Shape from Shading: A Method for Obtaining the Shape of a Smooth Opaque Object from One View

A method will be described for finding the shape of a smooth apaque object form a monocular image, given a knowledge of the surface photometry, the position of the lightsource and certain auxiliary information to resolve ambiguities. This method is complementary to the use of stereoscopy which relies on matching up sharp detail and will fail on smooth objects. Until now the image processing of single views has been restricted to objects which can meaningfully be considered two-dimensional or bounded by plane surfaces. It is possible to derive a first-order non-linear partial differential equation in two unknowns relating the intensity at the image points to the shape of the objects. This equation can be solved by means of an equivalent set of five ordinary differential equations. A curve traced out by solving this set of equations for one set of starting values is called a characteristic strip. Starting one of these strips from each point on some initial curve will produce the whole solution surface. The initial curves can usually be constructed around so-called singular points. A number of applications of this metod will be discussed including one to lunar topography and one to the scanning electron microscope. In both of these cases great simplifications occur in the equations. A note on polyhedra follows and a quantitative theory of facial make-up is touched upon. An implementation of some of these ideas on the PDP-6 computer with its attached image-dissector camera at the Artificial intelligence Laboratory will be described, and also a nose-recognition program.

Natural Language Input for a Computer Problem Solving System

The STUDENT problem solving system, programmed in LISP, accepts as input a comfortable but restricted subset of English which can express a wide variety of algebra story problems. STUDENT finds the solution to a large class of these problems. STUDENT can utilize a store of global information not specific to any one problem, and may make assumptions about the interpretation of ambiguities in the wording of the problem being solved. If it uses such information or makes any assumptions, STUDENT communicates this fact to the user. The thesis includes a summary of other English language questions-answering systems. All these systems, and STUDENT, are evaluated according to four standard criteria. The linguistic analysis in STUDENT is a first approximation to the analytic portion of a semantic theory of discourse outlined in the thesis. STUDENT finds the set of kernel sentences which are the base of the input discourse, and transforms this sequence of kernel sentences into a set of simultaneous equations which form the semantic base of the STUDENT system. STUDENT then tries to solve this set of equations for the values of requested unknowns. If it is successful it gives the answers in English. If not, STUDENT asks the user for more information, and indicates the nature of the desired information. The STUDENT system is a first step toward natural language communication with computers. Further work on the semantic theory proposed should result in much more sophisticated systems.

SIR: A Computer Program for Semantic Information Retrieval

SIR is a computer system, programmed in the LISP language, which accepts information and answers questions expressed in a restricted form of English. This system demonstrates what can reasonably be called an ability to "understand" semantic information. SIR's semantic and deductive ability is based on the construction of an internal model, which uses word associations and property lists, for the relational information normally conveyed in conversational statements. A format-matching procedure extracts semantic content from English sentences. If an input sentence is declarative, the system adds appropriate information to the model. If an input sentence is a question, the system searches the model until it either finds the answer or determines why it cannot find the answer. In all cases SIR reports its conclusions. The system has some capacity to recognize exceptions to general rules, resolve certain semantic ambiguities, and modify its model structure in order to save computer memory space. Judging from its conversational ability, SIR, is a first step toward intelligent man-machine communication. The author proposes a next step by describing how to construct a more general system which is less complex and yet more powerful than SIR. This proposed system contains a generalized version of the SIR model, a formal logical system called SIR1, and a computer program for testing the truth of SIR1 statements with respect to the generalized model by using partial proof procedures in the predicate calculus. The thesis also describes the formal properties of SIR1 and how they relate to the logical structure of SIR.

Causal and Teleological Reasoning in Circuit Recognition

This thesis presents a theory of human-like reasoning in the general domain of designed physical systems, and in particular, electronic circuits. One aspect of the theory, causal analysis, describes how the behavior of individual components can be combined to explain the behavior of composite systems. Another aspect of the theory, teleological analysis, describes how the notion that the system has a purpose can be used to aid this causal analysis. The theory is implemented as a computer program, which, given a circuit topology, can construct by qualitative causal analysis a mechanism graph describing the functional topology of the system. This functional topology is then parsed by a grammar for common circuit functions. Ambiguities are introduced into the analysis by the approximate qualitative nature of the analysis. For example, there are often several possible mechanisms which might describe the circuit's function. These are disambiguated by teleological analysis. The requirement that each component be assigned an appropriate purpose in the functional topology imposes a severe constraint which eliminates all the ambiguities. Since both analyses are based on heuristics, the chosen mechanism is a rationalization of how the circuit functions, and does not guarantee that the circuit actually does function. This type of coarse understanding of circuits is useful for analysis, design and troubleshooting.

