Home About us Contact
|
Home About us Contact | ||
|
|
||
Poses
Kinds of Poses Terms modified by Poses Selected AbstractsTriamcinolone-impregnated nasal dressing following endoscopic sinus surgery: A randomized, double-blind, placebo-controlled study,,THE LARYNGOSCOPE, Issue 6 2010David W. J. Côté MD Abstract Objectives/Hypothesis: To evaluate the impact of steroid-impregnated absorbable nasal dressing on wound healing and surgical outcomes after endoscopic sinus surgery (ESS). Study Design: A prospective, randomized, double-blinded, placebo-controlled trial. Methods: Chronic rhinosinusitis patients with polyposis who were to undergo bilateral endoscopic sinus surgery were recruited and randomized to receive triamcinolone-impregnated bioresorbable dressing (Nasopore; Stryker Canada, Hamilton, Ontario, Canada) in one nasal cavity and saline-impregnated dressing contralaterally. Postoperative healing assessments of edema, crusting, secretions, and scarring were done at postoperative days 7, 14, 28 and at 3 and 6 months using validated Lund-Kennedy and Perioperative Sinus Endoscopy (POSE) scores. Results: Analysis of 19 enrolled patients having completed observation shows no significant difference between the cavity scores preoperatively using both the POSE and Lund-Kennedy scores. There was, however, a statistically significant difference at day 7 and 14 in both the Lund-Kennedy (P = .04 and P = .03, respectively) and POSE scores (P = .03 and P = .001, respectively) for the treatment and control groups, and a significant difference was also detected between the groups at 3- and 6-month observations (Lund-Kennedy, P = .007 and P = .02, respectively; POSE, P = .049 and P = .01, respectively). Conclusions: Data analysis suggests a significant improvement in early postoperative healing in nasal cavities receiving triamcinolone-impregnated absorbable nasal packing following ESS and is also associated with improved healing up to 6 months postoperatively. [source] Impact of Perioperative Systemic Steroids on Surgical Outcomes in Patients With Chronic Rhinosinusitis With Polyposis: Evaluation With the Novel Perioperative Sinus Endoscopy (POSE) Scoring System,THE LARYNGOSCOPE, Issue S115 2007Erin D. Wright MDCM Abstract Objectives/Hypothesis: The objective of this randomized, double-blind, placebo-controlled study was to assess the effect of perioperative systemic steroids on subjective and objective surgical outcomes for patients undergoing endoscopic sinus surgery (ESS) for chronic rhinosinusitis with polyposis (CRSwP). The secondary objective was to begin validation of the newly developed Perioperative Sinus Endoscopy (POSE) scoring system. Methods: Patients who had failed maximal medical therapy and were scheduled to undergo ESS were eligible for the study. Participants were randomized to receive either 30 mg of prednisone or placebo for 5 days preoperatively and 9 days postoperatively. Operative and baseline clinical data were collected using the Lund-McKay staging system including its Sinus Symptom Questionnaire as well as additional data regarding mucosal health, the technical difficulty of surgery, and endoscopic data using the Lund-Kennedy Endoscopic Score (LKES) and POSE scale. Data were also collected at 2 weeks, 1 month, 3 months, and 6 months postoperatively. A sample size of 24 was calculated to detect a clinically relevant difference between groups of 40%. Routine statistical comparisons were performed as were repeated measures analysis of variance with Bonferroni adjustment because of the multiple comparisons performed. To address the secondary objective, data were also collected at all postoperative time points using the POSE instrument, which was designed with the intention of enhancing face validity and responsiveness to change. Comparisons were performed between the POSE and LKES, including assessment of sensitivity to change, correlation between the two scales, and correlation with symptom scores. Results: Twenty-six patients participated in the study. Operative data demonstrated a significantly higher percentage of severely inflamed sinonasal mucosa in patients not pretreated with systemic steroids, which was associated with technically more difficult surgery in the estimation of the operating surgeon. In terms of postoperative symptoms, there was no difference between treatment groups, with both placebo and prednisone significantly improved over baseline up to 4 weeks postoperatively. Endoscopic assessment of patients postoperatively demonstrated a treatment effect (P < .05), with clinically healthier cavities seen in patients treated with prednisone up to 6 months postoperatively as compared with baseline (P < .001), although the strongest effect was seen at the 2-week time point. In comparing the two endoscopic scales, the POSE and LKES correlated highly (R > 0.70; P < .001) both in terms of absolute score and change in score. There is some evidence that the POSE score may be more sensitive to change than the LKES, and the POSE scores did correlate more strongly with symptom scores than the LKES, although both endoscopic scores correlated only