
level(LLL), we show that the Laughlin wave function for the
case can be obtained exactly as a coherent state representation of an one
dimensional wave function. The system consists of copies of
free fermions associated with each of the electrons, confined in a common
harmonic well potential. Interestingly, the condition for this exact
correspondence is found to incorporate Jain's parton picture. We argue that,
this correspondence between the free fermions and quantum Hall effect is due to
the mapping of the system under consideration, to the Gaussian unitary
ensemble in the random matrix theory.Comment: 7 pages, Latex , no figure
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Room reflections and constancy in speech-like sounds: within-band effects
The experiment asks whether constancy in hearing precedes or follows grouping. Listeners heard speech-like
sounds comprising 8 auditory-filter shaped noise-bands that had temporal envelopes corresponding to those
arising in these filters when a speech message is played. The „context‟ words in the message were “next you‟ll
get _to click on”, into which a “sir” or “stir” test word was inserted. These test words were from an 11-step
continuum that was formed by amplitude modulation. Listeners identified the test words appropriately and quite
consistently, even though they had the „robotic‟ quality typical of this type of 8-band speech. The speech-like
effects of these sounds appears to be a consequence of auditory grouping. Constancy was assessed by comparing
the influence of room reflections on the test word across conditions where the context had either the same level
of reflections, or where it had a much lower level. Constancy effects were obtained with these 8-band sounds,
but only in „matched‟ conditions, where the room reflections were in the same bands in both the context and the
test word. This was not the case in a comparison „mismatched‟ condition, and here, no constancy effects were
found. It would appear that this type of constancy in hearing precedes the across-channel grouping whose
effects are so apparent in these sounds. This result is discussed in terms of the ubiquity of grouping across
different levels of representation
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