Articulation Model Research Articles

Dynamic modeling and analysis of wear in spatial hard-on-hard couple hip replacements using multibody systems methodologies

Wear plays a key role in primary failure of artificial hip articulations. Thus, the main goal of this work is to investigate the influence of friction-induced vibration on the predicted wear of hard hip arthroplasties. This desideratum is reached by developing a three-dimensional multibody dynamic model for a hip prosthesis taking the spatial nature of the physiological loading and motion of the human body into account. The calculation of the intra-joint contact forces developed is based on a continuous contact force approach that accounts for the geometrical and materials properties of the contacting surfaces. In addition, the friction effects due to the contact between hip components are also taken into account. The vibration of the femoral head inside the cup associated with stick-slip friction, negative-sloping friction and dynamic variation in intra-joint contact force has been also incorporated in the present hip articulation model. The friction-induced vibration increases the sliding distance of the contact point between the head and cup surfaces by altering its micro- and macro-trajectories, and consequently affects the wear. In the present work, the Archard’s wear law is considered and embedded in the dynamic hip multibody model, which allows for the prediction of the wear developed in the hip joint. With the purpose of having more realistic wear simulation conditions, the geometries of the acetabular cup and femoral head are updated throughout the dynamic analysis. The main results obtained from computational simulations for ceramic-on-ceramic and metal-on-metal hip prostheses are compared and validated with those available in the best-published literature. Finally, from the study performed in the present work, it can be concluded that an important source of the high wear rates observed clinically may be due to friction-induced vibration.

Feedforward and feedback control in apraxia of speech: effects of noise masking on vowel production.

This study was designed to test two hypotheses about apraxia of speech (AOS) derived from the Directions Into Velocities of Articulators (DIVA) model (Guenther et al., 2006): the feedforward system deficit hypothesis and the feedback system deficit hypothesis. The authors used noise masking to minimize auditory feedback during speech. Six speakers with AOS and aphasia, 4 with aphasia without AOS, and 2 groups of speakers without impairment (younger and older adults) participated. Acoustic measures of vowel contrast, variability, and duration were analyzed. Younger, but not older, speakers without impairment showed significantly reduced vowel contrast with noise masking. Relative to older controls, the AOS group showed longer vowel durations overall (regardless of masking condition) and a greater reduction in vowel contrast under masking conditions. There were no significant differences in variability. Three of the 6 speakers with AOS demonstrated the group pattern. Speakers with aphasia without AOS did not differ from controls in contrast, duration, or variability. The greater reduction in vowel contrast with masking noise for the AOS group is consistent with the feedforward system deficit hypothesis but not with the feedback system deficit hypothesis; however, effects were small and not present in all individual speakers with AOS. Theoretical implications and alternative interpretations of these findings are discussed.

Chapter 9 - Role of the auditory system in speech production

This chapter reviews evidence regarding the role of auditory perception in shaping speech output. Evidence indicates that speech movements are planned to follow auditory trajectories. This in turn is followed by a description of the Directions Into Velocities of Articulators (DIVA) model, which provides a detailed account of the role of auditory feedback in speech motor development and control. A brief description of the higher-order brain areas involved in speech sequencing (including the pre-supplementary motor area and inferior frontal sulcus) is then provided, followed by a description of the Hierarchical State Feedback Control (HSFC) model, which posits internal error detection and correction processes that can detect and correct speech production errors prior to articulation. The chapter closes with a treatment of promising future directions of research into auditory-motor interactions in speech, including the use of intracranial recording techniques such as electrocorticography in humans, the investigation of the potential roles of various large-scale brain rhythms in speech perception and production, and the development of brain-computer interfaces that use auditory feedback to allow profoundly paralyzed users to learn to produce speech using a speech synthesizer.

Estimating Dynamics On-the-Fly Using Monocular Video For Vision-Based Robotics

Estimating the physical parameters of articulated multibody systems (AMBSs) using an uncalibrated monocular camera poses significant challenges for vision-based robotics. Articulated multibody models, especially ones including dynamics, have shown good performance for pose tracking, but require good estimates of system parameters. In this paper, we first propose a technique for estimating parameters of a dynamically equivalent model (kinematic/geometric lengths as well as mass, inertia, damping coefficients) given only the underlying articulated model topology. The estimated dynamically equivalent model is then employed to help predict/filter/gap-fill the raw pose estimates, using an unscented Kalman filter. The framework is tested initially on videos of a relatively simple AMBS (double pendulum in a structured laboratory environment). The double pendulum not only served as a surrogate model for the human lower limb in flight phase, but also helped evaluate the role of model fidelity. The treatment is then extended to realize physically plausible pose-estimates of human lower-limb motions, in more-complex uncalibrated monocular videos (from the publicly available DARPA Mind's Eye Year 1 corpus). Beyond the immediate problem-at-hand, the presented work has applications in creation of low-order surrogate computational dynamics models for analysis, control, and tracking of many other articulated multibody robotic systems (e.g., manipulators, humanoids) using vision.