weakly with symptom scores. Conclusions: The data presented in this study support the practice of administering preoperative systemic steroids to patients undergoing ESS for CRSwP. Furthermore, in the practice of surgeons who provide intensive postoperative care post-ESS, including debridement and medical therapy based on the endoscopic findings, there is evidence to support administering systemic steroids in the postoperative period. The POSE scoring system compares favorably with the LKES and may confer advantages in terms of face/content validity and responsiveness to change and is worthy of further validation. [source] Letter: Benzyl Alcohol Preserved Saline Used to Dilute Injectables Poses a Risk of Contact Dermatitis in Fragrance-Sensitive PatientsDERMATOLOGIC SURGERY, Issue 11 2007ANTOINE AMADO MD No abstract is available for this article. [source] NURBS to Avoid Boundary Orientation Poses in Serial ManipulatorsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 12 2003Andrzej J. Cebula A procedure to build NURBS motion interpolants to avoid boundary orientation poses for serial manipulator architectures is presented. As an example, the PUMA architecture was used. The procedure, which emerged from B-spline curves theory, enables a local change of the NURBS motion interpolant. The change may be introduced in any arbitrary neighborhood of the chosen boundary orientation pose. Therefore, when tracking a trajectory, one may change NURBS motion interpolant value at any time instant, leaving its remaining values untouched. Recommendation for further research pertains to exploiting the flexibility of NURBS applied to robot kinematics. © 2003 Wiley Periodicals, Inc. [source] Children at Risk: Legal and Societal Perceptions of the Potential Threat that the Possession of Child Pornography Poses to SocietyJOURNAL OF LAW AND SOCIETY, Issue 3 2002Suzanne Ost This article examines legal and social discourses surrounding the phenomenon of child pornography, considering the legal responses to child pornography (particularly when an individual is found to be in possession of such material), and the way in which such material, the child, and the possessor of child pornography are socially constructed. The article raises the question of whether there has been a moral panic regarding child pornography and the possession of such material, but also considers whether there are real reasons to consider that the possession of child pornography should remain illegal. Research studies which aim to establish the existence of a causal link between possessing child pornography and the act of committing child sexual abuse are examined, as is the argument that criminalizing the possession of child pornography reduces the market for such material. Finally, there is an analysis of the possible impact of social constructions of the child as innocent. [source] Automatic muscle generation for character skin deformationCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2006Xiaosong Yang Abstract As skin shape depends on the underlying anatomical structure, the anatomy-based techniques usually afford greater realism than the traditional skeleton-driven approach. On the downside, however, it is against the current animation workflow, as the animator has to model many individual muscles before the final skin layer arrives, resulting in an unintuitive modelling process. In this paper, we present a new anatomy-based technique that allows the animator to start from an already modelled character. Muscles having visible influence on the skin shape at the rest pose are extracted automatically by studying the surface geometry of the skin. The extracted muscles are then used to deform the skin in areas where there exist complex deformations. The remaining skin areas, unaffected or hardly affected by the muscles, are handled by the skeleton-driven technique, allowing both techniques to play their strengths. In order for the extracted muscles to produce realistic local skin deformation during animation, muscle bulging and special movements are both represented. Whereas the former ensues volume preservation, the latter allows a muscle not only to deform along a straight path, but also to slide and bend around joints and bones, resulting in the production of sophisticated muscle movements and deformations. Copyright © 2006 John Wiley & Sons, Ltd. [source] A moving planar mirror based approach for cultural reconstructionCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2004Kyung Ho Jang Abstract Modelling from images is a cost-effective means of obtaining virtual cultural heritage models. These models can be effectively constructed from classical Structure from Motion algorithm. However, it's too difficult to reconstruct whole scenes using SFM method since general oriental historic sites contain a very complex shapes and brilliant colours. To overcome this difficulty, the current paper proposes a new reconstruction method based on a moving planar mirror. We devise the mirror posture instead of scene itself as a cue for reconstructing the geometry. That implies that the geometric cues are inserted