Automatic 2D Hand Tracking in Video Sequences

In gesture and sign language video sequences, hand motion tends to be rapid, and hands frequently appear in front of each other or in front of the face. Thus, hand location is often ambiguous, and naive color-based hand tracking is insufficient. To improve tracking accuracy, some methods employ a prediction-update framework, but such methods require careful initialization of model parameters, and tend to drift and lose track in extended sequences. In this paper, a temporal filtering framework for hand tracking is proposed that can initialize and reset itself without human intervention. In each frame, simple features like color and motion residue are exploited to identify multiple candidate hand locations. The temporal filter then uses the Viterbi algorithm to select among the candidates from frame to frame. The resulting tracking system can automatically identify video trajectories of unambiguous hand motion, and detect frames where tracking becomes ambiguous because of occlusions or overlaps. Experiments on video sequences of several hundred frames in duration demonstrate the system's ability to track hands robustly, to detect and handle tracking ambiguities, and to extract the trajectories of unambiguous hand motion.

Fast, Reliable Head Tracking under Varying Illumination

An improved technique for 3D head tracking under varying illumination conditions is proposed. The head is modeled as a texture mapped cylinder. Tracking is formulated as an image registration problem in the cylinder's texture map image. To solve the registration problem in the presence of lighting variation and head motion, the residual error of registration is modeled as a linear combination of texture warping templates and orthogonal illumination templates. Fast and stable on-line tracking is then achieved via regularized, weighted least squares minimization of the registration error. The regularization term tends to limit potential ambiguities that arise in the warping and illumination templates. It enables stable tracking over extended sequences. Tracking does not require a precise initial fit of the model; the system is initialized automatically using a simple 2-D face detector. The only assumption is that the target is facing the camera in the first frame of the sequence. The warping templates are computed at the first frame of the sequence. Illumination templates are precomputed off-line over a training set of face images collected under varying lighting conditions. Experiments in tracking are reported.

Fast, Reliable Head Tracking under Varying Illumination: An Approach Based on Registration of Texture-Mapped 3D Model

An improved technique for 3D head tracking under varying illumination conditions is proposed. The head is modeled as a texture mapped cylinder. Tracking is formulated as an image registration problem in the cylinder's texture map image. The resulting dynamic texture map provides a stabilized view of the face that can be used as input to many existing 2D techniques for face recognition, facial expressions analysis, lip reading, and eye tracking. To solve the registration problem in the presence of lighting variation and head motion, the residual error of registration is modeled as a linear combination of texture warping templates and orthogonal illumination templates. Fast and stable on-line tracking is achieved via regularized, weighted least squares minimization of the registration error. The regularization term tends to limit potential ambiguities that arise in the warping and illumination templates. It enables stable tracking over extended sequences. Tracking does not require a precise initial fit of the model; the system is initialized automatically using a simple 2D face detector. The only assumption is that the target is facing the camera in the first frame of the sequence. The formulation is tailored to take advantage of texture mapping hardware available in many workstations, PC's, and game consoles. The non-optimized implementation runs at about 15 frames per second on a SGI O2 graphic workstation. Extensive experiments evaluating the effectiveness of the formulation are reported. The sensitivity of the technique to illumination, regularization parameters, errors in the initial positioning and internal camera parameters are analyzed. Examples and applications of tracking are reported.

Simultaneous two-wavelength transmission quantitative phase microscopy with a color camera.

We present a quantitative phase microscopy method that uses a Bayer mosaic color camera to simultaneously acquire off-axis interferograms in transmission mode at two distinct wavelengths. Wrapped phase information is processed using a two-wavelength algorithm to extend the range of the optical path delay measurements that can be detected using a single temporal acquisition. We experimentally demonstrate this technique by acquiring the phase profiles of optically clear microstructures without 2pi ambiguities. In addition, the phase noise contribution arising from spectral channel crosstalk on the color camera is quantified.

''Setting 'Em Up'': Personal, Familial and Institutional Grooming in the Sexual Abuse of Children

The term ‘grooming’ has been used to describe the offender’s actions during the preparatory stage of sexual abuse. This paper will argue that current discourses on grooming have created ambiguities and misunderstandings about child sexual abuse. In particular, the popular focus on ‘stranger danger’ belies the fact that the majority of children are abused by someone well known to them, where grooming can also occur. Current discourses also neglect other important facets of the sex offending pattern. They fail to consider that offenders may groom not only the child but also their family and even the local community who may act as the gatekeepers of access. They also ignore what can be termed ‘institutional grooming’ – that sex offenders may groom criminal justice and other institutions into believing that they present no risk to children. A key variable in the grooming process is the creation and subsequent abuse of trust. Given that the criminal law may be somewhat limited in its response to this type of behaviour, ultimately concerted efforts must be made to foster social and organisational awareness of such processes in order to reduce the offender’s opportunity for abuse.