Markerless motion capture can provide reliable 3D gait kinematics in the sagittal and frontal plane

Estimating 3D joint rotations in the lower extremities accurately and reliably remains unresolved in markerless motion capture, despite extensive studies in the past decades. The main problems have been ascribed to the limited accuracy of the 3D reconstructions. Accordingly, the purpose of the present study was to develop a new approach based on highly detailed 3D reconstructions in combination with a translational and rotational unconstrained articulated model. The highly detailed 3D reconstructions were synthesized from an eight camera setup using a stereo vision approach. The subject specific articulated model was generated with three rotational and three translational degrees of freedom for each limb segment and without any constraints to the range of motion. This approach was tested on 3D gait analysis and compared to a marker based method. The experiment included ten healthy subjects in whom hip, knee and ankle joint were analysed. Flexion/extension angles as well as hip abduction/adduction closely resembled those obtained from the marker based system. However, the internal/external rotations, knee abduction/adduction and ankle inversion/eversion were less reliable.

Multimodal composition of the digital patient: a strategy for the knee articulation

Creating virtual bodies of real patients and using them for diagnosis and treatment planning offer the potential to further empower clinical decision making by medical experts. Virtual patient modeling allows to examine the mechanical and physiological conditions under which articulations are operating in a variety of activities without putting the patient in hazard. The continuous scientific progress has led to an increased range of musculoskeletal data and knowledge being available, covering multiple scales of the musculoskeletal system. A fuller integration of these modalities can broaden the scientific basis of virtual articulation modeling in patients, but poses challenges for data fusion and coupling of simulations. Here, we present a multimodal strategy to compose virtual models of the knee articulation based on a complementary spectrum of data that enables simulations on different scales.

Chinese-English Phone Set Construction for Code-Switching ASR Using Acoustic and DNN-Extracted Articulatory Features

This study proposes a data-driven approach to phone set construction for code-switching automatic speech recognition (ASR). Acoustic and context-dependent cross-lingual articulatory features (AFs) are incorporated into the estimation of the distance between triphone units for constructing a Chinese-English phone set. The acoustic features of each triphone in the training corpus are extracted for constructing an acoustic triphone HMM. Furthermore, the articulatory features of the last/first state of the corresponding preceding/succeeding triphone in the training corpus are used to construct an AF-based GMM. The AFs, extracted using a deep neural network (DNN), are used for code-switching articulation modeling to alleviate the data sparseness problem due to the diverse context-dependent phone combinations in intra-sentential code-switching. The triphones are then clustered to obtain a Chinese-English phone set based on the acoustic HMMs and the AF-based GMMs using a hierarchical triphone clustering algorithm. Experimental results on code-switching ASR show that the proposed method for phone set construction outperformed other traditional methods.

The path from trilling to frication: Synthesizing Puerto Rican Spanish velar fricative realizations of apical trills

Puerto Rican Spanish (PRS) speakers variably produce velar fricative realizations of etymological apical trills. One way to understand this alternation is by attributing it to the two types of trill realization having different gestural goals in PRS. Alternatively, both types of realization may be the result of invariant gestural goals that give rise to distinct attractor states. This study tests whether invariant articulator tasks specified for PRS apical trills can result in successfully synthesized trill and fricative realizations. Comparative measures present in the acoustics of tokens of both types of realization as recorded by native PRS speakers serve as landmarks to determine the success of the articulator model used to produce the synthesized versions. Manipulation of tongue tip gestural stiffness on the one hand and constriction degree on the other provide a way to test which parameter values best capture a bi-goal articulator task. While these findings do not argue against the possibility that PRS velar fricative realizations arise from gestural goals that differ from their apical trill counterparts, they show that this possibility is not the only candidate account for the alternation exhibited in PRS.