into the scene by compulsion. With this method, we can obtain the geometrical details regardless of the scene complexity. For this purpose, we first capture image sequences through the moving mirror containing the interested scene, and then calibrate the camera through the mirror's posture. Since the calibration results are still inaccurate due to the detection error, the camera pose is revised using frame-correspondence of the corner points that are easily obtained using the initial camera posture. Finally, 3D information is computed from a set of calibrated image sequences. We validate our approach with a set of experiments on some cultural heritage objects. Copyright © 2004 John Wiley & Sons, Ltd. [source] Wrinkling Coarse Meshes on the GPUCOMPUTER GRAPHICS FORUM, Issue 3 2006J. Loviscach The simulation of complex layers of folds of cloth can be handled through algorithms which take the physical dynamics into account. In many cases, however, it is sufficient to generate wrinkles on a piece of garment which mostly appears spread out. This paper presents a corresponding fully GPU-based, easy-to-control, and robust method to generate and render plausible and detailed folds. This simulation is generated from an animated mesh. A relaxation step ensures that the behavior remains globally consistent. The resulting wrinkle field controls the lighting and distorts the texture in a way which closely simulates an actually deformed surface. No highly tessellated mesh is required to compute the position of the folds or to render them. Furthermore, the solution provides a 3D paint interface through which the user may bias the computation in such a way that folds already appear in the rest pose. Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Animation, I.3.7 [Computer Graphics]: Color, shading, shadowing, and texture [source] A System for View-Dependent AnimationCOMPUTER GRAPHICS FORUM, Issue 3 2004Parag Chaudhuri In this paper, we present a novel system for facilitating the creation of stylized view-dependent 3D animation. Our system harnesses the skill and intuition of a traditionally trained animator by providing a convivial sketch based 2D to 3D interface. A base mesh model of the character can be modified to match closely to an input sketch, with minimal user interaction. To do this, we recover the best camera from the intended view direction in the sketch using robust computer vision techniques. This aligns the mesh model with the sketch. We then deform the 3D character in two stages - first we reconstruct the best matching skeletal pose from the sketch and then we deform the mesh geometry. We introduce techniques to incorporate deformations in the view-dependent setting. This allows us to set up view-dependent models for animation. Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism - Animation 7 Figure 7. Our system takes as input a sketch (a), and a base mesh model (b), then recovers a camera to orient the base mesh (c), then reconstructs the skeleton pose (d), and finally deforms the mesh to find the best possible match with the sketch (e). [source] Reanimating Faces in Images and VideoCOMPUTER GRAPHICS FORUM, Issue 3 2003V. Blanz This paper presents a method for photo-realistic animation that can be applied to any face shown in a single imageor a video. The technique does not require example data of the person's mouth movements, and the image to beanimated is not restricted in pose or illumination. Video reanimation allows for head rotations and speech in theoriginal sequence, but neither of these motions is required. In order to animate novel faces, the system transfers mouth movements and expressions across individuals, basedon a common representation of different faces and facial expressions in a vector space of 3D shapes and textures. This space is computed from 3D scans of neutral faces, and scans of facial expressions. The 3D model's versatility with respect to pose and illumination is conveyed to photo-realistic image and videoprocessing by a framework of analysis and synthesis algorithms: The system automatically estimates 3D shape andall relevant rendering parameters, such as pose, from single images. In video, head pose and mouth movements aretracked automatically. Reanimated with new mouth movements, the 3D face is rendered into the original images. Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Animation [source] Dynamic Textures for Image-based Rendering of Fine-Scale 3D Structure and Animation of Non-rigid MotionCOMPUTER GRAPHICS FORUM, Issue 3 2002Dana Cobza The problem of capturing real world scenes and then accurately rendering them is particularly difficult for fine-scale 3D structure. Similarly, it is difficult to capture, model and animate non-rigid motion. We present a method where small image changes are captured as a time varying (dynamic) texture. In particular, a coarse geometry is obtained from a sample set of images using structure from motion. This geometry is then used to subdivide the scene and to extract approximately stabilized texture patches. The residual statistical variability in the texture patches is captured using a PCA basis of spatial filters. The filters coefficients are parameterized in camera pose and object motion. To render new poses and motions, new texture patches are synthesized by modulating the texture basis. The texture is then warped back onto the coarse geometry. We demonstrate how the texture modulation and projective homography-based warps can be achieved in real-time using hardware accelerated OpenGL. Experiments comparing dynamic texture modulation to standard texturing are presented for objects with complex geometry (a flower) and non-rigid motion (human arm motion capturing the non-rigidities in the joints, and creasing of the shirt). Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Image Based Rendering [source] Semi-Automatic 3D Reconstruction of Urban Areas Using Epipolar Geometry and Template MatchingCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 7 2006José Miguel Sales Dias The main challenge is to compute the relevant information,building's height and volume, roof's description, and texture,algorithmically, because it is very time consuming and thus expensive to produce it manually for large urban areas. The algorithm requires some initial calibration input and is able to compute the above-mentioned building characteristics from the stereo pair and the availability of the 2D CAD and the digital elevation model of the same area, with no knowledge of the camera pose or its intrinsic parameters. To achieve this, we have used epipolar geometry, homography computation, automatic feature extraction and we have solved the feature correspondence problem in the stereo pair, by using template matching. [source] Robust gender and age estimation under varying facial poseELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 7 2008Hironori Takimoto Abstract This paper presents a method for gender and age estimation which is robust to changing facial pose. We propose a feature point detection method, called the adapted retinal sampling method (ARSM), and a feature extraction method. A basic concept of the ARSM is to add knowledge about the facial structure to the retinal sampling method. In this method, feature points are detected on the basis of seven points corresponding to facial organs from a facial image. The reason why we used seven points as the basis of feature point detection is that facial organs are conspicuous in the facial region, and are comparatively easy to extract. As features robust to changing facial pose, skin texture, hue, and the Gabor jet are used for gender and age estimation. For classification of gender and estimation of age, we use a multilayered neural network. We also examine the left, right symmetry of faces in connection with gender and age estimation by the proposed method. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(7): 32, 40, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10125 [source] An evaluation of logistic regression models for predicting amphipod toxicity from sediment chemistryENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2005Jeffrey D. Wetherington Abstract An empirical screening level approach was developed to assess the probability of toxicity to benthic organisms associated with contaminated sediment exposure. The study was based on simple logistic regression models (LRMs) of matching sediment chemistry and toxicity data retrieved from a large database of field-collected sediment samples contaminated with multiple chemicals. Three decisions were made to simplify the application of LRMs to sediment samples contaminated with multiple chemicals. First, percent mortality information associated with each sediment sample was condensed into a dichotomous response (i.e., toxic or nontoxic). Second, each LRM assumed that toxicity was attributable to a single contaminant. Third, individual contaminants present at low concentrations were excluded from toxic sediment samples. Based on an analysis of the National Sediment Inventory database, the LRM approach classified 55% of nontoxic sediments as toxic (i.e., false-positives). Because this approach has been used to assess the probability of benthic toxicity as reported by the U.S. Environmental Protection Agency (U.S. EPA), the resultant estimates of potential toxicity convey a misleading impression of the increased hazard that sediments pose to the health of aquatic organisms at many sites in the United States. This could result in important resources needlessly being diverted from truly contaminated sites to evaluate and possibly remediate sediments at uncontaminated sites. [source] Informal Work in Latin America: Competing Perspectives and Recent DebatesGEOGRAPHY COMPASS (ELECTRONIC), Issue 1 2009James J. Biles During the ,lost decade' of the 1980s, informal work and self-employment emerged as the most prevalent forms of work throughout Latin America. In response to the economic crisis, the majority of Latin American countries adopted a series of sweeping neoliberal reforms designed to open nations to trade and investment, promote export-led growth, and generate employment, ultimately reducing the incidence of informal