1,494 research outputs found
Translating programming languages for intermediate codes
Many of the important data structures used in a compiler are intermediate representations of the program being compiled. Often these representations take the form of trees, with several node types, each of which has different attributes. Tree representations can be described with grammars, just like programming languages. For each grammar rule, there is one constructor that belongs to the class for its left-hand-side symbol. I simply extend the abstract class with a concrete class for each grammar rule. Each grammar rule has right hand side components that must be represented in the data structures.compiler, lexical analysis, abstract syntax, intermediate representation, abstract machine language
Oxidation of gallium arsenide in a plasma multipole device. Study of the MOS structures obtained
The oxygen plasma oxidation of GaAs was studied in order to obtain extremely high frequency responses with MOS devices. In the multipole system a homogeneous oxygen plasma of high density can easily be obtained in a large volume. This system is thus convenient for the study of plasma oxidation of GaAs. The electrical properties of the MOS diodes obtained in this way are controlled by interface states, located mostly in the upper half of the band gap where densities in the 10 to the 13th power/(sq cm) (eV) range can be estimated. Despite these interface states the possibility of fabricating MOSFET transistors working mostly in the depletion mode for a higher frequency cut-off still exists
Gravitational Analogues of Non-linear Born Electrodynamics
Gravitational analogues of the nonlinear electrodynamics of Born and of Born
and Infeld are introduced and applied to the black hole problem. This work is
mainly devoted to the 2-dimensional case in which the relevant lagrangians are
nonpolynomial in the scalar curvature.Comment: 20 pages, 2 figures, included a detailed discussion of "non-trace"
field equation
Forensic Analysis of Fiber Dyes via Surface-Enhanced Raman Spectroscopy
Fibers are a common piece of evidence found at crime scenes that may become a link between the scene and a suspect, or allow for the reconstruction of certain crime events. Although a big portion of fibers are still white cottons, the advancement of commercial fiber production and dyeing in the past century led to an increase in types of synthetic fibers and dye applications that can be found and used in forensic analyses. Nonetheless, the fiber evidentiary value is not fully explored, as for the most part, the separation and analysis of the dye on the fiber is not routinely done. This is mostly because traditional methods for dye analysis require lengthy or expensive procedures, combining extractions or hydrolysis, solvent tailoring, separation procedures such as TLC or HPLC, and potential mass-spectrometry for the extract identification. Currently, the prescribed method of fiber forensic analysis involves the fiber macro and microscopical examination, determination of optical properties, cross-sectioning, and spectrophotometric and infrared analysis. In the case where fibers of same polymer make have similar colors that cannot be separated by spectrophotometric analysis, there is still a chance that those fibers could have been dyed using differing dyes. It is possible to analyze those dyes by surface-enhanced Raman spectroscopy, a method which allows for high enhancements of low concentration, microliter volume samples, allowing the analyst to extract single fibers in small volumes of solvents.b This research focused on the comparison of solvent systems, alongside hydrofluoric acid fuming and in situ SER analysis, to develop a working routine for forensic fiber dye analysis. The research was also expanded to simulate casework, showing that the extraction methods coupled with SERS and statistical analysis can be used to differentiate and successfully classify questioned fibers when compared to known sets. Tweaks and improvements to the method of analysis are presented by either acid-addition, or use of coffee-ring – SERS analysis on high performance thin-layer chromatography plates. Methods of improvement and further research are also presented, with the scope of validating of SERS by both forensic science and the courts. Because this project presents a novel approach to the completion of forensic fiber analyses, it shows that SERS can be a valuable tool and aid in the improvement of forensic science and the criminal justice system. The presented approach shows a successful, rapid and inexpensive technique that can also be expanded and utilized for the analysis of other evidence types
Object-based selection of irrelevant features is not confined to the attended object
Attention to one feature of an object can bias the processing of unattended features of that object. Here we demonstrate with ERPs in visual search that this object-based bias for an irrelevant feature also appears in an unattended object when it shares that feature with the target object. Specifically, we show that the ERP response elicited by a distractor object in one visual field is modulated as a function of whether a task-irrelevant color of that distractor is also present in the target object that is presented in the opposite visual field. Importantly, we find this modulation to arise with a delay of approximately 80 msec relative to the N2pc-a component of the ERP response that reflects the focusing of attention onto the target. In a second experiment, we demonstrate that this modulation reflects enhanced neural processing in the unattended object. These observations together facilitate the surprising conclusion that the object-based selection of irrelevant features is spatially global even after attention has selected the target object
Distribution of the Object Oriented Databases. A Viewpoint of the MVDB Model's Methodology and Architecture
In databases, much work has been done towards extending models with advanced tools such as view technology, schema evolution support, multiple classification, role modeling and viewpoints. Over the past years, most of the research dealing with the object multiple representation and evolution has proposed to enrich the monolithic vision of the classical object approach in which an object belongs to one hierarchy class. In particular, the integration of the viewpoint mechanism to the conventional object-oriented data model gives it flexibility and allows one to improve the modeling power of objects. The viewpoint paradigm refers to the multiple descriptions, the distribution, and the evolution of object. Also, it can be an undeniable contribution for a distributed design of complex databases. The motivation of this paper is to define an object data model integrating viewpoints in databases and to present a federated database architecture integrating multiple viewpoint sources following a local-as-extended-view data integration approach.object-oriented data model, OQL language, LAEV data integration approach, MVDB model, federated databases, Local-As-View Strategy.