Accuracy of maxillary repositioning in two-jaw surgery with conventional articulator model surgery versus virtual model surgery

The purpose of this study was to compare the accuracy of maxillary repositioning using the recently introduced computerized virtual model surgery (VMS) with conventional articulator model surgery (AMS). Forty-two patients who had undergone bimaxillary surgery were investigated retrospectively in this study. The patients were divided into two groups: conventional AMS (n=23) and VMS (n=19) for intermediate splint fabrication in maxillary positioning. Planned surgical movements and actual postsurgical changes of the lateral and frontal cephalometric measurements were compared. Although variations from the planned surgical movements were relatively small, both methods had statistically significant errors in some of the linear measurements. Both groups had a similar range of errors. The overall absolute mean discrepancy between the planned and actual surgical movements for the linear measurements was 1.17mm (0–3.6mm) in AMS and 0.95mm (0–3.2mm) in VMS. Of the total measurements, measurements reflecting a surgical discrepancy of more than 2mm or 2° comprised 12.0% of the cases in AMS and 7.9% in VMS. The surgical accuracy of maxillary positioning with VMS was comparable to conventional AMS. Because VMS has the definitive advantage of eliminating the complex laboratory step and shortening the laboratory time, this can be accepted as an alternative to AMS.

Developing automatic articulation, phonation and accent assessment techniques for speakers treated for advanced head and neck cancer

PurposeTo develop automatic assessment models for assessing the articulation, phonation and accent of speakers with head and neck cancer (Experiment 1) and to investigate whether the models can track changes over time (Experiment 2). MethodSeveral speech analysis methods for extracting a compact acoustic feature set that characterizes a speaker’s speech are investigated. The effectiveness of a feature set for assessing a variable is assessed by feeding it to a linear regression model and by measuring the mean difference between the outputs of that model for a set of recordings and the corresponding perceptual scores for the assessed variable (Experiment 1). The models are trained and tested on recordings of 55 speakers treated non-surgically for advanced oral cavity, pharynx and larynx cancer. The perceptual scores are average unscaled ratings of a group of 13 raters. The ability of the models to track changes in perceptual scores over time is also investigated (Experiment 2). ResultsExperiment 1 has demonstrated that combinations of feature sets generally result in better models, that the best articulation model outperforms the average human rater’s performance and that the best accent and phonation models are deemed competitive. Scatter plots of computed and observed scores show, however, that especially low perceptual scores are difficult to assess automatically. Experiment 2 has shown that the articulation and phonation models show only variable success in tracking trends over time and for only one of the time pairs are they deemed compete with the average human rater (Experiment 2). Nevertheless, there is a significant level of agreement between computed and observed trends when considering only a coarse classification of the trend into three classes: clearly positive, clearly negative and minor differences. ConclusionsA baseline tool to support the multi-dimensional evaluation of speakers treated non-surgically for advanced head and neck cancer now exists. More work is required to further improve the models, particularly with respect to their ability to assess low-quality speech.

Interactive generalized penetration depth computation for rigid and articulated models using object norm

We present a novel, real-time algorithm to accurately approximate the generalized penetration depth ( PD g ) between two overlapping rigid or articulated models. Given the high complexity of computing PD g , our algorithm approximates PD g based on iterative, constrained optimization on the contact space, defined by the overlapping objects. The main ingredient of our algorithm is a novel and general formulation of distance metric, the object norm , in a configuration space for articulated models, and a compact closed-form solution for it. Then, we perform constrained optimization, by linearizing the contact constraint, and minimizing the object norm under such a constraint. In practice, our algorithm can compute locally optimal PD g for rigid or articulated models consisting of tens of thousands of triangles in tens of milliseconds. We also suggest three applications using PD g computation: retraction-based motion planning, physically-based animation, and data-driven grasping.

Effective atomic numbers of some tissue substitutes by different methods: A comparative study

Effective atomic numbers of some human organ tissue substitutes such as polyethylene terephthalate, red articulation wax, paraffin 1, paraffin 2, bolus, pitch, polyphenylene sulfide, polysulfone, polyvinylchloride, and modeling clay have been calculated by four different methods like Auto-Zeff, direct, interpolation, and power law. It was found that the effective atomic numbers computed by Auto-Zeff, direct and interpolation methods were in good agreement for intermediate energy region (0.1 MeV < E < 5 MeV) where the Compton interaction dominates. A large difference in effective atomic numbers by direct method and Auto-Zeff was observed in photo-electric and pair-production regions. Effective atomic numbers computed by power law were found to be close to direct method in photo-electric absorption region. The Auto-Zeff, direct and interpolation methods were found to be in good agreement for computation of effective atomic numbers in intermediate energy region (100 keV < E < 10 MeV). The direct method was found to be appropriate method for computation of effective atomic numbers in photo-electric region (10 keV < E < 100 keV). The tissue equivalence of the tissue substitutes is possible to represent by any method for computation of effective atomic number mentioned in the present study. An accurate estimation of Rayleigh scattering is required to eliminate effect of molecular, chemical, or crystalline environment of the atom for estimation of gamma interaction parameters.