work. Despite the widespread adherence to the neoliberal model and implementation of structural adjustment reforms during the past quarter century, informal work has not diminished and in much of Latin America the odds of finding ,decent work' are no better today than during the economic crisis of the 1980s. In light of this seeming paradox, this article offers an overview of the recent debates and controversies surrounding informal work in Latin America. Drawing on recent research, as well as reports and policy documents from key international organizations, I pose and attempt to answer four core questions: What counts as informal work? Who works informally in Latin America? Why do men and women throughout Latin America increasingly resort to informal work? What role does informal work play as a livelihood strategy in Latin America and how has this role changed in recent years? [source] Speed of Processing and Face Recognition at 7 and 12 MonthsINFANCY, Issue 4 2002Susan A. Rose This research examined developmental and individual differences in infants' speed of processing faces and the relation of processing speed to the type of information encoded. To gauge processing speed, 7- and 12-month-olds were repeatedly presented with the same face (frontal view), each time paired with a new one, until they showed a consistent preference for the new one. Subsequent probe trials assessed recognition of targets that either preserved configural integrity (Study 1: 3/4 profile and full profile poses) or disrupted it while preserving featural information (Study 2: rotations of 160° or 200° and fracturings). There were developmental differences in both speed and in infants' appreciation of information about faces. Older infants took about 60% fewer trials to reach criterion and had more mature patterns of attention (i.e., looks of shorter duration and more shifts of gaze). Whereas infants of both ages recognized the familiar face in a 3/4 pose, the 12-month-olds also recognized it in profile and when rotated. Twelve-month-olds who were fast processors additionally recognized the fractured faces; otherwise, processing speed was unrelated to the type of information extracted. At 7 months then, infants made use of some configural information in processing faces; at 12 months, they made use of even more of the configural information, along with part-based or featural information. [source] Iterative algorithm for optimal fiducials under weak perspective projectionINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2009Alfred M. Bruckstein Abstract In previous work, we designed space fiducials with the aim of making camera pose determination as noise-insensitive as possible. These fiducials turned out to be sets of points that formed concentric regular polyhedra. Here, we apply an idea of Dementhon and Davis and test and analyze an iterative linear algorithm in conjunction with our optimal fiducials to increase the accuracy of the computed camera pose. We also analyze under what circumstances this iterative algorithm is guaranteed to converge to the correct solution. Comprehensive computer simulations illustrate the behavior of the algorithm and the degree of improvement in pose determination in case of convergence. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 27,36, 2009 [source] Economic Nationalism as a Challenge to Economic Liberalism?INTERNATIONAL STUDIES QUARTERLY, Issue 3 2002Lessons from the 19th Century What kind of challenge does economic nationalism pose to economic liberalism in today's global political economy? Conventional wisdom holds that economic nationalism is an outdated ideology in this age of globalization and economic liberalization. But this argument rests on understandings of economic nationalism that are increasingly being called into question by recent scholarship. In this article, I show how the history of economic nationalism in the 19th century provides strong support for two important but potentially controversial arguments made in recent literature about the nature of economic nationalism: (1) that this ideology is most properly defined by its nationalist content (rather than as a variant of realism or as an ideology of protectionism), and (2) that it can be associated with a wide range of policy projects, including the endorsement of liberal economic policies. With these two points established through historical analysis, I conclude that economic nationalism should be seen still to be a powerful ideology in the current period, but that its relationship to the policy goals of economic liberals is an ambiguous one, just as it was in the 19th century. [source] Reproductive ecology of three endangered African violet (Saintpaulia H. Wendl.) species in the East Usambara Mountains, TanzaniaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2006Johanna K. Kolehmainen Abstract Knowledge of the reproductive biology of endangered plants is essential for their effective conservation. It also provides important information for understanding the evolutionary processes that affect speciation, thus helping the definition of proper units for conservation