Superficialidad máxima. Superficie como posibilidad de sentido: imagen y síntoma

En estas páginas se pretende proponer un modo de entender lo visto siempre como adaptación inmanente, deseo y simbolización, esto es, entenderlo como imagen. Se hará conforme a un concepto de ‘superficie’ que prolonga la lectura que hiciera Didi-Huberman del concepto de imagen-síntoma de Aby Warburg, y se apoya en textos de teoría psicoanalítica de la mano de Jacques Lacan, en un intento no de arruinar la capacidad de hermenéutica del observador, sino de entender la búsqueda del sentido y de la esencia –del arte por ejemplo– como la investigación sobre un conflicto histórico de pérdidas, crisis y memoria. ‘Superficie’ en tanto que masa átona y sin sentido donde el ojo siempre visiona formas: ver superficie es que el ojo siempre adapte lo visto, deseando abrirlo visionariamente en su significado para recabar su verdad oculta, pero paradójicamente cerrándolo. Porque mirar imágenes supone siempre perder visión respecto de una supuesta totalidad en la que se darían todos los significados en todas sus ambigüedades y en todas sus posibilidades históricas, pérdida sólo decible en su retorno en tanto que resignificación traumática. Aquí postulamos que la ilusión será creer no que las apariencias son ilusorias, sino que más allá de ellas hay “más realidad”. Este planteamiento no sólo ratifica la posición del sujeto, inserto en una superficie/cuadro dada-a-ver, sino que descubre la brecha constitutiva que le rige y que es un “más en él” que él mismo.

El significado de la prosopopeya de las Leyes en el "Critón" de Platon

El objeto de este trabajo es realizar un estudio iusfilosófico sobre la aparición de las Leyes (nómoi) personificadas de Atenas en el Critón de Platón. La prosopopeya de las Leyes resulta ser un aspecto central para poder comprender la obra, ya que éstas entablan un diálogo imaginario con Sócrates en el cual instalan diversos argumentos filosóficos para fundamentar la autoridad de la pólis. A los fines de identificar el valor argumentativo de este recurso en la obra, analizaré el significado del nómos en la Atenas del siglo V a. C. y la naturaleza de las Leyes en el contexto general del diálogo. Se busca demostrar la importancia que tienen aquéllas para explicar la decisión de Sócrates de beber la cicuta.

Reconfiguring spaces of conflict: Northern Ireland and the impact of European integration

The Irish border has historically been one of the most contested borders in Europe. In the context of the peace process and EU membership, co-operation between Northern Ireland and the Republic of Ireland has been encouraged, supported and normalised, although internal borders of segregation stubbornly remain. This paper offers a conceptualisation of borders in conflict cases and a theoretical account of how European integration can affect their transformation. Analysis of the Northern Ireland case shows there are ambiguities within integration that allow for a ‘rebordering’ of identities at the same time as the state border diminishes in significance.

Discourse and Text

This article discusses tense and aspect in the context of attested forms of discourse and text. The emphasis is on the semantic, pragmatic, textual, and stylistic functions of tense in context, taking into account linguistic features in the surrounding discourse, as well as the importance of factors such as medium (spoken or written), register (degree of formality), text type (literary vs. journalistic vs. conversational etc.), and discourse mode (narrative vs. report vs. description, etc.). Thus, tense and aspect are analyzed not purely as part of a linguistic “system” as such, but in the context of particular texts or forms of discourse. The article also explores the concept of “markedness” through two case studies: the narrative present and the narrative imperfect. Finally, it assesses the roles played by tenses in conveying particular points of view in texts, including shifts and/or ambiguities in point of view; Segmented Discourse Representation Theory; internal focalization and the French imperfective past tense; and textual polyphony.

Per una genealogia della giustizia penale internazionale: ambiguita' e paradossi

This article aims to consider the role for a critical criminology outside the national dimension, highlighting its continuities with studies in the critical tradition which have suggested the need to address State criminality and criminogenic structures more in general, but also suggesting a critique of international criminal law as a governmentality project.It reconstructs the genealogy of the international criminal justice system, following on from Schmitt and other well known authors, but it focuses in specific on its paradoxes, contradictions and ambiguities rather than its purely political effect. The authors argue that critical criminologists should engage with the international dimension of crime and control and approach this venture of a international criminal justice system as the possibility of “telling the truth” about State atrocities without missing on using strategically the category of human rights and law to bring to the fore minoritarian interests which are
usually denied by power discourses and economic forces.

A frequency measure robust to linear filtering

It is noted that the determination of an oscillation frequency by used of the power spectrum of measured time series is susceptible to filtering of the signal. Similarly, frequency measurements made by period counting can yield different, results depending on how the signal is filtered for noise reduction. In an attempt to eliminate these ambiguities, a new measure of frequency, based on an approximate reconstruction of the phase-space trajectory of the oscillator from the signal, is introduced. This measure is shown to be invariant under linear filtering. For this reason, it is also inaccessible by spectral methods. The effect of filtering on frequency for weakly nonlinear, noisy oscillators, to which this definition applies only imperfectly, is quantified. This work provides the theoretical basis for frequency measurements employing MIRVA filtering.