Motor control primitives arising from a dynamical systems model of vocal tract articulation

We have previously presented a computational approach to derive interpretable movement primitives from speech articulation data using a convolutive Nonnegative Matrix Factorization with sparseness constraints (cNMFsc) technique (Ramanarayanan et al., Interspeech 2011; Ramanarayanan et al., J. Acoust. Soc. Am. 134(2), in press). However, it is not clear whether finding such a dictionary of primitives can be useful for speech motor control, particularly in finding a low-dimensional subspace for such control. In this paper, we examine this possibility in two steps. First, we use the iterative Linear Quadratic Gaussian (iLQG) algorithm to derive a set of control inputs to a dynamical systems model of the vocal tract that produces a desired movement sequence. Second, we use the cNMFsc algorithm to find a small dictionary of control input “primitives'' that can be used to drive said dynamical systems model of the vocal tract to produce the desired range of articulatory movement. We show, using both qualitative ...

The poetics of village space when villages are new: Settlement form as history making in Papua, Indonesia

ABSTRACTResettlement of dispersed populations into centralized villages has been a watershed cultural change across many world regions, often occurring under pressure from states, world religions, and markets. Recent village formation processes among Korowai of Papua, Indonesia, have been caused by such pressures but have also been heavily structured by Korowai understandings of geography. This article takes Korowai villages as a case study in the semiotics of space. The power of villages to be the pivot of historical transformation flows from this spatial form's “poetic density,” meaning its ladenness with a multiplicity of social principles, structures of feeling, and models of extralocal geopolitical articulation. Additionally, Korowai strongly orient to space as a field of heterogeneity. Their expectation that different spaces are charged with otherness of order has shaped their village‐forming actions and their intense focus on villages in thinking about contemporary history at large.

Speech Motor Programming in Apraxia of Speech: Evidence From a Delayed Picture-Word Interference Task

Apraxia of speech (AOS) is considered a speech motor programming impairment, but the specific nature of the impairment remains a matter of debate. This study investigated 2 hypotheses about the underlying impairment in AOS framed within the Directions Into Velocities of Articulators (DIVA; Guenther, Ghosh, & Tourville, 2006) model: The retrieval hypothesis states that access to the motor programs is impaired, and the damaged programs hypothesis states that the motor programs themselves are damaged. The experiment used a delayed picture-word interference paradigm in which participants prepare their response and auditory distracters are presented with the go signal. The overlap between target and distracter words was manipulated (i.e., shared sounds or no shared sounds), and participants' reaction times (RTs) were measured. Participants included 5 speakers with AOS (4 with concomitant aphasia), 2 speakers with aphasia without AOS, and 9 age-matched control speakers. The control speakers showed no effects of distracter type or presence. The speakers with AOS had longer RTs in the distracter condition compared to the no-distracter condition. The speakers with aphasia without AOS were comparable to the control group in their overall RTs and RT pattern. Results provide preliminary support for the retrieval hypothesis, suggesting that access to motor programs may be impaired in speakers with AOS. However, the possibility that the motor programs may also be damaged cannot be ruled out.

Captura de movimiento y reconocimiento de actividades para múltiples personas mediante un enfoque bayesiano

This work presents a general framework for tracking simultaneously the body posturas of multiple people from nonintrusive visual sensors. The method is based on a trainingthen-tracking philosophy, with the main addition of being able to handle more than just one person. We train the body postura from labelled motion capture datasets. The training process is based on popular non-linear dimensionality reduction techniques. Then, a mixed, discrete and continuous state particle filter is used to simultaneously detect the postura and the kind of motion performed by each of the human bodies. The resulting hypotheses, automatically selected from the particle distribution, are then refined using non-linear optimization methods with statistical priors. The whole framework is tested using a simple but standard method based on comparing articulated cylindrical models with SfS volumes, taken from several cameras. Our accuracy in public available datasets is near to the state-ofthe-art works that do not take into account multiple people in the problem.