in endangered plants with problematic taxonomy. We studied the reproductive potential and possibility for hybridization in the endangered genus Saintpaulia (Gesneriaceae) by examining flowering phenology, flower and seed production and pollination of three sympatric cross-compatible Saintpaulia species in the East Usambara Mts., Tanzania. The synchrony observed in flowering in S. confusa and S. difficilis may enable hybridization between these two species, whereas partial phenological separation may contribute to the integrity of S. grotei. Although the level of flower abortion is high in S. confusa, each pollinated flower yields about 1000 seeds. Saintpaulia confusa produces fruits following both self- and cross-pollination but spontaneous self-pollination seems not to occur. Thus, seed production depends on sufficient pollinator service. Floral heteromorphy (i.e. enantiostyly) and bee pollination are likely to further enhance cross-pollination, suggesting that the genus predominantly outcrosses. Thus, Saintpaulia populations are likely to suffer from negative effects of inbreeding if they become small and isolated. Résumé La connaissance de la biologie de la reproduction des plantes en danger est essentielle pour l'efficacité de leur conservation. Elle fournit aussi des informations importantes pour la compréhension des processus évolutifs qui touchent la spéciation et donc pour la définition d'unités adéquates pour la conservation de plantes en danger dont la taxonomie pose des problèmes. Nous avons étudié le potentiel reproductif et la possibilité d'hybridation du genre menacéSaintpaulia (Gesneriaceae) en examinant la phénologie de la floraison, la production de fleurs et de semences, et la pollinisation de trois espèces de Sainpaulia sympatriques de l'est des Usambara Mountains, en Tanzanie, qui peuvent se croiser. La synchronie de la floraison observée avec S. confusa et S. difficilis permet peut-être l'hybridation entre ces deux espèces, tandis qu'une séparation phénologique partielle pourrait contribuer à conserver l'intégrité de S. grotei. Même si le niveau d'avortement est élevé pour les fleurs de S. confusa, chaque fleur fécondée produit environ 1000 semences. S. confusa produit des fruits après la pollinisation par sa propre espèce ou par croisement avec une autre espèce, mais il semble qu'il n'y ait pas d'auto-pollinisation spontanée. Donc, la production de semences dépend de l'abondance des pollinisateurs. L'hétéromorphie florale (i.e. énantiomorphisme) et la pollinisation par les abeilles sont susceptibles de stimuler la pollinisation croisée, ce qui suggère que ce genre se reproduit surtout de cette façon. Il est donc probable que les populations de Saintpaulia risquent de souffrir des effets négatifs de l'inbreeding si elles deviennent trop petites et isolées. [source] Evaluation of library ranking efficacy in virtual screening,JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2005Maria Kontoyianni Abstract We present the results of a comprehensive study in which we explored how the docking procedure affects the performance of a virtual screening approach. We used four docking engines and applied 10 scoring functions to the top-ranked docking solutions of seeded databases against six target proteins. The scores of the experimental poses were placed within the total set to assess whether the scoring function required an accurate pose to provide the appropriate rank for the seeded compounds. This method allows a direct comparison of library ranking efficacy. Our results indicate that the LigandFit/Ligscore1 and LigandFit/GOLD docking/scoring combinations, and to a lesser degree FlexX/FlexX, Glide/Ligscore1, DOCK/PMF (Tripos implementation), LigandFit1/Ligscore2 and LigandFit/PMF (Tripos implementation) were able to retrieve the highest number of actives at a 10% fraction of the database when all targets were looked upon collectively. We also show that the scoring functions rank the observed binding modes higher than the inaccurate poses provided that the experimental poses are available. This finding stresses the discriminatory ability of the scoring algorithms, when better poses are available, and suggests that the number of false positives can be lowered with conformers closer to bioactive ones. © 2004 Wiley Periodicals, Inc. J Comput Chem 26: 11,22, 2005 [source] Forecasting plant migration rates: managing uncertainty for risk assessmentJOURNAL OF ECOLOGY, Issue 3 2003S. I. Higgins Summary 1Anthropogenic changes in the global climate are shifting the potential ranges of many plant species. 2Changing climates will allow some species the opportunity to expand their range, others may experience a contraction in their potential range, while the current and future ranges of some species may not overlap. Our capacity to generalize about the threat these range shifts pose to plant diversity is limited by many sources of uncertainty. 