On the Tykhonov Well-posedness of an Antiplane Shear Problem
We consider a boundary value problem which describes the frictional antiplane
shear of an elastic body. The process is static and friction is modeled with a
slip-dependent version of Coulomb's law of dry friction. The weak formulation
of the problem is in the form of a quasivariational inequality for the
displacement field, denoted by \cP. We associated to problem \cP a boundary
optimal control problem, denoted by \cQ. For Problem \cP we introduce the
concept of well-posedness and for Problem \cQ we introduce the concept of
weakly and weakly generalized well-posedness, both associated to appropriate
Tykhonov triples. Our main result are Theorems \ref{t1} and \ref{t2}. Theorem
\ref{t1} provides the well-posedness of Problem \cP and, as a consequence,
the continuous dependence of the solution with respect to the data. Theorem
\ref{t2} provides the weakly generalized well-posedness of Problem \cQ and,
under additional hypothesis, its weakly well posedness. The proofs of these
theorems are based on arguments of compactness, lower semicontinuity,
monotonicity and various estimates. Moreover, we provide the mechanical
interpretation of our well-posedness results.Comment: 21 page
Asymptotic Stability for a Class of Metriplectic Systems
Using the framework of metriplectic systems on we will describe a
constructive geometric method to add a dissipation term to a Hamilton-Poisson
system such that any solution starting in a neighborhood of a nonlinear stable
equilibrium converges towards a certain invariant set. The dissipation term
depends only on the Hamiltonian function and the Casimir functions
Spin dynamics in InAs-nanowire quantum-dots coupled to a transmission line
We study theoretically electron spins in nanowire quantum dots placed inside
a transmission line resonator. Because of the spin-orbit interaction, the spins
couple to the electric component of the resonator electromagnetic field and
enable coherent manipulation, storage, and read-out of quantum information in
an all-electrical fashion. Coupling between distant quantum-dot spins, in one
and the same or different nanowires, can be efficiently performed via the
resonator mode either in real time or through virtual processes. For the latter
case we derive an effective spin-entangling interaction and suggest means to
turn it on and off. We consider both transverse and longitudinal types of
nanowire quantum-dots and compare their manipulation timescales against the
spin relaxation times. For this, we evaluate the rates for spin relaxation
induced by the nanowire vibrations (phonons) and show that, as a result of
phonon confinement in the nanowire, this rate is a strongly varying function of
the spin operation frequency and thus can be drastically reduced compared to
lateral quantum dots in GaAs. Our scheme is a step forward to the formation of
hybrid structures where qubits of different nature can be integrated in a
single device
Separable mechanisms underlying global feature-based attention
Feature-based attention is known to operate in a spatially global manner, in that the selection of attended features is not bound to the spatial focus of attention. Here we used electromagnetic recordings in human observers to characterize the spatiotemporal signature of such global selection of an orientation feature. Observers performed a simple orientation-discrimination task while ignoring task-irrelevant orientation probes outside the focus of attention. We observed that global feature-based selection, indexed by the brain response to unattended orientation probes, is composed of separable functional components. One such component reflects global selection based on the similarity of the probe with task-relevant orientation values ("template matching"), which is followed by a component reflecting selection based on the similarity of the probe with the orientation value under discrimination in the focus of attention ("discrimination matching"). Importantly, template matching occurs at similar to 150 ms after stimulus onset, similar to 80 ms before the onset of discrimination matching. Moreover, source activity underlying template matching and discrimination matching was found to originate from ventral extrastriate cortex, with the former being generated in more anterolateral and the latter in more posteromedial parts, suggesting template matching to occur in visual cortex higher up in the visual processing hierarchy than discrimination matching. We take these observations to indicate that the population-level signature of global feature-based selection reflects a sequence of hierarchically ordered operations in extrastriate visual cortex, in which the selection based on task relevance has temporal priority over the selection based on the sensory similarity between input representations
- …