Políticas públicas y participación ciudadana en la esfera local. Análisis y reflexiones a la luz de la experiencia argentina reciente

El trabajo analiza las principales características que asume la participación ciudadana como dispositivo de gobierno en la esfera local argentina de los últimos años. Se consideran los elementos de cambio y continuidad que hacen al perfil institucional, modelo de gestión y tipo de articulación entre actores estatales y sociales en el plano territorial, así como los alcances que presentan los nuevos instrumentos de política local en términos de interacción y mayor apertura democrática.

Políticas públicas y participación ciudadana en la esfera local. Análisis y reflexiones a la luz de la experiencia argentina reciente

The paper examines the main features of citizen participation continuity and as a government tool in Argentina. We consider the elements of change make up the institutional profile, management model and model of articulation between new state and social actors within the territory, as well as the scope offered by new local policy instruments in terms of more democratic interaction and openness.

Brian Friel’s Transformation from Short Fiction Writer to Dramatist

In 1965, Irish playwright Brian Friel emphatically told Graham Morrison, don't concentrate on the theatre at all. I live on short stories. This is where my living comes from. As for play-writing, it began as a sort of and then eventually I got caught up more and more in it. But the short story is the basis of all the work I do. (1) By 1968, however, Friel had virtually stopped writing stories. To date, no critic has sufficiently explained why Friel moved from writing short fiction and drama solely to writing drama by the end of the 1960s, although one critic, citing Friel's statement about playwriting as self-indulgence has recently wrongly argued that Faber and Faber's inability to secure publishing rights to Friel's short fiction and its publication instead by smaller firms in the 1960s and 1970s have altered not only the Irish 'canon' but even the actual generic choices of a writer. (2) The more accepted narrative to emerge in criticism of Friel's work, however, suggests that not only did Friel find the formulaic requirements for short fiction in the New Yorker, which published many of his stories, stifling, but also that he realized that his short fiction was too imitative of the two Irish masters at the time, Sean O'Faolain and Frank O'Connor. (3) But there are several equally important reasons for Friel's commitment to drama and rejection of short fiction. They include Friel's experimentation with other genres such as radio drama and journalism, which may have helped him realize that he was better suited for a more fluid, experimental genre than short fiction, and his realization--expressed in his major essays on theater--that only drama, with its ability to enchant audiences, would allow him to depict his consistent theme of flux while also appealing to a potential community within the theater. Finally, Friel's interest in politics almost ineluctably kept him in the dramatic arena as the conflict in Northern Ireland lengthened and deepened through the 1970s and 1980s. This essay thus concludes with an assessment of the role of the Field Day Theatre Company, which enabled Friel to offer an exciting, fluid alternative on the stage to the hidebound, binary politics of Northern Ireland that provided both a model of communal interrogation and tentative articulation of deep-seated political, religious, and cultural problems that might augur a less divided society in the future. For a time, Friel seems to have wondered if radio drama would be the subgenre most suited to his desire to community through exploring the intellectual, social, spiritual, geographic, and political milieu of his region of Northern Ireland. As I have argued elsewhere, Nobel Laureate Seamus Heaney, also raised in Northern Ireland, used the platform of BBC Northern Ireland to create sonically an imagined regional community of the sort described by Benedict Anderson [in Imagined Communities], a new province, where the contributions of both Catholics and Protestants would be honoured. (4) While more reticent about his aim in this regard than Heaney has been, Friel has nonetheless long been interested in drawing together disparate members of the community in Northern Ireland. He realized early in his career that radio exercised a special hold on the minds of the Irish and had the sort of mesmerizing effect upon which he would later base his ritualized theory of theater, a theory metadramatically explored in his masterpiece, Faith Healer (1979). Heaney has recalled the intensity with which he and family members listened to the radio in the 1940s and 1950s: If an angel had passed or a mighty wind had arisen or tongues of flames descended, the occasion could not have been more prepared for or more expectant. (5) Even when became more popular in the 1960s, Rex Cathcart has shown that Northern Irish audiences remained loyal to the older medium in part because television long lacked any significant local component whereas radio continued to supply a regional service. …

Extensional Information Articulation from the Universe

Information must have physical support and this physical universe comprisesphysical interactions. Hence actual information processes should have a description byinteractions alone, i.e., an extensional description. In this paper, such a model of the processof information articulation from the universe is developed by generalizing the extensivemeasurement theory in metrology. Moreover, a model of the attribute creation processis presented to exemplify a step of the informational articulation process. These modelsdemonstrate the valuableness of the extensional view and are expected to enhance theunderstanding of the extensional aspects of fundamentals of information.