3In this paper we summarize sources of uncertainty for migration forecasts and suggest a research protocol for making forecasts in the context of uncertainty. [source] Maneuverability and path following control of wheeled mobile robot in the presence of wheel skidding and slippingJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 2 2010Chang Boon Low This paper addresses the path following control problem of wheeled mobile robots in the presence of wheel skidding and slipping. A conditional global positioning system (GPS)-based path following controller is proposed for four generic WMRs to achieve high-precision path following performance. The proposed controller utilizes real-time kinematic-GPS and other aiding sensors to determine the robot's pose and wheel skidding and slipping perturbations to achieve accurate path following control. The reported simulation and experimental results suggest that with this control scheme, the WMRs are able to maneuver with precision. © 2009 Wiley Periodicals, Inc. [source] Gamma-SLAM: Visual SLAM in unstructured environments using variance grid mapsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 1 2009Tim K. Marks This paper describes an online stereo visual simultaneous localization and mapping (SLAM) algorithm developed for the Learning Applied to Ground Robotics (LAGR) program. The Gamma-SLAM algorithm uses a Rao,Blackwellized particle filter to obtain a joint posterior over poses and maps: the pose distribution is estimated using a particle filter, and each particle has its own map that is obtained through exact filtering conditioned on the particle's pose. Visual odometry is used to provide good proposal distributions for the particle filter, and maps are represented using a Cartesian grid. Unlike previous grid-based SLAM algorithms, however, the Gamma-SLAM map maintains a posterior distribution over the elevation variance in each cell. This variance grid map can capture rocks, vegetation, and other objects that are typically found in unstructured environments but are not well modeled by traditional occupancy or elevation grid maps. The algorithm runs in real time on conventional processors and has been evaluated for both qualitative and quantitative accuracy in three outdoor environments over trajectories totaling 1,600 m in length. © 2008 Wiley Periodicals, Inc. [source] Vision-aided inertial navigation for pin-point landing using observations of mapped landmarksJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2007Nikolas Trawny In this paper we describe an extended Kalman filter algorithm for estimating the pose and velocity of a spacecraft during entry, descent, and landing. The proposed estimator combines measurements of rotational velocity and acceleration from an inertial measurement unit (IMU) with observations of a priori mapped landmarks, such as craters or other visual features, that exist on the surface of a planet. The tight coupling of inertial sensory information with visual cues results in accurate, robust state estimates available at a high bandwidth. The dimensions of the landing uncertainty ellipses achieved by the proposed algorithm are three orders of magnitude smaller than those possible when relying exclusively on IMU integration. Extensive experimental and simulation results are presented, which demonstrate the applicability of the algorithm on real-world data and analyze the dependence of its accuracy on several system design parameters. © 2007 Wiley Periodicals, Inc. [source] Two years of Visual Odometry on the Mars Exploration RoversJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 3 2007Mark Maimone NASA's two Mars Exploration Rovers (MER) have successfully demonstrated a robotic Visual Odometry capability on another world for the first time. This provides each rover with accurate knowledge of its position, allowing it to autonomously detect and compensate for any unforeseen slip encountered during a drive. It has enabled the rovers to drive safely and more effectively in highly sloped and sandy terrains and has resulted in increased mission science return by reducing the number of days required to drive into interesting areas. The MER Visual Odometry system comprises onboard software for comparing stereo pairs taken by the pointable mast-mounted 45 deg FOV Navigation cameras (NAVCAMs). The system computes an update to the 6 degree of freedom rover pose (x, y, z, roll, pitch, yaw) by tracking the motion of autonomously selected terrain features between two pairs of 256×256 stereo images. It has demonstrated good performance with high rates of successful convergence (97% on Spirit, 95% on Opportunity), successfully detected slip ratios as high as 125%, and measured changes as small as 2 mm, even while driving on slopes as high as 31 deg. Visual Odometry was used over 14% of the first 10.7 km driven by both rovers. During the first 2 years of operations, Visual Odometry evolved from an "extra credit" capability into a critical vehicle safety system. In this paper we describe our Visual Odometry algorithm, discuss several driving strategies that rely on it (including Slip Checks, Keep-out Zones, and Wheel Dragging), and summarize its results from the first 2 years of operations on Mars. © 2006 Wiley Periodicals, Inc. [source] 2D map-building and localization in outdoor environmentsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 1 2005R. Madhavan Determining the pose (position and orientation) of a vehicle at any time is termed localization and is of paramount importance in achieving reliable and robust autonomous navigation. Knowing the pose it is possible to achieve high level tasks such as path planning. A new map-based algorithm for the localization of vehicles operating in harsh outdoor environments is presented in this article. A map building algorithm using observations from a scanning laser rangefinder is developed for building a polyline map that adequately captures the geometry of the environment. Using this map, the Iterative Closest Point (ICP) algorithm is employed for matching laser range images from the rangefinder to the polyline map. Once correspondences are established, an Extended Kalman Filter (EKF) algorithm provides reliable vehicle state estimates using a nonlinear observation model based on the vertices of the polyline map. Data gathered during field trials in an outdoor environment is used to test the efficiency of the proposed ICP-EKF algorithm in achieving the localization of a four-wheel drive (4WD) vehicle. © 2005 Wiley Periodicals, Inc. [source] NURBS to Avoid Boundary Orientation Poses in Serial ManipulatorsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 12 2003Andrzej J. Cebula A procedure to build NURBS motion interpolants to avoid boundary orientation poses for serial manipulator architectures is presented. As an example, the PUMA architecture was used. The procedure, which emerged from B-spline curves theory, enables a local change of the NURBS motion interpolant. The change may be introduced in any arbitrary neighborhood of the chosen boundary orientation pose. Therefore, when tracking a trajectory, one may change NURBS motion interpolant value at any time instant, leaving its remaining values untouched. Recommendation for further research pertains to exploiting the flexibility of NURBS applied to robot kinematics. © 2003 Wiley Periodicals, Inc. [source] Robust Navigation and Mapping Architecture for Large EnvironmentsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 10 2003Favio Masson This paper addresses the problem of Simultaneous Localization and Mapping (SLAM) for very large environments. A hybrid architecture is presented that makes use of the Extended Kalman Filter to perform SLAM in a very efficient form and a Monte Carlo localizer to resolve data association problems potentially present when returning to a known location after a large exploration period. Algorithms to improve the convergence of the Monte Carlo filter are presented that consider vehicle and sensor uncertainty. The proposed algorithm incorporates significant integrity to the standard SLAM algorithms by providing the ability to handle multimodal distributions over robot pose in real time during the re-localization process. Experimental results in outdoor environments are presented to demonstrate the performance of the algorithm proposed. © 2003 Wiley Periodicals, Inc. [source] Contortion and Formation Structures in the Mappings between Robotic Jointspaces and WorkspacesJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 7 2003J. Rooney The concepts of formation in robotic workspace (WS) and contortion in robotic jointspace (JS) are developed, based on the notions of pose and posture, respectively. The approach focuses on the forward and reverse mappings between jointspace and workspace. It utilizes the Cartesian product space JS×WS to interpret these mappings, and, in particular, their singularities as determined by the Jacobians. The singularities are interpreted from the viewpoint of geometric (Clifford) algebra. Initially, systems that have 1D jointspaces and 1D workspaces are discussed before higher-dimensional examples are examined. © 2003 Wiley Periodicals, Inc. [source] Pose Optimization of Serial Manipulators Using Knowledge of Their Velocity-Degenerate (Singular) ConfigurationsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2003Scott B. Nokleby This work investigates the exploitation of velocity-degenerate configurations to optimize the pose of either nonredundant or redundant serial manipulators to sustain desired wrenches. An algorithm is developed that determines a desirable start point for the optimization of a serial manipulator's pose. The start-point algorithm (SPA) uses analytical expressions of the velocity-degenerate (singular) configurations of a serial manipulator to determine a pose that would be best suitable to sustain a desired wrench. Results for an example redundant serial manipulator are presented. The example results show that by using the SPA with the optimization routine, the resulting poses obtained require less effort from the actuators when compared to the poses obtained without using the SPA. It is shown that when no constraint is imposed on the position of the end-effector, the SPA excels at providing a better solution with less iterations than running the optimization without the SPA. © 2003 Wiley Periodicals, Inc. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||